JP3456309B2 - Continuous casting mold and continuous casting method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to continuous casting of molten metal in which an alternating magnetic field is applied to a molten metal in a mold with the aim of improving the quality of a continuously cast slab, and in particular, it is effective when an alternating current is directly applied to the mold. We propose a continuous casting mold that can generate an alternating magnetic field and a continuous casting method using the mold.

In continuous casting of molten metal, a method utilizing an alternating magnetic field is often used for casting steel and aluminum. This technology applies an alternating magnetic field near the surface of the molten bath in the casting mold for continuous casting, and the electromagnetic force causes the surface of the molten bath to curve upwards to expand the mold powder passage along the inner wall surface of the mold. The amount of heat removed by the mold is reduced and the amount of heat removed by the mold is reduced, and the vicinity of the molten metal bath surface is electromagnetically induction-heated to prevent the expected solidified shell from protruding horizontally along the bath surface to the initial solidified shell. It is intended to improve the surface quality of the slab by suppressing the inclusions and the trapping of bubbles.

[0003]

2. Description of the Related Art As a method for generating an alternating magnetic field in a mold, for example, as disclosed in Japanese Patent Publication No. 57-21408 (a method for casting molten metal), stainless steel or the like is used as a mold material. Using a metal with low electrical conductivity,
There is a method of installing an induction coil on the back surface of the mold and applying a magnetic field to the molten metal in the mold through the wall of the mold.

However, in this method, since the induction coil is installed on the outer periphery of the mold, the induction heating of the mold itself and the distance between the induction coil and the molten metal increase the magnetic field application efficiency. As a result, the application efficiency has been limited. This tendency becomes more remarkable as the frequency of the applied magnetic field becomes higher, and in the high frequency region where the frequency is 1 kHz or more, the efficiency is remarkably lowered and it is practically impossible to control the magnetic field.

As a method for solving such a problem,
There is a means disclosed in JP-A-4-100658 (mold for continuous casting). This means is to directly apply an alternating current to the mold, and since the mold plays the role of an induction coil, there is no decrease in magnetic field application efficiency due to magnetic field shielding or heat generation in the mold as described above, and the molten metal There is also no decrease in efficiency caused by the increased distance between the induction coil and the induction coil.

[0006] However, in this means, since the current flows through the entire mold including the back surface of the mold, the current density flowing near the surface of the molten metal, which is the area where the current should originally flow, is greatly reduced, and the magnetic field application efficiency is also reduced. There was a problem of lowering. In addition, "Electrical Theory A.110, Volume 9, P591-597
(1990), when an alternating current is applied to a conductor plate, the current concentrates on both edges as shown in Fig. 1 due to the interaction between the current and the magnetic field created by the current. There is a problem that the efficiency of applying a magnetic field is reduced at a place other than both ends of the mold.

Here, FIG. 1 is an explanatory view showing a current density distribution when electricity is applied in the left-right direction of the long side plate of the mold. In FIG. 1, 1 is an AC power source, 2 is a lead wire connection terminal, 3 is a molten metal bath surface, 4 is a long side plate of a mold, and 5 is a current path.

In order to solve this problem, Japanese Unexamined Patent Publication No. 6-142854 (a method for continuously casting steel using electromagnetic force and a die for continuous casting) corresponds to the vicinity of a portion to which a magnetic field is applied. There has been proposed and disclosed a means for improving the efficiency of applying a magnetic field by using a material having a high electric conductivity as the material of the template portion to be used in comparison with the material of other portions.

However, in this means, materials having different electric conductivities are used to adjust the distribution of current density flowing in the mold to improve the magnetic field application efficiency. It is limited to those having a high thermal conductivity, and in general, a substance having a high thermal conductivity tends to have a high electrical conductivity. Therefore, the ratio of the electrical conductivity of the two types of materials used as the mold material is 1: It was possible to do only a few. Moreover, when the frequency of the alternating current is high, the region where the current flows decreases in proportion to the skin depth due to the skin effect, but since the skin depth becomes shallower as the electrical conductivity becomes higher, the higher electric conductivity The effect of concentrating the electric current on the part having a certain degree was hindered, which was not expected. Therefore, the effect of improving the application efficiency of the alternating magnetic field near the target molten metal bath surface in the mold was insufficient only by increasing the electrical conductivity.

[0010]

SUMMARY OF THE INVENTION The present invention intends to advantageously improve the above-mentioned problems and to remarkably improve the current concentration effect, that is, to prevent the alternating magnetic field near the molten metal bath surface in the mold. It is an object of the present invention to propose a continuous casting mold which is remarkably improved in application efficiency and is excellent in durability, and a continuous casting method using the mold.

[0011]

The summary of the present invention is as follows. A continuous casting mold in which an alternating current is directly applied to the mold, and an alternating magnetic field is applied to the hot water of the mold, and an energization path is formed in a portion of the mold where an alternating current is to be applied, and the material of the energization path is an alternating current. A continuous casting mold (first invention) having a magnetic permeability lower than that of the material of at least the surface layer of the mold in a portion where current should not flow.

The continuous casting mold (second invention) according to the first invention, wherein the material of the energization path is a weak magnetic material, and at least the surface layer of the mold in a portion where an alternating current is not desired to flow is a ferromagnetic material.

The continuous casting mold (third invention) according to the first or second invention, wherein an electric current path is provided near the surface of the molten metal in the mold.

The continuous casting mold (fourth invention) according to the first, second or third invention, wherein the vertical width of the current path is at least 50 mm below the surface of the molten metal.

The continuous casting mold (fifth invention) according to the first, second, third or fourth invention, wherein the energization path comprises a plated layer of a low magnetic permeability material.

The first, second, and third parts of the surface layer of the mold where the alternating current does not flow include a plating layer of a high magnetic permeability material.
The continuous casting mold according to the third, fourth or fifth invention (sixth invention).

The plating layer of a high magnetic permeability material on the inner wall surface of the mold where the alternating current does not flow is made of a material having excellent durability at the plating surface layer, and the inner layer is made of a ferromagnetic material having a sufficiently high magnetic permeability. A continuous casting mold (seventh invention) according to the first, second, third, fourth, fifth or sixth invention, which comprises a composite plating layer or an inclined plating layer.

First, second, third, fourth, fifth and sixth
Alternatively, the mold for continuous casting according to the seventh invention, wherein an AC power supply terminal is provided on a long side plate of an assembled mold including a long side plate and a short side plate forming a casting space having a rectangular cross-section inner contour. A continuous casting mold (8th invention), in which an electric current path is formed on the inner surface of the long side plate near the inner molten metal bath surface, and the end of the short side plate in contact with the electric current path is coated with an insulating material.

For continuous casting by using an alternating current through the casting mold according to the first, second, third, fourth, fifth, sixth, seventh or eighth invention, Continuous casting method using mold powder (ninth invention).

Here, the weak magnetic material in the second invention is
It refers to diamagnetic materials other than ferromagnetic materials, paramagnetic materials and antiferromagnetic materials, such as Cu and Cr. Further, in the seventh invention, a material having excellent durability means a material having particularly excellent heat resistance, abrasion resistance and splash resistance (a property in which molten metal does not easily adhere).

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The operation of the present invention will be described below. This invention changes the magnetic permeability depending on the part of the casting mold for continuous casting, relatively lowers the part to which an alternating current is to be made to have a low magnetic permeability, and forms a current path, and makes the part to which an alternating current is not to be made to have a high magnetic permeability. It is the main idea.

According to the present invention, the portion of the mold where the current does not flow is formed of a material having a high magnetic permeability.
At this site, the skin effect acting on the alternating current becomes large,
Substantially reduced electrical conductivity makes it difficult for an alternating current to flow. On the contrary, the skin effect acting on the alternating current in the current-carrying path made of a material with low magnetic permeability is small, and the substantial decrease in electrical conductivity is also small. Therefore, the current will preferentially flow in the current-carrying path of low magnetic permeability in which the alternating current is desired to flow. By doing so, it becomes easy to efficiently generate an alternating magnetic field at an arbitrary position in the mold.

Further details will be described below. If the electric conductivity of the mold material is σ, the permeability is μ, and the angular frequency of the alternating current is ω, the skin depth δ is

[Equation 1] It is represented by. Therefore, it is considered that the current: I flowing on the mold surface due to the skin effect is almost proportional to the product of the electric conductivity: σ and the skin depth: δ, and is represented by the following formula.

[Equation 2]

Therefore, when the wall thickness of the mold is sufficiently thicker than the skin depth: δ (the shape of the mold is not taken into consideration), the current: I flowing through the mold, that is, the surface of the mold has a magnetic permeability of μ.
It is inversely proportional to 1/2 power, and is proportional to the electrical conductivity: 1/2 power of σ.

This means that the ratio of the two types of electric conductivity which can be used as the mold material is 1: 2 as described above.
For about 3 to about 3, ferromagnetic materials such as Ni and Fe alloys,
Since the magnetic permeability thereof is several thousand times or more as large as that of the paramagnetic substance, the substantial electric resistance can be remarkably increased. Therefore, if such a ferromagnetic material is used in a portion of the mold where an alternating current is not desired to flow, and if a paramagnetic material is used in the portion where an alternating current is desired to flow, that is, the current path, the material is concentrated in the paramagnetic material of the current path. An electric current can be passed, and an alternating magnetic field can be efficiently generated at an arbitrary position in the mold, that is, near the molten metal bath surface during continuous casting.

As described above, in the present invention, as a relative comparison, the material of the mold of the portion to which the alternating current is to be applied is made to have a low magnetic permeability so as to form a conduction path, and the material of the mold of the portion to which the alternating current is not applied is made to have a high permeability. Although it is magnetic susceptibility, as described above, the alternating current flows concentratedly near the surface of the mold due to the skin effect.Therefore, plating the surface of the mold with a low-permeability material and / or a high-permeability material also produces the same effect. Can be demonstrated.

That is, a material having a lower magnetic permeability than that of the mold body is plated on a portion where an alternating current is desired to flow, or a material having a higher magnetic permeability than that of the mold body is plated on a portion where no alternating current is desired to flow, or a lower magnetic permeability. Alternatively, a material having a high magnetic permeability may be plated on each part.

In the above, if copper or copper alloy having a relative magnetic permeability of about 1 is used as the mold base material and Ni, Co or Fe which is a ferromagnetic material or an alloy thereof is used as the high magnetic permeability material, Since these materials have a high magnetic permeability and a high thermal conductivity suitable as a mold material, a mold having a significantly high AC current concentration effect and an excellent cooling capacity can be obtained.

Also, Ni, Co or their alloys, which have already been used as the plating material for copper molds for continuous casting of molten metal, can be thinly plated on a portion where an alternating current is not desired to flow, by itself. This is an extremely effective means because the alternating current is concentrated on a portion (current-carrying path), and especially when the frequency of the alternating current becomes higher, the effect of concentrating the alternating current on the surface layer becomes greater.

In the present invention, in order to effectively concentrate the alternating current in the energizing path, the material of the energizing path is compared with the material of the portion where the alternating current is not desired to flow, and the ratio of the applied alternating current at the frequency is higher. Magnetic permeability is 1/10 or less, more preferably 1/100
It is desirable to use the following, and as a combination of these materials, for example, copper or copper alloy is used in the alternating current conducting path, and 36 permalloy (36Ni-0.3Mn
-Fe), 45 permalloy (45Ni-0.3Mn-Fe), 78 permalloy
(78.5Ni-0.3Mn-Fo), 3.8-78.5Cr Permalloy (78.5Ni-3.
8Cr-Fe), 4-79Mo Permalloy (79Ni-4Mo-5Cu-Fe), Mumetal (77Ni-2Cr-5Cu-Fe), 1040 Alloy (18Ni-3Mo-14C)
u-Fe), supermalloy (79Ni-5Mo-0.3Mn-Fe), and other permalloys, and birming bar (45Ni-30Fe-25Cr)
Etc.) such as Ni, Fe, etc. as the main components with a low iron loss and high permeability alloys or sendust (5% Al-10% Si-Fe).
Etc.), it is more practical to use a ferromagnetic alloy such as silicon steel with low iron loss or pure iron.

In this way, by forming a current path of a low magnetic permeability material in the continuous casting mold, in continuous casting, an alternating magnetic field is efficiently applied in the vicinity of the molten bath surface, and the electromagnetic force causes the molten bath surface to be applied. It is intended to improve the surface quality of the continuously cast slab by curving upwardly convex shape, heating the initially solidified portion, and the like. In this case, it is preferable that the width of the energizing path in the vertical direction is at least 50 mm below the molten metal bath surface. However, if the width exceeds 300 mm, the cooling and solidification of the molten metal is hindered, which is not preferable.

Further, in the case of a continuous casting mold having a plating layer of a high magnetic permeability material in a portion where an alternating current is not desired to flow, the surface of the plating layer on the inner surface of the mold is brought into contact with the molten metal through a thin mold powder melt. However, it is important to have excellent durability such as heat resistance, abrasion resistance, and splash resistance, because it will come into contact with hard solidified shells and splash the molten metal.

Therefore, if a plating material with a focus on durability is used, no plating material has a sufficiently high magnetic permeability, and there is a limit to the plating thickness from the viewpoint of preventing cracking due to thermal expansion during casting. As a result, the plating thickness cannot be set sufficiently with respect to the skin depth δ, and as a result AC current will flow even to the mold base material, and the application efficiency of the alternating magnetic field cannot be improved as expected. There are cases.

Therefore, in the present invention (seventh invention), the plating layer of high magnetic permeability material on the inner wall surface of the mold at the portion where the alternating current is not allowed to flow is made of a material having excellent durability,
The inner layer (mold base material side) is a composite plating layer or a gradient plating layer made of a material having a sufficiently high magnetic permeability. By doing so, it is possible to improve durability and improve the efficiency of applying an alternating magnetic field. A mold will be obtained.

Here, as the material of the plating surface layer portion having excellent durability, for example, 95Co-Ni alloy, 4-6% Fe-Ni alloy, or Cr, which has a proven track record as a plating material for molds, may be used. Well, the magnetic permeability is sufficiently high, and the material of the plating inner layer portion which is a ferritic loss is, for example, an alloy mainly composed of Ni, Fe or the like represented by permalloy or birming bar as described above, sendust, It is preferable to use silicon steel and pure iron.

Generally, a large number of slabs are cast in continuous casting, but a practical continuous casting mold for slabs is an assembly consisting of long side plates and short side plates that form a casting space with a rectangular cross-section inner contour. A mold is often used.An AC power supply terminal is provided on the long side plate to form an energization path on the inner surface of the long side plate near the molten metal bath surface in the mold, and the end of the short side plate in contact with this energization path is electrically connected. It is suitable to insulate.

On the other hand, it is preferable to use mold powder for continuous casting using such a continuous casting mold in which an alternating current is passed through the energizing path. The mold powder used is preferably one having a low electrical conductivity from the viewpoint of improving the electrical insulation between the continuous casting mold and the solidified shell, and its value is preferably 2.5 Ω ^-1 / cm or less. Note that the conductivity of normal mold powder is in the range of 1.5 to 3.5 Ω ^-1 / cm, but Ca in the mold powder should be reduced to reduce the conductivity.
It is preferable to reduce O _{2 and} increase Al ₂ O ₃ .

[0038]

EXAMPLE In continuous casting of a slab, casting in which an alternating current is directly applied to the mold is usually performed by applying an electric current to the long side plate of the mold. The embodiments described below are also those in which a current is passed through the long side plate.

Example 1 FIGS. 2 (a) and 2 (b) are explanatory views of a long side plate of a continuous casting mold according to a first conforming example of the present invention. (a) is an explanatory view of a longitudinal section of the long side plate, and (b) is an explanatory view of an inner surface of the long side plate.

In these figures, 1 is an AC power source, 2 is a lead wire connection terminal, 3 is a molten metal bath surface and 4 is a mold long side plate, and 7 is the long side plate surface of the inner surface of the mold excluding the vicinity of the molten bath surface ( A plating layer of a ferromagnetic metal having excellent durability plated on the back surface of the long side plate (8) and a long side plate base material surface 8 of a low magnetic permeability material exposed near the surface of the molten metal.

In this mold, in order to efficiently apply an alternating magnetic field near the surface of the molten metal, the surface of the long side plate 4 excluding the vicinity of the surface of the molten metal is made of a ferromagnetic material such as a Co-Ni-Fe alloy having excellent durability. A body metal plating layer 7 is provided, and a long-side plate base material surface 8 having a low magnetic permeability, such as copper, is exposed in the vicinity of the surface of the molten metal to provide a current path.

3 (a) and 3 (b) are explanatory views of the long side plate of the conventional continuous casting mold in which a high electric conductivity material is arranged near the surface of the molten metal. (a) is an explanatory view of a longitudinal section of the long side plate, and (b) is an explanatory view of the inner surface of the long side plate.

In these figures, 1 is an AC power source, 2 is a lead wire connection terminal, 3 is a molten metal bath surface, and 4 is a long side plate,
A high electric conductivity metal layer 9 is arranged on the surface (current path) of the long side plate 4 near the molten metal bath surface on the inner surface of the mold, and the long side plate base material surface 8 is exposed on the other long side plate 4 surfaces. It has become.

Using the continuous casting mold of the conforming example 1 having the long side plate shown in FIG. 2 and adapted to the present invention, and the conventional continuous casting mold having the long side plate shown in FIG. ,
In the air-core state, power was supplied at a power of 200 kw and a power frequency of 1 kHz, and the magnetic flux density distribution was measured at a position 10 mm from the inner surface of the long side plate of the mold.

It is to be noted that the same dimension specifications are used for the molds of the conforming example 1 and the conventional example, and the long side plate base material surface 8 in FIG. 2 of the conforming example and the high electric conductivity metal in FIG. The width of the layer 9 (both current paths) in the vertical direction was 200 mm, and the layer 9 was arranged from the surface of the molten metal to below the molten metal.

Also, as a mold material, the first suitable example is the long side plate 4.
Material: Copper (Relative permeability: 1, Electrical conductivity: 5 × 10 ⁷ Ω ^-1
m ^-1 ) Material of ferromagnetic metal plating layer 7 with excellent durability: 95% Co
-Ni alloy (estimated relative permeability: 10, electrical conductivity: 2 × 10 ⁷ Ω
^-1 m ^-1 ), and the conventional example is the material of the long side plate 4: Cu-8% Cr-0.15% Zr alloy (relative permeability: 1, electric conductivity: 2.1 × 10 ⁷ Ω ^-1 m ^-1 ). The material of the high electric conductivity metal layer 9 was copper (relative magnetic permeability: 1, electric conductivity: 5 × 10 ⁷ Ω ⁻¹ m ⁻¹ ).

The measurement results of the magnetic flux density distribution are shown collectively in FIG. FIG. 4 is a graph showing the relationship between the distance from the position corresponding to the molten metal bath surface and the magnetic density index.

Here, FIG. 4 shows the magnetic flux density distribution when a magnetic field is generated in the mold of the adaptation example 1 of the present invention and the conventional example with the same power source power. Shows the ratio of the magnetic flux densities at other measuring points including the case of the conventional example to the maximum magnetic flux density measured in the first conformity example of the present invention.

As is clear from FIG. 4, in the mold of the adaptation example 1 of the present invention, the electric current is efficiently concentrated in the portion (current path) where the alternating current is desired to flow, so that a strong magnetic field is generated in the portion corresponding to the molten metal bath surface. I know that

In the above-mentioned embodiment, the mold of the conforming example 1 of the present invention uses pure copper as the long-side plate base material, and a high-permeability Co-Ni alloy is plated on the surface of the mold where no alternating current flows. However, the long side plate base material is made of a material with high magnetic permeability, and the part where the alternating current is to be flown, that is, the energization path is a plated layer of the material with low magnetic permeability, or the material with high magnetic permeability is used for the part where the alternating current is not desired to flow. It is also possible to use the above-mentioned plating layer as the template, and to make the energization path a plating layer of a low magnetic permeability material, and the material of the long side plate itself as a mold using a high magnetic permeability material and a low magnetic permeability material. The same effect can be obtained.

Example 2 Using the molds of the conforming example 1 and the conventional example similar to those of Example 1, ultra low carbon steel of C: 0.005% was continuously cast into a slab size of 260 mm x 1.000 mm. The average value of the claw depths of these cast pieces is shown in FIG. 5, and the surface defect generation index is shown in FIG.
FIG. 5 is a graph showing the average value of the claw depth of each of the cast pieces cast using the molds of the conforming example 1 and the conventional example, and FIG. 6 is cast using the casting molds of the conforming example 1 and the conventional example. 3 is a graph showing a surface defect occurrence rate index of the cast slab. Here, the surface defect occurrence rate index is the number of scratches per unit area generated when rolling a slab, calculated with the value in the conventional example being 1. As is clear from these figures, the slab using the mold of the fitting example 1 has a smaller claw depth (oscillation mark depth) than the slab using the mold of the conventional example, and the surface It can be seen that the defect occurrence rate is also decreasing. This is because the application efficiency of the magnetic field to the molten steel meniscus portion is improved, and thus it is possible to apply a stronger magnetic field.

Example 3 In the plating layer on the inner wall surface of the mold where the alternating current is not desired to flow, the plating surface layer portion is made of a ferromagnetic material having excellent durability, and the inner layer is made of a high magnetic permeability material having a sufficiently high magnetic permeability. FIGS. 7 (a) and 7 (b) are explanatory views of the long side plate of the continuous casting mold of the conforming example 2 adapted to the present invention, which is a composite plating.
(A) is an explanatory view of a longitudinal section of the long side plate, and (b) is an explanatory view of the inner surface of the long side plate.

In these figures, 1 is an AC power source, 2 is a lead wire connection terminal, 3 is a molten metal bath surface, and 4 is a long side plate of the mold, and 6 is a long side plate surface of the inner wall surface of the mold excluding the vicinity of the molten bath surface. High-permeability metal plating layer (including the back surface of the long side plate), 7 is a composite metal plating layer on the plating layer 6 on the inner wall of the mold and has excellent durability, and 10 is a ferromagnetic metal plating layer, and 10 is near the molten metal bath surface. The low-permeability metal plating layer is shown in the current-carrying path on the inner wall surface of the long side plate.

A magnetic flux density distribution in an air-core state was obtained in the same manner as in Example 1 using the continuous casting mold of the conforming example 2 shown in FIG. 7 and the continuous casting mold of the conforming example 1 shown in FIG. Was measured respectively. The dimensions of the long side plate of the conforming example 2 (FIG. 7) and its current-carrying path 10 are the same as those of the conforming example 1.

Further, the mold material of the conformity example 2 is the material of the long side plate 4: Cu-1% Cr-0.2% Zr (relative magnetic permeability: 1, electric conductivity: 2.8 × 10 ⁷ Ω ^-1 m ^-1). ) High permeability metal plating layer 6 material: 45% Ni-Fe alloy (estimated relative permeability: 100, electric conductivity: 2.3 × 10 ⁶ Ω ^-1 m ^-1 , hardness: 110Hv) Ferromagnetism with excellent durability Material of metal plating layer 7: 95% Co-N
i alloy (estimated relative permeability: 10, electric conductivity: 7.5 × 10 ⁵ Ω
^-1 m ^-1 , hardness: 400Hv) Material of low magnetic permeability metal plating layer 10 (current path): Cu-1% Ag
(Relative magnetic permeability: 1, electric conductivity: 3.1 × 10 ⁷ Ω ^-1 m ^-1 ), the plated layer 6 has a high magnetic permeability, and the plated layer 7 has a high hardness from the viewpoint of durability. I prioritized something.

The measurement results of the magnetic flux density distribution are summarized in FIG. FIG. 8 is a graph showing the relationship between the distance from the position corresponding to the molten metal bath surface and the magnetic flux density index.

Here, the magnetic flux density index indicates the ratio of the magnetic flux densities at the other measurement points including the case of the conforming example 1 with the maximum magnetic flux density measured in the conforming example 2 being 1. Is.

As is apparent from FIG. 8, in the mold of the second conforming example, the high-permeability metal plating layer 6 is provided on the surface of the long side plate in the portion where the alternating current is not desired to flow and the high permeability of the inner wall surface of the long side plate is provided. Since the surface of the magnetic susceptibility plating layer 6 is covered with the ferromagnetic metal plating layer 7 having excellent durability, compared to the case of the conformity example 1, the current is efficiently concentrated at the portion (current path) where the alternating current is desired to flow. However, it can be seen that a strong magnetic field is generated in the portion corresponding to the molten metal bath surface. Further, since the surfaces of the plating layers on the inner wall surfaces of the molds of the conforming example 1 and the conforming example 2 are both 95% Co-Ni alloys, which have excellent durability, their durability is the same.

The material of the plating layer surface layer portion 7 on the inner wall surface of the mold of the conforming example 2 is such that the plating layer 7 of the surface layer portion is sufficiently thin or the magnetic permeability of the plating layer 6 of the inner layer is sufficiently high. Can be used as a material having a magnetic permeability lower than that of the Co—Ni alloy used above.

Example 4 Using the molds of adaptation example 1 and adaptation example 2 similar to that of example 3,
As in Example 2, C: 0.005% ultra low carbon steel 260 mm x
Continuously cast into slabs with a size of 1000 mm. The average value of the claw depths of these cast pieces is shown in FIG. 9, and the surface defect generation index is shown in FIG.

FIG. 9 is a graph showing an average value of the claw depths of the respective cast pieces cast by using the molds of the conforming example 1 and the conforming example 2, and FIG. 10 shows the molds of the conforming example 1 and the conforming example 2. It is a graph which shows the surface defect generation index of each cast piece cast using. The surface defect generation index is calculated in the same manner as in Example 2.

As is clear from these figures, the conformity example 2
The slab using the mold of No. 2 has a smaller claw depth (oscillation mark depth) and a smaller surface defect rate than the slab using the mold of Conformance Example 1. This is because the efficiency of applying the magnetic field to the vicinity of the molten metal bath surface was further improved as compared with the conformation example 1, and a stronger magnetic field was applied.

[0063]

INDUSTRIAL APPLICABILITY The present invention is a continuous casting mold and a continuous casting method in which an alternating current is directly applied to a mold when an alternating magnetic field is applied to a molten metal, and the alternating current is applied to the mold. A material having a low magnetic permeability is used in a portion where the AC current is not to be passed to the portion where the AC current is to be passed. According to the present invention, it becomes easy to concentrate the AC current in an arbitrary portion of the mold, It is possible to apply an alternating magnetic field to any part of the inner molten metal very efficiently,
It can greatly contribute to the quality improvement of continuous cast slabs and the reduction of power consumption.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a current density distribution when electricity is applied to a long side plate of a mold in a left-right direction.

FIG. 2 is an explanatory view of a long side plate of a continuous casting mold according to a first conforming example of the present invention. (A) is explanatory drawing of the longitudinal cross section of a long side plate. (B) is an explanatory view of the inner surface of the long side plate.

FIG. 3 is an explanatory view of a long side plate of a continuous casting mold of a conventional example. (A) is explanatory drawing of the longitudinal cross section of a long side plate. (B)
FIG. 6 is an explanatory diagram of an inner surface of a long side plate.

FIG. 4 is a graph showing the relationship between the distance from the position corresponding to the molten metal bath surface and the magnetic flux density index in the case of using the molds of the conforming example 1 and the conventional example.

FIG. 5 is a graph showing an average value of the claw depth of each of the cast pieces cast using the molds of the fitting example 1 and the conventional example.

FIG. 6 is a graph showing the surface defect occurrence rate index of each of the cast pieces cast using the molds of the fitting example 1 and the conventional example.

FIG. 7 is an explanatory view of a long side plate of a continuous casting mold according to a second conforming example of the present invention. (A) is explanatory drawing of the longitudinal cross section of a long side plate. (B) is an explanatory view of the inner surface of the long side plate.

FIG. 8 is a graph showing the relationship between the distance from the position corresponding to the molten metal bath surface and the magnetic flux density index in the case of using the molds of conforming example 1 and conforming example 2.

FIG. 9 is a graph showing the average value of the claw depth of each of the cast pieces cast using the molds of the conforming example 1 and the conforming example 2.

FIG. 10 is a graph showing the surface defect occurrence index of each slab cast by using the molds of conforming example 1 and conforming example 2.

[Explanation of symbols]

1 AC power supply 2 conductor connection terminal 3 Molten bath surface 4 Mold long side plate 5 Current path 6 High permeability metal plating layer 7 Ferromagnetic metal plating layer with excellent durability 8 Long side plate base material surface 9 High conductivity metal layer 10 Low magnetic permeability metal plating layer (current path)

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Bessho Nagayasu, 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Works, Ltd. Technical Research Institute (56) Reference JP-A-7-290197 (JP, A) JP-A 6-142854 (JP, A) JP-A-1-271033 (JP, A) JP-A-7-284896 (JP, A) Actual development Sho 64-38138 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 11/04 311 B22D 11/059 110 B22D 11/108 B22D 27/02

Claims (9)

(57) [Claims] 1. A continuous casting mold in which an alternating current is directly applied to the mold and an alternating magnetic field is applied to the hot water of the mold, wherein an electric current path is formed in a portion of the mold where the alternating current is desired to flow.
A continuous casting mold in which the material of the current path has a low magnetic permeability compared to at least the material of the surface layer of the mold in a portion where alternating current is not desired to flow. 2. The continuous casting mold according to claim 1, wherein the material of the energizing path is a weak magnetic material, and the material of at least the surface layer of the mold at a portion where an alternating current is not desired to flow is a ferromagnetic material. 3. The continuous casting mold according to claim 1, wherein an electric current path is provided in the vicinity of the molten metal bath surface in the mold. 4. The continuous casting mold according to claim 1, wherein the upper and lower widths of the energizing path are at least 50 mm below the molten metal bath surface. 5. The continuous casting mold according to claim 1, 2, 3 or 4, wherein the energization path comprises a plated layer of a low magnetic permeability material. 6. The surface layer of the mold, which is a portion where an alternating current is not desired to flow, is formed of a plated layer of a high magnetic permeability material.
The continuous casting mold according to 3, 4, or 5. 7. A ferromagnetic material having a high permeability of the plating layer on the inner wall surface of the mold at a portion where an alternating current is not desired to flow, the plating surface layer having excellent durability, and the inner layer having a sufficiently high permeability. The continuous casting mold according to claim 1, which comprises a composite plating layer or a gradient plating layer. 8. The method according to claim 1, 2, 3, 4, 5, 6 or 7.
In the continuous casting mold according to claim 1, the long side plate of the assembly mold consisting of the long side plate and the short side plate forming the casting space of the rectangular cross-section inner contour, the molten metal bath surface in the mold by providing an AC power supply terminal A continuous casting mold in which a current path is formed on the inner surface of a long side plate in the vicinity, and the end of the short side plate in contact with the current path is coated with an insulating material. 9. A continuous casting mold according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein a mold powder is used for continuous casting by passing an alternating current through the mold. A continuous casting method characterized in that