Heat treating 2017 and 2117 rivets 3

[rpjorgen]

I have been heat treating, driving, and testing 2017 "D" rivets and 2117 "AD" rivets and have been getting shear strengths about 15% less than I am getting out of a 2117 "AD" rivet without heat treating it.

I would have expected the heat treated 2017 to be a bit stronger and a the heat treated 2117 to be same as the "out of the box" 2117.

I was heat treating at 930 for 15-20 minutes and quenching.
Then immediatley driving.

Testing over several weeks yielded no significant change in shear strength.

The "D" rivets showed significant cosmetic changes after heat treating. They became darder and developed many small bumps and lumps on the surface.

The "AD" rivets discolered slightly darker, but didnt develope any lumps or bumps.

What am I doing wrong??

Thanks

Rick

 

[Sparweb]

First of all, you're not supposed to heat or chill AD rivets at all.

How are you testing the rivet strengths? Are you sure your oven's thermostat is correct? Have you tried keeping the rivets in the oven for a shorter period of time? (5 minutes instead of 20?)


Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

 

[rpjorgen]

Thanks for the reply about the rivets.
Where is the admonition about heat treating the AD rivets. I have heard that before but have never been able to find out where that came from.
We are verifying oven temp with infared sensor and temp sensitive paint on test pieces.
I have been following the recommendations in Standard Aircraft Handbook which has heat treating information that reflects the industry standard specifications for heat treating both 2017 and 2117. The 20 to 30 minute soad times are based on material thickness to get the heat all the way through the piece.

I am just learning this stuff, so feel free to give me any insight on this stuff you might have.

Email: rpjorgen(AT)dcn.davis.ca.us

 

[aviat]

AC43.13-1B 4-57(d) says that 2117 rivets may be driven in the conition received. I guess that does't mean you can't heat treat them, but they are purchased in a heat treated condition. Why would want to spend time and money doing something that doesn't add any value?

When you purchase the rivets they are in the T4 condition, which consists of heating, quenching, and naturally aging. Because you drove the rivets before they were aged it could account for the difference in shear strength. When you drive the rivets you further harden the rivet by coldworking and it becomes T3.

 

[Sparweb]

We're all here for the learning.

As an alternative, you could consider using "E" rivets. I believe that they are the designated substitutes for DD rivets, and don't need heat treating.


Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout

 

[rerig]

For clarification:
"DD" rivets, 2024, are driven in the "W" condition and temper from work hardening.

 

[Stache]

Being an old sheet metal man (person) who has driven thousands of rivets I can safely say that AD rivets 2117T do not need to be heat treated. They are called field rivets and can be driven straight out of the box. However, if the 2117 are 3/16 or larger they may require to be kept on dry ice until driven. I have found you can drive 3/16 rivets just fine if you use a 4X or 9X rivet gun. Reference AC 43.13 chapter 4,par. 4-57(4)(d).

My experience with DD 2024T rivets is after the second to third heat treatment they are very hard to drive. Something else that makes the DD rivet hard to drive is cutting them to length prior to being driven. This is very true in the 3/16 inch and up diameters. Having the rivets cut to size before heat treatment does make a difference.

Stache

 

[AeroE]

Multiple heat treats of these alloys drive the metallurgical precipitates out and change the grain size.

I never heard of anyone heat treating AD rivets, but anything is possible.

If you know the design loads, you ought to choose a fastener with the appropriate strength level and diameter to obtain a bearing critical joint for the gage of materials you are joining.

Icebox rivets are obsolete and have been for a while; I'm surprised they can be purchased (except for someone's ancient NOS).

 

[WKTaylor]

All. A few technical points...

Rivet sizes and corrosion protective coating types were NOT mentioned... which could make a big difference in this study.

The heat-treatment process used by RPJ does NOT appear conform to AMS2770G "heat treatment of wrought aluminum alloys". Not only is the target temp 5F below the spec [SB: 935F], the heat-soak times are probably too short for common rivet diameters. The spec is also VERY explicit regarding minimum heat-soak time VS heat-treat media [furnace or salt-bath]. Also AMS2770G is VERY critical regarding oven-loading and spacing of parts; time between oven and quench [a few critical seconds]; and quench bath type/temperature.

WARNING:

Aluminum driven rivets typically have (2) different kinds of corrosion protective coatings:

a. anodized [clear, dichromated or colored]

b. conversion coated ["alodine", chromated or clear].

These coating serve explicit purposes, as follows.

a1 Anodize clear: Heat treatable without damage and have good post heat treatment corrosion resistance. NOTE: all DD [2024] rivets come with this coating for ready heat treatment. Available for all other rivet alloys WHEN SPECIFIED... but not very common.

a2 Anodize/dichromated: Not recommended for heat treatment [will destroy dichromate and reduce protection slightly] and have very high corrosion resistance. NOTE: D [2017] and AD rivets can have this coating for enhanced corrosion resistance... but not very common.

a3 Anodize/colored: Not recommended for heat treatment [will destroy color and reduce protection slightly]. various colors typically used to segregate alloys [special callout, company specific]; good corrosion resistance. Color [red, blue, green, purple, etc] can be applied to any rivet alloys...but are typically applied to company-specific rivets for positive shop ID.

b1 chromated conversion coating ["golden-colored" alodine]: ABSOLUTELY NOT recommended for heat treatment [will destroy corrosion protective finish and result in possible surface damage to rivet and contamination of heat-treat salt baths]. This is BY FAR the "general purpose" coating for MOST rivets [except "D" ~2024], due to low cost and fairly good corrosion protection when installed "clean" [contamination-free] and "wet" with primer on installation.


b2 clear conversion coating [natural aluminum colored alodine]: ABSOLUTELY NOT recommended for heat treatment [will destroy corrosion protective finish and result in possible surface damage to rivet and contamination of heat-treat salt baths]. This is coating avoids use of chromates in order to improve electrical conductivity... and is typically used for electrical-bonding between parts. Coating is fairly low cost but not very common. NOTE: clear conversion coating finish can be confused with clear anodize [which is much tougher and corrosion resistant, but is far less conductive than clear alodine finish... and has a predominantly grey appearance]. Coating has relatively low corrosion resistance and MUST be installed very clean [contaminant free] and dry.


Regards, Wil Taylor