EFFECT OF OXYGEN-CONTENT ON SIZE DISTRIBUTION OF OXIDES IN STEEL

The effect of the oxygen content in steel on the size distribution of oxides was investigated using Ti deoxidized steels. The number and size of oxides in the continuously cast steel slabs have been observed and the volume fraction of the fine oxides and the amount of oxygen precipitated as oxides during cooling and solidification have been examined. The results obtained are as follows. The number and diameter of the fine complex oxides composed of mainly Ti2O3, Al2O3 and MnO increase with increasing the oxygen content in the steel. Almost all the oxygen in the steel is existing as oxides, namely the oxygen content of the steel is almost equal to the amount of the oxides. The oxides precipitated during the cooling and solidification correspond to about 70% of the total oxide amount in the steel and are mostly smaller than 10 mu m in size. Most of oxides present in molten steel before casting are also fine because these fine oxides can not float and separate from the molten steel and are resultantly suspended in the molten steel. The oxides smaller than around 10 mu m occupy a large proportion of the total oxide content in the steel and govern the oxygen content in the steel.