Mechanism for Loss of Hot Ductility Due to Deformation during Solidification in Continuous Casting of Steel

Abstract

Strand surface cracking is a problem that can lead to scrap the product of the continuous casting process. Stress and strain developed during continuous casting have been found to be effective in this respect. The crack susceptibility is usually evaluated by assessing the steel hot ductility at the straightening stage of the process. The hot ductility of two Nb-microalloyed steels was evaluated in in situ melted specimens. The billet surface thermal history was simulated in order to generate the billet surface microstructure. The effect of deformation incorporated with steel solidification was studied and it was found that any kind of deformation during solidification results in loss of hot ductility. Metallography of specimens revealed that deformation caused grain boundary cracking and changed the segregation pattern, leading to loss of hot ductility. Based on this, a mechanism for hot ductility loss was proposed.