JPS6229086A - Heater for coreless induction melting furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a heating device for an ironless core induction melting furnace, regardless of whether it is ferrous or non-ferrous.

<Prior Art> For melting metal in an ironless core induction melting furnace, various heating devices are employed as in the conventional method.

As shown in FIG. 5, the first heating device is a so-called 1 power source 1 in which a furnace heating coil 2 is connected to a high frequency power source equipment 1
It is a furnace device. Here, high frequency (or frequency exceeding commercial frequency, for example 100 Hz or more, the same applies hereinafter) is used. In the device of B, as shown in Fig. 6, high O/power pb is applied to the heating coil 2 during the time period 1-1. After printing and melting the metal in the furnace, 1.-t
The molten metal in the furnace is tapped during the time period. This tapping process may take several minutes to several tens of minutes depending on the intended use of the molten metal, and must be kept warm during this time. Electric power for this heat retention is secured by setting the power level of the power supply stage WIl to a low power level Pc necessary for heat retention.

The second heating device is as shown in FIG. This is a device that uses an eight-fold power supply equipment 3 and a heat retention power supply equipment 4 together. The power supply equipment 3 and 4 are connected to the heating coils 8 of the first and second furnaces through switching devices 5 and 6, respectively, and the heating coils of the first and second furnaces are connected to the heating coils of the first and second furnaces through switching devices 5 and 6, respectively. It is also connected to 6 and 5. Melting using 8 iron-free furnaces in such equipment requires conventional commercial frequency (low frequency)
On the other hand, in order to take advantage of the advantages of a fast melting furnace with high power density - energy saving, metallurgical properties (receptivity, etc.), high frequency furnaces are often used. Commercial frequency power supply equipment is used because there is no need for a high-frequency power supply.

By switching the switching devices 5 and 6, the heating coils 7 and 8 are alternately connected to the power supply equipment 3 and 4, and are used for melting or heat retention. It operates as shown in the figure. Figure 8 (a)
(b) shows the operating state of the first furnace having the heating coil 7, and (b) shows the operating state of the second furnace having the heating coil 8.

In FIG. 8, during the time period 1-1, the switching devices 5 and 6 of the device in FIG. Each functions. That is, within the time period 1-1, the metal in the first furnace is melted at a high power level pb, and the molten metal in the second furnace is tapped while being kept warm at a low power level Pc.

Then, during the time period t7-t, the switch 5 of the device shown in FIG.
, 6 are connected as shown by dashed lines, the first furnace has its heating coil 7 connected to the power supply equipment 4, and the second furnace has its heating coil 8 connected to the power supply equipment 3, Each functions as a heat retention furnace and a melting furnace. That is, 1. -1
Within the time period 2, the molten metal in the first furnace is tapped while being kept warm at the power level Pc, and the metal newly filled in the second furnace is melted at the power level pb. In this way, the first furnace and the second furnace can be used as a melting furnace or a heat retention furnace by switching the switching devices 5 and 6. In any case, the high frequency power supply installation/lI3 is used exclusively for melting, and the commercial frequency power supply equipment 4 is used for heat preservation.

The third heating device is powered by a high-frequency power supply facility 9 having the ability to provide both melting power and heat-retaining power. The power supply installation a9 and the heating coils 7.8 of the first and second furnaces are connected via one switch 10 as shown in FIG. 9, and the switch 1o alternately supplies power to each house. (Pa) is printed.

Here, the electric power Paζ, the melting power pb, and the heat-retaining power Pc.

That is, in FIG. 9, when the switch 1o is connected as a solid line, the power supply equipment 9 and the heating coil 7 of the first furnace are connected, and when the switch 1o is connected as a dashed line, the power supply equipment 9 is connected. and the heating coil 8 of the second furnace are connected. In this way, in this third heating device, when power is applied to one furnace, the other furnace is placed in the OFF state, but normally the one with the shorter OFF interval is used as the melting furnace, and the longer one is kept warm. Used as a furnace. For example, as shown in FIG. -1
During the time period of ゜, the furnace is used as a melting furnace and the second furnace is used as a heat retention furnace.1. In the time period -t2, the first furnace can be used as a heat retention furnace and the second furnace can be used as a 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 uses the high-power power supply equipment 1 by reducing the power level to the low power level required for heat retention, the operating rate of the equipment is low, and the equipment power is large compared to the production volume. The problem was that the basic electricity charge was high and the equipment was uneconomical.

The second heating device has the advantage that the power supply equipment 3 and 4 are dedicated for melting and heat retention, respectively, so that the equipment operation rate is ideally high and the productivity is extremely high.
Since commercial frequency power supply equipment is used for heat insulation, there is a problem in that the equipment becomes expensive for the following reasons.

■ The furnace heating coil must be an expensive commercial frequency coil.

■ Since low commercial frequency power is applied to the high frequency coil, the coil impedance becomes extremely low, making circuit components such as power factor correction capacitors and matching transformers expensive.

■ A three-phase balance device is required for commercial frequency e-power.

In addition, in the third heating device, the temperature (
△θ), for example, within about ±5°C, it is necessary to switch extremely frequently in a short period of about 1 minute, but switching at intervals of about 1 minute reduces the lifespan of the switch, and Operationally impossible.

If the interval between the switching devices is set to about 10 minutes, the temperature accuracy (Δθ) will be about ±50° C., which is not practical from a temperature standpoint.

Therefore, the third heating device has the problem of sacrificing the life of the switching device and requiring complicated operations.

Means for Solving the Problems〉 The present inventor has improved the problems of the above-mentioned conventional device, and although the melting furnace and the heat-insulating furnace are operated in parallel with one high-frequency power supply equipment, the melting furnace and the heat-insulating furnace are As a result of various studies with the aim of providing an economical facility that achieves the same performance as if the furnace were equipped with its own dedicated power supply equipment, we found that the same high-frequency power supply equipment could be used for different purposes of melting and heat retention. , when applying power to each, relatively inexpensive furnace coils are used for melting furnaces,
The present invention was completed after discovering that there are advantages that can be applied to each type of heat-retaining furnace.

The heating device for an iron-free induction melting furnace according to the present invention includes a first furnace heating coil connected to a high-frequency power supply equipment via a first switch, and a heating coil connected to a high-frequency power supply equipment via a first switch, and a heat retention power switch branched from the power supply equipment. a second furnace heating coil connected via a second switch to a matching transformer capable of responding to the heat insulation power impedance connected via a tap changer;
and a switching system that connects the heating coil of the second furnace to the second and first switching devices, respectively, and melts either the first or second furnace by operating the switching devices. One of the features is that one is a furnace, and the other is a heat-retaining furnace.

<Examples> The present invention will be specifically described below based on illustrated examples.

FIG. 1 shows an embodiment of the present invention (hereinafter abbreviated as device A).
In the figure, reference numeral 20 is a high-frequency power supply equipment that has both melting and heat retention capabilities. This power supply equipment 20 is connected to the heating coil 22 of the first furnace via a first switch 21, and is branched from the power supply equipment 20 and connected to a tap changer 24 via a heat retention power switch 23. A matching transformer 2 that can accommodate the thermal insulation power impedance connected through
5 and a second switch M26 to the heating coil 27 of the second furnace. In this device A (first
As shown in the figure, when the switching devices 21 and 26 are connected as shown by solid lines, the melting power Pb is applied to the heating coil 22, and the heating coil 27 is applied with the tap changer 24 and the matching transformer 25. The power level of the power supply equipment 20 is lowered and the heat-retaining power Pc is applied. Thus, the first furnace functions as a melting furnace, and the second furnace functions as a heat retention furnace.

In addition, by operating the switch, the switch N21 can be switched as shown in Figure 1.
, 26 are connected as shown by the dashed-dotted lines, the first furnace functions as a heat-retaining furnace and the second furnace functions as a melting furnace, contrary to the above description.

In this manner, the present apparatus A can alternately convert the first furnace and the second furnace into both melting and heat retention functions by operating the switchers 21 and 26. This can be explained in more detail as shown in Figure 2. FIG. 2 is a graph in which the vertical axis is the applied power P to the heating coil and the furnace temperature T, and the horizontal axis is time. (b) is the second state equipped with the heating coil 27.
The status of each furnace is shown below.

In Figure 4, 1. -1. During the time period t7, the first furnace and the second furnace function as a melting furnace and a heat retention furnace, respectively.
- It is shown that the first furnace and the second furnace function as a heat retention furnace and a melting furnace, respectively, during the time period.

That is, in this apparatus A, during the time period 1D-1, the metal in one first furnace is melted, the molten metal in the other second furnace is tapped while being kept warm, and the next 1. In the time period -1□, the molten metal in the first furnace that was melted in the previous time period is tapped out while being kept warm, and new metal is put into the empty second furnace and melted. This is the same as the graph shown in the conventional heating device that uses both the melting power supply equipment 3 and the heat retention power supply equipment 4 shown in FIG. In this way, it can be understood that the present device A has the same effect as a heating device having separate power supply equipment for melting and heat retention.

The price of electrical equipment in this case can be considered as follows. This example is an example in which the melting power is 100% and the heating power is 10%, but the price of the electrical equipment in this case is, for example, if the capacity is 110%, the cost will not be 110%. , for example, round bar is about 105% or less, but on the other hand, 10%
Capacity equipment costs cannot be reduced by 10% of the cost and are quite expensive. Therefore, it is more advantageous in terms of equipment cost to install power supply equipment that has both melting and heat retention capabilities, as in this embodiment, than to install dedicated power supply equipment for melting and heat retention, respectively.

In addition, as in this embodiment, power is applied to separate purposes of melting and heat retention from the same high-frequency power supply equipment, so the heating coils 22 and 27 used in the furnace can be replaced with relatively inexpensive furnace coils. It also has the advantage that it can be used.

In addition, in Fig. 2, the 2M 2Nr degree is controlled to be constant, but if you want to raise or lower it slightly, tap switch W12
The adjustment can be made by varying the melting power pb, and if it is necessary to raise the melting power pb step by step instead of keeping it constant, the tap changer 24 can be operated in conjunction with the pattern.

Moreover, this apparatus A has a dissolution time of t. -t, when the heat retention time is within a certain amount of time, that is, when the hot water tapping is completed in a time shorter than the melting time, the heat retention power switch 23 may be turned OFF at the time of completion. In this case, the heat-retaining furnace will be idle for a short time from the completion of tapping until it functions as a melting furnace, but even in this case, the apparatus A can function satisfactorily.

Furthermore, if it is desired to make effective use of the short idle time mentioned above, this becomes possible by combining this device A with another high frequency power supply equipment system.

This application example (hereinafter abbreviated as device B) will be described below. In the application example shown below, the incubation time is half the dissolution time. Components that are the same as this device A will be given the same symbols and their explanation will be omitted.

FIG. 3 is a single line diagram of this device B, and this device B is connected to another high frequency power supply equipment 28 via a switch 29.
The connection system of the heating coil 30 of the furnace is connected to the above-mentioned apparatus A. That is, one high-frequency power supply equipment 20 is connected to the heating coil 30 of the third furnace via the switching devices 21 and 26, and the other high-frequency power supply equipment 28 is connected to the first and second heating coils via the switch M29. The heating coils 22 and 27 are connected to the heating coils 22 and 27.

For example, the present device 1B is
It operates as shown in c). FIG. 4 is a graph showing the power P applied to the heating coil and the temperature T in the furnace @ the vertical axis and the time on the horizontal axis, and (a) shows the state of the first furnace equipped with the heating coil 22. (b) shows the state of the second furnace equipped with the heating coil 27, and (c) shows the state of the third furnace equipped with the heating coil 30.

In Figure 4, 1. -1. During the time period, the switch 21 is set to C connection, and the switch 26 is set to 1. -) After making a C connection between 1. -1. Make an f connection between the switch 291 and t.

After making one connection between -1 and ti, make an h connection between ti and ti.

At this time, the first furnace is at t. - The second furnace functions as a melting furnace for the entire period of time t2. - After the space between 2 and 1 functions as a heat retention furnace, the space between 1 and 1 functions as a melting furnace, /
J The third furnace is 1. -1. After serving as a melting furnace.

-1, the space between the two functions as a heat-retaining furnace.

During the time periods t and ty, the switch 21 connects the entire time period to C connection, and the switch 26 connects 12-t? After making a d connection between 1. Make 8 connections between 1.1 and switch 29bat2-
1. After maintaining the h connection of the previous time period between 1y-1. Make a g connection between them. At this time, the first furnace functions as a heat retention furnace for 12-1J, and then 1. -19 functions as a melting furnace, and the second furnace functions as a melting furnace. -1J after functioning as a melting furnace following the previous time period 1. -1. The third furnace functions as a melting furnace during all of the time periods t, t, and 7.

1, -1. During the time period, the switch N21 makes the b connection for the entire time period, and the switch 26 makes the f connection between LP and t, and then makes the 1. -16 to d connection, switch 29bat7-1-
After maintaining the g-connection of the previous time period between 1 and 2, there is one connection between 1 and 2. At this time, the first furnace functions as a melting furnace between 1 and 9, and then 1. ．． -1. functions as a heat retention furnace, and the second furnace functions as 1. The third
The furnace was 14t-1, and after functioning as a heat-insulating furnace,
The four chambers function as a melting furnace.

In this way, the switch 21 of the device B is set to B4C-+))-
2 at time intervals in the order of (4
It switches in the order of 4f 4 d-494f → d + at intervals of L time, and the switch 29 switches from l-h → g −1.
2 will be switched at time intervals in this order. This 2
m is the dissolution time, and t corresponds to the heat retention time (or hot water tapping time).

According to this device B, even if the heat retention time is half the melting time, it can be used effectively without having to rest each house.

<Effects of the Invention> As described above, the present invention uses high-frequency power supply equipment for both melting and heat retention to apply electric power to each of the separate purposes of melting and heat retention, so the equipment cost for the entire device is as low as the above. It is cheaper than using dedicated power supply equipment for each purpose.

Further, the present invention has the advantage in actual operation that the melting furnace and the heat-retaining furnace can be operated in parallel, so that the operating rate of the equipment is high and the productivity is high.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram of the heating device according to the present invention, and FIG. 2 is a graph showing the relationship between power (P) and temperature (T) in the furnace in the same device over one hour. Graph regarding the furnace, (b) is a graph regarding the second furnace, Figure 3 is a single line diagram of a heating device applying the same device, and Figure 4 is the power (P) and temperature of the state inside the furnace in the same device. (T) A graph showing the hourly relationship, (A) is the graph of the first furnace, (
b) is the graph of the second furnace, (c) is the graph of the third furnace,
Figures 5, 7, and 9 are wiring diagrams of conventional heating devices, Figures 6, 8 (a), (b), and 10 (a).
, (b) are graphs showing the relationship between power (P) and temperature (T) over one hour in the state inside the furnace corresponding to the above-mentioned conventional heating device. A This device, 20 High frequency power supply equipment, 21 First switching device, 22・First furnace heating coil, 23 Heat retention power switch, 24・Tap changer, 25・Matching transformer, 26 Second
switch,

Claims (1)

[Claims] A heating coil for a first furnace connected to a high-frequency power supply equipment via a first switch; and a heating coil branched from the power supply equipment and connected via a heat retention power switch and a tap switch. a heating coil of the second furnace connected via a matching transformer and a second switching device capable of corresponding to the thermal insulation power impedance; and a heating coil of the first and second furnaces connected to the second and a switching system connected to a first switching device, and is characterized in that by operating both of the switching devices, one of the first and second furnaces is used as a melting furnace, and the other is used as a heat retention furnace. Heating device for iron-free induction melting furnace.