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Posted by Dixon on March 3, 2008, 9:40 pm
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Although I do know the correct way to weld 6061 alum. to get max strength,
does anyone know the best "cheat" method of welding it to retain the most
strength? 6061-T6 is approx 45K tensile. After welding, the area around the
weld is approx 15K tensile or 1/3 of it's original strength. Would one weld,
then cool slowly or quench in water quickly? Possibly short quick beads to
minimize heat affected zone? I have a lot of 6061 T6 on hand, and I'm
looking to get the least softening at the weld area as possible. The very
best procedure I know is to buy 6061 T0, weld, then heat treat to T6. So,
what's a good "second best method"?
Dixon
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Posted by Ernie Leimkuhler on March 4, 2008, 2:15 am
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> Although I do know the correct way to weld 6061 alum. to get max strength,
> does anyone know the best "cheat" method of welding it to retain the most
> strength? 6061-T6 is approx 45K tensile. After welding, the area around the
> weld is approx 15K tensile or 1/3 of it's original strength. Would one weld,
> then cool slowly or quench in water quickly? Possibly short quick beads to
> minimize heat affected zone? I have a lot of 6061 T6 on hand, and I'm
> looking to get the least softening at the weld area as possible. The very
> best procedure I know is to buy 6061 T0, weld, then heat treat to T6. So,
> what's a good "second best method"?
> Dixon
Just wait.
Yes the heat affected zone will drop in hardness from T6 to around T2
after the weld, but if you just wait a few weeks it will eventually
regain most of it's hardness through precipitation hardening.
The most it can achieve by natural age hardening is a T5.
The only way to regain T6 is through re-heat-treating the aluminum.
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Posted by Dixon on March 4, 2008, 9:59 am
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>
>> Although I do know the correct way to weld 6061 alum. to get max
>> strength,
>> does anyone know the best "cheat" method of welding it to retain the most
>> strength? 6061-T6 is approx 45K tensile. After welding, the area around
>> the
>> weld is approx 15K tensile or 1/3 of it's original strength. Would one
>> weld,
>> then cool slowly or quench in water quickly? Possibly short quick beads
>> to
>> minimize heat affected zone? I have a lot of 6061 T6 on hand, and I'm
>> looking to get the least softening at the weld area as possible. The very
>> best procedure I know is to buy 6061 T0, weld, then heat treat to T6. So,
>> what's a good "second best method"?
>> Dixon
>
> Just wait.
> Yes the heat affected zone will drop in hardness from T6 to around T2
> after the weld, but if you just wait a few weeks it will eventually
> regain most of it's hardness through precipitation hardening.
> The most it can achieve by natural age hardening is a T5.
> The only way to regain T6 is through re-heat-treating the aluminum.
Ernie, I used to work in an aircraft materials testing lab and have pulled
thousands of tensile specimens. The idea of the alum gaining most of it's
strength back at room temp has raised my eyebrows. If I still had use of the
tensile machine, I would love to machine some test bars from welded alum.
and test them over a period of weeks to see the results for myself. Because
of your high credibility on this site, I'll consider your reply highly
possible, but I'd really like to put this one to the test.
Dixon
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Posted by Pete C. on March 4, 2008, 6:20 pm
Please log in for more thread options Dixon wrote:
>
> >
> >> Although I do know the correct way to weld 6061 alum. to get max
> >> strength,
> >> does anyone know the best "cheat" method of welding it to retain the most
> >> strength? 6061-T6 is approx 45K tensile. After welding, the area around
> >> the
> >> weld is approx 15K tensile or 1/3 of it's original strength. Would one
> >> weld,
> >> then cool slowly or quench in water quickly? Possibly short quick beads
> >> to
> >> minimize heat affected zone? I have a lot of 6061 T6 on hand, and I'm
> >> looking to get the least softening at the weld area as possible. The very
> >> best procedure I know is to buy 6061 T0, weld, then heat treat to T6. So,
> >> what's a good "second best method"?
> >> Dixon
> >
> > Just wait.
> > Yes the heat affected zone will drop in hardness from T6 to around T2
> > after the weld, but if you just wait a few weeks it will eventually
> > regain most of it's hardness through precipitation hardening.
> > The most it can achieve by natural age hardening is a T5.
> > The only way to regain T6 is through re-heat-treating the aluminum.
>
> Ernie, I used to work in an aircraft materials testing lab and have pulled
> thousands of tensile specimens. The idea of the alum gaining most of it's
> strength back at room temp has raised my eyebrows. If I still had use of the
> tensile machine, I would love to machine some test bars from welded alum.
> and test them over a period of weeks to see the results for myself. Because
> of your high credibility on this site, I'll consider your reply highly
> possible, but I'd really like to put this one to the test.
> Dixon
How about building a tester? For a non critical application like this I
expect it could be pretty simple and inexpensive. Hydraulic jack pushing
up against a lever with the test specimen attached between the jack and
the pivot point? Pressure gauge added to the jack and a camcorder aimed
at it to capture the peak pressure reached? Sounds like a $50 project to
me...
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Posted by RoyJ on March 5, 2008, 12:21 am
Please log in for more thread options 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
That tells me that the HAZ zone does not get cooled slowly enough to
anneal it too much , the weld itself should be -T4
Ernie says it will be slightly softer than that would indicate for all
cases. I certainly won't argue.
Sounds like a nice student project. Think I'll have to turn a bunch of
them loose on it!
Dixon wrote:
>>
>>> Although I do know the correct way to weld 6061 alum. to get max
>>> strength,
>>> does anyone know the best "cheat" method of welding it to retain the most
>>> strength? 6061-T6 is approx 45K tensile. After welding, the area around
>>> the
>>> weld is approx 15K tensile or 1/3 of it's original strength. Would one
>>> weld,
>>> then cool slowly or quench in water quickly? Possibly short quick beads
>>> to
>>> minimize heat affected zone? I have a lot of 6061 T6 on hand, and I'm
>>> looking to get the least softening at the weld area as possible. The very
>>> best procedure I know is to buy 6061 T0, weld, then heat treat to T6. So,
>>> what's a good "second best method"?
>>> Dixon
>> Just wait.
>> Yes the heat affected zone will drop in hardness from T6 to around T2
>> after the weld, but if you just wait a few weeks it will eventually
>> regain most of it's hardness through precipitation hardening.
>> The most it can achieve by natural age hardening is a T5.
>> The only way to regain T6 is through re-heat-treating the aluminum.
>
> Ernie, I used to work in an aircraft materials testing lab and have pulled
> thousands of tensile specimens. The idea of the alum gaining most of it's
> strength back at room temp has raised my eyebrows. If I still had use of the
> tensile machine, I would love to machine some test bars from welded alum.
> and test them over a period of weeks to see the results for myself. Because
> of your high credibility on this site, I'll consider your reply highly
> possible, but I'd really like to put this one to the test.
> Dixon
>
>
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> does anyone know the best "cheat" method of welding it to retain the most
> strength? 6061-T6 is approx 45K tensile. After welding, the area around the
> weld is approx 15K tensile or 1/3 of it's original strength. Would one weld,
> then cool slowly or quench in water quickly? Possibly short quick beads to
> minimize heat affected zone? I have a lot of 6061 T6 on hand, and I'm
> looking to get the least softening at the weld area as possible. The very
> best procedure I know is to buy 6061 T0, weld, then heat treat to T6. So,
> what's a good "second best method"?
> Dixon