Photonics Dictionary

Rockwell hardness

Rockwell hardness (Rc) refers to a method for measuring the hardness of a material, primarily metals, using an indentation test. It is named after the Rockwell scale, which was developed by Stanley P. Rockwell in the early 20th century. The Rockwell hardness test is widely used in industry and manufacturing to assess the hardness of materials, providing information about their resistance to deformation or indentation.

The Rockwell hardness test involves applying a known load to an indenter, typically a diamond cone or a hardened steel ball, and measuring the depth or penetration of the indenter into the material. There are several Rockwell scales designated by letters (e.g., HRC, HRB, HRA), each suitable for specific types of materials and hardness ranges. The most common scales are:

Rockwell c scale (HRC): Used for measuring the hardness of hard materials, such as steel and hard alloys. The indenter is a diamond cone.

Rockwell b scale (HRB): Suitable for softer materials like aluminum, brass, and softer steels. The indenter is a hardened steel ball.

Rockwell a scale (HRA): Used for measuring the hardness of thin steel and non-ferrous materials. The indenter is a diamond cone.

The Rockwell hardness value is expressed as a combination of a hardness scale symbol and a hardness number. For example, HRC 55 indicates a hardness of 55 on the Rockwell C scale.

The test procedure involves the following steps:

Application of preliminary load: A preliminary load is applied to ensure proper seating of the indenter.

Application of major load: The major load is applied for a specified period, and then it is released, allowing the indenter to penetrate the material.

Measurement of indentation: The depth or penetration of the indenter is measured, and the Rockwell hardness value is determined based on the scale used.

Rockwell hardness testing is popular due to its simplicity, speed, and repeatability. It is an important quality control method in industries where material hardness is a critical factor, such as metallurgy, engineering, and manufacturing.

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