Research On The Behavior Of Initial Solidification For IF Steel

The IF Steel has been widely used in the exterior panels of automobile and house hold and required high surface quality.In the initial solidification process of liquid steel,many complex physical phenomenon will result in the formation of OM and hook in the surface of slab.This paper observes the morphology of hook by optical microscopy and the influence of the position in the slab and OM depth on hook depth has been studied at the same time.The two dimensional longitudinal slice heat transfer model of initial solid shell has been built according to the hook growing process in the IF steel slab,which simulates hook growing behavior,and the effect of casting process parameters on hook depth has been discussed by combining the metallographic experiments.The variation of shell thickness has been studied by this paper's model and the effects of casting parameter on shell thickness has been analyzed.The main conclusions are as follows:The whole morphology of hook consists of the line of hook origin and randomly oriented dendrites originating from frozen meniscus and the growth direction of dendrites is perpendicular to the line of hook origin and grows on both sides.Hook depth gradually gets short from the 2 mm locations above the wide face to the 10 mm locations above the wide face in the narrow face of slab.On the narrow surface of the same slab,when the OM depth increases from 0.25 mm to 0.4 mm,the increase of the depth of the solidification hook is about 0.1~0.4 mm.During the initial solidification process,the shell moving downwards for 21 mold oscillation cycle from the meniscus,the hook undergoes the phase of forming,melting,and growing.At the same casting condition,hook depth decreases,with the increase of casting temperature,casting velocity and oscillation frequency.The numerical simulation results of hook are consistent with the actual production results.At the steady casting process situations,the shell thickness becomes thick when the shell moves down from the meniscus.The shell thickness decreases,with the increase of casting velocity and casting temperature.The influence of oscillation frequency on shell thickness is not obvious.