JP4327675B2 - Induction melting furnace heating and stirring method - Google Patents

Description

The present invention relates to a method for heating and stirring molten metal in an induction melting furnace capable of stirring molten metal .

  In general, when an alloy is produced in an induction melting furnace, it is necessary to stir the molten metal to obtain a uniform composition. As a conventional induction melting furnace with controlled stirring, for example, as shown in FIG. 10, two upper and lower coils 2 </ b> A and 2 </ b> B are provided separately on the outer periphery of the melting chamber 1 and connected to a single-phase AC power source 3. Two capacitors 4 and 4 are connected in parallel to each coil 2A and 2B, one capacitor 4 is provided with a switch 5 for adjusting the power factor, and the connection 6 of the upper and lower coils 2A and 2B has an upper portion. There is a switch provided with a switch 7 for cutting off the current to the coil 2B (for example, Patent Document 1).

In this induction melting furnace, during normal melting, if the same voltage V ₁ = V ₂ is applied to the upper and lower coils 2A and 2B and the same voltage V ₁ = V ₂ is applied, as shown by the arrows, the same stirring force is generated in the opposite direction. At the time of agitation, the switch 7 is turned off to cut off the energization of the upper coil 2B as shown in FIG. 11, and when the lower coil 2A is energized, the upper coil 2B becomes a mutual induction resonance circuit and is generated from the lower coil 2A. As shown in FIG. 12, a voltage V ₂ having a phase difference is induced by the magnetic flux. As a result, as shown in FIG. 11, the stirring force acts on the upper part of the molten metal 8 in the melting chamber 1 to stir the molten metal 8.

However, in the conventional induction furnace, upper coil 2B is during agitation, since the mutual induction resonant circuit deenergized, the phase deviates as shown in FIG. 12, the voltage V _2, the voltage of the lower coil 2A V ₁ V ₁ > V ₂ . As a result, the ability to heat the upper molten metal 8 is lowered and the stirring force is reduced. For this reason, when an alloy component having a specific gravity lighter than that of the molten metal is added, there is a problem that the whole cannot be uniformly stirred because the stirring force at the top is weak. Further increasing the voltage V ₁ applied to the lower coil 2A, it becomes smaller the phase difference between the voltage V ₂ of the upper coil 2B, and decreased stirring action eliminates the time difference above and below the stirring and spread the phase difference in the opposite There was a drawback that the voltage ratio was increased and the holding heating temperature and stirring force were not uniform in the vertical direction.
Japanese Patent Publication No.49-305

The present invention improves the above-mentioned problem, and applies a melt heating and stirring method for an induction melting furnace that can efficiently stir the entire furnace at a uniform temperature by applying substantially the same electric power that is out of phase to the upper and lower coils during stirring . It is to provide.

According to a first aspect of the present invention, there is provided a method for heating and stirring a molten metal in an induction melting furnace in which two coils wound up and down in a melting chamber are connected in series, and both ends thereof are connected to both ends of two capacitors connected in series. Are connected to the first terminal of the inverter power supply, and the other connection point is connected to the second terminal of the inverter power supply through the first switch. A second switch is provided between the intermediate point of the two sets of capacitors and a third switch between the second terminal of the inverter power supply and the intermediate point of the two sets of capacitors. The third switch is turned on during normal melting, the first switch and the second switch are turned off to heat by the double voltage method, and the first switch and the second switch are turned on during stirring. Turn off the third switch It is characterized in that it has to be heated to adjust the phase difference between the voltage of the coil.

The method for heating and stirring molten metal in an induction melting furnace according to claim 2 of the present invention is characterized in that in claim 1, at least one of the 22 sets of capacitors is formed by a capacitor whose capacity can be varied. .

The method for heating and stirring molten metal in an induction melting furnace according to claim 3 of the present invention is characterized in that, in claim 1, the first switch and the third switch are formed by one single-pole double-throw switch. Is.

According to the molten metal heating and stirring method of the induction melting furnace according to claim 1 of the present invention, heating is performed by a voltage doubler method using a condenser during normal melting that requires high power by switching a switch, and stirring is performed while maintaining low power. When this is done, the phase difference and voltage of the upper and lower coils are adjusted and heated, so that the upper and lower coils can be energized with a substantially equal voltage and a phase shift of about 90 degrees.

In this way, by providing a phase difference between the upper and lower coils and energizing, the position where the stirring force is generated moves up and down sequentially as time elapses. Even if it is added, it can be uniformly stirred to produce an alloy having a uniform component. Moreover, the stirring force can be easily adjusted by changing the oscillation frequency of the inverter power supply. It is also possible to vary the stirring force by changing the voltage sharing ratio between the upper and lower coils. Further, the circuit configuration is simplified, and a switch having a relatively small capacity can be used.

Further, according to the molten metal heating and stirring method of the induction melting furnace according to claim 2, by forming at least one of the two sets of capacitors with a capacitor whose capacity can be varied, it is optimal according to the type and melting amount of the alloy to be melted. Stirring can be controlled under the following conditions.

According to the molten metal heating and stirring method of the induction melting furnace according to claim 3, since the first switch and the third switch are replaced with one single-pole double-throw switch, the structure can be further simplified. .

Method for heating and stirring molten metal in an induction melting furnace in which the voltage of the upper and lower coils is made substantially equal, the phase difference is deviated by about 90 degrees and energized, and the position where the stirring force is generated as time elapses can be sequentially moved up and down Realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. FIG. 1 shows a basic configuration of an induction melting furnace, in which two coils 2A, 2B wound up and down of a melting chamber 1 are connected in series, and two sets of capacitors 12A, both ends of which are connected in series, 12B is connected to each. The one connection point 15 is connected to a first terminal 11A of the inverter power supply 10, the other connection point 16 is connected to the second terminal 11B of the inverter power source 10 via a first switch SW _1.

Further, the two coils 2A, the midpoint 13 of 2B, the two sets of capacitors 12A, a second switch SW ₂ is provided between the midpoint 14 of the 12B, the second terminal 11B of the inverter power source 10 When the third switch SW ₃ is provided between the midpoint 14 of the two pairs of capacitors 12A, 12B.

In the case of normal melting in the induction melting furnace having the above configuration, when the third switch SW ₃ is turned on and the first switch SW ₁ and the second switch SW ₂ are turned off as shown in FIG. As shown in 2. This is a voltage doubler circuit. When the output voltage of the inverter power supply 10 is V, a voltage of about 2 × V is applied to both the coils 2A and 2B, and a high voltage necessary for melting can be obtained and efficiently and in a short time. Metal can be dissolved.

When the molten metal 8 is formed and the alloy component is added and stirred here, the first switch SW ₁ and the second switch SW ₂ are turned on as shown in FIG. 3, and the third switch SW ₂ is turned on. _{When 3} is turned off, the equivalent circuit is as shown in FIG. V ₁ was in the lower coil 2A is applied from the inverter power source 10 a voltage V in this _state, the voltage of V ₂ is applied to the upper coil 2B. Here, V = V ₁ + V ₂ .

If the inductances of the lower coil 2A and the upper coil 2B are equal to L, and the capacitances of the capacitors 12A and 12B are equal to C, then V ₁ = V ₂ = V / 2, and there is a difference between the two coil voltages. There is no phase shift. However, when the capacitance of the capacitor 12A and 12B respectively C / ^{k 2} and ^{k 2} C, the difference between the resonance angular frequency omega _B of the lower coil 2A and the resonance angular frequency omega _A and upper coil 2B and a capacitor 12B of the capacitor 12A Will occur. Here, k ² is a constant slightly larger than 1, and ω _A = (1 / LC / k ² ) ^1/2 = kω ₀ , ω _B = (1 / Lk ² C) ^1/2 = ω ₀ / k, ω ₀ = (1 / LC) ^1/2 . When the frequency f of the inverter power supply 10 is ω ₀ / 2π, from ω _A > ω ₀ , ω _B <ω ₀ , the LC circuit of the lower coil 2A and the capacitor 12A is inductive, and the LC circuit of the upper coil 2B and the capacitor 12B is It becomes capacitive and a phase difference appears between the voltages of the two LC circuits. This is shown in FIG.

5, the voltage V ₁ of the lower coil 2A, the voltage V ₂ of the upper coil 2B is lower than the power supply voltage V, which is convenient for the purpose of maintaining the holding temperature. Phase difference and amplitude difference will vary depending on the ratio k ² and the inverter power supply frequency f of the mean capacitance of the capacitor 12A and 12B, it is possible to approximately 90 degrees phase difference as shown in FIG. At the time t1, the lower coil 2A is in a peak + feed, and the upper coil 2B is in a zero cross state and is not fed. Further, at time t2, the lower coil 2A and the upper coil 2B cross to be in a feeding state with the same voltage. Further, at time t3, the lower coil 2A is zero-crossed and no power is fed, and the upper coil 2B is in a peak + feeding state.

In this way, the molten metal 8 can be agitated by energizing the upper and lower coils 2A, 2B with a phase difference. That is, at the time t1, only the lower coil 2A is energized as shown in FIG. Stirring force indicated by arrows is generated upward and downward. Next, at time t2, as shown in FIG. 7, the upper and lower coils 2A and 2B are energized at the same time, and the stirring force indicated by the arrows is generated at the upper and lower portions of the molten metal 8, respectively. At time t3, as shown in FIG. 8, only the upper coil 2B is energized, and a stirring force indicated by an arrow is generated in the direction of the center of the upper molten metal. When a negative current flows, the current direction is reversed, but the stirring force is the same.

Therefore, the position where the stirring force is generated moves sequentially up and down over time, so even if an alloy component having a lighter specific gravity than the molten metal or a heavy alloy component is added, the alloy is uniformly stirred and the component is uniform. Can be manufactured. Further, since the voltages of the upper and lower coils 2A and 2B can be made substantially equal, the entire molten metal can be heated uniformly. Moreover, since the frequency can be lowered and the stirring can be carried out strongly, on the contrary, when the frequency is increased, the stirring force becomes weak, so that the stirring force can be easily adjusted. Note that the stirring force can be made different by changing the voltage sharing ratio between the upper and lower coils 2A, 2B. When an alloy component having a specific gravity lower than that of the molten metal is added, only the upper side can be stirred strongly.

The second switch SW ₂ is opposite the direction of provided voltage between both midpoint 13 and 14, the current flowing here may be a small switch since only the difference. Further, the first switch SW ₁ and the third switch SW ₃ are on the power source side of the capacitors 12A and 12B, and can be reduced in size because the flowing current is small.

FIG. 9 shows another embodiment of the present invention. A single pole is provided between the second terminal 11B of the inverter power supply 10, the connection point 16 on the capacitor 12B side, and the intermediate point 14 between the capacitors 12A and 12B. A double-throw switch SW ₄ is provided for switching. That replaced with a first switch SW ₁ and the third switch SW ₃ one single pole double throw switch SW ₄ shown in FIG. 1, can simplify the structure.

In the above embodiment, the capacitors 12A and 12B are shown as having fixed capacities. However, by configuring such that at least one of the capacities can be varied, depending on the type and melting amount of the alloy to be melted. Therefore, stirring can be controlled under optimum conditions.

In the above description, an induction melting furnace that melts in the atmosphere has been described. However, the present invention can also be applied to melting furnaces other than atmospheric conditions such as vacuum and inert gas.

It is a circuit block diagram of the induction melting furnace at the time of the normal melt | dissolution by the Example of this invention. FIG. 2 is an equivalent circuit diagram of FIG. 1. It is a circuit block diagram of the induction melting furnace at the time of stirring. FIG. 4 is an equivalent circuit diagram of FIG. 3. It is a voltage waveform diagram of the upper and lower coils during stirring. It is explanatory drawing which shows the stirring force which acts in the molten metal in the time t1. It is explanatory drawing which shows the stirring force which acts in the molten metal in the time t2. It is explanatory drawing which shows the stirring force which acts in the molten metal in the time t3. It is a circuit block diagram of the induction melting furnace by the other Example of this invention. It is a circuit block diagram of the induction melting furnace at the time of the conventional normal melt | dissolution. It is a circuit block diagram of the induction melting furnace at the time of stirring of FIG. It is a voltage waveform diagram of the upper and lower coils during the conventional stirring.

1 Dissolution chamber
2A Lower coil
2B Upper coil
3 Single-phase AC power supply
4 capacitors
5 switch
6 Connection
7 switch
8 Molten metal
10 Inverter power supply
11A First terminal 11B Second terminal 12A, 12B Capacitor
13 Midpoint
14 Midpoint
15 connection points
16 connection points
SW ₁ first switch
SW ₂ second switch
SW ₃ 3rd switch
SW ₄ single pole double throw switch

Claims (3)

Two coils wound up and down the melting chamber are connected in series, and both ends are connected to both ends of two series-connected capacitors, respectively, one of which is the first terminal of the inverter power supply The other connection point is connected to the second terminal of the inverter power supply through the first switch, and the second connection point is connected between the intermediate point of the two coils and the intermediate point of the two sets of capacitors. In addition, a third switch is connected between the second terminal of the inverter power supply and the intermediate point of the two sets of capacitors, and the third switch is turned on during normal melting, 1 switch and 2 switch are turned off and heated by voltage doubler system, and at the time of stirring, 1st switch and 2nd switch are turned on, 3rd switch is turned off, phase difference and voltage of upper and lower coils Adjusting the heating Molten metal heating method of stirring induction melting furnace, characterized. The method for heating and stirring molten metal in an induction melting furnace according to claim 1, wherein at least one of the two sets of capacitors is formed of a capacitor having a variable capacity. The method for heating and stirring molten metal in an induction melting furnace according to claim 1, wherein the first switch and the third switch are formed by one single pole double throw switch.