Welders needed!

I am by no means a welder, but i've been doing a lot of rust repair on my 71 and i'm getting better...But I have a question about 'cold welds'.

My last project was on the firewall. I needed to replace a section, and the only metal I had available was some 16 gauge. I welded the piece in with a series of continuous tacks. I had my 120 mig welder on the 'B' heat setting at the start but i was blowing holes in the firewall so i turned it down to 'A'. I welded it all up and then realized my welder's chart actually suggest the 'C' setting for 16 gauge. I'm concerned now it will crack out eventually because i wasn't getting enough penetration. Should i be worried??:huh:

I did turn the wire speed down below 2 when i turned the amps down to A. Hopefully that will help.

I am by no means a welder, but i've been doing a lot of rust repair on my 71 and i'm getting better...But I have a question about 'cold welds'.

My last project was on the firewall. I needed to replace a section, and the only metal I had available was some 16 gauge. I welded the piece in with a series of continuous tacks. I had my 120 mig welder on the 'B' heat setting at the start but i was blowing holes in the firewall so i turned it down to 'A'. I welded it all up and then realized my welder's chart actually suggest the 'C' setting for 16 gauge. I'm concerned now it will crack out eventually because i wasn't getting enough penetration. Should i be worried??:huh:

I did turn the wire speed down below 2 when i turned the amps down to A. Hopefully that will help.

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Hard to say with out seeing a picture of the weld..did you check the other side of the metal for penetration ? Thats usually the best way to check to see.

I wouldn't be to worried about it.

If it looks good it should be fine.

If your worried, check for cracks it with a light in behind.

The chart is just a basic guild line to get you close to the heat you want to start at.

If you where to weld a thin piece to a heavier one you need more heat.

likewise two thin piece you would need less heat.

But if you start to weld a bead on sheet metal it heats the surrounding metal up very fast and changes your amperage making it weld even hotter, so your method with short little weld should have been fine.

I use the A setting with the wire speed at about 2 1/2 when welding sheet metal butt joint.

I use the B setting with the wire speed at about 3 1/2 when puddle welding sheet metal to something like a frame rail.

The C setting is petty hot and the wire speed of about 4 -4.25 when welding 1/8" to 1/8"

Another thing to try is to tack at a little hot setting then turn down when you want to finish the weld.

The weld that you described would have welded up better if you used a copper backing tight to the back of the weld.

This method lets you weld a little hotter and a little longer stitches.

I use .025 hard wire with shielding gas and never use the flux core crap. 100x better welds

Good luck

Marc

You could grind a small areae out to see if you got penetration.

Hard to say with out seeing a picture of the weld..did you check the other side of the metal for penetration ? Thats usually the best way to check to see.

That's the thing, i'm not really sure what i'm look for. There is a discoloration of the metal behind the weld...

I was thinking of welding some 2 or 3 inch 16 gauge squares on the backside for added support. The squares would be welded half on the firewall metal and half on the new sheet metal - Like a gusset. Do you think that would help?

I didn't read this whole post but make sure you take out the insulation on the other side of the firewall or you'll be putting out a stenchy fire. Did it lol