La/Ce Control Of B-type Inclusions And Structural Researc

The effects of La/Ce addition and reaction time on the morphology and structure of type B inclusions（Al₂O₃）in high carbon SWRS82B steel were studied.The number,morphology,size and distribution,distribution uniformity,interface spacing and area density of inclusions before and after modification were observed and characterized by scanning electron microscopy,energy dispersive spectrometer and optical microscope.The precipitation law of La/Ce inclusion in molten steel was calculated by Factsage thermodynamic software,and the possibility of La/Ce inclusion as heterogeneous nucleation core of primary phaseγ-Fe and Al₂O₃ was calculated by edge-edge matching model mismatch.The results show that when rare earth is not added,the Al₂O₃ inclusions in the steel are mostly large in size and irregular in shape,and the size is about 7-8μm.When the addition amount of La was 0.032 wt.%and the reaction time in the molten steel was 300 s,the inclusions in the steel became regular round-like,and the size was reduced to 1-2μm,showing a dispersion distribution,no obvious segregation,and the distribution uniformity was improved.When the addition of Ce is0.036 wt.%and the reaction time in molten steel is 300 s,it is also found that the law is similar to that of La treatment.It shows that the modification effect of Al₂O₃inclusions in steel is remarkable after adding La/Ce in a reasonable range.The transformation route of Al₂O₃ inclusion modification process in steel may be:Al₂O₃→Al₂O₃+La Al O₃+La₂O₂S→La₂O₃+La₂S₃+Al₇La₃₃O₆₀→La₂O₃+La₂S₃ and Al₂O₃→Al₂O₃+Ce Al O₃+Ce₂O₂S→Ce₂O₃+Ce₂S₃.In addition,La₂O₂S and Ce₂O₂S preferentially form the core ofγ-Fe heterogeneous nucleation,and La S and Ce S preferentially form heterogeneous nucleation on Al₂O₃.The modification process of Al₂O₃ was amplified by a single La₂O₃/Ce O₂ powder,and the ratios of different oxides were simulated at 1200℃and 1600℃.The modification process between La/Ce and Al₂O₃ was analyzed by X-ray diffraction and Raman spectroscopy,and the changes of its products were observed.The results show that the modification effect is better when the sintering temperature is 1600℃and the ratio of Al₂O₃ to La₂O₃/Ce O₂ powder is 0.4:0.6.