超洁净与均质化高铁轴承钢连铸坯生产应用基础研究

Considering the lack of the research on the quantitative relationship between the as-cast for bearings employed in high-speed rails in China and the bottleneck problem about the unsatisfying cleanness and homogenization controlling of the strands, a series of innovation researches including the quantitative relationship between the inclusion and the carbide in bearing steel strands and the bearings for high-speed rails, the formation, evolution and removal mechanisms of the inclusion during the refining process, the evolution of the solidification structure of the bearing steel strands and the precipitation mechanism and the evolution rule of the carbide during the continuous casting process are carried out to establish the quantitative influences of the characteristics such as the species, the number and the distribution of the inclusion and the carbide on the fatigue property of bearings and the rating standard of the inclusion and the carbide aiming at the harmless using of the base strands for high-speed rail bearings. Meanwhile, the formation, evolution and removal mechanisms of the inclusion during the refining process of the ultra cleanness bearing steel are revealed. Accordingly, the present work develop the new refining process technologies consisting of the new slag system for LF refining, the new blowing model for RH refining, and the new argon blowing technology in induction heating channels in the tundish, etc. Moreover, the precipitation and the evolution mechanisms of the carbide of the bearing steel in different zones of the continuous casting are clearly illuminated, and the new hierarchically targeted and collaboratively controlling technology of secondary cooling, electromagnetic stirring, and heavy reduction of strand solidification final, aiming at the precipitation of the carbide with big sizes in the inter-dendritic zone of columnar dendrites, at the solidified front near the solidification end and in shrinkage cavity channels, is presented. Consequently, the present research can settle the theoretical and the technological foundations of highly efficient and stable production of continuously cast ultra cleanness and homogenization strands of bearings steel for high-speed rails in China and ultimately implement its industrial application.

针对我国高铁轴承铸坯母材与使用性能间定量化研究空白、洁净度与均质化控制不理想的瓶颈问题，通过创新研究轴承钢夹杂物与碳化物对高铁轴承使用性能的定量关系，冶炼过程夹杂物形成、演变与去除机理，连铸轴承钢凝固组织生长、碳化物析出机制及演变规律，建立轴承钢夹杂物与碳化物的种类、数量、尺寸、分布等对高铁轴承疲劳性能影响的定量关系以及高铁轴承铸坯母材无害化使用的夹杂物与碳化物评级标准，揭示超洁净轴承钢冶炼过程夹杂物生成、演变与去除机理，开发形成涵盖LF精炼新渣系、RH吹炼新模式与中间包感应加热通道吹氩新技术等超洁净轴承钢冶炼新工艺技术，阐明轴承钢连铸过程不同区域碳化物析出与演变规律，开发形成铸坯柱状晶间、凝固末端前沿与缩孔通道大尺寸碳化物析出的二冷、电磁搅拌、重压下靶向分级协同控制新技术，奠定我国高铁轴承钢高洁净与均质化高效稳定连铸坯生产的理论与技术基础，并实施工业化应用。

本项目围绕高铁轴承钢铸坯母材生产过程的钢液超洁净化（夹杂物控制）与铸母材均质化（碳化物析出控制）控制的需要，针对当前夹杂物细小化与均匀化、大尺寸夹杂物控制稳定性差而直接制约高铁轴承钢超洁净化的实际，重点开展高铁轴承钢生产过程中夹杂物的形成与演变及去除机理、高效率去夹杂物精炼工艺和中间包冶金新技术研究，同时聚焦制约高品质轴承钢均质化生产的铸坯凝固过程宏微观偏析行为机制、晶间碳化物析出与生长机制、凝固缩孔演变规律及其控制技术开展研究工作。项目揭示并掌握了高品质轴承钢冶炼过程不同反应器内夹杂物生成、演变与去除机理，发现转炉钢中的夹杂物也是夹杂物的重要来源，固态夹杂物相比液态夹杂物更容易去除，轴承钢中的大型夹杂物与引流砂有明显关联，钢包挂渣对钢液的洁净度有重要的影响，开发形成了涵盖LF精炼新渣系、冶炼钢包周转制度、RH吹炼新模式及弧形通道感应加热中间包等新技术在内的超洁净化轴承钢冶炼新工艺；项目阐明了轴承钢凝固组织与宏观偏析形成机理、演变规律以及碳化物分布特征，揭示了工艺参数对铸坯枝晶结构的影响规律，发现轴承钢铸坯V型偏析区域较宽且存在孤立孔偏析，塌落等轴晶间通道内的钢液流动是主因，冷却速率控制对碳化物的均匀性至关重要，电磁搅拌、压下等外场作用对凝固过程的溶质传输、晶粒形核与迁移等产生重要影响，研发提出了枝晶间、凝固末端前沿与缩孔通道大尺寸碳化物的二冷、电磁搅拌和重压下分级协同控制新技术。项目通过研究，解决了对高品质轴承钢铸坯母材生产具有决定性影响的铸坯洁净化、均质化所涉及的基本科学问题，通过与企业合作，实现了高品质轴承钢的稳定与高效化生产。.项目发表论文40篇，其中SCI收录21篇（MMTB 13篇、MMTA 2篇）；申请发明专利14项，其中授权8项；获得省部级科技奖励3项（一等奖2项、自然科学二等奖1项）；2项与本项目相关的科研成果成功实施转化应用；培养博士和硕士研究生共15人。