In high speed rail transport, reducing weight whilst maintaining performance is all important. Railcar structures are often fabricated from extruded aluminium alloy sections, which offer lightweight performance from a combination ofhigh specific strength and stiffness.
TWI is supporting one of its Member companies, Nippon Sharyo, in developing hybrid laser-MIG welding as a high speed, low heat input, non-contact welding process, with improved fit-up gap tolerance when compared with conventionallaser welding.
TWI has used a 7kW Yb fibre laser in this work with standard MIG welding equipment. Welding trials have been carried out on 6000 series aluminium alloy extruded plates. These trials have demonstrated that the process is capable ofproducing low porosity content, high quality butt welds, at speeds of up to 5m/min in 3mm thickness material. In the same work, fit-up gaps of up to 1mm width (if constant width gaps) or up to 1.5mm width (if tapering gaps) have beenbridged successfully.
As a follow on, welding trials have shown that high quality welds can also be made between extruded sections, at least in close-fitting butt joints, using a full penetration self-supporting joint configuration.
In ongoing work, joint configurations and welding procedures are now being developed for producing similar high quality welds between extruded sections with fit-up gaps.
The hybrid process is capable of producing high quality welds in a variety of materials and thicknesses, including steels, stainless steels, titanium alloys and nickel alloys, typically up to 10mm in thickness (depending on thelaser source), as well as aluminium alloys.
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