Straight seam steel pipe is parallel to the longitudinal weld steel pipe with steel pipe. Metric is usually divided into welded steel pipe, welded thin-walled tube, transformer cooling pipes and so on. 
 Production process 
 High-frequency straight seam welded steel pipe with a relatively simple process, the characteristics of rapid continuous production, in civil construction, petrochemical, light industry and other sectors is widely used. Used for conveying fluids or low-voltage components made of various engineering and light industrial products. 
 1 high-frequency straight seam welded pipe production process 
 Straight seam welded steel pipe is welded by high frequency unit to a certain size strip steel rolled into a round tube and straight seam welded steel pipe. Steel shapes can be round, square or it can be shaped, and it depends on the sizing rolling after welding. Welded steel pipe materials are mainly: low carbon steel and σs ≤ 300N/mm2, σs ≤ 500N/mm2 low-alloy steel or other steel. High-frequency straight seam welded steel pipe production process is as follows: 
 (2) high-frequency welding 
 High-frequency welding is based on the principle of electromagnetic induction and AC charge in a conductor skin effect, proximity effect and eddy current heating effect, so that local heating of steel weld to the edge of the molten state, the roller squeeze, so to achieve crystal indirect butt weld together to achieve the purpose of welding seam. High-frequency induction welding is a welding (or pressure contact welding), it did not weld filler, no welding spatter, narrow heat affected zone, weld forming beautiful, good mechanical properties, welding, etc., so in the production of steel by wide range of applications. 
 High-frequency welded steel pipe is the use of alternating current to the skin effect and proximity effect, steel (strip) by roll forming, the formation of a circular cross-section tube is disconnected, the inner tube near the center of rotation near the induction coil, a device or a group of resistance (bar magnet), impedance control and electromagnetic induction tube opening to form a loop in the skin effect and proximity effect under the action of the edge of the tube opening and a strong focus on the thermal effect of the weld edge rapidly heated to the desired temperature by welding roller extrusion, molten metal to achieve an indirect co-crystal, cooled to form a solid butt weld. 
 3 High-frequency welded pipe mill 
 High-frequency straight seam welded steel pipe in high-frequency welded pipe mill process is done. Usually by high-frequency welded pipe mill roll forming, high-frequency welding, extrusion, cooling, sizing, flying cut off saws and other components, the front-end unit with storage material live sets, the unit's back-end flip with a steel frame ; electrical part of the main high-frequency generator, DC generator and excitation control device composed of automatic meter