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Keyhole welding

A major advantage of Laserline’s diode lasers in terms of keyhole welding is the calm molten pool that minimizes the amount of spatter on the workpiece and laser optic, which leads to smoother and cleaner welding seams.

Besides aluminum welding or the joining of tailored blanks, the welding of thick steel with a laser power of up to 50 kW Is possible.

Keyhole laser welding – the method

With keyhole laser welding, very high beam intensities are used to process the material. Unlike heat conduction welding, here, a metal vapor is created in addition to the metal melt. This vapor partially displaces the melt, thereby leading to the creation of a vapor capillary (keyhole). This also applies for welding thick steel. The keyhole welding technique is characterized by a high process speed. The heat-affected zone is always highly limited, meaning that material distortion is correspondingly low. What remains is a narrow, evenly structured welding seam with a depth-gauge that is often bigger than its width.

Laserline_Keyhole_Welding

The advantages of a diode laser using the keyhole welding technique

A major advantage of Laserline’s diode lasers is the calm molten pool that minimizes the amount of metal splashes on the workpiece and laser optic, which leads to smoother and cleaner welding seams. With a protection class of IP54, the lasers guarantee process stability in tough application environments, even without protective enclosures. Their high electrical efficiency of up to 50 percent and their robust technology make Laserline’s systems a reliable, highly economical tool for keyhole welding. Designed for more than 30,000 operation hours, they are also very durable – and low maintenance, to boot.

Application examples

Welding thick sheets with 50 kW laser power

Processes for welding sheets with thicknesses between 10 mm and 25 mm are becoming increasingly popular for different industrial applications. As far as the laser-based process goes, seam preparation currently poses a key challenge in this area. Variable gap dimensions are often unavoidable and must be bridged reliably and efficiently. With 50 kW laser power and spot sizes of up to 4 mm,  Laserline’s LDF high-power diode  lasers offer a suitable system solution for these applications, too.

Journal

Welding thick steel sheets

To date, anyone wanting to weld thick-walled metal sheets has had to put up with long processes, not to mention irritating material distortions. Keyhole welding with fiber-coupled high power diode lasers from Laserline saves time and cuts costs.

The German expression “drilling thick planks” has long since become a popular metaphor for persistence. However, the welding of thick metal sheets is rarely discussed, even though persistence is also required for this, at least when established methods are used. But users know this all too well, especially those who opt for submerged-arc welding (SAW) or metal active gas (MAG) welding. For example, to join the thick steel walls of ships with a butt-joint, both methods require the welding seam to be prepared, and when using the typical laser MAG hybrid technique, multiple layers have to be welded. This takes time. When the sheets are more than 20 millimeters thick, there is often no other option than welding them from two sides or using a backing technique. This is no way to speed up the process, and the next time-intensive task is already waiting to be completed: the high heat input of conventional welding methods does not vanish without trace. Instead, it influences the steel structures of the sheets beyond the seam area and can lead to distortion in the components. This requires intensive post-processing.

Now, seams created by MAG or SAW welding are undoubtedly very solid and can also tolerate suboptimal seam preparation. Plus, they have proven themselves in practice over many decades. However, this does not mean that we cannot do it better: after all, the comparatively slow processes and material distortions that must be accepted with MAG welding pose an economic challenge. And this does not apply only to ship construction. The task of welding thick sheets is also present in other areas, as, for example, in pipe systems for oil and natural gas pipelines or in the foundations of offshore wind turbines.

For each of these application fields, one question crops up time and again: how can welding processes be made more efficient, and thus more economical?

Aluminum welding

Aluminum car body components used in visible areas require smooth and aesthetically appealing welding seams.
Here, Laserline’s diode lasers achieve excellent results, as the joints they create are uniform in shape and require no post-processing. The filler material of aluminum silicon (ALSi) is always required and serves to avoid hot cracks. It can be applied during the welding process with Laserline’s diode lasers in one of two ways: either via a tactile process optic or with the triple spot method using a supplementary wire, a method that was developed by Laserline. In this method, there are two side-spots positioned in front of the main spot, which first ablate the coating at the edge of the wire melting zone. This preparatory work results in a controlled melting process without the material being transferred to adjacent areas.

Over the course of three years, process investigations were conducted and diode laser requirements for aluminum welding were defined in close collaboration with Audi and other plant suppliers.