A Novel Investigation of Initial Solidified Shell Thickness of Continuously Cast Slab Based on Solidification Structure

Considering the big deviation of the measured initial shell thickness obtained by directly measuring the breakout shell in previous works, a new method has been proposed in this study in a microscopic and mesoscopic view. This innovative measuring method is based on the transformation point of the solidification structure of the initial solidified shell before and after the breakout occurs, which avoids the deviation induced by the attachment of the residual liquid steel. Due to the different heat transfer conditions along the casting direction of the mold, causing different segregation behaviors of the solute elements at the different positions, the micromorphology of solidified shell cannot be revealed just through the same etchant. In the present work, the appropriate etchants for the breakout shell at different positions along the casting direction have been explored through dendrite and grain etching experiments, and a black solute enrichment region appearing in the solidified structure after being etched is chosen to determine the shell thickness, therefore, the solidified structure of the initial solidified shell has been investigated in detail based on the experimental results. The result shows that solidification coefficient within the mold obtained by fitting the change curve of the initial shell thickness with the empirical equation is more competitive than the previous works.