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Q355B STRUCTURAL STEEL PLATE

Chemical element composition – hot-rolled Q355B low-alloy high-strength steel 🔍 Q355B Grade Lookup →

Product Overview

Q355B is a Chinese grade low-alloy high-strength structural steel conforming to GB/T 1591-2018 standard. Grade B provides guaranteed impact toughness at 20°C. With minimum yield strength of 355MPa (≤16mm) and excellent comprehensive properties, it is widely used in bridges, buildings, vehicles, pressure vessels, and general engineering structures. Q355B is the new designation that replaces the previous Q345B grade.

Equivalent grades: Q355B ↔ Q345B (domestic replacement), S355JR (EN 10025-2), S355B (ISO 630-2), ASTM A572 Gr.50 (USA).

International Grade Comparison

Europe (EN 10025-2)

S355JR

Impact: 20°C (27J)

Yield: 355MPa

C: ≤0.24%

Si: ≤0.55%

Mn: ≤1.60%

P: ≤0.035%

S: ≤0.035%

ISO 630-2

S355B

Impact: 20°C (27J)

Yield: 355MPa

C: ≤0.24%

Si: ≤0.55%

Mn: ≤1.60%

P: ≤0.035%

S: ≤0.035%

USA (ASTM A572)

Gr.50

Impact: Not specified

Yield: 345MPa

C: ≤0.23%

Si: ≤0.40%

Mn: ≤1.35%

P: ≤0.030%

S: ≤0.030%

China (GB/T 1591)

Q390D

Impact: -20°C (34J)

Yield: 390MPa

C: ≤0.20%

Si: ≤0.50%

Mn: 1.00-1.70%

P: ≤0.025%

S: ≤0.025%

China (GB/T 1591)

Q355B

Impact: 20°C (34J)

Yield: 355MPa

C: ≤0.20%

Si: ≤0.55%

Mn: ≤1.60%

P: ≤0.035%

S: ≤0.035%

Note: Q355B offers 20°C impact toughness comparable to S355JR and S355B; always verify specific requirements before substitution.

China Grade Comparison: Q355B vs Q355C vs Q355D

Q355B

Grade B

Impact: 20°C

KV2 (L): 34J

C: ≤0.20%

P: ≤0.035%

S: ≤0.035%

Q355C

Grade C

Impact: 0°C

KV2 (L): 34J

C: ≤0.20%

P: ≤0.030%

S: ≤0.030%

Q355D

Grade D

Impact: -20°C

KV2 (L): 34J

C: ≤0.20%

P: ≤0.025%

S: ≤0.025%

Note: Q355 series grades share identical tensile properties. The key differences are impact test temperature and impurity limits: B (20°C, 34J), C (0°C, 34J), D (-20°C, 34J), with progressively tighter P/S control for lower temperatures.

Key Advantages

Excellent Weldability

Low carbon content (≤0.20-0.22%) and low carbon equivalent (CEV ≤0.45) ensure superior weldability.

High Strength

Minimum yield strength of 355MPa (≤16mm) and tensile strength 470-630MPa.

Cost-Effective

Q355B replaces Q345B with improved properties while maintaining excellent cost-effectiveness.

Applications

Building Structures

High-rise buildings, industrial plants, steel structure workshops

Bridge & Transport

Highway bridges, railway bridges, vehicle frames

Q355B Chemical Composition (GB/T 1591-2018)

Grade C (≤40mm) C (>40-250mm) Si Mn P S Nb V Ti
Q355B ≤0.20 ≤0.22 ≤0.55 ≤1.60 ≤0.035 ≤0.035 ≤0.05 ≤0.12 ≤0.05

Q355B Mechanical Properties (GB/T 1591-2018)

Upper yield strength ReH/MPa ≥

Grade ≤16mm >16-40mm >40-63mm >63-80mm >80-100mm >100-150mm >150-200mm >200-250mm
Q355B 355 345 335 325 315 295 285 275

Tensile Strength Rm (MPa)

Grade ≤100mm >100-150mm >150-250mm
Q355B 470-630 450-600 450-600

Elongation A (%) min.

Grade Direction ≤40mm >40-63mm >63-100mm >100-150mm >150-250mm
Q355B Longitudinal 22 21 20 18 17
Transverse 20 19 18 17 17

Impact Energy KV2 at 20°C (J) min.

Grade Longitudinal Transverse
Q355B 34 27

Size & Specification

Product Form Thickness (mm) Width (mm) Length (mm)
Plate 3 - 250 1000 - 4000 3000 - 18000
Sheet / Coil 1.5 - 20 900 - 2000 Coil or cut to length

Customizable Options

Custom Dimensions
Surface Treatments
Edge Preparation
Custom Heat Treatment
Special Testing
Custom Marking

Quality & Manufacturing Assurance

Modern Production

Advanced continuous casting and controlled rolling

In-process Inspection

Spectral analysis, mechanical testing, 20°C impact

Full Documentation

Mill Test Certificate EN 10204 3.1

Packaging & Logistics

  • Packaging: Steel plates bundled with steel straps on wooden skids.
  • Marking: Each bundle marked with grade, size, heat number, weight.
  • Logistics: FOB, CIF, CFR from main Chinese ports. Lead time 25-35 days.

Frequently Asked Questions

Carbon content? ≤0.20% for ≤40mm and ≤0.22% for >40-250mm.
Weldability? Excellent due to low carbon equivalent (CEV ≤0.45).
Thickness range? 3mm to 250mm in standard plate form.
Q355B vs Q345B? Q355B replaces Q345B with 10-15MPa higher yield.
Mill certificates? EN 10204 Type 3.1 or 3.2 available.
MOQ? 5 tons for stock sizes, negotiable for mill orders.

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