Insights into the Effect of Cooling Regime Regulate Peritectic Steel Solidification Mode on Solidification Shrinkage

Understanding the solidification shrinkage characteristics of peritectic steel at different cooling rates is necessary for defect control during solidification. The influence of extreme cooling conditions on the solidification shrinkage of peritectic steel is studied by in situ observation experiment, and a predictive model for the solidification mode of peritectic steel is constructed. Furthermore, the degree of solidification shrinkage of the steel melt is quantitatively characterized by the surface roughness of the samples. Research indicates that the solidification path of peritectic steel is: L → L + δ – Fe → δ – Fe + γ – Fe → γ − Fe under extremely rapid and isothermal cooling conditions; the solidification path of peritectic steel transforms to: L → L + δ – Fe → L + δ – Fe + γ – Fe → γ − Fe under nonisothermal cooling conditions. Under nonisothermal cooling conditions (10–100 °C min −1 ), as the cooling rate increases, the surface roughness of the samples decreases from 8.59 to 5.14 μm. However, under extremely rapid and isothermal cooling conditions, the surface roughness decreases to 1.34 and 1.85 μm, respectively. The critical cooling rate for the peritectic reaction (L + δ – Fe → γ − Fe) and peritectic transformation (δ – Fe → γ − Fe) is 205.2 °C min −1 .