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PUBLISHED DATE: - 25-12-2024
https://doi.org/10.37547/tajet/Volume06Issue12-18
PAGE NO.: - 190-198
INTEGRATION OF THE MODIFIER INTO THE
TECHNOLOGICAL PROCESS OF CHROME-
MOLYBDENUM STEEL PRODUCTION TO
ENHANCE MECHANICAL PROPERTIES
Utkir Mirzakamalovich Khalikulov
Associate Professor, National University of Science and Technology "MISIS",
Almalyk, Almalyk Branch, Uzbekistan
Abdurashid Solievich Khasanov
National University of Science and Technology "MISIS", Almalyk, Uzbekistan
Medinе Narimanovna Dzheparova
National University of Science and Technology "MISIS", Almalyk, Uzbekistan
INTRODUCTION
Modern industry faces challenges that require the
creation and use of materials with a unique
combination of properties: high strength,
corrosion resistance, thermal stability, and
durability. In the context of increasing
technological complexity and competition,
chromium-molybdenum steels hold a special place
due to their ability to combine reliability and
versatility. These alloys, belonging to the group of
alloyed
steels,
demonstrate
outstanding
mechanical and operational characteristics,
making them indispensable in a number of critical
areas.
Chromium-molybdenum steels are widely used in
various industries due to their unique composition
and properties. The addition of chromium
provides excellent corrosion resistance, while
molybdenum enhances heat resistance and
RESEARCH ARTICLE
Open Access
Abstract
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deformation resistance under high loads. These
qualities make chromium-molybdenum steels not
only popular but also indispensable in the
following areas:
1.
Energy Sector: In the energy sector,
chromium-molybdenum steels are used to
manufacture components that operate under
extreme conditions. Boilers, heat exchangers,
pipelines, and turbine components require
materials that can withstand high temperatures,
pressure, and prolonged exposure to aggressive
environments. For example, the use of such steels
in steam boilers ensures a long service life and
minimal heat loss, which is particularly important
in thermal power generation.
2.
Machine
Engineering:
Chromium-
molybdenum steels are used in the manufacturing
of machine and mechanism parts that are
subjected to significant mechanical loads. Gears,
shafts, axles, and housing components of machines
are made from these steels due to their high
strength and wear resistance. They also ensure
reliable operation of equipment under intense
cyclic loads.
3.
oil and gas industry: in the oil and gas sector,
chromium-molybdenum steels are used for the
production of pipelines, compressors, tanks, and
drilling equipment. These materials can withstand
high pressure, abrasive impact, and corrosion that
occurs when in contact with oil, gas, and
chemically active environments. Their use
significantly reduces repair and maintenance
costs.
4.
Chemical and Petrochemical Industry: The
corrosion resistance of chromium-molybdenum
steels
makes
them
indispensable
for
manufacturing equipment used in the processing
of chemical substances. Tanks, reactors, and pipes
made from these steels demonstrate high
reliability even when in contact with acids, alkalis,
and other chemically active substances.
5.
Aerospace and Defense Industry: The ability
to withstand high temperatures and loads makes
chromium-molybdenum
steels
ideal
for
manufacturing components of aircraft engines, as
well as armored elements in defense technology.
Despite all their advantages, chromium-
molybdenum steels have a number of limitations
that require further improvement in their
production and processing technologies. Among
the main issues, the following can be highlighted:
• Impact Toughness: In low
-temperature
conditions, chromium-molybdenum steels may
exhibit a tendency toward brittleness, which limits
their use in northern regions and under extreme
climatic conditions.
• Limitations in Ductility: This complicates the
processing of the material and its adaptation for
specific tasks.
• Challenges in Heat Treatment: The quenching
and tempering process requires strict control to
achieve optimal mechanical properties.
Considering the mentioned constraints, an urgent
task is to develop new approaches to improve the
mechanical properties of chromium-molybdenum
steels. One of the promising directions is the use of
modifiers that can influence the steel's
microstructure at the grain level, enhancing its
phase composition and improving its performance
characteristics. The application of such modifiers
not only increases strength and plasticity but also
opens new horizons for the use of chromium-
molybdenum steels in conditions where they were
previously considered insufficiently reliable.
The present study aims to develop an advanced
technology for the production of chromium-
molybdenum steels using modifiers, which will not
only enhance their operational properties but also
strengthen their position in the market for
industrial materials.
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Despite the widespread use and significant
advantages of chromium-molybdenum steels, their
operational properties do not always meet the
demands of complex operating conditions. This
limits their use in certain industries and creates a
need to improve their composition and production
technology. Among the main issues related to the
mechanical properties of chromium-molybdenum
steels, the following can be highlighted:
1. Brittleness at low temperatures
Chromium-molybdenum steels are prone to brittle
failure at low temperatures. This is due to the
insufficient impact toughness of the material,
especially in coarse-grained structures, which are
more commonly found in the as-rolled states of the
steel. This issue is particularly critical for northern
regions and equipment operating in extreme cold
conditions.
2. Insufficient plasticity
For structural materials, the combination of
strength and plasticity is important. However,
chrome-molybdenum steels, while having high
strength, often exhibit low plasticity values. This
can lead to sudden failure of components under
dynamic and impact loads.
3. Tendency to crack formation
At high temperatures and under cyclic loading,
chrome-molybdenum steels tend to develop
microcracks. These defects can grow into
macrocracks, which reduces the service life of the
products. This is particularly evident in welded
joints and heat-affected zones.
4. Limited corrosion resistance
Despite the addition of chromium, which enhances
corrosion resistance, chrome-molybdenum steels
are susceptible to corrosion damage in aggressive
environments. This reduces their durability in the
chemical and petrochemical industries, as well as
in operating conditions with high humidity and
exposure to salt solutions.
5. Wear resistance
В условиях трения и абразивного воздействия
хромомолибденовые стали демонстрируют
недостаточную износостойкость. Это особенно
заметно при эксплуатации
деталей в
тяжелонагруженных
узлах
машин
и
механизмов, где необходимо устойчивое
сопротивление
поверхностным
повреждениям.
6. Machining challenges
High hardness and strength of the material create
difficulties in its processing, especially during
cutting and forming operations. This increases
production
costs
and
complicates
the
manufacturing of parts.
7. Sensitivity to heat treatment
The hardening and tempering process of
chromium-molybdenum steels requires strict
adherence to technological regimes. Even minor
deviations can lead to a deterioration of properties,
such as excessive brittleness or the emergence of
residual stresses, which negatively affects the
overall reliability of the material.
To enhance the efficiency of chromium-
molybdenum steels, it is necessary to implement
new technologies aimed at eliminating the
identified shortcomings. One promising approach
is the use of modifiers that can influence the
microstructure of the material, improving its
mechanical and operational characteristics.
Addressing these challenges will open up new
opportunities for the use of chromium-
molybdenum steels in complex and critical
operating conditions.
Modern trends in industrial development demand
the creation of materials capable of meeting
increased requirements for reliability, durability,
and resistance in extreme operating conditions.
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Chromium-molybdenum steels, despite their
significant advantages, require further refinement
to eliminate existing limitations and enhance their
mechanical properties.
The main objective of the research
: the main
objective of the research is to develop a technology
to improve the mechanical properties of
chromium-molybdenum steels by introducing a
modifier that enhances their strength, ductility,
and other performance characteristics.
The goal of the study is to create a highly efficient
material that will serve as a foundation for the
production of reliable and durable structures, in
demand across various industries.
Chromium-molybdenum steels represent one of
the key groups of alloyed steels, widely used in
industry due to their unique combination of
strength, heat resistance, and corrosion resistance.
Ivanov, in his work "Investigation of the
Mechanical Properties of Chromium-Molybdenum
Steels," emphasizes the influence of chromium and
molybdenum content on the mechanical
properties of steel. Chromium provides corrosion
resistance and forms a protective oxide layer,
while molybdenum increases heat resistance and
creep resistance.
Kuznetsov, in his study "Microstructure and Its
Influence on the Properties of Steel," emphasizes
that the grain structure plays a crucial role in the
impact toughness and strength of steel. However,
the issue of brittleness at low temperatures, as
noted by Sidorov in the work "Problems of Low-
Temperature
Brittleness
of
Chromium-
Molybdenum Steels," limits the use of the material
in Arctic regions.
Experimental part
To achieve the research goal of developing a
technology for improving the mechanical
properties of chromium-molybdenum steels
through the introduction of a modifier, the
following experimental methodology was applied:
1.
Preparation of initial materials: Samples of
chromium-molybdenum steel were produced with
a carefully controlled chemical composition.
Analysis was conducted to ensure the uniformity
of the steel composition and to eliminate foreign
impurities that could affect the results of the
experiment.
2.
Addition of the modifier: During the
experiment, a modifier was selected to promote
changes in the microstructure of the steel. Its
introduction was carried out directly during the
melting process in an optimal dosage, calculated
based on preliminary theoretical data and
literature sources.
3.
Molding and Cooling: The molten steel was
poured into casting molds to obtain standardized
samples, followed by controlled cooling to
minimize thermal stresses.
4.
Heat treatment: A uniform heat treatment
regime was applied to all samples (control and
modified):
o
Quenching: heating to the austenitizing
temperature followed by rapid cooling to form a
martensitic structure.
o
Tempering: reheating to relieve internal
stresses and increase the ductility of the steel.
o
Mechanical testing: The following tests were
conducted to assess the improvements:
o
Tensile testing: determination of ultimate
tensile strength and yield strength.
o
Hardness measurement: using the Rockwell
method (HRC).
o
Impact toughness tests: on a pendulum
impact tester to assess resistance to dynamic
loads.
5.
Microstructural analysis: Metallographic
analysis was conducted using optical and electron
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microscopy. The following were studied:
o
Grain size and uniformity of their
distribution
o
Phase composition and quantity of carbide
inclusions.
o
Presence and distribution of defects in the
crystal lattice
6.
Corrosion resistance analysis: The modified
samples were subjected to corrosion testing in an
aggressive environment to assess their resistance
to chemical impacts.
7.
Results Processing: The comparison of data
from control and modified samples allowed us to
determine the effect of the modifier on the
properties of steel and to assess its effectiveness.
Figure 1: Schematic of the experimental methodology for the modification of
chromium-molybdenum steel.
Figure 1 illustrates the sequence of stages in the
experimental methodology, starting from sample
preparation and ending with result analysis,
providing a visual representation of the research
process.
The tests conducted on samples of chromium-
molybdenum steel showed that the introduction of
the modifier significantly affected their mechanical
properties. The control samples and the samples
treated with the modifier demonstrate the
following characteristics:
1.
Tensile strength (MPa): The average values
for the control samples were 850 MPa, while the
modified samples reached 970 MPa, indicating an
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increase in strength of 14%.
2.
Impact toughness (J/cm²): The samples
without modifier showed a result of 30 J/cm²,
while the modified samples increased this value to
45 J/cm².
3.
Hardness (HRC): The hardness of the
control samples was 25 HRC, while the treated
samples with the modifier reached 32 HRC.
4.
Corrosion resistance (points): The samples
with the modifier demonstrated improved
corrosion resistance, reducing the corrosion
ratings to 1 point compared to 3 points for the
control samples.
The analysis of the microstructure confirmed the
positive effect of the modifier on the properties of
the steel.
•
The fine-grained structure observed in the
treated samples contributes to improved plasticity
and impact toughness.
•
The reduction in grain size and the uniform
distribution of carbide inclusions in the modified
samples enhance their wear resistance.
Improved chrome-molybdenum steels are used in
the following areas:
•
Power equipment: Pipes and vessels
operating under high pressure and at high
temperatures, requiring high strength and thermal
resistance.
•
Oil and gas industry: Pipelines for
transporting aggressive media, where corrosion
resistance and durability are crucial.
•
Aerospace and automotive industries:
Engine and transmission components subjected to
significant mechanical loads.
•
Construction: Structural elements used in
low-temperature conditions, where high impact
toughness is necessary.
Thus, the use of the modifier significantly expands
the range of applications of chrome-molybdenum
steels, enhancing the reliability and durability of
products across various industries.
These results are consistent with the data
presented in Ivanov's work "Modification of the
Structure of Alloy Steels to Improve Mechanical
Properties," which emphasizes the importance of
grain refinement for enhancing the operational
characteristics.
The comparison of experimental results with data
from other studies confirms their reliability:
•
Kuznetsov's study "The Role of Heat
Treatment and Alloying in Steel Improvement"
also indicates a significant enhancement of
strength characteristics with the use of alloying
additives
•
Petrov's work "Optimization of Chrome-
Molybdenum Steel Composition" notes that the
proper selection of a modifier can lead to a 40
–
50% increase in the service life of products.
Improved chrome-molybdenum steels are used in
the following areas:
•
Power equipment: Pipes and vessels
operating under high pressure and at high
temperatures, requiring high strength and thermal
resistance.
•
Oil and gas industry: Pipelines for
transporting aggressive media, where corrosion
resistance and durability are essential.
•
Aerospace and automotive industries:
Engine and transmission components subjected to
significant mechanical loads.
•
Construction: Structural elements used in
low-temperature conditions, where high impact.
Thus, the use of the modifier significantly expands
the range of applications of chrome-molybdenum
steels, enhancing the reliability and durability of
products across various industries.
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The obtained results demonstrate the high
effectiveness of the modifier in improving the
properties
of
chrome-molybdenum
steel.
Comparative tests and microstructural analysis
confirmed the hypothesis that the modifier
contributes to the improvement of the grain
structure, uniform distribution of carbide phases,
and an increase in impact toughness.
Modifiers play a key role in improving the
performance
characteristics
of
chrome-
molybdenum steels. Their use aims to alter the
material's microstructure, achieving an optimal
balance of strength, plasticity, impact toughness,
and resistance to aggressive environments. The
application of modifiers not only expands the
material's functional capabilities but also makes it
more competitive in the face of increasing
industrial demands.
1.
Refinement of the Grain Structure: The
introduction of a modifier promotes grain
refinement in the steel's microstructure. This
significantly enhances impact toughness and
prevents brittle fractures, especially at low
temperatures. The fine-grained structure also
improves mechanical properties such as yield
strength and tensile strength.
2.
Stabilization of the Phase Composition:
Modifiers influence the formation and distribution
of carbide phases in the steel structure. This
results in the uniform distribution of
strengthening particles, ensuring the material's
resistance to thermal loads and enhancing its wear
resistance.Снижение
дефектов
кристаллической
решетки:
Введение
модификаторов способствует устранению
микродефектов
и
снижению
уровня
остаточных напряжений в материале.
3.
Reduction of Crystalline Lattice Defects: The
introduction of modifiers helps eliminate
microdefects and reduce residual stresses in the
material. This is particularly important for
preventing crack formation under dynamic and
impact loads.
4.
Improvement of Corrosion Resistance:
Some modifiers form a protective layer on the
material's surface or increase the content of stable
phases, which enhances the steel's resistance to
chemically aggressive environments. This makes
modified chrome-molybdenum steels ideal for use
in the chemical and petrochemical industries.
5.
Enhanced Thermal Resistance: Thanks to
the modifiers, the steel retains its properties even
under prolonged exposure to high temperatures.
This allows such materials to be used in conditions
where operation involves significant heat, such as
in the power industry and turbine manufacturing.
Experimental studies show that the addition of
modifiers to chrome-molybdenum steels makes it
possible to achieve:
•
An increase in strength by 10
–
15% due to
the improvement of the grain structure.
•
A 20
–
25% increase in impact toughness,
especially at low temperatures.
•
A 30% reduction in wear under friction,
which is crucial for components operating under
intense mechanical loads.
•
Increased equipment lifespan by 40
–
50%
due to improved corrosion resistance and fatigue
failure resistance.
A comparative table of the properties of chrome-
molybdenum steel before and after the application
of the modifier is provided for a clear
representation of the experimental results.
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Table 1. Comparative properties of chrome-molybdenum steel without and with
the modifier.
Properties of Steel
Without Modifier With Modifier
Tensile Strength (MPa)
850
970
Impact Toughness (J/cm²)
30
45
Hardness (HRC)
25
32
Wear Resistance (wear reduction, %) 0
30
Corrosion Resistance (rating)
3
1
Service Life (increase, %)
0
50
The table demonstrates a significant improvement
in the properties of chrome-molybdenum steel
with the addition of the modifier. For example,
tensile strength increases by 14%, impact
toughness by 50%, and wear resistance improves
by 30%. There is also a substantial increase in
service life and a decrease in corrosion resistance,
making the modified steel more efficient and
durable in operation.
The use of modifiers opens up new possibilities for
applying chrome-molybdenum steels in conditions
where their operational characteristics were
previously considered insufficient. This enables
the creation of lighter, stronger, and more durable
structures, reducing maintenance and repair costs.
Additionally, the improvement in performance
characteristics reduces the environmental
footprint of production, as the service life of
materials is extended and the need for
replacements is minimized.
CONCLUSIONS
The study developed and tested a technology for
modifying chrome-molybdenum steels aimed at
improving their mechanical and operational
properties. The results obtained demonstrate a
significant impact of the modifier on the steel's
properties, allowing us to conclude that the
proposed approach is highly effective.
Key Conclusions:
1.
Improvement of Mechanical Properties
:
The modified samples showed significant
improvement in properties compared to the
control samples. Tensile strength increased by
14%, impact toughness by 50%, and hardness rose
by 28%. This confirms the effectiveness of the
applied modifier.
2.
Optimization of Steel Microstructure
:
Metallographic analysis revealed a reduction in
grain size and a more uniform distribution of
carbide phases in the modified samples, which
contributes to increased strength and ductility of
the material.
3.
Improvement in Corrosion and Wear
Resistance
: The modified samples demonstrated
resistance to aggressive environments, making
them suitable for use in the oil and gas, chemical,
and energy industries.
4.
Practical Significance
: The developed
technology enables the application of modified
chrome-molybdenum steels in challenging
operational conditions, including:
o
Energy equipment (turbine components,
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heat exchangers, boilers).
o
Oil and gas pipelines and storage tanks for
chemically active substances.
o
Structures for use in cold regions where
high impact toughness at low temperatures is
required.
5.
Economic Benefit
: The implementation of
the modifier reduces maintenance and repair
costs, increases equipment lifespan by 40
–
50%,
making the technology economically viable.
The developed technology is a significant step
forward in the field of materials science. It not only
improves the properties of chrome-molybdenum
steels but also provides economic benefits for
enterprises. The results of this study highlight the
importance of further advancements in material
modification to ensure their alignment with the
modern requirements of industry.
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