Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Improvement of the Strength and Toughness of Steel Plates by Direct-quenching and Tempering
Nozomi KOMATSUBARASeiichi WATANABEHiroo OHTANI
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1983 Volume 69 Issue 8 Pages 975-982

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Abstract

Direct-quenching after hot rolling above recrystallization temperature in austenite was investigated in low carbon and low alloy high tensile strength steels. Effects of cooling rates during direct-quenching on the microstructures, strength, and toughness were investigated, comparison being made with reheat-quenching.
It was clarified that the strength and toughness were remarkably improved by direct-quenching in a certain range of cooling rates, in which the microstructure of direct-quenching showed up as a mixture of martensite and fine bainite, while that of reheat-quenching was coarse bainitic. These results showed that the improvements of the strength and toughness were due to the enhancement of hardenability by direct-quenching.
By calculating ideal critical diameters from tensile strengths of as-quenched steel plates, it became clear that the increase in hardenability by diect-quenching was about by 40%. It was too large to ascribe the increase of hardenability only to the difference of austenite grain sizes in direct-quenching and reheat-quenching.
Some possible mechanisms for these interesting phenomena were discussed.

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© The Iron and Steel Institute of Japan
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