Stainless header question

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I was told that with stainless, the tubing needs to be flooded with gas. Is this the case? Just seems like a huge waste of gas, even with plugging the ends of the headers. Also, should I use 100% Argon? Thanks,Dave
Reply:You should use 100% Argon with stainless.Back purging should not be necessary for headers if you control your heat well and don't get too much sugaring on the back.Others probably will have a different opinion.
Reply:100% argon for the torch, but there's another gas can be used for the purge, I just can't think what it's called for some reason  that's a lot cheaper.  Really you only need to use it for food grade work or full coded welds unless you want to make it look pretty on the inside for another reason.I'd rather be hunting........USE ENOUGH HEAT.......Drifting around Aussie welding more pipe up, for something different.....wanting to get home.
Reply:You can use nitrogen to back purge SS welds as long as the weld joint is "closed root".  As long as the nitrogen is closed within the tubing by the tight fitting weld joint, it will not interact with the welding arc and it will remain non-reactive and protect the molten backside of the weld from oxidation.Still, unless you are doing this on a regular basis, the cost of an extra bottle of N2 and all may not save any $ over just splitting a feed off of your Ar bottle.
Reply:Thank you all. If it is not necessary then I wont back purge them as they are going to be Ceramicoated when finished.Thanks,Dave
Reply:I use a product called Solar Flux for stainless exhausts.http://www.solarflux.com/Rex