| 摘要 |
PROBLEM TO BE SOLVED: To provide excellent sliding characteristic by specifying the diameters of minor axes of cementite in ferrite grains containing specific amounts of C and having cementite in a specific area ratio, depending on aspect ratio. SOLUTION: A steel plate, in which the diameters of minor axes of cementite in the ferrite grain containing 0.05-0.8 wt.% C and having >=10% cementite by area ratio are regulated to >=300 nm in the case of <1.5 aspect ratio and to >=200 nm in the case of >=1.5 aspect ratio, is manufactured. This steel plate has a chemical composition consisting of, other than C, <=1%, by weight, Si, 0.1-2% Mn, <=0.2% P, <=0.05% S, 0.01-0.1%; sol.Al, <=0.05% N, and the balance Fe with inevitable impurities. By this method, the occurrence of structural change and quality deterioration due to abrupt thermal change can be prevented, and the steel plate useful for parts for machine structural use, such as gear and plate used as automobile transmission parts, can be obtained.
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