連鋳々片の固相線近傍での変形・脆化特性

Abstract

Tensile strength, ductility and sensitivity of internal crack formation of specimens sampled from continuously cast slabs and experimentaly cast small scale ingots were measured up to their solidification temperature by tensile tests. In the case of experimentaly cast ingots, manganese and sulphur contents were changed widely.The results obtained are summarized as follows.(1) In the brittle region, the tensile strength is below 1kg/mm2 and the apparent elastic modulus is about 100-200kg/ mm2.(2) The brittle-ductile transition mainly depends on the existence of residual (Mn, Fe) S liquid film along the dendritic interface.(3) The critical strain for internal crack formation varies from zero at ZST (Zero Strength Temperature) to about 1% at ZDT (Zero Ductility Temperature) in the brittle region and is found to be independent of strain rate or carbon contents. It was thought that these results come from the lack of molten metal in front of the crack in this tensile tests. On the contrary, it was suggested that the healing behavior of molten metal at the solidification front concerns to the crack formation in real steel strand.