2相ステンレス鋼の疲労強度について

Abstract

The present work was carried out so as to investigate the change in fatigue strength by pre-working, welding of stainless steel which has two phases, austenite and ferrite. The fatigue test was done by pulsating tension and the structural changes associated with the fatigue were also examined by means of X-ray, electron-microscopy and EPMA.The results obtained are summarized as follows:(1) The fatigue strength of austenitic-ferritic stainless steel was considerably stronger than that of austenitic stainless steel and that a difinite fatigue limit was obtained similary with carbon steel by means of age-hardening of ferrite during the fatigue test. The influence of martensitic transformation by pre-working on the fatigue strength was negligibly small.(2) In the γ-phase Cr was lower than Ni, while in the α-phase Ni was rather lower. The variation of composition by welding was considerably violent in the heat affected zone.(3) This alloy was not sensitive to a mechanical or welding notch. The decrease of fatigue strength was due largely to the change of composition and structure by welding heat.(4) The change of fatigue strength of this alloy was little by welding. Moreover the solution-treatment temperature of about 1100°C after welding was deemed adequate.(5) As stainless steel with two phases was relatively unstable in structure, a complicated striation pattern was obseved in the fatigue fractured surface.