JPH067527B2 - Ultra-low iron loss grain-oriented silicon steel sheet and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultra-low iron layer grain-oriented silicon steel sheet and a method for producing the same, and in particular, not only has excellent film adhesion but also high-temperature treatment such as strain relief annealing. The present invention aims to propose a grain-oriented silicon steel sheet with extremely low iron loss that can maintain excellent iron loss characteristics without causing deterioration of characteristics even when applied, together with its advantageous manufacturing method. .

The grain-oriented silicon steel sheet is mainly used as an iron core for transformers and other electric devices, and has excellent magnetization characteristics.
Especially, low iron loss (represented by W17 / 50) is required.

For this purpose, firstly, <001 of secondary recrystallized grains in the steel sheet is used.
> It is necessary to highly align the grain orientation with the rolling direction,
Secondly, it is necessary to reduce impurities and precipitates existing in the final product steel as much as possible. The iron loss value of _grain- oriented silicon steel sheets manufactured under such consideration has been improved year by year through many improvement efforts, and recently, the value of W _17/50 is 0.30 mm in the product and the value of W _17/50 is improved. A low iron loss of 1.05 W / kg is obtained.

However, with the danger of energy a few years ago, there is a growing tendency to seek electrical equipment with less power loss, and as a core material for them, unidirectional silicon steel sheets with even lower iron loss are required. Has become.

(Prior Art) By the way, as a method of reducing the iron loss of a grain-oriented silicon steel sheet, the Si content is increased, the product sheet thickness is reduced, the secondary recrystallized grains are fined, the impurity content is reduced, Although metallurgical methods are generally known, such as making secondary recrystallized grains of (110) [001] orientation more highly aligned, these methods are no longer available from the viewpoint of the current production means. It was extremely difficult to make further improvement, and even if some improvement was recognized, the effect of iron loss improvement was small for the effort.

In addition to these methods, as disclosed in Japanese Patent Publication No. 54-23647, a method is proposed in which secondary recrystallized grains are formed into fine particles by forming a secondary recrystallization inhibiting region on the surface of a steel sheet. Has been done. However, this method is not practical because the control of the secondary recrystallized grain size is not stable.

In addition, in Japanese Patent Publication No. 58-5968, a ball-point pen-like small ball is introduced into the surface of the steel sheet after secondary recrystallization to introduce a micro strain into the surface layer of the steel sheet, thereby reducing the width of magnetic domains and reducing iron loss. Technology, also, in JP-B-57-2252, the final product sheet surface, by irradiating a laser beam at intervals of several mm approximately at right angles to the rolling direction, by introducing a high dislocation density region in the steel plate surface layer, Techniques have been proposed to reduce the width of magnetic domains and reduce iron loss. Further, Japanese Patent Application Laid-Open No. 57-188810 proposes a similar technique in which a minute strain is introduced into the surface layer of a steel sheet by electric discharge machining to make the magnetic domain width finer and reduce the iron loss. These three types of methods all aim to reduce the magnetic domain width to reduce the iron loss by introducing a minute plastic strain into the surface layer of the base metal of the steel sheet after secondary recrystallization, and are equally practical. Although it is also excellent in iron loss reduction effect, the effect of plastic strain introduction is diminished by heat treatment such as strain relief annealing after punching, shearing, winding, etc. of iron plate and baking treatment of coating. There are drawbacks. If a small amount of plastic strain is introduced after the coating process, the insulating coating must be reapplied to maintain the insulation, resulting in a significant increase in strain application process and reapplication process, resulting in cost increase. Bring

In addition to these techniques, in Japanese Patent Publication No. 52-24499, the surface of the silicon steel sheet after finish annealing is mirror-finished, or thin metal plating is applied on the mirror-finished surface, and further on that. A method of manufacturing a low iron loss grain oriented silicon steel sheet by coating and baking an insulating coating has been proposed.

However, the iron loss improvement method by this mirror finish is
Basically, there were two important drawbacks as described below.

Since the surface in the first mirror surface state does not have insulation, it cannot be used as it is. Therefore, some kind of insulation coating must be applied. However, the phosphate coating that is usually used has extremely high adhesion to the mirror surface. It cannot be used badly, and in the second mirror surface state, iron loss is high W
_Although it decreases at _17/50 , the lower the induction, the worse the iron loss.

FIG. 1 shows the iron loss characteristics before and after mirror polishing with the number of induction stomachs.

As is clear from the figure, the iron loss is worse in the mirror state when the induction is smaller than 1.5T.

By the way, as the energy cost increases, the design magnetic flux density tends to decrease, and it has already become mainstream for winding cores to be used for low induction of 1.5T to 1.3T. Therefore, such a tendency of iron loss deterioration in the mirror-finished state makes industrial use of the material in the mirror-finished state difficult.

Further, the above-mentioned drawbacks are generally inherited also in the technique of applying a thin metal plating on the mirror surface, and again there is a drawback that it is difficult to apply a phosphate-based insulating coating.

In addition, such a thin metal layer has a problem in adhesion of the plating layer itself when an insulating layer is formed thereon as disclosed in JP-B-52-24499. However, there is a problem in that it cannot withstand use in a wound core, and when it is annealed at a high temperature of 800 ° C., the bending adhesion of the plating layer further deteriorates.

In addition, Japanese Patent Publication No. 56-4150 discloses a method for improving iron loss by vapor-depositing an oxide-based ceramics thin film on the surface after smooth finishing. When high temperature annealing is applied, it has the drawback of delamination of the ceramic layer, and it is also a problem that it cannot withstand use as a winding core material for distribution, which requires annealing at a temperature of about 800 ° C during transformer molding. was there.

(Problems to be Solved by the Invention) This invention advantageously solves the above problems.
The purpose is (1) to (3).

(1) To provide a grain-oriented silicon steel sheet capable of maintaining a low iron loss in a mirror surface state even in a low induction region and having an insulating coating having good adhesion, (2) The iron of the silicon steel sheet To make the loss even better,
(1) To provide a grain-oriented silicon steel sheet that enables the provision of an insulating coating having good adhesion, and (3) further increase the stability of iron loss and further improve iron loss.

(Means for Solving Problems) It is well known that when a tensile force is applied in the rolling direction of a silicon steel sheet, the iron loss of the silicon steel sheet decreases.

Fig. 2 shows a typical commercial grain-oriented silicon steel sheet having forsterite as an oxide layer on the surface and the surface oxide of the grain-oriented silicon steel sheet removed to obtain a mirror-finished surface. 2kg / longitudinal direction of finished steel plate
The results of examining the relationship between induction and iron loss in each case where a tensile force of mm ² is applied are shown.

As is clear from the figure, it was found that the iron loss becomes very good when the tensile force is applied even when the surface is mirror-finished and the induction is small.

A technique for forming a surface layer capable of applying a tensile force on the mirror-finished surface is a problem.

When forming a surface layer that gives tension to the mirror-finished surface, the conventionally used method is to apply a annealing separator containing MgO as a main component and anneal it to form a forsterite coating on the surface of the silicon steel sheet. It is a technique that is generally well known.

However, this technique loses the iron loss improving effect due to the mirror-like formation due to the non-uniform formation of oxides.

Further, so-called tension coating in which silica is added to the phosphate coating cannot be directly applied to the mirror surface as described above.

Other than that, the thin plating technology disclosed in Japanese Patent Publication No. 52-24499 and the oxide ceramic coating disclosed in Japanese Patent Publication No. 56-4150 have oxide ceramic coatings. In addition, the adhesiveness is poor and it cannot be put to practical use because of poor adhesion. On the other hand, in the latter case, there is a problem in the adhesiveness after high temperature annealing.

Therefore, the inventors have conducted various studies on a coating capable of effectively applying tension to the mirror-finished surface, and have obtained the following findings.

(A) Basically, by depositing a metal on a mirror-finished surface, a coating film having high adhesion and capable of effectively applying tension to a steel plate can be obtained.

(B) When depositing a metal deposition layer, the tension effect is increased by increasing the components such as N, C, O and S along the outer surface, and the adhesion with the insulating coating is also improved. To do.

(C) Furthermore, by applying tension from the outside in the longitudinal direction of the steel sheet during vapor deposition, the effect of reducing iron loss is further increased.

The present invention is based on the above findings, and its gist is as follows.

1. A grain-oriented silicon steel sheet having a smooth finish surface by polishing treatment on oxide removal traces, the finish surface being a mirror surface state with a center line average roughness of 0.4 μm or less, and a tension imparting metal Ultra-low iron loss grain-oriented silicon steel sheet comprising a vapor-deposited layer.

2. A grain-oriented silicon steel sheet having a smooth finish surface by polishing treatment on the oxide removal traces is used, and the finish surface is a mirror surface state with a center line average roughness of 0.4 μm or less, and the component in the thickness direction is In contrast, an ultra-low iron loss grain-oriented silicon steel sheet comprising a tension-imparting metal-based vapor-deposited layer whose outermost layer is substantially ceramics.

3. For finish-annealed grain-oriented silicon steel sheet, remove oxides from the surface, then polish to finish to a mirror surface state with a center line average roughness of 0.4 μm or less, and then on the mirror-finished surface. A method for producing an ultra-low iron loss grain-oriented silicon steel sheet, which comprises applying a tension-imparting metal vapor deposition layer by dry plating.

4. Regarding the grain-finished grain-oriented silicon steel sheet that has been finish-annealed, after removing the oxides on its surface, it is polished to a mirror surface state with a center line average roughness of 0.4 μm or less, and then the longitudinal direction of the steel sheet. On the other hand, a method for producing an ultra-low iron loss grain-oriented silicon steel sheet, which comprises applying a tension-imparting metal vapor deposition layer by dry plating on the mirror-finished surface under external tension.

5. For finish-annealed grain-oriented silicon steel sheet, after removing oxides on the surface, polishing is applied to finish to a mirror surface state with a center line average roughness of 0.4 μm or less, and then on the mirror-finished surface. In addition, while forming a metal vapor deposition layer by dry plating, by gradually introducing a gas containing at least one of N, C, O and S during the dry plating process from the end to the end, the outermost layer is substantially formed. A method for producing an ultra-low iron-oriented grain-oriented silicon steel sheet by coating a tension-imparting metal-based vapor-deposited layer on a ceramic.

6. Finish-annealed grain-oriented silicon steel sheet is cleaned of oxides on its surface, then polished to a mirror finish of 0.4 μm or less in center line average roughness, and then in the longitudinal direction of the steel sheet. On the other hand, while applying an external tension, a metal deposition layer is formed on the mirror-finished surface by dry plating, and at least one of N, C, O and S is added from the middle to the end of the dry plating process. A method for producing an ultra-low iron layer-oriented silicon steel sheet, which comprises forming a tension-imparting metal-based vapor-deposited layer in which an outermost layer is substantially made of ceramic by gradually introducing a gas containing therein.

The present invention will be specifically described below.

In the grain-oriented silicon steel sheet of the present invention, its component composition is not particularly limited, and any conventionally known composition is suitable, but the following composition is particularly preferable: C: 0.03 to 0.050%, Si: 2.50 to 4.5 %, Mn: 0.01 to 0.2%, Mo: 0.003 to 0.1%, Sb: 0.005 to 0.2%, N: 0.0005 to 0.01%, and a composition containing 0.005 to 0.05% of one or two kinds of S and Se in total. , C: 0.03-0.08%, Si: 2.0-4.0%, S: 0.005-0.05%, N: 0.001-0.01%, Al: 0.01-0.06%, Sn: 0.01-0.5%, Cu: 0.01-0.3%, Composition containing Mn: 0.01-0.2%, C: 0.03-0.06%, Si: 2.0-4.0%, S: 0.005-0.05%, B: 0.0003-0.0040%, N: 0.001-0.01%, Mn: 0.01- Composition containing 0.2%, C: 0.03-0.05%, Si: 2.0-4.0%, Sb: 0.005-0.2%, N: 0.0005-0.01%, any one or two of S and Se: 0.005- 0.0
Composition containing 5%, C: 0.03 to 0.05%, Si: 2.0 to 4.0%, N: 0.0005 to 0.01%, any one or two of S and Se: a composition containing 0.005 to 0.05%, Is preferred.

In the present invention, the surface of the grain-oriented silicon steel sheet that has undergone the final finish annealing having the above-mentioned preferable composition is
It is important that the center line average roughness is 0.4 μm or less.

Fig. 3 shows the results of examining the relationship between the surface roughness and the iron loss value when the coil samples having the iron loss W17 / 50 before surface polishing of 0.85 W / kg were polished to various degrees. .

As is clear from the figure, the surface roughness is the centerline average roughness Ra.
By setting the thickness to 0.4 μm or less, the iron loss characteristics are improved as compared with those before polishing. In this respect, the surface is Ra = 0.4μ
The iron loss characteristics deteriorate as the surface becomes rougher than m.

Therefore, in the present invention, the surface roughness of the grain-oriented silicon steel sheet after finish annealing is limited to 0.4 μm or less in Ra.

Ti, Al, Si and the like are suitable as the vapor deposition metal of the metal vapor deposition layer formed on the mirror-finished surface.

As the deposition means, so-called dry plating method such as vacuum deposition, ion plating, sputtering and CVD method is advantageously applicable, and such deposition means preferably deposits a metal having a thickness of about 0.1 to 10.0 μm. The layers are deposited.

By the way, as described above, a steel sheet having a mirror-finished surface on which a metal is vapor-deposited cannot be used as a laminated core or wound core as it is because of lack of surface insulation.

However, regarding this point, a gas containing N, C, O and / or S, for example, a nitrogen-based, carbon-based, oxygen-based and / or sulfur-based reaction gas is introduced into the processing atmosphere in the middle of the deposition process to form a vapor deposition layer. Evaporated metal nitride on the outermost layer,
An advantageous solution is to form a carbide or the like.

That is, since the outermost layer of the vapor deposition layer is substantially made of ceramics, the surface is provided with insulating properties, and when assembled into an iron core, good interlaminar resistance can be maintained. The effect of imparting tension is further enhanced, and when an insulating coating such as phosphate is applied on top of that, the insulating property and film adhesion are also greatly improved.

Next, the manufacturing process of the unidirectional silicon steel sheet according to the present invention will be described in more detail including a general description.

The molten metal adjusted to have a suitable composition as described above is made into a silicon steel slab by the continuous casting method or the ingot-casting method, and then hot-rolled according to a conventional method.

Next, the hot-rolled sheet is subjected to homogenizing annealing at 800 to 1100 ° C and then cold-rolled once to obtain the final sheet thickness by a single cold-rolling method or usually at 850 ° C.
In the latter case, the initial rolling reduction is about 50% to 80% and the final rolling reduction is about 50% to 85%. mm to 0.35
The final cold-rolled sheet thickness is mm.

After de-greasing the surface of the steel plate that has finished the final cold rolling and finished to the product thickness
Decarburization primary recrystallization annealing is performed in wet hydrogen at 750 ° C to 850 ° C.

After that, normally, an annealing separator having MgO as a main component is applied to the surface of the steel sheet, but in the present invention, it is generally the case that forsterite, which was indispensable to be formed after finish annealing, is not particularly formed. Al ₂ O ₃ , ZrO ₂ and T are used as annealing separators because they are effective for simplifying mirror surface treatment.
It is preferable to mix 50% or more of iO ₂ with MgO before use.

After that, secondary recrystallization annealing is performed. This step is {110} <0
This is performed in order to sufficiently develop the secondary recrystallized grains in the 01> orientation, and is usually performed by immediately raising the temperature to 1000 ° C. or more by box annealing 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 more advantageous to carry out the retention annealing at a low temperature of 820 ° C to 900 ° C.
The annealing may be performed at a temperature rising rate of ° C / h.

Then, a refining annealing is performed in dry hydrogen at 1100 ° C. or higher for about 1 to 20 hours.

After that, the oxide film on the surface of the steel sheet is removed by known chemical removal such as pickling, mechanical removal such as cutting and grinding, or a combination thereof.

After this oxide removal treatment, chemical polishing such as chemical polishing or electrolytic polishing, mechanical polishing such as buff polishing, or a combination of these is used to achieve a mirror-finished steel plate surface, that is, a centerline average roughness of 0.4 μm or less. To finish.

Next, a metal vapor deposition layer is deposited on the mirror-finished surface. As the deposition means, so-called dry plating methods such as vacuum vapor deposition, ion plating, sputtering and CVD method are advantageously applicable. As described above.

In this respect, when chemical plating or electroplating as disclosed in, for example, Japanese Patent Publication No. 52-24499 is used as the deposition means, the adhesion of the metal layer is poor, so that it cannot be used for actual use. .

Then, by applying such a vapor deposition film, a tensile force is effectively applied to the surface of the steel sheet, and an effective reduction of iron loss is brought about.

It is desirable that the tension applied by such a vapor deposition film is as high as possible, but if it is 0.1 kg / mm ² or more, a good iron loss improving effect can be obtained. The magnitude of the applied tension can be appropriately controlled by adjusting the vapor deposition conditions, that is, the vapor deposition metal, the thickness of the vapor deposition layer, the temperature of the base metal during vapor deposition, the atmosphere, and the like.

Further, by performing the vapor deposition process as described above in a state in which the external tension is applied in the longitudinal direction of the steel sheet, the iron loss characteristics are further improved.

FIG. 4 shows the results of examining the relationship between the external tension and the iron loss when the vapor deposition process was performed under the condition that the external tension of various magnitudes was applied in the longitudinal direction of the steel sheet.

As is clear from the figure, iron loss is improved by applying external tension, especially when the applied tension is 0.1 to 20 kg / mm ²
When the above range was satisfied, a remarkable iron loss reduction effect was observed.

Therefore, when vapor deposition is performed under the application of external tension, the applied tension is preferably about 0.1 to 20 kg / mm ² .

By the way, the above-mentioned steel plate on which the metal is vapor-deposited on the mirror-finished surface lacks the surface insulating property. Therefore, when it is used for laminated iron cores and wound iron cores, it is necessary to take measures to impart insulation, but since the metal layer surface has poor adhesion, a normal insulating coating such as phosphate coating should be used. Even if it is applied, an insulating coating having good adhesion cannot be obtained.

Therefore, in such a case, place it in the atmosphere during the vapor deposition process.
By introducing a gas containing N, C, O and / or S so that the surface of the vapor deposition layer is substantially made of ceramics, the adhesion of the coating is improved.

As the gas containing N, C, O and / or S, NH ₃ , N ₂ , CH ₄ , C ₂ H ₂ , O ₂ and H ₂ S are suitable.

As an example, a round bar with a phosphate coating treatment applied to a steel sheet with only metal Al vapor-deposited on the mirror-finished surface and a steel sheet with the outermost layer changed to AlN to form an insulating coating The adhesion was compared by a bending test to wrap a plate around and to find the minimum round bar diameter that the insulation coating is not destroyed. The minimum diameter is 55 mm in the stomach with a phosphate coating on evaporated metal Al. On the other hand, although the outermost layer was made of AlN, it was 15 mm and the adhesion was remarkably excellent.

Even when the outermost layer is changed to ceramics in this way, it is confirmed that further reduction of iron loss can be realized by performing the vapor deposition treatment while applying external tension to the longitudinal direction of the steel sheet. It was

(Examples) Example 1 A material (W _17/50 = 0.88 W / kg) after secondary recrystallization annealing was subjected to pickling and chemical polishing to obtain a mirror-finished surface of Ra = 0.3 µm. While applying a tension of 0 to ²⁰ kg / mm ² to this steel sheet, Al was vapor-deposited in a vacuum of 10 ₋₄ torr to form a vapor deposition layer having a thickness of 1 μm.

The results of examining the iron loss characteristics of the product thus obtained are shown in Table 1.

For comparison, the degree of chemical polishing was reduced and Ra = 0.6 μm.
While applying a tension of ² kg / mm ² to the above sample, the same investigation was conducted on the sample on which Al was vapor-deposited with a thickness of 1 μm, and the obtained results are also shown in Table 1.

As is clear from the table, all the steel sheets obtained according to the present invention have improved iron loss characteristics, particularly 1 to 20 kg.
Particularly excellent values were obtained when an external tension of / mm ² was applied.

Example 2 The same material as in Example 1 was used to obtain a mirror-finished surface with Ra = 0.3 μm. Applying 0 to 20 kg / mm ² tension to this steel plate, Cr
Was vapor-deposited.

In addition, NH ₃ gas was introduced into the atmosphere in the middle of vapor deposition to remove C in the outermost layer.
rN was formed.

Furthermore, a phosphate-based tension coating was applied to each sample.

Table 2 shows the results of examining the iron loss value and the adhesion of each of the products thus obtained.

Here, the adhesion is represented by ◯ when the minimum diameter is 30 mm or less at which the film is not broken when the plate is wound around a round bar, and by x when it is larger than 30 mm.

For comparison, the same investigation was conducted on steel sheets with a Cr layer formed by electroplating on the mirror-finished surface,
The obtained results are also shown in Table 2.

(Effects of the Invention) Thus, according to the present invention, it is possible to stably obtain a grain-oriented silicon steel sheet having excellent adhesiveness and excellent iron loss characteristics, particularly when the outermost layer of the vapor deposition layer is substantially made of ceramics. In addition, the adhesiveness of the insulating coating film is excellent, and such adhesiveness does not deteriorate even when the high temperature treatment is applied thereafter.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between induction and iron loss before and after mirror polishing, and FIG. 2 shows the induction when tension is applied in the longitudinal direction of the steel sheet before mirror polishing, after polishing, and after polishing. Fig. 3 is a graph showing the relationship with iron loss, Fig. 3 is a graph showing the relationship between the center line average roughness of steel after surface polishing and iron loss, and Fig. 4 is an external tension applied in the longitudinal direction of the steel sheet. 7 is a graph showing the relationship between applied tension and iron loss when a vapor deposition process is performed under the conditions described above.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Suzuki 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd. Technical Research Headquarters (72) Inventor Nariko Sueda 1 Kawasaki-cho, Chiba-shi Kawasaki Steel Co., Ltd. (56) Reference JP-A-53-144419 (JP, A) JP-A-49-96920 (JP, A) JP-A-60-39123 (JP, A)

Claims (6)

[Claims] 1. A grain-oriented silicon steel sheet having a smooth finished surface by oxide treatment on oxide removal traces, the finished surface comprising:
An ultra-low iron loss grain-oriented silicon steel sheet which is in a mirror surface state having a center line average roughness of 0.4 μm or less and which is provided with a tension-imparting metal vapor deposition layer. 2. A grain-oriented silicon steel sheet having an oxide removal trace and a smooth finished surface by polishing, the finished surface comprising:
A center-line average roughness of 0.4 μm or less, which is a mirror surface state, has different components in the thickness direction, and is provided with a tension-giving type metal-based vapor-deposited layer whose outermost layer is substantially ceramics. Ultra low iron loss grain oriented silicon steel sheet. 3. A finish-annealed grain-oriented silicon steel sheet, after removing oxides on the surface thereof, is polished to be finished to a mirror surface state having a center line average roughness of 0.4 μm or less, and then the mirror surface. A method for producing an ultra-low iron loss grain-oriented silicon steel sheet, which comprises depositing a tension-imparting metal vapor deposition layer on a finished surface by dry plating. 4. A finish-annealed grain-oriented silicon steel sheet, after removing oxides on the surface thereof, is polished to be finished into a mirror surface state having a center line average roughness of 0.4 μm or less, and then the steel sheet. Of an ultra-low iron loss grain-oriented silicon steel sheet, characterized in that a tension-imparting metal vapor deposition layer is formed by dry plating on the mirror-finished surface under external tension applied to the longitudinal direction of Method. 5. A finish-annealed grain-oriented silicon steel sheet, after removing oxides on the surface thereof, is polished to a mirror surface state having a center line average roughness of 0.4 μm or less, and then the mirror surface. The outermost layer is formed by gradually introducing a gas containing at least one of N, C, O and S from the middle of the dry plating process to the end while forming a metal vapor deposition layer on the finished surface by dry plating. A method for producing an ultra-low iron layer grain-oriented silicon steel sheet, characterized in that a tension-imparting metal-based vapor-deposited layer that substantially becomes a ceramic is formed. 6. A finish-annealed grain-oriented silicon steel sheet, after removing oxides from the surface thereof, is polished to a mirror surface state having a center line average roughness of 0.4 μm or less, and then the steel sheet. Of the N, C, O and S from the middle to the end of the dry plating treatment while forming a metal deposition layer by dry plating on the mirror-finished surface under external tension applied to the longitudinal direction of Manufacture of ultra-low iron layer grain-oriented silicon steel sheet characterized by forming a tension-imparting metal-based vapor-deposited layer in which the outermost layer is substantially ceramic by gradually introducing a gas containing at least one kind Method.