purge

[metaljoiner]

Hello

I noticed a lot being said about purging for welding stainless and Alloy, I am a complete novice at Tig, I've only just turned over to Tig, I all ways used Mig or Gas, If I wanted anything in ally or stainless welded up, I would take it along to a local welder shop, a small firm by me, they do nothing but stainless and ally welding, With the purging thing, I have never seen them do this, I had a stainless beer keg welded up once, say about 2 feet of weld, I waited there while the Guy did the job for me, All he had in is hands was the Torch and filler rod, Though I am not sure How to go about the purging thing while welding, the chap did a fantastic job without the Purge,
I have a good Idea whats meant, but the Back of the weld?

 

[knoba]

I'm not quite sure what your question is!

Purge is used where; an attractive, strong and/or non-porous (hygienic surface) welds are required.

As for using purge; I run a 2nd line, off a Y splitter (meant for Oxygen - RH threads), coming from the regulator. When I tig my stainless steel tube jobs, I seal up both ends with masking tape, and push the hose in one end. I leave the gas going for a time depending on the size of the tube (argon is heavier than air). I lower the purge pressure & bring up the regulator flow (until test welds look good) and proceed to weld.

HTH

 

[fingers99]

That's about it. I run a purge line off the same argon bottle via a T and two flowmeters -- one for the torch, one for the back purge. For small jobs you could use a disposable cylinder and reg for the purge, but it's a more expensive, long term, way of doing it. Purge only for stainless and titanium (for Magnesium I'm not sure). Some stuff on the Miller site.

 

[metaljoiner]

Thanks for the replies, But I am still a bit confused by what Purging is actually doing, is there anywhere I can see it being done, I ain't thick Honestly, when I purge my Welding Lines, I crack valves open turn knobs on my torch and let the gas through then shut um off again.

 

[Paul.]

Thanks for the replies, But I am still a bit confused by what Purging is actually doing, is there anywhere I can see it being done, I ain't thick Honestly, when I purge my Welding Lines, I crack valves open turn knobs on my torch and let the gas through then shut um off again.

Purging is providing a gas shield to the root of a weld from the reverse side, such as filling a pipe with argon to prevent atmospheric contamination. nothing to do with removing air from welding lines, (although that is good practice)
__________________

 

[hotrodder]

Couldn't find a pic of REALLY oxidised (aka coked or sugared) stainless welds though i think someone posted a link to another forum recentely that contained a good example of what it should NOT look like.

This is the best i could find from a quick google

Edit: Found it It was in the 'stainless pics' thread, posted by Fingers

 

[metaljoiner]

I am with you now, sorry just couldn't get my head round it, I know what you mean now, I will have to remember that, though don't think I will be doing too much Hygienic stuff in stainless.