JPH0448863B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to molybdenum for structural materials. [Technical background of the invention and its problems] Tungsten containing thorium oxide (ThO ₂ O-W) is generally used as a cathode material for electron tubes. However, ThO ₂ -W wire is difficult to be processed into a coil shape or the like, and therefore it is difficult to process the wire into a plate material or to perform secondary processing on this plate material. ThO ₂ −W when used as cathode material for electron tubes
A carbonized layer is formed on the surface of the wire, and the carbon in this carbonized layer is
It has electron-emitting properties as a reducing agent for ThO ₂ . However, ThO ₂ -W is originally a brittle metal, and by forming a carbonized layer on the surface of the wire, the embrittlement phenomenon becomes even more pronounced. Therefore, when external vibration impact force is applied, the ThO ₂ -W coil, which is the cathode material, may break, or
ThO ₂ is a radioactive substance and has the problem of being extremely troublesome to handle. To solve these problems, change W to Mo,
As a result of changing ThO ₂ to La ₂ O ₃ and researching its relationship with electron emission characteristics and lifetime, it was found that the initial electron emission characteristics and lifetime were greatly improved compared to ThO ₂ -W, but at the end of life The problem of carp deformation has become clear. In addition, the Mo wire for the outer lead used in halogen and lamps is
Since it is exposed to high temperatures when encapsulating quartz glass, it will become brittle if Mo wire, which has a low recrystallization temperature, is used. For this reason, Mo wires with a high recrystallization temperature are used, but this is still insufficient and there is still the problem of breakage. Also, like ThO ₂ in tungsten containing thorium oxide (ThO ₂ -W), La ₂ O ₃ in Mo does not form a solid solution with Mo or form a compound.
Dispersed as particles of La ₂ O ₃ . For this reason, Mo
If the La ₂ O ₃ inside is segregated or large La ₂ O ₃ particles are dispersed, it may become coiled or cylindrical, and when subjected to secondary processing such as bending,
There were problems with workability, such as wire breakage and cracking. In addition, if the dispersion state of La ₂ O ₃ in Mo is poor as described above, when used as a cathode material for an electron tube,
There were various problems in that it was difficult to obtain good electron emission characteristics. The present invention has focused on the various problems mentioned above, and has developed a
Mo material, for example, when used as a cathode material in an electron tube, has excellent electron emission characteristics and has a long service life.Moreover, it is used in applications that are exposed to high temperatures and require flexibility, vibration resistance, and impact resistance. It was found that the best suitable material is a Mo material in which La ₂ O ₃ is uniformly dispersed in Mo and appropriate amounts of Al, K, and Si are added as dispersion strengthening agents. [Object of the Invention] The object of the present invention is to solve the above-mentioned problems, and when used as a structural material, it is easy to process, has a high recrystallization temperature, and has good deformation resistance when used in a coiled form, for example, as a cathode material for an electron tube. The present invention provides a Mo material with excellent vibration resistance and impact resistance, as well as good electron emission characteristics. [Summary of the Invention] The Mo material of the present invention contains 1 to 5% by weight of La ₂ O ₃ in Mo, and the dispersion form of La ₂ O ₃ is such that the maximum particle size of La ₂ O ₃ is
7μm or less, and Al, K, and Si are each 10~
200ppm, 20~300ppm, 20~200ppm In order to be uniformly dispersed and easy to process, the processing rate (change rate of cross-sectional area) from the sintered body or final heat treatment size is 60% or more, and the powder metallurgy method is used. This is a Mo material obtained by In the present invention, the maximum particle size of La ₂ O ₃ is 7μ.
If La ₂ O ₃ with a particle size larger than this is present, it may cause serious problems such as wire breakage or cracking during secondary processing of wires or plates. Not only does processability decrease, but
When an electron tube is used as a cathode material, it is difficult to obtain stable electron emission characteristics for a long time. Furthermore, when the La ₂ O ₃ content is less than 1%, it is difficult to obtain the effect of adding La ₂ O ₃ , and when it exceeds 5%, the effect of adding La 2 O 3 is less than 5%. No major changes are observed, and problems such as poor secondary workability tend to occur. When the content of Al, K, and Si is below the claimed range of the present invention, the effect as a dispersion strengthening agent is difficult to appear, and the recrystallization temperature and high temperature strength are close to the properties of pure Mo. Recrystallization temperature if hot,
High-temperature strength tends to be the same as or lower than the properties within the scope of the present invention, and workability tends to deteriorate. Further, the processing rate from sintering is a major factor in the secondary workability of a wire or plate material, in addition to the La ₂ O ₃ content and dispersion form. In other words, like W and Mo, originally
Metals that are more brittle than CuAl etc. are produced by processing the non-directional crystal structure produced by sintering to form a crystal structure in the processing direction, that is, forming a texture. A common method is to improve flexibility by La ₂ O ₃ 1～
5% by weight, Al, K, Si 20~200ppm each, 20~
According to the inventor's experimental results for Mo materials containing 300ppm and 20 to 200ppm, the higher the processing rate from the sintered body, the easier the secondary workability is, but it is 60%.
It was found that there is no problem in practical use as long as the wire or plate material has a processing rate above the above. [Embodiments of the Invention] Examples of the Mo material for structural materials of the present invention will be described below. Mo material is manufactured using powder metallurgy.
The La ₂ O ₃ content was 0.5, 1.0, 2.0, and 6.0% by weight, and the addition amount and mixing method were changed so that the La ₂ O ₃ particle size was different.
Al is 10, 50, 300ppm, K is 10, 50, 400ppm,
Mo oxide was added in different amounts in terms of Mo powder so that Si was contained at 10, 50, and 300 ppm. These oxides were reduced in a hydrogen atmosphere, and this powder was mechanically pressed to form a green compact at a pressure of 1.5 ton/cm ² , and this green compact was sintered at 1850° C. for 8 hours in a hydrogen atmosphere. The sintered body obtained at this time has a specific gravity of approximately
9.55, the cross-sectional shape is 12mm x 12mm, and the length is 650mm. This sintered body was hot rolled and drawn to obtain wires with diameters of 0.60 mm and 0.20 mm. To check the La ₂ O ₃ particle _size in the Mo wire, embed the wire in a thermosetting resin, polish it to a mirror finish using a normal polishing method, and then polish only the Mo material using a special electrolytic polishing method. ₃ was left floating on the polished surface, and then observed using a scanning electron microscope. The contents of La ₂ O ₃ , Al, K, and Si in Mo were determined by chemical analysis. in Mo with wire diameter φ0.60mm
The relationship between the content of La ₂ O ₃ , Al, K, and Si, the dispersion form, line flexibility, and secondary recrystallization temperature was investigated. As a result, wires in which Al, K, and Si exceed the claimed range and the maximum particle size of La ₂ O ₃ exceeds the claimed range will suffer from cracks and breaks during rolling and drawing processes, resulting in poor flexibility (bending property). ) was at fault. As a result of the investigation, we found that the first representative example was
Shown in the table. As is clear from this result and the workability during the above-mentioned wire drawing process, aLa ₂ O ₃ Al,
It can be said that the K and Si contents are the most appropriate amounts. In addition, the green compact was molded using a 2 ton/cm ² isostatic press and sintered in a hydrogen atmosphere at 1850°C for 8 hours, with a specific gravity of 9.45, a shape of φ60 mm, and a length of A 400 mm sintered body was hammered and rolled to obtain a 0.2 mm thick plate. At this time, heat treatment was performed in a hydrogen atmosphere at a temperature higher than the secondary recrystallization temperature. The heat-treated plate thickness has a processing rate of up to 0.2mm.
The dimensions were 40%, 60%, and 80%. Table 2 shows the representative results of the investigation regarding the flexibility of the plate material at this time. As is clear from this result, it can be seen that the flexibility of the plate improves by processing it by 60% or more. The flexibility due to processing rate is also the same for wire. Next, we also investigated the electron emission characteristics of power tubes (diodes). The wire used at this time had a wire diameter of φ0.20.
mm. A representative example of this result is shown in Table 3.
Even if the La ₂ O ₃ content is constant at 2.0%, if the dispersion reinforcement is within the claimed range, the life will be extended. (Those with dispersion reinforcement below the claimed range deformed at the end of their lifespan, causing the coil to turn and shoot.

【table】

【table】

【table】

[Effects of the present invention]

As is clear from the above explanation, Mo for structural materials
La ₂ O ₃ content in Mo in material: 1-5% by weight
Maximum particle size of La ₂ O ₃ less than 7μm, as a dispersion strengthener
Al, K, and Si are 20 to 200 ppm and 20 to 300 ppm, respectively.
It can be seen that Mo materials containing 20 to 200 ppm are excellent Mo materials for structural materials.

Claims (1)

[Claims] 1. Lanthanum oxide (La ₂ O ₃ ) is uniformly dispersed in molybdenum (Mo) in an amount of 1 to 5% by weight.
The dispersion form of La ₂ O ₃ is such that the largest particle of La ₂ O ₃ is 7 μm or less, and the molybdenum contains Al, K, and Si as dispersion strengtheners at 20 to 200 ppm and 20 to 200 ppm, respectively.
Molybdenum for structural materials containing 300ppm, 20~200ppm. 2. In the molybdenum for structural materials according to claim 1, the sintered body or the final heat treatment
% or more of molybdenum for structural materials.