J. ^UBROVÁ et al.: EFFECTS OF ROTARY SWAGING, WIRE DRAWING AND THEIR COMBINATION ...
601–606
EFFECTS OF ROTARY SWAGING, WIRE DRAWING AND THEIR
COMBINATION ON THE RESULTING PROPERTIES OF
NICKEL-ALLOY WIRES
VPLIV ROTACIJSKEGA KOVANJA, VLE^ENJA @ICE IN
KOMBINACIJE OBEH POSTOPKOV NA MEHANSKE LASTNOSTI
NIKLJEVIH LEGIRANIH @IC
Jana ^ubrová
*
, Kateøina Mertová, Michal Duchek
Metallurgical Technologies Department, COMTES FHT a.s., Prùmyslová 995, 334 41 Dobøany, Czech Republic
Prejem rokopisa – received: 2019-07-26; sprejem za objavo – accepted for publication: 2020-04-23
doi:10.17222/mit.2019.177
This paper investigates the influence of drawing and rotary-swaging parameters, such as the area reduction, on the tensile prop-
erties of nickel-alloy wires. Rotary swaging and wire drawing were used to improve mechanical properties. Furthermore, the ef-
fect of the combination of these processes on the resulting hardness of the cross-sections of wires was studied. In the case of ro-
tary swaging, the highest amount of cold deformation (an increased value of hardness) is located in the middle of the wire. This
can be explained with the formation of deformation cones oriented to the centre of the wire. On the other hand, the highest
amount of cold deformation in the case of drawing is located on the surface (just under the surface layer) of the drawn wires. As
a result, our interest is focused on achieving large cross-sectional reductions during the wire-drawing process. In addition, the
largest approach angle is used in order to avoid redundant shear. Thanks to the combination of the rotary swaging and wire
drawing, there are negligible differences in the hardness across the wire diameter. The mechanical properties, the microstruc-
tures in the longitudinal and transverse directions and the hardness profiles (HV) of pure-nickel-alloy (Alloy 200) wires were
compared in this investigation.
Keywords: rotary swaging, wire drawing, nickel
V ~lanku avtorji opisujejo raziskavo vpliva tehnolo{kih parametrov hladnega vle~enja in rotacijskega kovanja na natezne
lastnosti nikljevih legiranih `ic. Oba postopka so uporabili za to, da bi izbolj{ali mehanske lastnosti `ic. Nadalje so {tudirali
vpliv kombinacije obeh postopkov na rezultirajo~o trdoto po preseku `ic. V primeru rotacijskega kovanja je pri{lo do najve~je
stopnje hladne deformacije (pove~anja trdote) v sredini `ice. To si razlagajo s tem, da je pri{lo do tvorbe deformacijskih con
orientiranih proti sredini `ice. Po drugi strani pa je pri{lo na hladno vle~enih `icah do najve~je stopnje hladne deformacije na
povr{ini `ic (v plasti tik pod povr{ino). Avtorji so `eleli med vle~enjem `ice dose~i ~im ve~je zmanj{anje njenega preseka.
Nadalje so uporabljali najve~ji vstopni kot, da bi se izognili pretiranim stri`nim deformacijam. Z uporabo kombinacije
rotacijskega kovanja in vle~enja so avtorji uspeli dose~i zanemarljive razlike v trdoti po preseku `ic. Med raziskavo so izvedli
tudi primerjavo mehanskih lastnosti in mikrostrukture `ic v vzdol`ni in pre~ni smeri ter profile HV trdot ~iste nikljeve legirane
`ice (Alloy 200) glede na uporabo izbranih postopkov.
Klju~ne besede: rotacijsko kovanje, vle~enje `ice, nikelj
1 INTRODUCTION
Nickel and nickel-based alloys are important to the
modern industry because of their ability to withstand a
wide variety of severe operating conditions involving
corrosive environments, high temperatures, high stresses
and combinations of these factors. The corrosion resis-
tance of pure nickel makes it particularly useful for
maintaining product purity in the food industry and med-
icine applications. It is widely used also in general struc-
tural applications where resistance to corrosion is a
prime consideration. Pure nickel is ductile and tough be-
cause it exhibits a face-centred cubic (fcc) structure. Al-
loy 200 is commercially pure wrought nickel (99.5 %)
with a carbon content of about 0.1 %. This is essentially
a pure metal with negligible alloying. The alloys are usu-
ally supplied in the annealed condition to give a virtually
pure nickel austenite microstructure. Pure nickel has a
low strength but it is a highly ductile material in the an-
nealed condition. The strength can be increased with a
work-hardening process.
1,2
One way of achieving better mechanical properties is
the process of rotary swaging or wire drawing. The ro-
tary swaging is a cold forming process, incrementally re-
ducing the cross-sectional area or otherwise changing the
shape of bars, tubes or wires due to repeated radial
blows. Thus, rotary swaging belongs to the suitable
near-net-shape production techniques with a great poten-
tial for lightweight constructions. During a swaging pro-
cess, the workpiece is fed into a swaging die in the axial
direction and is initially formed in the conical entry sec-
tion of the die. Radial movement and rotation
of the swaging die are used.
3,4
The basic principle of a wire-drawing process is that
a wire is pulled through a single opening or series of cir-
Materiali in tehnologije / Materials and technology 54 (2020) 5, 601–606 601
UDK 67.017:621.791.725:669.715 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 54(5)601(2020)
*Corresponding author's e-mail:
jana.cubrova@comtesfht.cz (Jana ^ubrová)

cular openings of a drawing die. It is usually performed
as a cold-working operation. Drawing is most frequently
used to produce a round cross-section, but square and
other shapes are also drawn. The dies are stationary. This
process is used to reduce the cross-section and increase
the length of a wire. Radial pressure is generated in the
conical part of the drawing die by reducing of the
cross-section. Deformation that occurs during the draw-
ing operation is sometimes referred to as indirect com-
pression. Thanks to the wire drawing, the surface quality
and a perfect shape of final products are obtained. Fur-
thermore, mechanical properties such as the strength and
hardness of the wires are increased.
5,6
The objectives of the present study were the investi-
gation and comparison of the above-mentioned methods
and their combination applied to commercially pure
nickel alloy 200.
2 EXPERIMENTAL PART
The material used to this research was commercially
pure nickel alloy 200. The chemical composition of the
samples can be found in Table 1. This composition was
analysed with a Bruker Q4 Tasman optical emission
spectrometer and a Bruker G8 Galileo gas analyser. The
input diameter of the nickel rods was 7.5 mm.
Table 1: Chemical composition of the processed material, in mass
fractions (w/%)
Element Ni Cu Fe Mn Si S C
Weight % >99 <0.25 <0.40 <0.35 <0.35 <0.01 <0.15
Different deformation processes were applied to in-
put wires. A series of experiments was performed on a
recess-swaging machine and draw bench. The test mate-
rial included wires with an initial diameter of 7.5 mm re-
duced to a final diameter of approximately 3 mm. The
methods used for the reduction of the diameters were ro-
tary swaging, wire drawing and their combinations. Four
options are described in this paper (Table 2).
Table 2: Specification of the experiment
Specimen Input / Final diameter
Experiment Rotary swaging (RS)
from 7.5 mm to 3.2
mm
Experiment
Rotary swaging »
wire drawing
from 7.5 mm » 5.1
mm » 3.0 mm
Experiment Wire drawing (WD)
from 7.5 mm to 2.9
mm
Experiment
Wire drawing » rotary
swaging
from 7.5 mm » 5.0
mm » to 3.1 mm
In the first experiment, the wire was processed in
nine steps using sequential rotary swaging. The material
was reduced from the initial diameter of 7.5 mm to a fi-
nal diameter of 3.2 mm. The total area reduction was
81 %. Values of area reduction per pass were 12–20 %.
The rotary-swaging process was carried out in an HMP
R4-4 rotary-swaging machine. During the swaging pro-
cess, the deformation of the workpiece was realized in
the swaging head. Four split swaging dies were used in
these experiments. The rotation speed of a swaging die
can reach up to 350 min
–1
. During the rotary swaging,
the wire moved through the swaging head and the prod-
uct was taken out from the opposite side of the machine.
The velocity of the wire movement was approximately
8.4 m/min.
The second experiment was carried out in a two
steps, using the rotary-swaging machine and draw bench.
In the first step, the wire was rotary swaged to 5.1 mm
and subsequently drawn to a final dimension of 3.0 mm.
The whole process was done in nine steps. In this opera-
tion, the cross-sectional area was reduced by 17–20 %
during each pass. The value of the total true deformation
at the end of this experiment was 1.80.
The wire-drawing process used for the third experi-
ment was observed by means of draw-bench WMW ma-
chinery. Eight wire-drawing dies were used for the
wire-drawing process. The nickel wire was reduced in
the dies from the initial diameter of 7.5 mm to a final di-
ameter of 2.9 mm. The drawing speed for the nickel al-
loy was set to 8 m/min. In this process, the reduction
from the initial to the final wire was more than 80 %.
The reduction was evenly distributed during the passes.
Nine passes through the wire dies were completed.
Tungsten-carbide dies were used for the wire production.
The last experiment was focused on combining wire
drawing and rotary swaging. In the first phase, the nickel
wire was drawn from the initial diameter of 7.5 mm to a
final diameter of 4.9 mm. The area reduction per pass
did not exceed 24 %. In the second phase, the wire was
swaged to a final dimension of 3.2 mm. The total area re-
duction was 81 %.
Table 3 shows the process parameters of rotary swag-
ing, wire drawing and their combination, performed in
order to compare the final mechanical properties and de-
termine the effects of individual processes on the
microstructure.
Table 3: Parameters of the process
Area reduction
(%)
True deforma-
tion (-)
1. Experiment – RS 81 1.65
2. Experiment – RS » WD 83 1.80
3. Experiment – WD 84 1.84
4. Experiment – WD » RS 81 1.65
For the purpose of observation with a light micro-
scope, all the samples were prepared using metallo-
graphic techniques like grinding, polishing and subse-
quent etching with Marble’s Reagent. After the
preparation, the microstructures were analysed by means
of optical microscope Carl Zeiss – Observer Z1. Tensile
tests were performed in an electromechanical testing ma-
chine for wires with final diameters of: 3.2 mm, 3 mm,
J. ^UBROVÁ et al.: EFFECTS OF ROTARY SWAGING, WIRE DRAWING AND THEIR COMBINATION ...
602 Materiali in tehnologije / Materials and technology 54 (2020) 5, 601–606

2.99 mm and 3.2 mm. The tests were executed at room
temperature. The deformation was measured using a me-
chanical extensometer. The Vickers hardness (HV1)
across the cross-section was processed by means of a
Durascan 50. The aim was to compare the hardness pro-
files, microstructures and mechanical properties of all
the samples.
3 RESULTS
The microstructures of the wires of nickel 200 alloy
are shown in Figure 1. In these figures, the formed tex-
ture is visible along the longitudinal direction. After the
swaging process, the structure becomes denser and elon-
gated grains appear in the axial direction, as shown in
Figure 1 (1
st
experiment – RS). This is because the mate-
rial in the forging zone is subjected to the triaxle com-
pressive stress, in which the circumferential stress is the
largest. In Figure 1 (3
rd
experiment – WD), the micro-
structure of the drawn wire after nine drawing passes is
shown. The microstructure of the drawn wire clearly
shows that the morphological texture of the grains was
prolonged along the wire-drawing axis. The grains after
the combination of the processes (2
nd
and 4
th
experi-
ments) were considerably stretched in the longitudinal
section.
Figure 2 shows the hardness distributions through
the cross-sections of the final wires. For the first experi-
ment, it is evident that the higher amount of cold defor-
mation (the increased value of hardness) is located in the
middle of the wires. This can be explained with the for-
mation of deformation cones oriented to the centre of the
wires. The hardness values in the middle of the wires
reached around 250 HV1.
Otherwise, during the third experiment, the hardness
on the surface was significantly higher than in the central
part of the drawn wire thanks to the non-uniform mate-
rial flow. The value of 260 HV1 was measured on the
surface, unlike the centre of the wire where the hardness
was 250 HV1.
However, the combination of rotary swaging and sub-
sequent wire drawing led to a homogeneous distribution
of hardness across the cross-section of the wire, as seen
on Figure 2 (2
nd
experiment). The differences between
the surface and middle-section hardness measurements
were less than 2 %. The fourth experiment showed that
wire drawing and the subsequent rotary swaging led to
the strengthening of the middle part of the wire. A high
J. ^UBROVÁ et al.: EFFECTS OF ROTARY SWAGING, WIRE DRAWING AND THEIR COMBINATION ...
Materiali in tehnologije / Materials and technology 54 (2020) 5, 601–606 603
Figure 1: Micrographs of the processed wire after the final reduction step – longitudinal direction

amount of hardness of around 270 HV1 was found in the
middle of the wire.
A tensile test of the final diameter of the wire was
performed. In Table 4, the original values of the me-
chanical properties of the input wires were compared
with the final values of the mechanical properties for in-
dividual experiments. The tensile strength of the material
increased with the increasing degree of cold-drawn de-
formation. The highest values of the ultimate tensile
strength and offset yield strength were observed for the
third experiment. Wire drawing led to an increase in the
tensile strength of up to 917 MPa. It was twice as high as
in the received material, while the lowest reached ductil-
ity value was 8 %. Thanks to this low ductility, an unsta-
ble defect could be formed in the material after the de-
formation. The highest value of the total elongation of
14 % was measured for the rotary-swaging process.
Table 4: Mechanical properties after rotary swaging, wire drawing
and combination of these methods: ultimate tensile strength (UTS);
offset yield strength (OYS); reduction in area (RA); total elongation
(El)
Condition
UTS
(MPa)
0.2 OYS
(MPa)
El
(%)
RA
(%)
As received 462 148 46 -
Rotary swaging 763±3.8 753±7.3 14±0.9 75±2.0
Rotary swaging »
wire drawing
850±3.1 834±5.3 11±0.3 68±1.5
Wire drawing 917±4.9 909±0.5 8±0.8 62±2.0
Wire drawing » ro-
tary swaging
823±6.8 814±2.2 13±2.1 68±1.2
Rotary swaging led to an increase in the ultimate ten-
sile strength of 763 MPa. In the second experiment, the
combination of rotary swaging and subsequent wire
drawing reached an ultimate tensile strength of 850 MPa
with a total elongation of 11 %. The second experiment
offers a good compromise between strength and ductil-
ity. Unfortunately, these techniques show a uniform ho-
mogeneous distribution of hardness across the cross-sec-
tion.
4 DISCUSSION
The yield strength of the material was observed to re-
duce with increasing degree of cold-drawing, an indica-
tion of reduction in the ductility and the tensile strength
of the material reduced with increasing degree of
cold-drawn deformation. The ability of the material to
resist impact loads when nails are hammered reduced
with increasing degree of drawn deformation as a result
of strain
hardening of the material after the drawing operation.
However the resilience of the material to further cold
drawn deformation increased with increasing degree of
deformation as evident in the Brinnel hardness number
which increases with the degree of drawing deformation.
This is an indication of the material’s approach to brittle-
ness as the degree of drawn deformation increases The
yield strength of the material was observed to reduce
with increasing degree of cold-drawing, an indication of
reduction in the ductility and the tensile strength of the
material reduced with increasing degree of cold-drawn
deformation. The ability of the material to resist impact
loads when nails are hammered reduced with increasing
degree of drawn deformation as a result of strain harden-
ing of the material after the drawing operation. However
J. ^UBROVÁ et al.: EFFECTS OF ROTARY SWAGING, WIRE DRAWING AND THEIR COMBINATION ...
604 Materiali in tehnologije / Materials and technology 54 (2020) 5, 601–606
Figure 2: Hardness-profile measurements in the cross-sections of the wires

the resilience of the material to further cold drawn defor-
mation increased with increasing degree of deformation
as evident in the Brinnel hardness number which in-
creases with the degree of drawing deformation. This is
an indication of the material’s approach to brittleness as
the degree of drawn deformation increases.
The yield strength of the material was observed to re-
duce with increasing degree of cold-drawing, an indica-
tion of reduction in the ductility and the tensile strength
of the material reduced with increasing degree of
cold-drawn deformation. The ability of the material to
resist impact loads when nails are hammered reduced
with increasing degree of drawn deformation as a result
of strain hardening of the material after the drawing op-
eration. However the resilience of the material to further
cold drawn deformation increased with increasing degree
of deformation as evident in the Brinnel hardness num-
ber which increases with the degree of drawing deforma-
tion. This is an indication of the material’s approach to
brittleness as the degree of drawn deformation increases
The influence of individual processing methods on
the final properties of wires were shown with the per-
formed experiments. It became evident how the ro-
tary-swaging and wire-drawing processes affect the de-
velopment of a microstructure. The microstructure in the
longitudinal section of all the tested samples showed
grain elongation along the longitudinal axis with a re-
duced grain size due to cold deformation.
Furthermore, the influence of individual methods on
the hardness profile was investigated. The measured val-
ues correspond to the hardness distribution described in
the article, written by H. P. Stuwe.
7
In this article, it was
mentioned that if the rotation angle is different, as is the
case with conventional commercial devices, the strain
path for each stroke varies irregularly. Kinetic softening
very nearly prevents work hardening in the outer layer of
a wire and even the centre of the wire work-hardens
much less than the drawn wire. This thesis was con-
firmed with the first experiment. The opposite is true of a
drawn wire. The core of a rod is work-hardened by the
unidirectional strain. The outer layers are work-hardened
somewhat more by an additional shear force. The homo-
geneous hardness distribution in the sample across the
cross-section was achieved with a combination of rotary
swaging and subsequent wire drawing. The ultimate ten-
sile strengths for all the variations ranged from 760 MPa
to 910 MPa. In the literature, the breaking strength was
increased
2
by cold rolling up to 760 MPa and the elonga-
tion was 8 %. In our case, the strength was 917 MPa at
the same elongation value.
The finished-product quality is strongly dependent on
the hardness distribution, mechanical strength and
microstructure. That is why investigations of different
options of cold-hardening processes are important. The
article, presented in the Journal of Material Research and
Technology by J. Zottis,
8
discusses the application of the
experimental and numerical methods, based on the hard-
ness measurement, which allows evaluation of the distri-
bution of strain and mechanical properties in a drawn
product. The author of this article concluded that the cal-
culated hardness values showed good correlation with
the experimentally measured microhardness values for a
cold-drawn product. Therefore, the opposite method can
be explored, i.e., the measurement of hardness distribu-
tion for a cold-drawn material can be used for calculating
strain distributions, correlating them with the numerical
simulation results. All of the knowledge obtained with
the performed experiments can be contributed to the
technological improvement. The experimental values
serve as the data used for a comparison with the FEM
model simulation of wire drawing, rotary swaging and
the combination of these processes.
5 CONCLUSIONS
This paper describes a successful processing of com-
mercially pure nickel 200 alloy using the rotary-swaging
and wire-drawing techniques with the goal of improving
mechanical properties and obtaining homogenous hard-
ness across the cross-section of a wire. The total area re-
duction was roughly 80 % for all the processes. Vickers-
hardness measurements and tensile tests were performed.
Microstructures were also observed. The main conclu-
sions are summarized as follows:
Rotary swaging and wire drawing further reduced the
average grain size. Grains were preferentially elongated
in the longitudinal direction and the sample had a very
intense fibre texture oriented parallel to the longitudinal
direction.
Nine passes through the rotary-swaging dies led to a
strength of 763 MPa and a yield stress of 753 MPa, with
a decrease in the elongation. In the rotary-swaging pro-
cess, there was a significant difference between the sur-
face hardness and the hardness measured at the centre of
the wire. The surface hardness was, on average, 25 HV1
lower than the hardness in the middle of the wire.
A high strengthening effect on each wire was ob-
served. The highest ultimate strength for the wire-draw-
ing process was 917 MPa, with a true deformation of
1.84. This increase was mainly due to the refinement of
the initial grain structure and an increased dislocation
density. The total elongation dropped below 10 % during
this process. In the case of wire drawing, the course of
hardening was opposite to that of rotary swaging. The
largest value was found on the wire surface. The surface
hardness was, on average, 10 HV1 higher than the hard-
ness in the middle of the wire.
The used combination of rotary swaging and subse-
quent wire drawing resulted in a homogenous hardness
distribution across the cross-section. The ultimate
strength was 850 MPa. The increase was mainly due to
the refinement of the initial grain structure. This process-
ing of the wire led to a compromise between good
strength and toughness of a nickel wire.
J. ^UBROVÁ et al.: EFFECTS OF ROTARY SWAGING, WIRE DRAWING AND THEIR COMBINATION ...
Materiali in tehnologije / Materials and technology 54 (2020) 5, 601–606 605

Acknowledgment
This paper was created under the project Develop-
ment of West-Bohemian Centre of Materials and Metal-
lurgy, No. LO1412, financed by the Ministry of Educa-
tion of the Czech Republic.
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606 Materiali in tehnologije / Materials and technology 54 (2020) 5, 601–606