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Development of low cost linear friction welding machines

By Stephan Kallee

An international project on linear friction welding of metals, which is partly funded by the European Community, is currently being conducted by 8 organisations. This project is designed to drastically reduce the cost of linear friction welding equipment, in order to make the technology more accessible to potential users especially from the power generation, automotive and aerospace industrial sectors.

Linear friction welding has been demonstrated for virtually all types of engineering alloys, such as titanium ( Fig.1), steel, stainless steel, aluminium and inter-metallics, but the uptake of the process by industry has been impaired by the high capital cost of existing mechanical linear friction welding machines. Novel solutions have been devised to reduce the manufacturing cost of the equipment, mainly based around more efficient use of the power sources required and by use of stored energy concepts. This will lead to a very substantial reduction in equipment price.

Workshop drawings of all modules of a prototype machine have been produced ( Fig.2), and the components are currently being machined or purchased. The prototype machine was trademarked LinFric TM by TWI [1] and has been designed to weld work pieces with a maximum weld area of 2000 mm 2 . The LinFric TM machine does not need any balancing, and its oscillator is driven by a hydraulic power pack through 8 accumulators, which can provide an oil flow of up to 750 l/min. It can vibrate at frequencies of 25-125 Hz with amplitudes of up to ±3mm. An axial force of up to 150 kN (15 t) can be applied during the friction phase. The force can then be increased to 200 kN (20 t) to permit consolidation during forging.

Linear friction welding ( Fig.3) can be used to join a variety of complex profiles. It is technically, commercially and environmentally a very attractive process, and is ideally suited to both mass production and to the manufacture of specialised components required in limited numbers. If different components have to be welded, only the tooling to hold the workpieces needs to be changed and different welding parameters may need to be developed.

The technology of friction welding is becoming more widely accepted in many industry sectors, as the economic benefits and the high quality that it provides are increasingly recognised. After the world-wide acceptance of rotary friction welding, this progress has been significantly helped by the advent of innovative variants on the process, such as vibration welding of plastics, friction stir welding and friction surfacing. Friction welding processes are very energy efficient compared to most competitive welding processes. Routine maintenance of friction welding machines is generally not expensive, and no consumables such as filler wire, flux or shielding gas are required, even for environmentally sensitive materials such as titanium alloys. As friction welding processes are substantially automated, quality and reproducibility are high compared to alternative manual welding processes. Friction processes are generally tolerant to wide changes in the welding parameters without compromising quality, thus reliability is high.

The consortium of this project consists of five small and medium sized enterprises (SMEs) from three countries, supported by one larger company, and two research and development organisations. The project will put European SMEs in a strong position to supply what is firmly believed to be a large and sustainable market in Europe and the rest of the world. The companies that are participating on the project are listed in the Table.

Small and Medium Sized Enterprises:

Blacks Equipment Ltd, Doncaster (United Kingdom)

Dartec Ltd, Stourbridge (United Kingdom)

Deltamatic srl, Pedrengo (Italy)

Harms & Wende GmbH & Co KG, Hamburg (Germany)

Klaus Raiser GmbH, Eberdingen (Germany)

Research and Development Institutes:

TWI Ltd - The Welding Institute, Cambridge (United Kingdom)

Technische Universität Graz (Austria)

Large Companies:

ABB Alstom Power nv, Lincoln (United Kingdom)

Fig.1. Linear friction welding of titanium in normal atmosphere
Fig.1. Linear friction welding of titanium in normal atmosphere
Fig.2. Artist impression of the LinFric TM machine [1]
Fig.2. Artist impression of the LinFric TM machine [1]
Fig.3. Principle of Linear Friction Welding
Fig.3. Principle of Linear Friction Welding

The project 'Development of Low Cost Linear Friction Welding Machines' is jointly funded by the industrial consortium and the European Commission under their CRAFT Initiative (Co-operative Research Action for Technology). The project is co-ordinated by Blacks Equipment in Doncaster (UK) and managed by TWI in Great Abington near Cambridge (UK) on behalf of the consortium. The total budget is 1.25 million Euro and involves an effort of more than 7 1/2 man-years.

This project offers small European companies an opportunity to secure world market leadership in the development, manufacture and operation of linear friction welding machines and in the provision of related services, such as establishment of sub-contract facilities. The wider use of linear friction welding will also generate a useful market for training of designers, production engineers and operators, who could incorporate the process into the production of their components and operations. Much of this training can be provided by the participants of this project. For further information on the project or the LinFric TM machines, please contact:

Dipl.-Ing. Stephan Kallee TWI Ltd Granta Park, Great Abington Cambridge CB1 6AL United Kingdom

Tel: +44 (0)1223 899000 Fax: +44 (0)1223 894367 E-mail: stephan.kallee@twi.co.uk

Dr.-Ing. Elmar Raiser Raiser GmbH Mönchswiesen 18 71735 Eberdingen Germany

Tel: +49 (0)7042 7013 Fax: +49 (0)7042 77440 E-mail: elmar@raiser.de

Roger Black Blacks Equipment Ltd Barton Lane, Armthorpe Doncaster DN3 3AA United Kingdom

Tel: +44 (0)1302 834444 Fax: +44 (0)1302 831834 E-mail: sales@blacksequipment.com

1 LinFric TM is a Trademark of TWI Ltd.

For more information, please email contactus@twi.co.uk

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