Title of the conference
Types of graphite electrodes
Table 1
RP
A conventional power graphite electrode is
also called a graphite molded column to allow
a current density through a graphite electrode
of less than 17 A/cm 2, Mainly used in
steelmaking,
yellow phosphorus, silicon and
other ordinary power electric furnaces.
HP
The high-current HP electrode is appropriate
for casting operations or occasionally in arc
furnaces.
High power graphite electrode wire
material for steelmaking of an electric arc
furnace, which is made of petroleum coke,
needle coke, coal asphalt, and high-
temperature wire material produced by a
series of strict process processes. In order to
allow the current density through the graphite
electrode to 18 ~ 25A / km 2, mainly used in
a high-power steelmaking arc furnace.
UHP
Ultrahigh graphite electrodes are used to
recycle steel in the arc furnace industry. The
main ingredient
is high-quality needle coke
made from oil or coal tar. In order to allow the
current density through the graphite electrode
to be larger than 25A/cm 2. Mainly used for
ultra-high power steelmaking electric arc
furnace.
Above are the types and classification of electrodes, of
which the most widely used in the steel melting process
are UHP graphite electrodes. Take as an example of
graphite electrodes, due to improper use of graphite
electrodes in technological processes and operation,
electrodes can be broken and damaged. As a result, the
metal melting time increases and the cost of the product
increases. If broken graphite electrodes fall into the
furnace, carbon content will be added to the slag and stop
the melting process in the furnace.
This leads to the
deterioration of the properties of steel and the decrease in
the price of the product by the purchasing companies, and
in some cases cases of non-purchase occur.
In addition, broken or damaged electrodes cause an
increase in the consumption of electrodes and an increase
in the price of the product. As a result, the amount of profit
metallurgical plants receive from the sale of these
products will decrease significantly. Therefore, it is
necessary to reduce the consumption of electrodes in
order to increase technical
and economic indicators in
steel production. In many countries (in particular, in
Uzbekistan) steel melting furnaces of large and medium
capacity are used.
Take a graphite electrodes as an example, the
production technology of high-quality graphite electrodes
for heavy-duty arc furnaces is quite complex. The high
cost of charge materials and high power consumption
determine the very high cost of special graphite electrodes
for heavy-duty furnaces ($1500-2000 per 1 ton). Because
of the high cost of graphite electrodes, the cost of
electrodes during the operation
of furnaces of ordinary
power for smelting carbon steels is 8% of the cost of steel;
when operating heavy-duty furnaces, such costs can
exceed 15% of the cost of steel, in some cases reaching
30%. The consumption of graphite electrodes fluctuates
within a significant range, which during normal operation
of furnaces is 4–8 kg/t (in a well-functioning heavy-duty
steel-smelting furnace, the total consumption of
electrodes was 4 kg/t of steel).
According to the above points, we can say that the
consumption of graphite electrodes in EAF steelmaking
depends not only on the quality of the electrodes, but also
on the level of operation and management of steelmaking.
So what factors influence electrode breakage or
failure? When these factors were analyzed, it was studied
that there was too much factor dependence. The below in
fig. 2 follows the main 3 factors, which are:
Fig.2.
Factors causing breakage and damage of
graphite electrodes
To minimize electrode
consumption and prevent
breakage and failure in steel melting furnaces, it is crucial
to employ proper electrode usage techniques. Fig.3.
illustrates key solution factors that mitigate electrode
damage.
Fig.3.
Strategies for preventing electrode breakage in
steel production.
Preparations
break the
graphite
electrodes
When smelting,
after the bottom
of
preparations
gradually melt, it
is like a main
shaft, the space
under
it
is
empty, the un-
melted
scrap
steel on furnace
wall
will
fall
down
to
the
electrodes,
causing
cracks.
Generally,
the
broken part is the
electrode holder.
Vibration
break
The electrode is
subjected
to
electromagnetic
force
during
smelting, and it
will
definitely
vibrate,
which
will easily cause
the electrode to
fatigue
and
break.
These
breaks have no
disciplines,
mostly
occurs
near the middle
of the electrode
nipples.
Inappropriate
operation of
electrode holder
It
is
not
allowed to have
foreign
matter
between
the
electrode
and
holder,
both
should be always
vertical,
holder
cannot be held out
of the safety line
of the electrode.
These
irregular
operations
will
cause
the
electrode to break.
The electrode gripper should avoid clamping at the
electrode joint and the hole of the electrode joint.
Keep the tilting system in good condition and keep the
tilting stable.
The electrode pillar is aligned with the furnace top hole,
and the electrode pillar is parallel.
Avoid the existence of non-conductive materials in scrap
steel.
The scrap is evenly distributed in the furnace, and the
large scrap is placed at the bottom of the furnace as far as
possible.
Correct electrode phase sequence, counterclockwise
direction.
Title of the conference
Preserving the integrity of graphite electrodes during
the steel melting process positively impacts both
economic efficiency and metal quality.
Another problem is that during steel production in
electric arc furnaces, there are high energy losses. Firstly,
they are associated with the unsatisfactory quality of
carbon-graphite electrodes and their improper operation.
Also, in below other reasons that reduce the efficiency of
the furnace installation are given:
Fig. 4.
Factors causing energy waste in steel smelting
technology.
Based on the above-mentioned issues, there are
concerns
regarding energy inefficiency, increased
electrode consumption, and the adequacy of electrode
strength and durability in the steel production process
when using electrodes. Addressing these challenges
through the provision of solutions enhances the
technological process quality.
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