annealing aluminum sheet , help
I am trying to make a part for a customer out of his supplied aluminum sheet .
16 GA 6061 T6 ( I think)
Customer said it was from a semi trailer side wall.
Every time I bend it in the brake it snaps off clean .
Tried to bend it in another direction , and also set the apron top back so it makes a rolled bend .
Still no luck .
Is there a way to anneal aluminum ?
this is just a small 8" long bend .
Seems I saw on one of those fabricator shows where they heat with a rosebud ,
then quenched with a wet rag .
Simple as that ?
6061 T6 is not great for bending.
annealing will help, some, but it wont magically change it into a softer alloy.
Anneal by taking an oxy acetylene torch, no oxy, just acetylene, and cover the whole thing with soot.
Then heat gently, with the biggest tip you have at a low heat- even propane, maybe, to avoid burning holes thru it, and just barely burn off the carbon. When the carbon disappears, its ideal annealing temp, but get it to hot, and you get puddles.
then just let it air cool.
Use the biggest radius you can for the bends- most people air bend aluminum with pretty big V gap bottom dies, or use out and out radiused dies.
Aluminum does not like sharp corners.
You need to bring it up to but not much above 800 degrees Mcmaster carr sell temp pens that melt at known temperatures or some soot it with acetylene flame the turn on oxygen and heat till carbon is burnt away hears told permanent marker burns of at coct temp failing al that if design allows used much larger radius .
I have successfully used the old trick of rubbing the area with a conventional bar soap. when the soap film chars you are there.
fwiw here's the industry spec for annealing 6061. Depending on the part you are making and it's use, I'd be hesitant to experiment with non spec workshop practices that you're not familiar with. Based on the recommended procedure, it's pretty obvious that an extended heating/cooling period is recommended...otherwise I would expect some failure at your brake line, or in the part, at some point in the future...
Originally Posted by FlatBeltBob
If it's just a small part, why not have your customer pay for some properly annealed material, rather that risk future failure to save a couple bucks, and shelve his existing hardened stock for the proper application in the future???
Aluminum 6061 - All Metals & Forge
Me too. Mid to darkish brown does the trick.
Originally Posted by chuckey
My Dad owned a camper/trailer sales and service for many years. He taught me how to bend Al sheets that works every time and its to soot the bend line with a torch and then heat just hot enough to remove the carbon (just like the posts above are saying) to anneal so it won't crack, just bend like your trying to do. Just try doing it this way...
the method I use for this is to draw a line across the back side of the bend with a Sharpie marker. Heat along that line with a regular old propane torch until the line disappears. Go bend.
Be mindful of the grain. folds in line with the rolling grain will crack.
Also, sand and polish the edges near the foldline.
Another trick that works is to bend a nose cover for the apron fingers. Use a piece of 16 ga steel or formable aluminum and put this between the apron and the stock you are trying to bend. It only needs to be a short leg angle the length of the bend you are trying to do. This has the effect of increasing the inside radius of the bend to something the 6061 can deal with. Its quick and easy and doesn't eliminate the heat treat of the stock T6 material.
Using a sharpie or felt pen works. Mark the back side of the aluminum and heat the aluminum untiil the line/ink dissapears. Douse with cold water immediately. Annealing non ferrous materials is similar on each type. Copper, you heat red hot then douse in cold water. Aluminum workhardens quickly so you might be annealing more than once for a large bend.
If you heat too much you will end up with a puddle on the floor.
Another sneaky trick which can save your bacon when alu alloy splits at the fold line is to grind a flat on the end of the V punch, so that you're forming two 45 degree bends.
This often still works even when the flat is small enough for the visual effect to be almost indistinguishable from a single 90 deg bend.