Abstract: Based on SGRS technology the effect of low basicity dephosphorization (De-P) slag in BOF slagless steelmaking was studied. According to the mass balance principle of slagless steelmaking, the lower basicity control of De-P slag, the more amount of CaO will be recycled and the amount of desilicication of liquid steel will be more. At the same time, the experimental results show that with the reduction of De-P slag basicity slag melting performance gradually improved, which lead to beneficial outcomes of the increasing of deslagging amount and the reducing of metallic iron content in De-P slag. When the basicity of De-P slag is around 1.2-1.8, the hemisphere temperature of De-P slag could be controlled within 1380℃ basically, the free CaO content of De-P slag could be controlled arount 0.4%, and the amount of BOF deslagging in the end of De-P stage could be controlled more than 8t (210t BOF) or 5t (100t BOF). And the purpose of efficiency De-P in converter can be achieved under the optimization of BOF bolwing system. In addition, the mineral phase of low basicity De-P slag was studied and the results show that: the main mineral composition of semisteel slag are merwinite (C3MS2), MgO-FeO solid solution (RO) and monticellite (CMS) , and the minor minerals are dicalcium silicate (C2S) and calcium silicate (CS).

Key words: converter furnace, slagless steelmaking, low basicity salg, De-P, mineral phase