Welding Tips and Tricks

Recently some of the guys in the shop were mad at the owner of our shop and all decided to start practicing 3G plate tests for another company lol. (While the owner was on vacation I might add) They were doing downhill mig roots on V grooved butt-joint with roughly 3/16" gap and no land. One of the guys asked me to come over and do one and let them watch because he considers me the best welder in the shop. Not bragging, just what he said. I haven't made this weld in forever and I'm rusty for sure. I make the weld and it looks beautiful on the inside of the bevel, but on the back side of the plate the weld is pretty much perfectly flush. I know most inspectors are looking for a little bit of push through on the back. If I had put a good hot flux pass over it uphill I think it might have pushed out a tad but I didn't go that far. So I guess I'm posting this to get a little feedback from you pros out there that are more pro than me as to what I might have forgotten? I have passed this very same test before, on the first try.

Facts: Puddle was run relatively quickly side to side in the gap with almost no pause on each bevel. Nozzle angle was approximately 45 degrees up angle. Wire size .035 running about 18.5V @ 210-225 wire speed. Plates were 1/2" as I recall.

I have my own suspicions about my mistakes on this. The plates were already tacked together for me so I had no say in the gap size or land setting. I suspect a small amount of land, perhaps 1/16" or so plus a gap of an 1/8" or tight 1/8" would have yielded much different results. Also I do tend to run fairly hot which may have contributed to the suck back.

Your thoughts?

I prefer a little land and less gap just as you stated. Downhill root passes are a little harder to get reinforcement on the backside.

ARRGH!

Thanks, Lazerbeam.... I misspoke. I was thinking 3/32 gap, no land (not 3/16). In that case, I'd burn 5/32 at 150-155 on that 3/16 knife edge. Same "bury-rod" technique at those amps, of course...



Steve S

Otto Nobedder wrote:I personally prefer the "bury-rod" method. For that 3/16 gap, no land, I'd use 1/8" 6010 at 105A, and jamb it in, straight down the middle, dragging at the speed the rod burns. This builds a nice back-bead.

The method is not for everyone, though.

Here's an example on 12" sch. 80 pipe done in 5G position (1/8" gap, 1/16" land):

6010 root.jpg

Steve S

Steve S, thanks for the reply, glad to see I'm getting some feedback so quickly. Just wanted to point out, I'm talking about a mig root =P I'm right there with you on the stick welding downhill technique. Just trying to figure out what went wrong with my mig root. I think I know, but I haven't experimented with it to see if I'm right. Just thought I'd toss it out there to the masses to see what you guys thought.

OOPS!

I read too quickly, and moved your topic to stick welding...


I'll put it back!

Steve S

Otto Nobedder wrote:OOPS!

I read too quickly, and moved your topic to stick welding...


I'll put it back!

Steve S

It's all good, and thank you!

My gut reaction on this...

MIG downhand is usually done with a drag angle for fillets and backed grooves, and it becomes a habit. MIG open root should be almost square-on, so the arc-force works to your advantage to push metal into the gap and build that reinforcement on the root side.

Just two cents, now that I understand the question....


Steve S

Old-ish thread. Blah blah...
Anyways. We are currently doing this at school.
Mig isn't my instructors high point. He messed up both of his 2g open root "demos." Had like 1/2 inch stick out/burn-through. Lol
Well on this 3g, he basically had none. Same as I'm getting.
We run the open root downhill, and all the rest uphill.
Also having a tad bit of trouble getting the cap the way he wants it, but after class I asked him to draw his motion on paper, which helped me a lot. I was trying a zigzag (look damn good imo), a L shape, etc. He's doing a upwards circle.
But to the point, mainly having trouble with the root. But reading above, I see what I was doing "wrong."
I was running about 22.5-45° degree up angle. I'll try straight in and see what happens. Basically "walking the cup" in this step. Kinda cool/fun.

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