JPH0557404A - Continuously casting device for steel sheet - Google Patents

Abstract

PURPOSE:To obtain a steel sheet excellent in surface property with a casting device providing on high frequency induction coil with large capacity. CONSTITUTION:In the twin roll type continuous casting device for steel sheet, the high frequency coils are provided on the outside of the weirs 3, 4 along the vicinity of the triple point part in contact with the cooling rolls 1a, 1b, the weirs 3, 4 and a molten steel, and also magnetic field amplifying plates 9a, 9b are disposed while approaching to the high frequency induction coils, and in these magnetic field amplifying plates 9a, 9b, parts, such as groove, gap for preventing the conduction of energizing of induction current are provided in a stripe-state toward the outside from the weir side. Thus, since the induction current flow is prevented with the parts such as groove, gap, and the current flows in surroundings of the magnetic field amplifying plates 9a, 9b at high density, strong magnetic pressure is concentrically impressed in the surroundings of the weir sides (in the vicinity of the triple point part) to form space there, and the solidification of the molten steel is not occurred in vicinity of the triple point part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel plate continuous casting apparatus.

[0002]

2. Description of the Related Art As an apparatus for directly and continuously casting a steel sheet from molten steel, for example, there is a technique proposed in Japanese Patent Laid-Open No. 63-80945. 9 (a) and 9 (b) show the above-mentioned conventional technique, FIG. 9 (a) is a partially cutaway front view, and FIG. 9 (b) is a perspective view of a main part. This apparatus is a so-called twin-roll type continuous casting apparatus, and includes a pair of cooling rolls 1a and 1b arranged in parallel and horizontally adjacent to each other and two cooling rolls 1a and 1b. The main parts are constituted by the end dams 3 and 3 and the top dams 4 and 4 for accumulating the molten steel 2 in the valley-shaped space formed by. The end weir 3 and the top weir 4 are arranged with a slight gap between them and the cooling rolls 1a and 1b, and the cooling rolls 1a and 1b are driven by a driving means (not shown) and face each other. The outer peripheral surface is adapted to rotate in the descending direction.

A high frequency coil 5 is embedded in the vicinity of the end dam 3 along the outer peripheral surfaces of the cooling rolls 1a and 1b and in the lower part of the end dam 3.

In the apparatus constructed as described above, the cooling rolls 1a and 1b are started, the high frequency coil 5 is energized, and then molten steel is placed in the valley-shaped space above the cooling rolls 1a and 1b surrounded by the weir. When 2 is supplied, the molten steel 2 is solidified on the outer peripheral surfaces of the cooling rolls 1a and 1b to form solidified shells 6 and 6. The solidification shells 6 and 6 move sequentially downward as the cooling rolls 1a and 1b rotate, and are pressure-bonded in the vicinity of the cooling rolls 1a and 1b to form a single steel plate 7. The steel plate 7 is continuously sent out and wound up by a winder (not shown).

In the above apparatus, the high frequency coil 5 is
It is prepared to prevent the following problems.

Without the high frequency coil 5, the following problems occur. The solidified shell 8 formed on the top weir 4 or the solidified shell formed on the end weir 3 gradually grows and is fixedly connected to the solidified shell 6 formed on the cooling rolls 1a and 1b. When the two solidified shells are connected, one solidified shell 6 moves with the rotation of the cooling rolls 1a and 1b, so that the fixed portion is cut. When such a situation is repeated, unevenness is formed on the surface and side portions of the cast steel plate 7, and the surface quality becomes extremely poor. Also, there is a slight gap between the cooling rolls 1a and 1b and the end weir 3 and the top weir 4, but when the molten steel 2 is inserted into this gap, a solidified shell is generated and this solidified shell is formed. Cooling roll 1a,
The solidified shell 6 of 1b is fixed and connected. Then, similarly to the above, the surface properties of the steel sheet 7 are remarkably deteriorated or breakout occurs.

In this way, the cooling roll 1a or the cooling roll
When the solidified shell is generated in the portion (hereinafter, referred to as the triple point portion) where the rule 1b, the end weir 3 or the top weir 4, and the molten steel 2 are in contact with each other, various problems as described above are caused.

In order to cope with this problem, the above-mentioned prior art is provided with the high frequency coil 5. FIG. 10 is an explanatory diagram related to the operation of the high frequency coil. When a current flows through the high frequency coil 5, a magnetic field H is generated in the molten steel in the direction of the arrow in the figure, and an eddy current having an opposite phase is induced. As a result, a magnetic pressure F is generated, and the molten steel at the triple points receives a force acting in a direction away from the weir 4. For this reason, when the value of the current flowing through the high-frequency coil 5 is set to a certain value or more, the magnetic pressure F becomes larger than the static pressure of the molten steel at the triple point, and the space where molten steel does not exist at the triple point (the molten steel and It is possible to create a state where the important point is non-contact.

[0009]

However, in the above-mentioned conventional device, even if a high frequency coil is energized to generate a magnetic field, the magnetic field diffuses, so that the efficiency is very poor. Therefore, in order to generate the magnetic pressure necessary for casting a steel sheet having a good surface quality, the capacity of the high frequency power source must be made extremely large. Also, if a high-capacity high-frequency coil is embedded in the weir near the triple point where the heat load is large, due to the thermal stress due to the induced current,
There is also a problem that the weir breaks (cracks).

It is an object of the present invention to provide a steel plate continuous casting apparatus capable of casting a steel plate having a good surface property without providing a high-capacity high frequency coil.

[0011]

In order to achieve the above object, in the present invention, an induced current is applied to the outside of the weir along the vicinity of the triple point where the cooling roll contacts the weir and the molten steel. It is equipped with a high-frequency coil for generating, and a magnetic field amplification plate is arranged in the vicinity of this high-frequency coil. A cooling box is attached to this magnetic field amplification plate, and a part for blocking conduction of an induction current generated from the high-frequency coil is provided. Striations are provided from the weir side to the outside.

The streak-like portion provided on the magnetic field amplifying plate for blocking the conduction of the induced current may be at least one groove or at least one gap (break).

The magnetic field amplification plate does not necessarily have to be provided as a single member, and the upper plate of the cooling box can also be used as the magnetic field amplification plate. That is, a high frequency coil for generating an induced current is provided outside the weir along the vicinity of the triple point where the cooling roll contacts the weir and the molten steel, and the cooling box is arranged in the vicinity of this high frequency coil. The upper plate of the cooling box may be provided with a portion that blocks the passage of the induction current generated from the high frequency coil in a streak shape from the weir side to the outside.

Hereinafter, the magnetic field amplification plate arranged close to the high frequency coil and the upper plate of the cooling box will be collectively referred to as a magnetic field amplification plate.

As a material of the magnetic field amplification plate, for example, a metal having a high electric conductivity such as copper or aluminum is suitable.

When a high-frequency coil is arranged near the metal plate and a high-frequency current is passed through it, an induced current flows due to the mutual induction action, and a magnetic pressure is generated there. When a metal plate, which is a magnetic field amplification plate, is provided with a groove or a gap as in the present invention, this portion becomes a portion that blocks the conduction of the induction current, so that the induction current flows around the magnetic field amplification plate. .. For this reason, the induced current flows at a high density around the dam side of the magnetic field amplification plate (near the triple point), whereby a strong magnetic pressure is concentratedly applied to the triple point.

Therefore, it is desirable to arrange the magnetic field amplification plate along a position as close as possible to the triple point.

The depth of the groove provided in the magnetic field amplification plate is preferably about twice or more of δ obtained by the following equation (1). That is, the magnetic field exponentially attenuates from the skin in the plate thickness direction, so if a groove having a depth of the above value or more is provided,
Most of the flow of induced current is blocked (current is substantially blocked). Further, the thickness of the magnetic field amplifying plate when the gap is provided is preferably about 0.3 times δ or more.

Δ = {2 / (ωσμ)} ^1/2 (1) where ω; angular frequency of high frequency current σ; electric conductivity of magnetic field amplification plate μ; magnetic permeability of magnetic field amplification plate Magnetic field amplification of the present invention Regarding the plate, there are a case where it is arranged alone and is simply in contact with the cooling box, and a case where it is also used as an upper plate of the cooling box. However, in any case, the depth and thickness of the groove may be set within the above range.

First, in a magnetic field amplification plate arranged alone, even if the magnetic field amplification plate and the cooling box are in contact with each other, the electrical contact resistance between them is very large, so most of the induced current is in the cooling box. It flows in the magnetic field amplification plate without flowing.
Therefore, it is not necessary to consider the presence of the cooling box.
When the plate thickness of the magnetic field amplification plate is smaller than 0.3δ, the conduction resistance increases and the region in which the magnetic field acts becomes narrower (because the action of the magnetic field extends only to the thickness of the plate and its periphery), The space (space where molten steel does not exist) generated in the triple point becomes small, and the necessary area cannot be secured.

On the other hand, when the magnetic field amplifying plate is also used as the upper plate of the cooling box, the magnetic field amplifying plate and the cooling box are electrically connected to each other. It is necessary to consider the dimensions so as to sufficiently reduce the leakage of the current flowing from the cooling box to the cooling box. However, as described above, since the magnetic field exponentially attenuates from the skin in the plate thickness direction, if the depth of the groove is at least twice δ, most of the induced current can be blocked. it can.

Further, in the present invention, a cooling box is attached to the magnetic field amplification plate. However, when the high frequency coil is energized, the magnetic field amplification plate is heated by the induced current, so that the temperature becomes extremely high. This is because the continuous use becomes impossible.

[0023]

FIG. 1 shows an embodiment of the present invention, (a) is a front view, (b) is a side view, and (c) is a plan view. In FIG. 1, the same parts as those in FIG. 9 are designated by the same reference numerals and the description thereof will be omitted. 1a and 1b are cooling rolls, 3 is an end dam,
4 is a top weir. In the present embodiment, the magnetic field amplification plate 9a is arranged along the vicinity of the triple point outside the end dam 3.
A magnetic field amplification plate 9b is also arranged on the top weir 4 side along the vicinity of the triple point. A high frequency coil 5 is provided on the magnetic field amplification plates 9a and 9b so as to surround the end weirs 3 and 3 and the top weirs 4 and 4 and at a position close to the end weirs 3 and 3 and the top weirs 4 and 4. ing. Then, the magnetic field amplification plates 9a, 9
On the lower surface of b, there is attached a cooling box which is in close contact with the magnetic field amplification plates 9a and 9b and has an integral structure.
This cooling box has a water cooling structure made of copper, and the cooling box 10 is attached to the magnetic field amplification plate 9a on the side of the end dam 3 and the cooling box 11 is attached to the magnetic field amplification plate 9b on the side of the top dam 4.
The magnetic field amplification plates 9a and 9b are cooled from the lower surface. The magnetic field amplification plates 9a and 9b have a special shape, which will be described later.

FIG. 2 shows another embodiment of the present invention, (a)
Is a front view and (b) is a side view. In FIG.
The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, only the end dam 3 is provided, and the magnetic field amplification plate 9a is arranged along the vicinity of the triple point outside the end dam 3. A high frequency coil 5 is provided above the magnetic field amplification plate 9a and in a position close to the end dam 3. The magnetic field amplification plate 9a is provided on the lower surface of the magnetic field amplification plate 9a.
A cooling box 10 that is in close contact with a and has an integral structure is attached. The shape of the magnetic field amplification plate 9a will also be described later.

FIG. 3 is a view showing the arrangement and shape of the magnetic field amplification plates in the continuous casting apparatus of FIG. 1, and FIG. 4 is a view showing the arrangement and shape of the magnetic field amplification plates in the continuous casting apparatus of FIG.

In FIG. 3, 9a is a magnetic field amplification plate on the side of the end weir, 9b is a magnetic field amplification plate on the side of the top weir, 1a and 1b are cooling rolls, 3 is an end weir, and 4 is a top weir. Show. The magnetic field amplification plates 9a and 9b are provided with a groove 12 that extends from the inside (sides of the weirs 3 and 4) to the outside, and is divided into two sections.
And the recessed part 13 is formed in each division. Further, the magnetic field amplification plates 9a and 9b are provided with a groove 14 that extends from the recess 13 to the inside (sides of the dams 3 and 4).

In FIG. 4, 9a is a magnetic field amplification plate on the side of the end dam, 1a and 1b are cooling rolls, and 3 is an end dam. This magnetic field amplification plate 9a is the same as the magnetic field amplification plate 9a on the side of the end dam in FIG.

5 to 7 are views showing various embodiments of the magnetic field amplifying plate. Since there is no fundamental difference between the magnetic field amplification plate on the side of the end weir and the magnetic field amplification plate on the side of the top weir, the magnetic field amplification plate disposed on the side of the end dam is given as an example. In each figure, 3 indicates an end weir.

FIG. 5 is an enlarged view of the magnetic field amplifying plate having the shape shown in FIG. 4, (a) is a plan view, and (b) is VV in (a).
It is an arrow view. In this magnetic field amplification plate 9a, the magnetic field amplification plate 9a
a from the groove 12 and the recess 13 that divide a into two (weir 3
The depth d of the groove 14 reaching the side) is set to about twice or more of δ obtained by the equation (1). The depth of the recess 13 is also set to be the same as the depth d of the groove 12 and the groove 14. Also, the groove 12
The width w _{1 of the} groove 14 is preferably about 0.5 to 3 times the above δ. Further, the interval B between the recess 13 and the end on the weir 3 side is preferably about 5 to 30 times the above δ.

FIG. 6 shows another embodiment of the magnetic field amplification plate,
(A) is a plan view, (b) is a VI-VI arrow view in (a). This magnetic field amplification plate is divided into two sections in the longitudinal direction of the end dam 3 with a gap 15 provided, and a cutout section 16 is provided in each section. Then, a gap 17 reaching the inside (side of the weir 3) from the cutout portion 16 is provided in each compartment, and each compartment has an open ring shape. The thickness t of the magnetic field amplification plate 9a is set to 0.3 times or more of δ obtained by the equation (1). However, the width w ₂ of a width w ₂ and the gap 17 of the gap 15 may be the same extent as the depth w ₁ of the groove provided in Figure 5.

7A and 7B are views showing still another embodiment of the magnetic field amplifying plate. FIG. 7A is a plan view and FIG. 7B is a view showing V in FIG.
It is a II-VII arrow line view. In this embodiment, the upper plate of the cooling box is also used as the magnetic field amplifying plate, and the upper plate of the cooling box 10 has a groove 12 and a recess for dividing the magnetic field amplifying plate 9a into two, as in FIG. A groove 14 that extends from the recess 13 and the recess 13 to the inside (the side of the dam 3) is provided. Then, the groove 12, the groove 14,
The depth of the recess 13 and the widths of the groove 12 and the groove 14 are the same as in the case of FIG.

In the magnetic field amplifying plate shown in FIGS. 5 to 7,
The number of grooves 12 and gaps 15 that partition the magnetic field amplification plate, and recesses 13
Only the case where the number of the grooves 14 and the gaps 17 reaching the inner side (the side of the weir 3) from the notches 16 is 1 has been described, but the number of the grooves and the gaps is determined by the size of the magnetic field amplification plate. , The number is not specified.

FIG. 1 equipped with a magnetic field amplification plate having the shape shown in FIG.
Or, in the apparatus of FIG. 2, when the high frequency coil is energized,
An induced current flows through the magnetic field amplification plate due to the mutual induction effect. The flow of the induced current at this time will be described with reference to FIG.
FIG. 8 is a diagram showing the flow of the induced current in the magnetic field amplification plate of FIG. The flow of the induced current is blocked at the grooves 12 and 14 and the recess 13, so that the induced current flows around the region defined by the grooves 12 and 14 and the recess 13 as shown by the arrow in the figure. Therefore, the inside of the magnetic field amplification plate 9a (the weir 3
The density of the induced current flowing to the side) becomes large, and a large magnetic pressure acts on the triple points extremely accurately.

The interval B between the concave portion 13 and the end portion on the weir 3 side of the magnetic field amplification plate 9a is δ of 5 determined by the above equation (1).
If it is less than twice, the induced currents repel each other and the flow thereof deteriorates. If the distance B exceeds 30 times δ,
Since the region where the current flows is too wide, the density of the induced current becomes small. Thus, in any of the above cases, the magnetic pressure at the triple point decreases.

In the device constructed as described above,
Even if a high current is not applied to the high frequency coil 5, a space is formed at the triple point and a steel sheet having a good surface quality can be manufactured. Further, in the triple point, heating accompanied by the generation of the eddy current is efficiently performed at the same time, so that the solidification of the molten steel in the vicinity of the triple point is prevented, and the surface quality of the manufactured steel sheet is further improved.

Next, the electromagnetic pressure in the device of the embodiment having the magnetic field amplifying plate of FIG. 5 and the electromagnetic pressure in the conventional device having no magnetic field amplifying plate were obtained by simulation. As a result, the values of the electromagnetic pressure at the three points are as follows, and the electromagnetic pressure in the example is 12 times that of the conventional technique. The electromagnetic pressure is expressed in terms of molten steel column.

Electromagnetic pressure of the apparatus of the example is about 120 cm Electromagnetic pressure of the conventional apparatus is about 10 cm Each condition is set as follows.

Conditions of Examples High-frequency current 3000 A Frequency 3000 Hz Material of magnetic field amplification plate High-purity copper Magnetic field amplification plate thickness 4.0 mm Depth of magnetic field amplification plate groove 2.0 mm Magnetic field amplification plate groove width 2.0 mm Magnetic field Relative permeability of the amplifying plate 1 Electric conductivity of the magnetic field amplifying plate 3.4 × 10 ⁷ Ω ⁻¹ m ⁻¹ Condition of the prior art High frequency current 3000 A Frequency 3000 Hz

[0039]

According to the present invention, a high frequency coil for generating an induced current is provided outside the weir along the vicinity of the triple point where the cooling roll contacts the weir and the molten steel. Then, the magnetic field amplification plate is provided, and the magnetic field amplification plate is provided with a groove, a gap, or the like that blocks conduction of an induced current in a streak shape from the weir side to the outside.

When the present invention is used, the flow of the induced current is blocked by the above-mentioned grooves and gaps and flows at a high density around the magnetic field amplifying plate. Strong magnetic pressure is applied intensively. For this reason,
In a stable state without increasing the capacity of the high frequency power supply,
It is possible to cast steel plates with good surface properties.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a view showing the arrangement and shape of magnetic field amplification plates in the continuous casting apparatus of FIG.

FIG. 4 is a view showing the arrangement and shape of magnetic field amplification plates in the continuous casting apparatus of FIG.

5 is an enlarged view of the magnetic field amplification plate arranged in FIG. 4, showing an embodiment of the magnetic field amplification plate provided in the device of the present invention.

FIG. 6 is a diagram showing another embodiment of the magnetic field amplification plate.

FIG. 7 is a view showing still another embodiment of the magnetic field amplifying plate, showing a configuration when the upper plate of the cooling box is also used as the magnetic field amplifying plate.

FIG. 8 is a diagram showing a flow of an induced current in the magnetic field amplification plate of the present invention.

FIG. 9 is a view showing a conventional twin-roll steel plate continuous casting apparatus.

FIG. 10 is an explanatory diagram related to the action of the high frequency coil.

[Explanation of symbols]

1a, 1b Cooling roll 2 Molten steel 3 Edge weir 4 Top weir 5 High frequency coil 6 Solidification shell 7 produced in cooling roll 7 Steel plate 8 Solidification shell produced in weir 9a, 9b Magnetic field amplification plate 10, 11 Cooling box 12 Grooves that extend from the inside (weir side) to the outside to partition the magnetic field amplification plate 13 Recesses provided on the magnetic field amplification plate 14 Grooves provided from the recesses to the inside (weir side) 15 Weir the magnetic field amplification plate 16 A gap formed in the longitudinal direction of the gap 16 A notch provided in the magnetic field amplification plate 17 A gap provided from the notch to the inside (weir side)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Nakata, 1-2, Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Takashi Osako, 1-2, Marunouchi, Chiyoda-ku, Tokyo Date Inside the Steel Pipe Corporation (72) Inventor Kentaro Mori 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Steel Pipe Corporation

Claims (4)

[Claims] 1. A pair of cooling rolls, each of which is arranged horizontally and parallel to each other, and whose outer peripheral surfaces facing each other rotate in a direction to move inward, respectively, and a pool for collecting molten steel together with the pair of cooling rolls. In a twin roll type continuous casting apparatus having a weir that divides and forms a section, for generating an induced current outside the weir along the vicinity of the triple point where the cooling roll contacts the weir and the molten steel. A high-frequency coil is provided, a magnetic field amplification plate is disposed in the vicinity of the high-frequency coil, a cooling box is attached to the magnetic field amplification plate, and a portion for blocking conduction of an induction current generated from the high-frequency coil is provided. A continuous casting apparatus for steel plates, which is provided in a streak shape from the weir side to the outside. 2. The continuous casting apparatus for a steel sheet according to claim 1, wherein the streak-like portion provided in the magnetic field amplifying plate for blocking the conduction of the induced current is at least one groove. 3. The continuous casting apparatus for a steel sheet according to claim 1, wherein the streak-like portion provided in the magnetic field amplifying plate for blocking the conduction of the induction current is at least one gap. 4. A pair of cooling rolls, each of which is arranged horizontally and parallel to each other, and whose outer peripheral surfaces facing each other rotate in a direction moving inward, respectively, and a pool for pooling molten steel together with the pair of cooling rolls. In a twin roll type continuous casting apparatus having a weir that divides and forms a section, for generating an induced current outside the weir along the vicinity of the triple point where the cooling roll contacts the weir and the molten steel. A high-frequency coil is provided, and a cooling box is arranged in the vicinity of the high-frequency coil, and a portion for blocking conduction of an induction current generated from the high-frequency coil is provided on the upper plate of the cooling box from the weir side to the outside. A continuous casting apparatus for steel plates, which is provided in a streak shape.