TWI758572B - Gaskets and Hard Disks - Google Patents

Abstract

This case realizes a gasket with good magnetic properties. The gasket (12) is formed by forming a plate of ferrite-based stainless steel into a ring shape, and then heating and pressurizing the plate formed into a ring at a temperature of 900° C. or higher and less than the temperature Ac1 of the iron transformation starting temperature Ac1 of Vostian. made.

Description

Gaskets and Hard Disks

The present invention relates to a gasket, a hard disk and a manufacturing method of the gasket.

The miniaturization and larger capacity of magnetic disk devices (eg, hard disks) have been continuously developed from the past. A magnetic disk device with a large storage capacity includes a plurality of magnetic disks, and an annular spacer is inserted between the magnetic disks, and the spacer rotates together with the magnetic disks.

Here, most of the conventional gaskets are manufactured by cutting free-cutting stainless steel with good machinability. However, since free-cutting stainless steel contains S or Pb, the price of steel is high and the cost rises. Therefore, compared with free-cutting stainless steel, the technical research on the production of gaskets by punching the sheet of ferrite-based stainless steel, which contains less S or Pb and is relatively inexpensive, is continuing.

For example, Patent Document 1 discloses a method for manufacturing a gasket, in which a metal plate with a specific thickness is punched to form a substantially annular prototype ring, and an annular tongue piece of the element ring is formed through a specific process The bottom end is cut with a shearing tool to make the gasket. In addition, for example, Patent Document 2 discloses a gasket in which the change in surface hardness is within 4% above and below the average value, the grain size number is 5.0 to 9.0, and the residual compressive stress is 80 MPa The following ferrite-based stainless steel rolled sheets are manufactured. This gasket is formed in a ring shape by punching a rolled sheet.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Gazette "Japanese Laid-Open No. 2001-167548 (Published on June 22, 2001)"

[Patent Document 2] Japanese Patent Laid-Open Publication “Japanese Unexamined Patent Publication No. 2013-222487 (Published on October 28, 2013)”

However, since residual stress is generated inside the gasket manufactured by the method disclosed in Patent Document 1, the shape of the gasket is unstable at the final stage of the manufacturing process or when it is assembled into a magnetic disk, which becomes a factor for the distortion of the magnetic disk. In this regard, the gasket disclosed in Patent Document 2 solves the problem of residual stress to a certain extent, but since it is formed by punching, its magnetic properties are impaired. The above-mentioned gasket is similarly subjected to punching or pressing, and thus the same magnetic properties as the above-mentioned gasket are impaired. However, Patent Documents 1 and 2 do not describe or suggest a technique for improving the rotational performance of a motor provided in a hard disk by applying a treatment that does not impair the magnetic properties of the gasket and the spacer.

One aspect of the present invention is, in view of the above-mentioned problems, an object of providing a spacer that realizes a hard disk with a small energy load with high efficiency and has good magnetic properties.

In order to solve the above-mentioned problems, a gasket of one aspect of the present invention is a gasket, which is arranged in a hard disk, and is formed into an annular shape after a plate of ferrite-based stainless steel is formed into an annular shape. The plate is produced under pressure while heating at a temperature of 900° C. or higher and lower than the Worstian iron transformation initiation temperature Ac1 (hereinafter simply referred to as “Acl”).

In addition, in order to solve the above-mentioned problems, a method for manufacturing a gasket of an aspect of the present invention is a method for manufacturing a gasket disposed on a hard disk, which includes: a first process of forming a plate of ferrite-based stainless steel into an annular shape and the second process, the plate formed into a ring shape in the first process is heated and pressurized at a temperature above 900° C. and less than the temperature Ac1 of the Worcester field iron transformation start temperature.

According to an aspect of the present invention, it is possible to provide a spacer that realizes a hard disk with low energy load with high efficiency and has good magnetic properties.

1: Hard Disk

2: Shield

11: Rotary hub

12: Gasket

20: Spindle motor

20a: Rotation axis

20b: stator core

20c: Subcoil

21: Rotary hub

21a: Magnet

S: S pole

N:N pole

22: Gripper

23: Screws

30: magnetic head

FIG. 1 is a cross-sectional view showing a schematic configuration of a hard disk according to an embodiment of the present invention.

[ FIG. 2 ] is a cross-sectional view showing a schematic configuration of a spindle motor disposed in a hard disk, and a view showing changes in magnetic flux density around the spacer.

[ Fig. 3 ] is a graph showing the relationship between the amount of strain and the magnetic flux density of the ferrite-based stainless steel.

Hereinafter, embodiments of the present invention will be described. In addition, the following description is for the purpose of promoting a sufficient understanding of the gist of the present invention, and does not limit the present invention unless otherwise specified. In addition, in this specification, "A to B" means A or more and B or less.

The fat-grained iron-based stainless steel used for manufacturing the gasket of one aspect of the present invention is a stainless steel suitable for manufacturing a relatively small (eg, diameter of 50 mm or less or height of 20 mm or less) and requiring high dimensional accuracy.

In addition, in this specification, the so-called Worcester iron transformation start temperature Ac1 (hereinafter or simply referred to as "Ac1") refers to the temperature at which the formation of worcester iron begins in the annular steel structure due to heating. The ratio of the components contained in the ferrite-based stainless steel varies. In the laboratory, it was confirmed that Acl used for the ferrite-based stainless steel of one aspect of the present invention has the relationship of the following formula 1 and the contained components. Therefore, in the present invention, the value AC [° C.] obtained by the formula (1) is used as an index of the upper limit of the heating temperature, that is, Acl. In this embodiment, the ferrite-based stainless steel containing the component ratios at which AC is about 1150° C. or lower is used.

(Formula 1) AC[℃]=-221C+64Si-40Mn-80Ni+20Cr-247N+1240Al+486Ti+602

<Structure of hard disk>

First, referring to FIG. 1 , the structure of the hard disk 1 in an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of a hard disk 1 according to an embodiment of the present invention. As shown in FIG. 1 , the hard disk 1 includes three disks 11 in a cover 2 , and the cover 2 is in the shape of an airtight box that hermetically seals the inside of the device. Disc 11 to borrow The magnetic head 30 slightly lifted from the surface of the disc 11 is rotated by the shaft motor 20 to perform writing and reading of the disc 11 .

Spacers 12 (details will be described later) are respectively provided between the two adjacent discs 11 . The spacer 12 is annular and is arranged to surround the rotating hub 21 of the rotating shaft motor 20 . The disc-shaped holder 22 is fastened to the upper end of the rotating hub 21 with screws. The inner peripheral portion of the disc 11 is pressed by the elastic deformation of the holder 22, and the plurality of discs 11 and the plurality of spacers 12 are held on the large diameter portion of the bottom of the rotating hub 21 and the holder 22. between. In addition, the holder 22 may be fixed by members other than the screws 23 .

Hard drives usually come in 2.5-inch and 3.5-inch sizes. In 3.5-inch hard drives, in order to use a combination of glass discs and stainless steel spacers, the dimensional accuracy of the stainless steel spacers is required.

<The relationship between the magnetic properties of the gasket and the performance of the shaft motor>

Next, the relationship between the magnetic properties of the spacer 12 and the performance of the shaft motor 20 will be described with reference to FIG. 2 . FIG. 2 is a cross-sectional view showing a schematic configuration of a spindle motor 20 disposed in a hard disk, and a diagram showing changes in magnetic flux density around the spacer 12 .

As shown in FIG. 2 , in the rotary shaft motor 20, six stator cores 20b protrude from the rotary shaft 20a toward the rotary hub 21, and extend along the side surface of the rotary shaft 20a. The stator coils 20c are wound around the respective stator cores, respectively.

First, a current flows through the stator coil 20c to magnetize the stator iron core 20b, thereby generating a repulsive force or an attractive force between the magnetized stator iron core 10b and the magnet 21a. The magnet 21a is arranged in a region of the rotating hub 21 on the side of the rotating shaft 20a, and faces the stator core 20b. Next, the rotating hub 21 , the clamper 22 , and the disk 11 are rotated by the generated repulsive force or the like.

Since a magnetic circuit for reducing the so-called "leakage magnetic flux" as much as possible is formed in the rotary hub 21, it functions as a yoke (specifically, a back yoke) for improving the performance of the rotary shaft motor 20. "Leakage magnetic flux" refers to the lines of magnetic force that pass through parts other than the original magnetic circuit and do not contribute to the generation of repulsion or the like.

Here, by using a spacer with good magnetic properties, the function of the rotating hub 21 as a yoke is enhanced. That is to say, since the magnetic properties of the gasket are determined by the magnetic flux density (or permeability) of the gasket, when the magnetic flux density (or permeability) of the gasket is larger, the "leakage magnetic flux" ” is smaller (in FIG. 2 from the state of facing the upper right corner of the paper to the state of the lower right corner), thereby improving the performance of the shaft motor 20 .

In particular, a 3.5-inch hard disk used for near-line applications or large-capacity servers has a large number of disk stacks per unit, which increases the rotational load applied to the shaft motor. Therefore, it is desired to have a high-efficiency rotary shaft motor different from the prior art, and in order to realize the high-efficiency rotary shaft motor, the improvement of the magnetic properties of the gasket has become a big problem.

In this regard, since the rotary shaft motor 20 uses the gasket 12 with good magnetic properties, the function of the rotary hub 21 as a yoke is enhanced, and its function is improved compared with the conventional rotary shaft motor.

<The composition of the components contained in the iron-based stainless steel>

The composition of the components contained in the ferrite stainless steel used for manufacturing the gasket 12 is as follows. In addition, the remainder other than the various components shown below is iron (Fe) and a small amount of impurities (unavoidable impurities) unavoidably mixed.

(chrome: Cr)

Cr is an essential element for ferrite-based stainless steel, and in order to secure the corrosion resistance, the Cr concentration is preferably 11 mass % or more. However, when a large amount of Cr is contained, the stainless steel is excessively hardened, so the Cr concentration is preferably 19 mass % or less, and more preferably 13 mass % or less. The method for adjusting the Cr content is not particularly limited. For example, the Cr content can be adjusted by controlling the reduction reaction of Cr oxides.

(Manganese: Mn)

Mn is an element that negatively affects outgas resistance and magnetic properties due to the generation of sulfides. Therefore, in the ferrite-based stainless steel used for manufacturing the gasket 12, the content of Mn is preferably as small as possible, preferably 0.60 mass % or less.

(Titanium: Ti)

Like Nb, Ti-based is an element that makes ferrous-based stainless steel into a ferrous-based single-phase at 900 to 1000° C. by reacting with C or N. On the other hand, the larger the grain size, the better the magnetic properties. Unlike Nb, Ti hardly hinders the grain growth of the ferritic stainless steel at high temperature. Therefore, from the viewpoint of the magnetic properties, adding Ti is better than Add Nb. On the other hand, since Ti is excessively added, the surface properties of the stainless steel are adversely affected and the manufacturability is lowered, so it is preferable to contain Ti in an amount of 0.05 to 0.50 mass % or less.

(carbon: C)

Since C is a harmful element that reduces the magnetic properties by generating carbides, the content of C is preferably 0.08% by mass or less, and preferably 0.02% by mass or less.

(Silicon: Si)

Si is an effective element as a deoxidizer in steel production. However, when a large amount of Si is contained, the stainless steel is excessively hardened due to solid solution strengthening. Therefore, the content of Si is preferably 0.80% by mass or less.

(phosphorus: P)

P reduces hot workability with its content. Therefore, the content of P is preferably not more than 0.04 mass %.

(Sulfur: S)

When the content of S in the fat-grained iron-based stainless steel is large, A-based inclusions mainly composed of MnS existing in the steel increase, thereby deteriorating the magnetic properties. Therefore, the content of S is preferably 0.03 mass % or less.

As a method for adjusting the content of S, the content of S can be reduced in order to promote the desulfurization reaction, since desulfurization occurs due to slagging along with deoxidation during reduction and deoxidation of Cr oxides during reduction and post-smelting. . As the adjustment method of the S content, a known method may be used, and the adjustment method is not limited.

(nickel: Ni)

Since Ni increases the proportion of the Worcester iron phase in a high temperature range, it is effective in improving the workability of the hot rolling delay time. However, if it contains excessively, the temperature of the α-γ transformation point decreases, and a sufficient recrystallization temperature cannot be ensured. In addition, Ni is also an expensive element. Therefore, the content of Ni is preferably 0.50 mass % or less.

(nitrogen: N)

If N is excessively added, nitrides are formed with other elements, and the magnetic properties are degraded. Therefore, the content of N is preferably 0.02 mass % or less.

(aluminum: Al)

Al is an element that improves the cleanliness of steel. On the other hand, if the content is high, it forms a compound with C and N to lower the magnetic properties, so it is preferably 0.05 mass % or less.

In addition, the composition of the above-mentioned components is only an example, and the magnetic flux density B10 when the external magnetic field 10Oe is applied to the gasket 12 can be realized to be 0.6 even when the content (mass %) of the various components is other than the above-mentioned examples. The spacer 12 having good magnetic properties of T or more, and the spacer 12 having a parallelism of 5 μm or less and a flatness of 1 μm. In addition, even if the gasket 12 contains components other than the above-mentioned various components, the magnetic flux density B10 is 0.6T or more, the parallelism is 5 μm or less, and the flatness is 1 μm or less.

<Manufacturing method of gasket>

Regarding the composition of the contained components, an example of the manufacturing method of the ferrite-based stainless steel gasket 12 that satisfies the above conditions will be described below. Specifically, the gasket 12 is manufactured by the following processes (1) to (4).

(1) First, precision punching is performed using a die for a rolled plate (plate: not shown) of annealed ferrite-based stainless steel. That is, by performing outer diameter punching and then inner diameter punching with respect to a rolled sheet material, a steel material (plate material: not shown) formed into an annular shape is obtained (first process).

In this ring-shaped steel material, there is almost no sagging on the punching end face, and the punching end face property is greatly improved. However, the magnetic properties of the ring-shaped steel sheet after the first process is ended by about 10-20% compared with the rolled sheet before the first process. In addition, in this process, the magnetic properties are reduced by about 10-20% compared to the rolled sheet before the first process. In addition, when further stamping is applied in this process, the magnetic properties are reduced by more than 50%.

(2) Next, the ring-shaped steel material obtained by the punching process is pressurized while being heated at a temperature of 900° C. or more but less than Acl (second process).

By applying the second process, in addition to being able to greatly reduce the amount of precipitates and inclusions generated, the size of the precipitates and the like can also be increased compared to other heat treatments and pressure treatments. In addition, the ring-shaped steel structure increases the crystal grain size by applying pressure while heating at a temperature of 900° C. or higher. In addition, since the heating temperature is less than Acl, the ring-shaped steel material is α single-phase. Further, residual stress smaller than that of the annular steel material can be effectively removed. Due to the occurrence of these situations, the magnetic properties of the annular steel material that has completed the second process are greatly improved due to the occurrence of these phenomena.

Specifically, the magnetic flux density B10 of the annular steel material after the end of the second process is at least 0.6T or more when the external magnetic field H=10Oe (796A/m). In addition, it is added that the magnetic flux density B10 of the ring-shaped steel is preferably 0.8T or more; this value can be obtained by appropriately adjusting the heating temperature or pressure.

As the second process, for example, pressure annealing is performed on a ring-shaped steel material at a temperature of 900°C or higher and less than Acl; or heat-sealing forging is performed at a temperature of 900°C or higher and lower than Acl.

Pressure annealing is a type of annealing, and refers to a process in which a ring-shaped steel material is heated to a specific temperature while being pressurized, and is maintained at the specific temperature for a specific period of time and then gradually cooled. In addition, heat-tight forging refers to placing a ring-shaped plate heated to a specific temperature into a mold in a closed state, so that a double acting punch enters the mold in a double-acting manner, thereby filling the steel Inside the mold. Both treatments are effective in removing the residual stress of the ring-shaped steel and helping to improve the magnetic properties of the gasket 12 .

Further, as the pressure annealing, in addition to the stack pressure annealing described later, for example, an annular steel material may be subjected to pressure tempering treatment, which is used for shape correction of sheet materials or various parts. Pressure tempering used. The pressurized tempering treatment refers to a pressurized treatment during tempering.

In addition, as the heat-sealing forging, for example, heat-sealing forging by a hydraulic multi-axis press or the like can be exemplified. Different from general forging, closed forging can form a ring-shaped plate without burrs in a closed die.

In addition, the pressing force of the stack pressure annealing is preferably 0.001 MPa to 200 MPa in terms of dimensional accuracy. When the pressure is less than 0.01 MPa, the control of flatness and parallelism becomes difficult due to insufficient pressure. On the other hand, when it exceeds 200 MPa, since the pressing force is too large, it becomes difficult to control the thickness of the plate.

(3) Next, lapping is performed on the annular steel material after the second process is completed, using, for example, a polishing agent (diamond slurry) as abrasive grains to polish the surface of the annular steel material. Then, the finished steel is placed in a drum along with granular abrasives and media (compounds) for drum grinding to remove burrs (third process).

Here, since the ring-shaped steel material can be suppressed from sagging on the punched end face, the grinding time in the finish grinding and barrel grinding can be shortened, and the cutting cost can be reduced. In addition, the polishing load applied just now can be reduced, and the occurrence of warpage of the spacer 12, which is the final product, can be suppressed. Through the above, the material yield can be improved while the production efficiency is improved.

(4) After that, the steel material after barrel grinding is cleaned (fourth process). Here, from the viewpoint of magnetic properties, it is necessary to reduce inclusions as much as possible. The cleanliness calculated by the cleanliness calculation method regulated by the industrial standard JIS G0555 is preferably 0.04% or less. However, when 0.004 mass % to 0.02 mass % of TiN-based inclusions are contained, the deterioration of magnetic properties can be suppressed to a minimum, and the sagging of the punching end face can be further suppressed, while the cleanliness of the parts is not reduced. .

The manufacturing of the gasket 12 is completed by performing the fourth process. In addition, in order to manufacture the gasket 12 with good magnetic properties, at least only the first process and the second process need to be performed, and the third process and the fourth process are not necessary for manufacturing the gasket 12 .

<Example>

In this example, gaskets were produced using various ferrite-based stainless steels (the first invention steel, the second invention steel, and the comparative steel) having the components and compositions shown in Table 1 below. In addition, the Acl of the first invention steel was 984°C; the Acl of the second invention steel was 1089°C. In addition, the magnetic properties of various gaskets are measured in a specific method and the magnetic properties of these gaskets are compared. In addition, the relationship between the amount of strain and the magnetic flux density is also discussed.

[Table 1]

(Manufacture of gaskets)

With regard to the first invention steel and the second invention steel, the cold rolling annealing pickled sheet (rolled sheet) with a thickness of 1.8 mm was thermally refined to a thickness of 1.80t/1.60t, and then fine punched. Fine blanking press (first process), and the obtained ring-shaped steel is subjected to stack pressure annealing in vacuum (0.005Pa) (second process). Thereafter, the third and fourth processes described above are performed to manufacture the gasket 12 .

Here, with respect to the first invention steel, stack pressure annealing was performed at a heating temperature of 950° C. for 2 hours. That is, the first invention steel is heated and pressurized at a temperature of 900° C. or higher and lower than the Worstian iron transformation initiation temperature Ac1 (984° C.). Furthermore, with respect to the second invention steel, the stack pressure annealing treatment was performed at a heating temperature of 1050° C. for 2 hours. That is, the second invention steel is heated and pressurized at a temperature of 900° C. or higher and lower than the Worstian iron transformation initiation temperature Ac1 (1089° C.). Stacked pressure annealing refers to laminating a plurality of ring-shaped steel materials in a state where a separator is inserted between two opposite ring-shaped steel materials, and the separator is a separator of the same material as the steel and pre-oxidized . Further, the sinkers were stacked so that the surface pressure of the upper surface of the laminate was 0.01 MPa, and annealing treatment was performed in a vacuum.

On the other hand, with respect to the comparative steel, the round bar of the comparative steel was sliced, and the obtained thin-plate-shaped steel material was further subjected to a cutting process to manufacture a ring-shaped gasket. This manufacturing method is the same as that of conventional gaskets for 2.5-inch hard drives.

Each of the gaskets 12 manufactured using the first invention steel and the second invention steel and the gasket manufactured using the comparative steel (hereinafter referred to as "the first comparative gasket") have a thickness of 1.60 mm, an inner diameter of 25.0 mm, and a thickness of 1.60 mm. Ring with an outer diameter of 32mm. This is the shape and size for a 3.5-inch hard drive.

(Method of measuring magnetism)

The magnetic properties of the respective spacers 12 and the first comparative spacers manufactured using the first invention steel and the second invention steel were measured in the same manner. Specifically, an enameled copper wire of 0.32 mmφ was used, and a 100-turn primary coil, a 90-turn secondary coil, and a B-H tracer (B-H tracer, magnetic Material magnetic properties measuring instrument) to measure the magnetic flux density B10 when the external magnetic field H=10Oe.

In addition, the measurement of flatness and parallelism was performed with respect to all each spacer 12 and the spacer for a 1st comparison. Regarding the flatness, 1.50 μm or less is qualified; as for the parallelism, 5.00 μm or less is qualified (marked by ○ in Table 2); The measurement results are shown in Table 2 below.

(Result of measuring magnetism)

As shown in Table 2, the magnetic flux density B10 of the gasket 12 manufactured using the steel of the first invention was 1.0T. In addition, the magnetic flux density B10 of the spacer 12 manufactured using the steel of the second invention was 0.9T. The magnetic flux density B10 of the two types of gaskets 12 is both 0.8T or more, showing good magnetic properties.

On the other hand, the magnetic flux density B10 of the first comparative shim was 0.5T, which was lower than the 0.6T reference value of the shim magnetic characteristics. In addition, cold rolling, annealing, and pickling for the first invention steel with a sheet thickness of 1.8 mm The magnetic flux density B10 of the second comparative gasket (corresponding to the "first invention steel/omission of the annealing process" in Table 2) produced by only applying heat quenching and tempering and precision punching to the plate is 0.4, which is also lower than 0.6T.

From these circumstances, it is obvious that the magnetic properties of the gasket manufactured according to the manufacturing method of one aspect of the present invention are greatly improved compared with the gasket manufactured according to other manufacturing methods.

In addition, regarding flatness and parallelism, regardless of the manufacturing method, the gaskets manufactured using the first invention steel or the second invention steel were all acceptable (○). In general, the flatness is preferably 1 μm or less and the parallelism is 5 μm or less. Therefore, it is obvious that in order to improve the flatness and parallelism of the gasket, the composition of the components contained in the present embodiment should be used. It is better to describe the condition of Fe-iron series stainless steel.

(Relationship between strain amount and magnetic flux density)

A specific pressure is applied to the gasket 12 made of the first invention steel and after the second process is completed, and the amount of strain generated by the pressure and the magnetic flux density B10 when the external magnetic field H=10Oe during pressurization are respectively measured. . And use the measurement results to make a graph with the magnetic flux density B10 on the vertical axis and the strain amount on the horizontal axis, as shown in Figure 3. In the graph of FIG. 3 , the dashed line is used as a graph for comparing the first comparative gasket.

As shown in FIG. 3 , it was found that the magnetic flux density B10 was 1.2T in the state where no strain occurred in the gasket 12 produced by using the first invention steel and up to the second process. The magnetic flux density B10 is twice or more than that of the first comparative spacer. In addition, the magnetic flux density B10 rapidly decreases when the amount of strain is increased from 0% to about 0.5%, and the decrease in the magnetic flux density B10 becomes moderate when the amount of strain exceeds about 0.5%.

From this, it is apparent that in order to manufacture a gasket with good magnetic properties, that is, a gasket with a high magnetic flux density, it is effective to remove the strain applied during forming. From this point of view, the manufacturing method of the gasket in one aspect of the present invention can be said to be useful, and the manufacturing method can effectively remove the residual stress of the annular steel material.

<Organize>

In order to solve the problem to be solved by the present invention, the gasket in one aspect of the present invention is a gasket arranged on a hard disk, which is formed by forming a ring-shaped plate of a ferrite-based stainless steel into a ring shape. This plate material is produced under pressure while heating at a temperature of 900° C. or higher and lower than the Worstian iron transformation initiation temperature Ac1 (hereinafter or simply referred to as “Acl”).

According to the above-mentioned configuration, the sheet of ferrite-based stainless steel formed into a ring shape is heated and pressurized at a temperature of 900° C. or higher and lower than Acl. Therefore, the magnetic properties of the sheet material whose magnetic properties are once degraded by being formed into a ring shape are improved due to the relationship between heating and pressing. Therefore, a spacer having improved magnetic properties can be realized compared to, for example, a spacer manufactured without any treatment after being formed into a ring shape.

In addition, in order to solve the above problems, preferably, the spacer in one aspect of the present invention has a magnetic flux density B10 of 0.6T or more when an external magnetic field of 10Oe is applied to the spacer, a parallelism of 5 μm or less, and a flatness of 5 μm or less. is 1 μm or less.

In addition, in order to solve the above problems, preferably, the gasket in one aspect of the present invention is composed of: the content of C is 0.08 mass % or less; the content of Si is 0.80 mass % or less; the content of Mn is 0.60 mass % or less; P The content of S is 0.04 mass % or less; the S content is 0.03 mass % or less; the Ni content is 0.50 mass % or less; the Cr content is 11 mass % or more and 19 mass % or less; the N content is 0.02 mass % The content of Al is 0.05 mass % or less, the Ti content is 0.05 mass % or more and 0.50 mass % or less, the remainder is composed of Fe and unavoidable impurities, and the purity is 0.04 % or less.

Furthermore, in order to solve the above-mentioned problems, in the gasket of one aspect of the present invention, the content of C is preferably 0.02 mass % or less.

In addition, in order to solve the above-mentioned problems, in the gasket of one aspect of the present invention, the content of TiN-based inclusions is preferably 0.004 mass % or more and 0.02 mass % or less.

Furthermore, in order to solve the above-mentioned problems, in the gasket of one aspect of the present invention, preferably, the ring-shaped plate material is pressure annealed at a temperature of 900° C. or higher and lower than Acl.

According to the above-mentioned configuration, the sheet of ferrite-based stainless steel formed into a ring shape is pressure annealed at a temperature of 900° C. lower than Acl. Therefore, the magnetic properties of the sheet material whose magnetic properties were once degraded by being formed into a ring shape are improved by pressure annealing. Therefore, a gasket with improved magnetic properties can be realized.

In addition, in order to solve the above-mentioned problems, preferably, in the gasket of one aspect of the present invention, the annular plate is heat-sealed and forged at a temperature of 900° C. or higher and less than Acl.

According to the above-mentioned configuration, the plate of the ring-shaped ferrite-based stainless steel is subjected to hot-sealing forging at a temperature of 900° C. or higher and lower than Acl. Therefore, the magnetic properties of the sheet material whose magnetic properties were once degraded by being formed into a ring shape can be improved by heat-tight forging. Therefore, a gasket with improved magnetic properties can be realized.

In addition, in order to solve the above problem, preferably, the hard disk of one aspect of the present invention is provided with the spacer. According to the above configuration, the rotational load applied to the shaft motor in the hard disk can be reduced by having the spacer having good magnetic properties.

In addition, in order to solve the above-mentioned problems, preferably, a method for manufacturing a gasket of one aspect of the present invention is a method for manufacturing a gasket disposed on a hard disk, which includes: a first process of forming a plate of ferrite-based stainless steel. In the second process, the plate formed into a ring shape in the first process is heated and pressurized at a temperature above 900° C. and less than the temperature Ac1 of the Worcester field iron metamorphosis initiation temperature.

According to the above-described configuration, a spacer having improved magnetic properties can be produced compared to, for example, a spacer that is not subjected to any treatment after being formed into a ring shape.

<Additional information>

The present invention is not limited by the above-mentioned embodiments, and various modifications can be made within the scope indicated in the claims. Regarding the embodiments obtained by combining the technical means disclosed in different embodiments and combining them appropriately, Also included in the technical scope of the present invention. In addition, new technical features can also be formed by combining the technical means disclosed in each embodiment.

Claims (5)

A spacer, which is arranged in a hard disk, and the spacer is formed of a plate of ferrite-based stainless steel with a C content of 0.02 mass % or less; and the magnetic field when an external magnetic field 10Oe is applied to the spacer The flux density B10 is 0.6T or more, the parallelism is 5 μm or less, and the flatness is 1 μm or less. A gasket is arranged in a hard disk, and the gasket is formed of a plate made of fat iron series stainless steel; and the magnetic flux density B10 when an external magnetic field 10Oe is applied to the gasket is more than 0.6T, and the parallelism is 5 μm or less, the flatness is 1 μm or less, and the plate system of the iron-based stainless steel of the fertilizer grain is composed of: the content of C is 0.08 mass % or less; the content of Si is 0.80 mass % or less; the content of Mn is 0.60 mass % or less; P The content of S is 0.04 mass % or less; the S content is 0.03 mass % or less; the Ni content is 0.50 mass % or less; the Cr content is 11 mass % or more and 19 mass % or less; the N content is 0.02 mass % or less; The content is 0.05 mass % or less; the Ti content is 0.05 mass % or more and 0.50 mass % or less, the remainder is composed of Fe and unavoidable impurities, and the purity is 0.04 % or less. The gasket according to claim 2, wherein the content of C in the plate of the ferrite-based stainless steel is 0.02 mass % or less. The gasket according to claim 2 or 3, wherein the content of TiN-based inclusions in the ferrite-based stainless steel sheet is 0.004 mass % or more and 0.02 mass % or less. A hard disk is characterized by having the gasket described in any one of claim 1 to 4.

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