JPH0525585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to continuous casting equipment for producing sound continuous slabs by rationally removing nonmetallic inclusions suspended in molten metal, such as molten steel.

For example, in continuous casting of molten steel, as schematically shown in FIG. It will be destroyed. To supply molten steel from the ladle 1 to the tundish 2, a long nozzle 3 whose upper end is connected to the bottom of the ladle 1 is used, and to guide molten steel from the tundish 2 to the mold 5, an injection nozzle 6 is used. Ru.

Conventionally, the long nozzle 3 has been a cylindrical body made of refractory material with open upper and lower ends. In this case, the opening at the top of the long nozzle 3 is connected to the outlet provided at the bottom of the ladle 1, usually through a sliding nozzle.
The lower part of the long nozzle 3 was inserted into the tundish 2, and molten steel was allowed to flow into the tundish 2 through the opening at the bottom of the long nozzle 3. Also, when pouring from tundish 2 to mold 5, tundish 2 and mold 3
This was performed using an injection nozzle 6 with upper and lower openings that communicated with each other. Therefore, nonmetallic inclusions suspended in the molten steel in the ladle 1 also enter the tundish 2 together with the molten steel, and although some of them float up in the tundish 2, most of them get mixed into the mold 5 and are Although a certain amount of floating separation occurs in the mold 5, some of it is captured by the solidified shell, which causes surface defects and internal defects in the continuously cast slab, which may impede the continuous casting of high-grade steel. , and also caused problems such as inhibiting hot charge and direct rolling.

In order to solve this problem, various methods have been used to clean the molten steel itself in the ladle in the previous process, or to clean the non-metallic inclusions that have surfaced in the tundish. Recipes such as installing a dam to prevent non-metallic inclusions from flowing into the mold were proposed or adopted. However, in the former case, the actual situation is that it is not very effective even though it requires extra processing. In the latter case, when the amount of hot water in the tundish is reduced, such as at the end of casting, the effect of the weir becomes ineffective, so the weir does not have enough hot water to stop the floating non-metallic inclusions. It is necessary to maintain the surface height. Therefore, it is necessary to leave a sufficient amount of hot water in the tundish even after casting is completed, which inevitably lowers the yield. Furthermore, even if this weir is provided, it only serves to dam up floating objects of non-metallic inclusions, and active separation of non-metallic inclusions cannot be expected completely.

As described above, in continuous casting, the separation of nonmetallic inclusions is a very troublesome problem, and there has been a strong desire to develop a formulation that is advantageous for operation and can effectively and reliably separate these inclusions.

The purpose of the present invention is to meet this need.
Equipment that reasonably achieves this purpose includes a ladle 1 for storing molten metal, a tundish 2 for also placing molten metal, one end of which is removably connected to an opening provided at the bottom of ladle 1, and the other end of which is a tundish. In normal continuous casting equipment, which consists of a long nozzle 3 inserted into a mold 5 and an injection nozzle 6 with one end connected to an opening 4 provided at the bottom of the tundish 2 and the other end inserted into a mold 5, As shown in the embodiment of FIG.
A refractory filter 7 through which molten metal can pass and which can trap non-metallic inclusions is disposed downstream of the long nozzle 3 and upstream of the opening 4 inside the
is installed so that substantially all of the molten metal injected into the tundish 2 from the long nozzle 3 passes through the refractory filter 7 and then flows toward the opening 4. is equipped with a refractory filter 8 through which molten metal can pass and which can capture non-metallic inclusions,
A facility is provided in which substantially all of the molten metal flowing from the long nozzle 3 toward the tundish 2 passes through the refractory filter 8. The refractory filter 7 and the refractory filter 8 through which the molten metal can pass and which can trap non-metallic inclusions are made of a refractory that has a three-dimensional network structure with an internal communication space. is more effective.

The equipment of the present invention will be specifically explained below with reference to the drawings.

As shown in FIG. 2, in the present invention, a refractory filter 7 is inserted into the tundish 2 so that substantially all of the molten steel supplied to the tundish 2 passes through the refractory filter 7 before being injected into the tundish 2. The nozzle 6 is installed so that it flows toward the opening 4 of the installation part. Since FIG. 2 shows an example of a two-set mold, this refractory filter 7 is also installed in two places, but virtually all of the hot water supplied to the injection nozzle 6 is As long as the relationship that the water passes through the material filter 7 is satisfied, no matter how many sets of molds there are, the number of refractory filters 7 corresponding to the number of sets of molds may be provided.
The most specific recipe that satisfies this relationship is to install a plate-shaped refractory filter 7 at the hot water level between the position of the long nozzle 3 inserted into the tundish 2 and the bottom opening 4 to which the injection nozzle 6 is connected. This means that the upper end should protrude more than the other side. That is, the interior of the tundish 2 is partitioned off with a plate-shaped refractory filter 7 so as to block the flow of hot water. In this case, the hot water surface will come into contact with this refractory filter 7 as in a normal weir, but a normal weir is basically constructed of a material that does not allow hot water to pass through, and a hot water communication path is provided below the weir. In contrast, in the present invention, the hot water is made of a material through which hot water permeates, and there is no communication path for hot water to bypass the refractory filter 7, and substantially all of the hot water is made of this refractory material. They are fundamentally different in that they are constructed so that they flow through the filter 7. The refractory filter 7 has an area large enough to cover the entire cross section of the hot water present in the tundish 2 (cross section perpendicular to the flow direction of the hot water). It may be configured such that the cross section is small, or it may be configured to be smaller than the entire cross section of the hot water. In the latter case, it is preferable to allow the hot water in the lower layer to pass through this filter function section.

The refractory filter 7 used has a nonmetallic inclusion filtering function that allows molten steel to pass through but can trap nonmetallic inclusions. As such a refractory, a refractory having a three-dimensional network structure with internal communication spaces is suitable. Porous refractories may be created by simply firing granular refractory powder in the presence or absence of a binder, but ceramic granules can also be created by carbonizing, removing, gasifying or volatilizing a portion of the base material during firing. In the case of porous ceramics in which internal communication spaces are formed in a complexly connected three-dimensional network structure, the pore surface area is extremely large, and the ability to trap nonmetallic inclusions in molten steel is high. Furthermore, since the pore surface area is large, even if non-metallic inclusions are captured, the flow of molten steel is not hindered to a large extent, and therefore the number of times of use can be increased. The material of this porous refractory is not particularly limited as long as it is a refractory that can be used, but in the example shown in FIG. 2, an alumina refractory is used.

FIG. 3 schematically shows an example of a refractory filter 7 made of a porous refractory in which an internal communication space with a three-dimensional network structure is formed.
The figure shows an enlarged view of the internal communication space of this three-dimensional network structure. As shown in the figure, this refractory has a structure in which three-dimensional lattices 10 are intricately intertwined.

In addition to installing a refractory filter 7 in the tundish 2, if a refractory filter 8 is also installed in the long nozzle 3, it is possible to produce even healthier slabs, and to prevent non-metallic particles from entering the system. Objects can be easily removed.

FIG. 5 is an enlarged view of a part of the equipment shown in FIG. 2 in which a refractory filter 8 is attached to the long nozzle 3. The long nozzle 3 is inserted into the opening provided at the bottom of the ladle 1 as described.
It is removably attached from the outside (usually via a sliding nozzle). A conventional long nozzle uses a cylindrical body with open upper and lower ends, with both the upper end to be attached to the ladle and the lower end to be inserted into the tundish. In the example of the present invention shown in FIG. 5, the lower end of this long nozzle is not simply an open end as in the conventional case, but a container-shaped refractory filter 8 with a bottom is attached below this long nozzle 3. be. The refractory filter 8 attached to the long nozzle 3 is also desirably made of a porous refractory having a three-dimensional network structure with internal communication spaces, similar to the refractory filter 7 described above.
As a result, all the molten steel moving from the ladle 1 to the tundish 2 passes through this refractory filter 8, and the filter 8 removes non-metallic inclusions suspended therein, ensuring a long service life. It can be captured with. When this long nozzle 3 is provided with the function of capturing non-metallic inclusions, this long nozzle 3 is detachably attached to the ladle 1, and the long nozzle 3 is attached to the ladle 1 substantially every time the steel is poured from the ladle 1 to the tundish 2. Since the nozzle 3 is removable, if the filter function deteriorates due to increased use, it can be replaced with a new one, and non-metallic inclusions caught here do not require any special operation. It can be easily removed from the system.

After filtering out non-metallic inclusions with this long nozzle 3, the non-metallic inclusions are further filtered out with a refractory filter 7 in the tundish 2, resulting in molten steel with a significantly reduced concentration of non-metallic inclusions. Since it is injected into the mold 5, a healthier slab can be manufactured. In this case, the load on the filter 7 made of refractory material in the tundish 2 for filtering out non-metallic inclusions is greatly reduced, so that its service life is extended and the number of replacements is reduced. As shown in FIG. 2, it is preferable to form a layer of artificial slag 9 on the molten steel upstream of this refractory filter 7.

FIG. 6 shows the two-set mold equipment shown in FIG. 2, with a refractory filter 8 in the long nozzle 3 and a refractory filter 7 in the tundish 2.
Changes in non-metallic inclusions in slabs between the case where they are installed and operated with the above-mentioned relationships and the conventional case where these are not installed (the first non-metallic inclusions in slab in the present invention) (The amount of material is compared with index 1) is organized by the number of times the tundish is used. The tandate has a capacity of 180 tons/time, and the sample molten steel is C: 0.06%, Si: 0.01%,
Mn: 0.30%, P: 0.010%, S: 0.010%, Sol.
Al: 0.040% low carbon aluminum killed steel, which is cast at a casting speed of 1.4m/min (180t/ch.) to 250mm
It was cast in a 1050 mm slag mold. In addition, regarding the refractory filter 8, the long nozzle 4, which has a nozzle hole of about 100 mmφ, was used in the past.
In order to ensure a discharge amount equivalent to the discharge amount, a material molded into the shape shown in FIG. 3 was used. As shown in FIG. 6, according to the present invention, non-metallic inclusions in the slab can be greatly reduced. It can be seen that in the conventional case, the non-metallic inclusions in the slab gradually increase as the tundish is used, whereas in the present invention, the non-metallic inclusions in the slab can be maintained at a completely constant low level.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an outline of conventional continuous casting equipment, FIG. 2 is a schematic sectional view showing an example of the casting equipment of the present invention, FIG. 3 is a perspective view showing an example of a refractory filter, and FIG. Fig. 4 is an enlarged view showing an example of the internal structure of a refractory filter, Fig. 5 is a schematic sectional view showing an example of a long nozzle used in the present invention, and Fig. 6 is an enlarged view showing an example of the internal structure of a refractory filter. It is a graph showing the amount of metal inclusions in comparison with a conventional method. 1... ladle, 2... tundish dish, 3... long nozzle, 4... opening at the bottom of tundish dish,
5... Mold, 6... Injection nozzle, 7... Refractory filter, 8... Refractory filter.

Claims (1)

[Scope of Claims] 1. A ladle 1 into which molten metal is placed, a tundish 2 into which molten metal is also placed, one end removably connected to an opening provided at the bottom of the ladle 1, and the other end inserted into the tundish 2. long nozzle 3,
In a continuous casting equipment consisting of an injection nozzle 6 whose one end is connected to an opening 4 provided at the bottom of the tundish 2 and whose other end is inserted into the mold 5, the injection nozzle 6 is placed downstream of the long nozzle 3 inside the tundish 2. A refractory filter 7 through which molten metal can pass and which can capture non-metallic inclusions is installed upstream of the opening 4, and a refractory filter 7 through which molten metal can pass through and which can trap non-metallic inclusions is installed in the removable long nozzle 3. This continuous casting equipment is characterized in that a refractory filter 8 capable of capturing metal inclusions is installed so that substantially all of the molten metal from the long nozzle 3 toward the tundish 2 passes therethrough. 2. The continuous casting equipment according to claim 1, wherein the refractory filter 8 and the refractory filter 7 are made of a refractory having an internal communication space of a three-dimensional network structure.