Heat treating of aluminum wire and cold headed rivets 1

[TVP]

I have a couple of quick questions. First, are aluminum rivets always cold headed from strain hardened wire, e.g. 2117-H13 or 7050-H13 or is the wire supplied in the fully annealed condition? Second, for rivets that are to be supplied in the artificially aged condition, is a solution heat treatment always performed after cold heading, or is it possible that the wire is annealed, the rivet is formed, and then the rivet is artificially aged? I understand that various aerospace product standards specify the heat treatment of the final product (rivet), but I am not totally clear on the incoming wire.

 

[metengr]

TVP;
Did you post this same question in the Aerospace engineering forum?

 

[TVP]

I contemplated posting it there, but decided against it. I think wktaylor and yates visit this forum as well, so I am hoping someone will be around shortly...

 

[WKTaylor]

TVP... hi!

Basics. for aerospace rivets...

1. The basic procurement spec for aluminum driven rivets [NASM5674] describes all aspects of the finished rivet... and certain mandatory processes such as heat treatment and finishing... but does NOT describe exactly how-to-get-there-from-here.

2. Aluminum wire material is QQ-A-430 [or possibly ASTM B316]. The rivet wire spec is[are] titled "Aluminum Alloy Rod and Wire: for Rivets and Cold Heading". This material is useful for a wide variety of cold headed parts, of which rivets are only a specific/limited application [note that various alloys are also included in the specs, which have never-been used for rivets]. In-general...

2.1 The alloys are provided in "-O" temper and "-Hxx" [strain hardened] conditions... which are NEVER used in final parts... except for non-heat treated alloys [generally limited to 1100 "A" rivets].

2.2 The annealed wire/rods are used for various cold headed products and probably larger diameter rivets.

2.3 Cold working is used to improve roundness, smoothness, straightness, etc... of fine-rod or wire wire, and would result in mild % strain hardenening [noted by the low "-H13" number]. The MOST LIKELY need for these characteristics is to improve "feeding" thru automated fabrication equipment, allowing hundreds-of-thousands of finished parts to be made at a blindingly-rapid pace. The improve stiffness and control of wire dimensions [roundness smoothenss, etc] facilitates this processing: whereas dead soft [annealed] "as-extruded" wire and rod would most-likely "gum-up" the processing equipment... or require significantly slower processing to avoid feeding problems.

3. After forming, ALL of the [heat-treatable] "raw" rivets are heat-treated to final temper per AMS2770... which would remove all affects of the strain hardening, except for grain flow characteristics [easily exposed by metallurgical cross-section and analysis, if needed].

Regards, Wil Taylor