Extrusion molding is a forming method with high production efficiency. The axial density distribution of the extruded products is relatively uniform, which is suitable for the production of long-line bars or pipes, such as electrodes for steel-making, various carbon rods, carbon plates for electrolysis, impermeable graphite plates for chemical equipment, graphite tubes, and graphite masonry for nuclear reactors.

The extrusion process can be divided into two stages. The first stage is compaction, also known as preloading stage. In this stage, after the paste is added into the feeding chamber, a baffle plate is added between the extrusion nozzle and the feeding cylinder to pressurize, so as to force the paste to discharge gas, achieve compactness, and make the paste move forward at the same time. In this process, the paste can be seen as a stable flow, and the material layers are basically parallel flow. The second stage is extrusion. After the paste is pre pressed, remove the pre pressure, remove the baffle and re pressurize. The essence of extrusion is to make the paste plastic. In the extrusion process, when the paste enters into the extrusion nozzle with circular arc deformation under pressure, the flow velocity of the periphery is slower than that of the center due to the friction between the paste and the extrusion nozzle wall. The faster flowing inner paste produces a force on the slower flowing outer paste due to internal friction. In turn, the outer paste also gives the inner paste a resistance. Therefore, laminar flow structure and internal stress are produced in the extruded block. Finally, the paste enters the linear deformation part and is extruded.

Extrusion molding is generally divided into five processes, namely cooling, charging, preloading, extrusion and cooling of raw products.