Features of the hydrogen distribution in a weld seam made by electron beam welding of titanium alloys

ABSTRACT

This paper presents the research results of the hydrogen distribution in welded joints made by electron beam welding of titanium alloys VT20 and VT23. The distribution of hydrogen in the cross-section of welded joints is measured in the following zones: the weld seam, the heat-affected zone and the base metal by means of through the use of spectral analysis through the use of a low-voltage pulse discharge on an ISP-51 spectrograph. It was found that hydrogen peaks in permanent joints made by electron beam welding, in contrast to argon arc welding, are located not only in the heat-affected zone, but mainly in the central part of the welded joint. Chemical analysis of the permanent joints fractures, investigated through the use of a electron-scan microscope HitachiS-3400N, established that pores in welded joints made by electron beam welding arise as a result of desorption into the melt of capillary-condensed contaminants located in defects at the ends of the edges, due to the occurrence a solid-phase compound in front of a molten bath. It is found that the changes in the hydrogen content with the formation of defects render next influence: temperature conditions for heating of the welded edges, the welding speed and the thickness of the welded blanks.

KEYWORDS:

• Titanium alloys
• electron-beam welding
• hydrogen in welded joints
• pore formation
• capillary-condensed moisture
• fractograms of welded joints fractures
• surface defects of butting edges