JPH0316689B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has high hardness and high strength, has intermetallic compounds uniformly and finely present in the base material, and has almost no nonmetallic inclusions, and is particularly suitable for use as a magnetic disk substrate that requires these characteristics. This invention relates to an Al alloy that enables high recording density of magnetic disks when used. Conventionally, magnetic disks have been known, for example, having a magnetic recording medium film formed on the surface of an Al alloy substrate, and the substrate is usually made of AA standard 5086 Al alloy (Mn: 0.20-0.70%, Mg: 3.5%). ~
4.5%, Cr: 0.05-0.25%, Al and unavoidable impurities: remainder) are used. On the other hand, in recent years, the storage capacity of magnetic disks has increased,
There are increasing demands for shorter access times, lower prices per bit, smaller size, and lighter weight.In order to meet these demands, it is necessary to increase the density of magnetic recording in magnetic disks. is an essential requirement. In order to achieve such high density magnetic recording, it is necessary that the magnetic recording medium be free from defects, have a smooth surface, and have a thin and uniform film thickness. However, when a magnetic recording medium is made thinner, the presence of large intermetallic compounds or nonmetallic inclusions in the base material of the substrate causes defects such as bit dropout (a phenomenon in which some information is not recorded). A substrate without large intermetallic compounds or nonmetallic inclusions is required, but in the 5086Al alloy mentioned above, nonmetallic inclusions can be significantly reduced by molten metal filtration, etc. Since it exists in a relatively large size, there is a limit to how thin a magnetic recording medium can be made. In addition, the smoothness of the magnetic disk surface is primarily due to the smoothness of the substrate surface, and therefore the substrate is given a mirror finish, but the above
5086Al alloy does not have sufficient hardness to facilitate these polishing operations. Furthermore, the higher the strength of the substrate, the smaller, lighter, and thinner the magnetic disk will be, but the 5086Al alloy does not have a sufficiently high strength to achieve these goals. Therefore, from the above-mentioned viewpoints, the present inventors have determined that the material has high hardness and strength, is free of non-metallic inclusions, and has a fine structure in which the intermetallic compounds distributed in the material have a fine structure. As a result of conducting research to develop an Al alloy containing Cu: 0.3 to 2.0%, Mg: 3.0 to 5.0%, and further containing Zr: 0.02 to 0.5% as necessary, and Si, Fe as unavoidable impurities
The contents of Mn, Cr, Ni, Zn, and Ti are: Si: 0.10% or less, Fe: 0.10% or less, Mn: 0.01% or less, Cr: 0.01% or less, Ni: 0.01% or less, Zn: 0.50 % or less, Ti: 0.01% or less, with the remainder consisting of Al and other unavoidable impurities (the above is weight %, the below % is weight %)
The inventors have found that an Al alloy with a It is. This invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained below. (a) Cu The Cu component has the effect of improving the strength and hardness of the alloy without forming large intermetallic compounds, and also suppressing the coarsening of Al-Mg intermetallic compounds. If the amount is less than 0.3%, the desired effect cannot be obtained, while if the content exceeds 2.0%, rolling workability and castability will deteriorate, as well as corrosion resistance. , its content was determined to be 0.3-2.0%. (b) Mg The Mg component has the effect of significantly improving the hardness and strength of the alloy, but if its content is less than 3.0%, the desired high hardness and strength cannot be achieved; If the content exceeds 100%, rolling becomes difficult and large Al-Mg-based intermetallic compounds are formed.
Its content was set at 3.0-5.0%. (c) Zr The Zr component has the effect of refining crystal grains and intermetallic compounds in the alloy, so it is included as necessary, but if its content is less than 0.02%, the desired refining effect cannot be obtained. On the other hand, if the content exceeds 0.5%, large Al-Zr based intermetallic compounds will be formed, so the content should be reduced from 0.02 to 0.5%.
It was set at 0.5%. (e) Si, Fe, Mn, Cr as inevitable impurities,
Ni, Zn, and Ti All of these components have the ability to form intermetallic compounds, and if their content exceeds the allowable value below, they will form large intermetallic compounds. Therefore, each
The content is Si: 0.10% or less, Fe: 0.10% or less, Mn: 0.01% or less, Cr: 0.01% or less, Ni:
0.01% or less, Zn: 0.50% or less, and Ti: 0.01%
It was determined as follows. Next, the Al alloy of the present invention will be specifically explained using examples. Example A commercially available Al base metal having a purity of 99.9% or more is melted, alloying elements are added to it to prepare a molten Al alloy having the composition shown in Table 1, and then chlorine gas is added. Blow to degas, perform settling treatment, pass through a fireproof filter to remove non-metallic inclusions, and then direct cooling continuous casting method Width: 1000mm x Length: 2500mm x Thickness:
An ingot with a dimension of 350 mm was made, and then this ingot was heat treated by holding it at a temperature within the range of 500 to 560 degrees Celsius for 12 hours and cooling, and then the top and bottom sides of this ingot were made into a thickness of 10 mm. The ingot was polished to a thickness of 580 mm and heated to 500℃.

[Table] This hot-rolled plate is heated and hot-rolled to a thickness of 5 mm, then this hot-rolled plate is cold-rolled to a cold-rolled plate of a plate thickness of 2 mm, and then this cold-rolled plate is cold-rolled to a thickness of 2 mm. Discs of Al alloys 1 to 8 of the present invention and conventional 5086 Al alloy were manufactured by punching out a disc with a diameter of 200 mm from a rolled sheet using a press. Next, the resulting Al alloys of the present invention 1~
8 and 5086Al alloy disks at a temperature of 350℃.
After time-hold pressure annealing, rough polishing and buff polishing were performed to give the surface a mirror finish. Note that the polishing allowance was 0.2 mm. In addition to measuring the buffing time required for each disc, the surface roughness of the mirror-finished surface was also measured, and the maximum dimension of the intermetallic compound on the mirror-finished surface was also measured. Furthermore, the above-mentioned Al alloys 1 to 8 of the present invention and
Mechanical properties were also measured for the 5086Al alloy.
The results of these measurements are shown in Table 2. From the results shown in Table 2, the present invention Al alloy 1
-8 are all compared to the conventional 5086Al alloy,
Has high strength and high hardness, this makes it shorter

[Table] It is clear from the fact that a mirror finish with better surface roughness can be achieved with a longer buffing time, and the size of nonmetallic inclusions present in the base material is also significantly smaller. Note that the Al alloy of the present invention can be used, for example, as described above.
It may also be used as a cladding material with a commercially available Al alloy such as 5086Al alloy, and in this case, it goes without saying that the film of the magnetic recording medium is formed on the surface of the Al alloy of the present invention. As mentioned above, the Al alloy of the present invention has high hardness, so when it is used as a substrate for a magnetic disk, the surface can be finished to an excellent mirror finish with a relatively short buffing time. Not only that, the intermetallic compounds present in the matrix are fine and uniform, and non-metallic inclusions are removed by means such as molten metal filtration.
Since the film thickness of the magnetic recording medium can be made thinner, it is possible to increase the density of magnetic recording.
Furthermore, since it has high strength, it has industrially useful properties such as making it possible to make magnetic disks smaller and lighter.

Claims (1)

[Claims] 1. Contains Cu: 0.3 to 2.0%, Mg: 3.0 to 5.0%, and the remainder is Al and unavoidable impurities (wt%), and Si as unavoidable impurities, The contents of Fe, Mn, Cr, Ni, Zn, and Ti are the same in weight%, Si: 0.10% or less, Fe: 0.10% or less, Mn: 0.01% or less, Cr: 0.01% or less, Ni: 0.01%. Aluminum for magnetic disk substrates characterized by: Zn: 0.50% or less, Ti: 0.01% or less
alloy. 2 Contains Cu: 0.3 to 2.0%, Mg: 3.0 to 5.0%, and further contains Zr: 0.02 to 0.5%, with the remainder consisting of Al and unavoidable impurities (wt%), And the contents of Si, Fe, Mn, Cr, Ni, Zn, and Ti as unavoidable impurities are the same in weight%: Si: 0.10% or less, Fe: 0.10% or less, Mn: 0.01% or less, Cr: 0.01 % or less, Ni: 0.01% or less, Zn: 0.50% or less, Ti: 0.01% or less.
alloy.