Overview
ISO 11971:2020 - "Steel and iron castings - Visual testing of surface quality" specifies acceptance criteria for the visual inspection of steel and iron casting surfaces. The standard defines how to use established visual/tactile comparators (BNIF and SCRATA/CTI) to assess surface roughness and common casting discontinuities, and sets out ordering, test, and reporting requirements for consistent, repeatable surface-quality decisions.
Key topics and requirements
- Scope: Acceptance criteria for visual testing of steel and iron castings, including surface roughness and specific discontinuities.
- Comparator systems: Uses BNIF (BNIF 359) and SCRATA or CTI comparators as reference standards for visual/tactile assessment. Comparators are intended to represent the worst (roughest) condition for an acceptance level.
- Surface conditions covered:
- Surface roughness
- Thermal dressing
- Mechanical dressing
- Non‑metallic inclusions
- Gas porosity
- Fusion discontinuities
- Expansion discontinuities
- Metal inserts
- Test method: Surfaces are examined visually without optical aids exceeding 1× magnification. Large-format comparators (recommended ≥ 15 000 mm²) are preferred to reflect the irregular nature of cast surfaces and improve repeatability.
- Acceptance criteria:
- SCRATA comparator set applicable to steel and iron castings.
- BNIF comparator categories S1 and S2 usable for all alloys; category S3 for steel castings only.
- Annex A provides optional roughness and discontinuity acceptance levels and equivalency guidance between BNIF and SCRATA systems.
- Ordering information: Purchaser and supplier should agree on areas to be inspected, number of castings, designated acceptance levels (multiple levels may apply to different surfaces), and any unacceptable discontinuity types.
- Test report contents: Identification of castings, tester name and qualification, comparator reference used, designated category/level for each area, and date of testing.
Applications and users
ISO 11971:2020 is used by:
- Foundries and casting manufacturers performing quality control and delivery inspection
- Quality, inspection, and NDT engineers defining acceptance limits for cast parts
- Purchasing and design engineers specifying surface acceptance criteria on drawings or models
- Third‑party inspectors and certification bodies assessing conformance to agreed surface standards
Practical applications include final inspection of as‑cast or finished cast surfaces, contract acceptance checks, and supplier quality agreements where visual surface quality is critical to function or appearance.
Related standards
- BNIF 359 (BNIF recommendation for reference samples)
- SCRATA / CTI comparator sets (surface quality comparators available from Casting Technology International)
- ISO 11971 references these comparator systems but contains no normative references to other ISO documents.
Keywords: ISO 11971:2020, visual testing, surface quality, steel castings, iron castings, BNIF, SCRATA, CTI, surface roughness, casting discontinuities, casting inspection.