JPS62275091A - Production of tungsten single crystal - Google Patents

Abstract

PURPOSE:To easily produce a W single crystal nearly free from gain boundaries and having improved processability by adding a specified amount of ZrO2 to W doped with Al2O3, K2O or SiO2 and subjecting them to pressing, a sintering and heat treatment at a specified temp. CONSTITUTION:Doped W powder contg. 0.01-1.0wt% one or more among Al2O3, K2O and SiO2 is mixed with 0.01-0.05% ZrO2 powder. The powdery mixture is compacted, sintered in hydrogen or the like, machined to a prescribed size and heat treated at >=2,600 deg.C. By this method, the grain boundaries of fine recrystallized grains are vanished and a large W single crystal is grown.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial application field] The present invention relates to a method for manufacturing tungsten single crystals.

It should be noted that the term "single crystal" here includes coarse crystals having a sufficiently large length compared to the diameter.

[Conventional technology]

Ordinary tungsten has the disadvantage that it recrystallizes at temperatures above 1800°C to 200°C and its high-temperature strength decreases. For this reason, coarse-crystal tungsten with few grain boundaries or single-crystal tungsten are considered promising as high-temperature materials, but the conventional method of manufacturing single crystals using zone melting limits the size and shape of the product, and the production volume per hour is limited. It also had the advantage of being limited. Furthermore, as a method for producing a single crystal by a recrystallization method, Japanese Patent Application Laid-Open No. 61-619.7 provides a method in which calcium and magnesium are added to tungsten, the molded body is processed to a predetermined size, and then the formed body is heat-treated. These oxides volatilize at high temperatures, so the sintering temperature is 1800 m
It is necessary to carry out the process at a relatively low temperature between ℃ and 2000℃.
Therefore, the specific gravity of the sintered body could not be sufficiently increased, resulting in poor workability.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for producing a tungsten single crystal that is easy to process and has few grain boundaries.

[Means to solve the problem]

The characteristics of the present invention are A Q, O,, K2O, S i O2
ZrO is added to normal doped tungsten with 0.
The method is to add 0.01% to 0.05% by weight, press sinter it, process it to a predetermined size, and then heat it to an assumed temperature of 2600°C.

[Effect]

For normal tungsten materials, the green compact is heated to a hydrogen atmosphere width of about 30
A molded body is obtained by sintering at oO°C, and then the molded body is hot- and warm-processed. When manufacturing tungsten materials, often Al2O3, K2O, Si
O203+ K, o, sio, alone or in combination, 0.
So-called doped tungsten added in an amount of 0.01% to 1.0% by weight is used. These doped tungstens contribute to improving the workability of tungsten materials. The tungsten single crystal that is the object of the present invention further contains 0.01% to 0.05% by weight of ZrO2 in addition to these doped tungsten.
1 obtained by adding it, processing it to a specified size by a normal method, and then heating it to a temperature of 2600°C or higher
ZrO2 used in the method of the present invention has a high melting point of 2700° C., and most of it remains without scattering even during normal sintering. Therefore, the sintering temperature can be set sufficiently high, and the density of the sintered body is 90% or more of the theoretical density, and the workability is also good.The tungsten material produced by the method of the present invention starts recrystallizing at around 1900°C. However, at temperatures below 2600°C, recrystallized grains are fine and granular, but at temperatures above 2600°C, the grain boundaries of the fine recrystallized grains disappear to form coarse single crystals.

The method of the present invention will be explained in more detail below with reference to Examples.

〔Example〕

AΩ201. ZrO2 was added to doped tungsten with a total of 0.63% of 20.5in2 added in the proportions shown in Table 1, then molded at a pressure of 1.3t/aJ, and then sintered at a hydrogen pressure of about 3000℃. A sintered body was obtained. Next, the sintered body is rolled and drawn using a conventional method to obtain a diameter of φ0,3.
A 9 mm wire was heat treated in hydrogen at various temperatures and the size of crystal grains was observed.

The results are summarized in Table 1.

Table 1 As is clear from Table 1, when ZrO□ is less than 0.01%, the recrystallized grains become elongated and close to a so-called non-sag structure, and the effect of ZrO2 addition is not apparent. Also 0,06
When it was added in excess of %, a fine granular structure formed and single crystal grains could not be obtained. In sample 2.3.4, the recrystallized structure became a fine granular structure at a heat treatment temperature of 2500°C or lower, and single crystal grains were obtained at a temperature of 2600°C or higher.

At temperatures above 2600'C, no significant difference was observed between temperature and structure.

〔Effect of the invention〕

As described above, according to the method of the present invention, tungsten single crystals can be obtained relatively easily, and the present invention is considered to have great industrial utility value.

Claims (1)

[Claims] 0.01% to 0.05% by weight of ZrO_2 to doped tungsten with 0.01% to 1.0% by weight of Al_2O_3, K_2O, and SiO_2 added alone or in combination.
A method for producing a tungsten single crystal, which comprises adding the tungsten powder to a predetermined size by press-sintering the tungsten powder, and then heating the tungsten powder to a temperature of 2,600° C. or higher.