The production process of ultra-high power graphite electrodes must meet stringent requirements for high current density, high thermal stress, and strict physicochemical properties. Its core special requirements are reflected in five key stages: raw material selection, molding technology, impregnation processes, graphitization treatment, and precision machining, as detailed below:
I. Raw Material Selection: Balancing High Purity and Specialized Structure
Primary Raw Material Requirements
Needle coke serves as the core raw material due to its high graphitization degree and low coefficient of thermal expansion (α₀-₀: 0.5–1.2×10⁻⁶/℃), meeting the stringent thermal stability demands of ultra-high power electrodes. The needle coke content is significantly higher than that in ordinary power electrodes, accounting for over 60% in ultra-high power electrodes, whereas ordinary power electrodes primarily use petroleum coke.
Auxiliary Material Optimization
High-temperature modified pitch is employed as a binder due to its high carbon residue yield and low volatile content, enhancing the electrode’s bulk density (≥1.68 g/cm³) and mechanical strength (flexural strength ≥10.5 MPa). Additionally, metallurgical coke is added to adjust particle size distribution, optimizing conductivity and thermal shock resistance.
II. Molding Technology: Secondary Molding Overcomes Size Limitations
Vibration-Extrusion Composite Molding
Traditional processes rely on large extruders for large-diameter electrodes, whereas ultra-high power electrodes adopt a secondary molding method:
- Primary Molding: An unequal-pitch spiral continuous extruder is used to preliminarily press the mixed material into green compacts.
- Secondary Molding: Vibration molding technology further eliminates internal defects in the green compacts, improving density uniformity.
This approach enables the production of large-diameter electrodes (e.g., up to 1,330 mm) using smaller equipment, overcoming traditional process limitations.
Application of Intelligent Extrusion Equipment
A 60 MN graphite electrode extruder equipped with intelligent length setting, synchronous shearing, and conveying systems improves length setting accuracy by 55% compared to traditional processes, enabling fully automated continuous production and significantly enhancing efficiency and product consistency.
III. Impregnation Process: High-Pressure Impregnation Enhances Density and Strength
Multiple Impregnation-Baking Cycles
Ultra-high power electrodes require 2–3 high-pressure impregnation cycles using medium-temperature modified pitch as the impregnant, with weight gain controlled at 15%–18%. Each impregnation is followed by secondary baking (1,200–1,250℃) to fill pores, achieving a final bulk density exceeding 1.72 g/cm³ and compressive strength of ≥26.8 MPa.
Specialized Treatment of Connector Blanks
Connector sections undergo high-pressure impregnation (≥2 MPa) and multiple baking cycles to ensure a contact resistance of ≤0.15 mΩ, meeting high-current transmission requirements.
IV. Graphitization Treatment: Ultra-High Temperature Conversion and Energy Efficiency Optimization
Acheson Furnace Ultra-High Temperature Processing
Graphitization temperatures must reach ≥2,800℃ to transform carbon atoms from a two-dimensional disordered arrangement into a three-dimensional ordered graphite structure, achieving low resistivity (≤6.5 μΩ·m) and high thermal conductivity. For instance, one enterprise shortened the graphitization cycle to five months and reduced energy consumption by optimizing insulation material formulations.
Integrated Energy-Saving Technologies
Variable frequency energy-saving technologies and dynamic energy efficiency models enable real-time monitoring of equipment loads and automatic switching of operating modes, reducing pump group energy consumption by 30% and lowering operational costs significantly.
V. Precision Machining: High-Precision Control Ensures Operational Performance
Mechanical Machining Accuracy Requirements
Electrode diameter tolerances are ±1.5%, total length tolerances are ±0.5%, and connector thread accuracy reaches Class 4H/4h. High-precision geometric control is achieved using CNC machining and online detection systems, preventing current fluctuations caused by electrode eccentricity during electric arc furnace operation.
Surface Quality Optimization
Waste-free extrusion technology minimizes machining allowances, improving raw material utilization. Curved nozzle designs optimize conductivity, increasing product yield by 3% and enhancing conductivity by 8%.
Post time: Jul-21-2025