JP2002080946A - 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 sheet 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 and 0.0001 to 0.03% N, and the balance Fe with practically inevitable impurities is prepared, and whose saturation magnetic flux density is controlled to 2.07 to 2.2 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, an alloy containing Fe as the remainder other than practically unavoidable impurities, and having a saturation magnetic flux density of 2.0.
7 Tesla or more and 2.2 Tesla or less, maximum relative permeability 100
0 to 20000, coercive force is 10 A / m to 400
It was confirmed that a hard disk voice coil motor with high characteristics can be manufactured by setting the ratio to A / m or less.

[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. Further, the present invention is characterized in that the saturation magnetic flux density is set to 2.07 to 2.2 T. Even if the saturation magnetic flux density is high, the maximum relative magnetic permeability is small or the coercive force is too large. In addition, the magnetic resistance of the magnetic circuit increases, and the gap magnetic flux density decreases. For this reason, the maximum relative magnetic permeability is 1000 or more and 20 or more.
000 or less and the coercive force is 10 A / m or more and 400 or more.
A / m or less.

[0008] The alloy component is adjusted to a desired range depending on the raw material and the steel making method, but 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.

[0009]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. [Example 1] A steel alloy ingot having the composition shown in Example 1 of Table 1 was melted and continuously cast to give a width of 200 mm and a length of 500 m.
m, an alloy lump having a plate thickness of 50 mm was obtained. 120
Start hot rolling by heating to 0 ° C.
%, And the hot rolling was completed at 850 ° C.
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 plate 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. As a comparative example, a commercially available SPCCSD product having a thickness of 1 mm was similarly punched into a yoke shape by a mechanical punching press to obtain two types of upper and lower yokes. The obtained yoke is subjected to electroless NiP plating with a coating thickness of about 8 microns, and the maximum energy product 38
A permanent magnet of 0 kJ / m ³ was bonded to the center of the yoke to produce a magnetic circuit. Compared with prepared yoke material of the present invention
The PCC material is cut into approximately 4 mm squares, and the maximum magnetic field is 1.9 MA /
The saturation magnetic flux density was measured with a vibrating sample magnetometer of m.

Further, a ring sample having an outer diameter of 45 mm and an inner diameter of 33 mm is prepared from the remaining plate material punched in a yoke shape, and the ring sample is prepared according to the method described in JIS C 2531 (1999). After stacking two sheets of paper between them and wrapping an insulating tape, a winding of 0.26 mmφ copper wire with 50 turns each as an excitation coil and a magnetization detection coil was applied, and the DC magnetization characteristics of the maximum magnetic field ± 1.6 kA / m A magnetic hysteresis curve was drawn by an automatic recording device, and the maximum relative magnetic permeability and the coercive force were measured. Further, in order to examine the performance of the magnetic circuit for the voice coil motor thus manufactured, the total magnetic flux between the magnetic circuit gaps was measured using a magnetometer (480 Fluxmeter manufactured by Lakeshore) using a planar coil used in an actual magnetic recording device. The amount was measured. Table 1 shows the results of the above experiments.

[0012]

[Table 1]

From Table 1, it can be seen that the alloy of Example 1 has an increased saturation magnetic flux density with respect to the SPCC, and correspondingly, an increased total magnetic flux in the magnetic circuit gap. The ratio in Table 1 indicates that the gap magnetic flux amount of the comparative example is 1
It is expressed as a relative ratio as 00.

Example 2 A steel ingot having the composition shown in Example 2 of Table 1 was melted and cast through an electric furnace, a converter-degassing, and a continuous casting process to obtain a slab having a thickness of 200 mm. . The hot metal was purified by RH degassing and VOD (vacuum-oxygen decarburization). The obtained 200 mm thick slab was
The sheet was heated and soaked at a temperature of 00 to 1200 ° C., rolled by a hot rolling mill, and finished at a temperature of 850 to 950 ° C. to a thickness of about 10 mm. After recrystallization annealing (850 to 900 ° C), the sheet was pickled and cold rolled to a thickness of about 4 mm. Thereafter, the sample was subjected to finish annealing at about 850 ° C. and then 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 has a coating thickness of about 6
Micron electroless NiP plating was applied.

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 of the produced yoke plate material were measured by the method described in Example 1. Also, in order to investigate the performance of the magnetic circuit for the voice coil motor, using a planar coil used in an actual magnetic recording device,
A range on the permanent magnet between the magnetic circuit gaps was run, and the total magnetic flux was measured. The above experimental results are also shown in Table 1. As a result, in the steel sheet having the composition of Example 2, the saturation magnetic flux density was improved with respect to SPCC, and the total magnetic flux amount in the magnetic circuit gap was correspondingly increased.

[0016]

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.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02K 33/18 H02K 33/18 B (72) Inventor Masaaki Nishino 2-5-1 Kitafu, Takefu-shi, Fukui Prefecture F-term in Shin-Etsu Kagaku Kogyo Co., Ltd. Magnetic Materials Research Lab. (Reference)

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
An iron alloy containing 0.1% by weight, N: 0.0001 to 0.03% by weight of each element, and the balance other than impurities that are practically unavoidable is Fe. Density is 2.07 Tesla or more and 2.2 Tesla or less, maximum relative permeability is 1000 or more and 20000 or less, and coercive force is 10
An iron alloy sheet material for a hard disk voice coil motor yoke, which is not less than A / m and not more than 400 A / m. 2. A yoke for a hard disk voice coil motor using the iron alloy plate material according to claim 1.