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Today, let’s take a look at common accidents involving medium-frequency furnace bodies, such as furnace leakage and furnace penetration. If an accident occurs and no measures are taken, it could lead to the rupture of the coil’s copper tubing, causing molten iron to come into contact with the coolant and resulting in an explosion. Next, let’s examine the causes of furnace penetration and water leakage in medium-frequency induction furnaces:

One, Build a furnace Quality factors of the materials used: Generally, quartz-based acidic furnace linings are employed. The quartz sand and quartz powder should have a silicon content of at least 99.5%, exhibit oily crystals, be transparent, and free from impurities. Typically, high-purity quartz sand produced by Xingchen Refractory Materials Co., Ltd. of Yima City, Henan Province, is used (with a silicon content of 99.85%, a hardness of 8, a density of 2.65, and a refractoriness of 1850°C).

II. Factors Related to Binders Used in Furnace Construction: Traditionally, boracic acid has been the common binder used in furnace construction. Boracic acid has both advantages and disadvantages: its advantage is that it bonds quickly at low temperatures—typically starting to bond at 600–700 degrees Celsius. However, its disadvantage is that it cannot withstand high temperatures or abrasive conditions; under high-temperature conditions, the lower part of the furnace wall may experience “scouring,” significantly reducing the number of usable furnace cycles. It is recommended to use boron anhydride instead of boracic acid as a binder, since boron anhydride boasts characteristics such as high-temperature bonding, a high melting point, excellent resistance to high temperatures, and superior resistance to abrasion.

3. Factors Affecting the Proportion of Materials Used in Furnace Construction: Typically, users prepare the mixture themselves. During the mixing process, workers often fail to follow the correct proportions, resulting in an uneven furnace lining with insufficient density. This leads to a shorter lining lifespan—generally around 40 to 50 furnace cycles. It is recommended to use pre-mixed furnace lining materials supplied by professional manufacturers. These materials feature consistent proportions, uniform mixing, and high density, significantly extending the lining’s service life by 1 to 2 times compared to furnace linings mixed manually.

4. Site factors affecting the preparation of furnace lining materials: When users prepare the lining materials themselves on a regular basis, they often lack a dedicated preparation area. As a result, foreign objects such as iron filings and iron pellets easily get mixed into the lining materials during the preparation process, significantly reducing the quality and yield of furnace batches. We recommend using furnace lining materials produced by manufacturers specializing in their production. Features: These manufacturers have professional production workshops free from contaminants such as iron filings and iron pellets.

5. Raw Material Factors: At this stage, raw materials are in short supply and prices are rising. To cut costs, some enterprises have been purchasing raw materials—including iron beans, iron scrap, and washed materials—at low prices. These materials often contain impurities that severely erode furnace linings, significantly shortening their service life.

6. Internal factors related to the furnace charge in medium-frequency induction furnaces: The furnace charge for a medium-frequency induction furnace consists of a combination of furnace charge material and an induction coil. The furnace shell is divided into left and right sections, which are connected by eight stainless steel screws and several asbestos gaskets. During operation, these eight stainless steel screws must remain tightly fastened, and the asbestos gaskets must not be missing. If any of the screws become loose, the furnace shell will twist back and forth when molten iron is tapped, causing the induction coil to twist as well. This can loosen the furnace lining, leading to cracks and ultimately allowing molten iron to leak through the furnace. Solution: Replace the asbestos gaskets and tighten all eight screws.

7. Induction Coil Factors: The induction coil is made by winding a copper tube into several coils, with each coil containing 5 to 8 copper screws connected by insulating bakelite. During operation, it is crucial that no screws are missing from the copper coils. Once screws are missing, the induction coil will generate electromagnetic vibration forces that continuously strike the furnace lining material, causing it to loosen and develop cracks, ultimately leading to molten iron leaking through the furnace wall.

8. Insulating Bakelite Components: The insulating bakelite is positioned between the turns of the induction coil and serves as a support structure. When molten iron is tapped from the furnace, the insulating bakelite bears the weight of the entire induction coil, the furnace lining material, and the molten iron itself. Once the insulating bakelite can no longer support the accumulated weight, it will bend, causing the furnace lining material to loosen. Cracks typically appear at the junction between the rear lower part of the furnace wall and the furnace bottom, leading to leakage of molten iron and eventually resulting in the phenomenon known as “furnace breakthrough.” Solution: Each insulating bakelite should be constructed using refractory bricks that are tightly bonded to the furnace shell, thereby integrating the furnace shell with the induction coil and significantly enhancing its structural integrity. Induction coil Its stability, to increase the number of furnace charges for which the lining material can be used.

9. Gap Factor Between the Furnace Shell and the Induction Coil: Most medium-frequency induction furnaces used by standard manufacturers come in capacities of 0.5 ton, 0.75 ton, 1 ton, 1.5 ton, 2 tons, 3 tons, and so forth. However, some manufacturers, in an effort to increase production capacity, have enlarged the induction coils—from 0.5 ton to 0.75 ton, or from 0.75 ton to 1 ton—thus reducing the gap between the induction coil and the furnace shell. During the melting process, this reduced gap creates a stronger magnetic field source between the induction coil and the furnace shell, resulting in increased consumption of refractory materials and higher energy costs. Solution: Replace the furnace with a standard medium-frequency induction furnace (the typical gap between the induction coil and the furnace shell is 250 mm to 300 mm).

Ten, Medium-frequency electric furnace Factors affecting furnace lining thickness: The standard thickness of a furnace wall is between 90mm and 120mm, while the furnace bottom typically has a thickness of 200mm to 280mm. However, some manufacturers, in order to increase production capacity, have enlarged the furnace chamber, thereby reducing the furnace wall thickness to between 40mm and 70mm and the furnace bottom thickness to between 150mm and 200mm. This practice is undesirable; only by constructing the furnace according to the standard wall thickness can stable, high-yield operation be achieved.