SULFIDE CAPACITY AND PROPERTIES OF MODIFIED BUCKET SLAGS

Ladle slag during the entire period of iron refining must have a sufficient degree of ability to hold sulfides while simultaneously ensuring the minimization of iron losses. In ladles with recycled cast iron entering the desulphurization department, slags are formed already during the release of cast iron from the blast furnace or pouring from the mixer, which differ significantly from blast furnace slag in terms of physical and chemical properties. The basicity and sulphide capacity of slags decreases, which due to their active mixing with cast iron is accompanied by an increase in sulfur in the metal.The composition of slags, formed from the remains of blast furnace or mixer slags and products of chemical reactions of sulfur removal by injection of mixtures based on lime and magnesium, needs adjustment to increase the sulfide capacity while simultaneously thinning them to prevent excessive losses of iron with the slag. The use of an additional amount of fluidized lime for adjustment leads to an increase in the processing cost. It is proposed to use a slag modifier based on CaO- and Al2O3-containing steel processing waste to reduce the costs of fluidized lime. The rational specific consumption of modifiers was determined depending on the initial composition of ladle slags and the change in their sulfide capacity was calculated using models based on the concept of optical basicity.The change in melting point, viscosity, and melting point of modified ladle slags was determined, and the concentration path of CaO- and Al2O3-containing waste modified with additives was investigated. It is shown that for the typical composition of the ladle slag of cast iron desulfurization plant of PrJSC «Kamet-Stal», the sulfide capacity values ​​range from 1.0.10-4 to 20.0.10-4, which corresponds to blast furnace slags of the CaO-SiO2-MnO-Al2O3-MgO system with increased desulfurizing ability. The change in the amount of the solid fraction in the final slag in the course of refining and the effect of the basicity of the modified slag on the sulfur distribution coefficient in non-stationary temperature conditions were determined. With the application of the linear programming method, the range of rational chemical composition of ladle slag for the conditions of cast iron desulfurization plant of PrJSC «Kamet-Stal» was determined. Modified ladle slag with a basicity of 1.11-1.41 and a content of 40-51% CaO; 36-51 %SiO2 and 6-21 %Al2O3 are proposed to be considered as satisfying the given range of selected metallurgical properties.