WELDING JOURNAL 25 It is one thing to have a desirable base material, but without a practical and reliable method of joining such a material, it becomes impractical to use it for fabrication. The development of welding procedures for aluminum alloys was somewhat different than that of carbon steel. Because of the many variations of aluminum base alloys and the different effects each alloying element would have on the weldability of the base materials, it was necessary to develop many different filler metal alloys to accommodate these variables. The addition of these elements produced aluminum alloys with varying amounts of crack sensitivity. The various degrees of sensitivity for each of the different alloys needed to be established to provide guidance for developing suitable welding procedures that would produce consistently crack-free welds. This welding development work was a major project in itself. Much of the work was performed by two groups — the aluminum base material manufacturers, as it was certainly to their advantage to show that aluminum could be reliably welded, and also by some of the first aluminum fabricators, who recognized the potential of this new material and were eager to use it within their manufacturing operations. Two of the pioneers in aluminum welding development in the United States were ALCOA (The Aluminum Corp. of America) and Kaiser Aluminum and Chemical Corp. Their publications, Welding ALCOA Aluminum, was first published in 1954, and Welding Kaiser Aluminum was first published in 1967. To be competitive in the modern industrial world, a structural metal must be readily weldable. The earliest welding methods used for aluminum were oxyfuel gas welding and resistance welding. Arc welding of aluminum was limited to shielded metal arc welding (SMAW), which was soon found to be not the most suited process for welding aluminum. It uses a flux-coated welding electrode, and even though these electrodes are still available today, the quality of the welds produced with them is generally poor. Also, SMAW is not recognized within the AWS structural welding code for aluminum. The breakthrough for aluminum welding occurred with the invention in the 1940s of the inert gas welding processes. The introduction of gas tungsten arc welding (GTAW), shortly followed by gas metal arc welding (GMAW), which used an inert gas to protect the molten aluminum during welding, and did not require the use of flux, made it possible to make high-quality and high-strength aluminum welds. Summary We have Hall and Heroult to thank for creating a readily accessible material that has provided challenges throughout recent years and promoted the development of new welding processes and filler metals required to weld this material successfully. Today, aluminum and its alloys are readily weldable using a variety of techniques and welding processes, including newer methods such as laser beam welding and friction stir welding; however, GMAW and GTAW remain the most popular.◆ TONY ANDERSON is director of aluminum technology, ITW Welding North America. He is a Fellow of the British Welding Institute (TWI), a Registered Chartered Engineer with the British Engineering Council, and holds numerous positions on AWS technical committees. He is chairman of the Aluminum Association Technical Advisory Committee for Welding and author of the book Welding Aluminum Questions and Answers currently available from the AWS. Questions may be sent to Mr. Anderson c/o Welding Journal, 8669 NW 36 St., # 130, Miami, FL 33166-6672, or via e-mail at tony.anderson@ millerwelds.com. For info, go to www.aws.org/ad-index
Welding Journal | February 2014
To see the actual publication please follow the link above