Overview
ISO 9034:1987 specifies tolerances on dimensions, shape and mass for hot-rolled structural steel wide flats of non‑alloyed and alloyed steels (excluding stainless steels). It applies to wide flats (width >150 mm up to 1250 mm, thickness generally >4 mm) supplied in lengths and to steels with specified minimum yield strength up to 700 N/mm2. The standard defines how to measure width, thickness, flatness, straightness and squareness and includes an annex on excess mass for deliveries at actual mass.
Key topics and technical requirements
- Scope and definitions
- Covers hot‑rolled wide flats (not coiled) with sharp edges; excludes stainless steels.
- Applies where specified minimum yield strength ≤ 700 N/mm2; some shape tolerances are limited to steels ≤ 460 N/mm2 or require agreement for higher‑strength or quenched/tempered steels.
- Width tolerance
- ±2% of nominal width, limited to a maximum deviation of 10 mm.
- Thickness tolerance
- Two tolerance classes:
- Class A: variable minus tolerance depending on nominal thickness (see table values in the standard).
- Class B: constant minus tolerance of 0.3 mm.
- Tolerances tabulated for nominal thicknesses up to 100 mm; over 100 mm by agreement.
- Measurement point: at least 15 mm from longitudinal edges (alternate agreed measurement 15–30 mm).
- Transverse thickness difference
- Maximum permissible difference across a cross‑section is specified by nominal width bands (values given in table 2).
- Shape tolerances
- Flatness
- Perpendicular to rolling (k1): typically 0.3% of width for thickness ≤ 50 mm (other cases by agreement).
- Along rolling (k2): measured over 1 000 mm with measuring points of 7 or 3 mm (default 7 mm).
- Over total length (k3): options of 0.7% of length (max 20 mm) or 0.3% of length (max 10 mm); default 0.7% if unspecified.
- Straightness: options of 0.25% or 0.125% of length (default 0.25%).
- Squareness and angular accuracy: tolerances vary with thickness; must be specified when ordering.
- Length tolerance
- Defined in the standard (order specification required for particular requirements).
- Mass / excess mass (Annex)
- Excess mass percentages for Classes A and B are tabulated by nominal thickness and delivered mass; theoretical mass uses steel density 7.85 kg/dm3.
Applications and users
- Practical for steel mills, rolling mills, steel service centers, fabricators, structural engineers, quality inspectors, and procurement specialists who need consistent dimensional and shape requirements for structural wide flats used in construction, infrastructure, heavy fabrication and welded assemblies.
- Useful during ordering, inspection, acceptance testing and contract specification to avoid disputes over dimensional compliance and delivered mass.
Related standards
- ISO 7788 - Steel: surface finish of hot‑rolled plates and wide flats - delivery requirements (referenced for surface discontinuities and ground parts).
- Many clauses in ISO 9034 note that specific tolerances or alternative measurement methods must be agreed at the time of ordering; users should reference the full standard for tables and measurement diagrams.
