JP2874564B2 - Manufacturing method of non-oriented electrical steel sheet with excellent magnetic properties - 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 a non-oriented electrical steel sheet having excellent magnetic properties and used as an iron core material for rotating equipment such as a motor and a generator.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets are roughly classified into iron core materials for rotating equipment such as generators and electric motors and iron core materials for stationary equipment such as small transformers and ballasts. For electrical equipment, miniaturization or higher efficiency is increasingly required from the viewpoint of recent energy saving, and there is a strong demand for improvement of magnetic properties such as low iron loss and high magnetic flux density of electrical steel sheets. I have. Non-oriented electrical steel sheets for the iron core material of stationary equipment are limited in the direction of magnetization, so it is advantageous to add directionality to the magnetism to improve the characteristics of the equipment. Since the non-oriented electrical steel sheet for use is magnetized in every direction of the sheet surface, the anisotropy of the magnetic properties must be extremely small. Therefore, the magnetic steel sheet for rotating equipment is required to have low anisotropy of magnetic properties and to have low core loss and high magnetic flux density as average magnetic properties in all directions of the plate surface.

[0003] The magnetic properties of non-oriented electrical steel sheets are usually J
As specified in IS-C-2550, evaluation is made by measured values of strip-shaped samples taken from a rolling direction and a direction perpendicular to the rolling direction. The magnetic properties of non-oriented electrical steel sheets evaluated by this method are reflected in the characteristics of stationary equipment whose magnetization direction is limited, but are magnetized in all directions on the plate surface, such as the iron core of rotating equipment. The performance of the iron core of the equipment cannot be properly evaluated. As magnetic properties of magnetic steel sheets for rotating equipment, it is appropriate to evaluate the magnetic properties of a ring sample close to the excited state of the rotating equipment, and it is important that good characteristics can be obtained by this test method. From these facts, recently, the development of non-oriented electrical steel sheets with good magnetic properties in the non-direction within the plate surface, which can obtain good iron loss and magnetic flux density even when measured with ring samples, has been promoted. Various proposals have been made on magnetic steel sheets and methods for manufacturing the same.

For example, C: 0.015% or less, Si:
0.1-1.0%, sol. Al: 0.001 to 0.0
05%, Mn: 1.5% or less, S: 0.008% or less,
N: 0.0050% or less; O: In a non-oriented electrical steel sheet containing 0.02% or less, SiO ₂ and Mn in the steel
Non-oriented electrical steel sheet in which the weight ratio of MnO to the total weight of the three types of inclusions of O and Al ₂ O ₃ is 15% or less (JP-A-63-195217); 0.5% or less, Mn: 1.0% or less, P: 0.2% or less, and the balance is 1% of a material slab substantially made of Fe.
After heating at a temperature of 300 to 1500 ° C. for 10 to 120 minutes and then performing a hot rolling at a finishing temperature of 600 to 800 ° C., a single cold rolling at a reduction of 40 to 85% is performed to obtain a final sheet thickness. Method of performing crystal annealing (JP-A-2-10771
No. 9), Si: 3.3% or less, Al: 1.5 to 8
%, Mn: 0.2% or less. Metal residue (Ni, Mo, T
i, Cu): 0.1% or less, C: 0.3% or less,
S: 0.2% or less, N: 0.2% or less, O: 0.2% or less, P: 0.5% or less, with the balance substantially consisting of Fe being subjected to hot rolling and intermediate annealing. Is produced by two cold rollings and a final annealing performed in the final cold rolling, and a reduction rate of the final cold rolling is 50 to 80%, preferably 60 to 75%, and the steel strip has a cubic crystal structure. And at least 40% of the crystal grains have an ideal cubic orientation (10
0) An electromagnetic steel sheet (Japanese Unexamined Patent Publication No. 3-24251) which does not deviate from [001] by 15 degrees or more has been proposed.

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 63-19 / 1988
The non-oriented electrical steel sheet disclosed in Japanese Patent No.
In order to adjust the ratio of the weight of MnO to the total weight of the three types of inclusions of iO ₂ , MnO and Al ₂ O ₃ to 15% or less,
Since the Si-Mn alloy is added before vacuum degassing,
There is a disadvantage that the loss of n increases and the cost of adding Mn increases. In the method disclosed in Japanese Patent Application Laid-Open No. 2-107719, the slab must be heated at a high temperature of 1300 to 1500 ° C. Not only is it difficult to remove the scale of the rolled steel sheet, but also the energy cost increases and the scale loss increases, which is economically disadvantageous. Furthermore, the electromagnetic steel sheet disclosed in JP-A-3-24251 is cold-rolled twice after intermediate annealing, which complicates the process, increases the manufacturing cost, and is economically disadvantageous. .

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned disadvantages of the prior art and to provide a low-cost, non-directional magnetic in-plane without performing high-temperature heating of a slab or two cold rolling steps with intermediate annealing. An object of the present invention is to provide a method for producing a non-oriented electrical steel sheet having excellent characteristics.

[0007]

Means for Solving the Problems The inventors of the present invention have found that sol. As a result of examining the effect of the amount of Al in detail, it was found that sol. A steel smelt was cast into a slab, and the material was heated to 1000 to 1300 ° C. and then hot-rolled so that the Al content was 0.001% or less.
After winding at a temperature of 50 ° C or more, cold rolling is performed at a rolling reduction of 75% or more, thereby eliminating the need for two cold rolling steps with high-temperature slab heating and intermediate annealing. Finding that the magnetic properties in the circumferential direction are further improved,
The invention has been reached.

That is, according to the present invention, C: 0.004% or less, Si: 1.0% or less, Mn: 0.4% or less, N:
0.004% or less, S: 0.006% or less, O: 0.0
Mn / S ≧ 10, with the balance being F
e and unavoidable impurities, the sol. After making the slab into a slab with the Al content being 0.001% or less, heating to 1000 to 1300 ° C, hot rolling, winding at a temperature of 650 ° C or more, and cold rolling at a reduction of 75% or more. This is a method for producing a non-oriented electrical steel sheet having excellent magnetic properties.

[0009]

According to the present invention, C: 0.004% or less;
Si: 1.0% or less, Mn: 0.4% or less, N: 0.0
04% or less, S: 0.006% or less, O: 0.015%
When melting steel containing Mn / S ≧ 10 and the balance being Fe and unavoidable impurities, the sol. The aluminum content was made 0.001% or less to form a slab, heated to 1000-1300 ° C., hot-rolled, wound at a temperature of 650 ° C. or more, and then reduced at a rate of 75%.
%, The oxide morphology changes to reduce the amount of the Si-Mn-Al-based composite oxide, promote grain growth in the hot-rolled steel sheet, and further perform cold rolling under high pressure. By performing the above, a texture advantageous for the average magnetic properties in the plate surface can be obtained, and an electromagnetic steel sheet excellent in the average magnetic characteristics in the plate surface can be obtained.

[0010] In the present invention, so
l. In the case of an Al trace-based steel having an Al content of 0.001% or less, the oxide is mainly made of a Si—Mn-based oxide,
l. When Si and Mn are added while Al is high, Si-
Al is partially mixed into the Mn-based oxide to have a low melting point (120
(0 ° C. or less), a Si—Mn—Al-based composite oxide is generated, which is considered to expand during hot rolling and inhibit grain growth of the hot-rolled steel sheet. It is well known that the magnetic properties deteriorate when the grain growth of a hot-rolled steel sheet is hindered. That is, in order to improve the magnetic characteristics, Si, Mn
Sol. Before addition. It is necessary to minimize the amount of Al. In the present invention, S is limited to the Al trace system.
sol. before addition of i, Mn. By reducing the amount of Al as much as possible, that is, suppressing the deoxidation by Al during vacuum degassing, Si-Mn-Al-based composite oxides are reduced, and the winding temperature and the rolling reduction of cold rolling are optimized. By doing so, it is possible to improve the average magnetic properties in the plate surface.

[0011] In the present invention, the sol. Al content 0.001
% Is limited to sol. S with high Al
When i and Mn are added, a part of A-
l is mixed and has a low melting point (1200 ° C. or less) of Si—Mn.
-An Al-based composite oxide is generated, which expands during hot rolling, and eliminates the grain growth of the hot rolled sheet, so that the content is 0.001% or less. Re-adding Al after adding alloying elements
Not desirable for similar reasons. The reasons for limiting the chemical components of steel in the present invention are as follows. C is preferably small from the viewpoint of reducing iron loss. If it exceeds 0.004%, an increase in iron loss due to magnetic aging occurs.
04% or less. The lower limit is not particularly limited. Si is an element which effectively contributes to the reduction of iron loss due to the reduction of eddy current loss by increasing specific resistance. Since the abrasion of the punching die becomes severe,
% Or less. Mn is 1 in Mn / S from the viewpoint of hot brittleness.
It is necessary to add 0 or more, but if too much is added, the magnetic flux density is reduced. N is preferably N smaller from the viewpoint of reducing iron loss,
If the content exceeds 0.004%, the amount of nitride increases and the magnetic properties deteriorate, so the content was made 0.004% or less. In addition,
There is no particular limitation on the lower limit. S is Mn between Mn
S is formed to suppress the grain growth of the hot-rolled steel sheet after the finish annealing, to inhibit the grain growth during annealing, to prevent the iron loss from decreasing, and to cause hot brittleness. 00
6% or less. Note that the lower limit of S is not required due to its characteristics. O forms an oxide with Si, Mn, and Al to hinder the growth of crystal grains.

In the present invention, the heating temperature at the time of hot rolling is set to 1000 to 1300 ° C. If the heating temperature is lower than 1000 ° C, the deformation resistance is too large and rolling becomes difficult. If it exceeds 1300 ° C, the slab sags in the heating furnace. Or the scale loss increases, which is economically disadvantageous. The reason why the winding temperature is set to 650 ° C. or higher is that if the temperature is lower than 650 ° C., crystal grains cannot be sufficiently grown. The reduction ratio in cold rolling was set to 75% or more because the reduction ratio was 7%.
By performing cold rolling at a high reduction rate of 5% or more,
This is because the in-plane anisotropy of the magnetic properties of the product is reduced. Note that the upper limit of the rolling reduction in the cold rolling is not set because it is determined solely by operational regulations. In the case of a product having a sheet thickness of 0.5 mm, which is the most common, a sheet thickness of a hot-rolled sheet is as large as 10 mm at a rolling reduction of 95%, and it can be said that a rolling reduction of more than this is practically impossible.

[0013] The cold-rolled steel sheet obtained as described above is annealed for the purpose of recrystallizing the work structure after the cold rolling and sufficiently growing the recrystallized grains, but continuous annealing is generally used. . The non-oriented electrical steel sheet is given a full process product which is shipped with given magnetic properties, and after shipping, after being processed by punching or the like on the user side, is subjected to a strain relief annealing at 750 ° C. for about 2 hours to give a predetermined magnetic property. And a semi-processed product. In the case of a full process product, strain relief annealing may be naturally performed on the user side, and it is required that the product exhibit specified magnetic characteristics not only at the time of shipment but also when the strain relief annealing is performed on the user side. The present invention is intended for both such a full-processed product and a semi-processed product. However, annealing after cold rolling is generally performed at 700 ° C. to 900 ° C. for about 5 seconds or more for a full-processed product. In the case of a process product, the temperature is set at about 650 ° C. to 900 ° C. for about 5 seconds or more. In the case of the present invention, a condition similar thereto may be used. In the case of manufacturing an electromagnetic steel sheet, a step of further applying an insulating coating is usually included. In the case of the present invention, however, it is possible to add a coating step as a final step of the manufacturing. Includes such a case.

[0014]

【Example】

Example 1 As base components, C: 0.003%, Si: 0.2
%, Mn: 0.3%, P: 0.07%, S: 0.005
%, N: 0.003%, O: 0.011 to 0.013%
When smelting steel, alloy elements (S
i, Mn) sol. Heating temperature 1180 ° C, finishing temperature 85
Hot rolling at a winding temperature of 680 ° C. was performed at 0 ° C. After descaling each of the obtained hot-rolled steel sheets, 0.1% was obtained at a rolling reduction of 80%.
After cold rolling to 5 mm, continuous annealing was performed at 830 ° C. for 30 seconds, and the obtained steel sheet was JIS ring (outer diameter of 45 mm).
mm, inner diameter 33 mm), and the magnetic properties in a ring shape were investigated. The result is shown in FIG. The magnetic properties are as follows: iron loss W15 / at a frequency of 50 Hz and a magnetic flux density of 1.5 T.
B5 at 50 and a magnetization force of 5000 A / m
It was rated 0. As shown in Table 1, the iron loss was determined by sol. Al is remarkably low at 0.001% or less. Regarding the magnetic flux density, sol. Al is remarkably large at 0.001% or less. That is, the sol. By controlling the Al content to 0.001% or less, the balance of magnetic properties can be improved.

Example 2 C: 0.002%, Si: 0.2 as base components
%, Mn: 0.3%, P: 0.05%, sol. Al:
0.0007%, S: 0.005%, N: 0.003
%, O: 0.011% steel slab, heating temperature 1200 ° C,
Finishing temperature is 880 ° C and winding temperature is 550-750
C. and hot rolling was performed. After descaling each obtained hot-rolled steel sheet, it was cold-rolled at a reduction of 78% between 0.5 mm and then continuously annealed at 740 ° C. for 30 seconds. Similarly processed into a JIS ring,
The magnetic properties of the ring were investigated. The result is shown in FIG. The magnetic characteristics are frequency 50Hz, magnetic flux density 1.5T
Loss W15 / 50 and magnetizing force 5000A / m in
Was evaluated by the magnetic flux density B50. As shown in FIG. 2, regarding the iron loss, the winding temperature in hot rolling is:
At 650 ° C. or higher, the temperature significantly decreased. As for the magnetic flux density, the winding temperature in hot rolling is significantly increased at 650 ° C. or higher. That is, the balance of magnetic characteristics can be improved by setting the winding temperature of hot rolling to 650 ° C. or higher.

Example 3 C: 0.002%, Si: 0.8 as base components
%, Mn: 0.2%, P: 0.02%, sol. Al:
0.0003%, S: 0.005%, N: 0.002
%, O: 0.008% steel slab, heating temperature 1170 ° C,
Hot rolling was performed at a finishing temperature of 840 ° C. and a winding temperature of 690 ° C. to produce hot-rolled steel sheets of various thicknesses. After descaling each of the obtained hot-rolled steel sheets, 0.1% at a rolling reduction of 65% to 85%.
After cold rolling to 5 mm, continuous annealing was performed at 780 ° C. for 30 seconds, and the obtained steel sheet was subjected to JIS in the same manner as in Example 1.
It was processed into a ring, and the magnetic properties of the ring were investigated. The result is shown in FIG. The magnetic characteristics are frequency 50 Hz,
Evaluation was made based on the iron loss W15 / 50 at a magnetic flux density of 1.5 T and the magnetic flux density B50 at a magnetization force of 5000 A / m. As shown in FIG. 3, regarding the iron loss, the rolling reduction of the cold rolling is remarkably low at 75% or more. As for the magnetic flux density, the rolling reduction in cold rolling is remarkably large at 75% or more. That is, the rolling reduction of the cold rolling is 7
By setting it to 5% or more, the balance of the magnetic characteristics can be improved.

Example 4 A steel having a composition shown in Table 1 was prepared by adding sol. Immediately before the addition of alloying elements (Si, Mn) during vacuum degassing. The aluminum content was varied as shown in Table 2 to produce a slab and a heating temperature of 118
Hot rolling was performed at 0 ° C., a finishing temperature of 850 ° C., and a winding temperature shown in Table 2. After descaling each obtained hot-rolled steel sheet, it was cold-rolled to a rolling reduction of 0.5 mm at a rolling reduction shown in Table 2, and the obtained test No. 780 ° C for cold rolled steel sheets 1-4
No. for 30 seconds. 5 to 11 cold rolled steel sheets at 850 ° C.
Continuous annealing for 0 seconds was performed, and the obtained steel sheet was processed into a JIS ring, and the magnetic properties in the ring shape were investigated. Table 2 shows the results. In addition, * mark in Table 1 and Table 2 shows out of the range of this invention.

[0018]

[Table 1]

[0019]

[Table 2]

As shown in Tables 1 and 2, Test No.
1, No. No. 5 is an electromagnetic steel sheet manufactured under the components and manufacturing conditions within the scope of the present invention, and each shows good magnetic properties excellent in iron loss and magnetic flux density balance. On the other hand, in Test No. in which the Mn content was larger than the range of the present invention. No. 2 is the test No. 1, the magnetic flux density is worse. Test No. S in which the amount of S was larger than the range of the present invention. Test No. 3 shows that MnS was deposited during hot rolling and no grain growth occurred in the hot-rolled steel sheet.
o. Both iron loss and magnetic flux density are worse than those of No. 1. Test No. 0 in which the amount of O was larger than the range of the present invention. No. 4 is the test No. Both iron loss and magnetic flux density are worse than those of No. 1. Test No. 1 in which the Mn / S ratio was lower than the range of the present invention. 6
Was broken and broken during hot rolling, and hot rolling was impossible. Sol. Before addition of alloying elements. Test No. 1 in which the amount of Al was larger than the range of the present invention. In Test Nos. 7 to 9, since a Si-Mn-Al-based composite oxide was formed, which spread during hot rolling and hindered the grain growth of the hot-rolled steel sheet. 5, the test iron loss and the magnetic flux density were both worse. Test No. in which the winding temperature of hot rolling was lower than the range of the present invention. In Test No. 10, the grain growth of the hot-rolled steel sheet was not sufficient, and in Test No. As compared with No. 5, both the iron loss and the magnetic flux density are worse. Test No. in which the rolling reduction of the cold rolling was lower than the range of the present invention. 11 is the test N
o. As compared with No. 5, both the iron loss and the magnetic flux density are worse.

[0021]

As described above, according to the method of the present invention, complicated and difficult steps such as high-temperature heating of a slab, cold rolling twice, or annealing of a hot-rolled steel sheet are not required as in the prior art. A non-oriented electrical steel sheet having low iron loss and high magnetic flux density and excellent magnetic properties as an iron core material for rotating equipment can be manufactured. Therefore, the present invention is practically extremely significant as a measure for improving the performance of non-oriented electrical steel sheets for iron core materials for rotating equipment.

[Brief description of the drawings]

FIG. 1 shows a sol. A
4 is a graph showing the relationship between the amount of l and magnetic properties.

FIG. 2 is a graph showing a relationship between a winding temperature and magnetic characteristics in hot rolling in Example 2.

FIG. 3 is a graph showing a relationship between a rolling reduction in cold rolling and magnetic properties in Example 3.

────────────────────────────────────────────────── ─── Continued on the front page (56) References JP 6-104865 (JP, B2) Patent 2560090 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) C21D 8/12

Claims (1)

(57) [Claims] 1. C: 0.004% or less, Si: 1.0%
Mn: 0.4% or less, N: 0.004% or less,
S: 0.006% or less, O: 0.015% or less,
When melting steel that satisfies Mn / S ≧ 10 and the balance consists of Fe and unavoidable impurities,
l. The aluminum content was made 0.001% or less to produce a slab, heated to 1000 to 1300 ° C., and then hot-rolled to 65%.
A method for producing a non-oriented electrical steel sheet having excellent magnetic properties, comprising: winding at a temperature of 0 ° C. or more, and then performing cold rolling at a reduction of 75% or more.