JPH0663061B2 - Method for manufacturing magnetic disk substrate material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a material for a magnetic disk substrate using a high-purity Al-Mg alloy.

[Prior Art] Conventionally, the material of the magnetic disk substrate is 0.4.
JIS 508 containing ~ 0.7 wt% transition metal (mainly Fe, Mn)
6 alloy materials are used.

In this technique, by containing 0.4 to 0.7% of a transition metal, secondary recrystallization (giant crystal) which may be generated by annealing for removing strain generated in the process of processing the material into a substrate is formed. The occurrence is suppressed.

However, in the magnetic disk substrate using JIS5086 alloy material, it is not possible to miniaturize the intermetallic compound in the magnetic disk substrate, and thus it is not possible to cope with the recent increase in recording density of magnetic disks. .

Therefore, in recent years, materials made of high-purity Al-Mg-based alloys in which the addition amount of transition metals such as Mn, Cr, and Ti are suppressed have been used, and a method for producing a material for a magnetic disk substrate using such a material. For example, there is known a technique of soaking at 450 to 560 ° C, hot rolling, and then cold rolling at a working rate of 55 to 90%.

[Problems to be Solved by the Invention] However, the above-described conventional techniques have the following problems.

Generally, a magnetic disk substrate is manufactured by processing a material according to the following steps.

(A) Punching (die punching) (b) Strain relief annealing (350 to 400 ° C) (c) Roughing (end face and surface roughening) (d) Annealing (350 to 420 ° C) (e) Surface mirror surface Machining (diamond turning, polishing) The reason for performing the cold working rate in the range of 55 to 90% is to increase the cold working rate to increase the material strength and reduce the sagging of the edge during punching. This is because

However, although it has not been a problem with Al-Mg alloys containing 0.4 to 0.7% of transition metals that have been used conventionally, the following problems occur with Al-Mg alloys using high-purity aluminum ingot. Come on.

Since a material made of such an Al-Mg alloy has a low secondary recrystallization temperature, secondary recrystallization (giant crystal) may occur when it is annealed at a high temperature.

Since a material having huge crystal grains has a step between crystal grains during surface finishing, sufficient performance cannot be obtained as a magnetic disk substrate.

On the other hand, although the secondary recrystallization can be prevented by lowering the annealing temperature, the flatness, which is an important characteristic of the magnetic disk substrate, cannot be stably improved. High temperature annealing is preferable for improving flatness.

Therefore, the secondary recrystallization temperature is high, and even in high temperature annealing,
A material for a magnetic disk substrate made of a high-purity Al-Mg-based alloy that does not cause secondary recrystallization has been desired.

It is an object of the present invention to provide a method for producing a material for a magnetic disk substrate, which is made of a high-purity Al-Mg-based alloy that does not generate huge crystal grains even at high temperature annealing.

[Means for Solving Problems] The above problem is that the content of the transition element is less than 0.2% by weight.
A material for a magnetic disk substrate made of an l-Mg alloy, which is the final in the cold rolling in the method for manufacturing the material for a magnetic disk substrate produced by hot rolling and cold rolling after the hot rolling. Cold working rate of 20
This is solved by a method for producing a material for a magnetic disk substrate, which is characterized by being performed in a range of up to 50%.

The present invention will be described in more detail below.

The material produced by the present invention has a transition element content of 0.2.
It is composed of an Al-Mg alloy that is less than wt%.

When the content of the transition element is 0.2% by weight or more, transition metals such as Fe, Mn, and Ti form intermetallic compounds and crystallize, and the crystallized intermetallic compounds impede high recording density of the magnetic disk substrate. Because.

In the present invention, the final substantially cold rolling working rate is set in the range of 20 to 50%, more preferably 30 to 45%.

The hot rolling and cold rolling may be performed as follows, for example.

When the rolling end temperature in hot rolling is the recrystallization temperature (300 to 340 ° C) of the Al-Mg alloy, annealing is performed at a temperature range higher than the recrystallization temperature after the hot rolling and without forming large crystal grains. After 20% to 50% cold rolling.

The rolling end temperature in hot rolling is less than the recrystallization temperature (25
0 to 300 ° C.), or if the temperature cannot be controlled sufficiently above the recrystallization temperature, after hot rolling is completed, annealing is performed within the temperature range above the recrystallization temperature and at which large crystal grains are not generated Method of performing 50% cold rolling When the plate thickness of the target material is thin, it is higher than the recrystallization temperature during the cold rolling process and lower than the temperature at which huge crystal grains are generated, specifically 300 to 400 ° C. After the intermediate annealing is performed in, the final cold rolling may be performed in the range of 20 to 50% working rate.

The reason why the cold working ratio is limited to the range of 20 to 50% in the present invention is as follows.

If the cold working ratio is less than 20%, annealing does not occur in the practical annealing temperature range (350 to 430 ° C), but secondary recrystallization and large crystal grains do not occur, but the primary recrystallized grains become coarse. In the surface finishing step, the crystal grain step becomes large. Further, since sufficient strength cannot be obtained, there is a problem that the edge sag at the time of punching becomes large, and sufficient performance cannot be obtained as a magnetic disk substrate.

If the cold working rate exceeds 50%, the primary recrystallized grains will be sufficiently small and the strength will be improved, but this will occur when processing the material into a substrate (punching, roughing, surface mirror finishing, etc.). The strain relief annealing performed to remove the strain
Secondary recrystallization is likely to occur, which is not preferable.

[Examples of the Invention] The present invention will be described in more detail with reference to Examples.

(Example 1) An Al-Mg alloy having the composition shown in Table 1 was melted. In Table 1, alloy No. 1 and alloy No. 2 are transition metal contents (F
The total content of e, Mn, Cr and Ti) is within the scope of the present invention.
On the other hand, alloy No. 3 is a comparative example in which the total content of Fe, Mn, Cr and Ti is higher than the range of the present invention.

Hot-rolling the ingot produced by the above, by cold rolling,
It was a 4 m / m thick plate. A 14 inch (355.6 mm) size disk blank was punched from this plate, annealed at 350 ° C. for 4 hours (first step annealing), and then annealed at various annealing temperatures shown in Table 2 (second step annealing). I went.

The hot rolling condition, the cold rolling condition and the annealing condition are as shown in Table 2, and the sagging during punching, the strength after cold working, and the grain size after the final annealing are also as shown in Table 2. is there.

As shown in Table 2, in the comparative example (No. 6) having a cold working ratio of 14%, which is lower than the range of the present invention, sagging occurred during punching.
Further, in the comparative example (No. 7) having a cold working ratio of 54%, which is higher than the range of the present invention, huge crystal grains were generated during annealing at 375 ° C.

On the other hand, in the examples (No. 1 to No. 4) of the present invention, sagging did not occur even at the time of punching, and giant crystal grains were not generated.
No. 4 was not removed. No. 4 also occurred for the first time at a high temperature of 425 ° C.

(Example 2) The No. 5 hot-rolled material used in Example 1 was annealed at 370 ° C x 4 hours, and then various cold rolling of 0 to 70% was performed. This plate was shear cut, annealed at 350 x 4 hr (first-stage annealing), and annealed at various annealing temperatures shown in Table 3 (second-stage annealing).
I went.

Table 3 shows the cold rolling working ratio, the crystal grain size after cold rolling and after the final annealing.

In Table 3, No. 9 is a comparative example with a cold working rate of 15%, and No. 13 and No. 14 have a cold working rate of 60% and 80%, respectively.
Is a comparative example. No. 10 to No. 12 are examples of the present invention.

As shown in Table 3, No. 9 caused sagging when punching,
No.13 and No.14 have large crystal grains generated by annealing at 400 ℃.

On the other hand, in the examples of the present invention, no sagging occurs, and no large crystal grains occur even at 425 ° C. annealing.

(Example 3) The No. 4 hot-rolled material used in Example 1 was cold-rolled to a predetermined plate thickness and then subjected to intermediate annealing (first-stage annealing) for 340 x 4 hours.
The above conditions were followed by cold rolling to obtain a cold rolled material of 1.5 mm. A disk blank of 95 mmφ × 25 mm was punched from this rolled material, annealed at 340 ° C. × 4 hr (first step annealing), and then annealed at various annealing temperatures shown in Table 4 (second step annealing). .

Table 4 shows cold rolling conditions, edge sagging during punching, strength after cold rolling, and grain size after final annealing.

In each of the examples (Nos. 16 to 19) of the present invention, sagging did not occur during punching. In addition, except for No. 19, 400 ℃
Generation of large crystal grains was not recognized even by the annealing in. No. 19 with high rolling rate of 45% in cold rolling
The formation of large crystal grains was first observed at 400 ℃.

On the other hand, in the conventional example (No. 20), generation of huge crystal grains was recognized by annealing at 375 ° C.

[Effects of the Invention] As is clear from the above-mentioned examples, the transition metal content is 0.2
% For high purity Al-Mg systems with
By controlling in the range of 50%, sagging at blank punching does not occur, primary recrystallized grain size can be controlled, and giant crystal grains do not occur even when annealed at a high temperature near 375 ° C. We are now able to provide materials for magnetic disk substrates.

Claims (1)

[Claims] 1. An Al having a transition element content of less than 0.2% by weight.
-A magnetic disk substrate material made of an Mg-based alloy, wherein in the method for producing a magnetic disk substrate material which is manufactured by hot rolling and cold rolling after the hot rolling, cold in the cold rolling A method for producing a material for a magnetic disk substrate, which is characterized in that the processing rate is in the range of 20 to 50%.