Development of Tungsten Carbide Used for Mining

       

Recent
years, since the development of mining and energy exploration as well
as some large-scale infrastructure construction projects, tungsten
carbide for mining, such as tungsten carbide buttons, bits, picks,
mills, DTH drills and some supporting tools has been widely used and the
market demands increased gradually. With the rapid development of
metallurgical industrial technology of our country, in gas, fuel oil,
natural gas drilling, some demands of mechanical mining equipment and
large and medium pore diameter drill with carbide ore also increased.
Mining tools take advantage of WOB and rotation of the impact load
itself broken rock, drill and buttons during operation when subjected to
high impact loads at the same time by twisting, bending, stretching,
compression and other complex stress. And it subjected to the wear and
corrosion by rocks, rock dust, mineral water, etc. at high-speed
rotation. So it requires that tungsten carbide used for mining not only
has high hardness and toughness, but also has good wear and corrosion
resistance.

In
order to combine wear resistance with toughness, relevant researchers
develop many new types of carbide, such as ultra-fine or nano cemented
carbide, high-temperature powder based carbides, functional gradient
tungsten carbide, low-Co and coarse grain carbide, double binder phase
and double crystalline structure, etc. Double binder phase was developed
by American company, which fully dense WC-Co pellets embedded in Co
matrix to remain the similar wear resistance of common alloys. The
binder phase can be any bonding metal, alloy or another kind of cemented
carbide.

The
most outstanding characteristic is that the hard phase is not a hard
compound (WC), which is composed of refractory metal compound and Co
sintered hard material into crystalline pellets (WC-Co) composition and
mixed with binder metal for secondary sintering. Compared with most of
double phase tungsten carbide, double binder phase carbide has greater
design freedom (size, hardness, toughness, strength of base and so on),
which has been widely used in rolling cutter bits, impacting bits,
dragging bits and other tools. Double crystalline tungsten carbide is
also called as non-uniform grain carbide. Since the WC grain size
distribution curve has two peaks, it can be also known as
bimodal-structure tungsten carbide. This kind of structure coarse grain
WC can provide good ductility and toughness, and a certain proportion of
fine grain WC is able to provide high wear resistance.