Rockwell Hardness Testing
The Rockwell Hardness test is a widely used method to determine the hardness of metallic materials, thanks to its simplicity and quickness. This hardness test is based on indentation and depth of penetration, and it can be performed on various metals, including aluminum, copper alloys, brass, soft steels, and hard carbon steels.
The HRB scale is used for softer materials, while the HRC scale is used for harder materials. This test is ideal for bulk metal hardness determinations because it utilizes heavy loads and is cost-effective.
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Additionally, the Rockwell hardness test is a non-destructive test because it only creates a small indentation on the material surface, and it provides a direct reading using the Rockwell Hardness scale, which is not the case for other hardness tests that require measurements and calculations to determine hardness levels.
Basic Procedure
To carry out Rockwell Hardness Testing, a sample is subjected to stress by a diamond cone or a hard steel ball. The test procedure involves applying a minor load to create an indentation in the material to measure the depth of penetration. Subsequently, a major load is applied, and the penetration depth is measured again. Finally, a minor load is applied once more. By calculating the difference between the first and last measurements, the permanent deformation of the sample material is determined. The results are then analysed using the Rockwell Hardness Scale.
Rockwell Hardness Scale
The Rockwell Hardness Scales comprise various types, depending on the material to be tested. Each scale utilizes different loads or indenters, and permits the testing of materials with different hardness. For instance, the HRB scale is employed for testing soft steels, aluminium, and brass, and involves applying minor loads of 10kgf and major loads of 100kgf.
On the other hand, the HRC scale is used for testing hard steels, deep case-hardened steel, and hard cast irons, and involves applying minor loads of 10kgf and major loads of 150kgf.