First, what are the technical requirements for straight seam welded steel pipes?
According to GB3092 “Welded Steel Pipes for Low-Pressure Fluid Transportation” standard, the nominal diameter of welded steel 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 steel 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 steel pipe, not exceeding the negative deviation of the wall thickness. Wall thickness increase at the weld and the presence of internal weld reinforcement are allowed. Welded steel pipes should undergo mechanical property tests, flattening tests, and flaring tests, and must meet the requirements specified in the standard. The steel pipe should be able to withstand the internal pressure; a 2.5MPa pressure test should be performed, 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 steel 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 steel 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 steel pipe should be flattened and chamfered, marked, and the finished pipes are packaged in hexagonal bundles before leaving the factory.
Secondly, what are the processing methods for straight seam steel pipes?
Straight seam steel pipes are steel pipes with the weld seam parallel to the longitudinal direction of the pipe. Their strength is generally higher than that of straight seam welded steel pipes. They can be produced from narrower blanks to produce welded steel pipes with larger diameters, and can also be produced from blanks of the same width to produce welded steel pipes with different diameters. However, compared to straight seam steel 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 for straight seam steel pipes?
1. Forging: A pressure processing method that uses the reciprocating impact force of a forging hammer or the pressure of a press to change a billet into the desired shape and size.
2. Extrusion: A processing method in which metal is placed in a closed extrusion chamber, pressure is applied to one end, and the metal is forced out 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: A pressure processing method in which steel billets are passed through the gap between a pair of rotating rollers (of various shapes), and the compression of the rollers reduces the cross-section of the material while increasing its length.
4. Drawing: A processing method in which rolled metal billets (shaped, tubing, products, etc.) are drawn through a die to reduce the cross-section and increase the length. It is mostly used for cold working.
Post time: Feb-28-2026