JPH06184763A - High magnetic flux density extra-low iron loss grain-oriented silicon steel sheet and its production - Google Patents

Abstract

PURPOSE:To provide an extra-low iron loss grain-oriented silicon steel sheet and to provide its producing method. CONSTITUTION:In this steel sheet, the average thickness of an insulating primary film contg. 1 to 7% Si and 0.03 to 0.15% P and essentially consisting of forsterite is regulated to 0.3mum. Steel contg. 1 to 7% Si and >0.45 to 0.20% P is coated with chloride or sulfide in such a manner that it is mixed to MgO before being subjected to finish annealing to regulate the average thickness of the primary film in the product into <=0.3mum, and furthermore, domain regulation is executed to produce the extra-low iron loss grain-oriented silicon steel sheet. Moreover, Sn is added thereto to obtain further lower iron loss.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art 1-7% with excellent magnetic properties for transformers, etc.
A primary coating that secures insulation properties and imparts tension to the steel plate surface to improve the magnetic properties necessary for improving the performance of the transformer when manufacturing a grain-oriented silicon steel plate containing Si, and that has good adhesion to the steel plate. In the prior art, the formation of slag was one of the important problems of grain-oriented silicon steel sheets. That is, in the usual technique, after the primary annealing accompanied by decarburization, a steel sheet is coated with a slurry of magnesium oxide (MgO) fine powder called magnesia dissolved in water, dried if necessary, and then subjected to secondary recrystallization. It burned in the annealing step, forsterite reaction with SiO ₂ and Si in the steel sheet (Mg ₂
A ceramic insulating film called SiO ₄ ) is formed. This is effective in giving tension to the steel sheet and improving the magnetic property, especially the characteristic value called iron loss, which governs the efficiency of the transformer. Moreover, the state of formation of this forsterite corresponds to the crystal orientation of the steel sheet by the secondary recrystallization, commonly known as G.
It is called the OSS orientation, and {110} <00 with respect to the steel plate longitudinal direction (rolling direction), which is indispensable 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 a crystal orientation of 1>. On the contrary, during the secondary recrystallization annealing temperature rising process, even if it is attempted to perform secondary recrystallization without forming a sufficiently dense film, fine nitrides and sulfides called inhibitors in the steel sheet remain as they are, or It disassembles and quickly escapes from the steel plate. Therefore, the inhibitor effect of the role of preferentially growing GOSS oriented grains during the temperature rise and suppressing the growth of other oriented grains cannot be exhibited, and is commonly called fine grains.
This results in a steel sheet having extremely poor magnetic properties, in which the secondary recrystallized grains of GOSS oriented grains are not partially or entirely grown.

However, in order to save energy as seen in the appearance of amorphous materials in recent years, there is a great demand for reducing iron loss of magnetic steel sheets, which greatly affects the energy conversion efficiency of transformers. It has become difficult to respond. In the prior art, in addition to the above method, a so-called product steel sheet surface after secondary recrystallization is intentionally provided with grooves or some damage by a method of energy irradiation such as mechanical or laser, and magnetic domain subdivision is performed. There are ways to improve the loss. However, even with this method, it was still difficult to realize a low iron loss that can counter Almorphus. On the other hand, since the primary coating containing forsterite as a main component is a hard solid substance, there is a problem in workability such as shearing of the product, resulting in a shortened tool life.

[0004]

SUMMARY OF THE INVENTION The present invention solves these problems and, based on the technical knowledge shown in the skeleton below, forms a solid substance containing forsterite as a main component called a primary film. This is a finding of a new product development technology in order to obtain a grain-oriented silicon steel sheet with an extremely low iron loss while suppressing it as much as possible.

[0005]

The gist of the present invention is as follows. (1) Si: 1 to 7%, P: 0.03 to 0.15%, and the average thickness of the insulating primary coating containing forsterite as a main component is 0.3 μm or less. High magnetic flux density and extremely low iron loss grain oriented silicon steel sheet.

(2) Si: 1 to 7%, P: 0.03 to
0.15%, Sn: 0.02 to 0.20%, and a high magnetic flux density, characterized in that the average thickness of the insulating primary coating containing forsterite as a main component is 0.3 μm or less. Ultra low iron loss grain oriented silicon steel sheet. (3) Si: 1 to 7%, P: more than 0.045% and 0.20%
In the production of a grain-oriented silicon steel sheet in which the steel containing the following is melted and hot rolling, cold rolling, primary recrystallization annealing and secondary recrystallization annealing are the basic steps, the form produced during secondary recrystallization annealing is performed. A method for producing a high magnetic flux density ultra-low iron loss grain oriented silicon steel sheet, characterized in that an average thickness of an insulating primary coating containing stellite as a main component is 0.3 μm or less.

(4) Li, K, Na, Ba, Ca, Mg, Zn, F with respect to 100 parts by weight of MgO in magnesia on the surface of the steel sheet between the primary recrystallization annealing and the secondary recrystallization annealing.
0.5 to 20 parts by weight of one or more sulfides of e, Zr, Sn, Sr, and Al and / or one selected from carbonates, nitrates, and chlorides of these elements, or The method for producing a high magnetic flux density ultra-low iron loss grain-oriented silicon steel sheet according to the above item 3, characterized by applying an annealing separator containing two or more kinds added in an amount of 0.5 to 20 parts by weight. (5) Al between the primary recrystallization annealing and the secondary recrystallization annealing,
4. The method for producing a high magnetic flux density ultra-low iron loss grain oriented silicon steel sheet according to the above 3, wherein one or more oxides of Zr, Ti and Ca are applied as an annealing separator. (6) At an angle of 45 to 90 degrees from the longitudinal direction of the plate on the steel plate,
The method for producing a high magnetic flux density ultra-low iron loss grain oriented silicon steel sheet according to any one of items 3 to 5 above, wherein grooves or irradiation marks are provided at intervals. (7) Si: 1 to 7% as a steel component, P: 0.045%
Manufacture of a high magnetic flux density ultra-low iron loss grain-oriented silicon steel sheet according to any one of items 3 to 6 above, which contains more than 0.20% and Sn: 0.02 to 0.20%. Law.

The present invention will be described in detail below. Secondary recrystallization of grain-oriented silicon steel sheet is called GOSS orientation {11
It is essential that grains having a 0} <001> orientation are sufficiently grown during secondary recrystallization annealing (also called finish annealing). This is to coarsely recrystallize only certain specific grains in the primary recrystallization annealing (also called primary annealing). At this time, fine precipitates such as AlN called an inhibitor (Inhibitor) are sufficiently prepared before finish annealing. It is well known that there is a technical need. 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 nitriding reaction is usually installed inside or close to a part of the equipment for the primary annealing that also functions as a decarburizing 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.

In the present invention, secondary recrystallization annealing, heat flattening annealing, and coating of an insulating film are performed as necessary. Before and after that, the average maximum depth of the steel sheet surface is 2 to 2.
It is important to provide grooves of 50 μm regularly. This is because it is possible to make the magnetic domain subdivision of the product finer by this groove, which contributes to the reduction of iron loss.
This groove can be applied by mechanical methods such as grooved rolls and presses, energy irradiation methods such as laser and plasma, high-pressure spraying of water, oil, etc., chemical corrosion by acids, etc. Basically, any method such as the method according to (1) or a method combining them may be used, and the effect is recognized as long as the above requirements for the groove are satisfied. 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 the combination with the average thickness of the forsterite-based primary coating on the surface of the steel sheet. It has been found that when the thickness is 0.3 μm or less, the magnetic characteristics are remarkably improved in combination with the above. The reason for this is not always clear, but if this primary coating is thick, it blocks the flow of magnetic flux in the steel sheet, especially if the coating has many irregularities, or if there are many oxides such as spinel (MgO.Al ₂ O ₃ ) directly under forsterite. It is easy to imagine that the tendency is large. 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 smoothly and regularly. As a result, iron loss can be sufficiently reduced. Of course, there will be restrictions on the depth and pitch of the grooves. The following points are further important in the present invention. What has been clarified in the present invention is that the fact that even if the thickness of the primary coating is 0.3 μm or less, the components of the present invention provide a sufficiently low iron loss and a sufficient magnetic domain refining effect is exhibited. Is. Grain-oriented silicon steel sheet having the chemical composition shown in Table 1 (N content of R1 is the value after primary annealing and nitriding)
Is hot-rolled, after hot-rolled sheet annealing, cold-rolled to 0.27 mm,
The obtained cold-rolled sheet was rolled with a depth of 15 μm and a pitch of 5 mm.
After making the groove, the primary annealing is carried out, and then the annealing separator which is added to the MgO powder by changing various additives is applied to finish annealing, and the average thickness of the primary coating is changed, and the insulation having more tension is obtained. FIG. 1 shows the iron loss of the sample applied with the coating. As is clear from this, iron loss decreases (improves) as the thickness of the primary coating decreases.
It can be seen that, especially, it is remarkable at 0.3 μm or less.

[0011]

[Table 1]

Next, in the case of significantly adding Al when performing secondary recrystallization, AlN or S is used as one of the inhibitors.
It was also found that i ₃ N ₄ is used, and that one of the methods of the present invention is nitriding during or after the primary annealing 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 when steel is melted, it is better to nitride it later with AlN and Si ₃ N ₄
It is easy to control the optimum amount of P. Even if the primary coating such as forsterite becomes thin or disappears as in the present invention during the secondary recrystallization annealing, the nitrogen partial pressure (P
_This is probably because it is easy to secure the optimum amount of nitrogen by controlling _N2 ).

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, chloride and sulfide are added to the surface of the steel sheet after primary annealing in a normal magnesia (MgO) powder. It was found to be effective to add it by mixing in. Among these, calcium chloride (CaCl ₂ ) and potassium sulfide (K ₂ S) are particularly effective. In addition to MgO, TiO ₂ and antimony compounds (Sb ₂ (SO ₄ ) ₃ ), boron compounds (Na ₂ (BO ₄ ) ₃ ), strontium
Barium-based, carbon / nitride-based, etc. are added to facilitate the reaction. However, since the effects of these additives are exerted in the present invention as well, addition of them does not change the essence of the present invention. Absent. By using an oxide such as alumina (Al ₂ O ₃ ) as an annealing separator other than magnesia, it is possible to sufficiently reduce the primary coating and obtain secondary recrystallization.

Next, the extremely important point in the present invention is the behavior of P. Table 2 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. Obviously, these values change with the amount of P.

[0015]

[Table 2]

Further, Sn is also important in the present invention. In particular, it was found that when coexisting with P, it is extremely effective in reducing iron loss. Figure 2 shows the results for 3% Si steel.

Now, it is necessary to touch on the method of manufacturing the grain-oriented silicon steel sheet. As described above, the grain-oriented silicon steel sheet according to the present invention contains Al as necessary in addition to Si, and Si
₃ N ₄ or AlN, and M when there is a large amount of S in steel
nS is the main inhibitor, and it is limited to the steel to which P is added and Sn is added to further reduce iron loss. Of course, in addition to Si, Al, P, Sn, Se, Sb, Cu,
B, Nb, Ti, V, Ni, Mo, Cr, Bi, W, H
Adding other additive elements such as f to improve the magnetic properties does not change the basics of the present 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, the manufacturing method is such that the primary annealing after cold rolling in the grain-oriented silicon steel sheet manufacturing process is performed on silicon steel containing 1 to 7% of Si and 0.1% or less of Al at the time of steel melting, if necessary. During or after the decarburization annealing in the process, by forcibly adding N in the state of the steel sheet through the direct nitriding reaction, it is possible to adjust the N content in the steel to 30 to 600 ppm before the secondary recrystallization annealing. Characterize.

In the present invention, Si is used as a source as described above.
A minimum of 1% is required for the formation of rusterite. one
On the other hand, if it exceeds 7%, the workability is extremely deteriorated and it is suitable for industrial production.
I don't. Al is effective in forming an AlN inhibitor.
However, if it exceeds 0.1%, Al ₂O₃The amount of production increases
Impairs the cleanliness of sound steel, which in turn adversely affects magnetic properties
Bring

N is indispensable for forming Si ₃ N ₄ and AlN inhibitor, and in the present invention, it is at least 30 p after the primary annealing, that is, before the secondary recrystallization of the finish annealing.
pm is required. 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.

P is extremely important in the present invention. When the steel is melted, if it is less than 0.045%, the effect of increasing the magnetic flux density is small, while if it exceeds 0.20%, the brittleness becomes large and cold rolling becomes difficult. The amount of P in the product is important in the present invention. P exists as a solid solution in iron and is partly precipitated, but it is extremely effective in reducing iron loss in the product, and at least 0.
If it does not exist, the effect cannot be exhibited. on the other hand,
If it exceeds 0.15%, the product becomes brittle, and the workability and punchability of the product are impaired, and the product cannot be used.

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. Other elements are not particularly characteristic in the present invention as compared with the conventional steel, but the following restrictions are preferable.

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. If Mn is 0.5% or less, it reacts with S to form a MnS inhibitor. If it is 0.15% or less, it is preferable for further improving the magnetic flux density. O is Al if 0.05% or less after steel is melted
_It is preferable in terms of cleanliness because it does not produce too much ₂ O ₃ .

In the present invention, Sn is remarkably effective in reducing iron loss when it coexists with P. If it is less than 0.02%, the effect is not obtained, while if it exceeds 0.20%, the primary coating cannot be sufficiently formed. Next, the production method of the present invention other than the chemical components will be described. Continuous casting method, ingot-agglomeration and rolling method, or thin slab continuous method for omitting hot rolling step, in which steel is tapped in a converter or electric furnace, and a refining step 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. Where 3
0 mm is the lower limit to ensure productivity, 400 m
m is an upper limit for preventing abnormal distribution of Al ₂ O ₃ etc. due to center segregation. In the thin slab continuous casting method, 5
0 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 a lower limit for melting AlN, and 1400 ° C. is an upper limit at which surface roughness and material deterioration do not occur. Further, the thickness of 10 mm is the upper limit at which it is possible to obtain 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, the thickness is preferably 10 mm or less. The hot coil thus produced is often annealed again at 800 to 1250 ° C. to improve the magnetism. 800 here
℃ is the lower limit for remelting AlN, 1250 ℃ is A
1N is the upper limit for preventing coarsening.

After this treatment step, the hot coil is pickled directly or batchwise and then cold rolled. Cold rolling is carried out at a rolling reduction of 60 to 95%, but 60% is the limit at which recrystallization is possible in the present invention, and preferably 70% or more by primary annealing and increasing {111} <112> oriented grains, This is the lower limit for promoting the generation of GOSS oriented grains during secondary recrystallization annealing, while on the other hand, if it exceeds 95%, it is a swinging GOS during secondary recrystallization annealing.
GOSS-oriented grains called S grains rotate in the plane of the plate to produce grains unfavorable to the magnetic properties. The above is the case of manufacturing by the so-called single cold rolling method, but when cold rolling-annealing-cold rolling is performed by calling 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 a lower limit reduction rate for properly leaving {111} <112> oriented grains during 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, and if it remains as an impurity, it causes deterioration of iron loss. If C is lowered during the melting of steel, the decarburization process will be shortened and {111} <
112> orientation grains are also increased, which is preferable. 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 for suppressing the generation of coarse particles. Further, in the present invention in which AlN or N of Si ₃ N ₄ inhibitor is forcibly added by the nitriding method or the like during this primary annealing, the nitriding method with ammonia (NH ₃ ) or the like is continuously performed during or immediately after the primary annealing. Is done. In this case, the temperature of the nitriding method is preferably 600 to 950 ° C. 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, the 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
Nitrogen is often nitrided in parallel with the primary recrystallization because the gas is supplied or it is carried out in close proximity. At that time, as described above, the lower the N ₂ partial pressure is, the larger the nitriding amount is, and the partial pressure ratio P _N2 / P _H2 of nitrogen and oxygen is preferably 0.5 or less.

On the other hand, regardless of whether or not nitriding is carried out during or after the primary annealing, the oxygen basis weight in the primary annealing is also important. The preferable oxygen basis weight is 25 to 1000 ppm. 25 ppm is the minimum amount of oxygen required for nitriding. On the other hand, when it exceeds 1000 ppm, the amount of SiO ₂ and FeO in the oxide layer of the primary annealed plate inevitably becomes too large, and the oxide film becomes thick, resulting in the finish annealing. It is disadvantageous in reducing the primary coating. It is preferably 400 to 800 ppm.

Further, the ratio of FeO / SiO ₂ in the oxide layer is also important. This ratio is preferably 0.40 or less. If it exceeds 0.40, the reactivity of forming the glass film in the first half of the finish annealing is extremely increased, the amount of forsterite formed in the first half is increased, and similarly the primary film cannot be reduced.
Primary annealing or the above nitriding treatment 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. At that time, as described above, the average thickness of the primary coating after the secondary recrystallization annealing was 3 μm.
In order to make m or less, 100 parts by weight of MgO in magnesia and Li, K, Na, Ba, Ca, M on the surface of the steel plate are used.
g, Zn, Fe, Zr, Sn, Sr, Al sulfide 1
0.5 to 20 parts by weight of one or more kinds and / or 0.5 to 20 parts by weight of one or more kinds selected from carbonates, nitrates and chlorides of these elements are added. It is preferable to apply an annealing separator and add chloride, sulfide or oxide. In this case, for example, among chlorides, calcium chloride (CaCl ₂ ) is representative, and among sulfides, potassium sulfide (K ₂ S) is representative. The amount of this addition is preferably 0.5 to 20 parts by weight (weight ratio when the weight of MgO is 100). If it is less than 0.5 parts by weight, there is no effect of thinning the primary coating, while if it exceeds 20 parts by weight, the reactivity is deteriorated and the secondary recrystallization is not sufficiently performed.

On the other hand, 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, it is preferably 1 to 15%, but 1% is the lower limit at which the effect of promoting the forsterite reaction is exhibited, and if it exceeds 15%, the amount of MgO decreases and the forsterite reaction does not proceed.

Antimony compounds such as Sb ₂ (SO ₄ ) ₃ are 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 if it exceeds 5%, it is too much to inactivate the original reaction of MgO forsterite. Boron-based compounds such as Na ₂ B ₄ O ₇ and strontium / barium-based, carbon / nitride-based, sulfide-based, and chloride-based compounds having the same action as MgO are relatively higher in temperature than antimony-based MgO.
Has the effect of melting
-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 is also possible to add these compounds in combination with each other. The% of the compound added here indicates the weight ratio when the weight of MgO is 100%. In the present invention, the annealing separator is magnesia (Mg
When O) is used, the water content of hydration is also important, and the amount is preferably 0.5 to 5%. If it is less than 0.5%, the reactivity of magnesia deteriorates. On the other hand, if it exceeds 5%, the dew point between the steel sheets becomes high, and additional oxidation occurs at the front stage during temperature increase, causing unevenness of the oxide film on the surface and stabilizing the glass. Cannot be evenly reduced to 3 μm or less.

On the other hand, magnesia (Mg
It is also possible to reduce the average thickness of the primary coating to 3 μm or less by not using O) or by reducing it as much as possible and by using an oxide such as alumina (Al ₂ O ₃ ) as an annealing separator. In this case, it is also possible to manufacture grain-oriented silicon steel sheets with a surface that is even thinner or almost mirror-like,
It is also possible to further reduce the iron loss in combination with the components and manufacturing conditions of the present invention.

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 is deteriorated. The important points in this secondary recrystallization annealing are as follows. In the present invention, the primary coating containing forsterite as the main component is extremely reduced or eliminated due to the effect of the special additive to the MgO powder. Therefore, the nitrogen-based inhibitor (AlN, Si ₃ N ₃₎ is added to the secondary recrystallization during annealing. ₄ etc.), N is included in the finish annealing and the inhibitor of the compound tends to escape. Therefore, by setting the nitrogen partial pressure (P _N2 ) in the atmosphere gas of the finish annealing to 30% or more. This can be prevented and stable secondary recrystallization can be obtained. On the other hand, when MnS or other compounds are used in addition to the N-based inhibitor, this restriction is not always a constraint, and particularly when MnS is used, the nitrogen partial pressure is rather 3%.
The secondary recrystallization tends to be more stable if the content of N is set to 0% or less to prevent excess N from penetrating. Furthermore, if the rate of temperature rise in the secondary recrystallization annealing is too high, the inhibitor easily escapes before sufficient secondary recrystallization occurs. Is 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.

Next, an important requirement in the present invention is groove formation after finish annealing or flattening annealing, and before and after applying an insulating film. This is combined with the method of reducing the primary coating containing forsterite as a main component to an average of 0.3 μm or less, and an extremely low iron loss which has never been seen in the past can be obtained. 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. Preferably 5 to 30 μ
m is good. The grooves should be regularly arranged. This is because the magnetic domain is subdivided regularly. Normal,
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. Also, the pitch of the grooves is 2 to 10 m.
m is preferred. If it is less than 2 mm, the subdivision of the magnetic domain proceeds too much, the 90 ° magnetic domain increases, and the core loss and magnetostriction are poor. On the other hand, 10 mm
If it is super, there is no effect of subdivision of magnetic domains.

The above is an important part of the method for producing a grain-oriented silicon steel sheet according to the present invention, but industrially, the steel sheet after secondary recrystallization is made of an organic or inorganic material for the purpose of further improving the insulating property and the magnetic property. It is particularly important to apply a high-strength coating (roll coating, Zolgel method, etc.) having an insulating coating according to (4) in combination with heat treatment or the like. The reason for this is that in the present invention, the primary coating having high tensile properties such as forsterite is extremely small or absent, so it is effective to apply an insulating coating having high tensile properties to complement it. Because.

[0039]

【Example】

 Example 1 Steel having a chemical composition as shown in Table 3 was melted in a converter, and Table 4
(Continued from Table 3-1), Table 5 (continued from Table 3-2), Table
6 (continued from Table 3-3).
Part of the hot-rolled sheet was annealed, but the conditions were 1120 ° C x 3
0 seconds. The aging between passes during cold rolling is B
Other conditions were the same, but the condition was 250 ° C. In addition, this
This is followed by the primary recrystallization anneal, which is particularly important for the present invention.
Nitriding is performed with the same gas inside the furnace with a partition in the same furnace.
The composition makes the atmosphere dry, and NH₃Flow a certain amount of gas
I went there. Amount of nitriding after such primary annealing (primary annealing
Table 4 shows the amount of nitrogen in the steel after blunting. In addition to this steel plate
Powder was applied, but MgO powder (various additives
(Added) is dissolved in water and applied as a slurry
Then, it was dried at 350 ° C. Where% is the weight of MgO
Is the weight ratio when is 100%. Also, E-1
~ E-10 is an annealing separator with Al without using MgO. ₂O₃
Was used to electrostatically coat the primary annealed plate by a dry method. After a while
Variously change the average temperature rise rate from 800 ℃ to the highest temperature
Secondary recrystallization annealing was performed. The highest temperature reached here is 1
It is 200 ° C. Furthermore, magnetic domain control is performed under each condition in Table 6.
In addition, a phosphoric acid-based high-strength insulating coating (secondary coating) is added.
Heat applied (however, laser method is followed by laser
After irradiating), the plate is removed and strain relief annealing is performed at 850 ° C. for 4 hours.
(N₂90% -H₂10%, Dry) and magnetic measurement
The test was conducted. Table 6 shows the results. The maximum of the groove
Depth, pitch and angle with rolling direction are all final products
It is the measurement in the product.

For magnetic measurement, a 60 × 300 mm single plate was SS
Measured by T test method, B ₈ (800 A / m magnetic flux density, unit is Tesla) and W _17/50 (iron loss at 50 Tesla at 1.7 Tesla, unit is watt / kg), W _13/50 (50
Iron loss at 1.3 Tesla at Hz, unit: watt / k
g) was measured. As shown in Table 6, those falling within the range of the present invention have high magnetic flux density and sufficiently low iron loss,
It can be seen that this is within the scope of the present invention.

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

Example 2 Steel having the chemical composition shown in Table 7 was melted in a converter and
Table 8 (continued-1 in Table 7), Table 9 (continued-2 in Table 7)
It was manufactured under the conditions shown in. The hot-rolled sheet was partially annealed under the conditions of 1120 ° C. for 30 seconds, and after the annealing, it was water-cooled. In addition, aging between passes during cold rolling was performed except for F ', but the condition is 250 ° C. Further, powder was applied to this steel sheet, but MgO powder (to which various additives were added) was dissolved in water to form a slurry, which was applied and then dried at 350 ° C. Here,% is the weight ratio when the weight of MgO is 100%.
Further, G'-1 and G'-2 were dry-electrostatically applied to the primary annealing plate by using Al ₂ O ₃ as an annealing separator without using MgO. After that, secondary recrystallization annealing was performed while changing the average heating rate from 800 ° C. to the highest reached temperature variously. The highest temperature reached here is 1200 ° C. Furthermore, magnetic domains were controlled under the conditions shown in Table 9, and a phosphoric acid-based high-strength insulating coating (secondary coating) was applied by heating (however, laser irradiation was performed after the laser method), followed by plate removal 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 10 (Continued from Table 7-
The results are shown in 3). The maximum groove depth, pitch, and angle with the rolling direction are all measurements on the final product.

For magnetic measurement, a 60 × 300 mm single plate is SS
Measured by T test method, B ₈ (800 A / m magnetic flux density, unit is Tesla) and W _17/50 (iron loss at 50 Tesla at 1.7 Tesla, unit is watt / kg), W _13/50 (50
Iron loss at 1.3 Tesla at Hz, unit: watt / k
g) was measured. As shown in Table 10, those falling within the range of the present invention have a high magnetic flux density and a sufficiently low iron loss, which is within the target range of the present invention.

[0047]

[Table 7]

[0048]

[Table 8]

[0049]

[Table 9]

[0050]

[Table 10]

[0051]

EFFECTS OF THE INVENTION A grain-oriented silicon steel sheet having an extremely low iron loss can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a primary coating and iron loss.

FIG. 2 is a diagram showing the effect of Sn addition on 0.06% P-3% Si steel.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hodaka Hodaka No. 1-1 Toibata-cho, Tobata-ku, Kitakyushu, Kitakyushu, Fukuoka Inside Nippon Steel Corporation Yawata Works

Claims (7)

[Claims] 1. Si: 1 to 7%, P: 0.03 to 0.1
A high magnetic flux density ultra-low iron loss grain oriented silicon steel sheet characterized in that the insulating primary coating containing 5% as a main component has an average thickness of 0.3 μm or less. 2. Si: 1 to 7%, P: 0.03 to 0.1
5%, Sn: 0.02 to 0.20%, and the average thickness of the insulative primary coating mainly composed of forsterite is 0.3 μm or less. Iron loss direction silicon steel sheet. 3. A steel containing Si: 1 to 7%, P: more than 0.045% and 0.20% or less is melted, hot rolled, cold rolled, primary recrystallization annealing and secondary recrystallization annealing. In the production of a grain-oriented silicon steel sheet having a basic step of, the average thickness of the insulative primary coating mainly composed of forsterite produced during secondary recrystallization annealing is set to 0.3 μm or less. High magnetic flux density Ultra low iron loss Directional silicon steel sheet manufacturing method. 4. Li, K, Na, Ba, Ca, Mg, Zn, Fe, relative to 100 parts by weight of MgO in magnesia on the surface of the steel sheet between the primary recrystallization annealing and the secondary recrystallization annealing.
0.5 to 20 parts by weight of one or more sulfides of Zr, Sn, Sr and Al and / or one or two selected from carbonates, nitrates and chlorides of these elements.
The method for producing a high magnetic flux density ultra-low core loss grain oriented silicon steel sheet according to claim 3, characterized in that an annealing separator containing 0.5 to 20 parts by weight of one or more species is applied. 5. The one or more kinds of oxides of Al, Zr, Ti, and Ca are applied as an annealing separator between the primary recrystallization annealing and the secondary recrystallization annealing. A method for producing the described high magnetic flux density ultra-low iron loss grain-oriented silicon steel sheet. 6. The height according to claim 3, wherein the steel plate is provided with grooves or irradiation marks at intervals of 45 to 90 degrees from the longitudinal direction of the plate. Magnetic flux density Ultra low iron loss Directional silicon steel manufacturing method. 7. As a steel component, Si: 1 to 7%, P: 0.
More than 045% and 0.20% or less, Sn: 0.02 to 0.20
% Is contained, The method for producing a high magnetic flux density ultra-low iron loss grain-oriented silicon steel sheet according to any one of claims 3 to 6.