JP2002266028A - Method for manufacturing grain-oriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for stably manufacturing a grain-oriented silicon steel sheet having excellent film characteristics. SOLUTION: The method for manufacturing the grain-oriented silicon steel sheet has a series of steps of: hot-rolling silicon-steel stock; subjecting the resultant hot-rolled plate to cold rolling once or two or more times to final sheet thickness while performing process annealing between the cold rolling steps; subjecting the resultant steel sheet to primary recrystallization annealing which doubles as decarburization; applying a separation agent at annealing composed essentially of MgO to the steel sheet and coiling the steel sheet; and then carrying out finish annealing while placing the resultant steel-sheet coil 3 with one edge downside. In this manufacturing method, a cover 8 is provided during the finish annealing in such a way that it comes into contact with the upper edge as the other edge of the above steel-sheet coil 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet.

[0002]

2. Description of the Related Art A grain-oriented electrical steel sheet is obtained by hot-rolling an electromagnetic steel material and subjecting a hot-rolled sheet to one or intermediate annealing.
After performing cold rolling more than twice to make the final sheet thickness, perform primary recrystallization annealing also serving as decarburization, and then apply an annealing separator.
After being dried and wound up in a coil shape, the steel sheet is manufactured by a series of steps of performing finish annealing including secondary recrystallization annealing and purification annealing.

[0003] The grain-oriented electrical steel sheet is required to have not only excellent electromagnetic properties but also excellent coating properties.

[0004] Therefore, the inventor of the present invention conducted a study for improving the coating properties of the electrical steel sheet in the above-mentioned manufacturing process. As a result, during the finish annealing, particularly during the secondary recrystallization annealing, the annealing separator applied to the steel sheet surface was used. It has been found that the coating properties of a magnetic steel sheet as a product are improved by keeping moisture between the winding layers of the steel sheet coil as much as possible and suppressing the flowability between the winding layers as much as possible.

[0005] At present, there is no literature that discloses a case in which the finish annealing is optimized based on the above-described idea in order to improve the coating properties of the electromagnetic steel sheet.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a grain-oriented electrical steel sheet having excellent coating properties by providing a cover on the upper end face of a steel sheet coil layer during finish annealing, especially during secondary recrystallization annealing. It is to provide a method for stably producing a.

[0007]

Means for Solving the Problems The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and found that a cover is provided on the upper end surface of the steel sheet coil during finish annealing, preferably during secondary recrystallization annealing. If it arrange | positions, while being able to hold | maintain the water which exists between the winding layers of the said steel sheet coil, the flowability between the said winding layers can be suppressed effectively, From these results, the coating property of the electromagnetic steel sheet as a product will be improved. I found that I could do it.

That is, the gist of the present invention is as follows. (1) A hot rolled sheet obtained by hot rolling an electromagnetic steel material
After performing cold rolling twice or more with intermediate or intermediate annealing to make the final sheet thickness, perform primary recrystallization annealing also serving as decarburization,
Next, after applying an annealing separator mainly composed of MgO and winding the steel sheet into a coil, a series of steps of placing the steel sheet coil so that its winding axis is vertical and performing finish annealing is performed. In the method for manufacturing a grain-oriented electrical steel sheet having, during the finish annealing, in contact with the upper end face which is the other end face of the steel sheet coil,
A method for manufacturing a grain-oriented electrical steel sheet, comprising disposing a cover.

(2) The finish annealing step comprises a secondary recrystallization annealing step and a purification annealing step, and in the finish annealing step, a cover is provided on the upper end surface of the steel sheet coil only in the secondary recrystallization annealing step. The method for producing a grain-oriented electrical steel sheet according to the above (1).

(3) In the finish annealing, the secondary recrystallization annealing is performed in a batch-type annealing furnace, and the purification annealing is performed in a continuous-type annealing furnace. Method.

(4) When the secondary recrystallization conditions of the steel sheet coil are different, the secondary recrystallization annealing is performed in a separate batch-type annealing furnace for each of the steel sheet coils having the same secondary recrystallization condition, and purified. The method for producing a grain-oriented electrical steel sheet according to the above (1), (2) or (3), wherein the annealing is performed in the same continuous annealing furnace on all the steel sheets subjected to the secondary recrystallization annealing.

(5) The secondary recrystallization annealing is performed in an inert gas atmosphere at a temperature of 900 ° C. or lower for 30 hours or more, and the purification annealing is performed in a reducing gas atmosphere at a temperature of 1100 ° C. or higher.
The method for producing a grain-oriented electrical steel sheet according to any one of (1) to (4), wherein the method is carried out by holding for 10 hours or less.

(6) When the furnace is changed from a batch type annealing furnace to a continuous type annealing furnace in the atmosphere, the steel sheet coil is cooled to 400 ° C. or less in the batch type annealing furnace, and then the continuous type annealing furnace is used. The method for producing a grain-oriented electrical steel sheet according to any one of claims (1) to (5), wherein the furnace is replaced with a furnace.

[0014]

Next, an embodiment of a method for manufacturing a grain-oriented electrical steel sheet according to the present invention will be described. First, the electromagnetic steel material is hot-rolled. The composition of the electromagnetic steel material is not particularly limited, but as an example, C: 0.02 to 0.10%, Si: 2.0 to 4.5%, Mn: 0.05 to 0.2 by mass%.
%, And one or two of Se: and S are preferably used in a total amount of 0.01 to 0.04%.

The electromagnetic steel material (slab) can be manufactured by a known method. For example, it may be produced by melting into molten steel having a desired component composition by a converter steelmaking method or the like, and then by a continuous casting method or an ingot-bulking rolling method.

Further, the electromagnetic steel material is preferably heated to a high temperature of 1250 ° C. or more before hot rolling, usually to sufficiently dissociate and solidify the inhibitor-forming element.
Thereafter, hot rolling is performed according to a known method to obtain a hot-rolled sheet having a predetermined thickness, preferably about 1.4 to 5.0 mm.

Next, the hot-rolled sheet is subjected to hot-rolled sheet annealing as required, and then subjected to an acid pickling treatment, and then subjected to one or two or more cold-rolling steps including intermediate annealing to obtain a final product. Cold rolled sheet of thickness. The cold rolling may be performed according to a known method, and the final thickness is preferably 0.20 to 0.35 mm.

Thereafter, the cold-rolled sheet is subjected to primary recrystallization annealing also serving as decarburization in order to remove C in the steel, which adversely affects magnetic properties, and then is applied with an annealing separating agent represented by MgO. Then, after winding the steel sheet into a coil, the grain-oriented electrical steel sheet can be manufactured by subjecting the steel sheet coil to finish annealing including secondary recrystallization annealing and purification annealing.

The main features of the configuration of the present invention are as follows.
In order to optimize the finish annealing method of the steel sheet coil, more specifically, during the finish annealing, the upper end face which is the other end face of the steel sheet coil is entirely coated, and during the finish annealing, A cover 8 that covers the entire upper end surface, which is the other end surface of the steel coil, suppresses the flow of atmospheric gas between the winding layers of the steel coil and retains moisture existing between the winding layers. In this case, the coating properties of the electromagnetic steel sheet can be improved.

Before the finish annealing, the above-mentioned annealing separating agent mainly composed of MgO or the like is applied. However, since this annealing separating agent is applied in the form of a slurry, Mg is added during the slurrying.
Bonding of moisture and an annealing separator such as O occurs (hydration). This hydrated water is not lost even after drying after application and is carried between the winding layers of the steel sheet coil during the final annealing. If the hydration amount is too large, the steel sheet is oxidized and the magnetic properties deteriorate, but if it is too small, the Si formed on the steel sheet surface after decarburization annealing
O ₂ is reduced and the film properties decrease, such as a decrease in the amount of film formation and the adhesion between the film and the steel sheet.Therefore, a predetermined amount of water must be retained until the film formation stage of finish annealing. is important. Therefore, by disposing the cover 8 on the upper end surface of the steel sheet coil during the finish annealing, the flow of the atmosphere gas between the winding layers is suppressed, and the moisture of the annealing separator applied to the steel sheet surface is reduced. As a result of holding between the winding layers between them, the inventors found that the coating properties of the electromagnetic steel sheet were improved, and succeeded in completing the present invention.

As shown in FIG. 1 as an example, the cover 8 is preferably shaped so as to cover at least the winding portion of the coil end, and is preferably arranged so as to be in close contact with the upper end surface of the steel coil 3. . Although the material of the cover 8 is not particularly limited, it is preferable that the material is not fused to the steel sheet coil 3 during the purification annealing, and examples thereof include a ceramic plate and a ceramic fiber sheet.

In addition, as described in Japanese Patent Publication No. 3-52521, for example, in a grain-oriented electrical steel sheet using MnSe and MnS as inhibitors, the finish annealing is performed in the range of {110} <0.
01> secondary recrystallization annealing, which requires relatively low-temperature and long-term treatment to develop secondary recrystallized grains aligned with the orientation, and removes S, Se, N, etc. in steel harmful to iron loss. To remove
In general, the heat treatment is performed in a so-called two-stage heating pattern, which is divided into two processes, namely, purification annealing which requires a relatively high-temperature and short-time treatment.

In this case, during the secondary recrystallization annealing, a cover 8 is provided on the upper surface of the steel coil to evaporate moisture existing between the winding layers of the steel coil and to release atmospheric gas between the winding layers. In addition to suppressing both flowability, during the purification annealing, it is possible to remove the cover 8 and increase the flowability of the atmosphere gas between the wound layers, as opposed to the case of the secondary recrystallization annealing, to improve the coating properties of the magnetic steel sheet. Was further improved.

Here, as described above, it is necessary to retain moisture by disposing the cover 8 until the film formation is started in the purification annealing step, and in particular, in the secondary recrystallization annealing step, usually a long time is required. Since the annealing is performed, it is necessary to dispose the cover 8 for retaining moisture at least during the annealing.
In the purification annealing, the cover 8 may be continuously provided. However, after forming the coating, increasing the flow of the atmosphere gas between the layers can shorten the time required for purifying the inhibitor component by the purification annealing. Therefore, it is preferable to remove the cover 8 in the purification annealing step.

Therefore, in the present invention, the finish annealing step comprises a secondary recrystallization annealing step and a purification annealing step,
In the finish annealing step, it is preferable to dispose a cover 8 on the upper end surface of the steel sheet coil 3 only in the secondary recrystallization annealing step.

By the way, in the conventional finish annealing, both the secondary recrystallization annealing and the purification annealing are performed in the same continuous annealing furnace. As shown in FIGS. 2 and 3, the continuous finish annealing furnace 1 is a furnace that travels on a coil cradle 4 on which a steel coil 3 covered with an inner cover 2 is mounted vertically, on a circumference having a predetermined radius. The coil receiver 4 is provided on the floor 5 so that the steel plate coils 3 can be placed in two rows in a single-stage stack. The mounting position 6 of the heating device (not shown) is It is configured to be installed above the upper end of the coil 3 and the furnace temperature is generally set to a two-stage heating heat pattern.

However, in the case where both the secondary recrystallization annealing and the purification annealing are performed in the same continuous annealing furnace, a heat pattern is formed in advance from the inlet to the outlet of the furnace, and the coil is continuously formed therein. Therefore, it is difficult to accurately control the furnace temperature (heat pattern) to an optimum temperature for each steel type, and it is difficult to manufacture an electromagnetic steel sheet having stable electromagnetic characteristics.
In addition, since the processing time of the secondary recrystallization annealing is much longer than the processing time of the purification annealing, the residence time of each coil in the continuous annealing furnace becomes longer, which is an advantage of the continuous annealing furnace. The superior productivity could not be fully utilized.

Further, when both the secondary recrystallization annealing and the purification annealing were performed in the same continuous annealing furnace by the two-step heat pattern, the cover could not be attached to or detached from the upper end surface of the steel sheet coil.

Therefore, according to the present invention, in the finish annealing, 2
The next recrystallization annealing is preferably performed in a batch annealing furnace capable of controlling the temperature accurately, and the purification annealing is preferably performed in a continuous annealing furnace capable of mass processing. That is, the secondary recrystallization annealing is performed in a batch annealing furnace capable of controlling the temperature accurately, and the secondary recrystallization conditions such as the secondary recrystallization temperature, the holding time, and the furnace atmosphere can be optimally set. , {110} <001>
Able to develop secondary recrystallized grains aligned in the orientation sufficiently, and to process a large number of steel sheet coils by performing only purification annealing in a continuous annealing furnace with no difference in annealing conditions for each steel type This makes it possible to efficiently and stably produce electrical steel sheets with remarkably excellent electromagnetic characteristics compared to the conventional manufacturing method in which both secondary recrystallization annealing and purification annealing are performed in a continuous annealing furnace. can do.

Further, when secondary recrystallization conditions such as a secondary recrystallization temperature, a holding time, and an atmosphere in a furnace, particularly a steel coil of a plurality of steel types having different secondary recrystallization temperatures are subjected to finish annealing, the following conditions are required.
The secondary recrystallization annealing is performed in a separate batch annealing furnace set to the optimum furnace temperature for each steel sheet coil group having the same secondary recrystallization conditions, and the purification annealing is performed in the secondary recrystallization annealing. If all the steel sheet coils are combined in the same continuous annealing furnace, the advantages of the batch annealing furnace and the continuous annealing furnace can be maximized as described above.

In the secondary recrystallization annealing, the atmosphere in the furnace is changed to N
_2, an inert gas atmosphere such as Ar, the annealing temperature 930 ° C. or less, preferably set to eight hundred and thirty to eight hundred seventy ° C., the retention time of the annealing temperature
It is preferably 30 hours or more, preferably 30 to 80 hours. If the annealing temperature exceeds 930 ° C., the formation and purification of the film to be performed by the purification annealing progress, so that the electromagnetic characteristics are deteriorated and the film characteristics tend to be deteriorated.

Further, in the purification annealing, the atmosphere in the furnace is H ₂ , N ₂
+ H ₂ or other reducing gas atmosphere, the annealing temperature is 1100 ° C. or more, preferably 1150 to 1200 ° C., and the annealing temperature holding time is
It is preferably 10 hours or less, preferably 3 to 10 hours. If the annealing temperature is lower than 1150 ° C., the film cannot be formed or purified sufficiently.

Further, when the furnace is changed from a batch type annealing furnace to a continuous type annealing furnace in a non-oxidizing atmosphere, the steel sheet coil heated and held in the batch type annealing furnace can be converted into a continuous type annealing furnace without cooling. Movement is preferable in that the amount of energy for heating the steel sheet coil in the purification annealing is reduced.However, when the furnace change is performed in the air, the steel sheet coil is batch-processed to prevent bluing and oxidation. It is preferable that the furnace is cooled to 400 ° C. or lower in the annealing furnace, and then the furnace is changed to a continuous annealing furnace. In the case of the batch type annealing furnace, when the cover is attached to the upper end surface of the steel sheet coil, and in the case of the continuous annealing furnace, the cover attached to the upper end surface of the steel sheet coil is removed, it may be performed at the time of the above furnace change.

The above is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0035]

[Example] C: 0.045 mass%, Si: 3.30 mass%, Mn: 0.
Silicon steel having a composition containing 087 mass% and Se: 0.025 mass% is subjected to final cold rolling to a thickness of 0.23 mm by twice cold rolling with intermediary annealing, followed by degreasing and then primary recrystallization. Annealing was performed, and then an annealing separator containing MgO as a main component was applied, and each of the coiled steel coils was subjected to finish annealing including secondary recrystallization annealing and purification annealing. The secondary recrystallization annealing is performed in a batch type annealing furnace at 850 ° C. for 50 hours in a dry N ₂ gas atmosphere, then cooled to 200 ° C., left in an air atmosphere for 4 hours, and then continuously. after Rokae the (rotary) annealing furnace, in a dry N ₂ atmosphere 700
After heating to ° C., the furnace atmosphere was switched to a dry H ₂ gas atmosphere, and purification annealing was performed at 1200 ° C. for 10 hours to produce an electrical steel sheet. The electromagnetic properties (iron loss W _17/50 and magnetic flux density B ₈ ) and coating properties (coat appearance,
(Peeling test) was evaluated. The peel test was evaluated based on the degree of peeling when cellotape (registered trademark) was applied to the surface of the film and peeled off. Table 1 shows the evaluation results. In addition, all of the above steel sheet coils were manufactured in the same lot, and the recrystallization temperature was 850 ° C. in each case.
In addition, inventive example 1 in Table 1 shows the case where the upper end surface of the steel sheet coil was kept covered during the time between the secondary recrystallization annealing and the purification annealing. When the cover is placed on the upper end of the steel coil only and the cover is removed from the upper end of the steel coil during the purification annealing, the comparative example covers the upper end of the steel coil during the secondary recrystallization annealing and the purification annealing. This is the case when it cannot be covered.

[0036]

[Table 1]

From the results shown in Table 1, Inventive Examples 1 and 2 show that
It can be seen that the film properties are superior to the comparative example. In addition, Invention Example 2 has more excellent film properties than Invention Example 1.

[0038]

According to the method of the present invention, by providing a cover on the upper end surface of the steel sheet coil layer during finish annealing, particularly during secondary recrystallization annealing, it is possible to stabilize a grain-oriented electrical steel sheet having excellent coating characteristics. It became possible to manufacture.

[Brief description of the drawings]

FIG. 1 is a diagram showing a shape of a cover according to the present invention and a state when the cover is put on an upper end surface of a steel sheet coil.

FIG. 2 is a schematic plan view of a conventional continuous (rotary) finish annealing furnace.

FIG. 3 is a cross-sectional view taken along line II of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous (rotary) annealing furnace 2 Inner cover 3 Steel plate coil 4 Coil pedestal 5 Hearth 6 Heating device attachment position 7 Heat insulation cover 8 Cover

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K033 AA02 HA01 HA03 JA04 LA01 MA00 MA01 MA02 RA04 SA02 TA02 UA02 5E041 AA02 HB09 HB11 HB19 NN18

Claims (6)

[Claims] 1. A hot-rolled sheet obtained by hot-rolling an electromagnetic steel material is subjected to one or two or more cold-rolling steps with intermediate annealing to a final sheet thickness, which also serves as decarburization. After applying the primary recrystallization annealing, and then applying an annealing separator mainly composed of MgO and winding the steel sheet into a coil, the steel sheet coil is placed so that one end face thereof faces downward. A method for producing a grain-oriented electrical steel sheet having a series of steps of performing a finish annealing, wherein during the finish annealing, the grain-oriented electrical steel sheet is provided in contact with an upper end face which is the other end face of the steel sheet coil, and a cover is provided. Manufacturing method. 2. The finish annealing step comprises a secondary recrystallization annealing step and a purification annealing step, and in the finish annealing step,
The method for manufacturing a grain-oriented electrical steel sheet according to claim 1, wherein a cover is provided on an upper end surface of the steel sheet coil only in a secondary recrystallization annealing step. 3. The method for producing a grain-oriented electrical steel sheet according to claim 2, wherein, in the finish annealing, the secondary recrystallization annealing is performed in a batch annealing furnace, and the purification annealing is performed in a continuous annealing furnace. 4. When the steel sheet coil has different secondary recrystallization conditions, the secondary recrystallization annealing is performed in a separate batch-type annealing furnace for each steel sheet coil group having the same secondary recrystallization condition. The method for producing a grain-oriented electrical steel sheet according to claim 2 or 3, wherein all the steel sheets subjected to the secondary recrystallization annealing are subjected to the same continuous annealing furnace. 5. The secondary recrystallization annealing is performed in an inert gas atmosphere at 900 ° C. or lower for 30 hours or more, and the purification annealing is performed in a reducing gas atmosphere at 1100 ° C. or higher and 10 hours or less. The method for producing a grain-oriented electrical steel sheet according to claim 2, wherein the method is performed. 6. When the furnace is changed from a batch annealing furnace to a continuous annealing furnace in the atmosphere, the steel sheet coil is cooled to 400 ° C. or less in the batch annealing furnace, and then the continuous annealing furnace is cooled. The method for producing a grain-oriented electrical steel sheet according to claim 3, wherein the furnace is replaced.