Study and Application of Dynamic Secondary Cooling on 240 mm×280 mm Rectangular Bloom

For understanding the internal defects of 0.45C steel of 240 mm×280 mm rectangular bloom,a real-time heat transfer and solidification mold of bloom based on pin-shooting and temperature measuring was established.Meanwhile,the amount of secondary cooling water was optimized according to the objective surface temperature and dynamic secondary cooling system was applied.The results showed that:(1)When casting speed fluctuated,dynamic secondary cooling could better control the surface temperature with considering the lag of heat transfer.(2)The quality of bloom improved obviously.The defects such as center porosity,shrinkage cavity,intermedium cracks and center cracks were reduced respectively;defects above grade 1 were basically eliminated.