Analysis of IAF Nucleation and Grain Refinement Behavior in EH460 Steel

The structure,composition,particle size of micro-inclusions in laboratory as-cast shipbuilding steel with different content and type of elements were analyzed. It was found out that some kinds of inclusions in steel can induce nucleation of IAF and the needle tip of IAF can insert into other ferrite grains or pearlite and thus splitting it into several smaller units in the process of growth,resulting in significant grain refinement. The component of inclusions capable of inducing IAF nucleation in the steel are mainly Al₂O₃-Ti₂O₃、Al₂O₃-Ti₂O₃-MnO/MnS、Al₂O₃-Ti₂O₃-MnO/Mn S-SiO₂ composite deoxidation inclusions,and their particle size was 1.0 ~10 μm. 89.3% of the inclusions are between 1.0 ~6.0 μm,about,and the rest 10. 7% are between 6. 0 ~10. 0 μm. By controlling the types of alloy elements and adding sequence,a large number of fine inclusions which can induce intensive IAF nucleation can be produced and then achieve grain refinement.