Thermodynamic analysis of the interaction processes of components in the Fe-Sr-Ca-O-C system under the conditions of the metal melt existence

At present, the production of high-quality construction materials is closely related to the development of microalloying technologies and the modification of steel with alloys of alkaline earth (AEM) and rare earth (REM) metals in a ladle furnace. Rationally selected compositions of refining and modifying additives can affect the microstructure of the metal, increase the strength and ductility of rolled steel, increase the cold resistance and corrosion resistance of steel, as well as globularize non-metallic inclusions, and drastically reduce their number and size. It is believed that the most effective modifiers are complex alloys containing, along with calcium, barium and strontium. The modifying ability of alkali earth metals in liquid iron increases in the order of Ca, Sr, and Ba, therefore, in terms of modifying ability, calcium is inferior to strontium and barium. At the same time, the processes of deoxidation of steel with alloys containing alkali earth metals, especially deoxidation with strontium, have not been sufficiently studied. For the development of scientifically grounded compositions of refining alloys for deoxidation and modification, it is necessary to carry out calculations that make it possible to assess, in particular, the deoxidizing ability of alkaline earth elements, including strontium. In this paper, using the method of constructing the surfaces of solubility of components in a metal (SSCM), the refining effect of strontium-containing alloys is considered. Calculations for the construction of the phase diagram of the FeO-SrO-CaO system and the SSCM of the Fe-Sr-Ca-O-C system have been performed. According to the calculation results, it is shown that with the simultaneous presence of calcium and strontium in liquid iron, a complex deoxidation mechanism is implemented with the formation of particles of a solid solution of |SrO, CaO (FeO)|ss oxides with a minimum content of iron oxide (about 0.001 wt%).