Welding Copper-to-Copper

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Hello All,I was wondering if anyone could bring me peace with an issue I have. I am currently using a Hobart spot welder. The electrodes are of course very high in copper content. Yet, I am needing to spot weld copper tubes. The problem is that there is a fair amount of adhesion at the end of every weld - making it hard to remove the copper tube from the copper electrode. I have tried running the spot welder in series with a high-powered variac to reduce the current through the electrodes to reduce adhesion - and this works well - as you have more control on the welds. (Any discontent with this solutions?)Now I am wondering on how to implement a shielding gas with my spot welding operation. I have cylinders of argon available. Do I need a high-pressure stream directed at the point of the weld in open atmosphere? Do I need an encapsulated working environment to "drown" the workpiece with the surrounding gas? What safety precautions are needed? In general - what is the most efficient/safest way to implement an inert gas with my copper-to-copper spot welding application?I appreciate all of the help! Thank you all.Scott
Reply:as far as shielding I can't help... but how about changing the tips on the spot welder to steel?  My line of thinking is that copper dont stick to steel when spotting sheet metal... maybe steel tips wont stick to the copper??The more I think of it, I seen a thread the other day they made an argon 'aquarium'.  Think of a sandblast cabinet.  Submerge the piece in the argon atmosphere and welded away.  I dont think there was much pressure involved.
Reply:Think tig welding handpiece for an argon shield. As for the welding maybe you fabricate steel covers for the tips to make them non stick.
Reply:I see I see.  I am beginning to learn that inhaling argon is not the end of the world, and that I may not need to isolate the argon - I can just let it be free?
Reply:Spot welding typically is two sheets or surfaces being welded together.  Directing a flow of shielding gas at the surface of a sheet will do nothing to get the shielding gas in between the two sheets/surfaces where the weld is actually taking place.Unless your physical geometry is such that you actually -can- get the gas to the welding zone.  As in you have two tubes (you mentioned something about tubes, didn't you?) that you are trying to spot weld together, OD to OD and your spot welder tongs are pinching from ID to ID of the two tubes?  In that case you can probably get decent shielding if you have two flows coming in from either side of the tubes (perpendicular to the tube axis).Or make a little inert 'box' to go around the welding area.  A bit of sheet metal, fold it over some, gently flow argon (plastic hose into a diffuser, which could be as simple as a piece of pipe with some steel wool stuffed into it) into the box and thus around the welding zone, and voila!  Diffused gentle flow of argon over and around the welding zone.And for shielding, think GENTLE flow of gas, not high speed stream.  You want to bathe and blanket the area in the argon and thus exclude the atmosphere (with its O2 and N2 and CO2, etc) from the welding zone.And in case you didn't realize it and a 'humor' smiley was missing about your quip about "inhaling argon", the argon won't hurt you EXCEPT that it will displace the oxygen you need to live.  At 'typical' welding flow rates of ~20 cfh in an open area, the oxygen displacement from the argon flow is no problem to the person and only is doing its thing for the weld.  But, and that is a big BUT, things change BIG time if the welding is in a small or enclosed area where oxygen displacement can be FATAL to a person in the enclosed area.
Reply:Try two pieces of stainless steel one each side of the copper to be welded .
Reply:Thanks for the information Moonrise.  As of now, I am doing the welding in a small lab inside.  If I opened the windows and bought an overhaning/filtered hood, should everything be safe?Thanks again,SCOTT
Reply:Shielding gas will do nothing for a spot weld. There's nothing it can do for the weld since its job is to prevent contamination which simply isn't a factor here. You are using electrical resistance and physical contact to melt the two pieces together in this weld. The sticking is from two "like" metals joining. You need a disimilar metal of a higher melting point than your copper. If you are doing many continuous welds, you need to shed the heat from the electrodes too. The cooler you can keep the electrodes, the less sticking you will get. Try metals other than copper and keep the main body of the electrodes LARGE (except the tips) to have a larger thermal mass to draw heat from the tips. A powerful blower can be directed right on your electrodes and weld and it will certainly help, unlike with other procedures where you merely blow the shielding gas away. Cooler=less resistance=more current=more efficient weld.