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LR Grade B Shipbuilding Steel Plate - LR-Certified Ordinary-Strength Marine Structural Steel

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LR Grade B is a standard-strength hull structural steel certified by Lloyd’s Register (LR). Compared to LR Grade A, its key improvement lies in its low-temperature impact toughness at 0°C, while maintaining excellent mechanical properties, weldability, and resistance to marine corrosion. The LR Grade B steel plates we supply strictly adhere to LR specifications, utilizing optimized smelting and hot-rolling processes to precisely control grain structure and chemical composition. Each batch undergoes comprehensive in-house inspection throughout the entire production process and receives official LR certification, fully meeting international shipyard procurement standards, offshore engineering construction specifications, and cross-border bidding requirements.

Certification :
LR Rules
Grade :
LR Grade B (LR B)
Thickness :
5.0 - 150.0 mm
Width :
1500.0 - 4000.0 mm
Length :
6000.0 - 18000.0 mm

Special thickness, width, and length can be negotiated separately.
We also provide customized processing services.If you have any questions, please contact us.

Overview

1. What is LR Grade B shipbuilding steel plate?

LR Grade B is a ordinary-strength structural steel for shipbuilding certified by Lloyd’s Register (LR). It has a yield strength of ≥235 MPa and a tensile strength of 400 - 520 MPa, and has passed the Charpy V-notch impact test at 0°C.

LR Grade B shipbuilding steel plates are resistant to marine corrosion and offer good weldability, formability, and stable mechanical properties. They are widely used in conventional load-bearing structures such as hulls, decks, and bulkheads of vessels operating in temperate waters and are one of the fundamental materials for the construction of ocean-going vessels.

2. Meaning of the Designation

LR: Certified by Lloyd’s Register (LR)

B: Quality grade B (Impact testing at 0°C must be performed)

We offer a full range of standard and customized LR Grade B shipbuilding steel plate solutions in a complete array of sizes and specifications to meet the diverse needs of commercial shipbuilding and medium- to low-temperature offshore engineering projects in areas such as manufacturing, processing, and maintenance.

Available Specifications and Dimensions

Product Name	LR Grade B Shipbuilding Steel Plate
Certification	LR (Supports third-party certification by SGS, BV, DNV, ABS, CCS, and others.)
Grade	LR B
Classification	Ordinary-Strength Structural Steel for Ship and Ocean Engineering
Thickness	5 - 150 mm
Width	1500 - 4000 mm
Length	6000 - 18000 mm
Delivery Conditions	Hot Rolled (HR), Normalized (N), Thermo-Mechanical Controlled Processed (TMCP), Quenched and Tempered (Q+T).
Surface Conditions	Original black oxide layer, No cracks, scarring, delamination, inclusions, or deep scratches.
Machining Services	Precision cutting, bending, drilling, beveling, surface rust removal, shot blasting, anti-corrosion coating, and customized secondary processing.
Inspection	Charpy V-notch impact test, Ultrasonic testing (UT), Z-direction property test (Grades Z15/Z25/Z35), Third-party test (such as SGS), etc.
Applications	Widely used in non-core load-bearing areas of ships, the main structures of small and medium-sized vessels, and secondary components of offshore engineering projects.
MOQ	5 tons (small orders can be negotiated).
Delivery Time	15 - 20 days after order confirmation (urgent orders accepted)
Packaging	Standard export packaging for sea transport, or as required.
Country of origin	China

Chemical Composition

Chemical Composition (Heat Analysis, wt %)

Grade	C	Si	Mn	P	S	Cu	Cr	Ni	Als
LR B	≤ 0.21	≤ 0.35	≥ 0.80	≤ 0.035	≤ 0.035	≤ 0.35	≤ 0.30	≤ 0.30	-

Carbon Equivalent (wt %)

Thickness (mm)	5 - 50	50 - 150
Typical CEV (wt %)	≤ 0.38	≤ 0.40

Calculation formula (IIW): CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

Mechanical Properties

Tensile test

Grade	Yield Strength (ReH), MPa	Tensile Strength (Rm), MPa	Elongation (A), %
LR B	≥ 235	400 - 520	≥ 22

Charpy (V-notch) impact test

Grade	Thickness, mm	Temperature, ℃	Impact Energy, KV₂ / J
Grade	Thickness, mm	Temperature, ℃	Longitudinal	Transverse
LR B	≤ 50	0	≥ 27	≥ 20
	> 50 - 70	0	≥ 34	≥ 24
	> 70 - 150	0	≥ 41	≥ 27

Applications

Due to its balanced mechanical properties and cost-effectiveness, LR Grade B shipbuilding steel plate is primarily used in ship and offshore engineering structures where general strength requirements apply. It is characterized by good strength, weldability, toughness, and resistance to marine environments. Its typical applications are as follows:

1. Ship Hull Structures

Main hull plating, decks and superstructures, bulkheads and compartment structures, hull frames and stiffeners, ship equipment, and outfitting components.

2. Offshore Engineering and Offshore Structures

Secondary load-bearing structures of offshore platforms, docks, port facilities, etc.

3. Ship Repair and Refitting

Plate replacement on older vessels, localized structural reinforcement, replacement of damaged bulkheads/decks, and refitting to add superstructures, etc.

Other Information

Key Advantages of Our LR Grade A Shipbuilding Steel Plates

1. Impact toughness at low temperatures (0°C)

2. Stable and balanced mechanical properties

3. Excellent weldability and machinability

4. Outstanding resistance to marine atmospheric corrosion

5. High cost-effectiveness and wide range of applications

6. Ample capacity for bulk supply

7. Fully certified by LR

FAQ

Q1:

What is the range of available dimensions for your LR Grade B marine steel plates?

Thickness: 6 mm - 250 mm (thicknesses ≥ 40 mm: require normalizing or TMCP heat treatment)

Width: 1,500 mm - 4,000 mm

Length: 6,000 mm - 18,000 mm

We offer custom flame-cutting or plasma-cutting services based on shipyard drawings, with cutting tolerances meeting LR rules requirements.

Q2:

Does your LR Grade B shipbuilding steel plate support third-party inspection?

Yes. All of our LR Grade B shipbuilding steel plates are subject to inspection by internationally recognized third-party organizations such as SGS, BV, and DNV, and come with complete official LR certification and original Mill Test Certificate (MTC) to ensure full quality traceability.

Q3:

Is LR Grade B marine steel suitable for offshore platforms?

Yes, LR Grade B marine steel is suitable for auxiliary structures on offshore platforms in temperate waters, such as pipe supports, guardrails, and secondary support members requiring low-temperature toughness. For primary load-bearing structures in extremely cold environments, it is recommended to use LR Grade D or LR Grade E marine steel.

Q4:

What is the main difference between LR Grade A and LR Grade B shipbuilding steel?

The key difference between the two lies in their low-temperature toughness requirements and intended applications.

LR Grade A does not require a mandatory low-temperature impact test and is suitable only for mild maritime environments at normal temperatures; LR Grade B, on the other hand, must pass a low-temperature impact test at 0°C, offers superior resistance to low-temperature embrittlement, and is suitable for temperate and colder maritime environments.

While their strength and weldability are essentially equivalent, LR Grade B offers greater environmental adaptability and a higher safety margin.

Q5:

What is the application of LR Class B shipbuilding steel plates?

LR Grade B shipbuilding steel plates are primarily used in various types of vessels operating in temperate waters, including bulk carriers, product tankers, container ships, tugs, barges, and various types of inland waterway vessels.

They are commonly used to fabricate non-critical, low-temperature load-bearing components such as hull plating, decks, bulkheads, frames, superstructures, and hull support structures.

It is also widely used in routine ship maintenance and refitting, port and terminal steel structures, auxiliary components for simple offshore engineering projects, and floating platforms.