Determining Hardenability of Steel ASTM A255

Determining Hardenability of Steel ASTM A255

This ASTM A255 test method covers the procedure for determining the hardenability of steel by the end-quench test.


    ASTM A255 is a test method used for determining the hardenability of steel by the end-quench
    test. This method of Jominy Hardenability calculation from the chemical ideal diameter (DI) on a
    steel provides increased accuracy by refinement of the carbon multiplying factors and the correlation of a boron factor (B.F.) with carbon and alloy content.

    Test Procedure:

    For ASTM A255, the wrought product from which the specimen is to be prepared is first normalized and then the specimen is obtained. The specimen is placed in a furnace at a specified austenitizing temperature for 30 minutes. The temperature is determined by inserting a thermocouple into a hole drilled axially at the top of the specimen. The heated specimen is then placed in support and water is turned on. The stream of water is directed at a temperature 40°F to 85°F for 10 minutes, then quenching is done in a still air condition. Hardness readings are made on the two flats 180° apart and grounded to a minimum depth of 0.015 inches along the entire length of the bar, Rockwell C Hardness (HRC) reading is taken along the bar as well.

     Specimen size:

    A fixture for support of a 1.0 inch (25.4mm) test specimen is used.

    A Water-quenching device is used to provide a vertical stream of water.


    Hardness is reported in inch-pound units and is considered as standard.

    The hardenability of steel can be designated by a specific HRC hardness value and hardness
    readings are recorded to the nearest integer for subsequent test results.


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