CONTROL OF TRANSVERSE DEPRESSION ON THE SIDE OF CONTINUOUS CASTING SLAB
The peritectic subperitectic steel with higher Al content has the highest tendency of depression on the surface of the primary shell.The heat transfer efficiency in the depression decreases,which aggravates the coarsening of austenite grains,weakens the shell and increases the sensitivity of transverse depresoion cracks on the slab surface.In view of the transverse depression micro-crack defect on the side of the continuous casting slab produced by Tangshan Iron and Steel Co.,Ltd.,it is analyzed that the cracks caused by the thermal stress caused by the local undercooling of the slab in the meniscus,the overflow of molten steel,the uneven solidification of the primary billet shell and the static pressure of slag ring and molten steel near the meniscus.By maintaining reasonable inverted taper of mold,optimizing the uniformity of mold and secondary cooling and mold oscillation process,strengthening the support and cooling of mold foot roller section,reasonably controlling the flow of molten steel in mold,increasing the viscosity of mold flux and the thickness of liquid slag layer,ensuring that the product of mold flux viscosity and casting speed is 0.15～0.35 P·s·m/min,and the thickness of mold slag is more than 10mm.As well as optimizing the carbon distribution process,the transverse depression micro-crack defects on the side of the continuous casting slab are obviously reduced.Through batch tests and application in large-scale production,the lateral concave micro-cracks of continuous casting slab are well controlled.
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