S355G10+M Offshore Steel Plate
EN10225 S355G10+M Offshore Structural Steel Plate Properties & Applications
Comprehensive guide to EN10225 Grade S355G10+M thermomechanically rolled offshore steel: composition, mechanical and physical properties, equivalents, and application examples.
Welding, flame cutting, cold and hot forming, machining, drilling
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S355G10+M Offshore Steel Plate Introduction
S355G10+M is a thermomechanically rolled weldable structural steel grade specified in EN 10225 for fixed offshore structures. It offers a minimum yield strength of 355 MPa for thicknesses up to 16 mm, excellent notch toughness down to -40 °C, and very good weldability due to its controlled chemical composition and processing route.
- Designed for critical structural components in harsh marine environments.
- Low carbon content and micro-alloyed elements ensure good formability and resistance to brittle fracture.
- The +M condition (thermomechanical rolling) imparts a fine-grained microstructure, enhancing strength and toughness without compromising weldability.
S355G10+M Offshore Steel Plate Chemical Composition
Ladle analysis according to EN 10225:2009 (Table 1 and Table 2) for grade S355G10 in the +M condition. All values are maximum limits unless a range or minimum is specified.
- The carbon equivalent (CEV) is typically limited to ≤ 0.43% to ensure good field weldability.
- Fine grain practice and inclusion shape control are mandatory; aluminium is used as a grain refiner.
| Element | Standard Value (max, wt%) | Remarks |
|---|---|---|
| Carbon (C) | ≤ 0.14 | Ladle analysis |
| Silicon (Si) | ≤ 0.50 | - |
| Manganese (Mn) | ≤ 1.65 | - |
| Phosphorus (P) | ≤ 0.020 | - |
| Sulfur (S) | ≤ 0.010 | - |
| Aluminium (Al) | ≥ 0.015 (total) | Grain refining element; acid-soluble Al may also be specified |
| Niobium (Nb) | ≤ 0.05 | - |
| Vanadium (V) | ≤ 0.10 | - |
| Titanium (Ti) | ≤ 0.05 | - |
| Chromium (Cr) | ≤ 0.30 | - |
| Nickel (Ni) | ≤ 0.50 | - |
| Molybdenum (Mo) | ≤ 0.20 | - |
| Copper (Cu) | ≤ 0.35 | - |
| Nitrogen (N) | ≤ 0.012 | - |
| Carbon Equivalent (CEV) | ≤ 0.43 | CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15; typical for plates ≤ 50 mm |
S355G10+M Offshore Steel Plate Thermal & Electrical Physical Properties
Typical physical properties for S355G10+M steel at room temperature unless otherwise noted.
- These values are taken from generic data for similar low-carbon structural steels and are suitable for most engineering calculations.
- Thermal properties vary slightly with temperature; linear thermal expansion coefficient is given between 20 °C and 100 °C.
| Property | Typical Value | Unit | Test Condition |
|---|---|---|---|
| Density (ρ) | ~7850 | kg/m³ | At 20 °C |
| Elastic Modulus (E) | ~210 | GPa | At 20 °C |
| Shear Modulus (G) | ~81 | GPa | Calculated from E and Poisson ratio |
| Poisson Ratio (ν) | ~0.3 | - | At 20 °C |
| Thermal Expansion Coefficient (α) | ~12.0 × 10⁻⁶ | K⁻¹ | Between 20 °C and 100 °C |
| Thermal Conductivity (λ) | ~50 | W/(m·K) | At 20 °C |
| Specific Heat Capacity (c) | ~460 | J/(kg·K) | At 20 °C |
| Electrical Resistivity (ρ_e) | ~0.23 | μΩ·m | At 20 °C |
S355G10+M Offshore Steel Plate Mechanical Properties
Tensile and impact properties for plates in the +M condition tested in the transverse direction, as required by EN 10225.
- Yield strength values are for the upper yield point (ReH) or 0.2% proof stress (Rp0.2) if no yield phenomenon appears.
- Impact test temperature for G10 quality is -40 °C; minimum average absorbed energy is 27 J (longitudinal) or 20 J (transverse) according to client specification.
- Bend test is carried out on a specimen with width ≥ plate thickness; no cracks or defects allowed after 180° bending.
| Property | Required Value | Unit | Test Condition |
|---|---|---|---|
| Yield Strength (ReH) | ≥ 355 | MPa | Thickness t ≤ 16 mm, transverse |
| Yield Strength (ReH) | ≥ 345 | MPa | 16 mm < t ≤ 25 mm, transverse |
| Yield Strength (ReH) | ≥ 335 | MPa | 25 mm < t ≤ 40 mm, transverse |
| Yield Strength (ReH) | ≥ 325 | MPa | 40 mm < t ≤ 63 mm, transverse |
| Yield Strength (ReH) | ≥ 315 | MPa | 63 mm < t ≤ 80 mm, transverse |
| Yield Strength (ReH) | ≥ 300 | MPa | 80 mm < t ≤ 100 mm, transverse |
| Yield Strength (ReH) | ≥ 280 | MPa | 100 mm < t ≤ 150 mm, transverse |
| Tensile Strength (Rm) | 470 – 630 | MPa | All thicknesses up to 150 mm, transverse |
| Elongation (A) | ≥ 22 | % | t ≤ 40 mm, transverse, gauge length 5.65√So |
| Elongation (A) | ≥ 21 | % | 40 mm < t ≤ 63 mm, transverse |
| Elongation (A) | ≥ 20 | % | 63 mm < t ≤ 100 mm, transverse |
| Elongation (A) | ≥ 19 | % | 100 mm < t ≤ 150 mm, transverse |
| Impact Energy (KV2) | ≥ 27 (average) | J | Test temperature -40 °C, longitudinal, V-notch |
| Impact Energy (KV2) – optional trans. | ≥ 20 (average) | J | Test temperature -40 °C, transverse, V-notch |
| Bend Test (mandrel diameter) | 3.5 × t | - | 180° bend, t = plate thickness, specimen width ≥ t, no cracks |
S355G10+M Offshore Steel Plate Identical Material Standards and Substitutable Grades
| Country/Region | Standard/Code | Grade | Remarks |
|---|---|---|---|
| All EU / EEA countries | EN 10225:2009 | S355G10+M | Original designation; identical requirements |
| United Kingdom | BS EN 10225:2009 | S355G10+M | Identical adoption of EN standard |
| Germany | DIN EN 10225:2009 | S355G10+M | Identical; former SE 355 G10+M under DIN 17102 or similar |
| France | NF EN 10225:2009 | S355G10+M | Identical |
| International (ISO) | ISO 19902:2020 (Annex A) | S355G10+M | Referenced from EN 10225; identical properties |
S355G10+M Offshore Steel Plate Application Introduction
S355G10+M plates are extensively used in the offshore industry where reliable weldability and fracture toughness at low temperatures are paramount.
- The steel is designed to resist lamellar tearing and brittle fracture in thick sections.
- Typical applications range from primary structural components of oil platforms to heavy foundations for offshore wind turbines.
- Due to the +M condition, the material can be cold formed and welded without post-weld heat treatment in many cases, simplifying fabrication.
Product Applications: Steel superstructures (topsides) for fixed platforms, Jacket structures and leg nodes, Monopile foundations for offshore wind turbines, Transition pieces joining monopile to turbine tower, Deck plates and grillage beams, Heavy load-bearing pads and crane mounting bases
Processed into products: Welded tubular joints (K-joints, T-joints, Y-joints), Stiffened panels for decks and bulkheads, Transition cones and forging-like thick rolled parts, Mooring system components and anchor points, Lifting padeyes and trunnions, Structural columns and bracing members
Application industries: Offshore Oil & Gas Exploration and Production, Offshore Wind Energy (fixed-bottom and transition pieces), Shipbuilding and Marine Construction (heavy lifting frames, jack-up legs), Civil Engineering (bridge components in aggressive environments)
S355G10+M Offshore Steel Plate Similar / Comparable Substitute Materials
| Country/Region | Standard/Code | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10225 | S355G8+M | Lower toughness requirement (impact tested at -20 °C); similar strength, less suitable for extremely low temperature service. |
| Europe | EN 10225 | S355G9+M | Intermediate toughness (impact tested at -30 °C); can replace G10 where -40 °C not mandatory. |
| Europe | EN 10025-3 | S355N / S355NL | Normalized structural steel; NL grade has -50 °C impact. Similar strength but processing route differs; verify through-thickness properties. |
| USA | API Spec 2H / 2W | Grade 50 (50 ksi min YS) | Offshore platform steel with 345 MPa min yield; may have different chemical restrictions. 2W grades are thermomechanically processed, similar toughness. |
| USA | API Spec 2Y | Grade 50 | Quenched and tempered structural steel for offshore use; higher strength and toughness, but processing route differs; consult specification for substitution. |
| Norway | NORSOK M-120 | Y35 (S355MLO) | Thermomechanically rolled steel for substructures; impact test at -40 °C, but nitrogen and oxygen limitations; generally acceptable as alternative. |
Notes:
Supplementary information:
- The +M condition is achieved by controlled rolling with accelerated cooling, which imparts a fine ferritic-pearlitic microstructure; this differentiates S355G10+M from normalized (N) or quenched+tempered (QT) grades.
- Plates are typically supplied with certificates type 3.1 or 3.2 according to EN 10204, including chemical analysis, tensile, impact, and optional through-thickness (Z-grade) testing.
- Preheating and interpass temperature control during welding are recommended according to EN 1011-2 based on plate thickness and hydrogen scale; post-weld heat treatment is usually not required for thicknesses below 50 mm.
- For applications requiring guaranteed through-thickness ductility (e.g. lamellar tearing resistance), order with the additional designation +Z35 (EN 10164) to ensure minimum reduction of area in Z-direction.
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