Kinetics Study on the Modification Process of Al2O3 Inclusions in High-Carbon Hard Wire Steel by Magnesium Treatment

Abstract

The aim of the experiment in this work is to modify the Al2O3 inclusions in high-carbon hard wire steel by magnesium treatment. The general evolution process of inclusions in steel is: Al2O3 → MgO·Al2O3(MA) → MgO. The unreacted core model was used to study the modification process of inclusions. The results show that the complete modification time (tf) of inclusions is significantly shortened by the increase of magnesium content in molten steel. For Al2O3 inclusions with radius of 1 μm and Mg content in the range of 0.0005–0.0055%, the modification time of Al2O3 inclusions to MA decreased from 755 s to 25 s, which was reduced by 730 s. For Al2O3 inclusions with a radius of 1.5 μm and Mg content in the range of 0.001–0.0035%, the Al2O3 inclusions were completely modified to MgO inclusions from 592 s to 55 s. The Mg content in the molten steel increased 3.4-fold, and the time for complete modification of inclusions was shortened by about 10-fold. With the increase of Al and O content in molten steel, the complete modification time increased slightly, but the change was small. At the same time, the larger the radius of the unmodified inclusion is, the longer the complete modification time is. The tf of Al2O3 inclusions with a radius of 1 μm when modified to MA is 191 s, and the tf of Al2O3 inclusions with a radius of 2 μm when modified to MA is 765 s. According to the boundary conditions and the parameters of the unreacted core model, the MgO content in inclusions with different radius is calculated. The experimental results are essentially consistent with the kinetic calculation results.