Graphite Electrode

Introduction

Graphite electrodes are made from petroleum coke after it is mixed with coal tar pitch. They are then extruded and shaped, baked to carbonize the binder (pitch), and finally graphitized by heating it to temperatures approaching 3000 °C, at which the carbon atoms arrange into graphite.

Graphite electrodes are mainly used in electric arc furnaces. They are presently the only products available that have high levels of electrical conductivity and the capability of sustaining the extremely high levels of heat generated in EAF. Graphite electrodes are also used to refine steel in ladle furnaces and other smelting processes. Graphite electrodes are divided into 4 Types: RP Graphite electrodes, HP Graphite electrodes, SHP Graphite electrodes, and UHP Graphite electrodes.

Graphite Electrode

Technology

Graphite Electrode Manufacturing Process 

1.Raw Material

Use of high-quality calcined petroleum coke production materials

2.Crushing & Screening

They are broken needle coke in mechanical equipment and screening according to the formula after the proportion of the ingredients.

3.kneading

Ingredients of the raw materials with a certain proportion of asphalt heated kneading, made with plastic paste.

4.Forming

After kneading of the paste by temperature cooled to process, and forming into the compressor according to the requirements of product specifications

5.Baking

Within the roasting road, will be “green” electrode roasting to the specified temperature, according to the requirements of the process. After roasting products with special dipping, density, and mechanical strength, improve product performance in order to improve the products and then to repeat the roasting of impregnated products.

6.Graphitization

Second after roasting the products within the graphitization resistance furnace power up to 3000 ℃, the carbon atoms rearrange into specific crystalline form structure, carbon into graphite.

Graphite ElectrodeGraphite ElectrodeGraphite Electrode

Usage

The graphite electrodes are primarily used to carry the electricity that melts scrap iron and steel in electric arc furnaces. As an increasing proportion of global steel is made using electric arc furnaces, the secondary production of steel becomes the major consumption of graphite electrodes. Additionally, the graphite electrode is also used in melting products in smelting furnaces, non-ferrous metals, ceramic products, and even the waste recycling industry. The demand for graphite electrodes is majorly dependent on its application in manufacturing steel through smelting by using an electric arc furnace (EAF). Steel manufacturers are shifting towards electric arc furnaces over the blast furnaces, owing to the advantages offered by EAF such as low cost of establishment, higher production flexibility, and low CO2 emissions.

Graphite Electrode

Statistics

World crude steel production was 444.1 mt in the first three months of 2019, up by 4.5% compared to the same period in 2018. Asia produced 312.9 mt of crude steel, an increase of 7.0% over the first quarter of 2018. The EU produced 42.3 mt of crude steel in the first quarter of 2019, down by 2.0% compared to the same quarter of 2018. North America’s crude steel production in the first three months of 2019 was 30.7 mt, an increase of 4.0% compared to the first quarter of 2018. China’s crude steel production for March 2019 was 80.3 mt, an increase of 10.0% compared to March 2018. India produced 9.4 mt of crude steel in March 2019, down 1.0% in March 2018. Japan produced 9.1 mt of crude steel in March 2019, unchanged from what it produced in March 2018. South Korea’s crude steel production stood at 6.3 mt, up 2.8% in March 2018. In the EU, Italy’s crude steel production for March 2019 was 2.3 Mt, down by 0.3% in March 2018. France produced 1.4 Mt of crude steel in March 2019, an increase of 2.3% compared to March 2018. Spain produced 1.4 Mt of crude steel in March 2019, an increase of 5.9% in March 2018. The US produced 7.8 Mt of crude steel in March 2019, a 5.7% increase in March 2018. Crude steel production in Ukraine stood at 2.0 Mt in March 2019, up 15.0% in March 2018. Brazil’s crude steel production for March 2019 was 2.8 Mt, down by 8.6% in March 2018. Turkey’s crude steel production for March 2019 was 3.0 Mt, down by 11.7% in March 2018.

Graphite Electrode
Ultra-High Power Electrode (UHP)

UHP grade is used in ultra-high power electric arc furnaces and ladle furnaces.

TECHNICAL PROPERTIES OF GRAPHITE ELECTRODES
ITEMUNITMMNPDIA 300-600mm
STANDARDSOLID SURVEY
ELECTRODENIPPLEELECTRODENIPPLE
RESISTIVITYμΩm6.2-6.55.55.0-6.04.5
BENDING STRENGTH≮MPa10.51614-1618-20
ELASTIC MODULUS≯GPa14181214
Ash≯%0.30.30.30.3
BULK DENSITY ≮g/cm31.64-1.651.70-1.721.72-1.751.78
CTE ≯ (100-600℃)×10-6/℃1.51.41.31.2

 

SPECIFICATIONS AND ALLOWANCE OF GRAPHITE ELECTRODES
Diameter(mm)Length(mm)
Nominal DiameterActual DiameterNominal LengthAllowance
mminchmaxminmmShort Dimension
300123073021600length
350143573521800±100
40016409403
45018460454
500205115051600/1800/2000/2200±100
1800/2000/2200
1800/2000/2200/2400
550225565531800/2000/2200
600246136071800/2000/2200
SUGGESTED CURRENT-CAPACITIES OF ELECTRODES
Nominal DiameterSuggested Current-Carrying Capacities (A)Current Density(A/cm2)
mminch
250109200-1510021-30
3001215000-2200020-30
3501420000-3000020-30
4001625000-4000019-30
4501832000-4500019-27
5002038000-5500018-27
5502248000-6000018-24
6002452000-7200018-24
7002762000-9500018-24
ELECTRODE SURFACE QUALITY
SepecificationNominal Diameter(mm)
Defect dimension300-400450-600
Diameter20-4030-50
Depth5–1010–15

 

Remarks:
1. There should be less than two defects or holes on the electrode surface, the max size of which is mentioned in the chart.
2. There should be no transverse crack on the electrode surface. For the longitudinal crack, the length should be less than 5% of the electrode circumference and the width between 0.3-1.0mm.
3. The width of the black area on the electrode surface should be less than 1/10 of electrode circumference and the length less than 1/3 of the electrode.”

High Power Electrode (HP)
TECHNICAL PROPERTIES OF GRAPHITE ELECTRODES
ITEMUNITMMNPDIA 300-600mm
STANDARDSOLID SURVEY
ELECTRODENIPPLEELECTRODENIPPLE
RESISTIVITY≯μΩm7.0-7.56.56.5-7.04.5
BENDING STRENGTH≮MPa9.8-10.51415-Dec15-18
 ELASTIC MODULUS≯GPa12161214
Ash≯%0.30.30.30.3
BULK DENSITY≮g/cm31.61.71.68-1.731.75
CTE ≯ (100-600℃)×10-6/℃2.42.22.22

 

SPECIFICATIONS AND ALLOWANCE OF GRAPHITE ELECTRODES
Dimeter(mm)Length (mm)
Nominal DiameterActual DiameterNominal LengthAllowance
mminmaxminmmlength
300123073021600±100
350143573521800
40016409403
45018460454
500205115051600/1800/2000/2200±100
1800/2000/2200
1800/2000/2200/2400
550225565531800/2000/2200
600246136071800/2000/2200

 

SUGGESTED CURRENT-CAPACITIES OF ELECTRODES
Nominal DiameterSuggested Current-Carrying CapacitiesCurrent Density
mminch
3001213000-1740017-24
3501417400-2400017-24
4001624000-3200016-24
4501832000-4000016-24
5002040000-4800015-24
6002448000-5600014-24

 

ELECTRODE SURFACE QUALITY
SepecificationNominal Diameter(mm)
Defect dimension300-400450-600
Diameter20-4030-50
Depth10–510–15

 

Remarks:
1. There should be less than two defects or holes on the electrode surface, the max size of which is mentioned in the chart.
2. There should be no transverse crack on the electrode surface. For the longitudinal crack, the length should be less than 5% of the electrode circumference and the width between 0.3-1.0mm.
3. The width of the black area on the electrode surface should be less than 1/10 of electrode circumference and the length less than 1/3 of the electrode.

Regular Power Electrode (RP)

RP grade is used in an electric arc, refining, ferroalloy, and submerged-arc furnaces.

TECHNICAL PROPERTIES OF GRAPHITE ELECTRODES
ITEMUNITMMNPDIA 300-600mm
STANDARDSOLID SURVEY
ELECTRODENIPPLEELECTRODENIPPLE
RESISTIVITY (max)μΩm9.0-10.58.58.0-9.07.5
BENDING STRENGTH (min)MPa6.4-7.8139.0-1015
ELASTIC MODULUS (max)GPa9.314913.7
Ash (max)%0.30.30.30.3
BULK DENSITY (min)g/cm31.521.681.56-1.621.7
CTE (max) (100-600℃)×10-6/℃2.92.82.42.2

 

SPECIFICATIONS AND ALLOWANCE OF GRAPHITE ELECTRODES
Diameter(mm) Length(mm)
Nominal DiameterActual DiameterNominal LengthAllowance
mminchmaxminmmShort Dimension
300123073021600length
350143573521800±100
40016409403
45018460454
500205115051600/1800/2000/2200±100
1800/2000/2200
1800/2000/2200/2400
550225565531800/2000/2200
600246136071800/2000/2200

 

SUGGESTED CURRENT-CAPACITIES OF ELECTRODES
Nominal DiameterSuggested Current-Carrying CapacitiesCurrent Density
mminch
3001210000-1300014-18
3501413500-1800014-18
4001618000-2350014-18
4501822000-2700013-17
5002025000-3200013-16
6002430000-3600015-Dec

 

ELECTRODE SURFACE QUALITY
SepecificationNominal Diameter(mm)
Defect dimension300-400450-600
Diameter20-4030-50
Depth10–510–15

 

Remarks:
1. There should be less than two defects or holes on the electrode surface, the max size of which is mentioned in the chart.
2. There should be no transverse crack on the electrode surface. For the longitudinal crack, the length should be less than 5% of the electrode circumference and the width in between 0.3-1.0mm.
3. The width of the black area on the electrode surface should be less than 1/10 of electrode circumference and the length less than 1/3 of the electrode.

Nipples for Graphite Electrodes

Precisely machined electrode nipples for preventing the loosening of the connection of the graphite electrode; the nipple is given special treatment.

 

Sizes of graphite nipples and electrode sockets with Т3 taper thread
DiameterNipple
mminchDL
30012177.16-0.5270.9-1
35014215.9-0.5304.8-1
40016215.9-0.5304.8-1
40016241.3-0.5338.7-1
45018241.3-0.5338.7-1
45018273.05-0.5355.6-1
50020273.05-0.5355.6-1
50020298.45-0.5372.6-1
55022298.45-0.5372.6-1

 

Detailer parameter of 4TPI NIPPLE
Sizes of graphite nipples and electrode sockets with Т4 taper thread
DiameterNipple
mminchDL
30012177.8-0.5215.9-1
35014203.2-0.5254-1
40016222.25-0.5304.8-1
40016222.25-0.5355.6-1
45018241.3-0.5304.8-1
45018241.3-0.5355.6-1
50020269.88-0.5355.6-1
50020269.88-0.5181.08-1
55022298.45-0.5226.58-1
55022298.45-0.5209.65-1
60024317.5-0.5245.63-1
60024317.5-0.5228.7-1

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