S350GD steel is a high-strength hot-dip galvanized structural steel grade compliant with the European EN 10346 standard, with the material number 1.0529. Its core defining feature is a minimum yield strength of 350 MPa, combined with a protective zinc coating for long-term corrosion resistance. As a versatile low-alloy structural steel, S350GD steel integrates excellent mechanical performance, formability, and weldability, making it widely used in construction, automotive, and renewable energy projects. It has clear equivalent grades across global standards, enabling seamless substitution for cross-border engineering and procurement.
S350GD steel is not a common carbon steel but a specialized hot-dip galvanized structural grade, where "S" stands for structural steel, "350" denotes the minimum yield strength of 350 MPa, and "GD" indicates its hot-dip galvanized processing and structural application orientation. Unlike uncoated high-strength steels, S350GD's zinc coating provides inherent corrosion protection, eliminating the need for additional post-processing in most scenarios.
1. Core Properties of S350GD Steel
S350GD steel's properties are optimized for structural load-bearing and corrosion resistance, balancing strength, processability, and durability. All properties comply with the EN 10346 standard, with slight variations based on coating type and thickness. The key properties include mechanical properties, chemical composition, coating characteristics, and fabrication performance.
1.1 Mechanical Properties (EN 10346)
The mechanical performance of S350GD steel is defined by its high yield strength and good ductility, ensuring reliability in structural applications. The following are the standard minimum values (varies slightly with product thickness):
|
Mechanical Indicator |
Minimum Value |
Notes |
|---|---|---|
|
Yield Strength (Rp0.2/ReH) |
350 MPa |
Applies to thickness ≤3.0mm; decreases slightly with thicker sheets |
|
Tensile Strength (Rm) |
420 MPa |
Typical range: 420–550 MPa, with a 140 MPa span for most specifications |
|
Elongation at Fracture (A80) |
16% |
Decreases with thinner sheets: -2 units for 0.5–0.7mm, -4 units for 0.35–0.5mm, -7 units for <0.35mm |
|
Density |
7.85 g/cm³ |
Consistent with standard structural steels, for engineering weight calculation |
|
Cold Bend Performance |
d=0a (no cracks) |
180° cold bend test, suitable for complex forming processes |
1.2 Chemical Composition (Heat Analysis, ≤%)
S350GD steel is a low-alloy steel with strict control over impurity elements to ensure weldability and toughness. The standard chemical composition (per EN 10346) is as follows:
|
Element |
Maximum Content |
Key Function |
|---|---|---|
|
Carbon (C) |
0.20% |
Controlled to maintain good weldability and formability |
|
Silicon (Si) |
0.60% |
Aids deoxidation during steelmaking, enhancing surface quality |
|
Manganese (Mn) |
1.70% |
Improves strength and toughness without reducing ductility |
|
Phosphorus (P) |
0.10% |
Minimized to avoid brittle fracture, especially in low temperatures |
|
Sulfur (S) |
0.045% |
Controlled to enhance ductility and weldability |
|
Microalloys (Nb/V/Ti) |
0.15% |
Refines grain structure, balancing strength and formability |
S350GD steel has a carbon equivalent (CEV) ≤0.48%, ensuring excellent weldability. No preheating is required for thickness ≤35mm at ambient temperatures ≥0°C, simplifying fabrication processes such as arc welding and spot welding.
1.3 Coating Properties
As a hot-dip galvanized steel, the zinc coating is a core feature of S350GD steel, providing long-term corrosion protection. It offers six coating variants to adapt to different environmental conditions:
+Z: Hot-dip zinc coating, standard variant with good corrosion resistance for general environments
+ZF: Hot-dip zinc coating with a fine spangle surface, suitable for subsequent painting
+ZA: Zinc-aluminum alloy coating, enhanced corrosion resistance for harsh environments
+ZM: Zinc-magnesium alloy coating, superior protection against salt spray and urban pollutants
+AZ: Aluminum-zinc alloy coating (55% Al + 43.4% Zn + 1.6% Si), ideal for coastal and industrial areas
+AS: Aluminum-silicon alloy coating, suitable for high-temperature applications
Common coating weights range from Z140 to Z275 (g/m² total), with Z275 offering the highest corrosion resistance, extending the service life of S350GD steel in outdoor and corrosive environments by 2–3 times compared to uncoated steel.
1.4 Fabrication Properties
Weldability: Excellent, with low carbon equivalent and uniform microstructure, suitable for spot welding, CO₂ gas shielded welding, and arc welding without special process adjustments.
Formability: Good dimensional stability and ductility, allowing for cutting, bending, stamping, and roll forming, suitable for complex structural components.
Machinability: Easy to process with standard tools, ensuring high precision in cutting and drilling operations.
Global Equivalent Grades of S350GD Steel
S350GD steel has well-established equivalent grades across major regional standards, ensuring seamless substitution for cross-border projects, international procurement, and project compliance. The equivalents maintain similar yield strength, corrosion resistance, and mechanical performance, with slight variations in coating standards and impurity limits.
|
Region |
Equivalent Grade |
Standard |
Key Matching Indicators |
Coating Compatibility |
|---|---|---|---|---|
|
Europe (Reference) |
S350GD+Z/ZF/ZA |
EN 10346 |
Yield strength ≥350 MPa, tensile strength ≥420 MPa |
Z140–Z275, AZ series |
|
United States |
ASTM A653 Grade 80 (G90) |
ASTM A653 |
Yield strength ≥350 MPa, tensile strength ≥448 MPa |
G60–G90 (60–90 g/m² total) |
|
China |
Q355GNHd / S350GD (Baosteel Q/BQB 425) |
GB/T 2518 / Q/BQB 425 |
Yield strength ≥345–350 MPa, functional match for most applications |
Z140–Z275, AZ series |
|
Japan |
SGHC 440 / SGLC490 |
JIS G3302 / JIS G3321 |
Yield strength ≥340–350 MPa, compatible for structural use |
Z120–Z275 |
|
South Korea |
SS 490 Gal |
KS D3506 |
Yield strength ≥340 MPa, matches S350GD's load capacity |
Z140–Z275 |
|
Australia/New Zealand |
G350 |
AS/NZS 3678 |
Yield strength ≥350 MPa, high-strength structural grade |
Zinc-aluminum alloy coating |
3. Typical Applications of S350GD Steel
S350GD steel's combination of high strength, corrosion resistance, and formability makes it a preferred choice for structural applications across industries, especially those exposed to harsh environments. Common applications include:
Construction: Load-bearing frames, columns, and beams for industrial halls and bridges; trapezoidal and standing seam roof/facade profiles; cold-formed sections (purlins, channels); sandwich and composite wall/ceiling panels for logistics centers.
Renewable Energy: Substructures for photovoltaic (solar) mounting systems, leveraging low maintenance and high load-bearing capacity.
Automotive: Chassis components, body panels, and structural parts, benefiting from its strength and corrosion resistance.
Drainage & Infrastructure: Gutters, downpipes, and rainwater barrels, durable in salty or urban environments; safety barriers and sound insulation wall panels for roads and railways.
Machinery & Equipment: Frames for mining machinery, crane components, and heavy-duty equipment, relying on its strength-to-weight ratio.
Agriculture: Greenhouse structures, resistant to outdoor weathering.
Photovoltaic Bracket Solar Mounting System：Photovoltaic support systems are the "skeleton" of a photovoltaic power station, referring to the metal structures used to install, support, and fix solar photovoltaic modules.
Frequently Asked Questions (FAQ)
1. What is S350GD steel exactly?
S350GD steel is a high-strength hot-dip galvanized structural steel compliant with EN 10346 (material number 1.0529). It has a minimum yield strength of 350 MPa, a protective zinc coating for corrosion resistance, and is designed for structural applications requiring strength and durability.
2. What do the letters "S", "350", and "GD" stand for in S350GD?
"S" = Structural steel (indicating its use for load-bearing applications); "350" = Minimum yield strength of 350 MPa; "GD" = Galvanized dual-phase or galvanized structural grade, referring to its hot-dip galvanized processing.
3. What are the key mechanical properties of S350GD steel?
S350GD steel has a minimum yield strength of 350 MPa, minimum tensile strength of 420 MPa, elongation of ≥16%, and a density of 7.85 g/cm³. It also has excellent formability and weldability.
4. What is the equivalent of S350GD steel in the US?
The US equivalent of S350GD steel is ASTM A653 Grade 80 (G90), which has a minimum yield strength of 350 MPa and a G90 zinc coating, matching S350GD's performance for structural applications.
5. Can Q355 steel replace S350GD steel directly?
Chinese Q355GNHd (a galvanized variant of Q355) is a functional equivalent for most applications, though its yield strength (345 MPa) is slightly lower. Uncoated Q355 cannot replace S350GD, as it lacks the protective zinc coating.
6. What coating options are available for S350GD steel?
S350GD offers six coating variants: +Z (standard zinc), +ZF (fine spangle zinc), +ZA (zinc-aluminum), +ZM (zinc-magnesium), +AZ (aluminum-zinc), and +AS (aluminum-silicon), adapting to different environmental conditions.
7. Is S350GD steel suitable for outdoor use?
Yes. Its hot-dip zinc coating provides long-term corrosion resistance, making it ideal for outdoor applications such as roof profiles, bridge components, and solar mounting systems, even in coastal or industrial areas.
8. What forms of S350GD steel are available?
S350GD steel is primarily available as coils, slit coils, and cut-to-length sheets, with thicknesses ranging from 0.40–4.00 mm and widths up to 1620 mm, supporting customization for various project needs.