Welding Tips and Tricks

I am welding welding a 3/4" x 3" flat ball mount plate to the 2" x 2" x1/4" vertical of a drop trailer hitch insert, all hot rolled mild steel. The vertical tube is beveled aprox 45% leaving about 1/8" of flat. Am thinking preheating the plate to about 350 degrees F (have a laser temperature gun) and .035 gap between vertical and plate. Welder is 250 amp c/w 75/25 gas, using Esab 7100 Ultra Outershield. Normally I use .035 but I do have a roll of .045 that I could switch too which according to a chart I have at 24V and 270ipm should be about 250a. Thoughts on this? 3/4" plate for a application like this is a bit out of my comfort zone as I normally deal with max 1/2" and under. Option is too take it too the local fab shop with the big guns if that's the prudent thing too do.

Mild steel won't benefit from preheat above room temp. Your power source has enough grunt for stacked smaller multi passes. Your outer shield is going to give good peno. Given one side is only 1/4" you can't go to hot on it. Focus more to the 3/4", stay with your 035, give it plenty if grunt and wire wheel your beads and go for it.

Coldman wrote:Mild steel won't benefit from preheat above room temp. Your power source has enough grunt for stacked smaller multi passes. Your outer shield is going to give good peno. Given one side is only 1/4" you can't go to hot on it. Focus more to the 3/4", stay with your 035, give it plenty if grunt and wire wheel your beads and go for it.

Thank you Coldman. What I needed to hear. Have lot of faith in outershield, hot and multiple passes.

I think he meant preheat not for stress control, but to help with penetration/whetting on the 3/4" bar since it is a 3 to 1 thick-to-thin and an edge weld on the thinner tube at that.

Preheat of the bar to maybe 300-400F certainly wouldn't hurt, IMO, but probably not really necessary.

Also, those IR thermometers (it has a laser, but that's only to see where you're pointing the IR sensor) are not a great tool for measuring metal temperatures accurately. Recommend you get some temp sticks. That's an aside, though. Not saying you need any of that for this job. But they're a great tool to have on hand.

Spartan wrote:I think he meant preheat not for stress control, but to help with penetration/whetting on the 3/4" bar since it is a 3 to 1 thick-to-thin and an edge weld on the thinner tube at that.

Preheat of the bar to maybe 300-400F certainly wouldn't hurt, IMO, but probably not really necessary.

That's what I was wondering about if preheating would help penetration for the first bead or so until the 3/4 plate heats up. It's only 3" x 6". Will preheat anyways. Wouldn't Hurt. The laser I realize is just an aiming device but darned if I could think of the proper name for the thermometer! Thanks for the help.

Spartan wrote:I think he meant preheat not for stress control, but to help with penetration/whetting on the 3/4" bar since it is a 3 to 1 thick-to-thin and an edge weld on the thinner tube at that.

Preheat of the bar to maybe 300-400F certainly wouldn't hurt, IMO, but probably not really necessary.

That's what I was wondering about if preheating would help penetration for the first bead or so until the 3/4 plate heats up. It's only 3" x 6". Will preheat anyways. Wouldn't Hurt. The laser I realize is just an aiming device but darned if I could think of the proper name for the thermometer! Thanks for the help.