JPS60197883A - Formation of insulating forsterite film on grain-oriented silicon steel sheet - Google Patents

Abstract

PURPOSE:To increase the adhesive strength and tension applied to a silicon steel sheet and to improve the magnetic characteristics by forming sub-scale on the surface of the steel sheet contg. prescribed amounts of S, Se and Mn and by subjecting the steel sheet to finish annealing in an atmosphere under a prescribed partial pressure of oxygen. CONSTITUTION:A silicon steel contg. <=0.01wt% S+0.405Se and 0.05+7(S+ 0.405Se)-0.8wt% man is cold rolled to the final thickness. The resulting silicon steel strip is decarburized to form sub-scale contg. SiO2 on the surface of the steel strip. The steel strip is then coated with an MgO-base protective coating material for annealing, and it is held at 850-1,100 deg.C annealing temp. under a partial pressure (PH2O/PH2) of oxygen in the range defined by points A, B, C, D, E in the diagram.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides an MgO-
The present invention relates to a method for forming an S to2 type insulating film.

(Prior art) The MgO-810□-based insulating film mainly composed of 7-orsterite on the surface of the unidirectional silicon steel plate does not just improve the appearance of the product, but also provides the necessary resistance between the steel plates and the 7-orsterite. It also plays an important role in terms of magnetic properties, reducing the iron loss of the product due to the tensile stress acting between the orsterite films.

This 7-orsterite film is usually produced by the following method. First, a material for unidirectional silicon steel containing about 3 to 4% by weight of silicon is cold-rolled once or twice or more with intermediate annealing to a final thickness, and then heated to a temperature of 700 to 700% by weight in wet hydrogen. 9
Decarburization annealing is performed in the range of 00°C, and at the same time an oxide film containing 5j02 is formed on the surface of the steel sheet. Next, a slurry-like annealing separation material containing MgO as the main component is applied to the surface of the steel plate, and then it is wound into a coil shape and subjected to final annealing, making use of the MgO-SiO2 system in-phase reaction that occurs during this process. forsterei) (Mg25in4').

However, the properties of the 7-orsterite film produced at this time depend on the properties of the decarboxylated film, the type of magnesia, the amount and nature of trace additives to magnesia/mother powder, and the atmosphere during final annealing for chirubutsu. Many studies have been conducted on methods for forming forsterite films with excellent mechanical and magnetic properties.

For example, according to Japanese Patent Publication No. 51-12451, adhesion is improved by adding TlO2 to magnesia powder.
It has been reported that a forsterite film with excellent uniformity can be obtained. Furthermore, JP-A No. 54-66935 discloses that in order to obtain a 7-orsterite film with good adhesion consisting of forsterite particles with a small average particle size, the amount of CaO and water in ζ magnesia powder is appropriately controlled. There are five. Further, JP-A-55-58331 discloses a method for obtaining a good forsterail film by limiting the activity of magnesia used.

What these methods have in common is 1. All of them are proposals for improving the annealing separation material whose main component is magnesia, and although many of them are recognized to be effective,
From an industrial perspective, process control is often difficult due to high costs.

Furthermore, the essential problem is that MgO-8 on the surface of the steel plate
When forming a forsterite film by a 102-based solid phase reaction, even if only the annealing separation material and the MgO side are unilaterally defined, there is a limit to improving the properties of the resulting forsterite film. This means that there is. for example,
The steel plate tension of the forsterite film obtained by such a method is about 40,096 at most, and in the actual process, as disclosed in Japanese Patent Publication No. 53-28375, the forsterite film is Furthermore, it is necessary to improve the steel plate tension by applying a secondary coating mainly composed of silica iodine.

On the other hand, as for regulating the atmosphere during finish annealing,
There are methods for controlling iron and iron oxides using inert neutral gas as shown in Japanese Patent Laid-Open No. 53-5800, and the dew point control method as shown in Japanese Patent Application Laid-Open No. 53-5800.

These methods were mainly proposed to solve the problems of the forsterite film forming method in the method for manufacturing unidirectional silicon steel sheets with high magnetic flux density, as disclosed in Japanese Patent Application Laid-open No. 49-61019.

That is, in the method disclosed in JP-A No. 49-61019, it is necessary to heat at a constant temperature of 800 to 920°C for 10 to 100 hours during final annealing, but during the final annealing, the oxidation in the oxide scale It was discovered that if a reducing atmosphere was applied to iron, the forsterite film would be severely damaged, and therefore it was necessary to make the atmosphere neutral or inert (Japanese Patent Application Laid-Open No. 116998-1983).
No. 55-110726). Also, 800
After maintaining the constant temperature between ~920°C, the atmosphere when raising the temperature to 1150~1250°C is hydrogen gas, and the dew point at that time is set to -2.
within the range of 0 to +20°C, and then increase the average dew point to +
A method for reducing the average grain size of forsterite to 0.7 μm or less by lowering the temperature to 10°C or lower is disclosed in JP-A-53-5800.
It was disclosed in the publication No. The former proposal is MgO-810
The second proposal is to ensure an appropriate amount of 5102 on the steel plate side during the reaction, and the latter proposal attempts to control the generation of forsterite grains at the start of the reaction and the subsequent grain growth by controlling the oxygen partial pressure of the atmosphere. It is.

All of these methods are based on the forsnalite insulating film proposed in JP-A No. 49-61019 on the premise of final annealing, which is characterized by constant temperature maintenance at a constant temperature between 800 and 920°C. However, the formation method cannot necessarily be said to be general to other finish annealing cycles. Further, even if the average crystal grain size of the obtained forsterite coating is 0.7 μm or less, the bending adhesion of the coating is only about 1011 at the minimum peeling radius, and it cannot be said that sufficient adhesion is necessarily ensured. Furthermore, in such a method, the tension applied to the steel sheet by the coating is insufficient, and a secondary coating mainly composed of tetraidal silica is often required, leading to an increase in manufacturing costs.

(Objective of the Invention) The purpose of the present invention is to eliminate and improve these various drawbacks in the conventional 7-orsterite film manufacturing method, and to improve the forsterite film, which has high adhesion and tension to the steel plate, and has significantly deteriorated magnetic properties. The purpose is to provide a manufacturing method.

In the present invention, since the nucleus where forsterite is generated is formed as MnO near the surface of the copper plate, the forsterite structure digs into the inside of the steel plate, resulting in extremely good adhesion, resulting in high tension. can be imparted to the steel sheet, thereby improving its magnetic properties.

(Structure of the invention) The present invention will be explained in detail below.

The characteristics of the Forste, Rai 14 film obtained by the present invention are that the tension is 500 g//n112 or more, the average grain size of 7 orsterite is 0.5 μm or less, and the adhesion corresponds to the minimum peeling radius of 3 mm. . Figure 2 shows the formula for improving iron loss due to the unaforsterite film in comparison with conventional materials. As shown in the figure, the formula for improving iron loss due to the forsterite film obtained in the present invention is B8 = 1
, 910(T) product has approximately 0.2 W/Kf, which is 0.2 W/Kf compared to the conventional technology. It is also larger than IW/Kf. The present inventors believe that in order to obtain such a forsterite film, it is important to sufficiently increase the Mn activity in the steel and to apply a constant oxygen partial pressure according to the Mn activity during final annealing. We newly discovered that S+0.
405Se≦0.010 and 0.8≧Mn≧0.05+
7 (S 〇, 405 Se), and the appropriate oxygen partial pressure in the temperature range of 850 to 1100°C during final annealing is Mn -1,,719 (S + 0.405 Sa
), specifically the diagonally shaded area in Figure 1 (AB in the figure).
The conclusion was reached that it is necessary to secure the area in the area surrounded by the CDE.

Further, the present invention will be explained in detail.

The forsterite film on the surface of grain-oriented silica steel is composed of an oxide scale mainly composed of 5io2 formed during decarburization annealing,
An annealing separation material mainly composed of MgO applied thereafter is produced by a solid phase reaction during final annealing.

The present inventors investigated the shape and crystal grain size of this 7-orsterite film by direct observation using a scanning Kameko microscope (hereinafter referred to as scanning electron microscope) and indirect observation using a transmission electron microscope using a two-stage replica method. The average grain size of forsterite is determined by the amount of free Mn in the steel (the amount of Mn that is not fixed as MnS or Mn8s) and the temperature at 850°C during final annealing.
It has been newly discovered that the temperature depends on the atmosphere at ~1100°C, especially its oxygen partial pressure. Furthermore, they found that there is a clear relationship between the amount of free Mn and the surface tension of the forsterite film, and found that in order to form a forsterite film that has an extremely excellent effect of improving magnetic properties, it is necessary to It was confirmed that it is necessary to limit the amounts of Mn, S, and Se and the perforation air for finishing annealing.

Figure 3 shows that after applying magnesia containing 5% TlO2 to the decarburized annealed surface of 3.3-81 steel with different amounts of Mn and S, under an atmosphere of PII2o/PH□ = 4 x 10-3. 7 shows the relationship between the surface tension of the orsterite film and the amount of Mn in the steel (total amount of Mn) when finish annealing. In this way, by increasing the amount of Mn in steel, 5501/m
It was experimentally confirmed that a surface tension of 2 or more can be obtained. Furthermore, due to the decrease in S content in the steel, as shown in the same figure,
It has become clear that the tension increasing effect of Mn becomes even more remarkable. This indicates that the amount of Mn in steel, especially MnS and
Free Mn other than being dragged in the form n 3 e
This shows that the amount, or more precisely the Mn activity, is important in determining the properties of 7 orsterite. This experiment revealed that the amount of Mn is important, but although some trends were observed regarding the relationship between Mni and trazzo elements such as S or Se, a quantitative determination could not be made. As a result of observing the forsterite film using a scanning electron microscope and a two-stage replica, it was found that the forsterite particle size changes depending on the conditions.

Generally, the 7-orsterite particle size has a very large effect on glass tension.

The mechanism by which the glass tension is generated without reaching the steel plate is thought to be as follows.

While the steel plate tends to shrink during the cooling process of final annealing, the 7-orsterite crystals, which have a small amount of shrinkage, do not resist the shrinkage of the steel plate, and as a result, give tension to the steel plate. This resistance is large when the forsterite structure has high high temperature strength, that is, when the 7 orsterite crystal grain size is small. This will give a strong tension to the steel plate. As a result of the experiment, the forsterite crystal grain size was 0.5 μm.
If it is below, a steel plate tension of 5001/vrm or more can be applied.

However, it is an essential condition that the glass does not peel off under such conditions, and this condition can be satisfied in the present invention because the adhesiveness is extremely good as described above.

Figure 4 shows scanning electron microscopy images and two-stage replica photographs of 7-orsterite films on steel sheets with different amounts of Mn and S (the amounts of Mn and S correspond to Figures 5 (a) to (d)). do.

). The magnesia powder used at this time was 5% TlO2.
and the oxygen partial pressure during final annealing is PH2o/P
H2=4XIO-3. Thus, it has become clear that the appearance and grain size of the 7-orsterite film strongly depend on the Mn and S contents in the steel.

FIG. 5 collectively shows the results of a wide range of such analyzes conducted for other Mn and S contents.

As shown in the figure, the 7 orsterite grain size is 0.5
In order to make it less than μm, Mn≧0.05+78 (Mn
, S: weight %).

Next, in order to investigate the effect of the atmosphere during finish annealing,
! Finish annealing was performed by changing the atmospheric oxygen partial pressure to various values with respect to the amount of j-Mn, and the characteristics of the obtained forsterite films were investigated. - As an example, in FIG. 6 Mn = 0.
2 wt%, S = 0.005 wt% material at 850 to 1100°C, (a) PH2o/PH□=
2.5XIOt(b) pH2゜/PH2= 1.5X
A two-stage Lenorica photograph of the 7 orsterite film annealed at 10-2 is shown. Further, Table 1 shows the characteristics of the forsterite film obtained in this example.

In this way, the final annealing temperature range is set to PH2°/PH2=1.
It was found that by making it weakly oxidizing to 5.times.10@-2, the 7.orsterite crystal grain size was small and the film tension was also improved.

From the above experimental results, the combination of Mn activity in the steel and finish annealing [H gas] is important in order to form a forsterite film with a grain size of 0.5 μm or less and high tension and adhesion. became clear.

The inventors considered and examined these results as follows.1
Mn required to obtain a good 7-orsterite film
, the limited range of elements such as S and Se, and the corresponding finishes and annealing atmosphere (particularly oxygen partial pressure) were established.

It was reported in Japanese Patent Publication No. 51-1245 that it is useful to add trace amounts of additives such as TiO2 and MnO to magnesian powder in order to promote the Mgo-5to□ system solid phase reaction.
It is publicly known from Publication No. 0 and the like. The reason why these TiO2r MnO etc. have a catalytic effect during the progress of the solid phase reaction is not necessarily clear, but the reason is that the melting point of the substance that contributes to the MgO-8102 reaction decreases in the vicinity of TiO2 and MnO, and the Mg++ As a result of the rapid diffusion rate of TiO2 and MnO, it is thought that forsterite is likely to be generated in the vicinity of TiO2 and MnO, that is, a kind of condition for heterogeneous nucleation is satisfied.

If the melting point decreases significantly, the final annealing temperature range (
MgO-8 (02-TiO□
It is presumed that a -MnO-based liquid phase is generated and has a significant effect on the sintering of forsterite.

Until now, the known technology of adding various trace additives to MgQ There was naturally a limit to the extent to which meditation students could contribute to their improvement. However, according to the present invention, the Mn activity in the steel and the selection of the final annealing atmosphere are
By forming MnO in the i02 scale through high-temperature oxidation, it is possible to generate 7-orsterite nuclei on the side of the steel plate, which greatly improves the properties such as tension and adhesion of the 7-orsterite film in the final product. I can understand that this has become possible.

Conditions for such MnO formation can be arranged based on the Mn activity in the steel and the oxygen partial pressure during final annealing. That is, Mn+H
20=MnO+H2,ΔG-(1)ΔG=ΔG'+R
Ttnξ−' (2) ΔG0 is the standard production confession energy change of reaction (1). (R is the gas constant, T is the absolute temperature)) In order for the reaction to proceed to the left, Δ
It is necessary that G〈0, and for that purpose, as is clear from equation (2), the oxygen partial pressure PH2 with respect to the Mn activity;
It is necessary to maintain o/P□2 above a certain value. Figure 1 shows the free Mn content,
Illustrated for Mn-1,719(S+0.405Se). In the figure, points corresponding to the atmosphere at the time of film formation corresponding to the replica photographs shown in FIGS. 6(a) and 6(b) are also shown. Thus, it has been found that the differences in the properties of the forsterite films shown in FIG. 6 and Table 1 can be rationally explained by the presence or absence of MnO formation.

Based on the above experimental results and considerations, the present inventors have arrived at the minimum value of the required oxygen partial pressure during finish annealing as shown in FIG.

By the way, in order to ensure sufficient Mn activity in steel as described above, it is necessary to reduce elements such as S and Ss that drag Mn in the form of precipitates such as MnS and MnSe.

This is contrary to conventional knowledge in terms of the stability of secondary recrystallization. For example, in Japanese Patent Publication Nos. 30-3651 and 47-25250, the use of MnS is essential for stabilizing secondary recrystallization. Also At
Even in the manufacturing method of high magnetic flux density unidirectional silicon steel sheets by a single cold rolling method using N, the necessity of S was established in Japanese Patent Publication No. 40-156.
It was applied as shown in Publication No. 44. However, the present inventors have separately discovered that it is possible to carry out secondary recrystallization in a sufficiently stable manner even in the range of S+0.405Se≦o, o io. That is, acid-soluble At and N are desirable as the main inhibitor components, but other inhibitor components, such as TiN, can also be used.
, NbC.

If secondary recrystallization can be performed using NbN or the like, these may be used. By combining this AtN-based inhibitor and finish annealing, it is possible to secure a magnetic flux density of 88=1.9 (T) or more, as shown in the examples of the present invention.

Next, the reasons for limiting the constituent elements of the present invention will be described.

If the amount of S+Se exceeds 0.010 wt% in terms of the amount of S, it becomes necessary to add a meaningless amount of Mn at the time of steel tapping in order to obtain the necessary Mn activity, which is not economical. (Here, S
e has the same effect as S in the sense of dragging Mn. Therefore, in order to secure the necessary Mn activity, S
The amount of e must also be regulated.

The S equivalent of Ss is 0.405 Ss (S
e: weight %), the amount of Mn was regulated relative to S+0,405Se. ) Furthermore, during purification annealing, S and Se are added to MgS # MnS I in the 7-orsterite film of the finished product.
Since S and Se are mixed in the form of MnSe and impair the adhesion and uniformity of the film, the amount of S and Se is 0.010 wt% in terms of S amount.
Below, that is, S+0.405Se≦0.010(w
t%). More preferably S+0.4
By setting 05Se≦0.007 (vrt%), the film tension shown in FIG. 3 is stabilized, and the adhesion and uniformity are improved. .

As is clear from the results in FIG. 5, Mn is a constant, and in order to obtain the necessary Mn activity, the amount of Mn is 0.
05+7 (S+0.405Se). The upper limit of the amount of Mn is determined not from the properties of the film but from the stability of secondary recrystallization of grain-oriented silicon steel. That is, as the amount of Mn increases beyond that shown in FIG. 7, the degree of directional integration of secondary recrystallized grains deteriorates, making it difficult to ensure magnetic flux density.

The cause of this is not clear, but at present it is harmful to add more than the required amount of Mn, and the upper limit of Mn is 9.8.
It was wt Chi.

The temperature at which forsterite crystals undergo nucleation and growth is approximately 850 to 1100° C. during final annealing. Therefore, the atmosphere within this temperature range determines the properties of the 7-orsterite.

The atmosphere in this temperature range will be described in detail below.

The final annealing atmosphere can be obtained by solving equation (2) for aMa, and its lower limit value is based on the literature (0, Kuboie et al.
hewski & Cm/L Alcook, Ms
tallurgical thermocbs+m1a
try5 tL ed, (1979) Pergam
on Press, p. 294). What is difficult here is the evaluation of Mn activity and aMll. What is now at issue is the conditions for producing the minimum necessary amount of MnO that contributes to the MgO-8102 solid phase reaction, and it is thought that this is different from the general Mn activity in silicon steel. For these reasons, the present inventors determined this experimentally as follows.

First, assuming Hsnry's law, alla = r ''11&...' (3) Mn. Here l) Mn amount (Mn-1,719 (S 10, 405 S *)) X O, 01 There is (Mn a
S*Se: weight %). Next, bMl.

Madanesia was applied to different decarburized annealed plates, and 1O-1
Finish annealing was performed in various PH2o/P12 atmospheres in the range of ~1O-4, and the average crystal grain size of the produced forsterite crystal grains was investigated. Then, r1=5 was obtained from the change in the average particle diameter of the 7 orstessites obtained, and this value was used to substitute equation (3) into equation (2). The temperature to which equation (2) is applied was from 850° C. at the initial stage of forsterite formation, and the value of PH2o/Pg□ at this temperature was taken as the lower limit. This value is the value indicated by line 11Bc in FIG. It is necessary to maintain the value of PH2o/P[2 in the final annealing atmosphere above this value, so that the required amount of MnO and SlO□ can exist in the scale at the time of forsterite formation, and fine crystal grains and vertical writing. A 7-orsterite film is obtained.

In addition, when considering the components in steel, the Mn amount 0.05 + 7 (S + 0.405
Se), whereas the Mn activity when considering the necessary critical partial pressure is amn=r, (Mn-1,719(S+
0.405S*))Xo, O+. That's 8+0.
Although the coefficient for 4058m is different, its meaning in the present invention is Mn≧o, o s + 7 (8+0.40
When considering the calm activity that affects forsterite properties in terms of the effect of oxygen partial pressure, &Mm=rka・(Mn-1,7
19 (S 〇, 405 Sa )) Xo, 01, which does not imply any contradiction.

PR□. The upper limit value DE of 72M2 is set at 72M2 because if the Mn activity is increased further or the atmosphere is made oxidizing, film defects will occur which are thought to be caused by the excessively generated liquid phase, which will deteriorate the interlayer resistance of the product. The settings were made as shown in the figure. Further, the upper limit AI is limited due to problems in on-site operations. That is, pH□. /PH□ of 5 x 10-2 or more requires a large-capacity humidifier to perform finish annealing, and furthermore, it is difficult to apply oxygen partial pressure evenly in the width and length directions of the coil. Since the formation of a non-uniform film becomes unavoidable and the product yield also decreases, the upper limit must be set at AE.

That's all, PH□. Due to the constraints on /P, □ and aMn, the oxygen partial pressure between 850 and 1100°C during finish annealing is as shown in Figure 1AB.
It is necessary to maintain it within the range shown in the CDE.

In order to limit the amount of Mar 8 and Se in the steel and the atmosphere within this range, it is necessary to limit the amount of Mar 8 and Se in the steel and the atmosphere.
It is possible to generate an appropriate amount of nO, and as a result, a forsterite film with a crystal grain size of 0.5 μm or less and a tensile strength of 50017wx2 or more and good adhesion can be obtained.

(Example) Example 1 C: 0.060%, 81: 3.30%, P: 0.036
Ch, ゛S: 0.004 chi, acid soluble A4: Q, 030 chi.

N: For molten steel containing 0.0082%, Mn was added to (a) 0.0051b) (b) 0.02ts (
c) 0. l Ofbs (d) 0.20% was added to prepare an ingot. After heating at 1200° C., a hot rolled sheet with a thickness of 2.3 mtn was produced by hot rolling. These hot-rolled plates were annealed at 1120°C x 2m1n, with a final plate thickness of 0.3
After cold rolling to zero and annealing, 850℃×1.5 in wet hydrogen
Decarburization annealing of m1n was performed. After subsequently applying magnesia containing 5% TiO□, N22 s fb
PH27s% 1 dew point -1O℃ (PR20/P[2=
600℃~1 in an atmosphere of 3.78 x 1O-3)
Finish annealing was carried out to 1200°C at a heating rate of 8°C/hr to 100°C, and then the material was held at the same temperature for 20 hours in a hydrogen atmosphere. The magnetic flux density, iron loss, and properties of the forsterite film of the obtained product were as shown in Table 2. In addition, 2 of the appearance of the 7 orsterite film shown in this example.
Photographs of the step legica are shown in FIGS. 4(a) to 4(d), and scanning electron microscope images are shown in FIGS. 4(a') to 4(d').

Table 2 (Example 1) ← Scope of the present invention → Example 2 C: 0.052%, 81: 3.35%, Mn:
Q, 20*, p:o, o+o%, s:o, oo4%,
Acid soluble At: 0.0271N: 0.0090%,
Continuous casting slag containing Cr: 0.1o%
After heating to a temperature of 0C, it was hot rolled to produce a 2.3fi hot rolled sheet.

This hot-rolled sheet was annealed to 1080"CX2m1n, then cooled to a final plate thickness of 0.30mg by the same method, and decarburized at 850°Cx2m1n in a wet hydrogen atmosphere. Thereafter, 2% TiO After applying magnesia containing N
225qb, 700-1200 in H275% atmosphere
℃ heating up to 1200℃ at a temperature increase rate of 6℃/hr,
Thereafter, it was maintained at the same temperature in a hydrogen atmosphere for 20 hours. At this time, the dew point from 800℃ to 1100℃ is -40℃ (PH2
0/pH □ = 2.49 x 10-'), ■+1
The temperature was set at 0°C (PH207PH2=0.0163). The magnetic properties and properties of the forsterite film obtained were as shown in Table 3.

Example 3 C: o, 053 qbs S: a, 45%
For molten steel containing 1Mn: 0.28%, tP: 0.035%, acid-soluble At: 0.030%, and N: 0.0085%, S (a) Q, 003fb s (b
) 0.009 To * (e) 0.015 To
, (d) 0.020 T.

to create in-/,). After heating at 1350℃, hot rolling! 12.51IIIO hot rolled sheet was made. After cold-rolling these hot-rolled sheets to a thickness of 1.8 m, l 120'
CX2mln annealed and cold rolled to a final thickness of 0.18m.

Thereafter, decarburization annealing was performed in wet hydrogen at 850° C. x 2 ml, magnesia containing 3% TiO2 was applied, and final annealing was performed. Atmosphere dN275, N225, & point i -40℃ (PH2゜/pH2=
The temperature increase rate from 600 to 1200°C was 10°C/hr. The magnetic flux density, iron loss, and properties of the 7-orsterite film of the obtained product are shown in Table 4.
The rules were as shown in .

Table 4 (Example 3) ← Scope of the present invention → Example 4 C: 0.059%, Sl: 3.33%, Mn: 0.3
5%.

P: 0.038 thi, S: 0.008 thi, acid soluble At:
0.024'16) N: 0-0095 q6
A continuous casting slab containing tCr: 0.205g was heated to a temperature of 1200°C and then hot rolled to 2.311
It was made into a hot rolled sheet of m. This Q hot-rolled plate was heated at 1120°C x 2m1n.
After annealing, the plate thickness (a) is 0.30 ms j by one cold rolling method.
(b) 0.23 m s (c) 0.17 m t
After cold rolling, decarburization annealing was performed at 850° C. x 2 ml in a humid atmosphere. Then, apply magnesia containing 5% Tie2, N275%, N225%, jI point -20℃
Finish annealing was performed in an atmosphere of (Pyo2°/PH□=4.96×10−5). At this time, the temperature increase rate from 600 to 1200°C was 15°C/hr. The properties of the 7 orsterite film of the obtained product were good regardless of the thickness of the product, with an average grain size of 0.2 μm and a minimum peeling radius of 4 plates, and the appearance was blackish gray and dense. The magnetism (indicated by magnetic flux density B8 and iron loss W17/!50) is k) 1.91, respectively.
(T) s 0.98 (W/Kf).

(b) 1.92 ('r), 0.87 (W/K
f), (o) 1.92 (T), 0.84(
w/Kf).

(Effects of the Invention) As detailed above, the present invention enables the production of a forsterite film in 3% silicon steel with an average grain size of 0.5 μm or less and excellent adhesion and steel sheet tension, which has been difficult until now. This method provides a method that enables the reduction of iron loss due to the tension effect of the film by a combination of the Mn activity of Moreover, the adhesion of the film was also achieved with a minimum peeling radius of approximately 31 m1. Therefore, since the present invention can provide a magnetic material with excellent magnetic properties, it is of great industrial benefit.

[Brief explanation of the drawing]

Figure 1 shows a crystal grain size of 0.5 μm or less and a tension of so. The amount of Mn, S, and se in steel necessary to obtain a 7-orsterite membrane of 17 mm2 or more and the amount of 850 during final annealing.
tl: PH20/PH of atmosphere between ~1100℃
A diagram showing the relationship between Diagram showing the relationship between magnetic flux density (B8) and iron loss (W17AO), 3rd
The figure shows the relationship between the amount of Mn in the steel and the tension due to the 7-orsterite film, and Figure 4 is a two-stage leglica photograph and a scanning electron beam diagram showing the particle structure of the 7-orsterite film of the product obtained in Example 1. The photomicrograph, Figure 5, is a diagram showing the relationship between the Mn and S contents in 3.3%St steel and the 7-orsterite crystal grain size (the numbers in the figure are the average crystal grain size (μm) of the forsterite grains). ), Figure 6 (&) (b) is a two-stage leglica photograph showing the grain structure of the forsterite film shown in Table 1, and Figure 7 shows the relationship between the amount of Mn in the steel and the magnetic flux density, B8σ). The figures shown in FIGS. 8(&) to (d) are scanning electron micrographs showing the particle structure of the 7-orsterite film of the finished product obtained in Example 3. Rod twice J
Cwb%) Rod 7 Hn (wt%) Procedural amendment (spontaneous) June 11, 1980 Mr. Kazuo Wakasugi, Commissioner of the Patent Office■, Indication of the case 1982 Patent Application No. 053819 2, Title of the invention 7 Method for Forming Orsterite Insulating Film on Unidirectional Silicon Steel Sheet 3, Relationship with the Amendment Case Patent Applicant Representative of Nippon Steel Corporation, 2-6-3 Otemachi, Chiyoda-ku, Tokyo (665) Take 1) Yutaka 6, Detailed explanation of the invention in the specification subject to amendment and Drawing 7, Contents of amendment (1) Page 6 line 5 r of the specification MgO-8102J was added to rMg
Corrected to o-8102J. (2) ``In the vicinity of the surface of the steel/plate'' on page 7, line 10 is corrected to ``in the oxidized scale on the surface of the steel plate'' 0 (3) 1, page 11 of the same
Make the following corrections for the 0th line to the last line. ``We discovered that the grain size of niforsterite varies depending on the conditions.''The grain size of general niforsterite has a very large effect on glass tension, but the mechanism by which glass tension occurs is thought to be as follows. (4) Same page 11, 10
Correct the line ``It is possible.'' to ``It is possible.'' (6) Correct the line 6-7 on page 19, ``The growth will occur'' to ``The grain growth will occur.'' (7) ``For the final annealing atmosphere, use equation (2)'' on page 19, line 12, is corrected to ``For the required oxygen partial pressure in the final annealing atmosphere, use equation (2).'' (8) 5 lines from the bottom of page 19 rKuboach*vrsk
i Correct J to rKubaschewski J 0
(9) Correct "Required critical partial pressure" to "Required critical partial pressure of oxygen" on page 21, line 5. Correct "critical partial pressure" to "oxygen partial pressure" on page 28, line 15. Correct α9 Figure 6 on the separate sheet◎

Claims (2)

[Claims] (1) Decarburize a silicon-copper strip that has been cold-rolled to a desired final plate thickness, generate Sarascale containing 5io2 on the surface of the steel plate, and then apply an annealing separation material containing MgO as the main component,
In the method for forming a forsterite film on a unidirectional silicon steel sheet that undergoes final finish annealing, the amount of S I S@ and Mn in the steel is S+0.405Se≦0.0 in weight percent.
10 Katsu0,8≧Mn≧0.05+7(S+0.405 S
o) and 850°C to 1100°C during the above final annealing.
Oxygen partial pressure (expressed as PH2o/PH2) in the temperature range of °C
1. A method for forming a 7-orsterite insulating film on a unidirectional silicon steel sheet, characterized in that Mn-1,719 (S+0.4058e) is maintained in a region surrounded by ABCDE in FIG. (2) The amount of S and So in steel is 8+0.4058 in weight%
The method according to claim 1, wherein e≦0.007.