NTGeorge,
It does looks like there may be multiple potential causes for the welds' appearance. First as you note the wax lube is not necessarily removed fully by acetone unless the area is wiped half dozen times even then a film may remain, I use a cooking product to lube blades.
The frying pan anti stick spray (Pam brand in the US ) or vegetable oil mix in a spray can is used to lube the blades but not on the work. I hold the running tool away from the work and spray the blade while turning and then use the tool. I use the spray to lube long 'stock cuts' where I may be ripping hull panels from original stock but I don't spray directly onto the tool's edge while back chipping to avoid adding any more lube to the future weld zone.
This stuff wipes off, vaporizes at low temperatures and seems to be a reliable way to keep tools free of melted metal while avoiding weld contamination.
Next, since these may be outside corners I'd look at the gas flow? I use much more argon on an outside corner because there is no natural "huddling of gas" as would the case on inside or flat joints, so I move from 5-7cubic ft per hour up to 20 maybe 25 cu. ft hr. if the weld is done with larger (5/32" -2mm) tungsten?
Also, I'm not aware of the TIG power supply (you're using) but the cleaning action of the weld AC wave form may not be
balanced as well as it could be to attain the best cleaning action? DCEN versus DCEP Some times when I see the 'pepper flakes' floating in the puddle I'll change the balance to increase the cleaning action. On the welder I use the 'balance' setting, the amount or percentage of the AC wave that is positive or negative is adjustable and that affects the 'cleaning action' of the puddle's surface and surrounding parent metal.
I turn UP the DCEN (negative component of the AC wave form) to increase penetration and DOWN to increase cleaning; on my power supply I'd turn down the Balance Setting if I got results as you show.
http://www.millerwelds.com/resources/TI ... _Chpt2.pdf
In this case I notice the flecks or pepper flakes are constant at a background level and that would cause me to work to lower the balance in the terms of my welding power supply (lots of different terms and dial settings in various welding equipment) to increase the cleaning and reduce the penetration. Further, there appear to be some areas along the welds where the contamination is not cleaned at all, these are areas where I'd be concerned the cover gas is being thinned or blow off?
IF the gas flow is too high, especially without a gas lens, and the torch is inclined too much to the weld surface; then atmosphere can be 'pulled' over the weld from the lead edge (under the gas cup) by gusting conditions in the shop and when this happens the lack of cover gas allows all sorts of soot as we see in the photos.
Last but not least, if there are pockets of oil/wax/grease/contaminates in the back up welds (?) or from the back chipping operations (?) then I find they tend to be very short localized bubbling instead of longer soot tracks near the edge, so that implies to me the contamination in the two photos may be from different causes? The surfaces next to the longer soot trail would be where I assumed the problem was in that photo and the intersection of three welds with even, but heavy, surface black flecks would make me think there were contamination in the underlying weld or in the bottom of the weld shown.
Gas coverage, AC wave form balance and lower vapor temp. lube along with a review of the gas cup handling angles would be the areas I'd investigate.
Cheers,
