1. Conductivity, volatilization, precipitation
The electrode paste does not conduct electricity at low temperatures. As the temperature increases, the conductivity of the electrode paste decreases sharply, and drops sharply at 700°C (about 30 times). When heated to 900°C, the rate of decrease becomes slower. Therefore, the self-baking electrode carbon block fired at 700°C is characterized by high electrical resistance. When there is an electrode shell, the electrode paste fired at 700°C for a thousand is actually not conductive, and the entire current load is conducted through the electrode shell.
2. Electrode paste volatilizes
The sintered paste or semi-liquid electrode paste on the upper part of the electrode is impermeable to air. In the case of an integrally welded electrode shell, the volatiles in the course of the adhesive coking process are filtered when passing through the heated part of the electrode with pores, and thermally decomposed at this time. The amount of volatile matter leads to the difference in the porosity of the fired electrode, which is related to the fluidity of the electrode paste. The fluidity is related to the quantity and variety composition of the binder, and the particle size composition of the fixed carbon part (normal calcined coal, electric calcined coal, coke, graphite, graphite crushed, etc.).
3. Precipitation of electrode paste
The sinking of large particles of wrought coal and coke causes uneven particle size distribution of the electrode paste over the entire height of the firing area. Related to the composition of the formula, precipitation reduces the mechanical strength and resistance of the electrode, which can easily lead to hard fracture. Under the condition of stable composition, it can be achieved by controlling the height of the liquid paste column in the electrode, adding graphite powder in the electrode shell and blowing the electrode (temperature control).