TWI Industrial Member Report Summary 1005/2011
By C M Allen
Laser welding of aluminium alloys is of interest to the automotive, rail, shipbuilding and aerospace sectors, to produce lightweight welded fabrications with low levels of distortion and/or with high productivity. Higher brightness fibre-delivered fibre and disk lasers can offer significant performance and/or productivity advances over other lasers, but precise joint fit-up and placement are necessary if welding defects are to be avoided. This is particularly so for the small focused spot diameters typical of these types of laser.
Wire fed and hybrid laser-arc welding processes are more tolerant to joint fit-up. However, weld quality can be maintained to even further relaxed tolerances, than those achievable using these processes with fixed conditions. A joint tracking sensor with feedback control can be used for real-time measurement of joint gap and mismatch, and corresponding real-time adjustment of, for example, hybrid welding parameters, thus compensating for poorer fit-up.
In recent work (Allen, 2010) it has been shown that hybrid welding with a fibre laser can be made more tolerant to joint fit-up, than hybrid welding using fixed conditions, if a sensor-driven control system is used. This system has proven capable of real-time measurement of, and response to, the joint position and fit-up characteristics during butt welding of 6mm thickness stainless steel plate at up to 2.5m/min.
The current work has continued the development of hybrid laser-MIG welding with adaptive control. As an example, 5083 aluminium alloy has been welded, representing a more fusion-weldable alloy used in shipbuilding and other surface transport industries, given its corrosion resistance and moderate strength. In particular, higher speed flat (PA) position butt welding of 4mm thickness wrought plate with adaptive control has been addressed, as would be pertinent to future light weighted applications.
- Develop and demonstrate adaptive control algorithms for laser hybrid applications with variable joint fit-up conditions in 5083 aluminium alloy.
- Establish the tolerance limits for ISO 13919-2 Class B welds with different joint fit-up conditions, when adaptively welding butt joints in 4mm plate.