FE-Simulation of the Heat Transfer by Defined Cooling Conditions during the Hot Stamping Process

2011 ◽  
Vol 473 ◽  
pp. 699-706 ◽  
Author(s):  
Thomas Svec ◽  
Martin Grüner ◽  
Marion Merklein
Keyword(s):  
Heat Transfer ◽  
Mechanical Properties ◽  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Process Data ◽  
Cold Forming ◽  
Stamping Process ◽  
Characteristic Values ◽  
Tempering Process

Increasing demands regarding security aspects and light weight construction lead to the application of advanced high strength steels (AHSS) and ultra high strength steels (UHSS) in the automotive sector. Due to high process forces and the reduced formability of these steel grades within cold forming new manufacturing technologies like the hot stamping process are required. Furthermore, crash-performance plays an important role in the automotive industry. Therefore functional optimized components are necessary. Hence, actual research work within the community is focused on manufacturing components with local adjusted mechanical properties. One of the strategies to realize the contradictorily requirements regarding energy absorption and structural integrity is the Tailored tempering process where the cooling rates are adjusted by controlled heating or cooling of different tool zones within the hot stamping process. Thereby knowledge concerning the influence of the different heated tool parts on the heat transfer and the resulting mechanical properties is necessary. Furthermore, the applicability and the accuracy of the calculation approaches used for characteristic values like the heat transfer coefficient in the FE-based simulation have to be analyzed and evaluated. Due to this experiments with a tool which exhibits a heated and a cooled zone were performed according to the Tailored tempering process. During the experiments contact pressures and tool temperatures in the heated tool part were varied and analyzed regarding the influence on the heat transfer. Furthermore, the heat transfer coefficients were calculated and verified by a numerical model built according to the experimental setup and the accuracy of the model was evaluated by the comparison of characteristic values calculated from the experimental and numerical process data.

Characterization of Heat Transfer Coefficients of Tool Materials and Tool Coatings for Hot Stamping of Boron-Manganese Steels

2010 ◽  
Vol 438 ◽  
pp. 81-88 ◽  
Author(s):  
Michael Wieland ◽  
Marion Merklein
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Tool Steels ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Coated Tool

One characteristic of hot stamping of ultra high strength steels is the high wear rate of the used tools which leads to shorter tool life. Coatings improving wear resistance can increase the lifetime of the used tools but process relevant data such as the heat transfer capability of coated tool steels are missing. Within this paper the heat transfer capabilities of coated tool steels for the hot stamping processes are determined. Therefore different coating systems based on AlCrN are applied on the tool steels and the pressure dependent heat transfer coefficient is determined using process relevant conditions. As semi-finished blank the hot stamping steel 22MnB5 with an aluminum-silicon pre-coating is used. With respect to a finite element analysis of the forming operation of the hot stamping process the heat transfer coefficient represents an important input data for the process layout.

Structure Analysis and Quality Prediction of DP Steel Engine Hood in the Process of Hot Stamping

2013 ◽  
Vol 791-793 ◽  
pp. 558-561
Author(s):  
Zhi Ping Zhang ◽  
Han Wu Liu ◽  
Tian Xiang Chen ◽  
Zhang Yi Yu
Keyword(s):  
Hot Stamping ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Limit ◽  
Dp Steel ◽  
Performance Requirements ◽  
Stamping Process ◽  
Work Hardening Rate ◽  
Initial Work ◽  
Parts Manufacturing

Due to its good formability characteristics, such as high strength, high initial work hardening rate, as well as continuous yielding, thin-walled DP steel possesses great advantages of weight loss and security, and has been used to replace ordinary steel for automotive parts manufacturing by a lot of automotive industry. But along with the improvement of the performance of the strength, the high strength steels formability is worsened dramatically, and failure and fracture often occurs in its cold stamping process. So, hot stamping technology must be adopted to make the formability available. In the paper, it took the hot stamping process of DP steel engine hood for example and took DP800 as object of research. The forming limit, variation of major strain, minor strain and thickness, as well as the potential equality defects were analyzed by using eta/DYNAFORM software. The research results show that duplex steel plate can meet the performance requirements of car engine dumping plank forming, which offers theory basis for the production of similar parts.

Effect of Dies Temperature on Mechanical Properties of Hot Stamping Square-Cup Part for Ultra High Strength Steel

2010 ◽  
Vol 129-131 ◽  
pp. 390-394
Author(s):  
Cheng Xi Lei ◽  
Zhong Wen Xing ◽  
Hong Ya Fu
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Hot Stamping ◽  
High Strength ◽  
Hot Forming ◽  
Forming Process ◽  
Stamping Process ◽  
Ultra High Strength Steel ◽  
Mechanical Properties Testing ◽  
Simulation Results

The numerical simulation of hot-stamping process was carried out for UHSS square-cup parts, and the influence of dies temperature on the hot-stamping process was anlysised. Besides, through the microstructure analysis and mechanical properties testing of the formed parts, effects of dies temperature on microstructures and mechanical properties of hot-stamping square-cup parts were obtained. The experiment and simulation results showed that the mechanical properties of the UHSS are strongly dependent on the temperature, so the dies temperature is one of the most important parameters that have to be taken into account in designing the hot-forming dies and the hot-forming process.

Effect of Heating Parameters on the Part’s Properties in Hot Stamping Process

2012 ◽  
Vol 557-559 ◽  
pp. 2417-2422
Author(s):  
Rui Ge ◽  
An Long ◽  
Yin Chen
Keyword(s):  
Hot Stamping ◽  
High Strength Steels ◽  
Dimensional Accuracy ◽  
High Strength ◽  
Hardness Measurement ◽  
Material Behavior ◽  
Hot Forming ◽  
Accuracy Test ◽  
Stamping Process ◽  
Proper Design

In the automotive industry, the hot forming of high strength steels offers the possibility to obtain significant reduction of weight without affecting the structural performances of final products. Compared with conventional sheet metal forming, the proper design of hot stamping process chain requires the deep knowledge of both interface phenomena and material behavior at high temperatures in order to obtain the desired properties of final products in terms of microstructure and strength characteristics. The work presented in this paper aims at accurately evaluate the effect of heating parameters on the properties of final sheet components produced in hot forming operations. Different from that in the lab, all the samples and parts used for the experimental test were produced in the production line, which can objectively show the manufacturing properties and microstructure character of products in mass. Microstructure evaluation, hardness measurement and dimensional accuracy test after hot stamping were performed and considered. The best heating parameters for the researched hot stamping B-Pillar’s production were obtained through the above research.

scholarly journals Evolution of Phase Transition and Mechanical Properties of Ultra-High Strength Hot-Stamped Steel During Quenching Process

Metals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 138 ◽  
Author(s):  
Shuang Liu ◽  
Mujun Long ◽  
Songyuan Ai ◽  
Yan Zhao ◽  
Dengfu Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Transition ◽  
Cooling Rate ◽  
Hot Stamping ◽  
Coupled Model ◽  
High Strength ◽  
Austenitizing Temperature ◽  
Stamping Process ◽  
Quenching Process ◽  
Hot Stamping Steel

Hot stamping process is widely used in the manufacture of the high strength automotive steel, mainly including the stamping and quenching process of the hot-formed steel. In the hot stamping process, the steel is heated above the critical austenitizing temperature, and then it is rapidly stamped in the mold and the quenching phase transition occurs at the same time. The quenching operation in the hot stamping process has a significant influence on the phase transition and mechanical properties of the hot-stamping steel. A proper quenching technique is quite important to control the microstructure and properties of an ultra-high strength hot-stamping steel. In this paper, considering the factors of the austenitizing temperature, the austenitizing time and the cooling rate, a coupled model on the thermal homogenization and phase transition from austenite to martensite in quenching process was established for production of ultra-high strength hot-stamping steel. The temperature variation, the austenite decomposition and martensite formation during quenching process was simulated. At the same time, the microstructure and the properties of the ultra-high strength hot-stamping steel after quenching at different austenitizing temperature were experimental studied. The results show that under the conditions of low cooling rate, the final quenching microstructure of the ultra-high strength hot-stamping steel includes martensite, residual austenite, bainite and ferrite. With the increase of the cooling rate, bainite and ferrite gradually disappear. While austenitizing at 930 °C, the tensile strength, yield strength, elongation and strength-ductility product of the hot-stamping steel are 1770.1 MPa, 1128.2 MPa, 6.72% and 11.9 GPa%, respectively.

Sign in / Sign up

Export Citation Format

Share Document