LAB 3: HEAT TREATMENT & TENSILE
STRENGTH
AILEEN JOHNSRUD
3/19/2015
Abstract
Figure 1
Metal alloys behave differently to thermal treatments 4 trials of;
1018 steel C3600 brass are compared with as received
specimens. Specimens are cooled by; quenched in water, oil, and
air cooled. Differences occur in the heat treatment and cooling
methods of 1018 steel higher carbon content contributes to the
strength of a steel alloy, due to the carbon atoms preventing
atomic dislocations that occur during plastic deformation. C3600
brass after heating remains soft no matter the quenching
technique.
LAB 3: Heat Treatment & Tensile Strength
Aileen Johnsrud
INTRODUCTION|one
Two primary reasons for plastically deforming engineering metals and alloys are to change their shape
for some particular purpose or to change their properties. Often times the deformation process alters the
mechanical strength of the material. Cold worked material is harder and stronger than material deformed at other
temperatures. These harder materials are advantageous for applications such as machine parts and mechanical
supports. The temperature at which the deformation takes place is an important determinant of the final
properties. If the temperature is relatively low with respect to the melting point of the material the deformation
process is termed "cold working". A material that is plastically deformed at temperatures near or at the melting
point is said to be hot worked.
There are significant differences between the effects of cold and hot working on the properties and
structure of materials. While cold-working a metal will tend to increase its strength, other properties such as
ductility or corrosion resistance may be negatively affected. Therefore, to remove internal stresses of cold work,
it is sometimes desirable to heat treat the metal after cold working. If this heat treatment, or annealing, is
conducted at a sufficiently high temperature, a reduction of the stress necessary to further deform the material
may be achieved as recrystallization occurs. This experiment introduces us to the relationship between cold work
and recrystallization processes and their associated properties.
During cold-working, it may take a considerable amount of energy to affect the change in size and
shape. Some of the energy expended will appear in the form of heat. A considerable amount of the energy will
also be stored in the material. This stored energy is associated with the defects created during the deformation.
The free energy of the worked metal will be increased by approximately the amount represented by the stored
energy.
The most important result of cold working, which accompanies this increase in the number of defects, is
strain hardening. Strain hardening is the increase in the yield stress of the metal after it has been deformed. This
makes it more difficult to further deform the material. The increase in yield stress comes from the fact that
deformation results in a higher density of dislocations. The strain fields around the dislocations most often repel
one another, limiting dislocation movement.
C36000 Free cutting Brass * 1018 cold rolled steel
These 2 metals will be tested within 3 temperature zones, & then tensile tested with the MTS Load frame
Ambient room 68oF * steel 1550o F * brass 900o F
Heat treating and cooling methods may result in brittle failure of an alloy, which might otherwise react as
ductile under other heat treating circumstances. A comparison of the results of temperature, hardness, and
tensile strength amongst these two engineering alloys will be made.
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LAB 3: Heat Treatment & Tensile Strength
Aileen Johnsrud
PROCEDURE|two
This is an outline of the steps taken in the heat treatment & tensile strength experiment as a function of testing
hardness by tempering or annealing. (Fig.2)

Steel & brass specimens are 3/8” stock, cut to 1” pieces
1. One each of C3600 brass and 1018 steel are Rockwell tested at room temperature as a baseline or control
for the experiment are summarized in Table T-1:.
Alloy
Rockwell Measurements at room temperature Average Rockwell
Table T-1
Measurement
C3600 brass
73.5, 75.5, 74.5, 74, 74, 69, 72.5, 73, 74,
73.5
73.35
0.240”ᴓ
1018 cold steel
90, 90, 90, 89.5, 89, 91, 86, 90, 89, 90
89.85
0.246”ᴓ
2. Specimens are Rockwell tested at the following temperatures after being held at temperature for a period of time;
3 specimens of 1018 cold steel at 1550o, held for 30 minutes
3 specimens of C3600 brass at 900o, held for 45 minutes in order to anneal them
3. After specimens are held at temperature for the designated times. One sample of each alloy will be
cooled in the following ways to determine the effects of hardening or annealing due to cooling rate;
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
QUENCHED IN WATER, THEY MUST BE REMOVED FROM FURNACE AND PLACED IN THE
WATER VERY QUICKLY

QUENCHED IN OIL (SAE 30), THEY MUST BE REMOVED FROM FURNACE AND PLACED IN
THE OIL VERY QUICKLY

AIR COOLED ON FIRE BRICK, UNTIL COOL TO TOUCH
LAB 3: Heat Treatment & Tensile Strength
4.
Aileen Johnsrud
Samples are then Rockwell hardness tested 10 times. Brass testing went no further to due to limited class time. It
was understood that all further measurements of brass samples would be equivalent to the air cooled sample.
Since brass lacks carbon, softening of the metal regardless of cooling technique occurs under heat treating, making
the brass more ductile. The results of these tests are summarized in Table T-2:
Table T-2
Rockwell B scale
Rockwell B scale
Rockwell B scale
Alloy
Oil Quenched SAE30
Water Quenched
Air cooled
1018
cold
Steel
78,80,78.5,78.5,79,79,78,79,8
0,80:
Average =79
0.247”ᴓ
96,94.5,93,92,96.5,86,92,93,90.5,9
0.5:
Average=92.4
0.246”IDᴓ
68,69,66,70,69,70,69,67,69,
69:
Average= 68.6
C3600
Brass
10,11,11.5,11.5,12,11,12.5,
12,12.5,12:
Average=11.7
5. After Rockwell testing, specimens are then loaded into the Instron tensile test machine to determine
yield strength, tensile strength, & percent elongation.
6. A sample of a material between two fixtures called “grips” which clamp the material. The material has
known dimensions, like length and cross-sectional area..
7. An extensometer is mounted to specimen for data logging. Machine grips are placed around the grip
sections of specimen (see below).
8. MTS load frame is then zeroed out, data for class & specimen type, diameters, length, thickness are
imputed.
9. We then begin to apply weight to the material gripped at one end while the other end is fixed. We keep
increasing the weight (often called the load or force) while at the same time measuring the change in
length of the sample
10. Brass is not tensile tested in this lab
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LAB 3: Heat Treatment & Tensile Strength
Aileen Johnsrud
RESULTS|three
We observed how the properties of 1018 steel and C3600 brass vary with the heat treatment condition.
250
1018 Cold rolled Steel
Stress Mpa (N/mm^2)
200
150
1018 CF Steel - Control
1018 Oil Quenched
100
1018 Water Quenched
1018 Air Annealed
50
0
-10
0
-50
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10
20
Strain
30
40
LAB 3: Heat Treatment & Tensile Strength
Aileen Johnsrud
DISCUSSION & CONCLUSION|four
Heat treatment has a tremendous impact on some of the properties of materials used by engineers,
and the effects of heat treatment should always be considered. We studied three different heat treatment
configurations; as-received, fully annealed, quenched and tempered. Pearlite is formed as steel is cooled.
Quenching is used to quickly reduce the temperature of the steel, preventing the pearlite from forming. The
fully annealed condition is reached by heating the steel enough to turn into austenite (Fig.2), an FCC phase of
steel, and then slow cooling it to room temperature.
The elastic modulus for three sample types (control, air, oil) was
Figure2
approximately the same. Heat treating and quenching lowered the strength of
the steel in all trials except that of water quenched steel. Using Rockwell
hardness testing machines, we determined that heat treatment roughly halves a steel sample’s yield strength
during oil quenching and air cooling. As the yield strength was decreased the plastic deformation hump
Figure3
seemed to double.
Water quenching raised the steel alloys strength tremendously, only to fail catastrophically and loudly
under the tensile test. If steel is forced to take a very steep cooling path a brittle, needlelike structure known
as martensite (Fig.3) is formed
Metallic alloys vary greatly in their material properties depending on their temperature history. This behavior
is both composition-dependent and time-dependent.
REFERENCES|five
Figure 1 http://www.alliedmineral.com/industries/heat-treat-forging/heat-treating.html
Figure2 http://www.pacmet.com/index.php?h=basicheattreat
Figure3 http://en.wikipedia.org/wiki/Martensite
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LAB 3: Heat Treatment & Tensile Strength
Aileen Johnsrud
Figure2 +3 http://www.scielo.br/scielo.php?pid=S1516-14392002000300020&script=sci_arttext
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