| 摘要 |
PURPOSE:To perform stably local hardening of a turbine blade consisting of a base metl which is an alloy steel having small tensile stress by a simple method by immersing partly the non-hardening part of said turbine blade into water and preheating the boundary part between the hardening part and the immersed part to a prescribed temp. then heating the hardening part to a hardening temp. CONSTITUTION:The front edge 3 of the turbine blade 1 is held horizontal and part of the non-hardening part 2a under the hardening part 2 is immersed in the water 11. The water in a water tank 10 is then circulated 13 and the boundary part 31 between the part 2 and the immersed part, i.e., the part 2a is preheated to 300-400 deg.C by plural pieces of auxiliary burners 32. A main burner pipe 5 is then moved from one end toward the other end of the part 2 and while the flame of the burner 32 is successively shut off, the part 2 is successively heated to 900-1,000 deg.C by the flame of the main burner pipe 5. When the flame of the pipe 5 passes by, the part 2 is deprived of heat by the water in the tank 10 and is thereby hardened. The hardened part 2 having hardening hardness of about 450-500 Vickers hardness and small residual tensile stress is tably obtd. |
