Technological intervention for continuously cast billet of martensitic stainless ultra high strength steel

Abstract

Substantial market exists for martensitic stainless Ultra High Strength Steel (UHSS) with 12–13 wt% Cr due to its high hardness and strength, moderate temperature tolerance and corrosion resistance. However, columnar crystals, center porosity, shrinkage cavity and surface quality of martensitic stainless UHSS depend on special continuous casting (CC) technology parameters. In order to control the quality of billets, an industrial plant trial for optimizing the process parameters in a square bloom continuous casting was performed, in which influences of caster parameters (such as casting speed, temperature, electromagnetic stirring (EMS), mold flux, secondary cooling) on the surface quality and solidification macrostructure of martensitic stainless UHSS were investigated. The results indicated that an excellent surface quality and a good billet solidification structure of martensitic stainless steel could be obtained with appropriate measures, in which all of subsurface crack and depression have disappeared, and the equiaxial crystals in the center of the martensitic stainless UHSS billet was up to 50%, even to the maximum of 57%, the central porosity was below level 1.5 and more than 90% of the central shrinkage cavities have reached to level 1.0.