Effect of Slag Modification on Inclusions in Si–Mn‐Killed 304 Stainless Steels

Abstract

Herein, plant trials are conducted to investigate the effect of slag modification on inclusions in Si–Mn‐killed 304 stainless steels. The slag basicity has a significant influence on inclusion compositions in 304 stainless steels. The Al2O3 content in inclusions shows a slight increase tendency with the slag basicity of 1.9. The addition of CaO increases the slag basicity from 1.9 to 2.2, which is beneficial to the removal of inclusions while increasing the Al2O3 content in inclusions from roughly 20% to 40%. The low slag basicity lowers the Al2O3 content in inclusions to around 20% while resulting in a higher total oxygen (TO) at the ladle furnace (LF) end. A kinetic model of slag–steel–inclusion reactions is developed to simulate the effect of slag modification on inclusion composition using FactSage Macro Processing. Evolutions of slag, steel, and inclusions during the slag modification process are well predicted.

Simulation of Ladle Refining Reactions in Si–Mn‐Killed Steel

“…The flow rate chosen for C2 (11.24 Nm 3 hr À1 ) is consistent with typical gas flow rates (7-12 Nm 3 hr À1 ) reported for refining other Si-Mn-killed steels. [8,36,37] To complete the model, a few additional assumptions and considerations are required. First, the alloy addition rate is tuned to match the dissolution and mixing rate determined from the measured steel composition data (for C1).…”

“…In an effort to improve desulphurization, certain steel producers [36,[41][42][43] have opted to change the slag basicity during refining. Similar to a previous study, [44] in this study, the slag basicity was increased from 1.5 to 2.0 by adding 250 kg CaO to the slag (denoted as P1) after about 6 min of refining.…”

“…The flow rate chosen for C2 (11.24 Nm 3 hr −1 ) is consistent with typical gas flow rates (7–12 Nm 3 hr −1 ) reported for refining other Si–Mn‐killed steels. [ 8,36,37 ]…”