| 摘要 |
PROBLEM TO BE SOLVED: To obtain an excellent press-formability capable of improving sliding characteristics by preparing a galvannealed steel sheet, on which a galvannealed uppermost layer composed ofζphase and a lower layer composed ofδ1 phase are formed and in which an X-ray diffraction peak ratio of theζphase to theδ1 phase is in a specified range and a lubricant containing one or more kinds of extreme- pressure additives, such as a P base one, an S base one, is applied. SOLUTION: The galvannealed steel sheet, on which the galvannealed uppermost layer composed of theζphase and the lower layer composed of theδ1 phase are formed and in which the X-ray diffraction peak ratioζ/δ1 of theζphase to theδ1 phase is 0.01-0.25 and the lubricant containing one or more kinds of the extreme- pressure additives, such as P base one, S base one, is applied is prepared. Consequently, such a galvannealed coating structure that the uppermost surface material isζphase during a time when the lubricant exists between the material and a jig at the starting time of press-formation, and theδ1 phase is appeared on the uppermost surface layer from the point of time when theζphase is worn according to the decrease of the lubricant by sliding and the lubricant is eliminated, can be obtd. Thus, the galvannealed steel sheet having excellent sliding characteristics, is obtd.
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