JPH0351676B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a tungsten single crystal and a method for manufacturing the same. The term "single crystal" as used herein refers to a material containing giant crystal grains that are extremely large compared to the plate thickness. [Prior Art] Polycrystalline tungsten, which has excellent high-temperature strength, is known as a heat-resistant material, but a drawback of this polycrystalline tungsten is that its grain boundaries are brittle. Furthermore, polycrystalline tungsten has extremely poor moldability at temperatures below room temperature, and when used at high temperatures, its crystal grains become coarse and recrystallization embrittlement occurs, making it unable to fully demonstrate its properties as a heat-resistant material. I can't. Therefore, the uses of polycrystalline tungsten are limited. Therefore, if it is possible to provide a tungsten single crystal with no or very few grain boundaries, even after forming into an arbitrary shape, it would be useful for high-power laser reflectors, IC substrate materials, reactor materials for nuclear fusion reactors, and nuclear reactors. When used in heating elements, crucibles, electronic parts, etc., it can be used until it wears out without mechanical damage due to grain boundary brittleness.
The field of application will be significantly expanded. As this type of tungsten material, a tungsten material containing giant grains or a single crystal tungsten material can be considered. Incidentally, although tungsten single crystals have conventionally been able to be produced by a zone melting method or the like, there have been problems in that the shape or production scale is limited, and furthermore, the production technique requires skill. [Object of the Invention] An object of the present invention is to provide a tungsten single crystal having an arbitrary shape without causing damage due to grain boundary embrittlement. Another object of the present invention is to provide a manufacturing method that does not require any skill and can therefore produce the above-mentioned tungsten single crystal very easily. [Configuration of the Invention] The tungsten single crystal according to the present invention contains at least one of calcium and magnesium in the total amount.
It contains 0.007 to 0.090 atomic percent. In addition, this tungsten single crystal contains at least one of calcium and magnesium in a total amount of 0.007 to 0.007.
It is obtained by molding a tungsten polycrystal containing 0.0090 atomic percent into a predetermined shape and annealing this molded body in a predetermined atmosphere. [Examples of the Invention] The present invention will be described below based on Examples. Calcium and magnesium were added to the tungsten oxide powder by a wet method in various ratios shown in sample numbers 1 to 6 as shown in Table 1, and metal powder was obtained using a powder metallurgy method. After molding this metal powder at a pressure of 3 tons/ ^cm2 , the temperature is 1800 to 2000.
A sintered body was obtained by sintering in a hydrogen atmosphere at ℃ for 10 hours.
Furthermore, this sintered body is subjected to hot processing (temperature 1600-1200
℃) and warm working (1000 to 500℃) to achieve a final rolling reduction of 70% or more to 1 to 2 mm.
Standard plate-shaped samples 1 to 6 of (thickness) x 30 mm (width) x 150 mm (length) were prepared. And this standard plate sample 1
-6 were annealed for 3 hours in a predetermined atmosphere at a temperature of 2500°C.

[Table] As is clear from the table above, the crystalline state of the plate-like sample No. 1 is fine grain, and
The crystalline state of the plate-shaped sample is substantially semi-crystalline containing giant grains. Also sample numbers 3, 4 and 5
The crystalline state of the plate-shaped sample is single crystal. According to experiments conducted by the inventors, when the total content of calcium and magnesium is less than 0.007 at%, it is difficult to make the crystal state into giant grains or single crystals without grain boundaries. If the total amount exceeds 0.090 atomic%,
It was found that the crystalline state was worse than when calcium and magnesium were not added (that is, the crystalline state became finer). This is considered to be because when the total content of calcium and magnesium exceeds 0.090 atomic %, the pinning effect on normal grain growth becomes strong and grain growth is suppressed. In the above embodiment, tungsten containing predetermined amounts of calcium and magnesium was molded and processed by a powder metallurgy method, but a melting method may also be used. However, when using the melting method, it is difficult to adjust the content and subsequent processing because the vapor pressure of magnesium and calcium is high. In addition, in the above-mentioned example, the case where both calcium and magnesium were added and the total amount was 0.007 to 0.090 at% was explained, but Table-2 and Table-
As shown in 3, it was found that either calcium or magnesium may be present in the range of 0.007 to 0.090 atomic %. Incidentally, the annealing temperature, annealing time, etc. in this case are the same as those in the example shown in Table 1 above.

【table】

〔Effect of the invention〕

As explained above, in the present invention, the total amount of at least one of calcium and magnesium is 0.007
A tungsten compact containing 0.090 to 0.090 atomic percent is sintered, processed into a predetermined shape, and then annealed to obtain a giant-grained or single-crystal tungsten material without grain boundaries. Therefore, the total amount of at least one of calcium and magnesium
Tungsten single crystals containing 0.007 to 0.090 atomic percent do not cause brittleness even in high-temperature conditions, and can be used in high-power laser reflectors, IC substrate materials, nuclear reactors, reactor materials for nuclear fusion reactors, and ordinary furnaces such as electric furnaces. It can be used for heating elements, crucibles, electronic parts, etc.

Claims (1)

[Claims] 1. A tungsten single crystal containing at least one of calcium and magnesium in a total amount of 0.007 to 0.090 atomic percent in tungsten. 2. Production of a tungsten single crystal, which is characterized by forming a tungsten polycrystal containing at least one of calcium and magnesium in a total amount of 0.007 to 0.090 atomic percent into a molded body of a predetermined shape, and annealing the molded body. Method.