UA64966A - Method for production of the powder - Google Patents

Abstract

Method for producing the copper powder that consists in that the scrap of copper conductors is burnt out in the hydrogen-containing medium, the carbonized isolation is eliminated by air separation, crushed in the ball mill into the fibres and reduced to powder. The scrap is preliminarily burnt out in the oxygen-containing medium at a temperature of 500-800 DEGREE C, and then in the hydrogen-containing medium at a temperature not below 800-850 DEGREE C it is maintained not less than 90 minutes, and then crushed and reduced to the powder-like condition.

Description

The invention relates to powder metallurgy, namely, to the production of copper powder and can be used in the processing of copper scrap.

There is a known method of obtaining copper powder by electrolysis, thanks to which the powder is obtained from aqueous solutions of copper sulfate under the action of a constant electric current. The process consists of smelting copper anodes from primary or secondary raw materials, electrolytic dissociation, as a result of which copper powder is deposited on the cathodes. Cathodes are periodically pulled out, and the powder is cleaned with scrapers. Then the powder is washed with hot water to remove electrolyte residues, washed with a solution of household soap to protect against corrosion and dried, after which it is crushed in mills and dispersed into fractions. The process is long, time-consuming, energy-intensive and multi-operational.

A method of obtaining copper powder from scrap copper current conductors is also known (see declaratory patent

of Ukraine, Me47841A, MPK7 B22 G9/02, NOT B15/00, publ. Bul. Mo7 2002|, which consists in the fact that scrap copper current conductors are annealed in a hydrogen-containing medium ЗОхв. at a temperature of 700-750"C, as a result of which the copper becomes brittle, the oxides are reduced to pure copper, and the insulation decomposes and easily separates from the surface of the conductors. The conductors are chopped into fibers from 1 to 20 mm long, the remains of the insulation are removed by air separation, and the resulting pure copper ground into powder.This method is chosen as a prototype.

The disadvantage of the known method is that during firing in a hydrogen-containing environment, part of the copper embrittles to a lesser degree than the main mass. The volume of this part in different batches of scrap is from 0 to 2090. Such copper, when processed in a ball or knife crusher, breaks into fibers with a length of 1 to 20 mm, but does not lend itself well to further crushing into powder. The grinding time increases, and some of the fibers are beaten into shapeless lumps and are not crushed at all. The reason for the higher plasticity of the copper part is as follows.

The brittle nature of copper after annealing in a hydrogen-containing environment is the result of the development of the so-called "hydrogen disease". It consists in the fact that hydrogen diffuses into the copper and interacts with the oxygen contained in it, while water vapor is formed, which creates pressure inside the metal, which leads to the formation of microcracks. Microcracks disrupt the integrity of the metal, are stress concentrators, and such copper is destroyed under the action of an external force. However, "hydrogen disease" is detected when the content of copper is more than 0.0595 oxygen and increases with increasing its concentration. The scrap received for processing contains various grades of copper, both with high and low oxygen content, which after annealing in a hydrogen-rich environment, has a higher plasticity.

The invention is based on the task of improving the method of obtaining copper powder from scrap current conductors by preliminary firing the scrap in an oxygen-containing environment at a temperature of 500-800C, as a result of which the insulation burns, the surface of the copper conductors is cleaned and actively interacts with oxygen, which diffuses deep into the metal and oxidizes him. During subsequent firing in a hydrogen-containing environment, copper oxides are restored, and in oxygen-saturated copper, "hydrogen disease" develops, which is facilitated by the high temperature of the process and long exposure. In addition, an increase in the temperature and duration of annealing leads to the growth of copper grains, which also increases its susceptibility to brittle failure.

The specified task is achieved by the fact that in the method of obtaining copper powder, which consists in the fact that scrap copper current conductors are annealed in a hydrogen-containing environment at a temperature of 700-750 "C, storage, charred insulation is removed by air separation, crushed in a ball mill into fibers and ground into powder, according to the invention, scrap copper current conductors are first fired in an oxygen-free environment at a temperature of 500-800"C, followed by annealing in a hydrogen-containing environment at a temperature not lower than 800-850"C and a duration of at least 90 minutes, and then crushed and ground in powder.

The method is implemented as follows. Scrap copper current conductors are subjected to visual inspection, and solder and soldered areas are removed, loaded into a container that is sealed with a sand seal. The container is placed in a furnace heated to a temperature of 600-800"C and blown with an oxygen-containing gas, for example, air for 30-60 minutes. After that, the container is blown with an inert gas, for example, nitrogen, and then a hydrogen-containing gas is supplied. After holding at a temperature of 800-850" 60- 90 min. the container is removed from the oven and cooled in the air to a temperature of 30-40"C, after which the gas supply is turned off and the container is opened.

The obtained copper is easily ground into powder.

Example:

Scrap copper current conductors, including those from failed electric motors, transformers, devices, clippings of telephone wires and cables, were burned according to the following regime:

Loading of the container with scrap into the furnace at a temperature of 600"C, heating to 800"C by blowing with air for 20 minutes, blowing with nitrogen - 15 minutes, blowing with hydrogen-containing generator gas for 9 hours. at a temperature of 800-850"C, cooling the container in air to 40"C. After wringing out, the current conductors were crushed by a knife crusher into fibers 3-17 mm long, blown with air to remove the remains of burnt insulation and ground into powder on a hammer mill. Tables 1 and 2 show the properties of copper powder obtained from scrap, as well as electrolytic powders according to DST 4960-75.

These tables show that the powder obtained from scrap copper has no worse properties compared to the properties of electrolytic powders. The powder was used for the production of anti-friction powder parts.

Table 1

bulk

Copper content, y y i o i

And g/cm

Received scrap )|99.7-99.9| 23-27 | 651 | | 324 | | 18 | 07 (Electrolytic PMO-1 | 99.5 | 1.25-1.9 | | 00.5 | 95.5 | 90 | | 65-80

PMS - In DST 4960-75 2,427 | UK | 575 | 3445 | -:ХХ | 25-35 | 10-25

Table 2

Pycnometric density Density

Brand of powder powder, g/cm Shape of shaking particles, g/cm3 part - fragmentary 8.74-8.77 (Dendritic cells//-/-:/ (| (4

Claims (1)

The method of obtaining copper powder, which consists in the fact that scrap copper current conductors are fired in a hydrogen-containing environment, charred insulation is removed by air separation, crushed in a ball mill into fibers and ground into a powder, which differs in that the scrap is pre-fired in an oxygen-containing environment at a temperature of 500 -800"C, and then in a hydrogen-containing environment at a temperature not lower than 800-850"C, kept for at least 90 minutes, and then crushed and ground to a powdery state.