SHOT-PEENING METHOD FOR FORMING GEAR EXCELLENT IN ABRASION RESISTANCE AND PITCHING STRENGTH

• Main Authors: UMEMORI NAOKI, ISHIKURA RYOHEI
• Format: Patent
• Language: English; Japanese
• Published: 13.11.2014
• Subjects: ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL; 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; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; GRINDING; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; MACHINE TOOLS; MAKING GEARS OR TOOTHED RACKS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METAL-WORKING NOT OTHERWISE PROVIDED FOR; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; PERFORMING OPERATIONS; POLISHING; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; TRANSPORTING

PROBLEM TO BE SOLVED: To provide a shot-peening method by which tooth surface fatigue strength of a gear can be excellently improved.SOLUTION: In the shot-peening method of the present invention, two-stage shot-peening is performed for projecting on the gear after being subjected to carburization treatment by using a grit having a hardness of 700HV or more under a condition of shot air pressure of 0.2-0.6 MPa. In the first stage, the grit having a particle size within the range of 0.3-1.0 mm is used and in the second stage, the grit having a particle size within the range of 0.05-0.2 mm is used. As a result, maximum compressive residual stress up to a depth position of 30 μm from a surface layer of a tooth surface of the gear is set to 1,500 MPa or more, compressive residual stress up to a depth position of 75 μm from the surface layer of the tooth surface is set to 600 MPa or more, and surface roughness Ra of the tooth surface is also set to 0.8 μm or less. 【課題】歯車の歯面疲労強度を良好に向上させ得るショットピーニング方法を提供する。【解決手段】本発明のショットピーニング方法では、７００ＨＶ以上の硬さの投射材を、投射エア圧力０．２〜０．６ＭＰａの条件下で、１段目の投射材の粒径としてφ０．３〜１．０ｍｍの範囲内のものを用い、２段目の投射材の粒径としてφ０．０５〜０．２ｍｍの範囲内のものを用いて浸炭処理後の歯車に投射する２段ショットピーニングを行うことにより、歯車の歯面の表層から３０μｍ深さ位置までの最大圧縮残留応力が１５００ＭＰａ以上、歯面の表層から７５μｍ深さ位置での圧縮残留応力が６００ＭＰａ以上、かつ歯面の表面粗さＲａが０．８μｍ以下に設定される。【選択図】図３