Argon/CO2 for backpurge?

[Gaslight]

I want to experiment with backpurging while tigwelding chromo steel. However I do not have a regulator with a dual exit, but I do have a MIG welder. The bottle is filled with 85 argon/15 CO2. Anyone ever tried this before? Insights, comments?

[arc]

no i have only used argon or helium. u have to use a inert gas so you dont get oxidization.:eek: other wise it was pointless!

[Gaslight]

That makes sense. How does the Argon/CO2 act as a shield for MIG then?

[Aerometalworker]

Hi there,
What alloy are you trying to weld? And why?
-Aaron

[stick man]

Buy you a splitter for your lines not that expensive.

[Gaslight]

Fairly thin 4130, like .035-.028, so while some might not backpurge it, there seems to be an advantage.

So just keeping with the concept, why can't I just run my hose from the existing MIG gas bottle and reduce the chance of oxydation on the inside of these tubes? Doubtless there are beter ways but what is it about the Argon/CO2 that works as a shield On the front for MIG, but won't backpurge my tubing?

[fun4now]

i plan on getting T fitting for my argon tank so i can run 2 gages off one take.;) cheapest way i could find being as i already have an extra gage.

[BigDTig]

That makes sense. How does the Argon/CO2 act as a shield for MIG then?

The CO2 is active, make no mistake about it. Argon/CO2 mixes are only useful as shelds for mild steel, for starters.

For backpurge, use Argon. It's the cheapest and most effective.

[phaxtris]

dont forget most mig mixes have a very small percentage of oxygen added to aid in breaking the surface tension, so you would have two active gasses that you are trying to backpurge with, pretty much just a waste of gas!

another option from the obvious argon is helium, cheaper than argon and works very well if your are purging from bellow

have you thought about using a 'chill strip' behind the weld area ?

[Darmik]

If you want to use a backing gas for tubing or pipe use a splitter off your
gage one end goes to your gun and the other end goes to your pipe or tube
put the hose in one end and cap the other end but make a vent hole 1/4"
so gas can escape because if you dont the gas traped in the pipe will hold the root out so you will get no penatration or root
( so basicly your going to cap both ends of the pipe then your going to put an inlet for the hose and an exit at the other end you should only use argon for this procedure mixed gas is not recommended mixed gas is only for sheilding solid wire or flux core Co2 in not a backing gas it is a sheilding gas.





:cool:

[Graham08]

Before I had two cylinders/regulators for purging, I bought a dual outlet regulator. I found a rebuilt one on Ebay for less than $100. The nice part about this is it has two flow meters, so you can adjust the flow from each outlet independently.

[fun4now]

a T at the tank befor the regulators and then 2 regulators is also a popular option. if you go that rought its usualy cheaper than a due flowmeeter setup(unless you find one one e-bay cheap). eather way you would do better to have a seperate reg. for the torch and the back purge so you can set your torch flow properly. a T after one regulator is not going to alow you to tell how much is going in the torch and how much is going into purging, just some thing to think about.;)

[Tex]

Before I had two cylinders/regulators for purging, I bought a dual outlet regulator. I found a rebuilt one on Ebay for less than $100. The nice part about this is it has two flow meters, so you can adjust the flow from each outlet independently.

That's the best idea I've heard yet. I use a splitter at school and I have a hard time balancing the backing gas and shielding gas. Look online on the AWS website because a couple months ago they had some articles about NASCAR welding cromoly tubing. They gave the best filler metal and a bunch of other tips. Try to get some modeling clay or cork to plug the ends and have one tube going through the cork with the gas and another smaller tube to let out the extral gas. Backing gas is essential when welding this tubing so do some further reading and have fun!

[fun4now]

some thing to consider if you go with a T at the tank and 2 gages 1 for purge and one for the welder. the flow meeters and flow gages exit opisit sides of the tank (see pic) this will alow you to read both as the flow meeter exits to the right and the flow gages exit to the left. so it would make a great setup for purging ti have both kinds. most due flow meeters run over $200 but a T at the tank and 2 gages can be had for under $100 easy. being as you alreadt have a gage on the welder all you need is a T and a flow meeter easy to find on e-bay for about $40. its the setup i intend to run, i have a flow meeter on my TIG now and will use the gage that came with it as the back purge controle, just need to get a T. sealing the tube for back gassing is easy just cover it in aluminum foil and a rubber band if you want, no presher involved so any thing will work, card board and tape whatever you have handy or feel comfertable using. gas in one end and a hole at the other to let it and the air out.;)