I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

Karl

"Karl Townsend" wrote in message
...
I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

Karl


Hi, Karl. 'Just stopped in to see if anyone talks about metalworking here
anymore. g

Stick with Plan A. If you have hard spots, your 7075 sucks, but you're
better off living with them if you do. If you want to anneal, it's 775 deg F
for 2 -3 hours.

Forget natural aging. Unlike 2024, 7075 has a hardening curve that runs out
for years. It's very unstable throughout its life in that state. To get a
true T6, it requires a fairly tricky two-stage heat-treat: solution
heat-treatment and quenching, followed by precipitation heat-treatment
(artificial aging).

Unless you want to get into all of that, you won't see T6 again after you
anneal the stuff.

Good luck.

--
Ed Huntress

....
Hi, Karl. 'Just stopped in to see if anyone talks about metalworking here
anymore. g

sorry 'bout that. There are a couple of us left that do metalworking.

Good to see you're still around. Thanks for the great advice.

Karl

On Thu, 10 Feb 2011 18:01:49 -0600, Karl Townsend
wrote:

I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

Karl

We once had a job machining some annealed aluminum, I don't remember
the alloy, and it was terrible gummy and hard to get a finish on so
the boss sent the whole lot out for heat treating, we machined it and
sent it back out for annealing.

We have parts cast from 356 aluminum alloy and heat treated at the
foundry. We machine them after heat treating. Never thought of doing
it any other way. The heat treatment can induce some distortion some
times (not often) so that would be bad if one was going to anneal,
machine and then heat treat.

Pete Stanaitis
------------------

Karl Townsend wrote:
I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

Karl

"Ed Huntress" wrote in message
...

"Karl Townsend" wrote in message
...
I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

Karl


Hi, Karl. 'Just stopped in to see if anyone talks about metalworking here
anymore. g

Stick with Plan A. If you have hard spots, your 7075 sucks, but you're
better off living with them if you do. If you want to anneal, it's 775 deg
F for 2 -3 hours.

Forget natural aging. Unlike 2024, 7075 has a hardening curve that runs
out for years. It's very unstable throughout its life in that state. To
get a true T6, it requires a fairly tricky two-stage heat-treat: solution
heat-treatment and quenching, followed by precipitation heat-treatment
(artificial aging).

Unless you want to get into all of that, you won't see T6 again after you
anneal the stuff.

Good luck.

--
Ed Huntress

Great Honk, Ed's Back!
Good to hear your voice, Ed.

Paul K. Dickman

Paul K. Dickman wrote:

(...)

Great Honk, Ed's Back!
Good to hear your voice, Ed.

Second that!
Welcome back, Ed!

--Winston

On 02/10/2011 06:01 PM, Karl Townsend wrote:
I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

Karl


Umm, how hard can 7075 get? Shouldn't be any problem, and really, the
harder it is the better it machines, usually.

Jon

Karl Townsend wrote in
rec.crafts.metalworking on Thu, 10 Feb 2011 18:01:49 -0600:

I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

My vote is don't anneal. Hard spots in 7075 aren't like hard spots in
steels.

--

Dan H.
northshore MA.

On Fri, 11 Feb 2011 22:49:30 GMT, (dan) wrote:

Karl Townsend wrote in
rec.crafts.metalworking on Thu, 10 Feb 2011 18:01:49 -0600:

I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

My vote is don't anneal. Hard spots in 7075 aren't like hard spots in
steels.
T6 is age hardened.
If you anneal, for instance, 6061T6 sheet to work it, and anneal it
again to take the working stress out, and leave it sit for a couple
months it is back to very close to T6 strength again.

Not sure how 7075 forgings will behave, but with the T6 designation I
suspect it would be somewhat similar.

wrote in message
...
On Fri, 11 Feb 2011 22:49:30 GMT, (dan) wrote:

Karl Townsend wrote in
rec.crafts.metalworking on Thu, 10 Feb 2011 18:01:49 -0600:

I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

My vote is don't anneal. Hard spots in 7075 aren't like hard spots in
steels.
T6 is age hardened.
If you anneal, for instance, 6061T6 sheet to work it, and anneal it
again to take the working stress out, and leave it sit for a couple
months it is back to very close to T6 strength again.

Not sure how 7075 forgings will behave, but with the T6 designation I
suspect it would be somewhat similar.

Not really similar, Clare. 7075 age hardens, but over years, not weeks. And
it will never reach T6.

The peak tensile strength of 6061 that's naturally age-hardened is roughly
the same as artificially aged 6061 T4 -- around 20 ksi yield. It achieves
that with natural age hardening after a couple of weeks. After eight years,
it climbs only to 22 ksi. For comparison, artificially aged 6061 T6 has a
yield strength of roughly 40 ksi.

7075, on the other hand, reaches around 60 ksi -- after 15 years. g It's
62 ksi or so after 25 years. But it reaches 45 ksi in around two months. It
just keeps climbing, in a steady rise, but the material is fairly unstable
all along the way. Artificially aged 7075 at the T6 temper is around 70 ksi
yield.

They don't use a number for naturally aged 7075. They call it "W" temper,
and to properly designate it, says the ASM, you include the time of aging
after the "W." For example, W 10h means the temper after 10 hours of
naturally aging. These designations are mostly of interest to metallurgists
and research engineers.

As a practical matter, natural age hardening doesn't work out very well for
7075 and some of the other 7xxx series. It can work fairly well for 6061,
and even better for 2024 (40 ksi after one hour; 42 ksi after 25 years).

I'll bet this info is available somewhere around the Web, but my primary
source is the non-ferrous edition of ASM's _Metals Handbook_.

--
Ed Huntress

"Paul K. Dickman" wrote in message
...

"Ed Huntress" wrote in message
...

"Karl Townsend" wrote in message
...
I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

Karl


Hi, Karl. 'Just stopped in to see if anyone talks about metalworking here
anymore. g

Stick with Plan A. If you have hard spots, your 7075 sucks, but you're
better off living with them if you do. If you want to anneal, it's 775
deg F for 2 -3 hours.

Forget natural aging. Unlike 2024, 7075 has a hardening curve that runs
out for years. It's very unstable throughout its life in that state. To
get a true T6, it requires a fairly tricky two-stage heat-treat: solution
heat-treatment and quenching, followed by precipitation heat-treatment
(artificial aging).

Unless you want to get into all of that, you won't see T6 again after you
anneal the stuff.

Good luck.

--
Ed Huntress

Great Honk, Ed's Back!
Good to hear your voice, Ed.

Paul K. Dickman

Thanks, Paul. I'll try to keep my eyes open for questions to which I may be
able to contribute. This one happens to lie right in the heart of what I
researched and studied when I was materials editor at _American Machinist_.

--
Ed Huntress

"Winston" wrote in message
...
Paul K. Dickman wrote:

(...)

Great Honk, Ed's Back!
Good to hear your voice, Ed.

Second that!
Welcome back, Ed!

--Winston

Ha! Thanks, but I'm not really back, Winston. I will try to check in from
time to time.

--
Ed Huntress

On 2011-02-11, Paul K. Dickman wrote:

"Ed Huntress" wrote in message
...

Hi, Karl. 'Just stopped in to see if anyone talks about metalworking here
anymore. g

[ ... ]

Unless you want to get into all of that, you won't see T6 again after you
anneal the stuff.

[ ... ]

Ed Huntress

Great Honk, Ed's Back!
Good to hear your voice, Ed.

Indeed so.

Yes -- some of us stick to metalworking.

Glad to see you back. Hopefully to stay?

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Ed Huntress wrote:
wrote in message
...
Paul K. Dickman wrote:

(...)

Great Honk, Ed's Back!
Good to hear your voice, Ed.

Second that!
Welcome back, Ed!

--Winston

Ha! Thanks, but I'm not really back, Winston. I will try to check in from
time to time.

Excellent!

--Winston

Thanks, Paul. I'll try to keep my eyes open for questions to which I may be
able to contribute. This one happens to lie right in the heart of what I
researched and studied when I was materials editor at _American Machinist_.

I also welcome your participation here.

I ran across a reference to anodizing causing weakness in AL and I can't
seem to find it again. I haven't found a narrow enough Google search to
be useful. Can you help?

David

On Fri, 11 Feb 2011 20:59:34 -0500, "Ed Huntress"
wrote:


wrote in message
.. .
On Fri, 11 Feb 2011 22:49:30 GMT, (dan) wrote:

Karl Townsend wrote in
rec.crafts.metalworking on Thu, 10 Feb 2011 18:01:49 -0600:

I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

My vote is don't anneal. Hard spots in 7075 aren't like hard spots in
steels.
T6 is age hardened.
If you anneal, for instance, 6061T6 sheet to work it, and anneal it
again to take the working stress out, and leave it sit for a couple
months it is back to very close to T6 strength again.

Not sure how 7075 forgings will behave, but with the T6 designation I
suspect it would be somewhat similar.

Not really similar, Clare. 7075 age hardens, but over years, not weeks. And
it will never reach T6.

The peak tensile strength of 6061 that's naturally age-hardened is roughly
the same as artificially aged 6061 T4 -- around 20 ksi yield. It achieves
that with natural age hardening after a couple of weeks. After eight years,
it climbs only to 22 ksi. For comparison, artificially aged 6061 T6 has a
yield strength of roughly 40 ksi.

7075, on the other hand, reaches around 60 ksi -- after 15 years. g It's
62 ksi or so after 25 years. But it reaches 45 ksi in around two months. It
just keeps climbing, in a steady rise, but the material is fairly unstable
all along the way. Artificially aged 7075 at the T6 temper is around 70 ksi
yield.

They don't use a number for naturally aged 7075. They call it "W" temper,
and to properly designate it, says the ASM, you include the time of aging
after the "W." For example, W 10h means the temper after 10 hours of
naturally aging. These designations are mostly of interest to metallurgists
and research engineers.

As a practical matter, natural age hardening doesn't work out very well for
7075 and some of the other 7xxx series. It can work fairly well for 6061,
and even better for 2024 (40 ksi after one hour; 42 ksi after 25 years).

I'll bet this info is available somewhere around the Web, but my primary
source is the non-ferrous edition of ASM's _Metals Handbook_.
Thanks Ed - like I said, I was not familiar with the 70 series alloys

wrote in message
...
On Fri, 11 Feb 2011 20:59:34 -0500, "Ed Huntress"
wrote:


wrote in message
. ..
On Fri, 11 Feb 2011 22:49:30 GMT, (dan) wrote:

Karl Townsend wrote in
rec.crafts.metalworking on Thu, 10 Feb 2011 18:01:49 -0600:

I'm preparing to machine several AL 7075 T6 forgings...

"The Kid" (my son) tells me I should anneal before machining because
there will be hard brittle spots. Easy enough to do at the anneal temp
of 775 (not sure how long). But, then I haven't got T6 grade 7075 AL
anymore. How would I get it back to T6 grade?

Or, am I better off with plan "A"? Don't anneal.

My vote is don't anneal. Hard spots in 7075 aren't like hard spots in
steels.
T6 is age hardened.
If you anneal, for instance, 6061T6 sheet to work it, and anneal it
again to take the working stress out, and leave it sit for a couple
months it is back to very close to T6 strength again.

Not sure how 7075 forgings will behave, but with the T6 designation I
suspect it would be somewhat similar.

Not really similar, Clare. 7075 age hardens, but over years, not weeks.
And
it will never reach T6.

The peak tensile strength of 6061 that's naturally age-hardened is roughly
the same as artificially aged 6061 T4 -- around 20 ksi yield. It achieves
that with natural age hardening after a couple of weeks. After eight
years,
it climbs only to 22 ksi. For comparison, artificially aged 6061 T6 has a
yield strength of roughly 40 ksi.

7075, on the other hand, reaches around 60 ksi -- after 15 years. g It's
62 ksi or so after 25 years. But it reaches 45 ksi in around two months.
It
just keeps climbing, in a steady rise, but the material is fairly unstable
all along the way. Artificially aged 7075 at the T6 temper is around 70
ksi
yield.

They don't use a number for naturally aged 7075. They call it "W" temper,
and to properly designate it, says the ASM, you include the time of aging
after the "W." For example, W 10h means the temper after 10 hours of
naturally aging. These designations are mostly of interest to
metallurgists
and research engineers.

As a practical matter, natural age hardening doesn't work out very well
for
7075 and some of the other 7xxx series. It can work fairly well for 6061,
and even better for 2024 (40 ksi after one hour; 42 ksi after 25 years).

I'll bet this info is available somewhere around the Web, but my primary
source is the non-ferrous edition of ASM's _Metals Handbook_.

Thanks Ed - like I said, I was not familiar with the 70 series alloys

It's a tricky material in several ways. There are one or two tempers above
T6, but they're not straightforward heat treatments. They're special
treatments intended to prevent exfoliation and stress corrosion. They aren't
harder or stronger than T6, just more complicated.

We used to machine some of it at the shop I was involved with in the
mid-70s. It was used for some aerospace research models at Princeton
University, which was our main customer. It was not as nice to machine as
2024 T4, which is, IMO, the sweetest grade of aluminum for turning or
milling.

--
Ed Huntress