Physical Simulation of Thin Slab Continuous Casting

Thin slab continuous casting (TSCC) has recently become a winning technology in production of automotive steels in particular those of deep-drawing quality for car body panels. By combining the TSCC with direct rolling while retaining the heat in the process, thin steel sheets can be produced with high efficiency at much lower cost than with the former cold rolling / annealing procedures. However, difficulties appear when higher strength medium-alloyed or micro-alloyed steels have to be manufactured by this method. Some alloying elements, which tend to segregate, make the as-solidified dendritic microstructure prone to hot cracking and then require well-controlled cross-reductions during subsequent rolling or thermal-mechanical treatment to homogenize microstructure and get optimum properties. Physical simulation appears to be an adequate method to generate dendritic microstructures characteristic of the continuously cast thin slabs, thus avoiding costly experiments on full- scale production lines. The direct rolling simulator HDS-V40, designed and manufactured by Dynamic Systems Inc., allows controlled melting and solidification of a central portion of 10*50*165mm flat bar, and after solidification deforming the dendritic microstructure by multistep plane strain compression to simulate hot rolling. In the molten pool formed in the sample, the dendrites grow similarly like it appears in the industrial thin slab casting, i.e. from the crystallization front defined by main directions of the heat flow to the supporting base and to the (already) solid portion of the slab. In the paper presented are metallographic evidences confirming the accuracy of this physical simulation method.