JPH03219039A - Rhenium-tungsten alloy material excellent in workability and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an Re-W alloy material excellent in workability, at the time of subjecting a compacted and sintered body by Re-W alloy powder to compacting treatment and recrystallization treatment for plural times, by appropriately maintaining the correlation between the percentage reduction of area and recrystallized grains in a compact. CONSTITUTION:The powder of an Re-W alloy contg., by weight, 0.5 to 10% Re and the balance W is compacted and sintered. This sintered body is repeatedly subjected to forming such as stamping and wire drawing and recrystallization treatment at a high temp., e.g., of 2000 to 2700 deg.C in a hydrogen atmosphere. At the time when the percentage reduction of area in the compact reaches 70 to 90%, final recrystallization treatment is executed to regulate the number of the recrystallized grains to 400 to 800 pieces/mm<2>. The Re-W alloy wire rod free from breaking even if processed into a wire rod or the like and excellent in workability can be obtd.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention is applicable to cathode heaters of TV electron guns, automobile lamps,
Rhenium-tungsten alloy materials and their manufacturing methods are used for filament materials for vibration-resistant light bulbs such as lighting lamps in home appliances, and in particular, rhenium-tungsten has excellent workability with fewer defects in the process of processing into final products. This invention relates to alloy materials and their manufacturing methods.

(Prior Art) Doped tungsten wire is widely known as a material for light bulb filaments or heaters that has excellent high-temperature strength and vibration resistance. However, dobutungsten wire has the drawback that when subjected to high temperature heat treatment, its elongation decreases and its vibration resistance strength decreases significantly.

Therefore, rhenium-tungsten alloys containing about 0.5 to 10% by weight of rhenium (Re) in tungsten are widely used as materials that require high-temperature strength such as filament materials. Re improves the elongation of the material, solidly dissolves in the tungsten structure, increases the high-temperature strength of the matrix, and has the effect of increasing electrical resistance. Therefore, when a wire having the same resistance value as a conventional tungsten wire is formed, it can be made thicker than the tungsten wire, and the strength can be increased.

Conventionally, this type of rhenium-tungsten alloy material was obtained by press-forming raw material powder and then sintering it, and then subjecting the resulting sintered body to processing such as rolling and wire drawing, and heat treatment such as recrystallization treatment in stages. It will be done. Specifically, the material sintered body is processed in stages to gradually reduce its cross-sectional area, and when the reduction rate of the cross-sectional area of the material reaches approximately 60%, the final process is completed. By performing recrystallization treatment, the size of crystal grains is adjusted and the work-hardened structure is softened. Since the rhenium-tungsten alloy material thus obtained is less hardened by working, it has good workability in the next step.

(Problem to be solved by the invention) However, the number of recrystallized grains of the conventional rhenium-tungsten alloy material, which was subjected to the final recrystallization treatment when the area reduction rate reached 60%, was 2000 per square mm. ~28
00 pieces, and has an extremely fine crystal structure. Therefore, there is still a drawback that the hardness is somewhat high.

If this rhenium-tungsten alloy material is used in the next process as it is, it is likely to crack or break, which is a major cause of lower product yield. In addition, it is not easy to maintain, as it requires a lot of effort to remove broken materials and restore equipment to normal operating conditions, and it also reduces the operating efficiency of manufacturing equipment and the yield of products based on raw materials. There is a problem with this.

The present invention has been made to solve the above problems, and provides a rhenium-tungsten alloy material that is difficult to crack or break when subjected to post-processing and has excellent workability, and a method for manufacturing the same. The purpose is to

[Structure of the invention]

(Means and Effects for Solving the Problems) The inventors of the present invention aimed to improve workability from the above points of view, and determined the number of recrystallized grains, which is an index of workability, and the cross section of a sintered body, which is a raw material, by processing. We conducted research by varying the relationship between the reduction rate and found that it was possible to maintain an appropriate correlation between the cross-section reduction rate of the molded product during recrystallization treatment and the number of recrystallized grains after recrystallization treatment. In other words, when the number of recrystallized grains after the final recrystallization treatment was set to 400 to 800 particles/mm2, a rhenium-tungsten alloy material with significantly improved workability compared to the conventional one was obtained. It is based on

A tungsten material containing 0.5 to 10% by weight of rhenium is used as a sintered body as a material for the rhenium-tungsten alloy material that is the object of the present invention.

Furthermore, the characteristics aimed at by the present invention are obtained by subjecting a sintered body of rhenium-tungsten alloy powder to multiple times of pressure molding treatment and recrystallization treatment to form a molded article, and producing a sintered body of the molded article obtained. When the cross-sectional reduction rate reaches 70-90%,
Perform the final recrystallization process to reduce the number of recrystallized grains to 400 to 8.
00 pieces/mm2.

In this case, the size of the area reduction rate during recrystallization treatment is as follows:
This has a large effect on the size of crystal grains produced by recrystallization treatment, and when heat-treating a material with a low working degree of less than 70%, uniform recrystallized grains cannot be obtained all the way to the center, resulting in mixed grains. This significantly reduces the mechanical properties of the alloy material.

On the other hand, if the area reduction rate exceeds 90% and processing is performed without recrystallization treatment, workability will deteriorate significantly due to work hardening. Therefore, the area reduction rate is set to 70 to 90%, more preferably 75 to 85%, which is practically desirable.

In addition, the number of recrystallized grains is a factor that greatly affects the workability of alloy materials, and if the number of recrystallized grains per 1 square mm is less than 400, the structure becomes coarse and grain boundary fractures are likely to occur, and during processing. Cracks, etc. are more likely to occur.

If the number of recrystallized grains exceeds 800, the hardness increases and cracks are also likely to occur during processing. Therefore, the number of recrystallized grains is set in the range of 400 to 800 grains per square mm, and more preferably in the range of 500 to 700 grains/#i.

In this case, the number of recrystallized grains is measured as the number of recrystallized grains in a cross section perpendicular to the processing direction of the alloy material.

The number of recrystallized grains is adjusted by the working degree and the heating temperature and time in the recrystallization treatment.

(Example) Next, the present invention will be explained by the following examples.

As Examples 1 to 3, each side of a square cross section was 1 from a sintered body of a tungsten alloy containing 3% by weight of rhenium.
0. 0mm, 12. 2mm, 16. A 0 mm square rod-shaped sintered body was cut out as a raw material. Each of the obtained rectangular bar-shaped sintered bodies was subjected to rolling and wire drawing processes to produce a linear molded product with a diameter of 6 mm. The area reduction rates at this time are 72%, 81%, and 89%, respectively, as shown in Table 1.

Next, 2000 to 2700 for each linear molded product obtained.
A rhenium-tungsten alloy material was manufactured by performing recrystallization treatment in a hydrogen stream at a temperature of ℃.

1 square mm of the cross section perpendicular to the processing direction of the obtained rhenium-tungsten alloy material after recrystallization treatment
The number of recrystallized grains per unit was measured.

In addition, in order to evaluate the workability of the alloy material, the obtained linear rhenium-tungsten alloy material was further subjected to a rolling and wire drawing process to finally form a rhenium-tungsten wire with a diameter of 1.0 mm. The number of breaks that occurred during the wire drawing process was measured, and the results shown in the right column of Table 1 were obtained.

On the other hand, as Comparative Examples 1 to 3, rectangular bar-shaped sintered bodies having a square cross section with sides of 8.4 mm+ were cut out from the sintered bodies prepared in Examples 1 to 3, and further subjected to rolling and wire drawing processes to obtain a diameter of 6 mm. A linear molded product was manufactured. The area reduction rate at this time was 60%, as shown in Table 1.

Next, the obtained linear molded products were subjected to recrystallization treatment in Comparative Examples 1 and 2, while rhenium-tungsten alloy materials were prepared without recrystallization treatment in Comparative Example 3. Then, the cross section of the obtained rhenium-tungsten alloy material in the direction perpendicular to the processing direction was examined with a microscope in the same manner as in Examples 1 to 3 to measure the number of recrystallized grains, and the material was further rolled and drawn, and the diameter A 1.0 mm rhenium-tungsten wire was formed, and the number of occurrences of breakage during this wire drawing process was similarly measured. The results are shown in the right column of Table 1 below.

[Margin below]

Table 1 [Margins below] As is clear from the results in Table 1, the area reduction rate is 72 as in the rhenium-tungsten alloy materials of Examples 1 to 3.
Those subjected to recrystallization treatment in the range of ~89%,
The number of recrystallized grains is 400 to 800 per square mm,
It can be seen that compared to Comparative Examples 1 to 3, the number of occurrences of breakage during the wire drawing process is small, and the workability is excellent.

〔Effect of the invention〕

As explained above, according to the rhenium-tungsten alloy material with excellent workability according to the present invention, the number of recrystallized grains is set in a range suitable for processing by the recrystallization 111 treatment. The incidence of defects such as cracks and breakage is low. Therefore, it is extremely excellent as a raw material for filaments of vibration-resistant lamps, etc., and has extremely great industrial effects.

Claims (1)

[Claims] 1. The number of recrystallized grains after the final recrystallization treatment is 400 to 800.
A rhenium-tungsten alloy material with excellent workability, characterized by the fact that it is set at 1/mm^2. 2. A sintered body of rhenium-tungsten alloy powder is subjected to multiple pressure molding treatments and recrystallization treatments to form a molded article, and the area reduction rate of the obtained molded article from the sintered body is 70.
A rhenium-tungsten alloy material with excellent workability characterized by performing a final recrystallization treatment when reaching ~90% and adjusting the number of recrystallized grains to 400 to 800 pieces/mm^2. manufacturing method.