Welding applications have come a long way, thanks to advancements in welding technology and machinery in recent years, and a wider knowledge when it comes to ascertaining the right combination of gases for the right process.
This is according to Sean Young, Welding Specialist at Air Products South Africa, a leader in the bulk, cylinder, specialty gas and chemicals supply markets. “Years ago there was only one mixture for MIG/MAG (metal inert gas/metal active gas) welding and that was carbon dioxide. Today, there are many more choices open to a welder. Whereas before, welders only used active gases (such as carbon dioxide), experiments led to a wider knowledge of how gases, and in particular how a combination of both active and inert gases can change the welding and mechanical properties as well as the aesthetic appearance of a weld,” he notes.
Josef Henning, Welding Specialist at Lincoln Electric South Africa, agrees, “Welding machines have become very ‘high-tech’ in terms of being able to assist in choosing the right gas combination, the right settings for the right material – all with a view to optimise cost savings. Through technology, a welder can gain a much higher tolerance range in terms of the settings on the machine, through which you can manipulate or ‘fine-tune’ the appearance of the weld, and reduce the splatter volume.”
Lincoln Electric offers welding solutions through both welding equipment and expertise, while Air Products supplies welding gases to the company, as well as to its distributors. “There are standard mixes which Air Products provide. Due to the availability of a wide range of welding materials and applications, we are also able to liaise directly with Lincoln, should a customer require a specialised welding mixture,” says Young. He adds that Air Products prides itself on its commercially proven technologies and innovative solutions tailor-made for individual customer requirements.
The most commonly used welding gases are carbon dioxide and argon, an inert gas, although oxygen is often used in either a two-part or three-part mix, in small percentages. Helium, another inert gas, is often used in combination with argon in the welding of aluminium, copper and other alloys. Argon generally forms the majority percentage of the welding gas mix as it protects the weld puddle from atmospheric contamination, according to Young.
“The choice of two-part (such as carbon dioxide and argon) or three-part (such as oxygen, carbon dioxide and argon) depends on the application, customer requirements and cost factors. For thinner materials, we would normally recommend a three-part mix which would typically be an argon-carbon dioxide mix, with a small amount of oxygen. For thicker materials, the amount of carbon dioxide is increased. Air Products’ sales engineers draw on their in-depth understanding of their customers’ product and equipment when it comes to identifying and advising customers on the most reliable and cost-effect gas mixtures designed for particular welding applications.
Such applications, or processes, range from MIG/MAG, also known as Gas Metal Arc Welding (GMAW), TIG (Tungsten Inert Gas Welding), and other more specialised processes. “These are dependent on the properties and thickness of the base/parent material to be welded, as well as the metal transfer mode, which can be short circuit, globular or spray arc,” says Young.
“In choosing the right shielding gas mixture, whether two-part or three-part, the customer needs to take into consideration a variety of factors, including splatter volume (the expulsion of weld metal from the weld pool), weld speed, and weld appearance,” says Henning. In terms of costs, with the right machine, the right settings and the right gases, you can cut down post-welding costs.
“The welding machinery available today can go a long way in analysing which mix will be the most cost-effective in the long-run,” he adds. “The cost-effectiveness depends on whether it is a 2% oxygen or 2% carbon dioxide mix for welding stainless steels, or whether it is a 75% /25% mix for welding with Flux cored wire – and this decision is almost entirely application-driven.”
According to Young, three-part gas mixes increase weld speeds, and less post-weld activity is required. This means an increase in efficiency and a decrease in costs.
“It is vitally important to get it right,” Young emphasises. “The wrong gases with the wrong application can be a disaster – it can affect the properties of the weld. Using the wrong gas mixture may lead to a decent-looking weld on the surface, but there could be inherent metallurgical defects inside the weld as well as mechanical property problems.
“While Air Products’ standard gas mixtures, such as the Coogar range, are well-known and commonly used in the welding industry, there are plenty of specialised gas mixtures available which can enhance the structural integrity of the weld, provide a superior cosmetic finish and provide long-term cost-saving benefits. At Air Products we can provide expert advice when it comes to fine-tuning the welding process to achieve optimum results,” concludes Young.