连铸工艺参数对轴承钢大方坏凝固行为的影响

Influence of Continuous Casting Process Parameters on Solidification Behavior of Bearing Steel Bloom

连铸工艺参数对连铸产品质量有重要影响。文章建立了考虑铸坏表面实际水量分布的连铸凝固传热模型和CAFE模型,针对国内某钢厂生产的CCr15轴承钢展开模拟分析,探究了拉速、过热度、比水量对铸坏表面温度分布和凝固组织的影响规律。结果表明:拉速变化对整个连铸过程铸坏表面温度分布、二冷末端铸坏表面回温和铸坏液芯长度影响较大,当拉速由0.78m/min升高至0.98m/min时,二冷区末端铸坏表面回温值从102.9℃/m降低至91.6℃/m,铸坏液芯长度由18.8m增大到25.2m;过热度主要影响连铸坏CET开始转变位置和铸坏等轴晶率的大小,当过热度从10℃升高至40℃时,CET开始转变位置由距结晶器弯月面5.0m增大到16.7m,铸坏等轴晶率由42.7%降低至16.7%;比水量变化主要影响二冷区域连铸坏表面温度分布情况和二冷末端铸坏表面回温,当比水量从0.15L/Kg增大到0.40L/Kg时,二冷区末端铸坏表面回温值从78.2℃/m增加到129.8℃/m。为提高CCr15轴承钢连铸坏质量,在满足安全冶金准则要求的前提下,连铸坏拉速应控制在0.81m/min以上,二冷比水量应小于0.25L/Kg。当钢水过热度处于20-30℃范围内时,其变化对GCr15轴承钢铸坏等轴晶率和CET开始转变位置的影响最小。

Continuous casting process parameters have an important effect on the quality of continuous casting products.In this paper,the continuous casting solidification heat transfer model considering the actual water distribution on the surface of the bloom and CAFE model were established.The simulation analysis was aim at the GCr15 bearing steel pro-duced by a domestic steel mill,and the influence of casting speed,superheat and cooling water ratio on the surface tem-perature distribution and solidification structure of the bloom were investigated.The results show that the change of cast-ing speed has significant influence of the surface temperature distribution of bloom during continuous casting process and the longitudinal temperature reheating of bloom surface at the end of secondary cooling zone and the liquid core length of bloom.When the casting speed increases from 0.78 m/min to 0.98 m/min,the longitudinal temperature reheating of bloom surface at the end of secondary cooling zone decreases from 102.9/m to 91.6 C/m,and the length of the liq-uid core of the bloom increases from 18.8 m to 25.2 m.The change of superheat mainly influence the CET transition po-sition and the size of equiaxed crystal ratio of bloom,When the superheat increases from 10℃to 40℃,the CET tran-sition position increases from 5.0 m to 16.7 m from the meniscus of the mold,and the equiaxed crystal ratio decreases from 42.7%to 16.7%.The change of cooling water ratio mainly influence the surface temperature distribution of bloom in secondary cooling zone and the longitudinal temperature reheating of bloom surface at the end of secondary cooling zone.When the cooling water ratio increases from 0.15 L/Kg to 0.40 L/Kg,the longitudinal temperature reheating of bloom surface at the end of secondary cooling zone increases from 78.2 C/m to 129.8/m.In order to improve the quality of continuous casting bloom for GCr15 bearing steel,the casting speed should be controlled above O.81 m/min and the secondary cooling water ratio should be less than 0.25 L/Kg on the premise of meeting the requirements of safe metallurgy criteria.When the superheat of molten steel is in the range of 20-30℃,the change of superheat has the least influence on the equiaxed crystal ratio and CET transition position of GCr15 bearing bloom.