JPS637355A - Annealing method for al-mg alloy - Google Patents

Abstract

PURPOSE:To prevent the generation of secondary recrystalized grains by annealing by annealing an Al-Mg alloy member contg. Cr at an extremely low ratio as a stock for a high-brightness alloy and magnetic disk under specific conditions. CONSTITUTION:The generation of the huge secondary recrystallized grains is prevented by heating the member to a 400-550 deg.C temp. range at >=50 deg.C/min heating up rate and holding the member at said temp. for >=10min, then cooling the same down to an ordinary temp. at the time of annealing the member after working the alloy to the member when the stock for the high-brightness alloy and magnetic disk is going to be produced by the Al-Mg alloy contg. Mg at 3.5%<=Mg<=5.5% by weight % as the essential condition and contg. <=0.1% Fe, <=0.2% Mn, <=0.06% Cr, and <=0.025% Ti. The deterioration in the appear ance and performance by the secondary crystallization in specular finishing is obviated in the case of the high-brightness material, and the generation of steps by the huge secondary recrystallized grains in precision finishing by ma chining is obviated in the case of the magnetic disk. The stock for the high- brightness material and magnetic disk having the excellent performance is thus obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of annealing an Al-Mg alloy, and more specifically, an Al-Mg alloy that is less likely to cause secondary recrystallization during annealing.
This invention relates to a method of annealing g-alloy.

[Prior art] Cr content: about 0.1% by weight or more and 0.3% by weight or less, Mn
3 A-5% Mg alloy with a content of 0.4% by weight or less
It is known that when annealing is performed at a temperature of about 50°C or higher, secondary recrystallization occurs at a temperature of about 350°C or higher. (light metals, Van, No6, p233 r50
"Abnormal coarse graining phenomenon of 56 alloy").

Incidentally, in recent years, the use of high-purity metals has become common in the fields of high-brilliance alloys, magnetic disk materials, etc. to improve performance, and A fL -M with a Cr content of less than 0.1% by weight has become common.
The use of g-alloy materials also became common.

In addition, as an annealing method for Al-Mg alloy, 34
A method is known in which the material is heated to a temperature of about 0 to 400° C. at a temperature increase rate of about 10 to b, and then maintained at that temperature for about 1 to 10 hours after heating.

[Problems to be Solved by the Invention] However, even in an Al-Mg alloy in which 0.1% by weight of Cr is not layered, a secondary recrystallization phenomenon occurs.

When secondary recrystallization occurs, in addition to the problem of reduced strength, for example, in the case of high brightness materials, crystal grains can be observed with the naked eye during mirror finishing, making it impossible to obtain the desired appearance performance.

In addition, in the case of magnetic disk materials, precision cutting finishing (Rmax≦0.02 lm) is performed after annealing the soft material, but if secondary recrystallization (giant recrystallization) is formed during this annealing, after cutting,
Huge crystal grains are observed with the naked eye. There is a step difference between these giant crystal grains, and there is a problem that sufficient performance as a base cannot be obtained. In the case of even more extreme giant grains,
There is also the problem that phenomena such as chatter occur.

Further, even if secondary recrystallization does not occur during annealing, giant crystal grains are likely to be formed by heating during each process of forming a magnetic disk.

[Means for solving the problems] The above problems essentially include 3.5% by weight≦Mg≦5.5% by weight, Fe≦0.1% by weight, Mn≦0.2i% by weight,
In a method for annealing a Hemi-Mg alloy containing Cr≦0.06% by weight and Ti≦0.02% by weight, annealing is performed at 400°C.
By heating to a temperature of ~550°C at a temperature increase rate of 50°C/min or more, it is possible to solve the problem of crystallization on the secondary page during pressurization of 370°C or more at that point and in subsequent steps.

(Reason for limited ingredients) First, the reason for limiting the ingredients will be explained.

3.5% by weight≦Mg≦5.5% by weight Mg is added to provide sufficient strength for the intended use. For this reason, 3. 1% or more of Si is added. In addition, if it exceeds 5.5% by weight, the strength will become too high and the workability will worsen, and MgO oxides will be likely to be generated during melting and casting, which will be incorporated into the AM-based alloy and during mirror finishing. Since it tends to cause defects, it is set at 5.5% by weight or less.

Fe≦0.1% by weight, Mn≦0, 2fi amount%, Cr≦
Compositions such as 0.063g% and Ti≦0.02i% are based on AfL-Fe, Al-Mn, and Al-Ti.
This is to suppress the formation of all-in-one compounds, such as silica, and to obtain sufficient mirror-finishing properties.

In addition, in order to obtain sufficient performance as a mirror surface, it is desirable to reduce the Si content, which is determined by the purity of the metal used and is usually 0.08% by weight or less. Other additions of Cu and Zn have little effect on mirror finish properties, and are usually added in an amount of 0.3% by weight or less.
．． Zn is added in an amount of 5% by weight or less.

(Reason for limited annealing conditions) Next, annealing will be explained.

In the present invention, annealing is performed at a temperature of 400°C to 550°C at 50°C.
This is done by heating at a temperature increase rate of at least /min. This is done by rapidly raising the temperature to such a high temperature, recrystallizing at this heating stage, and creating a stable structure that does not cause the formation of giant crystals during subsequent heating. This is for the purpose of

At a heating rate of less than 50°C/min, the
Huge crystals are formed when heated at temperatures between 00°C and 550°C.

If the heating temperature is less than 400°C, the effect of preventing the formation of giant crystal grains in subsequent heating or annealing (at 370°C or higher) is insufficient, and if the heating temperature exceeds 550°C, burning is likely to occur.

Note that the upper limit of the temperature increase rate does not need to be specified in particular in the present invention, but in the case of gas furnace heating, infrared furnace heating, etc., if the temperature increase rate is too fast, the plate surface will melt, so the upper limit is 1500℃/
It is desirable to keep it below min, and in the case of saltpeter furnace heating, it is 2000-b. Note that it is also possible to apply an electromagnetic induction heating method.

No particular holding time is required, and simply reaching a temperature of 400°C to 550°C is sufficient for the annealing effect, but for the stability of crystal grains during subsequent heating or annealing,
It may be held for less than 0 minutes.

There is no need to regulate the cooling rate from the viewpoint of preventing giant crystal grains from falling, but if it is too slow, the precipitation of the β phase will become noticeable, and if it is too fast, the plate will become distorted, so the temperature should be lowered from 0.5°C to 100°C.
C/m1n(r) range is preferred.

The AJI-Mg alloy soft material annealed in this manner will not form giant crystals during subsequent heating.

Note that depending on the application, the rapid heating in the present invention is effective even when heating only the surface layer of the plate.For example, in the case of a material for a magnetic disk, 0.05 to 0.2
It is normal to cut and grind to a depth of mm before use, and only this region is heated in such a way that giant crystal grains are not generated, that is, only the surface layer satisfies the annealing conditions according to the present invention. However, there is no practical problem.

[Example of the invention] Alloys (alloy A, alloy B) having the compositions shown in Table 1 were heated at 540°C
After soaking for 4 hours, hot rolling was performed. In addition, alloy A,
Alloy B is also an alloy having a composition targeted by the present invention. The hot rolling was completed when the plate thickness was 6 mm and the temperature was 260°C. Roughly cold rolling is performed after hot rolling, 1.
The thickness was 5 mm. This was punched into a ring shape with an outer diameter of 95 φmm to obtain a disc material.

The thus prepared materials were subjected to first-stage annealing and second-stage annealing at various heating temperatures and temperature raising conditions shown in Table 2.

Annealing and performance evaluation annealing (hereinafter referred to as A annealing and B annealing, respectively)
The grain size was observed after each annealing. The results are also shown in Table 2.

In Table 2, material Nos. 4, 6, 7°, 10.11 are examples of the present invention, and the others are comparative examples.

Examples will be explained below based on Table 2.

(Not) In annealing under this condition, pressure annealing is performed as A annealing to correct distortion, and after cutting both sides of the plate approximately 0.1 mm each,
Pressure annealing at 370°C for 6 hours to correct distortion (B annealing)
This is what was done. Approximately 3000 in this B annealing
Huge crystal grains of 1.0 m were formed. As a result, even if precision cutting is performed, crystal grains can be observed in the internal medicine.
Correspondingly, the surface precision deteriorated due to the step difference between the crystal grains, and sufficient performance as a magnetic disk could not be obtained.

(N o 2) For No. 2, pressure annealing for strain correction at 350'OX for 4 hours was performed as A annealing. The grain size at this point was as small as 35 gm, but after rough cutting, it was further
When pressure annealing (B annealing) was performed for 3 hours, approximately 50
Huge crystal grains of 00 JLm were formed.

(N o 3) In No. 3, when pressure annealing was performed at 370° C. for 6 hours in A annealing, giant crystal grains of about 2000 JLm were formed at that point.

(No. 4) In No. 4, A was heated at 400°C x 1 using an infrared heating furnace.
0mln, heating rate 300℃/min, cooling rate 1
Annealed at 00 °C/mL n. Furthermore, when pressure annealing (B annealing) was performed for 385×6 hours to correct the strain, giant crystal grains of 45 pm were formed, making the material unsuitable for use as a material for magnetic disks.

(No.5) No.5 is pressure annealing of A at 400℃X using electromagnetic induction heating method.
It was carried out under the conditions of 10 m1n and a temperature increase rate of 15° C./min, and the results were similar to No. 2, making it unsuitable as a material for magnetic disks. (No. 6.7) In No. 6.7, A annealing was performed in an infrared heating furnace under the annealing conditions according to the present invention, and it is clear that no giant crystal grains are generated even if B annealing is performed thereafter.

(No. 8) For No. 8, after heating and pressure annealing of A at 340° C. for 2 hours, rough cutting and precision cutting were performed, and the resultant material was used as a base for a magnetic disk. Furthermore, after alumite was anodized to a thickness of 12 pm and made to 10 pm at Kenfu, it was heated at 370°C for 2 hours (B
When annealing), giant crystal grains of approximately 3000 pm were formed, and perhaps due to the crystal rotation at this time, the surface roughness of the base became large, and sufficient performance as a magnetic disk could not be obtained.

(N　o　9) No. 9 is similar to No. 2.

(N　o　　0) In NolO, A annealing is performed in an infrared heating furnace.

Further, under the annealing conditions according to the present invention, in which pressure annealing (v & CB annealing) was performed at 385° C. for 6 hours, it is clear that no giant crystal grains are formed even in the second stage of heating.

(Noll) In Noll, heating in a saltpeter furnace is performed as A annealing, and then left to cool.
After surface puff polishing (cleaning).

Second stage pressure annealing (B annealing) was performed at 400° C. for 6 hours to correct distortion. Furthermore, after performing rough cutting and finishing cutting to obtain a disk base, it was anodized and further heated. Even during this heating, no giant crystal grains were formed, and the problem that occurred in magnetic disk No. 8 did not occur.

[Effects of the Invention] Since the present invention is configured as described above, there are no secondary recrystallized crystals even after annealing or other heating after annealing, and therefore: ■No decrease in strength■ In the case of high brightness materials, it has excellent external properties when finished with a mirror finish.■In the case of magnetic disk materials, even if a close cutting finish (Rmax≦0.02 lm) is performed after annealing the soft material, the cutting After that, no giant crystal grains were observed, and sufficient performance as a base was obtained.

■ Phenomena such as chatter do not occur.

Claims (1)

[Claims] 1 Essentially contains 3.5% by weight≦Mg≦5.5% by weight,
Fe≦0.1% by weight, Mn≦0.2% by weight, Cr≦0.
06% by weight, Al-M containing Ti≦0.02% by weight
A method for annealing an Al-Mg alloy, characterized in that annealing is carried out at a temperature of 400° C. to 550° C. at a temperature increase rate of 50° C./min or more.