JP2524697B2 - Ironless core induction melting furnace heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a heating device for an iron-free core induction melting furnace regardless of whether it is iron-based or non-ferrous.

<Prior Art> The following various heating devices have been conventionally used for melting metals in an iron-free core induction melting furnace.

As shown in FIG. 5, the first heating device is a so-called 1 power source 1 furnace device in which a heating coil 2 of the furnace is connected to a high frequency power source equipment 1. Here, a high frequency means a frequency exceeding a commercial frequency, for example, 100 Hz or higher, and the same applies hereinafter. In this apparatus, as shown in FIG. 6, high electric power Pb is applied to the heating coil 2 in the time period of t ₀ -t ₁ to melt the metal in the furnace, and then in the time period of t ₁ -t ₂ Discharge the molten metal in the furnace. This tapping takes several minutes to several tens of minutes depending on the purpose of use of the molten metal, and is performed while keeping the temperature warm during that time. The electric power for this heat retention is secured by setting the power level of the power supply equipment 1 to the low power level Pc required for heat retention.

As shown in FIG. 7, the second heating device is a device that uses the melting power supply equipment 3 and the heat insulation power supply equipment 4 together. The power supply facilities 3 and 4 are connected to the heating coils 7 and 8 of the first and second furnaces through the switches 5 and 6, respectively, and the heating coils of the first and second furnaces are switched respectively. It is also connected to the devices 6 and 5. In such equipment, the melting by the ironless core furnace is the conventional commercial frequency (low frequency)
On the other hand, in order to take advantage of the advantages of the fast melting furnace with high power density-energy saving, metallurgical superiority, etc., a high-frequency furnace is often used, and as the heat insulation power supply equipment 4, heat insulation power with low power density is used. Therefore, a commercial frequency power supply facility is used because it is not necessary to use a high frequency power supply.

Then, by switching the switches 5 and 6, the heating coils 7 and 8 are alternately connected to the power supply equipments 3 and 4, and are used for melting or for keeping heat, for example, the eighth coil. It operates as shown. FIG. 8A shows the operating state of the first furnace having the heating coil 7, and FIG. 8B shows the operating state of the second furnace having the heating coil 8.

In FIG. 8, the switches 5 and 6 of the apparatus shown in FIG. 7 are connected in the state shown by the solid line in the time period from t _{0 to} t ₁ , the first furnace serves as a melting furnace, and the second furnace is kept warm. Each functions as a furnace. That is, in the time period from t _{0 to} t ₁ , the metal in the first furnace is melted at the high power level Pb, and the molten metal in the second furnace is discharged while being kept warm at the low power level Pc. Next, in the time period from t _{1 to} t _2, the switches 5 and 6 of the apparatus of FIG. 7 are connected in the state shown by the broken line, and the heating coil 7 of the first furnace is connected to the power supply equipment 4 and the The heating coil 8 of the furnace No. 2 is connected to the power supply equipment 3 to function as a heat-retaining furnace and a melting furnace, respectively. That is, within the time of t ₁ −t ₂ , the first
The molten metal in the furnace is discharged while being kept warm at the power level Pc, and the metal newly filled in the second furnace is at the power level Pb.
Is dissolved in. In this way, the first furnace and the second furnace become a melting furnace or a heat-retaining furnace by the switching operation of the switching devices 5 and 6. In any case, the high frequency power supply equipment 3 is dedicated for melting, and the commercial frequency power supply equipment 4 is dedicated for heat retention.

The third heating device uses a high-frequency power supply facility 9 having a capability of adding melting power and heat retention power as a power source. The power supply equipment 9 and the heating coils 7, 8 of the first and second furnaces are the ninth
As shown in the figure, they are connected through one switch 10, and the switch 10 alternately applies electric power (Pa) to each furnace. Here, electric power Pa is melting electric power Pb + thermal insulation electric power Pc
Is.

That is, in FIG. 9, when the switch 10 is connected in the solid line state, the power supply facility 9 is connected to the heating coil 7 of the first furnace, and when the switch 10 is connected in the broken line state, the power supply facility 9 is connected. The heating coil 8 of the second furnace is connected. In this way, this third heating device keeps the other furnace in the OFF state when power is being applied to one furnace, but normally the one with the shorter OFF interval is used as the melting furnace and the one with the longer one is used for heat insulation. Used as a furnace. For example, as shown in FIG. 10, the furnace is used as a melting furnace and the second furnace is used as a heat-retaining furnace in a time period of t ₀ -t ₁ ,
In the time period from t _{1 to} t ₂ , on the contrary, the first furnace can be used as the heat retaining furnace and the second furnace can be used as the melting furnace.

<Problems to be Solved by the Invention> However, these conventional heating devices have many problems as described below.

Since the first heating device is used by lowering the power supply facility 1 of high power to the low power level necessary for keeping heat, the operating rate of the facility is low and the facility power is large compared to the production amount. There was a problem that the basic electricity charge was high and the equipment was uneconomical.

Since the second heating device is dedicated to melting and keeping the power supply facilities 3 and 4 respectively, it has the advantage that the facility operation rate is ideal and the productivity is very high. Since the commercial frequency power supply equipment is used, there is a problem that the equipment is expensive due to the following reasons.

The heating coil of the furnace must be an expensive commercial frequency coil.

Since low power of commercial frequency is applied to the high frequency coil, the coil impedance becomes very low, and the circuit components such as the power factor correction capacitor and the matching transformer become expensive.

 Since it is a commercial frequency power source, a three-phase balancing device is required.

Further, in the third heating device, if it is attempted to control the temperature (Δθ) in the heat-retaining furnace within ± 5 ° C., for example, it is necessary to switch it very frequently in a short time of about 1 minute. Switching at 1-minute intervals is impossible in terms of the life of the switch and in operation.

If the switching interval is set to about 10 minutes, the temperature accuracy (Δθ) will be about ± 50 ° C, which is not practical in terms of temperature.

Therefore, the third heating device sacrifices switch life,
In addition, there is a problem that complicated operations must be performed.

As described above, conventionally, there has been no accelerator which can efficiently and economically operate these two furnaces in parallel by supplying power to the melting furnace and the heat retaining furnace from a single power supply facility. I had no idea to develop a device.

Conventionally, this is considered as a completely different furnace electrically from the melting furnace in which the load impedance fluctuates drastically in the heating process and the heat-retaining furnace in which the load impedance is basically constant. It was considered difficult to operate in parallel with a single power supply facility.

<Means for Solving Problems> The present inventor has improved the problems of the conventional device described above, and despite the parallel operation of the melting furnace and the heat retaining furnace with one high-frequency power source equipment, the melting furnace and the heat retaining As a result of various studies aimed at providing economical equipment that exhibits the same performance as when a dedicated power supply equipment was installed in each furnace, as a result, it was decided to use separate high-frequency power supply equipment for different purposes of melting and heat retention. On the other hand, the present invention has been completed by finding that a relatively inexpensive furnace coil can be applied to each of the melting furnace and the heat retaining furnace when electric power is applied to each.

A heating device for an iron-free core induction melting furnace according to the present invention has a heating coil for a first furnace connected to a high-frequency power supply facility via a first switching device, and the same design as the first heating coil. The second transformer connected via the second switching unit and the matching transformer capable of dealing with the warming power impedance branched from the power supply facility and connected via the heat insulation power switch via the tap changer. The furnace heating coil and the first and second furnace heating coils are respectively the second and first
And a switching system connected to the switching device, and the first and second furnaces are alternately switched to the melting furnace and the heat-retaining furnace by operating the both switching devices.

<Examples> Hereinafter, the present invention will be specifically described based on illustrated examples.

FIG. 1 shows an embodiment of the present invention (hereinafter abbreviated as the present apparatus A), and reference numeral 20 is a high frequency power supply facility having both melting and heat retaining capabilities. This power supply equipment 20 is connected to the heating coil 22 of the first furnace via the first switching device 21, and is branched from the power supply equipment 20 to pass the tap switching device 24 via the heat insulation power supply switch 23. It is connected to the heating coil 27 of the second furnace via a matching transformer 25 and a second switching device 26, which can correspond to the heat insulation power impedance connected via the above. In this device A, as shown in FIG. 1, when the switches 21, 26 are connected in solid lines, the melting power Pb is applied to the heating coil 22 and tap switching is applied to the heating coil 27. The power level of the power supply equipment 20 is lowered by the transformer 24 and the matching transformer 25, and the heat insulation power Pc is applied. Thus, the first furnace functions as a melting furnace and the second furnace functions as a heat retaining furnace.

In addition, by operating the switch, as shown in FIG.
When connecting 1,26 to the broken line, the first
The second furnace functions as a heat retaining furnace and the second furnace functions as a melting furnace.

In this way, this device A can be operated by operating the switching devices 21 and 26 so that the first
The furnace and the second furnace can be alternately converted to both melting and heat retaining functions. A more detailed description of this is shown in FIG. FIG. 2 is a graph in which the applied power P to the heating coil and the temperature T in the furnace are plotted on the ordinate and the time is plotted on the abscissa, and (a) is the graph of the first furnace equipped with the heating coil 22. The state (b) shows the state of the second furnace provided with the heating coil 27.

In the time zone t ₀ -t ₁ in FIG. 2 the first furnace and a second
The furnace respectively function as a melting furnace and kept furnace, t ₁ -t ₂
In the time zone of, the first furnace and the second furnace are functioning as a heat retaining furnace and a melting furnace, respectively.

That is, in the present apparatus A, the metal in one of the first furnaces is melted in the time period of t ₀ -t ₁ , the molten metal in the other second furnace is discharged while being kept warm, and the next t ₁ -t _In the time zone of ₂ , the molten metal in the first furnace that was melted in the previous time zone is discharged while keeping the temperature
New metal is put into the empty second furnace and melted. This is the same as the graph shown by the conventional heating device which uses the melting power supply equipment 3 and the heat insulation power supply equipment 4 together shown in FIG. As described above, it can be understood that the present device A has the same operation as a heating device having separate power supply facilities for melting and keeping heat.

The price of electric equipment at this time is considered as follows.
The present example is an example in which the melting power is 100% and the heat retention power is 10%, but the price of the electric equipment at this time is 110%, for example, when the capacity is 110%. ,
For example, it is about 105% or less, but on the other hand, the equipment cost of 10% capacity cannot be done at 10% cost, and it becomes quite expensive. Therefore, it is more advantageous in terms of equipment cost to install the power supply equipment having both the ability of melting and the heat retention as in the present embodiment than the installation of the power supply equipment dedicated to the melting and the heat insulation.

Further, as in this embodiment, the heating coils 22 and 27 used in the furnace are used for a relatively inexpensive furnace because the power is applied to each of them for the purpose of melting and keeping heat from a single high frequency power source equipment. There is also the advantage that a coil can be used.

In addition, although the heat retention temperature is controlled to be constant in FIG.
If you want to raise or lower this slightly, you can adjust it by changing the tap changer 24.
If it is necessary to raise Pb in a stepwise manner instead of keeping it constant, the tap changer 24 may be operated in an interlocking manner according to the pattern.

Further, in the present apparatus A, when the heat retention time is shorter than the melting time, that is, when hot water is completed in a time shorter than the melting time, the heat insulation power switch 23 is turned off at the time of completion.
What should I do? In this case, the heat-retaining furnace is played for a short time from the completion of tapping until it functions as a melting furnace, but even in this case, the present apparatus A can sufficiently function.

Further, in order to effectively utilize the above-mentioned short play time, it becomes possible by combining the present apparatus A with another high frequency power supply equipment system.

Hereinafter, this application example (hereinafter, simply referred to as the present device B) will be described. The application example shown below is the case where the heat retention time is half the dissolution time. The same components as those of the present device A are designated by the same reference numerals and the description thereof will be omitted.

FIG. 3 is a single-line connection diagram of the present device B. The present device B is a system for connecting the heating coil 30 of the third furnace, which is connected to another high-frequency power supply equipment 28 via a switch 29, and the above-mentioned book. It is configured to be connected to the device A. That is, one high-frequency power equipment 20 is connected to the heating coil 30 of the third furnace via the switches 21 and 26, and the other high-frequency power equipment 28 is a switch.
It is connected via 29 to the first and second heating coils 22 and 27.

The device B is, for example, as shown in FIGS.
It operates as shown in (c). FIG. 4 is a graph in which the vertical axis represents the electric power P applied to the heating coil and the furnace temperature T, and the horizontal axis represents time. (B) is the second equipped with the heating coil 27
The state of the furnace of (3) is equipped with a heating coil 30
The furnace conditions are shown below.

In FIG. 4, in the time zone of t ₀ -t ₂ , the switch 21 is set to a connection and the switch 26 is set to e connection between t ₀ -t ₁ , and then t ₁ -t ₂
After making the f connection between the switches, and the switch 29 after making the i connection between t _{0 and} t _1,
Connect h between t _{1 and} t ₂ . At this time, the first furnace is t ₀ −t ₂
The entire time zone of T functions as a melting furnace, and the second furnace is t ₀ −
t ₁ between acts as a melting furnace between t ₁ -t ₂ after to function as thermal insulation furnace, after the third furnace to function as a dissolution furnace between t ₀ -t ₁
It functions as a heat insulation furnace between t _{1 and} t ₂ .

During the time period from t _{2 to} t ₄ , the switching device 21 uses c during the entire time period.
Then, the switch 26 connects t ₂ -t ₃ to d and then connects t _{3 to} t ₄ to e, and the switch 29 connects t _{2 to} t ₃ to h connection in the previous time period and then t. Connect g between _{3 and} t ₄ . At this time, the first furnace functions as a heat insulation furnace between t _{2 and} t ₃ and then functions as a melting furnace between t _{3 and} t ₄ , and the second furnace continues between t _{2 and} t ₃ in the previous time period. Functioning as a melting furnace after that, it functions as a heat-retaining furnace between t _{3 and} t ₄ , and the third furnace functions as a melting furnace for the entire time period of t ₂ -t ₄ .

t ₄ in the time zone of -t _6, the switching device 21 is all this time zone b
After connecting the switching device 26 to the f connection between t _{4 and} t ₅ and then connecting the d connection between t _{5 and} t ₆ , the switching device 29 maintains the connection between t _{4 and} t ₅ for the previous time period g. between t ₅ -t ₆ to i connection. At this time, the first furnace functions as a melting furnace between t _{4 and} t ₅ and then functions as a heat retaining furnace between t _{5 and} t ₆ , and the second furnace functions as a melting furnace for the entire time period from t _{4 to} t _6. The third furnace functions as a heat-retaining furnace between t _{4 and} t ₅ , and then functions as a melting furnace between t _{5 and} t ₆ .

In this way, the switching device 21 of the device B is switched in the order of a → c → b → ... at intervals of 2t time, and the switching device 26 is e → f → d →.
The order is e → f → d → ... At intervals of t time, and the switch 29 is switched at i → h → g → i → ... At intervals of 2t time. This 2t is the dissolution time, and t corresponds to the heat retention time (or tapping time).

According to the present apparatus B, even if the heat retention time is half the melting time, each furnace can be effectively used without rest.

<Effects of the Invention> As described above, the present invention is a completely different electrically electrically melting furnace in which the load impedance fluctuates drastically in the heating process, and a heat insulation in which the load impedance is basically constant. It was possible to provide a heating device capable of operating the furnace and the furnace in parallel with a single high-frequency power supply facility.

Therefore, in the present invention, the total equipment cost is lower than the power source equipment dedicated to the melting furnace and the heat-retaining furnace, and the operation rate of the equipment is high and the productivity is high due to the parallel operation of the melting furnace and the heat-retaining furnace. It also has the advantage in actual operation.

[Brief description of drawings]

FIG. 1 is a connection diagram of a heating apparatus according to the present invention, and FIG. 2 is a graph showing a relationship between electric power (P) / temperature (T) -time in a furnace in the same apparatus. Of the furnace, (b) is the graph of the second furnace, Fig. 3 is a single wire connection diagram of the heating device to which the same device is applied, and Fig. 4 is the electric power (P) / temperature in the furnace in the same device. (T) is a graph showing a time relationship, (a) is a graph of the first furnace,
(B) is a graph of the second furnace, (C) is a graph of the third furnace, and FIG. 5, FIG. 7, and FIG. 9 are wiring diagrams of conventional heating devices, FIG. 6, and FIG. (A), (b), and FIG. 10 (a), (b) are graphs showing the relationship between the electric power (P), temperature (T), and time in the state of the furnace corresponding to the conventional heating device. Is. A ... This device, 20 ... High frequency power equipment, 21 ... First switching device, 22 ... First furnace heating coil, 23 ... Insulation power switch, 24 ... Tap switching device, 25 ... … Matching transformer, 26 …… Second switch, 27 …… Second furnace heating coil

Claims (1)

(57) [Claims] Claim: What is claimed is: 1. A heating coil for a first furnace, which is connected to a high-frequency power supply facility via a first switch, and a heating coil for the first furnace, which have the same design.
For heating the second furnace connected via the matching transformer and the second switching device that can correspond to the warming power impedance branched from the above power supply facility and connected through the warming power source switch through the tap changer A coil and a switching system that connects the heating coils of the first and second furnaces to the second and first switching devices, respectively, and the first and second furnaces are operated by operating both switching devices. A heating device for an iron-free core induction melting furnace, characterized by alternately switching between the melting furnace and the heat-retaining furnace.