Sometimes late is better then never.
I was told this by an expert on late and never, so as second hand information...grain of salt kind of thing.
The reason why you guys are having this problem is more complicated then you realize.
One is the welding process. It's the complicated one.
Two is the purpose and application of the product.
And three is...probably because standing on one leg with your eyes closed touching your nose and counting to ten is impossible. Try it and you'll see. Welding is about the same. But your doing it with a weld thru primer. That's like the added pressure of doing the one leg thing on the side of the road with the cop as your witness to the effort.
One...While the welding power source does make a difference it's more the operator, his parameters, the out put and settings make the difference in the wire melting. ER70S-6. ER70s-2 ? Deoxidizers and puddle fluidity differences.
What size are you using? .023,.025,.030,.035? It makes a difference. Think of that wire diameter as a gun shooting bullets. Is the bullet the same size as the barrel or had it gotten bigger before it shorts off? How much powder propels the bullet?
You may not appreciate it as such, but it's a droplet, how wet has it become? What causes the wetness? Voltage. Or less wire fed speed? Shorter arc lengths? It's complicated, or it easy. Depends how much you think about it or how you see it sticking metal together.
Those weld thru primers are zinc based. Any appearance of or traces left behind will burn off, in the proper welding conditions, but, in turning that zinc to vapour you create a very ugly environment for the welding arc. That's why product formulations with a heavy solid require being well shaken into solution before applying. Well shaken. You don't want those zinc flakes heavy on the surface. The pressure of zinc vaporization is a pressure acting on the arc, and a repelling act against the droplet formation/ metal being deposited.
Here's some why. All that stuff does is from the heat of welding repel what isn't burnt off, as the weld cool it's drawn back in to encapsulate the spot weld or plug weld created. With out proper welding considerations, IMO, the tendency to over heat through welding is so much so, the heat effected zone changes, zones of the zone become wider, more zinc gets burnt away as a result, the HSLA steel is changed well past the narrow heat effected zone expected. That being the case, which is the lessor of the two evils when it comes to structural integrity? A weakness to the metal or the risk of corrosion?
https://www.youtube.com/watch?v=pDMznDYfKuENow, it's not all gloom and doom. Don't over use the product. Your not painting although you are required to provide coverage.
http://multimedia.3m.com/mws/media/3403 ... -05917.pdf3m says 1mm on each surface. The reason your doing such an application has to do with corrosion resistance in modern steels, the reaction to those metals from heating and cooling through welding, and in the case of HSLA steels, how heating and cooling in the Heat Effected Zone has changed mechanical and chemical properties, tensile strength loss with increased loss to corrosion protection in these areas. How much so depends however on the heat applied when welding?
So does shielding gas being used play a roll? Yes. CO2, 75/25? I didn't mention nozzle size but it to plays a roll.
Look at CO2...It comes out and releases energy hitting the plate. Arc plasma stuff. Wide and not as deep.
Mixed gas...heats the center and more radiant on the out sides. Deeper in the middle, not as wide. The end of the wire is melting in this.
What they do however is effect the squeeze and pinching of droplets off the wire end. Another way to think of it causing problems in filling plug welds with weld thru primer, is the efficiency electrical current flows through the gas. You could think of seeing through fog. Orientation and direction is effected.
Think of it this way, if you had x amount of gun powder, are you better off with a bunch of little bullets or a few big ones? The gas effects parameters to strip droplets, with Voltage and WFS requirements in this consideration of performance.
As well voltage, wire feed speed, nozzle size and stick out. That and believe it or not, how you weld the hole shut.
http://multimedia.3m.com/mws/media/3403 ... -05917.pdfMy pictures don't show any weld thru. That's because I didn't have any to use at the time. Normally I would have sprayed some down just as a bit of rust protection on the lapping surfaces. In new car construction it's part and parcel with proper repair procedures. This isn't such a repair.
If I had applied it, I would have scrapped the holes free and with a fresh cut end to the wire, struck the arc on the top overlapped edge, walked in and down, quick loop around and finished in the center. Higher voltages, WES, longer stick out to narrow the arc width and move steadily but quick to plug the hole. Some will do it differently. Smaller hole, fresh cut wire, a hot burst in the center with plastic flow creating fused edges. Different strokes, smaller circle to encompass.
Hopefully I've added something to the conversation? From a welding perspective, it's still crap to weld through.