Construction and Engineering news round-up - July 2012
MAINLINE action…well on track
A unique £4M rail project tailored to the needs of railway asset managers is about to complete its first quarter…already with considerable success.
Mainline, as it is dubbed, is an FP7 project which took off last Autumn and is aimed at maintenance, renewal and improvement of rail transport infrastructure to reduce economic and environmental impact.
By completion of its three year duration the project will develop methods and tools that will contribute to a more cost efficient and effective improvement of European railway infrastructure, including earthworks, bridges, tunnels, and track, based on whole life considerations. Its specific aims are to:
facilitate the uptake of improved assessment techniques and life extension
improve understanding of relevant damage and deterioration mechanisms and their effect on asset performance
identify and implement new cost effective replacement or renewal construction methods and logistics, bearing in mind the logistics and operational constraints across an expanding railway network, and the associated political aspirations towards a sustainable low carbon society
identify and compare new inspection and monitoring technologies in order to complement or replace existing techniques
develop methods for determining the whole life environmental and economic impact from track and infrastructure maintenance and renewal through the use of various scenarios and management policies.
The project consortium has 19 partners including TWI Industrial Member Network Rail
Friction stir in steel….promises of commercial success
Now in its third decade friction stir welding of aluminium is enjoying enormous commercial success in both the aerospace and automotive sectors…but in steel the story is less clear.
Shipbuilding, bridge building, the renewable energy sectors will all benefit from its commercialisation. A soon to be published report aims to establish the current state of the art in the friction stir welding of steel, and draws primarily upon published work. It has been augmented with data from TWI’s own research, both published and unpublished, and information provided by organisations and companies with whom TWI co-operates and who have given their consent for inclusion of their data in the report.
As well as establishing the current status of FSW in steel, this report seeks to identify those applications for which use of the process in steel might first be commercialised, and any obstacles that may need to be overcome in the short term, to facilitate these early applications.
Where any such obstacles are identified, recommendations will be made for programmes of research work to be undertaken to overcome them as potential follow-on phases of this Group Sponsored Project (GSP) or as part of TWI’s rolling Core Research Programme (CRP).
In identifying potential early applications for friction stir welding, note will be taken of the current relative immaturity of the technology for steel and its perceived high cost when compared with fusion welding techniques.
However, as will be seen, the potential benefits that may accrue from successfully transitioning FSW technology from the light metals to ferrous alloys indicate that the process should not be evaluated purely on the basis of the cost per metre of weld made, but on a more comprehensive total lifetime costing.
When such factors as reduced distortion during fabrication and the potential for stronger, tougher welds are brought into the economic consideration the use of friction stir welding for steel, in some applications, becomes considerably more attractive.
It is the identification of these applications, and an assessment of their possible costs and benefits, that forms perhaps the most important strand to this work. FSW of high temperature materials
Friction stir welding was developed initially for aluminium, and subsequently other light metals such as magnesium that were considered difficult to weld by traditional means.
The excellent properties attainable by friction stir welding led not only to a demand to develop the process for other materials that were also tough to weld by conventional fusion techniques, for example copper and titanium, but also to develop the process for steel.
Most grades of steel can be welded quite satisfactorily by fusion welding techniques, but the potential for bringing some or all of the proven benefits of FSW to the welding of steel promoted research into this material too.
The feasibility of welding steel by the friction stir process was reported by Thomas et al, 1999. Research into the FSW of steel confirmed that though sound welds could be made in steel, the high cost and poor longevity of the available tool materials meant that the process was not economically viable other than for very niche applications.
Subsequent research into the FSW of steel has been aimed primarily at improving the available FSW tool materials, seeking to enhance their reliability and longevity, and reduced cost, in order to make the FSW of steel an economically viable process.
As better FSW tool materials became available, allowing the production of longer and better welds, research also began to be conducted into the properties of the welds, and into the use of the friction stir technique to process steel, namely to use the thermo-mechanical nature of the FSW process to alter the microstructure and properties of the steel.
The basic principle of friction stir welding remains unchanged irrespective of the material being welded and thus progressing the friction stir welding process from a technique capable of welding aluminium to one capable of welding steel was essentially a development of enhanced tool materials.
When welding aluminium alloys, the temperatures recorded in the plasticised material around the FSW tool are of the order of 350 to 450ºC depending upon the exact alloy and welding parameters used. The FSW tool used can thus be made of a tool steel such as H13 for those alloys welded at the lower end of the temperature range and nickel based alloys such as MP159 for welds made at the higher end of the range.
However, as the plasticisation temperature of the workpiece material increases these tool materials become unsuitable as they begin to lose their mechanical and chemical properties at elevated temperature and therefore become prone to breakage, wear and dissolution in the workpiece.
The development of the FSW process for copper required a shift to nickel based alloys such as Nimonic 105 or materials based on tungsten carbide as the temperatures in the weld zone increased to between 700 and 850ºC.
Friction stir welding of steel poses a far greater challenge than the FSW of aluminium or copper. Steel FSW is carried out at temperatures calculated to be in excess of 1000°C at the tool work piece interface - direct measurement is difficult as temperature sensors embedded in the steel are destroyed by the friction stir process - and the tool must maintain its strength at these elevated temperatures whilst being subjected to complex bending, rotational and fatigue loads.
Furthermore, many potential tool materials oxidise at these high temperatures, or react with the workpiece material, and frequently both. Iron, the base element in steels, readily alloys with many of the potential candidate tool’s materials, and this high degree of chemical reactivity is further compounded by the presence of numerous other elements in steels, either present deliberately for alloying or as tramp elements.
Current R&D is addressing these points and the commercial exploitation of FSW of steel is coming closer.
SafeFlame work now underway - TWI-led consortium rolls out key FP7 project
Lower running costs, greater flame control, improved heat transfer and hugely improved safety are just a few of the advantages offered by a new EU project to develop a 21st century solution for flame brazing, cutting and welding.
It’s named SafeFlame and its singular objective is to develop hydrogen and oxygen from the electrolysis of water. The work will culminate in the development of a unit which will be portable, user friendly and require only electricity and distilled water.
The project began in November 2011 and expert partners from Germany, Italy, Spain, Finland and the UK are now working towards a new generation device that will modernise the traditional methods of oxy-acetylene and gas-air brazing.
Construction and engineering industry sector members able to benefit from the project’s findings will include those in the manufacturing and vehicle construction fields where sector members are expected to have numerous applications.
TWI is heading the consortium which includes luminaries like ITM Power in the UK, VTT of Finland, EABS, the European Association for Brazing and Soldering, HVCA, the Heating Ventilating Contractors Association in the UK, Cesol, the Spanish Welding Association, Webber Brenner Technik of Germany and LG Stucchi S.r.l of Italy.
For further information and to register your interests please go to www.safeflameproject.eu
The research leading to these results has received funding from the European Union's Seventh Framework Programme managed by REA - Research Executive Agency http://ec.europa.eu/research/rea [FP7/2007-2013] under grant agreement number: 286889
Five decades of Cambridge success and TWI’s part in it, now chronicled in print
Cambridge, and the technological explosion associated with it since the sixties, come under the spotlight in a prestigious new coffee table volume entitled The Cambridge Phenomenon. And between its covers several references to TWI’s significant contribution feature prominently.
Unlike many companies deemed as start-ups half a century ago, allusions to TWI relate to its origins in the 1940s when the British Welding Research Association, as it was known, was led by Dr Richard Weck.
‘Following government funding cuts The Welding Institute survived as an entrepreneurial private organisation’ it reads. ‘And under its third director, the late Bevan Braithwaite started negotiations with the District Council in 1992 over plans to develop the estate into a science park.’
Today TWI’s Cambridge headquarters named after him, and its significant presence on Granta Park, mark a dynamic epitaph to his work.
With a forward by Microsoft chairman Bill Gates the 224 page tome tells a colourful technological tale of the UK’s foremost university city both exhaustively and economically. It features high production values, classy photography and a page-turning prose style.
Available from Third Millennium Publishing, £50, ISBN:978 1 906507 57 7
Ancient and modern technologies overlap
Japanese jewellery creation, and the somewhat less ancient practice of friction stir welding (FSW) came together recently in a project involving the art and design sector of Sheffield Hallam university…..and TWI.
The work involves a novel method for producing mixed metal multi-coloured layered materials using FSW and compares the results with the ancient Far Eastern art of Mokume Gane.
Mokume Gane is a unique process involving sheets of different coloured metal alloys bonded together into a laminated billet before being carved or milled to expose interior layers. The material is then hammered or rolled into a flat sheet which is used to form jewellery or hollow ware.
The visual effect is stunning, whether it be with the noble metals of silver and gold, or the industrially popular materials of brass and copper. Early on in the development of friction stir the process was identified as ideally suited for joining dissimilar materials.
Using these multi-coloured layers in the process has given TWI a unique insight into how the material flows around the friction stir tool and has thereby enhanced TWI’s tool design capability.
- Work has shown that: It is clear that it would be feasible to use FSW to produce Mokume Gane materials from a number of different metals including gold, silver, platinum, palladium, copper and brass.
- FSW, used in the correct manner, can produce well-bonded materials in laminate form in which the materials have been both bonded and mixed, forming an attractive and repeating pattern that can be reproduced.
- The fact that mixing occurs at the same time as the bonding provides a reduction in the amount of subsequent work required to form the patterns that give Mokume Gane its appeal.
- The method does not require high-temperature furnaces or the need to avoid oxidation of the metals, and very little cleaning or sample preparation is required. It is also a relatively low-energy process since the whole sample does not require heating.
- The patterns formed are unique to FSW and have the potential to be widely varied by changing the lay-up of the materials to be bonded and the friction stir conditions. After reaching steady-state conditions the patterns formed are stable and repeat in a regular manner but with a small natural and random variation, making each piece unique.
- The bonds formed in the friction stir zone are a combination of the intimate physical contact between the metals resulting in metal-to-metal bonds plus thermally enhanced mechanical alloying, producing microstructures not possible by conventional processing.
- The nature of FSW means that large ingots of bonded material can be produced relatively easily using multiple passes of the friction stir tool through laminate layers. Other possible material lay-ups are possible, giving many possible variations in pattern, for example, bars of materials side by side or materials with regions inset with a second material.
- On the smaller machines, such as the TTI, the maximum ingot size is ~ 300mm x 150mm, with thickness determined by the number and thickness of the layers to be bonded but in the region of 10mm to 30mm. Such large sizes are impossible using any other Mokume Gane production technique. In theory the larger PowerStir machine could make much larger sheets measured in metres.
- With the constant development of FSW and the increasing availability of machines and tooling capable of carrying out FSW, there is a great potential for both large companies and smaller individual makers to begin to experiment and develop new Mokume Gane materials.
In time this approach could also lead to the production of visually stunning architectural panels.
Mobile electron beam welding provides the solution for fabricating large structures
A steel tubular, representative of a wind turbine tower foundation structure, in preparation for 'out-of-vacuum-chamber EB welding
Continuous developments in out-of-vacuum-chamber EB technology are pushing at techno-economic barriers previously preventing the uptake of single pass, thick-section, low distortion electron beam (EB) welding of large pressure vessels and structural fabrications. The ability to use EB technology outside a vacuum chamber, coupled with the introduction of new sliding seal vacuum technology means that the welding process is given greater mobility enabling an increasing number of technical applications and commercial opportunities across a range of industries.
In conjunction with the ManOS (Cost-Effective Manufacture of Offshore Wind Turbine Foundations) project, and specifically to showcase its reduced pressure EB gun and the capabilities of mobile local vacuum sliding seal technology, TWI hosted a recent seminar and technical demonstration at its Low Carbon Energy Manufacturing Technology Centre in Middlesbrough, UK. The event on 19 April 2012 was attended by partners of the ManOS project (see below) and delegates from UK industry and academia with interests in large-scale steel fabrication and offshore wind power engineering.
Chris Punshon, Consultant, Electron Beam Processes at TWI began by presenting the progress made by the ManOS project, which aims to enable faster, efficient and cheaper production of offshore marine foundations. The project, funded by the UK TSB, has successfully developed and demonstrated EB wedding in thick section steels with offshore application relevance and validated the resulting metallurgical and mechanical properties. The ManOS partnership comprises TWI, Nippon Steel Corporation and Aquasium Technology Ltd, with KBR acting in a consultative role.
Chris introduced the focus of the event – the demonstration of a full penetration, 60mm wall thickness, 1300mm longitudinal seam weld in a 2350mm diameter S355 steel tubular (representative of an offshore wind turbine tower foundation structure), which took less than 6 minutes to complete.
Prof. T Ishikawa, Nippon Steel Corporation, Japan, concluded by presenting delegates with details of a proprietary grade of S355 steel, which has recently been granted Germanischer Lloyd’s approval for EB welding due to its excellent as-welded and post-weld heat treated properties, including exemplary sub-zero impact toughness.
All attendees noted that they were impressed by the demonstration, the technology supporting the EB welding capability, and the opportunities that this mobile variant brings for application of EB welding to large structures where conventional EB has been prohibited due to the need to operate within a vacuum chamber.
Please contact Chris Punshon email@example.com for further details or if you wish to explore this technology further for your applications.