Abstract:Бурмасов С.П. 1 , к.т.н., профессор кафедры «Металлургия железа и сплавов» Гудов А.Г. 1 , к.т.н., доцент кафедры «Металлургия железа и сплавов» ( a.g.gudov@urfu.ru ) Ярошенко Ю.Г. 1 , д.т.н., профессор кафедры « Теплофизика и информатика в металлургии» Мелинг В.В. 2 , старший мастер участка внепечной обработки стали Дресвянкина Л.Е. 2 , начальник группы внепечной обработки металлургической лаборатории НИЦ 1 Уральский федеральный университет имени первого Президента России Б.Н. Ельцина (620002, Россия, Екатеринб… Show more
The article considers the issues of sulfur removal in the ladle-furnace unit. The sulfur distribution coefficient depends on sulfide capacity of the slag, sulfur activity coefficient, oxidizing potential of the medium and equilibrium constant. The sulfide capacity CS of slags is one of the most important characteristics of refining capacity of the slags used in extra-furnace steel processing. One of the factors affecting the sulfide capacity is temperature. The formula was proposed showing the dependence of sulfide capacity on the optical basicity and temperature, in the temperature range of 1650 – 1400 °C and when the optical basicity Λ is not more than 0.75; the error of the presented formula does not exceed 6 %. The formula for calculating the optical basicity is proposed, which takes into account the influence of basic, acidic oxides and amphoteric oxide Al2O3. It is shown that slags, completely consisting of a homogeneous phase, have an increased optical basicity of aluminum oxide. Heterogeneous slags have a reduced optical basicity of Al2O3 in comparison with homogeneous slags. Perhaps, this fact can be explained by the fact that in homogeneous slags there is a deficiency of the basic oxide CaO and in the conditions under consideration Al2O3 compound begins to exhibit more basic properties than acidic ones, thus, in homogeneous slags, the optical basicity of aluminum oxide is increased and approaches optical basicity of CaO oxide. Calculations carried out on the basis of real heats have shown that with an increase in the content of Al2O3 oxide in the slag, its optical basicity decreases. Known value of the optical basicity makes it possible to determine sulfide capacity of the slag, sulfur distribution coefficient between metal and slag, and, accordingly, final sulfur content in the metal. The research results have shown that it is advisable to apply the ionic theory of slags for the sulfide capacity determination.
To fulfil the requirements for pipe steels of strength group D in terms of sulfur content, the metal is subjected to ladle desulfurization. In the course of desulfurization, in order to reduce its duration, steel is mixed in the ladle by blowing with argon. To optimize the desulfurization process, a methodology has been developed for evaluating its technological parameters, which allows determining under production conditions the intensity of steel blowing in the ladle. As initial data for comparative calculations of the technological parameters of the process of desulfurization of pipe steel in a ladle according to the developed method, the indicators of industrial melts were used, including the chemical composition of steel and the main technological data characterizing the production parameters of desulfurization of pipe steels of strength group D. The algorithm for using the proposed technique provides for the calculation of sulfur activity and the coefficient of sulfur activity in a steel melt of a given composition; determination of the oxidizing potential of the slag-metal system and the sulfide capacity of the slag; calculation of the equilibrium sulfur distribution coefficient between steel and slag, as well as the volumetric mass transfer coefficient under equilibrium and production conditions. To determine the thermodynamic characteristics of the interaction of sulfur dissolved in a metal with slag, the sorption ability of the slags of the analyzed melts with respect to sulfur was calculated. Data are presented on the effect of sulfur activity in experimental melts on the final sulfur content in steel. The rational limits of the value of the integral indicator of the composition of refining slags and volumetric mass transfer coefficient, which provide the best indicators of the process of desulfurization of steel, were determined. The dependences of the influence of the volumetric mass transfer coefficient on the duration of the process and the final sulfur content in the metal were established. The proposed methodology for assessing the technological parameters of steel desulfurization can optimize the duration of its individual stages and, thereby, reduce the cost of the process as a whole.
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