Fasteners and Sealing
ESAB’s Hybrio HLAW system was claimed to be the first such process to be available commercially. This system can weld at three to ten times the speed of conventional processes, with 80 to 90 per cent less heat input, enabling greater 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. 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. Incorporating the GMAW process also allows filler metals to be added so as to adjust the weld’s metallurgical properties and create beads and fillets. In addition, the slower cooling rate associated with GMAW reduces hardness in the welds. These benefits are said to be especially advantageous when joining high-performance carbon steels and stainless steels. 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. Described as an advanced, next-generation intelligent control, it is said to broaden the welding performance envelope by a factor of five compared with HLAW processes utilising conventional controls.
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
Fig. 2. ESAB’s Hybrio hybrid laser arc welding system can weld at three to ten times the speed of conventional processes, with 80 to 90 per cent less heat input.
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 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
Low stress and no distortion S
olving the distortion problem typically found in welded structures can add to the cost of the manufacturing process. The Malco (Manufacture of Lightweight Components) project, which was a collaborative research and development project between British industry and academia, sought to address this issue by developing low-stress, no-distortion (LSND) welding methods that could lead to shorter manufacturing times
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and lower costs across a range of industries. These methods include thermal tensioning, auxiliary cooling and mechanical restraint, although the emphasis was placed on auxiliary cooling, which involves cooling of the region just behind the weld using water or carbon dioxide (CO2
). The overall
goal was to develop an LSND system for use in an industrial environment, with cryogenic cooling on the same side as the arc and integrated within existing robotic MIG
welding systems. This innovation is now the subject of a joint patent application. A team from the BOC group developed
delivery system that was integrated into an automated arc welding system to perform welding trials on a number of components. Following promising initial results, the process has been refined using thermomechanical computer models developed at Strathclyde University and TWI. l
a CO2
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