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01
JIS G3444 Carbon Steel Pipes for General Structures
Ordering Information
When ordering, the following must be specified:
- Standard number (JIS G 3444)
- Steel grade (e.g., STK290, STK400)
- Dimensions (outer diameter, wall thickness, length)
- Type of tube (plain end, threaded, etc.)
- Quantity
Main Steel Grades & Mechanical Properties
| Steel Grade | Tensile Strength (MPa) Min | Yield Strength (MPa) Min | Elongation (%) Min |
| STK290 | 290 | – | 30 |
| STK400 | 400 | 235 | 25 |
| STK490 | 490 | 325 | 20 |
| STK500 | 500 | 355 | 18 |
Manufacturing Process
- Tubes are manufactured by welding (electric resistance welding, arc welding, etc.) or seamless processes.
Chemical Composition (Typical, % Max)
- Carbon (C): Varies by grade (e.g., ≤0.30% for STK290)
- Phosphorus (P): ≤0.040%
- Sulfur (S): ≤0.040%
Inspection Requirements
- Tensile test (for mechanical properties)
- Bend test or flattening test (for ductility)
- Hydrostatic test or non-destructive testing (NDT) (for weld integrity)
- Visual inspection (surface defects, dimensions)
Surface Condition & Defects
- Tubes must be free from harmful defects.
- Light surface imperfections may be permitted if within tolerance.
Marking
Each tube must be marked with:
- Manufacturer’s name or trademark
- Steel grade (e.g., STK400)
- Size (outer diameter × wall thickness)
- Standard number (JIS G 3444)
Latest Revision (2025 Updates, if applicable)
- Enhanced NDT requirements for welded joints.
- Revised chemical composition limits for improved weldability.
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