By: Siltanen Jukka

Laser and laser hybrid welding processes have attracted interest during the last few years in engineering industry. The basic reason is the need to increase the productivity in order to be more competitive in global markets. In comparison to traditional arc welding processes, laser welding has several benefits such as low heat input resulting in low amount of distortion, deep weld penetration and high welding speed, high quality of welds and possibility to weld a wide spectrum of materials. However, laser welding means that the groove and processing tolerances become tighter as the focal point diameter of the laser beam used for deep penetration welding is very small. In one view this can be seen as a benefit, because it improves the accuracy of a product or component.

Laser hybrid welding (combination of laser and arc welding) permits looser groove tolerances compared to laser welding. The use of filler metal enables the filling of gaps formed during welding and due to inaccuracies in edge preparation or other earlier manufacturing phases as well as gives the possibility to mix the weld metal such to achieve the desired mechanical properties. Another restriction of laser welding is the high investment cost of the laser source and the welding system with a high accuracy. On the other hand, during the recent years the prices of the laser sources have lowered, but still they are a lot more expensive than the arc welding sources.

In 2006 Rautaruukki Oyj (www.ruukki.com) started a project called Rlaser, the aim of which was to find new ways to use laser technologies and discover new business areas and markets. All three business divisions (Construction, Engineering, and Metals) of Rautaruukki Oyj participate in the project. The project has several independent sub-projects focused on the research areas like mechanical properties of the welds and products, optimizing of the manufacturing chain, economical and technical comparison of the production methods and measuring techniques. The conference paper “Comparative analysis of GMA, laser, and laser-GMA hybrid welding” in ICALEO 2009 is especially focused on the mechanical properties of the joint of mild steel S355. Figure 1 shows the testing arrangement of laser-GMA hybrid welding.

Currently, Rautaruukki Oyj concentrates increasingly on the manufacturing of high and ultra high strength steels (up to 1100 MPa yield strength) and therefore in further studies these steels have an essential role. The use of laser and laser hybrid welding as a joining method is very attractive for such special steels. This is due to the established limits for welding energy and cooling time which are accomplished easily with the laser and laser hybrid welding.

Figure 1. Laser-GMA hybrid welding of mild steel S355

The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here