SU950500A1 - Method of heat treating of carbonyl containing nickel powders - Google Patents

Description

one

The invention relates to powder metallurgy, in particular, to the integration of fine-grained powder materials by heat treatment and the formation of metal powders with predetermined properties and structure.

There is a method of enlarging fine powder materials by secondary processing, which consists in the fact that the initial powder with a particle size of less than 10 µm is mixed in a mixer with water and sprayed at a high speed. The wetted powder is sintered for several minutes in an inert and reducing atmosphere at 680810 ° C.

The disadvantage of this method is the low quality of the powder, expressed in high bulk density (l, 7 + 2.7 g / cm), which indicates the absence of internal porosity

particles with a size of 20-150 microns, and the complexity of the process.

The closest to the invention in technical essence and the achieved result is the method 5 of heat treatment of metallic powder materials in a fluidized bed with heating, which consists in passing a gas carrier through a layer of powder when exposed to ultrasonic vibrations 2j.

The disadvantages of this method are high bulk density, small porosity, and a wide range of particle sizes of metallic particles, powder.

The purpose of the invention is to obtain porous coarse-grained powders in a narrow particle size range.

The goal is achieved by

20 that, according to the method of heat treatment of carbonyl nickel powders in a vibro-boiling layer, the treatment is carried out at + 50-600 ° C and kept at this temperature for a minute in an inert or reducing gas stream containing 0.5-1.5 oxygen. At temperatures below 50 ° C, the resulting coarse-grained powders are obtained with low mechanical strength and are destroyed during subsequent classification and use. In this case, a significant amount of fine particles appear in the powder used to form the cathodes of vacuum devices, which degrade the technical characteristics of the product. At temperatures above, the process of sintering fine particles of carbonyl nickel powder in a vibrocalling layer is sharply intensified and large, slightly porous conglomerates are formed. When the processing time of fine powders in a vibro-kip layer is less than 5 minutes, no noticeable coarsening of the powder particles takes place and the maximum of the particle size distribution curve (according to the results of sedimentation analysis) is in the DI range of 20–25 µm, which is much less (by size) industry. In addition, the powders formed in this process are characterized by insufficient mechanical strength and are destroyed by further classification and use. With a treatment time of more than 20 minutes, the bulk density of the powder increases dramatically and its porosity decreases. When the oxygen content in the flow gas is below 0.5%, the powder is enriched in a fraction of 10-20 µm (according to the results of sedimentation analysis). When the oxygen content in the gas is above 1, there is an intensive formation of large loose conglomerates and their subsequent rounding. In the resulting po. In this case, particles larger than 1000 microns predominate. Varying the temperature of the powder, weighed by a vibro-kiping layer in the range of i 50-600 ° C, a processing time in the range of 5-20 min, and an oxygen content in the range of 0.51, 5, receive highly porous powders of a given size in a narrow particle size range, mechanically strong The proposed technological parameters in the aggregate of operations allow to obtain coarse-grained nickel powder in a narrow particle size range, for example, fractions kO-JI µm and 71-125 µm, and to form highly porous powder structures with a low bulk density. th density and developed specific surface. . -Example. Nickel carbo: nil tokis dispersed powder of PNK1L5 brand in the amount of 1000 g is weighed with a vibro-kip layer with the following vibration parameters: oscillation frequency 55 Hz, oscillation amplitude 3 mm, the oscillation trajectory is vertical, oriented in space. The powder is heated to 50 ° C and kept at this temperature in a state of vibro roll-out for 5 minutes in a stream of technical carbon monoxide containing 0.5 oxygen. The resulting powder is classified according to particle size. The classification results are shown in Table 1. Table 1

With the selected process modes, the largest yield is the fraction size 271 ++ 0 µm. The bulk density of the powder fraction is µm 1, g / cm, and the specific surface is 0, MVr.

EXAMPLE 2. The initial data are the same as in Example 1. The powder is heated to and maintained at this temperature in a state of vibroextending for 12 minutes and in a stream of technical oxide carbon containing% oxygen. Received Route Fractions

With the selected process conditions, the largest yield of the fraction of -125 + 71 microns is observed. The study of powder fraction -125 + zo +71 microns shows that the bulk density is 1.3 g / cm, and the specific surface is 0.58 ./

PRI and e R 3. Baseline data

table 2

the same as in example 1. The powder is heated to 600 ° C and maintained at this temperature in a state of vibro-diplining for 20 minutes in a stream of technical carbon monoxide containing 1.5% oxygen. The resulting powder is classified according to particle size. The results of the classification are given in table 3.

Table 3 5950.5006 powder classification classifications are given in size. The results table. 2

Claims (1)

Claim A method of heat treatment of carbonyl nickel powders in a vibro-boiling layer, characterized in that, in order to obtain porous coarse-grained powders in a narrow range of particle size, the treatment is carried out at 450 -0000 ° C and kept at this temperature for 520 minutes in an inert or reducing gas stream, containing 0.5-1.5% oxygen.