Mechanism-based modelling of tempering phenomena in steels

基于机理的钢回火现象建模

• 批准号: 259019485
• 负责人: Professor Dr.-Ing. Christoph Broeckmann
• 金额: --
• 依托单位: Institut für Produktionstechnik (WBK)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/259019485?language=en
• 关键词: Mechanism; based; modelling; tempering; phenomena

To improve the operational capability of hardened components the process of martensitic hardening is classically supplemented by a subsequent tempering process. After the martensitic hardening, the material in its as-quenched condition has an extreme non-equilibrium state and lacks of toughness. In addition, destructive residual stresses can be generated. During tempering the material progresses towards its equilibrium by diffusion of carbon, carbide precipitation, dissolution of retained austenite as well as residual stress relaxations. As a consequence of these mechanisms, the material receives ductility required for many applications and the life time of the heat treated component will be increased. Although modelling and simulation of heat treatment is well-established in many fields of application, tempering is rarely considered despite its particular importance regarding the resulting performance characteristics of hardened steel parts. The objective of this project is to investigate the tempering and the preceding martensitic hardening process as well as their interactions and hence to develop a physically based model describing the occurring mechanisms. The characteristics of interests in modelling are the resulting microstructure, hardness, mechanical properties and residual stresses as well as the distortion of the parts. The different processes are to be investigated at different steels and heat treatments, whereat certain processes predominate in each case. The formation of carbides and mechanical properties are focused by the IWM of the RWTH Aachen based on the through hardening of the high-alloyed steel X40CrMoV5-1. Interactions between the formation of martensite, the stabilization of austenite and tempering processes which already occur during quenching (autotempering) as well as their effects on the subsequent tempering are analysed using the through heat treated bearing steel 100Cr6 at the IWT Bremen. The inhomogeneous microstructure in consequence of short time austenitization and short time tempering, as occurring in inductive surface hardening, are investigated using the tempering steel 42CrMo4 at the IAM-WK of the KIT. Finally, based on these collaborations a modelling is enabled containing all single effects during tempering.

为了提高硬化部件的操作能力，马氏体硬化过程通常由随后的回火过程补充。马氏体硬化后，材料在其淬火状态下具有极端的非平衡状态，并且缺乏韧性。此外，还可能产生破坏性的残余应力。在回火过程中，材料通过碳的扩散、碳化物沉淀、残余奥氏体的溶解以及残余应力松弛而向其平衡发展。由于这些机制，材料获得了许多应用所需的延展性，并且热处理部件的寿命将增加。虽然热处理的建模和模拟在许多应用领域中已经建立，但很少考虑回火，尽管它对淬火钢零件的性能特性特别重要。该项目的目标是研究回火和之前的马氏体硬化过程以及它们的相互作用，从而开发一个描述发生机制的物理模型。在建模中感兴趣的特点是所产生的显微组织，硬度，机械性能和残余应力以及零件的变形。不同的过程将在不同的钢和热处理条件下进行研究，其中某些过程在每种情况下占主导地位。通过对亚琛钢厂X40 CrMoV 5 -1高合金钢进行全淬试验，重点研究了碳化物的形成和力学性能。在IWT不莱梅，使用经过热处理的100 Cr 6轴承钢，分析了马氏体的形成、奥氏体的稳定化和淬火（自回火）过程中已经发生的回火过程之间的相互作用以及它们对随后回火的影响。采用42 CrMo 4钢在KIT的IAM-WK试验机上进行回火试验，研究了感应表面淬火中短时淬火和短时回火引起的组织不均匀性。最后，基于这些协作，能够在回火期间包含所有单一效果的建模。