Abstract: Based on the finite element method according to two dimensional solidification heat transfer model, the simulation of solidification structure of 280 mm x 325 mm bloom of GCr15 bearing steel casting with casting speed 0.6 m/min and 0.5 m/min, liquid superheated extent 30℃ and 10℃ , and secondary cooling water rate 0.25 L/kg and 0.20 L/kg has been carried out to study the effect of casting process parameters on structure of bloom. Results show that with increasing the liquid superheated extent from 10°C to 30℃ , the equiaxial crystal zone and mixed crystal zone decreases from 70% to 55% , so the effect of superheated extent on bloom solidification structure is very obvious ； with decreasing the casting speed from 0.6 m/min to 0.5 m/min the average length of columnar crystal grows by 6.5 mm, but the transition zone from columnar crystal to equiaxial crystal decreases, it is available to reduce the enrichment of solute elements in the zone ； with decreasing the sencondary cooling water rate from 0.25 L/kg to 0.20 L/kg, there is no obvious difference in columnar crystal and equiaxial crystal zone, therefore there is no obvious effect of decreasing secondary water rate on solidification of structure in casting bloom.

Key words: GCr15 Bearing Steel, 280 mm x325 mm Bloom Casting, Solidification Structure, Segregation, Numerical Simulation

摘要： 基于有限元法按照二维凝固传热模型对拉速0.6m/min和0.5 m/min,钢水过热度30℃和10℃以及比水量0.25 L/kg和0.20 L/kg连铸的GCr15轴承钢280 mm×325 mm坯进行凝固组织模拟,研究连铸工艺参数对铸坯组织的影响。结果表明，当过热度由10℃增大到30℃时,铸坯等轴晶和混晶区域面积由70%降低到55%,过热度对铸坯凝固组织的影响非常显著；拉速由0.6 m/min降低到0.5 m/min，柱状晶平均增长6.5 mm，但是由柱状晶向等轴晶转变的过渡区域减小，可以减轻溶质元素在此区域的富集；将比水量由0.25 L/kg降低到0.20 L/kg,铸坯柱状晶和等轴晶区域没有明显的区别，所以降低比水量对铸坯凝固组织没有明显的影响。

关键词: GCr15轴承钢, 280 mm x 325 mm坯连铸, 凝固组织, 偏析, 数值模拟