JPS6223912A - Production of fine metallic powder - Google Patents

Abstract

PURPOSE:To obtain a single-crystalline and polygonal fine metallic powder having high purity when a metallic halide is reduced with hydrogen, by lowering the heating temp. of the metallic halide and the flow rate of the hydrogen. CONSTITUTION:The metallic halide is reduced with gaseous hydrogen to produce metallic powder. At this time, the metallic halide is heated to a temp. which is below the m.p. of the metallic halide by about 400 deg.C so as to control the extent of evaporation. The flow rate of the gaseous hydrogen is regulated to <=about 100cm/min so as to slowly grow a nuclei and to make the resulting particles practically a single-crystalline. By this method, fine metallic powder having high purity useful as a magnetic material, a material for powder metallurgy or a filler is obtd. The metal may be Fe, Co, Ni or an alloy thereof.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a method for producing metal fine powder of iron, nickel, cobalt, etc., which is substantially single crystal and has high purity.
This invention relates to a method for producing fine metal powder useful as magnetic materials, powder metallurgy, various fillers, etc.

Conventional technology High-purity iron powder can be produced using the following methods. Nickel, cobalt, etc. can also be produced in the same way.

■Electrolysis is a method of crushing high-purity iron flakes obtained by.

(A method of thermally decomposing purified iron carbonyl (Fe (Co)5).

■A method of atomizing molten high-purity iron.

■7 people who processed 5 yuan of high-purity iron chloride or iron liquefaction with hydrogen, etc.

(Rino iron powder has an uneven surface and a flat shape, 257
If it becomes less than Lm, the flattening becomes severe. Also, since impurities are introduced during pulverization, the finer the powder, the lower the purity. The iron powder (2) is a spherical powder with a particle size of 1 to 108 LI11. 1
In the range of ~ lopLm, it has the highest purity among existing iron powders, but since the contamination of C is unavoidable, the total amount of impurities is approximately 1
%. Moreover, the powder particles are layered polycrystalline. ■The iron powder has a spherical shape and an irregular shape, but in any case,
It is difficult to make it into a fine powder of lopLm or less. Pure IW
However, if the purity of the molten metal is increased and atomization is performed in an inert atmosphere, the purity will be considerably high, but if the total impurity is reduced to 1.
% or less is difficult. The crystals of the particles are also polycrystalline. Iron powder produced by reducing iron oxide in step (2) has iron powders with shapes and sizes that correspond to the shape and size of iron oxide, but they are generally polycrystalline and leave iron oxide behind, making them porous and of poor purity.

In addition, the method for reducing iron chloride was published in Japanese Patent Publication No. 58-7785.
, Tokukai Showa 5! ]-170211, but
The fine powder obtained there is a string of beads, and the individual particles are not single crystals. In this method, an interfacial unstable region is formed at the interface between iron chloride vapor and hydrogen gas, and a large number of metal nuclei are rapidly generated there, resulting in a polycrystalline state naturally.

Problems to be Solved by the Invention Conventional fine powders of iron and the like are polycrystalline, flat in shape, and contain many impurities. Therefore, when used as a magnetic material, for example, a core material of a coil, it cannot fully exhibit its performance. Furthermore, if the material is flat, there will be problems in filling properties as a filler and in use in powder metallurgy.

The present invention is a high-purity Fe, old,
1- to provide Co powder or alloy powder thereof;
1 target.

Means for Solving the Problems The method of the present invention consists in converting metal halides by hydrogen reduction to substantially form the particles into single crystals.

Since the amount of evaporation of the metal halide is small, the reduction takes place mostly in the metal halide powder layer -I- or within the layer. Instead of moving the metal halide vapor to another zone and bringing it into contact with hydrogen gas there for a reduction reaction as described in the above-mentioned patent publication, the method of the present invention uses metal halide vapor as a starting material in the presence of the metal halide. This is a method in which metals are reduced and precipitated where they are present, that is, in the same zone. This reaction mechanism is not certain, but given that the reduced metal grows as a single crystal, it is not a solid-phase reaction; the metal halide is first evaporated, then reduced and twisted by hydrogen to form a metal halide. It is thought that the particles precipitate within or on the compound powder layer.

The heating temperature of the metal halide is below the melting point of the metal/halide because it is necessary to maintain the powder state as described above. The lower limit is necessary to make the reaction rate practical, and is preferably 400°C minus the melting point of the bimetallic compound. The temperature is preferably in the range of 400 to 600°C.

For example, metal halides are F e Cl 3
The temperature is 17° C., and since it does not react even when mixed with hydrogen gas at this temperature, dichlorides such as FeClycocI and NiCl2 are suitable if they have an appropriate melting point. These particle sizes are chosen to prevent agglomeration of the reduced metal.
It is preferably 0 gm or less. It is desirable to mix a small amount of the same metal oxide into the raw materials mentioned above.

This is because metal oxides are more easily reduced than halides, and by appropriately dispersing them, the reduced metal becomes a nucleus, and the grain size of the single crystal can be controlled. However, since a small amount of Fe2O3 etc. is usually mixed in FeCl2 etc., it is not necessary to add it in this case.

Geru. The appropriate flow rate varies depending on the reduction method, but for example, metal halide is placed in a dish-shaped container and hydrogen gas is passed from one side to the other, or the raw material is rotated using a rotary kiln method. In a method in which hydrogen gas is flowed from one end of the kiln, the flow rate of hydrogen gas is preferably 100 cm/min or less. and preferably 3
The speed is 0 to 80 cm/min. Further, in a method in which a cylinder is filled with raw material powder and hydrogen gas is flowed from the bottom of the cylinder to pass through the raw material layer, a suitable flow rate of hydrogen gas is 50 to 100 co+/min.

These flow rates are the inflow (J (Cm''/min)) divided by the cross-sectional area of the reaction zone (crn') at room temperature.

The hydrogen gas may contain an inert gas, C01H20 gas, etc.

The metal powder obtained by the method of the invention is substantially single crystal. Substantially means that the grains have no grain boundaries and a very low dislocation density.

By using an all-round crystal, a magnetic medium to +1, for example, a Histo T rigid curve can be made into a curve with less residual magnetism.

Next, the 11th round has a polyhedral shape of 17. Most of the shapes are polyhedrons with a hexahedron size of 1-1 or less, and are not oblate or sword-shaped, and most of them fall within the range of 1 to 3 when expressed in terms of aspect ratio. Because of their granular shape, the particles according to the present invention are extremely suitable for use in powder metallurgy and fillers. range.

Another feature of the metal powder according to the present invention is that it has high purity. That is, preferably the dull material is 0.5% by weight or less. The reason why there are so few impurities is that the powder grains r- have almost no crystal defects, so there are few impurities trapped in the defects.

Example 1 Commercially available reagent grade ferrous salt (Feel xH2
C. O) was crushed with a nylon ball for 1 hour until the particle size was 50 gm or more. When that 3g is transferred to a mild steel port,
゛、Including 1.150+nm Il1fi-tube as furnace core/6・
and 1. 1. Q/min (this l
This is the value at room temperature, divided by the i area of the electric furnace, which is 1
．． The speed is 50cm/min. ) in hydrogen at 450℃ 1. Also. Prefectural Junior High School, by avoiding the absorption of reactive gases (including HCI) in water and dividing the conductivity of the aqueous solution by A11l.
I caught the last 1 ha of the anti-I Yi. As a result, it took about 5 hours.

As shown in FIG. 1 (magnification +000 f:'i), the Bored iron powder produced in the form of a polyhedron has a polyhedral shape with almost no crystal defects. Most of them are 6 to 8 gm in size and have an average aspect ratio of 1. As a result of chemical analysis of these particles, the impurities are as follows (the numbers are p
pm).

A1, Sl, P, Ca, Ti, V, C
r5 or less 5 or less 20 or more 312 or more 2Kn,
Co, Ni, Cu, Zn, Mo, -1
Na135511 or higher 4 20 or higher
Similarly, single crystal, polyhedral particles are obtained from C1 and CoCl2.

Effects of the Invention According to the fuco method of the present invention, the beads are arranged in a string like the conventional method,
Moreover, since each particle is polycrystalline or forms particles, it exhibits excellent performance in many applications.

[Brief explanation of the drawing]

FIG. 1 is a scanning electron micrograph of iron powder obtained by the method of the present invention (1000x magnification).

Claims (2)

[Claims] (1) In a method of obtaining metal powder by reducing a metal halide with hydrogen gas, the heating temperature of the metal halide and the hydrogen gas are adjusted so that the metal is precipitated as a substantially single crystal in the same zone as the metal halide. A method for producing metal powder characterized by suppressing flow velocity. (2) The method for producing metal fine powder according to claim 1, wherein the metal is one of Fe, Ni, and Co or an alloy thereof.