7075 T651 Extruded or Cold Formed What's the Big Difference
I'm wanting to make a couple small parts from 7075
Not wanting to spend a lot of money ( which I don't have at this time ) I went to eBay to see what was available in my budget.
I noticed that on seller has several different pieces for sale.
Some say nothing but 7075 T651 and others say 7075 T651 Cold Formed
What is the major Pro and Cons to each of these ? Or is either one still ok ?
I believe the "cold formed" would be extruded mtl that has been ran through a draw process. Same idea as HR / CD steel.
The CD has much tighter size as well as roundness tols. "As extruded" can be fairly open on size...
Not sure if there would be a "hardness" gain with drawing the alum like there is with steel or not?
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I can't remember why, but 7075 is not extruded. Most of the extruded shaped are 6061 or 6063.
7075 just extrudes HARD... some places do extrude it, but it costs a lot more than 6061/ 6063 and unless you absolutely need the properties then its probably not worth it. I think the material you are likely talking about is the same stuff... I have never heard of a specifically "cold drawn" aluminum, but it may exist. Some material is plate cut, some is extruded bar size, I think they mean its extruded bar size to nominal duimensions.
"7075 just extrudes HARD"
An extruder told me it pushes at about 1/3rd the speed of 6061.
I've never even heard of extruded 7075
I've always like machining 7075. Can get a really nice finish on it. I like that extra hardness that it has. It's quite a bit more unstable than shitty shitty one and that can be annoying. I've made a lot of molds out of it. Don't they use it a lot in aerospace? Or is there something new and better that has the same qualities.
We use quite a few extruded profiles for helicopter parts, about 50/50 split between 2024-T3511 and 7075-T6511, rarely use 6061 and I don't think we have ever used 6063. The 7075 extrusions are usually particularly nice, maybe because only the companies that really know their stuff are extruding 7075(?)
Well - I don't know for sure if it is "drawn" or not. It IS listed as "cold FINISHED". The one line item that I find spec'd this way is 6262-T9. However I think that others are available just the same - just not worded quite the same?
I have never heard of a specifically "cold drawn" aluminum, but it may exist.
Others are worded as "Round alum rod" vs "Round extruded alum rod". No tols listed on the "round", but the extruded is listed with size tols and 1" for ex is listed @ +/- .003 as well as .005 is an option as well. Actually - all the sizes seem to have tighter/looser tol options. The "round alum rod" will be tighter tols yet. Likely .0015 (?) like normal CD steel?
The "extruded" stuff is considerably cheaper.
I only find 7075 listed as "round".
These are taken from the Copper and Brass Sales cat as well as my past conversations with sales.
Maybe someone can find some bit of knowledge in there - even if not 100% pertinent to the OP.
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To answer the original question, -T651 is -T651, it aint gonna matter how they shaped it before heat treat. T6 would mean just solution heat treated and aged (I doubt you will find plain "T6" 7075). T651 means it is also stretched to stabilize and will move around less when machined. (T6511 allows for straightening)
I ran across something a while back that had pricing on 6061 in both extruded and wrot (wrought??) forms. The extruded variety was a bunch cheaper.
Visited a place one time that was a foundry for the most part, but they were also extruding what looked like a 8" structural channel from cast iron.
The guy there said they made them for a company that made textile spinning frames. Said they originally used structural steel for those pieces but it caused a ringing noise that made it difficult for an operator to detect when there was a problem with one of the spindles going bad. They furnished the CI extrusion to the same dimensions as the structural channel and it damped out the ringing. He said the old timey spinning frames were mostly cast iron and the ringing problem only showed up as they attempted to modernize from castings to fabricated frames.
Ox, do you ever run any 6262-T9? Nice stuff. Makes you want to throw rocks at 6061. Seriously, its machinability is close to 2011 screw stock, but with the corrosion resistance of 6061, plus higher strength than 6061. Never have been able to figure out why its not used more than it is.
Wrought is held to much tighter surface finish and dimensional tolerances than bar stock extrusions, and they allow us to reimburse them for the effort.
It is very nice to machine, also anodizes well but in my experience is more expensive than 6061. I have also found it seems to be a bit more susceptible to fatigue cracking and even though it supposedly has strength equivalent to or higher than 6061 tapped threads are not as strong.
Originally Posted by metlmunchr
Nope - only seen it in the cat...
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