JP2012123884A - Method of manufacturing blank material for magnetic disk, and blank material for magnetic disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a blank material for magnetic disk which is made of an aluminum alloy and has superior flatness and shock resistance, and the blank material for magnetic disk manufactured by the method.SOLUTION: The method of manufacturing the blank material is characterized in, while placing a burden load of 1.5-4 MPa and applying pressure, carrying out annealing at a temperature (annealing temperature) of 210-280°C in a pressure annealing process (step 102).

Description

  The present invention relates to a method for manufacturing a magnetic disk blank made of an aluminum alloy suitable for a magnetic disk substrate (blank material), and a magnetic disk blank manufactured by the manufacturing method.

  Magnetic disks are used as storage media for storage devices such as hard disks. As materials for magnetic disks, aluminum alloys and glass are known. In particular, as a material for a hard disk used for a mobile personal computer or the like, a magnetic disk blank material (glass blank material) made of glass that can be designed thin and small because of its high rigidity is used.

  However, in recent years, it is expected that magnetic disk blanks made of aluminum alloys (hereinafter referred to as aluminum blanks) will be used as hard disk materials for mobile personal computers, etc. due to insufficient supply of glass blanks and cost reduction. Has been.

An aluminum blank is generally formed by performing the following steps on an aluminum alloy sheet produced by processing in the order of casting, solution treatment, hot rolling, and cold rolling.
(A) Punching process: A process of punching an aluminum alloy plate into a donut shape by pressing.
(B) Pressure annealing process: After the punching process (a), while pressing a plurality of punched donut-shaped aluminum alloy plates in order to remove residual strain generated by the punching process and improve flatness A step of performing annealing (hereinafter referred to as pressure annealing).
(C) Cutting process: A process of cutting the end surfaces of the outer peripheral edge of the blank and the inner peripheral edge of the blank until the target outer diameter and inner diameter are reached after the pressure annealing step (b).
(D) Grinding process: A process of grinding to a target plate thickness with a grindstone of a double-side grinder after the cutting process (c).
(E) Plating treatment step: A step of performing a pre-plating treatment after the grinding step (d) to form a Ni-P plating layer.

  As described above, the aluminum blank material has only a Ni-P plating layer formed on the aluminum alloy plate, and has a lower rigidity than the glass blank material, and is easily distorted by processing. A bad aluminum blank could be made. In particular, when the aluminum blank material needs to be designed to be thinner and smaller as in a hard disk such as a mobile personal computer, the problem of flatness has been noticeable.

  In order to solve such a problem of deterioration of flatness, a method of correcting the distortion of the aluminum blank material by annealing treatment (an annealing method in which the temperature is raised, and then the temperature is lowered after being heated) to obtain excellent flatness Is generally known.

For example, in patent document 1, in the pressure annealing process, it is heated to a temperature of 390 to 600 ° C., and an excellent flatness is obtained by applying a load of 11 × 10 ⁻⁴ to 75 × 10 ⁻⁴ N / mm ^2. A method for obtaining sex has been proposed. Further, in Patent Document 2, in the pressure annealing process, the temperature rising rate is 0.5 to 150 ° C./second, the ultimate temperature is 380 to 540 ° C., the holding time is 0 to 900 seconds, and the load is 10 × 10 ^−4. A method of obtaining excellent flatness by rapidly heating while applying a load under a condition of ˜75 × 10 ⁻⁴ N / (mm ² sheets), unloading the load after holding for a predetermined time, and lowering the temperature. Has been proposed. In Patent Document 3, an aluminum blank is sandwiched between spacers, further sandwiched between upper and lower surface plates, held at 350 ° C. for 5 hours while being loaded with a load of 300 to 400 kg, and then subjected to pressure annealing for cooling to room temperature. There has been proposed a manufacturing method for manufacturing an aluminum blank having excellent flatness by interposing a disc spring between upper and lower surface plates and spacers.

JP-A-5-117825 JP-A-6-145828 Japanese Patent Laid-Open No. 6-235052

  However, the aluminum blank produced by the conventional method as described above is annealed at a high temperature, so that the proof stress of the aluminum blank declines, and it can be used as a hard disk such as a mobile personal computer. There was a problem that sufficient impact resistance could not be obtained.

  Accordingly, the present invention has been made to solve the above-described problems, and is manufactured by a method for manufacturing a blank material for a magnetic disk made of an aluminum alloy and having excellent flatness and impact resistance, and the manufacturing method thereof. Another object of the present invention is to provide a magnetic disk blank.

The following invention is provided to solve the above-mentioned conventional problems.
The method for manufacturing a magnetic disk blank according to the first aspect of the present invention comprises a magnetic disk blank made of an aluminum alloy containing 3.0 to 6.0% by mass of Mg and the balance being Al and impurities. A pressure annealing step in which the magnetic disk blank material is annealed at an annealing temperature of 210 ° C. or higher and 280 ° C. or lower while being pressed with a load of 1.5 MPa or higher and 4 MPa or lower applied to the blank material for a magnetic disk. It is characterized by having.

  The method for manufacturing a magnetic disk blank according to the second aspect of the present invention is the method for manufacturing a magnetic disk blank according to the first aspect of the present invention, wherein the pressure annealing step includes the magnetic disk blank. A plurality of sheets are laminated via a flat intermediate spacer, and all the magnetic disk blank materials and all the intermediate spacers are sandwiched between flat lowermost spacers and uppermost spacers. Unsprung plates and springs arranged on the upper surface plate in a state where the spacers, all the magnetic disk blanks, all the intermediate spacers and the lowermost spacer are sandwiched between the upper surface plate and the lower surface plate Annealing is performed while applying a load to the magnetic disk blank through a heat-resistant coil spring sandwiched between the upper plate and pressurizing.

  The magnetic disk blank according to the first aspect of the present invention is a magnetic disk blank made of an aluminum alloy containing 3.0 to 6.0% by mass of Mg and the balance being Al and impurities, It is manufactured by the method for manufacturing a magnetic disk blank according to the first or second aspect of the present invention.

The magnetic disk blank according to the second aspect of the present invention is the magnetic disk blank according to the first aspect of the present invention, wherein the flatness is 5 μm or less and a JIS Z2201 test piece is used. The 0.2% yield strength measured by the Z2241 tensile test is 200 N / mm ² or more.

  According to the present invention, it is possible to manufacture a magnetic disk blank material (aluminum blank material) made of an aluminum alloy having excellent flatness and excellent impact resistance. Moreover, the processing cost of a hard disk can be reduced by using the aluminum blank manufactured by the method of this invention as hard disks, such as a mobile personal computer, instead of a glass blank.

It is a flowchart figure for demonstrating an example of the manufacturing method of the blank material for magnetic discs concerning embodiment of this invention. It is a figure for demonstrating an example of the pressure annealing process in the manufacturing method of the blank material for magnetic discs concerning embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The description in the present embodiment shows an example of a method for manufacturing a magnetic disk blank according to the present invention, and the present invention is not limited to this. The detailed configuration and the like of the manufacturing method of the magnetic disk blank material in the present embodiment can be changed as appropriate without departing from the spirit of the present invention.

FIG. 1 is a flowchart for explaining an example of a method for manufacturing a magnetic disk blank according to an embodiment of the present invention.
As shown in FIG. 1, the method for manufacturing a magnetic disk blank according to an embodiment of the present invention includes an aluminum alloy plate manufactured by first processing in the order of casting, solution treatment, hot rolling, and cold rolling. Is punched into a donut shape by pressing (step 101: S101). Here, content of Mg in an aluminum alloy plate is 3.0-6.0 mass% (3.0 mass% or more and 6.0 mass% or less), More preferably, it is 3.5-5. 0% by mass. In the aluminum alloy, Mg is the most effective element for improving the mechanical strength suitable for the material of the magnetic disk blank, and if it is less than 3.0% by mass, sufficient mechanical strength cannot be obtained, Moreover, it is because it will be easy to produce a crack at the time of hot rolling if it exceeds 6.0 mass%.

  Next, a load of 1.5 to 4 MPa (1.5 MPa or more and 4 MPa or less) is applied to an aluminum alloy plate (hereinafter referred to as an aluminum blank) punched into a plurality of donuts. While pressing, annealing is performed at a temperature (annealing temperature) of 210 to 280 ° C. (210 ° C. or higher and 280 ° C. or lower) (step 102: S102). For example, the annealing is performed by raising the temperature to an annealing temperature of 210 to 280 ° C., holding the temperature for about 1 hour, and then air-cooling to room temperature (about 20 ° C.). Considering productivity, the holding time of the annealing temperature is not desired to be long, and is preferably within one hour from the flow of the manufacturing process.

  After the pressure annealing step of step 102, the end surfaces of the outer peripheral edge (blank outer peripheral edge) and the inner peripheral edge (blank inner peripheral edge) of the aluminum blank material are cut until the target outer diameter and inner diameter are reached. (Step 103: S103). Next, both sides of the machined aluminum blank material are ground with a grindstone of a double-side grinding machine until the target plate thickness is reached (step 104: S104).

  Finally, a pre-plating treatment is performed on the ground aluminum blank material, and a Ni-P plating layer is formed on the surface of the aluminum blank material (step 105: S105), thereby forming a magnetic disk made of an aluminum alloy. A blank material (aluminum blank material) is formed.

  A feature of the method for manufacturing a magnetic disk blank according to an embodiment of the present invention is that it is 210 to 280 ° C. while applying a load of 1.5 to 4 MPa in the pressure annealing step (step 102). It is annealing at an annealing temperature.

  The reason why the annealing temperature is set to 280 ° C. or less is that the aluminum blank is not made into a complete crystal grain structure when annealed. In an aluminum blank, a structure that is not completely crystal grains (hereinafter referred to as a processed crystal grain structure) hardly undergoes plastic deformation, and has a tensile strength and a 0.2% proof stress (a material elongation reaches 0.2%). Tensile strength) and hardness increase. Therefore, an aluminum blank material excellent in impact resistance can be formed. Therefore, the annealing temperature is set to 280 ° C. or lower which is lower than the recrystallization temperature.

  Also, if the annealing temperature is set to 210 ° C. or more, if it is less than 210 ° C., residual stress due to the rolling process or the punching process in step 101 cannot be removed by annealing, and it can be used as a blank for magnetic disks. This is because the flatness cannot be obtained. Moreover, it is because the laminated | stacked aluminum blank material may break if it is less than 210 degreeC.

  The load load is set to 1.5 to 4 MPa when the load load is applied to correct the flatness of the aluminum blank material. When the load load is less than 1.5 MPa, the load load is too small and the magnetic disk blank. This is because it cannot be corrected so as to have a sufficient flatness that can be used as a material, and if it exceeds 4 MPa, the load is too large and the flatness is deteriorated.

  Next, a specific example of the pressure annealing process in step 102 of FIG. 1 will be described. FIG. 2 is a view for explaining an example of a pressure annealing step in the method for manufacturing a magnetic disk blank according to the embodiment of the present invention.

  As shown in FIG. 2, a plurality of aluminum blanks 3 are stacked via flat intermediate spacers 2c, and all magnetic disk blanks 3 and all intermediate spacers 2c are combined with flat uppermost spacers 2a. The upper surface plate 1a is sandwiched between the lowermost spacer 2b and the upper surface plate 1a above the uppermost spacer 2a, and the lower surface plate 1b is disposed below the lowermost spacer 2b. The uppermost spacer 2a, the lowermost spacer 2b, All the intermediate spacers 2c and all the aluminum blanks 3 are sandwiched from above and below by the upper surface plate 1a and the lower surface plate 1b. Further, an unsprung plate 5b is disposed on the upper surface plate 1a, and the heat-resistant coil spring 4 is sandwiched between the unsprung plate 5b and the unsprung plate 5a so that a load of 1.5 to 4 MPa is applied. The heat-resistant coil spring 4 is compressed into the lower surface plate 1b, and the lowermost spacer 2b, the aluminum blank material 3, the intermediate spacer 2c, the uppermost spacer 2a, the upper surface plate 1a and the unsprung plate 5b are attached. A bolt 6 that penetrates and protrudes onto the sprung plate 5 a is fixed with a nut 7. In the pressure annealing step, the aluminum blank 3 is heated to an annealing temperature of 210 to 280 ° C. in the state described above, held at the annealing temperature for about 1 hour, and then air-cooled to room temperature (about 20 ° C.).

  As the temperature change of the aluminum blank 3 is considered, it is thought that it is necessary to suppress the change of the load load as small as possible, and as shown in FIG. G6341) or a heat-resistant coil spring 4 equivalent to SWOSC-V was loaded. As a feature of the heat-resistant coil spring 4, the change rate of the transverse elastic modulus from a high temperature of 300 ° C. to a normal temperature of 20 ° C. is 15% or less. By applying a load through the heat-resistant coil spring 4, the load can be stably (uniformly) applied to the aluminum blank 3 having a different coefficient of thermal expansion depending on the annealing temperature.

For a magnetic disk manufactured by the method for manufacturing a magnetic disk blank according to the above-described embodiment of the present invention, comprising 3.0 to 6.0% by mass of Mg and the balance being Al and impurities. The blank material has a flatness of 5 μm or less, and a 0.2% proof stress measured by a JIS Z2241 tensile test using a test piece of JIS Z2201 is 200 N / mm ² or more, and is used as a blank material for a magnetic disk. It has sufficient surface strength (impact resistance) and sufficient flatness. In the above, 0.2% proof stress is used as an evaluation of impact resistance. However, it is not limited to 0.2% proof stress, but depends on values such as tensile strength, elongation, surface hardness, etc. corresponding to 0.2% proof stress. It is also possible to define a sufficient impact resistance for use as a magnetic disk blank.

  As described above, an aluminum blank material having excellent flatness and excellent impact resistance can be produced by the method for producing a magnetic disk blank material according to an embodiment of the present invention. Moreover, the processing cost of a hard disk can be reduced by using the aluminum blank manufactured by the method of this invention as hard disks, such as a mobile personal computer, instead of a glass blank.

  EXAMPLES Next, although an Example demonstrates this invention, this invention is not limited to a following example. While using an aluminum blank material punched into a donut shape having an outer diameter of φ66 mm, an inner diameter of φ19 mm, and a plate thickness of 1 mm, the load shown in Table 1 was applied and pressurized by the method shown in FIG. After the temperature is raised to the annealing temperature shown in FIG. 1, the aluminum blank is held at this temperature for 1 hour and then air-cooled to room temperature, and the aluminum blanks according to Examples 1 to 20 and Comparative Examples 1 to 52 of the present invention The material was made.

The total load load (kgf) is a load applied to an aluminum blank material punched into a donut shape having an outer diameter of φ66 mm, an inner diameter of φ19 mm, and a plate thickness of 1 mm, and the load load (MPa) ² ) The load applied per hit is shown. Further, as the heat-resistant coil spring 4 of FIG. 2, when the load load is 0.02 to 1.50 PMa, the heat-resistant coil spring 4 of SUS631J1 is used, and when the load load is 2.00 to 4.00 PMa, SWOSC A heat resistant coil spring 4 equivalent to −V was used. Further, when the load load is 4.5 MPa or more, there is no heat-resistant coil spring 4 that loads the load load. Therefore, the nut 7 is tightened with a torque wrench without using the heat-resistant coil spring 4, and the load load is applied.

About the aluminum blank material concerning Examples 1-20 of this invention shown in Table 1, and the aluminum blank material concerning Comparative Examples 1-52, 0.2% yield strength (N / mm < ² >) and flatness (micrometer) are shown. It was measured. Tables 2 and 3 show the results of the measured 0.2% proof stress (N / mm ² ) and flatness (μm), respectively.

In addition, the matrix shown in Table 2 and Table 3 is a measurement result of the aluminum blank material concerning Examples 1-20 of this invention, and the aluminum blank material concerning Comparative Examples 1-52, and respond | corresponds to the matrix of Table 1. . In Table 2, “0.2” indicates that the 0.2% proof stress is 200 (N / mm ² ) or more, and “x” indicates other values. In Table 3, “o” indicates that the flatness is 5.0 (μm) or less, and “x” indicates other values.

The 0.2% proof stress (N / mm ² ) was measured in a JIS Z2241 tensile test using a tensile tester manufactured by Instron, using a tensile test piece of JIS Z2201 as a test piece. The flatness (μm) was measured with a Zygo non-contact flatness measuring machine using an aluminum blank material punched into a donut shape having an outer diameter of φ66 mm, an inner diameter of φ19 mm, and a plate thickness of 1 mm as a test piece.

As shown in Tables 2 and 3, the aluminum blanks according to Examples 1 to 20 of the present invention have a 200% (N / mm) prescribing 0.2% yield strength sufficient for use as a magnetic disk blank. ² ) In the above range, a result of satisfying a range of 5.0 (μm) or less that defines a flatness sufficient for use as a magnetic disk blank was obtained.

On the other hand, in the aluminum blank materials according to Comparative Examples 1 to 52, when the load is less than 1.5 MPa, the flatness is large and the flatness is poor compared to the case where the load is 1.5 to 4 MPa. became. In addition, when the load load exceeded 4.0 MPa, the flatness increased and the flatness was poor as compared with the load load of 1.5 to 4 MPa. Further, when the annealing temperature was 310 ° or more, the result was out of the range of 200 (N / mm ² ) or more that defines 0.2% proof stress sufficient for use as a magnetic disk blank. Further, when the annealing temperature was less than 210 °, the flatness was increased and the flatness was poor as compared with the case where the annealing temperature was 210 to 280 °.

  From the above results, while having a pressure annealing step of annealing at an annealing temperature of 210 ° C. or more and 280 ° C. or less while applying a pressure of 1.5 MPa or more and 4 MPa or less, and having an excellent flatness, It was found that a magnetic disk blank (aluminum blank) made of an aluminum alloy having excellent impact resistance can be produced.

As measurement values for measuring the impact resistance of the aluminum blank material, measurement values such as tensile strength, elongation rate, surface hardness, etc. can be considered in addition to the measurement value of 0.2% proof stress. Table 4 shows 0.2% proof stress (N / mm ² ), tensile strength (N / mm ² ), elongation (%), and surface hardness (Hv) with respect to changes in annealing temperature when the applied load is 2.80 MPa. It is a measurement result.

As shown in Table 4, the change in the tensile strength with respect to the change in the annealing temperature and the change in the surface hardness with respect to the change in the annealing temperature increase the tensile strength and the surface hardness as the annealing temperature decreases. Further, the elongation with respect to the change in annealing temperature becomes smaller as the annealing temperature becomes smaller. That is, as the annealing temperature decreases, the impact resistance tends to increase as in the 0.2% yield strength result. Therefore, not only 0.2% proof stress, but also the tensile strength, elongation rate, and surface hardness values corresponding to 0.2% proof stress should provide sufficient impact resistance for use as a magnetic disk blank. Is also possible.

1a: Upper surface plate 1b: Lower surface plate 2a: Uppermost spacer 2b: Lowermost spacer 2c: Intermediate spacer 3: Aluminum blank material 4: Heat resistant coil spring 5a: Spring upper plate 5b: Spring lower plate 6: Bolt 7: Nut

Claims (4)

A method for producing a magnetic disk blank material comprising Mg in an amount of 3.0 to 6.0% by mass and the balance being Al and impurities,
The magnetic disk blank material is provided with a pressure annealing step of annealing at an annealing temperature of 210 ° C. or more and 280 ° C. or less while applying a load of 1.5 MPa or more and 4 MPa or less. A method for manufacturing a blank material for a magnetic disk. The pressure annealing step includes
Laminating the magnetic disk blank material every plural number via flat intermediate spacers, sandwiching all the magnetic disk blank materials and all the intermediate spacers between flat lowermost spacer and uppermost spacer, The uppermost spacer, all the magnetic disk blanks, all the intermediate spacers and the lowermost spacer are sandwiched between the upper surface plate and the lower surface plate, and are disposed on the upper surface plate. 2. Annealing is performed while applying a load to the blank material for magnetic disk via a heat-resistant coil spring sandwiched between an unsprung plate and an unsprung plate. Of manufacturing blank material for magnetic disk.   A method for producing a magnetic disk blank material according to claim 1 or 2, comprising 3.0 to 6.0% by mass of Mg, the balance being made of an aluminum alloy containing Al and impurities. A blank material for a magnetic disk, characterized by being manufactured by: 4. The magnetic disk according to claim 3, wherein the flatness is 5 [mu] m or less, and a 0.2% proof stress measured by a JIS Z2241 tensile test using a test piece of JIS Z2201 is 200 N / mm < ² > or more. Blank material.

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