In-situ observation on solidification of GCr15 bearing steel at cooling rates of continuous casting
LUO Teng-fei1,2, WANG Wei-ling1,2, LIU Zong-hui1,2, LUO Sen1,2, ZHU Miao-yong1,2
1. Key Laboratory for Ecological Metallurgy of Multimetallic Mineral (Ministry of Education), Northeastern University, Shenyang 110819, Liaoning, China; 2. School of Metallurgy, Northeastern University, Shenyang 110819, Liaoning, China
Abstract：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 of γ-Fe grains equivalent to the solid phase are 1.043, 0.973 and 1.015 μm/s, and the average radius of initial austenite grain after solidification are 148.53±58.41, 168.23±46.47 and 165.3±49.28 μm, 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.
罗腾飞, 王卫领, 刘宗辉, 罗森, 朱苗勇. GCr15轴承钢连铸冷却速率下凝固原位观察[J]. 钢铁, 2022, 57(2): 73-84.
LUO Teng-fei, WANG Wei-ling, LIU Zong-hui, LUO Sen, ZHU Miao-yong. In-situ observation on solidification of GCr15 bearing steel at cooling rates of continuous casting[J]. Iron and Steel, 2022, 57(2): 73-84.
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2022, Vol. 57 
