Overview
ISO 657-19:1980 - "Hot-rolled steel sections - Part 19: Bulb flats (metric series) - Dimensions, sectional properties and tolerances" - specifies the geometry, sectional properties and production tolerances for metric-series bulb flats produced by hot rolling. The standard defines designation rules, tabulated dimensions and sectional data (mass, area, centroids, moments of inertia and section moduli) and the acceptable dimensional tolerances and shape limits used for design, procurement and quality control.
Key topics
- Designation: Bulb flats are identified by width x thickness (example: 200 x 10).
- Dimensions and sectional properties: A comprehensive table lists standard widths, thicknesses and corresponding mass per metre, cross-sectional area, centroid positions, moments of inertia (Ix) and section modulus (zx) for each nominal size.
- Dimensional tolerances: The standard gives tolerances on width (b) and thickness (t) in tabulated form according to size ranges-used to control manufacturing and acceptance.
- Corner radius (r2): Maximum permitted corner radii are specified by thickness ranges (for example: t ≤ 6 mm → r2 up to 1.5 mm; >6–9 mm → about 2.0 mm; >9–13 mm → 3.0 mm; >13–17 mm → 4.0 mm).
- Camber: Maximum allowable camber (bow) is 0.35% of the total length.
- Length and mass: Cutting tolerances on length are provided; reduced length tolerances can be agreed between buyer and supplier. If a tolerance on linear mass is preferred instead of thickness tolerance, that arrangement should be recorded in the applicable national standard.
Applications
- Structural design and analysis where bulb flats are used as load-bearing elements, stiffeners or connection plates.
- Steel manufacturers and rolling mills for production planning, section tooling and quality control.
- Fabricators and detailers for accurate part specification, cutting and fit-up.
- Procurement and inspection: purchase specifications and acceptance checks use the standard’s designation, dimensions and tolerances.
- BIM libraries and engineering databases that require standardized section properties for calculations and documentation.
Who uses this standard
- Structural and civil engineers, detailers and fabricators
- Hot-rolling steel producers and quality control engineers
- Procurement officers and materials inspectors
- Standards bodies and national committees aligning steel section specifications
Related standards
- ISO 657 (other parts) - the broader series covering hot-rolled steel section types and metrics
- National and regional steel-shape standards (for alignment or substitution where needed)
Keywords: ISO 657-19:1980, bulb flats, hot-rolled steel sections, dimensions, sectional properties, tolerances, metric series, steel profile, camber, corner radius.
Open preview (PDF)Hot-rolled steel sections — Part 19: Bulb flats (metric series) — Dimensions, sectional properties and tolerances
