JPH0699752B2 - High magnetic flux density bi-directional electrical steel sheet manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has an easy axis <001> orientation in the longitudinal direction of a steel sheet and a direction perpendicular to the longitudinal direction, and a {100} plane appears on the rolling surface. Yes (Mirror index {100} <001>
(Indicated by the following), a so-called bi-directional electrical steel sheet composed of crystal grains.

Bi-directional electrical steel sheet has an easy axis of magnetization (<001> axis) in the rolling direction and in the direction perpendicular to the rolling direction, and has excellent magnetic properties in the two directions, so magnetic properties are excellent only in the rolling direction. It is advantageous to use it as a magnetic core material for equipment that needs to flow magnetic flux in two directions as compared with existing unidirectional electrical steel sheet, for example, a large rotating machine. Also, in the field of small static devices, non-oriented electrical steel sheets that do not highly integrate the easy axis of magnetization are generally used, but by using bi-directional electrical steel sheets, downsizing and higher efficiency can be achieved. There is a nature.

[Conventional technology]

As described above, since the bidirectional electrical steel sheet has excellent properties, it has not been generally used as an industrial product until now, despite the long-awaited commercialization thereof.

There are mainly the following two methods as a conventional manufacturing technique for a grain-oriented electrical steel sheet.

One of them is, as disclosed in JP-B-37-7110, high temperature annealing in an atmosphere containing a polar gas such as hydrogen sulfide, and using surface energy to generate {100} <001> oriented grains. This is a method of recrystallizing next. However, this method requires strict control of the steel sheet surface atmosphere,
Not suitable for mass production processes.

Another of the prior arts is, as disclosed in Japanese Patent Publication No. 35-2657, cold-rolled in one direction and then cold-rolled in a direction intersecting with the cold rolling direction. This is the so-called "cross cold rolling method". However, the magnetic property (B ₁₀ ) of the product obtained by this method is 1.85 Tesla or less, and since it does not have the excellent magnetic property commensurate with the high cost due to the complexity of the manufacturing process, the conventional unidirectional It cannot compete with electrical steel sheets.

The magnetization characteristic B ₁₀ of the unidirectional electrical steel sheet has been rapidly improved since the technology disclosed in Japanese Patent Publication No. 40-15644 and Japanese Patent Publication No. 51-13469 was invented, and B ₁₀ ≧ 1.89 Tesla is JIS. Standardized products with B ₁₀ values around 1.92 Tesla are commercially available.

Regarding bi-directional electrical steel sheets, improved technology was proposed in Japanese Patent Publication Nos. 35-17208 and 38-8218 to improve the magnetization characteristics. Products with a high magnetic flux density that can withstand steel plates have not been manufactured stably.

[Problems to be Solved by the Invention]

The present invention has heretofore solved the problem in the manufacturing technology that a product with a high magnetic flux density cannot be stably obtained in the manufacture of a grain-oriented electrical steel sheet.

[Means for Solving the Problems]

The present invention provides the following manufacturing method in order to solve the above problems. That is, the present invention is Si: 0.8 ~ 4.8 in wt%.
%, Acid-soluble Al: 0.008 to 0.048%, balance Fe and unavoidable impurities are annealed to a steel plate in the temperature range of 750 to 1200 ° C if necessary, and then cold rolled to apply a reduction ratio of 40 to 80%. And further, in a direction crossing the rolling direction in the cold rolling, cold rolling applying a reduction ratio of 30 to 70% is performed, and then after a short time annealing in a temperature range of 750 to 1000 ° C. In the method for producing a grain-oriented electrical steel sheet for performing final annealing, a method for producing a grain-oriented electrical steel sheet having a high magnetic flux density by causing secondary recrystallization to be completed in the temperature range of 950 to 1100 ° C. as the final annealing. Is provided
As a specific means for expressing secondary recrystallization, 950 ° C to 1
It is intended to provide a heat treatment method in which a temperature range of 100 ° C. is maintained for 5 hours or more, or the temperature range is raised at a heating rate of 25 ° C./hr or less.

Hereinafter, the present invention will be described in detail. The present inventors
The following findings were obtained from the investigation of secondary recrystallized grains of the product by the cross cold rolling method. The crystal orientation, which is the characteristic of the grain-oriented electrical steel sheet, is expressed by Miller index as {100} <001>, but in addition, the crystal grains expressed as {110} <uvw> are mixed, and the latter The increase in the number of grains in the azimuth causes the decrease in magnetic flux density. Therefore, in order to achieve a high magnetic flux density, it is necessary to suppress the secondary recrystallization of grains having the {110} <uvw> orientation. The present inventors examined various conditions for preferentially developing {100} <001> oriented grains, and when the secondary recrystallization temperature in the final finish annealing was limited to 950 to 1100 ° C., {110}
We have found that the growth of <uvw> oriented grains is suppressed and {100} <001> oriented grains preferentially undergo secondary recrystallization.

This fact was obtained by the following experiment.

C: 0.055%, Si: 3.3%, acid soluble Al: 0.028%, N: 0.007%,
A 1.8 mm thick hot-rolled sheet consisting of the balance Fe and unavoidable impurities was annealed at 1125 ° C for 2 minutes, and in the same direction as the hot rolling direction.
Cold rolling was applied with a reduction of 55%. Then, cold rolling was performed by applying a reduction ratio of 52% in a direction intersecting with the rolling direction to obtain a final plate thickness of 0.35 mm. This cold rolled steel sheet was annealed for 210 seconds at 810 ° C. in a wet hydrogen atmosphere.

Then, an annealing separator containing MgO as a main component is applied to the treated steel sheet, and then the temperature is increased to 900 ° C. in an atmosphere of N ₂ : 10% + H ₂ : 90%.
The temperature is raised at a rate of ℃ / hr, and then at a predetermined temperature in the temperature range of 950 to 1200 ° C at a rate of 150 ° C / hr, respectively,
Hold for 30 hours to complete secondary recrystallization.

The relationship between the B ₁₀ value of the product thus obtained and the holding temperature is
The crystal orientation of the secondary recrystallized grains is shown in FIG. 2 and FIG.

As is clear from Fig. 1, the magnetic flux density (B
₍₁₀ value) exceeds 1.88 Tesla, and especially the one that is maintained in the temperature range of 970 to 1050 ℃ and completed secondary recrystallization has a high magnetic flux density (B ₁₀ value) exceeding 1.92 Tesla.

Also, from FIG. 2, it can be seen that in this temperature range, secondary recrystallization of {110} <uvw> oriented grains is suppressed and {100} <001> oriented grains preferentially grow.

Next, using the same treated steel sheet, N ₂ : 1 as final finish annealing.
0% + H _2: in 90% of the atmosphere was raised at 900 ° C. up to 10 ° C. / hr, then temperature was raised at a rate of 5 to 150 ° C. / hr up to 1200 ℃, H ₂ 100
% Annealing was performed for 20 hours in the atmosphere.

FIG. 3 shows the relationship between the magnetic flux density (B ₁₀ value) of the product and the temperature rising rate in the temperature range of 900 to 1200 ° C. It can be seen from FIG. 3 that the magnetization characteristic (B ₁₀ value) is 1.88 Tesla or more at a temperature rising rate of 25 ° C./hr or less, and particularly 1.92 Tesla or more at 15 ° C./hr or less.

When the temperature rising rates of 5 ° C./hr and 15 ° C./hr of the secondary recrystallization completion temperature were examined, they were 1010 ° C. and 1045 ° C., respectively, and it was found that they were in the recommended temperature range of the experiment of the above method.

Next, an embodiment of the present invention will be described.

In the present invention, the components contained in the material before cold rolling are Si: 0.8 to 4.8%, acid-soluble Al: 0.008 to 0.048%, balance Fe and unavoidable impurities, and these are essential components other than those. Not limited.

If the Si content exceeds 4.8%, the material is easily cracked during cold rolling and rolling becomes impossible. On the other hand, the smaller the Si content, the better in terms of increasing the magnetic flux density of the product, but if the α → γ transformation occurs during finish annealing, the crystal orientation is destroyed, so the α → γ transformation will substantially change the crystal orientation. The limited range is 0.8% or more, which has no effect.

Acid soluble Al forms nitrides and forms inhibitors
The B ₁₀ of the product becomes high in the range of 0.008 to 0.048%, and the magnetic flux density B of the product is particularly high in the range of acid-soluble Al: 0.018 to 0.036%.
₁₀ is higher than 1.92 Tesla.

The material consisting of the above components is 1.2 ~
A 4.0 mm thick hot-rolled silicon steel sheet or a thin strip obtained by continuous casting of molten steel can be used. The hot-rolled sheet or the continuously cast strip is cold-rolled immediately or after a short-time annealing process.

The annealing is performed in a temperature range of 750 to 1200 ° C. for 30 seconds to 30 minutes, this annealing is useful for increasing the magnetic flux density of the product, and whether to adopt the annealing according to the desired magnetic flux density level. Good to decide.

The cold rolling process is basically the same as that disclosed in JP-B-35-2657 or JP-B-38-8218. In the present invention, cold rolling is performed in one direction at a reduction rate of 40 to 80%, and then cold rolling is performed at a reduction rate of 30 to 70% in a direction intersecting the direction.

In particular, in the case of cold rolling in the direction intersecting with the first cold rolling, according to the method disclosed in Japanese Patent Publication No. 62-45007, cold rolling can be performed in the form of strip, which is economically effective. is there.

The material after cold rolling is usually annealed for a short time of 30 seconds to 10 minutes in a temperature range of 750 to 1000 ° C. in a wet hydrogen atmosphere in order to remove a trace amount of C contained in steel.

The material thus obtained is coated with an annealing separator,
After drying, final finish annealing is performed. For the final finish annealing, as described in detail above, by holding or limiting the heating rate, 950 to 1100 ℃, desirably 970 to 1050 ℃
Secondary recrystallization was completed in the temperature range of
Purification annealing is performed at a temperature range of 1150 to 1200 ° C for 5 to 20 hours.

〔Example〕

Example 1 C: 0.048%, Si: 3.40%, Mn: 0.14%, acid-soluble A by weight%
l: 0.023%, total N: 0.0072%, balance: Fe and inevitable impurities, 1.65 mm thick hot-rolled sheet was annealed at 1070 ℃ for 2 minutes, and 65% in the same direction as the hot rolling direction. Cold rolling was performed by applying a reduction rate. Further, cold rolling was performed by applying a reduction ratio of 60% in a direction intersecting with the cold rolling direction to obtain a final plate thickness of 0.23 mm.

This cold rolled sheet was decarburized and annealed at 810 ° C. for 90 seconds in a wet hydrogen atmosphere.

Then, after applying MgO as an annealing separator, finish annealing and N ₂ : 10% + H ₂ : 90% atmosphere were performed in the following three annealing cycles.

(A) Heat up to 1200 ° C at 30 ° C / hr.

(B) The temperature is raised to 900 ° C at 30 ° C / hr and then 120 ° C at 5 ° C / hr.
Raise to 0 ° C.

(C) Heat up to 1020 ° C at 30 ° C / hr and hold for 5 hours, then 3
Temperature rises to 1200 ℃ at 0 ℃ / hr.

After that, it was held at 1200 ° C. for 20 hours in an atmosphere of H ₂ 100% for blunting.

The magnetic properties of the obtained product were as follows.

Example 2 A hot-rolled sheet having the same composition as in Example 1 and having a thickness of 1.8 mm was hot-rolled, one was hot-rolled, the other was 950 ° C. for 2 minutes, and the other one was Annealed at 1070 ° C for 2 minutes.

These are cold-rolled by applying a reduction ratio of 63% in the same direction as the hot-rolling direction, and further cold-rolled by applying a reduction ratio of 55% in the direction intersecting the cold rolling direction. 0.
The final plate thickness was 30 mm. The three types of cold-rolled sheets thus obtained were decarburized and annealed at 810 ° C. for 120 seconds in a wet hydrogen atmosphere.
Next, after applying MgO as an annealing separator, N ₂ : 10% +
The temperature was raised to 1000 ° C. at a heating rate of 25 ° C./hr in an atmosphere of H ₂ : 90%, and the temperature was maintained at 1000 ° C. for 20 hours to complete the secondary recrystallization.
After that, purification was performed at 1200 ° C. for 20 hours in an atmosphere of H ₂ : 100%. The magnetic properties of the obtained product are shown in Table 2.

Example 3 Weight%, C: 0.055%, Si: 3.30%, Mn: 0.14%, acid soluble Al: 0.028%, total N: 0.007%, balance: Fe and heat of 1.8 mm thickness consisting of unavoidable impurities The rolled sheet was annealed at 1070 ° C. for 2 minutes and cold-rolled in the same direction as the hot-rolled sheet, applying a reduction rate of 63%. Further, cold rolling in which 55% reduction was applied in the same direction as the cold rolling direction was performed to obtain a final plate thickness of 0.30 mm. This cold rolled sheet was decarburized and annealed at 810 ° C. for 120 seconds in a wet hydrogen atmosphere. Next, after applying MgO as an annealing separator, finish annealing was performed in the following 3 cycles in an atmosphere of N ₂ : 25% + H ₂ : 75%.

(A) Heat up to 1200 ° C at 30 ° C / hr.

(B) Heat up to 1000 ° C at 30 ° C / hr and hold for 5 hours, then 30
Temperature rises to 1200 ℃ at ℃ / hr.

(C) Heat up to 1100 ℃ at 30 ℃ / hr, hold for 5 hours, then 3
Temperature rises to 1200 ℃ at 0 ℃ / hr.

Then, keep it at 1200 ℃ for 20 hours in an atmosphere of H ₂ 100%,
Purified. The magnetic properties of the obtained product are shown in Table 3.

[Effects of the Invention] As described above, the present invention has a B ₁₀ value equal to or higher than the B ₁₀ value in the cold rolling direction of the highest level unidirectional electrical steel sheet at present, in the cold rolling direction and the direction perpendicular thereto. Since the bidirectional electrical steel sheet having two directions can be stably manufactured, its industrial effect is enormous.

[Brief description of drawings]

Fig. 1 shows the relationship between the holding temperature and the magnetic flux density (B ₁₀ value) in the final finish annealing, and Fig. 2 shows (a) 1000 ° C, (b) 1200 ° C, and the secondary The crystallographic orientation of the recrystallized and completed product is shown (20
0) Pole figure, FIG. 3 is a diagram showing the relationship between the temperature rising rate and the magnetic flux density (B ₁₀ value) in the temperature range of 900 to 1200 ° C. in the final finish annealing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuyuki Takahashi Nobuyuki Takahashi 1-1-1 Emitsu, Hachimanto-ku, Kitakyushu-shi, Fukuoka Inside Nippon Steel Co., Ltd. 3rd Technical Research Laboratory (56) Reference JP-A-1-139722 ( JP, A) JP 1-272718 (JP, A) JP 47-33019 (JP, A)

Claims (4)

[Claims] 1. By weight%, Si: 0.8-4.8%, acid-soluble Al: 0.
008 ~ 0.048%, cold rolling a steel sheet consisting of balance Fe and unavoidable impurities at a reduction rate of 40 to 80%, further in the direction intersecting with the cold rolling, cold rolling at a reduction rate of 30 to 70%, Then 75
After performing short-time annealing in the temperature range of 0 to 1000 ℃, when performing the final annealing, secondary recrystallization is completed in the temperature range of 950 to 1100 ℃, and then purification annealing is performed. For manufacturing high-performance electrical steel sheet. 2. The method according to claim 1, wherein the final annealing is held in a temperature range of 950 to 1100 ° C. for 5 hours or more. 3. The method according to claim 1, wherein in the final annealing, the temperature range of 950 to 1100 ° C. is raised at a heating rate of 25 ° C./hr or less. 4. A steel sheet comprising the above components is annealed in a temperature range of 750 to 1200 ° C. and then cold rolled.
The manufacturing method described.