Posted: 9/16/2006 9:26:22 PM EDT
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So I had to take apart some anodized aluminum parts that I had put together with hith temp loctite. I put the parts in my oven at 500 degrees for about an hour, then took them out and put them in a vise. When I went to get them out of the oven, they had turned a very pretty copper color. Sort of like the color that we see becomming popular these days with custom anodizing jobs where people try to get the desert coyote or tan color anodized on the aluminum so they don't have to paint or duracoat that same color later. It was quite interesting. Anybody have a clue as to why this happened? Chris |
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ah. good info. Its a good thing that I had to destructivly remove the pieces anyways and didn't care about keeping them to begin with. As far as the Colt upper went, it still has that nice desert tan look, and the anodizing seems just as hard as before, if not harder. But I don't really care about that either, so no worries if it screwed it up. It was one of those cheap, hardly used, Colt M4 uppers that you can get in the EE for about $115 from one of the vendors. After installing it, I know why it sold for so cheap. The barel index pin slot was machined improperly about 3 to 5 degrees to the left and when a barrel is installed, the front sight cants to the left pretty bad and makes the lockup of the bolt to the barrel lugs so shitty that the gun won't function. So I didn't mind experimenting with it insofar as baking it and possibly screwing up the anodizing. |
My question is this: If you do heat the aluminum at 500 degrees for an hour and this happens, will it destroy the anodizing? In simple brass brush and steel brush tests, the anodizing seems just as good as before, if not harder, and holds up very well to even the stainless steel brush when I try my hardest to scrub the crap out of the finish. Any thoughts? |
Copper? - Ok, sure, if it was a 2xxx series alloy, but most people don't anodize 2xxx series because of the side issues and inconsistancy. I agree the temp was WAY to high. |
The piece that came out the really nice copper color was a piece of (i'm guessing here because of its soft properties) extruded aluminum, with a pretty shitty, fairly shiny (more of a matt finish) anodizing job. I thought the copper came from the anodizing, and not the aluminum. On the other hand, the Colt flattop reciever, which we all know is aircraft grade 7075 with a very nice hardcoat anodizing, just became a nice desert tan and if my calibrated eyeball means anything, it came out with a harder surface finish then when it went in. Also, because I got the colt reciever that hot, well, maybe even hotter then 500 because my oven only goes to 500, I put the setting just past 500 degrees and the little light that goes on and off when the heating elements are actually on to maintain temp never actually turned off. So I don't know the actual heat that it got to. The house got pretty warm though...  I also left the upper in there for about 2 hours, and then turned off the oven and let it cool to room temp on its own. Perhaps I also did alittle heat treatment on the aluminum by accident, who knows. I am no metalluragist (sp?), so anything and everything I have observed may be the completely wrong thing... 
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HAHAHA!!! you funny guy!!... Read above as to why I CAN'T assmble the upper and fire it. Its too far out of spec to use, otherwise I would....hell, it seems soooooo well finished now that I would even bumpfire it in my bathtub....  
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A canted FSB never stopped Bushamster. 
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I am no metallurgist, but I am a jeweler and you just annealed that sucker. This means you may have made the aluminum more easily worked (ductile). Having not worked aluminum, I cannot be certain, but it seems like you just made it even worse off than it was before. Kill it with Tannerite. |
After a test which was by no means all that scientific, it appears that you are correct. I grabbed a punch and a hammer and another upper that I don't use, and did two small punch marks on each (alternating), trying to be as consistent as possible. The upper that went in the oven had deeper punches that mostly allowed the punch to push the metal out of the way and compress it instead of making it push up and out creating a lip around the punch mark, whereas the other upper had smaller punch marks, that pushed the metal out from the punch and up as to creat a sort of a small lip around the punch. The desert tan color still looks cool though...
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320 - 400 deg is what we use to heat treat aluminum wheels at work. As for reheat treating it good luck. We do a initial heat treat of 995 for quite a few hours, you then have the problem of quenching the wheels without fracturing the aluminum so you also need heated water tank. You might get a shop to re treat it but I would consider it trash and crush it. Omni |
Well, most of the time to change how the crystalline structure re-grows you have to change how it forms. Slow cooling allows large crystals to form, they are easily broken up into smaller crystals as the metal is worked (work hardening). If you cool the metal quickly the crystals form faster and you can get smaller crystals and thus a less ductile metal . . . but you can also crack the metals by quenching them, aluminum being one of those that this happens to , I believe. You see, some of this comes down to the durability of the metals in question. Steel is an inifinite flex material. It might flex 1,000,000 times before breaking or it might flex 10,000 times (normal flex, not acute). Aluminum is a finite flex material. It will flex a certain number of times (within a few hundred) and then it will break. I don't recall the numbers, but it is something like 10-15,000 flexes. While aluminum has good strength for its weight, it cannot compare to steel in durability. Quenched materials are also more brittle, tending to break instead of bending (this also has to do with chemical make-up of one type of material vs. another, like chro-moly vs carbon steel). But re-treating the upper . . . I doubt that you could do it at home. Some precision needed to hit the right temperatures for the right amount of time. |
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