JP2570924B2 - Method for preventing vibration and warpage of steel sheet passing continuously - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing vibration of a continuously passing steel sheet and warpage of the steel sheet in the width direction (so-called C warpage deformation).

[0002]

2. Description of the Related Art In a gas jet cooling zone of a continuous annealing furnace, a steel sheet is cooled while being conveyed by a roll, but vibration is generated by fluttering on the steel sheet because a high-speed cooling gas is sprayed on the roll. I do. When such vibration occurs in the steel sheet, the steel sheet comes into contact with the cooling gas blowing nozzle, and there is a problem that the steel sheet surface is damaged. Therefore, in order to avoid this, it is necessary to increase the distance between the cooling gas blow-out nozzle and the steel sheet, and as a result, the cooling efficiency of the steel sheet is reduced, and furthermore, the occurrence of thermal buckling due to uneven cooling is caused. Problems arise. In addition, for example, in an electroplating line or a hot-dip plating line, uneven plating thickness occurs due to sheet warpage or vibration of a steel sheet. There are various problems.

[0003]

In order to solve such problems of vibration and warpage of the steel sheet in various continuous threading lines, for example, a magnetic roll is provided in a plating bath, and the steel sheet is attracted by a magnetic force. A method of correcting sheet warpage by flattening (Japanese Patent Application Laid-Open No. Sho 52-1111839) and a method of preventing vibration by placing magnets on both sides in the width direction of a steel sheet (Japanese Patent Application Laid-Open No. Sho.
No. 7-5853) have been proposed, but none of these methods is a technique capable of simultaneously achieving correction of plate warpage and prevention of vibration.

In Japanese Patent Publication No. 2-16375, a method is proposed in which vibration is suppressed by pressing a steel plate with a holding roll before and after a gas jet cooling nozzle. In this method, vibration is completely suppressed. Not only is it impossible, but there is also the problem that the steel sheet is scratched by contact with the holding roll.

Japanese Patent Publication No. 44-7444 discloses a method of applying a high-frequency magnetic field by passing a steel sheet from a plating bath between coils through which a high-frequency current is applied, for the purpose of drawing hot-dip coating. It is proposed that the steel sheet passing between the coils is centered at the center between the coils by a magnetic repulsive force, in which the effect of suppressing the vibration of the steel sheet can be expected. However, when a high-frequency magnetic field is simply applied to a steel sheet, the magnetic attraction force acts strongly on the steel sheet, which is a ferromagnetic material. Is caused,
Vibration suppression cannot be expected at all. As described above, conventionally, there has not been known a method capable of effectively suppressing the vibration and the warpage of the steel sheet to be passed without contact.

The present invention has been made in view of such conventional problems, and provides a method capable of non-contact and effectively suppressing warpage and vibration of a continuously passing steel sheet by a relatively simple apparatus and method. What you want to do.

[0007]

[Means for Solving the Problems] Even if a magnetic field is simply applied to a ferromagnetic material such as a steel sheet to control the vibration of the steel sheet, a magnetic attraction force acts on the steel sheet, and the steel sheet is not vibrated. The more unstable state is as described above. With respect to such a problem, the present inventors have paid attention to the fact that the region showing the ferromagnetism of the steel sheet is limited to the non-saturation region as shown by the B to H curves in FIG. If a high-frequency magnetic field is applied in a state where the steel sheet is sufficiently saturated, the repulsive force generated between the current flowing through the high-frequency current path and the induced current in the steel sheet becomes stronger than the magnetic attractive force. The inventor found that the accompanying instability was eliminated, and completed the present invention.

That is, according to the present invention, a high-frequency current conduction path parallel to a steel sheet surface is disposed on the front side and the rear side of a steel sheet passing continuously so as to be substantially opposed to each other with the steel sheet sandwiched therebetween. An N pole and an S pole of a magnet are arranged outside both sides in the width direction of the steel sheet in the vicinity of the high-frequency current conduction path so as to be substantially opposed to each other across the width direction of the steel sheet, and the steel sheet is magnetically saturated by the magnet. In this state, an in-phase high-frequency current having a frequency of 3 kHz or more is passed through the high-frequency current conducting paths on the front and rear sides of the steel sheet to induce a high-frequency current of opposite phase in the steel sheet. The magnetic pressure acting on the steel plate surface is generated by the interaction with the high-frequency current in the passage, and the warpage and vibration in the width direction of the steel plate are suppressed by the magnetic pressure acting on both surfaces of the steel plate. Here, the "magnetic pressure" acting on the steel sheet surface due to the interaction between the induction current of the steel sheet and the high-frequency current of the high-frequency current conduction path is generated between the high-frequency current flowing through the high-frequency current conduction path and the induction current in the steel sheet. It refers to the magnetic pressure acting on the steel sheet surface due to magnetic repulsion.

In the present invention, two or more high-frequency current conducting paths can be provided at intervals in the sheet passing direction. The magnets arranged so as to face each other across the width of the steel sheet may be either electromagnets or permanent magnets.
It can be arranged at more than two places.

The high-frequency current conduction path needs to be provided in the width direction of the steel sheet, but it is not always necessary to provide the high-frequency current conduction path in parallel with the width direction of the steel sheet. It is possible to adopt a configuration in which a part of the high-frequency current conduction path is inclined with respect to the plate width direction. At the edge of the steel sheet, the direction of the current flowing through the steel sheet has a relationship of 90 ° with respect to the current flowing through the high-frequency current conduction path. Therefore, the magnetic pressure tends to weaken near this edge. As described above, the entire length of the high-frequency current conduction path is inclined with respect to the plate width direction, or the portion of the current conduction path facing the vicinity of the steel sheet edge is inclined with respect to the plate width direction. Is effective.

[0011]

The operation of the method of the present invention is illustrated in FIG. 12 (a diagram showing the relationship between the magnetic flux density and the strength of the magnetic field) showing the magnetic properties of a ferromagnetic steel sheet and FIGS. 1 and 2 which are one embodiment of the present invention. It is explained based on. FIG. 1 is a side view showing an embodiment, and FIG. 2 is a front view of the same.

According to the method of the present invention, high-frequency current conduction paths 2a and 2b parallel to the steel sheet surface are arranged close to the steel sheet 1 so as to be substantially opposed to the front side and the rear side of the steel sheet 1 to be continuously passed through the steel sheet. The N pole and the S pole of the magnet 3 made of a permanent magnet or an electromagnet are arranged on both sides in the width direction of the steel sheet 1 so as to be substantially opposed to each other across the width direction of the steel sheet. In this example, the high-frequency current conduction paths 2 on both sides of the steel plate
a, 2b are arranged in two stages, upper and lower, near the upper portions of the upper high-frequency current conducting paths 2a, 2b and the lower high-frequency current conducting paths 2
Magnets 3 are arranged at positions near and below a and 2b, respectively.

When a high-frequency current having the same phase flows through the high-frequency current conducting paths 2a and 2b opposed to each other with the steel sheet 1 interposed therebetween, a current having the opposite phase flows through the steel sheet 1. Since the direction of the current flowing through the steel sheet 1 is opposite to the direction of the current flowing through the high-frequency current conducting paths 2a and 2b, a magnetic repulsion occurs between the current flowing through the high-frequency current conducting paths 2a and 2b and the current flowing through the steel sheet 1. This acts on the steel sheet surface as magnetic pressure. However,
Since a ferromagnetic material such as a steel plate has a high magnetic permeability, the magnetic attraction force exceeds the repulsion force and the system becomes unstable if the current simply flows as described above. The magnets 3 disposed at both ends of the steel plate act to magnetically saturate the steel plate in order to remove such instability. That is, by the action of this magnet, the magnetic field in the steel sheet exists in the magnetic saturation region shown in FIG. 12, and the range of the magnetic field fluctuation generated by the high-frequency current also exists in the magnetic saturation region shown in FIG. Will be. By thus magnetically saturating and paramagnetic the ferromagnetic material, instability due to magnetic attraction can be eliminated, and the steel sheet receives only the repulsive force from the high-frequency current conduction path. That is, this action is similar to the action of a non-contact spring as shown in FIG. 13, thereby suppressing the vibration of the steel sheet and correcting the sheet warpage. In the present invention, the frequency of the high-frequency current applied to the high-frequency current conduction path is 3 kHz from the result of the embodiment described later.
Above. Further, the magnitude of the high-frequency current is appropriately selected according to the frequency of the current and the set distance between the high-frequency current conduction path and the steel sheet. Is 15mm, frequency is 3
In the case of kHz, the current value is about 3 × 104 A. For example, in the case of a frequency of 20 kHz, the current value may be about 500 A at the same set distance between the high-frequency current conducting path and the steel sheet.

[0014]

1 to 11 show an embodiment of the present invention.
1 and 2 show two sets of high-frequency current conducting paths 2a and 2b parallel to the surface of the steel sheet arranged vertically so as to face each other with the steel sheet 1 interposed therebetween as described above. Magnets 3 (permanent magnets) at positions near the upper and lower portions of the conduction path so as to sandwich the steel sheet in the width direction.
N and S poles are arranged. In-phase high-frequency currents are passed through the high-frequency current conducting paths 2a and 2b opposed to each other with the steel plate 1 interposed therebetween. In this example, the phases of the currents in the upper and lower high-frequency current conducting paths are opposite, but may be the same.

FIGS. 3 and 4 show an arrangement in which the N pole and the S pole of the magnet 3 are disposed between two upper and lower sets of high-frequency current conducting paths 2a and 2b. This is the same as the above embodiment. FIGS. 5 and 6 show a high-frequency current conducting path and a magnet arrangement similar to those shown in FIGS. 1 and 2, in which the magnet 3 is constituted by an electromagnet, and 4 is a yoke constituting the electromagnet. Is also a coil.

FIGS. 7 and 8 show that each of the high-frequency current conducting paths 2
A bent portion 21 is formed in a portion facing the vicinity of the steel plate edge portion along the steel plate passing direction. Also in this embodiment, two sets of upper and lower high-frequency current paths are provided, and the magnet 3 is disposed between the upper and lower high-frequency current paths. Such a configuration is applicable to each of the embodiments described above.

At the edge of the steel sheet, the direction of the current flowing through the steel sheet is 9 with respect to the current flowing through the high-frequency current conduction path.
Because of the relationship of 0 °, the magnetic pressure tends to weaken in the vicinity of the edge portion. To solve such a problem, the entire length of the high-frequency current conduction path is inclined with respect to the sheet width direction, or the steel sheet of the current conduction path is It is effective to make the portion facing the vicinity of the edge portion inclined in the plate width direction. 9 and 10
The figure shows an example of the arrangement of the current conducting paths in the former case, in which the entire length of the high-frequency current conducting paths 2a and 2b on both sides of the steel sheet is appropriately inclined with respect to the sheet width direction. FIG.
Are the high-frequency current conducting paths 2a, 2 facing the steel sheet edge.
The part 22 of b is inclined with respect to the plate width direction. The above configuration is applicable to each of the above embodiments.

The present inventors conducted the following simulation analysis to verify the effect of the present invention. In this analysis, first, in order to confirm that the steel sheet is magnetically saturated by the electromagnet, static magnetic field analysis was performed on the electromagnet and the steel sheet in an apparatus configuration shown in FIGS. 5 and 6. FIG. 14 shows an analysis model. Here, in consideration of symmetry,
Analysis was performed with a 1/2 model. The analysis conditions are as follows. Iron core relative permeability: 1000 Coil current: 2.6 × 10 ⁵ AT Steel plate dimensions: width 1800 mm × sheet thickness 2.3 mm

FIG. 15 shows the distribution of the magnetic field obtained by the analysis. The strength of the magnetic field in the magnetic material obtained here was 1.6 × 1
0 ⁵ A / m or more indicates that the steel sheet is magnetically sufficiently saturated, that is, the steel sheet is in the saturation region of FIG.

Next, a simulation was performed to calculate the magnetic pressure exerted on the steel sheet by the high-frequency current conduction path. FIG. 16 shows the analyzed model. Assuming that a current having a phase as shown in FIG. 5 flows in each high-frequency current conduction path, analysis was performed using a half model in consideration of symmetry. The analysis conditions are as follows. Since the steel sheet is magnetically saturated, the relative magnetic permeability of the steel sheet was set to 1. Coil cross-sectional dimension: 30 × 50 mm Coil current: 3 × 10 ⁴ A Frequency: 3000 Hz Steel plate thickness: 2.3 mm Steel plate relative permeability: 1

In this analysis, it is considered that the steel sheet vibrates between the opposing high-frequency current paths. As shown in FIG. 16, the steel sheet is located at the center position of both current paths, and 5 mm and 10 mm from the center position. 3 when it is shifted by
An analysis was performed on the levels. FIG. 17 shows the case where the steel plate is at the center position of both current conducting paths, and FIGS.
Shows the distribution of each magnetic pressure when the steel plate is shifted from the center position by 5 mm and 10 mm, respectively. According to this, it is shown that when the steel plate is displaced from the center position, a magnetic pressure is exerted to push the steel plate to the center position as a whole. Since the magnetic pressure increases as the steel sheet approaches the high-frequency current conduction path, it works effectively for the centering action of the steel sheet and is effective in preventing vibration. It is also effective as a C-slewing correction force.
It can be seen that it is pressed within mm.

Based on these results, the apparatus shown in FIGS. 5 and 6 was installed on three electroplating lines at intervals of about 2 m, and an actual machine test was performed. The conditions such as dimensions and current in this test were the same as those used in the above simulation. According to this test, the C warpage in the sheet width direction, which had conventionally occurred about 7 mm, was reduced to about 0.5 mm, and the vibration of the sheet could be almost completely suppressed. For this reason, the distribution of the coating amount in the plate width direction of the plating was improved from ± 50% in the past to ± 7% or less.

The method of the present invention as described above can be applied to all kinds of continuous steel sheet passing lines. In particular, it is a method for preventing the vibration of a steel sheet in a gas jet cooling zone of a continuous annealing furnace, which is a conventional problem, and in a hot-dip coating equipment. It is extremely useful for preventing the steel sheet from vibrating and warping at the gas wiping position, and also for preventing the steel sheet from warping in an electroplating line.

[0024]

As described above, according to the present invention, a stable magnetic pressure can be applied to the steel sheet from the high-frequency current conduction paths on both sides of the steel sheet. It has the versatility of being able to effectively and effectively suppress the warpage and vibration of a steel sheet to be passed without contact, and can be applied to all types of continuous sheet passing lines.

[Brief description of the drawings]

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

FIG. 2 is a front view of the embodiment shown in FIG. 1;

FIG. 3 is a side view showing another embodiment of the present invention.

FIG. 4 is a front view of the embodiment shown in FIG. 3;

FIG. 5 is a side view showing another embodiment of the present invention.

FIG. 6 is a front view of the embodiment shown in FIG. 5;

FIG. 7 is a side view showing another embodiment of the present invention.

FIG. 8 is a front view of the embodiment shown in FIG. 7;

FIG. 9 is a front view showing another embodiment of the present invention.

FIG. 10 is a side view of the embodiment shown in FIG. 9;

FIG. 11 is a front view showing another embodiment of the present invention.

FIG. 12 is a diagram showing the relationship between the magnetic flux density of a steel sheet and the magnetic field strength.

FIG. 13 is an explanatory view schematically showing the effect of the present invention.

FIG. 14 is an explanatory diagram showing an analysis model in a simulation for confirming that a steel sheet is magnetically saturated by a magnet.

15 is an explanatory diagram showing the distribution of the magnetic field obtained by the analysis of FIG.

FIG. 16 is an explanatory diagram showing an analysis model in a simulation for calculating a magnetic pressure exerted on a steel sheet by a high-frequency current conduction path.

FIG. 17 is a graph showing the magnetic pressure when the steel plate is at the center position in the analysis of FIG. 16;

FIG. 18 is a graph showing the distribution of magnetic pressure when the steel plate is shifted by 5 mm from the center position in the analysis of FIG.

FIG. 19 is a graph showing the distribution of magnetic pressure when the steel plate is shifted by 10 mm from the center position in the analysis model of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel plate, 2a, 2b ... High frequency current conduction path, 3 ... Magnet

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akira Yada 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-3-173755 (JP, A) JP-A-3 253549 (JP, A) JP-A-4-228528 (JP, A) Jpn.

Claims (1)

(57) [Claims] 1. A high-frequency current conduction path parallel to and parallel to a steel sheet surface is disposed on the front side and the rear side of the steel sheet to be continuously passed, and is substantially opposed to each other with the steel sheet interposed therebetween. N-poles and S-poles of magnets are arranged outwardly on both sides in the width direction of the steel sheet in the vicinity of the current conducting path so as to be substantially opposed to each other across the width direction of the steel sheet .
In the saturated state, a high-frequency current of the same phase having a frequency of 3 kHz or more is supplied to the high-frequency current conduction path on the front side and the rear side of the steel sheet to induce a high-frequency current of the opposite phase to the steel sheet,
The interaction between the induction current and the high-frequency current of each of the high-frequency current conducting paths generates a magnetic pressure acting on the steel sheet surface, and the magnetic pressure acting on both surfaces of the steel sheet suppresses sheet warpage and vibration in the width direction of the steel sheet. A method for preventing vibration and warpage of a continuously passing steel sheet, characterized in that: