JPH042721A - Production of double oriented silicon steel sheet having high magnetic flux density - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a steel plate having an easy magnetization axis <001> orientation in the longitudinal direction of the steel sheet and in a direction perpendicular to the longitudinal direction, and a (100) plane appearing on the rolled surface. (with Miller index (100
) The present invention relates to a method of manufacturing a so-called bidirectional electrical steel sheet composed of crystal grains (expressed as <001>).

Bidirectional electrical steel sheets have easy magnetization axes (<001> axes) in the rolling direction and in the direction perpendicular to the rolling direction, and have excellent magnetic properties in both directions, so they have excellent magnetic properties only in the rolling direction. It is advantageous to use it as a magnetic core material for devices that require magnetic flux to flow in two directions, such as large rotors, compared to unidirectional electrical steel sheets. In addition, in the field of small static devices, non-oriented electrical steel sheets that do not have a high concentration of easily magnetized axes are generally used, but by using bidirectional electrical steel sheets, it is possible to achieve smaller size and higher efficiency. There is sex.

[Conventional technology]

As mentioned above, bidirectional electrical steel sheets have excellent properties, and although their commercialization has been long awaited, to date they have not been generally used as industrial products.

There are two main methods for manufacturing conventional bidirectional electrical steel sheets:

One method, as disclosed in Japanese Patent Publication No. 37-7110, is to perform high-temperature annealing in an atmosphere containing a polar gas, such as hydrogen sulfide, and utilize surface energy to
) This is a method of secondary recrystallization of <001> oriented grains.

However, this method requires strict control of the surface energy of the steel plate and is unsuitable for mass production processes.

The other method, as disclosed in Japanese Patent Publication No. 35-2657, involves cold rolling in one direction and then cold rolling in a direction that intersects with the above-mentioned cold rolling. "Cold rolling method". However, the magnetic flux density (B8) of the product obtained by this method is less than 1.85 TeSia, and it does not have excellent magnetic properties that are commensurate with the high cost due to the complexity of the manufacturing process. cannot compete with electromagnetic steel sheets.

The magnetic flux density (B8) of unidirectional electrical steel sheet is
Since the technology described in Japanese Patent Publication No. 15644 and Japanese Patent Publication No. 51-13469 was invented, rapid progress has been made, and products with a high magnetic flux density (B6) of 1.92 T are now commercially available.

Regarding bidirectional electrical steel sheets, Japanese Patent Publication No. 35-17208 and Japanese Patent Publication No. 38-8213 are published to improve magnetic properties.
Although improved techniques have been proposed in the above publication, none of them have been able to stably produce products with high magnetic flux density that can compete with unidirectional electrical steel sheets and the like.

[Problem to be solved by the invention]

The present invention solves the problem in manufacturing technology that it is not possible to stably obtain products with high magnetic flux density from bidirectional electrical steel sheets.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention has been made to solve the above problems, in terms of weight%, Si:
1.8-6.7%, acid-soluble Aβ: 0.008-0,
048%, N≦0.010%, the balance Fe and unavoidable impurities, the hot rolled plate is cold rolled at a rolling reduction of 40 to 80%, and further rolled in a direction crossing the cold rolling at a rolling reduction of 30 to 7.
In the method for producing a bidirectional electrical steel sheet, the above-mentioned hot rolling The present invention provides a method for producing a bidirectional electrical steel sheet in which the cumulative rolling reduction rate of the final three passes is 80% or less.

The present invention will be explained in detail below.

The present inventors obtained the following new findings from an investigation of products of bidirectional electrical steel sheets manufactured by the cross cold rolling method.

The characteristic crystal orientation of bidirectional electrical steel sheets is (100)
<001> orientation, but among the secondary recrystallized grains, there are also (110) <uvw> orientation grains in addition to this oriented grain, and the latter oriented grains are the cause of lowering the magnetic flux density. ing. Therefore, in order to achieve high magnetic flux density, (
110) Secondary recrystallization of <uVW> oriented grains may be suppressed.

As a result of detailed research on these oriented grains, the present inventors found that the texture of the primary recrystallized plate before secondary recrystallization differs in the thickness direction, and the (110)<uVW> oriented grains It was found that (100) <001> oriented grains develop from the central layer from the surface layer.

This fact was obtained through the following experiment.

C: 0.055%, Si: 3.3%, acid soluble AA:
0.028%, N: 0.007%, balance Fe and unavoidable impurities.
Annealed at 25°C for 2 minutes, cold rolled in the same direction as the hot rolling direction at a rolling reduction of 55%, and then rolled in the same direction as the hot rolling direction at a rolling reduction of 55%.
It was cross-cold rolled at a rolling reduction of 0.35 mm to a final thickness of 0.35 mm. This cold-rolled sheet was subjected to primary recrystallization annealing, which also served as decarburization, at 810° C. for 210 seconds in wet hydrogen. When the texture of this -next crystal plate was investigated, as shown in Figure 1, the main orientations were (111) and <uvw> at the surface, and (211) <124> and (21N<231) at the center.
> direction as the main direction, and it was determined that the direction differs in the thickness direction. The secondary recrystallization orientation is, for example, T, Au5t, J, W, Rutter; Tran
s.

Met, Sor, AIME 215 (1959)
P119/127, as described in page 373 of the summary collection of the 96th Lecture Conference of the Japan Institute of Metals by Ushigami et al., it is strongly influenced by the -order recrystallization texture. As a result of examining the cause of the difference in the -order recrystallization texture in the sheet thickness direction, the second
It was found that this is greatly influenced by the gradient of the texture in the thickness direction of the hot rolled sheet shown in the figure. Therefore, a surface portion and a center portion were cut out from the hot-rolled sheet, and after primary recrystallization was performed under the same conditions as above, an annealing separator containing MgO as a main component was applied, and final annealing was performed.

FIG. 3 shows the orientation distribution of secondary recrystallized grains of each sample thus obtained. From Figure 3, (110)<uvt
v > oriented grains are present in the sample cut from the surface of the hot rolled sheet ((a) in the figure), and (100) <001> oriented grains are present in the sample cut from the center ((b) in the figure). I can see that it is developing.

Therefore, (110) < uv, which causes a decrease in magnetic flux density.
w > oriented grains can be suppressed by removing the surface portion of the hot rolled sheet.

As a result of detailed study of hot rolling conditions based on the above knowledge, the present inventors determined that the cumulative reduction rate of the final three passes should be 80% or less, and in particular, the hot rolling end temperature should be 950°C or higher. By changing the texture of the hot-rolled sheet, the (1
10) Suppressing the development of <uVW> oriented secondary recrystallized grains,
We have discovered that it is possible to stably produce bidirectional electrical steel sheets with high magnetic flux density.

The experimental results will be explained. The same 40 mm thick slab as mentioned above was processed by changing the pass schedule and was completed in 6 passes totaling 2.0 m.
It was hot-rolled into a hot-rolled sheet with a thickness of m. Hot rolling finish temperature is 900-95
It was 0°C. Thereafter, it was annealed at 1050° C. for 2 minutes, cold rolled in the same direction as the hot rolling direction at a rolling reduction of 50%, and then cross-cold rolled in a direction perpendicular to the rolling direction at a rolling reduction of 50%. After primary recrystallization annealing, which also serves as decarburization, at 800° C. in a wet hydrogen atmosphere for 90 seconds, an annealing separator was applied and final annealing was performed.

FIG. 4 shows the cumulative reduction ratio of the final three passes of hot rolling and the magnetic properties (B e value) of the product. From this figure, it can be seen that a product with a high magnetic flux density of 1.90 Tesla or more can be obtained with a cumulative reduction rate of 80% or less.

Based on this knowledge, we investigated the influence of the hot rolling end temperature by changing the inter-pass delay time under the condition of a cumulative reduction rate of 50% in the #3 pass, and found that the magnetic flux further increased when the hot rolling end temperature was 950°C or higher. It was found that the density was improved.

When the texture of the hot-rolled sheets was investigated, it was found that in all cases where the magnetic flux density was high, the number of (110) planes on the surface of the hot-rolled sheets decreased. Therefore, according to the present invention, when the cumulative reduction rate of the final three passes is set to 80% or less, crystal rotation due to surface shear deformation is suppressed, and when the hot rolling end temperature is set to 950°C or higher, surface shear Due to deformation, the formed (
110) It is thought that the texture was reduced by recrystallization or the like.

Below, the reasons for limiting the constituent elements of the present invention will be explained according to the embodiments.
explain.

The molten steel used in the present invention may be produced by any method such as a converter or an electric furnace, but the following content ranges as components are essential.

Increasing the content of Si is desirable because it can improve iron loss characteristics, but it conversely decreases magnetic flux density.

The lowest iron loss is reached when the content is around 6.5%, and even if it increases further, there is no improvement effect, so the upper limit was set at 6.7%. When the S1 content is increased, embrittlement becomes significant, and when the S1 content exceeds 4.5%, cold cracking occurs, but rolling is basically possible by performing warm rolling. On the other hand, if the S1 content decreases, α→γ transformation will occur during final annealing, and the crystal orientation will be impaired, so the lower limit is set at 0.8%, which has no substantial effect.

Acid-soluble Aβ forms nitrides such as AβN, (i, 5i)N, and forms inhibitors. The limited range is 0.008% to 0.048%, preferably 0.018% to 0.036%, where the magnetic flux density of the product is high.

If N is contained in an amount exceeding 0.010%, voids called blisters are formed in the steel sheet, so the upper limit is set at 0.010%. The lower limit is not particularly limited, as it can be adjusted by nitriding in an intermediate step.

In addition, Mn, S, Se, B, Bi, Nb, Sn, T1C
Inhibitor constituent elements such as r can also be added.

A slab made of the above components is heated and then hot rolled to a predetermined thickness. The final cumulative reduction rate at this time is 80
% or less is a feature of the present invention.

This hot-rolled sheet is subjected to cold rolling immediately or through a short-time annealing process of 30 seconds to 30 minutes at a temperature range of 750 to 1200°C. The above-mentioned annealing is useful for increasing the magnetic flux density of the product, and whether or not to apply the annealing may be determined depending on the level of the desired magnetic flux density of the product.

Cross cold rolling is basically the same as that disclosed in Japanese Patent Publication No. 35-2657 or Japanese Patent Publication No. 38-8213.

After cold rolling, the material is rolled in an atmosphere with a controlled dew point, which also serves to remove carbon contained in normal steel.
Annealing is performed in a temperature range of 1000° C. for 30 seconds to 10 minutes to form crystals.

After that, after applying an annealing separator mainly composed of MgO,
Final annealing is performed for the purpose of secondary recrystallization and purification.

In particular, as shown in Japanese Patent Application No. 63-293645,
The secondary recrystallization and purification steps are separated, and the temperature is 950-1100℃.
After completing secondary recrystallization in a temperature range of 1,100° C. or higher, it is effective to perform purification at a temperature of 1100° C. or higher in order to increase the magnetic flux density.

〔Example〕

Example 1 In weight%, C: 0.05%, Si: 3.2%, Mn:
0.1%, acid soluble/l:o, 03%, N: 0.
After heating a 26 mm thick slab containing 0.08% to a temperature of 1150 °C, ■ 26 → 20-18-15-8-4-
2 (mm)■26→15→7-3.5-3→2.5
→ Hot rolled under the condition of 2 (mm) 2. It was made into a hot-rolled sheet with a thickness of 0 mm. After hot rolling, air cooling for 1 second, then 550
The mixture was cooled with water to ℃ and kept for 1 hour, then cooled in a furnace. This hot rolled plate is 1
It was annealed at 120° C. for 2 minutes, cold rolled in the hot rolling direction at a rolling reduction of 50%, and then cross-cold rolled in a direction perpendicular to the cold rolling direction at a rolling reduction of 50%. Then 21 at 800℃
Primary recrystallization annealing, which also serves as decarburization, was performed for 0 seconds, an annealing separator was applied, and final annealing was performed for the purpose of secondary recrystallization and purification. The magnetic properties of the product are shown in Table 1.

Table 1 Table 2 Example 2 Using the same slab as Example 1, hot rolling start temperature ■110
Under the conditions of 0℃ ■ 1000℃ ■ 900℃, the following 6 passes, namely 26 → 15 → 6 → 3.2 → 2.8 → 2.4 → 2 (
mm) and was hot rolled to a plate thickness of 2.0 buttons. after that,
Finish annealing was carried out under the same conditions as in Example 1. The magnetic properties of the product are shown in Table 2.

Blank space below [Effects of the Invention] As described above, the present invention enables industrially stable production of bi-grained electrical steel sheets with a high magnetic flux density equal to or higher than that of the current highest level uni-grained electrical steel sheets. The effect is enormous.

[Brief explanation of the drawing]

Figure 1 is a (200) pole figure showing the texture of the surface layer ((a) in the same figure) and the center layer ((b) in the same figure) of the primary recrystallized plate, and Figure 2 is the (200) pole figure of the hot-rolled plate. FIG. 3 is a diagram showing the surface strength of the texture in the plate thickness direction, and FIG.
) is a (200) pole figure showing the orientation distribution of secondary recrystallization of the material cut out from each part of the material, and Figure 4 shows the cumulative reduction ratio of the #3 bath of hot rolling and the magnetic flux density of the product. FIG.

Claims (2)

[Claims] (1) In weight%, Si: 1.8-6.7%, acid-soluble A
l: 0.008 to 0.048%, N≦0.010%, balance Fe and unavoidable impurities.
Cold rolling at 0 to 80%, further cold rolling at a reduction rate of 30 to 70% in the direction crossing the cold rolling, then primary recrystallization annealing, applying an annealing separator, and secondary recrystallization. In a method for manufacturing bidirectional electrical steel sheets in which finish annealing is performed for the purpose of purification, the cumulative reduction rate of the final three passes of the above hot rolling is set to 8.
A method for producing a bidirectional electrical steel sheet with a high magnetic flux density, characterized in that the magnetic flux density is 0% or less. (2) The method according to claim 1, wherein the hot rolling end temperature is 950°C or higher.