Baking of self-baking electrodes
In the smelting process, with the consumption and lowering of the electrodes, it is necessary to continuously add electrode paste and continuously extend the electrode barrel from the upper part. In this process, the height of the paste column must be controlled well to fire a good quality sintered electrode. Generally, the height of the paste column is 4-5 times the electrode diameter. If the paste column is too high, the thick and fine particles in the electrode paste are prone to delamination. If the paste column is too low, it is difficult to obtain a dense electrode due to the low pressure of the paste column and the small filling ability. .
The self-baking electrode baking process can be roughly divided into the following stages according to the baking temperature and position:
1. Softening section: It rises from room temperature to 200 after heating. C. At this time, the electrode paste is all softened into a fluid state, and a small amount of yellow smoke is emitted;
2. Volatile section: the temperature reaches 200~600. At C, the electrode paste has been fully melted to fill the electrode paste and volatilized, and the electrode paste gradually thickens. Close to the upper part of the copper tile, the external temperature is lower than the center temperature due to the cooling effect of the copper tile, and the temperature rise is kept slower, so that the volatile matter of the electrode can be fully discharged. This stage is the key stage of electrode sintering, especially the lower half of the volatilization section is at the inner moon 3/5 of the copper tile. It happens to have a certain degree of plasticity on the outside and the center begins to coke, so it can conduct a small amount of electricity, and it can also make the electrode and the copper tile. Good contact.
3. Sintering section: At this stage, the electrode paste has been moved to the lower 2/5 of the copper tile, and the temperature has risen to 600~800. C. The electrode paste is coked, and the last small amount of volatiles is discharged and hardened. At this time, the current density is large, and the radiant heat at the furnace mouth also increases, and the center of the electrode and the outside temperature gradually reach the same level. When the electrode comes out of the copper tile, it is a hard electrode with good conductivity, and then it is further heated on the material surface. , Undergoes partial graphitization transformation, after entering the material surface, graphitization, the electrode with low resistance is carried out.