JPH0448542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for rapidly casting metal strip. In particular, the invention aims at a method and a device for rapidly stopping a casting operation.

To rapidly cast metal strip, a controlled flow of molten metal is applied onto a cooled casting surface. The tundish for injecting molten metal has a nozzle or orifice passageway of a predetermined configuration to control the flow of molten metal onto the casting surface.
This metal is poured into the tundish from a ladle or directly from a furnace or the like. Although strip casting is a continuous operation, there may be times when it becomes necessary to stop the casting operation.

Previous methods for stopping a continuous casting operation include stopping the injection of molten metal into the tundish. However, even if the supply of molten metal is stopped, the molten metal existing in the tundish
It continues to flow through the nozzle onto the casting surface. The cessation of molten metal replenishment to the tandate significantly disrupts casting operations that require strict maintenance of stable working conditions. That is, if molten metal replenishment stops, the feeder head pressure on the molten metal and the metal flow pattern against the casting surface will change, resulting in the production of poor quality strip, scrap strip, or molten metal splashing. Finally, the tundish is almost empty and the orifice passage is solidified and blocked.

The formation of low quality strips at the end of the casting operation can damage already produced high quality strips or damage the strip casting equipment. Furthermore, molten metal droplets from the tundish can fall on already manufactured high quality strips and cause damage such as burns.

It is therefore desirable in a strip casting method and apparatus to be able to stop the strip casting operation almost instantaneously when desired.

The continuous strip casting apparatus according to the present invention has a tundish having an internal space for receiving and holding molten metal, and the molten metal is internally passed through an orifice passage formed between two spaced apart lips provided in the tundish. The molten metal in the space is supplied to the casting surface, and the casting surface is approximately 0.120 inches (approximately 3 mm) or less from the orifice passage.
It passes at a linear speed of 10,000 ft/min (approximately 60 to 3,000 m/min). According to the invention, at least one opening communicating with the interior space of the tundish is provided, and a removable plug is engaged in the opening. The dimensions of the opening must be large enough to draw off molten metal within the interior space and to reduce the feeder head pressure in the orifice passageway to a value less than the strip casting pressure required. According to the present invention,
A method for substantially instantaneously stopping a casting operation includes selectively unplugging an aperture of desired size communicating with a tundish.

An advantage of the invention is that the casting operation is stopped almost instantaneously. This is a great advantage in that the metal flow can be immediately stopped when unforeseen problems arise during the casting operation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a strip casting apparatus to optionally stop the metal flow to the casting surface and prevent damage to the already cast strip. Rapidly stopping metal flow is
Prevent damage to stripping and casting equipment.

Another object of the invention is to remove the molten metal from the strip casting tundish after the casting operation is completed;
The objective is to enable the tandate to be reused for the next casting operation.

The present invention will be described with reference to illustrative embodiments and drawings.

1-4 illustrate a preferred strip casting apparatus according to the present invention. As shown in the figure, the device has a tundish 10. Tundish 10 has an interior space 12 for receiving and holding molten metal. There is an orifice passage 14 in the tandem tray 10.
That is, it has a nozzle, and the molten metal in the space 12 is supplied to the casting surface 16 through an orifice passage 14 .

In a preferred embodiment, the molten metal flows through nozzle 14.
is supplied to the outer peripheral surface 16 of the casting ring. The cast wheels are made of a water-cooled, precipitation-hardened copper alloy containing approximately 99% copper. Although copper and copper alloys were selected for their high thermal conductivity and high wear resistance, other materials may be used for the casting surface 16. In operation of the apparatus of the present invention, whether the casting surface 16 is circular, flat, or elliptical, the casting surface 16 extends in front of the nozzle 14 approximately 200 to
It moves at a linear speed of 10,000 ft/min (approximately 60 to 3,000 m/min).

As shown in FIG. 1, the tundish 10 includes at least one upper block 20 and at least one
It has two rear blocks 30 and an intermediate block 22. In this specification, up and down and front and back refer to the casting surface 1.
6, and upper and rear indicate positions away from the casting surface 16. Vertical refers to gravity.
In the example of FIG. 1, the upper and lower blocks 20, 30 are vertically stacked and fixed. This vertical arrangement is described in the same application. To prevent molten metal in a space 12 from leaking from a joint surface in the case of overlapping arrangement. As shown in FIG. 1, the orifice passage 14
coincides with the joint and passes the molten metal. "Leakage" of the mating surface does not include passage through the orifice passageway 14. In addition to the vertical arrangement shown in FIG. 1, the configuration of the tundish 10 may be horizontally stacked, or may be an integral structure.

Space 12 formed within the tundish
The molten metal can freely flow from the top opening to the space 12
It is shaped so that it flows through the orifice passage 14 and the casting surface 16. The tundish 10 need not be generally rectangular in shape as shown in the figures.

The tundish material used in the apparatus of the present invention must be resistant to erosion by molten metal. In this respect, insulating boards, such as fiberized kaolin, are suitable. Other materials such as graphite, alumina graphite, refractory clay, clay graphite, quartz, boron nitride, silicon nitride, silicon carbide, boron carbide,
Alumina, silica, zirconia, stabilized zircon silicate, magnesia, chromium magnesite,
Mixtures of these can be used.

In a preferred embodiment, the tundish 10 is
Formed by vertically or horizontally stacking 1.5 inch (approximately 38 mm) thick Kao Wool fireproof boards. Blocks of required thickness can be used depending on the required strip casting conditions. The reason for choosing 1.5in (approximately 38mm) is because it is available on the market. Further, fiberized kaolin blocks have the advantage of being relatively inexpensive and easy to process and drill the required space 12, orifice passageway 14. However, other materials can also be used, for example those mentioned above, and instead of machining it can also be cast.

Space 12 of the tundish 10 is the introduction part 3
It has 2. The introduction part 32 passes through the upper part of the tundish 10 from the upper surface of the tundish 10 and communicates with a base part 34 formed as a hollow part in the lower part of the tundish 10. Although the opening of the introduction space 32 is formed on the top surface as shown, it may also be formed on the side wall of the tundish. Further, in the illustrated example, the opening has a funnel-shaped curved surface to facilitate metal injection.

The structure of the base space 34 and orifice passageway 14 is important in the device of the present invention. The base space 34 is formed at the bottom of the tundish by machining or casting, and is preferably formed between the bottom surface of the intermediate block 22 and the curved surface 38 machined into the lower block 30.
As shown in the figure.

In the illustrated example, the bottom surface 3 of the base space 34
8 is located below the height of the orifice passage 14. In this embodiment, the base space 3
4 is at least 0.25 inches (approximately 6 mm) below the orifice passageway 14.
Additionally, in this embodiment, the bottom surface 38 of the base space 34 is sloped upwardly toward the orifice passageway 14 at an angle of at least 30 degrees from horizontal toward the orifice passageway.

The orifice passageway 14 through which molten metal flows onto the casting surface 16 has a substantially uniform width over its entire length. This width dimension is at least approximately 0.010in (approximately 0.25in)
mm) and approximately 0.120in (approximately 3mm) or less. As a preferred value, the width dimension range of the orifice 14 is approximately
0.020~0.060in (approximately 0.5~1.5mm) A more suitable value is approximately
It should be 0.03~0.05in (approximately 0.76~1.3mm).

Orifice passageway 14 may be manufactured in a variety of ways. In the example shown in FIG. 1, the orifice passage 14
is formed by a cut in the bottom surface 36 of the intermediate block 22 and the front wall of the bottom block 30. As shown, a molten metal resistant plate 40 is attached to the intermediate block 22.
It is preferable to fix it to. Regardless of the orifice passage forming method, the orifice width must maintain a narrow tolerance.

In a preferred embodiment, at least one surface forming the orifice passageway 14 is a surface of a plate 40 attached to one of the blocks. Preferably, the upper surface of the orifice passageway 14 is the surface of a plate 40 of molten metal resistant material. Since it is important to maintain the upper surface of the orifice passage during casting to the specified shape and dimensions,
A plate 40 is used on the top. However, the lower surface or the upper and lower surfaces of the orifice passage 14 can also be used as the surface of the plate 40. The plate 40 shall have at least the same resistance to molten metal as the block, and preferably has a higher resistance to molten metal than the material forming the tundish 10.
Significantly increases the molten metal resistance of the material. 1st
As shown, the plate 40 is secured within a slot cut into the bottom surface 36 of the intermediate block 22. The length of the plate 40 is greater than the length of the orifice passage 14. Thus, the ends of plate 40 are connected to blocks 22,3.
Sandwiched between 0.

In a preferred example, plate 40 is of the boron nitride type;
Other materials such as silicon nitride, silicon carbide, boron carbide,
Silica, alumina, zirconia, stabilized zircon silicate, graphite, alumina graphite,
It can be made of refractory clay, clay grahite, quartz, magnesia, chrome magnesite, and mixtures thereof.

As mentioned above, the introduction space 32 communicates with the base space 34. In a preferred embodiment, the introduction space 32 is a tubular passage within the tundish 10. The total height of the tubular passage is 10 mm.
orifice passageway 14 to provide the necessary spacing height to maintain control of the required feeder head pressure. By maintaining a nearly constant molten metal height approximately 2 inches (approximately 50 mm) above the orifice passageway, the feeder head pressure is approximately 1/2 psi (approximately 35
g/cm ² ), and the required value for strip casting can be obtained.

In the preferred embodiment, a device is provided for heating the plate 40 forming the lip of one or both of the orifice passageways 14. An example for this is to attach at least one blowpipe to the tundish, with the tip pointing towards the plate 40. Another opening is provided in the plate 40 through which the combustion products of the combustion gases blown from the blowpipe are discharged from the tundish. This allows the temperature of the plate 40 to rise to the required value before the start of strip casting. Heating the plate 40 to near the melting point of the alloy to be cast will prevent the alloy from solidifying in the orifice passageway at the beginning of the casting operation. Reactive gas is sent toward the plate 40 from a plurality of blowpipe, and high temperature flame is blown onto the plate 40. In order to prevent the erosive effect of the flames on the plate 40, the plate 40
A heat conductive layer can be fixed to a part of the upper surface of the plate, that is, the part where the flame impinges on the plate. This thermally conductive layer prevents flame erosion and transfers heat to the plate 40 below. In the preferred example, the thermally conductive layer is grahite, but other materials can be used, and this construction is described in the same application.

As shown in the figure, according to the present invention, at least one
An opening 60 is passed through the lower part of the tundish 10. The opening 60 communicates with a portion of the base space 34 and is vertically below the orifice passageway 14. A plug 62 is installed in the opening 60. Plug refers to any molten metal stop device that can be opened as required, such as a gate, flap, or stop rod. The purpose of opening 60 and plug 62 is to direct molten metal within tundish 10 and almost instantaneously stop the flow of molten metal through orifice passageway 14 to stop strip casting when desired.

As a result of strip casting practices, the casting operation must be stopped within 1 second, preferably within about 1/2 second, to prevent orifice passageway 14 from continuing to feed molten metal onto casting surface 16 in an uncontrolled manner. It turns out that there is. Therefore, the above-mentioned substantially instantaneously means within at least one second. In order to almost instantaneously stop the supply of molten metal to the orifice passageway 14, the dimensions of the opening 60 are such that the plug 6
The dimensions shall be such that a sufficient amount of molten metal can be discharged in sufficient quantity when 2 is removed. This molten metal flow must have the effect of reducing the feeder head pressure in the orifice passage below the pressure required for strip casting.

In a preferred embodiment, the orifice passageway 14 is vertically upward relative to at least a portion of the base space 34 relative to the direction of pressure in the tundish 10, as shown. In a preferred embodiment, the bottom of space 34 is at least about 0.25 inches (about 6 mm) below orifice passageway 14. The direction of pressure is usually the direction of gravity. The tundish 10 can be located anywhere on the outer circumference of the casting surface 16, and the casting pressure can be supplied from other pressure sources than the riser head. In the illustrated tundish arrangement, one or more openings may be provided below the orifice passageway in the direction of gravity and communicate with a portion of the tundish space for discharging the metal stream.

The dimensions of the openings through which molten metal exits the tundish will vary depending on the strip casting parameters used. Functionally, the openings are sized to reduce the riser head pressure in nozzle 14 below the pressure required for strip casting. As a specific example, the lip gap of orifice passage 14 is approximately
The gap between the orifice passage 14 and the casting surface 16 should be approximately 0.010 in.
~0.020in (approximately 0.25~0.5mm), the feeder head pressure in the orifice passage 14 is approximately 0.5psi.
(approximately 35 g/cm ² ). The gap between the lips of the orifice passage 14 is wide, for example about 0.060 to 0.100 inches (about
1.5 to 2.5 mm), and when the gap between the orifice passage and the casting surface is 0.010 to 0.020 inches (approximately 0.25 to 0.5 mm), the feeder head pressure in the orifice passage should be approximately
An opening large enough to lower the pressure to 0.25 Psj (approximately 18 g/cm ² ) is required. This pressure drop must be achieved within about 1 second after plug removal.

According to a preferred embodiment, plug 62 is fabricated from a molten metal resistant, heat resistant material, such as fiberized kaolin. A method is needed to facilitate sealing the plug. For example, a thin, flat or small diameter refractory seal may be applied to the plug and tundish interface to seal off leakage paths. Cementation is also possible, but the plug extraction device requires force to reliably break the cement seal when required.

To pull out the plug 62 from the hole 60 of the refractory tundish of the present invention, it is necessary to
Kg) force is required. For this purpose, a pneumatic cylinder is used to automatically withdraw the plug 62 when required. Any necessary device for withdrawing the plug 62 or moving the gate or stop rod may be used, such as hydraulics, screw jacks, etc.
It is also possible to remove the plug 62 by hand.

When the plug 62 is removed as shown in FIG. 4, molten metal flows out the opening. The diameter of the opening is large enough so that the flow rate of molten metal exiting the tundish space is greater than the flow rate fed into the space. In the example shown in FIGS. 3 and 4, a gutter 70 is provided to allow the discharged metal to flow into another container 72 or the like.

Casting operations must be stopped as quickly as possible. When the stop is not rapid, an uneven or intermittent flow of molten metal exits the nozzle at the end of the casting operation, and this intermittent flow exits onto the rapidly moving casting surface 16. At this time, the casting surface does not have the control necessary to produce high quality strips. This can result in uncontrolled splashes of molten metal falling onto and damaging the casting strip of the product or damaging parts of the strip casting equipment.

Furthermore, in order to reuse the tundish 10, it is necessary to extract the molten metal within the space 12 from the tundish 10 at the end of the work.
By removing the plug 62, substantially all of the molten metal within the tundish flows out through the plug hole 60, and the tundish requires little cleaning or processing for use in subsequent castings.

The internal geometry of the casting space is important with respect to the final quality of the metal strip produced. The importance of this shape increases as the width of the casting strip casting apparatus increases. When the melt temperature, riser head height, orifice opening, plate 40 temperature, casting surface speed, and orifice-to-casting surface gap are constant, a small change in the design of the tundish space can result in a wider metal strip width. The quality change in direction may be significant. The preferred shape has the following parameters: slope and cross-sectional shape of the space. According to a preferred embodiment, the bottom surface 38 of the base space 34 faces upwardly toward the orifice passageway 14 at an angle of at least 30 degrees from the horizontal. Furthermore, the bottom surface 38 of the base space 34 is dish-shaped. In particular, the height of the central base space is at least approximately 0.10 inches greater than the height measured at both lateral edges of space 34.
(approx. 2.5mm) higher. The introduction space 32 of the tundish of the present invention is formed by drilling one or more holes of a desired size in the tundish material. The shape of the tundish bottom is outwardly fan-shaped and flares outwardly from the tubular inlet space 32 in the direction of the orifice passageway 14 approximately equal to the width of the strip to be cast. The number of holes to be made when forming the inlet space 32 in the tundish is usually determined by the width of the strip to be cast, ie, the length of the orifice passage 14.

As mentioned above, the orifice passage 14 has a substantially uniform opening width along its entire length. This width dimension can vary slightly at the lateral edges of the orifice passage. In particular, to improve the quality of the edges of the metal strip produced by the apparatus of the invention, the edges of the orifice passage may be provided with a slightly wider opening width. If this edge is widened, it should not exceed 1.5 times the width of the orifice passage, and the length of the widened portion should not exceed twice the constant opening width of the orifice passage 14. By widening the opening width at the edges, slightly more molten metal is available at the edges compared to the center. The opening width is made wider so that it increases continuously toward the edge. The opening width must not decrease towards the edges.

Although the present invention has been described using preferred embodiments, the present invention can be modified in various ways, and the embodiments and drawings are illustrative and do not limit the invention.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the tundish of the strip casting apparatus of the present invention, Fig. 2, Fig. 3 is a sectional view showing another embodiment of the tundish, and Fig. 4 is a sectional view of the apparatus of Fig. 3 with the plug removed. be. 10...Tandateshiyu, 12...Internal space,
14... Orifice passage (nozzle), 16... Casting surface,
20, 22, 30...Block, 32...Introduction space, 34...Base space, 38...Bottom surface, 4
0...Plate, 60...Plug hole, 62...Plug.

Claims (1)

[Scope of Claims] 1. A tundish having an internal space for receiving and holding molten metal in a strip casting device, an orifice passage formed between two spaced apart lips of the tundish and supplying molten metal to a casting surface, and an orifice passage. and a casting surface that passes within approximately 0.120 inches (approximately 3 mm) from , the openings are sized to drain molten metal from the interior space to reduce the feeder head pressure in passage through the orifice to a pressure below the strip casting pressure; 1. A strip casting apparatus, comprising: a plug positioned downwardly and engaged with the opening to prevent molten metal from flowing out; and a device for removing the plug from the opening. 2. The device according to claim 1, wherein the orifice passage is located above at least a portion of the space with respect to the direction of pressure within the tundish. 3. The apparatus of claim 1, wherein the opening is dimensioned to allow at least the same flow rate of molten metal to be discharged from the tundish space as it is supplied to the tundish space. 4 The distance between the lips of the orifice passage is approximately
The gap between the orifice passage and the casting surface should be approximately 0.020~0.060in (approximately 0.5~1.5mm).
0.020 in ( ^approx .
35 g/cm ² ) or less. 5 The distance between the lips of the orifice passage is approximately
The gap between the orifice passage and the casting surface should be approximately 0.060~0.100in (approximately 1.5~2.5mm).
0.010 to 0.020 inches (approximately 0.25 to 0.5 mm), and the opening is designed to control the feeder head pressure in the orifice passage.
2. The device of claim 1, wherein the device is sized to be lower than 0.25 lb/in ² (approximately 18 g/cm ² ). 6 The tandate is made of boron nitride, silicon nitride,
silicon carbide, boron carbide, silica, alumina, zirconia, stabilized zircon silicate, graphite,
Alumina graphite, refractory clay, clay graphite, fiberized kaolin, quartz, magnesia,
2. The device of claim 1, wherein the device is made of a molten metal resistant material selected from the group consisting of chromium magnesite and mixtures. 7. A method of stopping strip casting work almost instantaneously, and it is a method for stopping strip casting work almost instantaneously.
The plug is removed from the opening communicating with the molten metal holding space of the tundish having an orifice passage that supplies the molten metal flow to the casting surface passing at a linear velocity of about 60 to 3000 m/min. 1. A method for casting strip, characterized in that the molten metal is withdrawn from within the metal holding space to reduce the feeder head pressure in the orifice passage below the pressure required for strip casting.