Study on Control of Inclusion Compositions in Tire Cord Steel by Low Basicity Top Slag

Abstract

AbstractTop slag melting experiment was conducted in a silicon molybdenum furnace with tire cord steel billet. The influence of top slag composition on the plasticity of CaO–Al2O3–SiO2–MgO inclusion and inclusion plasticization conditions was calculated by thermodynamic software FactSage. Use the thermodynamic calculation to guide the laboratory experiments to study slag compositions influence inclusions composition. Then industrial experiments were conducted based on the theoretical calculation and results of laboratory experiments. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to determine the morphology and composition of inclusions in steel. All studies show that in the CaO–Al2O3–SiO2–10% MgO diagram, when CaO = 8–48%, SiO2 = 35–75%, Al2O3 = 0–32%, inclusions are in the plastic area. When basicity of top slag is certain, Al2O3 content in inclusions increases with the increase of Al2O3 content in the slag, and the distribution of inclusions becomes scattered with the increase of Al2O3 content in slag. Inclusion plasticization can be achieved when the binary basicities of top slag are 0.6, 0.8–1.2, 1.4 and corresponding w(Al2O3)s are 2–15%, 2–10%, <2%. According to industrial experimental results, when top slag basicity decreases from 1.5 to 0.67–0.9 and Al2O3 content decreases below 10 wt%, the inclusion falls into plastic area. It is feasible in practice to control the CaO–Al2O3–SiO2–MgO inclusions plastic through adjusting Al2O3 content in slag.