Surface Cracks In Hot Rolled Plates

Hi, we face thicker plate hot rolling (>1 inch to 4.5 inch / 25 to 120mm, nominal thickness) in wide Plate Mill using cross rolling from continuously cast slabs ( 10 inches and 12 inches/ 260/300 mm thick) and width of 70 - 120 inches ( 2500 -5000 mm) .

Grades are normal Lower -Carbon non-alloyed and micro-alloyed steel grade.

Could some one in this field of Steel Plate rolling in Steel Plants , throw some light/input on how to arrest/combat this problem of sub-surface crack in plates hot rolled and get good surface quality plate without much of re-work like grinding off these surface cracks nearer to both edges ( 1/2 - 6 inches / 15 -150 mm ) on top or bottom surface.

Slab after casting are manually scarfed and visually checked for any sub-surface defects like transverse cracks, etc and if found are removed by scarfing, and same is then cleared for rolling after re-heating in walking beam furnace .