Development and Application of LF Refining Pre-Melted Slag Without CaF₂

In order to avoid the fluorine pollution, the LF refining pre-melted CaO-Al2O3-MgO-SiO2 slag without CaF2 was developed based on the molten slag theory. The industrial practice showed that the slag was suitable for the BOF-LF-CC route to produce oil-well pipe steel such as 37Mn5 and 34Mn5, etc, according to the standard of API.5CT of USA, and the operation period of LF refining was decreased from 42 min to 35 min, establishing the foundation of high efficiency production and short production cycle. Meanwhile the slag, compared with the slag with CaF2, has good properties for desulphurization, deoxidation, and arc submerging, quick slag forming at the beginning of refining and foaming, as well as the advantages of lower lining erosion and no pollution of fluorine.