Abstract: The technology of slag making and the return-slag operation by limestone was analyzed in this paper, which has been applied in Shijiazhuang Iron & Steel Co., Ltd., Hebei Iron and Steel Group and met the industrial requirements. The results showed that the technology could increase dephosphorizing rate, improve the quality of steel, and reduce smelting cost in converter steelmaking process. Contrast with conventional technology, the consumption of steel material of the new technology is dropped by 6 kg/t, slag is reduced by 25kg/t, the first hit-rate of temperature at steelmaking end-point is 11%, phosphorus content of endpoint is decreased by 0.003%, carbon content is increased by 0.06%, and the smelting cost is reduced by 19.7 yuan/t.

Key words: limestone slag forming, remaining slag operation, metallurgical effects, dephosphorization