JPH06220542A - Production of high magnetic flux density silicon steel sheet excellent in core loss - Google Patents

Abstract

PURPOSE:To provide the method for producing a high magnetic flux density silicon steel sheet excellent in core loss. CONSTITUTION:In the SL process for a silicon steel sheet contg. 1 to 7% Si and in which >0.045 to 0.20% P and 0.02 to 0.20% Sn are coexistent, between 300 to 950 deg.C in the intermediate stage (before and after primary annealing), intermediate domain control such as groove formation is executed, by which the grain-oriented silicon steel sheet having extremely high magnetic flux density and ultralow core loss 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 electrical steel sheet having excellent magnetic properties.

[0002]

2. Description of the Related Art In manufacturing silicon steel sheets having excellent magnetic properties for transformers, etc., it is necessary to secure insulation properties and to give tension to the steel plate surface to improve the magnetic properties necessary for improving the performance of the transformer and to adhere to the steel plate. The formation of a primary coating having good properties has been one of the important issues of grain oriented electrical steel sheets in the prior art.

That is, in the conventional technique, after the primary annealing accompanied by decarburization, a steel sheet is coated with a slurry of magnesium oxide (MgO) fine powder called magnesia, which is water-soluble, and dried if necessary. It is fired in the subsequent recrystallization annealing step, and a ceramic-like insulating primary film called forsterite (Mg ₂ SiO ₄ ) is formed by a reaction with SiO ₂ and Si in the steel sheet.

This is effective for imparting tension to the steel sheet and improving the magnetic characteristics, especially the characteristic value called iron loss, which governs the efficiency of the transformer. Moreover, this state of forsterite formation is commonly referred to as G
This is called the OSS orientation and is {110} [00] with respect to the longitudinal direction (rolling direction) of the steel plate, which is essential for improving magnetic permeability and magnetic flux density.
It is well known that it also plays an important role in growing slightly coarse secondary recrystallized grains having the crystal orientation of [1].

On the contrary, even if an attempt is made to carry out secondary recrystallization without forming a sufficiently dense film during the secondary recrystallization annealing temperature rising process, fine nitrides and sulfides called inhibitors in the steel sheet remain as they are. In the state or disassembled, it quickly comes out of the steel plate. Therefore, the inhibitor effect of growing the GOSS-oriented grains preferentially during the temperature rise and suppressing the growth of other oriented grains cannot be exhibited, and is commonly called fine grain. This results in a steel sheet with extremely poor magnetic properties, in which crystal grains do not grow partially or entirely.

In this MgO, titanium oxide (Ti
(O ₂ etc.) and other compounds may be added to form a denser primary film. However, there is a great demand for iron loss reduction of electrical steel sheets, which has a great influence on the energy conversion efficiency of transformers for energy saving as seen in the appearance of amorphous materials in recent years, and it is not possible to withstand this demand with the extension of the above conventional technology. It has become difficult.

In the prior art, in addition to the above method, a so-called product steel plate surface after secondary recrystallization is intentionally provided with a groove or some damage by a method such as mechanical irradiation or energy irradiation such as a laser, so as to subdivide magnetic domains. The method is carried out to improve iron loss. However, even with this method, it was still difficult to realize a low iron loss that can counter amorphous. On the other hand, since the primary coating containing forsterite as a main component is a hard solid substance, it has a difficulty in workability such as shearing of the product, resulting in a shortened tool life.

[0008]

DISCLOSURE OF THE INVENTION The present invention has clarified such problems, and based on the technical knowledge shown in the following outline, the formation of a solid substance containing forsterite as a main component called a primary film is formed. Provided is a new method for producing a high magnetic flux density silicon steel sheet having excellent iron loss in order to obtain a grain-oriented electrical steel sheet having an extremely low iron loss as much as possible.

[0009]

The gist of the present invention is as follows. (1) In the production of a grain-oriented electrical steel sheet in which a steel containing Si: 1 to 7% is smelted and hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing are the basic steps, Steel plate temperature from the start of temperature rising of crystal annealing to the end of cooling 300 ° C ~
The average maximum depth of the steel plate surface was 2 to 5 during 950 ° C.
From the longitudinal direction of the steel plate, a groove of 0 μm is provided in a direction of 45 to 90 degrees at intervals, and then a substance containing at least one kind of chloride and sulfide is applied to the steel plate surface. After that, secondary recrystallization annealing is performed, and the average thickness of the insulative primary coating mainly composed of forsterite produced during the secondary recrystallization annealing is set to 0.3 μm or less. Excellent manufacturing method of silicon steel sheet.

(2) Si: 1 to 7%, P: 0.045%
Directionality based on smelting steel containing super-0.20%, Sn: 0.02 to 0.20%, hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing In the production of an electromagnetic steel sheet, a groove having an average maximum depth of 2 to 50 μm is formed on the surface of the steel sheet at a steel sheet temperature of 300 ° C. to 950 ° C. from the start of the primary recrystallization annealing to the end of cooling. From 45 degrees to 90 degrees, it is given with an interval, and then a steel sheet surface is coated with a substance containing at least one of chloride and sulfide, and then secondary recrystallization annealing is performed. And an average thickness of the insulative primary coating mainly composed of forsterite produced during the secondary recrystallization annealing is set to 0.3 μm or less. Law.

(3) The distance between the grooves provided on the steel plate is set to 2 to 20.
mm is a method for producing a silicon steel sheet having excellent iron loss. (4) A method for producing a silicon steel sheet with excellent iron loss, which comprises nitriding during primary recrystallization annealing. (5) A method for producing a silicon steel sheet having excellent iron loss, which uses calcium chloride as a chloride and potassium sulfide as a sulfide to be contained in the substance to be applied to the surface of the steel sheet.

(6) A method for producing a silicon steel sheet in which the temperature rising rate during the secondary recrystallization annealing is 30 ° C. or less per hour and the nitrogen partial pressure in the atmosphere gas is 30% or more. (7) Si: 1 to 7% and P: 0.01 to 0.15% are included, and the average depth of the maximum portion is 2 to 50 μm on the steel plate surface in the direction of 45 ° to 90 ° from the longitudinal direction of the steel plate. Has a groove in which forsterite partially remains, and the average thickness of the solid hard primary coating mainly composed of forsterite is 0.
A silicon steel sheet with excellent iron loss, which has an iron loss of 3 μm or less at W17 / 50 of 0.70 Watt / kg or less.

(8) Si: 1 to 7%, P: 0.01 to
0.15%, Sn: 0.02 to 0.20%, and the forsterite on the bottom of the steel plate surface has an average maximum depth of 2 to 50 μm in the direction of 45 to 90 degrees from the longitudinal direction of the steel plate. Has a groove partially remaining therein, and has an iron loss of 0.70 Watt / kg or less at W17 / 50 when the solid hard primary coating containing forsterite as a main component has an average thickness of 0.3 μm or less. A silicon steel sheet with excellent iron loss.

(9) A silicon steel sheet having excellent iron loss, characterized in that the groove interval is 2 to 20 mm. The present invention will be described in detail below. 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 specific grains in the primary recrystallization annealing (hereinafter referred to as primary annealing). At this time, an inhibitor (Inhibitor) is used.
It is well known in the art that it is technically necessary to make fine precipitates called AlN etc. before finish annealing.

Then, nitrogen necessary for this purpose is added during steel melting, after primary annealing, or during other steps. For the purpose of the present invention, it has been found that the method of adding nitrogen after the primary annealing is rather the optimum method of adding nitrogen. If nitrogen is added during or immediately after the primary annealing, the equipment for 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.
A method of performing a nitriding reaction after the subsequent annealing or in parallel with it is also effective.

In the case of steel having a sufficiently low carbonization during steel melting, it is more important than the decarburizing function to change the oxide layer of the surface layer after the primary annealing so as to make it advantageous for the coating reaction. By the way, in the present invention, during the steel plate temperature 300 ° C. to 950 ° C. from the start of the temperature rise of the primary recrystallization annealing to the end of cooling, a groove having an average maximum depth of 2 to 50 μm is mechanically formed on the steel plate surface. It is important to apply them in a regular array by chemical, optical, thermal, electrical or other energy irradiation methods.

This is because the grooves can make the magnetic domains of the product finer and contribute to the reduction of iron loss. This groove can be applied by a mechanical method such as a grooved roll or a grooved press, an energy irradiation method such as laser or plasma, a method of spraying water or oil at a high pressure, a chemical corrosion by an acid or an electrical corrosion. Basically, any method such as a method or a method combining them,
The point is that the effect is recognized if the above groove requirements are met.

However, the low iron loss, which is the object of the present invention, cannot be obtained by this alone. The most important technical requirement in the present invention is the combination with the average thickness of the primary coating mainly composed of forsterite on the surface of the steel sheet. This thickness is 0.
It was found that when the thickness is 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 magnetic flux in the steel sheet, especially if the coating has many irregularities, or if oxides such as spinel (MgO.Al ₂ O ₂ ) are formed directly under forsterite. It can be easily imagined that the tendency is large when there are many.

Therefore, if the primary coating on the surface is reduced as much as possible to be thin or completely eliminated, and if regular grooves are formed instead, the magnetic flux flows regularly and smoothly. As a result, iron loss can be sufficiently reduced. Of course, the depth and pitch of the groove will be limited. Further important points in the present invention are as follows. In the prior art,
A method is used in which a so-called primary product after forming a so-called primary coating is provided with grooves to subdivide magnetic domains. This is because the magnetic domain control effect is larger than that of the prior art method in which a groove is formed in the intermediate step.

However, what has been made clear by the present invention is that if the thickness of the primary coating is extremely small or is not present, sufficient magnetic domain refinement can be achieved by the method of forming grooves during or before and after the primary recrystallization annealing which is inexpensive in terms of cost. This is the point that we found the fact that the chemical effect is exhibited. Hot-rolling a grain-oriented electrical steel sheet having the chemical composition shown in Table 1 (where N is a value after primary annealing and nitriding),
After hot rolling annealing, cold rolling was performed to 0.23 mm, and a steel plate immediately after primary recrystallization annealing was provided with a roll having a groove with a depth of 15 μm and a pitch of 5 mm in the temperature range of 600 ° C. to 700 ° C., and after cooling, FIG. 1 shows the iron loss of a sample in which a steel sheet was finish-annealed by changing various additives to MgO powder, the average thickness of the primary coating was changed, and an insulating coating having tension was further applied.

[0021]

[Table 1]

From this, it can be seen that as the thickness of the primary coating becomes smaller, the iron loss is reduced (improved), and particularly at 0.3 μm or less, this is remarkable. This is because the average thickness of the primary coating on the surface of the steel sheet is small or absent even if the groove is subjected to an intermediate step immediately after primary recrystallization annealing and forsterite etc. is clogged in the groove in the subsequent step and the magnetic domain control effect deteriorates. It shows that the magnetic domains are sufficiently subdivided.

Further, an important point in the present invention is that the steel sheet is grooved in a relatively high temperature region before or after the primary recrystallization annealing. Regarding the steels having the chemical compositions shown in Table 2, (a) when the steel sheet after primary recrystallization annealing is grooved by the roll method at room temperature (25 ° C), and (b) when it is grooved at 600 ° C. The result of the subsequent recrystallization is shown in FIG.

[0024]

[Table 2]

What is clear from this is that when the groove is formed at room temperature (a), fine grains are generated around the groove.
When a groove is formed at 600 ° C. in (b), such a phenomenon is not observed. That is, when grooves are formed on the primary recrystallized plate at a high temperature, the structure becomes normal even after the secondary recrystallization, and the magnetism becomes good.

Next, when Al is added during the secondary recrystallization, AlN or Si ₃ N ₄ is mainly used as an inhibitor. Here, as one of the methods of the present invention, nitriding is performed during or after the primary annealing. It has been found that the buffing method 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, forsterite etc. like the present invention is used. It is considered that even if the primary coating becomes thin or disappears, the optimum nitrogen amount can be easily secured by controlling the nitrogen partial pressure (P _N2 ) in the atmosphere.

Next, in order to reduce or eliminate the primary coating film during finish annealing as much as possible, in the present invention, chloride and sulfide are mixed on the surface of the steel sheet after primary annealing in ordinary magnesia (MgO) powder. It has been found effective to add. Among these, calcium chloride (CaC
1 ₂ ) and potassium sulfide (K ₂ S) are effective. In addition,
In the conventional method, in addition to MgO, TiO ₂ and antimony compounds (Sb ₂ (SO ₄ ) ₃ ) and boron compounds (Na ₂
B ₄ O ₇ ), strontium-barium-based, carbon-nitride-based, etc. are added to facilitate the reaction. However, even in the present invention, the effects of these additives are exerted, so that they can be added. It does not change the essence of the invention.

A very important point in the present invention is the behavior of P. Table 3 shows the {111} plane index strength of the crystal orientation by X-ray after primary recrystallization of the steel in which only the amount of P was changed. The magnetic flux densities of the steel sheets obtained by primary recrystallization, nitriding and secondary recrystallization are shown in the same table. Clearly, it can be seen that these values change with the amount of P. On the other hand, when Sn is added in coexistence with P, even iron loss is reduced as shown in FIG. 3 of the example of 0.06% P-3% Si steel, which is preferable. This is S
It is considered that this is due to the product refining effect of n.

[0029]

[Table 3]

Now, a method for manufacturing a silicon steel sheet will be described. As described above, the silicon steel sheet according to the present invention contains Al as needed in addition to Si, and contains Si ₃ N ₄ or A
In the case of 1N and a large amount of S in the steel, the steel is limited to MnS as a main inhibitor. Of course Si, Al,
In addition to P and Sn, Se, Sb, Cu, B, Nb, Ti,
Other additive elements such as V, Ni and Cr are additionally added,
Improving the magnetic properties does not change the basics of the invention.

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, in a steel containing 1 to 7% of Si, if necessary, Al is contained in an amount of 0.1% or less when the steel is melted, and N is directly applied to the steel sheet during or after decarburization annealing during primary annealing after cold rolling in the silicon steel sheet manufacturing process. It is characterized in that N is contained in the steel in an amount of 30 ppm to 600 ppm before the secondary recrystallization annealing by the method of forcibly adding N to the steel through the nitriding reaction.

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 the Si ₃ N ₄ inhibitor, and in the present invention, after the primary annealing, that is,
A minimum of 30 ppm is required before finish annealing. On the other hand, when Al is intentionally used, 60 ppm or more is necessary to secure the amount of AlN. However, if it exceeds 600 ppm, Al and Si are excessively eaten, which is not preferable. 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.

The other elements are not particularly characteristic in the present invention as compared with the conventional steel, but the following restrictions are preferable. P is extremely important in the present invention. When steel is melted, 0.
If it is 045% or less, the effect of increasing the magnetic flux density is small, while if it exceeds 0.20%, brittleness becomes large, and cold rolling is difficult.

The amount of P in the product is important in the present invention. P exists as a solid solution in iron and is also partly precipitated,
Extremely effective in reducing iron loss in products, at least 0.03%
If it does not exist, its effect cannot be exerted. On the other hand, 0.15%
If it is present too much, it causes brittleness of the product, impairs workability and punchability of the product, and cannot be used. C must be sufficiently low during steel melting or sufficiently low during decarburization annealing of the primary annealing, and 0.0 at the start of secondary recrystallization annealing.
It is preferably 3% or less.

If Mn is less than 0.5%, it reacts with S and becomes M.
Form nS inhibitors. When it is 0.15 or less, it is preferable for further improvement of the magnetic flux density. O is 0.05% after steel is melted
The following is preferable in terms of cleanliness without making too much Al ₂ O ₃ . In the present invention, Sn has a remarkable iron loss reducing effect when coexisting with P. If it is less than 0.02%, there is no effect. On the other hand, if it exceeds 0.20%, the inhibitor which is not sufficiently nitrided becomes weak, while the primary film cannot be sufficiently formed and the properties are deteriorated.

Next, the manufacturing method of the present invention other than the chemical components will be described. Continuous casting method, ingot slabbing method, or thin slab continuous method for skipping hot rolling process, where steel is tapped in a converter or electric furnace, and a 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 upper limit for preventing abnormal distribution of Al ₂ O ₃ etc. due to center segregation. 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 ° C. 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,
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 addition,
In the thin slab continuous casting method, it is possible to directly form a coil, and for that purpose, 10 mm or less is preferable. The hot coil thus produced is often annealed again at 800 to 1250 ° C. to improve magnetism.

Here, 800 ° C. is the lower limit for remelting AlN, and 1250 ° C. is the upper limit for preventing AlN coarsening. After such a treatment step, the hot coil is pickled directly or batchwise and then cold rolled. Cold rolling is 60-95% reduction
However, 60% is the limit of recrystallization in the present invention,
70% or more of primary annealing is preferably {111} [11
2] It is the lower limit of increasing the number of oriented grains to promote the generation of GOSS oriented grains during secondary recrystallization annealing, while above 95%, GOSS oriented grains called swinging GOSS grains in secondary recrystallization annealing are plates. Grains are generated which are unfavorable for the in-plane rotated magnetic properties.

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 heating the steel sheet in the range of 100 to 400 ° C by an appropriate method during the cold rolling is also effective for improving the magnetic properties. 10
Below 0 ℃, there is no effect of aging, while at 400 ℃
If it exceeds the limit, dislocations will be recovered. Next, primary recrystallization annealing is performed. An important requirement in the present invention is groove formation at a steel plate temperature of 300 ° C to 950 ° C during or before this process. Here, if the temperature is less than 300 ° C., the steel sheet will be distorted, and fine grains will be formed around the groove after the secondary recrystallization, which will significantly deteriorate the iron loss. It is preferably 600 ° C. or higher. On the other hand, if it exceeds 950 ° C., the primary recrystallized grains become coarse, and a GOSS orientation that is favorable for iron loss cannot be obtained during secondary recrystallization.

It is preferable to perform the groove formation in a high temperature range from the start of the temperature rise of the primary recrystallization annealing to the end of cooling in terms of energy saving, but the effect of the present invention is to reheat after the primary recrystallization annealing to 300 ° C. The same effect can be obtained by forming a groove in the range of 950 ° C. The grooves thus formed remain after finish annealing, and a low iron loss, which cannot be seen in the past, can be obtained in combination with the method of reducing the average primary coating containing forsterite to 0.3 μm or less. That is why. The reason for 0.3 μm is as described above, and if it is thicker than this, a sufficiently low iron loss cannot be obtained by the groove forming method in the intermediate step of the present invention. The method of forming the groove is as described above, but if the average depth of the maximum part of the groove is less than 2 μm, there is no magnetic domain subdivision effect. On the other hand, if it exceeds 50 μm, it is too deep and the smooth flow of the magnetic flux is hindered, and the iron loss deteriorates. It is preferably 5 to 30 μm. The grooves should be regularly arranged.

This is because the magnetic domain subdivision is regularly performed. Usually, it is preferable to engrave at a substantially constant pitch having an angle of 45 degrees to a right angle with respect to the longitudinal direction of the steel sheet. If it is less than 45 degrees, the direction of magnetic domain subdivision does not match the crystallographic orientation preferred for magnetism. The pitch of the grooves is preferably 2 to 20 mm. If it is less than 2 mm, the magnetic domains are subdivided too much and the 90 ° magnetic domains increase, resulting in poor core loss and magnetostriction. On the other hand, if it exceeds 20 mm, the effect of domain division is not obtained.

In the double cold rolling method, the first
It is possible to form the groove in any of the second annealings, and it is also possible to divide the groove into both. If necessary, nitriding is performed during the primary recrystallization annealing or immediately thereafter. Although the primary annealing is performed in both the single cold rolling method and the double cold rolling method, decarburization is effective in this annealing. As described above, C is not preferable for the growth of secondary recrystallized grains, and if it remains as an impurity, it causes deterioration of iron loss.

It is preferable that C is lowered during the melting of steel because not only the decarburization process is shortened but also {111} [112] oriented grains are increased. By setting an appropriate dew point in this decarburization annealing step, an oxide layer necessary for subsequent primary film formation is secured. Primary annealing temperature is 700-9
50 ° C is preferred. Here, 700 ° C. is the lower limit temperature at which recrystallization is possible, and 950 ° C. is the upper limit temperature at which the generation of coarse grains in primary recrystallization is suppressed.

Further, in the present invention in which AlN or N of Si ₃ N ₄ inhibitor is forcibly added during the primary annealing by the nitriding method or the like, the nitriding method is performed with ammonia (NH ₃ ) or the like during or immediately after the primary annealing. Is done. The temperature of the nitriding method in this case is 600 to 950 ° C.
Is this good. 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, nitriding is often performed in parallel with the primary recrystallization. At this time, as described above, the lower the partial pressure of N ₂ is, the larger the amount of nitriding is, and the partial pressure ratio P _N2 / P _H2 of nitrogen and oxygen is preferably 0.5 or less.

The surface temperature of the steel sheet is 300 from the start of the temperature rise of the primary annealing to the end of cooling, and in the case of performing the nitriding method, from the start of the primary recrystallization annealing to the end of cooling after nitriding.
Between ℃ and 950 ℃, the average of the maximum depth on the steel plate surface is 2
Grooves of .about.50 .mu.m are provided in a regular array by mechanical, chemical, optical, thermal, electrical or other energy irradiation method. The method of forming the groove is as described above, but if the average depth of the maximum part of the groove is less than 2 μm, there is no magnetic domain subdivision effect.

On the other hand, if it exceeds 50 μm, it is too deep and the smooth flow of the magnetic flux is hindered, and the iron loss becomes worse. It is preferably 5 to 30 μm. 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 degrees to a right angle with respect to the longitudinal direction of the steel sheet. If it is less than 45 degrees, the direction of magnetic domain subdivision does not match the crystallographic orientation preferred for magnetism.

The groove pitch is preferably 2 to 20 mm. If it is less than 2 mm, the magnetic domains are subdivided too much and the 90 ° magnetic domains increase, resulting in poor core loss and magnetostriction. On the other hand, if it exceeds 20 mm, the effect of domain division is not obtained. Primary annealing or, if necessary, the above nitriding method is performed, and then magnesium oxide (MgO as a main component; hereinafter referred to as MgO) powder is dissolved in water or an aqueous solution containing water as a main component to form a slurry, which is applied to a steel sheet. To do. At this time, a trace amount of an appropriate compound may be added for the purpose of facilitating the melting of the MgO powder during the subsequent secondary recrystallization annealing and promoting the forsterite formation reaction.

When TiO ₂ is added, 1 to 15% is preferable. Here, 1% is the lower limit for exerting the effect of promoting the forsterite reaction, and if it exceeds 15%, the amount of MgO decreases and the forsterite reaction proceeds rather. Absent. Sb ₂
An antimony-based compound such as (SO ₄ ) ₃ is effective in melting MgO at a relatively low temperature, and when added, 0.05 to 5% is preferable. Here, 0.05% is the lower limit for causing the above-mentioned low-temperature melting, while on the other hand, when it exceeds 5%, it is too much to inactivate the original reaction of MgO forsterite.

Boron compounds such as Na ₂ B ₄ O ₇ and strontium / barium compounds, carbon / nitride compounds, sulfide compounds, and chloride compounds having the same action as those of the compounds have a relatively higher temperature than antimony compounds. Is effective in melting MgO, and when added, 0.05 to 5% is preferable.
Here, 0.05% is the lower limit for exhibiting the above-mentioned effect, while if it exceeds 5%, the original reaction of MgO forsterite is inactivated, which is not preferable. It should be noted that these compounds may be added in combination with each other.

The percentage of the compound added here is MgO.
The weight ratio is shown in% when the weight of is 100%. In the present invention, when one or more kinds of the above-mentioned chlorides or sulfides are further added to the MgO powder, the primary coating film after finish annealing can be 0.3 μm or less on average, and sufficient secondary recrystallization orientation can be obtained. However, among these, calcium chloride (CaCl ₂ ) and potassium sulfide (K ₂ S) are particularly effective. These are at least 0.5% (Mg
It is effective if the O weight is 100 or more).

On the contrary, if it exceeds 20%, the process of forming two coating films becomes unstable. Secondary recrystallization annealing has a maximum arrival time of 1100
It is preferable to carry out at ˜1300 ° C. 1100 ° C. is the lower limit temperature at which the secondary recrystallization is performed, while if it exceeds 1300 ° C., the crystal grains become too coarse, and the iron loss is deteriorated. The important points in this secondary recrystallization annealing are as follows. In the present invention, M
Due to the effect of a special additive on gO powder, the primary coating containing forsterite as the main component is extremely reduced or eliminated, so nitrogen-based inhibitors (AlN, Si ₃ N _4, etc.) required for secondary recrystallization during annealing. ) Also tends to escape during the finish annealing, so that it is possible to prevent this by setting the nitrogen partial pressure (P _N2 ) in the atmosphere gas of the finish annealing to 30% or more, and to achieve stable secondary recrystallization. It is possible to obtain.

Further, if the rate of temperature rise in the secondary recrystallization annealing is too high, the inhibitor easily escapes before sufficient secondary recrystallization occurs, so rather it is more stable if the rate of temperature rise is kept below 30 ° C. per hour. Magnetic properties are obtained. 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. Industrially, for the purpose of further improving the insulation characteristics and magnetic characteristics, the steel sheet after secondary recrystallization is insulated with an organic or inorganic material. It is particularly important to apply a high-strength coating (coating) having a coating in combination with heat treatment or the like. The Zorgel method is also effective. The reason for this is
This is because, in the present invention, the primary coating having high tensile properties such as forsterite is extremely small or absent, and therefore it is effective to apply an insulating coating having high tensile properties to supplement it.

[0056]

EXAMPLES Steels having chemical compositions shown in Tables 4, 5, and 6 were melted in a converter and produced under the conditions shown in Tables 4, 5, and 6. Part of the hot-rolled sheet was annealed.
120 ° C. × 30 seconds. Aging between passes during cold rolling was performed except for B, but the condition is 250 ° C.

[0057]

[Table 4]

[0058]

[Table 5]

[0059]

[Table 6]

Here, the nitriding subsequent to the primary recrystallization annealing, which is particularly important in the present invention, is performed by drying the atmosphere with the same gas composition in the inside of the furnace where the partition is provided in the same furnace, and
It was performed by flowing a fixed amount of ₃ gases. The nitriding amount (nitrogen amount) after such primary annealing is shown in the same table. Further, a powder was applied to this steel sheet, and the powder was dissolved in water to form a slurry, and the powder was dried at 350 ° C. here,
% Is the weight ratio when the weight of MgO is 100%.

After that, secondary recrystallization annealing was carried out by changing the average heating rate from 800 ° C. to the maximum reached temperature variously. The maximum reaching speed is 1200 ° C. here. Further, a phosphoric acid-based high-strength insulating coating (secondary coating) is applied by heating, then plate-cut and strain relief annealing 850 ° C. × 4 hours (N ₂ 90-H ₂
10, Dry) was performed, and a magnetic measurement test was performed. Table 4,
The results are shown in 5 and 6. The maximum depth of the groove,
Both the pitch and the angle with the rolling direction are measured with the product after the secondary recrystallization annealing.

The magnetic measurement is SST of a single plate of 60 × 300 mm.
Measured by the test method, B ₈ flux density (800A / m), the unit Tesla and W _17/50 (iron loss at a 1.7 Tesla at 50 Hz, in watts / kg), W13 / 50 ( 50Hz The iron loss at 1.3 Tesla) was measured. Well, Table 4,
As shown in Nos. 5 and 6, those falling within the scope of the present invention have sufficiently low iron loss and fall within the scope of the present invention.

[0063]

As described above, according to the present invention,
It is possible to obtain a grain-oriented electrical steel sheet with ultra-low iron loss.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the average thickness of a primary coating and iron loss.

FIG. 2 is a photograph of a metal structure after magnetic domain control and secondary recrystallization.

FIG. 3 is a diagram showing the effect of Sn% during molten steel on various properties of 0.06% P-3% Si steel products.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Iwanaga 1-1 Tobahata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka New Nippon Steel Corporation Yawata Works

Claims (9)

[Claims] 1. Si: 1 to 7%, P: more than 0.045%
In the production of grain-oriented electrical steel sheet with the basic steps of hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing, smelting steel containing 0.20% and starting the primary recrystallization annealing temperature rise. From the steel plate longitudinal direction to the steel plate temperature 300 ℃ ~ 950 ℃ from the end of the cooling to the groove, the average of the maximum depth of 2 to 50 μm, in the direction of the steel plate longitudinal direction, in the direction of 45 ° ~ 90 °, intervals. It is opened and applied.After that, a substance containing at least one kind of chloride and sulfide is applied to the surface of the steel sheet, then secondary recrystallization annealing is performed, and the form generated during the secondary recrystallization annealing is performed. A method for producing a silicon steel sheet having extremely excellent iron loss, characterized in that an average thickness of an insulative primary coating mainly composed of stellite is 0.3 μm or less. 2. Si: 1 to 7%, P: more than 0.045% to
A grain-oriented electrical steel sheet produced by smelting steel containing 0.20% and Sn: 0.02 to 0.20% and having hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing as basic steps. In the production of, during the steel plate temperature 300 ℃ ~ 950 ℃ from the start of the primary recrystallization annealing temperature rise to the end of cooling, a groove having an average maximum depth of 2 to 50 μm on the steel plate surface from the steel plate longitudinal direction, Four
It is given with an interval in the direction of 5 to 90 degrees, and then a steel sheet surface is coated with a substance containing at least one of chloride and sulfide, and then secondary recrystallization annealing is performed. A method for producing a silicon steel sheet having extremely excellent iron loss, characterized in that an average thickness of an insulative primary coating mainly composed of forsterite produced during secondary recrystallization annealing is 0.3 μm or less. 3. The distance between the grooves provided to the steel plate is 2 to 20.
The method for producing a silicon steel sheet having excellent iron loss according to claim 1 or 2, wherein the thickness is mm. 4. The method for producing a silicon steel sheet with excellent iron loss according to claim 1, 2 or 3, wherein nitriding is performed during the primary recrystallization annealing. 5. The production of a silicon steel sheet having excellent iron loss according to claim 1, 2, 3 or 4, wherein calcium chloride is used as a chloride and potassium sulfide is used as a sulfide contained in the substance applied to the surface of the steel sheet. Law. 6. The method according to claim 1, 2, 3, 4, or 5, wherein the temperature rising rate during the secondary recrystallization annealing is 30 ° C. or less per hour, and the nitrogen partial pressure in the atmosphere gas is 30% or more. Manufacturing method of silicon steel sheet. 7. Si: 1 to 7%, P: 0.03 to 0.1
Including 5%, the steel plate surface is 45 degrees to 9 from the longitudinal direction of the steel plate.
In the direction of 0 degree, the average of the maximum depth is 2 to 50 μm, and the bottom has a groove in which forsterite partially remains, and the average thickness of the solid hard primary coating mainly composed of forsterite is 0.3 μm. The following iron loss is 0.70Wa at W17 / 50
Silicon steel sheet with excellent iron loss, which is less than tt / kg. 8. Si: 1 to 7%, P: 0.03 to 0.1
5%, Sn: 0.02 to 0.20%, and a forsterite is formed on the bottom surface of the steel plate surface having an average maximum depth of 2 to 50 μm in the direction of 45 to 90 degrees from the longitudinal direction of the steel plate. Iron having a residual groove and a solid hard primary coating containing forsterite as a main component and having an average thickness of 0.3 μm or less at W17 / 50 of 0.70 Watt / kg or less. Silicon steel plate with excellent loss. 9. The silicon steel sheet with excellent iron loss according to claim 7, wherein the interval between the grooves is 2 to 20 mm.