Overview - EN ISO 2400:2025 (Ultrasonic testing, Standard block No. 1)
EN ISO 2400:2025 (ISO 2400:2025) is the European endorsement of the ISO specification for standard block No. 1 used in ultrasonic non‑destructive testing (NDT). It defines the material, manufacture, dimensional and testing requirements for a steel block used to set, check and verify ultrasonic test equipment in manual inspections. This third edition supersedes EN ISO 2400:2012 and aligns CEN and ISO requirements.
Key topics and technical requirements
- Material: Steel grade S355J0 (EN 10025‑2) or equivalent.
- Pre‑machining size: Rough‑machined to about 320 mm × 120 mm × 30 mm before heat treatment.
- Heat treatment: Austenitizing at 920 °C for 30 min, water quenching, then tempering at 650 °C for 3 h; final cooling in still air.
- Surface finish: All external surfaces machined to Ra ≤ 0.8 µm.
- Internal soundness: Post‑treatment ultrasonic inspection with a longitudinal probe (≥10 MHz, 10–15 mm transducer) across all four long faces; gain set to yield grain scatter noise at 10% screen height and no echoes exceeding that level.
- Sound velocities: Determined in three perpendicular directions (Annex A). Required values:
- Longitudinal vL = 5920 m/s ± 30 m/s
- Transverse vT = 3255 m/s ± 15 m/s
- Measurement accuracy ±0.2% and isotropy limits (max directional differences: 25 m/s for vL, 15 m/s for vT).
- Marking & documentation: Permanent marking with ISO 2400, manufacturer ID, and serial number. Manufacturer must issue a declaration of conformity including measured velocities per direction.
- Resources: CAD file of the block is available from ISO; the standard references ISO 5577 and EN 10025‑2.
Applications and who uses this standard
- NDT technicians and inspectors - for routine setting/checking of ultrasonic flaw detectors and probes (time base, sensitivity, beam angle, index point).
- Inspection and testing laboratories - to verify instrument performance and ensure repeatable measurements.
- Manufacturers of calibration/standard blocks and ultrasonic equipment - to produce blocks compliant with international requirements.
- Quality managers and welding inspectors - for conformity evidence and equipment validation in industrial inspection programs (welds, forgings, plate testing).
Related standards
- ISO 5577 - Ultrasonic testing vocabulary (terms & definitions)
- EN 10025‑2 - Technical delivery conditions for S355J0 structural steel
- ISO 7963 - Standard block No. 2 (smaller, simpler block)
This standard is essential for consistent, repeatable ultrasonic testing and for suppliers and users who require traceable, documented verification of ultrasonic equipment.
