Question about gas welding Porsche sheet metal

[Iciclehead]

Ok, I thought I had posted this question separately from my thread on fitting a 6 speed into an '89 Carrera, but came back from church and it seems to have disappeared.....likely finger problems on my end.

In any event, I didn't get any comment about my problem with gas welding on the other thread (quite likely no one is reading the blessed thing!), so thought I would post it separately.

In short, I am backdating the '89 chassis in particular modifying the '89 fenders with the early signal light boxes to go with the long hood. Passenger side used a fairly rusty cut off from an early fender which had its challenges but went OK.

I started on the drivers side signal light box, idea was to use the little filler panel from behind the short hood bellows as it matches the fender lip, then extend it with a piece of sheet steel to fabricate the rearmost part of the fender behind the long hood signal light box.

Trim went well, decided to use a piece of original steel from where the condenser fan was mounted (from the bottom of the trunk), did that bit of cutting and then decided to gas weld the two together.

Well, something is fundamentally wrong. Did 3 attempts at the seam, not one of them worked. Now, I am not the best welder in the world, but I can do this normally, I mean, my dad was a welder and I grew up with the stuff. It would not puddle and pool like I normally see. The welds were very porous and almost created slag - odd in gas welding...here is a pic of the "best" result.



You can see the very poor weld and it had no strength at all.....an easy wiggle and the weld split - and that is not normal, even for me.

So after the 3 attempts, said screw it.....got some fresh steel, used the MIG welder and done in 15 minutes. Weld is strong, no issues other than needing to finish the surface of course....here it is in rough.



Thought went through my mind....was the problem with the gas welding that it was galvanized steel (the fender/bellow filler and the section all came off of the '89) ? I mean I ground the edges clean, nice and shiny.....and horrible welds.

MIG was dead easy...

Factory manual gives specs on MIG welding galvanized surfaces, increased gas volume etc...

Is it not possible to gas weld the galvanised stuff?

In any event the fender is done and leaded, I can post pictures if anyone is interested....but I was real surprised at this....

Any help from skilled welders would be very useful

Dennis

[timmy2]

LOL, you posted it in the classifieds... Here:
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/734587-question-about-gas-welding-porsche-sheet-metal.html

[fanaudical]

In general, gas welding of galvanized material (especially thin sheet) can lead to trouble. You're often applying a lot more "wasted heat" with oxy-acetylene than you would with MIG. This tends to vaporize more zinc (which melts at a comparatively much lower temp) which will lead to weld contamination (the minor problem) and inadvertent inhalation of zinc (the major problem).

I think "electric heat" is best for work such as this. The energy is much more concentrated which creates less vaporized zinc and the extra shielding gas keeps the zinc out of the weld.

[afterburn 549]

get a wire feed.......with gas shield

[tocobill]

Also get a smaller torch. I had done my fair share of gas welding sheet metal. I have very small mecco midget torch I like to use. I use the #1 and #2 tip for thin sheet ... 19-20guage. The smaller the tip the hotter you can get just that area on the puddle quicker without alot of heat you would get from a larger torch. Alot less warpage too. You also need to clean the weld area more. Seams like your slag might be a mixture of a dirty weld surface and some of the crap still on the sheet from when it was rolled.

Gas welding is nice and has its place. The welds are a ton softer. Mig is hard and grinding sucks. Tig is nice but not everyone can afford a machine. I got my mecco back when I didnt have the money to front for a nicer Tig machine. I was tired of grinding and wanted to try something new.

Good luck!

[rusnak]

something's contaminating that first weld.

[Iciclehead]

OK, I am technically incompetent....posted to the classified forum....sigh.

I do prefer gas welding as it is way softer, I did the work and it turned out OK, here are a couple of pics, one in progress right after welding:




And the finished product....




One guy posted (in the other thread) that I may have run into a high strength steel which may not be good for gas welding. Seems plausible.

I did grind down the zinc, but clearly there was another process/contaminant at work.

Dennis

[afterburn 549]

Its like this.When some one says you CANT !...... then someone else will.
OK.......
However..you will find for this shielded gas a lot more doable.
Its less shrinkage , Less stress no pin holes...(and they are PROBLEMS latter)

[Beschleunigt]

I have never tried to gas weld galvanized steel so I don't know the answer to that specifically but I did have to MIG weld some galvanized steel recently. I too tried to remove as much of the zinc coating as possible but still ran into problems with porosity and contamination. The biggest clue-in that you didn't get the surface clean enough will be the white vapor or streamers that fall from the air after welding. I assume that that is the stuff that you don't want to breath in.

I am glad that you were able to figure out a way around the problem. The finished result looks great. I would say for the future to just try and get rid of as much of the zinc as possible (on both sides of the weld if you can). The heat affected zone for gas welding will be wider than that of a MIG or TIG so you may have to clean further from the seam than you originally think. Good luck with your project.

[Iciclehead]

Originally Posted by afterburn 549

get a wire feed.......with gas shield

I do have a Miller MIG with wire and Argon/CO2 gas mix. It generally behaves well except when I do dumb things like not clean the nozzle (had a little issue the other day until I cleaned it).

My dad had a weld shop and I grew up with welding both gas and stick, that is why was so surprised when this particular piece of steel behaved that badly....geez...I was welding with gas when I was 10 years old, although I don't do enough of it to get to be any good.

MIG I find definitely more forgiving but I am burning through the grinding discs though. When I pulled out the sunroof and took of the drip rails on my 6 speed project I did a LOT of grinding...and hammer/dolly, cleaning, cursing, swearing as both the sunroof and rail removals are not fun jobs.

Dennis

[Iciclehead]

Originally Posted by Beschleunigt

The heat affected zone for gas welding will be wider than that of a MIG or TIG so you may have to clean further from the seam than you originally think. Good luck with your project.

Thanks for the good advice, I will keep an eye out for the white streamers.

As for the HAZ, yes MIG is quite nice that way but when I have worked with gas welded stuff, that soft steel and ability to hammer/dolly out the wrinkles is sooooo nice...

Dennis

[Daves911L]

I have both a MIG and a TIG, but I still like to occasionally pull out the torch and do some gas-welding (did so just this afternoon on a 356 fender!). As Dennis notes, the welds are soft and can be hammered so they virtually disappear. Gas welding is an art, and one worth pursuing just for the pleasure of working with metal. But the best reason to gas weld is it makes you a much better welder with the other tools. In my opinion no one should be allowed to purchase a MIG until they can do a passable job of butt welding 20ga with a torch.

[Jim2]

Originally Posted by tocobill

Also get a smaller torch. I use the #1 and #2 tip for thin sheet ... 19-20guage. The smaller the tip the hotter you can get just that area on the puddle quicker without alot of heat you would get from a larger torch.

Good luck!

This ^

Dennis, not necessarily a smaller torch body, but the tip: #2, #1 #0, #00 or #000. The real small ones like 000 are hard to find, good for brazing thin sheet. Anyhow, a wet rag on either side of the weld will help minimize warping. You can also buy reusable heat sink compound - eastwood.

You can also look for mig wire called Easy Grind for autobody. Much softer than typical 70s6 wire.

[Iciclehead]

Originally Posted by Daves911L

I have both a MIG and a TIG, but I still like to occasionally pull out the torch and do some gas-welding (did so just this afternoon on a 356 fender!). As Dennis notes, the welds are soft and can be hammered so they virtually disappear. Gas welding is an art, and one worth pursuing just for the pleasure of working with metal. But the best reason to gas weld is it makes you a much better welder with the other tools. In my opinion no one should be allowed to purchase a MIG until they can do a passable job of butt welding 20ga with a torch.

Hey, you sound like my dad....which is why I was gas welding at about 10 years old. I remember the old fart (rest his soul) could gas weld sheet ALUMINIUM without a pop or a drop. All I ever did was make swiss cheese.

I guess I will follow the good advice and get a smaller tip (I am using a Harris 0) and do some more practicing...might have to buy one of those ultralight handles as the standard one does get a little heavy when you are holding a tiny tip of flame into an almost invisible (through the visor) join line.

I have to make the rear bumperettes into RSR ones (swage the front end outwards to match my Carrera's rear fender. It is thicker guage and definitely not galvanized so it ought to be within my abilities.

Thanks all,

Dennis

[HawgRyder]

I havent seen them in a long time...but there used to be a torch (Oxy-Acet) called a Mark 4 I believe.
It was like a cutting torch...but had the Acet on the outside of the Oxy so that the Acet created the gas envelope.
I tried one...and even on Aluminum it worked very well.
Perhaps...if you have to use gas...this might solve your problem.
Also...the rig works on very low pressure...about 3 lbs I think.
Bob

[Iciclehead]

Originally Posted by Jim2

This ^

You can also look for mig wire called Easy Grind for autobody. Much softer than typical 70s6 wire.

I will seek out that Easy Grind stuff, suspect my local welding shop (which services the oil industry and seems like they can get anything) can at least order it in.

In terms of tip and handle, definitely good advice, although I have never seen a 000 for Harris stuff, so the handle may be a "must get" just to get the smaller tip. I was actually running the flame very tiny on the 0 and neutral which is the way I was taught....

Dennis

[HawgRyder]

Just did a search...J&S Enterprises....DHC 2000.
And it works on 4 lbs pressure.
Bob

[Jim2]

Dennis, in case your not using it, make sure to use 1/16 rod, not 3/32.

Easy Grind was on the shelf at Air Liquide about three years ago.

[tocobill]

Originally Posted by Jim2

This ^

Dennis, not necessarily a smaller torch body, but the tip: #2, #1 #0, #00 or #000. The real small ones like 000 are hard to find, good for brazing thin sheet. Anyhow, a wet rag on either side of the weld will help minimize warping. You can also buy reusable heat sink compound - eastwood.

You can also look for mig wire called Easy Grind for autobody. Much softer than typical 70s6 wire.

The tip can be changed but what is nice about a smaller torch is the control. The mecco is about 4-5 inches tall vs regular oxy torch that can be 10+inches with a smaller size tip. It gives a much better handle and control aspect to very thin sheet metal. It works very well for me and for $200-$300 is not a bad addition to anyone who wants to do a restoration on a car. I use ~3-5 lbs pressure.

I looked for EZ Grind once about a year ago and could not find it locally. I went on other sites like Pelican for welding and it got poor reviews .. AKA the Jalopy H.A.M.B. I didnt pursue it as it wasnt a huge deal. I ended up getting the mecco and I still use my miller Mig for various aspects of work. I just bought a new Tig so I have a rounded out gargage for projects. At work I have a Miller Synrcowave and it is awesome. I cant afford one at home so its out of the question. Again ... JMHO.

[wayner]

Nice job

I still maintain that adding that filler panel is less work and more desirable than starting with real long hood fenders and patching rusted areas that typically will leave seams across broad flat sections that warp easily and need more filler