Steel for gear, gear superior in strength of tooth surface and method for producing same

• Main Authors: YOSHIDA; MAKOTO, HATANO; ATSUMI, NAKAMURA; SADAYUKI, OKADA; YOSHIO, MATSUMOTO; TAKASHI
• Format: Patent
• Language: English
• Published: 21.01.1997
• Edition: 6
• Subjects: ALLOYS; BLASTING; CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; ENGINEERING ELEMENTS AND UNITS; FERROUS OR NON-FERROUS ALLOYS; GEARING; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVEFUNCTIONING OF MACHINES OR INSTALLATIONS; HEATING; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; LIGHTING; MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES,RIVETS, BOLTS OR WHEELS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; MECHANICAL ENGINEERING; MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVINGMATERIAL; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; PERFORMING OPERATIONS; PUNCHING METAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; THERMAL INSULATION IN GENERAL; TRANSPORTING; TREATMENT OF ALLOYS OR NON-FERROUS METALS; WEAPONS

A steel for gears consists essentially of 0.10-0.30 wt % of C, not more than 1.0 wt % of Si, not more than 1.0 wt % of Mn, 1.50-5.0 wt % of Cr, and balance including iron and impurity. A gear made by the steel forms a hardened surface layer by carbonizing-hardening-tempering or carbonitriding-hardening-tempering. The amount of C at the hardened surface layer is within a range 0.7 to 1.3 wt %, and the amounts of C, Si and Cr satisfies a relationship 5.5<3xC (wt %)+5.2xSi (wt %)+Cr (wt %). Therefore, the gear performs superior pitting-resistance and wear-resistance.