Effect of Al2O3 mass fraction in refining slag on inclusions in U71Mn heavy rail steel
Refining slag has a very significant effect on the cleanliness of molten steel,and it mainly plays the role of deoxidization,desulfurization and inclusions adsorption.MnS is a common non-metallic inclusion in heavy rail steel.Large-size long strip MnS has great harm to the performance of steel.Based on the idea of promoting the heteroge-neous nucleation of MnS on the surface of oxides to reduce the harm of class A inclusions,the influence of alumina ratio in slag on the composition,size and distribution of inclusions was discussed in combination with industrial test and thermodynamic calculation.It is found that when the mass fraction of alumina in slag decreases from 13.72％to 7.23％,the mass fraction of total aluminum in steel decreases from 0.002 4％to 0.002 0％,the mass fraction of Al2O3 in rail inclusions decreases from 83.35％to 75.07％,and the number density of oxide inclusions increases from 2.90/mm2 to 5.69/mm2.It is beneficial to increase the heterogeneous nucleation sites of MnS and promote the precipitation of MnS on the surface of oxides.Rating results show that with the decrease of alumina ratio in slag,the coarse grade of MnS rating of A method decreases from 2.0 to 1.5,and the fine grade decreases from 1.0 to 0.5.The coarse grade of MnS rating of B method decreases from 0.744 to 0.621,and the fine grade remains at 0.500.The thermodynamic calculation results show that the proportion of alumina in slag affects the content of[Al]in the molten steel by affecting the activity of Al2O3 in slag,thus affecting the content of Al2O3 in the inclu-sions.Controlling the precipitation of MnS inclusions on the surface of oxides is beneficial to improve the qualified rate of class A inclusions in finished rails.
heavy rail steelMnSheterogeneous nucleationinclusionthermodynamicsrefining slag
NETL
NSTL
万方数据
