FLUX LOADING APPARATUS, CONTINUOUS CASTING EQUIPMENT, FLUX
LOADING METHOD, AND CONTINUOUS CANING METHOD
Technical Field
[0001]
The present invention relates to a flux loading apparatus used at the time of
10 manufacturing steel pieces while supplying flux to a molten steel surface in a mold, and a
continuous casting equipment equipped with the flux loading apparatus. The present
invention further relates to a flux loading method for supplying flux into a mold, and a
continuous casting method using the flux loading method.
15 Background Art
[0002]
In a continuous casting equipment, flux (hereinafter, powder) containing 5i02 and
CaO as major components, is supplied to a surface of molten steel injected into a mold,
thereby manufacturing steel pieces while preventing oxidation of the surface of the molten
20 steel in the mold, absorbing inclusions in the molten steel in the mold, and moreover,
lubricating between an inner wall surface of the mold and the molten steel. In supplying
the powder, the apparatuses shown below have been proposed from the standpoint of
improving workability.
For example, Patent Document 1 discloses a powder loading apparatus equipped
25 with a loading hopper for supplying powder, and a loading chute cormected to the loading
hopper, and an inclination with a slight positive angle added to an angle of rest of the
powder is given to the loading chute. According to this powder loading apparatus, by
causing the powder to fall via the loading chute under its own weight, the powder can be
scattered into the mold.
5 Moreover, Patent Document 2 discloses a powder loading apparatus equipped
with a swivel chute that scatters powder into a mold, and a movable tip end chute provided
at a tip end of the swivel chute and movable in the vertical direction. The powder loading
apparatus also includes a vibration mechanism, and can load powder into the mold without
relying on the free fall thereof. According to this powder loading apparatus, the movable
10 tip end chute can be moved in the vertical direction simultaneously with rotation of the
swivel chute, thereby enabling to supply powder stably into the mold.
[0003]
Furthermore, conventionally, a.. storage hopper that stores granular powder (flux)
is arranged at a position away from around a continuous casting mold (hereinafter, also
15 simply referred to as a mold) to ensure a casting bed work space of a continuous casting
equipment, and the granular powder is supplied into the mold via a plurality of transport
pipes arranged in series from the storage hopper toward the mold.
For example, in a casting powder supply apparatus disclosed in Patent Document
3, two transport pipes are serially connected in communication with each other, and the
20 transport pipes and a transfer tube, and both transport pipes, are mutually connected so as
to be able to turn freely in a horizontal direction. Moreover, a drive motor is provided in
respective connection parts, and a spreading nozzle is communicatively connected to a
distal end of the transport pipe in a bent state.
Moreover in Patent Document 4, a supply apparatus for continuous casting
25 powder is disclosed in which after powder discharged from a storage tank is stirred, the
3
powder is pressure fed to a powder supply section and supplied to spray nozzles branched
into several parts, and the powder remaining in the powder supply section at the time of
switching the powder is recovered to the storage tame.
Furthermore in Patent Document 5, there is disclosed a powder supply apparatus
5 for continuous casting that has a powder storing hopper, a first storage container, a second
storage container, and a mechanical feeder, and the first storage container and the second
storage container are connected by a detachable joint.
Prior Art Documents
10 Patent Documents
[0004]
[Patent Document 1] Japanese Unexamined Patent Application, First Publication
No. 2004306060
[Patent Document 2] Japanese Unexamined Patent Application, First Publication
15 No.2007^181845
[Patent Document 3] Japanese Unexamined Patent Application, First Publication
No. H1U285796
[Patent Document 4] Japanese Unexamined Patent Application, First Publication
No. H0U118350
20 [Patent Document 5] Japanese Unexamined Patent Application, First Publication
No. H01 °215449
Disclosure of Invention
Problems to be Solved by the Invention
25 [0005]
4
However, the conventional techniques disclosed in Patent Documents 1 to 5
described above have the following problems to be solved.
That is to say, in the apparatus described in Patent Document 1, only a tilt angle of
the loading chute is defined, and a height range of a fall start position of the powder from
5 the molten steel surface is not defined. Therefore, as the height of the fall start position of
the powder becomes higher, the speed of the powder at the time of collision against the
molten steel surface increases, and hence, if the height becomes too high, mold level
fluctuation due to collision of the powder against the molten steel surface may occur. In
such a case, deterioration of product quality of steel pieces may occur due to the mold level
10 fluctuation.
Moreover, in the apparatus described in Patent Document 2, powder in the swivel
chute is supplied to the mold by using a vibration mechanism without using free fall of the
powder. However, this apparatus has a problem in that the device such as the vibration
mechanism becomes an obstruction when a worker performs the casting work, and
15 equipment cost increases. Furthermore, because free fall of the powder is not used, time is
required to supply the powder into the mold, and there is a problem when it is required to
supply powder quickly to the molten steel surface in the mold.
Furthermore, in the apparatus described in Patent Document 3, hollow powder or
granular powder is transported by using a screw feeder. However, when the powder is
20 transported over a long distance, if the screw feeder is intermittently operated for short
periods according to a casting condition, the powder is crunched between the screw and the
inner surface of the pipe containing the screw, thereby pulverizing the powder. In this case,
if the pulverized powder is loaded into the mold, the melting characteristics of the powder
are changed from an original state before pulverization, and lubrication on the inner
25 surface of the mold becomes unstable, so that operational problems may occur.
[0006]
As described above, in the apparatuses disclosed in Patent Documents 1 to 3, the
mold level fluctuation of the molten steel and a change in the melting characteristics of the
powder at the time of supplying the powder particularly become problems in improvement
5 of the product quality of the steel piece, and an apparatus and a method that can solve these
problems have been desired.
[0007]
Moreover, all the techniques described in Patent Documents 3 to 5 mainly use
pneumatic transport at the time of transporting the powder. Therefore, at the time of
10 transporting the granular powder, the granular powder collides against the inner surface of
the transport pipe and is pulverized, and the transport pipe may become clogged.
Therefore, stable supply of granular powder cannot be realized. Furthermore, there is also
a problem in that when the pulverized granular powder is supplied into the mold, its slag
forming property, lubrication property, and heat retaining property become unstable.
15 [0008]
As described above, in the apparatuses described in Patent Documents 3 to 5,
achieving both the prevention of pulverization, and the stable supply of granular powder
particularly becomes a problem in improving the product quality of the steel piece, and an
apparatus and a method that can solve these problems have been desired.
20 [0009]
The present invention takes into consideration the above situation, with amu object
of providing a flux loading apparatus, a continuous casting equipment, a flux loading
method, and a continuous casting method, that can improve the product quality of the steel
piece.
23
Moans for Solving the Problems
[0010]
The present invention has adopted the following measures in order to solve the
above problems and achieve the related objects. That is to say,
5 (1) a flux loading apparatus of the present invention includes: a loading hopper
that temporarily stores a flux; and a supply pipe disposed in a tilted manner with a rear end
thereof being connected to the loading hopper and a front end thereof being located above
a mold. A height H from a molten steel surface in the mold to the loading hopper is in a.
range of from 0.5 m to 3.0 m inclusive, a minimum tilt angle a, of the supply pipe relative
10 to a horizontal direction is 20 degrees or more, and a formed angle 0 of an imaginary line
connecting a flux discharge opening of the loading hopper and a lower position of the front
end of the supply pipe relative to the horizontal direction is 54.6 x H°S degrees or less.
[0011]
(2) In the flux loading apparatus described in (1), a configuration may be adopted
15 in which the supply pipe has a plurality of straight ducts connected to each other, and a
smallest tilt angle of a duct relative to the horizontal direction of these straight ducts is the
minimum tilt angle a.
[0012_]
(3) In the flux loading apparatus described in (1), the position in the horizontal
0 direction of the front end of the supply pipe may be in a range of from a position inward of
the mold by 50 mm to a position outward of the mold by 200 mm, when a position on an
inner wall surface of the mold at a position immediately below the supply pipe is
designated as a reference.
[0013]
5 (4) The flux loading apparatus described in (1) may further include a gas supply
I
unit that injects gas into the supply pipe at a flow rate of from exceeding 0 to 3
liters/minute inclusive , per flow passage cross^sect.ion of 1 cm2 in the supply pipe.
[0014]
(5) A continuous casting equipment of the present invention includes; the flux
loading apparatus according to any one of (1) to (4), and the mold.
[0015]
(6) In the continuous casting equipment described in (5), a casting speed of a steel
piece made by the mold may be 0.6 m/minute or higher.
[0016]
10 (7) In the continuous casting equipment described in (5), a configuration may be
adopted in which the continuous casting equipment further includes: a storage hopper that
stores the flux, a transport screw conveyor that transports the flux from the storage hopper;
a relay hopper that receives the flux transported by the transport screw conveyor; a
discharge screw conveyor provided between the relay hopper and the loading hopper; and
15 a control device that controls the operation of the transport screw conveyor. Moreover a
transport distance of the discharge screw conveyor may be shorter than a transport distance
of the transport screw conveyor, and the control device may control a transport amount by
the transport screw conveyor to a predetermined transport amount or more for a
predetermined time.
20 [0017]
(4) In the continuous casting equipment described in (7), the transport distance of
the discharge screw conveyor may be 7 m or less.
[0018]
(9) In the continuous casting equipment described in (7), the predetermined time
25 may be from 2 minutes to 5 minutes inclusive, and the predetermined transport amount
8
may be in a range of from 1 kg/minute to 20 kg/minute inclusive.
[0019]
(10) In the continuous casting equipment described in (7), a configuration may be
adopted in which the transport screw conveyor includes a plurality of screw conveyors and
an attachment hopper arranged between these screw conveyors, and the control device
may individually control a transport operation of each screw conveyor.
[0020]
(11) A flux loading method of the present invention is a method for causing flux to
fall through a supply pipe disposed in a tilted manner to supply flux to a molten steel
10 surface in a mold. A height H from the molten steel surface to a fall start position of the
flux is set to a range of from 0.5 m to 3.0 m inclusive, a minimum tilt angle a of the supply
pipe relative to a horizontal direction is set to 20 degrees or more, and a formed angle 0 of
an imaginary line connecting the fall start position and a lower position of a front end of the
supply pipe relative to the horizontal direction is set to 54.6 x H-0'5 degrees or less.
15 [0021]
(12) The flux loading method described in (11) may further include a process of
injecting gas into the supply pipe at a flow rate of from exceeding 0 to 3 liters/minute
inclusive, per flow passage cross section of 1 cm2 in the supply pipe.
[0022]
20 (13) A continuous casting method of the present invention includes a process of
supplying a flux to the molten steel surface in the mold by using the flux loading method
described in (11) or (12).
[0023]
(14r) In the continuous casting method described in (13), a casting speed of a steel
25 piece made by the mold may be 0.6 m/mimute or higher.
9
[0024]
(15) The continuous casting method described in (13) may further include: a
process of transporting the flux from a storage hopper that stores the flux to a relay hopper
via a transport screw conveyor; and a process of supplying the flux from the relay hopper
5 into the mold via the discharge screw conveyor, the loading hopper, and the supply pipe.
Moreover a transport distance of the discharge screw conveyor may be shorter than a
transport distance of the transport screw conveyor, and a transport amount by the transport
screw conveyor may be set to a predetermined transport amount or more for a
predetermined time.
10 [0025]
(16) Iru the continuous casting method described in (15), the transport distance of
the discharge screw conveyor may be 7 m or less.
[0026]
(17) In the continuous casting method described in (15), the predetermined time
15 may be from 2 minutes to 5 minutes inclusive, and the predetermined transport amount
may be in a range of from 1 kg/minute to 20 kg/minute inclusive.
[0027]
(18) In the continuous casting method described in (15), the transport screw
conveyor may include; a plurality of screw conveyors, and an attachment hopper arranged
20 between these screw conveyors, and a transport operation of each screw conveyor may be
individually controlled.
Effects of the Invention
[0028]
25 According to the flux loading apparatus of the present invention described in (1),
10
the height H indicating the fall start position of the powder, and the formed angle 0 of the
imaginary line connecting the fall start position and the lower position of the front end of
the supply pipe relative to the horizontal direction are set to an optimum range,
respectively. Therefore, the speed of the flux at the time of collision against the molten
5 steel surface can be adjusted to a speed that does not cause deterioration of product quality
due to mold level fluctuation.
Moreover, because the minimum tilt angle a of the supply pipe relative to the
horizontal direction is set to an optimum range, clogging of the flux in the supply pipe can
be prevented. As a result, supply of the flux to the molten steel surface in the mold can be
10 performed by using a low cost supply pipe without hampering the operation, and mold
level fluctuation of the molten steel is suppressed, thereby enabling to improve the product
quality further.
[0029]
In the case of the flux loading apparatus described in (2), the supply pipe can be
15 constituted by connecting a plurality of straight ducts. Therefore, a transport route of the
flux can be changed according to the enviromnent. Moreover, by setting the smallest tilt
angle of the duet relative to the horizontal direction of these straight ducts to the minimum
tilt angle a, clogging of the flux in the supply pipe can be prevented even if a plurality of
straight ducts is used.
20 [0030]
In the case of the flux loading apparatus described in (3), the position in the
horizontal direction of the front end of the supply pipe is set to a range of from a position
inward of the mold by 50 mm to a position outward of the mold by 200 mm, based on the
position on the inner wall surface of the mold. Therefore a situation where the supply pipe
5 interferes with a submerged nozzle can be prevented. Accordingly, it is not necessary to
11
provide a complicated control mechanism for preventing interference.
[0031]
In the case of the flux loading apparatus described in (4), gas is supplied to the
supply pipe by the gas supply unit supplementarily, in addition to the natural fall of the flux
under its own weight. As a result the supply of flux to the molten steel surface in the mold
can be more stably executed.
[0032]
According to the continuous casting equipment described in (5), because the flux
loading apparatus described in any of (1) to (4) is provided, mold level fluctuation due to
10 supply of the flux can be effectively suppressed. Consequently, product quality of the steel
piece can be improved.
[0033]
In the case of the continuous casting equipment described in (6), if the casting
speed of the steel piece becomes 0.6 rn/minute or higher, mold level fluctuation of the
15 molten steel is likely to occur. However, because the flux loading apparatus of the present
invention is provided, mold level fluctuation due to loading of the flux can be suppressed.
Consequently, the effects of the present invention can be developed more remarkably.
[0034]
In the case of the continuous casting equipment described in (7), the relay hopper
20 is provided between the transport screw conveyor and the discharge screw conveyor.
Therefore, with the relay hopper as a boundary, the transport screw conveyor arranged on
an upstream side of the relay hopper can adjust the transport amount of the flux according
to the amount of the flux (for example, granular powder) in the relay hopper, and the
discharge screw conveyor arranged on a downstream side of the relay hopper can adjust
25 the transport amount of the flux according to the casting situation, individually.
1
Generally, if the flux (for example, granular powder) is supplied by the discharge
screw conveyor into the mold by a predetermined amount from the relay hopper via the
loading hopper and the supply pipe (that is, if a short time intermittent operation is
performed), the pulverization rate of the flux increases. Therefore, conventionally the
5 melting rate of the flux supplied into the mold becomes unstable, to form a nonuniform
melt layer on the molten steel surface, and hence, formation of a solidifying shell is not
promoted stably, and the operation becomes unstable. On the other hand, in the present
invention, the transport screw conveyor is operated at high speed for a short period of time,
and the transport distance of the discharge screw conveyor is set to be shorter than the
10 transport distance of the transport screw conveyor. Therefore, even if the discharge screw
conveyor is used in an intermittent operation for a very short time, pulverization of the flux
supplied from the storage hopper into the mold can be suppressed. As a result, both the
prevention of pulverization, and the stable supply of the flux can be achieved. Accordingly,
the slag forming property, lubrication property, and heat retaining property at the time of
15 supplying the flux into the mold can be maintained in favorable conditions, thereby
enabling to perform stable casting.
[0035]
In the case of the continuous casting equipment described in (8), the transport
distance of the discharge screw conveyor is set to 7 m or less. Therefore, the rate of
20 pulverization of the granular powder due to the operation of the discharge screw conveyor
can be further decreased.
[0036]
In the case of the continuous casting equipment described in (9), the operation
time of the transport screw conveyor and the transport amount of the flux are appropriately
25 defined. Therefore, the rate of pulverization of the flux due to the operation of the transport
13
screw conveyor can be decreased more effectively. Here, when the pulverization rate of
the flux supplied into the mold is decreased to 15% by mass or less, the slag forming
property, lubrication property, and heat retaining property of the flux can be maintained in
even more favorable conditions.
[0037]
In the case of the continuous casting equipment described in (10), for example,
when the transport distance from the storage hopper to the mold is long, or even if an
obstacle is present in the middle of the transport route, an appropriate transport route of the
flux can be constructed by connecting aplurality of screw conveyors. As a result, transport
10 can be performed while achieving both the prevention of pulverization, and the stable
supply of the flux.
[0038]
According to the flux loading method described in (11), the same operation
effects as those of the flue loading apparatus described in (1) can be obtained. That is, the
15 height H indicating the fall start position of the powder, and the formed angle 0 of the
imaginary line connecting the fall start position and the lower position of the front end of
the supply pipe relative to the horizontal direction are set to an optimum range,
respectively. Therefore, the speed of the flux at the time of collision against the molten
steel surface can be adjusted to a speed that does not cause deterioration of product quality
20 due to mold level fluctuation.
Moreover, because the minimum tilt angle a of the supply pipe relative to the
horizontal direction is set to an optimum range, clogging of the flux in the supply pipe can
be prevented. As a result, supply of the flux to the molten steel surface in the mold can be
performed by using a low cost supply pipe without hampering the operation, and mold
25 level fluctuation of the molten steel is suppressed, thereby enabling to improve the product
1
quality further.
[0039]
In the case of the flux loading method described in (12), gas is supplied to the
supply pipe supplementarily, in addition to the natural fall of the flux under its own weight,
5 thereby enabling to supply the flux to the molten steel surface in the mold more stably.
[0040]
In the case of the continuous casting method described in (13), because the flux
loading method described in (11) or (12) is used, mold level fluctuation due to supply of
the flux can be effectively suppressed. As a result, product quality of the steel piece can be
10 improved.
[0041]
In the case of the continuous casting method described in (14), if the casting speed
of the steel piece becomes 0.6 m/minutee or higher, mold level fluctuation of the molten
steel is likely to occur. However, because the flux loading method of the present invention
15 is adopted, mold level fluctuation due to loading of the flux can be suppressed. As a result,
the effects of the present invention can be developed more remarkably.
[0042]
In the case of the continuous casting method described in (15), the relay hopper is
interposed between the transport screw conveyor and the discharge screw conveyor.
20 Therefore, with the relay hopper as a boundary, the transport screw conveyor arranged on
an upstream side of the relay hopper can adjust the transport amount of the flux according
to the amount of the flux (for example, granular powder) in the relay hopper, and the
discharge screw conveyor arranged on a downstream side of the relay hopper can adjust
the transport amount of the flux, according to the progress status of the casting work,
25 individually.
15
Generally, if the flux (for example, granular powder) is supplied by the discharge
screw conveyor into the mold by a predetermined amount from the relay hopper via the
loading hopper and the supply pipe (that is, if a short=-time intermittent operation is
performed), the pulverization rate of the flux increases. Therefore, conventionally the
5 melting rate of the flux supplied into the mold becomes unstable, to form a nonuniform
melt layer on the molten steel surface, and hence, formation of a solidifying shell is not
promoted stably, and the operation becomes unstable. On the other hand, in the present
invention, the transport screw conveyor is operated at high speed for a short period of time,
and the transport distance of the discharge screw conveyor is set to be shorter than the
10 transport distance of the transport screw conveyor. Therefore, even if the discharge screw
conveyor is used by an intermittent operation for a very short time, pulverization of the
flux supplied from the storage hopper into the mold can be suppressed. As a result, both
the prevention of pulverization, and the stable supply of the flux can be achieved.
Accordingly, the slag forming property, lubrication property, and heat retaining property at
15 the time of supplying the flux into the mold can be maintained in favorable conditions,
thereby enabling to perform stable casting.
[0043]
In the case of the continuous casting method described in (16), because the
transport distance of the discharge screw conveyor is set to 7 m or less, the rate of
20 pulverization of the granular powder due to the operation of the discharge screw conveyor
can be further decreased.
[0044]
In the case of the continuous casting method described in (17), because the
operation time of the transport screw conveyor and the transport amount of the flux are
25 appropriately controlled, the rate of pulverization of the flux due to the operation of the
16
transport screw conveyor can be decreased more effectively. When the pulverization rate
of the flux supplied into the mold is decreased to 15% by mass or less, the slag forming
property, lubrication property, and heat retaining property of the flux can be maintained in
favorable conditions.
5 [0045]
In the case of the continuous casting method described in (18), for example, when
the transport distance between the storage hopper to the mold is long, or even if an obstacle
is present in the middle of the transport route, an appropriate transport route of the flux can
be constructed by connecting a plurality of screw conveyors. As a result, transport can be
10 performed while achieving both the prevention of pulverization, and the stable supply of
the flux.
Brief Description of Drawings
[0046]
15 FIG. 1 is a side view showing equipment layout for a continuous casting
equipment including a flux loading apparatus according to a first embodiment of the
present invention.
FIG. 2 is a longitudinal sectional view showing the positional relationship
between a supply pipe of the flux loading apparatus and a molten steel surface in a mold.
20 FIG. 3 is a graph showing the relationship between surface collision velocity
when flux (powder) collides against the molten steel surface, and mold level fluctuation.
FIG. 4 is a graph showing an influence on the mold level fluctuation by a formed
angle 0 of an imaginary line connecting a fall start position of the flux and a lower position
of a front end of the supply pipe relative to the horizontal direction, and a height H from the
25 molten steel surface to a fall start position.
17
FIG. 5 is a side view showing equipment layout for a continuous casting
equipment according to a second embodiment of the present invention.
FIG 6 is a side view showing a modified example of the continuous casting
equipment.
5 FIG. 7 is an explanatory diagram showing the relationship between a transport
distance of the flux (granular powder) by screw feeders operated by a different operation
method, and a pulverization rate thereof.
FIG 8 is a diagram showing an embodiment of the present embodiment, and is an
explanatory diagram illustrating an operation method of a screw feeder with a low
10 operating rate and an operation method of a screw feeder with a high operating rate.
FIG 9 is an explanatory diagram showing the relationship between the operation
method of the screw feeder and the pulverization rate of granular powder.
Description of Embodiments
15 [0047]
Respective embodiments of a flux loading apparatus, a continuous casting
equipment, a flux loading method, and a continuous casting method of the present
invention will be described below. However, the present invention is not limited thereto.
[0048]
20 [First embodiment]
As shown in FIG. 1 and FIG. 2, the continuous casting method using the flux
loading method of the present embodiment is a method of manufacturing a steel piece by
causing the flux (hereinafter, powder 10) to fall under its own weight through a cylindrical
supply pipe I1 tilted obliquely downward, while supplying the flux onto a molten steel
25 surface 13 in a mold 12. Accordingly, the continuous casting method can suppress mold
18
level fluctuation of molten steel with a simple configuration without hampering operations
on the casting bed, and can improve product quality of the steel piece.
[0049]
The continuous casting equipment equipped with the flux loading apparatus of the
S present embodiment for performing the continuous casting method includes; a storage
hopper 15 that stores the powder 10, a down comer 16 connected to a bottom end of the
storage hopper 15 and extending toward immediately below in a vertical direction, a
transfer tube 17 connected to a bottom end of the down comer 16 and extending in a
horizontal direction, a flux loading apparatus 1 connected to an end of the transfer tube 17,
10 a mold 12 receiving an input of the powder 10 from the flux loading apparatus 1, and a
tundish 19 and a submerged nozzle 20 arranged above the mold 12.
The flux loading apparatus 1 includes; a powder loading hopper 18 that receives
the powder 10 fed from the transfer tube 17, and the supply pipe 11 connected to a bottom
end of the powder loading hopper 18 and disposed in a tilted manner. The supply pipe 11 is
15 disposed in a tilted manner with a rear end being connected to the powder loading hopper
18 and a front end being positioned above the inside of the mold 12.
[0050]
The powder 10 used in the present embodiment includes conventionally
wellmlalown powders such as; hollow powder in a. hollow form with voids formed
20 thereinside, granular powder, and powdery powder.
[0051]
After an appropriate amount of the powder 10 is discharged from the storage
hopper 15 installed on a tundish cradle 14, the powder 10 falls in the down comer 16 under
its own weight, and is fed to the powder loading hopper 18 by the transfer tube 17 having a
screw feeder incorporated therein. The powder 10 is supplied onto the molten steel surface
19
13 from the bottom end of the powder loading hopper 18 under its own weight via the
supply pipe 11.
The supply pipe 11 is piping tilted from the bottom end position of the powder
loading hopper 18 toward the molten steel surface 13, with the prerequisite that the powder
5 10 falls under its own weight . The configuration and arrangement of the supply pipe 11
will be described in detail below.
[0052]
The supply pipe 11 is formed by serially connecting a plurality of (four in the
present embodiment) straight ducts 21 to 24, and is bent in multistages. More specifically,
10 the supply pipe 11 includes the straight duct 21 connected to the bottom end of the powder
loading hopper 18 and extending downward in the vertical direction, the straight duct 22
connected to the bottom end of tl straight duct 21 and disposed in a tilted mariner
obliquely downward, the straight duct 23 connected to the bottom end of the straight duct
22 and extending downward in the vertical direction, and the straight duct 24 connected to
15 the bottom end of the straight duct 23 and disposed in a tilted manner toward above the
molten steel surface 13 in the mold 12. The number of the straight ducts constituting the
supply pipe 11 is not limited to the four of the present embodiment and, for example, the
number of the straight ducts may be two, three, or five or more (an upper limit is about ten),
according to the environmental conditions around the supply pipe 11.
20 [0053]
The minimum tilt angle a of the straight duct 24 having the smallest tilt angle
with respect to the horizontal direction (the straight duct positioned on the most
downstream side) of the respective straight ducts 21 to 24 constituting the supply pipe 11 is
20 degrees or more.
25 When the minimum tilt angle a is less than 20 degrees, clogging of the powder 10
>0
is likely to occur in the supply pipe 11, although the degree of clogging varies according to
the type of the powder 10. Moreover, when the minimum tilt angle a is less than 20
degrees, the straight duct becomes an obstruction when a worker is working on the casting
bed. Accordingly, it is preferable to set the minimum tilt angle a to be 30 degrees or more,
5 and more preferably, 35 degrees or more.
[0054]
In the present embodiment, a case in which the tilt angle of the straight duct 24
constituting the supply pipe 11 and positioned on the most downstream side is set to the
minimum tilt angle a has been described. However, the tilt angle of the straight duct
10 arranged on the most upstream side or in the middle of the supply pipe 11 can be the
smallest, and it can be set as the minimum tilt angle a. This is because setting of the
minimum tilt angle a is to prevent the occurrence of clogging of the powder 10, and if the
minimum tilt angle a of the straight duct having the smallest tilt angle with respect to the
horizontal direction, of the straight ducts 21 to 24, is defined, the occurrence of clogging of
15 the powder 10 can be prevented without particularly defining the tilt angle for the other
straight ducts.
Furthermore, in the present embodiment, the straight ducts 21 and 23 arranged in
the vertical direction are included in the straight ducts constituting the supply pipe 11.
However, only straight duct arranged with a tilt angle of 20 degrees or more and up to 90
20 degrees with respect to the horizontal direction can be used, without using these straight
ducts 21 and 23.
[0055]
Moreover, the configuration of the supply pipe i i is not limited to the one in
which a plurality of straight ducts 21 to 24 is serially connected as in the present
21
embodiment, and the supply pipe 11 may be constituted by only one straight duct forming
a straight line (riot shown). In this case, the tilt angle with respect to the horizontal
direction of the straight duct becomes the minimum tilt angle a described above.
Furthermore, the supply pipe 11 is not limited to the straight duct, and may be
5 constituted by one or two or more curved pipes in a circular are shape (not shown). The
minimum tilt angle a in this case is expressed by an angle formed by a tangent line at an
end on the downstream side of the curved pipe with respect to the horizontal direction. The
curved pipe can also be used as a part of the plurality of straight ducts constituting the
supply pipe 11.
10 [0056]
In the supply pipe 11 described above, a fall start position HT of the powder 10,
that is, a height H of a base end of the supply pipe 11 connected to the powder loading
hopper 18 (hereinafter, also simply referred to as height H) from the molten steel surface
13 is set to be in a range of from 0.5 m to 3 m inclusive. Moreover, in the supply pipe 11,
15 an angle 0 formed by an imaginary line (two-dot chain line shown in FIG. 1) connecting
the fall start position HT and the bottom end position of the supply pipe 11 (hereinafter,
referred to an end position P) with respect to the horizontal direction (hereinafter, also
simply referred to as "formed angle 0") is set to be an angle obtained by 54.6 x H0.5 or less.
As shown in FIG..1, therefore, the relationship between the minimum tilt angle a and the
20 formed angle 0 becomes such that the formed angle 0 is always greater than or equal to the
minimum tilt angle a (0 > a). The present inventors have found that, if the formed angle 0
is too large, when the powder 10 is supplied into the mold 12 the powder flies up into the
air when the powder 10 falls into the mold 12, thus degrading the work environment, and
further, it leads to an increase in the mold level fluctuation, which causes a deterioration in
22
steel piece quality.
[0057]
The reason why the height H and the formed angle 0 are defined as described
above, is described below.
5 The relationship between surface collision velocity V when the powder collides
against the molten steel surface, and the mold level fluctuation is described first with
reference to FIG. 3. Two types of powders, that is, hollow powder and granular powder are
used as the powder.
Generally, if the mold level fluctuation is small, the quality of the steel piece
10 (internal defects such as air bubbles or inclusions) is improved.
As is obvious from FIG 3, when the casting velocity is 0.6 m/minute or higher, an
increase in mold level fluctuation becomes noticeable when the surface collision velocity
V exceeds about 3.4 m/second. Accordingly, it has been found that the surface collision
velocity V of the powder needs to be set to 3.4 m/second or less.
15 Moreover, when a case in which the casting velocity is 0.6 in/minute or higher
(hereinafter, case 1) and a case in which the casting velocity is 0.3 to 0.5 m/minute
(hereinafter, case 2) are compared, a reduction effect of the surface collision velocity in
case 1 is larger than that in case 2. That is, when a reduction rate of the mold level
fluctuation when the surface collision velocity is decreased from 4 m/second to 3.4
20 m/second is compared between case 1 and case 2, the reduction rate of the mold level
fluctuation in case 2 is about 1/2 (= 2 nn/4 inn), whereas the reduction rate of the mold
level fluctuation in case 1 is 1/3 (= 5 nun/ 15 inn). As a result, it is confirmed that a larger
improvement can be seen in case 1 than in case 2. Consequently, it is confirmed that the
effect of the present invention can be manifested more in the case in which the casting
25 velocity is 0.6 nn/minute or higher.
23
According to the present invention, because the mold level fluctuation can be
suppressed to 5 mm or less, a desired steel piece quality can be maintained.
[0058]
Hereunder with reference to FIG, 4, is a description of the results of a study about
5 the relationship between the formed angle 0 and the height H (see FIG. 1) such that the
surface collision velocity of the powder 10 becomes 3.4 m/second or less at the time of
adjusting the height h of the end position P of the supply pipe 11 from the molten steel
surface 13 (see FIG, 2) to be in a range of from 100 to 300 mm. The height H was changed
in a range of from 0.5 in to 3 in inclusive. Moreover casting was performed by charging
10 molten steel of 350 tons/charge twice, and setting the casting velocity of the steel piece to
1.2 m/minute.
FIG. 4 shows experimental results ("o" in FIG. 4) for when the formed angle 0 and
the height H were changed so that the surface collision velocity V of the powder 10 became
3.4 m/second or less, and a solid line obtained by calculating a curved line fitted to the
15 experimental results. The solid line is an approximate line having a relation of 0 = 54.6 x
H-0.5
Thus, 0 = 54.6 x H-0.5 becomes a critical condition for maintaining the mold level
fluctuation to be 5 mm or less, and hence, the formed angle 0 is set to 54.6 x H-0.5 degrees
or less (0 < 54.6 x H-0.5)
20 [0.059]
FIG. 4 also shows the results of measurement of the mold level fluctuation by
using the hollow powder and the granular powder and by variously changing the formed
angle 0 and the height H. In FIG. 4, "o" indicates the results for when the mold level
fluctuation was 5 mm or less, and "x" indicates the results for when the mold level
24
fluctuation exceeded 5 mm.
As is obvious from FIG. 4, the measurement results of the mold level fluctuation
agree well with the calculation result. Furthermore, even when either powder of the
hollow powder and the granular powder was used, the mold level fluctuation of 5 mm or
5 less could be achieved by defining the formed angle 0. Variation in the mold level
fluctuation was small particularly at the time of using the hollow powder, and prediction
accuracy of the mold level fluctuation increased, and hence, it is particularly preferable to
use the hollow powder.
[0060]
10 According to the above results, it has been found that the height H of the fall start
position H1' of the powder 10 from the molten steel surface 13 needs to be set in a range of
from 0.5 m to 3 m inclusive, and the formed angle 0 needs to be set to 54.6 x H-0.5 or less.
It is preferred to set the lower limit of the height H to 1 m, taking the use
environment of the supply pipe I 1 into consideration. Moreover, it is preferred that the
15 formed angle 0 be set to 0 = 50 x HF0'5 or less, and more preferably, 45 X H-°'5 or less in
order to suppress the mold level fluctuation further.
[0061 1
As shown in FIG. , when the supply pipe 11 is seen in a side view, the end
position P is arranged so that the fall point of the powder 10 is inside the mold 12. On the
20 other hand, when the supply pipe 11 is seen in a plan view, it is preferred that the end
position P of the supply pipe 11 be within a range of from position R1 away from position
F on an inner wall surface of the mold 12 serving as a reference by 50 mnn toward the
molten steel surface 13 side (above the molten steel surface 13) to position R2 outward of
the mold 12 by 200 mm. Height h of the end position P of the supply pipe 11 from the
25 molten steel surface 13 is preferably in a range of from, for example, 100 nnn to 300 mm
25
inclusive.
For example, an inner space of the mold 12 for producing the steel piece has a
rectangular shape having a short side of about 250 mrn and along side of about 1000 mm,
as seen in a plan view. An outside diameter of the submerged nozzle 20 arranged in the
5 mold 12 is about 120 mm. Because the supply pipe 11 supplies the powder 10 from the
long side of the mold 12 toward between the inner wall surface forming the long side and
the submerged nozzle 20, the powder 10 is supplied into a gap of about 65 nun (_ (250
mm-120 mm) / 2).
[0062]
10 Accordingly, when the end position P of the supply pipe 11 is arranged at a
position toward the molten steel surface 13 side by 50 mm or more from the position F on
the inner wall surface, the supply pipe 11 interferes with the submerged nozzle 20 and a
complicated control mechanism is required for avoiding the interference, which is not
preferable.
15 Meanwhile, when the end position P of the supply pipe 11 is arranged at a position
outward of the mold 12 by 200 nun or more from the position F on the inner wall surface,
the powder 10 cannot fall reliably into the mold 12 under a condition in which the surface
collision velocity is 3.4 m/second or less. Consequently, the powder 10 is scattered around
the mold 12, and clogging of a cooling nozzle (not shown) of the continuous casting
20 equipment arranged on the downstream side of the mold 12, or deterioration of the dusty
envirornnent may occur.
[0063]
As described above, when the supply pipe 11 is seen in a plan view, the end
position P is within a range of from position R.1 away from the position F on the it-trier wall
25 surface of the mold 12 serving as a reference by 50 nun toward the molten steel surface 13
26
to position R2 outward of the mold 12 by 200 nun. However, in order to prevent
interference of the supply pipe 11 with other peripheral equipments in addition to the mold
12, or eliminate obstacles to monitoring the situation of the molten steel surface 13, it is
preferred that position R1 be set within a range of from a position away from the position F
5 on the inner wall surface of the mold 12 serving as a reference toward the molten steel
surface 13 by 20 mm to immediately above the position F on the inner wall of the mold 12
(on an extended line from the inner wall surface upward in the vertical direction).
Positioning of the end position P of the supply pipe 11 in the horizontal direction
and the height direction may be determined by actually supplying the powder 10. However,
10 the velocity and the like of the powder 10 discharged from the supply pipe 11 may be
substituted into an equation of motion to perform a simulation, thereby determining
positioning of the end position P based on the results thereof.
[0064]
Moreover, the powder 10 is loaded basically by using its own weight. However,
15 gas (for example, air) may be injected into the supply pipe 11, serving a role of assisting
the input. A flow rate of gas in this case is preferably from exceeding 0 to 3 liters/minute
inclusive, per flow passage cross-section of 1 cm2 in the supply pipe 11.
When auxiliary gas is injected into the supply pipe 11, clogging in the supply pipe
11, which may be caused according to the type of powder to be used (for example, hollow,
20 granular, or powdery powder, or grain diameter), can be reliably prevented. That is to say,
by injecting auxiliary gas into the supply pipe 11, the flow of the powder 10 in the supply
pipe 11 can be promoted and the powder 10 can be stably supplied into the mold 12.
[0065]
When the formed angle 0 was adjusted to 30 degrees, the height H was adjusted to
25 1 rri, and the injection flow rate of gas into the supply pipe 11 was adjusted to 1 liter/minute,
`I
2 liters/minute, and 3 liters/minute, respectively, to supply the powder 10, dust was not
generated and the powder 10 did not scatter around. However, when the injection flow rate
of gas in the supply pipe 11 became 4 liters/minute or more, the mold level fluctuation
increased, and dust was generated, deteriorating the surrounding environment. Thus,
5 when gas exceeding 3 liters/minute per flow passage cross-section of 1 cm2 in the supply
pipe 11 is injected, the surrounding environment deteriorates due to dust of the powder 10.
As described above, an appropriate flow rate of gas caused to flow in the supply
pipe 11 is set to be from exceeding 0 to 3 liters/minute or less per flow passage
cross-section of 1 cm2 in the supply pipe 11. It is more preferable to set the appropriate
10 flow rate of gas to be from 1 liter/minute as a lower limit, to 2 liters/minute as an upper
limit.
[0066]
When the speed of casting the steel piece made by the mold 12 is set to 0.6
m/minute or higher at the time of producing the steel piece while supplying the powder 10
15 into the mold 12 by using the supply pipe 11, the suppression effect of the mold level
fluctuation at the time of supplying the powder is particularly remarkable as described
above.
When the casting speed is lower than 0.6 in/minute, the flow of the molten steel
surface 13 in the mold 12 becomes slow and the mold level fluctuation is small originally,
20 and hence, the suppression effect of the mold level fluctuation at the time of supplying the
powder is not remarkable . On the other hand, as the casting speed increases, the
suppression effect of the mold level fluctuation at the time of supplying the powder
according to the present invention becomes remarkable . Accordingly, although the upper
limit is not defined , for example, 3 m/minute, which is the casting speed used in the general
25 operation, can be set as the upper limit.
28
The lower limit of the casting speed of the steel piece is set to 0.6 n1/minute
because of the reasons described above. However, the lower limit is preferably 0.8
m/minute, and more preferably, 1.0 m/minute.
[0067]
5 According to the flux loading apparatus, the continuous casting equipment, the
flux loading method, and the continuous casting method of the present embodiment
described above, the powder 10 can be supplied to the molten steel surface while
suppressing the mold level fluctuation of molten steel without hampering the operation on
the casting bed, by a simple configuration and method, thereby enabling to improve the
10 product quality of the steel piece.
[0068]
[Second embodiment]
Next, a second embodiment of the present invention will be described with
reference to the accompanying drawings.
15 As shown in FIG. 5, a continuous casting equipment of the present embodiment
includes; a transport device 110 for mold powder for continuous casting, a control device
(not shown) that controls operation of a transport screw feeder 118 and the li ke of the
transport device 110, and a mold 12.
At first, a flux loading apparatus using a flux loading method according to the
20 present embodiment, the continuous casting equipment equipped with the flux loading
apparatus, and a continuous casting method performed by the continuous casting
equipment will be described below.
[0069]
As shown in FIG. 5, the transport device 110 for mold powder for continuous
casting (hereinafter, also simply referred to as transport system) of the present embodiment
29
includes in the following order; a storage hopper 111 arranged along a transport direction
of granular powder (flux) used in the continuous casting method performed by the
continuous casting equipment, a screw feeder (an example of a screw conveyor) 112, an
attachment hopper 113, a screw feeder (an example of a screw conveyor) 114, a relay
5 hopper 115, a discharge screw feeder (an example of a discharge screw conveyor) 116, and
a swing apparatus 117, which is the flux loading apparatus of the present embodiment.
The two screw feeders 112 and 114 positioned on the upstream side of the relay
hopper 115 constitute a transport screw feeder (an example of a transport screw conveyor)
118. In the respective screw feeders 112 and 114, and the discharge screw feeder 116, the
10 internal diameters of their transport pipes and the configuration of their screws (not shown)
are the same, however these can be different.
[0070]
The storage hopper 111 stores granular powder.
An upstream side end of the screw feeder 112 disposed in a tilted manner
15 obliquely upward from the bottom end of the storage hopper 111 is fitted to the bottom end
of the storage hopper 111. The screw feeder 112 transports the granular powder in the
storage hopper 111 obliquely upward so as to pass through the attachment hopper 113. The
granular powder having passed through the attachment hopper 113 is transported to the
relay hopper 115 by the screw feeder 114. The attachment hopper 113 has only a function
20 of letting the granular powder pass therethrough. However, the attachment hopper 113
may have a function of temporarily storing the granular powder. In this case, operation of
the adjacent screw feeders 112 and 114 can be individually controlled with the attachment
hopper 113 as a boundary, according to an amount of the granular powder in the
attachment hopper 113.
25 In the present embodiment, a case in which the two screw feeders 112 and 114 are
0
arranged between the storage hopper 111 and the relay hopper 115 is described. However,
as shown in FIG. 6, the storage hopper 11 I and the relay hopper 115 may be directly
connected by one transport screw feeder (an example of a transport screw conveyor) 119
provided for the storage hopper 111. More specifically, an upstream side end of the one
5 transport screw feeder 119 is connected to the bottom end of the storage hopper 111, and a
downstream side end of the transport screw feeder 119 is connected to the relay hopper
115.
[0071]
The relay hopper 115 temporarily stores the granular powder.
10 A level meter (not shown) is installed in the relay hopper 115, and can measure a
stored amount of the granular powder in the relay hopper 115.
By providing the relay hopper 115, the screw feeders 112 and 114. on the upstream
side of the relay hopper 115 can transport the granular powder in the storage hopper 111
into the relay hopper 115, according to an amount of the granular powder in the relay
15 hopper 115 (that is, before the stored amount of the granular powder falls below a lower
limit set beforehand).
Moreover, the discharge screw feeder 116 on the downstream side of the relay
hopper 115 can transport the granular powder into the mold 12 by a predetermined amount,
according to the progress status of the casting work.
20 [0072]
The swing apparatus 117 includes; a loading hopper 120 to which the granular
powder is supplied by the discharge screw feeder 116, and a loading chute 121, which is a
supply pipe disposed in a tilted manner obliquely downward from a bottom part of the
loading hopper 120 to cause the granular powder supplied to the loading hopper 120 to fall
25 under its own weight thereby supplying the granular powder to the molten steel surface 13
31
in the mold 12.
Because the loading chute 121 is bent in an L shape as seen in a side view, a
connection portion between the loading chute 121 and the loading hopper 120 is turned
about a central axis along the vertical direction thereof, thereby enabling to scatter the
5 granular powder onto the molten steel surface 13 in the mold 12 in a circular are shape.
A distance from the storage hopper 111 to an upper end of the mold 12 (transport
distance of the granular powder) is, for example, from 7 in to 30 in inclusive. When the
distance is less than 7 in, a work, space on the casting bed on which the mold 12 is installed
cannot be ensured sufficiently. On the other hand, when the distance exceeds 30 m, the
10 pulverization rate of the granular powder rapidly increases at the time of remotely
transporting the granular powder by using the respective screw feeders. As a result, the
distance is preferably from 7 in to 30 in inclusive.
[0073]
The loading chute 121 is arranged substantially in the same manner as the supply
15 pipe 11 of the first embodiment with respect to the molten steel surface 13 in the mold 12.
That is to say, the height H from the molten steel surface 13 in the mold 12 to the loading
hopper 120 is set to a range of from 0.5 in to 3.0 m inclusive, the minimum tilt angle a of
the loading chute 121 relative to the horizontal direction is set to 20 degrees or more, and
the formed angle 0 of an imaginary line connecting a discharge opening of the granular
20 powder of the loading hopper 120 and a lower position of a front end of the loading chute
121 is set to 54.6 x H45 degrees or less. Furthermore, in the present embodiment, a tilt
angle of the loading chute 121 becomes the minimum tilt angle a.
[00 741
Next, the flux loading method using the flux loading apparatus (the continuous
casting method using the continuous casting equipment) of the present embodiment will be
32
described with reference to the transport system 110 for mold powder for continuous
casting.
In the continuous casting method of the present embodiment, the granular powder
used in continuous casting is transported from the storage hopper 111 to the relay hopper
5 1 1 5 via the transport screw feeder 1 ] 8, the attachment hopper 113, and the screw feeder
114. Moreover, the granular powder is supplied from the relay hopper 115 into the mold
12 by a predetermined amount via the discharge screw feeder 116, the loading hopper 120,
and the loading chute 121. At this time, according to the flux loading method of the
present embodiment, pulverization of the granular powder can be suppressed and
10 prevented.
The granular powder has, for example, a hollow shape having voids formed
therein, and an average grain diameter thereof is from about 200 l.cm `to 400 lim inclusive
(moreover, a lower limit is 250 μm, and an upper limit is 350 l.Lm). The granular powder
used in the present embodiment is powder known conventionally, and includes hollow
15 powder having voids formed therein, and granular powder. However, only powdery
powder is excluded.
[0075]
The continuous casting method including the control operation performed by the
control device provided in the continuous casting equipment of the present embodiment
20 will be described hereunder.
The screw feeder 114 and the screw feeder 112 constituting the transport screw
feeder 118 on the upstream side of the relay hopper 115 are sequentially operated to
transport the granular powder from the storage hopper 111 to the relay hopper 115. The
transport of the granular powder is automatically performed when the level meter installed
25 in the relay hopper 115 detects that the stored amount of the granular powder in the relay
33
hopper 115 becomes lower than the preset lower limit. As a result, the stored amount of
the granular powder in the relay hopper 115 can be automatically recovered.
[0076]
Moreover, the discharge screw feeder 116 on the downstream side of the relay
5 hopper 115 is operated to transport the granular powder in the relay hopper 115 to the
loading hopper 120. The transport of the granular powder is performed according to the
progress status of the casting work.
As a result, by turning the loading chute 121 about the central axis along the
vertical direction of the loading hopper 120, the granular powder can be evenly scattered
10 from the loading hopper 120 into the mold 12 via the loading chute 121.
[0077]
As described above, the transport screw feeder 118 that transports the granular
powder to the relay hopper 115 is operated only when the stored amount of the granular
powder in the relay hopper 115 becomes low. Therefore, the time interval from after
15 finishing transport of the granular powder to the relay hopper 115 until the granular
powder is transported to the relay hopper 115 again is long, and the utilization rate of the
respective screw feeders 112 and 114 is low (hereinafter, also referred to as l) w operating
rate).
On the other hand, the discharge screw feeder 116 that transports the granular
20 powder to the loading hopper 120 is operated according to the progress status of the casting
work. Therefore, transport and hold of the granular powder need to be performed
frequently and intermittently for short times, and hence, the utilization rate of the discharge
screw feeder 116 is very high (hereinafter, also referred to as high operating rate).
[0078]
25 Accordingly, by providing the relay hopper 115 between the transport screw
3 4
feeder 118 and the discharge screw feeder 116, the operation method of the transport screw
feeder 118 and the discharge screw feeder 116 can be changed with the relay hopper 115 as
a boundary.
Specifically, the transport screw feeder 118 with a low operating rate can perform
5 highspeed operation, such that one operation is performed in a time interval, for example,
of from 10 minutes to 30 minutes inclusive, for a short period of time of from 2 minutes to
5 minutes inclusive (that is, continuous operation), with the transport amount of the
granular powder being, for example, from 1 kg to 20 kg inclusive per minute. Moreover,
the discharge screw feeder 116 with a high operating rate can perform low-speed operation,
10 such that one operation is performed in a time interval, for example, of from 10 seconds to
1 minute inclusive, for a very short period of time of from 10 seconds to 1 minute inclusive
(that is, intermittent operation), with the transport amount of the granular powder being,
for example, from 0.1 kg to 3 kg inclusive per minute, so that the transport amount of the
discharge screw feeder 116 is less than the transport amount of the transport screw feeder
15 118.
[0079]
Here, the relationship between the transport distance of the granular powder, and
the pulverization rate thereof, at the time of transporting the granular powder by changing
the operation method of the screw feeders will be described with reference to FIG. 7.
20 FIG. 7 shows the results of a study of two operation modes of, a continuous
operation mode in which the granular powder is continuously transported, and an
intermittent operation mode in which the granular powder is intermittently transported in a
very short time. The number of revolutions of the screw of the screw feeder in the studied
respective operation modes is 90 rpm (revolutions per minute) and 00 rpm.
25 Moreover, the pulverization rate of the granular powder shown in FIG. 7 is
3 5
obtained by causing the granular powder after transport to pass through a finer mesh sieve
than the average grain diameter of the granular powder before transport, measuring the
weight of the sieved granular powder (that is, pulverized granular powder), and dividing
the measured value by the weight of the whole transported granular powder. Here, because
5 the average grain diameter of the granular powder before transport is about 3 00 μm, a sieve
in which the size of the sieve mesh is 70% or less of the average grain diameter of the
granular powder (here, 210 μm) is used.
[0080]
As shown in FIG. 7, when the screw feeder is continuously operated, the
10 pulverization rate of the granular powder gradually increases with an increase in the
transport distance of the granular powder. The pulverization rate fluctuates to a certain
extent by changing the number of revolutions of the screw. Howeve, the pulverization
rate is suppressed to 10% by mass or less, at which rate stable casting can be performed.
On the other hand, when the screw feeder is intermittently operated, the
15 pulverization rate of the granular powder rapidly increases with an increase in the transport
distance of the granular powder. When the number of revolutions of the screw is increased,
the increase rate of the pulverization rate also increases more rapidly.
From the above, it has been found that when the screw feeder is intermittently
operated for very short times, the pulverization rate of the granular powder increases and
20 stable casting may not be performed.
[0081]
The transport distance of the discharge screw feeder 116 is set shorter than the
transport distance of the transport screw feeder 118 (the total transport distance of the
screw feeders 112 and 114).
To perform stable casting, it is preferred to reduce the pulverization rate of the
36
granular powder to be supplied to the mold 12 to 15% by mass or less.
Consequently, it is preferred to set the transport distance of the discharge screw
feeder 116, which largely affects the pulverization rate of the granular powder, to 7 in or
less. However, it is preferred to set the transport distance of the discharge screw feeder 116
5 shorter (5 in or less), taking the rate of pulverization by the other transport screw feeder
118 into consideration. As the length of the discharge screw feeder 116 becomes shorter,
the pulverization rate of the granular powder rapidly decreases. Therefore, although the
lower limit is not defined, about 2 in (moreover, 3 m) can be used as the shortest length,
taking securement of the work space or the like into consideration.
10
Example
[0082]
Next, an example performed for confirming an operation effect of the present
embodiment will be described.
15 At first, FIG 8 illustrates operation methods of the respective screw feeders 112
and 114 constituting the transport screw feeder 118, and an operation method of the
discharge screw feeder 116 shown in FIG. 5.
The total transport distance of the respective screw feeders 112 and 114 arranged
between the storage hopper 111 and the relay hopper 115 was assumed to be 6 in, and the
20 transport distance of the discharge screw feeder 116 arranged between the relay hopper 115
and the loading hopper 120 was assumed to be 4 in. As a result, the transport distance of
the discharge screw feeder 116 became shorter than the transport distance of the transport
screw feeder 118.
[0083]
Moreover, the operation of the transport screw feeder 118 arranged between the
37
storage hopper ill and the relay hopper 115 was assumed to have a low operating rate
(that is, functions as a low operating rate feeder). Specifically, a continuous operation for
rotating the screw with a number of revolutions of 400 rpm for 3 minutes was performed
with intervals of 25 minutes. The transport amount of the granular powder at this time was
5 20 kg for 3 minutes.
On the other hand, the discharge screw feeder 116 arranged between the relay
hopper 115 and the loading hopper 120 was assumed to have a high operating rate (that is,
functions as a high operating rate feeder). Specifically, a continuous operation for rotating
the screw with a number of revolutions of 90 rpm for 30 to 40 seconds was intermittently
10 performed with intervals of 30 to 40 seconds. The transport amount of the granular
powder at this time was about 1 kg per one feed.
[0084]
The results are shown in FIG. 9. FIG. 9 also shows the results of a comparative
example obtained by performing a short time operation intermittently with intervals of 30
15 to 40 seconds, by arranging one screw feeder (transport distance: 10 m) between the
storage hopper 111 and the loading hopper 120 without providing the relay hopper 115,
and rotating the screw with a number of revolutions of 90 rpm for 30 to 40 seconds.
Here, because the average grain diameter of the granular powder before transport
was about 300 μm, the pulverization rate at this time was obtained by using a sieve having
20 a sieve mesh size of 210 μm.
As is apparent from FIG. 9, it was confirmed that the pulverization rate of the
granular powder could be suppressed to 15% by mass or less, which was a target value, by
providing the relay hopper 115, and changing the operation method of the transport screw
feeder 118 arranged on the upstream side thereof and the discharge screw feeder 116
25 arranged on the downstream side thereof. In the comparative example, the pulverization
38
rate increased up to about 30% by mass.
[0085]
From the above results, it was confirmed that with the continuous casting method
of the present embodiment, the pulverization of the granular powder could be suppressed.
5 Accordingly, the melting rate of the granular powder in the mold 12 can be
stabilized, a uniform melt layer is formed on the molten steel surface 13, and the granular
powder is caused to flow between the inner wall surface of the mold 12 and the solidifying
shell, thereby enabling to promote generation of the solidifying shell stably. As a result,
casting can be stably performed. Consequently, both the prevention of pulverization, and
10 the stable supply of the granular powder can be achieved, and stable casting can be
performed. As a result, product quality of the steel piece can be improved.
[0086]
The respective embodiments of the present invention have been described above.
However, the present invention is not limited to the configurations described in the
15 respective embodiments, and includes other embodiments or modified examples. For
example, a case in which a part or all of the respective present embodiments and the
modified example are combined to constitute the present invention is included in the scope
of the present invention.
In the second embodiment, a case in which the transport screw feeder 118
20 arranged between the storage hopper 111 and the relay hopper 115 includes the two screw
feeders 112 and 11 / serially arranged has been described. However, the configuration
thereof is not limited to this configuration, and the transport screw feeder 118 may include
three or more (actually, 10 or less) screw feeders serially arranged. In this case, it is
preferred to provide an attachment hopper that connects a downstream side end and an
25 upstream side end of the respective screw feeders, between the adjacent screw feeders.
39
Industrial Applicability
[0087]
According to the present invention, a flux loading apparatus, a continuous casting
equipment, a flux loading method, and a continuous casting method that can improve the
product quality of a steel piece can be provided.
Brief Description of the Reference Symbols
[0088]
10 10 Powder
11 Supply pipe
12 Mold
13 Molten steel surface
14. Tundish cradle
15 15 Storage hopper
16 Down corner
17 Transfer tube
18 Powder loading hopper
19 Tundish
20 20 Submerged nozzle
21 to 24 Straight ducts
110 Transport device for mold powder for continuous casting
111 Storage hopper
112 Screw feeder
25 113 Attachment hopper
4.0
114 Screw feeder
115 Relay hopper
116 Discharge screw feeder (discharge screw conveyor)
117 Swing apparatus (flux loading apparatus)
118 and 119 Transport screw feeders (transport screw conveyor)
120 Loading hopper
121 Loading chute (supply pipe)

CLAIMS
1. A flux loading apparatus comprising:
a loading hopper that temporarily stores a flux; and
5 a supply pipe disposed in a tilted mariner with a rear end thereof being connected
to the loading hopper and a front end thereof being located above a mold,
wherein a height H from a molten steel surface in the mold to the loading hopper
is in a range of from 0.5 m to 3.0 m inclusive;
a minimum tilt angle a of the supply pipe relative to a horizontal direction is 20
10 degrees or more; and
a formed angle 0 of an imaginary line connecting a flux discharge opening of the
loading hopper and a lower position of the front end of the supply pipe relative to the
horizontal direction is 54.6 x H-0.5 degrees or less.
15 2. The flux loading apparatus according to claim 1, wherein the supply pipe has a
plurality of straight ducts connected to each other, and a smallest tilt angle of a duct
relative to the horizontal direction of these straight ducts is the minimum tilt angle a.
3. The flux loading apparatus according to claim 1, wherein a position in the
20 horizontal direction of the front end of the supply pipe is in a range of from a position
inward of the mold by 50 mm to a position outward of the mold by 200 mm, when a
position on an inner wall surface of the mold at a position immediately below the supply
pipe is designated as a reference.
5 4. The flux loading apparatus according to claim 1, further comprising a gas supply
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unit that injects gas into the supply pipe at a flow rate of from exceeding 0 to 3
liters/minute inclusive, per flow passage cross-section of 1 cm2 in the supply pipe.
5. A continuous casting equipment comprising; the flux loading apparatus accordin
5 to any one of claim 1 through claim 4, and the mold.
6. The continuous casting equipment according to claim 5, wherein a casting speed
of a steel piece made by the mold is 0.6 m/minute or higher.
10 7. The continuous casting equipment according to claim 5, further comprising:
a storage hopper that stores the flux;
a transport screw conveyor that transports the flux from the storage hopper;
a relay hopper that receives the flux transported by the transport screw conveyor;
a discharge screw conveyor provided between the relay hopper and the loading
15 hopper; and
a control device that controls an operation of the transport screw conveyor,
wherein a transport distance of the discharge screw conveyor is shorter than a
transport distance of the transport screw conveyor; and wherein
the control device controls a transport amount by the transport screw conveyor to
20 a predetermined transport amount or more for a predetermined time.
8. The continuous casting equipment according to claim 7, wherein the transport
distance of the discharge screw conveyor is 7 m or less.
25 9, The continuous casting equipment according to claim `/, wherein
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the predetermined time is from 2 minutes to 5 minutes inclusive; and wherein
the predetermined transport amount is in a range of from 1 kg/minute to 20
kg/minute inclusive.
5 10. The continuous casting equipment according to claim 7, wherein
the transport screw conveyor includes:
a plurality of screw conveyors; and
an attachment hopper arranged between these screw conveyors, and wherein
the control device individually controls a transport operation of each screw
10 conveyor.
11. A flux loading method for causing flux to fall through a supply pipe disposed in a
tilted manner to supply flux to a molten steel surface in a mold, wherein:
a height H from the molten steel surface to a fall start position of the flux is set to
15 a range of from 0.5 m to 3.0 m inclusive;
a minimum tilt angle a of the supply pipe relative to a horizontal direction is set to
20 degrees or more; and
a formed angle 0 of an imaginary line connecting the fall start position and a
lower position of a front end of the supply pipe relative to the horizontal direction is set to
20 54.6 x H-0 .5 degrees or less.
12. The flux loading method according to claim 11, further comprising a process of
injecting gas into the supply pipe at a flow rate of from exceeding 0 to 3 liters/minute
inclusive, per flow passage cross-section of 1 cm2 in the supply pipe.
25
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13. A continuous casting method comprising a process of supplying a flux to the
molten steel surface in the mold by using the flux loading method according to claim 11 or
claim 12.
The continuous casting method according to claim 13, wherein a casting speed of
a steel piece made by the mold is 0.6 m/minute or higher.
15. The continuous casting method according to claim 13, further comprising:
a process of transporting the flux from a storage hopper that stores the flux to a
10 relay hopper via a transport screw conveyor; and
a process of supplying the flux from the relay hopper into the mold via a discharge
screw conveyor, the loading hopper, and the supply pipe, wherein
a transport distance of the discharge screw conveyor is shorter than a transport
distance of the transport screw conveyor; and wherein
15 a transport amount by the transport screw conveyor is set to a predetermined
transport amount or more for a predetermined time.
16. The continuous casting method according to claim 15, wherein the transport
distance of the discharge screw conveyor is 7 m or less.
20
17. The continuous casting method according to claim 15, wherein
the predetermined time is from 2 minutes to 5 minutes inclusive, and
the predetermined transport amount is in a range of from 1 kg/minute to 20
kn/minute inclusive.
25
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18. The continuous casting method according to claim 15, wherein:
the transport screw conveyor comprises a plurality of screw conveyors, and an
attachment hopper arranged between these screw conveyors; and
a transport operation of each screw conveyor is individually controlled.