SPA-H and Q355NH (B / C / D / E) are widely used hot-rolled weathering steel plates (HRP) designed for structural applications exposed to atmospheric environments. These steels are engineered to provide enhanced corrosion resistance, high strength, and long service life without heavy surface coatings.
- SPA-H: Japanese standard weather-resisting steel (JIS G3125)
- Q355NH(B/C/D/E): Chinese GB/T standard atmospheric corrosion-resistant structural steel
Both grades are commonly referred to as Weather Resisting Steel Plates and are ideal for bridges, buildings, railway vehicles, containers, and outdoor industrial structures.
GNEE Steel supplies SPA-H and Q355NH weathering steel plates with stable quality, global export experience, and customized solutions.
SPA-H Weathering Steel Plate (JIS G3125)
SPA-H is a weather-resisting steel grade specified under JIS G3125, widely used in international infrastructure and transportation projects.
Key Characteristics of SPA-H
- Excellent atmospheric corrosion resistance
- Stable mechanical properties
- Good weldability and formability
- Suitable for unpainted or lightly coated structures
SPA-H is often considered technically comparable to Q355NH weathering steel, depending on project standards.
Q355NH(B / C / D / E) Weathering Steel Plate (GB/T Standard)
Meaning of Q355NH Designation
Q – Yield-strength-based structural steel
355 – Minimum yield strength: 355 MPa
N – Normalized or TMCP delivery condition
H – Weathering (atmospheric corrosion-resistant) steel
B / C / D / E – Impact toughness grade
Impact Toughness Grades
| Grade | Impact Test Temperature |
|---|---|
| Q355NHB | +20°C |
| Q355NHC | 0°C |
| Q355NHD | −20°C |
| Q355NHE | −40°C |
This grading system allows precise material selection based on climate and service temperature.
Key Performance Advantages
✅ Superior Atmospheric Corrosion Resistance
All grades form a stable α-FeOOH protective rust layer after outdoor exposure, with a corrosion rate of 0.02-0.04mm/year in industrial/coastal environments, realizing bare use without painting and reducing long-term maintenance costs by 40-60%. Excellent salt spray and acid rain resistance, suitable for coastal, industrial zones and other harsh outdoor environments.
✅ High Strength & Graded Toughness
SPA-H: Tensile strength 480-620MPa, yield strength ≥295MPa, elongation ≥22%
Q355NHB/C/D/E: Tensile strength 470-630MPa, minimum yield strength 355MPa, elongation ≥21%Graded low-temperature impact toughness meets the construction needs of different climate zones from temperate to severe cold, with no brittle fracture risk.
✅ Excellent Processability & HRP Value-Added Finish
Weldability: Low carbon equivalent (CEV ≤0.42%), suitable for manual arc welding, submerged arc welding, gas metal arc welding; no post-weld heat treatment for most applications.
Machinability: Easy to laser/plasma/shear cutting, bending, rolling and punching; no cracking under standard processing conditions.
HRP finish advantage: Clean surface, direct processing, good coating adhesion (if painting is required), and fast formation of uniform rust patina (for bare use).
✅ Cost-Effective & Eco-Friendly
Lower price than stainless steel and imported weathering steel (20-40% cost saving); "no-paint" application reduces VOC emissions, in line with global green construction and sustainable engineering trends; HRP finish saves customer's secondary descaling cost and shortens project cycle.
SPA-H vs Q355NH Weathering Steel
Chemical Composition Comparison (Typical, wt.%)
Actual composition may vary depending on thickness and production route.
| Element | SPA-H (JIS G3125) | Q355NH (GB/T) |
|---|---|---|
| Carbon (C) | ≤ 0.15 | ≤ 0.16 |
| Silicon (Si) | 0.25 – 0.75 | ≤ 0.55 |
| Manganese (Mn) | ≤ 1.50 | ≤ 1.50 |
| Phosphorus (P) | ≤ 0.035 | ≤ 0.035 |
| Sulfur (S) | ≤ 0.030 | ≤ 0.030 |
| Copper (Cu) | 0.25 – 0.55 | 0.25 – 0.55 |
| Chromium (Cr) | 0.30 – 1.25 | 0.30 – 1.25 |
| Nickel (Ni) | ≤ 0.65 | ≤ 0.65 |
Key Point:
Both SPA-H and Q355NH rely on Cu-Cr-Ni alloying systems to form a dense protective oxide layer, giving them excellent atmospheric corrosion resistance.
Strength Properties
| Property | SPA-H | Q355NH |
|---|---|---|
| Yield Strength | ≥ 355 MPa | ≥ 355 MPa |
| Tensile Strength | 490 – 630 MPa | 470 – 630 MPa |
| Elongation | ≥ 21% | ≥ 20% |
Impact Toughness (Q355NH Grades)
| Grade | Impact Test Temperature | Impact Requirement |
|---|---|---|
| Q355NHB | +20°C | Qualified |
| Q355NHC | 0°C | Qualified |
| Q355NHD | −20°C | Qualified |
| Q355NHE | −40°C | Qualified |
SPA-H:
Impact requirements are defined by JIS G3125 but not subdivided into temperature grades like Q355NH.
Typical Applications
Our SPA-H, Q355NHB/C/D/E and HRP weathering steel plates are widely used in global engineering projects, covering:
Building & Architecture: Outdoor steel frames, curtain walls, roof panels, landscape sculptures, stadiums, airport terminals (HRP plates for direct processing of decorative components)
Bridge & Infrastructure: Highways/railway bridges, overpasses, transmission towers, highway guardrails, subway platform canopies
Coastal & Harsh Environment Engineering: Coastal defense structures, port facilities, offshore platform accessories, salt lake area infrastructure (resist salt spray and chemical corrosion)
Transportation Equipment: Railway freight car bodies, container frames, port crane structures, agricultural/ mining machinery frames
Municipal & Outdoor Facilities: Public square steel structures, garbage treatment plants, water conservancy projects, outdoor billboard frames
FAQ
Q: Is Q355NHB easy to bend, punch, or roll?
A: Q355NHB has good ductility, is easy to bend, punch, and roll, and will not crack under proper processing conditions.
Q: What engineering projects is Q355NHB suitable for?
A: Q355NHB is suitable for outdoor and harsh-environment projects such as bridge construction, building engineering, transportation equipment, and outdoor infrastructure.
Q: Is Q355NHB suitable for coastal areas with high humidity and salt spray?
A: Yes, Q355NHB has good corrosion resistance to salt spray and is suitable for use in coastal high-humidity environments.
Q: What is the difference between Q355NHB and Q355NHA/Q355NHC?
A: The main difference lies in impact toughness levels (A < B < C); choose Q355NHB for general low-temperature requirements, and NHC for harsher cold environments.
Q: Which manufacturers supply high-quality Q355NHB?
A: High-quality Q355NHB is supplied by large steel mills such as Baosteel, Ansteel, and Maanshan Iron & Steel.
Direct Procurement Inquiry
Whether you need SPA-H, Q355NHB/C/D/E weathering steel plates (hot rolled or HRP finish) for spot purchase or customized production for your project, GNEE Steel's professional sales team is ready to provide you with competitive quotes and technical support.
Contact us now to:
- Get free product datasheet and HRP sample
- Obtain FOB/CIF quote based on your quantity, specifications and destination port
- Discuss project-specific technical requirements (low-temperature impact, certification, rust acceleration treatment)
📧 Email:alloy@gneesteelgroup.com
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GNEE Steel – Your Reliable Global Partner for High-Quality Weathering Steel Plate & HRP Solution!
