Abstract
It has been noticed that a metal bellows made of high strength SUS631 reveals low fatigue life. On the other hand the author has been successful improving fatigue strength of SUS304 metal bellows by reflected shot peening method and improved tempering process to decrease the grain diameter. In this study, the experiment to improve fatigue strength of SUS631 bellows was studied. Grain diameter was adjusted by changing BA temperature after cold working. The hardness was increased by ageing treatment after bellows forming. Lastly shot peening was carried out using reflection plate. Grain diameter tends to decrease in proportion with decreasing BA temperature, and minimum grain diameter was 12μm. The optimum shot peening condition was found where the pressure is 0.3MPa and the glass beads size is 97μm. Fatigue limit of 107 cycles of SUS63l bellows was improved by 17% from SUS304 bellows when the optimum condition is applied.
