What is the principle of melting metal in a medium frequency electric furnace? What are the advantages and disadvantages of electric furnace melting?
1. The principle of melting metal in a medium frequency electric furnace
Electromagnetic induction generates current
The medium frequency electric furnace is mainly composed of a power supply, an induction coil and a crucible. When the power supply provides a medium frequency alternating current (generally at a frequency of 1000-10000Hz) through the induction coil, an alternating magnetic field is generated around the coil. The metal charge in this magnetic field will generate a closed induced current, also called eddy current, inside it due to electromagnetic induction.
Current generates heat
According to Joule's law, when current passes through a conductor, heat is generated, and the amount of heat is proportional to the square of the current, the resistance of the conductor and the power-on time. Since the metal charge itself has a certain resistance, when the induced current flows in it, a large amount of heat will be generated, causing the metal charge to heat up rapidly until it reaches the melting point and melts.
Skin effect improves efficiency
When the medium frequency current passes through the metal charge, there is also a skin effect, that is, the current will flow concentrated on the metal surface. This causes the surface temperature of the metal to rise rapidly, and the heat is conducted inward, which speeds up the melting speed of the metal as a whole and improves the smelting efficiency. At the same time, this heating method has high thermal efficiency and good temperature control accuracy, and can meet the process requirements of different metal smelting.
The influence of skin effect on metal smelting in medium frequency electric furnace
Positive influence
Improved heating efficiency: The skin effect causes the current to be concentrated on the metal surface, the surface current density is large, and the heat generated is large. The surface temperature of the metal rises rapidly, which speeds up the melting speed of the metal, thereby improving the smelting efficiency of the medium frequency electric furnace.
Accurate temperature control: Since the heat is mainly concentrated on the metal surface, by adjusting the parameters such as the size and frequency of the medium frequency current, the heating temperature of the metal surface can be more accurately controlled, thereby achieving precise control of the temperature of the entire smelting process, which is conducive to ensuring the quality of the smelted metal.
Reduce oxidation loss: The skin effect causes the metal surface to heat up quickly, shortens the exposure time of the metal at high temperature, relatively reduces the chance of oxidation of the metal in contact with air, reduces the oxidation loss of the metal, and improves the recovery rate of the metal.
Negative impact
Reduced utilization of furnace materials: The skin effect causes less heat inside the metal. If the size of the furnace materials is large, the surface may be overheated while the inside is not fully melted, resulting in reduced utilization of furnace materials and increased smelting time and energy consumption.
Increased requirements for equipment: In order to overcome the adverse effects of the skin effect and allow the metal to be fully heated, it is necessary to select appropriate intermediate frequency and power, which puts higher requirements on the equipment performance of the intermediate frequency electric furnace and increases the cost and complexity of the equipment.
2. What are the advantages and disadvantages of smelting metal in an intermediate frequency electric furnace?
Advantages
High heating efficiency: The electromagnetic induction principle is used to generate eddy current heating inside the metal. It is an internal heating method with small heat loss. It can quickly heat the metal to the required temperature and improve smelting efficiency.
Accurate temperature control: By adjusting the parameters of the intermediate frequency power supply, the heating temperature can be accurately controlled to meet the strict temperature requirements of different metal smelting, which is conducive to ensuring product quality.
Clean and environmentally friendly: Compared with traditional fuel heating methods, intermediate frequency electric furnaces do not produce combustion exhaust gas, have no dust emissions, and are environmentally friendly.
Easy to operate: The equipment has a high degree of automation, can realize remote control and monitoring, and is simple to operate, which reduces the intensity of manual labor and improves production safety.
Uniform metal composition: During the smelting process, the electromagnetic stirring effect makes the molten metal evenly mixed, which helps to ensure the uniformity of the metal composition.
Disadvantages
High equipment cost: The manufacture and installation of medium-frequency electric furnaces require a high level of technology and equipment investment, and the initial investment cost is relatively large.
High requirements for furnace charge: The furnace charge is required to have a regular shape and moderate size, otherwise it will affect the electromagnetic induction effect and heating uniformity, and may even cause equipment failure.
Complex maintenance: The equipment involves knowledge in multiple professional fields such as electrical and electronic, and maintenance requires professional technicians, and the maintenance cost is high.
Limited smelting volume: Generally speaking, the single smelting volume of the medium-frequency electric furnace is relatively small, and it may be difficult to meet the needs of large-scale continuous production.
