MANDREL OF COIL BOX
[Technical Field]
The present disclosure relates to a mandrel of a coil
box, and more part~cularly, to a mand,rel of a coil box for
prevknting cooling and plastic deformation of a leading end
portion of a bar inserted through a slot in the mandrel and
reducing the insertion length of the leading end portion.
[~ack~roun~dr t l
FIG. 1 is a view illustrating a rolling apparatus
including a coil box.100 in the related art.
Referring to FIG. 1, a continuous casting process is
performed using a ladle 5 filled with molten steel refined
in a steel making process, a tundish 10 configured to
receive the molten steel from the ladle 5 through an
injection nozzle connected to the ladle 5 and temporarily
store the molten steel, a mold 15 configured to receive the
molten steel and initially solidify the molten steel in a
predetermined shape, and a plurality of segments 20
disposed below the mold 15, to perform a series .of
operations for bending or stretching a non-solidified slab
while cooling the slab.
In such a continuous casting process, a slab is
Page 1
cooled and reduced while passing through the segments 20.
After passing through the segments 20, the slab may be '
subjected to rough rolling, shearing, and heating by a
roughing mill 25, shears 30 and 35, and an i r i d u c t i v e heater
40.
The slab may be formed as a bar 1 through such
processes and fed to the coil.box 100 so as to be coiled or
uncoiled.
For example, if coiling or uncoiling in the coil box
100 is delayed, a bar 1, being continuously fed, may be
processed as plate scrap by the shears 30 and 35
#
A shear 45, a finishing mill 50, a run-out table 55,
a final shear 60, and a coiler 70 may be sequentially
arranged after the coil box 100 so that the bar 1
discharged from the coil box 100 may be continuously rolled,
sheared, and coiled as a coil.
The above-explained processes are examples to which a
coil box of the present disclosure may be applied. The
coil box of the present disclosure may be used in various
steel processing processes.
In a hot direct rolling process, the coil box 100
functions as a buffer to allow a continuous process. The
coil box 100 will now be described in more detail with
reference to FIGS. 2 to 5.
Page 2
XPO' DEQHI 1 7 - 8 7 - 2 0 1 5 16117
FIG. 2 is a perspective view illustrating the coil
box 100 in 'the rolling apparatus illustrated in FIG. 1, FIG.
3 is another perspective view illustrating the coil box 100
of FIG. 2, FIG. 4 is a plan view illustrating the coil box
,100 of FIG. 2, and FIG. 5 is a.cross-sectional view taken
along line I-If of FIG. 4.
The coil box' 100 may coil a roughly-rolled bar 1 and
maintain the bar 1 at a constant temperature to redlice
temperature and texture differences between the leading and
trailing ends of the bar 1.
An introduction unit 112 is installed in front of the
coil box 100, and a bar 1 is introduced to the coil box 100
through the introduction unit 112. A leveler 116 is
installed behind the coil box 100, and the bar 1 is
discharged thro.ugh the leveler 116.
A carousel 130 may be disposed in the coil box 100
for coiling or uncoiling a bar 1. The carousel 130 may
swing mandrels 132 to shift the positions of the mandrels
132. The carousel 130 may be connected to a driving unit
140.
The carousel 130 may include the mandrels 132 and
rotating wheels 134.
The mandrels 132 are provided as a pair. One of the
mandrels 132 (first mandrel 132) is ,used to coil a bar 1
Page 3
introduced to the coil box 100, and the other of the
mandrels 132 (second mandrel 132') is used to uncoil and
discharge another bar 1, previously coiled.
After the first mandrel 132 coils a bar 1 and the
second mandrel 132' uncoils a bar 1, the carousel 130 may
rotate the. rotating. wheels 134 using the driving unit 140
to shift the positions of the first and second mandrels 132
and 132'. Then, the first mandrel 132 around which the bar
1 is coiled uncoils the bar 1, and the second mandrel 132'
around which no bar 1 is coiled coils a newly-introduced
bar 1.
In this manner, the carousel 130 shifts the positions
of the first and second mandrels 132 and 1.32' to shift
coiling and uncoiling and thus to allow for continuous
processing.
Motors 136 may be connected to the first and second
mandrels 132 and 132' to rotate the first and second
mandrels 132 and 132', and decelerators 138 may be
connected to the first and second mandrels 132 and 132' to
,control the rotating speeds thereof.
In the above-described coil box 100, a passage
through which a leading end portion of a bar 1 is inserted
into the mandrel 132 (hereinafter, the first and second
mandrels 132 and 132' will be collectively referred to as a
mandrel 132) for coiling may be precisely tracked and
controlled so as to prevent coiling failure and perform a
continuous process without interruption.
[Technical problem]
An aspect of the present disclosure may provide a
mandrel of a coil box, the mandrel including a guide part
protruding from an edge wall of a slot of the mandrel into
the mandrel to prevent a leading end portion of a bar
inserted through the 'slot from making contact with a center
shaft, thereby preventing coo'ling and plastic deformation
of the leading end portion and reducing the insertion
length of the leading end portion.
[Technical ~olutionl
According to an aspect of the present disclosure, a
mandrel of a coil box includes: a cylindrical mandrel main
body in which a center shaft is disposed, the mandrel main
body including a slot to receive a leading end portion of a
high-temperature bar; and a guide 'part formed from an edge
wall of the slot toward an inner side of the mandrel main
body so as to prevent cooling and plastic deformation of
the leading end portion of the bar inserted through the
slot.
The guide part may protrude from the edge wa.11 of the
Page 5
slot to prevent the leading end portion of the bar from
making contact with the center shaft when the leading end
portion of the bar is inserted through the slot.
An inner end of the guide part may be spaced apart
from an inner end of an opposite edge wall of the slot by
90 mm to 110 mm.
The guide part may be sloped in a manner such that an
inner gap of the slot is smaller than an outer gap of the
slot.
An outer end of the guide part may be spaced apart
from an outer end of an opposite edge wall of the slot by
200 mm to 300 mm.
The guide part may be formed in one piece with the
mandrel main body and may 'extend from the edge wall of the
slot toward the inner side of the mandrel main body.
The guide part may protrude from the edge wall of the slot
and taper toward the inner side of the mandrel main body
A counterweight may be provided 'on a side of the
mandrel main body opposite to the guide part so as not to
bias a center of gravity of the mandrel toward the guide
part.
[~dvantageous ~ffectsl
As set forth above, according to exemplary
embodiments of the present disclosure, the guide part
Page 6
protruding from the edge wall of the slot of the mandrel
into the mandrel prevents a leading end portion of a, bar
inserted through the slot from making contact with the
center shaft, thereby preventing cooling and plastic
deformation of the leading' end portion and reducing the
insertion length of the leading end portion.
Therefore, during thin-plate rolling, a tail portion
(corresponding to a leading end portion of a bar in mandrel
coiling) may have a uniform temperature and thus may not be
curled or tangled. Thus, work rolls may not be damaged by
a curled or tangled bar, and product quality may not be
deteriorated.
In addition, the length of a leading end portion of a
bar inserted through the slot into the mandrel may be
shortened, and when the bar is coiled around the mandrel, a
portion of the bar making cont'act with the opposite edge
wall of the slot may not be easily bent and plastically
deformed. That is, deflection of the leading end portion
of the bar may be prevented when the bar is coiled, and
since the leading end portion is brought into contact with
the guide part and supported on the guide part with an
appropriate contact force therebetween, initial turns of
the bar may be smoothly formed when the bar is coiled
around the mandrel. Thus, the coiling process may not be
Page 7
suspended due to initial turn errors.
[Description of Drawings]
F I G . 1 is a view illustrating a rolling apparatus
including a coil box according to the related art;
F I G . 2 is a perspective view illustrating the coil
box of the rolling apparatus illustrated FIG. 1;
FIG. 3 is another perspective view illustrating the
coil box of F I G . 2;
F I G . 4 is a plan view illustrating,the coil box of
F I G . 2;
F I G . 5 is a cross-sectional view taken along line II'
of FIG. 4 ;
F I G . 6 is a view illustrating how the leading end
portion of a bar is inserted into a slot oE a mandrel and
is coiled in the related art; and
F I G . 7 is a view illustrating how the- leading end
portion of a bar is inserted into a slot of a mandrel of a
coil box and is coiled according to an exemplary embodiment
of the present disclosure.
First, with reference to F I G . 6, an explanation will
be given of how a leading end portion l a of a bar 1 is
. .
inserted into a slot 132a of a mandrel 132 and is coiled. in
the related art.
Page 8
FIG. 6 is a view illustrating how the leading end
portion la of the bar 1 is inserted into the.slot 132a of
the mandrel 132 and is coiled in the related art.
Referring to FIG. 6, the bar 1, heated to a high
temperature and having a thickness of 16 mrn to 23 mrn, is
coiled in the mandrel 132 as follows. The leading end
portion la of the bar 1 is inserted into the mandrel 132
through the slot 132a (having a gap of 310 mm) by a length
of about 800 mm to 1,000 mrn. Then, the leading end portion
la of the bar 1 is brought into contact with a center shaft
133 o£ the mandrel 132, and as the mandrel 132 rotates, the
leading end portion la is brought into contact with an
opposite edge wall 132c of the slot 132a. Then, the
leading end portion la is bent at a position making contact
with the opposite edge wall 132c and brought into contact
with the outer surface of the mandrel 132. In this manner,
an initial inner turn of the bar 1 is formed and the bar 1
-
is coiled.
The center shaft 133 is disposed in the mandrel 132
to support the mandrel 132 placed in a coi.1. box having a
high temperature (1,100°~)a,n d coolant flows in the center
shaft 133.
Although the center shaft 133 is coated with an
insulator having a triple structure, the leading end
Page 9
portion la . (about 800 mm to 1,000 mm) of the bar 1,
inserted in the mandrel 132 and making contact with the
center shaft 133, is inevitably cooled because temperature
around the center shaft 133 is about 650°C due to the
influence of coolant flowing in the center shaft 133.
Furthermore, during finishing rolling, a cooled
portion of the bar 1 may be rolled at a temperature lower
than an Ar3 transformation point to cause structural
failures.and texture errors, and during thin-plate rolling,
a tail portion may have a non-uniform temperature and thus
may be curled or tangled. Such failures or defects may
damage- work rolls to result in product quality
deterioration and even workplace accidents such as roll
breakage. The above-mentioned tail portion may correspond
to the leading end portion la of the coiled bar 1. That is,
during uncoiling, the leading end portion 'la becomes a tail
portion.
In a.finishing rolling process, it may be important
to maintain the entire length and width of a hot-rolied
coil at a uniform finishing mill delivery temperature (FDT)
equal to or higher than an Ar3 transformation point (870"~).
However, when a bar 1 is processed by a finishing
mill (EM), the tail of the bar 1. (a leading end portion in
a mandrel coiling pro'cess) enters the FM in a state in '
Page 10
d which the tail has a temperature lower than that of the
other normal part of the bar 1 by 'about 100°C because 'the
structure of the mandrel 132 used to coil the bar 1. When
the tail exits the FM, the tail has a temperature of 800°C
or lower. Therefore, the bar 1 processed by the EM may not
satisfy properties required of steel sheets.
So .as not to deliver such defective products to
customers, defective portions o.f the products are removed
before packaging. However, this lowers the process yield.
Specific examples showing effects of such temperature
decreases are listed in Table 1.
[Table 11
[Sampling positions and texture test results]
* FDT: Finishing Mill Delivery Temperature (temperature of
bar 1 after finishing rolling).
A relatively low-temperature portion of a coil
corresponding to the tail of a bar 1 in a skin pass rolling
process (the tail was a leading end portion in a mandrel
Page 11
coiling process) was sampled at intervals of 5 m, and
mechanical properties of the samples were measured in a
length direction thereof. Samples collected within 5 m
from the end of the tail did not satisfy the lower lim'it of
a target range of elongation. , The results of texture
defects are shown in Table 1.
[Structure analysis results for different. sampling
positions]
In addition, the structures of the samples were
analyzed, and mixed-grain structures were observed until
about 20 m. Therefore, in the related art, a leading end
portion la (about 800 mrn to 1,000 mrn) of a bar 1 inserted
in the mandrel 132 is cut off because the leading end
portion la causes texture defects. For exampl.e, before
collecting quality test samples from a coil, the sampling
length is calculated based on the thickness of the coil so
as to fully detect and remove defective portions.
Therefore, an intermediate .inspector or an operator
of a skin 'pass mill may be overburdened, and a skin pass
rolling process may be additionally performed. In addition,
the yield. of the skin pass rolling process may be lowered
because defective' portions are cut off.
A bar 1 is coiled using the mandrel 132 as follows.
Page 12
A leading end portion la of the bar 1 is inserted into the
mandrel 132 through the slot 132a of the mandrel 132, and
then the leading end portion la is supported on the center
F
shaft 133 and the opposite edge ' wall 312. Therefore, as
the mandrel 132 is rotated, the leading end portion la is
bent, and an initial turn of a coil is formed.
At this time, the bar 1 may receive a force ( F ) and
torque expressed as follows:. torque = force ( F ) x length
( L ) where the length ( L ) is a distance between a point of
action and a rotation center. . As the length (L) increases,
the bar 1 may be bent by a smaller force. Therefore, the
bar 1 may be easily bent and plastically deformed. That is,
in the mandrel 132, the bar 1 may be plastically bent at a
portion between the center shaft 133 and the opposite edge
wall 312 of the slot 132a, and thus equilibrium of forces
may collapse due to plastic deformation of the bar 1.
In the worst case, initial turns of a coil may be
defectively formed due to deflection, and a coi.ling process
may be frequently suspended. . Therefore, a mandrel having
an improved structure may be required.
A mandrel 300 of a coil box improved according to the
present disclosure will now be described in comparison with
the mandrel 132 of the related art shown in FIG. 6.
FIG. 7 is a view illustrating how a leading end
Page 13
portion la of a bar 1 is inserted into a slot 310c of the
mandrel 300 and is coiled according to an exemplary
embodiment of the present disclosure.
Referring to FIG. 7, the mandrel 300 includes a
mandrel main body 310 in which the slot 310c is formed, and
a guide part 320 formed on an edge 'wall 311 of the slot
310c of the mandrel main body 310.
A center shaft 200 is disposed in the mandrel main
body 310, and the slot 310c is formed in the mandrel main
body 310 to receive the leading end portion la of the bar 1.
Coolant flows in the mandrel 300, and thus the temperature
of the mandrel 300 is lower than the bar 1 having a high
temperature.
The guide part 320 is formed from the edge wall 311
of the slot 310c toward an inner side of the mandrel main
body 310 so as to prevent cooling and plastic deformation
of the leading end portion la of the bar 1 inserted through
the slot 310c.
The guide part 320 may protrude from the edge wall
311 of the slot 310c so as to prevent the leading end
portion la of the bar 1 from making contact with the center
shaft 200 when the leading end portion la of the bar 1 is
inserted through the. slot 310c.
Owing this structure, when the leading end portion la
Page 14
of t h e bar 1 is i n s e r t e d , the leading end portion l a is not
-
brought i n t o contact with the c e n t e r s h a f t 200 having a
r e l a t i v e l y low temperature and thus is n o t cooled t o a
temperature lower t h a n a proper temperature.
Therefore, during t h i n - p l a t e r o l l i n g , a t a i l portion
( c o r r e s p o n d i n g . t o a l e a d i n g end portion of a b a r i n mandrel
c o i l i n g ) may have a uniform temperature.and thus may not be
curled o r t a n g l e d . Thus, work r o l l s may not be damaged,
and produ.ct q u a l i t y may not be d e t e r i o r a t e d .
In a d d i t i o n , s i n c e the leading end p o r t i o n l a of the
bar 1 is i n s e r t e d through the s l o t 310c by a length of
about 400 mm t o about 500 mm s h o r t e r than an i n s e r t i o n
length of about 800 mm t o about 1,000 mm i n the r e l a t e d a r t ,
and thus when the bar 1 is c o i l e d around the mandrel 300, a
p o r t i o n of the bar 1 making contact with the opposite edge
wall 312 of the s l o t 310c may not be e a s i l y bent and
1 p l a s t i c a l l y deformed.,
That is, when the bar 1 is c o i l e d , the leading end
p o r t i o n l a of t h e b a r 1 i n s e r t e d i n t o the s l o t 3lOc.may not
undergo d e f l e c t i o n but may make c o n t a c t with the guide p a r t
320 with an a p p r o p r i a t e c o n t a c t f o r c e therebetween.
Therefore, i n i t i a l inner t u r n s of the bar 1 may be smoothly
formed around the mandrel 300, and thus the c o i l i n g process
may not be suspended due t o d e f e c t i v e i n i t i a l i n n e r t u r n s .
Page 15
For example, the inner end of the guide part 320 is
...
spaced apart from the inner end of the opposite edge wall
312 of the slot 310c by a distance of 90 mm to 11.0 mm.
Since the guide part 320 protrudes until the guide part 320
is spaced apart from the inner end of the opposite edge
wali 312 by the distance, when the leading end portion la
of the bar 1 is inserted in the slot 310c, the leading end
portion la does not make contact with the center shaft 200.
In addition, when the bar 1 is coiled around the mandrel
300, a portion of the bar 1 making contact with the
opposite edge wall 312 may not be easily bent and
plastically deformed.
The guide part 320 may be sloped in a manner such
that an inner gap (inner width) of the slot 310c is smaller
than an outer gap (outer width) of the slot 310c.
hat is, since the outer gap of the slot 310c is
greater than the inner gap of the slot 310c, the bar 1 may
be easily inserted into the slot 310c, and the guide part
320 may stably guide the insertion of the bar 1 into the
slot 310c.
In addition, since the guide part 320 is disposed in
the mandrel main body 310 and narrows the inner gap of the
slot 310c, when the leading end portion la of the bar 1 is
inserted, the leading end portion la may be prevented from
Page 16
making contact w.ith the center shaft 200.
For example, the outer end of the guide part 320 may
be spaced apart form the outer end of the opposite edge
wall 312 by a distance of 200 mm to 300 mm, and in this
case, the guide part 320 may more effectively function as
an insertion guide.
In addition, the guide part 320 may be formed in one
piece with the.mandre1 main body 310 and may extend from
the edge wall 311 of the slot 310c into the mandrel main
body 310.
The leading end portion la of the bar 1 inserted in
the mandrel main body 310 may be cooled by the center shaft
200, close to the leading end portion la. However, since
the guide part 320 formed in one piece with the mandrel
main body 310 makes contact with the leading end portion la
of the bar 1 in the mandrel main body 310, the leading end
portion la may be maintained at an appropriate temperature
in the mandrel main body 310.
That is, the leading end portion la of the bar 1 may
receive heat from the other.high-temperature portion of the
bar 1 coiled around the mandrel main body 310 through the
mandrel main body 310 and the guide part 320 formed in one
piece, and thus the leading end portion la may be
maintained at a high temperature.
Page l7
For example, the guide part 320 may protrude from the .
edge wall 311 of the slot 310c and taper toward the inside
of the mandrel main body 310. In this case, although the
guide part 320 may transfer heat through a wide area
thereof, the guide part 320 may not make contact with the
center shaft 200.
In addition, counterweights 330 may be formed on a
side of the mandrel main body 310 opposite to the guide
part 320 so as not to bias the center of gravity of the
mandrel 300 toward the guide part 320.
In FIG. 7, the counterweights 330 protrude from an
inner side of the mandrel main body 310. However, the
current embodiment is not limited thereto. That is, the
number and shape of the counterweights 330 are not limited
as long as the counterweights 330 cancel out the weight of
the guide part 320
The mandrel 300 of the embodiment of the present
disclosure was applied to a production line, and as shown
in a graph below, the finishing mill delivery temperature
(FDT) of a leading end portion la of a bar 1 that had been
inserted in the mandrel 300 and processed through a
finishing rolling process was different as compared to an
FDT measured in a product line of the related ,art. In the
graph, the x-axis denotes a bar length, the y-axis denotes
Page 18
bar temperature ( "C) , FDT (before improvement) denotes FDT
measured according to the related art, FDT (after
improvement) denotes FDT measured according to the present
disclosure.
[Temperature profile of bars after rolling]
As shown in the graph, the F'DT .of a leading end
portion of a bar measured after improvement was higher than
the FDT of the leading end portion .of a bar measured before
improvement by about 4 0 " ~ to about 50°C, and the
temperature of one or two inner turns of a coil making
contact with the outer surface of the ,mandrel main body 310
was increased by about 1 0 " ~to about 20°C after improvement.
Therefore, according to the present disclosure, a steel
sheet or bar may be smoothly and stably rolled in a
finishing rolling process.
Therefore, intermediate inspectors may be less
burdened when'inspecting for texture defects caused by a
low temperature at the leading end of a bar, and operators
may be less burdened when performing a skin pass rolling
process.for correcting defects. Furthermore, the yield of
a skin pass rolling process may not be lowered due to
removal of a defective portion.
In the embodiments of the present disclosure,
Page 19 . .
I P Q DEEHI I1-01-22:015 PG.17
numerical values of materials such as thickness values of
bars are . given as exemplary values. That is, the
embodiments of the present disclosure are not limited
thereto.
As described above, according to the embodiments of
the present disclosure, in addition to productivity
improvements by qualitative effects such as a decreased
insertion length of a bar 1. into the mandrel 300, an
increased temperature of inner turns of a bar 1 coiled
around the mandrel 300, and an improvement in workpiece
passing characteristics in a rolling process, other effects
may be obtained such as an increase in the yield of a skin
pass rolling process resulted from a decrease of scrap, and
a decrease of overproduction by reducing defect rates in a
test and a re-test.
Furthermore, since it is not necessary to cut a hotfinal
workpiece in a skin pass rolling process to remove a
portion corresponding to a leading end portion la of a bar
1, costs necessary for the skin pass rolling process may be
reduced, and thus manufacturing costs may be markedly
reduced.
While exemplary embodiments have been shown and
described above, it will be apparent to those skilled in
the art that modifications and variations could be made
Page 2 0
without' departing from the spirit and scope of the present
disclosure as defined by the appended claims.

[CLAIMS]
[claim 11
A mandrel (300) of a coil box, the mandrel (300)
comprising:
a cylindrical mandrel main body (310) in which a
center shaft (200) is disposed, the mandrel main body (310) ' '
comprising a slot (310c) to receive a leading end portion
(la) of a high-temperature bar (1); and
a guide part (320) formed from an edge wall (311) of
the slot (310~) toward an inner side of the mandrel main
body (310) so as to prevent cooling and plastic deformation
of the leading end portion (la) of the bar (1) inserted
through the slot (310c) .
[claim 21
The mandrel (300) of claim 1, wherein the guide part
(320) protrudes from the edge wall (311) of the slot (310c)
to prevent the leading end po'rtion (la) of the.bar (1) from
making contact with the center shaft (200) when the leading
end portion (la) of the bar (1) is inserted through the
slot (310~.)
[claim 31
The mandrel (300) of claim 2, wherein an inner end of
the guide part (320) is spaced apart from an inner end of
an opposite edge wall (312) of the slot (310c) by 90 mm to
Page 22
110 mm.
[claim 41
The mandrel (300) of claim 2, wherein the guide part
(320) is sloped in a manner such that an inner gap of the
slot (310c) is smaller than an outer gap of the slot (310~).
[claim 51 .
The mandrel (300) of claim 4, wherein an outer end of
the guide part (320) is spaced apart from an outer end of
an opposite edge wall (312) of the slot (310c) by 200 mm to
300 mm.
[claim 61
The mandrel (300) of any one of claims 1 to 5,
wherein the guide part (320) is formed in one piece with
the mandrel main body (310) and extends from the edge wall
(311) ,of the slot (310c) toward the inner side of the
mandrel main body (310).
[claim 71
The mandrel (300) of any one of claims 1 to 5,
wherein the guide part (320) protrudes from the edge wall
(311) of the slot (310c) and tape'rs toward the inner side
of the mandrel main body, (310) .
[claim 81
The mandrel (300) of any one of claims 1 to 5,
wherein a counterweight'(330) is provided on a side of the
Page 2 3
I P 8 B E L H I 1 7 - 0 7 - 2 0 1 5 16:17
mandrel main body (310) opposite to the guide part (320) so
as not to bias a center of gravity of the mandrel toward
the guide part (320)