ばね鋼の結晶粒度と低温焼鈍と疲労強度に関する共同研究報告

抄録

Refining the grain size improves the strength of steel. This fact is well known, but the effect on the spring fatigue strength and the amount of spring relaxation is unclear. This study investigated the effect of grain size and annealing temperature on fatigue properties and resistance on relaxation of spring that can be manufactured within the normal manufacturing conditions using SWOSC-V oil-tempered wire. As a result, the fatigue life was improved by the refinement of the grain size, but not improved by lowing the low-temperature annealing temperature. Although an increase in yield strength was expected in both cases, this was thought to be because the increase in yield strength due to the refinement of the grains was greater than the increase in yield strength at the low-temperature annealing temperature. On the other hand, refining grain size and lowing the low-temperature annealing temperature reduced the amount of spring relaxation in room temperature when the effect of constant stress setting was taken into account. In both cases, this was thought to be caused by an increase of yield strength and hardness.