430不锈钢板坯横裂成因分析及控制措施

Cause analysis and control measures of transverse crack in 430 stainless steel slab

通过对430不锈钢连铸板坯存在横裂缺陷的试样进行低倍检验、金相检验及韧脆转变温度测定,确定铁素体晶界上大量的碳化物析出相加速裂纹的扩展,致使铸坯更容易发生脆性断裂。提出相应的工艺控制措施:提高铸机的对弧精度,足辊出口对弧精度为0.5mm,零段出口对弧精度为0.33 mm,一段出口对弧精度为0.27mm;板坯在500℃附近快速冷却,避免脆性相的产生;要求wC+wN小于0.03%;铸坯采用带温修磨,修磨温度控制到120℃以上,1周内完成铸坯的转序、轧制。对优化工艺进行工业试验得出,430板坯横裂缺陷得到了有效控制,杜绝了因板坯横裂引起的热轧断带事故及钢带孔洞缺陷,工艺措施效果显著。

Through the macroscopic examination,metallographic examination and determination of ductile brittle transition temperature of the transverse crack defect sample of 430 stainless steel continuous casting slab,it deter-mined that a large amount of precipitation of carbide in ferrite grain boundary accelerated the propagation of the crack in slab,which can make the brittle fracture happen more easily.Corresponding control measures were pro-posed,including improving the arc alignment precision of casting machine,making the arc alignment precision of the export of foot roller,zero period and first period equal to 0.5 mm,0.33 mm and 0.27 mm,respectively,controlling the temperature of slab fast cooling in the vicinity of 500 ℃to avoid brittle phase,making the total content of C and N less than 0.03%,and ensuring the grinding temperature over 120 ℃as well as completing the turn sequence and roll-ing of casting slab within one week.Industrial test was carried out on the optimized process.It concluded that the transverse crack defects in 430 slab had been effectively controlled,which can eliminate the heat strip breaking acci-dent and steel belt hole defects caused by transverse crack of slab.The effect of the process measures was remarka-ble.