JPH04202702A - Method for compacting powder - Google Patents

Abstract

PURPOSE:To compact a powder while shortening a manufacturing process by coating respective surfaces of main grains of micrometer order with specific percentages of subordinate grains of angstrom order and then applying pulse current to an aggregate of the above in a pressurized state. CONSTITUTION:Main grains 1 of 10-500 micrometers are coated or mixed with subordinate grains 2 of submicron size or smaller (e.g. about 100Angstrom ) so that the weight mixing ratio of the subordinate grains 2 to the main grains 1 is regulated to >=3%, by which a capsuled powder or a powder mixture is formed. Subsequently, a pulse current of about 400kg/cm<2> pressurizing force, about 800A electric current, and about 2-100Hz pulse frequency is applied to the aggregate of the capsuled powder or to the powder mixture, by which mutual subordinate grains 2 are bound together and the main grains 1 are firmly and stably compacted. By this method, the manufacturing process can be shortened, and the compaction of the powder can be performed at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for solidifying powder, and particularly to a method for solidifying powder used for powder in which mother particles are mixed or coated with child particles.

[Prior art and its problems] Methods for solidifying powder include powder molding, injection molding, casting method, sintering method in a sintering furnace, sintering method at high temperature and high pressure (HIP, CIP), and energization. methods (including discharge) are known.

In the case of the electrification (discharge@) sintering method, there are two methods: (a) adding a binder (a binder is an auxiliary additive other than the main component to improve bonding properties); and (b) not adding a binder. There is a method. In particular, in the current sintering method without adding a binder, as disclosed in JP-A-1-197369, etc., in order to conduct current sintering of 10-500 μm powder, a pulsed current is passed through the powder to create a gap between the powders. There is a method to purify the surface by micro-discharge of the powder, and then generate Joule heat by applying DC voltage to sinter and solidify the powder. Therefore, it requires two steps of applying pulse current and direct current, and there is a problem that it takes a long time to solidify.

[Problems to be Solved by the Invention] The inventors of the present invention conducted extensive research on the above-mentioned powder solidification method, and found that it is possible to solidify submicron-order powder using only pulsed current without using direct current. I found a headline. However, submicron-order powder is much more expensive than micron-order powder, and producing a solid product using only submicron-order powder has the problem of increasing costs.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a powder solidification method that shortens the manufacturing process and solidifies powder at low cost.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes child particles of submicron size or less in mother particles of 10 to 500 micrometers, and the weight mixing ratio of the child particles to the mother particles is 3% or more. Coating or mixing to produce a mixed powder or encapsulated powder,
A pulse current is applied to the aggregated powder or mixed powder of the encapsulated powder under a predetermined pressurized state.

[Function] When the mother particles are coated with the child particles so that the weight mixing ratio of the child particles to the mother particles of 10-500 μm is 3% or more, an encapsulated powder in which the child particles are distributed on the surface of the mother particles without segregation can be obtained. It will be done. A pulsed current is applied to the aggregated powder, which collects the required number of encapsulated powders to form the desired solid material.

! The particles are not bonded to each other, but the child particles are bonded to each other, and the mother particles are stably and firmly solidified.

10-500! Even when a pulse current is applied to a mixture of particles with a weight mixing ratio of 3% or more,
As in the case of capsule powder, the child particles are bonded to each other,
Good solidification of the powder is achieved.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

The powder used (powder with electrical conductivity) has the following composition.

FIG. 1 shows a conceptual diagram of solidification of mother particles 1 and child particles 2 according to the present invention.

As shown in the figure, first, a powder of angstrom order (e.g. 100A (0.01μm))
) are mixed in an amount of about 10 to 30% and the mixture is uniformly stirred, or the surface of the powder that will become the base particles 1 is coated with ultrafine powder in the form of small particles, for example, by electrostatic deposition. to make an aggregate powder of encapsulated powder. Aggregated powder here means simply collecting the required number of encapsulated powders necessary to form a solid prior to solidification.

In the case of encapsulated powder, the child particles 2 are uniformly distributed on the surface of the mother particle 1 by adhesion without segregation, so the mother particles 1
Compared to the mixed powder of the powder and child particles 2, handling as a raw material is extremely good. The mixed powder or encapsulated powder aggregate is then processed using a conventional current-carrying (including discharge) sintering device (
Specifically, using a sintering device disclosed in Utility Model Application Publication No. 1-197363 (discharge sintering device and abrasive grain manufacturing method), a high voltage, low current pulse current is applied under a predetermined pressure. (corresponds to the conventional 1st category).

Here, applying a pulse current refers to applying a large current with shocking handling (rising and falling), and applying a discharge current refers to controlling the voltage up to dielectric breakdown in an extremely short period of time to insulate the insulation. The setting of the device for solidifying aggregated powder or mixed powder, which refers to applying a large current (discharge current) at the time of breakdown (in the form of pulsed current), is to apply a pressure of 400
mg/■2, current 80OA, pulse frequency 2-10
It is preferable to set it to 0Hz.

As a result, the mother particles 1 were not bonded to each other, but the child particles 2 on the order of angstroms were bonded to each other, thereby making it possible to stably and firmly solidify the mother particles 1. In other words, in the powder solidification method of the present invention, without using submicron-order powder for all powders to solidify, bonding is only caused between submicron-order powders, and the powder to be solidified is By significantly reducing costs and omitting the second stage of electrification heat treatment in the conventional method (Utility Model Application No. 1-197363), the production time for solidification is greatly shortened, and the powder can be solidified at low cost. .

(Specific example) Specific examples will be shown below.

(Example 1) The surface of Fe-Nd-B magnetic powder with a particle size of 200 μm as the mother particle 1 is coated with 200A Fe-Ni magnetic powder as the child particle 2 at a predetermined weight mixing ratio to form a capsule. An encapsulated powder was formed, and a pulse current was applied to the aggregated powder of the encapsulated powder under a predetermined pressure using the above-mentioned apparatus to solidify the encapsulated powder.

For solidification, apply pressure to 400 kg/■2. The current was 800 A, the weight mixing ratio of Fe-Ni magnetic powder was 2%, 3
%, 10%, 15%, pulse width of pulse current 20ns
ec, 6011sec, 80nsec, 150
I changed it to 11sec.

The results are as shown in Table 1. At a weight mixing ratio of 3% or more and a pulse current pulse width of 6011 SeC, a good bond of Fe-Ni magnetic powder particles was obtained, and a good Fe-Nd-B solid material was obtained. It was done.

Table-1 0...Good solidification ×...Poor solidification (Example 2
) Sm, Co with a particle size of 200 μm to become the base particle 1.

Alternatively, encapsulated powder was formed by coating S m 2 CO+ on the surface of magnetic powder with 200 Fe-Ni magnetic powders as child particles 2 at a predetermined weight mixing ratio, and Example 1 was carried out using the above apparatus. Solidification was performed by applying a pulsed current under pressure to the aggregated powder of encapsulated powder under the following solidification conditions.

As in Table 1, the results show that when the weight mixing ratio is 3% or more and the pulse width of the pulse current is 60 m5ec, good bonding between Fe-Ni magnetic powder particles is achieved and good 5rrz COs' is obtained.
:4 or Sm2CO+t solid was obtained.

<Example 3> On the surface of 10 μm S m COs magnetic powder, a particle size of 10
Encapsulated powder was formed by coating 0A Fe-Co magnetic powder at a weight mixing ratio of 10%, and the aggregated powder of this encapsulated powder was subjected to the above-mentioned apparatus under the same solidification conditions as in Example 1. Solidification was performed by applying a pulsed current under pressure. As in Example 1, good bonding was obtained between the Fe--Co magnetic powders, and a good Sm+COs solid material could be obtained.

(Example 4) On the surface of 10 μm Nd, Fe, B fruit resin powder, particle size 10
0A Fe-Co magnetic powder or 100A Fe-Ni
The powders were coated at a weight mixing ratio of 10% to form encapsulated powders, and the aggregated powder of these encapsulated powders was pulsed under pressure using the above device under the solidification conditions of Example 1. A current was applied. The results are the same as in Example 1.
-Co magnetic powders or Fe-Ni powders were bonded to each other, and a good solid material mainly composed of Nd, Fe, and B-based resins was obtained.4 (Example 5) Fe with a particle size of 200 μm that became the mother particles 1 - The surface of the Nd-B magnetic powder is coated with 0.1μ strontium ferrite as child particles 2 at a weight mixing ratio of 50% to form an encapsulated powder, and the above device is used to encapsulate the powder. The aggregated powder was solidified by applying a pulse current under pressure under the same solidification conditions as in Example 1 using the above apparatus.

For solidification, apply pressure to 400 kg/2. 80 current
The pulse width of the OA pulse current was set to 60 m5ect.

The child particles 2 were bonded to each other and a good Fe-Nd-B solid material could be obtained.

(Example 6) An encapsulated powder was formed by coating the surface of carbon with a particle size of 50 μm as the mother particle 1 with carbon of 0.5 μm as the child particle 2 at a weight mixing ratio of 10%. A pulse current was applied to the aggregated powder of the encapsulated powder under a predetermined pressure to solidify the powder. For solidification, apply pressure to 400 kg/■2. The current was 80OA, and the pulse width was 8Qll5eC.The child particles (carbon) were bonded to each other, and a good carbon solid was obtained.

(Example 7) The surface of activated carbon powder of 10 to 50μ, n serving as the mother particle 1 is coated with activated carbon or carbon whiskers as the child particles 2 of 100 size at a weight mixing ratio of 10 to 30% for encapsulation. A powder was formed, and a pulsed current was applied to the aggregated powder under pressure under the solidification conditions of Example 1 using the above apparatus as in Example 1. As in Example 1, good bonding was obtained between the child particles, and a solid material mainly consisting of activated carbon could be obtained.

As is clear from Examples 1 to 7, the method for solidifying powder of the present invention can be achieved by simply applying a pulse current to the aggregated powder or mixed powder of encapsulated powder in which mother particles 1 are coated with child particles 2. It is now possible to bond and solidify between the two child particles, making it possible to
This makes it possible to omit the step (second section) which requires energization sintering at 1100''C for 3 minutes by applying a direct current as in Utility Model Application Publication No. 1-197363) and the time required to cool the mold.

As a result, the manufacturing process can be shortened, and expensive small particles are used only partially, making it possible to solidify powder at low cost.

In addition, unlike conventional methods, a power supply that directly applies current is not required, and only a pulse power supply is required, making it possible to solidify powder at low cost.

[Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) It is possible to bond and solidify the child particles simply by applying a pulse current, and since only a small amount of expensive small particles are used, the powder can be solidified at low cost.

[Brief explanation of the drawing]

The first figure shows a preferred embodiment of the present invention. In the figure, 1 is a mother particle and 2 is a child particle. Figure 7

Claims (1)

[Claims] 1. Encapsulated powder or mixed powder is produced by coating or mixing 10-500 micrometer mother particles with submicron or smaller child particles such that the weight mixing ratio of child particles to the mother particles is 3% or more. A method for solidifying powder, characterized in that a pulsed current is applied to the aggregated powder or mixed powder of the encapsulated powder under a predetermined pressurized state.