JP3174451B2 - Method for producing low iron loss oriented silicon steel sheet and plasma generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims to further reduce the core loss by imparting a linear thermal strain to the surface of a grain-oriented silicon steel sheet which has been subjected to final finish annealing so as to subdivide magnetic domains. It is about technology.

[0002]

2. Description of the Related Art Grain-oriented silicon steel sheets are mainly used in transformers,
It is used as an iron core for other electrical equipment and has excellent magnetizing properties, especially iron loss (maximum magnetic flux density 1.7 T,
W _17/50 which is iron loss when magnetized alternately at a frequency of 50 Hz
And a maximum magnetic flux density of 1.5 T, represented by _{W15 /} 60, which is iron loss when magnetized alternately at a frequency of 60 Hz).

[0003] For that purpose, first, it is necessary to highly align secondary recrystallized grains in a steel sheet to the (110) [001] orientation (usually called Goss orientation). It is necessary to reduce impurities and precipitates present in the final product steel as much as possible.

[0004] oriented silicon steel sheet to be produced to such a consideration of the group, by efforts to improve significantly until today, the iron loss value is also improved over the years, W _17/50 product with a thickness of 0.23mm in recent years Is 0.83 w / kg, W _15/60 is 0.35 w / lb
Low iron loss.

[0005] In recent years, techniques have been developed to introduce non-uniformity to the surface of a steel sheet by physical means and to reduce the magnetic loss by reducing the magnetic domain width.

For example, Japanese Patent Publication No. 57-2252 discloses that a surface of a final product sheet is irradiated with a laser beam at an interval of several mm substantially perpendicular to the rolling direction to introduce a high dislocation density region into the surface layer of the steel sheet. Techniques have been proposed for reducing the width of magnetic domains and reducing iron loss.

Japanese Patent Application Laid-Open No. Sho 62-96617 proposes a technique in which a plasma flame is locally radiated to the surface layer of a steel sheet to thereby reduce the width of a magnetic domain to reduce iron loss.

[0008]

[Problems to be solved by the invention]
In the method of irradiating a pulse laser as disclosed in JP 57-2252 or the method of irradiating a continuous laser as disclosed in JP-A-59-33802, the insulating coating on the steel sheet surface is peeled off. In addition, recoating is indispensable to cause equipment damage due to short circuit in transformers, etc. In addition, the life of laser excitation lamps is not long, and the change in the absorptivity of laser light according to the change in the color tone of the steel sheet surface is inevitable. Therefore, there is a disadvantage that the effect is not constant.

On the other hand, the plasma flame emission technique disclosed in Japanese Patent Application Laid-Open No. 62-96617 can avoid the problem of irradiating a laser to some extent. At present, it has not been possible to ensure the stability of the loss reduction effect and to avoid peeling and falling off of the insulating coating.

[0010] The reason is that the stability of the plasma flame is poor, and as described below, a sudden defect occurs due to the fluctuation of the convergence of the plasma flame.

That is, a conventionally used plasma generator has a structure having a torch having an orifice at the tip (see FIG. 2), and the thermal plasma generated by this is a cylindrical jet. When plasma is radiated on the surface of the steel sheet, the part becomes circular. Therefore, when irradiating the plasma flame to the steel sheet, make it linear and in a direction substantially perpendicular to the rolling direction, which is the longitudinal direction of the sheet. Since the torch needs to be moved in order to radiate the light, the following two problems have been raised.

First, as a first problem, since the convergence of the plasma flow is poor, the interval from the tip of the torch to the steel sheet surface must be controlled to about 0.3 to 1.0 mm. If it is insufficient, for example, if the above interval is too large, the effect of reducing the iron loss due to the emission of the plasma flame cannot be obtained, and if the interval is too small, the insulating coating on the steel sheet surface peels off and falls off. There was a problem such as doing.

The second problem is that when moving the plasma torch in the longitudinal direction of the steel sheet, it is necessary to adjust the distance from the tip of the torch to the surface of the steel sheet so that the moving speed is low. It had to be extremely slow, and the processing efficiency was extremely poor.

Under these circumstances, it is effective to increase the number of plasma torches to ensure a practical processing efficiency. However, it is necessary to actually operate equipment equipped with several hundred torches. Adjustment of the position of each torch,
Voltage control, flow control of carrier gas, and maintenance are difficult, and the operating rate drops sharply,
It was feared that it would cause poor quality such as poor magnetic properties of the steel sheet and peeling or falling off of the insulating coating.

An object of the present invention is to achieve instability of the effect of reducing iron loss, which often occurs when radiating a plasma flame, generation of defects due to peeling or falling off of an insulating film, and further, essentially increase efficiency. It is an object of the present invention to solve this problem and to propose a method and an apparatus capable of obtaining a grain-oriented silicon steel sheet having extremely low iron loss.

[0016]

According to the present invention, there is provided a plasma torch having an anode having a slit-shaped opening extending along a width direction of a steel sheet and a cathode disposed as desired in the opening of the anode. Using a magnetic field generator surrounding the tips of the anode and cathode, a sheet-shaped plasma flame is formed and radiated to the surface of the grain-oriented silicon steel plate that has been subjected to final finish annealing to subdivide magnetic domains. (A first invention).

Further, the present invention provides a plasma torch having an anode having a slit-like opening extending along the width direction of a steel sheet and a cathode disposed as desired in the opening of the anode, from the opening portion of the plasma torch. A plasma generator for radiating a plasma flame toward a grain-oriented silicon steel sheet which has been subjected to a final finish annealing, wherein the apparatus is provided with a magnetic field generator surrounding a tip portion of a cathode and an anode. Invention).

FIG. 1 shows the configuration of an apparatus according to the present invention. In the figure, reference numeral 1 denotes an anode, which has a slit-shaped opening (orifice) extending along the width direction of the steel sheet S.
1a.

Reference numeral 2 denotes a cathode, and the cathode 2 is disposed so as to be viewed from the opening 1a of the anode 1, and the anode 1 and the cathode 2
Thus, a plasma torch is formed. 3 is the anode 1
A DC power supply 4 disposed between the cathode 1 and the cathode 2 is a magnetic field generator that surrounds the tips of the anode 1 and the cathode 2, and the magnetic field generator 4 has an AC power supply 4a. Reference numeral 5 denotes an inlet tube for supplying a carrier gas into the plasma torch, and reference numeral 6 denotes an insulator disposed between the anode 1 and the cathode 2.

In the linear type apparatus having the above-described configuration, the opening 1a of the anode 1 is rectangular, and the tip of the cathode 2 is also linear. Thereby, thermal plasma is generated between a part of the tip of the anode 1 and a part of the tip of the cathode 2. The carrier gas supplied from the introduction pipe 5 serves as a carrier of the plasma flow,
The cooling thereby increases the convergence of the plasma, while the magnetic field generator 4 scans the magnetic field to form a sheet-like plasma (P in FIG. 1), and the steel sheet S passes through the opening 1a.
Radiated toward the surface of the

[0021]

The thermal plasma generated by the conventional plasma torch has a large temperature distribution in the plasma, and the temperature distribution cannot be eliminated even when the torch is moved along the longitudinal direction of the steel sheet. In addition, even when a plurality of such torches are arranged, a temperature distribution is naturally generated in the longitudinal direction of the steel sheet, which results in a thermal strain distribution, which results in an uneven iron loss reduction effect. Since the thermal plasma can be formed into a slit shape, the temperature distribution is uniform, and the thermal strain distribution in the longitudinal direction of the plate becomes very small.

In the present invention, the scanning of the magnetic field is performed.
Since the plasma can be made into a sheet shape by (oscillation), it is not necessary to move the torch in the width direction of the plate, and at the same time, the distance between the torch and the surface of the steel plate can be increased, so that it is intended for steel plates that run at high speed In such cases, the plasma flame can be radiated in the longitudinal direction in a very short time, stabilizing the effect of improving iron loss, preventing peeling and falling off of the insulating coating, and simplifying the equipment. (Requires fewer plasma torches), simplification of the electric circuit system is possible, and control of carrier gas flow,
It is extremely easy to adjust the position of the device or to maintain it.

The mechanism by which the diffusion of the plasma flame is suppressed by the application of a magnetic field is as follows. When a magnetic field is not applied, collision between particles constituting the plasma ((a) collision between similar particles (ion-to-ion or electron-to-electron) and (b)
Various particles are diffused by collision between different kinds of particles (ion-pair electrons, ion-pair neutral atoms, or electron-pair neutral atoms). That is, in the case of the same kind of particles, after the direction of movement is changed by Coulomb repulsion, the two particles move in the direction away from the plasma flame with the center of mass of the particles as the center of the plasma flame, and this becomes the driving force for diffusion.

In the case of collision between different kinds of particles, neutral electrons are generated by ion-pair electron collision, or the particles fly out with the opposite speed. At this time, the electrons jump and largely diffuse due to the difference in mass, but the ions move only slightly as a result of frequent collisions with the electrons. Further, in the case of collision between ions and neutral atoms, the ions move away from the initial position regardless of the speed of the neutral atoms.

As described above, ions and electrons are essentially moved in a direction away from the center of the plasma flame and diffused by various collisions.
In a plane perpendicular to the magnetic field, the ions and the electrons are orbiting about the magnetic field lines. At this time, as a result of the above various collisions, the speed and direction of the ions and electrons change, but thereafter, the swirling motion is continued around the line of magnetic force different from that before the collision, so that the distance from the center of the plasma flame is kept after the collision. Never. The diffusion of various particles is suppressed by such a mechanism, and the convergence of the plasma flame is improved. Therefore, the direction of the applied magnetic field must be parallel to the direction of the plasma flame, and this magnetic field must be generated by applying a current to the coil of the conductor surrounding the anode and cathode tips of the plasma generator. Can be.

Next, a description will be given of a method of manufacturing a steel sheet conforming to the present invention.

The material conforming to the present invention is manufactured by a known steel making method, for example, a converter, an electric furnace or the like, and is further subjected to slab-forming from a slab ingot or a continuous casting method.
(Slab), hot-rolled coils can be applied by hot rolling.

It is essential that the above-mentioned hot rolled coil has a composition containing about 2.0 to 4.5% of Si.
This is because if the Si content is less than 2.0%, the iron loss deteriorates greatly,
On the other hand, if it exceeds 4.5%, the cold workability deteriorates. Any other components can be applied as long as they are the material components of the grain-oriented silicon steel sheet.

The above-mentioned hot-rolled coil is cold-rolled until it reaches the final target thickness, and the cold-rolling is performed once or twice with intermediate annealing. At the time of this cold rolling, aging treatment may be performed between warm rolling and rolling passes in place of hot-rolled sheet annealing and cold rolling as necessary.

The cold rolled steel sheet finished to the final thickness is subjected to primary recrystallization annealing also serving as decarburization annealing, and thereafter, an annealing separating agent is applied to the surface of the steel sheet, wound into a coil, and then subjected to final finish annealing. . In the final finish annealing, secondary recrystallization progresses to complete the crystal structure of the steel sheet,
A purifying phenomenon in which harmful impurities such as N and N are removed proceeds, and furthermore, a ceramic polycrystalline insulating film is formed on the surface of the steel sheet.

After the final finish annealing, the unreacted separating agent is removed from the surface of the steel sheet and then subjected to a smoothing treatment. At this time, an insulating coating may be applied and baked if necessary.

The radiation of the plasma flame has its effect at any stage after the final finish annealing.
It is good to do it after baking the insulating coating.

In order to obtain the most efficient iron loss reduction effect when the plasma flame is radiated, the thickness of the line of the plasma flame must be 20 mm.
The thickness is preferably about 1000 μm, and the direction may be any direction that crosses the plate. However, in order to expect a greater effect, the direction is perpendicular to the longitudinal direction of the plate.

The radiation interval along the longitudinal direction of the plate of the plasma flame is about 3 to 30 mm at which the effect is most exhibited.

The distance between the plasma torch and the surface of the steel plate is set to 0.
Perform within a range of 1 to 50 mm.

The radiation of the plasma flame occurs during unwinding of the steel sheet.
This may be performed in a flat state (running state), or may be performed in a curved state during winding around a drum or the like, and this point is not particularly limited.

[0037]

Example: C: 0.078%, Si: 3.26%, Mn: 0.068%,
P: 0.01%, S: 0.004%, Se: 0.019%, Sb: 0.026
%, N: 0.0075% steel slab at a temperature of 1420 ° C
After heating and soaking for 10 minutes, a hot-rolled coil of 1.7 mm was formed by hot rolling.Then, this was annealed at 1150 ° C for 30 seconds, quenched with a mist, pickled, and heated at a temperature of 180 ° C. rolled to a thickness of 0.19mm by Zenjimamiru between further H _2: 50%, dew point: 60 ° C., under an atmosphere of N ₂ balance, 850
Decarburization annealing for 90 seconds at ℃, MgO containing 5% TiO ₂
, And wound up in a coil shape for final finish annealing. The conditions of the final annealing were as follows: holding in N ₂ at 840 ° C. for 40 hours and 1200 ° C. in an atmosphere of 25% N ₂ and 75% H _{2 at} a rate of 10 ° C./hr.
1200 ° C. in in the heating of H ₂ up to ° C., is intended to include the 10 hour hold and subsequent cooling. After the final finish annealing, the unreacted annealing separating agent on the coil surface is removed, then a tension insulating coating containing 50% colloidal silica and 50% magnesium phosphate as main components is applied, and the flattening treatment is also performed at 800 ° C.
Baking treatment.

The coil obtained in the above manner is subjected to a magnetic domain subdivision treatment by radiating a plasma flame under the following conditions using the apparatus shown in FIG. The state of peeling and falling off of the coating was investigated.
The results are shown in Table 1 together with the results obtained when ordinary magnetic domain refinement was performed.

Conditions Torch voltage: 30 V Torch current: 50000 A Torch output: 1500 kW Distance from torch tip to coil surface: 15 mm Coil passing speed: 30 m / min Magnetic field application condition Magnetic flux density: 5000 Gaussian carrier gas: Plasma flame emission interval in the longitudinal direction of the Ar coil: 5 mm Plasma flame irradiation width (line width): 150 μm

[0040]

[Table 1]

Conventional processing conditions The torches shown in FIG.
A torch is moved in the width direction of the coil and the plasma flame is radiated. Torch voltage: 45 V Torch current: 3000 A Torch output: 135 kW Distance from torch tip to coil surface: 0.5 mm Passing speed: 10m / min Carrier gas: Radiation interval of plasma flame in the longitudinal direction of Ar coil: 5mm Radiation width of plasma flame (line width): 150 μm

As is clear from Table 1, the coil treated according to the present invention had a large effect of improving the magnetic properties and was stable in quality without any peeling or falling off of the coating. For those that did, there was variation in quality.

[0043]

As described above, according to the present invention, not only the radiation efficiency of the plasma flame can be improved, but also the stability of the radiation effect increases, so that a stable supply of grain-oriented silicon steel sheets having excellent magnetic properties and coating properties can be achieved. Becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of a device according to the present invention.

FIG. 2 is a diagram showing a configuration of a conventional system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode 1a Orifice 2 Cathode 3 DC power supply 4 Magnetic field generator 5 Gas introduction hole 6 Insulator S Steel plate P Plasma flame

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C21D 8/12 C21D 9/46 501 H01F 1/16 H05H 1/24-1/52

Claims (2)

(57) [Claims] 1. A plasma torch including an anode having a slit-shaped opening extending along the width direction of a steel sheet and a cathode disposed as desired in the opening of the anode, and surrounding the anode and the tip of the cathode. Low iron loss directionality characterized by forming a sheet-like plasma flame using a magnetic field generator and radiating this to the surface of a grain-oriented silicon steel sheet that has been subjected to final finish annealing to subdivide magnetic domains. Manufacturing method of silicon steel sheet. 2. A plasma torch having an anode having a slit-like opening extending along the width direction of a steel sheet and a cathode arranged as desired in the opening of the anode, and a final finish annealing from the opening portion of the plasma torch. An apparatus for radiating a plasma flame toward a grain-oriented silicon steel sheet according to any one of claims 1 to 3, wherein the apparatus is provided with a magnetic field generator surrounding a tip portion of a cathode and an anode.