JP2001323352A - Nonoriented silicon steel sheet having low core loss and high magnetic flux density and excellent in workability and recyclability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet excellent in recyclability, in workability, and having low core loss and high magnetic flux density. SOLUTION: The steel sheet has a composition containing, by mass, 1.5-4.0% Si and 0.005-2.00% Mn, also containing C, Al and N in amounts reduced, by mass, to <=0.0050%, <=0.030% and <=0.0030%, respectively, and having the balance iron with inevitable impurities. Moreover, the product of the 100} inverse strength and the grain size (μm) of the steel sheet is regulated to >=100. Further, core loss W15/50 and magnetic flux density B50 are regulated to <=3.20 W/kg and >=(1.650+0.025×W15/50)T, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-oriented electrical steel sheet mainly used for electric equipment core materials, and more particularly to a non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density.

[0002]

2. Description of the Related Art In recent years, with the worldwide movement to save energy such as electric power, there has been a strong demand for higher efficiency of electric equipment. Also, from the viewpoint of reducing the size of electric devices, there is an increasing demand for reducing the size of iron core materials. Furthermore, from consideration for environment,
There is also an urgent need to respond to the recycling of iron core materials in electrical equipment.

In order to increase the efficiency of the electric equipment and reduce the size of the iron core material, it is effective to improve the magnetic properties of the magnetic steel sheet used as the material of the iron core. Here, in the field of conventional non-oriented electrical steel sheets, in order to reduce eddy current loss by increasing electric resistance as a means for reducing iron loss among magnetic properties, in particular, Si, Al and Mn are used. Techniques for increasing the content of have been generally used. However, this method has an essential problem that a reduction in magnetic flux density cannot be avoided.

On the other hand, in addition to simply increasing the content of Si, Al, and the like, it is also necessary to reduce C and S at the same time, or to add B as described in JP-A-58-15143. It is also a generally known method to increase the alloy component, such as adding Ni as described in JP-A-3-281758. With the method of adding these alloy components, although the iron loss is mainly improved, the effect of improving the magnetic flux density is small and not satisfactory. Furthermore, since the hardness of the steel sheet increases with the addition of the alloy and the workability deteriorates, the versatility of processing this non-oriented electrical steel sheet for use in electrical equipment is poor, and its use is extremely limited. Had become.

[0005] In addition, several methods have been proposed to improve the magnetic characteristics by improving the degree of integration of the crystal orientation of the product plate, that is, the texture, by changing the manufacturing process. For example, JP-A-58-181822 discloses that Si: 2.8 to
4.0 mass% and Al: 200 for steel containing 0.3-2.0 mass%
Warm rolling within the temperature range of ~ 500 ° C, {100} <UV
W> The method of developing a tissue is disclosed in
No. 422 discloses that Si: 1.5 to 4.0 mass% and Al:
After hot rolling of steel containing 0.1-2.0 mass%, {100} microstructure is developed by a combination of hot-rolled sheet annealing at 1000 ° C or more and 1200 ° C or less and rolling reduction of 80-90%. Methods are disclosed, respectively.

However, the effect of improving the magnetic properties by these methods has not been satisfactory yet, and there remains problems in workability and recyclability. That is,
If a certain amount of Al is contained in steel, the hardness of the steel sheet increases first, impairing the workability, and also damages the electrodes of the electric furnace when recycling core materials or scrapping at the customer , To develop the problem.

Further, when casting a motor shaft or the like by using a recycled iron core, 0.1% by mass or more of Al
When the steel is contained, the surface oxidation of the molten steel proceeds during casting to increase the viscosity, and the filling property of the molten steel in the mold is deteriorated, so that there is also a problem that sound casting is hindered.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a non-oriented electrical steel sheet having excellent workability and recyclability, low iron loss and high magnetic flux density.

[0009]

The gist of the present invention is as follows.
It is as follows. (1) Si: 1.5 to 4.0 mass% and Mn: 0.005 to 2.00 mass
%, And each of C, Al and N is C: 0.0050
mass% or less, Al: 0.030 mass% or less, N: 0.0030 mass%
The balance is reduced to the following composition of iron and unavoidable impurities. {100} inverse strength and grain size (μm) of steel sheet
Product of is not less than 100, the iron loss W _15/50: 3.20W / kg or less and a magnetic flux density B _50: workability and is characterized in that at _{(1.650 + 0.025 × W 15/50)} T or more Non-oriented electrical steel sheet with excellent recyclability and low iron loss and high magnetic flux density.

(2) In the above (1), Sb: 0.005
Non-oriented electrical steel sheet with low iron loss and high magnetic flux density, excellent in workability and recyclability, characterized by containing up to 0.50 mass%.

(3) In the above (1) or (2), the hardness of the steel sheet is 200 HV1 or less, and the non-directionality of low iron loss and high magnetic flux density excellent in workability and recyclability. Electrical steel sheet.

Here, the {100} inverse intensity means the ratio of the intensity of the {100} -oriented X-ray reflection surface of the final product plate to that of the random texture. Further, the crystal grain size is determined by a line segment method based on an optical micrograph of the cross-sectional structure of the steel sheet.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to increase the efficiency of a motor or a transformer of an electric device, it is necessary to reduce the copper loss and the iron loss. It is necessary to increase the magnetic flux density of the material and reduce iron loss. However, since a specific resistance increasing component such as Si, which is generally added to reduce iron loss, lowers the saturation magnetic flux density, it is very difficult to achieve both iron loss and magnetic flux density. In this regard, the improvement of the texture is an excellent means for achieving both iron loss and magnetic flux density, but this means has its own limitations.

Under these circumstances, in order to develop a new material, it is very important to first know how to balance the iron loss and the magnetic flux density of the material with a view to improving the efficiency of electric equipment. Becomes important. Then, the present inventors investigated the motor efficiency when various materials were applied to the iron core using a 500 W brushless DC motor that has recently been generally used. Here, the motor efficiency is D
The ratio of output to input for C motor, 92%
If it is above, it can be said that it is extremely high efficiency.

FIG. 1 shows that the iron loss W _15/50 is less than 3.2 W / kg and the magnetic flux density B ₅₀ is (1.650+
0.025 × W _15/50 ) It has been newly found that the motor efficiency is improved when a material having a range satisfying T or more is applied to the iron core. This is a result of adjusting the balance between the iron loss of the material and the magnetic flux density within the above-mentioned range, so that the iron loss and the copper loss in the device are highly balanced. This finding is basically the same for not only DC motors but also AC induction motors and small transformers. Therefore, satisfying the above-mentioned preferred ranges for iron loss and magnetic flux density is a clear guideline for developing new materials.

Next, based on the above findings, the present inventors have conducted intensive studies on the component composition of the non-oriented electrical steel sheet which can satisfy the above ranges of iron loss and magnetic flux density, and can also secure workability and recyclability. First, Al has conventionally been added as necessary for improving magnetic properties, but it is imperative to reduce Al here because it impairs workability and recyclability.

That is, Al is used in a steel sheet manufacturing process to promote oxidation of the steel sheet surface, to accelerate the wear of the rolling rolls in the rolling process, to impair the rollability, and to increase the hardness of the steel sheet. It is a disadvantageous component in terms of workability, such as increasing the working time and cost by accelerating the deterioration of the mold when the customer performs the punching process. In addition, when casting is performed using scraps of electric equipment and the like, if Al is contained, the surface oxidation of the molten steel proceeds during casting, the viscosity increases, and the filling property of the molten steel in the mold deteriorates. In addition, a sound casting may not be obtained, and the scrap containing Al becomes poor in recyclability.

Therefore, in order to improve workability and recyclability, it is effective to reduce the Al content. However, on the other hand, a reduction in Al leads to an increase in magnetic properties, especially iron loss. However, according to the study of the inventors, it is newly found that by reducing Al and appropriately adjusting other components in steel, it is possible to satisfy all of workability, recyclability, and magnetic properties. It turned out. In other words, the present inventors have analyzed many experimental results and found that when the amount of Si is sufficient and the amount of N is low, good iron loss characteristics can be obtained without adding Al almost. Was found. Therefore, the following experiment was conducted in order to systematically clarify the effects of the Al content and the N content.

First, C: 0.002 mass% as a component and
Mn: 0.20 mass% as a basic component, containing Si, N and
Various steel ingots containing various amounts of Al were melted. These ingots are heated to 1050 ° C and hot-rolled for 2.
Finished to 3 mm, then subjected to hot-rolled sheet annealing at about 1000 ℃, pickled the annealed steel sheet, cold rolled to a final sheet thickness of 0.35 mm, then about 1000 ℃ × 10 seconds Recrystallization annealing was performed to obtain a product plate. Samples were cut out from these product sheets in parallel with the rolling direction and at right angles to the rolling direction, and the iron loss was measured according to JIS C2550, and the average iron loss was determined. As a result, as shown in FIG. 2, it was quantitatively found that the iron loss was significantly reduced even when the Al content was 0.030 mass% or less only when the Si content was high and the N content was low.

As described above, in a high-grade non-oriented electrical steel sheet having a high Si content, a method of increasing the specific electric resistance by adding Al has conventionally been adopted in order to improve iron loss. In addition, the addition of Al also has the effect of aggregating and coarsening AlN, which is a precipitate in steel that suppresses crystal grain growth, and promoting the growth of crystal grains. In order to obtain these effects, it is necessary to secure a certain amount or more of Al. Conventionally, the content of Al is restricted to a range of at least more than 0.1 mass%, and is usually 0.4 to 0.1 mass%.
It was contained at about 1.0 mass%. However, according to the above experiments of the present inventors, even when the Al content is reduced much more than the range of the prior art, by controlling the N content, a texture that is equal to or better than that when Al is contained is obtained. It is newly found that iron develops and iron loss characteristics improve.

[0021] It is not always clear why the good texture is developed by reducing the Al content after reducing the N in the raw material components, but the inventors have found that the impurity particle size is low. The following is considered in relation to the field movement suppression effect. In other words, by reducing Al, it approaches a crystal lattice arrangement state closer to that of pure iron, so that an inherent difference in the movement speed depending on the grain boundary structure becomes apparent, and the difference in the grain growth process accompanying recrystallization becomes one. Only the grain boundaries move preferentially, and the growth of many magnetically disadvantageous grains such as {111}, {554}, and {321} is suppressed, and {100}
It is considered that the magnetic properties were improved as a result of the texture change in the direction of increasing the strength. In particular, when a sufficient amount of Si is contained and the amount of N is reduced to 0.0030 mass% or less, it is difficult to form AlN precipitates.
It is considered that grain boundary movement in the direction of increasing {100} strength is promoted.

As described above, in the method of improving the magnetic structure by improving the texture without adding a large amount of Al, the amount of Al is reduced, so that the recyclability of the material is improved, and the addition amount of the alloy element is reduced. Therefore, the saturation magnetic flux density can be increased. At the same time, when the addition amount of the alloy element is reduced,
Since the increase in hardness of the steel sheet is suppressed, the workability of the product is ensured, and the advantage that application to general-purpose electrical products is promoted is also obtained.

Next, the inventors have studied in detail the texture of the steel sheet for the purpose of further enhancing the effect of the reduction of Al and N described above. As a result, it has been newly found that the iron loss and the magnetic flux density can be more stably improved by defining the {100} inverse strength and the crystal grain size, which are indicators of the texture of the magnetic steel sheet, at a high level.

[0024] That is, Si, also a component composition defined Al and N amount in a predetermined range, since the case where the magnetic flux density B ₅₀ is disengaged from the fitted region shown in FIG 1 is scattered, this cause For clarification, Si: 1.5-3.5 mass%,
Various steel ingots containing Al: 0.0002 to 0.0150 mass% and N: 0.0020 mass% were melted and subjected to experiments. Then, these ingots were heated to 1100 ° C and then hot-rolled to 2.4 mm
After finishing to a large thickness, hot-rolled sheet annealing was performed under various conditions, the steel sheet was pickled, and then cold-rolled to a final thickness of 0.35 mm. Then, after cold rolling, in various atmospheres,
Recrystallization annealing was performed for 10 seconds in a temperature range of 00 to 1100 ° C. to obtain a product plate. From the product sheet thus obtained, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550, and the average magnetic flux density and iron loss were measured. I asked. For each steel sheet, the {100} inverse strength near the surface layer was determined by X-ray measurement, and the crystal grain size was determined by the line segment method based on observation of the microstructure of the cross section of the steel sheet by an optical microscope. The result is that the magnetic flux density and iron loss are B ₅₀ -1.
Fig. 3 shows the relationship between the product of {100} inverse strength and the crystal grain size after arranging 635 -0.025 x W _15/50 .

As shown in FIG. 3, when the product of {100} inverse strength and crystal grain size is 100 or more, B
It was found that a characteristic of ₅₀ ≧ 1.650 + 0.025 × W _15/50 was obtained. The reason for this is not necessarily clear, but the inventors consider as follows. That is, it is known that a high {100} inverse strength is advantageous for magnetic properties, but in a special material in which Al is reduced according to the present invention, the {100} inverse strength is increased and the crystal grain size is increased. By satisfying the requirements for diameter,
と こ ろ 100
｝ It is considered that stable magnetic properties can be obtained only when the balance between the inverse strength and the crystal grain size is properly maintained.

Further, in the non-oriented electrical steel sheet of the present invention, it is preferable that the Vickers hardness of the steel sheet is regulated to 200 HV1 or less so as not to impair the workability at the consumer. In other words, by reducing Al and suppressing oxidation on the steel sheet surface to avoid premature wear of the mold, the hardness of the steel sheet is controlled to 200 HV1 or less, thereby significantly improving the workability of the steel sheet. It will be improved. On the other hand, if the hardness of the steel plate is 12
0 If it is less than HV1, on the contrary, the punched end face may be distorted or crushed, preventing release from the mold, or increasing the burrs after punching, which may adversely affect the space factor of the steel sheet. Therefore, it is preferable that the pressure be 120 HV1 or more.

The regulation of the hardness of the steel sheet is mainly achieved by reducing the amount of Al. However, the steel element contains a large amount of impurity elements, an insufficient annealing temperature in final annealing, or When oxidation or nitridation occurs during annealing, it may be difficult to stably obtain a desired hardness. Therefore, it is effective not only to reduce impurities according to the present invention but also to make the annealing in the manufacturing process an atmosphere in which excessive oxidation or nitridation does not occur. In the present invention, since the amount of Al in steel, which is a nucleus of oxidation and nitriding, is reduced, there is an advantage that oxidation and nitriding hardly occur as compared with other steel types.

The addition of Sb, which has an effect of suppressing oxidation and nitridation, is also effective in reducing the hardness of the steel sheet to 200 HV1 or less. Furthermore, the addition of Sb is also effective in suppressing the fine precipitation of AlN in the case of low Al and suppressing the grain growth inhibiting action, thereby promoting the formation of a texture more advantageous in magnetic properties. is there. To obtain these effects, it is preferable to add Sb in the range of 0.005 to 0.50 mass%.

Hereinafter, the reasons for limiting the constituent elements of the present invention will be described in detail. First, as the component composition of the non-oriented electrical steel sheet of the present invention, Si: 1.5 to 4.0 mass% and Mn:
It is essential to contain 0.005 to 2.00 mass%. That is, it is necessary to increase the electric resistance by containing Si to reduce iron loss, and to improve the iron loss, the content of 1.5 mass% or more is required. On the other hand, the content of Si is 4.0 mass%
Above that, the magnetic flux density decreases and the secondary workability of the product deteriorates significantly.
To the range.

Mn is a component necessary for obtaining good hot workability. For that purpose, the content of Mn must be 0.005% by mass or more. On the other hand, if it exceeds 2.00 mass%, the saturation magnetic flux density decreases, so the range is limited to 0.005 to 2.00 mass%.

Further, C must be reduced to 0.0050 mass% or less in order to suppress deterioration due to magnetic aging and sufficiently exhibit the effect of improving the texture by reducing Al. In addition,
The reduction of C may be 0.0050 mass% or less at the stage of molten steel, or even if it exceeds 0.0050 mass% at the stage of molten steel, it may be reduced to 0.0050 mass% or less by decarburization in the middle of the process. It is important that the C content in the steel sheet is 50 ppm or less.

Next, in order to obtain excellent magnetic properties, it is important to reduce the Al content of the steel sheet to 0.030 mass% or less and the N content to 0.0030 mass% or less. That is, the Al content is
If the content exceeds 0.030 mass%, the texture of the product plate is deteriorated and the magnetic flux density is reduced, so that the content is reduced to 0.030 mass% or less, preferably 0.010 mass% or less. In addition, the amount of N is 0.
If the content exceeds 0030 mass%, an AlN precipitate is formed, and the development of texture and the growth of crystal grains during recrystallization annealing are suppressed, and iron loss is greatly deteriorated. Therefore, the N content is 0.0030 mass% or less, preferably Is reduced to 0.0025 mass% or less.

In addition, Sb is an effective component for AlN precipitation morphology and good texture formation during grain boundary migration.
Less than 0.005 mass% has little effect, while 0.5 mass%
%, The grain growth is adversely affected.
It is preferable to add in the range of 0.5 mass%.

It has been confirmed that Ni, Sn, Cu, P, Cr and the like also have an advantageous effect on the formation of the texture, and there is no problem in adding these. However, Ni is 2.0 mass
%, Sn 1.0 mass%, Cu 1.0 mass%, P 0.3 mass
% And more than 3.0 mass%, grain boundary migration is suppressed, and the formation of a texture and the growth of grains are inhibited. Therefore, it is necessary to add each component in a range not exceeding these upper limits. .

The steel sheet having the above component composition has an iron loss W
_15/50 ： 3.20W / kg or less and magnetic flux density B ₅₀: (1.650 + 0.
025 x W_15/50 ) It has magnetic properties of T or more and is processed
It has excellent recyclability and recyclability.

Further, in order to stably obtain excellent magnetic properties, {100} inverse strength and crystal grain size (μ
It is important that the product of m) and 100 be 100 or more. This is because, as shown in FIG. 3, the magnetic flux density _B50 is stabilized (1.
650 +0.025 x W _15/50 ) To obtain more than T, multiply the above product
This is because it must be 100 or more.

When the crystal grain size is less than 30 μm, iron loss is deteriorated, and when it exceeds 500 μm, workability is deteriorated. Therefore, it is preferable that the crystal grain size be in the range of 30 to 500 μm. Similarly, if the {100} inverse strength is less than 0.1, iron loss and magnetic flux density deteriorate, so it is preferable to be 0.1 or more.

By the way, the molten steel having the above-mentioned composition can be produced by a usual ingot-making method or a continuous casting method, or a thin slab having a thickness of 100 mm or less can be produced by a direct casting method. You may. Next, the slab is heated by a usual method and subjected to hot rolling. Alternatively, the slab may be subjected to hot rolling immediately after casting without heating. In the case of thin slabs, hot rolling may be performed,
The hot rolling may be omitted and the process may proceed to the subsequent steps. Next, hot-rolled sheet annealing is performed as necessary, and after one or more times of cold rolling with intermediate annealing as necessary, continuous annealing is performed, and an insulating coating is applied as necessary. In order to improve the iron loss of the laminated steel sheet, an insulating coating is applied to the steel sheet surface.
It may be a multilayer film composed of more than two kinds of coatings, or may be coated by mixing a resin or the like.

Here, in the above-mentioned production process, in order to control the product of the crystal grain size and the {100} inverse strength to be 100 or more, the crystal structure before cold rolling is made uniform, and At the time of final annealing, care must be taken to control the rate of temperature rise and the temperature reached, and to ensure that recrystallization and grain growth are sufficiently performed. Similarly, controlling the steel sheet temperature during cold rolling is also effective in controlling the product of the crystal grain size and the {100} inverse strength to 100 or more, and the temperature at that time should be 80 ° C or more. Is preferred.

[0040]

EXAMPLES Example 1 A steel slab having the composition shown in Table 1 was produced by continuous casting. The steel slab was heated at 1150 ° C for 50 minutes, finished to a thickness of 2.6 mm by hot rolling, annealed at 980 ° C for 1 minute, stripped by pickling, and then removed at 180 ° C. All of the steel sheets were finished to a final thickness of 0.35 mm except that the steel sheet G was finished to a thickness of 0.20 mm by cold rolling at a temperature of. Next, recrystallization annealing was performed at 1015 ° C. for 30 seconds in a hydrogen atmosphere, and a semi-organic coating solution was applied and baked at 300 ° C. to obtain a product. The texture was appropriately controlled by controlling the rate of temperature rise during recrystallization annealing.

Samples were cut out from the thus obtained product sheet in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550. In addition, for each steel sheet, ｛10
0 と と も に Inverse intensity is determined by X-ray measurement,
The crystal grain size was determined by the line segment method based on the observation of the structure of the steel sheet cross section with an optical microscope. Table 2 shows the measurement results.
As can be seen from the graph, according to the component range of the present invention, a product having good magnetic properties was obtained.

[0042]

[Table 1]

[0043]

[Table 2]

Example 2 A steel slab having the composition shown in Table 3 was produced by continuous casting. The steel slab was heated at 1150 ° C. for 50 minutes, hot-rolled to a thickness of 2.6 mm, then annealed at 980 ° C. × 1 minute, pickled to remove scales, and Cold-rolling was performed at various temperatures shown in Table 3 to finish to a final thickness of 0.35 mm. Next, recrystallization annealing was performed at 1015 ° C. for 30 seconds in a hydrogen atmosphere, and a semi-organic coating solution was applied and baked at 300 ° C. to obtain a product.

From the product sheet thus obtained, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, and the magnetic flux density and iron loss were measured in accordance with JIS C2550. In addition, for each steel sheet, ｛10
0 と と も に Inverse intensity is determined by X-ray measurement,
The crystal grain size was determined by a line segment method based on the observation of the structure of the steel sheet cross section with an optical microscope. Table 4 shows these measurement results.
As described above, it can be seen that by following the component range of the present invention, a product having good magnetic properties was obtained.

[0046]

[Table 3]

[0047]

[Table 4]

[0048]

According to the present invention, a non-oriented electrical steel sheet having excellent workability and recyclability, low iron loss and high magnetic flux density can be stably provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the influence of magnetic flux density B ₅₀ and iron loss W _15/50 on motor efficiency.

FIG. 2 is a graph showing the influence of Al, Si and N amounts on iron loss W _15/50 .

FIG. 3 is a diagram showing the influence of crystal grain size and {100} inverse strength on magnetic properties.

Continued on the front page (72) Inventor Yuka Komori 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. None) Kawasaki Steel Corporation Mizushima Works F-term (reference) 5E041 AA02 AA19 CA02 CA04 NN01 NN06 NN13 NN15

Claims (3)

[Claims] (1) Si: 1.5 to 4.0 mass% and Mn: 0.005 to
2.00 mass%, and C, Al and N are reduced to C: 0.0050 mass% or less, Al: 0.030 mass% or less, and N: 0.0030 mass% or less, and the balance is composed of iron and inevitable impurities. The product of {100} inverse strength and crystal grain size (μm) of the steel sheet is 100 or more, iron loss W _15/50 : 3.20 W / kg or less, and magnetic flux density B ₅₀ : (1.650
+ 0.025 × W _15/50 ) T A non-oriented electrical steel sheet with low iron loss and high magnetic flux density, excellent in workability and recyclability, characterized by being not less than + 0.025 × W _15/50 ) T. 2. The method according to claim 1, wherein the Sb content is 0.005 to 0.005.
A non-oriented electrical steel sheet having a low iron loss and a high magnetic flux density and excellent in workability and recyclability, characterized by having a composition containing 0.50 mass%. 3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the hardness of the steel sheet is 200 HV1 or less, and which has excellent workability and recyclability and has a low iron loss and a high magnetic flux density.