Abstract
It is shown that a thermal treatment which combines grain refinement with an intercritical temper (the 2BT treatment) may be used to achieve a promising combination of strength and toughness in a nickel-free ferritic steel of nominal composition Fe-5Mn-0.2Mo-0.04C at temperatures as low as -196 °C. The properties achieved are attributed to a symbiotic influence between the grain refinement treatment and the introduction of thermally stable retained austenite during intercritical tempering, a conclusion supported by a comparison of the results to those obtained with simpler heat treatments. The influence of carbon, manganese, and nickel additions to the base compositions are studied. An increase in carbon content above 0.04 wt pct causes a deterioration in toughness, as does an increase in manganese to 8 wt pct. An addition of 1 to 3 wt pct nickel is beneficial giving an increase in alloy strength at -196 °C without loss of toughness.
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Formerly Visiting Scientist, Lawrence Berkeley Laboratory.
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Niikura, M., Morris, J.W. Thermal processing of ferritic 5Mn steel for toughness at cryogenic temperatures. Metall Trans A 11, 1531–1540 (1980). https://doi.org/10.1007/BF02654516
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DOI: https://doi.org/10.1007/BF02654516