JPS6267106A - Production of metallic powder having composite structure - Google Patents

Abstract

PURPOSE:To develop metallic powder as a new stock for powder metallurgy having excellent characteristics by quickly cooling a molten alloy of a crystallization or precipitation type by a twin roll method, etc. to thin sheets, laminating the sheets and sintering the laminates, then working the sintered alloy to an electrode and forming the powder by a rotating electrode method using such electrode. CONSTITUTION:The crystallization or precipitation type alloy such as Al-8Cr alloy or Al-13Si alloy is melted in an inert gaseous atmosphere of Ar, etc. in a high-frequency induction heating furnace, etc. The molten metal is quickly cooled by a twin roll method or single roll method to produce the thin sheets of the Al alloy solutionized with Cr and Si. Plural sheets of such thin Al alloy are laminated and compressed, then the laminates are pressurized and sintered in a gaseous Ar atmosphere; at the same time the solid soln. phase is finely precipitated as the compd. of Al-Cr and Al-Si. Such sintered body is machined and is worked to a round bar- shaped electrode. The electrode is used as an electrode for a rotating electrode type metallic powder device. The new metallic powder stock having the excellent characteristic as the raw material for powder metallurgy is thus produced.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing metal powder.

(Prior Art) Demand for high quality metal powders has recently increased in the field of new materials.

Conventionally, these powders were produced using gas atomization method, rotating disk method,
In addition to being manufactured using the rotating electrode method, new materials with alloy compositions that cannot be achieved using the melting and casting method are now being manufactured using the mechanical alloying method.

Among these methods, the rotating electrode method is an excellent method for producing powder of active metals such as titanium, but there are problems with high-speed rotation to obtain fine powder of 50μ or less, and it is difficult to process brittle materials into electrodes. There is a problem.

Although the gas atomization method can produce quite fine powder, it cannot produce active metal or alloy powder that reacts with refractory crucibles or nozzles, and it also has problems such as using a large amount of argon gas.

The rotating disk method is an excellent method that almost solves these problems, but the problem is that the apparatus is large and a large amount of expensive helium gas is used to obtain a high cooling rate.

On the other hand, a method has been proposed in which a quenched ribbon or flake is made with a single roll or twin rolls and then ground into powder, which makes it possible to make metal powder with a sufficient amount of solute in solid solution. Furthermore, according to this method, it is also possible to produce amorphous metal powder.

In addition, even if the method of mixing fine powders of various pure metals to achieve the desired metal composition allows for a mixture that is close to homogeneous from a macro perspective, it is not easy to achieve micro homogeneity; The mechanical alloying method as a method for achieving this cannot be economically adopted unless the material is a high value-added material such as an oxide-dispersed alloy.

(Problems to be solved by the present invention) Crystallization type or precipitation type alloys such as Al-8%Cr and Ah
- When an alloy such as 13%St is made into an ingot by the usual melting and casting method, it is too brittle to be processed into an electrode using the rotating electrode method, or even if it can be processed, the rapid heating and cooling rate during pulverization is too high. Then, crystallization occurs during ingot casting,
Usually, the precipitated phase cannot be redissolved, resulting in separation of the crystallized/precipitated phase from the matrix, or a powder containing a coarse phase. In addition, to mechanically turn this into powder with high efficiency, a special ball mill such as a high-energy grinder is required.

An object of the present invention is to provide a method for easily obtaining a metal powder having a composite structure in which fine precipitated phases are uniformly dispersed even in such an alloy by a known rotating electrode method.

(Means for Solving the Problems) In a rotating electrode metal powder production method, a crystallization type or precipitation type molten alloy is rapidly cooled to form a thin strip or flake of a supersaturated solid solution, laminated and sintered, and then The present invention relates to a method for producing a composite metal powder having a fine precipitated phase, characterized in that a sintered body is processed to produce an electrode using a rotating electrode method, and the electrode is used to produce a metal powder.

The inventor of the present invention has obtained the following knowledge as a result of various studies on methods of producing powder from a quenched metal ribbon. In other words, in the above-mentioned crystallization type or precipitation type alloy system, the crystallized/precipitated phase during casting is not remelted by the rapid heating and cooling rate during powdering, and the crystallized/precipitated phase and the matrix are separated. Even if it becomes a powder containing separated or coarse phases, if it is made into a quenched ribbon or flake, it becomes an almost completely supersaturated solid solution.

Since this ribbon or flake is amorphous or pseudo-amorphous, it has considerable toughness and cannot be mechanically pulverized into powder efficiently without using a special ball mill or the like.

By the way, rapidly quenched ribbons or flakes of supersaturated solid solutions have excellent sintering properties and can be sintered at relatively low temperatures, so when thin strips or flakes are laminated and sintered, the fine precipitated phases are uniformly dispersed. A sintered body is obtained. By carving a round bar from this sintered body and pulverizing it using a rotating electrode method, a spherical powder with a composite structure in which fine precipitated phases are uniformly dispersed can be obtained.

This spherical powder itself has the same strength as short fiber-reinforced composite materials, so it is an interesting new material for metal-based fiber-reinforced composite materials.

(Embodiments) Next, embodiments of the method of the present invention will be described with reference to the flow sheets shown in the attached drawings.

An Al-8Cr alloy was used as the crystallization type or precipitation type alloy, melted in a high frequency induction melting furnace in an argon atmosphere, fed to twin rolls at 1000°C, and quenched into a ribbon in a conventional manner. Cr in the ribbon is uniformly dissolved into the matrix, as seen in the area analysis result showing the CrKα characteristic X-ray image by the X-ray microanalyzer in FIG.

This thin piece or ribbon was laminated and compressed using a mold, and sintered by heating at 450° C. for 90 minutes under a pressure of 2 atmospheres in an electric heating furnace in an argon gas atmosphere. At the same time, a solid solution phase was precipitated as an Al-Cr compound, and since the temperature was relatively low, this precipitate was fine and it was observed that crystallization was progressing.

This sintered body was mechanically cut into a round bar with a diameter of 25mm, used as an electrode for a known rotating electrode type metal powder manufacturing apparatus, and then pulverized. The main working conditions are as follows.

Atmosphere Helium gas Current voltage 40V, 120A Rotation speed: 20.00 Or, p, m.

The particle size distribution of the obtained powder is 1150 mesosh 90% +150 mesoyu 10% The powder was spherical and had good moldability.

This powder was filled into a mold, pressure-molded at a pressure of 0.3 tons/C-, and sintered at 450°C. The results of a 300°C tensile test of a test piece taken from the sintered body showed that the tensile strength was 14 kg
f/mJ proof stress 11 kgf/- elongation 4%, and when mixed with SIC fibers a composite material with even better high temperature tensile properties is obtained, the application of which is very interesting.

(Effects) As explained above, the metal powder manufacturing method of the present invention can be applied to crystallization type or precipitation type alloys in which the ingot obtained by the usual melting and casting method is bent or the precipitated phase is coarse. Since the strips or rapidly cooled flakes are layered and sintered, the precipitated phase becomes a uniformly precipitated sintered body.
This is processed into an electrode and pulverized using the rotating electric power method, so it is easy to pulverize, and since the precipitated phase is finely precipitated in the sintered body, even after pulverization, it remains finely dispersed and homogeneous. A fine powder can be obtained.

Further, when forming a quenched ribbon, it is sufficient to have a supersaturated solid solution structure, and there is no particular need to use an amorphous or slightly amorphous &11 weave structure, so the quenching conditions are not so varied.

The sintered body formed and sintered using this powder has excellent high-temperature tensile properties, and has excellent high-temperature tensile properties.
! It has a wide range of uses, such as the ability to obtain an excellent material with high-temperature strength equivalent to 1.

[Brief explanation of drawings]

Figure 1 is a flow sheet showing the method of the present invention, and Figure 2 is the result of surface analysis of the quenched ribbon using an X-ray microanalyzer (C
It is a photograph showing rKα radiation). Applicant's agent Patent attorney Kamoshi FI+ Second son Figure 1 Figure 2

Claims (1)

[Claims] In a rotating electrode type metal powder production method, a crystallization type or precipitation type molten alloy is rapidly cooled to form a thin strip or flake of a supersaturated solid solution, layered and sintered, and then the sintered body is formed. A method for producing a metal powder with a composite structure having a fine precipitated phase, characterized by manufacturing an electrode using a rotating electrode method and producing a metal powder using the electrode.