| 摘要 |
PURPOSE:To enable the hardening of the inside circumferential wall of a cylindrical body having a closed end face over the entire length thereof by attaching an end cooler to a preceeding heating coil and a succeeding injection ring for cooling fluid. CONSTITUTION:A preceding heating coil C and a succeeding injection pipe J for cooling fluid are advanced into a cylindrical body W having a closed end face, and the heating part is quickly cooled successively from an open end face direction, whereby the cylindrical body is hardened. The forward movement and current application to the coil C are stopped near the closed end face, and the cooling fluid from a supply source T is injected from the axial direction of the coil C through a pipe EJP, an end cooler EJ and a nozzle N toward the inside circumferential direction of the closed end face. The cooling fluid cooling against the inside wall is diffused and streamed in the entire circumferential direction along the inside wall by the injection pressure so that the cooling fluid flows down on the entire inside circumferential wall near the corner part through the clearance between the inside wall and the coil C. A solenoid valve B is closed after a prescribed time to stop supplying the cooling fluid. The part alpha of the inside wall near the closed end face is thus quickly cooled as well and the inside wall is uniformly hardened. |
