They are the same grade family under successive standards: GB/T 1591-2018 renamed Q345 to Q355 to match the 355 MPa yield designation used internationally. D remains the −20 °C impact quality.

Grades · Structural & HSLA Steel · Q355D

Q355D

Data under review

Q355D is the low-temperature quality of China’s Q355 HSLA series to GB/T 1591 — the successor designation to Q345D. It guarantees impact toughness at −20 °C with tightened P/S limits, and is the standard Chinese plate for bridges and structures that see real winters.

DINS355J2 (near)

AISIA572 Gr.50 (near)

JISSM520C (near)

CategoryStructural & HSLA Steel

Chemical composition

Element	Content (%)
C	≤0.18
Si	≤0.50
Mn	≤1.60
P	≤0.025
S	≤0.020

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

Properties

Yield strength	≥355 MPa (≤16 mm)
Tensile strength	470–630 MPa
Impact	−20 °C, ≥34 J
Density	7.85 g/cm³

Heat treatment

Supplied as-rolled, normalized or TMCP under GB/T 1591 delivery conditions; D quality is the −20 °C impact grade of the Q355 series.

Equivalent grades

Standard	Designation
din	S355J2 (near)
aisi	A572 Gr.50 (near)
jis	SM520C (near)
gb	Q355D (GB/T 1591)

Compare side by side: Q355D vs Q355B · Q355D vs Q345B / 16Mn · Q355D vs S355K2

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

Applications & Processing

Applications: Bridges, cold-region buildings, crane structures, pressure-bearing fabrications, export projects specified to GB standards.

Processing: Good weldability; the usual GB-specified counterpart when a design calls for S355J2-class performance with a Chinese mill certificate.

FAQ

Q355D vs Q345D?: They are the same grade family under successive standards: GB/T 1591-2018 renamed Q345 to Q355 to match the 355 MPa yield designation used internationally. D remains the −20 °C impact quality.

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Source: GB/T 1591 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.