Near-equivalents: both are ~325/345 MPa yield weldable HSLA grades with 490–610 vs 470–630 MPa tensile ranges and similar C/Mn caps. Certificates are commonly cross-accepted; impact grades differ (Q345B has a 20 °C Charpy class, SM490A does not).

Grades · Structural & HSLA Steel · SM490A

SM490A

Data verified

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.

DIN1.0570 (S355J2, near)

AISIA572 Gr.50 (near)

JISSM490A (JIS G3106)

CategoryStructural & HSLA Steel

Chemical composition

Element	Content (%)
C	≤0.20
Si	≤0.55
Mn	≤1.60
P	≤0.035
S	≤0.035

Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.

Properties

Tensile strength	490–610 MPa
Yield strength	≥325 MPa (≤16 mm)
Density	7.85 g/cm³
Impact	A grade: no mandatory Charpy (B/C grades add impact requirements)

Heat treatment

Hot rolled as supplied; normalized delivery can be agreed. No hardening treatment.

Equivalent grades

Standard	Designation
din	1.0570 (S355J2, near)
aisi	A572 Gr.50 (near)
jis	SM490A (JIS G3106)
gb	Q345B (near)

Compare side by side: SM490A vs Q345B / 16Mn · SM490A vs S355J2 · SM490A vs SM520B · SM490A vs SS490

Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.

Applications & Processing

Applications: Bridges, building frames, cranes, pressure-boundary supports, welded plate girders and general welded fabrication.

Processing: Good weldability with CEV discipline per the certificate; A grade carries no guaranteed impact value — move to SM490B/C when a Charpy requirement applies.

FAQ

SM490A vs Q345B?: Near-equivalents: both are ~325/345 MPa yield weldable HSLA grades with 490–610 vs 470–630 MPa tensile ranges and similar C/Mn caps. Certificates are commonly cross-accepted; impact grades differ (Q345B has a 20 °C Charpy class, SM490A does not).

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Source: JIS G3106 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.