What is Seamless Tubing?
Seamless tubes are tubes without welding seams, which makes them stronger and more reliable than welded tubes. However, due to the complex process of production of seamless tubes, they are also more expensive. Seamless tubing is completely welding-free – the pipes are produced using extrusion and connected via threads.
Seamless tubing is mostly used in extreme environments, such as compressed natural-gas lines, compressed hydrogen transfer pipes, sub-sea safety valves, various liquid-carrying pipes, hydraulic lines, and solar dishes. Thanks to the non-corrosive nature and strength of seamless tubing, it also finds use in the aerospace and defense industry, alternative energy industry, and Health Care.
The main advantage of seamless tubing is the lack of weak points. For example, a longitudinally-welded tube has a weak spot at the weld that is susceptible to corrosion and structural failure. Thus, seamless tubing has much higher corrosion resistance and structural integrity than welded pipe.
Seamless tubes can also be produced with much smaller inner diameters than welded tubes, which makes them a much better choice for high-precision equipment. Some examples of seamless tubing have capillary-sized inner diameters that are simply unattainable in welded pipes. Finally, seamless tubes can withstand higher temperatures, pressures, and mechanical stress. However, seamless tubes are also generally shorter in length than welded tubes, and more expensive as well.
Production of Seamless Tubing
Seamless tubing is produced using the extrusion method. More precisely, the material is first extruded from a billet that provides a full cylindrical shape and then redrawn through a die to obtain a semi-finished seamless tube. Then, the semi-finished tubing is heat-treated in a vacuum furnace (air-drying is not recommended due to danger of staining) and worked to the desired size. Seamless tubes can be produced from various alloys, but today mostly non-corrosive materials are used. These include Carbon steel, austenitic, duplex, and stainless steels, Nickel alloys, Molybdenum alloys, Tungsten alloys, Titanium alloys, and Zirconium alloys.