JPH0790306A - Production of hard powder - Google Patents

Abstract

PURPOSE:To produce a granulated powder excellen in fluidity and to obtain an alloy high in dimensional precision without defects such as cavities from the granulated powder by spray-driving slurry consisting of an organic solvent and a raw powder such as cermet, thereby forming granulated powder having prescribed fluidity. CONSTITUTION:The slurry is prepared by mixing an organic solvent such as alcohol, hexane with a raw powder such as a cemented carbide or cermet. The density, viscosity and concn, of the slurry are adjusted to 10 to 50% in terms of the ratio to the true density of the powder, 10 to 500cps and 50 to 80wt.%, respectively. The slurry is granulated by spray-drying it into a granulated powder having 0.24 to 0.04sec/cc fluidity measured by using the measuring funnel whose orifice diameter is 8mm and other shapes are specified by JIS Z-2502.

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 granulated powder of hard alloys such as cemented carbide and cermet used in powder metallurgy, particularly raw material powder and acetone for obtaining granulated powder having good fluidity, It relates to characteristics such as the density of a slurry in which a solvent such as hexane or alcohol is wet mixed.

[0002]

2. Description of the Related Art As a method for granulating hard powder such as cemented carbide or cermet used in powder metallurgy, generally, a raw hard alloy powder and a solvent are mixed with an attritor (wet mixer) to form a slurry. After that, the solvent is removed by drying and granulation is performed.

A spray-type drying method using a spray dryer is used as the above-mentioned dry granulation method. In this method, a wet-mixed slurry is pressure-fed by nitrogen gas and blown up in the chamber together with this nitrogen gas to about 200. Instantly dry and remove the solvent by contacting it with nitrogen gas at ℃
At the same time, the granulated powder is formed into a spherical shape by utilizing the fact that the surface area is minimized when the powder is dried from a liquid to a solid.

By the way, the granulation characteristics of a spray dryer are as follows: the inlet temperature when the slurry is sprayed into the chamber, the outlet temperature when the granulated powder exits the chamber, the air volume and temperature of cooling nitrogen, the spray pressure, and the feed of the slurry. It is controlled by variously changing the spray conditions such as the amount.

On the other hand, the slurry itself is adjusted under optimum conditions for wet mixing, but after mixing, it is stored in a slurry tank and sent to a spray dryer without adjustment as it is for dry granulation. Was being conducted.

[0006]

As in the prior art, merely controlling the conditions of the spray dryer does not stabilize the granulation characteristics depending on the raw material particle size of the work, mixing conditions, temperature, and the like. Of the granulation characteristics, for example, in order to control the fluidity of the finished powder, the bulk density, etc., it is of course necessary to control the above-mentioned spray conditions, that is, the spray pressure, the gas temperature, etc., but to adjust these. The required characteristics cannot be obtained by itself.

[0007]

Means for Solving the Problems The inventors of the present invention have solved the above problems in the production of hard alloy powders and studied a method for producing granulated powders of high quality and high fluidity. It has come.

In the present invention, the density and the like in a slurry state are measured, and the correlation between the density and the granulation characteristics is grasped in advance,
After wet-mixing and before drying and granulation, the characteristics of the granulated powder obtained by adjusting the density of the slurry, etc., such as particle size, fluidity and bulk density, are adjusted to obtain a granulated powder with excellent characteristics It is a manufacturing method.

[0009] The content of the slurry density, the true density ratio 10
% To 50%, a slurry viscosity of 10 to 500 CPS, and a slurry concentration of 50 to 80 wt% are granulated by spray drying.

The slurry density can be adjusted by adding a solvent after the wet mixing, and the slurry viscosity and the slurry concentration can be adjusted by the mixing time and the temperature during the wet mixing. After adjusting the density and the like of the slurry in this manner, dry granulation is performed with a spray dryer.

[0011]

In order to improve the fluidity of the granulated powder, it is necessary that the slurry is adjusted so as not to be dried into a spherical shape due to premature drying, or conversely, insufficient drying.

First, if the slurry density is more than 50%, the granulated powder does not become spherical, and if it is less than 10%, insufficient drying occurs. If the slurry viscosity is less than 10 CPS, drying will be insufficient, and if it exceeds 500 CPS, a spherical shape cannot be obtained. If the slurry concentration is lower than 50 wt%, the drying is insufficient, and if it is higher than 80 wt%, a spherical shape cannot be obtained.

Further, the slurry adjusted to the above range is
It is desirable to dry granulate with a spray nozzle type or rotary disk type spray dryer. It is difficult to obtain a spherical shape unless it is a spray nozzle method or a rotating disk method.
Also, the productivity is low and the number of defects after sintering is large.

[0014]

EXAMPLES Examples of the present invention will be shown below.

Cemented carbide powder composed of WC-10% Co was wet mixed for 6 hours with an attritor, and then dried and granulated with a nozzle type spray dryer. Table 1 shows the results of measuring the fluidity of the granulation obtained by changing the density of the slurry variously while keeping the dry granulation conditions constant. Sample No. Nos. 1 to 5 are examples of the present invention. 6 to 9 are comparative examples.

[0016]

[Table 1]

In Table 1, * (flow coefficient ratio of finished powder) is 0.9 to 1.0 and 0.10 sec / cc to 0.
It is equivalent to 24 seconds / cc.

[0018]

As described above, according to the present invention,
Since the fluidity of the granulated powder is improved to obtain the required granulation characteristics and the fluidity is stable, an alloy with high dimensional accuracy and an alloy without defects such as cavities can be manufactured.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Yoshihiro Minato 1-1-1 Kunyokita, Itami City, Hyogo Prefecture Sumitomo Electric Industries, Ltd. Itami Works

Claims (1)

[Claims] 1. A method for producing a hard powder, which comprises granulating a slurry comprising an organic solvent such as alcohol and hexane and a raw material powder for cemented carbide or cermet by spray drying,
The slurry density is 10 to 50% of the true density ratio of the powder, the slurry viscosity is 10 to 500 CPS, and the slurry concentration is 50 to 80.
Adjusted to wt%, the orifice diameter is 8.0 mm, and the other shape has a fluidity of 0.24 sec / cc to 0.04 sec / cc measured by a measuring funnel defined by JIS Z-2502.
2. A method for producing a hard powder, comprising: