Bulb Flat Bar - Marine Grade Bulb Flat Steel for Shipbuilding

1. What is bulb flat bar for shipbuilding?

Spherical flat bar (also known as marine spherical 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 spherical 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 for Round Flat Bar

Dimensions of Round Flat Bar

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.

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.