JPH11335719A - Intermediate vessel for separating non-metallic inclusion and method for separating non-metallic inclusion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate vessel for separating non-metallic inclusion which can efficiently and economically separate the non-metallic inclusion in molten metal, and a method for separating the non-metallic inclusion. SOLUTION: At the time of blowing while giving the rotation in the horizontal direction to the molten metal, gas blowing parts 3 having slender blowing surfaces 3a and 3b formed on the inner surface 1a, are arranged on the side surface and/or the bottom surface of the vessel. The gas blowing part is suitable to be a slit-like nozzle or a slender porous refractory. Further, the relation among the dimensional ratio (n) in the blowing surface, the gas blowing quantity Q and the rotating flow velocity V of the molten metal, is set so as to satisfy (Q/V)/n <=3.7×10<-4> to execute the separation of the non-metallic inclusion in the molten metal. In the gas blowing part, plural tubular nozzles may be used. In such a case, the relation among the distance L between mutually nozzles, the gas blowing quantity Q and the rotating flow speed V of the molten metal, may be set so as to satisfy Q/(L.V)<=1.7×10<-2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate container for separating non-metallic inclusions of molten metal for promoting the separation of non-metallic inclusions in molten metal and producing high quality metal products, and an intermediate container for separating molten metal. The present invention relates to a method for separating nonmetallic inclusions.

[0002]

2. Description of the Related Art Thorough separation of non-metallic inclusions in a molten metal in a tundish in a continuous casting method generally used widely in the production of steel and the like is an important technique for determining a product quality level. It is an issue. As a method for separating non-metallic inclusions in molten metal, for example, Japanese Patent Application Laid-Open No. 58-22317 discloses a method in which molten steel in a container is horizontally rotated by a magnetic field, and a centrifugal force is applied to the molten steel to rotate the non-metallic inclusions. There has been proposed a method of removing nonmetallic inclusions in which molten steel flows out from the bottom of a vessel far from the rotation center of molten steel while being concentrated and floated at a central portion.

Further, Japanese Patent Application Laid-Open No. 4-365809 discloses a non-metallic inclusion removing apparatus which applies a centrifugal force to a molten metal and further blows a gas such as Ar. This non-metallic inclusion removing device (FIG. 6 (a)) is composed of a rotating tank for horizontally rotating molten metal, and has a bottom and / or side wall extending from the inner surface of the side wall of the rotating tank to a center to a quarter of the radius. It has a buried refractory for gas injection on the side from the bottom to a quarter of the height of the molten metal, and a floating tank connected to the rotating tank.

Japanese Patent Application Laid-Open No. Hei 7-316627 discloses an intermediate holding container having a function of pouring and discharging molten metal (see FIG. 6).
In (b)), a method of removing non-metallic inclusions in the molten metal by horizontally rotating the molten metal and blowing gas upward from the bottom of the intermediate holding container immediately below the pouring nozzle has been proposed.

[0005]

SUMMARY OF THE INVENTION
In the technology described in 4-365809, JP-A-7-316627, when the gas bubbles blown into the molten metal are coarsened, the efficiency of capturing and separating nonmetallic inclusions is reduced, so that fine bubbles are blown. It becomes important. However, when a large amount of air bubbles are blown, the number of air bubbles per unit volume increases and the coalescence of the air bubbles occurs, and the air bubbles become coarse and blow out to the molten steel surface, thereby reducing the effect of capturing and separating nonmetallic inclusions. Resulting in. In this way, when the gas bubbles blown are coarsened, non-metallic inclusions are not separated even if the same amount of gas is blown, and disturbance of the molten steel surface occurs,
There is a possibility that slag entrainment and reoxidation of molten steel may be promoted.

The present invention advantageously solves the above-mentioned problems of the prior art, and enables an efficient and economical separation of non-metallic inclusions in a molten metal. The aim is to propose a method.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, in order to efficiently separate and remove nonmetallic inclusions in the molten metal, It has been found that it is effective to apply a rotational force and to blow a large amount of fine bubbles uniformly dispersed. When gas bubbles are blown into a rotating molten metal, the bubbles are considered to be broken down by being subjected to a shearing force due to the rotating flow of the molten metal and become finer, but at the same time, the bubbles are flowed and blown by the flow of the molten metal. It becomes difficult for the air bubbles to be uniformly dispersed.

Therefore, the present inventors pay attention to the shape of the gas blowing portion, and change the blowing surface formed on the inner surface of the container by the gas blowing portion provided in the container along the rotating flow of the molten metal on the blowing surface. The length of the direction is shorter than the length in the direction orthogonal to the inside of the blowing surface, specifically, it is less than 1/2, so that an elongated blowing surface is used to uniformly disperse bubbles and reduce the gas volume fraction. It has been found that it is effective to make the location uniform. Specifically, the gas blowing section is preferably a slit-shaped nozzle or an elongated porous refractory (porous plug). Also,
It has been found that a plurality of tubular nozzles may be provided as the gas blowing section, and in this case, it is necessary to arrange the plurality of tubular nozzles apart from each other to prevent the blown bubbles from uniting.

Further, by optimizing the flow rate of the molten metal near the inner wall of the container and the flow rate of the gas to be blown using the gas blowing section having the above-described shape, a large amount of fine bubbles can be blown into the molten metal. It has been found that non-metallic inclusions can be efficiently captured and the cleanliness of the molten metal can be improved. The present invention has been made based on the above findings.

That is, the present invention provides an intermediate container for separating non-metallic inclusions of molten metal, comprising a rotating force applying means for applying a rotating force to the molten metal in the horizontal direction, and a gas blowing section for blowing gas into the molten metal. , The intermediate container has a substantially cylindrical side wall and a bottom surface, the gas blowing portion is provided on a side wall and / or a bottom surface of the intermediate container, and the gas blowing portion is formed on an inner surface of the intermediate container. When the gas blowing portion is provided on the side wall, a ratio n of a maximum length w of an intersection line formed by the blowing surface with a horizontal plane and a maximum length 1 of an orthogonal line orthogonal to the intersection line in the blowing surface = L / w is 2 or more, and when the gas blowing portion is provided on the bottom surface, the blowing surface is defined by the maximum length w of the blowing surface in the circumferential direction and the radial length of the blowing surface. It is assumed that the blowing surface is such that the ratio n of the maximum length 1 is 1 or more. Non-metallic inclusions separating intermediate container to symptom, the blow surface, good to the slit-like, also, the gas blowing section may use a porous refractory. The intermediate container of the present invention is preferably a tundish for continuous casting of molten metal.

Further, the present invention provides a method for applying a horizontal rotational force to a molten metal by a rotational force applying means by using the above-mentioned intermediate container for separating nonmetallic inclusions, and supplying a gas to the molten metal from a gas blowing section. In separating and removing nonmetallic inclusions in the blown molten metal, a dimensional ratio n of a blowing surface formed by the gas blowing portion on the inner surface of the intermediate container, and a gas blowing amount Q
And the rotational velocity V of the molten metal is expressed by the following equation (1) (Q / V) /n≦3.7×10 ⁻⁴ (1) (where, Q: gas injection amount (Nm ³ / sec), V: rotational speed of the molten metal (m / sec), n: l / w, w: maximum length (m) of the line of intersection of the blowing surface with the horizontal plane, or maximum in the circumferential direction of the blowing surface Length (m), l: Condition that satisfies the maximum length (m) of an orthogonal line that intersects with the line of intersection between the blowing surface and the horizontal plane and the orthogonal line in the blowing surface, or the maximum radial length (m) of the blowing surface A method for separating non-metallic inclusions of molten metal, characterized in that:

[0012] The present invention also provides an intermediate for separating non-metallic inclusions of molten metal, comprising a rotational force applying means for applying a horizontal rotational force to the molten metal, and a gas blowing section for blowing gas into the molten metal. In the container, the intermediate container has a substantially cylindrical side wall and a bottom surface, the gas blowing portion is provided on a wall side and / or a side surface of the intermediate container, and the gas blowing portion is separated from a plurality of gas blowing portions. An intermediate container for separating non-metallic inclusions, comprising a tubular nozzle provided, wherein the intermediate container is preferably a tundish for continuous casting of molten metal.

Using the intermediate container for separating nonmetallic inclusions described above, a rotating force is applied to the molten metal in a horizontal direction by a rotating force applying means, and a gas is blown into the molten metal from a gas blowing portion to cause the molten metal to have a molten metal. In separating and removing the non-metallic inclusions, the distance L between the nozzles of the gas blowing section, the gas blowing amount Q, and the rotational velocity V of the molten metal are expressed by the following equation (2): Q / (LV) ≦ 1.7 × 10 ^-2 (2) (where, Q: gas injection amount (Nm ³ / sec), V: rotational speed of molten metal (m / sec), L: distance between nozzles (m ),
If the gas inlet is on the side wall, the average horizontal distance (m
), When the gas inlet is on the bottom, the distance in the circumferential direction (m
A method for separating non-metallic inclusions of molten metal, characterized by satisfying the conditions of (1) and (2).

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In an intermediate container 1 for separating nonmetallic inclusions according to the present invention, a molten metal 4 is poured from a ladle 20 or the like via a pouring nozzle 13, and a rotating force is applied to the molten metal 4 to rotate the molten metal 4. 6, a large amount of gas can be blown into the rotary flow 6 as fine bubbles 5, thereby facilitating capture and removal of nonmetallic inclusions in the molten metal 4 and improving the cleanliness of the molten metal. .
The molten metal from which nonmetallic inclusions have been separated and removed
It is poured out via 17. One example of the intermediate container of the present invention is shown in FIG.

The intermediate container 1 of the present invention includes a rotating force applying means 2 for applying a rotating force to the molten metal 4 in a horizontal direction, and a gas blowing section 3 for blowing a gas 5 into the molten metal 4. The shape of the intermediate container 1 of the present invention has a substantially cylindrical side wall for imparting a uniform horizontal rotating flow to the molten metal, and a bottom surface which closes the lower side. In addition, the substantially cylindrical shape is
In addition to the cylindrical shape, a shape obtained by deforming the rotational flow so as not to hinder the horizontal flow, such as an inverted truncated cone, is included.

As a rotation applying means 2 for applying a horizontal rotating flow to the molten metal, it is preferable to provide a moving magnetic field generating device outside the intermediate container 1 and to apply a driving force to the molten metal by an electromagnetic force. The gas blowing section 3 is provided on the side wall and / or the bottom of the intermediate container 1 as shown in FIG.
The surface formed by the gas blowing section 3 with the inner surface 1a of the intermediate container is referred to as blowing surfaces 3a and 3b. In the present invention, the shape of the blowing surface is elongated. Specifically, the gas blowing section is preferably a slit-shaped nozzle or an elongated porous refractory (porous plug) whose blowing surface satisfies the following conditions.

When the gas blowing portion is provided on the side wall, the maximum length w of the intersection line formed by the blowing surface 3a and the horizontal plane s and the maximum length l of the orthogonal line perpendicular to the intersection line in the blowing surface are defined. Ratio n = 1 /
It is preferable to use an elongated blowing surface where w is 2 or more. As a result, the gas blown into the molten metal becomes fine bubbles due to the action of the rotating flow, and is further uniformly dispersed without coalescence of the bubbles, so that the gas volume fraction is locally uniform.

When the gas blowing portion is provided on the bottom surface, the ratio n = l / w of the maximum circumferential length w of the blowing surface to the maximum radial length l of the blowing surface is 2 or more. It is preferable to use the blowing surface 3b. Further, in the present invention, using the intermediate container for separating non-inclusions described above, while applying a rotating force in the horizontal direction to the molten metal by the rotating force applying means, a gas is blown into the molten metal from the gas blowing unit to form the molten metal. Non-inclusions are separated and removed. According to the knowledge of the present inventor, when the flow rate of the molten metal is V (m / sec) and the gas injection amount is Q (Nm ³ / sec), the dispersion of bubbles is improved in proportion to V / Q. When V is constant, it is necessary to reduce Q in order to improve the dispersion of bubbles. However, when Q is reduced, the number of bubbles is reduced and the chance of capturing non-inclusions is reduced. On the other hand, when the flow velocity of the rotating flow is sufficiently large, the length of the gas injection surface in the direction along the horizontal rotating flow of the molten metal, that is, the maximum length w (m) of the line of intersection with the horizontal plane is determined by the intersection line And 1 / n of the maximum length l (m) of an orthogonal line perpendicular to the blowing surface, even if the gas is blown n times, a bubble dispersion density equivalent to that of a square blowing surface can be obtained. Based on such an idea, the present inventors considered a parameter of (Q / V) / n.

The dimensional ratio n of the blowing surface, the gas blowing amount Q,
The relationship between the rotational speed V of the molten metal and the rotational speed V is expressed by the following equation (1): (Q / V) /n≦3.7×10 ⁻⁴ (1) where, Q: gas injection amount (Nm ³ / sec), V: Rotational flow velocity of the molten metal (m / sec), n: l / w, w: maximum length (m) of the line of intersection of the blowing surface with the horizontal plane, or maximum length of the blowing surface in the circumferential direction ( m), l: The condition is to satisfy the maximum length (m) of the line of intersection of the blowing surface with the horizontal plane and the orthogonal line perpendicular to the blowing surface, or the maximum length (m) of the blowing surface in the radial direction. preferable.

When (Q / V) / n is not more than 3.7 × 10 ^-4 , there is little opportunity for bubbles to coalesce and good separation of nonmetallic inclusions is achieved. In the present invention, as the gas blowing section, instead of the slit-shaped nozzle or the elongated gas blowing section represented by the elongated porous refractory (porous plug),
It may be a gas blowing section using a tubular nozzle. As the tubular nozzle, it is preferable to use a high melting point metal pipe such as a stainless steel pipe. In the case of a tubular nozzle, it is preferable to arrange a plurality of tubular nozzles on the bottom surface and / or side wall of the intermediate container so as to be separated from each other. When the tubular nozzles are arranged on the side wall, it is preferable that the nozzles are arranged at a constant height position on the side wall surface, at equal intervals, at an average distance L between the nozzles, and in a staggered manner. You may. In the case of the staggered arrangement, the distance L between the nozzles uses the horizontal distance between the nozzles at the same height.

As described above, by using the intermediate container for separating non-metallic inclusions in which a plurality of tubular nozzles are separated from each other as the gas blowing section, the horizontal rotational force is applied to the molten metal by the rotational force applying means. At the same time, a gas is blown into the molten metal from the gas blowing section to separate and remove nonmetallic inclusions in the molten metal. At this time, when the number of tubular nozzles is large, the chances of bubbles being combined also increase, but assuming that the average horizontal distance between tubular nozzles is L (m), the larger L is, the better the dispersion of bubbles is. Become. From this, the flow rate of the molten metal is set to V
(m / sec), and assuming that the gas injection amount is Q (Nm ³ / sec), the dispersion of bubbles is improved in proportion to L · V / Q. Therefore, the present inventors, when using a tubular nozzle for the gas blowing portion,
We considered using Q / (LV) as a parameter.

The distance L between the nozzles of the gas injection section, the gas injection amount Q, and the rotational speed V of the molten metal are expressed by the following equation (2): Q / (LV) ≦ 1.7 × 10 ^−2. ... (2) (where, Q: gas injection amount (Nm ³ / sec), V: rotational speed of molten metal (m / sec), L: distance between nozzles (m),
If the gas inlet is on the side wall, the average horizontal distance (m
), When the gas inlet is on the bottom, the distance in the circumferential direction (m
It is preferable that the conditions satisfy the relationship of)). Q /
By setting (LV) to 1.7 × 10 ^-2 or less, the dispersion of bubbles is improved.

The intermediate container of the present invention is disclosed in, for example, JP-A-4-36.
A tundish for continuous casting as disclosed by the present inventors in JP-A-5809 and JP-A-7-316627 is advantageously applicable.

[0024]

EXAMPLE A 30 ton tundish of the shape shown in FIG.
160 tons of molten steel were injected from a ladle at a throughput of 3 tons / min to impart a horizontal rotating flow to the molten steel, and gas was sucked into the molten steel 4 as bubbles 5 to separate and remove nonmetallic inclusions. After such treatment, the amount of nonmetallic inclusions in the molten steel poured from the tundish was measured, and the state of separation of the nonmetallic inclusions in the molten steel by the tundish was investigated. The molten steel components used were C = 0.02%, Si = 0.01
%, Al = 0.02% low carbon aluminum killed steel.

In the embodiment of the present invention, a cylindrical container having an inner diameter of 0.9 m, a rotating magnetic generator as a rotating force applying means 2 for applying a rotating force to molten steel on the outside of the container, and a gas blowing unit 3 for blowing gas into the side wall or bottom surface of the container. Was used. Ar gas was blown into the molten steel from the gas blowing part while applying a rotating flow with a rotating flow rate of 0.8 m / s at the outermost circumference to the molten steel by the rotating magnetic generator. In addition, the gas injection part used the slit-shaped nozzle of various sizes shown in Table 1, a porous refractory (porous plug), and a plurality of tubular nozzles.

Further, as a comparative example, experiments were conducted using the same container as the example of the present invention, in which only molten steel rotation (without gas injection) and only gas injection (without molten steel rotation) were performed. The size of the gas blowing portion for the slit-shaped nozzle and the porous refractory (porous plug) is, when the gas blowing portion is on the side wall, the horizontal plane of the blowing surface formed by the inner surface of the intermediate container and the gas blowing portion. The maximum length w of the intersection line and the maximum length 1 of an orthogonal line orthogonal to the intersection line in the blowing plane. When the gas blowing section is located on the bottom surface, the maximum length w of the blowing surface in the circumferential direction and the maximum length l of the blowing surface in the radial direction are indicated. On the other hand, the size of the gas blowing portion in the case of a tubular nozzle is indicated by the distance L between the nozzles. The distance L between the nozzles was the horizontal average distance between the nozzles along the container wall surface when the nozzle was on the container side wall, and the circumferential average distance when the nozzle was on the bottom surface. The separation state of the non-metallic inclusions in the molten steel was determined by measuring the amount of inclusions in the molten steel poured out of the tundish and comparing the amount of inclusions in the case where the molten steel was simply rotated (Comparative Example 1) with reference to Comparative Example 1 (Only rotation is applied to molten steel). Table 1 shows the results.
Shown in

No. 6 is an example in which a plurality of tubular nozzles are arranged on the bottom of the container as shown in FIG. 5 as a gas blowing portion, and No. 9 is a plurality of tubular nozzles as shown in FIG. No. 1 was placed at the same height on the same side wall of the container.
0 is an example in which a plurality of tubular nozzles are arranged in a staggered manner on the side wall of the container as shown in FIG.

[0028]

[Table 1]

From Table 1, it can be seen that, in each of the examples of the present invention, the amount of nonmetallic inclusions in the poured steel is low, and the effect of trapping nonmetallic inclusions is large. On the other hand, molten steel rotation velocity,
In the comparative example in which the relationship between the gas injection amount and the shape and interval of the gas injection unit is out of the range of the present invention, the effect of capturing nonmetallic inclusions is small.

[0030]

According to the present invention, non-metallic inclusions in the molten metal can be efficiently and economically separated, product defects are reduced, and product quality is improved. In addition, the effect that the production efficiency of high cleanliness steel is remarkably improved can be expected.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

FIG. 2 shows the arrangement of the gas blowing section in the intermediate container of the present invention.
It is a schematic diagram which shows an example.

FIG. 3 is a schematic view showing one embodiment of a tubular nozzle arrangement.

FIG. 4 is a schematic diagram showing one embodiment of a staggered tubular nozzle arrangement.

FIG. 5 is a schematic view showing one embodiment of a tubular nozzle arrangement.

FIG. 6 is a schematic view showing an example of a conventional tundish.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Intermediate container 1a Container inner surface 2 Rotation applying means 3 Gas blowing part 3a Blowing surface (side wall) 3b Blowing surface (bottom surface) 4 Molten metal 5 Bubbles (gas) 6 Rotation direction 11 Rotating tank 12 Floating tank 13 Pouring nozzle 14 Magnetic field generation Equipment 15 Breathable refractory 16 Bubbles 17 Discharge nozzle 19 Partition wall 20 Ladle O Rotation center (rotation axis) s Horizontal plane

Claims (4)

[Claims] 1. An intermediate container for separating non-metallic inclusions of molten metal, comprising: a rotating force applying means for applying a rotating force in a horizontal direction to the molten metal; and a gas blowing unit for blowing gas into the molten metal. The container has a substantially cylindrical side wall and a bottom surface, the gas blowing portion is provided on a side wall and / or a bottom surface of the intermediate container, and the gas blowing portion forms a gas blowing surface formed on the inner surface of the intermediate container with the gas. When the blowing portion is provided on the side wall, a ratio n = l / w of a maximum length w of an intersection line formed by the blowing surface with a horizontal plane and a maximum length 1 of an orthogonal line orthogonal to the intersection line within the blowing surface. When the gas blowing portion is provided on the bottom surface, the blowing surface is defined as a maximum circumferential length w of the blowing surface and a maximum radial length l of the blowing surface. Non-metallic interposition, characterized in that the blowing surface has a ratio n = l / w of 2 or more. Separating intermediate container. 2. Using the intermediate container for separating non-metallic inclusions according to claim 1, applying a rotating force in a horizontal direction to the molten metal by a rotating force applying means, and applying a gas to the molten metal from a gas blowing unit. In separating and removing nonmetallic inclusions in the molten metal, a dimensional ratio n of a blowing surface formed by the gas blowing portion on the inner surface of the intermediate container, and a gas blowing amount Q
And the rotational velocity V of the molten metal satisfying the following expression (1). Note (Q / V) /n≦3.7×10 ⁻⁴ (1) where, Q: gas injection amount (Nm ³ / sec), V: rotational velocity of molten metal (m / sec), n : L / w, w: maximum length (m) of the line of intersection of the blowing surface with the horizontal plane, or, maximum length in the circumferential direction of the blowing surface (m) l: with the line of intersection of the blowing surface with the horizontal plane The maximum length of orthogonal lines that are orthogonal within the blowing plane (m) or the maximum radial length of the blowing plane (m) 3. An intermediate container for separating non-metallic inclusions of molten metal, comprising: a rotating force applying means for applying a rotating force in a horizontal direction to the molten metal; and a gas blowing section for blowing gas into the molten metal. The intermediate container has a substantially cylindrical side wall and a bottom surface, the gas injection portion is provided on a side wall and / or a side surface of the intermediate container, and the gas injection portion is provided with a plurality of separated tubular members. An intermediate container for separating nonmetallic inclusions, comprising a nozzle. 4. Using the intermediate container for separating non-metallic inclusions according to claim 3, applying a rotational force to the molten metal in a horizontal direction by a rotational force applying means, and applying a gas to the molten metal from a gas blowing unit. In separating and removing non-metallic inclusions in the molten metal, the distance L between the nozzles of the gas injection section, the gas injection amount Q, and the rotational velocity V of the molten metal are expressed by the following equation (2). A method for separating non-metallic inclusions of molten metal, characterized by satisfying the following conditions: Note Q / (LV) ≦ 1.7 × 10 ⁻² (2) where, Q: gas injection amount (Nm ³ / sec) V: melt flow rate (m / sec) L: nozzle mutual Distance (m) Average distance in the horizontal direction when the gas inlet is on the side wall (m) Distance in the circumferential direction (m) when the gas inlet is on the bottom