Aluminium bulb angles for marine application
1987 Edition

IS 6449 prescribes specific aluminium alloys and tempers for marine bulb angles to ensure optimal corrosion resistance and mechanical strength in marine environments. Commonly used alloys include Aluminium 6061 and 6063, valued for their marine-grade durability and mechanical attributes. The temper states frequently specified are T6 (solution heat-treated and artificially aged) offering higher strength, and T4 (solution heat-treated and naturally aged) which provides enhanced formability. These selections balance corrosion resistance, weldability, and strength essential for marine structural components.

Aluminium bulb angles under IS 6449 are designated as 'AMBA' followed by a numeric value representing the height in millimeters (e.g., AMBA 80). Plate thickness options are 5, 10, or 15 mm, with plate width defined as 40 times the thickness. Key dimensions include height (H), breadth (B), and other parameters like C and S detailed in Table 1. Mass per unit length is provided excluding the plate. Sectional properties comprise sectional area (a), centroid distance (ex), moment of inertia (Ix), and section modulus (Zx). For instance, the AMBA 80 has a height of 80 mm, breadth of 32 mm, thickness of 3.5 mm, and mass of 1.88 kg/m. The full range from AMBA 30 to AMBA 150 along with their properties is available in the standard.

The designation system for aluminium bulb angles in IS 6449 uses the prefix 'AMBA' followed by the height dimension in millimeters. For example, AMBA 30 indicates a bulb angle with a height of 30 mm. The standard also specifies other dimensional parameters such as width (B), thickness (t), and supplementary measurements like C and S. Sectional properties like sectional area, mass per length, centroid location, moment of inertia, and section modulus are tabulated for these designations. This systematic naming facilitates straightforward identification and selection for marine structural applications.

Dimensional tolerances for aluminium bulb angles as per IS 6449 refer to the provisions in IS 3936-1981, which outlines permissible deviations for aluminium alloy structural sections. Typical tolerances include thickness variations around ±0.2 mm, width of legs ±0.5 mm, bulb radius ±1 mm, and length deviations around ±5 mm or as specified. These tolerances ensure proper fit, structural integrity, and performance in marine applications. Exact tolerance details are specified in Table 1 of IS 6449 and should be consulted directly for precise values.

According to IS 6449 Clauses 7.1 and 7.2, each batch or bundle of aluminium bulb angles must be distinctly marked with the designation (e.g., AMBA 80), alloy and temper information, the manufacturer's name, and the lot number or year of production. Additionally, these angles may bear the BIS Standard Mark, confirming conformity with quality and inspection standards under BIS supervision. This marking protocol guarantees traceability, quality assurance, and facilitates identification throughout supply and construction processes.