The structure design of the induction furnace is the key to its performance and safety. Different furnace types, material selection and the application of refractory materials directly affect the melting efficiency, service life and operational safety of the induction furnace.
1. Tilting induction furnace
The tilting induction furnace is the most widely used furnace type at present. Its biggest feature is that the furnace body can be tilted to facilitate the tapping of steel water or the dumping of slag.
Structural features
Каркас печи: Usually built with high-strength steel structure (such as steel section, steel plate welding), with sufficient strength and rigidity to support the furnace body and withstand the load during tipping. There is usually a cooling water channel inside the frame to cool the coil and the furnace body.
Индукционная катушка: It is the core component of the induction furnace, generally wound by a high-conductivity copper tube (or square copper tube). Cooling water is passed through the copper tube to take away the heat generated when the coil is energized. The outer layer of the coil is usually coated with insulating material to prevent short circuit and leakage.
Furnace lining (рефрактерный материал): This is the part that is in direct contact with the high-temperature molten metal and is also the part of the furnace that wears out the fastest. The lining material is selected according to the type of smelting metal and the capacity of the furnace. The lining is usually composed of the furnace bottom, furnace wall and furnace mouth, and is compacted or poured on the inside of the induction coil.
Tipping mechanism: It is mainly composed of hydraulic cylinders, hydraulic stations and related control systems. The hydraulic cylinder drives the furnace body to tilt around the axis to achieve discharge. For safety, there are usually tilting limit and emergency stop functions.
Система охлаждения: Water cooling is usually used to cool the induction coil, furnace shell (some furnace types) and other parts that need to be cooled. The cooling water is usually softened and equipped with a cooling tower or chiller for circulation.
Lead and water head: The components that connect the induction coil to the power supply and cooling water pipelines need to have good insulation and sealing properties.
Выбор материала
Каркас печи: plain carbon steel, alloy steel, и т. д..
Индукционная катушка: high-purity copper (or square copper tube).
Furnace lining (рефрактерный материал):
- Acidic lining: The main component is quartz sand (SiO2), which is suitable for smelting cast iron and ordinary carbon steel, and has a low cost.
- Neutral lining: The main component is corundum (Al2O3) or zircon (ZrSiO4), which is suitable for smelting stainless steel and alloy steel, with good acid and alkali resistance and relatively long service life.
- Alkaline lining: The main component is magnesium oxide (MgO) or magnesium aluminum spinel, which is suitable for smelting high manganese steel, high alloy steel and other metals that are highly corrosive to the furnace lining. It has the best high temperature resistance and corrosion resistance, but the cost is high.
Insulating materials: Such as asbestos board (now mostly environmentally friendly alternatives), aluminum silicate fiber, и т. д., are used between the induction coil and the furnace lining to play a role in insulation and buffering.
2. Fixed induction furnace
The furnace body of the fixed induction furnace cannot be overturned. It is usually used in occasions with large smelting volume and siphon or bottom discharge, or as a refining furnace or insulation furnace.
Structural features
Каркас печи: Similar to the tilting type, but since there is no need to tilt, its base design may be simpler or directly fixed to the ground.
Индукционная катушка: Basically the same as the tilting furnace.
Furnace lining: Same as the tilting furnace, but since there is no tilting action, the overall stability requirements of the furnace lining may be higher.
Discharging method:
- Siphon discharging: Through external pressurization or internal vacuum, the liquid metal is drawn out from the furnace mouth or special discharging port by the siphon principle.
- Bottom discharging: There is a discharging port at the bottom of the furnace body, and the discharging is controlled by a stopper rod or a slide mechanism. This method is more common in refining furnaces and some large smelting furnaces.
Система охлаждения: Same as the tilting furnace.
Выбор материала
The material selection is basically the same as that of the tilting furnace, but in the fixed furnace with bottom discharging, the bottom refractory material and the discharging mechanism have higher requirements for high temperature resistance and corrosion resistance.
3. Application and selection of refractory materials
Refractory materials are the core components of the induction furnace body, which directly affect the life of the furnace and the smelting cost.
Application parts
Furnace bottom: Bear the heavy pressure and high temperature of the molten metal, and require sufficient strength and compressive creep resistance.
Furnace wall: Directly in contact with the molten metal, bear the high temperature and erosion of the molten metal, and require good erosion resistance, thermal shock resistance and wear resistance.
Furnace mouth: Bear high temperature and thermal shock, as well as wear during feeding and slag discharge, and require good wear resistance and thermal shock resistance.
Selection basis
Smelting metal types:
- Чугун, ordinary carbon steel: Commonly used acidic furnace lining (quartz sand), good economy.
- Stainless steel, alloy steel: Commonly used neutral furnace lining (corundum, zircon), good erosion resistance.
- High manganese steel, high alloy steel: Commonly used alkaline furnace lining (магнезия), best high temperature resistance and erosion resistance.
Melting temperature: Different refractory materials have their maximum use temperature, which needs to be selected according to the maximum temperature of the smelting metal.
Furnace capacity and working system: Large-capacity furnaces and continuous working furnaces have higher requirements for refractory materials.
Cost: Select economical and applicable materials on the premise of meeting the use requirements.
Construction process: Refractory materials are in the form of dry ramming materials, castables, prefabricated parts, и т. д., which need to be selected according to the furnace structure and construction conditions.
Construction and maintenance of furnace lining
Knotting (ramming): Dry ramming materials must be knotted strictly in accordance with process requirements to ensure density and uniformity.
Sintering (baking furnace): The new furnace lining must undergo a strict baking and sintering process before use to form a dense sintering layer to improve strength and service life.
Daily maintenance: Regularly check the wear of the furnace lining and repair it in time to avoid “furnace penetration” accidents.
In short, the design of the furnace structure of the индукционная печь is a complex process, which requires comprehensive consideration of multiple factors such as smelting process requirements, затраты на оборудование, operation and maintenance, and safety. The furnace type, material selection and reasonable application of refractory materials are the key to ensure the efficient and safe operation of the induction furnace.
