* HRB: Rockwell B Scale
* HRC: Rockwell C Scale
These are two of the most common scales used for measuring hardness.
Rockwell Hardness Testing:
The Rockwell hardness test is a widely used method for determining the hardness of materials. It involves indenting a material with a diamond cone or steel ball and measuring the depth of the indentation.
* HRB (Rockwell B Scale): Uses a 1/16" (1.58 mm) steel ball indenter and is typically used for softer materials like brass, copper, and aluminum.
* HRC (Rockwell C Scale): Uses a diamond cone indenter and is used for harder materials like steel, cast iron, and ceramics.
How it works:
1. A minor load is applied to the indenter, which positions the material for the test.
2. A major load is then applied, causing the indenter to penetrate the material.
3. The major load is removed, leaving the indenter in place.
4. The depth of the indentation is measured, and a hardness number is calculated based on a specific formula.
Important note: The Rockwell hardness test is a relative test, meaning that the hardness number is only relevant within the specific scale used (e.g., HRB or HRC). You cannot directly compare HRB and HRC values.