Physicochemical characteristics of ferroalloys of the Cr–C–Si–Fe system

The range of all types of ferroalloys is traditionally determined by the requirements of consumers, primarily steelmaking enterprises, as well as the technological capabilities of their pro-duction and the quality of the ore raw materials. Over the past half-century, steel production technology has undergone significant changes, including the transfer of operations for the introduction of ferroalloys for alloying, deoxidation, and refining of steel from melting units to the ladle. This necessitates the development of new ferroalloy compositions with the most favorable physicochemical characteristics for steel processing that account for the lower temperature in the ladle and the limited time for reagent interaction. One of the most widely used and important elements for steel alloying is chromium, which is utilized in the production of both structural and corrosion-resistant grades of steel. In this context, the study investigates the dependence of the physicochemical properties (density, melting temperature, and melting time in liquid steel) of alloys in the Cr-C-Si-Fe system on the chromium and silicon content. It has been demonstrated that increasing the silicon content to 10% and reducing the chromium content from 63 to 53% improves the performance characteristics of ferroalloys, including the following reductions: the crystallization onset temperature from 1620 to 1530 °C, and the density from 7540 to 6800 kg/m³. The melting time of high-carbon ferrochrome in steel depends on the Cr content: when the chromium content decreases from 63 to 45%, the melting time of the alloy decreases by 3.1 times, which is mainly due to the decrease in the temperature of the onset of crystallization of the ferroalloy from 1620 to 1570 °C. Chromium-containing ferroalloys are usually introduced into the volume of liquid steel and are slightly prone to corrosion. One of the main characteristics of ferrochrome, from the point of view of their use for alloying steel, is the time of their melting in liquid steel, which is greatly influenced by the melting temperatures of ferroalloys. The speed and degree of assimilation of alloying elements and, accordingly, the duration of extra-furnace steel treatment depend on the melting time of ferroalloys in molten steel, which significantly affects the technical and economic indicators of production. It is not possible to obtain standard grades of ferrochrome containing 63% or more Cr from low-grade chromium ores using existing process flow charts, since these ores are distinguished not only by a low chromium content, but also by a high iron content. High values of the Fe/Cr ratio determine low chromium concentrations in the resulting ferroalloys.