Effect Of Composite Deoxidation Process On The Formation And Removal Of Inclusions In Steel

With the rapid development of science and technology,better performances of steel materials are increasingly required.As a result,it is necessary to improve the original deoxidization process so that to reduce the number of inclusions,smaller size,more uniform distribution and appropriate shape of inclusions to improve the quality of steel.In this dissertation,Industrial pure iron,high purity manganese,high purity chromium and pure aluminum were chosen as the raw materials.Samples with different deoxidizing processes,different kinds of deoxidizers and different dosages of deoxidizers were prepared.Scanning electron microscopy(SEM)was applied to observe the composition and morphology of the inclusions.Metallographic microscope was applied to count the average diameter of inclusions.Changes of(T.O)content in steel during deoxidization process were determined by nitrogen and oxygen analyser.Detailed results and conclusions were listed as follows:(1)Calculation based on thermodynamic and research from experiment both indicated that the deoxidized products were FeO-Al₂O₃ in Early stage of deoxidization process by adding Al and Mn,which was elliptical.The inclusions in the end-point sample were MnO-Al₂O₃,which was spherical.The deoxidized products were MnO in Early stage of deoxidization process by adding Mn and Al,which was Spherical or chained.The inclusions in the end-point sample were MnO-Al₂O₃,which was spherical.(2)The deoxidized products were FeO-Al₂O₃ in Early stage of deoxidization process by adding Al and Cr.The inclusions in the end-point sample were Cr2O3-A12O3,which was Rod-shaped.The deoxidized products were FeCr2O4 in Early stage of deoxidization process by adding Cr and Al,which was Spherical.The inclusions in the end-point sample were Cr₂O₃-Al₂O₃,which was spherical.(3)The average diameter of inclusions in the end-point steel with weak deoxidizer Mn and Cr were smaller than that with Al,and the average diameter of inclusions increased with the increasing of Mn and Cr content.(4)The oxygen content(T.O)of the end-point samples with weak deoxidizer Mn and Cr was lower than that with Al.Compared with Mn deoxidization process,the oxygen content of final sample of Cr deoxidization process was smaller.The total oxygen content of the end-point specimens with Mn and Al was 0.005%,and that of the end-point specimens with Cr and A1 was 0.003%.