JP4729070B2 - Aluminum alloy substrate for magnetic disk and die for punching press of aluminum alloy substrate for magnetic disk - Google Patents

Description

The present invention (hereinafter this specification means used to. The "blank") aluminum alloy substrate for a magnetic disk relates stamping press die for an aluminum alloy substrate for 及 beauty magnetic disk.

As shown schematically in FIG. 1, a punching die (pushback method) for a magnetic disk substrate (hereinafter simply referred to as “substrate”) is used to punch an aluminum alloy strip 1 into a donut shape. It consists of a lower mold 2 and an upper mold 3 that are arranged opposite to each other in the vertical direction.
The lower die 2 is provided with an outer peripheral die 20 and a central hole punch 21, and the upper die 3 is a punch 30 disposed so as to descend between the die 20 and the hole punch 21, and the die 20 relative to the outer periphery thereof. And a stripper 31 arranged to do so. In FIG. 1, the knockout of the lower mold 2 facing the punch 4 is omitted.

The substrate is manufactured as follows.
The aluminum alloy strip 1 is supplied between the lower die 2 and the upper die 3 in the direction of the arrow, and the die 1 is held between the die 20 and the stripper 31, and the punch 30 is held at a predetermined pressure with the die 20 and the hole punch 21. Then, the tip is lowered so as to enter, and the doughnut-shaped substrate whose outer edge is defined by the die 20 and the punch 30 and whose inner edge is defined by the hole punch 21 and the punch 30 is punched out.
Substrate punched to a size slightly larger than the product substrate is subjected to pressure annealing to remove distortion caused by punching, and then substrate processing (inner and outer peripheral grinding, surface grinding) ⇒ plating processing ⇒ finishing process by polishing processing The product substrate is passed through.

  Due to the difference between the outer diameter of the punch 30 and the inner diameter of the die 20 and the difference between the inner diameter of the punch 30 and the outer diameter of the hole punch 21 (clearance necessary for punching), as shown in FIG. Occasionally, a burr 10b is formed on the outer edge of the upper surface, and a sag (end surface sag) 10a is formed on the outer edge of the lower surface. Burrs and end sagging are also formed on the inner edge. The size w of the sag 10a in the radial direction of the substrate 10 is the sag width, and the size h in the thickness direction is the sag depth. The clearance on the outer diameter side at the time of punching needs to be larger than the inner diameter side by design, and the end face sag at the outer edge is larger than that at the inner edge. It becomes.

That is, in order to improve the storage density of the product substrate and expand the storage area under a certain size, the substrate 10 has a sagging depth that is allowed to process the substrate 11 (FIG. 9) that matches the size of the product substrate. In the limit of h, it is necessary to remove the sagging width w by grinding. Therefore, the larger the end sag of the substrate (especially the sag depth h), the larger the grinding allowance during substrate processing must be designed, and the longer the grinding time and the greater the amount of grinding, the higher the manufacturing cost To do. Recently, there has been a demand for increasing the thickness of a substrate (for example, from about 1.3 mm to a little over 1.8 mm) by improving the memory density.
In order to reduce the edge sag, an inclined portion (inclination angle of 0.1 to 15 °) is formed on the die punching surface for punching the outer edge of the substrate. Has been proposed (see Patent Document 1 below).
However, if an inclined part that is continuously inclined downward in the outer peripheral direction is formed on the edge of the die, the sagging width of the outer edge of the substrate can be reduced to some extent, but it is not very effective in improving the sagging depth, and the gold Reduce mold life.
In addition, although the clearance can be reduced to improve the end face sagging, it adversely affects the life of the mold and is not suitable for mass production.
JP 2003-223714 A

  The problem to be solved by the present invention is to provide an aluminum alloy substrate for a magnetic disk having a small end face sagging, a small grinding allowance at the time of substrate processing, and excellent in productivity. Provided is a method for manufacturing an aluminum alloy substrate for a magnetic disk capable of further reducing end face sagging (especially sagging depth) of an outer edge portion, and a punching press die capable of smoothly and reliably carrying out the manufacturing method. There is.

A die for punching press of an aluminum alloy substrate for a magnetic disk according to the present invention is to first punch an aluminum alloy strip having a thickness of 1.292 to 1.84 mm into a donut shape in order to solve the above problems. A die for punching comprising a die, a punch, and a stripper, wherein a protruding portion having a flat portion having a predetermined width a larger than 0.01 mm having an inner edge constituting a cutting edge is formed on a die punching surface, The width b of the ridge portion including the inclined portion inclined downward from the outer peripheral portion of the ridge portion is greater than 0.2 mm and 10 mm or less.
Second, the height c of the ridges is greater than 0.05 mm and is ½ or less of the thickness t of the aluminum alloy strip.

By the present invention lever, in the process of punching an aluminum alloy Motojo in a donut shape, forming the flat portion of a predetermined width a1 recessed a predetermined amount in the direction of the stripper to the inner edge of the contact surface of the die of the skeleton (the (Formed by the flat portion of the ridge of the cutting edge of the die), the formation of edge sag at the outer edge of the substrate adjacent to the flat portion during punching is suppressed, and the sag depth is particularly reduced.

  According to the die for punching press of an aluminum alloy substrate for a magnetic disk according to the present invention, a convex strip having a flat portion with a predetermined width a whose inner edge constitutes the cutting edge is formed on the die punching surface. When the alloy strip is punched into a donut shape, a flat portion having a predetermined width is formed on the contact surface of the skeleton with the die so as to be continuous with the inner edge portion and correspond to the flat portion of the die. The flat part forming part of the skeleton is compressed in the thickness direction more than the other part. By this compression, the material of the strip of the compressed portion flows in the direction of the substrate being punched (direction of arrow d in FIG. 3), and the outer edge of the substrate being formed is pressed toward the inner edge. Therefore, the formation of the end face sagging of the substrate is suppressed, and in particular, the sagging depth is reduced. Therefore, the manufacturing method according to the present invention can be carried out smoothly and reliably.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a manufacturing method and a punching press die according to the present invention will be described below with reference to the drawings.
First Embodiment FIG. 1 is a schematic sectional view showing a first embodiment of a punching press die according to the present invention, FIG. 2 is an enlarged sectional view of a portion C of the die of FIG. 1, and FIG. 3 is a die of FIG. It is a partial expanded sectional view at the time of punching a strip using a type | mold.

Since the basic structure of the mold has been described above, a specific form of a die having characteristics will be described below.
The die 20 of the lower mold 2 that is disposed relative to the upper mold 3 has a height having a flat portion with a predetermined width a on the inner edge side of the punching surface (surface facing the stripper 31), the inner edge constituting the blade edge portion 20a. A convex ridge portion 20b of c is formed. The outer peripheral portion (outer peripheral wall) of the ridge portion 20b is vertical, and the punching surface in the outer peripheral direction of the ridge portion 20b is a relief portion 20d that is recessed by the height c of the ridge portion 20b.
As the material of the lower mold 2 and the upper mold 3, alloy tool steel (SKD) for cold mold, high-speed tool steel (SKH) and other commonly used mold materials are used.

With reference to FIG. 3, an embodiment of a mold operation and an aluminum alloy substrate manufacturing method of the first embodiment will be described.
An aluminum alloy strip 1 is intermittently supplied between the lower mold 2 and the upper mold 3. The supplied strip 1 is fixed by being sandwiched between a die 20 and a stripper 31, and the punch 30 is lowered by a predetermined pressure to be punched and then raised to the original level, and the punched substrate 10 is made gold by a knockout 22 or the like. Knock out of the mold.

In the punching process shown in FIG. 3, the protruding portion 20 b of the die 20 is sunk in the direction of the stripper 31 by the punching pressure at the inner edge portion of the contact surface of the skeleton 12 of the strip 1 with the die 20. The flat part 12a which became depressed in the said part is formed.
When the flat portion 12a is formed, the portion of the strip 1 is compressed in the plate thickness direction, and a part of the material of the portion flows in the direction of the substrate 10 being punched out as indicated by an arrow d in the figure. At this time, since the outer edge portion of the substrate 10 is strongly pressed in the direction of the inner edge portion, the formation of the end surface sag 10a at the outer surface of the lower surface of the substrate 10 is suppressed, and the formed end surface sag 10a has a sag width and a sag depth. Both become smaller. According to the experiment, the sagging depth tends to be suppressed as the strip 1 is thicker.
Thus, since the end face sag (particularly the sag depth) of the substrate 10 is reduced, the required amount of grinding in the radial direction during the substrate processing is reduced, and the grinding time is shortened, so that the product substrate can be manufactured at a lower cost. Can do.
In addition, when the flat part 12a hollow in the lower surface inner edge part of the skeleton 12 is formed, the other part of the material of the said part of the strip 1 flows in the direction of the escape part 20d.

  FIG. 4 is an enlarged cross-sectional view showing, as a comparative example, a punching state using a mold in which the entire punching surface of the die 20 is flat. As shown in FIG. 4, the punching surface of the die 20 is flat. Since the outer edge on the substrate 10 side is not pressed in the inner edge direction at the time of punching or the force is small even when pressed, the formation of the end face sag 10a is not suppressed, and the end sag 10a has a large sag width and sag depth. Become.

If the width a of the flat portion, which is the top of the ridge portion 20b, is too small, the mold life will be shortened (shortened) due to damage or rapid wear of the ridge portion 20b, and if the width a exceeds 10 mm, Deformation, damage, and the like are likely to occur in a portion (next workpiece) to be punched next to the strip 1. Therefore, it is preferable that the width a of the upper surface of the ridge portion 20b is 0.01 mm to 10 mm.
If the height (the depth of the relief portion 20d) c of the ridge portion 20b is too small, the effect of suppressing the end face sag as described above is reduced, and the height c is ½ of the thickness t of the strip 1. If exceeded, the mold life will be reduced. Therefore, it is preferable that the height c of the protruding portion 20b is 0.05 mm to a plate thickness t × 1/2 or less of the strip 1.

Second Embodiment FIG. 5 is a partially enlarged cross-sectional view showing a second embodiment of a die for punching press according to the present invention, and the outer peripheral portion (outer peripheral wall) of the ridge portion 20b of the die 20 is first lowered in the outer peripheral direction. It is formed in the inclined part 20c. Thus, by making the outer peripheral part of the ridge part 20b into the inclined part 20c, the flow of the material of the inner edge part on the skeleton side toward the escape part 20d becomes smooth at the time of punching, which has a positive effect on the mold life. (Long life)
The width b including the inclined portion 20c of the ridge portion 20b is preferably approximately 10 mm or less, although it depends on the inclination angle θ (plane width a) of the inclined portion 20c, and immediately after exceeding 10 mm. The possibility of adverse effects (deformation and damage) on subsequent workpieces increases.
The inclination angle θ of the inclined portion 20c is not particularly limited.
Since the other structure and effect of the metal mold | die of this embodiment are the same as that of the metal mold | die of 1st Embodiment, those description is abbreviate | omitted.

Third Embodiment FIG. 6 is a partially enlarged cross-sectional view showing a third embodiment of a die for punching press according to the present invention. For the same purpose as the die of the second embodiment, the projection 20b of the die 20 is shown. The outer peripheral inclined portion 20c is formed in a concave arc shape in cross section.
Also in this embodiment, the width b including the inclined portion 20c of the ridge portion 20b is preferably about 10 mm or less in the same meaning as in the second embodiment.
The radius R, which is the size of the arc of the concave arcuate inclined portion 20c, is not particularly limited, but is preferably within the range of values obtained by the following equation.
Formula: R = {(ba) 2 + c2} / (2c)
Since the other structure and effect of the metal mold | die of this embodiment are the same as that of the metal mold | die of 2nd Embodiment, those description is abbreviate | omitted.

Fourth Embodiment FIG. 7 is a schematic sectional view showing a fourth embodiment of a punching press die according to the present invention. The punching surface of the hole punch 21 has the following characteristics.
On the punching surface of the hole punch 21, a protruding strip portion 21 b having a height c ′ having a flat portion having a predetermined width a ′ is formed on the outer edge side constituting the cutting edge 21 a. The inner peripheral portion (inner peripheral wall) of the ridge portion 21b is vertical, and the punched surface in the inner peripheral direction of the ridge portion 21b is a relief portion 21d that is recessed by the height c ′ of the ridge portion 21b. .

  If the above-mentioned convex strip portion 21b is formed on the outer edge side of the punching surface of the hole punch 21, when the punch 30 descends and punches the strip (not shown), a part of the material of the portion of the strip is made. Flowing in the direction of the substrate being punched (peripheral direction), the inner edge of the substrate is strongly pressed in the direction of the outer edge, so that the formation of the end surface sag at the inner surface of the lower surface of the substrate is suppressed. Both sagging width and sagging depth become smaller. In particular, the sagging depth decreases, and this tendency becomes more prominent as the thickness of the strip increases.

It is preferable to form the inner peripheral part of the protruding line part 21b in the inclined part 21c having a downward-falling shape as shown by a two-dot chain line in FIG.
For the same reason, preferable values for the width a ′, the width b ′ of the ridge portion 21b including the inclined portion 21c, and the height c ′ of the ridge portion 21b are the widths a and b of the ridge portion 20b in the die. It is almost the same as the preferred value of the height c.

It is a metal mold | die (die | dye) of 1st Embodiment-3rd Embodiment, Comprising: The width | variety b of the flat part of the convex part 20b in the die | dye 20, and the width | variety b and height c of the convex part 20b containing the inclination part 20c are set. Various dice of each embodiment and various comparative dice in the form of FIG. 4 (no convex shape) and FIG. 8 (angle θ = 14 ° of the inclined portion of the cutting edge, flat portion width a = 0) are manufactured as prototypes. Then, 3.5-inch size aluminum alloy substrates were punched, and the size of the end face sag (sag width w and sag depth h) of these substrates was measured. The measurement results are shown in Table 1.
In addition, the dice | dies of Example 8 and Example 16 are examples in which the inclination part 20c in the protruding item | line part 20b is not a tip-down shape, and the inclination angle (theta) exceeds 90 degrees.
In addition, the die life of each die was evaluated and the influence on the next workpiece was investigated. Evaluation of mold life is based on the normal number of punches (5 million times) of the mold using the die shown in Fig. 4 as the standard, with ○ exceeding the standard and x indicating less than the standard. Indicates a case where no deformation or damage occurred, and a case where such deformation occurred.

Conditions such as mold dimensions, strips, punching conditions and sagging measurement methods are as follows.
Mold dimensions Die inner diameter: 96.0mm
Punch outer diameter: 95.8mm
Knockout outer diameter: 95.8mm
Stripper inner diameter: 96.4mm
Aluminum alloy strip Material: JIS5086
Thickness t: 1.84mm, 1.292mm
Punching conditions Continuous punching by pushback method 200ton press sag measurement method Measuring instrument: Contour shape measuring instrument (Form coder EF-12), Kosaka Laboratory Ltd.
Radius of curvature of stylus tip: 25 μm
Applied load: 30mN
Scanning speed: 0.05mm / s
Sagging width w and sagging depth h: As shown in FIG. 9, the reference points A and B are set on the back surface of the substrate in the horizontal posture at a distance interval more than twice the sagging width, and the outer peripheral direction connecting the reference points A and B An extension line extending to the horizontal reference line is defined as a vertical reference line and a vertical extension line extending downward from a sag depth starting point, which is a protruding end of the outer peripheral edge of the substrate. The sagging width w is defined as the sagging width start point from the starting point of the sagging width starting from the horizontal reference line on the lower surface of the substrate, and the sagging depth h is defined as the sagging depth h from the sagging depth starting point to the intersecting point of the two reference lines. The values of the sagging width w and sagging depth h in Table 1 are average values of measured values obtained by measuring the sagging width and sagging depth at one place (the place where the sagging is maximum in the circumferential direction of the board) for each of the 50 substrates. is there.
Table 1 also shows the ratio (w / t, h / t) of the average sag width w and the average sag depth h to the strip thickness t.

According to the results shown in Table 1, Examples 1 to 8 in the case where the strip thickness is 1.84 mm are smaller than both the average sag width w and the average sag depth h as compared with Comparative Examples 1 and 2, and are sufficient. Significant difference was shown.
In Examples 9 to 16 in the case of a plate thickness of 1.292 mm, the sagging width of Examples 12 and 15 (550.7 μm of Comparative Example 4) is compared with Comparative Examples 3 and 4 in both the average sagging width w and the average sagging depth h. , Except for 551.2 [mu] m and 556.4 [mu] m), respectively, and showed a significant difference in sagging depth.
As described above, the effect of forming the ridge portion 20b having a flat portion having a predetermined width a continuously from the cutting edge portion of the die is particularly remarkable in suppressing the sagging depth. Furthermore, the effect of the sagging depth improvement becomes more remarkable as the strip thickness increases.
In addition, since the size of the end face sagging of the substrate becomes smaller in proportion to the thickness of the raw strip, the effect of suppressing the sagging depth h when the above-described convex strip portion 20b is formed on the die punching surface is It is remarkable when the plate thickness is 50 mil (1.27 mm. 1 mil = 1 inch / 1000≈0.0254 mm. Normally, a substrate with a plate thickness of 1.292 mm is finished into a product with a plate thickness of 50 mil). However, the smaller the product plate thickness is less than 50 mil, the more significant difference disappears. That is, when manufacturing a thin product substrate such as 31.5 mil or 40 mil, for example, the strip plate thickness is also thin, so the effect of the punching press die according to the present invention is almost eliminated.
According to the above, the aluminum alloy substrate for a magnetic disk according to the present invention is an aluminum alloy substrate for a magnetic disk punched into a donut shape by a press die having a die, a punch, and a stripper. The average sag depth of the outer peripheral end face measured under the conditions of an applied load of 30 mN and a scanning speed of 0.05 mm / s is 150 μm or less.
The average sag depth is an average value of sag depths measured at one location (a location where sag is maximum in the circumferential direction of the substrate) for each of a large number of substrates.

Moreover, according to the comparison with Examples 1-5 and Examples 6-8, and the comparison with Examples 9-13 and Examples 14-16, the width | variety a of the plane of the protruding item | line part 20b is 10 mm or less, convex It can be seen that the height c of the strip portion 20b is preferably 0.05 to 1/2 of the plate thickness of the strip 1, and the width b including the inclined portion 20c of the convex strip portion 20b is approximately 10 mm or less.
Furthermore, the inclined portion 20c of the ridge portion 20b is not a tip-down shape, and the inclination angle θ is 5.7 ° higher than 90 °, and the width a of the flat portion exceeds 10 mm. In the example, the mold life and the subsequent workpiece are adversely affected. Therefore, it is preferable that the inclined portion 20c has a tip-down shape.

  The present invention can be applied not only to a push-back type die but also to other types of punching press die that use a die.

It is sectional drawing which shows the outline of the metal mold | die for punching presses of 1st Example of this invention. It is an expanded sectional view of the C section of the metal mold | die of FIG. It is a partial expanded sectional view which shows the state which has punched the strip by the metal mold | die of 1st Embodiment. It is the expanded sectional view which showed in a comparative example the punching state using the metal mold | die with which the punching surface whole surface of die | dye is flat. It is a partial expanded sectional view of the die | dye of the metal mold | die of 2nd Embodiment. It is a partial expanded sectional view of the die | dye of the metal mold | die of 3rd Embodiment. It is a partial expanded sectional view of the punch of a metal mold | die of 4th Embodiment, and a hole punch. It is a partial expanded sectional view of the die | dye in the metal mold | die of the comparative examples 2 and 4. FIG. It is a partial expanded sectional view of the pierced substrate.

DESCRIPTION OF SYMBOLS 1 Aluminum alloy strip 10 Board | substrate 11 Substrate 12 Skeleton 2 Lower mold | type 20 Dies 20a, 21a Blade edge part 20b, 21b Projection part 20c, 21c Inclined part 20d, 21d Escape part 21 Hole punch 22 Knockout 3 Upper mold | type 30 Punch 31 Stripper a, a 'Width of the flat portion of the ridge portion b, b' Width of the ridge portion including the inclined portion c, c 'Height of the ridge portion

Claims (2)

  A press die having a die, a punch and a stripper for punching an aluminum alloy strip having a thickness of 1.292 to 1.84 mm into a donut shape, and an inner edge forms a cutting edge on the die punching surface A ridge having a flat portion having a predetermined width a larger than 0.01 mm is formed, and the width b of the ridge including an inclined portion inclined downwardly from the outer periphery of the ridge is larger than 0.2 mm. A die for punching and pressing an aluminum alloy substrate for a magnetic disk, characterized by being 10 mm or less.   The die for punching press of the aluminum alloy substrate for magnetic discs of Claim 1 whose height c of the said protruding item | line part is 0.05 mm or less and is 1/2 or less of the thickness t of an aluminum alloy strip.

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