The raw material must be accurately weighed according to the prescribed proportions, with small errors. If the weighing is inaccurate, the condition of the furnace will not be easy to determine, and even waste may occur. The raw materials must be divided into batches in the following order: coke, silica and iron filings. The bulk density of coke is 0.5-0.6 g/cm3, the bulk density of silica is 1.5-1.6 g/cm3, and the bulk density of steel sawdust is 1.8-2.2 g/cm3. The density of raw materials varies greatly. This dosing procedure allows the raw material to be mixed more evenly after it is unloaded from the material pipeline.
Most materials are weighed on a scale, and usually 200 kg or 300 kg of silica is taken for a batch of materials. Only one batch of materials is allowed to be weighed at a time. The prepared raw materials are poured into the hopper and sent to the upper hopper of the furnace through a belt inclined bridge.
After discharging the cast iron, it is necessary to quickly level the surface of the material, accumulate hot materials, and accumulate hot materials during furnace firing. Excessively crushed raw materials should be distributed in the triangular zone and around the electrode, avoiding collision with the electrode, and then covered with new raw materials. According to the raw material requirements, new materials can be directly added to the furnace through the charging tube under the hopper or added to the furnace by the charging machine. Small electric furnaces usually stack the furnace materials on the work platform and add them to the furnace manually. However, no matter which feeding method is used, the raw materials must be completely mixed.
The feed should be even. Silica is reduced by the action of coke. Uneven feeding will result in areas in the furnace with too much or too little reducing agent, which will not only affect the smooth progress of the reduction, but also disrupt the current distribution in the furnace, affect the deep insertion of the electrode, cause an uneven temperature gradient in the furnace and shrinkage of the "crucible". Especially if the cast iron feed surface at the outlet is uneven, the consequences will be more serious.
To ensure that the different raw materials are evenly distributed in the furnace, it is necessary to add them less frequently and frequently to avoid too much or too little silica, and to avoid adding along the tangent to the electrode.