Burrs inside a tube could be formed by several resistance welding operations. It could be butt welding longitudinally to form the tube. It could be spot or projection welded to attach some lead or bracket to the tube. It could be an end closure weld to seal the end of the tube. Let’s look at these one at a time.
Butt Weld/Tube Forming (ERW Tube Mill)
This operation would take a sheet of material and form roll it until the two long edges meet. These edges would then be essentially butt welded together. The end result by nature of the process is flash or bulged material on both inside and outside of the formed joint. This excess material is normally scarfed from the inside and outside of the tube as it is produced in the tube mill.
Spot or Projection Weld on Outside Surface
Spot welds can generate some flash especially on a curved surface. It can be reduced if the electrode face shape and or part being spot welded to the tube can approach the curve of the tube diameter.
Projection weld flash can be reduced if the schedule allows for the part to seat well before the full power is applied. Adequate squeeze time or the addition of a little upslope might help. This could eliminate the flash.
Tube Weld End/Closure
In this process the electrode may be cutting the tube, crimping the end closed and welding the end closed across the very end, flash would be minimal.
Copper Tube Cut and Crimped/Welded Closed
Another version might be to simply mash the tube ends and weld them shut. This as in any spot weld could generate some flash out the end. The amount of flash would depend upon the how close to the end the weld is and the purpose of the weld – crimping or fluid tight closure. In all crimping or fluid tight operations a quick sanding or buffing operation would remove any flash generated.
Reference: RWMA – Resistance Welding Manual 4th Edition