Jominyendquenchtestet

Jominy end-quench test is a metallurgical procedure used to determine the hardenability of steel. Developed by Stan Jominy in the mid-20th century, the test provides a quantitative curve of hardness as a function of distance from the quenched end, enabling comparison of steel grades and heat-treatment responses.

Procedure: A cylindrical steel specimen is heated to the austenitizing temperature appropriate for the grade and then rapidly quenched from one end by a controlled water jet or other quenchant. The quench creates a cooling-rate gradient along the length of the specimen. After cooling, hardness is measured at specified distances from the quenched end, typically along the length, and a hardness versus distance plot—the Jominy curve—is constructed.

Interpretation: The curve characterizes hardenability, i.e., the ability of the steel to harden with depth under a given cooling condition. Steels with greater hardenability retain higher hardness deeper into the specimen. The curve is used to compare steels and to select heat-treatment parameters to achieve a desired surface or core hardness.

Standards and variations: The method is described in standards such as ASTM A255 and ISO/EN equivalents. Specimen geometry, austenitizing temperature, quenchant type and flow, and measurement procedures are defined to ensure repeatability. While water is common, certain steels require oil quenching to prevent cracking.

Limitations: The Jominy test provides a comparative, not an absolute, property; results depend on geometry, austenitizing conditions, and quenching setup and do not directly measure strength or toughness. Nevertheless, the Jominy curve remains a foundational tool in steel heat-treatment design.