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# 2024-O vs 2024-T3

## 2024-O vs 2024-T3

(OP)
Hello, I like to know if 2024-T3 requires heat treat to T42. I have decided to use 2024-T3 instead of 2024-O which required the heat treat to T42 but i am not sure if the 2024-T3 requires it?

### RE: 2024-O vs 2024-T3

The T3 designator is Heat treated then cold worked. The designation also applies to Products that are cold worked for the primary purpose of improving their strength i.e. 2024-T36 . It also applies to products in which flattening or straightening is recognized in applicable specifications such as flat sheet which is Designated 2024-T3.

The T4 designator is solution heat treated and naturally aged to a substantially stable condition. This designation applies when the product is NOT cold worked after heat treatment. The designation also applies when applicable specifications do not recognize the effects of cold work in flattening and straightening operations. The T4 designator applies when the product is heat treated by the customer.
Typical mechanical properties for 2024 : 2024-0 Ultimate 26,000 psi yield 11,000 psi . 2024 T3 ultimate 65,000 psi yield 45,000psi. 2024 T4 ultimate 64,000 psi yield 42,000psi.
So it would appear that if you can use 2024 T3 you may not have to heat treat.

B.E.

You are judged not by what you know, but by what you can do.

### RE: 2024-O vs 2024-T3

2024-O HT to -T42 is not normally required by engineering unless significant forming is required that CANNOT be safely accomplished [potential for cracks] in the -T3 temper.

Moderate forming in the -O [annealed] condition or [more preferred] in the -W temper [unstable temper within ~15--45-minutes after solution HT/Quench] can be done to tighter bend radii or greater total strain, than in the -T3 temper.

IF forming is done as recommended, then mechanical allowables for -T3 and -T42 tempers are quite similar and for practical considerations are more-or-less equal.

NOE: Berkshire's example of minor mechanical allowables differences between -T3 flat sheet and '-O HT -T42' flat sheet do NOT necessarily represent the real world. The effects of FORMING more or less 'equalizes' the allowables differences between -T3 [subtracts somewhat] and -T42 [relatively no effect]... if forming rules for both are obeyed.

I think I have this correct... anyone else want to give this a shot?

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

### RE: 2024-O vs 2024-T3

When I said ,If, you can use 2024-T3 I meant using the material as is with no forming, or very gentle forming as you would on a wing skin or flat part.
If you do have to do extreme forming, then heat treat and quench would be required then form and re- age to T4.
The information I posted came from Alcoa's book " Forming Aluminum".
B.E.

You are judged not by what you know, but by what you can do.

### RE: 2024-O vs 2024-T3

I'm confused by the idea of starting with T3 and ending up with T42 ... I consider them equivalent tempers.

any shape you can form in T42, you should be able to form in T3. If the drawing states T42 material, T3 should ab an acceptable substitute (so long as you can form it).

If the shape cannot be formed in T3; then HT to O, form, and HT to T42.

If the drawing states T42; then it is expecting that you'll buy T3 (or other), HT to O, form, HT to T42.

### RE: 2024-O vs 2024-T3

I am not clear what is being asked here.

It should be understood that 2024 T3 and 2024 T42 aluminum alloy has different "properties" that are stated in the two different specifications and general information about the materials. The materials 2024 T3 and 2024 T42 are dependent on the heat treatment that have undergone to become the designated temper T3 or T42.

You would normally choose to purchase material you will use on the basis of what you are trying to do, or heat treat from one condition to another as you require.

One fundamental difference of T3 & T42 is that T42 is usually used when forming a shaped section with large (90 deg) angles, as it is more ductile.
Another difference is that T3 is a bit stronger as it is not so ductile.

### RE: 2024-O vs 2024-T3

RB1957... this is a weird 'word problem'...

Listen to what Reldys Romero actually seez...

... I have decided to use 2024-T3 instead of 2024-O which required the heat treat to T42...

This fairly clearly implies some document [drawing, AMM repair, etc] REQUIRED...

2024-O... form/whatever... then SHT/Q/Age to -T42.
(or)
2024-O... SHT/Q [-W]... form-whatever... then age to -T42.

This guy has decided to 'form-whatever' directly from -T3 and avoid all those other 'nuisance HT steps'. Sometimes You can get away with this... but usually not. There is always a reason for the original engineering 'materials/methods'.

Unfortunately I see this all the time... in themes and variations that techs [and many engineers] don't get.

"Hey IF I can make it out of -T3 [ILO -O, SHT/Q/A -T42] I'll save time and "... and possibly crack the part or alter the metallurgy.
(or)
Drawing calls out to 'make from' 2024-T6 [now -T81] or 7075-T6 extrusion... but the part is joggled which is impossible... Isn't IT?!?!?. So 'they decide' to make from -O extrusion [or take -T81/-T6 HT/anneal it 'back' to -O], form it in -O, then HT to -T62. In reality, the original manufacturing intent was to make from [-T81]-T6 and HOT JOGGLE... which doesn't require any HT... and kept the part simple/cheap to make... except no-one HOT JOGGLES any more.

The general problem here is that 2024 or 7075 formed in the -O condition can see grain growth in the high strain regions which can substantially alter mechanical allowables. In these cases the cold-forming MUST [OK, LOUD SHOULD] be done in the -W [post SHT/Q temper state], then age-hardened to -T62... to avoid the grain-growth problems in high strain areas and maintain good mechanical allowables.

I am reminded of the old/wise saying: Know the rules to break the rules.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

### RE: 2024-O vs 2024-T3

I thought the properties of the two tempers were near enough the same.

If a formed part material is specified as T3, I'd expect it can be (should be) formed from T3 sheet.

If the material is specified at T42, I'd expect that the part can't be formed in T3, so it needs to be formed in some intermediate temper (O, W?) and then HT after forming which would make it T42 (you can't get T3 after forming, yes?).

It sounds like the part specifies T42, but the poster wants to substitute T3, presumably to save the HT step. One question is "can the part be formed ?" and the next one "Will the guys approving the part agree?" ... two very different questions !

### RE: 2024-O vs 2024-T3

A recent experience I had with heat treatment reminded me that all members of the production chain must be aware of what needs to be done to accomplish the intended result. Any break in the chain, and you may get the phone call from the production manager "can we accept this pretzel-shaped abomination, please?".

When your design passes through many hands on its way through many processes, each member of the team and each contractor outside your facility that touches it must maintain the integrity of the parts throughout the process and as they hand it to the next step in the chain. In my case I got the parts back severely warped by the solution heat-treat process partly because it was barely clamped at all to the fixture. In fact, the fixture didn't even have all of the necessary locating holes drilled, let alone parts secured in the right places. It turned out the welding shop had made the fixture without ever seeing the drawing, welded numerous assemblies, removing each from the fixture as soon as welding was done - no cooling time no PWHT. Production sent these parts to heat-treatment in that condition so when they came back from HT warped, they blamed the HT vendor, not the welder.

I have been learning the hard way that the number of special processes on any part should be kept to the MINIMUM if at all possible. I may start specifying right on my drawings vendor qualification requirements like sample coupons, rather than allow production to blindly accept the certificates the vendors send them. The "Trust, but verify" motto may apply here.

STF

### RE: 2024-O vs 2024-T3

(OP)
Hello all,

again, for information because it can be confusing.

I can see the confusion in the question. What i would really like to know is the reasoning behind why you can substitute 2024-T0 HT42 with 2024-T3. I have talked to some of the machinist at my job and they have said that they are both almost the same.

So, what i was told and know so far (correct me if i am wrong) 2024-TO after HT42 will become (lack of term) 2024-T4 but, 2024-T3 is already at and close to a 2024-T4 state.

I can see them being almost equivalent due to what berkshire said about their ultimate psi yield.

Additionally, i want to correct my statement. I decided to use it (not literally) because my understanding was that they are about equivalent. like previously mention T3 is harder to form to a desired bend due to ductility. But, TO can be formed to desired bend easier than T3 but, it must be then HT to T42 to achieve final state of sheet at formed bend.

### RE: 2024-O vs 2024-T3

The end products may seem "equivalent", but the process of getting there is very different.

T3: buy the cheapest temper T3, form the part, install the part
T4: pay extra for -O, form the part, normalize, temper, straighten if necessary, install the part... I hope you see that this is the more costly option.

It can be unavoidable in sheet-metal shapes with complex curves, but otherwise you will be questioned by production about the reason for the extra processing.

STF

### RE: 2024-O vs 2024-T3

There is also 2024-T4 Kaiser Aluminum T-Form with offers an alternative to starting at O condition .
http://www.kaiseraluminum.com/customers/products/p...

I have never managed to use T form, does anybody here have any experience with it?

### RE: 2024-O vs 2024-T3

"2024-TO after HT42 will become (lack of term) 2024-T4" ... actually it becomes T42 !

Yes T3 and T42 are almost equivalent but the issue I think we're trying to high-light is if you are forming a part in O condition, then you may not be able to form the same part in T3.

### RE: 2024-O vs 2024-T3

(OP)
Ok. So depending on the type of forming that i want to do. Will (more or less) reflect the choice between T3 or T42. Like for a sharp bend I should use O then HT42 but, if what i am looking for is almost (degree < 30 degrees) or a very small angle of degree then T3 is recommend. Moreover, its recommended because it would take longer to start at O and HT to T42; So, better off to start at T3 for something fairly straight rather than O. Right?

### RE: 2024-O vs 2024-T3

Yes, it would take longer to start with O and heat treat to -T42. It would also cost more. And take much longer. Design the part to work using T3 if you possibly can. If you must push the limits of standard practices to make a tight enough bend radius work, then it may still be cheaper to add an extra inspection process, rather then all of the heat-treatment processes.

STF

### RE: 2024-O vs 2024-T3

(OP)
ok great. The inspection is to very that no cracks are present during forming correct.

### RE: 2024-O vs 2024-T3

the radius of the bend is more important than the angle. T3 will usually work with 3t bend radius. If you need tighter (like 1t) than you need to form in O condition.

### RE: 2024-O vs 2024-T3

Reldys... my last attempt to explain this to YOU.

REF FAA-H-8083-31-V1 Aviation Maintenance Technician's handbook - Airframe V1
http://www.faa.gov/regulations_policies/handbooks_...

Open V1 and then Go-To Figure 4-125 Minimum bend radius [for aluminum alloys] (from the Raytheon Aircraft Structural Inspection and Repair Manual)

NOTE that the minimum permitted bend radius [BR] for 2024-O and 2024-T3/-T4 are in totally different columns; and are substantially different Radii!

For example, per this table...

(A) 2024-O, 0.100 thick, can be safely bent to BR 0.22. AFTER forming the part MUST BE heat treated to attain -T4 [-T42] temper (parts are NEVER used in -O [annealed] condition).

(B) 2024-3/-T4, 0.100 thick, can be safely bent to BR 0.44. After bending, NO FURTHER ACTION IS REQUIRED [except to visually inspect for cracks in the BR].

It IS OBVIOUS, or should be obvious, that these processes are completely different and may in fact be a order of magnitude different in cost...

Heat treatment [-O, form, HT to -T42, inspect, apply finish] WILL increase the cost for a simple part 5X to 15X+ and will take days to properly manufacture.

Whereas the no heat part [MF -T3, form, inspect, apply finish] can be made in minutes and be ready for installation shortly thereafter [after application of finish].

This draws a OBVIOUS POINT: The heat treatment option is ONLY specified when severe forming is required [various reasons]. IF The original engineering specified -O material HT-T42 there was a dammed good reason for it... IF it specified -T3 then no severe forming was expected so why bother pouring company resources into non-value-added work?

OK there are special cases where these guidelines can be violated.... but very rare/far-between. There are also a LOT OF DETAILS that are missing in his explanation to KISS.

IF THIS doesn't give You an 'AH-HA' moment, then You need aluminum fabrication training... not counseling/advice we're trying to provide in this thread.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

### RE: 2024-O vs 2024-T3

Piling on to WKTaylors comments .
It would appear that my original part of my reply " So it would appear that if you can use 2024 T3 you may not have to heat treat." was not worded strongly enough. What I should have said is " If you can use 2024-T3 you do not need to heat treat to T42 ". I think you need to back up and look at how this part is made Particularly what radii are present and the degree of deformation in the part.
B.E.

You are judged not by what you know, but by what you can do.

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