ISO 4997:2015

Overview

ISO 4997:2015 specifies requirements for cold‑reduced carbon steel sheet of structural quality - commonly supplied in grades CR220, CR250, CR320, and CH550. The standard covers chemical composition, manufacture, mechanical properties, surface quality, dimensional tolerances and testing for sheets and coils intended for structural fabrication (bolting, riveting, bending, forming and - where appropriate - welding). Typical dimensions are thicknesses from about 0.36 mm to 3 mm and widths from 600 mm upwards, supplied in coils or cut lengths.

Key topics and requirements

• Grades and metallurgy: Limits on carbon, manganese, phosphorus and sulphur (e.g., C max 0.15% for CR220; C up to 0.25% for other grades). Limits on minor elements (Cu, Ni, Cr, Mo, Nb, V, Ti) and rules for their sums are included.
• Manufacture and condition: Cold reduction followed by annealing and usually a light skin‑pass (except CH550 which is not annealed after reduction). Manufacturer’s processes are generally at their discretion but heat analysis can be supplied on request.
• Mechanical properties: Specified yield, tensile strength and elongation values for CR220, CR250 and CR320 (for example CR320: Re ≈ 320 MPa, Rm ≈ 400 MPa). CH550 is a high‑strength grade with yield approaching tensile strength and is tested using 0.5% proof strength per ISO 6892‑1.
• Weldability: Product is normally weldable under suitable parameters; however, welding becomes harder as carbon exceeds 0.15% and CH550 is generally not recommended for welding because welding heat can reduce its strength.
• Surface quality and finish: Two grades - Surface A (unexposed) allows minor defects that do not affect formability or coatings; Surface B (exposed) requires one face to be free of imperfections affecting coating appearance.
• Testing and conformity: Heat and product chemical analyses, tensile testing (per ISO 6892‑1), dimensional/shape tolerances (per ISO 16162), retest and inspection rules are specified.

Applications and users

• Useful for structural fabricators, steel producers, procurement/specification engineers, quality and inspection teams, and designers of bolted, riveted or formed steel components.
• Typical applications: structural panels, chassis, frames and fabricated assemblies where forming, bending and mechanical fastening are required.
• Specification helps ensure predictable formability, strength and surface condition for downstream painting or coating processes.

Related standards

• ISO 6892‑1 (tensile testing)
• ISO 16162 (dimensional and shape tolerances)
• Exclusions referenced in ISO 4997: ISO 3574, ISO 5954, ISO 13887, ISO 14590 (other cold‑reduced qualities and special formability/hardness/strength classes).

Keywords: ISO 4997, cold‑reduced carbon steel sheet, structural quality, CR220, CR250, CR320, CH550, weldability, surface quality, mechanical properties, chemical composition.