African Fusion July 2021

Cover story: Air Liquide

African Fusion talks to Mwali Kawawa and Michael Ashley of Air Liquide about the advancement of Air Liquide’s ARCAL™ range of gases and the reasons why this set of four excep- tional shielding gas mixtures continues to transform the welding market. ARCAL TM : reliable, smart and simple shielding

“ O ur ARCAL™NewGeneration gas offer puts the simple back into arc welding, without taking away any of our quality and safety prom- ises. We remain committed to delivering premium quality and high performance, but we see the way forward for advancing the welding industry as coupling these with simplicity,” begins Mwali Kawawa, Air Liquide’s national business developer for welding and cutting. “At the heart of the ARCAL™ New Gen- eration product line are four shielding gas mixtures: ARCAL™Prime; ARCAL™ Chrome; ARCAL™ Speed and ARCAL™ Force, which have been meticulously developed over many years to suit the broadest possible spectrum of gas shielded welding applica- tions in industry. We have found that there is now seldom any need to seek out more complicated gas mixtures,” he assures. “For TIG welding of duplex stainless steel, for example, there is an argument for using 2% nitrogen in an argon gas mixture to improve pitting resistance. We can, of course, still supply this and other special mixes, but for the vast majority of stainless steel fabrication requirements, ARCAL™ Chrome is ideal for MAG welding, while ARCAL™ Prime, our high purity argon

gas – more than N5.0 pure – is the estab- lished go-to gas for all TIGwelding of steels, stainless steels, aluminium and most pure metals and exotic alloys,” Kawawa tells African Fusion . “Where active gasmixtures are required for the MAG welding of steels, we have dis- covered that, for almost all applications, three part gas mixes, which typically con- sists of argon, carbon dioxide and oxygen, are detrimental in some ways and, inmost cases, removing the oxygen offers great benefits. None of our ARCAL shielding gas mixtures contains oxygen. The decision to go this route was motivated by a careful R&D programme to evaluate the effects of the elimination of oxygen, which were surprisingly positive,” he relates. Kawawa says that the first discovery was that oxygen makes it more difficult to weld in overhead and other awkward posi- tions. This is because the oxygen in the gas raises the fluidity of the weld pool, making itmore difficult to control themoltenmetal against gravity. Oxygen also raises fume emission levels because it readily reactswithhigh tempera- ture metal oxides to form fume, which can be carcinogenic. By removing the oxygen, therefore, welder safety is improved. In ad-

dition, the weld profile oxidation factor of carbon dioxide may be up to tenfold lower than oxygen. A mixture of 5% CO 2 -3% O 2 in argon, for example, has a factor of 5+30 = 35, whereas a simple mixture of 8% CO 2 in argon has a factor of only 8. “By removing the oxygen we substantially reduced the tendency to form non-metallic oxides on weld bead surfaces, therefore producing a cleaner and brighter finish that requires very little or no cleaning,” he says. Oxygen in the shielding gas also raises the concentration of iron oxide. Kawawa explains: “Ironhas a high affinity for oxygen thus an undesirable iron oxide FeO can form, which may negatively influence the microstructure of theweldmetal, therefore also affecting themechanical properties of the welded joint,” he adds. In terms of weld integrity, he explains that research suggests that no negative effects are related to the removal of the oxygen. With welds performed according to approved welding procedures (WPSs), there was no change in the mechanical properties of the welds completed using ARCAL™ gas mixtures compared to welds completed using equivalent three-part shielding gases. This, he assures, has been corroborated many times. “So for most common materials of construction, the simpler ARCAL™ New Generation gases offer several benefits and very few disad- vantages,” Kawawa tells African Fusion . Summarising the specific shielding ap- plications for each of the four ARCAL™ New Generation gas mixtures, Kawawa notes: • ARCAL™ Prime is the primary inert gas solution for a wide range of welding applications, materials and processes, including: TIG and plasma welding of all materials; MIGwelding of aluminium and copper alloys; and root shielding

In the autobody repair industry, for example, where high speed with low spatter levels and fume are important, ARCAL TM Speed is the ideal gas.

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July 2021

AFRICAN FUSION