Influence of rare earth elements on inclusions of HRB400E hot-rolled rebar billet
In order to explore the effect of rare earth on non-metallic inclusions in HRB400E steel,scanning electron microscope(SEM)and automatic inclusion analysis system(OTS)were used to compare and analyze the inclusions in the continuous casting billet without rare earth(w(S)is 0.023％,w(O)is 0.006％)and with rare earth(w(S)is 0.027％,w(O)is 0.011％,w(La+Ce)is 0.020 6％).The results show that after the addition of rare earth,the proportion of manganese sulfide(MnS)inclusions is about 70％,and there is little change.Silica-manganese sulfide(SiO2-MnS),silicate(Silicate)and silicate-manganese sulfide(Silicate-MnS)are mainly modified,and the proportion is reduced from 18.46％to 2.86％,5.54％to 0.40％and 4.00％to 1.15％,respectively.Rare earth inclusions such as rare earth composite oxide-manganese sulfide(REO-Oxide-MnS)and rare earth composite oxides(REO-Oxide)are formed,accounting for 15.78％and 5.88％,respectively.With the addition of rare earth ele-ments,the density of inclusions with particle size of[1,10]μm increases,while the density of inclusions with parti-cle size greater than 10 μm decreases,the overall inclusion density increases from 154 pieces/mm2 to 170 pieces/mm2,and the average size increases slightly from 2.52 μm to 2.63 μm.With the addition of rare earth elements,the position of the maximum size inclusion is transferred from one-fourth of the distance from the arc to the center,the decreasing trend of MnS and Silicate-MnS density from edge to center on continuous casting billet is not changed,while the decreasing trend of SiO2-MnS and silicate inclusion density from edge to center is changed to in-creasing trend,and the density of rare earth inclusion increases at first and then decreases from edge to center.The study results provide a basis for controlling inclusions in steel with rare earth.
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