ROCKWELL HARDNESS TESTING

DEFINITION OF THE ROCKWELL HARDNESS TEST

The Rockwell hardness test is often used as a ‘quick test’ on the production floor or in the laboratory, mainly for metallic materials. However, it can also be used for more advanced tests, such as the Jominy test (End Quench Test). Due to the relatively high loads used, application of the Rockwell hardness test is generally limited to larger sample geometries.

The Rockwell test calculation

The Rockwell hardness test calculation (HR) is made by measuring the depth of an indentation made with a diamond or tungsten carbide ball.

Indenters

The Rockwell hardness test utilizes 1 of 5 different indenters:

• Diamond cone
• Tungsten ball in sizes 1/16", 1/8", 1/4", or 1/2"

Main loads

The Rockwell hardness test utilizes 1 of 6 different main loads:

• 15 kgf, 30 kgf, 45 kgf, 60 kgf, 100 kgf, or 150 kgf

In total, this gives 30 different Rockwell scales. Each one is characterized by a different combination of indenter type and main load, and is suitable for a particular material or application (for example, HRA, HRB, HRC, HR30N).

Overview of typical applications for Rockwell hardness scales

Loads

• Indentation time: 2-6 seconds
• Sample thickness ASTM: At least 10 times the indentation depth for both indenters
• Sample thickness ISO: Diamond indenter: At least 10 times the indentation depth. Tungsten carbide indenter: At least 15 times the indentation depth

Jominy testing

A standardized test procedure used to determine the hardenability of steel, the Jominy test (End Quench Test) can be performed using either the Vickers or Rockwell hardness test method. When selecting which to use, you should consider relevant standards, as well as the usual criteria when choosing between different types of hardness test.

Find out more about the Jominy test method on our Vickers hardness test page