Study on porosity formation in the keyhole mode electron beam full-penetration welding of titanium alloys

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Colleges, School and Institutes

External organisations

  • Rolls Royce PLC

Abstract

Porosity formation during electron beam (KB) welding of titanium alloys needs to be better understood, particularly to minimise occurrence of porosity and to provide guidance for welding process optimisation. Porosity formation in KB welding of a titanium alloy is investigated under key- liole and fully penetrating conditions. Characterisation is carried out using high resolution X-Ray tomography, residual gas analysis, and metallographic sectioning; this confirms that porosity formation is associated with gas evolution, especially hydrogen. To investigate the effect of hydrogen on porosity formation and confirm whether hydrogen is the root cause for porosity formation, TH5A1-4V samples are electrochemically charged to achieve different hydrogen levels prior to welding. The results confirm that porosity can be suppressed even at every high hydrogen levels when welding is carried out with optimised EB parameters and perfect joint alignment ;on the other hand, porosity is exacerbated when a Small beam offset (BOF) is employed This is because any BOF alters the size of the liquid zone at the melting front, where joint edges are melted. Thus the thickness of the liquid film at the melting front is crucial for bubble nucleation and their survival in the weld pool. It would appear that the nucleation rate in the liquid zone at the melting front determines the likeliliood of porosity occurrence. This suggests that BOF is likely to be one factor influencing porosity formation in these circumstances. This work provides insights into the mechanism of porosity formation during the welding of titanium alloys and guidance to aid in its elimination.

Details

Original languageEnglish
Title of host publicationTi 2011 - Proceedings of the 12th World Conference on Titanium
Publication statusPublished - 1 Dec 2012
Event12th World Conference on Titanium, Ti 2011 - Beijing, China
Duration: 19 Jun 201124 Jun 2011

Publication series

NameTi 2011 - Proceedings of the 12th World Conference on Titanium
Volume2

Conference

Conference12th World Conference on Titanium, Ti 2011
CountryChina
CityBeijing
Period19/06/1124/06/11

Keywords

  • Elect ran beam welding, Keyhole, Titanium alloys, Welding porosity

ASJC Scopus subject areas