JP3492993B2 - Manufacturing method of high magnetic flux density thin unidirectional magnetic steel sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a grain-oriented electrical steel sheet used as a core material for electric equipment such as transformers and generators.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are used for magnetization in the rolling direction.
The iron loss characteristics must be good. The quality of the magnetization characteristics is determined by the level of the magnetic flux density induced in the iron core in the applied constant magnetic field, and the iron core can be downsized in products with high magnetic flux density. Iron loss is a power loss consumed as heat energy when a predetermined AC magnetic field is applied to the iron core. For its quality, magnetic flux density, plate thickness, coating tension, amount of impurities, specific resistance, crystal grains The size of the magnetic domain has an effect. Above all, high magnetic flux density and thin plate thickness are important for reducing iron loss.

Due to advances in manufacturing technology today, for example,
It is a steel plate with a thickness of 23 mm and has an excellent magnetic flux density B8 (value at a magnetizing force of 800 A / m) of 1.92 T and iron loss W17 / 50 (value at maximum magnetization of 1.7 T at 50 Hz) of 0.85 W / kg. Products can now be produced on an industrial scale. However, in order to cope with global warming in recent years, there is a demand for the development of even thinner thin unidirectional magnetic steel sheets with a high magnetic flux density such as 0.20 and 0.18 mm.

The unidirectional electrical steel sheet having such excellent magnetic properties is composed of a crystal structure in which the <001> orientation, which is the easy axis of iron, is highly aligned in the rolling direction of the steel sheet. During the final finishing annealing in the manufacturing process, it is formed through a phenomenon called secondary recrystallization in which crystal grains having a [110] <001> orientation, which is a so-called Goss orientation, grow preferentially.

The basic requirements for sharp and sufficient growth of these Goss-oriented grains are the presence of an inhibitor that suppresses the growth of grains having an unfavorable orientation other than the Goss orientation in the secondary recrystallization process. It is a well-known fact that the formation of a primary recrystallized structure in which Goss-oriented grains tend to develop preferentially is essential. Here, as the inhibitor, precipitates such as AlN, Mn (S, Se), and Cu ₂ (S, Se) are generally used, and additionally, components such as Sn, Sb having a strong tendency to segregate at the grain boundaries are used. Further, it is important for the primary recrystallized structure to have a crystal grain size and its uniformity, and to form a texture in which the Goss-oriented grains and the oriented grains having a correspondence relationship with the Goss orientation are aligned in the rolling direction.

A method of obtaining a grain-oriented electrical steel sheet having a high magnetic flux density has been known for a long time, and for example, Japanese Patent Publication No. 46-23820.
As disclosed in Japanese Patent Publication No.
The method of using N is widely known. This is to produce a unidirectional electrical steel sheet by heating the high temperature slab (≧ 1300 ° C.) to once form a solid solution of the inhibitor component of AlN and finely precipitating AlN during annealing before final cold rolling.

On the other hand, Japanese Patent Application Laid-Open No. 62-40315 discloses a method in which an AlN inhibitor is formed by a nitriding treatment in a subsequent step and low temperature slab heating (≦ 1250 ° C.) is performed. This method was developed to avoid the disadvantages of equipment and operation of high temperature slab heating. It is well known that in the manufacturing method using these AlN inhibitors, a high magnetic flux density cannot be obtained without a proper primary recrystallization structure. The formation of the primary recrystallized structure is greatly affected by the cold rolling conditions, and it is generally preferable that the final cold rolling has a high reduction ratio of 81% or more. Regarding other cold rolling, 1) Japanese Patent Publication No. 54-13846 discloses that 50 between cold rolling passes.
The technology of aging treatment for 1 minute or more at ~ 350 ℃ is also 2)
Japanese Patent Publication No. 54-29182 discloses a technique of holding at 300 to 600 ° C. for 1 to 30 seconds. The technique 1) is intended for reversal rolling, and the technique 2) is intended for tandem rolling.

High temperature rolling using a tandem mill is
It is difficult in terms of operation technology, and at the present time, high temperature rolling is performed by utilizing the processing heat of Levers rolling, and the aging effect after reel winding during rolling is used. The reversing mill is generally a 4-roll type, 6-roll type, or the like in which rolls are arranged in series, but if the work roll diameter is reduced, roll deformation easily occurs, and a large-diameter roll of 250 mmφ or more is generally used.

On the other hand, the Zenzimer mill and NMS mill in which rolls of 6, 12, and 20 rolls are arranged in a cluster form back up the work rolls in a diversified manner, and thus work rolls of small diameter can be used. Since the unidirectional electrical steel sheet contains a large amount of Si, it has a high rolling reaction force, and it is advantageous to use a work roll with a small diameter in order to reduce the product sheet thickness. Therefore, a cluster type reversing mill is often used for high-temperature rolling of unidirectional electrical steel sheets.

On the other hand, regarding the work roll diameter of the cold rolling machine,
3) Japanese Patent Publication No. 50-37130 discloses a technology for performing a small diameter roll of 300 mmφ or less in all passes of rolling or a subsequent pass. 4) Japanese Patent Laid-Open No. 02-282422 discloses a small diameter roll of 30 to 100 mmφ in a subsequent pass. Technology for hot rolling at 150-230 ° C at 5)
Japanese Patent Laid-Open No. 05-33056 discloses a technique for warm rolling at a temperature of 150 to 350 ° C. with a small diameter roll of 50 to 150 mmφ in the former pass, 6) JP-A-09-2.
Japanese Patent No. 87025 discloses a technique of increasing the rolling temperature (100 to 350 ° C.) with an increase in diameter of a work roll (40 to 500 mmφ).

[0011]

The cluster mill used for the conventional electromagnetic steel sheet is mainly the Zenzimer mill represented by the 21 and 22 type, and from the viewpoint of ensuring thin rollability,
Work rolls with a small diameter of 95 mmφ or less were mainly used.
For example, in the technique of 5) above, the roll diameter is 50 to 150 mmφ, but in the embodiment, only the examples of 80 and 90 mmφ are described.

Further, in the production of Al-containing unidirectional electrical steel sheet, as disclosed in 3) above, cold-rolled work rolls are said to have a small diameter, and a cluster mill that is advantageous for thinning is required to meet this requirement. It was in agreement. Further, as disclosed in the above 4) to 6), even in the rolling premised on the aging treatment between passes, the small diameter roll was considered to be advantageous from the viewpoint of magnetic characteristics.

The present inventors have studied in detail the influence of the work roll diameter on the magnetic properties in the production of an Al-containing unidirectional electrical steel sheet which is subjected to an aging treatment between passes using a cluster type reversing mill. As a result, the magnetic flux density was low when rolling with a work roll diameter of 90 mmφ or less in the related art, and rather, the effect of improving the magnetic flux density was discovered by rolling with a work roll having a diameter of 95 to 170 mmφ, which was larger than the conventional one, and a patent application was filed. (Specification of Japanese Patent Application No. 2000-002944).

However, in the production of thin material, a large diameter work roll is disadvantageous from the viewpoint of rolling reaction force. Therefore, it was investigated whether the effect of increasing the work roll diameter was effective in the first pass or the second pass of rolling. as a result,
It was found that the large-diameter work roll rolling is more effective in improving the magnetic properties in the first pass of rolling.
These results conflict with the techniques of 3) and 4) above. Therefore, in order to manufacture a thin material in the present invention,
170mmφ large diameter work roll cold rolling machine to carry out warm rolling to an intermediate thickness, and then another cold rolling machine, for example, rolling to the final plate thickness with a small diameter roll of 65mmφ or less, etc.
It may be rolled by two cold rolling machines. However, this method has a drawback that the fixed cost of cold rolling increases and the productivity is poor.

This problem can be overcome if, for example, the diameter of the work roll can be changed with one cold rolling machine. However, the Zenzimer mills represented by the 21 and 22 types used in the conventional production of unidirectional electrical steel sheets are Since the basic structure is a monoblock type housing, it is difficult to change the work roll diameter during the rolling pass. Therefore, the present inventors first applied a cluster mill composed of a split type housing to the production of unidirectional electrical steel sheet, rolling the former pass of rolling with a work roll diameter of 95 mmφ or more, and the latter pass to thin rolling. We succeeded in recombining with suitable small-diameter rolls and rolling, and established a technology to manufacture thin unidirectional electrical steel sheet with high magnetic flux density with one rolling mill at low fixed cost and high productivity.

This invention organically combines the metallurgical discovery that the large diameter work roll effect of the cluster mill is effective in the preceding stage of the rolling pass and the efficient cold rolling technology of the split type housing cluster mill. It is a thing.

[0017]

The present invention has been made on the basis of the above-mentioned findings, and its gist is as follows. (1)% by mass, C: 0.025 to 0.100%, S
i: 2.5-4.5%, Al: 0.007-0.040
% Hot-rolled electromagnetic steel slab, then hot-rolled sheet annealed once cold-rolled, or intermediate-annealed twice or more cold-rolled, then primary In the method for producing a grain-oriented electrical steel sheet to be subjected to recrystallization annealing and then secondary recrystallization annealing, the final cold rolling is performed with a revers mill, and the pre-stage process of the final cold rolling in the cold rolling is performed.
Use a work roll with a diameter of 95-180 mmφ
Cold rolled to an intermediate plate thickness of 0.40 mm or less and continued
Rolling from the intermediate plate thickness to the final plate thickness T _f (mm)
Work low with a diameter D (mmφ) such that ≦ T _f × 520
Of unidirectional electrical steel sheet characterized by cold rolling
Production method. (2) The strip temperature is set to 100 at least once during the final cold rolling pass in the cold rolling.
Hold in the range of ~ 350 ° C for at least 1 minute
The method for producing a unidirectional electrical steel sheet according to (1) above. (3) The product sheet thickness as described in (1) above is 0.23 mm or less.
Alternatively, the method for producing a unidirectional electrical steel sheet according to (2). (4) In the cold rolling, by using a cluster-type Levers rolling mill composed of a housing that can be divided into upper and lower parts, by exchanging work rolls with different diameters in a plate thickness step in the middle of multiple pass rolling, In any one of the above items (1) to (3) , the final cold rolling is performed with a single rolling mill.
A method for producing the described unidirectional electrical steel sheet.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION First, the test results on which the present invention is based will be described. [Experiment 1] C: 0.005%, Si: 3.3 by mass%
%, Mn: 0.1%, S: 0.07%, Al: 0.02
82%, N: 0.0070%, and Sn: 0.07
The electromagnetic steel slab containing% l was heated at a low temperature of 1150 ° C. and then hot rolled to obtain a hot rolled coil having a thickness of 1.8 mm.

After annealing this hot rolled coil at 1100 ° C., 20
Using a heavy-duty Sendzimir mill, cold rolling at a reduction rate of 90%,
Finished to a plate thickness of 0.18 mm. At that time, the work roll diameter of the rolling mill was changed within the range of 40 to 180 mmφ until the plate thickness reached 0.26 mm, and rolling was performed under the same conditions for the pass schedule and the number of passes (5 times). Further, aging treatment was performed at 200 ° C. for 5 minutes in the plate thickness stage in the middle of the second pass, the third pass and the fourth pass. Then, rolling from 0.26 mm to 0.18 mm was completed in one pass with a work roll diameter of 60 mmφ.

Next, the cold-rolled sheet had a primary recrystallized grain size of 23 μm.
After decarburization annealing by adjusting the temperature so that
Nitriding annealing was performed to reach ppm, and then magnesia slurry was applied. This coil was subjected to finish annealing by a usual method, and then an "insulating coating of Al phosphate + colloidal silica" was applied, and shape-correcting annealing that also served as coating baking was performed to obtain a product. Then, the magnetic flux density B8 of this product was measured.

The relationship between the work roll diameter and B8 is shown in FIG. From FIG. 1, it was clarified that the magnetic flux density B8 was improved when the work roll diameter was in the range of 95 to 180 mmφ. [Experiment 2] An electromagnetic steel slab having the same composition as in Experiment 1 was hot-rolled by low-temperature slab heating at 1150 ° C to produce a hot-rolled coil having a thickness of 2.0 mm. After annealing this hot-rolled coil at 1100 ° C, it was cold-rolled at a reduction rate of 90% using a 20-fold roll Sendzimir mill.
Finished to a plate thickness of 0.20 mm. At that time, the work roll diameter of the rolling mill is set to two levels, i) 100 mmφ and ii) 60 mmφ, and 0.60 mm
Rolled to multiple intermediate plate thicknesses ranging from ~ 0.20 mm. At this time, aging treatment was performed at 200 ° C. for 5 minutes in the intermediate plate thickness stage of the second pass (1.00 mm) and the third pass (0.80 mm). Then 0.22mm
The above is i) corresponding to the conditions i) and ii) above.
Was rolled into a work roll having a diameter of 60 mm and ii) was rolled into a work roll having a diameter of 100 mm, and rolled to 0.20 mm.

Then, the primary recrystallized grain size of the cold-rolled sheet was 23 μm.
After decarburization annealing by adjusting the temperature so that
Nitriding annealing was performed to reach ppm, and then magnesia was applied. This coil is finish-annealed by the usual method, and "insulating coating of Mg phosphate + colloidal silica"
After applying, the product was subjected to shape-correcting annealing that also served as coating baking. Then, the magnetic flux density B8 of this product was measured.

FIG. 2 shows the relationship between the minimum plate thickness (intermediate plate thickness) and the magnetic flux density B8 of the first-stage rolling when the work roll diameter is changed and rolled in the first-stage and second-stage passes. As a result, under the above condition i) in which the large-diameter work roll was used as the first pass of the rolling, high B8 can be secured by performing the large-diameter work roll rolling to a plate thickness of at least 0.40 mm, but the latter-stage pass has a large-diameter work roll. High B8 could not be obtained under any conditions in ii) rolled in.

As described above, the magnetic flux density of the grain-oriented electrical steel sheet is influenced by the inhibitor and the primary recrystallization structure. In [Experiment 1] and [Experiment 2], [N] after nitriding annealing did not change the inhibitor under a certain condition, so it is presumed that the rolling condition affected the magnetic flux density through the change of the primary recrystallization structure. To do. Therefore, primary recrystallization samples corresponding to the work roll diameters of 50, 95, and 150 mm in [Experiment 1] were taken and the primary recrystallization texture was investigated. SGH method (Harase et al .: Bulletin of the Japan Institute of Metals, No. 2)
The analysis was carried out according to Volume 9, No. 7, P552).

FIG. 3 shows the intensity (I
_N ) and the intensity (IcΣ9) of the azimuth corresponding to Σ9. As shown in FIG. 3, when the work roll diameter is larger, the I _N intensity in the Goth direction (rotation angle is 0 °) increases, the I _N intensity deviates by about 25 ° from the ND axis, and the ND axis is centered. It can be seen that the distribution of IcΣ9 is sharpened. In order to obtain a unidirectional electrical steel sheet having a high magnetic flux density, the conditions that the primary recrystallization texture should have are that there are many Goss orientations and that the Σ9 corresponding orientations for preferentially growing Goss are sharp. The work roll diameter controlled according to the present invention provides a primary recrystallization texture suitable for increasing the degree of goss accumulation of secondary recrystallization.

The above is the result of the low temperature slab heating method using an AlN inhibitor.
Similarly, the high-temperature slab heating method in which MnS, AlN + MnS (MnSe) inhibitors, and Sn, Sb, Cu, etc. were supplementarily added as shown in (3) was investigated. As a result, the effect of improving the magnetic flux density with increasing work roll diameter was confirmed for all the component-based materials containing AlN as an inhibitor. On the other hand, the effect could not be confirmed in the component system containing no AlN.

It is known that AlN has a stronger inhibitor strength than MnS (MnSe) and is thermally stable. When such an AlN inhibitor is used, it is presumed that the primary recrystallization texture obtained in the present invention effectively exerts a magnetic flux density improving effect. The mechanism of the relationship between work roll diameter control and primary recrystallization texture formation is not clear at present, but it is hypothesized as follows. It is known that when the work roll diameter is small, the shear deformation component of the steel plate surface portion increases during cold rolling, and after primary recrystallization, the (110) plane increases and the (111) plane decreases. (Kono et al .: Iron and Steel, 68 (1982), P.58). At this time, (1
For the 10) plane, it is estimated that the azimuth groups rotated around the ND axis from the Goth azimuth increase and become a broad texture unfavorable to the unidirectional electromagnetic steel plate. Therefore, it is estimated that the sharpening of the texture by increasing the diameter of the work roll is the effect of increasing the magnetic flux density. Further, the reason why the work roll diameter increasing effect is effective in the first pass of rolling is that the work roll has a larger biting angle to the material of the work roll and the shear deformation component of the steel plate surface portion is larger in the thicker stage. I think there is.

Next, the reasons for limiting the composition of the unidirectional electrical steel of the present invention and the preferred composition range will be described. The unit of the composition content is mass%. C
Is an important element for austenite formation, and 0.02
5% or more is necessary. If too much, decarburization becomes difficult, so the upper limit is made 0.100%. If Si is too small, the electric resistance becomes small and good iron loss characteristics cannot be obtained.
If it is too much, cold rolling becomes difficult, so its content is 2.
5% or more and 4.5% or less.

The lower limit of Mn as an unavoidable component is 0.03%.
On the other hand, if too much, it is difficult to solution heat MnS, MnSe, assuming high-temperature slab heating, so the upper limit is 0.
45% S and Se are appropriately added depending on the type of inhibitor used. These combine with the Mn to form MnS or MnSe which acts as an inhibitor. The content range of S and Se is preferably 0.01% or more and 0.04% or less in both cases of single and combined use. However, MnS,
High-temperature slab heating is necessary to finely precipitate MnSe. On the other hand, in the low temperature slab heating method using the post-process nitriding method, fine MnS and MnSe are not necessary, so 0.015%
The following is desirable. Therefore, the range of S and Se is not particularly limited.

In the present invention, especially containing Al as an inhibitor component is indispensable for obtaining a high magnetic flux density, and it is necessary to add a certain content or more. However, if the amount is too large, the heating time for the high temperature slab for solution treatment becomes long and the productivity deteriorates. Therefore, the Al content is set to 0.007% or more and 0.040% or less. If N is premised on high temperature slab heating, AlN is used for annealing before final cold rolling.
Since it is necessary to form the alloy, it is contained in the range of 0.003% or more and 0.020% or less. On the other hand, in the low temperature slab heating method,
Since AlN is formed by the nitriding treatment after the primary recrystallization, it is not essential to contain N in the steelmaking stage. Therefore, the range of N is not particularly limited.

In addition to the above, in order to improve magnetism, S
Ingredients such as n, Sb, Cu, Ni, Cr, P, V, B, Bi, Mo, Nb and Ge can be appropriately added within a known range. Next, the conditions relating to the manufacturing process will be described. In the present invention, a known manufacturing method is applied to the manufacturing process of the steel material. The produced ingot or slab is processed, if necessary, adjusted in size, heated, and hot-rolled. The slab heating temperature is set in the range of 1100 ° C to 1450 ° C as required, and a normal gas heating furnace or an induction heating furnace is used for heating. The steel strip after hot rolling is made to have the final thickness by a single cold rolling method after hot-rolled sheet annealing or a plurality of cold rolling methods with intermediate annealing sandwiched.

Before the final cold rolling, annealing is performed under known conditions. When presuming high temperature slab heating,
To ensure insufficient AlN fine precipitation during hot rolling,
Annealing before the final cold rolling is essential. On the other hand, if low temperature slab heating is assumed, annealing before the final cold rolling for AlN precipitation control is not essential, but because of the control technology of carbides and solid solution C, rapid cooling after annealing, cooling process Techniques such as work strain addition and retention for carbide precipitation make the aging treatment between passes of the present invention more effective, so that the effect of the present invention is not impaired even if the final annealing before cold rolling is performed. .

After that, the steel sheet is subjected to the final cold rolling by the reversal rolling. At this time, in order to obtain a high magnetic flux density, the rolling reduction should be 81% or more as conventionally known. preferable. In the present invention, aging treatment during cold rolling and performing warm rolling are important for improving magnetic properties. In particular, it is known that high temperature slab heating is more effective from the viewpoint of preventing the generation of linear fine particles than the effect of improving magnetic properties. And in the present invention,
As shown in Example 3, 100 to 350 at the plate thickness stage during rolling.
It is important to maintain the temperature range of ° C for 1 minute or more.

Another feature of the present invention is to manufacture a grain-oriented electrical steel sheet having excellent magnetic properties by increasing the diameter of the work roll in the first pass of cold rolling.
As shown in Fig. 1, the magnetic flux density is 90 mmφ for the work roll diameter.
Remarkably inferior below, improved over 95mmφ, 120mmφ
Above, it tends to be almost saturated. Therefore, in the present invention,
The work roll diameter is 95 mmφ or more, preferably 120 mmφ or more. On the other hand, if the work roll diameter is too large, not only the effect will be saturated, but also the cluster mill will be large-scale and the equipment cost will increase, so the upper limit is 180 mmφ. Further, the range of applying a large-diameter work roll having a diameter of 95 to 180 mmφ is such that the plate thickness is thick, effective in the preceding pass of rolling, and it is necessary to perform at least the plate thickness 0.40 mm or less, preferably 0.26 mm or less, It can be seen from FIG.

On the other hand, in the rolling in the latter pass, the rolling reaction force increases as the finished plate thickness decreases, so that the diameter
Rolling becomes difficult with large diameter work rolls of 95 to 180 mmφ. Therefore, it is necessary to select the work roll diameter according to the required product thickness. Therefore, the present inventors
The relationship between the work roll diameter and the minimum rollable plate thickness was experimentally obtained using a rolling machine with a variable work roll diameter.
As a result, when the work roll diameter was D mm and the minimum plate thickness was T _f mm, the relationship of T _f = D / 520 was obtained. This relationship is
Although it is slightly higher than the theoretical formula of Stone (μ = 0.1), this is considered to be due to the bad influence of thermal crown and the like caused by high temperature rolling.

In conclusion, as shown in FIG. 4, the relationship between the work roll diameter and the final rolling thickness can be illustrated. Hereinafter, the rolling method of the present invention will be described by dividing it into a first pass and a second pass of rolling. The work roll diameter is 95 to 180 mmφ up to a plate thickness of at least 0.40 mm in the first pass of rolling. The rolling at this time is premised on high temperature rolling and aging treatment between passes.
Next, the rolling of the latter pass, when the finishing plate thickness is T _f mm,
A thin material can be stably obtained by rolling with a work roll diameter of (520 × T _f ) mm or less. For example, in the case of 120 mmφ work roll, which is preferable for improving the magnetic flux density, 0.23 m
Since the plate thickness of m is the rolling limit, it is difficult to finish the product plate thickness of 0.23 mm or less by rolling. Further, when the product plate thickness is 0.20 mm, the lower limit of the former pass of the present invention is 95 mm.
It is possible to finish with a φ work roll, but it is difficult to obtain a stable and high magnetic flux density. If the product plate thickness is 0.18 mm or less, it cannot be rolled with a work roll having a diameter of 95 mm. Therefore, it is necessary to change to a small diameter roll having a diameter of 60 mm. For the above reason, in order to obtain a stable magnetic flux density improvement effect, it is necessary to replace the work roll with a small-diameter work roll in the latter pass of rolling, and the product plate thickness of 0.23 mm is the upper limit of the present invention.

The cold rolling mill is limited to cluster type Levers rolling mills (Sendzimir mill, NMS mill, etc.) of 6-fold, 12-fold, 20-fold, etc. from the viewpoint of stability of high temperature rolling and thin rolling. Further, it is a feature of claim 2 of the present invention that the housing is divided and the work roll diameter is changed to a suitable one in the intermediate rolling stage, and the above rolling is performed by one rolling mill. FIG. 5A shows a conceptual diagram of a conventional monoblock type housing, and FIG. 5B shows a conceptual diagram of a split type housing. In (a), it is possible to change the diameter of the work roll by changing the diameter of the intermediate roll, but the change range is as small as about 10 mm, and the work of reassembling is large and unrealistic. In (b), the work roll diameter can be changed by elevating the upper and lower housings and adjusting the distance between the bores. Further, since the cluster mill has no chocks on the work rolls, it is possible to quickly replace the work rolls during the rolling of the coil, and the productivity is not deteriorated.

The steel sheet after the final rolling is subjected to a degreasing treatment, and then subjected to an annealing that also serves as decarburization and primary recrystallization. In the case of the low temperature slab heating method in which the slab heating temperature is 1250 ° C or lower, it is effective to perform nitriding treatment between the primary recrystallization and the secondary recrystallization to form an AlN inhibitor. As a method of nitriding treatment, a method performed in the middle of finish annealing disclosed in JP-A-60-179885 and the like, and JP-A-1-82393.
There is a method disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 2003-187, in which a strip is annealed in a mixed gas of "hydrogen + nitrogen + ammonia" while running. To stably develop good secondary recrystallized grains,
The nitrogen content must be 120 ppm or more, preferably 150 ppm or more. Further, when the control of the primary recrystallized grain size disclosed in JP-A-1-82939 is used together, the magnetic characteristics are further improved.

Next, the steel sheet is coated with an annealing separator containing MgO slurry as a main component, and then wound into a coil shape and subjected to final finish annealing. After that, apply an insulating coating if necessary, laser, plasma, mechanical method,
It is also effective to perform the magnetic domain subdivision processing by etching or another method.

[0040]

Example 1 An electromagnetic steel slab containing the components shown in Table 1 was produced under the manufacturing process conditions shown in Table 2 from 1350 to
1400 ℃ high temperature slab heating a), b) and c), 1150 ~ 1290
Low temperature slab heating at ℃ d), e) and f) were hot rolled to obtain hot rolled steel strip.

A), c) and f) were two-time cold rolling method with intermediate annealing sandwiched between them, and b), e) and d) were one-time cold rolling method after hot-rolled sheet annealing. The final cold rolling was performed using a Levers rolling mill, and the rolling reduction was 75 to 92%. Intermediate plate thickness and final plate thickness are shown in the table. In cold rolling, the work roll diameter was changed as shown in Table 1, and rolling was performed in 2 to 5 passes up to a plate thickness of 0.30 mm. Select at least 2 passes of intermediate thickness during rolling and select 200 ℃
Aged for 5 minutes. Subsequently, a work roll diameter of 60 mm was used to roll to a plate thickness of 0.18 mm in one pass. The cold-rolled steel strip was decarburized and annealed by a usual method. Of these, for d) and e), nitriding and annealing was added after decarburization and the nitriding amount shown in Table 1 (after nitriding-before nitriding ) Was added to the inhibitor. Then, the magnetic flux density (B8) of the obtained product steel strip was measured by applying a magnesia coating, a finish annealing, an insulating coating, a shape correction / baking annealing by a usual method. Then, the magnetic domain was controlled by a mechanical method, and then the iron loss (W17 / 50) of the obtained product steel strip was measured. As shown in Table 1, it is understood that a product having excellent magnetic properties can be obtained by controlling the work roll diameter of cold rolling within the range specified by the present invention with the component containing Al.

[0042]

[Table 1]

[0043]

[Table 2]

(Example 2) Using an annealed material having an intermediate plate thickness of 1.6 mm shown in a) of Table 1 and a) of Table 2 as shown in Table 3 by using a Levers rolling mill, 10 kinds of workpieces were prepared. Roll diameter
A combination of 120 mmφ and 60 mmφ was cold-rolled to a final plate thickness of 0.20 mm. The aging between passes was carried out by treating at 200 ° C. for 5 minutes at the plate thickness stages shown in Table 2. The cold-rolled steel strip was subjected to decarburization annealing, magnesia coating, finish annealing, insulation coating, shape correction / bake annealing by the usual methods, and the magnetic flux density (B8) of the obtained product steel strip was measured. After that, the magnetic domain was controlled by a mechanical method, and the iron loss (W1
7/50) was measured. As shown in Table 2, it can be seen that a product having an excellent magnetic flux density can be obtained by applying a large-diameter work roll of 120 mmφ at least to a plate thickness of 0.4 mm or less in the preceding pass of rolling.

[0045]

[Table 3]

(Example 3) The annealed material having an intermediate plate thickness of 1.6 mm shown in a) of Table 1 and a) of Table 2 was prepared with a work roll diameter of 1 mm.
Using a Levers rolling machine with a diameter of 65 mm, rolling was performed to 0.30 mm under the conditions of holding temperature and time between passes in 12 ways shown in Table 4, and then cold rolling was performed to a final sheet thickness of 0.15 mm with a work roll diameter of 50 mmφ. Decarburization annealing, magnesia coating, finish annealing, insulation coating, shape correction
Baking annealing was performed, and the magnetic flux density (B8) of the obtained product steel strip was measured. Then, after controlling the magnetic domains by etching, the iron loss (W17 / 50) of the obtained product steel strip was measured.
As shown in Table 4, a product having excellent magnetic properties was obtained by holding the material in the temperature range of 100 to 350 ° C. for 1 minute or more at the plate thickness stage during rolling.

[0047]

[Table 4]

[0048]

According to the present invention, in a thin unidirectional electrical steel sheet containing Al and having a product sheet thickness of 0.23 mm or less, it is possible to improve the magnetic characteristics by improving the magnetic flux density. Therefore, the present invention contributes to lower iron loss and downsizing of transformers and the like.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a work roll diameter and a magnetic flux density.

FIG. 2 is a diagram showing the relationship between the minimum strip thickness and the magnetic flux density in the preceding rolling.

FIG. 3 is a diagram showing an analysis result regarding a primary recrystallization texture of a steel plate when a work roll diameter is changed.

FIG. 4 is a diagram showing a relationship between a work roll diameter and a minimum rollable plate thickness.

FIG. 5 is a schematic view of a 20-stage cluster mill having a monoblock housing and a split housing.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C22C 38/60 C22C 38/60 (72) Inventor Shinya Hayashi 1-1 Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka Shin Nippon Steel shares Company Yawata Steel Works (72) Inventor Toshiyuki Shiraishi 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technology Development Division (56) References JP 2000-2944 (JP, A) (58) Survey Fields (Int.Cl. ⁷ , DB name) C21D 8/12 B21B 3/00 H01F 1/16 C22C 38/00 303 C22C 38/06 C22C 38/60

Claims (4)

(57) [Claims] 1. C: 0.025 to 0.100 in mass%.
%, Si: 2.5-4.5%, Al: 0.007-0.
After hot rolling an electromagnetic steel slab containing 040%, hot rolled sheet annealing is performed once cold rolling, or two or more cold rolling with intermediate annealing interposed, and then In the method for producing a grain-oriented electrical steel sheet, in which primary recrystallization annealing and then secondary recrystallization annealing are performed, final cold rolling is performed with a levers mill, and final cold rolling in the cold rolling is performed.
With the work roll with a diameter of 95-180 mmφ
Cold rolling to an intermediate plate thickness of at least 0.40 mm or less
From the intermediate plate thickness to the final plate thickness T _f (mm)
Rolling with a diameter D (mmφ) of D ≦ T _f × 520
A method for manufacturing a grain-oriented electrical steel sheet , comprising cold rolling with a work roll . 2. A least one of the inter-pass of the final cold rolling in the cold rolling, claims, characterized in that to retain at least a minute or more strips temperature in the range of 100 to 350 ° C. 1. The method for producing a unidirectional electrical steel sheet according to 1 . 3. The grain- oriented electrical steel sheet according to claim 1, wherein the product sheet thickness is 0.23 mm or less.
Manufacturing method. 4. In the cold rolling, a cluster type reversing mill comprising a housing that can be divided into upper and lower parts is used, and the work rolls having different diameters are exchanged in a plate thickness step in the middle of multi-pass rolling. According to the above, the final cold rolling is performed by one rolling mill .
4. The method for manufacturing a grain-oriented electrical steel sheet according to any one of 3 above.