Oct 18, 2011
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As a family of related yet diverse joining technologies, welding continues to evolve - though designers and production engineers are always demanding greater process improvements. Paul Stevens reports on some of the latest developments in welding that could offer major advances.
Welding is one of the most commonly used methods of joining metals, with designers and production engineers having a broad range of processes from which to choose. Manufacturers of welding equipment and consumables continue to make incremental improvements to these processes, but some recent developments have the potential to deliver a step-change in quality and productivity, and even give design engineers the opportunity to create new fabrications that would not previously have been feasible.
Gas metal arc welding (GMAW) was developed during the Second World War for joining aluminium and other non-ferrous metals. Metal inert gas (Mig) welding is the most widely used of the GMAW processes, being suitable for everything from small fabrications through to large structures (Fig. 1). Its close relative, metal active gas (Mag) welding differs principally in the type of gas used; often the two processes are simply referred to as Mig/Mag welding.
One of the most frequently cited drawbacks with welding is distortion of the workpiece. However, this can be controlled to a great extent through a combination of joint design, the use of clamping and fixtures, optimised welding procedures and the application of state-of-the-art welding equipment. This last point is included because, for example, some of the latest Mig welding machines have sophisticated control functions that can reduce significantly the heat input into the weld and, therefore, the distortion. Minimising distortion is one of the most important factors in a successful and economical weld, especially when repairs are being performed and there is less scope for clamping/fixturing. Uncontrolled or excessive distortion increases the job cost due to the expense of rectification - or replacement in the event of the distorted part being beyond economical repair. It also has to be remembered that controlling distortion by means of clamping and fixturing can lead to the finished component having high residual stresses, which can cause problems later unless stress-relieving procedures are employed.
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