[Tireman9]

OK first off I know these welds look like crap. To hot, wrong TIG angle, not consistent tip distance etc, BUT I haven't done SS tube for a couple of years and then I only did about 20" total. Also I have some eye problems now due to injury and permanent scar in one eye which cause serious depth perception issues. But if you can get past these issues I think you might find what I have to show you interesting.

I want to do my own SS exhaust on a 51 Chevy truck I am building as a Hot Rod. I do have a Mig & TIG welder and did take the Lincoln welding class a few years ago so learned the importance of purging backside of SS. Over the past few years I have seen a number of magazine articles showing guys welding SS but none have ever purged the tube based on pictures shown and no mention of the importance of purging mentioned in text. I know these "experts" were doing it wrong and I will be sending the editors some info on this but needed more than just my "opinion" to back up my Letter to the Editor.

At Lincoln I had access to some nice dual feed flow regulators but I wasn't ready to buy another regulator if I could manage it so I set up a test. I cobbled together some vinyl tube and did three tests on some 2" SS tube. For all three welds I used a Gas lens and #8 cup with 100% Ar shielding from the TIG torch.

I did one weld with no purge. One test with a 100% Ar purge using a borrowed tank of gas. The final test was using my Mig 75/25 Ar/CO2 gas. I then cut the tube open to see the results.
The results speak for themselves. I feel the 75/25 purge gave a very acceptable result and if my general welding skill improves to what it was in the past I am confident my Ss exhaust will outlast the stuff done by the "experts" in the magazines.

Outside of tube (yes too hot or cold and inconsistent but no corrosion of SS) I think all three welds look similar to untrained eye


Inside of tube with No purge


Inside tube 100% Ar purge


Inside tube 75/25 Ar/CO2 purge


To me the 75/25 looks as good as the 100% Ar and other with less than $10 in various brass fittings and some vinyl tubing, I think I got something that will certainly be "good enough" to quote Jody, for a non-critical application.

Your thoughts and comments welcome.

[weldin mike 27]

Hi there,

Glad it worked out although the mig gas can lead to problems later on.

Here is a link that explains mig gasses it should clear up some more technical questions.

http://www.bocworldofwelding.com.au/shi ... teels.html

Keep up the practice.
Mick

[Tireman9]

Mick
Thanks for the reply. I am sure the use of some optimum gas just as using optimun welder settings for pulse, ramp etc would be desirable in critical applications however I was just trying to get to the proverbial "good enough" for a home built exhaust system.

My TIG is an old Lincoln 175 Square Wave with no fancy settings. I have a mix of Lanthinated & Ceriated electrodes pre sharpened and ready for use. They have been in and out of my gun so many times the paint has been worn off so I don't know which i am using. Once this old batch is used up I will be using just the lanthinated electrodes but I can't afford to throw the old electrodes away yet.
I definately am not even a good welder though I do hope to get better with a bunch of practice before I get to the more important items on the truck.

One has to wonder how the manufacturers of stainless exhaust components manage to make their pieces and even mufflers without any shield gas.
You are correct that for SS I would be better of with 100% Ar but getting a new regulator and tank or making a dual flow regulator just isn't in my budget.

[weldin mike 27]

Hi there,

Here is a post that I hijacked from another forum. It out lines a cheap way to do it.

I've done some back purging TIG welding stainless. I had something similar to this on the inert gas outlet of the machine.

http://www.toolfetch.com/Category/Weldi ... 411-SP.htm

Hook the torch up to one, and the back purge up to the other. The valves allow you to control the flow rate for each leg. Can easily turn off the back purge when not needed.

With both legs wide open I would set up the flowmeter to say 30 cfm. I would then close both valves completely. Flowmeter will read 0 cfm. Slowly open torch until I get my desired 15 - 20 cfm. Slowly open back purge valve until I get close to 30 cfm at the flowmeter. Now I was set to weld.

That's pretty slick, gradstdnt_99. Thanks for the info

Not that I need something like this yet, but if and when I do, it's definitely cheaper than a dual flowmeter.

Mick

[Tireman9]

Thanks for the link. That splitter would work.

Back purge for tube is pretty easy and you really don't need much gas.
If you use 10 CFH on 2.5" dia tube you will do a complete purge every minute per foot length if I did the math correctly.