JPH1080754A - Twin roll type continuous caster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a twin roll type continuous caster which can adjust electromagnetic force generated in plurality of pieces of divided core parts in a simple constitution without developing heat loss. SOLUTION: In the continuous caster having one pair of mold rolls 2 arranged in mutually parallel state and electromagnetic weirs 1 arranged at the end parts of both mold rolls 2, a core body 3 in the electromagnetic weir 1 is vertically divided into plural pieces and also, number of turns of a coil 4 for generating the magnetic field wound on the divided core parts 3a positioned at the upper part is made more than that on the divided core part 3a positioned at the lower part. By this constitution, the necessary magnetic flux density to hold molten metal and the magnetic flux density generated with the electromagnetic force can be almost equallized, and the recession at the center part in the end part of the cast slab is not developed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twin-roll type continuous casting machine, and more particularly to a twin-roll type continuous casting machine using an electromagnetic weir for a short side weir.

[0002]

2. Description of the Related Art In a twin-roll type continuous casting machine,
A pair of mold rolls (hereinafter, referred to as rolls) and short-side weirs disposed at the ends of these rolls form a molten steel reservoir above the rolls. And recently,
Instead of such a short side weir, as shown in FIG. 3 and FIG. 4 (a), an electromagnetic force (Lorentz force) F is used.
There has been proposed an electromagnetic weir (also referred to as EMD) 52 that prevents molten steel from flowing out of the molten steel reservoir 51.

The shape of the end face portion 54a of the core body 54 of the electromagnetic weir 52 disposed on the end faces of the pair of rolls 53 is set to have the same shape as the gap (gap) between the two rolls 53. ing. That is, as shown in FIG. 5, the gap b between the end surfaces 54a of the core body 54 is suddenly widened upward.

For this reason, the core members 54 extend from the closest part (the middle position between the rolls) of the two rolls 53 along the height direction.
The relationship between the generated magnetic flux density generated between the end surfaces 54a and the magnetic flux density actually required to hold the molten steel is shown in FIG.
(B). FIG. 4A shows a cross section of the molten steel reservoir 51, and the generated magnetic flux density and the required magnetic flux density according to the height of the cross section from the roll center are shown in FIG.
Is shown in the graph.

As can be seen from the graph of FIG. 4 (b), if an attempt is made to generate a magnetic flux density (required flux density) at any position between both end portions 54a of the core body 54 so that molten steel does not flow out. The generated magnetic flux density at the closest part increases.

That is, at the closest part of the roll 53, an excessive electromagnetic force F acts, so that the side end face of the cast slab is inwardly concave. Therefore, it is desirable that the generated magnetic flux density generated between the end surfaces 54a of the core body 54 from the center position of the roll 53 to the height direction upward is proportional to the height from the roll center.

As described above, the generated magnetic flux density is
As a technique for increasing the strength in a height direction from the center position of the roll to the surface of the molten steel in proportion to the height position, there is a technique disclosed in Japanese Patent Publication No. 6-503035.

The feature of the electromagnetic weir disclosed in this publication is that the core body of the electromagnetic weir is divided into a plurality in the height direction, that is, the vertical direction, and the current applied to each divided core portion is made different. Things.

The number of AC power supplies connected to the plurality of divided core portions is one or three. In the case of a single power supply, two variable reactors are respectively inserted in series with respect to the two split core members so that the electromagnetic force generated in the three split core portions can be individually adjusted.

When there are three power supplies, it is necessary to control each of the power supplies so that the electromagnetic force generated in each of the divided core portions satisfies a predetermined relationship.

[0011]

As described above, in order to change the electromagnetic force generated in the core body in accordance with the gap of the roll, for example, when one power supply is used, the variable reactor is used. It is necessary to insert and control the phase and the like, respectively, so that the control becomes very troublesome and heat loss due to resistance occurs.

Further, when three power supplies are provided, it is necessary to control the strength of the electromagnetic force generated in each of the divided core portions so as to satisfy a predetermined relationship, and the control is also troublesome. Therefore, an object of the present invention is to provide a twin-roll continuous caster capable of adjusting the electromagnetic force generated in a plurality of split core portions with a simple configuration and without causing heat loss.

[0013]

In order to solve the above-mentioned problems, a twin-roll type continuous casting machine according to the present invention is provided with a pair of mold rolls arranged in parallel with each other and at the ends of both mold rolls. In a continuous casting machine having an electromagnetic weir, the core body of the electromagnetic weir is divided into a plurality of upper and lower parts, and the number of windings of a magnetic field generating coil wound around these divided core parts is set at a lower divided core. The number of the divided core portions located above is larger than the number of the divided core portions.

According to the above construction, the core body is divided into a plurality of upper and lower parts, and the number of windings of the coil is changed in accordance with the width of the gap at the tip of the core body. In the above, the required magnetic flux density required for holding molten steel and the generated magnetic flux density generated by the electromagnetic force can be made almost the same strength, and therefore, a dent at the center of the end of the cast slab occurs. Disappears.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A twin-roll continuous casting facility according to an embodiment of the present invention will be described below with reference to FIGS.

Since the gist of the present invention is an electromagnetic weir corresponding to a short-side weir in a twin-roll continuous casting facility, this embodiment will be described focusing on this part, and other parts will be described. Will not be described.

That is, as shown in FIGS. 1 and 2,
Reference numeral 1 denotes an electromagnetic weir arranged at positions corresponding to ends of a pair of mold rolls (hereinafter, referred to as rolls) 2 arranged in parallel with each other.
-Shaped core body 3 and gap a of this core body 3
The coil 4 is wound around a part opposite to the coil 4 and an AC power supply 5 for supplying a high-frequency current to the coil 4.

The core body 3 is vertically divided into a plurality of pieces, for example, five pieces. Therefore, the width of each gap a of these divided core portions 3a is equal to the height from the center position of the roll 2. Is different depending on.

The number of turns of the coil 4 wound around each of the divided core portions 3a is changed according to the width of the gap between the pair of rolls 2. That is, the number of turns of the upper divided core portion 3a is sequentially increased from the number of turns of the lower divided core portion 3a.

Here, the divided core portions 3a in the upper and lower portions
The number of turns of the coil 4 in the above will be described. First, the magnetic flux density required to hold the molten steel so as not to flow out of the molten steel reservoir will be determined.

That is, molten steel has its static pressure energy W
It is maintained by the balance between _S (J / m ³ ) and the magnetic energy W _m (J / m ³ ) generated from the core body.
Incidentally, the static pressure energy W _S can be expressed by the following equation (1), also the magnetic energy W _m can be expressed by the following equation (2).

[0022]

W _S = ρ × g × (h _max −h) (1) W _m = (1/2) × [B ² / (μ _O × μ _S )] (1) 2) However, ρ: density of molten steel (kg / m ³ ) g: acceleration of gravity h: height of roll (height of molten steel from roll center position) (m) B: magnetic flux density (Wb / m ² ) μ _O : Permeability in vacuum (H / m) μ _S : Relative permeability Therefore, from the above equations (1) and (2), the magnetic flux density B _O required for holding the molten steel is expressed as W _m > W _S From the relationship, it can be obtained as follows.

[0023]

(1/2) × [B _O ² / (μ _O × μ _S )]> ρ × g × (h _max −h) (3) When the above equation (3) is transformed, The following equation (4) is obtained.

[0024]

## EQU3 ## B _O > {(α × 2 × μ _O × μ _S × ρ × g × (h _max −h)} ^1/2 (4) In the above equation (4), α is safe. The coefficient is usually α = ^2. By substituting numerical values (for example, about 7200 kg / m ³ and g = 9.8 m / s ² as density in the case of stainless steel) into the equation (4), Equation (5) is obtained.

[0025]

B _O > 0.421 {α × (h _max −h)} ^1/2 (5) On the other hand, the magnetic flux density B and the magnetomotive force (N × I) are expressed by the following (9) It is in the relationship of the formula.

[0026]

R _C = l _C / (μ _O × μ _SC × S) (6) R _g = l _g / (μ _O × S) (7) φ = N × I / ( _RC + _Rg ) (8) By substituting equations (6) and (7) into equation (8), equation (9) is obtained.

[0027]

B = φ / S = μ _O × N × I / ｛(l _C / μ _SC ) + lg _g (9) where, in the above equations (6) to (9), R _C : Magnetic resistance of core (AT / Wb) R _g : Magnetic resistance of gap (AT / Wb) S: Cross-sectional area of magnetic path (m ² ) φ: Magnetic flux (Wb) l _C : Core length (m) l _g : total length of the gap (m) μ _SC : relative permeability of the core body (≒ 10 ^{3 in} the case of a silicon steel sheet) Accordingly, the magnetomotive force and the gap are set so that the expression (5) <the expression (9). By setting the width (gap length), it is possible to hold molten steel (molten metal).

Incidentally, since the design is usually made such that l _g ≫l _C / μ _SC , the expression (9) is simply expressed by the following expression (10).

[0029]

Equation 7] _{B = φ / S = μ O} × N × I / l g ···· (10) Accordingly, the divided core portions 3a at the closest portion of the roll 2
The number of turns (N _O ) of the coil wound on the right side is expressed by the following equation (13) by making the right side of the equation (5) equal to the right side of the equation (10).

[0030]

## EQU8 ## 0.421 {α × (h _max −h)} ^1/2 = μ _O × N _O × I / l _gO (12) Expression (12), l _gO : closest roll It is the gap length in the part. By substituting the following values into the above equation (12) and rearranging, the following equation (13) is obtained. h: h = 0 α: 2 at the roll closest part

[0031]

N _O = 0.421 (2 × h _max ) × I _gO / μ _O × I (13) where, in the above formula (13), specific examples are given as examples here. In the case where a numerical value is substituted, the number of turns of the coil will be obtained.

Roll diameter = 120 cm, h _mas = 32 cm, l
_{Assuming that gO} = 6 cm, I = 4000 A, and the number of divisions of the core body is 2, the number of turns of the coil wound around the divided core portion at the closest part of the roll is four, and the number of turns of the coil wound around the divided core portion above it. Is six times.

As described above, the core body is divided into upper and lower parts, and the number of windings of the coil is changed in accordance with the width of the gap (gap length) at the tip of the core body. Since the required magnetic flux density required for holding the molten steel and the generated magnetic flux density generated by the electromagnetic force were made substantially the same, no dent at the center of the end of the cast slab was found.

[0034]

As described above, according to the structure of the present invention, the core body is divided into a plurality of upper and lower parts, and the number of windings of the coil is changed according to the width of the gap (gap length) at the tip end. In the height direction above the center of the roll, the required magnetic flux density required for holding the molten steel and the generated magnetic flux density generated by the electromagnetic force are made substantially the same, so that simple and heat loss is caused. Without
A high-quality cast product can be obtained by preventing the occurrence of a central depression at the side end of the cast slab.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a twin-roll continuous casting machine according to an embodiment of the present invention.

FIG. 2 is a perspective view of an electromagnetic weir in the continuous casting machine of the embodiment.

FIG. 3 is a plan view of a conventional electromagnetic weir.

FIG. 4 is a cross-sectional view illustrating a conventional electromagnetic weir and a diagram illustrating a magnetic flux density at a roll height.

FIG. 5 is a perspective view of a conventional electromagnetic weir.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electromagnetic weir 2 Roll 3 Core body 3a Split core part 4 Coil

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironari Arai 5-3-28 Nishikujo, Konohana-ku, Osaka-shi, Osaka Inside Hitachi Zosen Corporation (72) Inventor Kunihiko Onishi 5-cho, Nishikujo, Konohana-ku, Osaka-shi, Osaka No. 28 of Hitachi Zosen Corporation (72) Katsuichi Mori Inventor 5-28 Nishikujo, Konohana-ku, Osaka City, Osaka Prefecture

Claims (1)

[Claims] 1. A continuous casting machine having a pair of mold rolls arranged in parallel with each other and electromagnetic weirs arranged at the ends of both mold rolls, wherein a plurality of core members in the electromagnetic weir are vertically divided. In addition, the number of windings of the magnetic field generating coil wound around these divided core portions is larger in the upper divided core portion than in the lower divided core portion. Twin roll continuous casting machine.