JPH06322404A - Composition for metal powder injection molding - Google Patents

Abstract

PURPOSE:To provide a composition for metal powder indection molding capable of improving the flowability at indection molding while form preservability at degreasing and after deyreasing. being the advantage of water atomized powder, is maintained in metal indection molding method. CONSTITUTION:It is characterized that the prescribed quantity of a gas atmomized powder 7 is added to a water atomized powder 1, as to the composition 12 for metal powder injection molding in metal powder injection molding method, in which a molding 13 in the prescribed shape is produced by injection molding of metal powder, a raw material powder 10 consisting of the water atomized powder 1 and gas atomized powder 7 is used for the metal powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for metal powder injection molding, and particularly in the metal powder injection molding method, metal powder injection having good fluidity and less deformation or cracking of the product. The present invention relates to a molding composition.

[0002]

2. Description of the Related Art Conventionally, in a metal powder injection molding method, carbonyl iron powder which is pure iron (average particle size 1 to 5 μm)
Development has been advanced using fine spherical powders such as.

However, when a material such as stainless steel which requires functions such as corrosion resistance is required, it is indispensable to use an alloy powder capable of obtaining a uniform structure.

Therefore, alloy powders produced by the water atomizing method or the gas atomizing method have come to be used.

The powder (water atomized powder 1) produced by the water atomizing method is produced by the spraying device 2 shown in FIG. This spraying device 2 has a molten metal container 3 and a spraying nozzle 4, and atomizes a molten metal 5 in the molten metal container 3 with a high-pressure water stream 6 to produce a water atomized powder 1.

The water atomized powder 1 has been generally used in the metal powder injection molding method because it is easy to obtain a fine powder having an average particle diameter of 5 to several tens of μm and a relatively small diameter.

However, since the powder shape of the water atomized powder 1 is irregular and complicated, the molded article molded using the water atomized powder 1 has a particular problem in shape retention during and after degreasing. However, there is a problem that the fluidity during injection molding before degreasing is poor.

Therefore, when the water atomized powder 1 is used, the fluidity is poor, so that injection molding must be carried out at high pressure and high speed, which is caused by residual stress and non-uniformity of density. As a result, problems such as deformation of the product and occurrence of cracks occurred in some cases.

On the other hand, the powder by the gas atomizing method (gas atomized powder 7) is manufactured by the spraying device 8 shown in FIG. In this spraying device 8, the molten metal 5 is atomized by the high pressure gas flow 9 to produce the gas atomized powder 7.

The gas atomized powder 10 has an average particle size of 10 to several hundreds of μm, but since it has a spherical shape, it has good fluidity during injection molding, but retains it during and after degreasing. It is inferior in shape, and causes problems such as deformation due to gravity during degreasing and damage after degreasing.

As described above, the metal injection molded product is manufactured through many steps, but the key to the quality of the final product is the powder property of the material, and improvement in this respect has been demanded.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in the metal injection molding method, the shape retention property during and after degreasing, which is an advantage of water atomized powder, is maintained. It is an object of the present invention to provide a composition for metal powder injection molding which can improve the fluidity during injection molding.

[0013]

That is, the present invention focuses on adding a predetermined amount of gas atomized powder to water atomized powder, and produces a molded product having a predetermined shape by injection molding a metal powder. A composition for metal powder injection molding in a metal powder injection molding method, wherein, as the metal powder, a raw material powder obtained by mixing a water atomized powder and a gas atomized powder is used. is there.

The amount of the gas atomized powder mixed may be in the range of 10 to 60% by weight.

Further, a water atomized powder having an average particle diameter of 1 to 30 μm and a gas atomized powder having an average particle diameter of 10 to 70 μm can be used.

Further, a material for injection molding can be obtained by heating and kneading with a binder.

The mixing ratio of the gas atomized powder is 1
If it is less than 0% by weight, the fluidity is not sufficiently improved, and if it is more than 60% by weight, the molded body is deformed and damaged during and after degreasing as in the case of the gas atomized powder alone.

The metal powder material in the present invention is not limited to stainless steel, and any alloy material can be adopted.

[0019]

In the composition for metal powder injection molding according to the present invention, since the gas atomized powder having a spherical shape is mixed, the injection pressure and the injection speed at the time of injection molding can be set low, and residual stress and filling density can be reduced. It is possible to obtain a molded product with less unevenness, and because of the presence of water atomized powder with an irregular shape, the shape retention during and after degreasing is good and the yield of the final product is improved. Accuracy is also improved.

[0020]

EXAMPLE Next, a composition for metal powder injection molding according to an example of the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, as the material metal powder,
The average particle size is 6μ due to the alloy powder of SUS304L composition.
A mixture (metal injection molding composition 10) was prepared in which the water atomized powder 1 of m was 70% by weight and the gas atomized powder 7 having an average particle size of about 15 μm was 30% by weight.

A metal injection molding composition 12 was prepared by using this mixture 10 as a raw material powder and heating and kneading the mixture with 55% by volume and 45% by volume of the binder 11 together with the binder 11.

Using the obtained metal injection molding composition 12, a spiral flow test, which is a fluidity test, is performed, and a molding (green body) 13 having a shape as shown in the drawing is formed by injection molding. And maximum heating temperature 3
Degreasing was performed by gradual heating and slow cooling at 00 ° C. for 2 days, and a sintering test was performed at a heating temperature of 1300 ° C. for 2 hours in vacuum.

As a comparative example, the same test was conducted on a powder material using only the water atomized powder 1 and not adding the gas atomized powder 7.

The results of such a test are shown in the chart of FIG.
As is clear from the chart, the fluidity (spiral flow length) of this example is about 1.5 times greater than that of the comparative example, and the occurrence of cracks and dimensional defects are significantly reduced. I understand.

[0026]

As described above, according to the present invention, a predetermined amount of gas atomized powder is mixed with water atomized powder, so that the flowability during injection molding as well as the shape retention after molding can be improved. Can be maintained.

[0027]

[Brief description of drawings]

FIG. 1 is a metal injection molding composition 1 according to an embodiment of the present invention.
It is explanatory drawing of 0, 12 and the molded object 13 manufactured using this.

FIG. 2 is a table of test results of Examples and Comparative Examples.

FIG. 3 is a schematic explanatory view of a spraying device 2 for producing a conventional water atomized powder 1.

FIG. 4 is a schematic explanatory view of a spraying device 8 for manufacturing a conventional gas atomized powder 7.

[Explanation of symbols]

 1 Water Atomized Powder 2 Spraying Device 3 Molten Container 4 Spraying Nozzle 5 Molten Metal 6 High Pressure Water Flow 7 Gas Atomized Powder 8 Spraying Device 9 High Pressure Gas Flow 10 Metal Injection Molding Composition (Mixture) 11 Binder 12 Metal Injection Molding Composition 13 Molded body (green body)

Claims (4)

[Claims] 1. A composition for metal powder injection molding in a metal powder injection molding method for producing a molded product having a predetermined shape by injection molding a metal powder, wherein the metal powder is water atomized powder and gas atomized powder. A composition for metal powder injection molding, characterized in that a raw material powder obtained by mixing and is used. 2. The mixing amount of the gas atomized powder is
The composition for metal powder injection molding according to claim 1, wherein the composition is in the range of 10 to 60% by weight. 3. The composition for metal powder injection molding according to claim 1, wherein a water atomized powder having an average particle size of 1 to 30 μm and a gas atomized powder having an average particle size of 10 to 70 μm are used. 4. The composition for metal powder injection molding according to claim 1, wherein the composition is heated and kneaded together with a binder.