JPH07126752A - Production of grain oriented silicon steel sheet extremely excellent in core loss and roll - Google Patents

Abstract

PURPOSE:To produce a grain oriented silicon steel sheet excellent in magnetic properties. CONSTITUTION:A kind of so-called intermediate-stage magnetic domain controlling method is used. At the time of preparing a mirror finished material, grooves are formed by means of a roll in a steel sheet after primary annealing. At the time of pressing, the fact that, when rolling is applied to the primary- annealed steel sheet to which a powder of oxide, chloride, or sulfide is allowed to adhere by using a roll having projections, the powder is press-fixed and does not fall is led by a theoretical formula. As a result, the production of the sheet with ultralow core loss by combining the control of intermediate magnetic domain with the dry application of powder is made possible. By this method, the magnetic domain fractionized grain oriented silicon steel sheet can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented silicon steel sheet having excellent magnetic properties, particularly excellent iron loss, and a roll thereof.

[0002]

2. Description of the Related Art 1-7 excellent magnetic properties for transformers, etc.
%, When manufacturing a grain-oriented silicon steel sheet containing Si,
In the final annealing step of performing so-called secondary recrystallization, it is industrially extremely advantageous to obtain secondary recrystallized grains having a sharp {110} <001> orientation, which is generally called the Goss orientation, whose directionality is favorable for magnetic properties such as iron loss. is important. On the other hand, there are many physical factors that control iron loss, but the size of the magnetic domain is particularly important, and it is well known that subdivision is effective in reducing iron loss. It is also known that a smooth surface smoothes the flow of magnetic flux, which is also effective in reducing iron loss. For this reason, in the prior art, so-called products after secondary recrystallization annealing (also referred to as finish annealing) are provided with grooves, or by irradiation marks with a laser or the like to subdivide magnetic domains, or after cold rolling, A method of forming a groove in a steel sheet after primary recrystallization annealing (also referred to as primary annealing) is also performed.

However, these methods are basically based on the formation of a so-called ordinary primary film of forsterite (Mg ₂ SiO ₄ ). However, it is difficult for this method to reduce the iron loss to the level of amorphous.
The reason is that this insulative primary coating called forsterite does not pass magnetic flux, so it is considered that there is an extra additive in terms of the magnetic characteristics per unit weight of the entire steel sheet, and in order to obtain a high magnetic flux density, The thicker the primary coating, the more disadvantageous. From this point, recently, there have been some attempts to manufacture silicon steel plates that have no or little primary coating, but none of them are sufficient from the viewpoint of combination with the above-mentioned magnetic domain control. From an economical point of view, there is a lot of room for industrial improvement.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a method for producing a grain-oriented electrical steel sheet having extremely excellent iron loss and a roll thereof.

[0005]

[Means for Solving the Problems] Usually, in a silicon steel sheet, a slurry in which magnesia (MgO) is dissolved in water is applied to the surface of the steel sheet by a coater roll after primary annealing.
A method is used in which this is dried at a low temperature and then brought to finish annealing. As a matter of course, with finish annealing, MgO
Reacts with Si or SiO ₂ in steel to form forsterite. Even if the grooves are formed on the surface of the steel sheet in the step prior to the finish annealing to control the magnetic domains, the same result can be obtained. Therefore, for the above reason, the magnetic flux density cannot be improved, and the iron loss cannot be decisively reduced. On the other hand, from the viewpoint of manufacturing, in finish annealing that needs to be performed at a high temperature, some sort of annealing separator is necessary also in the sense of preventing adhesion of steel sheets.

For this reason, MgO is not used in the present invention, or the amount of MgO is reduced as much as possible, and other oxides such as oxides such as alumina, which have a weak direct reactivity with Si or SiO ₂ , or chlorides or sulfides. This is a method in which more than one type is used as a finish annealing separator. As a result, a steel sheet in a state where the primary film of forsterite is basically not formed or only a very small amount is formed is obtained,
Finally, it was found that a steel sheet with extremely low surface roughness can be manufactured as a product.

Another important component of the present invention is the method of applying its oxides, chlorides and sulfides to one or more steel sheets. The method in which the oxide is made into a slurry with water and applied with a coater roll or the like as in the prior art cannot be used in the present invention. The reason is that it is better not to make forsterite basically in the present invention, so that when the steel plate surface is activated and a large amount of water is present, rust occurs on the steel plate surface, which later forms foreign matter in the finish annealing, and after the finish annealing. This is because a large amount of foreign matter is generated on the surface of the steel sheet and the reduction of the roughness of the steel sheet surface is significantly hindered. That is, the purpose of the present invention is not to achieve the effect of making the surface of the steel sheet smooth and reducing the iron loss by itself and reducing the iron loss by using the magnetic domain control together.
Therefore, it is necessary to spray one or more of the oxides, chlorides and sulfides on the steel sheet in a dry manner or to apply it by the following method. The atmosphere at this time may be air or a gas such as N ₂ , Ar or H ₂ . A solvent other than water, which does not cause rust on the steel plate, such as alcohol, or an appropriate amount of water containing a rust preventive agent does not necessarily go against the spirit of the present invention.

By the way, oxides, chlorides and sulfides have almost no reactivity with the steel sheet at room temperature, so if they are simply sprayed from above, they are immediately peeled off at the winding stage to bring them to the final annealing in the next step. It is not enough because it does.
Therefore, the following method was considered in the present invention. In other words, before winding the primary annealed steel sheet, first dry-spray one or more kinds of oxides, chlorides and sulfides from the top surface of the steel sheet, and then crimp this with a roll having protrusions on the surface at a certain pitch. However, it is a method of adhering it to the steel plate and winding it as it is. Needless to say, this step may be incorporated in the same equipment as the primary annealing step or may be a single piece of equipment.

It goes without saying that the method of pressure bonding with a roll can secure the adhesiveness more than that of the case of merely spraying, but the aim of the present invention is not limited to this. First, one or more kinds of oxides, chlorides and sulfides are used as an annealing separator,
In order to reduce the surface roughness after finish annealing and increase iron loss, it is of utmost importance to increase the reactivity of oxides, chlorides and sulfides with base iron, and for this purpose, oxidation should be performed as much as possible. It is necessary to keep particles of chloride, chloride and sulfide small. Next, it is necessary to adhere the oxides, chlorides and sulfides to the steel sheet as much as possible so that the powders of the oxides, chlorides and sulfides do not peel off from the steel sheets when wound up. The roll with protrusions according to the present invention has both the crushing effect and the adhesion improving effect. That is, in the present invention, a particularly important point is the effect of the roll with protrusions.

It is natural that the protrusions form a groove in the steel sheet, and it remains in the product to bring about a magnetic domain refining effect. On the other hand, since the protrusions are present at a certain pitch during the pressure-bonding rolling, this results in It was found that the so-called powder was clamped down, and the pulverizing effect of the above oxides, chlorides and sulfides and the effect of adhering to the steel sheet were particularly good. In other words, it was found that this roll with protrusions is more effective than two birds with one stone. The following reasoning was attempted for the purpose of examining this effect. Considering the deformability as an aggregate of oxide, chloride, and sulfide particles as that of one kind of plastic body is as shown in FIG.

In FIG. 1, σ _{W is} the stress in the roll rotation direction, σ _{L is} the stress in the roll axis direction at right angles to it, and σ _T is the stress in the direction perpendicular to the plate surface. On the other hand, the equivalent stress σ _eq of a plastic body is expressed by an equation.

[0012]

[Equation 1] Plastic yield is assumed to occur when this σ _eq reaches a constant value σ _O. When there is no protrusion on the roll as shown in FIG. 1A, σ _L can be set to about 0 and σ _W can be set to about 0.
The yield condition is as shown in the formula. σ _eq = σ _T = σ _O ………………………………………… On the other hand, if there is a protrusion on the roll as shown in Fig. 1 (b), the roll rotation direction will be constrained. While σ _L is about 0, σ _W has the following significant values, and the yield condition is then given by the equation.

[Equation 2]

As is clear from a comparison of the equations, when the roll has a protrusion, the stress perpendicular to the plate surface is larger than when the roll has no protrusion. Therefore, when a constant compressive strain (that is, σ _{eq of} is the same) is given to the plastic body,
The stress σ _{T, which} is perpendicular to the plate surface, is increased by adding protrusions to the roll. When the powder of oxide, chloride and sulfide is sprinkled on the steel sheet to increase the σ _T and pressure-bonded and rolled, the adhesion of the oxide, chloride and sulfide to the steel sheet is improved, and the oxide, The crushing condition of chloride and sulfide particles becomes finer and the reactivity also increases. FIG. 2 is a graph showing the adhesion of chlorides to the steel sheet and the iron loss characteristics of the product after finish annealing in an experiment for the steel sheet (sheet thickness 0.23 mm) of the components shown in Table 1.

[0014]

[Table 1]

That is, dried fine powder of Bi chloride having an average particle size of 8 μm and a ratio of the standard deviation of the particle size to the average particle size (described later) of 20% was used to form protrusions having a rectangular cross section (height 30) with an average interval of 7 mm.
(300 μm in width, 50 μm in width) and a steel roll with a diameter of 300 mm and a steel roll of the same type without protrusions, after rolling with the same pressing amount (23%) for Bi chloride, this steel sheet was bent with a radius of curvature R = 150 mm. In the test (n = 5), the peeling surface area ratio of Bi chloride and the iron loss value when this steel sheet was made into a product by finish annealing were examined. In addition, crimping amount (%)
Is defined by how much the thickness (T ₁ ) of the oxide, chloride and sulfide powder before entering the roll has been reduced relative to the thickness (T ₀ ) of the oxide, chloride and sulfide powder before entering the roll. Yes, and is represented by 100 × (T ₀ −T ₁ ) / T ₀ .

As shown in FIG. 2, when the roll was provided with protrusions, the powder did not peel off and the adhesion was good. Also, the iron loss characteristics of the product were good when the groove was formed on the roll, because a stable and low value was obtained. In order to improve the adhesion of the oxide, chloride and sulfide to the base iron in the present invention, it is preferable to perform activation treatment such as pickling after primary annealing to activate the steel sheet surface. And good. Note that this kind of activation method is of course the use of other chemicals besides pickling, mechanical methods such as brush, shot blasting, high water pressure, electrical methods such as static electricity and magnetism, ultrasonic waves, etc. There are various physical methods. In addition, in order to adhere the oxide, chloride, and sulfide powders to the steel sheet, pressure bonding with a roll having protrusions was performed in the present invention, but the principle of the electrostatic coating method or the like may be used as an auxiliary means. In some cases, it does not change the essence of the invention and is rather preferable.

Next, constraints on the shape of the protrusions on the roll will be described. If the height of the protrusion is less than 1 μm, the constraint of deformation of the plastic body of the powder in the roll rotation direction is weak and the effect is not sufficient. On the other hand, if it exceeds 100 μm, the contact with the steel plate body is larger than that with the powder restraint, and the tightening of the powder is not sufficiently effective. If the width of the protrusion is less than 2 μm, the powder cannot be sufficiently restrained. On the other hand, if it exceeds 400 μm, there are too many parts to which the powder is applied, resulting in an imbalance in the thickness of the powder after rolling and pressure bonding, which eventually causes variations in the magnetism of the product. Here, the width of the protrusion refers to the width of the roll surface (bottom surface) of the protrusion. If the average spacing between the protrusions is less than 2 mm, too much powder is applied to the powder, resulting in an imbalance in the powder thickness, resulting in variations in the magnetism of the product. On the other hand, 50
When it is more than mm, the constraint of the deformation of the powder plastic body in the roll rotation direction is weak, and the sufficient effect of the present invention cannot be obtained. If the longitudinal direction of the protrusion is less than 45 ° with respect to the roll rotation direction, the magnetic domain control effect cannot be fully exerted, and improvement of magnetism cannot be expected.

Regarding the shape of the protrusions, it is not always necessary to regularly attach the same shape to one roll, and the pitch may not be constant. It is determined only by the ease of roll manufacturing, and usually the same protrusions are regularly attached. In addition to this protrusion, it is not unbalanced to the purpose of the present invention to use an unspecified pattern for the purpose of tightening the powder, for example, a checkered pattern, but in this case, it is light enough not to disturb the magnetic domain control. There is a need to. In the present invention, the use of a roll with protrusions on the upper surface of the steel sheet, and oxides, chlorides and sulfide powders are considered in principle, but of course oxides from the lower surface,
The application of chloride and sulphide does not prevent this.
In particular, the combination of electrostatic coating or the like is extremely effective.
Also, of course, the use of opposite rolls or backup rolls as a pair of raised rolls is in accord with the purpose of the present invention.

It is also effective to provide a filter for leveling powder of oxides, chlorides and sulfides on the steel plate to a certain height before the roll with protrusions. Further oxides, non-oxidizing atmosphere in the range of 600 to 1000 ° C. prior to spray chlorides and sulfides itself steel (N _2, A
Heating with r, H ₂ gas, etc.) is extremely useful.
The reason is that the oxide, chloride and sulfide powders are activated to increase the adhesion to the steel sheet, and on the other hand, when making grooves in the steel sheet with a roll with protrusions, it is easy to form grooves neatly and This is because it is difficult to form a group of fine grains due to cold strain in the vicinity of this groove during finish annealing, and it is also effective for improving the magnetic characteristics of the product. In that sense, it is also useful to heat the steel plate to the above temperature immediately before or during rolling with a projection roll. Here, 600 ° C. is the lower limit temperature at which oxides, chlorides and sulfides adhere to the steel sheet and do not form fine particles in the vicinity of the grooves later, while above 1000 ° C., oxides, chlorides and sulfides are rather returned. Objects are aggregated with each other, and abnormal particles are likely to appear near the groove.

Now, the average particle size of oxides, chlorides and sulfides dispersed in the present invention has an optimum range. The smaller the size, the better the reactivity with the surface and the crimp tightening property. However, if the size is too small, aggregation is likely to occur, and the lower limit is preferably 0.5 μm. On the other hand, if it is too large, it does not adhere to the steel sheet first, and it is difficult to be crushed even by rolling, resulting in deterioration of adhesion and reactivity, so the upper limit is 100 μm. Preferably 8 to 30 μ
m is good. Further, it is important that the particle diameters of oxides, chlorides and sulfides vary. If the ratio of the standard deviation of the particle size represented by the following and the average particle size multiplied by 100 exceeds 70%, it is difficult to uniformly grind during rolling, and oxide, chloride and sulfide steel sheets are formed. In addition to being poor in reactivity, the depth of the groove is difficult to be uniform for the purpose of regularly forming the grooves with protrusions, and the magnetism varies depending on the location. Generally, this value can be controlled to 20% or less unless particles having significantly different particle diameters are mixed.

Standard deviation: σ _n = [{ΣX ² − (ΣX) ²
/ N)} / n] ^1/2 where X: particle size n: number of particles

Further, the amount of powder pressure-bonded by the roll is also important. As a matter of course, when the pressure-bonding amount is extremely small, the powder cannot be adhered to the steel plate, which is the object of the present invention, and the pressure-bonding amount of at least 3% is necessary. Further, in order to sufficiently form the groove by the projection on the steel plate, it is preferably 10
% Is required. On the other hand, if it exceeds 90%, the powder will be pressed and aggregated. Further, if the groove formed by the projection on the steel plate is too deep, the magnetism is rather deteriorated depending on the shape of the projection, so 70% or less is preferable.

Next, the shape of the projection attached to the roll will be described. This has a sectional shape perpendicular to the longitudinal direction of the protrusion, but any of the following may be used. Squares, rectangles, triangles, trapezoids, parts of circles, parts of ellipses, parts of parabolas, spindles, parts of polygons, and combinations thereof. Further, a shape obtained by modifying some of these portions, for example, a trapezoid, a rectangle, a triangle, or the like having rounded corner portions with a certain curvature does not of course change the essence of the present invention. A method for facilitating the above-mentioned principle industrially, including tool life, meets the object of the present invention.

Further, although the material of the roll is not specified, any material may be used as long as it is hard and has appropriate toughness. For example, steel, non-ferrous metal, ceramics, diamond, etc. can be considered as an example, but this manufacturing method is also a forging method,
Any method such as casting method and powder metallurgy method may be used. Further, it is also useful to make the inside steel and only the outside non-steel as described above, or to treat only the surface with a special heat resistant and wear resistant hard material by CVD, PVD or the like. Further, it can be said that it is preferable in terms of cost to manufacture the protrusions on the roll main body only by using another substance, and to attach and combine the protrusions with each other to reduce the basic unit.

Next, the types of oxides, sulfides and chlorides will be described. In short, as mentioned above, Si and SiO in steel
By reacting with ₂ such forsterite (Mg ₂ SiO ₄₎ it is important not to much generated, filled it, and high temperature refractory oxides to withstand the finish annealing, any at chlorides and sulfides Anything is fine. Be, B, Al, S
i, P, Ca, Se, Ti, V, Cr, Mn, Co, N
i, Cu, Zn, Ga, Ge, Sr, Y, Hf, Zr,
Nb, Mo, Te, Ba, Sb, La, Ce, Ta,
Oxides such as W, Bi, Pb and Na, chlorides and sulfides can be used. These oxides, sulfides and chlorides can also be used in combination with one another. Among these, Bi oxides, chlorides and sulfides are particularly effective for mirror-finishing the steel sheet after finish annealing.

As will be described later, if the thickness of forsterite is 0.3 μm or less, the target low iron loss can be sufficiently obtained on the premise of magnetic domain control by groove formation in the steel sheet according to the method of the present invention. In this sense, mixing the oxides of the above elements, chlorides, and sulfides with Mg oxides, if any, does not change the essence of the present invention. In the present invention, unlike conventional silicon steel sheets, forsterite is basically not generated, and therefore tension is applied to improve iron loss after finish annealing, and coating is particularly required to ensure insulation. There are various possible methods for this,
Current coating method of phosphoric acid or chromic acid-based coating and firing, or repetition of this method, coating of oxide such as alumina, spinel, cordierite having a lower thermal expansion coefficient than iron by sol-gel method and firing , Or CVD, PV
Any method such as a method of directly adding an oxide or a nitride to the surface by D or the like may be used as long as it is a method of providing the steel with tension and insulation.

Here, a method for manufacturing the grain-oriented silicon steel sheet of the present invention will be described. In the secondary recrystallization of the grain-oriented silicon steel sheet, it is important to grow grains of {110} [001] orientation called Goss orientation during secondary recrystallization annealing (also called finish annealing). This is to coarsely recrystallize only certain grains in the primary recrystallization annealing (also called primary annealing).
At this time, it is well known in the art that fine precipitates such as AlN called an inhibitor (Inhibitor) should be sufficiently prepared before finish annealing.

Then, nitrogen necessary for this purpose is added during steel melting, after primary annealing, or during other steps. In that case, it was also found that the method of adding nitrogen after the primary annealing is the optimum method of adding nitrogen for the purpose of the present invention. If nitrogen is added during or immediately after the primary annealing, the equipment for performing the nitriding reaction is usually installed inside or close to a part of the equipment for the primary annealing that also functions the decarburization reaction, and after or after the primary annealing. A method of nitriding reaction in parallel is also effective. In the case of steel that has been sufficiently carbonized during the melting of steel, it is rather important to change the oxide layer of the surface layer after primary annealing so that it has an advantageous shape for the coating reaction, rather than the decarburizing function. By the way, in the present invention, secondary recrystallization annealing is performed, and heat flattening annealing and insulating film coating are performed as necessary. In the present invention, it is desirable to regularly provide grooves having an average maximum depth from the base metal surface of 2 to 80 μm, which will introduce strain on the surface of the steel sheet after the primary annealing. This is because the grooves can make the magnetic domains of the product finer and contribute to the reduction of iron loss.

However, with this alone, the extremely low iron loss targeted by the present invention cannot be obtained. The most important technical requirement in the present invention is that it does not form a forsterite coating. Even if formed, it was found that when the average thickness of the primary film containing forsterite as a main component is 0.3 μm or less, the magnetic properties are remarkably improved in combination with the above.
The reason for this is not necessarily understood, but if this primary coating is thick, it obstructs the flow of the magnetic flux of the steel sheet, especially if the coating has many irregularities, or if spinel (MgO
It can be easily imagined that this tendency is large when there are many oxides such as Al ₂ O ₃ ). Therefore, if the primary coating on the surface is reduced as much as possible to be thin or completely removed, and if regular grooves are formed instead, the magnetic flux flows regularly and smoothly. As a result, iron loss can be sufficiently reduced. As will be described later, the depth and pitch of the groove are naturally limited.

[0030]

[Table 2]

A grain-oriented electrical steel sheet having the chemical composition shown in Table 2 (N content of R1 is a value after primary annealing and nitriding) is hot-rolled, hot-rolled and annealed, and cold-rolled to 0.15 mm, and then primary-annealed. Done,
Dry-rolled BiCl powder on a steel sheet, MgO powder with various additives changed, and then sprayed and rolled with projections (maximum projection height 25 μm, width 30 μm, pitch 45 mm) and MgO powder with water. FIG. 3 shows the results of examining the iron loss of a sample in which the slurry was dissolved into a slurry and applied as a slurry by means of a coater roll, followed by finish annealing and further applying an insulating coating having tension.

From this, it is apparent that the one coated with Bi chloride has the lowest iron loss, while the one using MgO shows a reduction (improvement) in the iron loss as the thickness of the primary coating becomes smaller, It can be seen that it is particularly remarkable at 0.3 μm or less. Especially dry type is excellent. In the present invention, forsterite is basically unnecessary, and it is preferable that it is not. However, even if it is mixed as a part of the oxide powder, if it is forsterite of such a degree, there is no harm to the object of the present invention.

Next, in the case of significantly adding Al when performing secondary recrystallization, AlN or S is used as one of the inhibitors.
It has also been found that i ₃ N ₄ is used, but the method of nitriding during or after the primary annealing as one of the methods of the present invention is more preferable for the purpose of the present invention. This is for the following reason.
Unlike the case where a large amount of nitrogen is added during steel melting, it is easier to control the optimum amount of AlN and Si ₃ N ₄ by nitriding later, and during secondary recrystallization annealing, it is possible to perform primary recrystallization such as forsterite as in the present invention. It is considered that the optimum nitrogen amount can be easily secured by controlling the nitrogen partial pressure (P N ₂ ) in the atmosphere even if the film becomes thin or disappears.

Next, as described later, in order to reduce or eliminate the primary coating film during finish annealing as much as possible, in the present invention, the surface of the steel sheet after the primary annealing is dry-processed with an oxide, chloride or sulfide other than MgO. It is known that this purpose can be sufficiently achieved by coating, but on the other hand, even if special chloride or sulfide is mixed in ordinary magnesia (MgO) powder and sprinkled, the average primary coating of 3 μm or less is obtained. It is also known as knowledge that the thickness can be set.

Among these, oxybismuth chloride (BiOCl), bismuth chloride (BiCl ₃ ), calcium chloride (CaCl ₂ ), potassium sulfide (K ₂ S) and the like are particularly effective. Even in the normal method, in addition to MgO, Ti
Add O ₂ or antimony oxide (Sb ₂ (SO ₄ ) ₃ ), boron oxide (Na ₂ (BO ₄ ) ₃ ), strontium / barium oxide, carbon / nitride oxide, etc. However, since the effects of these additives are exerted in the present invention, addition of these additives does not change the essence of the present invention. Furthermore, what is important in the present invention is that when Bi chloride, oxide or sulfide is used as powder, the primary coating of forsterite is extremely reduced, which is preferable for mirroring. Now, a method for manufacturing a silicon steel sheet will be described next.

As described above, the silicon steel sheet that can be used in the present invention is S
In addition to i, if necessary, Al is contained, and if Si ₃ N ₄ or AlN and S in the steel are large, MnS is used as the main inhibitor, and in order to further reduce iron loss, P and S are added.
n, Se, Sb, Cu, B, Nb, Ti, V, Ni, M
The addition of other additive elements such as o, Cr, Bi, W, and Hf to improve the magnetic characteristics does not change the basis of the present invention. P, Bi, etc. are also effective in improving the magnetic flux density.

By the way, AlN or Si ₃ N ₄ , Mn
Steel containing S as an inhibitor is known, and the technique of the present invention can be applied to any of the cases. However, the following production method is most suitable for further exerting the characteristics of the present invention. That is, Si
Steel containing 1 to 7% of Al, if necessary, 0.1
% Or less, and secondary recrystallization annealing is performed by a method of forcibly adding N to steel through denitrification reaction during or after decarburization annealing during primary annealing after cold rolling in a silicon steel sheet manufacturing process. The method is characterized by including N in 30 to 600 ppm steel before.

In the present invention, at least 1% of Si is necessary for forming forsterite as described above. On the other hand, if it exceeds 7%, the workability is extremely deteriorated and it is not suitable for industrial production. Al is effective in forming an AlN inhibitor.
However, if it exceeds 0.1%, the amount of Al ₂ O ₃ produced increases, impairing the cleanliness of sound steel, and thus adversely affecting the magnetic properties. N is indispensable for forming Si ₃ N ₄ and AlN inhibitor, and when AlN is used as an inhibitor, in the present invention, at least 30 ppm is required after the primary annealing, that is, before the secondary recrystallization of the finish annealing.
Is necessary. On the other hand, if Al is used intentionally, AlN
From the viewpoint of securing the amount of 60ppm or more is necessary. However, 6
If it exceeds 00 ppm, Al and Si are eaten too much, which is not preferable. This is not the case when AlN is not used.

P is useful in the invention for increasing the magnetic flux density. When the steel is melted, if it is less than 0.04%, the effect of increasing the magnetic flux density is small, while if it exceeds 0.20%, the brittleness becomes large and cold rolling is difficult. In the present invention, Sn and Cu are significantly effective in reducing iron loss when they coexist with P.
If the total of seeds or more is less than 0.02%, the effect is not obtained, while if over 0.20%, the primary coating cannot be sufficiently performed. When S is positively used, at least 0.01% of S is necessary for effectively using MnS as an inhibitor. on the other hand,
If it exceeds 0.05%, aggregation is not preferable. In the present invention, other elements are not particularly characteristic as compared with the conventional steel, but it is preferable to restrict them as follows.

C must be sufficiently low during steel melting or sufficiently low during decarburization annealing of primary annealing, and is preferably 0.03% or less at the start of secondary recrystallization annealing. Mn is 0.
If it is 5% or less, it reacts with S to form an MnS inhibitor. If it is 0.15% or less, it is preferable for further improving the magnetic flux density. If O is 0.05% or less after steel is melted, Al ₂ O
₃ is not too much and is preferable for cleanliness.

Next, the production method of the present invention other than the chemical components will be described. Continuous slab continuous casting method, ingot slabbing method or thin slab for skipping hot rolling step, where steel is tapped in a converter or electric furnace and the refining process is added as necessary to adjust the composition. A slab having a thickness of 30 to 400 mm (50 mm or less in the thin slab continuous casting method) is formed by a casting method or the like. Here, 30 mm is the lower limit of productivity and 400 mm is the center segregation A
This is the upper limit for preventing the distribution of l ₂ O ₃ etc. from becoming abnormal. Further, 50 mm is the upper limit for suppressing the generation of coarse particles due to the low cooling rate.

The slab is reheated to 1000 to 1400 ° C. by gas heating, electric heating, etc., and then hot rolled to obtain a hot coil having a thickness of 10 mm or less. Here, 1000 ° C. is the lower limit of AlN melting, and 1400 ° C.
Is the upper limit of surface roughness and material deterioration. Further, 10 mm is an upper limit for obtaining a cold speed at which an appropriate precipitate is formed. In the thin slab continuous casting method, it is possible to directly form a coil, and for that purpose, it is preferably 10 mm or less. The hot coil thus produced is often annealed again at 800 to 1250 ° C. to improve the magnetism. 8 here
00 ° C is the lower limit for remelting AlN, and 1250 ° C is Al
N is the upper limit for preventing coarsening.

After this treatment step, the hot coil is directly or batch-pickled and then cold-rolled. Cold rolling is performed at a rolling reduction of 60 to 95%, 60% being the limit of recrystallization in the present invention, preferably 70% or more by primary annealing {1
11} [112] is a lower limit for increasing the number of oriented grains to promote the generation of Goss oriented grains during secondary recrystallization annealing, while above 95% is a Goss orientation referred to as swinging Goss grains in secondary recrystallization annealing. The grains are rotated in the plane of the plate, and grains which are not favorable for the magnetic properties are generated.

The above is the case of manufacturing by the so-called single cold rolling method. However, in the case of performing cold rolling-annealing-cold rolling called the double cold rolling method, the first rolling reduction is 10 to 80%, The second rolling reduction is 50 to 95%. Here, 10% is the minimum reduction ratio necessary for recrystallization, 80% and 95% are the upper limit reduction ratios for producing proper Goss-oriented grains during secondary recrystallization, respectively, and 50% in the double cold rolling method. Is the lower limit of the reduction ratio that appropriately leaves the {111} [112] oriented grains during the primary annealing.

It is also commonly called "interpass aging" and it is effective to improve the magnetic properties by heating the steel sheet in the range of 100 to 400 ° C by an appropriate method during the cold rolling. 10
Below 0 ℃, there is no effect of aging, while at 400 ℃
If it exceeds the limit, dislocations will be recovered. After that, primary annealing is performed, and at this time, nitriding is performed if necessary. Both the single cold rolling method and the double cold rolling method perform primary annealing, but it is effective to perform decarburization by this annealing. As described above, C is not preferable for the growth of secondary recrystallized grains, but also causes deterioration of iron loss remaining as an impurity. In addition, if C is lowered during melting of steel, not only the decarburization process is shortened but also {111} [1
12] It is preferable because the number of oriented grains is also increased. By setting an appropriate dew point in this decarburization annealing step, the oxide layer necessary for the subsequent formation of the primary coating can be secured.

The primary annealing temperature is preferably 700 to 950 ° C. Here, 700 ° C. is the lower limit temperature at which recrystallization is possible, and
50 ° C. is an upper limit temperature that suppresses the generation of coarse particles. Further, in the present invention in which N of AlN or Si ₃ N ₄ inhibitor is forcibly added by the nitriding method during the primary annealing, the nitriding method by ammonia (NH ₃ ) or the like may be performed continuously during or immediately after the primary annealing. Done.

The temperature of the nitriding method in this case is 600 to 950.
C is preferred. Here, 600 ° C. is the lower limit for causing the nitriding reaction, while 950 ° C. is the upper limit for suppressing the generation of coarse particles. In the present invention, nitriding is preferably performed after the primary recrystallization annealing, but industrially, a partition is provided on the rear surface of the same furnace and the atmosphere is slightly changed as necessary, and NH ₃ gas is passed or a nearby facility is installed. Therefore, it is often nitrided in parallel with primary recrystallization. At this time, as described above, the lower the N ₂ partial pressure is, the larger the nitriding amount is, and the partial pressure ratio P N ₂ / P H ₂ of nitrogen and oxygen is preferably 0.5 or less.

The step of spraying one or more kinds of oxides, chlorides or sulfides on the surface of the steel sheet after the primary annealing and press-bonding them with a roll having protrusions is particularly important in the present invention.
The oxide or the like may be any of the above-mentioned substances other than MgO, but when a part of MgO is mixed and used, the following method is preferable. In this case, in particular, as described above, the average thickness of the primary coating after secondary recrystallization annealing needs to be 3 μm or less. For this purpose, 100 parts by weight of MgO in magnesia (MgO) and Li on the surface of the steel sheet are required. , K, Na, Bi, Ba, Ca, M
0.5 to 20 parts by weight of one or more sulfides such as g, Zn, Fe, Zr, Sn, Sr, and Al and / or carbonates, nitrates, and chlorides of these elements It is preferable to apply one or two or more selected from 0.5 to 20 parts by weight of an annealing separator and add chloride, sulfide or oxide.

In this case, for example, among chlorides, bismuth chloride (BiCl ₃ ) or calcium chloride (CaCl ₂ ),
Among sulfides, potassium sulfide (K ₂ S) is the representative.
The amount of this addition is preferably 0.5 to 20% (weight ratio when the weight of MgO is 100). If it is less than 0.5%, there is no effect of thinning the primary coating, while if it exceeds 20%, the reactivity deteriorates and secondary recrystallization is not sufficiently performed.

On the other hand, it is also possible to facilitate the melting of the MgO powder during the subsequent secondary recrystallization annealing and add a small amount of an appropriate compound. When MgO is used, TiO ₂ , Sb ₂ (S
It is useful that addition of O ₄ ) ₃ and Na ₂ B ₄ O ₇ is also performed. However, for the purpose of the present invention, it is possible to manufacture a grain-oriented silicon steel sheet having a surface in which other oxides, chlorides or sulfides are thinner or almost mirror-like without using MgO. It is possible to further reduce the iron loss in combination with the components and the manufacturing conditions. Next, the groove formation will be described. The method for forming the groove is as described above, but more preferably the average depth of the maximum part of the groove is 2 μm.
Above, the magnetic domain subdivision effect becomes large, while 80 μm
If it is too deep, it will be too deep to prevent the smooth flow of magnetic flux and worsen iron loss.
m is good. The grooves should be regularly arranged. This is because the magnetic domain is subdivided regularly.

Usually, it is preferable to engrave at a substantially constant pitch having an angle of 45 ° to a right angle with respect to the longitudinal direction of the steel sheet. This is because if the angle is less than 45 °, the direction of magnetic domain subdivision does not match the crystallographic orientation preferred for magnetism. The groove pitch is preferably 2 to 50 mm. The reason for this is as described above, but if it is less than 2 mm, the domain division will be too advanced.
The 0 ° domain increases, and the iron loss and magnetostriction are bad. On the other hand, if it exceeds 50 mm, the effect of subdividing the magnetic domain is not obtained.

In the present invention, the secondary recrystallization annealing is preferably carried out at the highest temperature reached of 1100 to 1300 ° C.
1100 ° C. is the lower limit temperature at which secondary recrystallization is performed,
On the other hand, if the temperature exceeds 1300 ° C., the crystal grains become too coarse, and the iron loss deteriorates. The important points in this secondary recrystallization annealing are as follows. In the present invention, there is no primary coating containing forsterite as a main component, or even when MgO is used, it is extremely reduced or eliminated, so that a nitrogen-based inhibitor (AlN, Si ₃ N 2) is added to secondary recrystallization during annealing. ₍₄ etc.) is mainly used, N is included in the finish annealing, and the inhibitor of the compound tends to escape. Therefore, the nitrogen partial pressure (P N ₂ ) in the atmosphere gas of the finish annealing should be 30% or more. By doing so, this can be prevented and stable secondary recrystallization can be obtained.

On the other hand, when MnS or another compound is used in addition to the N-based inhibitor, the secondary recrystallization tends to be stable even if it is not always restricted by this restriction. In addition,
After completion of the secondary recrystallization, it is better to reduce the N ₂ partial pressure to 0 or increase the H ₂ partial pressure to 100% before or after reaching the maximum temperature for purification. Further, if the rate of temperature rise in the secondary recrystallization annealing is too high, the inhibitor easily escapes before sufficient secondary recrystallization occurs. Therefore, it is rather preferable to keep the rate of temperature rise below 50 ° C. for stable magnetic properties. can get. Note that, as described above, the nitriding method in which nitrogen is additionally added from the atmosphere or the like may be performed at a relatively previous stage during the secondary recrystallization annealing.

The above is an important part of the method for producing a silicon steel sheet according to the present invention, but industrially, the steel sheet after secondary recrystallization is insulated with an organic or inorganic material for the purpose of further improving the insulation characteristics and magnetic characteristics. It is particularly important to apply a high-strength coating having a coating (roll coating or sol-gel method) in combination with heat treatment or the like. The reason for this is that, in the present invention, there is basically no primary coating having high tensile properties such as forsterite, or even if there is extremely few, it is necessary to apply an insulating coating having high tensile properties to supplement it. Is effective. It should be noted that heat treatment for heat flattening before and after the coating or heat treatment for facilitating the high tension coating to be closely applied to the steel sheet and further improving iron loss and the like may be carried out according to the present invention. It is also preferable from the point of view.

[0055]

EXAMPLE Steels having chemical compositions shown in Tables 3, 4, 5, 6 and 7 were melted in a converter and produced under the conditions shown in Tables 3, 4, 5, 6 and 7.

[0056]

[Table 3]

[0057]

[Table 4]

[0058]

[Table 5]

[0059]

[Table 6]

[0060]

[Table 7]

[0061]

[Table 8]

A part of the hot-rolled sheet was annealed under the conditions of 11
After being carried out at 20 ° C. for 30 seconds, it was rapidly cooled. Aging between passes during cold rolling was performed except for B-5, but the condition was 25.
It is 0 ° C. Although a part of the nitriding subsequent to the primary recrystallization annealing was performed, it was performed by making the atmosphere dry with the same gas composition in the inner part of the furnace where the partition was provided in the same furnace and flowing a certain amount of NH ₃ gas. It is a thing. The amount of nitriding after the primary annealing (the amount of nitrogen in the steel after the primary annealing) is shown in the same table. Further, this steel sheet was sprayed with oxide, chloride or sulfide powder by the method of the present invention, and various shapes and conditions were changed, and pressure bonding was performed using a roll with protrusions. A-20, B-5,
All were performed dry except for B-7. In B-6, Bi chloride was rolled down (compression rolling) in an N ₂ gas atmosphere. Also,
B-7 was pressure-bonded with Bi chloride containing a small amount of an organic solvent.

On the other hand, with respect to B-5, a small amount of water containing a rust preventive agent was included in the oxide and pressure-bonded. For A-2 and A-4, powders of chloride and sulfide were heated to 900 ° C. in an atmosphere of N ₂ 70% + H ₂ 30%, and then sprayed on a steel plate. A-
In Nos. 4, A-19, the steel sheet was rolled by a burner at 800 ° C. in an Ar atmosphere immediately before rolling the steel sheet with a roll having protrusions and then rolled. In addition, A-20 was prepared by dissolving an oxide in water to form a slurry, and then applying it to the upper and lower surfaces of a steel sheet with a normal coater roll, and further sealing the steel sheet in an atmosphere of N ₂ 50% + H ₂ 50% to 820 ° C. After heating, it was rolled by a roll with protrusions. It should be noted that the triangular apex portion of the protrusion of A-1 and both the apex portions of the trapezoid of A-4 are each 5 to 10
It is rounded with a large radius of curvature of mm.

A-19 and A-20 are steel rolls with diamond and powder metal projections. Further, the pitch of the protrusions indicates the average distance between the protrusions, and for B-1, the pitches of 5 mm and 15 mm are alternately provided and expressed as the average. In addition, B-1, B-
For No. 2, powders of oxides and chlorides were also applied from the lower surface of the steel sheet by using the electrostatic application method together. After that, wind it up, 80
Secondary recrystallization annealing (finish annealing) was performed while changing the average temperature rising rate from 0 ° C. to the highest reached temperature and the atmosphere gas composition in various ways.

The highest temperature reached here is 12000.degree. After reaching the maximum temperature, the atmosphere gas is set to 100% H ₂
Switched to. Furthermore, various coatings were applied to produce a high-strength coating that provides tension and insulation, and heated for firing. Then, the plate was removed and subjected to strain relief annealing at 850 ° C. for 4 hours (N ₂ 90-H ₂ 10, Dry), and a magnetic measurement test was performed. The results are shown in Tables 3, 4, 5, 6 and 7.

Magnetic measurement is SST of 60 × 300 mm single plate.
Measured by the test method, magnetic flux density of B ₈ (800 A / m), unit is Tesla and W _17/50 (iron loss at 1.7 Tesla at 50 Hz, unit is watt / kg), W _13/15 ( At 50Hz 1.
The iron loss at 3 Tesla) was measured. Now, Tables 3, 4,
As shown in Nos. 5, 6 and 7, the products within the scope of the present invention are excellent in that the roughness is small, the magnetic flux density is high, the iron loss is low and the products are sufficiently within the scope of the present invention. I understand.

[0067]

The present invention makes it possible to obtain an ultra-low iron loss grain-oriented electrical steel sheet.

[Brief description of drawings]

1A and 1B are explanatory views of stress conditions of a steel plate,
(C) is a conceptual diagram regarding a roll with protrusions.

2 (a) and 2 (b) are charts showing the adhesion and iron loss characteristics of oxides according to the examples of the present invention.

FIG. 3 is a chart showing the relationship between the average thickness of the primary coating and iron loss.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Murakami 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technical Development Division

Claims (6)

[Claims] 1. A method for producing a grain-oriented electrical steel sheet, which comprises smelting steel containing Si: 1 to 7% and hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing as basic steps. Characteristic of adding one or more kinds of oxides, chlorides and sulfides to the surface of the steel sheet after the primary recrystallization annealing, and thereafter, press-bonding this with a roll having protrusions and winding up A method of manufacturing grain-oriented electrical steel sheets with extremely excellent iron loss. 2. In the roll with the protrusion, the protrusion of the roll has a maximum height of protrusion of the protrusion from the roll reference surface of 1 to 100 μm, a width of 2 to 400 μm, an average interval between the protrusions of 2 to 50 mm, A roll characterized in that the longitudinal direction of the protrusions is 90 to 45 ° with respect to the roll rotation direction. 3. The production method according to claim 1, wherein the rolls according to claim 2 are used to set the pressure bonding amount of oxides, chlorides and sulfides to 3 to 90%. 4. The method according to claim 1 or 3, wherein a compound of Bi (bismuth) is used as at least one of oxide, chloride and sulfide. 5. The oxide, chloride, and sulfide particles have an average particle size of 0.5 to 100 μm, and the ratio of the standard deviation of the particle size to the average particle size is 70% or less. Item 4. The method according to Item 1, 3 or 4. 6. When applying one or more kinds of oxides, chlorides and sulfides to a steel sheet, the steel sheet after cold rolling is subjected to any of chemical treatment, physical treatment, mechanical treatment and electrical treatment. The method according to claim 1, 3, 4 or 5, characterized in that: