WO1987005945A1 - Process for producing low core loss, thin, unidirectional silicon steel plate having excellent surface properties - Google Patents

Abstract

A process for consistently producing a low core loss, thin, unidirectional silicon steel plate. The process makes it possible to produce a low core loss, unidirectional silicon steel plate having a thickness of 0.1 to 0.25 mm for use in producing transformers with advantageously avoiding deterioration of surface properties by considering chemical ingredients of steel, optimizing rolling conditions, particularly cold-rolling conditions, and forming allomeric microzones on the surface of a steel plate. The steel plate does not undergo deterioration by stress-relieving annealing.

Description

 Description Low iron loss with excellent surface properties

 Manufacturing method of silicon steel sheet

(Technical field)

The technical contents described in this specification in relation to the low iron loss unidirectional silicon steel sheet, especially for the improvement of the surface shape when it is thin and the improvement of the magnetic flux density by controlling the secondary recrystallization texture, are as described above. ϊ 6 to propose the results of development research about what makes it possible to manufacture in stable process of silicon steel sheet ₀

 (Background technology)

Grain oriented silicon steel sheet transformer (represented by ₁₀ values B.) The magnetic flux density that can be used as core materials of the electrical equipment髙rather, iron loss (represented by W _17/5 o value.) Low is required.

Numerous improvements have been made to this end, and today magnetic flux density B ,. Iron loss « _17/5 with values above _1.89T . A unidirectional silicon steel sheet having a low iron loss of 1.05 W / kg or less has been produced.

However, since the energy crisis, the production of unidirectional silicon steel sheets with lower iron loss has become an urgent issue, and now a system to provide bonuses for ultra-low iron loss silicon steel sheets mainly in Europe and the United States (Loss evalution system) is becoming popular. The following method has recently been proposed as a method for producing a grain-oriented silicon steel sheet with an extremely low iron loss value.

 No. 57-2252, No. 57-53419, No. 58-5968, No. 58-26405, No. 58-26406, No. 58-26407 and No. 58- As described in each publication of 36051, the A1N precipitated phase is used as an inhibitor to suppress the growth of crystal grains with inappropriate orientation in the final finish annealing, and the production of unidirectional silicon steel sheet On the surface with respect to the rolling direction: By irradiating a laser beam at a right angle at a distance of several mm, an artificial grain boundary is introduced on the surface, and iron loss is reduced by this artificial grain boundary. How to

 However, the proposed method of introducing an artificial grain boundary locally forms a high dislocation density region, so that a product subjected to such treatment can be used stably only at a low temperature of about 350 ° C or less. There is.

 In the method for producing a unidirectional silicon steel sheet using an A 1 N precipitated phase as cited above, MnS coexisting with A 1 N as an inhibitor is dissociated and solid-dissolved before hot rolling. Slab heating needs to be performed at a higher temperature than in the case of ordinary steel.However, if slab heating is performed at such a high temperature, hot cracking will occur during slab heating or hot rolling, and the product will have a surface Defects are likely to occur, especially if the Si content, which inhibits hot workability, exceeds 3.0%, the surface properties of the product will be significantly deteriorated.

In this regard, as disclosed by the inventors in Japanese Patent Application Laid-Open No. 59-85820, when the A1 N precipitated phase is used, the Si content is high. Focusing on the fact that silicon steel material of 3.1 to 4.5% is essentially a material suitable for obtaining products with high magnetic flux density and low iron loss, the deterioration of surface properties which is a disadvantage in that case is considered. As a means to solve the problem, by concentrating Mo in the material surface layer before hot rolling, it is possible to obtain a good surface property even with a high Si content. However, although the surface properties of the product have been greatly improved by this new method compared to before, recently, products with a thinner thickness of 0.23 to 0.17 mm have been developed to obtain low iron loss. The effect of improving the surface properties is small and remains as a major problem.

 Separately from this, the use of the precipitated phase is based on the single-hot-rolling method, so when manufacturing a thinner product, the secondary recrystallized grains became extremely unstable and strongly accumulated in the Goss orientation. The question that it is difficult to develop secondary recrystallized grains

I'm sorry.

 Very recently, in Japanese Patent Application Laid-Open No. 59-126722, in order to stably produce a thin product using a high Si content / N precipitate phase, a conventional one-time strong cold rolling method was used. It has been disclosed that two cold rollings with a drastically changed Nb, particularly applied to a hot rolled material having a composition in which a small amount of Cu and Sn are added in addition to / N.

Although this method is effective for stably reducing iron loss of thinned products, it usually requires high-temperature heating of the slab under conditions where Si is increased, so it also has excellent surface properties. The problem is still to be solved, such as the difficulty of obtaining the product, and the addition of small amounts of Sn and Cu to stabilize the secondary recrystallized grains, resulting in a significant cost increase of the product Many problems remain. By the way, as a method of reducing the iron loss of a grain-oriented silicon steel sheet,

 (1) Increasing the Si content in silicon (2)

 (2) Reduce the product thickness.

 ③ to increase the purity of the steel sheet,

 ④ Basically, it is considered to develop fine secondary recrystallized grains without lowering the Goss orientation accumulation of secondary recrystallized grains of the product.

 Firstly, it was attempted to increase the Si content in (1) above the normal 3.0%, and in (2) to 0.23, 0.20 mm which is thinner than the normal product thickness of 0.35, 0.30 ram. In both cases, the secondary recrystallized structure becomes non-uniform, causing a problem that the integration degree of G oss orientation decreases. In addition, if the Si content is increased more than usual according to (1), hot embrittlement becomes remarkable, hot cracking occurs during slab heating or hot rolling, and the surface properties of the product deteriorate significantly. That has already been mentioned.

 On the other hand, the improvement of the purity of the steel sheet or the improvement of the directionality of (3) has reached the point where it is considered to be the limit at present. For example, the Goss orientation of the secondary recrystallized grains of the current product is already accumulated within the average of 3 ° to 4 ° in the rolling direction, and in such a highly aggregated condition, the grain size should be further reduced. Is extremely difficult in metallurgy.

In view of the above-mentioned circumstances, the present invention has been developed in view of the recent trends in the prior art described above, and is intended to industrially produce a thin unidirectional silicon steel sheet having extremely excellent surface properties and extremely small iron loss and high magnetic flux density. Providing a method that enables stable and particularly advantageous production It is intended to provide.

 (Disclosure of the Invention)

 The above objectives are achieved as follows.

 Si 3.1 to 4.5wt¾,

 Mo 0.003--0.lwt%,

 Acid soluble Al 0.Q05 ~ 0.06wt%,

 And one or two of S and Se in total

0.005 ~ 0.lwt%,

Hot rolled into a hot rolled sheet, followed by primary cold rolling at a draft of 10 to 60%, followed by intermediate annealing, followed by secondary cooling at a draft of 75 to 90% Cold rolled sheet finished to a final thickness of 0.1 to 0.25 mm by cold rolling, decarburized in wet hydrogen, primary recrystallization annealing, and then high-temperature finish annealing. Method for producing a thin unidirectional silicon steel sheet with excellent low iron loss (first invention).

 Si 3.1 ~ 4.5wt%,

 Mo 0.003-0.lwt%,

 Sb 0.005-0.2wt%,

 Acid-soluble Al 0.005-0.06wt%,.

 And one or two of S and Se in total

0.005-0.lwt%,

Hot-rolled slabs with hot rolling to form a hot-rolled sheet, subjected to primary cold rolling at a reduction rate of 10 to 60%, and then subjected to intermediate annealing, followed by secondary cold rolling at a reduction rate of 75 to 90%. The surface is characterized in that a thin cold-rolled sheet that has been subjected to cold rolling and finished to a final thickness of 0.1 to 0.25 mm is decarburized in wet hydrogen, primary recrystallization annealing, and then high-temperature finish annealing. Manufacturing method of low-loss thin unidirectional silicon steel sheet with excellent properties (No.

2 invention).

 S i 3.1 to 4.5w t

 o 0.003 to 0. l t¾.

 Acid soluble A l 0.005 to 0.006wt¾,

 And one or two of S and Se in total

0.005 to 0.lwtj,

Hot-rolled slabs containing hot-rolled slabs are subjected to primary cold rolling at a reduction rate of 10 to 60%, followed by intermediate annealing, followed by secondary cold rolling at a reduction rate of 75 to 90%. Rolled and finished to a final thickness of 0.1 to 0.25 mm, and the thin cold rolled sheet is decarburized in wet hydrogen.

 Low iron loss sheet with excellent surface properties characterized by being subjected to high-temperature finish annealing in advance by applying a treatment to give formation of heterogeneous micro-domains on the steel sheet surface that has been subjected to subsequent high-temperature finish annealing. Method for producing high magnetic flux density unidirectional silicon steel sheet (third invention).

 S i 3.1 ~ 4.5wt%,

 Mo 0.003-0.lwt%,

 Sb 0.005 to 0.2 wt%,

 Acid-soluble A l 0.005-0.006wt¾,

 And one or two of S and Se in total

0.005 to 0.lwt%,

Hot-rolled slabs containing, are subjected to primary cold rolling at a reduction rate of 10 to 60%, followed by intermediate annealing, and then secondary cold rolling at a reduction rate of 75 to 90% To a final thickness of 0.1 to 0.25, and the thin cold rolled sheet is decarburized in wet hydrogen. When performing crystal annealing,

 Preliminary treatment to give the formation of heterogeneous micro-domains on the steel sheet surface that has been subjected to subsequent high-temperature finish annealing,

A method for producing a low-iron-loss thin high-flux-density unidirectional silicon steel sheet having excellent surface properties, which is characterized by being subjected to high-temperature finish annealing (a fourth invention).

 S i 3.1 to 4.5 t¾

 Mo 0.003-0.lwt%,

 Acid soluble A l 0.005-0.006 t¾,

 And one or two of S and Se in total

0.005 to 0.lwt%,

Hot rolled into a hot rolled sheet, followed by primary cold rolling at a draft of 10 to 60%, followed by intermediate annealing, followed by secondary cold rolling at a draft of 75 to 90% The cold rolled sheet, which has been cold rolled to a final thickness of 0.1 to 0.25 mm, is decarburized in humid hydrogen.After primary recrystallization annealing, it is annealed at high temperature, followed by surface annealing. A method for producing a low-iron-loss thin unidirectional silicon steel sheet having excellent surface properties, characterized by forming a heterogeneous microregion section on the upper surface (fifth invention)

S i 3.1 ~ 4.5wt%,

 Mo 0.003-0.lw t%,

 Sb 0.005 to 0.2 wt¾.

 Acid soluble / 0.005 ~ 0.06wt¾,

 And one or two of S and Se in total

0.005 to 0.lwt%,

Hot-rolled into a hot-rolled sheet, followed by primary cold rolling at a draft of 10 to 60%, followed by intermediate annealing. Reduced cold-rolled thin cold-rolled sheets that have been subjected to secondary cold rolling at 75 to 90% and finished to a final thickness of 0.1 to 0.25 ram have been decarburized in wet hydrogen.After primary recrystallization annealing A high-temperature finish annealing, and a method for producing a low-iron-loss thin unidirectional silicon steel sheet having excellent surface properties, characterized by forming a heterogeneous microregion on the surface of the steel sheet (Sixth invention) Through the above inventions, it is practically preferable to heat or cool the intermediate annealing between 500 and 900 ° C., particularly at 5 ° C. or more per second, in both the temperature raising process and the temperature lowering process.

 The inventors added a small amount of Mo to the material when producing thin unidirectional silicon steel sheets by using the A 1 N precipitated phase under a high silicon content of 3.1 to 4.5 wt. A product with excellent surface properties can be obtained by this process, and a unidirectional silicon steel sheet with low iron loss in an extremely stable process by adopting two cold rolling methods including rapid annealing and rapid cooling intermediate annealing It was discovered that it was possible to manufacture the above, and the above inventions were completed.

 (Brief description of drawings)

 Fig. 1 shows the relationship between the magnetic properties of the product and the reduction rate of the first and second cold rolling and the state of the surface properties, and Fig. 2 shows the heating rate and cooling rate during intermediate annealing. Figure showing the relationship between the product and the magnetic properties of the product.

 Fig. 3 is a diagram showing the relationship between the magnetic properties of the product, the primary cold rolling and the secondary cold rolling reduction, and the surface properties.

 (Best mode for carrying out the invention)

 First, the experimental case that led to the completion of the first invention will be specifically described.

C 0.048 t%, Si 3.40wt%, Mo 0.025wt%, acid soluble Al- 0.026wt% and S 0.025wt% lump (test steel I), C 0.053wt%, Si 3.42wt%. Acid soluble Al 0.027wt%, S 0.024wt%. Sn 0.llwt and Cu 0.09wt % Ingot (Comparative Steel I) was 1420. After heating at C for 4 hours to dissociate the inhibitor and form a solid solution, it is hot-rolled to form a hot-rolled sheet of 2.2 thickness.

 After the first cold rolling at a rolling reduction of 70% or less, intermediate annealing was performed at 1050 ° C for 3 minutes. During the intermediate annealing, the temperature was raised from 500 ° C to 900 at a rate of 10 and a rapid heat treatment of 10 / s was applied, and after the intermediate annealing, a rapid cooling treatment from 900 ″ to 500: / s was performed.

 After that, it is subjected to secondary cold rolling at a reduction rate of 70% to 91% to make a cold rolled sheet with a final thickness of 0.20 [ran thickness, and then decarburized in 850: wet hydrogen.Primary recrystallization annealing Was given. '

 After that, the surface of the steel sheet is coated with an annealing separator containing MgQ as a main component, and the temperature is raised from 850; to U00 C at a rate of 8: / hr to perform secondary recrystallization. C was subjected to high-temperature finish annealing, that is, purification annealing in dry hydrogen for 10 hours.

 Fig. 1 shows the magnetic properties of the product and the incidence of surface defects (the incidence of surface flaws on the surface of the steel plate is expressed in%).

As is evident from the plot shown by Hata in Fig. 1, the product of test steel I containing Mo in the material has a primary cold rolling reduction of 10 to 60% (particularly 20 to 40%). The magnetic properties are good and the surface defect occurrence rate of the product is 2% or less (0.5% or less when the rolling reduction of the first cold rolling is in the range of 20 to 50%). It is noted that.

On the other hand, the magnetic properties of the product made of the conventional steel I with the same composition as in the plots marked with B and B are as apparent from the plots marked with 〇 in the same figure. Value, W17 _{/ 5} . Both values are slightly worse than those of test steel I, and the incidence of surface defects of the product is extremely high, 6-18%.

 Next, a steel ingot (sample steel を) having C 0.04 · 9¾, Si 3.45¾.o 0.02%, acid-soluble / 0.028%, and S 0.026% was heated to 1410 ° C. ♦ The solution was dissociated by heating for 5 hours. ♦ After solid solution, it was hot rolled to form a 2.2 mm thick hot rolled sheet.

 After that, primary cold rolling was performed at a rolling reduction of about 40%, and intermediate annealing was performed at 1050 ° C for 3 minutes. Experiments were performed at a temperature increase rate of 500 to 900 t during the intermediate annealing and a cooling rate of 900 to 500 ° C after the intermediate annealing in the range of 1: to 100 ° C. .

 The intermediately annealed steel sheet is subjected to secondary cold rolling at a rolling reduction of about 83% to give a final cold-rolled sheet with a thickness of 0.23 mm, followed by decarburization in wet hydrogen at 850 and primary recrystallization annealing. After applying an annealing separator containing MgO as the main component on the surface of the steel sheet, the temperature was raised from 850 ° C to 1100 at 10 ° C / hr to perform secondary recrystallization. Time Purification annealing was performed in dry hydrogen. Figure 2 shows the magnetic properties of the product at that time.

As is evident from Fig. 2, during the intermediate annealing, the heating rate from 500 to 900 ° C and the cooling rate from 900 ° C to 500 after the intermediate annealing were 10 ° C / s, especially at 5 ° C / s or more. When the value is longer than s, a product with remarkably excellent magnetic properties can be obtained.o The reason for the property improvement by rapid heating and quenching treatment after the intermediate annealing is the same as that disclosed by the present inventors in Japanese Patent Application Laid-Open No. 59-35625 (supra). This is considered to be an advantage for preferentially developing the texture. As mentioned earlier, the method of manufacturing a thin unidirectional silicon steel sheet using the A1N precipitation phase in the double cold rolling method disclosed in Japanese Patent Application Laid-Open No. In the present invention, the fine precipitation treatment of MN by the quenching treatment after the homogenizing annealing is merely used for the cooling process after the intermediate annealing after the primary cold rolling. In addition, it has been newly clarified that excellent magnetic properties can be obtained especially when Mo is contained in combination with rapid heating during the temperature rise process of intermediate annealing.

 Next, the development history of the second invention will be described below.

 A continuous slab containing C O. Q46wt%, Si 3.36wt%. Mo 0.026wt%, Sb 0.025wt%, acid-soluble Al 0.024t% and Se 0.020wt%. Test steels A) and C slabs (comparative steel B) containing 0.049%. Si 3.45%, acid soluble A1 0.025 t¾. Sb 0.023wt% and 0.022wt% Was heated at 1360 for 3 hours to dissociate and solid-solve the inhibitor, and then hot-rolled to form a 2.2 mm thick hot-rolled sheet.

 After that, these hot rolled sheets were subjected to quenching after uniform annealing at 1050 for 2 minutes.

After that, primary cold rolling was performed at a rolling reduction of about 40%, and then intermediate annealing was performed at 1000 for 2 minutes. During this intermediate annealing, a rapid heat treatment of 500/900: After the intermediate annealing, a quenching treatment of 12 ° C / s was performed from 900 ° C to 500 ° C.

 Then, it was subjected to secondary cold rolling at a rolling reduction of 85% to obtain a final cold-rolled sheet having a thickness of 0.20, and then subjected to primary recrystallization annealing combined with decarburization in 830 ° C wet hydrogen.

 After that, an annealing separator containing MgQ as a main component is applied on the surface of the steel sheet, and then the temperature is increased from 850 ° C to 10 ° C / hr for secondary recrystallization, and then in dry hydrogen at 1200 ° C for 10 hours. Then, after annealing treatment of the insulating film, strain relief annealing was performed at 800 ° C for 3 hours.

Table 1 shows the magnetic properties of the products and the incidence of surface defects (the incidence of surface flaws on the steel sheet surface is expressed as a percentage).

Table 1 Magnetic characteristics

Ingot composition (wt%)

B ₁₀ (T) W ₁ 7/5 o (W / kg) Surface scratch

 Occurrence rate (%)

1.94 0.82 1.8

 CO

1.93 0.85 8

As can be seen from the magnetic properties and surface shape of the products shown in Table 1, the magnetic properties of the products based on the test material A containing Mo in the material B _{1 Q} value is 1.94T, W _17/50 value is 0.82W / It is noteworthy that the surface defect rate of the product is 1.8, which is good with kg.

On the other hand, the magnetic properties of the product according to the conventional composition comparison B are as follows. It is 1.93T and W17 _{/ 5Q} is 0.85W / kg, which is worse than that of test steel B containing Mo in the material, and the incidence of surface defects of the product is extremely high at 8%.

 Next, typical developments of the third and fourth inventions will be described.

 Steel ingot containing C 0.053%, Si 3.43%, Mo 0.023%, acid-soluble Al 0.028%, S 0.027% (Hot Test Steel C) C 0.056%, Si 3.46-acid-soluble Al 0.026%, S 0.026% Ingot containing 0.1% Sn, 0.1% Cu and 0.1% Cu (Comparative steel No.) were heated at 1430C for 3 hours to dissociate the inhibitor and form a solid solution. It was a rolled sheet.

 After the first cold rolling at a rolling reduction of 70% or less,

Intermediate annealing was performed at 1100 for 3 minutes. During the intermediate annealing, the temperature rise from 500 t: to 900 is performed by rapid heating at a heating rate of 13 C / s, and the cooling rate from 900 to 500 ° C after the intermediate annealing

It was quenched at 18 t / s.

 After that, secondary cold rolling was performed at a rolling reduction of 70% to 91% to obtain a final cold-rolled sheet with a thickness of 0.20. During the cold rolling, warm rolling was performed at 250 ° C.

Then, the surface of the plate was degreased at a temperature of 110. Then, a dilute aqueous solution of MgSO. It was applied with a width of 5 at right angles and 0.5 mm width at intervals. For reference, a sample with the steel plate surface degreased (Reference Example) was also prepared.

 These samples were subjected to decarburization and primary recrystallization annealing in 850 ° C wet hydrogen, and then an annealing separator containing MgG as the main component was applied on the steel sheet surface.After 850 to 1100 ° C After the temperature was raised at 10 ° C / hr for secondary recrystallization, purification annealing was performed in dry hydrogen at 1200 ° C for 10 hours.

 Fig. 3 shows the magnetic properties of the product and the incidence of surface defects (the incidence of surface flaws on the surface of the steel plate is expressed as a percentage).

As can be seen from Fig. 3, the test specimen W (added in the material) with 4ο added (Fig. 3, □) shows the magnetic properties when the primary cold rolling reduction is 10 to 60% (particularly 20 to 40%). It is noteworthy that the properties are good and the surface defect occurrence rate of the product is 3% or less (especially 1.0 or less when the primary cold rolling reduction is in the range of 20 to 50%). Comparison leash conventional composition Π contrast (▲, △ mark) characteristics of, beta, o values, W _{1 7/5.} Both values are slightly worse than the Mo-added material, and the surface defect occurrence rate of the product is extremely high at 6 to 20%.

Then magnetic properties when MgSO ₄ in a dilute aqueous solution was coated at 0.5 picture scroll at right angles to 5 mm interval and the rolling direction by spraying a final cold-rolled sheet on the surface, as Eshirushi plot of test steels ΠΙ The primary cold rolling reduction rate is 30 to 40% (secondary cold rolling reduction rate is 87 to 85%),

_7/5. The magnetic properties are extremely good at 0.72 W / kg, and the incidence of surface defects on the product is good at 1% or less.

On the other hand, in the application treatment by comparison し な い し な い without adding Mo As shown in the plot, the iron loss W 17/5 _Q value is as good as 0.75 W / kg at the primary cold rolling reduction of 30 to 40%, but the surface defects of the product The incidence is 6 ~? % And high.

Therefore, from these experimental examples, to produce low iron loss thin unidirectional silicon steel sheet with excellent surface properties, it is necessary to add a small amount of Mo to a high silicon material, adopt the cold rolling twice method, Then it shows that it is by connexion achieved in binding to perform a coating of a drug solution or suspension shown in the example of MgSO ₄ in dilute aqueous solution the final cold-rolled sheet surface.

 This point has already been partially mentioned in Japanese Patent Application Laid-Open No. 60-39124 ^ Decarburization · Decarburization promoting area or decarburization on the steel sheet surface before primary recrystallization annealing almost perpendicular to the rolling direction The inventors have just proposed a method for producing a unidirectional silicon steel sheet with low iron loss by alternately forming lagged regions, developing secondary recrystallized grains inhomogeneously, and introducing heterogeneous minute region sections. By using this in conjunction with the double cold rolling method including rapid annealing and rapid cooling intermediate annealing prior to the final cold rolled sheet surface coating, stable growth of secondary recrystallized grains can be achieved. Further, such a method of alternately forming a decarburization promoting region or a decarburization delayed region on the surface of a steel plate is also effective by applying after decarburization and primary recrystallization annealing. This point has already been partially mentioned in Japanese Patent Application Laid-Open No. '60'-8'952.

Next, a lump with a C 0.048%, Si 3.41%, Mo 0.024%, acid-soluble Al 0.025% Sb 0.025%, S 0.026% C) and C 0.052%, Si 3.38%, acid soluble A 10.023%, S 0.025% (test 鐧 C) containing lump heated at 1420 ° C for 3 hours And Inhibit After dissociating and solid-solving the sample, it was hot-rolled into a hot-rolled sheet with a thickness of 2.0 mm.

 After that, a final cold-rolled sheet of 0.20 mm thickness was formed by two cold rollings (intermediate annealing at 980 ° C for 3 minutes) (50% primary cold reduction, 80 secondary cold reduction). And 'In the case of this intermediate annealing, 500 to 900. The temperature was raised to C by rapid heat treatment at a heating rate of 10 ° C / s, and after intermediate annealing, from 900 ° C to 500 ° C at a cooling rate of 13 ° C / s.

After performing primary recrystallization annealing combined with decarburization annealing in 840 ° C wet hydrogen, then, before applying an annealing separator containing MgO as a main component on the surface of the annealed sheet, the M ₂ 0 ₃ powder as the reaction inhibiting substance with separating agent and the steel plate subscale in Si0 _2, the adhesion amount of 0.5 g / m ^2, substantially perpendicular to the attachment width to the rolling direction of the steel sheet 2 mtn and repeatedly, At a distance of 8 mm, attach linearly to the surface of the steel sheet, and then apply an annealing separator containing MgQ as a main component, then from 850 ° C to 1050 ° C at 10 ° C / hr. After secondary recrystallization by raising the temperature, purification treatment was performed at 1200 C for 8 hours, and then the absolutely green coating film was baked and subjected to strain relief annealing at 800 ° C for 3 hours.

Note follow the usual manner by omitting the deposition process of the A 1 ₂ 0 ₃ powder for comparison, to create a directional silicon鐧板by a method of applying an annealing separator mainly comprised of MgO, and a comparative example.

For space but homogeneous Forusuterai bets coating gray Tatte I to Tsunaban front had been formed was coated with A1 ₂ 0 ₃ powder was conducted in the Comparative Example was examined for coating properties, 0.7 ίπι only little thickness Forusuterai DOO The coating is formed The magnetic properties and surface shapes of these products are shown in Table 2 in comparison (

> 3

Table 2

 O CO CocO c

 Decarburization · Primary recrystallization annealing Magnetic properties Surface properties Application of annealing separator after rope mass component (wt%)

Method Β, ο (Τ) Wi 7 /50 (W / kg) surface flaws of Bro rr click incidence ^)

MgO is evenly applied to steel sheet 1.94 0.84 0.4

A1 ₂ 0 ₃ coated topically applied 1.94 0.77 0.5 After MgO to

Uniform application of MgO on rope 1.93 0.90 9

A1 ₂ 0 ₃ coated topically applied 1.93 0.86 10 After MgO to

As is evident from the magnetic properties and surface properties of the products shown in Table 2, the magnetic properties of the products made of test steel C containing Mo in the material are decarburized and the MgQ annealing separator after primary recrystallization annealing is always used. When uniformly applied to steel sheet according to the method of Β ,. Is 1.94T and _17/50 is 0.84W / f (g), and the surface defect occurrence rate of the product is 0.4%. Decarburization and _primary recrystallization annealing using the same _test steel C If the post a 1 ₂ 0 ₃ was coated with MgO After topically applied to form a non-uniform Fuorusuterai bets coating 1.94T, W _{I 7 / 5Q} is very good as 0.77 W / kg, yet product It is noted that the incidence of surface defects is also 0.5%.

On the other hand, the magnetic properties of the product using the comparative steel D with the same composition as before are decarburized. に よ っ て, ο is 1.93Τ, and W17 / _5Q is 0.86 to 0.90 W / kg depending on the handling conditions after the primary recrystallization annealing. This is worse than the test steel C containing Mo in the material, and the incidence of surface defects on the product is extremely high at 9 to 10%.

 In this regard, as already mentioned in Japanese Patent Application Laid-Open No. 60-92479, the domain width can be subdivided by creating regions of different thickness in the forsterite film constituting the surface film of grain-oriented silicon steel sheets. It is useful as a method for producing a unidirectional silicon steel sheet with low iron loss.

 Next, typical developments of the fifth and sixth inventions will be described below.

C. 0.053%, Si 3.43%, Mo 0.026%, acid soluble Al 0.029%, Se 0.021%, Sb 0.020% steel ingot (test E) and 0.058%, Si 3.49%, acid soluble A1 0.026%, S 0.026%, Cu 0.1%, Sn 0.05% After the inhibitor was dissociated and solid-dissolved by heating for a period of time, it was hot-rolled to obtain a hot-rolled sheet having a thickness of 2. Q mm.

 Then, after quenching after homogenizing annealing at 1080 ° C for 2 minutes, cold rolling is performed twice with intermediate annealing at 950 ° C for 3 minutes (primary cold reduction is 50%, 2%). The final cold-rolled sheet was 0.20 iMi thick at the next cold reduction of 80%.

 During the intermediate annealing, the temperature was raised from 500 ° C to 900 ° C by rapid heat treatment at a heating rate of 11 ° C / s, and after the intermediate annealing, the cooling rate was 12 ° c / s from 900 ° C to 500 ° C. Processed.

 After the first recrystallization annealing combined with decarburization in wet hydrogen at 850, the surface of this steel sheet was coated with an annealing separator mainly composed of MgQ, and then from 850 ° C to 12 ° C / hr. After the temperature was raised to 1050 ° C at the temperature rising rate and secondary recrystallization was performed, purification annealing was performed in dry hydrogen at 1220: 5 for 5 hours. -·

After that, a part of the steel plate was used, and a laser beam was used to apply a laser to the steel sheet in the direction perpendicular to the rolling direction at intervals of 8 mni (laser irradiation conditions: pulse interval D = 0.4 ram. Irradiation line interval ^ = 6 咖, pulse frequency f _a = 8 KHz, after introducing a small distortion in the energy E = 3.5x10- ³ J) of spot per bets steel, the SbCl ₃ was pickled processed C. in H ₂ S0 ₄ (60%) solution at 80 An immersion treatment was performed.

 Then, after baking treatment of the insulating coating mainly composed of phosphate and colloidal force, the laser irradiation position was recovered and recrystallized at 800 for 3 hours for strain relief. The product.

For comparison, after the finish annealing was performed, the green coating was baked, and then the strain relief annealing was performed at 800 t for 3 hours. Table 3 compares the magnetic properties and surface properties of these products.

Table 3

 Magnetic properties & [1

 Steel ingot composition (wt%) Treatment method after finish annealing

B ₁₀ (T) Wl 7/50 (W / kg)

 Occurrence rate (%)

 Insulation coating treatment 1.94 0.84 0.2

 Laser irradiation-pickling →

Immerse in SbCl ₃ solution → 1.94 0.76 0.4

 Insulation coating treatment C

 CO

 (F) C 0.058¾, Si 3.49%, insulation coating 1.93 0.90 9

 Al 0.0261 S 0.0261

 Cu 0.1%, Sn 0.05¾ Laser irradiation → pickling

 Submerged in SBC liquid 1.93 0.85 11

Insulation coating treatment

If insulated coating treatment according magnetic characteristics and test steel magnetic characteristics are final annealing after a conventional method of how the product by E for舍有the Mo to the Filling As apparent from the surface properties of the product B ₁₀ shown in Table 3 1.94T, W _17/5 . Is 0.84 W / kg, and the surface defect rate of the product is 0.2%.

Further pickling after finish annealing after the laser irradiation using the same test試鐧E, facilities recovery * recrystallization annealing which further serves as a absolute緣被film formed after strain relief annealing was dipped in SbCl ₃ solution If B _{1 Q} is 1.94T, W _{I 7 /} s. Is 0.76 W / kg, which is remarkably good, and the surface defect occurrence rate of the product is 0.4%.

On the other hand, the magnetic properties of the product using the comparative steel F of the conventional composition depend on the handling conditions after finish annealing. There 1.93T, _7/5. Is 0.85 to 0.90 W / kg, which is worse than that of test steel E containing Mo in the material, and the incidence of surface defects on the product is extremely high, 9 to 11%. No. 57-2252-JP-B-57-53419, JP-B-58-5968, JP-B-58-26405- JP-B-58-26406, JP-B-58-26407 and JP-B-58-36051 As described above, this method is to reduce the iron loss by introducing artificial grain boundaries by laser irradiation on the surface of the unidirectional silicon steel sheet after finish annealing almost perpendicular to the rolling direction. However, this method has the disadvantage that it can be used stably only at low temperatures due to the formation of localized high dislocation density regions, but after introducing small strain locally by laser irradiation. The base iron is completely exposed by pickling, The _c can be produced less oriented silicon steel sheet is preferably iron loss by the this to form a heterogeneous micro region partitioned by One Manzanillo with this to promote the recovery and recrystallization of the local area reacted steel sheet on the surface with warm The manufacturing method is an epoch-making manufacturing method in which iron loss does not deteriorate even when subjected to high-temperature heat treatment, unlike the above-mentioned product plate irradiated with laser, and a part of this structure is disclosed in Japanese Patent Application Laid-Open No. 60-255926. Is disclosed.

 As described above, in the present invention, the addition of Mo to the material, the adoption of the twice-rolling method, and particularly the limitation on the rate of temperature rise and fall in the intermediate annealing, Decarburization ・ In the first recrystallization annealing or by forming a heterogeneous micro-area section on the steel sheet after finish annealing, a unidirectional silicon steel sheet having good iron loss and surface properties can be obtained in a stable process. The idea is different from the above-mentioned prior art in that it can be manufactured, and the effects obtained by adopting these processes are far superior to those of the prior art.

In each invention, Si is an element effective to increase the electrical resistance of the silicon steel sheet and reduce the overcurrent loss as described above. In particular, it is necessary to reduce the iron loss of thin products. is there. However, if the Si content exceeds 4.5 wt%, brittle cracks are likely to occur during cold rolling, so the Si content was set in the range of 3.1 to 4.5 wt%. Note that the Si content of a normal grain-oriented silicon steel sheet that uses conventional A 1 N as an inhibitor is about 2.8 to 3.0%. As shown in Fig. 3, the surface properties of the product deteriorated remarkably, as shown in Fig. 3, steel I and m, but in each of the first and second inventions, 0.0003 to 0.1wt% By adding Mo, surface defects can be prevented.

 If the amount of Mo added to this material is less than 0.003 wt%, the improvement of magnetic properties and the ability to prevent surface defects are weak, and if it exceeds 0.1%, decarburization in steel during decarburization is delayed by Jen. / U 0..0 υ0 υ3 0. lw · tι¾ '".

 A1 combines with Ν contained in the steel to form fine precipitates of A1N and acts as a strong inhibitor. In particular, in the production of thin unidirectional silicon steel sheets, acid-soluble A1 in the range of 0.005 0.06 wt% is necessary to develop secondary recrystallized grains that are strongly integrated in the Goss orientation.

 When the acid solubility / is less than 0.005 wt%, the amount of A1N fine precipitates as an inhibitor is insufficient and the development of secondary recrystallized grains of {110} <001> orientation becomes insufficient, while 0.06 wt% Beyond this, the development of secondary recrystallized grains in the {110} <001> direction is remarkably worse again.

S Se forms a dispersed precipitate phase of MnSe together with A1N and enhances the inhibitory effect. If the total amount of S or Se is less than 0.005 wt%, the inhibitory effect of MnS or MnSe is weak, and if the total amount exceeds 0.1 wt%, the hot and cold workability deteriorates significantly. One or two types of S Se must be in the range of 0.005 0.1wt% in total. Even within such a total amount range, the inhibitory effect is insufficient when S is less than 0.005 wt% or when Se is less than 0.003 wt%, respectively, while when the content exceeds 0.05 wt%, respectively. Does hot and cold workability deteriorate? Therefore, it is desirable that S should be within the range of 0.005 to 0.05 wt% and Se should be within the range of 0.003 to 0.05 wt%.

 In each of the second, fourth and sixth inventions, Sb is particularly expected to have the function of suppressing the growth of primary recrystallized grains.However, if the content is less than 0.005 wt%, the effect is small, while if it exceeds 0.2 wt%, the magnetic flux density is reduced. In order to lower the magnetic properties by lowering the content, the content must be within the range of 0.005 to 0.2 wt%.

 Materials suitable for the method of each invention need to contain 3.1 to 4.5% of Si and small amounts of Mo, A1, S and Se, and also Sb, as described above. It does not prevent the existence of other known elements added to ordinary silicon steel.

 For example, it is preferable that about 0.02 to 2% by weight be contained. -Also, C is required to cause τ transformation in a part of the sheet during hot-rolled sheet annealing, related to the fine precipitation of A1N. In the range, the C content is suitably about 0.030 to 0.080w ^.

 Further, it contains 0.5% by weight or less in total of any one or more of Sn, Cu, and B as known primary recrystallized grain growth inhibitors that may be added to ordinary silicon. In addition, it is permissible to contain trace amounts of general unavoidable elements such as Cr, Ti, V, Zr, Nb, Ta, Co, Ni, P and As.

Next, a series of manufacturing steps according to the present invention will be described. First, as a means for melting the material used in the method of the present invention, an LD converter, an open hearth furnace, or another known manufacturing method may be used. It goes without saying that vacuum treatment and vacuum melting may be used together.

 In addition, as a means for preparing a slab, a continuous ingot can be suitably used in addition to a usual ingot-bulking rolling method.

 The silicon steel slab obtained as described above is subjected to hot rolling after heating by a known method. The thickness before hot rolling obtained by this hot rolling differs depending on the rolling reduction in the subsequent cold rolling process, but it is usually desirable to be about 1.5 to 3.0 mm.

 In the present invention, in order to obtain a silicon steel sheet having good surface properties, it is necessary to add a small amount of Mo to the material, but as disclosed in Japanese Patent Application Laid-Open No. 59-85820. Of course, it is also possible to use a means for concentrating Mo on the steel sheet surface layer by means such as applying a Mo compound to the surface by the end of hot rolling. After the hot rolling, the hot-rolled sheet is subjected to primary cold rolling.Before the primary cold-rolling, in some cases, 900% of the C in the hot-rolled sheet is dispersed in order to achieve a fine uniform dispersion. After uniform annealing in the temperature range of ~ 1200 ° C, quenching is also applied.

 Although the rolling reduction during the primary cold rolling slightly varies depending on the product sheet thickness, in order to obtain a thin product having good characteristics in the present invention, as shown in FIGS. Limited to 60% (preferably 20-50%).

The next intermediate annealing is performed at a temperature of 900 to 1100 ° C for about 30 seconds to 30 minutes, but in order to obtain good magnetic properties stably, raise the temperature from 500 to 900 and after the intermediate annealing. It is desirable to lower the temperature from 900 to 500 at 5: / s or more, especially 10 ° C / s or more. This rapid heating and quenching treatment is performed in a normal continuous furnace or A known technique such as a switch furnace may be used.

 As shown in Fig. 1 and Fig. 3, the following secondary cold rolling is suitable at a reduction rate of 75 to 90%, and the final cold rolled sheet thickness is 0.1 to 0.25 (finished to MI thickness).

 The purpose of each invention is to manufacture a thin high magnetic flux density magnetic steel sheet, and the thickness of the hot-rolled sheet is about 1.5 to 3.0 mm, and the cold rolling and hot rolling shown in Figs. A steel sheet with excellent properties can be obtained by finishing a thin final cold-rolled sheet with a thickness of 0.1 to 0.25 mm at each rolling reduction in the secondary cold rolling.

 At this time, aging treatment at 50 to 600 ° C may be performed between a plurality of passes as disclosed in Japanese Patent Publication No. 54-13866.

 The cold rolled sheet having a small thickness of 0.1 to 0.25 mm is subjected to decarburization annealing also serving as primary recrystallization in a temperature range of about 750 to 87 Q ° C. This decarburization annealing may be performed for several minutes in a wet hydrogen gas atmosphere or a hydrogen / nitrogen mixed gas atmosphere at a dew point + 30 to 65 or so.

 Next, an annealing separator containing MgG as a main component is applied to the steel sheet after decarburization annealing, and then subjected to finish annealing to develop secondary recrystallized grains of {110} <001> orientation. The specific conditions of this finish annealing may be the same as those conventionally known, but usually, the temperature is raised from 1150 to 1250 ° C at a rate of 3 to 50 ° C / hr to reduce the secondary recrystallized grains. After development, it is desirable to perform purification annealing in dry hydrogen for 5 to 20 hours.

Then, after the final cold rolling, the steel sheet finished to the product thickness is subjected to decarburization and primary recrystallization annealing after surface degreasing. The third and fourth inventions have already been covered. So, decarburizing · At the time of the primary recrystallization annealing, that is, before or after this annealing treatment, a treatment for forming a heterogeneous micro-region is formed on the steel sheet surface that has been subjected to the subsequent high-temperature finish annealing, and then subjected to the high-temperature finish annealing. As described in the fifth and sixth aspects of the invention in which laser irradiation is also performed, a unidirectional silicon steel sheet with low iron loss can be manufactured.

 The process leading to the formation of this heterogeneous microregion compartment, as already mentioned,

 ① Decarburization · During primary recrystallization annealing 3 Decarburization is promoted almost perpendicular to the rolling direction o

The advance zone or the decarburization delay zone is formed on the steel sheet surface using a coating agent.

 (2) After high-temperature finish annealing (2) On the plate surface, laser, electric discharge machining, marking or micro-strain is introduced at a local position by a ball-shaped ball or a region where different tension acts.

 3) Temperature unevenness is created on the steel sheet surface by heat treatment at local positions on the sheet surface.

Such a technique can be used.

The method (1), as already disclosed in Japanese Patent Application Laid-Open No. 60-39124, prefers a decarburization accelerating region and a retardation region on the surface of the steel sheet, preferably at intervals of 1 to 50 bands and almost half the width ₍ 2: The area width and width are narrow. ₎ '.1' The fine grained secondary recrystallized grains change the crystallographic structure; The diameter is usually in the range of 1.5 to 25, and within 2 times the secondary particle size, ie, 3 to 50 widths, the secondary recrystallization of fine grains can be achieved by changing the primary recrystallization texture on the steel sheet surface. Crystal grains can be obtained. In addition, such a surface coating is sufficiently effective even on one side of the steel sheet, but it is usually more effective to apply it on both sides of the steel sheet. Although it is considered optimal to apply using a rubber roll, a method such as an injection method in which a masking plate is applied to an area where no application is required may be used.

 Regarding the coating liquid for forming the decarburization promoting region and the retardation region on the steel sheet surface, refer to the teachings of the inventors (Y. inokuti: Trans. ISIJ, Vol. 15 (1975), P. 324). It is advisable to follow, but here are some quotes just in case:

Decarburization _{accelerator: MgCl 2 · 6H 2 0,} Mg (N0 3) 2 - 6H 2 0, CaC - 2H 2 0, Ca (N0 3) 2 - 4H 2 0, SrC - 2H 2 0, Sr (N0 3 _{) 2 · 4H 2 0, BaC} - 2H 2 0, Ba (NQ 3) 2, KC1, n0 4) 2P 2O 7, KBr, C1Q 3, Br0 3, KF, NaCi, NaI0 4, NaOH, NaHP0 4, NaH _{2 P0 4 · 2H 2 0,} NaF, NaHC0 3 - Na 2 0 5, Na 4 P 2 0 7 · 10H 2 0, Nal · (NH 4) 2 Cr 2 0 7, Cu (N0 3) 2, · 3H ₂ 0, Pe (N0 ₃ ) ₃ * 9H ₂₀ , Co (N0 ₃ ) ₂ ♦ 6H ₂ 0,

_{Ni (N0 3) 2 · 6H} 2 0, Pd (N0 3) 2, Zn (CH 3 C00), Zn (N0 3) 2 - 6H 2 0 like.

Decarburization retarder: K ₂ S, Na ₂ S ₂ 0 ₃ ♦ 5H ₂ 0, Na ₂ S-9H ₂ 0, MgSO SrSO Al ₂ (SO4) 3-18H ₂ 0, S ₂ C1 ₂ , NaHS0 ₃ , FeS0 _{4 - 7H 2 0, KHSO4,} Na 2 S 2 0 8l K 2 S 2 0 7, Ti (S0 4) 2 - 3H 2 0, CuSQ 4 ♦ 5H 2 0, ZnS0 4 · 7H 2 0, CrSQ4 - 7H 2 _{0, (NH 4) 2 S} 2 0 8, H 2SO 4, H 2 Se0 3, SeOC, Se 2 Cl 2, Se0 2, H 2 Se0 4, K 2 Se, Ha 2 Se, Na 2 Se0 3, K _{2 Se0 3, Na 2 Se0 4} , 2 Se0 4, H 2 TeO, .2H 2 0, Na 2 Te0 3, K 2 Te0 3, K 2 Te0 4 ♦ 3H 2 0, TeC, a 2 Te0 4, Na 2 _{As0 2, H 3 As 0 4} , AsC, (NH 3 As0 4, KH 2 As0 4, SbOCl, SbC, SbBr 3, _{Sb 2 (S0 4) 3,} Sb 2 0 3, BiCl 3, Bi (OH) 3, BiF 3, aBi0 3,

_{Bi 2 (S0 4) 3,} SnCl 2 * 2H 2 0, Snl 2, PbC, PbO (OH) 2, Pb (N0 3) , etc..

Therefore, it is clear that the non-processing area is divided into the delay area in the processing using only the former, and the promotion area is formed in the non-processing area when using only the latter.

 The method of partitioning the steel sheet surface after decarburization and primary recrystallization annealing with a secondary recrystallization accelerating and inhibiting agent may already be in accordance with the teaching of Japanese Patent Application Laid-Open No. 60-89521. Then, it becomes as follows.

 (a) Secondary recrystallization accelerator for S, Se, Te, As, Sb, Bi, Sn and Pb:

S _{compounds: K 2 S, a 2 S} 2 0 3 · 5H 2 0, Na 2 S - 9H 2 0, MgSO

_{SrSO Al 2 (S0 4) 3} · 18H 2 0, S 2 C1 2, aHS0 3, FeS · 7H 2 0, HSO4, Na 2 S 2 0 8, K 2 S 2 0 7,

_{Ti (S0 4) 2 · 3H} 2 0, CuS0 4 · 5H 2 0, ZnS0 4 ·

_{7H 2 0, CrS0 4 · 7H} 2 0, (NH 4) 2 S 2 0 8, H 2 SQ 4

Se _{Compound: H 2 Se0 3, SeOC,} Se 2 Cl 2, Se0 2, H 2 Se0 4, K 2 Se,

_{Na 2 Se, Na 2 Se0 3} , K 2 Se0 3, Na 2 Se0 4, K 2 Se0 4

Te _{compounds: H 2 Te0 4 · 2H 2} 0, Na 2 Te0 3, K 2 Te0 3, K 2 Te0 4 - 3H 2 0, TeCl 4, Na 2 Te0 4

As _{Compound: Na 2 As0 2, H 3} As0 4, AsC, (MA) 3 AS0 4, H 2 AS

 O 4

Sb _{compounds: SbOCl, SbC, SbBr 3,} Sb 2 (S0 4) 3, Sb 2 0 3

Bi _{Compound: BiCl 3, Bi (OH)} 3, BiF 3, NaBiQ 3, Bi 2 (S0 4) 3 Sn _{compound: SnCl 2 · 2H 2 0,} Snl 2 (b) Ce, Na, K , and Sr of secondary recrystallization inhibitor: Ce _{compounds: Ce0 2, Ce (N0 3} ) 2 · 6H 2 0, CeC - 7H 2 0

Ca _{compound: CaCl 2, Ca (N0 3} ) 3 - 6H 2 0, CaHPO 2H 2 0 Na _{compound: NaOH, NaCl 'Na 2 HP0} ,, Na 2 Cr 2 0 7 · 2H 2 0,

_{a 4 P 2 0 7 · 10H} 2 0, NaHC0 3, ^ a [Q 4

K _{Compound: KN0 2, KC1, KMn0 4} > KN0 3, C10 3

Mg compound: MgCl ₂ · 6H ₂ 0, g (N0 ₃ ) 2 * 6H 2O

Sr _{compound: SrCl 2 · 2H 2 0,} Sr (N0 3) 2 · 4H 2 0

 Three

Ba compound: BaCl ₂ , 2H ₂ 0, Ba 3 (N0 ₃ ) 2

 Next, for the technique (2), for example, the conditions for introducing micro-strain by laser treatment may be in accordance with the teachings of known literature (Japanese Patent Application Laid-Open No. 60-96720, etc.). It is.

 The most suitable laser is YAG laser-pulse oscillation multi-mode. Next, the preferred irradiation conditions for the surface of laser treatment

 Pulse interval D = 0.2 to 0.6 ram Irradiation row interval in rolling direction i-4 to 15 ram

Pulse frequency f _a = ΙΟΚΗζ or less Energy per steel surface area U = 1.0 to 3. OmJ / mm ^2nd O ₀

 The conditions for introducing micro-strain by electric discharge machining may be in accordance with the teachings of a known document (Japanese Patent Publication No. 57-18810, etc.).

 Width or diameter of discharge mark d = 0.004 to 2

Distance between discharge marks on steel sheet D = 0.1 to 0.8 咖 Spacing in rolling direction of discharge train = ~ 15πιπι

 The conditions for introducing micro-strain at the local position by marking (pressing) or a ballpoint pen-shaped ball may be in accordance with the teaching of a known document (Japanese Patent Publication No. 58-5968).ゥ

 Gap between dents on steel plate surface 1 to 15rain

 5 m or less dent depth from steel plate surface

 Dent width 10 to 100 jum on steel plate surface

 The method (3), ie, the formation of compartments for the temperature difference on the steel sheet surface by heat treatment, may follow the teachings of known literature (JP-A-60-103132, etc.). is there.

 High temperature treated temperature on steel plate

 Between normal and normal steel sheet annealing temperature 15 ~: LOO "C

 High temperature area on steel plate surface 2 to 25 mm width Area processed at normal annealing temperature 2 to 25 IMI width

Performed by these repeated annealing treatments, the non-uniform heat treatment

 (For example, JP-A-59-100221, JP-A-59-1QQ222, JP-A-60-103120, etc.) The methods are: local heating by flash lamp, infrared lamp, high frequency Any conventionally known method such as induction heating and pulse type heat treatment may be used.

In particular, in case (1) of the above-mentioned methods, after the treatment, a steel sheet surface is coated with an annealing separator mainly composed of MgO and then subjected to high-temperature finish annealing to make {110} <001> Develop secondary recrystallized grains that are strongly integrated in the orientation. The specific conditions of this finish annealing may be the same as those of the conventionally known annealing method, but usually, the temperature is increased from 1150 to 1250 ° C at a heating rate of 3 to 50 ° C / hr, and the secondary recrystallized grains are heated. After developing, annealing in dry hydrogen for 5-20 hours It is desirable to perform

 An insulating coating is applied on the forsterite coating on the steel sheet surface after finish annealing to ensure reliable insulation, but the finish annealing was applied as already described in the fifth and sixth inventions. The production of unidirectional silicon steel sheet with low iron loss by forming a heterogeneous micro area section on the steel plate surface.

In this case, Japanese Patent Publication No. 57-2252, Japanese Patent Publication No. 57-53419, Japanese Patent Publication No. 58-5968, Japanese Patent Publication No. 58-26405, Japanese Patent Publication No. 58-26406, Japanese Patent Publication No. 58-26407 and Japanese Patent Publication No. 58-36051 However, the method of introducing an artificial grain boundary by the laser irradiation method disclosed in Japanese Patent Publication No. it is necessary to adopt a method of defining a heterogeneous region on the surface of the steel sheet according to _(magnetic characteristics are not deteriorated even if subjected to high temperature annealing heterogeneous micro territory. zone forming method parcels

aPartitioning the regions with different thicknesses of the forsterite coating on the steel sheet surface,

b Compartments of different types of tension coating on the forsterite coating,

 c As described above, after the forsterite film is locally removed using a laser or the like, the local region is distorted, and recovery and recrystallization together with annealing are performed to form a non-uniform region. Can be used.

The method (a) may be in accordance with the method disclosed in Japanese Patent Application Laid-Open No. 60-92479, but the following four methods are cited just in case. a - i) in the coating fabric process of the annealing separator to the primary recrystallization annealing after the steel sheet surface, prior to coating, the substance that inhibits the reaction of the annealing separator on the steel sheet surface 1 g / m ² or less of A method of applying locally in a range.

S i 0 ₂ as a reaction inhibitor in this method, and Alpha 1 ₂ 0 _3, oxides such as _{Zr 0 2, Z n, A} l, S n, ΝΊ, metals such as F e can be mentioned up. If such a reaction inhibitor is attached in excess of 1 g / m ² , the reaction inhibitory effect will be excessive and a forsterite coating will not be formed. Therefore, the thickness of the forsterite film must be suppressed within the range of lg / m ² or less. As a means for attaching these reaction-inhibiting substances to the steel sheet, any of coating, spraying, plating, printing and electrostatic coating can be used.

a-ii) In the process of applying the annealing separator to the steel sheet surface after the first recrystallization annealing, prior to the application, an annealing separator slurry (a suspension of water and the annealing separator) is applied to the steel sheet surface. A method of locally adhering a water-repellent substance to water in a range of 0.1 lg / m ² or less.

As such a water-repellent substance, an oil-based paint varnish or the like is loosely adapted to prevent contact between the steel sheet surface and the annealing separator, thereby delaying the forsterite-forming reaction to form a reduced-thickness region. is there. However, if it exceeds 0.1 g / m ² , the reaction delay effect will be excessive and no forsterite film will be formed at all. Therefore, forsterite should be used within the range of 0.1 g / m ' ² or less. It is necessary to control the thickness of the coating. Means for attaching these water-repellent substances to the steel sheet are the same as those for the reaction inhibitor described above, such as coating, spraying, printing and the like. Electrostatic painting can be used.

a-iii) In the process of applying the annealing separator to the steel sheet surface after the primary recrystallization annealing, prior to the application, 2 g / m ^{2 of} a substance that becomes an oxidizing agent for Si in the steel is applied to the steel sheet surface. A method to adhere locally within the following range.

These substances are oxidized subsequent final finish Si in the steel at a high temperature in annealing, by increasing the amount of Si0 ₂ particles in the steel sheet surface subscale, increasing the thickness of the false Terai bets film after final annealing Therefore, it is possible to locally form an over-thick film on the surface. Is a such an oxidation agent _{adapted, FeO, Fe 2 (] 3} , Ti0 2 oxide such as Fe ₂ SiO. Reduced easily silicates such as, etc. are free hydroxide such as Mg (0H) ₂ Suruga, and beyond the amount of deposition of these oxidizing agents is 2 g / m ^2, past Nari thickness of the coating is rather large, loses adhesion to the steel sheet, the coating is flaked off want connexion intended purpose Cannot be achieved.

a-iv) A method of forming a reduced thickness region by removing the forsterite film formed on the steel sheet surface after secondary recrystallization without applying plastic strain to the steel sheet surface.

 Such methods include chemical polishing and electrolytic polishing, removal using a rotating conical grindstone, removal using an iron needle using light pressure, and optical removal such as a laser beam with appropriately adjusted output. There is. In particular, when using one laser beam as an optical removal method, multiple beams from one light source are used.

-Efficiently perform multiple operations in a single operation by removing the memory and irradiating the entire surface in the presence of appropriate masking. This is advantageous in that a different thickness region can be formed.

According to the method (b), a method of forming a different type of tension coating on the forsterite coating is disclosed in Japanese Patent Application Laid-Open No. 60-103182, which discloses a method of thermal expansion of an insulating coating. factor ^{8. 5 X 10 - 6 1 /} ° C or less, and as long coefficient between different types of co-Ti in g coating 1.1 or more, 1 Koti ring solution known heterologous alternately ~ It may be applied and baked at intervals of 30 mm.

 The method of c is disclosed in JP-A-60-255926 or JP-A-60-255926.

Three

 8

As disclosed in Japanese Patent No. 89545, after the steel sheet coating is peeled off by means of a laser or a scribing method that applies stress on the steel sheet surface after finish annealing, the steel sheet is treated with an acid such as hydrochloric acid or nitric acid. After removing the base iron, it is immersed in an aqueous solution of a semimetal, metal or an inorganic compound containing these metals, and then filled with the removed part, and then recovered as a strain relief annealing. Average—A region may be defined.

 In addition, in order to guarantee reliable insulation after such treatment, coating and baking of an insulating coating mainly composed of phosphate and colloidal silicide force is required. Naturally, it is necessary for the use of the sensor. For the formation of the insulated coating baking layer, a conventionally known method may be used as it is.

After such an insulating film is formed, strain relief annealing is performed at a temperature of 600 or more, and the above-described manufacturing method of the present invention does not cause deterioration of magnetic properties even if such high temperature annealing is performed. It is special. Example 1

 C 0.059%, Si 3.49%, Mo 0.024%,

 A continuous slab containing 0.034% of acid-soluble Al and 0.029% of S was heated with U30: for 3 hours, and then hot-rolled into a hot-rolled sheet having a thickness of 2.2 ram. Then, after about 50% primary cold rolling, it was subjected to intermediate annealing at 1100 ° C for 3 minutes. During this intermediate annealing, a rapid heat treatment of 12 ° C / s from 500 ° C to 900 ° C and a rapid cooling treatment of 15 ° C / s from 900 ° C to 500 ° C after the intermediate annealing were performed.

 Then, it was cold rolled by about 80% to finish the final cold rolled sheet with a thickness of 0.20 ram, and then subjected to primary recrystallization annealing combined with decarburization in 830 ° C wet hydrogen.

 After that, the temperature was raised to llOOt: at 850 ° C at 10 ° C / hr, and secondary recrystallization was performed. Then, purification annealing was performed in dry hydrogen at 1200 ° C for 10 hours. The magnetic properties and surface properties of the product at that time are as follows:

. Seldom ο

Magnetic properties are B ,. : 1.93T, WI ₇ / _5o : 0.80w / kg. The surface properties were extremely good, with a 0.8% incidence of surface defects. <Example 2>

 C 0.064%, Si 3.39 ¾, Mo 0.019%,

A continuous slab containing 0.029% of acid-soluble Al, 0.020% of Se and 0.022% of Sb was heated at 1420: for 4 hours and then hot-rolled to a 2.2mm thickness. After about 40% primary cold rolling, intermediate annealing was performed at 11001: 2 for 2 minutes. During the intermediate annealing, a rapid heat treatment of 12 t: / s from 500 t to 900 ° C and a quenching treatment of 18 / s from 900 ° C to 500 ° C after the intermediate annealing were applied. 0.23 concealed final cold rolled sheet After that, decarburization and primary recrystallization annealing were performed in wet hydrogen at 840 ° C.

 After that, an annealing separator containing MgQ as a main component was applied on the steel sheet surface, and the temperature was raised from 850 ° C to 1100 ° C at 10 ° C / hr, followed by secondary recrystallization. Purification annealing was performed in dry hydrogen for hours. The magnetic properties and surface properties of the product at that time are as follows: C:

The magnetic properties were as good as B, _Q : 1.93 T, W _I 7/5 o: 0.80 w / kg, and the surface texture was 0.6, the rate of occurrence of surface defect blocks. Example 3

 C 0.058%, Si 3.59%, o 0.035%,

 A lump containing 0.033% of acid-soluble Al, 0.023% of S, 0.15% of Cu, and 0.11% of Sn was hot-rolled into a hot-rolled 2.0-mm thick sheet, and then subjected to primary cold rolling (cold rolling). The rate is about 40). After that, intermediate annealing was performed at 1050 ° C for 5 minutes, but the temperature rise from 500 ° C to 900 ° C was rapid heat treatment at 18 ° C / s and 900 ° C to 500 ° C after intermediate annealing. The temperature was reduced by quenching at 20 ° C / s.

After that, a cold rolled sheet of about 89% was applied to make a final cold rolled sheet of 0.17 thickness, but 300 was warm rolled during the cold rolling. Decarburization in 840 ° C wet hydrogen · After primary recrystallization annealing, the temperature was raised from 850 ° C to 1100 ° C at 15 / hr and secondary recrystallized. The inside was subjected to purification annealing. Products of the magnetic characteristics are B _1Q of that time: 1.93T, W. 7/50: 0.76w / kg, blocked the incidence of Recessed Surface discontinuities of surface texture is been made as good as 0.9%.

Example 4

C 0.064%, Si 3.45%, Mo 0.025%, After heating the joint slab containing 0.025% of acid-soluble Al and 0.028% of S at 1420 ° C for 4 hours, it was hot-rolled to a 2.2-mm thick hot-rolled sheet. After cold rolling, intermediate annealing was performed at 1080 ° C for 3 minutes. During the intermediate annealing, a rapid heat treatment at 13 ° C / s from 500 to 900 ° C and a quenching treatment at 18 ° C / s from 900 to 500 ° C after the intermediate annealing were performed.

After that, it was cold rolled by about 85% to finish 0.23ratn final cold rolled sheet. Then the steel sheet (surface temperature: 70 .C) using a jig of 0.5 nun width _{MgS0 4 (0.01 mol / £)} 5 mm intervals dilute aqueous 85 ° C in the direction of almost a right angle to the rolling direction after degreased After spraying, applying and alternately forming the coating area and the non-coating area, decarburizing in wet hydrogen at 840 ° C * First recrystallization annealing, and then annealing separator mainly composed of MgO Was applied, the temperature was gradually reduced from 850 to 1100 ° C at a rate of 10 ° C / hr, and then a purification annealing was performed at 1200 ° C for 10 hours in a hydrogen atmosphere. The magnetic properties and surface properties of the obtained product were as follows.

Magnetic properties are B ,. _{: L.93T, W I7 / 5O:} . 0.82w / kg surface texture is off-locking incidence table surface defects was very good at 1.2%. Example 5

 C 0.066%, Si 3.51%, Mo 0.035%,

A continuous mirror slab containing acid-soluble Al 0.030%, S 0.026%, Sb 0.026 Sn 0.1%, and Cu 0.1% was heated at 1430t; for 4 hours, and then hot-rolled to a 2.2mm thick hot-rolled sheet. did. After that, about 40% primary cold rolling was performed, and intermediate annealing was performed at 1050t for 5 minutes. During this intermediate annealing, the rapid heat treatment at 500'C to 900 at 15: / s and the intermediate annealing from 900: to 500: 20 A quenching treatment was performed at ° c / s.

 Next, cold rolling was performed at about 85% to obtain a cold rolled sheet with a thickness of 0.20 rara. During this cold rolling, warm rolling was performed at 250 ° C.

Then degreased steel sheet surface, after retaining the surface temperature to about _{100 ° C MgS0 4 (0.01 mol} / i?) And _{Mg ( '0 3) 2 (} 0.01 mol / · δ) mixture (90 ° C) Is applied to the steel sheet surface with a rubber roll having an uneven surface, and the coating area and the non-coating area are alternately formed, followed by decarburization in wet hydrogen at 850 ° C ♦ First recrystallization annealing, followed by MgO After the annealing separator was applied, the temperature was gradually decreased from 850 to 1100 ° C. at 8 ° C./hr, and then, purification annealing was performed in a hydrogen atmosphere at 1200: 1 for 10 hours. The magnetic properties and surface properties of the obtained product were as follows.

Magnetic properties _{B 10: l.94T, W, 7/5} O:. 0.73w / kg blocks incidence of the front surface defect surface texture was filed extremely good at 1.2%.

Example 6

 1430 continuous slab containing 0.058% C, 3.40% Si, 0.026% Mo, 0.021% acid soluble Al 0.030% and Sb 0.025%. After heating at C for 3 hours, it was hot-rolled into a hot-rolled sheet with 2.2 thickness. After about 50% primary cold rolling, intermediate annealing was performed at 110 (TC for 3 minutes. During this intermediate annealing, a rapid heat treatment of 12 t / s from 500 ° C to 900 ° C was performed. After the intermediate annealing, quenching was performed from 900 ° C to 500 ° C at 15 ° C / s.

 After that, it was cold-rolled by about 80% to finish the final cold-rolled sheet with a thickness of 0.20 mm, and then subjected to primary recrystallization annealing combined with decarburization in 830 ° C wet hydrogen.

Next, on the surface of the annealed plate, annealed mainly MgO Agent A 1 ₂ 0 ₃ powder adhesion amount which is a reaction inhibitor of the annealing separator and the steel sheet subscale Si0 ₂ prior to applying the = 0.3 g / tn ^2, attached to the substantially perpendicular direction to the rolling direction of the steel sheet At a condition of width of 1.5 ram and repetition interval of 8 mm, it is adhered in a line on the steel sheet surface, and then an annealing separator mainly composed of MgO is applied.

Thereafter, the temperature was raised from 850 ° C to 10 ° C / hr to llOO: to perform secondary recrystallization, and then purification annealing was performed at 200 ° C in dry hydrogen for 10 hours. Steel plate surface after final annealing is A 1 ₂ 0 ₃ powder only 0.6 thickness For a coated area less nonwoven Rusute La wells film had been made form.

On the thus-formed forsterite coating, an insulated coating consisting mainly of phosphate and cobalt-dialsilicide was baked, and then strain-attached annealing was performed at 800 ° C for 3 hours. Was. The magnetic properties and surface properties of the product at that time were as follows. Magnetic properties: B _{1 Q} : 1.94T, W _17/5 . : 0.78 w / kg, surface texture was extremely good, with a flocculation rate of surface defects of 0.9%. Example 7

 C 0.054%, Si 3.36%, Mo 0.024%,

 A continuous slab containing 0.025% of acid-soluble M and 0.020% of Se was heated at 1420: for 4 hours and then hot-rolled to a thickness of 2.2 mm. After about 40% of the first cold rolling, intermediate annealing was performed at 1100 for 2 minutes. During the intermediate annealing, a rapid heat treatment of 12: / s was performed from 500 to 900 t and a rapid cooling treatment of 18 / s from 900 to 500 after the intermediate annealing.

After that, about 83% of secondary cold rolling is performed and the final cold rolled sheet of 0.23 After that, decarburization and primary recrystallization annealing were performed in wet hydrogen at 840 ° C.

After that, a pulsed laser was used to irradiate linearly (in a line width of 0.3 mm) in the direction perpendicular to the rolling direction at intervals of 8 nun, and an SbCl ₃ (0.01 rnol / £, 90 ° C) solution was applied to the laser irradiation position. Was applied.

 After that, an annealing separator containing MgG as a main component was applied on the steel sheet surface, and the temperature was raised from 850 ° C to 1100 ° C at 10 ° C / hr, followed by secondary recrystallization. Purified annealing in dry hydrogen for hours.

 After that, an insulating film mainly composed of phosphate and colloidal silica was baked, and then subjected to strain relief annealing at 800 ° C. for 2 hours. The magnetic properties and surface properties of the product at that time were as follows: o

Magnetic properties are B ,. : L.94T, W _17/5 . : 0.79 w / kg, and the surface properties were very good, with a 0.8% occurrence of surface defects. Example 8

 C 0.054%, Si 3.49 ¾, Mo 0.025%,

A steel ingot containing 0.030% of acid-soluble Al, 0.022% of S, 0.15% of Cu, and 0.10% of Sn was hot-rolled into a hot-rolled 2.0-mm-thick sheet, and then subjected to primary cold rolling (cold rolling). Rate is about 40%). After that, intermediate annealing was performed at 1050 for 5 minutes.At this time, the temperature rise from 500 to 900 ° C was quenched at 18 ° C / s and the temperature was lowered from 900 ° C to 500 after intermediate annealing. A quenching treatment of 20 t / s was performed. After that, a cold rolled sheet of about 89% was applied to make a final cold rolled sheet with a thickness of 0.17 mm. After that, decarburization in wet hydrogen at 840 and primary recrystallization annealing were performed, but before this treatment, an elector beam was used in a direction perpendicular to the rolling direction. Then, scanning was performed at intervals of 12 mm over a width of 0.5 mm to form a non-uniform heat area.

 After that, the surface of the steel sheet was coated with an annealing separator mainly composed of MgO, then the temperature was raised from 850 ° C to 1100 ° C at 15 ° C / hr, followed by secondary recrystallization. Purified annealing in dry hydrogen for hours.

After that, an annealing separator mainly composed of phosphate and colloidal silica was applied and baked, followed by strain relief annealing at 800 ° C for 5 hours. The magnetic properties of the product at that time are B ₁₀ : l.94T,

_{7/5 o: 0.77w / kg} , the surface texture is always been made as good as 1.2% in the block incidence of surface defects.

Example 9

 C 0.057%, Si 3.35 ¾, o 0.025%,

A continuous slab containing 0.020% of acid-soluble Al, 0.022% of Se, and 0.023% of Sb was heated to 142 (TC for 4 hours and hot-rolled to a 2.2 nun thick hot-rolled sheet. After the first cold rolling of, an intermediate annealing was performed for 3 minutes at 1080. During the intermediate annealing, a rapid heat treatment at 500 to 900 at 13 / s and an intermediate annealing after 900: From 500 to 500: was quenched at 18 / s ₍ after that, it was cold-rolled by about 85% to finish 0.23 mm thick cold-rolled sheet. Then decarburized in wet hydrogen at 840 Primary recrystallization Annealing, then applying an annealing separator mainly composed of MgD, gradual heating from 850 ° C to 1100 at 10: / hr, and then in a hydrogen atmosphere at 1200 ° C for 10 hours Was subjected to purification annealing.

After that, using a pulsed laser, micro-strain was introduced at intervals of 11 lines in a line (line width 0.5 width) in the direction perpendicular to the rolling direction, and then pickled, and then SbCl ₃ (0.01 mo \ / &, 90:) liquid Immersed in Then, after applying an insulating film mainly composed of phosphate and colloidal force, recovery and recrystallization annealing combined with strain relief annealing at 800 ° C. for 5 hours were performed. The magnetic properties and surface properties of the obtained product were as follows.

Magnetic properties B ₁₀ : l.94T, W, ₇ / s _O : 0.78 / kg. The rate of occurrence of surface defect surface defects was 1.1%, which was very good. Example 10

 C 0.056%, Si 3.41%, Mo 0.025%,

 A continuous slab containing 0.030% of acid-soluble Al, 0.020% of Se, 0.1% of Sn, and 0.1% of Cu was heated at 1430 ° C for 4 hours and then hot-rolled into a hot-rolled sheet having a thickness of 2.2 mm. After that, it was subjected to primary cold rolling of about 40 mm, followed by intermediate annealing at 1Q50 ° C for 5 minutes. During the intermediate annealing, a rapid heat treatment at 500 ° C to 900 ° C at 15 ° C / s and a rapid cooling treatment at 900 ° C to 500 ° C at 20 ° C / s after the intermediate annealing are performed.

 Next, about 85% of secondary cold rolling was performed to obtain a cold-rolled sheet having a thickness of 0.20 mm. The rubbing of the cold rolling was performed by warm rolling at 250 ° C. After that, decarburize in wet hydrogen at 850 ° C ♦ Perform primary recrystallization annealing, then apply an annealing separator mainly composed of MgG, and gradually reduce the temperature from 850 t to 1100 at 8 ° C / hr. After the heating, the sample was subjected to purification annealing at 1200 in a hydrogen atmosphere for 10 hours.

After that, a marking was introduced on the steel sheet surface in the direction perpendicular to the rolling direction in a direction perpendicular to the rolling direction at 0.5 strokes and an interval of 8 fflin, and then an insulating coating mainly composed of phosphate and colloidal silicide was baked, and strained at 800 for 5 hours. Recovery combined with removal annealing · Recrystallization annealing was performed. Get The magnetic properties and surface properties of the obtained product were as follows. Magnetic properties B ,. : L.94T, W17 _{/ s} . : 0.76w / kg, the rate of occurrence of surface defects was 1.1%, which was extremely good.

(Industrial applicability)

As is clear from the above description, B,. If the value is 1.92T or more, W17 _{/ 5} . It is capable of industrially producing thin unidirectional silicon steel sheets with low iron loss of less than 0.85 K / kg (0.23 mm thick) and extremely excellent product surface properties. It has a remarkable effect that can be achieved.Especially when Mo and A1 are contained in the material and the final cold-rolled sheet is formed by the cold rolling twice method, and then during decarburization and primary recrystallization annealing or By forming heterogeneous micro-domains on the surface of the steel sheet after finish annealing, it develops a non-uniform and fine-grained secondary grain recrystallization structure and has excellent iron loss characteristics and excellent surface properties. Products can be manufactured in a stable process.

Claims

δ 冃

1.S i 3.g 4.5 wt%,

 o 0.1 to 0.1 wt%,

 Acid soluble Μ 0.005 to 0.06 wt%,

 And one or two of S and Se in a total amount of 0.005 to 0.1 wt%,

 Hot rolled into a hot rolled sheet, followed by primary cold rolling at a draft of 10 to 60%, followed by intermediate annealing, followed by secondary rolling at a draft of 75 to 90% The thin cold-rolled sheet, which has been cold-rolled to a final thickness of 0.1 to 0.25 i !, is decarburized in wet hydrogen. * It is characterized by high-temperature finish annealing after primary recrystallization annealing. A method for producing low-iron-loss thin unidirectional silicon steel sheets with excellent surface properties.

2. S i 3. 1 to 4.5 w t

 Mo 0.003 to 0.1 wt%,

 Sb 0.005 to 0.2 wt

 Acid soluble / Q. 005 ~ 0.06 w,

 Then, one or two of S and Se in a total amount of 0.005 to 0.1 wt%,

After hot-rolling a slab with a hot rolled sheet, it is subjected to primary cold rolling at a reduction rate of 10 to 60%, followed by intermediate annealing, and a reduction rate of 75 to 90%. The thin cold-rolled sheet that has been subjected to the next cold rolling and finished to a thickness of 0.1 to 0.25 is decarburized in wet hydrogen. • It is characterized by high-temperature finish annealing after primary recrystallization annealing. You A method for producing low iron loss thin unidirectional silicon steel sheet with excellent surface properties.

3.S i 3. 1 ~ 4.5t%,

 Mo 0.003-0.1 t%,

 Acid soluble A l 0.Q05 ~ 0.06 wt%,

 Then, one or two of S and Se in a total amount of 0.005 to 0.1 wt%,

 Hot-rolled slabs containing hot rolled steel are subjected to primary cold rolling at a draft of 10 to 60%, and then subjected to intermediate annealing, and then to secondary cold rolling at a draft of 75 to 90%. Rolled and finished to a final thickness of 0.1 to 0.25 mm thick, and then decarburize this cold rolled sheet in wet hydrogen. ・ During primary recrystallization annealing, on the steel sheet surface that has been subjected to successive high-temperature finish annealing. A method for producing a unidirectional silicon steel sheet having excellent surface properties and a low iron loss and a high magnetic flux density, which is characterized in that a treatment for forming a heterogeneous micro-region is formed in advance and subjected to high-temperature finish annealing.

4.S i 3.1 to 4.5 wt%,-Mo 0.003 to 0.1 wt%,

 Sb 0.005 to 0.2 wt%,

 Acid soluble A l 0.005-0.006 wt%,

 Then, one or two of S and Se in a total amount of 0.005 to 0.1 wt%,

Hot-rolled slabs containing slabs are subjected to primary cold rolling at a draft of 10 to 60%, followed by intermediate annealing. Secondary cold rolling with a reduction rate of 75 to 90% to a final thickness of 0.1 to 0.25 mni, and decarburize the thin cold rolled sheet in wet hydrogen.Primary recrystallization annealing In this case, the steel surface has been subjected to high-temperature finish annealing after preliminarily applying a treatment that causes the formation of heterogeneous micro-regions on the steel sheet surface that has undergone high-temperature finish annealing. Manufacturing method for magnetic flux density unidirectional silicon steel sheet.

5. S i 3.1 to 4.5 w t I

 Mo 0.003 to 0.1 w t ヽ

 Acid soluble A 1 0.005 to 0,06 wt%,

 Then, one or two of S and Se in a total amount of 0.005 to 0.1 wt%,

 Hot-rolled slabs with hot rolling are subjected to primary cold rolling at a draft of 10 to 60%, followed by intermediate annealing, and secondary cold rolling at a draft of 75 to 90%. The cold rolled sheet finished to a final thickness of 0.1 to 0.25 mm by cold rolling is decarburized in wet hydrogen. • After the first recrystallization annealing, it is annealed at high temperature, and then on the surface of this steel sheet. A method for producing a low-iron-loss thin unidirectional silicon steel sheet having excellent surface properties.

4. S i 3.1 to 4.5 wt ヽ

 o 0.003-0.1 wt,

 Sb 0.005 to 0.2 wt%,

Acid soluble A l 0.005-0.006 wt%, And one or two of S and Se in a total amount of 0.005 to 0.1 w t¾,

 Hot-rolled slabs containing slabs are subjected to primary cold rolling at a draft of 10 to 60%, and then subjected to intermediate annealing, followed by secondary cold rolling at a draft of 75 to 90%. Rolled thin cold rolled sheet finished to 0.1 to 0.25 mm final thickness is decarburized in wet hydrogen. • After primary recrystallization annealing, high-temperature finish annealing, and then on the steel sheet surface A method for producing a low-iron-loss thin unidirectional silicon steel sheet having excellent surface properties, characterized by forming a heterogeneous micro-region section.

7. Intermediate annealing is performed at a heating rate of 5 ° c / sec or more in the temperature range of 500 ° C to 900 ° C, and a cooling rate of 5 ° c / sec in the temperature decreasing process of 900 to 500 ° C. The method according to any one of the above items 1 to 6 under the above conditions.