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Q355NB STRUCTURAL STEEL

Chemical element composition – Chinese grade Q355NB low alloy high strength structural steel 🔍 Q355NB Grade Lookup →

Product Overview

Q355NB is a Chinese grade low-alloy high-strength structural steel conforming to GB/T 1591-2018 standard. It features a normalized or normalized plus tempered delivery condition, offering improved toughness and consistent properties. Grade B provides guaranteed impact toughness at 20°C. With minimum yield strength of 355MPa, it is widely used in building structures and heavy machinery requiring enhanced reliability.

Equivalent grades: Q355NB ↔ Q345B (previous domestic grade), EN 10025 S355JR (Europe), ASTM A572 Grade 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%

Nb: ≤0.05%

V: ≤0.12%

Ti: ≤0.05%

USA (ASTM A572)

Gr.50

Impact: Not specified

Yield: 345MPa

C: ≤0.23%

Si: ≤0.40%

Mn: ≤1.35%

P: ≤0.025%

S: ≤0.025%

Nb: ≤0.05%

V: ≤0.15%

Ti: ≤0.05%

China (GB/T 1591)

Q345B

Impact: 20°C (34J)

Yield: 345MPa

C: ≤0.20%

Si: ≤0.50%

Mn: 1.00-1.60%

P: ≤0.035%

S: ≤0.035%

Nb: ≤0.07%

V: ≤0.15%

Ti: ≤0.20%

Note: Q355NB is the normalized version of Q355B, offering improved toughness and consistent properties compared to hot-rolled grades; always verify specific requirements before substitution.

Grade Comparison: Q355NB vs Q355NC vs Q355ND vs Q355NE vs Q355NF

Q355NB

Grade B

Impact: 20°C

KV2 (L): 34J

C: ≤0.20%

P: ≤0.035%

S: ≤0.035%

Q355NC

Grade C

Impact: 0°C

KV2 (L): 34J

C: ≤0.20%

P: ≤0.030%

S: ≤0.030%

Q355ND

Grade D

Impact: -20°C

KV2 (L): 40J

C: ≤0.20%

P: ≤0.030%

S: ≤0.025%

Q355NE

Grade E

Impact: -40°C

KV2 (L): 31J

C: ≤0.18%

P: ≤0.025%

S: ≤0.020%

Q355NF

Grade F

Impact: -60°C

KV2 (L): 27J

C: ≤0.16%

P: ≤0.020%

S: ≤0.010%

Note: Q355N series grades share identical tensile properties (yield strength, tensile strength, elongation). The key differences are impact test temperature and corresponding impurity limits: B (20°C, 34J), C (0°C, 34J), D (-20°C, 40J), E (-40°C, 31J), F (-60°C, 27J), with progressively tighter P/S control for lower temperatures.

Key Advantages

Normalized Condition

Delivered in normalized or normalized plus tempered state for improved grain refinement and consistent mechanical properties.

Controlled Chemistry

Controlled carbon content and P/S levels ensure excellent weldability and toughness.

20°C Impact Toughness

Grade B provides guaranteed impact energy of 34J at 20°C (longitudinal), suitable for general applications.

Applications

Building Structures

High-rise buildings, industrial plants, stadiums, steel frameworks requiring normalized steel.

Heavy Machinery

Construction machinery, crane booms, mining equipment, heavy vehicles requiring normalized steel.

Q355NB Chemical Composition (GB/T 1591-2018)

Grade Quality C Si Mn P S
Q355N B ≤0.20 ≤0.50 0.90-1.65 ≤0.035 ≤0.035
Nb V Ti Cr Ni Cu Mo N Als (min)
0.005-0.05 0.01-0.12 0.006-0.05 ≤0.3 ≤0.5 ≤0.4 ≤0.1 ≤0.015 ≥0.015

Notes:

a. For bars, P/S upper limit +0.005%.

b. V+Nb+Ti ≤0.22%, Mo+Cr ≤0.30%.

c. Ti up to 0.20% maximum.

d. Alt (total aluminum) can substitute Als with minimum 0.020%. When Nb/V/Ti added at specified levels, Als lower limit not required.

e. Steel must contain at least one grain-refining element (Al, Nb, V, Ti) with content not less than specified minimum.

Q355NB Tensile 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
Q355NB 355 345 335 325 315 295 285 275
Property Thickness Range Value
Tensile Strength Rm ≤100mm 470-630 MPa
100-200mm 450-600 MPa
200-250mm 450-600 MPa
Elongation A % ≤16mm 22%
16-40mm 22%
40-63mm 22%
63-80mm 21%
80-200mm 21%
200-250mm 21%
Impact Temperature 20°C 0°C -20°C -40°C -60°C
KV2 (J) ≥ Longitudinal 34 34 47 31 27
Transverse 27 27 27 20 16

Notes: Normalized condition includes normalized and tempered condition. When yield not obvious, use Rp0.2.

Customizable Options

We offer comprehensive customization services to meet your specific project requirements:

Custom Dimensions
Non-standard sizes, laser cutting		 Surface Treatments
Shot blasting, priming		 Edge Preparation
Beveling, machining
Custom Heat Treatment
Normalizing, stress relieving		 Special Testing
Third-party inspection		 Custom Marking
Special labeling

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

Other sizes can be produced upon request. Custom cutting available.

Quality & Manufacturing Assurance

Modern Production

Advanced continuous casting and normalized heat treatment for optimal grain refinement

In-process Inspection

Rigorous testing at each stage, including spectral analysis and impact testing at 20°C

Full Documentation

Mill Test Certificate (MTC) compliant with EN 10204 3.1/3.2

Packaging & Logistics

  • Packaging: Steel plates bundled with steel straps on wooden skids. Coils wrapped with waterproof paper and steel covers.
  • Marking: Each bundle/coil marked with grade, size, heat number, weight.
  • Logistics: FOB, CIF, CFR from main Chinese ports. Lead time 25-35 days after order.

Request a Quote

Emails go directly to customize@cehesteel.com — reply within 2h.

Frequently Asked Questions

What is Q355NB?

Q355NB is a normalized low-alloy structural steel per GB/T 1591-2018 with 355MPa min yield and 34J impact at 20°C.

What are the equivalents of Q355NB?

Q355NB is comparable to Q345B (previous domestic), EN 10025 S355JR (Europe), and ASTM A572 Grade 50 (USA).

Weldability?

Excellent weldability due to controlled chemistry and fine-grain normalized structure.

Available thickness?

3mm to 250mm plates, 1.5-20mm coils/sheets with custom cutting available.

Mill certificates?

Yes, EN 10204 3.1 MTC with full data including 20°C impact test results.

MOQ?

Standard 5 tons. Sample orders possible.

What are the typical applications of Q355NB?

Q355NB is widely used in building structures and heavy machinery requiring normalized steel.