Conclusions
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1.
Molten NaCl and KCl used to heat steel articles to quenching temperatures are oxidized and decarburized. The KCl salt has a lower viscosity and washes the oxides off the surface, while NaCl favors the accumulation of oxides on the surface.
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2.
Preliminary oxidation of steels leads to an increase of decarburization during heating in salts as compared to that resulting from heating of undeoxidized surfaces.
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3.
Activated BAU birch charcoal is the best deoxidizing agent as compared to graphite, borax, and ferrosilicon from the viewpoints both of its time of action and its deoxidizing capacity.
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4.
Molten KCl salt deoxidized with 1% activated birch charcoal does not induce decarburization or oxidation during heat treatment of structural steels.
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5.
After tempering of articles quenched in baths deoxidized with BAU charcoal in a chamber furnace at temperatures up to 500°C and in alkali and sodium nitrate up to 650°C, the surface of the articles does not require sandblasting.
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Literature cited
E. A. Smol'nikov, MiTOM, No. 3 (1962).
E. A. Smol'nikov, Salt Baths for Heat Treatment [in Russian], Mashgiz (1963).
E. A. Smol'nikov, MiTOM, No. 2 (1964).
Additional information
Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 43–46, July, 1966.
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Murav'ev, V.I., Tarnetskii, B.A. Heating of structural steels to quenching temperature in molten NaCl and KCl. Met Sci Heat Treat 8, 564–566 (1966). https://doi.org/10.1007/BF00673503
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DOI: https://doi.org/10.1007/BF00673503