JP5901168B2 - Aluminum alloy substrate for magnetic disk and method for manufacturing the same, and aluminum alloy substrate for base treatment magnetic disk and method for manufacturing the same - Google Patents

Description

  The present invention relates to an aluminum alloy substrate for a magnetic disk that has few pits after plating and is excellent in plating surface smoothness, and a method for manufacturing the same.

  2. Description of the Related Art Magnetic disks used in computer storage devices are those in which a magnetic material is coated on an aluminum alloy substrate or glass substrate. In general, aluminum alloys for magnetic disks have good plating properties and excellent mechanical properties and workability. JIS 5086 (Mg: 3.5 to 4.5 mass% (hereinafter simply referred to as%)), Fe ≦ 0.50%, Si ≦ 0.40%, Mn: 0.20 to 0.70%, Cr: 0.05 to 0.25%, Cu ≦ 0.10%, Ti ≦ 0.15%, Zn ≦ 0.25%, balance Al and unavoidable impurities), impurities in Fe and Si in JIS5086 are limited to reduce intermetallic compounds in the matrix, and Cu and Zn are added consciously to increase plating properties Improved alloys are used.

A general aluminum magnetic disk is manufactured by manufacturing an annular aluminum alloy substrate, and then attaching a magnetic material to the alloy substrate. An annular aluminum alloy substrate is obtained by, for example, hot rolling an ingot made of the JIS5086 alloy, then cold rolling it while annealing, punching the rolled material into an annular shape, and then forming an annular aluminum alloy plate. It is manufactured in a process of stacking and performing annealing (pressure annealing) by pressing from both sides and flattening.
The annular aluminum alloy substrate thus manufactured is subjected to cutting, grinding, polishing, degreasing, etching, zincate treatment (Zn substitution treatment) as a pretreatment, and then Ni—P which is a hard nonmagnetic metal as a ground treatment. Is electrolessly plated, and the plated surface is polished, and then a magnetic material is sputtered to finish the magnetic disk.

Incidentally, in recent years, a magnetic disk is required to have a large capacity and a high density because of the need for multimedia and the like, and a surface recording density of ² Tb / in ² is about to be achieved in the near future. In order to further improve the recording density of the magnetic disk, it is necessary to make the flying height of the magnetic head with respect to the magnetic disk smaller and more stable. For that purpose, high smoothness is required for the Ni-P plating surface of the aluminum alloy substrate for magnetic disks.

  In addition, since the magnetic area per bit is further miniaturized due to the higher density, even if there are extremely fine pits on the plating surface, it causes an error when reading data. Under such circumstances, in recent years, it has been strongly desired to suppress the generation of pits on the plating surface and make the Ni-P plating surface highly smooth, and various studies have been made.

  Patent Document 1 proposes an aluminum alloy substrate for a magnetic disk in which the range of the alloy composition is limited and the size of Al—Fe-based and Mg—Si-based intermetallic compounds that cause the loss of smoothness is optimally controlled. Patent Document 2 proposes a method for improving the smoothness of the Ni—P plating surface by defining the annealing conditions and controlling the number of Al—Mg—Zn intermetallic compounds.

JP 2002-275568 A JP 2004-143559 A

However, generation of pits on the Ni-P plating surface is limited only by limiting the size and number of intermetallic compounds (Al-Fe, Mg-Si, Al-Mg-Zn) shown in Patent Documents 1 and 2. The present situation is that high smoothness of the target Ni—P plating surface has not been obtained.
As a result of intensive investigations and investigations on the surface of the aluminum alloy substrate for a magnetic disk at the position where the pit is generated, the present inventors have found that the Al—Cu—Mg—Zn intermetallic compound is involved in the generation of the pit. . The intermetallic compound remains on the surface of the aluminum alloy substrate for the magnetic disk even after the zincate treatment. Since the dissolution reaction of Zn continues on this intermetallic compound for a longer time than other parts, the generation of Ni-P plating is delayed, It is considered to be.

  The present invention has been made against the background of the above investigation and examination, and provides an aluminum alloy substrate for a magnetic disk that has few Ni-P plating and has excellent Ni-P plating surface smoothness and a method for producing the same. Is an issue.

That magnetic aluminum alloy disk substrate of the present invention, Mg: 2.0~6.0mass%, Cu (hereinafter, simply referred to as%.): 0.005~0.15%, Zn : 0.05~ Aluminum containing 0.6%, Cr: 0.01-0.3%, Si: 0.001-0.03%, Fe: 0.001-0.03%, the balance being Al and inevitable impurities It is an aluminum alloy substrate for a magnetic disk which is made of an alloy and has no more than one Al—Cu—Mg—Zn intermetallic compound having a longest diameter exceeding 1 μm per 0.2 mm ² . The method for producing an aluminum alloy substrate for a magnetic disk according to the present invention includes Mg: 2.0 to 6.0%, Cu: 0.005 to 0.15%, Zn: 0.05 to 0.6%, Cr : 0.01-0.3%, Si: 0.001-0.03%, Fe: 0.001-0.03%, aluminum alloy ingot composed of the balance Al and inevitable impurities, heat The hot rolling is performed so that the end temperature of the hot rolling is 280 to 360 ° C., and the difference in the surface temperature between the center portion of the sheet width and the end portion at the end of the hot rolling is within 30 ° C.

Further, the aluminum alloy substrate for the ground-treated magnetic disk of the present invention has Mg: 2.0 to 6.0%, Cu: 0.005 to 0.15%, Zn: 0.05 to 0.6%, Cr: An aluminum alloy substrate containing 0.01 to 0.3%, Si: 0.001 to 0.03%, Fe: 0.001 to 0.03%, the balance Al and inevitable impurities, and the substrate surface A zincate treatment part and an electroless Ni—P plating part on the surface of the zincate treatment part are provided. In the aluminum alloy substrate, an Al—Cu—Mg—Zn-based intermetallic compound having a longest diameter exceeding 1 μm is 1 per 0.2 mm ^2. The number of generated pits is 1 or less per 0.2 mm ^{2 on the} surface of the aluminum alloy substrate subjected to electroless Ni—P plating . Moreover, the manufacturing method of the aluminum alloy board | substrate for base-treatment magnetic discs of this invention is Mg: 2.0-6.0mass%, Cu: 0.005-0.15%, Zn: 0.05-0.6% , Cr: 0.01-0.3%, Si: 0.001-0.03%, Fe: 0.001-0.03% on the aluminum alloy substrate surface comprising the balance Al and inevitable impurities A zincate treatment is performed, and electroless Ni-P plating is performed on the surface of the zincate treatment .

  According to the aluminum alloy substrate for magnetic disk and the method of manufacturing the same of the present invention, aluminum for magnetic disk that generates few pits after plating, has excellent smoothness of the plating surface, and can increase the capacity and density of the magnetic disk. An alloy substrate can be provided.

It is a figure which shows the flow of the manufacturing method of the aluminum alloy board | substrate for magnetic discs. FIG. 2 is a view showing a COMP image in which an Al—Cu—Mg—Zn-based intermetallic compound existing on an aluminum alloy substrate for a magnetic disk is specified. FIG. 3 is a photograph of the presence of aluminum (Al) that forms an Al—Cu—Mg—Zn intermetallic compound. FIG. 4 is a photograph of the presence of copper (Cu) that forms an Al—Cu—Mg—Zn intermetallic compound. FIG. 5 is a photograph of the presence of magnesium (Mg) that organizes an Al—Cu—Mg—Zn-based intermetallic compound. FIG. 6 is a photograph of the presence of zinc (Zn) that forms an Al—Cu—Mg—Zn intermetallic compound.

  Hereinafter, the present invention will be described in detail.

First, the manufacturing process of the magnetic disk will be described with reference to the flow shown in FIG.
Step 1: Adjust the aluminum alloy. For example, an aluminum alloy having a composition shown in Table 1 described later is adjusted.
Step 2: Cast the adjusted aluminum alloy.
Step 3: Homogenize the cast metal (not essential).
Step 4: The metal is hot rolled.

Step 5: Cold-roll the hot-rolled plate to obtain an aluminum alloy rolled plate Step 6: The aluminum alloy rolled plate is punched into an annular shape to create a disc blank.
Step 7: Pressurize and flatten the disc blank.
Step 8: The flattened disk blank is cut, ground, polished, degreased and etched to form a magnetic disk substrate.

Step 9: A zincate process (Zn substitution process) is performed on the surface of the magnetic disk substrate.
Step 10: The surface of the zincate-treated surface is treated (Ni-P plating).
Step 11: A magnetic material is deposited on the surface of the ground surface by sputtering to obtain a magnetic disk.

  The adjustment of the aluminum alloy in step 1 will be described in detail. The reasons for limiting the component composition of the aluminum alloy are as follows.

Mg: 2.0-6.0%
Mg added to Al is mainly effective in improving the strength of the aluminum alloy substrate for magnetic disks.
The reason why the content is specified to be 2.0 to 6.0% is that the effect is not sufficiently obtained if it is less than 2.0%, and if it exceeds 6.0%, a coarse Al—Mg intermetallic compound is formed. This is because, during the etching, the zincate treatment, the cutting and the grinding, the intermetallic compound is dropped and a large dent that causes pits is generated. The content of Mg is particularly preferably 2.0 to 5.0% in view of strength and ease of manufacture.

Cu: 0.005-0.15%
Cu added to Al has an effect of reducing the amount of dissolved Al during the zincate treatment in Step 9 and also making the zincate film uniformly, thin and densely adhered. As a result, the adhesion of the underlying plating layer made of Ni-P in the next process (step 10) is improved.
The reason why the content of Cu is specified to be 0.005 to 0.15% is that the effect cannot be sufficiently obtained if the content is less than 0.005%, and is coarse if the content exceeds 0.15% (the longest diameter is 1 μm or more). Al—Cu—Mg—Zn-based intermetallic compounds are generated, and pits are generated after the base plating (Ni—P) treatment, resulting in a decrease in smoothness. Furthermore, since the corrosion resistance of the material itself is lowered, the zincate film generated by the zincate treatment becomes non-uniform, and the adhesion and smoothness of the base plating are lowered. A preferable Cu content is in the range of 0.005 to 0.1%.

Zn: 0.05-0.6%
Zn added to Al reduces the amount of dissolved Al during the zincate treatment in Step 9 as well as Cu, and also adheres the zincate film uniformly, thinly and densely to improve the adhesion of the underlying plating layer in the next step. effective.
The reason why the Zn content is specified to be 0.05 to 0.6% is that if the content is less than 0.05%, the effect cannot be sufficiently obtained. If the content exceeds 0.6%, coarse Al—Cu—Mg— A Zn-based intermetallic compound is generated, pits are generated after the base plating process, and the smoothness is lowered. Furthermore, the workability and corrosion resistance of the material itself are reduced. A preferable Zn content is in the range of 0.05 to 0.5%.

Cr: 0.01 to 0.3%
Cr added to Al produces a fine intermetallic compound during casting, but a part of it is dissolved in the matrix and contributes to strength improvement. In addition, there is an effect that the machinability and grindability are improved, the recrystallized structure is made finer, and the adhesion of the underlying plating layer is improved.
The reason why the content of Cr is specified to be 0.01 to 0.3% is that the effect is not sufficiently obtained when the content is less than 0.01%, and when the content exceeds 0.3%, an excess amount is crystallized at the time of casting. This is because a coarse Al—Cr-based intermetallic compound is generated, and the intermetallic compound is dropped during etching, zincate treatment, cutting or grinding, and a large dent that causes pits is generated. A preferable Cr content is in the range of 0.01 to 0.2%.

Si: 0.001 to 0.03%
Since Si combines with Mg, which is an essential element of the present invention, to generate an intermetallic compound that becomes a defect in the underlying plating layer, it is not preferable that Si be contained in the aluminum alloy. However, Si exists as an inevitable impurity in the aluminum ingot. For the adjustment of the aluminum alloy in Step 1, an aluminum ingot having a high purity, for example, a purity of 99.9% or more is adopted, but such a ingot also contains Si. It is not preferable to remove Si from the aluminum ingot to less than 0.001% because the aluminum ingot is refined with high purity, resulting in high cost. On the other hand, if the Si content exceeds 0.03%, a coarse Mg-Si intermetallic compound is generated, which causes generation of pits and the like. Therefore, the Si content is adjusted to 0.03% or less. The Si content is preferably suppressed to less than 0.025%.

Fe: 0.001 to 0.03%
Fe hardly dissolves in aluminum and exists in an aluminum metal as an Al—Fe intermetallic compound. Since Fe present in the aluminum is bonded to Al, which is an essential element of the present invention, and forms an intermetallic compound that becomes a defect in the underlying plating layer, it is not preferable that Fe be contained in the aluminum alloy. However, removing Fe to less than 0.001% is not preferable because it refining aluminum ingots with high purity, resulting in high costs. On the other hand, if the content exceeds 0.03%, a coarse Al—Fe-based intermetallic compound is generated, which causes generation of pits and the like, which is not preferable. The Fe content is preferably suppressed to less than 0.025%.

  In general, an aluminum alloy containing Mg may add a small amount of Be during casting in order to suppress molten metal oxidation of Mg. Therefore, the aluminum alloy for magnetic disks of the present invention is allowed to contain a trace amount of Be. However, if the amount of Be is less than 0.0001%, the above effect cannot be obtained. On the other hand, even if the amount of Be exceeds 0.005%, the addition effect is saturated, and a significant improvement effect beyond that. Cannot be obtained. Accordingly, the amount of Be added when Be is added is preferably within the range of 0.0001 to 0.0025%.

  In addition to the above elements, Al and inevitable impurities are included. Here, inevitable impurities (excluding Si and Fe, for example, Ti, V, Ga, B, etc.) are each 0.05% or less and a total of about 0.15% or less, the present invention. The properties of the aluminum alloy for magnetic disks obtained in the above are not impaired.

Al-Cu-Mg-Zn-based intermetallic compound is Al-Cu-Mg-Zn-based intermetallic compound longest diameter exceeds 1μm present in one or less aluminum alloy substrate surface per 0.2 mm ² of the longest diameter is more than 1μm By setting the number to 1 or less per 0.2 mm ^2, it is possible to obtain a smooth plating surface with few pits after the base plating process.
When the longest diameter of the Al—Cu—Mg—Zn intermetallic compound generated on the surface of the aluminum alloy substrate exceeds 1 μm, the size of the pits generated on the surface of the underlying plating by this compound has some influence on the magnetic disk. However, if the number of this compound is 1 or less per 0.2 mm ² , the influence can be ignored.
The Al—Cu—Mg—Zn intermetallic compound formed on the surface of the aluminum alloy substrate is about several μm even at its longest diameter. If the length of the Al—Cu—Mg—Zn based intermetallic compound existing on the surface of the aluminum alloy substrate is 1 μm or less, the size of pits generated by this compound is not regarded as a problem. However, the presence of compounds exceeding 10 μm is also observed. If it exceeds 10 μm, the size of pits due to the Al—Cu—Mg—Zn intermetallic compound becomes large, which is not preferable. For this reason, the longest diameter of the Al—Cu—Mg—Zn intermetallic compound existing on the aluminum alloy substrate surface is preferably 1 μm or more and 10 μm or less per 0.2 mm ² .
In the present invention, based on the measurement field of view of the Al—Cu—Mg—Zn-based intermetallic compound, it is defined that the number of the longest diameter is 1 μm or more and 10 μm or less is preferably 1 or less per 0.2 mm ² . This regulation corresponds to 5 or less per 1 mm ^2, but since intermetallic compounds may exist in a narrow range, it is defined that 1 or less per 0.2 mm ² is preferable in the present invention. .

  Next, the manufacturing method of the aluminum alloy substrate for magnetic disks will be described in detail.

  The aluminum alloy ingot adjusted to the alloy composition range of the present invention in Step 1 is cast according to a conventional method such as a semi-continuous casting (DC casting) method (Step 2), and the resulting ingot is homogenized ( Step 3), hot rolling (step 4), and cold rolling (step 5) are performed to produce a rolled aluminum alloy sheet. The homogenization process in step 3 may not be performed, but when it is performed, it is preferably performed at 500 to 570 ° C. for 4 hours or more. Although any process is related to the intermetallic compound, the present inventors particularly paid attention to the rolling end temperature and the temperature distribution during the hot rolling in Step 4.

Hot rolling (step 4) finish temperature: 280-360 ° C
When the hot rolling end temperature is less than 280 ° C., precipitation of Al—Cu—Mg—Zn intermetallic compound occurs during hot rolling, and pits are generated on the surface after the base plating process in step 10, and the surface of the base plating surface Smoothness decreases.
On the other hand, when the hot rolling finish temperature exceeds 360 ° C., the crystal grains are likely to be coarsened at the end of hot rolling, and fine recrystallized grains are obtained when pressure annealing (step 7) after cold rolling is performed. It becomes difficult. If the recrystallized grains are coarse, the zincate film in the next step (step 9) becomes non-uniform, and the adhesion of the underlying plating layer and the smoothness of the plating surface decrease.
Therefore, by keeping the hot rolling end temperature in the range of 280 to 360 ° C., precipitation of the Al—Cu—Mg—Zn intermetallic compound does not occur during hot rolling, and the surface after the base plating treatment in step 10 Thus, a magnetic disk substrate with no pits and high smoothness of the underlying plating surface can be produced.

Difference in surface temperature between center and end of sheet width at end of hot rolling (step 4): within 30 ° C. Difference in surface temperature between center of sheet width and end at end of hot rolling in step 4 is 30 It shall be below ℃. When the temperature difference exceeds 30 ° C., the heat transfer from the region having a high surface temperature to the region having a low surface temperature becomes large, and the cooling rate in the region having a low surface temperature becomes slow. Therefore, the Al—Cu—Mg—Zn system is used during cooling. Precipitation of intermetallic compounds occurs, and pits are generated in the subsequent plating process or the like in the subsequent process, resulting in a decrease in the smoothness of the surface of the underlying plating layer. For this reason, the difference in the surface temperature between the center portion and the end portion of the plate width at the end of hot rolling (step 4) is set to be within 30 ° C.

After the hot rolling is finished, the product is finished to the required product thickness by cold rolling (step 5). The conditions for cold rolling are not particularly limited, and may be determined according to the required product plate strength and plate thickness. Usually, the rolling rate is 20 to 80%.
An annealing treatment may be performed before cold rolling or during cold rolling to ensure cold rolling processability. In the case of carrying out the annealing treatment, for example, batch heating is preferably performed at 200 to 550 ° C. for 0 to 10 hours.

  Thereafter, the aluminum alloy rolled sheet thus produced is punched into an annular shape (step 6), and is subjected to pressure annealing at 200 to 450 ° C. for 30 minutes or more in the atmosphere (step 7) to obtain an aluminum alloy for a magnetic disk. A substrate is used.

Hereinafter, the present invention will be described in detail with reference to examples.
Step 1: A molten aluminum alloy having the composition shown in Table 1 was melted.

Step 2: The aluminum alloy melt was made into an ingot having a thickness of 500 mm by a DC casting method.
Step 3: Alloy No. Except 6 was homogenized at 560 ° C. for 6 hours.
Step 4: Hot rolling was performed under the conditions shown in Table 2 to obtain a hot rolled sheet having a sheet thickness of 4.0 mm.

Step 5: Alloy No. Hot rolled sheets other than 7 were rolled to a final sheet thickness of 1.7 mm by cold rolling (rolling rate: 57.5%) without performing intermediate annealing to obtain rolled sheets.
Alloy No. In No. 7, first cold rolling (rolling rate 25%) was performed, and then intermediate annealing was performed at 300 ° C. for 2 hours using a batch annealing furnace. Subsequently, it rolled to the final board thickness of 1.7 mm by the 2nd cold rolling (rolling rate 43.3%), and was set as the rolled board.

Step 6: An annular plate having an outer diameter of 96 mm and an inner diameter of 24 mm was punched out from the rolled plate to prepare a disc blank.
Steps 7 and 8: After the disk blank was annealed at 340 ° C. for 4 hours, end face processing and grinding processing (surface grinding) were performed. Then, after degreasing for 5 minutes at 60 ° C. with AD-68F (manufactured by Uemura Kogyo), etching is performed for 1 minute at 65 ° C. with AD-107F (manufactured by Uemura Kogyo), and a 30% HNO ₃ aqueous solution (room temperature ) For 20 seconds.
Step 9: The surface of the disk blank whose surface was prepared was subjected to double zincate treatment using AD-301F-3X (manufactured by Uemura Kogyo).
Step 10: Electroless Ni-P plating solution (Nimden HDX (manufactured by Uemura Kogyo Co., Ltd.)) is electrolessly plated on the surface treated with zincate to a thickness of 17 μm, and then finish polishing with a blanket (polishing amount: 4 μm) )).

  The following evaluation was performed on the aluminum alloy substrate for magnetic disk after the surface grinding (step 8) and after the base plating process (step 10).

[Number of Al-Cu-Mg-Zn-based intermetallic compounds]
A composition (COMP) image of the surface of an aluminum alloy substrate for a magnetic disk after surface grinding was taken at a magnification of 1000 times (field of view: 0.2 mm ² ) with an electron beam microanalyzer (EPMA), and the longest diameter was Al exceeding 1 μm. The number of —Cu—Mg—Zn-based intermetallic compounds was counted to determine the number per 0.2 mm ² (number density: pieces / 0.2 mm ² ).
The Al—Cu—Mg—Zn intermetallic compound was specified based on the results of concentration mapping of Al, Cu, Mg, and Zn.
3 to 6 indicate that the higher the lightness, the higher the concentration of the target element. The black portion of the Al concentration mapping in FIG. 3 (the circled portion in the photograph) and the Cu and Mg in FIGS. The portion where the white part of Zn concentration mapping (the part circled in the photograph) overlaps corresponds to the Al—Cu—Mg—Zn-based intermetallic compound (the part circled in the photograph in FIG. 2).

[Ni-P plating surface smoothness]
The surface of the aluminum alloy substrate after the Ni-P plating treatment was observed with an optical microscope (field of view: 0.2 mm ² ), the number of pits was counted, and the number per unit area (number density: pieces / 0.2 mm ² ) Asked. The case where the number of pits is 0 / 0.2 mm ² is excellent (◎ mark), the case where 1 pit / 0.2 mm ² is good (○ mark), and the case where ² pits / 0.2 mm ² or more is bad (× mark) ). The above evaluation results are shown in Table 3.

  As shown in Table 3, the example No. 1-No. In No. 7, an aluminum alloy substrate for a magnetic disk with few pits after the base plating and excellent plating surface smoothness was obtained.

  Comparative Example No. In No. 8, since the amount of Mg was too large, six pits were generated on the surface of the base plating, and the smoothness of the plating surface was inferior. This is presumably because a large amount of Mg produced a coarse Al—Mg-based intermetallic compound, and the smoothness of the surface of the base plating was impaired by the removal of the intermetallic compound.

  Comparative Example No. In No. 9, since the amount of Cu was too much, there were six Al—Cu—Mg—Zn intermetallic compounds having a longest diameter exceeding 1 μm. As a result, five pits were generated on the base plating surface, and the smoothness of the plating surface was inferior.

  Comparative Example No. In No. 10, since the amount of Zn was too large, there were 38 Al—Cu—Mg—Zn intermetallic compounds having a longest diameter exceeding 1 μm. As a result, 30 pits were generated on the base plating surface, and the smoothness of the plating surface was inferior.

  Comparative Example No. In No. 11, since the amount of Cr was too much, 21 pits were generated on the surface of the base plating, and the smoothness of the plating surface was inferior. The cause is presumed that since the amount of Cr was large, a coarse Al—Cr-based intermetallic compound was generated, and the smoothness of the surface of the base plating was impaired by the removal of this intermetallic compound.

  Comparative Example No. In No. 12, since the amount of Si was too large, 15 pits were generated on the surface of the base plating, and the smoothness of the plating surface was inferior. The cause is presumed that since the amount of Si was large, a coarse Mg-Si intermetallic compound was generated, and the smoothness of the surface of the base plating was impaired by the removal of the intermetallic compound.

  Comparative Example No. In No. 13, since the amount of Fe was too large, 33 pits were generated on the surface of the base plating, and the smoothness of the plating surface was poor. This is presumably because a large amount of Fe produced a coarse Al—Fe-based intermetallic compound, and the smoothness of the underlying plating surface was impaired due to the removal of the intermetallic compound.

  Comparative Example No. In No. 14, since the amount of Cu was too small, the zincate film was not uniform. As a result, 11 pits were generated on the plating surface, and the smoothness of the plating surface was inferior.

  Comparative Example No. In No. 15, since the amount of Zn was too small, the zincate film became non-uniform. As a result, eight pits were generated on the plating surface, and the smoothness of the underlying plating surface was inferior.

  Comparative Example No. In No. 16, since the amount of Cr was too small, fine recrystallized grains were not obtained when pressure annealing was performed after cold rolling, and the zincate film became non-uniform. As a result, 16 pits were generated on the base plating surface, and the smoothness of the plating surface was inferior.

  Comparative Example No. In No. 17, since the hot rolling end temperature was too low, there were two Al—Cu—Mg—Zn intermetallic compounds having a longest diameter exceeding 1 μm. As a result, two pits were generated on the base plating surface, and the smoothness of the plating surface was inferior.

  Comparative Example No. In No. 18, since the hot rolling end temperature was too high, the crystal grains became coarse at the end of hot rolling, and fine recrystallized grains were not obtained when pressure annealing was performed after cold rolling. As a result, the zincate film became non-uniform, 15 pits were generated on the base plating surface, and the smoothness of the plating surface was inferior.

  Comparative Example No. In No. 19, since the temperature difference between the center portion and the end portion in the sheet width direction at the hot rolling end temperature was too wide, three Al—Cu—Mg—Zn intermetallic compounds having a longest diameter exceeding 1 μm were present. As a result, three pits were generated on the plating surface, and the smoothness of the plating surface was inferior.

From the above examples, according to the aluminum alloy substrate for magnetic disk of the present invention and the manufacturing method thereof, the generation of pits is less after the base plating, the plated surface is excellent in smoothness, and the capacity and density of the magnetic disk are increased. A possible aluminum alloy substrate for a magnetic disk can be provided.
On the other hand, since all the comparative examples included elements that deviated from the limiting conditions of the present invention, pits were observed after the base plating, the smoothness of the plated surface was impaired, and the capacity and density of the magnetic disk were increased. A possible aluminum alloy substrate for a magnetic disk could not be obtained.
In particular, when the amount of added Cu or Zn is large, the Al-Mg-Zn intermetallic compound is the cause, and depending on the amount of added Mg, Cr, Si, or Fe, the formation of an unfavorable intermetallic compound (presumed to be) It seems that these caused the generation of pits and produced undesirable results.
Moreover, an unfavorable Al-Cu-Mg-Zn type intermetallic compound will be produced | generated by a hot rolling process, especially the temperature control at the time of completion | finish.

  From the above results, the aluminum alloy substrate for magnetic disk of the present invention and the method for producing the same provide an aluminum alloy substrate for magnetic disk that has excellent smoothness of the plating surface and can increase the capacity and density of the magnetic disk. be able to.

Claims (4)

Mg: 2.0-6.0 mass% (hereinafter simply referred to as%), Cu: 0.005-0.15%, Zn: 0.05-0.6%, Cr: 0.01-0. Al—Cu containing 3%, Si: 0.001 to 0.03%, Fe: 0.001 to 0.03%, the balance being Al and inevitable impurities , and the longest diameter exceeding 1 μm An aluminum alloy substrate for a magnetic disk, wherein the number of Mg—Zn intermetallic compounds is 1 or less per 0.2 mm ² . It is a manufacturing method of the aluminum alloy substrate for magnetic discs of Claim 1, Comprising: Mg: 2.0-6.0%, Cu: 0.005-0.15%, Zn: 0.05-0.6 %, Cr: 0.01 to 0.3%, Si: 0.001 to 0.03%, Fe: 0.001 to 0.03%, and an aluminum alloy ingot consisting of the balance Al and inevitable impurities to a feature line Ukoto the hot rolled to hot-rolling end temperature of 280-360 ° C., and the difference between the surface temperature of the plate width central portion and the end portion during hot rolling termination is within 30 ° C. A method of manufacturing an aluminum alloy substrate for a magnetic disk . Mg: 2.0-6.0%, Cu: 0.005-0.15%, Zn: 0.05-0.6%, Cr: 0.01-0.3%, Si: 0.001- An aluminum alloy substrate containing 0.03%, Fe: 0.001 to 0.03%, the balance being Al and inevitable impurities , a zincate treatment part on the substrate surface, and an electroless Ni-P on the surface of the zincate treatment part Aluminum having a plated portion, wherein the aluminum alloy substrate has no more than one Al-Cu-Mg-Zn-based intermetallic compound with a longest diameter exceeding 1 μm per 0.2 mm ² and electroless Ni-P plated An aluminum alloy substrate for a ground-treated magnetic disk, wherein the number of generated pits is 1 or less per 0.2 mm ^{2 on the} surface of the alloy substrate . It is a manufacturing method of the aluminum alloy board | substrate for base-treatment magnetic discs of Claim 3, Comprising: Mg: 2.0-6.0mass%, Cu: 0.005-0.15%, Zn: 0.05-0 .6%, Cr: 0.01 to 0.3%, Si: 0.001 to 0.03%, Fe: 0.001 to 0.03%, an aluminum alloy comprising the balance Al and inevitable impurities A method for producing an aluminum alloy substrate for a ground-treated magnetic disk, characterized in that a zincate treatment is applied to a substrate surface, and electroless Ni-P plating is applied to the zincate treatment surface.

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