Overview
EN ISO 642:2024 - Steel: Hardenability test by end quenching (Jominy test) defines the standardized method for measuring the hardenability of steels using the Jominy end-quench test. The document specifies test-piece geometry, heating, quenching and hardness-measurement procedures to produce a reproducible Jominy curve (hardness vs. distance from quenched end). The 2024 edition supersedes EN ISO 642:1999 and includes revised test-piece dimensions, updated heat‑treatment and apparatus requirements, and options to calculate the Jominy curve by accepted mathematical models (Annex C).
Key topics and technical requirements
- Test-piece geometry: cylindrical specimen machined to 25 mm diameter and at least 100 mm length; test length L = 97 ± 0.5 mm.
- Sampling and preparation: guidance for obtaining specimens from product or forging; recommended minimum reduction ratio 5:1 before sampling for continuous-cast products.
- Heat treatment: austenitizing at a specified temperature for 30 minutes (t), with a maximum 5 s lag between removal from furnace and start of quenching.
- Quenching apparatus and conditions: vertical water supply pipe internal diameter 12.5 ± 0.5 mm, water jet height 65 ± 10 mm, distance from pipe to lower end 12.5 ± 0.5 mm; standardised fixture/centring devices and water temperature requirements are defined.
- Hardness measurement: flats are machined along the axis (flat depth 0.4–0.5 mm) and hardness values (HRC or HV30) are measured at defined distances from the quenched end to produce the Jominy hardness profile (symbols such as Jd, Jxx‑d, JHVxx‑d).
- Results and codification: procedures for drawing hardness curves, expressing hardenability characteristics, and codifying test results are included. Calculation of the Jominy curve by an accepted mathematical model is permitted by agreement.
Applications and practical value
- Heat‑treatment design: determine the depth and variation of hardening for selecting quench/temper parameters.
- Material selection and specification: compare steels by hardenability for gears, shafts, fasteners and other critical components.
- Quality control and R&D: routine lab testing to verify production lots, validate heat-treatment cycles, and support metallurgical development.
- Failure analysis: assess whether inadequate hardening contributed to component failure.
Who should use this standard
- Steel manufacturers and foundries, heat‑treatment shops, metallurgists, materials testing laboratories, design engineers and quality managers involved in specifying or verifying steel hardenability and heat‑treatment processes.
Related standards
- ISO/TC 17 (Steel) and CEN/TC 459 technical committees prepare and maintain related test methods; Annex C of EN ISO 642:2024 provides computational methods for the Jominy curve. For procurement and conformity, consult product-specific standards referenced by purchasers or national standards bodies.
Keywords: EN ISO 642:2024, Jominy test, hardenability, steel hardenability test, end quenching, Jominy curve, hardness profile, test-piece dimensions.
