JPH07211440A - Method for controlling billet heater - Google Patents

Abstract

PURPOSE:To enhance the yield of heated billets by improving a method for controlling a billet heater. CONSTITUTION:A billet heater comprises a commercial power supply 1, a switch 2, a high-frequency inverter 3, a high-frequency capacitor 4, a heating coil 5, a control unit 7, a motor 8, and a pinch roller 9. When billets 6 are first conveyed to the heating coil 5 by the pinch roller 9, the control unit 7 controls the output power of the high-frequency inverter 3, and when the last billet 6 has been conveyed to the heating coil 5 by the pinch roller 9, the control unit controls the output power of the high-frequency inverter 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a billet heater control method for heating a billet of an object to be heated, which is a conductor, by electromagnetic induction.

[0002]

2. Description of the Related Art In a conventional billet heater control method, a high frequency inverter for supplying high frequency power for generating a magnetic flux in a heating coil outputs an output voltage irrespective of the state of a work carried in the heating coil. Is controlled to a desired value by voltage control or output power is controlled to a desired value by power control.

[0003]

When the method of controlling the voltage of the output of the high frequency inverter for supplying the high frequency power for generating the magnetic flux in the heating coil is adopted, there is no object to be heated in the heating coil. When the object to be heated is sequentially conveyed from the state to the heating coil and the billet heater is operated, the number of objects to be heated in the heating coil increases and the heating power to each of the objects to be heated becomes insufficient. In order to prevent this, the output voltage of the high-frequency inverter is raised or the speed of the pinch roller that conveys the object to be heated is slowed down to cope with this, but the number of objects to be heated in the heating coil increases. Therefore, there is a problem that it is difficult to adjust the impedance because the impedance changes during the heating process.

Further, when the method of controlling the electric power of the output of the high frequency inverter is adopted, since the last object to be heated is conveyed into the heating coil via the dummy bar, the object to be heated is Since the heating power becomes too large, there is a problem that the object to be heated is overheated. An object of the present invention is to provide a billet heater control method that solves the above problems.

[0005]

According to the first aspect of the present invention, in a billet heater for generating a magnetic flux in a heating coil and inductively heating a billet which is an object to be heated and conveyed in the heating coil, the billet heater includes: A high-frequency inverter that supplies high-frequency power for generating magnetic flux to the heating coil when the billet heater is operated by sequentially transporting the object to be heated into the heating coil from a state in which there is no object to be heated is Power control of the inverter output is performed.

According to the second aspect of the invention, in the billet heater for generating magnetic flux in the heating coil and inductively heating the billet which is the object to be heated conveyed in the heating coil, the last object to be heated is the heating object. After being conveyed through the dummy bar into the coil, the high frequency inverter supplying the high frequency power for generating the magnetic flux to the heating coil controls the voltage of the inverter output.

[0007]

According to the first aspect of the invention, when the billet heater is operated by sequentially transporting the object to be heated into the heating coil from a state where the object to be heated is not present in the heating coil, the magnetic flux is applied to the heating coil. The high-frequency inverter that supplies the high-frequency power for generating the power controls the output power, so that even if the impedance of the heating process changes due to the increase of the heated object, the heating power of the heated object can be easily changed. Can be changed or adjusted.

Further, in the second invention, from the time when the last object to be heated is conveyed into the heating coil via the dummy bar, a high frequency power for supplying a high frequency power for generating a magnetic flux to the heating coil. By controlling the output voltage, the inverter can easily change and adjust the heating power of the object to be heated even if the impedance of the heating process changes due to the decrease in the object to be heated.

[0009]

1 is a block diagram of a billet heater showing an embodiment of the present invention, in which electric power is supplied from a commercial power source 1 to a high frequency inverter 3 via a switch 2 and converted into high frequency power by the high frequency inverter 3. Then, high frequency power is supplied to the resonance circuit including the high frequency capacitor 4 and the heating coil 5. The billet 6, which is the object to be heated, rotates the motor 8 in response to a conveyance speed command from the control device 7, and is conveyed into the heating coil 5 by the pinch roller 9 mechanically connected to the motor 8.

When the billet 6 is not conveyed in the heating coil 5 and the billet 6 is sequentially conveyed by the pinch roller 9 into the heating coil 5 to operate the billet heater, the control device 7 causes magnetic flux to the heating coil 5. The high-frequency inverter 3 that supplies high-frequency power for generating the power detects the power of the high-frequency inverter 3 in order to control the output power, compares it with the power setting value, and adjusts it to provide a gate signal to the high-frequency inverter 3. ing.

Further, the control device 7 controls the high frequency inverter 3 for supplying high frequency power for generating magnetic flux in the heating coil 5 from the time when the last billet 6 is conveyed into the heating coil 5 via the dummy bar. In order to control the voltage of the output, the voltage of the high frequency inverter 3 is detected, and the high frequency inverter 3 is provided with a gate signal by comparing with and adjusting the voltage setting value.

In a normal operating condition, the high frequency inverter 3
Operates by either voltage control for controlling the output voltage suitable for the billet heater to a desired value by a gate signal from the control device 7 or power control for controlling the output power to a desired value.

[0013]

According to the present invention, when the billet is sequentially conveyed from the state where there is no billet in the heating coil to operate the billet heater, high frequency power for generating magnetic flux in the heating coil is supplied. By controlling the output power of the high-frequency inverter to be supplied, the billet that does not reach a desired temperature is reduced and the yield is improved.

Since the last billet is conveyed into the heating coil via the dummy bar, the high frequency inverter supplying the high frequency power for generating the magnetic flux in the heating coil controls the output voltage. The billet is not overheated and the last one can be heated to the desired temperature, and the yield is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a billet heater showing an embodiment of the present invention.

[Explanation of symbols]

 1 Commercial Power Supply 2 Switch 3 High Frequency Inverter 4 High Frequency Capacitor 5 Heating Coil 6 Billet 7 Controller 8 Motor 9 Pinch Roller

Claims (2)

[Claims] 1. A billet heater for inductively heating a billet, which is an object to be heated, which is carried in the heating coil by generating a magnetic flux in the heating coil. When operating the billet heater by sequentially transporting the object to be heated in the coil,
A method for controlling a billet heater, wherein a high-frequency inverter that supplies high-frequency power for generating magnetic flux to the heating coil performs power control of the inverter output. 2. A billet heater for inductively heating a billet, which is an object to be heated, which is carried in the heating coil by generating a magnetic flux in the heating coil, wherein the last object to be heated passes through a dummy bar in the heating coil. A billet heater control method, wherein a high-frequency inverter that supplies high-frequency power for generating a magnetic flux to the heating coil performs voltage control of the inverter output even after being conveyed.