Is ship Grade A the same as ASTM A36?

No. Strength is similar (235 vs 250 MPa yield) but Grade A is a class-society grade: chemistry follows IACS rules (including the Mn ≥ 2.5×C rule) and plates carry classification-society certification.

Grades · Structural & HSLA Steel · Grade A (ship)

Grade A (ship)

Data under review

Grade A is the baseline ordinary-strength hull steel of the classification-society system (IACS UR W11, mirrored by ASTM A131 and GB/T 712). At 235 MPa yield with no impact-test requirement, it covers the least demanding hull zones — internal structure and sheltered areas on classed vessels.

AISIA131 A

JISKA (near)

GBA (GB/T 712)

CategoryStructural & HSLA Steel

Chemical composition

Element	Content (%)
C	≤0.21
Si	≤0.50
Mn	≥2.5×C
P	≤0.035
S	≤0.035
Note	Chemistry per classification-society rules (IACS UR W11)

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

Properties

Yield strength	≥235 MPa
Tensile strength	400–520 MPa
Impact	No impact test required
Density	7.85 g/cm³

Heat treatment

Supplied as-rolled under class survey; no impact (Charpy) requirement applies to Grade A.

Equivalent grades

Standard	Designation
aisi	A131 A
jis	KA (near)
gb	A (GB/T 712)

Compare side by side: Grade A (ship) vs Grade B (ship) · Grade A (ship) vs Grade D (ship)

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

Applications & Processing

Applications: Internal hull structure, superstructures, non-critical marine fabrications, general shipyard plate.

Processing: The most forgiving ship plate to weld and form; still ordered with class certificates when the vessel is classed.

FAQ

Is ship Grade A the same as ASTM A36?: No. Strength is similar (235 vs 250 MPa yield) but Grade A is a class-society grade: chemistry follows IACS rules (including the Mn ≥ 2.5×C rule) and plates carry classification-society certification.

Need Grade A (ship) from stock?

Steel.Wiki is sponsored by Shenzhen NewAsia Special Steel (Nasteel), a special-steel stockholder in Shenzhen stocking mold, tool and alloy steels with EN 10204 3.1 certification.

Ask for a quotation Visit Nasteel

Source: Classification-society rules (IACS UR W11) published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.