Research And Application Of Refining Slag Containing Barium In LF

With the progress of the clean steel smelting technique, desulphurization in the secondary refining process with fine refining slags has become a focal problem concerned all over the world. The main purpose is how to choose proper refining slag in accordance to different steel grade.Based on predecessor' work, the author seeks the refining slag with the low melting point, high melting velocity according to the melt thermodynamics and kinetics theory. The CaO-Al₂O₃ base slags containing MgO, BaO, CaF₂ as auxiliary components are designed by quadratic orthogonal regression method. The author conducts melting point, melting velocity experiments and desulphurization test in the condition of charging different quantities of raw materals. Base on experimental results, mathematical models between composition and properties were established. And the effects of composition on molten properties and desulphurization rate were discussed. Optimized composition was obtained by orthogonal direct-visual method. Optical basicity was used to calculate sulfur capacity. The confirming test shown that the mathematical models were highly reliable. By comprehensive consideration of physicochemical properties of slag in the study, the optimized composition of refining slag ought to be 7%MgO, 9%BaO, 8%CaF₂, 6%SiO₂ and Al₂O₃/CaO=0.7.The physical properties such as viscosity, surface tension and melting density at high temperature have been measured and the properties are excellent compared with empirical value. The optimal refining slag is examined at the second steel mill of ShouGang. It can shorten refining period and save energy consumption, so decrease cost. Its average comprehensive desulphurization rate reaches 73.2%, and maximum value is 83.8%. The value is higher by contrast with 58% reported. [%S] in steel can be reduced to 0.005%⁰.011%(average 0.007%), which can satisfy the requirement of deep desulfurization. In addition, the slag possesses certain abilities of deoxidation and removing inclusions. Any product defects have not been found by inspecting slab about longitudinal, central split, piezoglypte, inslusion etc, and qualification rate of...