JPH04311815A - Production of magnetic disk substrate made of titanium - Google Patents

Abstract

PURPOSE:To obtain the magnetic disk substrate made of titanium which has decreased pits and has high surface hardness by polishing the surface of a substrate blank material, then rinsing, washing and drying the material and subjecting the material to finish polishing after a heat treatment. CONSTITUTION:The surface of the disk substrate blank material is successively polished and is subjected to the polishing by alumina abrasive grains as finish polishing; thereafter, the material is rinsed, washed and dried. The substrate is then supported in the state of inserting a supporting rod 2 into the bore of the substrate blank material 1 and is heat treated. The substrate is finally subjected to the finish polishing. The decrease in the yield by the generation of the pits is drastic and the yield is as low as <80% if the rinse time is below 10 seconds. The decrease in the yield by damages is drastic and the yield is as low as <80% if the rinse time exceeds 10 minutes.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a titanium magnetic disk substrate, and more particularly to a method for manufacturing a titanium magnetic disk substrate with excellent wear resistance at a high yield.

0002

BACKGROUND OF THE INVENTION A magnetic disk used as a recording medium for a computer includes a substrate and a magnetic film (magnetic recording layer) formed on the substrate. Among these, magnetic disk substrates include
Conventionally, aluminum alloys such as Al-Mg alloys have been used. Further, in order to cover inclusions inevitably included in the substrate and obtain excellent surface quality, a substrate is used in which Ni--P plating is applied on the aluminum alloy as described above.

On the other hand, in recent years, there has been a trend toward higher recording densities and smaller sizes of magnetic disks, so heat resistance is required to form high-performance magnetic films on substrate materials by sputtering at high temperatures. , excellent surface properties and high cleanliness are required to reduce the flying height of the magnetic head, and high rigidity and high strength are required for miniaturization and thinning. Therefore, the currently used aluminum alloy substrates have the following problems. (a) Insufficient heat resistance of the aluminum alloy itself. (b) The yield of Ni-P plating is low. (c) Peeling between Ni-P plating and aluminum alloy substrate. (d) Ni-P plating crystallizes at a relatively low temperature of about 350° C. and becomes non-magnetic. For this reason, as a magnetic disk substrate,
Titanium, which does not have these drawbacks, is attracting attention.

By the way, a magnetic disk substrate needs to have excellent surface properties, but since titanium is an active metal, the surface after mirror polishing undergoes surface roughening due to changes over time due to hydrogen and the like. As a result of detailed studies to prevent this and obtain titanium with excellent surface quality, this was achieved by "polishing to a certain level of surface quality, then applying heat treatment and final polishing." It has been found that this can be done (Japanese Patent Application Laid-Open No. 02-148484). By using this method in the manufacture of titanium magnetic disk substrates, mirror surfaces that do not change over time can be obtained, and this problem can be solved.

However, according to this method, the dirt remaining on the substrate surface often reacts with the surface and pits are generated there, and the problem is that the yield of manufacturing magnetic disk substrates decreases due to the generation of pits. There is.

Furthermore, magnetic disk substrates are required to have wear resistance against contact with magnetic heads, and are desired to have high surface hardness. The hardness of titanium is about 120 Vickers hardness in CP-2 pure titanium, and improvement in surface hardness is desired.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a titanium magnetic disk substrate that can obtain a titanium magnetic disk substrate with few pits and high surface hardness. shall be.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a method in which the surface of a substrate material is rinsed after polishing, then washed and dried, then subjected to heat treatment, and then subjected to final polishing. A method for manufacturing a titanium magnetic disk substrate with features is provided.

[0009] The inventors of the present application believe that the pits that cause a decrease in yield are caused by reactions with the mirror-polished surface that is heated while dirt such as abrasive grains remaining in the polishing process before heat treatment, or by reaction with the mirror-polished surface during heat treatment. They discovered that this is caused by environmental contaminants adhering to and reacting with the substrate surface. In addition, as a result of repeated studies on various heat treatment methods, we found that when the mirror-finished surface comes into contact with an object, it reacts.
It was also found that the surface quality was impaired. Furthermore, as a result of detailed studies on surface hardening to improve wear resistance, it was discovered that surface hardening is possible by forming an oxygen-rich layer on the surface. The present invention having the above structure has been made based on the knowledge of the inventors of the present application. Note that in this invention, titanium includes both pure titanium and titanium alloy.

0010

[Operation] Rinsing after polishing has the role of removing dirt such as abrasive grains remaining on the surface after polishing. The rinsing time at this time is preferably 10 seconds or more and 10 minutes or less. If the time is less than 10 seconds, dirt cannot be removed sufficiently, and the dirt reacts with the substrate surface during heat treatment, causing pits. Furthermore, if the time is longer than 10 minutes, scratches or other damage may occur on the substrate surface during rinsing, resulting in a decrease in yield.

[0011] After this rinsing, washing and drying are performed, and heat treatment is performed. This heat treatment is performed to form an oxygen-rich hardened layer on the surface of the substrate material. The cleanliness of the atmosphere during this heat treatment is preferably class 10,000 or lower. If the cleanliness is worse than class 10000, dirt from the environment will adhere to the surface during heat treatment and react with the surface, which will also cause a decrease in yield. Furthermore, it is desirable that the substrate material during heat treatment be supported so that only the inner or outer diameter sides thereof are in contact with each other. If parts other than the side surfaces of the inner or outer diameter, that is, mirror-finished parts, are in contact with the supporting jig, they may be crimped or diffusion bonded during heat treatment, or react with dirt and cause pits. or In addition, the heat treatment conditions include a temperature range of 500°C.
above, 700℃ or less, holding time for 30 minutes or more, 30
It is desirable that the time is 0 minutes or less. If the time is less than 500° C. or less than 30 minutes, a sufficiently thick oxygen-rich layer will not be formed, and therefore a sufficient hardened surface layer will not be obtained after final polishing. Further, at a temperature higher than 700° C., there arises a disadvantage that the flatness of the substrate deteriorates due to heat. Further, if the time is longer than 300 minutes, the oxide film becomes too thick and cannot be removed by final polishing, making it impossible to obtain a surface quality sufficient for a substrate. After this heat treatment, final polishing is performed to obtain a titanium magnetic disk substrate with few pits and high surface hardness.

0012

[Example] (Example 1)

CP-2 class pure titanium cold rolled plate (1.5mmt
), a ring-shaped flat plate with an outer diameter of 95 mm and an inner diameter of 25 mm was punched out, and after hot straightening at 600°C for 6 hours,
The surface of these disk substrate materials is #400, #800, #
After sequentially polishing with #1500 and #4000 whetstones, and finishing polishing with alumina abrasive grains,
A 15 minute rinse was applied. After cleaning and drying, the substrate is supported with the support rod 2 inserted into the inner diameter of the substrate material 1, as shown in FIG.
Heat treatment was performed at 600° C. for 1 hour in an environment of 0 or less. Finally, finishing polishing was performed. At this time, 100 substrates were produced under each rinse condition, and the occurrence of pits and scratches was examined. The results are shown in Table 1 and FIG. 2.

[0014]

[Table 1]

As shown in Table 1 and FIG. 2, when the rinsing time is less than 10 seconds, the yield is severely reduced due to the occurrence of pits, and the yield is less than 80%, and when the rinsing time exceeds 10 minutes, the yield is lower than 80%. It was confirmed that the yield was significantly reduced due to scratches, and the yield was less than 80%. (Example 2)

Similar to Example 1, a CP-2 class pure titanium cold-rolled plate (1.5 mmt) was prepared with an outer diameter of 95 mm and an inner diameter of 25 mm.
mm ring-shaped flat plates were punched out and hot straightened at 600°C for 6 hours.
After polishing with 00, #800, #1500, and #4000 grindstones in sequence, polishing with alumina abrasive grains was performed as a final polishing, and rinsing was performed for 1 minute. After washing and drying, cleanliness class 1000 or less (measured value 900), 10000
Heat treatment was performed at 600° C. for 1 hour under an environment of 1000° C. (measured value of about 9000) and indoors (measured value of about 150,000). Finally, finishing polishing was performed. At this time, 100 substrates were heat-treated at each cleanliness level, and the occurrence of pits was examined. The results are shown in Table 2.

[0017]

[Table 2]

As shown in Table 2, indoors (where the cleanliness level is worse than class 10,000), the yield decreases significantly due to the occurrence of pits, and the yield is less than 10%, but when the cleanliness level is below 10,000, the yield decreases. was confirmed to be 93% or more. (Example 3)

[0019]
Similarly to Example 1, a CP-2 class pure titanium cold-rolled plate (1.5
mmt), a ring-shaped flat plate with an outer diameter of 95 mm and an inner diameter of 25 mm was punched out, and after hot straightening at 600°C for 6 hours, the surface of these disk substrate materials was #400, #80.
0, #1500, and #4000 grindstones, polishing with alumina abrasive grains was performed as a final polishing, and rinsing was further performed for 1 minute. After washing and drying, it is cleaned at 600°C x 1 in an environment of cleanliness class 1000 or less using various methods as shown in Figure 1 (a) to (d).
Heat treatment was performed for an hour. Finally, finishing polishing was performed. At this time, 100 substrates were heat treated using each method, and the condition of the substrates was examined. The results are shown in Table 3. 1(b) shows the substrate material 1 placed on the alumina surface plate 3, and FIG. 1(c) shows the quartz glass surface plate 4.
(c) shows one substrate material 1 placed on an alumina surface plate 3.

[0020]

[Table 3]

As shown in Table 3, with methods other than (a), that is, methods other than supporting only on the inner or outer diameter side surfaces, a large decrease in yield was confirmed due to crimping and pitting. (Example 4)

Similar to Example 1, a CP-2 type pure titanium cold-rolled plate (1.5 mmt) was prepared with an outer diameter of 95 mm and an inner diameter of 25 mm.
mm ring-shaped flat plates were punched out and hot straightened at 600°C for 6 hours.
After polishing with 00, #800, #1500, and #4000 grindstones in sequence, polishing with alumina abrasive grains was performed as a final polishing, and rinsing was performed for 1 minute. After washing and drying, it is heated to a temperature of 400 to 600 in an environment of cleanliness class 1000 or less using the method shown in Figure 1(a).
Heat treatment was performed at 0° C. for 5 minutes to 5 hours. Finally, finishing polishing was performed. At this time, 100 substrates were heat treated under each condition, and the flatness, surface texture, and surface hardening were examined. The results are shown in Table 4 and Figure 3.
- Shown in 4.

[0023]

[Table 4]

As shown in these figures, the heating temperature is 500°C.
or if the heating time is less than 30 minutes, Hv
= less than 200, sufficient surface hardness cannot be obtained, and
It was confirmed that when the heating time exceeded 300 minutes, an oxide film remained and a sufficient surface quality was not obtained. Furthermore, if the heating temperature exceeds 700℃, the flatness will be 40μm.
As above, deterioration of flatness was observed.

[0025]

According to the present invention, there is provided a titanium magnetic disk substrate which can be produced with a high yield and has less pit formation and excellent wear resistance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a method of supporting a substrate.

FIG. 2 is a diagram showing the relationship between rinsing time and the incidence of pits and scratches.

FIG. 3 is a diagram showing the relationship between heat treatment temperature, surface hardness, and flatness.

FIG. 4 is a diagram showing the relationship between heat treatment time and surface hardness and flatness.

[Explanation of symbols]

1; Substrate, 2; Support rod, 3, 4; Surface plate

Claims (5)

[Claims] 1. A method for manufacturing a titanium magnetic disk substrate, which comprises polishing and rinsing the surface of the substrate material, then cleaning and drying, then heat-treating, and then final polishing. 2. The method for manufacturing a titanium magnetic disk substrate according to claim 1, wherein the rinsing time after polishing is 10 seconds or more and 10 minutes or less. 3. The heat treatment is carried out in cleanliness class 10.
3. The method for manufacturing a titanium magnetic disk substrate according to claim 1, wherein the manufacturing method is carried out under an environment of 0.0000000000000 or less. 4. The heat treatment according to claim 1, wherein the heat treatment is performed while supporting the substrate material so that only the inner or outer diameter side surfaces of the substrate material are in contact with each other. A method for manufacturing a titanium magnetic disk substrate. 5. The heat treatment according to claim 1, wherein the temperature range is 500° C. or more and 700° C. or less, and the holding time is 30 minutes or more and 300 minutes or less. A method for manufacturing a titanium magnetic disk substrate.