HRA: It is the hardness measured by a diamond cone press under a load of 60kg. Used for extremely hard materials (such as cemented carbide).
HRB: Hardness is obtained from hardened steel balls with a load of 100kg and a diameter of 1.58mm, and is used for materials with low hardness (such as annealed steel and cast iron).
HRC: It is the hardness measured by a diamond cone press with a load of 150kg. Used for materials with high hardness (such as hardened steel).
2. Different conversion: HRB100 = HRC 20; ; HRB99.2 = HV226 = HRC20.0HRB 96 = HV 2 1 1 = HRC 17.0 .
3. Different scales: A, B and C in HRA, HRB and HRC in Rockwell hardness are three different standards, which are called A scale, B scale and C scale respectively ... Rockwell hardness test is one of several common indentation hardness tests used today. The initial pressure of the three scales is 98.07N (10kgf), and finally the hardness value is calculated according to the indentation depth.
The extended data can be directly converted into Rockwell hardness by using the indentation diameter of Brinell hardness.
In the production site, due to the limitation of testing instruments, Brinell hardness tester is usually used to measure the hardness of large quenched parts. If you want to know the Rockwell hardness value of the workpiece, the usual method is to measure the Brinell hardness value first, and then find out the corresponding Rockwell hardness value according to the conversion table, which is obviously a bit cumbersome.
According to the conversion table of Brinell hardness and Rockwell hardness, an empirical formula with simple calculation and easy memory can be obtained: HRC =(479- 100D)/4, where d is the measured indentation diameter of φ 10mm steel ball indenter pressed on the workpiece under the pressure of 30KN. The error range between the calculated value and the converted value is 0.5 ~- 1.
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