O. BEGANOVI] et al.: INFLUENCE OF WARM ROLLING AND HEAT TREATMENT IN THE ALPHA-GAMMA AREA ...
251–255
INFLUENCE OF WARM ROLLING AND HEAT TREATMENT IN
THE ALPHA-GAMMA AREA OF A THREE-LAYER STRIP ON
THE APPEARANCE OF EARS DURING CUP DEEP DRAWING
VPLIV TOPLEGA VALJANJA IN TOPLOTNE OBDELAVE V
AUSTENITNO-FERITNEM PODRO^JU TROSLOJNEGA TRAKU NA
POJAV U[ES MED GLOBOKIM VLEKOM SKODELIC
Omer Beganovi}, Mustafa Had`ali}, Suvad Kesi}
University of Zenica, Institute "Kemal Kapetanovi}" in Zenica, Travni~ka cesta 7, Bosnia and Herzegovina
Prejem rokopisa – received: 2018-06-29; sprejem za objavo – accepted for publication: 2018-11-22
doi:10.17222/mit.2018.131
Eearing is the most common defect that may occur during cup deep drawing. A removal of excess material from drawn parts
causes a wastage of the material. Therefore, it is necessary to minimize earing as much as possible. A negative effect of warm
rolling and annealing in the alpha-gamma area on the earing in the case of an explosive-welded three-layer strip consisting of
CuZn10 clad layers and the central DC04 steel layer is described in this article. Warm rolling of all samples started in the
alpha-gamma area (850 °C) of the steel layer. Some of them were reheated to the same temperature after each pass while others
were not reheated after the last three passes. In both cases, ears appeared. The final annealing was carried out at temperatures
between 700–930 °C. Regardless of the thermomechanical history of the samples, the final annealing in the alpha-gamma area
(750, 800 and 850) °C caused earing, even in the case of a sample exposed to a higher degree of cold deformation, including
intermediate recrystalization annealing at 700 °C, which, after the final annealing at 700 °C, does not have the tendency to
create ears. Because of this negative effect, annealing and prolonged warm rolling in the alpha-gamma area should be avoided.
Key words: three-layer strip, anisotropy, deep drawing, earing
Nastajanje u{es je najbolj pogosta napaka, ki se pojavlja med globokim vlekom skodelic. Odstranjevanje odve~nega materiala z
globoko vle~enih delov predstavlja odpadni material. Zato je potrebno nastajanje u{es zmanj{ati na najmanj{o mo`no mero.
Avtorji opisujejo negativen vpliv toplega valjanja in `arjenja v feritno-austenitnem podro~ju (alfa-gama) na nastanek u{es med
medsebojnim eksplozivnim varjenjem treh slojev (plasti) sestavljenih iz dveh zunanjih plasti CuZn10 in sredinsko plastjo DC04
jekla. Toplo valjanje vseh vzorcev se je za~elo z valjanjem jekla v afa-gama podro~ju (850
o
C). Nekaj vzorcev je bilo vsakokrat
ponovno ogretih na dano temperaturo pred vsakim prehodom skozi valje, nekaj vzorcev pa niso ponovno ogrevali med zadnjimi
tremi prehodi. V vseh primerih so se pojavljale valjarske napake (u{esa). Kon~no `arjenje so izvali pri temperaturah med 700 in
930
o
C. Ne glede na termo-mehansko zgodovino vzorcev in kon~no `arjenje (pri 750
o
C, 800
o
Cin850
o
C) so se vedno pojav-
ljala u{esa, celo v primeru vzorcev z vi{jim dele`em hladne deformacije z vklju~enim vmesnim rekristalizacijskim `arjenjem pri
700
o
C, ki po zaklju~nem `arjenju na 700
o
C ni kazalo tendence pojava u{es. Zaradi tega negativnega efekta `arjenja se je
potrebno izogibati dolgotrajnega toplega valjanja v alfa-gama podro~ju.
Klju~ne besede: trislojni trak, anizotropija, globoki vlek, nastajanje u{es
1 INTRODUCTION
Deep drawing is a manufacturing process for chang-
ing flat sheets/strips into geometrical cup-shaped metal
products without a failure or excessive localized
thinning.
1–2
In this process, a sheet/strip metal blank is
radially drawn into a forming die with the mechanical
movement of the punch to form a cup.
3
The most
common defect that may occur during cup deep drawing
is the earing. The earing is the appearance of waviness
(ears) on the upper edges of a deep-drawn cup. The
formation of ears results in unequal metal flows in
different directions due to the anisotropy of the metal
sheet/strip. The earing is not desirable as additional
processing is required to trim the excess metal, causing a
wastage of the material.
4
Therefore, it is necessary to
minimize the earing as much as possible. The purpose of
this paper is to describe the influence of warm rolling
and heat treatment in the alpha-gamma area of the earing
in the case of explosive-welded three-layer strip consist-
ing of CuZn10 clad layers and the central DC04 steel
layer.
The explosion-welding process is primarily used for
cladding certain metals with other metals with a better
corrosion resistance as in the case of cladding low-
carbon steel with copper alloys. Explosion welding is a
solid-state welding process that can be used for joining
metallurgically compatible metals but also metallurgi-
cally non-compatible metals that cannot be joined with
any other welding technique. A weld surface with a
metallurgical bond between the joined materials is
produced due to a controlled detonation of a chemical
explosive
5
that is placed on the cladding metal (flyer
plate). The pressure created by the explosive detonation
directs the flyer plate to the fixed base-metal plate,
Materiali in tehnologije / Materials and technology 53 (2019) 2, 251–255 251
UDK 620.1:621.787:669.112.227.1'228 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 53(2)251(2019)
*Corresponding author e-mail:
omer.beganovic@miz.unze.ba

making them to collide and bond at their interface.
6
Because of the high pressure produced by the explosive
detonation, the metals at the interface are locally plas-
tically deformed and metallurgically bonded. Since the
bonded metals have different mechanical and physical
properties, they behave differently during the plastic
deformation. Since the melting temperature of alloy
CuZn10 is significantly lower (a melting range of
1025–1045 °C)
7–8
than the melting temperature of steel
DC04 (a melting range of 1400–1500 °C), the hot-
working temperature range of the CuZn10 alloy
(750–900 °C)
7–8
is significantly lower than the normal
hot-working temperature range of the DC04 steel.
Because of that, the rolling of the steel (the central layer
of the three-layer strip) should be done in the alpha-
gamma and ferrite-pearlite area. This allows a different
microstructure compared to the cases when the rolling
process is performed in the gamma area.
Regardless of the thermomechanical conditions of
warm rolling, the microstructures of the rolled strips are
similar to each other after warm rolling and after recrys-
tallization annealing.
9
Thermomechanical cycles include
heating in the alpha-gamma or ferrite-pearlite tempera-
ture range, rolling, reheating, in different manners, to the
rolling temperature and repeated rolling causing frag-
mentation
10–11
of cementite lamellae and their partial
spheroidisation inside the pearlite areas.
12–13
Therefore,
the recrystallization annealing for the elimination of
strain effects is also soft annealing because of a complete
spheroidisation of the cementite in the ferrite matrix.
9
The subsequent cold rolling of the strips with such
microstructures, in combination with the final recrys-
tallization annealing, gives similar microstructures
(spheroidized cementite in the ferrite matrix). Unlike the
case, in which recrystallization annealing produces a
strong recrystallization texture after a very heavy cold
deformation, there are several cases, in which nearly
random textures are produced after only a small cold
deformation.
14
The development of a recrystallization
texture indicates the appearance of the preferred orienta-
tion, anisotropy of the mechanical properties and thus
the increased earing sensitivity.
2 EXPERIMENTAL PART
2.1 Materials
The sample for rolling was a three-layer plate ob-
tained with explosive welding. Plates of a copper alloy
(CuZn10 according to the standard EN 1652) were
applied to the plate of low-carbon steel (DC04 steel for
deep drawing according to the standard EN 10130) on
both sides (the top and bottom side). The chemical com-
positions of particular layers are presented in Table 1.
The dimensions of the three-layer plate obtained with
explosive welding were (35 × 1200 × 2000) mm. Strips
with a nominal width of 90 mm were cut with a water jet
from the three-layer plate.
2.2 Experiments
Warm rolling of the three-layer strips was performed
on light-section rolling mill SKET with  370 mm from
35 mm to 4.3 mm in thickness (8 passes), and a labora-
tory light-section rolling mill with  250 mm from
4.3 mm to 2.3 mm in thickness (3 passes). Cold rolling
of the three-layer strips was performed on cold rolling
mill LOMA from 4.3 mm or 2.3 mm to 1.33 mm in
thickness (Table 2).
After warm rolling and recrystallization annealing
(700 °C/1 h), and before cold rolling, an oxide film was
removed from the strip surface with a 7.5 % sulphuric
acid heated to a temperature of 35–40 °C. The holding
time of the strip in the sulphuric acid was 8 min. After
the final heat treatments, the newly formed oxide film
was removed in the same way as after the warm rolling.
The microstructure of all the samples with a thickness of
2.3 mm, consisting of ferrite with completely sphero-
idized cementite was a common microstructure obtained
after the described thermomechanical treatments.
9
The
thickness of individual layers was 0.098 and 0.094 mm
in the case of CuZn10 clad layers and 1.138 mm in the
case of the central steel layer, so the ratio of the total
thickness of the CuZn10 layers and the total thickness of
the three-layer strip was 14.4 %.
15
Consequently, the
behaviour of the three-layer strip was mainly determined
by the behaviour of the central steel layer. The final
width of the strips after warm and cold rolling was 102
mm and after the longitudinal slitting of the side edges of
the strip by circular knives, it was 84 mm. The final heat
treatments were carried out with the aim that the grain
size of all the strips (samples) should be between G 6.0
and G 8.0. Skin-pass rolling as the last step of the strip
processing was performed on cold-rolling mill LOMA
with an approximately 2 % reduction in thickness.
NOTE: Annealing at 700 °C is a recrystallization
process consisting of heating (1 min/mm) and holding
the samples (1 h) at that temperature. Heat treatments at
other (higher) temperatures consist of heating (1 min/mm)
and holding the samples (18 min) at these temperatures.
Strips were in coils with dimensions of  200/ 235 mm
and a weight of up to 8 kg.
O. BEGANOVI] et al.: INFLUENCE OF WARM ROLLING AND HEAT TREATMENT IN THE ALPHA-GAMMA AREA ...
252 Materiali in tehnologije / Materials and technology 53 (2019) 2, 251–255
Table 1: Chemical compositions of steel DC04 and CuZn10 alloy layers
Material
Content of elements in mass fractions (w/%)
C Mn Si P S Al N Cu Zn Pb Fe
DC04 0.08 0.30 0.03 0.009 0.003 0.023 0.005 – – – Rem.
CuZn10 –––––– 89.9 10.1 <0.01 <0.01

O. BEGANOVI] et al.: INFLUENCE OF WARM ROLLING AND HEAT TREATMENT IN THE ALPHA-GAMMA AREA ...
Materiali in tehnologije / Materials and technology 53 (2019) 2, 251–255 253
Table 2: Basic parameters of warm and cold rolling and the final heat treatments of different strips/samples
Strip/
sample
Warm rolling Cold rolling Temperature of
the final heat
treatment
Process content
Height
reduction (%)
Process content
Height
reduction (%)
S 1.1
Heating to 850 °C; rolling: 34.8 mm
 4.3 mm with reheating to 850 °C
after each pass
87.7
Annealing: 700 °C; rolling:
4.3 mm  2.3 mm;
annealing: 700°; rolling: 2.3
mm  1.33 mm
69.1
700 °C
S 1.2 800 °C
S2
Heating to 850 °C; rolling: 34.8 mm
 2.3 mm with reheating to 850 °C
after each pass
93.4
Annealing: 700 °C; rolling:
2.3 mm  1.33 mm
42.2 700 °C
S 3.1
Heating to 850 °C; rolling: 34.8 mm
 4.3 mm with reheating to 850 °C
after each pass; rolling: 4.3 mm  2.3 mm without reheating between the
passes
93.4
Annealing: 700 °C; rolling:
2.3 mm  1.33 mm
42.2
700 °C
S 3.2 750 °C
S 3.3 800 °C
S 3.4 850 °C
S 3.5 930 °C
Table 3: Tensile properties of the samples (strips) and the corresponding grain size
Sample (strip) S1.1 S 1.2 S 2 S 3.1 S 3.2 S 3.3 S 3.4 S 3.5
Yield strength, R
p0,2
(MPa) 208 234 200 231 238 232 219 215
Tensile strength, R
m
(MPa) 315 340 327 349 323 354 331 346
Elongation, A (%) 32.0 29.5 29.0 31.0 27.5 27.5 27.0 32.0
Grain size no, G 6.5 6.5 6.5 6.5 7.0 6.5 6.5 7.5
Figure 1: Microstructures of the steel-layer samples after rolling and final heat treatment (2 % HNO
3
)

3 RESULTS AND DISCUSSION
The tensile tasting of all the obtained strips was per-
formed according to standard BAS EN ISO 6892-1:2017.
The average grain size was determined according to
standard ASTM E112-13. The results of the tensile
testing and the corresponding grain size are presented in
Table 3.
The achieved values of the tensile properties are
common for a three-layer strip of this type after skin-
pass rolling. The applied heat-treatment parameters, the
heating time and holding time (Table 2), provided a
grain size between G 6.5 and G 7.5 for the steel layer of
all rolled samples (strips). The microstructures of the
steel layers of all the samples (strips) are presented in
Figure 1. Depending on the final heat-treatment tem-
perature, the microstructures consist of ferrite with com-
pletely spheroidized cementite (samples S 1.1,S2andS
3.1), ferrite + pearlite with the residues of non-dissolved
spheroidized cementite (samples S 1.2, S 3.2 and S 3.3)
and pure ferrite + pearlite (samples S 3.4 and S 3.5). The
presence of non-dissolved spheroidized cementite in
samples S 1.2, S 3.2 and S 3.3 is a result of an
insufficient duration of the heat treatment at appropriate
temperatures of the strip coils with  200/ 235 mm
(18 min for heating and 18 min for holding). With the
increasing temperature, the quantity of the non-dissolved
spheroidized cementite reduces. The microstructure of
sample S 3.5 consists of ferrite and lamellar pearlite.
This structure is common for low-carbon steel after nor-
malizing.
Circular blanks with a diameter of 16.5 mm were cut
from all the strips. These blanks were radially drawn into
cups with dimensions of  9.38/ 6.98 mm and a height
of approximately 10 mm on an industrial machine for
deep drawing. These cups are used for deep drawing of
bullet jackets for ammunition. Since the thickness of the
strips was 1.30 mm and the thickness of the cup wall was
1.20 mm, the achieved plastic deformation was 7.7 %.
On six samples (S 1.2, S 2, S 3.1, S 3.2, S 3.3 S 3.4),
four ears were formed while on two samples (S 1.1, S
3.5), ears were not formed (Figure 2). The ears were
formed in the directions that were 45° from the rolling
direction and 45° to the transverse direction. The wavi-
ness of the upper edges of the cups was measured with
3D coordinate measuring machine Carl Zeiss Contura
G3 (an accuracy of ±0.010 mm). The results of these
measurements are presented in Figure 3. Insufficiently
smooth lines on this figure are results of the unevenness
of the blanks’ cutting surfaces.
Sample S 3.5 was deep drawn without any occur-
rence of ears because it was previously annealed at a
temperature of 930 °C. This annealing is practically a
normalization with a full phase transformation and ran-
domly oriented grains that ensure isotropic strip pro-
perties in different directions. Sample S 1.1 was also
deep drawn without the occurrence of ears, unlike sam-
ples S 2 and S 3.1, although these samples have a similar
thermomechanical history. The basic difference is related
to the fact that sample S 1.1 was cold rolled, subjected to
a higher amount of cold deformation, i.e., 69.1 %
(rolling: 4.3 mm  2.3 mm; annealing: 700 °C; rolling:
2.3 mm  1.33 mm), unlike samples S 2 and S 3.1 that
were subjected to a cold deformation of 42.2 % (rolling:
2.3 mm 1.33 mm).
A higher amount of cold deformation in the case of
sample S 1.1, including recrystallization annealing
(700 °C) reduces the negative effects of warm rolling in
the alpha-gamma area on the earing process. The nega-
tive effect of heating in the alpha-gamma area on the
earing can be seen on sample S 1.2 (Figure 3) that has
O. BEGANOVI] et al.: INFLUENCE OF WARM ROLLING AND HEAT TREATMENT IN THE ALPHA-GAMMA AREA ...
254 Materiali in tehnologije / Materials and technology 53 (2019) 2, 251–255
Figure 3: Variation in the cup height with the angle
Figure 2: Deep-drawn cups

the same thermomechanical history as sample S 1.1 but
its final annealing was carried out in the alpha-gamma
area (800 °C). This negative effect in the cases of
samples S 2 and S 3.1 is a result of a prolonged warm
rolling of the strips in the alpha-gamma area while in the
cases of strips S 3.2, S 3.3 and S 3.4, the negative effect
is a result of a prolonged warm rolling of the strips in the
alpha-gamma area and the final annealing in this area.
4 CONCLUSIONS
The earing effect in the case of cup deep drawing
involving a three-layer strip can be avoided with a nor-
malization and a higher degree of cold deformation,
including intermediate recrystallization annealing. This
type of normalization of strips is impractical because of
a relatively high annealing temperature (930 °C). Inter-
mediate recrystallization annealing performed during
cold deformation is necessary to avoid the occurrence of
the preferred crystallographic orientation causing aniso-
tropy of mechanical properties. The heating of the strips
in the alpha-gamma area due to annealing and warm
rolling has a negative effect on earing. For this reason,
annealing and prolonged warm rolling in the alpha-
gamma area should be avoided.
Acknowledgements
The authors acknowledge the financial support of the
Federal Ministry of Education and Science of the
Federation of Bosnia and Herzegovina.
5 REFERENCES
1
H. I. Demirci, Ö. Karaçali, Computer Aided Engineering (CAE) Ex-
perimental Application for Deep Drawing Processes of a Sheet
Metal, 12
th
International Research/Expert Conference Trends in the
Development of Machinery and Associated Technology TMT 2008,
Istanbul, Turkey, 2008, 161–164
2
A. Tali}-^ikmi{, M. Trako, M. Karivan, Finite Element Analysis of
Deep Drawing, 14
th
International Research/Expert Conference
Trends in the Development of Machinery and Associated Technology
TMT 2010, Mediterranean Cruise, 2010, 81–84
3
K. Shah, D. Bhatt, T. Panchal, D. Panchal, B. Dogra, Influence of the
process parameters in deep drawing, International Journal of
Emerging Research in Management and Technology, 3 (2014) 11,
16–22, ISSN: 2278-9359
4
P. Ravikant, D. Harshit, R Harit, Study of earing defect during deep
drawing process with finite element simulation, Key Engineering
Materials, 639 (2015), 91–98, doi:10.4028/www.scientific.net/
KEM.639.91
5
O. Saresoja, A. Kuronen, K. Nordlund, Atomistic simulation of the
explosion welding process, Advanced Engineering Materials, 12
(2012) XX, 1–4, doi:10.1002/adem.201100211
6
F. Findik, R. Yilmaz, T. Somyurek, The effects of heat treatment on
the microstructure and microhardness of explosive welding, Scien-
tific Research and Essays, 6 (2011) 19, 4141–4151, doi:10.5897/
SRE11.1018
7
http://admin.copperalliance.eu/docs/librariesprovider5/pub-tn26-
the-brasses-technical-data/copper-zinc-alloys-(brasses)/cuzn10-(cw5
01l)-datasheet-d2.pdf?sfvrsn, 26.05.2018
8
http://www.mueller-hespert.de/images/uploads/emhPDF/Data-
sheet_CuZn10.pdf, 26.05.2018
9
O. Beganovi}, B. Faki}, A. M. A. Mohammedzain, A. O. M.
Babekir, F. Uzunovi}, Effect of Deformation and Heat Treatment on
Microstructure of Warm Rolled Steel in Alpha-Gamma Area, 12
th
Scientific/Research Symposium with International Participation
“Metallic and Nonmetallic Materials“ B&H, 2018
10
M. Umemoto, Y. Todaka, K. Tsuchiya, Mechanical properties of
cementite and fabrication of artificial pearlite, Materials Science
Forum, 426–432 (2003), 859–864
11
H. S. Valberg, Applied Metal Forming Including FEM Analysis,
Cambridge University Press, 2010, 3
12
R. Song, D. Ponge, D. Raabe, R. Kaspar, Microstructure and
crystallographic texture of an ultrafine grained C–Mn steel and their
evolution during warm deformation and annealing, Acta Materialia,
53 (2005), 845–858, doi:10.1016/j.actamat.2004.10.051
13
B. L. Bramfitt, Structure/Property Relationships in Irons and Steels,
Metals Handbook Desk Edition, 2
nd
ed., J. R. Davis, Editor, ASM
International, 1998, 153–173
14
Kumkum Banerjee: Physical Metallurgy and Drawability of Extra
Deep Drawing and Interstitial Free Steels, IntechOpen, doi:10.5772/
35073, March 7
th
2012, Available from: https://www.intechopen.
com/books/recrystallization/physical-metallurgy-and-drawability-of-
extra-deep-drawing-and-interstitial-free-steels, 15.06.2018
15
O. Beganovi}, A. ^amd`i}, F. Uzunovi}, Effect of Uneven Plastic
Deformation on Width of Clad Layers of Explosive Welded Three-
Layer Strip, 12
th
Scientific/Research Symposium with International
Participation "Metallic and Nonmetallic Materials" B&H, 2018
O. BEGANOVI] et al.: INFLUENCE OF WARM ROLLING AND HEAT TREATMENT IN THE ALPHA-GAMMA AREA ...
Materiali in tehnologije / Materials and technology 53 (2019) 2, 251–255 255