JP2637667B2 - Non-oriented electrical steel sheet for micromotor / rotor - Google Patents

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 as a material for a micromotor / rotor.

[0002]

2. Description of the Related Art In recent years, the production of micromotors has been rapidly increasing with the miniaturization and weight reduction of electric equipment. These micromotors are various motors for automobiles, motors for video, motors for video cameras, motors for OA equipment,
It covers a variety of industrial fields, such as motors for electric shaving. Since non-oriented electrical steel sheets for micromotors are not usually subjected to magnetic annealing at the customer, they belong to the category of so-called full-process products. The structure of the micromotor uses a permanent magnet as a stator and a non-oriented electrical steel sheet as a rotor. The non-oriented electrical steel sheets of the rotor are laminated, but the lamination is often fixed by press-fitting the shaft without caulking or welding.

[0003] At the time of this shaft press-fitting, a linear scratch is often formed on the shaft surface. Shaft scratches are a serious problem because they generate noise during rotation and wear the shaft bearings. The scratch on the shaft surface has a width ranging from several μm to several tens of μm and a depth of 10 μm or less in many cases, and is visible under a microscope as a streak extending in the shaft press-fitting direction. Conventionally, as to the causes and countermeasures of the scratches, the thickness of the shaft, the material of the shaft, the hard plating on the shaft, and the like have been intensively studied. Also, it was known that there were lots and lots of non-oriented electrical steel sheets with many scratches, but since the root of the scratches was not known, there was no countermeasure. That is, the present has been reached without a drastic solution being presented.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-oriented electrical steel sheet for a micro motor / rotor which fundamentally solves a scratch generated on a micro motor shaft.

[0005]

In order to achieve the above-mentioned object, the present invention provides a method of the present invention, wherein C.ltoreq.0.005% by weight, Si.ltoreq.4%,
Mn ≦ 1.5%, P ≦ 0.2%, S ≦ 0.03%, A
l: 0.001 to 1.5%, B ≦ 0.005%, N ≦
0.004%, O ≦ 0.01%, the balance contains Fe and unavoidable components, and the ratio of the weight of SiO _{2 to} the total amount of the three oxides of SiO ₂ , Al ₂ O ₃ and MnO is 0.1%. micromotor, characterized in that it is 30 or less,
Non-oriented electrical steel sheet for rotor .

The present invention is based on the following three findings. First, one point is that the true cause of shaft scratches is often caused by oxides in non-oriented electrical steel sheets. The second point is that among these oxides, oxides having a high content of SiO ₂ cause a problem because they cause wide and deep scratches. Third, the amount of SiO ₂ in the oxide can be controlled in the steelmaking process. In other words, hard particles that form a scratch on the shaft are present in the vicinity of the punched surface of the hole on the steel plate side where the shaft enters, and there is a problem if the particles are hard and large. The particles containing a large amount of SiO ₂ are other Al ₂ O ₃ ,
Larger in size than oxides with high MnO, several μm
It is hard and causes scratches.

Hereinafter, the reasons for limiting the scope of the present invention will be described. The reason for limiting the C content to 0.005% or less is that
This is because if the amount of C is larger than this, the magnetic characteristics are greatly deteriorated due to magnetic aging. The reason why the amount of Si is set to 4% or less is that Si has an effect of improving iron loss, but if it exceeds 4%, the steel plate becomes brittle, and the steel plate breaks during punching work into the motor core. The reason that the Mn content is set to 1.5% or less is that Mn has an effect of improving iron loss, but is due to the problem of addition cost.

[0008] P may be added in order to facilitate punching at the customer, but if it exceeds 0.2%, there is a problem of addition cost. The reason why the amount of S is set to 0.03% or less is that if it exceeds this, the amount of MnS precipitates increases and the magnetic properties deteriorate. The Al content of 0.001% to 1.5% is defined as 0.1%.
If the content is less than 001%, an oxide rich in SiO ₂ is generated, so that the object of the present invention cannot be achieved. Further, the reason why the content is set to 1.5% or less is due to the problem of addition cost.

The content of B is set to 0.005% or less because B has an effect of improving iron loss, but is due to the problem of addition cost. The present invention can be achieved without adding B. The reason why the N content is set to 0.004% or less is that a blister defect called a blister is generated on the surface of the steel sheet when the N content is exceeded. When the amount of O is limited to 0.01% or less, naturally, the amount of oxide increases, so that the shaft has many scratches, and if it exceeds 0.01%, the yield drops due to the damage is too much.

In addition to the above elements, Sn, Sb, Cu, Zr, Cr, etc., which are known to improve magnetic characteristics, may be added. However, oxides must be strictly controlled as follows. No.

The oxides of the non-oriented electrical steel sheet containing these component compositions must satisfy the following composition distribution by weight ratio. SiO ₂ / (SiO ₂ + Al ₂ O ₃ + MnO) ≦ 0.30 SiO ₂ / (SiO ₂ + Al ₂ O ₃ + MnO) is 0.3
In than 0 becomes a composite oxide containing a large amount of SiO ₂ alone system or SiO _2, causing the shaft scratch becomes several μm larger oxide size. Note that these SiO
_{2 A} single oxide or a composite oxide containing a large amount of SiO ₂ is
Hardness is higher than other oxides, which may contribute to shaft scratches. In general, oxides SiO _2, Al ₂ O _3, in addition to MnO, CaO,
In many cases, it is complexly precipitated with many oxides such as MgO and ZrO ₂ , but the content of CaO, MgO, ZrO _{2 and the} like can be standardized by the above formula since the content is very small.

The control of the ratio of SiO ₂ , Al ₂ O ₃ and MnO is carried out in the steel making process. That is, after decarburization in a vacuum degassing process to prevent the formation of SiO _2, a method of adding Al first and sufficiently deoxidizing with Al, and then adding Fe—Si or Fe—Mn, or a converter. first adding an Fe-Si during tapping from, there is a method of reducing the SiO ₂ in the steel by reducing the Fe-Si amount of late vacuum degassing.

The steps such as hot rolling, annealing and cold rolling are performed by a known method. Since the composition ratio and the amount of the oxide do not change in the steps after the hot rolling, the oxide should be controlled in steel making. Hereinafter, examples of the present invention will be specifically described.

[0014]

EXAMPLE A continuous casting slab containing components obtained by adjusting the timing of adding the additional element and the deoxidizing element was heated at 1150 ° C. and hot rolled to a 3 mm hot rolled sheet. This hot rolled sheet was pickled and then cold rolled to 0.5 mm. This cold rolled sheet is 30% H ₂ ,
Performed annealing at 720 ° C. for 30 seconds in a 70% N ₂ atmosphere,
An organic / inorganic composite film was coated to a thickness of 2 μm (one-side thickness) to obtain a product. This is the micro motor low
A prototype was made for the shaft, and the scratch on the shaft was observed with a microscope. When 1,000 or more scratches occurred in 1000 shafts, the result was evaluated as x, when 1 to 29 scratches occurred, Δ, and when none occurred, the result was evaluated as ○. The shaft used was a round steel having a diameter of 2 mm and plated with Ni-P having a thickness of 3 μm.
This Ni-P plating had a micro Vickers hardness of 550 under a load of 10 g. Table 1 shows the test results. The components in the table are the results of a chemical analysis of the steel sheet from which the film of the product has been removed, and the unit is wt%.

[0015]

[Table 1]

[0016]

[Table 2]

As shown in Table 1, the amount of O is not more than 0.01% and SiO ₂ / (SiO ₂ + Al ₂ O ₃ + Mn
Experiment No. 0, in which the ratio of O) satisfies 0.30 or less. ,,
Thus, a non-oriented electrical steel sheet free of shaft scratches was obtained.

[0018]

As described above, by defining the composition ratio of the oxide, it is possible to provide a non-oriented electrical steel sheet for a micromotor / rotor having no shaft scratch.

Claims (1)

(57) [Claims] 1. C ≦ 0.005%, Si ≦ 4%, Mn ≦ 1.5%, P ≦ 0.2%, S ≦ 0.03%, Al: 0.001 to 1.5% by weight %, B ≦ 0.005%, N ≦ 0.004%, O ≦ 0.01%, the balance containing Fe and unavoidable components,
A non-oriented electrical steel sheet for a micromotor / rotor , wherein a weight ratio of SiO _{2 to} a total amount of three kinds of oxides of O ₂ , Al ₂ O ₃ and MnO is 0.30 or less.