12. How is high-frequency welded steel pipe produced?

12.1. Raw material preparation
Uncoiling: The coiled metal strip, such as steel strip, is uncoiled and sent to the production line.
Strip leveling: Leveling the uncoiled strip to eliminate the bending and wavyness of the strip during the winding process and ensure the flatness of the strip.
12.2. Pretreatment
Head and Tail Shearing: Perform precise shearing on the head and tail of the strip to remove irregularities.
Strip butt welding: As needed, multiple strip sections are butt welded to ensure the continuous feeding of the production line.
12.3. Forming and welding
Forming: Through multiple rolling and forming molds, the strip is gradually deformed into the required tube shape (such as round pipe, square pipe, etc.).
High-frequency welding: High-frequency induction heating technology is used to weld the formed pipe billets. The high-frequency current passes through the edge of the billet to quickly heat it to a melted state, and the weld joint is achieved by the action of the extrusion roller.
12.4. Post-processing
Remove burrs: Remove burrs and flash from the welding process to ensure the smoothness of the steel pipe surface.
Sizing: Accurately sizing the welded pipe, adjusting the diameter and wall thickness of the pipe through extrusion rollers to meet product specifications.
Flaw detection: Conduct non-destructive testing on the welded pipes, such as ultrasonic testing, X-ray testing, eddy current testing, magnetic leakage testing, etc., to find and eliminate welding defects.
12.4.1. What is eddy current testing?
Principle: Use alternating magnetic fields to generate eddy currents in metal materials, and detect defects by detecting changes in eddy currents.
Features: Fast detection speed, no need to couple with the surface of the workpiece, suitable for online production; However, due to the limitation of the skin-teasing effect, it is difficult to find deep defects.
12.4.2. What is magnetic leakage detection?
Principle: After the ferromagnetic material is magnetized, its surface and near-surface defects form a magnetic leakage field on the surface of the material, and the defect is found by detecting the magnetic leakage field.
Characteristics: The requirements for the surface state of the pipe are not high, the detection depth is large, and it is suitable for detecting defects above a certain depth from the surface of the welded pipe.
Application: It is often used for welded pipe inspection with high quality requirements such as petroleum welded pipes.
12.4.3. What is ultrasonic flaw detection?
Principle: Uses the propagation and reflection properties of ultrasonic waves in materials to find defects.
Features: High detection sensitivity, can find internal defects; However, the operation is relatively complex and requires high skills from the inspectors.
Applications: Suitable for offline inspection of thick-walled welded pipes, especially for the verification of weld quality.
12.5. Flying cut
According to the order requirements, the sized pipe is cut according to the specified length to form the final steel pipe product.
12.6. Finished product treatment
Steel pipe straightening: Straighten the cut steel pipe to ensure its straightness and roundness.
Pipe section processing: According to customer needs, the steel pipe is further processed, such as punching, tapping, etc.
Hydrostatic Testing: Conduct hydrostatic tests on steel pipes to test their tightness and pressure-bearing capacity.
Coding and coating: Printing identification information on steel pipes and applying anti-corrosion coatings or other surface treatments.