Luoyang Judian Metal Hot Processing Equipment Co., LTD is mainly engaged in the manufacture of complete sets of equipment in the metal thermal processing industry and the integration of the entire production line.
Furnace Body Structure of Medium Frequency Induction Furnaces
1. Furnace Body Structure of Medium Frequency Induction Furnaces
Medium Frequency Induction Furnaces
The furnace body structure of a medium frequency induction furnace is basically the same as that of a power frequency induction furnace. The furnace body consists of the furnace frame, furnace body, including frame type and cylindrical shell type, furnace cover, tilting mechanism, cooling water system, and power input system.
Figure 2-19 shows the furnace body and hydraulic tilting device of a 150 kg medium frequency induction furnace. Figure 2-20 shows the furnace body and hydraulic tilting device of a 500 kg medium frequency induction furnace.
2Figure 2-20: 500 kg Medium Frequency Induction Furnace
The main structural difference between a medium frequency induction furnace and a power frequency induction furnace lies in the relative position of the crucible and the inductor, as well as the cross-sectional size of the inductor.
Figure 2-21 shows the relative positions of the inductor and liquid metal in medium frequency and power frequency induction furnaces. It can be seen from the figure that the liquid metal in a medium frequency induction furnace is usually completely surrounded by the inductor, while in a power frequency induction furnace, the metal liquid level is higher than the inductor.
This arrangement is used to reduce the stirring effect of electrodynamic force in the power frequency furnace. Since the electrodynamic force of a power frequency furnace is greater than that of a medium frequency furnace, the liquid column height must be increased to reduce the hump height of the liquid surface and weaken the scouring effect of molten steel through gravity.
Figure 2-21: Relative Positions of the Inductor and Liquid Metal in Induction Furnaces
The relationship between the inductor height H and the liquid column height HL is as follows:
Medium Frequency Induction Furnace
H ≈ (1.1–1.3)HL
Power Frequency Induction Furnace
H ≈ (0.8–0.9)HL
In summary, the liquid column height of a medium frequency induction furnace is 1–2 turns lower than the inductor, while that of a power frequency induction furnace is 1–2 turns higher than the inductor.
In terms of the cross-sectional size of the inductor, the tube wall used for a medium frequency inductor is thin. This is because the skin effect of current is strengthened as the frequency increases, and because the terminal voltage of the medium frequency inductor is high while the current in the oscillating circuit is small.
The cross-sectional dimensions of the medium frequency inductor are shown in Figure 2-22.
Figure 2-22: Cross-Sectional Shapes of Inductors Used in Medium Frequency Induction Furnaces
The structural shape and insulation treatment of the inductor in a medium frequency furnace are the same as those of a power frequency induction furnace.
IV. Tilting Mechanism
The capacity of medium frequency induction furnaces is usually below 10 tons. Most furnaces currently in operation in China are below 1 ton. The tilting mechanisms of small and medium-sized medium frequency induction furnaces mainly include the following four types.
1. Lifting Type Tilting Furnace
This is the oldest tilting method. A crane or a special small hoist is used to lift the lifting rings installed on the furnace body, causing the furnace body to tilt and complete the tilting process. This method has gradually been eliminated.
2. Screw Drive Tilting Mechanism
This mechanism uses a motor to drive the screw lifting device through a reducer, completing the tilting process of the furnace body. This mechanism is only suitable for small furnaces.
The worm gear and worm are installed on the horizontal shaft that rotates the furnace body, and the tilting action is completed by motor drive. A medium frequency induction furnace using this tilting mechanism is shown in Figure 2-24.
Furnaces of about 1 ton can use this mechanism for tilting.
4. Hydraulic Device Tilting Furnace
Using a single-cylinder or double-cylinder hydraulic system to complete furnace tilting is the most widely used method.
