The working frequency of a medium-frequency induction electric furnace (hereinafter referred to as a “medium-frequency furnace”) ranges from 50 to 2000 Hz, and it is widely utilized for the smelting of both ferrous and non-ferrous metals. Compared to other casting equipment, medium-frequency induction furnaces offer numerous advantages, including high thermal efficiency, short melting times, minimal burn-off of alloying elements, versatility in the types of materials that can be melted, low environmental pollution, and the ability to precisely control the temperature and composition of the molten metal.

These eddy currents exhibit certain properties characteristic of medium-frequency currents—specifically, the flow of the metal’s own free electrons within the resistive metal body generates heat. By employing a three-phase fully controlled bridge rectifier circuit to convert AC power into DC, one can demonstrate this effect: for instance, if a cylindrical metal object is placed inside an induction coil carrying an alternating medium-frequency current—without making direct physical contact with the coil—the surface of the cylinder will heat up to a glowing red, or even melt, even though the coil itself remains relatively cool. Moreover, the rate at which this glowing and melting occurs can be precisely controlled simply by adjusting the frequency and current intensity. If the cylinder is positioned at the exact center of the coil, the temperature distribution across its entire circumference remains uniform; furthermore, the heating and melting processes generate neither harmful gases nor intense light pollution that would adversely affect the environment.

Equipment-Saving Features

Rapid heating speed, high production efficiency, minimal oxidation and decarburization, material and cost savings, and extended mold life.

Since the principle of medium-frequency induction heating is electromagnetic induction, the heat is generated internally within the workpiece itself. Consequently, an ordinary worker can commence continuous forging operations just ten minutes after starting their shift, eliminating the need for specialized furnace operators to perform preliminary furnace preheating and sealing tasks. Due to the rapid heating rate inherent in this method, oxidation is minimized; the oxidation loss for medium-frequency heated forgings is merely 0.5%, whereas gas-fired furnaces incur a loss of 2%, and coal-fired furnaces reach 3%. This medium-frequency heating process is highly material-efficient, saving at least 20 to 50 kilograms of raw steel material per ton of forgings compared to coal-fired furnaces. Its material utilization rate can reach as high as 95%. Furthermore, because this heating method ensures uniform heating—resulting in a negligible temperature difference between the core and the surface—it significantly extends the lifespan of forging dies. Additionally, the surface roughness of the forgings is kept below 50 µm. The process is also energy-efficient: medium-frequency heating saves 31.5% to 54.3% more energy than heavy oil heating, and 5% to 40% more than gas heating. Finally, the superior heating quality reduces the scrap rate by 1.5%, boosts production efficiency by 10% to 30%, and extends die life by 10% to 15%.

Environmental Features of the Equipment

Compared to coal-fired furnaces, induction heating furnaces spare workers from the scorching heat and smoke typically associated with coal furnaces under the blazing sun. Furthermore, they fully meet the various regulatory standards set by environmental protection agencies, while simultaneously enhancing the company’s external image and aligning with the future trends of the forging industry. Among all types of electric furnaces, induction heating represents the most energy-efficient method; heating one ton of forged material from room temperature to 1100°C consumes less than 360 kilowatt-hours of electricity.

Uniform heating, minimal temperature difference between the core and surface, and high temperature control precision.

In induction heating, heat is generated internally within the workpiece itself, resulting in uniform heating and a minimal temperature difference between the core and the surface. By utilizing a temperature control system, precise temperature regulation can be achieved, thereby enhancing product quality and yield rates.

Other Features

Induction heating systems—characterized by their compact size, light weight, high efficiency, superior thermal processing quality, and environmental friendliness—are rapidly displacing coal-fired, gas-fired, oil-fired, and conventional resistance furnaces, establishing themselves as the new generation of metal heating equipment.

The induction furnace serves as a core component in casting, forging, and heat treatment workshops; its operational stability, reliability, and safety are the critical guarantees for the smooth and consistent functioning of automated production lines in these sectors. The induction furnace holds immense promise within the field of thermal processing, particularly in the manufacture of pre-forging heating furnaces and through-heating furnaces, as well as in induction heating applications for processes such as through-heating, rolling, forging, pipe bending, heat treatment (quenching), and welding.

The medium-frequency three-phase stirring furnace operates primarily through a high-precision digital control system that dynamically alters the direction of the electromagnetic field. This generates an electromagnetic force that drives the molten metal to churn both upward and downward, thereby homogenizing the various metallic constituents within the melt and effectively achieving a uniform dispersion.

Precautions

Before starting the furnace, thoroughly inspect the electrical equipment, water cooling system, induction coil copper tubing, and other components to ensure they are in good working order; operation is strictly prohibited if any defects are found.
If the furnace lining suffers erosion exceeding prescribed limits, it must be repaired immediately; melting operations within a crucible that has sustained excessive erosion are strictly prohibited.
The energizing of the power supply and the starting of the furnace must be the responsibility of a designated individual. Once the power is on, strictly avoid touching the induction coil or power cables. The operator on duty must not leave their post without authorization and must remain vigilant regarding the condition of the induction coil and the exterior of the crucible.
When charging the furnace, inspect the charge material to ensure it does not contain any flammable, explosive, or other hazardous contaminants; if such items are present, remove them immediately. The direct addition of cold or wet materials into the molten steel bath is strictly prohibited. Once the molten metal level reaches the upper section of the furnace, the addition of large pieces of charge material is prohibited to prevent the formation of a solidified crust on the surface.
When patching the furnace lining or ramming a new crucible, strictly avoid mixing in iron filings or iron oxides; the rammed crucible lining must be dense and compact.
The casting area and the pit in front of the furnace must be kept free of obstructions and standing water to prevent explosions should molten steel spill onto the ground.
Ladles must not be filled beyond their capacity. When pouring using a hand-carried ladle, two operators must coordinate their movements precisely and walk steadily; sudden starts or stops are prohibited. After casting, any residual molten steel must be poured into a designated disposal area; indiscriminate dumping is strictly prohibited.
The intermediate-frequency generator room must be kept clean and tidy. Bringing flammable, explosive, or other miscellaneous items into the room is strictly prohibited, and smoking is forbidden within the premises.