Notch Toughness Evaluation of HT80 Electron Beam Weld Metal by Charpy Test

Abstract

Electron beam welded joints of structural steels have occasionally remarkable mechanical heterogeneity because the electron beam welding is a high energy density welding process. Fracture toughness evaluation is considerably affected by the local mechanical heterogeneity, in paticular the use of V-notch charpy test brings a difficult problem such as missing of fracture path from the net section. In the present paper, Charpy impact tests have been carried out of the electron beam welded joints of HT80 steel. The elastoplastic calculations based on FEM analysis have been conducted for considering the significance of absorbed energy of Charpy test, and Charpy tests of specimen with both-side deep groove also have been done in order to clarify how to use Charpy impact tests for evaluating fracture transition behaviors of electron beam welds.
The absorbed energy of the V-notch Charpy specimen of electron beam welds is not necessarily a proper measure due to the existence of locally mechanical heterogeneity. In the Charpy test of specimen with both-side deep groove, fracture propagates straightly along net section and the transition temperature obtained in that test is useful index to evaluate the fracture transition behavior of electron beam welds. By using the evaluation method proposed in the present paper, the fracture toughness of weld metal of electron beam welded joint depends upon the heat input of electron beam welding, that is the width of weld metal. The weld metal of welded joint with lower heat input occasionally has a sufficient toughness as same as the base metal, although hardness of weld metal is considerably higher than that of base metal.