Experiment on Rockwell Hardness Testing Machine

Introduction:
Heat treatment of metal is the main concept which this lab is able to introduce.
Understanding the effects of heat treatment on the microstructure of materials and
the relevant changes in properties compose the objective of the lab. Heat treatment
process is essential for industrial engineers especially the ones in machine design,
civil engineers and manufacturing industry. Through this lab, the students are able
to test for hardness of the materials using equipments used to measure hardness
and durability values.
The resistance to penetration on a particular surface for an object is measured
through hardness tests. The depth of penetration on the object is usually measured
and then the testing machine converts the depth values to hardness number. On
the other hand, the impact test is done by subjecting the objects on sudden intense
blow whereby the strain rate is rapid. Through the testing, the strain rate may seem
to be more brittle manner than it is observed in the tensile test. Lastly, the
materials provided were heat treated to 1050 degrees Celsius, which is above the
materials crystallization point and different tests were performed to find properties
of the materials.
Equipment:
The following equipment were used in the carrying out the experiment
- Rockwell Hardness Testing Machine
- Impact Testing Machine (Charpy)
- As Is Sample
- Aluminum
- Oil(3 batch 3)
- Water-Quenched Sample
- Metal tongs
- Sand Paper
Procedure:
Different sections were used in the carrying out the experiment. The key
subsections included sanding (Preparing metal), Hardness testing (Rockwell Testing)
and impact testing:
 Sanding (preparing metal):
1. Get the Oil treated and As Is sample
2. Using the sand paper to sand the two samples above
3. Finish sanding until an area is exposed on the metal to use the
Rockwell testing machine.
 Hardness testing (Rockwell Testing):
1. Calibration of the machine correctly is first carried out.
1

2. Ensuring that the correct indenters are in place for the metals. (Use
C indenter for Water Quenched, Oil and As Is materials; And use B
indenter for Aluminum)
3. Lock on the metal on to the machine’s calipers until a clicking
sound is heard.
4. Press start on the digital screen
5. Read value from the digital screen
6. Repeat process for 3 trials.
 Impact testing:
1. Lift the big lever of the impact testing machine and lock the safety
switch ON (the lever should be lifted using two people).
2. Place the material sample into the slot using the metal tongs.
3. Ensure that the metal sample is in the correct spot and firmly held
in place with minimal wiggle room.
4. Step away from machine and press the switch to release the lever
causing it to swing and breaking the material sample into two
pieces.
5. Obtain the charpy value off the scale and record this value
6. Examine the broken sample.
Data:
The following table shows the values recorded for hardness and impact tests:
As Is [3]
(HRC)
Aluminu
m [3]
(HRB)
Water
Quenched
[3] (HRC) Oil [3]
Air (3) Dry ice (3)
Har
dne
ss
1
9.
1
1
9.
8
1
8.
9
1
9.
3
2
0.
3
2
0
.
8
3
2
33
.1
3
1.
1
2
7
.
2
26
.3
34
.6
76
.3
74
.3
67 20.
6
1
9
19
Cha
rpy 12 20 9.5 21
49 4.5
The following table shows the average values recorded for the hardness and impact
tests:
As
Is[3]
Aluminum[
3]
Water[
3] Oil [3]
Dry Ice
[3]
Air (3)
Hardne
ss 19.3 20.13 31.1 29.4 19.5
72.53
Charpy 12 20 9.5 21 4.5 49
The following are histogram graphs obtained for the required for the recorded
values for hardness and impact tests:
2

0
10
20
30
40
50
60
70
80
Hardness
Charpy
The data found for other samples and their graphs are as follows:
As Is (Steel ) Sample:
As Is
sampl
e 1
sampl
e 2
sampl
e 3
Hardne
ss 17 18.9 19.27
Charpy 17.5 15 12.0
sample 1 sample 2 sample 3
0
5
10
15
20
25
Hardness
Charpy
As Is
sampl
e 4
sampl
e 5
sampl
e 6
Hardne
ss 16.9 18.6 17
3

Charpy 12.0 9.5 9.5
sample 4 sample 5 sample 6
0
2
4
6
8
10
12
14
16
18
20
Hardness
Charpy
Aluminum Sample
Aluminum
sampl
e 1
sampl
e 2
sampl
e 3
Hardness
18.46
7 22.1
20.13
3
Charpy 19.5 17.5 20
sample 1 sample 2 sample 3
0
5
10
15
20
25
Hardness
Charpy
Aluminum
sampl
e 4
sampl
e 5
sampl
e 6
4