The Effect Of Ladle Slag Reforming On Distribution Of Mn Between Slag And Steel And Inclusions In Steel

The distribution equilibrium of Mn between ladle slag and liquid steel during therefining of ultra low carbon Al-Si killed steel was simulated in a LaCrO3hightemperature furnace at1873K, the influencing factors on the distribution of Mnbetween ladle top slag and liquid steel was investigated. It is concluded that:(1) The FetO content in slag has a significant effect on the distribution of Mnbetween ladle slag and liquid steel, which increases with the increasing of FetOcontent in the range of0~20%.(2) When the basicity increases in the range of0.5~5, the distribution ratiodecreases to the minimum and then increases. With increasing the Al2O3content inslag, the distribution ratio decreases to the minimum value and then increases. Inorder to obtain high yield of Mn alloy, FetO content should be below5%, Al2O3content is between20%and25%, and the CaO/SiO2value is about2.5.(3) The distribution ratio of Mn decreases after reforming. In all of the fourmodifiers(CaC2+Al2O3, Al+CaC2, Al+CaCO3, Al+CaO), the effect of (Al+CaO) is thebest and the distribution obtained is the lowest.(4) Csof all slags have been calculated, it shows that slag6#(46.11%CaO-21.52%SiO2-20.98%Al2O3-0.32%FetO-1.40%MnO-9.67%MgO),9#(43.64%CaO-18.92%SiO2-24.78%Al2O3-0.11%FetO-0.28%MnO-12.27%MgO)and11#(43.47%CaO-16.97%SiO2-25.79%Al2O3-0.03%FetO-1.38%MnO-12.36%MgO) have higher Cs, which is good for desulfurization during steelmaking.In addition, inclusions statistical analysis after reforming has been carried out basedon the above research. The effect of slag composition on the type, size and amount ofinclusion in steel is also studied, it shows that:(1) According to different types, inclusions in steel after reforming can be roughlydivided into two types: one kind is MnO and MnS complex inclusions, mixed with asmall amount of SiO2. The proportion of MnO in inclusion ranges between2%and35%, this has certain relations with the MnO content in slag. When the MnO content is relatively high in slag, the inclusions in steel will also have more MnO. Anotherkind is Al2O3complex oxide inclusions or magnesium aluminate spinel. Allinclusions contain FeO.(2) The size of most inclusions in steel is below2microns, which are mainlyFe-Mn oxides. With the increase of slag basicity, the average particle size ofinclusions in steel decreases. With increasing the slag basicity, the number ofinclusions in steel decreases to the minimum, where the basicity is1.5, and thenincreases.(3) When Al2O3content in slag increases, the average particle size of inclusions insteel decreases to the minimum, where the Al2O3content is20%, and then increases.The effect of Al2O3content on the number of inclusions in steel is similar, whenAl2O3content is20%, the number of inclusions is the smallest.