Gordon England Surface Engineering Forum

Rockwell Hardness Test

The Rockwell hardness test method consists of indenting the test material with a diamond cone or hardened steel ball indenter. The indenter is forced into the test material under a preliminary minor load F0 (Fig. 1A) usually 10 kgf. When equilibrium has been reached, an indicating device, which follows the movements of the indenter and so responds to changes in depth of penetration of the indenter is set to a datum position. While the preliminary minor load is still applied an additional major load is applied with resulting increase in penetration (Fig. 1B). When equilibrium has again been reach, the additional major load is removed but the preliminary minor load is still maintained. Removal of the additional major load allows a partial recovery, so reducing the depth of penetration (Fig. 1C). The permanent increase in depth of penetration, resulting from the application and removal of the additional major load is used to calculate the Rockwell hardness number.

HR = E - e


F0 = preliminary minor load in kgf
F1 = additional major load in kgf
F = total load in kgf
e = permanent increase in depth of penetration due to major load F1 measured in units of 0.002 mm
E = a constant depending on form of indenter: 100 units for diamond indenter, 130 units for steel ball indenter
HR = Rockwell hardness number
D = diameter of steel ball
Rockwell hardness test principle
Fig. 1.Rockwell Principle


Rockwell Hardness Scales
Scale Indenter Minor Load
F0
kgf
Major Load
F1
kgf
Total Load
F
kgf
Value of
E
A Diamond cone 10 50 60 100
B 1/16" steel ball 10 90 100 130
C Diamond cone 10 140 150 100
D Diamond cone 10 90 100 100
E 1/8" steel ball 10 90 100 130
F 1/16" steel ball 10 50 60 130
G 1/16" steel ball 10 140 150 130
H 1/8" steel ball 10 50 60 130
K 1/8" steel ball 10 140 150 130
L 1/4" steel ball 10 50 60 130
M 1/4" steel ball 10 90 100 130
P 1/4" steel ball 10 140 150 130
R 1/2" steel ball 10 50 60 130
S 1/2" steel ball 10 90 100 130
V 1/2" steel ball 10 140 150 130


Typical Application of Rockwell Hardness Scales

HRA . . . . Cemented carbides, thin steel and shallow case hardened steel
HRB . . . . Copper alloys, soft steels, aluminium alloys, malleable irons, etc.
HRC . . . . Steel, hard cast irons, case hardened steel and other materials harder than 100 HRB
HRD . . . . Thin steel and medium case hardened steel and pearlitic malleable iron
HRE . . . . Cast iron, aluminium and magnesium alloys, bearing metals
HRF . . . . Annealed copper alloys, thin soft sheet metals
HRG . . . . Phosphor bronze, beryllium copper, malleable irons HRH . . . . Aluminium, zinc, lead
HRK . . . . }
HRL . . . . }
HRM . . . .} . . . . Soft bearing metals, plastics and other very soft materials
HRP . . . . }
HRR . . . . }
HRS . . . . }
HRV . . . . }

Advantages of the Rockwell hardness method include the direct Rockwell hardness number readout and rapid testing time. Disadvantages include many arbitrary non-related scales and possible effects from the specimen support anvil (try putting a cigarette paper under a test block and take note of the effect on the hardness reading! Vickers and Brinell methods don't suffer from this effect).





LINKS TO:
Hardness Testing
Rockwell Hardness Test
Rockwell Superficial Hardness Test
Brinell Hardness Test
Vickers Hardness Test
Microhardness Test
Mohs Hardness Test
Scleroscope and other hardness testing methods

TABLES and CHARTS:
Hardness Conversion Table (colour version - may take time to load)
Hardness Conversion Table (non-colour version)
Hardness Conversion Chart (1)
Hardness Conversion Chart (2)
Chart of Brinell, Vickers and Ultimate Tensile Strength Equivalents (1)
Chart of Brinell, Vickers and Ultimate Tensile Strength Equivalents (2)
Hardness Conversion Table related to Rockwell C Hardness Scale (hard materials) (colour)
Hardness Conversion Table related to Rockwell C Hardness Scale (hard materials) (non-colour)
Hardness Conversion Chart related to Rockwell C Hardness Scales (hard materials)
Estimated Hardness Equivalent Chart related to Rockwell C and Vickers (hard materials)
Hardness Conversion Table related to Rockwell B Hardness Scale (soft metals) (colour)
Hardness Conversion Table related to Rockwell B Hardness Scale (soft metals) (non-colour)
Hardness Conversion Chart related to Rockwell B Hardness Scale (soft metals)
Table of Minimum Test Piece Thickness for Rockwell Hardness Testing using Ball Indenters
Table of Minimum Test Piece Thickness for Rockwell Hardness Testing using Diamond Indenters
HV, MPa and GPa Conversion Calculator

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