JPS58186193A - Induction heater - 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 (al Description of the Technical Field) The present invention involves inserting a material to be heated made of a material such as steel and having a cylindrical shape such as a billet or roll into a solenoid-like induction heating coil, and then quenching and heating the material. The present invention relates to an induction heating device for induction heating for purposes such as heat treatment processing.

fb) Description of the Prior Art When phosphorizing and heat-treating a cylindrical material to be heated, a method is generally used in which heating is performed near the surface and conduction heating is utilized. On the other hand, if heating in the low temperature range is performed at i speed V, there is a risk that the material to be heated may crack or lose quality due to thermal distortion due to the difference in thermal expansion. In this case, this tendency is reversed by wssvc. Also, in the radial direction, the center temperature must be kept below a certain temperature.

For this reason, the heating temperature increase rate in the low temperature region is slowed down and the %ff1-
It is necessary to increase the heating rate of IijI. In the case of induction heating, since the applied power is proportional to the temperature increase rate, the applied power must be small in the low m@ region and large in the high temperature region. Since the applied power is proportional to the square of the coil terminal road pressure, it is necessary to reduce the voltage in the low temperature region and increase the voltage in the high temperature region. For this reason, conventionally, a transformer was installed on the power supply side and a tag was attached to lower the voltage. , the voltage is lowered through an induction voltage regulator or a nested transformer, and the power is generated when heating a low-temperature area.11
-It was small. This not only increases the number of equipment configurations and requires a large installation space, but also makes them expensive.

(C)@Ming's Purpose The present invention has a structure in which the primary or secondary windings of a supply transformer can be switched in series/parallel, and the switching is performed using a switching device, etc., so that the normal tap switching voltage can be maintained. It is possible to switch the voltage up to the h voltage range, and by making the heating solder pressure in the low temperature region small and the heating voltage in the high temperature region large, it is possible to prevent cracking and quality deterioration during heating. An object of the present invention is to provide an induction heating device.

(d) Structure of the Invention An embodiment of the present invention will be described below with reference to the drawings. 1st
2, a material to be heated 1 is inserted into an induction heating coil 2, and a transformer tap changer 4 is installed on the primary side or the secondary side as required via a coil tap changer 3. 9 connected to the secondary side of the transformer 50, and furthermore, a switching disconnector 1 for series is connected to the primary side of the transformer 50 in order to widen the voltage change range.
1 and 1. A switching disconnection 61O for parallel connection is connected to the AC power source 7.

(e) Operation of the invention An alternating voltage of a certain frequency from the AC power source 7 is applied to the heating coil 2.
, an alternating current flows through the heating coil 2 wound around the heated material 1 , and a magnetic flux is generated within the heating coil 2 . When this alternating magnetic flux interlinks with the heated material 1 in the heating coil 2, a conductive current of 1Km is generated in the heated material,
Due to this current and the specific resistance of the first layer of the material to be heated, dicole heat is generated and heating is performed. The degree of heating is proportional to the applied power VC, and the applied power is proportional to the square of the applied voltage.
1 is turned ON, the parallel switching new circuit switch 10 is turned OFF, and the applied voltage is increased in the high temperature region, that is, series switching disconnection! arp 11
Then, by turning on the parallel switching disconnector 10, the desired temperature increase can be obtained. In addition, as an example of how to time the switching from the low temperature region to the high temperature region, that is, the series/parallel switching, 2 is as follows.
There are two ways to set up a timer: one is to switch the timer after a certain period of time using a dashed line, and the other is to use a coil with a peephole, detect the temperature with a radiation temperature needle, and switch the switch when a certain temperature V is reached.

Also, the switching means of the coil tap switching device 3 will be explained. Coil 2 wound and arranged around stepped heating material l K ii”l r t)l + '1 + d
+ #”2 Hbl + C! H'l and upper and lower stands 4
Step taps are provided so that the coil feeding length at 'l+dl' is the shortest, and the length is the same as the length of the large diameter portion 1a of the material to be heated l. These taps are connected to an AC power source 7 via a tag switch 3 and a transformer 5. Depending on the heating temperature, the coil taps are switched into four stages by a tap switching control circuit 12 that can programmatically control the set value using a timer. The order is al 1m, b, , b, dl dB.

It is set as C1-C5. The heating temperature of taps d1-d in @3 stage is around soo'o, which is the point where the temperature has passed through the magnetic transformation point, and the state diagram of the magnetic flux distribution is shown in Figure @3. FIG. 1114 shows an example of the temperature distribution on the surface of the heated material 1 in the longitudinal direction.

When an alternating voltage of a certain frequency is applied to the heating coil 2 from the AC power source 7, an alternating current flows through the heating coil 2 wound around the single-stage heated material 1, and magnetic flux is generated within the coil. This magnetic flux interlinks with the heated material l inside the heating coil 2.

A conductive current of 1 kfC@ is generated in the material to be heated, and due to this current and the specific resistance of the material to be heated, Joule heat is generated and heating is performed. This means that the heating temperature Fi of the heated material 1 depends on the magnetic flux distribution with respect to the heated material IK. Since the heating temperature distribution is 11K tonne in the center, the heating temperature distribution tends to be convex with high temperature in the center, so the coil tap should be 17 degrees from the outside to avoid an extremely convex shape. When the temperature rises in this state, μ=1 state near the center of the large diameter portion 1m of the heated material 441, and 1M1 East becomes biased toward the ends of the heated material 1 rather than the center.

On the other hand, when i11 degrees rises to around μ-1, the impedance seen from the coil end changes more significantly than in the μ > 1 region, so the coil tap must be adjusted to keep the force density constant. It is advantageous to keep it inside and wear coils. This shortening ratio is determined in relation to the degree to which the temperature distribution in the longitudinal direction of the surface of the heated material 1 becomes concave due to the bias of the magnetic flux toward the end of the large diameter portion 1a of the heated material 1. This 2
When heating the surface temperature to about 900°C by step heating, the small diameter part 1b is in the μ>1 region, so the smaller the difference in diameter from the large diameter part 1m, the easier it is to be heated. For example, if the small diameter part 1b is heated below the quenching temperature. If you want to do so, you will not be able to satisfy that condition. Therefore, as the heating temperature rises, the coil taps are sequentially shortened in advance using the tap switching control circuit 12 for heating time, and especially when passing the magnetic transformation point (near about 800 degrees Celsius), the coil feeding length is set to about the length of the large diameter section. Toshiku dldm 3rd stage) small diameter part 1
In this process, only the large diameter section 1m is heated without interlinking the bK magnetic flux, and the temperature of the small diameter section 1b is lowered.
Since the temperature distribution on the m surface is convex, in the fourth stage of the next step, the coil feeding length is set so that the temperature at the end of the large diameter @1 m rises and the temperature distribution on the large diameter surface becomes appropriately concave. The appearance of these temperature rises is shown in a model and compared, Figure 4 shows 'l
It is heated in the order of +'l H'S 1'4. This makes it possible to control the temperature of the small diameter portion 1b.

Coil tap switching control includes timer control and 5th coil tap switching control.
As shown in the figure, the taps may be switched using the radiation thermometer 14 through the sight hole 13 provided in the middle of the coil and via the multi-point setting controller 15.Of course, the control by a timer and the radiation thermometer control It is also possible to combine.

(f) Effects of the Invention As described above, according to the present invention, in order to apply small power and large power, the internal winding structure of the conventional transformer can be improved without manufacturing and installing special equipment. 1. By simply preparing a switching disconnector, which is commonly used, it is possible to easily change the power as desired from a low temperature range to a high temperature range, and it is possible to heat large diameter materials. The danger of time can be eliminated.

[Brief explanation of drawings]

Figures 1 and 2 are wiring diagrams showing embodiments of the present invention;
FIG. 3 is an explanatory diagram showing magnetic flux distribution, FIG. 4 is a characteristic diagram showing heating temperature rise, and FIG. 5 is a wiring diagram showing another embodiment of the present invention. l... Material to be heated 7... AC M source 2... Induction heating coil 3... Coil tap switch 5... Transformer 4...
...Converter tap switch 10...Parallel switch 11...Series switch (7317) Agent Patent attorney Noriyuki Chika (
1 other person) Figure 1 Figure 2

Claims (1)

[Claims] 1iI in which the material to be heated is inserted into an induction heating coil and heated.
4 Heating equipment is equipped with a transformer on the power supply side that can switch the primary or secondary windings in series and parallel and has a secondary voltage switcher, and is capable of switching between low-temperature region heating and high-temperature region heating. An induction heating device characterized in that heating is performed using small power in the former case and large power in the latter case.