Metal memory on buckled fender how to fix it?

[Braukuche]

I am doing body work on a 356 Porsche which is like a Ghia in that it is uni-body. Anyway, the front was hit years ago and repaired poorly. The impact wiped out the nose and caused the front fenders to buckle out about 3/4 of an inch. For whatever reason, they didn't take the buckle out when they cut out the bashed in nose and welded a donor nose in. I have cut out the donor nose as it was brassed in, and have tried to straighten the fender by applying pressure with a porta power and a 4X4 piece of wood on the buckle, but all it does it forces a counter bulge out elsewhere on the fender. I then tried positioning the porta power on the inside of the fender pushing the fender front (counter direction to the impact). This causes the bulge to disappear, but as soon as I remove the pressure of the porta power the fender goes back to its damaged state. My question is how do I keep it from going back to the damaged state once I remove the pressure applied by the porta power?
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Go Reds! Smash state!

Retirement is here!
1956 Ghia
1959 SO-23 Westfalia
1960 double cab
1960 Baja Bug
1963 stretched double cab
1962 Golde sunroof Ghia
1963 356 B coupe
1963 Notchback
1967 21 window less rusty now

[Anthonyisawsome]

Sounds like you need to shrink some metal.

[Braukuche]

[beetlenut]

So if I recall from a materials class taken long ago, it sounds like the metal in the bulge area has become work hardened due to the accident damage. This makes the metal in that area harder than the surrounding metal. It's actually a process used to strengthen metal during manufacturing. This is all happening at the molecular level, within the crystal structure of the metal.

Another process called annealing is used relieve internal stresses caused by practices like work hardening. It involves heating the metal to sufficient temperatures and then cooling for the purpose of positively altering its chemical properties. It's like a reset of sorts, where a metal can be restored to its original properties after being altered.

So while under pressure, I would heat the bulge area to a cherry red, and then allow it to slowly cool. You could also do some hammer and dolly work once it cools, while still under pressure, to slightly work harden the metal in its new configuration. Google work hardeneing and annealing to better understand this process.

I had to do something similar to some accident damage on the rear of my super a few years ago, and it held its shape once I took it out of tension.

Good luck
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scrapyards are for quitters
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[Anthonyisawsome]

What he said haha.

[Braukuche]

[Matt K.]

If I find a buckle like that that will not stay I will add the pulling pressure like you talked about....what I do is take a rag and soak it in water....I fire up the torch and heat the buckle....I put a dollie behind it if I can get to it the use my shrinking hammer( a shrinking hammer has a serrated face that looks like a meat tenderizer) I heat a spot about an inch or two in diameter.......when its red I smack the metal down and take my wet rag and quench the metal cool........that usually will shrink a buckle or high spot....repeat as needed until you are satisfied the release the pressure and see if it will hold.
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This is my 23rd year in the Auto Body/Paint Game!
*Take a look at some of my custom paint: http://s110.photobucket.com/albums/n119/mrpaint_2006/ .( NOTE: these are some older jobs but still neat.)

[Braukuche]

Well, I took a torch, heated a few spots about an inch wide cherry red, used a hammer and dolly and then tapped around the perimeter of the hot spot driving the "cold"metal into the hot. I then used compress air and cooled it. Did this while I had the fender under stress where I wanted it. Heated about four spots and it worked like a charm. Fender is back where it is supposed to be and is holding its shape. Thanks guys for the help!
_________________
Go Reds! Smash state!

Retirement is here!
1956 Ghia
1959 SO-23 Westfalia
1960 double cab
1960 Baja Bug
1963 stretched double cab
1962 Golde sunroof Ghia
1963 356 B coupe
1963 Notchback
1967 21 window less rusty now