What are the primary aluminium alloys specified for these bulb angles?

The standard covers alloys like N5, N8, H20, and H30, with properties corresponding to those specified in IS 733.

What are the standard supply lengths for these bulb angles?

The standard lengths are generally between 4 and 7 metres, unless otherwise agreed upon between the purchaser and manufacturer (Clause 9.1).

What is the material designation for the most common marine grade alloy?

Alloy N8 (corresponding to international designation 5083) in the 'M' (as manufactured) temper is very common for its excellent corrosion resistance and good weldability.

Are custom sizes available?

Yes, sizes other than those listed in Table 1 may be supplied by mutual agreement between the purchaser and the manufacturer (Note under Table 1).

IS 6449

: 1987

Aluminium bulb angles for marine application

CurrentSpecializedSpecificationBIMStructural Engineering · Structural Engineering and Structural Sections

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This standard specifies the dimensions, sectional properties, material requirements, and manufacturing tolerances for aluminium alloy bulb angles. These sections are intended for use in shipbuilding and other marine structural applications where a high stiffness-to-weight ratio is required.

Aluminium bulb angles for marine application

Quick Reference Values

Minimum 0.2% Proof Stress (Alloy N8/5083-O)125 MPa

Minimum Tensile Strength (Alloy N8/5083-O)275 MPa

Minimum Elongation (Alloy N8/5083-O)12 %

Standard length of bulb angles4 to 7 m

Straightness toleranceNot exceeding 1.33 mm per metre run

Standard length tolerance+100 mm, -0 mm

Practical Notes

Ensure the correct alloy grade (e.g., N5, N8, H20, H30) is specified based on the required strength, weldability, and corrosion resistance for the specific marine environment.

Pay close attention to the temper condition (e.g., M for as manufactured, WP for solution treated and artificially aged) as it significantly affects the mechanical properties of the final product.

The bulb increases the section modulus and resistance to local buckling, making it a very efficient profile for stiffening plates on ships' hulls and superstructures.