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Indentation with a hard metal ball or diamond cone with spherical cap of 200 µm radius in tree steps:
F0 ... Preliminary test load
Rockwell Hardness scale |
Hardness symbol |
Typ of Indenter |
Preliminary test force Fo |
Total test force F |
Field of application (Rockwell hardness range) |
A | HRA | Diamond cone | 98.07 N | 588.4 N | 20 to 88 HRA |
B | HRB | Ball 1.5875 mm | 98.07 N | 980.7 N | 20 to 100 HRB |
C | HRC | Diamond cone | 98.07 N | 1.471 kN | 20 to 70 HRC |
D | HRD | Diamond cone | 98.07 N | 980.7 N | 40 to 77 HRD |
E | HRE | Ball 3.175 mm | 98.07 N | 980.7 N | 70 to 100 HRE |
F | HRF | Ball 1.5875 mm | 98.07 N | 588.4 N | 60 to 100 HRF |
G | HRG | Ball 1.5875 mm | 98.07 N | 1.471 kN | 30 to 94 HRG |
H | HRH | Ball 3.175 mm | 98.07 N | 588.4 N | 80 to 100 HRH |
K | HRK | Ball 3.175 mm | 98.07 N | 1.471 kN | 40 to 100 HRK |
As suggested by Ludwik (1903), according to whom a reproducible hardness value can be deduced from a measured indentation depth, Rockwell presented the method developed in 1922. The major advantage of this method: the hardness value is easy to read directly on the testing machine (Indentation depth)
Valid standards
DIN EN ISO 6508 1 - 4 Metallic materials - Rockwell hardness test