Effects of Titanium Microalloying on Steel Feeding and Contraction

Proper content of titanium, microalloying in steel ZG200-400 smelted in intermediate frequency induction furnace, could effectively increase the volume of concentrated shrinkage cavity, and restrain the forming of shrinkage porosity. The concentrated shrinkage cavity was analyzed quantitatively by stuffing wet gluten and draining water method. The maximal cavity arrived at 0.18wt.% titanium microalloying. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, diminish the strong dendrites, and increase the fluidity and feeding capacity of steel liquid. However, overdoes titanium microalloying easily caused mass nitrides or oxides, which kept solid phases with high meting point in metal liquid to increase its viscosity, decrease the fluidity and enlarged the composition supercooling. So the metal liquid, with poor feeding, left more shrinkage porosity, less concentrated shrinkage cavity in solidification.