JPH0131918Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a high-frequency induction electric furnace for melting metal materials for casting.

(Prior art) Conventional high-frequency induction electric furnaces for casting
As shown in the figure, a heating coil 2 is wound around the outer periphery of a container-shaped electric furnace main body 1 with an open top end, and is heated by electric power from a power source 3. Electric furnace body 1
is constructed of fire-resistant material. A high frequency generator such as a thyristor inverter is used as the power source 3, and the generated frequency can be automatically changed even in response to large changes in load impedance to supply stable power. Inside the electric furnace main body 1, a metal material for casting is melted into a molten metal 4.

(Problem that the invention aims to solve) However, although electric power is efficiently supplied to this type of electric furnace when the temperature is rising, the molten metal is heated to the part close to the surface even when it is kept warm, so the overall molten metal is heated. Stirring is continued. As a result, during heat retention, components such as C, Si, and Cr in the molten metal, which tend to react with oxygen in the air, flow to the surface of the molten metal and their oxidation progresses.

Furthermore, since the input power is distributed over the entire molten metal even during heat retention, there was a drawback that when the molten metal was pumped out, it was not possible to obtain sufficient agitation to move the slag on the surface of the molten metal to the vicinity of the electric furnace.

Furthermore, as the amount of molten metal in the electric furnace decreases as the molten metal is pumped out, the electric power efficiency decreases and it becomes difficult to control the holding temperature.

In order to eliminate these drawbacks, an electric furnace with the heating coil positioned differently as shown in Figure 4 or Figure 5 can be considered, but the electric furnace shown in Figure 4 holds molten metal. Although the stirring of is suppressed,
When pumping out molten metal, we cannot expect the stirring power to move the slag around the electric furnace. Also, when the temperature of the electric furnace increases,
Efficient power application cannot be expected either. Similarly, the electric furnace shown in FIG. 3 cannot overcome the conventional drawbacks.

This idea eliminates the drawbacks of the conventional method, (1) Electric power can be applied efficiently when raising the temperature of molten metal.

(2) When keeping the molten metal warm, the flow of the molten metal components can be suppressed by reducing the amount of stirring near the molten metal surface.

(3) When pumping out molten metal, the stirring near the surface of the molten metal can be increased and the slag can be moved to the vicinity of the electric furnace.

(4) Electric power can be applied efficiently even when the amount of molten metal is low.

The purpose of the present invention is to provide a high frequency induction electric furnace that satisfies each of the above items.

(Means for Solving the Problems) This invention consists of an electric furnace body which is shaped like a container with an open top and holds a metal material for casting inside the electric furnace body, and two wires which are separately wrapped around the upper and lower parts of the electric furnace body. This is a high-frequency induction electric furnace consisting of a heating coil and an electric circuit including a power source that simultaneously and separately supplies power to the heating coil by means of a changeover switch.

(Function) The high-frequency induction electric furnace according to this invention simultaneously heats the entire molten metal using both the upper and lower heating coils during temperature rise. Then, when keeping warm, only the lower heating coil is used, and when pumping the molten metal, only the upper heating coil is used.

(Example) This invention will be described below based on drawings showing examples. FIG. 1 and FIG. 2 are a longitudinal cross-sectional view and a heating coil wiring diagram of a high-frequency induction electric furnace, respectively. Components that are the same as those in the prior art are designated by the same numbers as in FIG. 3, and explanations thereof will be omitted. 5 and 6 are heating coils according to this invention, and the upper heating coil 5 and the lower heating coil 6 are separately wound around the upper and lower parts of the electric furnace main body 1, respectively. Heating coils 5, 6
The power supply circuit is constructed as shown in FIG. 2, and the heating coils 5 and 6 are
simultaneously and separately. The winding directions of the heating coils 5 and 6 are such that magnetic fluxes of the same phase are generated.

The operation of the high frequency induction electric furnace configured as above will be explained. First, when the temperature rises, switch 7 and 8
is closed, and both the upper and lower heating coils 5 and 6 are energized at the same time to raise the temperature. However, when the amount of molten metal 4 is small, only the changeover switch 8 is closed to raise the temperature.

Next, when keeping warm, it is necessary to keep the water level warm by keeping the movement of the hot water quiet, so only the changeover switch 8 is closed and power is applied only to the lower heating coil 6. By doing this, the stirring of the molten metal 4 is suppressed, the molten metal surface becomes calm, and the electric power applied to the lower heating coil 6 keeps the entire molten metal warm.

When pumping out the molten metal 4, the changeover switch 7 is closed and the switch 8 is opened to apply electric power only to the upper heating coil 5. As a result, only the upper part of the molten metal is heated, the molten metal surface rises, the slag floating on the molten metal surface moves to the vicinity of the electric furnace, and clean molten metal 4 can be pumped out from the center.

In the above action, the electric power applied to the molten metal 4 is W, the inner diameter of the molten metal holding part of the electric furnace body 1 is d, the depth of the molten metal 4 is h, the inherent resistance of the molten metal 4 is r, the power source 3
The stirring force P is given by the following formula. That is, P=0.316W/πdh√ For example, considering a simple case, if the applied power is the same and the height of the molten metal is halved, the stirring force P will be doubled from this formula. In other words, according to this idea, slag can be pushed around the electric furnace with twice the stirring force compared to when the temperature is rising. In addition, in the case of a standard electric furnace, the electric power required for keeping warm is about 1/3 of the electric power used for melting, so when keeping warm only with the partial heating coil 6 using this idea, it is possible to use only 2/3 of the stirring power during melting. It will be tripled. However, in this case, the stirring force is generated only in the lower part of the electric furnace, and the influence of the stirring force on the molten metal level is further reduced.

(Effects of the invention) As explained above, this invention is a high-frequency induction electric furnace that is divided into upper and lower parts and has heating coils whose energization is controlled by respective switching switches. Electric power can be applied efficiently for both melting and warming, and when keeping warm, the movement of the surface of the hot water is small, preventing oxidation.
Furthermore, when pumping out the molten metal, the stirring force is increased only in the upper part of the electric furnace, which has the effect of moving the slag on the surface of the molten metal to the periphery of the electric furnace and pumping out clean molten metal. Furthermore, since there is no large stirring of the molten metal during heat retention, there is less consumption of furnace construction materials, which has the effect of extending the life of the electric furnace.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of this invention, FIG. 2 is a wiring diagram of the embodiment of FIG. 1, and FIGS. 3 to 5 are longitudinal sectional views of various conventional electric furnaces. 1... Electric furnace main body, 3... Power supply, 5, 6... Heating coil, 7, 8... Changeover switch.

Claims (1)

[Scope of utility model registration request] An electric furnace body that is shaped like a container with an open top and melts and holds a metal material for casting inside, two heating coils that are separately wound around the upper and lower parts of the electric furnace body, and a changeover switch that allows the heating coils to be simultaneously and A high-frequency induction electric furnace consisting of an electric circuit including a power source that separately supplies power.