JP2002309361A - Method for producing thermal spray powder and thermal spray powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a metal powder having a high packing density and excellent fluidity used for a thermal spraying powder or the like, and a thermal spraying powder. SOLUTION: The method for producing a thermal spraying powder is characterized in that metal agglomerates generated by welding powder produced by a gas atomization method are crushed by collision in a high-speed gas. The high-speed gas is 2 to 5 kg / cm ²
A method for producing a thermal spraying powder, characterized in that the thermal spraying powder is separated or crushed by a pressurized gas, and the thermal sprayed powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal powder having a high packing density and excellent fluidity used for thermal spraying powder and the like, and to a thermal spraying powder.

[0002]

2. Description of the Related Art Conventionally, metal spraying represented by arc spraying, gas spraying, plasma spraying, etc., has been developed as a method for coating various structures with a metal to obtain decoration, rust prevention, wear resistance and corrosion resistance. I've been. The required properties can be selectively utilized by this thermal spraying technique, so that the material cost can be reduced and a material having a composite function can be supplied.
However, in order to perform stable thermal spraying, it is necessary to strictly control the thermal spraying speed, temperature, and the like. Further, since thermal spray powder used as a coating material needs to be supplied in a fixed quantity with high precision, severe restrictions are required on the size and shape of the powder. For this reason, a spherical powder produced by a gas atomizing method or the like is often sieved to obtain a powder having a certain degree of fluidity or bulk density.

[0003] When the supply of powder is made constant, it is desired to reduce the resistance during supply by making the shape and size of each powder uniform and at the same time increasing the flow rate. The gas atomized powder is used to utilize the high fluidity characteristic of the spherical powder. However, powders produced by gas atomization often contain agglomerates welded due to collisions between the powders during solidification, and therefore tend to have poorer fluidity than ideal sphere-only powders. Was. In addition, when the agglomerated powder is separated during construction, powders having different particle sizes are mixed, and there is a concern that quality may be adversely affected.

[0004]

The gas atomization method is excellent as a method for mass-producing spherical powder, but has the above-mentioned problems in quality. Therefore, JP
As disclosed in Japanese Patent Application Laid-Open No. 3-71642, a method of obtaining a spherical powder by polishing the surface of the powder has been proposed. However, spheroidization by polishing not only requires high energy, but also involves grinding the surface. There has been a problem that the yield is reduced.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the inventors of the present invention have made intensive developments and found that powders produced by gas atomization collide with each other under conditions where the surfaces of the powders are not polished. It has been found that the powder that is secondarily deposited during solidification can be separated into individual powders and returned to the original spherical shape of the gas atomized powder.
By using this method, it is possible to obtain a spherical powder without secondary welding utilizing the characteristics of gas atomization without lowering the yield.

[0006] The gist of the invention is that an agglomerate obtained by secondary welding of powder produced by a gas atomization method or the like is impinged in a high-speed gas to form a single spherical spherical shape formed during gas atomization. A method for producing a powder crushed into particles. (1) A method for producing a thermal spray powder, which comprises crushing metal agglomerates produced by welding a powder produced by a gas atomizing method by colliding them in a high-speed gas. (2) The method according to the above (1), wherein 2 to 5 kg
A method for producing a thermal spraying powder, wherein the powder is separated or crushed by a pressure gas of / cm ² . (3) A sprayed powder having a high packing density and excellent fluidity manufactured by the method described in (1) or (2).

Hereinafter, the present invention will be described in detail. When producing a metal powder with good fluidity used for thermal spraying, etc., a method of producing a spherical powder by gas atomization is used.However, since powder or molten metal once separated during gas atomization adheres to form an aggregate. However, it was difficult to obtain only a single spherical powder. Therefore, they have found that it is possible to separate the welded agglomerated powder by colliding the powder produced by the gas atomization in a high-speed gas, and to return the powder to the original spherical shape of the gas atomized powder. The high-speed gas can be separated or crushed by a pressure gas of ^{2 to} 5 kg / cm ² , and if it is less than 2 kg / cm ² , a sufficient effect cannot be obtained, and more than 5 kg / cm ² If the gas is a high-pressure gas, the collision of the powder becomes severe and stable separation or crushing cannot be obtained. Therefore, the optimum range is 2 to 5 kg / cm ² .

[0008]

The present invention will be specifically described below with reference to examples. (Example 1) 16Cr-16Mo-4W-7Fe-57
A molten metal adjusted to Ni (weight ratio) is ejected from a nozzle, and a powder obtained by blowing a high-pressure gas onto the molten metal is sieved on a 63 μm sieve through a wire mesh and into a 250 μm sieve.
The mixture was classified under an m sieve to obtain a raw material powder. 10 kg of this powder
Was charged into a crushing vessel adjusted so that the gas ejected from the jet nozzle collides at one point. At this time, the gas ejected from the jet nozzle is 3 kg / cm ² at 4 kg / cm ² .
It was made to squirt at ³ / min. In addition, a circulating gas for stirring the powder upward from the bottom of the container was introduced so that the powder did not accumulate on the bottom. After holding for 30 minutes after charging, the powder was taken out and classified again with a wire mesh on a 63 μm sieve and under a 250 μm sieve to obtain Sample 1.

(Example 2) A raw material powder having the same particle size and components as in Example 1 was placed in a crushing vessel adjusted so that a gas ejected from a jet nozzle was ejected at 3 kg / cm ² at ³ Nm ³ / min. I put it in. After holding for 30 minutes after charging, the powder was taken out and classified again with a wire mesh on a 63 μm sieve and under a 250 μm sieve to obtain Sample 2.

(Example 3) A raw material powder having the same particle size and components as in Example 1 was placed in a crushing vessel adjusted so that a gas ejected from a jet nozzle was ejected at 4 kg / cm ² at 4 Nm ³ / min. I put it in. After holding for 30 minutes after charging, the powder was taken out and classified again with a wire mesh on a 63 μm sieve and under a 250 μm sieve to obtain Sample 3.

(Example 4) A raw material powder having the same particle size and components as in Example 1 is charged into a crushing vessel adjusted so that a gas ejected from a jet nozzle is ejected at 2 kg / cm ² at ² Nm ³ / min. did. After holding for 30 minutes after charging, the powder was taken out and classified again with a wire mesh on a 63 μm sieve and under a 250 μm sieve to obtain Sample 4. Table 1 shows the results described above.

[0012]

[Table 1]

FIG. 1 is a photomicrograph of the gas atomized powder and the powder processed according to the present invention, and FIG. 1 (a) is a photomicrograph of the powder processed according to the present invention.
(B) is a micrograph of a conventional gas atomized powder. As shown in FIG. 1 (a), by the treatment according to the present invention, the secondary welded powder in the raw material powder is separated into individual spherical powders. The weight and packing volume of the obtained powder were measured, and the yield and packing density before and after the treatment were investigated. Further, the time during which 50 g of the powder flows down from the orifice (flow rate) was measured for fluidity comparison.

As a result of examining the yield of the obtained powder by this treatment, the yield was found to decrease when the pressure of the jet nozzle was increased. This is considered to be due not only to the separation of the agglomerated powder into individual powders, but also to the separation of the powder surface or the destruction of the powder due to the effect of crushing. In addition, the packing density and the fluidity tend to decrease as the gas pressure of the jet nozzle increases, which is considered to be because the powder obtained by atomization was broken by the above-mentioned powder exfoliation or destruction.

[0015]

As described above, although the powder originally produced by the gas atomization method has a spherical shape, the spherical characteristics have not been effectively utilized due to the welding of the powders that collided during solidification. . However, by bombarding the combined powder under certain conditions,
It can be separated into individual spherical powders obtained by the gas atomizing method, and the fluidity and packing density, which are the characteristics of the spherical powders, can be improved. In addition, since it is not necessary to newly form a spherical shape but only to separate the settled powder, it is possible to produce a high-quality thermal spray powder capable of minimizing a decrease in yield due to processing. Is played.

[Brief description of the drawings]

FIG. 1 is a micrograph of a gas atomized powder and a powder treated according to the present invention.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Kenichi Nakatsuka 3007 1-letter Nakajima character in Shima, Ward, Himeji City, Hyogo F-term (reference) 4K017 EA13 EB00 4K031 AA08 AB08 AB09 CB01 CB08 CB22 CB23 CB24

Claims (3)

[Claims] 1. A method for producing a powder for thermal spraying, comprising crushing metal agglomerates produced by welding a powder produced by a gas atomizing method by collision in a high-speed gas. 2. The method according to claim 1, wherein
A method for producing a thermal spraying powder, wherein the powder is separated or crushed by a pressure gas of 5 kg / cm ² . 3. A sprayed powder having a high packing density and excellent fluidity, produced by the method according to claim 1.