Analysis and control of central cracks in the bloom continuous casting of microalloy 49MnVS3 steel

In order to control central cracks in continuous casting of microalloy 49MnVS3 steel, the formation mechanism of central cracks has been studied by analysing the element segregation, crack morphology, hot ductility, precipitates and centre macrosegregation. It was found that the centre macrosegregation of carbon and sulphur and the precipitation of (Mn, Fe)S in grain boundary at the later stage of solidification could decrease the solidus temperature and enlarge the high temperature brittle zone, meanwhile, the precipitations of MnS and Ti(C, N) in grain boundary could make cracks easier to propagate, both of which lead to the formation of central cracks. Based on the above analysis, the centre macrosegregation of carbon and sulphur and the inclusions including MnS and the total in the centre of bloom were decreased by using final electromagnetic stirring and machine soft reduction together, thus, the central cracks of bloom were controlled successfully.