| 摘要 |
To provide a metallic material, in particular, brass, which is excellent in mechanical strength, cutting performance, ductility in hot working, and anticorrosion. Brass according to the invention is roughly classified into four types including ".alpha. + .gamma.", ".alpha. + .beta. + .gamma.", ".alpha. + normal .beta." and ".alpha. + reinforced .beta.". Brass of .alpha. + .gamma. type is .alpha. + .gamma. at room temperature, and its .alpha. phase has an area ratio of 97 to 70 %. Brass of .alpha. + .beta. + .gamma. type is .alpha. + .beta. + .gamma. at room temperature, and its .beta. phase and .gamma. phase, respectively, have area ratios of 3 to 30 %. In these two types, the .gamma. phase contains 8 wt.% Sn or more. Brass of .alpha. + normal .beta. type is .alpha. + .beta. at room temperature, and its .beta. phase has an area ratio of 20 % or more. Brass of .alpha. + reinforced .beta. type is .alpha. + .beta. at room temperature, and its .beta. phase has an area ratio of 15 % or more, and its .beta. phase contains 1.5 wt.% Sn or more. Brasses of all the types are .alpha. + .beta. in recrystallization temperature region, and their .beta. phases have area ratios of 30 to 80 %. Average crystal grain sizes of .alpha. and .beta. are 15 .mu.m or less, and preferably 10 .mu.m or less. An average crystal grain of .gamma. has an average minor axis of 8 .mu.m or less, and preferably 5 .mu.m or less. Brasses of .alpha. + .gamma. and .alpha. + .gamma. + .beta. have an apparent Zn content of 37 to 46 wt.%, and an entire Sn content of 0.9 to 7 wt.%. Brasses of the other two types have an apparent Zn content of 37 to 44 wt.%.
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