Graphite Electrodes
Graphite electrodes are used for the recycling of steel in the electric arc furnace industry, so called "mini-mills." We do not simply provide graphite electrodes and nipples as stand alone products to our customers. Rather, the focus is on the delivery of an entire "product system", supported by sales and technical experts from the receipt of the customer's order, throughout the entire production process, to final product in the steel plants.
Properties and Characteristics - Matching your needs
The graphite electrode load diagram shows mean values based on our experience. Precise evaluation is only possible under specific furnace conditions.
Graphite electrodes from SGL Group are designed for increased productivity and customer value. Our continuous improvements in material properties as
well as increased dimensions provide the customer the benefit of applying higher current loads.
The pioneer size of 800 mm / 32 inches has recently been successfully established as a new standard.
Simulation left: Current density in bottom joint
Simulation right: Temperature inside electrode tip after high current load
Typical Properties of Graphite Electrodes
| Diameter | mm inches |
SIGRA-LF | MELT | ||
|---|---|---|---|---|---|
| 350 - 450 14 - 18 |
350 - 450 14 - 18 |
500 - 650 20 - 26 |
700 - 800 28 - 32 |
||
| Apparent Density | g/cm³ | 1.63 - 1.72 | 1.66 - 1.76 | 1.67 - 1.77 | 1.68 - 1.77 |
| Specific Electrical Resistivity | μΩm | 5.5 - 7.5 | 4.9 - 5.7 | 4.5 - 5.5 | 4.0 - 5.5 |
| Flexural Strength | N/mm² | 9.0 - 15.0 | 8 - 13 | 10 - 13 | 10 - 13 |
| Thermal Conductivity | W/(K.m) | 160 - 210 | 220 - 270 | 250 - 280 | 250 - 300 |
| Coefficient of Thermal Expansion | μm/(K.m) | 0.7 - 1.8 | 0.3 - 0.7 | 0.3 - 0.6 | 0.3 - 0.6 |
Influences Governing Graphite Electrode Consumption
| Type | Mechanism | Influencing Parameters |
|---|---|---|
| Tip Consumption | Sublimation of Graphite in the Arc Erosion of Graphite Particles Chemical Wear of Graphite by Slag and Liquid Steel |
Current Level Power-On Time Slag Consistency and Chemistry |
| Side Consumption | Surface Oxidation | Tap-to-Tap and Downtimes Current Level Electrode Temperature/ Water Spraying Oxygen Use Dust Collecting System |
| Electrode Breakage | Excessive Mechanical Stress | Scrap and Method of Furnace Charging Electrode Regulation Electrode Joining |
| Stub-End (Butt) Losses | Thermal Stress | Current Level Electrode Jointing Electrode Regulation |
Recommended Joining Torque
| Electrode Diameter | Torque | |||
|---|---|---|---|---|
| mm | Inch | Nm | ft.lbs | |
| 350 | 14 | 850 | 630 | |
| 400 | 16 | 1100 | 810 | |
| 450 | 18 | 1500 | 1100 | |
| 500 | 20 | 2500 | 1850 | |
| 550 | 22 | 3500 | 2570 | |
| 600 | 24 | 4000 | 2940 | |
| 650 | 26 | 5000 | 3680 | |
| 700 | 28 | 6000 | 4410 | |
| 750 | 30 | 7500 | 5510 | |
| 800 | 32 | 10000 | 7350 | |
Mechanical Joining Procedure
A sufficiently high and well-defined torque is essential to ensure the proper performance of the electrode joint. For diameters exceeding 450 mm / 18 inches, mechanical joining with torque control by a hydraulic assembly station or robot joining is highly recommended.
Graphite Electrode Dimensions
|
Nominal-
Diameter |
Full Toleranz
|
Nominal Length
|
|||||
|---|---|---|---|---|---|---|---|
|
Lower Tolerance
|
Upper Tolerance | ||||||
|
mm
|
Inch
|
min.
mm |
max.
mm |
min.
mm |
max.
mm |
mm
|
Inch
|
|
350
|
14
|
352
|
355
|
355
|
359
|
1500, 1800, 2100
2400 |
60, 72,84,
96 |
|
400
|
16
|
403
|
406
|
406
|
409
|
1500, 1800, 2100
2400 |
60, 72,84,
96 |
|
450
|
18
|
454
|
457
|
457
|
460
|
1800, 2100, 2400
|
72, 84, 96
|
|
500
|
20
|
505
|
508
|
508
|
511
|
1800, 2100, 2400
2700 |
72, 84, 96,
110 |
|
550
|
22
|
556
|
558
|
558
|
562
|
2100, 2400, 2700
|
84, 96, 110
|
|
600
|
24
|
607
|
609
|
609
|
613
|
1500, 2100, 2400,
2700 |
60, 84, 96,
110 |
|
650
|
26
|
657
|
660
|
660
|
663
|
2100, 2400, 2700
|
84, 96, 110
|
|
700
|
28
|
708
|
711
|
711
|
714
|
2100, 2400, 2700
|
84, 96, 110
|
|
750
|
30
|
759
|
762
|
762
|
765
|
2400, 2700
|
96, 110
|
|
800
|
32
|
810
|
812
|
812
|
816
|
2400, 2700
|
96, 110
|
Length Tolerance
|
Nominal
|
Full Tolerance
|
||||
|---|---|---|---|---|---|
|
|
Lower Tolerance
|
Upper Tolerance
|
|||
|
mm
|
Inch
|
min. mm
|
max. mm
|
min. mm
|
max. mm
|
|
1500
|
60
|
1400
|
1510
|
1511
|
1610
|
|
1800
|
72
|
1689
|
1790
|
1791
|
1915
|
|
2100
|
84
|
1969
|
2095
|
2096
|
2220
|
|
2400
|
96
|
2273
|
2399
|
2400
|
2525
|
|
2700
|
110
|
2526
|
2704
|
2705
|
2906
|
Graphite Electrode 800 mm / 32 inch - World-first introduction of 800 mm graphite electrode
SGL Group is the first company in the world to develop a graphite electrode with a diameter of 800 mm, designed for industrial steel production in electric arc furnaces. Development of the electrode was based on close cooperation with Peiner Träger GmbH, which has successfully used the electrode under real-life production conditions since the start of 2001.
SGL Group‘s innovative venture into these 800 mm electrodes has two main advantages. On the one hand, they can increase furnace productivity, allowing the steelworks to produce more steel in the same time period and therefore significantly reduce costs. On the other, they open up the possibility of constructing a new generation of even higher performance direct-current arc furnaces, which can be powered by currents of over 150 kA. Until now, the maximum current used has been between 130 and 140 kA. With the development of the 800 mm graphite electrode, SGL Group and Salzgitter/Peine have made a significant contribution to further technical advances in the electric steel technology.
Forging ahead with a new dimension for productivity
800 mm / 32 inch DC graphite electrode. Made by SGL Group
Current carrying capacity
This diagram illustrates the gain of allowable maximum current as a key to productivity increase. It is based on our experience and engineering background. An exact evaluation within the suggested range needs the application of specific furnace parameters and conditions.
| Typical Material Properties | Unit | ||
|---|---|---|---|
| Apparent Density | g/cm3 | 1.69 - 1.-75 | |
| Porosity | % | 14 - 19 | |
| Specific Electrical Resistance | Ω µm | 4.0 - 4.8 | |
| Flexural Strength | N/mm2 | 10 - 14 | |
| Thermal Conductivity | W/(K•m) | 240 - 300 | |
| Thermal Expansion | µm/(K•m) | 0.3 - 0.6 | |
| Typical Dimensions | |||
| GE Diameter | min. | 810 mm | 31.8 inch |
| max. | 816 mm | 32.1 inch | |
| GE Length | min. | 2705 mm | 106.5 inch |
| max. | 2906 mm | 114.4 inch | |
| Typical Weights | |||
| GE | approx. | 2500 kg | 5500 lb |
| Nipple | approx. | 128 kg | 280 lb |
| Joint | 432 T4L635 | 17 T4L 25 | |
| Mechanical Joining Procedure | Torque (Nm) | ||
| 700/28 inch | 6000 | ||
| 750/30 inch | 7500 | ||
| 800/32 inch | 10000 |
With increasing diameter a sufficiently high and well defined torque is essential to ensure the performance of the electrode joint. Mechanical joining with torque control by hydraulic assembly station or robot is strictly recommended.
The information is based on our present state of knowledge and is intended to provide general notes on our products and their uses.