JP3527276B2 - Manufacturing method of ultra high magnetic flux density unidirectional electrical 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 for producing an ultrahigh magnetic flux density unidirectional electrical steel sheet having a highly developed degree of {110} <001> orientation used as an iron core of a transformer or the like.

[0002]

2. Description of the Related Art Unidirectional electrical steel sheets are mainly used as iron core materials for transformers and other electric equipment, and are required to have excellent magnetic characteristics such as excitation characteristics and iron loss characteristics. The value that shows the excitation characteristics is usually 800 A /
Magnetic flux density B in a magnetic field of m (this is shown below as B ₈ )
Is used. W _17/50 (iron loss per unit kg when magnetized to 1.7 T at a frequency of 50 Hz) is used as a representative numerical value representing the iron loss characteristic.

The magnetic flux density is an important controlling factor of the iron loss characteristics, and generally speaking, the higher the magnetic flux density, the better the iron loss. However, if the magnetic flux density becomes too high, the abnormal eddy current loss may increase due to the increase in the size of the secondary recrystallized grains, which may deteriorate the iron loss. On the other hand, iron loss can be improved by controlling the magnetic domains regardless of the secondary recrystallized grains. The product thickness is also an important controlling factor of iron loss characteristics. By reducing the plate thickness while maintaining the magnetic flux density, the eddy current loss is reduced and the iron loss characteristics can be improved.

The unidirectional electrical steel sheet undergoes secondary recrystallization during finish annealing in the manufacturing process to cause {110},
It is obtained by developing a so-called Goss structure having <001> in the rolling direction. Among them, B ₈ ≧ 1.
Those having excellent excitation characteristics of 88T are called high magnetic flux density grain-oriented electrical steel sheets. As a typical method for producing a high magnetic flux density grain-oriented electrical steel sheet, Taguchi et al.
No. 15644 and Japanese Patent Publication No. 51-13469. MnS and AlN are used in the former, and MnS, MnSe, Sb, etc. are used in the latter as main inhibitors that cause secondary recrystallization of the Goss structure. Products based on the above patents are currently produced on a global scale. According to Japanese Examined Patent Publication No. 40-15644, the manufacturing method is as follows.
The feature is that cold rolling is performed once to 95%.

However, the manufacturing method according to Japanese Patent Publication No. 40-15644 has the following problems. First, when attempting to thin the product sheet thickness of 0.23 mm or less as one of the measures to reduce iron loss, it was caused by the crystal structure and texture after cold rolling and primary recrystallization, or the inhibitor behavior during finish annealing. Secondary recrystallization becomes unstable, and B ₈ ≧ 1.88T cannot be stably obtained. In particular, it is known that the crystal structure and texture after cold rolling and primary recrystallization strongly depend on the cold rolling rate for finishing a hot rolled sheet into a product sheet thickness. Therefore, in order to stably obtain B ₈ ≧ 1.88 T, a so-called two-time cold rolling method in which preliminary cold rolling is performed before hot-rolled sheet annealing is a method for maintaining an optimum cold rolling rate.
It is proposed in Japanese Patent No. 2 publication. Further, JP-B-62-50529 discloses that so-called pre-annealing in which annealing is performed before preliminary cold-rolling in the double cold-rolling stabilizes secondary recrystallization and B ₈ ≧ 1.88 T is obtained. Has been introduced.

In any case, 0.23 mm or less 0.1
While trying to reduce the product plate thickness of 5 mm or more, B ₈ ≧ 1.
In order to obtain 88T stably, it is necessary to perform preliminary cold rolling, or further to perform preliminary cold rolling and then preliminary cold rolling, or to perform main annealing, and it is essential to increase costs with the increase in the number of processes. Is. Another attempt to maintain the optimum cold rolling rate is thinning of the hot rolled sheet. However, there is a problem that it is difficult to secure the finish hot rolling temperature for avoiding the above AlN precipitation in the hot rolling process, or there is a problem that productivity is reduced, and various problems are involved in stable production.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to avoid such a problem and to provide a method for manufacturing a grain-oriented electrical steel sheet having a very high magnetic flux density.

[0008]

The features of the present invention are as follows. 1) wt%, C: 0.03 to 0.15%, S
i: 2.5 to 4.0%, Mn: 0.02 to 0.30%,
S and / or Se: 0.005-0.040%, acid-soluble Al: 0.010-0.065%, N: 0.0
030 to 0.0150%, Bi: 0.0005 to 0.0
5%, balance: Fe and a slab consisting of unavoidable impurities as a starting material , the slab was heated to 1350 ° C. or higher , hot-rolled, then hot-rolled sheet annealed, and then cold-rolled.
81-94.25 % 0.23 to 0.15 in one strong cold rolling
B ₈ ≧ by decarburization annealing and finish annealing after obtaining the product thickness of mm.
A method for producing an ultra-high magnetic flux density grain- oriented electrical steel sheet, characterized in that the iron loss is 1.94 T and a low iron loss is obtained after the magnetic domain refinement treatment .

2) In addition , Sn: 0.05-
B according to 1) above, which contains 0.50%.
₈ ≧ 1.94 T Ultra-high magnetic flux density grain-oriented electrical steel sheet manufacturing method.

3) C: 0.03 to 0.15 by weight%
%, Si: 2.5 to 4.0%, Mn: 0.02
0.30%, S and / or Se: 0.005 to 0.
040%, acid soluble Al: 0.010 to 0.065%,
N: 0.0030 to 0.0150%, Sn: 0.05
~ 0.50%, Cu: 0.01-0.10%, B
i: 0.0005 to 0.05%, balance: Fe and a slab consisting of inevitable impurities as a starting material , and the slab was 1
After heating to 350 ° C or higher , hot rolling, and then hot-rolled sheet annealing, cold rolling rate 81 to 94.25 %, single strong cold rolling 0.23 to 0.15 mm product sheet thickness To obtain B ₈ ≧ 1.94 T by decarburization annealing and finish annealing , and subdividing the magnetic domains.
A method for producing an ultra-high magnetic flux density grain- oriented electrical steel sheet, characterized in that a low iron loss is obtained after the treatment .

The details of the present invention will be described below. The present invention has earnestly studied variously to further increase the magnetic flux density of a so-called thin high magnetic flux density unidirectional electrical steel sheet without increasing the manufacturing process. After the slab for heat-resistant electrical steel sheet is heated as a starting material, it is hot-rolled, then hot-rolled sheet is annealed, and then cold-rolled, decarburized, and finish-annealed. Cold rolling rate 81-94.
0.23 to 0 by performing 25% of the single strength cold rolled.
At product thickness of 15 mm, B ₈ ≧ 1.94 T
High magnetic flux density and low iron loss due to magnetic domain refinement processing
We have succeeded in producing a super high magnetic flux density unidirectional electrical steel sheet that can be manufactured.

The component conditions of the present invention will be described. If C is less than 0.03%, crystal grains grow abnormally during slab heating prior to hot rolling, and secondary recrystallization defects called linear fine grains occur in the product, which is not preferable. On the other hand, when the content exceeds 0.15%, decarburization annealing after cold rolling requires a long time for decarburization, which is not economical, and the decarburization is likely to be incomplete, resulting in a magnetic aging called magnetic aging in the product. It is not preferable because it causes defects. Si is an extremely effective element for increasing the electrical resistance of steel and reducing the eddy current loss that constitutes a part of iron loss, but if it is less than 2.5%, the eddy current loss of the product cannot be suppressed. Further, if it exceeds 4.0%, the workability is remarkably deteriorated and cold rolling at room temperature becomes difficult, which is not preferable.

Mn is an important element that forms MnS and / or MnSe, which is called an inhibitor that influences secondary recrystallization. If it is less than 0.02%, the absolute amount of MnS necessary for causing secondary recrystallization is insufficient, which is not preferable. On the other hand, if it exceeds 0.30%, not only is it difficult to form a solid solution during heating of the slab, but also the precipitation size during hot rolling tends to become coarse, and the optimum size distribution as an inhibitor is impaired, which is not preferable. S and / or Se
Is an important element forming Mn and MnS and / or MnSe described above. If it deviates from the above range, a sufficient inhibitory effect cannot be obtained, so 0.005-0.04
It should be limited to 0%.

Acid-soluble Al is the main inhibitor constituent element for high magnetic flux density grain-oriented electrical steel sheets, and is 0.0
If it is less than 10%, the amount is insufficient and the inhibitor strength is insufficient, which is not preferable. On the other hand, if it exceeds 0.065%, AlN precipitated as an inhibitor becomes coarse and, as a result, the inhibitor strength is lowered, which is not preferable. N is an important element that forms AlN with the acid-soluble Al described above. If it deviates from the above range, a sufficient inhibitory effect cannot be obtained, so it is necessary to limit the content to 0.0030 to 0.0150%.

Further, Sn is effective as an element for stably obtaining secondary recrystallization of thin products, and also has an effect of reducing the secondary recrystallization particle size. In order to obtain this effect, it is necessary to add 0.05% or more, and if it exceeds 0.50%, the action is saturated, so from the viewpoint of cost increase, it is limited to 0.50% or less. Sn for Cu
It is effective as an element for improving the primary coating of added steel. 0.01
If it is less than 0.1%, the effect is small, and if it exceeds 0.10%, the magnetic flux density of the product decreases, which is not preferable.

Bi is 0.23 to 0.15 of the present invention.
of a super high magnetic flux density unidirectional electrical steel sheet, characterized in that cold rolling to obtain B ₈ ≧ 1.94 T at a product sheet thickness of mm is carried out by single strong cold rolling at a cold rolling rate of 81 to 94.25 %. In the manufacturing method, it is an essential element in the starting slab. That is, there is an effect of improving the magnetic flux density. If it is less than 0.0005%, the effect is not sufficiently obtained, and if it exceeds 0.05%, not only the effect of improving the magnetic flux density is saturated, but also cracks occur at the ends of the hot-rolled sheet, which is not preferable. .

The inclusion of Bi in the material for unidirectional electrical steel sheets is described in JP-A-50-72817, JP-A-51-78733, JP-A-53-39922 and the like. However, all of these patents contain S and Se as essential inhibitors, and Sb and As
It is meant as one of the elements having the same action and effect as the above, and is merely positioned as an alternative element of Sb.
Furthermore, these patents do not essentially contain Al as an inhibitor element, and it can be said that these patents have completely different characteristics from the present invention. Furthermore, it is disclosed in JP-A-51-51
It is also described in JP-A-107499 and JP-A-63-100127. Although these patents are similar to the present invention in that they contain Al as an essential inhibitor constituent element, they are all positioned as the same element such as Sb and As, and accordingly, there is no description of an example containing Bi added. .

Next, the manufacturing method of the present invention will be described. The molten steel for producing an ultra-high magnetic flux density unidirectional electrical steel sheet in which the components are adjusted as described above and Bi or a Bi-containing material is added is cast by a usual method. There is no particular limitation on the casting method. Then, it is rolled into a hot rolled coil by ordinary hot rolling. The hot rolled coil is continuously heated at 950 to 1200 ° C for 30
It is annealed for 2 seconds to 30 minutes, and then rapidly cooled to homogenize the crystal structure and control the precipitation of AlN, and at the same time pickled.

After that, the final product sheet thickness is cold-rolled, but in order to obtain B ₈ ≧ 1.94 T at a thin product sheet thickness of 0.23 to 0.15 mm , the cold rolling rate 81 to
It is a feature of the present invention that the single strong cold rolling is performed at 94.25 %. After cold rolling, continuous decarburization annealing / primary coating film forming agent coating, finish annealing, continuous strain relief annealing / secondary coating coating and baking are carried out by usual methods. Further, laser irradiation and magnetic domain subdivision processing such as grooves are performed.

Up to now, thinning of hot-rolled sheet has been attempted as an attempt to maintain an optimum cold rolling rate for obtaining B ₈ ≧ 1.88T in a thin product of 0.23 to 0.15 mm. However, as described above, it becomes difficult to secure the finish hot rolling temperature in the hot rolling process, coarse AlN precipitates and the inhibitor strength decreases, and B ₈ ≧ 1.88 T was not stably obtained. In addition, if the production is carried out once from the normal hot-rolled sheet thickness by strong cold rolling, the cold rolling rate is too high and the {110} <001> nuclei are extremely reduced.
₈ ≧ 1.88T was not stably obtained.

However, by using a slab containing Bi added as a starting material, even if the slab is manufactured by single strong cold rolling, the inhibitor effect of Bi is retained up to a high temperature because of the inhibitor strengthening effect. , Coarse AlN due to difficulty in securing finish hot rolling temperature in hot rolling process
Even if precipitation does not decrease inhibitor strength, thus the {110} <001> it is possible to selectively grow the nuclei, more {110} <001> very good B orientation integration degree ₈ ≧ 1 It is considered that the manufacturing of .94 T has become possible. In addition, the fact that the inhibitor strengthening effect of Bi maintains the inhibitor effect up to a high temperature means that the reduction of {110} <001> nuclei due to the too high cold rolling rate increases the grain boundary migration speed in the high temperature region during finish annealing. It is possible to compensate by selective growth of {110} <001> nuclei at the stage, and it is considered that B ₈ ≧ 1.94 T, which has an extremely high degree of {110} <001> orientation integration, can be manufactured. To be

[0022]

EXAMPLES (Example 1) C: 0.078%, Si: 3.28%, Mn: 0.08
%, S: 0.025%, acid-soluble Al: 0.025%,
A slab containing N: 0.0082% and Bi: 0.0078% was heated at 1350 ° C. and immediately hot rolled to give a hot rolled coil having a thickness of 2.3 mm. The hot rolled coil was annealed at 1050 ° C. and once cold rolled to a thickness of 0.170 mm. Continue to 85
Decarburization annealing was performed at 0 ° C., and a primary coating / annealing separating agent containing MgO as a main component was applied, followed by finish annealing at 1200 ° C. After washing with water, shearing to 60mm width x 300mm length, 850 ℃
After the strain relief annealing was performed, the magnetic field was measured. Table 1 shows the product magnetic flux density. As is clear from Table 1, the slab containing Bi was obtained with B ₈ ≧ 1.94 T after the hot-rolled sheet even in the single strong cold rolling of 92.6%.

[0023]

[Table 1]

Example 2 The product obtained in Example 1 was irradiated with a laser at a pitch of 5 mm to subdivide the magnetic domains. The results are shown in Table 2.
As is clear from Table 2, the material of the present invention has an extremely high magnetic flux density and a thin plate thickness.
It was possible to obtain iron loss characteristics which were not obtained by the conventional method of W / kg or less.

[0025]

[Table 2]

Example 3 The hot rolled coil of Example 1 was annealed at 1050 ° C. and once cold rolled to a thickness of 0.145 mm. The subsequent steps were the same as in Example 1. The results are shown in Table 3. As is clear from Table 3, the slab containing Bi added was subjected to a cold rolling reduction of 9 after hot rolling.
B ₈ ≧ 1.94 T was obtained even after 3.7% single strong cold rolling .

[0027]

[Table 3]

(Example 4) The product obtained in Example 3 was irradiated with laser at a pitch of 5 mm to subdivide the magnetic domains. The results are shown in Table 4.
As is clear from Table 4, the magnetic material of the present invention has an extremely high magnetic flux density and a thin plate thickness.
It was possible to obtain iron loss characteristics which were not obtained by the conventional method of W / kg or less.

[0029]

[Table 4]

(Example 5) C: 0.079%, Si: 3.29%, Mn: 0.08
%, S: 0.025%, acid-soluble Al: 0.025%,
N: 0.0084%, Sn: 0.12%, Bi: 0.0
The slab containing 033% was heated at 1350 ° C. and immediately hot rolled to give a hot rolled coil having a thickness of 2.3 mm. The hot rolled coil was annealed at 1050 ° C. and once cold rolled to a thickness of 0.220 mm. The subsequent steps were the same as in Example 1. The product magnetic flux density is shown in Table 5. As is clear from Table 5, the slab containing Bi was obtained with B ₈ ≧ 1.94 T even after the hot-rolled sheet and even after the single strong cold rolling of the cold rolling rate of 90.4%.

[0031]

[Table 5]

Example 6 The hot rolled coil of Example 5 was annealed at 1050 ° C. and once cold rolled to a thickness of 0.170 mm. The subsequent steps were the same as in Example 1. The results are shown in Table 6. As is clear from Table 6, the slab containing Bi added was 9% cold rolled after hot rolling.
B ₈ ≧ 1.94 T was obtained even in a single strong cold rolling of 2.6%.

[0033]

[Table 6]

(Example 7 ) C: 0.078%, Si: 3.30%, Mn: 0.08
%, Se: 0.026%, acid-soluble Al: 0.026
%, N: 0.0084%, Sn: 0.12%, Cu:
A slab containing 0.074% and Bi: 0.0174% was heated at 1350 ° C. and immediately hot rolled to obtain a hot rolled coil having a thickness of 2.3 mm. The hot rolled coil is annealed at 1050 ° C,
Cold rolled once to a thickness of 0.220 mm. The subsequent steps were the same as in Example 1. Table 7 shows the product magnetic flux density. As is apparent from Table 7, after the slab has been added containing Bi is hot-rolled sheet, B ₈ ≧ 1.94 at once strong cold rolled in cold rolling ratio 90.4%
T has been obtained.

[0035]

[Table 7]

Example 8 The hot rolled coil of Example 7 was annealed at 1050 ° C. and once cold rolled to a thickness of 0.145 mm. The subsequent steps were the same as in Example 1. The results are shown in Table 8 . As is clear from Table 8 , the slab containing Bi added was subjected to a cold rolling reduction of 9 after hot rolling.
B ₈ ≧ 1.94 T was obtained even after 3.7% single strong cold rolling .

[0037]

[Table 8]

(Example 9 ) C: 0.078%, Si: 3.30%, Mn: 0.08
%, Se: 0.025%, acid-soluble Al: 0.026
%, N: 0.0084%, Sn: 0.12%, Cu:
Bi of 0 to 0.048% in molten steel containing 0.074%
The slab containing the addition was heated at 1350 ° C. and immediately hot rolled to obtain a hot rolled coil having a thickness of 1.8 mm. 105 for hot rolled coil
It was annealed at 0 ° C. and once cold rolled to a thickness of 0.170 mm.
The subsequent steps were the same as in Example 1. The product magnetic flux density is shown in FIG. At Bi = 3 ppm, B ₈ = 1.912T, which is almost no effect on improving the magnetic flux density.
At i = 5 ppm, B ₈ = 1.968T, which is a remarkable magnetic flux density improving effect.

Example 10 C: 0.078%, Si: 3.30%, Mn: 0.08
%, Se: 0.025%, acid-soluble Al: 0.026
%, N: 0.0084%, Sn: 0.12%, Cu:
A slab containing 0.074% and Bi = 0.08% was heated at 1350 ° C. and immediately hot rolled to obtain a hot rolled coil having a thickness of 1 to 5 mm. The hot rolled coil was annealed at 1050 ° C. and once cold rolled to a thickness of 0.230 mm. Subsequent steps are those in Example 1.
I went the same way. The product magnetic flux density is shown in FIG.

Hot-rolled sheet thickness 1.0 mm, that is, cold rolling rate = 77.0
%, B ₈ = 1.866T, hot rolled sheet thickness 1.1 mm, ie cold rolling rate = 79.1%, B ₈ = 1.902 T, hot rolled sheet thickness 5.0 mm, ie cold rolling rate = 95.4%, B ₈
= 1.870T, while the hot-rolled sheet thickness is 1.4 mm,
That is, when the cold rolling rate = 83.6%, B ₈ = 1.978T,
When the hot-rolled sheet thickness is 2.0 mm, that is, when the cold rolling rate is 88.5%, B
₈ = 1.992T, hot rolled sheet thickness 2.3 mm, that is, cold rolling rate = 9
In the case of 0.0%, B ₈ = 1.985T, hot rolled sheet thickness 4.0
mm, that is, when the cold rolling rate is 94.25%, B ₈ = 1.94
0T was obtained, and it can be said that all are ultrahigh magnetic flux densities.

[0041]

The hot rolling coil obtained from the slab for a grain- oriented electrical steel sheet containing Bi is cold-rolled at 81 to 94.25.
%, A product with a plate thickness of 0.23 to 0.15 mm is produced by a single strong cold rolling, and a product with an extremely high magnetic flux density of B ₈ ≧ 1.94 T is obtained, and the iron loss after magnetic domain refinement treatment is obtained. It has extremely excellent characteristics and can be said to be industrially very valuable and valuable.

[Brief description of drawings]

FIG. 1 is a chart showing the relationship between the Bi addition content and the magnetic flux density B ₈ .

FIG. 2 is a chart showing the relationship between cold rolling rate and magnetic flux density B ₈ .

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Claims (3)

(57) [Claims] 1. By weight%, C: 0.03-0.15%, Si: 2.5-4.0%, Mn: 0.02-0.30%, S and / or Se: 0. 005 to 0.040%, acid-soluble Al: 0.010 to 0.065%, N: 0.0030 to 0.0150%, Bi: 0.0005 to 0.05%, balance: Fe and unavoidable impurities the becomes slabs as the starting material, after heating the slab to above 1350 ° C., heat rolled, then the after subjected to hot rolled sheet annealing, cold rolling ratio 81-9
To obtain a product thickness of 0.23~0.15mm 4.25 percent one strong cold rolled, B ₈ ≧ 1.94 by decarburization annealing, finish annealing
A method for producing an ultra-high magnetic flux density unidirectional electrical steel sheet, wherein T is T and a low iron loss is obtained after the magnetic domain subdivision processing . 2. Further , Sn: 0.05-0.
50% is contained, The manufacturing method of the ultra high magnetic flux density grain-oriented electrical steel sheet of Claim 1 characterized by the above-mentioned. 3. By weight%, C: 0.03-0.15%, Si: 2.5-4.0%, Mn: 0.02-0.30%, S and / or Se: 0. 005 to 0.040%, acid-soluble Al: 0.010 to 0.065%, N: 0.0030 to 0.0150%, Sn: 0.05 to 0.50%, Cu: 0.01 to 0. 10%, Bi: 0.0005 to 0.05%, balance: Fe and a slab consisting of unavoidable impurities as a starting material , the slab is heated to 1350 ° C. or higher , hot rolled, and then hot rolled sheet annealing After applying the cold rolling rate 81 to 9
To obtain a product thickness of 0.23~0.15mm 4.25 percent one strong cold rolled, B ₈ ≧ 1.94 by decarburization annealing, finish annealing
A method for producing an ultra-high magnetic flux density unidirectional electrical steel sheet, wherein T is T and a low iron loss is obtained after the magnetic domain subdivision processing .