Centrifugal SHS-metallurgy of nitrogen steels

The possibility of obtaining alloyed nitrogen steel by centrifugal SHS-metallurgy at atmospheric pressure is shown. The initial mixture for obtaining alloyed cast steel included iron, manganese, nickel, molybdenum, vanadium and silicon oxides, as well as aluminum, chromium and chromium nitride. The experimental studies were carried out in a centrifugal installation under overloading (a) of 1 - 50g. It is shown that at a = 1g combustion is accompanied by a significant scattering of the mixture. In the case of overloading, the scattering is suppressed. The combustion products, steel and slag, are in cast state and divided into two layers; they have practically no adhesion. The mixture combustion is accompanied by intensive convective mixing of the combustion products. Gravitational convection of the two-phase melt above the combustion front and bubbling of the gaseous products provides intensive mixing, ensure high completeness of the chemical transformation of the initial mixture, and uniformity of the steel composition. Most of the experiments were carried out at a = 50g. It is shown that in the ranges of Cr and Cr2N concentrations under study, the mixtures retain the ability to burn and are well separated. Introduction of chromium nitride into the initial mixture makes it possible to obtain nitrogen steel with a nitrogen content of up to 0.3 - 0.4 wt. %. According to X-ray phase analysis, this steel has gamma-Fe lattice. The displacement of the peaks and their broadening indicate the dissolution of the alloying elements in gamma-Fe. Steel has a grain structure with narrow grain boundaries. Point inclusions concentrated in the grains and at the boundaries were also detected. The analysis of the elemental distribution and structural components composition proves that the steel base is formed by Cr, Mn and Ni solution in Fe, narrow boundaries between the grains are formed by Fe, Mn, Mo and V solution in Cr. Point inclusions mainly contain Mn and Mo.