JPS6363299B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an intermediate container for molten metal that is excellent in flotation and separation of nonmetallic inclusions. (Prior art) Molten metal, such as molten steel, generally contains nonmetallic inclusions that have a lower specific gravity than molten steel, and are often not completely removed even during the refining process, especially large inclusions exceeding 100μ. There are things to do. If such large inclusions are introduced into a cast slab obtained by continuous casting, for example, when it is processed into a finished product in the subsequent rolling process, it may remain as flaws such as blisters and hege flaws. This results in defective products and lowers the product yield. Furthermore, recent steel materials have come to be required to be so-called high-cleanliness steels that have extremely few nonmetallic inclusions, that is, have no inclusion defects. Therefore, in order to reduce these inclusions, for example, in the refining process, it is necessary to review the deoxidation method, to adopt a method of refining under vacuum to suppress the generation of inclusions as much as possible, and to improve the stirring process using a ladle. Then,
Techniques have been developed to promote floating and separation of inclusions. Furthermore, in the continuous casting process, JP-A No. 56-4351,
One or more stages of weirs such as a submerged weir and an overflow weir were installed in the intermediate container for molten steel as seen in Japanese Patent Application Laid-Open No. 56-26662 and Japanese Utility Model Application No. 56-29650, with the aim of surfacing inclusions. Monoya, JP-A-56-36366, JP-A-50-
As shown in Japanese Patent No. 47821, a tundish is provided with a pool at the bottom to prevent inclusions from penetrating deeply due to the pouring flow when pouring from the intermediate container into the mold. Recently, in consideration of the floating of inclusions in the mold, so-called large-section slabs, in which the cross section of the slab is enlarged, have been manufactured. However, although large-section casting has advantages in terms of inclusion characteristics, it is not necessarily a perfect method due to problems with the internal quality of the slab and increased equipment costs, and it is generally not easy to modify the intermediate vessel. be. The method of providing one or more stages of weirs in the intermediate container described above is as follows:
The removal efficiency of inclusions varies greatly depending on the structure of the weir. Generally, the floating ability of nonmetallic inclusions is interpreted as floating according to Stokes' law.
Whether the inclusions are completely separated from the molten steel (hereinafter referred to as the system) depends on the levitation speed, the velocity vector of the molten steel flow, the levitation time determined by the distance to the outside of the system, and the amount of time in the intermediate container. It is determined by the size of the stay time. Therefore, for inclusion flotation separation,
Reducing the flow rate of molten steel in the intermediate vessel is considered to be an effective means. On the other hand, the weir installed in the intermediate container divides the flow path inside the container into multiple parts, which reduces the cross-sectional area of molten steel passing through it, resulting in an increase in the molten steel flow velocity, which leads to the floating of inclusions. It has inherent disadvantages. The advantage of a weir is that it creates turbulence in the molten steel in the intermediate container, so non-metallic inclusions are expected to coalesce, for example, alumina clusters are formed, which may improve the floating speed as large inclusions. It is. In order to improve this ascent speed,
A method has also been devised in which inert gas is blown into the bottom of the intermediate container to create bubbles and cause it to float. As described above, although there are various methods for flotation and separation of nonmetallic inclusions in conventional intermediate containers, the method found in multistage weirs, for example, has advantages and disadvantages at the same time, and is an extremely difficult technique for separating inclusions. . Furthermore, the use of inert gas, etc. not only causes air bubbles to remain in the steel, but also increases the cost of steel materials, so it cannot be a technology that can be used for all steel materials. Recently, a method has been proposed in which inclusions in the steel are adsorbed by using a filter made of refractory material instead of a weir in the intermediate container, etc., but the absorption efficiency is extremely low and it is not efficient or economical. There are many problems in practical application. (Objective of the Invention) The present invention provides an intermediate container for molten metal that efficiently removes nonmetallic inclusions from molten metal and produces steel materials with good cleanliness. (Structure and operation of the invention) In the separation of impurity inclusions (particles) in a fluid, the present inventors focused on and studied the labyrinth solid-liquid separation method, which is one of the water treatment technologies, and The present invention was developed in consideration of the fact that the behavior of impurity particles and the behavior of nonmetallic inclusions in molten metal are completely opposite. That is, the gist of the present invention is to provide an intermediate container for molten metal whose inner wall surface has excellent fire resistance, which has a flow path through which the molten metal passes, and in which the flow path has an angle of 80° to a side surface of the flow path with respect to the flow. It is characterized by installing one or more baffles with an angle of attack of 130° to form a main channel and a circulation section, and providing a lower weir at the molten metal introduction section and outlet section, and an upper weir at the circulation section. This is an intermediate container for molten metal that is excellent in flotation and separation of non-metallic inclusions, and by using it, it is possible to manufacture slabs with high cleanliness. Hereinafter, the present invention will be explained in detail using the drawings. FIG. 1 is a plan view of the intermediate container of the present invention, and FIG. 2 is a sectional view taken along line AA in FIG. In FIGS. 1 and 2, the outer shape of the intermediate container is formed by a fireproof wall 1, and one or more barrier plates 2 having an arbitrary angle of attack α with respect to the longitudinal side wall of the container are installed inside the container, and the flow path is A main flow path 3 having a length L, a width W, and a depth H, and a circulation portion 4 having a length L ₁ , a width D, and a depth H are configured. Next, lower weirs 7 and 9 are provided in the molten metal introduction section 6 and outflow section 8, and an upper weir 5 is provided in the circulation section 4 to connect the ends of the baffles 2 and 2 to form a container. Here, the size of the blocking plates 2, 2 can be changed to some extent depending on the size of the intermediate container to be installed, and in FIG. 1, W:D=1:1 to 3, D:L ₁ =2 :
1 to 3 are preferable, W:D=1:2, D:L ₁ =
A ratio close to 1:1 is appropriate for vortex generation. The heights of the shock plates 2, 2, lower weirs 7, 9, and upper weir 5 are preferably set as follows. From Figure 2, if the height of the hot water surface is _H0 , the height to the top of the upper weir is H, the height to the bottom is _H1 , and the height of the lower weir _H2 , then H> _H0 > _H2 > Assume that the relationship H ₁ is satisfied. The angle of attack α is set to be 80° to 130°, but 90° to 120° is a desirable range for guiding the flow of molten steel to the circulation path 4. In the intermediate container for molten metal of the present invention configured as described above, the molten metal containing non-metallic inclusions (hereinafter referred to as molten metal) enters the introduction part 6 from the container 10 such as a ladle, crosses the lower dam 7 The hot water then flows through the main channel 3, the level of which rises until it exceeds the lower weir 9, and flows from the outflow hole 11 while contacting the upper weir 5. At this time, the flow of the molten metal is disturbed by the impact plate 2,
A wake is generated in the vicinity of the shock plate 2, and a rotating vortex is generated in the circulation section 4. The rotating vortex does not have a velocity component in the three directions of the main flow path, and since it is a rotating flow, nonmetallic inclusions accumulate toward the rotating shaft due to the difference in centrifugal force. Therefore, the nonmetallic inclusions in the rotating part have only a floating velocity component determined by their size, and are separated out of the system. Furthermore, accumulation by the rotational flow also promotes the coalescence of inclusions, resulting in an even higher floating ability. Furthermore, flux that absorbs inclusions can be introduced into the circulation section 4, and the upper weir 5 can also prevent flux components from flowing out. The molten metal flows from the main channel 3 to the circulation section 4 because
As is known from the labyrinth solid-liquid separation method used in water treatment, inflow and outflow are repeated periodically. By having one or more baffles 2, the number of circulation parts 4 increases, so a multi-stage inclusion separation area can be secured, and the inclusion separation efficiency becomes extremely high. The molten metal that has been separated by the rotating vortex in this manner returns to the main flow path 3, and finally becomes a molten metal with very few nonmetallic inclusions, reaches the outflow hole 11, and is injected into the mold. FIG. 3 is a plan view showing another example of the present invention.
This is an example in which efficiency is further improved compared to those shown in FIGS. 1 and 2 by providing a shield plate 2 on the core 12 inside the intermediate container 1. (Effects of the Invention) By using the intermediate container for molten metal of the present invention, non-metallic inclusions can be separated and removed reliably, and clean slabs with few inclusions can be easily produced, which is useful for industrial use. Extremely useful. (Example) (1) Molten steel amount: 300Kg (2) Molten steel composition: Shown in Table 1 (a).

[Table] (3) Intermediate container (hereinafter referred to as tundish) Channel: W = 50 mm, D = 100 mm, L ₁ = 100 mm,
L = 800mm, H = 150mm, H ₁ = 100mm,
H ₂ = 110 mm, H ₀ = 130 mm, α = 90° Circulation section: 4 stages Under the above conditions, molten steel is injected into the tundish, and after passing through the tundish flow path, 300 kg
Manufactured steel ingots. As a result, extremely clean steel with 96 Al ₂ O ₃ inclusions (20 μ or less)/25 mm ² could be produced. (Comparative Example) A comparative steel ingot was produced by pouring 300 kg of molten steel having the components shown in Table 1 (b) into a tundish without a plate, and then casting it into a mold. The produced steel ingot contains Al ₂ O ₃ inclusions (20μ or less)
The number of steel ingots was 251 pieces/25 mm ² , resulting in a steel ingot that was significantly inferior to the examples of the present invention.

[Brief explanation of drawings]

FIG. 1 is a plan view of an intermediate container for molten metal according to the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a plan view of another example of the present invention. 1: Intermediate container wall, 2: Bumper plate, 3: Main channel, 4:
Circulation section, 5: Upper weir, 6: Molten metal introduction section, 7: Lower weir, 8: Outflow section, 9: Lower weir, 10: Container, 11:
Outflow hole, 12: Core.

Claims (1)

[Claims] 1. In the intermediate container for molten metal, a plurality of baffles with an angle of attack of 80° to 130° are installed on the side of the flow path where the molten metal passes from the inlet to the outlet, and the main flow path is 1. A molten metal intermediate container having a sieve plate, which forms a circulation path, and is characterized in that a lower dam is provided at the molten metal introduction section and an outflow section, and an upper dam is provided at the circulation section.