Melting Furnace : Iron Induction Furnace

Iron induction furnace is an electric furnace that uses the induction electrothermal effect of the material to heat or melt the material. It is mainly used for smelting and heat preservation of cast iron, and heat preservation of molten iron.

Structure

The furnace body of the iron induction furnace is composed of four parts: the furnace shell, the induction coil, the furnace lining, and the tilting furnace reduction box.

The furnace shell is made of non-magnetic material;

The induction coil is a helical cylinder made of a rectangular hollow tube, and cooling water is passed through the tube during smelting. Coil lead-out copper bars are connected with water-cooled cables;

The furnace lining is close to the induction coil and is made of quartz sand and sintered. The tilting of the furnace body is directly rotated by the tilting reducer.

The tilting furnace reducer is a two-stage turbine variable speed, with good self-locking performance and stable and reliable rotation. When there is an emergency power failure, it is necessary to stop the work and turn the furnace to avoid danger.

The control of the tilting gearbox motors of the two furnace bodies can be selected through the furnace selection switch. The switch box with four-core rubber wires allows the operator to stand at a suitable position to control the tilting and resetting of the furnace body.

Tilting Way of Furnace Body

In addition to the rotary motion of the furnace body around its axis, the iron induction furnace also includes the tilting motion of the furnace body axis in order to meet the requirements of feeding, pouring out slag liquid, and repairing the furnace. Although the tilting motion of the furnace body can be adopted in many ways, hydraulic cylinders are more common.

There are three ways for the hydraulic cylinder to realize the tilting of the furnace body, and their respective characteristics and application conditions are as follows:

(a) Tilt the furnace body with a vertical hydraulic cylinder arranged under the furnace body.

This structure is beneficial for maintenance personnel to easily access the furnace body and facilitate the maintenance of the furnace body;

The taphole can be arranged on the side of the middle section of the furnace body, or on the cone of the end face of the furnace body. However, the depth of the pit required by the hydraulic cylinder is relatively large, and the foundation construction cost is relatively high. At the same time, it may involve the impact of groundwater on the pit. At the same time, the stroke of the hydraulic cylinder is large, because the distance between the tilting axis and the center of gravity of the furnace is relatively large, the pressure of the hydraulic cylinder is high, the cost of the hydraulic station is high, and the power consumption is large.

(b) Tilt the furnace body with a hydraulic cylinder arranged under the furnace body and the axis is horizontal. The advantages and disadvantages are similar to the structure (a).

Due to the reasons of cost and power consumption, the tilting structure of the furnace body with vertical or horizontal oil cylinders under the furnace body is rarely seen.

(c) The furnace body is tilted by using two hydraulic cylinders arranged on both sides of the furnace body, no deep pit is required, and because the tilting axis is close to the center of gravity of the furnace, the tilting moment is small, and the manufacturing cost of the hydraulic cylinder and hydraulic station Low, low power consumption.

But this structure has limited the opening position of the taphole, and the taphole can only be opened at the two ends of the furnace body. The tilting structure of the furnace body mostly adopts this form

Melting Process & Superheating Of Molten Iron

The melting process of the iron induction furnace includes three stages: 

furnace material melting, composition homogenization, and molten iron superheating, which are described as follows:

(1) Furnace charge melting stage.

The charge first changes from a solid state to a soft plastic state in the iron melting furnace. After the charge is added into the furnace, in order to protect the furnace lining, the furnace body first rotates intermittently and slowly in both directions. Under the action of mechanical force and heat, the large metal charge is gradually decomposed into small blocks. When the temperature in the furnace rises to the melting point of the metal, the one-way continuous rotation of the furnace body improves the heat transfer effect between the furnace body and the charge.

(2) Component homogenization stage.

The FeO and slagging materials (sand and limestone) formed in the melting stage first form slag, which covers and protects the molten metal. The charge changes from a plastic state to a liquid, the alloying elements begin to dissolve into the molten iron, and the carbon in the recarburizer begins to dissolve into the molten iron. At this stage, the furnace body continues to rotate in one direction, which promotes the homogenization of the molten iron composition, and elements such as carbon, silicon, and manganese are quickly dissolved into the molten iron.

(3) The superheating stage of molten iron.

The molten iron is superheated to the tapping temperature, and the carbon is completely dissolved in the molten iron. The slag and undissolved recarburizer cover the molten iron, and the molten iron is superheated by the heat conducted by the lining to reach the tapping temperature.

The principle of overheating of molten iron in an iron melting furnace is the same as that of other industrial furnaces. The temperature of the furnace top lining is the highest, and the heat stored in the furnace lining is the most. During the rotation process of the furnace body, the heat accumulated in the top furnace lining is continuously brought into the molten iron to achieve the purpose of superheating the molten iron.

The application of induction furnace has brought cast iron production into a new stage, and intermediate frequency induction furnace has developed rapidly due to its advantages of high thermal and electrical efficiency, short melting time, low power consumption, small footprint, low investment and easy implementation of process automation. The adoption of the static frequency converter presents a new trend in its application in cast iron production.

The above is the sharing about the iron induction furnace. Welcome to continue to follow my blog to learn more about induction furnaces, EAF, LF, SAF and other melting furnaces.

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