Jominyendquenchtest

The Jominy end-quench test, commonly referred to as the Jominy test, is a metallurgical procedure used to determine the hardenability of a steel alloy. Hardenability describes the depth to which a steel can harden under a given quenching condition, as distinct from the surface hardness itself. The test yields a Jominy curve, which plots hardness against distance from the quenched end and allows comparison of how different steels respond to quenching.

Procedure: A standardized cylindrical specimen is heated into the austenitic range (typically around 850–950 °C) and then quenched from one end with a calibrated water jet, while the opposite end remains insulated. The cooling rate is highest at the quenched end and decreases with distance along the bar, producing a gradient of hardness. After cooling, the bar is sectioned and hardness is measured at regular intervals along its length. The resulting hardness data are plotted as hardness versus distance from the quenched end to form the Jominy curve.

Interpretation and use: Hardenability is inferred from the curve rather than surface hardness alone. The Jominy curve enables engineers to compare steels, assess the influence of alloying elements (such as chromium, molybdenum, nickel, vanadium, and others), and predict the depth of hardness achievable under specified quenching conditions. It is widely used in alloy development, quality control, and heat-treatment planning.

Standards and limitations: The method is defined in standards such as ASTM A255/A255M (Standard Test Methods for Determining Hardenability of Steel by the End-Quench Method). Limitations include the idealized quench environment and the need to correlate the curve with actual component geometries and service conditions.