JP2003145249A - Casting mold for manufacturing ingot having minute unidirectionally solidified columnar crystal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting mold for manufacturing an ingot having a unidirectionally solidified columnar crystal structure in which the structure of a cross section orthogonal to the growth direction of the unidirectionally solidified columnar crystal is minute. SOLUTION: Holes 2 are provided at a bottom surface in the casting mold 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a unidirectionally solidified columnar crystal structure having a fine cross-sectional structure perpendicular to the growth direction of the unidirectionally solidified columnar crystal (hereinafter referred to as "fine unidirectionally solidified columnar crystal structure"). A mold for producing an ingot having, in particular, a fine directionally solidified columnar crystal structure having a purity of 99.99%.
The present invention relates to a mold for producing the high-purity metal ingot.

[0002]

2. Description of the Related Art Generally, the molten metal in the mold cavity is gradually cooled from the lower part to the upper part by gradually lowering the mold from the inside of the heating furnace or gradually raising the heating furnace. A method of forming an ingot having a unidirectionally solidified columnar crystal structure by ascending upward from the bottom is called Bridgman method and is generally known. When a high-purity metal, in particular, a high-purity metal ingot of 99.99% or more is produced by this method, the crystal grains grow coarsely because of the high purity of the molten metal and the slow solidification rate. It is also known that an ingot having a unidirectionally solidified columnar crystal structure having grains can be obtained.

On the other hand, it is known to form a high-purity copper thin film as a conductivity-imparting film formed when manufacturing a semiconductor device such as IC, LSI, ULSI. This high-purity copper thin film is a high-purity copper target. It is known to be formed by sputtering. However, in order to make the high-purity copper thin film obtained by sputtering uniform in thickness and to reduce the generation of particles during sputtering, it is necessary to use a target having fine crystal grains. The high-purity copper ingot manufactured by the above-mentioned Bridgman method is generally guaranteed to have a high purity, but since the crystal grains are coarse, the high-purity copper ingot manufactured by this Bridgman method is cut as it is to prepare a target. It is not possible. Therefore, in order to manufacture a sputtering target from a high-purity copper ingot manufactured by the Bridgman method, an ingot having a unidirectionally solidified columnar crystal structure having a coarse cross-section crystal grain is parallel to the growth direction of the unidirectionally solidified columnar crystal structure. After hot forging at least once, cold forging is performed in a direction perpendicular to the hot forging direction, and this is repeated to produce a sputtering target having fine crystal grains (Japanese Patent Laid-Open No. 2001-2001).
-240949).

[0004]

However, when plastic working such as rolling or forging is performed on an ingot having a unidirectionally solidified columnar crystal structure having coarse cross-sectional crystal grains, cracks are likely to occur during the plastic working, and therefore, In addition, the yield becomes poor, and the number of times of plastic working must be increased in order to manufacture a plastically worked body having fine crystal grains, and the cost increases as the number of plastic workings increases.

[0005]

Therefore, the present inventors have
A study was conducted to produce an ingot having a unidirectionally solidified columnar crystal structure with fine cross-section grains. As a result, (a) In the Bridgman method in which the solidification interface of the molten metal in the mold rises upward from the bottom, if a mold with multiple holes at least on the bottom of the mold is used, the holes are filled first. The molten metal solidifies to form a plurality of fine primary crystals, which are unidirectionally solidified to produce an ingot having a fine unidirectionally solidified columnar crystal structure. It is possible to manufacture an ingot having a unidirectionally solidified columnar crystal structure that is finer than the ingot obtained by the method. (B) The plurality of holes provided in the bottom surface of the mold have molten metal at the bottom of the holes. It must be a hole having an opening opening area that is wide enough to reach up to a hole depth D, a hole opening area S, a mold bottom thickness T. Then, 1 <[D / 2 ^{S / π) 1/2] ≦ T} / 2 (S / π) 1/2 ( provided that it is more preferably a hole that satisfies the equation D> 1 mm), provided in (c) the mold inner bottom surface The shape of the opening of the hole may be any shape such as triangular, quadrangular, pentagonal, hexagonal and other polygonal shape, star shape, + type, etc., but the hole was drilled on the bottom surface inside the mold. It is most preferable that it is a circular hole because it is easy to process, and the wall of the hole has a hole provided at the bottom of the mold in order to improve the releasability of the ingot from the mold. It is preferable that the holes are tapered holes having a small area, and these holes are circular holes provided by the above-mentioned drill, and a taper angle is provided by a reamer so that the area of the opening of the hole becomes the largest, or It is preferable to drill a hole with a taper angle in advance. Arbitrariness. (D) In the Bridgman method, since the mold is always placed on the cooling plate, even if the plurality of holes provided in the bottom surface of the mold are through holes that penetrate the bottom of the mold, the molten metal in the mold is through holes. The result of the study was that, when it reached the cooling plate through it, it solidified immediately and did not leak outside.

The present invention has been made on the basis of the above research results, and (1) a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure having holes in the bottom surface inside the mold, (2) A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure in which a hole having a taper whose area decreases from the opening toward the hole bottom is provided on the bottom surface inside the mold, (3) ) The hole provided on the bottom surface inside the mold is 1 <[D / 2 (S / π) ^{1/2, where} D is the depth of the hole, S is the opening area of the hole, and T is the thickness of the bottom of the mold. ] ≦ T / 2 (S / π) ^1/2 (however, D> 1 mm) The ingot having the fine unidirectionally solidified columnar crystal structure according to (1) or (2), which is a hole satisfying the formula The mold for manufacturing, (4) the holes provided in the bottom surface inside the mold are A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to the above (1), (2) or (3), which is a bottom hole or a through hole penetrating the bottom of the mold. It is a thing.

Further, when an ingot having a fine unidirectionally solidified columnar crystal structure is produced by using a mold having holes on the bottom surface inside the mold, the crystal grains growing from the side wall inside the mold become coarse. There is. In order to avoid this, it is preferable to provide a bottomed hole in the side wall inside the mold. Therefore, the present invention provides (5) a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure in which holes are provided in the bottom and side walls inside the mold, (6) openings in the bottom and side walls inside the mold. From the mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure in which a hole having a taper whose area decreases toward the hole bottom is provided,
(7) The hole provided on the bottom surface inside the mold is 1 <[D / 2 (S / π) ^{1 where} D is the depth of the hole, S is the opening area of the hole, and T is the thickness of the bottom of the mold. ^{/ 2} ] ≦ T / 2 (S / π) ^1/2 (however, D> 1mm) is a bottomed hole or through hole, while the hole provided on the side wall is 1 <[D / 2 (S / π) ^1/2 ] <T / 2 (S / π) ^1/2 (where D> 1 mm), which is a bottomed hole satisfying the formula (5) or (6). For producing an ingot having fine unidirectionally solidified columnar crystal structure of (8)
The hole provided in the bottom surface inside the mold is a bottomed hole or a through hole penetrating the bottom of the mold, and the hole provided in the side wall is a bottomed hole (5), (6) or (7) A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to (7).

If an attempt is made to manufacture an ingot having a fine unidirectionally solidified columnar crystal structure by the Bridgman method using the mold described in the above (1) to (8) having a bottomed hole on the bottom surface inside the mold, at least As many primary crystals as there are holes are generated. Therefore, the larger the number of holes formed on the bottom surface of the mold, the larger the number of primary crystals generated, which is preferable.
The number of bottomed holes formed on the bottom surface inside the mold is 1 / cm ²
The above is necessary. However, when the number exceeds 50 / cm ² ,
Since the diameter of the hole to be formed becomes too fine and the molten metal cannot penetrate into the hole, the number of primary crystals generated decreases, and an ingot having a fine unidirectionally solidified columnar crystal structure can be produced. It is not preferable because it cannot be done. Therefore, according to the present invention, (9) the number of bottomed holes and through holes provided on the bottom surface inside the mold, and the number of bottomed holes provided on the side wall inside the mold are 1 to 50 / c.
A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to any one of (1) to (8) having m ² .

Each of the holes provided inside the mold of the present invention must be an independent hole. With a hole having a shape in which it is connected to the adjacent hole on the inner surface of the mold, an ingot having a fine unidirectionally solidified columnar crystal structure cannot be obtained.

In the molds described in (1) to (9) above, holes are formed at least at the bottom inside the mold. However, forming holes inside the mold is costly, and especially at the bottom of a deep mold. It costs money to open. Therefore, it is preferable to have a separable structure in which the bottom portion having the hole and the tubular portion are detachable. Therefore, the present invention provides (10) the mold is
A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to any one of (1) to (9), which has a separable structure in which a bottom with a hole and a cylinder are detachable. , Are characterized.

A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure of the present invention will be described with reference to the drawings. FIG. 1 shows a state in which a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to the above (1) to (3) of the present invention is charged with a molten metal and placed on a cooling plate. It is a cross-sectional front view. In FIG. 1, 1 is a mold, 2 is a hole provided in the bottom of the mold, 3 is a cooling plate, and 4 is a molten metal. The molten metal 4 injected into the mold is cooled by the cooling plate 3 and solidification starts from the molten metal filled in the holes 2, and more primary crystals (not shown) than the number of holes are formed, and then by the Bridgeman method. When an ingot having a unidirectionally solidified columnar crystal structure is produced, a large number of the primary crystals grow and an ingot having a finer unidirectionally solidified columnar crystal structure is formed by the ordinary Bridgman method. The hole 2 may have any opening shape, but if the opening area is small, the molten metal cannot reach the bottom of the hole due to the surface tension of the molten metal, and the generation of primary crystals is reduced. Therefore, it is necessary to provide a hole having an opening area large enough to be filled with molten metal, and the opening area is related to the depth of the hole, and a hole having a small opening area has a small depth. On the other hand, if the hole having a large opening area is not deep, an ingot having a fine unidirectionally solidified columnar crystal structure cannot be obtained.

FIG. 2 is a sectional view showing a state in which a molten metal is charged into a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to the above (4) of the present invention and placed on a cooling plate. It is a front view. In FIG. 2, 1 is a mold, 21 is a through hole provided in the bottom of the mold, 3 is a cooling plate, and 4 is a molten metal. Even if the hole provided in the bottom surface of the mold 1 is the through hole 21 penetrating the bottom of the mold 1, the molten metal 4 in the through hole is the cooling plate 3
It is cooled and solidified by and does not leak outside.

The hole 2 provided at the bottom of the mold is
The shape of the hole may be
D, the opening area of the hole is S, and the thickness of the bottom of the mold is T, 1 <[D / 2 (S / π)^1/2] ≦ T / 2 (S / π)^1/2 (However, D> 1 mm) Bottomed hole that satisfies the formula or
It is a through hole, while the hole provided on the side wall is 1 <[D / 2 (S / π)^1/2] <T / 2 (S / π)^1/2 It is a bottomed hole that satisfies the formula (however, D> 1 mm).
It is even more preferable. Fine unidirectionally solidified column of this invention
Inside of mold for producing ingot with crystal structure
If a hole is formed in the
It is possible to manufacture ingots that have
S: Since D is more preferable to exceed 1 mm, D> 1
mm. Also, in this equation, (S / π)^1/2Is up to
It is the square root of the value obtained by dividing the opening area S of the desired shape hole by π.
It This is (S / π) when the opening of the hole is circular^1/2
Is the radius of the circular hole, which is doubled to 2 (S / π)
^1/2Corresponds to the inner diameter of the circular hole. On the other hand, the opening shape of the hole is non-
If it is a circle, for example a rectangle,
Let S be (S / π)^1/2Turns the rectangle into a virtual circle
2 (S / π), which is equivalent to the radius when^1/2
Corresponds to the inner diameter of the virtual circular hole. Provided on the bottom inside the mold
Depth of the bored hole: D must be larger than the inner diameter of the virtual circular hole
Is required, so 1 <[D / 2 (S / π)^1/2] No
I have to. However, the holes provided on the bottom inside the mold
May be a through hole that penetrates the bottom of the mold,
If the thickness of the bottom is T, the depth of the hole is the thickness of the bottom of the mold.
Must be less than or equal to T. Therefore the bottom surface inside the mold
Since the hole provided in can be a through hole, D =
Since it may be T, 1 <[D / 2 (S / π)
^1/2] ≦ T / 2 (S / π)^1/2(However, D> 1mm)
The formula holds. However, on the side surface inside the mold
Since the cut hole cannot be a through hole, 1 <
[D / 2 (S / π)^1/2] <T / 2 (S / π)^1/2(However
Then, the equation of D> 1 mm) is established.

FIG. 3 is a sectional front view of a mold for producing the ingot having the fine unidirectionally solidified columnar crystal structure according to (5) to (7) of the present invention. In FIG. 3, 1 is a mold, 2 is a hole provided in the bottom of the mold, and the hole 2
Is also provided on the side wall inside the mold, and by providing the hole 2 in the side wall, it is possible to avoid coarsening of crystal grains growing from the side wall inside the mold.

FIG. 4 is a sectional front view of a mold for producing the ingot having the fine unidirectionally solidified columnar crystal structure according to (8) of the present invention. In FIG. 4, 1 is a mold,
Reference numeral 2 is a bottomed hole, and 21 is a through hole provided on the bottom surface inside the mold. Even if the hole provided in the bottom surface of the mold 1 is the through hole 21 penetrating the bottom of the mold, the molten metal in the through hole is cooled by the cooling plate to be solidified and does not leak to the outside.

FIG. 5 shows a method for producing an ingot having a fine unidirectionally solidified columnar crystal structure having a separable structure in which a holed bottom portion and a cylindrical portion are detachable as described in (10) of the present invention. It is a cross-sectional front view of a mold. In FIG. 5, 10
Is a bottom portion provided with the hole 2, 11 is a tubular portion, and the tubular portion 1
1 is fitted in the bottom portion 10 and has a detachable and separable structure. By having such a detachable and separable structure, the ingot can be easily removed from the mold, and only the bottom portion 10 in which the hole 2 with the most wear is opened can be replaced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Example 1 A carbon mold having an inner diameter of 110 mm and a depth of 150 mm was prepared, and the inner bottom surface of the mold 1 had an inner diameter of 4
The bottomed holes 2 having the dimensions of mm, depth: 5 mm, taper angle: 2 ° were formed at a rate of 4 holes / cm ² to prepare the mold shown in FIG. Hold this mold in the heating furnace 1
After heating to 100 ° C., pure copper molten metal having a purity of 99.99% is poured, and the mold is gradually pulled down from the heating furnace to unidirectionally solidify from below to above to produce an ingot having a unidirectionally solidified columnar crystal structure. did. The ingot having this unidirectionally solidified columnar crystal structure was cut at a right angle to the solidification direction, and the average crystal grain size of the cut surface was measured and found to be 0.9 cm.

Example 2 Inner diameter prepared in Example 1: 110 mm, depth: 150 m
Through holes 21 having an inner diameter of 4 mm and a depth of 10 mm were formed at a rate of 4 holes / cm ^{2 on} the bottom surface of a carbon mold having m, to produce the mold shown in FIG. This mold is placed on a cooling plate, held in a heating furnace and heated to 1100 ° C., and then a pure copper molten metal having a purity of 99.99% is poured in, and the mold is gradually pulled down from the heating furnace to move upward from the bottom. Was unidirectionally solidified toward the direction to prepare an ingot having a unidirectionally solidified columnar crystal structure. The ingot having the unidirectionally solidified columnar crystal structure was cut at a right angle to the solidification direction, and the average crystal grain size of the cut surface was measured and found to be 0.8 cm.

Example 3 Inner diameter prepared in Example 1: 110 mm, depth: 150 m
A carbon mold having m is prepared, and 4 holes / cm having bottomed holes 2 having an inner diameter of 4 mm, a depth of 5 mm, and a taper angle of 2 ° are provided on the inner bottom surface and side wall of the mold 1.
^It was formed at a ratio of ² to produce the mold shown in FIG. After holding this mold in a heating furnace and heating it to 1100 ° C., pure copper molten metal having a purity of 99.99% was poured, and the mold was gradually pulled down from the heating furnace to unidirectionally solidify from below to above, An ingot having a directionally solidified columnar crystal structure was produced. The ingot having this unidirectionally solidified columnar crystal structure was cut at a right angle to the solidification direction, and the average crystal grain size of the cut surface was measured and found to be 0.9 cm.

Example 4 Inner diameter: 110 mm, depth: 150 m prepared in Example 1
Through holes 21 having an inner diameter of 4 mm and a depth of 10 mm were formed at a rate of 4 holes / cm ^{2 on} the bottom surface of a carbon mold having m, and further, an inner diameter of 4 mm, a depth of 5 mm, and a taper angle of 2 ° were formed on the side wall. The bottomed holes 2 having the size of 4 were formed at a rate of 4 holes / cm ² to prepare the mold shown in FIG. This mold is placed on a cooling plate and held in a heating furnace for 1100
After heating to ℃, a pure copper molten metal having a purity of 99.99% was poured, and the mold was gradually pulled down from the heating furnace to unidirectionally solidify from below to above to produce an ingot having a unidirectionally solidified columnar crystal structure. . The ingot having this unidirectionally solidified columnar crystal structure was cut at a right angle to the solidification direction, and the average crystal grain size of the cut surface was measured,
It was 0.9 cm.

Conventional Example 1 Internal diameter prepared in Example 1: 110 mm, depth: 150 m
An ingot having a unidirectionally solidified columnar crystal structure was produced in the same manner as in Example 1, using the m-shaped carbon mold as it was without forming holes. The ingot having the unidirectionally solidified columnar crystal structure was cut at a right angle to the solidification direction, and the average crystal grain size of the cut surface was measured to be 5c.
It was m.

As is clear from Examples 1 to 4 and Conventional Example 1, an ingot having a finer unidirectionally solidified columnar crystal structure can be obtained by using a mold having holes in the bottom surface or bottom surface and side walls inside the mold. It turns out that it can be manufactured. In addition, in Examples 1 to 4 and Conventional Example 1,
Although an ingot having a unidirectionally solidified columnar crystal structure was produced by the usual Bridgman method, an ingot having a unidirectionally solidified columnar crystal structure was produced while applying rotational vibration to the mold, and a finer unidirectionally solidified columnar crystal was produced. It has been found that an ingot with a texture can be produced.

[0023]

INDUSTRIAL APPLICABILITY Since the ingot manufactured using the mold of the present invention can provide an ingot having a finer unidirectionally solidified columnar crystal structure throughout, the plastic working for grain refinement is possible. The number of steps can be reduced and the cost can be reduced, resulting in an excellent industrial effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional front view showing a state in which a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure of the present invention is charged with a molten metal and placed on a cooling plate.

FIG. 2 is a cross-sectional front view showing a state in which a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure of the present invention is charged with a molten metal and placed on a cooling plate.

FIG. 3 is a sectional front view of a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure of the present invention.

FIG. 4 is a sectional front view of a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure of the present invention.

FIG. 5 is a sectional front view of a mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure having a separable structure in which a holed bottom portion and a cylindrical portion are detachable according to the present invention.

[Explanation of symbols]

1: mold, 2: hole, 21: Through hole, 3: cooling plate, 4: molten metal,

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B22D 27/04 B22D 27/04 A C23C 14/34 C23C 14/34 A

Claims (11)

[Claims] 1. A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure, characterized in that a hole is provided in the bottom surface inside the mold. 2. An ingot having a fine unidirectionally solidified columnar crystal structure, characterized in that a hole having a taper whose area decreases from the opening to the hole bottom is provided on the bottom surface inside the mold. Mold for doing. 3. The hole provided on the bottom surface of the mold has a depth of D, an opening area of the hole of S, and a thickness of the bottom of the mold of T: 1 <[D / 2 (S / π ) ^1/2 ] ≤ T / 2 (S / π) ^1/2 (where D> 1 mm), which is a hole satisfying the formula; A mold for producing an ingot having a crystal structure. 4. The fine hole according to claim 1, 2 or 3, wherein the hole provided on the bottom surface inside the mold is a bottomed hole or a through hole penetrating the bottom of the mold. A mold for producing an ingot having a directionally solidified columnar crystal structure. 5. A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure, characterized in that holes are provided in a bottom surface and a side wall inside the mold. 6. An ingot having a fine unidirectionally solidified columnar crystal structure, characterized in that holes having a taper whose area decreases from the opening to the hole bottom are provided on the bottom and side walls inside the mold. A mold for manufacturing. 7. The hole provided on the bottom surface of the mold is 1 <[D / 2 (S / π, where D is the depth of the hole, S is the opening area of the hole, and T is the thickness of the bottom of the mold). ) ^1/2 ] ≦ T / 2 (S / π)
^{It is} a bottomed hole or through hole that satisfies the formula ^1/2 (where D> 1 mm), while the hole provided in the side wall is 1 <[D / 2 (S / π) ^1/2 ] < T / 2 (S / π)
7. A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to claim 5 or 6, which is a bottomed hole satisfying the formula ^1/2 (where D> 1 mm). . 8. The hole provided in the bottom surface of the mold is a bottomed hole or a through hole penetrating the bottom of the mold,
The mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to claim 5, 6 or 7, wherein the hole provided in the side wall is a hole having a bottom. 9. The number of bottomed holes or through holes provided on the bottom surface inside the mold, and the number of bottomed holes provided on the side wall inside the mold are 1 to 50 / cm ^2. A mold for producing an ingot having a fine unidirectionally solidified columnar crystal structure according to any one of claims 1 to 8. 10. The ingot having a fine unidirectionally solidified columnar crystal structure according to claim 1, wherein the mold has a structure in which a bottom portion and a cylindrical portion can be divided. Mold for manufacturing. 11. The unidirectional fine grain structure according to claim 1, wherein the mold is a mold for casting a high-purity metal having a purity of 99.99% or more. A mold for producing an ingot having a solidified columnar crystal structure.