JPH0774387B2 - Method of manufacturing bidirectional electrical steel sheet with high magnetic flux density - 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 grain-oriented electrical steel sheet has excellent properties, it has not been generally used as an industrial product until now, though its commercialization has been long-awaited.

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

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

The other is, as disclosed in Japanese Patent Publication No. 35-2657, a so-called "crossover" in which cold rolling is performed in one direction and then cold rolling is performed in a direction intersecting with the cold rolling. Cold rolling method ". However, the magnetic flux density (B ₈ ) of the product obtained by this method is 1.85 Tesla or less, and it does not have the excellent magnetic characteristics commensurate with the high cost due to the complexity of the manufacturing process, so it is one-way Can't compete with electrical magnetic steel sheet.

The magnetic flux density (B ₈ ) of unidirectional electrical steel sheet is as follows.
Since the technology described in Japanese Patent Publication No. 4 and Japanese Patent Publication No. 51-13469 has been invented, a product having a high magnetic flux density with a magnetic flux density (B ₈ ) of 1.92T is now commercially available.

Regarding bi-directional electrical steel sheets, improved technology was proposed in Japanese Patent Publication No. 35-17208 and Japanese Patent Publication No. 38-8213 in order to improve magnetic properties. Products with magnetic flux density have not been manufactured stably.

[Problems to be Solved by the Invention]

The present invention solves the problem in the manufacturing technology that a product having a high magnetic flux density cannot be stably obtained in a grain-oriented electrical steel sheet.

[Means for Solving the Problems]

The present invention, in order to solve the above problems, by weight Si: 0.8 ~ 6.
7%, acid soluble Al: 0.008 to 0.048%, N ≦ 0.010%, balance F
The hot-rolled sheet or thin cast piece consisting of e and unavoidable impurities is or is annealed and then cold-rolled at a reduction rate of 40 to 80%, and further, at a reduction rate of 30 to 30 in the direction intersecting with the cold rolling.
Cold rolling at 70%, after primary recrystallization annealing, applying an annealing separating agent, in the method for producing a bidirectional electrical steel sheet, which comprises finish annealing for the purpose of secondary recrystallization and purification, the above cold rolling is performed. It is intended to provide a method for manufacturing a grain-oriented electrical steel sheet, which is characterized in that the work roll having a diameter of 150 mm or more is used.

Hereinafter, the present invention will be described in detail.

The present inventors have obtained the following new findings from a survey of products of the grain-oriented electrical steel sheet produced by the cross cold rolling method.

The characteristic crystal orientation of the grain-oriented electrical steel sheet is {100} <001
> Orientation, but in the secondary recrystallized grains, the orientation grains and {110} <uvw> orientation grains coexist, and the latter orientation grains cause the magnetic flux density to decrease. . Therefore,
In order to achieve a high magnetic flux density, it is sufficient to suppress secondary recrystallization of {110} <uvw> oriented grains.

As a result of detailed studies on the behavior of these oriented grains, the present inventor suppresses the development of {110} <uvw> oriented grains by increasing the diameter of the work roll for cold rolling to a certain size or more. However, it has been found that the magnetic flux density can be increased.

Such knowledge is 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, cold-rolled in the same direction as the hot-rolling direction with a reduction rate of 55%, and then in the direction perpendicular to the rolling direction. %
Cross cold rolling was carried out at a rolling reduction of to obtain a final plate thickness of 0.35 mm. The diameter of the work roll during this cold rolling is 60mm, 100mm, 150mm, 270
mm and 490 mm. These cold-rolled sheets were subjected to primary recrystallization annealing in wet hydrogen for 210 seconds, which also serves as decarburization, after which an annealing separator containing MgO as a main component was applied and finish annealing was performed.

Figure 1 shows the relationship between the work roll diameter and the product magnetic flux density (B ₈ ). As can be seen from this figure, the work roll diameter during cold rolling is 150 mm or more, and the magnetic flux density (B ₈ value) is 1.90 T.
The product has a high magnetic flux density of esla or higher.

Fig. 2 shows the work roll diameter of 60 mm ((a) in the figure) and 490 m.
The distribution of the secondary recrystallization orientation of the product cold-rolled at m ((b) in the figure) is shown. From this figure, it can be seen that increasing the work roll diameter can suppress the development of the {110} <uvw> orientation.

The present inventors presume the cause of this as follows.

That is, the work roll diameter of cold rolling has a great influence on the metal flow in the plate thickness direction, and as the work roll diameter becomes smaller, the crystal rotation near the surface of the plate thickness progresses {110} <uvw>
It is considered that orientation recrystallization is promoted.

Hereinafter, the reason for limiting the constituent requirements of the present invention according to the embodiment,
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 are essential as components.

When Si is contained in a large amount, it is possible to improve iron loss characteristics, but it is desirable, but on the contrary, the magnetic flux density is lowered. The minimum iron loss is around 6.5%, and even if the iron loss is further increased, there is no improvement effect, so the upper limit was made 6.7%. When the Si content is increased, embrittlement is remarkable, and cold cracking is increased at 4.5% or more, but it is basically possible to perform rolling by performing warm rolling. On the other hand, when the Si content decreases, during finish annealing Occurs, and the crystal orientation is impaired, so the lower limit is made 0.8%, which has no substantial effect.

Acid-soluble Al forms nitrides such as AlN, (Al, Si) N,
Form an inhibitor. The magnetic flux density of the product becomes high 0.
The limiting range is 008 to 0.048%, preferably 0.018 to 0.036%. If N is contained in excess of 0.010%, vacancies called blisters are generated in the steel sheet, so 0.010% is made the upper limit. The lower limit is not particularly limited because it can be adjusted by nitriding in the intermediate step. Elsewhere, M
Inhibitor constituent elements such as n, S, Se, B, Bi, Nb, Sn, Ti and Cr may be added.

The molten steel composed of the above components can be provided as a hot-rolled sheet produced in a usual process or as a thin cast piece obtained by continuously casting molten steel. This hot-rolled sheet or continuously cast ribbon is cold-rolled immediately or after a short-time annealing process.

The annealing is performed in the 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 it is advisable to decide whether or not to use the annealing according to the desired level of the magnetic flux density of the product.

The distribution of reduction ratio in cold rolling is basically the same as that disclosed in Japanese Patent Publication No. 35-2657 or Japanese Patent Publication No. 38-2183.

The feature of the present invention is that the diameter of the work roll during the cold rolling is specified to be 150 mm or more.

The material after cold rolling is 750 to 100 for the purpose of primary recrystallization.
Anneal for a short time of 30 seconds to 10 minutes in the temperature range of 0 ° C.
Usually, in order to remove C contained in steel, decarburization is performed by adjusting the atmospheric dew point.

After that, after applying an annealing separator with MgO as the main component,
Finish annealing. Finish annealing is intended for secondary recrystallization and purification.

In particular, as shown in Japanese Patent Application No. 63-293645, the secondary recrystallization and the purification are separated, the secondary recrystallization is performed in the temperature range of 950 to 1100 ° C., and then the temperature is raised to 1100 ° C. or higher to perform the purification. It is desirable to do so in order to increase the magnetic flux density.

〔Example〕

Example 1 C: 0.04%, Si: 3.0%, Mn: 0.1%, acid-soluble A by weight%
l: 0.025%, N: 0.008% Molten steel consisting of the balance Fe and unavoidable impurities was rapidly solidified into a thin piece of 1.0 mm. After this slab was annealed at 1050 ° C. for 2 minutes, it was cold-rolled at a reduction rate of 50%, and then cross cold-rolled at a reduction rate of 50% in the direction perpendicular to the cold rolling. The diameter of the work roll during this cold rolling was 50 mm and 270 mm. These cold-rolled sheets were subjected to primary recrystallization annealing at 800 ° C for 90 seconds in a wet hydrogen atmosphere in order to also serve as decarburization. Then, an annealing separator was applied and finish annealing was performed. In the finish annealing, the temperature was raised to 1030 ° C at a heating rate of 30 ° C / hr, the temperature was maintained at 1030 ° C for 20 hours to complete the secondary recrystallization, and then the temperature was maintained at 1200 ° C for 20 hours for purification treatment. The magnetic properties of the obtained product were as follows.

Example 2 By weight, C: 0.05%, Si: 3.3%, Mn: 0.15%, acid-soluble Al:
A 1.6 mm thick hot-rolled sheet consisting of 0.027%, N: 0.007%, balance Fe and unavoidable impurities was annealed at 1120 ° C for 2 minutes, cold-rolled in the hot-rolling direction at a rolling reduction of 50%, and then cooled as described above. Cross cold rolling was performed at a reduction rate of 50% in a direction orthogonal to the hot rolling. afterwards,
Also serves as decarburization in a wet hydrogen atmosphere, and is annealed at 800 ° C for 210 seconds,
After applying the annealing separator, finish annealing was performed. The cold rolling schedule was changed by using work rolls with diameters of 50 mm and 270 mm during cold rolling. The magnetic properties of the obtained product were as shown in Table 2. From this result, it can be seen that it is more effective to perform at least one of the two cold rolling steps with a work roll having a large diameter.

[Advantages of the Invention] As described above, the present invention can stably produce a bidirectional electrical steel sheet having a magnetic flux density equivalent to that of the current highest level unidirectional electrical steel sheet. The effect is enormous.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the diameter of the work roll during cold rolling and the magnetic flux density (B ₈ value) of the product, and FIG. 2 is the diameter of the work roll during cold rolling of 50 mm (see drawing ( It is a (200) pole figure which shows the orientation distribution of secondary recrystallization of the product of (a)) and 400 mm (the same figure (b)).

Claims (1)

[Claims] 1. Si: 0.8-6.7% by weight, acid-soluble Al: 0.008
~ 0.048%, N≤0.010%, balance Fe and inevitable impurities, hot-rolled sheet or thin slab, as it is or after annealing, cold-rolled at a rolling reduction of 40-80%, and further cold-rolled as described above. Cold rolling at a reduction rate of 30 to 70% in the direction intersecting with, after the primary recrystallization annealing, the annealing separator is applied, and the finish annealing for the purpose of secondary recrystallization and purification. In the manufacturing method, the cold rolling is performed with a work roll having a diameter of 150 mm or more, and a method for manufacturing a grain-oriented electrical steel sheet having a high magnetic flux density.