1. Why should the extruded green body be cooled immediately?

The green body just out of the molding machine is composed of plastic paste, and the binder coal tar pitch is in a dense state, and its shape and size are not stable yet. Therefore, immediately after the green body leaves the molding machine, it should be soaked in cold water for cooling, so that the temperature of the green body can drop below the softening point of asphalt. The asphalt cools and solidifies into a solid state, stabilizing the green body so it does not bend and deform. Graphite electrode is widely used in electric furnace steelmaking with coal tar pitch as a binder. The temperature of the cooling water should not be higher than 30ºC. Generally, large-size green bodies are soaked in cold water for 3 to 5 hours, and small and medium-sized green bodies can be completely cooled after soaking in 1-3 hours. The cooling time of the extruded green body in summer is longer.

2. How is the uneven density of the green body produced?

①. Carbon paste is thermoplastic and has a certain degree of viscoelasticity. The ability to transmit pressure is not as good as liquid, and the pressure in the paste shows a decreasing trend, resulting in an uneven density of the green body.

②. The friction between the paste and the mold wall and the conflict between the paste particles lead to pressure loss, making the pressure distribution uneven and resulting in uneven density.

③. There are differences in the orientation of the anisometric particles in the paste on the surface and inside of the green body, which affects the uniformity of the density of the green body.