PRODUCTION OF THICK WALLED HOLLOW SPHERICAL SHELL

摘要

PURPOSE:To obtain a thick walled hollow spherical shell having high weld strength by forming a notched annular groove on the outer side in the outside opening edge part of each semispherical shell which is formed by drawing and bulging a projecting part to the inside then subjecting the two semispherical shells to butt welding. CONSTITUTION:A thick walled metallic plate of a circular shape is drawn to a semispherical shell shape having a projected opening edge surface 1a and a notched annular groove 2 is formed on the outer side in an opening edge part 1b. Such shell 1 is fitted in a receiving die 3, and the inside part in the opening edge part projecting from the die 3 is compressed with a plunger die 4 to form a regular semispherical shell 5; at the same time, the compressed part is bulged to the inside surface of the opening edge part 5b to form a bulging projection 5c. Two pieces of such regular semispherical shells 5 are butted and the butt joint part 6 is welded. The butt joint part 6 is polished after welding, whereby the thick walled hollow spherical shell which is a regular spherical shell is formed.