JPS58144401A - Preparation of tungsten alloy - Google Patents

Abstract

PURPOSE:To obtain a W-alloy with high specific gravity having the same quality as one prepared according to a doping process, by a method wherein a W-powder and two kinds or more of metal powders selected from Ni, Fe, Co and Cu are accommodated in a dry forcedly stirring crusher to be ground and mixed under an inert gas atmosphere by specific spheres as ginding mediums and the resulting mixture is molded and annealed. CONSTITUTION:A W-powder and two kinds or more of metal powders selected from Ni, Fe, Co and Cu are accommodated in a dry forcedly stirring crusher and ground and mixed by spheres of which tap densities are 15 times or more as compared to that of the resulting mixed powder and diameters are 8mm. or less as grinding mediums under an inert gas atmosphere. The obtained mixture is cooled in an inert gas atmosphere and molded and sintered to obtain a W-alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Minute Hand of the Invention] The present invention relates to a method for manufacturing a tungsten alloy with a high specific gravity, and more particularly, to a method for manufacturing a raw material powder therefor.

[Technical background of the invention and its problems]

Tungsten has a high specific gravity (theoretical density: 192P/cm
j) Therefore, the alloy is widely used as components for radiation shielding materials, weights, etc.

Tungsten alloys are generally manufactured as follows. That is, tungsten (W) powder is mixed with the other metal powder or its compound in a predetermined proportion, the obtained mixed powder is molded into a predetermined shape, and the molded body is pre-sintered in, for example, a hydrogen stream. , main sintering □ Among the above process groups, the process that takes effort to prepare the mixed powder is -
Since it has a great influence on the specific gravity of the tungsten alloy produced, it is extremely important for the production of high specific gravity tungsten alloys. Generally, the following three methods are widely applied as a method for preparing this mixed powder.

The first method involves adding tungsten oxide powder such as tungsten dioxide (WO3) to iron (Fe) and nickel (N).
i) , =r Baltic (CO), copper (Cu) 17) Salts (
For example, two or more types of hydrochloride, nitrate) are mixed in a prescribed manner.
2. After stirring and drying by heating, the surface of the W powder is coated with the above-mentioned two kinds of metals in amounts A by reducing the powder in a hydrogen stream, for example.

The second method is similar to the first method, except that W powder itself is used instead of tungsten oxide.

The first method and the second method are generally called doping methods, and are a method that enables the production of tungsten alloys with high specific gravity.
However, in the doping method, since the salts used are usually acid solutions, it is unavoidable that harmful gases such as hydrochloric acid gas and nitric acid gas are generated during the above-mentioned heating and drying process, resulting in corrosion of manufacturing equipment and damage to workers. This can lead to adverse health effects. Protective measures for this purpose are industrially inconvenient because they complicate processes and equipment and increase product costs.

The third method is to add Fe, Ni, Co, Cu to W powder.
Two or more kinds of metal powders are blended in a predetermined proportion, and these are sufficiently mixed in a mixer such as a ball mill or a miller.

If this powder mixing method is applied, it is industrially advantageous because the drawbacks of the doping method can be overcome and a mixed powder can be prepared easily and inexpensively.

However, it is extremely difficult to produce a high specific gravity dungesten alloy from the mixed powder obtained by this method. This is because the wettability between W and the above metal is poor.
This is because many pores (cavities) are generated in the alloy at mutual interfaces during sintering, making the alloy more porous than when using the doping method.

On the other hand, powder mixing methods include wet mixing methods and dry mixing methods.

The wet mixing method is a method of adding and mixing appropriate amounts of water, various organic solvents, etc., and is characterized by high mixing efficiency. However, this method requires a step of drying the mixed powder after mixing. The use of water may lead to oxidation of the metal powder; on the other hand, if an organic solvent is used, the risk of oxidation is eliminated, but explosion-proofing and recovery processes must be performed in the drying equipment, which increases product costs. invite.

The dry mixing method does not suffer from the above-mentioned disadvantages of the wet mixing method, but it also results in a decrease in the efficiency of mixing powders with each other.

[Object of the Invention] An object of the present invention is to provide a method for producing a high specific gravity tungsten alloy, and in particular, a method for producing a mixed powder of raw materials suitable for the production by a dry powder mixing method.

[Summary of the invention]

The present inventors have discovered that the mixed powder produced by the doping method contains Fe precipitated by hydrogen reduction on the surface of the W powder.

We focused on the fact that it is coated with metals such as Ni, Co, and Cu. Therefore, if a similar state can be obtained in the dry powder mixing method by some means, the mixed powder could be used as a raw material powder for high-density dungesten alloys, comparable to those obtained by the doping method. Therefore, the present invention was completed by applying a mechanical alloying method, which is carried out using a dry forced stirring pulverizer and has been attracting attention recently.

That is, in the method of the present invention, in a dry forced stirring pulverizer,
W powder and two or more kinds of metal powders selected from the group of li'e, Ni, Co, and Cu are simultaneously housed, and the tap density of the mixed powder having a specific gravity of the W powder and the metal powder is determined. After pulverizing and mixing in an inert gas atmosphere using a sphere with a value of 15 times or more as a medium; cooling in an inert gas atmosphere! This method is characterized by molding and sintering the obtained treated powder.

In the method of the present invention, first, W powder and ii'e, Ni,
Co.

A predetermined amount of Cu metal powder of class 2'IIi or higher is simultaneously stored in a dry forced stirring pulverizer as a pulverizer.

Here, the dry-type forced stirring pulverizer is a pulverizer commercially available as, for example, Dry-type Attritor (trade name, manufactured by Mitsui Miike Manufacturing Co., Ltd.), which is used for manufacturing heat-resistant high-strength alloys such as rocket and jet engine parts. 1. This pulverizer, which is used at the time, has a structure in which a stirring shaft equipped with a plurality of stirring blades (or arms) is housed inside a pulverizing tank equipped with a water-cooled jacket on the outer periphery. When crushing crushed materials,
After a large number of media consisting of, for example, steel balls having a predetermined diameter are stored in the tank together with the crushed material, the stirring shaft is rotated at high speed.

The medium and the crushed material are forcibly stirred by stirring blades and flowed within the crushing tank. At this time, due to mutual collisions and friction between the media, phenomena such as deformation and breakage occur repeatedly in the crushed material, and each time a new atomically fresh surface is formed on the crushed material, causing the mutual friction between the crushed materials. Joining and alloying progress.

Therefore, in the method of the present invention, if the grinder is used to forcefully stir and grind, W powder, Fe, and Nj are produced.

The metal powders of CO and CLI are each subjected to the above-mentioned action, and relatively t! ! ! Relatively soft Fe 2 , Ni 2 , Co 2 , and Cu 2 bond to the surface of the high-quality W powder, making it possible to form a kind of coating state.

Now, in the method of the present invention, a true sphere with a specific gravity of 1.5 times or more than the tap density of the crushed material (a mixture of W powder and metal powder) and a diameter of 8 wm or less is used as the medium.

If the specific gravity is smaller than the above value, the medium will float away from the granules (mainly W, which has a high specific gravity), and the granules will stay in a layer at the bottom of the mill, and the pulverization of the granules will not proceed smoothly.

°However, if the diameter of the true sphere that is the medium exceeds 8 mm, the space formed between the media will become large and it will not be possible to sufficiently disperse (sprinkle) the crushed material into the upper area of the crusher. In this case as well, the crushed material remains at the bottom of the crusher. Historically, the medium does not move smoothly in the space between the screw and the bottom of the crusher (usually the distance is 2 to 3 times the diameter of the medium), and only impact noise is generated. The medium usually has a diameter of 6
~7- steel balls are preferred.

During the crushing process, a large amount of heat is generated due to friction between the medium and the crushed material. Then, Fe, N which is the object of the present invention
Metal powders such as i, Co, and Cu usually have a particle size of 1 to
Since it is approximately 4 μm, its specific surface area is significantly increased, and the surface is hygroscopic and easily oxidized.

Therefore, in order to prevent oxidation of the metal powder during crushing, an inert gas such as nitrogen, argon, helium, etc. must be introduced into the crusher cylinder to create an inert gas atmosphere in the crushing area.

After finishing the crushing process, the crushed material is cooled in an inert gas atmosphere and then taken out.

If the crushed material is taken out into the air immediately after pulverization, it is dangerous because the ultrafine powder that has formed in some parts will gradually generate heat and eventually ignite.

The treated powder thus obtained has a surface of W powder of l
It is in an alloyed state with i'e, Ni, Co, and Cu, and its wettability is improved compared to when these powders are simply mixed by a dry powder mixing method.

In the method of the present invention, this treated powder is formed into a predetermined shape according to a conventional method and then sintered to form a desired tungsten alloy.

[Embodiments of the invention]

Example In a dry attritor (trade name, MA-ID type: ■ manufactured by Mitsui Miike Seisakusho), W powder with an average particle size of 1.5 μm and 1.5
Carbonyl-nickel powder (average particle size 43μ) at weight t%
m) and 2.51i1% amount of electrolytic copper powder (average particle size 1.2
μm) were stored at the same time.

The overall powder tap density was 4.5 y/crn''.

The medium has a diameter of 6.35 wm and a specific gravity of 7. f3 y
7 cm" steel balls were used. After sealing the crusher, N2 gas was introduced into the cylinder to replace air. The water temperature at the outlet of the jacket was raised to 42C.While the screw was rotating, the bottom discharge [J
The mixed powder was taken out into a container kept in a nitrogen atmosphere and cooled.

Take out the mixed powder from the pulverizer, fill it into a specified mold, and
．． 51'n n10n'' after pressure molding 13soc-
The specific gravity of the 1° sintered body is 19. Of 17 cm". This value corresponds to 99% of the theoretical density. A solution of NO3) 2 and a Cu CQ 2 solution equivalent to 25% heavy density in terms of Cu were added and stirred.The resulting slurry was dried at 10 Orr with stirring for 3 hours, and then dried at 850C. The resulting powder was mixed with a sintered body under the same conditions as in the example.The specific gravity of the sintered body was 19.01 f 7cm3.

Comparative Example 2 Each powder having the same specifications as in the example was ground and mixed in a ball mill for 4 hours. The obtained powder was made into a sintered body under the same conditions as in the example. The specific gravity of the sintered body is 1824 no/crn3
Met. This corresponds to 95% of the theoretical density.

(11) [Effects of the Invention] According to the method of the present invention, it is possible to produce a starting material for a high-density tungsten alloy with properties equivalent to those of the doping method despite applying the powder mixing method; , Since the dry mixing method is applied, various problems associated with the wet mixing method are solved (■ Industrial inconveniences associated with the dope method are solved,
It has the following effects and is of extremely great industrial value as a method for producing high-density tungsten alloys.

(12)

Claims (2)

[Claims] (1) In the dry forced stirring pulverizer, tungsten powder and 2 metals selected from the group of iron, nickel, cobalt, and copper are added.
At the same time, these powders are stored in an inert gas atmosphere using a sphere whose specific gravity is at least 15 times the tap density of the mixed powder consisting of the tungsten powder and the metal powder. A method for producing a tungsten alloy, which comprises: cooling in an inert gas atmosphere after pulverizing and mixing; and molding and sintering the obtained treated powder. (2) The method for producing a tungsten alloy according to claim 1, wherein the sphere is a true sphere with a diameter of 8u or less.