In situ observation of solidification under transient and average cooling rate of 20CrMnTi continuous casting
SHANG Ting-rui1,2, WANG Wei-ling1,2, KANG Ji-bai1,2, ZHU Miao-yong1,2, LUO Sen1,2
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：Wide hardenability band and large-size TiN precipitates seriously endanger the product quality of 20CrMnTi gear steel. The key basis for its control is to master the behavior mechanism of solidification structure evolution during continuous casting. The traditional high temperature laser confocal scanning microscopy(HT-CSLM) in situ observation and research usually sets the cooling rate of mushy zone as a fixed value,which can not effectively reflect the change of cooling rate during continuous casting solidification. Therefore,20CrMnTi 160 mm×160 mm billet was the research object. Through the two-dimensional slice solidification heat transfer calculation,the thermal history,transient and average cooling rate of the paste area 20,40 and 60 mm below the inner arc surface were determined,and then the heating and cooling scheme of HT-CSLM experiment was designed. Then,HT-CSLM experiments under the conditions of transient and average cooling rate in the mushy zone at these locations were carried out to reveal the solidification process of 20CrMnTi under different cooling conditions δ grain growth kinetics and peritectic phase transformation mechanism. Finally,the effect of cooling conditions on solidification structure size was investigated by electron probe microanalysis(EPMA). The results show that due to the compensation of solidification latent heat,the cooling rate at the position of 20,40 and 60 mm under the inner arc is small in the initial solidification stage,and gradually increases in the middle and later stages of solidification,and becomes more significant with the deeper into the billet. The average cooling rates at these locations are 102.81,44.63 and 34.93 ℃/min,respectively. δ grain precipitates first from the liquid steel,and its average growth rate increases with the increase of cooling rate. Under the condition of transient cooling rate,instantaneous growth rate increases with the progress of solidification,but decreases slightly under the condition of average cooling rate. This is because under the condition of transient cooling rate,the cooling rate of mushy zone changes from slow to fast,which continuously compensates the latent heat of solidification,at the same time,the number of initial nucleation is small,the growth space is large,and the influence of solute undercooling is relatively weak. When the melt temperature decreases to the critical temperature of peritectic phase transformation,δ grain transition to γ grain rapidly,that is,massive transformation occurs,leading to a rapid increase in the solid fraction,accompanied by some γ grain polymerization rapidly. On the whole,the critical temperature of peritectic phase transition decreases with the increase of cooling rate,but it is also affected by the initial content of solute. After that,the remaining liquid phase transitions to the γ phase until complete solidification. The grain radius decreases with the increase of cooling rate,and it is smaller under the condition of average cooling rate than that under the condition of transient cooling rate,which depends on the number of nucleation in the initial solidification stage.
商庭瑞, 王卫领, 康吉柏, 朱苗勇, 罗森. 20CrMnTi连铸瞬态与平均冷速条件下凝固原位观察[J]. 钢铁, 2022, 57(7): 73-85.
SHANG Ting-rui, WANG Wei-ling, KANG Ji-bai, ZHU Miao-yong, LUO Sen. In situ observation of solidification under transient and average cooling rate of 20CrMnTi continuous casting[J]. Iron and Steel, 2022, 57(7): 73-85.
[1] 亓海全. 20CrMnTi钢成分优化对组织及接触疲劳寿命的影响研究[D]. 昆明:昆明理工大学,2010.(QI Hai-quan. Effect of Composition Optimization on Microstructure and Contact Fatigue Life of 20CrMnTi Steel[D]. Kunming:Kunming University of Technology,2010.) [2] 邓永康. BOF-LF-VD-CC流程生产20CrMnTi钢的工艺优化研究[D]. 重庆:重庆大学,2019.(DENG Yong-kang. Study on Process Optimization of Producing 20CrMnTi Steel by BOF-LF-VD-CC Process[D]. Chongqing:Chongqing University,2019.) [3] 吴树漂,刘占江,武云峰,等. 我国齿轮钢的生产与应用[J]. 特殊钢,2003(5):30.(WU Shu-piao,LIU Zhan-jiang,WU Yun-feng,et al. Study on rolling quality control of gear steel 20CrMnTi bar production and application of gear steel in China[J]. Special Steel,2003(5):30.) [4] 张亮. 齿轮钢20CrMnTi棒材轧制质量控制研究[D]. 沈阳:东北大学,2015.(ZHANG Liang. Study on Rolling Quality Control of Gear Steel 20CrMnTi Bar[D]. Shenyang:Northeastern University,2015.) [5] 王晓英. 齿轮钢20CrMnTi非金属夹杂物的控制研究[D]. 沈阳:东北大学,2018.(WANG Xiao-ying. Study on Control of Non-Metallic Inclusions in Gear Steel 20CrMnTi[D]. Shenyang:Northeastern University,2018.) [6] 李茂林,郭德朋,焦殿辉,等. 汽车用齿轮钢国内外概述及其发展趋势[J]. 现代制造技术与装备,2013(4):13.(LI Mao-lin,GUO De-peng,JIAO Dian-hui,et al. Overview and development trend of automotive gear steel at home and abroad[J]. Modern Manufacturing Technology and Equipment,2013(4):13.) [7] 吴振华. 含钛钢中夹杂物析出行为及其对钢组织的影响研究[D]. 武汉:武汉科技大学,2015.(WU Zhen-hua. Study on Precipitation Behavior of Inclusions in Titanium Containing Steel and Its Effect on Steel Structure[D]. Wuhan:Wuhan University of Science and Technology,2015.) [8] 傅杰,朱剑,迪林,等. 微合金钢中TiN的析出规律研究[J]. 金属学报,2000(8):801.(FU Jie,ZHU Jian,DI Lin,et al. Study on precipitation law of TiN in microalloyed steel[J]. Acta Metallurgica Sinica,2000(8):801.) [9] 李尧,成国光,鲁金龙,等. 20CrMnTi齿轮钢中TiN夹杂物的特征与分布[J]. 中国冶金,2020,30(12):28.(LI Yao,CHENG Guo-guang,LU Jin-long,et al. Characteristics and distribution of TiN inclusions in 20CrMnTi gear steel[J]. China Metallurgy,2020,30(12):28.) [10] MA W J,BAO Y P,ZHAO L H,et al. Control of the precipitation of TiN inclusions in gear steels[J]. International Journal of Minerals Metallurgy and Materials,2014,21(3):234. [11] YANG F,ZHAO W,HOU Y,et al. Precipitation behavior of nitride inclusions in K418 alloy under the continuous unidirectional solidification process[J]. ISIJ International,2021,61(1):229. [12] 康吉柏,王卫领,罗腾飞,等. 20CrMnTi钢160 mm×160 mm方坯内部质量控制[J]. 钢铁,2021,56(2):82.(KANG Ji-bai,WANG Wei-ling,LUO Teng-fei,et al. Internal quality control of 20CrMnTi 160 mm×160 mm billet[J]. Iron and Steel,2021,56(2):82.) [13] 仲红刚,刘海宁,徐智帅,等. 脉冲磁致振荡凝固均质化技术及装备[J]. 钢铁,2019,54(8):174.(ZHONG Hong-gang,LIU Hai-ning,XU Zhi-shuai,et al. Pulse magnetic oscillation solidification homogenization technology and equipment[J]. Iron and Steel,2019,54(8):174.) [14] 吴清明,许伟阳,颜慧成,等. 20CrMnTiH齿轮钢大方坯轧制圆钢宏观碳偏析控制[J]. 钢铁,2012,47(5):23.(WU Qing-ming,XU Wei-yang,YAN Hui-cheng,et al. Macro carbon segregation control of 20CrMnTiH gear steel bloom rolled round steel[J]. Iron and Steel,2012,47(5):23.) [15] 林寒,岳峰,吴华杰,等. 合金元素对20CrMnTi钢凝固组织影响的模拟[J]. 钢铁,2016,51(11):36.(LIN Han,YUE Feng,WU Hua-jie,et al. Simulation of effect of alloying elements on solidification structure of 20CrMnTi steel[J]. Iron and Steel,2016,51(11):36.) [16] WANG Ya-dong,JIANG Dong-bin,JI Sha,et al. Simulation for solidification structure of continuous casting bloom using cellular automaton-finite element model[C]//Proceedings of Materials Processing Fundamentals 2020. California:The Minerals,Metals and Materials Society,2020:13. [17] Kurz W,Giovanola B,Trivedi R. Theory of microstructural development during rapid solidification[J]. Acta Metall Mater,1986,34(5):823. [18] 王昌,王辉,张超,等. 高温激光共聚焦显微镜在钢铁材料中研究进展[J]. 物理测试,2019,37(6):15.(WANG Chang,WANG Hui,ZHANG Chao,et al. Research progress of high temperature laser confocal microscope in iron and steel materials[J]. Physics Examination and Testing,2019,37(6):15.) [19] Shibata H,Arai Y,Suzuki M,et al. Kinetics of peritectic reaction and transformation in Fe-C alloys[J]. Metallurgical and Materials Transactions B,2000,31(5):981. [20] Griesser S,Bernhard C,Dippenaar R. Effect of nucleation undercooling on the kinetics and mechanism of the peritectic phase transition in steel[J]. Acta Materialia,2014,81:111. [21] LIU T,LONG M,CHEN D,et al. Investigation of the peritectic phase transition in a commercial peritectic steel under different cooling rates using in situ observation[J]. Metallurgical and Materials Transactions B,2019,51(1):338. [22] 李亚强,刘建华,邓振强,等. 15CrMoG钢包晶凝固特征与机制[J]. 金属学报,2020,56(10):1335.(LI Ya-qiang,LIU Jian-hua,DENG Zhen-qiang,et al. Characteristics and mechanism of peritectic solidification in 15CrMoG steel[J]. Acta Metallurgica Sinica,2020,56(10):1335.) [23] 郭军力,文光华,符姣姣,等. 冷却速率对包晶钢凝固过程中包晶转变收缩的影响[J]. 金属学报,2019,55(10):1311.(GUO Jun-li,WEN Guang-hua,FU Jiao-jiao,et al. Effect of cooling rate on peritectic transformation and shrinkage of peritectic steel during solidification[J]. Acta Metallurgica Sinica,2019,55(10):1311.) [24] 罗腾飞,王卫领,刘宗辉,等. GCr15轴承钢连铸冷却速率下凝固原位观察[J]. 钢铁,2022,57(2):73.(LUO Teng-fei,WANG Wei-ling,LIU Zong-hui,et al. In situ observation of solidification of GCr15 bearing steel under continuous casting cooling rate[J]. Iron and Steel,2022,57(2):73.) [25] 朱宝晶,秦东,汤艳梅. 20CrMnTiH和GCr15钢中TiN析出热力学计算[J]. 冶金丛刊,2010(1):10.(ZHU Bao-jing,QIN Dong,TANG Yan-mei. Thermodynamic calculation of TiN precipitation in 20CrMnTiH and GCr15 steels[J]. Metallurgical Collections,2010(1):10.) [26] Wielgosz Ewa,Tomasz Kargul. Differential scanning calorimetry study of peritectic steel grades[J]. Journal of Thermal Analysis and Calorimetry,2015,119(3):1547. [27] 王卫领. 钢凝固过程枝晶生长模拟方法及行为特征研究[D]. 沈阳:东北大学,2017.(WANG Wei-ling. Study on Simulation Method and Behavior Characteristics of Dendrite Growth in Steel Solidification Process[D]. Shenyang:Northeastern University,2017.) [28] 胡汉起. 金属凝固原理[M]. 2版. 北京:机械工业出版社,2000.(HU Han-qi. Metal Solidification Principle[M]. 2nd ed. Beijing:Machinery Industry Press,2000.) [29] YANG Y,LUO S,WANG P,et al. Multiphase field modeling of dendritic solidification of low-carbon steel with peritectic phase transition[J]. Metallurgical and Materials Transactions B,2021,52(6):3708. [30] 崔忠圻,刘北兴. 金属学与热处理原理[M]. 3版. 哈尔滨:哈尔滨工业大学出版社,2007.(CUI Zhong-qi,LIU Bei-xing. Principles of Metallurgy and Heat Treatment[M]. 3rd ed. Harbin:Harbin Institute of Technology Press,2007.)
2022, Vol. 57 
