Welding with the HPDDL system

The HPDDL naturally generates a beam shape that is ideal for continuous seam welding, such as those found of tube mills. Unlike the GTAW and the conventional laser welding, which generate plasma and round heating spots, the diode laser generates a line of light. The line of light allows for a longer interaction time at the seam. The resulting weld pool is only at the seam; it penetrates deeper allowing molten metal to wet together in a very controllable fashion. This yields a conduction mode weld similar to those produced by a GTAW process, with no spatter, however there is less sagging and a much narrower heat affected zone which results in an increase in mechanical properties such as fatigue strength and formability10.

An application that is getting much attention is welding zinc-coated steels using the HPDDL. The HPDDL is the ideal laser source for welding zinc-coated steels. The line of light, independent of plasma issues, acts to preheat and vaporize the zinc such that there is no zinc present at the weld pool. This results in an excellent ductile weld.

304 Stainless Steel Welding of Tubing

The ISL-4000L HPDDL was used on a GTAW tube mill to weld 0.035 3/8" inch tubing. The laser head was small enough to fit within the profile of the existing tube mill without major retrofits and the beam size is such that no seam tracking devices were required.

Welds produced on the tube mill exhibited exceptionally smooth surfaces on both sides, very low distortion which is consistent with the small heat affected zone, and very little oxidation on the surface as a result of the good coverage by the shielding gas. The resulting weld and HAZ are approximately 3X ?4X smaller than that resulting from a GTAW. Metallographic inspection of welds made on the tube indicated a minimal variation in hardness in the heat affected and fusion zone from the base metal (Figure 2).