Hot Products
- Carbon & Carbon Alloy Steel
- Stainless Steel
- Copper & Nickel Alloy
- Heat Efficiency Tubes
- Pipe Fittings
- Pipe Flanges
- Gasket, Stud Bolt &Nut
- Industrial Valves
0102030405
China JIS G3444 Carbon Steel Pipes for General Structures - Leading Suppliers & Factory Quality
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):
Enhanced NDT requirements for welded joints.
Revised chemical composition limits for improved weldability.
📩 Want to order the same? Contact us Now to send your request!
🔍 Frequently Asked Questions (FAQ)
Q
What is JIS G 3444 and what types of tubes does it cover?
JIS G 3444 is a Japanese Industrial Standard that specifies carbon steel tubes used for general structural purposes. It covers both welded and seamless tubes in various grades, including STK290, STK400, STK490, and STK500, suitable for construction, machinery, and infrastructure applications.
Q
What information is required when placing an order for JIS G 3444 tubes?
When ordering, you must specify the standard number (JIS G 3444), the steel grade (e.g., STK290 or STK400), dimensions including outer diameter, wall thickness and length, the type of tube end (plain end, threaded, etc.), and the required quantity.
Q
What is the difference between STK400 and STK490 steel grades?
STK400 has a minimum tensile strength of 400 MPa and a minimum yield strength of 235 MPa with at least 25% elongation. STK490 offers higher strength with a minimum tensile strength of 490 MPa, yield strength of 325 MPa, and a minimum elongation of 20%. STK490 is preferred for heavier structural applications requiring greater load-bearing capacity.
Q
What inspections and tests are required for JIS G 3444 tubes?
JIS G 3444 tubes must undergo a tensile test to verify mechanical properties, a bend or flattening test to confirm ductility, a hydrostatic test or non-destructive testing (NDT) to ensure weld integrity, and a visual inspection to check for surface defects and dimensional compliance.
Q
Are surface imperfections allowed on JIS G 3444 tubes?
Tubes must be free from harmful defects that could compromise structural integrity. However, minor or light surface imperfections may be permitted provided they remain within the specified tolerance limits defined by the standard.
Q
What are the key updates in the 2025 revision of JIS G 3444?
The 2025 revision of JIS G 3444 introduces enhanced non-destructive testing (NDT) requirements for welded joints to improve quality assurance, as well as revised chemical composition limits designed to enhance the weldability of the steel grades covered by the standard.