EN10225 Offshore Structural Steel Sheet

EN10225 Offshore structural steel sheet

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EN10225 standard steel plate has good comprehensive mechanical properties, welding performance, and process performance. It is required to ensure technical indicators such as impact energy at 1/2 of the plate thickness, strain aging, and Z-term tensile strength. The technical requirements are significantly higher than ordinary structural steel, and it is a high-end product. . It is mainly used in the manufacturing of key structural parts such as wind power equipment, oil production platforms, and terminal equipment.

 

Delivery Conditions: +N, +M, +QT, +LO - What They Mean

Each grade designation also carries a suffix indicating the delivery condition:

Suffix	Condition	Characteristics
+N	Normalized	Uniform fine-grain microstructure through controlled heating and air cooling; good toughness consistency across thickness
+M	Thermomechanically Rolled (TMCP)	Achieves high strength with low carbon content; excellent weldability with reduced preheat requirements
+QT	Quenched & Tempered	Highest strength levels (up to S690); superior hardness and wear resistance for heavy-duty components
+LO	Low Carbon Equivalent	Optimized for maximum weldability in thick sections; CEV strictly controlled

 

 

S355G2	S355G3	S355G4
S355G5	S355G6	S355G7
S355G8	S355G9	S355G10

 

S355G2+M	S355G3+M	S355G4+M
S355G5+M	S355G6+M	S355G7+M
S355G8+M	S355G9+M	S355G10+M

 

S355G2+N	S355G3+N	S355G4+N
S355G5+N	S355G6+N	S355G7+N
S355G8+N	S355G9+N	S355G10+N

 

 

Nominal Size Thickness (inches)	Weight (lb/ft2)
3/16 inches	7.065
1/4 inches	10.020
5/16 inches	12.075
3/8 inches	15.030
7/16 inches	17.085
1/2 inches	20.040
9/16 inches	22.095
5/8 inches	25.050
11/16 inches	28.005
3/4 inches	30.060
13/16 inches	33.015
7/8 inches	35.070
1 inches	40.080
1 1/8 inches	45.090
1 1/4 inches	51.000
1 3/8 inches	56.010
1 1/2 inches	61.020
1 5/8 inches	66.030
1 3/4 inches	71.040
1 7/8 inches	76.050
2 inches	81.060
2 1/8 inches	86.070
2 1/4 inches	91.080
2 1/2 inches	102.000
2 3/4 inches	112.020
3 inches	122.040
3 1/4 inches	132.060
3 1/2 inches	142.080
3 3/4 inches	153.000
4 inches	163.020
4 1/4 inches	173.040
4 1/2 inches	183.060
5 inches	204.000
5 1/2 inches	224.040
6 inches	244.080
6 1/2 inches	265.020
7 inches	285.060
7 1/2 inches	306.000
8 inches	326.040
9 inches	367.020
10 inches	408.000

 

 

Weight Chart Of EN10025-2 Structural Steel Plate

Plate Thickness (mm)	Weight (kg/m2)
1.06 mm	12.06
2.00 mm	15.07
2.05 mm	19.06
3 mm	23.06
3.02 mm	25.01
4 mm	31.04
5 mm	39.03
6 mm	47.01
8 mm	62.08
10 mm	78.05
12.05 mm	98.01
15 mm	118
20 mm	157
22.05 mm	177
25 mm	196
30 mm	236
32 mm	251
35 mm	275
40 mm	314
45 mm	353
50 mm	393
55 mm	432
60 mm	471
65 mm	510
70 mm	550
75 mm	589
80 mm	628
90 mm	707
100 mm	785
110 mm	864
120 mm	942
130 mm	1051
150 mm	1178
160 mm	1256
180 mm	1413
200 mm	1570
250 mm	1963

 

 

EN 10225 maintains strict limits on impurities like Phosphorus (P) and Sulfur (S) and controls the Carbon Equivalent Value (CEV) to ensure maximum weldability.

Grade	C	Mn	Si	P ≤	S ≤	CEV ≤
S355G2+N	0.20	0.90–1.65	0.50	0.035	0.030	0.43
S355G3+N	0.18	0.90–1.65	0.50	0.035	0.025	0.43
S355G10+M	0.12	≤1.65	0.15–0.55	0.015	0.005	0.43
S420G2+M	0.16	≤1.70	0.50	0.030	0.025	0.45
S460G2+M	0.16	≤1.70	0.50	0.030	0.025	0.47

 

 

Grade	C (max)	Si	Mn	P (max)	S (max)	CEV (max)
S355G7+N / G8+N	0.18%	0.15-0.55%	1.60%	0.020%	0.005%	0.43
S355G7+M / G8+M	0.14%	0.15-0.50%	1.60%	0.020%	0.005%	0.39

 

 

These grades are specifically tested for impact energy at -40°C to ensure the material does not become brittle in freezing ocean waters.

 

Grade	Yield Strength (MPa)	Tensile Strength (MPa)	Elongation (%)	Impact Test Temp.	Min. Impact Energy
S355G2+N	≥355 (t≤16 mm)	470–630	≥22	-20°C	≥27 J
S355G10+M	≥355 (t≤16 mm)	460–630	≥22	-40°C	≥27 J
S420G2+M	≥420 (t≤16 mm)	520–680	≥19	-40°C	≥27 J
S460G2+M	≥460 (t≤16 mm)	550–720	≥17	-40°C	≥27 J
S460QL0	≥460 (t≤50 mm)	550–720	≥17	-40°C	≥27 J

 

Grade	Yield Strength (min)	Tensile Strength	Impact Test (-40°C)	Z-Direction Property
S355G7+M/N	355 MPa	470-630 MPa	min 50J	Optional
S355G8+M/N	355 MPa	470-630 MPa	min 60J	Mandatory (Z35)

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In heavy offshore welded joints, the risk of lamellar tearing - a delamination-type fracture that propagates parallel to the plate surface - is a persistent concern. Lamellar tearing is triggered by high through-thickness shrinkage strains during multi-pass welding of thick sections. EN 10225 addresses this risk through Option 12: the tensile test in the thickness direction, commonly called Z-quality testing.

 

Three Z-quality levels are available:

• Z15: Minimum 15% reduction of area in through-thickness tensile test
• Z25: Minimum 25% reduction of area (standard for most offshore structural applications)
• Z35: minimum 35% reduction of area (mandatory for offshore wind monopile foundations and critical node joints)

GNEE standard practice: All EN 10225 offshore structural steel sheets ≥ 40 mm shipped from our factory are supplied with Z35 through-thickness properties as default - no surcharge, no delays.

 

 

Superior Weldability: The low Carbon Equivalent (CEV) of the +M grades reduces the need for preheating, significantly lowering fabrication costs.

 

Resistance to Lamellar Tearing: G8 grades are typically tested for Z-direction properties, making them ideal for high-stress welded nodes.

 

Low-Temperature Toughness: Guaranteed performance at -40°C prevents brittle fracture in arctic and deep-sea conditions.

 

Fatigue Resistance: Engineered to withstand the constant cyclic loading of waves and wind over a 25+ year service life.

 

 

EN 10225 plates and sections are fundamental to the construction of every major type of permanent offshore installation. The core application areas include:

• Offshore wind turbine foundations: Monopiles, transition pieces, jacket structures and suction buckets - S355 and S420 grades in thicknesses 60–150 mm
• Fixed oil & gas production platforms: Primary structural framing, deck plating, helideck supports and topside module steelwork
• Wellhead protection structures and subsea templates
• Offshore substation platforms (HVAC/HVDC) for wind farm power collection and transmission
• Marine terminal structures, quay walls, breasting dolphins and mooring bollards

Excluded applications (per EN 10225 scope): subsea flowlines, production risers, process pressure vessels and process utility piping.

 

GNEE STEEL can provide dual-certified plates that meet EN 10225 and other global standards:

EN 10225 Grade	API Equivalent (USA)	Shipbuilding Equivalent
S355G7+M	API 2W Gr. 50	ABS/DNV Grade EH36 (TMCP)
S355G7+N	API 2H Gr. 50	ABS/DNV Grade EH36 (Norm.)
S355G8+M	API 2W Gr. 50 (w/ Z-test)	EH36-Z35

 

 

Offshore Specialists: We understand the complex documentation and technical requirements of the offshore energy sector.

 

Premium Supply Chain: Our steel comes from the world's leading mills, ensuring compliance with the latest EN 10225:2019 standards.

 

In-House Processing: We offer CNC plasma/laser cutting, edge beveling, and shot-blasting/priming (SA2.5) to prepare your plates for immediate fabrication.

 

Global Logistics: Decades of experience in exporting heavy steel to major shipyards and offshore hubs worldwide.

 

 

Building offshore requires materials that can survive the world's most unforgiving environments. With GNEE STEEL's EN 10225 S355G7 and S355G8 plates, you get a combination of high strength, weldability, and proven reliability.

Request A Quote

 

Ready to proceed?

Submit your grade, dimensions and quantity using the inquiry form above. One of our offshore steel specialists will confirm availability, pricing and the fastest delivery option to your destination within hours - not days. Let us demonstrate why major offshore fabricators across Europe and Asia trust GNEE as their EN 10225 steel partne

 

 

 

 

 

 

 

 

We have enough EN10225 Offshore structural steel sheet in stock, and we can also customize it according to your needs.

 

Relying on many first-class equipment, such as CNC Shearing machine, Press Brake machine, Straightening machine, Roll Bending machine, Flat Bar Machine, Deburring machine etc, GNEE STEEL could provide various semi-productsand extensive forming services to customers.

 

GNEE STEEL  PROCESSING

1.CTL & SL SERVICE (141 SETS)

Currently, GNEE STEEL has imported manyadvanced CTL/SL equipment from Italy and Korea and could provide customized CTL/SL services from cold rolled stainless steel and carbon steel to hot rolled stainless steel and carbon steel as well as strips and ultra-wide sheet.

CTL FACILITIES
Max Length:16500mm

Max Width:2200mm

Max Thickness:25.4mm

Max Yield Strength:1500Mpa
SL FACILITIES

Max Width:2200mm

Max Thickness:18mm

Max slit Quantity:31

Max Yield Strength:1200Mpa

 

2.CUTTING SERVICE

GNEE STEEL imported lots of advanced cutting machines from Germany, Sweden, America and Japan, including plasmas cutting machine, water jet cutting machine, laser cutting machine, flame cutting machine and saw machine. In order to meet customers' diversified needs, GNEE STEEL also adopts nest working multi-cutting methods and intensive production to improve production capacity and save costs for the customers.

Laser Cutting Machine

Max Cutting Length:40,000mm

Max Width:4,600mm
Max Thickness:100mm

 

Flame Cutting Machine

Max Cutting Length:40,000mm

Max Width:8,000mm
Max Thickness:500mm

Plasmas Cutting Machine

Max Cutting Length:30,000mm

Max Width:5,000mm
Max Thickness:100mm

 

Water-jet Cutting

Max Cutting Length:12,000mm

Max Width:4,010mm
Max Thickness:250mm

3.FORMING SERVICE

Steel Plate Roll Bending
Maximum Rolling Thickness: up to 200mm
Maximum Width: 4200mm

   

Automatic Bending Machine-Press Brake
Max Bending Capability:3000Ton
Max Bending Length:15,000mm

Expert in Bending High-Strength & Wear-Resistant Steels

  

  

Punching Machine

Max Width:3,070mm
Max Thickness:8mm

Max Pressure:250t

BEVELING SERVICE

GNEE STEEL beveling platform has edge milling machine, edge planer, flame / plasma groove cutting machine, flame groove cutting robot, desktop chamfering machine, gantry planerand other advanced equipment to provide customers with parts prefabrication services,daily processing of V-type, Y-type, X-type and U-type grooves, and guarantee subsequent processes such as welding and assembly of products.

 

Milling：
Max Cutting Length:18,000mm

Max Width:4500mm
Max Thickness:120mm

 

  

Beveling:
Max Length:16,000mm

Max Thickness:80mm

MACHINING SERVICE

GNEE STEEL owns CNC Portal-type Boring and Milling machine,CNC Floor-type Boring and Milling machine, Vertical Precision 5-axis Milling Machine, Portal-type Planer, Vertical Lathe, Cylindical Grinding machine, Hydraulic Planer and CNC Lathe and could provide fine machining of large spare parts and structural parts for customers.

Gantry Type Boring & Milling Maching Center

Max Length:48000mm

Max Width:12500mm
Max Height:8000mm

Max Diameter:10500mm

Deep-hole Drilling Equipment
Max Driling Depth:1,100mm
Max Bore Diameter:φ80mm
Max Diametar:φ4,500mm

MMulti-hole Drilling Equipment

Max Length:13,000mm
Max Width:10,000mm
Max Bore Diameter:φ105mm
Max Drilling Depth:250mm

Floor Boring And Milling Machine
Max Length:24,000mm
Max Height:8,000mm
Turntable Dimensions:9x5m

Vertical Lathe

Max Height:6,000mm

Max Diametar:φ22,00mm

Automated Edge Milling Machine

The Automated Edge Milling Machine is a leading product in heavy-duty milling equipment. It is primarily used for weld groove preparation (beveling) on large-format plates made of stainless steel, carbon steel, and special steel grades. It can process plates with a maximum thickness of up to 90mm, a length of 16 meters, and a width of 4 meters.

 

It is equipped with dual milling units and a fully automatic milling cutter head changing system, enabling automated 4-edge beveling. Its standout feature is the profiling technology used when milling wavy plates and irregularly shaped products, which ensures absolute consistency of the groove after milling.

 

Utilizing specially designed milling cutter heads, it can execute highly difficult and complex groove profiles in a single pass.

 

Materials: Plain carbon steel, pressure vessel steel, wear-resistant steel, high-strength steel, stainless steel, nickel-based alloys, etc.
Width: 1200 - 4200 mm
Length: 5800 - 16000 mm
Thickness: 5 - 90 mm
Weight: Up to 35 tons

 

This edge milling machine is the world's premier automated bevel milling equipment. With its excellent structural design and advanced data algorithms, it achieves full automation from plate detection to the actual milling process, significantly improving processing efficiency while guaranteeing high precision.

 

• Processing Accuracy

Length accuracy: ±1mm when L < 10m; ±2mm when L > 10m;

Width accuracy: ±1mm;

Diagonal accuracy: ±2mm;

Root face accuracy (blunt edge): ±1mm for Y-grooves; +0.5mm for X-grooves.

• Processing Efficiency

The processing efficiency is more than 10 times that of conventional edge milling or edge planing equipment.

HEAT TREATMENT

Heat Treatment Furnace
Max Furnace Size:36x12x13.5m
Max Rated Temperature:1100℃
Max Loading Capacity:800t

Heat Treatment of Pressure Vessels
Heat Treatment of Mining Equipment
Heat Treatment of Tube Sheet
Heat Treatment of Pressure Vessel Head

 

 

GNEE STEEL is currently participating in the procurement phase of a 100,000m³ full containment ammonia storage tank project, supplying high-quality steel plates for critical tank components. Due to the corrosive nature of ammonia and the risk of Ammonia Stress Corrosion Cracking (SCC), the project requires strict metallurgical control of materials according to EN 10028-3 standards.

 

One of the most important technical requirements of this project is the strict limitation of the actual Yield Strength (Re) for all NL2 grade materials. To prevent SCC risks in ammonia storage environments, the actual yield strength must not exceed 390 MPa, regardless of the nominal values specified in the standard or plate thickness ranges. This requirement places higher demands on steelmaking process control, heat treatment stability, and material testing.

 

Raw high-strength steel plates ready for the 100,000 m³ full containment ammonia storage tank production

 

Project Materials and Technical Requirements

 

The project mainly uses P355NL2 and P275NL2 normalized pressure vessel steel plates, which are widely applied in low-temperature storage tanks due to their excellent toughness and weldability.

 

Key technical specifications include:

• Material grades: P355NL2 and P275NL2 (Normalized)
• Yield strength: Standard minimum / Maximum limited to 390 MPa
• Hardness: ≤ 225 HBW in base material
• Impact testing: Charpy-V notch test at -50°C, minimum 27J
• Certification: EN 10204 3.1 certificate, with optional 3.2 certification

 

These strict requirements ensure that the steel plates maintain stable mechanical properties and high resistance to ammonia-induced stress corrosion during long-term operation.

 

Precision rolling and forming of steel plates into curved sections for the 100,000 m³ ammonia storage tank.

 

Project Plate Quantities and Thickness Distribution

 

The total steel demand for this ammonia storage tank project is several thousand tons, mainly distributed across different tank sections:

 

P355NL2 – Inner & Outer Tank Shell Plates

• Lower shell courses: 50 mm thickness – approx. 2,000 tons
• Middle shell courses: 25 mm thickness – approx. 1,400 tons
• Upper shell courses: 10 mm thickness – approx. 500 tons

 

P275NL2 – Tank Bottom Plates

• Thickness: 10–15 mm – approx. 750 tons

 

P275NL2 – Suspended Roof Structure

• Thickness: 5–8 mm – approx. 180 tons

 

S275JR – Outer Roof (Ambient Structure)

• Thickness: 10 mm – approx. 450 tons

 

To improve tank fabrication efficiency and reduce circumferential welds, the project also requires wide steel plates to minimize welding joints, which helps reduce the potential risk of SCC in ammonia service conditions.

 

Formed steel segments wrapped and racked for protection, ready for 100,000 m³ ammonia storage tank assembly.

 

GNEE STEEL provides high-precision steel plate rolling and cylinder fabrication solutions for tank manufacturers worldwide. Send us your plate specifications or fabrication drawings for a fast quotation.

Request A Quote

 

TYPE	GRADE	SPECIFICATIONS
Carbon Steel / Low Alloy Coil	Q235A/B/C/D/Q355B(Q345B)/C/D/E/SS400/SAPH400-C/ASTMA283Grade C	0.7~2.0*1250/1500mm*C 2.3~19.5*1250/1500/1800/2000mm*C
Medium Heavy Plate	Q235B/Q355B(Q345B)/C/D/E	6.0-200x150mm-4000mmxL
Vessel Plate	Q245R/Q345R/HP295/SA516MGR485/SA516GR70/P355NL2/P275NL2/ S275JR//SPV490/ASTM A537 Class 1/Class 2	2.5-120x1500mm-3000mmxL
High Strength Steel	510L/610L/700L/750L/BS600MCK4/BS700MCK2/BS700MCK4/ BS960E/BWELDY700QL2/L4/BWELDY960QL4/HG60D/70D/785D/ Q460D/Q550D/690D/690E/TQ600MCD/TQ700MCD/S700MCD/ WYS600/700/STRENX700MCE/Q490E/Q490D	1.2-60x 1500mm-2500mmxL
Patterned Steel	HQ235A|B	1.2-60x 1500mm-2500mmxL
Wear-resistance Steel	NM360/400/450/500/NM300TP/400TP/450TP/ ABREX400/450/500/B-HARD450XKY/ CREUSABRO4800/8000/EH C400LE/450LE/500LE/ HADOX450/500	3.0-50x1250mm-3300mmxL
Cold Rolled Coil	DC01/RECC/REDT/SPCC/ST12	0.5-3.0x1250mm-1500mmxC
Galvanized Plate	DC51D+AZ/DC51D+Z/DX51D+Z/SGH340+Z275/Z275/Z120/S350GD+ZM275	0.45-3.0x1250mm-1500mmxC
Pickled Coil	DD11/SPHC	2.0-6.0x1500xC

Stainless Steel Material and Surface Specifications

TYPE	GRADE	THICKNESS	SURFACE
Austenitic	304/304H/304L/304J1	0.25-150mm	2B/BA/NO.4/8K/SB/HL/NO.1
Austenitic	321	0.4-80mm	2B/BA/NO.4/8K/SB/HL/NO.1
Austenitic	316/316L/317L/316Ti	0.3-80mm	2B/BA/NO.4/8K/SB/HL/NO.1
Austenitic	201(J1/J2/J5)	0.35-12mm	2B/NO.1/1D
Ferrite	430	0.4-3.0mm	2B/BA/NO.4/8K/SB/HL
Ultra Pure Ferrite	443	0.4-2.0mm	2B
Ultra Pure Ferrite	436L/439/444/441	0.5-3.0mm	2B/2D

Special Steel / Nickel Base Alloy

TYPE	GRADE	GRADE (ASTM)	GRADE (EN)	THICKNESS
Heat-resistant Steel	309S	S30908	1.4833	0.5-40mm
Heat-resistant Steel	310S	S31008	1.4845	0.5-40mm
Duplex Stainless Steel	2101	S32101	1.4162	1.5-50mm
Duplex Stainless Steel	2304	S32304	1.4362	3.0-50mm
Duplex Stainless Steel	2205	S32205/S31803	1.4462	0.5-60mm
Duplex Stainless Steel	2507	S32750	1.4410	1.0-60mm
Super Austenitic-Steel	904L	N08904	1.4539	0.6-50mm
Super Austenitic-Steel	254SMO	S31254	1.4547	0.5-50mm
Super Austenitic-Steel	1.4529	N08926	1.4529	0.5-50mm
Super Austenitic-Steel	AL-6XN	N08367	1.4478	0.5-50mm
Nickel Base Alloy	Alloy 31	N08031	1.4562	1.0-50mm
Nickel Base Alloy	800	N08800	1.4876	0.8-50mm
Nickel Base Alloy	800H	N08810	1.4958	0.8-50mm
Nickel Base Alloy	800HT	N08811	1.4959	0.8-50mm
Nickel Base Alloy	Alloy 28	N08028	1.4563	1.0-20mm
Nickel Base Alloy	Alloy 20	N08020	2.4660	1.0-20mm
Nickel Base Alloy	825	N08825	2.4858	0.8-40mm
Nickel Base Alloy	C276	N10276	2.4819	0.5-50mm
Nickel Base Alloy	C22	N06022	2.4602	1.0-50mm
Nickel Base Alloy	625	N06625	2.4856	0.8-20mm
Nickel Base Alloy	400	N04400	2.4360	1.0-20mm
Nickel Base Alloy	600	N06600	2.4816	1.0-50mm
Nickel Base Alloy	Pure Ni 201	N02201	2.4061	0.5-20mm
Titanium	TA1	Gr.1	Class 1	0.5-50mm
Titanium	TA2	Gr.2	Class 2	0.5-50mm

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