ASTM A255 Determining Hardenability of Steel

Scope:

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 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 for ASTM A255 testing 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 towards the specimen at a preferred temperature between 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:

For ASTM A255 testing, a fixture for support of a 1.0 inch (25.4 mm) test specimen is used. A Water-quenching device is used to provide a vertical stream of water.

Data:

In ASTM A255 testing, 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.

Conclusion :

ASTM A255 is a test method used for determining the hardenability of steel by the end-quench test.