JPH0130268B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating method and apparatus for controlling the heating temperature of only a necessary local part of a metal material.

Recently, for the purpose of energy saving, a so-called direct rolling method has been implemented in which slabs cast by continuous casting are subjected to a product rolling process as hot slabs. By the way, the average temperature of high-temperature slabs cast by continuous casting is such that direct rolling is possible, but there are localized low-temperature areas, and if the rolling process is performed directly, the crystal structure in the low-temperature areas will become defective. This will adversely affect the quality of the product. For example, in the temperature distribution example of a steel piece 1 with a rectangular cross section manufactured by continuous casting shown in FIG. 1, the corner portion 1a has the lowest temperature.

Conventionally, an induction heating method has been known as a means for temperature compensation of such a localized low-temperature portion of a steel material, but the well-known induction heating method has the following drawbacks. Figure 2 shows an example of a conventional device, in which a piece of steel to be heated 1
In the case of an inductor 2 consisting of a coil configured to be wound around the entire circumference of the inductor 2 and an AC power source 3 supplying power to the inductor 2, the entire circumference near the surface of the cross section of the steel piece is heated almost uniformly. However, when applied to a steel piece having the cross-sectional temperature distribution shown in FIG. 1, it was inevitable that the central surface portion 1b would be excessively heated and the corner portions 1a would be underheated. Therefore, in order to heat the steel slab 1 to the temperature required for rolling, the corner 1a is heated slightly excessively, and the temperature of the entire cross section is raised by the equalizing effect of heat conduction within the steel slab. was once. In other words, the central surface portion 1b of the steel billet is heated even more excessively, which wastes a lot of power, and also increases the installed capacity of the induction heating device, which is extremely uneconomical.

The present invention has been made in order to solve the above-mentioned conventional difficulties, and when directly rolling metal materials, especially steel materials such as high-temperature steel billets manufactured by continuous steel construction, the desired heated parts of the steel materials can be efficiently rolled. Moreover, it is an object of the present invention to provide an induction heating method and apparatus that can adjust the heating temperature to any desired temperature. Hereinafter, the present invention will be explained in detail based on examples.

FIG. 3 shows an example of the basic configuration of an apparatus for carrying out the present invention, and for the sake of simplicity, the first
The heating means in the case where the upper left corner of the corner 1a of the steel piece shown in the figure is used as the heated part will be explained. A side inductor 4a is provided close to the side surface of the corner 1a of the heated steel piece 1, and an upper inductor 4b is provided similarly close to the top surface of the corner 1a. Each inductor 4a, 4b consists of an iron core 41a, 41b and a coil 42a, 42b wound around each iron core, and one end of the coil 42a, 42b is connected to the AC power source 3 having the same phase and the same frequency.

Now, in the above configuration, the alternating current is transferred to the coil 42.
a, 42b, an alternating magnetic flux 43 flows from the legs of the iron cores 41a, 41b through the inside of the steel piece 1 as a magnetic path.
a and 43b are generated, and induced currents (eddy currents) 44a and 44b are generated inside the steel piece 1, which becomes Joule heat and heats the steel piece 1. Here, the feature of the induction heating method of the present invention is that if the directions of the alternating magnetic fluxes 43a and 43b are relatively opposite at any instant, the direction of the induced current generated by each alternating magnetic flux is also opposite. The focus is on the fact that the induced currents act on the steel piece 1 so that the directions of the induced currents merge. In other words, the density of the heating heat amount increases and the heating efficiency improves. As described above, the direction of the alternating magnetic fluxes 43a and 43b can be easily reversed by winding the coils 42a and 42b in opposite directions as long as AC power supplies with the same phase and frequency are used. It is. Now, based on the above principle, the polarity of either of the inductors 4a, 4b is changed, and the alternating magnetic fluxes 43a, 43b are
If the directions of are relatively the same (at any instant), the directions of the induced currents will act to cancel each other out, and the density of the amount of induction heating will be lower than when the directions of the induced currents are the same. becomes smaller. Furthermore, if the inductors 4a and 4b are constructed so that they can approach each other freely with respect to the heated steel piece 1, it is possible to change the density of the amount of induction heating in any part.

As described above, the present invention takes advantage of the fact that the heating density changes by providing a plurality of inductors and changing the direction of the induced current, and that the heating density of any part can be adjusted by making each inductor freely approachable. This makes it possible to most efficiently adjust the temperature of metal materials by induction heating. Hereinafter, the present invention will be explained in more detail based on specific examples.

In FIG. 4, the steel slab 1 is a material to be heated that is transferred in the direction of the arrow S by a transfer device such as a conveyor roller (not shown), and in this embodiment, the four corners 1a of the steel slab 1 are This shows the case where the part is heated by induction. A side inductor 4a is provided on the side of the steel piece 1, an upper inductor 4b is provided at the top, and a lower inductor 4c is provided at the bottom.
are arranged symmetrically in the width direction of the steel piece 1, respectively. The upper and lower inductors 4b and 4c are connected by a support device 5, and the steel piece 1 is connected via a drive device 6.
It is supported so that it can move freely in the width direction. The AC power supply 3 is a common power supply connected to each of the inductors, but only the side inductor 4a has a polarity converter 7 interposed between it and the power supply 3. Temperature detector 8 is steel piece 1
It is installed above the steel strip and detects the temperature distribution in the width direction of the steel strip. The temperature reference setting device 9 is preset with a heating reference temperature that satisfies a desired temperature of the steel billet 1, for example, the rolling temperature in the subsequent rolling process of the induction heating apparatus of the present invention. The heating control device 10 outputs an operation command signal to the drive device 6 and the polarity conversion device 7 based on input signals from the temperature reference setting device 9 and the temperature detector 8.

The operation of the apparatus configured as described above will be explained next.
The temperature distribution in the width direction of the steel piece 1 is detected by a temperature detector 8, and the heating reference temperature of the steel piece 1 is simultaneously inputted from the temperature reference setting device 9 to the heating control device 10 at the same time as the signal thereof.
The heating control device 10 compares the temperature detection value of each part in the width direction with the heating reference temperature, and compares the temperature detection value of each part in the width direction with the heating reference temperature.
If the temperature of b satisfies the heating reference temperature and the temperature of the corner 1a is below the reference temperature, an operation command signal is issued to the drive device 6, and the upper and lower inductors 4b and 4c are moved to the position corresponding to the corner 1a. move it. At the same time, the heating control device 10 determines whether polarity conversion device 7 needs to perform conversion, depending on the difference between the temperature of corner 1a and the heating reference temperature. In other words, when there is a large temperature difference and a large amount of heating heat is required, the inductor 4a
so that the induced currents between the inductors 4a and 4b and between the inductors 4a and 4c are in the same direction. If the temperature difference is small, no instruction is given from the heating control device 10 to the polarity conversion device 7, and alternating magnetic flux in the same direction is generated in all the inductors, and the amount of heating heat becomes small. According to the polarity conversion operation of the polarity conversion device 7 described above, the amount of heating heat is changed in two steps, either large or small, but when continuously making minute temperature adjustments, the time pattern of polarity conversion is changed according to the temperature difference. It may be provided in advance to the heating control device 10.

Fig. 5 shows an example of the arrangement of inductors when the thickness of the heated steel billet 1 is large.Two side inductors 4a are provided on the sides of the steel billet 1, making it possible to increase the amount of heating heat at each corner. ing. In this embodiment, the side inductor 4 is
a and the upper and lower inductors 4b, 4c can also be made movable vertically or horizontally. Incidentally, in the configuration in which one set of inductors is disposed only in one cross-sectional direction of the steel piece 1 as shown in the embodiment shown in FIGS. 4 and 5, there is a limit to the amount of heating heat. Therefore, when a large amount of heating heat is required, it is also effective to arrange a plurality of sets of inductors in a row in the length direction of the steel piece to be heated. Further, in the above embodiment, the direction of power supply from the AC power supply is changed to convert the polarity of the inductor, but other conversion means may be used such as a thyristor high frequency inverter capable of changing the phase of the AC current or an induced voltage phase adjuster. Of course, technology can be used. The present invention is also effective as a heating means for metal materials other than steel pieces, and can be handled by changing the shape of the inductor in the case of metal materials having a heated portion with a unique cross-sectional shape.

As described above, when selectively inductively heating a local part of a metal material, the present invention can adjust the temperature to a desired temperature using an extremely simple device, and has excellent thermal efficiency, reducing power consumption. The energy saving effect is significant.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the temperature distribution of a rectangular cross-sectional steel piece, Fig. 2 is a schematic diagram showing the conventional induction heating method, Fig. 3 is an explanatory diagram showing the principle of the present invention, and Fig. 4 is an explanatory diagram showing the principle of the present invention. FIG. 5 is a schematic diagram showing the configuration of the embodiment. FIG. 5 is an explanatory diagram showing different examples of arrangement of the inductor of the present invention. 1... Steel billet to be heated, 3... AC power supply, 4a, 4b,
4c...Inductor, 5...Support device, 6...Drive device, 7
...Polarity converter, 8...Temperature detector, 9...Temperature reference setting device, 10...Heating control device.

Claims (1)

[Scope of Claims] 1. A plurality of inductors are arranged so that the respective induced currents interfere with each other around the heated part of the metal material,
A method for local induction heating of a metal material, characterized in that the heating temperature of a heated part is arbitrarily adjusted by converting the polarity of each inductor or the alternating current phase of the inductor. 2. A support device that supports a plurality of inductors so as to be accessible near the heated portion of the metal material to be heated, and a temperature detector that detects the temperature of the heated portion of the metal material to be heated;
a temperature reference setting device for setting a heating reference temperature of the metal material to be heated; a polarity converter or an alternating current phase converter for converting the polarity of one or more of the plurality of inductors; and the temperature The input signal from the reference setting device and the input signal from the temperature sensor are compared, and an operation command signal is given to the polarity converter or the alternating current phase converter so as to reduce the temperature difference, or the input signal is supported with the polarity converter. A local induction heating device for metal materials consisting of a heating control device that sends an operation command signal to the device.