| 摘要 |
PURPOSE:To obtain the titled rod in which breaking loss is decreased to the min., by heat treating the collar part of rod, then high frequency heat treating the shank side and stem side separately or simultaneously to cause hardness difference corresponding to difference of striking stress between prescribed positions in rod. CONSTITUTION:Hollow steel alloy is forged by e.g. hot upset forging, then whole of the body is quenched and temper treated, to manufacture lenthened product having the collar part 3 and 40-45 hardness over the whole. Next a shank part 1 and a stem part 4, and a root part A of the part 3, a root part B at shank side in rod prepared in such a way are heat treated by high frequency heating apparatus. By such split heat treatments, the titled rod having different HRC hardness at the vicinity of the part 3 is obtd. Namely, by causing hardness difference corresponding to striking stress difference between prescribed positions of rod, the breakage loss of rod can be decreased to the min.
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