Effect of the Loading Time for Stress Aging Treatment
1969 Volume 18 Issue 188 Pages 379-384
Details
1969 Volume 18 Issue 188 Pages 379-384
Various investigations have hitherto been reported of stress aging treatment, but they have been confined to its effect on the mechanical properties of the material, and to its effect on the fatigue limit of the material but little attention has so far been paid. The measurement of fatigue limit was performed therefore of austenitic and precipitation hardening stainless steels at the intervals respectively of 15min, 30min and 60min of loading and stress aging at 375C.
The tensile stress 26.9kg/mm2 was given to the stress aging of austenitic stainless steel, and 52.0kg/mm2 to that of precipitation hardening stainless steel, which corresponded respectively to 130% and 60% of 0.2% yield stress.
The fatigue test was carried out at room temperature by means of Ono type rotary bending fatigue testing machine (3400rpm).
The results obtained are outlined below.
(1) In austenitic stainless steel the progression rate of its loading time 15min, 30mm and 60mm showed increase in percentage 17, 30 and 33 of the fatigue limit of the specimen only subjected to solution treatment.
(2) The fatigue limits of precipitation hardening stainless steel showed an increase of 7, 6 and 12% the value of the specimen subjected to only solution treatment.
(3) With increse in the loading time there is less difference between the time strength(2×105) and the fatigue limit (107).
(4) The treatment of stress aging at stress level higher than 0.2% yield stress is considerably effective in a short time, but for the treatment of stress aging at stress level lower than 0.2% yield stress a longer time is necessary in order to be effective.
(5) In spite of the fact that the time required for stress aging is subject to variation, there is no variation of the tensile strength of austenitic stainless steel subjected to stress aging, nor of its 0.2% yield stress. Though there is a little decrease in the tensile strength of precipitation hardening stainless steel, there is no variation in its 0.2% yield stress.
