JP2002080947A - Iron alloy sheet material for hard disk voice coil motor yoke, and yoke for hard disk voice coil motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic material for hard disk voice coil motor yoke with which leaked magnetic flux is eliminated and all the characteristics of the high magnetic flux density of a permanent magnet can be made the most of. SOLUTION: In the case the thickness of a yoke material is 0.1 to 5 mm, for efficiently introducing magnetic flux generated from a permanent magnet having high magnetic flux density into a magnetic circuit, an alloy containing the components of, by weight, 0.0001 to 0.02% C, 0.0001 to 0.05% Si, 0.001 to 0.2% Mn, 0.0001 to 0.05% P, 0.0001 to 0.05% S, 0.0001 to 0.1% Al, 0.001 to 0.1% O, 0.0001 to 0.03% N and 0.1% to 10% Co, and the balance Fe with practically inevitable impurities is prepared, and whose saturation magnetic flux density is controlled to 2.07 to 2.3 tesla, the maximum relative magnetic permeability to 1,000 to 20,000, and coercive force to 10 to 400 A/m.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high magnetic flux density iron-based yoke material constituting a magnetic circuit for providing a magnetic circuit suitable for a small and thin voice coil motor in a magnetic recording apparatus.

[0002]

2. Description of the Related Art A magnetic circuit of a voice coil motor includes a permanent magnet for generating a magnetic flux and a yoke connecting the permanent magnets, and is used as an actuator for driving a hard disk head. In recent years, computers have tended to be reduced in size and weight in consideration of portability and portability, and accordingly, magnetic recording devices have also been reduced in size and thickness. Further, the reduction in size and thickness has spread to permanent magnets and yoke material components constituting a magnetic circuit. Until now, in order to realize the miniaturization and thinning of the magnetic circuit, it has been general to cope with the decrease in the magnetic flux density between the gaps caused by the volume reduction by compensating for the high magnetic flux density of the high-performance magnet.

[0003] However, while the magnetic flux density generated by high-performance magnets is increasing year by year, yoke materials are made of SPCC and SPC.
Since a rolled steel plate such as D and SPCE is used, the saturation magnetization of the yoke material cannot be increased in accordance with the improvement in the magnetic flux density of the magnet. Since the thickness of the yoke is also limited by the constraints of the entire device, it is not possible to effectively use all the magnetic flux of the high-performance magnet, and eventually saturation occurs partially in the magnetic circuit and leakage of the magnetic flux occurs Or Such leakage of the magnetic flux not only reduces the gap magnetic flux density of the magnetic circuit, but also affects the surrounding magnetic recording medium and control devices. There is a certain regulation for the amount of leakage magnetic flux from the VCM circuit, and the amount of leakage magnetic flux of a product must be less than this prescribed value.

[0004]

As a magnetic material for a magnetic circuit yoke of a magnetic recording device or the like, SPCC,
Cold rolled steel sheets such as SPCD and SPCE are most often used because they are excellent in productivity such as punching, molding, drilling and bending, embossing, and inexpensive. However, since these steel materials do not have a sufficient saturation magnetization, it is difficult to avoid magnetic saturation in a partial VCM magnetic circuit due to the aforementioned miniaturization and thinning, and a permanent magnet having a high magnetic flux density has The magnetic flux could not be guided sufficiently to the magnetic circuit. There has been a strong demand for the development of a magnetic material for a yoke that eliminates these leakage magnetic fluxes and makes full use of the high magnetic flux density characteristics of a permanent magnet.

[0005]

In order to solve the above-mentioned problems, various studies have been made. As a result, the thickness of the yoke plate material is reduced to 0.1.
In order to efficiently guide the magnetic flux generated from the permanent magnet having a high magnetic flux density into the magnetic circuit in the case of not less than 5 mm and not more than 5 mm, the contained component is C: 0.0001 to 0.0
2% by weight, Si: 0.0001 to 0.05% by weight, M
n: 0.001 to 0.2% by weight, P: 0.0001 to
0.05% by weight, S: 0.0001 to 0.05% by weight,
Al: 0.0001 to 0.1% by weight, O: 0.001 to
0.1% by weight, N: 0.0001 to 0.03% by weight, C
o: 0.1 to 10% by weight, other than practically unavoidable impurities, the balance is Fe alloy, and the saturation magnetic flux density is 2.07 Tesla or more and 2.3 Tesla or less, the maximum relative magnetic permeability. It was confirmed that a hard disk voice coil motor having high characteristics can be manufactured by setting the coercivity to 1000 to 20000 and the coercive force to 10 A / m to 400 A / m. In particular, Co, which has been refrained from use because of its high cost, is effective in improving the saturation magnetization, and the magnetic flux generated from the high-performance permanent magnet can be efficiently guided to the magnetic circuit by the high saturation magnetization of the plate material. It was confirmed.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have studied various materials in order to achieve the object, and have examined elements that affect the reduction of magnetic flux density from components such as SPCC materials. For iron, C, Al, Si, P, S, and Mn do not have a magnetic moment or the magnetic moment is different from that of the iron base, so that the presence of these elements lowers the magnetic moment of the surrounding iron. A phenomenon occurs. In particular, P and S have an adverse effect on corrosion resistance in addition to a decrease in magnetic flux density. However, unnecessarily reducing these elements is disadvantageous from the viewpoint of the production cost of the raw material, and even if it is contained in a small amount in terms of performance, it can be satisfied.

[0007] From the above viewpoint, C: 0.0001-0.
02% by weight, Si: 0.0001 to 0.05% by weight, M
n: 0.001 to 0.2% by weight, P: 0.0001 to
0.05% by weight, S: 0.0001 to 0.05% by weight,
Al: can be in the range of 0.0001 to 0.1% by weight. O and N also affect magnetic properties, and O:
0.001-0.1% by weight and N: 0.0001-
The content is preferably 0.03% by weight, and within this range, the saturation magnetic flux density is not particularly deteriorated.

In contrast to these elements, Co, which has a larger number of outer shell electrons than iron atoms, is the most important element in the present invention because it increases the magnetic flux density. Co amount is up to 10
% Can be added to increase the saturation magnetic flux density of the alloy, but beyond that, the strength of the alloy is too large to be hard, which makes it difficult to roll, or at the same time, it is an expensive metal, so it costs less. From disadvantages. Therefore C
The amount o is in the range of 0.1 to 10% by weight. further,
The present invention is characterized in that the saturation magnetic flux density is set to 2.07 to 2.3T. Even when the saturation magnetic flux density is high, the maximum relative magnetic permeability is small or the coercive force is too large.
The magnetic resistance of the magnetic circuit increases, and the gap magnetic flux density decreases. For this reason, the maximum relative magnetic permeability is in the range of 1000 or more and 20000 or less, and the coercive force is 10 A / m or more.
The range is not more than 00 A / m.

The alloy component is adjusted to a desired range depending on the raw material and the steelmaking method. However, from the viewpoint of productivity and quality, a continuous casting method is preferable, and a vacuum melting method is suitable for small lot production. After casting, hot rolling, cold rolling, or the like is performed to obtain a steel material having a predetermined thickness. The iron alloy sheet material obtained in this way is formed into a predetermined yoke shape by plastic working such as punching, molding, drilling, bending, embossing by a mechanical press, a hydraulic press, a fine blanking press, or the like. After processing, after deburring, chamfering, and pickling, surface treatment is performed by electroplating of Ni, Cu, Cr, Al, etc., electroless plating, PVD, CVD, ion plating, etc., and used for hard disk voice coil motor. It can be manufactured as a yoke material. Here, when the plate thickness of the yoke material is less than 0.1 mm, the effect of improving the characteristics of the magnetic circuit is not so much observed even if the saturation magnetization of the plate material is slightly improved, and when it exceeds 5 mm, the reverse is applied. Therefore, the problem of saturation of the magnetic circuit does not occur without using the present invention.

[0010]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. [Examples 1 to 3] Steel ingots having the component compositions shown in Examples 1 to 3 shown in Table 1 were melted and continuously cast to obtain alloy ingots having a width of 200 mm, a length of 500 mm and a plate thickness of 50 mm. The alloy ingot is heated to 1200 ° C. to start hot rolling, and 950 ° C.
The hot rolling was completed at 850 ° C. with a cumulative reduction of 60% below. After the completion of the hot rolling, it was air-cooled to room temperature. Thereafter, after cold rolling, finish annealing was performed at 900 ° C., and pickling was performed to obtain a steel sheet having a thickness of 1 mm.

The obtained steel sheet was punched into a yoke shape by a mechanical punching press to obtain two types of upper and lower yokes. The obtained yoke was subjected to electroless NiP plating with a coating thickness of about 8 μm. A permanent magnet having a maximum energy product of 380 kJ / m ³ was adhered to the center of the yoke inside the upper and lower yokes to produce a magnetic circuit. The obtained yoke was subjected to electroless NiP plating with a coating thickness of about 8 μm, and the maximum energy product was 380 kJ / m inside the upper and lower yokes.
The permanent magnet of No. ³ was adhered to the center of the yoke to produce a magnetic circuit.

[0012] The produced yoke material is cut into about 4 mm squares,
The saturation magnetic flux density was measured with a vibrating sample magnetometer having a maximum magnetic field of 1.9 MA / m. Also, a ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm was prepared from the remaining plate material punched in a yoke shape, and the above-mentioned ring sample was inserted between paper sheets in accordance with the method described in JIS C 2531 (1999). Sandwich 2
After stacking and winding an insulating tape, 0.26 mm for 50 turns each for the excitation coil and the magnetization detection coil
A copper wire of φ was wound, and a magnetic hysteresis curve was drawn with a DC magnetic property automatic recording device having a maximum magnetic field of ± 1.6 kA / m, and a maximum relative permeability and a coercive force were measured. Also, the hardness of the produced yoke material was measured using a Rockwell hardness tester (RMT manufactured by Matsuzawa).
-3). Further, in order to check the performance of the magnetic circuit for the voice coil motor thus manufactured, a flat magnet used in an actual magnetic recording device was used to measure the magnetic flux (Lak).
Esore 480 Fluxmeter)
The total magnetic flux between the magnetic circuit gaps was measured.

[Comparative Examples 1 and 2] As a comparative example, a general commercially available SPCCSD product, a material having a plate thickness of 1 mm (Comparative Example 1)
And about the steel plate of 1 mm thickness which obtained the steel alloy ingot of the component composition shown in the comparative example 2 shown in Table 1 like Examples 1-3, the magnetic property and hardness were carried out similarly to Examples 1-3. It was measured.

[Examples 4 and 5] A steel ingot having the component composition of Examples 4 and 5 also shown in Table 1 was melted and cast through an electric furnace, a converter-degassing, and a continuous casting process, and a slab having a thickness of 200 mm was obtained. I got The hot metal was purified by RH degassing and VOD (vacuum-oxygen decarburization). The obtained slab having a thickness of 200 mm is heated and soaked at 1100 to 1200 ° C., rolled by a hot rolling mill, and has a thickness of about 10 m at a finishing temperature of 850 to 950 ° C.
m. After recrystallization annealing (850-900 ° C), pickling,
The thickness was reduced to about 4 mm by cold rolling. Then about 850
After finish annealing at ℃, it was pickled to obtain a test steel sheet.

The obtained steel plate was punched into a yoke shape by a mechanical punching press to obtain two types of upper and lower yokes. The obtained yoke is made of electroless NiP having a coating thickness of about 6 microns.
Plated. A permanent magnet having a maximum energy product of 400 kJ / m ³ was adhered to the center of the yoke inside the upper and lower yokes to produce a magnetic circuit. The magnetic properties and hardness of the produced yoke plate material were measured by the methods described in Examples 1 to 3. Table 1 shows the experimental results of the above examples and comparative examples.
Shown in In addition, the increase rate in Table 1 represents each increase rate with respect to the magnetic flux amount of Comparative Example 1 by%.

[0016]

[Table 1]

From Table 1, the steel sheets of the compositions of Examples 1 to 5 are:
In each case, it can be seen that the saturation magnetic flux density increased with respect to the SPCC of Comparative Example 1, and the total magnetic flux amount in the magnetic circuit gap also increased accordingly. In Comparative Example 2 similar to the composition of the steel sheet of the present invention except that Co was not added, it was found that the hardness was considerably low.

[0018]

As described above, the present invention is constructed by improving the magnetic properties of a yoke material having a thickness of 0.5 mm to 5 mm used as a magnetic circuit member for a voice coil motor of a magnetic recording apparatus. It is possible to improve the magnetic flux density between the gaps by effectively utilizing the magnetic flux input from the magnet to the magnetic circuit, and to provide a magnetic circuit that does not magnetically affect the surrounding magnetic recording media and control devices. Become.

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[Procedure amendment]

[Submission date] September 11, 2000 (2009.1.
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Iron alloy plate for hard disk voice coil motor yoke and yoke for hard disk voice coil motor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Nishino 2-5-1, Kitafu, Takefu-shi, Fukui Shin-Etsu Kagaku Kogyo Co., Ltd. F-term (Reference) 5E041 AA11 AA19 CA04 NN01 NN06 NN12 NN13 NN14 5H002 AA02

Claims (2)

[Claims] 1. A yoke plate material having a thickness of 0.1 mm or more and 5 mm or less used for a magnetic circuit of a hard disk voice coil motor, wherein the plate material is C: 0.0001-0.
02% by weight, Si: 0.0001 to 0.05% by weight, M
n: 0.001 to 0.2% by weight, P: 0.0001 to
0.05% by weight, S: 0.0001 to 0.05% by weight,
Al: 0.0001 to 0.1% by weight, O: 0.001 to
0.1% by weight, N: 0.0001 to 0.03% by weight, C
o: An iron alloy containing 0.1 to 10% by weight of each element, and the balance other than impurities that are practically unavoidable is Fe, and whose saturation magnetic flux density is 2.07 Tesla or more. 3 Tesla or less, maximum relative magnetic permeability is 1000 or more and 20
An iron alloy sheet for a hard disk voice coil motor yoke, wherein the coercive force is 10 A / m or more and 400 A / m or less. 2. A yoke for a hard disk voice coil motor using the iron alloy plate material according to claim 1.