Aiming at the high incidence of fire cutting crack in die steel,the characteristics and mechanism of fire cutting crack were analyzed according to the actual process parameters.It is determined that hydrogen stress,thermal stress and structure stress are the causes of fire crack.The stress of steel plate was alleviated by four controls:stacking and cooling to 150℃before the slab was put into the furnace,the heating time of slab was extended to 400 min,stacking and cooling to 250℃after the steel plate was rolled off the line,and stacking and cooling to 100℃after the steel plate was cut.The crack rate of steel plate was reduced from 80%to 10.4%.
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