Q420NB STRUCTURAL STEEL
Product Overview
Q420NB 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 420MPa, it provides higher strength than Q355 and Q390 series and is widely used in bridges, buildings, pressure vessels, and engineering structures requiring enhanced load-bearing capacity.
International Grade Comparison
Europe (EN 10025-3)
S420N
Impact: -20°C (40J)
Yield: 420MPa
C: ≤0.20%
Si: ≤0.60%
Mn: 1.00-1.70%
P: ≤0.025%
S: ≤0.020%
Nb: ≤0.05%
V: ≤0.12%
Ti: ≤0.05%
China (GB/T 1591)
Q420NB
Impact: 20°C (34J)
Yield: 420MPa
C: ≤0.20%
Si: ≤0.60%
Mn: 1.00-1.70%
P: ≤0.035%
S: ≤0.035%
Nb: 0.01-0.05%
V: 0.01-0.20%
Ti: 0.006-0.05%
Delivery: Normalized / N+T
USA (ASTM A572)
Gr.60
Impact: Not specified
Yield: 415MPa
C: ≤0.26%
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)
Q420B
Impact: 20°C (34J)
Yield: 420MPa
C: ≤0.20%
Si: ≤0.60%
Mn: 1.00-1.70%
P: ≤0.035%
S: ≤0.035%
Nb: 0.01-0.05%
V: 0.01-0.20%
Ti: 0.006-0.05%
Delivery: As-rolled / Normalized
China Grade Comparison: Q420B vs Q420NB
Q420B
Yield: 420MPa
Impact 20°C: 34J
P: ≤0.035%
S: ≤0.035%
Delivery: As-rolled or normalized
Q420NB
Yield: 420MPa
Impact 20°C: 34J
P: ≤0.035%
S: ≤0.035%
Delivery: Normalized (guaranteed grain refinement)
Key Advantages
Higher Strength
Min yield 420MPa (≤16mm), tensile 520-680MPa.
Normalized Condition
Delivered normalized/N+T for refined grain structure.
Good Weldability
Low carbon equivalent, excellent welding performance.
Applications
Building Structures
High-rise buildings, stadiums, industrial facilities.
Heavy Machinery
Crane booms, mining equipment, bridge components.
Shipbuilding
Hull structures, offshore platforms.
Q420NB Chemical Composition (GB/T 1591-2018)
Chemical element composition of Chinese grade Q420NB low alloy high strength structural steel
Q420NB Approximate Grade Lookup Table
| Grade | Quality | C | Si | Mn | P | S |
| Q420N | B | ≤0.20 | ≤0.60 | 1.00-1.70 | ≤0.035 | ≤0.035 |
| Nb | V | Ti | Cr | Ni | Cu | Mo | N | Als (min) |
| 0.01-0.05 | 0.01-0.20 | 0.006-0.05 | ≤0.3 | ≤0.8 | ≤0.4 | ≤0.1 | ≤0.015 | ≥0.015 |
Notes:
a. For structural steel and bar stock, the upper limit for phosphorus and sulfur content can be increased by 0.005%.
b. V+Nb+Ti≤0.22%, Mo+Cr≤0.30%.
c. Ti can be as high as 0.20%.
d. All-aluminum (Alt) can be used as a substitute, in which case the minimum content of all-aluminum is 0.020%. When grain-refining elements such as niobium, vanadium, and titanium are added to the steel and their content is not less than the lower limit specified in the table, there is no limit to the lower limit of aluminum content.
e. The steel should contain at least one of the grain-refining elements such as aluminum, niobium, vanadium, and titanium. When added alone or in combination, the content of at least one alloying element should not be less than the lower limit specified in the table.
Q420NB 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 | |
| Q420NB | 420 | 400 | 390 | 370 | 360 | 340 | 330 | 320 | |
| Property | Thickness Range | Value |
| Tensile Strength Rm | ≤100mm | 520-680 MPa |
| 100-200mm | 500-650 MPa | |
| 200-250mm | 500-650 MPa | |
| Elongation A % | ≤16mm | 19% |
| 16-40mm | 19% | |
| 40-63mm | 19% | |
| 63-80mm | 18% | |
| 80-200mm | 18% | |
| 200-250mm | 18% |
| Impact Temperature | 20°C | |
| KV2 (J) ≥ | Longitudinal | 34 |
| Transverse | 27 | |
Notes: Normalized condition includes normalized and tempered condition. When yield not obvious, use Rp0.2.
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 available upon request. Custom cutting available.
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 |
Quality & Manufacturing Assurance
Modern Production
Normalized heat treatment for grain refinement.
In-process Inspection
Spectral analysis & mechanical testing.
MTC 3.1/3.2
Full documentation & traceability.
Packaging & Logistics
- Packaging: Bundled plates with steel straps on wooden skids / coils wrapped waterproof.
- Marking: Each bundle/coil marked with grade, size, heat number, weight.
- Logistics: FOB, CIF, CFR from main Chinese ports. Lead time 25-35 days.
Request a Quote
Emails go directly to customize@cehesteel.com — reply within 2h.
Frequently Asked Questions
Q420NB is a normalized low-alloy high-strength steel per GB/T 1591-2018, with minimum yield strength 420MPa and guaranteed impact toughness of 34J at 20°C (longitudinal).
Q420NB is comparable to Q420B (domestic), EN 10025 S420N (Europe), and ASTM A572 Grade 60 (USA).
Same chemical composition. NB is normalized with guaranteed grain refinement, B can be as-rolled or normalized.
Nb 0.01-0.05%, V 0.01-0.20%, Ti 0.006-0.05%, Als ≥0.015%.
Excellent with low CE and fine grain normalized structure.
3mm to 250mm plates, 1.5-20mm coils/sheets with custom cutting available.