JPH03100146A - Production of high capacitance-aluminum disk - Google Patents

Abstract

PURPOSE:To improve the surface preparation characteristic of a high capacitance-Al disk base and to remove defects after plating, such as pits, by heating and holding a semicontinuously cast ingot of an Al-Mg alloy in which specific amounts of Cu and Zn are added at a specific temp. and then carrying out rolling. CONSTITUTION:A semicontinuously cast ingot of an Al alloy having a composi tion consisting of, by weight, <=0.05% Si, <=0.05% Fe, 0.05-0.4% Cu, 3.5-4.5% Mg, 0.05-0.4% Zn, and the balance essentially Al is heated at 500-560 deg.C for >=2hr and is then held, without cooling, at 530-560 deg.C for >=4hr, by which Mg2Si precipitating in the ingot is allowed to enter into solid solution again. Then, hot rolling and cold rolling is applied to the above to the prescribed sheet thickness. By this method, defects after plating can be reduced and the disk base can be made high-capacitance.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of manufacturing an aluminum disk substrate used as a magnetic recording medium for computers with a high storage capacity. (Prior Art) Methods for manufacturing aluminum magnetic disk substrates used as magnetic recording media for computers can be roughly divided into two types depending on the type of storage medium. One type is one in which a magnetic film is coated on a mirror-finished aluminum substrate (coating type media), and the other is in which a base treatment such as N1-P plating is applied to the aluminum substrate, and then a magnetic film is plated on top of that. It is applied by sputtering or sputtering (thin film type media). Conventionally, coated media have been the mainstream, and Al-Mg alloys (eg, 5086) have been used for the disk substrate. On the other hand, in order to achieve high storage capacity, it is necessary to make the magnetic film as thin as possible, and for this reason, recent efforts have been made to make the magnetic film as thin as possible. Thin film media is becoming mainstream. Aluminum substrate materials for thin film media include:
An alloy in which Cu, Zn, etc. are added to an Al-Mg alloy has been developed and put into practical use. (Problems to be Solved by the Invention) By the way, methods for manufacturing thin film media can be roughly divided into the following three types. ■Metsuki-metsuki type: Plating (Ni-P) → Polish → Metzki (Go-Ni-P) ■Metsuki sputter type: Plating (Ni-P) → Polish-Sputter (γ-Fa, O,, C. -Ni) ■Alumite sputter type: Alumite → Polish → Sputter (γ-Fe, O, Go-Ni) Among these, in the case of the Metsuki-Metsuki type and the Metsuki-Sputter type, prior to plating, degreasing and zincate treatment ( Etching (processing to uniformly form a zinc-substituted film layer on the surface of aluminum) is performed, but in the subsequent plating process, good zincate treatment properties and excellent plating adhesion and smoothness are required. Ru. In addition, it is necessary to avoid forming non-uniform portions such as pits in the pretreatment process. However, the conventional A Q -Mg -Cu -Zn
When using a base alloy for thin-film media, more specifically, when using a base treatment such as N1-P plating, minute pits (holes) are formed during the chemical treatment performed before the main treatment, and the plating Since the pits remain unrepaired even after the process is completed, and the pits remain even when the media is made into a product, there is a problem in that it causes problems such as magnetic properties and errors. The present invention eliminates the drawbacks of the conventional techniques, improves the surface treatment properties, especially the zincate treatment properties, of high-capacity aluminum disks for thin-film media, and eliminates defects such as pits after plating. The purpose is to provide a method that can be used. (Means for Solving the Problems) In order to achieve the above object, the inventors of the present invention investigated the causes of the deterioration of zincate processability and the occurrence of pit defects, and conducted extensive research on countermeasures. As a result, (1) the uniformity of the zincate treatment is obtained by uniformly dispersing precipitates in the aluminum alloy, especially Zn and Cu, and (2) the aluminum alloy contains HeΩ-Fe and Mg- Numerous 8L-based intermetallic compounds exist and become the core of pit formation during the etching process. In order to prevent this, impurity elements such as Fe and Si are regulated and heat treatment conditions for the ingot are controlled. It has been found that the formation of intermetallic compounds, which are the source of pits, can be controlled by doing so, and the present invention has been made here. That is, the method for manufacturing a high-capacity aluminum disk substrate according to the present invention includes Si≦0.05% and Fe50.05%.
, Cu: 0.05-0.4%, Mg: 3.5-4.5%
and Zn: 0.05 to 0.4%, and the balance is substantially Al.
It is characterized by being heated at a temperature of ~530°C for 2 hours or more, then held at a temperature of 530~560°C for 4 hours or more without cooling, and then rolled to a predetermined thickness. be. The present invention will be explained in more detail below. (Function) First, the reason for limiting the chemical components in the present invention will be explained. Si: Si is unavoidably mixed in from aluminum ingots and melting furnace refractories, etc., and combines with Mg, the main component of this alloy, to form Mg-8i-based intermetallic compounds (mainly Mg and Si). To prevent this, the amount of Si is set to 0.05%.
The following regulations apply. Fe: Like Si, Fe is unavoidably mixed in from the aluminum base metal, the melting furnace body, jigs, etc., and combines with Al to form AQ-Fe-based intermetallic compounds (mainly FeAfls).
To prevent this, the amount of Fe is 0.05.
% or less. Cu: Cu is uniformly dissolved in Al and precipitated uniformly during heat treatment, and has the effect of making the zincate treatment uniform. However, if it is less than 0.05%, it has no effect, and if it exceeds 0.4%, it will concentrate at grain boundaries, strengthen grain boundary etching during zincate treatment, and impair surface roughness. is in the range of 0.05 to 0.4%. Zn: Like Cu, Zn is also uniformly dissolved in Al and precipitated uniformly during heat treatment, which has the effect of making the zincate treatment uniform. However, if it is less than 0.05%, it has no effect, and if it exceeds 0.4%, it will precipitate concentrated at the grain boundaries, and the grain boundary etching during zincate treatment will become stronger, so the amount of Zn should be 0.05 to 0. .4% range. Mg: Mg is an element that ensures the strength of this alloy through solid solution strengthening. However, if it is less than 3.5%, the desired strength cannot be obtained;
Moreover, if it exceeds 4.5%, it is not preferable because it inhibits workability during rolling and combines with impurity Si to form an Mg-8i intermetallic compound. Therefore, Mg
The amount should be in the range of 3.5-4.5%. Next, the manufacturing process and conditions of the present invention will be explained. The aluminum alloy having the above chemical components is melted by a conventional method and made into an ingot by semi-continuous casting. The obtained ingot has a non-uniform internal structure, and impurities and alloying elements are segregated. Therefore, first. Heat treatment is required to uniformly disperse this. In this case, if the heating temperature is less than 500°C, the effect will be small, and if it exceeds 530°C, it will cause eutectic melting and cause defects such as burning, which is not preferable, so the heating temperature should be in the range of 500 to 530"C. In addition, regarding the heating time, since the effect cannot be obtained if the heating time is less than 2 hours, it is necessary to heat in the above temperature range for 2 hours or more.
It is necessary to perform heat treatment to maintain the temperature at 60°C. This is a heat treatment for re-dissolving Mg and SL precipitated in the ingot. However, at temperatures below 530°C, solid solution does not occur and further growth occurs, and at temperatures above 560"C,
The ingot is not preferable because it causes local re-melting (burning). Further, the holding time is set to 4 hours or more, since the effect cannot be obtained if the holding time is less than 4 hours. The ingot subjected to the above heat treatment is subjected to hot rolling and/or cold rolling to obtain a predetermined thickness. Naturally, it is also possible to reduce the thickness to a predetermined thickness by just hot rolling. It goes without saying that after rolling, an aluminum base is formed in the same manner as before. For example, after punching, it is mirror finished, the base treatment (metsuki), polishing, and main treatment (
used for plating or sputtering). Next, examples of the present invention will be shown. (Example) A semi-continuous ingot of an aluminum alloy having the chemical components shown in Table 1 was heat treated and rolled under the conditions shown in Table 2. After punching the obtained rolled plate into 130Qlllφ. It was annealed at 350°C for 2 hours and subjected to the following various tests. The results are shown in Table 3. (1) Distribution of intermetallic compounds After mirror cutting with a diamond cutting tool, the distribution (size and number) of AQ-Fe and Mg-8i intermetallic compounds was examined using a scanning electron microscope. (2) Plating After mirror cutting, degreasing → alkali etching (5% Na
OH 130 seconds) → Pickling (HNO, :HF:H. 0=3:1:2) → Zincate treatment (NaOH, ZnO
, FeCQ3・6H1O, KNaC4H,0,4H20
etc.) → Pickling (HNO, ) → N1-P plating → Polishing. The pits and surface roughness during polishing were investigated. As is clear from Table 3, examples of the present invention Nα3 to Nl14
, Na 9 have less intermetallic compounds, less plating bits, and no roughness of the plating surface is observed. On the other hand, Comparative Examples Ncil to Nn2 contain many intermetallic compounds,
A large number of metsuki bits are also recognized. Comparative Example 5 has less intermetallic compounds and less plating bits, but the plating surface is rough. Comparative Example No. 116 contains a large amount of Mg-8i based intermetallic compounds and also contains a large amount of metsukivit. In Comparative Examples N117 to Nα8, microcracks occurred during rolling. The number of bits has increased and the surface has become rough. Comparative example NQ10 is an example in which the sample was cooled after the first heat treatment and reheated to the temperature of the second heat treatment, but there were many Mg-5i-based intermetallic compounds and a large number of metki bits. Incidentally, FIG. 1 shows the above results in a graph, and it is clear at a glance that the example of the present invention has excellent performance in all aspects.

[Left below]

(Effects of the Invention) As described in detail above, according to the present invention, defects after plating can be reduced, so that the capacity of the disk substrate can be increased. Furthermore, since the polishing allowance after plating can be reduced, costs can also be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between various alloys and manufacturing methods, intermetallic compound distribution, plating pits, and plating surface roughness.

Claims (1)

[Claims] In weight% (the same applies hereinafter), Si≦0.05%, Fe≦0
．． 05%, Cu: 0.05~0.4%, Mg: 3.5~
A semi-continuous ingot of an aluminum alloy containing Zn: 4.5% and Zn: 0.05 to 0.4%, with the remainder substantially consisting of Al, is heated at a temperature of 500 to 530°C for 2 hours or more, and then cooled. 1. A method for producing a high-capacity aluminum disk substrate, comprising: holding the substrate at a temperature of 530 to 560° C. for 4 hours or more without heating, and then rolling it to a predetermined thickness.