JPS6332849B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial application field) Improvement of electrical and magnetic properties of unidirectional silicon steel sheets,
In particular, the remarkable development efforts made in recent years to meet the extreme requirements of reducing iron loss are gradually bearing fruit, but one serious problem associated with their implementation is the use of grain-oriented silicon steel sheets. It has been pointed out that when so-called strain-relief annealing is applied after initial processing and assembly, deterioration of properties inevitably occurs, resulting in restrictions on usage. In this specification, the following is related to the results of research and development to open up a new method that can advantageously meet the above requirements, regardless of whether or not it undergoes a high-temperature thermal history such as strain relief annealing. state As is well known, unidirectional silicon steel sheets are products in which secondary recrystallized grains are highly concentrated in the (110) [001], or Goss, orientation, and are mainly used in transformers and other electrical equipment. Used as an iron core, the product is required to have high electrical and magnetic characteristics such as high magnetic flux density (represented by the B ₁₀ value) and low iron loss (represented by the W _17/50 value). This unidirectional silicon steel plate is manufactured through a wide variety of complicated processes, but numerous inventions and improvements have been made so far, and today products with a thickness of 0.30mm have magnetic properties of B ₁₀ 1.90T or more, W _{17/ 50} 1.05W/Kg or less, and the magnetic properties of products with a plate thickness of 0.23mm are B ₁₀ 1.89T
As described above, ultra-low core loss unidirectional silicon steel sheets with a W _17/50 of 0.90 W/Kg or less are being manufactured. In particular, recently there has been a marked increase in the demand for reducing power loss as a top priority from the standpoint of energy conservation.・The "evaluation" (iron loss evaluation) system is becoming popular. (Prior art) Under these circumstances, recently, a method has been developed in which micro-strain is introduced into the surface of a unidirectional silicon steel plate after final annealing by laser irradiation in a direction approximately perpendicular to the rolling direction to subdivide the magnetic domains. It was proposed to reduce iron loss by
No. 57-53419, Special Publication No. 58-26405 and Special Publication No. 58-
(See Publication No. 26406). This magnetic domain refining technology is effective for transformer materials for laminated cores that are not subjected to strain relief annealing, but for transformer materials for rolled cores that are subjected to strain relief annealing, it is difficult to introduce it by tozer irradiation. The disadvantage is that the laser irradiation effect is lost because the local microstrain is released by the annealing treatment and the magnetic domain width becomes wider. On the other hand, earlier in Japanese Patent Publication No. 52-24499, the surface of a unidirectional silicon steel plate after finish annealing was mirror-finished, or the mirror-finished surface was coated with metal thinning or an insulating coating was applied thereon. A method of manufacturing an ultra-low core loss unidirectional silicon steel sheet by coating and baking has been proposed. However, this method of improving iron loss through mirror finishing cannot be adopted from a process standpoint, as it does not make a sufficient contribution to reducing iron loss at the cost of a significant increase in cost. It has not been adopted in current manufacturing processes because it has problems with adhesion to the steel plate during long strain relief annealing at high temperatures of 600°C or higher. Japanese Patent Publication No. 56-4150 also proposes a method in which a thin film of oxide ceramics is deposited on the surface of a steel plate after mirror finishing. However, this method cannot be used in actual manufacturing processes because the steel sheet and the ceramic layer will separate when subjected to high-temperature annealing at 600°C or higher. (Problems to be Solved by the Invention) The inventors have sought to more effectively bring out the effect of improving iron loss due to the mirror finish described above, and in particular, from the viewpoint of today's development of energy-saving materials, it is an object of the present invention to outweigh the disadvantage of increased costs as described above. We believe that it is important to overcome the problems of adhesion and durability of the insulating layer without deteriorating the properties, especially during high-temperature treatment, and based on this basic understanding, we have developed a method for processing steel sheets after mirror finishing. This invention was arrived at after a fundamental reexamination. (Means for solving the problem) As a result of the above study, C: 0.01-0.06wt%, Si: 2.5-4.0wt%, Mn: 0.01-0.2wt%, Mo: 0.003-0.1wt%, Sb: 0.005 ~0.2wt%, a total of 0.005 to 0.05wt% of any one or both of S and Se, with the remainder essentially consisting of Fe, C: 0.01 to 0.08wt%, Si: 2.0 to 4.0wt %, Mn: 0.01~0.2wt%, solAl: 0.005~0.06wt%, S: 0.005~0.05wt%, N: 0.001~0.01wt%, Sn: 0.01~0.5wt%, Cu: 0.01~0.3wt% Contains, the remainder substantially consists of Fe, C: 0.01-0.06wt%, Si: 2.0-4.0wt%, Mn: 0.01-0.2wt%, S: 0.005-0.05wt%, B: 0.0003-0.004wt% , N: 0.001 to 0.01wt%, the balance substantially consisting of Fe, C: 0.01 to 0.08wt%, Si: 2.0 to 4.0wt%, Mn: 0.01 to 0.2wt%, solAl: 0.005 to 0.06wt %, S: 0.005 to 0.05 wt%, N: 0.001 to 0.01 wt%, and the remainder substantially consists of Fe. The steel plate is cold rolled twice with annealing to obtain the final thickness, then subjected to decarburization and primary recrystallization annealing.Then, an annealing separator mainly composed of MgO is applied to the surface of the steel plate before final finishing. After a forsterite base film is formed by annealing, the forsterite base film is removed, and then the surface is polished to a mirror finish with a center line average roughness of 0.4 μm or less, and then the mirror finish is applied. Ti, Nb, Si, V, Cr, Al, Mn, B, Ni,
Forming an ultra-thin tension coating of 0.005 to 5 μm consisting of one or more and four or less selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides (first to fourth inventions) ) or by further forming an insulating coating film thereon (fifth to eighth inventions), it is possible to manufacture an ultra-low core loss unidirectional silicon steel sheet with excellent thermal stability of magnetic properties. The explanation will proceed according to specific experiments that led to the success of each of the above inventions. C0.046% by weight (hereinafter simply indicated as %), Si3.46%,
Mn0.072%, Se0.024%, Sb0.025%, Mo0.025%
A continuously cast silicon steel slab containing 2.0
It was made into a hot-rolled plate with a thickness of mm. Thereafter, after homogenization annealing at 900°C for 3 minutes, cold rolling was performed twice with intermediate annealing at 950°C for 3 minutes, to obtain a final cold-rolled plate with a thickness of 0.23 mm. After that, after decarburization and primary recrystallization annealing in a wet hydrogen atmosphere at 820℃, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, and then secondary recrystallization annealing is performed at 850℃ for 50 hours. After this, purification annealing was performed in dry hydrogen at 1200°C for 7 hours. Thereafter, the forsterite base film on the surface of the steel plate was removed by pickling in HCl solution at 80°C. Next, chemical polishing was performed in a solution of 3% HF and H ₂ O ₂ to finish the steel plate surface to a mirror surface with a center line average roughness of 0.1 μm. After that, the surface was polished using the plasma CVD equipment shown in Figure 1, and TiN CVD was applied to the surface with a film thickness of 1.5 μm.
I processed it. In the figure, 1 is a plating material, 2 is a constant flow reaction gas supply pipe, 3 is a mirror-finished sample, 4 is a heater, and 5 is an electrode. The feature of this plasma CVD device is that after ionization, molecules are dissociated and attached to a mirror-finished sample through a surface reaction. Coating treatment with coating liquid (molding of insulating coating and baking layer)
I went there. For comparison, a similar polished surface was plated with copper to a thickness of 1 .mu.m in accordance with a conventionally known technique, and then coated with a coating liquid containing phosphate and colloidal silica as main components. The experimental results of the magnetic properties and adhesion of the products at this time are summarized in Table 1.

【table】

[Table] ** Good adhesion ○
Poor adhesion ×
As is clear from Table 1, the magnetism of the conventionally processed product (a), which is currently manufactured in a process, and in which a coating treatment is applied on the forsterite base film formed on the surface of the steel sheet during final annealing. The characteristics are
B ₁₀ is 1.901T, W _17/50 is about 0.88W/Kg, and the adhesion of the insulating coating is good. However, after final annealing, the forsterite coating was removed by pickling, and then the surface was The magnetic properties of the product (b), which is chemically polished to a mirror finish, copper plated, and coated, have B ₁₀ of 1.909T and W _17/50 .
Although it is slightly improved to about 0.74W/Kg, the adhesion is poor. However, according to the present invention, after final annealing, the forsterite coating was removed, the surface was chemically polished to a mirror finish, and then a similar coating was applied through CVD treatment.The magnetic properties of the product (c) were as _follows :
1.918T, W _17/50 was 0.67W/Kg, which was not only a remarkable improvement in properties, but also extremely good adhesion of not only the tension coating but also the insulating coated and baked layer. (Effect) The above-mentioned improvement in magnetic properties and adhesion was achieved by the CVD method, which was produced on the surface of the steel plate in the above experiment.
TiN improves adhesion to the steel plate, and at the same time, the coefficient of thermal expansion of TiN is 5.1×10 ^-6 (1/℃), which is 13.5×10 ^-6 to the steel plate.
(1/°C), elastic tension acts on the surface of the steel sheet, achieving ultra-low iron loss unparalleled in the past. In addition to TiN, Nb, Si, V, Cr, Al,
The nitrides and/or carbides of Mn, B, Ni, Co, Mo, W, Zr, Hf and Ta are also listed above.
It is an effective substance that exhibits almost the same function as TiN. Since this method does not utilize the action of compositional microstrain, there is no problem with thermal stability, and electrical and magnetic properties are not affected by high-temperature thermal history such as strain relief annealing. There isn't. Here, the center line average roughness of the finished surface is R _a ≦0.4μm
When R _a >0.4 μm, the surface is rough and sufficient iron loss reduction cannot be expected. Next, the thickness of the tension coating is suitable in the range of 0.005 to 5 μm; if it is less than 0.005 μm, it will not be able to contribute to providing the necessary tension, while if it exceeds 5 μm, the cost will increase and the space factor will decrease. A disadvantage occurs in adhesion. Next, the manufacturing process of the unidirectional silicon steel sheet will be described in more detail, including a general explanation. First, the reason for limiting the composition of the material for unidirectional silicon steel sheet, which is the object of this invention, will be described below. C is an element that plays an important role in controlling fine and uniform microstructure during hot rolling or cold rolling, but at 0.08%
If the amount is more than
If it is less than 0.01%, it becomes difficult to control the hot rolling texture and large elongated grains are formed, resulting in deterioration of magnetic properties, so the content was limited to a range of 0.01 to 0.08%. Furthermore, in a component system that does not use AlN and MnS as inhibitors at the same time, the heating temperature can be lowered, so it is possible to reduce the C content to 0.06% or less. If Si is less than 2.0%, the electrical resistance will be low and the iron loss value will increase due to increased eddy current loss;
%, brittle cracks are likely to occur during cold rolling.
Si needs to be within the range of 2.0 to 4.0%. In addition,
S and/or Se-Mo-Sb system and S and/or Se
-In order to better improve iron loss in the Sb system,
The lower limit of Si was set at 2.5%. Mn is an inhibitor that controls the formation of secondary recrystallized grains with {110}<001> orientation, that is, an element essential for the precipitation of MnS or MnSe as a dispersed precipitation phase. If the amount of Mn is less than 0.01%, the absolute amount of MnS or MnSe to suppress primary recrystallized grain growth is insufficient, causing incomplete secondary recrystallization. On the other hand, Mn
If the amount exceeds 0.2%, when heating the slab
It becomes difficult to dissociate solid solution of MnS or MnSe, and even if dissociated solid solution occurs, the dispersed precipitate phase that precipitates during hot rolling tends to become coarse, and the optimal size distribution as an inhibitor is impaired, resulting in magnetic properties. deteriorates. For these reasons, Mn
It was limited to the range of 0.01-0.2%. Both Sb and Mo suppress the growth of primary grains during secondary recrystallization by coexisting with S and Se, which will be described later, and promote the growth of secondary recrystallized grains in the {110}<001> orientation. This serves to further improve the magnetic properties of the product. Therefore, the silicon steel material used in the method of the present invention should contain Sb and Mo in addition to S and/or Se, which will be described later. However, if Sb exceeds 0.2%, cold workability deteriorates, magnetic flux density begins to decrease, leading to deterioration of magnetic properties, and Mo
If it exceeds 0.1%, not only hot workability and cold workability deteriorate, but also iron loss characteristics deteriorate. on the other hand
If Sb is less than 0.005% and Mo is less than 0.003%, the effect of these additions will be poor, so the Sb content should be 0.005%.
~0.2%, and the Mo content must be regulated within the range of 0.003~0.1%. S and Se are MnS and MnSe as inhibitors that suppress the growth of primary grains during secondary recrystallization.
It is an element necessary for the formation of
%, hot and cold workability deteriorates, so the upper limit of the content is 0.05%, while the content
If it is less than 0.005%, the absolute amount of MnS and MnSe is insufficient,
Since it cannot function as an inhibitor, the lower limit of the content was set at 0.005%. Al combines with N contained in steel to form fine AlN precipitates and acts as a strong inhibitor. In particular, in order to develop secondary recrystallization by a strong cold rolling method with a cold rolling reduction of 70 to 95%, it is necessary to contain solAl in a range of 0.005 to 0.06%. This is because if the Al content is less than 0.005%, there will be insufficient precipitated grains of AlN fine precipitates as an inhibitor.
The development of secondary recrystallized grains with {110}<001> orientation becomes insufficient, and on the other hand, if it exceeds 0.06%, the {110}<
This is because the development of secondary recrystallized grains in the 001> orientation becomes poor. N is an essential element when using AlN or BN as an inhibitor. If the amount of N is less than 0.001%, the inhibitor effect of AlN or BN will be weak, while if the amount added exceeds 0.01%, surface defects called blisters will occur. Since this occurs frequently and the product yield decreases, N needs to be regulated within the range of 0.001 to 0.01%. B combines with N contained in steel to form fine BN precipitates and acts as a strong inhibitor. When B is less than 0.0003%, it acts as an inhibitor.
B should be limited to a range of 0.0003 to 0.004% because the amount of BN fine precipitates will be insufficient, and if it exceeds 0.004, the development of secondary recrystallized grains with {110}<001> orientation will deteriorate. . Sn is useful for refining secondary recrystallized grains and is 0.01
Below 0.5%, the effect is weak, while above 0.5%, Cu
Because it is added in combination with the above, rolling properties and pickling properties deteriorate. Cu is preferred for film formation and is 0.01%
If it is less than 0.3%, it will have little effect on improving the coating, while if it exceeds 0.3%, it is unfavorable from the viewpoint of magnetic properties. Next, the hot-rolled sheet is either uniformly annealed at 800-1100℃ and then cold-rolled once to reach the final thickness, or it is usually subjected to intermediate annealing at 850-1050℃ and further processed. In the two-step cold rolling method, in the latter case, the initial rolling reduction is about 50% to 80%, and the final rolling reduction is 50%.
The final cold-rolled plate thickness is 0.15mm to 0.35mm at a rate of 85% to 85%. After the final cold rolling, the steel plate is finished to the product thickness.
After surface degreasing, decarburize in wet hydrogen at 750℃ to 850℃・1
Perform the next recrystallization annealing treatment. After that, an annealing separator, usually consisting mainly of MgO, is applied to the surface of the steel plate. After that, secondary recrystallization annealing is performed, but this step is carried out to sufficiently develop secondary recrystallized grains with {110}<001> orientation, and is usually box annealed to immediately raise the temperature to 1000℃ or higher. This is done by heating and holding at that temperature. In this case, in order to develop a highly aligned secondary recrystallized grain structure in the {110}<001> orientation, it is advantageous to perform retention annealing at a low temperature of 820°C to 900°C.
In addition, slow heat annealing at a heating rate of 0.5 to 15° C./h may also be used. Purification annealing after secondary recrystallization annealing is performed in dry hydrogen.
It is necessary to perform annealing at 1100° C. or higher for 1 to 20 hours to form a forsterite film on the surface of the steel sheet and to purify the steel sheet. After this purification annealing, the forsterite coating on the surface of the steel sheet is removed by known chemical removal methods such as pickling, mechanical removal methods such as cutting and grinding, or a combination thereof. After this removal treatment, the surface of the steel plate is finished to a mirror-like state, that is, to a center line average roughness of 0.4 μm or less, by a conventional method such as chemical polishing such as chemical polishing or electrolytic polishing, mechanical polishing such as buffing, or a combination thereof. It is then firmly adhered to the mirror-finished surface via the mixed phase of the tension coating using CVD techniques. This CVD method depends on the parameters that cause the chemical reaction and the method used (a) low-temperature CVD,
High temperature CVD, (b) low pressure CVD, atmospheric pressure CVD, (c) plasma
It is classified into CVD, (d) laser CVD, and (e) optical CVD, and any of these methods can be used, but plasma CVD, laser CVD, and CVD, optical CVD, etc. are particularly advantageous. The ultra-thin tensile coating produced on the steel plate surface by this CVD method is made of TiN, TiC, Si ₃ N ₄ , SiC, NbN,
NbC, CoN, CoC, NiC, NiN, BN, MoC,
Suitable materials include one or more and four or less selected from MoN, WC, WN, ZrC, ZrN, HfC, HfN, etc. Although the effects of the present invention are not affected in any way by any combination of compounds constituting this ultra-thin film, the number is limited to four or less in view of processing complexity and cost. Furthermore, an insulating film containing phosphate and colloidal silica as main components is applied and baked onto these ultra-thin tension films. A conventionally known method may be used for forming this insulating film. The silicon steel plate treated as described above can be subjected to flattening heat treatment. (Example) Example 1 C: 0.048%, Si: 3.36%, Mn: 0.066%,
A hot-rolled plate containing Mo: 0.025%, Se: 0.022%, Sb: 0.025%, with the remainder substantially consisting of Fe, was uniformly annealed at 900°C for 3 minutes and then intermediately annealed at 950°C. Cold rolling was performed twice to obtain a final cold rolled sheet with a thickness of 0.23 mm. After that, after decarburization annealing in wet hydrogen at 820℃, an annealing separator mainly composed of MgO is applied to the steel plate surface.
Secondary recrystallization annealing at 850℃ for 50 hours, 8 hours at 1200℃
Purification annealing was performed in dry hydrogen for hours. Thereafter, the forsterite coating was removed by pickling, and then chemically polished in 3% HF and H _{2 O} to give a mirror finish. Thereafter, a TiN tension film with a thickness of 0.5 μm was formed by CVD using the apparatus shown in FIG. Next, an insulating coated and baked layer containing phosphate and colloidal silica as main components was formed, and then strain relief annealing was performed at 800°C for 2 hours. The magnetic properties and adhesion of the product at that time were as follows. Magnetic properties B ₁₀ = 1.90T, W _17/50 = 0.70W/Kg Adhesion Even when bent 180° with a bending diameter of 30 mm, there was no peeling and the adhesion was good. Example 2 C: 0.065%, Si: 3.38%, Mn: 0.080%, Al:
Contains 0.028%, S: 0.030%, N: 0.0068%,
A hot-rolled sheet, the remainder of which is essentially Fe, is heated at 1150°C for 3
After uniform annealing for 30 minutes, rapid cooling treatment is performed, and then 300 minutes
A final cold-rolled sheet with a thickness of 0.23 mm was obtained by warm rolling at ℃. After decarburization annealing in wet hydrogen at 850℃, the surface
850℃ after applying an annealing separator mainly composed of MgO
After secondary recrystallization by raising the temperature from 1150°C to 1150°C at a rate of 8°C/hr, purification annealing was performed in dry hydrogen at 1200°C for 8 hours. Thereafter, the forsterite coating was removed by pickling, and then chemically polished in 3% HF and H _{2 O} to give a mirror finish. After that, an ultra-thin tension film of Si ₃ N ₄ was formed with a film thickness of 2.5 μm using the CVD method, and for some samples, an insulating coated and baked layer containing phosphate and colloidal silica as the main components was further formed. After that, heat at 800℃ for 2
Time strain relief annealing was performed. The magnetic properties and adhesion of the product at that time were as follows. Without Γ insulating film Magnetic properties B ₁₀ = 1.95T, W _17/50 = 0.69w/Kg Adhesion Even when bent 180° with a bending diameter of 25 mm, there was no peeling and the adhesion was good. With Γ insulation film Magnetic properties B ₁₀ = 1.95T, W _17/50 = 0.66W/Kg Adhesion Even when bent 180° with a bending diameter of 30 mm, there was no peeling and the adhesion was good. Example 3 C: 0.045%, Si: 3.44%, Mn: 0.068%,
A hot-rolled plate containing Mo: 0.026%, Se: 0.023%, Sb: 0.025%, with the remainder substantially consisting of Fe, was uniformly annealed at 900°C for 3 minutes and then intermediately annealed at 950°C. Cold rolling was performed twice to obtain a final cold rolled sheet with a thickness of 0.20 mm. After that, after decarburization annealing in wet hydrogen at 800℃, an annealing separator containing MgO as the main component was applied to the surface of the steel sheet, followed by secondary recrystallization annealing at 850℃ for 50 hours, and then at 1180℃.
Purification annealing was performed in dry hydrogen for 10 hours. Thereafter, the forsterite film on the surface of the steel plate was removed by pickling, and then chemically polished in a 3% HF and H ₂ O _solution to give a mirror finish. Thereafter, an extremely thin tension film of TiC was formed with a film thickness of 0.60 μm by CVD using the apparatus shown in FIG. The magnetic properties and adhesion of the product at that time were as follows. Magnetic properties B ₁₀ = 1.91T, W _17/50 = 0.69W/Kg Adhesion Even when bent 180° with a bending diameter of 30 mm, there was no peeling and the adhesion was good. Example 4 C: 0.042%, Si: 3.43, Mn: 0.062%, Mo:
Contains 0.025%, Se: 0.021%, Sb: 0.025%,
After uniform annealing of the hot-rolled sheet, the remainder of which is essentially Fe, at 900°C for 3 minutes, intermediate annealing at 950°C is performed for 2 minutes.
Cold rolling was performed twice to obtain a final cold rolled sheet with a thickness of 0.23 mm. After that, after primary recrystallization annealing that also served as decarburization in wet hydrogen at 820°C, an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, followed by secondary recrystallization annealing at 850°C for 50 hours, followed by 1180°C. Annealing was performed in dry hydrogen for 10 hours. After that, the forsterite film on the steel plate surface is removed by pickling, and the center line average roughness is improved by electrolytic polishing.
Finished with a mirror finish of 0.05μm. After that, a thin film (1.0 to 1.5 μm thick) of various nitrides and carbides was formed on the surface of the steel plate using a CVD device, and then an insulating film mainly composed of phosphate and colloidal silica was applied and baked at 800℃. Strain relief annealing was performed for 3 hours. Table 2 shows the magnetic properties of the product at that time.

【table】

[Table] Example 5 C: 0.052%, Si: 3.29%, Mn: 0.072%, Al:
0.030%, S: 0.020%, N: 0.0073%, Sn: 0.05
%, Cu: 0.1%, and the remainder substantially consists of Fe. After uniform annealing at 1180℃ for 2 minutes, a hot-rolled plate was subjected to rapid cooling treatment, and then warm rolled at 350℃.
A final cold-rolled sheet with a thickness of 0.23 mm was obtained. After that, after primary recrystallization annealing in wet hydrogen at 840℃, which also serves as decarburization, the surface of the steel plate is coated with an annealing separator mainly composed of MgO, and then heated to 850℃ until 1150℃.
After secondary recrystallization by raising the temperature to hr, annealing was performed in dry hydrogen at 1200°C for 10 hours. Thereafter, the forsterite coating was removed by pickling, and then mirror-finished in a solution of 3% HF and H _{2 O.} After that, a 3.2 μm thick TiN tension film was formed using the CVD method, and for some samples, an insulating coated and baked layer containing phosphate and colloidal silica as main components was formed, and then heated at 800°C for 30 minutes. Time strain relief annealing was performed. The magnetic properties and adhesion of the product at that time were as follows. Without Γ insulating film Magnetic properties B ₁₀ = 1.95T, W _17/50 = 0.71w/Kg Adhesion Even when bent 180° with a bending diameter of 20 mm, there was no peeling and the adhesion was good. With Γ insulation film Magnetic properties B ₁₀ = 1.95T, W _17/50 = 0.68W/Kg Adhesion Even when bent 180° with a bending diameter of 30 mm, there was no peeling and the adhesion was good. Example 6 (A) C: 0.039%, Si: 3.36%, Mn: 0.072%,
S: 0.026%, Sb: 0.020%, Mo: 0.013%, (B) C: 0.043%, Si: 3.20%, Mn: 0.052%,
A hot-rolled sheet of unidirectional silicon steel containing 0.031% S, 0.0028% B, and 0.0078% N, with the remainder substantially consisting of Fe was used. The hot-rolled sheets of (A) and (B) were uniformly annealed at 900℃ for 3 minutes, then cold-rolled twice with an intermediate annealing at 950℃, resulting in a final cold-rolled sheet with a thickness of 0.20mm. did. After that, the cold-rolled sheet in (A) is degreased at 820℃, and the cold-rolled sheet in (B) is degreased and then subjected to primary recrystallization annealing in wet hydrogen at 840℃, which also serves as decarburization. After applying the annealing separator on the steel plate surface, the steel plate in (A) has 850
Secondary recrystallization annealing at ℃ for 50 hours, (B) steel plate at 850℃
Goss direction 2 by increasing the temperature from 8℃/hr to 1050℃
After developing the recrystallized grains, in dry _H2 at 1180℃
A 10-hour blunt annealing was performed. Thereafter, oxides on the surface of the steel plate were removed by strong pickling, and then electropolishing was performed to finish the surface of the steel plate to a mirror finish. Thereafter, an ultra-thin tension film (about 1 μm thick) of 2 to 4 kinds of nitrides, carbides, and nitrides and carbides shown in Table 3 was formed on the surface of the steel plate by CVD method, and then phosphate and An insulating film containing colloidal silica as a main component was baked, and some parts were subjected to strain relief annealing at 800°C for 2 hours in _N2 with the ultra-thin tension film intact. Table 3 shows the magnetic properties of the product at that time.

[Table] (Effects of the Invention) According to the first to fourth inventions, an appropriate manufacturing method for ultra-low iron loss unidirectional silicon steel sheets that is advantageously suitable for applications where strain relief annealing is applied has been established; ~
8 invention further adds insulation enhancement.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a plasma CVD apparatus.

Claims (1)

[Claims] 1 C: 0.01-0.06wt%, Si: 2.5-4.0wt%, Mn: 0.01-0.2wt%, Mo: 0.003-0.1wt%, Sb: 0.005-0.2wt%, S and Se Any one or two types in total
A hot-rolled sheet obtained by hot rolling a silicon steel slab containing 0.005 to 0.05wt% with the remainder substantially consisting of Fe is cold-rolled once or twice with intermediate annealing in between to form a final sheet. After reducing the thickness of the steel sheet, decarburization and primary recrystallization annealing were performed, and then an annealing separator containing MgO as a main component was applied to the surface of the steel sheet, followed by final annealing to form a forsterite base film. After that, this forsterite base film is removed, and the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then Ti, Nb, Si, V, Cr, Al, Mn, B, Ni,
Strain relief characterized by forming an ultra-thin tensile film of 0.005 to 5 μm consisting of one or more and four or less selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides. A method for producing ultra-low iron loss unidirectional silicon steel sheets that do not deteriorate in properties even after annealing. 2 C: 0.01-0.08wt%, Si: 2.0-4.0wt%, Mn: 0.01-0.2wt%, solAl: 0.005-0.06wt%, S: 0.005-0.05wt%, N: 0.001-0.01wt%, Sn : 0.01 to 0.5 wt%, Cu: 0.01 to 0.3 wt%, and the remainder is essentially Fe. After cold rolling to achieve the final plate thickness, decarburization and primary recrystallization annealing are performed, and then an annealing separator containing MgO as the main component is applied to the steel plate surface, and final finish annealing is performed to form a fixed steel sheet. After a territe base film is formed, the forsterite base film is removed, and the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then CVD is applied to the mirror-finished surface. By Ti, Nb, Si, V, Cr, Al, Mn, B, Ni,
Strain relief characterized by forming an ultra-thin tensile film of 0.005 to 5 μm consisting of one or more and four or less selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides. A method for producing ultra-low iron loss unidirectional silicon steel sheets that do not deteriorate in properties even after annealing. 3 Contains C: 0.01-0.06wt%, Si: 2.0-4.0wt%, Mn: 0.01-0.2wt%, S: 0.005-0.05wt%, B: 0.0003-0.004wt%, N: 0.001-0.01wt%. A hot-rolled plate obtained by hot rolling a silicon steel slab with the balance substantially composed of Fe is subjected to cold rolling once or twice with intermediate annealing to achieve the final plate thickness, and then decarburized. - Perform primary recrystallization annealing, then apply an annealing separator mainly composed of MgO to the surface of the steel sheet, and perform final annealing to form a forsterite base film. After removing the coating, the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then Ti, Nb, Si, V, Cr, Al, Mn are deposited on the mirror-finished surface by CVD. ,B,Ni,
Strain relief characterized by forming an ultra-thin tensile film of 0.005 to 5 μm consisting of one or more and four or less selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides. A method for producing ultra-low iron loss unidirectional silicon steel sheets that do not deteriorate in properties even after annealing. 4 Contains C: 0.01-0.08wt%, Si: 2.0-4.0wt%, Mn: 0.01-0.2wt%, solAl: 0.005-0.06wt%, S: 0.005-0.05wt%, N: 0.001-0.01wt% A hot-rolled plate obtained by hot rolling a silicon steel slab with the balance substantially composed of Fe is subjected to cold rolling once or twice with intermediate annealing to achieve the final plate thickness, and then decarburized. - Perform primary recrystallization annealing, then apply an annealing separator mainly composed of MgO to the surface of the steel sheet, and perform final annealing to form a forsterite base film. After removing the coating, the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then Ti, Nb, Si, V, Cr, Al, Mn are deposited on the mirror-finished surface by CVD. ,B,Ni,
Strain relief characterized by forming an ultra-thin tensile film of 0.005 to 5 μm consisting of one or more and four or less selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides. A method for producing ultra-low iron loss unidirectional silicon steel sheets that do not deteriorate in properties even after annealing. 5 C: 0.01-0.06wt%, Si: 2.5-4.0wt%, Mn: 0.01-0.2wt%, Mo: 0.003-0.1wt%, Sb: 0.005-0.2wt%, any one of S and Se Or the total of 2 types
A hot-rolled sheet obtained by hot rolling a silicon steel slab containing 0.005 to 0.05 wt% with the remainder substantially consisting of Fe is cold rolled once or twice with intermediate annealing in between to form a final After making the steel sheet thick, it is decarburized and subjected to primary recrystallization annealing. Then, an annealing separator mainly composed of MgO is applied to the surface of the steel sheet, and final finish annealing is performed to form a forsterite base film. This forsterite base film is removed, and the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then Ti, Nb, Si, and V are deposited on the mirror-finished surface by CVD. , Cr, Al, Mn, B, Ni,
An ultra-thin tension film of 0.005 to 5 μm is formed from one to four selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides, and further on the tension film. A method for producing an ultra-low iron loss unidirectional silicon steel sheet that does not deteriorate in characteristics even when subjected to strain relief annealing, which is characterized in that an insulating baked-on layer is deposited on top of the steel sheet. 6 C: 0.01-0.08wt%, Si: 2.0-4.0wt%, Mn: 0.01-0.2wt%, solAl: 0.005-0.06wt%, S: 0.005-0.05wt%, N: 0.001-0.01wt%, Sn : 0.01 to 0.5 wt%, Cu: 0.01 to 0.3 wt%, and the remainder is essentially Fe. After cold rolling to obtain the final plate thickness, decarburization and primary recrystallization annealing are performed. Next, an annealing separator containing MgO as a main component is applied to the steel plate surface, and final finish annealing is performed to form forsterite. After the forsterite base film is once formed, the forsterite base film is removed, and the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then CVD is applied to the mirror-finished surface. Therefore, Ti, Nb, Si, V, Cr, Al, Mn, B, Ni,
An ultra-thin tension film of 0.005 to 5 μm is formed from one to four selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides, and further on the tension film. A method for producing an ultra-low iron loss unidirectional silicon steel sheet that does not deteriorate in characteristics even when subjected to strain relief annealing, which is characterized in that an insulating baked-on layer is deposited on top of the steel sheet. 7 Contains C: 0.01-0.06wt%, Si: 2.0-4.0wt%, Mn: 0.01-0.2wt%, S: 0.005-0.05wt%, B: 0.0003-0.004wt%, N: 0.001-0.01wt% A hot-rolled plate obtained by hot rolling a silicon steel slab with the balance substantially composed of Fe is subjected to cold rolling once or twice with intermediate annealing to achieve the final plate thickness, and then decarburized.・Perform primary recrystallization annealing, then apply an annealing separator mainly composed of MgO to the steel plate surface, and perform final annealing to form a forsterite base coat. is removed, and then the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then Ti, Nb, Si, V, Cr, Al, Mn, B, Ni,
An ultra-thin tension film of 0.005 to 5 μm is formed from one to four selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides, and further on the tension film. A method for producing an ultra-low iron loss unidirectional silicon steel sheet that does not deteriorate in characteristics even when subjected to strain relief annealing, which is characterized in that an insulating baked-on layer is deposited on top of the steel sheet. 8 Contains C: 0.01-0.08wt%, Si: 2.0-4.0wt%, Mn: 0.01-0.2wt%, solAl: 0.005-0.06wt%, S: 0.005-0.05wt%, N: 0.001-0.01wt% A hot-rolled plate obtained by hot rolling a silicon steel slab with the balance substantially composed of Fe is subjected to cold rolling once or twice with intermediate annealing to achieve the final plate thickness, and then decarburized.・Perform primary recrystallization annealing, then apply an annealing separator mainly composed of MgO to the steel plate surface, and perform final annealing to form a forsterite base coat. is removed, and then the surface is polished to a mirror-like state with a center line average roughness of 0.4 μm or less, and then Ti, Nb, Si, V, Cr, Al, Mn, B, Ni,
An ultra-thin tension film of 0.005 to 5 μm is formed from one to four selected from Co, Mo, W, Zr, Hf, and Ta nitrides and/or carbides, and further on the tension film. A method for producing an ultra-low iron loss unidirectional silicon steel sheet that does not deteriorate in characteristics even when subjected to strain relief annealing, which is characterized in that an insulating baked-on layer is deposited on top of the steel sheet.