The Microstructure Formation in Slag Solidification at Continuous Casting Mold

The microstructure of slag film solidified on the inner wall of mold in continuous casting of low carbon steel has been examined experimentally and analyzed theoretically. A puzzle for the crystallization sequence has been solved by this work, which is useful to guide the modification of slag microstructure in efficient casting of advanced steels. The experiments observed three crystalline bands, each containing an initial block-shaped crystal sub-band and late-developed dendrite sub-band. The grain size and morphology change monotonically across the crystalline layers to form a gradient structure. The reason for this is that the solute segregation causes considerable surging of viscosity and constitutional undercooling in the liquid phase. This is rarely seen in the casting of alloys and have not been pointed out previously in the casting of oxide mixtures.