JPH059564A - Method for coating grain-oriented silicon steel strip with separation agent for annealing and apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain a steel strip having uniform and excellent magnetic properties over the whole length of a coil at the time of coating the steel strip with a separation agent for annealing, coiling it into the shape of a coil and executing final annealing, by forming a separation agent layer with different components and thickness on the inwardly and outwardly coiled sides of the coil by the use of powder. CONSTITUTION:A steel strip 1 is uniformly coated with a slurried separation agent contg. MgO having relatively high activity by a roll coater 3. Furthermore, the surface of the steel strip 1 is fed with MgO powder having low activity from a hopper 6 by a scattering apparatus 5, and the steel strip is passed through a drying furnace 2 and is coiled around a coiling machine 1. At this time, the diameter of the coil is computed by a sequencer 8, and the opening degree of a powder cutting valve 7 is regulated in accordance with the diameter of the coil. Then, a thick coating layer constituted of MgO having relatively high activity and low activity is formed in the range on the inwardly coiled side of the coil, and then, a thin coating layer of MgO having relatively high activity is formed in the range on the outwardly coiled side of the coil. In this way, additional oxidation by the water of crystallization of MgO is reduced, and approximately uniform purification annealing can be executed both to the inward coiling and outward coiling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for applying an annealing separator on a grain-oriented electrical steel strip.

[0002]

2. Description of the Related Art In a secondary annealing process for the purpose of forming a surface oxide layer (firelite silica) on a grain-oriented electrical steel sheet and decarburizing annealing, MgO mixed with a water repellent agent by electrostatic coating.
An example of applying is disclosed in JP-B-60-14105. This aims at applying the same component MgO 2 uniformly in the longitudinal direction.

By the way, as for the magnetic properties after the tight annealing, the inner winding of the coil had poor saturation magnetic flux density and iron loss as compared with the outer winding. This is called inner winding deterioration. The cause is (1) There is a difference in the temperature rise and soaking patterns between the inner and outer windings of the coil. (2) The inner winding of the coil has a large strain in order to flatten the one having a small radius of curvature when further flattening annealing is performed in the next step. Was explained.

On the other hand, it is pointed out in Japanese Patent Laid-Open No. 2-70020 that the cause of the deterioration of the inner winding is the problem of air permeability in which the atmospheric gas in the furnace passes through the laminated layers of the coil during the tight annealing. As shown in Fig. 1, the inner winding portion of the coil has a cold spot with a slow rate of temperature rise in the middle winding portion, so that the inner winding is intimately contacted between the coil layers toward the middle winding portion due to the difference in thermal expansion. Is significantly reduced.

The atmosphere gas H _{2 in the} furnace has a purifying action of sucking out the inhibitor which is an impurity in the steel, but one reason is that the purification is not sufficiently performed in the range of 1000 ° C. or higher due to poor air permeability. there were. Another cause is that the air permeability is also poor.MgO retains water in the form of water of crystallization, but as the temperature rises, the water of crystallization becomes water vapor, and the steel sheet near 450 ° C Although it acts to oxidize the surface (this is referred to as additional oxidation), since the air permeability is poor, the rate at which water vapor escapes from the interlayer is also slowed down, so additional oxidation becomes excessive. At this time, Mn and Al in the steel are sucked up to the undercoat, and Mn and Al in the steel are insufficient, so that S, Se or N, which is an inhibitor, easily moves.

Nn compounds represented by inhibitors such as MnS, MnSe and AlN have the role of suppressing the growth of other orientations (inhibit) in order to preferentially grow the crystal orientation to the Goss orientation. Excessive oxidation → Suction of Mn and Al from steel → Decrease in inhibitor inhibitory power → Poor crystal orientation → Deterioration of magnetic properties.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above problems in the conventional final annealing and produces a grain-oriented electrical steel strip having uniform and excellent magnetic properties over the entire length of the coil. In particular, it is an object of the present invention to propose a method and apparatus for applying an annealing separator.

[0008]

According to the present invention, when an annealing separator is applied to a grain-oriented silicon steel sheet, the coil is wound into a coil, and the final annealing is performed, the activity is relatively high in the range on the coil inner winding side. After applying a slurried separating agent containing high MgO uniformly with a roll coater, MgO powder with low activity is further sprayed on the plate and dried to form a thick coating layer of MgO, and then the coil is wound on the outside. In the range on the side, the directional silicon is characterized in that a thin coating layer of MgO is formed by uniformly applying the slurrying separating agent containing MgO having relatively high activity by a roll coater and then drying. A method for applying an annealing separator for a steel strip, and in an apparatus for applying an annealing separator for a grain-oriented silicon steel sheet, which is subsequently equipped with a roll coater and a drying furnace and a coiler, the roll coater and the drying furnace. Between the two, the powder hopper is provided with a powder spraying device connected through a powder cut-out valve, and the opening of the powder cut-out valve is adjusted based on the value of the coil diameter measuring device of the coiler. This is an apparatus for applying an annealing separator for a grain-oriented silicon steel strip.

The activity of MgO in the present invention means citric acid activity (CAA) and is defined as follows. Citric acid activity is a measure of the hydration rate of magnesium oxide and is determined by measuring the time required for a given weight of magnesia to supply hydroxide ions to fully neutralize a given weight of citric acid. . That is, 0.400 containing 2 ml of 1.1% phenol fretane indicator
Bring 100 ml of the specified aqueous citric acid solution to 30 ° C in a 237 cc (80unce) wide-mouth bottle. Attach the screw cap and magnetic stirrer bar to this bottle. 2. Weigh out 2.00 g magnesia, add to this bottle and immediately start the stopwatch, Simultaneously add the magnesia sample and cap the bottle. Shake the bottle and its contents vigorously at 5 seconds. Stop stirring at 10 seconds. 4. Place the sample on the magnetic stirrer unit at 10 seconds. By mechanical agitation, when the inner diameter of the bottle is 6 cm, a vortex having a depth of about 2 cm is formed at the center. 5. As soon as the suspension turns pink, stop the stopwatch and note the time. This time becomes citric acid activity.

[0010]

In the present invention, since the MgO is thicker coated than the outer winding side in the range of the coil inner winding side where the winding tightness becomes strong, the air permeability can be maintained almost the same as that of the outer winding side. The average activity of MgO in the thick coating layer was compared with the MgO in the thin coating layer.
Since the average activity is lower than the average activity of MgO, the additional oxidation of MgO due to water of crystallization is reduced, and almost uniform purification annealing is achieved for both inner and outer windings.

Further, since the coating apparatus of the present invention is constructed as described above, it is possible to easily coat MgO having a predetermined activity with the powder spraying apparatus according to the winding position of the steel strip. You can Further, in the present invention, since the powdery separating agent is additionally sprayed before the drying after uniformly applying the slurry-like separating agent, the powder can be easily adhered to the slurry, and only the normal drying is performed. Can increase the film thickness arbitrarily. Moreover, since the water content does not increase at all, the drying capacity is the same as the conventional one.

Since it is only necessary to increase the film thickness between the layers, additional spraying by the powder spraying device is sufficient only on the upper surface of the plate.

[0013]

[Examples] Although MgO has different activity (CAA) depending on its manufacturing method and firing temperature, A and B shown in Table 1 were selected as representative brands. In the coating line of the present invention shown in FIG. 2 for the silicon steel strip coils No. 1 and No. 2 having the composition shown in Table 2 and a plate thickness of 0.23 mm, under the coating conditions shown in Table 3, the above-mentioned MgO brand A,
B was applied.

The results are shown in Table 4. It can be seen that, by adopting the present invention, even if the coating condition of the inner winding is thick, the magnetic characteristics are not deteriorated and uniform characteristics are obtained over the entire length of the coil. The coating device of the present invention is shown in FIG. 1 is a strip, 2 is a winder, 3 is a roll coater, 4 is a drying furnace, 5 is a powder spraying device, and 6 is a powder hopper. Reference numeral 7 is a powder cut-out valve, and 8 is a sequencer for calculating a coil diameter and issuing a command for a powder spraying amount.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

As described above, by changing the activity of MgO, the inner winding is thick and the outer winding is thin, and the annealing separating agent is applied to obtain uniform and excellent magnetic characteristics over the entire length of the coil. I was able to do it. Further, in implementing the present invention, it is not necessary to modify or enhance the existing equipment.

Further, since the powder dispersion is required only on the upper surface, it is very easy to carry out.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a coil state.

FIG. 2 is an explanatory diagram of a coating device of the present invention.

[Explanation of symbols]

1 strip 2 winder 3 roll coater 4 drying oven 5 Powder spraying device 6 powder hopper 7 Powder cutting valve 8 sequencer

Claims (2)

[Claims] 1. An annealing separator is applied to a grain-oriented silicon steel sheet,
When the coil is wound into the coil and the final annealing is performed, a slurry-type separating agent containing MgO, which has a relatively high activity in the area on the coil winding side, is uniformly applied using a roll coater, and then the activity is further applied to the plate. Of MgO powder having a low content of MgO is sprayed and dried to form a thick coating layer of MgO, and then the slurryed separating agent containing MgO having relatively high activity is rolled by a roll coater in the range on the coil outer winding side. A method for applying an annealing separator for a grain-oriented silicon steel strip, which comprises forming a thin coating layer of MgO by uniformly coating and then drying. 2. An apparatus for applying an annealing separator for a grain-oriented silicon steel sheet, comprising a roll coater followed by a drying furnace and a coiler. Of the directional silicon steel strip characterized in that the opening of the powder cut-out valve is adjusted based on the value of the coil diameter measuring device in the coiler. Annealing agent coating device.