JPH10118750A - Continuous casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an intense magnetic field having high uniformity by arranging one pair of superconducting coils so that the direction of a current between electrodes crosses the generated magnetic field direction. SOLUTION: The electrodes 2 are arranged so as to contact with both side surfaces of a cast slab 1. The electrodes 2 are fixed to electrode fixed frames 7 with springs 6 and slidingly shifted to the shifted cast slab 1. The superconducting coil 20 is built in a superconducting coil incorporating rigid frame 22. By using this device, electromagnetic force is improved in the casting direction at solid-liquid co-existing phase of the cast stab 1 in a continuous casting. Then, at least one pair of the superconducting coils 20 are arranged so that the direction of the current between these electrodes crosses the generated magnetic field direction to obtain the intense magnetic field having high uniformity in the wide space of the device. In an electromagnetic force impressing device, plural roll pairs (upper roll and lower roll) 24, 25 for supporting and compressing the cast slab 1 and giving rolling reduction gradient so that the rolling reduction rate becomes larger as the cast slab goes to further the downstream side of the cast slab 1. Current density distribution can freely be controlled by using the slidingly shifting electrode system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting apparatus for eliminating a central defect generated in continuous casting.

[0002]

2. Description of the Related Art The present inventors have previously filed Japanese Patent Application No.
No. 5942 filed an application for a method and apparatus for eliminating central defects in continuous casting. In the solid-liquid coexisting phase extended in the casting direction, the method focuses on the pressure drop of the liquid phase mainly caused by the liquid phase flow between dendrites induced by solidification shrinkage, finds a region where a central defect occurs, and in the region, An attempt is made to eliminate the generation of the defect by applying an electromagnetic force in the casting direction so as to maintain a liquid phase pressure equal to or higher than the defect generation critical liquid pressure.

Further, it has been shown that the required electromagnetic force for suppressing the generation of the central defect can be reduced by supplementing a slight reduction gradient near the electromagnetic force application region.

As an example of the electromagnetic force casting method, FIG. 10 shows an outline of a continuous casting system when applied to a typical continuous casting of steel.

That is, the system comprises a water-cooled mold,
Electromagnetic force is applied to a tundish for receiving molten steel from the ladle outlet, a plurality of bending rolls for bending a slab that has passed through a water-cooled mold, a plurality of straightening rolls, and a solid-liquid coexisting portion inside the slab. It consists of an electromagnetic booster and so on. The electromagnetic booster is provided with arithmetic means for calculating the position, magnitude and range of the applied electromagnetic force based on the operation data. That is, the detection unit is a device that captures the input signal of the operation parameter, and the computer system performs a numerical operation process of the solidification process based on the operation data from the detection unit and performs an operation amount to the continuous caster main body to be controlled through the operation unit. Feedback function. Further, the coagulation status can be monitored at any time by the display device.

[0006]

SUMMARY OF THE INVENTION The present invention intends to show a more detailed mechanism in an electromagnetic booster device for applying an electromagnetic force generated by a direct current and a direct magnetic field described in the above-mentioned prior application. It is another object of the present invention to provide a specific mechanism for combining and applying the electromagnetic force and the light reduction to the slab. Then, a mechanism for reducing the tensile force generated in the slab will be described.

[0007]

First, a superconducting coil is used as a means for generating a DC magnetic field, and a single or multiple pairs of coils are arranged so as to sandwich a slab. For blooms, billets, etc., where the short and long sides of the slab cross section are not so different, use a racetrack-type coil that extends in the length direction of the slab. Uses a race-track-type coil correspondingly wide. The superconducting coil is currently in liquid helium temperature (4.2
K), it is necessary to cool it down, so it is stored in a cooling container made of liquid helium or the like, and the reaction force corresponding to the electromagnetic force generated in the casting direction of the slab acts on the coil. Care should be taken when designing containers.

Further, since an attractive force is generated between the coils when energized, the coils are accommodated in a frame having a high rigidity so as to support this force, and the frames are fixed by a plurality of columns.

Next, as a method of applying a direct current to both side surfaces of the cast slab, a plurality of sliding electrodes fixed in a space with respect to the movement of the cast slab are arranged so as to contact the side surfaces.

A thin oxide layer containing Fe as a main component is formed on the surface of the slab. Since the oxide layer is insulative, it is desirable to remove it by means such as cutting. In addition, as one means for improving the contact between the cast slab side surface and the electrode, the present invention employs plane cutting.

Further, in order to prevent reoxidation of the cut surface, the cut surface is shielded from the atmosphere by using an inert gas such as argon, N ₂ or a reducing gas.

The light reduction gradient applied to the slab is given through a plurality of rolls, and a pressurization method using a fluid such as oil is applied to the bearing portion of each roll, so that an independent reduction force distribution can be given to the bearing. Be able to control. In order to obtain a strong magnetic field, the distance between the superconducting coils must be reduced as much as possible, so it is important to reduce the diameter of the roll.

Rolls used for reducing blooms, billets and the like can effectively reduce the solid-liquid coexistence phase at the center of the cross section of the slab, and do not generate cracks due to unnecessary plastic deformation at the corners. It is preferable to use a shape in which the center of the roll is swollen. An ordinary flat roll is used for a wide slab. Further, it is preferable to use a so-called split roll that is split in the longitudinal direction so as to minimize bending due to rolling force and thermal stress.

If the electromagnetic force applied in the casting direction is too large, a large tensile force is generated in the slab having the solid-liquid coexisting portion, which may cause internal cracks and the like. As means for reducing such an excessive tensile force, the tensile force is alleviated by the pull-out resistance force of the slab as a result of imparting a rolling gradient to the slab, and a driving device is attached to the roll.

[0015]

The above is the main mechanical means, which makes it possible to appropriately control the current density distribution and the electromagnetic force distribution in the casting direction. In addition, a desired rolling gradient can be given.

The present inventors have shown in the above-mentioned prior application that the electromagnetic force required to suppress the generation of a central defect can be reduced by supplementarily applying a light reduction gradient. That is, by appropriately balancing both of them, it is possible to eliminate the occurrence of the center defect, and to adjust the balance between the drawing resistance and the casting direction electromagnetic force resulting from the application of the rolling gradient. The balance between these two forces varies depending on operating parameters such as the profile of the continuous caster, casting speed, slab cross-sectional shape, and steel type.

When the two are balanced, the tensile force generated by the electromagnetic force on the solidified shell (solid portion) is canceled out (from a macro viewpoint). If the pull-out resistance is sufficiently larger than the electromagnetic force, a roll driving force may be applied in the casting direction. Conversely, when the electromagnetic force is too large and a large tensile force is generated in the solidified shell, the number of roll rotations is controlled to be constant so as to correspond to the casting speed. At this time, a reverse torque is applied to the roll to act as a brake, so that the tensile force generated in the solidified shell can be offset.

In summary, the electromagnetic force device of the present invention has the following three functions. Function I. Only electromagnetic force Function II. Combination of electromagnetic force + light pressure. Function III. Combination of electromagnetic force + light pressure + positive or negative roll rotation drive By properly using these functions, the purpose of each continuous casting operation (defect free slab / high speed casting) can be realized. The application range and magnitude of the electromagnetic force, the range for applying the light reduction gradient, the reduction amount distribution, and the like have been described in detail in the above-mentioned prior application, and will not be described herein.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

[Specific Example 1] FIG. 1 shows a specific example in the case where the present invention is applied to a steel bloom or billet. The profile of the continuous casting machine is generally a vertical bending type or a bending type, as shown in the outline of FIG. FIG. 1 shows a case where an electromagnetic force device (electromagnetic booster) is installed near the upstream side of a final solidified portion (also called a crater end) in a horizontal portion of a slab. FIG. 1 (a)
Is a cross-sectional view of the slab, FIG. 1B is a cross-sectional view of the slab in the length direction AA, and arrows in the drawing indicate the casting direction. FIG. 2 shows a BB section viewed from above.

In the drawing, reference numeral 1 denotes a cast slab, and 2 denotes an electrode arranged so as to come into contact with both side surfaces of the cast slab. The electrode is fixed to a fixed frame 7 (not shown in detail) by a spring 6 and moves. Sliding against the piece. As shown in FIG. 1B, a plurality of electrodes are arranged over the electromagnetic force application range and are independent of each other. The space between the electrodes should be as small as possible. FIG. 3 shows a method of connecting the electrodes. FIG. 3A shows a parallel type in which the current densities flowing through the respective electrodes are substantially equal (provided that the contact resistance is constant). FIG. 3B is a series type, which is suitable for changing the current density in the slab, for example, when it is desired to positively increase the current density toward the downstream side of the slab. FIG. 2C shows a mixed type in which (a) and (b) are combined, and a current value is given to each parallel group.

Obviously, the parallel type requires a larger DC power supply than the series type. Further, by changing the material of the electrode, the current density of each electrode can be changed. These may be appropriately selected as needed.

The individual electrodes are housed in an insulating box 5 and connected to the L-shaped bus bar 4 and the plate bus bar 3. The bus bar 3 shown in the BB sectional view of FIG.
Corresponding to the parallel method.

FIG. 6 shows a state in which the gas shield box 9 for preventing oxidation of the slab side electrode sliding portion and the plane cutting milling machine 8 are attached. FIG. 6A is a side view, and FIG. 6B is a view seen from above. Reference numeral 10 denotes an electrode box chamber, 11
Is a milling machine box room, and both rooms are separated.
Reference numerals 12 and 13 denote gas inlets, and the air in both chambers is once replaced by the gas and then flows out little by little from the gap 16 with the slab. A plurality of cutting tools 14 are attached to the milling machine. Reference numeral 15 denotes a cutting chiriko discharge port. The gas inlet box is not shown in the electrode part of FIG. 1 to avoid drawing complexity.

Reference numeral 20 in FIGS. 1 and 2 denotes a race track type coil wound with a superconducting wire, which is built in a rigid frame 22. Reference numeral 21 denotes a coil cooling tank which is cooled to a liquid helium temperature (4.2 K). Upper frame 17
Since the temperature of the lower frame 18 rises due to radiant heat from a high-temperature slab or the like, a device such as providing a water-cooled outer tank 23 between these frames and the (superconducting storage) rigid frame 22 may be provided. .

The upper and lower frames 17 and 18 are supported by columns 19, are vertically movable, and can be locked at predetermined positions. Since these frames and struts receive a force such as an attractive force between the coils and a reaction force from a rolling roll, it is necessary to sufficiently increase a section modulus so as to minimize elastic deformation such as bending. A non-magnetic material such as stainless steel is used.

The rigid frame 28 for fixing the upper and lower frames receives a reaction force corresponding to an electromagnetic force acting in the casting direction or a pull-out resistance force due to the above-mentioned roll reduction, so that the rigid frame 28 has sufficient rigidity and has a long slab length. Be able to move and lock in both directions. These mechanisms are not specifically shown because they can be implemented by known and publicly used techniques.

Reference numerals 24 and 25 denote rolls for imparting a slight reduction gradient to the slab, which avoid unnecessary and harmful plastic deformation at the corners of the slab and are effective for the solid-liquid coexisting phase at the center. A roll crown is provided at the center of the roll to expand so that compression deformation is transmitted. In the case of this example, the reduction is performed by the hydraulic cylinder 27 mounted on the upper bearing portion. The hydraulic cylinder need not necessarily be on top. A plurality of rolls are arranged in the longitudinal direction, and the rolling force on each roll is independently controlled. The predetermined amount of reduction is given by the reduction force. The rolling force generally needs to be increased toward the downstream side where the solidified layer is thick as shown in FIG. Also, since the amount of reduction is small (on the order of the amount of coagulation and shrinkage in the solid-liquid coexisting phase), the stroke of the hydraulic cylinder is small, and therefore the cylinder length may be short.

Further, the roll is provided with a drive mechanism (usually attached to the lower roll). The number of driving rolls may be determined according to the required driving force or the like. The driving device is not particularly shown because it can be easily implemented by a known technique.

Next, the relationship between the distance between the superconducting coils and the width of the coil will be described. For convenience of consideration, assuming that the coil is circular, the radius is a (m), and the distance between the coils is b (m), the center between both coils, that is, Z = b /
The magnetic flux density B _z (Tesla) at 2 is Given by Here, μ ₀ is the magnetic permeability of vacuum 4π × 10
⁻⁷ (H / m), I is the coil current (A). It can be seen that a stronger magnetic field can be obtained by reducing the distance b between the coils. Further, a coil having a relationship of a = b is called a Helmholtz type, and a magnetic field with a high degree of uniformity can be obtained. (For these matters, standard textbooks such as those written by Saburo Adachi, Electromagnetism, p. .79 and p.89).

[Embodiment 2] In view of this point, in Embodiment 2, as shown in FIG. 7A, in order to obtain a stronger magnetic field as compared with Embodiment 1, the width of the coil is increased and the distance between the coils is increased. It is a shortened example (slab slab cross-sectional view). That is,
By providing a space for storing the rolls in the upper and lower frames 17 and 18, the distance between the coils is reduced. If the distance between the coils is too short, the slab and the coil may collide with or approach each other at a portion crossing the slab. In such a case, a hollow coil may be used as shown in FIG.

This example is based on the case where the roll drive is not required by appropriately adjusting the balance between the electromagnetic force and the pull-out resistance caused by the application of the low pressure gradient (function II). [If roll drive is absolutely necessary, it will be possible to attach a gear to the roll shaft end and drive the chain along the length of the slab. The other mechanisms are the same as those in the first embodiment, and will not be described.

[Specific Example 3] FIG. 8 shows a specific example in which an electromagnetic force and a slight reduction gradient are applied to a wide slab. Since the pressing roll is elongated and is easily bent by the pressing load and the thermal stress, a split roll is used. The rolling force is given by a hydraulic cylinder. The rolling is usually performed by an upper roll, and a hydraulic cylinder 27 of oil or the like is installed in each bearing. The cylinder stroke may be small as described above, but if more room is desired, the type of the specific example 2 may be employed. The split rolls may use a single roll and reduce the diameter at the bearing portion, or may be independently split at the bearing portion. It is also desirable to attach a roll crown only to the both ends of the roll to avoid plastic deformation at the corners of the cross section.
Roll drive is usually performed with a lower roll. The other mechanisms such as the electrodes are the same as in the case of the first embodiment, and thus are omitted.

[Specific Example 4] In a continuous casting machine for simultaneously casting a plurality of slabs simultaneously, both types in which the distance between the slabs is sufficiently large and in which the slabs are close to each other are available. is there. In the former case, the electromagnetic force and the screw-down device may be independently installed. In this example, the latter type will be described.

In this case, the adjacent slabs may be connected by a flexible bus bar or cable 31, as shown in FIG. The electrode box 5 is fixed to an electrode frame 7 extending in the slab length direction. Further, a plane milling machine 8 and a gas shield box 9 are mounted on both opposing sides. A magnetic field is generated by a pair of upper and lower superconducting coils.
In addition, a roll reduction device is provided for each slab. Other mechanisms are as described above.

[When Only Electromagnetic Force is Applied] In this case,
Only the roll reduction function shown in the above four specific examples becomes unnecessary, and the specific examples are not shown because they are included in the above examples. That is, in the case of the blooms described in the specific examples 1, 2 and 4, the cast slab is firmly supported by the solidified layer developed from each side of the cross section, so that the upper roll for supporting the cast slab is provided. Is not necessarily required or may be a minimum number. On the other hand, the lower side requires an appropriate number of rolls to support the slab. However, considering that a considerable amount of electromagnetic force acts on the slab in the casting direction, it is better to support it with a certain number of rolls.

In the case of the slab of the above-mentioned specific example 3, considering that the width of the solid-liquid coexisting phase is wider than that of bloom or the like and that a considerable electromagnetic force acts, the upper and lower rolls are the same as in the case of ordinary slab continuous casting. Need to be firmly supported by

In both the bloom and the slab, when the electromagnetic force is large and an excessive tensile force is generated in the solidified shell region including the solid-liquid coexisting phase, the solidification in the downstream solidification completed portion of the electromagnetic booster shown in FIG. It is also possible to provide a normal roll pressure reduction device (not shown) to apply a brake by the frictional force between the roll and the cast slab due to the pressure reduction and to alleviate the tensile force.

[Outline of Electromagnetic Force Design] The outline of the electromagnetic force design will be described below. In the above example, the magnitude of the electromagnetic force is set to 20 times the gravity, and the shape of the superconducting coil is circular for ease of calculation (using FIG. 5 and equation (1)). The DC current density to the solid-liquid coexisting portion is J (A / m ² ), the DC magnetic flux density is B (Tesla), and the liquid phase density of steel is ρ = 7.0 (g / m ² ).
cm ³ ) and the acceleration of gravity is gr = 980.665 (cm
/ S ² ), the gravity magnification G is given by the following equation. Now, the current density is set to J = 5 × 10 ⁵ (A / m ² ). The required magnetic flux density corresponding to this is given by B =
It is 2.75 (T).

In the above specific example 1, the bloom had a cross-sectional dimension of 300 mm × 400 mm, the coil radius was a = 0.34 (m), and the distance between the coils was B = 0.92.
(M). At this time, the required coil current is I = 3543112 (A) from equation (1). Now, assuming that the applied current of the superconducting wire is 2000 A, the number of turns N is 35431.
12/2000 = 1777 times. When the cross-sectional area of one superconducting wire (square) is 10 (mm ² ) (the current density is 200 A / mm ² ), the cross-sectional area of the coil is S = 1772 × 10 (mm ² ) = 177.2 cm ^2. .

Next, for a specific example 2 in which the coil radius is increased to a = 0.48 (m) and the distance between the coils is reduced to b = 0.66 (m) for a bloom having the same dimensions as the specific example 1. When the same calculation is performed, the design value is as follows: Required coil current I = 18772224 (A) Number of turns of the superconducting wire N = 936 (times) (Current density of one superconducting wire = 200 A / mm ² ) Coil Cross-sectional area S = 93.9 (cm ² ) That is, N is reduced from 1772 to 936 (times), and the efficiency is improved.

In the case of the slab of Example 3, the slab cross-sectional dimension was 220 mm thick x 1500 mm wide, and the corresponding coil radius a and coil distance b were equal and a = b = 0.9.
The design values for a Helmholtz type of 4 (m) are as follows: Required coil current I = 2874853 (A) Number of turns of superconducting wire N = 1438 (times) (Current density of one superconducting wire = 200 A / mm ² ) Coil cross-sectional area S = 143.7 (cm ² )

The specific example 4 is obtained in the same manner, but is omitted. All of the above design values of the superconducting coil are sufficiently within the practical range of the current superconducting coil using NbTi, and there is no technical problem. It is sufficiently possible to obtain a larger magnetic field (magnetic flux density). For details, refer to standard textbooks, for example, published by Nikkan Kogyo Shimbun, written by Hiroyasu Hagiwara, “Applied Superconductivity”. In the above calculations, the coil shape was circular for simplicity. Further, in the above specific example, the number of upper and lower coil pairs is one, but a plurality of coil pairs can be provided so as to optimize the uniformity and strength of the magnetic field. In actual design, a static magnetic field numerical analysis by a finite element method or the like may be performed in consideration of these points and in accordance with the coil shape.

[When Electromagnetic Force is Applied in the Reverse Direction to the Casting Direction] The present inventors have filed the above-mentioned prior application (Japanese Patent Application No. 1559/1996).
No. 42), when the liquid phase flows in the solid-liquid coexisting phase elongated in the casting direction, the liquid phase pressure drop due to the liquid phase flow between dendrites mainly induced by solidification shrinkage is focused on. Reaches the critical condition for microporosity generation (formula (65) of the prior application), microporosity is generated between the dendrite crystals, and this triggers the formation of a liquid phase with a high solute concentration around the porosity into a V-shaped porosity. It was shown that a run-in V-shaped segregation band occurred. Rewriting the above equation (65), Here, P is the liquid phase pressure, Pgas is the equilibrium gas partial pressure in the porosity that equilibrates with the gas dissolved in the liquid phase, σ _LG
Is the surface tension at the interface between the liquid phase and the porosity, and r is the radius of curvature of the porosity (see FIG. 11A). The porosity is arranged in a V-shape as shown in FIG.
The flow at this time occurs in the casting direction along the V band.

Therefore, the formation of V segregation can be reduced by applying an electromagnetic force in the direction in which this flow is blocked, that is, in the direction opposite to the casting direction. Any of the electromagnetic boosters described in the above embodiments can be used for this purpose. That is, the electromagnetic force may be applied in the upstream direction by reversing either the current direction or the magnetic field direction. The location where the electromagnetic force is applied is the same as described in the prior application, that is, the range from the vicinity of the upstream side of the position where the critical condition expression (3) is reached on the upstream side of the final solidification part (crater end) to the above crater end. It is.
Since the magnitude of the reverse electromagnetic force is to prevent the flow, the magnitude of the reverse electromagnetic force may be extremely small as compared with 20G in the above calculation example. If the electromagnetic force is too small, there is no flow inhibiting effect, while if it is too large, the liquid phase with a high solute concentration flows backward, causing reverse V segregation, and is meaningless. The magnitude of the appropriate electromagnetic force can be easily known by an actual machine test. Since the electromagnetic booster according to the present invention is used for a DC current and a DC magnetic field, it is possible to obtain an electromagnetic force with excellent uniformity (of course, to design it), and it will be possible to effectively prevent the flow of V segregation. However, microporosity remains in this method.

[Comments] Finally, the gist of the present invention will be described, including matters not mentioned above. (1) electrode material graphite system, the electrical conductivity, such as ZrB _2, it may be selected suitable material in consideration of abrasion resistance.

(2) In the case of the above specific example, if the contact area of one electrode is 100 mm × 120 mm, a current of 6000 (A) flows through the electrode and the bus bar. A copper plate is usually used for the bus bar. The current density is 3-4 (A /
mm ² ), and when cooling with water, the cross-sectional dimension of the bus bar is determined using a value of about 10 (A / mm ² ). In the specific example, an L-shape and a plate with a bus bar are shown, but these are not indispensable items, and a thick cable (with flexibility) made of a copper wire may be used. These are extremely ordinary techniques, and it goes without saying that they are devised for detailed design.

(3) Electromagnetic force is generated in these parts due to the interaction between the current flowing through the electrodes and the busbars and the magnetic field, and therefore these parts need to be firmly fixed.

(4) Since a large magnetic field is generated in the vicinity of the application of the electromagnetic force, a frame, a column, a roll device and the like existing in this space are basically made of a non-magnetic material such as stainless steel. However, a magnetic material (usually iron) may be appropriately arranged to create a uniform magnetic field. In addition, the influence of the magnetic field on the instruments and the like, the necessity of shielding the magnetic field, and the like can be solved by a known and publicly-known technology, and thus are omitted in this specification.

(5) The upper and lower frames 17 and 18 in FIGS. 1, 7, 8 and 9 need not necessarily be integrated. The frame may be appropriately divided into a rigid frame for accommodating the superconducting coil, a rigid frame for supporting the roll device, and the like.

(6) The superconducting wire is generally made of a composite material in which an ultrafine superconducting wire such as NbTi is embedded in a matrix such as copper. The coil is made by winding a superconducting wire around a bobbin (guide jig). Superconducting coils are mostly used without iron cores. At present, it is necessary to cool to a very low temperature (liquid helium temperature, 4.2 K) at which a superconducting state occurs, so that the inside of the cooling tank 21 is composed of a layer combining liquid helium, a vacuum heat insulating layer, liquid nitrogen and the like. . Superconducting technology has already been put to practical use in many applications such as particle accelerators and MRI. It is expected that high-temperature superconducting materials will be widely spread in the future when they are developed and put into practical use.

(7) In order to apply a pressure to the slab surface via a roll by a hydraulic cylinder or the like to give a predetermined light reduction amount gradient, it is necessary to know the roll reduction force distribution (see FIG. 4). . For this purpose, by using a stress analysis such as a finite element method, it is possible to know an appropriate rolling condition with a minimum of experiments. The same applies to the roll crown.

(8) The gap 16 between the gas shield box and the cast slab is made as small as possible, and the other parts are devised so as to maintain confidentiality. One idea is to place a fine stainless steel scourer lightly in contact with the cast piece in the gap 16. As a result, the amount of gas flowing out can be saved, and the inside of the box can be maintained at a slightly positive pressure, which is effective in preventing reoxidation.

(9) As a method of removing the oxidized layer on the surface of the slab, various methods other than the plane milling machine, such as a method of cutting by fixing a tool having a long cutting tool in response to the movement of the slab, can be considered.

(10) Since the temperature around the slab rises due to radiant heat and conduction heat from the slab surface, roll bearings, hydraulic cylinders, busbars, etc. may be appropriately cooled, such as water cooling.

[0055]

As a method for applying an electromagnetic force in the casting direction of a continuous cast slab, the present invention has described a mechanism using a plurality of sliding electrodes and a superconducting coil. In other words, by adopting a racetrack type or kura-type superconducting coil adapted to the cross-sectional shape of the slab, the slab, roll, A strong magnetic field with high uniformity can be obtained in a wide space including electrodes and the like. It is generally accepted that superconducting coils are superior to conventional electromagnet systems, both economically and in space, for the applications described herein.

Next, as a method of applying a direct current, in the present invention, the current density distribution can be freely controlled by using a plurality of sliding electrode systems (see FIG. 3). This produces an effect that the electromagnetic force distribution can be freely controlled. The contact resistance between the electrode and the slab surface can be kept low by cutting the slab surface and preventing reoxidation of the gas.

When the light reduction is used as an auxiliary means for reducing the required electromagnetic force, the distribution of the reduction force can be freely controlled by using the independent hydraulic control system of the present invention, whereby the gradient of the reduction amount can be reduced. Control becomes possible. In this case, it is not always necessary to perform independent control one by one, and in some cases, hydraulic control may be performed for some rolls. Further, the pressure transmission medium is not necessarily limited to oil. Further, by providing the roll with a driving device, it is possible to appropriately control the tensile force generated in the slab and prevent cracks.

As described above, since the apparatus according to the present invention can provide the desired magnitude and distribution of the electromagnetic force and the rolling force to any position and range of the slab, the slab having no internal defect, which is the original object, can be provided. , Or an improvement in productivity due to an increase in speed. At this time, it is not necessary to use all the functions of the electromagnetic force, the light reduction gradient, and the roll braking described in this specification.

Although the present specification has described the continuous casting of steel such as blooms, billets, and slabs having a rectangular cross section, the electromagnetic booster according to the present invention has a so-called near-net-shape having an irregular cross section such as an H shape. shape
Needless to say, the present invention can be applied to a continuous casting method, a so-called composite continuous casting method of different steel types, in which different steel types are simultaneously cast, and the outside and inside of the slab are made of different steel types. aluminum,
The same applies to continuous casting of non-ferrous alloys such as copper.

[Brief description of the drawings]

FIG. 1 is a specific view in which an electromagnetic booster according to the present invention is applied to continuous casting having a rectangular cross-sectional shape such as a bloom or billet, where (a) is a cross-sectional view and (b) is an AA.
FIG. The broken line in (a) indicates the line of magnetic force, and the arrow in (b) indicates the casting direction.

FIG. 2 is a plan view of the electromagnetic booster of FIG. (A)
1 shows a BB cross section of FIG. 1 and (b) shows a race track type superconducting coil.

FIG. 3 is a connection diagram of a DC electrode, (a) is a parallel type,
(B) shows a series type and (c) shows a mixed type.

FIG. 4 is a diagram showing a general roll load distribution state when a light reduction gradient is applied to a slab.

FIG. 5 is a diagram showing a pair of circular coils. a is the coil radius and b is the distance between the coils.

FIGS. 6A and 6B are views showing the state of attachment of the antioxidant gas shield box, wherein FIG. 6A is a side view of the cast slab, and FIG. Reference numeral 8 denotes a plane milling machine.

FIG. 7 is a specific diagram of an electromagnetic booster devised so as to reduce the distance between superconducting coils as compared with the electromagnetic booster of FIG. 1; (A) shows a cross-sectional view and (b) shows a clad superconducting coil.

FIG. 8 is a specific diagram in a case where the electromagnetic booster according to the present invention is applied to continuous casting having a rectangular cross-sectional shape with a wide slab such as a slab. The figure is a cross-sectional view, and reference numerals 29 and 30 denote split rolls.

FIG. 9 is a specific diagram (transverse section) when an electromagnetic booster is applied to twin-type continuous casting. Reference numeral 31 indicates a flexible bus bar or cable.

FIG. 10 is a configuration diagram of a continuous casting system of the present invention.

FIG. 11 is a diagram for explaining formation of a V defect;
(A) shows microporosity between dendrites and (b) shows V segregation. The sign + in (b) indicates positive segregation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cast piece 2 Electrode 3 Flat bus bar 4 L-shaped bus bar 5 Insulated electrode box 6 Spring 7 Electrode fixing frame 8 Plane milling machine 9 Oxidation prevention gas shield box 10 Electrode box room 11 Plane milling machine box room 12 Gas inlet 13 13 14 Cutting Tool 15 Cutting Kiriko discharge port 16 Antioxidant gas escape gap 17 Upper frame 18 Lower frame 19 Prop 20 Superconducting coil 21 Superconducting coil cooling tank 22 Superconducting coil storage rigid frame 23 Cooling outer tank 24 Upper roll 25 Lower roll 26 Bearing 27 Hydraulic cylinder 28 Rigid frame that can be moved and fixed in the slab length direction 29 Upper split roll 30 Lower split roll 31 Flexible busbar or cable

Claims (10)

[Claims] 1. A device for applying an electromagnetic force in a casting direction in a solid-liquid coexistence phase of a slab in continuous casting, wherein a plurality of sliding electrodes are arranged in contact with both side surfaces of the slab,
A continuous casting apparatus, wherein at least one pair of superconducting coils is arranged so that the direction of the inter-electrode current and the direction of the generated magnetic field intersect. 2. The electromagnetic force applying device according to claim 1, wherein a reduction gradient is provided for supporting the slab or compressing the slab so that the reduction amount increases toward the downstream side of the slab. Continuous casting apparatus characterized by arranging a plurality of roll pairs. 3. The roll reduction device according to claim 2, wherein the roll rotation is performed so that the drawing resistance of the slab and the applied electromagnetic force in the casting direction, which are obtained as a result of imparting a reduction gradient to the slab, maintain an appropriate balance. A continuous casting device comprising a driving device. 4. A continuous casting apparatus according to claim 2, wherein said means for applying a compressive load uses a hydraulic cylinder which can be independently controlled. 5. The continuous casting apparatus according to claim 1, further comprising means for cutting and removing an oxide layer on the surface of the slab upstream of the electrode portion. 6. The continuous casting apparatus according to claim 5, wherein
Continuous casting characterized by comprising means for shielding a sliding portion between an electrode and a slab or a slab surface cut portion in an inert gas atmosphere such as an inert gas such as argon, nitrogen gas or a reducing gas. apparatus. 7. The continuous casting apparatus according to claim 1, further comprising a mechanism that can move back and forth in a casting direction and that can be fixed at a predetermined position. 8. A continuous casting apparatus according to claim 1, wherein when casting a plurality of slabs simultaneously in parallel, the electrodes of said electrode apparatus are electrically connected. 9. The continuous casting apparatus according to claim 1, wherein an electromagnetic force is applied in a direction opposite to a casting direction. 10. A roll pressing device is provided in a complete solid phase region of a slab downstream of the electromagnetic force applying device according to claim 1, and an applied electromagnetic force in a casting direction is generated by a frictional force with the slab caused by roll reduction. A continuous casting apparatus characterized in that a braking force corresponding to a force is applied to a slab.