Aluminum wafer for thin mechanical hard disk and flatness control method thereof

Abstract

The present application relates to a kind of thin mechanical hard disk with aluminium round sheet, the aluminium round sheet thickness is 0.5~0.8mm, diameter is 95.0~98.2mm, surface flatness is less than 5 μm;The present application also relates to a kind of flatness control method of thin mechanical hard disk with aluminium round sheet, including the following steps: aluminium coiled material striping, stamping blanking, flattening and primary annealing treatment, rough grinding treatment, secondary annealing treatment, fine grinding treatment;Wherein aluminium round sheet is flattened and primary annealing treatment when pressure is 120‑200Kg, annealing heating rate is 80℃ / h~200℃ / h, cooling rate is 30℃ / h~70℃ / h after annealing ends, annealing holding temperature is 320°C~360°C, holding time is 2h~5h.The flatness value of aluminium round sheet of the present application is not higher than 5 μm, can guarantee the stable performance of mechanical hard disk, reduce the influence of mechanical hard disk disc in work, guarantee the stable flatness of aluminium round sheet, flatness has no rebound phenomenon, and the processing yield is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aluminum material processing technology, in particular to an aluminum disc for thin mechanical hard disk and a flatness control method thereof. BACKGROUND

[0002] The aluminum disc is a product obtained by deep processing of aluminum coil material, and has a bright and beautiful surface, and is widely used in kitchen utensils, lamps, mechanical hard disks and other products. The mechanical hard disk has the highest requirement on the flatness of the aluminum disc.

[0003] The disc in the hard disk is the core component for storing information in the HDD (hard disk drive), and the disc mostly adopts a thin film composite structure. A thin layer of magnetic film and a protective layer containing carbon material are sputtered on a very smooth substrate. A thin layer of lubricating film is on the protective layer, which is used to improve the interface performance between the magnetic head and the disc. The substrate material is plastic, metal material and amorphous glass. The subsequent main base disc is made of durable metal material, mainly aluminum magnesium alloy. Amorphous glass has poor shock resistance and high production of finished products, and is less used. Therefore, the surface flatness of the aluminum disc for manufacturing mechanical hard disk directly affects the performance of the mechanical hard disk. SUMMARY

[0004] Therefore, the purpose of the present application is to provide an aluminum disc for thin mechanical hard disk and a flatness control method thereof. The flatness value of the aluminum disc is not higher than 5 μm, which can ensure the stable performance of the mechanical hard disk, and the preparation process is simple and reasonable, and the batch production is easy to realize in industry.

[0005] The present application adopts the following scheme: an aluminum disc for thin mechanical hard disk, the thickness of the aluminum disc is 0.5-0.8mm, the diameter is 95.0-98.2mm, and the surface flatness is <5 μm.

[0006] Another technical scheme of the present application: a flatness control method of an aluminum disc for thin mechanical hard disk, comprising the following steps: aluminum coil material slitting, punching and blanking, flattening and primary annealing treatment, rough grinding treatment, secondary annealing treatment and fine grinding treatment. The pressure of the aluminum disc during flattening and primary annealing treatment is 120-200 Kg, the annealing heating rate is 80°C / h-200°C / h, the cooling rate after annealing is 30°C / h-70°C / h, the annealing holding temperature is 320°C-360°C, and the holding time is 2h-5h.

[0007] Further, the surface roughness of the aluminum disc after rough grinding treatment is 1.5-2.0 μm.

[0008] Further, the holding temperature of the secondary annealing treatment is 290-350°C, and the holding temperature of the secondary annealing treatment is lower than that of the primary annealing treatment, and the holding time is 30min-120min.

[0009] Further, the surface roughness of the aluminum disc after the fine grinding treatment is 0.5-0.9 μm.

[0010] Further, the flattening and primary annealing treatment uses a flattening annealing tool to mount the aluminum disc, the flattening annealing tool comprises a connecting shaft, a plurality of aluminum pressing blocks are sleeved on the connecting shaft and can slide along the axial direction, a disc group is clamped between adjacent two aluminum pressing blocks, the disc group is formed by stacking a plurality of aluminum discs, a rear stopper is fixedly connected to the rear end of the connecting shaft and abuts against the rear side of the last aluminum pressing block, and a pressing block is arranged on the front side of the frontmost aluminum pressing block.

[0011] Further, the front end of the connecting shaft is provided with an external thread part and a pressing nut is threadedly connected to the external thread part, a front stopper is arranged on the rear side of the pressing nut, and a pressing spring is sleeved on the front part of the connecting shaft and clamped between the front stopper and the pressing block.

[0012] Further, the stamping and blanking is performed on a stamping machine, the stamping machine is provided with a stamping die, the stamping die is composed of an upper die assembly and a lower die assembly, the lower die assembly comprises a shearing die, a circle of upwardly protruding blades are arranged on the upper end face edge and the upper opening edge of the blanking hole in the middle of the shearing die, the cross section of the blade is in the shape of a right-angled trapezoid, the height of the upwardly protruding blade is 0.2 mm, and the width of the upper surface of the blade is 0.13 mm.

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] The flatness value of the aluminum disc is not higher than 5 μm, the stable performance of the mechanical hard disc is ensured, the influence of the shaking of the disc of the mechanical hard disc in the working process is reduced, the stable flatness of the aluminum disc is ensured by adjusting the pressing force and the annealing process parameters, the flatness has no rebound phenomenon, and the processing yield is high; moreover, the preparation steps are simple and reasonable, batch production is easy to realize in industry, and the technology is universally applicable to aluminum disc products with high flatness requirements.

[0015] In order to make the purpose, technical scheme and advantages of the present application more clear, specific examples and related drawings will be used to further describe the present application in detail. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a structure schematic view of the flattening annealing tool of the present application;

[0017] Figure 2 is a perspective view of the shearing die of the present application;

[0018] Figure 3 is a longitudinal sectional view of the shearing die of the present application;

[0019] Figure 4 is Figure 3A close-up view of one of the blades;

[0020] Figure 5 is a 5-piece aluminum disc flatness detection image of embodiment 2 of the present application;

[0021] Label explanation in the figure: 1-connection shaft, 2-aluminum block, 3-disc group, 4-rear stop block, 5-pressing block, 6-pressing nut, 7-pressing spring, 8-front stop block, 9-shear die, 10-blade. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0023] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0024] An aluminum disc for a thin mechanical hard disc, the aluminum disc has a thickness of 0.5-0.8 mm, a single disc thickness tolerance of ≤3 μm, a diameter of 95.0-98.2 mm, a tolerance of ≤0.1 mm, and a surface flatness of <5 μm, and the surface flatness of the aluminum disc fluctuates in a range of 0-1 μm during processing; the flatness value of the aluminum disc is not higher than 5 μm, which can ensure stable performance of the mechanical hard disc and reduce the influence of disc shaking during work.

[0025] Through detailed investigation and research on the influencing factors of flatness after flattening annealing, it is found that the influencing factors of the flatness of the aluminum disc after flattening annealing include the thickness tolerance of the aluminum alloy strip for punching the aluminum disc, the edge burr height of the punched aluminum disc, the pressing force of flattening annealing, the heating speed of flattening annealing, the cooling speed of flattening annealing, and the holding temperature of flattening annealing. Before flattening annealing, some parameters of the raw material will also affect the flatness after flattening annealing, that is, the thickness change of the same aluminum disc is ≤3 μm (maximum thickness-minimum thickness), which determines the optimal flatness after flattening annealing. The second factor is the burr height after punching, and when the burr height is higher than the surface of the aluminum disc, the burrs between the discs will be embedded in each other during flattening annealing, which will cause difficulty in separating the discs and easily lead to disc deformation.

[0026] The flatness control method of the aluminum disc for thin mechanical hard disk comprises the following steps: aluminum coil strip division, stamping blanking, flattening and primary annealing treatment, rough grinding treatment, secondary annealing treatment and fine grinding treatment; wherein the pressure of the aluminum disc during the flattening and primary annealing treatment is 120-200 Kg, the annealing heating speed is 80°C / h-200°C / h, the cooling speed after the annealing is completed is 30°C / h-70°C / h, the annealing holding temperature is 320°C-360°C, and the holding time is 2h-5h. The aluminum disc manufactured by using the flatness control method can ensure that the surface flatness of the aluminum disc is less than 5μm, the flatness fluctuation range during the processing is 0-1μm, and the flatness has no rebound phenomenon, thereby meeting the technical requirements of the aluminum disc for thin mechanical hard disk, ensuring the stable performance of the mechanical hard disk, and reducing the shaking influence of the disc during the working; the present application adjusts the pressing force and the annealing process parameters, thereby ensuring the stable flatness of the aluminum disc, the flatness has no rebound phenomenon during the subsequent processing, and the processing yield is high; moreover, the preparation steps are simple and reasonable, and the batch production can be easily realized in industry, and the technology is universally applicable to the aluminum disc products with high flatness requirements.

[0027] During the flattening annealing treatment, under the condition of continuously increasing the annealing pressure, the flatness is gradually improved with the increase of the pressing force, and when the pressing force exceeds 200 Kg, the flatness deteriorates, and the deformation amount of the aluminum pressing block after the annealing also increases with the increase of the clamping force. The lower the heating and cooling speed, the smaller the thermal stress residue during the press annealing process, but in combination with the actual production benefit, a relatively appropriate heating and cooling speed is selected. The annealing holding temperature should be greater than or equal to 320°C, so that the aluminum disc is completely recrystallized and the internal stress generated during the cold processing is eliminated, and meanwhile, if the holding temperature is higher than 350°C, the mechanical properties of the material will decrease. If the aluminum disc has annealing thermal stress and residual stress after the cold processing after the flattening annealing, the flatness will obviously multiply and rebound after the subsequent rough grinding- annealing-fine grinding.

[0028] After the flattening annealing of the aluminum disc, the stress relief treatment is performed, the material is completely recrystallized, the uniformity of the mechanical properties of the material is improved, and the basic flatness of the aluminum disc and the flatness after the subsequent mechanical processing are ensured.

[0029] In the embodiment, the surface roughness of the aluminum disc after the rough grinding treatment is 1.5-2.0μm.

[0030] In the embodiment, the holding temperature of the secondary annealing treatment is 290-350°C, and the holding temperature of the secondary annealing treatment is lower than that of the primary annealing treatment, and the holding time is 30min-120min; the secondary annealing can relieve stress.

[0031] In the embodiment, the surface roughness of the aluminum disc after the fine grinding treatment is 0.5-0.9μm.

[0032] As Figure 1 shown in the figure, in the present embodiment, the flattening and primary annealing treatment adopts a flattening annealing tool to install the aluminum round sheet, the flattening annealing tool comprises a connecting shaft 1, a plurality of aluminum pressing blocks 2 are sleeved on the connecting shaft 1 and can slide in the axial direction, a disc group 3 is clamped between adjacent two aluminum pressing blocks, the disc group is composed of a plurality of aluminum round sheets stacked together; a rear stop block 4 is fixedly connected to the rear end of the connecting shaft and abuts against the rear side of the last aluminum pressing block, and a pressing block 5 is arranged on the front side of the frontmost aluminum pressing block.

[0033] In the present embodiment, the front end of the connecting shaft is provided with an external thread part and is threadedly connected with a pressing nut 6, the rear side of the pressing nut 6 is provided with a front stop block 7, and the front part of the connecting shaft is sleeved with a pressing spring 8 clamped between the front stop block and the pressing block.

[0034] As Figures 2-4 shown in the figure, in the present embodiment, the stamping and blanking is performed on a stamping machine, and a stamping die is arranged on the stamping machine, and the specific structure of the stamping die has been disclosed in Chinese patent CN209393850U Mechanical Hard Disk Aluminum Alloy Substrate Stamping Die, and the present application only improves the structure of the shearing die. The stamping die is composed of an upper die assembly and a lower die assembly, the lower die assembly comprises a shearing die 9, and a row of upwardly protruding cutting edges 10 are arranged on the upper end face edge and the upper opening edge of the blanking hole in the middle of the shearing die respectively, the cross section of the cutting edge is in the shape of a right-angled trapezoid, the height h of the upward protrusion of the cutting edge is 0.2mm, and the width d of the upper surface of the cutting edge is 0.13mm; the special structure design of the shearing die 9 can ensure that the inner and outer round burrs of the aluminum round sheet obtained by stamping and blanking are not higher than the surface of the product.

[0035] The following is compared through specific examples:

[0036] The thickness difference of the incoming aluminum material is 2μm, and the height of the edge burr of the aluminum round sheet is not higher than the surface of the sheet, and then different flattening annealing processes (i.e. flattening and primary annealing) are performed. The aluminum round sheet with a size of 0.523mm*Ø24.0mm*Ø98.2mm is subjected to flattening annealing at 30 sheets / group.

[0037] For the analysis of the aluminum round sheet, the sheet after flattening annealing (i.e. flattening and primary annealing) is subjected to flatness analysis, and then is subjected to rough grinding processing→310℃×30min stress relief secondary annealing→fine grinding processing, after each process is completed, FT-17 flatness detection instrument is used for detection, FT-17 flatness detection equipment is used for analyzing the flatness of each process and taking pictures for saving.

[0038] Examples 1~3 and Comparative Examples 1~2:

[0039] The test sample was continuously punched on the same cold-rolled coil, and then was subjected to flattening annealing treatment with different compacting forces and holding temperatures. The FT-17 flatness detector was used to analyze the flatness of the aluminum disc and the flatness after fine grinding, and the statistical results are shown in Table 1. The flattening annealing processes of Examples 1-3 are 120 kg-320°C x 3h, 150 kg-320°C x 3h, and 180 kg-320°C x 3h, respectively, and the flatness after fine grinding is less than 5 μm. The flattening annealing processes of Comparative Examples 1 and 2 are 210 kg-320°C x 3h and 240 kg-320°C x 3h, and the statistical average of the flatness after fine grinding is relatively increased.

[0040] Example 4:

[0041] In addition to the compacting force of the above flattening annealing, the heating rate, the cooling rate, and the holding temperature of the annealing process will also affect the flatness. The FT-17 flatness detector was used to analyze the flatness of the aluminum disc and the flatness after fine grinding, and the statistical results are shown in Table 1. The flattening annealing process of Example 4 is 150 kg-330°C x 3h, and the flatness of the aluminum disc is qualified.

[0042] Comparative Examples 3-5:

[0043] The aluminum discs punched continuously from the same mother coil were used, and Comparative Example 3 was subjected to flattening annealing at 150 kg-310°C x 3h. The FT-17 flatness detector was used to analyze the flatness of the aluminum disc and the flatness after fine grinding, and the statistical results are shown in Table 1. Since the flatness after fine grinding of the finished product is greater than 5 μm, it is evaluated as unqualified. Comparative Examples 4 and 5 increase the heating temperature rate by 200°C / h and the cooling temperature rate by 150°C / h, respectively, and the changes in the flatness of the aluminum disc and the flatness after fine grinding are compared.

[0044] Table 1: Flatness and flatness after fine grinding of aluminum disc under different conditions

[0045]

[0046] Although Comparative Examples 1-5 can also obtain some qualified products, it can be seen from the comparison of the detected flatness that the flatness has gradually deteriorated, and even unqualified, so the process of Comparative Examples is likely to be unqualified, and the fluctuation range is large in the processing process, and the quality cannot be guaranteed. The flatness of the products obtained by using the processes of Examples 1-4 can be basically controlled to be less than 3 μm, and the flatness has no rebound phenomenon, and the fluctuation range is small in the processing process, thereby ensuring the stable flatness of the aluminum disc.

[0047] The FT-17 flatness detector was used to analyze 5 aluminum discs in Example 2, numbered 1, 2, 3, 4, and 5, and the specific images are as follows: Figure 5As shown, wherein A represents the front side, and B represents the back side.

[0048] Any of the technical solutions disclosed in the present application, if not otherwise stated, if it discloses a numerical range, the disclosed numerical range is a preferred numerical range, any person skilled in the art should understand that the preferred numerical range is only one of the many values that can be implemented, the technical effect is more obvious or representative. Because there are many values, it is impossible to enumerate, so the present application discloses some values to illustrate the technical solutions of the present application, and the above enumerated values should not constitute a limitation on the protection scope of the present application.

[0049] If the present application discloses or involves mutually fixed connecting parts or structural parts, except otherwise stated, the fixed connection can be understood as: detachable fixed connection (for example, using bolt or screw connection), but also can be understood as: non-detachable fixed connection (for example, riveting, welding), of course, the mutual fixed connection can also be replaced by an integral structure (for example, using casting process integral forming manufacturing) (obviously, except for integral forming process).

[0050] In addition, the terms used to represent the position relationship or shape in any of the technical solutions disclosed in the present application, except otherwise stated, its meaning includes the approximate, similar or close state or shape.

[0051] Any of the components provided by the present application can be assembled by a plurality of individual components, or can be a single component manufactured by integral forming process.

[0052] The above is only the preferred embodiment of the present application, not the other forms of the present application, any person skilled in the art may use the disclosed technical content to change or modify the equivalent embodiment of equivalent change. But any simple modification, equivalent change and modification of the above embodiment without departing from the technical solution content of the present application, according to the technical essence of the present application, still belongs to the protection scope of the present application technical scheme.

Claims

1. A flatness control method for an aluminum disc for a thin mechanical hard disk, characterized by: The method comprises the following steps: The aluminum coil is divided into strips, punched, flattened, and once annealed, coarsely ground, twice annealed, finely ground, and the aluminum disc has a thickness of 0.5-0.8 mm and a diameter of 95.0-98.2 mm; The pressure during the flattening and once annealing is 120-200 Kg, the annealing temperature is raised at a speed of 80-200 °C / h, the temperature is lowered at a speed of 30-70 °C / h after the annealing is completed, the annealing temperature is 320-360 °C, and the annealing time is 2-5 h.

2. The flatness control method of an aluminum round sheet for a thin-type mechanical hard disk according to claim 1, characterized in that: The surface roughness of the aluminum disc after the coarse grinding is 1.5-2.0 μm.

3. The flatness control method of an aluminum round sheet for a thin-type mechanical hard disk according to claim 1, characterized in that: The annealing temperature of the twice annealing is 290-350 °C, and the annealing temperature of the twice annealing is lower than that of the once annealing, and the annealing time is 30-120 min.

4. The flatness control method of an aluminum round sheet for a thin-type mechanical hard disk according to claim 1, characterized in that: The surface roughness of the aluminum disc after the fine grinding is 0.5-0.9 μm.

5. The flatness control method of an aluminum round for a thin-type mechanical hard disk according to claim 1, characterized in that: The flattening and once annealing are performed by using a flattening annealing tooling to mount the aluminum disc, the flattening annealing tooling comprises a connecting shaft, a plurality of aluminum blocks are arranged at intervals on the connecting shaft and can slide in the axial direction, a disc group is clamped between adjacent two aluminum blocks, the disc group is formed by stacking a plurality of aluminum discs, a rear stopper is fixedly connected to the rear end of the connecting shaft and abuts against the rear side of the last aluminum block, and a pressing block is arranged on the front side of the frontmost aluminum block.

6. The flatness control method of an aluminum round sheet for a thin-type mechanical hard disk according to claim 5, characterized in that: A threaded portion is arranged at the front end of the connecting shaft and is threadedly connected with a pressing nut, a front stopper is arranged on the rear side of the pressing nut, and a pressing spring is sleeved on the front part of the connecting shaft and is clamped between the front stopper and the pressing block.

7. The flatness control method of an aluminum round for a thin-type mechanical hard disk according to claim 1, characterized in that: The punching and blanking are performed on a punching machine, the punching machine is provided with a punching die, the punching die is composed of an upper die assembly and a lower die assembly, the lower die assembly comprises a shearing die, a straight blade is arranged on the upper end surface edge and the upper opening edge of the blanking hole in the shearing die, the cross section of the straight blade is in the shape of a right-angled trapezoid, the height of the straight blade is 0.2 mm, and the width of the upper surface of the straight blade is 0.13 mm.

Images