What You Should Know about Hybrid Laser Arc Welding BY PAUL DENNEY WELDING JOURNAL 39 The process of combining lasers with gas metal arc welding (GMAW) in a single weld pool, known as hybrid laser arc welding (HLAW), has been in existence for almost 30 years — Figs. 1, 2 (Refs. 1, 2). The HLAW process was developed to meet many of the shortcomings of autogenous laser welding. The first issues that HLAW addressed were fitup and the need in some applications to alter the chemistry. In the past, the only highpower lasers (greater than 5 kW) that really could benefit from HLAW were carbon dioxide (CO2), but their high costs to purchase and operate limited their use. But with advances in fiber-delivered solid-state lasers (Yb-disk and Yb-fiber), the “ownership costs” have drastically lowered for high-power lasers. In 1995, a 10-kW CO2 laser cost approximately $1 million. Today, with inflation factored in, a similar Yb-fiber laser costs about one-third that amount. In addition to the reduction in procurement cost, the reliability and maintenance for the new solid-state lasers are significantly better than for the older gas lasers. Today, with these lower costs and higher powers for the lasers, there is a renewed interest in the use of HLA welding for a wide range of applications. Many have predicted that, with these changes, HLAW technology would displace traditional arc welding for a large number of applications. However, the numbers of HLAW systems sold do not support those predictions. The question is, “Why?” Even before the development of the new solid-state lasers, there were successes using HLAW. These applications were based on HLAW that used highpower CO2 lasers. The most notable was the installation of a panel line at the Meyer Werft Shipyard in Pappenburg, Germany, which was made operational in 2001 (Ref. 3). The system used three high-power CO2 lasers to weld bulkhead/ deck panels max. 12 mm (1⁄2 in.) together and then attach the bulb “Ts” to the panels. While the higher welding speed was a benefit compared with submerged arc welding (SAW), another advantage was the lower distortion compared to arc welding. In addition, postwelding processes such as leveling and dealing with general distortion could be reduced or eliminated. The panel line at Meyer Werft Shipyard has been used as a model for the implementation of HLAW, but implementation has not been as successful at other shipyards or in other industries. While these lessons are now almost 15 years old, heeding the lessons learned and evaluating some simple recommendations may help to successfully implement HLAW. Some of the issues that may impact the successful implementation of HLAW are as follows. Joint Design When examining whether HLAW will be of benefit, many engineers look at their present weld joints and simply substitute a “laser weld” for the existing process. However, for most arc welding processes, the joints have been designed with a considerable amount of the weld joint consisting of filler material supplied by the welding process. With this in mind, and the fact that most arc processes have high deposition rates and slower welding speeds, filling these root openings and addressing mismatch can be accomplished by making minor corrections to welding speed or wire feed speed, or by moving the torch in a weaving pattern. Also, the profile/geometry of an acceptable weld has been defined around these arc processes. However, for an edge fillet application, the ability to meet the leg and/or throat thickness is determined by the amount of welding wire that can be melted with the root opening/mismatch and travel speed desired — Fig. 3. Combining lasers with your gas metal arc welding line may offer several advantages, but first consider all the pros and cons PAUL DENNEY (paul_denney@lincolnelectric. com) is senior laser applications engineer, Automation Division, The Lincoln Electric Co., Cleveland, Ohio.
Welding Journal | January 2013
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