| 摘要 |
PURPOSE:To remove austenite in carburized surface layer of steel material, by performing induction hardening or flame hardening of the steel material after it has been subjected to carburizing hardening and tempering according to prescribed specification. CONSTITUTION:Steel for carburization is subjected to carburizing hardening and tempering to 0.5-0.8mm. carburizing depth and HRC60+ or -3 hardness, then it is induction hardened in order to remove residual austenite. For example, steel material is gas carburized in C3H8 atmosphere gas at 910-920 deg.C carburising temp. for 2hr 15min-2hr 30min, and is kept at 850-860 deg.C temp. for 15min. Subsequently it is dip quenched with quenching oil at 70-170 deg.C temp., and heated at 170-180 deg.C temp. for 2hr, and is tempered by air cooling. Hereby the steel material attains HRC 58-60 hardness and 0.6-0.7mm. effective carburized depth. In addition, the steel material is induction hardened for 5-15sec quenching time by a high frequency generator of 40kW capacity and 10-30kc frequency, then it is cooled with water mixed with 10-30% preventing agent for quenching crack. Hereby its hardness is increased by HRC4-5 hardness, and the austenite in the surface layer is transformed to martensite. |
