Electric Edge welding (tubing) question.

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Something that hopefully someone here can provide an answer to...At a previous job, I worked a crane at a steel tubing plant and noticed that they didn't seem to use any shielding gas when making the tubing. At the time, I didn't have the interest in knowing but thinking back on it now has me wondering. The tubing being made was cold rolled edge welded stuff between 22ga and 10ga. I'm not certain the exact method for welding the seem.Since it seems a vast majority of welding processes requires some type of shielding from atmospheric gasses, how is it that welding steel like that can be made without shielding?
Reply:ERW, using current up to 5-10kA, is a commonly used process to weld pipe and HSS.  For an overview of the forming process, step inside....."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:I'm assuming you're referring to Electric Resistance Welding (ERW). Where the tube is pressed between two rolling electrodes which passes a current through the tube and the seam has a lot of resistance so it heats up glowing red and is then pressed together to be fused, then water cooled. That is a good question though. It doesn't use shielding gas. I would assume it has something to do with the fact that it doesn't get quite as hot as conventional welding does, and the fusion comes from a mix of heat and pressure.John 3:16(2) Miller Pheonix 456(2) Millermertic 252Dynasty 210DXHobart 210MVPDoringer D350 SA Cold SawScotchman 350LT Cold SawWebb 10x50 MillWebb 15x40 LatheGeka Bendicrop Ironworker
Reply:Fantastic!  the youtube video - it looks very close to what I remember and it has the following mentioned in the description. which basically answers the question. During ERW, a high frequency electrical current is transmitted to the material by means of copper sliding contacts so that the abutting edges initiate fusion as they come into contact.