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.

Current Carrying Capacity

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 4.9 - 7.5 4.9 - 5.7 4.5 - 5.5 4.0 - 5.5
Flexural Strength N/mm² 9 - 15 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
All values measured parallel to extrusion direction. Graphite electrodes from SGL Group are produced with a high degree of purity so as to have no adverse effect on the refining of steel.

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
SGL Carbon electrodes and nipples are machined according to internal standards (derived from international standards IEC 239, NEMA, JIS).

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
This document is based on our best current knowledge and is intended to provide information on specific properties of our products and their applications. The above data have been obtained under laboratory conditions by employing the test methods described. This information should not, therefore, be taken as guaranteeing specific properties or the suitability of the product for a specific application under working conditions unknown to us. In particular, the specific data should not be taken as a warranty for the durability or performance of a product in the stated application. SGL Group cannot assume any liability in respect thereof. Any existing intellectual property rights must be observed.

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.

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