Welded steel pipes must undergo mechanical performance tests, flattening tests, and flare tests to ensure they meet the requirements outlined in the relevant standards. The pipes should be capable of withstanding a certain level of internal pressure. If required, a pressure test at 2.5 MPa should be conducted, maintaining no leakage for at least one minute. In some cases, hydrostatic testing can be replaced by eddy current testing, which is performed according to GB 7735, "Steel Tube Eddy Current Testing Method." During this process, the probe is fixed on a frame, maintaining a distance of 3–5 mm from the weld seam. As the pipe moves quickly, the entire weld area is scanned, and the flaw detection signal is automatically processed and sorted by the eddy current testing equipment, ensuring accurate and efficient inspection.
After flaw detection, the welded pipes are cut to the specified length using a flying saw and then removed from the frame by a flipping mechanism. Both ends of the steel pipe should be chamfered, marked with identification, and finally packaged in hexagonal packaging before being shipped.
Processing Methods
The primary processing methods used for straight-seam steel pipes include:
Forging: This method involves shaping the metal billet using the impact of a forging hammer or the pressure from a press, resulting in the desired shape and size.
Extrusion: A technique where metal is placed inside a sealed extrusion chamber and forced through a die to produce a product with a consistent cross-section. It is commonly used for non-ferrous metals.
Rolling: In this process, the metal billet is passed between rotating rolls with a specific gap, reducing its cross-sectional area while increasing its length due to compression.
Drawing: This involves pulling the rolled metal blank (such as a bar, tube, or other form) through a die to reduce its cross-sectional area and achieve the desired dimensions.
Cold working: This refers to the shaping of steel at temperatures below its recrystallization point, often used to improve strength and surface finish without heat treatment.
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