JPH08188825A - Manufacturing method of slab for ultra high magnetic flux density grain-oriented electrical steel sheet - Google Patents

Abstract

(57) [Summary] [Purpose] A predetermined amount of essential elements for producing ultra-high magnetic flux density grain-oriented electrical steel sheets used for transformers is added in good yield. [Structure] Bi, Pb, Ca, and Mg elements are added in a tundish to form a slab. [Effect] Since the yield reaches 45% or more by the above method, a predetermined amount can be easily contained, and stable production of a slab for ultra-high magnetic flux density grain-oriented electrical steel sheet, which has never been possible, and low cost are possible. Becomes

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 a slab used for producing an ultrahigh magnetic flux density unidirectional electrical steel sheet having a highly developed {110} <001> orientation integration degree used as an iron core of a transformer or the like. Regarding

[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 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.

Typical methods for producing high magnetic flux density unidirectional electrical steel sheets are Japanese Patent Publication No. 40-15644 and Japanese Patent Publication No. 51-13469 by Taguchi et al. In the former, MnS and AlN were used as the main inhibitors that caused the secondary recrystallization of the Goss structure.
In the latter, MnS, MnSe, Sb, etc. are used. 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.
It is characterized by performing cold rolling.

By the way, recently, by Takashima et al., B ₈ ≧
An ultra-high magnetic flux density grain-oriented electrical steel sheet having an excellent excitation characteristic of 1.95T has been reported. As a typical example,
JP-A-6-88174 can be cited. According to this, 0.0005 to 0.0500% of Bi is contained. However, since Bi is an element having a low boiling point and a high vapor pressure, it is difficult to effectively enter the molten steel, the yield is poor, and each effect may not be sufficiently satisfied.

Such elements include Pb and C in addition to Bi.
a, Mg, etc. may be mentioned. Each of these elements is a low boiling point element and exhibits a high vapor pressure of 1 mmHg or more at a molten steel temperature of 1450 to 1550 ° C.

In order to improve the yield of the above-mentioned elements, the present inventors have tried to add the above-mentioned elements by using a converter or a ladle during secondary refining in order to improve the yield of the above-mentioned elements, but the yield is not stable. However, it was difficult to obtain the predetermined content. Further, there is a problem that the addition cost is high because a predetermined amount cannot be obtained.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to avoid such problems and to enable stable production and cost reduction of slabs for unidirectional electrical steel sheets having extremely high magnetic flux density.

[0010]

The features of the present invention are as follows. (1) While pouring molten steel containing Si: 2.5 to 4.0% by weight from a ladle into a tundish, B
One of i, Pb, Ca, and Mg, or two or more elements are added in a tundish to form 0.0005-
A method for producing a slab for an ultra-high magnetic flux density unidirectional electrical steel sheet, which comprises a slab containing 0.0500%.

(2) C: 0.03 to 0.15 by weight%
%, Si: 2.5 to 4.0%, Mn: 0.02 to 0.3
0%, S and / or Se: 0.005-0.040
%, Acid-soluble Al: 0.010 to 0.065%, N:
0.0030 to 0.0150%, Bi, Pb, Ca, M
Any one of g, or two or more: 0.0005
Molten steel consisting of 0.0500%, balance: Fe and unavoidable impurities is poured into a tundish from a ladle, and at least one of Bi, Pb, Ca, and Mg is tundished. Added in 0.00
A method for producing a slab for ultra-high magnetic flux density unidirectional electrical steel sheet, which comprises a slab containing 05 to 0.0500%.

(3) C: 0.03 to 0.15 by weight%
%, Si: 2.5 to 4.0%, Mn: 0.02 to 0.3
0%, S and / or Se: 0.005-0.040
%, Acid-soluble Al: 0.010 to 0.065%, N:
0.0030 to 0.0150%, Sn: 0.05 to 0.
50%, one kind of Bi, Pb, Ca, Mg, or two or more kinds: 0.0005 to 0.0500%, the balance:
Molten steel consisting of Fe and unavoidable impurities is poured into a tundish from a ladle, and at the same time Bi, Pb, Ca,
For ultra-high magnetic flux density unidirectional electrical steel sheet, characterized in that one kind of Mg or two or more kinds of elements are added in a tundish to form a slab containing 0.0005 to 0.0500% Slab manufacturing method.

(4) C: 0.03 to 0.15 by weight%
%, Si: 2.5 to 4.0%, Mn: 0.02 to 0.3
0%, S and / or Se: 0.005-0.040
%, 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, Pb, C
Any one of a and Mg, or two or more: 0.00
05-0.0500%, balance: Fe and molten steel consisting of unavoidable impurities are poured into a tundish from a ladle, and at least one of Bi, Pb, Ca and Mg is added,
Or add two or more elements in a tundish,
A method for producing a slab for ultrahigh magnetic flux density grain-oriented electrical steel sheet, which comprises a slab containing 0.0005 to 0.0500%.

(5) C: 0.03 to 0.15 by weight%
%, Si: 2.5 to 4.0%, Mn: 0.02 to 0.3
0%, S and / or Se: 0.005-0.040
%, Acid-soluble Al: 0.010 to 0.065%, N:
0.0030 to 0.0150%, Sb and / or M
o: 0.0030 to 0.30%, Bi, Pb, Ca, M
Any one of g, or two or more: 0.0005
Molten steel consisting of 0.0500%, balance: Fe and unavoidable impurities is poured into a tundish from a ladle, and at least one of Bi, Pb, Ca and Mg is tundished. Added in 0.00
A method for producing a slab for ultra-high magnetic flux density unidirectional electrical steel sheet, which comprises a slab containing 05 to 0.0500%.

The details of the present invention will be described below. The present inventor has found that Bi, Pb, C having so-called low boiling point and high vapor pressure
As a result of various studies to further improve the production stability of slabs for ultra-high magnetic flux density grain-oriented electrical steel sheets containing a predetermined amount of a and Mg elements, the yield was dramatically increased by adding them in the tundish. We have succeeded in stable manufacturing and cost reduction of slabs for ultra-high magnetic flux density grain-oriented electrical steel sheets.

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 products. 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 it becomes difficult to cool at room temperature, which is not preferable.

Mn is an important element that forms MnS and / or MnSe 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 are Mn and M listed above.
It is an important element that forms nS and / or MnSe. If it deviates from the above range, a sufficient inhibitory effect cannot be obtained, so it is necessary to limit the content to 0.005 to 0.040%.

Acid-soluble Al is a main inhibitor constituent element for high magnetic flux density grain-oriented electrical steel sheet, 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 mentioned above. If it deviates from the above range, a sufficient inhibitory effect cannot be obtained, so 0.0030 to 0.0
It should be limited to 150%.

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 grain 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.

Cu is effective as an element for improving the primary coating of Sn-added steel. If it is less than 0.01%, the effect is small, and if it exceeds 0.10%, the magnetic flux density of the product decreases, which is not preferable.

Sb and / or Mo are effective as elements for stably obtaining secondary recrystallization of thin products.
In order to obtain this effect, addition of 0.0030% or more is necessary, and when it exceeds 0.30%, its action is saturated, so from the viewpoint of cost increase, it is limited to 0.30% or less.

Next, the manufacturing method of the present invention will be described. First, the above components excluding Bi, Pb, Ca, and Mg are subjected to secondary refining in a converter and then in a ladle to adjust the components. And Bi, Pb, Ca, M which are indispensable for obtaining super high magnetic flux density
The feature of the present invention is to add g together with pouring molten steel from a ladle into a tundish.

Until now, attempts have been made to add the above-mentioned elements in a converter or a ladle during secondary refining, but the yield was not stable, and it was difficult to obtain a predetermined content.
In addition, since the yield was not good, it was necessary to increase the amount of input, and the addition cost was very high. However, it has been clarified that the yield is dramatically improved and the predetermined amount can be easily obtained by limiting the addition place to the tundish.

It is considered that in the case of the tundish, the yield is improved because the molten steel temperature is 1560 ° C. or lower, which is lower than the molten steel temperature in the converter or the ladle during the secondary refining. This means that the input amount can be drastically reduced and the addition cost can be expected to be reduced.

When considering only the temperature of molten steel, it may be considered that a mold is added. However, in the case of adding a mold,
Although the yield is certainly improved, there is a problem that the ultra-high magnetic flux density effect cannot be stably obtained because it cannot be uniformly dispersed in the molten steel.

[0029]

【Example】

(Example 1) C: 0.078%, Si: 3.28%, M
n: 0.08%, S: 0.025%, acid-soluble Al:
After adjusting the molten steel composition to 0.025% and N: 0.0082%, pour the molten steel into the tundish from the ladle and add the amount of 100 ppm assuming that Bi is retained at 100%. I made it a slab. For comparison, RH was also added. The results are shown in Table 1.

[0030]

[Table 1]

As is clear from Table 1, the Bi yield amount is excellent when the tundish is added.

(Example 2) C: 0.079%, Si:
3.29%, Mn: 0.08%, S: 0.025%, acid-soluble Al: 0.025%, N: 0.0084%, S
After adjusting the molten steel composition to n: 0.12%, pouring the molten steel into the tundish from the ladle and adding it to a slab, assuming that the Bi content is 50 ppm, assuming a 100% yield. . For comparison, DH was also added.
Table 2 shows the results.

[0033]

[Table 2]

As is clear from Table 2, the Bi yield amount is excellent when the tundish is added.

(Example 3) C: 0.078%, Si:
3.30%, Mn: 0.08%, Se: 0.026%,
Acid-soluble Al: 0.026%, N: 0.0084%, S
After adjusting the molten steel composition to n: 0.12% and Cu: 0.074%, pour the molten steel into the tundish from the ladle, assuming that the Bi content is 150 ppm assuming 100% yield. Was added together with it to form a slab. For comparison, addition in a converter was also performed. The results are shown in Table 3.

[0036]

[Table 3]

As is clear from Table 3, when the tundish is added, the Bi yield amount is excellent.

Example 4 C: 0.078%, Si:
After adjusting the molten steel composition to 3.28%, Mn: 0.08%, S: 0.025%, acid-soluble Al: 0.025%, N: 0.0082%, it was assumed that Pb was retained at 100%. In this case, the content of 100 ppm was added to the tundish by adding molten steel from a ladle to form a slab.
For comparison, addition in a converter was also performed. The results are shown in Table 4.

[0039]

[Table 4]

As is clear from Table 4, the Pb yield is excellent when added in the tundish.

Example 5 C: 0.078%, Si:
After adjusting the molten steel components to 3.28%, Mn: 0.08%, S: 0.025%, acid-soluble Al: 0.025%, and N: 0.0082%, it was assumed that Ca had a 100% yield. In this case, the content of 200 ppm was added at the same time as the molten steel was poured into the tundish from the ladle to form a slab.
For comparison, RH was also added. The results are shown in Table 5.

[0042]

[Table 5]

As is clear from Table 5, the Ca yield amount is excellent when added in the tundish.

(Example 6) C: 0.077%, Si:
3.25%, Mn: 0.08%, S: 0.025%, acid-soluble Al: 0.028%, N: 0.0082%, S
After adjusting the molten steel components to n: 0.010% and Cu: 0.07%, Bi was poured into the tundish from the ladle at the same time Bi was added to form a slab. For comparison, RH was also added.

The slab was heated at 1350 ° C. and immediately hot rolled to a hot rolled coil having a thickness of 2.3 mm, further annealed at 1100 ° C., and once cold rolled to a thickness of 0.220 mm.

Subsequently, decarburization annealing is performed at 850 ° C. to obtain Mg
After applying the primary coating and annealing separator containing O as a main component, 12
Finish annealing was performed at 00 ° C. After washing with water, 60mm width x 300
It was sheared to a length of mm, subjected to strain relief annealing at 850 ° C., and then subjected to magnetic measurement.

Table 6 shows the place where Bi is added, the input amount, the content, the yield rate, and the magnetic flux density of the product.

[0048]

[Table 6]

When adding by TD, B ₈ ≧ 1.95T
It can be seen that the input amount for obtaining the ultra high magnetic flux density of 1 is less than 1/10 of that in the case of RH.

[0050]

Bi, Pb, C having low boiling point and high vapor pressure
By adding the elements a and Mg in the tundish, the yield is extremely excellent, and a slab containing a predetermined amount can be stably manufactured. As a result, a product having an extremely high magnetic flux density of B ₈ ≧ 1.95T can be obtained stably and at low cost, which is industrially very valuable and useful.

Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location C22C 38/60 (72) Inventor Kunihide Takashima 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technical Development Division

Claims (5)

[Claims] 1. Molten steel containing Si: 2.5 to 4.0% by weight is poured into a tundish from a ladle, and at least one of Bi, Pb, Ca and Mg, or 2 Add more than one element in tundish,
A method for producing a slab for an ultra-high magnetic flux density unidirectional electrical steel sheet, which comprises a slab containing 0005 to 0.0500%. 2. By weight%, C: 0.03 to 0.15%, Si: 2.5 to 4.0%, Mn: 0.02 to 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%, any one kind of Bi, Pb, Ca, Mg, or two or more kinds: 0.0005-0.0500%, balance: Molten steel consisting of Fe and unavoidable impurities is poured into a tundish from a ladle, and Bi, Pb,
Add any one of Ca and Mg, or two or more elements in a tundish, and add 0.0005 to 0.050.
A method for producing a slab for ultra-high magnetic flux density unidirectional electrical steel sheet, which is a slab containing 0%. 3. By weight%, C: 0.03 to 0.15%, Si: 2.5 to 4.0%, Mn: 0.02 to 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%, Bi, Pb, Ca, Mg Any one kind or two kinds or more: 0.0005 to 0.0500%, the balance: molten steel consisting of Fe and unavoidable impurities is poured into a tundish from a ladle, and Bi, Pb,
Add any one of Ca and Mg, or two or more elements in a tundish, and add 0.0005 to 0.050.
A method for producing a slab for ultra-high magnetic flux density unidirectional electrical steel sheet, which is a slab containing 0%. 4. By weight%, C: 0.03 to 0.15%, Si: 2.5 to 4.0%, Mn: 0.02 to 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%, any one of Bi, Pb, Ca, Mg, or two or more: 0.0005 to 0.0500%, the balance: Fe and molten steel consisting of unavoidable impurities are poured into a tundish from a ladle. As well as Bi, Pb,
Add any one of Ca and Mg, or two or more elements in a tundish, and add 0.0005 to 0.050.
A method for producing a slab for ultra-high magnetic flux density unidirectional electrical steel sheet, which is a slab containing 0%. 5. By weight%, C: 0.03 to 0.15%, Si: 2.5 to 4.0%, Mn: 0.02 to 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%, Sb and / or Mo: 0.0030 to 0.30%, Bi, Pb, One or more of Ca and Mg, or two or more: 0.0005 to 0.0500%, the balance: molten steel consisting of Fe and unavoidable impurities is poured from a ladle into a tundish, and Bi, Pb,
Add any one of Ca and Mg, or two or more elements in a tundish, and add 0.0005 to 0.050.
A method for producing a slab for ultra-high magnetic flux density unidirectional electrical steel sheet, which is a slab containing 0%.