Modification And Multi-dimensional Characterization Of Type B Inclusions In Hard Wire Steel By Rare Earth La/

In order to refine and modify B-type inclusions in aluminum deoxidized steels.This paper adopts the experimental scheme of adding rare earth lanthanum(La),rare earth yttrium(Y)and rare earth lanthanum-yttrium mixed.The effects of rare earths on parameters such as size distribution,number density,degree of homogeneity,inter-surface distance and area density of inclusions in high-carbon wire steel were studied.The results show that the average size of the inclusions is reduced by 2～3 μm,the distribution is more uniform,the proportion of the intersurface distance greater than 10 μm is increased,and the area density is reduced from 0.1 to0.01～0.04.It shows that the addition of rare earth has different degrees of refinement and homogenization effect on the inclusions in the steel.In the experimental plan: the best solution for treating inclusions with lanthanum is the addition of 0.063%;the best solution for treating inclusions with yttrium is the addition of 0.087%;when the total amount of addition is the same,the treatment effect of lanthanum-yttrium mixed rare earth is better than one rare earth.Based on classical thermodynamics,the effect of La/Y activity in steel on inclusion formation was calculated using Factsage software,and the results showed that the rare earth was mainly combined with O and S in the molten steel after adding.Alumina inclusions are surrounded by rare earth inclusions,which hinder the aggregation and growth of alumina inclusions.Through the evolution of inclusions during solidification,the modification of alumina inclusions by rare earths and the types of inclusions are discussed.Through experiments such as electrolytic extraction of inclusions in steel and tomographic scanning of samples,the changes of three-dimensional morphology of inclusions in steel after rare earth treatment were studied.The results show that the morphology of the irregular inclusions in the steel after rare earth treatment is close to spherical,which is in good agreement with the twodimensional plane shape of the inclusions photographed by electron microscope.Both the 2D and3 D morphology of the inclusions in the steel and the various parameters of the inclusions reflect that the inclusions in the steel have been refined and modified after the rare earth treatment,which improves the quality of the high-carbon wire steel.