JPS63286224A - Production of alminum substrate for memory disk - Google Patents

Abstract

PURPOSE:To improve the quality and productivity of a product by coining a blank with the die having a flat and smooth pressure face inside the die and executing a cutting or grinding. CONSTITUTION:A circular blank 4 is made from the plate stock in the specified thickness and arranged inside the annular die 1 regulating the spread of the material outer diameter. A coining is then executed after coating a lubrication oil by interposing between the lower die 2 and upper die 3 having the work face equipped with the specified surface roughness and flatness. A cutting or coining is executed on the blank 4 after working and the Al substrate for a memory disk is obtd. A coining is executed in advance on the blank 4 and a cutting or grinding is further executed, hence the smoothness and flatness of the product substrate are improved. Consequently the quality and productivity of a product are improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an aluminum substrate for memory disks with an extremely flat and smooth surface made of a blank material made of aluminum, aluminum alloy, or a composite material thereof (hereinafter simply abbreviated as AJl). The present invention relates to a method for manufacturing.

[Conventional technology]

Conventionally, memory disks for storing and reproducing various types of information (text, audio, video, etc.) usually have a structure in which a donut disk-shaped A1 substrate with an ultra-precise surface finish is coated with a magnetic material, and the storage is carried out using a magnetic head. , discs for accurate playback.

The surface is required to have a high degree of flatness and smoothness.

To manufacture such A and e substrates for memory disks, a blank material is punched out from an Ai plate, the warpage and undulations of the plate are corrected by white pressure annealing, rough machining, etc., and then ultra-precision cutting is performed using a natural diamond cutting tool. There are methods such as polishing both sides at the same time with a whetstone, and polishing both sides simultaneously with abrasive grains and hot water using a lapping machine, but both methods require the blank material to have a certain degree of good flatness before processing. be done.

[Problem that the invention seeks to solve]

Correcting the waviness by pressure annealing the blank material before precision processing has problems such as there is a limit to the flatness after straightening, and there is large variation among the blank materials, resulting in a lack of stability in quality.

For this reason, although the flatness may be improved by further cutting, the problem remains that productivity is poor due to the long machining time.

[Means for solving problems]

In view of this, as a result of various studies, the present invention has been developed to improve the flatness of A (blank material) by using a coining process using a press, and to produce high-quality Al substrates for memory disks by subsequent cutting or grinding. A manufacturing method is provided.

The above-mentioned coining process is a technique normally used in the production of coins, and the common method is to press the material with a die that has an uneven pattern on the pressure surface to form an uneven pattern on the material surface. However, the present invention uses a flat and smooth die without forming any unevenness on the pressurizing surface of the die.

That is, in a method of manufacturing a memory disk substrate by cutting or grinding a blank material made of aluminum, an aluminum alloy, or a composite material thereof, the blank material is placed on a pressurized surface in a mold that regulates the spread limit of the material. It is characterized in that it is sandwiched between two flat and smooth dies, coined, and then cut or ground.

[For production]

In this way, the coining process is performed using a die with a flat and smooth precision finish on the pressurized surface in a mold that restricts the spread of the material.By regulating the flow of the A1 blank material due to pressure, it is possible to achieve a precise finish. This is because the surface texture of the surface of the die can be easily transferred to the A1 blank material, and as a result, the A1 blank material with excellent surface precision can be obtained.

Furthermore, since the final shape of the memory disk □ is a donut-shaped disc, the expansion of the inner diameter of the donut disc-shaped blank is controlled using a core bar passing through the center of the upper and lower dies. By coining, an outer diameter and an inner diameter with good dimensional accuracy can be obtained at the same time.

〔Example〕

Next, the present invention will be explained in detail.

JIS 5086 (A 1-0.2~0.7%Mn-
3.5~4.5%M (j -0.05~2.5%Or
Alloy) O material (tensile strength σa = 27KI/1ar)
A circular blank material was prepared from a 1.5M thick plate material. At this time, the outer diameter of the blank material is the inner diameter of the ring-shaped mold (A = 65 m> that regulates the spread of the material outer diameter of the coining machine as shown in Figure 1), and the thickness of the blank material after coining. The reduction rate was set to be 0.5%.The average value of the surface roughness 1a of the produced blank material at 5 locations was 0.2 μm.
The flatness is 10 μm or more for warpage and 15 μm for waviness.
It was more than m. Place such a blank material on the lower die (2) of the coining machine shown in Fig. 1, and place it on the upper die (3).
) and the pressing force was set to 81 kg/7, which is three times the tensile strength of the blank material (4), and after applying lubricating oil (machine oil, viscosity 1.4) to the blank material. Coining was done. At this time, the surface roughness Ra of the pressurizing surface of the die
1. tO, 020μ It was □ at the door. After cutting the surface of the blank using a natural diamond tool, the surface roughness and flatness of the surface were measured, and the average value for the five blanks was calculated as the average value for the five blanks before cutting. They are shown in Table 1 together with their average values.

For comparison, the above-mentioned circular blank material made from a plate material with a thickness of 1.5#2#l was subjected to surface straightening by pressure annealing without coining, and the surface was further corrected by pressure annealing after pressure annealing. After rough cutting and surface correction, the surface of each blank material was then cut using a natural diamond cutting tool, and the surface roughness and flatness of the blank material surface before and after the cutting process were measured.
For each, the average value of five blank materials is also listed in Table 1.

As is clear from Table 1, the surface roughness Ra after cutting with a diamond cutting tool was 0.009μ for both the method of the present invention and the conventional method, which is a good value. On the other hand, regarding warpage and waviness, the method of the present invention is less than half that of the conventional method even before cutting with a diamond tool, and furthermore, after cutting, the waviness is 174.
Hereinafter, it can be seen that the warpage is 1/9, which is extremely excellent.

〔Effect of the invention〕

As described above, according to the present invention, the flatness of the Al blank material can be significantly improved, and therefore, it is possible to manufacture high-quality aluminum substrates for memory disks, and furthermore, productivity can be significantly improved, which is an industrially significant improvement. It has the following effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a coining device. １・・・・・・Ring-shaped mold 2・・・・・・Bottom die 3...Top die 4...Blank material A・・・・・・Inner diameter Figure 1 ↓

Claims (1)

[Claims] In a method for manufacturing a memory disk substrate by cutting or grinding a blank material made of aluminum, an aluminum alloy, or a composite material thereof, the blank material is placed in a mold that controls the spread limit of the material, and the pressing surface is A method for producing an aluminum substrate for a memory disk, which comprises sandwiching the aluminum substrate between two flat and smooth dies, performing a coining process, and then cutting or grinding the substrate.