[FirePig]

Hi all,

New here and my first post. Hobbyist welder.

I want to MIG weld square tubing with 0.10” wall thickness to a 0.25” plate. A36 carbon steel and will be using C-25. I have spools of 0.024, 0.030, and 0.035 wire.

I have not even attempted this yet as I would like to get a little feedback first as how to approach this. (Maybe I am making a mountain out of a mole hill too?) Should I think about settings using the thinner wall thickness as a guide, thicker wall thickness, an average between the two, or? Keep the wire held more on the thinner or thicker material? Any or ideas from the more experienced crowd?

Thank you for any suggestions offered.

[cj737]

Wire diameter and heat for the thicker part, gun pointed at the thicker part too. Wash onto the thinner piece quickly then back onto thicker.

[FirePig]

Wire diameter and heat for the thicker part, gun pointed at the thicker part too. Wash onto the thinner piece quickly then back onto thicker.

Thank you.

[Louie1961]

I would do exactly the opposite, TBH. What CJ recommends works with TIG but not MIG. Set your wire feed and voltage for the thinner material and weld like normal.

[cj737]

I use this approach regardless of the process whenever welding 2 different thicknesses. It is more critical that the thicker piece get the penetration required than the thinner piece.

Otherwise, you run the great risk of insufficient heat to securely weld to thick material (creating likelihood of failure). But hey, choose your own path in life.

[Spartan]

Wire diameter and heat for the thicker part, gun pointed at the thicker part too. Wash onto the thinner piece quickly then back onto thicker.

I'm with CJ on this one. That's exactly how I do it for MIG on structural type things when needing to go thick to thin. I always default to the "hotter" setting for MIG in those situations, and tend to run MIG just a bit hot in general. Because it's MIG, and erring on the hot side is always a good thing, IMO. So long as you're not over penetrating or under cutting, of course.

However, if the thick to thin difference is a lot, like some 16ga plate to 1/4" tubing that I was welding out yesterday, I won't go full bore on settings for 1/4"...I'll probably go with settings for 3/16" or similar. So still well into the hot side of the settings, but not quite maxed out for 1/4" if that makes sense. This is also all assuming flat position welds.

Oh, and it should probably also be mentioned that I am no MIG expert. I mostly run TIG, and only pull out the MIG gun when TIG is not practical. So take my MIG opinions for what they're worth

[cj737]

The issue with running based upon the “thin” side of a weld is that the weld will not be sufficient on the “thick” side. That is far more dangerous potentially and cause for concern. Feathering the heat to the “thin” side is the proper approach.

[tweake]

the other thing is manipulation.
i tend to do O's or e's (sweep the front edge of the puddle, back down a bit and through the centre to the other side then back up the side.) keep the side you go up on, on the thicker piece. that tends to put a tad more heat on the thicker side.

[FirePig]

Thank you all for replies. Really appreciate them.