Papers by Keyword: Hot Stamping

Abstract: One of the main targets in automotive industry is to reduce the weight of vehicle as well as increase the safety. To accomplish this goal, press-hardening steel and hot stamping parts have been used in car body. However, the possibility of hydrogen-induced delayed fracture (HDF) of hot stamping parts exits, which will decrease the car’s passive safety. A solution has been presented to reduce the sensitivity of HDF and improve hydrogen-induced delayed fracture resistance (HDFR) by Niobium micro-alloying technology. Traditional press-hardening steel 22MnB5 and new steel 22MnBNb2, 22MnBNb5 and 22MnBNb7 were studied, and it is shown that the appropriate addition of Nb is beneficial to the improvement of the delayed fracture resistance of the hot stamping steel, which indicates that Niobium micro-alloying technology is an effective solution to the HDF in hot stamping steels.

Abstract: In this study, based on the metallo-thermo-mechanical coupling theory, a FEM model of hot stamping including forming and quenching is built to investigate the cooling behavior and the microstructure evolution, and to predict the final mechanical properties of hot-stamped components. The results show that, after about 16s, the temperature of the entire component is lower than Mf of 22MnB5 boron steel and with a continuous uniform distribution. Most of austenite in component has transformed into martensite. To satisfy the required mechanical properties, the sufficient holding time of quenching in die is essential and it plays an important role in ensuring the required hardness. The predicted Rockwell hardness of component after hot stamping process is almost 512HV, which shows a good agreement with the experimental results. It implies that the metallo-thermo-mechanical numerical model established in this study is reasonable and reliable, which can provide a theoretical guidance for optimizing the hot stamping procedure.

Abstract: The final mechanical properties of hot stamped components are affected by many process and material parameters due to the multidisciplinary nature of this thermal-mechanical-metallurgical process. The phase transformation, which depends on the temperature field and history, determines the final microstructure and consequently the final mechanical properties. Tailored hot stamping parts – where the cooling rates are locally chosen to achieve structures with graded properties – has been increasingly adopted in the automotive industry. Robustness of the final part properties is more critical than in the conventional hot stamping. In this paper, the robustness of a tailored hot stamping set-up is investigated. The results show that tailored hot stamping is very sensitive to tooling temperature, followed by latent heat radiation emissivity, and convection film coefficient. Traditional hot stamping has higher robustness compared to tailored hot stamping, with respect to the stamped component’s final material properties (i.e. phase fraction, hardness).

Abstract: Ultra High Strength Steel (UHSS) hot stamping technology is a special process which can enhance the steel tensile strength to 1500MPa. Appling this technology in producing vehicle structure parts can make car lighter and safer. In China there are more and more automobile enterprises adopt this technology. To master and extend the skill, China Academy of Machinery Science & Technology (CAM) have done systematic research, such as the strengthen mechanism of the steel, hot stamping key devices designing, forming and quenching integrated mould designing, stamping process parameters optimization, etc.. By now, CAM has mastered the mass production technology of vehicle parts, which can guarantee its shape and tensile strength, and produced such typical parts as door-beam, B pillar, etc.. The paper is an introduction of the research work and achievement about UHSS hot stamping developed by CAM.

Abstract: Combined numerical simulations and experimentally measured data, the relationship between the initial temperature of the workpiece was described, the stamping speed, and the required forming force. Air cooling was included to determine the temperature of the part within the mold, and the required stamping force was optimized by studying the impact of the cooling time on the temperature of the part. The optimized model was verified and validated by comparing simulated data for an anti-collision beam with the experimental results of the hot-forming process. The results showed that the model provides a useful description of the hot-forming process; however, an empirical factor of 0.95 was required to achieve agreement between the simulated and experimentally measured data.

Abstract: The development process of hot stamping front pillar reinforcement is introduced from hot stamping material selection, hot stamping parts simulation analysis and hot stamping die processing and debugging process of the problems.This paper discussed the development and application of existing process problems in hot stamping parts. There are some suggestions for application of hot stamping parts in the end.

Abstract: Press hardening steel is the best solution for application of extremely high strength steel in automotive structures in order to reduce the weight of body-in-white. Effect of austenitizing temperature on the grain coarsening of a press hardening steel has been investigated by using dilatometer at first. The mechanical properties of press-hardened steel austenitized at temperature between 850 to 950oC by using a pilot hot stamping line have been investigated. The strength, especially the ultimate tensile strength, was improved by the grain refinement with lower austenitization temperature.

Abstract: Due to the complexity of hot stamping mechanism, including the coupling of material formability, thermal interaction and metallurgical microstructure, it makes the process design more difficult even with the aid of the finite element analysis. In the present study, the experimental platforms were developed to measure and derive the friction and heat transfer coefficients, respectively. The experiments at various elevated temperatures and contact pressures were conducted and the friction coefficients and heat transfer coefficients were obtained. A finite element model was also established with the experimental data and the material properties of the boron steel calculated from the JMatPro software. The finite element simulations for the hot stamping forming of an automotive door beam, including transportation analysis, hot forming analysis and die quenching analysis were then performed to examine the forming properties of the door beam. The validation of the finite element results by the production part confirms the efficiency and accuracy of the developed experimental platforms and the finite element analysis for the process design of hot stamping.

Abstract: Hot stamping is today the most efficient method to lighten automotive parts by keeping or even increasing vehicle security. The B-pillar of this report is from a well-known SUV’s style 2013 from a big JV OEM in Shanghai. 3 steps job were completed: die designing, blank generation and optimization, hot stamping simulation. Customer’s feedback showed a good correlation between FE analysis and trial out results.

Abstract: As to the conventional hot stamping furnance’s shortcomings of long heating time, easy oxidized, high energy consumption, the application of induction heating for hot stamping were studied. By using COMSOL Multiphysics software, we calculated the electromagnetic induction field and temperature field by use of the direct coupling (Direct Coupling Method) in the heating process of hot forming sheet and studied the influence of inductor device parameters (such as induction length, distance between inductor and sheet etc.) and various process parameters (such as the power supply frequency, current density, sheet thickness etc.) on heating rate and temperature distribution. That will have a good guidance on the application of induction heating to hot stamping field.