GCr15轴承钢连铸冷却速率下凝固原位观察  

In-situ observation on solidification of GCr15 bearing steel at cooling rates of continuous casting

作　　者：罗腾飞[1,2] 王卫领 刘宗辉[1,2] 罗森 朱苗勇[1,2] LUO Teng-fei;WANG Wei-ling;LIU Zong-hui;LUO Sen;ZHU Miao-yong(Key Laboratory for Ecological Metallurgy of Multimetallic Mineral(Ministry of Education),Northeastern University,Shenyang 110819,Liaoning,China;School of Metallurgy,Northeastern University,Shenyang 110819,Liaoning,China)

机构地区：[1]东北大学多金属共生矿生态化冶金教育部重点实验室,辽宁沈阳110819 [2]东北大学冶金学院,辽宁沈阳110819

出　　处：《钢铁》2022年第2期73-84,共12页Iron and Steel

基　　金：国家自然科学基金资助项目(52174306,51804067,52074076,U1708259);辽宁省“兴辽英才计划”资助项目(XLYC1802032);中央高校基本科研业务专项资金资助项目(N2025027)。

摘　　要：GCr15轴承钢在连铸凝固过程中的组织生长与溶质偏析是碳化物液析的重要诱因,成为产品质量提升的关键。为此,针对国内某钢厂240 mm×240 mm GCr15轴承钢的连铸过程,选取方坯表面下方40、80和120 mm位置处的坯样为研究对象,首先建立二维凝固传热模型,结合红外测温试验,求解它们在糊状区的平均冷却速率,然后借助高温激光共聚焦扫描显微镜(HT-CSLM)原位观察它们在连铸条件下的凝固过程,研究揭示不同冷却速率对晶粒生长动力学、晶粒尺寸和溶质偏析的影响。结果表明,距方坯表面40、80和120 mm位置处的糊状区平均冷却速率分别为24.70、17.02和18.95℃/min,固相等效的γ-Fe晶粒生长速率分别为1.043、0.973和1.015μm/s,完全凝固后原始奥氏体晶粒半径分别为148.53±58.41、168.23±46.47和165.30±49.28μm。随着冷却速率的降低,固液界面趋于稳定,晶粒形貌由不规则长条形逐渐转变为规则圆形,凝固组织变得粗大,溶质元素C和Cr在晶界处分布较高。随着凝固的进行,不同晶粒相互接触形成晶界。该现象随着冷却速率的降低愈加明显,且伴随着晶界的迁移。The growth of solidification microstructure and the segregation of solute are important factors for the precipitation of carbide from the liquid during continuous casting of GCr15 bearing steel,which are the key to improve the quality of product.Therefore,the present work focused on the continuous casting process of GCr15 bearing bloom with the transverse section of 240 mm×240 mm in a domestic steel plant,and took samples 40,80 and 120 mm below the bloom surface as research objects.First,a two-dimensional solidification heat transfer model was developed,and the average cooling rate in the mushy zone was obtained combined with temperature measurement of infrared thermal imager.Then,the in-situ observation of their solidification process under continuous casting conditions by means of high temperature laser confocal scanning microscopy(HT-CSLM)was carried out,and the effects of cooling rate on grain growth kinetics,grain size and solute segregation were investigated.The results show that the average cooling rates in mushy zone are 24.70,17.02 and 18.95℃/min at the positions of 40,80 and 120 mm below bloom surface,respectively.The growth rates ofγ-Fe grains equivalent to the solid phase are 1.043,0.973 and 1.015μm/s,and the average radius of initial austenite grain after solidification are 148.53±58.41,168.23±46.47 and 165.3±49.28μm,respectively.With the decrease of cooling rate,the solidification interface tends to be stable in the solidification,and the grain morphology gradually changes from irregular strip shape to the regular circular shape.Meanwhile,the solidification microstructure becomes coarser,and the solute concentration of C and Cr are more highly distributed at grain boundaries.With the solidification proceeding,different grains contact each other to form grain boundaries.This phenomenon becomes more significant with the decrease of cooling rate,and it is accompanied by the migration of grain boundary.

关 键 词：GCR15轴承钢 原位观察 糊状区平均冷却速率 凝固动力学 溶质偏析 

分 类 号：TF777[冶金工程—钢铁冶金]