改良オースフォーム処理を施した1800MPa級ばね鋼の長寿命疲労特性

概要

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High-cycle fatigue properties up to 10^8 cycles were investigated for a modified-ausformed spring steel SUP 12 with the tensile strength δ_B=1772 MPa. The surface-type fracture occurred at the higher stress level. On the hand, some specimens had the fish-eye-type fracture origin at the inclusion, and others endured 108 cycling at the lower stress level. The fatigue limit at 10^8 cycles δw=900 MPa for the fish-eye fracture was higher than δ=886 MPa estimated from δ_w=0.5δ_B, which is the empirical equation for the surface-type fracture of ordinary quenched and tempered low alloy steels. The optically dark area was not found around the inclusion. Excluding the fish-eye-type fracture, the higher fatigue limit δ_w=1090 MPa for the surface-type fracture was expected. It corresponds to δ_W=0.62δ_B. It is concluded from these results that the modified-ausforming improves the fatigue properties for both surface and fish-eye type fractures of the high strength steel.
社団法人日本機械学会の論文
2002-01-25