rolled steel bulb flats
1979 Edition

IS 1863 defines the standardized dimensions and sectional properties for hot-rolled steel bulb flats, which feature a flat web and a bulbous flange. The widths typically span from approximately 40 mm up to 125 mm, with thicknesses ranging between 6 mm and 25 mm. Sectional attributes covered include cross-sectional area, moments of inertia about principal axes, section moduli, and radii of gyration. These parameters are essential for structural design and are systematically tabulated within the standard.

Per IS 1863 Clause 2.1, bulb flats must be fabricated from steel grades conforming to the following Indian Standards: IS 226 (standard structural steel), IS 961 (high tensile structural steel), IS 2062 (structural steel suitable for fusion welding), and IS 3039 (steel tailored for shipbuilding applications). The selected grade depends on the intended application, ensuring the required mechanical properties, weldability, and toughness are met.

IS 1863 specifies dimensional tolerances on width and thickness based on the size ranges, detailed in Table 1 of the standard. Typically, width tolerances vary roughly between ±1.5 mm to ±4 mm depending on the dimensions, while thickness tolerances range from +0.7/-0.3 mm up to +1.2/-0.4 mm. Weight is allowed a tolerance of ±2.5% of the theoretical mass per unit length, and length tolerance is generally +100 mm unless otherwise agreed upon.

According to Clause 5.2 and Table 3 of IS 1863, the permissible maximum radius of curvature at corners is assigned relative to the thickness of the section. For thicknesses up to 6 mm, the radius must not exceed 1.5 mm; for thicknesses over 6 mm up to 9 mm, the limit is 2.0 mm; over 9 mm up to 13 mm, 3.0 mm; and for thicknesses over 13 mm up to 17 mm, the maximum radius allowed is 4.0 mm. This ensures smooth corner profiles that reduce stress concentrations and maintain structural integrity.

Yes, IS 1863 includes supplementary sizes in Table 1A that are not encompassed by ISO/DIS 4974. These additional dimensions can be procured subject to mutual agreement between the purchaser and supplier. This provision offers flexibility in sourcing bulb flats outside the standard ISO range, accommodating specialized structural requirements.