600 mm 35CrMo钢立式连铸圆坯宏观组织分析

Analysis on the macrostructure of 600 mm 35CrMo round steel billet produced by vertical continuous casting

基于中原特钢股份有限公司立式连铸工艺与CAFE形核理论,建立了Φ600 mm 35CrMo钢立式连铸圆坯传热凝固耦合模型,采用薄片移动边界法对圆坯宏观组织进行数值模拟,分析了钢液浇注过热度和二冷水制度对宏观组织的影响,并在现场进行了Φ600 mm 35CrMo钢圆坯的连铸生产。结果表明:圆坯宏观组织形貌模拟结果与现场低倍组织相一致,过热度为40℃时中心等轴晶率为29.16%。当过热度由30℃升高到50℃时,晶粒数由9 332个减小到7 155个,降低了23.33%;晶粒平均半径由1 302μm增大到1 622μm,增大了24.58%;中心等轴晶率由35.75%减小到21.13%。当冷却强度由弱冷变为强冷时,晶粒数由9 391个减小到7 228个,晶粒平均半径由1 259μm增大到1 576μm,中心等轴晶率由36.05%减小到23.04%。

Based on ZhongYuan Special Steel’s continuous casting process parameters and CAFE nucleation theory,a mathematic model coupling heat transfer and solidification in a Φ600 mm vertical continuous casting round steel billet was established. Using chip-moving boundary method,the macrostructure in a Φ600 mm 35CrMo round billet was numerically simulated. In this work,the influence of the molten steel superheat and the secondary cooling intensity on the macrostructure in the 35CrMo round billet was analyzed,and the continuous casting of Φ600 mm round billet was carried out in the steelworks. The results show that simulation and practical cases both reveal consistent macrostructure morphology; when the superheat is 40 °C the round billet has the center equiaxial grain ratio of 29.16%; when the superheat increases from 30 °C to 50 °C,the number of grains decreases from 9 332 to 7 155 corresponding to 23.33% reduction while the average radius of the grains increases from 1 302 μm to 1 622 μm corresponding to 24.58% increase with the center equiaxial grain ratio decreasing from 35.75% to 21.13%. When the cooling intensity increases from low cooling to strong cooing,the number of grains decreases from 9391 to 7 228,and the average radius of the grains increases from 1 259 μm to 1 576 μm with the center equiaxial grain ratio decreasing from 36.05% to 23.04%.