Hot Rolled Bulb Flat Steel / Marine Bulb Flat / Shipbuilding Bulb Flat Bar
Mild Steel Bulb Flat Steel - HW354 S275JR S235JR Carbon Steel Bulb Flat for bridge building
Q235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building Material
Q235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building MaterialQ235 Q345 Q275 ASTM A36 A106 12# Mild Steel U shape Hot Rolled U Channel for Building Material
| Core Item |
Detailed Specification |
| Product Name |
Hot Rolled Bulb Flat Steel / Marine Bulb Flat / Shipbuilding Bulb Flat Bar |
| Executive Standards |
GB/T 9945, EN 10067, JIS G3192, IACS Member Classification Society Rules |
| Standard Steel Grades |
Marine Grade: A, B, D, E, AH32, AH36, DH32, DH36
Carbon Steel: Q235B, Q255B, S235JR, S355JR, Q355B/C/D |
| Standard Size Range |
No.5 - No.43 Full Series, Non-Standard Sizes Customizable |
| Standard Length |
6m, 9m, 12m, Cut-to-Length as Customer Requirements |
| Surface Condition |
Black Hot Rolled, Pickled, Painted, Hot Dip Galvanized, Anti-Corrosion Coating (Customizable) |
| Tolerance Control |
Dimensional Tolerance ±0.1mm, Straightness ≤1mm/m, Better than National & International Standards |
| Core Certifications |
ISO 9001:2015, Factory Approval from CCS, ABS, LR, BV, DNV-GL, NK, KR |
| Minimum Order Quantity (MOQ) |
1 Ton for In-Stock Items, 5 Tons for Customized Orders |
Hot Rolled Bulb Flat Steel / Marine Bulb Flat / Shipbuilding Bulb Flat Bar
Product Description
Hot rolled marine bulb flat steel, low carbon steel bulb flat bar, shipbuilding grade bulb flat profile for ship hull reinforcement and marine engineering construction.
We supply a complete range of sizes and lengths for
Marine Bulb Flat Steel.
All our bulb flat steel products are sourced from qualified mills with full mill test certificates and classification society approval.
MARINE BULB FLAT STEEL
Specification: GB/T 9945, EN 10067, JIS G3192
Grade: S235JR, S275JR, Q235B, Q355B, Ship Grade A/B/D/E, AH36, DH36
Size Range: No.5 - No.43 full series
Length Range: 600mm-12000mm
Surface Finish: Hot rolled black surface, pickled, painted or hot dip galvanized available
Mild Steel Bulb Flat / Marine Bulb Flat Steel
Also known as shipbuilding bulb flat bar, measured by height × thickness × weight per meter.
Made from S235JR, S275JR and marine grade steels, with excellent weldability, machinability and bending performance. Available in hot rolled, painted or hot-dip galvanized finishes for enhanced corrosion resistance.
Ideal for ship hull reinforcement, deck structures, marine engineering and steel construction projects requiring high stability and toughness.
Supplied in standard lengths up to 12m, easily cut, drilled and welded to meet your project requirements. Manufactured to EN 10067, GB/T 9945 and EN 10025-2 standards, using widely accepted grades for shipbuilding and general structural use.
Steel Bulb Flat Steel Introduction
What Are Steel Bulb Flat Steel?
Bulb flat steel, also known as marine bulb flat or shipbuilding bulb bar, features a unique single bulb edge structure that provides higher rigidity and stability compared with ordinary flat steel. The dimensional tolerances comply with EN 10067, GB/T 9945 and international ship classification standards. Unlike ordinary profile steel, the special bulb-shaped design of bulb flat steel effectively improves bending resistance and structural strength, making it easier for welding and assembly. Common applications for bulb flat steel include ship hull reinforcement, marine engineering, deck construction, bridge structures and industrial steel fabrication.
Zhuosheng Steel Warehouse stocks a full range of ready-to-ship bulb flat steel in complete specifications, from No.5 to No.43 full series. In addition, we also offer full-service processing capabilities, such as cutting to custom lengths, surface treatment, galvanizing and painting to meet diverse project requirements.
| Nominal Size (Model) |
Depth of Section (mm) |
Flange Width (mm) |
Flange Thickness (mm) |
Web Depth (mm) |
Web Thickness (mm) |
Weight (kg/m) |
Metres/ Tonne (m/t) |
6m |
9m |
12m |
| No.5 (50×25) |
50 |
25 |
6.00 |
44 |
4.50 |
3.77 |
265 |
√ |
√ |
√ |
| No.6 (60×30) |
60 |
30 |
7.00 |
53 |
5.00 |
4.86 |
206 |
√ |
√ |
√ |
| No.8 (80×40) |
80 |
40 |
8.00 |
72 |
6.00 |
7.05 |
142 |
√ |
√ |
√ |
| No.10 (100×50) |
100 |
50 |
9.00 |
91 |
7.00 |
9.76 |
102 |
√ |
√ |
√ |
| No.12 (120×60) |
120 |
60 |
10.00 |
110 |
8.00 |
12.93 |
77 |
√ |
√ |
√ |
| No.14 (140×70) |
140 |
70 |
11.00 |
129 |
9.00 |
16.56 |
60 |
√ |
√ |
√ |
| No.16 (160×80) |
160 |
80 |
12.00 |
148 |
10.00 |
20.65 |
48 |
√ |
√ |
√ |
| No.18 (180×90) |
180 |
90 |
13.00 |
167 |
11.00 |
25.20 |
40 |
√ |
√ |
√ |
| No.20 (200×100) |
200 |
100 |
14.00 |
186 |
12.00 |
30.21 |
33 |
√ |
√ |
√ |
| No.22 (220×110) |
220 |
110 |
15.00 |
205 |
13.00 |
35.68 |
28 |
√ |
√ |
√ |
| No.24 (240×120) |
240 |
120 |
16.00 |
224 |
14.00 |
41.61 |
24 |
√ |
√ |
√ |
| No.27 (270×135) |
270 |
135 |
17.00 |
253 |
15.00 |
49.57 |
20 |
√ |
√ |
√ |
| No.30 (300×150) |
300 |
150 |
18.00 |
282 |
16.00 |
58.38 |
17 |
√ |
√ |
√ |
| No.33 (330×165) |
330 |
165 |
19.00 |
311 |
17.00 |
67.94 |
15 |
√ |
√ |
√ |
| No.36 (360×180) |
360 |
180 |
20.00 |
340 |
18.00 |
78.25 |
13 |
√ |
√ |
√ |
| No.40 (400×200) |
400 |
200 |
21.00 |
379 |
19.00 |
91.44 |
11 |
√ |
√ |
√ |
| No.43 (430×215) |
430 |
215 |
22.00 |
408 |
20.00 |
102.96 |
10 |
√ |
√ |
√ |
Bulb Flat Nominal Size Web Height Web Thickness Bulb Height Bulb Transition Radius Cross Sectional Area Theoretical Weight 80×5 80 5 19 4 5.41 4.25 80×6 80 6 20 4 6.21 4.88 100×7 100 7 22.5 4.5 8.74 6.86 100×8 100 8 23.5 4.5 9.74 7.65 120×6 120 6 23 5 9.32 7.32 120×7 120 7 24 5 10.52 8.26 120×8 120 8 25 5 11.72 9.20 140×7 140 7 26 5.5 12.43 9.75 140×8 140 8 27 5.5 13.83 10.85 140×10 140 10 29 5.5 16.63 13.05 160×7 160 7 29 6 14.60 11.46 160×8 160 8 30 6 16.20 12.72 160×9 160 9 31 6 17.80 13.97 160×11 160 11 33 6 21.00 16.49 180×8 180 8 33 7 18.86 14.80 180×9 180 9 34 7 20.66 16.22 180×10 180 10 35 7 22.46 17.63 180×11 180 11 36 7 24.26 19.04 200×9 200 9 37 8 23.66 18.57 200×10 200 10 38 8 25.66 20.14 200×11 200 11 39 8 27.66 21.71 200×12 200 12 40 8 29.66 23.28 220×10 220 10 41 9 29.00 24.50 220×11 220 11 42 9 31.20 26.22 220×12 220 12 43 9 33.40 27.94 240×10 240 10 40 10 33.49 25.50 240×11 240 11 45 10 34.89 27.39 240×12 240 12 46 10 37.29 29.27 260×10 260 10 47 11 36.11 28.35 260×11 260 11 48 11 38.71 30.39 260×12 260 12 49 11 41.31 32.43 280×11 280 11 51 12 42.68 33.50 280×12 280 12 52 12 45.48 35.70 280×13 280 13 53 12 48.28 37.90 300×11 300 11 54 13 46.78 36.70 300×12 300 12 55 13 49.79 39.09 300×13 300 13 56 13 52.79 41.44 320×12 320 12 58 14 54.25 42.60 320×13 320 13 59 14 57.25 45.09 320×14 320 14 60 14 60.85 47.60 340×12 340 12 61 15 58.84 46.20 340×13 340 13 62 15 62.24 48.86 340×14 340 14 63 15 65.54 51.50 370×13 370 13 66.5 16.5 69.70 54.70 370×14 370 14 67.5 16.5 73.40 57.60 370×15 370 15 68.5 16.5 77.10 60.50 400×14 400 14 72 18 81.48 63.96 400×15 400 15 73 18 85.48 67.10 400×16 400 16 74 18 89.48 70.20 430×14 430 14 76.5 19.5 89.70 70.60 430×15 430 15 77.5 19.5 94.19 73.90 430×17 430 17 79.5 19.5 102.79 80.70 430×19 430 19 81.5 19.5 111.39 87.40 430×20 430 20 82.5 19.5 115.00 90.80 50×4 50 4 16 2.5 2.87 2.26 60×5 60 5 19 3.5 4.31 3.38 70×5 70 5 21 3.5 5.09 4.00 80×5 80 5 22 4 5.87 4.61 90×5.5 90 5.5 24 4 7.07 5.55 100×6 100 6 26 5 8.67 6.81 120×6.5 120 6.5 30 5 11.19 8.78 140×7 140 7 33 6 14.13 11.10 140×9 140 9 35 6 16.93 13.30 160×8 160 8 36 7 18.04 14.17 160×10 160 10 38 7 21.24 16.68 180×9 180 9 40 7 22.26 17.50 180×11 180 11 42 7 25.88 20.32 200×10 200 10 44 8 27.47 21.58 200×12 200 12 46 8 31.47 24.72 220×11 220 11 48 8.5 32.94 25.87 220×13 220 13 50 8.5 37.34 29.33 240×12 240 12 52 9 38.91 30.55 240×14 240 14 54 9 43.71 34.32 270×12 270 12 55 9.5 43.92 34.53 270×14 270 14 57 9.5 49.37 38.77
Bulb Flat Steel in S275JR
Bulb flat steel is widely applied in shipbuilding, marine engineering, bridge construction and general steel structure projects. Featuring outstanding flatness, good weldability and superior bending performance, it provides stable structural reinforcement for ship hulls, deck structures and various engineering steel components. In marine and shipbuilding fields, it is commonly used for ship side plates, deck stiffeners, bulkhead reinforcements and hull internal structural parts. Owing to its high rigidity, stable dimension and reliable durability, bulb flat steel has become an essential profile for shipyards, offshore platforms and port engineering construction.
As a mainstream grade for bulb flat steel, S275JR is well recognized for its excellent weldability, good toughness and strong impact resistance, which makes it highly popular in shipbuilding and structural engineering. It owns a tensile strength of 370-530 MPa and a minimum yield strength of 275 N/mm², perfectly suitable for manufacturing ship structural parts, marine reinforcing components and general engineering load-bearing structures.
Bulb Flat Steel S235JR / S275JR
Bulb flat steel is mainly used for shipbuilding, marine engineering, bridge and steel structure construction. It has good weldability, bending performance and dimensional stability, widely applied in hull reinforcement, deck stiffeners and bulkhead structural parts.
S235JR and S275JR grade bulb flat steel features excellent weldability and impact resistance. Tensile strength 370-530 MPa, minimum yield strength 235/275 N/mm², ideal for marine stiffeners, bridge components and general construction structural parts.
What is Bulb Flat Steel and what is it used for?
Bulb flat steel, also known as marine bulb flat or shipbuilding bulb flat bar, is measured by height × thickness × weight per metre.
These sections are manufactured from S235JR, S275JR and marine grade steel, featuring excellent machinability, weldability and bending performance. Our stocks are available in hot rolled mill finish, painted or hot dip galvanized finish to provide good corrosion resistance for marine and engineering projects. To further improve anti-rust performance, bulb flat steel can be painted or galvanized after processing.
Bulb flat steel is widely used in shipbuilding, marine engineering, bridge building and steel structure projects. It is mainly used for hull reinforcement, deck stiffeners and internal bulkhead structures where high rigidity and stability are required.
If you are uncertain whether your project needs bulb flat steel or other structural steel profiles, we recommend you consult a structural engineer or other qualified professional.
Bulb flat steel is supplied in standard lengths up to 12 metres long and can be easily cut, drilled, bent and machined. It is perfectly suitable for all common welding methods. Bulb flat steel is produced in accordance with EN 10067, GB/T 9945 and EN 10025-2 standards, adopting S235JR and S275JR grades, which are the most widely used steel specifications for shipbuilding and general structural construction.
Shandong Zhuosheng Steel Co.,Ltd is a large-scale iron and steel enterprise integrating iron and steel production, processing, distribution and trade. The comprehensive strength has jumped to the forefront of the domestic steel industry.
Zhuosheng Steel is committed to the research and development, production and processing of carbon steel and profiles and pipes, with strong research and development strength and reliable quality assurance capabilities. Products are suitable for nuclear power, aviation, marine engineering, oil exploration, construction and other fields. The comprehensive annual production capacity is 500,000 tons, and the products are exported to more than 100 countries and regions.
Q: Can you send samples?
A: Of course, we can send samples to all parts of the world, our samples are free, but customers need to bear the courier costs.
Q: What product information do I need to provide?
A: Quality grade, width, thickness, coating, and the number of tons you need to purchase.
Q: What are the shipping ports?
A: Under normal circumstances, we ship from Shanghai, Tianjin, and Qingdao ports, you can choose other ports according to your needs.
Q: About product prices?
A: Prices vary from period to period due to cyclical changes in the price of raw materials.
Q: How long does your delivery time take?
A: In general, our delivery time is within 7-15 days, and may be delayed if the demand is extremely large or special circumstances occur.
Q: Can I go to your factory to visit?
A: Of course, we welcome customers from all over the world to visit our factory. However, some of the plants are not open to the public.
Q: Does the product have a quality inspection before loading?
A: Of course, all our products are strictly tested for quality before packaging, and unqualified products will be destroyed.
Q: How to pack the products?
A: The inner layer has a waterproof paper outer layer with iron packaging and is fixed with a fumigation wooden pallet. It can effectively protect products from corrosion during ocean transportation.
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