The emergence of fiber lasers as a viable alternative to CO2 lasers in laser beam welding (LBW) is exciting for tube and pipe producers, largely because fiber lasers don’t require the use of helium.
Helium is necessary in CO2 LBW—which is easily the most predominant LBW method—because even though the process is called simply CO2, the resonator gas includes helium. Helium is also needed as a shielding gas.
The price of crude helium has nearly doubled in price in the past 15 years, and the cost of grade-A helium has quadrupled—so being able to eliminate the use of helium has grown considerably in importance.
Fiber lasers also reduce electricity use because they run more efficiently than a CO2 laser (30 percent compared to 5-10 percent).
For tube and pipe producers, LBW has several important advantages over conventional GTAW and PAW— higher welding rates, stronger welds, and deeper, narrower keyholes. For fabricators already using LBW—or considering moving to LBW—the availability of fiber laser technology offers the potential to gain these advantages at lower cost.
The Challenge
The problem for tube and pipe producers is that fiber lasers don’t eliminate the primary challenge of LBW—compared to GTAW or PAW, it requires significantly better weld monitoring because of the precision of the process.
Just as with GTAW and PAW, the strip edge presentation and seam location in LBW must be controlled to minimize defects such as mismatch, edge wave, edge gap, and seam wandering. However, because a laser beam spot is about 10 percent the size of a GTAW or PAW arc, achieving this control is much more difficult.
While the narrower heat-affected zone of laser welding creates stronger welds, the small spot size makes it difficult to keep the laser on the seam as the seam wanders from left to right. It requires very precise monitoring to keep the seam on track.
Achieving Greater Precision
Fortunately for tube and pipe producers, weld monitoring technology has improved to keep pace with LBW advancements such as fiber lasers.
Laser-based Weld Inspection Systems, such as the Xiris WI2000p, have proven to be an effective way to achieve the enhanced process control that LBW demands. Using triangulated lasers and a trailing camera to monitor the weld seam, the weld head in a typical laser-based Weld Inspection System can track the seam over an area of (1”)—enough to compensate for seam wandering in properly maintained mills.
Once the system has been taught the correct weld parameters, it monitors the process and alerts operators when parameters are exceeded.
Weld Cameras are another tool that progressive tube and pipe fabricators are using to improve their monitoring of LBW—allowing for real-time operator monitoring of the process. With a Weld Camera with High Dynamic Range imaging—such as the Xiris XVC-O—operators can follow the process as it occurs, with clear visibility of the entire brightness range of the weld scene, without having to delay the process to change lighting.
This immediate visibility allows operators to use their judgment and experience—which even the best laser seam tracker can’t match—to make adjustments that improve quality and productivity.
Conclusion
LBW offers tube and pipe producers many benefits—and the use of fiber lasers can add to the advantages—but these productivity and quality gains are only possible if the precise LBW process can be sufficiently controlled. This requires advanced weld monitoring solutions, such as Weld Inspection Systems to automatically track the seam and Weld Cameras that allow operators to exercise in-process control.
