400 mm特厚板坯尾坯表面横裂纹的控制

板坯尾坯浇铸属于非稳态浇铸,随着板坯厚度的增加,尾坯表面横裂纹成为影响铸坯质量的主要因素。通过研究钢种的化学成分、二次冷却制度和尾坯浇铸时拉速的变化等因素对尾坯表面横裂纹的影响,确定了特厚板尾坯表面横裂纹的产生机理,提出了相应的改进措施。低碳微合金钢二次冷却制度采用弱冷,控制尾坯浇铸拉速小于0.5m/min的时间要小于5min,尾坯浇铸阶段二冷水的比水量从0.35 L/min减少到0.25 L/min,控制尾坯矫直温度在933℃以上,能够有效地减少尾坯表面横裂纹,使特厚板尾坯废品率降低到5%以下。

Control of surface transverse crack on tail of 400 mm ultra-heavy slab

The casting of the tail slab belongs to the unsteady state casting.With the thickness of slab increasing,the surface transverse crack on the tail slab becomes the main factor that influences the quality of the slab.By studying the influences of some factors such as chemical composition of steel grade,the secondary cooling system and the speed change of the tail slab casting on the surface transverse crack,the formation mechanism of the surface transverse crack on the tail of the ultraheavy slab was determined and the corresponding improvement measures were put forward.The soft cooling control was adopted for the secondary cooling system while casting low carbon microalloyed steel When the casting time of the tail slab under the casting speed less than 0.5 m/min was less than 5 min,the specific water flow of the secondary cooling in the casting stage of the tail slab was reduced from 0.35 L/m to 0.25 L/min,and the straightening temperature of the tail slab was controlled above 933 ℃,the surface transverse crack on the tail slab could be decreased efficiently.The reject rate of the tail slab was reduced to less than 5 ％.