JPS6260803A - Production of amorphous alloy powder - Google Patents

Abstract

PURPOSE:To stably produce powder of a proper particle size in simple stages by continuously feeding a molten alloy to the surface of a cooling roll, solidifying it by rapid cooling on the surface of the roll, separating a formed thin strip and crushing it. CONSTITUTION:A molten alloy is continuously fed to the surface of a cooling roll 2 rotating at a high speed from a pouring nozzle 1. It is solidified by rapid cooling in close contact with the surface of the roll 2 to form a thin amorphous alloy strip (amorphous alloy ribbon) 4. When the temp. of the strip 4 is within the range of the crystallization temp. -200 deg.C - the crystallization temp. +50 deg.C, air is jetted from an air nozzle 3 to separate the strip 4. The strip 4 is then crushed. By this method, amorphous powder can easily be produced only in two stages, that is, rapid cooling and crushing stages.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention provides a method for producing amorphous alloy powder suitable for use as a raw material for powder metallurgy or composite materials. In particular, the present invention provides an advantageous simplification of the processing steps.

(Prior art) A method for producing amorphous alloy powder is disclosed in Japanese Patent Application Laid-Open No. 57-
Japanese Patent No. 29505 proposes a method in which molten metal is injected from an orifice opening into a cooling fluid on the inner wall of a rotary cup to rapidly solidify it, and then solid powder is recovered from the cooling fluid.

However, this method had the disadvantage that the opening gradually eroded and expanded during long production times, changing the diameter of the produced powder, and also required a step to separate the produced powder from the cooling liquid. .

Furthermore, in Japanese Patent Application Laid-Open No. 58-6907, two stages of rotating rolls are provided, upper and lower stages, and the molten metal is dropped and supplied to the single or twin rolls in the upper stage, divided into droplets, and released at high speed by centrifugal force. A method has been proposed for producing an amorphous alloy powder by colliding droplets onto the surface of a lower cooling rotary roll and causing rapid solidification.

However, the amorphous alloy powder obtained by this method has a wide range of particle sizes ranging from 20 to 506 μm and contains quite coarse particles, and unless the entire apparatus is covered with an inert gas atmosphere, the powder surface The problem was that oxidation could not be prevented.

Furthermore, in Japanese Patent Publication No. 60-401, after producing a ribbon-shaped amorphous alloy, it is heat-treated at a temperature below the crystallization temperature.
A method has been proposed in which the material is embrittled without causing the formation of a crystalline phase and then ground into powder.

Since this method creates a ribbon in the first step, it is possible to ensure a high degree of amorphousness, and it has the advantage of producing powder with 100% amorphous phase, but on the other hand, the second step However, there was a drawback in that it required complicated steps such as heat treatment to make it embrittle.

(Problems to be Solved by the Invention) As mentioned above, all of the conventional methods require complicated processing steps and leave problems in that it is not always possible to obtain powder with an appropriate particle size. was.

This invention advantageously solves the above problems, and proposes a method for producing amorphous alloy powder that can stably produce powder with an appropriate particle size using only two steps: rapid casting and pulverization. The purpose is to

(Means for Solving the Problems) That is, the present invention continuously supplies molten alloy from a pouring nozzle to the surface of a cooling roll rotating at high speed,
While forming an amorphous alloy ribbon through rapid cooling and solidification while adhering closely to the surface of the roll, the temperature of the ribbon is (crystallization temperature +50°C to crystallization temperature -200°C) on a cooling roll. This is a method for producing amorphous alloy powder, which is characterized by separating the powder from the surface and then pulverizing it.

The background to the elucidation of this invention will be explained below.

When a normal amorphous alloy ribbon is produced by the single roll method having the configuration shown in FIG. By forcing the ribbon to cool to 200° C. while keeping it in close contact with the cooling roll 3, a ribbon with high toughness and 100% amorphousness is produced.

At this time, when the ribbon is peeled off from the cooling roll 3 using an air jet from the air nozzle 4 shown in FIG. 1, by shifting the installation position of the air nozzle 4, the distance in which the ribbon adheres to the cooling roll can be changed as appropriate.

When the air nozzle 4 is moved and the position of the air jet is gradually brought closer to the pouring nozzle 1 side, thereby shortening the close contact distance of the ribbon 2, the crystalline phase becomes mixed. Therefore, we investigated various properties of the ribbon as a function of the ribbon adhesion distance, and found that as the adhesion distance decreased, (2) The mechanical properties change from an extremely tough state to a brittle ribbon; (3) However, even though the mechanical properties are extremely brittle, X-ray It is completely amorphous, and OSC
There is a relatively wide range of conditions for producing a ribbon in which the exothermic peak due to crystallization can be clearly confirmed even in thermal analysis tests conducted by We obtained the knowledge that by crushing using a crusher mill, hammer mill, etc., it is possible to produce amorphous alloy powder without going through the embrittlement annealing process.

Therefore, in order to obtain a brittle amorphous alloy, we considered the timing at which the amorphous alloy ribbon that is in close contact with the cooling roll should be separated from the roll.

A molten alloy with a composition of FetJl+oSi+3 was
It was injected onto the surface of an internal water-cooled copper alloy roll of mmφ through a slit-shaped nozzle. At this time, the rotational circumferential speed of the single roll was 35 m/sec.

FIG. 2 shows the results of investigating the relationship between the adhesion distance and ribbon properties by changing the installation location of the ribbon-peeling air nozzle and changing the adhesion distance of the ribbon.

When producing the amorphous alloy powder targeted by this invention by a pulverization method, the starting material before pulverization must be an amorphous and brittle alloy ribbon, which is clear from the results shown in Figure 2. An amorphous alloy ribbon that meets this condition has a temperature of about 600°C to about 350°C when the ribbon adhesion distance is from 1/8 to 1/4 of the roll, that is, from about 600°C to about 350°C in terms of carbon temperature. It can be seen that this is obtained when it is peeled off from the cooling roll at the time of cooling.

The crystallization temperature of this amorphous alloy was increased at a heating rate of 20°C/min.
It was determined by thermal analysis to be approximately 540"C. In other words, the preferred roll cooling end temperature is between 50°C above the crystallization temperature and 200°C below the crystallization temperature. Therefore, when we investigated the appropriate roll cooling end temperature for amorphous alloys with other compositions, we found that (crystallization temperature + 50℃
It was confirmed that the desired amorphous alloy ribbon could be obtained if the crystallization temperature was -200°C).

Any known means such as a ball mill, Grafshear mill, or hammer mill can be used to grind the embrittled amorphous alloy. In order to reduce contamination of powder as much as possible during such pulverization, it is desirable to use cemented carbide, ceramics, etc. for the worn parts of these devices, or to apply a surface coating treatment. Furthermore, if surface oxidation becomes a problem during the pulverization process, it is desirable to pulverize in a neutral atmosphere such as nitrogen or argon, or in a vacuum.

(Function) Since the powder obtained according to the present invention has a uniform composition, the structure of parts compacted and sintered using this powder as a raw material is extremely fine and uniform. The mechanical properties can be improved compared to the case where the

(Example) Example I FeyoMO5Cr5B? Molten alloy with Si+3 composition,
When injecting onto the surface of a single roll with a diameter of 30 cm through a slit nozzle to produce an amorphous alloy ribbon with a thickness of 30 μm, the ribbon is cooled at a temperature of approximately 450°C (crystallization temperature of amorphous ribbon: 550°C). Removed from roll.

Although the ribbon thus obtained was X-ray amorphous, it was extremely brittle and could then be easily ground using a ball mill.

Example 2 Fe6°B. Si,. A molten alloy of the composition was treated in the same manner as in Example 1. However, the ribbon was removed from the cooling roll at a temperature of about 400°C (crystallization temperature of amorphous ribbon: 540°C).

The obtained ribbon was X-ray amorphous and could be easily pulverized in a ball mill.

Comparative Example 1 In Example 2, the ribbon temperature at the time of ribbon peeling was set to about 2
The temperature was 00°C.

Although the resulting ribbon was completely amorphous in terms of X&'i, it had high toughness and was therefore extremely difficult to mill in a ball mill.

(Effects of the Invention) Thus, according to the present invention, an amorphous alloy powder can be easily produced with only two steps: quench casting and pulverization.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the manufacturing procedure for an amorphous alloy ribbon according to the present invention, and FIG. 2 is a graph showing the relationship between the distance of adhesion of the ribbon to the cooling roll and each property of the obtained ribbon. Fig. 2 9-hole close contact huge difficulty

Claims (1)

[Claims] 1. Continuously supplying the molten alloy from the pouring nozzle to the surface of a cooling roll rotating at high speed, and rapidly solidifying it while closely adhering to the roll surface to form an amorphous alloy ribbon, A method for producing an amorphous alloy powder, characterized in that the ribbon is separated from the surface of a cooling roll in a temperature range of (crystallization temperature +50°C to crystallization temperature -200°C) and then pulverized.