Achieving a high-quality welded joint not only has an impact on the aesthetics of an item, but also on its integrity, durability, strength and safety.
Air Products South Africa believes that there are a number of factors differentiating a superior welded joint from an inferior, unacceptable one. Primarily, these include the experience of the welder, the quality of the welding equipment used and the choice of gas mix for the application. Sean Young, Welding Specialist for Packaged and Bulk Gases at Air Products, explains that two predominant gas types are used in welding.
“These are inert gases such as Argon and Helium and active gases such as carbon dioxide (CO2) or oxygen. Typical mixes include Argon and CO2, Argon and oxygen or Argon and Helium. Argon forms the majority percentage because it protects the weld puddle from atmospheric contamination.”
When using a two-part gas mix, one needs to consider the welding process that will be used. “These processes are known as Gas Metal Arc Welding, MIG (Metal Inert Gas) or MAG (Metal Active Gas) and Tungsten Inert Gas Welding (TIG). These are dependent on the type and thickness of the base/parent material to be welded, and the metal transfer mode (short circuit, globular or spray arc) with regards to GMAW process,” says Young.
“To optimise the weld properties of the shielding gas one needs to consider the penetration depth of the weld, the quality of fusion (how molten metal bonds with the base metal), the bead profile (concave or converse), the porosity (entrapment of gas in the weld after solidification) and the spatter (expulsion of weld metal from the weld pool),” Young explains.
According to Young, three-part gas blends result in a flatter weld, which means that welding speeds are increased and less post-weld grinding is required. This equates to increased productivity, quality and efficiency as well as decreased costs.
ESAB, an international and local supplier of consumables and equipment for welding and cutting process and applications, understands the importance of using the correct gas blend in its range of high-quality welding machines.
“We supply welding equipment for the entire series of processes within applications ranging from the DIY market right up to the large manufacturing end-users. Our customers expect uncompromising quality in all their welding functions,”
says Brett Cameron, Process specialist at ESAB.
Cameron says that ESAB uses both two-part and three-part gas blends. “The two-part flux blend shielding gas is perfect for cored wires. Swift Arc Transfer (SAT) which is ESAB’s high speed MIG/MAG transfer mode, enables manufacturers using robotic welding applications to maximise their output.
Due to the fact that this type of transfer mode by far out classes the known three basic types of transfer modes in MIG/MAG welding, SAT uses Coogar Shielding Gas for maximum welding characteristics and mechanical properties.
Cameron says that two-part gas blends are typically used for positional welding, where the molten pool needs to reach a plastic state relatively quickly, thus making it easier for the welder to manipulate the weld pool. ESAB recommends three-part gas blends for MIG/MAG welding applications. Coogar84 and Magmix3 are the most popular blends from Air Products.
“Three-part gas blends provide minimum post weld issues, have a superior cosmetic appearance, and reduce the need for joint preparation since the molten pool is extremely fluid,” says Cameron. “These blends are ideal for MIG/MAG welding of thin to thick steels.”
“Air Products takes great pride in the confidence its customers place in the choice of gas blend used in a wide range of applications. The end result needs to provide superior aesthetic finish, while simultaneously ensuring the structural integrity of the joint for ensured safe operation over an extended period of time,” Young concludes.