Initial Solidification Behavior of Ultra Low, Low and Middle Carbon Steel.

The cooling curves at initial stage of solidification of carbon steel sample were measured using a new temperature measurement system that consisted of a two-dimensional optical pyrometer. Undercooling and recalescence phenomena were observed on the measured cooling curve of ultra low, low and middle carbon steel samples, and the solidification sequence at initial stage of solidification was shown to be different from normal solidification. A numerical analysis employing the dendrite tip growth model has been constructed, and fitted to a measured cooling curve by the parameter of interfacial heat transfer coefficient, and then the interfacial heat transfer coefficient between sample and chill plate which made of a transparent sapphire glass can be predicted accurately. The evenness of solidified shell is made clear to be influenced mainly by thermal deformation.