Q355D vs S355K2
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.
Q355D
Structural & HSLA Steel
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.
Standards: DIN S355J2 (near) · AISI A572 Gr.50 (near) · JIS SM520C (near) · GB Q355D (GB/T 1591)
S355K2
Structural & HSLA Steel
S355K2 is the high-toughness quality of S355 to EN 10025-2. Where S355J2 guarantees 27 J at −20 °C, K2 raises the bar to 40 J at −20 °C, which designers use for fracture-sensitive, dynamically loaded or thick welded structures.
Standards: DIN 1.0596 (S355K2) · AISI A572 Gr.50 (near) · JIS SM520C (near) · GB Q355D class (near)
Chemical composition compared (%)
| Element | Q355D | S355K2 |
|---|---|---|
| C | ≤0.18 | ≤0.20 |
| Si | ≤0.50 | ≤0.55 |
| Mn | ≤1.60 | ≤1.60 |
| P | ≤0.025 | ≤0.025 |
| S | ≤0.020 | ≤0.025 |
| Cu | — | ≤0.55 |
Properties compared
| Property | Q355D | S355K2 |
|---|---|---|
| Yield strength | ≥355 MPa (≤16 mm) | ≥355 MPa (≤16 mm) |
| Tensile strength | 470–630 MPa | 470–630 MPa |
| Impact | −20 °C, ≥34 J | 40 J at −20 °C |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
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: Q355D · S355K2. Substitution decisions for certified parts stay with the design authority.