1. Outer diameter and wall thickness:
Outer diameter range: 21.3 mm (seamless) to 3620 mm (spiral welded).
Conventional seamless and LSAW tubes primarily cover an outside diameter of 21.3-1219 mm.
Wall thickness range: 2 mm to 120 mm (seamless) or thicker (welded).
2. Production process
Seamless pipes: produced by hot rolling, cold drawing, or hot expanding processes, the outer diameter is usually ≤ 762 mm.
Welded pipes: including straight seam submerged arc welding (such as specifications 273 × 8 mm, 325 × 9 mm) and spiral welding (outside diameter up to 3620 mm).
3. The mechanical properties and chemical composition
Tensile strength: ≥ 570 MPa (X70 steel grade base requirements).
Yield strength: ≥ 485 MPa.
Chemical composition: The content of sulfur (S ≤ 0.03%) and phosphorus (P ≤ 0.03%) is strictly controlled, and some products add chromium (Cr), nickel (Ni), and other alloying elements to enhance corrosion resistance.
4. Application and testing
Applicable scenarios: high-pressure oil and gas transmission, sulphur-containing media, or low-temperature environments.
Testing requirements: mandatory hydrostatic testing, ultrasonic flaw detection, and Charpy impact testing (to ensure low-temperature toughness).
