JP6954556B2 - Induction melting furnace - Google Patents

Description

The present invention relates to an induction melting furnace that melts a material to be heated stored in the furnace by supplying high frequency power to a heating coil provided on the outer periphery of the furnace wall via a power supply means.

Conventionally, as this type of induction melting furnace, as shown in Patent Document 1 below, in a metal melting furnace in which a material to be heated is heated and melted by a heating coil provided on the outer periphery of the furnace wall, the material to be heated is covered through the furnace lid. Those equipped with an optical fiber type radiation thermometer that measures the melting temperature of the heating material are known.

Japanese Unexamined Patent Publication No. 6-159944

Here, in the conventional metal melting furnace, in a relatively small induction melting furnace, the amount of raw material required for casting is heated and melted for each casting and sequentially supplied, and a large melting furnace is used. However, when the amount of molten metal equivalent to multiple castings is melted and then the amount of molten metal required for one casting is discharged and supplied to the mold, the amount of heat taken out each time the molten metal is discharged. There was a problem that the amount of the remaining molten metal changed and it was difficult to accurately control the holding temperature.

Therefore, an object of the present invention is to provide an induction melting furnace capable of accurately controlling the holding temperature even when the amount of molten metal changes each time the hot water is discharged.

The induction melting furnace of the first invention is an induction melting furnace that melts a material to be heated stored in the furnace by supplying high frequency power to a heating coil provided on the outer periphery of the furnace wall via a power supply means. hand,
A weight measuring means for measuring the weight of the material to be heated stored in the furnace, and
A first temperature measuring means including a radiation temperature measuring means provided on the furnace lid of the furnace and measuring the temperature of the material to be heated housed in the furnace in a non-contact manner.
A second temperature measuring means for directly measuring the temperature by temporarily contacting the material to be heated stored in the furnace, and
It is provided with a power control means for controlling the supply of high frequency power to the heating coil via the power supply means .
Before Symbol power control means,
In the heating process of raising the temperature of the material to be heated housed in the furnace, the temperature measured by the second temperature measuring means out of the temperature measured by the first temperature measuring means and the temperature measured by the second temperature measuring means is determined. With priority, the temperature rise completion time is calculated from the temperature measured by the second temperature measuring means, and the material to be heated is heated and melted until the calculated temperature rise completion time.
The tapping process after heating and dissolving, to determine the return from tilting and the tilting of the furnace, as a trigger that has returned after tilting, heated measured by the measuring temperature and the weight measuring unit by the first temperature measuring means The feature is that the mass of the material is acquired, the holding power is calculated from the acquired measured temperature and the mass, and the calculated holding power is applied to the heating coil.

According to the induction melting furnace of the first invention, in the heating process of raising the temperature of the material to be heated housed in the furnace, the material to be heated is subjected to the first temperature measuring means which is a non-contact type radiation temperature measuring means. The temperature can be continuously measured to obtain the set temperature.

Further, in the hot water discharge process, the holding temperature is calculated from the mass of the material to be heated (melted metal) measured by the weight measuring means in addition to the temperature measured by the first temperature measuring means, so that the amount of the molten metal is increased each time the hot water is discharged. Accurate holding temperature control is possible even if it changes.

As described above, according to the induction melting furnace of the first invention, it is possible to accurately control the holding temperature even when the amount of molten metal changes each time the hot water is discharged.

Here, according to the induction melting furnace of the first invention, in the heating process of heating and melting the material to be heated, inclusions such as slag are present on the surface of the melted material to be heated, and the radiation temperature provided on the furnace lid. Since it may be difficult to accurately control the melting temperature with a meter, a second temperature measuring means that measures the temperature in direct contact with the material to be heated in addition to or instead of the first temperature measuring means in the heating process. By calculating the temperature rise completion time from the temperature measured by the above and heating and melting the material to be heated until the calculated temperature rise completion time, the temperature controllability in the temperature rise process can be improved.

As described above, according to the induction melting furnace of the first invention, the second temperature measuring means for directly contacting the material to be heated to measure the temperature can be used as a complement or a substitute for the temperature measurement by the first temperature measuring means. In addition to improving the temperature controllability in the temperature rise process, it is possible to accurately control the holding temperature even when the amount of molten metal changes each time the hot water is discharged in the hot water discharge process.

The system block diagram which shows the overall structure of the induction melting furnace of this embodiment. The flowchart which shows the processing content in the induction melting furnace of FIG.

As shown in FIG. 1, in the induction melting furnace of the present embodiment, the induction melting furnace melts the material Y to be heated housed in the melting furnace main body X.

Specifically, the induction melting furnace includes a power source 1, a high-voltage power receiving board 2, a harmonic filter 3, a transformer for a converter 4, a high-frequency inverter 5, a high-frequency matching device 6, a heating coil 7, and a weight. It includes a measuring means 8, a temperature measuring means 9 (9A, 9B), a control circuit 10, and a controller 100 (corresponding to the power control means of the present invention).

The power supply 1 is a rated AC power supply and is connected to the high-voltage power receiving board 2.

The high-voltage power receiving board 2 is a device that energizes / stops the power supply to the induction heating device and shuts off the power supply when a failure occurs, and is a power fuse 21, a breaker 22, an instrument transformer 23, and an instrument transformer. A vessel 24 is provided.

The power fuse 21 is a means for shutting off the current in the event of a short-circuit accident, and the circuit breaker 22 performs an opening / closing operation when the power supply is energized and stopped. Further, the instrument transformer 23 converts the circuit current of this circuit into an output signal to the control circuit 10 and outputs it to the control circuit 10. Similarly, the instrument transformer 24 converts the circuit voltage of this circuit into an output signal to the control circuit 10 and outputs it to the control circuit 10.

The harmonic filter 3 is a device connected to the high-voltage power receiving panel 2 to suppress the harmonic current from flowing out from the high-frequency inverter 5 to the power system, and is a current limiting reactor 31, a series reactor 32, and a harmonic capacitor. It is composed of 33. Further, the harmonic filter 3 outputs a signal which is an abnormal signal to the control circuit 10 when the harmonic current exceeds a predetermined value.

The transformer 4 for a converter is a device connected to a harmonic filter 3 and adjusts an input voltage to the high-frequency inverter 5 in order for the high-frequency inverter 5 to output a predetermined output voltage. A signal that is an abnormal signal is output to the control circuit 10 in the event of a pressure abnormality or the like.

The high-frequency inverter 5 is a device connected to a transformer 4 for a converter to generate an arbitrary high-frequency current from a commercial power source of 50 Hz or 60 Hz, and is a forward converter 51 which is an AC / DC converter and a direct current. It is composed of an inverse converter 52, which is an AC converter, and is controlled by a start / stop / output control signal from the control circuit 10.

Further, the high-frequency inverter 5 has a built-in DC reactor 53, which removes the ripple component superimposed on the DC voltage generated by the forward converter 51, and at the same time, when the load of the reverse converter 52, the heating coil 7, etc. is damaged. Suppresses the sudden outflow of overcurrent.

Further, the high-frequency inverter 5 transmits a signal for transmitting the failure state to the control circuit 10 at the time of failure and electrical data (corresponding to the power supply state) during operation such as voltage, current, power, and frequency to the controller 100 as needed. Output.

The high-frequency matching device 6 is a device connected to the high-frequency inverter 5 to achieve impedance matching between the high-frequency inverter 5 and the heating coil 7. The high-frequency matching device 6 includes a high-frequency matching transformer 61 for impedance matching and a power factor adjusting capacitor 62 for advancing the delayed power factor of the heating coil 7 and compensating for the power factor. An abnormal signal such as damage is output to the control circuit 10.

The heating coil 7 generates a vortex current in the material Y to be heated such as iron housed in the melting furnace main body X by the high frequency power supplied from the high frequency inverter 5, and the Joule heat generated between the metal materials by the vortex current. The temperature of the material Y to be heated is raised to melt it.

At this time, an abnormal signal is output to the control circuit 10 at the time of a temperature detecting means (not shown), a circulation mechanism of a cooling water channel, or the like.

The weight measuring means 8 is, for example, a load cell which is a mass measuring means provided below the melting furnace main body X, measures the mass of the material Y to be heated housed in the melting furnace main body X, and measures the mass signal thereof. Is output to the controller 100.

The weight measuring means 8 may be a mass measuring means other than the load cell. For example, the mass of the material to be heated is measured in advance and the mass of the amount of hot water discharged is measured when the material is put into the melting furnace main body X. The mass in the melting furnace main body X may be indirectly calculated by the mass measuring means.

The temperature measuring means 9 is provided so as to penetrate the furnace lid Z of the melting furnace main body X, and is a first temperature measuring means which is a radiation temperature measuring means for measuring the temperature of the material Y to be heated in the melting furnace main body X in a non-contact manner. The means 9A and the second temperature measuring means 9B for directly measuring the temperature of the material Y to be heated melted in the melting furnace main body X are provided.

The measured temperatures of the first temperature measuring means 9A and the second temperature measuring means 9B are output to the controller 100, respectively.

The control circuit 10 is a control circuit for causing the induction melting furnace to perform a predetermined operation, and executes power control to the heating coil 7 via a control signal to the high frequency inverter 5. In addition, the control circuit 10 protects the induction melting furnace when each component of the induction melting furnace is damaged or the operating conditions exceed the rating, and is an arithmetic unit for processing various signals ( It is composed of a sequencer) and a program (software).

The controller 100 controls the overall operation of the induction melting furnace, such as the operation / stop of the induction melting furnace, the calculation processing of the output value based on the weight measuring means 8 and the temperature measuring means 9, which will be described later.

Next, the calculation process of the output value of the applied power by the controller 100 based on the weight measuring means 8 and the temperature measuring means 9 will be described with reference to the flowchart shown in FIG.

First, the controller 100 acquires the mass of the material Y to be heated, which is housed in the melting furnace main body X and is heated and melted, from the weight measuring means 8 (STEP 11).

Next, the controller 100 acquires the set value of the molten metal temperature of the material Y to be heated (STEP 12). The set value of the molten metal temperature may be set from the type of the material Y to be heated or the like, and if the operation schedule is registered in advance, it may be automatically set from the operation schedule registration contents.

Next, the controller 100 calculates the temperature rising time t [h] based on the following equation (STEP 13).

Here, M [kg] is the mass of the material Y to be heated, ΔT [° C.] is the temperature difference from the set value of the molten metal temperature, which is the target temperature, and P [kW] is the applied power. Ks and Kp are constants, nc is the efficiency of the heating coil 7, and (LOSS) is the heat loss value determined from the design value of the induction melting furnace.

When the applied power P [kW] is preset in the controller 100 (for example, when the maximum output is set so as to minimize the temperature rise time), the controller 100 rises based on the above equation. The warm time t [h] is calculated, and the temperature rise of the material Y to be heated is started via the control circuit 10.

On the other hand, when the applied power P [kW] is not set in advance (for example, when the melting completion time is set), the controller 100 calculates the applied power P [kW] based on the above equation. Then, the temperature of the material Y to be heated is started via the control circuit 10.

Next, the controller 100 acquires the measured temperatures of the first temperature measuring means 9A and the second temperature measuring means 9B at predetermined timings (STEP 14).

Here, when there is a temperature difference between the measured temperatures of the first temperature measuring means 9A and the second temperature measuring means 9B, the controller 100 gives priority to the measured temperature of the second temperature measuring means 9B and raises the next temperature. Performs completion alarm processing, etc. This is because in the process of raising the temperature, inclusions such as slag are present on the surface of the melted material to be heated, and it may be difficult to obtain an accurate melting temperature with a radiation thermometer provided on the furnace lid.

Next, based on the measured temperature acquired in STEP 14, when the temperature rise completion time is after a predetermined time (for example, 30 seconds) from the above equation, the controller 100 gives a temperature rise completion alarm to a speaker and a monitor (not shown). Notify the user (worker) via the like (STEP 15).

Then, when the temperature rise completion time is reached, the controller 100 shifts to a holding mode (corresponding to the hot water discharge process of the present invention) in which the material Y to be heated is held at the set value of the molten metal temperature (STEP 21).

In the holding mode, the controller 100 determines whether the melting furnace main body X has tilted due to hot water (whether the tilt button has been selected) (STEP 22) and whether the melting furnace body X has returned from tilting (whether the return button has been selected). Judgment (STEP23).

Then, if there is no tilt (NO in STEP22), the holding mode is maintained as it is, and tilt is selected (YES in STEP22), but if it does not return (NO in STEP23), it waits until it returns.

Then, when returning after tilting (YES in STEP 23), the controller 100 acquires the mass of the material Y to be heated in the melting furnace main body X (STEP 24).

Further, the controller 100 acquires the temperature of the material Y to be heated in the melting furnace main body X by the first temperature measuring means 9A (STEP 25). Here, in the holding mode, the measurement temperature of the first temperature measuring means 9A is preferentially used because even if inclusions such as slag are present on the surface of the melted material to be heated at the time of hot water, it is already removed by slag or the like. This is because it has been removed.

Next, the controller 100 calculates the holding power based on the above equation from the mass acquired in STEP 24 and the measured temperature acquired in STEP 25 (STEP 26), and transfers the calculated holding power to the heating coil 7 via the control circuit 10. Apply.

Next, the controller 100 repeats the processes STEP 22 to 26 in the above-mentioned holding mode until the hot water discharge is completed (until the hot water discharge completion button is selected) (STEP 27).

The above is the details of the calculation processing of the output value of the applied power by the controller 100 based on the weight measuring means 8 and the temperature measuring means 9, and according to the processing by the controller 100, the amount of heat taken out and the amount of heat remaining each time the hot water is discharged. Accurate control of the holding temperature is possible even when the amount of molten metal changes.

In the present embodiment, as the temperature measuring means 9, the first temperature measuring means 9A, which is a radiation temperature measuring means, and the second temperature measuring means 9B, which measures the temperature by temporarily directly contacting the molten metal, are used in combination. The case where the second temperature measuring means 9B is preferentially used in the temperature raising process and the first temperature measuring means 9A is preferentially used in the holding mode (hot water discharge process) has been described, but the present invention is not limited to this. In the process of raising the temperature, there are few inclusions such as slag on the surface of the melted material to be heated, or even if there are inclusions, the removal is performed in a timely manner. The temperature measuring means 9B may be omitted.

Further, without omitting the second temperature measuring means 9B, the first temperature measuring means 9A and the second temperature measuring means 9B are used in combination in the temperature raising process, and there is a difference in the measured temperatures exceeding a predetermined threshold value. In some cases, the measured temperature of the second temperature measuring means 9B may be adopted instead of the first temperature measuring means 9A.

1 ... Power supply, 2 ... High voltage power receiving board, 3 ... Harmonic filter, 4 ... Transformer for converter, 5 ... High frequency inverter, 6 ... High frequency matching device, 7 ... Heating coil, 8 ... Weight measuring means, 9A ... 1st Temperature measuring means, 9B ... Second temperature measuring means, 10 ... Control circuit, 100 ... Controller (electric power control means), X ... Melting furnace body, Y ... Heated material, Z ... Furnace lid.

Claims (1)

An induction melting furnace that melts the material to be heated stored in the furnace by supplying high-frequency power to a heating coil provided on the outer periphery of the furnace wall via a power supply means.
A weight measuring means for measuring the weight of the material to be heated stored in the furnace, and
A first temperature measuring means including a radiation temperature measuring means provided on the furnace lid of the furnace and measuring the temperature of the material to be heated housed in the furnace in a non-contact manner.
A second temperature measuring means for directly measuring the temperature by temporarily contacting the material to be heated stored in the furnace, and
It is provided with a power control means for controlling the supply of high frequency power to the heating coil via the power supply means .
Before Symbol power control means,
In the heating process of raising the temperature of the material to be heated housed in the furnace, the temperature measured by the second temperature measuring means out of the temperature measured by the first temperature measuring means and the temperature measured by the second temperature measuring means is determined. With priority, the temperature rise completion time is calculated from the temperature measured by the second temperature measuring means, and the material to be heated is heated and melted until the calculated temperature rise completion time.
The tapping process after heating and dissolving, to determine the return from tilting and the tilting of the furnace, as a trigger that has returned after tilting, heated measured by the measuring temperature and the weight measuring unit by the first temperature measuring means An induction melting furnace characterized in that the mass of a material is acquired, the holding power is calculated from the acquired measured temperature and the mass, and the calculated holding power is applied to the heating coil.

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