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Defect Control in the Fade-Out Region of Electron Beam Welds

 

Development of Techniques for Defect Control in the Fade-Out Region of Electron Beam Welds in 70mm Thick C-Mn Steel

TWI Industrial Member Report Summary 362/1988

By C S Punshon and B G I Dance

Background

In-vacuum electron beam welding is being used increasingly as an alternative welding process in the heavy fabrication industries where there is a growing demand for improved productivity and weld quality. When conducting circumferential welds, however, some difficulties still exist in terminating welds in thick steel using a beam current fade-out technique, due to the formation of porosity defects and occasionally solidification cracking. The main objectives of the work reported here, which covers part of a continuing research programme, are:

1. To identify some of the factors responsible for fade-out problems, and

2. To develop techniques for improving fadeout quality.

Constant current partial penetration (CCPP) welds and fade-out tests were conducted in 70mm thick C-Mn steel, and the effects of various process variables on weld quality were isolated. Methods were developed by which satisfactory fade-out integrity could be achieved, for this material and thickness.

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