Q355NHB is a weather-resistant steel plate, which also belongs to the low-alloy series.
The letter Q is the first letter of the Chinese phonetic alphabet for yielding.
The number 355 refers to the yield strength of 355MPa. The letter HN is the first letter of Chinese phonetic alphabet weather-resistant.
The letter B stands for level. Q355NHB weathering steel plate has the characteristics of rust resistance, corrosion resistance and longevity of components, thinning and consumption reduction, and labor and energy saving.
Q355NHB weathering steel plate characteristics:
1. Excellent Atmospheric Corrosion Resistance
The most important characteristic of Q355NHB weathering steel is its ability to form a stable protective oxide layer (patina) on the surface when exposed to the atmosphere.
- Alloying elements such as Cu, Cr, and Ni promote patina formation
- The patina effectively slows further corrosion
- Atmospheric corrosion resistance is 2–8 times higher than ordinary carbon steel
- Suitable for unpainted or lightly coated structures
- This significantly reduces long-term maintenance costs.
2. High Strength and Stable Mechanical Properties
Q355NHB provides a good balance between strength and toughness:
- Minimum yield strength: 355 MPa
- Tensile strength: 470–630 MPa
- Good elongation and ductility
These characteristics ensure structural safety under static and dynamic loading conditions.
3. Good Impact Toughness (Grade B)
As a Grade B weathering steel:
- Q355NHB meets specified impact toughness requirements at room temperature
- Suitable for standard outdoor environments and general climate conditions
For colder environments, higher grades such as Q355NHC, Q355NHD, or Q355NHE may be selected.
4. Excellent Weldability
Q355NHB weathering steel plate shows good weldability due to:
- Controlled carbon equivalent
- Balanced alloy content
It can be welded using appropriate weathering steel welding consumables, helping maintain corrosion resistance in welded joints.
5. Good Formability and Machinability
Q355NHB steel plate is suitable for common fabrication processes:
- Flame, plasma, and laser cutting
- Cold bending and forming
- Drilling and machining
This makes it easy to process into complex structural components.
6. Hot Rolled Plate (HRP) Delivery Condition
Q355NHB weathering steel plates are commonly supplied in:
- Normalized (N) condition
- TMCP (Thermo-Mechanical Controlled Process) condition
Both delivery conditions ensure uniform microstructure and stable mechanical performance.
The use of Q355HNB weathering steel plate:
1. Bridge Engineering
It is used for the main girders, piers, inspection channels and guardrails of urban overpasses, railway bridges, highway bridges and cross-river/coastal bridges. Its salt spray and humidity resistance can adapt to the harsh environment of bridges in coastal or river-crossing areas, and high strength can bear the long-term dynamic load of traffic, avoiding structural deformation and corrosion damage.
2. Building & Architectural Engineering
Applied to the steel frames, external curtain walls, roof panels and decorative structural parts of large public buildings such as stadiums, airport terminals, exhibition centers and industrial plants. It can form a unique natural rust patina on the surface after outdoor exposure, realizing the integration of structural performance and architectural aesthetics; it is also used for the load-bearing frames of open-air storage buildings and logistics warehouses, suitable for long-term outdoor use.
3. Transportation Equipment Manufacturing
Manufactures the car bodies, frame structures and container frames of railway freight cars, as well as subway platform canopies, highway guardrails and port terminal auxiliary facilities. Its good forming and welding performance is easy to process into various structural parts of transportation equipment, and corrosion resistance can adapt to the outdoor operation environment of equipment in rain, snow and road salt erosion.
4. Coastal & Outdoor Infrastructure
Used for coastal defense engineering, port crane bases, wharf steel structures, transmission towers, substation frames and highway billboard frames. It has strong resistance to industrial atmosphere, acid rain and coastal salt spray corrosion, and can maintain structural integrity in high-humidity, high-salt and industrial waste gas environments, suitable for the construction of infrastructure in coastal industrial zones and harsh outdoor areas.
5. Heavy Machinery & Open-Air Equipment
Applied to the frame structures of mining machinery, agricultural machinery and open-air industrial cranes, as well as the supporting parts of port and bulk cargo handling equipment. High strength can bear the heavy load of machinery operation, and weather resistance can avoid rapid corrosion of equipment in open-air working conditions, extending the service life of mechanical parts.
6. Municipal & Public Facilities
Used for the steel structures of urban public squares, open-air scenic spot facilities, garbage treatment plants and water conservancy project auxiliary structures. It meets the low-maintenance demand of municipal facilities (no regular painting and rust removal), reduces the later maintenance investment of urban public projects, and is in line with the green and low-carbon construction concept of modern cities.
All above applications of Q355NHB weathering steel plate can be matched with hot-rolled
Q355NHB Chemical Composition (wt%)
| Element | C | Si | Mn | P | S | Cr | Ni | Cu |
|---|---|---|---|---|---|---|---|---|
| Content | 0.12–0.21 | 0.20–2.00 | 0.50–1.50 | ≤0.030 | ≤0.030 | 0.40–0.80 | ≤0.65 | 0.25–0.55 |
Key alloying elements:
Cu, Cr, Ni – promote formation of a compact protective oxide layer
Si & Mn – improve strength and deoxidation
Low P & S – ensure good toughness and weldability
Mechanical Properties
| Property | Requirement |
|---|---|
| Yield Strength (Rp0.2) | ≥ 355 MPa |
| Tensile Strength (Rm) | 490 – 630 MPa |
| Elongation (A) | ≥ 21 % |
| Impact Energy (KV, −20°C) | ≥ 41 J |
| Reduction of Area (Z) | ≥ 23 % |
If you want to learn more about GNEE's products, you can send an email to alloy@gneesteelgroup.com. We are more than happy to assist you.
Q: Can Q355NHB be exported?
A: Yes, Q355NHB can be exported, with ISO, SGS, and other certification documents to meet international project requirements.
Q: What after-sales support is provided for Q355NHB?
A: After-sales support for Q355NHB includes technical consultation, quality problem handling, and relevant document supplement.
Q: How to accelerate the formation of the protective rust layer on Q355NHB's surface?
A: Sandblasting the surface of Q355NHB can accelerate the formation of a stable and dense protective rust layer.
Q: If Q355NHB is painted, what surface treatment is required to ensure coating adhesion?
A: If painting Q355NHB, remove surface oxide scale first through sandblasting or pickling to ensure coating adhesion.
Q: What maintenance measures are needed for Q355NHB structures during long-term use?
A: Long-term use of Q355NHB structures requires regular inspection of the rust layer, with no additional maintenance needed under normal circumstances.
