U.S. patent application number 16/756483 was filed with the patent office on 2022-04-21 for steel wire having excellent straightness quality and manufacturing method thereof.
This patent application is currently assigned to Hongduk Industrial Co., Ltd.. The applicant listed for this patent is Hongduk Industrial Co., Ltd.. Invention is credited to Gi Hwan Kim, Pyeong Yeol Park.
Application Number | 20220119903 16/756483 |
Document ID | / |
Family ID | 1000006107026 |
Filed Date | 2022-04-21 |
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United States Patent
Application |
20220119903 |
Kind Code |
A1 |
Park; Pyeong Yeol ; et
al. |
April 21, 2022 |
Steel Wire Having Excellent Straightness Quality and Manufacturing
Method Thereof
Abstract
Provided are a steel wire having excellent straightness quality
and a method of manufacturing the steel wire, wherein the steel
wire includes a wire, after undergoing a drawing operation,
undergoing a heating operation of performing heating in a state in
which tension is applied, and undergoing a cooling operation,
wherein, when winding the wire around a winding portion having a
diameter greater than a diameter of the wire for a preset period of
time and then measuring straightness of the wire of 400 mm, the
straightness of the wire is less than or equal to 30 mm, and the
method includes a wire preparation operation, a heating operation,
a cooling operation, and a straightness measurement operation.
Inventors: |
Park; Pyeong Yeol; (Daejeon,
KR) ; Kim; Gi Hwan; (Pohang-si, Gyeongsangbuk-do,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hongduk Industrial Co., Ltd. |
Pohang-si, Gyeongsangbuk-do |
|
KR |
|
|
Assignee: |
Hongduk Industrial Co.,
Ltd.
Pohang-si, Gyeongsangbuk-do
KR
|
Family ID: |
1000006107026 |
Appl. No.: |
16/756483 |
Filed: |
March 3, 2020 |
PCT Filed: |
March 3, 2020 |
PCT NO: |
PCT/KR2020/003182 |
371 Date: |
April 16, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 7/13 20130101; C21D
9/525 20130101; C21D 9/5732 20130101; C21D 8/065 20130101; C21D
9/5735 20130101 |
International
Class: |
C21D 8/06 20060101
C21D008/06; C21D 7/13 20060101 C21D007/13; C21D 9/52 20060101
C21D009/52; C21D 9/573 20060101 C21D009/573 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 2019 |
KR |
10-2019-0079697 |
Claims
1. A steel wire needing straightness having excellent straightness
quality, the steel wire comprising: a wire, after undergoing a
drawing operation, undergoing a heating operation of performing
heating in a state in which tension is applied, and undergoing a
cooling operation, wherein, when winding the wire around a winding
portion having a diameter greater than a diameter of the wire for a
preset period of time and then measuring straightness of the wire
of 400 mm, the straightness of the wire is less than or equal to 30
mm.
2. The steel wire of claim 1, wherein a heating temperature in the
heating operation is about 80.degree. C. to 220.degree. C.
3. The steel wire of claim 2, wherein the heating temperature and a
heating time in the heating operation of the wire satisfy Equation
A below, and the heating temperature in the heating operation is
higher than or equal to 80.degree. C., wherein Equation A: T+15.67
ln(t).gtoreq.300, wherein T denotes absolute temperature K of the
heating temperature, and t denotes the heating time s.
4. The steel wire of claim 3, wherein the heating time in the
heating operation is about 0.02 s to about 10 s.
5. The steel wire of claim 1, wherein tension applied to the wire
in the heating operation is about 1% to about 50% of a cutting
strength.
6. A method of manufacturing a steel wire needing straightness
having excellent straightness quality, the method comprising: a
wire preparation operation of preparing a wire that is drawn; a
heating operation of heating the wire in a state in which tension
is applied; a cooling operation of cooling the wire; and a
straightness measurement operation of winding the wire around a
winding portion having a diameter greater than a diameter of the
wire for a preset period of time and then measuring straightness of
the wire, wherein, when measuring the straightness of the wire of
400 mm in the straightness measurement operation, the straightness
of the wire is less than or equal to 30 mm.
7. The method of claim 6, wherein the wire comprises a plurality of
wires, wherein the method further comprises a stranding operation
of twisting and stranding the plurality of wires to each other.
8. The method of claim 6, wherein a heating temperature in the
heating operation is about 80.degree. C. to about 220.degree.
C.
9. The method of claim 8, wherein the heating temperature and a
heating time in the heating operation of the wire satisfy Equation
A below, and the heating temperature in the heating operation is
higher than or equal to 80.degree. C., wherein Equation A: T+15.67
ln(t).gtoreq.300, wherein T denotes absolute temperature K of the
heating temperature, and t denotes the heating time s.
10. The method of claim 9, wherein the heating time in the heating
operation is about 0.02 s to about 10 s.
11. The method of claim 6, wherein tension applied to the wire in
the heating operation is about 1% to about 50% of a cutting
strength.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a steel wire having
excellent straightness quality and a manufacturing method thereof,
and more particularly, to a steel wire having excellent
straightness quality and a manufacturing method thereof, wherein as
the steel wire is heated at a preset temperature or higher for a
short period of time, strain aging of the steel wire may be
promoted to improve straightness quality after aging.
BACKGROUND ART
[0002] In general, steel wires have been used in various industrial
fields and have been used for vehicle tires, industrial belts, and
the like. Steel wires used for various purposes as described above
are needed to have various quality characteristics. In particular,
when steel wires are used as tire reinforcement materials, the
straightness of the steel wires is needed.
[0003] Steel wires used in the industrial fields are not used
immediately after the steel wires are manufactured but are used
several months after the steel wires are wound and stored around
spools having preset inner diameters. However, when the steel wires
are used after being wound and stored around the spools as
described above, the straightness of the steel wires is not
maintained.
[0004] When the straightness of the steel wires is not maintained,
the steel wires may not be used in the industrial fields needing
the straightness. In detail, if straightness is poor when steel
wires are used as tire reinforcement materials, the poor
straightness may affect work processability when manufacturing
tires and may cause buckling and tip rising phenomena, and thus,
tire manufacturers may have difficulty in rolling and cutting
processes. Also, when the straightness of steel wires is not
maintained, the steel wires may be difficult to be used in various
fields needing the straightness of the steel wires.
[0005] The straightness of steel wires changes because of the
following causes. Steel wires use carbon steel as a material
thereof, and interstitial solid solution atoms C and N exist in the
carbon steel and diffuse over time to move to and fix to adjacent
potentials. Therefore, when steel wires are manufactured and wound
around spools having preset inner diameters, the straightness
thereof changes due to the diffusion and fixation of atoms C and N
and thus deteriorates.
[0006] Existing steel wires may not provide steel wires having
excellent straightness due to drawbacks as described above. In
other words, although existing steel wires have excellent
straightness characteristics at the beginning of manufacturing,
after the existing steel wires are wound around spools having
preset inner diameters and a long period of time passes, the
straightness characteristics thereof change due to strain aging
under stress within an elastic section and thus do not satisfy
straightness quality characteristics.
DESCRIPTION OF EMBODIMENTS
Technical Problem
[0007] Provided are a steel wire having excellent straightness
quality and a manufacturing method thereof, wherein as the steel
wire is heated at a preset temperature or higher for a short period
of time, strain aging of the steel wire is promoted to improve
straightness quality after aging.
Solution to Problem
[0008] According to an aspect of the preset disclosure, a steel
wire having excellent straightness quality, may include a wire,
after undergoing a drawing operation, undergoing a heating
operation of performing heating in a state in which tension is
applied, and undergoing a cooling operation, wherein, when winding
the wire around a winding portion having a diameter greater than a
diameter of the wire for a preset period of time and then measuring
straightness of the wire of 400 mm, the straightness of the wire is
less than or equal to 30 mm.
[0009] A heating temperature in the heating operation may be about
80.degree. C. to 220.degree. C.
[0010] The heating temperature and a heating time in the heating
operation of the wire may satisfy Equation A below, and the heating
temperature in the heating operation may be higher than or equal to
80.degree. C., wherein Equation A: T+15.67 ln(t).gtoreq.300,
wherein T denotes absolute temperature K of the heating
temperature, and t denotes the heating time s.
[0011] The heating time in the heating operation may be about 0.02
s to about 10 s, and tension applied to the wire in the heating
operation may be about 1% to about 50% of a cutting strength.
[0012] According to another aspect of the present disclosure, a
method of manufacturing a steel wire having excellent straightness
quality, may include: a wire preparation operation of preparing a
wire that is drawn; a heating operation of heating the wire in a
state in which tension is applied; a cooling operation of cooling
the wire; and a straightness measurement operation of winding the
wire around a winding portion having a diameter greater than a
diameter of the wire for a preset period of time and then measuring
straightness of the wire, wherein, when measuring the straightness
of the wire of 400 mm in the straightness measurement operation,
the straightness of the wire is less than or equal to 30 mm.
[0013] The wire may include a plurality of wires, wherein the
method further includes a stranding operation of twisting and
stranding the plurality of wires to each other.
[0014] A heating temperature in the heating operation may be about
80.degree. C. to about 220.degree. C.
[0015] The heating temperature and a heating time in the heating
operation of the wire may satisfy Equation A below, and the heating
temperature in the heating operation may be higher than or equal to
80.degree. C., wherein Equation A: T+15.67 ln(t).gtoreq.300,
wherein T denotes absolute temperature K of the heating
temperature, and t denotes the heating time s.
[0016] The heating time in the heating operation may be about 0.02
s to about 10 s, and tension applied to the wire in the heating
operation may be about 1% to about 50% of a cutting strength.
Advantageous Effects of Disclosure
[0017] The present disclosure relates to a steel wire having
excellent straightness quality and a manufacturing method thereof,
wherein as the steel wire is heated at a preset temperature or
higher for a short period of time, strain aging of the steel wire
may be promoted to improve straightness quality after aging.
[0018] Also, as the steel wire is heated at the preset temperature
or higher for the short period of time, a microstructure of the
steel wire may not significantly change. Therefore, strain aging of
the steel wire may be promoted without deteriorating physical
properties of the steel wire to improve the straightness quality
after aging.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 is a view illustrating measuring straightness of a
steel wire having excellent straightness quality, according to an
embodiment;
[0020] FIG. 2 is a graph illustrating productivity according to
heating time of a steel wire having excellent straightness quality,
according to an embodiment;
[0021] FIG. 3 is a table illustrating straightness when
manufacturing a steel wire by applying tension of 1% of a cutting
strength and heating a wire while changing a heating time and a
heating temperature of the wire, according to an embodiment;
[0022] FIG. 4 is a table illustrating straightness when
manufacturing a steel wire by applying tension of 5% of a cutting
strength and heating a wire while changing a heating time and a
heating temperature of the wire, according to an embodiment;
[0023] FIG. 5 is a table illustrating straightness when
manufacturing a steel wire by applying tension of 15% of a cutting
strength and heating a wire while changing a heating time and a
heating temperature of the wire, according to an embodiment;
[0024] FIG. 6 is a table illustrating straightness when
manufacturing a steel wire by applying tension of 30% of a cutting
strength and heating a wire while changing a heating time and a
heating temperature of the wire, according to an embodiment;
[0025] FIG. 7 is a table illustrating straightness when
manufacturing a steel wire by applying tension of 50% of a cutting
strength and heating a wire while changing a heating time and a
heating temperature of the wire, according to an embodiment;
[0026] FIG. 8 is a table illustrating straightness when
manufacturing a steel wire by applying tension of 1% of a cutting
strength and heating a wire while increasing a heating time of the
wire, according to an embodiment;
[0027] FIG. 9 is a table illustrating Equation A values according
to heating temperature and heating time and straightness values
after 30 days, according to an embodiment;
[0028] FIG. 10 is a graph illustrating changes in a tensile
strength of a wire according to heating temperature; and
[0029] FIG. 11 is a flowchart illustrating a method of
manufacturing a steel wire having excellent straightness quality,
according to an embodiment.
MODE OF DISCLOSURE
[0030] The present disclosure relates to a steel wire having
excellent straightness quality and a manufacturing method thereof,
wherein as the steel wire is heated at a preset temperature or
higher for a short period of time, strain aging of the steel wire
is promoted to improve straightness quality after aging. Example
embodiments will now be described in detail with reference to the
accompanying drawings.
[0031] Referring to FIG. 1, a steel wire having excellent
straightness quality according to an embodiment includes a wire 110
that, after undergoing a drawing operation, undergoes a heating
operation of performing heating in a state in which tension is
applied and undergoes a cooling operation. Although the wire 110 is
wound around a wining portion for a preset period of time or more,
straightness thereof is less than or equal to 30 mm.
[0032] Referring to FIG. 1, straightness according to an embodiment
may be measured as follows. The wire 110 is wound around a winding
portion having a diameter greater than a diameter of the wire 110
for a preset period of time. Thereafter, an end 111 of the wire 110
that is wound is fixed to a point 120, and the wire 110 is
vertically lowered. Here, the wire 110 is lowered to 400 mm. In
other words, a distance between the end 111 of the wire 110 and an
other end 112 of the wire 110 is 400 mm.
[0033] Straightness of the wire 110 may be determined by an
interval between a first axis 121 forming a vertical line from the
point 120 and the other end 112 of the wire 110. In detail, as the
interval between the first axis 121 and the other end 112 of the
wire 110 is narrow, the steel wire has excellent straightness, and
as the interval between the first axis 121 and the other end 112 of
the wire 110 is wide, the steel wire has poor straightness.
[0034] As the steel wire according to the embodiment is heated at a
preset temperature or higher for a short period of time to promote
strain aging of the steel wire, when measuring the straightness
after winding the wire 110 around the winding portion for a preset
period of time, the straightness of the wire 110 may be maintained
to be less than or equal to 30 mm. (Here, the preset period of time
for which the wire 110 is wound around the winding portion may be
about six months to about one year but is not limited thereto.)
[0035] The wire 110 according to the embodiment may be formed of a
carbon steel material, and the wire 110 may be formed of a carbon
steel material of about 0.5 wt % to about 1.1 wt %.
[0036] After undergoing a drawing operation, the wire 110 may be
heated in a state in which tension is applied, and the undergoing
of the drawing operation may indicate that the wire 110 may undergo
a process including a drawing process. In detail, patenting
processing may be performed for the wire 110 to secure high
strength and processability. A pearlite microstructure that is an
aggregation of carbon-based cementite and ferrite formed of Fe is
acquired by performing patenting processing for the wire 110.
[0037] A plurality of wires 110 that undergo the drawing process
may be provided and may undergo a stranding operation of twisting
and stranding the plurality of wires 110 to each other. However,
the stranding operation may be omitted as needed, and thus, when
the wire 110 is used as a single steel wire, the stranding
operation may be omitted.
[0038] The drawing process is a process that involves a large
deformation in a material and deforms a pearlite structure of high
carbon steel and promotes decomposition of cementite in a lamellar
layer. When the cementite is decomposed by the deformation
occurring in the drawing process, fractions of interstitial solid
solution atoms C and N in ferrite matrix increase.
[0039] Here, strain aging occurs as an interstitial solid solution
atom such as C or N fixes to a potential over time, and factors
thereof may include not only a density of a solid solution atom,
but also time, temperature, a density of a potential, and the like.
Moreover, through the drawing process, a high-density potential
exists inside a material accompanied by large plastic deformation,
and an aging phenomenon is further promoted.
[0040] In other words, when the steel wire that is completely drawn
is wound around a spool having a preset inner diameter, cementite
is decomposed over time to produce strain aging, a change in
straightness is accompanied, and thus, targeted straightness may
not be acquired.
[0041] To prevent this, the wire 110 according to the embodiment
undergoes a heating operation in which the same is heated in a
state in which tension is applied and then undergoes a cooling
operation, thereby artificially promoting and completing diffusion
of solid solution atoms. As the diffusion of the solid solution
atoms is artificially promoted and completed as described above,
even after the wire 110 is wound around the winding portion having
a preset inner diameter, an aging phenomenon does not occur in the
wire 110.
[0042] As described above, the steel wire according to the
embodiment is capable of improving the straightness thereof by
promoting the strain aging of the wire 110, but the strain aging
may be promoted not to affect other physical properties of the wire
110.
[0043] For this, a heating time in the heating operation of the
wire 110 according to the embodiment may be about 0.02 s to about
10 s and may also be about 0.02 s to about 5 s.
[0044] When the wire 110 is heated for too long in the heating
operation of the wire 110, the strain aging of the wire 110 may be
promoted, but productivity of steel wire manufacturing may
decrease.
[0045] Referring to FIG. 2, as a heating time becomes longer in the
heating operation of the wire 110, productivity of the steel wire
decreases, and the productivity rapidly decreases at the heating
time longer than or equal to 10 s. In other words, when the heating
time increases in the heating operation of the wire 110, as a
productivity speed slows down, the productivity may decrease, and
thus, manufacturing cost may increase.
[0046] Also, when the wire 110 is not heated for a sufficient time
in the heating operation of the wire 110, strain aging is not
promoted. In detail, at the heating time of 0.01 s shorter than
0.02 s in the heating operation of the wire 110, as the heating
time is too short, carbon atoms decomposed from cementite at an
interface between cementite and ferrite do not have an enough
driving force to move into a ferrite area, and thus, an
acceleration where carbon is fixed to a potential does not occur.
Therefore, the heating time in the heating operation of the wire
110 may be about 0.02 s to about 10 s and may also be about 0.02 s
to about 5 s.
[0047] At the same time, a heating temperature and the heating time
in the heating operation of the wire 110 according to the
embodiment may satisfy Equation A below, and the heating
temperature in the heating operation of the wire 110 may be higher
than or equal to 80.degree. C. Equation A: T+15.67
ln(t).gtoreq.300, wherein T denotes absolute temperature K of the
heating temperature, and t denotes the heating time s.
[0048] Referring to FIGS. 3 through 7, when the heating temperature
and the heating time in the heating operation of the wire 110 do
not satisfy Equation A, the strain aging of the wire 110 is not
sufficiently promoted, and thus the straightness of the wire 110 is
not improved.
[0049] (FIG. 3 illustrates that the wire 110 is heated while
applying tension of 1% of a cutting strength thereto, FIG. 4
illustrates that the wire 110 is heated while applying tension of
5% of the cutting strength thereto, FIG. 5 illustrates that the
wire 110 is heated while applying tension of 15% of the cutting
strength thereto, FIG. 6 illustrates that the wire 110 is heated
while applying tension of 30% of the cutting strength thereto, and
FIG. 7 illustrates that the wire 110 is heated while applying
tension of 50% of the cutting strength thereto. Numerical values in
FIGS. 3 through 7 are measured from the straightness of the wire
110 through a straightness measurement method as described
above.)
[0050] Here, the heating temperature of the wire 110 may be higher
than or equal to 80.degree. C. When the heating temperature of the
wire 110 is lower than 80.degree. C., although the heating
temperature and the heating time in the heating operation of the
wire 110 satisfy Equation A, the strain aging of the wire 110 is
not promoted.
[0051] In detail, embodiments of 60.degree. C.--1 s and 40.degree.
C.--1 s in FIG. 3, 60.degree. C.--1 s and 40.degree. C.--1 s in
FIG. 4, 60.degree. C.--1 s and 40.degree. C.--1 s in FIG. 5,
60.degree. C.--1 s and 40.degree. C.--1 s in FIG. 6, and 60.degree.
C.--1 s and 40.degree. C.--1 s in FIG. 7 satisfy Equation A, but as
the heating temperature is lower than 80.degree. C., the strain
aging is not promoted, and thus, the straightness becomes poor.
[0052] FIG. 8 illustrates that the heating temperature of the wire
110 is lower than 80.degree. C., and the heating time becomes
longer (longer than or equal to 10 seconds). Referring to FIG. 8,
although the heating time becomes longer at the heating temperature
lower than 80.degree. C., the strain aging of the wire 110 is not
promoted. As described above, when the heating temperature of the
wire 110 is lower than 80.degree. C., although the heating time of
the wire 110 becomes longer, the strain aging is not promoted.
[0053] The strain aging occurs as an interstitial solid solution
atom such as C or N fixes to a potential over time, and factors
thereof may include not only a density of the solid solution atom,
but also time, temperature, a density of a potential, and the like.
In other words, a preset temperature is needed to fix an
interstitial solid solution atom such as C or N to a potential over
time, and when the heating temperature of the wire 110 is lower
than 80.degree. C., the interstitial solid solution atom such as C
or N is not fixed to the potential over time, and thus the strain
aging is not promoted.
[0054] Therefore, although the heating temperature and the heating
time in the heating operation of the wire 110 satisfy Equation A,
when the heating temperature in the heating operation is lower than
80.degree. C., the strain aging is not promoted.
[0055] Also, although the heating temperature in the heating
operation of the wire 110 is higher than 80.degree. C., when the
heating temperature and the heating time in the heating operation
of the wire 110 do not satisfy Equation A, the strain aging is not
promoted. In detail, with reference to 80.degree. C.--0.01 s, 0.02
s, and 0.03 s in FIG. 9, since the heating temperature in the
heating operation is higher than or equal to 80.degree. C. but does
not satisfy Equation A, the strain aging is not promoted, and thus,
the straightness is not improved.
[0056] Also, although the heating temperature in the heating
operation of the wire 110 is higher than or equal to 80.degree. C.,
when the heating time in the heating operation of the wire 110 is
shorter than 0.02 s, the strain aging is not promoted. In detail,
with reference to 100.degree. C.--0.01 s, 150.degree. C.--0.01 s,
and 200.degree. C.--0.01 s in FIG. 9, since the heating temperature
in the heating operation is higher than or equal to 80.degree. C.
and satisfies Equation A, but the heating time is insufficient, the
strain aging is not promoted.
[0057] This is because the heating time in the heating operation of
the wire 110 is considerably short. Although the heating
temperature in the heating operation of the wire 110 is higher than
or equal to 80.degree. C., when the heating time in the heating
operation of the wire 110 is considerably short, the interstitial
solid solution atom such as C or N is not fixed to the potential
over time, and thus, the strain aging is not promoted.
[0058] Therefore, the heating temperature and the heating time in
the heating operation of the wire 110 may satisfy Equation A below,
and the heating temperature in the heating operation of the wire
110 may be higher than or equal to 80.degree. C. In other words,
although the heating temperature is higher than or equal to
80.degree. C., when the heating time is too short, the strain aging
is not promoted, and thus, the heating time in the heating
operation of the wire 110 may be longer than or equal to 0.02
s.
[0059] According to an embodiment, tension applied to the wire 110
in the heating operation of the wire 110 may be about 1% to about
50% of a cutting strength. The tension applied to the wire 110 in
the heating operation of the wire 110 affects the heating
temperature and the heating time.
[0060] As described above, the heating operation promotes the
strain aging through the diffusion of interstitial solid solution
atoms, and when the tension applied to the wire 110 increases, the
straightness of the wire 110 increases, and a more excellent
straightness improvement effect is exhibited under the same heating
conditions. Therefore, the tension applied to the wire 110 in the
heating operation of the wire 110 may be greater than 1% of the
cutting strength.
[0061] However, when the tension applied to the wire 110 in the
heating operation of the wire 110 is too great, physical properties
of the wires 110 may be deteriorated by the tension. Therefore, the
tension applied to the wire 110 in the heating operation of the
wire 110 may be less than 50% of the cutting strength. (Here, a
cutting strength is one of physical properties of a wire and refers
to a strength at a point in time at which the wire is cut when
tension is applied from both ends of the wire to an axial
direction.)
[0062] However, the tension applied to the wire 110 is not limited
to about 1% to about 50% of the cutting strength, and appropriate
tension may be applied as needed.
[0063] The heating temperature in the heating operation of the wire
110 according to an embodiment may be about 80.degree. C. to about
220.degree. C. The point that the heating temperature may be higher
than or equal to 80.degree. C. is the same as described above and
thus is omitted herein. Referring to FIG. 10, when the heating
temperature is lower than or equal to 220.degree. C. in the heating
operation of the wire 110, a tensile strength may be increased
without significantly changing a microstructure.
[0064] However, when the heating temperature becomes excessively
higher than 220.degree. C., a physical property aspect of the wire
110 becomes inappropriate enough to observe changes in the
microstructure, and the tensile strength gradually decreases. In
other words, when the heating temperature is higher than
220.degree. C., the strain aging may be promoted, but the tensile
strength of the wire 110 may decrease. Therefore, the heating
temperature in the heating operation of the wire 110 may be about
80.degree. C. to about 220.degree. C.
[0065] The steel wire having the excellent straightness quality
according to the embodiment described above may be manufactured by
the following method. All of the properties of the steel wire
having the excellent straightness quality described above may be
applied to a method of manufacturing a steel wire having excellent
straightness quality according to an embodiment, which will be
described below.
[0066] Referring to FIG. 11, the method according to the embodiment
includes a wire preparation operation S110, a heating operation
S130, a cooling operation S140, and a straightness measurement
operation S150.
[0067] The wire preparation operation S110 is an operation of
preparing a drawn wire. When the wire preparation operation S110
includes an operation of drawing the wire 110, various types of
processes may be included therein.
[0068] The method of manufacturing the steel wire having the
excellent straightness quality according to the embodiment may
further include a stranding operation S120. The stranding operation
S120 is an operation of providing a plurality of wires 110, and
twisting and stranding the plurality of wires 110 to each other.
The stranding operation S120 may be included when manufacturing a
steel wire including stranded wires but may be omitted when
manufacturing a single steel wire.
[0069] The heating operation S130 is an operation of heating the
wire 110 that is drawn, in a state in which tension is applied. In
the heating operation S130, a heating temperature may be about
80.degree. C. to about 220.degree. C.
[0070] Also, the heating temperature and a heating time in the
heating operation S130 may satisfy Equation A: T+15.67
ln(t).gtoreq.300 (wherein T denotes absolute temperature K of the
heating temperature, and t denotes the heating time s), and the
heating temperature in the heating operation S130 may be higher
than or equal to 80.degree. C.
[0071] Also, the heating time in the heating operation S130 may be
about 0.02 s to about 10 s, and tension applied to the wire 110 in
the heating operation 130 may be about 1% to about 50% of a cutting
strength. However, the tension applied to the wire 110 is not
limited to about 1% to about 50% of the cutting strength, and thus
appropriate tension may be applied as needed.
[0072] The delimited significance of numerical values of the
heating temperature, the heating time, and the tension in the
heating operation S130 is the same as described above in the steel
wire having the excellent straightness quality according to the
embodiment, and thus detailed description thereof is omitted
herein.
[0073] The cooling operation S140 is an operation of cooling the
wire 110 that undergoes the heating operation S130. Since the wire
110 that undergoes the heating operation S130 is exposed to an
environment appropriate to diffuse C and N in the wire 110, when
cooling is insufficiently performed, and winding is performed,
strain aging may not be completely suppressed. Therefore, the wire
110 that undergoes the heating operation S130 may be cooled in the
cooling operation S140.
[0074] A cooling temperature in the cooling operation S140 may be
lower than or equal to 50.degree. C., and as the cooling
temperature in the cooling operation S140 is low, an effect may be
increased, and thus, cooling may be performed at a cooling
temperature lower than or equal to 50.degree. C. In detail, the
cooling operation S140 may be performed at room temperature.
However, the cooling temperature in the cooling operation S140 is
not limited thereto and may be changed as needed. The cooling
operation S140 may be performed in various methods, and methods
such as air cooling, reducing and inert gas cooling, water cooling,
and the like may be used.
[0075] The straightness measurement operation S150 is an operation
of winding the wire 110 around a winding portion having a diameter
greater than a diameter of the wire 110 for a preset period of time
and then measuring straightness of the wire 110.
[0076] Referring to FIG. 1, the straightness may be measured in the
straightness measurement operation S150 as follows. The wire 110 is
wound around the winding portion having the diameter greater than
the diameter of the wire 110 for the preset period of time.
Thereafter, the end 111 of the wire 110 that is wound is fixed to
the point 120, and the wire 110 is vertically lowered. Here, the
wire 110 is lowered to 400 mm. In other words, a distance between
the end 111 of the wire 110 and the other end 112 of the wire 110
is 400 mm.
[0077] The straightness of the wire 110 measured in the
straightness measurement operation S150 may be an interval between
the first axis 121 forming a vertical line from the point 120 and
the other end 112 of the wire 110. In detail, as the interval
between the first axis 121 and the other end 112 of the wire 110 is
narrow, the steel wire has excellent straightness, and as the
interval between the first axis 121 and the other end 112 of the
wire 110 is wide, the steel wire has poor straightness.
[0078] In the method of manufacturing the steel wire having the
excellent straightness quality according to the embodiment, when
winding the wire 110 around the winding portion for the preset
period of time as in the method described above and then measuring
the straightness of the wire 110 of 400 mm in the straightness
measurement operation S150, a steel wire including the wire 110
having straightness less than or equal to 30 mm may be
manufactured.
[0079] The steel wire having the excellent straightness quality and
the method of manufacturing the same according to the embodiments
as described above have the following effects.
[0080] In the steel wire having the excellent straightness quality
and the method of manufacturing the same according to the
embodiments, as the steel wire is heated at a preset temperature
for a short period of time, strain aging of the steel wire may be
promoted to improve the straightness quality after aging.
[0081] Also, in the steel wire having the excellent straightness
quality and the method of manufacturing the same according to the
embodiments, as the steel wire is heated at the preset temperature
for the shorter period of time, a microstructure of the steel wire
may not be significantly changed, and thus, the strain aging may be
promoted without deteriorating physical properties of the steel
wire to improve the straightness quality after aging.
[0082] In detail, in the steel wire having the excellent
straightness quality and the method of manufacturing the same
according to the embodiments, as a wire is heated for a short
period of time (about 0.02 s to about 10 s or about 0.02 s to about
5 s), straightness of the wire may be improved without changing
physical properties of the wire.
[0083] Here, to promote the strain aging of the wire while heating
the wire for the short period of time, a heating temperature and a
heating time in a heating operation of the wire may satisfy
Equation A: T+15.67 ln(t).gtoreq.300 (wherein T denotes absolute
temperature K of the heating temperature, and t denotes the heating
time s), and the heating temperature in the heating operation may
be higher than or equal to 80.degree. C.
[0084] Referring to FIGS. 3 through 9, when the conditions as
described above are not satisfied, the strain aging is
insufficiently promoted. However, in the steel wire having the
excellent straightness quality according to the embodiment, the
wire may be heated while satisfying the above conditions, and thus,
the straightness of the wire may be improved without changing the
physical properties of the wire.
[0085] In a steel wire having excellent straightness quality and a
method of manufacturing the same according to embodiments, Equation
A: T+15.67 ln(t).gtoreq.300 (wherein T denotes absolute temperature
K of the heating temperature, and t denotes the heating time s) may
be modified as follows. Equation A above may be modified into
420.gtoreq.T+15.67 ln(t).gtoreq.300, and Equation A may have an
upper limit of 420.
[0086] As values of the heating temperature and the heating time
increase, and a value of Equation A increases, the strain aging may
be promoted. However, when the upper limit of Equation A exceeds
420, economic and workability aspects may be inefficient. Also, as
the values of the heating temperature and the heating time are
increased to exceed the upper limit of 420 in Equation A, a risk of
affecting the physical properties of the wire may increase, and
thus, Equation A above may be formed of 420 T+15.67
ln(t).gtoreq.300.
[0087] While the present disclosure has been particularly shown and
described with reference to example embodiments thereof, the
present disclosure is not limited to the embodiments, and various
changes in form and details may be made therein without departing
from the spirit and scope of the present disclosure. Therefore, the
scope of the present disclosure should be defined by the spirit of
the appended claims.
* * * * *