第三代汽车用钢中锰钢的连续退火生产新工艺的基础研究

项目名称： 第三代汽车用钢中锰钢的连续退火生产新工艺的基础研究

项目编号： No.U1460203

项目类型： 联合基金项目

立项/批准年度： 2015

项目学科： 矿业工程

项目作者： 罗海文

作者单位： 钢铁研究总院

项目金额： 200万元

中文摘要： 各国科学家经大量研究，多认为含5-10%Mn的中Mn奥氏体铁素体双相TRIP钢是最有前景的第三代先进汽车用钢之一。申请人团队前期工作已试制出性能出色的中Mn含量原型钢（抗拉强度在0.9-1.5GPa，延伸率在30-45%），但该钢的亚临界退火时间较长，不能通过企业广泛采用的连续退火生产线生产。本项目通过研究中Mn钢的起始组织状态对退火过程奥氏体逆相变影响的内在科学规律，来寻找在短时退火时加快奥氏体形成速度的途径；拟在中Mn钢退火前通过特定的预处理工艺，来优化奥氏体逆相变前的组织准备，使得短时连续退火后得到的奥氏体数量明显增多，以保证优秀的拉伸性能。本项目的研究内容包括利用各种先进实验技术深入细致表征中Mn钢退火过程中的组织演变，以及退火过程中奥氏体逆相变动力学、溶质元素配分和残余奥氏体稳定性、退火组织和拉伸性能之间的关系等。预研工作的初步结果也证明了项目的研究思路是可行的。

中文关键词： 亚临界退火；；奥氏体逆相变；；残余奥氏体；连续退火；汽车用钢

英文摘要： The 3rd Generation AHSS for autos, firstly presented as a concept in USA in 1996, has received increasing attention globally in the circle of steel research scientists. Most of them now agree that austenite-plus-ferrite dual phase TRIP steels that usually contain 5-10%Mn are the most promising choice for the 3rd Generation AHSS. Our previous works have led to prototype steel with an excellent combination of the tensile strength (1-1.5GP) and elongation (30-45%), which results from the presence of 20-40% retained austenite in the steel. The key process to achieve such outstanding property is to heat the steel with the original martensitic microstructure to the intercritical region, in which part of the martensite will be reversely transformed to the austenite. However, this generally requires quite a long intercritical annealing so that batch annealing, instead of the continuous annealing, has to be employed in the present industrial production of this steel, although the latter is a more modern production process for higher efficiency and better quality control..This proposal is targeting the optimization of the microstructural preparation for the maximum formation of austenite during the intercritical annealing (IA) so that more austenite can be retained after a short continuous annealing in industry. Various microstructures are produced by the new designed heating paths or pre-heat treatments before the IA and then their influences on the reverse austenitization kinetics were studied both experimentally and theoretically. Microstructural evolutions during both heating and the intercritical annealing are followed and characterized by the modern technique, such as SEM, HR-TEM and 3DAP. Based on the.results, we may expect to propose a novel process of pre-treatment of the medium Mn steel before the reverse transformation so that the fraction of retained after IA can be maximized. Moreover, such a process can be easily applied in the steel industry and combined with the continuous annealing process line.

英文关键词： intercritical annealing ;reverse austenitization ;retained austenite;continuous annealing ; steel sheets for automotive