JPS599278B2 - Manufacturing method for high temperature brazing materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brazing material for refractory metals, and more particularly to a method for producing a brazing alloy used for joining magnetron cathode structures.

Among refractory metals, tungsten, molybdenum and their alloys are useful in high temperature applications.

For example, in the electron tube industry, it is widely used for cathodes, grids, and their supports. Tungsten and molybdenum have been joined by melt bonding, diffusion bonding, brazing, etc., but in practice many joint structures and tight tolerances are encountered where only brazing can be used. Satisfactory braze alloys are available for low and moderate temperatures, but not for certain high temperature operations, particularly in the relevant temperature range, ie, 1700-2200°C.

At these temperatures, available braze alloys tend to corrode the base metal or exhibit poor flow properties due to volatilization of alloy components during brazing. Other features desirable in braze alloy systems that allow for the selection of specific compositions for a given temperature in this temperature range are a rapid increase in remelting temperature to provide high temperature operation capability and embrittlement during diffusion during operation. It is necessary to avoid phase formation. It is therefore an object of the present invention to provide a brazing material for joining tungsten, molybdenum and their alloys.

Conventionally, in the electron tube industry, transmitting tubes and industrial transmitting tubes,
In magnetron cathode assembly, etc., due to the high operating temperature and high degree of vacuum inside these tubes, brazing materials such as Pt and Ru-Mo are used to bond the tungsten, molybdenum, etc. that make up the cathode. It is used.

This brazing filler metal has both advantages and disadvantages, but from the point of view of the way PT wire is handled, it can be easily supplied to the joint at the component assembly stage without going through any special processes, which eliminates the obstacle of high cost. You are welcome.

On the other hand, Ru-Mo soldering is lower in cost than PT soldering, but it is usually made by binding fine powder of around 1 micron with a binder and applying the paste-like soldering material with a brush. There is. For example, in the case of joining the filament 2 and the upper and lower end shields 1a and 1b in FIG. Then, apply a predetermined amount of the powder paste and insert it into the center support 3.

Subsequently, the paste is similarly applied to the filament 3 and the upper end shield 1a, and the paste is inserted, and the joints of the assembled cathode structure are put together into a brazing device and brazed. In some cases, the first assembly may be assembled and brazed individually.
The structure shown in the figure may also be formed. Conventionally, this brazing filler metal is made by uniformly mixing MO powder and RU2O3 powder, and then
It is produced by reducing in a hydrogen furnace at a temperature of 950 to 1100°C for about 1 hour, sieving, and mixing.

However, with this method, segregation is unavoidable from a macroscopic perspective, and the results of diffusion studies using X-ray diffraction also indicate that M
A considerable amount of O and Ru remained alone, and the manufacturing method was insufficient to obtain a 43%-MO eutectic alloy at the eutectic point of MO and Ru (1945 C), which is the lowest brazing temperature. be. In contrast, the main purpose of the present invention is to reduce the defects of the above-mentioned method, and the method first involves roasting ammonium paramolybdate and adding fine grained MOO3 powder to ammonium chloride ruthenate [(NH4 ) RuCl6] aqueous solution is added at a predetermined ratio, dried while mixing, hydrogen-reduced in the same manner as above, sieved, and mixed to obtain Ru-MO brazing alloy powder.

The powder thus obtained was subjected to X-ray diffraction, and as a result of comparison with the above method, almost no single element remained. In the decomposition and reduction process of the MOO3 mother salt, the M
It is thought that since it is POrOus rather than O metal powder, it is easier to substitute and diffuse. Furthermore, since Ru is added in the ionic state of an aqueous solution, it can be uniformly coated on the surface of the base material, and segregation can also be reduced. Next, examples will be shown.

Precisely weigh 15.6 tons of anhydrous crystalline salt of ammonium ruthenate chloride using a Metra direct-view balance, add 150 cc of distilled water in a 10 CTnφ magnetic dish, and adjust the pH to further increase solubility.
To adjust the ratio to 1-2, add hydrochloric acid and dissolve by heating and stirring.

Precisely weigh 8.49 f of high purity MOO7 powder with an average particle size of 1 μm or less, put it in a 500 CC beaker, add the above ruthenium salt solution, and evaporate to dryness while stirring on a hot water bath. (This requires about 2.5 hours:). The obtained gray-brown powder was transferred to a 10CTnφ agate mortar, ground, and passed through a 120-meter sieve.

The sieved powder is placed in a magnetic boat and reduced at 950°C for 1.5 hours in a dry hydrogen atmosphere at Dp-45°C or lower.

After cooling in the furnace, the gray-black powder is ground and passed through a 200 mesh sieve. The Ru-MO alloy brazing material thus obtained is
There is no segregation and the wax powder is sufficiently diffused.

Then, this brazing material is kneaded with an acrylic resin to form a paste, or is supplied to the joined body in the form of pellets or the like.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a conventional thorium and tungsten cathode for magnetrons, and FIG. 2 is a schematic manufacturing process diagram of the high-temperature brazing material of the present invention. 1... End shield, 3, 4... Support.

Claims (1)

[Claims] 1 In the production of 40-45% by weight Bu-Mo powder solder, fine grain MoO_3 powder is doped with an aqueous ammonium chloride ruthenate solution, the mixed and dried powder is reduced at high temperature in a hydrogen stream, and the resulting powder is made into a fine powder. , a method for producing a high-temperature brazing material, which is characterized by sieving.