JPH01319607A - Production of metal or alloy powder - Google Patents

Abstract

PURPOSE:To produce the metal powder adequate for injection molding by charging the metal of a half-melted state into the melt of an org. high polymer and solidifying the same at the time of forming the metal powder by bringing gas into collision against the molten metal flowing out of a nozzle. CONSTITUTION:The melt 2 of the metal (or alloy) is caused to flow out of the injection nozzle 1 and the high-pressure gaseous Ar is ejected from an annular nozzle 3 to the outflowing melt 2 to atomize the molten metal 2. The atomized melt 2 is charged in the half-melted state prior to solidification into a bath chamber 4 packed with a melt mixture composed of paraffin wax and polymer kept at the temp. above the m.p. by a heater 7 by which the melt is rapidly solidified to form the metal powder. The metal powder is then recovered from a recovering vessel 5 and the mixture composed of the paraffin wax and polymer sticking uniformly on the surface of the metal powder is solidified to form the composite powder. The composite powder having the excellent characteristics as the raw material powder for injection molding is produced in this way at a low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves degreasing and sintering a molded body obtained by injection molding a material obtained by mixing and kneading metal powder or alloy powder and an organic binder. The present invention relates to a method for producing metal or alloy powder used in a powder metallurgy process that takes into account so-called near-screw shapes to obtain sintered bodies of arbitrary shapes.

[Prior Art] Conventionally, methods for forming metal articles of arbitrary shapes include: 1. weaving method; 2. weaving method; Casting method, 3. Powder metallurgy method, etc.Each of them has many advantages/AC, and in recent years, powder metallurgy method has become increasingly important especially when the target metal is drill-formable metal or high melting point metal. There is. By the way, in the conventional powder metallurgy method, a molded body is produced by applying a constant pressure after metal powder is loaded into a predetermined mold, and a metal article is obtained through a subsequent sintering process. However, in this method, for simple shapes such as columnar and cylindrical shapes, it is easy to manufacture and contributes greatly to the reduction of cost l~.
It is necessary to perform secondary processing such as cutting and grinding after forming or sintering the platform, which has a dimensionally more complicated shape, and this is also a cause of an increase in cost.

On the other hand, near-terminals that do not require secondary processing compared to before
Powder metallurgy methods that take shape into consideration are, for example, CI
Although it has been put into practical use by technologies such as P, 1-I I P and slip cast ink method, the process is complicated, it is not suitable for mass production, and the cost is high. Currently, it is mainly applied to high-value-added parts made of processable metals, and has not spread to lower-level general parts.

However, in recent years, by injection molding a material obtained by mixing and kneading metal powder and organic binder into a molded body of a predetermined shape, and then subjecting the molded body to debinder treatment (degreasing) and sintering, complex shapes can be easily formed. It has become possible to manufacture metal articles with high precision and in large quantities. The important technical requirements in this sintered body manufacturing process include: ■ Production of highly accurate molded bodies ■ Complete degreasing of the binder that contains a large amount.
In order to achieve this, the powder properties required for metal powder are:
There is a wide range of options as shown below.

■ Considering moldability, create a fluid spherical powder.

■ The powder should have a smooth surface so that the binder can be easily degreased.

■ Considering sinterability, use fine powder with an average particle size of 10 μm or less.

Conventionally, the V-formation method for powder to satisfy these powder #I properties has been achieved by the so-called atomization method, in which high-pressure fluid collides with molten metal (molten metal) flowing out of a nozzle, and the resulting energy is used to pulverize it. It has become common to use powdered powder. Note that this atomization method is roughly divided into water atomization method and gas atomization method depending on the spray medium, and each has various advantages, but according to the water atomization method, the average particle size is It is easy to produce fine powder of 10 μm or less.

Further, according to the gas atomization method, a spherical powder with a smooth surface can be obtained.

However, the water and gas atomization method has a number of problems as described below, which are one of the reasons why the injection molding process is not recognized by society.

■ Water atomization method: The powder has an irregular shape and has poor fluidity during injection molding.As a countermeasure, it is necessary to increase the amount of binder, making degreasing difficult.

Furthermore, since the medium is water, the oxygen concentration in the powder is high, resulting in poor sinterability.

■ Gas atomization method: Since the average particle size of the powder is large and it is a true sphere, the entanglement of the powders with each other is small, making it easy to blister and crack during the degreasing process, making it difficult to improve the sintered density.

As a measure to improve these atomization methods, the spray medium may be changed to oil, fat,
A method using mineral oil, pure organic compounds, etc. has been proposed, which has the effect of suppressing oxidation and makes it possible to make the particle shape intermediate between gas and water atomized powder, and also causes moderate entanglement of the powders. However, powders with good properties as injection molding powders have also been obtained.

[Problems to be Solved by the Invention] - Bow - However, in the method using the above-mentioned organic compound spray medium, carburization of powder resulting from adhesion of carbon derived from thermal decomposition of the spray medium, and alloy containing a large amount of active metal. To prevent oxidation from progressing due to the water content in the oil that is sprayed, and also to prevent such thermal decomposition and ignition of the oil.
The viscosity of the spray medium increases due to the need to lower the temperature of the oil in order to reduce the temperature of the oil, and its use has been limited due to problems such as 6, which requires increased capacity for IJJ & Kirikawa pumps.

In view of this, the technical problem of the present invention is to follow the concepts of various conventional atomization methods, add a new invention that improves the powder properties required for the injection molding process, and create an inexpensive and large-scale atomization method. The present invention aims to provide a method for producing metal or alloy powder that can produce composite powder.

The present inventors have completed the present invention as a result of intensive research to establish a method that takes advantage of the strengths of the conventional water atomization method, gas atomization method, and oil atomization method and compensates for the weaknesses. It is something.

= 6-1 Means for Solving the Problems According to the present invention, gas is caused to collide with the molten metal or alloy flowing out from a nozzle to form a substantially semi-molten metal or alloy powder and then cooled. There is obtained a method for producing a metal or alloy powder, characterized in that the metal or alloy in a semi-molten state is poured into a heated organic polymer melt and solidified.

Here, in the present invention, it is desirable that the organic polymer melt comprises at least one type of wax 7 polymer.

That is, the feature of the present invention is that the molten metal is atomized by the so-called gas atomization method, and the wax and polymer or This is where the molten polymer liquid is directly poured into the tank and rapidly solidified. As a result, the effect of suppressing oxidation is extremely large compared to the conventional water atomization method, and when the molten metal comes into direct contact with organic substances as in the oil atomization method, the contact occurs in a semi-molten state at a lower temperature. By doing so, the effect of preventing powder carbonization is also great.

On the other hand, when the powder is in a semi-molten state and collides with the molten liquid surface, the impact energy causes the truly spherical powder characteristic of gas atomization to be deformed or fragmented and solidified. Therefore, the shape thereof becomes a so-called T:f: shape powder, which is intermediate between the gas atomized powder and the water atomized powder, and is an ideal form for the above-mentioned injection molding powder. On the other hand, organic polymer melting? When the powder collected from the night body is cooled and dried in the atmosphere, the surface becomes a mixture of paraffin and polymer, which is the main component of the binder during injection molding, or a composite state in which the polymer is uniformly coated. , it can be used directly as a raw material powder for injection molding without going through the deoiling process that was conventionally done with the oil amalization method, and has a great effect on reducing powder manufacturing costs by 1. It doesn't bring.

Next, embodiments of the present invention will be described with reference to the drawings.

``Example'' 1 shows an example of a powder manufacturing apparatus configured to carry out the present invention. In this figure, Fe-5 flows out from the molten metal injection nozzle 1 provided in the melting crucible.
High-pressure Ar gas is ejected from an annular nozzle 3 to collide with a molten metal 2 made of ONi (1%) to atomize the molten metal 2. Furthermore, before solidifying the atomized metal, a mixture of paraffin wax and polymer in a semi-molten state is kept in a bathtub filled with a mixed molten liquid maintained by a heating device 7 at a temperature above the melting point of this mixture. 4 and rapidly solidified into metal powder.

Next, the metal powder is collected from the collection container 5 and the filter 6, and the mixture of paraffin wax and polymer uniformly adhered to the surface of the metal powder is solidified at room temperature to form a composite powder consisting of the polymer, paraffin wax, and metal powder.

As comparison materials, water aluminized powder, gas aluminized powder, and oil aluminized powder having the same composition were used.

Table 1 shows the difference between metal powders produced by the present invention and the water atomization method, gas atomization method, and oil atomization method after removing the organic components attached to the surface of the metal powders. Measure agricultural yield using an oxygen and carbon analyzer. As a result, it was found that the present invention is extremely excellent as a method for preventing contamination with impurities, and in particular, the effect of the present invention in preventing carbon burning was significant.

Next, the powder according to the present invention to which paraffin wax and polymer are added as appropriate, the powder and water atomized, gas atomized, oil 7'1-mice powder, paraffin wax and a binder mainly composed of polymer are mixed and kneaded. These were then injection molded, degreased, and sintered. Table 2 shows the results of examining the injection moldability, degreasing properties, and sinterability of these samples. As shown in Table 2, when the powder produced by the manufacturing method of the present invention is used, the sintered body has extremely good degreasing properties, has a high sintered density, is less deformed, and has fewer impurities than conventional powders. 7+1' cannot be recognized as being obtained.

1, L″′F′ F ax b, −, ] 0 − ~ 12 − [Effects of the invention] As described above, the powder produced by the method for producing metal or alloy powder of the present invention is superior to conventional production methods. Compared to the powder produced by the method, it has extremely less contamination and has a spherical shape, so it not only has extremely excellent properties as a raw material powder for injection molding, but also significantly reduces the powder manufacturing cost. This makes it possible and has great practical value.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a powder manufacturing apparatus for carrying out the present invention. In the figure, 1... Molten metal injection nozzle, 2... Molten metal, 3
... ring nozzle, 4 ... bathtub, 5 ... collection container,
6... Filter, 7... Heating device.

Claims (1)

[Scope of Claims] 1. A method for producing metal powder in which gas collides with a molten metal or alloy flowing out from a nozzle to form substantially semi-molten metal or alloy powder and cooling the semi-molten metal or alloy powder, comprising: 1. A method for producing a metal or alloy powder, which comprises introducing the metal or alloy into a heated organic polymer melt and solidifying the metal or alloy.