Hi Tom!

That's on the upper limit to being too much with respect to your flow rate for GTAW but then again, I don't know the specifics to the configuration you're using so, of course I could be judged as being speculative by some... Those numbers make me think of flow rates for GMAW. ;)

Respectfully,
Henry

Tom,

wow, this thread is just like an avalanche!

Allowing myself to adding some humble points to what the other appreciated gentlemen have already posted, I would say, Yes.

Yes?

Yes!

Yes what?

Hmmm… this however, is not that easy to say. But I promise to keep it extensively short.

In my humble opinion porosity in welding – btw certainly one of the most fascinating physical phenomena – may strongly be influenced by ‘heat input’ (whatsoever this means).

I mean the first fact is that the welds are being conducted as manual applications, isn’t it? This brings – even though working in between the qualified levels – a great fraction of variability to the entire issue. As far as I personally have recognised at those times I had to carry out GTAW ‘hardfacing’ applications, porosity issues were based on a very fine line between filler- (often flux covered as regularly suitable for Gas Welding) and parent metal. It was demanded to keep the dilution ratios low to meet the required hardness levels. This again required to keep the current to welding speed ratios high. I.e. relatively low welding current heights at appropriate welding speeds. This however, points to the direction of weld pool- and degassing reactions. The less the height of weld current, the smaller the weld pool volume and the less the dilution, since the magnitude of weld pool depression equals approximately the square of the weld current chosen. Let’s stay there for a little while and let’s consider the welders who are accomplishing the applications may use exact similar parameters, not only electrical, but also – and in particular – peripheral parameters. That is, electrode to workpiece angle, electrode to workpiece distance,…, and of course, exact similar electrode tip conical angles, electrodes having the same composition, cycles the electrodes have been in use, filler composition, base metal composition, gas flow rates, etc. etc. This, at least from my humble standpoint, should yield quite similar results  in both hardness and porosity, just so, as the application would have been performed by a robot. If however, one of those parameters is changing, e.g. by inclining the torch differently, the weld result may be supposed to change as well. This, by changing both the way of filler- and base metal reaction one to each another and hereby the time for metallurgical reactions, e.g. degassing. Now its
well-known that there are two basic ways of the origin of porosity:

1.  Mechanical porosity generation

2.  Metallurgical porosity generation

Just want to treat the latter of both, as I assume that no kind of primer or cavity is being welded over. So, just as already – and usually – excellently stated by Allan, where do the gases (see js55) like Oxygen, Nitrogen, or Hydrogen come from? I guess, as it should be rather unlikely that these come from the base metals or from the shielding gases, they might come from the combination of the weld pool reactions (filler- and base metal) and the varying conditions from the surroundings, i.e. torch inclination and all these tricky items Henry has also listed in his post. Here we have to consider – from my point of view – two oppositional phenomena. On the one hand:

1.  Welding with low power to reduce the dilution (= proper hardness)
2.  Welding with sufficiently high power to enable the weld pool to appropriately degassing

The secret is to find out the golden mean and this you did, since you’re able to obtain proper results, as you say. As you have mentioned the porosity issues often in coherence with hardfacing applications my assumption is that the gases as listed above may come from high temperature reactions (dissociation processes of eventually fluxes etc. under the involvement of carbon/carbides e.g. to generate Carbon monoxide) and some varying conditions like changing torch inclination angles etc. And the latter again influences the former and of course items like seam solidification geometry and so forth, understandably. I guess this is the reason for that some welders achieve sound results whereas others do excess the narrow process envelope between good and poor result.

I would chose the parameters like they’ve been chosen by those welders who have obtained sound hardfacing results, i.e. meeting both low porosity amounts and appropriate hardness values. Then furthermore I would limit the process envelope towards even those parameters. Then I would have a closer look at the handling performance of those the welders who obtain sound results and would compare those ones with the worse conditions. I guess hereby a first step towards a general clarification could be made, to find out in how far the welders and their skill may have influence on the results and the cause of porosity. There is no offence intended with respect to the welders themselves, but I guess mainly they have it formally in their hands what the final outcome may be.

So far my two cents for what it’s worth.

Best,
Stephan

Henry-
That is a brilliant idea- we happen to have a Metalax system that I have grown to hate, but this hardsurfacing application might be a situiation that could make a difference!!!  I need to work on that.  Thanks.