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.
[1] Bhadeshia H. Steels for bearings[J]. Progress in Materials Science, 2012, 57(2): 268. [2] FU J W. Microstructure and corrosion behavior of hot-rolled GCr15 bearing steel[J]. Applied Physics A, 2016, 122: 416. [3] 王坤, 胡锋, 周雯, 等. 轴承钢研究现状及发展趋势[J]. 中国冶金, 2020, 30(9): 119. (WANG Kun, HU Feng, ZHOU Wen, et al. Research status and development trend of bearing steel[J]. China Metallurgy, 2020, 30(9): 119.) [4] 杜刚. 基于电渣重熔GCr15轴承钢中碳化物控制的研究[D]. 北京: 北京科技大学, 2018. (DU Gang. Study on the Control of Carbides in Bearing Steel GCr15 Based on Electroslag Remelting Process[D]. Beijing: University of Science and Technology Beijing, 2018.) [5] 李永超, 卢彩玲, 左健成, 等. 轴承钢中间包首炉大型夹杂物分析及控制[J]. 连铸, 2021(3): 35. (LI Yong-chao, LU Cai-ling, ZUO Jian-cheng, et al. (Analysis and control of macro-inclusion of bearing steel in tundish first heat[J]. Continuous Casting, 2021(3): 35.) [6] Raudensky M, Horsky J. Secondary cooling in continuous casting and Leidenfrost temperature effects[J]. Ironmaking and Steelmaking, 2005, 32(2): 159. [7] 宋超伟, 田勇, 王昊杰, 等. 预氮化对Cr-Co-Mo-Ni轴承钢渗碳层组织和性能的影响[J]. 中国冶金, 2020, 30(9): 83. (SONG Chao-wei, TIAN Yong, WANG Hao-jie, et al. Effect of preliminary nitriding treatment on microstructure and mechanical properties of carburized layer of Cr-Co-Mo-Ni bearing steel[J]. China Metallurgy, 2020, 30(9): 83.) [8] Choudhary S K, Ganguly S. Morphology and segregation in continuously cast high carbon steel blooms[J]. ISIJ International, 2007, 47(12): 1759. [9] SUN H, LI L, CHENG X, et al. Reduction in macrosegregation on 380 mm × 490 mm bloom caster equipped combination M plus F-EMS by optimising casting speed[J]. Ironmaking and Steelmaking, 2015, 42(6): 439. [10] GUO J, QIAN D S, DENG J D. Grain refinement limit during hot radial ring rolling of as-cast GCr15 steel[J]. Journal of Materials Processing Technology, 2016, 231: 151. [11] Oh K S, Chang Y W. Macrosegregation behavior in continuously cast high-carbon steel blooms and blooms at the final stage of solidification in combination stirring[J]. ISIJ International, 1995, 35(7): 866. [12] 毛明涛. H13钢中的液析碳化物及其控制方法研究[D]. 北京: 北京科技大学, 2019. (MAO Ming-tao. Investigation of Precipitation and Elimination of Primary Carbide in H13 Steel[D]. Beijing: University of Science and Technology Beijing, 2019.) [13] 叶玉奎, 姚骋, 刘宇, 等. 大方坯轴承钢GCr15凝固传热数值模拟[J]. 连铸, 2020(6): 1. (YE Yu-kui, YAO Cheng, LIU Yu, et al. Numerical simulation of solidification and heat transfer in bloom bearing steel GCr15[J]. Continuous Casting, 2020(6): 15.) [14] 王康, 刘剑辉, 杨树峰, 等. GCr15轴承钢EAF-LF-VD-CC流程非金属夹杂物的演变[J]. 钢铁, 2020, 55(2): 48.(WANG Kang, LIU Jian-hui, YANG Shu-feng, et al. Evolution of non-metallic inclusions in EAF-LF-VD-CC process of GCr15 bearing steel[J]. Iron and Steel, 2020, 55(2): 48.) [15] 吕皓天, 杨亮, 陈浩, 等. 轴承钢的长寿命化设计[J]. 中国冶金, 2020, 30(11): 16. (LÜ Hao-tian, YANG Liang, CHEN Hao, et al. Long-life design of bearing steel[J]. China Metallurgy, 2020, 30(11): 16.) [16] 肖微, 包燕平, 王敏, 等. 非铝脱氧GCr15轴承钢的夹杂物演变和控制[J]. 钢铁, 2021, 56(1): 37. (XIAO Wei, BAO Yan-ping, WANG Min, et al. Inclusions evolution and control of non-aluminum deoxidized GCr15 bearing steel[J]. Iron and Steel, 2021, 56(1): 37.) [17] 李权辉, 陶镳, 徐志祥, 等. 连铸保护渣对GCr15轴承钢铸坯渣沟缺陷的影响[J]. 连铸, 2021(1): 55. (LI Quan-hui, TAO Biao, XU Zhi-xiang, et al. Effect of mold slag on slag-scratch on continuous casting billet of GCr15 bearing steel[J]. Continuous Casting, 2021(1): 55.) [18] 刘天祥, 杨卯生, 李绍宏. 高温渗碳轴承钢旋弯疲劳裂纹萌生与扩展行为[J]. 钢铁, 2021, 56(9): 136. (LIU Tian-xiang, YANG Mao-sheng, LI Shao-hong. Fatigue crack initiation and propagation behavior of high temperature carburized bearing steel during rotary bending[J]. Iron and Steel, 2021, 56(9): 136.) [19] Utter B, Ragnarsson R, Bodenschatz E. Experimental apparatus and sample preparation techniques for directional solidification[J]. Review of Scientific Instruments, 2005, 76:013906.