Crack resistance of homogeneous and inhomogeneous butt welded joints

Abstract

We describe the methods used for the evaluation of strength of butt welded joints according to their crack resistance both by the axial tension of small-sized cylindrical specimens with circular cracks and three-point bending of beam specimens with lateral cracks induced in low-or medium-strength surfacings welded into the high-strength bases of these specimens. We perform the comprehensive investigation of the near-weld zone of butt welded joints, where the lowest crack resistance is exhibited by the metal of the zone of fusion and the highest crack resistance is detected for the source material independently of the type of tested specimens. Metals of the weld and the heat-affected zone are characterized by higher values of crack resistance than the zone of fusion and lower values of crack resistance than the source material. By analyzing, as an example, the case of axial tension of a tubular specimen with internal circular crack in the surfacing, we study the crack resistance of seven types of inhomogeneous welded joints depending on the mode of thermal treatment of 35 and St. 3 steels after normalization and 09G2S, 20Kh, and 30KhGSA steels after hardening, medium tempering, and normalization.