JP2020002466A - Heat treatment apparatus - Google Patents

Abstract

To provide a heat treatment apparatus in which optical heating can be performed for a steel sheet without moving it after induction heating.SOLUTION: The heat treatment apparatus includes an induction heating coil for heating a metal plate by induction heating, and a light source for optically heating the metal plate. The induction heating coil has a heating space in which a metal plate can be accommodated. The light source includes a light emitting part that emits light. The light emitting part is disposed inside the induction heating coil.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a heat-treated metal plate and a heat treatment apparatus.

  In recent years, from the viewpoint of reducing the weight of automobiles and improving safety during collisions, high-strength steel sheets having increased toughness by heat treatment have been used. As a method for forming such a high-strength steel sheet, a forming method called hot pressing has been put to practical use. Hot pressing is a method in which a steel sheet heated to 900 ° C. to 1000 ° C. is pressed with a mold at normal temperature to form the steel sheet while quenching the steel sheet. By using this method, the strength of the steel sheet can be increased. it can.

  Conventionally, as a method of heating a steel sheet to a temperature range of 900 ° C. to 1000 ° C., electric heating (for example, see Patent Literature 1), induction heating (for example, see Patent Literature 2), and optical heating with infrared rays (for example, see Patent Literature 3) ).

  The energization heating is a method in which electrodes are attached to both ends of a steel sheet and a current is applied between the electrodes, thereby heating the workpiece by Joule heat generated inside the work.

  Induction heating is a method in which a high-frequency current is applied to a coil to generate a magnetic field, a magnetic flux is applied to the steel sheet, and the steel sheet is heated by Joule heat generated by an eddy current generated inside the steel sheet.

JP-A-2002-18531 JP 2005-122983 A JP 2011-095567 A

  However, in the heating method using electric heating or induction heating, it is difficult in principle to uniformly heat the entire steel sheet without temperature unevenness. In particular, in recent years, the shape of a steel sheet is various, and a steel sheet having a different shape (a steel sheet that is not a rectangular plate shape) in which an acute angle portion or the like partially exists, or a difference thickness steel sheet having portions having different thicknesses (for example, Tailored blanks, see JP-A-2013-184221). It is more difficult to uniformly heat such a steel sheet, and it is difficult to suppress temperature unevenness. For example, in energization heating, unless the cross-sectional area and the width of the steel sheet between the two electrodes are constant, heating cannot be performed uniformly in principle and temperature unevenness occurs. In addition, in the case of induction heating, if there is a portion with a different thickness, such as a thick steel plate, it is difficult to raise the temperature in the thick portion, but it is easy to raise the temperature in the thin portion. I do. Then, when the temperature unevenness occurs, there arises a problem that the strength of the steel sheet after hot pressing varies and a predetermined quality cannot be obtained. For example, there is a problem that a crack is generated in a part that is partially overheated, and a problem that quenching of a part that is insufficiently heated is not performed well, resulting in a decrease in strength.

  On the other hand, light heating by infrared rays can take measures to suppress the occurrence of temperature unevenness to some extent. For example, among a plurality of light heating lamps, the output of a lamp that heats a portion of a steel plate where the temperature is likely to rise (for example, a thin portion in the case of a differential thickness steel plate) is made weaker than other lamps. Next, there is a method of controlling the output of each light heating lamp. As another example, there is a method in which the arrangement of a plurality of lamps is set to an arrangement suitable for the shape of a work.

  The present inventors arrange | positioned the thickness difference steel plate (the difference thickness steel plate of a shape like FIG. 2A, FIG. 2B) which has a 3.2-mm-thick part and a 1.6-mm-thick part in several matrix form. In a test for heating from room temperature (25 ° C.) to around 1000 ° C. using a light-heated lamp, studies have been made to suppress temperature unevenness. As a result, when the output of the lamp that heats the 3.2 mm thick portion and the lamp that heats the 1.6 mm thick portion are the same, the temperature of the 3.2 mm thick portion becomes 900 ° C. At that time, the temperature difference between the 1.6 mm thick portion and the 1.6 mm thick portion was about 230 ° C., whereas the output of the lamp for heating the 1.6 mm thick portion was changed to the 3.2 mm thick portion. When the temperature of the 3.2 mm thick portion reaches 900 ° C. when the temperature is lowered in a specific manner from the lamp to be heated, the temperature difference from the 1.6 mm thick portion is reduced to approximately 90 ° C. We have succeeded in suppressing it.

  In the heat-treated metal plate, it is desirable that unevenness in temperature be as small as possible. Further, in recent years, further improvement in temperature unevenness has been demanded for a heat-treated metal plate.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method for manufacturing a heat-treated metal plate that can further suppress temperature unevenness when heating a metal plate such as a steel plate. Is to do.
Another object of the present invention is to provide a heat treatment apparatus that can further suppress temperature unevenness when heating a metal plate such as a steel plate.
Another object of the present invention is to provide a heat treatment apparatus capable of performing light heating without moving a steel plate after induction heating.

  The present inventors have intensively studied a method for further suppressing the temperature unevenness. As a result, the inventors have conceived that it is possible to further suppress temperature unevenness when heating a metal plate such as a steel plate by employing the following configuration, and have completed the present invention.

That is, the method for producing a heat-treated metal plate according to the present invention includes:
Step A of starting heating of the metal plate by induction heating;
After the step A, a step B of heating the metal plate by the induction heating until the temperature Y at the lowest temperature point X of the metal plate reaches a specific value Z based on the Curie temperature,
A step C of starting heating of the metal plate by optical heating after the temperature Y reaches the specific value Z.

The Curie temperature is a temperature above which the magnetism of the magnetic material is lost (for example, about 770 ° C. for iron).
According to the configuration, after starting the heating of the metal plate by induction heating, the temperature Y of the lowest temperature point X of the metal plate is set to a specific value Z (for example, lower than the Curie temperature) based on the Curie temperature. The heating of the metal plate by the induction heating is performed until the temperature becomes lower by 5 ° C. (step B).
The portion of the metal plate that is easily heated reaches the Curie temperature earlier than the portion X that is hardly heated. Here, the portion X that is difficult to be heated is formed, for example, in a region where the magnetic flux density is low in the induction heating device. However, when the temperature reaches the Curie temperature, the magnetism is lost, and the induction heating does not further heat. Therefore, even if induction heating is continued, the temperature does not greatly change from the Curie temperature. Therefore, induction heating is performed until the temperature Y of the location X reaches the specific value Z, but the location where heating is easy is maintained near the Curie temperature, and the temperature does not substantially rise any more. On the other hand, the location X is heated to the specific value Z by the induction heating even while the location that is easily heated is maintained near the Curie temperature without being heated.
As a result, when the temperature Y at the location X reaches the specific value Z, the temperature difference between the most easily heated location and the least heated location (location X) is the difference between the Curie temperature and the specific value Z. About. For example, in the case of a steel plate, when a portion that is easily heated reaches a specific value Z (for example, a temperature lower by 5 ° C. than the Curie temperature: 765 ° C.), the other portions have a Curie temperature (770 ° C.). Therefore, when the temperature reaches around the Curie temperature (around 770 ° C.), the temperature deviation (temperature difference between the lowest temperature portion and the highest temperature portion) of the entire steel sheet is determined by the Curie temperature and the specific value Z. (In this example, about 5 ° C.).
Then, at this timing, that is, at the timing when the temperature Y reaches the specific value Z, heating of the metal plate by optical heating is started (step C). Thus, light heating is started from around the Curie temperature. Since the optical heating is started after the temperature deviation is reduced near the Curie temperature, the temperature deviation at the time when a desired temperature (for example, 1000 ° C.) is reached can be reduced. That is, at the specific value Z (around 770 ° C.), there is almost no temperature unevenness, and the temperature rises from there to a desired temperature (for example, 1000 ° C.) (for example, 1000 ° C.-770 ° C. = 230 ° C.). Therefore, the configuration is such that temperature unevenness is unlikely to occur.
According to the present inventors, in a test using the above-described steel plate having a thickness of 3.2 mm and a thickness of 1.6 mm, the temperature of the 3.2 mm thick portion was 900 ° C. The temperature difference from the portion having a thickness of 1.6 mm at the time when the temperature reaches ° C can be suppressed to approximately 40 ° C.
As described above, according to the above-described configuration, even if the metal plate has any shape, such as a metal plate having a different shape (a metal plate having a shape other than a rectangular plate) or a metal plate having portions having different thicknesses, temperature unevenness when heating is performed. Can be further suppressed.
In addition, although the heating rate decreases, the power is increased on the power supply side, a transverse heating device is used as the induction heating device, the frequency of the current flowing through the induction coil is increased, and the number of turns of the induction coil is increased. It is possible to heat to a temperature higher than the Curie temperature by induction heating. However, in the present invention, the heating is not performed at a temperature equal to or higher than the Curie temperature by induction heating, and the temperature is not greatly increased near the Curie temperature. For example, there is a configuration in which heating at or above the Curie temperature is restricted by the device configuration of the induction heating device, the setting of the frequency of the current flowing through the induction coil, the setting of the heating conditions for induction heating, and the like. Specifically, a device having no function or control capable of changing the power or frequency required for heating at or above the Curie point, or a device having a normal induction coil that does not use a transverse type device or the like can be given. . This makes it possible to suppress temperature unevenness near the Curie temperature. There is also an advantage that a simpler device can be used than a device that has been used for heating a metal plate.

  In the above configuration, the step C may be a step of starting heating the metal plate by light heating after a predetermined period has elapsed from the step A.

  For example, when a metal plate of the same material and shape is heated by a line or the like, as long as the conditions of induction heating are the same, in each induction heating process, the temperature Y at the point X after starting the induction heating becomes the specific value Z. The period until becomes approximately the same. Therefore, for example, if the time from when induction heating is started using a sensor or the like until the temperature Y at the location X reaches the specific value Z is measured in advance, when heating is actually performed using a line or the like, induction heating is performed. By measuring only the elapsed time from the start of heating, the timing at which the temperature Y becomes the specific value Z can be grasped. Therefore, if the timing for starting the step C, that is, the elapsed time from the step A (the predetermined period) is determined based on the elapsed time measured in advance, the temperature of the metal plate is measured by a sensor or the like every time heating is performed. Heating by optical heating can be started at an appropriate timing without measurement.

The configuration includes a step B-1 of monitoring the temperature Y of the location X during the step B,
The step C may be a step of starting heating the metal plate by optical heating after the monitored temperature Y has reached the specific value Z.

  If the process B-1 for monitoring the temperature Y at the location X is provided during the process B, the timing at which the temperature Y reaches the specific value Z can be reliably grasped. As a result, after the temperature Y reaches the specific value Z, the heating of the metal plate by light heating can be reliably started. For example, when heating a plurality of metal plates having different materials and shapes (when heating various types of metal plates little by little), this method is more effective.

Further, the heat treatment apparatus according to the present invention,
An induction heating coil for heating the metal plate by induction heating,
A light source for optically heating the metal plate,
The induction heating coil has a heating space in which a metal plate can be installed,
The light source has a light emitting unit that emits light,
The light emitting unit is installed inside the induction heating coil.

According to the heat treatment apparatus, after the induction heating, the light heating can be performed without moving the steel plate.
Further, according to the heat treatment apparatus, the heat treatment apparatus can be suitably used in the method for producing the heat-treated metal plate.

In the heat treatment apparatus having the above configuration,
The light emitting unit has a long light emitting surface in one direction,
It is preferable that the light emitting unit is arranged such that a longitudinal direction of the light emitting unit and an axial direction of the induction heating coil are in the same direction.

  The metal plate to be subjected to the heat treatment is usually rectangular or the like, and often has a longer shape in one direction than in the other direction. Therefore, the light emitting unit has a light emitting surface that is long in one direction, and the light emitting unit is arranged so that the long direction of the light emitting unit and the axial direction of the induction heating coil are in the same direction. Is suitable for heating a long metal plate.

In the heat treatment apparatus having the above configuration,
The light source has a sealing portion at an end of the light emitting portion,
It is preferable that the sealing portion is disposed outside the induction heating coil.

  Usually, both ends of the light emitting portion of the light source are often sealed via metal foil. When this metal foil is heated, there is a concern that cracks or the like may occur in the sealing portion. Therefore, if the sealing portion is disposed outside the induction heating coil, the sealing portion (metal foil) can be prevented from being heated by the induction heating coil.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the heat-processed metal plate which can suppress the temperature nonuniformity at the time of heating a metal plate further can be provided.
Further, according to the present invention, it is possible to provide a heat treatment apparatus capable of further suppressing temperature unevenness when heating a metal plate.

It is a mimetic diagram for explaining the manufacturing method of the heat-treated metal plate concerning this embodiment. It is a front view of the steel plate shown in FIG. It is a top view of the steel plate shown in FIG. It is a schematic diagram which shows an example of a heat treatment apparatus. It is a flowchart which shows the control flow (1) of the heat processing performed by a heat processing apparatus. It is a flowchart which shows the control flow (2) of the heat processing performed in a heat processing apparatus. It is a flowchart which shows the control flow (3) of the heat processing performed in a heat processing apparatus.

  A method for manufacturing a heat-treated metal plate and a heat treatment apparatus according to the present embodiment will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram for explaining a method for manufacturing a heat-treated metal plate according to the present embodiment. FIG. 2A is a front view of the steel plate shown in FIG. 1. FIG. 2B is a plan view of the steel plate shown in FIG. 1. In the present embodiment, as an example, a case will be described in which a thick steel plate (curie temperature around 770 ° C.) is heated from room temperature (25 ° C.) to 1000 ° C. in about 60 seconds. In the present embodiment, a case where heating is performed from room temperature (25 ° C.) to 1000 ° C. in about 60 seconds will be described, but the heating is not limited to 60 seconds and can be set as appropriate.

The method for producing a heat-treated metal plate according to the present embodiment includes:
Step A of starting heating of the differential thickness steel plate 20 (hereinafter, also simply referred to as “steel plate 20”) by induction heating;
After the step A, a step B of heating the steel sheet 20 by the induction heating until the temperature Y of the lowest temperature portion X of the steel sheet 20 becomes a specific value Z based on the Curie temperature,
After the temperature Y reaches the specific value Z, at least a step C of starting heating of the steel plate 20 by light heating is provided.

  In the method for manufacturing a heat-treated metal plate according to the present embodiment, first, the steel plate 20 is disposed inside the coil 12. The steel plate 20 corresponds to the metal plate of the present invention. The coil 12 corresponds to the induction heating coil of the present invention.

  In the present embodiment, the steel plate 20 has a long plate shape, and has a thick rectangular plate portion 22 and a thin rectangular plate portion 24.

  The shape of the coil 12 is not particularly limited, and may be appropriately selected according to the size of the steel plate 20 or the like. For example, as shown in FIG. 1, the shape of the coil 12 may be wound in a circular shape in side view, may be wound in an elliptical shape, or may be wound in a rectangular shape.

  The length of the coil 12 is preferably longer than the long side of the steel plate 20. The entire steel plate 20 can be disposed inside the coil 12, and the temperature can be easily increased uniformly.

  After disposing the steel plate 20 inside the coil 12, heating of the steel plate 20 by induction heating is started (step A). The coil 12 is connected to a power supply (not shown). In step A, the application of an AC voltage for causing a predetermined high-frequency current to flow through the coil 12 is started.

  The AC voltage may be determined in consideration of the time required to raise the temperature to a desired temperature (in this embodiment, 1000 ° C.). When the temperature of the steel sheet 20 is raised to 1000 ° C. in 60 seconds as in the present embodiment, as an example, the frequency and the voltage are set so that the temperature Y at the location X becomes the specific value Z in 45 seconds. You only have to decide.

  In the present embodiment, the steel plate 20 is arranged inside the coil 12, but in the present invention, the arrangement position of the metal plate is not limited to this example. Any location can be used as long as induction heating by the coil 12 can be performed. For example, a metal plate may be arranged outside the coil (for example, below the coil 12).

  After the heating of the steel sheet 20 by the induction heating is started (after the step A), the induction heating is performed until the temperature Y of the lowest temperature portion X of the steel sheet 20 reaches a specific value Z based on the Curie temperature. (Step B).

The specific value Z is preferably as close as possible to the Curie temperature from the viewpoint of suppressing temperature unevenness. However, in general, in induction heating, the heating rate decreases as the temperature approaches the Curie temperature. Therefore, if the specific value Z is set to a temperature as close as possible to the Curie temperature, the timing at which light heating is started is delayed, and the time until the desired temperature (1000 ° C. in the present embodiment) is reached (tact time). Becomes longer. Therefore, it is preferable to determine in consideration of suppression of temperature unevenness and shortening of the tact time. In view of the above, the specific value Z may be determined, for example, within a temperature range of about ± 40 ° C. from the Curie temperature, or may be determined within a temperature range of about ± 20 ° C. The temperature may be determined within a temperature range of about 10 ° C.
The determination as to whether the metal plate has reached the Curie temperature can be derived from the heating time until the temperature is saturated or the saturation temperature, by heating the target metal plate only by induction heating.
Whether the temperature Y at the location X of the metal plate has reached the specific value Z based on the Curie temperature is determined, for example, by starting induction heating of the target metal plate and then heating each region. The relationship between the heating time until the temperature is saturated and the temperature is determined in advance, and the heating time can be controlled. The temperature measurement at this time is a contact thermometer (thermocouple or other contact-type thermometer), a non-contact type thermometer (for example, a radiation thermometer, a fiber-type radiation thermometer, a pyrometer, a multicolor Thermometer or the like) can be used. In each case, the Curie temperature can be estimated from the temperature saturation caused by induction heating. Naturally, it is also possible to derive the temperature from the correlation between the respective measurement results based on the measurement results of the contact type thermometer and the measurement results of the non-contact type thermometer.

During the step B, the voltage and frequency applied in the step A may or may not be changed, but it is preferable not to change. If the voltage and the frequency applied in the step A are not changed during the step B, the apparatus for induction heating can be simplified.
During the step B, heating (for example, light heating) different from the induction heating may be performed in parallel with the induction heating for a part of the period of the step B. The other heating is intended to assist heating. However, when the another heating is performed, the process ends before the temperature Y reaches the specific value Z. This is because if the another heating is continued even after the temperature Y reaches the specific value Z, the effect of suppressing the temperature unevenness near the Curie temperature cannot be obtained.

During the step B, the temperature Y at the location X is monitored by a non-contact or contact temperature sensor (step B-1). The monitoring of the temperature Y at the point X may be continuously performed during the step B, and after the start of the step B, for a certain period (for example, 30 seconds when it is expected to reach the vicinity of the Curie temperature in 45 seconds). Seconds).
During the process B, the temperature Y at the location X may be monitored using a thermoviewer. Specifically, the temperature may be calibrated in advance, and the value of a specific portion in the temperature distribution observed by the thermoviewer may be monitored as the temperature Y at the location X.

The portion X where the temperature is the lowest on the steel plate 20 is formed in a region where the magnetic flux density in induction heating is low. For example, the region having a low magnetic flux density in the present embodiment is formed in an end region in the axial direction of the induction heating coil (the left-right direction in FIG. 1, that is, the direction perpendicular to the annular surface formed by the lines forming the coil). Cheap. Although the magnetic flux density is high inside the induction heating coil, the magnetic flux density is relatively low in the end region of the coil, and the steel sheet located in that region has a low heating rate and the heating temperature is low. is there. It is desirable that a test similar to the process B be performed in advance and which temperature of the entire steel plate 20 should be monitored to determine which portion of the steel plate 20 is the lowest temperature portion (location X).
In the present embodiment, as shown in FIG. 2B, the lowest temperature portion X of the steel plate 20 is located in the terminal region in the coil axis direction of the induction heating coil where the magnetic flux density is low. It is the left end.

Thereafter, after the temperature Y monitored in the step B-1 reaches the specific value Z, heating of the metal plate by optical heating is started (step C).
Note that the “start of heating” in the step C means the start of light heating that is performed for the first time after the temperature Y has reached the specific value Z. For example, when light heating is performed in parallel with induction heating during step B, the light heating ends before step B ends (until the temperature Y reaches the specific value Z). Therefore, even if the light heating is performed in parallel with the induction heating during the process B, the first light heating after the temperature Y reaches the specific value Z is the “heating” in the process C. Start ”. That is, the “start of heating” in the step C includes a case where the optical heating that has been completed before the step B is completed is restarted.
The light heating in the step C is light heating of the entire metal plate. Therefore, light heating of only a part of the metal plate does not correspond to light heating in the step C.

  In the present embodiment, the lamp 14 for light heating is arranged inside the coil 12. More specifically, the lamp 14 is disposed inside the coil 12 so as to be located above the steel plate 20. Therefore, after induction heating, light heating can be performed without moving the steel plate 20. The lamp 14 corresponds to the light source of the present invention.

  The lamp 14 is not particularly limited as long as it can heat the steel plate 20 by light. As such a lamp 14, a lamp that emits light in the infrared or near-infrared region can be suitably used, and among them, a halogen heater lamp is preferable.

  The shape, number, arrangement, output, and the like of the lamps 14 may be determined in consideration of the time required to raise the temperature to a desired temperature (1000 ° C. in the present embodiment). As in the present embodiment, when the temperature of the steel plate 20 is raised to 1000 ° C. in 60 seconds and the start of the process C is 45 seconds after the process A, the steel plate 20 is heated to 770 in the remaining 15 seconds. What can be heated from around ℃ to 1000 ℃ may be adopted.

  The induction heating may be ended at the same time as the start of the step C, or may be ended after a certain period (for example, 1 to 5 seconds) has elapsed after the start of the step C. Further, the induction heating may be performed for the purpose of preliminary heating or the like, after the start of the step C, by reducing the electric power until the end of the light heating. Basically, the heating after the Curie temperature is succeeded by the light heating, and thus may be finished at the same time as the start of the step C. However, immediately after the lamp 14 is turned on, sufficient heating may not be performed. Therefore, after the lamp 14 is turned on, induction heating may be performed in parallel until heating is sufficiently performed.

  After the process C, the heating by the lamp 14 is terminated at the timing when the steel plate 20 is heated to around 1000 ° C. The timing for ending the heating may be, for example, a time when a predetermined period has elapsed, similarly to the timing for starting the process C. The temperature of the steel plate 20 is monitored, and the monitored temperature is set in advance. A value (for example, 1000 ° C.) may be reached. The location to be monitored may be determined as appropriate, and may be a portion of the metal plate where the temperature is least likely to rise, or a portion of the metal plate where the temperature is most likely to rise.

  Thereafter, the steel plate 20 is formed into a desired shape by hot pressing or the like.

  As described above, the heat-treated steel sheet 20 can be manufactured. In the steel sheet 20 obtained in this manner, the occurrence of cracks due to overheating is suppressed because the temperature unevenness is suppressed during the heat treatment. In addition, quenching of a portion where heating is insufficient is not performed well, and a decrease in strength is suppressed.

The above-described method of manufacturing the heat-treated metal plate can be executed by the control unit 16 (not shown). Specifically, the control unit 16 controls the drive signal for driving the coil 12 at a predetermined timing (for example, an operation by an operator or reception of a signal that detects that the steel plate 20 has been placed at a predetermined position). Is transmitted to the power supply device of the coil 12. Thereby, the heating of the steel plate 20 starts. Thereafter, the control unit 16 drives the temperature sensor by transmitting a measurement start signal or the like to the temperature sensor, and continuously receives information on the measured temperature (temperature information) in real time. Further, the control unit 16 continues to determine whether or not the temperature Y has reached the specific value Z based on the received temperature information. When it is determined that the temperature Y has reached the specific value Z, the control unit 16 transmits a command signal for turning on the lamp 14 to a driving device (not shown) of the lamp 14 to start light heating. I do. The temperature sensor may be always driven, and the control unit 16 may receive the temperature information at a necessary timing without transmitting the drive signal.
The control unit 16 includes, for example, at least a CPU and a memory, and performs the above-described control by the CPU reading and executing a program stored in the memory.

  The above-described method of manufacturing a heat-treated metal plate can also be performed without using the control unit 16. For example, a worker or the like operates a power supply device for induction heating to start heating by induction heating. Thereafter, the worker measures the temperature Y in real time using the temperature sensor, and at the timing when the measured value reaches the specific value Z, the worker operates the driving device of the lamp 14 to start optical heating. You may.

In the above-described embodiment, during the process B, the temperature Y at the location X is monitored, and after the monitored temperature Y reaches the specific value Z, heating of the steel sheet 20 by light heating is started. explained. However, in the present invention, the timing to start heating the metal plate by light heating is not limited to this example.
For example, after a predetermined period has elapsed from the step A, heating of the metal plate by light heating may be started. When the steel plates 20 of the same material and shape are heated by a line or the like, as long as the conditions of the induction heating are the same, in each induction heating step, the temperature Y at the point X after the induction heating is started becomes the specific value Z. The period until is almost the same. Therefore, the time from when the induction heating is started using a sensor or the like to when the temperature Y at the location X reaches the specific value Z is measured in advance. Then, when actually heating by a line or the like, the timing at which the temperature Y becomes the specific value Z can be grasped by measuring only the elapsed time from the start of the induction heating. Therefore, if the timing for starting the step C, that is, the elapsed time from the step A (the predetermined period) is determined based on the elapsed time measured in advance, the temperature of the metal plate is measured by a sensor or the like every time heating is performed. Heating by optical heating can be started at an appropriate timing without measurement. For example, if the measurement result using a sensor or the like is 45 seconds, the step C may be started after a lapse of 45 seconds from the step A.

In the embodiment described above, the case where the metal plate of the present invention is a differential thickness steel plate having portions having different thicknesses has been described. However, the shape of the metal plate of the present invention is not limited to this example, and the thickness may be uniform. Further, the shape in plan view may be a rectangle, or may be a different shape in which an acute portion or the like partially exists. This is because according to the configuration of the present invention, it is possible to suppress temperature unevenness when heating a metal plate of any shape.
Regarding the portion of the metal plate where the temperature is most difficult to be heated (that is, location X), a heating test may be performed in advance and the temperature rising status may be monitored and determined regardless of the shape of the metal plate. .

  In the embodiment described above, the case where the metal plate of the present invention is a steel plate has been described. That is, the case where the material of the metal plate of the present invention is steel (iron alloy containing carbon) has been described. However, the material of the metal plate in the present invention is not limited to a steel plate as long as it is made of a material having a Curie temperature. Other examples of the material of the metal plate include stainless steel, copper, and aluminum.

The above-described method for producing a heat-treated metal plate can be performed by a heat treatment apparatus. For example, as one embodiment, it can be carried out by the heat treatment apparatus 10 shown in FIG.
That is, the heat treatment apparatus 10 according to the present embodiment
A coil 12 for performing induction heating;
A lamp 14 for performing light heating;
A control unit 16;
After starting the heating of the steel sheet 20 by the coil 12, the control unit 16 controls the steel sheet 20 by the coil 12 until the temperature Y at the lowest temperature point X of the steel sheet 20 reaches a specific value Z based on the Curie temperature. Heating of
After the temperature Y reaches the specific value Z, the heating of the steel plate 20 by the lamp 14 is started.

The heat treatment apparatus according to the present invention can have the following configuration.
(1) A heat treatment apparatus for heating a metal plate,
An induction heating unit for performing induction heating,
A light heating unit for performing light heating,
And a control unit,
After starting heating of the metal plate by the induction heating unit, the control unit performs the induction until the temperature Y of the lowest temperature point X of the metal plate reaches a specific value Z based on the Curie temperature. Heating the metal plate by heating,
The heat treatment apparatus, wherein after the temperature Y reaches the specific value Z, heating of the metal plate by the light heating unit is started.

(2) The heat treatment apparatus according to the above (1),
The heat treatment apparatus, wherein the control unit starts heating the metal plate by the light heating unit after a lapse of a predetermined period from the start of heating the metal plate by the induction heating unit.

(3) The heat treatment apparatus according to the above (1),
A sensor for monitoring the temperature Y at the location X;
The heat treatment apparatus, wherein the control unit starts heating the metal plate by the light heating unit after the temperature Y monitored by the sensor reaches the specific value Z.

The induction heating unit is not particularly limited as long as it can heat the metal plate by applying a current to the metal plate using the principle of electromagnetic induction, and examples thereof include the coil 12 and the like.
The light heating unit is not particularly limited as long as the metal plate can be heated by light, and examples thereof include a lamp 14 and the like.
The control unit is not particularly limited as long as it has a function of performing the above control, and includes, for example, a control unit 16.
The sensor is not particularly limited as long as it can monitor the temperature Y of the lowest temperature portion X of the metal plate, and includes a conventionally known non-contact or contact temperature sensor.
The material of the metal plate is not particularly limited as long as it is made of a material having a Curie temperature. In addition, the thickness of the metal plate may be uniform, or there may be partially different portions. Further, the shape in plan view may be a rectangle, or may be a different shape in which an acute portion or the like partially exists.

  Hereinafter, a more specific example of the heat treatment apparatus will be described.

  FIG. 3 is a schematic diagram illustrating an example of the heat treatment apparatus. As shown in FIG. 3, the heat treatment apparatus 110 includes an induction heating coil 112, a lamp 114, a transport unit 122, a mounting table 124, a lamp control unit 126 for controlling the operation of the lamp 114, and an induction heating coil. And an induction heating control unit 128 for controlling the operation of 112. The lamp 114 corresponds to the light source of the present invention.

  The lamp 114 has a light emitting unit 116 that emits light, and caps 118 provided at both ends of the light emitting unit 116. The sealing portion is accommodated in the base 118. Specifically, both ends of the light emitting unit 116 in the base 118 are sealed by a sealing unit via a metal foil. Since the metal foil is present in the sealing portion, there is a concern that cracks or the like may occur in the sealing portion when the metal foil is heated. Therefore, in the present embodiment, the sealing portion is disposed outside the induction heating coil 112.

  The base 118 is preferably made of a non-magnetic material such as ceramics. When the base 118 is made of a non-magnetic material, it is possible to prevent the base 118 from being heated by the induction heating coil 112.

  The light emitting unit 116 includes a light emitting surface 117 that is long in one direction (the horizontal direction in FIG. 3). Further, the light emitting section 116 is arranged such that the longitudinal direction of the light emitting section 116 and the axial direction of the induction heating coil 112 are the same. The metal plate to be subjected to the heat treatment is usually rectangular or the like, and often has a longer shape in one direction than in the other direction. Therefore, in the present embodiment, since the long direction of the light emitting unit 116 and the axial direction of the induction heating coil 112 are arranged in the same direction, it is suitable for heating a long metal plate. I have.

  The light emitting section 116 of the lamp 114 is provided inside the induction heating coil 112. In this specification, the expression “the light emitting unit 116 is installed inside the induction heating coil 112” means that at least a part of the light emitting unit 116 is installed inside the induction heating coil 112. Not all of 116 need be installed inside induction heating coil 112. Since the lamp 114 is arranged inside the induction heating coil 112, light heating can be performed without moving the metal plate 120 after the induction heating.

  The mounting table 124 is installed movably in the axial direction in the induction heating coil 112. The mounting table 124 is driven by the transport unit 122 to be movable in the axial direction. The metal plate 120 can be mounted on the mounting table 124. Therefore, after the metal plate 120 is mounted on the mounting table 124, the metal plate 120 can be moved together with the mounting table 124 into the induction heating coil 112, and the heat treatment can be performed. Then, after the heat treatment, the metal plate 120 can be moved from the induction heating coil 112 to the outside together with the mounting table 124 by the transfer unit 122. That is, the induction heating coil 112 has a heating space in which the metal plate 120 can be installed. The mounting table 124 is preferably made of a non-magnetic material such as ceramics. Further, the mounting table 124 may partially support the metal plate 120.

  Next, a control flow of the heat treatment by the heat treatment apparatus 110 will be described. The control flow of the heat treatment by the heat treatment apparatus 110 includes the following control flow (1), control flow (2), and control flow (3). Hereinafter, description will be made in order.

  FIG. 4 is a flowchart showing a control flow (1) of the heat treatment performed by the heat treatment apparatus. The control flow (1) is executed by the control unit 130 (not shown) included in the heat treatment apparatus. This control flow (1) is based on the fact that a predetermined start condition is satisfied (for example, a signal that detects that an operation input has been made by an operator or that the metal plate 120 has been arranged at a predetermined position, or the like). ).

  First, the control unit 130 transmits an induction heating start signal to the induction heating control unit 128 in step 10. Upon receiving the induction heating start signal, the induction heating control unit 128 drives the induction heating coil 112 to start induction heating of the metal plate. Thereafter, the process proceeds to step S12.

  In step 12, the control unit 130 monitors the temperature information transmitted from the temperature detection unit (not shown) and checks whether the temperature has been saturated. Specifically, based on the received temperature information, the control unit 130 continues to determine whether or not the temperature Y at the location X has reached the specific value Z, and determines that the temperature Y has reached the specific value Z. Then, the process proceeds to step 14.

  In step 14, the control unit 130 transmits an induction heating stop signal to the induction heating control unit 128. Upon receiving the induction heating stop signal, the induction heating control unit 128 stops driving the induction heating coil 112. Thereafter, the process proceeds to step S16.

  In step 16, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step 18.

  In step 18, the control unit 130 monitors the temperature information transmitted from the temperature detection unit and checks whether the temperature has reached a desired temperature. Specifically, the control unit 130 continues to determine whether or not the temperature has reached a desired temperature based on the received temperature information, and when determining that the temperature has reached the desired temperature, sends a light heating stop signal to the lamp control unit 126. Send. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thus, the control flow (1) ends.

  FIG. 5 is a flowchart illustrating a control flow (2) of the heat treatment performed by the heat treatment apparatus. The heat treatment apparatus 110 may be configured to perform the control flow (2) instead of the control flow (1). The control flow (2) is executed by the control unit 130 (not shown) included in the heat treatment apparatus, similarly to the control flow (1). In the control flow (2), similarly to the control flow (1), a predetermined start condition is satisfied (for example, an operation input by an operator or a metal plate 120 is disposed at a predetermined position). Is received, etc.).

  First, in step 20, the control unit 130 transmits an induction heating start signal to the induction heating control unit 128. Upon receiving the induction heating start signal, the induction heating control unit 128 drives the induction heating coil 112 to start induction heating of the metal plate. Thereafter, the process proceeds to step S22.

  In step 22, the control unit 130 maintains the heating of the induction heating until a desired time. Specifically, the control unit 130 measures the elapsed time since the transmission of the induction heating start signal, and continuously checks whether or not a predetermined first elapsed time has elapsed. When the control unit 130 determines that the elapsed time after transmitting the induction heating start signal has exceeded the first elapsed time, the process proceeds to step 24.

  In step 24, the control unit 130 transmits an induction heating stop signal to the induction heating control unit 128. Upon receiving the induction heating stop signal, the induction heating control unit 128 stops driving the induction heating coil 112. Thereafter, the process proceeds to step S26.

  In step 26, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step 28.

  In step 28, the control unit 130 measures the elapsed time from the transmission of the light heating start signal, and continuously checks whether or not a predetermined second elapsed time has elapsed. When the control unit 130 determines that the elapsed time after transmitting the light heating start signal has exceeded the second elapsed time, the control unit 130 transmits a light heating stop signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thus, the control flow (2) ends.

  FIG. 6 is a flowchart showing a control flow (3) of the heat treatment performed by the heat treatment apparatus. The heat treatment apparatus 110 may be configured to perform the control flow (3) instead of the control flows (1) and (2). The control flow (3) is executed by the control unit 130 (not shown) included in the heat treatment apparatus, similarly to the control flows (1) and (2). This control flow (3) is similar to the above control flows (1) and (2), when a predetermined start condition is satisfied (for example, when an operation input is made by an operator, or when the metal plate 120 is moved to a predetermined position). (E.g., reception of a signal that detects the arrangement).

  First, in step 30, the control unit 130 transmits an induction heating start signal to the induction heating control unit 128. Upon receiving the induction heating start signal, the induction heating control unit 128 drives the induction heating coil 112 to start induction heating of the metal plate. Thereafter, the process proceeds to step S32.

  In step 32, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step S34.

  In step 34, the control unit 130 determines whether or not the metal plate 120 has reached an arbitrary temperature based on, for example, temperature information from the temperature detection unit and the elapsed time from the start of the light heating. When it is determined that the temperature has reached an arbitrary set temperature, a light heating stop signal is transmitted to the lamp control unit 126. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thereafter, the process proceeds to step S36. The arbitrary temperature set here is a temperature set before the temperature of a part of the metal plate 120 reaches the specific value Z. As a result, it is possible to increase the temperature raising rate until the specific value Z is reached.

  In step 36, the control unit 130 monitors the temperature information transmitted from the temperature detection unit (not shown) to check whether the temperature has been saturated. Specifically, based on the received temperature information, the control unit 130 continues to determine whether or not the temperature Y at the location X has reached the specific value Z, and determines that the temperature Y has reached the specific value Z. Then, the process proceeds to step 38.

  In step 38, the control unit 130 transmits an induction heating stop signal to the induction heating control unit 128. Upon receiving the induction heating stop signal, the induction heating control unit 128 stops driving the induction heating coil 112. Thereafter, the process proceeds to step S40.

  In step 40, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step S42.

  In step 42, the control unit 130 monitors the temperature information transmitted from the temperature detection unit and checks whether the temperature has reached a desired temperature. Specifically, the control unit 130 continues to determine whether or not the temperature has reached a desired temperature based on the received temperature information, and when determining that the temperature has reached the desired temperature, sends a light heating stop signal to the lamp control unit 126. Send. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thus, the control flow (3) ends.

  The control flow (1), the control flow (2), and the control flow (3) of the heat treatment performed by the heat treatment apparatus 110 have been described above.

  In the above embodiment, the case where the lamp control unit 126 controls the driving of the lamp 114 and the induction heating control unit 128 controls the driving of the induction heating coil 112 has been described. That is, the case where the lamp 114 and the induction heating coil 112 are controlled by separate control units has been described. However, the heat treatment apparatus of the present invention is not limited to this example, and may have a configuration in which the lamp 114 and the induction heating coil 112 are controlled by one controller.

  In the above-described embodiment, the method of confirming whether or not the temperature is saturated and the method of measuring various elapsed times are merely examples, and can be appropriately changed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described examples, and design changes can be appropriately made within a range that satisfies the configuration of the present invention.

Reference Signs List 10, 110 Heat treatment device 12, 112 Coil 14, 114 Lamp 20 Steel plate 22 Thick rectangular plate portion 24 Thin rectangular plate portion 116 Light emitting unit 117 Light emitting surface 118 Base 126 Lamp control unit 128 Induction heating control unit

The present invention relates to a thermal processing apparatus.

  In recent years, from the viewpoint of reducing the weight of automobiles and improving safety during collisions, high-strength steel sheets having increased toughness by heat treatment have been used. As a method for forming such a high-strength steel sheet, a forming method called hot pressing has been put to practical use. Hot pressing is a method in which a steel sheet heated to 900 ° C. to 1000 ° C. is pressed with a mold at normal temperature to form the steel sheet while quenching the steel sheet. By using this method, the strength of the steel sheet can be increased. it can.

  Conventionally, as a method of heating a steel sheet to a temperature range of 900 ° C. to 1000 ° C., electric heating (for example, see Patent Literature 1), induction heating (for example, see Patent Literature 2), and optical heating with infrared rays (for example, see Patent Literature 3) ).

  The energization heating is a method in which electrodes are attached to both ends of a steel sheet and a current is applied between the electrodes, thereby heating the workpiece by Joule heat generated inside the work.

  Induction heating is a method in which a high-frequency current is applied to a coil to generate a magnetic field, a magnetic flux is applied to the steel sheet, and the steel sheet is heated by Joule heat generated by an eddy current generated inside the steel sheet.

JP-A-2002-18531 JP 2005-122983 A JP 2011-095567 A

The purpose of the present invention, after the induction heating is to provide a heat treatment apparatus capable of performing light heat without moving the steel plate.

The heat treatment apparatus according to the present invention,
An induction heating coil for heating the metal plate by induction heating,
A light source for optically heating the metal plate,
The induction heating coil has a heating space in which a metal plate can be installed,
The light source has a light emitting unit that emits light,
The light emitting unit is installed inside the induction heating coil.

According to the heat treatment apparatus, after the induction heating, the light heating can be performed without moving the steel plate .

In the heat treatment apparatus having the above configuration,
The light emitting unit has a long light emitting surface in one direction,
It is preferable that the light emitting unit is arranged such that a longitudinal direction of the light emitting unit and an axial direction of the induction heating coil are in the same direction.

  The metal plate to be subjected to the heat treatment is usually rectangular or the like, and often has a longer shape in one direction than in the other direction. Therefore, the light emitting unit has a light emitting surface that is long in one direction, and the light emitting unit is arranged so that the long direction of the light emitting unit and the axial direction of the induction heating coil are in the same direction. Is suitable for heating a long metal plate.

In the heat treatment apparatus having the above configuration,
The light source has a sealing portion at an end of the light emitting portion,
It is preferable that the sealing portion is disposed outside the induction heating coil.

  Usually, both ends of the light emitting portion of the light source are often sealed via metal foil. When this metal foil is heated, there is a concern that cracks or the like may occur in the sealing portion. Therefore, if the sealing portion is disposed outside the induction heating coil, the sealing portion (metal foil) can be prevented from being heated by the induction heating coil.

According to the present invention, after induction heating, light heating can be performed without moving the steel plate.

It is a mimetic diagram for explaining the manufacturing method of the heat-treated metal plate concerning this embodiment. It is a front view of the steel plate shown in FIG. It is a top view of the steel plate shown in FIG. It is a schematic diagram which shows an example of a heat treatment apparatus. It is a flowchart which shows the control flow (1) of the heat processing performed by a heat processing apparatus. It is a flowchart which shows the control flow (2) of the heat processing performed in a heat processing apparatus. It is a flowchart which shows the control flow (3) of the heat processing performed in a heat processing apparatus.

  A method for manufacturing a heat-treated metal plate and a heat treatment apparatus according to the present embodiment will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram for explaining a method for manufacturing a heat-treated metal plate according to the present embodiment. FIG. 2A is a front view of the steel plate shown in FIG. 1. FIG. 2B is a plan view of the steel plate shown in FIG. 1. In the present embodiment, as an example, a case will be described in which a thick steel plate (curie temperature around 770 ° C.) is heated from room temperature (25 ° C.) to 1000 ° C. in about 60 seconds. In the present embodiment, a case where heating is performed from room temperature (25 ° C.) to 1000 ° C. in about 60 seconds will be described, but the heating is not limited to 60 seconds and can be set as appropriate.

In the heating method using electric heating or induction heating as in Patent Documents 1 and 2, it is difficult in principle to uniformly heat the entire steel sheet without temperature unevenness. In particular, in recent years, the shape of a steel sheet is various, and a steel sheet having a different shape (a steel sheet that is not a rectangular plate shape) in which an acute angle portion or the like partially exists, or a difference thickness steel sheet having portions having different thicknesses (for example, Tailored blanks, see JP-A-2013-184221). It is more difficult to uniformly heat such a steel sheet, and it is difficult to suppress temperature unevenness. For example, in energization heating, unless the cross-sectional area and the width of the steel sheet between the two electrodes are constant, heating cannot be performed uniformly in principle and temperature unevenness occurs. In addition, in the case of induction heating, if there is a portion with a different thickness, such as a thick steel plate, it is difficult to raise the temperature in the thick portion, but it is easy to raise the temperature in the thin portion. I do. When the temperature unevenness occurs, there arises a problem that the strength of the steel sheet after hot pressing varies and a predetermined quality cannot be obtained. For example, there is a problem that a crack is generated in a part that is partially overheated, and a problem that quenching of a part that is insufficiently heated is not performed well, resulting in a decrease in strength.

On the other hand, light heating using infrared rays as in Patent Document 3 can take measures to suppress the occurrence of temperature unevenness to some extent. For example, among a plurality of light heating lamps, the output of a lamp that heats a portion of a steel plate where the temperature is likely to rise (for example, a thin portion in the case of a differential thickness steel plate) is made weaker than other lamps. Next, there is a method of controlling the output of each light heating lamp. As another example, there is a method in which the arrangement of a plurality of lamps is set to an arrangement suitable for the shape of a work.

The present inventors arrange | positioned the thickness difference steel plate (the difference thickness steel plate of a shape like FIG. 2A, FIG. 2B) which has a 3.2-mm-thick part and a 1.6-mm-thick part in several matrix form. In a test for heating from room temperature (25 ° C.) to around 1000 ° C. using a light-heated lamp, studies have been made to suppress temperature unevenness. As a result, when the output of the lamp that heats the 3.2 mm thick portion and the lamp that heats the 1.6 mm thick portion are the same, the temperature of the 3.2 mm thick portion becomes 900 ° C. At that time, the temperature difference between the 1.6 mm thick portion and the 1.6 mm thick portion was about 230 ° C., whereas the output of the lamp for heating the 1.6 mm thick portion was changed to the 3.2 mm thick portion. When the temperature of the 3.2 mm thick portion reaches 900 ° C. when the temperature is lowered in a specific manner from the lamp to be heated, the temperature difference from the 1.6 mm thick portion is reduced to approximately 90 ° C. We have succeeded in suppressing it.

In the heat-treated metal plate, it is desirable that unevenness in temperature be as small as possible. Further, in recent years, further improvement in temperature unevenness has been demanded for a heat-treated metal plate.

An object of the present embodiment is to provide a method for manufacturing a heat-treated metal plate that can further suppress temperature unevenness when heating a metal plate such as a steel plate.

The present inventors have intensively studied a method for further suppressing the temperature unevenness. As a result, the inventors have conceived that by employing the following configuration, it is possible to further suppress temperature unevenness when heating a metal plate such as a steel plate.

The method for producing a heat-treated metal plate according to the present embodiment includes:
Step A of starting heating of the differential thickness steel plate 20 (hereinafter, also simply referred to as “steel plate 20”) by induction heating;
After the step A, a step B of heating the steel sheet 20 by the induction heating until the temperature Y of the lowest temperature portion X of the steel sheet 20 becomes a specific value Z based on the Curie temperature,
After the temperature Y reaches the specific value Z, at least a step C of starting heating of the steel plate 20 by light heating is provided.

  In the method for manufacturing a heat-treated metal plate according to the present embodiment, first, the steel plate 20 is disposed inside the coil 12. The steel plate 20 corresponds to the metal plate of the present invention. The coil 12 corresponds to the induction heating coil of the present invention.

  In the present embodiment, the steel plate 20 has a long plate shape, and has a thick rectangular plate portion 22 and a thin rectangular plate portion 24.

  The shape of the coil 12 is not particularly limited, and may be appropriately selected according to the size of the steel plate 20 or the like. For example, as shown in FIG. 1, the shape of the coil 12 may be wound in a circular shape in side view, may be wound in an elliptical shape, or may be wound in a rectangular shape.

  The length of the coil 12 is preferably longer than the long side of the steel plate 20. The entire steel plate 20 can be disposed inside the coil 12, and the temperature can be easily increased uniformly.

  After disposing the steel plate 20 inside the coil 12, heating of the steel plate 20 by induction heating is started (step A). The coil 12 is connected to a power supply (not shown). In step A, the application of an AC voltage for causing a predetermined high-frequency current to flow through the coil 12 is started.

  The AC voltage may be determined in consideration of the time required to raise the temperature to a desired temperature (in this embodiment, 1000 ° C.). When the temperature of the steel sheet 20 is raised to 1000 ° C. in 60 seconds as in the present embodiment, as an example, the frequency and the voltage are set so that the temperature Y at the location X becomes the specific value Z in 45 seconds. You only have to decide.

  In the present embodiment, the steel plate 20 is arranged inside the coil 12, but in the present invention, the arrangement position of the metal plate is not limited to this example. Any location can be used as long as induction heating by the coil 12 can be performed. For example, a metal plate may be arranged outside the coil (for example, below the coil 12).

  After the heating of the steel sheet 20 by the induction heating is started (after the step A), the induction heating is performed until the temperature Y of the lowest temperature portion X of the steel sheet 20 reaches a specific value Z based on the Curie temperature. (Step B).

The specific value Z is preferably as close as possible to the Curie temperature from the viewpoint of suppressing temperature unevenness. However, in general, in induction heating, the heating rate decreases as the temperature approaches the Curie temperature. Therefore, if the specific value Z is set to a temperature as close as possible to the Curie temperature, the timing at which light heating is started is delayed, and the time until the desired temperature (1000 ° C. in the present embodiment) is reached (tact time). Becomes longer. Therefore, it is preferable to determine in consideration of suppression of temperature unevenness and shortening of the tact time. In view of the above, the specific value Z may be determined, for example, within a temperature range of about ± 40 ° C. from the Curie temperature, or may be determined within a temperature range of about ± 20 ° C. The temperature may be determined within a temperature range of about 10 ° C.
The determination as to whether the metal plate has reached the Curie temperature can be derived from the heating time until the temperature is saturated or the saturation temperature, by heating the target metal plate only by induction heating.
Whether the temperature Y at the location X of the metal plate has reached the specific value Z based on the Curie temperature is determined, for example, by starting induction heating of the target metal plate and then heating each region. The relationship between the heating time until the temperature is saturated and the temperature is determined in advance, and the heating time can be controlled. The temperature measurement at this time is a contact thermometer (thermocouple or other contact-type thermometer), a non-contact type thermometer (for example, a radiation thermometer, a fiber-type radiation thermometer, a pyrometer, a multicolor Thermometer or the like) can be used. In each case, the Curie temperature can be estimated from the temperature saturation caused by induction heating. Naturally, it is also possible to derive the temperature from the correlation between the respective measurement results based on the measurement results of the contact type thermometer and the measurement results of the non-contact type thermometer.

During the step B, the voltage and frequency applied in the step A may or may not be changed, but it is preferable not to change. If the voltage and the frequency applied in the step A are not changed during the step B, the apparatus for induction heating can be simplified.
During the step B, heating (for example, light heating) different from the induction heating may be performed in parallel with the induction heating for a part of the period of the step B. The other heating is intended to assist heating. However, when the another heating is performed, the process ends before the temperature Y reaches the specific value Z. This is because if the another heating is continued even after the temperature Y reaches the specific value Z, the effect of suppressing the temperature unevenness near the Curie temperature cannot be obtained.

During the step B, the temperature Y at the location X is monitored by a non-contact or contact temperature sensor (step B-1). The monitoring of the temperature Y at the point X may be continuously performed during the step B, and after the start of the step B, for a certain period (for example, 30 seconds when it is expected to reach the vicinity of the Curie temperature in 45 seconds). Seconds).
During the process B, the temperature Y at the location X may be monitored using a thermoviewer. Specifically, the temperature may be calibrated in advance, and the value of a specific portion in the temperature distribution observed by the thermoviewer may be monitored as the temperature Y at the location X.

The portion X where the temperature is the lowest on the steel plate 20 is formed in a region where the magnetic flux density in induction heating is low. For example, the region having a low magnetic flux density in the present embodiment is formed in an end region in the axial direction of the induction heating coil (the left-right direction in FIG. 1, that is, the direction perpendicular to the annular surface formed by the lines forming the coil). Cheap. Although the magnetic flux density is high inside the induction heating coil, the magnetic flux density is relatively low in the end region of the coil, and the steel sheet located in that region has a low heating rate and the heating temperature is low. is there. It is desirable that a test similar to the process B be performed in advance and which temperature of the entire steel plate 20 should be monitored to determine which portion of the steel plate 20 is the lowest temperature portion (location X).
In the present embodiment, as shown in FIG. 2B, the lowest temperature portion X of the steel plate 20 is located in the terminal region in the coil axis direction of the induction heating coil where the magnetic flux density is low. It is the left end.

Thereafter, after the temperature Y monitored in the step B-1 reaches the specific value Z, heating of the metal plate by optical heating is started (step C).
Note that the “start of heating” in the step C means the start of light heating that is performed for the first time after the temperature Y has reached the specific value Z. For example, when light heating is performed in parallel with induction heating during step B, the light heating ends before step B ends (until the temperature Y reaches the specific value Z). Therefore, even if the light heating is performed in parallel with the induction heating during the process B, the first light heating after the temperature Y reaches the specific value Z is the “heating” in the process C. Start ”. That is, the “start of heating” in the step C includes a case where the optical heating that has been completed before the step B is completed is restarted.
The light heating in the step C is light heating of the entire metal plate. Therefore, light heating of only a part of the metal plate does not correspond to light heating in the step C.

  In the present embodiment, the lamp 14 for light heating is arranged inside the coil 12. More specifically, the lamp 14 is disposed inside the coil 12 so as to be located above the steel plate 20. Therefore, after induction heating, light heating can be performed without moving the steel plate 20. The lamp 14 corresponds to the light source of the present invention.

  The lamp 14 is not particularly limited as long as it can heat the steel plate 20 by light. As such a lamp 14, a lamp that emits light in the infrared or near-infrared region can be suitably used, and among them, a halogen heater lamp is preferable.

  The shape, number, arrangement, output, and the like of the lamps 14 may be determined in consideration of the time required to raise the temperature to a desired temperature (1000 ° C. in the present embodiment). As in the present embodiment, when the temperature of the steel plate 20 is raised to 1000 ° C. in 60 seconds and the start of the process C is 45 seconds after the process A, the steel plate 20 is heated to 770 in the remaining 15 seconds. What can be heated from around ℃ to 1000 ℃ may be adopted.

  The induction heating may be ended at the same time as the start of the step C, or may be ended after a certain period (for example, 1 to 5 seconds) has elapsed after the start of the step C. Further, the induction heating may be performed for the purpose of preliminary heating or the like, after the start of the step C, by reducing the electric power until the end of the light heating. Basically, the heating after the Curie temperature is succeeded by the light heating, and thus may be finished at the same time as the start of the step C. However, immediately after the lamp 14 is turned on, sufficient heating may not be performed. Therefore, after the lamp 14 is turned on, induction heating may be performed in parallel until heating is sufficiently performed.

  After the process C, the heating by the lamp 14 is terminated at the timing when the steel plate 20 is heated to around 1000 ° C. The timing of ending the heating may be, for example, when a predetermined period has elapsed, similarly to the timing of the start of the process C. The temperature of the steel plate 20 is monitored, and the monitored temperature is set in advance. A value (for example, 1000 ° C.) may be reached. The location to be monitored may be determined as appropriate, and may be a portion of the metal plate where the temperature is least likely to rise, or a portion of the metal plate where the temperature is most likely to rise.

  Thereafter, the steel plate 20 is formed into a desired shape by hot pressing or the like.

  As described above, the heat-treated steel sheet 20 can be manufactured. In the steel sheet 20 obtained in this manner, the occurrence of cracks due to overheating is suppressed because the temperature unevenness is suppressed during the heat treatment. In addition, quenching of a portion where heating is insufficient is not performed well, and a decrease in strength is suppressed.

The above-described method of manufacturing the heat-treated metal plate can be executed by the control unit 16 (not shown). Specifically, the control unit 16 controls the drive signal for driving the coil 12 at a predetermined timing (for example, an operation by an operator or reception of a signal that detects that the steel plate 20 has been placed at a predetermined position). Is transmitted to the power supply device of the coil 12. Thereby, the heating of the steel plate 20 starts. Thereafter, the control unit 16 drives the temperature sensor by transmitting a measurement start signal or the like to the temperature sensor, and continuously receives information on the measured temperature (temperature information) in real time. Further, the control unit 16 continues to determine whether or not the temperature Y has reached the specific value Z based on the received temperature information. When it is determined that the temperature Y has reached the specific value Z, the control unit 16 transmits a command signal for turning on the lamp 14 to a driving device (not shown) of the lamp 14 to start light heating. I do. The temperature sensor may be always driven, and the control unit 16 may receive the temperature information at a necessary timing without transmitting the drive signal.
The control unit 16 includes, for example, at least a CPU and a memory, and performs the above-described control by the CPU reading and executing a program stored in the memory.

  The above-described method of manufacturing a heat-treated metal plate can also be performed without using the control unit 16. For example, a worker or the like operates a power supply device for induction heating to start heating by induction heating. Thereafter, the worker measures the temperature Y in real time using the temperature sensor, and at the timing when the measured value reaches the specific value Z, the worker operates the driving device of the lamp 14 to start optical heating. You may.

In the above-described embodiment, during the process B, the temperature Y at the location X is monitored, and after the monitored temperature Y reaches the specific value Z, heating of the steel sheet 20 by light heating is started. explained. However, in the present invention, the timing to start heating the metal plate by light heating is not limited to this example.
For example, after a predetermined period has elapsed from the step A, heating of the metal plate by light heating may be started. When the steel plates 20 of the same material and shape are heated by a line or the like, as long as the conditions of the induction heating are the same, in each induction heating step, the temperature Y at the point X after the induction heating is started becomes the specific value Z. The period until is almost the same. Therefore, the time from when the induction heating is started using a sensor or the like to when the temperature Y at the location X reaches the specific value Z is measured in advance. Then, when actually heating by a line or the like, the timing at which the temperature Y becomes the specific value Z can be grasped by measuring only the elapsed time from the start of the induction heating. Therefore, if the timing for starting the step C, that is, the elapsed time from the step A (the predetermined period) is determined based on the elapsed time measured in advance, the temperature of the metal plate is measured by a sensor or the like every time heating is performed. Heating by optical heating can be started at an appropriate timing without measurement. For example, if the measurement result using a sensor or the like is 45 seconds, the step C may be started after a lapse of 45 seconds from the step A.

In the embodiment described above, the case where the metal plate of the present invention is a differential thickness steel plate having portions having different thicknesses has been described. However, the shape of the metal plate of the present invention is not limited to this example, and the thickness may be uniform. Further, the shape in plan view may be a rectangle, or may be a different shape in which an acute portion or the like partially exists. This is because according to the configuration of the present invention, it is possible to suppress temperature unevenness when heating a metal plate of any shape.
Regarding the portion of the metal plate where the temperature is most difficult to be heated (that is, location X), a heating test may be performed in advance and the temperature rising status may be monitored and determined regardless of the shape of the metal plate. .

  In the embodiment described above, the case where the metal plate of the present invention is a steel plate has been described. That is, the case where the material of the metal plate of the present invention is steel (iron alloy containing carbon) has been described. However, the material of the metal plate in the present invention is not limited to a steel plate as long as it is made of a material having a Curie temperature. Other examples of the material of the metal plate include stainless steel, copper, and aluminum.

The above-described method for producing a heat-treated metal plate can be performed by a heat treatment apparatus. For example, as one embodiment, it can be carried out by the heat treatment apparatus 10 shown in FIG.
That is, the heat treatment apparatus 10 according to the present embodiment
A coil 12 for performing induction heating;
A lamp 14 for performing light heating;
A control unit 16;
After starting the heating of the steel sheet 20 by the coil 12, the control unit 16 controls the steel sheet 20 by the coil 12 until the temperature Y at the lowest temperature point X of the steel sheet 20 reaches a specific value Z based on the Curie temperature. Heating of
After the temperature Y reaches the specific value Z, the heating of the steel plate 20 by the lamp 14 is started.

The heat treatment apparatus according to the present invention can have the following configuration.
(1) A heat treatment apparatus for heating a metal plate,
An induction heating unit for performing induction heating,
A light heating unit for performing light heating,
And a control unit,
After starting heating of the metal plate by the induction heating unit, the control unit performs the induction until the temperature Y of the lowest temperature point X of the metal plate reaches a specific value Z based on the Curie temperature. Heating the metal plate by heating,
The heat treatment apparatus, wherein after the temperature Y reaches the specific value Z, heating of the metal plate by the light heating unit is started.

(2) The heat treatment apparatus according to the above (1),
The heat treatment apparatus, wherein the control unit starts heating the metal plate by the light heating unit after a lapse of a predetermined period from the start of heating the metal plate by the induction heating unit.

(3) The heat treatment apparatus according to the above (1),
A sensor for monitoring the temperature Y at the location X;
The heat treatment apparatus, wherein the control unit starts heating the metal plate by the light heating unit after the temperature Y monitored by the sensor reaches the specific value Z.

The induction heating unit is not particularly limited as long as it can heat the metal plate by applying a current to the metal plate using the principle of electromagnetic induction, and examples thereof include the coil 12 and the like.
The light heating unit is not particularly limited as long as the metal plate can be heated by light, and examples thereof include a lamp 14 and the like.
The control unit is not particularly limited as long as it has a function of performing the above control, and includes, for example, a control unit 16.
The sensor is not particularly limited as long as it can monitor the temperature Y of the lowest temperature portion X of the metal plate, and includes a conventionally known non-contact or contact temperature sensor.
The material of the metal plate is not particularly limited as long as it is made of a material having a Curie temperature. In addition, the thickness of the metal plate may be uniform, or there may be partially different portions. Further, the shape in plan view may be a rectangle, or may be a different shape in which an acute portion or the like partially exists.

  Hereinafter, a more specific example of the heat treatment apparatus will be described.

  FIG. 3 is a schematic diagram illustrating an example of the heat treatment apparatus. As shown in FIG. 3, the heat treatment apparatus 110 includes an induction heating coil 112, a lamp 114, a transport unit 122, a mounting table 124, a lamp control unit 126 for controlling the operation of the lamp 114, and an induction heating coil. And an induction heating control unit 128 for controlling the operation of 112. The lamp 114 corresponds to the light source of the present invention.

  The lamp 114 has a light emitting unit 116 that emits light, and caps 118 provided at both ends of the light emitting unit 116. The sealing portion is accommodated in the base 118. Specifically, both ends of the light emitting unit 116 in the base 118 are sealed by a sealing unit via a metal foil. Since the metal foil is present in the sealing portion, there is a concern that cracks or the like may occur in the sealing portion when the metal foil is heated. Therefore, in the present embodiment, the sealing portion is disposed outside the induction heating coil 112.

  The base 118 is preferably made of a non-magnetic material such as ceramics. When the base 118 is made of a non-magnetic material, it is possible to prevent the base 118 from being heated by the induction heating coil 112.

  The light emitting unit 116 includes a light emitting surface 117 that is long in one direction (the horizontal direction in FIG. 3). Further, the light emitting section 116 is arranged such that the longitudinal direction of the light emitting section 116 and the axial direction of the induction heating coil 112 are the same. The metal plate to be subjected to the heat treatment is usually rectangular or the like, and often has a longer shape in one direction than in the other direction. Therefore, in the present embodiment, since the long direction of the light emitting unit 116 and the axial direction of the induction heating coil 112 are arranged in the same direction, it is suitable for heating a long metal plate. I have.

  The light emitting section 116 of the lamp 114 is provided inside the induction heating coil 112. In this specification, the expression “the light emitting unit 116 is installed inside the induction heating coil 112” means that at least a part of the light emitting unit 116 is installed inside the induction heating coil 112. Not all of 116 need be installed inside induction heating coil 112. Since the lamp 114 is arranged inside the induction heating coil 112, light heating can be performed without moving the metal plate 120 after the induction heating.

  The mounting table 124 is installed movably in the axial direction in the induction heating coil 112. The mounting table 124 is driven by the transport unit 122 to be movable in the axial direction. The metal plate 120 can be mounted on the mounting table 124. Therefore, after the metal plate 120 is mounted on the mounting table 124, the metal plate 120 can be moved together with the mounting table 124 into the induction heating coil 112, and the heat treatment can be performed. Then, after the heat treatment, the metal plate 120 can be moved from the induction heating coil 112 to the outside together with the mounting table 124 by the transfer unit 122. That is, the induction heating coil 112 has a heating space in which the metal plate 120 can be installed. The mounting table 124 is preferably made of a non-magnetic material such as ceramics. Further, the mounting table 124 may partially support the metal plate 120.

  Next, a control flow of the heat treatment by the heat treatment apparatus 110 will be described. The control flow of the heat treatment by the heat treatment apparatus 110 includes the following control flow (1), control flow (2), and control flow (3). Hereinafter, description will be made in order.

  FIG. 4 is a flowchart showing a control flow (1) of the heat treatment performed by the heat treatment apparatus. The control flow (1) is executed by the control unit 130 (not shown) included in the heat treatment apparatus. This control flow (1) is based on the fact that a predetermined start condition is satisfied (for example, a signal that detects that an operation input has been made by an operator or that the metal plate 120 has been arranged at a predetermined position, or the like). ).

  First, the control unit 130 transmits an induction heating start signal to the induction heating control unit 128 in step 10. Upon receiving the induction heating start signal, the induction heating control unit 128 drives the induction heating coil 112 to start induction heating of the metal plate. Thereafter, the process proceeds to step S12.

  In step 12, the control unit 130 monitors the temperature information transmitted from the temperature detection unit (not shown) and checks whether the temperature has been saturated. Specifically, based on the received temperature information, the control unit 130 continues to determine whether or not the temperature Y at the location X has reached the specific value Z, and determines that the temperature Y has reached the specific value Z. Then, the process proceeds to step 14.

  In step 14, the control unit 130 transmits an induction heating stop signal to the induction heating control unit 128. Upon receiving the induction heating stop signal, the induction heating control unit 128 stops driving the induction heating coil 112. Thereafter, the process proceeds to step S16.

  In step 16, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step 18.

  In step 18, the control unit 130 monitors the temperature information transmitted from the temperature detection unit and checks whether the temperature has reached a desired temperature. Specifically, the control unit 130 continues to determine whether or not the temperature has reached a desired temperature based on the received temperature information, and when determining that the temperature has reached the desired temperature, sends a light heating stop signal to the lamp control unit 126. Send. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thus, the control flow (1) ends.

  FIG. 5 is a flowchart illustrating a control flow (2) of the heat treatment performed by the heat treatment apparatus. The heat treatment apparatus 110 may be configured to perform the control flow (2) instead of the control flow (1). The control flow (2) is executed by the control unit 130 (not shown) included in the heat treatment apparatus, similarly to the control flow (1). In the control flow (2), similarly to the control flow (1), a predetermined start condition is satisfied (for example, an operation input by an operator or a metal plate 120 is disposed at a predetermined position). Is received, etc.).

  First, in step 20, the control unit 130 transmits an induction heating start signal to the induction heating control unit 128. Upon receiving the induction heating start signal, the induction heating control unit 128 drives the induction heating coil 112 to start induction heating of the metal plate. Thereafter, the process proceeds to step S22.

  In step 22, the control unit 130 maintains the heating of the induction heating until a desired time. Specifically, the control unit 130 measures the elapsed time since the transmission of the induction heating start signal, and continuously checks whether or not a predetermined first elapsed time has elapsed. When the control unit 130 determines that the elapsed time after transmitting the induction heating start signal has exceeded the first elapsed time, the process proceeds to step 24.

  In step 24, the control unit 130 transmits an induction heating stop signal to the induction heating control unit 128. Upon receiving the induction heating stop signal, the induction heating control unit 128 stops driving the induction heating coil 112. Thereafter, the process proceeds to step S26.

  In step 26, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step 28.

  In step 28, the control unit 130 measures the elapsed time from the transmission of the light heating start signal, and continuously checks whether or not a predetermined second elapsed time has elapsed. When the control unit 130 determines that the elapsed time after transmitting the light heating start signal has exceeded the second elapsed time, the control unit 130 transmits a light heating stop signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thus, the control flow (2) ends.

  FIG. 6 is a flowchart showing a control flow (3) of the heat treatment performed by the heat treatment apparatus. The heat treatment apparatus 110 may be configured to perform the control flow (3) instead of the control flows (1) and (2). The control flow (3) is executed by the control unit 130 (not shown) included in the heat treatment apparatus, similarly to the control flows (1) and (2). This control flow (3) is similar to the above control flows (1) and (2), when a predetermined start condition is satisfied (for example, when an operation input is made by an operator, or when the metal plate 120 is moved to a predetermined position). (E.g., reception of a signal that detects the arrangement).

  First, in step 30, the control unit 130 transmits an induction heating start signal to the induction heating control unit 128. Upon receiving the induction heating start signal, the induction heating control unit 128 drives the induction heating coil 112 to start induction heating of the metal plate. Thereafter, the process proceeds to step S32.

  In step 32, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step S34.

  In step 34, the control unit 130 determines whether or not the metal plate 120 has reached an arbitrary temperature based on, for example, temperature information from the temperature detection unit and the elapsed time from the start of the light heating. When it is determined that the temperature has reached an arbitrary set temperature, a light heating stop signal is transmitted to the lamp control unit 126. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thereafter, the process proceeds to step S36. The arbitrary temperature set here is a temperature set before the temperature of a part of the metal plate 120 reaches the specific value Z. As a result, it is possible to increase the temperature raising rate until the specific value Z is reached.

  In step 36, the control unit 130 monitors the temperature information transmitted from the temperature detection unit (not shown) to check whether the temperature has been saturated. Specifically, based on the received temperature information, the control unit 130 continues to determine whether or not the temperature Y at the location X has reached the specific value Z, and determines that the temperature Y has reached the specific value Z. Then, the process proceeds to step 38.

  In step 38, the control unit 130 transmits an induction heating stop signal to the induction heating control unit 128. Upon receiving the induction heating stop signal, the induction heating control unit 128 stops driving the induction heating coil 112. Thereafter, the process proceeds to step S40.

  In step 40, the control unit 130 transmits a light heating start signal to the lamp control unit 126. The lamp control unit 126 that has received the light heating start signal drives the lamp 114 to start light heating of the metal plate. Thereafter, the process proceeds to step S42.

  In step 42, the control unit 130 monitors the temperature information transmitted from the temperature detection unit and checks whether the temperature has reached a desired temperature. Specifically, the control unit 130 continues to determine whether or not the temperature has reached a desired temperature based on the received temperature information, and when determining that the temperature has reached the desired temperature, sends a light heating stop signal to the lamp control unit 126. Send. The lamp control unit 126 that has received the light heating stop signal stops driving the lamp 114, and ends the heating of the metal plate by the light heating. Thus, the control flow (3) ends.

  The control flow (1), the control flow (2), and the control flow (3) of the heat treatment performed by the heat treatment apparatus 110 have been described above.

  In the above embodiment, the case where the lamp control unit 126 controls the driving of the lamp 114 and the induction heating control unit 128 controls the driving of the induction heating coil 112 has been described. That is, the case where the lamp 114 and the induction heating coil 112 are controlled by separate control units has been described. However, the heat treatment apparatus of the present invention is not limited to this example, and may have a configuration in which the lamp 114 and the induction heating coil 112 are controlled by one controller.

  In the above-described embodiment, the method of confirming whether or not the temperature is saturated and the method of measuring various elapsed times are merely examples, and can be appropriately changed.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described examples, and design changes can be appropriately made within a range that satisfies the configuration of the present invention.

Reference Signs List 10, 110 Heat treatment device 12, 112 Coil 14, 114 Lamp 20 Steel plate 22 Thick rectangular plate portion 24 Thin rectangular plate portion 116 Light emitting unit 117 Light emitting surface 118 Base 126 Lamp control unit 128 Induction heating control unit

Claims (3)

An induction heating coil for heating the metal plate by induction heating,
A light source for optically heating the metal plate,
The induction heating coil has a heating space in which a metal plate can be installed,
The light source has a light emitting unit that emits light,
The heat treatment device according to claim 1, wherein the light emitting unit is provided inside the induction heating coil. The light emitting unit has a long light emitting surface in one direction,
2. The heat treatment apparatus according to claim 1, wherein the light emitting unit is arranged such that a longitudinal direction of the light emitting unit and an axial direction of the induction heating coil are in the same direction. 3. The light source has a sealing portion at an end of the light emitting portion,
The heat treatment apparatus according to claim 1, wherein the sealing portion is disposed outside the induction heating coil.