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Old 04-15-2007, 02:13 PM   #1
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metal shrink advice ?

I"m tapping out some dents on my a/s and have a few places where the alum. is stretched. The areas are about as big as a half dollar. Can I apply heat to the inside and put a cold,wet rag on it like shrinking steel?
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Old 04-15-2007, 02:16 PM   #2
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I have the same issue and would like to see an answer from the knowlegable people on this forum.

Does that make the aluminum brittle when you do that?

All I know is that aluminum doesn't give you the color changes with heat that steel does, so one moment you've got a solid and the next you've got a liguid. So you need to take it easy!
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Old 04-15-2007, 03:08 PM   #3
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You need to be very careful. Heat the area to 550F, no more, no less. I would use a heat gun, not a torch. Use a wooden dolly and work around the edges. If you're good you can make lots of bucks doing aluminum repair.

No guarantee this method works. I've just "heard about it".
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Old 04-15-2007, 11:47 PM   #4
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Yes it can be done, But you have to be very careful. I've done it on several spots on my current Globetrotter project. I used a propane torch. I outlined how I did it on this thread: http://www.airforums.com/forums/f381...ion-26902.html Post#65
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Old 04-16-2007, 12:24 AM   #5
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Oh you are playing with fire! I would have one of the point it and read digital thermometers. keep the temps well below tempering temp of 900 degrees F. If I remember correctly Al will melt around 1100-1200 degrees. A proane torch can achieve this. If the metal starts to get glossy remove heat now! it is about to melt. The AL alloy should be 2024-T3 aircraft aluminum. It ia already heat treated you are going to locally changed that. are you sure you want to do this? Cooling to quickly will cause localized stress and a place for future cracks.

Michelle the Aircraft mechanic speaking.
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Old 04-16-2007, 03:37 AM   #6
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Quote:
Originally Posted by thecatsandi
Oh you are playing with fire! I would have one of the point it and read digital thermometers. keep the temps well below tempering temp of 900 degrees F. If I remember correctly Al will melt around 1100-1200 degrees. A proane torch can achieve this. If the metal starts to get glossy remove heat now! it is about to melt. The AL alloy should be 2024-T3 aircraft aluminum. It ia already heat treated you are going to locally changed that. are you sure you want to do this? Cooling to quickly will cause localized stress and a place for future cracks.

Michelle the Aircraft mechanic speaking.
Dead on the money...and it becomes white hot moletn metal at 1300-1600 BTW I am currently doing heavy maintenance work at an Aluminum Smelter No Alclad sheets tho Just the ingots. Had not thought about the loss of temper to the T2024...

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Old 04-16-2007, 08:21 AM   #7
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Originally Posted by thecatsandi
Oh you are playing with fire! I would have one of the point it and read digital thermometers. keep the temps well below tempering temp of 900 degrees F. If I remember correctly Al will melt around 1100-1200 degrees. A proane torch can achieve this. If the metal starts to get glossy remove heat now! it is about to melt. The AL alloy should be 2024-T3 aircraft aluminum. It ia already heat treated you are going to locally changed that. are you sure you want to do this? Cooling to quickly will cause localized stress and a place for future cracks.

Michelle the Aircraft mechanic speaking.
Yes I am playing with fire, and this procedure is not for everyone. To heattreat 2024-T3 from 2024-O, heat the aluminum to 1120-1140 long enough to heat all the way through. The thicker it is the longer the heat soak time. Then rapid quench in water. This will get you 2024-W. the alum. then needs to be air age hardened for 24 hours to get 2024-T4. The end cap skins on my 71 are not T3. I think the only hardening they have is around T1 from work harding being stretched over the forming die, as they are quite soft. Cooling to quickly is not an issue as this is how aluminum is heat treated to to begain with, unless yo get up to the melting point, if anything the aluminum will be softer in the localized area, unless you go over 1140 degrees, over this temp the aluminum will fracture when quenched. I heat the alum just long enough to see it move , and you can see it move well below 1120 degrees, and then quench with water. This is a dangeress game to play with the chance of failure high and if you are not willing to live your life with some risk then this procedure is not for you.
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