1. Raw Material Preparation
Uncoiling: Uncoil the curled metal strips (such as steel strips) and feed them into the production line.
Strip Leveling: Level the uncoiled steel strips to eliminate bends and waves caused during coiling, ensuring the flatness of the strips.
2. Pretreatment
Head and Tail Shearing: Precisely shear the heads and tails of the steel strips to remove irregular portions.
Strip Butt Welding: As needed, butt-weld multiple steel strip segments to ensure continuous feeding of the production line.
3. Forming and Welding
Forming: Gradually deform the steel strips into the desired tube shapes (such as round or square tubes) through multiple passes of roller pressing and forming dies.
High-Frequency Welding: Utilize high-frequency induction heating technology to weld the formed tube blanks. High-frequency current passes through the edges of the tube blanks, rapidly heating them to a molten state and achieving welding bonding under the action of squeeze rollers.
4. Post-Processing
Deburring: Remove burrs and flash generated during welding to ensure the smoothness of the steel pipe surface.
Sizing: Precisely size the welded tubes by adjusting their diameter and wall thickness through squeeze rollers to meet product specifications.
Non-Destructive Testing: Conduct non-destructive testing on the welded tubes, 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: Utilize an alternating magnetic field to generate eddy currents within the metal material, and detect defects by measuring changes in the eddy currents.
Characteristics: Fast testing 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 magnetic flux leakage field on the material surface, which is detected to identify defects.
Characteristics: Less demanding on the surface condition of the tube, capable of detecting deeper defects, suitable for detecting defects at a certain depth from the welded tube surface.
Application: Commonly used for high-quality welded tube inspection, such as welded tubes for petroleum use.
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, relatively complex operation, requiring high skill levels from testing personnel.
Application: Suitable for offline inspection of thick-walled welded tubes, especially for verifying weld quality.
5. Flying Cut-Off
According to order requirements, cut the sized tubes to specified lengths to form the final steel pipe products.
6. Finished Product Processing
Steel Pipe Straightening: Straighten the cut steel pipes to ensure their straightness and roundness.
Tube Section Processing: Further process the steel pipes according to customer requirements, such as drilling holes, tapping threads, etc.
Hydrostatic Testing: Conduct hydrostatic testing on the steel pipes to verify their seal tightness and pressure-bearing capacity.
Marking and Coating: Print identification information on the steel pipes and apply anticorrosive coatings or other surface treatments.
