Is re-tempering 6061-T6 necessary in some instances?

[Brian Jackson]

Greetings all. As I prepare for the end-game of my build, I'm curious if it is worth having some items heat treated again. Some of the plate parts that required grinding/sanding to shape grew quite hot to the touch, and I do not know if this heat has diminished their strength in any way. My expertise is not in metallurgy so it's worth asking the question. Thank you.

Brian

 

[Vance]

Greetings all. As I prepare for the end-game of my build, I'm curious if it is worth having some items heat treated again. Some of the plate parts that required grinding/sanding to shape grew quite hot to the touch, and I do not know if this heat has diminished their strength in any way. My expertise is not in metallurgy so it's worth asking the question. Thank you.

Brian

I found this from Wikipedia, and felt it was on point and helpful.

6061 is highly weldable, for example using tungsten inert gas welding (TIG) or metal inert gas welding (MIG). Typically, after welding, the properties near the weld are those of 6061-T4, a loss of strength of around 40%. The material can be re-heat-treated to restore near -T6 temper for the whole piece. After welding, the material can naturally age and restore some of its strength as well. Most strength is recovered in the first few days to a few weeks. Nevertheless, the Aluminum Design Manual (Aluminum Association) recommends the design strength of the material adjacent to the weld to be taken as 165 MPa/24000 PSI without proper heat treatment after the welding. Typical filler material is 4043 or 5356.

In other words after welding it is weaker near the weld and gets better with age.

From thefabricator.com:

Solution heat treatment is done by raising the alloy temperature to about 980 degrees F and holding it there for about an hour. The purpose of this is to dissolve all the alloying elements in a solid solution in the aluminum. Then we quench the alloy in water.

Based on experience I suspect you would need to be over 200c (392F)to over age 6061-T6 making it more ductile.

As I recall a powder coating oven is 184°F to 240°C (350°F to 450°F) so in my opinion it could over age 6061 T6 and make it more ductile.

 

[Brian Jackson]

Thank you, Vance. Want to do more research into this but nothing got as hot as the temperatures you've posted.

 

[Abid]

Greetings all. As I prepare for the end-game of my build, I'm curious if it is worth having some items heat treated again. Some of the plate parts that required grinding/sanding to shape grew quite hot to the touch, and I do not know if this heat has diminished their strength in any way. My expertise is not in metallurgy so it's worth asking the question. Thank you.

Brian

No. Hot to the touch is nothing. Powder coating alone gets billet 6061-T6 parts to 400 degrees for about an hour. No need to over analyze your situation. Just build properly with proper safety factors in choice of tubing and materials

 

[Brian Jackson]

No. Hot to the touch is nothing. Powder coating alone gets billet 6061-T6 parts to 400 degrees for about an hour. No need to over analyze your situation. Just build properly with proper safety factors in choice of tubing and materials

Thank you, Abid. I appreciate your expert guidance. Didn't want to overlook something important out of ignorance. Now that the question has been asked and answered I'll scratch that off the list of things to worry about. Cheers.

 

[Doug Riley]

Keep in mind, too, that Bensen called out 6063-T5 for most of the aluminum-angle braces on his gyro (all but the mast-keel brace and engine mount braces). The tow boom, keel-axle braces, front seat supports and various other small bits could be T5 -- in some kits, without a radiused inner corner, either. Then you whittled away most of the cross-section by tapering the ends and drilling a big 1/4" hole in the remaining 3/4x 1/8" strip.