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Determination of forming limits of the martensitic chromium steels in hot forming processes

马氏体铬钢热成形过程成形极限的测定

基本信息

批准号：
385989694
负责人：
Professor Dr.-Ing. Bernd-Arno Behrens
金额：
--
依托单位：
Institut für Umformtechnik und Umformmaschinen (IFUM)
依托单位国家：
德国
项目类别：
Research Grants (Transfer Project)
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/385989694?language=en
关键词：
Determination forming limits martensitic chromium

项目摘要

The aim of the planned research project is numerical simulation of the hot forming of a martensitic chromium steel taking into account the forming limit at elevated temperatures, the resulting microstructure and their effects on the product properties. In the sheet metal forming, hot forming of martensitic chromium steels has various advantages over hot stamping of manganese-boron steels, such as a lower critical cooling rate, a higher elongation at break (fracture strain) along with higher strengths and a better corrosion resistance of the material. During the hot forming processes, complex interactions between the workpiece temperature, the tool temperature and the process time exist which significantly influence the microstructure, the final component properties and the residual stresses as well as the component distortion thus numerical modelling and prediction of the process limits is of particular importance for this process. In particular, the higher material costs of martensitic chromium steels compared to the manganese-boron steels make a simulative process design vital in order to save resources, tests and thus reduce the costs. The planned development of a material model for the numerical simulation of hot forming of martensitic chromium steels will be carried out based on a material model which was developed in the DFG funded preceding research projects for hot stamping of the manganese-boron steel (22MnB5). A comprehensive material characterization is required in order to adapt the material model to the martensitic chromium steels and their microstructural behavior.For the determination of the forming limits of sheet metals, the use of forming limit diagrams is state of the art. As the flow behavior and the deformability of a material are dependent on the temperature, conventional forming limit diagrams obtained at room temperature cannot be used for hot forming processes. In order to predict the deformability of martensitic chromium steels as well as the influence of the forming temperature on the deformability in the hot forming process, the further objective of this project lies in the determination of temperature-dependent forming limit diagrams and their implementation in the numerical simulation. This allows a realistic evaluation of the forming limit and the resulting component properties after cooling. The numerical model is validated with the help of hot formed demonstrator components.

计划中的研究项目的目的是对马氏体铬钢的热成形进行数值模拟，考虑高温下的成形极限、由此产生的组织及其对产品性能的影响。在板料成形中，马氏体钢的热成形比锰-硼钢的热冲压具有更低的临界冷却速度、更高的断裂伸长率(断裂应变)、更高的强度和更好的耐腐蚀性。在热成形过程中，工件温度、刀具温度和加工时间之间存在着复杂的相互作用，这些因素对成形过程中的组织、最终零件性能、残余应力和零件变形都有很大的影响，因此，工艺极限的数值模拟和预测对该工艺尤为重要。特别是，马氏体型铬钢的材料成本高于锰硼钢，这使得模拟工艺设计变得至关重要，以节省资源和试验，从而降低成本。马氏体铬钢热成形数值模拟材料模型的开发计划将基于DFG资助的先前的锰-硼钢(22MnB5)热冲压研究项目中开发的材料模型。为了使材料模型适应马氏体型铬钢及其微观组织行为，需要对材料进行全面的表征。在确定板材的成形极限时，成形极限图的使用是最先进的。由于材料的流动行为和变形能力依赖于温度，因此在室温下获得的常规成形极限图不能用于热成形工艺。为了预测马氏体铬钢在热成形过程中的变形性以及成形温度对其变形性的影响，本课题的进一步目标在于确定随温度变化的成形极限图及其在数值模拟中的实现。这允许对成形极限和冷却后产生的零部件特性进行真实的评估。利用热成形演示件对数值模型进行了验证。