JIS G3106 — Welded structural steel
Grades
SM400A, SM400B, SM400C, SM490A, SM490B, SM490C, SM490YA, SM490YB, SM520B, SM520C, SM570
Chemical composition and mechanical properties
| Grade | Chemical composition | Mechanical properties |
|---|---|---|
| SM400A | C≤0.23 (>100mm≤0.25), Mn≥2.5×C%, P≤0.035, S≤0.035 | Rm 400-510 MPa, Rp0.2 ≥245 MPa, A≥23% |
| SM400B | C≤0.20(>100mm≤0.22), Mn 0.60-1.40, P≤0.035, S≤0.035 | Rm 400-510 MPa, Rp0.2 ≥245 MPa, A≥23%, 0℃ Akv≥27J |
| SM400C | C≤0.18 (>100mm≤0.20), Mn≤1.40, P≤0.035, S≤0.035 | Rm 400-510 MPa, Rp0.2 ≥245 MPa, A≥23%, 0℃ Akv≥47J |
Application scope
JIS G3106 specifies hot-rolled steel sections for welded structures such as bridges, ships, and vehicles, with grades ranging from SM400 to SM570 and their A, B, and C toughness levels. The standard strengthens carbon equivalent and controls impact toughness to ensure weldability, specifies composition, tensile, and impact requirements, and offers a wide strength range. Various types of steel can be combined to form load-bearing frames, making it suitable for primarily welded load-bearing components and structural applications requiring good toughness.
Typical applications
Widely used in load-bearing components such as bridges, ships and marine structures, welded building structures, engineering machinery, and storage tanks, various types of steel can be combined to form beams, columns, and trusses. Grades are classified according to strength and impact toughness, allowing selection based on stress and operating temperature; Grade C offers better low-temperature performance. With its excellent weldability and strength-toughness combination, it is suitable for structural engineering projects involving extensive welding and requiring high-quality joints.
