JP2001323345A - Nonoriented silicon steel sheet having high magnetic flux density and excellent in workability, recyclability and magnetic property after strain relieving annealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet excellent in workability and recyclability, and further in magnetic properties after strain relieving annealing. SOLUTION: The steel sheet has a composition containing, by mass, 1.5-4.0% Si and 0.005-2.00% Mn, also containing Al, C and N in amounts reduced, by mass, to <=0.030%, <=0.0020% and <=0.0020%, respectively, and having the balance Fe with inevitable impurities. Further, as to the magnetic properties, the steel sheet has core loss W15/50 and magnetic flux density B50 satisfying the following ranges: W15/50<=3.20 W/kg and B50>=(1.650+0.025×W15/50)T.

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 as an iron core material of electric equipment, and particularly to an advantageous improvement of its workability, recyclability and magnetic properties after strain relief annealing. Things.

[0002]

2. Description of the Related Art In recent years, with the worldwide movement to save energy such as electric power, electric equipment has been
There is a strong demand for higher efficiency. 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, recently, due to environmental considerations, there is an urgent need to cope with recycling of iron core materials in electrical equipment.

In order to improve 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, Mn, etc. Techniques for increasing the content have been commonly used. However, this method has an essential problem that a decrease 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 iron loss is improved,
The effect of improving the magnetic flux density was small and unsatisfactory. In addition, since the hardness of the steel sheet increases with the addition of the alloy and the workability deteriorates, the versatility of processing such non-oriented electrical steel sheet and using it for electrical equipment is poor, and its application is extremely It was limited.

Further, several methods have been proposed for improving the magnetic characteristics by improving the degree of integration of the crystal orientation in the product plate, that is, improving the texture by changing the manufacturing process. For example, Japanese Patent Application Laid-Open No. 58-181822 discloses S
i: 2.8-4.0 mass% and Al: 0.3-2.0 mass% steel is warm-rolled in a temperature range of 200-500 ° C.
A method of developing a {100} <UVW> structure is disclosed in Japanese Patent Application Laid-Open No. 3-294422.
After hot-rolling a steel containing ss% and Al: 0.1 to 2.0 mass%, a combination of hot-rolled sheet annealing at 1000 ° C or more and 1200 ° C or less and cold rolling at a reduction ratio of 80-90% is performed. Methods for developing 100% tissue are disclosed, respectively.

[0006] However, the effect of improving the magnetic properties by these methods has not been satisfactory yet, and there remains a problem in workability and recyclability. That is, if a certain amount of Al is contained in the steel, the hardness of the steel sheet first increases and the workability is impaired.In addition, when recycling the iron core material or performing scrap treatment at the customer, the electric furnace There was a problem of damaging the electrodes.

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 a problem still remains where sound casting is hindered.

[0008]

SUMMARY OF THE INVENTION The present invention advantageously solves the above-mentioned problems and, needless to say, has excellent workability and recyclability as well as high magnetic properties after strain relief annealing. The purpose is to propose a magnetic flux density non-oriented electrical steel sheet.

[0009]

To simply improve the recyclability, it is sufficient to reduce the Al content to a predetermined level. However, if the Al content is reduced, the deterioration of the magnetic properties is inevitable. Therefore, the present inventors have conducted intensive studies to improve this point. As a result, even when the material is a low Al material, when both C and N are reduced, the crystal grain growth property is remarkably improved, and It has been found that excellent magnetic properties comparable to those of the additive can be obtained. It has also been found that the addition of Sb not only promotes the formation of a favorable texture in terms of magnetic properties, but is also useful for adjusting the hardness of the steel sheet. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. Si: 1.5 to 4.0 mass% and Mn: 0.005 to 2.00 mass
%, And each of Al, C and N is 0.030
mass% or less, C: 0.0020 mass% or less, N: 0.0020 mass%
And the balance becomes Fe and unavoidable impurities, and the iron loss W _15/50 ≤ 3.20 W / kg and the magnetic flux density B ₅₀
High magnetic flux density non-oriented electrical steel sheet excellent in workability, recyclability and magnetic properties after strain relief annealing characterized by satisfying ≧ (1.650 + 0.025 × W _15/50 ) T.

2. The high-magnetic-flux-density non-oriented electrical steel sheet according to the above item 1, wherein the composition further contains Sb: 0.005 to 0.50 mass%, and is excellent in workability, recyclability and magnetic properties after strain relief annealing.

3. The high magnetic flux density non-oriented electrical steel sheet according to 1 or 2 above, wherein the steel sheet has a hardness of 200 HV1 or less and is excellent in workability, recyclability, and magnetic properties after strain relief annealing.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the invention will be described below. Now, it is important to reduce the copper loss and iron loss in order to increase the efficiency of motors and transformers of electrical equipment, and to reduce copper loss and iron loss simultaneously,
It is necessary to increase the magnetic flux density of the material and reduce iron loss.
However, since an element which increases the specific resistance, such as Si, added to reduce iron loss generally lowers the saturation magnetic flux density, it was 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 also 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 to improve the efficiency of electric equipment. Become. Therefore, the inventors have investigated the motor efficiency when a brushless DC motor of 500 W which has recently been generally used and various materials are applied to the iron core. Here, the motor efficiency is a ratio of the output to the input in the DC motor, and it can be said that the efficiency is extremely high if it is 92% or more.

FIG. 1 shows the obtained results. As shown in the figure, the iron loss of the material falls within a range where the iron loss W _15/50 is 3.2 W / kg or less and the magnetic flux density B ₅₀ satisfies (1.650 + 0.025 × W _15/50 ) T or more. It has been found that by controlling the magnetic flux density, extremely good motor efficiency can be obtained. This is the result of a good balance between the iron loss and the copper loss of the device by adjusting the iron loss-magnetic flux density balance of the material.

This finding should be basically the same for not only DC motors but also AC induction motors and small transformers. Therefore, controlling the iron loss and the magnetic flux density within the above-mentioned preferred ranges was used as a guideline for developing new materials.

Then, based on the above findings, the composition of the non-oriented electrical steel sheet was examined in which the iron loss and the magnetic flux density satisfy the above-mentioned ranges, and can also secure good workability and recyclability. First, Al has conventionally been added as necessary for improving magnetic properties, but because it hinders workability and recyclability, here
It is important to reduce Al.

That is, Al promotes oxidation of the surface of the steel sheet in the manufacturing process of the steel sheet. Therefore, Al not only accelerates the abrasion of the rolling rolls in the rolling process and impairs the rollability but also increases the hardness of the steel sheet. This is a disadvantageous component in terms of workability, such as increasing the working time and cost by accelerating the deterioration of the die 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.
Nevertheless, on the other hand, the reduction of Al leads to an increase in magnetic properties, especially iron loss.

However, according to the inventors' research on this point, even if the Al content is reduced, if the other steel components are properly adjusted, all of the workability and recyclability and the magnetic properties can be satisfied. What can be done has been newly determined. In other words, the present inventors have analyzed a large number of 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. I found that. 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% is fixed as a basic component, and Si, N
And various ingots containing various amounts of Al were melted. Then, these ingots were heated to 1050 ° C, hot-rolled to a thickness of 2.3 mm, then hot-rolled at about 1000 ° C, pickled, and cold-rolled to a final thickness. ： 0.35mm
After that, recrystallization annealing was performed at about 1000 ° C. for 10 seconds to obtain a product plate.

From these product sheets, samples were cut out in parallel with the rolling direction and at right angles to the rolling direction, respectively.
The iron loss was measured according to C2550, and the average value was determined. FIG. 2 shows the obtained results. As shown in the figure,
When the amount of Si is high and the amount of N is low, Al is 0.030 mass%
It was also found that the iron loss was significantly reduced in the following ranges.

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. Further, 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 amount of Al is restricted to a range exceeding at least 0.1 mass%, and usually contains about 0.4 to 1.0 mass%. It had been. However, according to the above experiments of the inventors, even when the Al content is much reduced than the range of the prior art, by regulating the N content, a texture as good as or better than the case where Al is contained is obtained. It is newly found that iron develops and iron loss characteristics improve.

As described above, although the reason why a good texture is developed by reducing the Al content after reducing the N in the raw material components has not necessarily been clearly elucidated, the inventors of the present invention have found that. Consider the following in connection with the effect of suppressing the migration of impurities to the grain boundaries. 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 of the parts move preferentially, and {111}, # 55
It is considered that the growth of many magnetically disadvantageous crystal grains such as 4} and {321} is suppressed, and the texture changes in the direction of increasing the {100} strength, resulting in improved magnetic properties. In particular, it contains a sufficient amount of Si and
If the amount is reduced to 0.0030 mass% or less, it is considered that AlN precipitates are less likely to be formed, so that grain boundary movement in the direction of increasing {100} strength is promoted.

As described above, in the method for improving the magnetic properties by improving the texture without adding a large amount of Al, since the amount of Al is reduced, the recyclability of the material is improved, and the addition amount of the alloy element is reduced. The saturation magnetic flux density can be increased to reduce it. Furthermore, when the addition amount of the alloy element is reduced, an increase in the hardness of the steel sheet is suppressed, so that 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 the effects of trace elements for the purpose of improving the magnetic properties after strain relief annealing, while having the effect of promoting the above-described texture formation and grain growth. Study was conducted. as a result,
It has been ascertained that further reduction of N and C in steel enhances the above-mentioned effects, and more stably improves iron loss and magnetic flux density after strain relief annealing.

That is, when the amounts of Si, Al, and N are simply set within predetermined ranges, the iron loss after strain relief annealing tends to be equal to or slightly deteriorated as it is when shearing. Therefore,
To clarify the cause, Mn is fixed at 0.2 mass%, Si is 1.5-1.8 mass%, and Al is 0.0004-0.0100 mass%.
%, N and C were varied in the range of about 0.0010 to 0.0040 mass%, respectively, and the steel ingot was melted and subjected to an experiment (partially decarburized). Then, these ingots are heated to 1000 ° C., and then hot-rolled to a thickness of 2.8 mm, then subjected to hot-rolled sheet annealing at about 1020 ° C., pickled, and then cold-rolled to a final thickness: Finished to 0.50mm. Subsequently, after cold rolling, recrystallization annealing was performed at about 1000 ° C. for 10 seconds to obtain a product sheet. 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 average magnetic flux density and iron loss were measured in accordance with JIS C 2550. This measurement was carried out on the as-sheared specimen and on the specimen subjected to strain relief annealing at 750 ° C. for 2 hours in a nitrogen atmosphere. FIG. 3 shows the obtained results.
It is arranged and shown.

As shown in the figure, N and C are respectively
It was found that the iron loss after the strain relief annealing was stably recovered when the values were reduced as much as possible to N ≦ 0.0020 mass% and C ≦ 0.0020 mass%. Although the reason for this is not necessarily clear, it is considered that N forms a solid solution during recrystallization annealing and becomes supersaturated during cooling, and as a result, carbide precipitates during the soaking process of strain relief annealing. Therefore, by reducing these elements, the above harm can be reduced, and as a result,
It is considered that extremely good magnetic properties can be obtained even after the strain relief annealing.

Further, in the non-oriented electrical steel sheet of the present invention, the Vickers hardness of the steel sheet is preferably 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 surface of the steel sheet to avoid premature wear of the mold, and by restricting the hardness of the steel sheet to 200 HV1 or less, the workability of the steel sheet is markedly improved. It will be improved. Nevertheless, if the hardness of the steel plate is less than 120 HV1, the end face punched out may be distorted or crushed, preventing removal from the mold,
Since the burr after punching becomes large and may adversely affect the space factor of the steel sheet and the like, it is preferable to set it to 120 HV1 or more.

The regulation of the hardness of the steel sheet is mainly achieved by reducing the amount of Al. However, if the amount of impurity elements is large, the annealing temperature in the final annealing is insufficient, 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.

Also, it has an effect of suppressing oxidation and nitridation.
The addition of Sb is also effective in regulating the hardness of the steel sheet to 200 HV1 or less. Also, the addition of Sb is
Suppressing the fine precipitation of AlN and suppressing these grain growth inhibiting effects are also effective in promoting the formation of a texture more advantageous in magnetic properties. To obtain these effects, Sb is preferably added in the range of 0.005 to 0.50 mass%.

Next, the reasons for limiting the constituent elements of the present invention will be described in detail. First, the component composition of the non-oriented electrical steel sheet of the present invention will be described.
4.04.0 mass% and Mn: 0.005 to 2.00 mass%. Si: 1.5 to 4.0 mass% In other words, it is necessary to increase the electric resistance by containing Si and reduce iron loss.
% Or more is required. On the other hand, the Si content is 4.0 mass
%, Not only does the magnetic flux density decrease, but also the secondary workability of the product deteriorates significantly.
Limited to the range of ss%.

Mn: 0.005 to 2.00 mass% Mn is a component necessary for obtaining good hot workability, and for that purpose, at least 0.005 mass% must be contained. On the other hand, if it exceeds 2.00 mass%, the saturation magnetic flux density will decrease, so the Mn content is limited to the range of 0.005 to 2.00 mass%.

Al: 0.030 mass% or less In order to obtain excellent magnetic properties, the amount of Al in the steel sheet is set to 0.030 ma.
It is necessary to reduce it to ss% or less. That is, if the Al content exceeds 0.030 mass%, the texture of the product sheet is deteriorated and the magnetic flux density is reduced. Therefore, the Al content needs to be 0.030 mass% or less, preferably 0.010 mass% or less.

C: 0.0020 mass% or less, N: 0.0020 mass%
As shown in FIG. 3 above, in order to stably obtain good magnetic properties after strain relief annealing in low Al steel, it is important to reduce both C and N to 0.0020 mass% or less. . C is 0.0020 at the molten steel stage.
mass% or less, and if it exceeds 0.0020 mass% in the molten steel stage, it is 0.0020 mass
It is important to keep the C content in the steel sheet during recrystallization annealing at 20 ppm or less.

Sb: 0.005 to 0.50 mass% Sb is an effective component for AlN precipitation morphology and good texture formation during grain boundary migration.
If it is less than 0.5 mass%, on the other hand, if it exceeds 0.5 mass%, it adversely affects the grain growth.
It is preferable to add in the range of.

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
2.0 mass%, Sn 1.0 mass%, Cu 1.0 mass%, P
If the content of 3 mass% and Cr exceeds 3.0 mass%, the movement of grain boundaries is suppressed, and the formation of a texture and the growth of grains are inhibited. Therefore, it is necessary to add each component within a range not exceeding these upper limits. preferable.

The steel sheet adjusted to the above-described composition has the iron loss W
_15/50 is not more than 3.20 W / kg, and the magnetic flux density B ₅₀ is (1.65
0 + 0.025 × W _15/50 ) T or more, and excellent in workability and recyclability, and also in magnetic properties after strain relief annealing.

Next, a method for manufacturing the steel sheet of the present invention will be described. From the molten steel adjusted to the above preferred component composition, a slab may be manufactured by a normal ingot-bulking method or a continuous casting method, or a thin slab having a thickness of 100 mm or less is manufactured by a direct casting method. You may. Then, the slab is heated by a usual method and subjected to hot rolling, but may be immediately subjected to hot rolling without heating after casting. In the case of a thin slab, hot rolling may be performed, or hot rolling may be omitted and the process may proceed to the subsequent steps. Subsequently, hot-rolled sheet annealing is performed as necessary, and further, one or more times of cold rolling with intermediate annealing as necessary is performed, then 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. For this purpose, a multilayer film composed of two or more kinds of films may be used, or a resin or the like may be mixed. It may be a coating.

[0040]

EXAMPLE A steel slab having the composition shown in Table 1 was produced by continuous casting. After heating this steel slab at 1180 ° C for 50 minutes, it was hot rolled into a hot rolled sheet having a thickness of 2.8 mm,
After hot-rolled sheet annealing for 1 minute, remove the scale after pickling, cold-roll at 180 ° C to obtain 0.50 mm
Or finished to a final thickness of 0.35mm. Then, (50% H ₂ +
After performing recrystallization annealing at 950 ° C. for 10 seconds in a 50% N ₂ ) atmosphere, a semi-organic coating solution was applied and baked at 300 ° 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 average magnetic flux density and iron loss were measured in accordance with JIS C 2550. This measurement was carried out on the as-sheared specimen and on the specimen subjected to strain relief annealing at 750 ° C. for 2 hours in a nitrogen atmosphere. Table 2 summarizes the obtained results.

[0042]

[Table 1]

[0043]

[Table 2]

As shown in Table 2, when the component composition was adjusted within the range of the present invention, a product plate having good magnetic properties was obtained after strain relief annealing, not to mention shearing. . In addition, it can be seen that the hardness of the product plate is also appropriate and has good workability.

[0045]

As described above, according to the present invention, a high magnetic flux density non-oriented electrical steel sheet having excellent workability and recyclability and excellent magnetic properties after strain relief annealing can be stably obtained.

[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 effect of Al, Si and N amounts on iron loss W _15/50 .

FIG. 3 is a view showing the influence of the amounts of N and C in steel on magnetic properties.

Continued on the front page (72) Inventor Keiji Sakai 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref.

Claims (3)

[Claims] 1. An alloy containing Si: 1.5 to 4.0 mass% and Mn: 0.005 to 2.00 mass%, and Al, C and N, respectively, Al: 0.030 mass% or less, C: 0.0020 mass% or less, N: 0.0020 mass % Or less, and the balance is composed of Fe and unavoidable impurities.
Furthermore, iron loss W _15/50 ≤ 3.20 W / kg and magnetic flux density B ₅₀ ≥ (1.650+
A high magnetic flux density non-oriented electrical steel sheet having excellent workability, recyclability, and magnetic properties after strain relief annealing characterized by satisfying 0.025 × W _15/50 ) T. 2. The high magnetic flux density according to claim 1, wherein the composition further contains Sb: 0.005 to 0.50 mass%, and is excellent in workability, recyclability and magnetic properties after strain relief annealing. Grain-oriented electrical steel sheets. 3. The high magnetic flux density non-directional sheet according to claim 1, wherein the steel sheet has a hardness of 200 HV1 or less, and is excellent in workability, recyclability and magnetic properties after strain relief annealing. Electrical steel sheet.