Practical Welding Today - March/April 2009

PWT: What are the advantages of
combining laser with GMAW, GTAW,
or PAW?

Bratt: One of the main advantages of the laser process is that because of its high energy density, deep and narrow welds can be produced at higher speeds than those normally associated with arc welding processes. The downside to the laser process is that it requires extremely precise fit-up between the parts to be welded to achieve consistent weld quality.

On the other hand, arc welding processes, particularly GMAW, have the ability to bridge relatively wide fit-up gaps between the parts being welded. The downside to conventional arc welding processes is their travel speeds, which typically are slower than the laser process, with much wider fusion zones and higher heat input and distortion in the surrounding material.

When the laser beam process is combined with an arc from, for example, GMAW, the travel speeds achieved can be equal to or faster than those associated with the laser process alone. As an added benefit, GMAW helps compensate for part fit-up variation, which allows the laser to be introduced into applications that would otherwise not be possible.

The laser acts as a stabilizer for the arc, which helps to root the arc to the weld joint of the material being welded, resulting in improved weld bead consistency due to the increased arc stability.

Which materials are best-suited for
HLAW?

Any material you can weld with a conventional laser or arc process can be welded using hybrid technology. So far most applications have focused on steel and aluminum, where reduced distortion, increased welding speeds, and improved weld quality are some of the benefits that have been reported. We have worked on successful development programs for applications with steel, aluminum, copper, and titanium to date.

How do you determine which HLAW
process to use?

This is mainly governed by material thickness and, to some degree, the requirements of the individual application. In general,

Design for manufacture really is the key to

successful implementation of hybrid laser-arc

welding. Joint access, joint configuration, and

part tolerances all play a part in improving the

chances for success.

laser/GTAW and laser/PAW tend to be used for thinner sheet metal applications. Laser/GMAW generally is reserved for welding thicker sections, although it has been used on automotive sheet metal applications as well.

In what applications is hybrid weld-
ing most beneficial?

The automotive and shipbuilding industries were among the first to adopt this technology. However, many others have followed suit or are currently evaluating the process, such as the aerospace and nuclear energy sectors.

In the shipbuilding industry, the laser/GMAW process has facilitated a significant reduction in weld distortion and associated rework compared to the previous arc welding processes used. Likewise, automotive applications have used both laser/GMAW and laser/PAW for body assembly welding, particularly for aluminum sheet metal components.

What is an ideal candidate for
HLAW?

Any component or assembly that requires high weld quality, increased welding speeds, and minimal heat input and distortion but might not be readily adaptable to the conventional laser welding process, particularly where part fit-up is an issue.

If you can get your components to fit together tightly enough for laser welding alone then you should go ahead and [use laser welding by itself]. But in certain applications, manufacturers just aren’t able to do that. That’s when you need to pair it with [GMAW, GTAW, or PAW] to improve the tolerance of the process and to close those gaps.

What is the most important factor
in ensuring success with HLAW?

Design for manufacture really is the key to successful implementation of hybrid laser-arc welding. Joint access, joint configuration, and part tolerances all play a part in improving the chances for success.

The process will benefit you more if you design the joint in such a way that you know you have the right access, the right approach to the joint, and the best possible fit-up. That makes a huge difference. All too often manufacturers have component designs that have been around for 10 or 20 years and they try and throw a whole new process at it, and that doesn’t necessarily work. That’s not the fault of the process; that’s the fault of the component, which was designed for something totally different. ■

Associate Editor Amanda Carlson can be reached at amandac@thefabricator.com.

Fraunhofer Center for Coatings and Laser Applications, 46025 Port St., Plymouth, MI 48170, 734-738-0550, www.ccl.fraunhofer.org, laserinfo@fraunhofer.org.