China Forge Forging & Metalforming Forging → 2025English

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Sino-US joint venture

The special welding alloys of EUREKA US for die welding

Our company established a joint venture with US Eureka Welding Alloys Inc. in 2019

at the Zoucheng base to produce special welding alloys for dies, and significantly

reducing the cost of the welding alloys.

The EUREKA US was established in 1926 and has accumulated nearly a hundred

years of technical experience,it is a world-renowned manufacturer of die welding

alloys. Our company fully adopts the equipment, technical processes and production

standards of EUREKA US,the outstanding technology and strict quality management

ensure that the welding alloys are of superior quality and stable.

Besides meeting the demands of the Chinese market, our welding alloys are also

exported in large quantities to overseas markets.

IMITATION

WELDING

EUREKA US welding alloys

DGWELD welding robot

the overlay,repairing and manufacturing for dies

the R&D and production of welding alloys

the design and manufacturing of new dies

SHANDONG KAITAI WELDING TECHNOLOGY CO.,LTD.

Add: Hongtai Rd 1368#,Economic Development Zone,Zoucheng City,

Shandong Province, China.

Tel: +86-537-5291368 5836799 5836899

Fax: +86-537-5271368 Email: sdkthj@126.com

Mobile: +86-15376531333 Website: www.kaitaiweld.com

24-hour service hotline: +86-15376531333

KAITAI WELD

CNC Forging Hammers：The Inevitable Trend Forged by Years of Expertise.

Integrated Hammer & Manipulator

Remote Operation

Manual & Auto Modes

Stepless Speed Control

Manual Mode

Automatic Mode

Semi-Automatic Mode

Synchronized HammerManipulator Operation

Guiyang Wanli Forging Technology Co., Ltd.

Focus

Core

Add guiyang,guizhou,China

Tel：+86 851 8383 9693; +86 13595076881; +86 13985432344

CONTENTS

18

24

39

47

54

59

Figure

Pioneering New Paths for Die Intelligent

Manufacturing and Writing a Scientific

Chapter for the Country

Hotspot

Exploration of Flexible Green Automated

Manufacturing Production Line for

Aviation Precision Ring Forgings

Research on the Process Route of Split

Welding Hollow Motor Shaft for New

Energy Vehicles

Technology

Research on Low-Carbon Manufacturing

Technology for High-End Lightweight

Hollow Front Axle Beam

Maunfacture

Development of Precision Forging Process

for Automotive Outer Race with Inclined

Tracks

Analysis and Solutions of Aluminum

Alloy Upper and Lower Receiver Forging

Problems

Die & Tooling

Research on the Forging Die Warehouse

Picking System Based on Electronic Tags

Research on Lubrication and Anti-wear

Phosphating Technology for Cold Forging

China Forge Forging & Metalforming Forging

President, CCMI Zhang Jin

zhj@chinaforge.org.cn

Publisher/Chief Editor Feng Zhong

fengzhong@chinaforge.org.cn

Circulation Manager Zhou Cunmin

magazine@chinaforge.com.cn

Art Director Han Wei

magazine@chinaforge.com.cn

Sales Staff Luo Wenhui

magazine@chinaforge.com.cn

CONTACT US

10/F, Boya Tower C, Zhongguancun Life Science Park,

Beiqing Rd., Changping Beijing, 102206, P.R.China.

Tel:0086-10-53056669 Fax:0086-10-53056644

E-mail:magazine@chinaforge.com.cn

STATEMENT OF POLICY

The FM’s objective is to disseminate new and complete

information relating to the forging & metal forming

industry. The main editorial text consists of articles and

news releases designed to assist owners, managers,

manufacturing engineers, supervisors in the evaluation of

new methods and techniques. It is an official publication

of the Confederation of Chinese Metalforming Industry

(CCMI). The policy of the publisher and this journal is to

be nonpartisan, favoring no one product or company. The

representations of facts and opinions expressed in the

articles are those of the author and are not necessarily

endorsed by the publisher and this journal. By including

information on new products, new literature, news of

the industry, articles etc., and this impartiality is strived

for the extending to the mention of trade names. Unless

product identification makes reference unavoidable, the

generic name is used. We acknowledge that on occasion

there may be oversight or errors, the editors regret such

oversights and re-emphasize their policy to be impartial

at all times. The publisher reserves the right to refuse

advertising it deems inappropriate for publication in The

FM ,including ads for classes of products and services

not considered of significant interest to the readership.

(ISSN1672-5638) FM is a trademark of the CCMI. All

rights reserved. CCMI maintain a policy of keeping

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subject to space availability, and open to all interested

parties that submit items meeting our editorial style and

format as determined by the publisher.

中 国 锻 压 协 会

Confederation of Chinese Metalforming Industry

10

32

Jiangsu Longyan Machinery Co., Ltd.

National High-Tech Enterprise

Single-arm Rapid Forging

Hydraulic Press

CNC Swing Rolling Machine

Rapid Forging Hydraulic Press

Website: www.longyaniixie.com

Address: No. 10 Hongxiang Road, Hudai Industrial Park, Wuxi City, Jiangsu Province

Qilong Wang

137 9267 7321 156 1060 0788 

Vertical Fully Automatic Loading/

Unloading CNC Ring Rolling Machine

Jiangsu Longyan Machinery Co., Ltd. is a high-tech enterprise specializing in the

research, development and manufacturing of digital forging equipment. The company's

main products include: CNC ring rolling machines, CNC precision forging machines,

CNC swing rolling machines, CNC expanding machines, CNC forging hydraulic presses, CNC rapid forging machines, wedge cross rolling machines, robotic arms,

discharge machines, operating machines, and complete forging production lines.

CNC Automatic High-Diameter Flange Forging Line

D53 Series Radial-Axial Ring Rolling Machine

Longyan Machinery

Di e s a s c r i t i c a l e q u i p m e n t i n t h e

manufacturing industry, are often referred

to as the \"mother of industry\" and are

also an important indicator of a country's industrial

development level. Forging dies, which frequently

endure high temperatures and high stresses, are the

shortest-lived type of dies. In key national projects

such as advanced aircraft, gas turbines, and nuclear

power, large forging dies used for large presses (such

as 80,000-ton presses) manufactured with traditional

methods face the issue of very short service life

when forming hard-to-deform material components

(such as high-strength steel landing gear). This

severely impacts the stability of the forging quality

and the international competitiveness of the

products. It has become a critical bottleneck in the

forging of hard-to-deform materials.

In key national industries such as automotive

and energy, medium and small forging dies used

for forming key components like crankshafts and

Pioneering New Paths for Die Intelligent

Manufacturing and Writing a Scientific

Chapter for the Country

Written by Zhang Minglun·FM 华，牟浩，沈建·中车齐齐哈尔车辆有限公司

Zhou Jie

Personal Honors

PhD, Professor, PhD Supervisor; National \"Ten Thousand Talents Program\" Leading

Talent.

Chongqing Talent Program A II-level.

Director of the Key Laboratory of Advanced Mold Intelligent Manufacturing of

Chongqing.

Director of the Key Laboratory of Long-Life Mold Additive Manufacturing Technology,

China National Machinery Industry.

Chief Expert of the \"Brainstorm\" program of the China Forging Association.

Vice Chairman of the Forging Committee of the China Mold Industry Association.

Vice Chairman of the Plastic Engineering (Forging) Branch of the Chinese Mechanical

Engineering Society.

President and Director of the Expert Committee of the Chongqing Mold Industry

Association.

Vice Chairman and Expert Group Leader of the Chongqing Forging Industry

Association.

Director of the Forging Equipment and Forming Technology Engineering Research

Center of Chongqing.

Director of the Chongqing Mold Remanufacturing Engineering Research Center.

Chairman of the Academic Committee of the Chongqing Gear Parts Precision Forming

Engineering Research Center.

Research Areas

Large components’ extreme forming and small/medium components’ precision forming

process methods and mold technology.

Low-cost long-life mold manufacturing methods and theories, mold life extension and

remanufacturing methods and theories.

Mold arc additive manufacturing process, equipment, production lines, and application

technology.

10 Forging 2025 CF

Figure

turbine blades also face low lifespan issues. How to

achieve green remanufacturing of dies and extend

their super-long lifespan has become a bottleneck

restricting high-quality development and affecting

the core competitiveness of enterprises.

Professor Zhou Jie’s team, over 15 years,

with the support of 9 national-level and 3

provincial-level projects, invented a gradient

functional heterogeneous series structure for

forging dies, established a new structural design

theory, developed new materials matching the

new structure, proposed a novel arc additive

manufacturing process (welding-forging composite)

and integrated shape control technology, and

established the world’s largest CNC gantrytype “additive-forging composite” arc additive

manufacturing equipment and production lines.

They have achieved major original results, and

the overall technology level is internationally

leading. These results have been applied in leading

enterprises in aviation, energy, and automotive

fields, improving the service life of large forging

dies by more than 2 times (some dies improved by

more than 50 times), and small/medium forging

dies by more than 1 time; comprehensive costs were

reduced by more than 50%, and manufacturing

cycles shortened by more than 50%.

This issue of Forging and Metalforming Magazine

(FM) is honored to invite Professor Zhou Jie from

Chongqing University for an FM interview.

Professor Zhou Jie is a professor and PhD

supervisor at the Department of Materials Forming

and Control Engineering, School of Materials

Science and Engineering, Chongqing University.

He is also the Director of the Key Laboratory

of Advanced Die Intelligent Manufacturing in

Chongqing. He has led over 100 projects, including

the National Natural Science Foundation, the

National Key R&D Program, national major

projects, and industrial research projects, publishing

2025 CF Forging 11

Figure

焊接房

碳刨房

碳弧气刨房

Largest CNC gantry-type “additive-forging composite” arc additive manufacturing system and production lines

Die Storage Area Inspection and Reconstruction

Processing Die Tranfer Area

Heating Furnace + Heat Preservation Flat Car

Welding Room

Carbon Arc Gouging Room

Carbon Arc Gouging Room Over head Crane Heating Preservation Flat Car Heating Hood Auto Matie Surfacing Welding Machine

more than 350 academic papers in professional

journals, with 148 included in SCI and EI. He holds

39 invention patents and 9 utility model patents, and

has won 10 provincial and ministerial-level research

awards, including 3 first-class or above in scientific

and technological progress.

Now, let’s follow the FM reporter and step into

Professor ZhouJie’s academic world.

Starting from the Key Laboratory,

Empowering Die Manufacturing to New

Heights

Professor Zhou Jie majored in Forging and

Material Processing during his studies, a time

when China's forging industry was flourishing.

However, the industry also faced challenges such

as high manufacturing costs, poor environmental

conditions, and short die life, with the issue of short

die life being particularly troubling for enterprises.

\"Those who aim for the difficult will succeed, and

those who face challenges will progress.\" Since

then, Professor ZhouJie made improving die life

his research focus and has led his team between

laboratories and forging workshops. Over the course

of more than 20 years, they have made significant

progress.

During that period, Professor Zhou's team

established the Advanced Die Intelligent

Manufacturing Chongqing Key Laboratory, focusing

on research and engineering applications related to

long-life, low-cost forging die manufacturing and

remanufacturing technology. Their achievements

are remarkable:

(1) Research on the design method and theoretical

aspects of gradient functional heterogeneous

structures for long-life, low-cost forging die

manufacturing and remanufacturing.

(2) Material design, organizational performance,

constitutive models, and research on the

heterogeneous material connection mechanisms of

low-cost cast steel or forged steel substrates and

their matching materials for gradient functional

heterogeneous structures.

(3) Research on failure mechanisms, die

life prediction methods, die longevity, and

remanufacturing technologies, as well as additive

material matching techniques for different types of

presses such as hydraulic presses, high-energy spiral

High Rib and Ultra-thin

Wall Window Frame

Ti-Alloy Tail Suspension

Frame of Aircraft

Aircraft Wheel Hub Forgings Additive-forging composite

Process of large forging die

12 Forging 2025 CF

Figure

presses, hot forging presses, and hammers.

(4) Research on the integrated arc additive

(remanufacturing) equipment, control systems,

additive software systems, additive (welded)

forging composite process methods, and additive

manufacturing production line development for

gantry-type and articulated robotic systems.

(5) Research on the application of large-scale

(super) cast steel gradient functional additive

manufacturing dies for forging on 800MN and

300MN hydraulic presses.

(6) Application technology research of large

(super) forging dies based on gradient functional

structural additive remanufacturing technology for

800MN and 300MN hydraulic presses.

(7) Research on the application technology

of medium and small-sized forging dies based

on gradient functional structural additive

(remanufacturing) technology on forging equipment

such as hydraulic presses, high-energy spiral

presses, hot forging presses, and hammers.

(8) Research on the application of arc additive

manufacturing technology for integrated die-casting

dies and ultra-high-strength steel hot stamping dies.

(9) Research on materials, processes, and

structures in laser cladding additive manufacturing

for automotive body panel stamping dies.

Since its establishment in 2021, the laboratory

has undertaken over 10 vertical projects, including

National Natural Science Foundation projects,

National Key R&D Program projects, and key

projects funded by the Chongqing Natural Science

Foundation. The team has published more than 50

academic papers in SCI journals, been granted over

20 domestic and international invention patents, and

received 9 provincial and ministerial-level scientific

Gradient Functional

Structural Additive

(Remanufacturing)

Technology of Die for

Aircraft Main Spar

Forging Die for Ti-Alloy Tail Suspension Frame of Aircraft

via Gradient Function Structural Additive Manufacturing on

Cast Steel Substrate

Gradient Functional Structural Additive

(Remanufacturing) Technology of Forging

Dies for the Landing Gear of Large Aircraft

2025 CF Forging 13

Figure

research awards, including 2 first prizes and special

prizes at the provincial and ministerial levels.

In 2022, Professor Zhou Jie was awarded the

First Prize of the Machinery Industry Science

and Technology Progress Award for the project

\"Long-Life, Low-Cost Died Manufacturing

and Remanufacturing Technology and Its

Industrialization.\"

\"Next, the laboratory will continue its research

in areas such as the high-flexibility die intelligent

additive manufacturing system based on articulated

robots, model processing software, design methods

for high-performance alloy materials suitable for

continuous additive manufacturing processes,

die life prediction and longevity methods under

extreme service conditions, and the shape-structureperformance synergistic regulation methods for

ultra-long additive manufacturing processes,\"

Professor Zhou Jie explained.

Industry-University-Research

Collaboration: A Brilliant Chapter from

'First Encounter' to 'Marriage'.

\"Industry-University-Research collaboration

is essentially the cooperation between the soft

power of universities, such as technology and

talent, and the hard power of enterprises, such

as equipment and product manufacturing, to

achieve complementary advantages and resource

sharing. This demand relationship makes it easy

for universities and enterprises to cooperate.

Whether they can collaborate depends on whether

the stronger party is willing to cooperate with the

weaker party and establish the first stage of the

relationship. Whether the collaboration continues

depends on evaluating the contributions and benefits

of both sides. If the evaluation of contributions

and benefits is reasonable, it naturally leads to the

second stage, and even to the third stage.\"

Currently, there are three main models of

Industry-University-Research collaboration: project

cooperation, platform cooperation, and joint venture

cooperation. The cooperation process can roughly

be divided into three stages, which Professor Zhou

Jie humorously and vividly refers to as the \"First

Encounter Phase,\" \"Honeymoon Phase,\" and

\"Marriage Phase.\"

First Stage: Cooperation should begin by

solving specific engineering problems. Through

mutual understanding, both sides work together

to successfully complete the collaborative project.

This first stage is crucial; if either side does not try

or actively cooperate, the collaboration will come to

a halt.

Second Stage: After several successful

collaborations, and especially after having a

\"pleasant cooperation,\" mutual trust is established.

At this point, both sides can start to address the

scientific issues behind product quality (engineering)

problems, such as the influence of materials,

process methods, and parameters on product quality.

Together, they can explore and formulate short-term

and medium- to long-term cooperation plans. This

is when the possibility of establishing a long-term

cooperative relationship and setting up platforms

like joint R&D centers and joint laboratories arises.

Both sides need to enjoy their cooperation and

collaborate joyfully to reach this stage.

Third Stage: After evaluating joint platforms

like R&D centers and laboratories, if both sides

find that they have benefited significantly and feel

that they can no longer work without each other,

they can consider \"marriage\" when an opportunity

for the enterprise's transformation and upgrade

arises. At this point, both parties can jointly

develop existing or new enterprises, forming a

14 Forging 2025 CF

Figure

joint venture with not only technological but also

economic ties. Establishing a joint venture is a rare

and opportunistic event, typically occurring when

an enterprise has been struggling with continuous

losses and is in urgent need of transformation

and upgrading through mechanisms such as

technological innovation. Only then are enterprises

willing to take this step, and only at this point can

both sides potentially reach this stage. Of course,

the joint venture post-\"marriage\" holds limitless

possibilities.

Professor Zhou Jie has always been committed

to collaborating with top domestic and international

enterprises, focusing on research addressing critical

engineering issues and the scientific problems

behind them. To date, Professor Zhou Jie has

established good cooperative relationships with

dozens of excellent domestic companies, many

of which are in the \"First Encounter Phase,\" but

more are in the \"Honeymoon Phase.\" Chongqing

University has jointly established the \"Advanced

Die Intelligent Manufacturing Chongqing Key

Laboratory\" and the \"Machinery Industry LongLife Die Additive Manufacturing Technology Key

Laboratory\" with Chongqing Jiepin Technology Co.,

Ltd. and Chongqing Dajiang Jiexin Forging Co.,

Ltd. Chongqing University serves as the research

and graduate training base, while Jiepin Technology

and Dajiang Jiexin act as application demonstration

bases. The focus of the research is on the critical

technologies for material precision forming processes

and long-life die manufacturing and remanufacturing

in the fields of aerospace, shipbuilding, and

automotive industries. The platform generates annual

revenue of about 700 million yuan.

The team has also established the \"Large Die

Forging Forming Process and Die Technology

Joint R&D Center\" with China Second Heavy

Machinery Group (China Erzhong) and Wanhang

Forging. Every year, Chongqing University sends

around 6 graduate and doctoral students to work

at the enterprise, collaborating with the company's

engineering staff on real-world forging product

modeling, process simulation, and optimization.

Since 2016, they have trained dozens of graduate

and doctoral students, while also cultivating several

engineering doctors for the company.

The team has established joint R&D centers with

companies such as Erzhong Wanhang, Dajiang

Jiexin, Chuangjing Warm Forging, and Nanjing Ship

Equipment, forming stable and long-term IndustryUniversity-Research cooperation relationships that

achieve mutual benefits and resource sharing. They

have also collaborated with enterprises and research

institutes such as Southwest Aluminum, Guizhou

Anda, Dongfang Turbine, Aerospace Technology,

Steel Research High-Tech, Seres Automobile,

Changan Automobile, SAIC-GM-Wuling, 625

Institute, Liaoshen Industrial, and 59 Institute,

successfully solving key bottleneck technology

issues for these enterprises.

Research Should \"Come from

Enterprises and Go Back to Enterprises\"

\"I believe that universities have three main

missions: to impart knowledge, create knowledge,

and transfer knowledge. Universities not only need

to teach existing knowledge but also collaborate

with enterprises to explore scientific problems,

study and discover natural laws, and create new

knowledge. At the same time, universities must

also cooperate with enterprises to transfer existing

research outcomes, turning knowledge into practical

applications that create wealth for both enterprises

and society.\"

Based on this philosophy, Professor Zhou Jie has

2025 CF Forging 15

Figure

developed a unique, practical, and effective training

system for his graduate students.

The basic training roadmap for students joining

Professor ZhouJie's team is as follows:

First Year: Students complete all required

courses and attend weekly project seminars. They

participate in senior students' research projects,

assist with scientific experiments, learn 3D

modeling and simulation software, build material

constitutive models, and become familiar with the

research process.

Second Year: Students are assigned to industryacademia-research cooperation platforms (such as

joint research centers) for hands-on internships.

They follow the work schedule of engineering

staff at the company, fully participate in product

development, identify engineering and scientific

problems, uncover common technical issues,

establish research topics, and complete engineering

projects in collaboration with the enterprise.

Third Year: Students return to the university

to explore the material science issues behind the

engineering problems they encountered. They

study material forming processes and application

technologies, conduct experiments to explore

the thermodynamic behavior of materials, build

material constitutive models, investigate the

formation mechanisms of product defects, discover

how process parameters affect product quality,

refine scientific problems and innovations, and

complete their master's thesis.

\"Only by going deep into the field and immersing

16 Forging 2025 CF

Figure

yourself in the real situation can you find the true

problems and key issues, which will lay a solid

foundation for conducting valuable academic

research in the future.\"

Engaging with enterprises and collaborating

with them has become a daily routine for Professor

ZhouJie. He often encourages young researchers in

his team to step out of the academic environment

and go to enterprises to find real problems.

They should understand the entire process of

manufacturing, connect with workers, and ask

\"why\" every day.

\"If you work diligently on real problems in

industry-academia-research cooperation, it will, in

turn, help you obtain various funding projects in the

future. In fact, several of the fundamental research

projects I have won over the last 20 years stemmed

from the earlier cooperation with enterprises.\"

Professor ZhouJie frequently advises the

young faculty members in his team that

receiving government-funded projects is not

guaranteed but rather a matter of luck. If they

can't obtain vertical (government-funded)

projects, horizontal (industry-funded) projects

are even more effective in showcasing their

capabilities and skills. By successfully handling

these projects and satisfying the needs of

enterprises, researchers can establish long-term,

mutually beneficial cooperation, create value

for enterprises, and deepen their research in the

areas they are passionate about. This leads to

unexpected discoveries and breakthroughs.

\"Talent cultivation should follow the people's

route 'come from the people, go back to the

people,' and research should follow the 'come from

enterprises, go back to enterprises' route. Problems

arise from enterprises, and after gaining experience

and innovative results, they should be applied back

into enterprises.\" Professor Zhou Jie said.

Sticking to the Original Intention, and

Tirelessly Striving for Scientific Research

to Serve the Nation

Low cost and (ultra) long lifespan are the

perpetual goals of the die manufacturing

industry. Based on recent market demands and

years of research, the future development of die

manufacturing and remanufacturing will focus on

the following directions:

(1) Research and application of various die

substrate materials to meet the lifespan requirements

of dies for forming different materials;

(2) Research and application of long-lifespan,

low-cost gradient functional structural die design

and manufacturing technologies based on additive

manufacturing;

(3) Research and application of die longevity and

remanufacturing technologies for high-temperature,

long-duration forming of difficult-to-deform

materials;

(4) Research and application of localized repair

and green remanufacturing technologies for medium

and small dies in automotive, energy, and other

fields;

(5) Research and application of long-lifespan,

high-precision die surface treatment technologies;

(6) Research and application of intelligent

additive manufacturing equipment and production

lines for long-lifespan dies.

As a veteran in the forging and die industry,

Professor Zhou Jie has devoted himself to China’s

transformation from a forging minor to a forging

powerhouse. He says that he will never relax his

determination to serve the nation through scientific

research and will dedicate his life to helping China

become a strong nation in forging.

2025 CF Forging 17

Figure

Exploration of Flexible Green Automated

Manufacturing Production Line for Aviation

Precision Ring Forgings

Authored by Liu Jun, Zou Chaojiang, Zhang Lihong, Luo Hongfei, Zhang Hua · Sichuan Forge Future Co., Ltd.

The development direction of modern industrial manufacturing enterprises is high-end manufacturing, green

manufacturing and intelligent manufacturing. At the same time, the upgrading of aero-engine manufacturing

technology puts forward higher requirements for aviation parts manufacturing. How to realize intelligent

transformation of traditional aviation forging enterprises has become an urgent problem to be solved for aviation

forging enterprises. This paper introduces the flexible green automatic manufacturing production line of aviation

precision ring forgings newly built by GATD, and gives the practical plan of intelligent manufacturing in aviation

forging enterprises. This production line consists of an automated unmanned blanking production line, a flexible

forging production line, and a fully automatic heat treatment production line. It uses many advanced technologies

of modern warehousing, uses the SCADA system to realize the networked joint control of the main forming

equipment and peripheral equipment, is connected with the MES system, and uses many green manufacturing

technologies, such as oil fume purification, water circulation, and photovoltaic power generation. Practice the

\"dual carbon\" concept of modern manufacturing. After the completion of the production line, it has achieved

remarkable results. It is a successful attempt of intelligent manufacturing of traditional aviation forging and can

be popularized and applied in the forging industry and even aviation forging subdivision.

Modern industrial manufacturing

enterprises need to continue to develop

towards high-end manufacturing,

green manufacturing and intelligent manufacturing,

which inevitably requires the production line

to have informatization, digital and automated

manufacturing capabilities, and the main forming

equipment must have digital control and networked

joint control capabilities. However, the forging

industry is a typical asset-heavy industry, and

the equipment of forging production lines is not

easily replaced. The main forming equipment of

many forging enterprises has a service life of more

than 20 years, so it is difficult to digitalize and

automate these outdated equipment. Therefore, it

is difficult for many forging enterprises to keep up

with the development process of modern industrial

manufacturing enterprises.

Among forging enterprises, aviation forging

enterprises are the most difficult to transform,

because traditional aviation forging enterprises

invest more in equipment, and equipment upgrading

also involves quality control requirements such

as the replacement of equipment certification of

aviation forgings, which makes it more difficult

to transform. At the same time, the manufacturing

mode of aviation forgings has always been

dominated by multi-varieties and small batches.

Production line manufacturing requires frequent

type changes, which cannot compete with the

automated manufacturing scheme of few varieties

and large batches of automotive forgings, thus once

again increasing the difficulty of digitalization,

automation and intelligence.

18 Forging 2025 CF

Hotspot

The traditional forging operation of aviation

forgings is mainly with open-die forging operated

by many people collectively, which not only has

high operation intensity, but also has low production

efficiency, poor quality stability, poor uniformity

and batch stability, and high manufacturing cost.

With the continuous upgrading of aero-engine

manufacturing technology, the new generation of

aero-engines puts forward higher requirements for

forging product quality: higher performance, better

uniformity and better stability of quality of batch

manufacturing.

In recent years, there have been some researches

on the development of industrial intelligence and

even the intelligent management and control of

aerospace forging. Sun Yong et al. proposed a multilevel closed-loop collaborative forging intelligent

management and control platform for aerospace

large ring forgings. Zhou Yulong et al. proposed and

developed an intelligent management and control

system platform technology for production dynamic

disturbance factors based on fault tolerance and

error correction mechanism. Liu Qiang gave a

new understanding of intelligent manufacturing in

the era of Industry 4.0, and then put forward the

overall architecture of intelligent manufacturing

theoretical system. Digital twins are an advanced

means of intelligent manufacturing. Tao Fei et

al. discussed the application of digital twins. Liu

Qing et al. proposed the basic model of digital

twins. Luo Shaokang et al. proposed the digital

twins workshop system model. Peng Yusheng et

al. proposed the concept of intelligent aviation

forging unit based on digital twins. Ning Ruxin et

al. proposed a digital manufacturing model. These

theoretical studies provide a necessary theoretical

basis for the digital and intelligent development of

aviation manufacturing industry, and put forward

feasible solutions. However, how to implement the

theory into the actual manufacturing process and

how to combine their respective manufacturing

characteristics and product characteristics to develop

suitable digital and intelligent manufacturing

requires line construction and actual production

verification.

Guizhou Aviation Technology Development Co.,

Ltd. (referred to as \"GATD\" for short) has been

committed to the manufacturing and development

of aviation precision ring forgings. Its products are

mainly difficult-to-deform superalloys and titanium

2025 CF Forging 19

Hotspot

Deputy technical director, engineer, mainly engaged in die

forging forming process research, whole process parameterization

research of ring forgings, ring rolling parameters design and

strategy control research, special-shaped ring blank making

method research, ring forging process design method research,

ring forging forming process simulation research, research on the

connection between process data and informatization, etc., has 8

patents and 4 national core journal papers.

Liu Jun

alloys. In order to meet the rapidly growing market

demand of aviation forgings and the needs of highprecision and small-batch flexible production of

precious metals, GATD implements the concepts

of green manufacturing and lean manufacturing

in accordance with the 4.0 standard of modern

industrial enterprises, integrates informatization,

digitalization and automation, and explores

the modern transformation and upgrading of

aviation forgings enterprises, and builds the first

domestic and international leading flexible green

manufacturing production line for aviation precision

ring forgings.

At present, the production line has been built in

Deyang City, Sichuan Province, and has been put

into trial operation. The production line includes a

fully automatic unmanned blanking production line,

two flexible forging units, and a fully automatic

heat treatment flexible production line for the whole

manufacturing process of forgings.

Fully automatic unmanned blanking

production line

The fully automatic unmanned blanking

production line includes an automatic threedimensional warehouse, a titanium alloy robot

blanking unit, a superalloy robot blanking unit, a

robot painting unit, and a robot turnover unit. As

shown in Fig. 1, AGV is used among each unit for

automatic material transfer.

The automatic three-dimensional warehouse

uses modern warehousing radio frequency

technology, automatic overhead warehouse, and

tunnel stacker. Its automatic three-dimensional

warehouse management system and MES and ERP

are integrated to realize production order reception

and integrated analysis, intelligent discharge and

blanking scheduling, and the remaining materials

can be automatically returned to the warehouse and

stored.

The titanium alloy robot blanking unit and the

superalloy robot blanking unit are composed of an

automatic sawing machine, a robot, an automatic

lathe, an automatic marking machine and a digital

balance. The automatic sawing machine has the

functions of automatic transferring, automatic

determination and verification of sawing length,

and bar diameter detection. The sawing system of

superalloy robot blanking unit

robot painting unit

automatic threedimensional warehouse

robot turnover unit

titanium alloy robot blanking unit

Fig. 1 Fully automatic unmanned blanking production line

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the sawing machine can intelligently calculate the

bar sawing length according to the actual diameter

and process requirements and feed it back to the

automatic transferring system. Automatic lathe

can give the optimal chamfer size and machining

path according to the bar diameter. The automatic

marking machine marks the material tracking

information on the end face of the bar according

to the production order information and the bar

ingot section number information to meet the

requirements of aviation product quality traceability.

The digital balance can weigh the bar stock and

feed the weight back to the sawing system, which

corrects the sawing dimensions in time.

The robot painting unit consists of a transfer

platform, a drying box, a painting robot, etc. It can

select the paint type according to product materials

and realize automatic painting and automatic

turnover.

The robot turnover unit consists of a material

transferring plate and a robot, which can place the blank

evenly on the material transferring plate according to

the production order. After placing the material, use the

transferring tool to transfer the material transferring

plate to the forging production line.

Flexible forging production line

According to the difficult-to-form characteristics

of aviation ring forging materials and the key points

of precision annular forging control, Aerospace

Technology adopts the concept of single-process

automation, and uses transfer tools between

processes for whole batch turnover. The flexible

forging production line (Fig. 2) includes forging

process automation, automatic coating system,

cleaning unit and furnace temperature centralized

control system.

The automation of the forging process

requires the main equipment and peripheral

related equipment (heating furnace, loading and

discharging machine) to have digital and automated

operation capabilities, and to have networked joint

control capabilities. SCADA system is arranged on

site, and the main equipment and peripheral related

equipment are networked and jointly controlled, and

associated with MES system to realize production

Fig. 2 Flexible forging production line

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order receipt, process parameter import, on-site

manufacturing data feedback, etc.

The furnace temperature centralized control

system is integrated with MES to realize the

centralized control of forging heating furnace, and

can be associated with MES system to realize the

reference, transfer and control of heating process

parameters. On-site display screen is equipped to

display the heating status of each forging heating

furnace in real time.

The automatic coating system adopts the loop

process flow design scheme, which occupies a

small area and has high production efficiency.

The cleaning unit has grinding and shot blasting

capabilities to achieve surface quality control of

forgings in intermediate processes. It is equipped

with a water curtain dust removal system and

a water circulation system to achieve clean

manufacturing and green manufacturing.

Fully automatic heat treatment flexible

production line

The fully automatic heat treatment flexible

production line (Fig. 3) adopts high-precision

heat treatment equipment and high-precision

manipulator that meet the highest global standards

(American aerospace standard AMS 2750G), and

adopts displacement sensor technology, video

technology, oil fume purification system, water

circulation system, furnace temperature centralized

control system, material tracking system, etc., so

as to realize the reconfigurability, high flexibility,

energy saving and environmental protection of

the heat treatment production line, and meet the

requirements of multi-variety, small batch, highquality production and green manufacturing of

aviation forgings.

Production line implementation results

(1) The production line has achieved flexible

manufacturing of hundreds of varieties and nearly a

thousand batches of mixed lines in a single month,

the comprehensive utilization rate of equipment

has increased of 10%, the on-duty output has

increased of 20%, and the product manufacturing

cycle has been shortened to 45 days, reaching the

Fig. 3 Fully automatic heat treatment flexible production line

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international leading level;

(2)The numerical control rate of production line

equipment reaches over 98%, and the networking

rate of key equipment is over 90%. It realizes

automatic collection of manufacturing data in the

whole process and quality traceability. The number

of production line workers is reduced by 50%,

human factors of product problems are reduced, the

qualified rate of forgings is increased of 30%, the

accuracy of ring forgings is increased of 20%, and

the comprehensive manufacturing cost is reduced

by 30%; Digital and automated manufacturing have

been realized, and some parts of processes have

intelligent manufacturing capabilities.

(3)Completely change the dirty, messy and poor

situation of traditional forging sites and realize

clean manufacturing;

(4)Photovoltaic solar panels are arranged on

the roof of the factory building and equipped

with energy storage devices. Using photovoltaic

power generation, it can meet the daily electricity

consumption of office buildings and manufacturing

auxiliary buildings, reduce industrial electricity

consumption, implement the \"dual carbon\" strategy,

and realize green manufacturing.

Economy and scalability

(1)Economy: The total investment of this

production line exceeds 500 million yuan, with an

annual output of 120,000 forgings and an additional

output value of 1.5 billion yuan per year. It meets the

production capacity development needs of GATD

during the \"14th Five-Year Plan\" and is expected

to recover the investment in 3 years; At the same

time, the production line has improved the digital

and intelligent level of ring forgings manufacturing

of GATD and its efficient, high-quality and lowcost manufacturing capabilities, doubled production

capacity and upgraded management of GATD, and

met the quality requirements of the new generation

of aero-engine forgings.

(2) Scalability: This production line is the first

flexible intelligent production line for the whole

forging process in China and the world's leading,

and it has great popularization and demonstration

value in the forging industry.

Concluding remarks

The flexible green automated manufacturing

production line of aviation precision ring forgings

built by GATD has successfully integrated the

advanced concepts of modern industry into

the traditional forging industry, and has made

substantial explorations for the automation and

intelligence of the forging industry. The results

are remarkable, and the operating capabilities and

market competitiveness of forging enterprises have

been greatly improved. During the construction

of the production line, the \"dual carbon\" strategy

was also implemented, clean energy was actively

adopted, and green manufacturing was realized.

The detailed plans such as automation, intelligence

and green manufacturing implemented in the

construction of this production line can be used as

a reference for the forging industry and even the

aviation forging subdivision.

GATD will continue to upgrade and transform the

production line, and deeply apply AR, AI, digital

twins, cloud platforms and other technologies

to build typical scenarios such as AR remote

maintenance guidance, AI safety identification,

and digital twin factories, as well as intelligent

manufacturing cloud platforms, and build a

complete intelligent manufacturing demonstration

factory, presenting a modern intelligent forging

production line with Industry 4.0 version.

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Research on the Process Route of Split

Welding Hollow Motor Shaft for

New Energy Vehicles

By Gou Wenxing, Song Hong, Shen Huihong, Xia Yu, Shen Ming, Tan Zhanyao· Tianjin Pacific Driveline Technology Ltd.

Deputy director of Technology Department, intermediate

engineer, mainly engaged in the development of passenger car

differential bevel gear and new energy motor shafts. Lead the

development of differential bevel gears and motor shafts for

clients such as Volkswagen, Volvo, Vremt, and Magna. Hold

four utility model patents and have been awarded the Second

Prize of the Taizhou Science and Technology Progress Award.

Complete the Major National Science and Technology Project

on \"High-end CNC Machine Tools and Basic Manufacturing

Equipment.\"

This paper introduces the development and research of the process

route for hollow motor shafts in new energy passenger vehicles,

covering the entire process including forging, machining, and

heat treatment. It provides a detailed overview of the mainstream

structural types of hollow motor shafts and their corresponding

new technologies and processes. Standardized process routes

and equipment selection are established for different motor

shaft structures, including the machining processes for internal

and external splines and helical cylindrical gears, as well as the

design concepts for fixtures. These measures aim to improve the

development efficiency and first-time pass rate of new energy

hollow motor shafts and shorten the development cycle.

T Gou Wenxing

he drive motor is one of the three core

components of new energy vehicles,

responsible for converting electrical energy

into mechanical energy. The motor shaft, as a critical

component within the drive motor, serves to secure

the rotor core and transfer power. Its performance

directly impacts the NEV power system. As a result,

the comprehensive service capabilities of motor shaft

suppliers—such as process expertise, machining

precision, and project experience are crucial. The

accuracy of the spline tooth profile, the mechanical

strength of the teeth, production efficiency during

manufacturing, and material utilization rate all have

a significant impact on the product competitiveness

of motor shaft companies.

The hollow design of the motor shaft enhances

heat dissipation and contributes to the lightweight

design of the motor. Historically, the vast majority

of motor shafts were of solid type. However, stress

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is mainly concentrated on the shaft surface, while

the stress in the core part is relatively low during

the service of a motor shaft. Based on the flexural

and torsional resistance in material mechanics, the

hollow shaft can achieve the same performance and

functionality as the solid shaft when the interior

of the motor shaft is appropriately hollowed out

and only a minor increase in the outer diameter

is made on the outer part, while its weight can be

significantly reduced. At the same time, the hollow

design of the motor shaft allows cooling water or

oil to circulate within the shaft, thereby increasing

the heat dissipation area and enhancing the cooling

efficiency. Under the current trend of 800V highvoltage fast charging, The hollowing of the motor

shaft offers greater advantages.

Currently, there are three main production

methods for hollow motor shafts: hollowing out

a solid shaft, welding, and one-piece forming.

Among these, welding and one-piece forming are

more widely applied in production. The solidshaft hollowing method is generally a product

of initial design. In terms of this manufacturing

method, there are no major challenges in blank

forming and machining. Moreover, the high

material consumption and the large mass of the

finished motor shafts are not conducive to the

development of electric vehicle range and fast -

charging capabilities. In contrast, split-welding and

one-piece forming methods address these issues.

The typical characteristics of such motor shafts are

their hollow structure, thin walls, and lightweight.

However, while achieving weight reduction through

the hollow structure, these methods also increase

manufacturing costs.

Process Route Analysis

The split-welded hollow shaft (Figure 1) mainly

realizes the stepped inner hole of the shaft through

extrusion forming, and then it is formed by machining

and butt welding. Through extrusion forming,

the shape changes of the inner hole that meet the

requirements of the product's structure and strength

are retained to the greatest extent possible. Generally,

the basic wall thickness of the product can be

designed to be less than 5mm. The welding equipment

typically adopts magnetic arc welding or laser

welding. If magnetic arc welding is used, there will

generally be a welding protrusion of about 3mm on

both the inner and outer parts of the butt joint seam.

Although the welding strength of this type is high, the

welding of the components at both ends is achieved

by applying pressure to both ends. This places

extremely high demands on the precision of pressure

control and the coaxiality of the fixtures at both ends.

Otherwise, the issue of non-coaxiality of the two

ends after welding will arise, ultimately resulting in

the dynamic balance of the product out of tolerance .

When laser welding is adopted, the welding depth is

generally between 5 and 8 millimeters. The welding

strength can be ensured to be greater than 80% of that

of the base material. Some suppliers, by using strict

process control measures, can even achieve a strength

that is more than 90% of the base material's strength.

Once the welding of the hollow shaft is completed,

ultrasonic flaw detection must be conducted on the

microstructure of the welded area and weld seam

quality must be conducted in accordance with the ISO

13919-1 B standard to ensure product consistency.

Figure 1 Schematic diagram of the hollow motor shaft of a

certain new energy passenger vehicle

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Process Route Formulation and

Verification

A c c o r d i n g t o t h e s t r u c t u r a l t y p e s a n d

technological characteristics of the split-welded

motor shaft, the following process route has

been summarized through the verification of trial

processing.

process flow for the left-side part

The process flow of the left - side part (Figure 2) is

as follows: sawing→chamfering→warm forging→

normalizing→machining→spline broaching→local

induction quenching, tempering→magnetic powder

detection→spline hard broaching→inspection.

For the motor shaft with a split - welded structure,

the forgings before welding are formed by multi -

station warm forging or hot forging processes. The

aim is to utilize the minimum amount of material

to form forgings with reasonable allowances in

accordance with the product shape. During the

simulation of the preliminary forging scheme, it is

necessary to consider the reasonable distribution

of materials. Through simulation analysis, the

maximum principal stress does not exceed 2300

MPa, and the risk of mold cracking is extremely

low. Moreover, the streamline is complete and

smooth, and the stress field is evenly distributed.

After the actual trial production, the actual

streamline of the forging is basically consistent

with the streamline obtained from the simulation

analysis, as shown in Figure 3 and Figure 4.

After forging and forming, the forgings will be

pre-treated to homogenize the structure and refine

the grains. Then, carry out the rough machining

process, adopt the method of turning the workpiece

around on the CNC lathe (as shown in Figure 5

and Figure 6) for machining the outer diameter,

end face, and inner hole of the forging blank.

Since the first rough machining takes the forging

surface rough datum as the positioning datum, it is

necessary to select in conjunction with the forming

process datum of the forging (Figure 5) to ensure

Figure 2 Forging schematic diagram of the left-side part

Figure 5 Schematic

diagram of the 1st process

for left-side part

Figure 6 Schematic

diagram of the 2nd process

for left-side part

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Figure 3 Streamline

Simulation Analysis Diagram

Figure 4 Physical diagram

of the streamline

positioning stability during batch machining.

The broaching process is adopted for the internal

splines of the sample product. This process has

high machining efficiency and precision, and is

very suitable for the machining of such parts. When

encountering a blind hole spline, we generally use

gear shaping or axial pulse forming for the internal

splines. Gear shaping is a traditional process, which

has low precision and efficiency. Additionally, due

to the limited internal space within the splines, the

overall rigidity of the gear shaper cutter is poor and

it is difficult to remove chips, which ultimately leads

to the low precision of the finally formed splines.

However, when the axial pulse forming process

is adopted for the internal splines, this process forms

the internal splines through the high-frequency pulse

extrusion of the spline shaft die without material

removing(Figure 7).The spline forming efficiency is

extremely high, and the precision is also very high.

the spline forming efficiency is extremely high,

and the precision is also very high. Generally, it

can reach the precision level of Grade 9 according

to the DIN5480 standard. However, there will be

some material accumulation or deformation at the

addendum circle and the end of the spline teeth after

the forming. (Figure 8). From the perspective of

functional analysis, it will not affect the usability.

The local induction hardening and tempering

processes are applied to the internal splines and

internal holes of the sample product, which is

related to the customer's design and requirements. If

medium and high carbon steels are used, the process

of quenching and tempering + local induction

hardening and tempering is generally chosen. In

contrast, if low-carbon alloy steels are used, the

process of overall carburizing and quenching is

preferred. Overall, medium- and high-carbon steels

are increasingly preferred in numerous application

scenarios, as they provide significant cost benefits in

terms of both material and heat treatment processes

compared to low-carbon alloy steels.

The process of using a carbide broacher to broach

the spline tooth flanks and the addendum circle

after the internal spline surface hardened, it’s aim

is to eliminate the deformation of the spline tooth

profile and helix caused by induction hardening.

After spline hard broaching, taking the addendum

circle of the spline as the reference, the spline pitch

circle runout is detected to be within 0.005mm, and

the coaxiality is very good, as shown in Figure 9.

Therefore, the addendum circle of the spline can

serve as a key datum for subsequent machining

positioning, which is also the key to ensuring the

runout of the internal spline relative to the outer

diameters of the bearings at both ends.

process flow for the right-side part

The process flow of the right - side part (Figure

10) is as follows: sawing→chamfering→warm

forging→normalizing→machining→inspection.

For the motor shaft with a split - welded structure,

the forgings before welding are formed by multi -

station warm forging or hot forging processes. The

aim is to utilize the minimum amount of material

to form forgings with reasonable allowances in

accordance with the product shape. During the

simulation of the preliminary forging scheme, it is

necessary to consider the reasonable distribution

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Figure 7 Schematic Diagram

of the Principle of Axial Pulse

Forming Splines

Figure 8 Physical Diagram

of Axially Pulsed Spline

Forming

Figure 9 Hard Broached Spline Precision Inspection Report

of materials. Through simulation analysis, the

maximum principal stress does not exceed 2300

MPa, and the risk of mold cracking is extremely

low. Moreover, the streamline is complete and

smooth, and the stress field is evenly distributed.

After the actual trial production, the actual

streamline of the forging is basically consistent

with the streamline obtained from the simulation

analysis, as shown in Figure 11.

After forging and forming, the forgings will be

pre-treated to homogenize the structure and refine

the grains. Then, carry out the rough machining

process, adopt the method of turning the workpiece

around on the CNC lathe (as shown in Figure 12

and Figure 13) for machining the outer diameter,

end face, and inner hole of the forging blank.

Since the first rough machining takes the forging

surface rough datum as the positioning datum, it is

necessary to select in conjunction with the forming

process datum of the forging (Figure 12) to ensure

positioning stability during batch machining.

Figure 10 Forging schematic diagram of the right-side part

Figure 11 The streamline simulation analysis diagram is

basically consistent with the actual streamline diagram.

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amount is generally designed to be 0.01 - 0.05mm.

When the interference amount exceeds 0.06mm,

the probability of cracks occurring after welding

increases, and the cracks are mainly distributed

at the connection part. The reason is that a large

interference amount will cause the connection part

after welding to be prone to stress concentration

areas. As time goes by, delayed cracks may even

appear. Therefore, during the verification stage of

the welding process parameters, we will conduct

ultrasonic flaw detection and cutting metallographic

inspection under different interference amounts and

time periods, so as to determine the optimal laser

welding parameters.

Preheating Step: Whether preheating is necessary

depends on the carbon content of the base material.

If the base material is medium or high carbon

steel, local induction heating is generally used

for preheating to reduce the probability of crack

generation due to its high carbon content. The

typical preheating temperature ranges from 100°C

to 160°C.The higher the carbon content, the

relatively higher the preheating temperature. If the

base material is low-carbon alloy steel, preheating

is not required before welding.

Laser welding: Laser welding utilizes highenergy laser pulses to locally heat the material

within a small area. The energy radiated by the laser

diffuses into the interior of the material through

heat conduction, and a specific molten pool is

formed after melting the material. It is a new type

of welding method, mainly aimed at the welding

of thin-walled materials and precision parts. It can

achieve spot welding, butt welding, overlap welding,

seal welding, etc. It has a high depth-to-width ratio,

a small weld width, a small heat-affected zone, little

deformation, a fast welding speed, a smooth and

beautiful weld seam. After welding, there is no need

Figure 12 Schematic diagram

of the 1st process for rightside part

Figure 13 Schematic diagram

of the 2nd process for rightside part

Process Flow of Integrated Laser Welding

Machining

Process flow of integrated laser welding

machining: cleaning before welding→laser

welding→ultrasonic detection→rough machining

the intermediate outer diameter→fine machining

o u te r c i r c l e s a t b o th e n d s a n d t h e i n n e r

hole→milling keyway, drilling, deburring-grinding

outer circle→dynamic balance detection→100%

inspection for key characteristics→ultrasonic

cleaning-packaging

The laser welding process has been maturely

applied in various fields. Welding can be achieved

for the same base metal materials or different base

metal materials. In this example, the motor shaft is

made of the same base material. The laser welding

process involves several steps, including cleaning

before welding, press-fitting, pre-heating, and

welding itself. Cleaning before welding is mainly

to remove residual organic such as oil stains and

impurities on the weld seam surface. Because

the residual organic substances have a very high

probability of causing defects such as cracks,

pores, and even explosion holes during the welding

process.

Press fitting step: In order to ensure the coaxiality

of the left and right parts and the welding stability

during the welding process, we have designed an

interference fit for the weld seams at both the left

and right ends. Through verification, the interference

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for treatment or only simple treatment is required.

The weld quality is high, there are no pores, it can

be precisely controlled, the focused light spot is

small, the positioning accuracy is high, and it is easy

to achieve automation. The key parameters mainly

monitored during the laser welding process include

welding power, focal length, arc starting angle,

arc starting rotation speed, welding angle, welding

rotation speed, arc ending angle, and arc ending

rotation speed. For these key control parameters, we

will conduct trial production verification through

different parameter permutations and combinations,

and finally select the optimal welding parameters

through cutting inspection and comparison.

The deeper the weld depth, the fewer the defects

such as cracks. According to the debugging

results, the weld depth should be between 5.6

mm and 6.7 mm. After determining the optimal

welding parameters, 50 pieces will be continuously

processed, and one in every five pieces will be

randomly selected for cutting inspection. The

inspection results are shown in Figure 14 below.

Ultrasonic flaw detection. According to the

ISO13919 - 1 B standard, 100% ultrasonic flaw

detection is required for the weld area. Before

the ultrasonic flaw detection, the part needs to be

air-cooled to below 45℃. The sample part used

immersion method for ultrasonic flaw detection.

Since the weld is located in the middle of the motor

shaft, two probes need to be set up. One probe is

placed at the weld area and perpendicular to the outer

circular surface of the part. The other probe covers

the entire depth direction of the weld at an angle. The

flaw detection results are shown in Figure 15 below.

After ultrasonic flaw detection, various machining

operations are carried out on the motor shaft. In the

first process after welding, the key lies in how to

reasonably transform the spline datum so that after

the final external cylindrical grinding, the runout of

the internal spline evaluated with the AB bearing

datums at both ends meets the requirement of less

than 0.06 mm, and the process capability also meets

the requirements. This is also a significant potential

risk for the split - welded motor shaft. Taking the

sample motor shaft as an example, let's elaborate

on the datum transformation process between the

internal spline and each process:

The first operation after welding is crucial

for ensuring the spline runout accuracy. Using

the addendum circle of the internal spline as the

reference, the fixture locates and clamps the part

via expansion and end support. The purpose of this

process is to transfer the spline reference to the large

outer circle in the middle. Verification confirms that

Figure 15 Ultrasonic flaw detection results

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180° Sample weld depth6.06mm(10×)

270° Sample weld depth6.06mm(10×)

180° Sample maximum microcrack0.208×3(100×)

270° no microcarcks in the sample(100×)

Figure 14 Weld quality inspection results

the spline runout is within 0.02mm when measured

using the processed large outer circle as the

reference. This indicates that the reference has been

successfully transferred from the internal spline to

the large outer circle.

The second operation. Taking the turned large

outer circle as the reference, center and clamp the

part with double-barrel chucks. Leveraging the

advantages of a double-ended lathe, the outer circles

and inner holes at both ends can be machined in one

clamping. In this way, the large outer circle datum is

transferred to the center holes at both ends. With the

machined center holes as the new datum, the runout

of the large outer circle is measured to be within

0.015 mm. This indicates that the large outer circle

datum has been successfully transferred to the center

holes at both ends, and the center holes at both

ends are the positioning datum for the subsequent

keyway milling and outer circle grinding.

The third operation. Taking the center hole at both

ends as the reference, clamp the workpiece with a

floating chuck and perform keyway milling driven

by a four-axis indexing system.

The forth operation. Taking the center hole at

both ends as the reference, drive the workpiece by

floating and expanding to tighten the inner hole.

Complete the grinding of the outer circles at four

locations in one clamping, which includes the AB

bearing datum, the large outer circle for assembling

the iron core rotor in the middle, and the outer circle

of the sensor.

A f t e r t h e d a t u m t r a n s f e r t h r o u g h t h e

aforementioned processes and batch data verification,

the internal spline runout is basically controlled

within 0.035mm when detected with the AB datum.

In addition, all the aforementioned form and position

tolerances meet the drawing requirements. The spline

runout and the roundness of the AB datum have a

significant impact on the motor noise. Therefore,

these three items need to be specially managed as key

characteristics. We even conduct Fourier analysis on

the roundness of the AB datum, where an abnormality

in a fixed order can lead to noise generation. This

item is an area that requires in-depth research in the

next stage to address NVH problem.

Endings

Regarding the split-type welded motor shafts

for new energy passenger vehicles, through the

decomposition and analysis of the product structure,

technical requirements, application scenarios,

material properties, etc., we have formulated

a manufacturing process route suitable for this

type of motor shaft structure. After batch process

verification, it has been confirmed that this process

route meets our expectations in terms of processing

economy, processing efficiency, processing

accuracy, the first-time pass rate of products off the

production line, etc.

The development of the aforementioned process

route has laid the foundation for establishing

a standardized mass production line for splittype welded hollow motor shafts in new energy

passenger vehicles in our company. This provides

a clear roadmap for future large-scale production.

During the construction of the production line,

we introduced numerous articulated robots and

truss automation systems, significantly enhancing

the automation level. These advancements enable

operations with fewer workers or even unmanned

production, thereby minimizing human-induced

variations, increasing the product qualification rate,

and boosting customer satisfaction. Overall, this has

positioned the company as an industry leader in the

production of split-type welded hollow motor shafts

for new energy vehicles.

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Research on Low-Carbon Manufacturing

Technology for High-end Lightweight Hollow

Front Axle Beam

Written by Zhu Guojun · Hubei Tri-ring Axle Co., Ltd.

In recent years, low-carbon and environmental protection have become the focus of the automotive industry. For

every 10% reduction in vehicle weight, fuel consumption decreases by 6%-8%, and pollutant emissions decrease

by 4%. Lightweighting of automotive forgings is one of the most important and effective measures for energy

conservation and emission reduction in the forging industry. The front axle is the largest long rod forgings on a

vehicle. In addition to bearing the weight of the vehicle, it also supports vertical loads between the ground and

the frame, braking forces, lateral forces, and bending moments caused by lateral forces. This article introduces

the structural design and performance research of a high-end lightweight hollowed front axle, It also discusses the

improvement of the product’s intrinsic performance through special heat treatment quenching process. Through the

identification of application scenarios and the evaluation of verification standards, the strength and performance

of the automotive front axle is enhanced while achieving lightweight design, and low-carbon emissions, energy

conservation, and consumption reduction in the design and manufacturing processes.

Design and Analysis of Lightweight

Hollow Front Axle Beam

Structure

Hollowed Front Axle Beam

In the non-strength area between I-section and

spring seat, a long-waist-hole design is adopted,

which reduces the weight of the forgings while

improving its toughness. This design helps to

achieve more uniform stress distribution at each

area of the forgings, thus realizing the effect of

lightweight design and energy-saving emission

reduction. Additionally, considering braking

conditions, the I-beam cross-section is designed

asymmetrically with staggered profiles, the KP

boss and the neck area of the beam adopts a curved

design to enhance reliability. The earliest hollow

structure originated from Daimler in Germany in

the early 20th century, and it is now widely used

in mass production of vehicles across Europe and

around the world. Compared with traditional nonhollow front axles of the same load, the weight is

reduced by 8 to 12 kg(Figure 1).

Special Technical Requirements of Hollow

Front Axle Beam

The hollowed front axle beam has higher

technical standards, especially in mechanical

properties, requiring the uniformity of the intrinsic

performance of heat treatment. 16 tensile test bars

32 Forging 2025 CF

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are taken from different areas of the front axle beam

to obtain a consistent tensile strength of 880-1030

MPa. The traditional heat treatment process cannot

meet the requirement of consistency of the intrinsic

performance of the product. At the same time, its

appearance requirements are also higher. After

shot blasting, the arc height value is ≥ 0.45mmA2,

the surface coverage rate is 200%, and the surface

residual compressive stress is ≥ 250MPa; and 200%

flaw detection is required (Figure 2).

Comparative Study

To facilitate the study of the performance of the

hollowed front axle, we compare the stress analysis

of the same front axle forging before and after

hollowing (Figure 3, Table 1).

Through CAE analysis, it is found that the

maximum stress point and maximum stress value

of the hollowed front axle change with the shape

and location of the hollowing. Through continuous

optimization and correction, the maximum stress

value can be significantly reduced. At the same

time, in order to further study the influence of the

hollowed structure on the product performance, two

stiffness comparison tests in different states were

Figure 1 Diagram of Hollowed Front Axle Structure

Figure 2 Diagram of Sampling and Detection of Hollowed

Front Axle beam

section B-B

H H

A B

AB

H C

D C

D

EF G

EF G

section D-D section F-F

Tensile sample

Impact sample

Hardness

Figure 3 Diagram of Stress Analysis Results of Hollowed

Front Axle

Max Stress

535MPa

Max Stress

581MPa

Max Stress

535MPa

Max Stress

581MPa

State

Front Axle Weight A B C D Maximum Displacement

kg N/mm2

(MPa) N/mm2

(MPa) N/mm2

(MPa) N/mm2

(MPa) mm

Before Hollowing 102 344.8 580.7 425.6 322.8 10.59

After Hollowing 89.5 374.0 535.2 387.4 313.3 10.34

Table 1 Stress Analysis Results Table of Hollowed Front Axle

conducted, and the results were unexpected: when

the load is less than 1 times, the deformation of the

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hollowed front axle is smaller, and the maximum

deformation in the middle tends to be uniform.

When the load is 2 times, the effect is the same

as that of the non-hollowed one. When the load

exceeds 2 times, the deformation of the hollowed

front axle is significantly larger (Figure 4).

and an average lifetime of over 700,000 cycles for

a group of 5pcs. And this standard is far higher than

foreign standards:

American standard: 0.5G - 3G, 100,000 cycles

Indian standard: 0.5G - 3G, 100,000 cycles

The standard of company A in the United States:

0.5G - 3G, 250,000 cycles

The standard of company A in Japan: 0.2G - 1.8G,

300,000 cycles

The standard of company A in Germany: 0.2G -

1G, 2,000,000 cycles

The standard of company A in Sweden: 0.5G -

1.5G, 1,000,000 cycles

Another fact is that in India, there is no restriction

on overload, and the fatigue test standard is very

low, with a 3× loading and 100,000-cycle lifetime

requirement. Hubei Tri-Ring Auto Axle Co., Ltd.

has been producing 6.5tons front axles according

to the Indian standard since 2005. Every year, tens

of thousands of units are exported to India, and

not a single instance of fracture has occurred. This

suggests that the 3× loading and 100,000-cycle

lifetime standard can still meet the practical service

life requirements for driving safety.

The road conditions in 1999 were definitely much

worse than they are now. yet OEMs still use the

same standards from over 20 years ago to accept

front axle forgings. This is no longer appropriate for

the following reasons: For the same load, foreign

front axles are generally 10-20 kg lighter. Front axle

beam produced according to international standards

Verification and Check of Front Axle

Forging Products

The most important product characteristic of the

front axle is the safety characteristic, which is the

basis of lightweight design. The hollowed front

axle needs to be verified. Usually, use theoretical

calculation first, and then use the CAE analysis.

After the lightweight design sample of the forging

is completed, a large number of experiments need

to be done. The main experiments of the front axle

beam include: vertical fatigue test, lateral braking

test, static stiffness test and deflection test. The most

commonly used and basic verification method in

China is the vertical fatigue test (Figure 5).

The verification standards used by domestic

OEMs have been based on QC/T513 and QC/T483

since 1999. The specific requirements, in simple

terms, are: loading at 3.5 times, with a lower limit

of 0.5 times, a minimum lifetime of 300,000 cycles,

Figure 4 Schematic Diagram of Stiffness Test Results of

Hollowed Front Axle

Center distance(mm)

3.5times load

3times load

2.5times load

2times load

1.5times load

1times load

0.5times load

0.1imes load

Figure 5 Schematic Diagram of Vertical Force Condition of

Front Axle

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for export have reached over 1 million units, with

zero PPM failures over the past 18 years. In the

domestic market, no real fatigue fractures have

occurred in front axle forgings; if there were fatigue

fractures, they would occur in batches. Even if there

are individual fractures, they would be caused by

abnormal defects. We randomly inspected some

low-end agricultural cannula front axles: the verified

fatigue life is all less than 200,000 times, and they

are applied in large quantities in the market. Cast

front axles: the verified fatigue life is all less than

100,000 times, and they are also widely used in

harsh environments.

The fatigue test standard is the fundamental basis

for our lightweight design. Based on the above

comparison and verification of the fatigue test

standard, we can see that given the significantly

improved road conditions in China, and the stricter

overload limitations, the 3.5G loading in the test

conditions is too high. In most cases, the actual load

does not exceed 1.5G, and high-load situations are

rare. The test results for fatigue life do not directly

correspond to the actual vehicle mileage failure

results. The B5>300,000 cycles and B50>700,000

cycles requirements are excessive, leading to

oversized front axle forgings, with excessive

strength, which directly impacts the lightweight

design.

A more practical method is to learn from the

Japanese standard or the Daimler standard, reduce

the maximum load of the test to about 1G for

highway vehicles, which is closer to the actual

working conditions. For engineering vehicles and

other vehicles with poor road conditions and severe

overloading, the maximum load can be increased to

1.5G - 2G. On this basis, the fatigue life standard

could be established.

For the maximum load, we need a static stiffness

testing to measure the maximum deformation

and permanent deformation. This would validate

whether the design strength can meet the

requirements. Currently, there are no national

standards or industry standards for this, but we have

accumulated a large amount of experimental data.

By using comparative methods,we can determine

whether there is a risk of bending deformation of

the front axle during actual operation.

Under braking conditions, we need to perform

deflection tests to measure the maximum twisting

deformation angle and permanent deformation

angle of the KP boss. Currently, there are also no

national standards and industry standards for this.

Using the comparative methods, we can assess the

risk of twisting deformation of the front axle under

the actual driving conditions.

Low-carbon Manufacturing Technology

and Online Control

The front axle beam is a large long-rod forging

and a safety component, so the stability of its

manufacturing process is very crucial. It is the

fundamental guarantee of the intrinsic performance

and strength life of the forging.

Ensuring stable raw materials performance

It is unacceptable to directly purchase materials

based on national standards. Materials must be

custom-ordered with specific agreements. The

compression ratio of raw materials produced by the

continuous casting and continuous rolling process

should be no less than 7. The alloy composition

should be in the upper-middle range, and the

fluctuation of target values should not exceed

0.02. There must be ladle refining and vacuum

degassing, and the content of S and P components

must be controlled. Impurities and banded

structures must meet higher standards than national

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specifications. The consistency of raw materials

is the fundamental guarantee for a stable and lowcarbon manufacturing process. At the same time,

high-strength bainitic non-quenched and tempered

steel should be prioritized. This eliminates the need

for heat treatment, directly contributing to carbon

reduction and emission control.

Energy conservation and carbon reduction in

the forging process

Forging is a special process and one of the most

energy-intensive operations. The key to achieving

low-carbon energy conservation in forging is

improving heating efficiency and continuous

production. Intermediate frequency heating is

typically used, and it is essential to match the

appropriate furnace diameter to maximize thermal

efficiency. The high efficiency and full automation

of forging production are key to energy savings.

First, ensure the consistency and controllability

of the heating temperature. This requires infrared

monitoring systems for automatic adjustment,

enabling temperature retention and control. After

the medium-frequency heating, a three-channel

sorting device must be installed to ensure that

overheated or burnt billets are discarded, while lowtemperature material can be reheated and reused.

Before the material enters the roll-forging process

from the medium-frequency heating outlet, an

automatic deoxidation device must be installed,

typically using high-pressure spray or mechanical

wire brushes to ensure good surface quality of the

forged parts.

The roll-forging process is used to form the blanks

for front axle beam. Through continuous partial

deformation and overall forming, the roll-forging

process improves the metal flow lines, resulting in

better internal quality while achieving the desired

forging shape. One of the main advantages of roll

forging is its ability to significantly reduce flash,

improve material utilization, and enhance the

fatigue life of the forging.

The biggest disadvantage of the roll forging

process is that the design and commissioning are

relatively difficult. The direct forging simulation

and actual verification results often have certain

deviations. This requires a high theoretical level and

on-site experience of the designers. The best results

can be achieved through compensation design

and repeated corrections, that is, while saving

raw materials, the forging is fully formed without

surface defects and can achieve stable production

(Figure 6).

Figure 6 Schematic Diagram of the Front Axle Roll

Forging Process

The main forging equipment for front axle forging

line typically includes screw press or hot die forging

press of more than 4000tons. The bending and final

forging equipment must have sufficient pressure

to ensure that the forging is fully formed, without

surface folding and incomplete filling defects.

After final forging and trimming, the production

line can be equipped with fully automatic hightemperature online detection system to monitor the

appearance quality of the forgings. These systems

can monitor the hot-state dimensions and surface

defects of the forgings online,preventing the

occurrence of abnormal situations where defects

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are detected after the forgings cool down, which

would otherwise result in batch scrap. Additionally,

these online inspection systems make it easier for

process designers to analyze data and study the

thermal shrinkage and distortion of the forgings at

different temperatures. This ensures the consistency

of forgings and provide a data basis for forging

to achieve net forming and reduce machining

allowances (Figure 7).

cooling, followed by heat treatment and quenching

for secondary heating. However, this approach does

not utilize residual heat. Some manufacturers do use

residual heat for quenching, but this often results

in unstable quality, poor hardness consistency, and

an increased risk of cracking or bending failure.

Many manufacturers connect forging and heat

treatment, but due to the mismatch of production

cycle time, hot billets are also accumulated and

stored, preventing the effective utilization of

residual heat. The three-channel flexible suspension

line production method can solve the problem of

cycle time mismatch, ensure the consistency of

heat treatment hardness while utilizing the residual

heat, and also be suitable for the production of nonquenched and tempered steel, truly achieving an

energy-saving, consumption-reducing and lowcarbon manufacturing process (Figure 8).

Core process of low-carbon manufacturing:

Layered spray quenching process

As mentioned earlier, the high-end lightweight

hollowed front axle has a special process

requirement: 16 tensile test bars are taken from

the designated areas on the same front axle, and

the tensile strength must all be within the range of

880-1030 MPa to be qualified. This requirement,

after countless tests and breakthroughs, cannot

be guaranteed by the traditional heat treatment

process. Because it is hollowed in the middle, the

Figure 7 Schematic Diagram of Hot-State Online Detection

Post-forging cooling: Three-channel flexible

low-carbon production line

Most people often overlook the importance of

post-forging cooling and do not treat it as a critical

process to control. In fact, different materials have

varying requirements for post-forging cooling.

The cooling rate affects the internal performance

of the forgings, for example, if the forgings are

cooled in a pile at too high a

temperature, it can lead to coarse

grain structures in the front axle

forgings. More importantly, the

post-forging cooling method

is crucial for low-carbon and

energy-saving efforts. Traditional

post-forging cooling methods

involve direct air cooling or fan

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Figure 8 Schematic Diagram of the Three-Channel Flexible Low-Carbon

Production Line after Forging

section thickness difference between the two ends

and the middle is further increased, making the

heat treatment of the two ends and the middle part

unable to be synchronized, resulting in a hardness

difference in the core.

According to the results of heat treatment

simulation analysis and the variation in section

size, the front axle is divided into 5 regions. The

quenching spray tank is set as a 5-layer square

pipe. Each layer of square pipe corresponds to

one region of the front axle. A certain number

of nozzles are evenly installed in each region to

ensure that the sprayed water forms a swirl, and the

distance between the edge of the spray tank and the

workpiece is basically the same. The flow rate and

time of each electric nozzle are precisely controlled

by CNC to adjust the cooling shrinkage of different

areas of the front axle and achieve the desired effect

(Figure 9).

Conclusion

Based on the current global trends of \"energy

conservation, environmental protection and

lightweighting design\" as well as \"carbon

neutrality and carbon compliance\", the application

of lightweight design will only become more

widespread. The hollowed front axle optimizes

the structure while ensuring strength and reliable

performance and has been successfully applied,

with obvious effects in carbon reduction and

emission control.

The high requirements of verification and test

standards, the lack of standards, and deviation

between standards and actual application scenarios

are important factors that restrict and affect

lightweight design. Therefore, as designers, it is

necessary to fully verify and evaluate the standards

and identify the application scenarios to design the

optimal system solutions.

Another prerequisite for lightweight forging

is the improvement of the technological level

and the guarantee of the process stability . The

forging process is a key special process that affects

performance. Forging temperature, equipment

pressure, and mold conditions are critical factors for

ensuring the appearance quality of forgings. The use

of an automated online infrared detection system

is a very effective control method, while postforging cooling and the utilization of residual heat

are also important components of energy saving and

consumption reduction.

Layered spray quenching is an advanced

automated precision control process that

fundamentally solves the issue of consistency in

the intrinsic properties of forged parts. It represents

a systematic improvement in heat treatment levels

and serves as the foundational process for achieving

lightweight design.

Figure 9 Schematic Diagram of Layered Spray Quenching Process

38 Forging 2025 CF

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For universal joint outer race with inclined tracks, a precision forging process that can directly get the inclined

tracks was introduced in this paper. Firstly, an elastically cold sizing punch and a warm forging billet with

outer lugs are designed. Subsequently, the flow stress model of the material used in this forging is constructed

and coupled into commercial finite element software. The numerical simulation program was established

and the initial shape of forging billet was determined through simulation. Then, a four step warm forging and

cold finishing process was designed. Furthermore, based on the results of finite element simulations and site

production tests, the dimensions of the part and the parameters of the process are optimized. As shown by the

small-batch trials, the process is stable and reliable, eliminating the subsequent rough milling step and reducing

the material weight of the forging from 2360g to 2150g, with good economic benefits.

Development of Precision

Forging Process for Automotive

Outer Race with Inclined Tracks

Zeng Fan, Shanghai GKN HUAYU Driveline Systems Co., Ltd.

The universal joint is a critical component in

automotive transmission systems, enabling

rotational speed and torque transmission

between two non-parallel shafts. It can be considered

as the \"articulation joint\" in automotive motion

system. The VL-type universal joint is a kind of

telescopic constant velocity joint. As shown in

Figure 1, the VL outer race component typically has

two groups of oppositely distributed inclined tracks?.

If conventional forging methods are employed, when

the punch is withdrawn axially, the tracks fields will

interfere with the forging, resulting in inability to

eject. In mass production, this outer race is typically

manufactured using hot forging or warm forging

methods. Firstly, the shank and the cylindrical bowl

portion are forged, and then the inclined ball tracks

are machined by milling. The processing efficiency is

relatively low. At the same time, the metal material in

the track area becomes waste, reducing the material

utilization. In addition, the track is the critical area

that bears the dynamic load during working. The

metal flow lines in the ball track portion are cut off

during machining, which also reduces the service

life of the part. Therefore, developing a new process

that can directly forges the inclined ball track has

significant importance for improving product quality

and reducing production costs.

In recent years, with the continuous development

of computer technology and numerical computation

methods, the theoretical research and technical

accumulation of finite element numerical simulation

have gradually matured. Through numerical

simulation, we can understand the movement

Figure 1. The VL-type universal joint outer race

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patterns, stress distributions, flow lines, filling

conditions, and forming loads during the material

deformation process. This has significant influence

for forming processes design, dies design, billets

design, equipment selection, and quality control.

Development of cold precision finishing

process

Current structure of cold finishing die

To produce inclined tracks by precision forging,

the first priority is to solve the problem of punch

release. Figure 2 presents the traditional structure of

a cold precision finishing mold. For the types with

smaller deformation during track deformation, this

structure can successfully achieve cold precision

finishing. However, when this structure is used for

cold precision finishing of VL outer race, cracks

appear prematurely at the corner connections of

the punch. The location where the cracks appear is

marked in Figure 2. Analysis indicates that during

the forging process of the workpiece, the lower part

of the punch corner is subjected to lateral pressure

directed outwards; whereas, during the ejection

process, after the mandrel is withdrawn, the same

location experiences lateral pressure directed

inwards. Each time the punch moves, this area is

subjected to an alternating shear stress. For the VLtype outer race, the deformation is larger, and the

elastic deformation stroke during ejection is also

larger, resulting in a higher value of alternating

shear stress. This ultimately leads to fatigue

cracking of the metallic material at the punch corner

connections.

A combination cold finishing punch was

developed by Nichidai company to solve this

problem. As shown in Figure 3, the punch corner

was divided into separate blocks. The advantage of

this structure is that it eliminates the risk of fatigue

cracking at the punch corner. However, this solution

needs to assembled the head of the punch and its

working blocks with high precision. During the

punch release process, the working blocks is pushed

inwards by pneumatic springs. The mold structure

is relatively complex, and additional tooling is

required.

Figure 2. Current structure of cold finishing die

Crack occurrence location

Force during deformation

Force during demolding

Figure 3. Punch structure of Nichidai company

Optimized structure of cold finishing die

To solve this problem, an optimized structure

with an elastic and openable cold finishing punch

has been designed, as shown in Figure 4. The

upper region of the punch is a thin-walled straight

cylinder, while the outer shape of the lower region

matches the inner cavity of the part, featuring six

inclined ball tracks with a centerline angle of 16°

to the axial direction. The inner side has a conical

through-hole. A rectangular slot is cut between

every two tracks for elastic mold release. The width

2025 CF Forging 41

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of the slot is determined t ≥ (πdmax-πdmin)/6+1, where

dmax represents the diameter of the circumscribed

circle of all track contours, and dmin represents the

diameter of the cylindrical surface of the part's inner

cavity. Corresponding mandrel and sleeve were

also prepared. The upper region of the mandrel is

cylindrical, while the lower region tapers, with an

angle that matches the inner bore of the lower part

of the punch. The sleeve is a hollow cylindrical

shape, with an inner bore size that corresponds to

the shape of the upper part of the mandrel. The axial

relative position of the mandrel and the mandrel

sleeve is adjustable.

Figure 5 shows the die structures before

deformation, before release after deformation,

and after release, respectively. At the beginning of

the processing, the elastic openable punch moves

downwards and extends into the inner cavity

of the warm-forged billet. While the mandrel

and sleeve extend in and expand to tighten the

punch. Subsequently, the punch continues to

press downwards to complete the cold finishing

deformation, achieving the necking of the part.

Then, the mandrel and sleeve are withdrawn

upwards, allowing the punch to release inward due

to the material's elasticity. Finally, the punch is

pulled upwards to complete the die release process.

The advantage of this structure is that during the

cold forming process, lateral force is applied to the

mandrel within the region of the conical hole, while

the connection area of the punch is not affected by

shear forces. This, in turn, reduces the risk of fatigue

cracking caused by cyclic stresses. Meanwhile,

the punch retains the monolithic structure. So that

it is easy to manufacture and assemble, making it

suitable for automated mass production.

Warm-forged billet design

As shown in Figure 1, the central axes of six

tracks are alternately distributed with a \" ╱ ╲ \"

or \" ╲ ╱ \" shape between every two tracks. Since

the billet is formed by warm forging, no metal

material should be existed above the contour line

of the tracks to ensure successful punch release.

So, the metal flowed into the upper part of the \" ╲

╱ \" shape need to be much more than that into the

\" ╱ ╲ \" shape during the cold forming process.

To ensure that the material flows mainly along the

radial direction during cold finishing and to reduce

the risk of cracks caused by circumferential flow, a

warm-forged billet with external lugs was designed.

As shown in Figure 6, three external lugs were

designed on the sides of the \" ╲ ╱ \" shape, aiming

to pre-distribute the material in the upper cylindrical

region of the billet along the circumferential

direction. Compared to traditional billet with

circular outer contours, the new design achieves

Figure 4. Optimized cold finishing punch Figure 5. Assembly cold finishing punch

Sleeve

Mandrel

punch

42 Forging 2025 CF

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more uniform wall thickness reduction during cold

finishing, which helps to reduce local stress and the

risk of cracks caused by local torsion. Additionally,

it reduces the friction between the material and the

die surface during circumferential flow, contributing

to a lower forming load.

To determine the specific dimensions and shape

of the warm-forged billet at each station, and to

reduce the number of trial-and-error attempts, it is

considered to simulate the precision forging process

finite element analysis. This simulation aims to get

a proper warm-forged shape that can ensure filling

well and eliminate the risk of folding.

Construction of Numerical Simulation

Scheme and Process Design

During plastic deformation, the deformation

resistance of materials changes continuously with

increasing deformation, which directly affects

the metal flow and determines the forming result.

The annual report published by International

Cold Forging Organization in 2014 pointed out

that selecting an appropriate material flow stress

model to accurately describe the material flow

stress behavior is a prerequisite for successful finite

element simulation, directly affecting the final

solution accuracy. In this paper, a mathematical

model of the material flow stress was firstly

constructed.

In this study, a kind of medium carbon steel

(the materials brand is UC1, an internal grade of

GKN) was used. The main chemical composition

of this steel (wt%) was shown in Table 1. Since

the precision forging of the part involves complex

plastic volumetric forming processes under

compressive conditions, a series compression tests

were conducted at different temperatures (850–1000

℃, at intervals of 50 K) and imposed constant strain

rates (0.01, 0.5, 1, and 10s-1) using a Gleeble-1500

thermal simulator. The material was machined to a

series of cylindrical specimens with a size of 8 mm

in diameter and 12 mm in height. All compressions

were terminated when the true strain reached 0.6.

The entire testing process was conducted under an

argon atmosphere to avoid oxidation.

As shown in Figure 7, the flow stress curves

of the material were measured at strain rates of

0.1s-1, 0.5s-1, 1s-1, and 10s-1, and at temperatures

of 850°C, 900°C, 950°C, and 1000°C. The effects

of temperature and strain rate on flow stress were

significant. At a certain strain, higher temperature

and smaller strain rate resulted in lower flow stress.

For a single curve, in most cases, with an increase

in strain, the flow stress increased rapidly at first,

and then fell towards a steady-state stress value

after peak stress was reached. While at a strain rate

of 10s-1, the curve does not exhibit a clear steadystate stress value.

Figure 6. Warm-forged billet with outer lugs

Type C Si Mn P S Cu Ni Cr Mo Al Ti

Content (%) 55 25 75 1.4 1.2 2 1 23 2 2.3 0.11

Table 1 Material chemical composition

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According to the results of the hot compression

tests, it is evident that the flow stress of this material

is influenced by temperature, strain, and strain

rate during the deformation process. Referring to

the modeling methods in the literature, this study

established a mathematical relationship among

these parameters using the Arrhenius model.

The predicted stress results from the model were

compared with the experimental data, as shown in

Figure 8.

The predictability of the constitutive model can

be described using the correlation coefficient (R),

which reflects the linear relationship between the

predicted and experimental values, the root mean

square error (RMSE), which is the standard error

indicating differences between values, and the

average absolute relative error (AARE), which is a

measure of accuracy of a method for constructing

fit. The values of R, RMSE, and AARE were

determined as 0.927, 8.245 MPa, and 4.768%,

respectively. The errors arose mainly from the

fitting calculation in the process of modeling and

from the measurement error in the hot compression

experiments; however, these values were relatively

small, demonstrating the good capabilities of the

developed model.

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0

50

100

150

200

250

0.1s-1

0.5s-1

1s-1

10s-1

Stress/MPa

Strain

Temperature=850℃

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0

50

100

150

200

250 Temperature=900℃

0.1s-1

0.5s-1

1s-1

10s-1

Stress/MPa

Strain

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0

50

100

150

200

250

Temperature=950℃ 0.1s-1

0.5s-1

1s-1

10s-1

Stress/MPa

Strain

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0

50

100

150

200

250

Temperature=1000℃

0.1s-1

0.5s-1

1s-1

10s-1

Stress/MPa

Strain

Figure 7. Flow stress–strain curves under different deformation conditions

0 50 100 150 200 0

50

100

150

200

Experiment Stress/MPa

Prediction Stress/MPa

Flow Stress

Theoretical Line

R=0.927

RMSE=8.245MPa

AARE=4.768%

Figure 8. Comparison of predicted stress and

measured stress

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Finite element applications

The modeled constitutive equations were

embedded in the commercial FE code, DEFORM

-3D. The key parameters of the FE models are listed

in Table 2.

for circular runout. Due to the complexity of the

shape and the high precision requirements for its

external dimensions, the 4th stage die was designed

with a closed-cavity scheme. The parting surface is

designed at the maximum cross-section of the lug

edges, which facilitates the smooth removal of the

part from the die cavity. A 2mm gap is left between

the punch and the die at the lug area of the parting

surface to ensure sufficient material flow and filling

at the punch corners. For areas other than the lugs,

the die clearance at the parting surface is controlled

within 0.5mm to ensure precise control of the inner

cavity and outer circular runout. The ejection position

is set at the flash area of the maximum outer lug.

Given the complexity of the blank shape and the

high precision required for its external dimensions,

the four-step die design adopts a closed-cavity

scheme to ensure sufficient filling of the external

As shown in Figure 9, a finite element

simulation model for the cold finishing process was

established. To improve computational efficiency

and reduce the calculation time for individual cases,

some simplifications were made to the simulation

process. The die was set as a rigid body, while the

workpiece was defined as a plastic body, neglecting

its elastic deformation during the forming process.

Due to the geometric symmetry of the workpiece, a

1/6 model was used to reduce the number of finite

elements. The primary goal of the simulation was

to determine an appropriate warm-forged preform,

as well as to optimize the dimensions and shapes of

the cold finishing punch and die. Through iterative

optimization calculations, a design solution with

well-filling of the workpiece was achieved.

Warm Forging Process Design

Based on the previously optimized warm-forged

preform, a four-step warm forging process was

designed. The warm forging steps are illustrated

in Figure 10, with the forming process divided

into four stages: small shaft extrusion, large shaft

extrusion, pre-forging of the inner cavity shape, and

final forming. This step-by-step process effectively

distributes the press load and meets the requirements

Parameters Value Unit

Speed of top die 50 mm/s

Initial forging temperature 20 ℃

Mesh remeshing threshold 0.7 -

Friction factor 0.12 -

Table 2 Parameters of finite-element model for cold finishing

Figure 9. Finite element simulation scheme for cold finishing

Figure 10. Warm forging process steps diagram

Parting line

Parting line

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lugs and inner spherical tracks, as well as to control

the height of the flash at the parting surface. The

parting surface is designed at the maximum crosssection of the lug edges, which ensures the smooth

removal of the part from the bottom die. A 2mm

gap is designed between the punch and the bottom

die at the lug area to ensure well-filling at the

punch corners. For other areas, the gap is designed

at 0.5mm to ensure precise control of the runout

between inner cavity and outer circular. The top

ejection position is set at the flash area of the

maximum outer lug.

Based on the material flow stress model

established above, combined with the rigidviscoplastic finite element method, a simulation

model for warm forging was constructed. The key

simulation parameters for the warm forging process

are listed in Table 3.

Figure 11 illustrates the simulation scheme for

the four-step warm forging process of this part.

Based on the simulation results, the billet shape at

each station was adjusted to ensure rational material

flow, uniform load distribution, well filling, and

the elimination of folding risks during the forming

process. Additionally, based on the material flow

behavior at the fourth station. A series of vent

holes were designed in the punch at the locations

corresponding to the final filling areas.

Field Validation and Process Optimization

Then the trial production of the product was

conducted on-site. It was observed that significant

cracking occurred on the side of the forging with

larger deformation, specifically at the lug region, as

shown in Figure 12.

By analyzing the simulation results, it was found

that during the cold finishing process, the metal

material in the inner cavity of this region was

under significant tensile stress. Further, focusing

on the metal material in this area, the damage

accumulation during the cold finishing process

was analyzed by simulating. As shown in Figure

13, the damage value in this region reached over

0.5, exceeding the material's fracture threshold of

0.45. It was concluded that the excessive tensile

Parameters Value Unit

Speed of top die 300 mm/s

Initial forging temperature 920 ℃

Preheating temperature of die 200 ℃

Heat transfer coefficient

(workpiece/tool) 1.5×104 W/(m2

·℃ )

Thermal capacity 500 J/(kg·℃ )

Friction factor 0.25 -

Coefficient of expansion 13.32×10-6 ℃ -1

Heat transfer coefficient

(workpiece/environment) 150 W/(m2

·℃ )

Table 3 Parameters of finite-element model for warm forming

1st stage 2nd stage 3rd stage 4th stage

Figure 11. Warm forging simulation scheme

Figure 12. Photo of cracking on the lug side

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stress in this region during forming was the cause

of the cracking. As shown by the simulation, the

start point where cold deformation begins to occur

was too low in initial design. This caused the

upper part of the inner cavity to be subjected to

an outward force from the punch, while the lower

part under an inward force from the bottom die.

The middle region of the metal was subjected to

shear stress, leading to a rapid increase in damage.

The optimized design raised the starting point in

cold forming process, as illustrated in Figure 14.

After the modification, the damage value in the

target region was reduced to below 0.3, effectively

eliminating the risk of cracking.

Trial production of the forgings was conducted

using the optimized scheme. As shown in Figure

15, the resulting forgings exhibited well filling of

the inclined tracks without any cracks. A small

batch trial production of 200 pieces was carried

out with automated line using this scheme, as

illustrated in Figure 16. All the forgings met the

product standard. The new process eliminated the

subsequent rough milling process for the tracks and

reduced the material weight from 2360g to 2150g,

demonstrating significant economic benefits. The

batch of forgings underwent subsequent machining

and was assembled into the final product, which

successfully passed the functional and bench tests

Figure 13. Damage values

before optimization

Figure 14 Damage values

after optimization

required before actual use.

Conclusion

(1) An elastic, openable cold finishing punch was

developed for the precision forging production of

VL-type universal joint outer race. The warm-forged

billet design with external lugs addresses the issue

of uneven circumferential deformation distribution

in the forging, helping to reduce equipment load

and improve process stability and reliability. This

process features a simple die structure, requires

no additional equipment, and can be implemented

using conventional production lines, facilitating

rapid batch production switching.

(2) By optimizing the starting point of the cold

punch for cold forming, the problem of excessive

shear stress during the cold finishing process of

VL outer race can be resolved, thereby eliminating

the risk of crack formation. The optimized process

has successfully achieved small-batch continuous

production of the forgings, laying the foundation for

subsequent mass production of the product.

Figure 15. Photo of the forging

Figure 16. Photo of the small-batch trial production.

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Analysis and Solutions of Aluminum Alloy

Upper and Lower Receiver Forging Problems

Wang Chaoqing, Shen Junjian, Yang Xiaolong, Huang Lei · Wuhan Newwish Technology Co.,Ltd

This document takes the forging products

d e s i g n e d f o r a c t u a l p r o d u c t i o n a t

Wuhan Newwish Technology Co.,Ltd.

As an example,deeply analyzes the problems that

occur during the forging process of aluminum

alloy forgings for upper and lower receivers,and

formulates targeted and guiding measures.By

adopting appropriate operations,the product's

technical requirements are met,and experience

and technical requirements are provided for the

subsequent design and production of related

products.

Forging Process Route and Technical

Requirements

The upper and lower receivers are the main parts

of firearms,where the gun mechanism performs

actions such as locking,firing,and shell ejection

within the metal shell/wall,mainly serving to bear

force and contain.The forging material is 7075

T6(aluminum alloy),with the upper receiver forging

weight being 0.78kg and the lower receiver forging

weight being 0.72kg.Schematic diagrams of the

forgings are shown in Figures 1 and 2.

The upper receiver is pre-forged and finally

forged using round bar material,while the lower

receiver is pre-forged and finally forged using

square bar material.Their work step diagrams are

shown in Figures 3 and 4.

The product requirements are that the appearance

should be defect-free,fully formed,without

cracks,and the surface should be free of bubbles.

The materials used must comply with the drawing

design requirements,and the dimensions must be

consistent with the drawing requirements.

Forging Process Simulation Results and

Equipment Selection

After determining the specific parameters of the

simulation process scheme for the upper and lower

receivers,the upper and lower receiver models

were simplified and initial conditions for numerical

simulation were set:

The forging died and initial blank are modeled

in 3D using NX software tools,converted into STL

Figure 1 Schematic diagram

of the upper receiver

Figure 2 Schematic diagram

of the lower receiver

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format,and imported into the Deform-3D simulation

system;

The upper receiver blank specification is

φ 48mm×170,and the lower receiver blank

specification is 60mm×40mm×170mm.The American

grade ALUMINUM-7075 is selected,which

corresponds to the Chinese grade 7A09;

The initial forging temperature for both the

roughing and pre-forging and finish forging steps is

defined as 420℃ to replace the heat transfer of the

workpiece in the environment;

The control grid method is used,with the premise

that the blank is a plastic body and the died is a

rigid body.The geometric temperature and material

are set,and the element type is set to tetrahedral

grids;

The blank is gridded by the system,with the

relative value of the number of elements defined as

80,000.

When defining the contact boundary,the upper

and lower dies and the blank are sheared,and the

friction factor is set to 0.4;

The upper die movement speed for roughing,preforging,and finish forging is set to 500mm/s;

The press-down amount for each step is defined

as 0.5mm;

The died temperature is set to 200°C.

Upper Receiver Calculation Results and

Equipment Selection

Based on the settings mentioned above,the upper

receiver is simulated using the deform software,and

the results are shown in Figures 5 and 6.The

appropriate equipment is selected based on the

results,as shown in Table 1 below.

Figure 3 Work step diagram of the upper receiver

Pre-forging Trimming

Finish-forging Trimming

Figure 4 Work step diagram of the lower receiver

Blank Trimming

Trimming Trimming

Pre-forging

Finish-forging

Figure 5 Pre-forging:Forming force F=707t,

Energy E=43.3kJ