Dick,
I've tried the torch-quench method of shinkage you describe, not on weld
warpage but on stretched areas from large dents or on a oil canned roof or bed
sides. While I've found it will shrink metal, learning how much and where has
prooved elusive for me. Frequently I will make an improvment but then go too
much trying to get it better. What kind of luck have you had?
Grant
50 Chevy 3100
52 GMC 150
Marlene Rzepkowski wrote:
> Deve,
> You've been given great advice so far on how to do it better next time, this
> note tries a little twist on how to save it this time without a total re-do.
>
> First, warping is caused because the molecules in the metal expand on one
> side (The top side where you were welding) more than on the other and don't
> get reassembled back into their original place as they slowly cool. To
> counteract the "set" that the steel has taken, you can apply some heat from
> the back side of the original weld if you can get at the back side. If you
> can only get at the top side, then try the following.
>
> If you have an Oxy-Acetylene torch (I suppose a propane torch could also
> be used but I have no experience with propane for what follows) you can
> heat a small spot, then quench with cold water and the steel on the top
> will suddenly cool quicker than the steel below giving you the opposite
> direction of warp from the slowly cooled weld joint. Do this in small
> spots, almost like tack welding, no more than an inch at a time. I use a
> Rag dipped in cold water and still dripping profusely to quench the hot spot
> I create. This also works for tightening up sheet metal in places that tend
> to "oil can". You can heat the bulge, quench it to shrink the top side
> metal and "tighten up" an area that is "oil canning".
>
> The suggestion of using cold air to cool a weld as you go is very similar to
> this. If the weld spot is cooled with air right after the weld is completed
> you can better equalize top and bottom cooling and end up with less warping.
> Try these techniques on a scrap piece to see the effects. Heat is a pretty
> amazing force in dealing with sheet metal! Good Luck.
>
> Dick,
> 1959 1 ton Apache - "Chief"
>
> ----- Original Message -----
> From: "Deve Krehbiel" <dkrehbiel@kscable.com>
> To: <oletrucks@autox.team.net>
> Sent: Thursday, May 11, 2000 9:55 AM
> Subject: Re: [oletrucks] Welding Help Needed!
>
> > It was a flanged weld that warped so badly. I flanged it and then left
> about
> > a 1/8" gap so the weld could sit low in the seam making it easier to
> grind.
> > The location is clear across the inside bottom of the door (about 4 inches
> > up).. no strength there. I will try the 80/20 mix, and spot weld the whole
> > thing alternating around to reduce heat. I am using .025 wire. I will also
> > try further reducing the voltage and see if that wont help.
> >
> > A few people (including my local professional welder) said to INCREASE the
> > voltage and run the bead faster. I do not like this!! To make that weld
> with
> > the increased voltage, I would have to VERY quickly zip across that seam
> and
> > I cant imagine how its even possible to get a decent result. I tried. All
> I
> > get is holes in the metal. Its very frustrating and as an electronics tech
> > for years, soldering wasnt anywhere near this hard. Same principle tho and
> > to me, you need just enough heat. More than that is wasted. I am hoping I
> > can reduce the voltage to just get good penetration and then work slower
> and
> > more accurately.
> >
> > If I use a hammer and dolly, I have to put the dolly inside the door panel
> > and hit it from above.. exactly backwards from what it really needs. The
> > warpage is concave and needs pounded OUT. I will try that anyway and see
> > what happens. I am pretty sure tho I will be cutting it all out and
> redoing
> > the job. Good lesson learned anyway. And it WAS my first attempt at
> welding
> > sheet metal.
> >
> > Thanks everyone for the encouragement and advice. Please keep it coming!
> >
> > Deve Krehbiel
> > Hesston, Kansas
> > 1950 3100 * 1949 3600
> > www.speedprint.com/Deves50/index.html
> >
> >
> > oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
> >
>
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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