Welding Tips and Tricks

Hey guys, recently i welded up a couple of these braces, basically chopped off the flat bar, shortened the c channel, and rewelded the flat bar. now normally id use MIG no question but since i have a new tig 200 sitting in my shop i figured itd be a good practice part, since its not a super critical part. anyways my coworker question why id use tig since mig is "A lot stronger than TIG". im a newb at tig i have maybe 5 hours hood time total, so i couldnt really argue.

so whatever i welded them with tig anyways, 180 amps 1/16 ER70S2. 3/32 is probably recommended but i dont have any just yet, i made 1 pass, then a second quick weave over it.

anyways, i decided after to do a test, welded one of the cutoffs to a scrap piece of 3/8 flat bar same as i did before, but only welded one side, yanked on it with a 24 inch crescent wrench and it yielded easier than i expected. so i did it again at 200 amps, 2 passes, basically the same result, then tried a third time with MIG.

the tig welds broke, so basically the weld failed. however with the MIG piece the base metal failed not the weld

any thoughts on this? or is it as simple as using 3/32 or 1/8 filler next time to give a beefier tig weld? any comments appreciated guys thanks

It's all about the throat thickness of your weld. Tig and mig have technically the same tensile strength. The tig weld, and all tig welds contain less metal through the throat therefore less strength. The effective throat is the largest right angle triangle that you can fit inside the cross section of a weld. I hope this helps

the tig looks concave and the mig convex, so the tig has less metal in the joint, ie thinner, so its going to be easier to break.
try it with the same sized welds.

Typically I use 70S-6 for tig filler which is the same as the mig wire so it should yield the same tensile strength. I'm not an expert but would heat input have any impact on this as well?

tweake wrote:the tig looks concave and the mig convex, so the tig has less metal in the joint, ie thinner, so its going to be easier to break.
try it with the same sized welds.

That was my thought. ill try it later with either bigger filler or more passes.

So theres no truth to tig is stronger than mig or vise versa? if you take the extra time to do the extra cleaning that tig needs. id assume theyre the same since youre basically doing the same thing, melting a puddle and pushing in filler.

Both processes yield the same strength if parameters are equal: weld size and material. Ours is simply an issue of insufficient weld filler as was said. 3/8” material wants 1:8” filler minimum, and possibly 3 passes to produce the same depostin as a MIG running 0.035 wire.

Simply run a section of MIG and measure the throat for proper comparisons. There’s also no guarantee that MIG would penetrate sufficiently unless you have a WPS that’s been certified. Me, I’d rather TIG that for assurance I got penetration but I’d also cover it for strength, maybe even bevel it first.

cj737 wrote:Both processes yield the same strength if parameters are equal: weld size and material. Ours is simply an issue of insufficient weld filler as was said. 3/8” material wants 1:8” filler minimum, and possibly 3 passes to produce the same depostin as a MIG running 0.035 wire.

Simply run a section of MIG and measure the throat for proper comparisons. There’s also no guarantee that MIG would penetrate sufficiently unless you have a WPS that’s been certified. Me, I’d rather TIG that for assurance I got penetration but I’d also cover it for strength, maybe even bevel it first.

I agree. the main reason im so hooked on TIG is the fact you can pinpoint your heat. grind in a bevel, turn up the heat to insure you have extra pentration, should you need it. with MIG i never liked the fact that the more you turn up the heat, the more wire speed you need, so theres almost no adjustment for more penetration, less penetration. even smaw you can turn up the amps if you wanna dig in deeper, without adding filler faster. anyways that how i see it

did you cut and etch to see what kind of penetration you were getting
on either weld?
craig

motox wrote:did you cut and etch to see what kind of penetration you were getting
on either weld?
craig

No, what would you use for that? Rust disolver or something?

jaywal
check out jody's video
http://welding-tv.com/2014/06/03/tips-e ... -products/

motox wrote:jaywal
check out jody's video
http://welding-tv.com/2014/06/03/tips-e ... -products/

Cool, Thanks!