Q: Below are the questions and answers for the Aluminum Q&A quiz published in the October 2016 Welding Journal. I would like to thank everyone who participated in this quiz. I received many comments as to how individuals enjoyed researching the answers. The six winners, selected at random from all who sent me 100% correct answers, are listed below in alphabetical order. 1. Pedro Aranda, San Diego, Calif. 2. Steven Blevins, Richwood, Ohio 3. Eric Caswell, Ucluelet, BC, Canada 4. Billy Frazier, Atkins, Va. 5. Baljinder Singh (Deepak), Blainville, Québec, Canada 6. Carolyn Tucker, Newport News, Va. 1. Who was the Danish professor credited for the first isolation of the element aluminum by reducing aluminum chloride with a potassium-mercury amalgam in 1825? A — Charles Martin Hall B — Paul T. Heroult C — Karl Joseph Bayer D — Hans Christian Oersted The answer is D. Hans Christian Oersted (1777–1851), portrayed below, is best known for his discovery in 1820 that electricity and magnetism are linked. The discovery of electromagnetism set the stage for the eventual development of our modern technology based world. Oersted also achieved the first isolation of the element aluminum in 1825. 2. According to AWS D1.2/ D1.2M:2014, Structural Welding Code — Aluminum, why is the wraparound guided bend jig the preferred method for guided bend testing of aluminum weldments? A — It is less expensive. B — It is more tolerant of significant variations in as-welded mechanical properties of some aluminum alloys. C — It uses a larger bending diameter than the plunger type. D — It is able to tolerate more variation in plate thickness. E — It is not as sensitive to the rolling direction of the test plate being tested. The answer is B. Look in AWS D1.2, Figure 3.13, Wraparound Guided Bend Jig, Note 1. Wraparound guided bend jig is the preferred method of bend testing aluminum weldments (see C- 3.8). Clause C-3.8 indicates: Because of significant variations in the as-welded mechanical properties of some aluminum alloys, the wrap-around bend test method (see Figure 3.13) is the preferred method of bend testing aluminum weldments. The plunger test method is an alternative method; however, it may prove to be unsuitable for some base alloy-filler alloy combinations addressed in this code. It is not uncommon for a groove weld to meet the minimum transverse tensile strength during the reduced section tension testing process, and the same weld fail during the guided bend test because the incorrect bend fixture was used. It is always advisable to specify that the wraparound test be used when ordering guided bend tests of aluminum weldments. 3. When plasma cutting aluminum on a water table, what is the gas that can be created through a reaction of the water and molten aluminum, become trapped, and potentially cause an explosion? A — Hydrogen B — Nitrogen C — Ozone D — Acetylene E — Propane The answer is A. See the Aluminum Association’s Welding Aluminum Theory and Practice, 4th Ed., Chapter 18: Health and Safety Considerations – Explosion: Although publications and standards dealing with weld safety cover most of the possible causes of explosion, there is one cause that is quite rare and thus not well known. When aluminum is plasma arc cut on a water table, molten aluminum dropping into the water will “steal” oxygen from the water and release free hydrogen gas. If the hydrogen becomes trapped between the aluminum and the water surface, an explosive mixture can develop and be ignited by the cutting arc. Forced air cross flow must be used between the aluminum and the water to avoid a buildup of hydrogen. Similarly, when aluminum is plasma arc cut under water, the molten aluminum reacts with the water to release hydrogen. Dangerous concentrations should be avoided by inserting a perforated piping system in the tank to aerate the water. 4. In accordance with the requirements of AWS D1.2/ D1.2M:2014, Structural Welding Code — Aluminum, what is the maximum preheat temperature when welding base metal 5005? A — 150˚F B — 250˚F C — 350˚F D — It does not provide a max preheat for this base metal. The answer is D. As stated in AWS D1.2, Clause 4.9, Preheat and Interpass Temperatures: “When fabricating the heat-treatable aluminum alloys or the 5000-series aluminum-magnesium alloys containing more than 3% magnesium, the preheat and interpass temperatures shall not exceed 250ºF. Holding time at this temperature shall not exceed 15 min.” The 5005 base metal has a maximum magnesium content of only 1.1%; therefore, the code does not provide a maximum preheat for this base metal. ALUMINUM Q&A 22 WELDING JOURNAL / DECEMBER 2016 BY TONY ANDERSON Hans Christian Oersted
Welding Journal | December 2016
To see the actual publication please follow the link above