Cracking phenomenon during strip casting of AISI 304 stainless steels

The cracking occurring during strip casting of an AISI 304 stainless steel was micro structurally examined, and then methods to prevent it were suggested. Detailed microstructural analyses of the cracked regions showed that the cracks were mostly deep, sharp, and longitudinal ones parallel to the casting direction. They initiated at the root of dendrites, and propagated along the segregated liquid films between primary dendrites, indicating that they were typical solidification cracks. This cracking phenomenon was closely related with the unhomogeneous solidification of cast strips represented by depressions, i.e., uneven and somewhat concave areas on the strip surface. The depressions, which were inevitable in flat rolls due to the presence of the gas gap between a roll and a cast strip, were distributed fine and evenly all over the cast strip by artificially providing homogeneous roughness on the roll surface, and then the number and size of cracks were considerably reduced. In addition, the nitrogen gas atmosphere which had excellent solubility and wettability in the melt, was successfully used to prevent the cracking because the thickness of the gas gap was minimized