Improving the fracture resistance of forging medium manganese steel under static, dynamic and cyclic loading conditions by means of fine-dispersed, partitioning-stabilized retained austenite

利用细分散、配分稳定的残余奥氏体提高锻造中锰钢在静、动、循环载荷条件下的断裂抗力

• 批准号: 504849602
• 负责人: Professor Dr.-Ing. Ulrich Krupp
• 金额: --
• 依托单位: Institut für Eisenhüttenkunde (IEHK)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/504849602?language=en
• 关键词: Improving; fracture; resistance; forging; medium

Modern steels used for advanced forgings require a combination of high strength and fracture toughness/resistance under static, dynamic and cyclic load conditions. Moreover, they need to be easy machined, and an excellent hardenability is required to guarantee stable microstructures and mechanical properties throughout the whole forging. Up to now, there are no steel processing concepts available that effectively combine the above-mentioned mechanical properties at an acceptable production cost. The most advanced material to be used for forgings are currently medium-Mn steels with RA belonging to the 3rd generation of Advanced High Strength Steels. The RA of adequate stability and morphological homogeneity prevents the formation of cracks by ensuring local plasticity, while the martensite formed as a result of plastic deformation contributes to blocking the propagation of possible microcracks. The concept of the project is based on the use of Quenching and Partitioning (Q&P) heat treatment. The obtained structure of low-carbon martensite and carbon-enriched retained austenite, will ensure favorable mechanical properties. The role of retained austenite will be considered in a novel approach, which is completely different than in the case of Q&P sheet steels. In the proposed research, the new concept of medium-Mn forging steels shall be explored with respect to microstructure evolution during quenching and partitioning and defining the respective mechanical properties. The proposed research aims at the development of 3rd generation advanced high strength Q&P steels tailored for high fatigue strength and fatigue damage tolerance that are first time produced by an energy efficient forging process applying direct air-quenching from the hot-working heat. The following fundamental scientific and research issues will be resolved in the project: (i) ensuring morphological homogeneity of fine-dispersed retained austenite; (ii) determining the strengthening mechanism, and in particular the kinetics of strain-induced martensitic transformation under impact and cyclic loads conditions. No quantitative dependences between a type of loading and the transformation have been defined yet; (iii) characterization of the effect of retained austenite morphology and martensite matrix on the fracture mechanism and crack propagation behavior. Tests will be carried out including thermodynamic calculations, dilatometric tests, thermomechanical simulations using Gleeble simulator, comprehensive microstructure tests using research techniques of various resolutions including EBSD / EBSD 3D; APT; XRD and TEM and fatigue strength tests with the characteristics of the cracking mechanism. Multiscale modelling including a finite element method approach coupled with mean-field models will be used to simulate the process-microstructure relationship during the hot deformation of medium-Mn Q&P steels to be applied/tested under static, dynamic, and cyclic loading conditions.

用于先进锻件的现代钢材需要在静态、动态和循环负载条件下兼具高强度和断裂韧性/抗力。此外，它们需要易于加工，并且需要优异的淬透性以保证整个锻件具有稳定的微观结构和机械性能。到目前为止，还没有可用的钢材加工概念能够以可接受的生产成本有效地结合上述机械性能。目前用于锻件的最先进材料是中锰钢，RA属于第三代先进高强度钢。足够稳定性和形态均匀性的RA通过确保局部塑性来防止裂纹的形成，而塑性变形形成的马氏体有助于阻止可能的微裂纹的扩展。该项目的概念基于淬火和分配（Q&P）热处理的使用。所获得的低碳马氏体和富碳残余奥氏体的结构将确保良好的机械性能。残余奥氏体的作用将通过一种新方法来考虑，这与 Q&P 钢板的情况完全不同。在本研究中，应探索中锰锻钢的新概念，包括淬火和分配过程中的微观结构演变以及定义各自的机械性能。拟议的研究旨在开发第三代先进高强度 Q&P 钢，该钢具有高疲劳强度和疲劳损伤容限，首次通过采用热加工热直接空气淬火的节能锻造工艺生产。该项目将解决以下基础科研问题：（i）确保细分散残余奥氏体的形态均匀性； (ii) 确定强化机制，特别是冲击和循环载荷条件下应变诱导马氏体转变的动力学。尚未定义载荷类型和变换之间的定量依赖性； (iii)表征残余奥氏体形态和马氏体基体对断裂机制和裂纹扩展行为的影响。将进行的测试包括热力学计算、膨胀测试、使用Gleeble模拟器进行热机械模拟、使用EBSD/EBSD 3D等各种分辨率的研究技术进行全面的微观结构测试；易于; XRD和TEM及疲劳强度测试具有开裂机理的特征。包括有限元方法与平均场模型相结合的多尺度建模将用于模拟在静态、动态和循环加载条件下应用/测试的中锰 Q&P 钢热变形过程中的工艺-微观结构关系。