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Technical requirements for straight seam welded pipes: According to GB3092 "Welded Steel Pipes for Low-Pressure Fluid Transportation" standard, the nominal diameter of straight seam welded pipes is 6~150mm, the nominal wall thickness is 2.0~6.0mm, and the length is usually 4~10 meters, which can be shipped in fixed length or multiple lengths. The surface of the straight seam welded pipe should be smooth, and defects such as folds, cracks, delamination, and lap welds are not allowed. Minor defects such as scratches, scrapes, weld misalignment, burns, and scabs are allowed on the surface of the straight seam welded pipe, not exceeding the negative deviation of the wall thickness. Wall thickness increase at the weld seam and the presence of inner weld reinforcement are allowed. Straight seam welded pipes should undergo mechanical performance tests, flattening tests, and flaring tests, and must meet the requirements specified in the standard. Straight seam welded pipes should be able to withstand a 2.5MPa pressure test at internal pressure, maintaining no leakage for one minute. Eddy current testing is allowed to replace the hydrostatic test. Eddy current testing is performed according to GB7735 "Eddy Current Testing Method for Steel Pipes". The eddy current testing method involves fixing the probe to a frame, maintaining a distance of 3-5 mm from the weld seam, and using the rapid movement of the straight seam welded pipe to comprehensively scan the weld seam. The testing signals are automatically processed and sorted by the eddy current tester to achieve the testing objective. After testing, the welded pipe is cut to the specified length using a flying saw and removed from the production line via a turnover rack. Both ends of the straight seam welded pipe should be flattened and chamfered, and marked. Finished straight seam welded pipes are packaged in hexagonal bundles before leaving the factory.
Straight Seam Welded Pipe Processing Methods: Straight seam steel pipes have a weld seam parallel to the longitudinal direction of the pipe. Their strength is generally higher than that of straight seam welded pipes. Larger diameter straight seam welded pipes can be produced from narrower blanks, and pipes of different diameters can be produced from blanks of the same width. However, compared to straight seam welded pipes of the same length, the weld seam length increases by 30-100%, and the production speed is lower. So, what are the processing methods?
1. Forging: Straight seam welded pipe is a pressure processing method that uses the reciprocating impact force of a forging hammer or the pressure of a press to change the billet into the desired shape and size.
2. Extrusion: Straight seam welded pipe is a processing method in which steel is placed in a closed extrusion chamber, pressure is applied to one end, and the metal is extruded through a specified die to obtain a finished product with the same shape and size. It is mostly used in the production of non-ferrous metal steel.
3. Rolling: Straight seam welded pipe is a pressure processing method in which steel billets are passed through the gap between a pair of rotating rollers (of various shapes). Due to the compression of the rollers, the cross-section of the material is reduced, and the length is increased.
4. Drawing: Straight seam welded pipe is a processing method in which rolled metal billets (shaped, tube, products, etc.) are drawn through a die to reduce the cross-section and increase the length. It is mostly used for cold working.
