Abstract: Industrial trial was carried out by adding 5 % fly ash into molten steelmaking slag and air-granulation process. The experimental results show, compared with the original slag, the content of calcium ferrite, dicalcium silicate and merwinite in the modified slag increase, and the content of Fe, RO and free CaO decreases. The results of grinding test show that the surface area of the powder of the modified steelmaking slag is 22.4 % higher than that of the unmodified steelmaing slag. The theoretical analysis shows that the content of Fe and RO phase can be reduced effectively after the modification and air quenching, which improvies the grindability of the steelmaking slag. The results provide theoretical support and new technical direction for steelmaking slag processing.

Key words: steelmaking slag, high temperature modification, air quench, industrial trial, grindability