JPH1110312A - Method for continuously producing single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain large sized single crystal at a quick drawing speed without developing a nucleus by using raw material and a seed crystal being a castable metal or alloy and a heat-insulating mold and continuously and intermittently drawing out a corresponding length of the single crystal grown from the seed crystal by cooling of the seed crystal. SOLUTION: Al is charged as the seed crystal 4 into a graphite mold 3 at the bottom part of a graphite crucible 2, and a water-cooling nozzle 5 is set at a prescribed position of the seed crystal in the reverse direction to molten Al-0.5% copper alloy 1 as the raw material from the outlet end 3" of the mold, and the Al-0.5% copper alloy 1 charged into the graphite crucible 2 is melted while cooling with the water at the room temp. The temp. of the Al alloy at the inlet part 3' of the mold is stabilized at 720 deg.C and the seed crystal is partially melted in the graphite crucible 3, and after confirming that the solidified interface position is fixed, the cooling position of the seed crystal 4 is shifted to the crucible 3 side by 10 mm and held for 15 min. Thereafter, the seed crystal 4 is drawn out by 0.2 mm at 100 mm/min speed and successively, drawn at 2 sec interval by each 0.2 mm to start the casting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing single crystals, which can produce large single crystals stably at a high casting speed without generating new nuclei.

[0002]

2. Description of the Related Art Conventionally, a method of using a mold in which the temperature of the inner wall surface of a mold outlet is maintained at a temperature equal to or higher than a freezing point is used for a single crystal material (Japanese Patent Laid-Open No.
No. 46265). In this method, since the raw material is solidified outside the heated mold, the risk of breakout increases particularly in the casting of a large ingot. Therefore, it is necessary to precisely control the shape of the solidification interface, and it is difficult to increase the size and increase the crystal growth rate to increase the productivity. Also, Japanese Patent Application Laid-Open No. 7-30066
In the method for producing an aluminum alloy single crystal target using a seed crystal described in Japanese Patent Publication No. 7, it is necessary to precisely control the direction in which the cast material is drawn out within 2 ° with respect to the center axis of the mold.
It is not always sufficient that a slight variation in the drawing direction causes a crystal nucleus to be generated on the mold surface.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for continuously producing a single crystal with high productivity, which can produce a large single crystal stably at a high crystal growth rate without generating nuclei.

[0004]

Means for Solving the Problems In a continuous production method of a large single crystal using a seed crystal, the present inventors focused on a solidification interface where a single crystal grows, and used a mold for a solidification interface portion where a single crystal grows. The material, structure, temperature distribution, and cooling mechanism of the seed crystal were eagerly studied. As a result, by controlling the amount of growth and extraction of the single crystal by cooling the seed crystal to a specific condition using an adiabatic template, a large single crystal can be stabilized without generating crystal nuclei on the mold surface. It has been found that the present invention can be manufactured at a high growth rate, and the present invention has been completed.

That is, the present invention is as follows. (1) Continuous production of a single crystal using a heat insulating template and a seed crystal, in which a single crystal material heated and melted is brought into contact with the seed crystal to partially dissolve the seed crystal and then start growing the single crystal. In the method, the single crystal raw material and the seed crystal are castable metals or alloys thereof, and the seed crystal is grown by starting or strengthening the cooling of the seed crystal after the dissolution of the seed crystal has substantially stagnated, The single crystal grown by seeding the single crystal grown from the seed crystal in the direction opposite to the crystal growth direction continuously or intermittently from the template in an amount corresponding to the length of the single crystal grown from the seed crystal by the cooling. A continuous production method for crystals. (2) The method according to the above (1), wherein the material of the heat insulating mold is graphite or ceramic. (3) The production method according to the above (1), wherein the heat insulating mold is kept at a temperature lower than the melting point of the raw material. (4) The manufacturing method according to the above (1), wherein the heat-insulating mold is a box-shaped or cylindrical shape without a bottom. The method according to the above (1), wherein the raw material is charged into the mold while holding the raw material. Hereinafter, the present invention will be described in detail.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a continuous production method of a single crystal, there is a continuous casting method using a seed crystal. Seed crystals are usually
A crystal having the same crystal orientation as the single crystal to be manufactured is required. A single crystal obtained by a general strain annealing method or the Bridgman method can be used as a seed crystal.

[0007] The continuous casting method is a method of continuously drawing a molten metal with a mold having no bottom or a closed end (continuous casting mold) to obtain a long product having a square, rectangular, circular or other cross-sectional shape. Means a method for producing Generally, the mold is made of an aluminum alloy, copper, or a material such as ceramics or graphite that does not require deformation and does not require a lubricant. The continuous casting apparatus includes a vertical type and a horizontal type, and the manufacturing method of the present invention can be applied to both.

The single crystal material having a crystal orientation used in the present invention is obtained by unidirectionally growing a raw material dissolved in a seed crystal charged in a mold. The term "single crystal" as used herein includes a single crystal with a completely uniform crystal structure, as well as a single crystal with a slightly incomplete crystal structure including defects such as vacancies, dislocations, and subgrains obtained by a general solidification method. .

In order to grow a single crystal that inherits the crystal orientation of the seed crystal, the seed crystal is partially melted by contact with a heat-melted single crystal raw material, and after the melting is substantially stopped, the crystal growth is stopped. To start. The mold has a high temperature gradient above the melting point of the seed crystal on the entrance side and a low temperature gradient below the melting point on the exit side. When the dissolution in the mold is substantially stagnant, the seed crystal dissolves and mixes with the raw material from the entrance of the mold to a point in contact with the mold portion that is above the melting point, and the solid-liquid interface at the tip of the seed crystal is It is stationary at a certain position in the mold. Thereafter, the cooling of the seed crystal is started or strengthened, and the single crystal is grown from the seed crystal without substantially changing the temperature distribution of the template. Subsequently, the single crystal grown from the seed crystal in the direction opposite to the crystal growth direction by an amount corresponding to the growth length of the single crystal is pulled out of the mold to start casting. Since the temperature of the mold corresponding to the growth portion of the single crystal is equal to or higher than the melting point of the raw material, no solidification occurs due to crystal nuclei generated from the mold in this drawing operation. Since the single crystal grows in accordance with the amount of the seed crystal pulled out, the single crystal grows by continuously or intermittently pulling out the growth amount of the single crystal.

Although there are no limitations on the raw materials and seed crystals that can be used by the method of the present invention, it is easy to produce a single crystal of a metal or an alloy thereof on the material of the heat insulating mold. In addition, the use of a graphite-based heat-insulating mold for aluminum or its alloy has the advantage that particularly high-purity raw materials can be used without contamination.

The heat-insulating mold is preferably made of graphite or ceramic having low thermal conductivity, which does not react with the raw material melt. In addition, when the heat insulating mold is kept at a temperature lower than the melting point of the raw material, it is easy to control the growth amount and the extraction amount of the single crystal at the solidification interface. Further, in the method of the present invention, a heat-insulating mold is preferable in order to prevent solidification due to crystal nuclei generated from the mold surface, and graphite and ceramics are preferable.

The method of the present invention is applicable to castable metals and their alloys. Specifically, it can be applied to metals and alloys thereof, from magnesium having an atomic number of 12 to lead having an atomic number of 82. Among these metal elements, aluminum, copper, zinc, gallium, tin, lead, gold, and silver, which have low melting points, can be easily applied since a general material such as graphite can be used as a mold material.

Next, a case where an aluminum alloy single crystal is manufactured by the continuous manufacturing method of the present invention will be described as an example. An aluminum alloy as a raw material is melted in a crucible, and a seed crystal is charged in a mold attached to a lower part of the crucible. Before the start of casting, the mold temperature distribution is such that the inlet of the mold is heated above the melting point of the aluminum alloy due to the inflow of heat from the crucible and the melted aluminum alloy, and cooled at the outlet of the mold as necessary at the outlet of the mold. ing. The periphery of the mold may be heated so that the entrance of the mold is higher than the melting point of the aluminum alloy.

The cooling position of the seed crystal is maintained at a fixed position with respect to the mold outlet, and the heat removal from the seed crystal side and the supply of heat from the molten aluminum alloy are balanced to partially dissolve the seed crystal. Cool the seed crystal. By this operation, the solid-liquid solidification interface between the raw material melt and the seed crystal is formed at a certain position in the mold, and after the solid-liquid solidification interface of the seed crystal has stopped at a certain position, the cooling of the seed crystal is started or strengthened, and from several seconds Hold for tens of minutes. As a result, crystal growth from the seed crystal occurs, the solidification interface moves to the aluminum alloy melt side, and a single crystal that inherits the crystal orientation of the seed crystal grows. The growth proceeds toward the high temperature side of the mold, and the mold temperature at the position corresponding to the solidification interface of the grown single crystal material is higher than the melting point of the aluminum alloy.There is no generation of crystal nuclei generated from the mold, and the single crystal grows only from the seed crystal. I do. The cooling of the seed crystal can be enhanced by moving the cooling position of the seed crystal to the mold side at the time of de-heating / supplying heat, or by increasing the amount of a cooling medium such as cooling water. For example, the movement of the cooling position of the seed crystal to the mold side is performed so that the temperature balance at the solidification interface is not significantly changed for the continuous growth of the single crystal.
It is good to be about 50 to 100 mm from mm.

Subsequently, the same distance or less as the solidification progress amount of the aluminum alloy due to the change of the cooling condition is drawn out in the direction opposite to the solidification direction, and casting is started. After starting the drawing under such conditions, a time for growing the single crystal is set, and the operation of drawing out the grown portion is repeated to continue casting. This operation can be performed not only intermittently but also continuously if the coagulation amount and the withdrawal amount can be substantially matched. The withdrawal speed is desirably 2 mm / min or more, preferably several mm / min to 300 mm / min. At 2 mm / min or less, alloying elements are segregated, so there is no problem in the case of pure aluminum, but a single crystal material having a uniform concentration cannot be obtained with an alloy material. At 300 mm / min or more, it is difficult to balance single crystallization due to the mechanism of the apparatus, and it is difficult to control the amount of extraction.

A continuous single crystal material can be obtained by repeating a cycle of drawing out the cast material for a preset time or length at an arbitrary speed, stopping the cast material for a predetermined time, and then drawing out the cast material. By using such an intermittent or continuous drawing method, solidification in the mold becomes regular, and from the start to the end of casting, the generation of new nuclei other than seed crystals can be prevented, and stable casting can be achieved. Single crystallization at a high casting speed is easily achieved, and a smooth casting surface is obtained.

According to the method of the present invention, a single crystal can be continuously produced, and a particularly large single crystal can be obtained. The single crystal produced according to the present invention can be used for, for example, a sputtering target. The sputtering method is widely used industrially as a reflection film, a light-shielding film, a moisture-proof film, a wiring material, and the like because a high-quality thin film is obtained, the productivity is high, and the material to be coated is less damaged. Further, by controlling the crystal orientation of the sputtering target, the film formation characteristics can be improved.

[0018]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

EXAMPLE 1 As shown in FIG. 1, the inner dimensions of a graphite crucible 2 horizontally mounted on the bottom were 400 mm wide, 15 mm high, and 200 mm long.
In a graphite mold 3, aluminum having a width of 395 mm, a thickness of 15 mm, and a length of 300 mm and having a (110) plane as a seed crystal 4 is charged into the mold, and an exit end 3 ″ of the mold is provided.
5 sets of water-cooling nozzles at the position of a seed crystal of 100 mm in the opposite direction to the melt of the raw material (Al-0.5% Cu) alloy 1 and graphite while cooling with 1 liter / minute of water at room temperature (about 20 ° C) The aluminum alloy containing 0.5% copper of the raw material charged in the crucible 2 was melted. After confirming that the temperature of the aluminum alloy melt at the mold entrance (mold entrance end 3 ′ in FIG. 1) is stabilized at 720 ° C., the seed crystal partially dissolves in the graphite mold 3 and the position of the solidification interface becomes constant. Then, the cooling position of the seed crystal 4 was moved by 10 mm toward the graphite mold 3 and held for 15 minutes. Thereafter, the seed crystal 4 was drawn out at a rate of 100 mm / min by 0.2 mm, and then draw drawing was started at an interval of 2 seconds by 0.2 mm. A large continuous cast plate having a length of 600 mm was obtained.
As a result of orientation measurement by X-ray diffraction, the obtained plate was confirmed to be a single crystal of an aluminum (Al-0.5% Cu) alloy having a (110) plane continuously grown from a seed crystal. The crystal orientation was determined by cutting the measurement surface of the measurement sample cut from the continuous cast plate and the seed crystal with a lathe by about 1 mm, removing an extremely thin deformed layer on the surface with aqua regia, and using an X-ray diffractometer (Co., Ltd.). ) Rigaku: RU-200) to determine from the pole figure measured in the Schultz reflection direction.

Example 2 Using the same apparatus as in Example 1, an aluminum alloy containing 0.5% of copper was melted.
An aluminum alloy containing 5% copper was melted. After confirming that the temperature of the aluminum alloy melt at the mold entrance (mold entrance end 3 ′ in FIG. 1) is stable at 720 ° C., the seed crystal is partially melted, and the position of the solidification interface becomes constant, the seed crystal is cooled. While maintaining the position, the cooling water amount was increased to 2 liter / min and held for 15 minutes. Thereafter, the sheet was drawn under the same conditions as in Example 1, stopped, started, and continuously cast to obtain a large continuous cast plate having a length of 600 mm. It was confirmed that the obtained plate was a single crystal of an aluminum alloy continuously grown from a seed crystal.

Example 3 A cast was made under the same conditions as in Example 1 except that a graphite mold containing 10% boron carbide was used as the mold material.
A large continuous cast plate of 00 mm was obtained. It was confirmed that the obtained plate was a single crystal of an aluminum alloy continuously grown from a seed crystal.

COMPARATIVE EXAMPLE 1 Using the same apparatus as in Example 1, an aluminum alloy containing 0.5% of copper was melted, and the temperature of the molten aluminum alloy at the entrance of the mold (mold entrance end 3 'in FIG. 1) was 720. After the temperature was kept constant at 0 ° C., the mixture was left for 15 minutes (the temperature was kept constant at 720 ° C.).
A continuous cast plate having a length of 600 mm was obtained by casting under the same conditions as described above. The obtained plate had a polycrystalline structure in which crystals having a width of about 5 mm were continuously generated in the casting direction from the casting start portion.

COMPARATIVE EXAMPLE 2 Using the same apparatus as in Example 1, an aluminum alloy containing 0.5% of copper was melted, and the temperature of the molten aluminum alloy at the entrance of the mold (mold entrance end 3 'in FIG. 1) was 720. After the temperature was stabilized at ° C, the cooling position of the seed crystal was moved 10 mm to the mold side and held for 15 minutes. Then, at a speed of 100 mm / min, 5
Then, the seed crystal 4 was pulled out of the mm, and casting was started. Then 2
At a time interval of 0.2 mm, the sheet was drawn out by 0.2 mm to obtain a continuous cast plate having a length of 600 mm. The obtained plate had a polycrystalline structure in which crystals having a width of about 5 mm were continuously generated in the casting direction from the casting start portion. This is considered to be due to the fact that more than the growth amount of the single crystal was extracted by the cooling enhancement of the seed crystal.

[0024]

According to the present invention, a large single crystal without segregation can be stably produced without any nucleation during growth, not only in pure metals but also in alloys. The value is extremely large.

[Brief description of the drawings]

FIG. 1 is a drawing of a casting apparatus used in the present invention.

[Explanation of symbols]

 1. 1. Raw material (Al-0.5% Cu) alloy Graphite crucible 3. Graphite mold 3 '. Mold entrance end 3 ''. 3. Mold exit end Seed crystal 5. Water cooling nozzle 6. Nozzle slide rail

Claims (8)

[Claims] 1. A method for producing a single crystal, comprising: a step of bringing a single crystal material heated and melted into contact with the seed crystal to partially dissolve the seed crystal using a heat insulating template and a seed crystal; In a typical manufacturing method, a single crystal raw material and a seed crystal are castable metals or alloys thereof, and the seed crystal is grown by starting or strengthening the cooling of the seed crystal after the dissolution of the seed crystal has substantially stopped. A single crystal is grown by continuously or intermittently withdrawing the single crystal grown from the seed crystal from the template in the direction opposite to the crystal growth direction by an amount equivalent to the length of the single crystal grown from the seed crystal by the cooling. A method for continuously producing a single crystal. 2. The method according to claim 1, wherein the castable metal is a metal having an atomic number of 12 to 82. 3. The method according to claim 1, wherein the castable metal is aluminum, copper, zinc, gallium, tin, lead, gold or silver. 4. The method according to claim 1, wherein the castable metal is aluminum. 5. The method according to claim 1, wherein the material of the heat insulating mold is graphite or ceramic. 6. The method according to claim 1, wherein the heat insulating mold is kept at a temperature lower than the melting point of the raw material. 7. The method according to claim 1, wherein the heat-insulating mold has a box shape or a tubular shape without a bottom. 8. The method according to claim 1, wherein the raw material is melted in a melting or holding crucible having a heat insulating mold attached to a lower portion, the raw material is held at a constant temperature, and the raw material is charged into the mold. .