To achieve maximum tube mill output material weldability, shielding gas, tube mill, and welding systems should all be considered.  Weldability is the ease in which a metal material forms a weld.  

• GTAW. Manufacturing stainless steel tubing with arc welding usually employs the gas tungsten arc welding (GTAW/Tig) process as the source of the electric arc that melts the base material and forms the weld.
• A capacitor dumps current into this electrical path, which reduces the arc voltage to a level at which the power supply then can supply current for the arc.
• In the plasma welding torch, the tungsten electrode is located within a copper nozzle that has a small opening at the tip.
• Whether using the GTAW or plasma arc process, the output of the tube mill depends on the arc welding speed and total time spent welding.
• The word "weldability" usually means the ease with which a metal material melts and flows together to form a weld joint that exhibits almost as much mechanical, thermal, and corrosion resistance properties as the base metal.
• The 400 series stainless steels also are weldable, but postweld treatment is an issue to consider. Copper, aluminum, nickel-based alloys (INCONEL®, MONEL®, and HASTELLOY®), titanium, and other precious metals possess some degree of weldability but may present challenges with surface oxides and molten metal flow.
• A hydrogen addition is not suitable for welding all tube materials, especially some exotic alloys, because it can cause hydrogen embrittlement in the resultant weld.
• Failure to accomplish this will result in decreased weld quality and most likely a reduction in tube mill speed to achieve the required quality.
• With any welding system, the equipment used must provide a stable welding arc within close tolerances to produce consistent-output weld quality.
• Arc distance control in conventional welding provides the ability to hold constant the distance the electrode remains from the part to be welded.
• The tungsten welding electrode, the source of the welding arc, is one of the most important elements of the welding system, but it also is one of the most commonly ignored by tube mill users.
• Modifying tungsten electrode material, keeping electrode tip geometry consistent, and using polished electrode surface finishes can improve electrode arc starting ability, improve arc stability, and increase electrode life.

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