Porosity and Slag in SAW

By Lawrence (*****)

Date 07-09-2019 20:55

Slag trap is strange indeed.

Assuming you have clean cut edges with no cutting dross, no cutting fluid/oil.

Arc blow is the first culprit to look for in my opinion... And yes you can have Arc-blow with AC.
* Perfect work lead connections
* Weld toward the work clamp... If that does not work, weld away from the work clamp.. If that does not work split the work lead to both ends.

Flux recycling... Even fresh bagged flux.. If you are vacuuming and reusing will lose it's chewy goodness after a few cycles... Meaning that when your drum gets half empty, refill with fresh to keep the flux in optimal condition.. If it goes from grainy to powdery, you have waited too long. Empty everything and start 100% fresh every 5 days-ish

A loose work connection with powdery flux is the perfect storm for Arc/Blow & porosity.

Tandem power supplies and tandem electrodes, or "Tiny Twin" side by side wires with one power supply ?

I'm still thinking Arc Blow...….. But say more about the porosity and slag..

Is it very fine centerline porosity? Big holes evenly spaced... What are you finding with the slag when you gouge.. What does it look like. ??

By supermoto (***)

Date 07-10-2019 09:40

I thought the trapped slag was strange also, it may be from the FCAW backing weld we used to close the gaps to prevent blow through.

We do make sure the ground clamps are tight. We will mess with locations for sure.

Our hoppers are fairly small and we are running pretty long welds 80' or so and tend to load new flux quite often. I don't think its ever gotten to a powdery state.

Tandem electrodes meaning lead and trail, with individual power sources. Not the tiny twins, which we have ran in the past.

The Porosity pretty random in and size and all subsurface is near the root of the double bevel. This next one we marked out the FCAW tack welds to see if there is any sort of correlation with these indications and the tacks.