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.

[eaglefordracer]

Take a look at Tin Man’s website and he has a really thorough write up about annealing various aluminum alloys. He specifically talks about 5052. Do a search for annealing 5052 and it should pop up. Or go to his site and search. Using a Tempilstik is the easiest way IMO.

[crystallographic]

This torch-annealing aluminum subject is actually pretty simple.
The devil is in the details, though.
750-775F for 1100, 3003, 6061
650 - 675F for 5052 (Better get this right, FIRST : LOWER your heat to anneal 5052)

I'll offer some little practical pointers to help make it a smooth flow that yields success. (Aside from my own mischief, I have worked with other crews on jobs away from my own shop.)

Some time ago I had to sort out some badly- annealed 5052 for a job.
I saw a lot of problems clearly on this one part, which helped me clarify key points that lead to non-damaged success.

5052 alloy is very common in some industries, as it is weldable, has very good strength, and enough corrosion-resistance to enable Coast Guard cutters to be made from it.
(You don't see unpainted C.G. cutters very often, but I walked along one in Seward, AK in 2010 - and the uncoated 5052 was a dark gray.)

When torch annealing 5052, you can end up with the odd colors by overheating or having transient oils on the surface. Improper annealing can make the surface very grainy. And sometimes it cracks. Or melts.
I've found that of all the aluminum alloys I have worked with(10?), the 5052 is most sensitive to overheating.
Accurate temperature indication is therefore pretty important. The IR guns are sure nice. Temp crayons, too.

Lower-grade low-cost low-tech "country" accuracy (THINK : now that your heating goal is 100F LOWER than the more popular alloys) :
Sharpie markers are popular with 3003/1100 but vary a lot in the INK dept, from the Factory. Ink = temp. when heated. ink variations = variations in temps.
Soap, soft pine (matchstick ends), acetylene soot, Dykem blue, and etc etc all can be used "country style" accuracy - "Kentucky windage" and that stuff, on 1100 and 3003. (Might want to up the game if the part is 5052 or important?)
Soot is an insulator when applied in a good thick layer: The "Fat" quiet flame with lurid yaller color with black birds rising off the end is Not the right torch setting for thin sheet, But On 1/4" 1100/3003 plate this is fine.

1) So ... Might want to rethink "soot thickness" when using 5052 .032" (.8mm) or .040" (1.mm) metal, hence add some oxy to the flame so the flame tip is clean and then use only the "bright" inch or two at the flame-end to "paint the surface" - soot coverage need not be "perfect" but "good and even" and should cover the surface without any bare spots - Aluminum is Very Heat Conductive, right? Seeing the aluminum metal through a soot coat might be just fine ... BUT if you see the soot Glow when the flame hits it - wipe it all off and start over. (Like a good paint job - keep the coats thinner than Thicker. on the 5052)

2) You need not burn it all off spotlessly clean. You are only trying to heat the surface EVENLY. So try to be methodical with the torch sweeps / passes (like wheeling the metal or mowing the lawn or spray painting the kitchen ...)
Avoid the "Jazz Improv" or the "here and there and back again" style... Always gives uneven results, from what I have observed...BAD for 5052.
(Heat treat ovens are very methodical and accurate. Be like the oven when doing 5052. Shut off the wind/fan/AC/Heater. Work out a good consistent way to back-and forth the torch methodically over the surface, one side to the other.
AND - keep the flame-to-metal distance consistent. (Again, like spray painting.)

3) Torch tip size can matter a lot. Small oxy-acet torches can adequately do small parts, using tip sizes #2,3,4,5,6.
Using an over-sized tip can be dangerous to the part being annealed.
I have used a big brass "Western" weed burner for large parts up to 5ft-6ft-8ft. (No reason to paint the barn with a 1inch brush... right?) But my "flame tip to metal" distance is set for metal thickness and air temp. Outdoors in winter can need more heat on the metal. (like the two Feb. night photos below.

Summary:
Even perforated metal shapes can be done with a big old weed burner and a good temp indicator, when you master the flame size, distance of flame- to - metal, and the steady speed of flame across the metal ... on the 5052.

P1030889 copy.jpg
P1000463 copy2.jpg
P1030572 copy2.jpg
Good luck on your 5052,

[boltboy49]

So the no.4 rosebud might be a little much? I don't know why an ir thermometer didn't occur to me. I have one not 10 ft away that I use to keep an eye on flue temperatures. The purple color I was seeing is definitely caused by oil on the part. I put some good ol WD on the panel to because it seemed to keep sticking to the dies a little. Maybe sticking isn't the right word, dark grey buildup that made the aluminum grabby. I should have titled this topic more broadly, I am having trouble with alot more than just annealing.

[DavidB]

AL,

Just be aware that an IR thermometer will only give a good reading if the emissivity setting is somewhere near correct and with metal surfaces it can vary considerably. Many common surfaces tend to be 0.95 and above but many metal surfaces especially polished can be much lower, see https://en.wikipedia.org/wiki/Emissivity . You may want to try and compare a known accurate temperature indicator with your IR thermometer and find a emissivity setting that agrees before using it for annealing your items as too high an emissivity setting will lead to it under reading your actual temperature.