Modelling kinetics of phase transformation for the indirect hot stamping process to focus on car body parts with tailored properties

Hippchen, Paul; Lipp, Arnulf; Grass, Hannes; Craighero, Philipp; Fleischer, Michael; Merklein, Marion

doi:10.1016/j.jmatprotec.2015.01.003

Cited by 35 publications

(11 citation statements)

References 12 publications

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“…The favoured sheet metal material 22MnB5 reaches a tensile strength between 550 MPa in delivery condition and 1500 MPa after forming depending on the prior heat treatment. The technological process flow is comparable with the indirect press hardening process [22,23]. First the sheet is pre-formed in cold state, then locally heated up above austenitization temperature according to the component requirements and afterwards directly quenched while leaving the rollers.…”

Section: Roll Forming Of Press Hardening Steels With Integrated Heat mentioning

confidence: 99%

Manufacturing of Long Products Made of Innovative Lightweight Materials

Richter

Müller

Kunke

et al. 2015

Acta Metall. Sin. (Engl. Lett.)

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The processing of innovative lightweight materials to sheet metal components and assemblies with globally or locally defined properties is the object of this work. It takes a load-dependent design of components and assemblies, for example, based on the composition of different construction materials or a targeted setting of component areas with specified characteristics to fully exploit the lightweight potential when substituting conventionally used materials. Different process chains for the manufacturing of roll-formed long products made of magnesium alloys and high-strength steels with locally defined properties will be presented in this paper. Depending on the kind of material to be formed and the desired product characteristics, different temperature managements are needed for capable processes. Due to limited formability at room temperature, magnesium alloys require a heating of the forming zones above 200-225°C throughout the bending process in order to activate additional gliding planes and to avoid any failures in the radii. The realization of local hardening effects requires at least one process-integrated heat treatment when roll forming manganese-boron steels. For both processes, it is imperative to realize a heating and cooling down or quenching appropriate for the manufacturing of long products with the required quality. Additionally, proper line speeds that allow a continuously operated economical production have to be considered. Research results including design, FEA, realization and experimentation of the mentioned process chains and strategies will be described in detail.

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Section: Roll Forming Of Press Hardening Steels With Integrated Heat mentioning

confidence: 99%

Manufacturing of Long Products Made of Innovative Lightweight Materials

Richter

Müller

Kunke

et al. 2015

Acta Metall. Sin. (Engl. Lett.)

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“…It can be divided into direct hot stamping and indirect hot stamping. The indirect hot stamping is mainly used to form sheet with complex shapes and the sheet needed to be pre-formed before heating and quenching [14][15][16]. Seo et al investigated the formability of direct and indirect hot stamping processes under different blank holding forces of ultra-high strength steel [17].…”

Section: Introductionmentioning

confidence: 99%

Research on Lightweight Design and Indirect Hot Stamping Process of the New Ultra-High Strength Steel Seat Bracket

Tang

Jia

et al. 2019

Metals

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Aiming at the need for lightweight requirements of the electric bus components, combined with the performance advantages of the hot stamping ultra-high strength steel, a new type of seat bracket structure is proposed. The new structure was analyzed by finite element method and the variable density topology optimization results. Subsequently, the new seat bracket was manufactured by the indirect hot stamping process. The results showed that the new type of seat bracket can reduce the weight by 17.04% after topology optimization, which achieved the goal of lightweight design of the structure. After indirect hot stamping, the bottom of the seat bracket microstructures were mainly martensite and the ultimate tensile strength was about 1560 MPa, the microhardness was equally distributed at about 513.5 HV. Finally, according to the stiffness check test, the seat bracket satisfied the user requirements.

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“…In addition, the transformation kinetics and microstructural behaviour of some different steel grades devoted to hot stamping is investigated and analyzed [4][5]. And a variety of finite element models to simulate the microstructure transformation in hot stamping process have been developed [6][7][8]. In previous studies, most scholars obtain typical photographs of ultra-high-strength steel in hot stamping process by using optical microscopes, scanning electron microscopes or transmission electron microscopes and analyze the morphology and distribution of metallurgical structures (such as bainite and martensite) under different heat treatment conditions in hot stamping.…”

Section: Introductionmentioning

confidence: 99%

In situ observation on microstructure evolution of 22MnB5 in hot stamping process

Kong

Peng

2019

Metall. Res. Technol.

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High temperature confocal laser scanning microscopy (CLSM) was used to investigate the microstructure evolution of high-strength boron steel 22MnB5 during hot stamping. The experimental results show that it is complete austenitized at temperatures about 810 °C during the heating process. Most of the initial austenite grain size is small and locally coarse. At 920 °C to 1000 °C, the phenomenon of B remelted and solidified was observed which played a very good pinning role at the austenite grain boundary, preventing coarsening of austenite grains. The segregation of B and the addition of Mn result in a significant reduction in both the minimum boron reverse melt content and the final solidification temperature. In the continuous cooling stage, martensitic transformation occurs at the cooling rate of 60 °C/s, and the martensite start point is 400 °C and martensite finish point is 280 °C. A large number of bursts are concentrated from 380 °C to 330 °C. There are two main forms of martensitic transformation: first, martensite begins to appear at the coarse austenite grain boundary, and grows transgranularly. Second, the new martensite laths starts from the previously formed laths and grows at a certain angle into the austenite grains. The main factor in the increase of martensite in continuous cooling is the formation of variable temperature martensite rather than the growth of martensite laths. At the cooling rate of 20 °C/s, the bainite and ferrite transformation appeared and the conversion temperature of bainite was about 600 °C. The cooling speed has a great influence on the performance of the 22MnB5 hot stamping component. The room temperature microhardness at cooling rates of 5 °C/s, 20 °C/s, and 60 °C/s was 194 HV, 243 HV, and 430 HV, respectively. Therefore, ensuring sufficient cooling rate is a key condition for obtaining ultra-high strength hot stamping components.

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Modelling kinetics of phase transformation for the indirect hot stamping process to focus on car body parts with tailored properties

Cited by 35 publications

References 12 publications

Manufacturing of Long Products Made of Innovative Lightweight Materials

Manufacturing of Long Products Made of Innovative Lightweight Materials

Research on Lightweight Design and Indirect Hot Stamping Process of the New Ultra-High Strength Steel Seat Bracket

In situ observation on microstructure evolution of 22MnB5 in hot stamping process

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