Tube-Welding Mill

a system of machines for performing all technical operations necessary for the production of metal pipe and tubing by bending metal strip or plate and welding the edges together. The main features characterizing the type of tube-welding mill are the location of the weld (longitudinal or helical) and the welding process.

The most common tube-welding mills use pressure or fusion welding. In pressure welding, the edges are heated by high-frequency current, or such methods as resistance forge welding and welding in fuel-fired furnaces are used. Fusion welding includes submerged-arc welding and inert gas-shielded arc welding. The first two processes are widely used for pipe up to 500 mm in diameter, with longitudinal or helical seams. A reducing mill is added to the tube-welding mill for production of pipe less than 100 mm in diameter. Tube-welding mills with arc welding are used primarily to produce pipe with a diameter of 500–1,620 mm; the welding is performed inside and outside the pipe. Natural-gas and water pipes 10–114 mm in diameter, with longitudinal seams, are manufactured in mills using welding in fuel-fired furnaces. This welding process is the most productive, especially when a reducing mill is added, thus increasing the mill’s output of pipe because of the resulting decrease in pipe diameter and wall thickness.

Modern tube-welding mills have attained an output fate of up to 20 m per sec for pipe 10 mm in diameter. The original material in most cases is coiled strip, and the mills normally operate in the “endless” mode, which is made possible by continuous butt welding of the strip without stopping the mill operation. Tube-welding mills are being developed for the production of two-layer and multilayer natural-gas pipe more than 1 m in diameter. The original material in this case is coiled strip 3–14 mm thick.