Abstract: In order to understand the cooling mechanism of steel slag treatment and realize the clean utilization of steel slag, the high temperature cooling test of molten steel slag was carried out. And the effect of cooling rate on the physical phase structure, phase transformation law, microstructure and stability of steel slag were studied by four different cooling treatment methods, viz., furnace cooling, air cooling, water mist cooling, and water quenching. The results of thermodynamic equilibrium calculations show that some of calcium crystallizes in the form of calcium silicate and calcium ferrite, and some exist in the form of metal oxide solid solution. The higher the basicity of the steel slag, the higher the content of free calcium oxide. The results of high temperature slag cooling experiments show that as the cooling rate increases, the content of silicate and solid solution oxides in the slag increases, while the content of free calcium oxide decreases significantly, the stability of the slag can be significantly improved. 

Key words: steel slag, thermodynamic, cooling rate, phase structure, slag stability