| 摘要 |
PROBLEM TO BE SOLVED: To prolong the service life of a steel rod in the case of being used for a rock drill by executing carburizing and quenching/tempering, thereafter applying induction hardening to a bit fitting part and subsequently executing tempering at a specified temp. SOLUTION: A holow steel rod material is subjected to carburizing treatment over the whole length, is thereafter quenched and is tempered at 150 to 250 deg.C. The carburizing and quenching are executed under ordinary conditions. By this heat treatment, high hardness and wear resistance are imparted to the surface layer part of a hollow steel rod 1, and tenacity is imparted to the inside. Next, for improving the fatigue strength of a bit fitting part 3, the part is subjected to induction hardening and tempering. As to the induction hardening, heating is executed at least till an austenitic layer is formed in the carburizing layer in the heated part. Then, tempering is executed at 150 to 250 deg.C. The tempering may be executed to the whole of the hollow steel rod 1 or only to the induction hardened part.
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