Effects of Microstructure, Composition, and Strength on the Strength-Differential Phenomenon Observed in HY-80 Steel.
NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BETHESDA MD
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Steel from 22 heats of low-carbon Ni-Cr-Mo steel MIL-S-16216G and ASTM A543-65 were heat treated to study the effects on the strength-differential effect and the difference between tensile and compressive yield strength of 1 commercial variation in composition and inclusion content, 2 variation in microstructure such as prior austenitic grain size and the relative amount of isothermally produced ferrite or bainite in a tempered martensitic matrix, and 3 the observed variation in strength obtained after a 1-hour 1150 F temper followed by a water quench to prevent embrittlement while cooling from the temperating temperature. The difference between the tensile and compressive yield strength, sometimes called the strength differential S-D effect, was observed in this study to be at least 5 percent of the tensile yield strength. Data are cited to show that in the low-carbon Ni-Cr-Mo steels studied here, the S-D effect observed was a relatively constant percent of the tensile yield strength, and was markedly structure-sensitive to prior austenitic grain size, microstructural constituents, tempering temperature, type and distribution of carbides formed during tempering, and tempering slightly above the lower critical temperature. Author
- Properties of Metals and Alloys