碳的梯度扩散分配对硅锰钢显微组织与力学性能的影响

Effects of gradient diffusion and partitioning of carbon in SiMn steel on its microsctructure and mechanical properties

利用碳在马氏体与奥氏体之间的扩散分配实现钢的组织结构与力学性能调控,是近年来钢铁材料领域的重要研究方向。基于碳的完全均匀分配,Speer提出了淬火-分配(Q-P)热处理工艺,本文总结了近年Q-P工艺碳分配机理研究和工艺实践。同时,根据碳在奥氏体和马氏体中的扩散分配过程分析,提出了碳的梯度扩散分配与控制理念,并开发出了分级-淬火-分配(S-Q-P)工艺,希望能获得低碳马氏体、残留奥氏体、高碳马氏体相间分布的组织。对35SiMn钢分别进行淬火-回火(Q-T)、Q-P及S-Q-P工艺试验,并测量力学性能及观察显微组织。结果表明,S-Q-P工艺处理后钢的强塑性积达到31.2 GPa%(1240 MPa×25%),比传统Q-T和现行Q-P工艺分别提高67%和32%,其显微组织也接近于工艺设计的理想组织,证明了利用碳的梯度扩散分配可以实现对钢的组织与性能的调控。

Microstructure and mechanical properties of steels can be controlled by manipulating the partitioning process of carbon from martensite to austenite , and it becomes an important research direction in the field of iron and steel materials in recent years .Based on the concept of full carbon partitioning , Speer developed a novel process for the heat treatment of steels , that is the quenching and partitioning （Q-P） process.According to analysis on the diffusion and distribution process of carbon in austenite and martensite , stepping-quenching and partitioning （ S-Q-P） process was developed in order to get a better combination of low-carbon martensite , retained austenite and high-carbon martensite , and to enhance the mechanical properties of steels .Mechanical properties tests and microstructure observation have been done to 35SiMn steel treated by Q-T, Q-P and S-Q-P process.The results show that compared to Q-T and Q-P process, the product of strength and ductility of 35SiMn steel is increased by 67% and 32% respectively after S-Q-P process, reaching 31.2 GPa%（1240 MPa ＆#215;25%）, and microstructure of 35SiMn steel is also close to the designed ideal .All this prove that the microstructure and properties of steels can be controlled by carbon gradient diffusion and partitioning .