Journal of Minerals and Materials Characterization and Engineering, 2012, 11, 859-862
Published Online September 2012 (
Evaluation of Mechanical Properties of Medium Carbon
Steel Quenched in Water and Oil
J. K. Odusote1, T. K. Ajiboye2, A. B. Rabiu2
1Department of Metallurgy and Material Engineering, University of Ilorin, Ilorin, Nigeria
2Department of Mechanical Engineering, University of Ilorin, Ilorin, Nigeria
Received March 7, 2012; revised April 10, 2012; accepted April 30, 2012
Samples of medium carbon steel were examined after heating between 900˚C - 980˚C and soaked for 45 minutes in a
muffle furnace before quenching in palm oil and water separately. The mechanical behavior of the samples was inves-
tigated using universal tensile testing machine for tensile test and Vickers pyramid method for hardness testing. The
microstructure of the quenched samples was studied using optical microscope. The tensile strength and hardness values
of the quenched samples were relatively higher than those of the as-cast samples, suggesting improved mechanical
properties. However, samples quenched in palm oil displayed better properties compared with that of water-quenched
samples. This behavior was traced to the fact that the carbon particles in palm oil quenched samples were more uniform
and evenly distributed, indicating the formation of more pearlite structure, than those quenched in water and the
as-received samples.
Keywords: Medium Carbon Steel; Muffle Furnace; Quenching Media; Tensile Strength; Hardness Value
1. Introduction
Plain carbon steels are widely used for many industrial
applications and manufacturing on account of their low
cost and easy fabrication [1]. Their major alloying ele-
ment is carbon, and classified based on their carb on con-
tents. According to Rajan et al. [2], steels with carbon
content varying from 0.25% and 0.65% are classified as
medium carbon, while those with carbon up 0.25% C, are
termed low carbon. High carbon steels usually have car-
bon content ranges between 0.65% - 1.5%. Hardness and
other mechanical properties of plain carbon steels in-
crease with the rise in concentration of carbon dissolved
in austenite prior to quenching during hardening heat
treatment [2,3], which may be due to transformation of
austenite into martensite [4]. Thus, the mechanical streng-
th of medium carbon steels can be improved by quench-
ing in appropriate medium. However, the major influ-
encing factors in the choice of the quenching medium are
the kind of heat treatment, composition of the steel, the
sizes and shapes of the parts [5].
Based on the parameter of “quenching severity” H,
cooling capacity of water is treated to be unity [6]. The
H-parameters of various quenching media, which reflects
their capacity for removing heat in the quenching process,
are thus compared with that of water. Mineral oils have
been found to exhibit best cooling capacity for the ma-
jority of alloy steels [7], but they are relatively expens ive,
toxic and non-biodegradable. Therefore, there has been
considerable work in the past on the possibility of re-
placing mineral oils with aqueous solutions of chemical
substances and polymers [7-9]. More recen tly, the use of
local available cooking oils, which are relatively cheap,
non-toxic and environmental friendly, as quenching me-
dia, has begun to generate attention [10]. In the present
study, medium carbon steel samples are heat-treated at
different temperature above the austenitic region and
quenched in water and palm oil, in order to investigate
the effect of different heating and quenching regimes on
the mechanical properties of the steel. The changes in
mechanical behavior as compared with un-quenched sam-
ples are explained in terms of microstructural develop-
ment within the surface and changes in tensile strength
and hardness after quenching treatments.
2. Materials and Method
The chemical composition of medium carbon steel sam-
ples used for this investig ation is given in Table 1.
2.1. Test Specimen Preparation
As set of specimens were prepared for hardness tests and
microstructural analyses. Tensile test specimens were also
produced from the as-received medium carbon steel sam-
ples of the same composition. The specimens were prepared
Copyright © 2012 SciRes. JMMCE
after series of machining operation follo wing the Interna-
tional Test Standard, as shown in Figure 1. Other set of
specimens were also prepared for hardness tests and mi-
crostructural analysis.
2.2. Heat Treatment and Quenching
The prepared tensile test samples and other samples were
heated to 900˚C, 940˚C and 980˚C and soaked for 45
minutes using a muffle furnace. Test samples were quickly
taken out of the furnace after each of the heat treatment
temperatures, and quenched in water and palm oil sepa-
rately. Surface morphologies of the quenched samples
were examined, and hardness and tensile test were also
carried out on each of the samples.
2.3. Mechanical Test
2.3.1. Tensile Testing
Tensile test were carried out on both the water and palm
oil quenched specimens using Instron Universal Tester.
Each of the specimens was loaded till fractured, and the
fracture load for each sample was recorded as well as the
diameter at the point of fracture and the final gauge leng-
th. The initial diameter and initial gauge length for each
sample was noted before the application of the uniaxial
load. The percentage elongation and reduction of each
sample was determined, and the ultimate tensile strength
and yield strength were obtained from the data generated.
2.3.2. Hardness Test
Vickers pyramid method was used for the determination
of the hardness of the quenched samples. Each of the test
specimens was flatten after the different heating and quen-
ching regimes, and then mounted on the anvil. The
specimens were brought in contact with the pyramid in-
denter and allowed to rest for a dwell time. The hardness
of the specimen is indicated by the penetration of the
indenter on the test specimen, and displayed by the ma-
chine. Average values were recorded after repeating the
test for each of the test specimens.
3. Results and Discussion
Table 2 shows the mechanical properties of the quen-
ched steel samples compared with the un-quenched sam-
ples at different heat treatment temperatures. The effects
of the heat treatment temperatur es on the tensile strength,
Young’s modulus of elasticity, percentage elongation and
hardness of both the water quenched and oil quenched
test samples are shown in Figures 2-5, respectively.
As shown in Figure 2, the tensile strength of both the
water quenched and oil qu enched samples increases with
increase in the heat treatment temperature. The increase
in the tensile strength of the quenched samples as com-
pared with that of un-quenched (as-received) sample
showed that the heat treatment and quenching operations
influenced the strength of the steel samples. However,
the tensile strength of the water quenched samples were
Table 1. Chemical composition of the mild steel sample (wt%).
Element C Si S P Mn Ni Cr Mo V Cu
Average content 0.3302 0.1894 0.04530.05270.75800.10900.11700.11690.0018 0.0033
Element W As Sn Co Al Pb Ca Zn Fe
Average content 0.0878 0.0028 0.02040.01240.00060 0 0.003498.0413
Fillet radius at 45
= 22mm L
= 15mm
= 15mm
6 mm
10 mm
Figure 1. Tensile test specimen from medium carbon steel.
Table 2. Effect of cooling rates on the mechanical properties of medium carbon steel.
Sample quenching medium Temperature (˚C) Tensile strength
(N/mm2) Modulus of elasticity
(N/mm2) % Elongation Hardness (VHN)
As-received - 649.4 2020.0 32 286
Water 900 852.2 3436.6 24.8 376
Water 940 905.6 2959.5 30.6 418
Water 980 1063.9 3409.9 31.2 464
Oil 900 834.1 2598.4 32.1 336
Oil 940 889.2 2569.9 34.6 394
Oil 980 996.7 2831.5 35.2 438
Copyright © 2012 SciRes. JMMCE
Figure 2. Change in tensile of the medium carbon steel on
quenching in water and oil after heating to different.
Figure 3. Change in % elongation of a medium carbon steel
on quenching in water and oil after heating to different
temperatures; soaking 45 minutes.
higher than those quenched in oil, which may be to due
to formation of fine pearlite as a result of fast cooling
[11]. Ndliman [10] investigated the mechanical proper-
ties of a medium carbon steel heat treated at 850˚C and
quenched in both water and oil. He found that the tensile
strength of the heat treated samples were higher than th at
of the standard AISI C1035 steel sample, with water
quenched sample showing higher strength.
Figure 3 shows that the percentage elongation of the
steel samples increased with increasing heating tempera-
ture for both quenching media. However, the elongation
tends to improve for oil quenching compared with water
quenching, as faster cooling rate has been reported to
have a negative effect on elongation [11]. Transforma-
tion temperature is lowered by increased cooling rate,
and finer peralite grains are formed at lower temperatures
[12]. Martensitic structure, which has a detrimental effect
on toughness, is also produced during continuous water
quenchi n g [13].
The Young’s Modu lus v alu es were calculated fro m the
tensile strength and strain values, and the graph is pre-
Figure 4. Varition of young modulus of a medium carbon
steel on quenching in water and oil after heating to different
temperatures; soaking 45 minutes.
Figure 5. Change in hardness values of a medium carbon
steel on quenching in water and oil after heating to different
temperatures; soaking 45 minutes.
sented in Figure 4. From the Figure, it is revealed that
the value decreased with increasing temperature from
900˚C to 940˚C for both the water quenched and oil
quenched samples. Above 940˚C, the value further de-
creased for the water quenched sample, while it slightly
increased for the oil cooled sample, indicating possible
The hardness measurement, Figure 5, showed that
water quenched samples had higher Vickers hardness
compared to oil quenched samples. This may be due to
faster cooling rate of water, resulting in highest free car-
bon in martensite [11]. Furthermore, presence of fine
dispersion of small particles in the pro-eutectoid ferrite
and pearlitic ferrite, which will hinder the dislocation
movement, may have also contributed to higher hardness
value of the water-quenched sample.
4. Conclusions
1) It has been established that palm oil can also be
used as a quenching medium for medium carbon steel,
Copyright © 2012 SciRes. JMMCE
since mechanical strength of some of the samples quen-
ched with palm oil improved when compared with those
of the as-received sample.
2) Quenching in water resulted in higher tensile streng-
th and hardness possibly due to formation of martensitic
structure after quenching.
3) Palm oil cooling improves the ductility of the steel
because of its lower cooling rate compared with water.
Thus, palm oil will be a viable qu enching medium, where
improve elongation of the sample is critical.
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