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Welding_aluminumby different processes:SOLUTIONS with Effective, Powerful Advice
Welding_aluminum, aluminum alloy types, weldability of aluminum, aluminum heat treatments and welding processes, resistance welding, welding techniques, welding links, welding tips, improving welding results, joining questions needing answers: these are some of the items developed in this Site for the benefit of interested readers. What is in here for me? If you work with some type of Welding aluminum you already know what you need. But in case you want to expand welding to a new kind of material, don't you think you might profit from condensed information addressing the most important characteristics which affect Welding_aluminum alloys? In a previous page on Welding_aluminum, a short review of Welding_aluminum was offered, including some basic properties which make aluminum alloys the natural choice for quite a large range of applications. We presented there the main difference between aluminum alloys whose mechanical properties cannot be improved by heat treatment, and can be easily welded, and those that can be strengthened by heat treatment known as solutioning and precipitation process but cannot be readily welded. Here we are going to enter in some more detail in the processes used for this important class of materials.
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Different Processes... Friction Welding aluminum is used for joining of aluminum alloys both to themselves and to different materials like copper alloys and stainless steels. When applicable this process is unique in its capability to permit joining combinations which could not be performed with any other method, except possibly by Brazing with certain limiting requirements. One recent development which has already interesting applications for space related hardware is called FRICTION STIR WELDING and is designed to perform butt Welding_aluminum in sheet and plate of aluminum alloys and other materials as well. A special rotating tool is forced into the joint and moved along, between the two abutting surfaces. Friction heats the material to a plastic state and produces a defect free weldment with finer grain size and better properties than those of the original materials. For short reviews of this process one can link to any of the following: Different results... RESISTANCE WELDING is used for Welding aluminum alloys, not only for those not hardenable by heat treatment but also for those special types (of 2xxx and 7xxx classes) hardenable by heat treatment, or more precisely through solutioning and aging: in fact resistance Welding_aluminum is almost the only process recommended for this last classes of materials, because its influence is local and does not degrade the material properties. Any other fusion process would impair strength, hardness and resistance to corrosion. However some special properties affecting Welding_aluminum alloys should be considered: higher electrical and thermal conductivity (than low carbon steel): these two properties combined require higher current to perform welding in a shorter time. Lower softening and melting temperature, lower strength, the presence of a naturally formed surface layer of aluminum oxide, which produces useful corrosion resistance properties but hinders Welding_aluminum processes if not removed, all these pose a challenge to be specially addressed when developing welding schedules for Welding_aluminum. These characteristics influence the selection of parameters for resistance Welding_aluminum. Therefore process control is much important and equipment must be capable of precisely selected settings. Surface preparation and cleanliness are essential to obtain consistent results. Not all available aluminum alloys and conditions are welded with the same ease. In particular soft alloys (in annealed condition) are prone to higher surface indentation and sheet separation which may be objectionable if not dealt with by special means. Requirements for resistance Welding_aluminum alloys (and also for other materials) can be found in Specification Not recommended... Gas Welding_aluminum of weldable aluminum alloys in thin gages is not outright impossible, it requires nevertheless the use of an active flux in order to remove the oxide layer. Flux remnants must be thoroughly cleaned, removed or neutralized after welding to avoid corrosion. Therefore oxyacetylene welding is not the preferred solution if a suitable arc welding can be applied. Mostly used... Practically only GAS TUNGSTEN ARC WELDING (Tig) and GAS METAL ARC WELDING (Mig) are employed for Welding_aluminum because of their advantages where compared with other less convenient arc processes. Again only weldable alloys should be considered, excluding 2xxx and 7xxx classes (except that special alloys were developed to allow acceptable special Welding_aluminum procedures). They permit welding in all positions even for hard to reach spots, there is no need for application of flux, and the results are of best quality.
Filler metals commonly used are listed in:
Also Castings of aluminum alloys can be repaired by Welding_aluminum, with some exceptions, preferably in fully annealed condition. Those responsive are then heat treated as required. In summary, weldability is best for non heat treatable aluminum wrought alloys except that those which gain some hardness and strength through mechanical deformation (strain hardening like cold rolling or stretching) risk to lose them when heated for welding. Welding_aluminum alloys is usually performed with alternating current, except that for thin gages also direct current reverse polarity (electrode positive) is used, with a good cleaning effect of the oxidized layer, produced on the surface by bombardment of argon ions. Alloys of series 6xxx are easily welded and can then be strengthened by heat treatment if necessary. Welding_aluminum of other heat treatable alloys is generally not recommended. Cast alloys fall within the same criteria depending upon their chemical composition, and their weldability varies accordingly. Filler metal selection... Proper filler metal selection permits Welding_aluminum of different alloys together but the choice may be influenced by the most important feature from those following: ease of welding, strength, ductility, response to subsequent heat treatment, color match after anodizing and corrosion resistance. An Article on the Selection of Aluminum Alloy Filler Metal was included in our Practical Welding Letter No. 04 of December 2003. To see the article click here An Article on Filler Metals for Aluminum-Lithium Alloys was published on the May 2005, Issue No. 21 of Practical Welding Letter. To read the article click on Issue No. 21. An Article on Weld repair of Aluminum Castings was published in Issue 42 of Practical Welding Letter for February 2007. Click on PWL#042 to read it. An Article on Welding Effects on Aluminum Structures was published in section (3) of Issue 44 of Practical Welding Letter for April 2007. Click on PWL#044 to read it.
To suscribe and receive regularly by e-mail at no cost the periodic publication above, click on Subscription. Best weld quality depends on thorough cleaning of the base metal before Welding_aluminum and should be conducted by chemical or mechanical means in order to remove not only foreign material but also the oxide layer which forms on the surface by normal exposition in air. Other Specifications and reference documents are listed hereafter:
High power density processes... Electron Beam Welding_aluminum of weldable aluminum alloys is readily performed with good results even in very deep welds. As usual the remarkably high depth to width ratio permits to join configurations not possible with other means. The heat input being low and the heat affected zone of limited extent, there is often no remarkable damage to the mechanical properties so that further heat treatment is not required. Also LASER Beam Welding_aluminum is performed on weldable alloys, with the usual precautions needed to insulate the weld from air. NEW RESOURCES
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Which processes are used to weld aluminum alloys? Why is Resistance welding applicable to heat treatable alloys? What about alloy conditions? We should better know before trying. See here... -
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