[Josephbonney23]

I have a syncrowave 210 and i know 1/4” aluminum is listed as the limit for amperage availability. With preheating ive been able to tig 1/4” without too much trouble (all non load bearing simple hobby stuff) my question is today i had need to make some cleats for a boat out of 3/4” round stock. I didnt think the machine would do it but after preheating for a couple minutes longer than usual i was able to make short work of it. Everything puddled beautifully and without issue... at what point is aluminum damaged due to overheating when welding or preheating? I definitely got the parts pretty hot even though i had 1/2” chill blocks of aluminum backed to the part while welding. Im just curious what everyones take on this is as this is way above the machines stated capability, and is there an easy way to tell when aluminum is just way too hot. Distortion was not a problem.

[Oscar]

I've read that pre-heating should be kept to about 250°F no higher. When you weld aluminum, you will always weaken the HAZ, but you can make up for it by heat-treating if you have that at your disposal and if you use a filler rod that responds to heat treatment.

[cj737]

A slightly different response than you asked- If those round bars were to become T handled cleats, you would have done better to taper the leg quite a bit to afford you a bevel to fill. 3/4" round stock in that configuration is not going to give you much area for penetration in the joint. So your entire weld bead is outside the two surfaces, which will be much weaker than you hope for.

Even a bit of an ugly bevel grind on the leg would be better because you will fill and weld over it with a socket-type weld.

Allowing the parts to cool fully for a day or two should help them anneal back to their original tensile strength. If you quick shock them with water or air, you would likely see some cracking in the bead.

[Josephbonney23]

Thanks for the replys. With regard to tapering the leg i did raper a bit on either side where i knew it would be easy to get my torch in though i agree i could go with more for better strength. My main concern is if its possible or likely i’ll see a failure from overheating the part. They came out ok as far as looks go.

[Arno]

My main concern is if its possible or likely i’ll see a failure from overheating the part.

For alloyed alu types like 6061 the most 'damage' you do by heating it a lot is that it can lose some of it's strength that was incorporated in the (usualy) T6 hardening. Of course the weld itself and HAZ are the most affected anyway.

Alu welds are nearly always weaker than the base material and the base material in the HAZ is weaker than the area outside it.

Only 'pure' alu (99.8% pure or better) like many flat sheets are made from does pretty much nothing until you reach the melting point, but it's pretty soft and on the bottom end of the scale anyway.

Smallish parts like you have could be heat-treated again to restore some of the hardness if it's an alloyed type if you are worried about that.

Bye, Arno.