IIW White Paper

9 Needs and challenges of major industry sectors for future applications

The FSW process has been considered by the aerospace industry in recent years, mainly because the fabrication process of high value components can support the use of relatively new and expensive friction welding equipment. Also, the use of relatively soft materials such as aluminium alloys perceived to be ideal for the utilisation of the solid state processes further provided impetus to the development of tool materials and equipment requiring reasonable levels of input power. Rapid developments on tool materials has however opened the door for investigation on the application of the FSW process to higher strength materials such as carbon steel and stainless steel which in effect now opened the door to investigate the feasibility of the wider application of solid state welding in the industry. Improvement to efficiencies by extending the economical life of existing plant with the aim of also reducing the burden on the environment involves elaborate studies to determine accurately the condition of the plant critical components. The life extension of plant operating up to mid and advanced percentage of the design life requires detailed evaluation of the high pressure and temperature components with special emphasis on: Fraction of creep life consumed. Fatigue damage (combination of environmental, mechanical and thermal). Material wastage due to flow induced mechanisms. Corrosion damage effects. Once the leading components with respect to life consumption are identified, refurbishment involves a combination of repairs of some of the components and replacement of components beyond economic repair status. Philosophies around the economics of weld repairs typically rely on an intricate balance between: Their required extension of life. Introducing state of the art new technology into dated infrastructure. Available investment. Refurbishment technology to be used. Replacement materials available. From this point onwards in the refurbishment process, the welding function features prominently in a company’s strive to contribute to the effort in slowing the deterioration of the environment by: Refurbish rather than replacing components where possible. Optimal use of scarce resources including raw materials and energy. Recycling of discarded material and consumables. Utilisation of procedures and techniques that put a lower burden on the environment. Legislation for mandatory minimum responsibilities of the suppliers of power plant towards the design of components with minimised ‘carbon footprints’ is another aspect that require urgent attention. In the same way as electronic companies and car manufacturers in certain countries are required by law to take full responsibility to supply products to consumers, that can be fully recycled in an environmentally friendly way after expiry of the product’s useful life, the same should apply to suppliers of heavy power plant equipment. For example, components such as turbine casings and large valves manufactured from heavy wall castings, should lend themselves to easy refurbishment by welding through careful selection of more weldable alloys and a modular type of design, that is designs where areas prone to wear and/or material exhaustion can be readily replaced by new material through weld joints at non-critical areas. Cast iron is popular for its good casting characteristics while being relative cheap as well, but is notoriously difficult to refurbish successfully through welding processes. By rather opting for a slightly more expensive basic good steel casting that is

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Through Optimum Use and Innovation of Welding and Joining Technologies

Improving Global Quality of Life