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Recently with the aim of increasing the stability of converter linings there has been extensive use of a new class of synthetic magnesia modifiers that are added directly to the converter melt during steel melting. The chemical composition of modifiers and method for their preparation are provided. The basis of the magnesia modifiers is MgO oxide and its compounds. Modifier properties (density, open porosity) are studied in relation to a change in specimen heating and the mineral composition of modifiers of different chemical composition, and the change in the structure of modifier specimens during heating is examined. The mechanism of modifier dissolution in molten slag is suggested.Processing iron in an oxygen converter is accompanied by formation of slag saturated with a considerable amount of iron oxides that have a negative effect on the converter lining. The corrosive nature of slag with respect to the converter lining, and in fact the amount of MgO passing from the lining into the molten slag in a unit of time is considerable at the start of blowing, it decreases during the decarburizing period and increases towards the end of blowing as a result of an increase in the solubility of refractory MgO in the iron slag [1].The wear mechanism of periclase-carbon refractories is accompanied by the following processes:liquid-phase decarburization of the lining surface layer by iron oxides and free oxygen;infiltration of slag into the decarburized layer; reaction between the refractory and slag that leads to transfer of MgO into the slag.Thus wear of periclase-carbon refractories of the converter lining is explained by the fact that iron oxide reacting with the refractory at high temperature during blowing of the metal (above 1600°C) by the reaction C + 2(FeO) = CO 2 + [Fe] forms pores through which there is penetration of slag into the decarburized layer.Wear rate v, kg/sec, of the lining is generally described by the equation [2]:where F is lining contact area with the slag, m 2 ; C 1 and C 2 are the concentration of the diffusing component into the refractory and slag respectively, kg/m 3 ; d is diffusion boundary layer effective thickness, m; D 1 and D 2 are the diffusion coefficients in the refractory and slag respectively, m 2 /sec.It follows from Eq. (1) that the lining wear rate is directly proportional to the concentration of the diffusing component into the solid and liquid phases, i.e. it depends on the concentration of iron and magnesium oxides in the slag. Therefore a reduction in the corrosive action of high iron slag on the lining may be provided by introducing magnesium-containing materials into the melt.As applied to the solubility of periclase refractory in converter slag Eq. (1) may be replaced by the expression [3]:where dn/dt is magnesium oxide dissolution rate; t is time; D is MgO diffusion coefficient in the slag; F is slag' refractory reaction surface; d is diffusion layer thickness at the inCompany (OAO), Magnezit Plant OAO, Tormag Limited Liability Company (OOO), Russia. terface; n s is ...

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669.18The Ural Institute of Metals has gained a great deal of experience in developing, studying, and introducing technologies for making steels from pig irons with a low content of manganese. For example, the Nizhniy Tagil Metallurgical Combine (NTMK) makes steel from a carbon-bearing low-manganese (0.02-0.05% Mn) semifinished product, the company "Severstal'" makes steel from pig iron containing 0.15-0.35% Mn, and the West Siberian Metallurgical Combine (ZSMK) makes steel from pig iron it smelts itself and pig iron transported in mixer ladles from the Kuznetsk Metallurgical Combine (KMK).The use of low-manganese pig irons in converters makes it possible to reduce or completely eliminate the use of scarce manganese ore, increase the production of pig iron [1][2][3], and reduce the production costs of pig iron and steel [1][2][3][4][5]. Studies [5] show that the quality of steel produced from low-manganese pig irons is the same as that of steel made from conversion pig iron containing more than 0.8% Mn.It has established that if no special measures are used to improve slag formation processes, the conversion of low-manganese pig iron is accompanied by an increase in the amount of metal sprayed from the furnace and a deterioration in the service conditions of the equipment. These problems are caused by an increase in the tendency of the slag to "coagulate" during the period of intensive decarbonization [5, 6]. There is also an increase in the consumption of fluorspar and a decrease in the residual content of manganese in the steel after the blow [5,[7][8][9][10], which requires the use of a larger quantity of manganese ferroalloys.Ways of alleviating or eliminating the above adverse effects have been found as a result of many years of studies. The use of recycled converter slag in liquid or solid form, changes in the blowing regime and the regime for addition of the slag-forming materials, the use of specially designed lances for blowing, and the use of different slag-forming mixtures and complex fluxes are allowing the oxygen-converter conversion of low-manganese pig irons and significantly improving the technical-economic indices of the process.Thus, the changeover to a more advanced technology for the oxygen-converter conversion of low-manganese pig irons is being delayed not only by the need to introduce a number of modifications and the lack of a universal method of fundamentally improving slag-forming processes, but also by the need to increase the unit consumption of scarce manganese-bearing ferroalloys.One promising direction is the use of manganese slags in steelmaking, particularly in the oxygen-converter conversion of low-manganese pig irons. The addition of such slags in the necessary amounts simultaneously solves the problems of increasing the efficiency of oxygen-converter steelmaking and saving manganese ferroalloys.Studies were performed on the use of ladle residues (crests) of slag from the production of silicomanganese at the Nikopol' Ferroalloys Plant to make steels at the Nizhniy Tagil combine...