Hardenability refers to the ability of steel to obtain satisfactory hardening to some desired depth when cooled under prescribed conditions. It is governed almost entirely by the chemical composition (carbon and alloy content) at the austenitizing temperature and the austenite grain size at the moment of quenching. This article describes the Jominy end-quench test, the Grossman method, and the air hardenability test to evaluate hardenability. It also reviews the factors that influence steel hardenability and selection.

Hardenability is a composition-dependent property of steel and depends on carbon content and other alloying elements as well as the grain size of the austenite phase. This article provides an overview of a wide range of testing procedures used to determine and quantify hardenability of shallow-hardening, low-carbon, plain carbon, and low-alloy medium-carbon steels ranging from classical fracture and etching, Grossmann hardenability, and Jominy end-quench testing to manual and computerized computational methods. The article then uses this as a backdrop for the implementation of the core concepts of hardenability in a variety of predictive tools for calculating hardenability. The Caterpillar 1E0024 Hardenability Calculator, a personal computer-based program, calculates the Jominy curve based on the steel composition. The article also describes the method for boron and nonboron steels, with calculation examples for 8645 steel and 86B45 steel.

Hardenability is usually the single most important factor in the selection of steel for heat-treated parts. The hardenability of steel is best assessed by studying the hardening response of the steel to cooling in a standardized configuration in which a variety of cooling rates can be easily and consistently reproduced from one test to another. These include the Jominy end-quench test, the carburized hardenability test, and the surface-area-center hardenability test. This article discusses the effects of varying carbon content as well as the influence of different alloying elements on hardenability of steels. The basic information needed before a steel with adequate hardenability can be specified as the as-quenched hardness required prior to tempering to final hardness that will produce the best stress-resisting microstructure; the depth below the surface to which this hardness must extend; and the quenching medium that should be used in hardening.

Hardenability of steel is the property that determines the depth and distribution of hardness induced by quenching. Hardenability is usually the single most important factor in the selection of steel for heat-treated parts. The hardenability of a steel is best assessed by studying the hardening response of the steel to cooling in a standardized configuration in which a variety of cooling rates can be easily and consistently reproduced from one test to another. These include the Jominy end-quench test, the carburized hardenability test, and the air hardenability test. Tests that are more suited to very low hardenability steels include the hot-brine test and the surface-area-center test. The article discusses the effects of varying carbon content as well as the influence of different alloying elements. It includes charts and a table that serve as a general steel hardenability selection guide.

This article discusses the classification of carbon steels based on carbon content, and tabulates the compositional limits of medium- and high-carbon steels based on the AISI code and other similar codes. It describes recrystallization annealing and spheroidizing of carbon steels, and discusses the classification of carbon steels for heat treatment. The article also discusses the estimation of continuous cooling curves from isothermal transformation curves. It provides information on the Jominy end-quench test and the Grossmann method and the procedures to increase hardenabilty of carbon steels. The article includes information on the purpose of tempering and heat treating guidelines for different grades of steels, including cast carbon steels.

This article discusses the various methods for evaluating the quench sensitivity of aluminum alloys, namely, time-temperature-property diagrams, the quench factor analysis, the Jominy end-quench method, and continuous-cooling precipitation diagrams. It briefly describes the procedures, applications, advantages, and limitations of these methods.