JP2002080945A - Iron alloy sheet material for head 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: 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 to 10% Co, and the balance Fe and containing, as addition elements, a least one or more kinds of alloy elements selected from Ti, Zr, Nb, Mo, Cr, V, Ni, W, Ta and B by 0.01 to 5% in total is prepared, and whose saturation magnetic flux density is controlled to 2.07 to 2.3 tesla, the maximum relative magnetic permeability to 1,200 to 22,000, and corercive force to 20 to 380 A/m. It is preferable that the carbides or oxides of the alloy elements added as the addition elements are finely dispersed and precipitated on the grain boundaries or/and into the grains of the alloy.

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 0.5.
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 to 10% by weight, other than practically unavoidable impurities, an alloy consisting of Fe, and Ti, Zr, Nb, Mo, Cr, V, Ni, W,
It contains at least one or more alloying elements selected from Ta and B in a total amount of 0.01 to 5% by weight, and has a saturation magnetic flux density of 2.07 to 2.3 Tesla and a maximum relative magnetic permeability of 1200 or more. 22000 or less, coercive force 20A
/ M to 380 A / m, it was confirmed that a hard disk voice coil motor with high characteristics can be manufactured. 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. Ti added as an additional element,
Carbides and / or oxides of at least one or more alloying elements selected from Zr, Nb, Mo, Cr, V, Ni, W, and Ta are finely dispersed and precipitated in the grain boundaries or / and grains of the alloy. Is preferred.

[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,
Co: 0 to 10% by weight. O and N similarly affect the magnetic properties, and O: 0.001 to
0.1% by weight and N: 0.0001 to 0.03% by weight
The saturation magnetic flux density is not particularly degraded within this range.

[0008] In contrast to these elements, Co, which has a larger number of shell electrons than iron atoms, is an important element in the present invention because it increases the magnetic flux density. The amount of Co can be added up to 10% by weight to increase the saturation magnetic flux density of the alloy, but beyond that, the strength of the alloy is too large to be hard, so that the rolling process is difficult, or at the same time, the expensive metal is used. This is disadvantageous in terms of cost. Therefore, the Co content is more preferably in the range of 0.1 to 10% by weight.

Ti, Zr, N added as additional elements
At least one or more alloying elements selected from b, Mo, Cr, V, Ni, W, and Ta, when dissolved in a ferrite phase in the material, cause a decrease in magnetic flux density. Generates intermetallic compounds with O to form carbides and oxides. As a result, these precipitates are finely and uniformly precipitated in the alloy structure, and can inhibit the movement of the transition during the plastic working. For this reason, excessive ductility of the alloy is reduced, and the occurrence of burrs on the shearing surface when punching the sheet material can be suppressed.

[0010] Mo, Cr, V, and Ni have the effect of improving the corrosion resistance of the iron alloy sheet as seen in examples of stainless steel and the like. W, Ta, and B have the effect of improving the rolling workability of the sheet material, and can contribute to reduction of the processing cost. However, since these elements all reduce the saturation magnetization, it is not preferable to add 5% by weight or more in total. Further, in the present invention, the saturation magnetic flux density is set to 2.07 to
The characteristic is that the magnetic flux density is set to 2.3T. If the maximum relative magnetic permeability is small or the coercive force is too large even if the saturation magnetic flux density is high, the magnetic resistance of the magnetic circuit increases and the gap magnetic flux density increases. It will be lower. Therefore, the maximum relative magnetic permeability is in the range of 1200 to 22000, and the coercive force is 2
The range is from 0 A / m to 380 A / m.

[0011] The alloy component is adjusted to a desired range depending on the raw material and the steelmaking 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.

[0012]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. [Examples 1 to 8] Steel ingots having the component compositions shown in Examples 1 to 8 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 microns. 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. The produced yoke material was cut into about 4 mm squares, and the saturation magnetic flux density was measured with a vibration sample magnetometer having a maximum magnetic field of 1.9 MA / m.

Further, 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 ring sample was 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. In addition, the hardness of the produced yoke material was measured using a Rockwell hardness meter (Matsuzawa RMT-
Measured in 3). Further, in order to examine 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 (Lake).
The total magnetic flux between the magnetic circuit gaps was measured using a Shore 480 Fluxmeter. Further, the distribution of the added elements was measured with an electron beam microanalyzer (IDMA) using a characteristic X-ray image.

[Comparative Examples 1-2] 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 lump of the component composition shown in the comparative example 2 shown in Table 1 like Example 1-8, the magnetic property and hardness were carried out similarly to Example 1-8. It was measured.

[Examples 9 to 14] Steel ingots having the component compositions of Examples 9 to 14 also shown in Table 1 were 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 to 1100 to 1200 ° C., rolled by a hot rolling mill, and subjected to a finishing temperature of 850 to 950 ° C. and a thickness of about 1 mm.
0 mm. After recrystallization annealing (850 to 900 ° C), the sheet was pickled and cold rolled to a thickness of about 4 mm. Then about 8
After finish annealing at 50 ° C., pickling was performed to obtain a test steel sheet.

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 6 microns. 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 8. Table 2 shows the experimental results of the examples and the comparative examples.
In addition, the additive element distribution (characteristic X
Line images: Ti-Kα1 and C-Kα) are shown in FIGS.
Shown respectively. In addition, the increase rate in Table 1 is comparative example 1.
Of each magnetic flux amount is expressed in%.

[0018]

[Table 1]

[0019]

[Table 2]

From Table 2, it can be seen that the steel sheets having the compositions of Examples 1 to 14 all have an increased saturation magnetic flux density with respect to the SPCC of Comparative Example 1, and correspondingly, the total amount of magnetic flux in the magnetic circuit gap. It can be seen that also increased. 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. Further, as can be seen from Example 10 by element distribution measurement, the additive element was substantially uniformly dispersed in the plate material, and the additive element, Example 1
In the case of 0, the distributions of Ti and C match.

[0021]

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.

[Brief description of the drawings]

FIG. 1 is a photograph of an electron microanalyzer of a characteristic X-ray image Ti-Kα1 of a plate material obtained in Example 10.

FIG. 2 is a photograph of a characteristic X-ray image C-Kα of the plate material obtained in Example 10 taken by an electron beam microanalyzer.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H02K 33/18 H02K 33/18 B (72) Inventor Masaaki Nishino 2-5-1 Kitafu, Takefu-shi, Fukui Prefecture Shin-Etsu Chemical F-term in the Magnetic Materials Research Laboratories of Industry Co., Ltd. (reference) 5E041 AA11 AA19 CA04 NN01 NN06 NN12 NN13 NN14 5H002 AA02 AA09 AB06 5H633 BB09 GG03 GG18 HH02 HH16 JB04

Claims (3)

[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: contains 0 to 10% by weight of each element, and further contains Ti, Zr, Nb, Mo, Cr, V, Ni, W,
An iron alloy containing at least one or more alloying elements selected from Ta and B in a total amount of 0.01 to 5% by weight, and a balance of Fe other than impurities practically inevitable;
And its saturation magnetic flux density is 2.07 Tesla or more and 2.3.
An iron alloy sheet for a hard disk voice coil motor yoke, characterized by having a Tesla or less, a maximum relative magnetic permeability of 1200 or more and 22000 or less, and a coercive force of 20 A / m or more and 380 A / m or less. 2. The iron alloy sheet for a hard disk voice coil motor yoke according to claim 1, wherein Ti, Zr, Nb, Mo, Cr, V, N
An iron alloy sheet for a hard disk voice coil motor yoke, wherein carbides and / or oxides of at least one or more alloy elements selected from i, W, and Ta are finely dispersed and precipitated. 3. A yoke for a hard disk voice coil motor using the iron alloy plate material according to claim 1.