Overview
ISO 16859-1:2015, "Metallic materials - Leeb hardness test - Part 1: Test method", specifies the procedure for determining the dynamic hardness of metallic materials using the Leeb hardness test. The standard defines seven Leeb scales (HLD, HLS, HLE, HLDL, HLD+15, HLC, HLG), the principle of measurement (ratio of rebound to impact velocity), instrument and test-piece requirements, and the measurement and reporting rules for the Leeb hardness (HL) value.
Key topics and technical requirements
- Measurement principle: HL is calculated from the rebound and impact velocities (HL = 1000 · vR / vA), making Leeb hardness a dimensionless ratio.
- Leeb scales and impact devices: Seven scale/types are covered (D, S, E, DL, D+15, C, G). Results depend on impact device used and are identified as e.g., 570 HLD.
- Testing instrument: Consists of an impact device and electronic unit to measure impact/rebound velocities. Instruments must meet verification and calibration requirements (see ISO 16859-2).
- Test-piece requirements:
- Shape: local surface must be normal to the impact vector; minimum radii of curvature specified for curved surfaces.
- Mass and thickness: minimum mass/thickness requirements depend on impact device; small or thin parts may need rigid support or coupling.
- Surface preparation: remove coatings/scale; follow recommended surface roughness Ra per device (e.g., 2.0 μm for many devices).
- Procedure and environmental controls:
- Daily verification (Annex B) before first use.
- Typical ambient test range suggested: 10 °C to 35 °C (many users control tighter, e.g., 23 °C ± 5 °C).
- Avoid magnetic fields, vibration and relative motion; hold impact device perpendicular to the surface.
- Measurement rules: arithmetic mean of at least three readings; if span >5% of mean, increase to at least 10 readings.
- Uncertainty and corrections:
- Guidance on sources of uncertainty and corrections for testing directions other than gravity (Annex A).
- Procedures for periodic checking and instrument reference information included in Annexes.
Practical applications and users
- Used for rapid, portable hardness checks on metal components, in-process inspection, repair/maintenance, and material verification.
- Typical users: metallurgists, quality assurance/quality control engineers, inspection and maintenance technicians, calibration laboratories, and production engineers who need quick, on-site hardness assessment.
- Useful when comparing material batches, checking heat-treatment effectiveness, or verifying hardness where traditional stationary testers are impractical.
Related standards
- ISO 16859-2 - Verification and calibration of Leeb testing devices (instrument performance).
- ISO 16859-3 - Calibration of reference test blocks (traceability and reference materials).
Keywords: ISO 16859-1, Leeb hardness test, Leeb scales, dynamic hardness, metallic materials, hardness testing, HL, portable hardness tester, calibration.
