JPS6138160B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a copper single crystal material, and particularly provides a method for producing a copper single crystal material with good industrial reproducibility.

It goes without saying that copper materials are used in a wide range of industrial fields. In one such field, copper material is used as an electrode material for electron tubes, and in particular, this copper material, which has excellent thermal conductivity and electrical conductivity, is used as an anode member of electron tubes. For example, the anode structure of an X-ray tube is one example, and this application is particularly exposed to high temperatures, and the temperature is repeatedly raised and cooled due to repeated operation. For this reason, during use of the electron tube, grain boundary cracks may occur in the anode material, and thermal conductivity may deteriorate due to the growth of crystal grains. As a result of research conducted by the present inventors, it has become clear that these disadvantages can be completely eliminated in such applications by using a copper single crystal material. However, no method has been established to industrially produce copper single crystal materials with good reproducibility.

The present invention meets the above-mentioned needs and provides a method for producing a copper single crystal material with good reproducibility.

That is, the main points are as follows.

First, the copper material is reductively purified in an atmosphere of a high-purity reducing low-pressure gas such as hydrogen.

Second, the solidification and crystallization temperature of the molten copper material (1083 ℃) The slow cooling rate is set to 5℃/min or less.

Thirdly, in order to be suitable for mass production, we use a container that has a recess in a part of the internal space to house the copper material, and this recess is located at the top of the relative temperature distribution when the temperature in the heating furnace decreases. Place it in a low position so that nucleation and crystal growth occur from this part. This creates the same conditions as if a seed crystal were placed in this area to form a nucleus and the copper liquid was solidified on top of it.

Examples thereof will be described below with reference to the drawings.

1 and 2 are examples of apparatus used to carry out the method of the invention. In this device, a vacuum heating furnace 11 made of a quartz bell gear and capable of reducing the internal pressure to a vacuum state and heating the furnace is placed on a flange 13 via a packing 12 that is airtightly arranged at the open end of the furnace. There is. Flange 13
is connected to an oil rotary pump 16 via an exhaust conduit 14 and a valve 15. Inside the heating furnace 11,
A hollow cylindrical bisque baking table 1 placed on a flange 13
A plurality of containers 18 made of a hardly soluble metal such as graphite are placed in a circle via 7 . This container 18 has a bottom wall 18a whose upper surface is tapered and a cylindrical portion 18b which are fixed together. As a result, the most concave tapered edge portion 18c is formed at the bottom of the internal space of the container. A gas introduction hole 1 is provided on the top surface of the bisque baking table 17.
9 and several exhaust holes (not shown) on the sides. A gas introduction nozzle 20 is provided which penetrates the bottom of the exhaust conduit 14 and has one end protruding into the bisque baking table 17 through the inside of the exhaust conduit 14, and the other end is connected to a high purity hydrogen gas supply source 22 via a minute leak valve 21. A small conduit 23 is provided which is connected to. A high-frequency induction heating coil 24 is wound around the outer periphery of the heating furnace 11, and the inside of the furnace is heated by this.

Therefore, as shown in FIG.
Arrange them in a circle inside. At this time, each container 1
8 are arranged so that the tapered edge portions 18c on the bottom surface, that is, the tips of the recesses, respectively, face outward. That is, all the edge portions 18c of each container are directed outward with respect to the center of the furnace.

In this state, the oil rotary pump 16 is operated, the valve 15 is opened, and the inside of the heating furnace is evacuated to 10 ^-1 to ^{10 -2} Torr.

Next, with the oil rotary pump 16 operating, the minute leak valve 21 is opened, hydrogen is introduced, and the inside of the furnace is adjusted to several Torr to several tens of Torr, for example, 8 to 10 Torr. In this way, a circulation path is created in which the hydrogen gas displaces and cleans the impure gas in the furnace and is discharged by the oil rotary pump 16.

Next, the inside of the furnace is heated with a heating coil according to the temperature raising steps shown in FIG. This process can be roughly divided into three areas as shown in the figure.

Region A is a preliminary degassing step, in which the inside of the container 18 is maintained at 800 to 900° C., and the container and the copper material 25 are cleaned by reduction. This allows sufficient time to remove impurities from each surface area. This is important in suppressing the generation of impurity seeds that tend to accelerate the formation rate of nuclei during solidification and crystallization in region C, which will be described later.

Next, move to area B. In this step, once the container and copper material are clean, the heating temperature is raised to above the melting point, preferably 1200 to 1300°C. This causes intense gas release from the copper material, but 5~
Continue introducing hydrogen gas for 10 minutes. Oxygen in the molten copper material can be actively removed as water using dissolved hydrogen gas. After this, stop introducing hydrogen. As a result, the hydrogen dissolved in the copper material is quickly discharged out of the furnace. The state with hydrogen discharged is approx.
Make the vacuum pressure less than 10 ^-2 Torr.

Next, move to area C. This step is a slow cooling step to obtain a single crystal. In particular, this process eliminates supercooling, reduces the nucleation rate to substantially zero, and promotes crystal growth. According to the inventor's experiments, in this process, slow cooling in the temperature range around the solidification and crystallization temperature of copper (1083°C) at a temperature decreasing rate of 5°C/min or less produces a single crystal with good reproducibility. Moreover, it was confirmed that this method is important as a method that can be industrially mass-produced. This slow cooling rate can be easily controlled by gradually lowering the high frequency power supplied to the high frequency heating coil.

After solidification and crystallization at about 900° C. or lower, rapid cooling is performed using nitrogen gas as shown in region D. This will shorten the process. In this way, a copper single crystal material is obtained.

The single crystal structure of the copper single crystal material obtained according to the present invention was confirmed by chemical etching, X-ray diffraction, and Laue photographic images. In the above example, a copper single crystal material with a diameter of 38 mm and a length of 100 mm is processed at once.
I got 10 pieces.

Note that the hydrogen introduction pressure described above is required to be at least several Torr in order to prevent oxidizing gas from penetrating into the anode material and to create a reducing atmosphere. Furthermore, in consideration of the safe operation of the oil rotary pump, the amount of hydrogen consumed, and the prevention of cavities caused by impure gas in the molten copper material, it is preferable that the upper limit hydrogen pressure is kept at several tens of Torr.

The slower the slow cooling rate, the better; however, from an industrial standpoint, ie, from the standpoint of mass production, the upper limit for single crystallization is 5° C./min or less.

A method with even better reproducibility can be obtained by forming a tapered edge, that is, a recess, in the container and arranging this edge toward the outside of the furnace. In other words, in the slow cooling process, the temperature is lowered using a cylindrical heating furnace and induction heating, so the temperature decreases faster at the periphery than at the center due to heat dissipation, although the temperature is lower at the periphery than at the center. Because it is smaller, the temperature drops the quickest, making it possible to limit the location where nuclei can occur. Therefore, solidification and crystallization starts from this portion and progresses throughout, ensuring that a single crystal structure is obtained.

In the embodiment shown in FIGS. 5 to 7, a container 18 for containing a copper material is provided, and a container 18 is provided at the inner bottom corner.
This is a case where one in which two hole-shaped recesses 18c are formed is used. That is, this container 18 has a recess 18c formed in its flat bottom, and when installed in the heating furnace 11, all the recesses 18c are arranged facing outward.
Even when this is used, the concave portion of this embodiment corresponds to the taper edge portion of the previous embodiment, and the molten copper material begins to crystallize from the concave portion of the container and progresses throughout the container to obtain a single crystal.

In this way, a tapered edge part or a hole-shaped recess as shown in Figs. A single crystal of copper can be obtained with good reproducibility by positioning it toward the point where the temperature distribution is lowest and slowly cooling it.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an example of an apparatus used to carry out the method of the present invention, FIG. 2 is a cross-sectional view thereof, FIG. 5
The figures show another embodiment, FIG. 6 is a cross-sectional view taken along line 6--6 in FIG. 5, and FIG. 7 is a schematic cross-sectional view corresponding to FIG. 2. DESCRIPTION OF SYMBOLS 11... Heating furnace, 16... Exhaust pump, 18... Container, 18c... Recess (taper edge part), 22... Gas source, 24... Heating coil, 25... Copper material.

Claims (1)

[Scope of Claims] 1. A step of placing a container containing a copper material in a reduced pressure heating furnace and heating the copper material in a low pressure reducing gas atmosphere, and following this step, melting the copper material and heating the copper material with the reducing gas. A method for producing a copper single crystal material, comprising the steps of: discharging the copper; and, after this step, slowly cooling the temperature in a temperature range around the solidification and crystallization temperature of copper at a temperature decreasing rate of 5° C./min or less. 2 Set the low pressure reducing gas atmosphere to several torr (Torr).
The manufacturing method according to claim 1, wherein the pressure range is from several tens of Torr to several tens of Torr. 3. The manufacturing method according to claim 1, wherein a container having a recess in a part of the internal space is used as the container for accommodating the copper material. 4. The manufacturing method according to claim 1, wherein the containers containing the copper material are arranged in a circle in a reduced-pressure heating furnace, and the recesses of each container are directed toward the outside of the furnace.