连铸过程铸坯皮下裂纹的产生及控制

Generation and control of subsurface cracks in billet during continuous casting

通过数值模拟的方法研究了典型大方坯(325 mm×280 mm)连铸过程中温度场和应力场分布,分析了铸坯皮下裂纹产生的原因和主要影响因素,制定了控制铸坯皮下裂纹的具体措施。结果表明:在连铸过程中铸坯的最大回温为121℃,二冷一区最高回热速率达到217.48℃/m,二冷二区最高回热速率达到131.95℃/m,其他各区回热速率都较低。温度回升后铸坯横断面距铸坯表面15~30 mm处的最大应力应变值已经超过了钢的极限应力应变值,因此,二冷一区和二区温度回升是铸坯产生皮下裂纹的主要原因。增加二冷一区水量,将此水量在二冷三区和四区相应地减小,可以降低二冷一区回热速率,降低最大回热温度到88℃,控制铸坯皮下裂纹的产生。

The temperature field and stress field of typical bloom(325 mm×280 mm)in continuous casting process were studied by numerical simulation method.The causes and main influencing factors of the billet subsurface cracks were analyzed,and the specific measures to control the billet subsurface cracks were formulated.The results show that during the continuous casting process,the maximum reheating temperature of billet is 121℃;the maximum reheating rate of the secondary cooling zone 1 is 217.48℃/m;the maximum reheating rate of the secondary cooling zone 2 is 131.95℃/m,and the reheating rate of other zones is low.After temperature rising,the maximum stress and strain value at 15-30 mm away from the slab surface has exceeded the limit stress-strain value of the steel.Therefore,the temperature rise in zone 1 and zone 2 of secondary cooling was the main reason for subsurface cracks of the billet.Increasing the amount of water in zone 1 of secondary cooling can reduce the amount of water in zone 3 and 4 of secondary cooling,which can reduce the reheating rate in zone 1 of secondary cooling and reduce the maximum reheating temperature to 88℃to control the occurrence of subsurface cracks.