JP2671084B2 - High magnetic flux density grain-oriented electrical steel sheet having excellent iron loss characteristics and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet having no glass coating (forsterite or spinel coating) and a method for producing the same, and is particularly excellent in workability such as cutting property and punching property, and is low in iron content. The present invention relates to a grain-oriented electrical steel sheet having a loss and a high magnetic flux density, and an inexpensive manufacturing method thereof.

[0002]

2. Description of the Related Art Grain-oriented electrical steel sheets are generally used as a soft magnetic material, mainly for transformers and other electric equipment, and are required to have good magnetic characteristics such as excitation characteristics and iron loss characteristics. In order to obtain good magnetic properties, it is important that the <001> axis, which is the axis of easy magnetization, is highly aligned in the rolling direction. Also, plate thickness, grain size, specific resistance,
The coating properties are also important because they have a great influence on the magnetic properties.

The crystal orientation has been significantly improved by a method characterized by final cold rolling under high pressure using AlN as an inhibitor, and it is now possible to manufacture magnetic flux density close to the theoretical value. . On the other hand, when the grain-oriented electrical steel sheet is used in a consumer, what is important together with the magnetic characteristic are the coating characteristic and the workability. In general, grain-oriented electrical steel sheets are surface-treated with a glass film and an insulating film formed during final annealing.

The glass film is mainly composed of forsterite (Mg ₂ SiO ₄ ) which is a reaction product of MgO which is an annealing separator and SiO _{2 which} is an oxide film formed during decarburization annealing. Resulting Al
It is a film made of a spinel compound of ₂ O ₃ , SiO ₂ , MgO and the like. This glass film is hard and has strong abrasion resistance, and has a significant effect on the durability of tools such as slit cutting and punching when processing a transformer core. For example, when punching a grain-oriented electrical steel sheet having a glass coating, the die wears and the return of the punched sheet becomes large after several thousand punches, which causes a problem during use. . For this reason, it is necessary to re-polish the mold and replace it with a new one. This results in a decrease in work efficiency and an increase in cost at the time of processing the iron core in the customer. Similarly, with respect to slitting property, cutting property, etc., the adverse effect of the glass film is a problem.

With respect to the magnetic properties of grain-oriented electrical steel sheets, this glass coating improves iron loss due to the coating tension. In the case of a material having a high magnetic flux density, this effect is remarkable, and compared with the case without a coating. , An effect of improving iron loss of nearly 20% is obtained. However, the formation state thereof, particularly the increase of the film thickness and the presence of the inner film layer, adversely affect the decrease of the magnetic flux density and the iron loss improving effect at the time of domain segmentation.

In particular, in recent years, there have been developments in processing technology for high-strength insulating coatings, and developments in magnetic domain subdivision technology by means of mechanical, optical, chemical, etc. Improvements have been made. For this reason, when the magnetic flux density is reduced by the glass film and the iron loss is reduced by the magnetic domain refinement technique, a surface state that does not adversely affect the iron loss improvement due to the unevenness of the internal oxide has been demanded. For this reason, high magnetic flux density grain-oriented electrical steel sheets without a glass coating have come into the limelight due to their higher magnetic flux density and ultra-low iron loss.

A method for producing a grain-oriented electrical steel sheet having no glass film is disclosed, for example, in JP-A-53-22113. This uses fine particles of alumina containing 5 to 40% of hydrous silicate mineral powder as an annealing separator, with the thickness of the oxide film being 3 μm or less in decarburizing annealing.
This is a method of applying this to a steel plate and performing finish annealing. According to this method, it is said that the oxide film is thinned, and a glass film that is easily peeled off is formed by blending a hydrous silicate mineral, and a glass having a metallic luster is obtained.

Further, as a method for suppressing the formation of a glass film by an annealing separator, in JP-A-56-65983, 20 parts by weight of an additive for removing impurities and 10 parts by weight of an inhibitory substance were mixed with aluminum hydroxide. A method of applying an annealing separator to a steel sheet to form a thin glass film of 0.5 μm or less is disclosed. Further, in Japanese Patent Laid-Open No. 59-96278, Al ₂ O ₃ having a weak reactivity with SiO _{2 of} an oxide layer formed by decarburization annealing and MgO having a reduced activity by firing at a high temperature of 1300 ° C. or higher. An annealing separator composed of and is disclosed. The use of this annealing separator suppresses the formation of forsterite.

Each of these prior arts is a grain-oriented electrical steel sheet called a normal orient core, and has a magnetic flux density of 1.8.
It is based on a low-grade grain-oriented electrical steel sheet having a low value of less than 8 Tesla, and may have an effect similar to that of the present invention in that it does not have a glass film. We have not yet acquired the technology to develop high-grade grain-oriented electrical steel sheets with low iron loss.

[0010]

DISCLOSURE OF THE INVENTION An object of the present invention is to industrially produce a high magnetic flux density grain-oriented electrical steel sheet having a low iron loss and having no glass coating, which has been conventionally difficult to realize in terms of inhibitor control. To provide a manufacturing method. Furthermore, by applying a magnetic domain subdivision technology utilizing high-strength insulating film and surface shape effect and strain to this steel plate,
The purpose of the invention is to obtain a material with ultra-low iron loss, which is dramatically superior to the conventional glass film forming technology. It is another object of the present invention to obtain a product having excellent workability such as punching, cutting, slitting, and the like by suppressing glass film formation almost completely.

[0011]

In order to obtain the product of the present invention, as a starting material, C: 0.02 as a steel component in a weight ratio.
1 to 0.075%, Si: 2.5 to 4.5%, acid-soluble A
l: 0.010-0.040%, N: 0.0030-
0.0130%, S ≦ 0.014%, Mn: 0.05 to
An electromagnetic steel slab containing 0.45% and the balance of Fe and unavoidable impurities is used, and the slab is heated to a temperature of less than 1280 ° C. and then hot rolled and sandwiched once or with intermediate annealing.
After cold rolling more than one time to obtain the final plate thickness, then decarburization annealing, nitriding treatment, applying an annealing separator, high temperature finish annealing, and before or after heat flattening, magnetic domain refinement According to a manufacturing method, which comprises applying a treatment and coating and baking an insulating film agent.

That is, in the present invention, the inhibitor elements such as Al, N, Mn, and S are not dissolved in the steel during the slab heating step, and after decarburization annealing, the material is nitrided in a strong reducing atmosphere. As a result, the basic step is to form an inhibitor containing (Al, Si) N as a main component, develop good secondary recrystallization in the finish annealing process, and then subdivide the magnetic domains.

In the method for producing an ultra-low iron loss grain-oriented electrical steel sheet having no glass coating according to the above components and steps, the surface in the process of applying an annealing separator, finishing annealing, and insulating film application. There is a feature in the processing method. The final cold rolled material is decarburized and annealed in a continuous line. By this decarburizing annealing, removal of C in the steel and primary recrystallization are performed, and at the same time, an oxide film mainly composed of SiO ₂ is formed on the surface of the steel sheet. Decarburization annealing is performed at 800 to 875 ° C. in an atmosphere of N ₂
+ H ₂ and dew point is controlled.

Next, nitriding is performed in the same line or another line after the latter half or after the end of the decarburization annealing. The nitriding amount at this time is 150 ppm or more, preferably 150 to 300.
Treated as ppm. After that, an annealing separator is applied, dried, wound, and finally finish annealed. At this time, as an annealing separator, MgO: 100 parts by weight, L
i, Na, K, Ba, Ca, Mg, Zn, Fe, Zr,
Use is made of at least 1 part by weight of Cl compound such as Sn, Sr and Al as Cl, and 1 to 15 parts by weight of the total amount of Cl and S of 1 or 2 or more of Cl compound and S compound. .

In the present invention, what is important with the annealing separating agent is the finish annealing condition which is the second elemental technique. The present inventors performed nitriding treatment after decarburization annealing as in the present invention, and
l, Si) N-based inhibitor is formed, and when the glass film formation is suppressed and the decomposition reaction is simultaneously performed by the annealing separator and the finish annealing, the final annealing is performed in the case of obtaining a steel sheet having no glass film. It was found that the atmosphere and the heating conditions are very important for stabilizing the secondary recrystallization and increasing the magnetic flux density.

That is, in the process of using (MnS) as an inhibitor and forming (Al, Si) N and then changing to AlN as in the present invention, the secondary recrystallization starting temperature is around 1100 ° C. , Conventional AlN,
It is higher than in the case of a high magnetic flux density material that simultaneously uses MnS and the like. Therefore, it is necessary to keep the inhibitor stable while suppressing and decomposing the glass film forming reaction up to the temperature range where the secondary recrystallization starts. This is because, as in the present invention, in the step of slightly forming the glass film and suppressing the reaction at a low temperature at the time of temperature rise, and causing the decomposition reaction on the high temperature side, nitriding from the atmospheric gas at the time of forming the glass film layer is performed. The reason for this is that N increases due to the reaction and decomposition of the inhibitor from the surface occurs at the time of decomposition of the glass film. Therefore, unless a special temperature rising condition as in the present invention is used, not only a high magnetic flux density can be obtained but also secondary recrystallization failure occurs.

As the finish annealing conditions, N _{2 is} 30% or more when the temperature is raised to promote the formation and decomposition of the glass film, and the heating rate is 20 ° C./hr or less. As a result, (A
l, Mn) N and AlN stabilization on the high temperature side are maintained,
Good secondary recrystallization is obtained. The thus treated high magnetic flux density material having no glass film is subjected to shape correction and strain relief annealing, and is applied with an insulating film agent and heat flattened in a continuous line. At this time, the insulating treatment for applying tension is important, and tension is applied to the steel sheet by means of application of a coating agent having a low coefficient of thermal expansion, plating, vapor deposition, or the like. In order to obtain high tension, the insulating film agent at this time is made of SiO ₂ , ZrO ₂ , SnO ₂ , Al ₂ as a colloidal substance.
Al, M for 100 parts by weight of O ₃ etc. as a solid content
1 or 2 or more primary phosphates such as g and Ca 13
A mixture of 0 to 200 parts by weight and 12 to 40 parts by weight of chromic acid or one or more chromates as chromic acid is used. At this time, the coating thickness of the film is 2 to 6
μm.

When the insulating film is treated under such conditions,
The film tension applied to the steel sheet is 0.5 to 2.0 kg / mm
² is obtained. In this series of manufacturing process, after cold rolling,
After decarburization annealing, after final finishing annealing, after insulating film treatment, etc., at any one place or at two or more places, 4 in the rolling direction by pressing, tooth profile roll, marking, laser, etching, etc.
In the direction of 0 to 90 degrees, linear or dot-shaped depressions or strains
The interval is 1 to 15 mm, the depth is 1 to 25 μm, and the width is 500 μm or less. After subdividing these magnetic domains, an insulating film agent is treated or heat-treated as necessary to obtain a product.

Next, the reasons for limiting the constituents of the present invention will be described. First, the reasons for limiting the component composition of the material slab used as the starting material are as follows. If the content of C is less than 0.021%, secondary recrystallization becomes unstable,
1.8 the magnetic flux density of the product even when the secondary recrystallization at B ₈
It will be as low as 0 Tesla. On the other hand, 0.075
If it exceeds%, the decarburization annealing process requires a long time, which hinders the productivity.

The specific resistance of Si changes depending on its content. If it is less than 2.5%, a good iron loss value cannot be obtained. On the other hand, if it exceeds 4.5%, the material frequently cracks and breaks during cold rolling, making stable cold rolling impossible.
One of the characteristics of the component system of the starting material of the present invention is that S is 0.0140% or less. In the conventional known technique, for example, the technique disclosed in Japanese Examined Patent Publication No. 47-25220, S is an element that forms a precipitate necessary for causing secondary recrystallization as MnS. There is a content range in which is most effective,
It is a slab heating step that is carried out prior to hot rolling.
Was defined as an amount capable of forming a solid solution.

However, in recent research, in a manufacturing process of a grain-oriented electrical steel sheet using (Al, Si) N as a precipitate required for secondary recrystallization, a slab containing a large amount of Si in a material is kept at a low temperature. When slab heating and hot rolling, S
Was found to promote secondary recrystallization failure. When the amount of Si in the material is 4.5% or less, if S is 0.014% or less, preferably 0.0070% or less, occurrence of secondary recrystallization failure does not occur at all.

In the present invention, (Al, Si) N is used as a precipitate necessary for secondary recrystallization. Therefore, the minimum required Al
To secure N, acid-soluble Al is 0.010% or more,
N needs to be 0.0030% or more. However, if the acid-soluble Al content exceeds 0.040%, AlN during hot rolling becomes inappropriate, and secondary recrystallization becomes unstable.
Limited to 0-0.040%.

On the other hand, if the content of N exceeds 0.0130%, cracks called blister on the surface of the steel sheet occur, and the grain size of primary recrystallization cannot be adjusted.
To 0.0130%. If Mn is less than 0.05%, secondary recrystallization becomes unstable. But although the higher number becomes the B ₈ value, the addition of a certain amount or more it is disadvantageous in cost. Therefore, it is limited to 0.05 to 0.45%.

As the annealing separating agent, Li, K, Na, Ba, Ca, Mg, Zn, F is added to 100 parts by weight of MgO.
At least 1 part by weight of Cl compound selected from e, Zr, Sr, Sn, Al and the like is contained as Cl, and 1 or 2 or more of Cl compound and S compound is contained as the total amount of Cl and S. -15 parts by weight are blended. The reason why the Cl compound is required to be at least 1 part by weight or more as Cl is that it is important for suppressing formation and decomposition of the glass film during the finish annealing temperature raising process. In particular, in the decomposition reaction of the glass film, Cl is used to etch Fe in the film layer to release SiO ₂ , spinel, etc. in the film layer from the surface layer of the base metal, and to absorb the reaction into the annealing separator on the surface. is necessary.

If the total amount of Cl and S is less than 1 part by weight, it is difficult to obtain a product without a glass film uniformly on the entire surface of the coil, and the total amount of the forsterite and spinel compounds, which is the main object of the present invention, is 0.6 g / It becomes difficult to control to m ² or less. On the other hand, if the total amount of Cl and S exceeds 15 parts by weight, the constituent elements of the additive diffuse into the steel and adversely affect the inhibitor, or grain boundaries and intragranular etching due to excess Cl and S occur to cause surface It is not preferable because it may worsen the condition or may have an adverse effect on the subsequent purification.

With these additives, the MgO surface firstly has a low melting point in the finish annealing temperature raising stage, and the Si
It diffuses into the oxide layer developed in the form of a ramen mainly composed of O _2, and forms a glass film layer mainly composed of forsterite at an early stage. This suppresses additional nitriding and additional oxidation into the steel. In the latter stage at the time of temperature rise, the Fe portion in the oxide film that has developed into a rigid frame is etched by Cl or S, and the film layer is decomposed. After that, when the film decomposition reaction proceeds at a higher temperature, the film-free surface is subjected to thermal etching to obtain a smooth mirror-like surface.

In the process of appropriately forming and decomposing the glass film as described above in the final finishing annealing process as in the present invention, good magnetism cannot be obtained without controlling the atmosphere of the finishing annealing. Under conditions such that the atmospheric gas at the time of temperature increase during finish annealing is less than 30% N ₂ , the decomposition and disappearance reaction of the glass film causes weakening of (Al, Si) N, AlN, etc., resulting in poor secondary recrystallization. Or a decrease in magnetic flux density occurs. Particularly, under the condition of N _{2 of} 20% or less, remarkable secondary recrystallization failure occurs. On the other hand, when N _{2 is} 100%, depending on the MgO physical property value of the annealing separator, the space between the steel sheets becomes extremely oxidative and the surface of the steel sheet is oxidized, and unevenness is likely to occur on the surface. The most preferable range is N ₂ : 50 to 80%.

The heating rate at the time of heating is limited to 20 ° C./Hr or less. In rapid heating exceeding this, suppression of glass formation in the temperature rising process, decomposition reaction, deinhibitor speed,
This is because the balance in grain growth and the like is lost and good secondary recrystallization cannot be obtained. The conditions for soaking are not particularly specified, but in the present invention, 1150 to 120
Preference is given to 0 ° C. In the method of the present invention, the decomposition reaction of the glass film is almost completed at the stage where the soaking temperature is reached, and in the subsequent soaking stage, thermal etching occurs together with the purification reaction, and further the mirror finish of the steel sheet is obtained. . The purification reaction at this time occurs very smoothly because there is no glass film, and there is an advantage that the purification reaction is higher than that in the case where the ordinary glass film forming process is applied. Thereby, the effect of further reducing iron loss can be obtained.

The steel sheet thus obtained is applied with an insulating film agent and subjected to heat flattening, or after the heat flattening, the insulating film agent is treated to impart tension to the steel sheet. As the treatment conditions, an insulating film agent having a low coefficient of thermal expansion may be applied and baked, or tension may be applied to the steel sheet by means such as plating and vapor deposition. When applying an insulating film agent and baking, SiO ₂ , ZrO ₂ , SnO ₂ , Al ₂ O
Colloidal substances such as ₃ to 100 parts by weight of solid content,
1 of primary phosphates selected from Al, Mg, Ca, etc.
130 to 200 parts by weight of one kind or two or more kinds, and one or more kinds of chromic acid or chromate as CrO ₃ 1
2 to 40 parts by weight are used.

SiO ₂ , Colloidal substances such as ZrO ₂ are important because they form an amorphous film, which creates a tension effect due to binding with phosphate. The phosphate reacts with the colloidal substance and acts as a binder for adhering to the steel sheet, but produces a tension effect in the case of a specific blending ratio. 130 for 100 parts by weight of colloidal substance
If it is less than part by weight, the effect of tension decreases, which is not preferable.
On the other hand, if it exceeds 200 parts by weight, the tension effect is similarly reduced, and seizure during stress relief annealing becomes remarkable, which is not preferable.

Chromic acid and chromate are 1 as CrO _3.
2 to 40 parts by weight are blended. If it is less than 12 parts by weight, a sufficient effect for preventing stickiness due to phosphoric acid or free phosphoric acid cannot be obtained. On the other hand, if the amount exceeds 40 parts by weight, excessive CrO ₃ may cause stickiness and the film appearance may be deteriorated. In such tension imparting insulating coating technology, the thickness of the coating is limited to 2 to 6 μm. In this case, the film tension is 0.5 to 2.0 kg / mm.
² is obtained. If the film thickness is less than 2 μm, a sufficient effect for improving iron loss cannot be obtained. When it exceeds 6 μm, the effect of improving iron loss due to tension approaches a saturated state, and the space factor decreases due to the film thickness, which causes problems beyond the effect of tension, which is not preferable.

In the series of steps from cold rolling to treatment with insulating film agent, press, tooth profile roll, scribing, laser,
The magnetic domain is subdivided by imparting linear or dot-like depressions, distortions, etc. by means of mechanical, optical, chemical or other means such as local etching. The conditions for imparting these are 4 in the rolling direction.
The angle is 5 to 90 degrees, the interval is 2 to 15 mm, and the depth is 1 to 25 μm.

This interval is determined by the relationship between the recesses and the depth of strain applied, but if it is less than 2 mm, the magnetic flux density is lowered, which is not preferable. Fifteen
On the other hand, if it exceeds mm, a sufficient magnetic domain refining effect cannot be obtained. The depth is 1 to 25 μm. If it is less than 1 μm, the effect of subdividing the magnetic domains is weak and the improvement of iron loss is insufficient. If it exceeds 25 μm, the decrease in magnetic flux density becomes large, which is a problem.

The width of the depressions and strains is 500 μm or less.
If it exceeds 500 μm, the magnetic flux density is lowered and the slipperiness of the plate at the time of processing the iron core is affected as in the above-mentioned conditions, so that it is limited. The mechanism by which the present invention provides an ultra-low iron loss material having no glass coating is considered as follows. In the present invention, the reaction between the novel annealing separator and the decarboxylated film forms a proper amount of glass film before the temperature rising of the finish annealing. As a result, an appropriate sealing effect is generated on the surface of the steel sheet, and (Al, Si) N is stabilized and additional oxidation of the steel sheet is prevented.

Then, the glass film layer is chemically etched by the additive component at the latter stage of the temperature increase during the finish annealing to decompose the SiO ₂ in the oxide and react with the MgO side of the surface. After this, a thermal etching effect is further brought about in the high temperature soaking step of finish annealing. At this stage, irregularities on the surface of the steel sheet base metal, which are caused by surface roughness during cold rolling and uneven oxide film during decarburization annealing, are smoothed to give a mirror-like surface. This is because the disappearance of the glass film at a high temperature facilitates the movement of atoms on the surface and lowers the surface tension, resulting in smoothing.

In order to stabilize the decomposition of the inhibitor (Al, Si) N in the glass film decomposition process until the end of the secondary recrystallization at the time of temperature rise, the atmosphere should have an N ₂ ratio of N ₂ 30% or more by weight. By doing so, it is kept extremely stable, and good secondary recrystallization is obtained. The high-flux-density directional material without a glass film thus obtained is continuously treated by a high-strength insulating film agent or a magnetic domain subdivision process which is processed in the steps after cold rolling. , Ultra low iron loss. This is because the surface of the steel sheet is smooth and there is no adverse effect due to the internal oxide layer found in the conventional glass film forming treatment material. In the present invention, since the non-magnetic material portion is not affected by the glass coating, even if the thickness of the high-strength insulating coating agent is increased, it does not affect the space factor or the excitation characteristic unlike the conventional material. The thickness can be increased, and problems with tension effect, insulation, etc. can be sufficiently avoided.

[0037]

【Example】

Example 1 C by weight; 0.054%, Si; 3.35%, Mn;
0.10%, acid-soluble Al; 0.030%, S; 0.00
70%, N: 0.0070%, a steel material consisting of the balance Fe and unavoidable impurities is hot-rolled to 2.0 mm, annealed at 1130 ° C. for 2 minutes, pickled, and cold-rolled to a final plate thickness of 0. 225m
m.

Next, N_Two25% + H_Two75%, dew point 55
Decarburization annealing was performed at 830 ° C for 100 seconds in an atmosphere of ℃
After that, 750 ℃ × 30 seconds, N_Two25% + H_Two75% + N
H_ThreeSteel sheet [N] amount increased to 250ppm in Dry atmosphere
Nitriding treatment was performed so as to obtain a test material. Table on this steel plate
1 is applied to an annealing separator having a composition as shown in FIG.
Finish by changing the atmospheric conditions as shown in (A) and (B)
It was annealed. This steel plate is 2% H_TwoSO _FourAt 80 ℃ x 1
After light pickling for 0 seconds to activate the surface, an insulating film agent
20% colloidal SiO_Two80 ml, 20% roll
Id-shaped ZrO_Two20 ml, 50% Al (H_TwoPO_Four)_Three
50 ml, CrO_ThreeApplying a treatment agent consisting of 7g
Apply it to a thickness of 4 μm, and leave it at 830 ° C for 30 seconds.
A baking process was performed. Surface condition of steel plate in this experiment
Table 2 shows the conditions, coating amount, and magnetic properties.

[0039]

[Table 1]

[0040]

[Table 2]

As a result, none of the ones according to the present invention formed a glass film on almost the entire surface, and a good surface condition without a glass film was obtained. However, the magnetic characteristics are that the finish annealing condition (A) is high magnetic flux density,
The iron loss value was also better than that of the comparative material with the glass film formed, whereas the finish annealing conditions (B) were all poor because the magnetic flux density was extremely reduced. It was also confirmed that the surface roughness of each of the present invention was much smoother than that of the glass film forming material, and the surface properties were modified. Further, the punchability as a workability evaluation was also dramatically improved in the present invention.

Example 2 The same material as in Example 1 was treated in the same manner to obtain the final plate thickness.
It was rolled to 0.225 mm. Use a laser on this steel plate
5mm, 5μm in depth, 1 in width
After applying linear flaws at 00 μm, N at 830 ° C for 100 seconds
_Two25% + H_TwoDecarburization anneal in 75% atmosphere, then
N_Two25% + H_Two75% + NH_ThreeAmong them, the steel plate [N] amount is 2
Nitriding treatment was performed so that the concentration was 20 ppm. Then annealed
After applying the composition shown in Table 3 as a separating agent, finish annealing
Was performed under the conditions shown in FIG. 20% rolling on this steel plate
Id-like SiO_Two70cc + 20% colloidal ZrO_Two2
5cc + 20% colloidal SnO_Two5cc + 50% first
Phosphate Mg50cc + CrO _ThreeInsulating film agent consisting of 5g
Baking treatment was performed by changing the coating film thickness. In this experiment
Table 4 shows the state of the coating and the results of the magnetic properties.

[0043]

[Table 3]

[0044]

[Table 4]

As a result, none of the devices according to the present invention formed a glass film uniformly over the entire surface and exhibited a metallic luster.
On the other hand, with the annealing separator of Comparative Example, a uniform glass film was formed as in Example 1. All of the magnetic properties according to the present invention have a good iron loss value and the amount of the insulating film deposited is 3 to
At 4.5 μm, a particularly good iron loss value was obtained. On the other hand, in the case of the comparative example, the arrival point of the iron loss value was a bad result as compared with the present invention.

[0046]

According to the present invention, a grain-oriented electrical steel sheet having an ultra-low iron loss and having a smooth surface without a glass film can be obtained.

[Brief description of the drawings]

1A is a diagram showing a finish annealing cycle of the present invention, and FIG. 1B is a diagram showing a finish annealing cycle of a comparative example.

Claims (3)

(57) [Claims] 1. A weight ratio of Si: 2.5 to 4.5%, MgO, SiO ₂ , Al ₂ as oxides on the surface of a steel sheet.
The total amount of forsterite and spinel substance composed of O ₃ is 0.6 g / m ² or less, and the thickness of the insulating coating agent is 6 μm or less, and the surface tension generated on the steel sheet surface by the coating agent is 0.5. A high magnetic flux density grain-oriented electrical steel sheet having excellent iron loss characteristics of B ₈ ≧ 1.88 (Tesla), which is ２．０2.0 kg / mm ² . 2. A weight ratio of C: 0.021 to 0.075,
Si: 2.5-4.5%, acid-soluble Al: 0.010
0.040%, N: 0.0030 to 0.0130%, S
≦ 0.0140%, Mn: 0.05 to 0.45%, the balance consisting of Fe and unavoidable impurities is heated at a temperature of less than 1280 ° C., then hot rolled, and then hot rolled if necessary. A low temperature slab that is annealed and cold rolled one or more times to sandwich it to a final plate thickness, then decarburized and annealed, nitrided, annealed and coated with an annealing separator, and annealed and annealed. In the method of manufacturing a grain-oriented electrical steel sheet for heating,
MgO: 1 part by weight or more of at least a Cl compound as Cl to 100 parts by weight, and 1 or 2 or more of a Cl compound and an S compound in a total amount of Cl and S of 1 to 15
The annealing separator was applied, including parts, finishing the atmosphere during the temperature increase in annealing N _2: 30% or more comprising N ₂ + H ₂ atmosphere, and annealing the NoboriAtsushiritsu at 20 ° C. / Hr or less, then the tension A method for producing a high magnetic flux density grain-oriented electrical steel sheet having no glass coating and having excellent iron loss characteristics, which comprises applying and baking an imparting type insulating coating agent so that the thickness after baking is 2 to 6 μm. 3. Cold rolling, decarburization annealing, finish annealing, and insulating film treatment in any one or more steps, such as press, tooth profile roll, scribe, laser, local etching, etc., with respect to the rolling direction of the steel sheet. 3. The core loss according to claim 2, wherein the magnetic domain is subdivided by applying linear or dot-like dents or distortions of 90 degrees, an interval of 2 to 15 mm, a dent depth of 1 to 25 μm, and a dent width of 500 μm or less. A method of manufacturing a high magnetic flux density grain-oriented electrical steel sheet having excellent characteristics.