FIELD OF THE INVENTION
[0001] The present invention relates to a continuous casting mold which is used for a continuous
casting machine.
DESCRIPTION OF THE PRIOR ART
[0002] Continuous casting of steel is generally conducted with the use of a continuous casting
machine comprising a tundish, a mold, a group of guide rolls, and a group of pinch
rolls. Continuous casting machines are broadly classified into the vertical type continuous
casting machine and the horizontal type continuous casting machine. In the case of
a vertical type continuous casting machine, molten steel charged into the tundish
is poured through an immersion nozzle provided in the bottom wall of the tundish into
the mold. The molten steel cooled in the mold forms a solidified shell. The molten
steel having thus formed the solidified shell is withdrawn, while being guided by
the group of guide rolls sequentially arranged below the mold, through the group of
pinch rolls. In the meantime, the solidified shell, cooled by cooling water sprayed
from a plurality of nozzles arranged between said rolls, gradually increases the thickness
thereof, and forms a continuously cast strand having a prescribed cross-sectional
shape.
[0003] In the above-mentioned continuous casting operation, there is a problem of the molten
steel seizing to the inner surface of the mold at the time of withdrawing the molten
steel having formed the solidified shell from the mold. It is therefore the usual
practice to vibrate the mold with a certain amplitude in the withdrawing direction
of the cast strand with a view to preventing seizure of molten steel to the inner
surface of the mold. This vibration of the mold has usually been effected by a mechanical
means. However, in order to vibrate a mold by a mechanical means, it was necessary
to provide large-scale facilities with huge quentities of energy. In addition, a mechanical
means, which is difficult to vibrate the mold at a high frequency, causes wavy vibration
marks on the cast strand surface under the effect of mold vibration, which may in
turn cause surface cracks of the cast strand and was therefore problematic in terms
of the quality of cast strand.
[0004] Recently, the horizontal type continuous casting machine forming a cast strand by
horizontally withdrawing molten steel having formed a solidified shell from a horizontal
mold provided at the lower part of a side wall of the tundish has been industrially
applied because of the low installation costs and other advantages. In the case of
this horizontal type continuous casting machine, the horizontal mold is directly connected
to the lower part of a side wall of the tundish. It was therefore impossible to vibrate
the horizontal mold alone by a mechanical means.
[0005] As a measure to solve the above-mentioned problems, we have proposed a vibrating
apparatus of a continuous casting mold, disclosed in Japanese Patent Provisional Publication
No. 86,432/79 dated July 10, 1979 (hereinafter referred to as the "prior art"), which
comprises:
a plurality of ultrasonic vibrators, fitted to the outer surface of each of the side
walls of a continuous casting mold, at prescribed intervals in the axial direction
of said mold; said mold being vibrated in the axial direction thereof by the vibration
of said plurality of ultrasonic vibrators.
[0006] The above-mentioned prior art is applicable to a vertical type continuous casting
machine as well as to a horizontal type continuous casting machine. According to the
vibrating apparatus of the above-mentioned prior art, it is possible to vibrate the
mold in the axial direction thereof, i.e., in the withdrawing direction of cast strand,
at a high frequency, thus permitting prevention of seizure of a cast strand to the
inner surface of the mold. Unlike a vibrating apparatus based on a mechanical means,
this does not require huge quantities of energy nor large-scale facilities, without
causing wavy vibration marks on the surface of cast strand under the effect of vibration
of the mold. In the application thereof to a mold for a horizontal type continuous
casting machine, furthermore, the fine vibration at a high frequency imparted to the
mold keeps a high degree of seal at the junction between the tundish and the mold,
without leakage of molten steel from this junction caused by vibration of the mold.
[0007] With a view to improving the vibration efficiency of the mold in the above-mentioned
prior art, we carried out various studies. As a result, we reached the following conclusion.
Each of the side walls of the mold is fixed to the mold frame by such means as bolts.
If the fixing position corresponds to a loop of the vibration wave produced in the
axial direction of the mold, the above-mentioned vibration wave is inhibited by the
mold frame, thus resulting in such problems as a largely decreased vibration efficiency
of the mold and loosening or even breakage of the bolts used for fixing each of the
side walls of the mold to the mold frame under the effect of vibration. In addition,
each of the side walls of the mold has at least one conduit for cooling water in the
axial direction of the mold. This conduit has a cooling water supply opening and a
cooling water discharge opening on the outer surface of each of the side walls of
the mold, the cooling water supply opening being connected to a cooling water supply
pipe with a fixed end, and the cooling water discharge opening being connected to
a cooling water discharge pipe with a fixed end. If the positions of the cooling water
supply opening and the cooling water discharge opening correspond to loops of the
vibration wave, however, the above-mentioned vibration wave is inhibited by the cooling
water supply pipe and the cooling water discharge pipe, thus resulting in such problems
as a largely decreased vibration efficiency of the mold and breakage of the junctions
of the cooling water supply pipe and the cooling water discharge pipe with the cooling
water supply opening and the cooling water discharge opening.
SUMMARY OF -THE INVENTION
[0008] An object of the-present invention is therefore to provide, when vibrating the mold
in a continuous casting machine in the axial direction of the mold with the use of
a plurality of ultrasonic vibrators, a continuous casting mold for vibrating the mold
at a high efficiency in the continuous casting machine.
[0009] Another object of the present invention is to provide a continuous casting mold in
which bolts for fixing each of the side walls of the mold to the mold frame do not
loosen nor break under the effect of vibration of the mold.
[0010] Further another object of the present invention is to provide a continuous casting
mold in which the junctions of the cooling water supply opening and the cooling water
discharge opening provided on the outer surface of each of the mold side walls with
the cooling water supply pipe and the cooling water discharge pipe do not break under
the effect of vibration of the mold.
[0011] In accordance with one of the features of the present invention, in a continuous
casting mold which comprises:
a plurality of ultrasonic vibrators, fitted to the outer surface of each of the side
walls of said mold, along at least one straight line in the axial direction of said
mold at prescribed intervals; each of said side walls of said mold being fixed to
a mold frame; each of said side walls having in the inside thereof at least one conduit
for cooling water, and said conduit having a cooling water supply opening and a cooling
water discharge opening on the outer surface of each of said side walls;
the improvement characterized in that:
each of said side walls is fixed to said mold frame at positions corresponding to
at least two nodes of vibration waves produced in the axial direction of said mold
by vibration of said plurality of ultrasonic vibrators; and,
said cooling water supply opening and said cooling water discharge opening are arranged
at respective positions corresponding to said nodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
Fig. 1 is a plan view showing the continuous casting mold of the present invention;
Fig. 2 is a partial cutaway descriptive view of the mold of Fig. 1 cut along the line
A-A;
Fig. 3 is a sectional view of Fig. 2 cut along the line B-B; and,
Fig. 4 is a plan view showing another embodiment of the continuous casting mold of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] With a view to solving the above-mentioned problems involved in the prior art for
vibrating a continuous casting mold with the use of ultrasonic vibrators, we carried
out intensive studies. As a result, we developed a continuous casting mold as follows:
in a continuous casting mold which comprises:
a plurality of ultrasonic vibrators, fitted to the outer surface of each of the side
walls of said mold, along at least one straight line in the axial direction of said
mold at prescribed intervals; each of said side walls of said mold being fixed to
a mold frame; each of said side walls having in the inside thereof at least one conduit
for cooling water, and said conduit having a cooling water supply opening and a cooling
water discharge opening on the outer surface of each of said side walls;
the improvement characterized in that:
each of said side walls is fixed to said mold frame at positions corresponding to
at least two nodes of vibration waves produced in the axial direction of said mold
by vibration of said plurality of ultrasonic vibrators; and,
said cooling water supply opening and said cooling water discharge opening are arranged
at respective positions corresponding to said nodes.
[0014] Now, the continuous casting mold of the present invention (hereinafter referred to
as the "mold of the present invention") is described below by means of an example
with reference to drawings.
[0015] Fig. 1 is a plan view of the mold of the present invention; Fig. 2 is a partial cutaway
descriptive view of Fig. 1 cut along the line A-A; and, Fig. 3 is a sectional view
of Fig. 2 cut along the line B-B. In Figs. 1 to 3, 2 is a mold; the side walls of
the mold 2 are divided into individual side walls, to the outer surface of which a
plurality of ultrasonic vibrators 4 are fitted, through a mold frame 1 described later,
along at least one straight line at prescribed intervals in the axial direction of
the mold 2. The plurality of ultrasonic vibrators 4 are individually connected to
electric source not shown for generating ultrasonic vibration and generate vibration
waves of identical wave lengths in the axial direction of the mold 2.
[0016] Therefore, when the plurality of ultrasonic vibrators 4 are vibrated at a frequency
of about 20 kHz, for example, the resultant horizontal vibration waves are deviated
vertically by 90°, become longitudinal vibration waves 11 in the axial direction of
the mold 2, i.e., in the same direction as the withdrawing direction of cast strand,
and vibrate the mold 2 in the axial direction thereof, as shown in Fig. 2.
[0017] Also in Fig. 2, lla are nodes of the vibration wave 11, and llb are loops of the
vibration wave 11. Positions at which the plurality of ultrasonic vibrators 4 are
fitted to the individual side walls of the mold 2 should be such that a loop llb of
the vibration wave 11 may be located at the both end faces of the mold 2 and the distance
between two adjacent ones of the ultrasonic vibrators 4 may be a half the wave length
of the vibration wave 11, to achieve an efficient vibration of the mold 2. The resultant
positions of the ultrasonic vibrators 4 correspond respectively to the positions of
the nodes lla of the vibration wave 11.
[0018] The plurality of ultrasonic vibrators 4 are fixed, such means as bolts, to a plurality
of projections 3 provided at positions on the outer surface of the side walls of the
mold corresponding to the positions of the above-mentioned nodes lla. In Fig. 3, 10
are fitting bores of the ultrasonic vibrators 4, provided in the above-mentioned projections
3. In the illustrated example, two ultrasonic vibrators 4 are fitted to each of the
side walls of the mold 2. However, depending on the size of the mold 2, an appropriate
number of ultrasonic vibrators 4 should be provided to efficiently vibrate the mold
2.
[0019] In the drawings, 1 is a mold frame for supporting the mold 2; and each of the side
walls of the mold 2 is fixed to the mold frame 1. In the mold of the present invention,
the mold frame is fixed to the side walls of the mold 2 at positions corresponding
to at least two nodes lla of the vibration waves 11 produced in the axial direction
of the mold 2 under the effect of vibration of the plurality of ultrasonic vibrators
4. Also in the drawings, 6 are a plurality of bolts for fixing the side walls of the
mold 2 to the mold frame 1; and 7 are a .plurality of nuts. The mold frame 1 is fixed
to the side walls of the mold 2 through the plurality of projections provided at positions
on the outer surfaces of the side walls of the mold 2 corresponding to the above-mentioned
nodes lla. In Fig. 3, 8 are fitting bores of the bolts 6, provided in the projections
3.
[0020] Each of the side walls of the mold 2.has in the inside thereof at least one conduit
9 for cooling water in the axial direction of the mold 2. This conduit 9 has, on the
outer surface of the side wall of the mold 2, a cooling water supply opening 9a and
a cooling water discharge opening 9b.
[0021] A cooling water supply pipe 5 with a fixed end is connected, through the mold frame
1, to the cooling water supply opening 9a, and a cooling water discharge pipe 5' with
a fixed end is connected, through the mold frame 1, to the cooling water discharge
opening 9b. The above-mentioned cooling water supply pipe 5 is connected through a
pipe to a cooling water source not shown. Thus, each side wall of the mold 2 is cooled
by cooling water fed from the cooling water supply pipe 5, flowing through the conduit
9 and discharged from the cooling water discharge pipe 5'.
[0022] In the mold of the present invention, the cooling water supply opening 9a and the
cooling water discharge opening 9b are arranged on the projections 3 at positions
corresponding to the nodes lla of the vibration wave 11 produced in the axial direction
of the mold 2. The cooling water supply pipe 5 and the cooling water discharge pipe
5' are thus connected respectively to the cooling water supply opening 9a and the
cooling water discharge opening 9b provided on each side wall of the mold 2 at positions
corresponding to the nodes lla of the vibration wave 11.
[0023] In the example shown 'in Figs. 1 to 3, the cooling water discharge opening 9b is
arranged at the position on each side wall of the mold 2 corresponding to the uppermost
node of the nodes lla of the vibration wave 11, and the cooling water supply opening
9a is arranged at the position corresponding to the lowermost node of the nodes lla.
Two ultrasonic vibrators 4 are fitted at the positions corresponding to two intermediate
nodes of the nodes lla. Each side wall of the mold 2 is fixed to the mold frame 1
at the positions corresponding to all the nodes lla of the vibration wave 11. It is
however possible to select appropriate positions from among the positions corresponding
to the nodes lla of the vibration wave ll, depending upon the size of the mold 2 and
other conditions, as the positions of the cooling water supply opening 9a and the
cooling water discharge opening 9b, and as the fixing positions of the side walls
of the mold 2 to the mold frame 1. However, each side wall of the mold 2 should be
fixed to the mold frame 1 at positions corresponding to at least two nodes lla of
the vibration wave 11.
[0024] The positions on each of the side walls of the mold 2 corresponding to the nodes
lla of the vibration wave 11 may be easily detected by a known means or may be determined
through calculation.
[0025] In the mold of the present invention, as described above, each of the side walls
of the mold 2.is fixed to the mold frame 1 at positions corresponding to at least
two nodes lla of the vibration wave 11 produced in the axial direction of the mold
2 by vibration of the plurality of ultrasonic vibrators 4. Therefore, the vibration
wave 11 produced in the mold 2 by the plurality of ultrasonic vibrators 4 is never
inhibited by the mold frame 1, and the bolts 6 for fixing each side wall of the mold
2 to the mold frame 1 never loosen nor break under the effect of vibration.
[0026] In each of the side walls of the mold 2, the cooling water supply opening 9a to be
connected with the cooling water supply pipe 5 and the cooling water discharge opening
9b to be connected with the cooling water discharge pipe 5' are arranged respectively
at the positions corresponding to the nodes lla of the vibration wave 11. Therefore,
the vibration wave 11 produced in the mold 2 by the plurality of ultrasonic vibrators
4 is never inhibited by the cooling water supply pipe 5 and the cooling water discharge
pipe 5'. In addition, the junction between the cooling water supply pipe 5 and the
cooling water supply opening 9a, and the junction between the cooling water discharge
pipe 5' and the cooling water discharge opening 9b are never broken. The vibration
efficiency imparted to the mold 2 by the ultrasonic vibrators 4 is largely improved,
and it is thus possible to vibrate the mold 2 at a high efficiency in the axial direction
thereof.
[0027] Fig. 4 is a plan view showing another embodiment of the mold of the present invention.
This example is the same as that shown in Figs. 1 to 3 except that the side walls
of the mold 2' are formed'into an integral structure, and each of the side walls of
the mold 2' has a plurality of conduits 9"for cooling water provided in the inside
of each side wall of the mold 2' in the axial direction of the mold 2'. A cooling
water supply opening and a cooling water discharge opening may be provided for each
of the plurality of conduits 9' for cooling water on the outer surface of each side
wall of the mold 2', or the plurality of conduits 9' may be gathered into one conduit
at each end to provide one cooling water supply opening and one cooling water discharge
opening for each side wall of the mold 2'.
[0028] In the above-mentioned examples, the plurality of ultrasonic vibrators are fitted
to the outer surface of each of the side walls of the mold along a straight line at
prescribed intervals in the axial direction of the mold. Preferably, by fitting the
plurality of ultrasonic vibrators at prescribed intervals.along a plurality of straight
lines in the axial direction of the mold, these plurality of straight lines being
arranged at prescribed intervals, it is possible to further improve the vibration
efficiency of the mold in the axial direction thereof. The mold of the present invention
is applicable to a vertical type continuous casting machine as well as to a horizontal
type continuous casting machine. In all cases, it is possible to vibrate the mold
in the axial direction thereof at a high efficiency.
[0029] According to the mold of the present invention, as described above in detail, it
is possible to vibrate the mold in the axial direction thereof at a high efficiency
with the use of a plurality of ultrasonic vibrators which are fitted to the outer
surface of each of the side walls of the mold in the axial direction thereof along
at least one straight line at prescribed intervals, thereby permitting prevention
of seizure of a cast strand to the inner surface of the mold. Bolts for fixing each
of the side walls of the mold to the mold frame never loosen nor break under the effect
of vibration of the mold. In addition, the junctions of the cooling water supply opening
and the cooling water discharge opening provided on the outer surface of each of the
side walls of the mold with the cooling water supply pipe and the cooling water discharge
pipe are never broken by vibration of the mold.
[0030] In the case where the mold of the present invention is applied to a horizontal type
continuous casting machine, the mold can be vibrated in the axial direction thereof
at a high efficiency in a state where a perfect seal is maintained at the junction
between the tundish and the mold. According to the mold of the present invention,
therefore, many industrially useful effects are provided.