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rschap
Mar 3, 2009, 5:15 AM
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Good information, thank you. I like the site you posted, found out a lot about anodizing I didn’t know. I knew the anodizing was only on the surface but I thought it was deeper than that. We tend to deal with anodizing when someone brings an item in that needs to be welded and we grind the anodizing off.
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atlnq9
Mar 7, 2009, 4:29 PM
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Sorry, haven't been paying much attention over here lately.
The anodized layer won't affect the hardness of the base metal very much. This is because the aluminum oxide, anodized layer, is a ceramic which is very hard but very brittle and easily cracks. Also, the ceramic layer is very thin compared to the depth of of the indenter. If you are interested in the depth of the indent then that can easily be calculated knowing the indenter size and hardness value. I don't have the rockwell equations handy otherwise I would do this. However, you will see a difference in hardness when taking microhardness. Although normally we aren't concerned with the hardness of the anodized layer but with its abrasion resistance.
Just some side information you guys may already know. Aluminum will actually form an oxide layer on its own. Aluminum corrodes very easily but what makes it corrosion resistant is the fact that when it corrodes it forms a protective layer (self healing from scratches as well). Contrary to steel which forms a non-bonding flaky oxide upon corrosion. This aluminum oxide layer which forms on its own is very thin. To get a thicker protective layer we anodize.
Anouther note to make is Arics cam lobe, the alien and the BD lobe all would have had a very thin naturally formed oxide layer. The BD and alien lobes were ground that way because they were severely warped from pull testing.
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rschap
Mar 7, 2009, 4:48 PM
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That makes sense, I didn’t think it would have a big affect but I thought it might change it a little. Of course I thought the anodized layer was thicker.
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atlnq9
Mar 11, 2009, 5:01 AM
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In case anybody is interested in what else I have done on this, yesterday I did a proper T6 age condition on the alien lobe and from the one hardness test I had room for I got a rockwell B of 55. This means that they are capable of reaching the hardest condition and there is nothing wrong with their alloy, (wrong composition, etc.) although it does not prove that they are using 6061 it is strong evidence.
I am still unsure if I want to figure out exactly what they are doing wrong in their heat treatment. I do not want to hand them the answer for free... Any thoughts?
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rschap
Mar 11, 2009, 5:09 AM
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Have you thought about spectral analysis? The local scrap yard has one for people that come in insisting they have some expensive metal or something. If you send me a chunk I can have them do it for free, they owe us a few favors. If you do find out what they did you don’t have to tell them but you could tell me .
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atlnq9
Mar 11, 2009, 5:27 AM
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I could run DC arc elemental here on it but I would have to pay the metallurgical department for the time and use. I don't know if the scrap yards process is accurate enough for different aluminum alloys, but if you want to check sure. I am 98% positive it is 6061 since when I did what is a T6 age for it I got the right hardness value.
But to find out what they are doing wrong starts with optical microscopy, then that could lead to SEM or just further aging to see if it gets harder or softer. Quite a bit of work for them to get for free.
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rschap
Mar 11, 2009, 5:39 AM
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I’m not sure how accurate it is either. When I was thinking about making my ice tools I was going to take a hammer and my X15s down to see what they made of but then I got some AR plate for free and never went. let me call them tomorrow and find out what they can do.
(This post was edited by rschap on Mar 11, 2009, 5:40 AM)
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mojomonkey
Mar 11, 2009, 2:13 PM
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Thanks for the testing and info guys. Any chance of repeating for more samples? I am curious if the softness of this particular Alien (was this my old one Aric?) was a fluke, or is consistent for all Aliens. It would be interesting to know if they come up consistently soft for 6061T6, it was an outlier, or they do not rate consistently.
Have any pieces from destroyed ones Aric? The one that bound up?
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adatesman
Mar 11, 2009, 2:25 PM
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atlnq9
Mar 11, 2009, 3:12 PM
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imnotclever wrote: I guess I'd assume any strain hardening from the pull test to be minimal, but have you given any thought to that? The numbers match out the same as with the known sample.
I considered it but feel it to be minimal in my opinion. They really didn't have that much deformation in them. Just for hardness testing you want them perfectly flat. But yes it is could affect it by a hardness value...
Aric, wow that sounds like a quality process there. If they are heat treating with a torch I won't even bother trying to find out what they are doing wrong. Because they aren't really even trying to hit T6. They should invest in a proper furnace.
Yeah, I should be able to test some more cam lobes.
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adatesman
Mar 11, 2009, 3:44 PM
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rschap
Mar 12, 2009, 1:27 AM
Post #38 of 48
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So an on topic drift if you don’t mind me picking you’re brains too much. We carry 6061 T6 plate and 6061 T651 flat bar at work, I understand the T651 means that they have distressed the material as the process goes on. My question is, is there a difference between making a part from a T0 and bringing it up to a T6 after and just using the T6 to begin with? It would make sense to me to start with a T0 if the hardening wasn’t all the way though the material but it’s my understanding that it is, I could be wrong. Also do they really get it to T6 by baking the metal at 350 for 6-8 hours?
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moof
Mar 13, 2009, 6:14 AM
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From the interweb thingy...
From http://www.suppliersonline.com/propertypages/6061.asp:
Solution heat treat at 990 F for adequate time to allow for thorough heating and then water quench. Precipitation hardening is done at 320 F for 18 hours and air cool, followed by 350 F for 8 hours and air cooling.
From http://www.rittercnc.com/...1-aluminum-7975-.htm:
Heh, I wandered off to the bookshelf for the metallurgical text book.
Found 6061, interesting stuff. Heat to 750F, cool 50 degrees per hour to 500F and it is -T0 (annealed). Heat to 975F long enough to get even temp, quench in water (or water spray for large items) and you have -T4. Age harden by heating to 320F for 16 hours or 350F for 8 hours and you have -T6. If you let -T4 sit for several years, it will gradually drift to almost -T6
Take all interweb crap with a grain of salt, and for sure don't shove your alien lobes into the oven thinking they'll get harder, your oven is very uncontrolled in temp.
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edavidso
Mar 14, 2009, 12:01 AM
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Just to clear up a few things and answer some questions:
Unlike most steels, aluminum when heat treated has pretty much the same hardness throughout the part. This is because the heat treatment process for aluminums relies on a completely different mechanism from that of steels. Not all aluminum alloys can be heat treated but those that can are done by a process called precipitation hardening. Precipitation hardening generally consists of a solution treatment followed by an aging treatment at an elevated temperature. The aging is used to grow tiny, dispersed precipitates and occurs over several hours; more than enough time for the entire part to come up to temperature resulting in similar hardness throughout the part.
Steels, on the other hand, owe their heat treating gains in strength to a phase transformation, which in most steels happens on the order of seconds and that is why they tend to be harder on the surface than the interior (the extent of which depends strongly on the alloy). An exception is precipitation hardening stainless steels (e.g. 17-7 SS), which rely on the same mechanism as aluminums for heat treating.
As for specific precipitation hardening treatments, T4 simply refers to naturally aging at room temperature and T6 refers to aging at an elevated temperature. Not all heat treatable aluminum alloys can be naturally aged. The TX51 designation, for example T651, means that the alloy was stress relieved by stretching. The annealed condition is just "O", e.g. 6061 O, and has not been solution treated or aged.
As for working with aluminum in the T6 condition or prior to aging, it is much easier to machine in the T6 condition as the annealed or prior to aging conditions are too soft and tend to gum up tools. As for forging or extruding, I'm sure it's easier to do it in the annealed or after solution heat treatment condition and then age the finished part to achieve the desired strength. I believe the alien lobes are extruded and so they are probably starting with a soft condition and doing the heat treatment later resulting in their problems. I really can't believe they would be reckless enough to attempt to do the heat treatment with a torch.
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rschap
Mar 14, 2009, 12:58 AM
Post #42 of 48
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Thank you for the info. You guys answered my questions but it just raises more, but they are not related to cams or climbing so I’ll leave it at that. I have a curious mind and could ask questions on the subject all day.
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adatesman
Mar 14, 2009, 2:45 AM
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atlnq9
Mar 14, 2009, 3:26 PM
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edavidso did a good explanation, sorry I must have skipped over your post rschap. Only one thing I would say though just for giggles is one could argue that hardening steel and hardening aluminum are really the same they just get contributions from different mechanisms. But that is for another day.
Aric: your ternery, really taking binarys of each side and matching them together to get 3D would be better for seeing...
and this little tid bit, although we consider 6xxx aluminums Al:Mg:Si
Edit: I'll see if I can get you a better more relevant one on monday 
(This post was edited by atlnq9 on Mar 14, 2009, 3:29 PM)
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moof
Apr 10, 2009, 12:51 AM
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Interesting thought. Maybe it's just too much of a hassle to machine gummy T4 for the assorted slots, holes, and such but they wanted the softer heat treat for more grip?
On a side not, I sent 20 aliens for pull testing a month back, and just got them back. As I'm cutting all my identification tags off something caught my eye. One cam, a red alien, had a shiny new swage on it. The cable and head also look shiny and new, with no cam lube spooge on them, or dirt in the crevices like every other cam I own. I'll take pics for posterity when I can find my camera.
Best part? They reused they old PVC tube for the thumb loop! WTF? I'm not sure if it was just them being amazingly cheap, or if they were intentionally trying to hide that one failed. Date code on this one was 01/2004, not in the recall, and it was not dimpled.
(This post was edited by moof on Apr 10, 2009, 4:31 AM)
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atlnq9
Apr 10, 2009, 3:10 AM
Post #47 of 48
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I don't see much need for them to soften after already tempering to T6, they don't need to do any deformation, they are getting the lobes as extruded stock... I am still saying they don't know what they are doing, maybe they want them soft but that is beside the point.
Reasons for heating like rschap mentioned are different: you are heating to get above the recrystalization temp (hot working); the more energy put in by heat means less energy for deformation, you are deforming a age hardened alloy which does not respond well to cold working like a work hardening alloy, etc.
Very weird that the replaced your stem and didn't inform you, I would have thought it would have been required, sounds like they were trying to hide it too, maybe they are trying to pretend like it didn't fail so they don't have to do another recall, could come back to bite them later though if they are trying to ignore a data point, that is a definite no no in the engineering world.
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