| 摘要 |
PURPOSE:To increase growing rate of nitriding layer and to increase the thickness of nitride layer, by heating iron base material, the surface of which having been washed with rust-preventive washing fluid, to form oxide coating on the surface thereof, then by soft-nitriding the surface. CONSTITUTION:The surface of iron-base material is washed with mineral oil base, emulsion tyPe rust-preventive fluid, then heated at 450-550 deg.C for 1-2min. to form iron oxide coating on the surface thereof. The mineral oil base, emulsion type washing fluid is burned and removed completely during heating. The iron base material having oxide coating is inserted in a soft-nitriding furance, where it is soft-nitrided at, e.g., 570 deg.C in the presence of nitriding gas contg. NH3 gas. This nitriding treatment permits to increase the thickness of soft-nitrided layer about 30% compared with onventional method in the same soft-nitriding time because the material is preliminarily oxidized before the soft-nitriding treatment. |
