JPS6179721A - Manufacture of grain-oriented silicon steel sheet having superior surface property and low iron loss - Google Patents

Abstract

PURPOSE:To obtain stably a grain-oriented silicon steel sheet having superior surface properties and a low iron loss by subjecting a silicon steel slab having a specified composition to hot rolling, primary cold rolling, process annealing, secondary cold rolling, decarburization in wet hydrogen, primary recrystallization annealing and finish annealing. CONSTITUTION:A steel slab contg., by weight, 3.1-4.5% Si, 0.003-0.1% Mo, 0.005-0.6% acid-sol. Al and 0.005-0.1% S and/or Se is hot rolled and subjected to primary cold rolling at 10-60% draft, process annealing and secondary cold rolling at 75-90% draft. The resulting cold rolled steel sheet having 0.1-0.25mm final thickness is decarburized in wet hydrogen and subjected to primary recrystallization annealing and finish annealing at a high temp. By this method a grain-oriented silicon steel sheet having superior surface properties, a low iron loss and high magnetic flux density can be manufactured industrially.

Description

[Detailed description of the invention] (Industrial field of application) Improvement of surface properties of thin unidirectional silicon steel sheet with low core loss and further 2
The technical content described in this specification in relation to improving magnetic flux density by controlling the secondary recrystallization texture is to propose the results of research and development to enable the production of the silicon steel sheet in a stable process. .

(Prior Art) Unidirectional silicon steel sheets can be used as iron core materials for transformers and electrical equipment, and have a high magnetic flux density (represented by the value B) and iron loss (W l 7/'S. value). ) is required to be low.

Numerous improvements have been made to achieve this goal, and today the magnetic flux density B + o is 1.89T or more, and the iron loss is WI7/S. A grain-oriented silicon steel sheet having a low core loss of 1.05 W/kg or less has now been manufactured.

However, in the wake of the energy crisis, the production of unidirectional silicon steel sheets with lower iron loss became an urgent issue, and today, especially in Europe and the United States, bonuses are given for ultra-low iron loss silicon steel sheets.
0 (Prior Art) Recently, the following method has been proposed as a method for producing unidirectional silicon steel sheets with extremely low iron loss values.

That is, as described in Japanese Patent Publication No. 57-2252, the AAN precipitated phase is used as an inhibitor to suppress the growth of crystal grains with inappropriate orientation during final finish annealing, and the unidirectionality of the product is In this method, artificial grain boundaries are introduced onto the surface of a silicon steel sheet by irradiating the surface of the steel sheet with a laser beam at intervals of several mm approximately perpendicular to the rolling direction, and the iron loss is reduced by these artificial grain boundaries.

However, this proposed method of introducing artificial grain boundaries causes the formation of locally high dislocation density regions, which poses the problem that products subjected to such treatment can only be used stably at low temperatures of around 350°C or lower. Furthermore, since the insulation properties of the product deteriorate after laser irradiation, it is necessary to perform a re-insulating film formation process, which causes various problems such as an increase in cost and an extremely high price of the product. In the production method of unidirectional silicon steel sheet using /IN precipitation as cited above, AIN is used as an inhibitor!
, In order to dissociate and solidify I n S, it is necessary to heat the slab before hot rolling at a higher temperature than in the case of ordinary steel, but if the slab is heated at such a high temperature, Alternatively, hot cracking is likely to occur during hot rolling and surface defects are likely to occur in the product, especially if the content of Si, which inhibits hot workability, exceeds 3.0% (f) The surface quality of the product will deteriorate significantly.

When the inventors use the Al1N precipitate phase for this black light as disclosed in JP-A-59-85820, the silicon steel material with a high Si content of 3.1 to 4.5% is essentially Focusing on the fact that this material is suitable for obtaining products with low core loss due to magnetic flux density, we decided to add Ao (Ao) to the surface layer of the material before hot rolling as a means to solve the problem of poor surface quality. Even with high 81 content, the surface quality is good. However, with this new method, the surface quality of products has been greatly improved compared to before, but recently, products that have been made thinner to 0.23 to 0.17 mm in order to obtain low iron loss have had the effect of improving surface quality. However, this remains a major problem.

Separately, when trying to manufacture a thinner product using the AβN precipitate phase, secondary recrystallized grains became extremely unstable and strongly accumulated in the GO8S orientation because the strong cold rolling process was originally used. There was a problem in that it was difficult to develop secondary recrystallized grains.

Very recently, in Japanese Patent Application Laid-Open No. 59-126722, in order to stably manufacture thinned products using Aj2N precipitation under high Si content, the conventional hard cold ductility of one time has been greatly improved. It has been disclosed that two times of cold rolling with a change in temperature is applied to a hot-rolled material having a composition in which small amounts of Cu and Sn are added in addition to AnN.

Although this method is effective in stably lowering the iron loss of thinned products, it usually requires heating the slab to a high temperature under conditions where S1 is increased, so it is possible to obtain products with excellent surface properties. In addition, there are many problems that still need to be solved, including the fact that small amounts of Sn and Cu are added to stabilize the secondary recrystallized grains, which significantly increases the cost of the product. ing.

(Problems to be Solved by the Invention) Methods for reducing the core loss of a unidirectional silicon steel plate include: (1) increasing the Si content in the silicon steel; and (2) reducing the thickness of the product plate.

The basic ideas are: (1) increasing the purity of the steel sheet; (2) developing fine secondary recrystallized grains without reducing the Ga55 orientation integration degree of the secondary recrystallized grains of the product.

First, attempts were made to increase the Si content from the usual 3.0% for (■) and to reduce the thickness of the regular product plate to 0.23. A problem arises in that the subsequent recrystallization structure becomes non-uniform and the Goss orientation degree of integration decreases.

In addition, if the Si content is increased more than usual according to ■,
As already mentioned, hot embrittlement becomes noticeable, hot cracking occurs during slab heating or hot rolling, and the surface quality of the product deteriorates significantly.

On the other hand, improvements in the purity of steel sheets in (1) or in the directionality in (2) have now reached the limit. For example, the Ga55 orientation of the secondary recrystallized grains of current products is already accumulated within an average of 3° to 4° in the rolling direction, and it is difficult to further reduce the grain size in such a highly integrated situation. It is considered extremely difficult.

Against the background of the above-mentioned circumstances and in view of the recent trends in the prior art described above, this invention has been developed to produce industrially stable thin unidirectional silicon steel sheets with extremely excellent surface properties and extremely low iron loss, as well as with high magnetic flux density. The purpose is to provide a particularly advantageous method of manufacturing and humiliating.

(Means for solving problems) The above objectives are achieved as follows.

■, Si3.1-4.5wt%, Mo0.003-0.1wt%, acid-soluble AAO, 005-0.06wt%, and either one or two of S and Se in a total amount of 0 .005
After hot-rolling a slab containing ~0.1 wt% to make a hot-rolled plate, it is subjected to primary cold rolling with a rolling reduction of 10 to 60%, and then undergoes intermediate annealing to form a hot-rolled plate with a rolling reduction of 75 to 90%. A thin cold-rolled sheet that has been subjected to secondary cold rolling to a final thickness of 0.1 to 0.25n+n+ is decarburized and primary recrystallized annealed in wet hydrogen, and then subjected to high-temperature finish annealing. A method for producing a thin, unidirectional silicon steel sheet with excellent surface properties and low core loss (first invention).

2.5i 3.1~4.5 wt%, ! , (o O,003~0.1 wt%, acid soluble Aβ0
．． 005 to 0.06 wt%, and 0.005 to 0.1 wt% of one or both of S and Se in total
After hot rolling a slab containing Rolled between 0.
A thin cold-rolled sheet finished to a final thickness of 1 to 0.25 mm is mainly coated locally with Sn, P0. As, S
b.

B i, s, Se, Te, Mg, Ca, S
After decarburization and primary recrystallization annealing in wet hydrogen, high-temperature finishing is carried out through the formation of sections of application areas of a dilute solution or dilute suspension containing at least one compound selected from compounds containing r, Ba, and Na. A method for producing a thin, high magnetic flux density, unidirectional silicon steel sheet with excellent surface properties and low core loss, which comprises annealing (second invention).

Regarding intermediate annealing, 5.
In practice, it is preferable to heat or cool between 00 and 900°C at a rate of 5°C or more per second.

We found that A under high silicon content of 3.1-4.5%
When manufacturing thin unidirectional silicon steel sheets using AN precipitated phase, products with excellent surface properties can be obtained by adding a small amount of Mo to the material. The inventors discovered that it is possible to manufacture unidirectional silicon steel sheets with low iron loss in an extremely stable process by employing a double cold rolling method, and have completed this invention.

First, the experimental example that led to the completion of the first invention will be specifically explained.

C0,048wt%, Si3,4(ht%, Mo 0
．． Steel ingot containing 0.025 wt% acid-soluble Aj20.026 wt% and SO, 025 wt% (sample steel I)
and C0,053wt%.

Si 3.42wt%, acid soluble A i' 0.027wt
%, SO, 024wt%.

SnO, 11 wt% and Cu0. Each of the steel ingots (comparative steel I) containing 0.09 wt% was heated at 1420° C. for 4 hours to dissociate and dissolve the inhibitor, and then hot rolled to form a hot rolled sheet with a thickness of 2.2 mm.

Thereafter, primary cold rolling was performed at a reduction rate of 70% or less, and intermediate annealing was performed at 1050° C. for 3 minutes.

During this intermediate annealing, the temperature was raised from 500°C to 900 t' by rapid heating treatment at 10°C/S, and after the intermediate annealing, 900 t' was heated.
A rapid cooling process of 15°C/S was performed from 00°C to 500°C.

After that, it is subjected to secondary cold rolling at a reduction rate of 70% to 91%.
．． After making a cold rolled sheet with a final thickness of 20 mm, 850
Decarburization and primary recrystallization annealing were performed in wet hydrogen at t:.

Thereafter, an annealing separator containing MgO as a main component was applied to the surface of the steel sheet, and the temperature was raised at a rate of 8°C/hr from 850°C to 1100 t for secondary recrystallization.
Purification annealing was performed in dry hydrogen for 10 hours at t:.

The magnetic properties and surface defect occurrence rate (block occurrence rate of surface flaws present on the steel plate surface expressed in %) of the product at that time are shown in FIG.

As is clear from the plot shown in Fig. 1, the product made from sample steel I containing MO in the material has a magnetic field when the reduction ratio in the primary cold rolling is 10 to 60% (particularly 20 to 40%). It is noteworthy that the properties are good, and the surface defect incidence rate of the product is 2% or less (0.5% or less when the rolling reduction of the primary cold rolling is in the range of 20 to 50%).

On the other hand, the magnetic properties of the product made of Comparative Steel I with the conventional composition are B + o as shown in the plot marked with ○ in the same figure
, WIT/sO are both slightly worse than the MO-added material, and in particular, the surface defect rate of the product is extremely high at 6-18%.

Next, CO, 049%, Si3.45%, Mo 000
20% acid soluble A! 0.028%, SO,026
% (sample steel ■) was heated at 1410° C. for 5 hours to dissociate and dissolve the inhibitor, and then hot-rolled into a hot-rolled sheet with a thickness of 2.2 mm.

After that, after primary cold rolling with a reduction rate of about 40%, 105
Intermediate annealing was performed at 0°C for 3 minutes. During this intermediate annealing, the temperature increase rate from 500°C to 900°C and the cooling rate from 900°C to 500°C after intermediate annealing are both 1°C to 1°C.
Experiments were conducted at temperatures up to 00°C.

The steel plate after intermediate annealing is subjected to secondary cold rolling at a reduction rate of approximately 83% to form a final cold rolled plate with a thickness of 0.23 mm, and then heated at 850°C.
After decarburization and primary recrystallization annealing in wet hydrogen, an annealing separator containing MgO as the main component was applied to the surface of the steel sheet, and the temperature was increased from 850°C to 1100°C at a rate of 10°C/hr. After secondary recrystallization, purification annealing was performed in dry hydrogen at 1200° C. for 10 hours. The magnetic properties of the product at that time are
As shown in the figure.

As is clear from Figure 2, from 500℃ to 9℃ during intermediate annealing.
The temperature increase rate to 00℃ and the cooling rate from 900℃ to 500℃ after intermediate annealing should be 5℃/S or more, especially 10℃.
/S or more, a product with extremely excellent magnetic properties can be obtained.

The reason for the improvement in properties due to the rapid heating and cooling treatment during intermediate annealing is as previously disclosed by the inventors in JP-A-59-35625 (mentioned above) (110) <001>
This is thought to be because it is advantageous for preferentially developing the texture of the orientation. In addition, as mentioned earlier, JP-A-59-1
In the method for producing a thin unidirectional silicon steel sheet by utilizing the AIN precipitate phase in the two-step cold rolling method disclosed in Publication No. 26722, fine Al On the contrary, in this invention, precipitation treatment is only used in the cooling process after intermediate annealing after primary cold rolling, but in this invention, precipitation treatment is applied not only to rapid cooling after intermediate annealing, but also to rapid heating in the temperature rising process of intermediate annealing. (especially for combinations of) 110
It has been newly clarified that excellent magnetic properties can be obtained only when containing .

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

CO, 053%, S13°43%, Mo 0.023
%, acid-soluble AAO, 028%, SO, 027% (sample steel I) CO, 056%, Si
3.46%, acid soluble Aβo, o2eqgS O,026
%, SnO, 1%, and Cu0.1% (comparative steel ■) were heated at 1430°C for 3 hours to dissociate and dissolve the inhibitor, and then hot rolled to a thickness of 2.2 mm. It was made into a hot rolled sheet.

Thereafter, primary cold rolling was performed at a rolling reduction ratio of 70% or less, and intermediate annealing was performed at 1100 for 3 minutes. During this intermediate annealing, the temperature was raised from 500°C to 900°C at a heating rate of 13°C/S, and after the intermediate annealing, the material was rapidly cooled from 900°C to 500°C at a cooling rate of 18°C/S.

Thereafter, secondary cold rolling was performed at a rolling reduction ratio of 70% to 91% to obtain a final cold rolled plate having a thickness of 0.20 mm, but warm rolling at 250° C. was performed during the cold rolling.

After that, the surface of the steel plate was degreased at a temperature of 110℃! A
g S O4 dilute aqueous solution (0.01 mo at 80 °C
l/I) by spraying at 5 mm intervals perpendicular to the rolling direction.
．． It was applied in a width of 5 mm. Also for reference Igltff
A sample (reference example) whose surface was left degreased was also prepared at the same time.

These samples were subjected to decarburization and primary recrystallization annealing in wet water at 850°C, then coated with an annealing separator mainly composed of MgO on the steel plate surface, and then annealed from 850°C to 1100°C. After secondary recrystallization by heating at 10°C/hr,
Purification annealing was performed in dry hydrogen for 10 hours at °C.

The magnetic properties and surface defect occurrence rate of the product at that time (the occurrence rate of surface scratches on the surface of the A-plate is expressed in %) are shown in FIG.

As is clear from Figure 3, the reduction ratio in the primary cold rolling of the sample steel ■ (■ 1 mark) in which MO was added to the material was 10 to 6.
Good magnetic properties at 0% (especially 20-40%),
Moreover, it is noteworthy that the surface defect occurrence rate of the product is 3% or less (particularly 1.0% or less when the primary cold rolling reduction is in the range of 20 to 50%). In terms of stiffness, the characteristics of comparative steel with conventional composition ■ (mu, △ mark) are B IQ + WB7s. Both are slightly worse than Moi filler material, and the surface defect rate of the product is extremely high at 6 to 2096.

Next, when a dilute aqueous solution of Mg5O < is sprayed on the surface of the final cold-rolled sheet at 5 mm intervals perpendicular to the rolling direction in a width of 5 mm, the magnetic properties are as shown in the plot marked with ■ for the test steel. At a secondary cold rolling reduction rate of 30 to 4096 (secondary cold rolling reduction rate of 87 to 85%), Wltyso is 0, 7
The magnetic properties are extremely good at 2 W/kg, and the surface defect rate of the product is also good at 1% or less.

On the other hand), even in the coating treatment with comparative steel H without the addition of 10, the iron loss W1? /So
is 0.75 at the primary cold rolling reduction rate of 30 to 40%.
W/kg is good, but the surface defect rate of the product is 6~6
It is high at 7%.

Therefore, from these experimental examples, in order to produce a thin, unidirectional silicon steel sheet with excellent surface quality and low core loss, it is necessary to add a small amount of Ma to the high-silicon material, and to adopt a two-step cold rolling method. It is shown that this can be achieved by a combination of sectioning the application of a dilute aqueous solution or suspension containing the specified elements on the surface of the final cold-rolled sheet.

Some of these structures have already been disclosed in Japanese Patent Application No. 58-220134.
In this specification, Sn, P0. As, S0. Bi, S
, Production of a grain-oriented silicon steel sheet with low core loss by applying a dilute aqueous solution or dilute suspension containing at least one selected from Se and Te or their compounds to define deoxidation retardation regions. As a method, the inventors have proposed, and compared this with the second invention, it was found that by using a two-step cold rolling method including intermediate annealing of rapid heating and rapid cooling before final coating on the surface of the cold rolled sheet, Aiming for stable growth of secondary recrystallized grains, and treating the temperature of the coating liquid during final coating on the surface of the cold rolled sheet at 40 to 100°C and/or the temperature of the steel sheet at 20 to 300°C, and further the above-mentioned. Not only with decarburization retarders and retarders, but! 4g, Ca, Sr
It has been further discovered that properties can be improved in a very stable process by applying a dilute aqueous solution of a compound containing , Ba, K and Na or by mixing these decarburization promoters.

Next, sample steel (■) was made of CO, 061% and Si 3.45%.

M, o O, 025%, acid soluble An 0.026%,
SO, 030%.

A steel ingot containing 2.2
It was made into a hot-rolled plate with a thickness of mm.

After that, after performing the first cold rolling at a reduction rate of about 30%,
Intermediate annealing was performed at 1050°C for 3 minutes. During this intermediate annealing, the temperature increase from 500℃ to 900℃ is 15℃/
Rapid heat treatment with S, and after intermediate annealing 900℃ to 500℃
The temperature was lowered by rapid heat treatment at 20°C/S.

After that, secondary cold rolling was performed at a reduction rate of about 85% to obtain a cold rolled sheet with a final thickness of 0.23 mm.
Warm rolling was performed at 50°C.

After that, the surface of the steel plate is cleaned by degreasing treatment, and while the surface temperature of the steel plate is maintained at about 100℃, the type of dilute aqueous solution and the temperature of the aqueous solution are variously changed below 100℃, and the temperature is approximately perpendicular to the rolling direction. 5mm.

Spray coating was applied to a width of 0.5 mm. For comparison, a sample with the surface of the steel plate left degreased was also prepared at the same time.

These samples were subjected to decarburization and primary recrystallization annealing in wet hydrogen at 830°C, then coated with an annealing separator containing MgO as a main component on the steel plate surface, and then heated from 850°C to 1100°C for 1 time.
After secondary recrystallization by heating at 0°C/hr, 1200°C
Purification annealing was performed in dry hydrogen for 10 hours.

Figure 4 shows the magnetic properties of the product at that time. As is clear from Figure 4, the temperature of the coating liquid on the steel plate surface is (A)
It is noteworthy that all of the coating liquids shown in (E) show good magnetic properties at temperatures of 40° C. or higher, regardless of the type of coating liquid.

In other words, when spray coating the surface of the final cold-rolled sheet after degreasing at regular intervals in a direction approximately perpendicular to the rolling direction, the spray temperature of the dilute aqueous solution is raised to a high temperature to reduce the concentration difference between the sprayed area and the non-sprayed area. This shows that it is possible to further improve the characteristics by increasing the strength.

As described above, the second invention involves adding Mo to the material, adopting a two-step cold rolling method, and applying a limited dilute aqueous solution onto the surface of the steel sheet before decarburization and primary recrystallization. The basic idea is different from the prior art mentioned above in that it has been discovered that by forming compartments, it is possible to manufacture unidirectional silicon steel sheets with good iron loss and surface properties in a stable process, Furthermore, the effects obtained by adopting these processes are far superior to those of the conventional methods.

(Function) In each invention, Si is an element effective in increasing the electrical resistance of silicon steel sheets and reducing eddy current loss, as described above.
In particular, in order to reduce iron loss in thin products, it is necessary to set the content to 3.1 wt% or more. However, the Si content is 4.5 wt%.
If the Si content exceeds the Si content, brittle cracks are likely to occur during cold rolling, so the Si content is set in the range of 3.1 to 4.5 wt%. Note that the 31 content of a conventional unidirectional silicon steel sheet using conventional AnN as an inhibitor is 2.8 to 3. Owt%
Comparative steel 1. shown in FIGS. 1 and 3 when Si was increased. As in III, the surface quality of the product is significantly deteriorated, but in each of the first and second inventions, zero
．． By adding 0.03 to 0.1 wt% of Mo, it is possible to prevent surface defects from occurring.

The Mol added to this material is 0. If OO' is less than 3 wt%, the ability to improve magnetic properties and prevent surface defects is weak, and if it exceeds 0.1%, decarburization in the steel will be delayed during decarburization, so it is limited to a range of 0.003 to 0.1 wt%. Should.

Al is supplied with N contained in steel to form fine precipitates of Alx, and acts as a strong inhibitor. In particular, in the production of thin unidirectional silicon W4 plates, in order to develop secondary recrystallized grains that are strongly concentrated in the Goss orientation, it is necessary to
Acid-soluble Al in the range of 0.05 to 0.06 wt% is required.

When acid-soluble Al is less than 0.005 wt%, the amount of AIN fine precipitates as an inhibitor is insufficient, (110)
The development of secondary recrystallized grains with <Ool> orientation becomes insufficient, and on the other hand, if it exceeds 0.06 wt%, (110) <0
01> The development of secondary recrystallized grains in the orientation is extremely poor.

S, Se is MnS with Alx or! A
A dispersed precipitated phase of n S e is formed to enhance the inhibitor effect. The total amount of S or Se is 0.005wt%
If less than! J n S or M n S e
The inhibitor effect of
If the amount exceeds wt%, hot and cold workability will be significantly deteriorated, so the total amount of one or both of S and Se should be 0.
It is necessary to keep it within the range of 0.005 to 0.1 wt%. Even within this total amount range, S is 0.008w
When it is less than t% or when Se is less than 0.003wt%, the inhibitor effect is insufficient, respectively.
On the other hand, if each exceeds 0.05wt%, hot and cold workability deteriorates, so S is 0.008 to 0.05wt%.
%, and Se is preferably within the range of 0.003 to 0.05 wt%.

As mentioned above, there are three materials that are compatible with the methods of each invention.
．． It must contain 1 to 4.5% Si and small amounts of Mo, Aβ, S, and Se, but must not contain any other known elements added to ordinary silicon steel. isn't it.

For example, it is preferable that Mn is contained in an amount of about 0.02 to 2 wt%.

Further, C is necessary to cause T transformation in a part of the steel sheet during hot-rolled sheet annealing in connection with fine precipitation of AβN, and the 81 content of this invention is in the range of 3.1 to 4.5 wt%. Then C
A suitable content is about 0.030 to 0.080 wt%.

Furthermore, S0. Sn, Cu.

0, 2w of any one or two or more of B in total amount
It may be contained in an amount of t% or less. Others Cr, Ti, v.

Zr, N0. Ta, Co, Ni, p, A
It is permissible for general unavoidable elements such as s to be contained in trace amounts.

Next, a series of manufacturing steps of this invention will be explained.

First, as means for melting the material used in the method of this invention, a converter furnace, an open hearth furnace, and other known steelmaking methods can be used, and vacuum treatment and vacuum melting may also be used in combination. Of course.

In addition to the usual ingot-blubber rolling method, continuous casting can also be suitably used as a means for producing the slab.

The silicon steel slab obtained as described above is heated by a known method and then subjected to hot rolling. The thickness before hot rolling obtained by this hot rolling varies depending on the rolling reduction rate in the subsequent cold rolling step, but it is usually desirably about 1.5 to 3.0 mm.

In this invention, it is necessary to add a small amount of MO to the material in order to obtain a silicon steel sheet with good surface quality.
As disclosed by the inventors in JP-A No. 59-85820, it is of course also possible to use a method of concentrating Mo in the surface layer of the steel sheet by applying an MO compound to the surface after hot rolling. It is.

The hot rolled sheet that has been hot rolled is then subjected to primary cold rolling.

The rolling reduction rate during the primary cold rolling differs slightly depending on the product plate thickness, but in order to obtain a thin product with good properties in this invention, it is 10 to 60% (preferably 20% ~50%).

The next intermediate annealing is at a temperature of 900-1100℃ for 30 seconds to 3
Annealing is performed for about 0 minutes, but in order to obtain good magnetic properties, the temperature must be increased from 500°C to 900°C and 90°C after intermediate annealing.
Temperature drop from 0℃ to 500℃ more than 5℃/S, especially lO℃
It is desirable to set it to /S or more. This rapid heating and cooling process may be carried out using a known method such as an ordinary continuous furnace or a batch furnace.

As is clear from Figures 1 and 3, the subsequent secondary cold rolling is suitable for a reduction ratio of 75 to 90%, and the final cold rolled plate thickness is 0.1 to 90%.
Finish to a thickness of 0.25mm.

The purpose of each invention is to manufacture thin high magnetic flux density electrical steel sheets, and the hot-rolled sheets have a thickness of about 1.5 to 3.0 mm. By finishing the steel plate into a thin final cold-rolled plate having a thickness of 0.1 to 0.25 mm at each reduction rate in the subsequent cold rolling, a steel plate with good properties can be obtained.

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

The cold-rolled sheet thus made thin with a thickness of 0.1 to 0.25 mm is subjected to decarburization annealing, which also serves as primary recrystallization, in a temperature range of approximately 750 to 870°C.

This decarburization annealing can normally be carried out for several minutes in a wet hydrogen gas atmosphere or a hydrogen/nitrogen mixed gas atmosphere with a dew point of about +30 to 65°C.

Next, an annealing separator containing MgO as a main component was applied to the steel plate after decarburization annealing, and finish annealing was performed (110) <
Develop secondary recrystallized grains with ool> orientation. The specific conditions for this final annealing may be the same as those conventionally known, but usually, after developing 3-b to 1150-1250°C, purification annealing is performed for 5-20 hours in saturated hydrogen. is desirable.

After finishing the final cold rolling, the steel plate finished to the product thickness is subjected to surface degreasing, followed by decarburization and primary recrystallization annealing, but in the second invention, as already mentioned, the final cooling after degreasing is performed. Sn, P0. As, S0. Bi, S
.

Se, Te, Mg, Ca, Sr, Ba, K
A dilute solution or dilute suspension of at least one kind selected from inorganic compounds containing Na and Na is applied. By the way, when applying such a treatment liquid, as disclosed by the inventors in JP-A-58-220134, areas to be coated and areas not to be coated may be formed alternately at intervals of 1 to 50 mm. More preferred.

The narrower the area width, the finer the secondary recrystallized grains will be, but it should be within twice the two-way recrystallized grain size of the product, that is, 3 to 50+.
By changing the primary recrystallized texture on the surface of the steel sheet with a width of r+m, fine secondary recrystallized grains can be obtained. Also, this kind of surface coating is usually done on both sides of the steel plate,
It is fully effective even when applied to only one side.

Furthermore, as a coating method for the surface of a steel plate, a method in which coating is normally performed using a grooved or uneven rubber roll, and a method in which spraying is performed after applying a masking plate to areas where coating is not required are particularly advantageous.

As mentioned above, the temperature of the coating liquid on the surface of the steel plate is 40~
The temperature of the steel plate at the time of application should be within the range of 100℃2.
It is desirable to limit the temperature to 0 to 300°C.

Any conventionally known method may be used to control the temperature of the coating liquid or the temperature of the steel plate. Further, Sn, P0. As, S0. S,
Se, Te.

Mo, Mg, Ca, Sr, Ba, k and N
Regarding the compound a, there are known documents showing the influence of applying dilute aqueous solutions of various elements on graphite precipitation on the surface of low carbon cold rolled steel sheets (for example, Y. Inokuti: Trans.
, [SIJ, Vol. 15 (1975), P, 324)
You can just follow the teachings, but just to be sure, I quote them as follows:

a) Compounds containing Sn: 5nC1z, Sn (NO
3) 4.5n12. Compounds containing Na25nOb)pb: PbCl2. PbO(OH) 2. Pb (
NO3) 2+Pb (C)1. cOO) 2 c) Compound containing As: A9S3. NaAs03.
H3ASO4, KH2ASO4Na2HAs03.
(NH4) 3ASO4, ASC+2. AS203.
K3ASO3d) Compound containing Sb: 5bC13,
5bBr3.5bOC1,5b2o3゜5LS3.5b
2(SO4) 3 e) Compounds containing Bi: Na2B+Oa, BiCl
3.812(S04)3゜Bi(NL)3 f) Compound containing S + K, S, Na2S2O3,K
2S2O5, Na2S.

FeSO4, KHSO3, NaH3O4, 52C12,
2SO4, Al2(SO4)! +Cr5Os, LSJ
t, to 2S208. Na2S2O3, Na25Ja, N
a2SO3゜(NH4)2SO4,NH4tlsOa,
(N)14)2S208. NH-O302NH2゜Na
zSO<.

Zn5O=, TI (SO4)4 g) Compound containing Se: H2Se0. ,5eC12,
SeO[:l. , 5eS2゜H2SeO4,5eOz
, 2Se, Na25e, 2Se03. 2SeO4
゜NazSeL, Na25eL.

h) Compounds containing Te: )lsTeos, K2S2
O5, K2Te04゜Na2TeO*, Na2TeO4
, TeCl<i) Mg-containing compound: MgCl2.
Mg(NO3) 2j) Compound containing Ca: CaC1
□, Ca(No,) 2k) Compound containing Sr: 5
rC12, Sr (NO3) 21) Compound containing Ba: BaCl2. Compounds containing Ba(NOs>2m)Na: NaJO<, NaCrzOt, NaOH
.

Na104. NaJPO<, NaH2P[14, Naa
C611sOv, NaF, NaHCO+NanP20t
, Na[n)K-containing compound: KNO, 10. ,Kl,K
CI, KM,,O,.

K4P2O7, ni8r, KNO3, KClO3, KBr
Including those with crystal water of Oa, KF and above.

After dividing the steel plate surface into areas coated with the treatment liquid and areas not coated, the steel plate undergoes primary recrystallization in wet hydrogen for about 3 to 15 minutes at a temperature range of 750 to 880°C. Perform decarburization annealing that also serves as decarburization. This decarburization annealing usually has a dew point of +30~
This may be carried out for several minutes in a wet hydrogen gas atmosphere or a hydrogen/nitrogen mixed gas atmosphere at about 65°C.

Next, an annealing separator containing MgO as a main component is applied to the surface of the steel sheet after decarburization annealing, and finish annealing is performed (110).
Develops secondary recrystallized grains that are strongly concentrated in the <ool> orientation. The specific conditions for this final annealing may be the same as those of conventionally known annealing methods, but usually, secondary recrystallized grains are developed at 1150 to 1250°C for 3 to 5 hours, and then for 5 to 20 hours in a hydrogen bath.
``It is desirable to perform purification annealing.

Examples of the first invention will be shown below.

Example I CO, 059%, Si 3.49%, Mo 0.024
%.

A continuously cast slab containing 0.034% of acid-soluble Aβ and 0.029% of S O was heated at 1430° C. for 3 hours and then hot-rolled into a hot-rolled plate with a thickness of 2.2 mm. Thereafter, it was subjected to primary cold rolling of approximately 50%, and then intermediate annealing was performed at 1100° C. for 3 minutes. During this intermediate annealing, a rapid heat treatment was performed from 500° C. to 900° C. at 12° C./S, and after the intermediate annealing, a rapid cooling treatment was performed from 900° C. to 500° C. at 15° C./S.

Thereafter, the sheet was cold rolled by about 80% to produce a final cold rolled sheet with a thickness of 0.20 mm, and then primary recrystallization annealing was performed in wet hydrogen at 830° C., which also served as decarburization.

Thereafter, the temperature was raised from 850°C to 1100°C at a rate of 10°C/hr for secondary recrystallization, and 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 were as follows.

Magnetic properties are Baa: 1.93T, WI7/so
+0.80 W/kg The surface quality was extremely good, with a block generation rate of surface defects of 0.8%.

Example 2 CO, 064%, Si 3.39%, Mo0. 01
9%.

Acid soluble AA 0.029%, SeO, 020%, S
Continuously cast slab containing 0.022% b was heated at 1420℃ for 4 hours.
After heating for a period of time, it was hot rolled to a thickness of 2.2 mm. After that, after primary cold rolling of about 40%, 2
Intermediate annealing was performed for 1 minute. During this intermediate annealing, 50
After rapid heat treatment from 0°C to 900°C at 12°C/S and intermediate annealing, rapid cooling treatment at 18°C from 900°C to 500°C was performed. After that, it was subjected to secondary cold rolling of about 83% to 0.23
After forming a final cold-rolled sheet with a thickness of m1Tl, decarburization and primary recrystallization annealing were performed in wet hydrogen at 840°C.

After that, an annealing separator mainly composed of MgO was applied to the surface of the steel sheet, and the temperature was raised from 850°C to 1100°C at 10°C/hr for secondary recrystallization, followed by purification in dry hydrogen at 1200°C for 15 hours. Annealed. The magnetic properties and surface properties of the product at that time were as follows.

Magnetic properties are Baa: 1.93T, W+tzso
:0.83 W/kg The surface quality was very good with a block generation rate of surface defects of 0.6%.

Example 3 CO, 058%, S13.59%, Mo0.035%
.

Acid soluble Aβ 0.033%, S 0.023%, CuO
,15%.

A steel ingot containing 0.11% Sn was hot-rolled into a hot-rolled sheet with a thickness of 2.0 mm, and then subjected to primary cold rolling (cold rolling rate was about 40%). After that, intermediate annealing was performed at 1050℃ for 5 minutes, but the temperature increase from 500℃ to 900℃ at this time was 18℃/S quenching treatment and 900℃ to 5 minutes after intermediate annealing.
The temperature was lowered to 00°C by rapid cooling at 20°C/S. Thereafter, it was hard-rolled by about 89% to obtain a final cold-rolled sheet with a thickness of 0.17 mm, and warm-rolled at 300° C. during the cold rolling. After that, after decarburization and first crystal annealing in wet hydrogen at 840℃, the temperature was raised from 850℃ to 1100℃ at 15℃/hr.
After recrystallization, purification annealing was performed in dry hydrogen at 1200° C. for 15 hours. The magnetic properties of the product at that time are Boo
:1.93T, W+tzso :0.76W/kg
The block occurrence rate of surface defects was as good as 0.9%.

Examples of the second invention are shown below.

Example 4 CO, 064%, Si 3.45%, Mo0.025
%.

2. A continuously cast slab containing 10.025% acid-soluble and 028% SO was heated at 1420° C. for 4 hours and then hot rolled.
It was made into a hot-rolled plate with a thickness of 2 mm. Thereafter, after primary cold rolling of about 30%, intermediate annealing was performed at 1080° C. for 3 minutes.

During this intermediate annealing, the temperature is 13°C from 500°C to 900°C.
After rapid heat treatment and intermediate annealing at t/s from 900℃ to 500℃
A rapid cooling process was performed at 18°C/S. After that, about 85
% cold rolling to produce a final cold rolled sheet with a thickness of 0.23++++++. After that, after degreasing the steel plate (surface temperature near 0℃), 85% of Mg5On (0, Olmol/β) was removed.
℃ dilute aqueous solution was spray coated at 5 mm intervals in a direction almost perpendicular to the rolling direction using a jig with a width of 0.5 mm, and after forming coated areas and uncoated areas alternately, 840℃
decarburization and primary recrystallization annealing in wet hydrogen, then M
g After applying an annealing separator mainly composed of O, 850
After removing heat from 1100°C at a rate of 10°C/hr, 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 B. : 1.93 T, W, 1/S.

: 0.82W/kg.

The block occurrence rate of surface defects was 1.2%, which was very good.

Example 5 CO, 066%, s13.51%, Mo0.035%
.

Acid soluble Al101030%, SO,026%, S
14 continuous cast slabs containing n0.1%, CuO, 1%
After heating at 30° C. for 4 hours, it was hot rolled to obtain a hot rolled sheet with a thickness of 2.2 mm.

After that, after primary cold rolling of about 40%,
Intermediate annealing was performed for 1 minute. During this intermediate annealing, 50
After rapid heat treatment from 0°C to 900°C at 15°C/S and intermediate annealing, rapid cooling treatment was performed from 900°C to 500°C at 20°C/S. Next, about 85% secondary cold rolling is applied to 0.2
A cold rolled sheet with a thickness of 0 mm was used, but during this cold rolling, 25
Warm rolling was performed at 0°C.

Next, after degreasing the steel plate surface and maintaining the surface temperature at approximately 100°C, Mg5O< (0, Olmol/Il) and Mg
A mixed solution (90°C) of (NL)2(0,Olmol/jl!) was applied to the steel plate surface using a rubber roll with an uneven surface, and after forming coated areas and uncoated areas alternately, it was heated to 850°C. After decarburizing and primary recrystallization annealing in hydrogen, then applying an annealing separator mainly composed of MgO, and removing heat from 850°C to 1100°C at a rate of 8°C/hr, heating to 1200°C in a hydrogen atmosphere. , 10 hours of purification annealing was performed. The magnetic properties and surface properties of the obtained product were as follows.

Magnetic properties B1°: 1.94T, W=qys. 20.72W/kg.

The block occurrence rate of surface defects was 1.0%, which was very good.

(Effect of the invention) As is clear from the above explanation, according to the method of the first invention, B
IO is 1.92 T or more, annealing is 0.85 W/kg
This method has the remarkable effect that it is possible to industrially and stably manufacture thin unidirectional silicon steel sheets with a bottom core loss of (0.23 mm thickness) or less and an extremely excellent product surface quality.

Further, according to the second invention, the inorganic compound is contained in the raw material to form a final cold-rolled sheet in a two-step cold-rolling process, and then the inorganic compound is limited to locally partitioned areas on the surface of the steel sheet. By coating, a non-uniform, yet fine-grained Goss-oriented secondary recrystallized structure is developed, and products with excellent iron loss characteristics and surface properties can be manufactured in a stable process.

[Brief explanation of the drawing]

Figure 1 is a chart showing the relationship between the magnetic properties of the product and the rolling reduction ratio in primary cold rolling and two-way rolling, as well as the surface texture. Figure 2 shows the relationship between the temperature rise rate and cooling rate during intermediate annealing. A chart showing the relationship between the product's magnetic properties, Figure 3 is a chart showing the relationship between the product's magnetic properties and the primary cold rolling and secondary rolling reduction ratios, and the surface properties, and Figure 4 is the final cold rolled plate. Coating liquid on the surface (A) ~ (IE
) is a chart showing the relationship between the temperature of the coating liquid and the magnetic properties of the product. Figure 1 f 挾枠/Ill Sai T hit (%) 10 20 30 40
5t) 60 70Figure 2

Claims (1)

[Claims] 1. 3.1 to 4.5 wt% of Si, 0.003 to 0.1 wt% of Mo, 0.005 to 0.06 wt% of acid-soluble Al, and one or two of S and Se. A slab containing a total of 0.005 to 0.1 wt% of , subjected to secondary cold rolling with a rolling reduction of 75 to 90%.
A low-iron product with excellent surface properties, which is produced by decarburizing and primary recrystallization annealing in wet hydrogen, followed by high-temperature finish annealing of a thin cold-rolled sheet finished to a final thickness of 1 to 0.25 mm. A method for producing a loss-resistant thin unidirectional silicon steel sheet. 2. The intermediate annealing according to 1, wherein the heating rate is 5°C per second or more in the temperature rising process in the temperature range from 500°C to 900°C, and the cooling rate is 5°C per second or more in the temperature decreasing process in the temperature range from 900°C to 500°C. Method. 3. 3.1 to 4.5 wt% of Si, 0.003 to 0.1 wt% of Mo, 0.005 to 0.06 wt% of acid-soluble Al, and a total amount of 0.0. After hot-rolling a slab containing 0.005 to 0.1 wt% to form a hot-rolled plate, it is subjected to primary cold rolling at a rolling reduction of 10 to 60%, and then subjected to intermediate annealing to a rolling reduction of 75 to 90%. % secondary cold rolling.
A thin cold-rolled sheet finished to a final thickness of 1 to 0.25 mm is locally coated with Sn, Pb, As, Sb, and B.
After partitioning the application area of a dilute solution or dilute suspension containing at least one compound selected from compounds containing i, S, Se, Te, Mg, Ca, Sr, Ba, K, and Na, in wet hydrogen. A method for producing a thin, low core loss, high magnetic flux density unidirectional silicon steel sheet with excellent surface properties, characterized by performing decarburization and primary recrystallization annealing at a temperature followed by high-temperature finish annealing.