逐次オーステンパ処理球状黒鉛鋳鉄のころがり疲労強度 [in Japanese] Rolling Contact Fatigue Strength of Successive Austempered Ductile Cast Iron [in Japanese]
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Successive austempering process, in which upper bainite transformation was immediately followed by lower bainite transformation, remarkably improved the machinability of ADI without impairing the tensile properties. In this paper, the rolling contact fatigue strength (<i><b>F</b></i><sup>∗</sup>) of successive austempered ductile iron (SADI) was investigated by using a Nishihara-type wear test machine with a gear oil lubricant. The ductile iron containing 3.52 % C, 2.07% Si. 0.24 % Mn and 0.04 % Mg was austempered at 648 K for 1.8ks and then austempered at 588 K for 0.9 to 18 ks. The amount of γ-pool decreased from 6.52 % to 0.19% with increasing the holding time at 588 K. The <i><b>F</b></i><sup>∗</sup> value decreased with the progress of lower bainite transformation until 9 ks, however that of the iron held for 18 ks exhibited a higher <i><b>F</b></i><sup>∗</sup>. Although this <i><b>F</b></i><sup>∗</sup> value is still 30 MPa smaller than that of ordinary ADI austempered at 648 K for 7.2 ks, the machinability of the SADI was considerably higher. This indicates that, the SADI can be provided with a good combination of superior machinability and higher rolling contact fatigue strength.
- THE JOURNAL OF THE JAPAN FOUNDRYMEN'S SOCIETY
THE JOURNAL OF THE JAPAN FOUNDRYMEN'S SOCIETY 70(4), 260-265, 1998-04
Japan Foundry Engineering Society