JP2002266030A - 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 decreased side strain. 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 to the steel sheet and drying it and then coiling the steel sheet; and carrying out finish annealing while placing the resultant steel-sheet coil in such a way that its axis of coiling becomes vertical. In this manufacturing method, during the above finish annealing, the steel-sheet coil is placed again after it is reversed so that the respective positions of both edges in the vertical direction of the steel-sheet coil become reversed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain-oriented electrical steel sheet, and in particular, proposes a technique for suppressing the occurrence of side distortion of 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.
It is manufactured by winding a steel sheet in a coil shape after drying, and then performing finish annealing in a predetermined atmosphere gas.

[0003] In the above-mentioned finish annealing, the steel sheet coil is subjected to a high-temperature and long-time heat treatment in a state where the coil is placed on the upper surface of the coil receiving stand such that the winding axis is vertical. At the lower end of the steel coil on the side in contact with the upper surface of the coil holder, deformation is likely to occur due to the load of the steel coil itself under high temperature conditions,
Distortion called so-called “side distortion” tends to occur.

[0004] This side distortion tends to occur particularly in the case of a thin material having a thickness of 0.30 mm or less. In addition, since the grain-oriented electrical steel sheet is used in a state in which a plurality of sheets that have been sheared into the shape of an iron core are used in a laminated state, if such coil end distortion occurs, shearing becomes extremely difficult, and furthermore, the magnetic properties after lamination are further increased. A major obstacle in terms of Therefore, the coil end where such distortion has occurred is cut off after the final finish annealing. However, if the distortion is large, the yield of the product is deteriorated, so it is necessary to reduce the distortion at the coil end as much as possible. is there.

[0005] As a conventional means for reducing the side distortion of the coil end in the finish annealing, for example, Japanese Patent Application Laid-Open No. 7-4862 is known.
No. 9, publication No. 9 etc., a method of improving a base plate for placing a coil in an annealing furnace, as described in Japanese Patent Publication No. 3-33766, etc., coil winding tension And the like.

[0006] However, although these methods can reduce the side strain, the problem is that a large side strain remains as compared with the amount of cut-off at the end of the plate, which is usually required to secure a good coating state and magnetic properties. was there.

[0007] Therefore, the inventor of the present invention has determined that the steel sheet coil is subjected to high-temperature and long-time finish annealing in a state where the coil is placed on the upper surface of the coil receiving stand such that the winding axis is vertical. When the cause of occurrence was examined in detail, the following findings were obtained.

[0008] That is, the side strain generated at the end of the steel sheet coil (on the side where the self-weight is concentrated and placed on the upper surface of the coil receiving stand) of the steel sheet coil when the finish annealing is performed, is generated at the fixed temperature at the end of the steel sheet coil. It was found that the state where a constant load (self-weight of the steel sheet coil) was applied was due to creep deformation caused by long-lasting state.

Further, when the finishing annealing step was divided into two parts, a pre-step and a post-step, and the investigation was carried out, the end of the steel sheet coil where the weight of the steel sheet was concentrated was located at the end of the post-step in the relatively low temperature pre-step. It was found that a small strain, which is considered to be the starting point of creep, was introduced. Next, it is considered that creep deformation has occurred from the starting point in a post-process at which the temperature is relatively high, and as a result, it is estimated that the above-mentioned large side strain has occurred at the end of the steel sheet coil.

[0010]

SUMMARY OF THE INVENTION An object of the present invention relates to a method for manufacturing a grain-oriented electrical steel sheet, and in particular, to propose a technique for suppressing the occurrence of side strain of a grain-oriented electrical steel sheet.

[0011]

Means for Solving the Problems The inventor of the present invention has made intensive studies to solve the above-mentioned problems. As a result, during the finish annealing, the end of the steel coil where the own weight is concentrated is made different, that is, the starting point of creep occurrence It has been found that the side strain is remarkably suppressed by moving the introduction part of the minute strain considered to be the upper end part of the coil during the finish annealing, and succeeded in completing the present invention.

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,
Then, after applying and drying an annealing separating agent, winding the steel sheet in a coil shape, the steel sheet coil is placed so that its winding axis is vertical, and a series of steps of finish annealing is performed. In the manufacturing method of the electrical steel sheet, during the finish annealing,
A method for manufacturing a grain-oriented electrical steel sheet, wherein the steel sheet coil is inverted and remounted so that both end face positions in the vertical direction are reversed.

(2) The finish annealing is divided into a secondary recrystallization annealing and a purification annealing. After the secondary recrystallization annealing, the steel sheet coil is inverted and mounted as described above, and thereafter, the purification annealing is performed. The method for producing a grain-oriented electrical steel sheet according to 1).

(3) The method for producing a grain-oriented electrical steel sheet according to the above (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 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 steel sheet coil group having the same secondary recrystallization condition to purify the steel sheet coil. The method for producing a grain-oriented electrical steel sheet according to the above (2) or (3), wherein the annealing is performed by using the same continuous annealing furnace for all the steel sheets subjected to the secondary recrystallization annealing.

(5) The secondary recrystallization annealing is performed in an inert gas atmosphere by holding at 900 ° C. or lower for 30 hours or more. The purification annealing is performed in a reducing gas atmosphere at 1100 ° C. or higher.
(2), performed by holding for 10 hours or less,
(3) The method for producing a grain-oriented electrical steel sheet according to (4).

(6) When the furnace is changed from the batch annealing furnace to the 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. (3), in which the steel sheet coil is turned over as described above and then placed in a continuous annealing furnace.
(4) The method for producing a grain-oriented electrical steel sheet according to (5).

[0018]

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 if necessary, and then subjected to an acid pickling treatment. Thereafter, the sheet is subjected to one or two or more cold-rolling steps with intermediate annealing, so as to be finally finished. 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 for removing 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 method of finish annealing of the steel sheet coil, more specifically, during the finish annealing, the steel sheet coil is placed upside down so that the positions of both end faces in the vertical direction are reversed. Therefore, the occurrence of side distortion at the end of the steel sheet coil can be significantly suppressed.

The inventor investigated the coil during finish annealing, and found that even at the stage where the side strain did not appear in the early stage of finish annealing, a minute strain was found inside the steel sheet at the end where the weight of the steel sheet coil was concentrated. It was found to have occurred. It is considered that such a small strain acts as a starting point of the creep deformation in the subsequent finish annealing, and the creep deformation is increased. That is, by changing the end of the steel sheet coil where its own weight is concentrated during finish annealing, the starting point of creep deformation is reduced at the lower end of the steel sheet coil, so that the occurrence of side strain at the end of the steel sheet coil is reduced. Is considered to be suppressed as a whole.

Further, as described in Japanese Patent Publication No. 3-52521, for example, in a grain-oriented electrical steel sheet using MnSe or MnS as an inhibitor, the finish annealing is performed at {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, after the secondary recrystallization annealing, the steel sheet coil is turned upside down as described above, and thereafter,
It is preferable to perform purification annealing. Secondary recrystallization annealing is 800
At this point, no side strain appears at this point because the heating is performed at a relatively low temperature of about 900 ° C. However, as described above, even during secondary recrystallization annealing at a relatively low temperature, a small strain is generated inside the steel sheet, which acts as a starting point of creep deformation in high-temperature purification annealing, and creep deformation increases. It seems to be done. That is, by inverting the end of the steel sheet coil where its own weight is concentrated by secondary recrystallization annealing and purification annealing, the starting point of creep deformation during purification annealing is reduced at the lower end of the steel sheet coil. It is considered that the occurrence of side distortion at the end of the coil is suppressed as a whole.

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. 1 and 2, the continuous finish annealing furnace 1 is a furnace that runs on a coil cradle 4 on which a steel sheet coil 3 covered with an inner cover 2 is mounted vertically, on a circumference having a predetermined radius. The coil support 4 is provided on a floor 5 and the steel plate coil 3
Can be placed in two rows in a single stack, and the mounting position 6 of the heating device (not shown) is
Has a configuration installed above the upper end of the
In general, the furnace temperature is set to a heat pattern of two-stage heating.

However, when 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.

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 of Ar or the like, an annealing temperature of 930 ° C. or less, preferably 830 to 870 ° C., and an annealing temperature holding time of 30 ° C.
The time is preferably at least 30 hours, 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. At the time of the furnace change, one end face of the steel sheet coil was placed on the coil holder in the batch annealing furnace, whereas the other end face of the steel sheet coil was placed on the coil holder in the continuous annealing furnace. What is necessary is just to invert so that it may be placed.

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% was made to have a final thickness of 0.23 mm by twice cold rolling with intermediate annealing, then degreased, and then subjected to primary recrystallization annealing. ,
Next, the steel sheet coil wound after applying the annealing separator containing MgO as a main component was subjected to finish annealing consisting of 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, after heating to 700 ° C. in a drying N ₂ gas atmosphere, by switching the furnace atmosphere to a dry atmosphere of H ₂ gas 1200
A magnetic steel sheet was produced by performing purification annealing by holding at 10 ° C. for 10 hours. In addition, all of the above steel sheet coils,
The recrystallization temperature was 850 ° C. in each case using those manufactured in the same lot.

FIG. 3 shows a plot of the amount of side strain (mm) with respect to the length of the steel sheet drawn from the steel sheet coil. In the case of the invention shown in FIG. 3, the secondary recrystallization annealing and the purification annealing are performed by inverting the steel sheet coil and placing different ends on the coil receiving pedestal. This is the case where the same end is placed on the coil receiving base without reversing the steel sheet coil and the purification annealing is performed, and the amount of side strain is shown as a total measured at both ends in the invention example. In the conventional example, the value is measured at the end on the side mounted on the coil receiver.

From the results shown in FIG. 3, it can be seen that the inventive example has a smaller amount of side distortion than the conventional example.

[0038]

According to the method of the present invention, during the finish annealing, the steel sheet coil is inverted and placed so that the positions of both end faces in the vertical direction are reversed, so that the direction in which the side distortion is small is obtained. It has become possible to manufacture stable electrical steel sheets stably.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a conventional continuous (rotary) finish annealing furnace.

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

FIG. 3 is a diagram in which a side strain generation amount (mm) is plotted against a steel plate length (m) drawn from a steel plate coil.

[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 installation position 7 Heat insulation cover

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K033 AA02 HA01 HA03 JA04 LA01 MA00 MA01 MA02 RA04 SA02 TA02 5E041 AA02 HB09 HB11 HB19 NN17 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 performing primary recrystallization annealing, then applying and drying an annealing separating agent, winding the steel sheet in a coil shape, placing the steel sheet coil so that its winding axis is vertical, and finishing annealing. In the method for manufacturing a grain-oriented electrical steel sheet having a series of steps of applying, during finish annealing, the steel sheet coil is reversed and remounted so that the positions of both end faces in the vertical direction are reversed. Manufacturing method of grain-oriented electrical steel sheet. 2. The finish annealing is divided into a secondary recrystallization annealing and a purification annealing, and after the secondary recrystallization annealing, the steel sheet coil is inverted and mounted as described above, and thereafter, the purification annealing is performed. 3. The method for producing a grain-oriented electrical steel sheet according to item 1. 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 manufacturing 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 by holding at 900 ° C. or lower for 30 hours or more. 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 furnace is changed, and at this time, the steel sheet coil is turned over as described above, and then placed in the continuous annealing furnace.
3. The method for producing a grain-oriented electrical steel sheet according to item 1.