Overview
EN ISO 4545-4:2018 / ISO 4545-4:2017 specifies a standardized table of Knoop hardness values for metallic materials. The document provides tabulated HK values calculated from the Knoop hardness formula for use in tests performed in accordance with ISO 4545-1 (Knoop test method). The European adoption (EN ISO 4545-4:2018) endorses the ISO text without modification and supersedes the 2005 edition.
Key topics and requirements
- Purpose: A ready reference table (Table 1) for converting measured Knoop indentation diagonals into Knoop hardness numbers (HK) across a range of test forces.
- Test forces covered: Values include very low to comparatively high forces (examples given in the standard: 0.009807 N (HK 0.001), 0.01961 N (HK 0.002), 0.04903 N (HK 0.005) up to 19.613 N (HK 2) and intermediate forces).
- Data origin: The tabulated HK values were calculated using the Knoop hardness formula as defined in ISO 4545-1.
- Technical change from previous edition: The 2017/2018 edition adds data for several very low and one high test force and removes the separate calculation clause - users are expected to rely on the table together with ISO 4545-1 procedures.
- Normative reference: ISO 4545-1 (Knoop hardness test - Part 1: Test method) is required reading for correct test execution and interpretation.
Applications
- Metallurgical testing laboratories: Use the table to convert measured Knoop indentation diagonals into HK numbers quickly and consistently.
- Quality control & production: Manufacturers of metals and metal components apply EN/ISO 4545-4 when verifying hardness specifications for parts, coatings and heat-treated materials.
- Materials research & development: Researchers assessing microhardness (especially with low test forces) will find the expanded low-force data helpful.
- Calibration and conformity assessment: Test houses and certification bodies use the standard to ensure comparability of Knoop hardness results across labs and contracts.
- Typical users: Metallurgists, hardness technicians, materials engineers, QA/QC personnel, and standards administrators.
Related standards
- ISO 4545-1 - Metallic materials - Knoop hardness test - Part 1: Test method (normative reference)
- Other parts of the ISO 4545 series (see ISO catalogue for the full list)
- EN ISO 4545-4:2018 - European adoption/endorsement of ISO 4545-4:2017
Keywords: Knoop hardness, ISO 4545-4:2017, EN ISO 4545-4:2018, Knoop hardness table, HK values, metallic materials, hardness testing, ISO 4545-1, test forces, indentation diagonal.