I. KILERCI et al.: SIMULATION-AIDED INVESTIGATION OF THE EFFECT OF A PRE-FORMING PROCESS ...
389–396
SIMULATION-AIDED INVESTIGATION OF THE EFFECT OF A
PRE-FORMING PROCESS ON THE INITIATION OF CRACKS, THE
REQUIRED FORGING FORCES AND MATERIAL FLOWLINES
FOR MINING GROUND SUPPORT CLAMPS’ MANUFACTURE
USING THE HOT-FORGING TECHNIQUE
S SIMULACIJO PODPRTA RAZISKAVA VPLIVA PROCESA
PREDOBLIKOVANJA NA NASTANEK RAZPOK, ZAHTEVANIH SIL
KOVANJA IN LINIJ TE^ENJA PRI SPONAH RUDARSKIH PODPOR,
IZDELANIH Z VRO^IM KOVANJEM
Ilter Kilerci
1
, Osman Culha
2
1
Manisa Celal Bayar University, Mechanical Engineering Department, Ilhan Varank Campus, 45140, Manisa, Turkey
2
Manisa Celal Bayar University, Metallurgical and Materials Engineering Department, Ilhan Varank Campus, 45140, Manisa, Turkey
ilter.kilerci@cbu.edu.tr
Prejem rokopisa – received: 2017-11-20; sprejem za objavo – accepted for publication: 2018-01-09
doi:10.17222/mit.2017.195
In this study, the influence of the number of forging stages on the crack formation and forging forces in the hot-forging process
for mining support clamps that were produced from 31Mn4 material was investigated. In this context, a single-stage process has
been considered and a multiple-stage forging process that included a pre-forming stage was fictionalized with the aim of
preventing crack formation by obtaining crack-formation zones. It is aimed to improve the toughness properties of the final
product by ensuring that the material flow lines are obtained in accordance with the product geometry as well as preventing the
formation of cracks by the forging process design, including the preforming step of the mining support clamp. Designed dies
and workpieces were simulated using the finite-volume method. According to the simulation results of forging process, the
stress and strain variation of materials is obtained as max. 229 MPa and 3.969 MPa. Damage analysis of the sample with
effective stress and strain is exposed as 0.438-1.0 flash surface of material. The increase in the forming step decreased the
forging forces per step and the crack formation was prevented and the material flowlines can be arranged in accordance with the
product geometry in the presence of the preforming stage in the hot-forging process and that this regulation has a reducing effect
on the forging forces. The material flowlines of the samples obtained from real production were examined and validation of the
simulations and actual production was provided.
Keywords: Toussaint-Heintzmann mining support clamp, hot forging, pre-forming, Cockroft-Latham simulation
Avtorji v prispevku opisujejo {tudijo vpliva {tevila stopenj kovanja na nastanek razpok ter sil pri procesu vro~ega kovanja med
izdelavo spon rudarskih podpor, izdelanih iz jekla 31Mn4. Raziskovali so enostopenjski in ve~stopenjski proces kovanja. V
drugem primeru so izvedli nami{ljeno predoblikovanje z namenom prepre~evanja nastanka razpok v conah preoblikovanja.
Namen naloge je bil izbolj{ati `ilavost kon~nega izdelka z zagotavljanjem ustreznih linij te~enja v skladu z geometrijo izdelka,
kakor tudi prepre~evanje nastanka razpok med oblikovanjem v procesu kovanja, vklju~no s fazo predoblikovanja spon rudarskih
podpor. Simulacije dizajna orodij in odkovkov so izvedli z metodo kon~nih volumnov. Rezultati simulacij procesa kovanja so
podali variiranje napetosti in deformacij z maksimalnimi vrednostmi 229 MPa oz. 3,969 MPa. Analiza po{kodb vzorca pri
efektivnih napetosti in deformacijah 0,438-1,0 se je pokazala kot ble{~e~a povr{ina materiala. Pove~anje {tevila stopenj
oblikovanja je zmanj{alo mo`nosti za nastanek razpok in linije te~enja materiala so potekale v skladu z geometrijo izdelka, kar
je tudi zmanj{alo sile kovanja. Linije te~enja materiala so avtorji prispevka preverili tudi na vzorcih v pogojih dejanske
proizvodnje in jih ocenili oz. primerjali z rezultati simulacij.
Klju~ne besede: Toussaint-Heintzmannove spone rudarskih podpor, vro~e kovanje, predoblikovanje, Cockroft-Lathamova
simulacija
1 INTRODUCTION
The magnitude of the investment capital in mining
activities is important thanks to the properties of in-
creasing employment and providing raw material for the
industrial sectors.
1
Underground mining is a sector in
which the studies based on reliability and productivity
are conducted by mainly the mining engineering and
other engineering disciplines due to the fact that it is the
most risky profession in the world. The difficulty of the
underground conditions requires a technical and syste-
matical work, investment and organization for the
mining activities to be able to be carried out.
2–4
A
significant part of the fatal accidents occurring in mining
happens due to the fall of materials such as stone-coal
and the collapses occurring in a direct or indirect way
and this condition directly shows the importance of
ground supports. It is absolutely necessary that the
ground-support systems are used for the underground
orifices to have long-life span and to allow working in a
safe way during its service life.
5
Materiali in tehnologije / Materials and technology 52 (2018) 4, 389–396 389
UDK 67.017:621.73:62-229.3:621.7.019.1 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 52(4)389(2018)

Forging is defined as the metal-forming method in
which the workpiece is placed between the dies and the
desired product shape is given under the pressing
forces.
6,7
Hammers and presses are used during the
forging process. The forging processes are used for the
purpose of giving outstanding mechanical properties to
the piece to be produced and realizing the production
with a minimum rate of waste. The process starts with
the workpieces having a basic geometry compared to the
final product. The workpiece is subjected to plastic
deformation in one or more operations and pieces with
complex shapes are attained. While the forging processes
give superior mechanical properties to the materials,
compared to other production methods, some manu-
facturing defects could be observed as a result of the
incorrect mounting of the forging process design.
6
The forging process is the most popular method in
metal forming. A significant part of the industrial pieces
are produced by forging thanks to their conformity to
mass production and the ability to give superior mecha-
nical properties. The parameters such as temperature,
raw-material geometry and die designs are efficient in
increasing the quality of the products and decreasing the
manufacturing costs.
7
The process of forming the
geometry of a workpiece having a shape close to the
final product geometry in hot forging is called as
pre-forming. While the pre-forming process ensures a
reduction in the material waste depending on the flash
formation and the significant decrease in the machining
processes, it decreases the die stress.
8
The performance
of the designs of the pieces that is planned to produce
with forging according to trial and error causes a great
loss of time and manufacturing costs. The foreseeing of
the material flow is only possible with computer-aided
simulations.
7
An important issue in metal shaping is being able to
carry out the desired deformation without causing
damage to the workpiece. Although the materials are
formed without any crack with the empirical experiences
of the designers in the industrial applications, sometimes
high-cost trial and error productions are needed.
9
For this
reason, foreseeing and preventing damage are the main
properties in the forming process and the determination
of the product quality.
10
Today, new products and manufacturing methods are
developed for the purpose of attainment as a result of
low costs and short production processes. Although the
design and optimization of the forming process are
generally conducted by professionals having experience
in the manufacturing operations, it is still obligatory for
them to conduct trial and error. The use of numerical
simulations for the purpose of avoiding this experimental
procedure is an important tool for the improvement and
development of the forming process.
11,12
Most metal-forming methods are limited due to the
internal or surface cracks of the workpiece.
10
Increasing
the strength of the workpiece without any damage with
plastic deformation is limited to formability. The form-
ability of the materials are followed by the workability of
that material.
13
If the conditions causing the crack during
the deformation of the workpiece could be foreseen;
convenient process conditions could be selected, forming
process could be changed and tough products could be
obtained.
14,15
In this study, the condition of real production in
single or multiple stages by conducting the hot-forging
simulations of the bottom-clamp component used in
Toussaint-Heintzmann (TH) ground support systems
with the infrastructure of finite volumes method has been
examined within the direction of Cockroft Latham cri-
tical damage theory. Within the scope of the study, which
has been conducted for the purpose of improving the
surface, physical and mechanical properties of TH34
bottom-clamp which will be manufactured by the
hot-forging processes and revealing the optimized sec-
tions; the process design, press selection, effect of raw
material preparation, die design, final product geometry
and the simulation of all the process and the material
flow during the plastic deformation and the residual
stress-strain distribution have been determined by
examining the impact of temperature and the verification
of the design has been ensured by pilot productions with
the use of parameters attained as a result of the optimi-
zation works.
2 EXPERIMENTAL PART
The 31Mn4 steel is used in accordance with the DIN
21530-3 standard used for the final product within the
scope of the study.
16
The chemical composition of the
steel is shown in Table 1.
Table 1: Chemical composition of 31Mn4 according to DIN 21530, in
mass fractions (w/%)
CS iM n
P
(max.)
S
(max.)
Al
(min.)
Cu
0.28-036 0.2-0.5 0.8-1.1 0.035 0.035 0.02 0.35
The DIN 21530 standard that determines the struc-
ture and properties of the ground support systems that
also includes the TH supports is the standard that regu-
lates the issues related to the quality and safety of the
mine pit supports in the underground mine pits. It could
also be used for the ground support of the space areas
under the ground having no relation with mining and it
ensures the realization of the function of the mine-pit
supports in accordance with the plan both in terms of
safety and operation by taking the standards into con-
sideration. The TH34 Bottom clamp has been modeled
with the use of the Solidworks 2014 program according
to the measurements in Table 2 within the direction of
DIN 21530-2 standard and the image belonging to the
attained design is shown in Figure 1a.
17
I. KILERCI et al.: SIMULATION-AIDED INVESTIGATION OF THE EFFECT OF A PRE-FORMING PROCESS ...
390 Materiali in tehnologije / Materials and technology 52 (2018) 4, 389–396

Table 2: TH34 Bottom Clamp Dimensions According to DIN 21530
Bottom
clamp
Profile
class
a (mm) b (mm)
c (mm)
min.
Ød (mm)
G400 - G40 34 212
0
2 +
212
4
1
−
+
111 30
In Figure 1a following the design of the final stage
of final product of TH34 bottom clamp has been dealt
during the stage of the hot-forging process. The flash
design of the forged piece was conducted by taking as
the basis the equations developed by Voigtlander, Doege
and Awiszus and the sections and forging dies belonging
to all the other stages have been designed.
18–20
Following
the determination of the flash dimensions, a shrinkage
allowance of 1.5 % has been given to the final product
geometry in the forging design of the final product for
the purpose of meeting the volume changes of the
material during cooling.
21,22
The sections and forging
dies have been designed by taking the design principles
of hot-forging dies.
20–23
The 31Mn4 flow curves shown in Figure 2 by using
31Mn4 alloy properties as input in the JmatPro program
environment have been attained for usage in simulation
works. The 31Mn4 alloy formed in the computer
environment has been integrated in Simufact forming
program.
Hot-forging simulations of the TH34 bottom clamp
used in Toussaint–Heintzmann ground supports within
the scope of simulation activities and process optimiza-
tion works have been carried out within the direction of
the parameters shown in Table 3.
24
Kang et al. and Han et al. analyzed the friction beha-
vior by using the Coulomb friction model in the envi-
ronment of FE simulations.
7–9
However; because this
model loses its validity in the event that the friction
sliding stress increases the material shearing strength, its
implementation area is limited. A constant sliding fric-
I. KILERCI et al.: SIMULATION-AIDED INVESTIGATION OF THE EFFECT OF A PRE-FORMING PROCESS ...
Materiali in tehnologije / Materials and technology 52 (2018) 4, 389–396 391
Figure 1: a) TH34 bottom clamp solid model, b) TH34 ground
support assembly solid model
Figure 2: 31Mn4 material flow curves created in the JmatPro program
Table 3: Process parameters used in simulation studies
Simulation 1 and 2 Simulation 3
Number of stage 1 Number of stage 3
Type of raw material 31Mn4 Type of raw material 31Mn4
Raw material temperature 1200 °C Raw material temperature 1200 °C
Die temperature 350 °C Die temperature 350 °C
Ambient temperature 50 °C Ambient temperature 50 °C
Friction factor 0.1 Friction factor 0.1
Mesh type Surface mesh Mesh type Surface mesh
Mesh element type Triangles Mesh element type Triangles
Mesh element size 2 mm Mesh element size 2 mm
Mesh element count Mesh element count
Simulation 1 13748 First pre-forming stage 13748
Simulation 2 14086 Second pre-forming stage 36460
- - Finisher forging stage 92378
Press Type and Tonnage Friction press 1200 t Press type and tonnage Friction press 1200 t

tion model is frequently used in 3D FE simulations of
the forging process.
10–15
The deformation processes in the industrial applica-
tions were applied according to the experimentally
determined ductile fracture criterion. Today, the Cock-
roft-Latham damage criterion has become convenient for
the metal-forming simulations. Generally, the critical
damage value is taken as equal to the flow limit of the
material. However, Cockroft and Latham have not
explained the issue of whether critical damage value is
dependent on the temperature and strain rate.
5,9
By using
the Cockroft-Latham criteria, the fracture formation risk
of the formed piece could be examined.
Cockroft and Latham have developed the accumu-
lated damage theory in which variable loading conditions
could be successfully applied.
12–14
As a result of many
studies conducted by Cockroft and Latham, they have
examined the change between the applied equivalent
strain and the effective stress ( ) of the maximum tensile
strength ( T
) of the damage in plastic deformation, in
Equation (1):
C =
∫
    T
f
d
0
(1)
 f
is the total equivalent strain at the end of forming
process.
The magnitude of C should not exceed C
max
(critical
damage value) for the non-occurrence of any damage.
When the C value is compared to C
max
, material damage
risk is assessed during the process. Equation (1) should
be turned into a separate expression that is convenient for
FE code for the purpose of calculating the C value with
FE simulation, Equation (2):
C
t
t
t
t
t
==≅
∫∫
∑
      
 TTT
ff
f
d
d
d
00
0
  Δ
(2)
where
  is the equivalent strain rate as Equation (1) cal-
culated from the individual principal strain-rate compo-
nents, and  t is the variable time increment used in the
FE analysis. Cockroft Latham constant (C
max
)i s
dependent on the same material parameters on which
the forming limits are dependent. While the metallur-
gical properties such as microstructure, alloy constant,
grain dimension and particle structure and non-metallic
inclusion content have a little impact on the strength and
hardness, they have a significant impact for the critical
damage value.
15
In order to predict the occurrence of
surface fracture, the value of the Cockcroft-Latham
equation expressed by means of Equation (1) is calcul-
ated at the integration point inside the elements.
A symmetrical half of the piece has been taken for
the purpose of shortening the solution period in all the
simulation works due to the fact that the TH34 bottom
clamp aimed to be attained in hot-forging simulations
has a symmetrical geometry. The workpiece attained at
the end of each forging stage has been used as the input
of the next stage, together with all the deformation pro-
perties. In simulation 1 and simulation 2, the raw
material with the dimensions Ø50 × 286 mm has been
forged at a single stage, as shown in Figure 3a.
In simulation 3, the section designs of the forged
piece were conducted within the direction of the prin-
ciple of volume stability, die designs convenient for the
section designs have been made and the forging process
has been realized in three stages, as shown in Figure 3b.
The optimized parameters of simulation 3 were used in
the pilot production without any modification and the
bottom clamp was manufactured, as shown in Figure 4.
In order to observe the forging flowlines in the
process of deformation of the workpiece, the specimens
were prepared by using a wire erosion machine which
were manufactured by the hot-forging method. In
accordance with the ASTM E381-01 standard, 50 % HCl
and 50 % purified watered etchant was prepared. The
specimens were macro-etched for 15 min at 80 °C in a
temperature-controlled heating table.
I. KILERCI et al.: SIMULATION-AIDED INVESTIGATION OF THE EFFECT OF A PRE-FORMING PROCESS ...
392 Materiali in tehnologije / Materials and technology 52 (2018) 4, 389–396
Figure 4: TH34 bottom clamp after pilot production
Figure 3: Schematic view of simulations: a) simulation 1 and simu-
lation 2, b) simulation 3

3 RESULTS
Analyses have been realized for simulation 1 fiction-
alized within the direction of the process parameters
shown in Table 3 and the effective stress, effective strain
and critical damage value results belong to simulation 1
are shown in Figure 5. As shown in Figure 5, the un-
filled zones of the die as a result of the forging of the raw
material with the dimensions Ø50 × 286 mm at single
stage and the zones with the critical damage value
regarding Cockroft-Latham criterion in Figure 5.
Because it is clear that the die has not been filled
within the direction of the results attained in simula-
tion 1, the raw-material dimensions were increased as
Ø50 × 292 mm and simulation 2 has been carried out.
The effective stress, effective strain and critical da-
mage value results attained as a result of simulation 2 are
shown in Figure 6.
It is clear that the die has been completely filled. as
shown in Figure 6, in the forging process realized with
the raw material with the dimensions Ø50 × 292 mm.
The zones having critical damage value regarding
Cockroft-Latham criterion are shown in Figure 6.
The flow lines have been added to the material sec-
tion during the forging process in simulation 2 and the
final situation of the material flow attained as a result of
the forging process at single stage is shown in Figure 8.
Analyses were carried out for simulation 3 fiction-
alized as forging of the raw material with the dimensions
Ø50 × 286 mm in three stages within the direction of the
I. KILERCI et al.: SIMULATION-AIDED INVESTIGATION OF THE EFFECT OF A PRE-FORMING PROCESS ...
Materiali in tehnologije / Materials and technology 52 (2018) 4, 389–396 393
Figure 6: Effective stress, effective plastic strain and critical damage
value distribution in simulation 2
Figure 5: Effective stress, plastic strain and critical damage value dis-
tribution in simulation 1
Figure 7: Effective stress and critical damage values: a) first pre-
forming stage, b) second pre-forming stage, c) finisher forging stage
Figure 8: Material flow and flowlines results in simulation 3 and si-
mulation 2

process parameters shown in Table 3 and the results
belonging to simulation 3 are shown in Figure 7.
It was observed that the die has been completely
filled, as shown in Figure 7, in the forging process
realized with the raw material with the dimensions
Ø50 × 286 mm. The zones having critical damage value
regarding the Cockroft-Latham criterion are shown in
Figure 7d.
Flow lines were added to the material section during
the forging processes in simulation 2 and simulation 3
and the final situation of the material flow attained as a
result of the forging process is shown in Figure 8.
The forged piece attained at the end of simulation 3
has been taken to the trimming die for the purpose of
taking its flashes and this process has been carried out.
The TH34 bottom clamp with high temperature shown in
Figure 9a was cooled down in air with the ambient
temperature of 50 °C and the distribution of the surface
temperatures regarding the clamp attained at the end of
the cooling of 30 min is shown in Figure 9.
The force and energy data regarding the hot-forging
simulations are shown in Table 4.
Table 4: Force and energy data regarding the hot-forging simulations
Simula-
tion
name
Stage name
Stroke
(mm)
Force (kN)
Energy
(kJ) Bottom die Top die
Simula-
tion 1
Finisher forging 140.4 –13449.8 14081.4 65.6
Simula-
tion 2
Finisher forging 140.4 –18963.5 19299.9 71.3
Simula-
tion 3
First pre-
forming
61.52 –2208.5 1965.7 14.6
Second pre-
forming
91.97 –11743.3 12033.8 34.3
Finisher forging 26.3 –15270.1 15216.2 27.6
As shown in Figure 4, the TH34 bottom clamp was
produced by using the hot-forging process and the
macro-etching sample was obtained according to the
standards. The regions where the material flowlines are
observed and the flowlines obtained as a result of the
macroscopic examinations are shown in Figure 10.
4 DISCUSSION
Section and die designs have been completed for the
hot-die forging processes planned to be carried out in
single and multiple stages and realized upon the final
product measurements of the TH34 ground support
bottom clamp. According to the performed designs, the
I. KILERCI et al.: SIMULATION-AIDED INVESTIGATION OF THE EFFECT OF A PRE-FORMING PROCESS ...
394 Materiali in tehnologije / Materials and technology 52 (2018) 4, 389–396
Figure 10: Macroscopic flowlines examination after the macro-etching process
Figure 9: a) Clamp temperature distribution after forging, b) clamp
temperature distribution after cooling

installation of the simulation was completed and the
following results were obtained:
Firstly, the flash design has been carried out within
the direction of the forged piece design made according
to the volume calculation principles of hot forging die
making and it has been determined that the flash dimen-
sions should be 4 mm × 16 mm according to the cal-
culation made according to Voigtlander, Doege and
Awiszus and the volume of the raw material should be
561,560 mm
3
within the direction of the fact that the
shrinkage allowance peculiar to steel material should
also be given.
19,20
It has been determined that the shrinkage allowance
added to the piece in the forging design has been
correctly assigned, as seen in the measurements as a
result of cooling the workpiece in air at the end of hot-
forging process.
25
When simulation 1 which includes the forging of the
workpiece with the dimensions of Ø50 × 286 mm in
single stage is examined; it has been determined that
13449.8 kN forging force has an impact on the bottom
die and 14081.4 kN forging force has an impact on the
upper die. It has been determined that 65.6 kJ is needed
for the production of the TH34 bottom clamp with hot
die forging method from the workpiece with the
dimensions of Ø50 × 286 mm. As can be seen in Figure
5, as a result of the forging simulation, it has been
observed that the flash formation increases in the base
zone of the material due to not being able to direct the
material flow and for this reason, the die is not filled.
The critical damage value of this piece forged in single
stage and the zones with the probability of damage
formation have been examined. It has been determined
that the Cockroft-Latham critical damage value reached
1 and the zones with the probability of damage
formation include the majority of the material.
The volume of the raw material has been increased
by 11781 mm
3
for the purpose of being able to terminate
the deficient filling problem of the die in simulation 1
and simulation 2 has been realized. When the results of
simulation 2 has been examined; it has been determined
that 18963.5 kN forging force has an impact on the
bottom die with an increase of 41 % and 19299.9 kN
forging force has an impact on the upper die with an
increase of 37 %. It has been determined that 71.3 kJ is
needed for the production of the TH34 bottom clamp
with the hot die forging method from the workpiece with
the dimensions of Ø50 × 292 mm. As can be seen in
Figure 6; as a result of the forging simulation in which
the volume of the work piece has been increased by
11781 mm
3
, it has been observed that the die has been
completely filled. The critical damage value of this piece
forged in single stage and the zones with the probability
of damage formation have been examined. It has been
determined that Cockroft-Latham critical damage value
reached 1 and the zones with the probability of damage
formation include the majority of the material.
When simulation 3, which includes the forging of the
workpiece with the dimensions of Ø50 × 286 mm in 3
stages, was examined, it was observed that the final stage
die has been completely filled, flash formation has been
distributed in a more homogenous way when compared
to simulation 1 and simulation 2. When the forces having
impact on the dies belonging to 3-stage forging simula-
tion have been examined; it has been determined that
15270.1 kN forging force has an impact on the bottom
die and 15216.2 kN forging force has an impact on the
upper die at the final forming stage in which the greatest
forces occur. It is shown in Table 4 that the maximum
energy requirement is 34.3 kJ in the 3-stage forging
process for the production of TH34 bottom clamp. When
the critical damage value of this piece forged in three
stages and the zones with the probability of damage
formation have been examined; it has been determined
that Cockroft-Latham critical damage value has reached
maximum 1 in the flash zone as shown in Figure 7c and
the maximum critical value is 0.5 in the areas covering
the clamp. As a result of the attained data, it is expressed
that the amount of Cockroft-Latham criterion is within
the range 0.7-0.8. The flashes of the forged piece have
been taken in the trimming die following the realization
of the hot die forging process of TH34 bottom clamp.
The forged piece has been cooled for 30 min in the
ambient temperature of 50 °C. At the end of 30 min, it
has been determined that the temperature is 80 °C in the
maximum zone of the surface temperature as shown in
Figure 9 in which the distribution of the surface tempe-
ratures of the forged piece is given. It has been observed
that the zones in which critical damage may occur are
not existent in the clamp examined at the end of the
trimming and cooling process.
When the formation of the material flow lines be-
longing to the products attained as a result of simulation
2 and simulation 3 have been examined, it was clear that
the material flow lines attained in simulation 2 are not in
accordance with the final product geometry. The attain-
ment of the flow lines in accordance with the product
geometry has an importance in the improvement of the
strength and toughness of the product attained with
forging.
6
When the material flow attained in simulation 3
has been examined, it is seen that the material flow in
accordance with the final product geometry has been
realized. It has been determined that when the flow lines
at the end of the macro-etching processes of the samples
taken from the pilot production performed in the direc-
tion of the parameters obtained in Simulation 3 are
examined, similar material flow lines are obtained with
simulation 3.
5 CONCLUSIONS
It has been determined that subjecting the raw mate-
rial belonging to the piece to be produced with mould
hot forging method to the pre-forming stage is an
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Materiali in tehnologije / Materials and technology 52 (2018) 4, 389–396 395

important factor in attaining the minimum forging forces
and the minimum raw-material wastes and with the
impact on the complete filling of the die.
It is seen that in the hot-forging process, determining
the forging steps in such a way that the total forging
force required for the forging operation is evenly as
distributed as possible is the most suitable method for
forging operations.
The direction of the material flow in the forging in
accordance with the final product geometry both im-
proves the mechanical properties of the final product and
it also decreases the energy needs during the forging
process.
While the increase in temperature decreases C, which
is the strength constant, it increases the strain-rate
sensitivity (m). Because the forming process is applied at
high temperatures, it is necessary to decrease the
deformation speed as much as possible. The attainment
of products is possible with a press or hammers with low
capacity by increasing the forging stages and decreasing
the energy needs per stages in the conditions in which
the infrastructure of the establishment is insufficient in
the attainment of the pieces planned to be produced in
the hot-forging industry.
6 REFERENCES
1
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