Ady Wilson | 22/10/2013 20:46:58 |
41 forum posts 14 photos | Hi, I have been trying to educate myself in the grades of different metals but there is a lot of data to take in so I thought somebody might be able to help me out here. I want to purchase some aluminium and am looking for something which can be machined to a high standard finish, strength is not important. I have been looking on ebay and it all seems to be 6xxx grades but I dont know which will suit my needs. cheers, Adrian. |
JasonB | 22/10/2013 20:54:23 |
![]() 25215 forum posts 3105 photos 1 articles | 6082, the old ref was HE30 should do you. This is all from 6082 externally Edited By JasonB on 22/10/2013 20:56:15 |
Clive Hartland | 22/10/2013 21:56:48 |
![]() 2929 forum posts 41 photos | Adrian, during my working years I used nothing but HE30, unless I was able to recover from scrapping a machine then I would use what I could find. Beware cast alu. it can be difficult or easy to machine depending whats in it. I have seen, 'Aircraft grade alu' for sale but have never found out what it is. Most stuff on Ebay seems to be what it says it is as they are usually offcuts just being sold on. Clive |
richardandtracy | 23/10/2013 09:07:36 |
![]() 943 forum posts 10 photos | If you want a good combination of strength, moderate ductility (10% to failure or so), good machinability, adequate corrosion resistance, good weldability etc., then 6082 is the one to go for. Aluminium's come in different grades. 6082-T6 can be anodized but does not look as good as the much weaker 6061 or somewhat weaker 6063 aluminium. In the 6xxx series the stronger it is, the worse the look of the anodizing. The 6xxx series can be heat treated and naturally/artificially aged (not at home, it's too difficult) to a series of different tempers. The tempers of interest are (simplified, as there are pages & pages I could write, but it would bore both you & me & neither of us would be enlightened further) 'O' = annealed, 'M' = no one knows, just as it came out of the extruder/rollers T2 = 1/4 hard T4 = 1/2 hard T6 = Full hard & is the one you should use if possible. This is also known as 'Heat treated & artificially aged'. If tou weld 6082-T6, then the heat affected zone becomes the same strength as the -T4 condition, so approx. a 50% strength reduction. For home use, if you see a designation -T6511, don't bother with the numbers after the T6 as it doesn't make a whole lot of difference unless you are after the last scintilla of performance,
If you are desperate for strength and can cope with brittleness, stress corrosion and other unpleasant stuff, then 7075-T6511 in that specific temper (important because the plain T6 temper is very, very prone to stress corrosion cracks even in apparently benign environments) - but do a thorough investigation of the material first so you know what nasty's you are letting yourself in for. None of the 7xxx series are weldable without great care, and even then weld cracking is VERY likely.
If using the alloy in sea water without anodizing or paint, then use 5086-H8. This is an alloy that cannot be heat treated, but can be work hardened, with the H8 indicating full hard, H6 3/4 hard, H4 half hard etc. I have seen this alloy used on boats that service the Great Barrier Reef tourist trade in the unpainted condition. Good stuff, but a bit weaker than 6082-T6 and a bit more expensive. For use in fresh water without anodizing or paint, 5083-H6 or -H8 is suitable - it's cheaper than 5086 but has less corrosion resistance. Both 5083 and 5086 are mig weldable.
For casting alloys, the ductility is catastrophic. Most have a maximum ductility to failure of 4%, with 1% being common. Basically it'll shatter before you have any warning it's in distress. For home casting LM4 and LM6 are the ones to go for. LM4 is a bit claggy when machining, and LM6 is worse. LM6 is the more marine friendly, but both need protection from salt water. LM6 is the more expensive. Regards, Richard |
Ady1 | 23/10/2013 09:20:23 |
![]() 6137 forum posts 893 photos | Used ebay T6 to replace my damaged small backgear cog a couple of years ago and it's been fine so far. Has done many hours of milling/screwcutting/turning and seems to be tuff stuff Edited By Ady1 on 23/10/2013 09:23:37
Edited By Ady1 on 23/10/2013 09:28:26 |
Michael Gilligan | 23/10/2013 09:38:53 |
![]() 23121 forum posts 1360 photos | Richard, That's a very useful summary. ... Thanks for Posting I think this is the sort of information that MEW should publish as "Reference Cards". MichaelG. |
Versaboss | 23/10/2013 10:25:47 |
512 forum posts 77 photos | Posted by Michael Gilligan on 23/10/2013 09:38:53:
I think this is the sort of information that MEW should publish as "Reference Cards".
Right, Michael. But the frosting on the cake would be a cross reference to more internationally used (in contrary to US practices) designations. E.g. AlMgSi1, AlCuMgPb, AlZn5.5MgCu, AlMg4,5Mn0,7 ...... My Al provider shows the US designations (and some T numbers) only for sheet stuff. Greetings, Hansrudolf |
Ady Wilson | 25/10/2013 19:44:07 |
41 forum posts 14 photos | Thanks for all the replies very much appreciated, and special thanks to Richard for his detailed post I appreciate you taking the time to make it. I have ordered a few bars of 6082 T6 off Ebay to play with. Ady.
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