Mathematical Simulation of the Melting of Nitrided Ferroalloys in an Iron–Carbon Melt

Abstract

The melting of nitrided Cr–N–Fe–Si–Al ferroalloys in an iron–carbon melt under static conditions is studied by mathematical simulation. The influence of the initial ferroalloy lump sizes, the chromium content in ferroalloy, and the iron–carbon melt temperature on the alloy melting time is determined. The introduction of 12% chromium into the composition of a low-carbon FKh010 ferrochrome is shown to decrease the temperature of the end of solidification of the ferroalloy, and it passes from the group of high-melting to the group of low-melting alloys. As a result, the mechanism of melting the ferroalloy in an iron–carbon melt changes, and the time of its melting in steel decreases, especially at low temperatures (1540–1560°C). An increase in the chromium content from 61 to 74% at 12–16% N in the alloys under study transfer them from low-melting to high-melting ones, which is accompanied by a sharp increase in the time of melting the ferroalloys in an iron–carbon melt. The temperature of the steel to be processed significantly affects the ferroalloy melting time. The sharp decrease in the total melting time of FKhN20 and FKh010 alloys induced by an increase in the iron–carbon melt temperature from 1540 to 1560°C is caused by the transition of these ferroalloys from ultrahigh-melting to high-melting alloys. The lump sizes in the nitrided ferroalloys are found to affect their melting time: when the lump size increases eightfold (from 6 to 50 mm), the frozen solid steel skin thickness increases by a factor of 5–6 and the total melting time increases by a factor of 30. A nitrided FKhN10 ferroalloy has the best characteristics for processing steel due to its low melting point and the shortest melting time in an iron–carbon melt, which facilitates the assimilation of alloying elements by steel.