JP2002317254A - Nonoriented silicon steel sheet having excellent high frequency magnetic property used after heating stage subsequently to finish annealing and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet which exhibits low core loss in high frequency, and is suitable as electric materials such as core materials used in high frequency. SOLUTION: The nonoriented silicon steel sheet having excellent high frequency magnetic properties has a composition containing, by weight, <=0.0015% C, 1.0 to 4.0% Si, 0.1 to 2.0% Al, 0.05 to 2.0% Mn, <=0.1% (inclusive of zero) P, <=0.005% (inclusive of zero) N, <=0.02% (inclusive of zero) S and 0.4 to 5.0% Cr, and the balance substantially Fe.

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 used at a high frequency (200 Hz to 1 KHz) for a core material of electric equipment through a heating process after finish annealing, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art In recent years, the driving frequency of electric equipment has been increased from the viewpoint of miniaturization and higher efficiency of electric equipment. Accordingly, a material having low high-frequency iron loss is also desired for a non-oriented electrical steel sheet used as a core material.

Conventionally, as a technique for reducing high-frequency iron loss, there is a technique focusing on Cr. For example, JP-A-11-2
No. 29095 proposes a technique for reducing high-frequency iron loss by adding 0.5 to 5.5% of Cr. Also, Japanese Patent Application Laid-Open No. 12-119822 discloses that
A technique has been proposed to reduce the high-frequency iron loss by defining the ferrite grain size of the steel sheet to 100 to 200 μm by adding%.

[0004] In a compressor motor for a high-efficiency air conditioner, refrigerator, or the like, a non-oriented electrical steel sheet serving as a core material is punched, laminated, and then subjected to a heat treatment called magnetic annealing for the purpose of removing processing strain. , Bluing shrink fit or the like. However, the conventional technique for reducing iron loss by adding Cr mentions only reduction of high-frequency iron loss after finish annealing, and is based on the premise that magnetic iron, heat treatment, and the like are used as they are. Materials with low iron loss values before magnetic annealing or heat treatment, etc., do not always have low iron loss values even after magnetic annealing, heat treatment, etc., and such steel sheets are used as they are as materials for magnetic annealing, heat treatment, etc. I can't. Therefore, development of a non-oriented electrical steel sheet having excellent high-frequency characteristics even after magnetic annealing, heat treatment, or the like is desired.

The present invention has been made in view of such circumstances, and shows a low core loss at a high frequency (200 Hz to 1 KHz) even after magnetic annealing, heat treatment, and the like, and a core material used at a high frequency. It is an object of the present invention to provide a non-oriented electrical steel sheet suitable for use as an electric machine material and the like, and a method for manufacturing the same.

[0006]

The first means for solving the above-mentioned problems is that, by weight%, C: 0.0015% or less, Si: 4%
Hereinafter, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less, N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 5%
Is a non-oriented electrical steel sheet having excellent high-frequency magnetic properties and used through a heating process after finish annealing in which the balance substantially consists of Fe (Claim 1).

[0007] A second means for solving the above-mentioned problems is as follows.
C: 0.0009% or less, Si: 4% or less, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less, N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 100% by weight A non-oriented electrical steel sheet containing 5% and having a balance of substantially Fe, which is used after a final annealing and further through a heating process, and which is excellent in high-frequency magnetic properties (Claim 2).

[0008] A third means for solving the above problems is as follows.
The non-oriented electrical steel sheet according to the first or second means is characterized in that the range of the Cr content is limited to 0.4 to 1.4% (Claim 3).

A fourth means for solving the above problem is as follows.
C: 0.005% or less, Si: 4% or less, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less, N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 100% by weight A slab containing 5% and the balance substantially consisting of Fe is hot-rolled, pickled and rolled to a predetermined thickness, and then subjected to a reducing atmosphere in any of the continuous annealing processes. After decarburizing,
The method for producing a non-oriented electrical steel sheet according to the first means, wherein the C content after decarburization is 0.0015% or less.

A fifth means for solving the above-mentioned problem is as follows.
C: 0.005% or less, Si: 4% or less, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less, N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 100% by weight A slab containing 5% and the balance substantially consisting of Fe is hot-rolled, pickled and rolled to a predetermined thickness, and then subjected to a reducing atmosphere in any of the continuous annealing processes. After decarburizing,
A method for producing a non-oriented electrical steel sheet as the second means, wherein the C content after decarburization is 0.0009% or less (Claim 5).

A sixth means for solving the above-mentioned problem is as follows.
The method for producing a non-oriented electrical steel sheet according to the fourth or fifth means, wherein the slab has a Cr content of 0.4 to 1.4%.
A method for producing a non-oriented electrical steel sheet having excellent high-frequency magnetic properties according to claim 3 (claim 6).

Here, "the balance substantially consists of Fe" means that, in addition to the specified elements, a trace amount of other elements including unavoidable impurities is contained within a range not to impair the effects of the present invention. It is shown that what is included is included in the scope of the present invention. In addition, the percentages indicating the components of steel described in this specification, including the tables, are all percentages by weight, and ppm is also ppm by weight.

[0013] The non-oriented electrical steel sheet to which all of the above means are applied is an invention for use, which is limited to one that is used through a heating process after finish annealing.
In this case, it has a special effect.

(Circumstances leading to the invention and reasons for limiting Cr and C) The inventors of the present invention do not use the steel as it is after the finish annealing,
By heat treatment such as magnetic annealing, bluing, shrink fit
When used after heating at 300 ° C or higher, carbides precipitate during cooling after the heating, so the magnetic properties deteriorate, and the conventionally known method of controlling Cr is insufficient. Was found to be.

By adding a predetermined amount of Cr and controlling C within a predetermined range, the precipitation of carbides during heat treatment such as magnetic annealing, bluing, shrink fitting, etc. is suppressed, and high-frequency iron loss is suppressed. Can be reduced. Less than,
The circumstances leading to the invention and the reasons for limiting Cr and C will be described in detail based on experimental results.

First, in order to investigate the effect of Cr on magnetic properties after magnetic annealing, C: 0.0035%, Si: 2.5%, Mn:
0.18%, P: 0.01%, Al: 1.0%, S: 0.0005%, N:
0.0020%, steel of Cr = tr. (Steel type X) and steel containing 1% of Cr (steel type Y) are melted in a laboratory, hot-rolled, pickled, and then put in a 100% H ₂ atmosphere. The sheet was annealed at 860 ° C. for 3 hours and rolled to a sheet thickness of 0.35 mm.

Next, at 1000 ° C. in a 10% H ₂ -90% N ₂ atmosphere.
× 1 minute finish annealing was performed, and the magnetic properties after the finish annealing were measured. Furthermore, after magnetic annealing at 750 ° C. for 2 hours in a 100% N ₂ atmosphere, the magnetic properties were measured. Here, the magnetic properties were evaluated using a ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm.
The high-frequency characteristics were measured for the windings of the next 100 turns and the second 100 turns. Table 1 shows the iron loss W _{1 0/400} (W / kg) at 400Hz and after magnetic annealing after the finish annealing of the steel X and Y.

[0018]

[Table 1]

Table 1 shows that iron loss after magnetic annealing in Cr-added steel is deteriorated. In order to investigate the cause, the structure of the 1% Cr-added steel after the magnetic annealing was observed.
As a result, many Cr carbides were observed in the grain boundaries and in the grains.
Furthermore, in the sample after the finish annealing of the Cr-added steel, such a carbide was not recognized, and therefore, during the magnetic annealing,
It is probable that iron carbide deteriorated because Cr carbide precipitated and movement of the domain wall was hindered.

A number of methods have been proposed to reduce high-frequency iron loss by adding Cr. However, all of these methods refer only to the magnetic properties after finish annealing, and the precipitation of Cr carbide during magnetic annealing is not considered. This is a new finding that has never been seen before. However, when Cr is added, ferrochrome, which is relatively inexpensive industrially, is generally used as a raw material, but mixing of C from impurities cannot be avoided.

Therefore, the inventors of the present invention have conducted studies on decarburization during the manufacturing process to suppress the precipitation of Cr carbide during magnetic annealing. In order to investigate the effect of C on magnetic properties after magnetic annealing, C: 0.0050%, S
i: 2.5%, Mn: 0.18%, P: 0.01%, S: 0.0005%, A
l: 1.0%, Cr: 1.0%, N: 0.0020% steel was melted in a laboratory and pickled after hot rolling.

Thereafter, decarburization treatment was performed under the conditions shown as B to L in Table 2, and the decarburization annealing was not performed.
And the C content shown in Table 2 respectively. Then 10
The hot rolled sheet was annealed at 860 ° C. for 3 hours in a 0% H ₂ atmosphere.
Further, the sheet was rolled to a sheet thickness of 0.35 mm, and subjected to finish annealing at 1000 ° C. for 1 minute in a 10% H ₂ -90% N ₂ atmosphere.
After magnetic annealing at 750 ° C. for 2 hours in a% N ₂ atmosphere, the magnetic properties were measured.

[0023]

[Table 2]

FIG. 1 shows the correlation between the C content of the sample thus obtained and the iron loss (W _10/400 ) at 400 Hz after magnetic annealing. From FIG. 1, it can be seen that the iron loss after magnetic annealing is critically increased in the region where the C content exceeds 15 ppm. In order to investigate the cause, a sample B of C: 0.0003% and a sample K of C: 0.0035% were observed by SEM. As a result, in Sample K, precipitation of Cr carbide was recognized in the grain boundaries and in the grains. On the other hand, in sample B, such precipitation of carbide was not observed.

From the above, it can be understood that by controlling C to 0.0015% or less, the precipitation of Cr carbide can be suppressed, and the magnetic properties after magnetic annealing can be reduced. Therefore, in the present invention, the upper limit of C is set to 0.0015% or less. However, from the viewpoint of iron loss, it is more desirable that the content be 0.0009% or less as shown in FIG.

Such carbide precipitation occurs in the temperature range of 300 to 600 ° C. In the case of magnetic annealing, carbide precipitates at the time of cooling after soaking. Further, even in heat treatment such as bluing, the material is heated to about 500 ° C., so that carbides are precipitated during cooling. Therefore, when such a heat history is given, the C content must be 0.0015% or less.

Further, from the viewpoint of iron loss, the content is more preferably 0.0009% or less. Thus, the non-oriented electrical steel sheet of the present invention is based on the premise that it is used after being further heated to 300 ° C. or more after the finish annealing has been performed. Has the effect of

In FIG. 1, the C amounts at the points plotted by black circles are 3, 5, 7, 9, 10, 1 in order from the left.
2, 14, 16, 18, 20, 25, 32, 40, 50
ppm.

Next, in order to investigate the effect of Cr on magnetic properties after magnetic annealing, C: 0.0035%, Si: 2.5%, Mn:
0.18%, P: 0.01%, S: 0.0005%, Al: 1.0%, N: 0.0
020%, Cr: tr.-5.5% steel was melted in a laboratory and pickled after hot rolling. Then, 15% H2 atmosphere, dew point 25 ℃
At 750 ° C. × 2 hours for decarburizing annealing to reduce the C content to 0.0005%. Then, hot rolled sheet annealing at 860 ° C. for 3 hours was performed in a 100% H ₂ atmosphere, and the sheet was rolled to a sheet thickness of 0.35 mm. Then 10% H
Performs final annealing of 1000 ° C. × 1 minute at ₂ -90% N ₂ atmosphere, 750 ° C. × after magnetic annealing of 2hr at 100% N ₂ atmosphere, magnetic characteristics were measured.

FIG. 2 shows the amount of Cr and the iron loss at 400 Hz after magnetic annealing.
(W _10/400 ) is shown. From FIG. 2, it can be seen that the iron loss is critically reduced when Cr is in the range of 0.4% or more.
This is because the eddy current loss was reduced due to the increase in the electric resistance. Therefore, in the present invention, the lower limit of Cr is 0.4%
And On the other hand, the upper limit of Cr is set to 5% from the viewpoint of cost and since the magnetic flux density decreases as the Cr content increases.
However, as shown in FIG. 2, the iron loss becomes critically low when Cr is in the range of 0.4 to 1.4%. Therefore, it is preferable to set the range of Cr to this range.

The Cr content at the points indicated by black circles in FIG. 2 is 0, 0.25, 0.45, 0.6, 0.85, 1.0, 1.2, 1.
4, 1.6, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 5.5%.

(Reasons for Limiting Other Components) Next, reasons for limiting other components will be described. Si: When Si exceeds 4%, the magnetic flux density decreases, so the upper limit is set to 4.0%.
Since the element is effective for increasing the specific resistance of the steel sheet, the lower limit is preferably set to 1.0%. Al: If Al exceeds 2.0%, the magnetic flux density deteriorates, so the upper limit is made 2.0%. It is to be noted that, like Si, it is an element effective for increasing the specific resistance, and if it is less than 0.1%, fine AlN is formed, which becomes a hindrance to grain growth, so the lower limit is preferably made 0.1%. .

Mn: Mn is required to be 0.05% or more in order to prevent red-hot brittleness during hot rolling, but if it exceeds 2%, the magnetic flux density is reduced, so Mn is set to 0.05 to 2.0%. P: P
If the content exceeds 0.1%, the steel sheet becomes hard, so the upper limit is set to 0.1%. N: Since N forms AlN and causes an increase in iron loss, the upper limit is made 0.005%. S: S is
If it exceeds 0.02%, the precipitation of MnS causes an increase in iron loss, so the upper limit is made 0.02%. In addition, if Sb and Sn are added within a range that does not lose the effect of the present invention, iron loss can be further reduced.

[0034]

[Manufacturing method] In the present invention, as long as C and Cr are controlled within a predetermined range, the other manufacturing method may be a method of manufacturing a normal non-oriented electrical steel sheet. That is, the molten steel blown in the converter is degassed and adjusted to a predetermined component, and subsequently casting and hot rolling are performed. Here, the method of reducing C to 0.0015% or less may be any method of controlling the steelmaking stage or decarburizing treatment in a reducing atmosphere during hot-rolled sheet annealing or finish annealing. However, as described above, if Cr is within the scope of the present invention, the C content is unavoidably increased. Therefore, the C content is adjusted by decarburization as described in claims 4 to 6. It is preferable to perform annealing. The decarburization treatment may be performed during hot-rolled sheet annealing, finish annealing, or any other annealing. Also, the finish annealing temperature during hot rolling and the winding temperature do not need to be particularly specified,
The temperature at which a known non-oriented electrical steel sheet is manufactured may be used.

Next, after hot-rolled sheet annealing is performed, cold-rolling is performed once or cold-rolling two or more times with intermediate annealing is performed to obtain a predetermined sheet thickness, and then finish annealing is performed. Next, a film is applied and baked, and thereafter, magnetic annealing is performed by a customer to remove processing strain.

[0036]

EXAMPLES (Example 1) Using the steel shown in Table 3, the steel was blown in a converter and then degassed, adjusted to a predetermined composition and cast, and the slab was heated at 1140 ° C for 1 hour. Board thickness 2.
Hot rolling was performed to 0 mm. The hot rolling finishing temperature was 750 ° C, and the winding temperature was 610 ° C. After that, pickle and 100% H2
The hot rolled sheet was annealed at 860 ° C. for 3 hours in an atmosphere, and then rolled to a sheet thickness of 0.35 mm. Then, in a 10% H ₂ -90% N ₂ atmosphere, finish annealing at 1000 ° C. × 1 min is performed, and 100%
After magnetic annealing at 750 ° C. for 2 hours in an N ₂ atmosphere, the magnetic properties were measured. Magnetic properties of each steel sheet (W _10/400, B ₅₀₎ are also shown in Table 3. From Table 3, the experiment N in which C and Cr were within the scope of the present invention.
In the steels of o.1 to 9, it is understood that a material having a low high-frequency iron loss and a high magnetic flux density can be obtained.

On the other hand, in the steel of No. 10, the iron content is high because the Cr content is low. In the case of No. 11 steel, Cr
Due to the high content, the magnetic flux density is low. No.12
In steels Nos. To 15, the iron content is high because the C content is high. In the steels of Nos. 16, 17, and 18, Si, Al, and Mn are out of the range of the present invention, respectively, so that the magnetic flux density is low. In the steels of No. 19 and No. 20, S and N are out of the range of the present invention, respectively, so that the iron loss is high.

[0038]

[Table 3]

(Example 2) Using the steel shown in Table 4, the steel was blown in a converter and then degassed, adjusted to a predetermined composition and cast, and the slab was heated at 1140 ° C for 1 hour. Thick
Hot rolling was performed to 2.0 mm. The hot rolling finishing temperature was 750 ° C, and the winding temperature was 610 ° C. Then pickled, 100% H
Hot rolled sheet annealing at 860 ° C. for 3 hours was performed in _two atmospheres. Then, the sheet was rolled to a thickness of 0.35 mm, and subjected to finish annealing at 1000 ° C. for 1 minute in a 10% H ₂ -90% N ₂ atmosphere, followed by 100%
After magnetic annealing of 750 ° C. × 2 hr in an N ₂ atmosphere, magnetic characteristics were measured. The decarburization treatment of each steel type was performed under the conditions shown in Table 4. Table 4 shows the C content of each steel sheet after decarburization and the magnetic properties (W _10/400 , B ₅₀ ) after magnetic annealing. Table 4,
From Table 5, it can be seen that, in the steels of Experiment Nos. 1 to 12 in which C and Cr are in the range of the present invention, a material having low high-frequency iron loss and high magnetic flux density can be obtained.

On the other hand, the No. 13 steel has a high Cr loss due to a low Cr content. In the case of No. 14 steel, Cr
Due to the high content, the magnetic flux density is low. No.15
In steels No. to No. 20, since the C content is high, the iron loss is high in each case. In the steels of Nos. 21, 22, and 23, since Si, Al, and Mn are out of the range of the present invention, the magnetic flux density is low. In steels No. 24 and No. 25, S and N are out of the range of the present invention, respectively, so that iron loss is high.

[0041]

[Table 4]

[0042]

[Table 5] (Example 3) Table 6 shows 500 ° C which is a heat treatment equivalent to booing.
The results of heating for 1 hour are shown. From this, C ≦ 15ppm
It can be seen that excellent iron loss can be obtained from the results.

[Table 6]

As described above, according to the present invention,
Since the precipitation of carbides can be suppressed, a non-oriented electrical steel sheet having low high-frequency iron loss and used through a heating process after finish annealing can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the C content and iron loss W _10/400 .

FIG. 2 is a diagram showing the relationship between the Cr content and iron loss W _10/400 .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiko Ono 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Yasushi Tanaka 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Date F-term (reference) in Honko Pipe Co., Ltd. 4K033 AA01 CA07 CA08 CA09 FA00 GA00 JA00 JA04 KA00 RA03 SA00 SA01 SA02 SA03 5E041 AA02 CA01 CA04 NN01

Claims (6)

[Claims] (1) C: 0.0015% or less, Si: 4% or less, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less by weight%
N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 5%, the balance is substantially Fe, and after the final annealing, it is used through a heating process after the final annealing. Electrical steel sheet. 2. In weight%, C: 0.0009% or less, Si: 4% or less, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less,
N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 5%, the balance is substantially Fe, and after the final annealing, it is used through a heating process after the final annealing. Electrical steel sheet. 3. The non-oriented electrical steel sheet according to claim 1 or 2, wherein the range of Cr content is limited to 0.4 to 1.4%. Non-oriented electrical steel sheet with excellent high frequency magnetic properties. 4. C: 0.005% or less by weight, Si: 4% or less, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less,
A slab containing N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 5%, and the balance substantially consisting of Fe is hot-rolled,
After pickling and rolling to a predetermined thickness, in any of the continuous annealing processes, a decarburizing treatment is performed in a reducing atmosphere to reduce the C content after decarburizing to 0.0015% or less. A method for producing a non-oriented electrical steel sheet having excellent high-frequency magnetic properties, which is used through a heating process after the finish annealing according to claim 1. 5. C: 0.005% or less by weight, Si: 4% or less, Al: 2% or less, Mn: 0.05 to 2%, P: 0.1% or less,
A slab containing N: 0.005% or less, S: 0.02% or less, Cr: 0.4 to 5%, and the balance substantially consisting of Fe is hot-rolled,
After pickling and rolling to a predetermined thickness, in any of the continuous annealing processes, decarburizing treatment is performed in a reducing atmosphere to reduce the C content after decarburization to 0.0009% or less. 3. A method for producing a non-oriented electrical steel sheet having excellent high-frequency magnetic properties, which is used through a heating process after the finish annealing according to claim 2. 6. The method for producing a non-oriented electrical steel sheet excellent in high-frequency magnetic properties according to claim 4 or 5,
4. The method for producing a non-oriented electrical steel sheet having excellent high-frequency magnetic properties, wherein the Cr content in the slab is limited to 0.4 to 1.4% and further used after a final annealing step through a heating process. .