JPH0330280A - Heating method using high frequency induction heating furnace - Google Patents

Abstract

PURPOSE:To enable the reheating of the material to be heated immediately after pulling out of a heating furnace by taking temperature of the material to be heated, and deciding the operating output on the basis of the square root of a difference between the target temperature and the real temperature. CONSTITUTION:Heating of the material 10 to be heated is stopped on the way to be pulled out of a high frequency induction heating furnace 14, and thereafter, when it is heated again in the high frequency induction heating furnace 14, temperature of the material 10 to be heated pulled out of the high frequency induction heating furnace 14 is taken, and a difference between the target temperature and the real temperature is computed to decide the operating output on the basis of the square root of the temperature difference, and the high frequency current proportional to the operating output is fed. Immediate reheating of the material 10 to be heated is possible even if heating of it is stopped on the way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heating method using a high frequency induction heating furnace 9, and particularly relates to a heating method in which heating of a material to be heated is stopped midway and reheated. be.

Conventional Technology A high-frequency induction heating furnace is used to inductively heat a material to be heated, which is sent through the heating coil, to a predetermined target temperature by passing a high-frequency current through the heating coil. It is used in cases such as when carrying out. In such a high-frequency induction heating furnace, the heating temperature of the material to be heated is determined by the output voltage of the high-frequency power source that passes a high-frequency current through the heating coil and the feeding speed of the material to be heated; however, the output voltage of the high-frequency power source Since the responsiveness of the heating temperature to changes in is extremely fast, it is generally difficult to feedback-control the heating temperature. Therefore, the material to be heated is fed at a predetermined constant speed, and the output voltage of the high frequency power source is set based on the processing conditions such as the feeding speed, the material of the material to be heated, and the target temperature. The heating temperature was set to be the target temperature.

Problems to be Solved by the Invention By the way, in such a high frequency induction heating furnace, when a trouble occurs in the forging machine in the subsequent stage or when changing the mold, etc., the feeding of the material to be heated is stopped. It is also necessary to stop heating the material to be heated. In such a case, if the material to be heated is pulled out of the heating furnace and immediately reheated, the heating temperature will exceed the target temperature due to residual heat. It was necessary to leave the material to be heated until the temperature reached the target temperature.

The present invention has been made against the background of the above-mentioned circumstances, and its purpose is to enable immediate reheating even if heating of the material to be heated is stopped midway.

First Means for Solving the Problems In order to achieve the above object, the first invention provides a means for transmitting high-frequency current through the heating coil at a predetermined constant feed rate. In a high-frequency induction heating furnace that inductively heats a material to be heated to a predetermined target temperature, the heating of the material to be heated is stopped midway, the material is pulled out of the high-frequency induction heating furnace, and then the material is heated again in the high-frequency induction heating furnace. When heating, (a) a temperature measurement step of measuring the temperature of the material to be heated drawn out from the high frequency induction heating furnace, and (b) a temperature difference between the temperature measured in the temperature measurement step and the target temperature. (C) a manipulation output determination step of determining a manipulation output based on the square root of the temperature difference; and (d) heating with an output voltage proportional to the manipulation output. A special primary feature is that the method includes an energizing step of passing the high-frequency current through the coil, and (e) a feeding step of feeding the material to be heated into the high-frequency induction heating furnace at the constant feeding speed.

In addition, in the above-mentioned operation output determination step, when the target temperature is T and the temperature difference is ΔT, the operation output U is determined according to the following equation (1), for example.
It is structured to ask for. However, the function a (T) in equation (1) is determined theoretically or experimentally by adjusting the feed rate in advance when passing through a transformation point where the specific heat, electrical conductivity, magnetic permeability, etc. of the heated material change significantly during the heating process. It is determined according to the heating process, and if the specific heat etc. do not change significantly during the heating process, it will be a fixed constant. Further, although the constant b is theoretically 0, it is experimentally determined in advance due to electrical and thermal deviations.

u = a (T) Jma1r+ b...
・(1) Function and effect of the first invention, that is, the amount of human heat produced by the high-frequency induction heating furnace is proportional to the square of the output voltage of the high-frequency power supply, and if the feed rate of the material to be heated is constant, the heating temperature is is proportional to the amount of human heat, so if you set the output voltage of the high-frequency power supply so that it is proportional to the square root of the temperature difference between the target temperature and the actual temperature, the material to be heated will always be heated to the target temperature regardless of its temperature. can do.

Therefore, if the heating of the material to be heated is stopped midway due to a problem with the forging machine, etc. in the subsequent stage, the material to be heated is pulled out from the high frequency induction heating furnace and the temperature is measured, and the temperature is compared with the target temperature. Calculate the temperature difference, determine the operating output based on the square root of the temperature difference, for example, according to equation (1) above, and apply a high-frequency current to the heating coil with an output voltage proportional to the operating output. If the material to be heated is fed into the high-frequency induction heating furnace at a predetermined constant feed rate, even if the temperature of the material to be heated is higher than room temperature due to residual heat, it will not be heated beyond the target temperature. , the material to be heated is successfully heated to its target temperature.

As described above, according to the heating method of the present invention, even if the temperature of the material to be heated is higher than room temperature, it can be heated well to the target temperature, so it is not necessary to leave the material to be heated until the temperature of the material to be heated falls to room temperature. This makes it possible to reheat the material immediately, eliminating the need for a place to leave the material to be heated and cumbersome work, and improving work efficiency.

Second means for solving the problem Also, a second invention made to achieve the above object is:
By applying a high-frequency current to each of the heating coils of a plurality of heating stages provided at equal intervals, the material to be heated that is fed through the heating coils at a predetermined constant feeding speed is predetermined for each heating stage. In a high-frequency induction heating furnace that performs induction heating in stages to a target temperature set, heating of the material to be heated is stopped midway, and the material to be heated is pulled out from the high-frequency induction heating furnace halfway through the plurality of heating stages. After that, when heating it again in the high frequency induction heating furnace, (
f) a temperature measuring step of measuring the temperature of the material to be heated for each heated portion by the plurality of heating stages; and measuring the temperature difference between the target temperature and the temperature measured in the temperature measuring step for each heating stage. (h) an operation output determination step that determines the operation output for each heating stage based on the square root of the temperature difference calculated for each heating stage;
i) an energization step of energizing the high-frequency current to the heating coil of each heating stage with an output voltage proportional to the operating output determined for each heating stage, and (j) drawing the high-frequency current halfway through the plurality of heating stages. and a feeding step of feeding the heated material by one heating stage at the constant feeding speed.

Functions and Effects of the Second Invention The second invention provides a high-frequency induction heating furnace that heats a material to be heated in stages using a plurality of heating stages, in which the material to be heated whose heating is stopped midway is removed from the plurality of heating stages. In this method, the temperature measurement step, the temperature difference calculation step, the operation output determination step, and the energization step in the first invention are performed for each heating stage.
This heating is performed only while the material to be heated is fed through one heating stage. As a result, the material to be heated is heated to the target temperature in each heating stage, and thereafter, heating may be performed using a preset normal output voltage.

Also in this case, the material to be heated can be immediately reheated, and the same effects as in the first invention can be obtained.

Note that if each heating stage is considered to be an independent high-frequency induction heating furnace, the heating method in each heating stage is substantially the same as the first invention, and the second invention is a collection of the first invention. It can also be considered.

Third Means for Solving the Problems The third invention, which has been made to achieve the above-mentioned object, is a third invention in which high-frequency current is applied to each of the heating coils of a plurality of heating stages provided at equal intervals. In a high-frequency induction heating furnace that inductively heats a material to be heated that is sent through a heating coil in stages to a predetermined target temperature for each heating stage, the heating of the material to be heated is stopped midway and the material to be heated is heated. (g) When heating the material in the high-frequency induction heating furnace again after it is pulled out from the high-frequency induction heating furnace to the middle of the plurality of heating stages, (g) the temperature of the material to be heated is adjusted for each portion heated by the plurality of heating stages The temperature measurement process to be measured and (
1) a temperature difference calculation step of calculating the temperature difference between the target temperature and the temperature measured in the temperature measurement step for each heating stage, and (e) calculating the temperature difference based on the temperature difference calculated for each heating stage. (n) a speed determination step of determining a feed rate that allows each of the heating stages to heat the material to be heated to the target temperature; and (n) calculating the feed speed determined in the speed determination step and for each heating stage. 2 of the temperature difference
(0) applying an output voltage to the heating coil of each heating stage in proportion to the operating output determined for each heating stage; (p) a feeding step of feeding the material to be heated, which has been drawn halfway through the plurality of heating stages, by one heating stage at the feed speed determined in the speed determining step; It is characterized by having the following.

Here, the speed determining step may include, for example, the plurality of speed determination steps. Based on the maximum heating capacity of each heating coil in the heating stage and the temperature difference calculated for each heating stage, determine the feed rate when heating to the heating temperature by the maximum heating capacity for each heating stage, The structure is such that the slowest one of the feeding speeds determined for each heating stage is determined as the feeding speed. That is, the operating output that provides the maximum heating capacity in each heating stage is defined as u. ．． ．． ■、Temperature difference ΔTo、
If the target temperature is T7, then the feed speed Va of each heating stage that can be heated to the target temperature T7 with the maximum heating capacity is calculated according to the following equation (2), and the slowest feed speed ml, v7, is calculated as the feed speed. It is determined as follows. However, the function a1(T7) and the constant b1 in the equation (2) are the same as the function a(T) and the constant b in the equation (1), and are determined for each heating stage. Note that if the specific heat, electrical conductivity, magnetic permeability, etc. of the material to be heated are approximately constant regardless of temperature, and if the temperatures that can be heated with the same heating capacity are approximately the same, the feed rate should be determined based only on the temperature difference. You can also decide.

V,l= ((u...,-b,)/an(Tn))
”/ΔT1...(2) In addition, in the operation output determination step, the feed rate determined in the speed determination step is V, the temperature difference between each heating stage is ΔT7,
If the target temperature is T, then the operating output u7 of each heating stage is determined according to the following equation (3), for example. However, the function an(Tn) and constants b and l in this equation (3) are the same as in the above equation (2).

u B - a 6(T,)dvAT. +b.・・・
- (3) Functions and effects of the third invention In this third invention, compared to the second invention, the temperature drop of the material to be heated is relatively large when heating is stopped, and the material to be heated can be heated at a preset feed rate. This was done assuming that when the material is sent, it cannot be heated to the target temperature even if it is heated at the maximum heating capacity, and the material is heated at all heating stages based on the temperature difference calculated for each heating stage. In addition to determining the feed rate that can heat each material to the target temperature,
The operation output for heating the material to be heated to the target temperature at that feed rate is determined for each heating stage. In that case, the heating temperature of the material to be heated is inversely proportional to the feed rate, so when changing the feed rate, the output voltage of the high frequency power source should be adjusted to match the feed rate so that the amount of human heat changes in proportion to the feed rate. It is necessary to change it in proportion to the square root, and in the operation output determination step, the operation output at each heating stage is determined based on the feed rate and the square root of the temperature difference, for example, according to the equation (3) above. Note that the above formula (2) was obtained based on the formula (3).

Then, by feeding the abrasive to be heated for one heating stage at the feeding speed determined above while passing a high frequency current to the heating coil of each heating stage with an output voltage proportional to the operation output, The heating material is heated to a predetermined target temperature for each heating stage, and thereafter heating may be performed at a preset normal output voltage and feed rate.

Also in the third invention, the material to be heated can be immediately reheated, and the same effects as in the first and second inventions can be obtained. Moreover, in the present invention, the feed rate is determined so that the material to be heated can be heated to the target temperature in all heating stages, so even if the temperature drop of the material to be heated is relatively large when heating is stopped, the material to be heated can be heated to the target temperature. can be satisfactorily heated to the target temperature of each heating stage.

In addition, when determining the above-mentioned feeding speed, based on the maximum heating capacity of each heating coil of the plurality of heating stages and the temperature difference calculated for each heating stage, the maximum heating capacity of each heating stage is determined. If the feed rate for heating up to the target temperature is determined, for example, according to the equation (2) above, and the slowest one of the feed rates for each heating stage is determined as the feed rate, all heating stages will be heated to the target temperature. Since the material to be heated is fed at the fastest possible feeding speed, reheating can be carried out efficiently.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 shows an apparatus for hot forging a steel bar 10 as a material to be heated.
4 to a target temperature T of, for example, about 1200° C., and is cut into a predetermined size by a shear 18 of a forging machine 16 to perform a forging process. Steel bar 10
For example, the bolt material has a length of about 6 m, is cut into a size of about 10 cm, and is subjected to multi-stage forging processing to produce bolt materials and the like.

The feeding device 12 sends drive signals DM, DM. By supplying 2
The steel bar 10 is conveyed by rotating drive rollers 24 and 26 of each type. The drive roller 26 located near the forging machine 16 is intermittently rotated by a feed cam or other intermittent rotation mechanism, and intermittently feeds the steel bar 10 in conjunction with the operation of the shear 18. A presser roller 28 is arranged at each. Further, the drive roller 24 is used to place the steel bar 10 and move it at a preset constant feed speed.
The feeding speed is set to be approximately equal to the average moving speed of the steel bar 10 that is intermittently fed by the drive roller 26. When the tip of the bar 1410 sent by the drive roller 24 reaches the drive roller 26, the steel bar 10 is intermittently fed by the drive roller 26 while slipping between it and the drive roller 24.

The high-frequency induction heating furnace 14 has a plurality of heating stages (5 stages in this embodiment) provided at equal intervals, and each heating stage has heating coils 30a, 30b, 30 with the same number of turns.
c, 30d, 30e, and the heating coils 30a, 30b, 30c, 30d, 30e.
are respectively provided with high frequency power supplies 32a, 32b, 32c, and 32.
A high frequency current is supplied from the coils d and 32e (hereinafter referred to as heating coil 30 and high frequency power source 32 unless otherwise specified). The copper bar lO is made to pass through the heating coils 30, and an induced current is generated in the steel bar 10 by the electromagnetic induction action of the heating coil 30 at each heating stage, and the accompanying heat generation occurs. It is heated by The output voltages of the high-frequency currents outputted from each of the high-frequency power sources 32 are equal to each other, and the output voltages are set so that the bar 1110 at room temperature is heated to the target temperature T by passing through the five heating stages. It is set in advance based on the feed speed of the feed device 12 and the like. As a result, in normal hot forging work, the rod ml
o is heated to the target temperature T by the high-frequency induction heating furnace 14, and the forging process is performed satisfactorily by the forging machine 16.

The length of the heating coils 30 is, for example, about 80 cm, and they are arranged at intervals of about 20 cm from each other, and even if the steel bar 10 is intermittently fed by the drive roller 26, the passing time of each heating stage is is the same as when it is sent by the drive roller 24, and the steel bar 10 is always kept at the target temperature T.
It heats up well. In addition, when heating a steel material such as Steel Bar 10 to about 1200°C, it passes through a transformation point during the heating process and its specific heat, electrical conductivity, magnetic permeability, etc. change greatly, so the high frequency at each heating stage is Even when the output voltage of the current is the same and the heating capacity is the same, the accompanying temperature rise width differs depending on the temperature of the rod w410 in the heating stage.

On the other hand, a temperature sensor 34 such as a radiation thermometer is disposed at a position upstream of the high frequency induction heating furnace 14 in the feeding direction of the steel bar 10. This temperature sensor 34 is for measuring the temperature Tx of the bar w410 pulled out from the high frequency induction heating furnace 14 when the heating of the steel bar 10 is interrupted due to trouble in the forging 616 or die replacement, etc. A temperature signal ST. The operation output control device 3
Supply to 6. The operation output control device 36 is also supplied with a temperature signal ST representing the target temperature T set by the setting device 38. The temperature T of the steel bar 10 is measured by the temperature sensor 34. The process of measuring corresponds to the temperature measurement process.

The operation output control device 36 is composed of a microcomputer, etc., and has the functions shown in the functional block diagram of FIG. The temperature difference ΔT between the temperature signal STM and the temperature TM of the steel bar 10 is calculated. This process corresponds to a temperature difference calculation process. Then, in the operation output determination block 42, the operation output U is determined according to the following equation (4) based on the square root of the temperature difference ΔT, and the operation signal Su representing the operation output U is applied to each heating stage. It is supplied to the high frequency power source 32. Equation (4) is such that the operating output obtained from equation (1) is divided by the number of heating stages, 5, and this step corresponds to the operating output determining step.

5. The high frequency power source 32 of each heating stage is configured to supply the high frequency current to each heating coil 30 at an output voltage proportional to the operation output U represented by the operation signal Su. This step corresponds to the energization step. The amount of human heat applied to the steel bar 10 by the heating coil 30 is proportional to the square of the operating output U, and
The heating temperature lo is proportional to the amount of human heat if the feeding speed is constant, but as is clear from equation (4) above, the operation output U is proportional to the square root of the temperature difference ΔT, if the constant b is O. The amount of human heat is changed in proportion to the temperature difference ΔT. Therefore, in a state where a high frequency current is applied to the heating coil 30 of each heating stage with an output voltage proportional to the operation output U, the steel bar 10 is subjected to high frequency induction heating at a predetermined constant feeding speed by the feeding device 12. By being fed into the furnace 14, the steel bar 10 is heated to the target temperature T regardless of the magnitude of the temperature difference ΔT. Feeding device 1
2, the rod #410 is heated at a constant speed in the high frequency induction heating furnace 1.
4 corresponds to the feeding process.

Note that the function a (T) in the above equation (4) is
Specific heat and conductivity as the temperature rises at 0. It is determined theoretically or experimentally in advance according to the feed rate based on changes in magnetic permeability and the like. Further, the constant b is theoretically O, and is experimentally determined in advance from electrical and thermal deviations.

Also, the aforementioned operation output control device? &36 and feeder 12
, a restart signal S is generated by pressing the restart push button PB.
S is supplied.

This restart push button PB is used to press the steel bar 1 whose heating has been stopped midway due to the operation of the high frequency induction heating furnace 14 and feeding device 12 being stopped due to trouble in the forging machine l6, etc.
0 is pulled out to the upstream side of the high-frequency induction heating furnace 14, and the pressing operation is performed when the hot forging process is restarted from that rod @10.

In such a hot forging processing apparatus, when the heating of the bar 1i10 is stopped midway due to trouble with the forging machine 16, etc., the bar 1i10 is moved so that the tip of the bar 1i10 is located at the location where the temperature sensor 34 is disposed. When the steel bar 10 is pulled out from the high-frequency induction heating furnace 14 and the hot forging process is resumed by pressing the restart push button PB, the temperature TM of the steel bar 10 is detected by the temperature sensor 3.
4 and its temperature T. The operating output U is determined according to the above equation (4) based on the temperature difference ΔT between the target temperature T and the operating output U, and a high-frequency current is applied to the heating coil 30 of each heating stage with an output voltage proportional to the operating output U. be done. In addition, the steel bar 10 is fed into the high frequency induction heating furnace 14 at a predetermined constant feed rate by the feeding device 14, and is passed through five heating stages, so that the steel bar 10 is heated at a predetermined rate regardless of the temperature difference ΔT. It is heated to the target temperature T. Therefore, even if the temperature TM of the rod 14lO is higher than room temperature due to residual heat, it will not be heated beyond the target temperature T, and the rod! 410 temperature T. It is possible to reheat the stick immediately without leaving it to cool down to room temperature.
This eliminates the need for a place to leave the i110 unattended and troublesome work, and improves work efficiency.

Note that when the hot forging process of the steel bar 10 whose heating has been interrupted is completed, the high frequency power supply 32 supplies a high frequency current to the heating coil 30 at a preset output voltage, and the subsequent steel bar 10 is heated.
Normal heating is performed on the

Next, another embodiment of the present invention will be described. In the following description, parts common to those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The high-frequency induction heating furnace 50 shown in FIG. 3 is composed of five heating stages like the high-frequency induction heating furnace 14 of the previous embodiment, and operates in exactly the same way as the previous embodiment in normal hot forging processing. The steel bar IO is heated to the target temperature T in stages.

In this case, the output voltage of the high-frequency power source 32 in each heating stage is determined by passing a high-frequency current with the same output voltage to each heating coil 30 as described above, so that the steel strip 10 at room temperature is finally It is set to be heated to a target temperature T, and the target temperature at each heating stage is not particularly set, but the temperature after heating of the steel bar 10 heated at each heating stage during this normal hot forging process. T. ．． (n=a, b,
c, d, e) correspond to the target temperature of each heating stage. The target temperature T1 is determined in advance by actual measurement or the like, and is set in the setting device 38. Note that the target temperature T. of the final heating stage is coincides with the target temperature T.

Further, temperature sensors 52a, 52b, 52c, and 52d are provided at upstream positions of each heating stage of the high-frequency induction heating furnace 50, respectively.
, 52e (hereinafter referred to as temperature sensor 52 unless otherwise specified) are provided. These temperature sensors 5
2 is the steel bar 1 due to trouble with the forging machine 16 or die replacement.
0 heating interrupted? In this case, the temperature of the portion of the steel strip 10 that is pulled out until its tip is located before the final heating stage, that is, the portion to be heated by each heating stage, that is, the upstream part of each heating stage, is 11% (n = a , b, c, d, e),
Temperature signal ST■ (n=a, b,
c, d, e) to the operation output control device 54. The process of measuring the temperature T0 of each heated portion of the rod @IO with these temperature sensors 52 corresponds to the temperature measurement process.

The operation output control device 54 also includes a temperature signal ST.ST. (n=a, b, c, d, e) are supplied. This operation output control device 54 is made up of a microcomputer or the like and has the functions shown in the functional block diagram of FIG. The target temperature T7 represented by and the temperature T of the steel bar IO represented by the temperature signal STM■. Calculate the temperature difference ΔTFI (n=a, b, c, d, e).

This process corresponds to a temperature difference calculation process.

In the temperature difference calculation block 56, the temperature difference Δ is calculated for each heating stage.
Once Tn is calculated, next, in the speed determination block 58, based on the operation output umaxn (n=a, b, Cd, e) that provides the maximum heating capacity in each heating stage and the temperature difference ΔT7, Feeding speed v, (n=
a, b, c, d, e) according to the above formula (2),
The slowest feed speed mincn is determined as the feed speed V. This is because the steel bar 10, which has been partially heated due to a problem with the forging machine 16, is left for a long time, and its temperature TI
．． ! , is significantly reduced, it may not be possible to heat to the target temperature T, l even if heated at the maximum heating capacity at the feed rate during normal hot forging processing, and the above feed rate V is Sticks in the heating stage! This is the fastest feed rate capable of heating iI10 to its respective target temperature T7. The step of determining the feed rate (■) corresponds to a speed determining step, and a speed signal Sv representing the feed rate V is supplied to the operation output determining block 60 and the feed device 12. Note that the operating outputs u and Xfi of each of the heating stages are set in advance.

For the heating stage with the slowest feed rate einVn determined as the feed rate V, the operation output determination block 60 determines the operation output u ffiaxn at which the maximum heating capacity is obtained.
is determined as the operating output u1, while for the other heating stages, the operating output u7 is determined based on the feeding speed V and the square root of the temperature difference ΔT7 according to the equation (3). And the operating output U of each heating stage. An operation signal S representing
u. is supplied to the high frequency power source 32 of each heating stage. This step corresponds to the operation output determination step.

The high frequency power source 32 of each heating stage receives the operation signal Su as in the above embodiment. The operation output U represented by The high frequency current is applied to each heating coil 30 at an output voltage proportional to . This step corresponds to the energization step. The amount of human heat applied to the bar m10 by each heating coil 30 is proportional to the square of the operating output u7, and the heating temperature of the steel bar 10 is proportional to the amount of human heat and inversely proportional to the feed speed V.
As is clear from the equation, if the constant b7 is O, the operating outputs u and l are changed in proportion to the square root of the feed rate V and the temperature difference ΔT, and the amount of human heat is changed by the feed rate V and the temperature difference ΔT.
It can be changed in proportion to 7. For this reason, when the steel bar 10 is fed through each heating stage at the feeding speed V in a state where a high frequency current is applied to the heating coil 30 of each heating stage with an output voltage proportional to the operation output u7, the steel bar 10 is heated to the target temperature T7 at each heating stage, regardless of the magnitude of the temperature difference ΔT,1.

Further, the feeding device 12 to which the speed signal Sv is supplied,
The drive signal DM of the drive motor 20 that rotationally drives the drive roller 24 is changed so that the steel bar 10 is fed by one heating stage at the feed speed V represented by the speed signal Sv. As a result, the steel bar 10 that has been pulled out until its tip is located before the final heating stage is fed at the feed rate V only while the tip passes through the final heating stage, and thereafter the bar is fed at the preset normal feed rate. brought back to speed. The process of feeding the steel bar 10 by one heating stage at this feeding speed V corresponds to the feeding process.

Note that the high frequency power source 32 in each heating stage is connected to the steel bar 1.
The operation output u7 is sent only while 0 is sent at the above feed speed V.
A high-frequency current is output with an output voltage proportional to , and thereafter the output voltage is returned to the preset normal output voltage. Further, the drive motor 22 is operated in a normal state.

The restart signal SS from the restart push button PB is supplied to the operation output control device 54, and the rod mlO, whose heating has been stopped midway, is controlled until the tip of the rod mlO is located before the final heating stage. By pressing the restart button PB after pulling it out, the temperature T of each part of the steel bar IO is measured by the temperature sensor 52 as described above, and the temperature T,4 and the target temperature T7 are measured. Based on the temperature difference ΔT7 between
The feed rate V that allows heating up to is determined.

Then, based on the feeding speed V and the square root of the temperature difference ΔT7, the operation output u7 of each heating stage is calculated according to the formula (3) above.
is determined, and a high-frequency current is applied to the heating coil 30 of each heating stage with an output voltage proportional to the operating output u7, and the steel bar 10 is fed by the feeding device 12 at the above-mentioned feeding speed ■ for one heating stage. Sent. This results in bar @1
0 is heated to the target temperature T7 at each heating stage regardless of the temperature difference ΔT7, and thereafter the normal feeding speed and output voltage are returned to perform normal heating.

Therefore, also in this embodiment, the steel bar 10 can be immediately reheated, and the same effects as in the first embodiment can be obtained. Moreover, in this embodiment, it is not necessary to completely pull out the steel bar 10 from the high-frequency induction heating furnace 50, but it is sufficient to pull it out until the tip is located before the final heating stage, making the work even easier. In this case, the feed rate V is determined so that the steel bar 10 can be heated to the target temperature T7 in all heating stages, so even if the temperature drop of the steel bar 10 at the time of stopping heating is relatively large, the steel bar 10 can be satisfactorily heated to the target temperature T7 of each heating stage.

Further, the above-mentioned feed rate v7 is the feed rate v7 when each heating stage is heated to the target temperature T7 by its maximum heating capacity, based on the maximum heating capacity of each heating stage and the temperature difference ΔT7. Find the slowest feed rate s of the feed speed v7! +
Since sVn is determined as the feed rate V, the steel bar 10 is fed at the fastest feed rate capable of heating to the target temperature T in all heating stages, and reheating can be performed efficiently. It can be done.

Although the embodiments of the present invention have been described above in detail based on the drawings, the present invention can also be implemented in other embodiments.

For example, in the above embodiment, the case where the steel bar 10 is reheated by the high frequency induction heating furnace 14.50 during hot forging processing was explained, but the method of the present invention can also be applied to various other processing devices that perform heating using the high frequency induction heating furnace. This method can be applied in the same manner, and can also be applied to heating coil materials and the like.

Further, in the above embodiment, the steel bar 10 whose heating was stopped midway
Although the case of reheating has been described, it is also possible to utilize the method of the present invention in an apparatus that handles materials to be heated at different temperatures.

Further, although the high frequency induction heating furnaces 14 and 50 of the embodiments described above are constructed of five heating stages, the number of heating stages may be any number.In particular, the high frequency induction heating furnace 1 of the first embodiment
Regarding No. 4, depending on the target temperature T, it may be constructed from only one heating coil.

Further, the heating capacity of each heating stage does not necessarily have to be the same, and in the first embodiment as well, different operation outputs can be determined for each heating stage and the output voltage of the high frequency power source 32 can be controlled separately.

Further, in the first embodiment, the temperature of the rod mio is T. This is based on the assumption that is approximately the same over its entire length, but
Temperature T of rod w410. In cases where the temperature differs greatly in each part of the support 110, it is also possible to continuously change the operating output U in accordance with changes in the temperature T, 4. This also applies to the second embodiment.

In addition, all of the above embodiments are effective when the temperature drop of the steel bar 10 is relatively large, but in the second embodiment, the temperature drop of the steel bar 10 is relatively large.
0 temperature drop is small and preset? Even if the steel bar 10 is fed at a feed rate of is also high, determine the operation output u7 for each heating stage according to (1) 2 without changing the feed rate, and perform the operation while feeding the rod @10 by one heating stage at the preset feed rate. A high frequency current may be applied to each heating coil 30 at an output voltage proportional to the output u7.

In addition, in the second embodiment, the rod 12 is
! 10 is pulled out and reheated, but the amount pulled out can be changed as appropriate. In particular, when the feed rate is not changed as described above, it is desirable to determine the withdrawal amount according to the temperature T0 of the steel bar 10 so that the steel bar 10 can be heated to the target temperature T at each heating stage.

In addition, in the second embodiment, the target temperatures T and l of each heating stage are set by the setting device 38, but the heating temperature of each heating stage is detected during normal hot forging processing, and It is also possible to automatically set the target temperature of each heating stage.

Further, in the second embodiment, the slowest mince of the feed speeds v7 when heating to the target temperature T9 using the maximum heating capacity is determined as the feed speed V, but the feed speed V must be slower than the min V n. For example, it is possible to select from a plurality of predetermined feed speeds.

Although no other examples are given, the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a structural diagram illustrating an example of a hot forging processing apparatus to which the method of the present invention is suitably applied. FIG. 2 is a block diagram illustrating the functions of the operation output control i1 [1 device in the device shown in FIG. 1. FIG. 3 is a structural diagram illustrating another hot forging processing apparatus to which the method of the present invention is suitably applied. FIG. 4 is a blotter diagram illustrating the function of the operation output control device in the device of FIG. 3. lO: Steel bar (material to be heated) 14,50: High frequency induction heating furnace

Claims (4)

[Claims] (1) By passing high frequency current through the heating coil,
In a high-frequency induction heating furnace that inductively heats a material to be heated, which is fed through the heating coil at a predetermined constant feeding speed, to a predetermined target temperature, the heating of the material to be heated is stopped midway and the high-frequency A temperature measurement step of measuring the temperature of the material to be heated drawn out from the high frequency induction heating furnace when it is heated again in the high frequency induction heating furnace after being pulled out from the induction heating furnace; a temperature difference calculation step of calculating a temperature difference between the temperature and the target temperature; a manipulation output determination step of determining a manipulated output based on the square root of the temperature difference; and an output voltage proportional to the manipulated output. A heating method using a high-frequency induction heating furnace, comprising: an energization step of supplying the high-frequency current to the heating coil; and a feeding step of feeding the material to be heated into the high-frequency induction heating furnace at the constant feeding speed. . (2) By applying a high frequency current to each of the heating coils of a plurality of heating stages provided at equal intervals, the material to be heated is fed through the heating coils at a predetermined constant feeding speed for each heating stage. In a high-frequency induction heating furnace that performs induction heating in stages to a predetermined target temperature, the heating of the material to be heated is stopped midway, and the material to be heated is transferred from the high-frequency induction heating furnace midway through the plurality of heating stages. a temperature measuring step of measuring the temperature of the material to be heated for each portion heated by the plurality of heating stages when heating the material again in the high-frequency induction heating furnace after the material has been pulled out to the target temperature; and measuring the target temperature in the temperature measuring step. a temperature difference calculation step of calculating a temperature difference between the heating stage and the calculated temperature for each heating stage; and a manipulation output determining a manipulation output for each heating stage based on the square root of the temperature difference calculated for each heating stage. a determining step; an energizing step of passing the high-frequency current through the heating coil of each heating stage at an output voltage proportional to the operating output determined for each heating stage; a feeding step of feeding the material to be heated by one heating stage at the constant feeding speed. (3) By applying high-frequency current to each of the heating coils of a plurality of heating stages provided at equal intervals, the material to be heated that is sent through the heating coils is staged to a predetermined target temperature for each heating stage. In a high-frequency induction heating furnace that performs induction heating, heating of the material to be heated is stopped midway, and the material to be heated is pulled out from the high-frequency induction heating furnace to the middle of the plurality of heating stages, and then the material is heated by induction again. When heating in a heating furnace, there is a temperature measurement step of measuring the temperature of the material to be heated for each heated portion by the plurality of heating stages, and a temperature difference between the target temperature and the temperature measured in the temperature measurement step. a step of calculating a temperature difference for each heating stage, and determining a feed rate capable of heating the material to be heated to the target temperature in all heating stages based on the temperature difference calculated for each heating stage. a speed determining step for determining the operating output for each heating stage based on the feed rate determined in the speed determining step and the square root of the temperature difference calculated for each heating stage; an energization step of energizing the high-frequency current to the heating coil of each heating stage with an output voltage proportional to the operating output determined for each heating stage; 1 at the feed rate determined in the speed determination step.
1. A heating method using a high-frequency induction heating furnace, characterized by having a feeding step of feeding for the number of heating stages. (4) The speed determining step is performed by determining the maximum heating capacity for each heating stage based on the maximum heating capacity of each heating coil of the plurality of heating stages and the temperature difference calculated for each heating stage. 4. The heating method using a high frequency induction heating furnace according to claim 3, wherein a feed rate is determined when heating to the heating temperature, and the slowest feed rate among the feed rates for each heating stage is determined as the feed rate.