【DESCRIPTION】
【Invention Title】
HOT ROLLING DEVICE, AND DEVICE AND METHOD FOR
CONTINUOUS CASTING/HOT ROLLING
【Technical Field】
The present invention relates to a hot rolling device,
and a device and a method for continuous casting and hot
rolling. More particularly, the present invention relates
to a technique that improves the quality of a hot-rolled
product by repeated heating at multiple points to evenly
heat a cast part prior to being provided to a hot roller,
and prevents a decrease in quality of a steel sheet and a
reduction in a yield percentage that occur when switching to
a continuous or a discontinuous hot rolling mode.
【Background Art】
A process of performing hot rolling using a high
temperature solidified cast part in a continuous casting
device is currently widely used, due to equipment costs and
operating costs thereof being more inexpensive than those of
conventional equipment and processes.
Also, a discontinuous process capable of performing hot
rolling separately from continuous casting, while
continuously undertaking continuous casting and the hot
rolling can also be performed. This discontinuous process
Page 3
is disclosed in detail in published Korean Patent No. 1990-
7001437.
That is, as illustrated in FIG. 1, a continuous hot
rolling mode of continuously performing continuous casting
and hot rolling, and a discontinuous hot rolling mode of
discontinuously performing continuous casting and hot
rolling can be used, respectively.
Here, FIG. 1(a) illustrates a facility 1’ capable of
performing continuous hot rolling. When a cast part 2’
having a constant thickness is generated in a continuous
casting device 100’, the cast part 2’ is first hot-rolled in
a first hot-rolling unit 210’, the temperature is retained
in a heat insulating means 320’, and a steel sheet 2a’ that
presses the cast part 2’ down is heated by heaters 310’ to a
temperature for hot-rolling to finish the final hot rolling
in a second hot rolling section 220. The steel sheet 2a’,
after finishing hot rolling, is cut with a third cutter 430’
and wound with a rewinder R to produce a hot-rolled steel
sheet 2a’.
Meanwhile, FIG. 1(b) illustrates facility 1’ capable of
performing discontinuous hot rolling. When the cast part 2’
having a constant thickness is produced in the continuous
casting device 100’, the cast part 2’ is first hot-rolled in
the first hot-rolling unit 210’ and is cut with the first
cutter 411’ before moving to the heat insulating means 320’,
Page 4
thereby performing hot rolling without being restricted to
the casting speed of the continuous casting device 100’.
Here, the cutting steel sheet 2a’ provided by cutting
the steel sheet 2a’ that presses the cast part 2’ down is
wound, and is then provided to finish the final hot rolling
in the second hot rolling section 220’ again. After being
heated by the heater 310’ to the temperature for hot-rolling,
the cutting steel sheet 2a’ is finally hot-rolled, is wound
by the rewinder R and is produced as a hot-rolled steel
sheet 2a’.
However, when performing such a hot-rolling process,
since the hot rolling is performed by the first hot rolling
section 210’ in a state in which the temperature
distribution of the cast part 2’ provided by being produced
in the continuous casting device 100’ is uneven, there may
be a problem of a reduction in the quality of the hot-rolled
steel sheet 2a’.
Further, in the case of switching from the
discontinuous hot rolling mode to the continuous hot rolling
mode, when the cast part 2 provided by being produced in the
continuous casting device 100’ is depressed into the first
hot rolling section 210’, the speed of the continuous
casting device 100’ is restricted, thereby causing a problem
of forming a strap on the cast part 2’.
To solve this problem, conventionally, the hot rolling
process has been sequentially performed by gradually
Page 5
reducing an interval between top and bottom rolls of a
plurality of hot rolling rolls of the first hot rolling
section 210’. However, a transition zone in which the
thickness is reduced has been generated at a tip portion of
the sequentially hot-rolled steel sheet 2a’, thereby causing
another problem of lowering the quality of the produced hotrolled
steel sheet 2a’.
Therefore, there is a need for research into a hot
rolling apparatus, and an apparatus and a method for
continuous casting and hot rolling to solve the abovementioned
problems.
【Disclosure】
【Technical Problem】
An aspect of the present invention provides a hot
rolling apparatus, and an apparatus and a method for
continuous casting and hot rolling that improve the quality
of a hot-rolled steel sheet by evenly heating the cast part
produced in the continuous casting device and by
transmitting the cast part to the hot roller, remove steel
sheet defects generated when switching to the continuous or
discontinuous hot rolling mode, and enhance yield percentage.
【Technical Solution】
According to an aspect of the present invention, there
is provided a hot rolling apparatus that includes a cast
Page 6
part supply section producing a cast part, a hot roller
receiving and hot-rolling the cast part, and disposed to be
linked to the cast part supply section, and a heating unit
disposed between the cast part supply section and the hot
roller and provided to reheat an outer surface portion of
the cast part in a thickness direction while latent heat
from preheating is retained in a central portion in the
thickness direction of the cast part.
Further, the cast part produced by the cast part supply
section of the hot rolling apparatus according to an
embodiment of the present invention is formed to have a
thickness of 70 to 120 mm, and the heating unit may heat the
outer surface portion of the cast part to a temperature of
1250°C or less, thereby maintaining the average temperature
in the thickness direction of the cast part at 1000°C or
higher.
Further, according to another aspect of the present
invention, there is provided a continuous casting and hot
rolling apparatus that includes a continuous casting device
producing a cast part, a hot roller receiving and hotrolling
the cast part, and disposed to be linked to the
continuous casting device, and a heating unit provided at a
front end of the hot roller and evenly and repeatedly
heating the cast part at a plurality of points.
Further, the heating unit of the continuous casting and
hot rolling apparatus according to another aspect of the
Page 7
present invention may include a plurality of heaters,
disposed to be dispersed in a transportation direction of
the cast part.
Further, the heater of the continuous casting and hot
rolling apparatus according to another aspect of the present
invention may be disposed to be dispersed in a region in a
length direction of the slab provided by cutting the cast
part so that can be used in a discontinuous hot rolling mode.
Further, the heating unit of the continuous casting and
hot rolling apparatus according to another aspect of the
present invention may further include a heat insulating
means provided between the plurality of adjacent heaters and
provided to surround at least one surface of the cast part
to heat-insulate the cast part.
Further, the heater of the continuous casting and hot
rolling apparatus according to another aspect of the present
invention may include an inductive coil connected to a power
supply source and provided to heat the cast part.
Further, the heater of the continuous casting and hot
rolling apparatus according to another aspect of the present
invention may further include a front-rear transport section
connected to the induction coil to move the induction coil
in the transportation direction of the cast part.
Also, the front-rear transport section of the
continuous casting and hot rolling apparatus according to
another aspect of the present invention may be provided to
Page 8
move the induction coil so as to be disposed at the same
interval.
Moreover, the continuous casting and hot rolling
apparatus according to another aspect of the present
invention further includes a cutting and drawing unit
provided with a cutter for cutting portions of the cast part,
and a drawer for removing the cut portions of the cast part,
the hot roller includes a first hot rolling section provided
to be connected to the rear end of the continuous casting
device, and a second hot rolling section provided to be
connected to the rear end of the first hot rolling section,
and the cutting and drawing unit may be provided between the
first hot rolling section and the second hot rolling section.
Further, the cutting and drawing unit of the continuous
casting and hot rolling apparatus according to another
aspect of the present invention may also be provided at the
front end of the heating unit.
Further, the hot roller of the continuous casting and
hot rolling device according to another aspect of the
present invention includes a first hot rolling section
provided to be connected to a rear end of the continuous
casting device, and a second hot rolling section provided to
be connected to the rear end of the first hot rolling
section, and the heating unit may be provided between the
first hot rolling section and the second hot rolling section.
Page 9
According to another aspect of the present invention,
there is provided a method for continuous casting and hot
rolling that includes a continuous casting operation of
producing a cast part, an even heating operation of
repeatedly heating the cast part at multiple points in a
transportation direction of the cast part, and a hot rolling
operation of pressing the cast part down after the even
heating operation.
Further, the method for continuous casting and hot
rolling according to another embodiment of the present
invention may further include a first cutting and drawing
operation of cutting and removing a tip portion of the cast
part discharged from the continuous casting device, in the
initial continuous casting in which the continuous casting
operation is started.
Further, the hot rolling operation of the method for
continuous casting and hot rolling according to another
aspect of the present invention includes a sequential hot
rolling operation of pressing the cast part down using a
plurality of pairs of rolling rolls, while gradually
reducing the width, at the time of switching to the
continuous hot rolling mode in which the cast part is
continuously provided and hot-rolled from a discontinuous
hot rolling mode in which the cast part produced in the
continuous casting operation is provided as a cut slab and
hot-rolled, and may further include a second cutting and
Page 10
drawing operation of cutting and removing a cast part
portion formed after the sequential hot rolling operation
and provided so that a thickness thereof is gradually
reduced.
【Advantageous Effects】
According to a hot rolling apparatus, and an apparatus
and a method for continuous casting and hot rolling of an
aspect of the present invention, there is provided an effect
capable of providing a cast part so as to be evenly hotrolled
and transmitted to the hot roller, by repeatedly
heating the cast part produced in the continuous casting
device at a plurality of points.
Thus, an effect in which a hot-rolled steel sheet of
high quality is produced by being evenly hot-rolled in the
hot roller may be realized.
Moreover, since the temperature range of the heating
temperature is within a range in which oxidation or the like
does not occur in the cast part, there is also an advantage
capable of preventing scale from being generated on the cast
part, while increasing the temperature for hot-rolling.
Meanwhile, an effect of removing the defect from the
cast part with an uneven thickness that may be generated
when switching from the discontinuous hot rolling mode to
the continuous hot rolling mode, by providing the cutting
and drawing unit between the first hot rolling section and
the second hot rolling section of the hot roller can be
Page 11
realized, thereby improving the overall quality of a hotrolled
steel sheet.
Further, when providing the cutting and drawing unit at
the front end of the first hot rolling section, there is
also an advantage in that the overall quality of a hotrolled
steel sheet may be improved, by removing the abnormal
cast part tip portion of the initial production of the
continuous casting device.
【Description of Drawings】
FIG. 1 is a diagram illustrating a conventional
continuous casting and hot rolling apparatus.
FIG. 2 is a side view illustrating a continuous casting
and hot rolling apparatus of the present invention.
FIG. 3 is a diagram and a graph illustrating a
temperature change of a cast part and a steel sheet
depending on positions of the continuous casting and hot
rolling apparatus of the present invention.
FIG. 4 is a plan view illustrating a heating unit in
the continuous casting and hot rolling apparatus of the
present invention.
FIG. 5 is a flowchart illustrating a method for
continuous casting and hot rolling of the present invention.
【Best Mode】
Page 12
Hereinafter, embodiments of the invention will be
described in detail with reference to the accompanying
drawings. The drawings are attached hereto to help explain
exemplary embodiments of the invention, and the present
invention is not limited to the drawings and embodiments.
In the drawings, some elements may be exaggerated, reduced
in size, or omitted for clarity or conciseness.
The hot rolling apparatus and the apparatus and method
for continuous casting and hot rolling of the present
invention relate to an invention that improves the quality
of a hot-rolled product by evenly heating a cast part 2 by
repeated heating the cast part 2 at multiple points prior to
being provided to a hot roller 200, and prevents a decrease
in quality of a steel sheet 2a and a reduction in a yield
percentage that may occur when switching to a continuous or
a discontinuous hot rolling mode.
Thus, it is possible to produce a high-quality hotrolled
steel sheet 2a by even hot-rolling the cast part 2 in
the hot roller 200.
Meanwhile, by providing a cutting and drawing unit 400
between a first hot rolling section 210 and a second hot
rolling section 220 of the hot roller 200, it is possible to
remove a defective steel sheet 2a with an uneven thickness
that may be generated when switching from the discontinuous
hot rolling mode to the continuous hot rolling mode, thereby
Page 13
improving the overall quality of the hot-rolled steel sheet
2.
Further, when the cutting and drawing unit 400 is
provided at the front end of the first hot rolling section
210, even by removing the tip portion of the abnormal cast
part 2 from the initial production of a continuous casting
device 100, the overall quality of the steel sheet 2a may be
improved.
Specifically, FIG. 2 is a side view illustrating the
continuous casting and hot rolling apparatus 1 of the
present invention, and FIG. 3 is a diagram and a graph
illustrating the temperature change of the cast part 2 and
the steel sheet 2a depending on the positions of the
continuous casting and hot rolling apparatus of the present
invention. That is, in FIG. 3, it is possible to check the
effect of even heating, by allowing a graph of temperature
change and the position of the continuous casting and hot
rolling apparatus of the present invention 1 to correspond
to each other.
Referring to FIGS. 2 and 3, the hot rolling apparatus
according to an embodiment of the present invention may
include a cast part supply section that produces the cast
part 2, the hot roller 200 receiving and hot-rolling the
cast part, and disposed to be linked to the cast part supply
section, and a heating unit 300 disposed between the cast
part supply section and the hot roller 200, and provided to
Page 14
reheat an outer surface in a thickness direction z of the
cast part 2, while latent heat is maintained in the central
portion in the thickness direction z of the cast part 2 by
preheating.
Further, the cast part 2 produced in the cast part
supply section of the hot rolling apparatus according to an
embodiment of the present invention is formed to have a
thickness of 70 to 120 mm, and the heating unit 300 heats an
outer surface portion of the cast part 2 to a temperature of
1250°C or less to allow an average temperature in the
thickness direction z of the cast part to be 1000°C or
higher.
Further, a continuous casting and hot rolling apparatus
1 according to another embodiment of the present invention
that includes the continuous casting device 100 producing
the cast part 2, the hot roller 200 receiving and hotrolling
the cast part 2, and disposed to be linked to the
continuous casting device 100, and a heating unit 300
provided at a front end of the hot roller 200 and evenly and
repeatedly heating the cast part 2 at a plurality of points.
Further, the heating unit 300 of the continuous casting
and hot rolling apparatus 1 according to another embodiment
of the present invention may include a plurality of heaters
310 which are disposed to be dispersed in a transportation
direction x of the cast part 2.
Page 15
Further, the heater 310 of the continuous casting and
hot rolling apparatus 1 according to another embodiment of
the present invention may be disposed to be dispersed in a
region corresponding to the length SL of the slab provided
by cutting the cast part 2 so that it is used in a
discontinuous hot rolling mode.
Further, the heating unit 300 of the continuous casting
and hot rolling apparatus 1 according to another embodiment
of the present invention may further include a heat
insulating means 320 provided between the plurality of
adjacent heaters 310 and provided to surround at least one
surface of the cast part 2 to heat-insulate the cast part 2.
Moreover, the continuous casting and hot rolling
apparatus 1 according to another embodiment of the present
invention further includes a cutting and drawing unit 400
provided with a cutter for cutting portions of the cast part,
and a drawer for removing the cut portions of the cast part
2, the hot roller 200 includes a first hot rolling section
210 provided to be connected to a rear end of the continuous
casting device 100, and a second hot rolling section 220
provided to be connected to a rear end of the first hot
rolling section 210, and the cutting and drawing unit 400
may be provided between the first hot rolling section 210
and the second hot rolling section 220.
Further, the cutting and drawing unit 400 of the
continuous casting and hot rolling apparatus 1 according to
Page 16
another embodiment of the present invention may also be
provided at the front end of the heating unit 300.
Further, the hot roller 200 of the continuous casting
and hot rolling apparatus 1 according to another aspect of
the present invention includes a first hot rolling section
210 provided to be connected to a rear end of the continuous
casting device 100, and a second hot rolling section 220
provided to be connected to the rear end of the first hot
rolling section 210, and the heating unit 300 may be
provided between the first hot rolling section 210 and the
second hot rolling section 220.
The cast part supply section serves to supply the cast
part 2 to the hot roller 200 and can be provided to produce
the cast part 2 for this purpose.
Here, the cast part 2 can be provided as a slab with a
thickness of 70 to 120 mm, and particularly, as an
embodiment, the cast part supply section can be provided as
the continuous casting device 100 in the continuous casting
and hot rolling process. That is, the following description
of the continuous casting device 100 may be a description of
the cast part supply section.
The continuous casting device 100 can serve to produce
the cast part 2 from the molten steel through the casting
process. That is, the continuous casting device 100
supplies the molten steel to a mold from a tundish, and the
supplied molten steel forms the cast part 2, while being
Page 17
deprived of quantity of heat, and the cast part 2 is guided
and moved by a segment roll and a pinch roll and can be
supplied to the hot roller 200 to be described later.
However, because the continuous casting device 100
produces the cast part 2 depending on the solidification
rate of the molten steel, it is difficult to adjust the
production rate. Therefore, when continuously receiving the
cast part 2 produced by the continuous casting device 100
and pressing by the hot roller 200 to be described later to
produce the hot-rolled steel sheet 2a, there is a limitation
in terms of speed.
Meanwhile, when the cast part 2 produced by the
continuous casting device 100 is discontinuously provided to
the hot roller 200 to produce the hot-rolled steel sheet 2a,
the hot roller 200 can rapidly perform the hot-rolling
operation independently of the production speed of the
continuous casting device 100 to produce a hot-rolled steel
sheet 2a.
In this manner, the process of producing the cast part
2 produced by the continuous casting device 100 into the
hot-rolled steel sheet 2a by the hot roller 200 can be
distinguished by a continuous hot rolling mode and a
discontinuous hot rolling mode, and the hot-rolling
operation can be performed, while varying the hot rolling
production modes.
Page 18
However, when varying the operation modes, there is a
problem of a degradation of the quality of the hot-rolled
steel sheet 2a. The cutting and drawing unit 400 can be
provided in the present invention in order to solve this
problem, and this will be described later in the description
of the cutting and drawing unit 400.
Also, there is also a problem of a degradation of the
quality of the hot-rolled steel sheet 2a in the initial
production of the continuous casting device 100, and this
will also be described later in the description of the
cutting and drawing unit 400.
The hot roller 200 can serve to receive the cast part 2
produced by the continuous casting device 100 and to press
the case slab 2, thereby producing the hot-rolled steel
sheet 2a. To this end, the hot roller 200 can press the
cast part 2, while causing the cast part 2 to pass between a
pair of hot-rolling rolls, and a plurality of pairs of hotrolling
rolls can be provided.
Furthermore, the hot roller 200 can be distinctively
provided in a first hot rolling section 210 or a second hot
rolling section 220, depending on the positions available.
Here, the first hot rolling section 210 is the hot
roller 200 provided to be connected to the rear end as an
output side of the continuous casting device 100, and
produces the hot-rolled steel sheet 2a in cooperation with
the second hot rolling section 220 in the continuous hot
Page 19
rolling mode. That is, because the hot-rolling process is
performed in the continuous hot rolling mode, by utilizing
the cast part 2 connected to the continuous casting device
100, when suddenly performing the hot-rolling, the
continuous casting device 100 is influenced. Thus, a first
hot-rolled steel sheet 2a having a constant thickness is
produced in the first hot rolling section 210, and the
completed second rolled steel sheet 2a is produced in the
second hot rolling section 220.
However, the first hot rolling section 210 can also
produce the hot-rolled steel sheet 2a in the discontinuous
hot rolling mode in cooperation with the second hot rolling
section 220, without being limited only to being used in the
continuous hot rolling mode.
In particular, the first hot rolling section 210
performs a sequential rolling operation, at the time of
transition from the discontinuous hot rolling mode to the
continuous hot rolling mode. That is, the hot-rolling
operation is initially performed using the cut cast part
(slab: 2) provided by cutting the cast part 2 in the
discontinuous hot rolling mode, and then, after transition
to the continuous hot rolling mode, the first hot rolling
section 210 continuously receives the provision of the cast
part 2 produced in the continuous casting device 100. At
this time, when the first hot rolling section 210 suddenly
presses down the cast part 2, the continuous casting device
Page 20
100 is influenced. In this case, a strap is generated,
while the cast part 2 is pushed, thereby causing defects on
the cast part 2.
To prevent these defects, the first hot rolling section
210 sequentially reduces a gap between the pair of hotrolling
rolls to perform the sequential hot-rolling when
switching from the discontinuous hot rolling mode to the
continuous hot rolling mode.
However, when performing such a sequential hot-rolling,
a steel sheet 2a including a thickness transition zone in
which the thickness of the first hot-rolled steel sheet 2a
produced by the first hot rolling section 210 is gradually
reduced is produced, which degrades the quality of the hotrolled
steel sheet 2a. In order to remove such defective
steel sheet 2a, a cutting and drawing means can be provided
in the present invention, and a detailed description thereof
will be provided later in the description of the cutting and
drawing unit 400.
Meanwhile, the first hot rolling section 210 receives
the cast part 2 produced by the continuous casting device
100 to produce the first hot-rolled steel sheet 2a. At this
time, because the cast part 2 provided by being produced in
the continuous casting device 100 is provided in a state of
an uneven temperature distribution in the thickness
direction z of the order cast part 2, the quality of the
produced hot-rolled steel sheet 2a is degraded. To solve
Page 21
this problem, the present invention provides a heating unit
300, and a description of the heating unit 300 will be
provided later.
The second hot rolling section 220 can serve to
directly receive the first hot-rolled steel sheet 2a
produced in the first hot rolling section 210 or the cast
part 2 produced in the continuous casting device 100, and to
produce a final second rolled steel sheet 2a. The second
hot rolling section 220 also presses down the cast part 2
moved between a pair of hot-rolling rolls to produce the
hot-rolled steel sheet 2a, and the hot-rolled steel sheet 2a
thus produced is wound around a rewinder R and is finally
discharged.
To this end, the second hot rolling section 220 can be
provided to be connected to a rear end as an output side of
the first hot rolling section 210, and the cutting and
drawing unit 400 or the like can be provided between the
second hot rolling section 220 and the first hot rolling
section 210.
The heating unit 300 can serve to evenly heat the cast
part 2 provided by being produced in the continuous casting
device 100 and to provide it to the hot roller 200. That is,
the heating unit 300 is provided between the rear end as the
output side of the continuous casting device 100 and the
front side as the input side of the hot roller 200, and can
be provided to form an even temperature distribution in the
Page 22
thickness direction z of the cast part 2, by repetitive
heating in a plurality of points.
In addition, the heating unit 300 may also be provided
between the first hot rolling section 210 and the second hot
rolling section 220. That is, even after the first hot
rolling section 210 is formed into the cast part 2 by the
first hot-rolled steel sheet 2a, since it may be necessary
to raise the temperature for hot-rolling using the second
hot rolling section 220, the heating unit 300 can also be
provided in the first hot rolling section 210 and the second
hot rolling section 220.
Here, when the cast part 2 is generally heated only
once, due to the short heating time, in the process of the
heat transferred to the surface of the cast part 2 being
transferred to the center of the cast part 2, the surface of
the cast part 2 is cooled. At the time when the cast part 2
is transferred to the hot roller 200, an uneven temperature
distribution is formed in the thickness direction z of the
cast part 2, and the hot rolling is performed using the cast
part 2 of the uneven temperature distribution.
However, because heating is performed at a plurality of
points before transferring the cast part 2 to the hot roller
200 in the present invention, the time being provided to the
even temperature distribution increases, and the hot roller
200 hot-rolls the cast part 2 of even temperature
Page 23
distribution. Accordingly, it is possible to produce a
high-quality hot-rolled steel sheet 2a.
That is, by performing heating on the surface of the
cast part 2, and by re-heating the surface of the cast part
2 during the time when heat is transferred to the center of
the cast part 2, it is possible to extend the time at which
the cast part 2 is distributed at an even temperature in the
thickness direction z.
Furthermore, when repeating this process, it is
possible to increase the time of such an even temperature
distribution, and the evenly heated cast part 2 is
transmitted to the hot roller 200 and is provided at an even
temperature distribution even during the pressed-down time,
and it is possible to produce a high-quality hot-rolled
steel sheet 2a.
In this manner, the even heating of the cast part 2 can
be determined due to the fact that the cast part 2 is
provided to reheat the outer surface in the thickness
direction z of the cast part 2, while latent heat is
maintained at the central portion in the thickness direction
z of the cast part 2 by preheating.
That is, when heat is transferred to the outer surface
portion as the surface of the cast part 2 by preheating, the
heat is conducted and transferred to the central portion as
an intermediate portion in the thickness direction z of the
cast part 2. The outer surface portion is cooled during the
Page 24
time when heat is conducted, and an uneven temperature
distribution is generated.
At this time, the outer surface portion is reheated
again for the even temperature distribution. However, such
reheating needs to be performed before the central portion
is cooled, in order to allow the average temperature of the
cast part 2 to rise at the even temperature distribution.
Further, the temperature for heating the outer surface
portion is desirably limited to a temperature at which the
outer surface portion is not oxidized in order to improve
the quality of the final hot-rolled steel sheet 2a. That is,
it is desirable to heat the outer surface portion to about
1250°C or less in order to prevent an occurrence of scale
caused by oxidation. In addition, heating to the
temperature of 1500°C or higher is less desirable because
this temperature is close to the melting point of the cast
part 2.
Meanwhile, it is also desirable to provide a plurality
of heaters 310 and perform repeated heating, in order to
improve the temperature in the thickness direction z of the
cast part 2 including the central portion, while the
temperature of the outer surface portion is restricted.
According to this, since it is possible to set an
average temperature in the thickness direction z of the cast
part 2 including the central portion and the outer surface
portion of the cast part 2 to 1000°C or higher, preferably
Page 25
1200°C or higher, the average temperature can be provided as
a temperature for hot-rolling.
In this manner, the heating unit 300 may provide a
plurality of heaters 310 for repeatedly heating at a
plurality of points. Since such heaters 310 are disposed to
be dispersed in the transportation direction x of the cast
part 2, the heaters can be provided to heat the cast part 2
a plurality of times, while the same portion of the cast
part 2 is transferred.
Meanwhile, the heater 310 can be provided by being
distributed in a region corresponding to the length SL of
the slab, namely, the cut cast part 2 provided by cutting
the cast part 2 in the discontinuous hot rolling mode. In
such a case, by evenly heating the entire cut cast part 2
before being cut by the hot roller 200, it is possible to
produce a high-quality hot-rolled steel sheet 2a even in a
discontinuous hot rolling mode.
Here, the heater 310 can provide an induction coil 311
for heating the cast part 2, and in such a case, the heating
temperature can be adjusted. This will be described later
in detail with reference to FIG. 4.
Further, as a transport means for adjusting the
distance between the plurality of the heaters 310 or
disengaging the heater 310 in the transportation path of the
cast part 2, a front-back transport section 312 and a leftPage
26
right transport section 313 can be included. This will also
be described later with reference to FIG. 4.
The heating unit 300 may further include a heat
insulating means 320 to further extend the even temperature
holding time of the cast part 2 that forms an even
temperature region by the heater 310. That is, the heat
insulating means 320 is provided to surround at least one
surface of the cast part 2, and can serve to maintain the
temperature of the cast part 2.
To this end, the thermal insulating means 320 can be
provided in a portion between a plurality of the heaters 310.
That is, in order to wrap the cast part 2, the heat
insulating means 320 can be provided except for the portions
in which the heaters 310 are provided.
Meanwhile, the heat insulating means 320 is desirably
provided to wrap the cast part 2 in all circumferential
directions thereof, for efficient thermal insulation, and in
order to increase the thermal insulation ratio, the heat
insulating means 320 may be provided to supply a heatinsulating
gas.
Such a heat insulating means 320 can also be formed of
refractory brick made of a ceramic-based material.
Meanwhile, the heat insulating means 320 may also be
provided as a heat insulation holding furnace. That is, the
heat insulating means 320 may also be provided inside the
Page 27
hest insulating means serving as a heat insulation holding
furnace.
The cutting and drawing unit 400 may serve to cut and
draw a part of the cast part 2. That is, the cutting and
drawing unit 400 can serve to remove the defective cast part
2 or steel sheet 2a of the cast part 2 and the steel sheet
2a to the outside after cutting. To this end, the cutting
and drawing unit 400 can include a cutter such as a first
cutter 411, a second cutter 421 and a third cutter 430, and
a drawer such as a first drawer 412 and a second drawer 422.
Meanwhile, a plurality of cutting and drawing units 400
can be provided in a plurality of positions, and can be
provided as a first cutting and drawing section 410 provided
at the rear end of the continuous casting device, and a
second cutting and drawing section 420 provided between the
first hot rolling section 210 and the second hot rolling
section 220.
The first cutting and drawing section 410 may serve to
remove the defective cast part 2 in the cast part 2 provided
by being produced in the continuous casting device 100.
That is, in the initial state of the continuous casting
process using the continuous casting device 100, the
defective cast part 2 having failed to reach the required
condition is produced and discharged. When such a cast part
2 is transmitted to the hot roller 200 without change, the
Page 28
quality of the hot-rolled steel sheet 2a is significantly
degraded.
Therefore, in order to remove such a defective cast
part 2, the first cutting and drawing section 410 is
provided at the rear end of the continuous casting device
100. That is, when the first cutter 411 of the first
cutting and drawing section 410 first cuts the defective
cast part 2, the first drawer 412 of the first cutting and
drawing section 410 removes the cut defective cast part 2 to
prevent it from being transmitted to the hot roller 200.
The second cutting and drawing section 420 is provided
between the first hot rolling section 210 and the second hot
rolling section 220, and can serve to remove a defective
cast part 2 of the first hot-rolled steel sheet 2a
discharged from the first hot rolling section 210.
That is, in a case where the first cutting drawer
portion 410 is not provided, when the first hot rolling
section 210 presses and provides the defective cast part 2
generated in the continuous casting device 100 in the
initial continuous casting, the second cutting and drawing
section 420 can serve to remove the defective steel sheet 2a
provided by pressing the defective cast part 2 down.
In particular, the second cutting and drawing section
420 can improve the overall quality of the hot-rolled steel
sheet 2a by removing the defective steel sheet 2a with the
uneven thickness generated when switching from the
Page 29
discontinuous hot rolling mode to the continuous hot rolling
mode.
To this end, the second cutting and drawing section 420
can also provide a second cutter 421 for cutting the
defective steel sheet 2a, and a second drawer 422 for
removing the cut defective steel sheet 2a.
Meanwhile, the cutting and drawing unit 400 can also
include a third cutter 430 provided at the rear end as the
output side of the second hot rolling section 220 so as to
cut the coil steel sheet 2a produced in the continuous hot
rolling mode.
FIG. 4 is a plan view illustrating the heating unit 300
in the continuous casting and hot rolling apparatus 1 of the
present invention. Referring to FIG. 4, the heater 310 of
the continuous casting and hot rolling apparatus 1 according
to another embodiment of the present invention may include
an induction coil 311 connected to a power supply source 315
to heat the cast part 2.
Further, the heater 310 of the continuous casting and
hot rolling apparatus 1 according to another embodiment of
the present invention can further include a front-back
transport section 312 connected to the induction coil 311 so
as to move the induction coil 311 in the transportation
direction x of the cast part 2.
Further, the front-back transport section 312 of the
continuous casting and hot rolling apparatus 1 according to
Page 30
another embodiment of the present invention can provide the
induction coil 311 by moving it so as to be arranged at the
same interval.
That is, the heater 310 provides the induction coil 311
capable of being induction-heated, and can include the
front-back transport section 312 or the like capable of
setting the position of the heater 310.
Here, when the heater 310 is heated using the induction
coil 311, although it is possible to adjust the temperature
for heating the cast part 2. The heating amount may be
differently set depending on the position at which the
heater 310 is provided accordingly, and it may also be
provided to gradually increase the heating amount.
However, when the heater 310 utilizes the induction
coil 311, since the outer surface portion in the thickness
direction z of the cast part 2 adjacent to the induction
coil 311 has a magnetic flux greater than that of the
central portion in the thickness z of the cast part 2, the
outer surface portion generates much more heat and is heated
more.
In this manner, in order to adjust the heating amount
of the induction coil 311, the induction coil 311 may be
connected to the power supply source 315, and a control unit
314 for control may be provided.
The adjustment of the heating amount of the induction
coil 311 may also include the on/off function of the
Page 31
induction coil 311. That is, turning the induction coil 311
on or off can also be controlled by controlling whether or
not to supply the power in the power supply source 315.
The induction coil 311 can be provided by winding the
coil around the core for induction heating. The core can be
provided in the width direction y of the cast part 2, and
the coil can be provided by being wound around the core to
be able to heat the cast part 2 in the overall width
direction y thereof.
Meanwhile, the induction coil 311 may be provided on
both of the upper and bottom surfaces of the cast part 2, is
provided in a “U” shape for structural stability, and can
also be provided so that the side surface of the cast part 2
is inserted.
The front-back transport section 312 can adjust the
interval of the adjacent induction coil 311, while moving
the induction coil 311 in the transportation direction x of
the cast part 2. To this end, the front-back transport
section 312 is provided to be connected to the induction
coil 311 and may be provided as an oil pneumatic cylinder.
Further, in order to stably move the induction coil 311
provided long in the width direction y of the cast part 2
back and forth, an oil pneumatic cylinder of the front-back
transport section 311 may be provided at each end portion of
the induction coil 311.
Page 32
Meanwhile, the front-back transfer 312 can be provided
to be able to adjust the interval by being connected to the
control unit 314, and by adjusting the interval between the
adjacent induction coils 311, the induction coil 311 can be
disposed at an interval with the highest even heating effect.
Thus, the induction coil 311 disposed by the front-back
transport section 312 may also be provided to be disposed
between the adjacent induction coils 311 at equal intervals,
and in this case that, since the cast part 2 is heated at
the same interval, it is possible to perform the temperature
rise and the even heating at a constant rate, and it is
possible to stably improve the even heating efficiency.
Further, the heater 310 may also include a left-light
transport section 313 that can move the induction coil 311
in the width direction y of the cast part 2. That is, the
induction coil 311 can be provided to be movable onto or to
be removed from the transportation path of the cast part 2.
According to this, in order to heat the cast part 2,
the induction coil 311 comprises cast part 2 can be provided
to move to the top surface or the bottom surface of the cast
part 2, and when not heating the cast part 2, the heater 310
is removed from the transportation path of the cast part 2
to prevent an occurrence of a problem such as collision with
the cast part 2.
To this end, the left-right transport section 313 can
provide a moving plate 313b provided with the front-back
Page 33
transport section 312 and the induction coil 311, and a
motor 313a for driving the moving plate 313b. That is, the
induction coil 311 and the front-back transport section 312
can be moved as a whole left and right. The moving plate
313b can be connected to the motor 313a through a chain, and
the chain can move by receiving the transmission of the
driving force by sprocket provided by the motor 313a.
However, the driving force for moving the moving plate
313b is not limited to being provided by the motor 313a, and
the driving force may be transmitted by hydraulic or
pneumatic cylinders.
Further, in order that the moving plate 313 is provided
on the moving path of the cast part 2, a wheel may also be
coupled to the bottom surface.
Meanwhile, a plurality of moving plates 313b may be
provided by being spaced apart from each other to move the
respective induction coils 311 while supporting the coils,
and a moving roll for supporting the cast part 2 may be
provided between the moving plates 313b spaced apart from
each other.
FIG. 5 is a flowchart illustrating the method for
continuous casting and hot rolling of the present invention.
Referring to FIG. 5, the continuous casting and hot rolling
method according to another embodiment of the present
invention may include a continuous casting operation of
producing a cast part 2, an even heating operation of
Page 34
repeatedly heating the cast part 2 at multiple points in a
transportation direction x of the cast part 2, and a hot
rolling operation of pressing the cast part down after the
even heating operation.
Further, the method for continuous casting and hot
rolling according to another embodiment of the present
invention may further include a first cutting and drawing
operation of cutting and removing a tip portion of the cast
part 2 discharged from the continuous casting device 100, in
the initial continuous casting in which the continuous
casting operation is started.
Further, the hot rolling operation of the method for
continuous casting and hot rolling according to another
aspect of the present invention includes a sequential hot
rolling operation of pressing the cast part 2 down using a
plurality of pairs of rolling rolls, while gradually
reducing the width, at the time of switching to the
continuous hot rolling mode in which the cast part 2 is
continuously provided and hot-rolled from a discontinuous
hot rolling mode in which the cast part 2 produced in the
continuous casting operation is provided as a cut slab and
hot-rolled, and may further include a second cutting and
drawing operation of cutting and removing the cast part 2
portion formed after the sequential hot rolling operation
and provided so that a thickness thereof is gradually
reduced.
Page 35
The continuous casting operation is a operation of
generating the cast part 2 by the continuous casting device
100, and provides the cast part 2 by receiving the molten
steel by the continuous casting. At the initial continuous
casting, a defective cast part 2 may fail to reach the
required state. However, this may be cut and removed by the
cutting and drawing unit 400 connected to the rear end of
the continuous casting device 100 at the first cutting and
drawing operation.
The even heating operation is a operation for
generating a cast part 2 with an excellent quality, by
evenly heating the cast part and transmitting it to the hot
roller 200. To this end, the cast part 2 can have an even
temperature distribution, by being repeatedly heated at a
plurality of points through the heating unit 300.
Such an even heating operation needs to be performed
prior to a hot rolling operation to be described later to
improve the quality of the hot-rolled steel sheet 2a
produced by pressing the cast part 2 down. That is, it is
desirable to perform the even heating operation prior to the
first hot rolling operation, the second hot rolling
operation and the sequential hot rolling operation of the
hot rolling operation to be described later in order to
improve the quality of the hot-rolled steel sheet 2a.
The hot rolling operation is a operation of receiving
the cast part 2 produced in the continuous casting operation
Page 36
and pressing the cast part down to produce a hot-rolled
steel sheet 2a. It is desirable to perform the hot rolling
operation after passing through the even heating operation
in order to produce a hot-rolled steel sheet 2a with an
excellent quality.
Here, in the hot rolling operation, the cast part can
be pressed down separately into the first hot rolling
operation and the second hot rolling operation to prevent an
influence on the continuous casting device 100 in the
continuous hot rolling mode of receiving the cast part 2
produced in the continuous casting operation and producing
the hot-rolled steel sheet 2a.
That is, the first hot rolling operation is a operation
provided by pressing the cast part down to form only the
thickness of the constant portion, before forming the final
thickness of the hot-rolled steel sheet 2a, and the second
hot rolling operation is a operation of producing a final
second hot-rolled steel sheet 2a, by pressing down the first
hot-rolled steel sheet 2a after passing through the first
hot rolling operation.
The first hot rolling operation is performed after the
continuous casting operation, and the second hot rolling
operation can be performed after the first hot rolling
operation. However, in order to improve the quality of the
hot-rolled steel sheet 2a, the even heating operation can be
performed between the continuous casting operation, the can
Page 37
be performed during the first hot rolling operation and the
first hot rolling operation, and can also be performed
between the first hot rolling operation and the second hot
rolling operation.
Here, the even heating operation between the first hot
rolling operation and the second hot rolling operation can
be defined as an additional heating operation, since the
meaning of additional heating is present.
Meanwhile, the cast part 2 having failed to reach the
requested state is produced in the initial continuous
casting, the first cutting and drawing operation of removing
the defective cast part 2 can be performed, and such a first
cutting and drawing operation can be performed by
determining whether there is initial continuous casting.
When the first cutting and drawing operation is
performed, the first cutter 411 provided at the rear end of
the continuous casting device 100 is operated to cut a
defective tip portion produced in the continuous casting
device 100, and thereafter, the cut defective cast part 2 is
drawn and removed to the outside by the first drawer 412.
In addition, the method for continuous casting and hot
rolling of the present invention may be performed, while
changing the production mode to the continuous hot rolling
mode and the discontinuous hot rolling mode. There is no
problem at the time of the change from the continuous hot
rolling mode to the discontinuous hot rolling mode. However,
Page 38
at the time of the change from the discontinuous hot rolling
mode to the continuous hot rolling mode, since the
continuous casting device 100 may be affected, a special
operation can be performed.
That is, when the cast part 2 provided by being
continuously produced by the continuous casting device 100
is suddenly pressed down by the hot roller 200, due to a
decrease in thickness, the production rate of the continuous
casting device 100 suddenly becomes slower and the cast part
2 is pushed, and a strap may be generated on the cast part 2
accordingly.
In order to prevent an occurrence of the strap, a
sequential hot rolling operation is provided in the hot
rolling operation. That is, by performing hot rolling,
while reducing a gap of the rolling roll pair of the first
hot rolling section 210, it is possible to prevent an impact
from being applied to the continuous casting device 100.
However, a steel 2a in which a thickness transition
portion having a gradually decreasing thickness exists is
produced in such a continuous hot rolling operation, and
since the portion of the steel sheet 2a degrades the quality
when pressing down in the second hot rolling section 220, it
is desirable to cut and remove the portion.
To this end, the second cutting and drawing operation
can be performed after the sequential hot rolling operation.
The second cutting and drawing operation cuts the portion of
Page 39
the defective steel sheet 2a discharged from the first hot
rolling section 210 using the second cutter 421, and the cut
defective steel sheet 2a is discharged to the outside from
the second drawer 422 to improve the overall quality of hotrolled
steel sheet 2a.
Meanwhile, since the hot-rolled steel sheet 2a is
produced so as not to include such a defective steel sheet
2a, it is possible to prevent a problem in which an overall
coil steel sheet 2a produced by some of defective steel
sheet 2a.
Page 40
【WE CLAIM:】
【Claim 1】
A hot rolling apparatus comprising:
a cast part supply section producing a cast part;
a hot roller receiving and hot-rolling the cast part,
and disposed to be linked to the cast part supply section;
and
a heating unit disposed between the cast part supply
section and the hot roller and provided to reheat an outer
surface portion of the cast part in a thickness direction,
while latent heat is retained in a central portion in the
thickness direction of the cast part by preheating.
【Claim 2】
The hot rolling apparatus of claim 1, wherein the cast
part produced by the cast part supply section is formed to
have a thickness of 70 to 120 mm, and
the heating unit heats the outer surface portion of the
cast part to a temperature of 1250°C or less, thereby
allowing an average temperature in the thickness direction
of the cast part to be 1000°C or higher.
【Claim 3】
A continuous casting and hot rolling apparatus
comprising:
a continuous casting device producing a cast part;
Page 41
a hot roller receiving and hot-rolling the cast part,
and disposed to be linked to the continuous casting device;
and
a heating unit provided at a front end of the hot
roller and evenly and repeatedly heating the cast part at a
plurality of points.
【Claim 4】
The continuous casting and hot rolling apparatus of
claim 3, wherein the heating unit comprises a plurality of
heaters, disposed to be dispersed in a transportation
direction of the cast part.
【Claim 5】
The continuous casting and hot rolling apparatus of
claim 4, wherein the heaters are disposed to be dispersed in
a region corresponding to a length of a slab provided by
cutting the cast part so that the heaters are used in a
discontinuous hot rolling mode.
【Claim 6】
The continuous casting and hot rolling apparatus of
claim 5, wherein the heating unit further comprises a heat
insulating means provided between the plurality of adjacent
heaters and provided to surround at least one surface of the
cast part to heat-insulate the cast part.
【Claim 7】
Page 42
The continuous casting and hot rolling apparatus of
claim 4, wherein the heater comprises an inductive coil
connected to a power supply source and provided to heat the
cast part.
【Claim 8】
The continuous casting and hot rolling apparatus of
claim 7, wherein the heater further comprises a front-rear
transport section connected to the induction coil to move
the induction coil in the transportation direction of the
cast part.
【Claim 9】
The continuous casting and hot rolling apparatus of
claim 8, wherein the front-rear transport section is
provided to move the induction coil so as to be disposed at
the same interval.
【Claim 10】
The continuous casting and hot rolling apparatus of
claim 3, further comprising:
a cutting and drawing unit provided with a cutter for
cutting portions of the cast part, and a drawer for removing
the cut portions of the cast part,
wherein the hot roller comprises
a first hot rolling section provided to be
connected to the rear end of the continuous casting
device; and
Page 43
a second hot rolling section provided to be
connected to the rear end of the first hot rolling
section, and
the cutting and drawing unit is provided between the
first hot rolling section and the second hot rolling section.
【Claim 11】
The continuous casting and hot rolling apparatus of
claim 10, wherein the cutting and drawing unit is also
provided at the front end of the heating unit.
【Claim 12】
The continuous casting and hot rolling apparatus of
claim 3, wherein the hot roller comprises:
a first hot rolling section provided to be connected to
a rear end of the continuous casting device; and
a second hot rolling section provided to be connected
to the rear end of the first hot rolling section, and
the heating unit is provided between the first hot
rolling section and the second hot rolling section.
【Claim 13】
A method for continuous casting and hot rolling, the
method comprising:
a continuous casting operation of producing a cast
part;
Page 44
an even heating operation of repeatedly heating the
cast part at multiple points in a transportation direction
of the cast part; and
a hot rolling operation of pressing the cast part down
after the even heating operation.
【Claim 14】
The method of claim 13, further comprising:
a first cutting and drawing operation of cutting and
removing a tip portion of the cast part discharged from the
continuous casting device, in the initial continuous casting
in which the continuous casting operation is started.
【Claim 15】
The method of claim 13, wherein the hot rolling
operation comprises a sequential hot rolling operation of
pressing the cast part down using a plurality of pairs of
rolling rolls, while gradually reducing the width, at the
time of switching to the continuous hot rolling mode in
which the cast part is continuously provided and hot-rolled
from a discontinuous hot rolling mode in which the cast part
produced in the continuous casting operation is provided as
a cut slab and hot-rolled, and
the method further comprising:
a second cutting and drawing operation of cutting and
removing a cast part portion formed after the sequential hot
Page 45
rolling operation and provided so that a thickness thereof
is gradually reduced.