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When adding metallic materials into the medium-frequency furnace, their size should be appropriate—specifically, they must not exceed half of the furnace’s static volume. Moreover, the charge material should be added in small batches and multiple times. When introducing larger pieces of material, it’s advisable to first add some smaller-volume materials as a base layer. This approach ensures that the furnace doesn’t get jammed and reduces the impact force exerted by the metallic materials on the furnace bottom and walls.

When a medium-frequency furnace encounters sudden accidents, it will shut down. After the molten iron inside the furnace solidifies, if you wish to restart the furnace, you should be aware that it cannot be reactivated immediately. Therefore, we need to install several steel pipes—each with a diameter of about two millimeters—inside the furnace, typically three to five pipes. This arrangement facilitates the efficient release of gases during the furnace’s restart. Before the solidified iron at the bottom of the furnace melts, the furnace should be gently rocked and tilted by 15 to 30 degrees. Additionally, power should be supplied at a lower heating level than the furnace’s normal operating power. The power must not be increased until the solidified metal has softened. If the temperature rises too rapidly, the thermal expansion of the metal could exceed the furnace’s structural integrity, causing severe stress on the furnace lining and, in extreme cases, even leading to cracks or fractures in the furnace itself.

After the solidified metal has softened, the power can be increased again to around the holding-power level. This continues until the hard crust formed on top of the solidified metal is melted by the liquid metal below, at which point the medium-frequency furnace can be leveled and the temperature can be raised gradually to its normal operating power for melting. Once melted, the molten metal is tapped out of the furnace. The remaining molten iron can be allowed to sit for a short period without compromising its material quality or causing splashing of the slag. Doing so not only speeds up the melting process of the next batch of metal charge but also prevents the charge from directly impacting the bottom of the medium-frequency furnace.

To reduce cracking of the furnace lining caused by repeated rapid heating and cooling, it is crucial to operate the furnace continuously in order to extend its service life. This point has already attracted sufficient attention from many users. If the medium-frequency furnace cannot be used continuously, after one use is completed, metal charge materials should be added into the furnace and the furnace lid should be securely closed. This not only preheats the metal charge materials but also helps prevent cracks in the furnace lining caused by rapid cooling.

When the medium-frequency furnace is running at around 20 tons, all the furnace mouth components should be removed. The purpose is to check whether iron has penetrated through the furnace lining and to verify whether the dry materials in the lining are loose or have gaps. When re-patching the furnace mouth, try to use metal furnace mouth rings of varying heights. Special attention should be paid to ensuring that the joints between new and old sections are thoroughly cleaned. During the next furnace-repair operation, remove material down to just below the previous repair joint, and continue this process sequentially. The furnace spout and furnace mouth are areas that frequently accumulate slag, suffer from erosion, and endure impacts from furnace charge materials; therefore, they require regular maintenance and repairs by qualified professionals.