Development of a calculation method for evaluating technological parameters of the desulphurization process in a ladle

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.

Surface and interfacial properties of Fe-C-O-Cr alloys in contact with alumina

In this paper, temperature and concentration dependencies on density and surface tension of liquid Fe-C-O-Cr alloys (1.93 - 4.80 wt.% Cr) were investigated in high-temperature resistance observation furnace by a sessile drop method during heating from liquidus temperature to 1600?C. The interfacial characteristics (interfacial tension, wetting angle, work of adhesion, and spreading coefficient) of liquid alloy/alumina system were also determined depending on temperature. The effect of temperature and chromium content on surface and interfacial properties was proven in case of all examined alloys. Based on the fact that the content of surface-active elements such as oxygen (up to 195 ppm) and sulfur (up to 545 ppm) was higher, the influence of activities of both mentioned elements on surface tension of alloy samples was assessed. Particular attention was paid to the dependence of the surface tension temperature coefficient on oxygen and sulfur activity.

Theory and Experimental Research on Inclusion Modification in Improved Carbon Structural Steel

By means of the thermodynamics analysis of inclusion modification in the process of calcium treatment, and the advantage area chart of calcium, aluminum, sulfur, oxygen activity in inclusion midification, this paper analyzes the effects of molten steel temperature, aluminum activity, sulfur activity and other factors on inclusion modification. After calcium treatment, inclusions in high-quality carbon steel S48 will become massive or globular calcium aluminate, MnS inclusion and the composite inclusions of MgO·Al2O3 in kernel and CaO·Al2O3 in shell.