JP2002115035A - Nonoriented silicon steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonoriented silicon steel sheet having, in a high frequency region, low core loss magnetic flux density in an allowable range, rigidity, durable calking properties and proper hardness. SOLUTION: This nonoriented silicon steel sheet has a composition containing, by weight, <=0.005% C, 1 to 4% Si, 0.1 to 2.5% Al, <=3.5% Mn, 0.4 to 1.4% Cr and <=0.001% O, and the balance substantially Fe, and also, the average crystal grain size after finish annealing is 50 to 90 μm.

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, and more particularly, to a non-oriented electrical steel sheet suitable for use as a material for an iron core of electric equipment used at a high frequency of 200 to 1000 Hz. It is about.

[0002]

[Prior Art] Following the enforcement of the revised Energy Conservation Law in April 1999,
Efforts to save energy have been active in the electrical equipment industry. One of the approaches is to increase the efficiency of the motor, and one of the measures is to increase the driving frequency of the motor. Along with this,
It is also desired that non-oriented electrical steel sheets used as core materials of these motors have a low iron loss at high frequencies (200 to 1000 Hz).

[0003] Iron loss is divided into hysteresis loss and eddy current loss, and the occupation ratio of eddy current loss is particularly high in a high frequency range. Therefore, in order to reduce high-frequency iron loss, it is essential to reduce eddy current loss. Since the eddy current loss is proportional to the square of the plate thickness and inversely proportional to the specific resistance, the electric steel sheet has been made thinner and the specific resistance has been increased by increasing the Si.

The former is disclosed, for example, in JP-A-8-602.
No. 52 proposes a method for producing a non-oriented electrical steel sheet having a low iron loss by reducing the thickness of the steel sheet to 0.1 to 0.25 mm. Regarding the latter, for example, Japanese Patent Application Laid-Open No. Sho 62-103321 proposes a method for producing a silicon steel sheet having a low iron loss by increasing the specific resistance by setting the Si content to 4 to 7%. I have.

[0005]

However, the former method has a problem that when the plate thickness is less than 0.20 mm, the rigidity is greatly reduced and the caulking property is also deteriorated. In the latter method, since 4% or more of Si is contained, there is a disadvantage that the punchability is deteriorated due to an increase in hardness.

The present invention has been made in view of such circumstances, and has a low iron loss and an acceptable magnetic flux density in a high-frequency region (200 to 1000 Hz), and does not deteriorate rigidity or caulking property. It is another object of the present invention to provide a non-oriented electrical steel sheet having a hardness not excessively high.

[0007]

The first means for solving the above-mentioned problems is as follows: C: 0.005% or less by weight%;
4%, Al: 0.1-2.5%, Mn: 3.5% or less, Cr: 0.4-1.4
%, O: 0.001% or less, the balance being substantially composed of Fe, and a non-oriented electrical steel sheet having an average crystal grain size after finish annealing of 50 to 90 μm (Claim 1).

[0008] A second means for solving the above problems is as follows.
C: 0.005% or less by weight, Si: 1-4%, Al: 0.1-2.
5%, Mn: 3.5% or less, Cr: 0.4 to 0.9%, O: 0.001% or less, the balance being substantially Fe, and having an average crystal grain size after finish annealing of 50 to 90 μm. A grain-oriented electrical steel sheet (Claim 2).

The phrase “the balance is substantially composed of Fe” means that a substance containing other trace elements including unavoidable impurities is included in the scope of the present invention as long as the function and effect of the present invention are not lost. It is shown. In addition, unless otherwise specified, in this specification including the tables,% indicating the components of steel is% by weight.

(Process leading to the invention and the reason for limiting the contents of Cr and O) As a result of repeated investigations to solve the above-mentioned problems, the present inventors found that a predetermined amount of Cr was contained and the O content was reduced. By controlling the non-oriented electrical steel sheet of low iron loss in the high frequency region, furthermore, by adjusting the average crystal grain size of the finish annealed sheet within a predetermined range, the adhesion of the coating is improved, From these facts, it has been found that a steel sheet excellent in iron loss and magnetic flux density in a high frequency region can be obtained.

Hereinafter, the present invention will be described in detail based on experimental results. First, in order to investigate the effect of Cr on magnetic properties, C: 0.0025%, Si: 3.0%, Mn: 0.18
%, Al: 1.0%, O: 0.0020%, Cr: 0-2.0% steel A
And C: 0.0025%, Si: 3.0%, Mn: 0.18%, Al: 1.0
%, O: 0.0007%, Cr: 0 to 2.0% steel B was vacuum melted in a laboratory to produce a cast slab. Next, the cast slab was pickled after hot rolling, and annealed at 860 ° C. for 3 hours in a 100% H ₂ atmosphere, and cold rolled to a sheet thickness of 0.35 mm. And 10
Finish annealing was performed at 1000 ° C. for 1 minute in an atmosphere of% H ₂ -90% N ₂ , and the magnetic properties were measured. For the evaluation of the magnetic properties, one ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm was prepared, and a primary-side 100-turn, secondary-side 100-turn winding was used.

FIG. 1 shows the amount of Cr, the iron loss at 800 Hz (W _10/800 ), and the magnetic flux density B of the sample thus obtained.
_{Shows 50} correlations. In FIG. 1, the mark “x” corresponds to steel A, and the mark “○” corresponds to steel B. The Cr content of each plotted point is 0%, 0.15%, 0.30%, 0.42%, 0.60% from left to right.
%, 0.80%, 0.90%, 1.00%, 1.20%, 1.38%, 1.60
%, 1.80% and 2.00%.

FIG. 1 shows that in steel A having an O content of 20 ppm,
r When the content is 0.4% or more, iron loss W _10/800 decreases critically,
It can be seen that iron loss is greatly reduced in steel B having an O content of 7 ppm. When the Cr content exceeds 1.4%, the iron loss starts to increase sharply.

On the other hand, the magnetic flux density B ₅₀ is such that the Cr content is 0.9%.
It can be seen that the decrease gradually increases until the Cr content exceeds 0.9%, and the degree of reduction increases when the Cr content exceeds 1.4%. From the above, in the invention according to claim 1, the lower limit of the Cr content is set to 0.4.
%, And the upper limit is 1.4%. As a more desirable form, in the invention according to claim 2, the upper limit of the Cr content is 0.9%.

Next, in order to investigate the characteristic difference between the steel A and the steel B, when the form of the inclusion was observed by SEM, the (Al-Cr) O composite oxide was observed in the sample of the steel A. In the sample of steel B, almost no (Al-Cr) O composite oxide was found.

In order to investigate the effect of the O content on the magnetic properties, C: 0.0025%, Si: 3.0%, Mn: 0.18
%, Al: 1.0%, Cr: 0.9%, O: 0.0003 to 0.0050% steel was vacuum melted in a laboratory to produce a cast slab. Next, the slab was pickled after hot rolling, and 860 ° C. × 100% H ₂ atmosphere.
The hot rolled sheet was annealed for 3 hours and rolled to a sheet thickness of 0.35 mm.
Then, finish annealing was performed at 1000 ° C. for 1 minute in a 10% H ₂ -90% N ₂ atmosphere, and the magnetic properties were measured. For the evaluation of the magnetic properties, one ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm was prepared, and a primary-side 100-turn, secondary-side 100-turn winding was used.

FIG. 2 shows the relationship between the O content of the sample thus obtained and the iron loss at 800 Hz (W _10/800 ). In FIG. 2, the O contents at the plotted points are 0.0003%, 0.0005%, 0.0007%, 0.0009%, and 0.
0010%, 0.0011%, 0.0016%, 0.0021%, 0.0030%, 0.
0040% and 0.0050%.

FIG. 2 shows that the iron loss is critically reduced in the range where the O content is 0.001% or less. This is considered to be due to a decrease in hysteresis loss due to the elimination of the (Al-Cr) O composite oxide. Therefore, in the present invention, the upper limit of the O content is set to 0.001%.

(Reasons for Limiting Other Components) Next, reasons for limiting other components will be described. C: C is set to 0.005% or less because of the problem of magnetic aging. Si: Since Si is an element effective for increasing the specific resistance of the steel sheet, the lower limit is set to 1%. On the other hand, if it exceeds 4%, the magnetic flux density decreases, so the upper limit is made 4%. Mn: Mn is also an effective element for increasing the specific resistance, but the magnetic flux density is reduced, so the upper limit is set to 3.5%.

Al: Like Si, Al is an element effective for increasing the specific resistance, but if it exceeds 2.5%, the magnetic flux density deteriorates, so the upper limit is made 2.5%. On the other hand, if it is less than 0.1%, fine AlN is formed and becomes a factor inhibiting grain growth, so the lower limit is made 0.1%.

(Reason for limiting the average crystal grain size) Next, assuming that the user uses the motor core,
An insulating film was applied to the manufactured magnetic steel sheet, baked, and the magnetic properties of the laminated ring-shaped samples were evaluated.

C: 0.0025%, Si: 3.0%, Mn: 0.18%, A
l: 1.0%, O: 0.0007%, Cr: 0.9% steel was vacuum melted to produce a slab. Next, the slab was pickled after hot rolling, and then annealed at 860 ° C. for 3 hours in a 100% H ₂ atmosphere, and rolled to a thickness of 0.35 mm. And 10% H ₂ -90%
Finish annealing was performed at 1000 ° C. for 1 minute in a N ₂ atmosphere. Then, a chromic acid-based semi-organic film was applied to the surface and baked.

The magnetic characteristics were determined by punching a ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm, and stacking one (sample X) and six (sample Y) on the primary side for 100 turns, The next 100 turns of the winding were applied and evaluated by comparison.

Table 1 shows the iron loss W _10/800 of the samples X and Y. From Table 1, it can be seen that the core loss of Sample Y in which the ring cores were stacked and the magnetic characteristics were measured was significantly deteriorated.

(Table 1)

[Table 1]

In order to investigate the cause, the vicinity of the punched portion of the sample Y was observed with an optical microscope, and it was confirmed that the coating had peeled off. It is considered that the reason for this is that when Cr was added, the adhesion of the film was weakened due to the formation of a Cr-based oxide on the surface layer, and peeling was likely to occur. That is, it is considered that the peeling of the film caused insufficient interlayer insulation of the laminated ring samples, increased eddy current loss, and deteriorated iron loss.

In the high frequency range, the ratio of the eddy current loss to the total iron loss increases. Therefore, when Cr is added, it is important to improve the adhesion of the film. Therefore, in order to reduce the sagging of the punched fracture surface, a study was made on the refinement of crystal grains.

C: 0.0025%, Si: 3.0%, Mn: 0.18%, A
l: 1.0%, Cr: 0.9%, O: 0.0007% steel was vacuum-melted in a laboratory to produce a slab. Next, the slab was pickled after hot rolling, and then annealed at 860 ° C. for 3 hours in a 100% H ₂ atmosphere, and rolled to a thickness of 0.35 mm. And 10%
Finish annealing at 750 to 1150 ° C for 1 minute in an H ₂ -90% N ₂ atmosphere to change the crystal grain size of the steel sheet, apply and bake a semi-organic film of chromic acid, measure the magnetism and observe peeling of the film Was done.

The magnetic properties were determined by punching a ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm.
The evaluation was performed by applying a winding of the next 100 turns and performing comparison. The peeling of the film was observed by using an optical microscope near the punched portion.

Table 2 shows the average crystal grain size, magnetic properties (W _10/800 , B ₅₀ ) of the finish-annealed sheet, and the results of observation of peeling of the coating. Regarding the “peeling of the coating”, those where no peeling of the coating was observed in the vicinity of the punched portion of the ring core were “none”, and those where the peeling was observed even a little were “present”.

(Table 2)

[Table 2]

From Table 2, it can be seen that the average grain size of the finish-annealed sheet is 90%.
It can be seen that the iron loss is low and no peeling of the film occurs when the thickness is less than μm. It is considered that this is because, when the crystal grain size is fine, the grain boundary increases and the anchor effect is strengthened, and the sag during punching is reduced. When the average grain size of the finish-annealed sheet exceeded 90 μm, peeling of the film was observed near the punched portion. On the other hand, when the average crystal grain size of the finish annealed sheet is smaller than 50 μm from the magnetic properties, the iron loss W
You can see that _10/800 is higher. This is because the hysteresis loss increases. From the above results, in the present invention, the range of the average crystal grain size is limited to 50 to 90 μm.

(Manufacturing method) In the present invention, if the predetermined components such as Cr and O fall within the predetermined range and the average crystal grain size is within the predetermined range, the manufacturing method is the same as the normal non-directional method. A method of manufacturing an electrical steel sheet may be used. That is,
The molten steel blown in the converter is degassed to adjust to a predetermined component, and then cast and hot-rolled. The finish annealing temperature and the winding temperature at the time of hot rolling do not need to be particularly specified, and may be within a range where a normal non-oriented electrical steel sheet is manufactured. Hot rolled sheet annealing may be performed, but is not essential. Next, after finishing to a predetermined plate thickness by one rolling or two or more rollings with intermediate annealing, finish annealing is performed. Magnetic annealing after finish annealing may be performed, but is not essential. When applying and baking an insulating film, the film may be semi-organic or inorganic.

[0034]

EXAMPLES Using the steel shown in Table 3, the steel was blown in a converter and then degassed, adjusted to predetermined components as shown in the table, cast, and the slab was heated at 1140 ° C. for 1 hour. rear,
Hot rolling was performed to a thickness of 2.0 mm. Hot rolling finish temperature is 750
° C, and the winding temperature was 610 ° C. Then pickle, 100
The sheet was annealed at 860 ° C. for 3 hours in a% H ₂ atmosphere. Next, the sheet was cold-rolled to a sheet thickness of 0.35 mm, subjected to finish annealing for 1 minute at a temperature shown in Table 3 in an atmosphere of 10% H ₂ -90% N ₂ , coated with a chromic acid-based semi-organic film, and baked.

Thereafter, the average crystal grain size and magnetic properties of the finished annealed sheet and the adhesion of the film were evaluated. The evaluation of the magnetic properties was performed by punching a ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm, laminating six sheets, and performing winding of 100 turns of primary and 100 turns of secondary. The adhesion of the coating was evaluated by observing the vicinity of the punched portion of the ring sample with an optical microscope.

Table 3 also shows the average crystal grain size, magnetic properties (W _10/800 , B ₅₀ ) of the finish-annealed sheet of each steel sheet, and the results of observation of film peeling. In Table 3, steel plates Nos. 1 to 8 are steel plates according to examples of the present invention, and steel plates Nos. 9 to 21 are comparative examples. In each of the comparative examples, the component values or the average crystal grain size surrounded by the thick frame indicate that they are out of the range of the present invention.

(Table 3)

[Table 3]

As can be seen from Table 3, in each of the examples, the _iron loss value W _10/800 is 51.5 (W / kg) or less, and the magnetic flux density B ₅₀ is 1.64 (T) or more. I have.

On the other hand, in the comparative example, the steel sheet No. 1
Except for 5 and 16, the iron loss values are significantly higher than those in the examples. Steel plates No. 15 and 16 are Si, Mn
Is higher than the range of the present invention, the iron loss value is almost the same as that of the embodiment of the present invention, but the magnetic flux density is low. Further, although not shown in the table, the steel sheet No. 15 had poor punching properties due to the high Si content.

As clearly shown in Table 3, when the average grain size is larger than the range of the present invention, the iron loss value is greatly increased.

[0041]

As described above, according to the present invention, a non-oriented electrical steel sheet having a low iron loss in a high frequency range of about 200 to 1000 Hz and a magnetic flux density within an allowable range can be obtained. Can be This magnetic steel sheet has low iron loss without thinning, so that rigidity and caulking properties do not deteriorate, and since the Si content is not high, it is necessary to prevent the punchability from deteriorating due to an increase in hardness. Can be. The non-oriented electrical steel sheet according to the present invention has electrical characteristics suitable for use in electrical equipment such as a motor used in a high frequency range (200 to 1000 Hz).

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the Cr content and iron loss and magnetic flux density.

FIG. 2 is a diagram showing the relationship between the O content and iron loss.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshihiko Ono 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Toshiaki Obube 1-1-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) in Nippon Kokan Co., Ltd. 5E041 AA11 AA19 CA04 NN01 NN06

Claims (2)

[Claims] 1. C: 0.005% or less by weight, Si: 1-4
%, Al: 0.1 to 2.5%, Mn: 3.5% or less, Cr: 0.4 to 1.4
%, O: 0.001% or less, a balance substantially consisting of Fe, and an average crystal grain size after finish annealing is 50 to 90 μm. 2. C: 0.005% or less by weight, Si: 1-4
%, Al: 0.1 to 2.5%, Mn: 3.5% or less, Cr: 0.4 to 0.9
%, O: 0.001% or less, a balance substantially consisting of Fe, and an average crystal grain size after finish annealing is 50 to 90 μm.