JPH11269593A - Aluminum alloy blank for magnetic disk base and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum alloy blank for a magnetic disk base securing plating properties equal to those of the conventional alloy and capable of improving the grindability in substrate working and to provide a method for producing the same. SOLUTION: A blank for a magnetic disk base made of an aluminum alloy is the one in which I (110)/I (100), i.e., the ratio of the X-ray integrated intensity I (110) of the crystal orientation (110) face to the X-ray integrated intensity I (100) of the crystal orientation (100) face exceeds 0.4. This blank has a compsn. contg., by weight, >=3.0% Mg, contg. one or more kinds of elements selected from the group of 0.02 to 0.l% Cr and 0.005 to 0.1% Zr, and the balance Al with inevitable impurities, and in which, among the impurities, the contents of Fe and Si are respectively regulated to <=0.05%. This aluminum alloy is cast and is subjected to each stage of facing, homogenizing treatment, hot rolling and cold rolling by a cold working ratio of 70 to 90%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy blank for a magnetic disk substrate and a method for manufacturing the same, and more particularly, to an aluminum alloy blank for a magnetic disk substrate showing excellent grindability during GR grinding and a method for manufacturing the same. It is about.

[0002]

2. Description of the Related Art In general, as a base material of a magnetic disk or the like used as a recording medium of a computer or the like, a light-weight, non-magnetic, high-rigidity, high-precision machining and polishing can easily obtain good surface accuracy, and a low cost. For this reason, aluminum alloys have been used. In particular, 5000 series aluminum alloys such as 5086 alloy,
Because of the good properties described above, it has been used as an aluminum alloy base material for HDDs through coating type media and thin film media.

[0003] Usually, a method for producing this aluminum alloy disk is according to the following procedure. That is, an aluminum ingot is formed, then subjected to a soaking and hot rolling step, and then to a predetermined thickness by cold rolling or the like. Thereafter, punching is performed into a disk shape to obtain a so-called blank. Then, while sandwiching the disc material between flat surface plates,
The so-called flat baking of annealing at the above temperature is performed. This flat baking is also necessary to create a thermally stable state during the sputtering of the magnetic layer performed in a later step. After that, substrate processing is performed. This substrate processing is a step of polishing an aluminum alloy substrate with a grindstone of about # 3000,
The purpose is as follows. That is, one is to finish to a predetermined size, and the second is to remove the oxide film layer on the surface of the blank for plating and polishing steps performed in a later step,
It is also for reducing the roughness of the aluminum surface before plating. By this substrate processing, the surface roughness of the aluminum alloy becomes about 30 nm. Thereafter, the substrate is plated with Ni-P having a thickness of 20 μm or less to give the disk strength and hardness, thereby preventing the disk from being damaged and causing a data error. Furthermore,
Since this Ni-P plating layer has a so-called plating defect, such a defect is removed and the plating film is polished so that the Ni-P plating film becomes smooth. This step makes it possible to lower the flying height of the magnetic head and obtain high-density recording. Thereafter, a magnetic layer is formed on the plating layer by sputtering and used as a magnetic disk.

[0004] In recent years, as the cost of computers has been reduced, the cost of aluminum alloy substrates has also been reduced.
Cost reduction is also required in substrate processing. As a technique for reducing the processing cost of the substrate, for example, a technique of removing an oxide film of a surface layer for the purpose of suppressing clogging of a grinding wheel which causes a reduction in a grinding speed in order to improve workability of the substrate is known. It has been proposed (Japanese Patent Laid-Open No. 5-248866).

However, the above-mentioned processing method improves the workability of the substrate by removing the oxide film of the surface layer, but does not improve the grindability of the aluminum alloy substrate itself.

As a method of improving the workability of the aluminum alloy substrate itself, it is conceivable to increase the Fe content of the aluminum alloy.

[0007]

However, if the Fe content of the aluminum alloy is increased in order to improve the workability of the aluminum alloy substrate itself, convex defects called nodules at the time of plating increase.
There is a disadvantage that the polishing amount after plating increases, and the polishing cost increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an aluminum alloy blank for a magnetic disk substrate capable of securing the same plating property as that of a conventional alloy and improving the grinding property of substrate processing. And a method for producing the same.

[0009]

An aluminum alloy blank for a magnetic disk substrate according to the present invention is a magnetic disk substrate blank made of an aluminum alloy, which has an X-ray integrated intensity I (110) of the crystal orientation (110) plane and a crystal orientation. The ratio I (1) to the X-ray integral intensity I (100) of the azimuth (100) plane
10) / I (100) is more than 0.4.

The method of manufacturing an aluminum alloy blank for a magnetic disk substrate according to the present invention comprises Mg: 3.0% by weight or more, Cr: 0.02 to 0.1% by weight, and Z:
r: contains at least one element selected from the group consisting of 0.005 to 0.1% by weight, with the balance being Al and impurities, of which Fe and Si are Fe:
Casting an aluminum alloy regulated to 0.05% by weight or less and Si: 0.05% by weight or less, each of face milling, homogenizing treatment, hot rolling, and cold rolling at a cold working rate of 70 to 90%. The process is carried out, and the ratio I (110) / I (100) of the integrated X-ray intensity I (110) of the (110) plane and the integrated X-ray intensity I (100) of the (100) plane is obtained. 0.
It is characterized by producing more than 4 aluminum alloy blanks.

In the method for manufacturing an aluminum alloy blank for a magnetic disk substrate, the method further comprises:
Mn: 0.05 to 0.5% by weight can be contained. Further, as the selected element, one or more elements selected from the group consisting of 0.02 to 0.1% by weight of Cu and 0.02 to 0.5% by weight of Zn can be contained. Furthermore, an annealing step at an annealing temperature of 260 to 400 ° C. can be provided before the cold rolling step.

In the present invention, the chemical composition of the aluminum alloy itself is the same as that of the conventional aluminum alloy for magnetic disk substrates, with the object of avoiding the deterioration of the plating layer and improving the substrate workability. is there.

According to the present invention, the present inventors have conducted various studies to solve the above-mentioned problems. As a result, in order to obtain the substrate workability without impairing the plating property, the surface of the recrystallized grains generated during the final annealing is required. The present inventors have obtained a new finding that it is extremely effective to control the azimuth, and have completed the present invention.

First, the present inventors investigated the workability of the recrystallized grains according to the plane orientation, and found that the (110) plane of the recrystallized grains, which is said to be one-sided, has excellent grinding workability. Then, by controlling the plane direction, the R-direction:
It has been found that it is effective to leave many (110).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail. First, the plane orientation will be described.

(1) Influence of the crystal grain size on the plane orientation If the recrystallized grains are small, the thermal energy consumed for each recrystallization itself during final annealing is dispersed, and the growth size is small and large. Therefore, the R-direction (1)
10) Recrystallized grains having a plane orientation increase. Since the recrystallized grains have the work strain introduced at the time of cold working as a nucleus, the higher the cold work rate, the smaller the recrystallized grains. On the other hand, there is a limit to the accumulation of working strain due to only the cold working rate, and by adding Mn or Cr as a transition element,
Precipitation as an aluminum compound in crystal grains occurs,
This is effective for accumulating processing strain.

(2) Influence of Intermediate Annealing on Plane Orientation When intermediate annealing is applied to a hot-rolled coil, recrystallization occurs, and a cubic (100) plane and an R-orientation: (110) plane grow. The cubic orientation with poor workability is dispersed by cold working performed in a later step, but the R-direction remains. Since the R-direction grows by final annealing even from various directions dispersed from the cubic direction by cold working, the occupancy of the R-direction increases by the amount of the R-direction generated by the intermediate annealing.

According to the above findings, there is no need to control the crystal grains, and it is possible to manufacture an aluminum alloy base blank having excellent grinding workability by using a conventionally used aluminum alloy. I understand.

Next, the reason for limiting the plane orientation ratio of recrystallized grains in the present invention will be described. In substrate processing, the (110) plane of recrystallized grains is excellent in grinding workability. When the X-ray integrated intensity ratio I (110) / I (100) is less than 0.40, the (110) plane of the recrystallized grains has insufficient (110) planes and sufficient grinding workability. I can't get it. Therefore, the X-ray integrated intensity ratio I (110) / I
(100) is set to 0.40 or more.

Next, the reasons for limiting the chemical components of the aluminum (Al) alloy will be described.

Mg: 3.0% by weight or more Mg is an element effective for improving the strength of an Al alloy magnetic disk substrate blank, and is usually 4% by weight as a disk material.
To some extent. If the Mg content is less than 3.0% by weight, sufficient strength as a disk material cannot be obtained.
The g content is 3.0% by weight or more. On the other hand, when the amount of Mg is 6
If the content exceeds 5% by weight, rolling cracks occur and the rolling process becomes difficult. Therefore, the content is preferably set to 6% by weight or less.

Cr: 0.02 to 0.1% by weight Cr is an element that contributes to refining of recrystallized grains. In order to obtain this effect, it is necessary to add Cr in an amount of 0.02% by weight or more. However, if Cr is added in excess of 0.1% by weight, coarsening of the crystallized material tends to proceed.
The amount of r is in the range of 0.02 to 0.1% by weight.

Zr: 0.005 to 0.1% by weight Zr is also an element that contributes to refining of recrystallized grains. In order to achieve this effect, it is necessary to add 0.005% by weight or more of Zr. However, if the amount of Zr exceeds 0.1% by weight, coarsening of the crystallized material tends to proceed, so the amount of Zr is set in the range of 0.005 to 0.1% by weight.

Mn: 0.05 to 0.5% by weight Mn is an element that contributes to refining of recrystallized grains.
This has the effect of reducing the size of plating defects. This is M
n replaces a part of the coarse Al-Fe crystallized product to form Al
(Mn · Fe), resulting in coarse Al-Fe
This is due to a decrease in system crystallization. However, Mn
If less than 0.05% by weight, a sufficient refining effect cannot be obtained, and if more than 0.5% by weight, Mn is segregated at the grain boundaries and plating defects increase rapidly. Therefore, the Mn content is 0.05 to 0.5% by weight.

Cu: 0.02 to 0.1% by weight Cu has a uniform solid solution in the Al alloy, and has an effect of uniformly and finely depositing Zn on the substrate surface during zincate treatment. Thereby, generation of nodules on the plating surface can be suppressed. However, when the amount of Cu added is 0.0
If the amount is less than 2% by weight, the above-mentioned effects cannot be obtained. If the amount exceeds 0.1% by weight, nodules are greatly generated or crystal grain boundaries are excessively etched, thereby impairing the smoothness of the plated surface. It is not preferable. Therefore, the amount of Cu is set to 0.02 to 0.1% by weight.

Zn: 0.02 to 0.5% by weight Zn also forms a solid solution in the Al alloy uniformly, has an effect of minimizing precipitation of Zn on the substrate surface during zincate treatment, and suppressing generation of nodules. doing. However, if the amount of Zn is less than 0.02% by weight, the above effect cannot be obtained, and if the amount exceeds 0.5% by weight, nodules are generated significantly or the grain boundary is excessively etched. ,
It is not preferable because it impairs the smoothness of the plated surface.
The Zn content is between 0.02% by weight and 0.5% by weight.

Fe: 0.05% by weight or less Fe is usually mixed as ingot impurities, and Al-Fe-based intermetallic compounds are easily generated in a casting process or the like. This intermetallic compound falls off during processing as a disk base, so-called substrate processing, such as cutting and polishing / grinding, and becomes a depression, or drops off in a plating pretreatment step, resulting in pits on the plating surface. Or cause nodules. Therefore, the content of Fe is set to 0.05% by weight or less. Fe is an element mixed as an unavoidable impurity. However, in order to reduce the Fe content to 0.005% by weight or less, extremely expensive metal having a purity of 99.99% by weight or the like is required. With the increase, the punchability and the substrate processability are reduced, and the effect of miniaturization of the crystallized substance when plating is saturated is also saturated, which causes a problem in the adhesion of the plating. Therefore, the Fe element must be restricted to 0.05% by weight or less as an impurity, and the regulated value is preferably 0.005% by weight or more.

Si: 0.05% by weight or less Si is usually mixed as a metal impurity, and Mg-Si-based crystallization occurs in a casting process or the like. This Mg
-Si-based crystals fall off during the pre-plating process and cause pits, so the Si content is 0.05% by weight.
The following is assumed. On the other hand, if the amount of Si is reduced to 0.005% by weight or less, an extremely expensive metal having a purity of 99.99% by weight or the like is required.
Punching properties and substrate workability are reduced, and the effect of miniaturization of crystallization is also saturated when plating is performed, which causes a problem in the adhesion of plating. Therefore, the Si element is restricted to 0.05% by weight or less as an impurity, and the regulated value is preferably 0.005% by weight or more.

Next, the manufacturing conditions of the present invention will be described.

First, a slab is formed by a conventional method and subjected to a soaking heat treatment. Subsequently, after hot rolling is performed to produce a hot coil, intermediate annealing is performed and cold rolling is performed.

The intermediate annealing is performed in order to recrystallize the hot-worked structure, promote the growth of the R-direction, and increase the R-direction of the final annealing by an amount corresponding to the growth. For this reason, it is necessary to cause recrystallization by intermediate annealing. Therefore,
If the intermediate annealing temperature is lower than 260 ° C., sufficient heat energy for recrystallization cannot be obtained, and sufficient recrystallization occurs unless industrially inappropriate annealing (approximately 50 hours or more) is performed. Absent. However, if the intermediate annealing temperature exceeds 400 ° C., the recrystallized structure at the time of intermediate annealing becomes coarse, and sufficient strength cannot be obtained after flat baking. For this reason, the intermediate annealing temperature is set to 260 to 400 ° C. In addition,
The intermediate annealing time is not particularly limited, but is preferably 30 minutes or more in order to sufficiently obtain the above-described effects. Further, if the annealing time exceeds 10 hours, the initial purpose is achieved, so that the manufacturing cost increases,
10 hours or less is desirable.

Next, the working ratio of the cold working after the intermediate annealing is similarly regulated as follows in order to sufficiently obtain recrystallization nuclei. If the working rate of the intermediate annealing is less than 70%, the working strain is insufficient, and sufficient recrystallization nuclei cannot be obtained. Therefore, the working rate is required to be 70% or more. However, when the cold working ratio exceeds 90%, the thickness of the hot coil becomes too large relative to the finished plate thickness, and it becomes difficult to obtain a product plate thickness by finish rolling, which is industrially unsuitable. For this reason, the working ratio after the intermediate annealing needs to be 70 to 90%.

In the present invention, the flat baking conditions are not particularly defined. However, this step is a process performed to improve the flatness (flatness) of the magnetic disk. And heat treatment at a temperature of 300 to 400 ° C. for 30 minutes or more while pressing.

The post-process of the cold working process is as follows.
It is sufficient to follow a conventional method, and an example is shown below. A normal rolled plate has a roughness of, for example, R = 0.1 to 0.5 μm, which is large as a disc base, and it is necessary to further reduce the distortion. Therefore, the disc surface is removed by cutting or polishing, and the so-called substrate is formed. I do. Base plating is performed on this substrate.

The plating process is usually performed by degreasing, etching, and Z
It consists of a pretreatment step such as n-substitution and an actual plating film forming step. A non-magnetic material such as Ni-P is usually used for the plating film. This plating step is performed to impart hardness to the disk surface and to prevent damage due to head crash or the like when used as an HDD. Therefore, in order to improve the strength, it is desirable that the plating thickness is at least 5 μm or more. If the thickness is too large, a large amount of plating solution is required, and the production cost increases. Not preferred. By this plating step, a so-called base plating base can be manufactured.

The underplated substrate is then subjected to a polishing step to remove plating defects and enhance surface smoothness. Further, so-called texture processing is performed as necessary, and a magnetic film is formed by sputtering or the like, and then the magnetic disk is completed.

[0037]

Next, a description will be given of a result of manufacturing a magnetic disk substrate blank according to an embodiment of the present invention and evaluating the characteristics thereof, in comparison with a comparative example which is out of the scope of the present invention.

First Example An aluminum alloy having the chemical components shown in Table 1 below was ingoted, subjected to a soaking treatment at 510 ° C., and then hot-rolled for 5 m.
m thickness, then cold-rolled to a thickness of 0.83mm
(A cold working rate of 83%). Heat treatment was performed at 350 ° C. for 3 hours, hardness was measured with a Vickers hardness tester, and tensile strength was measured using a JIS No. 5 test piece. Evaluation is hardness 60 MHv or more, yield strength 100 N / mm
² or more ◎ (excellent), hardness 57 MHv or more, proof stress 90 N /
mm ² or more was rated as (good), and less than ² mm was rated as x (poor). Further, the obtained cold-rolled sheet was 95 mm in outer diameter and 2 mm in inner diameter.
Punching to 5 mm, then performing strain relief annealing at 350 ° C. × 3 h to produce a so-called blank disk,
The integrated intensity by X-ray was measured by RAD-C manufactured by Rigaku Corporation. The measurement conditions were: tube voltage 40 KV, tube current 5
0 mA, and the target was a Cu target, 2θ angle =
30 to 140 °. The substrate processing was performed under the conditions shown in Table 2 below. Evaluation of grinding speed is 15μ
◎ (excellent) for m / min or more, ○ (good) for 10 μm / min or more,
Below that, it was evaluated as x (poor).

Further, using a commercially available plating solution, Ni-P
Was performed and plating defects were evaluated. The evaluation method was 200
Counting was performed under an optical microscope field of 1.times., And after measuring 60 fields of view per disc and 10 discs, 1
It was converted to per mm ^2. The evaluation was performed when nodules having a size of 10 μm or more were less than 1 / mm ² and there were no pits.
(Excellent) Nodules of 10 μm or more are 1 piece / mm ² or more
Less than 5 / mm ² and no pits
A sample having nodules of 5 / mm ² or more or having pits was evaluated as x (poor).

The results of these evaluations are shown in Table 3 below. All of the aluminum alloys of the examples of the present invention had excellent grinding workability and sufficient strength and plating properties.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

Second Example Next, the result of investigation on the effect of the cold working rate on the grindability will be described. An aluminum alloy having the chemical components shown in Table 4 below was agglomerated in the same manner as in the first example, and was 510 ° C.
, And hot rolling was performed to a sheet thickness at which a predetermined cold working ratio was obtained in a subsequent cold working step. Table 5 below shows the plate thickness in this hot working. Furthermore, cold rolling was performed to reduce the sheet thickness to 0.83 mm. Then 350
A heat treatment of heating to 3 ° C. for 3 hours was performed, the hardness was measured with a Vickers hardness tester, and the tensile strength was measured using a JIS No. 5 test piece. Evaluation: hardness 60 MHv or more, proof stress 1
00N / mm ² or more ◎ (excellent), hardness 57MHv more,
A proof stress of 90 N / mm ² or more was rated as ○ (good), and less than 90 N / mm ² was rated as x (poor). Further, the obtained cold-rolled sheet was made to have an outer diameter of 95.
mm, inner diameter 25mm, then 350 ° C
For 3 hours to perform strain relief annealing to produce a so-called blank disk, and to perform integrated intensity measurement using X-rays and substrate processing under the conditions shown in Table 2 above, as in the first embodiment. The evaluation of the grinding speed was evaluated as ◎ (excellent) for 15 μm / min or more, ○ (good) for 10 μm / min or more, and × for less than 10 μm / min.
(Poor).

The results of these evaluations are shown in Table 6 below. It can be seen that the aluminum alloys of the examples of the present invention are all aluminum alloys having both excellent grinding workability and sufficient strength.

[0046]

[Table 4]

[0047]

[Table 5]

[0048]

[Table 6]

Third Embodiment In this embodiment, the effect of the intermediate annealing conditions on the grindability was investigated. Similarly to the second embodiment, an aluminum alloy having the chemical components shown in Table 4 was used to form an ingot in the same manner as in the first embodiment. After that, intermediate annealing was performed under the conditions shown in Table 7 below, and the sheet thickness was finished by cold rolling to 0.83 mm (83% cold work rate). Further, a heat treatment of heating at 350 ° C. for 3 hours is performed, and the hardness is measured with a Vickers hardness meter.
The tensile strength was measured using a JIS No. 5 test piece. The evaluation was ◎ (excellent) when the hardness was 60 MHv or more and the proof stress was 100 N / mm ² or more, and the hardness was 57 MHv or more and the proof stress was 90 N / mm ^2.
The above was rated as （(good), and the one below it as × (poor). Further, the obtained cold-rolled sheet was made to have an outer diameter of 95 mm and an inner diameter of 25 mm.
Then, a so-called blank disk was prepared by performing strain relief annealing by heating to 350 ° C. for 3 hours, and the integrated intensity by X-ray was measured in the same manner as in the first embodiment. Substrate processing was performed.

The grinding speed was evaluated as ◎ (excellent) for 15 μm / min or more, ○ (good) for 10 μm / min or more, and × (poor) for less than 15 μm / min. Table 8 below shows the evaluation results of the mechanical properties and the grindability. It can be seen that the examples of the present invention are all aluminum alloys having both excellent grinding workability and sufficient strength.

[0051]

[Table 7]

[0052]

[Table 8]

[0053]

As described in detail above, according to the present invention,
The present invention significantly contributes to a reduction in the processing cost of an aluminum alloy base for a hard disk, because the aluminum alloy base for a hard disk can be manufactured with extremely improved grindability and a good plating property and sufficient strength.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C22F 1/00 661 C22F 1/00 661D 684 684C 691 691B 694 694A

Claims (5)

[Claims] In a blank for an aluminum alloy magnetic disk substrate, the ratio of the integrated X-ray intensity I (110) of the (110) plane to the integrated X-ray intensity I (100) of the (100) plane. An aluminum alloy blank for a magnetic disk substrate, wherein I (110) / I (100) exceeds 0.4. 2. Mg containing not less than 3.0% by weight,
r: at least one element selected from the group consisting of 0.02 to 0.1% by weight and Zr: 0.005 to 0.1% by weight, the balance being Al and impurities; , Fe and Si are cast from aluminum alloys in which Fe: 0.05% by weight or less and Si: 0.05% by weight or less are respectively cast, face milled, homogenized, hot rolled, and 70 to 90% cold. Each step of cold rolling is performed according to the hot working ratio, and the integrated X-ray intensity I (110) of the crystal orientation (110) plane is obtained.
And (X-ray integrated intensity of crystal orientation (100) plane I (100)
A method for producing an aluminum alloy blank for a magnetic disk substrate, comprising producing an aluminum alloy blank having a ratio I (110) / I (100) exceeding 0.4. 3. Mn: 0.05 as an essential element.
3 to 0.5% by weight.
3. The method for producing an aluminum alloy blank for a magnetic disk substrate according to item 1. 4. Further, as an optional element, Cu: 0.02
To 0.1% by weight and Zn: 0.02 to 0.5% by weight
The method for producing an aluminum alloy blank for a magnetic disk substrate according to claim 2, wherein the method comprises at least one element selected from the group consisting of: 5. An annealing temperature of 2 before the cold rolling step.
The method for producing an aluminum alloy blank for a magnetic disk substrate according to any one of claims 2 to 4, wherein an annealing step at 60 to 400 ° C is provided.