RH精炼真空度对超低碳钢夹杂物去除的影响  

Effect of vacuum degree on inclusion removal in ultra low carbon steel during RH refining process

作　　者：朱国森 邓小旋 季晨曦 ZHU Guo-sen;DENG Xiao-xuan;JI Chen-xi(Research Institute of Technology,Shougang Group Co.,Ltd.,Beijing 100043,China)

机构地区：[1]首钢集团有限公司技术研究院,北京100043

出　　处：《钢铁》2022年第11期99-105,共7页Iron and Steel

摘　　要：大尺寸非金属夹杂物是引起超低碳钢冷轧钢板表面线状缺陷的重要原因。以IF钢为例,铸坯中大尺寸夹杂物主要有3类,即结晶器保护渣卷入后被凝固坯壳捕获;连铸过程中钢水二次氧化产生且未上浮去除的;钢液中未充分去除的夹杂物在浸入式水口处粘连、堵塞,后续堵塞物脱落被凝固坯壳捕获。钢液一次脱氧生成的夹杂物中,不低于100μm的夹杂物在RH处理过程中较容易去除,100μm以下的夹杂物受钢液的流动影响较大,特别是不超过20μm的夹杂物由于其上浮时间长、钢液流动的跟随性好,去除难度较大。RH是超低碳钢最重要的精炼设备,也是夹杂物去除的关键环节,研究RH去除20μm夹杂物的新技术具有重要的意义。研究了RH脱碳结束加铝后真空度对夹杂物去除的影响,创新性提出了低真空度去除不超过20μm夹杂物的新技术。研究结果表明,与高真空度处理工艺(常规工艺)相比,低真空度(压力5 kPa)处理的钢液中夹杂物数量降低更显著,中间包钢液总氧质量分数平均降低0.0002%,钢液增氮水平相当。冷轧钢板因炼钢原因导致的线状缺陷降级率比常规工艺降低了29%。夹杂物在钢液中的跟随性理论分析表明,低真空度处理工艺下RH内钢液循环流量和钢液流速减小,降低了RH处理过程中夹杂物随钢液的跟随性,提高了不超过20μm夹杂物的去除效率,有效改善了水口堵塞程度、提高了轧板表面质量。The large size non-metallic inclusions are mainly responsible for slivers defects in ultra low carbon steels.Taking IF steel for example,macro inclusions are caused by entrapped and captured mold flux in the continuous casting mold,remained re-oxidation products of molten steels,dropping of nozzle clogs due to accumulated small size non-metallic inclusions.As for the deoxidation products,it is easy to be removed during RH treatment for the size high than 100μm.While,the flow of molten steel has great influence on the float up of the non-metallic inclusions less than 100μm,especially for those less than 20μm.RH is not only the most important facility for mass production of ultra low carbon steel,but also the most important place for inclusion removal.The influence of different vacuum degrees on the removal of inclusions during the production of IF steel was studied and new technology using low vacuum degree cycling for removing≤20μm inclusions were proposed.The results show that the inclusion density during RH process decreased faster under the treatment of lower vacuum degree(5 kPa)than that under conventional process.The average T.O content of molten steel in the tundish was decreased by 0.0002%and[N]pickup under these two processes is nearly the same.In addition,the downgrade rate of cold-rolled sheet due to metallurgical defects was reduced approximately 29%when applying the new technology.The following index between inclusions and steel was proposed to explain the experimental results.The calculated results indicated the reduction of the RH vacuum degree decreased the cycling velocity of the steel and reduced the following tendency of inclusions,therefore enhance the removal efficiency of inclusions less than 20μm,relieve the nozzle clogging and improve the surface quality of cold rolled steel sheets.

关 键 词：真空度 夹杂物去除 RH精炼 IF钢 连铸 超低碳钢 

分 类 号：TF769[冶金工程—钢铁冶金]