Analysis for Graphite Electrode Unit Consumption in Manufacture System and Use System of Steelmaking EAF

Based on the analysis on the consumption of electrode manufacture system and
users’ system, the universality and characteristic of electrode industry development
were revealed. The electrode consumption should be analyzed correctly and fully and
relative content affecting discontinuous consumption should be added. The method of
analyzing electrode consumption as well as consumption reduction has been presented.

Application & Consumption of Graphite Electrode for EAF Steelmaking

Graphite will be oxidized at a temperature of approximately 4000C and sublimated at
36500C. It is a kind of brittle non-metal material. During operating in electric furnace,
the top of graphite column which located in air is cooled by spraying water; In the
bottom of graphite column, the temperature at the arc discharging point reaches
4000~200000C. Affecting heat and phase transition, the electrode will be consumed
continuously during oxidation, melt and sublimation processes; on the other hand, under
the independent or combined effect of different external factors such as process,
equipment and operation (for example, gravity, pressure, pulling force, fracturing force,
vibration, power, looseness electromagnetic force, thermal stress, thermal shock etc),
the electrode will be consumed discontinuously due to looseness, breakage or cracks.
The former consumption could only be reduced but not to be avoided; while for the
latter consumption, we should try our best option to avoid it. Since the graphite
electrode is used in steel industry, both the manufacturers and users have hard trying to
improve its quality and reduce its consumption. After forty years scientific endeavor in
this field, the following work has been done and relative result has been obtained:

1.1 An Effort for Reducing Electrode Consumption made by EAF Steelmaking Enterprises
Heating, in which main factors affecting the unit consumption of electrode is listed .
1.1.2 The Development of EAF Steelmaking Technology shows the development of EAF steelmaking technology in different stages. thanks to the development and application of some new
technology, EAF steelmaking cycle has been reduced from 180 min in 1965 to less than 60 min, and even 35 min minimally; power consumption has been reduced from 630kW·h/t to min 200 kW·h/t; and electrode consumption has been reduced from 6.5kg/t to
min 1.0kg/t.

focuses on the development of steelmaking technology, which could be concluded as below:

1) To reduce the steelmaking cycle:
a) to increase the input power of transformer of electric furnace: from
RP (100~400 kVA/t) ,HP (400~700 kVA/t) ,UHP (700~1000 kVA/t);
b) to make more use of physical and chemical heat; to add liquid iron; to pre-heat waste
steel; to adopt oxygen blowing; to adopt C-O gun;
c) to melt in EAF and refine in LF;
d) to stir from the bottom of furnace;
2) To reduce the time of power-off:
a) water-cooling furnace door and wall;
b) to adopt computer control;
c) to add waste steel and liquid iron continuously;
d) eccentric bottom tapping;
3) To increase the capacity of furnace, so as to improve energy efficiency and reduce
unit consumption. The furnace capacity has been increased from
Main Factors 5~10t G 80~100tG max. 400t.
4) To reduce the oxidation area of electrode:
a) to cool electrode by spraying water;
b) to change three-phase AC to DC;
c) to replace low-quality electrode with high-quality electrode, from
RP  HP  UHP;
5) To decrease electrode temperature, so as to decrease oxidation and sublimation:
a) to change low-voltage high-current short-arc operation to high-voltage low-current
long-arc operation;
b) to change the power supply by optimizing the connection: from connection with AC
power to cathode connection only with DC power.
1.2 Effort on Reducing Electrode Consumption made by Electrode Manufacturing Enterprises
In the past 40 years, electrode manufacturers all over the world have been trying hard
to develop and improve electrode technology so as to meet the development of EAF
steelmaking.which could be concluded as below:

1) To adopt high-quality raw material, including localizing petroleum and coal needle
coke and stabling their quality, so as to produce electrode and nipple with low CTE.
2) To improve mixing and forming technology; to put lengthwise graphite (LWG) into
application; to adopt tapered connection instead of column connection.
3) To use long nipple, so as to decrease the proportion of fall-off of remnant electrode.
4) To adopt anti-oxidizing treatment