JP2020163391A - Stopper - Google Patents

Abstract

To provide a stopper adjusting the flow rate of a molten metal exhausted from a nozzle at the bottom of a container by the degree of nozzle blockage at a head part, and further performing the blowing of a gas to the molten metal, in which the damage of the lower edge part in the head part is suppressed.SOLUTION: A stopper 1 comprises: a cylindrical core grid 10; a ceramic sintered compact layer 30 covering the outer circumferential face at the lower edge part thereof; and a refractory layer covering the outer circumferential face and the upper edge face 35b of the ceramic sintered compact layer and the outer circumferential face of the core grid. An immersion part immersed at least in a molten metal in the refractory layer is an integrated structure of a monolithic refractory layer 20 formed by a castable refractory material including a head part, a recessed face part 33 is provided between a diameter reduction face part 32 in which the diameter of the outer circumferential face of the ceramic sintered compact layer is reduced toward the lower edge and a diameter expansion face part 31 having a diameter expanded toward the lower edge, and further, the diameter expansion face part is adjacent to the lower edge face 35a.SELECTED DRAWING: Figure 1

Description

The present invention relates to a stopper that adjusts the flow rate of molten metal discharged from a container such as a ladle during casting and blows gas into the molten metal.

For casting, the molten metal transferred in the ladle may be discharged from the ladle and directly injected into the mold, or the molten metal discharged from the ladle may be injected into the mold via an intermediate container such as a tundish. However, stoppers are used when discharging molten metal from containers such as ladle and tundish. The flow rate of the molten metal is adjusted by the degree to which the nozzle provided at the bottom of the container is blocked by the head portion of the stopper.

Some of these stoppers have a gas flow passage inside and blow an inert gas such as argon or a nitrogen gas into the molten metal. When the molten metal flows into the nozzle, a negative pressure is generated along with the flow and air is entrained, so that the molten metal may be oxidized, and a gas such as argon is blown through the stopper. This prevents oxidation of the molten metal. Further, by decompressing the tank in which the mold is installed and using a gas blowing type stopper when injecting the molten metal into the decompression tank, the particles of the molten metal are made finer by blowing the gas, which is effective. Refining for degassing such as dehydrogenation and denitrification is also performed.

In the conventional gas blowing type stopper, the outer peripheral surface of the tubular core metal constituting the gas flow passage was covered with refractory bricks. More specifically, the coating layer of the stopper is composed of a plurality of sleeve-shaped refractory bricks and a head portion formed of the refractory bricks, and these refractory bricks are joined to each other by a mortar so that they are adjacent to each other. Joints were formed between the refractory bricks.

The stopper expands when immersed in extremely hot molten metal, but the coefficient of thermal expansion of the metal core metal is extremely large compared to refractories. Therefore, in the conventional stopper, the joint portion between the refractory bricks is opened due to the thermal expansion of the core metal. Then, when the molten metal infiltrates through the open joint portion, the core metal may be melted, and the gas flowing through the core metal may be ejected from the melted portion to scatter the molten metal.

Therefore, in the past, the applicant has proposed a gas-blown type stopper in which melting damage of the core metal is suppressed (see Patent Document 1). This is an integral part of the amorphous refractory layer formed of a castable refractory material, including the head portion, at least the immersed portion immersed in the molten metal, among the refractory layers covering the outer peripheral surface of the core metal. It is a structure.

Since the stopper having such a configuration has no joint in the refractory layer at least in the immersion portion immersed in the molten metal, even if the core metal thermally expands when immersed in the high-temperature molten metal, the joint It is possible to avoid the problem that the core metal is melted and damaged due to the infiltration of the molten metal through the portion. In addition, since irregular refractories made of castable refractory materials generally have lower thermal conductivity than refractory bricks of the corresponding material, heat transfer from high-temperature molten metal to the core metal is suppressed, and thermal expansion of the core metal is suppressed. It can be reduced.

In addition, with the conventional stopper, the head portion may fall off due to the opening of the joint portion existing between the refractory bricks of the head portion and the sleeve-shaped refractory bricks. In particular, if the head portion falls off while the nozzle is blocked by the head portion, the flow rate of the molten metal cannot be adjusted. On the other hand, in the stopper of Patent Document 1, at least the refractory layer in the immersion portion is an integral structure of the amorphous refractory layer made of castable refractory material including the head portion, so that the head portion may fall off significantly. It has the advantage of being reduced to.

Therefore, the stopper of Patent Document 1 can significantly extend the usage time as compared with the conventional stopper, and can be used for large-scale casting over a long period of time. However, the stopper of Patent Document 1 also has room for improvement in that the lower end portion of the head portion is easily damaged.

Specifically, as schematically shown in FIG. 4, there is a problem that the amorphous refractory layer 120 of the head portion 122 is easily damaged so as to be partially lost at the peripheral edge of the lower end opening 115 of the core metal 110. was there.

Japanese Patent No. 4638932

Therefore, in view of the above circumstances, the present invention adjusts the flow rate of the molten metal discharged from the nozzle at the bottom of the container according to the degree of blocking the nozzle at the head portion, and blows gas into the discharged molten metal. An object of the present invention is to provide a stopper for which damage to the lower end portion of the head portion is suppressed.

In order to solve the above problems, the stopper according to the present invention is
"The flow rate of the molten metal discharged from the container accommodating the molten metal through the nozzle provided at the bottom of the container is adjusted by closing the nozzle with the head portion, and the molten metal is discharged. It is a stopper that blows gas.
Cylindrical or elliptical tubular core metal that allows gas to flow inside,
A ceramic sintered body layer that covers the outer peripheral surface of the lower end of the core metal,
A refractory layer covering the outer peripheral surface and the upper end surface of the ceramic sintered body layer and the outer peripheral surface of the core metal is provided.
The refractory layer constitutes the head portion in a shape in which the lower end portion is continuously curved and bulges, and at least the immersion portion immersed in the molten metal is castable fire resistant including the head portion. It is an integral structure of an amorphous refractory layer formed of a material.
The outer peripheral surface of the ceramic sintered body layer has a concave shape because the reduced diameter surface portion whose diameter is reduced toward the lower end and the enlarged diameter surface portion whose diameter is increased toward the lower end are adjacent to each other. It has at least one concave surface
The lower end surface of the ceramic sintered body layer is adjacent to the enlarged diameter surface portion. "

"Container for accommodating molten metal" refers to an intermediate container such as a ladle or a tundish.

"Upper and lower" in this document, such as "lower end" and "upper end" in "stopper", are "up and down" with respect to a stopper in use that closes the nozzle at the bottom of the container with the head portion of the stopper.

As described above with reference to FIG. 4, the reason why the amorphous refractory layer 120 of the head portion 122 is easily damaged so as to be partially lost at the peripheral edge of the lower end opening 115 of the core metal 110 in the conventional stopper is described in the present invention. The inventors considered as follows. That is, as schematically shown in FIG. 5, when the nozzle 152n opened at the bottom portion 152b of the container is partially closed by the head portion 122 of the stopper, the gap between the head portion 122 and the opening edge of the nozzle 152n is opened. The molten metal flows into the nozzle 152n through the nozzle (see the arrow on the alternate long and short dash line in the figure). At that time, when the gas G is blown into the molten metal through the core metal 110 (see the dotted arrow in the figure), the blown gas G hits the vicinity of the opening edge of the nozzle 152n and bounces off so that the molten metal is wound up. (See the solid arrow in the figure). In this way, the amorphous refractory layer 120 is physically eroded by repeated contact with the molten metal that flows so as to be rolled up. Further, in the amorphous refractory layer 120, elution of components due to a chemical reaction with the molten metal, peeling due to alteration, and the like also occur. As a result, at the lower end of the head portion 122, which is a portion that comes into contact with the molten metal that flows so as to be wound up, the amorphous refractory layer 120 is damaged at the peripheral edge of the lower end opening 115 of the core metal 110.

On the other hand, the stopper of the present invention has a ceramic sintered body layer that covers the outer peripheral surface with the lower end portion of the core metal. The ceramic sintered body is a molten metal because it has higher heat resistance and mechanical strength at high temperatures than the amorphous refractory layer formed of castable refractory material, and is also excellent in heat impact resistance and spalling resistance. High resistance to. The stopper of this configuration, in which such a ceramic sintered body layer is provided at a portion in contact with a molten metal that flows so as to be wound up by blowing gas, has an amorphous refractory at a portion in contact with the molten metal. Damage due to contact with molten metal is significantly suppressed as compared with the conventional stopper which is a layer.

Moreover, in the stopper having this configuration, among the outer peripheral surfaces of the ceramics sintered body layer, the enlarged diameter surface portion is adjacent to the lower end surface of the ceramics sintered body layer. That is, the lower end of the ceramic sintered body layer is formed so as to become thicker toward the lower end. Therefore, since the ceramic sintered body layer is thickly formed at the lower end portion that is in contact with the molten metal, damage due to contact with the molten metal is more effectively suppressed.

In addition, the upper end surface and the outer peripheral surface of the ceramics sintered body layer are covered with an amorphous refractory layer, but the outer peripheral surface of the ceramics sintered body layer has at least one concave surface portion. Since the amorphous refractory layer enters the inside of the concave surface portion, the ceramic sintered body layer and the amorphous refractory layer are joined so as to mesh with each other. Therefore, the ceramics sintered body layer interposed between the core metal and the amorphous refractory layer is firmly integrated with the amorphous refractory layer, so that the amorphous refractory layer and the ceramics sintered body layer are combined. The risk of cracks occurring between them and the risk of the ceramic sintered body layer falling off are greatly reduced.

The stopper according to the present invention has, in addition to the above configuration,
"The lower end surface of the ceramics sintered body layer is a curved surface continuous with the outer surface of the head portion."

In this configuration, the outer surface of the head portion and the lower end surface of the ceramic sintered body layer are combined to form an overall “shape in which the lower end portion of the stopper is continuously curved and bulged”. If the lower end surface of the ceramic sintered body layer is flat, the lower end portion of the stopper is flat, and the resistance when it comes into contact with the molten metal flowing so as to wind up is large. On the other hand, in this configuration, the molten metal easily flows along the outer shape of the lower end portion of the stopper, and the resistance due to contact with the molten metal is small. As a result, damage to the lower end portion of the head portion due to contact with the molten metal is more effectively suppressed.

In addition, the outer surface of the head portion and the lower end surface of the ceramic sintered body layer are combined so that the outer shape of the lower end portion of the stopper is "a shape that bulges while being continuously curved" as a whole. The stopper of the configuration has an advantage that the degree of closing the nozzle can be easily adjusted by the depth of insertion into the nozzle, and the flow rate of the molten metal can be easily adjusted.

As described above, as an effect of the present invention, the flow rate of the molten metal discharged from the nozzle at the bottom of the container is adjusted according to the degree of blocking the nozzle at the head portion, and gas is blown into the discharged molten metal. It is possible to provide a stopper which is a stopper in which damage to the lower end portion of the head portion is suppressed.

(A) is a vertical cross-sectional view of a main part of the stopper according to the first embodiment of the present invention, and (b) is a vertical cross-sectional view of the ceramic sintered body layer in the stopper of FIG. 1 (a). (A) is a vertical sectional view of a main part of a stopper according to a second embodiment of the present invention, and (b) is a vertical sectional view of a ceramic sintered body layer in the stopper of FIG. 2 (a). It is explanatory drawing of the use state of the stopper of FIG. 1 and FIG. It is a vertical cross-sectional view which shows the damage in the head part of the conventional stopper. It is a schematic diagram of the phenomenon considered as the cause of the damage of the stopper of FIG.

Hereinafter, the stopper 1 of the first embodiment and the stopper 1b of the second embodiment of the present invention will be described with reference to FIGS. 1 to 3.

As shown in FIG. 3, the stoppers 1 and 1b discharge the molten metal M from the ladle 51 into the intermediate container 52, and further from the nozzle 52n provided at the bottom 52b of the intermediate container 52 to the mold 54 in the pressure reducing tank 53. This is a stopper that adjusts the flow rate of the molten metal M discharged from the nozzle 52n and blows gas into the molten metal M when the molten metal M is injected. That is, the stoppers 1 and 1b are stoppers used in the intermediate container when performing so-called "vacuum pouring casting".

For example, with the nozzle 52n closed by the head portion 22 of the stoppers 1 and 1b, the molten metal M is discharged from the ladle 51 and received in the intermediate container 52. Then, when the stoppers 1 and 1b are raised to open the nozzle 52n, the molten metal M is injected into the mold 54 in the pressure reducing tank 53 via the nozzle 52n. At this time, the flow rate of the molten metal M discharged from the intermediate container 52 is adjusted by not completely opening the nozzle 52n but partially closing the nozzle 52n by the head portion 22 and adjusting the degree of the closing. be able to.

Further, by blowing a gas such as argon that has flowed inside the core metal 10 into the molten metal M from the lower end opening 15 of the core metal 10, the negative pressure generated when the molten metal M flows into the nozzle 52n Oxidation of the molten metal M due to the entrainment of air is prevented. Further, when the molten metal M is injected into the pressure reducing tank 53 in which the mold 54 is installed, the particles of the molten metal M are refined by the blown gas, so that the refining effect by dehydrogenation, denitrification, etc. Is enhanced.

As shown in FIG. 1, the stopper 1 of the first embodiment has a tubular core metal 10 for circulating gas inside and a ceramic sintered body layer 30 whose outer peripheral surface is covered with the lower end portion of the core metal 10. And a refractory layer that covers the outer peripheral surface and the upper end surface 35b of the ceramic sintered body layer 30 and the outer peripheral surface of the core metal 10 and the lower end portion constitutes the head portion 22. ..

More specifically, the core metal 10 is made of a heat-resistant metal such as steel or alloy steel, is formed in a cylindrical shape, and is gradually reduced in diameter toward the lower end. The core metal 10 can circulate gas in its internal space. Examples of the "gas" to be distributed through the core metal 10 include an inert gas such as argon and a nitrogen gas.

The refractory layer is composed of a stopper rod portion 21 formed in a substantially cylindrical shape concentric with the core metal 10 and a head portion 22 at the lower end portion. The head portion 22 has a shape that is continuously curved and bulges downward. Hemispherical shapes and spindle shapes can be exemplified as the “continuously curved and bulging” shapes.

Of the refractory layers, at least the immersion portion immersed in the molten metal is an integral structure of the amorphous refractory layer 20 formed of the castable refractory material, including the head portion 22. Here, the immersed portion is a refractory layer in the range represented by the length L in FIG. 3, and is, for example, a portion corresponding to a length of 1/4 to 2/3 of the total length of the refractory layer. be able to. Here, the portion of the refractory layer formed of the castable refractory material to be an integral structure of the irregular refractory layer 20 may be "at least an immersion portion immersed in molten metal", and is other than the immersion portion. The portion may be a structure in which a precast block or refractory bricks are joined with mortar, or a structure in which the entire refractory layer including a portion other than the immersion portion is an integral structure made of a castable refractory material.

The type of castable refractory material is not particularly limited, and for example, an alumina-silica, alumina-magnesia, alumina-carbon, alumina-magnesia-carbon, and alumina-spinel castable refractory materials are used. can do. Further, the amorphous refractory layer 20 can be formed by solidifying and drying mud prepared by mixing a powder of a castable refractory material with an adjusting agent such as water, a binder, a curing agent, and a dispersant. it can.

The ceramic material constituting the ceramic sintered body layer 30 is not particularly limited, but oxide ceramics such as mullite, alumina, magnesia, and spinel can be preferably used.

The ceramic sintered body layer 30 is tubular because the lower end of the cylindrical core metal 10 covers the outer peripheral surface thereof, and has irregularities on the outer peripheral surface. Specifically, on the outer peripheral surface of the ceramic sintered body layer 30, the reduced diameter surface portion 32 whose diameter is reduced toward the lower end and the enlarged diameter surface portion 31 whose diameter is increased toward the lower end are adjacent to each other. Therefore, it has a concave surface portion 33 having a concave shape between them. The stopper 1 of the first embodiment includes two combinations of an adjacent enlarged diameter surface portion 31, a reduced diameter surface portion 32, and a concave surface portion 33 formed between them.

Further, in the ceramic sintered body layer 30, the lower end surface 35a thereof is adjacent to the enlarged diameter surface portion 31 on the lower end side of the two enlarged diameter surface portions 31. That is, the lower end of the outer peripheral surface of the ceramic sintered body layer 30 has a diameter increasing toward the lower end. In addition, the lower end surface 35a of the ceramic sintered body layer 30 is a curved surface continuous with the outer surface 22s of the head portion 22.

The ceramic sintered body layer 30 can be formed, for example, by firing a molded body that has been dry-molded or wet-molded using a molding die corresponding to the above shape. Alternatively, it can be formed by molding a cylindrical molded body by extrusion molding and cutting the outer peripheral surface into the above shape before or after firing.

The amorphous refractory layer 20 has a core metal 10 arranged in the center of a molding mold that defines the outer shape thereof, and keeps a state in which a tubular ceramic sintered body layer 30 is fitted to one end side of the core metal 10. , Castable refractory material can be formed by pouring a mud of a mixture of water, a binder, a curing agent, a dispersant and other modifiers into a molding die, molding the castable refractory material, solidifying it, and then drying it.

The stopper 1 having the above configuration has a ceramics sintered body layer 30 that covers the outer peripheral surface with the lower end portion of the core metal 10, and the ceramics sintered body layer 30 is a molten metal from the amorphous refractory layer 20. High resistance to. Then, in the stopper 1, it is mainly the ceramic sintered body layer 30 that comes into contact with the molten metal that flows so as to be wound up with the blowing of gas, so that the portion that comes into contact with the molten metal is an amorphous refractory layer. Compared with the conventional stopper of 20, damage to the lower end portion of the head portion 22 due to contact with the molten metal is suppressed.

Moreover, in the stopper 1, since the enlarged diameter surface portion 31 is adjacent to the lower end surface 35a of the ceramic sintered body layer 30, the lower end portion that comes into contact with the molten metal is burned with ceramics toward the lower end. The uniting layer 30 is formed to be thick. Therefore, damage due to contact with the molten metal is more effectively suppressed.

In addition, the upper end surface and the outer peripheral surface of the ceramic sintered body layer 30 are covered with the amorphous refractory layer 20, but the outer peripheral surface of the ceramic sintered body layer 30 has a concave surface portion 33. Since the amorphous refractory layer 20 is inserted inside the concave surface portion 33, the ceramic sintered body layer 30 and the amorphous refractory layer 20 are joined so as to mesh with each other, so that the core metal 10 and the amorphous refractory layer 20 are indefinite. The ceramics sintered body layer 30 interposed between the refractory layer 20 is firmly integrated with the amorphous refractory layer 20.

In particular, in the present embodiment, since the plurality of concave surface portions 33 are provided, the joint in which the ceramic sintered body layer 30 and the amorphous refractory layer 20 mesh with each other is stronger. In addition, by having a plurality of combinations of the adjacent enlarged diameter surface portion 31 and the reduced diameter surface portion 32, and the concave surface portion 33 formed between them, the adjacent enlarged diameter surface portion 31 and the reduced diameter surface portion 32 are provided. It also has a convex surface portion 34 between the two. Since the convex surface portion 34 bites into the amorphous refractory layer 20, the joint in which the ceramic sintered body layer 30 and the amorphous refractory layer 20 mesh with each other is even stronger.

Further, since the lower end surface 35a of the ceramic sintered body layer 30 is a curved surface continuous with the outer surface 22s of the head portion 22, the entire outer shape of the lower end portion of the stopper 1 is continuously curved and expanded. It has a shape that is exposed. Therefore, the resistance at the time of contact with the flowing molten metal is small, and the damage to the lower end portion of the head portion 22 due to the contact with the molten metal is more effectively suppressed.

Next, the stopper 1b of the second embodiment will be described with reference to FIG. The same components as those of the stopper 1 of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The difference between the stopper 1b and the stopper 1 is the shape of the outer peripheral surfaces of the ceramic sintered body layers 30 and 30b. The ceramic sintered body layer 30b of the stopper 1b has one reduced-diameter surface portion 32 and one enlarged-diameter surface portion 31, and also has one concave surface portion 33 formed between them.

Even with the stopper 1b having such a configuration, the same effect as that of the stopper 1 of the first embodiment can be obtained. The action of meshing the ceramic sintered body layers 30 and 30b with the amorphous refractory layer 20 is greater in the stopper 1 having a plurality of concave surface portions 33, but the ceramic sintered body layer 30b of the stopper 1b is a ceramic firing of the stopper 1. It has the advantage of being easier to manufacture than the body layer 30.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to the above embodiments, and as shown below, various improvements are made without departing from the gist of the present invention. And the design can be changed.

For example, in the above embodiment, the stopper 1 having two concave surfaces 33 on the outer peripheral surface of the ceramics sintered body layer 30 and the stopper 1b having one concave surface 33 on the outer peripheral surface of the ceramics sintered body layer 30b are provided. Although illustrated, the number of concave surface portions 33 on the outer peripheral surface of the ceramic sintered body layer is not limited as long as it is one or more. The shape of the outer peripheral surface of the ceramic sintered body layer can be set according to the use of the stopper, the required size, and the like.

Further, in the above, the case where the stoppers 1 and 1b are used in the intermediate container for vacuum casting is illustrated, but the present invention is not limited to this. For example, the stopper of the present invention can be used as a stopper used for directly injecting molten metal from a ladle into a mold, or for adjusting the flow rate of molten metal and blowing gas in atmospheric pressure casting.

1,1b Stopper 10 Core metal 20 Amorphous refractory layer 21 Stopper rod part 22 Head part 22s Outer surface of head part 30, 30b Ceramics sintered body layer 31 Expanded diameter surface 32 Reduced diameter surface 33 Concave surface 35a Lower end surface (ceramics) Lower end surface of sintered body layer)
35b Upper end surface (upper end surface of ceramic sintered body layer)
M molten metal

Claims (2)

The flow rate of the molten metal discharged from the container accommodating the molten metal through the nozzle provided at the bottom of the container is adjusted according to the degree to which the nozzle is blocked by the head portion, and the discharged molten metal is gas. It is a stopper that blows in
Cylindrical or elliptical tubular core metal that allows gas to flow inside,
A ceramic sintered body layer that covers the outer peripheral surface of the lower end of the core metal,
A refractory layer covering the outer peripheral surface and the upper end surface of the ceramic sintered body layer and the outer peripheral surface of the core metal is provided.
The refractory layer constitutes the head portion in a shape in which the lower end portion is continuously curved and bulges, and at least the immersion portion immersed in the molten metal is castable fire resistant including the head portion. It is an integral structure of an amorphous refractory layer formed of a material.
The outer peripheral surface of the ceramic sintered body layer has a concave shape because the reduced diameter surface portion whose diameter is reduced toward the lower end and the enlarged diameter surface portion whose diameter is increased toward the lower end are adjacent to each other. It has at least one concave surface
A stopper characterized in that the lower end surface of the ceramic sintered body layer is adjacent to the enlarged diameter surface portion. The stopper according to claim 1, wherein the lower end surface of the ceramics sintered body layer is a curved surface continuous with the outer surface of the head portion.

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