U.S. patent application number 15/578974 was filed with the patent office on 2018-05-17 for solidification apparatus.
The applicant listed for this patent is POSCO. Invention is credited to Il-Sin BAE, Byeong-Ha HAN, Jong-Yeon HWANG, Hee-Tae JEONG, Seong-Yeon KIM, Sang-Hyeon LEE, Min-Chul SHIN.
Application Number | 20180133785 15/578974 |
Document ID | / |
Family ID | 57440792 |
Filed Date | 2018-05-17 |
United States Patent
Application |
20180133785 |
Kind Code |
A1 |
BAE; Il-Sin ; et
al. |
May 17, 2018 |
SOLIDIFICATION APPARATUS
Abstract
Provided is a solidification apparatus that makes variations in
the surface height of a molten metal relatively non-affected by the
proceeding speed of a metal sheet to significantly increase the
proceeding speed of the metal sheet and to increase the
productivity of the metal sheet. The solidification apparatus for
producing a metal sheet by solidifying molten metal includes rows
of rollers arranged in a proceeding direction of the metal sheet,
wherein when the rows of rollers are grouped into a plurality of
sections, an average of roller pitches each being a distance
between centers of rollers adjacent in the proceeding direction of
the metal sheet is smaller in a given section than in a preceding
section.
Inventors: |
BAE; Il-Sin; (Gwangyang-si,
KR) ; LEE; Sang-Hyeon; (Pohang-si, KR) ; KIM;
Seong-Yeon; (Gwangyang-si, KR) ; JEONG; Hee-Tae;
(Gwangyang-si, KR) ; HAN; Byeong-Ha;
(Gwangyang-si, KR) ; HWANG; Jong-Yeon;
(Gwangyang-si, KR) ; SHIN; Min-Chul;
(Gwangyang-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
POSCO |
Pohang-si |
|
KR |
|
|
Family ID: |
57440792 |
Appl. No.: |
15/578974 |
Filed: |
June 7, 2016 |
PCT Filed: |
June 7, 2016 |
PCT NO: |
PCT/KR2016/006000 |
371 Date: |
December 1, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 11/1282 20130101;
B22D 11/1287 20130101; B22D 11/12 20130101; B22D 11/128
20130101 |
International
Class: |
B22D 11/128 20060101
B22D011/128 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2015 |
KR |
10-2015-0079173 |
Claims
1. A solidification apparatus for producing a metal sheet by
solidifying molten metal, the solidification apparatus comprising
rows of rollers arranged in a proceeding direction of the metal
sheet, wherein when the rows of rollers are grouped into a
plurality of sections, an average of roller pitches each being a
distance between centers of rollers adjacent in the proceeding
direction of the metal sheet is smaller in a given section than in
a preceding section.
2. The solidification apparatus of claim 1, wherein the average of
roller pitches is smaller in the given section than in a subsequent
section.
3. The solidification apparatus of claim 1, wherein each of the
sections is a space comprising at least four roller pitches.
4. The solidification apparatus of claim 1, wherein each of the
sections is a space comprising rollers arranged within a length of
1 m or greater.
5. The solidification apparatus of claim 1, wherein the sections
are physically defined.
6. The solidification apparatus of claim 5, wherein the sections
are physically defined on a segment basis.
7. The solidification apparatus of claim 1, wherein each of the
sections is a space between a driving roll and a next driving
roll.
8. The solidification apparatus of claim 1, wherein a difference
between the average of roller pitches in the given section and the
average of roller pitches in the preceding section is 10 mm or
greater.
9. The solidification apparatus of claim 8, wherein the difference
in the average of roller pitches is 20 mm or greater.
10. The solidification apparatus of claim 8, wherein a proceeding
speed of the metal sheet is 4 m/min or greater.
11. The solidification apparatus of claim 8, wherein the sections
comprise: a horizontal section transferring the metal sheet
horizontally; a curved section having a predetermined curvature and
located between an exit through which the molten metal is
discharged and the horizontal section; and a curvature variation
section provided in at least one of a region between the exit and
the curved section and a region between the curved section and the
horizontal section, the curvature variation section having a
different curvature.
12. The solidification apparatus of claim 11, further comprising a
vertical section connected to the exit perpendicularly so as to
transfer the metal sheet vertically, the vertical section also
being connected to the curved section.
13. The solidification apparatus of claim 1, wherein the average of
roller pitches in each of the sections is defined by Equation 1
below: Pa(k)=.SIGMA..sub.iP(k,i)/N Equation 1 where N is the number
of roller pitches in a given section, k is a section number, and i
is a serial number of a roller pitch in a section k.
14. The solidification apparatus of claim 1, wherein the given
section having the average of roller pitches smaller than that of
the preceding section is within a solidification length in which
the metal sheet solidifies, and the solidification length of the
metal sheet is defined by Equation 2 below: L = V .times. ( H 2
.times. K ) 2 Equation 2 ##EQU00003## where L is a length in
millimeters (mm) required to complete solidification of the metal
sheet, V is a proceeding speed of the metal sheet in mm/min, H is
the thickness of the metal sheet in mm, and K is a solidification
constant ranging from 20 mm/min.sup.1/2 to 30 mm/min.sup.1/2.
15. The solidification apparatus of claim 1, wherein the given
section having the average of roller pitches smaller than that of
the preceding section is repeated at least twice.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a solidification apparatus
for producing a metal sheet by continuously solidifying molten
metal.
BACKGROUND ART
[0002] In general, apparatuses for continuously solidifying molten
metal are made up of a mold into which molten metal enters and a
plurality of rows of rollers arranged in series on an exit side of
the mold. Usually, the plurality of rows of rollers are provided in
segment units.
[0003] In addition, molten metal exits the mold in a half solid
state in which the molten metal has solidified on the surface
thereof but has not yet solidified in the inside thereof, and the
inside of the molten metal gradually solidifies as the molten metal
passes through the rows of rollers, thereby leaving the
solidification apparatus in a fully solidified state.
[0004] At this time, when a metal sheet formed as the molten metal
solidifies passes through the rows of rollers, the metal sheet is
in a half solid state for a considerable period of time, and thus
molten metal remains intact inside the metal sheet. Therefore, a
considerably large amount of pressure is applied to the inside of
the metal sheet because of a height difference between the inside
of the metal sheet and the surface of molten metal contained in the
mold, and thus rollers, roller bearings, and roller support
structures are designed to support this load.
[0005] In addition, as the metal sheet proceeds downwardly, the
pressure caused by the height difference from the surface of molten
metal increases, and thus it is common to design lower rollers to
have a relatively large diameter. In addition, large-diameter
rollers also have a large roller pitch, the distance between the
centers of rollers adjacent to each other in the proceeding
direction of the metal sheet.
[0006] In addition, outward swelling of the metal sheet caused by
the pressure of molten metal present inside the metal sheet is
suppressed by rollers making contact with the surface of the metal
sheet. Thus, if the roller pitch of the rollers is large, sections
of the metal sheet located between the rollers, and thus not making
contact with the rollers, are large, and thus the metal sheet
swells to some extent.
[0007] That is, referring to FIG. 1, in the process of passing a
metal sheet between rollers, swelling slightly occurs in regions of
solidified layers of the metal sheet that do not make contact with
the rollers.
[0008] Therefore, it is necessary to arrange rollers as closely
together as possible to minimize the pitch of the rollers and thus
to prevent swelling of solidified layers.
[0009] In addition, when the solidified layers swell, the amount of
swelling may periodically vary, and it is considered that this
phenomenon causes variations in the surface height of molten metal.
In addition, this phenomenon also causes variations in the volume
of the half-solidified inside of the metal sheet, and since the
metal sheet passes between the rollers in this state, periodic
variations occur in the surface height of molten metal contained in
the mold.
[0010] It is observed that the period of variations in the surface
height of the molten metal closely relates to the pitch of rollers.
Although it is experientially known that variations in the surface
height of molten metal tend to increase in proportion to the
proceeding speed of a metal sheet and the pitch of rollers, the
mechanism thereof has not yet been clearly found.
[0011] Meanwhile, if variations in the surface height of molten
metal exceed an allowable limit, non-uniform solidification occurs,
which has a negative effect on quality. Furthermore, in severe
cases, weak portions of solidified layers may be ruptured, and
molten metal that has not yet solidified may leak to the outside,
thereby causing considerable damage such as suspension of
production or damage to production equipment.
[0012] Therefore, in general, work is performed while limiting the
proceeding speed of a metal sheet according to an allowable range
of variations in the surface height of molten metal. However, this
serves as a factor decreasing the productivity of metal sheets.
DISCLOSURE
Technical Problem
[0013] An aspect of the present disclosure may provide a
solidification apparatus in which the repeatability of roller
pitches is removed, in addition to changing the arrangement of
rollers so as to reduce periodic variations in the surface of
molten metal and to make variations in the surface height of molten
metal relatively non-affected by the proceeding speed of a metal
sheet. Therefore, the proceeding speed of metal sheets may be
significantly increased, and thus the productivity of metal sheets
may be increased.
Technical Solution
[0014] According to an aspect of the present disclosure, a
solidification apparatus for producing a metal sheet by solidifying
molten metal may include rows of rollers arranged in a proceeding
direction of the metal sheet, wherein when the rows of rollers are
grouped into a plurality of sections, an average of roller pitches
each being a distance between centers of rollers adjacent in the
proceeding direction of the metal sheet may be smaller in a given
section than in a preceding section.
[0015] In addition, the average of roller pitches may be smaller in
the given section than in a subsequent section.
[0016] In addition, each of the sections may be a space including
at least four roller pitches.
[0017] In addition, each of the sections may be a space including
rollers arranged within a length of 1 m or greater.
[0018] In addition, the sections may be physically defined
spaces.
[0019] In addition, the sections may be physically defined on a
segment basis.
[0020] In addition, each of the sections may be a space between a
driving roll and a next driving roll.
[0021] In addition, a difference between the average of roller
pitches in the given section and the average of roller pitches in
the preceding section may be 10 mm or greater.
[0022] In addition, the difference in the average of roller pitches
may be 20 mm or greater.
[0023] In addition, a proceeding speed of the metal sheet may be 4
m/min or greater.
[0024] The sections may include: a horizontal section transferring
the metal sheet horizontally; a curved section having a
predetermined curvature and located between an exit of a mold
through which the molten metal is discharged and the horizontal
section; and a curvature variation section provided in at least one
of a region between the exit and the curved section and a region
between the curved section and the horizontal section, the
curvature variation section having a different curvature.
[0025] In addition, the solidification apparatus may further
include a vertical section connected to the exit perpendicularly so
as to transfer the metal sheet vertically, the vertical section
also being connected to the curved section.
[0026] In addition, the average of roller pitches in each of the
sections may be defined by Equation 1 below:
Pa(k)=.SIGMA..sub.iP(k,i)/N Equation 1
[0027] where N is the number of roller pitches in a given section,
k is a section number, and i is a serial number of a roller pitch
in a section k.
[0028] In addition, the given section having the average of roller
pitches smaller than that of the preceding section may be within a
solidification length in which the metal sheet solidifies, and the
solidification length of the metal sheet may be defined by Equation
2 below:
L = V .times. ( H 2 .times. K ) 2 Equation 2 ##EQU00001##
[0029] where L is a length in millimeters (mm) required to complete
solidification of the metal sheet, V is a proceeding speed of the
metal sheet in mm/min, H is the thickness of the metal sheet in mm,
and K is a solidification constant ranging from 20 mm/min.sup.1/2
to 30 mm/min.sup.1/2.
[0030] In addition, the given section having the average of roller
pitches smaller than that of the preceding section may be repeated
at least twice.
Advantageous Effects
[0031] According to an embodiment of the present disclosure, the
proceeding speed of a metal sheet may have a less influence on
variations in the surface height of molten metal contained in a
mold, and thus the proceeding speed of the metal sheet may be
markedly increased.
DESCRIPTION OF DRAWINGS
[0032] FIG. 1 is a schematic view illustrating a proceeding state
of a metal sheet.
[0033] FIG. 2 is a schematic view illustrating a solidification
apparatus according to the embodiment of the present
disclosure.
[0034] FIGS. 3A to 3C are schematic views illustrating rows of
rollers of the solidification apparatus according to the embodiment
of the present disclosure.
[0035] FIG. 4 is a graph illustrating the average of roller pitches
in each section of the solidification apparatus in inventive
examples of the present disclosure in comparison with the average
of roller pitches in each section in the related art.
[0036] FIG. 5 is a view illustrating a relationship between the
solidification length, rate, and thickness of a metal sheet
according to an embodiment of the present disclosure.
[0037] FIG. 6 is a graph showing the average of roller pitches in
each section of the solidification apparatus in an inventive
example.
BEST MODE
[0038] Hereinafter, embodiments of the present disclosure will be
described in detail with reference to the accompanying drawings.
However, the embodiments of the present disclosure may be modified
in various forms, and the scope of the present disclosure is not
limited to the embodiments. In the drawings, the shapes and
dimensions of elements may be exaggerated for clarity, and the same
reference numerals will be used throughout to designate the same or
like elements.
[0039] FIG. 2 is a schematic view illustrating a solidification
apparatus according to an embodiment of the present disclosure, and
FIG. 3 is a schematic view illustrating rows of rollers of the
solidification apparatus according to the embodiment of the present
disclosure.
[0040] Referring to FIGS. 2 and 3, according to the present
embodiment, the solidification apparatus 10 may include a mold 20
configured to produce an initially-solidified molten sheet B by
cooling molten metal Y supplied from a tundish 1.
[0041] The mold 20 includes a cooling device therein, and thus
molten metal making contact with the mold 20 is cooled from the
surface thereof and is discharged from the mold 20 in the form of a
metal sheet B with the inside of the metal sheet B being not yet
solidified.
[0042] In addition, rows of rollers may be arranged at an exit side
of the mold 20 in the proceeding direction of the metal sheet B so
as to guide the metal sheet B discharged in a half-solidified
state, and the rows of rollers may form a transfer unit 30 in
association with a driving unit.
[0043] The transfer unit 30 cools and solidifies the
half-solidified metal sheet B and transfers the metal sheet B to a
subsequent process.
[0044] In the present embodiment, the transfer unit 30 may be
divided into a plurality of sections according to the average of
roller pitches of the rows of rollers.
[0045] Here, referring to FIG. 3A, each section may be a space
having at least four roller pitches. That is, each section may be
defined as being a space including five rollers and at least four
roller pitches each being the distance between the centers of
rollers. In the present embodiment, roller pitches are a key factor
causing variations in the surface height of molten metal, and thus
sections may be defined by roller pitches rather than the number of
rollers.
[0046] In addition, the average of roller pitches in each section
may be expressed by Equation 1 below.
Pa(k)=.SIGMA..sub.iP(k,i)/N Equation 1
[0047] where N is the number of roller pitches in a given section,
k is a section number, and i is a serial number of a roller pitch
in a section k.
[0048] In the present embodiment, each section is defined as being
a space having at least four roller pitches. However, the same
roller arrangement is not required in a section opposite and
symmetric to the section, or it is not required to define, in the
same manner, a section opposite and symmetric to the section. That
is, sections may be defined independently of each other.
[0049] In addition, although each section is defined as being a
space having at least four roller pitches in the present
embodiment, the definition of each section is not limited thereto.
For example, sections may be defined according to the length
thereof.
[0050] That is, in the present embodiment, each section may be
defined as being a space including rollers arranged within a length
of 1 m or greater.
[0051] In the present embodiment, if each section has a length less
than 1 m, rollers are quite densely arranged in the section, and
thus variations in the surface height of molten metal may not
easily occur. Furthermore, in the present embodiment, each section
may be defined as being a space including rollers arranged along a
sufficient length allowed by equipment conditions.
[0052] In addition, each section may be a physically defined
space.
[0053] For example, the physically defined space may be a space
defined on a segment basis as shown in FIG. 3B. In each segment, a
plurality of rollers for guiding the movement of the metal sheet B
may be provide, and rows of the rollers may be physically grouped
to be, for example, exchanged or replaced on a segment basis.
[0054] In addition, referring to FIG. 3C, the physically defined
space may not be a space defined on a segment basis but may be a
space between a driving roll and the subsequent driving roll.
[0055] In general, each segment may have one driving roll, for
example, in a center region of the segment. In addition, each
segment may include a plurality of rows of rollers in addition to
the driving roll. Here, the space between a driving roll and the
subsequent driving roll may be a space between a driving roll of a
segment and a driving roll of the subsequent segment, or may be a
space between driving rolls of structures other than segments. In
the space, a plurality of rows of rollers may be arranged.
[0056] In rows of rollers grouped into a plurality of sections as
described above, the average of roller pitches, each being the
distance between the centers of two rollers adjacent to each other
in the proceeding direction of the metal sheet may be greater in a
given section than in the preceding section or may be the same in
both of the sections.
[0057] In this case, as the metal sheet B proceeds along the
sections of the rows of rollers, a load caused by the height
difference between the surface of molten metal and the metal sheet
B increases, and pressure acting on the rows of rollers
increases.
[0058] On the other hand, in a given section of the plurality of
sections of the present embodiment, the average of roller pitches
each being the distance between the centers of two adjacent rollers
in the proceeding direction of the metal sheet B may be smaller
than the average of roller pitches in the preceding section. That
is, when the rows of rollers are grouped into a plurality of
sections, the average of roller pitches each being the distance
between the centers of two adjacent rollers in the proceeding
direction of the metal sheet B may be smaller in a given section
than in the preceding section.
[0059] When the average of roller pitches each being the distance
between the centers of two adjacent rollers in the proceeding
direction of the metal sheet B is smaller in a given section than
in the preceding section, the average of roller pitches in the give
section may also be smaller than the average of roller pitches in
the subsequent section.
[0060] That is, the average of roller pitches may be reversed in a
given section, and thus the average of roller pitches in the given
section may be smaller than the average of roller pitches in the
preceding section and the average of roller pitches in the
subsequent section.
[0061] The average of roller pitches in each section may be as
shown in the graph of FIG. 4. FIG. 4 is a graph illustrating the
average of roller pitches in each section of the solidification
apparatus according to inventive examples of the present disclosure
in comparison with the average of roller pitches in each section in
the related art. In FIG. 4, the x-axis is sections, and the y-axis
is an average of roller pitches.
[0062] Referring to FIG. 4, when the difference between the average
of roller pitches in a given section and the average of roller
pitches in the preceding section is 10 mm or greater, meaningful
results for increasing the rate of casting may be obtained.
[0063] That is, when the average of roller pitches in a given
section is less than the average of roller pitches in the preceding
section by less than 10 mm, there is no effect on variations in the
surface height of molten metal in a mold.
[0064] On the other hand, the average of roller pitches in a given
section is less than the average of roller pitches in the preceding
section by 10 mm or greater, variations in the surface height of
molten metal in a mold may be reduced.
[0065] For example, when the average of roller pitches in a given
section is less than the average of roller pitches in the preceding
section by about 17 mm, variations in the surface height of molten
metal in a mold are reduced, and thus the rate of casting may be
increased by about 0.5 m/min compared to the related art. That is,
when the rate of casting is 6.5 m/min in the related art, it could
be understood that the rate of casting is increased to 7.0 m/min
after the average of roller pitches is reduced according to the
technique of the present disclosure.
[0066] When the average of roller pitches in a given section is
less than the average of roller pitches in the preceding section by
about 20 mm or greater, variations in the surface height of molten
metal in a mold may be much more reduced.
[0067] For example, when the average of roller pitches in a given
section is less than the average of roller pitches in the preceding
section by about 38 mm, variations in the surface height of molten
metal in a mold are reduced, and thus the rate of casting may be
increased by about 1.5 m/min compared to the related art. That is,
it could be understood that although the rate of casting is 6.5
m/min in the related art, the rate of casting is 7.0 m/min when a
decrease in the average of roller pitches is about 17 mm, and 8.0
m/min when a decrease in the average of roller pitches is about 38
mm.
[0068] Therefore, according to the above-described data, it could
be understood that when the average of roller pitches is smaller by
20 mm or greater in a given section than in the preceding section,
desired results can be obtained.
[0069] However, the degree to which the average of roller pitches
is reduced may have an upper limit according to the allowable load
of equipment. In general, if the degree of reduction in the average
of roller pitches is increased, a large load may be transmitted to
roller supporting structures and driving systems such as bearings,
and thus an upper limit to reduction of the average of roller
pitches may be determined according to the load that equipment can
endure.
[0070] As described above, it will be understood that when the
average of roller pitches in a given section is smaller than the
average of roller pitches in the preceding section, variations in
the surface height of molten metal in a mold may be reduced. In
addition, after the average of roller pitches is reduced in the
given section compared to the preceding section, the average of
roller pitches may be increased in the subsequent section.
[0071] FIG. 5 is a view illustrating a relationship between the
solidification length, rate, and thickness of a metal sheet
according to an embodiment of the present disclosure.
[0072] Referring to FIG. 5, in the present embodiment, the length
required for a metal sheet B to completely solidify may be reduced
as the proceeding speed of the metal sheet B is increased.
[0073] The proceeding speed of the metal sheet B may be increased
as described above because before the metal sheet B completely
solidifies, variations in the surface height of molten metal are
relatively non-affected by the proceeding speed of the metal sheet
B, owing to a section having the average of roller pitches smaller
than that of the preceding section.
[0074] As described above, the section having the average of roller
pitches smaller than that of the preceding section may exist within
a length in which the metal sheet B is not yet completely
solidified, thereby reducing pressure caused by the height
difference between the metal sheet B and the surface of molten
metal contained in a mold before the metal sheet B is completely
solidified, and suppressing outward swelling of the metal sheet B
caused by the pressure of molten metal in the metal sheet B while
the metal sheet B moves.
[0075] Therefore, in the present embodiment, the maximum length of
a reverse section having the average of roller pitches smaller than
that of the preceding section is equal to the length required for
solidification of the metal sheet B, which may be expressed by
Equation 2 as a function of the proceeding speed V of the metal
sheet B.
L = V .times. ( H 2 .times. K ) 2 Equation 2 ##EQU00002##
[0076] where L is a length (mm) required to complete solidification
of a metal sheet, V is the proceeding speed of the metal sheet in
mm/min, H is the thickness of the metal sheet in mm, and K is a
solidification constant ranging from 20 mm/min.sup.1/2 to 30
mm/min.sup.1/2.
[0077] In the solidification apparatus of the present embodiment,
the average of roller pitches each being the distance between the
centers of two rollers adjacent in the proceeding direction of a
metal sheet B may be smaller in a given section than in the
preceding section, thereby reducing variations in the surface
height of molten metal in a mold and maintaining the proceeding
speed of the metal sheet B at 4 m/min or greater.
[0078] Furthermore, in the present embodiment, as shown in FIG. 2,
the transfer unit 30 may be divided into a vertical section 100
perpendicularly connected to the exit side of the mold 20, a
horizontal section 300 connected to a subsequent process section,
and a curved section 200 located between the vertical section 100
and the horizontal section 300.
[0079] In this case, a curvature variation section 400 curved with
a different slope may be provided in one of a region between the
vertical section 100 and the curved section 200 and a region
between the curved section 200 and the horizontal section 300.
[0080] In addition, the vertical section 100 of the transfer unit
30 may include at least one segment, and the average of roller
pitches each being the distance between the centers of two rollers
adjacent in the proceeding direction of the metal sheet B may be
smaller in the curvature variation section 400 located between the
vertical section 100 and the curved section 200 than in the
preceding section.
[0081] After the reverse section, of which the average of roller
pitches, each being the distance between the centers of two rollers
adjacent in the proceeding direction of the metal sheet B, is
smaller than the average of roller pitches in the preceding
section, the average of roller pitches may increase again in the
subsequent section.
[0082] Although the transfer unit 30 is divided into the vertical
section 100, the curved section 200, and the horizontal section 300
in the present embodiment, the transfer unit 30 may include only
the vertical section 100, or the transfer unit 30 may include only
the curved section 200 and the horizontal section 300 in a state in
which the curved section 200 is directly connected to the exit side
of the mold 20 without the vertical section 100. In addition, the
curvature variation section 400 in which the slope of curve varies
may not be provided if the slope of the curved section 200 is
constant.
[0083] In addition, a section having the average of roller pitches
smaller than that of the preceding section may appear two or more
times, and in this case, variations in the surface height of molten
metal in a mold may be further reduced.
[0084] Variations in the surface height of molten metal in the mold
20 increase as the proceeding speed of the metal sheet B increases
and the arrangement in which the average of roller pitches
increases uniformly is repeated many times. Therefore, if the
arrangement in which the average of roller pitches increases
uniformly is minimally repeated, variations in the surface height
of molten metal may be less sensitive to the proceeding speed of
the metal sheet B. In this case, if variations in the surface
height of molten metal are maintained at the same degree as that in
the related art, as a result, the proceeding speed of the metal
sheet B may be increased.
[0085] FIG. 6 is a graph showing the average of roller pitches in
each section of the solidification apparatus in an inventive
example. In FIG. 6, the x-axis is sections, and the y-axis is an
average of roller pitches.
[0086] Referring to FIG. 6, according to the embodiment, the degree
of reduction in the average of roller pitches in a given section is
less than 10 mm compared to the average of roller pitches in the
preceding section, and even when the average of roller pitches
increases somewhat in the subsequent section, the total decrease in
the average of roller pitches in the given section and the second
subsequent section is 10 mm or greater. In this case, the degree of
reduction of variations in the surface height of molten metal in a
mold may be improved.
[0087] That is, even when the average of roller pitches is not
sufficiently reduced by 10 mm or greater in a certain section, if
the sum of the average of roller pitches in consecutive sections is
reduced by 10 mm or greater showing a decreasing trend as a whole,
meaningful results for reducing variations in the surface height of
molten metal in a mold may be obtained.
[0088] Specifically, the average of roller pitches may be reduced
by 8 mm between D1 and D2, increased by 4 mm between D2 and D3, and
then decreased by 8 mm between D3 and D4.
[0089] In this case, the degree of reduction in the average of
roller pitches is 10 mm or less between sections, and only with
this degree of reduction in the average of roller pitches between
sections, meaningful results for reducing variations in the surface
height of molten metal in a mold may not be obtained.
[0090] However, the sum of decreases in the average of roller
pitches may be 12 mm between D1 and D4, and in this case, since the
average of roller pitches is reduced by 10 mm or greater as a
whole, variations in the surface height of molten metal in a mold
may be reduced.
[0091] As described above, after the average of roller pitches is
reduced in a preceding section (for example, a section between D1
to D4), the average of roller pitches may be increased again in a
following section (for example, a section D5 or a later
section).
[0092] The above-described embodiments and the accompanying
drawings are not non-limiting examples, and it will be apparent to
those skilled in the art that various replacements, modifications,
and variations could be made without departing from the scope of
the present invention as defined by the appended claims.
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