Researchers Investigate Laser Welding of Aluminum
COLUMBUS, Ohio -- Researchers are perfecting the laser welding of aluminum alloys to overcome a roadblock in the development of more fuel-efficient cars and trucks. Over the last decade, automotive manufacturers have used laser-welded sheet steel, combining metals of different thicknesses and properties into one tailor-made blank, but steel is not the only candidate.
Aluminum, in particular, offers a high strength-to-weight ratio, enabling manufacturers to reduce the mass and thus increase the fuel efficiency of a vehicle. The easily recyclable aluminum parts also display crash worthiness and a resistance to corrosion. Aluminum, however, is particularly sensitive to the heat of laser welding, resulting in buckling, the cracking of welds, hydrogen contamination and the boiling away of alloying elements such as magnesium, which affects weld hardness.
Charles E. Albright of Ohio State University and Siva Ramasamy of Emhart in Mount Clemens, Mich., reported in the June issue of Journal of Laser Applications the results of their investigations into the laser welding of aluminum blanks. They found that they could minimize losses in the metal's mechanical properties as well as reduce the evaporation of magnesium by controlling the laser power and welding speed.
The researchers compared the welding performance of four laser systems on 1-mm-thick sheets of 6111-T4 aluminum alloy. The 2-kW Nd:YAG pulsed laser produced the 13-in. butt welds with the highest elongation value, which determines the ultimate formability of a stamped blank. However, they found that the elongation values were more sensitive to the weld-travel speed of the pulsed laser than to that of the continuous-wave lasers in the study: an axial-flow 3-kW CO2, transverse-flow 5-kW CO2 and 3-kW Nd:YAG.
The evaluation quantified how important the proper laser parameters are to maximizing weld hardness by minimizing magnesium burn-off. The researchers suggest that by welding aluminum at medium to high power and rapid travel speeds, the vaporization of alloying elements can be minimized and large-scale aluminum blank welding operations can be realized.
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