General technical index requirements for electrode paste
Electrode occupies an important position in submerged arc furnace. The working conditions of the electrode are bad, the current passing through is high, the temperature difference between the two ends is large, and the production is affected by the impact of mechanical, electrical and charge collapse… Mechanical strength, higher electrical resistivity, better thermal shock resistance, oxidation resistance and smaller thermal expansion coefficient. Generally speaking, the quality of electrode paste is controlled by the following five indicators:
1. Ash: Ash is the residue of electrode paste when it is burnt to constant weight at 850℃-870℃. It belongs to inorganic minerals. It has high ash resistivity, poor strength, high power consumption, and large electrode consumption. In the event of a hard breaking accident, the ash content is a very important indicator, and the lower the better.
2. Volatile matter: Volatile matter refers to the mass loss of electrode paste under the condition of heating in isolation of air. Volatile matter is generally low-molecular hydrocarbons. The level of volatile matter has a great influence on the quality of electrode paste.
If the volatility is too high, the electrode sintering speed is slow, the shrinkage rate after sintering is large, the porosity is high, it is easy to oxidize, the strength is low, and it is prone to “soft break” or “hard break” accidents. The volatile content is too low, the electrode sintering speed is fast, the adhesion is not good, the contact resistance between the electrode and the holder is large, and it is prone to “hard break” and electrode “stabbing” accidents. The volatile content of the electrode paste must be strictly controlled within a certain range Inside.
3. Compressive strength: Compressive strength mainly refers to the ultimate compressive load per unit area of the sample after the electrode paste is baked, which is an important mechanical strength index. The electrode is subjected to tension, compression, bending, shearing and other stresses in the submerged arc furnace, and the compressive strength can indirectly reflect other strength values, and it is easy to test. Electrodes with low compressive strength have poor mechanical strength and are prone to “hard break” accidents during use.
4. Resistivity: Resistivity refers to the resistance per unit sample after the electrode paste is fired. Resistivity is a physical quantity that indicates the conductivity of an electrode. The resistivity is small, the electrode resistance is small, and the power consumption is low. For carbon products, there is an inverse relationship between electrical resistivity and thermal conductivity. Therefore, electrical resistivity is not only an electrical index but also a thermal index. The resistivity is low, the thermal conductivity is large, the temperature conductivity is high, the resulting thermal stress is small, and the thermal stability is good. , The electrode is not easy to be broken by rapid cold and heat.
5. Bulk density: Bulk density refers to the mass per unit volume of the sample after the electrode paste is fired. Bulk density is a physical quantity that measures the compactness of the macroscopic structure of the carbon material, and characterizes the tightness and regular arrangement of the particles in the electrode. characteristic. The bulk density is large, the true porosity is small, the denser the electrode, the higher the mechanical strength, the stronger the oxidation resistance, the better the thermal conductivity and thermal shock resistance.