JP2500025B2 - Method for manufacturing titanium magnetic disk substrate - Google Patents

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 excellent in wear resistance with a high yield.

[0002]

2. Description of the Related Art A magnetic disk used as a recording medium for a computer comprises a substrate and a magnetic film (magnetic recording layer) formed thereon. Of these, aluminum alloys such as Al—Mg alloys have been conventionally used as the magnetic disk substrate. Further, in order to cover the inclusions unavoidably included in the substrate and obtain excellent surface properties, a substrate plated with Ni—P on the aluminum alloy as described above is used.

On the other hand, in recent years, magnetic disks tend to have higher recording densities and smaller sizes. Therefore, heat resistance for forming a high-performance magnetic film on a substrate material by sputtering at high temperature. In addition, excellent surface properties for reducing the flying height of the magnetic head, high cleanliness, and high rigidity and strength for downsizing and thinning are required. Therefore, the aluminum alloy substrates currently used 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) The Ni-P plating crystallizes at a relatively low temperature of about 350 ° C. and becomes non-magnetic. From this, as a magnetic disk substrate,
Titanium, which does not have such defects, is attracting attention.

By the way, a magnetic disk substrate is required to have excellent surface properties, but since titanium is an active metal, the surface after mirror-finishing undergoes surface roughening due to aging due to hydrogen and the like. As a result of detailed investigations to prevent this and obtain titanium with excellent surface properties, this was achieved by "finishing polishing by performing heat treatment after polishing to a certain degree of surface properties". It has been found that this can be done (Japanese Patent Laid-Open No. 02-148484). Also in the production of a titanium magnetic disk substrate, a mirror surface that does not change with time can be obtained by using this method, and this problem can be solved.

However, according to this method, stains remaining on the surface of the substrate may react with the surface, and pits may be generated there, and the pits may reduce the yield of magnetic disk substrate manufacturing. There is.

Further, the magnetic disk substrate is required to have abrasion resistance against contact with the magnetic head, and high surface hardness is desired. The hardness of titanium is about Vickers hardness 120 in CP-2 type pure titanium, and improvement of the surface hardness is desired.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for manufacturing a titanium-made magnetic disk substrate capable of obtaining a titanium-made magnetic disk substrate having few pits and high surface hardness. And

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a method of polishing the surface of a substrate material after rinsing, followed by washing and drying, followed by heat treatment and further finish polishing. A method of manufacturing a characteristic magnetic disk substrate made of titanium is provided.

The inventors of the present invention have found that the pits which cause a decrease in yield react with the mirror-polished surface after being heated with stains such as polishing abrasive grains remaining in the polishing step before the heat treatment, or during the heat treatment. It has been found out that the stains from the environment are caused by the reaction on the surface of the substrate. Moreover, as a result of repeated studies on various heat treatment methods, when the mirror-finished surface comes into contact with an object, it reacts,
It has also been found that the surface properties are impaired. Furthermore, as a result of detailed studies on surface hardening for improving wear resistance, it was found that surface hardening is possible by forming an oxygen-rich layer on the surface. The present invention having the above-described configuration is made based on the findings of the inventors of the present application. In the present invention, titanium includes both pure titanium and titanium alloy.

[0010]

The function of rinsing after polishing serves to remove dirt such as abrasive grains remaining on the surface after polishing. At this time, the rinse time is preferably 10 seconds or more and 10 minutes or less. If it is less than 10 seconds, the stain cannot be removed sufficiently, and the stain reacts with the substrate surface during the heat treatment to cause pits. On the other hand, if it is longer than 10 minutes, scratches or the like will be scratched on the substrate surface during rinsing, which will cause a decrease in yield.

After this rinsing, washing and drying are performed and heat treatment is performed. This heat treatment is performed to form a hardened layer rich in oxygen on the surface of the substrate material. The cleanliness of the atmosphere during this heat treatment is preferably class 10,000 or less. If the cleanliness is lower than class 10000, stains from the environment adhere to the surface during the heat treatment and react with the surface, which also causes a decrease in yield. Further, it is desirable that the substrate material at the time of heat treatment is supported so that only the side surface having the inner diameter or the outer diameter is in contact. If a portion other than the inner or outer diameter side surface, that is, the mirror-finished portion is in contact with the supporting jig, it will be pressure-bonded or diffusion-bonded during heat treatment, or will react with dirt and cause pits. Or Further, the heat treatment condition is that the temperature range is 500.
℃ or more, 700 ℃ or less, holding time 30 minutes or more, 3
It is preferably 00 minutes or less. If the temperature is less than 500 ° C. or less than 30 minutes, an oxygen-rich layer having a sufficient thickness cannot be formed, and a sufficient surface-hardened layer cannot be obtained after finish polishing. Further, if the temperature is higher than 700 ° C., the flatness of the substrate deteriorates due to heat, which is a disadvantage. Furthermore, if the time is longer than 300 minutes, the oxide film becomes too thick, and this film cannot be completely removed by finish polishing, so that sufficient surface properties cannot be obtained as a substrate. After this heat treatment, finish polishing is performed to obtain a titanium magnetic disk substrate with few pits and high surface hardness.

[0012]

[Example] (Example 1)

CP-2 type pure titanium cold rolled sheet (1.5 mm ^t )
After punching a ring-shaped flat plate having an outer diameter of 95 mm and an inner diameter of 25 mm and hot-straightening at 600 ° C. for 6 hours, the surface of these disk substrate materials is # 400, # 800, # 150.
Polishing was sequentially carried out with 0 and # 4000 whetstones, polishing was performed with alumina abrasive grains as finish polishing, and then rinsing was performed for 0 to 15 minutes. And after washing and drying,
As shown in (a), the substrate is supported with the support rod 2 inserted in the inner diameter of the substrate material 1, and the cleanliness class 1000
Heat treatment was performed at 600 ° C. for 1 hour under the following environment.
Finally, finish polishing was performed. At this time, 100 substrates under each condition of rinsing were produced, and pits and scratches were examined. The results are shown in Table 1 and FIG.

[0014]

[Table 1]

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

In the same manner as in Example 1, CP-2 type pure titanium cold rolled sheet (1.5 mm ^t ), A ring-shaped flat plate with an outer diameter of 95 mm and an inner diameter of 25 mm is punched out, and hot-straightening is performed at 600 ° C. for 6 hours.
Polish with 800, # 1500, and # 4000 grindstones in order,
After finishing polishing with alumina abrasive grains, rinsing for 1 minute was performed. After cleaning and drying, the cleanliness class is 1000 or less (measured value 900), 10000 or less by the method as shown in FIG.
Greater than 000 (measurement value about 9000), indoor (measurement value about 1)
The heat treatment was performed at 600 ° C. for 1 hour in an environment of 50,000). Finally, finish polishing was performed. On this occasion,
Each of the 100 substrates at each cleanness was heat-treated and examined for pit generation. The results are shown in Table 2.

[0017]

[Table 2]

As shown in Table 2, indoors (cleanliness is worse than class 10000), the yield is drastically reduced due to pit generation, and the yield is less than 10%, but when the cleaning degree is 10000 or less, the yield is low. Was 93% or more. (Example 3)

Similar to Example 1, CP-2 type pure titanium cold rolled sheet (1.5 mm ^t ), A ring-shaped flat plate with an outer diameter of 95 mm and an inner diameter of 25 mm is punched out, and hot-straightening is performed at 600 ° C. for 6 hours.
Polish with 800, # 1500, and # 4000 grindstones in order,
Polished with alumina abrasive grains for finish polishing,
An additional 1 minute rinse was applied. Then, after cleaning and drying, 600% under an environment of a cleanliness class of 1000 or less by various methods as shown in (a) to (d) of FIG.
The heat treatment was performed at ℃ × 1 hour. Finally, finish polishing was performed. At this time, 100 substrates were heat-treated by each method and the state of the substrates was examined. Table 3 shows the results. In addition, FIG. 1 (b) shows a substrate material 1 stacked and placed on an alumina surface plate 3, (c) shows a quartz glass surface plate 4 and substrate material 1 alternately laminated, (c). Indicates that one substrate material 1 is placed on the alumina surface plate 3.

[0020]

[Table 3]

As shown in Table 3, with the exception of the method other than the method (a), that is, the method of supporting only the side surface of the inner diameter or the outer diameter, it was confirmed that the yield was largely decreased by the pressure bonding and the pits. (Example 4)

Similar to Example 1, CP-2 type pure titanium cold rolled sheet (1.5 mm ^t ), A ring-shaped flat plate with an outer diameter of 95 mm and an inner diameter of 25 mm is punched out, and hot-straightening is performed at 600 ° C. for 6 hours.
Polish with 800, # 1500, and # 4000 grindstones in order,
After finishing polishing with alumina abrasive grains, rinsing for 1 minute was performed. Then, after washing and drying, a temperature of 400 to 600 ° C. under an environment of a cleanliness class of 1000 or less by a method as shown in FIG.
The heat treatment was performed under the conditions of time 5 minutes to 5 hours. Finally, finish 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 FIGS.
Shown in

[0023]

[Table 4]

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

[0025]

According to the present invention, there is provided a titanium magnetic disk substrate capable of producing a titanium magnetic disk substrate which has few pits and is excellent in wear resistance with high yield.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a relationship between a rinse time and a pit generation rate and a scratch generation rate.

FIG. 3 is a diagram showing a relationship between a heat treatment temperature and 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

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroyoshi Suenaga 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) Reference JP-A-2-148484 (JP, A)

Claims (5)

(57) [Claims] 1. A method of manufacturing a titanium magnetic disk substrate, which comprises rinsing a surface of a substrate material after rinsing, followed by washing and drying, then heat treatment, and further finish polishing. 2. The method for manufacturing a titanium magnetic disk substrate according to claim 1, wherein the rinse time after polishing is 10 seconds or more and 10 minutes or less. 3. The heat treatment is a cleanliness class 100.
2. The process is performed in an environment of 00 or less.
Alternatively, the method for manufacturing a titanium magnetic disk substrate according to the item 2). 4. The heat treatment according to claim 1, wherein the heat treatment is performed by supporting the substrate material so that only side surfaces of the substrate material having an inner diameter or an outer diameter are in contact with each other. Manufacturing method of titanium magnetic disk substrate. 5. The heat treatment according to claim 1, wherein a temperature range of the heat treatment is 500 ° C. or more and 700 ° C. or less, and a holding time is 30 minutes or more and 300 minutes or less. Manufacturing method of titanium magnetic disk substrate.