JP2878348B2 - Induction heating device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION (Industrial application field) The present invention relates to an induction heating apparatus, and more particularly to an apparatus for performing uniform heating over the entire period of an induction heating process.

(Prior Art) In recent years, a so-called induction heating furnace capable of rapid heating has been used as a heat treatment of a billet requiring high-temperature heating such as a slab for oriented silicon steel sheet.

In such an induction heating furnace, charging and extraction of a billet into the furnace is generally performed by a lifting operation of a lifting beam on which the billet is placed.
This is done from below the furnace.

FIG. 2 shows the entire vertical induction heating furnace, and FIG. 3 shows details of the support structure.

In the figure, reference numeral 12 denotes a billet, 13 denotes a furnace wall, 14 denotes an induction coil, and 15 denotes a support beam. This support beam 15
Is composed of a support hardware 15-1, a water cooling pipe 15-2, and a refractory heat insulating material 15-3. The billet 12 is a support hardware 15-1
It is placed on the top and loaded into the furnace from below by a lifting device (not shown).

Now, as shown in FIG. 3, support hardware 15-1 made of a heat-resistant metal is arranged at an appropriate interval in the longitudinal direction of the slab,
It is in direct contact with and supports the billet 12. The heat-resistant metal support 15-1 is supported by a water-cooled pipe 15-2. Furthermore, this pipe 15-2 is used for supporting hardware 15-1
Including a part of, lining with fireproof insulation 15-3,
The structure is such that heat transfer to the cooling water is prevented as much as possible.

By the way, in such a support structure, there is a problem that it is difficult to maintain a uniform temperature distribution in the width direction of the slab due to remarkable heat dissipation from the lower part of the slab.

As a measure to prevent this, in Japanese Patent Application Laid-Open No. 61-78087,
Divide the induction coil in the width direction of the billet, that is, in the vertical direction,
A technique has been proposed in which a coil loss power is calculated from each coil current, and a net heating power to be heated is obtained by subtracting the loss power, thereby achieving uniform heating in the width direction.

However, as shown in Fig. 4 for the power flow in the induction heating coil, not all of the power except for the coil loss (including the power mechanical loss) contributes to the temperature rise of the object to be heated, and part of the power dissipates heat. Consumed as Here, the amount of heat dissipated fluctuates greatly depending on the condition of the furnace body, that is, a change in the amount of heat stored in the furnace body and the temperature of the object to be heated.

(Problems to be Solved by the Invention) Uniform heating obstruction factors in the above-described power control method, i.e., 1) Difference in heat radiation amount due to difference in initial temperature of heating target (changes depending on shape of heating target and furnace structure), 2) Advantageously eliminates the effects of differences in the amount of heat stored due to changes in furnace body conditions (caused by aging of the furnace body, heating intervals, size of objects to be heated, etc.), seeks appropriate input power, and provides effective uniform heating It is an object of the present invention to achieve

(Means for Solving the Problems) That is, according to the present invention, in an induction heating device having a plurality of induction heating coils, a radiated heat amount sensor and a heat storage amount for measuring a radiated heat amount and a furnace body heat storage amount for each induction coil unit. A sensor is provided, and a dissipated heat amount calculation device and a heat storage amount calculation device for calculating a temporal change of the dissipated heat amount and the furnace body heat storage amount measured by the dissipated heat amount sensor and the heat storage amount sensor are further provided. An induction heating device including an input power pattern setting device that adjusts the input power amount for each induction coil based on the temporal change amount of the body heat storage amount and the temporal change amount of the coil loss power amount obtained from each coil current. .

 Hereinafter, the present invention will be specifically described with reference to the drawings.

FIG. 1 schematically shows an induction heating device according to the present invention. In the figure, number 1 is a frequency power converter, 2a, 2b... 2n are induction heating coils, 3a, 3b.
... 4n is a power factor improving condenser for each coil, 5 is a furnace body,
6 is a material to be heated, 7a... 7n are heat radiation amount sensors of each coil,
8n are heat dissipation amount calculating devices for the respective coils, 9a ... 9n are heat storage amount sensors for the respective coil portions, 10a ... 10n are heat storage amount calculating devices for the respective coil portions, and 11 is an input power pattern setting device.

Now, the method of setting and correcting the input power to each of the induction heating coils 2a ... 2n will be described. The heat storage distribution in consideration of the specific heat and the temperature gradient, etc., is sent to the input power pattern setting unit 11, and the input power pattern setting unit 11 sets the initial input power amount for each coil unit so that uniform heating can be performed. Thereafter, in the same manner, the heat storage amount calculation system 9a... 9n, 10a... 10n calculates the heating time-series heat storage distribution, while the heat storage amount calculation system composed of 7a. The amount of heat dissipated for each coil portion due to the temperature rise of the material 6 is calculated and sent to the input power pattern setting device 11 respectively. In this input power pattern setting device 11,
From the obtained heat quantity and the time-dependent change amount of the coil loss power quantity separately obtained from each coil current, an appropriate input power quantity for each induction coil is calculated, and based on the calculated value, the single-phase power of each coil is calculated. The set values of the transformers 3a ... 3n and the power factor improving capacitors 4a ... 4n of each coil are changed.

Here, the amount of heat storage and the amount of heat dissipated for each coil unit change from moment to moment.
7n, 8a... 8n and the heat storage amount calculation systems 9a... 9n, 10a... 10n always detect such a temporal change in the heat amount and feed back to the input power pattern setting unit 11 to correct the input power amount of each coil. As a result, uniform heating over the entire heating operation period is realized.

(Effects of the Invention) Thus, according to the present invention, induction heating for the purpose of uniform heating of the material to be heated, particularly in the initial stage of heating when the heat balance of the furnace body and the material to be heated is unsteady in the setting of the input power, Uniform heating can be achieved over the entire heat treatment period.

[Brief description of the drawings]

 FIG. 1 is a schematic view of an induction heating apparatus according to the present invention, FIG. 2 is an overall view of a conventional vertical induction heating furnace, FIG. 3 is a detailed view of a support structure, and FIG. It is a flowchart. 1 ... frequency power converter, 2a ... 2n ... induction heating coil 3a ... 3n ... single-phase transformer of each coil 4a ... 4n ... ... capacitor for improving power factor of each coil 5 ... furnace body, 6 ... Material to be heated 7a ... 7n ... Dissipated heat amount sensor for each coil 8a ... 8n ... Dissipated heat amount calculation device for each coil 9a ... 9n ... Heat storage amount sensor for each coil unit 10a ... 10n ... Heat accumulation amount calculation for each coil unit Equipment 11 Input power pattern setting device 12 Steel billet 13 Furnace wall 14 Induction coil 15 Support beam 15-1 Support hardware 15-2 Water cooling pipe 15-3 … Fireproof insulation

Continuation of front page (56) References JP-A-61-78087 (JP, A) JP-A-62-126581 (JP, A) JP-A-63-143781 (JP, A) JP-A-60-236487 (JP, A) JP-A-63-13292 (JP, A) JP-A-63-228589 (JP, A) JP-A-63-314792 (JP, A) Japanese Utility Model Laid-Open No. 62-118385 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B 6/06 393

Claims (1)

(57) [Claims] In an induction heating apparatus having a plurality of induction heating coils, a heat dissipation amount sensor and a heat accumulation amount sensor for measuring a heat dissipation amount and a furnace body heat amount are provided for each induction coil portion. A heat dissipation amount calculating device and a heat storage amount calculating device for calculating the heat dissipation amount and the furnace body heat storage amount measured by the sensor and the heat storage amount sensor over time, and the heat dissipation amount and the furnace body heat storage amount over time and An induction heating device comprising an input power pattern setting device for adjusting an input power amount for each induction coil based on a temporal change in a coil loss power amount obtained from a coil current.