ISO 642:2024

Overview

ISO 642:2024 – Steel - Hardenability Test by End Quenching (Jominy Test) is an international standard published by the International Organization for Standardization (ISO). This document outlines the uniform method for determining the hardenability of steel using the end quenching (Jominy) test. The test involves heating a cylindrical steel sample and quenching one end with water under specified conditions, then measuring the hardness at various distances from the quenched end. The results provide critical data on a steel’s capacity to harden in depth, which is vital for steels used in engineering, automotive, and construction applications. When appropriate and by agreement, ISO 642:2024 allows for the use of accepted mathematical models to calculate the Jominy hardenability curve instead of physical testing.

Key keywords: steel hardenability, Jominy test, ISO 642:2024, end quenching, hardness measurement, standard test method.

Key Topics

• Sample Preparation: The standard requires a cylindrical test piece 25 mm in diameter and at least 100 mm long, prepared by machining or hot working per specified guidelines.
• Testing Principle: The sample is heated to the austenitic range, then quenched at one end with a controlled water jet. This simulates cooling rates encountered during real-world steel processing.
• Measurement of Hardness: After quenching, flats are ground along the sample, and hardness is measured at set intervals. Both the Rockwell and Vickers hardness scales are supported.
• Expression of Results: Hardness values are recorded as a function of distance from the quenched end, forming a Jominy hardenability curve. Codification formats and guidance for reporting are standardized.
• Alternative Methods: By agreement, hardenability can also be determined using computational models based on steel composition, reducing the need for extensive laboratory testing.
• Reporting Requirements: A complete test report includes details on the steel grade, sampling method, heat treatment, hardness testing method, and the resulting data.

Applications

Industrial and Engineering Relevance

• Quality Control: The Jominy end quench test is essential for manufacturers, material suppliers, and laboratories to evaluate the hardenability of steel batches before use in heat-treated parts.
• Material Specification: Steel grades are often specified by their Jominy curves to ensure they meet the required hardening depth for applications such as gears, shafts, and automotive components.
• Process Optimization: Knowing the hardenability profile helps engineers optimize heat treatment cycles, ensuring strength and toughness while minimizing defects.
• Research and Development: The method supports new alloy development and the validation of alternative hardenability prediction techniques, including computational models.
• Dispute Resolution: When there is uncertainty or specified requirements for hardenability, ISO 642:2024 provides a recognized, reproducible test for resolution.

Related Standards

• ISO 6507-1: Metallic materials - Vickers hardness test - Part 1: Test method.
• ISO 6508-1: Metallic materials - Rockwell hardness test - Part 1: Test method.
• SEP 1664:2004: Regression equations for calculating hardenability in the Jominy test based on chemical composition.
• SFS 7512:2023: Functional calculation of the Jominy curve.

Standards for Test Equipment and Measurement

• Proper reference to these standards ensures compatibility and comparability of results across labs and international supply chains.

Utilizing ISO 642:2024 ensures consistent measurement of steel hardenability, supporting material reliability and performance in critical manufacturing sectors. Adherence to international standards like ISO 642 aids in global trade, product quality assurance, and technical communication between suppliers and users.