Abstract
Low cycle fatigue tests of the dissimilar metal electron beam welded joints between A387, Gr. 22 steel and SUS 405 steel (A387-SUS 405), and between A387, Gr. 22 steel and SUS 316 steel (A387-SUS 316) were carried out under the strain controlled cycling over the welded joints at a temperature of 839K. It was shown that the fatigue lives of the dissimilar metal welded joints were significantly shorter than those of base metals. In order to discuss the fatigue fracture behavior, the distribution of local strain and that of hardness were investigated. In A387-SUS 405, the strain concentration occurred on SUS 405 side during all strain cycling. While in A387-SUS 316, the uniform strain distribution was produced at the early stage of strain cycling, and thereafter the strain concentration occurred on A387 side. The change of strain distribution with strain cycling qualitatively corresponded to that of hardness. From the foregoing results, it was concluded that the shorter fatigue lives of the dissimilar metal welded joints resulted from the strain concentration which occurred on the base metal with lower deformation resistance.
