WO2019131084A1

WO2019131084A1 - Spacer, hard disk drive, and production method for spacer

Info

Publication number: WO2019131084A1
Application number: PCT/JP2018/045292
Authority: WO
Inventors: 西田　幸寛; 明訓河野; 耕一坪井; 太一朗溝口; 鈴木　聡
Original assignee: 日新製鋼株式会社
Priority date: 2017-12-26
Filing date: 2018-12-10
Publication date: 2019-07-04
Also published as: CN111511937B; JP2019112706A; CN111511937A; JP6753613B2; PH12020550939A1; TWI758572B; TW201930613A

Abstract

Provided is a spacer having excellent magnetic characteristics. This spacer (12) is produced by forming a sheet of a ferrite stainless steel into a ring shape, and thereafter, applying heat and pressure to the ring-shaped sheet at a temperature of not lower than 900°C but lower than the austenite transformation start temperature Ac1.

Description

Spacer, hard disk drive and method of manufacturing spacer

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

2. Description of the Related Art Conventionally, miniaturization and capacity increase of magnetic disk drives (for example, hard disk drives) have been increasingly developed. A magnetic disk drive having a large storage capacity comprises a plurality of magnetic disks, and a ring-shaped spacer is inserted between the magnetic disks, and the spacer and the magnetic disk rotate together.

Here, the conventional spacer is often manufactured by cutting free-cutting stainless steel excellent in machinability, but free-cutting stainless steel contains S and Pb, so the steel price is high, and the cost is high. It was connected to up. Therefore, research on technology for manufacturing a spacer by punching a relatively inexpensive ferritic stainless steel sheet having a smaller content of S and Pb than free-cutting stainless steel is being advanced.

For example, in Patent Document 1, a metal plate having a predetermined thickness is punched out to form a substantially ring-shaped element ring, and through a predetermined process, a proximal end of an annular tongue formed in the element ring is sheared using a shearing tool. A method of shearing to produce a spacer ring is disclosed. For example, in Patent Document 2, rolling of a ferritic stainless steel having a variation of surface hardness within 4% up and down centering on an average value, a grain size number of 5.0 to 9.0, and a residual compressive stress of 80 MPa or less A spacer manufactured using a plate material is disclosed. The spacer is formed by processing the rolled plate material into a ring shape by punching.

Japanese Patent Publication No. 2001-167548 (published on June 22, 2001) Japanese Patent Publication "Japanese Unexamined Patent Publication No. 2013-222487 (October 28, 2013)"

However, the spacer ring manufactured by the method disclosed in Patent Document 1 has a residual stress in its inside, so that the shape is not stable when it is incorporated into the final stage of the manufacturing process or when it is incorporated into the magnetic disk. It was a cause of distortion. In that respect, although the spacer disclosed in Patent Document 2 solves the problem of the residual stress to some extent, since the spacer is formed by punching, the magnetic characteristics are impaired. Since the spacer ring is also subjected to punching and pressing, the magnetic properties are impaired as in the case of the spacer. However, neither Patent Document 1 nor 2 describes or suggests a technique for improving the rotational performance of the motor provided in the hard disk drive by performing processing such that the magnetic properties of the spacer ring and the spacer are not impaired. .

SUMMARY OF THE INVENTION One aspect of the present invention is made in view of the above problems, and an object thereof is to provide a spacer having excellent magnetic characteristics that can realize a hard disk drive with high efficiency and small energy load.

In order to solve the above problems, a spacer according to one aspect of the present invention is a spacer provided in a hard disk drive, and the above-mentioned plate formed into a ring shape after forming a plate material of ferritic stainless steel into a ring shape. The plate material is manufactured by heating and pressing at a temperature of 900 ° C. or more and a temperature lower than the austenite transformation start temperature Ac1 (hereinafter, simply described as “Ac1”).

Further, in order to solve the above-described problems, a method of manufacturing a spacer according to one aspect of the present invention is a method of manufacturing a spacer provided in a hard disk drive, and a method of forming a plate material of ferritic stainless steel into a ring shape And a second step of heating and pressing the plate material formed into a ring shape in the first step at a temperature of 900 ° C. or more and less than Ac 1.

According to one aspect of the present invention, it is possible to provide a spacer with excellent magnetic characteristics that can realize a hard disk drive with high efficiency and small energy load.

FIG. 1 is a cross-sectional view showing a schematic configuration of a hard disk drive according to an embodiment of the present invention. FIG. 6 is a cross-sectional view showing a schematic configuration of a spindle motor provided in the hard disk drive, and a diagram showing a change in magnetic flux density around a spacer. It is a graph which shows the relationship between distortion amount and magnetic flux density about the said ferritic stainless steel.

Hereinafter, embodiments of the present invention will be described. The following description is for the purpose of better understanding the spirit of the invention, and does not limit the present invention unless otherwise specified. Further, in the present specification, “A to B” indicates that A or more and B or less.

The ferritic stainless steel used for manufacturing the spacer according to one aspect of the present invention is for manufacturing a molded product which is relatively small (for example, 50 mm or less in diameter or 20 mm or less in height) and for which high dimensional accuracy is required. Stainless steel suitable for

Further, in the present specification, the austenite transformation start temperature Ac1 (hereinafter, also simply described as “Ac1”) refers to a temperature at which austenite starts to form in the structure of the ring-shaped steel material by heating, and ferritic stainless steel It changes according to the ratio of the ingredient of It was laboratory-confirmed that there is a relationship of Formula 1 below between Ac1 and the contained component of the ferritic stainless steel used for the spacer according to one aspect of the present invention. Therefore, in the present invention, the value AC [° C.] obtained by the equation 1 is used as an index of the heating temperature upper limit, that is, Ac1. In the present embodiment, a ferritic stainless steel is used in a proportion of the contained components such that AC is about 1150 ° C. or less.

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

<Structure of Hard Disk Drive>
First, the structure of a hard disk drive 1 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a schematic configuration of the hard disk drive 1. As shown in FIG. 1, the hard disk drive 1 includes three platters 11 in a sealed case-like shroud 2 for sealing the inside of the apparatus. The platter 11 is rotated by a spindle motor 20, and a magnetic head 30 slightly floating from the surface of the platter 11 performs writing and reading of the platter 11.

Spacers 12 (details will be described later) are provided between two adjacent platters 11, respectively. The spacer 12 is in the form of a ring and is disposed around the rotation hub 21 of the spindle motor 20. A disc-like clamper 22 is fastened to the upper end portion of the rotating hub 21 with a screw 23. The elastic deformation of the clamper 22 presses the inner peripheral portion of the platter 11 to hold the plurality of platters 11 and the plurality of spacers 12 between the large-diameter portion at the bottom of the rotating hub 21 and the clamper 22. The clamper 22 may be fixed by a member other than the screw 23.

Hard disk drives typically have a 2.5 inch standard and a 3.5 inch standard. In a 3.5 inch standard hard disk drive, in order to use a combination of a glass platter and a stainless steel spacer, the dimensional accuracy of the stainless steel spacer is more required.

<Relationship between spacer magnetic characteristics and spindle motor performance>
Next, with reference to FIG. 2, the relationship between the magnetic characteristics of the spacer 12 and the performance of the spindle motor 20 will be described. FIG. 2 is a cross-sectional view showing a schematic configuration of the spindle motor 20 and a diagram showing a change in magnetic flux density around the spacer 12.

As shown in FIG. 2, the spindle motor 20 is fixed to each of six stator iron cores 20b projecting from the rotating shaft 20a toward the rotating hub 21 and extending along the side of the rotating shaft 20a. The child coil 20c is wound.

First, current is supplied to the stator coil 20c to magnetize the stator core 20b, thereby generating repulsive force or attractive force between the magnetized stator core 10b and the magnet 21a. The magnet 21a is arrange | positioned in the area | region by the side of the rotating shaft 20a in the rotating hub 21, and is facing the stator core 20b. Next, the rotating hub 21, the clamper 22 and the platter 11 are rotated using the generated repulsive force or the like.

The rotary hub 21 serves as a yoke (specifically, a back yoke) that improves the performance of the spindle motor 20 by constructing a magnetic circuit in which the so-called "leakage flux" is reduced as much as possible. "Leakage flux" refers to a line of magnetic force that passes through parts other than the original magnetic circuit and is not useful for generating repulsion or the like.

Here, the role of the rotating hub 21 as a yoke is further strengthened by using a spacer having excellent magnetic properties. That is, while the magnetic properties of the spacer are determined by the magnitude of the magnetic flux density (or permeability) of the spacer, the "leakage flux" becomes smaller as the magnetic flux density (or permeability) of the spacer becomes larger (see FIG. From the state of the upper right to the state of the lower right), the performance of the spindle motor 20 is improved.

In particular, 3.5 inch standard hard disk drives used for near-line applications and high-capacity servers have a large number of stacked platters per unit and a large rotational load on the spindle motor. Therefore, a spindle motor with high efficiency has been desired conventionally, and in order to realize this spindle motor with high efficiency, improvement of the magnetic characteristics of the spacer has been a major issue.

In that respect, since the spindle motor 20 uses the spacer 12 having excellent magnetic characteristics, the role of the rotating hub 21 as a yoke is further strengthened, and its performance is improved as compared with the conventional spindle motor. ing.

<Composition of Components of Ferritic Stainless Steel>
The composition of the components of the ferritic stainless steel used to manufacture the spacer 12 is as follows. In addition, remainders other than each component shown below are iron (Fe) and a small amount of unavoidable impurities (unavoidable impurities).

(Chrome: Cr)
Cr is an element essential to ferritic stainless steel, and in order to ensure corrosion resistance, the Cr concentration is preferably 11% by mass or more. However, when a large amount of Cr is contained, the stainless steel is excessively hardened. Therefore, the Cr concentration is preferably 19% by mass or less, and more preferably 13% by mass or less. The adjustment method of content of Cr is not specifically limited, For example, content of Cr can be adjusted by controlling the reductive reaction of Cr oxide.

(Manganese: Mn)
Mn is an element that adversely affects the outgas resistance and the magnetic properties by forming sulfides. Therefore, in the ferritic stainless steel used for manufacturing the spacer 12, the content of Mn is preferably as small as possible, and is preferably 0.60% by mass or less.

(Titanium: Ti)
Ti, like Nb, is an element capable of turning a ferritic stainless steel into a ferritic single phase at 900 to 1000 ° C. by reacting with C or N. On the other hand, the larger the crystal grain size, the better the magnetic properties, but since Ti, unlike Nb, hardly interferes with the grain growth of ferritic stainless steel at high temperature, from the viewpoint of magnetic properties Ti It is more preferable to add. On the other hand, excessive addition of Ti adversely affects the surface properties of stainless steel and impairs manufacturability, so it is preferable to contain 0.05 to 0.50 mass% or less of Ti.

(Carbon: C)
Since C is a harmful element that degrades magnetic properties by forming carbides, the content of C is set to 0.08 mass% or less, and preferably 0.02 mass% or less.

(Silicon: Si)
Si is an element effective as a deoxidizer at the time of steel making. 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.

(Rin: P)
P reduces the hot workability according to its content. Therefore, the content of P is preferably 0.04% by mass or less.

(Sulfur: S)
When the content of S in the ferritic stainless steel is high, the inclusions of the A-based material containing MnS as a main component present in the steel increase and the magnetic properties are degraded. Therefore, the content of S is preferably 0.03% by mass or less.

As a method of adjusting the content of S, desulfurization takes place by deoxidization together with deoxidation at the time of reduction and deoxidation of Cr oxides in the reduction and finishing smelting phase, so this desulfurization reaction is promoted By doing this, the content of S can be reduced. A known method may be used as a method of adjusting the content of S, and the adjustment method is not particularly limited.

(Nickel: Ni)
Ni increases the proportion of the austenite phase in the high temperature range, and thus is effective in improving the workability during hot rolling. However, if it is contained excessively, the temperature of the α-γ transformation point is lowered, and a sufficient recrystallization temperature can not be secured. In addition, Ni is also an expensive element. Therefore, the content of Ni is preferably 0.50% by mass or less.

(Nitrogen: N)
Excess addition of N forms nitrides with other elements to cause deterioration of the magnetic properties. Therefore, the content of N is preferably 0.02% by mass or less.

(Aluminum: Al)
Al is an element that improves the cleanliness of the steel, but on the other hand, if the content is large, it forms a compound with C and N to lower the magnetic properties, so the content is preferably 0.05% by mass or less.

The composition of the above-mentioned components is merely an example, and even when the content (mass%) of each component is other than the above-described example, the magnetic flux density B10 when the external magnetic field 10Oe is applied to the spacer 12 is It is possible to realize the spacer 12 excellent in the magnetic characteristics of 0.6 T or more, and the spacer 12 having a parallelism of 5 μm or less and a flatness of 1 μm or less. In addition, even if the spacer 12 contains the components other than the above-described components, the spacer 12 having a magnetic flux density B10 of 0.6 T or more, a parallelism of 5 μm or less, and a flatness of 1 μm or less can be realized.

<Method of manufacturing spacer>
An example of the manufacturing method of the spacer 12 using the ferritic stainless steel which satisfies the said conditions about the composition of a component is demonstrated below. Specifically, the spacer 12 is manufactured by performing the following steps (1) to (4).

(1) First, precision punching is performed on a annealed rolled plate material (plate material: not shown) of a ferritic stainless steel using a die. That is, an outer diameter punching process is performed on the rolled plate material, and then an inner diameter punching process is performed to obtain a steel material (plate material: not shown) formed into a ring shape (first step).

This ring-shaped steel material has substantially no occurrence of sagging on the punched end face, and the punched end face properties are significantly improved. However, in the ring-shaped steel material after the completion of the first step, the magnetic properties are reduced by about 10% to about 20% as compared with the rolled plate before the first step. In this step, when pressing is further performed, the magnetic properties are reduced by about 50% or more.

(2) Next, with respect to the ring-shaped steel material obtained by the said punching, it is pressurized, heating at the temperature of 900 degreeC or more and less than Ac1 (2nd process).

By performing this second step, the amount of precipitates and inclusions generated is significantly reduced as compared with the case of performing other heat treatment or pressure treatment, and the size of the formed precipitates and the like Becomes larger. Moreover, about the structure | tissue of ring-shaped steel materials, a crystal grain becomes large by pressurizing, heating at 900 degreeC or more. In addition, since the heating temperature is less than Ac1, the ring-shaped steel material becomes an α single phase. Furthermore, the residual stress of the ring-shaped steel material is effectively removed. The occurrence of these events significantly improves the magnetic properties of the ring-shaped steel material after the second process.

Specifically, in the ring-shaped steel material after completion of the second step, the magnetic flux density B10 in the external magnetic field H = 10 Oe (796 A / m) is at least 0.6 T or more. In addition, the ring-shaped steel material preferably has a magnetic flux density B10 of 0.8 T or more, and this numerical value can be obtained by appropriately adjusting the heating temperature and pressure.

As a 2nd process, the process which carries out the pressure annealing of ring-shaped steel materials at the temperature of 900 degreeC or more and less than Ac1, and the process which carries out the hot closing forging press at the temperature of 900 degreeC or more and less than Ac1 can be illustrated.

The pressure annealing is a type of annealing, and refers to a process of pressing a ring-shaped steel material while heating it to a predetermined temperature, holding the steel material at the predetermined temperature for a certain period of time, and gradually cooling it. In addition, a hot closed forging press is a method in which a punch is made to double-dynamically penetrate into a mold in a state in which a ring-shaped plate material heated to a predetermined temperature is confined in a mold and closed. It refers to the process of filling the steel material in the mold. Both treatments have the effect of effectively removing the residual stress of the ring-shaped steel material, which contributes to the improvement of the magnetic properties of the spacer 12.

In addition, as a pressure annealing, the case where the steel materials of a ring shape are provided with the press temper process employ | adopted by shape correction of a board | plate material or various components other than the loading pressure annealing mentioned later can be illustrated. The press tempering process refers to a process of pressing (tempering) when tempering.

Moreover, as a hot closing forging press, the hot closed forging press using a hydraulic multi-axial press etc. can be illustrated. In the case of closed forging, unlike a normal forging, a ring-shaped plate material confined in a mold is formed without burrs.

Furthermore, with respect to the pressing force at the time of stacking pressure annealing, it is preferable that the pressure is 0.001 MPa to 200 MPa from the viewpoint of dimensional accuracy. When the pressure is smaller than 0.001 MPa, the control of the flatness and the parallelism becomes difficult due to the insufficient pressure. On the other hand, when the pressure exceeds 200 MPa, the pressing force is too large, which makes it difficult to control the plate thickness.

(3) Next, lapping is performed on the ring-shaped steel material after completion of the second step using, for example, a lapping agent (diamond slurry) as abrasive grains, and the surface of the ring-shaped steel material is polished. Then, the above-described steel material after lapping is put in a barrel container together with a particulate abrasive and a medium (compound), barrel-polished and deburred (third step).

Here, in the ring-shaped steel material, since the occurrence of sagging on the punched end surface is suppressed, the polishing time in lapping polishing and barrel polishing can be shortened, and the cutting allowance can be reduced. Further, the polishing load to be applied to the steel material can be reduced, and the occurrence of warpage in the final product spacer 12 can be suppressed. As mentioned above, while being able to improve production efficiency, material yield can be improved.

(4) Thereafter, the steel material after barrel polishing is cleaned (fourth step). Here, it is necessary to reduce inclusions as much as possible from the viewpoint of the magnetic properties, and the ferritic stainless steel used for manufacturing the spacer 12 has the cleanliness calculated by the method of calculating the cleanliness specified in JIS G0555. It is preferable that it is 0.04% or less. However, when containing TiN-based inclusions of 0.004% by mass to 0.02% by mass, it is possible to further suppress the occurrence of sagging on the punched end face while minimizing the deterioration of the magnetic characteristics. As well as being able to do this, parts cleanability does not deteriorate.

By performing the fourth step, the manufacturing of the spacer 12 is completed. Note that at least the first and second steps may be performed to manufacture the spacer 12 having excellent magnetic characteristics, and the third and fourth steps are not essential steps for manufacturing the spacer 12.

<Example>
In this example, spacers were manufactured using ferritic stainless steels (the first invention steel, the second invention steel, and the comparison steel) having the components and compositions shown in Table 1 below. Note that Ac1 of the first invention steel was 984 ° C., and Ac1 of the second invention steel was 1089 ° C. And the magnetism of each spacer was measured by a predetermined method, and those magnetic characteristics were compared. In addition, the relationship between strain and magnetic flux density was also investigated.

(Manufacture of spacer)
For the first and second invention steels, cold-rolled annealed pickled sheet (rolled sheet material) with a thickness of 1.8 mm is refined to a thickness of 1.80 t / 1. Step) The obtained ring-shaped steel material was stacked and pressure annealed in a vacuum (0.005 Pa) (second step). Thereafter, the third and fourth steps described above were performed to manufacture the spacer 12.

Here, the first invention steel was stacked and pressure annealed at a heating temperature of 950 ° C. for 2 hours. That is, the first invention steel was pressurized while being heated at a temperature of 900 ° C. or more and less than the austenite transformation start temperature Ac1 (984 ° C.). The second invention steel was stacked and pressure annealed at a heating temperature of 1050 ° C. for 2 hours. That is, the second invention steel was pressurized while heating at a temperature of 900 ° C. or more and less than the austenite transformation start temperature Ac1 (1089 ° C.). In stacking pressure annealing, a plurality of ring-shaped steel materials are stacked in a state in which a partition plate subjected to preoxidation with the same material as the steel material is inserted between two ring-shaped steel materials facing each other. Then, a weight is loaded on the top surface of the laminate so that the surface pressure is 0.01 MPa, and the processing is performed to perform annealing in vacuum.

On the other hand, for the comparative steel, a round bar of the comparative steel was sliced, and the obtained thin plate-like steel material was further cut to produce a ring-shaped spacer. This manufacturing method is identical to the conventional spacer manufacturing method compatible with 2.5 inch standard hard disk drives.

Each spacer 12 manufactured using the first and second invention steels and a spacer manufactured using a comparative steel (hereinafter referred to as “first comparative spacer”) have a thickness of 1.60 mm, It has a ring shape with an inner diameter of 25.0 mm and an outer diameter of 32 mm. This is shaped and sized to fit a 3.5 inch standard hard disk drive.

(Method of magnetic measurement)
The magnetism of each spacer 12 and the first comparative spacer manufactured using the first and second invention steels was measured by the same method. Specifically, using a 0.32 mm diameter enamel coated copper wire, the BH tracer is used as a primary coil of 100 turns and a secondary coil of 90 turns for all the spacers 12 and the first comparison spacer described above. The magnetic flux density B10 at an external magnetic field H = 10 Oe was measured using

At the same time, the flatness and the parallelism were also measured for all the spacers 12 and the first comparison spacer described above. The flatness was 1.50 μm or less and the parallelism was 5.00 μm or less (○ in Table 2), and those exceeding these values were rejected (× in Table 2). The measurement results are as shown in Table 2 below.

(Result of magnetic measurement)
As shown in Table 2, the spacer 12 manufactured using the first invention steel had a magnetic flux density B10 of 1.0 T. The spacer 12 manufactured using the second invention steel had a magnetic flux density B10 of 0.9 T. Both of the spacers 12 have a magnetic flux density B10 of 0.8 T or more, and exhibit excellent magnetic characteristics.

On the other hand, the magnetic flux density B10 of the first comparison spacer is 0.5 T, which is less than 0.6 T, which is a reference value of superiority or inferiority of the magnetic characteristics of the spacer. In addition, a second comparative spacer manufactured by subjecting a cold-rolled, annealed, pickled plate of a first invention steel of 1.8 mm thickness to only a heat treatment and a fine blanking press (“first invention spacer in Table 2 The magnetic flux density B10 is 0.4 T, which is less than 0.6 T.

From these facts, it was revealed that the spacer manufactured by the manufacturing method according to one aspect of the present invention has significantly improved magnetic properties as compared to the spacer manufactured by the other manufacturing method. .

With regard to the flatness and the parallelism, a spacer manufactured using the first invention steel or the second invention steel became a pass (o) regardless of the manufacturing method. Generally, it is preferable if the flatness is 1 μm or less and the parallelism is 5 μm or less. Therefore, in order to improve the flatness and the parallelism of the spacer, the conditions described in the present embodiment for the composition of the components are satisfied. It has become clear that it is preferable to use a ferritic stainless steel.

(Relation between strain amount and magnetic flux density)
A predetermined pressure was applied to the spacer 12 after completion of the second step using the first invention steel, and the strain amount generated by the pressure and the magnetic flux density B10 at the external magnetic field H = 10 Oe at the time of pressurization were measured respectively . When a graph in which the vertical axis represents the magnetic flux density B10 and the horizontal axis represents the strain amount was created using the measurement results, a graph as shown in FIG. 3 was obtained. In the graph of FIG. 3, the graph of the first comparison spacer is indicated by a broken line for comparison.

As shown in FIG. 3, for the spacer 12 manufactured to the second step using the first invention steel, the magnetic flux density B10 is 1.2 T in the state where no strain occurs, and the first comparative example is used. It was found that the magnetic flux density B10 was twice or more that of the spacer. Also, while the amount of strain increased from 0% to about 0.5%, the magnetic flux density B10 rapidly decreased, and the decrease in magnetic flux density B10 became moderate after the amount of strain exceeded about 0.5%. .

From this, it became clear that it is effective to remove the strain applied at the time of molding in order to manufacture a spacer having excellent magnetic properties, ie, a spacer having a high magnetic flux density. Also from this point, it can be said that the method of manufacturing a spacer according to an aspect of the present invention, which can effectively remove the residual stress of the ring-shaped steel material, is useful.

<Summary>
In order to solve the above problems, a spacer according to one aspect of the present invention is a spacer provided in a hard disk drive, and the above-mentioned plate formed into a ring shape after forming a plate material of ferritic stainless steel into a ring shape. The sheet material is manufactured by heating and pressing at a temperature of 900 ° C. or more and a temperature lower than the austenite transformation start temperature Ac1 (hereinafter, also simply described as “Ac1”).

According to the above configuration, the plate material of the ferritic stainless steel formed into a ring shape is pressurized while being heated at a temperature of 900 ° C. or more and less than Ac1. Therefore, the above-mentioned plate material whose magnetic characteristics have once deteriorated due to being formed into a ring shape has its magnetic characteristics improved by the above heating and pressing. Therefore, for example, a spacer with improved magnetic characteristics can be realized as compared to a spacer manufactured without being subjected to any treatment after being formed into a ring shape.

Further, in order to solve the above problems, the spacer according to one aspect of the present invention has a magnetic flux density B10 of 0.6 T or more and a parallelism of 5 μm or less when the external magnetic field 10 Oe is applied to the spacer. It is preferable that it is 1 micrometer or less.

Moreover, in order to solve said subject, content of C is 0.08 mass% or less, content of Si is 0.80 mass% or less, and content of Mn of the spacer which concerns on one aspect of this invention 0.60 mass% or less, P content is 0.04 mass% or less, S content is 0.03 mass% or less, Ni content is 0.50 mass% or less, Cr content is 11 mass % To 19% by mass, the content of N is 0.02% by mass or less, the content of Al is 0.05% by mass or less, and the content of Ti is 0.05% by mass to 0.50% by mass or less Preferably, the balance consists of Fe and unavoidable impurities, and the cleanliness is 0.04% or less.

Moreover, in order to solve said subject, it is preferable that content of C which is the spacer which concerns on one aspect of this invention is 0.02 mass% or less.

Moreover, in order to solve said subject, it is preferable that content of a TiN type | system | group inclusion is 0.004 mass% or more and 0.02 mass% or less of the spacer which concerns on one aspect of this invention.

Moreover, in order to solve said subject, it is preferable that the spacer which concerns on 1 aspect of this invention pressure-anneals the said board | plate material of the said ring shape at the temperature of 900 degreeC or more and less than Ac1.

According to the above configuration, the plate material of the ferritic stainless steel formed into a ring shape is pressure annealed at a temperature of 900 ° C. or more and less than Ac1. Accordingly, the above-mentioned pressure annealing improves the magnetic properties of the above-mentioned plate whose magnetic properties have once been lowered by being formed into a ring shape. Therefore, a spacer with improved magnetic properties can be realized.

Moreover, in order to solve said subject, it is preferable that the spacer which concerns on 1 aspect of this invention is hot closing forging press the said board | plate material of the said ring shape at the temperature of 900 degreeC or more and less than Ac1.

According to the above configuration, the plate material of the ferritic stainless steel formed into a ring shape is subjected to the hot close forging press at a temperature of 900 ° C. or more and less than Ac1. Therefore, the above-mentioned plate material whose magnetic characteristics have once deteriorated due to being formed into a ring shape is improved in its magnetic characteristics by the above-mentioned hot close forging press. Therefore, a spacer with improved magnetic properties can be realized.

Moreover, in order to solve said subject, it is preferable that the hard disk drive which concerns on 1 aspect of this invention is equipped with the said spacer. According to the above configuration, by providing the spacer having excellent magnetic characteristics, it is possible to reduce the rotational load applied to the spindle motor in the hard disk drive.

According to the above configuration, it is possible to manufacture a spacer having improved magnetic characteristics as compared to, for example, a spacer which has not been subjected to any treatment after being formed into a ring shape.

<Additional items>
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

1 Hard Disk Drive 12 Spacer

Claims

A spacer provided in a hard disk drive,
A spacer manufactured by forming a plate material of ferritic stainless steel into a ring shape and then heating and pressing the plate material formed into the ring shape at a temperature of 900 ° C. or more and less than austenite transformation start temperature Ac1.
The spacer according to claim 1, wherein a magnetic flux density B10 when an external magnetic field 10 Oe is applied to the spacer is 0.6 T or more, parallelism 5 μm or less, and flatness 1 μm or less.
The content of C is 0.08% by mass or less, the content of Si is 0.80% by mass or less, the content of Mn is 0.60% by mass or less, the content of P is 0.04% by mass or less, S The content is 0.03% by mass or less, the content of Ni is 0.50% by mass or less, the content of Cr is 11% by mass to 19% by mass or less, the content of N is 0.02% by mass or less, Al The content is 0.05% by mass or less, the content of Ti is 0.05% by mass or more and 0.50% by mass or less, and the balance is composed of Fe and unavoidable impurities,
The spacer according to claim 1 or 2, wherein the cleanliness is 0.04% or less.
The spacer according to claim 3, wherein the content of C is 0.02 mass% or less.
The spacer according to claim 3 or 4, wherein the content of the TiN-based inclusions is 0.004% by mass or more and 0.02% by mass or less.
The spacer according to any one of claims 1 to 5, wherein the ring-shaped plate material is pressure annealed at a temperature of 900 ° C or more and less than an austenite transformation start temperature Ac1.
The spacer according to any one of claims 1 to 5, wherein the ring-shaped plate material is subjected to hot closing forging press at a temperature of 900 ° C or more and less than an austenite transformation start temperature Ac1.
A hard disk drive comprising the spacer according to any one of claims 1 to 7.
A method of manufacturing a spacer provided in a hard disk drive, comprising:
A first step of forming a plate material of ferritic stainless steel into a ring shape;
And a second step of heating and pressing the plate material formed into a ring shape in the first step at a temperature of 900 ° C. or more and less than an austenite transformation start temperature Ac1.