Overview
ISO 642:1999 - "Steel - Hardenability test by end quenching (Jominy test)" is an International Organization for Standardization (ISO) method for determining the hardenability of steel using the Jominy end‑quench procedure. The standard defines test-piece geometry, heating and quenching conditions, hardness measurement locations, result expression (J‑codes), and reporting requirements. It also includes informative annexes on specification, additional reporting details and calculation of hardenability.
Key topics and technical requirements
- Test piece: cylindrical bar, 25 mm diameter × 100 mm length (with specified end forms and marking for orientation).
- Sampling & preparation: guidelines for machining or forming test pieces, recommended normalizing before machining, and precautions to avoid decarburization or scale.
- Heating: uniform heating into the austenitic range, maintained for the agreed period (standard reference: 30 min holding time unless otherwise agreed or validated).
- Quenching apparatus: controlled water jet from a vertical supply pipe; water temperature (20 ± 5 °C); jet height and pipe-to-piece spacing are specified to ensure reproducible cooling.
- Timing: maximum 5 s between removal from furnace and start of quench; minimum 10 min spraying time (cooling may be completed by immersion).
- Hardness measurement: two longitudinal flats (0.4–0.5 mm deep) ground 180° apart; hardness measured as mean from both flats. Rockwell C (HRC) is standard; Vickers HV30 is permitted by agreement (references: ISO 6508 and ISO 6507 series).
- Measurement points: typical distances from quenched end - 1.5, 3, 5, 7, 9, 11, 13, 15 mm (subsequent at 5 mm intervals). For low‑hardenability steels: first point at 1.0 mm and 1 mm spacing to 11 mm, then 13, 15, 20, 25, 30 mm.
- Results and notation: hardness-distance values plotted as a Jominy curve or reported as Jxx‑d (e.g., J35‑15 = 35 HRC at 15 mm). Annex C provides calculation methods by agreement.
Applications and users
- Purpose: quantify how deep a steel will harden under rapid cooling - essential for selecting steels and designing heat‑treatment cycles.
- Typical users:
- Metallurgists and materials engineers validating steel grades
- Heat‑treatment shops and QA laboratories performing routine hardenability testing
- Design engineers specifying materials for components requiring controlled hardness profiles (gears, shafts, fasteners)
- Standards bodies and product specification writers requiring reproducible test methods
- Practical benefits: produces reproducible Jominy curves for comparing steel grades, verifying production batches, and guiding quench/tempering processes.
Related standards
- ISO 6507‑1 (Vickers hardness test)
- ISO 6508‑1 / ‑2 / ‑3 (Rockwell hardness test - methods, verification, calibration)
Keywords: ISO 642, Jominy test, hardenability test, steel hardenability, Jominy curve, end quenching, hardness testing, Rockwell C, Vickers HV30.
