1. Bulk density and porosity
The volume density and porosity of the electrode paste baked sample are important technical indicators for whether the particle size composition of the reaction electrode paste aggregate is reasonable, and whether the amount of asphalt is reasonable.
2. Mechanical properties
The electrode must have sufficient strength, and must be able to adapt to the stress shock generated during the normal operation of the furnace. For most commercial electrode pastes, there is a contradiction between the strength and the ability to adapt to stress shocks, so a proper balance must be maintained between the two.
The index of reaction strength is compressive strength, flexural strength and tensile strength; the technical index of reaction resistance to thermal shock is elastic modulus. A mathematical model is established for the self-baking electrode, and the mathematical model prediction shows that for the electrode paste with low elastic modulus, the moderate flexural strength 3MPA can resist the impact of the fully and safely amplified thermal stress.
In order to obtain an electrode with less brittleness and better adaptability, a low Young’s modulus is ideal, and the optimal range is 2-4 GPA.
In the firing area, the electrode paste should have sufficient conductivity to be able to conduct electrical energy from the copper tile to the electrode end. After firing, the resistivity value of the electrode paste must be at least 100μΩ·m to ensure the normal conduction of current. Large-scale submerged arc furnaces require the electrical resistivity of the electrode paste to be less than 65μΩ·m.
4. Segregation index
After the vertical cylindrical electrode paste is fired, the density of the top and bottom is different. This difference is expressed as a percentage, which is the segregation index. The segregation index of a good electrode paste should be less than 5%.
5. Baking shrinkage
Between 500-900°C, the electrode paste may still shrink, which is basically related to the type of asphalt and the amount of asphalt. Experience has shown that the firing shrinkage of the electrode paste should not be too large. When it is too large, the fired electrode will crack from the ribs, and the electrode ends will fall off. Generally, the firing shrinkage of the electrode paste cannot be greater than 1%.
6. Thermal conductivity
The electrode paste used in foreign ferroalloy furnaces requires the thermal conductivity to be tested. This is because the thermal conductivity is related to the sintering speed of the electrode paste. The greater the thermal conductivity, the easier the electrode paste will be sintered.
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