JIS G3444 — Carbon steel pipes for general structures
Grades
STK290, STK400, STK490, STK500, STK540
Chemical composition and mechanical properties
| Grade | Chemical composition | Mechanical properties |
|---|---|---|
| STK290 | C (no requirements), Mn (no requirements), P≤0.050, S≤0.050 | Rm ≥290 MPa, Rp 0.2 (no requirement), A ≥30% |
| STK400 | C≤0.25, Mn(no requirement), P≤0.040, S≤0.040 | Rm ≥400 MPa, Rp0.2 ≥235 MPa, A≥23% |
| STK490 | C≤0.18, Mn≤1.40, P≤0.035, S≤0.035 | Rm ≥490 MPa, Rp0.2 ≥315 MPa, A≥23% |
Application scope
JIS G3444 specifies carbon steel pipes for general structures, also known as STK pipes. These are classified into several grades based on strength, ranging from STK290 to STK540, and are mostly circular in cross-section. The standard specifies tensile properties and process tests, with stricter composition control for high-strength grades. These pipes exhibit good load-bearing capacity, processing, and connection performance, making them suitable for welded or bolted hollow structural components. They are commonly used round pipe profiles in scaffolding and light steel structures.
Typical applications
Widely used in load-bearing and supporting components such as building and civil structures, bridge railings, machinery and equipment frames, supports and scaffolding, STK400 is the most common, while high-strength grades are used for larger loads. With its excellent compressive and torsional resistance due to its circular hollow cross-section and ease of connection, it is suitable for scaffolding, railings, space frames, and various light to medium-sized structures and temporary projects primarily composed of circular tubes.
