I have an automatic weld procedure that uses a 5/32" tungsten, a 1.125" diameter gas saver assembly from CK (gas lens) and a max tungsten extension of 7/16". If I were to change this procedure to using a #10 gas nozzle (with a gas lens), would that have a large effect on any resulting characteristics such as rate of erosion on the tungsten, HAZ, etc. My assumption is that by reducing the size of the gas nozzle orifice, and when using the same CFH, you might get turbulent gas flow, an unstable arc, etc. What are the detrimental effects that could occur from deciding to reduce the size of the gas nozzle?
Thanks
Zeek,
Some things to think about.
The smaller orifice will have several effects that may need do be addressed.
1. Your electrode stickout may need to be reduced, your cup size is almost cut in half.. Under perfect conditons a tungsten stickout can usually be about the same as the cup diameter, but this depends on things like travel speed, how stable the ambient air is in the weld zone and the size of the puddle and how fast it freezes.
A #10 cup with a clean gas lens could possibly accomodate a 7/16 stickout, but since your usng a 5/32 electrode I am assuming that your dealing with some pretty high currents and travel speeds. The problems that may be associated with this would be related to the gas shield envelope leaving the weld pool before it's sufficiently cooled; this is the same with the HAZ... The effect on both needs to be judged by the alloy type and acceptence criteria you are bound to. Excessive oxidation and the negative effects related to it would be paramount in my opinion.
Hello Zeek, you are correct about a possible increase in turbulence without adjusting the flow when reducing cup size. Why would you not simply reduce the flow to account for the possibility of turbulence? Are you reducing cup size for interference reasons or access, why not continue to use the larger cup? Just wondering. Best regards, Allan
PS. with a gas lens there is much more tolerance for velocity/turbulence related issues, you might not see a change at all.
As usual Zeek, after reading Lawrence's reply, he is spot on in describing additional concerns and considerations. For a more detailed and accurate reply from everyone you may wish to describe the machine parameters, tungsten grade, materials, speeds and other variables if you can disclose them. Best regards, Allan
Shielding Gas: Argon
Flow: 40-50CFH
Current: 230-270A DC
Voltage: 11.5-12.5
Travel Speed: 14 ipm
Bead on plate on OD of carbon steel pipe - OD
Procedure calls out for 1-1/8" diameter lens. If we switch to a #12 which is 3/4" i can't imagine we'd have any problem with gas turbulence, but I'm interested in the differences in arc characteristics. For example, if we switch to a #12, the arc column is narrower, so what does that do to the temperature of the arc and what happens to the material.
Hello Zeek, unless I have missed something along the way, I don't believe the arc column is influenced by cup size, I believe that is a result of tungsten angle grind, possibly some by shielding gas mixture, pulse parameters(if applicable), and arc length. Just my $.02. Best regards, Allan
I don't think the problem will be gas turbulence, it that you'll be out running your shielding moving at 14ipm. We routinely use a 3/4" gas cup with a lens on automated TIG equipment in our shop at those kinds of settings, and 45 CFH is our go to flow rate for torch gas, but we run in the 3-6 ipm range typically. And to say we're particular about shielding is an understatement, all high pressure cylinder gas goes through chemical filters, we run with trailing shields, we leak check every connection when we make it, etc. If the weld isn't silver, something is wrong.
Arc column is not affected by gas cup size.
Thanks for the info. That definitely makes sense. It is a rather quick travel speed.
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