Optimal treatment of star cracks on full-arc continuous casting slab of low alloy steel
The star cracks are hidden in the subsurface of continuous casting slab,which are difficult to be detected in manual on-line inspection,and it is easy to cause a large number of peeling defects when the burning loss of heat-ing furnace is insufficient.Through metallographic analysis of rolled piece and slab,it is clear that the cause of de-fects comes from star cracks of the slab.In view of the star crack of the slab using the full-arc continuous casting machine,the influences of typical elements(C,Al,N,V),cooling intensity of mold,slag in the continuous cast-ing,secondary cooling strength and others on the crack defects of casting slab were analyzed.The causes of the cracks in casting slab were clarified that deep vibration marks and a large amount of precipitates form the crack initi-ation,and the slab is located in the brittle zone in the caster and suffers excessive stress.The effective measures to control the cracks are put forward,including reducing the contents of typical elements,increasing and stabilizing the casting speed,employing improved continuous casting slag,weakening the mold strength and secondary cooling strength,improving the quality of caster,etc.After a large number of actual applications,the crack defects of low alloy steel slab are reduced,and the peeling defect rate of hot-rolled plate is reduced from 21.84％to 0.47％.
continuous casting slabstar crackHSLA steelsteel propertycooling process
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