Effect of Ti and Zr Deoxidation on Inclusions and Microstructure of Low Carbon Steel

In order to investigate the effects of Ti, Zr deoxidants on inclusions and microstructure of low carbon steel, the experiments by Ti and Zr addition were carried out. After smelting, forging, and rolling of the steel, the effects of Ti and Zr deoxidation on inclusions and steel microstructure were studied. The inclusion characteristics (size, quantity, morphology and composition) of samples were analyzed using optical microscope and scanning electron microscopy (SEM), and the grain size and density were measured. The following results were found. The diameter of most inclusions is less than 3 mu m. A linear relationship exists between inclusions density and Ti content when Ti content ranges from 0.004% to 0.032%. With the increasing of the Ti content in steel, the proportion of inclusions diameter less than 0.5 mu m decreases. The inclusions distribution changes a little when Ti content ranges from 0.01% to 0.03%. The typical inclusions are TiN and TiN-M(x)O(y), with oxide core and MnS wrapper layer, and the components change with Ti content. The average grain equivalent diameter ranges from 11.8 to 15.9 mu m in the experiments. The consistent linear relationship exists between grain density and the total density of the inclusions with the diameter range from 0.5 to 3 mu m.