SS490 vs SM490A
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
SS490
Structural & HSLA Steel
SS490 is the higher-strength grade of JIS G3101, a 490–610 MPa tensile class structural steel with yield of at least 285 MPa in thin sections. Like SS400 it is specified by properties only, with phosphorus and sulfur capped and no carbon control.
Standards: DIN 1.0044 (S275JR, near) · AISI A572 type (near) · JIS SS490 (JIS G3101) · GB Q275 (near)
SM490A
Structural & HSLA Steel
SM490A is the weldable structural steel of JIS G3106 — rolled steel for welded structures with controlled chemistry (C ≤0.20%, Mn ≤1.60%) and a 490–610 MPa tensile range. It is the Japanese counterpart class to Q345B and A572 Gr.50 and the default upgrade from SS400 for welded primary structures.
Standards: DIN 1.0570 (S355J2, near) · AISI A572 Gr.50 (near) · JIS SM490A (JIS G3106) · GB Q345B (near)
Chemical composition compared (%)
| Element | SS490 | SM490A |
|---|---|---|
| P | ≤0.050 | ≤0.035 |
| S | ≤0.050 | ≤0.035 |
| C / Si / Mn | Not specified by JIS G3101 — the grade is defined by its tensile properties, not by chemistry | — |
| C | — | ≤0.20 |
| Si | — | ≤0.55 |
| Mn | — | ≤1.60 |
Properties compared
| Property | SS490 | SM490A |
|---|---|---|
| Tensile strength | 490–610 MPa | 490–610 MPa |
| Yield strength | ≥285 MPa (≤16 mm) | ≥325 MPa (≤16 mm) |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Impact | — | A grade: no mandatory Charpy (B/C grades add impact requirements) |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: SS490 · SM490A. Substitution decisions for certified parts stay with the design authority.