#11
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I have restored a few Evinrude outboard motor fuel tanks from the 1930's, and those were made of the 1100 alloy, and were originally gas welded. On some of the tanks, made after 1939 when ALCOA had developed brazing for aluminum alloys, the bungs were brazed into the tank bodies. Yes, the brazing is a darker color, more of a gray-silver. I can send you a small bundle of flux-cored brazing rods that will join your 1000 alloys to the 6000 alloys very well, and it flows out like you were soldering copper. PM me your mailing address? As far as the fear of joint strength in vibration goes, I would personally rather have 1000 or 6000 brazed because I can get a better joint on threaded parts without having an undercut on the weld because my technique was not perfect the first time. For many guys, making a brazed joint is easier than welding. And, the engine surge tanks and fuel tanks on old US airplanes, from the old rickety P51's down to the little Pipers had brazed fittings on them. Also, funny thing, but most modern automobiles with automatic transmissions have aluminum torque converters that are brazed together. (This is just my own personal opinion, and info gained from the American Welding Society and the Aluminum Association of North America, and from my own little puttering on a few old "has-been" aluminum contraptions, so it's worth just about what you would pay for it .)
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. Last edited by crystallographic; 02-01-2015 at 11:10 PM. |
#12
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The original specification included sections of rod attached to the tank to provide mountings. Brazing fittings like filler necks and tappings is perfectly acceptable but I'd weld the mounting points in the interests of reliability because whatever way you look at it the joint strength of a weld is way more then that of brazing.
Will
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Here to learn. William Pointer |
#13
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6061
Hi Will,
I was searching for some information about 6061 and got this from Wikipedia: Welding 6061 is highly weldable, for example using tungsten inert gas welding (TIG) or metal inert gas welding (MIG). Typically, after welding, the properties near the weld are those of 6061-O, a loss of strength of around 80%. The material can be re-heat-treated to restore -T4 or -T6 temper for the whole piece. After welding, the material can naturally age and restore some of its strength as well. Nevertheless, the Alcoa Structural Handbook recommends the design strength of the material adjacent to the weld to be taken as 11,000 psi (75 MPa) without proper heat treatment after the weld.[citation needed] Typical filler material is 4043 or 5356. Is the loss of strength the cause of welding TIG or MIG or is this the same case with oxywelding. What I mean is this: What do they mean with the information above, is the loss of strength caused by the heat input of welding(in that case the loss of strength should be the same with oxywelding) or is it caused by the very narrow local heat input(TIG/MIG) Richard.
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Richard |
#14
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Hi Richard,
Yes, it's the same regardless of the heat source though as a gas flame imparts energy more slowly than a TIG flame you end up with a bigger HAZ (Heat Affected Zone) and therefore a greater amount of metal affected so it's actually worse than TIG or MIG. Welding basically un-heat-treats the metal. But for what you are wanting to do I wouldn't worry about it. After all, the way those old Seagull outboards rattle around you don't want anything to stiff bolted up there in case it starts to crack. Will
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Here to learn. William Pointer |
#15
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Quote:
But if I get it right, if something is gaswelded the larger area is weaker than other welding methods but because the larger area is more even heated therefor more flexibel and more durable? Richard.
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Richard |
#16
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Any part of the weldment that goes above its annealing temperature will be annealed. That temperature is 775 degrees F for 6061. There are temp sticks available that could be used to check the temperature of your weldment in various places.
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Bob Don't believe everything you think. |
#17
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It depends on how long it's above the solution temperature and how quickly it cools. Rub ordinary household soap on the piece, or mark it with a Sharpie. The soap will turn brown as you approach solution temp, the Sharpie will disappear. Either method will let you get a look at the extent of your HAZ but making a few welds will not normally hold things over the solution over the solution temp for long enough to achieve full annealing. Add to this that the temp will come down quickly and what you get is partial annealing so if you start with tempered material you are left with a finished job that is softer than it used to be but still stronger than annealed material.
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Here to learn. William Pointer |
#18
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I'd like to weigh in and inject a touch more accuracy on the “anneal” issue.
Nothing wrong has been said in the overall sense, but what has been said may lead the uninitiated and distracted to misunderstandings and expose some to a waste of $$ and effort. The "low temp" anneal is described in the Alcoa Technical Reference, more correctly as "W" Temper. It is described as relieving work hardening, and is not considered a true anneal. mjb
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Marc |
#19
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Annealing heat-treatable aluminum alloys
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(Maybe this now should be its own thread?) The key point, as I explain in my classes, is that there is a temporary anneal and a permanent anneal of heat-treatable aluminum alloys. To gain a temporary anneal, or what the Aluminum Association refers to as a field annealing, you simply heat the 6061, in this case, to 775F and then quench it, usually by water spray, soaking wet rag, toss in a snowbank, or blast with a CO2 fire extinguisher. It is soft for a few hours, and then regains some but not all, of its original hardness after 10 to 20 additional hours. I have done this many times. Field work is inherently inaccurate, by laboratory/aviation/aerospace standards. The manner of temperature measurement in the field can be relatively accurate with a temp crayon, or relatively inaccurate (650F to 780F) by heating off either black marker marks or O/A sooty flame marks (watch the amount of soot!!), or rubbing when hot with either bar soap or a stick of soft pine (chars on contact). If you are thinking of using a digital laser temp-o-meter, remember that aluminum is inherently reflective, and not prone to accurate measurement by those devices, according to both personal experience and the manufacturers' disclaimers. A permanent anneal of heat-treatable aluminums may best be accomplished in an oven with controls, and not by field working. To do this, the aluminum must be heated to 775F and held until it is thoroughly soaked. After this point the temperature is allowed to drop at the prescribed rate of 50F per hour, until the metal part has reached 350F, at which point any method of cooling - immersion quench, air quench, or leaving in the dwindling oven may suffice. In summation, annealing of heat-treatable aluminums can be done in the above two ways, in addition to a partial anneal which draws back the temper from a full T6, to a measured T4 or T3. Final note: The oldest family of heat-treatable aluminums goes back to 1914, in Duern (umlaut over U), Germany, where an engineer developed extrusions for lighter-than-air ships (dirigbles) having rigid internal frameworks. He named this family of aluminum alloys Duralumins, and they are still known today in the US as Durals, having alloy numbers 2024, 2017, 2117, and two others I have to look up, and all having over 5% copper in the alloy mix. Hope this clarifies a very common tangle - a little bit,
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Kent http://www.tinmantech.com "All it takes is a little practical experience to blow the he!! out of a perfectly good theory." --- Lloyd Rosenquist, charter member AWS, 1919. Last edited by crystallographic; 02-04-2015 at 07:29 PM. |
#20
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It all comes back to what I mentioned in an earlier post. To do the job right you put all your material into the heat treatment plant, have it annealed back to T-0, make your weldment then take it back and have it stress relieved and tempered to your requirements.
Will
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Here to learn. William Pointer |
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