First, technical requirements of straight seam welded steel pipes: Technical requirements and inspection of straight seam welded steel pipes According to the provisions of GB3092 “Welded steel pipes for low-pressure fluid transportation”, the nominal diameter of welded steel pipes is 6~150mm, the nominal wall thickness is 2.0~6.0mm, and the length of welded steel pipes is usually 4~10 meters, which can be shipped at fixed length or multiple lengths. The surface of the steel pipe should be smooth, and no defects such as folding, cracks, delamination, and lap welding are allowed. Minor defects such as scratches, scratches, weld dislocation, burns, and scarring that do not exceed the negative deviation of the wall thickness are allowed on the surface of the steel pipe. Thickening of the wall thickness at the weld and the presence of internal seam weld ribs are allowed. Welded steel pipes should be subjected to mechanical property tests, flattening tests, and expansion tests, and must meet the requirements specified in the standard. The steel pipe should be able to withstand the internal pressure of 2.5Mpa pressure test and maintain no leakage for one minute. Eddy’s current flaw detection is allowed to replace the water pressure test. Eddy current flaw detection is carried out by GB7735 “Eddy Current Flaw Detection Method for Steel Pipes”. The eddy current flaw detection method is to fix the probe on the frame, keep the flaw detection and the weld 3~5mm away, and use the rapid movement of the steel pipe to conduct a comprehensive scan of the weld. The flaw detection signal is automatically processed and automatically sorted by the eddy current flaw detector to achieve the purpose of flaw detection. After flaw detection, the welded steel pipe is cut to the specified length with a flying saw and unloaded through the flip frame. The two ends of the steel pipe should be flat-headed and chamfered, printed, and marked, and the finished pipe should be packed in hexagonal bundles before leaving the factory.
Second, the processing method of straight seam steel pipe: The straight seam steel pipe is a steel pipe with a weld parallel to the longitudinal direction of the steel pipe. The strength is generally higher than that of the straight seam welded steel pipe. It can produce welded steel pipes with larger diameters with narrower billets, and welded steel pipes with different diameters can also be produced with billets of the same width. However, compared with straight seam pipes of the same length, the weld length increases by 30~100%, and the production speed is lower. So what are its processing methods?
1. Forging steel: A pressure processing method that uses the reciprocating impact force of the forging hammer or the pressure of the press to change the blank into the shape and size we need.
2. Extrusion: It is a processing method in which the metal is placed in a closed extrusion cylinder, and pressure is applied at one end to extrude the metal from the specified die-hole to obtain a finished product with the same shape and size. It is mostly used to produce non-ferrous metal steel.
3. Rolling: A pressure processing method in which the steel metal billet passes through the gap (various shapes) of a pair of rotating rollers, and the material cross-section is reduced and the length is increased due to the compression of the rollers.
4. Drawing steel: It is a processing method in which the rolled metal billet (profile, tube, product, etc.) is pulled through the die hole to reduce the cross-section and increase the length. It is mostly used for cold processing.
Post time: Jan-06-2025