RP Graphite Electrode: Properties, Tempers & Uses

RP Graphite Electrode tempers and conditions

RP Graphite Electrode is supplied in 5 conditions, soft to hard. D350-400 is the default FabDigit quotes; the values on this page are for it.

Compare all 5 conditionsHide

Condition · open for datasheet	Best for	Tensile MPa	Elong. %	Hardness	Conductivity
D550-600 Φ550–600 mm	Big submerged-arc furnaces (FeSi, CaC₂, FeMn) where cross-section, not current density, carries the load.	6	0.2	28 HV	125 W/m·K
D450-500 Φ450–500 mm	Large ordinary-power EAF and calcium-carbide/silicon furnaces; slightly lower strength and higher resistivity from larger billet size.	7	0.22	30 HV	130 W/m·K
D350-400Default Φ350–400 mm	The workhorse RP size for ordinary-power EAF, LF and submerged-arc ferroalloy furnaces.	7	0.25	32 HV	140 W/m·K
D200-300 Φ200–300 mm	Small ladle furnaces, ferroalloy and foundry furnaces; best resistivity and strength of the RP family.	8	0.3	35 HV	150 W/m·K
NIPPLE Nipple / connecting pin stock	Denser, higher-strength graphite used for the tapered connecting pin so the joint outlives the electrode body.	12			170 W/m·K

What is RP Graphite Electrode?

RP Graphite Electrode is a petroleum-coke-based extruded and graphitised electrode covering the regular-power class of GB/T 3079 and JIS R7601, stocked in D200-300 through D550-600 sizes with matching nipples. It is the most economical electrode grade for low-power arc furnaces, ferroalloy smelting and resistor elements, with density 1.56 g/cm3, thermal conductivity 140 W/m·K, tensile strength 7 MPa and modulus 9 GPa. Current-carrying capacity and strength are the lowest in the family and the porous body picks up moisture, so sockets should stay sealed. HP is the next step up as furnace power rises. RP Graphite Electrode has a density of 1.56 g/cm³ (0.0564 lb/in³), lighter than 96% of ceramic grades. It melts at 3,650°C (6,602 °F). RP Graphite Electrode has a tensile strength of 7 MPa (1.02 ksi), weaker than 95% of ceramic grades. Elongation at break is 0.25% and the elastic modulus is 9 GPa (1.31 Msi).

What is RP Graphite Electrode used for?

low-power arc furnaces
ferroalloy smelting
resistor elements

Advantages

Lightweight — 1.56 g/cm³ (0.0564 lb/in³), better than 96% of ceramic grades
Easy to machine — 90/100, better than 94% of ceramic grades
Conducts heat well — 140 W/m·K (80.9 BTU/hr·ft·°F), better than 92% of ceramic grades
Ductile — tolerates forming and impact — 0.25%, better than 85% of ceramic grades

Limitations

Hard to polish — 25/100, worse than 97% of ceramic grades
Low stiffness — 9 GPa (1.31 Msi), worse than 95% of ceramic grades
Low fracture toughness — 1 MPa·√m (0.91 ksi·√in), worse than 84% of ceramic grades
Limited service temperature — 450°C (842 °F), worse than 77% of ceramic grades

RP Graphite Electrode properties

Typical room-temperature values for RP Graphite Electrode-D350-400; bars are the position among ceramic grades.

Physical3

RP Graphite Electrode has a density of 1.56 g/cm³ (0.0564 lb/in³), lighter than 96% of ceramic grades. It melts at 3,650°C (6,602 °F).

Density1.56 g/cm³0.06 lb/in³

Melting Point (Solidus)3,650°C6,602 °F

Porosity25%

Mechanical11

RP Graphite Electrode has a tensile strength of 7 MPa (1.02 ksi), weaker than 95% of ceramic grades. Elongation at break is 0.25% and the elastic modulus is 9 GPa (1.31 Msi).

Elastic (Young's) Modulus9 GPa1.3 Msi

Shear Modulus3.8 GPa0.55 Msi

Poisson's Ratio0.15

Tensile Strength (Ultimate)7 MPa1 ksi

Elongation at Break0.25%

Compressive Strength22 MPa3.2 ksi

Flexural Strength11 MPa1.5 ksi

Shear Strength6 MPa0.87 ksi

Fracture Toughness (K_IC)1 MPa·√m0.91 ksi·√in

Hardness, Vickers32 HV

Hardness, Mohs1.5

Thermal5

RP Graphite Electrode is rated for continuous service to 450°C (842 °F). It conducts heat at 140 W/m·K (80.9 BTU/hr·ft·°F), better than 92% of ceramic grades. Thermal expansion is 2.2 µm/m·K (1.22 µin/in·°F).

Thermal Conductivity140 W/m·K80.9 BTU/hr·ft·°F

Specific Heat Capacity710 J/kg·K0.17 BTU/lb·°F

Thermal Expansion (CTE, 20–100 °C)2.2 µm/m·K1.2 µin/in·°F

Max Service Temperature (continuous)450°C842 °F

Min Service Temperature-200°C-328 °F

Electrical2

RP Graphite Electrode has an electrical resistivity of 8×10⁻⁶ Ω·m.

Electrical Resistivity8×10⁻⁶ Ω·m315 µΩ·in

Volume Resistivity8×10⁻⁴ Ω·cm

Chemical & Environmental2

Corrosion resistance is good (65/100), worse than 67% of ceramic grades.

Corrosion ResistanceGood65/100

Chemical Resistance SummaryInert to nearly all mineral acids, alkalis, salts, molten non-oxidizing metals and slags; attacked by strong oxidizers (hot concentrated HNO₃, H₂SO₄, chromic acid, molten alkali nitrates), and oxidizes progressively in air, CO₂ or steam above ~400–500 °C.

Sustainability4

Producing a kilogram of RP Graphite Electrode takes about 65 MJ of energy and emits 6 kg of CO₂ — less than 74% of ceramic grades. Typical recycled content is 5%.

Embodied Energy (primary production)65 MJ/kg27,945 BTU/lb

Embodied Carbon (primary production)6 kg CO₂/kg

Embodied Water25 L/kg3 gal/lb

Typical Recycled Content5%

Manufacturability3

RP Graphite Electrode's machinability is excellent (90/100, better than 94% of ceramic grades).

MachinabilityExcellent90/100

PolishabilityPoor25/100

Sintering / Firing Temperature2,900°C5,252 °F

Common Calculations4

Specific Strength (UTS / density)calculated4 kN·m/kg

Specific Stiffness (E / density)calculated5.8 MN·m/kg

Thermal Diffusivitycalculated126.4 mm²/s

Thermal Shock Resistance Indexcalculated49

Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.

Strength versus weight in the ceramic family

Yield strength against density for every ceramic grade FabDigit runs. RP Graphite Electrode is highlighted; hover a dot for its name, or open the interactive family chart.

Working with RP Graphite Electrode

Is RP Graphite Electrode easy to machine?

Machines very easily dry with sharp carbide or PCD tooling at high speed and zero coolant; mandatory dust extraction, and support the part because edges chip.

Can RP Graphite Electrode be welded?

Not weldable — sections are joined only by machined tapered threaded nipples with graphite cement, or bonded with carbon/furan cements.

Can RP Graphite Electrode be formed, bent or molded?

Made by extruding a hot coke/pitch paste, multi-stage baking to ~1000 °C, optional pitch impregnation, then graphitization at 2800–3000 °C; no post-forming of the finished rod.

RP Graphite Electrode chemical composition (wt %)

Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.

Element	Spec limit (wt %)	Nominal
ashGB/T 3079 limit ≤0.5 %; Si, Fe, Al, Ca oxides	≤ 0.5	0.3
Sresidual sulfur from petroleum coke; drives puffing control	≤ 0.25	0.12
volatile matterafter graphitization	≤ 0.2	0.05
Cfixed carbon after graphitization; petroleum coke + coal-tar pitch binder	≥ 99 (balance)

What surface finishes work on RP Graphite Electrode?

Turned to size and socket-threaded (3TPI/4TPI); optional anti-oxidation aluminium/SiC coating or ceramic paint on the column, and sealed sockets to keep out moisture.

Other Carbon & graphite ceramic grades

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Compare RP Graphite Electrode with…

Benchmark RP Graphite Electrode against the top 3 neighbours

How much does RP Graphite Electrode cost?

RP Graphite Electrode is a standard-cost ceramic ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.

RP Graphite Electrode — frequently asked

What is RP Graphite Electrode used for?

RP Graphite Electrode is typically used for low-power arc furnaces, ferroalloy smelting and resistor elements. In short: most economical electrode grade; petroleum-coke regular-power class; lowest current density rating.

What is the tensile strength of RP Graphite Electrode?

RP Graphite Electrode has a typical tensile strength of 7 MPa (1.02 ksi) — weaker than 95% of ceramic grades. Strength varies by condition: see the 5 listed tempers.