The Rockwell Hardness Test was initially proposed by Americans S.P. Rockwell and H.M. Rockwell in 1914. The design of the hardness tester was improved in 1919 and 1921, laying the foundation for the prototype of the modern Rockwell hardness tester.

The basic method of the Rockwell hardness test is as follows: First, an initial test force is applied, followed by a main test force to reach the required total force value, and then the force is reduced back to the initial test force. The initial test force establishes the zero point or reference point. The main test force is held for a predetermined duration to allow for elastic recovery. Afterward, the main test force is removed, while the initial test force is retained to measure the deviation from the zero or reference point, thereby determining the Rockwell hardness value.

Commonly used Rockwell hardness test scales:

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  HRA: Uses a diamond indenter, applies a force of 60 kgf, and the hardness value is read from the outer scale of the dial. Suitable for measuring the hardness of hard or thin hard materials, such as cemented carbide, case-hardened and quenched steel, hardened thin steel strips, and thin steel plates.

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  HRB: Uses a steel ball indenter, applies a force of 100 kgf, and the hardness value is read from the inner scale of the dial. Suitable for measuring materials of medium hardness, such as annealed medium and low-carbon steels, malleable cast iron, various types of brass and most bronzes, and age-hardened aluminum alloys after solution treatment.

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  HRC: Uses a diamond indenter, applies a force of 150 kgf, and the hardness value is read from the outer scale of the dial. Suitable for measuring materials such as carbon steel, alloy steel, and tool and die steel after quenching and low-temperature tempering, as well as chilled cast iron, pearlitic malleable cast iron, and titanium alloys. Generally, materials with HRB > 100 can be measured using the C scale.