| 摘要 |
PURPOSE:To prevent the formation of unequally carburized grain sizes and uneven carburization on the surface of a metallic material after treatment by heating the matallic material of temp. slightly lower than the prescribed carburization temp. quickly to the prescribed carburization temp. by gaseous plasma and shorting the time for the high temp. state in a carburization period. CONSTITUTION:The inside of a carburizing furnace in which the metallic material is positioned is evacuated 14 to a prescribed reduced pressure atmosphere 32. On the other hand, the above-described metallic material is heated 22 to temp. slightly lower than the prescribed carburization temp. by an electric resistance method. Thereafter, an inert gas and a carburizable gas as gaseous plasma are injected to the metallic material to heat 91 the metallic material quickly and uniformly to a prescribed carburization temp. 42. Here the temp. in the furnace decreases 82 gradually while the pressure in the furnace rises, and in this state the 1st carburization period 63 for a prescribed time is elapsed, then the remaining gas in the furnace is discharged 15. Again the material is subjected similarly to ejection 2 of gaseous plasma, quick and uniform heating 92, a prescribed carburization temp. 43, cooling 83, the 2nd carburization period 64 and evacuation 16, and while the temp. in the furnace is kept reduced 84, the material is subjected to, for example, hardening, etc. after a diffusion period 73. |
