45钢大方坯凝固传热数值分析  

Numerical analysis of heat transfer in 45 steel bloom solidification

作　　者：沈宏俊 张西超[1] 方忠强[1] 孙彦辉[1] 葛亮[1] 白雪峰[1] 

机构地区：[1]北京科技大学冶金与生态工程学院,北京100083

出　　处：《炼钢》2015年第4期47-53,共7页Steelmaking

摘　　要：以某钢厂45钢大方坯为研究对象，建立了45钢凝固传热的数学模型。用双混合模型计算了45钢的热物性参数，并通过射钉试验及坯壳测温测定窄面坯壳厚度和表面温度对模型进行了验证，结果表明该数学模型能够较好的模拟45钢凝固传热过程。模拟结果表明：在现行拉速0．5m／min，过热度为35℃工艺条件下，合适的轻压下位置在距弯月面21．8～23．1m处；铸坯出结晶器表面温度回升幅度大，容易导致表面裂纹；稳定拉速是提高铸坯质量的关键。改进后，中心疏松等级从1．5级降到不大于1.0级，中心缩孔不大于0．5级，最大碳偏析比小于1．12，铸坯表面裂纹率由3．25％降低到0．5％；铸坯凝固末端的凝固加速是由于铸坯中心大过冷条件下钢液中等轴晶的快速生长造成的。Taking 45 steel bloom as object for the study, a solidification heat transfer model has been built. The pair-wise mixture model was used to calculate the thermal pa- rameters of 45 steel. Besides, actual temperatures and shell thicknesses of narrow face were measured by pin shooting method and infrared pyrometer to verify the correctness of heat transfer model and the results indicate the model could simulate the heat transfer process of 45 steel well. Simulation results have showed that appropriate position of soft reduction was 21.8--23. 1 m from the meniscus at the condition that superheat was 35 ~C and casting speed was 0. 5 m/min. And the amplitude of rising temperature on the surface of bloom after going out of the mould was huge, which easily leads to surface cracks. Steadying the casting speed was the key factor for improving quality of 45 steel. After the application of those results, centre porosity grades have decreased from 1.5 to not more than 1.0; centre shrinkage grades were not more than 0. 5; the largest carbon segregation was not more than 1.12; rates of surface cracks has dropped from 3. 25% to 0. 5 %. As for the accelerated solidification at the end of solidification of bloom, that＇s because of the rapid growth of equiaxed grains in the slab center with a great undercoo- ling for liquid steel.

关 键 词：凝固传热 凝固速率 数值模拟 45钢 

分 类 号：TF777.1[冶金工程—钢铁冶金]