Description

Marine steel plate, also known as shipbuilding steel plate, is a hot-rolled steel plate specifically designed for ship hull structures. It must conform to the specifications of classification societies (such as CCS, ABS, DNV, etc.), and its core characteristics are high strength, high toughness, good corrosion resistance, and excellent weldability.

Features of Marine Steel Plate:

1. High Strength and Clear Classification: Marine steel plates are classified into general strength steel (A/B/D/E grades, ≥235 MPa) and high strength steel (such as AH32/DH36/EH40, 315–690 MPa) based on yield strength. The letters (A/D/E/F) represent the low-temperature impact toughness grade (corresponding to 0℃, -20℃, -40℃, -60℃).

2. Excellent Low-Temperature Toughness: Marine steel plates must pass a V-shaped impact energy test (≥34–50 J) at specified temperatures (e.g., -40℃ for grade E, -60℃ for grade F) to prevent brittle fracture under extreme cold or impact conditions.

3. Strict Composition Control: Carbon equivalent (Ceq) and crack sensitivity coefficient (Pcm) are limited; Mn/C ratio ≥ 2.5; P/S impurity content is extremely low (≤ 0.025%–0.035%), ensuring a balance between weldability and toughness.

4. Seawater Corrosion Resistance and Environmental Adaptability: Marine Steel Plate contains microalloying elements such as Cu and Ni to enhance atmospheric/seawater corrosion resistance; some grades (such as steel for cargo oil tanks) meet IMO corrosion resistance standards; Z-axis steels (Z15/Z25/Z35) resist lamellar tearing and are used for critical welds in thick plates.

5. Good Weldability and Formability: Utilizing TMCP (Thermomechanical Controlled Rolling) or normalizing processes, it supports high heat input welding (up to 700 kJ/cm); surface quality and dimensional tolerances must meet shipyard assembly requirements.

6. Mandatory Certification Production: Production is limited to steel mills approved by classification societies. Each batch must be accompanied by a quality certificate and stamp, and must comply with national standards such as GB/T 712 and international classification society specifications (such as IACS UR W11).

7. Marine steel plates account for 25%–30% of the hull cost. Marine steel plates are widely used in the hull, decks, bulkheads, and other main load-bearing structures. Special vessel types such as very large ships or LNG carriers also require high-end varieties such as crack-arresting steel, 9Ni low-temperature steel, and duplex stainless steel.

Applications of Marine Steel Plate:

Marine steel plates are high-strength, high-toughness, corrosion-resistant hot-rolled steels specifically designed for constructing ship hull structures and marine engineering equipment. Core applications include:

1. Constructing the main hull structure: such as bottom plates, side plates, decks, bulkheads, keels, etc., bearing the impact of waves, loads, and water pressure during navigation;

2. Manufacturing various types of ships: covering bulk carriers, tankers, container ships, LNG carriers, passenger ships, warships, and offshore platforms, with high-strength grades of Marine Steel Plate (such as AH36, EH36, and crack-arresting steel) used in critical load-bearing components;

3. Meeting harsh service environments: Marine Steel Plates must be resistant to seawater corrosion, withstand low-temperature impacts (down to -60℃), possess excellent weldability and formability, and comply with classification society standards such as CCS, DNV, and ABS;

4. Supporting special functional requirements: such as 9Ni steel for LNG ships (-163℃ low temperature), corrosion-resistant steel for oil tanker cargo tanks, duplex stainless steel for chemical tanker liquid cargo tanks, and ultra-high strength special steel for aircraft carriers/submarines (not in the scope of ordinary commercial ships).

Standards of Shipbuilding Steel Plate:

ASTM A131 Steel Plate Chemical Composition (max.)
Grade	C	Mn	Si	P	S	Others
Grade A	0.21	2.5xC	0.5	0.035	0.035
Grade B	0.21	0.6	0.35	0.035	0.035
Grade D	0.21	0.6	0.01-0.35	0.035	0.035
Grade E	0.18	0.7	0.01-0.35	0.035	0.035
AH32/DH32/EH32	0.18	0.90-1.60	0.10-0.50	0.035	0.035	Cb 0.02-0.05, V 0.05-0.10, Ti 0.02, Cu 0.35, Cr 0.20, Ni 0.40, Mo 0.08, Als min. 0.015
AH36/DH36/EH36
AH40/DH40/EH40
FH32/FH36/FH40	0.16	0.90-1.60	0.10-0.50	0.025	0.025

ASTM A131 Steel Plate Mechanical Properties
Grade	Yield Strength	Tensile Strength	Elongation in 8 in.	Elongation in 2 in.
Grade	min. MPa)	MPa	min. %	min. %
Grade A, B, D, and E	235	400-520	21	24
AH32 DH32 EH32 FH32	315	440-590	19	22
AH36 DH36 EH36 FH36	355	490-620	19	22
AH40 DH40 EH40 FH40	390	510-650	19	22

ASTM A131 Steel Plate Charpy V-Notch Impact Test Temperature
Grade	Temperature ⁰F [⁰C]
Grade A	68 [20]
Grade B AH32 AH36 AH40	32 [0]
Grade D DH32 DH36 DH40	-4 [-20]
Grade E EH32 EH36 EH40	-40 [-40]
FH32 FH36 FH40	-76 [-60]

Standard	Shipbuilding and Offshore Structure Steel Grades
ASTM A131	Grade A	Grade B	Grade D	Grade E
	AH32	DH32	EH32	FH32
	AH36	DH36	EH36	FH36
	AH40	DH40	EH40	FH40
EN 10225	S355G2+N	S355G3+N	S355G5+M	S355G6+M
	S355G7+M	S355G7+N	S355G8+M	S355G8+N
	S355G9+N	S355G9+M	S355G10+N	S355G10+M
	S420G1+Q	S420G1+M	S420G2+Q	S420G2+M
	S460G1+Q	S460G1+M	S460G2+Q	S460G2+M
API SPEC 2H	API 2H-42	API 2H-50

Steel Grade	C	Si	Mn	P	S	Als
A	≤0.21	≤0.50	≥2.5c	≤0.035	≤0.035
B	≤0.21	≤0.35	0.8~1.2	≤0.035	≤0.035
D	≤0.21	≤0.35	0.6~1.2	≤0.035	≤0.035	≥0.015
E	≤0.18	≤0.35	0.7~1.2	≤0.035	≤0.035	≥0.015
AH32	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
DH32	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
EH32	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
FH32	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
AH36	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
DH36	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
EH36	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
FH36	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
AH40	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
DH40	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
EH40	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015
FH40	≤0.18	≤0.50	0.9~1.6	≤0.035	≤0.035	≥0.015

Standards and Classifications

Standard	Shipbuilding and Offshore Structure Steel Plate Grades
ASTM A131	Grade A	Grade B	Grade D	Grade E
	AH32	DH32	EH32	FH32
	AH36	DH36	EH36	FH36
	AH40	DH40	EH40	FH40
EN 10225	S355G2+N	S355G3+N	S355G5+M	S355G6+M
	S355G7+M	S355G7+N	S355G8+M	S355G8+N
	S355G9+N	S355G9+M	S355G10+N	S355G10+M
	S420G1+Q	S420G1+M	S420G2+Q	S420G2+M
	S460G1+Q	S460G1+M	S460G2+Q	S460G2+M
API SPEC 2H	API 2H-42	API 2H-50