JPS61507A - Manufacture of metallic powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Field of application of the invention) This invention relates to an improvement in a method for producing high quality metal powder.

(Conventional technology and problems to be solved) To increase the fatigue strength of materials for high-speed rotating bodies that are subjected to high-temperature loads, such as gas turbine blades and disks, there is less segregation, fine grain structure, and high cleanliness. Demand for metal powders is increasing.

Conventional methods for obtaining metal powder include the rotating electrode method and the atomization method using water or gas, but the powder obtained by these methods has a cooling rate of 104°C/sec or less, so dendrite segregation is large and crystal grains are The size is relatively large, approximately 10 μm or more, and when molten metal is atomized, it becomes spherical due to the action of surface tension, so it has disadvantages such as being unsuitable for making high-density products. Therefore, in addition to requiring a large container, there are other problems such as a low yield of non-defective products.

Especially since the grain size of the metal powder is not small enough,
It is difficult for superplastic flow to occur when it is made into a billet by strong high-temperature processing, such as extrusion or forging, and then processed into a product shape. ``To solve this problem, it has been proposed to spray the molten metal onto the surface of a twin roll or single roll in an atmosphere of non-oxidizing gas such as an inert gas, cool it at a cooling rate of approximately 106°C/sec, and solidify it into a thin tape. There is. This thin tape has ideal properties such as suppressed dendrite segregation, finely dispersed nonmetallic inclusions, very fine crystal grains of approximately 0.5 μm, and a yield close to 100%. However, if the material is used as a raw material and densified, good bonding between the thin tapes cannot be obtained, as can be seen in the micrograph shown in FIG. 3, for example.

In contrast, a method of cutting into small pieces has been adopted in some cases, but since the thin tape is hard, the cutting tool is easily worn out, and it is impossible to make it into fine powder. There are some problems.

(Objective of the Invention and Means for Solving the Problems) In view of the above circumstances, the present invention involves pulverizing a thin tape obtained by cooling molten metal at high speed with twin rolls or a single roll into fine powder instead of cutting it. (In a metal powder production method, molten metal is sprayed onto the surface of a rotating roll in a non-oxidizing gas atmosphere and rapidly cooled to produce a thin tape with crystal grain size of 2 μm or less. After solidifying into a shape, the thin metal tape is placed in a container containing steel balls in a non-oxidizing gas atmosphere, and a rotating shaft attached to the container is rotated at high speed to crush the thin metal tape into pieces of 200 μm or less. The present invention relates to a method for producing metal powder, which is characterized by obtaining fine-grained, irregularly shaped metal powder.

(Embodiments) Next, embodiments will be described with reference to the accompanying drawings.

As shown in FIG. 1(a), a crucible 2 heated by a high-frequency induction coil 1 is used to conduct nitrogen in an argon gas atmosphere.
The i-base superalloy Mar M 247 is melted and sprayed from the nozzle 3 at the bottom of the crucible 2 onto the surface of a single roll 4 rotating at a circumferential speed of 20 to 30 m/sec in an argon gas atmosphere, followed by rapid cooling. It was solidified into a thin tape 5. Since cooling is performed by direct heat transfer, the size of the container that provides the non-oxidizing gas atmosphere is sufficient to surround the melting system and the rolls.

The obtained tape has a thickness of 40 to 80 μm, a crystal grain size of approximately 0.5 μm, precipitates such as carbides and dendrite segregation are suppressed, and the cooling rate reaches 106 ° C / sec. It was estimated that

The content of oxygen gas and nitrogen gas was several ppm, which was significantly lower than that of the conventional method.

The obtained thin tape was placed in a ball mill and pulverized by collision with steel balls in a non-oxidizing gas stream. For this purpose, as shown in FIG. 1(b), a rotating shaft 8 to which a stirring arm 7 is attached is provided at the center of the cylindrical container 6. A ball mill called a high-energy gear lighter that rotates at a rotational speed of 10 mm to agitate steel balls 9 with a diameter of about 10 mm in a container and impart large collision energy to the steel balls is suitable. This method made it possible to pulverize thin metal tape by the impact force of high-energy steel balls in the attritor.

By processing in this manner, the tape was completely pulverized to obtain a powder with an average particle size of 100 to 300 mesh. The powder particles had a high cold distortion due to the grinding process using the attritor, and were irregular in shape, closer to flake than spherical.

After vacuum sealing this powder in a stainless steel container,
When extrusion processing was performed at 1200° C. and an extrusion ratio of 8 to 12, good elongation was obtained, and a billet with much more ductility than cast material could be obtained. The microscopic structure was uniformly fine as shown in FIG.

(Effects of the Invention) As explained above, since the method of the present invention is a method of pulverizing with high-energy steel balls of an attritor, thin metal tape can be pulverized, and the particle size of the metal powder is smaller than that of the conventional method. It is finer at 0.5 μm compared to about 10 μm for particles, has cold strain, and has an irregular shape.
When densified by extrusion using this material, it exhibits good superplasticity and has excellent workability.

In addition, it has the characteristics of a roll-quenched, rapidly solidified thin metal, such as finely dispersed nonmetallic inclusions, suppresses precipitation of carbides, dendrite segregation, and high cleanliness. This metal powder has extremely excellent properties as a raw material powder for mechanical parts, and the fact that it has become possible to produce such a metal powder using this method has an extremely large industrial effect.

[Brief explanation of drawings]

FIG. 1(a) is a conceptual diagram showing the manufacturing procedure for the thin metal tape used in the method of the present invention, and FIG. 1(b) is a diagram illustrating the internal structure of a high-energy crushing device suitable for crushing the thin metal tape. FIG. 2 is a perspective view showing the microstructure of a billet extruded using the metal powder according to the present invention, and FIG.
The figure is a photograph showing the a-like structure of a billet densified using a thin metal tape according to the prior art. ■... High frequency induction coil, 2... Crucible, 3...
Nozzle, 4... Single roll for cooling, 5... Thin tape,
6... Cylindrical container, 7... Stirring rod, 8... Rotating shaft Patent attorney Patent attorney Kamoshi 1) Second son 1 (b)

Claims (1)

[Claims] In a method for producing metal powder, molten metal is sprayed onto the surface of a rotating roll in a non-oxidizing gas atmosphere to rapidly cool it and solidify it into a thin tape shape with a crystal grain size of 2 μm or less, and then steel balls are formed. The thin metal tape is placed in a container containing a non-oxidizing gas atmosphere, and a rotating shaft attached to the container is rotated at high speed to crush the thin metal tape into irregularly shaped metal powder with fine particles of 200 μm or less in size. A method for producing metal powder characterized by obtaining