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Fasteners & Sealing


performance gains to be achieved than have been possible in a generation of welding process developments (Fig. 2). The technology combines the deep weld penetration and low heat input of laser welding with the superior weld properties and gap tolerance of GMAW.


one pass. To put that in perspective, using HLAW instead of conventional methods to weld the aircraft carrier USS Saratoga could have saved nearly 800 tons of weld metal and reduced the welding time by 80 per cent.


l Reduced shipping costs: Traditionally, welding takes place in a manufacturing environment far from where the finished product is required, so time-consuming and costly transportation is required. However, because GE’s HLAW system is portable, large assemblies can be fabricated at the final location.


l Higher efficiency: Because HLAW can weld in just one pass, the new process is far more efficient than its predecessors.


In common with ESAB’s Hybrio system, GE’s HLAW process uses a combination of laser welding and arc welding. With high-power fibre lasers, steels thicker than 12mm can be welded in a single pass at speeds greater than 1 m/minute. The result is a weld of higher quality than can be achieved with traditional multi-pass welding methods (Fig. 3). Over the years, GE says it has pioneered the use of lasers in manufacturing applications ranging from laser hole drilling in aircraft turbine blades to the first use of lasers for surface treatment of fan blades for improved durability. Lasers are also used to weld filaments for lighting products, lamination spacers for generators, and components for X-ray tubes.


Fig. 2. ESAB’s Hybrio hybrid laser arc welding system can weld at three to 10 times the speed of conventional processes, with 80 to 90 per cent less heat input.


Laser welding produces narrow, deep welds at very high speeds. This puts less heat into the joint and results in reduced weld shrinkage and distortion; in turn, this avoids the problems and costs associated with unpredictable post-welding fit-up and rework/repairs. Laser-only welding, however, is limited in its ability to produce acceptable welds in joints with wide gaps. Hybrio solves this by using GMAW in tandem with the laser, adding a relatively modest amount of filler metal. The wider weld beads can bridge gaps that are four times wider than those that can be handled by conventional laser-only processes. An important element of the Hybrio process is ESAB’s


patented adaptive control system that permits monitoring of the weld joint in real time so that the process parameters can be modified to accommodate joint gaps and component mismatches.


Manufacturing improvements


Another company that has recently introduced a HLAW process is GE, which claims that its system can revolutionise the way products are made. The company suggests three primary ways in which HLAW can improve manufacturing:


l Production speed: Welding is a fundamental aspect of making many products that contain metal parts. It is also one of the most time-consuming elements of the manufacturing process. HLAW welds faster, meaning that many industrial products can be produced at greater speeds. To achieve this, GE’s HLAW system uses high- powered fibre lasers that weld steels up to 2 cm thick in just


Fig. 3. GE’s hybrid laser-arc welding process enables steels thicker than 12 mm to be welded in a single pass at speeds greater than 1 m/minute.


Able to specify processes such as hybrid-laser arc welding and low-stress, no-distortion welding, design engineers can take a fresh look at fabrications that might otherwise have to be assembled in different ways at greater cost or in such a way that performance is compromised. Production engineers can also use these innovative processes to remove cost from existing fabrications. While hybrid-laser arc welding and low-stress, no-distortion welding will not be suitable for every welding application, they represent significant advances in welding technology and warrant close investigation for those projects which could benefit from them. l


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