JPH10121173A - Aluminum alloy clad plate for high capacity magnetic disk substrate excellent in plating property and blistering resistance and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a low-cost aluminum alloy clad plate for a magnetic disk substrate excellent in adhesion, surface smoothness, surface quality and corrosion resistance, capable of forming a substrate plating layer free from the generation of blustering an annealing stage and free from the generation of difference in level between a core material and a surface material at the time of etching. SOLUTION: In an aluminum alloy clad plate for a high capacity magnetic disk substrate in which one side of both sides of an aluminum alloy core material are clad with a surface material, the compsn. of the surface material is composed of the one contg., by weight 0.01 to 0.15% Cu and 0.05 to 2.0% Zn, contg. one or two kinds among <=2.0% Mg, 0.01 to 0.5% Mn,. 0.01 to 0.3% Cr, 0.01 to 0.12% Zr and 0.01 to 0.05% Ni, contg., as impurity elements, <=0.05% Si, <=0.05% Fe and <=0.02% Ti and contg. other inevitable impurity elements respectively by <=0.02%, and the balance Al.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an undercoating layer which is excellent in adhesion, surface smoothness, surface quality, and corrosion resistance and which does not swell during the annealing step. The present invention relates to a low-cost, low-cost aluminum alloy clad plate for a high-capacity magnetic disk substrate and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, a magnetic disk has been required to have a large capacity and a high density due to needs of multimedia and the like, and a magnetic area per bit of the magnetic disk has been further miniaturized. The distance from the magnetic disk also tends to decrease. Substrates used for such magnetic disks are required to have the following characteristics. It is made of a non-heat-treated (non-precipitation hardened) light alloy and has sufficient strength to withstand high speed rotation during various processing and use.
A good mirror surface free of micropits and the like can be obtained by polishing, the surface after the base plating is smooth and no defects such as micropits are generated, and the adhesion of the base plating layer is good.

Conventionally, a magnetic disk substrate is provided with impurity elements such as Fe and Si which cause micropits or the like.
JIS-A-5086 alloy is used. And this substrate is hot rolled ingot (slab) obtained by semi-continuous casting method,
Next, cold rolling is performed while annealing is performed, and the rolled material is punched into a disc shape. This disc shape is subjected to cutting, grinding, polishing, degreasing, etching, zincate treatment as a pretreatment, and then Ni- as a base treatment. It is manufactured by subjecting a hard non-magnetic metal such as P to electroless plating and polishing, and then sputtering a magnetic material such as a Co-Ni-P alloy.

However, the JIS-A-5086 alloy substrate has insufficient surface smoothness after electroless plating. That is, cutting,
During pretreatment such as grinding, polishing, and zincate treatment, the intermetallic compound protrudes and remains or the intermetallic compound falls off, causing nodules (hemispherical protrusions) or Micro pits occur. The nodules collide with the magnetic head and cause a head crash, and the micro pits cause an electrical error. Therefore, to improve the surface quality of the magnetic disk, measures have been taken to reduce the number and size of the intermetallic compounds in the aluminum alloy substrate, but a sufficient effect has not always been obtained. Various other measures have been taken, but all have complicated processing steps and high manufacturing costs. The nodules may be caused by an Al-Fe intermetallic compound or the like protruding into the surface layer and this protruding portion being plated to form a nodule, or zincate growing preferentially in a small concave portion in a convex shape. May be plated to form nodules.

Recently, for the purpose of increasing the strength, an Al-Mg-Zn alloy (7000) of an age hardening type aluminum alloy has been used as a core material.
(Alkali-based alloys) and clad Al-Mg-based alloys (5000-based alloys) as a skin material having good plating properties on this core material have been developed (JP-A-5-9633 and JP-A-5-9633). -Four
No. 3970). However, since this clad plate uses a 7000 series alloy containing a large amount of Zn (usually 4 wt% or more) as the core material, the potential difference between the core material and the skin material is large, and the core material is used in the etching process before zincate treatment. May be preferentially dissolved and a step may occur with the skin material. When the step is large, the step may be caught when the magnetic disk is loaded on the shaft, and the skin material may peel off. Further, if the compositions of the core material and the skin material are not properly combined, sufficient bonding strength may not be obtained by rolling welding.

[0006] From the above, the present inventors have proposed a method for a magnetic disk substrate in which an underlying plating layer (electroless Ni-P alloy plating layer) with few defects can be obtained by controlling the type and addition amount of alloying elements. An aluminum alloy clad plate was proposed (Japanese Patent Laid-Open No. 2-97639). This aluminum alloy clad plate for a magnetic disk substrate has already been put to practical use and has been highly evaluated.

[0007]

The capacity of magnetic disks has been increasing year by year, and in recent years, a storage capacity of 2 GB / sheet or more has been required. To increase the capacity, it is considered to reduce the flying height (glide height) of the magnetic head. However, in the current substrate, as described above, nodules and micro pits may be formed on the front and back surfaces after the base plating. There is a problem that the influence of the nodules and micro pits increases as the glide height decreases. In order to reduce nodules and micropits, a method using a high-purity metal with few impurity elements such as Si and Fe can be considered.
(9.99wt% purity) is much more expensive than the usual one (99.9wt% purity), and its amount is limited.
Also, the strength is not enough.

[0008] From the above, the present inventors have conducted various investigations and studies for the purpose of reducing the micropits and nodules. As a result, among intermetallic compounds, M
g ₂ Si intermetallic compound and Al-Fe intermetallic compound are larger in size than others, thus reducing the number of Al-Fe intermetallic compound and Mg ₂ Si intermetallic compound, By reducing the size, micropits and nodules can be significantly reduced. In addition, since the Al-Fe intermetallic compound and the Mg ₂ Si intermetallic compound have a higher (noble) spontaneous potential than the matrix, It has been found that micropits and nodules can be reduced by increasing the natural potential of the sample and reducing the natural potential difference between the two, and applied for a patent earlier (Japanese Patent Application No. 8-258607).

Further, the corrosion resistance of the magnetic disk substrate is one of the important characteristics, but the conventional one is not satisfactory. As a result of various studies, the present inventors have clarified that as a cause of reducing the corrosion resistance, not only the corrosion resistance of the substrate but also the minute defects in the plating film have a great effect. In addition, blisters are a surface defect that may cause a head crash similarly to the nodule. This swelling occurs when a dent or the like is made on the substrate material after punching the plate material or before sputtering the medium (magnetic material), and a region having a locally high residual stress is formed in this portion, It occurs when the residual stress is released in the subsequent annealing step. As a result of examination, it was found that this swelling had a correlation with the material strength. Mg is an alloy element that greatly contributes to the material strength, and swelling is likely to occur in proportion to the content of Mg.
It is also considered that the alloy containing Mg tends to increase the amount of hydrogen gas because Mg is easily bonded to oxygen and hydrogen. However, the strength,
50 containing about 4wt% Mg from the viewpoint of machinability, grindability, etc.
Since a 00-based material was used, no significant improvement could be expected with regard to blistering. A clad plate using a low-strength aluminum alloy containing no or a small amount of Mg as a skin material has also been proposed (JP-A-63-319142 and JP-A-63-319143). However, it is inferior in cutability and grindability due to inappropriateness.

The present invention has been made in view of the above problems, and as a result of various studies,
The adhesion and surface smoothness of the base plating layer (electroless Ni-P alloy plating layer) can be adjusted by applying a thin and uniform pre-treatment zincate film, making the crystal grains of the material fine, and adding a small amount. They have found that improvement can be achieved by controlling the potential difference between the matrix and the intermetallic compound by an element, and that a synergistic effect can be obtained by combining them, and further research has led to the completion of the present invention. When the surface smoothness and the surface quality of the base plating layer are improved, the corrosion resistance is increased, and the trace addition element for controlling the potential difference also reduces the minute defect of the base plating layer. The present invention is excellent in adhesion, surface smoothness, surface quality, corrosion resistance,
It is an object of the present invention to provide a low-cost aluminum alloy clad plate for a magnetic disk substrate and a method for producing the same, which can form a base plating layer that does not cause swelling in an annealing step and does not generate a step between a core material and a skin material during etching.

[0011]

According to the first aspect of the present invention,
In an aluminum alloy clad plate for a high-capacity magnetic disk substrate having a clad clad on one or both sides of an aluminum alloy core, the composition of the clad is Cu 0.01 to 0.15 wt%.
, Zn 0.05-2.0 wt%, Mg 2.0 wt% or less, Mn 0.01-
0.5wt%, Cr0.01 ~ 0.3wt%, Zr0.01 ~ 0.12wt%, Ni0.01 ~
One or two or more of 0.05 wt%, as an impurity element, Si 0.05 wt% or less, Fe 0.05 wt% or less, Ti0.02 wt% or less,
And an aluminum alloy clad plate for a high capacity magnetic disk substrate having excellent plating properties and swelling resistance, characterized by containing 0.02 wt% or less of each of the other unavoidable impurity elements and the balance being Al.

According to a second aspect of the present invention, the core material contains at least less than 3.0 wt% of Zn, and the balance is composed of Al and an unavoidable impurity element. This is an aluminum alloy clad plate for a high capacity magnetic disk substrate with excellent performance.

According to a third aspect of the present invention, the ratio [Fb / Fs] of the F value (Fb) of the core material and the F value (Fs) of the skin material represented by the following formula:
3. The aluminum alloy clad plate for a high-capacity magnetic disk substrate according to any one of claims 1 and 2, wherein the aluminum alloy clad plate has excellent plating properties and swelling resistance. F = Si + Fe + 2Cu + 2Mn + 3Mg + 0.5Zn (where Si, Fe, Cu, M
n, Mg, and Zr are wt% of each).

According to a fourth aspect of the present invention, there is provided an aluminum alloy clad for a high-capacity magnetic disk substrate, which comprises subjecting a composite material in which a cladding material is clad on one or both sides of an aluminum alloy core material to hot rolling, cold rolling and final annealing. In the sheet manufacturing method, cooling after hot rolling, cooling after intermediate annealing during cold rolling, and cooling after final annealing are each 240 to 15 times.
0 ° C at a rate of 30-600 ° C / hr.
4. The method for producing an aluminum alloy clad plate for a high-capacity magnetic disk substrate according to claim 3, wherein the rolling is performed three times or more at a rolling rate of 0% or more and at a total rolling rate of 60% or more.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, alloy elements of a skin material will be described. When an appropriate amount of Cu is added, it reduces the amount of Al dissolved during zincate treatment, furthermore, makes the zincate film thin and uniform and densely adheres, increases the surface smoothness of the underlying plating layer, and reduces fine defects in the plating layer. The important properties of corrosion resistance are improved. Cu content 0.01 ~ 0.15wt
The reason for specifying% is that if the content is less than 0.01% by weight, the effect is not sufficiently obtained, and if it exceeds 0.15% by weight, the corrosion resistance of the skin material itself is significantly reduced. When the corrosion resistance of the skin material itself is reduced, the zincate treatment film is formed unevenly, and the adhesion and the surface smoothness of the base plating layer are reduced.

Zn reduces the amount of Al dissolved during zincate treatment, and smoothes the surface of the plating layer in the subsequent base plating. The reason for defining the content to be 0.05 to 2.0 wt% is as follows:
If the content is less than 0.05 wt%, the effect cannot be sufficiently obtained, and if the content exceeds 2.0 wt%, the rolling workability and the corrosion resistance deteriorate. When the corrosion resistance decreases, the zincate treatment becomes uneven, and the adhesion and surface smoothness of the base plating layer decrease.

[0017] Mg contributes to the improvement of the strength, and also improves the machinability and grindability to enhance the surface quality. However, if the strength is increased by the addition of Mg, the base plating layer is likely to swell in the annealing step. As described above, as described above, a region having a high residual stress is locally formed when a dent is made after punching a plate material or before sputtering a medium (magnetic material), and the subsequent annealing step Occurs when the residual stress is released. Therefore, the Mg content is specified to be 2.0 wt% or less. The decrease in the machinability and grindability due to the reduction in the Mg content or the absence of Mg is compensated for by adding an appropriate amount of transition elements such as Mn, Cr, Zr, and Ni.
Mn, Cr, Zr, and Ni generate minute intermetallic compounds during casting and annealing to make the recrystallized structure fine. Thereby, the cutting and grinding properties of the substrate are improved, and the adhesion of the base plating layer is improved. The content of each of Mn, Cr, Zr, and Ni is set to 0.
01-0.5wt%, 0.01-0.3wt%, 0.01-0.12wt%, 0.01-0.
The reason specified in 05wt% is that below the lower limit, each effect is not sufficiently obtained, and above the upper limit, coarse intermetallic compounds are formed in all cases, and this intermetallic compound is etched, zincate treated, and cut. This is because they may fall off during grinding and become pit defects. Among these elements, Mn, Cr, Zr
The effect can be sufficiently obtained by adding singly, however, a further effect can be obtained by adding a plurality of them.

Si, Fe and Ti hardly form a solid solution in the Al matrix and exist as intermetallic compounds. The upper limit of each content was specified because, if the amount is large, Al-Fe based, Mg ₂
This is because a large number of coarse intermetallic compounds such as Si are generated and are likely to become pit defects at the time of cutting or grinding a substrate, at the time of zincate treatment, or the like. Other unavoidable impurity elements (eg, N
i, B, etc.) do not affect the characteristics of the clad plate of the present invention if each is 0.02 wt% or less.

Next, the alloying elements of the core material will be described.
Zn makes the potential of the core material base. The Zn content is desirably less than 3.0 wt%. If Zn is contained in an amount of 3.0 wt% or more, the potential difference with the skin material becomes too large, and the core material is preferentially dissolved in the etching step performed before the base plating, and a step occurs at the boundary with the skin material, or extreme In such a case, the core material and the skin material may peel off.

In the present invention, various methods can be applied to clad the skin material and the core material. For example, there is a rolling pressure welding method usually used for manufacturing a brazing sheet. This rolling pressure welding method uses hot rolling,
Cold rolling and final annealing are performed. In the rolling pressure welding method, F = Si + Fe + 2Cu + 2Mn + 3Mg + 0.5Zn (where Si, F
e, Cu, Mn, Mg, Zn are each wt%) F value of core material expressed by the formula
If the ratio [Fb / Fs] of (Fb) to the F value (Fs) of the skin material is 0.6 or more, good joining can be achieved. When the ratio [Fb / Fs] is less than 0.6, the core material is preferentially rolled during hot rolling, so that the skin material is not sufficiently rolled and the bonding strength may be insufficient. Since lamination may occur even when the ratio [Fb / Fs] is 0.6 or more, the ratio is particularly preferably 1.0 or more.

The aluminum alloy clad plate of the present invention comprises:
Since the core material is clad with a skin material, when increasing the purity of the metal to reduce defects such as micropits and nodules, high-purity metal only needs to be used for the skin material where surface defects are a problem. As the material, an inexpensive low-purity metal can be used as long as the above composition is satisfied. Therefore, the manufacturing cost can be reduced comprehensively.

Clad ratio per side of skin material in the above-mentioned rolling pressure welding method 圧 [Thickness of skin material / (thickness of core material + thickness of skin material)] ×
100%｝ is preferably 30% or less. This is because, when the cladding ratio exceeds 30%, the shearing force generated at the time of pressing against the interface between the skin material and the core material is weakened, and sufficient bonding strength cannot be obtained.

In the present invention, the cooling after the hot rolling, the cooling after the intermediate annealing performed during the cold working, and the cooling after the final annealing are performed at a speed of 30 to 600 ° C./hr at 240 to 150 ° C., respectively. It is desirable. This is because Mg ₂ Si
Does not precipitate, and there is no problem even at temperatures lower than 150 ° C. Cooling rate is 30 ℃
If it is less than / hr, the amount of Mg ₂ Si deposited increases, and if it exceeds 600 ° C / hr, thermal strain occurs and the flatness of the substrate decreases. Here, the hot rolling temperature for joining the skin material and the core material may be heated to a temperature at which rolling can be performed, and is not particularly limited. However, considering the problem of coarsening and melting of the crystal grain size of the material to be rolled, the range of 350 to 550 ° C is desirable.

In the present invention, the rolling reduction in one cold rolling is
Preferably, the cold rolling is performed three times or more, and the total rolling ratio is 60% or more. Under these conditions, Al-Fe intermetallic compounds that cause surface defects, particularly nodules, are sufficiently pulverized.

In producing the clad sheet of the present invention by the rolling pressure welding method, the skin material is obtained by homogenizing an ingot obtained by a semi-continuous casting method and then hot rolling to a sheet material having a predetermined size. The temperature conditions for the homogenization and hot rolling at this time are optimally selected according to the composition of the skin material. However, if the rolling temperature is too high, the crystal grains of the ingot become coarse, and in extreme cases, they melt. If the rolling temperature is too low, the deformation resistance increases and rolling cannot be performed. Taking these factors into consideration, the homogenization treatment temperature or the hot rolling start temperature is desirably 350 to 550 ° C. When the sheet material after hot rolling is washed with nitric acid, caustic soda, or the like, an oxide layer generated by hot rolling is removed, and good pressure contact with the core material is performed.

The core material is made into an ingot by a semi-continuous casting method,
The ingot is covered with a skin material. After the homogenization treatment, the side of the ingot for core material which is covered with the skin material is chamfered, so that the internal structure becomes uniform, and the oxidized layer on the surface is removed, so that good pressure welding is achieved. Homogenization treatment temperature is the same as that for leather 350 to 550
C is desirable. The clad plate joined by hot rolling is finished to a predetermined thickness by cold rolling and annealing.

In the present invention, the diameter of the intermetallic compound contained in the skin material is desirably 10 μm or less. that is,
The pits formed by dropping the intermetallic compound of 10 μm or less are
The reason for this is that although the size of the pit is considerably reduced by electroless plating or grinding after plating, pits formed by dropping an intermetallic compound exceeding 10 μm are likely to ultimately remain as defects.

[0028]

The present invention will be described below in detail with reference to examples. (Example 1) Using a skin material and a core material having the compositions shown in Table 1, a single-sided mating material having a cladding ratio of 10% was produced, and this mating material was reheated to 500 ° C and then hot-rolled to a thickness of 2.30 mm. Rolled and then cold rolled to a thickness of 0.82 mm. Next, the cold-rolled material was cut into a predetermined size, and then unwashed to obtain a clad plate.

The details of the method for producing the skin material and the core material and the conditions for hot rolling, cold rolling and unwashing of the combined material are shown below. Production method of skin material: 30mm thick ingot is cut into 5mm by 5mm on both sides to 20mm thickness and homogenized (450 ℃ × 2hr + 5
After performing 20 ° C x 2 hours), hot rolling (rolling start temperature 470 ° C, end temperature 230 ° C, cooling rate 50 ° C / hr) to make a 5mm thick plate, cut this plate into predetermined dimensions, Unwashed [hot water →
3% nitric acid desmut (1 minute) → 5% caustic soda (5 minutes) → 3% nitric acid desmut (1 minute) → Hot water]. Manufacturing method of core material: Homogenize 60mm thick ingot (450 ℃)
× 2hr + 520 ℃ × 2hr), then cut both sides 10mm each, thickness 40
mm. The casting of the skin material or the core material was performed after filtering the molten alloy adjusted to a predetermined composition with a filter after degassing and calming treatment. Hot rolling of laminated material: reheating temperature 500 ℃, rolling start temperature
470 ℃, coil winding temperature 260 ℃, cooling rate 50 ℃ / hr,
2.30mm thickness after hot rolling. Cold rolling of laminated material: 1.60 mm in the first pass (30% reduction),
1.12mm at second pass (30% rolling reduction), 0.82mm at third pass (rolling reduction)
27%), total reduction 64%. Unwashing of laminated material: Same as unwashing of skin material.

Next, an outer diameter of 96 mm and an inner diameter of 96 mm
A 24 mm donut plate was punched out, annealed at 340 ° C. for 4 hours, cooled at a cooling rate of 50 ° C./hr, and further subjected to grinding. Thereafter, surface treatment and electroless plating were performed according to the following procedure. That is, degreasing with acetone → 5%
Etching by immersing in NaOH aqueous solution (40 ° C) for 30 seconds → 30% H
Desmut with NO ₃ aqueous solution (room temperature) for 30 seconds → ARB 302ZN
(Trade name, Okuno Pharmaceutical Co., Ltd.) Double zincate treatment → Ni-P 17μ using Niclad 719 (trade name, Okuno Pharmaceutical Co., Ltd.)
Electroless plating to a thickness of m, finish polishing: lapping, polishing amount 4 μm.

Donut plate after finish polishing
(B) The properties of the end face, (b) the adhesion of the plating film, (c) the surface smoothness, (d) the surface defects, (e) the corrosion resistance, and (f) the swelling resistance were investigated. (A) The properties of the end face were evaluated as x when a step was formed on the end face and as ○ when the end face was healthy without any step. (B) To determine the adhesion of the plating film, cut out a 50 mm ² sample, heat it to a temperature of 400 ° C for 30 minutes, and immediately cool it with water, and then examine the peeling or swelling of the substrate and Ni-P alloy plating layer due to the difference in thermal expansion. Was. A sample without peeling or swelling was evaluated as ○, a sample slightly generated was evaluated as △, and a sample generated many times was evaluated as ×. (C) The surface smoothness was measured by measuring the surface roughness of the ground plating layer after polishing with a universal surface roughness meter SE-3H (manufactured by Kosaka Laboratories) and measuring the center line roughness specified in JIS-B-0601. Sa Ra (μ
m) was measured at four points and represented by the average value. (D) Surface defects were evaluated as x when the maximum size of defects such as pits or nodules was 3 µm or more, and evaluated as o when the size was less than 3 µm. (E) The corrosion resistance was evaluated by a hydrochloric acid resistance test (immersion in a 1N hydrochloric acid solution at room temperature for 24 hours). When the peeling or swelling did not occur in the plating film, it was evaluated as ○, when it slightly occurred, as Δ, and when many occurred, it was evaluated as ×. (F) The swelling resistance is determined by applying a load of 5 Kgf with a Vickers hardness tester to any part of the substrate after grinding to form an indentation, and then annealing at 270 ° C. for 1 hour, thereby increasing the degree of swelling at the indented part. The universal surface roughness was measured. The height of the blister is
0.5 μm or less was judged as a pass level. The results are shown in Tables 1 to 3.
Shown in The table also shows whether cladding is possible.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

As is clear from Tables 1 to 3, the present invention
Nos. 1 to 12 had no step on the end face, excellent adhesion of the underlying plating layer, a smooth surface, no surface defects, excellent corrosion resistance, and no swelling. On the other hand, No. 13 of the comparative example had Si as the skin material, No. 14 had Fe as the skin material, and No. 24
Since the skin material contained a large amount of Ti in each case, many coarse intermetallic compounds were generated, and surface defects also occurred. In No. 15, the skin material does not contain any of Mg, Mn, Cr, Zr, and Ni, so the machinability and grindability are reduced, the corrosion resistance is reduced, and the adhesion of the base plating layer is also reduced. did. The surface became rough. No. 16 has Mn and Ni as the skin material, but No.
In No. 23, a large amount of Zr was contained in the skin material, so that coarse intermetallic compounds were formed, and the surface quality, corrosion resistance, and adhesion were reduced. In No. 17, since the skin material did not contain Cu, the zincate treatment was uneven and the adhesion was poor. N
In o.18, since the skin material contained a large amount of Cu, the corrosion resistance of the skin material itself was reduced, the surface became extremely rough, and the adhesion was also reduced. In addition, since a large amount of Zn was contained in the core material, a large amount of the core material was dissolved in the etching step, resulting in a difference in the end face. In No. 19, a large amount of Mg was contained in the skin material, and large swelling occurred in the annealing step. In No.20, a large amount of Cr and Ni were contained in the skin material, so that coarse intermetallic compounds were formed and defects occurred on the surface. In addition, the adhesion was reduced and the surface became rough. No. 21 has a low Zn content in the skin material.
Since there were many of them, the zincate treatment was uneven and the adhesion was lowered. No.25 has a ratio [Fb / Fs] of 0.6
Therefore, the bonding between the core material and the skin material was insufficient.

Example 2 Alloys of the alloys of the present invention shown in Table 1
A laminated material was prepared using the skin material and core material of No. 1 and the alloy No. 15 of the comparative material, and after reheating this laminated material to 500 ° C, hot rolling was started at 470 ° C to various thicknesses. Rolling, then 0.82mm
Was cold rolled. Next, the cold-rolled material was cut into a predetermined size and washed with a light to produce a clad plate. The coil winding temperature, cooling rate, plate thickness, cold rolling reduction ratio, and intermediate annealing conditions in hot rolling were variously changed. The unwashing was performed in the same manner as in Example 1. The production of the core material and the skin material was performed in the same manner as in Example 1. Next, a donut plate having an outer diameter of 96 mm and an inner diameter of 24 mm was punched from the clad plate, annealed at 340 ° C for 4 hours, cooled at a cooling rate of 20 ° C / hr, and further subjected to grinding. After that, the following quality evaluation was performed on those subjected to surface treatment and electroless plating according to the same procedure as in Example 1. Evaluation of the donut plate after the grinding process Mg ₂ Si: The number in a field of view of 3 mm ² was measured with a scanning electron microscope (SEM). Those exceeding 5 μm are 20 / mm ² or less as acceptable levels. Al-Fe-based intermetallic compound: The number in a visual field of 3 mm ² was measured by SEM. Those exceeding 5 μm are 10 / mm ² or less as acceptable levels.

Evaluation of donut plate after base plating Micro pits: The number in a visual field of 3 mm ² was measured with an optical microscope. When the number is less than 5, A is indicated, when 5 or more is less than 15, B is indicated, when 15 or more is less than 25, C is indicated, and when 25 or more is indicated, D. Nodule: The number in a visual field of 3 mm ² was counted with an optical microscope. The case where the number exceeding 10 μm is less than 5 is indicated as A, the case where the number is 5 or more and less than 15 is B, the case where the number is 15 or more and less than 25, and the case where the number is 25 or more.

Evaluation of Donut Plate After Etching The presence or absence of a step at the end face was examined. In the case of a healthy end face without a step, it was indicated by ○, and in the case of a step, × was indicated. Finally, the micro pits, nodules, and the properties of the end face are comprehensively evaluated.
To E were evaluated in five steps. A, B, C are acceptable levels,
X indicates rejection, and production failure indicates ━. The results are shown in Table 4 together with the production conditions.

[0039]

[Table 4]

As is clear from Table 4, all of the products of the present invention (samples Nos. 26 to 30) had few micropits and nodules, and had good end face properties. Was. In sample No. 34, the cooling rates after hot rolling and after final annealing were slow and the total rolling ratio was low, so that micropits and nodules having a larger size than the others increased. On the other hand, since the sample No.31~34 is the alloy composition is out of scope of the present invention, depending on production conditions Mg ₂ Si and A
Some of the compounds, such as l-Fe-based compounds, had a small content of 5 μm or more, but all of them generated many large-sized micropits or nodules, and all were rejected as a whole.

[0041]

As described above, according to the present invention,
Low cost aluminum for magnetic disk substrates with excellent adhesion, surface smoothness, surface quality, and corrosion resistance, capable of forming a base plating layer that does not cause swelling during the annealing process, does not generate a step between the core material and the skin material during etching An alloy clad plate is obtained,
The media is well coated. In addition, low-purity Al can be used for the core material, and it is inexpensive. Furthermore, it can be easily manufactured by the rolling pressure welding method. Therefore, there is an industrially significant effect.

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[Procedure amendment]

[Submission date] April 8, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0032

[Correction method] Change

[Correction contents]

[0032]

[Table 1]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

[0033]

[Table 2]

Continuation of the front page (51) Int.Cl. ⁶ identification code FI G11B 5/84 G11B 5/84 Z // C22F 1/00 627 C22F 1/00 627 661 661D 685 685Z 686 686A 692 692A 694 694A G11B 5/62 G11B 5/62

Claims (4)

[Claims] An aluminum alloy clad plate for a high-capacity magnetic disk substrate in which a skin material is clad on one or both sides of an aluminum alloy core material, wherein the skin material has a composition of Cu
0.01 ~ 0.15wt%, Zn0.05 ~ 2.0wt%, Mg2.0wt% or less, Mn0.01 ~ 0.5wt%, Cr0.01 ~ 0.3wt%, Zr0.01 ~ 0.12wt
%, Ni 0.01 to 0.05 wt%, one or more of Ni, and 0.05 wt% or less of Si, 0.05 wt% or less of Fe, Ti0.
02 wt% or less and other unavoidable impurity elements
Aluminum alloy clad plate for high-capacity magnetic disk substrates with excellent plating properties and swelling resistance, containing up to 02 wt% and the balance being Al. 2. The high-capacity magnetic material according to claim 1, wherein said core material contains at least less than 3.0 wt% of Zn, and the balance consists of Al and unavoidable impurity elements. Aluminum alloy clad plate for disk substrate. 3. The ratio [Fb / Fs] of the F value (Fb) of the core material and the F value (Fs) of the skin material represented by the following formula, which is 0.6 or more: An aluminum alloy clad plate for a high-capacity magnetic disk substrate excellent in plating properties and swelling resistance according to any one of the above. F = Si + Fe + 2Cu + 2Mn + 3Mg + 0.5Zn (where Si, Fe, Cu, M
n, Mg, and Zr are wt% of each). 4. A method for producing an aluminum alloy clad plate for a high-capacity magnetic disk substrate, comprising subjecting a composite material in which a cladding material is clad on one or both surfaces of an aluminum alloy core material to hot rolling, cold rolling and final annealing. Cooling after hot rolling, cooling after intermediate annealing during cold rolling, and cooling after final annealing are performed at 240 to 150 ° C and 30 to 600 ° C / h, respectively.
4. The aluminum alloy for a high-capacity magnetic disk substrate according to claim 3, wherein the cold rolling is performed at a rolling rate of 20% or more at least three times, and the total rolling rate is 60% or more. Manufacturing method of clad plate.