Howse, D. S. (2002) Improved productivity in fusion welding : executive summary. EngD thesis, University of Warwick.

PDF WRAP_THESIS_Howse_2002.pdf - Requires a PDF viewer. Download (8Mb)

Request Changes to record.

Abstract

This document is an Executive Summary of individual submissions of work that the
author has submitted towards the degree of Engineering Doctorate. The work
comprises three main themes, which can be demonstrated in a broader sense as
contributing towards improved productivity in fusion welding:
i) The use of active fluxes for Tungsten Inert Gas (TIG) welding.
ii) An investigation into the reduction of porosity when Metal Active Gas (MAG)
welding galvanneal coated steel sheet used in the automotive industry.
iii) The use of high power Nd:YAG laser welding for the production of large
diameter, long distance land pipelines.
Active fluxes give improved productivity by increasing the penetration depth of the
TIG welding process by the simple addition of a flux applied to the surface.
Although the productivity benefits of the process had been proven through a joint
TWIIindustry project, the mechanism by which the fluxes produced this
improvement was not fully understood. The first theme investigated the mechanisms
at work in providing increased penetration and concluded that the primary
mechanism responsible for the action of the fluxes was not due to a change in the
flow of the molten pool but, as others had suggested, due to arc constriction. This
work contributed to a greater understanding of the welding process and,
furthermore, a greater understanding of the potential opportunities and limitations of
the process when designing new fluxes for other alloy systems.
MAG welds in coated steel sheet used in the automotive industry are prone to
porosity leading to high reject rates. The second phase of work reported here
determined welding procedures capable of delivering low porosity welds developed
through statistical experimental design. These procedures demonstrated how low
porosity welds could be made using conventional MAG welding techniques on
steels that had been galvanneal coated to provide corrosion resistance. The
procedures developed could be easily implemented at high production rates in an
industrial manufacturing environment to reduce defect levels, and thus costly repairs
or high scrap rates.
The third theme of the work demonstrated how Nd:YAG laser welding could
potentially be used to replace conventional arc welding techniques for land lay of
gas transmission pipelines. The application of a single laser fill pass, made at high
production rates, could replace the use of multiple MAG welding stations greatly
reducing the costs associated with pipeline fabrication. BP has claimed that half
pipeline cost savings of up to $300 million dollars are achievable through the
implementation of such a technique. The justification for the use of lasers in
pipelines is discussed in terms of both technical and economic suitability.
Preliminary experimental work showed that high power Nd:YAG laser welds could
achieve productivity targets, although in order to reduce defects and achieve the
necessary structural performance it would be necessary to combine laser welding
with a MAG welding process.

Item Type:	Thesis (EngD)
Subjects:	T Technology > TS Manufactures
Library of Congress Subject Headings (LCSH):	Gas metal arc welding, Flux (Metallurgy), Gas tungsten arc welding, Laser welding
Official Date:	November 2002
Dates:	Date Event November 2002 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	EngD
Status:	Not Peer Reviewed
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Barnes, Stuart ; Lucas, W.
Sponsors:	CRC Evans International ; British Petroleum Company
Extent:	xi, 74 p.
Language:	eng

Request changes or add full text files to a record

Repository staff actions (login required)

View Item

Downloads