Laser cutting and laser welding

Laser cutting and laser welding have established themselves as effective, fast and cost-efficient methods for material processing in numerous industries. These process technologies are used in the automotive, airplane and shipbuilding industry as well as in the semiconductor industry and in medicine. In laser welding, the light is concentrated on one focal spot (Ø 0.2 - 0.3 mm) by means of a focusing optic and the material to be welded is melted quickly thanks to the high energy density. Once the melting point of the material is reached, it evaporates and a vapor canal is created. This is called a keyhole. Around the vapor canal, a melting zone forms in this method. When the laser beam and the workpiece move towards each other, the melted material runs directly behind the laser into the vapour canal and a clean weld is formed. Since this entire process only takes fractions of a second, a very high speed can be achieved in laser welding.

Keyhole welding and 3D laser welding with high laser intensity

In keyhole welding, the material being processed can be almost completely penetrated with the laser’s high energy. The intensity of the laser beam is above the limit of 10 6W/cm2 and its energy ensures that the mixture of evaporated material and shielding gas ionises resulting in laser-induced plasma. In heat conductivity welding, the intensity of the laser beam is below the threshold of 10 6W/cm2 . In this method, metal plasma is formed and there is no deep welding effect. 3D laser welding and cutting is suitable for processing 3D components, profiles or pipes. Even in places that are difficult to access, exact cuts and clean weld seams in high quality are produced. The material-friendly processing reduces follow-up operations and increases the degree of automation. An important argument for laser welding is the high laser welding speed which can guarantee work at a high level.

Which operating or protective gases are used for laser welding?

Depending on the application, different laser gases can be used for laser welding. Due to the better reproducibility, more and more ready-mixed resonator gases are used in the industry. Among the most popular gases are CO2 4.5, N2 5.0 (nitrogen gas for laser cutting), helium for laser welding 4.6 and argon gas for laser welding 4.6.

MESSER SOLUTION

3D printing involves the use of a variety of gases at different stages of the production chain.The latter essentially begins with the production of the powders used in 3D printing. Metallic powders are atomized with a gas jet to give them their spherical shape. Plastic powders, by contrast, undergo a cryogenic grinding process. This involves the use of liquid nitrogen. To guarantee their quality, some powders have to be permanently stored in a shielding gas atmosphere. Special containers filled with shielding gas are used for this purpose.

Depending on the specific process, printing a component involves the use of shielding gases, carrier gases and/or cooling gases. In the majority of printing processes, the type of gas required – and its purity – depends on the material. The following table provides an overview of possible shielding gases. Gases are also needed for subsequent treatment of components. This is done either through subsequent heat treatment designed to achieve homogeneous component properties or by carrying out a subsequent sintering process. Stress relieving annealing, a process that requires the use of a shielding gas, is the typical heat treatment. But other types of heat treatment may also be required.

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Contact us and we will gladly provide advice about these gases

PROCESS DESCRIPTION

3D printing (also called additive manufacturing) of metals has only been developed in the last few years but is already seen as one of the technologies for the future. Many companies and research centres are investing in research and development with the aim of standardising 3D printing in production.

3D printing involves making components by adding layers of material one by one. This method differs from conventional production processes in that the component is produced directly by melting powder or wire feedstock. The process is well developed in the production of plastics and has been used in this segment for some time. 3D printing of metals is quite another matter: the units are fairly expensive by comparison and are used in industry or at research facilities.

In contrast to conventional manufacturing, 3D printing offers advantages in the production of complex components. The addition of layers one by one very effectively facilitates the production of complex structures that would be difficult or impossible to achieve using traditional manufacturing techniques. 3D printing is frequently used for the manufacture of individual items or small batches as it would be too expensive to set up a conventional production facility. Typical examples include hip or dental prostheses in medicine as well as turbine blades or turbochargers.
 

Aspects of the technique

Present-day methods for additive manufacturing with metals can be organised according to the aspects of material feed and energy sources:

Powder bed

The most common techniques nowadays involve a bed of powder. This means layering coats of powder onto the blank and melting the layers onto the existing component. The source of energy for this can be a laser or an electron beam. In the former case, the process is called Laser Powder Bed Fusion (L-PBF), whereas in the latter, it is referred to as Electron Beam Melting (EBM)

Powder spraying 

Spraying powder requires the use of a carrier gas, meaning that electron beams cannot be used for the energy source. Powder spraying by lasers is already used for additive manufacturing and is known by the name laser metal deposition (LMD). Use of a welding arc in the form of a plasma beam has been known by the name plasma-arc welding for many years. Efforts are being made to adapt this method for additive manufacturing.

Wire feed 
Additive manufacturing techniques using a wire feed can in principle be used with any kind of energy source. Use of these techniques is becoming increasingly widespread due to the relatively low cost of the filler material.

Binder 

Metallic powders are mixed with a binder (often polymer). This binder is used to print a component layer by layer. The first step after printing is to burn out the binder. The next step involves sintering the component at a high temperature. Debinding and sintering cause the component to shrink. This shrinkage must be taken into account in the printing process.