Overview
EN ISO 6506-2:2018 - "Metallic materials - Brinell hardness test - Part 2: Verification and calibration of testing machines" defines how Brinell hardness testing machines are verified and calibrated. It specifies both direct and indirect verification procedures to ensure testing machines produce reliable Brinell hardness results in accordance with ISO 6506-1. The standard applies to fixed-location and portable hardness testing machines and explains when each verification type is required. For machines that cannot meet the specified force‑time profile, a modified direct verification is possible using Annex B.
Key topics and technical requirements
- Direct verification (checks individual machine parameters)
- Measurement of test forces across the working range; each force measurement must be within ±1.0% of the nominal test force.
- Force measurement methods include force‑proving instruments per ISO 376 (Class 1) or balancing against calibrated masses/force accurate to ±0.2%.
- Verification of indenter ball properties: diameter tolerances by ball size (e.g., 10 mm ±0.005 mm; 5 mm ±0.004 mm; 2.5 mm ±0.003 mm; 1 mm ±0.003 mm), hardness ≥ 1500 HV for tungsten‑carbide balls, and density ~ 14.8 ±0.2 g/cm³.
- Calibration of the indentation diameter measuring system (scale accuracy typically within ±0.5%) for each objective lens and measurement axis.
- Verification of the testing cycle/force‑time profile (modified procedure available for non‑conforming machines via Annex B).
- Environmental and traceability requirements: verification at (23 ±5) °C when possible and use of instruments traceable to the SI.
- Indirect verification
- Uses Brinell reference blocks calibrated per ISO 6506-3 to check overall machine performance by comparing measured hardness values against certified block values.
- Scope notes
- Machines used for multiple hardness methods must be verified separately for each method.
- Clause references cover intervals between verifications and reporting/calibration certificate content.
Applications and practical value
- Ensures measurement accuracy and reproducibility of Brinell hardness results used in quality control, incoming inspection, and material certification.
- Supports traceable calibration practices for manufacturers of hardness testers, calibration laboratories, and metallurgical test labs.
- Critical for regulated industries (automotive, aerospace, heavy engineering, steel production) where hardness measurement forms part of material acceptance criteria.
Who uses this standard
- Calibration laboratories and metrology labs
- Quality assurance and inspection teams in manufacturing
- Hardness tester manufacturers and service engineers
- Metallurgists and materials testing laboratories
Related standards
- ISO 6506-1 - Brinell hardness test: Test method
- ISO 6506-3 - Calibration of Brinell reference blocks
- ISO 376 - Calibration of force‑proving instruments
Keywords: EN ISO 6506-2:2018, Brinell hardness test, verification and calibration, hardness testing machine verification, indenter ball, reference blocks, ISO 6506-3, ISO 376, calibration certificate.