Intriduction High frequency welded pipe is based on solid resistance heat energy. Resistor thermal welding, using high-frequency current is generated in the workpiece so that the surface of the workpiece weld zone is heated to the melting or close to the plastic state, then applied (or not applied) upsetting force is achieved for such a steel pipe of the metal combination.
Advantage of HFW pipe In the welding process, HFW steel pipes do not need to add filling meta. So it has fast welding speed and high efficiency in production. HFW pipe is widely used in the fields of oil and gas transportation, oil well pipeline, building structure and various kinds of mechanical pipe. However, HFW steel pipe quality is affected by many factors, such as raw material and process. And the production quality control becomes difficult. So the yield and welding process still need to be improved continuously.
Electric resistance welded (ERW) pipe is manufactured by cold-forming a sheet of steel into a cylindrical shape. Current is then passed between the two edges of the steel to heat the steel to a point at which the edges are forced together to form a bond without the use of welding filler material. Initially, this manufacturing process used low-frequency A.C. current to heat the edges. This low-frequency process was used from the 1920s until 1970. In 1970, the low-frequency process was superseded by a high-frequency ERW process which produced a higher quality weld.
Over time, the welds of low-frequency ERW pipe was found to be susceptible to selective seam corrosion, hook cracks, and inadequate bonding of the seams, so low-frequency ERW is no longer used to manufacture pipe. The high-frequency process is still being used to manufacture pipe for use in new pipeline construction.
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