Rockwell hardness

The Rockwell hardness is an index of the hardness value determined by the depth of the indentation plastic deformation, and 0.002 mm as a hardness unit. Using of different indenters and different test forces in the Rockwell hardness test results in different combinations, corresponding to different scales of Rockwell hardness. There are three rulers that are commonly used and their applications cover almost all commonly used metal materials.

Rockwell Hardness (HR) Test Rockwell hardness measurement is used when the sample under test is too small or the Brinell hardness (HB) is greater than 450.

When the measured sample is too small or the Brinell hardness (HB) is greater than 450, Rockwell hardness measurement is required. The test method is to use a diamond cone with a vertex angle of 120 degrees or a steel ball with a diameter of 1.5875mm/3.175mm/ 6.35mm/ 12.7mm to press the surface of the material to be tested under a certain load, and determine the material from the indentation depth. The hardness.

The three most commonly used scales are A, B, and C, that is, HRA, HRB, and HRC. According to the hardness of the experimental material, different hardness scales are used to represent:

HRA is a hardness obtained with a 60Kg load and a diamond cone press, and is used for materials with higher hardness. For example: steel sheet, carbide.

HRB is a hardness obtained with a hardened steel ball with a diameter of 1.5875mm with a load of 100Kg. It is used for materials with low hardness. For example: mild steel, non-ferrous metals, annealed steel and so on.

HRC is a hardness obtained with a 150Kg load and a diamond cone press for high hardness materials. For example: hardened steel, cast iron, etc.

The Rockwell hardness test uses three test forces, three indentations, and a total of nine combinations that correspond to the 9 scales of Rockwell hardness: HRA, HRB, HRC, HRD, HRE, HRF, HRG, HRH, and HRK. HRA 60kg load diamond cone presser; HRB 100kg load 1/16" diameter ball indenter; HRC 150kg load diamond cone presser; most commonly used ruler is HRC, HRB and HRF, HRC scale is used to test hardened steel, Tempered steel, quenched and tempered steel and part stainless steel. This is the most widely used hardness test method in the metal processing industry. The HRB scale is used to test various annealed steels, normalized steels, mild steels, some stainless steels, and harder copper alloys. The HRF scale is used to test pure copper, softer copper alloys, and hard aluminum alloys. Although the HRA scale can also be used for most ferrous metals, the practical application is generally limited to testing hard alloy and thin hard material.

Conventionally, there are HB, HRC, HV, and HL hardness, among which HB and HRC are more commonly used.