Insights Into Characteristics of Slag Film and Its Influence on the Hot‐Tearing Susceptibility for Casting Advanced High‐Strength Steels

The characteristics of slag films and their influence on the hot‐tearing susceptibility of advanced high‐strength steel (AHSS) were investigated by combining mold simulator technology, single hot thermocouple technology (SHTT), scanning electron microscopy (SEM), JMatPro calculation, and ProCAST simulation. The results show that the slag film formed by YH mold flux in AHSS 1 has a thickness of 1.78 mm, which is significantly greater than the 1.06 mm obtained for CH mold flux in AHSS 2, owing to a larger solidification shrinkage of AHSS 1. Compared with CH slag, YH slag exhibits a much higher crystalline layer fraction (84.5% vs. 37.1%) and a lower liquid layer fraction (9.4% vs. 14.7%). Quantitative thermal resistance analysis further indicates that the total thermal resistance of the YH slag film is approximately twice that of the CH slag film, mainly due to its thicker crystalline layer. ProCAST simulations further reveal that the hot‐tearing indicator of AHSS 1 is markedly lower than that of AHSS 2. The reduced hot‐tearing susceptibility of AHSS 1 is attributed to the coupled effect of larger shrinkage‐induced slag infiltration, higher slag film thermal resistance, and more uniform shell solidification.