Hello waqasmalik, the simple answer would be that having a larger tungsten likely will prevent any over-heating issues that smaller diameter tungstens sometimes exhibit. The downside to going with an over-sized tungsten might have to do with arc starting and arc stability and wander. I believe that some general comments with regard to tungsten selection are, that unless the uses relate to automated systems as opposed to hand welding that there is minimal difference realized, seen, or experienced. For better and more concise answers you will likely need to include a detailed description of the material and thicknesses, whether manual or automated welding, and specific machine(s) being used. Best regards, Allan
My rule of thumb (for an air cooled/"dry rig"/manual operated) is to estimate the maximum amperage in use, add to the left of that a decimal point (in inches) and consider that the minimum size. For instance if welding at 120 amps = 0.120"; since 0.125" = 1/8", that is the size electrode I'd select.
This helps reduce overheating (as long as electrode stick-out is kept reasonable).
With a water cooled torch, I've run 500 amps with 3/16" tungsten.
Qualify the procedure with the electrode size the production. Welders prefer.
Great question.
The following is pertaining to my experience with DC work:
Some years back, for purely logistical reasons, I standardized our shop with 1/8" diameter. We recently got into some 3/32" 2% thoriated that I had left over from years ago. I forgot how well that stuff runs. We are using it on small pipe 2" - 8" range. We are using it up to 175 amps. It holds up to erosion well, better than our 1/8" La or Ce, and seemlingly at least as well as our newer 1/8" 2% thoriated, including the cryogenically treated stuff. It also surpasses the proprietary "Tri-Mix" from Diamond Ground Products.
Now I don't see how diameter could be the factor in play here when comparing the different 2% thoriated electrodes. It seems to me that it is more likely a by product of the electrode composition / manufacturing method / and/or quality. In the last 5 or 10 years I have used lots of ESAB, Diamond Ground Products, and Wolfram (which is what we currently use the most). Also some newer Chicom stuff. Our old stock U.S. made 3/32" 2% thoriated seems to out perform them all, and it is outperforming the 1/8" La / Ce electrodes by a country mile.
Are you using inverter power sources when GTAW?
Both conventional transformer and inverter.
