JPS6376819A - Grain-oriented electrical steel sheet having small iron loss and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture an electrical steel sheet having a more significant iron loss reducing effect and causing no deterioration in the iron loss characteristics even by annealing at high temp. by making linear grooves by which groups of fine recrystallized grains are not formed during strain relief annealing in a grain-oriented electrical steel sheet subjected to finish annealing. CONSTITUTION:A grain-oriented electrical steel sheet subjected to finish annealing, contg. 2.0-4.5wt% Si and having a forsterite film on the surface is prepd. The forsterite film on the surface of the steel sheet is linearly removed within the angle range of + or -45 deg. having a base line in a direction perpendicular to the rolling direction under conditions under which <=30% strain is produced in the base iron. The steel sheet is electrolytically or chemically etched through the film to make linear grooves in the base iron. Thus, the desired electrical steel sheet having linear grooves which reach the base iron within the angle range of + or -45 deg. is obtd. High strain parts in which groups of fine recrystallized grains are formed during strain relief annealing are not present around the linear grooves.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a low core loss grain-oriented electrical steel sheet used mainly as an iron core for transformers and other electrical equipment, and a method for manufacturing the same, and in particular to a method for manufacturing the same. This is intended to prevent deterioration of characteristics.

(Prior Art) Grain-oriented electrical steel sheets are mainly used as iron cores for transformers and other electrical equipment, and are required to have good magnetic properties. In particular, it is important that the energy loss, that is, iron loss, be low when used as an iron core, and as the energy situation has worsened in recent years, the demand for electrical steel sheets with particularly low iron loss is increasing further.

By the way, conventionally, in order to reduce iron loss, the crystal orientation has been aligned to a higher degree with the (110) (001) orientation.
Various attempts have been made to increase the St content, thereby increasing the electrical resistance of the steel sheet, and to reduce impurities. However, reduction of iron loss by these metallurgical methods has almost reached its limit due to recent technological improvements.

Therefore, various methods for improving iron loss other than metallurgical methods have been proposed. For example, Japanese Patent Publication No. 5B-5968 describes a method for reducing iron loss by introducing microscopic strain in a line by pressing small balls or the like onto the surface of a grain-oriented electrical steel sheet that has been finish annealed. -2252 publication has the following information:
A method of irradiating the surface of a finished annealed steel plate with a laser has been proposed.

However, although these methods are effective as a means of reducing iron loss, they all have the fatal flaw that strain relief annealing causes deterioration of iron loss. It is not used as a material for iron cores.

Special Publication No. 50-3567 as a technology capable of stress relief annealing
Publication No. 9 proposes a method to reduce and improve iron loss by scratching or scratching the steel plate, and also by scribing with a knife or the like in a direction perpendicular to the rolling direction of the finish annealed steel plate. The knowledge that iron loss can be reduced is also disclosed.

Furthermore, JP-A-56-130454 and JP-A-61
Japanese Patent No. 117218 proposes a method of reducing iron loss by utilizing fine recrystallized grain groups produced by introducing strain into a finish annealed steel plate and annealing it.

(Problems to be Solved by the Invention) The above method utilizes the fact that strong strain is locally applied to the steel plate, and the strain introduced area forms fine recrystallized grain groups during annealing at approximately 800°C. However, this method did not achieve a sufficiently satisfactory iron loss reduction effect, and had the disadvantage that such fine recrystallized grains would grow at high temperatures of 1000°C or higher, leading to deterioration of iron loss. .

By the way, wound cores are usually subjected to strain relief annealing at about 700 to 900°C to remove processing strain after forming the core, but in some cases, it is expected that the temperature will locally reach 1000°C or higher, so Materials whose properties deteriorate when annealed at high temperatures of ℃ or higher lack reliability as materials for wound cores.

Furthermore, if the steel plates are scratched or scribed with a knife or the like, severe unevenness or burrs will occur around the scribes, resulting in a problem of deterioration of the space factor when the steel plates are laminated.

This invention advantageously solves the above problems, and it goes without saying that compared to conventional materials, it is possible to improve the iron loss properties after normal strain relief annealing at about 800℃, and even at high temperatures of 1000℃ or more. The purpose of the present invention is to propose a low core loss grain-oriented electrical steel sheet that does not cause deterioration of core loss characteristics even when annealed, together with an advantageous manufacturing method thereof.

(Means for Solving the Problems) Now, as a result of intensive research to solve the above problems, the inventors found that for finish annealed grain-oriented electrical steel sheets,
By forming linear grooves that do not produce fine recrystallized grain groups during strain relief annealing, the effect of reducing core loss is even more excellent, and the characteristics are maintained even after strain relief annealing at high temperatures of 1000°C or higher. They discovered that it is possible to obtain grain-oriented electrical steel sheets with low core loss that do not deteriorate, and were able to complete this invention.

This invention is based on the above knowledge.

That is, the gist of the present invention is as follows.

1. A finish-annealed grain-oriented electrical steel sheet containing 2.0 to 4.5% Si by weight and having a forsterite coating on the surface, the surface of the steel sheet having a direction perpendicular to the rolling direction. It has a linear groove that extends to the base iron within an angular range of ±45'' from the reference line, and around this linear groove,
A low core loss grain-oriented electrical steel sheet (first invention), characterized in that there is no high strain introduction part that causes the formation of fine recrystallized grain groups during strain relief annealing.

2. A finish-annealed grain-oriented electrical steel sheet containing 2.0 to 4.5% Si by weight and having a forsterite coating on the surface, the surface of the steel sheet having a direction perpendicular to the rolling direction. It has a linear groove that extends to the base iron within an angular range of ±45'' from the reference line, and around this linear groove,
There is no high strain introduction area that causes the formation of fine recrystallized grain groups during strain relief annealing, and furthermore, on the forsterite coating,
A low core loss grain-oriented electrical steel sheet (second invention), characterized in that it is provided with an overcoat coating having a film-deficient region over the same region as the film.

3. A finish-annealed grain-oriented electrical steel sheet containing 2.0 to 4.5% Si by weight and having a forsterite coating on the surface, the surface of the steel sheet having a direction perpendicular to the rolling direction. There is a linear groove that extends to the base iron within an angular range of ±45@ as a reference line, and around this linear groove,
There is no high strain introduction area that causes the formation of fine recrystallized grain groups during strain relief annealing, and furthermore, on the forsterite coating,
Low core loss grain-oriented electrical steel sheet (No. 3) characterized by having a top coat applied over the entire surface of the steel sheet.
invention).

4. A silicon steel slab containing 2.0 to 4.5% St by weight was hot-capture rolled and then cold-rolled once or twice with intermediate annealing to obtain the final thickness. After that, decarburization and primary recrystallization annealing were performed, after which an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and final annealing was performed to produce a grain-oriented electrical steel sheet with a forsterite coating. , the amount of strain introduced into the base steel within an angular range of ±45° using the direction perpendicular to the rolling direction as a reference line for the forsterite coating on the surface of the grain-oriented electrical steel sheet is 30.
% or less, and then electrolytically or chemically etched to form linear grooves in the base steel (fourth invention).
.

5. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. Afterwards, decarburization and primary recrystallization annealing are performed, and then the Mg
When applying the annealing separator mainly composed of O, a cotton-like forsterite film-free area is defined within an angular range of ±45° using the direction perpendicular to the rolling direction as a reference line, and then final finishing is performed. Directional electromagnetic t+i with a forsterite coating that has been annealed and has a linear coating defect area
A method for producing a low core loss grain-oriented electrical steel sheet (No. 5 inventions).

6. A silicon steel slab containing 2.0 to 4.5% St by weight was hot rolled and then cold rolled once or twice with intermediate annealing to obtain the final thickness. Afterwards, decarburization and primary recrystallization annealing are performed, after which an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, final annealing is performed, and a top coat is then applied to form a forsterite film and a top coat. After making a grain-oriented electrical steel sheet with an insulating coating, the forsterite coating and top insulation coating on the surface of the grain-oriented electrical steel sheet are
±45° from the reference line perpendicular to the rolling direction
The process consists of linearly removing the grooves within the angular range of 30% or less under the condition that the amount of strain introduced into the base metal is 30% or less, and then applying electrolytic or chemical etching to form linear grooves in the base metal.
A method for manufacturing a grain-oriented electrical steel sheet with low core loss (seventh invention).

7. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. After that, decarburization and primary recrystallization annealing were performed, after which an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and final annealing was performed to produce a grain-oriented electrical steel sheet with a forsterite coating. , the forsterite coating on the surface of the grain-oriented electrical steel sheet is
Within the angle range of 45", the amount of strain introduced into the base steel is 30%
A low core loss directional electromagnetic method consisting of removing the steel in a linear manner under the following conditions, then electrolytically or chemically etching it to form a linear groove in the base steel, and then applying an overcoating treatment to the entire surface of the steel plate. Method for manufacturing a steel plate (seventh invention).

8. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. Afterwards, decarburization and primary recrystallization annealing are performed, and then M
When applying the annealing separator containing go as the main component, a linear forsterite coating-free area is defined within an angular range of ±45'' using the direction perpendicular to the rolling direction as a reference line, and then final finishing is performed. After annealing to produce a grain-oriented electrical steel sheet with a forsterite coating having a linear coating defect area, electrolytic or chemical etching is performed on the base metal part in the forsterite coating defect area to form linear grooves in the base steel. A method for manufacturing a grain-oriented electrical steel sheet with low core loss (eighth invention), which comprises forming a top coat on the entire surface of the steel sheet.

9. A silicon field slab containing 2.0 to 445% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to obtain the final thickness. Decarburization and primary recrystallization annealing are performed, then an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, final annealing is performed, and then a top coating is applied to form a forsterite film and a top insulating coating. After making a grain-oriented electrical steel sheet, the forsterite coating and the top insulation coating on the surface of the grain-oriented electrical steel sheet are applied to the base steel within an angle range of ±45'' with the direction perpendicular to the rolling direction as a reference line. It is removed in a linear manner under the condition that the amount of strain introduced is 30% or less, and then electrolytic or chemical etching is performed to form a linear groove in the base steel, and then only the coating defect area or s + vi, the entire surface, A method for manufacturing a grain-oriented electrical steel sheet with low core loss, which comprises reapplying a top coat (ninth invention).

Below, the experimental results that led to this invention will be explained.

The inventors first manufactured a board with a thickness of 0.23cm, B, o 1.91T, 14+tys manufactured using the same ingredients and the same manufacturing process.
. Two Epstein specimens of grain-oriented electrical steel sheets that had been finish annealed at 0.91/kg were prepared, and one specimen had the following (
The other sheet was subjected to the treatment shown in (b).

(A pulsed laser beam having an energy density of 7 cm'' was linearly irradiated to remove a portion of the coating and base metal, and then a linear groove was formed by pickling.

fb) After linear irradiation with pulsed laser light having an energy density of 0.8 J/cm'' to locally remove only the coating, linear grooves were formed by pickling.

The grooves had a width of 100 μm and a depth of 15 μm, and were formed at intervals of 7 grooves in a direction perpendicular to the rolling direction.

Next, these specimens were subjected to strain relief annealing at 800°C for 3 hours in N
T).

As a result, although the composition, plate thickness, B10, and groove shape are all the same, (a) is Mu/S@0.
82W/kg, (b) is 'lht/so 0.15H
/kg, and although the iron loss was reduced by forming the grooves in all specimens, it was found that the material treated with the grooves showed a lower iron loss value.

Next, FIG. 1 shows the relationship between the annealing temperature and 11 shoes 5° when these specimens were annealed at a higher temperature.

The properties of the specimen in (b) hardly changed even when the annealing temperature was increased, whereas the properties of the material in (a) significantly deteriorated after annealing at 1000°C, and at 1180°C, the properties remained unchanged even when the annealing temperature was increased. It has deteriorated to almost the same level.

Therefore, the inventors conducted a detailed investigation into the cause of the difference in iron loss values despite the same composition, plate thickness, 8111, groove shape, etc., and found (a) After strain relief annealing at 800℃, the specimen of
It became clear that fine recrystallized grain groups were observed around the grooves, and that they grew as the annealing temperature increased. On the other hand, it has a better iron loss value than the sample in (a), and there is no deterioration in properties even after high-temperature annealing at 1000°C or higher (b)
) such fine recrystallized grain groups were not observed after strain relief annealing.

When experiments similar to those described above were conducted on a number of other materials, similar results were obtained in all cases.

Next, the inventor prepared two types of finish-annealed grain-oriented electrical steel sheets A and B, each having a thickness of 0.23 mm as shown below. A: Steel sheet with no local forsterite coating.

B: A steel plate with a forsterite film and a top coat, from which these films have been locally removed.

Steel plate A was manufactured by the method disclosed in JP-A-60-92487. That is, it was manufactured by printing an oil-based paint locally on a steel plate after decarburization annealing, and then applying a separating agent containing MgO as a main component to the entire surface of the steel plate. The defective region of the forsterite coating is a linear region in a direction perpendicular to the rolling direction, and its width is 0.1 fi, and the interval between the linear regions is 6 squares.

In addition, steel plate B is a steel plate with a top coat applied to the steel plate after finish annealing, and the forsterite film and top coat are locally removed using molten NaOH. The magnetic properties of these steel plates were then measured using a veneer magnetic testing device with a width of 150 mm and a length of 280 mm, followed by electrolytic etching as described below.

Both steel plates A and B were placed in an NaCl electrolyte as they were, faced with a flat electrode (cathode), and electrolytically etched using the steel plate as an anode. Current density and etching time are each 1
Steel plate A that is 0-200 A/bi', 0.5-5S
, B, only the portion without the film was electrolytically etched, and the depth was approximately 20 μm. After measuring the magnetic properties of these steel plates, they were further subjected to strain relief annealing at 800° C. for 3 hours in Nz gas, and the magnetic properties were again measured.

The results of these magnetic measurements are summarized in Table 1. In addition, the same table also lists the measurement results for comparative materials obtained by subjecting each steel plate to stress relief annealing for 3 hours at 800°C in N2 gas. .

Iron loss (W/kg) when the magnetic flux density is 1.7T and 5011z Both steel plates are significantly iron-reinforced by electrolytic etching. The loss was improved, and the properties did not deteriorate even after annealing at 800°C. When these steel plates were observed under a microscope, no fine recrystallized grains were observed in the etched areas.

Furthermore, the inventors conducted a similar experiment on a steel plate with a forsterite coating, in which grooves were formed as described above, and then an insulating coating was applied over the surface of the steel and sheet metal. The results were obtained.

From the above experimental results, we found that in order to have an iron loss value that is better than before and to ensure stable characteristics even after high-temperature annealing at 1000°C or more, strain relief annealing is required around the linear grooves. It has been found that sometimes it is important to prevent the formation of all fine recrystallized grain groups.

The reason why properties of materials containing fine recrystallized grains deteriorate after high-temperature annealing is that the orientation of fine recrystallized grains is generally deviated from the Goss direction, and when high-temperature annealing is performed at 100°C or higher, This is thought to be due to the growth of misoriented grains.

Next, a method for forming grooves that prevents formation of fine recrystallized grain groups during strain relief annealing will be explained.

The grooves are first formed by removing the coating of a grain-oriented electrical steel sheet that has been finish annealed in a localized linear manner by laser irradiation, scribing with a knife, etc. After applying
Etching is carried out using methods such as electrolytic etching and chemical etching.

The inventors conducted a detailed investigation of materials in which fine recrystallized grain groups were generated and materials in which they were not after strain relief annealing, and found that
It was found that the amount of strain applied to the steel base during coating removal is involved in the formation of fine recrystallized grain groups.

Figure 2 shows the relationship between the amount of strain applied to the steel base during coating removal and the probability of generating fine recrystallized grain groups during strain relief annealing. (Disclosed in Japanese Patent Application Laid-Open No. 58-244504).

As is clear from Figure 2, as the amount of strain decreases, the probability of occurrence of fine recrystallized grain groups gradually decreases, and when the amount of strain decreases to 30%.
In the following cases, the probability that a fine recrystallized grain group will be generated is 0%.

Therefore, in order to prevent the formation of fine recrystallized grain groups during strain relief annealing, it is necessary to reduce the amount of strain applied to the base steel by 3.
Therefore, it is important to control it to 0% or less.

Such methods include removing only the coating using pulsed laser light with a weak energy density as described above, and removing the forsterite coating after final annealing when applying an annealing separator during the manufacturing process of grain-oriented electrical steel sheets. There is a method of applying a film formation inhibitor or a water repellent substance to create a defective area.

Next, the shape of the groove to be introduced will be explained.

A pulsed laser beam having an energy density of 0.8 J/cm was irradiated on an Epstein specimen of a finish-annealed grain-oriented electrical steel sheet with a thickness of 0.23 m1 in a direction perpendicular to the rolling direction to remove only the coating. Later, grooves with different depths were formed by pickling at different times.Also, the width of the grooves was changed by shifting the focus of the laser beam.The spacing between the linear grooves was set to 7 cranes in each case. Next, these specimens were heated at 800°C in Nz.

After 3 hours of strain relief annealing, a single plate magnetic testing machine (SS
T). In addition, no fine recrystallized grain group was observed in the groove forming part in any of the specimens after strain relief annealing.

Figure 3 shows the width and depth of the grooves formed and the iron loss improvement effect (
Δw, ? /S. ).

Here Δ-1. /,. is the iron loss Wl of the finish annealed steel plate
? 150 and steel sheet steel plate subjected to strain relief annealing after groove formation, 7. . This is the difference between

As shown in the figure, if the width of the groove is less than 5 μm, the iron loss improvement effect is poor, while if it exceeds 500 μm, the iron loss will still deteriorate, so the width of the groove should be 5 to 500 μm.
It is better to set it to rm.

In addition, regarding the depth of the groove, if it exceeds 100 μm, the iron loss will deteriorate, so it is preferably 100 μm or less, preferably 5 to 30 μm.
It is appropriate to set it to μm.

Furthermore, the direction in which the grooves are formed is within ±45" from the reference line, with the direction perpendicular to the rolling direction as the reference line, and the groove spacing is 2 to 2".
It is preferable to set it to about 30 dragons.

Next, the manufacturing method of the present invention will be specifically explained.

Grain-oriented electrical steel sheets are generally made of MnS, MnSe +
A hot-rolled plate containing so-called inhibitors such as BN and sb is heat-treated as necessary, and then cold-rolled once or twice with intermediate annealing to achieve a product thickness.
It is manufactured by performing decarburization annealing, then applying an annealing separator containing MgO as a main component, and final annealing at approximately 1200°C. The final annealing causes the steel sheet to undergo secondary recrystallization, resulting in a so-called Goss-oriented steel sheet. is completed.

Here, if the 5iil of the steel plate is less than 2.0% (hereinafter simply expressed in %), it will have a poor effect of increasing resistivity and reducing eddy current, while if it exceeds 4.5%, problems will occur in cold rollability. Therefore, in this invention, the Si content is limited to a range of 2.0 to 4.5%.

In the present invention, prior to forming the grooves, it is necessary to form a defective region of the coating on the surface of the finish annealed steel sheet. A method for local removal will be explained.

The coating can be removed by any means such as laser irradiation or scraping with a knife, but if the amount of strain introduced into the steel sheet during coating removal is too large, fine recrystallized grain groups will occur during strain relief annealing, as mentioned above. Therefore, it is important to suppress the amount of introduced strain to 30% or less, and for this purpose, when using laser irradiation, it is approximately 0.01 to IJ/cI11! The energy density is about 50,000 yen when using a knife etc.
It is desirable that the load be approximately 500 g.

At this time, the removed region of the film is linear within an angular range of ±45° from a direction perpendicular to the rolling direction of the steel plate, and the width of the linear defect region is 5 to 500 μm.

The spacing is preferably about 2 to 30 fins. Note that in this invention, the word "linear" does not simply mean a continuous straight line, but also includes a series of points that are connected intermittently.

Next, during final annealing, the forsterite coating is
A method for forming the jJl region will be described.

Such methods include the following methods.

i) In the step of applying an annealing separator to the surface of the steel sheet after primary recrystallization annealing, prior to the application, a substance that inhibits the reaction with the annealing separator, such as 5ift + AhO, is applied to the surface of the steel sheet.
s + Oxides such as Zr0z, Zn, AlSn
+ A method of locally depositing metals such as Ni and Pe.

1i) In the step of applying an annealing separator to the surface of the steel sheet after primary recrystallization annealing, a method of locally adhering a tθ aqueous substance such as oil-based paint or varnish to the surface of the steel sheet prior to the application.

1ii) In the step of applying an annealing separator to the surface of the steel sheet after primary recrystallization annealing, a substance that acts as an oxidizing agent for Si in the steel, such as FeO, Fe, etc., is applied to the surface of the steel sheet prior to the application.
Oxides such as zO3, Ti1t + MnO, MnO2, silicates that are easily reduced such as Fe2SiO4, Mg
A method of locally depositing hydroxides such as (OH) z.

1v) Application of annealing separator to the steel plate surface after primary recrystallization annealing
A method of locally removing the annealing separator after coating and drying in the coating process.

By each of the methods listed in i) to iv) above, in which the forsterite film-free area is partitioned during application of the annealing separator, forsterite is removed after final annealing without introducing strain into the steel base. Defect areas in the coating can be effectively formed.

Next, the steel plate from which the coating has been locally removed as described above is subjected to etching, that is, chemical etching such as electrolytic etching or pickling, to form linear grooves in the base steel. The depth of the groove to be formed is preferably 100 μm or less. As mentioned above, the shape of the grooves may be not only a continuous straight line but also a discontinuous straight line or a curved line. Although methods other than etching may be used to form such grooves, electrolytic Etching or chemical etching is suitable.

In electrolytic etching, a flat cathode electrode is generally etched facing the steel plate to be treated, and the groove depth varies depending on the type of electrolytic solution, current density, and processing time. It is important to select conditions such that the groove depth is 100 μm or less.

Sulfuric acid, nitric acid, etc. are suitable as the processing liquid used for chemical etching.

Furthermore, the finish annealed steel sheet may be coated with or without a phosphate-based topcoat, and after forming the linear grooves, a topcoat may be applied or reapplied to the grooved area or the entire surface of the steel sheet. good.

The steel sheet obtained in this way exhibits an extremely low iron loss value, and not only does the iron loss not deteriorate due to normal strain relief annealing, but also maintains good properties even after high-temperature annealing at 1000°C or higher. It can be stably used as a material for industrial use. It goes without saying that it may also be used for stacked iron cores that generally do not require strain relief annealing.

(Function) The reason why an extremely low iron loss value can be obtained by forming a linear groove extending over the base metal according to the present invention has not yet been clearly elucidated, but it is due to the reaction generated around the groove. This is thought to be due to the subdivision of magnetic domains due to magnetic field effects.

(Example) Example I A grain-oriented electrical steel sheet with a thickness of 0.23 mm and Boo 1.91T containing 3.2% Si and manufactured by a normal manufacturing method.

Divide into two parts B, and the energy density of steel plate A is 10.
A portion of the coating and the base metal were removed in a linear manner by irradiation with a pulsed laser beam of 0 J/cm", and then linear grooves were formed by electrolytic etching in a NaCl electrolyte. Also, regarding steel plate B. has an energy density of 0.8 J/
After the coating was locally removed linearly by irradiation with a pulsed laser beam of 1.5 cm", grooves were formed by electrolytic etching. The grooves had a width of 100 mm for both steel sheets A and B.
micrometers and a depth of 10 micrometers, and were formed linearly at intervals of 71 m in a direction perpendicular to the rolling direction. Furthermore, when the amount of strain applied to the steel base during coating removal was measured using a percolation cell device, it was 32% for A and 7% for B.

Next, these steel plates were subjected to strain relief annealing in N2 at 800°C for 3 hours, and then iron loss measurements and macrostructure observations were performed. In steel plate A, fine recrystallized grain groups were observed in the groove forming part, whereas in steel plate B, they were not observed. Next, these steel plates were further annealed at 1000°C and 1180°C for 3 hours, and then iron loss measurements and macrostructure observations were performed again. Table 2 shows the results of investigating the iron loss characteristics at each stage.

Steel plate A, which had a strain of 32% at the time of film removal, had a group of fine recrystallized grains in the groove formation area, and the fine recrystallized grains grew due to high-temperature annealing at 1000°C or higher and the properties deteriorated, but the strain No fine recrystallized grains were observed in steel plate B with a content of 7% at 800°C.
During annealing, it showed a lower iron loss value than Steel Plate A, and also showed stable characteristics even after high temperature annealing at 1000°C or higher. Note that no unevenness or burrs were observed in the groove forming portion.

Example 2 A grain-oriented electrical steel sheet containing 3.4% Si and having a thickness of 0.27n+ and Boo 1.92T manufactured by a normal manufacturing method was divided into two C9D parts, and the steel plate C was subjected to a load of 1200g with the edge of a knife. After removing a part of the coating and base iron in a linear manner by scribing while adding, linear grooves were formed by applying IIN (h pickling).Meanwhile, for the steel plate, a load of 150 g was applied with the edge of a knife. After the coating was removed locally in a linear manner by scribing while adding 100% chloride, grooves were further formed by pickling with 11N0ff.

The shape of the groove is 120μm wide and 15μm deep for both steel plates C and D.
m, and were introduced linearly at intervals of 51 in the direction perpendicular to the rolling direction. Further, when the amount of strain applied to the steel base during coating removal was measured using a percolation cell device, it was 45% for A and 12% for B.

These steel plates were then heated to 800℃, 1000℃, 118
Annealing was performed at each temperature of 0° C. for 3 hours, and iron loss measurements and macrocomposition observations were performed at each stage. The results obtained are shown in Table 3.

Table 3 Steel plate C, which had a strain of 45% when removing the coating, had a strain of 800%.
After annealing at 1000° C. for 3 hours, a group of fine recrystallized grains was observed in the groove forming portion, and the fine recrystallized grains grew due to high-temperature annealing at 1000° C. or higher, resulting in deterioration of characteristics. On the other hand, for the steel sheet whose strain amount was 12% at the time of film removal, no fine recrystallized grain groups were observed, and it showed a lower iron loss value than steel sheet A when annealed at 800℃, and It showed stable properties even after high temperature annealing. Further, in steel plate C, burrs were observed in the groove forming portion, but in steel plate C, there were no burrs and the shape was good.

Example 3 0.23 mm thick forsterite coated steel plate (G)
and steel plate with forsterite and top coating (H
) has an energy density of 0.5J10 in the direction perpendicular to the rolling direction.
The coating was locally removed by irradiation with a 111" pulsed laser. The width of the removed area was 50 μI, and the interval between the removed areas was 5 mm. These steel plates were electrolytically etched in a NaCl electrolyte to remove the coating. A groove of 15μI was formed on the steel plate.Furthermore, a top coat was applied to the surface of these steel plates, and then 80μI grooves were formed on the surface.
Annealing was performed at 0°C for 3 hours.

The magnetic properties of the steel plates at each stage are shown in Table 4 along with comparative examples in which each steel plate was not subjected to electrolytic etching.

Example 4 A silicon steel material containing 3.3% St was made into a cold-rolled steel plate with a thickness of 0.30 m according to a conventional method, and then subjected to decarburization and primary recrystallization annealing, and then divided into two parts, One of the steel plates was coated with an annealing separator containing MgO as a main component and subjected to final annealing to obtain a steel plate (■).

The other is adhesion of Ah (h powder), which is a reaction inhibitor between the annealing separator and Sing in the steel plate subscale, on the surface of the steel plate at an adhesion amount of 1.3 g/m'' and an angle of 90@adhesion with respect to the rolling direction. Width 0.2mm and repeat interval in rolling direction: 1
After being deposited in a linear manner under 0n conditions, an annealing separating agent was applied thereon and final annealing was performed.

The surface of the obtained steel plate is Al2O! No forsterite film was formed in the area where the powder was applied.

This steel plate was further divided into two parts, one of which was used as steel plate J. Other steel plates were heated at 60°C with 10% H and SO.

Pickling was carried out for 30 seconds to dissolve the base iron portion in the forsterite film defective region to form a groove with a depth of 15 μm, and a steel plate was obtained.

A top coating was further applied to the surface of these steel plates I and J, and then annealing was performed at 800°C for 3 hours.

Table 5 shows the magnetic properties of the steel sheets at different grades.

Table 5 Example 5 A silicon steel material containing 3.25% Si was made into a cold rolled steel plate with a thickness of 0.23 mm according to a conventional method, and then decarburized and 1
After recrystallization annealing was performed and an annealing separator containing MgO as a main component was applied, the steel plate was divided into two parts. One side was subjected to final annealing and made into a steel plate. In the other one, the annealing separator on the surface was removed linearly. The removal width was 0.111 m, the angle with the rolling direction was 90'', and the repetition interval in the rolling direction was 13 mm.

When this steel plate was final annealed, almost no forsterite film was formed in the areas where the annealing separator had been linearly removed. Next, the steel plate was divided into two parts, and one of the steel plates was used as steel plate M. Other steel plates are) 13PO4-LO
Chemically polish for 20 seconds with □ to remove forsterite.
The base metal part in the SI area was melted to form a groove with a depth of 12 μm,
Steel plate N was used.

A top coating was further applied to the surfaces of these M and N steel plates, and then annealing was performed at 800°C for 3 hours.

Table 6 shows the magnetic properties of the steel plate at each stage.

Example 6 Forsterite coating with a thickness of 0.23 mm, 100 cc of colloidal silica, 100 cc of magnesium phosphate,
A treatment solution consisting of 10 cc of chromic anhydride was applied to a steel plate with a tension coating film obtained by baking, and the film was locally removed by scribing with the edge of a knife while applying a load of 150 g in the direction perpendicular to the rolling direction. The width of the section is 8
It was removed at 5-meter intervals at 0 μm.

Next, this steel plate was electrolytically etched in a NaCl electrolyte to form grooves with a depth of 12 μm in the portion where the film was removed. Furthermore, these steel plates are divided into two, each of which is made into a steel plate P.

Q, magnesium phosphate 60cc, chromic anhydride 1
A normal coating obtained by applying and baking a treatment solution consisting of 0 cc and 5 cc of fluoric acid was applied to the entire surface of the steel plate P, while only the groove forming portion of the steel plate Q was applied.
Annealing was performed at 800°C for 3 hours.

Table 7 shows the magnetic properties of the steel plate at each stage in comparison with a steel plate made of the same material without grooves.

(Effects of the Invention) Thus, according to the present invention, it is possible to further reduce iron loss in grain-oriented electrical steel sheets compared to the conventional one, and furthermore, such iron loss characteristics can be maintained even during strain relief annealing at normal temperatures. Needless to say, even when annealing is performed at a high temperature of 1000° C. or higher, no deterioration occurs.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between annealing temperature and iron loss for a steel plate (al) in which fine recrystallized grain groups were observed after strain relief annealing at 800°C for 3 hours, and a steel plate (b) in which no fine recrystallized grains were observed. The figure shows the relationship between the amount of strain introduced into the steel base during coating removal and the probability that fine recrystallized grain groups will be generated after strain relief annealing. Figure 3 shows the relationship between groove width and depth and iron loss reduction. Fig. 1 ff, IL (3h) Fig. 2 t (%) Fig. 3 a Loss reduction height ∆Wtt/so (phantom to W/0.10 ~ Groove t+ 'PM(〕m)

Claims (1)

[Claims] 1. A finish-annealed grain-oriented electrical steel sheet containing 2.0 to 4.5% Si by weight and having a forsterite coating on the surface, the surface of the steel sheet having a It has a linear groove that extends to the base iron within an angular range of ±45° with the direction perpendicular to the reference line as the reference line, and around this linear groove,
A grain-oriented electrical steel sheet with low core loss characterized by the absence of a high strain introduction part that causes formation of fine recrystallized grain groups during strain relief annealing. 2. A finish-annealed grain-oriented electrical steel sheet containing 2.0 to 4.5% Si by weight and having a forsterite coating on the surface, the surface of the steel sheet having a direction perpendicular to the rolling direction. It has a linear groove that extends to the base iron within an angle range of ±45° with reference line, and around this linear groove,
There is no high strain introduction area that causes the formation of fine recrystallized grain groups during strain relief annealing, and furthermore, on the forsterite coating,
A low core loss grain-oriented electrical steel sheet, comprising a top coating having a film defect area over the same area as the film. 3. A finish-annealed grain-oriented electrical steel sheet containing 2.0 to 4.5% Si by weight and having a forsterite coating on the surface, the surface of the steel sheet having a direction perpendicular to the rolling direction. It has a linear groove that extends to the base iron within an angle range of ±45° with reference line, and around this linear groove,
There is no high strain introduction area that causes the formation of fine recrystallized grain groups during strain relief annealing, and furthermore, on the forsterite coating,
A low iron loss grain-oriented electrical steel sheet characterized by having a top coat applied over the entire surface of the steel sheet. 4. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. After that, decarburization and primary recrystallization annealing were performed, after which an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and final annealing was performed to produce a grain-oriented electrical steel sheet with a forsterite coating. , the forsterite coating on the surface of the grain-oriented electrical steel sheet is
Within the angle range of 45°, the amount of strain introduced into the base steel is 30%
A method for manufacturing a grain-oriented electrical steel sheet with low core loss, which comprises removing the base metal in a linear manner under the following conditions, and then subjecting it to electrolytic or chemical etching to form a linear groove in the base metal. 5. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. Afterwards, decarburization and primary recrystallization annealing are performed, and then the Mg
When applying the annealing separator containing O as the main component, a linear forsterite film-free area is defined within an angular range of ±45° using the direction perpendicular to the rolling direction as a reference line, and then final finishing is performed. After annealing to produce a grain-oriented electrical steel sheet with a forsterite coating having a linear coating defect area, electrolytic or chemical etching is performed on the base metal part in the forsterite coating defect area to form linear grooves in the base metal. 1. A method for manufacturing a grain-oriented electrical steel sheet with low core loss, characterized by forming a grain-oriented electrical steel sheet. 6. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. Afterwards, decarburization and primary recrystallization annealing are performed, after which an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, final annealing is performed, and a top coat is then applied to form a forsterite film and a top coat. After making a grain-oriented electrical steel sheet with an insulating coating, the forsterite coating and top insulation coating on the surface of the grain-oriented electrical steel sheet are ground within an angle range of ±45° with the direction perpendicular to the rolling direction as a reference line. A low iron loss grain-oriented electrical steel sheet, which is formed by linearly removing the steel under conditions where the amount of strain introduced into the steel is 30% or less, and then applying electrolytic or chemical etching to form linear grooves in the base steel. manufacturing method. 7. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. After that, decarburization and primary recrystallization annealing were performed, after which an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and final annealing was performed to produce a grain-oriented electrical steel sheet with a forsterite coating. , the forsterite coating on the surface of the grain-oriented electrical steel sheet is
Within the angle range of 45°, the amount of strain introduced into the base steel is 30%
A low iron loss directional electromagnetic electromagnetic material that consists of removing the steel in a linear manner under the following conditions, then electrolytically or chemically etching it to form a linear groove in the base steel, and then applying an overcoating treatment to the entire surface of the steel plate. Method of manufacturing steel plates. 8. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to obtain the final thickness. Afterwards, decarburization and primary recrystallization annealing are performed, and then the Mg
When applying the annealing separator containing O as the main component, a linear forsterite film-free area is defined within an angular range of ±45° using the direction perpendicular to the rolling direction as a reference line, and then final finishing is performed. After annealing to produce a grain-oriented electrical steel sheet with a forsterite coating having a linear coating defect area, electrolytic or chemical etching is performed on the base metal part in the forsterite coating defect area to form linear grooves in the base steel. A method for manufacturing a grain-oriented electrical steel sheet with low iron loss, which comprises forming a gravitational force on the entire surface of the steel sheet, and then applying an overcoating treatment to the entire surface of the steel sheet. 9. A silicon steel slab containing 2.0 to 4.5% Si by weight was hot rolled and then cold rolled once or twice with intermediate annealing to give the final thickness. Afterwards, decarburization and primary recrystallization annealing are performed, after which an annealing separator containing MgO as a main component is applied to the surface of the steel sheet, final annealing is performed, and a top coat is then applied to form a forsterite film and a top coat. After making a grain-oriented electrical steel sheet with an insulating coating, the forsterite coating and top insulation coating on the surface of the grain-oriented electrical steel sheet are ground within an angle range of ±45° with the direction perpendicular to the rolling direction as a reference line. It is removed in a linear manner under the condition that the amount of strain introduced into the steel is 30% or less, and then electrolytic or chemical etching is performed to form linear grooves in the base steel, and then only the coating defect area or the entire surface of the steel plate is removed. , a method for producing a low core loss grain-oriented electrical steel sheet, comprising reapplying a top coating.