LASER-WELDING OF ALUMINUM LIGHTWEIGHT MATERIALS - PROBLEMS, SOLUTIONS, READINESS FOR APPLICATION

Using high-power CO2 and Nd:YAG lasers of high beam quality, high proc ess efficiencies and excellent seam qualities are achieved. A particul ar method for obtaining almost pore-free weld seams without blowholes is the combining of the beams of two CO2 lasers. Without the need for filler material, crack-free welds can be produced in sheets of hot-cra ck susceptible, precipitation hardened alloys up to a welding speed of 5-7 m min(-1) for full penetration and up to 3-4 m min-(1) for partia l penetration. In contrast, AIMS alloys containing more than 2.5 wt% M g and AlSi cast alloys are insensitive to hot-cracking even at high pr ocessing speeds. Laser welds possess much better static mechanical pro perties than gas tungsten are (GTA) or gas metal are (GMA) butt welds. For the alloys AlMgSi1 and AlMg5Mn the maximum static strength which can be achieved in laser welding is determined by the alloy type, i.e. the hardening mechanism and the heat-treated condition. Laser butt we lded car body sheets without filler material exhibit the same load-bea ring capacity under dynamical load as GMA welds with filler material. The latest research work has demonstrated that high-quality 'tailored blanks' with good mechanical properties can also be made out of differ ent aluminium plates.