| 摘要 |
PURPOSE:To form a quench-hardened layer continuous to the surface layer of a tooth part by conducting high frequency electric current to the surface of a tooth profile from one end to the other end of the tooth part to raise the temp. up to prescribed temp. then cooling said part. CONSTITUTION:The tooth part L of a rack shaft W and the plane part 5 of a hardening device A are placed to face each other. The valley parts v', v'' at both terminals of the part L are inserted onto the leading ends of contactors 4a, 4b, and the contactors 4a, 4b are inserted and held in the parts v', v'' with a pressing mechanism 7, whereby a closed circuit is formed. When electric current is flowed to the closed circuit by turning a high frequency electric power source E on, the high frequency electric current flows through the surface layer of the member; at the same time, the surface layer of the part L evolves heat only in the surface layer part of the tooth profile G by the effect of the magnetic lines of force from the conductors 1a, 1b, thereby attaining the prescribed hardening temp. in a short time. At this time, the power source E is turned off and immediately cooling fluid is supplied to the hollow parts of the conductors 1a, 1b through pipes 6, and is injected through the injector holes provided in the plane part 5, whereby the surface of the tooth part L is cooled quickly. |
