Abstract
Shrinkage deformation based on the upsetting mechanism can be generated by laser irradiation of the pipe periphery. Here, step forming based on shrinkage deformation was performed. CO2 laser beams with a beam diameter of about 1.7 mm, laser power of 400 W, duty factor (DF) of 50%, and traveling speed of 1.0 m/min were applied to 304 grade stainless steel pipe with a diameter of 25 mm and wall thickness of 0.5 mm. When the laser beam was irradiated along a length of 20 mm from 5 mm inside the edge in the direction of the axis around the periphery of the pipe, step-like deformation can be generated over a length of 10 mm in the center portion. The diameter shrinkage was about 0.85 mm, and its ratio to the base material outer diameter was about 3%. Furthermore, correction of the partial roundness of a pipe with a wall thickness of 1 mm was attempted. The laser was used to irradiate the pipes along a straight line axially with DF=25%, v=1.6 m/min at the convex location. When the irradiation was repeated 4 times, the roundness of 29μm was improved to 10μm.
