JPH03165489A - Re-heating of continuous feed induction heating device - Google Patents

Abstract

PURPOSE:To reduce the amount of material cooled after heating and reduce a buildup time at the time of re-heating by feeding at a speed slower than normal to re-heat in the first half stage, supplementally re-heating in the latter half stage, and increasing the feed speed in accordance with the restoration of the temperature. CONSTITUTION:When a heater is stopped because of a press failure, the temperature of an object 10 to be heated decreases over the entire length of a heating coil 1. When the heating is started again, the re-heating is performed at a speed SL lower than the normal speed SO. The heating coil 1a for the first stage is adjusted to the output commensurate with the speed SL while the heating coil 1b for the latter half stage is adjusted to the output for producing a specified temperature at the outlet when the speed is SL. When the temperature of the object 10 to be heated is restored, the speed SL is increased accordingly to approach the normal speed SO. The output of the first stage 1a is increased according to the speed. The speed and the output power are returned to the normal values when the temperature of the inlet of the latter half stage 1b reaches the normal temperature. This permits to reduce the amount of the material cooled after being heated and to shorten the buildup time.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention solves the problem of the generation of burnt material when restarting a continuous feed type induction heating device mainly used for forging after a trouble occurs. The present invention relates to a reheating method for a continuous feed type induction heating apparatus, which minimizes the power of the continuous feed induction heating apparatus and shortens the start-up time when restarting the apparatus.

[Conventional technology]

The conventional continuous feed induction heating device was developed by the Japanese Patent Publication No. 63-1087.
As shown in Publication No. 5, since the complete stop heat insulation was made of wax, slow-speed feed heat retention was adopted.

Slow feed heat retention means 50 to 6
Set the transport speed to 0%. In other words, the aim is to reduce the waste material during standby by reducing the speed to a point where the temperature increase pattern can be maintained.

(, l'uBE+;&JQbI?AL-ner1tll-
j) Conventional reheating methods for continuous feed induction heating equipment used slow feed heat retention, which resulted in a large amount of waste material and bypass if the heat retention time was long or the coil length was long in a large device. They were having trouble disposing of the waste materials. The present invention provides a method for reheating a continuous feed type induction heating device in which the generation of waste material is reduced by reheating.

[Means to solve the problem]

The reheating method for a continuous feed type induction heating device according to the present invention is such that when the operation of the induction heating device is stopped due to reasons other than induction heating equipment, the speed S is reduced to less than the co-steady speed SO at the time of restarting the induction heating device.
Start with l, the output of the front stage near the entrance is speed 81
The output power of the downstream stage near the exit is adjusted to a predetermined temperature at the exit of the downstream stage when the output power is conveyed at speed SL with the initial temperature being the temperature that decreased due to heat dissipation during the shutdown. Adjust the output to heat, and when the temperature of the heated object gradually recovers due to the effects of restarting the operation, adjust the speed S accordingly.
L approaches the steady speed S0, the output of the front stage increases in accordance with the speed, and when the temperature of the heated object at the inlet of the rear stage approaches the steady temperature, the feed speed, output power of the front stage, and output power of the rear stage increase. The output power is returned to a steady value, and during reheating, the object to be heated in the former stage fill is reheated to a steady temperature by the latter stage coil.

[Effect]

In this invention, during reheating, the material to be heated is conveyed at a slower speed than usual, and while being reheated in the first stage, the insufficient amount is reheated in the second stage, so that at least the material to be heated in the first stage is heated to a predetermined temperature.

〔Example〕

FIG. 1 is a block diagram for implementing an embodiment of the present invention. In the figure, (la) and (lb) are heating fi's
(2) is a pinch roller, (3) is a skid rail, (
4a) (4b) is a power supply consisting of an inverter, (5
) is the 7 Lee roller, (6) is the proximity switch, (7) is the metal blade facing the switch (6), (8) is the insertion conveyor, (9) is the heater body, and 110 is the object to be heated. .

An example of the reheating method is shown in FIG. As shown in FIG. 1, the object to be heated αO is conveyed by pinch rollers (2). In FIG. 2, the speed is S0 in the steady state. The 7-ree roller (5) in contact with the object to be heated αO
Since it rotates as O moves, the metal blade (7) attached to its shaft also rotates. If a proximity switch (6) is installed to detect when the metal blade (7) approaches, pulses will be generated periodically as the workpiece GO moves. Therefore, by counting the pulses, the progress of the object to be heated αO can be determined. distance can be determined.

Now, assume that the heater has been stopped due to a malfunction of the press or the like. In FIG. 2(d), the timer starts operating and starts to keep track of the stop time. The temperature of the heated object an is heating coil/l/ (1
) begins to decrease in temperature along its entire length. The temperature change depends on the cooling time, but for example, the curve (2
). Therefore, when the line restart signal is input, power is applied only to the latter stage power supply (4b), and the feeding is not restarted, resulting in a static heating period. This is because the heating pipe in the latter stage is 7s/(l
b) In order to bring the heated object α0 in the heating coil (1b) as close to the predetermined temperature as possible, the heated object α0 in the latter heating coil (1b) is
This is to prevent a case where the output of the subsequent stage power supply (4b) cannot be increased due to overcurrent when the temperature is below 0°C. Now, regarding the restart of operation, first, since the stop time can be determined by a timer or the like, the material temperature at that time can be determined from the energy loss determined by the Stefan-Boltzmann heat radiation tt loss and the heat transfer loss. Figure 4 shows an example of calculation for φ70.0 This value is an example of calculation using the example constants in the table below, such as specific heat, thermal conductivity, etc. according to the case of change. (Table) Cooling curve The constant to be determined The temperature drop is compensated for by the downstream power source (4b), and the capacity of the downstream power source (4b) and the downstream heating coil (lb
) depending on the carp y length and the temperature increase value required for reheating, the second
The feed rate STJ at the time of restart shown in the figure is determined. S
Normally, I is lower than the steady state feed rate S0. When the power source (4a) at the front stage is sent at sL, it is adjusted to the power vTJ at the front stage outlet based on the steady temperature. Post-stage power supply (4b)
Initially, the output power vR2 is the power to restore the temperature at the inlet of the heating coil/L/(4b) to a predetermined temperature at the time of restarting the heating coil/L/(1b). Naturally, it comes out due to insufficient temperature, but it gradually rises and by the time the material at the inlet of the heating coil/I/(lb) in the latter stage is taken out, it has reached the specified temperature. If it is left off, the material in the heating coil A/(11)) in the previous stage gradually recovers its temperature, so that it becomes as shown in curve (3) in FIG. 3. Therefore, it is necessary to gradually lower the output chamber cover turn of the power source (4b) so that it approaches a predetermined power. However, when restarting, it is required to return to a steady state as quickly as possible.Therefore, in the present invention, rather than reducing the power in the latter stage, the paper feed speed is gradually restored to compensate for this. While reducing the temperature compensation amount, the speed can be brought close to the specified speed. In the first stage, the power is adjusted according to the speed change, and the temperature increase value of the first stage coil always maintains the temperature increase value in the steady state. Here, a specific design example will be shown. The material diameter of the object to be heated αO is φ 0. The heating temperature is 1200"C.If the feed speed is 1m/mil, the processing weight per hour is 1812Kg/By.The net power required to raise the temperature from room temperature to 1200"C is the required amount at each temperature. When calculating energy and converting it into electric power, Q,
23 KWH/Kg. In the case of curve (1) in Figure 3, where the temperature is raised to 1200°C in the first stage and kept warm in the second stage, the power in the first stage is 181!2Kg/Hr X O, 23Kwa/
Kg “417!: Obtained by w.Heating carp /L/(
1! If the average fill efficiency of the power supply (L) is Q,6, then the power supply (
The required power for 4&) is 695 Kw. The second stage is 1
It is enough to cover the heat dissipation of 200"C, so if we design carp # (lb) with 5QOmm,
The heat dissipation energy is approximately 25 W, and the coil efficiency of Coil/I/(more) is 0.5, which is necessary for the power supply (4b) (worse than the previous stage because the material is completely non-magnetic). The electric power will be 50Kv. Assuming that the system is stopped for 10 minutes, the temperature increase curve becomes curve (2) in Figure 3. Suppose that the steady-state special voltage of the previous stage is 10007 and set to 695.
If the design is such that the output is W and the subsequent stage is 5007 which outputs 50KW, each set voltage can be calculated using the following formula.

The material of the coil (1b) is 15, l Kg, '100
In order to raise the temperature of the material 'C to more than 7 degrees C in the non-magnetic region, set the specific heat to Q, 15 KO&l/Kg"C, and the coil efficiency to 0.1 (the efficiency is better because it is in the magnetic region). ing). Now, set the static heating voltage vR1 in Fig. 2(g) to 7
When the voltage is 0, the output is 100 Kv, and the material is supplied with OKW. The material of Koi/I/(1b) is about 9
．． The temperature can be raised to muff Q''C in 5 seconds.0 Now, regarding reheating, in order to raise the temperature of the material at the front fill outlet of '10O'C to 1200°C at the rear stage fill outlet, the temperature increase value is 500. °
C9 net electric energy specific heat 0.15 Kcal/Kg 'C
Then, it becomes 0.0872rvu/Kg. 10
Since it takes about 70 seconds to soak the temperature from 0°C to 1200°C, the feeding speed needs to be 0.8 m/win. Therefore, the fine velocity in Fig. 2 (&) is 1 at steady state.
Since the temperature is raised to a predetermined temperature at a feed rate of m/man, the voltage vTJ of the front stage power supply (4&) at the feed rate BL is as shown in equation (1).

...... (1) Since vo is assumed to be 10007 in the current example, vIl is 6
If set at 54v, the material entering the previous stage will ensure a predetermined temperature rise. Now, the temperature of the material entering the latter stage is 00°C at the exit of the former stage, but the temperature has risen by the amount of time it has stayed in the former stage carp, and the material at the entrance point of the former stage is now at the rear stage carp! By the time it reaches the entrance, it has reached the predetermined temperature of 1200°C. Therefore, if the feed speed is continuously changed from 0.428 m/win to a steady speed of 1 m/win, the temperature increase value will decrease continuously, so the temperature at the outlet of the subsequent coil can be maintained at the specified temperature. 0 For example, the steady state 100"C point of carp/l/(1&) becomes approximately 550°C after 10 minutes. If the normal pattern is followed when restarting, the temperature will normally rise by 500°C. First of all, to get the FoO'C to 1200°C, it requires 0.42
Since 500"C is raised at 8 m/m workn, the throughput is 175 Kg/Hr, and the net electric energy is o, 08fu2!cwH/Kg, so if the net 6fu, 6Kv efficiency is o5, it is about 1351ff. Heat dissipation amount 501Cw
If 185 Kv is applied in consideration of the above, it can be heated to 1200°C. In the case of the material at the 700°C point during steady state, it is 1050°C at the inlet of the latter stage coil, so the temperature rise value is 150°C, and the net power consumption is 0,0262 KwH/Kg, so it is 1 as it is.
When 85Kw is applied, the power input to the workpiece is 6
Since it is 5KW, it is possible to process 2.5F and 6Kg/Hr. In other words, even if the speed is 1.42 m/win, the temperature increase value can be covered in the latter stage. Therefore, the more the heating in the previous stage contributes, the less it is necessary to slow down the restart speed.
It can be seen that the speed can be returned to steady state. It was found that it is possible to increase the speed when restarting, but if you speed it up too fast, the capacity of the power source (41) in the previous stage will be insufficient. Therefore, the rated speed S0 can be approached as quickly as possible. When the rated speed is reached, the power source (4b) in the latter stage is turned on to return to a steady state.

As mentioned above, when restarting, the speed is changed, and it is necessary to always apply power to the previous stage so that a steady temperature increase value can be obtained according to the speed.

For this purpose, a method called y control is usually adopted.

Reference speed, for example, voltage vI at restart.

If it is set to 0.428 a/min, the correction voltage can be output continuously by correcting the relationship between the actual speed signal and the reference voltage in a form close to the square root. For example, any speed Vx,
If the required voltage at that time is V, then equation (2) is obtained. 0 α is Q, 5 if the fill constant does not change depending on the applied voltage, and 0.5 to 5 if it changes.
1. It is known that it is between o. As another example, if the power supply (4b) at the latter stage is divided into two parts, the restart time can be further shortened. The speed Sp at restart is the coil (
1b) sets the time for soaking, so the power supply (
If 4b) is divided into a wetting section and a soaking section like a normal heating device, the speed Sz can be further increased.

〔Effect of the invention〕

As described above, according to the present invention, even in a continuous feed type induction heating device, it is possible to reduce the amount of material that is burnt out after the operation is stopped, and furthermore, when restarting, the temperature can be gradually recovered. By increasing the feed speed in accordance with the above, it became possible to shorten the restart time.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an induction heating device implementing the present invention, Fig. 2
FIG. 3 is an explanatory diagram showing an embodiment of the operating method according to the present invention, FIG. 3 is an explanatory diagram showing a temperature change of a workpiece in a coil, and FIG. 4 is an explanatory diagram showing an example of calculation of a cooling curve. In the figure, (1m) (lb) is a heating filter, (4a)
(4b) is a power source. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In the reheating method for a continuous feed type induction heating device equipped with a first heating coil, a second heating coil, and a heating power source, when the operation of the induction heating device is stopped due to a cause other than the induction heating device, When restarting the operation, start at a speed S_L that is slightly below the co-steady speed S_O, adjust the output of the front stage near the entrance to the output power commensurate with the speed S_L, and the output power of the rear stage near the exit dissipate heat while the operation is stopped. When transported at speed S_L with the temperature lowered by as the initial temperature,
Adjust the output to heat to the specified temperature at the outlet of the subsequent stage,
When the temperature of the heated object gradually recovers after restarting,
Accordingly, the speed S_L is brought closer to the steady speed S_O, and the output of the previous stage is continuously changed to the power according to the speed,
When the temperature of the object to be heated at the inlet of the latter stage approaches the steady temperature, the feed rate, the output power of the first stage, and the output power of the second stage are returned to the steady values, and the temperature of the object to be heated in the heating coil of the former stage is increased during reheating. A reheating method using a continuous feed induction heating device that enables reheating to a steady temperature using the heating coil in the latter stage.