JPH10204542A - Production of grain oriented silicon steel sheet small in side strain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remarkably reduce the occurrence of strains in the edge part of a coil on the side to be contacted with a pedestal of the coil in a box type annealing furnace by secondarily recrystallizing the edge part of the coil on the side to be contacted with the pedestal of the coil by finish annealing simultaneously at the same time as the center part of the width direction on the coil or at the time earier than that prior to finish annealing in the box time annealing furnace. SOLUTION: As for a means of secondarily recrystallizing the edge part of a coil on the sice to be contacted with a pedestal of the coil in a box type annealing furnace at the same time as the center part of the width direction on the coil or at the time earier than that by finish annealing, e.g. the edge part of a decarburized and annealed sheet on the side to be contacted with the pedestal of the coil is applied with prestrains by 0.1 to 5% prior to the finish annealing. The region to be applied with prestrains is regulated to about 5 to 100mm from the edge part of the coil. In this way, the generation of strains in the edge part of the coil is advantageously evaded to remarkably improve the yield of the product, and since voids are hard to be generated at the time of lamination, its magnetic properties can be improved.

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 silicon steel sheet, and more particularly to a coil end portion on a side in contact with a coil cradle, which is a concern when finish annealing a grain-oriented silicon steel sheet in a coil state. This is a proposal for a technique for effectively reducing the occurrence of distortion in the.

[0002]

2. Description of the Related Art A grain-oriented silicon steel sheet is prepared by subjecting a hot-rolled sheet prepared to a predetermined composition to cold rolling one or more times with intermediate annealing, followed by decarburizing annealing and then annealing separation. It is manufactured by applying and drying the agent, winding it up in a coil shape under the application of winding tension, and then performing finish annealing in a predetermined atmosphere gas. In the above-mentioned finish annealing, the coil is placed in an annealing furnace with its winding axis being perpendicular to the upper surface of the coil holder, and the coil is placed at a high temperature for a long time. Distortion called "side distortion" occurs at the end. This tendency is especially true when the thickness is 0.
Mostly used for thin materials of 30mm or less. The distortion of the coil side edge is
Since the grain-oriented silicon steel sheets are used in a laminated state, it becomes a major obstacle in both magnetic properties and workability. Therefore, it is necessary to reduce such side edge distortion as much as possible.

Conventionally, as a measure for reducing the distortion of the coil side edge, for example, in Japanese Patent Application Laid-Open No. 55-110721, the amount of an annealing separator applied before box annealing is increased at the coil side edge. Has proposed a method of reducing the deformation of the side edge. However, if the amount of the annealing separating agent at the side edge of the coil is large, the magnetic properties at the end are likely to deteriorate. In addition, when the amount of the annealing separator is large, there is a tendency that a film defect tends to occur in a product. Also, in Japanese Patent Application Laid-Open No. 58-61231, a base plate made of the same material as the steel coil to be annealed is placed on a coil receiving stand, and the steel coil is disposed thereon, so that the occurrence of distortion at the lower end of the steel coil is reduced. Suggesting ways to prevent it. In this method, when the material to be treated is silicon steel, the material of the sole plate is also Si steel,
Ferritic steels such as Si steels have very low hot strength at high temperatures, and as a result, the coil end faces easily bite into the bottom plate during finish annealing at high temperatures, so that the coil and the bottom plate are restrained. For this reason, when the coil and the floor plate make different movements, distortion also occurs. Further, Japanese Unexamined Patent Publication No.
Japanese Patent No. 6526 proposes a method in which a hoop coil wound tighter than the coil is installed between the coil and the coil receiver. This method is also effective, but
Since hoop coils buckle after only a few annealings, they require frequent replacement, and the cost rise is remarkable.
When the buckling of the hoop coil occurs during annealing, there is a problem that a large distortion is generated in the product coil. Furthermore, Japanese Patent Application Laid-Open No. 2-97622 proposes a method for preventing the occurrence of distortion by setting the grain size of the coil end surface before annealing to 15 μm or more. Although this method can reduce the buckling distortion of the lower end face of the coil,
On the contrary, it was often found that the coil shape was rather deteriorated. There is also a problem that the magnetic properties of the coil ends are significantly deteriorated. Further, Japanese Patent Application Laid-Open No.
In US Pat. No. 9353, the distance between the coil and the coil receiver is
A method of performing high-temperature finish annealing in a state in which a steel material containing 0.2 wt% or more of C and having a transformation point is interposed as a bottom plate has been proposed. Although this method also shows a considerable strain reduction effect, the component design (for example, Al
System) was not very effective.

[0004]

As described above, each of the conventional methods has had a considerable problem in practical use. The present invention advantageously solves the above problems, and advantageously avoids the occurrence of distortion at the lower end of the coil, which is a concern in high-temperature finish annealing performed in a state wound on a coil, and furthermore, product yield. Another object of the present invention is to propose a method for manufacturing a grain-oriented silicon steel sheet that can significantly improve the magnetic characteristics because it is difficult to form a gap at the time of lamination when being incorporated in a transformer.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a silicon-containing steel slab is hot-rolled, subjected to one or two or more cold-rolling steps including intermediate annealing, and then, after decarburizing annealing, MgO is removed. After applying the annealing separating agent as a main component, in a method for producing a grain-oriented silicon steel sheet comprising a series of steps of performing a finish annealing in a box-type annealing furnace, the side of the side in contact with the coil cradle of the box-type annealing furnace A means for performing secondary recrystallization by finish annealing at the same time as or earlier than the center of the coil width direction with the coil width direction center, prior to this finish annealing. It is a manufacturing method. Here, means for secondary recrystallizing the coil end on the side in contact with the coil receiver at the same time as or earlier than the center in the coil width direction includes, for example,
0.1 to 0.1 mm at the end of the decarburized annealed plate
A pre-strain of 5% may be applied prior to finish annealing.

[0006] The inventors of the present invention have studied in detail the mechanism of distortion generation at the coil end during finish annealing. First, the coil was pulled out of the annealing furnace at each temperature during the finish annealing to examine when the coil ends were strained. As a result, the following became clear. In other words, it is clear that the secondary end of the secondary recrystallization is slower at the coil end than at the center of the coil, and that the amount of strain entering the coil edge is small in the region where the secondary recrystallization start temperature is low even at the coil edge It became.

[0007] For this reason, the strength of silicon steel at high temperatures was measured in order to further research in the laboratory. As the material for this experiment, standard Si: 3.25 wt%, Mn: 0.07
A decarburized annealed plate was prepared as a component containing wt% and S: 0.020 wt%. Then, an annealing separator containing MgO as a main component is applied to the surface, and then subjected to finish annealing in a hydrogen atmosphere at 10 ° C./hr and holding at 1200 ° C. for 10 hr to perform secondary recrystallization. A secondary recrystallized plate comprising secondary recrystallized grains having a size of about 7 mm was obtained. On the other hand, a decarburized annealed plate having the same composition as the secondary recrystallized plate was used, and after applying an annealing separator in the same manner, a plate rapidly heated at 50 ° C / s and annealed at 1200 ° C for 10 hours was also prepared. . It is clear from past knowledge that such rapid heating does not cause secondary recrystallization. As a result, the average particle size of this plate was about 1 mm. Below this,
The plate obtained in this way is called a secondary recrystallization defective plate.

Here, the strength was measured at each temperature using the decarburized annealed plate, the secondary recrystallized plate obtained by the above-described method, and the secondary recrystallized defective plate. The result is shown in FIG. It is newly found from FIG. 1 that the strength at room temperature increases in the order of decarburized annealed sheet> defective secondary recrystallization sheet> secondary recrystallized sheet, whereas secondary recrystallized sheet at 900 ° C or higher. > Defective secondary recrystallization plate> decarburized annealed plate.

This phenomenon can be explained as follows. In a low temperature region such as room temperature, the strength of the grain boundary is high, and the greater the grain boundary area, the higher the strength of the sheet. That is,
The finer the grain, the higher the grain boundary area per unit volume and thus the higher the strength, and the higher the strength in the order of decarburized annealed sheet> defective secondary recrystallization sheet> secondary recrystallized sheet. On the other hand, at a high temperature, the grain boundary strength decreases, and grain boundary sliding easily occurs. Therefore, the smaller the grain boundary area per unit volume, that is, the larger the grain size, the higher the strength. For this reason, on the high temperature side, it is considered that the strength increases in the order of the secondary recrystallized plate> the poor secondary recrystallization plate> the decarburized annealed plate.

From the above, the cause of the distortion at the coil end during the finish annealing is considered as follows. The start of secondary recrystallization is slower at the coil end in contact with the coil receiver than at the center in the width direction of the coil, and the state of fine grains continues up to high temperatures. Therefore, at high temperatures, grain boundary slip occurs and buckles at the coil end. This reason can explain the reason why the amount of strain entering the coil end portion is low especially when the secondary recrystallization initiation temperature is low even at the coil end portion. That is, if secondary recrystallization occurs at a low temperature also at the coil end, the strength of the coil edge is high due to the presence of secondary recrystallized grains having a high strength at a high temperature, and the coil does not buckle. From the above, it is considered that reducing the secondary recrystallization temperature at the coil edge portion to at least equal to or lower than the coil central portion is effective in reducing the side distortion.

Therefore, as a result of research and development of a method for lowering the secondary recrystallization temperature at the coil end to be equal to or lower than that of the coil center, the present invention was newly devised. The experimental contents on which the present invention is based are shown below. C: 0.06wt%, Si: 3.
5 wt%, Mn: 0.07 wt%, N: 0.0090 wt%, Se: 0.020 wt
%, Al: 0.022 wt%, Cu: 0.07 wt% and Sb: 0.020 wt%
Was adjusted in the steelmaking process to obtain a 200 mm thick slab by a normal continuous casting method. These slabs were heated in a gas furnace at 1390 ° C. for 8 hours, and then subjected to ordinary hot rolling to obtain a hot-rolled sheet having a thickness of 2.3 mm. After this,
After hot-rolled sheet annealing at 1130 ° C for 100 seconds, cold rolling was performed to a sheet thickness of 1.7 mm, followed by intermediate annealing at 1150 ° C for 30 seconds. Then, it was rolled to a final thickness of 0.22 mm. After degreasing these steel sheets, they were subjected to decarburization annealing at 820 ° C for 100 seconds. Veneers were cut from these coils, and in the laboratory, these decarburized annealed plates were rolled to give strains of various values from 0.01 to 10%. Thereafter, an annealing separator containing MgO 2 as a main component was applied and finish annealing was performed. Further, the sample was pulled out of the furnace at each temperature during the temperature rise during the finish annealing, and the secondary recrystallization behavior was observed. FIG. 2 shows the secondary recrystallization ratio at each temperature during the temperature rise in the finish annealing. From FIG. 2, it can be seen that the application of a strain of 0.1% or more lowers the secondary recrystallization temperature so that secondary recrystallization occurs even at 900 ° C.

[0012] Based on these results, after applying various strains of 0.05 to 10% to the edge (side edge) 20 mm of the actual decarburized annealing coil, the annealing separator containing MgO as a main component was added. At 1200 ° C, 10 ° C in a hydrogen atmosphere in a box-type annealing furnace.
Time finish annealing was performed. Thereafter, unreacted MgO was removed, and the strain generation depth at the coil edge was measured. Maximum strain depth at this time (Place the plate on a flat plate and place 1 mm
This refers to the length of the part to be lifted. ) Is shown in FIG. As shown in FIG. 3, a remarkable effect is observed in the range of 0.1 to 5%. Particularly preferred was a range of 0.5-3%. On the other hand, if an excessively large strain of more than 5% is applied, the coil shape deteriorates, which is rather undesirable. This cause is considered to be caused by the application of strain by rolling itself. As a result of these experimental studies, a new method for producing a grain-oriented silicon steel with reduced side strain according to the present invention has been found.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing grain-oriented silicon steel according to the present invention, a coil end portion of a box type annealing furnace which is in contact with a coil cradle is finished at the same time as or earlier than the center portion in the coil width direction. It is characterized in that means for secondary recrystallization by annealing is performed prior to this finish annealing. As a result, there is an effect that side distortion can be effectively reduced while suppressing deterioration of magnetic characteristics and shape.

The composition of the silicon-containing steel according to the present invention will be described. As the silicon steel as the starting material, any of the conventionally known component compositions is suitable, but the typical compositions are as follows. C: 0.01 to 0.10 wt% C is a component useful not only for uniform micronization of the structure during hot rolling and cold rolling but also for the development of Goss-oriented grains.
It is desirable to add 0.01 wt% or more. However, 0.10wt
%, The upper limit is preferably about 0.10 wt%, since the Goss orientation is disturbed if the content exceeds 0.1%. Si: 2.0 to 5.5 wt% Si increases the specific resistance of the steel sheet and effectively contributes to the reduction of iron loss. However, if the content exceeds 5.5 wt%, the cold-rolling property is impaired. Not only does resistance drop,
During the high-temperature final finish annealing performed for secondary recrystallization and purification, α-γ transformation causes randomization of crystal orientation,
Since a sufficient iron loss improvement effect cannot be obtained, the Si content is 2.0
It is preferably set to と す る 5.5 wt%. Mn: 0.02 to 2.5 wt% Mn needs to contain at least about 0.02 wt% in order to prevent hot embrittlement, but if it is too much, it deteriorates magnetic properties, so the upper limit is about 2.5 wt%. It is preferable to stop. In addition, the content of this range as an inhibitor
MnS and MnSe can be deposited.

In order to highly accumulate crystal grains aligned in Goss orientation by secondary recrystallization, it is essential to have an inhibitor which precipitates uniformly and finely in steel prior to secondary recrystallization. This inhibitor includes so-called MnS, Cu _2-X
Precipitate types such as S, MnSe, Cu _2-X Se and AlN, and Sn, A
There are grain boundary segregation types such as s and Sb. MnS among precipitate types
, Cu _2-X S, MnSe, in the case of Cu _2-X Se system, S, 1 kind of Se or two: 0.005 ~0.06wt% S, both Se, the secondary directional silicon steel sheet It is a useful component as an inhibitor for controlling recrystallization. From the viewpoint of securing such suppressing power, at least about 0.005 wt% is required, but if it exceeds 0.06 wt%, its effect is impaired, so the lower and upper limits should be about 0.005 wt% and 0.06 wt%, respectively. desirable. When Cu is used as an inhibitor component, the content of Cu is desirably 0.005 to 0.50% by weight.
In the case of AlN system, Al: 0.005 to 0.10 wt%, N: 0.004
-0.015 wt% The range of the contents of Al and N is also the same as that of MnS, Cu described above.
_2-X S, MnSe, Cu For the same reason as in the case of _2-X Se,
The above range is preferable. Here, the above-mentioned MnS, Cu
_{2-X S, MnSe, Cu} 2-X Se system and AlN system may be more desirable combination, respectively. Further, as a grain boundary segregation inhibitor, Sn and Sb are as follows: Sn: 0.01 to 0.25 wt%, Sb: 0.005 to
0.15 wt%, and each of these inhibitor components may be used alone or in combination. These upper limits are due to the fact that the addition of more than this lowers the saturation magnetic flux density and makes it impossible to obtain good magnetic properties. Further, conventionally known Cr, Te, Ge, As, Bi, P and the like can be added for improving magnetic properties. The preferred range for these is Cr: 0.01 to
0.15 wt%, Te, As, Ge and Bi: 0.005 to 0.1 wt%, P:
It is 0.01 to 0.2 wt%. Each of these inhibitor components may be used alone or in combination.

Next, the conditions of the manufacturing process of the present invention will be described. The silicon-containing steel slab used as a material is intended to be continuously cast or slab-rolled from an ingot, but it goes without saying that slabs pre-rolled after continuous casting are also included.

In the above-mentioned silicon-containing steel slab, it is necessary to form a solution of the inhibitor by heat treatment of the slab. In the present invention, the conditions for the solution treatment are not particularly limited, but it is desirable to heat at a temperature equal to or higher than the solubility product of each inhibitor component for 5 minutes or more by a gas furnace or an induction electric heating furnace or a combination of both. . Further, it is also possible to make the slab structure after heating fine by reducing the pressure to 20% or less during or before heating. The slab after heating is subjected to ordinary rough rolling to obtain a sheet bar, and then subjected to hot finish rolling. Next, hot-rolled sheet annealing is performed as necessary. When performing the cold rolling twice after the hot rolled sheet annealing, the first cold rolling is performed at a rolling reduction of about 5 to 50%.
Next, after intermediate annealing, final cold rolling is performed to achieve a target sheet thickness, but the final cold rolling is subjected to warm rolling or inter-pass aging treatment in a known manner to further improve the texture of primary recrystallization. Therefore, adopting it as the manufacturing method of the present invention can obtain more preferable results.
It goes without saying that a single strong cold rolling method may be performed. After the final cold rolling, it is also possible to perform a process of providing a linear groove on the surface of the steel sheet for magnetic domain refinement as is known.

The steel sheet having the final thickness obtained by the above method is subjected to primary recrystallization annealing by a known method. After this,
Prior to the finish annealing, means for secondary recrystallization of the coil end on the side in contact with the coil cradle at the same time as or earlier than the center in the coil width direction is provided. As a preferable means, the edge of the decarburized annealed plate on the side that comes into contact with the coil receiver is 0.1 to 5 mm.
Add a% prestrain. The pre-strain is desirably applied by rolling down with a roll or a press. The lower limit is set to 0.1% because if it is less than this, the effect of distortion addition does not appear. Further, if a strain of 5% or more is applied, the coil shape is deteriorated. More preferably, it is in the range of 0.5 to 3%. The pre-strain area is 5 to 5 mm from the coil side end.
It is about 100 mm.

Thereafter, an annealing separating agent is applied and a final finish annealing is performed. After the final finish annealing, after removing the unreacted annealing separator, an insulating coating is applied to the steel sheet surface to produce a product.If necessary, the steel sheet surface is mirror-finished before applying the insulating coating. Alternatively, a tension coating may be used as the insulating coating. Further, the coating baking treatment of the coating may be performed also as the flattening treatment. Further, in order to obtain an iron loss reduction effect, the steel sheet after the secondary recrystallization is subjected to a known magnetic domain refining treatment, that is, plasma jet or laser irradiation is performed on the linear region, or a linear dent region is formed by a projection roll. Alternatively, a process of providing the same may be performed.

[0020]

[Example] C: 0.07 wt%, Si: 3.2 wt%, Mn: 0.07 wt
%, S: 0.020 wt%, Al: 0.023 wt%, and N: 0.0090, with the balance being silicon steel containing iron and unavoidable impurities. After cold rolling into a 0.23 mm thick and 1200 mm wide rolled sheet by rolling, the steel sheet was annealed at 860 ° C for 140 seconds in a continuous decarburizing annealing furnace. After this, 0-8% is applied to the edge 30mm on one side of each coil.
A variety of strains in the range were applied under roll pressure. Then MgO
Was applied, and wound around a coil. Next, the coil was placed in the furnace so that the edge on the side to which the strain was applied was on the side of the coil cradle of the box type annealing furnace, and then finish annealing at 1190 ° C. for 20 hours was performed in a hydrogen atmosphere. Fig. 4 shows the results of investigation of the strain generation depth of the obtained coil.
Shown in As can be seen from the figure, the case where the distortion of 0.1 to 5% is applied to the coil edge portion can effectively suppress the generation of the distortion at the coil end portion. Further, as shown in FIG. 5, when a strain exceeding 5% is applied to the coil edge portion, it can be seen that the magnetic characteristics of this portion are deteriorated. For this reason 5%
Applying a strain exceeding the range degrades the shape and magnetic properties. As described above, by applying a strain of 0.1 to 5% to the coil edge, both the shape and the magnetic characteristics can be satisfied.

[0021]

As described above, according to the present invention, when finish-annealing a grain-oriented electrical steel sheet in a coil state, it is possible to significantly reduce the occurrence of distortion at the coil end in contact with the coil cradle.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between particle size and strength at each temperature.

FIG. 2 is a diagram showing a relationship between an applied strain and a secondary recrystallization temperature.

FIG. 3 is a diagram showing a relationship between added strain and a maximum strain depth.

FIG. 4 is a diagram showing the relationship between the total coil strain after finish annealing and the strain applied to a decarburized annealed plate.

FIG. 5 is a diagram showing a relationship between magnetic characteristics of a coil edge portion after finish annealing and an added strain amount.

Claims (2)

[Claims] After the silicon-containing slab is hot-rolled, it is subjected to one or two or more cold-rollings with intermediate annealing, and after decarburizing annealing, an annealing separator mainly composed of MgO is added. A method for producing a grain-oriented silicon steel sheet comprising a series of steps of applying and then performing a finish annealing in a box-type annealing furnace, wherein a coil end on a side in contact with a coil cradle of the box-type annealing furnace is centered in a coil width direction. A method for performing secondary recrystallization by finish annealing at the same time as or earlier than the part, prior to the finish annealing. Means for secondary recrystallizing the coil end in contact with the coil cradle at the same time as or earlier than the center portion in the coil width direction; 2. The method for producing a grain-oriented silicon steel sheet according to claim 1, wherein a pre-strain of 0.1 to 5% is applied to the end portion before the finish annealing.