Dirty? Wire

[Hass]

Originally Posted by dougspair

Even a partially spatter-clogged MIG gun nozzle can upset the gas enough to be the culprit...

I was the victim of this the other day in fact.
Was doing a 20+ minute weld (root pass before it gets hit with SAW), then i started seeing pinholes and was like FAWK...
looked at my nozzle, and part of it was clogged to the contact tip.
:\

[wesdavidson]

You may want to change gas, just to hit all the bases. I used to work with guys that were doing basic research on weld metals, the real deep metalurgical stuff. We would try about a dozen different mixes, and delivery methods, Argon, co2, helium, oxygen, hydrogen, sometimes nitrogen, all in 5% steps. section and etch the welds to determine the best for a given base metal and wire. analyzing penetration, grain growth, transmetalic compounds, wetting, porosity, alloy effect, (nitrogen will combine with ti, co2 with iron in others, oxygen with silicon) etc. AWS journal articles etc. Nickel superalloys, titanium, stainless, carbon steel, lithium -aluminum etc the whole bunch. We had some lots of gas that were bad. inadequate purging, and stratification, last year I had a bad mix, too much oxygen, with marginal steel and personel it just made a foam of the weld metal. With perfect technique it was ok, with anything off, in this case the steel alloy, it was impossible. A few years ago we used to use a gas manifold that ran around the shop, a couple hundred feet of pipe. At restart after a shutdown it gave us bad gas until it got purged out completely. and each regulator had to be purged as well. .

I'm with Transit, get a roll of generic wire, and a couple of bottles of pure gas, argon and co2, see if you can get a good weld on 1010 steel, so as to rule out the air currents, stickout etc, then change one thing at a time until you get good results.

Don't rule out bad steel, we had some lots from some US minimills, that were as stringy as wrought iron, think of string cheese. and brittle as glass. It would snap or tear out like a glued wood "t" joint. A lot of the chinese steel is like that as well. We had one air tank that we modified to a vacuum ballast tank, that had so much silicon it was nearly unweldable. Alloy control is pretty difficult when they use a single melt from scrap to rolling mill.

As for the lube, or black stuff, the mill may have changed something since the material was qualified, or it may have been qualified clean. You may also be seeing a reaction with the acetone. Acetone is a reactive chemical with some metals.

IF you are using the new "one pulse, one droplet" transfer procedures, we did some work on them over the years. Mig, wire fed tig, and laser. Bleeding edge stuff. The idea was to limit energy transfer into the base metal. What I noticed was that they are super picky about contamination. There is not the heat there to fully vaporize and blow out the contaminants. It provides only enough energy to melt the end of the wire, melt a micro puddle to receive and bond the droplet, plus ever so little to allow wetting,and then it goes to the next drop. . it makes steel as picky as aluminum about contamination. a little more background amperage may help, but if you are working with a defined process, you may be stuck cleaning.

If the wire is the rolled tubular stuff with a seam down the side, it may also have absorbed some lube into the flux, we had that problem as well. Moisture will leave when you heat the wire and store it hot, it just increases the transfer of the lube into the flux however. With more heat, contamination burns away, with tight amp limits it can drive you nuts.

Dirt or lube pickup from the liners, binder resin from abrasive wheels or belts, rust preventative migration on the base metal, excess fume removal velocity, volatiles pulled into the weld zone with air from hot surrounding metal, dirty gloves, (or new gloves with oils in the leather), synthetic gloves with plasticizer, dirty gas, bad mix, contaminated shot blast media. Spatter sprays and tip gels that have little effect on most shop welds can also play hob with some processes. Some guys use more when under stress.

Look at the whole process, good quality control procedures include all the personnel, most important, don't threaten any jobs, you need all the brains to find and fix problems. Stress kills quality. Pride in a good job is essential, but fear will kill it.

[Apples]

I have a little bit of info here on mig welding wire.

It covers some basic stuff that most people are not aware of in mig wire. Although it may not help you out with you problem specifically it could offer some ideas.

[weldrwomn]

The other day, I started getting a little porosity and after I checked everything obvious (nozzle, gas level in the bottle, etc), I ended up pulling the gun out of the wire feeder and sure enough, one of the o-rings was worn out and allowing air to be introduced into the system.

You might check the o-rings on the end of the gun that is towards the wire feeder.