The traditional ways of scrap processing often do not meet the modern environmental requirements. In other cases they are not sufficiently effective for technological and economic reasons. For example, cast iron shavings are usually melted in metallurgical ovens. Due to fragility which is inherent in cast iron, shavings are poorly briquetted and melting of loose shavings is accompanied with a significant waste of metal (up to 40 percent) and with discharging large quantities of disperse oxides, soot and noxious gases. The operations of shavings collection and transportation from their origin places to melting places are expensive. The above-mentioned problems result in that significant part of cast iron shavings is not processed at all and piled up in dumps, littering the earth.

Shavings and lump scrap of fragile metallic materials are processed into powders in the way of mechanical pounding. In the way of mechanic pounding fragment form powders have been obtained from cast iron shavings, tool steel shavings, and lump scrap of hard alloys on the basis of tungsten carbide.

For processing scrap of plastic metals and alloys, a complex technology has been developed including scrap preparation for melting and melting with centrifugal dispersion of liquid metal into powder. In preparing shavings scrap for melting, the shavings are reduced to fragments, cleaned from foreign admixtures, and briquetted with a density of 0.6-0.7 of the theoretical magnitude. The high briquette density sharply reduce the waste of metal in melting. An original construction of the centrifugal dispersing plant and its small size make the centrifugal dispersion process highly productive and most economical in comparison with the existing ways of dispersing liquid metals with gas or water. The spherical form of the particles with a smooth surface is ensured. The size of particles is easily regulated by changing the speed of rotation of the dispersing device. When the particles are hardening, their cooling speed reaches 10 K/sec which creates in the dispersed particles a unique microcrystal structure with dispersion and homogeneous distribution of admixtures and strengthening phases. This feature of the dispersed particles structure enable to obtain from them highly strong and wear-resistant powder materials with minimum content of expensive and scarce alloying elements and - in certain cases - without them. For example, white cast iron can be obtained which is easily amenable to hot plastic deformation with a breaking point in stretching of 1500 Mpa. In the way of centrifugal dispersion, powders were obtained from scrap of aluminum, copper, various alloys on the basis of iron and nickel.

Comparing prices of powders and scrap and taking into account the cost of metallurgical alteration, one can approximately forecast the economic

efficiency of powders production from scrap. The results of the forecast calculations reduced to 1 ton of powder production for different metal scrap are presented in table.

The analysis of the table data shows high economic efficiency of powder production from scrap. A number of business projects for creating production of powders from cast iron shavings and lump scrap of hard alloys, as well as for production of dispersed powders from titanium, tool steels and melting-on materials. There is a large scientific work already done and technological equipment for pilot industrial production of powders from scrap.

Back