Patent ID: 7399372
Filing Date: 2008-07-15
Classification: C21D,F15B,F16J

Abstract:
1. A method for manufacturing metallic bellows, comprising steps of: cold rolling a pipe constructed such that both edges of a plate composed of precipitation hardening stainless steel are connected to each other by welding; fining an average grain size of the precipitation hardening stainless steel to 10 to 15 μm by annealing; forming the pipe into a bellows having an axial direction; precipitation age hardening heat treating on the bellows; setting the bellows by tensile loading or compressive loading in the axial direction of the bellows, so that the bellows has a predetermined height with no load; and providing compressive residual stress of not less than 500 MPa to an inside face or an outside face of the bellows by surface working, wherein in the precipitation age hardening heat treating, the bellows is hardened, thereby having a hardness of 450 to 600 Hv at a thickness direction center portion of a ridge portion and having a hardness of 250 to 450 Hv at a thickness direction center portion of a valley portion.