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Table of Contents 1. Introduction ........................................................................................................................ 1

1.1 HPF Review ................................................................................................................ 2

2. HPF processes and technology ........................................................................................... 3

2.1 Laser Cutting process ....................................................................................................... 3

2.2 Hard cutting process ........................................................................................................ 3

2.3 Warm Cutting Process ..................................................................................................... 3

2.4 Forming Process............................................................................................................... 3

2.4.1 Cold Forming ............................................................................................................ 4

2.4.2 Warm Forming .......................................................................................................... 5

2.4.3 Hot Forming .............................................................................................................. 6

3. Conclusion ....................................................................................................................... 10

4. References ........................................................................................................................ 11

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1. INTRODUCTION

The uses of hot stamping technological processes in forming almost all types of parts is

becoming more and more robust as industries looking forward for easy and flexible

manufacturing. Hot Press Forming (HPF) consists of the press forming and moves onto the

cooling of the press form parts within the die technology. Nowadays, hot stamping, hardening

and forming are integrated as a single process leading to both direct and indirect methods.

The direct method however enables heating of the raw material (iron, steel or iron-based

metal) to a specified temperature between 900 to 950 degree Celsius and about ten minutes in

a furnace and transfer to a cooled dies between 50 to 100 degree Celsius per second while the

overall time taken for stamping and cooling is about 15 to 25 seconds. At the other hand,

indirect stamping method requires part to be drawn using 3-D software like Cad/Cam

whereas the final shape requires partial trimming after the process pass through a

conventional dies heated to approximately 95%, also the forming process in material data lies

in between 600-900 degree Celsius.

Many researcher has successfully contributed to the technology of HPF among these are

[16-17, 26, 31, 34] focused on HPF design and simulation [20, 21] concentrated on

experiment and measurement, [24] design of boron steel for HPF without cooling system,

[25] design with heated and cooled tooling, [27] Design of hot V-bend test for boron steel

heating and forming process, [30] design of high vehicle strength steel by the influence of

HPF, [28] design of hot stamping vehicle door beams, [29] presented improvement of hot

press stamping formability design, [33] design for metal forming. The advancement of this

technology has been a proven factor for sustainability as discussed in the paper of [38] and

more effort about the overall HPF process was demonstrated in [40]. This report however

focuses on the HPF process cycle in forming almost all parts, the process and the

technologies employed into the system will be presented in more details in the group

presentation.

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1.1 HPF Review

Hot press forming was review in 2010 by [4] looking at the areas of mechanical,

thermal, technological and microstructural of hot stamping. The study shows great potential

for innovation and further investigations of hot sheet metal forming. An early study by [9]

investigated the design for HPF process to manufacture automotive plate found that the

indirect approach which involve pre-forming phase and the direct oil quenching to achieve

uniform and rapid cooling rate. More recent work conducted by [10] investigating the design

of the cooling channel for HPF specifically for hot stamping tools to achieve a uniform

component were finalized with an evidence of experimental design founded out that in order

to maintained a uniform components, energy balance principle is required with a critical

calculation using sophisticated measurement device. Moreover [11] studied how to

minimized the cooling time which will facilitate the cooling efficiency and maintain a high

uniformity simply by improving the dimensions of the cooling channel whereas [12] tends to

developed a model that will quench cooling time by introducing easy calculations by

considering thermal conductivity as a benchmark for the analysis of the tool material, the

temperature of the cooling water part as well as the velocity while at the other hand [18]

developed 3D Finite Element (FE) numerical model for thermo-mechanical-based hot press

stamping by investigating the effect of two processing parameters of tool punch speed on the

final properties and temperature of hot stamped component, [19] critically analysed the effect

of elastic plastic phase transformation during HPF, [22] using FE to investigate non-quadratic

anisotropic function and nonlinear kinematic hardening in the plasticity transformation during

HPF was fully discussed. Furthermore [13] designed an optimal cooling system for HPF to

improve the efficiency of quenching during hot stamping of high-strength boron steel over

thermal evaluation and analysis, similarly [35] worked on hot press stamping optimization

while [36] Smart hot stamping processes. The importance and the usefulness of simulation

for forming and forging was detail described in [14-15] using Computer-aided

design/Computer-aided engineering CAD/CAE technology as well as Process-Chain

Simulation-System to study the material behaviour in real world analysis.

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2. HPF PROCESSES AND TECHNOLOGY

Conventional sheet metal forming process chain after forming, piercing or cutting is the

next stage in hot stamping. The process are discuss in this section

2.1 Laser Cutting process

It has been proved by [5] that laser cutting is the most famous used process for cutting

hot stamped parts due to the high strength of the material after hot stamping and the fact that

it does any failure on the cutting edge in contrast to traditional cutting process that requires

contact trimming and tool wear. Further advantage shows that the use of laser has no limits to

the shape of the parts to be trimmed or cut.

2.2 Hard cutting process

Because of the high tensile strength of the press-hardened parts leads to severe tool

wear in the blanking process whereby the quality of the dimension precision and the sheared

surface are influenced by certain development parameters, such as blanking angles, punch

speeds, punch-die clearances, the mechanical properties of the material as well as the tool

cutting edge geometries. Further analysis of the hard cutting process was investigated by [6]

founded that the high hardness of punch-die prompts the use of low wear cutting edge, hence,

at some point in time it become more and more sensitive to high load because of the micro-

fractures which is likely to occur at the cutting edge. Similarly at a high-toughness of the

punch induces small amount of reduction of wear resistance at the cutting edge. The cutting

process of hard press cutting part according to [7] argued that the optimum high-toughness is

compromise to advance the mechanical performance of tools

2.3 Warm Cutting Process

Warm cutting process is another alternative method deployed in hot stamped parts.

This process occurs at the cutting of parts during quenching at higher temperatures. The

benefits of this process enable quenching cutting force which will result in optimized cutting

edge over a short process sequence. In order to avoid a very hard for of steel transformation,

the cooling degree in the cutting areas must be quenched.

2.4 Forming Process

The blank should be transfer as fast as possible from the furnace of the hot press in

order to avoid part cooling before forming. Again this process must finish before

commencing the hard part of the steel crystal structure (martensite) transformation. This

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implies that a very fast object like the programmed robot arm is an ideal for a successful

forming process control. The closed tool is responsible for quenching the part immediately

after forming which will be cooled by water ducts in order to evacuate the hot heat from the

tool system.

2.4.1 Cold Forming

Cold forming begin at normal room temperature which is characterized by forming of

the work piece whereby there is no external heating require during this process. There are two

commonly known types of cold forming processes called upsetting and extrusion. The

upsetting process which described the manufacturing processes in greater details for instance

an open die as an example of upsetting whereby the work-piece dimensions lies between

parallel or flat effective surfaces. At the other hand extrusion is the act of pushing through

work-piece between two compactible tool parts which can be a rigid tools or active media

extrusion. The following figures illustrated the upsetting and extrusion.

Images of cold forming product [32]

Figure 1: Upsetting and partial upsetting Process [32]

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Figure 2: Classification flow chart of Extrusion Processes [32]

2.4.2 Warm Forming

At the very beginning of the blank temperature, the warm forming lies in between

cold forming and hot forming. The benefits of cold forming such as close tolerances, strain

hardening and high surface qualities tends to achieve higher true strain, when comparing

warm forming with hot forming, the yield stresses are found to be 3 times greater and the

desired true strain is lower. Below shows an image of warm forming

Images of warm forming product [32]

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Manufacturing Forming processes [32]

2.4.3 Hot Forming

The manufacturing through forming a work-piece using separating, heating and

joining refers to as forging whereas tensile forming, compressive forming processes, shear

forming processes, bend forming and rolling processes, the different mixtures of which

constitute various process alternatives or manufacturing sequences refers to as hot forming as

described below. This can be classified into open and close die forging. Experimented result

and simulated result of forging is given by [37].

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Images of open and close die forging

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2.5 Comparing Hot-stamping technology to conventional technology

Comparing the traditional cold formed parts, the new highly developed hot stamp parts

provides better stamping shape at a very high temperature, the conventional cold stamping

approach and micro-alloyed boron steel can be processed with non-isothermal hot sheet metal

forming process further known as direct hot-stamping. However, the modern technological

process conglomerates hot forming and simultaneously satiate hardening in a single operating

process. The following attributes advantages over the traditional technology for producing

parts

High material tensile strength

Reduction of weight/reduction of material sheet thickness (50%)

Hot stamping is compatible with boron-alloyed steel’s chemical composition,

Hot-stamping technology can be used to manufacture complex and sophisticated parts

such as house roof nails, car bumpers and pillars/beams reinforcement

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HPF Process Cycle [39]

Hot stamping process of Boron 22MnB5 diagram [39]

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3. CONCLUSION

Finite Analysis helps to overcome one of the greatest weaknesses in hot stamping

technology when the cooling temperature distribution is not insufficient which can lead to

poor part performance. Furthermore, the manufacturing process of thermo-mechanical or

steels boron treatment go through hot rolling of furnace and then to a low quench-able

temperature and lastly, produce a very good structural homogeneity whereby leading to a

good response of mechanical stress. The HPF technology is an alternative method for

reducing computational time for the realistic mechanical and thermal phenomena in the

production of parts through hot forming process. Hence, the development of simulation using

3D-software to be embedded into the hot stamping tends to reduces overall time wastage in

the production process and therefore facilitate parameters optimization.

StartInput blank

material(Blank Tem (Tb))

Det. Cycle time

Det. The tool surface tem (Ts)

Det. The diameter of the cooling channel

Cal. The velocity of the cooling water (Ve)

Cal. the number of cooling channel (n)

Split tool to increase cooling performance & machinability

Arrange the cooling channel at 2D section by triangular method

Connect the cooling channel

Cooling analysis & thermal analysis

Tb>Ts of the blank after cooling

processVe>=10,000

Tmax-Tmin>Tallowance

End

Yes

YesNo

No

Yes

No

GS 38235GS 37432GS 37433

EMM5702

Flow chart process of HPF

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