JPS6151018B2 - - 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 non-metallic inclusions is required, but in the 5086Al alloy mentioned above, non-metallic 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%, Zn: 0.5 to 3.0%, Mn: 0.1 to 0.5%, and further containing Contains Zr: 0.02 to 0.5%, and contains Si, Fe, and unavoidable impurities.
The contents of Cr, Ni, and Ti are, respectively, Si: 0.20% or less, Fe: 0.05% or less, Cr: 0.05% or less, Ni: 0.04% or less, Ti: 0.01% or less, and the rest is Al and Ti. Composition consisting of other unavoidable impurities (the above weight %, below % shows weight %)
The researchers discovered that an Al alloy with a . 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;
If the content exceeds 2.0%, rolling workability and castability will deteriorate, as well as corrosion resistance.
It was set at 0.3-2.0%. (b) Mg The Mg component has the effect of significantly improving the hardness and strength of the alloy, but its content is 3.0
If the content is less than 5.0%, it will not be possible to secure the desired high hardness and high strength, while if the content exceeds 5.0%, rolling will be difficult and large
Since Al--Mg-based intermetallic compounds are formed, the content is set at 3.0 to 5.0%. (c) Zn The Zn component has the effect of improving the strength and hardness of the alloy without forming large intermetallic compounds, but if its content is less than 0.5, the desired effect of improving the above effect cannot be achieved. On the other hand,
If the content exceeds 3.0%, castability and rolling workability deteriorate, so the content was set at 0.5 to 3.0%. (d) Mn The Mn component contains Fe and Si, which are unavoidable impurities.
Al-Fe and Al-Fe-Si formed by
Mn has the effect of refining intermetallic compounds, but if the content is less than 0.1%, the desired effect cannot be obtained, while if the content exceeds 0.5%, Mn itself will form intermetallic compounds. The content was set at 0.1 to 0.5%. (e) Zr The Zr component has the effect of refining the crystal grains and intermetallic compounds of the alloy, so it is included as necessary, but if the 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.
It was set at 0.02-0.5%. (f) Si, Fe, Cr, Ni, and Ti as unavoidable impurities All of these components have the effect of forming intermetallic compounds, and if their content exceeds the permissible value below, none of them will occur. If the content is less than 0.20% for Si and less than 0.20% for Fe, since large intermetallic compounds will be formed.
Cr: 0.05% or less, Ni: 0.04% or less, and Ti: 0.01% or less. 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 99.7% 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 a settling process, filter with a refractory filter to remove non-metallic inclusions, and then use direct cooling continuous casting to width: 1000 mm x length: 2500 mm x thickness. : An ingot with a dimension of 600 mm is made, and then this ingot is heat treated by holding it at a temperature within the range of 500 to 540 degrees Celsius for 12 hours and cooling, and then the top and bottom sides of this ingot are made into a 15 mm thick ingot. The ingot was face-faced to a thickness of 570 mm, then heated to 500°C and hot-rolled to form a hot-rolled plate with a thickness of 7.5 mm. The aluminum alloys 1 to 12 of the present invention and conventional 5086

[Table] Al alloy discs were manufactured. Next, the resulting Al alloys of the present invention 1~
12 and 5086Al alloy discs at a temperature of 350°C.
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 12 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
-12 are all compared to the conventional 5086Al alloy.
It has high strength and hardness, which is clear from the fact that it can be finished to a mirror surface with better surface roughness in a shorter buffing time, and it also reduces the size of nonmetallic inclusions present in the base material. is also extremely small. Note that the Al alloy of the present invention can be used, for example, as described above.
5086

[Table] It may be used as a cladding material with commercially available Al alloys such as Al alloys, 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. A composition containing 1 Cu: 0.3 to 2.0% Msg: 3.0 to 5.0% Zn: 0.5 to 3.0% Mn: 0.1 to 0.5%, with the remainder consisting of Al and unavoidable impurities (in weight percent). and the contents of Si, Fe, Cr, Ni, and Ti as unavoidable impurities are the same in weight%: Si: 0.20% or less, Fe: 0.50% or less, Cr: 0.05% or less, Ni: 0.04%. Below, Al for magnetic disk substrates characterized by Ti: 0.01% or less
alloy. 2 Contains Cu: 0.3 to 2.0%, Mg: 3.0 to 5.0%, Zn: 0.5 to 3.0%, Mn: 0.1 to 0.5%, further contains Zr: 0.02 to 0.5%, and the rest is Al. It has a composition consisting of unavoidable impurities (wt% or more), and the content of Si, Fe, Cr, Ni, and Ti as unavoidable impurities is also in wt%, Si: 0.20% or less, Fe: 0.50% or less , Cr: 0.05% or less, Ni: 0.04% or less, Ti: 0.01% or less.
alloy.