1.A588 GrA structural steel angle

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Weathering steel angle (also called corrosion-resistant steel angle, Corten steel angle) is hot-rolled angle steel with alloying elements such as Cu, Cr, Ni, P to form a dense protective rust layer under atmospheric exposure.

 

It is widely used in bridges, steel structures, curtain walls, transmission towers, outdoor frames, and landscape engineering.

 

2.Main Material Grades & Standards

 

2.1 Chinese Standard (GB/T 4171) – Most Common

Grade	Key Property	Typical Application
Q235NH	General weathering steel, yield strength ≥235MPa	General outdoor structures, simple steel frames
Q295NH	Medium strength & weather resistance	Steel structures, support frames, brackets
Q355NH	High strength + good weatherability; most popular	Bridges, curtain walls, steel structures, towers
Q355GNH	High weather resistance (better than Q355NH)	Coastal, industrial, high-corrosion environments
Q460NH	High-strength weathering steel	Large-span structures, heavy-duty components

Toughness levels (by suffix):

A / B / C / D / E: indicating impact test temperature from 0℃ down to -40℃Example: Q355NHD, Q355NHE for cold regions.

 

Difference Between Q235NH, Q295NH, Q355NH, Q355GNH, Q460NH

All are weathering structural steels (GB/T 4171) with added Cu/Cr/Ni/P for atmospheric corrosion resistance. The main differences are strength level, corrosion resistance, and application scenarios.

 

Core Mechanical Properties (≤16mm thickness)

Grade	Min Yield Strength (MPa)	Tensile Strength (MPa)	Min Elongation (%)	Key Strength Level
Q235NH	≥235	360–510	≥25	Low-strength weathering steel
Q295NH	≥295	430–560	≥24	Medium-strength weathering steel
Q355NH	≥355	490–630	≥20	High-strength weathering steel (most popular)
Q355GNH	≥355	490–630	≥19	High-strength + high weathering steel
Q460NH	≥460	550–710	≥17	Ultra-high-strength weathering steel

 

2. Corrosion Resistance (Key Distinction)

Q235NH / Q295NH / Q355NH: Standard weathering resistance (NH = Normal Weathering). Good for general outdoor use.

Q355GNH: G = High Weathering → 2–8× better corrosion resistance than Q355NH, especially in coastal/industrial/salt-fog environments.

Q460NH: Standard weathering resistance (same as NH series), focused on ultra-high strength.

 

3. Chemical Composition (Simplified)

Grade	C (max)	Cu	Cr	Ni	P
Q235NH	≤0.16	0.25–0.55	0.40–0.80	0.20–0.50	0.07–0.15
Q295NH	≤0.16	0.25–0.55	0.40–0.80	0.20–0.50	0.07–0.15
Q355NH	≤0.16	0.25–0.55	0.40–0.80	0.20–0.50	0.07–0.15
Q355GNH	≤0.12	0.25–0.55	0.30–1.25	0.20–0.75	0.07–0.15
Q460NH	≤0.16	0.25–0.55	0.40–0.80	0.20–0.50	0.07–0.15

Note: Q355GNH has higher Cr content for superior corrosion protection.

 

4. Typical Applications

Grade	Best For
Q235NH	Light structures, landscape, guardrails, simple brackets
Q295NH	Medium-load frames, supports, general welded structures
Q355NH	Bridges, curtain walls, steel structures, towers (most widely used)
Q355GNH	Coastal, industrial, high-corrosion zones; long-life structures
Q460NH	Large-span, heavy-duty, high-rise structures; minimal-section designs

2.2 Transmission Tower Grades (YB/T 4835)

Q355DNHT

Q420BNHT

Special for power transmission towers with high weatherability and mechanical performance.

 

Difference Between Q355DNHT & Q420BNHT

Both are high‑strength weathering steels for transmission towers (per YB/T 4835), with NHT = Normalized + High Weathering + Transmission Tower. The main differences are strength level, low‑temperature toughness, and application load capacity.

 

1. Grade Nomenclature Breakdown

Q355DNHT

Q: Yield strength

355: Min yield strength ≥ 355 MPa (≤16mm)

D: Quality grade → -20°C impact toughness guaranteed

NHT: Normalized + High Weathering + Transmission Tower

Q420BNHT

Q: Yield strength

420: Min yield strength ≥ 420 MPa (≤16mm)

B: Quality grade → +20°C impact toughness guaranteed

NHT: Normalized + High Weathering + Transmission Tower

 

2. Core Mechanical Properties (≤16mm thickness)

Property	Q355DNHT	Q420BNHT	Difference
Min Yield Strength (MPa)	≥355	≥420	Q420BNHT +65 MPa (+18%)
Tensile Strength (MPa)	490–630	520–680	Q420BNHT higher range
Min Elongation (%)	≥20	≥18	Q355DNHT better ductility
Impact Toughness	≥34 J at -20°C	≥34 J at +20°C	Q355DNHT better low‑temp toughness
Weathering Level	High (G‑level)	High (G‑level)	Same excellent corrosion resistance

 

3. Key Design & Application Differences

 

Strength & Load Capacity

Q355DNHT: Standard high‑strength for general transmission towers (110kV–500kV). Balances strength and ductility.

Q420BNHT: Ultra‑high‑strength for heavy‑duty / long‑span / extra‑high‑voltage (EHV) towers (≥500kV). Allows smaller cross‑sections and lighter structures for the same load.

 

Low‑Temperature Performance

Q355DNHT (Grade D): Designed for cold regions (down to -20°C). Safer in northern/winter environments.

Q420BNHT (Grade B): For mild/temperate climates (≥+20°C). Not recommended for severe cold without additional testing.

Cost & Weight

Q355DNHT: More cost‑effective for standard projects.

Q420BNHT: Higher material cost, but saves weight and foundation costs in large towers.

 

4. Typical Applications

Grade	Best For
Q355DNHT	Most transmission towers (110kV–500kV); cold‑region projects; general high‑weathering structures
Q420BNHT	EHV transmission lines; long‑span / heavy‑load towers; high‑altitude / wind‑heavy areas; weight‑optimized designs

2.3 European Standard (EN 10025‑5)

S355J0W

S355J2W (common for export projects)

S460NHWidely used in European construction and engineering projects.

 

2.4 US & International Grades (Corten / ASTM)

Corten A (corresponding to Q235NH / Q295NH)

Corten B (corresponding to Q355NH / Q355GNH)Widely recognized in global markets, especially for landscape and bridge steel.

 

2.5 Japanese Standard (JIS G 3125)

SMA400AW / BW

SMA570W

Used in Japanese-funded projects and Asian markets.

 

3. Key Advantages of Weathering Steel Angle

Excellent atmospheric corrosion resistance

Can be used unpainted or with reduced coating

Longer service life, lower maintenance cost

High strength, good weldability and formability

Stable and aesthetic surface oxide layer

4. Typical Applications

Bridge steel structures

Building curtain wall frameworks

Transmission and telecom towers

Outdoor steel frames & brackets

Landscape architecture, sculptures

Industrial steel structures in coastal or corrosive environments

 

 

Steel grade	Carbon, max, %	Manganese, %	Phosphorus, max, %	Sulfur, max, %	Silicon, %	Nickel, max, %	Chromium, %	Copper	Vanadium, %
A588 Grade A	0.19	0.80 - 1.25	0.04	0.05	0.30 - 0.65	0.40	0.40 - 0.65	0.25 - 0.40	0.02 - 0.10

 

 

Steel grade	Styles	Tensile strength, ksi [MPa]	Yield point, min, ksi [MPa]	Elongation in 8 in. [200 mm], min, %	Elongation in 2 in. [50 mm], min, %
A588 Grade A	Steel angles	70 [485]	50 [345]	18	21

 

 

 

 

 

 

 

 

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