Annealed rivet storage time vs. temp 2

[2Badknees]

I am an aircraft sheet metal tech and I have a question-our company has no engineers!
AMS 2770 Rev.L table 6 tells us that if we have 'AD" rivets annealed(2114} we can store for 90 days in a freezer that is set at -10F. We are looking at purchasing a lab surplus freezer that has both a digital readout and a graphing chart. It comes preset to -20F. Will the rivets be able to be stored longer? If so,how much? Or will the 10 degree difference have an effect on the usage ie: brittleness?
Thanks!

 

[WKTaylor]

2Badknees..

Two elements of Your statement already idicate You have been misinformed about solid aluminum rivets and heat treating.

1. 'AD' rivets MUST NEVER BE HEAT-TREATED. They are intended to be driven as recieved.

2. YOU stated that these rivets become annealed, which is ABSOLUTELY incorrect if propr heat treatment prctices are observed! Rivets heat treated for the purpose of reducing installation forces and improve installation ductility [D-2017 and DD-2024 must have anodized-finishes only], are solution heat treated, quenched and immediately frozen [below 0F]... to preserve them for a short-time in the "-W" temper... which is an unstable transition temper that will spontaneously age harden to -T4 upon warming.

It is in this unstable -W temper that they have a short-period in-which they can be bucked with low force and great ductility. To do this mechanics remove the rivets a few-at-a-time from the 'freezer' and install them quickly while in the "-w" temper driving 'window-of-opportunity"...usually 15--30 minutes 'depending'... otherwise they harden quickly. About 1-hour or less total-out-time at RT after quenching they are well on their-way to -T4 strength [hence reason for immediately freezing them after quench, to retard this natural aging process].

This scary airworthieness issue ['rivet heat treatment'] has been discussed in several Aero engineering forums...

http://www.eng-tips.com/viewthread.cfm?qid=103368

http://www.eng-tips.com/viewthread.cfm?qid=142319

http://www.eng-tips.com/viewthread.cfm?qid=373555

http://www.eng-tips.com/viewthread.cfm?qid=226777

http://www.eng-tips.com/viewthread.cfm?qid=296391

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[WKTaylor]

2BadKnees..

NOTE. Just to clarify.

'Anneal' is a term specifically related to the solution heat treatment, then air-cooling to RT, of an aluminum alloy [heat treatable or not heat treatable, makes no difference]. All effects of strain and thermal hardening are completely removed from the material, resulting in a dead-soft highly ductile condition that is stable.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[2Badknees]

We are not heat treating-we are annealing the AD rivets, stored on dry ice back to our facility, then placed in a sub-zero freezer-the standard only shows storage time to -10 degrees-90 days.
The freezer is preset to -20-how much longer will they be able to keep at this temp.
We are doing this due to the thin skin/metal thickness of the structure-it should allow for faster,easier,less rework rivet installations.

 

[WKTaylor]

B2K... Your statement...

"We are not heat treating-we are annealing the AD rivets... stored on dry ice back to our facility..." has has multiple contradictory elements.

AD rivets MUST NEVER BE HEAT TREATED.

The only way to anneal is by heat treatment.

Annealing [to a dead-soft temper] is a different HT process that SHT/Quench to attain the unstable -W [as-quenched] temper.

You are obviously having a vendor do this HT work for You... then the HT parts are stored in dry-ice for return to Your shop.

IF in-fact You are doing exactly what You say, then You have created un-airworthy rivets. IF ANY of these have been installed in a aircraft structural application, this is an airworthiness emgergeny.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[EdStainless]

But to address the original question
No, you must store them no warmer than -10, and for no longer than 90 days.
You could buy a -100 freezer and you are still limited by the 90 days.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[berkshire]

2Badknees
Do you really mean AD rivets ? The storage and out times you are referring to, are usually for DD rivets 2024, or D rivets 2017.
Also AD rivets are usually made from 2117 T4 material . I have never heard of a 2114 alloy 2014 is the closest I can find.
There is an annealing procedure for 2117 to remove the effects of prior cold work which is to heat the material at 775* for two to three hours with no quench. This brings the material to the T0 condition. which is too soft for aircraft use at 26000psi , compared to 43000 psi for T4. I sincerely hope you guys are not doing this.
I think you need to go back and look at your rivets to see what the designator on the package is, and see what material they are really made of , then get back on here.
B.E.

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

 

[berkshire]

It would appear that the original poster 2 bad knees did not like the answers he got , and has dropped out of sight.
B.E.

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