Several more passes are made to get the new tube ready to weld. The seam on the tube is welded by a solid state welder or high frequency welder. Sometimes the inner and outer bead are removed before the sizing section. There, the tube is made to conform to the desired dimensions. Finally the new pipe is cut to length.
Like it does with other metal forming lines, a coil end joiner shears ends of strips, butts them, and then makes a smooth weld so that the joined coil can proceed through the metal forming line. Maintaining continuous flow of stock coil metal through a processing line can cause productivity gains of up to 70% and reduce scrap production and tooling wear. There are several things to consider in choosing a coil joiner for a given processing line.
For one thing, the joiner must do its shearing, butting, and welding before the accumulated coil is used up. With a strip accumulator between the coil joiner and the processing line, the minimum accumulator storage time will determine that upper limit to the coil end joiner's cycle time. Calculate the time required for shearing, fitting, and welding for the widest strip and heaviest gauge and add strip feed time to it to learn if a particular coil end joiner is appropriate for a given tube or pipe mill.
Another important consideration is the coil end joiner's duty cycle. When a power source halts during a welding operation, it usually follows too-frequent use near or at its maximum output. This causes enough heat to build up to trip a thermostat that shuts down the unit automatically to prevent permanent damage. Usually, variable displacement hydraulic units that shut down between cycles are enough to prevent overheating, however. But choosing water-cooled weld torches and choosing torches whose ratings exceed maximum requirements are an added buffer against overheating.
Tube and Pipe Mills - Coil End Joiners Increase Productivity