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Bulb Flat Bar - Marine Grade Bulb Flat Steel for Shipbuilding

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Marine-grade bulb flat bar is a special type of hot-rolled structural steel profile and serves as a critical reinforcing material in shipbuilding and offshore engineering. It is widely used in applications such as longitudinal stiffeners for ship hulls, deck reinforcement, bulkhead supports, and structural reinforcement for offshore platforms. We supply marine-grade bulb flat bar in all sizes and grades, accompanied by complete certification documents and original factory test reports, and fully support inspections by internationally recognized third-party organizations such as SGS, BV, DNV, and ABS.

Standard :
ABS / CCS / DNV / BV / LR
Grade :
A / B / D / E / AH32 / AH36 / DH32 / DH36 / EH32 / EH36
Thickness :
4.0 - 20.0 mm
Width :
60.0 - 430.0 mm
Length :
6,000.0 - 12,000.0 mm

* Specifications and dimensions can be customized.

* Machining services are available.

Overview

1. What is bulb flat bar for shipbuilding?

Bulb flat bar (also known as marine bulb flat bar) is a hot-rolled structural steel specifically designed for reinforcing ships and offshore structures. Its unique integrated cross-section design—featuring a flat web and a thickened circular spherical head—combines high structural rigidity, excellent load-bearing capacity, superior bending and torsional stability, and good weldability. It effectively addresses the structural shortcomings of traditional flat bars and angle bars, preventing deformation and damage caused by long-term marine loads and harsh environments, and serves as a core reinforcement material for ship hulls, decks, bulkheads, and offshore platform structures.

Compared to ordinary flat steel, the single-sided spherical head design of bulb flat steel provides a higher section modulus, lighter dead weight, and more uniform stress distribution. This effectively disperses structural stress, prevents local stress concentration, and significantly enhances bending, shear, and compressive resistance. The dual advantages of light weight and high rigidity ensure structural stability while reducing the vessel’s overall weight, helping to save costs and improve construction efficiency. It is suitable for various types of civilian vessels, cargo ships, offshore engineering equipment, and offshore auxiliary structures, and is widely used in areas such as longitudinal hull stiffeners, deck reinforcement, bulkhead supports, and platform structural reinforcement.

Specifications and Dimensions

Specifications for Bulb Flat Bar

Product Name	Bulb Flat Bar
Material	AShipbuilding Steel
Standards	ABS / CCS / DNV / BV / LR
Grades	A / B / D / E / AH32 / AH36 / DH32 / DH36 / EH32 / EH36
Delivery Condition	Hot Rolled
Surface Treatment	Original hot-rolled black scale, pickling (optional), painted (optional), galvanizing (optional).
MOQ	20 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

Dimensions of Bulb Flat Bar

Design Drawing for Bulb Flat Bar

Model	Nominal Dimensions (mm)					Sectional Area (cm²)	Weight (kg/m)
Model	b	t	h	r1	r	Sectional Area (cm²)	Weight (kg/m)
HP 80 × 5	80	5	19	4	≤ 1.5	5.41	4.25
HP 80 × 6	80	6	20	4	≤ 2	6.21	4.88
HP 100 × 7	100	7	22.5	4.5	≤ 2	8.74	6.86
HP 100 × 8	100	8	23.5	4.5	≤ 2	9.74	7.65
HP 120 × 6	120	6	23	5	≤ 2	9.32	7.32
HP 120 × 7	120	7	24	5	≤ 2	10.52	8.26
HP 120 × 8	120	8	25	5	≤ 2	11.72	9.20
HP 140 × 7	140	7	26	5.5	≤ 2	14.43	9.75
HP 140 × 8	140	8	27	5.5	≤ 2	12.83	10.85
HP 140 × 9	140	9	28	5.5	≤ 2	15.20	11.93
HP 140 × 10	140	10	29	5.5	≤ 3	16.63	13.05
HP 160 × 7	160	7	29	6	≤ 2	14.60	11.46
HP 160 × 8	160	8	30	6	≤ 2	16.20	12.72
HP 160 × 9	160	9	31	6	≤ 2	17.80	13.97
HP 160 × 11	160	11	33	6	≤ 3	21.00	16.49
HP 180 × 8	180	8	33	7	≤ 2	18.86	14.80
HP 180 × 9	180	9	34	7	≤ 2	20.66	16.22
HP 180 × 10	180	10	35	7	≤ 3	22.46	17.63
HP 180 × 11	180	11	36	7	≤ 3	24.26	19.04
HP 200 × 9	200	9	37	8	≤ 2	23.66	18.57
HP 200 × 10	200	10	38	8	≤ 3	25.66	20.14
HP 200 × 11	200	11	39	8	≤ 3	27.66	21.71
HP 200 × 12	200	12	40	8	≤ 3	29.66	23.28
HP 220 × 10	220	10	41	9	≤ 3	29.00	22.77
HP 220 × 11	220	11	42	9	≤ 3	31.20	24.50
HP 220 × 12	220	12	43	9	≤ 3	33.40	26.22
HP 240 × 10	240	10	44	10	≤ 3	32.49	25.50
HP 240 × 11	240	11	45	10	≤ 3	34.89	27.39
HP 240 × 12	240	12	46	10	≤ 3	37.29	29.27
HP 260 × 10	260	10	47	11	≤ 3	36.11	28.35
HP 260 × 11	260	11	48	11	≤ 3	38.71	30.39
HP 206 × 12	260	12	49	11	≤ 3	41.31	32.43
HP 260 × 13	260	13	50	11	≤ 3	43.85	34.43
HP 280 × 11	280	11	51	12	≤ 3	42.68	33.50
HP 280 × 12	280	12	52	12	≤ 3	45.48	35.70
HP 280 × 13	280	13	53	12	≤ 3	48.28	37.90
HP 300 × 11	300	11	54	13	≤ 3	46.78	36.70
HP 300 × 12	300	12	55	13	≤ 3	49.79	39.09
HP 300 × 13	300	13	56	13	≤ 3	52.79	41.44
HP 320 × 12	320	12	58	14	≤ 3	54.25	42.60
HP 320 × 13	320	13	59	14	≤ 3	57.25	45.09
HP 320 × 14	320	14	60	14	≤ 4	60.85	47.60
HP 340 × 12	340	12	61	15	≤ 3	58.84	46.20
HP 340 × 13	340	13	62	15	≤ 3	62.24	48.86
HP 340 × 14	340	14	63	15	≤ 4	65.54	51.50
HP 370 × 13	370	13	66.5	16.5	≤ 3	69.70	54.70
HP 370 × 14	370	14	67.5	16.5	≤ 4	73.40	57.60
HP 370 × 15	370	15	68.5	16.5	≤ 4	77.10	60.50
HP 400 × 14	400	14	72	18	≤ 4	81.48	63.96
HP 400 × 15	400	15	73	18	≤ 4	85.48	67.10
HP 400 × 16	400	16	74	18	≤ 4	89.48	70.20
HP 430 × 14	430	14	76.5	19.5	≤ 4	89.70	70.60
HP 430 × 15	430	15	77.5	19.5	≤ 4	94.19	73.90
HP 430 × 17	430	17	79.5	19.5	≤ 4	102.79	80.70
HP 430 × 19	430	19	81.5	19.5	≤ 4	111.39	87.40
HP 430 × 20	430	20	82.5	19.5	≤ 4	115.00	90.80

Characteristics and Advantages

1. Higher Structural Strength and Stability

The unique asymmetrical profile design, combined with thickened edges at the spherical head, increases the cross-sectional moment of inertia and load-bearing capacity, providing excellent bending resistance and significantly enhancing structural stability.

2. Lightweight Design

Compared to angle steel and standard flat steel of the same strength grade, spherical flat steel is lighter in weight, effectively reducing the deadweight of ships and offshore platforms while lowering energy consumption during navigation and engineering loads. This lightweight design does not compromise structural strength, achieving dual optimization of “lightweight + high rigidity” and saving on raw material and transportation costs.

3. Excellent Welding Performance

It supports both automated and manual welding processes, delivering high welding precision and strong welds, ensuring stable and reliable welding quality throughout the shipbuilding process.

4. Standardization, Certification, and Wide Adaptability

It complies with ISO, ASTM, GB, and international classification society standards, and supports customization across multiple grades, including Grade A, B, D, E, AH32, AH36, DH32, DH36, EH32, and EH36.

Applications

1. Shipbuilding

Primarily used for deck stiffeners, longitudinal and transverse hull frames, bulkhead stiffeners, bottom support structures, and internal superstructure frames in various types of vessels, including container ships, bulk carriers, oil tankers, passenger ships, and engineering vessels.

2. Offshore Engineering

Primarily used for platform deck stiffeners, jacket auxiliary supports, offshore wind turbine foundation accessories, and offshore pipeline support structures.

3. Port Engineering and Industrial Construction

Primarily used for structural supports in port trestles, port equipment brackets, wharf structural reinforcements, heavy-duty factory frameworks, and structural reinforcement components for large-scale machinery and equipment.

FAQ

Q1:

Can you provide custom sizes for your bulb flat bars?

We offer customized processing for bulb flat bars, including cutting to non-standard lengths, custom sizing, surface rust removal, anti-corrosion coating, and other value-added services. We can manufacture products according to customer drawings and project specifications to meet the diverse needs of various construction projects.

Q2:

What are the primary applications of bulb flat bar?

Bulb flat bar is a structural profile specifically designed for marine engineering. It is primarily used in applications such as ship hull stiffeners, deck and bulkhead reinforcement, structural supports for offshore platforms, and port and bridge facilities. Thanks to its high rigidity, lightweight design, and excellent adaptability to marine environments, it has become a core structural profile in the shipbuilding and marine engineering sectors.