Question

How to make copper powder lowiest cost

Answer 1

Powdered copper is a raw material that is used extensively in several industries, including the paint, electrical and bearing industries. In the paint field, color and "leafing" properties in paint vehicles are important; in' the electrical field, conductivity, and mechanical strength of molded products made from the powder, are the prime considerations; while in the bearing field, mechanical strength of the bearings produced is, of course, by far the most important property. In all cases, maximum resistance to atmospheric corrosion is likewise desirable.

Copper powder has been produced by the electrical method, which consists of electrolytic deposition, employing current densities (cathodic) between 50 and 150 amperes per square inch of cath.ode deposition surface, in the presence of suitable addition reagents (colloids), causing the copper to be plated out of solution in a loose, sponge-like mass. This sponge-like copper product is washed as free as possible of the electrolyte solution- and dried under non-oxidizing condi80 tions. The outstanding disadvantage of this type of copper powder is its high cost, and Its marked tendency to reoxidize when exposed to atmospheric conditions. The traces of electrolyte salts increase the rate of oxidation of the copper powder.

Another method of making copper powder has been to stamp it out of thin sheets of copper alloy metal, using a lubricant. The resultant powder, when examined under the microscope, is in the form of flat sheets, boated with lubricant. While excellent color and leafing are obtained in paint vehicles, the lubricant results in poor mechanical strength and electrical conductivity. Such flake powder is dense, has no mobil6 ity, does not weld, and is not suitable for bearings, and only in special cases for brushes. The excellent color is due to the alloying of small percentages of zinc or aluminum with copper.

It has also been proposed to obtain copper 0powder by reducing cupric or cuprous oxide powder, in a furnace, by the use of various reducing gases. The process may be carried out on the furnace hearth, or in trays. The mass that is removed from the furnace in the form of sintered lumps or cakes, is then broken up by milling. The resultant powder has an apparent gravity ranging from Just above 2.5 up to 3.0 and higher; under the microscope, it gives the appearance 0, of solid nodules. It has fair electrical conductivity, and may be used in bearings with fair results.

According to the present invention, a process is provided whereby a new form of copper powder is produced having superior properties as to electrical conductivity and mechanical strength, and is characterized by its low apparent gravity (below 2.5 grams per c. c.), its porous structure under a microscope, and its ability to withstand atmospheric conditions without blackening.

The invention comprises the conversion of copper wire or other pieces of copper metal such as punchings, shot, etc., into copper powder. The steps comprise first, oxidizing the copper to copper oxide, preferably cuprous oxide, breaking up this oxide, and then reducing the powdered oxide to copper. By this procedure, a pyrometallurgical method is provided for the production of copper powder from copper, which powder has the properties and advantages enumerated above.

My process comprises first, roasting of pieces of copper, of uniform cross-section, continuing the roasting to the point where the bulk of the copper has been oxidized, but there still remains a core of metal. An oxidizing atmosphere is maintained, and I have found that the presence of water vapor accelerates the reaction. The charge is pulled, and allowed to co6l in air; a thin film of cupric oxide forms on the surface only. The oxide is separated from the metal core by grinding in a rod or ball mill, and screening or air classifying. The resultant product is a cuprous oxide which contains 2% or less of cupric, and at least 98% of cuprous oxide. The temperature is preferably between 800* and 1780* F., as at these temperatures cuprous oxide is formed.

As an example, a charge of 2,000 pounds of 10 gauge'pure copper wire was placed in a hand rabbled furnace, and heated at 1650° F. in an oxidizing atmosphere in the presence of water vapor for 48 hours. The charge was rabbled from time to time. A 79.0% conversion to cuprous oxide was obtained, after separation of the oxide from the metal core. Using the same charge, without adding water vapor, the same percentage conversion took 68 hours.

HPPE IT HELP YOU