25963271-Rockwell-Hardness-Test

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3. To perform hardness test on given
steel specimens using Rockwell Hardness
Testing Machine.
(17-09-08)
Apparatus



Shimadzu Rockwell hardness Testing Machine
Diamond Cone and Steel Ball Indenters
Steel Specimen
Purpose



To check the hardness of material
Indirect strength test of material
Quality control in industries
Related Theory
Hardness
Hardness is the property of material that enables it to resist plastic deformation usually by penetration.
However, the tern hardness may also refer to resistance to bending, scratching, abrasion or cutting.
Hardness testing Methods



Brinall Hardness Test
Vivkers Hardness Test
Rockwell Hardness Test
1
To perform hardness test using Rockwell Hardness Testing Machine
07 CIVIL 73
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Rockwell hardness Test (BS-891)
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
Fig. 1.Rockwell Principle
2
To perform hardness test using Rockwell Hardness Testing Machine
07 CIVIL 73
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Rockwell Hardness Scales
Scale
A
B
C
D
E
F
G
H
K
L
M
P
R
S
V
Indenter
Minor Load Major Load Total Load Value of
F0
F1
F
E
kgf
kgf
kgf
Diamond cone
10
50
60
100
1/16" steel ball
10
90
100
130
Diamond cone
10
140
150
100
Diamond cone
10
90
100
100
1/8" steel ball
10
90
100
130
1/16" steel ball
10
50
60
130
1/16" steel ball
10
140
150
130
1/8" steel ball
10
50
60
130
1/8" steel ball
10
140
150
130
1/4" steel ball
10
50
60
130
1/4" steel ball
10
90
100
130
1/4" steel ball
10
140
150
130
1/2" steel ball
10
50
60
130
1/2" steel ball
10
90
100
130
1/2" steel ball
10
140
150
130
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).
Rockwell Hardness Test Procedure
1. Bring the specimen in contact with indenter and continuously raise the sample until a small inset
pointer on the dial das reached the reference point.
2. Set the main dial to correct reference point (At ‘0’ for diamond cone and at ‘30’ for steel ball
indenter)
3. After application of seating load (Minor Load i.e. 10 kgf) apply major load (depends on the scale)
and maintain it for approximately 4-7 seconds.
4. Remove the major load to permit elastic recovery while keeping on the minor load.
Read the hardness number from the dial directly and write it in the standard format i.e. HR 70B (HR
means Rockwell Hardness, ‘70’ is the hardness number and “B” represents the scale.)
3
To perform hardness test using Rockwell Hardness Testing Machine
07 CIVIL 73
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Rockwell Hardness Test Specifications




Depth of indentation should not be more that 1/8th of the thickness of the specimen.
Two consecutive indentations should not be made very close to each other.
Indentations should not be made near the edge of specimen.
Minimum three observations should be taken.
Simple Hardness Test
In this we use 2 types of Balls,
Type of
Specimen
indenter
Sr. No
Mild
1/16"
Carbon dimater
2 Steel
Steel ball
3 Specimen Indenter
Scale
1
High
Diamond
Carbon
Cone
2 Steel
Indenter
3 Specimen
B
1
C
130 for Steel ball (B Scale)
Load (kg)
Major
Minor
Load
Load
Hardness Mean
Number hardness
10
90 HR 92.5 B
10
90 HR 96 B
10
90 HR 92.5 B
10
140 HR 43.5 C
10
140 HR 43 C
10
140 HR 43.5 C
HR 93.66 B

100 for diamond ball (C Scale)
HR 43.3 C

Comments
By performing this experiment and knowing the hardness of any material we can control the quality of
products in industries. We come to know that medium carbon steel has HR 93.66B and that of High
Carbon Steel is HR 43.3C. Hence by increasing percentage of carbon its strength decreases.
4
To perform hardness test using Rockwell Hardness Testing Machine
07 CIVIL 73
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