Corten Steel (weathering steel) is widely used in construction, bridges, transportation and other fields due to its excellent self-protective performance. However, different international standards have formulated diverse grades of Corten Steel, among which ASTM A588 (American standard), EN 10025-5 S355J2W (European standard) and GB/T 4171 Q355NH (Chinese standard) are the most mainstream. The differences in mechanical properties (yield strength, impact toughness) and corrosion resistance among these grades directly affect project selection, service life and cost control. This article will systematically compare these core performance indicators to provide a clear reference for foreign customers.
Mechanical Properties of Grade A588
| GRADE | THICKNESS | TENSILE KSI | YIELD KSI | % ELONG. MIN | |
| 8" | 2" | ||||
| A588 | .75"THRU 4" | 70MIN | 50 YP MIN | 16 | 19 |
| >4"THRU 4" | 67MIN | 46 YP MIN | - | ||
| >5"THRU 8" | 63MIN | 42 YP MIN | |||
Mechanical Properties of S355J2W+N Plate
|
Yield Strength |
Tensile Strength |
Minimum Elongation A (Lo = 5.65 vSo) % |
|
355 MPa |
510 - 680 MPa |
20 |
Mechanical Properties of Q355NH
| Grade | Q355NH mechanical property | |||
| Yield Strength(MPa) | Tensile Strength(MPa) | % Elongation min | ||
| China GB/T 4171 Q355NH | 325-355 | 490-630 | 20 | |
1. Comparison of Mechanical Properties
Mechanical properties are the basic guarantee for the structural safety of Corten Steel, and the key indicators include yield strength (the minimum stress that the material can withstand without permanent deformation) and impact toughness (the ability to resist fracture under sudden load). The following is a detailed comparison of the three grades:
1.1 Yield Strength
Yield strength determines the load-bearing capacity of Corten Steel components. The three grades all belong to medium and high-strength Corten Steel, but there are slight differences in the minimum yield strength requirements:
ASTM A588 (American Standard): The minimum yield strength is ≥ 345 MPa (50 ksi). It is divided into multiple sub-grades (such as Gr.A, Gr.K), and the yield strength requirements of different sub-grades are consistent, mainly differing in impurity content and grain refinement elements (such as Gr.K contains Nb/V to optimize grain structure).
EN 10025-5 S355J2W (European Standard): The minimum yield strength is ≥ 355 MPa, which is 10 MPa higher than A588. The "355" in the grade directly represents the minimum yield strength value, and the standard has strict control over the fluctuation range of yield strength to ensure the stability of structural bearing capacity.
GB/T 4171 Q355NH (Chinese Standard): The minimum yield strength is ≥ 355 MPa, which is the same as S355J2W. Compared with the old version of Q345NH, the yield strength has been increased by 10 MPa, and the overall mechanical performance is aligned with international advanced standards.
1.2 Impact Toughness
Impact toughness is particularly critical for projects in low-temperature environments, as it determines the material's resistance to brittle fracture. The three grades have obvious differences in impact temperature and impact energy requirements:
ASTM A588: The standard requires impact tests at 0℃, and the minimum impact energy is ≥ 27 J. For projects in colder regions (such as -20℃), high-toughness sub-grades need to be customized, and the default grade is not suitable for ultra-low temperature environments.
EN 10025-5 S355J2W: The "J2" in the grade indicates that the impact test is carried out at -20℃, and the minimum impact energy is ≥ 27 J. It has better low-temperature toughness than A588's default grade and is suitable for most temperate and cold regions in Europe.
GB/T 4171 Q355NH: The standard requires impact tests at -20℃, and the minimum impact energy is ≥ 34 J, which is higher than A588 and S355J2W. It has excellent low-temperature performance and is especially suitable for projects in high-cold regions such as northern China.
2. Comparison of Corrosion Resistance
The corrosion resistance of Corten Steel mainly depends on the type and content of alloying elements (Cu, Cr, Ni, P, etc.), which jointly promote the formation of a dense α-FeOOH protective rust layer. The corrosion resistance differences of the three grades are reflected in the alloying element configuration and corrosion resistance index:
2.1 Alloying Element Composition
ASTM A588: It belongs to the Cu-Cr-Ni alloy system, with Cu content of 0.25-0.40%, Cr content of 0.40-0.65%, and Ni content ≤ 0.40%. The phosphorus (P) content is strictly controlled (≤ 0.03%), which prioritizes welding performance while ensuring corrosion resistance. It is a "low-phosphorus type" Corten Steel.
EN 10025-5 S355J2W: The standard clearly requires that the total content of Cu + Cr + Ni ≥ 0.80%, with Cu content of 0.20-0.50%, Cr content of 0.30-1.20%, and Ni content ≤ 0.65%. It can be customized into "high-phosphorus type" (S355J0WP, P content 0.06-0.15%) according to needs, and the high-phosphorus type has better corrosion resistance but slightly reduced welding performance.
GB/T 4171 Q355NH: It adopts the Cu-Cr-Ni alloy system, with Cu content of 0.25-0.55%, Cr content of 0.40-0.80%, and Ni content ≤ 0.65%. The total content of Cu + Cr + Ni is also ≥ 0.80%, which is consistent with S355J2W. It has two types: ordinary type (P ≤ 0.03%) and high-weather resistance type (Q355GNH, P 0.07-0.15%), covering different corrosion environment needs.
2.2 Corrosion Resistance Performance
ASTM A588: The weather resistance index (I) ≥ 6.0, and the annual corrosion rate in industrial and rural atmospheres is 0.015-0.025 mm/year. It is suitable for medium-corrosion environments, and auxiliary anti-corrosion measures (such as silane impregnation) need to be added in high-salt-spray coastal areas.
EN 10025-5 S355J2W: The weather resistance index (I) ≥ 6.0, and the high-phosphorus type (S355J0WP) has a weather resistance index ≥ 7.0. The annual corrosion rate in medium-corrosion environments is 0.010-0.020 mm/year, which is slightly better than A588. The S355J2W(H) sub-grade specially designed for railway bridges has stronger resistance to chloride ion corrosion.
GB/T 4171 Q355NH: The weather resistance index (I) ≥ 6.0, and the high-weather resistance type Q355GNH has a weather resistance index ≥ 7.0. Its corrosion resistance is equivalent to that of S355J2W, and the annual corrosion rate is 0.010-0.020 mm/year. Compared with the other two grades, it has obvious cost advantages (15-20% lower than A588 and S355J2W).
3. Summary and Practical Selection Suggestions
To sum up, the core performance differences of the three mainstream Corten Steel grades are as follows: In terms of mechanical properties, S355J2W and Q355NH have higher yield strength than A588, and Q355NH has the best low-temperature impact toughness; in terms of corrosion resistance, S355J2W and Q355GNH (high-weather resistance type) are better than A588, and Q355NH has the highest cost performance.
For foreign customers, the following selection suggestions are provided according to different project needs:
If the project is located in North America and needs to comply with local standards, or prioritizes welding performance in medium-corrosion environments, ASTM A588 is recommended;
If the project is located in Europe, or needs to be used in low-temperature (-20℃) and medium-high corrosion environments, and has high requirements for performance stability, EN 10025-5 S355J2W is recommended; for high-corrosion environments such as coastal areas, S355J0WP (high-phosphorus type) can be selected;
If the project pursues cost performance, or needs to balance high strength, low-temperature toughness and corrosion resistance, GB/T 4171 Q355NH is recommended; for high-corrosion environments, Q355GNH (high-weather resistance type) can be matched.
