JP2000030922A - Magnetic steel sheet having high machinability and magnetic characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic steel sheet having high machinability and a high magnetic characteristic by specifying the number of inclusions having a specific particle size or larger of the inclusions observed on the end face of steel sheet against the total number of inclusions. SOLUTION: Test pieces of a nonoriented magnetic steel sheet which contain nearly the same number (about 8,000-10,000 particles/mm2) of inclusions having particle size of >=0.1 μm, about 1 wt.% (Si+Al), about 110-130 Vickers hardness, and inclusions in various particle size distributions are examined and the test pieces are put in order based on the ratio (%) of the number per unit area of inclusions having particle sizes of >=0.1 μm to the number per unit area of inclusions having particle sizes of >=2 μm. When the number of the inclusions having particle sizes of >=2 μm exceeds the 10% of the total number of the inclusions having particle sizes of >=0.1 μm, the machinability of the magnetic steel sheet is improved. In addition, the kinds of the inclusions have no relation to the magnetic characteristic and machinability of the steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic steel sheet used as an iron core of electric equipment, and more particularly, to a rotor of a rotating machine,
The present invention relates to an electromagnetic steel sheet which has excellent machinability in lathing of a stator and excellent magnetic properties.

[0002]

2. Description of the Related Art Magnetic steel sheets are used as core materials for stationary equipment such as transformers and stabilizers, and for rotating machines such as electric motors and generators. Such materials are required to have excellent magnetic properties, but at the stage of manufacturing the iron core, punching, crimping,
Good workability such as machinability is also required. However, hitherto, the machinability of the non-oriented electrical steel sheet has been seldom regarded as important as compared with the punching property and the caulking property.

[0003] The rotor and the stator of the rotating machine are formed by punching out electromagnetic steel sheets, laminating them, and then performing cutting with a lathe in order to improve the dimensional accuracy of the air gap between the rotor and the stator. In particular, the rotor iron core often performs high-precision cutting because dynamic balance during rotation is important. If a material having poor machinability is used, the frequency of changing the cutting tool in the stage of manufacturing the iron core increases, and workability and production cost decrease.

On the other hand, a material having poor machinability tends to generate burrs due to cutting. The rotor or the stator is provided with a groove for forming a magnetic pole, and burrs are easily generated at the edge or end of the groove. If the core is incorporated into a rotating machine with cutting burrs remaining, an electrical short circuit may occur between the cores, resulting in an increase in iron loss or overheating of the core. Alternatively, burrs may be caught in the air gap between the rotor and the stator, causing damage to the lamination and dielectric breakdown of the coil. Therefore, it is necessary to remove cutting burrs before assembling. However, this deburring operation involves problems such as extra work steps, necessity of deburring equipment, and impairment of handling safety. .

Therefore, there is a need for an electromagnetic steel sheet that is easy to cut and does not generate burrs. In response to this request, for example, the following technology has been proposed.

Japanese Patent Publication No. 54-1169 discloses a notch effect by adding graphite to an electromagnetic steel or an electromagnetic steel sheet.
It is stated that a lubricating effect is produced and the machinability is improved, but the addition of graphite is not preferable because it adversely affects the magnetic properties of the steel sheet.

Japanese Patent Publication No. 56-34616 discloses a technique for improving machinability by adding a large amount of Mn to non-oriented electrical steel sheets in an amount of 1 to 3%. The reason for this is clarified. However, addition of a large amount of Mn is not preferable because it increases the cost.

Japanese Patent Application Laid-Open No. 4-293724 discloses that by adding P to a steel sheet, the machinability is improved without deteriorating the magnetic properties of the non-oriented electrical steel sheet.
In order to compensate for the decrease in toughness due to the addition, ultra-low C and ultra-low S are required to increase the de-C and de-S costs, and there is a restriction of (Si + Al) <1.5% by weight. There is a problem that the amount of Si as a component is restricted.

Japanese Patent Application Laid-Open No. Hei 5-331602 discloses a technique in which the amount of Mn and the amount of Al in a steel sheet are regulated to adjust the hardness of the steel sheet to maintain the machinability. However, it is difficult to say that sufficient machinability can be obtained by simply maintaining the value.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnetic steel sheet having excellent machinability and magnetic properties.

[0011]

Means for Solving the Problems The inventors of the present invention have prepared a non-oriented electrical steel sheet, which is a material for a rotor that uses a lot of cutting, by melting raw steel under various manufacturing conditions, and performing various rolling and annealing processes. Test materials were prepared under the conditions.

The relationship between the number of inclusions in the steel of these test materials and the magnetic properties was investigated, and it was found that the particle size was approximately 0.1 μm.
m or more for inclusions of 10,000 or more
It was confirmed that when the number was not more than the number / mm ² , predetermined magnetic properties were satisfied.

Next, the test materials were laminated in the form of an iron core, and a test of machinability was performed. Of the various test specimens, when carefully examining the test specimens with low tool damage and long tool life, that is, the test specimens evaluated as having good machinability, compared to the test specimens evaluated as having poor machinability, We have found that many inclusions are large in size.

[0014] Further, among the test pieces evaluated as having good machinability, those having good magnetic properties were investigated. As a result, a relatively large number of inclusions having a particle diameter of 2 μm or more was found to be more than a certain number in the total inclusions. (10% or more).

The gist of the present invention, which has been completed based on the above findings, is that among the particles of inclusions in steel observed in a cross section, the number of particles having a particle diameter of 2 μm or more is reduced to the number of particles having a particle diameter of 0.1 μm or more. An electrical steel sheet having excellent machinability and magnetic properties characterized by being 10% or more.

Here, the inclusions refer to sulfides, oxides, carbides, nitrides, and composites thereof. The particle diameter refers to the diameter of a circle having the same area.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reasons for limiting each condition in implementing the present invention will be described below. FIG. 1 is a graph showing the relationship between the number of inclusions in steel and magnetic properties (iron loss W15 / 50) of a test piece having a chemical composition in which the amount of (Si + Al) is about 0.2% by weight. As shown in FIG.
It can be seen that when the number exceeds 00 pieces / mm ² , the magnetic properties deteriorate. This is considered because the growth of crystal grains is suppressed by inclusions.

The number of particles was measured for inclusions of 0.1 μm or more that can be efficiently observed with an optical microscope.

Next, the inventors pay attention to the size and magnetic characteristics of the inclusions, and the number of the inclusions having a particle diameter of 0.1 μm or more in steel materials having substantially the same chemical composition (8000 to 10).
000 pieces / mm ² ) Test pieces were selected and their magnetic properties were investigated. Some of the test pieces of these materials had excellent and inferior magnetic properties. Examination of a material with poor magnetic properties with an optical microscope reveals that many fine inclusions are dispersed, and that a material with excellent magnetic properties has a small number of fine inclusions and a large number of inclusions with a large particle size. Was. That is, when the number of inclusion particles is the same, those distributed on the side where the particle diameter is large have excellent magnetic properties. At this time, when the number of inclusions was stratified according to the particle size, it was found that inclusions having a particle diameter of less than 2 μm deteriorated the magnetic properties as described below.

FIG. 2 is a graph showing the relationship between the particle diameter of inclusions and the ratio of the number of inclusions. In the figure, the number of all the inclusions having a particle diameter of 0.1 μm or more in each test piece is almost the same (800
0-10000 pieces / mm ²⁾ a but, inclusions or 2μm less, and the iron loss inferior to fine inclusions often steel other steel in A.

As shown in the figure, when the particle diameter is arranged at 2 μm, it is understood that the correlation between the number of particles of the inclusions and the magnetic characteristics is strong.

Next, when the cut surface of the specimen having good machinability was observed with a scanning electron microscope (SEM), it was found that inclusions were present at the starting point of the cut fracture. From this, it was presumed that when the material was subjected to cutting, the inclusion particles hit the tool, causing a crack in the work material, which accelerated the cracking and advanced the cutting. Furthermore, a comparison of the form of the shavings and burrs with the form of the inclusions shows that the inclusions should be at least a certain size in order for the inclusions to be the starting point of the fracture during cutting. I found it.

FIG. 3 is a graph showing the relationship between the particle size of inclusions and the amount of wear of the cutting tool. The figure shows various inclusion particle diameters in which the total number of inclusions having a particle diameter of 0.1 μm or more is almost the same (8000 to 10000 / mm ² ), (Si + Al) is about 1% by weight, and Vickers hardness is 110 to 130. This is a survey of non-oriented electrical steel sheets having a distribution. In the figure, the horizontal axis represents the number of inclusions having a particle diameter of 0.1 μm or more per unit area as a denominator, and the particle diameter is 2 μm.
The number (m) or more of the inclusions was arranged as a ratio (%) as a molecule. As can be seen from the figure, the number of inclusions having a particle diameter of 2 μm or more accounts for 10% of the total number of particles having a particle diameter of 0.1 μm or more.
It can be seen that when the ratio exceeds 1, the machinability of the magnetic steel sheet is improved.

From the above, in order to achieve both the machinability and the magnetic characteristics, at least 10 μm or more of inclusions having a size of 2 μm or more should be included when targeting inclusions having a size of 0.1 μm or more.
%. Preferably, this ratio is at least 15%, more preferably at least 20%.
Further, the type of the inclusion is not limited in view of the influence on the magnetic characteristics and the effect on the machinability.

Next, a method for producing the magnetic steel sheet of the present invention will be described. The type of the magnetic steel sheet of the present invention may be applied to any of non-directional, one-directional, and two-directional. What is important for the machinability is the rotor of the rotating machine, and is particularly suitable for non-oriented electrical steel sheets.

In the case of an electrical steel sheet, the steel composition has a chemical composition in weight%, C: ≦ 0.005%, Mn: 0.1 to 4%, S
i: 0.1 to 4.5%, Al: ≤ 8%, P: ≤ 0.1
%, S: ≦ 0.05%, the balance being Fe and unavoidable impurities is a typical composition.

In the present invention, since inclusions having a relatively large grain size are dispersed in the steel, it is desirable that the type of the inclusions be large and easy to obtain, and that the inclusions are hard to be finely divided in the rolling step. It is preferred that oxides or composites thereof are mainly deposited. Therefore, in the above chemical composition, it is desirable to adjust the balance between both the S amount and the O amount.
Carbides and nitrides are also suitable as inclusions in the present invention,
Ti, Zr, Al, V, Nb, C capable of forming them
It is desirable to add r, B, W and the like.

In accordance with a conventional method, after melting in a converter,
Decarburization treatment and deoxidation treatment are performed by a vacuum degasser, and Si, Al, and Mn necessary for the basic composition of the magnetic steel sheet are added. At this time, it is desirable to control the deoxidation and desulfurization methods to increase the particle diameter of the inclusions. This molten steel is continuously cast according to a conventional method.

Although the hot rolling conditions are not particularly specified,
The heating temperature is desirably 1150 ° C. or lower so as not to make the inclusions fine. Thereafter, pickling, cold rolling, if necessary, warm rolling, annealing, and if necessary, re-cold rolling and re-annealing are performed. Annealing may be batch annealing or continuous annealing, but continuous annealing with easy control is desirable. The annealing temperature is desirably 750 to 1100 ° C. in order to provide predetermined magnetic properties.

[0030]

EXAMPLES (Example 1) When the chemical composition is% by weight and C: 0%.
002-0.005%, Mn: 0.1-0.4%, S
i: 0.1 to 0.2%, Al: 0.0001 to 0.00
50%, P: 0.05-0.08%, S: 0.005-
0.050%, O: 0.003 to 0.020%, the balance being made of steel consisting of Fe and unavoidable impurities by a conventional method, and subjected to hot rolling, cold rolling and annealing to carry out numbers A to I. Non-oriented electrical steel sheet was produced. Numbers A to C as manufacturing conditions
For the group of No. D, S was set low, No. E was set to increase the hot-rolling heating temperature, No. F was set to lower the S content and set the hot-rolling heating temperature high, and No. G was set to increase the cold rolling reduction. No. H reduced the oxygen content and No. I increased the oxygen content so that the particle sizes of various inclusions could be obtained.

The obtained steel sheet was coated with an insulating film to have a final thickness of 0.50 mm. The steel sheets were punched out in a disk shape and laminated to obtain cutting test pieces A to I corresponding to steel sheet numbers A to I.

This test piece was cut with a lathe and the cutting properties were compared. The cutting test conditions were as follows: cutting speed: 150 m / min, feed: 0.2 mm / rev, cutting depth: 0.5 mm. The cutting tool used was a cermet chip with a breaker. For the machinability, the tool wear was evaluated based on the average flank wear of the insert. The magnetic properties were measured for iron loss and magnetic flux density by the Epstein test method described in JIS.

The inclusions of the test specimen were observed with an optical microscope at a magnification of 400 at a magnification of 400 in 60 fields of view, and the particle diameter of each inclusion was calculated as an equivalent circle diameter by an image processing apparatus. In each specimen, the inclusions were mostly sulfides, oxides and their composite inclusions, and a small amount of nitrides,
And carbides were dispersed.

FIG. 4 is a graph showing the relationship between the type of test specimen and the ratio of inclusions having a particle diameter of 2 μm or more.

As shown in FIG. 4, in the test pieces A to C, the ratio of the inclusions having a particle diameter of 2 μm or more was 10% or more, which satisfied the range of the present invention (test pieces A to C). Is an example of the present invention). Specimens D to I did not satisfy the scope of the present invention (specimens D to I are comparative examples).

FIG. 5 is a graph showing the relationship between the cutting time for each specimen and the amount of tool wear. Table 1 shows the magnetic properties (iron loss: W15 / 50 and magnetic flux density: B50) of each specimen.

[0037]

[Table 1]

In FIG. 5, test pieces A to A of the present invention are shown.
C shows a small tool wear and good magnetic properties as shown in Table 1 (iron loss 7.0 (W / kg) or less, magnetic flux density 1.8).
(T) or more). Workpieces D, E, F as Comparative Examples
Indicates that the tool wear is large as shown in FIG.
The magnetic properties were also poor as shown in FIG. Specimens G, H, and I, which are comparative examples, had a small tool wear amount as shown in FIG.

(Example 2) The chemical composition is expressed in% by weight, and C:
0.002 to 0.003%, Mn: 0.1 to 0.3%,
Si: 0.9 to 1.1%, Al: 0.3 to 0.5%,
P: 0.06 to 0.08%, S: 0.0005 to 0.0
50%, O: 0.002 to 0.012, the balance being made of steel consisting of Fe and unavoidable impurities by a conventional method, subjected to hot rolling, cold rolling and annealing, and subjected to non-directional numbers P to X An electrical steel sheet was prepared. As for the production conditions, for the groups of numbers P to R, the number S increases the cold rolling reduction, and the number T
No. U increases the hot rolling temperature, No. V decreases the oxygen content, No. W increases the oxygen content, X decreases the oxygen content and increases the hot rolling temperature, Various particle sizes of inclusions were obtained.

These steel sheets were coated with an insulating film to have a final thickness of 0.35 mm. This steel plate was punched and laminated in a disk shape with four grooves on the outer periphery, and the specimens P to X for intermittent cutting corresponding to the numbers P to X were obtained. The intermittent cutting test conditions were as follows: cutting speed: 320 m / min, feed: 0.05 mm / re
v, depth of cut: 0.05 mm, and a cutting tool used a carbide tip.

The cutability (tool wear) and magnetic properties (iron loss, magnetic flux density) were evaluated in the same procedure as in Example 1. In order to investigate the cutting burr generated in the notch groove of the work material,
After 1200 seconds of cutting time, the length of the cutting burr was measured.

FIG. 6 is a graph showing the relationship between the type of test specimen and the ratio of inclusions having a particle diameter of 2 μm or more. As shown in the drawing, the ratio of the inclusions having a particle diameter of 2 μm or more was 10% or more in the test pieces P to R, which satisfied the scope of the present invention. Example). Specimens SX
Did not satisfy the scope of the present invention (specimens SX
Is a comparative example).

FIG. 7 is a graph showing the relationship between the cutting time for each test piece and the amount of tool wear. FIG. 8 is a graph showing the cutting burr length for each test piece. Table 2 shows the magnetic properties (iron loss: W15 / 50 and magnetic flux density: B50) of each specimen.

[0044]

[Table 2]

As shown in FIG. 7, the specimen P of the present invention example
For Q and R, the amount of tool wear was small, and the cutting burr length was small as shown in FIG. In addition, as shown in Table 2, the magnetic properties of the test pieces P, Q, and R were good (iron loss 4.0 (W / k
g), the magnetic flux density was 1.8 (T) or more).

As shown in FIG. 7, the test pieces S and T of the comparative example
In Fig. 8, the amount of tool wear was large, and as shown in Fig. 8, the length of the cutting burr was also large. Further, as shown in Table 2, the magnetic properties of the test pieces S and T were also poor.

In the specimen U, which is a comparative example, a tool defect occurred during the cutting test, and the test was stopped. Therefore, data on the tool wear amount and the cutting burr length were not collected. The specimen U
Also had poor magnetic properties.

As shown in FIG. 7, with respect to the test pieces V, W, and X as the comparative examples, the tool wear was smaller than the test pieces S and T, and as shown in FIG. 8, the cutting burrs were relatively small. However, as shown in Table 2, the magnetic properties were inferior.

[0049]

The electromagnetic steel sheet of the present invention satisfies both the machinability and the magnetic properties, and when assembling and cutting into a laminated iron core, the life of the cutting tool is prolonged and there is no generation of cutting burrs. The efficiency is improved, and the burr removal operation can be omitted.

[Brief description of the drawings]

FIG. 1 Number of inclusions in steel and magnetic properties (iron loss W15 / 5
It is a graph which shows the relationship of 0).

FIG. 2 is a graph showing the relationship between the particle size of inclusions and the number ratio of inclusions.

FIG. 3 is a graph showing the relationship between the particle size of inclusions and the amount of wear of a cutting tool.

FIG. 4 is a graph showing the relationship between the type of test specimen and the ratio of inclusions having a particle diameter of 2 μm or more.

FIG. 5 is a graph showing the relationship between cutting time and tool wear for each test piece.

FIG. 6 is a graph showing the relationship between the type of test specimen and the ratio of inclusions having a particle diameter of 2 μm or more.

FIG. 7 is a graph showing the relationship between cutting time and tool wear for each test piece.

FIG. 8 is a graph showing the cutting burr length for each test object.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasutaka Okada 4-33 Kitahama, Chuo-ku, Osaka-shi F-term in Sumitomo Metal Industries Co., Ltd.

Claims (1)

[Claims] 1. Among particles of inclusions in steel observed in a cross section, the number of particles having a particle diameter of 2 μm or more is 0.1 μm or more.
An electrical steel sheet having excellent machinability and magnetic properties, characterized in that it is at least 10% with respect to the number of particles.