Effect of high temperature tempering on the phase composition and structure of steelmaking slag

Abstract Blast furnace slag and steelmaking slag, as the main accessory products of iron and steel smelting, are piled up in large quantities due to their huge output, high treatment difficulty and low comprehensive utilization rate, which has a serious impact on the land and environment. In order to improve the comprehensive utilization of steelmaking slag, low basicity blast furnace slag was added to the existing steel slag for quenching and tempering. The influence of basicity on the chemical composition and phase precipitation of mixed slag was analyzed. In the research process, the phase composition and morphology of blast furnace slag and steel slag of Baotou Steel were analyzed using FactSage7.1 thermodynamic calculation software, ZEISS high-resolution scanning electron microscope (SEM), modern fast high-resolution Bruker energy dispersive spectrometer and AMICS-Mining automatic mineral analysis software. The results show that the mineral phase composition of blast furnace slag is mainly calcium aluminum yellow feldspar and that of steelmaking slag is mainly dicalcium silicate(C2S), magnesium-iron phase solid solution, rose pyroxene and calcium iron aluminate. When the basicity of the mixed slag is 2.0, it can effectively inhibit the formation of non-cementitious mineral anorthite and promote the formation of better cementitious mineral C2S. At the same time, it is found that the melting temperature of mixed slag decreases with the increase in Al2O3 content.