Mn-Cr-Bばね鋼の機械的性質および疲労強度に及ぼす連続冷却加工熱処理の影響

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タイトル別名
  • On the Mechanical Properties and Fatigue Strength of Mn-Cr-B Spring Steel in Consequence of its Thermomechanical Treatment by Gradually Cooling It
  • Mn-Cr-Bバネ コウ ノ キカイテキ セイシツ オヨビ ヒロウ キョウド ニ オヨボス レンゾク レイキャク カコウ ネツ ショリ ノ エイキョウ

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説明

In this study an experiment is reported of subjecting Mn-Cr-B spring steel to thermomechanical treatment by gradually cooling the material. The steel was first austenitized at 850°C, which temperature was gradually lowered to 620°∼720°C. At these lowered degrees of temperature the steel was reduced in thickness, and there was its 50% plastic deformation. Then the steel was tempered at 480°C for an hour. Then the steel was tested respecting its mechanical properties by submitting the material to tension test, hardness test and fatigue test. The chief results obtained are as follows.<br>(1) By this thermomechanical treatment about 13∼48% improvement in yield strength has been realized, keeping up higher rate of improvement than in tensile strength. The elongation is above 10%.<br>(2) This thermomechanical treatment of the steel, while it makes no difference to the relationship between its strength and ductility, improves the relationship between the tensle strength of the material and its yield ratio, i. e. given the tensile strength of the material as balanced in both the kinds of treatment, its yield strength is higher in the thermomechanical treatment than in the conventional.<br>(3) This thermomechanical treatment of the steel has raised its fatigue limit to approximately 15∼34%, or 0.2∼0.5kg/mm2 rise per 1% reduction over the fatigue limit of the steel treated by the conventional process.<br>(4) This thermomechanical treatment of the steel at 650°∼720°C has prolonged its fatigue life about 7∼60 times as long as the steel in its pre-treatment state.<br>(5) Developing pearlite in austenite, while it scarcely affects the mechanical properties of the steel, does greatly affect its fatigue life over the amplitude of high stress. For processing the ausform of spring steel, therefore, it recommended that the temperature for the treatment will be raised to over 650°C.

収録刊行物

  • 材料

    材料 20 (216), 1024-1030, 1971

    公益社団法人 日本材料学会

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