JPH11229095A - Nonoriented silicon steel sheet for high frequency use and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet for high frequency use having excellent high frequency iron loss and magnetic flux density, and its production by utilizing minimal Gr quantity. SOLUTION: The nonoriented silicon steel sheet for high frequency use has a composition consisting of, by weight, <=0.005% C, 0.5 5.5% Cr, 0.5-4% Si, 0.1-5% Al, <=3% Mn, <=0.3% P, <=0.005% S, <=0.005% N, <=0.01% Ti, <=0.01% Nb, and the balance Fe with inevitable impurities and also has 10-170 μm average ferrite crystalline grain size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a high-grade non-oriented electrical steel sheet, particularly a motor core material having excellent specific resistance used at high frequencies and a method for producing the same.

[0002]

2. Description of the Related Art From the viewpoint of the global environment, the harmful effects of recent energy-intensive civilization have been regarded as a problem. For this reason, in the field of electrical equipment in which non-oriented electrical steel sheets are used, further reduction in power consumption is demanded for motors for cooling and heating equipment, main motors for electric vehicles, stepping motors for high-speed printers, and the like. . In addition, since variable speed motors from low frequency to high frequency are controlled by inverter control instead of conventional ON-OFF control, excellent electromagnetic steel sheets are required over a wide range of frequencies. Was.

Conventionally, non-oriented electrical steel sheets have been produced by increasing the electrical resistance (hereinafter referred to as the specific resistance) by increasing Si and Al in order to improve high-frequency iron loss.
Further, the thickness of the product has been reduced as much as possible. However, the problem was the brittleness of the steel sheet due to the large amount of Si + Al. That is, particularly in winter, a production obstacle such as cracking at a place where bending deformation of a steel sheet after hot-rolled sheet annealing is applied or breakage in a cold-rolling mill was a very important problem.
For this reason, effective elements other than Si and Al have been studied, but they have not been put to practical use.

For example, there is a technique focusing on Cr. In chronological order, U.S. Pat. No. 3,615,367 discloses that 9-20% Cr-0.01-3% Si and / or A
An iron loss core excellent in corrosion resistance by l-Fe has been proposed. However, there was a problem that Ti ≧ 0.02% was essential. Ti was found to be iron loss in our investigation,
In particular, it is a very harmful element for greatly increasing the hysteresis loss, and the component system described in this publication did not have a sufficient iron loss value at high frequencies.

In Japanese Patent Publication No. 39-20644, 11.5-20% Cr-1-6% Si and / or
Corrosion resistant soft magnetic materials of 0.5-5% Ti-Fe have been proposed. However, since this steel is a component system that does not contain Al, high-frequency magnetic characteristics are not sufficient, and Ni, C
There is also a problem that the production cost is increased because it includes expensive elements such as o and Mo.

As a technique focusing only on the corrosion resistance of Cr, Japanese Patent Publication No. 50-135135 discloses an 8-18% Cr-
0.3-0.75% Si-Fe has been proposed. In Japanese Patent Publication No. 51-1646, 8-18% Cr-0.
A 3 to 0.75% Si-Fe stainless steel electromagnetic steel sheet has been proposed. Japanese Patent Publication No. 56-15705 discloses a method for producing a 1 to 5.5% Cr-1 to 3.5% Si-Fe-based weatherable electrical steel sheet. However, none of these three cases contained Al, so that the high-frequency magnetic characteristics were not sufficient.

On the other hand, 5.5 to 11.5% Cr-1.5 to 3.5% Si-0 in Japanese Patent Publication No. 2-38646.
Production method of high hardness corrosion-resistant electrical steel sheet of Al-Fe series, 4-13% in JP-A-5-295637
Manufacturing method by rapid solidification of corrosion-resistant magnetic steel sheet based on Cr-2-4% Si-0-2% Al-Fe
No. 4-13% similar to Cr-2-4% Si
In all three inventions, such as a method for producing a corrosion-resistant electrical steel sheet by rapid solidification of -0 to 2% Al-Fe system, the high-frequency magnetic properties were not sufficient because the product had a large crystal grain size.

[0008] All of the patents described above are limited to special applications such as electromagnetic switches (magnet switches) from the viewpoint of corrosion resistance, and have not been focused on high-frequency applications.

As a technique focusing on the specific resistance of Cr,
There is one described in JP-A-8-47235. This technology relates to a stepping motor material using a high Cr-based high electric resistance of 9% or more. However, Ti, which is considered to be essential for stabilizing the ferrite phase in this material, is a very harmful element in our investigation because it greatly increases iron loss, particularly hysteresis loss. In the component system, the iron loss value at a high frequency was not sufficient.

Incidentally, a so-called electric heating material has been used for 20 years.
It has been known that a specific resistance of about 26 to 26% Cr-Al-Si-Mn-Fe can be obtained in the range of about 120 to 150 µΩ-cm. For example, JIS C 2520 (1
986), but it seems that no investigation has been made regarding the iron loss and magnetic flux density of the magnetic steel sheet. In the prior art described above, most of the components are Cr
The content is set to 5.5% or more, which causes a problem of a decrease in magnetic flux density and an addition cost.

[0011]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a non-oriented electrical steel sheet having excellent high-frequency iron loss and magnetic flux density and excellent in high-frequency applications using a small amount of Cr. It is.

[0012]

SUMMARY OF THE INVENTION The present invention is as follows. (1) By weight%, C ≦ 0.005%, Cr: 0.5-5.5%, Si: 0.5-4%, Al: 0.1-5%, Mn ≦ 3%, P ≦ 0.3%, S ≦ 0.005%, N ≦ 0.005%, Ti ≦ 0.01%, Nb ≦ 0.01%, with the balance being Fe and unavoidable impurities, A high-frequency non-oriented electrical steel sheet having a diameter of 10 to 170 μm.

(2) By weight%, C ≦ 0.005%, Cr: 0.5-5.5%, Si: 0.5-4%, Al: 0.1-5%, Mn ≦ 3% , P ≦ 0.3%, S ≦ 0.005%, N ≦ 0.005%, Ti ≦ 0.01%, Nb ≦ 0.01%, with the balance being Fe and unavoidable impurities A method for producing a high-frequency non-oriented electrical steel sheet for high frequency, characterized in that a sheet is annealed, then cold-rolled, and then subjected to continuous annealing so that the average ferrite grain size is 10 to 170 μm.

The points of the present invention are the following three points. : The relationship between the Cr content, the Al content, the Si content and the specific resistance value of the steel sheet was more accurately grasped than in the past. Realizing a component system with a resistance value. : Ti, commonly used in high Cr stainless steel sheets,
S, N, etc. are avoided because they degrade the high frequency characteristics of the magnetic steel sheet. : Brittle fracture is less likely to occur even when Cr is added, as compared to conventional Si or Al steel.

Hereinafter, the relationship between Cr, Al, Si and the specific resistance will be described in detail. Si ≦ 4% by weight, Al
≦ 5%, Mn ≦ 3%, Cr ≦ 15% Within the range of 21 vacuum-melted ingots with different components, hot rolling was performed, the specific resistance was measured, and multiple regression analysis was performed. The following results with a correlation coefficient of 0.98 were obtained. ρ (μΩ-cm) = 19.3 + 2.7Cr + 14.2Si + 11.9Al + 0.7Cr × Al +
0.2Cr × Si

That is, Si and Al have a large effect of improving the specific resistance as conventionally known, but Cr alone has a small effect of improving the specific resistance. In particular, Al
It was found that Cr had an interaction with the amount, and the integrated value of the amount of Cr and the amount of Al greatly contributed to the specific resistance. Although the amount of Si is slight, the integrated value with the amount of Cr contributes to the specific resistance.

The equation for giving the conventional specific resistance is expressed by US Pat.
The following were allegedly found in the steel catalog. ρ (μΩ-cm) = 10.45 + 6.0C + 11.6Si + 13.2Al + 4.5Mn + 13.7P +
10.4S

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the component system of the steel of the present invention will be described. C content is 0.
005% or less. The reason is that if the amount of C exceeds this, there is a problem in magnetic aging.

The amount of Cr is 0.5-5.5%. Cr
Is effective in increasing the specific resistance alone or by interaction with Al or Si, as described above. 0.5%
If it is less than 5.5%, the improvement in the specific resistance is small, and it is also 5.5%.
Exceeding the maximum value avoids the deterioration of the magnetic flux density and the addition cost. Therefore, the Cr content is 0.5 to 5.5.
%.

The amount of Si is 0.5-4%. As the Si content increases, the specific resistance increases and the iron loss decreases.
If it is less than 0.5%, α-γ transformation occurs during hot rolling or annealing to deteriorate magnetic properties. If it exceeds 4%, there is a problem in brittleness such as breakage in a steel sheet production line. %.

The amount of Al is 0.1 to 5%. Al also increases the specific resistance and reduces iron loss, but the Al content is 0.1%.
If it is less than 5%, the iron loss is not sufficiently reduced, and if it exceeds 5%, there is a problem in brittleness. Therefore, the Al content is set to 0.1 to 5%.

The Mn content is 3% or less. Mn also increases the specific resistance and reduces iron loss, but if it exceeds 3%, there is a problem in brittleness, so it is set to 3% or less.

The amount of P is set to 0.3% or less. P also increases iron resistance and reduces iron loss, but if it exceeds 0.3%, a brittleness problem occurs, so P is set to 0.3% or less.

The amount of S is set to 0.005% or less. If the amount of S exceeds 0.005%, sulfides such as MnS increase, which hinders domain wall movement in a product and deteriorates magnetic properties.

The N content is set to 0.005% or less. If the N content exceeds 0.005%, blister-like surface defects called blisters are generated.

The Ti content is set to 0.01% or less. Ti is
Form nitrides, sulfides, oxides, carbides, or composites thereof to degrade magnetic properties. The limit is 0.01
%.

The Nb content is set to 0.01% or less. Nb also
They form nitrides, sulfides, oxides, carbides or composites thereof to deteriorate magnetic properties, but the limit is 0.0
1%.

In addition to the above-mentioned elements, Sn, Ni, Cu, Sb, Cr, M which are known as those which do not deteriorate magnetic properties
Even if o is added, the effect of the present invention is not impaired, but it is preferable to add 0.1% or less from the viewpoint of cost.

The slab heating for hot rolling is not particularly limited, but the temperature is preferably low for the purpose of preventing fine precipitates.
0 ° C. is preferred. Next, normal hot rolling is performed, and the thickness of the hot rolled sheet may be 0.8 to 3.0 mm.

Next, the hot rolled sheet obtained by hot rolling is annealed. Annealing the hot-rolled sheet increases the magnetic flux density and can reduce the hysteresis loss, so that the iron loss is particularly excellent at low frequencies (300 Hz or less). The annealing temperature of the hot-rolled sheet is preferably 700 to 1200 ° C. in the related art.

Before or after the hot-rolled sheet annealing, pickling is performed, and then cold rolling is performed. Cold rolling is performed by ordinary reversing or tandem, but reversing such as Sendzimer mill is preferable because a high magnetic flux density can be obtained as is known. As is known, warm rolling at a temperature of 100 to 300 ° C. is also preferable because it improves the magnetic flux density. The plate thickness is preferably thinner to improve high frequency magnetic characteristics.
1-0.6 mm is preferred.

After cold rolling, it is degreased and subjected to continuous annealing. The annealing temperature is preferably as high as 700 [deg.] C. or more, and it is particularly necessary to control the crystal grain size to 10 to 170 [mu] m. If the crystal grain size is less than 10 μm, the iron loss of the steel sheet cannot be sufficiently reduced, and if the crystal grain size is more than 170 μm, the magnetic flux density of the steel sheet deteriorates, which is not preferable. The crystal structure having such a crystal grain size needs to be a ferrite structure. This is because high frequency iron loss deteriorates in the transformed structure. The temperature conditions for continuous annealing vary depending on the components and time, but for example, a temperature range of 650 to 1150 ° C. for 20 seconds of soaking. In this continuous annealing, a reducing atmosphere of a mixture of hydrogen and nitrogen is preferable as disclosed in JP-A-56-16623 in order to prevent deterioration of high-field iron loss due to surface oxidation of a steel sheet.

After the continuous annealing as described above, usually, a mixture of an organic substance and an inorganic substance, an organic or inorganic insulating coating is applied and baked. On the other hand, there is a non-oriented electrical steel sheet which is not laminated depending on a product to be used, and in such a case, it is shipped with the steel sheet surface as it is. Rust prevention oil may be applied to prevent rust.

Although it is possible to repeat the cold rolling and annealing several times as in the conventional case, it is disadvantageous in terms of cost.

[0035]

Embodiments of the present invention will be described below. [Example 1] A steel ingot in which the amount of C was fixed to 0.001% and various components were changed was prepared by vacuum melting, and the heating temperature was set to 10%.
The temperature was set to 00 ° C. and hot rolling was performed to obtain a hot rolled sheet having a thickness of 2.5 mm.
Thereafter, annealing was performed in nitrogen at 1000 ° C. for 30 seconds, followed by pickling and cold rolling in tandem to obtain a cold rolled steel sheet having a thickness of 0.35 mm. This cold-rolled steel sheet was subjected to continuous annealing at 850 to 950 ° C. × 10 seconds to reduce all the average crystal grain sizes to 50 to 60.
3 g of 1 g / m ² of organic (epoxy resin) and inorganic (magnesium hydroxide and chromic acid) mixed coating
After baking at 00 ° C., the specific resistance and high frequency magnetic properties were measured. Magnetism is measured by Epstein system using JIS C 2
It measured according to 550. Table 1 shows the results.

[0036]

[Table 1]

In Experiment No. 2, 59 μΩ-cm was the critical resistivity of the Cr-free system.
An excellent specific resistance was obtained with the help of the interaction effect with the amounts of l and Si. Further, the high-frequency iron loss and the magnetic flux density further
Good results were obtained by controlling i, Al, S, Ti, and Nb within the range of the present invention.

Example 2 Experiment No. 7 of Example 1
Using a 4% Cr cold-rolled sheet, the annealing temperature was changed in hydrogen to control the crystal grain size. The soaking time was 20 seconds.
Next, the chromic acid-epoxy resin mixed film was baked to obtain the results shown in Table 2.

[0039]

[Table 2]

As shown in Table 2, the crystal grain size of the product was within the range of the present invention, and excellent high-frequency iron loss and magnetic flux density were obtained.

[0041]

As described above, by utilizing a small amount of Cr,
A non-oriented electrical steel sheet having excellent high-frequency iron loss and magnetic flux density and excellent in high-frequency applications could be provided.

Claims (2)

[Claims] C .: 0.005%, Cr: 0.5 to 5.5%, Si: 0.5 to 4%, Al: 0.1 to 5%, Mn.ltoreq.3% by weight%. P ≦ 0.3%, S ≦ 0.005%, N ≦ 0.005%, Ti ≦ 0.01%, Nb ≦ 0.01%, the balance being Fe and unavoidable impurities, A high-frequency non-oriented electrical steel sheet having a crystal grain size of 10 to 170 µm. 2. In weight%, C ≦ 0.005%, Cr: 0.5-5.5%, Si: 0.5-4%, Al: 0.1-5%, Mn ≦ 3%, Hot rolled sheet containing P ≤ 0.3%, S ≤ 0.005%, N ≤ 0.005%, Ti ≤ 0.01%, Nb ≤ 0.01%, with the balance being Fe and unavoidable impurities A non-oriented electrical steel sheet for high frequency use, characterized in that the steel sheet is annealed, cold rolled, and then continuously annealed to make the average ferrite crystal grain size 10 to 170 μm.