The present study was carried out on the variation of the fatigue strength and the mechanical properties (tensile strength, yield strength, spring limit, elongation, hardness, and number of torsion) due to cold drawing and annealing for the specimens of 18-8 stainless steel wire. The specimens were cold drawn and straightened again into 2m/mφ, and Haigh Robertson testing machines were uesed in the fatigue test.
The followings are the results obtained:
(1) The fatigue strength of 18-8 stainless steel wire shows the highest value, namely, about 60kg/mm2 in case of 80% reduction factor. When reduced more severely, the value may be lowered.
(2) The fatigue strength of the specimens with low annealing (250°C-600°C×1/2h) may be reduced much more than that of just as cold drawn.
(3) The value of tensile strength and hardness may be increased rapidly due to cold working, but the value of spring limit and yield strength may not be increased greatly. However, considering the effects of low annealing temperature from the standpoint of these characteristics, a considerable increase may be recognized between 350°C and 450°C. Consequently, it is hard to estimate the fatigue strength of 18-8 stainless steel wire from the other characteristics such as the values of hardness, spring limit, yield strength, and tensile strength.