help needed annealing 5052

[boltboy49]

What's the best approach for annealing 5052? I used the soot method and I keep melting the surface in a few spots. Also, is a purplish discoloration normal for 5052?



Thanks for the help
Al

[heinke]

I've used the soot method to anneal quite a bit of 5052. Melted or near melted spots can occur when the torch remains stationary in a given spot too long. Always keep the torch moving over the surface and don't let it become stationary.

I always get some discoloration when annealing 5052. Sometimes it's just a gold color, sometimes a bit darker but purple sounds like you might be using too hot of a flame. You might want to back off on the heat some and go a bit slower. That should also help prevent the melting spots from happening.

[cliffrod]

I had burn-through and notable discoloration when learning to anneal aluminum with soot method. If I focused heat on the soot and tried to “make” it burn off, bad things happened.

Slowing to to make sure the entire area/panel was fully heat soaked before trying to burn off the soot made it work much better. After the panel was complete hot, the soot burned off easily and quickly under the flame.

An easy way to tell what I was doing was wrong or right was that an inadequately heated panel was cool enough to handle almost immediately after I did it. But Without quenching with water or compressed air to cool it, an adequately heated panel was HOT!!! when I finished burning off the soot. Way too hot to handle, even with gloves.

Fwiw- I learned it was just caramelizing sugar with a torch when doing crème brûlée. You heat the entire area of sugar before heating any specific portion to the level of melt & caramelization. Then you can quickly easily melt/collapse the sugar to the desire color with only a minor additional amount of focused flame. It kind of collapses all by itself (just like the soot will on aluminum) If you rush it and try to force the sugar to caramelize by focusing heat, all you’ll do is scorch the sugar and ruin the product. Not cool…

[sandmanred]

I've used sharpie pen marks as the 'soot' and it works okay, as they fade to almost nothing around annealing temperature of 650F for 5052. The more sure fire way is to get a tempilstick that indicates 650F. Periodically touch the workpiece as you heat with the tempilstick and it will liquify once you reach 650F or above. The only problem is they leave a mark that needs to be sanded out if you over heat the mark. The marks will wipe off with acetone if you don't get them too burnt.

[dwmh]

I too prefer to use a felt tip such as a sharpie. I have found some brands fade at different temperatures. I found when using soot and that I could easily overheat it.

[boltboy49]

Thanks for all the suggestions. I'll try sharpie and see if I like that better.