Technical Field
[0001] The present disclosure relates to an alloy steel for a railway vehicle coupler and,
more particularly, to an alloy steel for a railway vehicle coupler, the alloy steel
being able to meet all mechanical properties required for AAR couplers mainly used
in Korea (i.e., the Republic of Korea) and China (i.e., the People's Republic of China)
and mechanical properties required for CA-3 couplers mainly used in Russia (i.e.,
the Russian Federation) and the like, thereby enabling the railway vehicle coupler
to be safely used in the railway system connecting Russia and the other Northeast
Asian countries.
Background Art
[0002] A coupler for a railway vehicle is a very important safety component serving to transmit
driving force and braking force to railroad cars. Recently, due to the necessity to
lengthen railway vehicles including cars, the importance of the structural stability
of the railway vehicle coupler is increasing.
[0003] Recently, the importance of the economy of Northeast Asia including Russia is increasing,
and the improvement of the transportation, logistics, and connectivity of Northeast
Asia is emerging as one of future growth engines.
[0004] Thus, research to the continental railway intended to connect the Korean Peninsula,
China, Central Asia, Russia, and Europe is actively underway. In particular, in the
case of freight cars, the Korean Peninsula and China use Association of American Railroads
(AAR) couplers, while commonwealth independence states (CIS) countries and Mongolia
use CA-3 couplers. It is impossible to connect these two types of couplers, due to
different head shapes thereof. In addition, the materials of the two types of couplers
are required to have different mechanical properties.
[0005] In this regard, technologies related to a variable coupler and a coupler adapter
able to connect an AAR coupler and a CA-3 coupler having different head shapes to
each other are being actively developed. However, the development of a material meeting
the mechanical properties required for the two types of couplers is not sufficient.
[0006] A related-art technology for solving these problems is disclosed in
Korean Patent No. 10-1931494 as an ally steel for a railway vehicle coupler. The major technical composition of
this ally steel are characterized by including, as essential ingredients, carbon (C),
manganese (Mn), silicon (Si), chromium (Cr), nickel (Ni), copper (Cu), molybdenum
(Mo), aluminum (Al) , phosphorus (P), and sulfur (S), with the balance being iron
(F) and unavoidable impurities.
[0007] That is, due to the above-described composition, the related-art ally steel has mechanical
properties applicable to transcontinental trains exposed to severe climate changes.
Thus, as a technical characteristic, the related-art ally steel may have the ability
to reduce wear caused by climate changes and the friction between railway vehicle
couplers, thereby improving durability. However, in the related-art ally steel, only
whether or not criteria for "AAR M201, Gr.E" (hereinafter, referred to as "AAR M201"),
i.e., the specification for the mechanical properties of AAR couplers, are met is
considered. Thus, it is impossible to determine whether or not criteria for Russian
national standard "GOST 22703, 20 GL" (hereinafter, referred to as "GOST 22703"),
i.e., the specification for the mechanical properties of CA-3 couplers, are met.
[0008] In addition, for the continental railway exposed to severe climate changes, hardness
from among the mechanical properties of couplers is significantly important in relation
to cracking, wear, or the like. The related-art ally steel also has a problem in that
whether or not criterion for the hardness condition from among the mechanical properties
is met may not be determined.
[0009] Accordingly, there is urgent demand for the development of an alloy steel for a coupler,
the alloy steel being able to meet AAR M201, i.e., the specification for the mechanical
properties of AAR couplers, and GOST 22703, i.e., the specification for the mechanical
properties of CA-3 couplers.
Disclosure
Technical Problem
[0010] Accordingly, the present disclosure has been made keeping in mind the above problems
occurring in the prior art, and an objective of the present disclosure is to provide
an alloy steel for a railway vehicle coupler, the alloy steel being able to meet both
AAR M201, i.e., the specification for the mechanical properties of AAR couplers, and
GOST 22703, i.e., the specification for the mechanical properties of CA-3 couplers,
thereby enabling the railway vehicle coupler to be safely used in the railway system
connecting Russia and the other Northeast Asian countries.
Technical Solution
[0011] In order to accomplish the above objective, the present disclosure provides an alloy
steel for a railway vehicle coupler.
[0012] The alloy steel for a railway vehicle coupler may include carbon (C), silicon (Si),
manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), nickel (Ni), and copper
(Cu) as essential ingredients, and may further include nanoparticles made from one
of titanium nitride (TiN), cubic boron nitride (cBN) , aluminum oxide (Al
2O
3) , and zirconium dioxide (ZrO
2).
[0013] The alloy steel may further include molybdenum (Mo), vanadium (V), and aluminum (Al)
as the essential ingredients.
[0014] In addition, the essential ingredients may include, by weight, 0.240% of C, 0.380%
of Si, 1.160% of Mn, 0.014% of P, 0.006% of S, 0.250% of Cr, 0.250% of Ni, 0.030%
of Cu, 0.180% of Mo, 0.020% of V, and 0.020% of Al, with the balance being iron (Fe)
and impurities.
[0015] In addition, the alloy steel including the essential ingredients and the nanoparticles
may be first heat-treated at 870°C for 4 hours, followed by air cooling, be second
heat-treated at 870°C for 4 hours, followed by water cooling, and be third heat-treated
at 570°C for 4 hours, followed by air cooling.
[0016] In addition, from among the essential ingredients, Ni may have a content ranging
from 0.25% to 0.30% by weight, Mo may have a content ranging from 0.15% to 0.25% by
weight, and V may have a content ranging from 0.01% to 0.02% by weight.
[0017] The essential ingredients may include, by weight, 0.233% of C, 0.427% of Si, 1.222%
of Mn, 0.006% of P, 0.012% of S, 0.261% of Cr, 0.260% of Ni, 0.042% of Cu, 0.175%
of Mo, 0.019% of V, and 0.022% of Al, with the balance being Fe, impurities, and the
nanoparticles.
[0018] According to another embodiment, provided is an alloy steel for a railway vehicle
coupler.
[0019] The alloy steel may include carbon (C), silicon (Si), manganese (Mn), phosphorus
(P), sulfur (S), chromium (Cr), nickel (Ni), and copper (Cu) as essential ingredients,
and may further include nanoparticles made from one of magnesium oxide (MgO) or a
material combination of, by weight, 99% of silicon oxide (SiO
2) and 1% of silicon carbide (SiC).
[0020] The alloy steel may further include molybdenum (Mo), vanadium (V), and aluminum (Al)
as the essential ingredients.
[0021] In addition, the essential ingredients may include, by weight, 0.240% of C, 0.380%
of Si, 1.160% of Mn, 0.014% of P, 0.006% of S, 0.250% of Cr, 0.250% of Ni, 0.030%
of Cu, 0.180% of Mo, 0.020% of V, and 0.020% of Al, with the balance being iron (Fe),
impurities, and the nanoparticles.
[0022] In addition, the alloy steel including the essential ingredients and the nanoparticles
may be first heat-treated at 870°C for 4 hours, followed by air cooling, be second
heat-treated at 870°C for 4 hours, followed by water cooling, and be third heat-treated
at 580°C for 4 hours, followed by air cooling.
[0023] In addition, the essential ingredients may include, by weight, 0.220% of C, 0.430%
of Si, 1.200% of Mn, 0.016% of P, 0.006% of S, 0.260% of Cr, 0.250% of Ni, 0.030%
of Cu, 0.150% of Mo, 0.020% of V, and 0.030% of Al, with the balance being iron (Fe),
impurities, and the nanoparticles.
[0024] In addition, the alloy steel including the essential ingredients and the nanoparticles
may be heat-treated at 580°C for 4 hours, followed by air cooling.
Advantageous Effects
[0025] According to the present disclosure, the nanoparticles able to reduce the hardness
of the alloy steel and the nanoparticles able to improve the strength of the alloy
steel to the alloy steel for a railway vehicle coupler are selectively added to the
alloy steel for a railway vehicle coupler according to the present disclosure as described
above includes, in addition to the ingredients included as essential ingredients in
AAR couplers and CA-3 couplers, thereby having an excellent effect in that both the
specification for the mechanical properties of AAR couplers and the specification
for the mechanical properties of CA-3 couplers may be meet.
[0026] In addition, according to the present disclosure, the alloy steel may meet mechanical
property criteria for the two types of couplers most widely used in the world. Advantageously,
the alloy steel according to the present disclosure may be compatibly used in most
countries in the world and be safely used in the railway system currently in progress
to connect Russia and the other Northeast Asian countries.
Best Mode
[0027] Hereinafter, exemplary embodiments of an alloy steel for a railway vehicle coupler
according to the present disclosure will be described in detail.
[0028] The present disclosure relates to an alloy steel for a railway vehicle coupler and,
more particularly, to an alloy steel for a railway vehicle coupler, the alloy steel
enabling a railway vehicle coupler to meet all mechanical properties required for
AAR couplers mainly used in Korea (i.e., the Republic of Korea) and China (i.e., the
People's Republic of China) and mechanical properties required for CA-3 couplers mainly
used in Russia (i.e., the Russian Federation) and the like, thereby enabling railway
vehicle couplers made from the alloy steel to be safely used in railway systems connecting
Russia and the other Northeast Asian countries. First, the specification of AAR M201
specifying mechanical properties required for AAR couplers and the specification of
GOST 22703 specifying mechanical properties required for CA-3 couplers are as illustrated
in Table 1 below. The contents of chemical ingredients in Table 1 below are indicated
in weight percent.

[0029] As illustrated in Table 1 above, it may be found that the AAR M201 standard regarding
the chemical composition of the coupler is not strict and only specifies maximum values
of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), and sulfur (S). In contrast,
the GOST 22703 standard regarding the chemical composition of the coupler is relatively
strict to further specify the maximum values of chromium (Cr), nickel (Ni), and copper
(Cu) and define the content ranges of C, Si, and Mn.
[0030] The AAR M201 standard and the GOST 22703 standard also have different specifications
about mechanical properties. In Russia where the GOST 22703 standard are applied,
railway vehicles must be able to operate in an environment having a relatively low
temperature. Thus, it may be found that requirements for yield strength (Y/P), tensile
strength (T/S), and hardness (HB) are relatively low and impact strength at -60°C
is further required for cold resistance.
[0031] Since the objective of the present disclosure is to meet the chemical ingredients,
i.e., the chemical composition, and the mechanical properties required by the AAR
M201 standard and the GOST 22703 standard, the present disclosure may meet the chemical
composition and the mechanical properties illustrated in the rightmost column of Table
1 above.
[0032] Described in more detail, the alloy steel for a railway vehicle coupler according
to the present disclosure is provided as an alloy steel including the chemical ingredients
required by the AAR M201 standard and the GOST 22703 standard, i.e., carbon (C), silicon
(Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), nickel (Ni), and
copper (Cu) as essential ingredients. The alloy steel is characterized by further
including nanoparticles made from one of titanium nitride (TiN), cubic boron nitride
(cBN), aluminum oxide (Al
2O
3) , and zirconium dioxide (ZrO
2) .
[0033] TiN, cBN, Al
2O
3, and ZrO
2 described above may be included in the alloy steel to reduce the hardness thereof,
and may be included in the alloy steel as nanoparticles to obtain a hardness reduction
effect even if in a minute amount.
[0034] That is, according to test results, it was possible to easily meet target conditions
for some mechanical properties, such as the elongation El, the reduction of area R/A,
and impact strength, from among the target conditions for the mechanical properties
illustrated in the rightmost column of Table 1 above by adjusting the contents of
C, Si, Mn, P, S, Cr, Ni, and Cu. However, there have been limitations in meeting the
target conditions for the remaining mechanical properties, i.e., the yield strength
Y/P, the tensile strength T/S, and the hardness HB, by adjusting the contents of the
essential ingredients.
[0035] Described in more detail, there has been a problem in that, when the target conditions
for the yield strength Y/P and the tensile strength T/S of the alloy steel were met,
the hardness HB exceeded the target condition, and when the target condition for the
hardness HB of the alloy steel was met, either the target condition for the yield
strength Y/P or the target condition for the tensile strength T/S was met.
[0036] Thus, nanoparticles made of one from among TiN, cBN, Al
2O
3, and ZrO
2 may be included in the alloy steel so as to reduce the hardness HB of the alloy steel
while minimizing changes in the yield strength Y/P and the tensile strength T/S of
the alloy steel.
[0037] Table 2 below illustrates test results regarding hardness changes in the alloy steel
with the hardness HB of 203 when TiN nanoparticles and cBN nanoparticles were added
to the alloy steel. It may be found that the hardness HB was reduced by 3.94% and
6.4%, respectively, in response to the addition of the TiN nanoparticles and the cBN
nanoparticles.
Table 2
Nanoparticle Additive |
Not Added |
Titanium Nitride (TiN) |
Boron Nitride (cBN) |
hardness HB |
203 |
195 |
190 |
[0038] In addition, in a similar test, it was found that the Al
2O
3 nanoparticles and the ZrO
2 nanoparticles were able to reduce the hardness by 27% and 38%, respectively. Thus,
according to the magnitude of the hardness of the alloy steel to be reduced, one from
among TiN, cBN, Al
2O
3, and ZrO
2 may be selected so as to be included in the alloy steel as nanoparticles.
[0039] In addition, in an alloy steel for a railway vehicle coupler according to another
embodiment of the present disclosure, nanoparticles included in the alloy steel including
essential ingredients may be made from one of magnesium oxide (MgO) or a material
combination of, by weight, 99% of silicon oxide (SiO
2) and 1% of silicon carbide (SiC). These two materials are used in a situation in
which either the yield strength Y/P or the tensile strength T/S of the alloy steel
does not meet the target condition while the target condition for the hardness HB
of the alloy steel is met.
[0040] That is, MgO and the material combination of, by weight, 99% of SiO
2 and 1% of SiC is used in order to improve the strength of the alloy steel. When these
materials are included in the alloy steel even in a very small amount, the effect
of improved strength may be obtained.
[0041] Described in more detail, when MgO nanoparticles are added to a carbon steel, it
an improvement effect of the yield strength Y/P by about 22.4% and an improvement
effect of the tensile strength T/S by about 53.1% may be obtained according to the
amount of nanoparticles input, as may be found from Table 3 below.
Table 3
Mass Fraction (%) of MgO Nanoparticles |
0 |
0.01 |
0.03 |
0.05 |
0.07 |
Yield Strength (MPa) |
232 |
233 |
264 |
294 |
284 |
Tensile Strength (MPa) |
293 |
425 |
427 |
448 |
441 |
[0042] In addition, when nanoparticles made from the material combination of, by weight,
99% of SiO
2 and 1% of SiC are added to the carbon steel, a strength improvement effect of up
to about 60% may be obtained without a significant change in the hardness HB, as may
be found from Table 4 below.
Table 4
Modifier Weight (g) |
0 |
77 |
120 |
460 |
Hardness HB |
185-210 |
210 |
220 |
190 |
Strength (MPa) |
168-180 |
270 |
240 |
200 |
[0043] As described above, in the present disclosure, it is possible to reduce the hardness
HB of the alloy steel including C, Si, Mn, P, S, Cr, Ni, and Cu or improve the strength,
i.e., the yield strength Y/P and the tensile strength T/S, of the alloy steel by adding
nanoparticles to the steel alloy. When intended to reduce the hardness HB, nanoparticles
made from one from among TiN, cBN, Al
2O
3, and ZrO
2 are added to the alloy steel. When intended to improve the strength, nanoparticles
made from one of MgO and the material combination of, by weight, 99% of SiO
2 and 1% of SiC are added to the alloy steel. In addition, first specimens cast from
a material including chemical ingredients meeting both the AAR M201 standard and the
GOST 22703 standard described above were heat-treated in different heat treatment
conditions, and then, the mechanical properties thereof were tested. The results of
the test are illustrated in Table 5 below.

[0044] Although the tensile strength T/S, the elongation (El) , the reduction of area R/A,
and the hardness HB were improved to meet target conditions for mechanical properties,
it may be found that the yield strength Y/P and the impact strength were less than
the target values.
[0045] In addition, the alloy steel for a railway vehicle coupler according to the present
disclosure may further include molybdenum (Mo), vanadium (V), and aluminum (Al), in
addition to the above-described essential ingredients. First, Al is typically included
in the alloy steel and is used to improve the ductility of the alloy steel.
[0046] Next, Mo is added to improve the impact strength, i.e., sock absorption rate, of
the alloy steel. This feature may be found from Table 6 below.
[0047] That is, Table 6 below illustrates results obtained by heat-treating second specimens
cast from a material further including Mo, in addition to the chemical ingredients
meeting both the AAR M201 standard and the GOST 22703 standard, in different heat
treatment conditions, and then, testing the mechanical properties of the second specimens.
It was found that, when the heat treatment was performed so that the hardness HB is
within the target range, most mechanical properties met the target ranges.
[0048] In particular, it may be found that, while the impact strength was improved twice
or more by the addition of Mo, the yield strength Y/P and the tensile strength T/S
were reduced so that the tensile strength T/S did not meet the target value.

[0049] Next, V is added to improve the strength of the alloy steel, and this feature may
be found from Table 7 below.
[0050] That is, Table 7 below illustrates results obtained by heat-treating third specimens
cast from a material further including Mo and V, in addition to the chemical ingredients
meeting both the AAR M201 standard and the GOST 22703 standard, in different heat
treatment conditions, and then, testing the mechanical properties of the second specimens.
It may be found that, while the yield strength Y/P and the tensile strength T/S were
improved to meet the target values by the addition of V, the hardness HB was also
improved proportionally to exceed the target value and the impact strength was reduced,
thereby failing to meet the target value.

[0051] According to the results of the tests described above, it may be found that the impact
strength was improved by adding Mo to the specified essential ingredients of the alloy
steel and the yield strength Y/P and the tensile strength T/S were improved by adding
V to the essential ingredients.
[0052] However, in the case of Mo, the yield strength Y/P and the tensile strength T/S were
reduced by the heat treatment intended to meet the range of the hardness HB. When
V was added to solve the reduction, the impact strength was also reduced. Thus, in
order to overcome these problems, it is necessary to limit the contents of Mo and
V.
[0053] Accordingly, fourth and fifth specimens cast by limiting the contents of Mo and V
to, by weight, 0.15% to 0.25% and 0.01% to 0.02% and setting the content of Ni having
superior impact strength, from among the essential ingredients specified in the AAR
M201 standard and the GOST 22703 standard, to 0.25% to 0.30% by weight were heat-treated
in different heat treatment conditions, and then, mechanical properties thereof were
tested. The results of the test are illustrated in Table 8 below.

[0054] First, the fourth specimen was cast by limiting the contents of Ni, Mo, and V to
0.25%, 0.18%, 0.02% by weight, respectively, while meeting the contents of the essential
ingredients specified in the AAR M201 standard and the GOST 22703 standard, followed
by heat treatment. It may be found that the fourth specimen met the target values
for all mechanical properties, except for the hardness HB.
[0055] Next, the fifth specimen was cast by limiting the contents of Ni, Mo, and V to 0.260%,
0.175%, and 0.019% by weight, while meeting the contents of the essential ingredients
specified in the AAR M201 standard and the GOST 22703 standard, followed by heat treatment.
It may also be found that the fifth specimen met the target values for all mechanical
properties, except for the hardness HB.
[0056] That is, it was found that both the fourth specimen and the fifth specimen met the
target conditions for all mechanical properties, i.e., the yield strength Y/P, the
tensile strength T/S, the elongation (El), the reduction of area R/A, and the impact
strength, except for the hardness HB. As described above, the hardness HB may be reduced
by the addition of nanoparticles made from one of TiN, cBN, Al
2O
3, and ZrO
2. Thus, it is possible to manufacture a carbon steel having mechanical properties
meeting both the AAR M201 standard and the GOST 22703 standard by adding the nanoparticles.
[0057] In addition, the mechanical properties of the above-described alloy steel for a railway
vehicle coupler according to the present disclosure may be changed according to heat
treatment conditions. Table 9 below illustrates test results for the mechanical properties
of alloy steel specimens having the same composition as the fourth specimen illustrated
in Table 8, tested two times by the Korea Testing and Research Institute (KTR) and
the Korea Railroad Research Institute (KRRI), and test results for the mechanical
properties of alloy steel specimens respectively having a new composition of, by weight,
0.220% of C, 0.430% of Si, 1.200% of Mn, 0.016% of P, 0.006% of S, 0.260% of Cr, 0.250%
of Ni, 0.030% of Cu, 0.150% of Mo, 0.020% of V, and 0.030% of Al, tested by the KTR,
together with heat treatment conditions.

[0058] First, in alloy steel specimens having the same composition as the fourth specimen,
i.e., the composition including, by weight, 0.240% of C, 0.380% of Si, 1.160% of Mn,
0.014% of P, 0.006% of S, 0.250% of Cr, 0.250% of Ni, 0.030% of Cu, 0.180% of Mo,
0.020% of V, and 0.020% of Al, a total of three heat treatments was performed. In
the first test by the KTR and the first and second tests by the KRRI, the heat treatments
were performed in the same conditions. In the second test by the KTR, the heat treatment
was performed by changing the temperature conditions of the third heat treatment.
[0059] Described in more detail, in the first test by the KTR and the first and second tests
by the KRRI, the first heat treatment corresponding to normalizing was performed at
870°C for 4 hours, followed by air cooling. In the second heat treatment corresponding
to quenching, the heat treatment was performed at 870°C for 4 hours in the same manner
as above, followed by water cooling. In the third heat treatment corresponding to
tempering, the heat treatment was performed at 570°C for 4 hours, followed by air
cooling. Afterwards, the mechanical properties of the specimens were measured.
[0060] As a result, it was found that all mechanical properties except for the hardness
HB, i.e., the yield strength Y/P, the tensile strength T/S, the elongation (El), the
reduction of area R/A, and the impact strength, were met in the three tests. In the
first test by the KTR, the hardness HB was measured to exceed the target range by
about 3.4%. in the first and second tests by the KRRI, the hardness HB was measured
to exceed the target range by about 2.7% and about 5.0%.
[0061] It was found from Table 2 above that the hardness HB might be reduced by 3.94% and
6.4% by the addition of the TiN nanoparticles and the boron nitride (cBN) nanoparticles,
respectively. Thus, when one of the TiN nanoparticles and the boron nitride (cBN)
nanoparticles is selectively added to the alloy steel including, by weight, 0.240%
of C, 0.380% of Si, 1.160% of Mn, 0.014% of P, 0.006% of S, 0.250% of Cr, 0.250% of
Ni, 0.030% of Cu, 0.180% of Mo, 0.020% of V, and 0.020% of Al, an alloy steel for
a railway vehicle coupler able to meet the target conditions for all mechanical properties
including the hardness HB condition may be manufactured.
[0062] In addition, in the second test by the KTR for the alloy steel having the same composition
as above, the heat treatment was performed in the same conditions as the foregoing
three heat treatments, except for varying the temperature of the third heat treatment
corresponding to tempering to be 580°C, and then, the mechanical properties thereof
were measured.
[0063] As a result, it was found that the target conditions for all mechanical properties
except for the yield strength Y/P were met. The yield strength Y/P was determined
to be less than the target value by about 3.2%.
[0064] It was found from Table 3 and Table 4 above that the yield strength Y/P may be improved
by the addition of the MgO nanoparticles or the nanoparticles made from the material
combination of, by weight, 99% of SiO
2 and 1% of SiC. In a situation in which the temperature of the third heat treatment
is 580°C, when one of the MgO nanoparticles and the nanoparticles made from the material
combination of, by weight, 99% of SiO
2 and 1% of SiC is selectively added to the alloy steel, an alloy steel for a railway
vehicle coupler able to meet the target conditions for all mechanical properties except
for the yield strength Y/P may be manufactured.
[0065] Next, in the alloy steel including, by weight, 0.220% of C, 0.430% of Si, 1.200%
of Mn, 0.016% of P, 0.006% of S, 0.260% of Cr, 0.250% of Ni, 0.030% of Cu, 0.150%
of Mo, 0.020% of V, and 0.030% of Al, the mechanical properties thereof were measured
after the heat treatment corresponding to tempering was performed in order to reduce
a heat treatment time and prevent the hardness HB from exceeding the target range.
The heat treatment was performed at a temperature of 580°C for 4 hours, followed by
air cooling.
[0066] As a result, it was found that the target conditions for the mechanical properties
except for the yield strength Y/P and the tensile strength T/S were met. The yield
strength Y/P and the tensile strength T/S were determined to be less than the target
values by about 6.2% and about 4.1%, respectively.
[0067] As described above, when the MgO nanoparticles or the nanoparticles made from the
material combination of, by weight, 99% of SiO
2 and 1% of SiC are added to the alloy steel, the yield strength Y/P and the tensile
strength T/S may be improved without a significant change in the hardness HB. Thus,
Thus, by heat-treating the alloy steel including, by weight, 0.220% of C, 0.430% of
Si, 1.200% of Mn, 0.016% of P, 0.006% of S, 0.260% of Cr, 0.250% of Ni, 0.030% of
Cu, 0.150% of Mo, 0.020% of V, and 0.030% of Al, and further including the MgO nanoparticles
or the nanoparticles made from the material combination of, by weight, 99% of SiO
2 and 1% of SiC, at a temperature of 580°C for 4 hours, an alloy steel for a railway
vehicle coupler able to meet the target conditions for all mechanical properties including
the yield strength Y/P and the tensile strength T/S may be manufactured.
[0068] Accordingly, since the nanoparticles able to reduce the hardness of the alloy steel
and the nanoparticles able to improve the strength of the alloy steel to the alloy
steel for a railway vehicle coupler are selectively added to the alloy steel for a
railway vehicle coupler according to the present disclosure as described above, in
addition to the ingredients included as essential ingredients in AAR couplers and
CA-3 couplers, both the specification for the mechanical properties of AAR couplers
and the specification for the mechanical properties of CA-3 couplers may be meet.
Thus, the alloy steel according to the present disclosure may meet mechanical property
criteria for the two types of couplers most widely used in the world. Advantageously,
the alloy steel according to the present disclosure may be compatibly used in most
countries in the world and be safely used in the railway system currently in progress
to connect Russia and the other Northeast Asian countries.
[0069] Although the foregoing embodiments have been described with respect to most exemplary
examples of the present disclosure, it will be apparent to those skilled in the art
that the present disclosure is not limited thereto and a variety of modifications
is possible without departing from the technical principle of the present disclosure.
Industrial Applicability
[0070] The present disclosure relates to an alloy steel for a railway vehicle coupler. More
particularly, the present disclosure relates to an alloy steel for a railway vehicle
coupler, the alloy steel being able to meet all mechanical properties required for
AAR couplers mainly used in Korea (i.e., the Republic of Korea) and China (i.e., the
People's Republic of China) and mechanical properties required for CA-3 couplers mainly
used in Russia (i.e., the Russian Federation) and the like, thereby enabling the railway
vehicle coupler to be safely used in the railway system connecting Russia and the
other Northeast Asian countries.
1. An alloy steel for a railway vehicle coupler, the alloy steel comprising carbon (C),
silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), nickel (Ni),
and copper (Cu) as essential ingredients,
the alloy steel further comprising nanoparticles made from one of titanium nitride
(TiN), cubic boron nitride (cBN), aluminum oxide (Al2O3), and zirconium dioxide (ZrO2).
2. The alloy steel according to claim 1, further comprising molybdenum (Mo), vanadium
(V), and aluminum (Al) as the essential ingredients.
3. The alloy steel according to claim 2, wherein the essential ingredients include, by
weight, 0.240% of C, 0.380% of Si, 1.160% of Mn, 0.014% of P, 0.006% of S, 0.250%
of Cr, 0.250% of Ni, 0.030% of Cu, 0.180% of Mo, 0.020% of V, and 0.020% of Al, with
the balance being iron (Fe) and impurities.
4. The alloy steel according to claim 3, wherein the alloy steel comprising the essential
ingredients and the nanoparticles is first heat-treated at 870°C for 4 hours, followed
by air cooling, is second heat-treated at 870°C for 4 hours, followed by water cooling,
and is third heat-treated at 570°C for 4 hours, followed by air cooling.
5. The alloy steel according to claim 2, wherein, from among the essential ingredients,
Ni has a content ranging from 0.25% to 0.30% by weight, Mo has a content ranging from
0.15% to 0.25% by weight, and V has a content ranging from 0.01% to 0.02% by weight.
6. The alloy steel according to claim 5, wherein the essential ingredients include, by
weight, 0.233% of C, 0.427% of Si, 1.222% of Mn, 0.006% of P, 0.012% of S, 0.261%
of Cr, 0.260% of Ni, 0.042% of Cu, 0.175% of Mo, 0.019% of V, and 0.022% of Al, with
the balance being Fe, impurities, and the nanoparticles.
7. An alloy steel for a railway vehicle coupler, the alloy steel comprising carbon (C),
silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), nickel (Ni),
and copper (Cu) as essential ingredients,
the alloy steel further comprising nanoparticles made from one of magnesium oxide
(MgO) or a material combination of, by weight, 99% of silicon oxide (SiO2) and 1% of silicon carbide (SiC) .
8. The alloy steel according to claim 7, further comprising molybdenum (Mo), vanadium
(V), and aluminum (Al) as the essential ingredients.
9. The alloy steel according to claim 8, wherein the essential ingredients include, by
weight, 0.240% of C, 0.380% of Si, 1.160% of Mn, 0.014% of P, 0.006% of S, 0.250%
of Cr, 0.250% of Ni, 0.030% of Cu, 0.180% of Mo, 0.020% of V, and 0.020% of Al, with
the balance being iron (Fe), impurities, and the nanoparticles.
10. The alloy steel according to claim 9, wherein the alloy steel comprising the essential
ingredients and the nanoparticles is first heat-treated at 870°C for 4 hours, followed
by air cooling, is second heat-treated at 870°C for 4 hours, followed by water cooling,
and is third heat-treated at 580°C for 4 hours, followed by air cooling.
11. The alloy steel according to claim 8, wherein the essential ingredients include, by
weight, 0.220% of C, 0.430% of Si, 1.200% of Mn, 0.016% of P, 0.006% of S, 0.260%
of Cr, 0.250% of Ni, 0.030% of Cu, 0.150% of Mo, 0.020% of V, and 0.030% of Al, with
the balance being iron (Fe), impurities, and the nanoparticles.
12. The alloy steel according to claim 11, wherein the alloy steel comprising the essential
ingredients and the nanoparticles is heat-treated at 580°C for 4 hours, followed by
air cooling.