Influence of Deoxidation Methods on Inclusions in Sub-Rapid Solidified Low Carbon Steel

The size, distribution, content and type of inclusions under Al, Si-Mn, Ti deoxidized conditions in sub-rapid solidified low carbon steel were investigated using VLM, SEM and TEM. Results indicated that after deoxidizing by Al, Si-Mn and Ti, the largest size of inclusions was 7.5μm, 5.6μm and 6.5μm respectively. Large amount of inclusions were tiny and dispersed in the sub-rapid solidification condition. The number of inclusions was 5423 per mm2 and the size was mainly smaller than 4μm in Al deoxidized condition. After deoxidized by Si-Mn and Ti, the number of inclusions was much less than before, with the amount of 1307 per mm2 and 1819 per mm2, respectively, and most of them were smaller than 3μm. Type of inclusions varies with different deoxidizer. The inclusions produced by Al deoxidation were Al2O3 and Fe-O-S. Inclusions were Al2O3, Al-O-Mn-S, Si-O-Mn-S and MnS in Si-Mn deoxidation sample. Inclusions produced by Ti deoxidation were Al2O3, Al-O-Mn-S and Ti-O-Fe-Si-Mn-S.