Aluminum 6061-T4 Welding will change temper?

[soldanr]

I would like to know if the anybody has experience or tips on welding 6061-T4 material and the material properties after the welding.

We have a weld assembly that is basically a 3.5 x 3.5 square plate of 6061-T4 being welded to a 6061-T4 2.5 inch diameter aluminum tube that is 2 inches in height.

Someone told me that the plate can also be in the Annealed condition, 6061-O material, since when you weld the material becomes Annealed.

Is that true?
I can't find any data to back that up?

I can see where the material would change temper, but how much of the weld area?

My motto is:
In God we trust... everybody else bring data!

Thanks in advance,
Raf

 

[cpretty]

I did a bit of work in this area, and eventually found the information. I am struggling to find it again though.

http://en.wikipedia.org/wiki/6061_aluminium_alloy

- provides some insight.

We were designing for marine applications, and found that Lloyds etc would derate aluminiums strength to that of T0 state when welds were applied.

I wouldn't consider the whole plate to be in T0 condition, but the Heat Affected Zone around the weld will be.

http://www.lincolnelectric.com/knowledge/articles/content/comistakes.asp

- is a good link relating to this.

There is also a discussion here

http://www.homebuiltairplanes.com/forums/sheet-metal/3583-welding-6061-t6-question.html

- but I don't entirely trust the statement about natural aging to T4 state over time.

Craig Pretty
Tru-Design Plastics

 

[metengr]

Someone told me that the plate can also be in the Annealed condition, 6061-O material, since when you weld the material becomes Annealed.

Reply; Incorrect. The weld region (surrounding base metal)will change temper from heat to somewhere between T4 and 0, but it is not in a fully annealed condition.

The plate and tube bulk properties should remain in the T4 temper condition. One can locally treat the weld region as an annealed condition for mechnical properties used in the determination of load-carrying capacity of the weld (conservative approach).

Here is some information on welding, specifically filler metal for 6061

http://www.brazing.com/PDF/Aluminum Data Sheets/AL_4043.pdf

 

[Ron]

Agree with metengr....somewhere between T0-T4...could be different with two different welds on same material.

Generally, weld stress allowables are taken within 1 inch of the weld in either direction. This is from the Aluminum Association, Aluminum Design Manual.

 

[tbuelna]

soldanr,

The T4 condition is solution heat treated and naturally age hardened. What you get in the heat affected zone of a TIG or MIG fusion welded 6061 alloy aluminum structure, immediately after welding, is a material condition that has been heated and air-quenched, or a "W" condition. The natural age hardening process for a T4 condition would require exposure up to 96 hours at room temp.

If your plate is 6061-0, only the heat affected zone of the weld joint will achieve T4 properties. The rest of the plate will remain at an annealed condition.

Good luck to you.
Terry