MIG Welding

You'd be wrong then because MIG is as good a process as any of the others. It's the easiest to do but it does have a downside and you found out what that is. One can make welds that look great but in reality they are nothing but glued together metal. If I recall they call them cold welds. Penetration is vital to a proper weld. A MIG welder will do whatever you want just about but you have to set the machine properly or your welds are no good. The guidelines on the machines are a good starting place but every welder that I know of that uses MIG always does some test welds on metal like he's going to weld. Once you test your machine settings on similar metal of the same gauge as your project you will be fine. Someone once said that a chimp could MIG weld. But the caveat was that a human had to set the machine up for it first. MIG is all about getting the right settings on your welder. Once you have them right the welding is a breeze.

Hawke

Good point! When in doubt I always do some practice welds with similar (scrap) metal in similar configuration to see what settings are gonna work. It doesn't take long to discover what works with the "usual stuff": flats, angle, channel and tube of thickness from

It gives a LOT more penetration and significantly more spatter. An antispatter spray such as PAM cooking spray etc are de rigor for anything you want to be pretty.

Gunner

So, you make practice welds, and then you try to break them, is that right?

I've used an elcheapo flux core 120VAC welder for years. Two heat settings and variable wire speed. I just go slow and match it melt in on both sides as I go and I have welded material upto 1/4" with good results. The biggest problem for me is the very limited duty cycle. I have fabricated trailer hitches on trailers, satellite mounts, gate handles, and a variety of other things with it. I found pretty much universally if my welds looked good with it, they were good. (with steel).

Curt, I would have to respectfully disagree. A weld with some slag trapped, is a bad thing, but it would hold a lot better than a weld with no fusion. Also, slag usually gets entrapped with multiple passes, and I usually do not need multiple passes anyway. In any case, a couple of classes ago I had a great chance to practice welding thick beveled plate with 7018, and I think that I have a grip now as far as how to avoid entrapping slag.

I will definitely try to stress test some welds, they have a simple machine for that at school.

Can you tell me what exactly you did not like in a LN-25?

Yeah, for sure. Trapped slag will make it less strong than the metal you are welding, and that will show up very nicely in a bend test when the metal just pops open and breaks instead of bending. But it will still be

Yes, it's far more common of a problem for multiple passes, but it can happen in single passes as well. It's a common problem for vertical open grove welds even on a single pass for example.

I would suspect that if you didn't get to do a bend test on it, it's probably not as good as you think it is - at least if it was thick enough to require multiple passes. I know it sure fooled me. The welds looked very strong and clean to me, but when you bend them, even a small amount of trapped slag can cause it to break at the bend.

Maybe with your experience you have mastered it, but like I said, is sure fooled me.

Steve, I have not yet decided 100%, but I think that I will take a followup stick welding class, that is dedicated to stick only.

Also, section the welds. polish or surface grind the sectioned faces, then etch with 2% nitric acid in alcohol. It will show the penetration very clearly.

Mark Rand RTFM

Yes, it is easy to trap slag and other inclusions in 7018 welds. But for each 50# can you do, you improve. One of the most important things about welding, as you pointed out, is watching the puddle, as when you pointed out where to point the wire in relationship to the puddle and to have it dig into the base metal. So it is with the 7018, and what that particular rod has is almost a clear glass cover to the puddle. Notice when you stop welding that the glasslike slag covers the former puddle. So, when welding with 7018, one of the most important things I have seen is watching the puddle for things floating in it and letting them boil out, keeping a short arc, and no whipping out of the puddle. No offense meant to anyone, but it takes burning a lot of 7018 to learn these things unless you have a teacher who will show you and shorten your learning curve. So it is with MIG and getting fusion and penetration. Lots of people can make pretty welds, but few ever fully understand the behavior of the molten puddle, and what it is actually doing just under the surface.

Steve

"Ignoramus1054" wrote

In any case,

When you can do 1" beveled plate 6010 open root 7018 cover and x ray, you got it. I've done it, but don't think I could do so now, as it has been so long.

Steve

I have enough ruddy trouble getting the stuff to strike easily! At the moment I only have AC, but even so...

Mark Rand RTFM

"Ignoramus1054" wrote

I think you can do it. I looked at your welds, and they looked good. Trouble is, that unless you have a LOT of inclusions, you won't see them when milled only. You need an x ray for that. You'll do that, too soon enough.

Steve

The LN-25 would run straight off of 440v 30a 3 phase power, making it easier for us to move around in the yard, but it lacks the programmable settings and extra features that are available on the Lincoln V350 power source connected to a LN-15 feeder (power and "brain" cable connections). Those extra settings make pulsing a breeze, and virtually eliminated our ultrasound test (UT) failures.

I have a manual at work, but I'm sure you could do a comparison online at the Lincoln website. FWIW, I haven't run a LN-25 in over a year, maybe they have a newer, improved model out now.

My LN-25 is a suitcase wirefeed that can work with CC welders, getting power from across the arc.

There are a number of ways to test welds. Destructive testing is one of them. Then there is X-raying them. There are also guys with the occupation of weld inspector. They go to the job sites where workers are welding and they have to certify them as safe or they don't pass inspection. I don't know how they are able to determine the quality of welds but they can do it. You could always find one of these guys and have him inspect your welds. Of course, that's a lot easier said than done as they generally expect to be paid for their services.

Hawke

Steve

I,m not sure what the charts in some of these machines are up to. With the little Millermatics the charts are straight forward and usually close, little Lincoln powermigs seem to assume you're gonna weave everything (with a lot of surface weld and little penetration? Thermal Arc fabricators have conflicting info on the same chart!!! But I do believe (as at least one other has stated) that they assume flat butt joint or horizontal fillet.

I would suspect the Lincoln you were using was the PM250 or 255 (I hope it wasn't 90's mig with the touchpad). Anyway Lincolns own GMAW guide (Google "C4.200" for a bunch of hits) calls for .045 at 200IPM at 20-22V (Co2 sheild, -2V for Ar rich) welding 1/4" flat butt and horizontal fillet welds on page 67.

This is calling for 200 amps, your setting of .035" at 320IPM and 19V (C25 settings) is gonna come in running about 160amps at best. Turn it up to

BTW you won't be weaving much, your torch travel will be 3/4" every 3 count (12-17IPM) to hold the leg size, and if you section and etch you should have at least 1/8" in solution at the root and a bit less 1/8" up the leg. These settings aren't near the limits of semi-auto welding with

You can get and idea of gas affects on penetration profiles from the same Lincoln guide at the bottom of page 13.

I've got the PM300 (now 350?) I'll check the chart in it tomorrow (probably has the same starting points). I never use it in straight CV GMAW mode.

Matt