ТЕХНОЛОГИЯ CВС КОМПОЗИЦИОННЫХ ФЕРРОСПЛАВОВ ЧАСТЬ I. МЕТАЛЛУРГИЧЕСКИЙ СВС ПРОЦЕСС. СИНТЕЗ НИТРИДОВ ФЕРРОВАНАДИЯ И ФЕРРОХРОМА

Abstract

The article presents research findings in the development of a  specialized SHS technology for composite ferrous alloys for steel melting and blast furnace iron-making. To resolve the principle goal of creating metallurgical production lines it was developed a new approach to practical implementation of the SHS method – a metallurgical SHS process. The metallurgical version of SHS is based on using different metallurgical alloys as the main raw stock; those include dust-type wastes of ferrite alloys production. In this case, the process of synthesis by combustion is implemented via exothermic exchange reactions. Here, composite materials form; they are based on inorganic compositions bound with iron and/or an alloy based on iron. It has been shown that depending on the aggregate state of source reagents, metallurgical SHS processes can be gasless, gasabsorbing or gas-yielding. Combustion modes for these processes largely differ. To arrange for metallurgical SHS process in weakly exothermic systems, one can use different versions of the thermal bonding principle. The authors have investigated self-propagating high-temperature synthesis of nitrided ferrovanadium and ferrochrome. It has been shown that the phase composition of the source alloy has strong impact on the consistent behaviors of the combustion flow and the combustion mechanism of ferrovanadium (if combustion is taking place in nitrogen atmosphere). In the course of nitriding σ-(Fe – V), process activation takes place; the activation is related to the transformation of the intermetallide into α-solid solution when the phase transition temperature is reached (~1200  °C). The composition structure of ferrovanadium nitride products is formed by the confluence of solid-liquid droplet-particles that consist of molten Fe and solid vanadium nitride. A 3-phase mechanism of ferrochrome interaction with nitrogen facilitates the achievement of a high degree of nitriding. It was shown that the combustion rates of ferrochrome (and chrome) during nitriding in coflow filtration mode increase as the nitrogen flow rate is increased. Here, the degree of ferrochrome nitriding during forced filtration (4.7  –  7.5  %  N) is much less than that during non-forced filtration (8.8  –  14.2  %  N).