The hardness test of the three kinds of test force, three kinds of pressure head, they are a total of 9 combinations, corresponding to the 9 scales of the hardness of the.

The application of these 9 scales covers almost all the metal materials used. The most commonly used scale is HRC, HRB and HRF, which is used to test the HRC rod hardened steel, tempering steel, Quenched and tempered steel and some stainless steel. This is the metal processing industry application most of the hardness test method.

HRB scale is used for testing all kinds of steel, steel, steel annealing normalizing, stainless steel and hard alloy of copper. HRF scale is used to test the soft copper, copper alloy and aluminum alloy. Although the HRA scale can be used in most of the black metal, but the actual application is generally limited to test hard alloy and thin hard steel tape.

The surface of the hardness test of the three kinds of test force, two kinds of pressure head, they have 6 combinations, corresponding to the surface of the hardness of the 6 scales. Surface hardness test is a supplement to the test of the hardness test. When the material is thin, the sample is small, the surface hardening layer is shallow or the surface coating layer is coated with surface.

At this time, the same pressure head with the hardness test, using only a fraction of a fraction of the size of the test force, it can be effective in the above test results of the hardness test results. The N scale of surface hardness of the HRF rod is suitable for HRB, HRA and HRC testing of similar to the hardness of the T.

The use of the HRC scale is 20~70HRC, when the hardness value is less than 20HRC, because the cone part of the pressure head is too much pressure, the sensitivity decreased, then should switch to HRB scale. Although the HRC scale is provided with the upper limit of 70HRC, but when the specimen hardness is greater than 67HRC, the pressure head is too large, the diamond is easy to damage, and the pressure head life will be greatly shortened, therefore, the general should switch to HRA scale.

HRA scale is the scope of application of 20-88HRA, by American standards ASTME140 can be obtained following conversion relation: 27HRA PRG 30HRB 60HRA PRG 100HRB PRG 20HRC 85.6HRA hundredth the 68hrc visible, HRA scale test range covers the hard alloy hardness range from mild steel (HRB), steel (HRC) to.