ISO 2400:2025

Overview

ISO 2400:2025 - "Non‑destructive testing - Ultrasonic testing - Specification for standard block No. 1" defines the material, manufacture, dimensions and verification procedures for a steel standard block No. 1 used to set, check and verify ultrasonic test equipment in manual ultrasonic testing (UT). The third edition updates terminology (from “calibration block” to “standard block”), tightens sound‑velocity measurements (three perpendicular directions) and adds a CAD file reference.

Keywords: ISO 2400, ultrasonic testing, standard block No. 1, non‑destructive testing, NDT, calibration block, S355J0 steel, sound velocity.

Key Topics

• Material and grade: Blocks shall be made from steel grade S355J0 or equivalent (EN 10025‑2).
• Manufacture and heat treatment:
  • Rough‑machined to ~320 × 120 × 30 mm before heat treatment.
  • Austenitize at 920 °C for 30 min, quench in water, temper at 650 °C for 3 h, then air cool.
  • Final surface finish Ra ≤ 0.8 µm.
• Ultrasonic inspection for internal quality: Post‑heat‑treatment UT using a longitudinal probe (≥10 MHz, 10–15 mm transducer) over all four long faces; grain scatter noise set to 10% of screen height and no echo may exceed that noise level.
• Sound‑velocity requirements:
  • Determined in three perpendicular directions (Annex A procedures).
  • Longitudinal velocity: 5 920 m/s ± 30 m/s; transverse velocity: 3 255 m/s ± 15 m/s.
  • Measurement uncertainty ±0.2% (±12 m/s longitudinal, ±6 m/s transverse); isotropy limits: max difference 25 m/s (long.) and 15 m/s (trans.).
• Marking & conformity: Permanent marking with “ISO 2400”, manufacturer and serial number. Manufacturer must issue a declaration of conformity including measured velocities by direction.
• Optional features: Two zero‑point slots or a circular reflector can be included to assist angle‑beam probe setup; block thickness may exceed 25 mm if declared.

Applications

• Routine setting, sensitivity checks and verification of manual ultrasonic equipment.
• Verification of time base, beam angle and probe index point for angle‑beam transducers.
• Production and calibration of reference blocks by manufacturers and calibration laboratories. Primary users: NDT technicians, inspection bodies, calibration labs, welding/NDT engineers, asset owners and providers of UT equipment and reference blocks.

Related Standards

• ISO 5577 (UT vocabulary)
• EN 10025‑2 (steel grade S355J0)
• See also ISO 7963 (standard block No. 2) and other UT block specifications referenced in the ISO 2400 bibliography.

Practical note: a CAD file of the standard block is available from ISO for manufacturers and labs to ensure dimensional compliance.