Solidification structure and central segregation of 6Cr13Mo stainless steel under simulated continuous casting conditions

Abstract

Central macrosegregation and coarse microstructure are the main defects in ingot castings of high alloy steels. Rapid cooling associated with continuous casting could be beneficial in improving the internal quality of ingot castings. This work evaluated the effects of superheat and cooling intensity on the solidification structure and macrosegregation in 6Cr13Mo stainless steel billet. Numerical modeling was performed to determine the cooling conditions of a continuous casting billet. The simulated cooling conditions were used to solidify 6Cr13Mo steel samples in a thermal simulator. Experimental results suggest that low superheat of the melt combined with an increased cooling intensity reduce central segregation and form refine microstructure. Relationships between the macrosegregation index, (Km_i), of solute elements in the final solidification zone and secondary dendritic arm spacing (λ2), which inversely proportional to cooling rates, conform to simple monotonic equations. Such monotonic relationships indicate that increasing cooling rates is an effective way of reducing central macrosegregation and refining microstructure of 6Cr13Mo steel billet.

Keywords

• Thermal simulation
• High carbon high chromium steel
• Continuous casting
• Solidification structure
• Macrosegregation