9. Which of the listed aluminum filler metal classifications would be the most appropriate to weld the 5052 base metal going to be used in a service environment with a sustained elevated temperature of 250°F? A — ER5356 B — ER4043 C — ER5556 D — ER5183 The answer is B. Sustained elevated temperature for aluminum alloys is recognized as being between 150° and 350°F. If 5xxx series base metal or filler metal with more than 3% magnesium (Mg) content is subjected to prolonged exposure to these temperatures, precipitate can form within it that is highly anodic to the aluminummagnesium matrix. This continuous grain boundary network of precipitate produces susceptibility to stress corrosion cracking (SCC) and the potential for premature component failure. The 5052 base metal contains less than 3% Mg and is, therefore, suitable for use at prolonged elevated temperature. ER5356, ER5556, and ER5183, however, are all filler metals that contain more than 3% Mg (around 5% Mg). While they could be used to weld 5052 base metal, none are suitable for prolonged elevated temperature service. Filler metal ER4043 contains no Mg and is, therefore, suitable for use at an elevated temperature. Arguably, the ER5554 filler metal could be a good, or even the better choice, for this application as it has a maximum Mg content of 3%, making it suitable for prolonged elevated temperature service, and it also has improved strength and toughness when compared to ER4043 (unfortunately, it was not one of the answer options given for this question). 10. What is the principal alloying element(s) in the 8xxx series alloy group? A — Copper B — Lithium C — Zinc and Tin D — Any other element than the 1xxx through 7xxx series The answer is D. ANSI H35.1, Alloy and Temper Designation System for Aluminum, is clear in defining the 8xxx series alloys as being those with principal alloying elements other than the 1xxx through 7xxx series. The series consists of 1xxx pure aluminum, 2xxx copper, 3xxx manganese, 4xxx silicon, 5xxx magnesium, 6xxx magnesium and silicon, and 7xxx zinc. The 8xxx series alloys are comprised of some aluminum/lithium (Li) alloys that contain higher Li content than copper (Cu), unlike the 2xxx series Li alloys that contain more Cu than Li. Also, some aluminum/ferrite (Fe) alloys are included in the 8xxx series. The 8xxx series is often described as the catchall series because it contains any alloy that does not fit the principal alloy category of the 1xxx to 7xxx series. 24 WELDING JOURNAL / DECEMBER 2016 WJ 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 36th St., #130, Miami, FL 331666672; tony.anderson@millerwelds.com. For info, go to aws.org/adindex
Welding Journal | December 2016
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