Property Optimization On Refining Slag Of LF Furnace In Changcheng Special Steel

LF is the key element in modern steelmaking process, and the guarantee for improving product quality. Nowadays in Changcheng Steelworks, the unreasonable LF process has become the bottleneck for high speed steelmaking of "EAF-LF-(VD/VOD)-CC/ingot casting". In order to optimize the matching between steelmaking and continuous casting, aiming at the LF refining slag, the research work of this paper was conducted emphasizing on the slag property optimizing, the LF refining process promotion, the producing rhythm accelerating and the production efficiency improving.By using the statistic method, the current situation of LF refining process, especially the metallurgical properties of refining slag in Changcheng Steelworks was collected. The main problem that weakened the refining capability of LF was the poor properties of the refining slag, whose high contents of FeO and MnO, poor foaming performance and poor desulphurizing performance. This paper contributed to the refining slag database in the Changcheng Steelworks, and it has a significant meaning for the future research and manufacturing process. By using the three-factor quadratic orthogonal regression optimizing method, the relationships among slag component (Al2O3/CaO, BaO, MgO), melting point, viscosity and desulphurizing ratio in the refining slag were researched in laboratory. Combining with the characteristic analyzing of the refining task in Changcheng Steelworks and the performances of different basic slag systems, the calcium aluminates slag has been selected as the primary system of the refining slag for the low / medium carbon plain steel and the low / medium carbon alloy structure steel. For the refining of bearing steel, the use of the low basicity slag was suggested. The developed submerged arc foaming slag, whose relative foaming height of slag reached as high as 114%, possesses a good heat insulating property. The desulphurizing ratio of optimized refining slag in the smelting of low /medium carbon plain steel and low / medium carbon alloy structure steel was increased by 7.4%, and for the bearing steel it was increased by 8.1%, and the defects of spot inclusion almost disappeared.Compared in the trial production, both the foaming performance and desulphurizing ability of optimizing LF refining slag were superior to the slag current using. Thereout, EAF has a less stringent acquirement for sulphur content in the tapping steel. The smelting time can be shortened, and the electricity consumption, electrode consumption and the MgO-C refractory line erosion in both EAF and LF can be reduced. This will benefit steelworks a lot.