Laser Welding
with Diode Lasers

High strengths and low distortion characterize laser welding with one of our lasers. Even at high welding speeds, excellent seam surfaces can be achieved on the workpiece. Typical application fields for laser welding machines are the joining of steel, aluminum, copper or plastics.

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Laser welding machines in the Industry

Hardly any industrial branch today can do without laser welding technology, because in almost every manufacturing process there are metals or plastics that have to be joined. Laser beam welding is ideally suited for this purpose, especially when high welding speeds, narrow weld seams and low thermal distortion are required.

Diode lasers are used in many laser-assisted joining processes. A distinction is made between laser soldering, heat conduction welding and deep welding with lasers.

Laser beam soldering generally involves melting an additional material. This filler material wets the surfaces of the components to be joined and thus joins them after solidification. This process is mainly used in the automotive industry by laser welding robots for joining steel bodies.

Heat conduction welding and deep penetration welding, on the other hand, cannot be directly assigned to any industry or individual application. From control cabinets to sensor housings, bellows, electronic devices, batteries, sheet metal in various applications, coated and uncoated sheet metal, heat exchangers, saw blades and band saws, thick sheet metal in shipbuilding, drinking water pipes, sinks, tailored blanks, stainless steel and aluminium car bodies, beer barrels and much more is welded and joined with the diode laser.

Laser Beam Welding in Process Engineering

Due to process-related advantages, such as high welding speeds or high degrees of automation, laser welding systems are increasingly assuming a key function in production technology. By means of narrow, almost parallel seam flanks, resource-saving seam preparations can be used which result in low shrinkage. The latter can also be implemented using laser-MSG hybrid welding, which combines the advantages of two different welding processes through synergy effects. In particular, this ensures greater gap bridging capability and consequently reacts insensitively to tolerances within the weld seam preparation.

 

Materials Engineering

Irrespective of sheet thickness and component geometry, different material combinations ranging from unalloyed and high-alloy steels to non-ferrous metals can be welded without irregularities. In addition to these, different material pairings are becoming increasingly important in today's application technology. The mechanical-technological properties to be fulfilled, such as for tailored blanks, are at the forefront of the respective joining task. These correlate with the respective heat guidance of the process, which can be influenced by special optics or the feeding of cold or hot wire.

LDF Diode Lasers in Car Body Construction

A central application field for Laserline's diode laser solutions is the joining of shell components in the visible area of the vehicle, e.g. tailgates, roof seams, doors or C-pillars.

Besides the requirements of higher firmness and possibly a small heat-affected zone, as far as these visible seams are concerned, particularly high demands are made on the appearance of the welding seam.

Remote laser welding with beam converter

To reach a quicker and more flexible process control when welding vehicle bodies or ships’ sides, remote laser welding is increasingly used. Because the laser beam is here directed from a distance of over one meter onto the workpiece, the application requires the combination of high laser power and high beam quality. Laserline LDF diode lasers with beam converter offer an optimal system solution for this special manner of keyhole welding.

Welding Tailored Blanks

At the laser-based tailored blanks welding using several sub sheets, shaped blanks are put together that will later be transformed to car body parts. However, the process is often afflicted with inefficient and easily soiled lasers that furthermore leave unpleasant metal splashes on the sheet and welding optic. Laserline's laser welding machines generate an extremely calm molten pool that hardly creates a splash. They also resist dust and moisture-intense process environments throughout the entire welding process.

Journal

Diode lasers and metal welding

Having clarified at the start of our small series what exactly a diode laser is, today we look at the application fields. These are, as already mentioned, broadly diversified even though there are certain key areas in which diode lasers can clearly attract attention. One of them is the metal welding process. Diode lasers play a decisive role in various industrial areas, from the wafer-thin electric contact-sheet to the centimeter-thick side of ships made of steel and countless metal components joined by welding. Today, diode lasers cover a complete array of joining spectrum and offer suitable tools for different welding applications. Compared to classic arc welding methods like MIG/MAG or WIG welding as well as other laser-based welding techniques, welding with diode lasers is often superior.

In fact, diode lasers are actually meant for industrial welding processes. This are several reasons for it. First, the combination of high power output and comfortable spot sizes allows for an optimal gap bridgeability. Second, the energetic homogeneity of the spot and the high absorption capacity of a typical wavelength mix generate unusual calm melt pools that leave almost no impurities by spatters or wavelets at the adjoining areas of the seams. This guarantees excellent seam qualities. Third, diode lasers provide the highest energy efficiency of any industry lasers, which also qualifies them along with their low maintenance costs – for welding in series production. Fourth, with these lasers, heat conduction as well as keyhole welding applications can be executed.

Using components with medium to substantial material thicknesses, keyhole welding is a typical laser welding method. The joining partners are irradiated with high intensity so that a vapor capillary is created in the direction of the beam - a tube-like one with a metal vapor filled hollow (keyhole). Thus, the material is molten up to the deeper layers; the depth of the melt zone is usually higher than its width. The inner walls of the vapor capillary also reflect the laser beam so that the absorption of the yielded energy is strengthened, thereby causing a sizable melting volume. Between the joining partners, highly stable connections are created that withstand even the most demanding stress. Typical applications are, for example, the joining of tailored blanks in the automotive assembly or thick-sheet welding. As combined diode laser systems today can reach powers of up to 60 kW, even ships’ sides of 50 mm thickness made of massive steel braces in foundations or offshore wind turbines can all be welded with only two welding runs (layer and opposite side).

When workpieces of a low material thickness have to be joined, keyhole welding is no longer automatically suitable. The high energy input could cause material separations instead of joining, but definitely with heavy deformations. Thus, in such cases, heat conduction welding is almost always used. With its welding penetration depth at a maximum of 2 to 3 millimeters, the method is also suitable for thin sheets or metal foils. The diode laser fuses the joining partners along the planned seam; the melts merge and then solidify towards the desired weld seam. The material distortion is low, while the joining is totally uncomplicated and clearly quicker than WIG-welding, for example. Because of the homogeneous and even heat exposure of the diode laser, the seams are smooth and non-porous and do rarely need post-processing. This high seam quality makes the method especially for visible areas interesting, as, for example, in the joining of metallic sinks. Besides, it has also proven itself quite apart from design-related spheres, even at geometrically very demanding components such as gaiters for pipes.

With the development of the LDMblue, a laser with 450 nm and hence the blue light wavelength, meanwhile even the world’s first high-power diode laser is now available, which allows for a controlled spatter-free heat conduction welding of very thin non-ferrous components made of copper or precious metals such as gold. Here, with the classical infrared lasers, heat conduction welding is not feasible due to the infrared radiation being strongly reflected by non-ferrous metals, such that the surface can only be molten with a high-intensity beam. However, blue laser light is very well absorbed by non-ferrous metals so that the workpieces can be molten with clear lower energy input as well. In this, even wafer-thin electrical contacts made of copper, e.g. those used in electromobility, can be reliably joined. Here as well, very smooth and visually pleasing seams are created that can additionally prove themselves with their excellent electrical conductivity.

You see: for metal welding, the diode laser is a real universal tool that has no equal. And because work will continue on optimizing the relation between laser power and beam quality on all types of diode lasers, the spectrum of application fields in welding will probably grow.

Interested in our diode laser systems for applications in industrial materials processing?
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