An Interesting Question

admin

Hello,I have some 1/2 inch sch 80 stainless pipe that I would like to but weld together in the same sort of fashion that it would be for 20,000 psi applications.  Obviously the most pressure I will put through it will be a 50 -100 psi or so of nitrogen in a leak test.  I am just practicing and trying to see what it is like.  I have stick machines and dc tig machines at my disposal, up to 135 amps.  I presumed that you do a tig root followed by stick hot passes.  What stick rod would you use if this is the way to go or what is the way you would do the above for a 20,000 psi job if you had to come up with the WPS. Please keep in mind I have now intention now or in the foreseeable future of doing anything remotely close to that pressure.  This is a simple exercise I want to try.  Thanks
Reply:Tig all the way. Match filler wire to the material you are welding.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG
Reply:What grade of stainless pipe is it?I usually use 316L for all my stainless work, only because that's all I have on hand in my shop. Tig weld all the way out would be my preferred method for welding stainless pipe as well.JasonLincoln Idealarc 250 stick/tigThermal Dynamics Cutmaster 52Miller Bobcat 250Torchmate CNC tableThermal Arc Hefty 2Ironworkers Local 720
Reply:At that kind of pressures I'd be thinking steam and 347 is what we typically use in high pressure steam applications. Purge the tube and tig it all the way. Only other stainless we use is 304 unless it's a odd ball situation/material.
Reply:It is 316 grade, would 130 amps be enough, even for the hot passes?
Reply:Hot pass can be the same amperage as the root pass. More amps means you can move faster/use larger filler/push more filler into the joint. 316 filler. You will need to purge the tube.Airco Ac/Dc 300 HeliwelderMillerMatic 200 (stolen)Miller Maxstar 150STLMiller AEAD200LE (welding and generating power) Hobart MIG
Reply:130 is ime way to hot. 75-85 is plenty on small bore stainless.
Reply:Your 1/2" sch. 80 has a .150" wall thickness.  My notes say that at some time I was happy with 90-100 amps for .200 wall.  You'll be fine with your machine.  The term hot pass isn't very significant when you tig the root.  More important with a 6010 root where you might have to burn out wagon tracks.  In your case, root and cap will do it.WoW....lots of fast replies on this oneLast edited by OldSparks; 03-12-2014 at 08:48 PM.
Reply:Unless your already good and fast at joint welding your gonna smoke your small stainless at 90-100. I do this for a living. If your interested here is some reading. Good info on small bore stainless. http://www.millerwelds.com/resources...t-I-do-at-work