Summary of the Forming Process of Longitudinal Welded Steel Pipes
Longitudinal welded steel pipes refer to pipes where the weld seam is parallel to the length of the pipe. Its production process is relatively straightforward, and the strength of helical steel pipes is generally higher than that of longitudinal welded steel pipes. This process can produce larger diameter welded pipes from narrower blanks or create welded pipes of various diameters using the same width of the blank. However, compared to longitudinal welded pipes of the same length, the length of the weld seam increases by 30%-100%, causing a reduction in production speed. Based on the manufacturing process, these can be categorized into high-frequency longitudinal welded steel pipes, submerged arc welded longitudinal steel pipes, and further categorized into UOE, RBE, and JCOE pipes according to their forming methods.
Forming Process of Longitudinal Welded Steel Pipes
Longitudinal welded steel pipes need to undergo mechanical performance tests, flattening tests, and flaring tests to ensure they meet the standard requirements. The pipes should be capable of withstanding a certain internal pressure. If necessary, a pressure test of 2.5 MPa should be performed and maintained without leaks for one minute. Eddy current testing methods can replace hydraulic tests. According to the standard GB7735 "Eddy Current Testing Method for Steel Pipes," the eddy current inspection probe is fixed to the framework, maintaining a distance of 3-5mm from the weld seam, and quickly scanning the entire weld seam. The eddy current inspection instrument automatically processes and classifies the inspection signals, achieving the purpose of inspection. After inspection, the welded pipes are cut into specified lengths using a flying saw and moved along the offline flipping frame. Both ends of the steel pipe should be chamfered, and a printed mark is applied. Before leaving the factory, the finished pipes are bundled hexagonally and packaged.
There are several processing methods for longitudinal welded steel pipes:
1. Forging: Changing the shape and size of the blank into the required shape and size using the repeated impact force of a forging hammer or the pressure of a press.
2. Extrusion: Placing the metal in a sealed extruder and extruding it from a specified die hole under pressure to obtain the processed finished product with the same shape and size. This method is primarily used for the production of non-ferrous metals.
3. Rolling: This method involves passing the steel billet through a gap between a pair of rotating rollers, compressing the material due to the rollers' pressure, reducing the cross-section, and increasing the length.
4. Drawing: Processing the already rolled metal blank through a die hole to reduce the cross-section and increase the length, commonly used for cold processing.
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