1070-4272/04/7711-1743C2004 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 77, No. 11, 2004, pp. 1743!1745. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11,
2004, pp. 1761!1763.
Original Russian Text Copyright + 2004 by Zarubitskii, Orel, Dmitruk.
AND INDUSTRIAL INORGANIC CHEMISTRY
Pyrochemical Processing of Tungsten- and Cobalt-Containing
O. G. Zarubitskii, V. P. Orel, and B. F. Dmitruk
Vernadsky Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine,
Received June 30, 2004
Abstract-A method for processing of secondary tungsten- and cobalt-containing materials is suggested.
The optimal parameters of the processes involved and the consumption of chemicals are determined.
Processing of secondary tungsten-containing raw
materials, and primarily the recovery of tungsten and
cobalt from worn-out drilling and cutting tools, is
an urgent problem.
Hydrometalurgical, pyrometallurgical, physical,
and electrochemical methods for processing of tung-
sten3cobalt alloys of the VK type are known .
These processes are low-intensive, have low selectiv-
ity, and involve discharge of noxious substances (ni-
trogen oxides, hydrogen fluoride) into the atmosphere.
The existing techniques are mainly applicable to proc-
essing of lump scrap of cutting tools, but show low
efficiency in recovery of tungsten and cobalt from
worn-out roller drill bits used in mining and geo-
logical prospecting. Chemical and electrochemical
methods performed in melts based on alkali metal
hydroxides show promise for processing of raw mate-
rials of this kind .
Of particular interest is recovery of tungsten from a
tungsten-containing alloy by oxidative calcination. It
has been suggested to perform this procedure at 7803
820oC with subsequent leaching-out of tungsten com-
pounds . A technique for recovery of tungsten
from lumps of high-alloy materials has been patented
. This technique consists in heating of the starting
product in air at 8003900oC for 48 h followed by
treatment of the oxidized products with a solution of
an alkali metal hydroxide in an autoclave at 1403
195oC for 6310 h. The total duration of the process is
543 64 h.
The method suggested for processing of worn-out
roller drill bits (drilling tools) is based on oxidation
of a hard composite alloy (tungsten carbide with a
cobalt binder) in an air flow, mechanical disintegra-
tion of the brittle oxidized product, and removal of its
residual amounts from sockets in an alkali melt.
Samples of the same type, 2003250-g fragments of
roller drill bits, were used in the experiments. Each
sample contained two picks made of a WC3Co hard-
alloy formulation. Part of the samples contained picks
12 mm in diameter, embedded to a depth of 10 mm,
and part, picks 8 mm in diameter, embedded to a
depth of 5 mm. The roller drill bit from which the
samples were cut was completely worn out: the picks
were completely worn virtually to the level of the
steel base. The samples were treated in a muffle fur-
nace with apertures for in- and outflow of air. Air was
pumped with a compressor through the aperture in the
furnace at a flow rate of 10330 l h
. The hydroxide
melt was fused in a corundum crucible.
Worn-out roller drill bits were heated to 950 3
1050oC and kept in the furnace for a time sufficient
for oxidation of the hard-alloy picks. The components
of the hard alloy are oxidized by the reactions
WC + 2.5O
+ Co = CoO + CO. (2)
The oxidation product is formed as a kind of
[columns] or [flowers] growing from the sockets and
occupies a volume exceeding by a factor of 6 that of
the initial hard alloy (Fig. 1). The above temperature
interval is the optimal. At lower temperatures, the
oxidation rate markedly decreases. The same occurs as
the temperature is raised from 1050 to 1100oC, and
upon further increase in temperature, the oxidation of