JPH0686602B2 - Method for producing composite powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a method for producing a composite powder in which powders of the same kind or two or more kinds are mixed for use mainly in powder metallurgy.

[Prior art and its problems] In the powder metallurgy method, powders having the same component but different particle sizes may be mixed, or powders of different components may be mixed, but in both cases, the mixing should be performed uniformly. It goes without saying that it must be done.

By the way, in the mixed powder thus mixed, for example, fine powder may scatter during handling such as when taking out from a mixer or when filling in a molding die, and the component ratio may change, and the mixed powder may have a difference in specific gravity. There is a risk of separation and segregation due to differences in particle size. As a result, the desired powder characteristics cannot be obtained, and the mechanical or chemical characteristics of the sintered product are impaired. That is, even if they are uniformly mixed, there is a possibility that the above-mentioned scattering or segregation may occur during the handling.
Especially when the difference in particle size between the two powders to be mixed is more than double, such segregation is more likely to occur, and it has been demanded to find a solution to the problem immediately.

[Means for Solving Problems] The present invention aims to provide a method for producing a composite powder that solves the above problems. That is, the feature of the method for producing the composite powder according to the present invention is that the mother powder and the sizing agent are mixed and the sizing agent is coated on the surface of the mother powder. Fine powder of ½ or less is added to adhere the fine powder to the surface of the mother powder, and then the pasting agent is mixed and stirred again to combine mother powders having relatively small particle diameters. This is to make the particle diameter uniform.

[Function] The fine powder adheres to the mother powder through the sizing agent, and when the sizing agent is mixed again, the mother powders having a small particle size are combined and the particle size becomes uniform as a whole, preventing scattering and eliminating segregation. And the filling property during molding is improved.

[Examples] Next, examples of the present invention will be described.

An iron-based powder having an average particle size of about 100 μm is used as a mother powder, and manganese sulfide having a maximum particle size of 44 μm is used as a fine powder. A phenol resin is used as a sizing agent. As shown in FIG. 1, 100 g of the mother powder is placed in a mixing container 1 and 0.5 g of a phenolic resin as a sizing agent is added thereto, and both are stirred and mixed for about 10 minutes, and the sizing agent is applied to the surface of the mother powder. To be evenly coated. Next, 0.6 g of the fine powder is added to this and mixed by stirring to adhere the fine powder to the surface of the mother powder as shown in FIG. By adopting such a mixing order, the fine powder can be more reliably attached to the mother powder. That is, when the mother powder, the fine powder and the sizing agent are mixed at the same time, the fine powders tend to adhere to each other. Can be attached. Next, 0.5 g of a sizing agent is again added to this, and the mixture is stirred. A known stirrer may be used for this stirring, or the stirring may be performed manually, but by adjusting the stirring strength, the resulting particle size can be made substantially uniform. That is, by adjusting the stirring strength so that the particle size does not exceed a certain size, as shown in FIG. 3, the large and small mother powders having relatively small particle sizes adhere to each other. The particle size can be made uniform. In addition, it may be necessary to adjust the dilution concentration of the sizing agent in order to uniformly attach the sizing agent to the powder surface, but the dilution rate is not constant because it depends on the properties of each powder.

In the above example, the iron-based powder was used as the mother powder, and the fine powder of manganese sulfide was adhered to the mother powder to improve the free-cutting property of the sintered alloy, but there are various combinations thereof, for example, To improve the wear resistance of the sintered alloy by adhering a fine powder of tungsten carbide, to improve the sinterability by adhering the same type of fine powder to the iron-based mother powder, or to use a ceramic as a mother powder There are many application examples such as adhering fine powders of various ceramics to this to improve its characteristics. When a mixture of two or more powders of different components is used as the mother powder, the characteristics are further diversified.

As the sizing agent, in addition to the above-mentioned phenolic resin, various chemical products such as polyethylene glycol, polypropylene glycol, glycerin, polyvinyl alcohol, etc., which have adhesive properties and show little change over time, can be used.

[Effects of the Invention] According to the method for producing a composite powder according to the present invention as described in the above examples, the fine powder can be reliably attached to the mother powder, and the mother powders are bonded to each other to give a particle size. As a result, the fine powder can be prevented from scattering, and segregation due to the difference in particle diameter of the mother powder can be prevented. For this reason, the filling into the mold becomes more uniform, and there is a remarkable effect in improving the dimensional accuracy and quality of the sintered product.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a schematic view showing a process, and FIGS. 2 and 3 are enlarged vertical sectional views of mixed particles.

Claims (2)

[Claims] 1. A base powder and a sizing agent are mixed, and a sizing agent is coated on the surface of the base powder, and then fine powder having an average particle diameter of ½ or less of that of the base powder is added thereto. A powder characterized in that a fine powder is attached to the surface of the mother powder, and then a sizing agent is mixed and stirred again to combine mother powders having relatively small particle diameters to make the particle diameter uniform. Method for producing composite powder for metallurgy. 2. The method for producing a composite powder for powder metallurgy according to claim 1, wherein the mother powder is a mixture of two or more kinds of powders of different components.