JPH05311361A - Method for stress relieving anneling aluminum alloy substrate - Google Patents

Abstract

PURPOSE:To improve the flatness of a substrate by releasing the load of a spacer on a disk material and cooling the substrate. CONSTITUTION:The aluminum alloy disk substrate which has been rolled and punched into a doughnut shape is stress relieving annealed. One to six disk materials are laminated with a spacer in between, the laminate is pressed under 20X10<-4> to 120X10<-2>N/mm<2> load, heated to 250-500 deg.C and kept at that temp. for 0 to 1800sec, then the upper spacer and load are released, and the disk material is cooled. The spacer is made of ceramic or heat-resistant steel, preheated and used to center the disk at ordinary temp.

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 an aluminum alloy substrate, and more particularly to a method for strain relief annealing an aluminum alloy substrate for magnetic disks for computers and the like.

[0002]

2. Description of the Related Art An aluminum alloy is usually used for a magnetic disk substrate used in an external storage device for a computer, and when manufacturing this aluminum alloy substrate, donuts are removed from a base plate. After being punched into a shape, heat treatment is necessary to correct the distortion. This is a heat treatment performed to change the rolling structure into a recrystallized structure and prevent the base shape from changing over time.

On the other hand, it is necessary to reduce the flying height of the head in order to increase the recording density, and the demand for lowering the flatness is becoming stricter. As a method for solving the decrease in flatness due to the increase in capacity, conventionally, a plurality of metal disks to be strain-corrected are stacked on an iron surface plate, and a load of 100 to 2000 kg is applied from above. , There was a method of straightening them by inserting them into a heating furnace.
(See Jitsukai Sho 62-88748).

However, in the method disclosed in Japanese Utility Model Laid-Open No. 62-88748, when an Al spacer is used, the spacer is polished every time it is used due to a decrease in flatness and surface defects. It takes a long time to straighten because of batch annealing. When using an Al spacer, it is difficult to separate the spacer from the disc material. When ceramics or heat-resistant steel is used as the spacer instead of Al, it is difficult to use it for straightening the strain because of different thermal expansion coefficients. There are problems such as.

For this reason, the demand for higher capacity is becoming more and more strict, and in recent years, the demand for improvement in flatness has been demanded, and these conventional straightening processes satisfy these demands. I can't do it.

As a countermeasure against this, Japanese Patent Laid-Open No. 63-14441
No. 4 proposes a method by hot pressing. This method is a method in which after heating a disk substrate, a spacer held at the same temperature as the disk is used to pressurize and correct the distortion. However, even with such a development example, only the flatness equivalent to that of the above-mentioned Japanese Utility Model Laid-Open No. 62-88748 can be obtained, and the correction effect cannot be obtained unless pressure is applied during the disk temperature rising process. When ceramics or heat-resistant steel is used as the spacer in place of Al, there is a problem that it is difficult to use it for strain correction because of different thermal expansion coefficients. Furthermore, the conventional method is
Because of the batch annealing, it took about 10 hours to enter the furnace and it was difficult to make it continuous.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is possible to continuously use aluminum alloy disk materials having excellent flatness without the problem of separation between substrates or between the substrate and spacers. Moreover, it aims at providing the flatness correction technique which can be manufactured in a short time.

[0008]

In order to solve the above problems, the present inventor has taken measures to prevent deterioration of flatness due to a difference in thermal expansion in spacers (platens) made of heat-resistant steel, ceramics or the like having excellent durability. As a result of intensive studies, the present invention has been completed here.

That is, according to the present invention, in an aluminum alloy base for a magnetic disk containing Mg, when pressing the disk material sandwiched between the spacers and cooling after annealing, cooling is performed with the upper spacer and the pressure released. The gist is a strain relief annealing method for an aluminum alloy substrate, which is characterized by

The present invention will be described in more detail below.

[0011]

[Action]

The aluminum alloy disc substrate produces residual stress when processed into a donut shape during the rolling and punching process. In order to remove this, a load is sandwiched between spacers with excellent flatness with the same coefficient of thermal expansion to apply a load, and the flatness is increased by the synergistic effect of the apparent flatness improvement and the elastic deformation stress removal effect due to heating. Is said to improve. However, if this spacer material is different from the disc material and the coefficient of thermal expansion is significantly different, heating / pressing the spacer and disc material under pressure
It is said that when cooled, thermal distortion occurs due to a difference in thermal expansion coefficient, and a good straightening effect cannot be obtained.

In this respect, as a method of preventing the deterioration of the flatness due to the difference in the coefficient of thermal expansion, it is possible to correct it by repeatedly applying pressure and absorb the thermal expansion in the released state. In the method, it was found that the accuracy of the pressing force is indispensable, such as the handling of the repeated pressurization under high temperature, the method, etc., and therefore it is not preferable.

On the other hand, in the present invention, since it was found that the correction effect appears in the temperature rising process, cooling is performed with the upper spacer and the pressure being released. If it is corrected during the cooling process, the flatness is adversely affected by the difference in cooling rate due to the difference in thermal conductivity between the spacer and the disk material, the restriction during thermal contraction, and the like.

This cooling may be forcedly performed by a fan or the like, and it is not particularly necessary to perform in-furnace cooling or natural cooling. In the past, since the disk material was sandwiched between two spacers and cooled while the load was applied, it took a long time to cool down. However, the upper spacer (upper surface plate) and the load were removed like this. By cooling with, the cooling time can be significantly shortened.

The method until the above-mentioned cooling in the strain relief annealing is not particularly limited, and the same method as the conventional method is also possible, but in order to make the strain straightening continuous treatment and shorten the treatment. The following modes are preferable.

In a first mode, one or more disc members are sandwiched between the spacers to apply pressure and heat, and when the maximum temperature is reached, cooling is performed with the upper spacer and the pressure released. Is. The temperature is raised to a predetermined processing temperature with an appropriate pressure in consideration of the size and thickness of the disc material. The rate of temperature increase is not particularly limited, but for example, if the O material is annealed, it may be structurally recrystallized. Also, it is not necessary to hold at the maximum temperature,
It is preferable to hold it appropriately.

The second mode is a method in which a disk at room temperature is sandwiched between spacers that have been heated in advance, and heating and pressing are performed rapidly. The heating temperature of the spacer in advance is preferably in the range of 250 to 500 ° C. The pressure holding time after heating for a short time is preferably 0 seconds or more and 1800 seconds or less.

In the conventional batch annealing method, high load load
It is heated for a long time, and with a pressure of about 100 kg / side, 34
Heating at 0-380 ° C for about 10 hours was required. However, when the main purpose is continuous, short time processing is desirable, and according to the present invention, short time processing is possible as in the above-mentioned aspect.

Moreover, according to the present invention, in the case of short-time treatment, contrary to the conventional wisdom, it is possible to obtain better flatness under a low load. The preferred pressure of low load is 20 × 10 ^-4 N / mm ² or more, 120 × 10 ^-4 N / mm ² per disc material.
It is below.

Even if a spacer (ceramics, heat-resistant steel, etc.) having a different thermal expansion coefficient from that of the disk is used, it is needless to say that ceramics or stainless steel is superior to Al in high temperature strength, and the spacer is flat. In addition, due to the good sliding property between the surfaces, a better straightening effect can be seen as compared with the case where the spacer made of the same aluminum alloy as the disc is used. Examples of ceramics include alumina, Zr-alumina, and SiC, and examples of heat-resistant steels include stainless steel such as SUS304.

The number of disks sandwiched between the spacers is preferably 1 or 6 or less. If the number of disks exceeds 6, it is not preferable because in the cooling process, distortion is adversely affected between the loaded disks and a difference in cooling rate occurs.

Needless to say, as the aluminum alloy, Al alloys of various compositions containing Mg can be used as in the conventional case. The disk material includes a blank material and a substrate material.

Next, examples of the present invention will be described.

[0025]

[Example 1] 97 mm that has been processed to have a highly accurate flatness in advance
With a spacer of φ × 23mmφ × 10mmt (heat resistant steel, ceramics), sandwich one or more 3.5 inch Al alloy punched disc materials (Al alloy equivalent to A5086),

[Table 1] The temperature and temperature were increased to the pressure and temperature shown in (1) (see FIG. 1) and cooled. The method of releasing pressure and cooling was performed by releasing the upper spacer and pressure and cooling (FIG. 2) (Example of the present invention). For comparison, a method (FIG. 2) in which the disc material was sandwiched between the spacers and cooled was also performed (conventional example).

Table 1 shows the flatness of the obtained disc material. The flatness was measured after straightening with "NIDEK" (trade name). From the table, it can be seen that the examples of the present invention exhibit excellent flatness even when heat-resistant steel or ceramics is used as the spacer.

[0027]

[Example 2] As a spacer, a spacer processed in the same manner as in Example 1 (Al material, heat-resistant steel, ceramics)
Prepared. Further, an Al alloy disk material (Al alloy corresponding to A5086) of 1.35 t × 95φ × 24φ (mm) which was rolled and punched by a conventional method was prepared.

Then, one or more disc materials at room temperature are sandwiched between the spacers heated to a predetermined temperature in the heating furnace, a load is applied to the spacers to pressurize them, and they are held in the furnace for a predetermined time and immediately after the holding. It was extracted from the furnace, the upper spacer and the pressure were released and cooled in the manner shown in FIG. 2 (Example of the present invention). For comparison, it was also cooled by the pressure release and cooling method shown in FIG. 3 (comparative example).

The strain after straightening of the obtained disc material is shown in Table 2.
As shown in, it is understood that the example of the present invention exhibits excellent flatness.

[0030]

Example 3 In addition, in order to investigate the relationship between the applied load and the strain after straightening,

[Table 3] The conditions other than those shown in (1) were corrected in the same manner as in the example of the present invention of Example 2. As a result, as shown in Table 3, it can be seen that excellent flatness can be obtained by appropriately setting the additional load.

In order to investigate the relationship between the spacer material and post-correction strain,

[Table 4] The conditions other than those shown in (1) were corrected in the same manner as in the example of the present invention of Example 2. As a result, as shown in Table 4, it is found that excellent flatness is obtained when ceramics or heat resistant steel is used as the spacer.

Further, in order to investigate the relationship between the number of straightened sheets and the strain after straightening,

[Table 5] The conditions other than those shown in (1) were corrected in the same manner as in the example of the present invention of Example 2. As a result, as shown in Table 5, it can be seen that the effect of improving the flatness tends to decrease when the number of disk materials is more than 6.

Further, the heating method (heating furnace, hot press,
(Spacer preheating) and heating temperature, in order to investigate the relationship between holding time and post-correction strain,

[Table 6] The conditions other than those shown in (1) were corrected in the same manner as in the example of the present invention of Example 2. In the table, the case where the heating method is “spacer preheating” is the same as the heating method similar to that of the example of the present invention in Example 2, but in the case of “heating furnace” and “hot press”,
This is the case where the disc material is sandwiched between the spacers and heated under pressure in a heating furnace or hot press. As shown in Table 6, in the case of the example of the present invention, excellent flatness was obtained by short-time annealing with a low applied load.

[0034]

As described in detail above, according to the present invention,
In the strain relief annealing of the aluminum alloy substrate for magnetic disks, by cooling in a state where the upper spacer and the pressure are released, excellent flatness can be obtained and annealing can be performed for a short time. Further, it is also possible to use durable heat-resistant steel or ceramics which could not be used for strain relief annealing because of different thermal expansion coefficients as spacer materials.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a state where a disc material is sandwiched between spacers.

FIG. 2 is a diagram for explaining the cooling method of the present invention, showing that cooling is performed with the upper spacer and the pressing force released.

FIG. 3 is a diagram illustrating a conventional cooling method, which illustrates cooling with a disk material sandwiched between spacers.

[Table 2]

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Keiji Okada 15 Kinugaoka, Moka-shi, Tochigi Prefecture Kobe Steel Works Moka Works

Claims (7)

[Claims] 1. An aluminum alloy substrate for a magnetic disk containing Mg, characterized in that when pressure is applied to the disk material sandwiched between the spacers and cooling after annealing, cooling is performed with the upper spacer and the pressure released. Strain relief annealing method for aluminum alloy substrate. 2. The method according to claim 1, wherein one or a plurality of the disc members are sandwiched between the spacers to apply pressure and heat, and when the maximum temperature is reached, the upper spacer and the pressurization are cooled. the method of. 3. Between the pre-heated spacers,
The method according to claim 1, wherein at least one disk material at room temperature or up to six disk materials stacked so that the centers of the disk materials are not separated from each other is sandwiched, pressed, and held for a short time, and then cooled with the upper spacer and the pressure released. The method described in. 4. The heating temperature of the spacer is 250 to 500.
The method according to claim 3, wherein the method is at ° C. 5. The pressing force per disk material is 20 ×
The method according to claim 3, wherein the amount is 10 ^-4 N / mm ² or more and 120 × 10 ^-4 N / mm ² or less. 6. The method according to claim 3, wherein the pressure holding time is 0 seconds or more and 1800 seconds or less. 7. The method according to claim 1, wherein ceramics or heat resistant steel is used as the spacer.