Effect of magnesium addition on inclusions in H13 die steel

The effect of magnesium addition on the number, morphology, composition, size, and density of inclusions in H13 die steel was studied. The results show that the total oxygen content in the steel can be significantly decreased to 0.0008wt%. Al2O3 and MnS inclusions are changed into nearly spherical MgO center dot Al2O3 spinel and spherical MgO center dot MgS inclusions, respectively. The number of inclusions larger than 1 mu m decreases and the number of inclusions smaller than 1 mu m increases with increasing magnesium content. V(N,C) precipitates around MgO center dot Al2O3 and MgO center dot MgS inclusions during solidification of liquid steel. The densities of MgO center dot Al2O3 spinel inclusions are lower than that of alumina inclusions. With increasing magnesium content in the Mg-containing inclusions, the density of inclusions decreases, leading to the improvement of inclusion removal efficiency.