SHS Introduction of Nitrogen in the Composition of Alloy Steel under Gas Pressure
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Introduction of Nitrogen in the Composition of Alloy Steel under Gas Pressure M. I. Alymova, D. E. Andreeva, Yu. S. Vdovina, P. A. Miloserdova, V. A. Gorshkova, V. I. Yukhvida, *, and M. Yu. Shiryaevaa aInstitute
of Structural Macrokinetics and Materials Sciences, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: [email protected]
Received October 10, 2019; revised January 27, 2020; accepted February 13, 2020
Abstract—The possibility of producing cast alloyed nitrided steel (up to 1.3 wt % N) by SHS metallurgy is shown. The initial mixture for making alloy cast steel includes iron, chromium, manganese, nickel, molybdenum, vanadium, silicon, and aluminum oxides. Chromium nitride is used as the main nitrogen source. Initial mixtures are shown to be capable of burning over a wide range of reagent ratios, and the combustion temperature exceeds the melting temperature of the condensed combustion products (steel, reducing-metal oxide), which makes it possible to perform their gravitational separation and to make steel in an as-cast form. Experimental studies are carried out in a reactor under nitrogen pressure and in a centrifugal installation under the combined action of overload and pressure to exclude the spread of a mixture during combustion. When the pressure in the reactor is increased from 0.1 to 5.5 MPa, the nitrogen content in steel alloyed with chromium, manganese, nickel, molybdenum, vanadium and silicon is found to increase from 0.4 to 1.3 wt %. Under overload (150g) and an increase in the pressure from 0.1 to 1 MPa, the nitrogen content increases from 0.4 to 0.55 wt %. According to X-ray diffraction and electron-probe microanalysis data, the base of the steel has the γ-Fe lattice and is a solution of alloying elements in iron. The shift of the diffraction peaks and their broadening indicate the dissolution of alloying elements in iron. α-Fe precipitates and point inclusions of vanadium, chromium, and impurity-aluminum nitrides are also detected. Keywords: SHS-metallurgy, combustion, chemical transformation, gravitational separation, nitrided steel, composition and structure of steel DOI: 10.1134/S0036029520090025
INTRODUCTION One of the important problems in the development of the Arctic is the creation of new steels and technologies for their production. Economically alloyed coldresistant steels with a high strength at temperatures below –30°C are most promising. Their main alloying elements are chromium, manganese, and nickel. Additionally, small additives of silicon, molybdenum, and vanadium, which significantly increase the strength of steel at low temperatures, can be introduced into the composition of cold-resistant steels [1]. The addition of nitrogen to steel decreases its brittleness and increases its cold resistance [2–7]. When nitrogen is introduced into steel, gaseous nitrogen or a nitrogen-containing master alloy (metal nitrides or nitrided ferroalloys) is usually applied. Corrosion-resistant steels of the martensitic (up to 0.1 wt % N) and austenitic–martensitic (
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