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As a joining method, welding has been around for centuries. Today, roughly 100 welding methods are used in different industry sectors. The use of industrial gases (whether as individual gases or gas mixtures) to optimise welding processes dates back to the 40s and 50s. Since then the gas based welding processes have emerged to be the predominant group of welding methods.
Important gas shielded welding processes can be found in arc welding and laser welding. Within its ARCLINE product offering Linde has developed several families of shielding gas, such as CORGON®, CRONIGON®, VARIGON® and MISON®
In all arc processes, the electrode, molten pool and heat-affected zones must be protected from reaction with the ambient air. This is the primary role of the shielding gas. In addition, the correct shielding gas can also positively affect:
Weld properties such as strength, toughness and corrosion resistance
Weld porosity, bead shape and size
Welding speed, arc stability and amount of spatter
Your choice of shielding gas depends on your daily use and your weld specifications. Shielding gas represents only a small portion of the welding cost per inch, but the use of an appropriate gas can significantly reduce labor costs, by increasing weld speed or reducing finishing efforts (e.g., spatter removal or removal of excessive crown).
Special materials such as aluminum or nickel base alloys sometime require a fine-tuned shielding gas to achieve optimal welding results in high volume production environments. Here Linde’s doped shielding gases offer quality gains at reduced production cost.
During high-power laser welding, light energy melts and evaporates the metal. The pressure of the vapor displaces the molten metal so that a keyhole is formed, which guides the laser beam deep into the material. In this way, keyhole welding allows for very deep and narrow welds and is therefore also called “deep penetration welding.” It is a fast welding process with low heat input and low distortion rate.
Shielding gas plays an important role in laser welding and fulfills several tasks:
Shielding of the weld pool and the HAZ
Protection of the optics against fumes and spatter
Plasma control during CO2 laser welding
To control this plasma, pure helium (which has a high ionization potential) can be used as a shielding gas. Helium, however, is expensive. Under the trademark LASGON® Linde has therefore developed several argon-based shielding gases for laser welding that offer performance and quality gains.
LASGON® C are mixtures of helium, argon and carbon dioxide. They are especially suitable for mild and low-alloy steel, including galvanized sheet metal. LASGON® H mixtures have been developed for laser welding of stainless steel components such as pipes, sensor casings, cabinets etc. with CO2 lasers and also diode, Nd:YAG or fiber lasers.
Compared to pure inert gases, LASGON® H allows higher welding speeds and produces less oxide build-up, resulting in a clean and shiny surface.