| 摘要 |
PROBLEM TO BE SOLVED: To prevent decrease in hardness of a polar surface layer, in a quenched hollow power transmission shaft. SOLUTION: In the hollow power transmission shaft 1, almost all area L in an axial direction is subjected to high frequency quenching for forming a hardened layer S. Amount of decrease in hardness of the polar surface part Sf with respect to the maximum hardness is set to beΔHv50 or less. A coolant is supplied to an outer circumferential surface 1g of hollow power transmission shaft material so that a cooling rate by the coolant is 130°C/sec. COPYRIGHT: (C)2006,JPO&NCIPI
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