1. Raw Material Preparation
Uncoiling: Uncoil the curled metal strip material (such as steel strip) and feed it into the production line.
Steel Strip Straightening: Straighten the uncoiled steel strip to eliminate bends and waves produced during the curling process, ensuring its flatness.
2. Pretreatment
Head and Tail Shearing: Precisely shear the head and tail of the steel strip to remove irregular parts.
Butt Welding of Steel Strips: As needed, butt weld multiple steel strip segments together to ensure continuous feeding of the production line.
3. Forming and Welding
Forming: Gradually deform the steel strip into the desired tube shape (such as round tube, square tube, etc.) through multiple passes of rolling and forming dies.
High-Frequency Welding: Utilize high-frequency induction heating technology to weld the formed tube blank. High-frequency current passes through the edges of the tube blank, rapidly heating them to a molten state and achieving welding junction under the action of extrusion rolls.
4. Post-Processing
Deburring: Remove burrs and flash produced during the welding process to ensure the smoothness of the steel pipe surface.
Sizing: Precisely size the welded tube by adjusting its diameter and wall thickness through extrusion rolls to meet product specification requirements.
Non-Destructive Testing: Conduct non-destructive testing on the welded tube, such as ultrasonic testing, X-ray testing, eddy current testing, and magnetic flux leakage testing, to detect and eliminate welding defects.
4.1. What is Eddy Current Testing?
Principle: Generate eddy currents in metal materials using an alternating magnetic field and detect defects by monitoring changes in the eddy currents.
Characteristics: Fast detection speed, no need for coupling with the workpiece surface, suitable for online production; however, limited by the skin effect, it is difficult to detect deep defects.
4.2. What is Magnetic Flux Leakage Testing?
Principle: After ferromagnetic materials are magnetized, surface and near-surface defects form a leakage magnetic field on the material surface, which is detected to identify defects.
Characteristics: Low requirements for the surface condition of the tube, large detection depth, suitable for detecting defects above a certain depth from the welded tube surface.
Application: Often used for high-quality welded tube inspection, such as welded tubes for the oil industry.
4.3. What is Ultrasonic Testing?
Principle: Utilize the propagation and reflection characteristics of ultrasonic waves in materials to detect defects.
Characteristics: High detection sensitivity, capable of detecting internal defects; however, the operation is relatively complex and requires high skills from the inspector.
Application: Suitable for offline inspection of thick-walled welded tubes, especially for verifying weld quality.
5. Flying Cut
Cut the sized tube to the specified length according to order requirements to form the final steel pipe product.
6. Finished Product Processing
Steel Pipe Straightening: Straighten the cut steel pipe to ensure its straightness and roundness.
Pipe Section Processing: Further process the steel pipe according to customer requirements, such as drilling holes, tapping, etc.
Hydrostatic Testing: Conduct hydrostatic testing on the steel pipe to verify its sealability and pressure-bearing capacity.
Inkjet Marking and Coating: Print identification information on the steel pipe and apply an anticorrosive coating or perform other surface treatments.
