Abstract: Facing the serious problem of corner transverse cracks on steel slab while manufacturing SS400B steel in some domestic steel plants, which leads surface up warping on hot rolling, steel plants use chamfering mould instead of right angle mould to solve this. But the longitudinal cracks on slab appear near the chamfering copper plate working face because the different friction and the temperature change the liquid steel flow field and solidified shell. Based three aspect of crystallization, lubricating and carbon composition, a new casting powder was design for chamfering mould casting boron steel. The test shows the cracks on SS400B steel slab have been effective controlled, the crack ratio dropped from 8.2 % to 0.3 %, which meets the customers’ requirement.

Key words: chamfering-mold powder, boron bearing steel, corner crack, develop, application