Journal of Minerals and Materials Characterization and Engineering, 2012, 11, 1034-1038
Published Online October 2012 (http://www.SciRP.org/journal/jmmce)
Investigation into the Deep Drawability of 0.1%C
Samson Oluropo Adeosun, Olatunde Israel Sekunowo*, Sanmbo Adewale Balogun
Department of Metallurgical and Materials Engineering, University of Lagos, Lagos, Nigeria
Email: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Received June 10, 2012; revised July 18, 2012; accepted August 2, 2012
The phenomenon of anisotropism in most rolled products necessitates that the rolling direction that enhances desirable
mechanical property is established. In this paper, the comparative deep drawability of as-received and annealed mild
steel containing about 0.1%C was investigated. The flat steel sample was divided into two and classified as as-received
and heat treated respectively. The heat treated sample was obtained by annealing at 950˚C after been soaked for 5 hours
and deep drawn at ambient temperatures (35˚C - 42˚C). From both samples, circular specimens were machine- blanked
parallel to the rolling directions inclined at 0˚, 45˚ and 90˚ respectively and were prepared for deep drawability test
while rectangular specimens were prepared for tensile test. Both specimens, as-received and annealed were then sub-
jected to tensile, cupping and microstructural analyses. Results show that the contribution to increased formability at
90° rolling direction seems to have come from the spheroid-like pearlite grains induced during annealing while the sta-
bility of spread observed was achieved through a modest increase in strength. Thus, the resistance of annealed eutectoid
steel to cupping is quite minimal at 90° to the rolling direction. The desirable drawability characteristics developed by
the annealed eutectoid steel specimen are: cup-height, 30 mm maximum and ear, 6.4% maximum.
Keywords: Eutectoid Steel; Drawability; Annealing; Cupping; Anistropism
The ease and extent of plastic deformation suffered by
low carbon steel employed in the production of flat sheet
profiles is a measure of its drawability. With minimal
resistance to deformation, significant reduction in tool
wear rate is often achieved. In recent years, a lot of re-
search has been carried out on deep drawing of alumi-
num and steel alloys probably because they are amenable
to heat treatment during plastic deformation. According
to Miller et al. , deep drawing process finds applica-
tion in numerous fields such as in automobile industries
where the trend is towards safety and fuel economy.
However, the stability of spread of an extensively drawn
aluminum alloys is often a major concern. Hence, the
application of high strength steels is connected with their
characteristics improved spring back as a measure of
spread stability during deformation. In most deep drawn
components, adequate spring back is one of the means of
ensuring accuracy of shape geometry .
Consequently, the role of grain size refinement in im-
proving both strength and toughness in deep drawn ma-
terials has become imperative. Fine grained structures
can be conventionally obtained by recrystallization dur-
ing thermo mechanical treatment of steels. This has given
rise to the development of various processing techniques
leading to the refinement of ferrite grains for enhanced
formability . In this regard, the development of cold
rolled steel sheets with very good drawability is indeed
witnessing increased demand in the automotive industry.
The research in this direction is towards producing steels
with ultra low carbon comparable to interstitial free qua-
lity. It is established  that steel with very low carbon
content produces better quality plastic deformation char-
acteristics in drawing. However, this type of innovative
process technique requires the use of vacuum degassing
to improve formability, which is rather expensive. In
contrast, decarburization heat treatment after cold reduc-
tion has proved to be an effective alternative. The tech-
nique makes use of process-gas (N2 + H2) atmospheres
which when wet will react with the carbon in the steel
while the carbon leaves as carbon monoxide (CO). The
steel obtained have good grain size and desirable me-
chanical properties . Similarly, through a novel thermo
mechanical processing of low carbon steel having carbon
in the range of 0.02 - 0.15 wt%C and phosphorous up to
0.28 wt%,  obtained tough and significantly ductile
characteristics equivalent to high strength low alloy
Copyright © 2012 SciRes. JMMCE
S. O. ADEOSUN ET AL. 1035
The above new found technique presents clearly dif-
ferent conventional rolled product microstructure trans-
formation regime. Normally in practice, after conven-
tional hot rolling of mild steel, a lamellar pearlite is
formed during austenite-ferrite transformation. The la-
mellar morphology of pearlite often leads to impaired
mechanical properties which may render the steel un-
suitable for further cold treatment. The globular mor-
phology of cementite however, provides some benefits
such as high toughness, good cold formability and ma-
chinability. According to Storojeva et al., for such
higher cold formability to occur, the strip must either un-
dergo a long annealing treatment or it must be quenched
with subsequent tempering for a good combination of
strength and toughness. However,  achieved signify-
cant improvement in ductility and toughness in low car-
bon steel through the development of dual matrix struc-
ture by combining fast quenching from austenite phase
followed by annealing in the intercritical temperature
range of 710˚C - 790˚C.
As earlier suggested by Bello et al. , it is imperative
that a method is developed for the measurement of the
extent of plastic deformation suffered by steel undergo-
ing various degree of microstructure evolution. Although
the deep drawing process of high strength/low formabil-
ity metals has an extensive industrial application, deep
drawing at room temperature has serious difficulties be-
cause of the large amount of deformations required cou-
pled with high flow stresses of the materials . Thus
crumples, wrin- kles and earrings invariably occur on the
product surface because of the anisotropic property of the
materials. At some elevated temperatures however, the
flow stresses decrease giving rise to increased formabil-
ity and thus, deformation becomes easier. The current
study employs process annealing to simulate the form-
ability response of eutectoid steel.
The spectrochemical analysis result of the as-received
flat steel sample used for this study is presented in Table
1. The steel sample was divided into as-received and heat
treated (annealed) respectively. From the annealed sam-
ple, two types of specimens were prepared at ambient
temperatures (35˚C - 42˚C).
These consist of circular blanks, 60 mm in diameter
and 1.2 mm thickness for cupping test while rectangular
blanks of 100 × 25 × 1.2 mm were machined for tensile
test. Both types of specimens were then heat treated at
950˚C, soaked for 5 hours and furnace cooled.
In order to simulate the anisotropic characteristics of
the material, the circular blanks specimens were cut at 0˚,
45˚ and 90˚ to the rolling direction and then deep drawn
using an Erickson cupping machine. The minimum and
maximum heights of cups formed were measured using a
digital vernier caliper. The results of these measurements
and computations with regard to cup ears and height in
relation to their variation with angle of inclination to the
rolling direction are illustrated in Figures 1 and 2.
Tensile test was carried out on both the as-received
and annealed rectangular specimens in accordance with
ASTM E8 using Monsanto tensometer at the rate of 10−3
s until fracture occurred. The ultimate tensile strengths
exhibited by the specimens are shown in Figure 3.
Test pieces of as-received and annealed specimens for
microstructural analyses were prepared by grounding in
succession on 80, 240 and 360 grit emery papers and
polished using alumina powder paste. The specimens mir-
ror-like surfaces were then etched in Nital solution for 20
seconds and the microstructures viewed under an optical
metallurgical microscope at a magnification of ×800. The
photo micrographs are presented in Plates 1 and 2.
3. Results and Discussion
3.1. Tensile Strength Response of Test Specimens
Both the annealed and as-received specimens demon-
strated decreasing ultimate tensile strengths as the angle
of inclination to the rolling direction changes from 0˚-90˚
(Figure 3). This behaviour is attributable to the type of
microstructure transformation that occurred, particularly
in the annealed test specimens.
As observed in Plate 1(a), coarse pearlite precipitates
clustered around the ferrite-pearlite grain boundaries in
the rolling direction. Though the clustering of coarse
precipitates reduced considerably at 45˚ rolling direction,
higher volume fraction of the precipitates remained in the
matrix (Plate 1(b)). The ensued tensile strength variation
(Figure 3) apparently can be associated with the Hall-
Petch relation considering the apparent change in grain
size. Further, the 450 - 550 MPa range of tensile strengths
exhibited by the annealed test specimens indicate sig-
nificant reduction in tensile strength compared with 750 -
787 MPa for the as-received specimen. This is due to the
homogeneous dispersion of pearlite crystals within the
matrices during annealing.
It is expected that such quantum decrease in strength,
about 35% will translate to appreciable level of reduction
Table 1. Composition of the steel sample.
Element C Si Mn P S Cu Sn Ni Cr Pb Fe
Composition (%) 0.095 0.009 0.141 0.012 0.016 0.028 0.002 0.022 0.004 0.001 99.67
Copyright © 2012 SciRes. JMMCE
S. O. ADEOSUN ET AL.
Figure 1. Cup height against inclination to rolling direction.
Figure 2. Earing against inclination to rolling direction.
Figure 3. Ultimate Tensile Strength against Inclination to rolling direction.
Plate 1. Micrographs of annealed 0.1%C eutectoid steel specimens in varying directions (a) 0˚; (b) 45˚ and (c) 90˚.
Copyright © 2012 SciRes. JMMCE
S. O. ADEOSUN ET AL. 1037
Plate 2. Micrographs of as-received 0.1%C eutectoid steel specimens in varying directions (a) 0˚; (b) 45˚ and (c) 90˚.
in resistance to flow thereby enhancing formability. This
structural condition significantly contributed to the re-
duction in the amount of obstacles to the motion of dis-
location during deformation hence, the progressive
downward reduction in strength.
The observed trend further validates the need for the
estimation of forming load in deep drawing operation in
order to ensure minimal tool wear rate . Plate 2
shows the micrographs of the as-received specimens at
various angles of inclination to the rolling direction. The
matrices contain quite a few pearlite crystals sparsely
dispersed in ferrite matrix which increases progressively
from the rolling direction 0˚ (Plate 2(a)) to 45˚ (Plate
2(b)) and 90˚ (Plate 2(c)) respectively.
The rolling condition of the as-received specimens in
this study is similar to the state of a steel undergoing
normal cold drawing operation. In such a state, the ori-
ginal microstructure of the eutectoid steel which consists
mainly of lamellar pearlite remains substantially un-
changed. The difference however as observed in this
study is the progressive reduction in the pearlite lamellar
spacing as indicated by the change from coarse to fine
crystals. The work of Toribio et al.  shows similar
microstructure evolution during a continuously cold
drawing of eutec- toid pearlitic steel. This microstructure
condition is capa- ble of achieving remarkable increase
in yield strength while the tensile strength is lowered
thereby impairing the stability of spread of the article
3.2. Drawability Behaviuor of Test Specimens
Deep drawability is the property of a material indicating
its ability to be drawn to a predetermined depth (cup)
without fracture. The depth to which the material is
drawn is normally indicated by the cup height while the
quality of the cup surface finish (degree of smoothness
without tears and wrinkles) is measured by the ear in
The deep drawability behavior of the test specimens is
illustrated in Figure 1. Under the same load and other
operating conditions, the test specimens demonstrated
30.5 mm and 29.5 mm cup heights for annealed and
as-received respectively at 45˚ direction.
The higher cup height exhibited by the annealed test
specimens may be attributed to the profound structure
refinement that occurred (Plate 1). However, the narrow
variation in cup height values for both specimens in all
rolling directions is an indication that rolling direction
does not influence significantly the subsequent deep
Figure 2 describes qualitatively the surface finish
characteristics of test specimens after undergoing the
process of deep drawing. Minimum ear of 5.4% occurred
in the annealed specimens along the rolling direction (0˚)
with peak value of 6.4% at 90˚ direction. However, the
as-received specimens exhibited minimum ear of 5.6%
with 7.4% maximum at 0˚ and 45˚ rolling directions re-
From these results, it is observed that the variation of
ear for the annealed specimens is quite low, 5.4% - 6.4%
resulting in a range of 1. In contrast, the as-received
specimens demonstrated a rather higher ear variation,
5.6% - 7.4% which translated to a range of 1.8. The rela-
tively wide disparity in ear value of the as-received
specimens at different rolling directions becomes more
obvious by the concave shape of its curve. The presence
of discontinuities with other structure defects particularly
inclusions, undisolved carbide and in-homogeneity in the
structure coupled with high tensile strength must have
been responsible for this behavior. The near linear cur-
vature of the curve that describe the surface finish char-
acteristics of the annealed specimens shows that the an-
nealing process has actually aided refinement of the
structure in terms of grains morphology, volume fraction
The deep drawability of 0.1%C eutectoid steel in an un-
treated condition is rather difficult due to its high tensile
strength, 700 - 787 MPa coupled with obvious microstru-
cture defects. These conditions were substantially altered
by annealing. However, variation in tensile strength, ear
and the cup height (limited influence) along the different
rolling directions underscores the strong influence of
structures anisotropy. This behavior was reasonably sub-
Copyright © 2012 SciRes. JMMCE
S. O. ADEOSUN ET AL.
dued in the annealed specimens as demonstrated by close
range values of the properties investigated namely; ten-
sile strength, 450 - 550 MPa, cup-height, 29.5 - 30.0 mm
and ear, 5.4% - 6.4%.
All characteristics that promote deep drawability oc-
curred along the rolling direction (0˚) except that the de-
sirable tensile strength was obtained along 90˚ inclina-
tions. The results of this study have further demonstrated
that deep drawing of high strength low formability alloys
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