Overview
ISO 4967:2013 - Steel: Determination of content of non‑metallic inclusions - micrographic method using standard diagrams - defines a standardized metallographic procedure to assess non‑metallic inclusions in rolled or forged steels (reduction ratio ≥ 3). The standard uses chart diagrams (Annex A) for visual comparison at 100× magnification in a 0.50 mm² square field and also provides for the use of image‑analysis technologies (Annex D). It is widely used in steel testing, quality control and material acceptance, with caveats about operator influence and reproducibility.
Keywords: ISO 4967, non‑metallic inclusions, micrographic method, steel testing, metallography, inclusion content, image analysis
Key topics and technical requirements
- Scope and applicability
- Applies to rolled or forged steel products with a reduction ratio of at least 3; some steels (e.g., free‑cutting steels) may require special treatment.
- Principle
- Compare observed microscope fields to standard chart diagrams representing five inclusion groups: A (sulfide), B (aluminate), C (silicate), D (globular oxide) and DS (single globular).
- Observation conditions
- Standard observation at 100× magnification on a square field of 0.50 mm²; same magnification/method must be used for charts and test.
- Use of a reticle or overlay (grid) is required for reproducible rating and measurements.
- Methods of examination
- Method A: record the worst field for each inclusion type (fine and thick series).
- Method B: rate each field individually against the chart diagrams and record indices.
- Indices and reporting
- Diagrams carry index numbers (0.5 to 3) indicating increasing inclusion content; thickness classes (fine, thick) and oversized inclusion reporting are required.
- Non‑traditional inclusions are assigned to the best morphological group and identified with a descriptive subscript in the report.
- Sampling and specimen prep
- Specimen polished surface ≈ 200 mm² (example: 20 mm × 10 mm), cut parallel to the product axis and located between surface and center; sampling details and number of samples are defined in product standards or by agreement.
- Image analysis
- Annex D provides guidance for using image‑analysis technologies to determine total inclusion length, count or diameter for better reproducibility.
Applications and users
- Who uses ISO 4967
- Steel producers, metallurgists, inspection laboratories, quality control engineers, material certifiers and product specifiers.
- Practical uses
- Acceptance testing for mechanical components, process control in steelmaking, failure analysis, supplier qualification, and assessing steel suitability for critical applications (bearing, forging, structural components).
Related standards / references
- ISO 4967 was prepared by ISO/TC 17/SC 7 (Methods of testing other than mechanical tests and chemical analysis). Product‑specific standards or contractual agreements often define sampling frequency and acceptance criteria; users should consult applicable product standards when applying ISO 4967.