JIS G3101 — Rolled steels for general structure
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Scope
Technical delivery conditions for hot-rolled plate, sheet, strip, sections, bar and flat bar in the general structural grades SS330, SS400, SS490, SS540 and SS590. The standard specifies tensile strength, yield point by thickness and elongation; chemical composition is limited only for phosphorus and sulphur on the lower grades. There is no impact requirement and no carbon equivalent — weldable structural grades with guaranteed toughness are in JIS G3106 (SM400, SM490, SM520, SM570).
Grades covered by JIS G3101
| Grade | No. | Type | C % | Yield MPa | Tensile MPa | Nearest equivalents |
|---|---|---|---|---|---|---|
| SS400 | — | Rolled steel for general structure (Japanese national standard) | — | 245 | 400–510 | s235jr, a36, q235 |
Revision history and superseded standards
| Year | Change |
|---|---|
| 1995 | SS41 / SS50 renamed SS400 / SS490 when the designation moved from kgf/mm² to MPa |
| 2004 | Thickness bands and elongation test pieces aligned with ISO practice |
| 2015 | Editorial revision; SS330 retained |
| 2020 | Current edition |
Supersedes: JIS G3101:1995 (SS41, SS50 designations in kgf/mm²); JIS G3101:2004; JIS G3101:2015.
Where to buy the standard
The full text is copyrighted by JISC and is not reproduced here. Purchase the current edition from Japanese Standards Association (JSA) or your national standards body. The values on this site are the normative limits as published; the standard's own tables, notes and test methods govern.
Related standards
The number is tensile strength
SS400 is the most quoted Japanese grade name and the most misread. SS means rolled steel for general structure; 400 is the minimum tensile strength in MPa. It is not a yield figure — the yield is 245 MPa up to 16 mm — and reading it as one overstates the steel by more than half.
The ladder runs SS330, SS400, SS490, SS540 and SS590, all named after tensile. The standard covers plate, sheet, strip, sections, bar and flat bar under the same designations.
What G3101 deliberately leaves out
For SS400 the standard limits only phosphorus and sulphur, each at 0.050 %. Carbon, silicon and manganese are not controlled, there is no carbon equivalent ceiling and there is no impact requirement at any temperature.
That is a design decision rather than an oversight: SS grades are general structural material for simple, lightly loaded fabrication. Where welding matters, Japanese practice moves to JIS G3106 — SM400, SM490, SM520 — which adds full chemistry, a carbon equivalent limit and a graded Charpy test. Treating SS400 and SM400 as interchangeable defeats the purpose of having both.