Staff of the NZ Welding Centre (NZWC) presented five conference papers in the Stainless Steel and Productivity sessions. Presentations covered various aspects of welding technology such as productivity, fatigue design, welding cost, technical standards, quality management, stainless steel metallurgy and corrosion aspects.
In the presentation entitled Corrosion Performance of Alternative Stainless Steel Grades, NZWC Manager Dr Michail Karpenko reported on preliminary results of the research project that has been conducted in cooperation with New Zealand Stainless Steel Development Association (NZSSDA) and international research partners. The project aim was to identify weldability aspects and corrosion performance of some new ferritic, manganese bearing austenitic and duplex stainless steels.
The paper discussed results of 24-months atmospheric exposure test conducted on steel grades 304, 316, 430, J4, 404GP, 445M2 and LDX 2101 in welded conditions and different finishes ranking relative performance of individual grades. The feedback from the audience indicated that the project results are of great interest to the NZ stainless steel industry and more research is needed to validate some of the observations made. HERA, in cooperation with NZSSDA, will continue working on this interesting project. Dr Karpenko’s second paper was entitled Recent Proposed Changes to the Stainless Steel Welding Standard AS/NZS 1554.6. The paper reported in-depth on some key upcoming changes to the standard.
The NZWC, in close cooperation with the NZSSDA and a group of overseas experts, has significantly contributed to the standard review with the outcome that the draft for public comments was published in early April 2011. The draft document DR 1554.6 can be downloaded for public comments from the Standards NZ webpage: www.standards.co.nz
In the Productivity Session, NZWC engineer Alan McClintock presented a paper entitled Cost Effective Fabrication Through Applying Principles of AS/NZS ISO 3834. Quality requirements for welding are beginning to be specified by major overseas clients. However this is not the case for the local work typically undertaken by fabricators who can be defined as SMEs. The usual reason for this is that formal quality systems are not adequately understood, and are often seen as pedantic and too costly.
Alan discussed recent costly experiences where the expected quality was not achieved because of a failure by clients and fabricators to apply even basic quality requirements. He concluded that the most effective way to reduce welding fabrication risks is to follow basic principles of AS/NZS ISO 3834
In the presentation Design of Welded Beams - Influence on Cost and Fatigue Performance, Dr Michail Karpenko discussed issues around fabrication costs and fatigue performance of flange to web joints of welded beams.
Fatigue is a significant factor in the design of steel bridges because the live loads regularly approach the maximum design loading. Ideally, everything required to design a bridge would be covered by published standards. However, for various reasons, design standards do not usually prescribe the “optimal” design solution for every situation.
This is the case with joint design where designers are often left with an open option to either specify a more conservative, but more expensive weld such as full penetration butt weld or consider less costly alternatives such as deep penetration fillet weld.
The paper covered issues around fabrication costs and fatigue performance of flange to web joints of welded beams outlining some optimal design solutions which demonstrate the potential to safe considerable in fabrication cost without diminishing fatigue performance. The conclusion was that the cost for full penetration butt weld is about 4 times higher than that of deep penetration weld with the same fatigue performance and the weld penetration should be optimised in order to avoid root cracking and reduce fabrication costs. It can be done using novel FEA based fatigue analysis methods.
The concluding presentation was Study of Trends and Productivity in the Welding Fabrication Industry given by Dr Michail Karpenko. The paper analysed relevant statistics, trends and productivity aspects that characterise NZ welding fabrication industry making links to international studies.
A large part of the New Zealand (NZ) economy is dependent on welding as a key fabrication process. An estimated 6,500 people's work involves welding, and a further 800 people are involved as welding supervisors, engineers, or inspectors. The value-added of welding and joining technology in 2007 was estimated as NZ$813 million. The value of exported welded products is on average 3 times lower than the value of imports and that gap is increasing.
Michail concluded that many manufacturing companies have been able to maintain current fabrication methods because of a protected market, brand strength, or good profit margins. Global competition will force many manufacturers to change their production methods to be less wasteful and more competitive. Key considerations are labour cost, productivity and automation. Detailed statistics are available from the study published as HERA Report No R8-29 " Characterisation of the New Zealand Welding Industry”. Some presentations will be available on the conference web site on www.metals.org.nz
For more details on individual projects and papers, please contact NZ Welding Centre at HERA – Email or phone 09 262 4849.