| 摘要 |
PURPOSE:To easily form the precipitation hardening layer of Fe3C of superior abrasion resistance on the required portions of parts surfaces by heating the surfaces of cast iron-made parts to a half molten state by a high-frequency induction heating method then quick cooling the same thereby allowing hard Fe3C to precipitate. CONSTITUTION:A machine part 1 made of spheroidal graphite cast iron is fixed onto a truck 2 by jigs 3, 4. A high-frequency coil 6 for heating and a cooling nozzle 7 are disposed along the truck rails 5. The high-frequency coil 6 is set by leaving a gap G of 1-1.5mm. to the surface of the portion to be hardened of the cast iron made part and high-frequency current of about 200kHz is flowed thereto to heat the surface of the portion to be hardened by that induction current to at least >=1153 deg.C, to a half molten state. Thence, the truck is immediately moved on the rails 5 to the position of the cooling nozzle 7, where polyvinyl alcohol 3.5% liquid is injected to quickly cool the molten portion. Extremely hard Fe3C is precipitated by the quick cooling, and this considerably improves abrasion resistance. |
