JPH059565A - Method for coating grain-oriented silicon steel strip with separation agent for annealing and apparatus therefor - Google Patents

Abstract

PURPOSE:To provide 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 changing the components and thickness of the separation agent on the inwardly coiled side and outwardly coiled side of the coil. CONSTITUTION:A steel strip is fed with MgO from a nozzle 5, and after pressurizing and coating by a corter roll 4, this steel strip is passed through a drying furnace 2 and is coiled around a coiling machine 1. At this time, the opening degree of the coater roll 4 is regulated in accordance with the diameter of the coil by a computing element 7. Furthermore, a flow rate regulating valve 6 is regulated in accordance with the diameter of the coil by a computing element 8 to change and control a balance of two kinds of discriptions of MgO, i.e., A and B with differences in activity. Then, a thick coating layer of MgO having low average activity is formed in the range on the inwardly coiled side of the coil, and then, a thin coating layer of MgO having average activity higher than that of the inwardly coiled side is formed in the range on the side of the outwardly coiled side of the coil. In this way, added oxidation by the water of crystallization of MgO is reduced, and approximately uniform purification annealing can be executed both to 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 strip 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 to apply MgO of the same component 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 deficient, so that the inhibitor S, Se or N easily moves.

Nd compounds represented by MnS, MnSe and AlN, which are inhibitors, have the role of suppressing 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 the 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 average activity is within a range on the coil winding side. Of a directional silicon steel strip characterized by forming a thick coating layer of low MgO and then forming a thin coating layer of MgO having a higher average activity than the inner winding side in the range of the outer coil side. This is a method of applying a separating agent, and in an annealing separator applying apparatus for oriented silicon steel sheets, which is equipped with a roll coater, followed by a drying furnace and a coiler, it is connected to at least two types of MgO agitation supply systems with different activities. A roll coater part facing the roll coater, and adjusting the opening of the coater roll based on the value of the coil diameter measuring device in the coiler, and adjusting the flow rate of at least two kinds of MgO respectively. Flow control An apparatus for applying an annealing separator for a directional silicon steel strip, which is provided with a regulating valve.

Regarding the change in the activity of MgO on the inner winding side and the outer winding side of the coil, it is desirable to apply it to the steel sheet by changing the mixing ratio of MgO having at least two kinds of activity differences. The MgO 2 activity in the present invention means citric acid activity (CAA), and is defined as follows. Citric acid activity is a hydration rate measurement of magnesium oxide,
It 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 at 10 seconds. By mechanical stirring, when the inner diameter of the bottle is 6 cm,
Make a vortex with a depth of about 2 cm 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.

Since the coating apparatus of the present invention is constructed as described above, there is at least two types of MgO having different activities depending on the winding position of the steel strip from the nozzle of the roll coater. By supplying with stirring, MgO 2 having a predetermined average activity can be easily applied.

[0012]

[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.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

In FIG. 2, 1 is a winder, 2 is a drying furnace, 3 is a coater roll, 4 is a coater roll reduction device, 5 is an MgO supply nozzle, 6 is an MgO flow rate adjusting valve, and 7 is a computing unit. The controller 8 gives an instruction to control the pressure amount of the coater roll according to the coil diameter, and 8 also gives an instruction to change and control the balance of the MgO brands A and B according to the coil diameter by a computing unit.

[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.

[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 coiler 2 drying oven 3 coater rolls 4 coater roll reduction mechanism 5 MgO supply nozzle 6 Flow control valve 7 arithmetic unit 8 arithmetic unit

Claims (3)

[Claims] 1. An annealing separator is applied to a grain-oriented silicon steel sheet,
When wound in a coil shape and subjected to final annealing, a thick coating layer of MgO with a low average activity is formed in the area on the inner coil side, and then on the outer coil side, it is more averaged than on the inner coil side. A method for applying an annealing separator for a grain-oriented silicon steel strip, which comprises forming a thin coating layer of MgO 2 having high activity. 2. A method for applying an annealing separator for a grain-oriented silicon steel strip according to claim 1, wherein the mixing ratio of at least two kinds of MgO having different activities is changed and the mixture is applied to the steel sheet. . 3. An apparatus for applying an annealing separator for a grain-oriented silicon steel sheet, which is equipped with a roll coater, followed by a drying furnace and a coiler, is equipped with a nozzle connected to at least two types of MgO agitation supply systems having different activities. A coater roll reduction mechanism that faces the roll coater unit and adjusts the opening of the coater roll based on the value of the coil diameter measuring device in the coiler, and a flow rate adjusting valve that adjusts the flow rate of at least two kinds of MgO, respectively. An apparatus for applying an annealing separator for a directional silicon steel strip, characterized by being provided with.