Nitrogen saturation of steel during annealing in PSO-09 atmosphere

Autor: N. V. Shavrikova, M. N. Leonidova, Yu. M. Brunzel, L. F. Korotkova
Rok vydání: 1982
Předmět:
Zdroj: Metal Science and Heat Treatment. 24:693-698
ISSN: 1573-8973
0026-0673
Popis: 1. Nitrogen saturation of iron alloyed with various elements is observed during the heat treatment of a foil composed of these alloys in a PSO-09 atmosphere at 690, 770, and 950°C and in endogas at 950°C. In this connection, the molecular nitrogen present in the controlled atmospheres should be treated as a potential source of nitriding, the intensity of which depends on the temperature-time parameters of the process, and the composition of the atmosphere, as well as on the extent to which the metal is alloyed. 2. Of the alloying elements investigated, manganese, chromium, and aluminum increase the tendency to nitriding to the maximum extent possible; the maximum increase in nitrogen concentration in the alloys after heat treatment in exogas is observed when these metals are used as alloying elements. 3. The nitriding process in exogas is characterized by significant concentration non-uniformity over the area of the specimens. 4. Values of nitrogen concentration in steels annealed in exogas at 950°C exceed the values obtained under standard conditions at a pressure of 1 atm in the majority of cases; this can be explained by the catalytic effect of the oxygen absorbed by the alloys during annealing in the exogas (and also endogas). 5. An increase in the annealing temperature from 690–770°C to 950°C effects an intensification of the nitriding process. 6. An PSO-09 atmosphere containing molecular nitrogen cannot be used to anneal thin-sheet steels alloyed with elements that promote nitriding in cases when according to technological considerations (e.g., in welding certain thin-sheet alloy steels), the content of nitrogen in the steel should not increase after annealing. An atmosphere of hydrogen, and a vacuum can be proposed as replacements for nitrogen-containing atmospheres.
Databáze: OpenAIRE
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