Gas mixing valve Idea-Need your input!

[hooda]

How exact do the proportions of He and Ar have to be to perform a quality weld? Even though we all have that favorite spot on the shower valve that delivers water at just the right temperature, finding the exact spot on the He/Ar setup may take a lot of experimenting and may not be immediately or easily repeatable from session to session.

Without going back to do the research, I believe that Jakeru was getting excellent results at about the 12% He level, which would be a significant cost savings over buying pre-mixed 75%ar/25%He. That is of course assuing that one fell in love with the idea of using Helium on a regular basis. I believe that people only use helium when absolutely necessary. I have a thread on this forum from waqy back where I got a bottle of 75%HE/25%Ar to try to weld a cylinder head, and due to my inexperience more than anything, it did NOT go well. Bunner of it is that my dad was involved, as I didn't at that time have my own account at the LWS, and he raised a stink, so I turned in the 90% full tank rather than listen to his yammering, so my experiments with Helium were put on hold. As soon as I get a TIG machine again, I will resume experimenting. As far as consistency, my educated guess is that since my shower faucet ends up at the same 2 spots relatively consistently (regular shower, and HOT shower), I think there will be a spot or 2 on the faucet in this application that I'll be able to mark as the general start point, and fine tune from there. If you're familiar with the movie "Spinal Tap" you'll remember that Nigel's amps are custom made to go up to "11" for when you need that little xtra oomph to put it over the top. I look at the addition of Helium as turning your TIG welder up to 11!

[jakeru]

I find myself mixing in some Helium for when I weld aluminum about 1/8" or thicker, especially if extra penetration is desired. I don't do it for stainless or mild steel. But on aluminum, the He % allows concentrating the heat more, and I find I can often get away with 1/16" tungsten (or a "sharper" tip grind), where with argon I'd have needed a 3/32" tungsten (and/or a "blunter" tip grind.) This makes a deeper, narrower puddle which is often a good thing. There can be less heat input into the work. Being able to penetrate deeper saves me prep work (don't need to bevel as deeply to get the same penetration.) And as a result, I find I can get my aluminum jobs done more quickly. What would have normally taken me 45 minutes, I am getting done 10 minutes quicker.

So really, I use some Helium % more often than not on any aluminum work.

Since I often run a light arc over the surface before I start to weld, to check the cleanliness of the surface (especially on repair jobs where things aren't clean to start with, and dirtiness will be detected and can corrected before porosity is introduced), I like to use a small enough He % that it doesn't adversely affect arc starting and stability under the light arc needed for cathodic etch cleaning, but yet still give me the heat boost I want when it come time to weld, and penetrate. So I put it at a small He% flow, so I don't have to vary the gas mix after cathodic etch cleaning is done, before I go for the deep puddle melting action.

I often find myself running about the minimum He flow I can get away with while having the mix remain stable. It is not totally scientific, and I am still experimenting, but would say, maybe it's somewhere in the ballpart of 2-5cfh Helium. Compared to maybe 10 cfh argon if using a #5 cup, to 12-15 if using a #6 or with more stick-out.

If the He % varies after the solenoid opens (I can hear it in the sound it makes coming out of the cup), I can abort the arc start and keep the gas flowing long enough (say, 3-4 seconds) to let the mix stabilize before I triggering the arc start. If the mix is varying and I start the arc, it can make hard arc starts and unexpected heat input until it stabilized.

Best of luck...