轴承钢大方坯凝固末端特性与中心质量控制  

Solidified end characteristics and center quality control of bearing steel bloom

作　　者：夏帅康 王璞 汤群伟 李伟涛 扈凯 张家泉[1] XIA Shuaikang;WANG Pu;TANG Qunwei;LI Weitao;HU Kai;ZHANG Jiaquan(School of Metallurgical and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China;Joint Research Center,Weifang Iron and Steel Group Co.,Ltd.,Weifang 262400,Shandong,China)

机构地区：[1]北京科技大学冶金与生态工程学院,北京100083 [2]潍坊特钢集团有限公司联合研究中心,山东潍坊262400

出　　处：《钢铁》2024年第2期99-110,共12页Iron and Steel

基　　金：国家自然科学基金资助项目(U1860111)。

摘　　要：连铸流程取代模铸锻造生产高端轴承钢是当前的发展趋势。为了改善GCr15轴承钢200 mm×240 mm大方坯连铸中常见的中心缩孔和中心偏析问题,借助数值模拟研究连铸坯传热与凝固进程,并通过工业试验调整拉速探究末端电磁搅拌(final electromagnetic stirrer,F-EMS)和轻压下(soft reduction,SR)对连铸内部质量的协同影响机制和效果,通过低倍酸侵观察不同工艺下铸坯的横纵截面缩孔疏松和裂纹情况,通过钻屑取样检测铸坯横截面上碳偏析分布。结果表明,拉速为0.95 m/min时铸坯凝固终点仅为13.0 m,此时提升F-EMS强度且使用轻压下虽然可以改善中心缩孔,但F-EMS也将更多高浓度钢液搅入铸坯中心,由于铸坯中心熔池宽度小,对高浓度溶质的稀释作用小,熔池难以稀释这些钢液从而使得铸坯中心偏析反而加剧。而在F-EMS电流强度为540 A、SR总压下为7 mm的工艺下,拉速提升至1.2和1.4 m/min时,铸坯内弧侧都产生了压下裂纹,且由于GCr15轴承钢连铸凝固两相区较宽,拉速为1.4 m/min时铸坯在铸机上产生裂纹的压下辊处,铸坯内部裂纹敏感区间较白亮带更靠近铸坯表面,最终导致白亮带较压下裂纹更靠近铸坯中心。拉速为1.1 m/min时,虽然中心缩孔得以控制,但中心区域出现负偏析,导致断面均质性无法控制到较高水平。而在拉速为1.0 m/min工况下,F-EMS处的铸坯中心固相率在0.1附近,在合理位置,其2号和3号压下辊处铸坯中心固相率都处于合理的压下区间0.30~0.75,铸坯横截面中心缩孔评级为0.5以内,中心偏析为1.003,碳极差为0.125%,其质量最优。It is presently a dominant process to produce quality bearing steel by continuous casting and rolling instead of traditional ingot casting and forging.To improve the frequently observed severe center shrinkage and center segregation in the bloom continuous casting process of GCr15 bearing steel,the numerical simulation has been carried out to predict the solidification process of the continuous casting,and the industrial trials of adjusting the casting speed have been made to explore the influence mechanism and effect of external-field control technology such as F-EMS and soft reduction.The center shrinkage and cracks of the cross-sectional and longitudinal sections of the casting bloom under different processes were observed by the thermal acid etching tests.The distribution of C segregation on the cross-section of the casting bloom was detected by drilling cuttings sampling The results showed that the solidification endpoint at a casting speed of 0.95 m/min was only 13.0 m.Accordingly,although the center shrinkage could be improved by increasing the F-EMS strength and using soft reduction.But F-EMS also stirred more high-concentration molten steel into the center of the bloom.Due to the small width of the molten pool in the billet center,the dilution effect on the high-concentration solute was small,and the molten pool was difficult to dilute these molten steel,so that the segregation of the bloom center was worsened.However,under the process of F-EMS current intensity of 540 A and 7 mm under soft reduction,when the casting speed increased to 1.2 and 1.4 m/min,internal cracks were generated on the inner arc side of the strand,and due to the wide mushy zone of the GCr15 bearing steel,when the casting speed was 1.4 m/min,the crack sensitive interval of the casting blooms was closer to the surface of the casting bloom than the white bright band at the press-down roller where the crack was generated,and finally the white bright band is closer to the center of the billet than the depressed crack.At a casting speed o

关 键 词：GCR15轴承钢 末端电磁搅拌 轻压下 压下裂纹 白亮带 中心质量 

分 类 号：TF777[冶金工程—钢铁冶金]