JP2784661B2 - Manufacturing method of high magnetic flux density thin unidirectional magnetic steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention has an easy axis <100> in the rolling direction of a steel sheet. The present invention relates to a method for manufacturing a so-called high magnetic flux density hand-oriented electrical steel sheet having excellent magnetic properties.

(Prior Art) A grain-oriented electrical steel sheet is mainly used as a core material of transformers and other electrical devices, and it is required that magnetic properties have good excitation characteristics and iron loss characteristics.

As a numerical value representing this excitation characteristic, for example, the magnetic field strength 10
Using magnetic flux density B ₁₀ in the 00A / m, the iron loss characteristics iron loss W _17/50 in an alternating current electric flux density 1.7 tesla of 50 hertz (Hz) (T) is used.

By the way, recently, there is a strong demand that iron loss be lower due to the current situation where energy saving is an urgent issue. The unidirectional electromagnetic steel plate is manufactured by growing a so-called Goss structure having a {110} <001> orientation by finish refining in the manufacturing process using a secondary recrystallization phenomenon.
In order to enhance the magnetic properties, it is important that the <001> axis is highly aligned in the rolling direction and the {110} plane is stably developed with secondary recrystallized grains parallel to the steel sheet surface. As a method of greatly reducing iron loss, there is a magnetic domain refinement technique. In order to make the most of the iron loss improving effect, it is important to increase the crystal grain size after secondary recrystallization.

It is said that for this purpose, it is necessary to optimize the rolling reduction at the time of final high-pressure cold rolling and to perform warm rolling.

Various studies have been made on the method of cold rolling under high pressure. For example, in the method described in Japanese Patent Publication No. 50-26493,
A cold rolling method of an electrical steel sheet containing small amounts of C and Al has been proposed. This is done when the rolling reduction at the time of final strong cold rolling is 81-95% and the material temperature is in the range of 50-350 ° C, and the thermal effect duration changes according to the material temperature.
A slight change in the slip system during cold rolling gives a change to the crystallization method of the primary recrystallized grains.
Selective growth of specific orientation crystal grains, specifically,
It is said that it promotes the growth of {110} <001> crystal grains. As a result, high magnetic flux density and low iron loss can be obtained.

By the way, to reduce iron loss, increase of Si content, reduction of thickness of steel sheet, method of applying tension to steel sheet, method of subdividing magnetic domain by applying external strain, etc. There is. However, increasing the Si content makes the steel brittle,
A problem arises in actual production because the cold rolling property is significantly deteriorated. On the other hand, if the thickness of the steel sheet is reduced, for example, to 0.18 mm thickness, the appearance of secondary recrystallization in finish annealing becomes unstable,
Magnetic properties may be degraded. Further, since the application of tension has a limit in the action of tension due to the coated insulating film, it is not expected that iron loss will be significantly reduced. Further, since domain refining is greatly affected by the size of the secondary recrystallized grain size of the material, a technique for increasing the secondary recrystallized grain size of the material is required.

(Problems to be Solved by the Invention) The present invention has a high magnetic flux density and significantly reduced iron loss,
It is another object of the present invention to provide a method of manufacturing a thin unidirectional magnetic steel sheet having an excellent magnetic domain refining effect.

(Means for Solving the Problems) In order to respond to the recent strong demand for low iron loss materials, the present inventors have conducted various experiments and studies on reducing the iron loss of the grain-oriented electrical steel sheet. As a result, using Al N as an inhibitor, when manufacturing a unidirectional electrical steel sheet with a high magnetic flux density, hot-rolling a magnetic steel material containing acid-soluble Al, and in the range of 950-1200 ° C before final strong cold rolling. After high-temperature continuous annealing, it is quenched to precipitate AlN, and is subjected to one or two or more cold rolling operations including a final strong cold rolling operation in a rolling reduction range of 81 to 95%.
In the method of producing a thin unidirectional magnetic steel sheet having a final thickness of 15 to 0.23 mm, decarburized, and finish-annealed, the cold rolling performed at the above-described high reduction rate is performed with a small-diameter roll having a diameter of 30 to 100 mm per unit area. rolling tension under high tension 10~35kg / mm ^2, the front path
Higher flux rate is 30% or more, and the average sheet temperature of the subsequent pass is 0.40mm or less. It has been confirmed that a thin unidirectional magnetic steel sheet having an excellent effect of forming can be manufactured.

C: 0.025-0.085%, Si: 2.5-4.5%
%, Acid-soluble Al (hereinafter referred to as sol.Al): 0.010-0.065%,
Mn: 0.03 to 0.15%, S: 0.010 to 0.050%, N: 0.0030 to 0.0120
%, With the balance consisting of iron and unavoidable impurities. In addition to these components, one or more of Cu, Sn, Cr, and Mo may be contained in a total of 1.5% or less.

 Hereinafter, the present invention will be described in detail.

 First, the steel components of the electromagnetic steel material of the present invention will be described.

C needs to cause r transformation in at least a part of the steel according to the amount of Si when the electromagnetic steel material is heated. Therefore, the content of C is required to be 0.025% or more. On the other hand, if the content is excessive, a product with a high magnetic flux density cannot be obtained.
5% or less. Si is 2.5% to reduce iron loss
The above is necessary. On the other hand, if it exceeds 4.5%, the cold rolling property deteriorates. sol.Al precipitates Al N by annealing before final strong cold rolling, and to obtain a product with high magnetic flux density
0.010% or more is required. On the other hand, as the content increases, it becomes brittle, and it is disadvantageous in terms of cost.
0.065% or less.

N must be contained in an amount of 0.0030 to 0.0120% in order to combine with the sol. Al and form AlN as an inhibitor.

Mn and S are elements necessary for forming MnS,
For this reason, Mn is contained at 0.03% or more. On the other hand, if the content increases, the purification time in finish annealing will be prolonged.
0.15% or less. S is 0.01 for the same reason as for Mn.
0% or more is required and 0.050% or less.

In order to further enhance the magnetic properties, one or more of Cu, Sn, Cr, and Mo may be included. At this time, the upper limit of the total content is 1.5%. If the upper limit is exceeded, the cold rolling property will deteriorate and the decarburization property will deteriorate.

The silicon steel slab containing the above components, the balance being iron and unavoidable impurities, is a molten steel melted into a predetermined component,
Manufactured by continuous casting or by ingot and slab rolling. The silicon steel slab is hot-rolled after being heated to a predetermined temperature or immediately after continuous casting. The hot rolling conditions do not need to be special conditions. The resulting hot-rolled sheet may be cold-rolled once after hot-rolled sheet annealing, or may be cold-rolled two or more times with intermediate annealing as necessary. In the annealing before the final cold rolling (in the case of one-time cold rolling, hot rolled sheet annealing), 950 to 1200
Continuous annealing is performed by heating to a high temperature of ℃ and then rapidly cooling. The cold rolling is carried out one or more times, including the final strong rolling at a rolling reduction of 81 to 95%, but the final strong rolling is 81 to 95%.
% Is for obtaining excellent magnetic properties in a plate in which the main inhibitor is AlN.

The cold rolling will be described in detail with reference to experimental data.

The hot-rolled sheet-annealed sample composed of the steel components shown in Table 1 was cold-rolled under the following conditions.

Cold rolling conditions Hot rolled sheet (original sheet) sheet thickness: 2.3mm Finished sheet thickness: 0.20mm Total rolling reduction: 91.3% Rolling mill work roll diameter: 70mm φ Rolling tension: 25kg / mm ² Post-pass average sheet temperature: 20 to 350 ° C The hot-rolled sheet subjected to hot-rolled sheet annealing is cold-rolled by changing the average sheet temperature of the subsequent pass having a thickness of 0.40 mm or less in the range of 20 to 350 ° C, and then at 850 ° C for 150 seconds. After decarburizing annealing, applying and drying an annealing separator, finish annealing was performed at 1200 ° C.

The iron loss W _17/50 , magnetic flux density B ₁₀ , crystal grain size, and laser treatment iron loss improvement rate were measured for the thus obtained unidirectional magnetic steel sheet samples 1, 2, and 3, and the results are shown in FIGS. As shown in FIG.

As is clear from these figures, 0.40 mm
In the following post-pass, the average sheet temperature was warm-rolled at 150 to 230 ° C, and the iron loss W _17/50 and magnetic flux density B ₁₀ were greatly improved.
The crystal grain size increases, and the iron loss improvement rate by laser treatment is excellent.

As described above, when warm rolling is performed at the time of final cold rolling, particularly at the time of thinning, the magnetic properties are improved and the crystal grain size is considered to be as follows. In order to obtain the high magnetic flux density which is a feature of this component system, the final cold rolling reduction exceeds 90%, especially for a thin material having a thickness of 0.23 mm or less. On the other hand, in order to improve the magnetism of the final product, it is desirable that the matrix after the primary recrystallization has a large number of (110) grains. But (110)
Since the abundance of grains rapidly decreases at a cold rolling rate of 80% or more,
It is generally difficult to achieve high magnetic flux density and the presence of (110) grains. In particular the work roll diameter is 100mmΦ smaller cold rolling mill, to cold rolling at a high tension of the rolling tension 10~35kg / mm ^2, large-diameter work roll, it makes variations within drawing trend compared with the low tension rolling, relative In addition, (110) grains are further reduced. However, the remaining (110) grains are very sharp, and those subjected to secondary recrystallization show a high magnetic flux density, low loss, and a tendency to the crystal grain size.

In particular, in the case of a thin product, when the sheet pressure during cold rolling is reduced, it is possible to prevent or enrich the (110) grains as described above by increasing the sheet temperature during cold rolling. . Therefore, when manufacturing a product with a plate thickness of 0.23 mm or less, use a cold rolling machine with a work roll (WR) diameter of 100 mm
If you do not apply a high tension of 5 kg / mm ^2, it is difficult to thin to a predetermined thickness, in this case, while compared with the conventional rolling method (110) grains relatively decreased, especially sheer By increasing the sheet temperature during cold rolling to 150-230 ° C, the decrease (110) can be compensated for by the grains, and therefore, the sharp (1)
10) Since grains may be present, a product having a high magnetic flux density, a low iron loss, and a large grain size can be obtained. When the diameter of the work roll is smaller than 30 mmφ, iron loss is deteriorated and the life of the roll is shortened. If the average plate temperature in the subsequent pass with a plate thickness of 0.40 mm or less in the middle is less than 150 ° C, the above-mentioned effects cannot be obtained. Grains are reduced, and the effect of improving properties is lost.

(Example) Example 1 A silicon steel slab shown in Table 2 was hot-rolled to obtain a sheet thickness of 2.
A hot-rolled 3 mm sheet was cold-rolled to a thickness of 1.5 mm, subjected to precipitation annealing of AlN, and finally cold-rolled under the conditions shown in FIG. Thereafter, decarburization annealing was performed at 850 ° C. × 120 seconds, an annealing separator containing MgO as a main component was applied, dried, and then subjected to finish annealing at 1200 ° C. × 20 hours.

The iron loss W _17/50 and the magnetic flux density B ₁₀ were measured for each sample of the _grain- oriented electrical steel sheet manufactured in this manner. The results are shown in FIG. 4 together with the sheet temperature in finish cold rolling.

Example 2 A silicon steel slab composed of the steel components shown in Table 5 was hot-rolled into a hot-rolled sheet having a thickness of 2.4 mm. Next, hot-rolled sheet annealing is performed, finish cold rolling is performed under the conditions shown in Table 6, decarburization annealing is performed at 850 ° C. × 120 seconds, and an annealing separator containing MgO as a main component is applied.
After drying, finish annealing was performed at 1200 ° C. for 20 hours.

The iron loss W _17/50 , the magnetic flux density B ₁₀ , the crystal grain size, and the iron loss improvement rate during laser treatment were measured for each sample of the manufactured grain-oriented electrical steel sheet. The results are shown in Table 7.

(Effects of the Invention) As is clear from the results of the above examples, according to the present invention, a grain-oriented electrical steel sheet with significantly reduced iron loss and excellent laser treatment effect can be manufactured, and The contribution is extremely large.

[Brief description of the drawings]

Fig. 1 shows the relationship between the average sheet temperature and the core loss of 0.40mm or less in the middle of the cold rolling during finishing, and Fig. 2 shows the 0.40mm in the middle of the cold rolling during finishing.
The relationship between the average sheet temperature and the magnetic flux density below, FIG. 3 shows the relation between the average sheet temperature and the crystal grain size of 0.40 mm or less in the middle during finish cold rolling,
FIG. 4 is a graph showing the relationship between the average sheet temperature of a sheet thickness of 0.40 mm or less during finish cold rolling and the iron loss improvement rate by laser treatment.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Katsuro Kuroki Inventor 1-1-1 Edamitsu, Yawatahigashi-ku, Kitakyushu-shi, Fukuoka Prefecture Inside Nippon Steel Corporation 3rd Technical Research Institute (58) Field surveyed (Int. Cl. ⁶ , DB name) C21D 8/12

Claims (2)

(57) [Claims] C .: 0.025 to 0.085% by weight, Si: 2.5 to 4.5% by weight.
%, Acid soluble Al: 0.010 ~ 0.065%, Mn: 0.03 ~ 0.15%, S: 0.
Hot rolled electromagnetic steel slab containing 010 ~ 0.050%, N: 0.0030 ~ 0.0120%, balance is iron and unavoidable impurities, and quenched after continuous annealing at 950 ~ 1200 ° C before final strong cold rolling , AlN is precipitated, and is subjected to one or two or more cold rolling operations including a final strong cold rolling operation in a rolling reduction range of 81 to 95%.
In the method for producing a thin unidirectional magnetic steel sheet having a final thickness of 0.23 mm, decarburized, and finish-annealed, the cold rolling performed at the above-described high rolling reduction is performed by a small-diameter roll having a diameter of 30 to 100 mm, and is rolled per unit area. tension under high tension 10~35kg / mm ^2, the front path 30%
A method for producing a thin magnetically unidirectional magnetic steel sheet having a high magnetic flux density, characterized in that the above-mentioned high-pressure reduction is performed, and the average sheet temperature of a subsequent pass whose sheet thickness is 0.40 mm or less is 150 to 230 ° C. 2. C .: 0.025 to 0.085% by weight, Si: 2.5 to 4.5% by weight.
%, Acid soluble Al: 0.010 ~ 0.065%, Mn: 0.03 ~ 0.15%, S: 0.
010 to 0.050%, N: 0.0030 to 0.0120%, Cu, S
One or two or more of n, Cr and Mo are contained in a total of 1.5% or less, and the remainder is hot-rolled from an electromagnetic steel slab composed of iron and unavoidable impurities. Quenching after continuous annealing in the range, AlN is precipitated, and the final sheet thickness is 0.15 to 0.23 mm by one or more cold rolling including final strong cold rolling performed in the rolling reduction range of 81 to 95%, In the method for producing a thin unidirectional magnetic steel sheet to be decarburized and subjected to finish annealing, the cold rolling performed at the high reduction rate is performed using a small-diameter roll having a diameter of 30 to 100 mm, and the rolling tension per unit area is 10 to 35 kg / mm ^2. The pre-pass is performed at a high pressure reduction of 30% or more under high tension of
A method for producing a high magnetic flux density thin unidirectional magnetic steel sheet, wherein the average sheet temperature of the following second pass is 150 to 230 ° C.