Large-diameter welded pipes come in a variety of specifications, with common outer diameters ranging from approximately 219mm to 2000mm. Wall thicknesses also vary widely, typically from 6mm to 20mm.
1. Specifications and Size Range
Large-diameter welded steel pipes typically refer to spiral welded pipes with a diameter of 508mm or more. Common specifications include:
- Diameter range: 508mm-3620mm
- Wall thickness range: 6mm-25.4mm
- Single length: 6m-18m (customizable)
2. Material Grades
The following steel grades are mainly used:
- Q235B: The most commonly used low-carbon steel, with good weldability and plasticity.
- Q345B: Low-alloy high-strength steel, yield strength ≥345MPa
- X42-X80: API standard pipeline steel, used for high-pressure transmission.
- L245-L485: GB/T9711 standard oil and gas pipes.
3. Mechanical Properties
Taking Q235B as an example:
- Yield Strength: ≥235MPa
- Tensile Strength: 375-500MPa
- Elongation: ≥20%
- Impact Energy (-20℃): ≥27J
4. Process Parameters
- Forming Method: Spiral Submerged Arc Welding (SAWL)
- Welding Process: Double-sided Submerged Arc Automatic Welding
- Weld Reinforcement: ≤3.2mm
- Misalignment: ≤1.6mm
5. Corrosion Resistance
Common Corrosion Protection Treatments:
- 3PE Corrosion Protection: Corrosion resistance life of over 30 years
- Epoxy Powder Coating: Temperature resistance up to 100℃
- Zinc Plating: Zinc layer ≥ 200g/m²
6. Material Selection Guide
- Common fluids: Q235B/Q345B
- Corrosive media: L245N/L360N
- High pressure conditions: X60-X80
- Low temperature environments: L415Q/X65Q
7. Key Inspection Items
- Ultrasonic Testing: 100% full pipe inspection
- X-ray Inspection: 20% random inspection of the entire weld length
- Hydrostatic Test: Pressure holding time ≥ 10s
- Dimensional Inspection: Perimeter deviation ≤ ±0.5%
Large diameter welded pipe Factory
