frog-eyes when purge welding stainless piping.
Firstly, I am new to purge welding SS pipe--and have only tried to teach myself from what others have said "how it is supposed to be done".
However, every time I stop my weld I end up with a little Frog-eye or A-hole on the inside. The outside looks fine. I try to taper the heat out of the weld (unless the cup slips--because everyone has such a hard-on for walking the cup, and I've been freehanding since 1994), to prevent this but I still end up with the hole on the inside.
I'm using a miller maxstar 150 STL (with lift-start) @ 30-35amps, pure argon, 1/8" 2% Thoriated Tungsten. 308SS, 2" diameter sanitary pipe, with .065 wall thickness. 20cfm argon on the torch, 20cfm in the pipe through a rubber plug & diffuser. Taped on the opposite end, with three 3/32 holes poked in it. I was also told I should be looking for a swirling pattern in the puddle. Any thoughts on gas flow, amperage adjustments--anything else I should be thinking of? Whether Purge welding is static/dynamic? ie once all the oxygen is out of the pipe its purged, vs. continuous flow...
Thanks, you and your site are fantastic, and very helpful.
First off, the fish eye you are seeing might just be a ball of oxide ...at least some of the time.
that is kind of unavoidable.
for those times when it is actually a hole, the only thing I have found to help is to gradually speed up and trial out like a comet tail or long tear drop. You might even add a drop or two of filler while you are trailing out that can be filed or ground off later.. you may have to free hand to do this right. this leaves an oxidized area but should help on the hole.
good luck bro,