Note: Descriptions are shown in the official language in which they were submitted.
132~875
SIDE WALL CONSTRUCTION FOR CONTINUOUS BELT CASTER
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates generally to a
continuous belt caster for casting thin cast block. More
specifically, the invention relates to a side wall construction
of a continuous belt caster.
Description of the Background Art
In the recent years, various continuous belt caster
have been developed and proposed for effectively casting
relatively thin and continuous cast blocks. One of such
continuous belt caster is a synchronous belt caster which
defines a funnel-like path having a wider inlet and a narrower
outlet so as to form solidified shell during travel
therethrough. In general, such synchronous belt caster has a
pair of endless belts forming a moving wall of the caster and a
- pair of stationary side walls for defining the aforementioned
funnel-like path. Each of the side walls has wider transverse
width at the portion in the vicinity of the inlet and narrower
transverse width at the portion in the vicinity of the outlet
so as to define the funnel-like path gradually narrowing the
path area toward the outlet.
Molten metal, such as molten pig iron or molten
steel, is supplied to such belt caster through the inlet and
cooled by transferring of heat between the helts for gradually
forming and gradually growing solidified shell in the caster.
The cast block is fed out or withdrawn through the outlet.
During this process, the thickness of the solidified shell is
reduced at a predetermined reduction rate by essentially funnel
shaped path. In such continuous casting process, it is
desirable to maintain the melt in the vicinity of the side wall
in liquidus state. For this purpose, Japanese Patent First
(unexamined) Publication (Tokkai) Showa 58-218360 proposes a
side wall construction provided with a refractory at the
transverse center thereof. In the proposed construction, the
~k
132~875
refractory is supported on a metallic side wall body. The side
wall body has positions extending along the side edge of the
refractory and establish tight contact with the endless belt.
Despite of the presence of the refractory, it is
still difficult to provide satisfactory delay of
solidification. Namely, when the temperature of the melt is
relative low or when the speed of the melt flowing though the
path is relatively low, substantial heat exchange is caused
between the melt and the refractory for causing growth of
solidified shell on the refractory. in such occasion, the
solidified shell grown on the refractory is drawn together with
the shells grown on the belt or the metallic edge portion of
the side wall. If the stiffness of the solidified shell on the
refractory is relatively low, it still be possible to compress
the shell during travel through the path toward the outlet.
However, if the stiffness of the shell is substantial in such
an extent that can resist against compression force exerted by
the walls of the caster, since the solidified shell forms wedge
shaped block, metal penetration can be caused. If metal
penetration occurs, movement of the solidified shell at the
portion in the vicinity of the side wall can be completely
prevented and movement of the solidified shell at the
transverse central portion where the solidifying block mates
with the belt is permitted to move. This tends to cause
break-out of the cast block. In the alternative, because of
exessive thickness of the shell, the belt will subject
substantial bending stress to cause damaging of the belt.
As a material to form the refractory layer on the
side wall, one of silica, boron nitride, sialon and so forth
can be used. Such material generally has high heat
conductivity to cause greater magnitude of heat transfer
between the metal to promote growth of the solidified shell
when such material is solely used for forming the refractory
layer. In addition, these material as the refractory has
relatively large linear expansion coefficient. Therefore,
deformation can be caused in the metallic side wall body when
132~87~
.~
-- 3 --
substantial thermal expansion of the refractory is caused. On
the other hand, when material having low heat transfer
coefficient, such as molten silica brick, is used for forming
the refractory layer on the side wall, solidified layer can
grow not only at the metallic side edge portion but only on the
refractory layer. The solidified shell on the refractory layer
tends to cause wearing of surface of the refractory layer.
Therefore, the refractory layer formed of the material having
low heat transfer coefficient would not be applicable for the
belt caster for long period of use.
~ In order to obtain satisfactory delay in
- solidification of the melt in the portion in the vicinity of
; the refractory of the side wall, Japanese Patent First
(unexamined) Publication (Tokkai) Showa 58-218326 discloses a
15 technology of positively heating the refractory so as to
prevent the melt from solidifying. However, this clearly
increases cost of facility and will require satisfactory
isolation of electricity used for heating.
SUMMARY OF THS INVENTION
Therefore, it is an object of the present invention
; to provide a novel and useful side wall construction for a
continuous belt caster, which can solve the problems in the
background art set forth above.
~; In order to accomplish aforementioned and other
., .
objects, a side wall construction for a continuous belt caster,
according to the present invention, includes a metallic side
wall body and a refractory layer attached on the central
portion of the side wall body. The metallic side wall body has
side edge portion extending substantially in flush with the
surface of the refractory layer. The refractory layer is
formed with a center projection of essentially triangular
cross-section. The height of the peak of the projection is
gradually decreased toward downstream of transfer direction of
the liquidus and solidus metal.
On the other hand, it may be possible to formulate
the refractory layer as double layer construction of a heat
.
'' '
.
,
::
" 1325875
.
insulating refractory layer and a wear-resistantive
~.refractory layer.
:;According to one aspect of the invention, there is
provided a side wall structure of a continuous caster which
j 5has a pair of endless circulating bodies forming moving
walls of the caster and a pair of side walls forming
stationary walls of the caster, the stationary walls being
cooperative with the moving walls for defining a casting
chamber to which a molten metal is supplied fr casting a
locontinuous cast block, the side wall comprising:
a metallic wall body formed of a metal,
a refractory layer provided on the transverse
central portion of the metallic wall body having a surface
portion interfacing with molten metal for preventing the
15latter from solidifying thereon, said refractory layer being
formed with àn essentially triangular projection extending
into said casting chamber and positioned substantially
. centrally with respect thereto, said triangular projection
having a substantially rounded apex portion; and
20metallic side edge members integrally formed with
the metallic wall body and extending along both transverse
'~ edges of the refractory layer to expose surfaces thereof.
i: According to another aspect of the invention,
there is provided a side wall structure of a continuous
25caster which has a pair of endless circulating bodies
forming moving walls of the caster and a pair of side walls
forming stationary walls of the caster, the stationary walls
; being cooperative with the moving walls for defining a
casting chamber to which a molten metal is supplied for
30casting a continuous cast block, the side wall comprising:
a metallic wall body formed of a metal;
a refractory layer provided on the transverse
central portion of the metallic wall body having a surface
-
.
.~
... .... .
.
, , .
. ..
1325875
portion interfacing with molten metal for preventing the
latter from solidifying thereon, which solidification
preventive surface portion comprise an essentially
triangular projection extending at transverse center and
projecting into the casting chamber, said projection having
a contour with a substantially rounded apex portion and
which extends along the feed direction of the cast block and
reduces on height in the downward direction;
metallic side edge members integrally formed with
the metallic wall body and extending along both transverse
edges of the refractory layer to expose surface thereof.
Preferably, the triangular projection is provided
a taper in an axial direction of the casting chamber and the
side edge members are also provided taper in axial direction
of the casting chamber, tapers of the triangular projection
and the side edge members being opposite to each other.
Further preferably, the triangular projection has height
decreasing toward downstream.
According to a further aspect of the invention,
there is provided a side wall structure of a continuous
caster which has a pair of endless circulating bodies
forming moving walls of the caster and a pair of side walls
forming stationary walls of the caster, the stationary walls
being cooperative with the moving walls for defining a
casting chamber to which a molten metal is supplied for
casting a continuous cast block, the side wall comprising:
a metallic wall body formed of a metal
a refractory layer provided on the transverse
central portion of the metallic wall body having a surface
portion exposed to the casting chamber, said surface portion
having a substantially triangualr cross-section with an apex
extending into the casting chamber and positioned
substantially centrally with respect thereto and being
:
~ .
!
132~87~
tapered and decreasing in height from the inlet to the
outlet, the refractory layer comprising an inner heat
insulative refractory layer and an outer wear-resistantive
refractory layer which has the surface exposed to the
casting chamber.
metallic side edge members integrally formed with
the metallic wall body and extending along both transverse
edges of the refractory layer to expose surfaces thereof.
lo The side wall structure may further comprise a
heat insulative layer formed on the surface of the wear-
resistantive refractory layer. The heat insulative layer
may be provided in a region below a meniscus of the molten
metal. The wear-resistantive refractory layer may be formed
of a material having shore hardness at a predetermined high
temperature range greater than a shore hardness of cast
block immediately after casting.
The material of wear-resistantive refractory layer
is selected to have 15 of shore hardness at 1200C.
Preferably, the wear-resistantive refractory layer is formed
of a material selected among silicon nitride, sialon,
alumina, mullite and
132~
zirconium boride or composition of any one of these and boron
nitride. The heat insulative refractory layer is formed of a
material selected among MgO board, SiO2 type board, molten
silica brick. The heat insulative layer is formed of a
material selected among asbestos fabric, glass fiber fabric or
rock wool.
~RIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood more fully
from the detailed description given herebelow and from the
accompanying drawings of the preferred embodiments of the
invention, which, however, should not be taken to limit the
invention to the specific embodiment of embodiments, but are
for explanation and understanding only.
In the drawings:
Fig. 1 is a fragmentary perspective illustration of a
continuous belt caster, for which a side wall construction
according to the present invention is applicable;
Fig. 2 is a perspective view of the first embodiment
of a side wall construction to be employed in the belt caster
of Fig. l;
Figs. 3 and 4 are respectively sections taken along
line A - A and B - B of Fig. 2;
Fig. 5 is a section taken along line C - C of Fig. 2;
Fig. 6 is a perspective view of the second embodiment
of a side wall construction to be employed in the belt caster
of Fig. l;
Fig. 7 is a section taken along line D - D of Fig. 6;
Fig. 8 is an explanatory front elevation of the side
wall of Fig. 6;
Fig. 9 is a graph showing relationship with amount of
refractory being molten, in relation to length of caster;
Fig. 10 is an arrangement used for experiment; and
Fig. 11 is a graph showing variation of wall surface
temperature depending upon period of casting operation.
DESCRIPTION OF THE PREFERRED EM~ODIMENT
Referring now the drawings, particularly to Fig. 1,
1325875
-- 7 --
the general construction of a continuous belt caster, for which
a side wall construction, according to the present invention is
applicable, will be discussed briefly in order to facilitate
better understanding of the invention. As shown in Fig. 1, the
belt caster, herewith illustrated, includes a pair of metallic
endless belts 1 and 2 forming moving wall of the catser, and a
pair of side walls 4 and 5 forming stationary wall of the
caster. Each of the endless belts 1 and 2 is associated with
guide rollers 3a, 3b and 3c, one of which is drivingly
connected to a driving device to be rotatingly driven for
circulating the belt. The portion of the belt extending
~ between the guide rollers 3a and 3b forms the moving wall of- the caster and is associated with a cooling pad 7a or 7b, to
which coolant, such as cooling water, is circulated for cooling
the associated one of the belt 1 or 2.
As can be seen from Fig. 1, the side walls 4 and 5
are formed into an essentially funnel shape in front elevation
to have the greatest width at the top end and gradually
reducing the width in downward direction. The side walls 4 and
S also have a predetermined length of constant width portion
adjacent the lower end thereof. Therefore, the belts 1 and 2
and the side walls 4 and 5 forms essentially wedge-shaped
casting chamber. Molten metal, such as molten pig iron or
molten steel, is supplied to the casting chamber from the top
` 25 end inlet from a tundish via a nozzle 6.
As seen from Figs. 1 and 2, the side walls 4 and 5
has a metallic wall bodies 8 which are generally formed of a
metal. The metal body 8 is formed with an essentially
triangular recess 8a defined by frame-like side edge portions
9. A refractory layer 10 is disposed within the recess 8a to
form the side wall assembly.
~, In the casting chamber, the melt is cooled by heatexchange with the belts 1 and 2 and thus gradually grow
solidified shell on the belts. Also, the portion of the melt
interfacing with the side edge portions 9 of the side walls 4
and 5 is also cooled by heat exchanging with the side edge
~-, ~ , -
. .
-" ' ~' ,:
132587~ '
-- 8
portion and thus grow solidified shell. The solidified shell
growing on the side edge of the side walls 4 and 5 serves for
preventing the melt inpregnating into a space between the belt
and the side wall. During travel in the casting chamber, the
5 melt is thus gradually solidified and withdrawn through the
lower end outlet.
As shown in Figs. 2 through 4, the wall body 8 of the
side wall 4 and 5 is formed with a coolant path 11 for
circulating coolant, such as cooling water, for cooling the
10 metallic wall body. As can be seen from Figs. 3 and 4,the
major section of the refractory layer 10 is supported on the
recess 8a. The refractory layer 10 has an essentially
triangular projection lOa. The triangular portion 10a is
oriented at the transverse center of the refractory layer 10
1 15 and extends along the casting direction. The height of the
peak of the triangular projection 10a is the highest at the end
adjacent the inlet and is gradually decreased to zero toward
downstream end.
As particularly shown in Fig. 5, by declining the
20 peak height downwardly, the profile of the triangular
projection 10a is provided positive taper with a gradient of
~ where ~1 is peak height difference between the inlet side
q end and outlet side end of the triangular projection and ~1 is
length of the triangular projection. On the other hand, the
25 height of the side edge portion 9 of the wall body 8 is
inclined downwardly to gradually increase toward the downstream
end. The gradient of the side edge portion can be illustrated
as ~2/~2' where ~2 is a height difference of the side edge
portion 9 at the inlet side end and the outlet side end, and ~2
is overall length of the side wall.
Because the metallic wall body 8 is cooled by coolant
circulating the coolant passage, heat exchange is performed
~ between the side edge portions 9 exposed toward the casting
', chamber, and the melt for cooling the melt. By this, the
solidified shell is grown on the side edge portion 9. During
the continuous casting operation, the solidified shell is
, ~, .
132~87~
g
released from the surface of the exposed surfaces of the side
walls 4 and 5 will never cause break out or defect on the cast
block because of presence of the opposite tape of the
refractory layer and the side edge portion 8a.
In order to demonstrate the performance of the belt
caster employing the shown embodiment of the side walls
according to the present invention, an experiment was performed
for casting a low carbon aluminium killed steel cast block
having thickness of 30 mm and width of 1200 mm. The casting
speed was 12 m/min. The refractory layer 10 was formed of
molten silica brick. The relevant dimensions ~ 2~ ~1 and ~2
were as follows:
: ~ = 35 mm
~2 = 12 mm
= 65 cm
~2 = 100 cm
~nder the condition set forth above, continuous
casting for 600m per one heat was performed.
During casting operation, operation was performed
very smoothly without causing break out or defects on the cast
block.
Alternative embodiment is shown in Figs. 6 and 7, the
refractory layer 10 supported in the metallic wall body 8
comprises a heat insulative refractory layer lOb and a
wear-resistantive refractory layer 10c. In the shown
embodiment, as shown in Fig. 7, the coolant passage lla
extending through the major section of the metallic wall body
8, and the coolant passage llb extending through the side edge
sections 9 of the wall body are formed for respectively
associated section of the wall body. As can be seen from Figs.
6 and 7, the heat insulative refractory layer lOb is oriented
inside and the wear-resistantive refractory layer lOc is
provided outside exposed to the casting chamber. In addition,
a heat insulative layer lOd is at least partially formed on the
132587~
-- 10 --
surface of the wear-resistantive layer 10c. As can be seen
from Fig. 8, the heat insulative layer 10b is formed in a area
starting immediately below the meniscus line M and terminated
at the portion where the constant transverse section starts.
Preferably, the heat insulative refractory layer 10b
is selected among a material having heat transfer rate lower
than or equal to 0.002 cal/cm.s. C. For example, MgO board,
SiO2 type board, molten silica brick may be selected for
forming the heat insulative refractory layer. On the other
hand, the material for forming the heat insulative layer 10b is
, selected among asbestos wool, glass fiber fabrics, rock wools
3 and so forth, for example. The preferred thickness of the heat
insulative layer 10b to be formed on the wear-resistantive
refractory layer lOc is in a range of 1 mm to 3 mm. When the
thickness of the heat insulative layer lOb is less than 1 mm,
~1 heat insulation becomes insufficient. On the other hand, if
-. the thickness of the heat insulative layer 10b becomes thicker
~ than 3 mm, amount of slag to be created by melting becomes
i substantial. Furthermore, material of the wear-resistantive
refractory layer is is required high spalling resistance and
mechanical strength. To this respect, since the shore hardness
of the cast block immediately after withdrawn from the casting
chamber is less than or equal to 10. Therefore, the
wear-reistantive refractory layer must have shore hardness
greater than or equal to 10. Preferably, as the material for
wear-resistantive refractory layer is selected to have shore
hardness greater than or equal to 15 at a temperature of 1200
- C. As a material satisfying such condition, silicon nitride,
sialon, alumina, mullite, zirconium boride or composition of
the above-mentioned material and boron-nitride may be
advantageously selected.
In the preferred construction, the thickness of the
~` wear-resistantive refractory layer 10c is in a range of 2 mm to
10 mm. If the thickness of the wear-reistantive refractory
layer is less than 2 mm, it becomes easy to cause breakage to
make handling it difficult. Furthermore, such thin layer may
, .
' ' ~ . : .
~ ~. ,. . ' ' . . .
~325875
not have satisfactory resistance against heat shock to cause
breakage when it subjects heat shock. On the other hand, in
case that the thickness of the wear-resistantive refractory
layer 10c is thicker than 10 mm, heat absorption at the initial
stage of casting becomes substantial to cause formation of
solidified shell thereon.
In order to demonstrate the performance of the belt
caster employing the shown embodiment of the side walls
according to the present invention, an experiment was performed
for casting a low carbon aluminium killed steel cast block
having thickness of 25 mm and width of 1350 mm. The casting
speed was 12 m/min. The metallic wall body 8 was formed of Cu
material containing Ag. The heat insulative refractory layer
lOb was formed of MgO board of thickness of 15 mm. On the
other hand, the wear-resistantive refractory layer 10c was
formed on sialon containing 20~ of 8N was used. The property
of these refractory layers are shown in the following table:
TABLE
Refractory Thermal Linear Expansion High Temp.
: Layer Conductivicy Coefficiect Hardnessc
(Material) ~Kcal~m ho ) (cm/o ) (1200 o )
~ MgO Board 0.2 10.8 x 10 Hs = 15 to 20 ¦
30 Sialon-BN 8.6 2.4 x 10 Hs = 25 to 30 ¦
In order to compare with the example set forth above,
a comparative examples were prepared by single layer refractory
formed of sialon-BN and SiO2 -type material. Results of
experimental casting utilizing the preferred embodiment of the
side wall and the comparative example are shown in Fig. 9.
In case of the SiO2 single layer refractory,
thickness of melting out of the refractory becomes
approximately 1 mm for casting length of 300m. In this
.. .
1325875
- 12 -
comparative example, break out wad observed. On the other
hand, in case of sialon-BN single layer refractory, force
required for withdrawing the cast block was increased at the
initial stage of casting. After casting length of 6m, break
5 out was observed. In contrast to these, casting was smoothly
performed without causing melting of the refractory when the
preferred embodiment of the side wall set forth above was used.
Additional experiment was performed by attaching
asbestos fabric of 2.0 mm thick was attached on the
10 wear-resistantive layer in a manner shown in Fig. 8. An
experiment was performed for casting a low carbon aluminium
killed steel cast block having thickness of 25 mm and width of
1350 mm. The casting speed was 12 m/min. The temperature of
the melt supplied to the casting chamber was 1,568 C.
15 Temperature of the wear-resistantive refractory layer was
measured by means of a thermocouple 12 embedded at a position
of 1.5 mm from the surface, as shown in Fig. 9. Measured
temperature by the thermocouple 12 is shown in Fig. 10. In
Fig. 10, the line A shows the temperature variation in the
20 wear-resistantive refractory layer when asbestos layer was not
attached and the line B shows the temperature variation in the
wear-resistantive refractory layer as coupled with the asbestos
layer. As can be seen from Fig. 11, the temperatures of both
case becomes substantially equal to each other after 14 sec. of
~ 25 starting casting operation. In case that the asbestos layer is
J provided, by the heat insulative effect of the asbestos layer,
solidified shell was not formed even at the low temperature
period, i.e. approximately 9 sec. of starting casting
operation. In contrast, in case that the asbestos layer was
30 not provided, slight solidification was observed in a period
until 5 sec. after start casting.
' While the present invention has been disclosed in
terms of the preferred embodiment in order to facilitate better
understanding of the invention, it should be appreciated that
35 the invention can be embodied in various ways without departing
from the principle of the invention. Therefore, the invention
: . . .
132587~
- 13 -
should be understood to include all possible embodiments and
modifications to the shown embodiments which can be embodied
without departing from the principle of the invention set out
in the appended claims.
For example, though the shown embodiments are
concentrated to the belt caster, the present invention will be
applicable of any type of continuous caster which employs a
slde wall wIth a re~ractory Iayer.
.:
,J,
, '
~ . " ' . , ' ' '-
''' ..
