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LFX™ Graphite Electrode Typical Physical Properties

UCAR® Grade LFX™ Graphite Electrodes for Ladle Furnace Applications

UCAR® Graphite Electrodes Typical Properties*

 

U.S. Standard Units
    LFX®    
Electrodes Units of Measure 250 - 350 400 - 450 Method of Measurement
Bulk Density t/m3 1.67 - 1.73 1.66 - 1.72 ASTM C559
Specific Resistance µOhm.m 5.5 - 6.0 5.2 - 5.8 ASTM C611
Flexural Strength MPa 10.0 - 13.0 9.0 - 12.0 Four Point ASTM C651
Young's Modulus GPa 9.0 - 11.0 8.0 - 9.5 ASTM C747
Coefficient of Thermal Expansion cm/cm/º10-6(30 to 100ºC) 0.4 - 0.6 0.4 - 0.6 PATE Machine/UCAR® Method
Porosity % 20 - 22 21 - 23 Calculation:100(RD-BD)/RD
Thermal Conductivity W/mºC 210 - 230 220 - 240 Calculation: 1.3 10-3/Resistivity
Nipples for LFX™ Electrodes     LFX ASTM C747
Bulk Density t/m3   1.76 - 1.82  
Specific Resistance µOhm.m   3.6 - 4.3  
Tensile Strength MPa   15.0 - 21.0  
Young's Modulus GPa   12.0 - 16.0  
Thermal Conductivity cm/cm/º10<sup>-6</sup>(30 to 100ºC)   0.1 - 0.3  

*Typical range, property values not guaranteed.

 

Mean CTE:
Final Temperature Degrees Celcius Added factor
100 0
200 2.0 x 10-7
300 4.0
400 6.0
500 7.7
600 9.2
700 10.4
800 11.4
900 12.3
1000 13.2
1500 17.2
2000 21.2
2500 25.2

*Typical range, property values not guaranteed.

Footnotes to Tables:

*Electrodes and nipples are extruded products. Thus, these tables show only typical values which may vary from size to size, piece to piece or even within a piece.

UCAR® Graphite Electrodes and connecting nipples meet dimensional tolerances by IEC, JIS and NEMA as required by customers worldwide. Norms are available on request.

Ash Content: UCAR® Graphite Electrodes typically have less than 0.1% impurities and do not contain elements harmful to steelmaking.

Definitions:

Bulk Density

– A measurement of weight per unit volume. A higher bulk density will generally be reflected in improved mechanical properties.

Flexural Strength – A measurement of stress required to cause rupture in bending. (Also called Bending Strength or Modulus of Rupture). Higher flexural strength in electrodes will generally result in lower electrode breakage frequency.

Note: As graphite is a brittle material, UCAR employs the ASTM 4-Point loading method for strength testing. This method yields test values about 25% lower than those obtained by the 3-Point loading method.

Tensile Strength – A measurement of pure tensile force per unit area required to cause rupture by pulling apart. Higher tensile strength in nipples will generally result in lower nipple breakage frequency.

The strength characteristics of graphite increase significantly with increasing temperature.

Coefficient of Thermal Expansion (CTE)

– A measurement of increase in length per unit length per degree rise in temperature. Lower CTE will generally give better resistance to thermal shock. Also, CTE compatibility between the graphite electrode and connecting nipple is important for satisfactory performance of the electrode joint.

The change in CTE with temperature is about the same for all graphite at high temperature. The mean linear CTE between room temperature and any final temperature can be obtained using the factors shown to the left.

Specific Resistance – A measurement of opposition to electric current flow. Low specific resistance of graphite electrodes allows maximum current carrying capability without overheating of the electrode column. The chart below shows the effect of temperature on the relative electrical resistivity of graphite electrodes.