The process of making extruded graphite involves blending fine graphite powder with a binder, pressing this mixture through a die, and then subjecting the resulting shape to multiple firing and graphitization steps.
Key Steps in Extruded Graphite Production
Extruded graphite is a widely used material in various industries due to its unique properties. Its production follows a specific sequence of steps that determine its final characteristics.
Raw Material Preparation
The fundamental building blocks for extruded graphite are fine graphite powder and a binding agent, often pitch or another suitable binder. These components are carefully blended together to create a homogeneous mixture ready for shaping.
The Extrusion Phase
The core shaping step is extrusion. This involves:
- Taking the blended graphite powder and binder mixture.
- Pressing this mixture through a die.
- Applying pressure during the pressing process to form the desired shape.
This step is analogous to squeezing toothpaste from a tube, where the die dictates the cross-sectional form of the material being extruded.
Post-Extrusion Processing
After being extruded into the initial shape, the material undergoes a series of crucial thermal treatments to transform it into dense, graphitized carbon:
- Firing: The initial extruded shape is fired to carbonize the binder, giving the material structural integrity.
- Impregnation: Often, the material is then impregnated with pitch or a similar substance under pressure to fill pores and increase density.
- Second Firing: The impregnated material is fired again to carbonize the impregnant.
- Graphitization: The final and most critical step is graphitization. The material is heated to extremely high temperatures, typically 2000°C, converting the amorphous carbon structure into crystalline graphite.
Characteristic Grain Size
A distinguishing feature of extruded graphite, compared to Iso-graphite (Isostatically pressed graphite), is its grain size. The extruded graphite grain size is about 10 [times] larger than Iso-graphite.
This controlled process of blending, shaping by extrusion, and rigorous heat treatments results in a final product with specific mechanical, thermal, and electrical properties suitable for diverse applications.
