The Study Of Rare Earth Cerium On The Precipitation Behavior Of Titanium Inclusions In Steel

TiC,TiN and Ti₄C₂S₂ precipitated from steel can refine grain,strengthen precipitate,improve anisotropy of steel toughness,improve corrosion resistance of steel and eliminate temper brittleness.Rare earth can purify molten steel,microalloying,morphology,size and composition of metamorphic inclusions.Because the Ti（C,N）inclusion in steel has sharp edges and corners,it is not easy to deform and will not disappear after rolling and heat treatment,which is adverse to the fatigue performance and toughness of steel.The effect of rare earth on the morphology and composition of titanium inclusions was studied by adding cerium into steel.First of all,the research of rare earth by thermodynamic equilibrium calculation of precipitation containing titanium inclusions in steel and the effect of thermodynamic equilibrium calculation is carried out under the 800¹600℃,did not join the rare earth containing titanium inclusion precipitation in the form of FCC#2,Ti₄C₂S₂,Ti₃O₅,after joining the rare earth containing titanium inclusions with FCC#2,Ti₂O₃（rare earth addition amount to 100 PPM）began to appear when Ti₃O₅,Ti₄C₂S₂ form precipitate.With the increase of rare earth content,the precipitation amounts of Ti₃O₅,Ti₄C₂S₂ and Ti₂O₃gradually decreased,and the precipitation amounts of FCC#2 gradually increased.There is no change in the form of rare earth inclusions in steel,which are rare earth oxides and rare earth sulfur oxides.When the rare earth elements are not added to the cast steel,the titanium inclusions have hard edges and regular shapes and larger sizes.With the addition of 50ppm rare earth Ce,it was observed that the average size of the titanium inclusions decreased,but the morphology was still regular square.With the addition of 100ppm rare earth Ce,the morphology of the titanium inclusions changed and a smooth surface began to appear.With the addition of 150ppm rare earth Ce,the appearance of the inclusion containing titanium also appears smooth surface.The bright part in the middle is the inclusion containing rare earth,and the outer layer is coated with the inclusion containing titanium.With the addition of 200ppm rare earth Ce,the inclusion was a composite inclusion of TiC-CeAlO₃,and the size of the composite inclusion was relatively small.Based on the statistical analysis of the quantity and size of titanium inclusions in cast steel,the amount of titanium inclusions in steel increased with the increase of rare earth addition,and the average size of titanium inclusions gradually decreased,and the number of small titanium inclusions also increased with the increase of rare earth addition.The cast steel was electrolyzed to obtain complete titanium inclusions.When the addition of rare earth cerium was 0ppm,the titanium inclusions had a typical cubic shape and large size.When adding 50ppm of Ce to the steel,the titanium inclusions were still cubic in shape but reduced in size compared to those without rare earth elements.When adding 100ppm cerium,the edges and corners of the titanium inclusion began to disappear,and the morphology also changed to oval shape.When the addition amount of cerium is150ppm,the titanium inclusion turns into a quasi-spherical one,and the hardness Angle is basically eliminated and the size is reduced.When the rare earth content was 200ppm,the titanium inclusions were transformed into spherical inclusions with small size.Cerium aluminate was used as the core outer layer of the nucleation core to cover the titanium inclusions.