JPS61204304A - Production of metallic powder - Google Patents

Abstract

PURPOSE:To produce inexpensively irregular shaped metallic powder contg. oxygen at a low ratio and having excellent cold press formability by bringing an org. solvent mode of the adequate compsn. consisting of C, H, O, etc. as a spraying medium into collision against a molten metal. CONSTITUTION:This method produces the metallic powder by supplying the molten metal obtd. by melting a material metal in an electric furnace 1 via a tundish 2 disposed with a heater 5 for holding heat, bringing the spraying medium supplied from a pressurizing pump 8 into collision against the molten metal in a spraying nozzle 6 to form the metallic powder and cooling and solidifying the metallic powder in a storage tank 9 provided with an overflow port 10. The org. solvent consisting preferably of C, H, and O and having <=4 C, <=1 O and <=150 deg.C b.p. is used as the spraying medium in the above-mentioned method. The resulted metallic powder can be easily dried by heating or evacuation. The irregular shaped metallic powder which does not contain impurities such as C and contains the oxygen at a low ratio is thus inexpensively obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing metal powder by impinging a spray medium on molten metal to obtain metal powder, and in particular, a method for producing metal powder with high purity and low surface oxidation at a low cost. It relates to a method of manufacturing.

[Conventional technology]

Many methods are known for producing metal powder, from chemical methods to mechanical methods. Industrially, two methods are used: the reduction method, which reduces mill scale generated in the steel industry process and turns it into powder, and the molten metal atomization method, which obtains metal powder by spraying a high-speed fluid onto a flow of molten gold metal. is mainly used. The former method uses mill school, which is a by-product of rolling, as a raw material, and therefore contains many impurities, making it impossible to adjust the composition, and limiting the range of composition of the obtained metal powder. On the other hand, in the latter method, the composition can be adjusted at the molten metal stage, so the composition range of the obtained metal powder is not limited, mass production is possible, and it is advantageous in terms of energy. . For this reason, the latter method has become the mainstream of recent capital investment.

[Problem that the invention seeks to solve]

In the molten metal spray method, water or an inert gas is generally used as the spray medium. When water is used as the atomizing medium, the cooling rate of the molten powder is extremely fast at 101 to 10"C/Sec, so irregularly shaped powder can be obtained. Good flanging and good moldability.In this case, since the spray medium is water,
Although this method is industrially inexpensive, oxidation of the metal powder is unavoidable during atomization9, and when obtaining iron powder, 0.3 to 1.0%
When using this as a powder metallurgy iron powder, an oxide reduction step is required.

This reduction process requires a reducing gas such as H, Co, etc., and also requires reduction at a high temperature. Therefore, the reduction process is a main factor in increasing the manufacturing cost of metal powder in terms of equipment costs and operating costs, and is one of the main reasons for increasing the price of products made from this metal powder as a raw material. The raw material price of the water-sprayed iron powder, which is used to some extent as machine sintered parts, is almost twice as high as that of the ingot process. Furthermore, in the production of alloy powder containing alloy components such as Cr and Mn, Cr and Mn are preferentially oxidized, and it is difficult to reduce these oxides, and if high temperature reduction is attempted, the powder will sinter. Difficult to disintegrate. When water-sprayed alloy powder is used as a raw material for mechanically sintered parts, sinterability decreases due to oxidation of the alloy components, making it difficult to achieve high density, and strength, ductility, and corrosion resistance do not improve as expected, and quenching There are also problems such as deterioration in performance.

As a molten metal atomization method that attempts to prevent or minimize oxidation of metal powder, the molten metal flow is isolated from the atmosphere with an atmospheric gas such as inert gas 1 combustion gas, and the molten metal flow is atomized with an inert gas to atomize it. There is.

This method uses an inert gas as a propellant, so
The cooling rate of the powder is slower than that in the case of 100~b, and therefore the shape of the obtained powder becomes spherical or nearly spherical due to the effect of the surface tension of the molten powder.

This spherical powder is convenient when used to fill metal capsules for HIP (hot isostatic pressing), but the entanglement of the powder is insufficient for general cold press forming. Difficult to use. In addition, in terms of manufacturing costs, it is costly to maintain the inert gas at a high purity.

For this reason, Ni.

The reality is that it is an expensive high-alloy powder for small quantities and special uses such as base superalloys and high-speed tool steels, and it has not been put to practical use.

In response to this situation, a method using kerosene, non-polar solvents such as benzene, mineral oil, animal oil, etc. as the spray medium is used as a molten metal spraying method that satisfies both cooling speed, powder shape, and oxidation prevention. (Japanese Unexamined Patent Publication No. 55-82701) has been proposed. However, when such a fluid is used as a spray medium, although oxidation of the metal powder is suppressed, the spray medium adheres to the powder, and C from its thermal decomposition also adheres to the powder, and the spray medium itself and decomposed C The problems of the conventional molten metal spraying method cannot essentially be solved, such as requiring large-scale equipment to separate the powder from the powder, and carburization occurring during separation and during heat treatment to improve the cold-open formability of the powder. was there.

[Means for solving problems]

The present invention solves the problems of the molten metal spraying method as described above, and as a result of research to establish a method for inexpensively manufacturing deformed metal powder with low oxygen content and excellent cold press formability,
It is complete. The features of the present invention are as follows:
In a method for producing metal powder in which metal powder is obtained by colliding a spray medium with molten metal, the spray medium has a C atom number of 4.
Hereinafter, an organic solvent having a C atom number of 1 or less and a boiling point of 150° C. or less is used.

It is preferable to use a gillfish. C,H
, O. If an organic solvent containing elements other than O is used as a spraying medium, impurity elements may be included in the metal powder, which may adversely affect the performance of the final product. The reason why the number of C atoms in the spray medium is set to 4 or less is because if the number of C atoms exceeds 4, C from decomposition of the spray medium will remain in the metal powder, which will have a negative impact on the performance of the final product. . The reason why the number of zero atoms in the spray medium is set to 1 or less is that if the number of zero atoms exceeds 1, the oxygen content in the metal powder will increase, which will also have a negative effect on the performance of the final product. In the present invention, the number of C atoms is limited for this reason, so
The spray medium may contain no zero atoms. The reason for setting the boiling point of the spray medium to 150°C or lower is that if a spraying medium with a boiling point exceeding 150°C is used, it will take time to volatilize and remove it in the separation process from the metal powder, increasing manufacturing costs. That's because there isn't. The boiling point of the spray medium used is 1
By heating the mixture of metal powder and spray medium together with its storage container by keeping the temperature below 50°C, or by reducing the pressure, the spray medium can be easily separated from the metal powder, and there is less impact on the powder price. .

[For production]

By using the above-mentioned spray medium, the present invention can
Although the cooling rate of the powder is slightly slower than the water atomization method (a molten metal atomization method that uses water as an atomization medium), it is better than the atomization medium conventionally used in the gas atomization method (a molten metal atomization method that uses gas as an atomization medium). A much faster cooling rate is obtained, with the result that the molten metal cools down to K1 for a very short time.
1. Failure/Coagulation [Effects of the Invention] As explained above, the present invention uses an organic solvent having one or less O atoms as a spraying medium, so oxidation of the molten metal is suppressed during spraying, and the oxidation of the molten metal is suppressed during the powder manufacturing process. The reduction step can be omitted or greatly reduced, and as a result, the powder manufacturing cost can be reduced. Nine, the boiling point of the present invention is 1.
Since an organic solvent at 50°C or lower was used as the atomizing medium, the molten metal was atomized and solidified in a very short time, and as a result, it was possible to obtain irregularly shaped powder similar to the powder produced by water atomization, with almost the same particle size distribution. There is an effect that it can be done.

In addition, since the present invention conveniently uses a low-molecular liquid organic solvent as a spraying medium, the equipment for conventional water atomization methods can be reused with almost no changes, and metal powder can therefore be produced at low cost. effective. In addition, since the present invention uses an organic solvent with a boiling point of 150°C or less as a spray medium, heating can be done by simply reducing the pressure. ljg medium can be volatilized, therefore, the metal powder and the spray medium can be
Compared to the oil atomization method, it has the advantage of being able to be separated extremely easily.

Furthermore, conventionally, in a molten metal containing a large amount of A4, St, etc., AA*81 etc. were easily oxidized, and therefore it was not possible to form a rapidly solidified powder using the water atomization method. Since the oxidation of the alloy is suppressed, its production becomes possible, and therefore, the solid solubility limit is expanded and a special alloy powder that is uniform and free from segregation can be produced.

〔Example〕

Next, examples of the present invention will be described. FIG. 1 is an explanatory diagram of an apparatus for carrying out the present invention, and FIG. 2 is an enlarged explanatory diagram of its main parts. In these figures, (1) is an electric furnace for melting material metal to obtain molten metal, and (2) is an electric furnace for storing a part of the molten metal in electric furnace (1). The tundish (3) is a nozzle installed at the bottom of the tundish (2) to allow a trickle of molten metal (4) to flow down, and the nozzle (5) is placed at the bottom of the tundish (2) to keep the molten metal in the tundish (2) warm. A heating device (6) provided surrounding the tundish (2) sprays a spray medium (7) onto a trickle of molten metal (4) flowing down from a nozzle (3) to atomize and solidify the molten metal (4). Therefore, Tanditshu (2
(8) is a pressurizing pump that supplies high-pressure spray medium (7) to the injection nozzle (6); 9 is a storage tank provided below the injection nozzle (6) to store the obtained powder together with the spray medium (7).
) is an overflow provided on the upper side of the Here, an induction heating furnace is used as the electric furnace (1), and an external heating type resistance furnace is used to heat the tundish (2) for holding the molten metal. In order to minimize fluctuations in the height of the molten metal surface, the radial cross-sectional area of the tandyshi-3-(2) is made sufficiently large compared to the diameter of the molten metal nozzle (3). The spray nozzle (6) for spraying the spray medium (7) has a known annular slit.

In the above-mentioned apparatus, material metal is melted in an electric furnace (1) to become a molten metal, and the molten metal is supplied to a tundish (21).

The molten metal supplied to Tanditshu (2) is passed through the molten metal nozzle (
3) flows down as a trickle of molten metal (4). Spray medium (
7) is supplied to the injection nozzle (6) by the pressurizing pump (8), and from the annular slit becomes a film-like flow with an inverted conical surface, and a thin stream of molten metal (4) flows down from the molten metal nozzle (3).
collide with The molten metal (4) is atomized by the spray medium (7), cooled and solidified before becoming spherical due to surface tension, becoming metal powder, which is temporarily held together with the spray medium in the storage cage (9). The metal powder settles to the bottom of the storage tank (9), and excess spray medium is discharged from the overflow αQ and led to a processing device (not shown) for use as a spray medium again.

The metal powder that has sunk to the bottom of the storage tank (9) is collected together with the spray medium, deliquified by a deliquifier (not shown), and dried under an inert gas atmosphere.

Using various spray media, under the conditions of a molten metal temperature of 1610 ° C. and a spray media discharge pressure of 80 Kz/- (in the case of ether alcohol, the average discharge flow rate was approximately IQ Om/m).
A molten metal of the same composition is sprayed and heated and dried in a computer atmosphere to obtain pure iron powder.9. Among these, the results of chemical analysis of iron powder sprayed with water are shown in Part 1. In addition, the results of analyzing C1O in pure iron powder are shown in the second thorn for each type of spray medium. Further, the relationship between the number of C atoms in the spray medium molecule and the Ct in the powder is shown in FIG. 3, and the relationship between the number of C atoms in the spray medium molecule and the amount of 00 in the powder is shown in FIG. 4, respectively.

The metal powder obtained by the present invention has a significantly lower amount of oxygen than the conventional method using water as the atomizing medium using the same nozzle and the same pressure. . However, when the number of C atoms in the spray medium is 5 or more, the amount of attached C increases and the amount of C increases significantly. Therefore, if the material is heated and softened as it is, there is a risk of carburization. On the other hand, the number of C atoms in the spray medium is 2
When the amount exceeds that amount, the amount of oxygen in the metal powder increases. Therefore, the result takes into account the allowable range of C amount and 0 amount in metal powder.

It was considered that an organic solvent having 4 or less C atoms and 1 or less Oi atoms in one molecule should be selected as the spray medium.

Next, the results of investigating the particle size distribution of the powder were shown to the 6th group, and there was no difference in the particle size distribution compared to the powder obtained by the water atomization method. In addition, the shapes of the powders were all manufactured by the water atomization method and were similar to the following powders.

As another example in Table 3, powder of low carbon stainless steel 304L was manufactured. The conditions other than the molten metal temperature ft 1600° C., the spray medium methyl alcohol, and the ethyl alcohol doshita were the same as in the above-mentioned example. As shown in Section 4, the amount of oxygen in the powder was overwhelmingly lower than that in the water atomization method. Furthermore, both the particle size and initial distribution were almost the same as those of the water atomization method.

Fourth Cost Layer Unit (a) As yet another example, aluminum powder was produced. The same manufacturing equipment as above was used, and the spraying conditions were as follows: molten metal temperature at 960°C, spraying medium: ethyl alcohol, spraying medium discharge pressure: 55 m/s, 1 (spraying medium flow rate:
The speed was set at 83 m/s. As shown in Table 5, the amount of oxygen in the obtained aluminum powder was overwhelmingly lower than that in the water atomization method. Furthermore, the particle size and particle size distribution were almost the same as those of the water atomization method.

Lesson 5 jar unit)

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an apparatus for implementing the present invention, Fig. 2 is an enlarged explanatory diagram of the main part of Fig. 1, and Fig. 3 is an explanatory diagram of the main part of Fig. 1.
FIG. 4 is a graph showing the relationship between the number of atoms and the amount of C in the powder, and FIG. 4 is a graph showing the relationship between the number of O atoms in the spray medium molecule and the amount of O in the powder. In the figure, (4) is the molten metal, (6) is the injection nozzle, and (7) is the injection nozzle.
) is a propellant. Agent Patent Attorney Sanro Kimura 8th grade

Claims (1)

[Claims] In a method for producing metal powder in which metal powder is obtained by colliding a spray medium with molten metal, the spray medium has a C atom number of 4.
Hereinafter, a method for producing metal powder, characterized in that an organic solvent having an O atom number of 1 or less and a boiling point of 150° C. or less is used.