Study On Intermediate Crack Prevention In Continuous Casting Slab

Nowadays, how to improve slab internal quality, especially to avoid the appearance of serious intermediate cracks that affect the final rolling performances under condition of guaranteeing its surface quality, is general problem in the metallurgical process of EF-slab-mediate thickness plate. In this research, through combining the production practices of EF-slab process of No. 1 steelmaking and rolling plant Anyang Iron and Steel Company, the change of CC slab mechanics performance of typical steel grades at high temperature is researched and the effects of chemical composition in steel, especially [O], [S] and [P] on the intermediate cracks are analyzed in detail. From the production in bulk, test data and relative process parameters in No.1 steelmaking and rolling plant, the effects of [C], [S], [P] and [Al] content in steel on intermediate cracks of continuous casting slab are investigated in detail. From simulation calculation results and actual measurement data of solidification thickness with second cooling model DYNACS in shot tack test, the effects of continuous casting process parameters on the formation and extension of intermediate cracks are obtained. Atthe same time the abnormal effects of continuous casting equipment without good maintainance on intermediate crack of slab are clarified on the basis of the production practices. Finally, in terms that the production practices of steelmaking and continuous casting and relative theory analyses, the preventive measures through which intermediate crack of continuous casting slab is avoided are proposed.On the basis of the research about high temperature ductility, malleability andplastic property of typical steel grades CC slab, such as 16Mn, Q235, ship platesteel, micro-alloy steel containing vanadium, micro-alloy steel containing niobiumin No.1 steelmaking and rolling plant, Anyang Iron and Steel Company, themechanism of samples brittle rupture in brittleness area is obtained. In brittlenesstemperature area â…  the reason for samples brittle rupture is that impurities ofoxygen, sulfur and so on concentrating at crystal boundaries cause the melting ofcrystal boundary under high temperature. In brittleness temperature area â…¡ thereason for sample brittle rupture is that the melting of impurities of FeS, Fe(S,O)and so on at crystal boundaries causes the fracture of crystal boundaries.