JP3101750B2 - Carriage for magnetic disk drive, method of manufacturing the same, and magnetic disk drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive and its carriage, and more particularly to a magnetic disk drive and a highly reliable carriage which is light in weight, can be accessed at high speed, and has a small thermal deformation. Related to a magnetic disk drive.

[0002]

2. Description of the Related Art In a magnetic disk drive, there has been a demand for further increasing the speed of access of a carriage, and in order to achieve this high-speed access, the weight of the carriage has been increasingly reduced. To reduce the weight of this carriage, the material of the carriage that supports the head for recording and reproducing magnetic information on the magnetic disk is changed from an aluminum (hereinafter, referred to as Al) alloy to a lower-density, magnesium (hereinafter, referred to as Mg) alloy. It is being changed. As a prior art of a carriage using an Mg alloy, JP-A-63-298881
And JP-A-1-319126.

However, Mg alloys have a higher coefficient of thermal expansion than Al alloys and stainless steels (hereinafter referred to as SUS), so when Mg alloys are used in combination with Al alloys or SUS,
Thermal stress is generated due to the difference in thermal expansion coefficient, resulting in deformation of the carriage,
That is, it causes heat off-track. Therefore, various studies have been made to reduce the coefficient of thermal expansion of the Mg alloy.
Powder or fiber-like boron (hereinafter referred to as Mg alloy)
B), and a method of dispersing silicon carbide (hereinafter referred to as SiC) to lower the coefficient of thermal expansion is described in JP-A-2-193373.

[0004]

The Mg alloy is lighter than the Al alloy, so that the carriage can be made up of about 30% of the Al alloy.
%, Which is extremely effective for high-speed access. Further, the Mg alloy has a high damping capacity, and is an optimal material for a magnetic disk drive which is not sensitive to vibration. However, there is a problem that the Mg alloy has low corrosion resistance and a large coefficient of thermal expansion.

[0005] Corrosion resistance has been remarkably improved in recent years by suppressing the amounts of nickel (hereinafter, referred to as Ni), iron (hereinafter, referred to as Fe), and copper (hereinafter, referred to as Cu) contained as impurities. In particular, AZ91, a typical Mg alloy for die casting
(ASTM standard) shows excellent corrosion resistance by suppressing the amount of Ni, Fe, and Cu. Note that the nominal composition of AZ91 is Al = 8.7 to
9.0%, manganese (hereinafter, referred to as Mn) = 0.13%, zinc (hereinafter, referred to as Zn) = 0.68 to 0.7%, and Mg = remaining (R
obert. S. Busk, Magnesium Product Design, 1988,
40). AZ91 is classified from A rank to the highest D rank according to the amount of Ni, Fe, and Cu contained. D rank, which has the highest corrosion resistance, the nominal composition of impurities of AZ91D is Fe = 0.032.
× Mn content (%) or less, Ni = 0.005% or less, Cu = 0.07
% (Robert S. Busk, Magnesium Product Design, 1988, 270). The above percentages are all percentages by weight, and hereinafter, all percentages are represented by percentages by weight unless otherwise specified.

The environment in which the magnetic disk drive is used is relatively low in both humidity and temperature, and is good in corrosion resistance. Therefore, even if it is a Mg alloy, extreme corrosion hardly occurs. In particular, when AZ91D is used, corrosion resistance can be sufficiently prevented by a simple surface treatment.

However, AZ91 has a coefficient of thermal expansion of 26/10 ⁶ (1 /
° C), and the difference in thermal expansion coefficient from other component materials used in the magnetic disk drive is large. For example, SUS304 is used for the load arm and carriage shaft, its coefficient of thermal expansion is about 17/10 ⁶ (1 / ° C), and high carbon chromium bearing steel (hereinafter, SUJ) is used for the bearing. The coefficient of thermal expansion is about 12/10 ⁶ (1 / ° C.). The mounting board of the IC, the magnetic disk, the spacer for the magnetic disk, etc. are made of Al alloy, and the coefficient of thermal expansion is about 23. / 10 ⁶ (1 / ° C.). Therefore, when the temperature in the magnetic disk device rises, thermal stress or deformation occurs in the carriage due to the difference in the coefficient of thermal expansion, and this deformation causes a displacement of the magnetic head, that is, thermal off-track, This will reduce the reliability of the performance of the device. In particular, this is an important issue in a magnetic disk device in which the density is increasing.

The coefficient of thermal expansion of the AZ91 is calculated by the compound rule shown in the following equation (1), and almost the same value is obtained by actual measurement by us.

Α (AZ91) = V (Mg) × α (Mg) + V (Al) × α (Al) (1) α (AZ91): coefficient of thermal expansion of AZ91 V (Mg): volume of Mg in AZ91 % Α (Mg): Coefficient of thermal expansion of Mg ｛26.1 / 10 ⁶ (1 / ° C.)｝ V (Al): Volume% of Al in AZ91 α (Al): Coefficient of thermal expansion of Al ｛23.9 / 10 ⁶ (1 / ° C)｝ The coefficients of thermal expansion of Mg and Al are values up to 100 ° C (edited by The Japan Institute of Metals, Metals Data Book, published in 1984, paragraph 13).

Therefore, when an Mg alloy is used as the material of the carriage, AZ91D may be used in consideration of corrosion resistance. However, in consideration of suppression of deformation of the carriage and generation of stress due to the coefficient of thermal expansion, the material of AZ91D is modified. Must be performed. In particular, a magnetic disk on which magnetic information is written and Al alloy which is a spacer for the magnetic disk and AZ91D
It is important to match the thermal expansion coefficients of

The prior arts described in JP-A-63-298881 and JP-A-1-319126 disclose the use of an Mg alloy of the same quality as that of a carriage for a magnetic disk, a spacer for a magnetic disk, and the like. A method has been proposed for reducing thermal off-orac caused by a difference in thermal expansion between a magnetic disk and a carriage. However, if an Mg alloy of the same quality as that of the carriage is used for the magnetic disk, magnetic disk spacer, etc., the difference in the coefficient of thermal expansion between spindles and bearings made of SUS or SUJ will be the same as conventional Al alloy magnetic disks, In this case, thermal off-track occurs due to a difference in thermal expansion coefficient between the spindle or bearing and the magnetic disk or carriage, and is not so effective in reducing the thermal off-track of the entire magnetic disk drive. Furthermore, magnetic disks are required to have strict smoothness and dimensional stability, and special Al alloys are currently used. Changing to a homogeneous Mg alloy simply to match the thermal expansion coefficient with the carriage has many other issues and is not practical.

In the prior art described in Japanese Patent Application Laid-Open No. 2-193373, since the B and SiC are non-uniformly dispersed in the Mg alloy, the carriage becomes inhomogeneous, and in particular, the arm (guide arm) of the carriage. In the above, B and SiC are segregated, and a difference occurs in the coefficient of thermal expansion, thereby causing thermal off-track. Carriage production is best achieved by die casting. However, it is difficult to uniformly disperse B or SiC, which is a high melting point material and has a low density, in a dissolved Mg alloy, and B or SiC may be easily segregated.

It is an object of the present invention to provide an excellent corrosion resistant, homogeneous,
Also, by providing a highly reliable Mg alloy carriage that suppresses thermal stress and deformation by reducing the difference in thermal expansion coefficient from other materials, and a method for manufacturing the carriage, furthermore, using the carriage, heat off An object of the present invention is to provide a magnetic disk device having small tracks, high reliability, and high-speed access.

[0014]

The above object is achieved by the following means. A spindle driven to rotate, a plurality of magnetic disks concentrically arranged around the spindle and rotating together with the spindle, and arranged outside the magnetic disk to record and reproduce magnetic information on the magnetic disk A carriage for use in a magnetic disk drive including a load arm having a head, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage In the above, the carriage is formed of an alloy containing magnesium and aluminum as main components, and a γ phase, which is an intermetallic compound of magnesium and aluminum, is continuously precipitated in a network, and the average of particles of the γ phase The area should be at least 0.5 μm ² .

Alternatively, a spindle driven to rotate,
A load comprising a plurality of magnetic disks arranged concentrically about the spindle and rotating with the spindle, and a head disposed outside the magnetic disk and recording and reproducing magnetic information on the magnetic disk An arm, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage. the aluminum is formed by an alloy whose main component, and the precipitation amount of γ-phase is an intermetallic compound of magnesium and aluminum, the strongest peak intensities I ₁ of γ-phase in X-ray diffraction is the mother phase magnesium Strongest peak intensity
Compared to I _2, the intensity ratio I ₁ / I ₂ it is to be at least 0.1.

Alternatively, a spindle driven to rotate,
A load comprising a plurality of magnetic disks arranged concentrically about the spindle and rotating with the spindle, and a head disposed outside the magnetic disk and recording and reproducing magnetic information on the magnetic disk An arm, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage. It is made of an alloy containing aluminum as a main component, and its coefficient of thermal expansion does not exceed 25/10 ⁶ (1 / ° C.).

Furthermore, in the magnetic disk drive carriage according to any one of claims 1 to 3,
The density of the carriage should not exceed 1.95 g / cm ³ .

Alternatively, a spindle driven to rotate,
A load comprising a plurality of magnetic disks arranged concentrically about the spindle and rotating with the spindle, and a head disposed outside the magnetic disk and recording and reproducing magnetic information on the magnetic disk 5. A magnetic disk drive comprising an arm, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage, wherein the carriage is configured as described in claims 1 to 4. Among them, the carriage described in any one of the above items is used.

Alternatively, a spindle driven to rotate,
A load comprising a plurality of magnetic disks arranged concentrically about the spindle and rotating with the spindle, and a head disposed outside the magnetic disk and recording and reproducing magnetic information on the magnetic disk An arm, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage. It is formed of a magnesium alloy containing magnesium and aluminum as main components, and is heated at a temperature of 200 ° C to 300 ° C for at least 8 hours.

[0020]

[Action] As a result of examining changes in various physical properties due to aging of an Mg-Al alloy, it was found that when a certain amount or more of an intermetallic compound γ phase is precipitated, a thermal expansion coefficient sharply decreases. gamma phase
The coefficient of thermal expansion is smaller than that of the Mg phase, and the γ phase is continuously precipitated in a predetermined amount or more in the matrix Mg, and the particle area of the precipitated γ phase is at least larger than 0.5 μm ^2. Indeed, the coefficient of thermal expansion of Mg in the parent phase is reduced.

Therefore, there is an amount of γ phase necessary to suppress the coefficient of thermal expansion of Mg. Quantitatively showing the amount,
In X-ray diffraction, the strongest peak intensity of the γ phase (hereinafter referred to as I ₁ ) is compared with the strongest peak intensity of the parent phase Mg (hereinafter referred to as I ₂ ), and the intensity ratio I ₁ / I ₂ (hereinafter referred to as Ir) Is equivalent to at least 0.1.

The aging condition for forming the above-mentioned amount of γ phase is heating at a temperature of 200 ° C. to 300 ° C. for at least 8 hours. In principle, even if the temperature does not exceed 150 ° C, γ
Although precipitation of the phase is possible, the deposition rate is low and not suitable for industrial use. Further, when heated at a temperature exceeding 350 ° C., the precipitated γ phase is eluted into the mother phase again, so that the γ phase is not effectively precipitated and the phenomenon of reducing the coefficient of thermal expansion is not observed.

[0023]

1 to 3 show a magnetic disk drive using an Mg alloy carriage according to an embodiment of the present invention. A magnetic disk drive 1 shown in FIG. 1 includes a spindle 3 driven to rotate by a motor (not shown), a plurality of magnetic disks 2 arranged concentrically around the spindle 3 and rotating together with the spindle 3, and a magnetic disk 2 And a load arm 5 having a head 4 for recording and reproducing magnetic information on the magnetic disk 2, and converting the information on the magnetic disk 2 into a weak electric signal by the head 4. Lead wire 8
A flexible printed circuit board (hereinafter, referred to as an FPC board) 9 for supporting a plurality of signal lines to be transferred by a carriage 10, a carriage 10 having a guide arm 11 connected to the load arm 5 and held by a carriage shaft 7. , And an actuator 6 for operating the carriage 10.

FIG. 2 is a perspective view of the carriage 10 according to one embodiment of the present invention. The carriage 10 includes a coil 15 on which a magnetic force acts relative to the actuator 6.
And the carriage shaft 7 with the
And a plurality of guide arms 11 symmetrically positioned with respect to the coil support portion 16 through the support arm, and aligning and supporting the guide arms 11 at right angles to the axial direction of the carriage shaft 7 and parallel to each other at equal intervals. Guide arm support portion 17 having a cylindrical structure and
FPC supporting portions 18 and 19 provided for mounting the FPC plate 9 and a bearing supporting portion 13 for tightly connecting the bearings 14 to each other.
It is composed of

The carriage of this embodiment is formed by using a magnesium alloy, AZ91D, as a material and heating the die at a temperature of 200 ° C. to 300 ° C. for at least 8 hours. The composition analysis result of AZ91D was as follows: Al = 8.9%, Mn = 0.32%, Zn = 0.8%, and Fe = 0.03%.
002%, Ni = 0.0008%, Cu = 0.005%, Mg = remaining.

FIG. 3 shows a magnetic disk drive 1 showing a relative positional relationship between the magnetic disk 2, the head 4 and the guide arm 11.
FIG. The magnetic disk 2 is overlapped with a spacer 22 and fixed to a hub 23 rotated by a motor (not shown). The magnetic disk 2 and the spacer 22 are made of an Al alloy, and have a coefficient of thermal expansion of about 23/10 ⁶ (1
/ ° C). The spindle 3 is SUS and the hub 2
3 is an Fe alloy, and both have a coefficient of thermal expansion of about (12 to 17) / 10
⁶ (1 / ° C).

The thermal expansion coefficient of the Mg alloy carriage according to the embodiment of the present invention will be described with reference to FIGS. FIG.
9 shows data obtained by measuring a change in the coefficient of thermal expansion of a carriage made of an Mg alloy according to an example of the present invention. The horizontal axis indicates the heating time, and the vertical axis indicates the coefficient of thermal expansion. In the figure, the line marked with a circle indicates the result of heating at 200 ° C, and the line marked with a triangle in the figure indicates the result of heating at 300 ° C. The sample for measuring the coefficient of thermal expansion is a test piece for measuring the coefficient of thermal expansion cut out from a carriage manufactured by die casting using AZ91D as the material. The cut-out position was the guide arm 11 and the cut-out position was always constant. The coefficient of thermal expansion was measured using a laser-type precision thermal expansion measuring device LIX-1 manufactured by Vacuum Riko Co., Ltd. As measurement conditions,
The measurement temperature range was evaluated using the average thermal expansion coefficient from 0 ° C. to 50 ° C., considering the operating temperature range of the magnetic disk device, from −10 ° C. to 60 ° C., the temperature rising rate at 2 ° C./min. Measurement is -10 ° C
Only when the temperature was raised from to 60 ° C.

As shown in FIG. 4, when the heating time exceeds 8 hours, the coefficient of thermal expansion sharply decreases to about 24/10 ⁶ (1 / ° C.).
Reach This reduction in the coefficient of thermal expansion cannot be explained by the simple compound rule (1), but is a result of the influence of the intermetallic compound γ phase. As a result of detailed observation of the structure of AZ91D having a reduced coefficient of thermal expansion, a state in which fine γ-phases were continuously precipitated in a network was observed. The intermetallic compound γ phase continuously deposited in a network plays a role corresponding to the filler of the composite material, and reduces the coefficient of thermal expansion of the entire material AZ91D.

As a result of performing similar experiments at various heating temperatures,
When the temperature exceeded 350 ° C., no decrease in the coefficient of thermal expansion was observed. In order to investigate this phenomenon, the structure of the sample heated above 350 ° C. was observed while changing the heating time. As a result, a phenomenon was observed in which the precipitation amount of the γ phase decreased with the elapse of the heating time. This is because the γ phase once precipitated is dissolved in the mother phase again with the elapse of the heating time. In particular, it was recognized that when the heating temperature exceeded 400 ° C., the re-dissolution phenomenon of the γ phase became remarkable.

FIG. 6 shows the correlation between the precipitation state of the γ phase and the coefficient of thermal expansion. The average particle area of the γ phase (μ
m ² ), and the vertical axis indicates the coefficient of thermal expansion. The average area of the γ-phase particles was calculated by image processing of a scanning electron micrograph (using a device name: Luzex II). As a result, the larger the precipitated γ-phase particle area, the lower the coefficient of thermal expansion. I understood.

FIG. 5 shows the result of X-ray diffraction of the test piece at each heating time, and the correlation between the amount of precipitation of the γ phase and the coefficient of thermal expansion was examined. The horizontal axis represents the ratio of the strongest peak intensity I ₂ of the strongest peak intensity I ₁ and Mg of γ phase in X-ray diffraction results, the Ir = I ₁ / I _2. That is, the larger the value of Ir, the larger the amount of the intermetallic compound γ phase precipitated. The vertical axis indicates the coefficient of thermal expansion. Incidentally, the strongest peak intensity I ₁ of the crystal γ-phase having the cubic crystal is diffraction if Shimese at Miller index (411). The strongest peak intensity I ₂ of Mg whose crystal is hexagonal is (10 · 1) diffraction.
Note that, as in FIG.
The line marked with Δ is the result of heating at 300 ° C. In addition, the squares indicate the values of the coefficient of thermal expansion and the value of Ir when the sample was cooled rapidly in the air after holding at 400 ° C. for 6 hours, and almost no γ phase was precipitated. FIG.
As shown in Fig. 7, when Ir exceeds 0.1, the coefficient of thermal expansion sharply decreases. That is, when the γ phase is precipitated in an amount where Ir exceeds 0.1, the coefficient of thermal expansion of AZ91D decreases. Incidentally, the value of Ir when the Al contained in the Mg alloy was all in the γ phase,
Estimated from conventional data, it is between 0.12 and 0.15.

As shown in FIG. 4, by heating at 300 ° C. for 10 hours, the coefficient of thermal expansion of the Mg alloy carriage 10 is reduced to about
24/10 ⁶ (1 / ° C). That is, by heating under the above conditions, the coefficient of thermal expansion of the carriage 10 is reduced to Al
The coefficient of thermal expansion of the magnetic disk 2 made of an alloy and the spacer 22 can be made almost equal to 23/10 ⁶ (1 / ° C.).
The thermal off-track caused by the difference in the thermal expansion coefficient between the spacer 22 and the carriage 10 can be eliminated. Furthermore, compared to the untreated AZ91D, the difference between the thermal expansion coefficient of the load arm 5 and SUS304 is reduced by about 23%, and the thermal expansion coefficient of the load arm 5 and the carriage 10 is reduced. This is also effective in reducing thermal off-track caused by the above.

In this embodiment, AZ91D is used as the Mg alloy. However, the present invention uses a method of reducing the coefficient of thermal expansion of the Mg alloy by precipitating an intermetallic compound in a mesh form. It is not limited to AZ91D. A Mg alloy having a low Al content, for example, AZ31, AZ61, or AZ81 may be used.

Conversely, increasing the weight ratio of Al in the Mg alloy,
It is also possible to make the coefficient of thermal expansion smaller by increasing the amount of the γ phase. In this case, although the weight of the carriage increases with an increase in the Al content, the difference in thermal expansion coefficient with SUS decreases,
Thermal off-track generated between the parts using the above method can be reduced. When increasing the Al content, the Al ratio is practically up to about 30% by weight, which is the eutectic point of the γ phase and the Mg phase. Assuming that the ratio of Al in the Mg-Al alloy is about 30% by weight, the calculated density determined by the composite rule is 1.945 g / cm ³ . That is, in a practical Mg-Al alloy to which the present invention can be applied, the density is a maximum of 1.945 g / cm ³ .

The present invention is effective for a magnetic disk drive having a high magnetic recording density or a large magnetic recording capacity. In particular, the present invention is particularly effective for a magnetic disk drive of a servo surface servo system in which the control method of the positioning of the magnetic head is performed using only the position information of the servo surface.

[0036]

According to the present invention, the specific gravity is about 1.8 g / cm ³
And a Mg alloy having a small thermal expansion coefficient can be used for the carriage, and its thermal expansion coefficient can be made substantially the same as the thermal expansion coefficient of the Al alloy as the magnetic disk material. As a result, most of the thermal off-track caused by the difference in thermal expansion coefficient between the magnetic disk and the carriage can be eliminated.

Further, since the coefficient of thermal expansion is reduced by about 23% as compared with the conventional Mg alloy carriage, the difference in the coefficient of thermal expansion between materials other than the Al alloy, for example, SUS, is also small, and the thermal expansion coefficient with SUS is small. Thermal off-track due to a difference in expansion coefficient is reduced.

Since the thermal off-track is reduced, the positioning of the magnetic head becomes easy, and the magnetic recording density can be increased. Furthermore, there is no need to use a data surface servo method for recording position information on each magnetic disk and positioning the magnetic head, and it is possible to use a servo surface servo method capable of providing a large magnetic recording capacity.

[Brief description of the drawings]

FIG. 1 is a perspective view of a magnetic disk drive using a Mg alloy carriage according to an embodiment of the present invention.

FIG. 2 is a perspective view of a magnesium alloy carriage according to an embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of a magnetic disk drive according to an embodiment of the present invention.

FIG. 4 is a graph showing the relationship between the coefficient of thermal expansion and the aging time of a magnesium alloy carriage according to an embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the coefficient of thermal expansion of a magnesium alloy carriage according to an example of the present invention and the highest peak intensity ratio Ir of a γ phase and a Mg phase in the result of X-ray diffraction.

FIG. 6 is a graph showing the relationship between the average particle area of the γ phase and the coefficient of thermal expansion of the magnesium alloy carriage according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Magnetic disk drive 2 Magnetic disk 3 Spindle 4 Head 5 Load arm 6 Actuator 7 Carriage shaft 8 Lead wire 9 FPC board 10 Carriage 11 Guide arm 12 Load arm attachment part 13 Bearing support part 14 Bearing 15 Coil 16 Coil support part 17 Guide arm Support part 18 FPC board support part 19 FPC board support part 20 Guide arm back part 21 Cover 22 Spacer 2
3 hub

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-193373 (JP, A) JP-A-54-113312 (JP, A) JP-A-1-156448 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G11B 21/02 C22C 23/02

Claims (5)

(57) [Claims] A rotating spindle; a plurality of magnetic disks arranged concentrically about the spindle and rotating with the spindle; and a magnetic disk disposed outside the magnetic disk and mounted on the magnetic disk. A magnetic disk including a load arm having a head for recording and reproducing information, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage In the carriage used in the apparatus, the carriage is formed of an alloy containing magnesium and aluminum as main components, and a γ phase, which is an intermetallic compound of magnesium and aluminum, is continuously precipitated in a network, and γ magnetic disk drive for carriage average area of the phase of the particles being at least 0.5 [mu] m ² 2. A spindle driven to rotate, a plurality of magnetic disks concentrically arranged about the spindle and rotating with the spindle, and a magnetic disk disposed outside the magnetic disk and mounted on the magnetic disk. A magnetic disk including a load arm having a head for recording and reproducing information, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage In the carriage used in the apparatus, the carriage is formed of an alloy containing magnesium and aluminum as main components, and a precipitation amount of a γ phase, which is an intermetallic compound of magnesium and aluminum, is determined by X-ray diffraction. strongest peak intensity I ₁ is compared with the strongest peak intensity I ₂ of the magnesium mother phase, the intensity ratio I ₁ / I ₂ Magnetic disk drive carriage, characterized in that even without 0.1. 3. The carriage for a magnetic disk drive according to claim 1 , wherein the density of the carriage is 1.95.
A carriage for a magnetic disk drive, wherein the carriage does not exceed g / cm ³ . 4. A spindle driven to rotate, a plurality of magnetic disks concentrically arranged about the spindle and rotating with the spindle, and a magnetic disk disposed outside the magnetic disk and disposed on the magnetic disk. A magnetic disk including a load arm having a head for recording and reproducing information, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage A magnetic disk drive, wherein the carriage uses the carriage according to any one of claims 1 to 3 . 5. A spindle driven to rotate, a plurality of magnetic disks concentrically disposed about the spindle and rotating with the spindle, and a magnetic disk disposed outside the magnetic disk and disposed on the magnetic disk. A magnetic disk including a load arm having a head for recording and reproducing information, a carriage having a guide arm connected to the load arm and held by a carriage shaft, and an actuator for operating the carriage in the method for manufacturing a carriage used in the apparatus, the carriage, magnesium
90-95%, aluminum 3-9%, zinc 0.6-
A method of manufacturing a carriage for a magnetic disk drive, wherein the carriage is formed of a magnesium alloy containing 1% and heated at a temperature of 200 ° C. to 300 ° C. for at least 8 hours.