The Interaction Between Liquid Steel And MgO-C Refractories With Different Carbon Sources And Contents

As one of the most important varieties of carbon composite materials,MgO-C refractories are widely used in the steelmaking industry.With the development of clean steel,ultra low carbon steel production,people's views are transferred from the simple pursuit of long life of refractory and also need to consider the influence of refractory on the quality of steel,so it has important significance that studying the interaction between refractory and steel for improving the quality of molten steel in industrial practice.In this paper,flake graphite,nano carbon NC220,and nano carbon NC990 are three kinds of carbon source from MgO-C refractory.It was investigated that the effects of carbon containing in the MgO-C refractories on material and mechanical properties of MgO-C refractories,using static method,the interaction between MgO-C refractories with an external diameter of 30 mm and a pore diameter of 14 mm and 300 g ultra low carbon steel keep 1873K in 1h with high purity argon atmosphere,system atically studied effect of different carbon sources and carbon containing of MgO-C refractories on the composition of steel samples and the erosion of the interaction interface between MgO-C refractories and ultra low carbon steel.The conclusions are as follows:(1)With the content of carbon in traditional MgO-C increased from 3%to 10%,the apparent porosity of MgO-C refractories was increased from 10.46%to 11.45%;the bulk density decreased from 2.98 g/cm~3 to 2.86 g/cm~3,the cold crushing strength decreased from 61.60 MPa to 22.83 MPa,the hot modulus of rupture decreased from16.35 MPa to 12.01 MPa.There was magnesia-alumina spinel in the refractories no matter before or after reaction with steel,the magnesia-alumina spinel in the NO.C3refractories increased after reaction.(2)With the content of carbon in traditional MgO-C increased from 3%to 10%,the thickness of the transition layer near the interface between traditional MgO-C refractories and ultra low carbon steel increased from 30.8?m to 42.3?m.(3)With the content of carbon in traditional MgO-C increased from 3%to 10%,after the interaction between MgO-C refractory and molten steel,the content of N in steel increased from 14.05 ppm to 83.6 ppm;the content of C in steel increased from261 ppm to 1360 ppm;the content of Al in steel increased from 123 ppm to 183 ppm;the content of Mg in steel increased from 144 ppm to 268 ppm,the content of O in steel decreased from 46 ppm to 8.5 ppm.(4)With the content of nano carbon in MgO-C refractories in increased from 1%to3%,in the MgO-C refractories with NC220,the apparent porosity increased from 11.4%to 13.06%,the bulk density decreased from 2.99 g/cm~3 to 2.87 g/cm~3,the cold crushing strength decreased from 29.47 MPa to 19.01 MPa;in the MgO-C refractories with NC99,the apparent porosity was reduced from 11.77%to 9.98%,the bulk density increased from 2.93 g/cm~3 to 3.04 g/cm~3,the cold crushing strength increased from30.68 to MPa 65.03 to MPa.(5)With the content of nano carbon in MgO-C refractories in increased from 1%to3%,the thickness of the transition layer near the interface between MgO-C refractories with the NC220 and ultra low carbon steel increases from 34.3?m to 233.3?m;the thickness of the transition layer near the interface between MgO-C refractories with the NC990 and ultra low carbon steel is decreased from 46?m to 11.7?m.(6)With the content of nano carbon in MgO-C refractories in increased from 1%to3%,after the interaction between MgO-C refractory with the NC220 and molten steel,the content of C in steel increased from 255 ppm to 292 ppm,the content of Mg in steel increased from 98 ppm to 228 ppm,the content of Al in steel increased from 92 ppm to136 ppm,the content of O in steel decreased from 31.6 ppm to 15.8 ppm,the content of N in steel increased from 24.1 ppm to 34.3 ppm;after the interaction between MgO-C refractory with the NC990 and molten steel,the content of C in steel is reduced from312 ppm to 229 ppm,the content of Mg in steel decreased from 82 ppm to 68 ppm,the content of Al in steel decreased from 144 ppm to 117 ppm,the content of O in steel increased from 20.6 ppm to 36.1 ppm,the content of N in steel decreased from 28.6ppm to 16 ppm.(7)Compared with the traditional MgO-C refractories,the MgO-C refractories containing nano carbon effectively limited the carbon dioxide of refractory materials.Compared with NC220 MgO-C refractories,because NC990 nano carbon existed as a single particle,and it increased the density of NC990 MgO-C refractories,making NC990 MgO-C refractories increased the cold crushing strength,after the reaction wirh the liquid steel,the oxygen content of the molten steel increased,the content of C,N,Mg and Al are decreased.From the point of view of ultra-low carbon steel smelting,it is more conducive to purification of molten steel for MgC refractories with NC990 as carbon source.