JP2006244763A - Magnetic heating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic heating apparatus which can heat different kinds of metals by magnetic heating uniformly and rapidly. <P>SOLUTION: The magnetic heating apparatus performs heat treatment that a material to be heated 6 is heated by heating action of iron loss up to a predetermined temperature. The apparatus comprises main cores 1, 2, 3 which are magnetically coupled to each other by laminated magnetic steel sheets and have a gap 20; heating coils 4, 5 which are set on the main cores so as to coil around the main cores, respectively; the material to be heated 6 which is placed in the gap of the main cores through the intermediaries of auxiliary cores 14, 15; a power supply 7 which supplies an AC power to the heating coils; a controller 8 which specifies a voltage and a frequency of the AC power generated by the power supply; a current detector 11 which measures a current supplied to the heating coils; a magnetic flux detector 17 which detects a flux amount penetrating the material to be heated; and a temperature detection means 10 which detects a temperature of the material to be heated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic heating device used for heat treatment of a metal material, or preheating or postheating of a welding process of a metal material.

  Several conventional metal heating devices have been proposed that utilize the magnetic heat generation of metal. For example, a magnetic loop is formed using a core with high permeability having a void portion, and a metal material placed in the void portion is heated by a heat generation action by magnetization. (For example, refer to Patent Document 1).

Japanese Patent No. 3181620

  In the conventional metal material heating device, the cross-sectional shape of the core (iron core) that generates the magnetic flux penetrating the heated object placed in the gap is different from the cross-sectional shape of the heated object. The distribution of the magnetic flux inside the magnet was not uniform, and the magnetic heat generation distribution almost proportional to the distribution of the magnetic flux was not uniform.

  When the size of the metal material to be heated is relatively small, even if the heat distribution is not uniform, the temperature could be raised almost uniformly as a result of heat conduction. It is difficult to raise the temperature uniformly due to heat conduction, and in the case of an object to be heated whose cross-sectional area is not constant in the direction perpendicular to the direction of magnetic flux penetration, the heat generation distribution itself is not uniform. However, there was a problem that the temperature did not rise.

Further, since the heat generation effect due to the magnetization of the object to be heated is due to magnetic hysteresis loss and eddy current loss, it varies depending on the material and temperature of the metal material and the voltage and frequency of the power supply to be supplied.
Therefore, when the object to be heated is a magnetic material, it is necessary to set the appropriate frequency and voltage so that the magnetic flux density in the object to be heated is not saturated and the maximum possible power can be supplied. In the apparatus disclosed in Patent Document 1, no consideration has been given to this aspect.

Also, in the case of heating exceeding the magnetic transformation point of the magnetic material, or when the object to be heated is a non-magnetic material, the ratio of magnetic hysteresis loss is significantly reduced compared to the case of heating the magnetic material. It is necessary to make maximum use of heat generation due to current loss. However, since there is no magnetism, the penetration depth of the eddy current is increased. As a result, it is necessary to increase the frequency as compared with the case of a magnetic body below the magnetic transformation point.
However, the apparatus disclosed in Patent Document 1 has a problem that this point is not taken into consideration.

  Further, when the object to be heated is a ferromagnetic material, there is residual magnetism even if the magnetic flux is interrupted by the magnetic flux penetrating the object to be heated, and the object to be heated conveyed to the next process is magnetically There was also an adverse effect.

  The present invention has been made to solve the above-described problems, and performs appropriate heating according to the size and material of the object to be heated, and heats the object to be heated uniformly and rapidly. An object of the present invention is to provide a magnetic heating device that can be used for the above-mentioned use.

  A magnetic heating device according to the present invention is a magnetic heating device that heats an object to be heated to a predetermined temperature by heat generation due to iron loss, and heat-treats the main iron core that is magnetically coupled by laminated electromagnetic steel plates and has a gap. , A heating coil attached to the main iron core in a circular manner, an object to be heated disposed through an auxiliary iron core in a gap of the main iron core, a power supply device for applying an alternating current to the heating coil, and generation of the power supply device A control device for setting the voltage and frequency to be operated, a current detector for measuring the current supplied to the heating coil, a magnetic flux detector for detecting the amount of magnetic flux passing through the heated object, and detecting the temperature of the heated object Temperature detecting means is provided.

  Since the magnetic heating apparatus according to the present invention is configured as described above, an object to be heated of various magnetic materials can be rapidly and uniformly heated to a predetermined temperature.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the magnetic heating device according to the first embodiment, and FIGS. 2 and 3 are explanatory views showing the configuration near the gap in FIG. 1 in an enlarged manner.

  As shown in FIG. 1, the magnetic heating device according to the first embodiment is formed in an L-shaped upper iron core 1 and is similarly formed in an L-shape, with a gap 20 between the upper iron core 1. It has an iron core structure composed of a lower iron core 2 arranged oppositely and a rear iron core 3 arranged so as to be magnetically coupled to both the iron cores.

  The upper iron core 1, the lower iron core 2, and the rear iron core 3 are each made of laminated electromagnetic steel sheets, and the cross-sectional shape thereof is square or rectangular from the viewpoint of ease of manufacture. An auxiliary iron core 14 is provided on the upper iron core 1 side of the gap 20 between the upper iron core 1 and the lower iron core 2, an auxiliary iron core 15 is provided on the lower iron core 2 side, and between the auxiliary iron cores 14, 15. For example, a cylindrical object to be heated 6 is placed, and together with the upper iron core 1, the lower iron core 2, and the rear iron core 3 constitute a magnetic circuit.

  An upper coil 4 is wound around the upper iron core 1, and a lower coil 5 is wound around the lower iron core 2. Both coils are connected in series and connected to a power supply device 7 containing an inverter (not shown). Voltage and frequency alternating current is applied to generate magnetic flux in the upper iron core 1 and the lower iron core 2.

  Further, the magnetic flux penetrates the object to be heated 6 through the auxiliary iron cores 14 and 15, and generates heat due to iron loss inside the object to be heated 6, that is, heat generation due to magnetic hysteresis loss and eddy current loss. Is heated to raise the temperature.

  Here, in order to generate a magnetic flux efficiently, it is necessary to make each space | gap of the to-be-heated material 6 and the upper iron core 1 and the lower iron core 2 as small as possible. In addition, since the object to be heated 6 is generally processed in various sizes and shapes, the upper iron core 1 can be moved up and down so that the upper iron core 1 can be raised and lowered according to the height of the object to be heated 6. A mechanism 12 is attached. A known cylinder device is used for the lifting mechanism 12.

  On the other hand, the object to be heated 6 is carried into a gap 20 between the upper iron core 1 and the lower iron core 2 by a conveyance mechanism (not shown), heated to a predetermined temperature, and then carried out again by the conveyance mechanism. Further, in order to prevent interference with the rear iron core 3 when the upper iron core 1 is moved up and down, since the rear iron core 3 needs to be separated from the upper iron core 1, a mechanism 13 for horizontal movement is attached to the rear iron core 3. ing. The mechanism 13 also uses a cylinder device.

Here, in the state where the auxiliary iron cores 14 and 15 are not provided, the magnetic flux Φ ₁ generated from the upper iron core 1 and the lower iron core 2 does not penetrate the object to be heated 6 vertically as shown in FIG. When 6 is a ferromagnetic material such as carbon steel, the magnetic flux Φ ₁ enters the object to be heated 6 through a path having a small magnetic resistance, that is, a path having a short gap distance.

Further, even if the object to be heated 6 is a metal material such as a non-magnetic material other than a ferromagnetic material, the leakage magnetic flux Φ emitted from the upper iron core 1 and the lower iron core 2 near the end surfaces of the upper iron core 1 and the lower iron core 2. ₂ passes only through the upper and lower surfaces of the article 6 to be heated. The upper iron core 1 and the lower iron core 2 are usually made to have a larger cross-sectional area than that of the object to be heated 6 assuming the maximum cross-sectional area of various objects to be heated 6 processed by the magnetic heating device. ing. Therefore, in the vicinity of the upper surface and the lower surface of the object to be heated 6, the non-uniform magnetic flux distribution as described above tends to be remarkable, and the upper surface and the lower surface of the object to be heated 6 generate mainly heat and are in the object to be heated 6. The heat generation is not uniform.

  In the magnetic heating apparatus of the first embodiment, as shown in FIG. 3A, auxiliary iron cores 14 and 15 are arranged at the lower part of the upper iron core 1 and the upper part of the lower iron core 2, respectively. The cross-sectional shapes of the auxiliary iron cores 14 and 15 are formed in accordance with the cross-section of the object to be heated 6, and the cross-sectional area thereof is also the same as the cross-sectional area of the object to be heated 6.

  The auxiliary iron cores 14 and 15 are made of a material having the same magnetic characteristics as the object to be heated 6. That is, when the heated object 6 is a ferromagnetic material, the auxiliary iron cores 14 and 15 are also made of a ferromagnetic material, that is, a steel material, and the heated object 6 is a so-called non-magnetic material such as a paramagnetic material. The auxiliary iron cores 14 and 15 are also made of a nonmagnetic material. In the case of a non-magnetic material, it is desirable to manufacture with stainless steel (austenite) in order to increase the strength.

By arranging these auxiliary iron cores 14 and 15, since the cross-sectional shape and magnetic material are the same at the boundary surface between the auxiliary iron cores 14 and 15 and the article 6 to be heated, as shown in FIG. The magnetic flux Φ ₁ passes through the boundary surface vertically. Further, the leakage magnetic flux in the vicinity of the upper iron core 1 and the lower iron core 2 does not affect the object 6 to be heated, and the magnetic flux is not uniform in the object 6 to be heated. For this reason, the object 6 to be heated generates heat uniformly due to iron loss, that is, magnetic hysteresis and eddy current, in any part, so that the temperature can be raised uniformly. The magnetic detector 17 shown in FIG. 3B will be described later.

  The auxiliary iron cores 14 and 15 are respectively coupled to the upper iron core 1 and the lower iron core 2 which are main iron cores by nonmagnetic bolts or the like. Therefore, the auxiliary iron core 14 on the upper side of the article to be heated 6 moves up and down integrally with the upper iron core 1 and does not affect the carry-in and carry-out of the article to be heated 6 to the gap 20. In addition, since the lower auxiliary iron core 15 is fixed together with the lower iron core 2, the article 6 to be heated may be placed on the lower auxiliary iron core 15 and heated. In order to avoid mechanical damage to the auxiliary iron core 15, a thin insulating plate (not shown) is placed on the lower auxiliary iron core 15.

  Further, since the auxiliary iron cores 14 and 15 are subjected to the same heat generating action as that of the article 6 to be heated, as shown in FIG. It can be used.

  Since the auxiliary iron cores 14 and 15 are individually manufactured according to the magnetic material and shape of the article 6 to be heated, the auxiliary iron cores 14 and 15 are also replaced when the type of the article 6 to be heated is changed.

  2 and 3 show the case where the cross-sectional area of the object to be heated 6 is smaller than that of the upper iron core 1 and the lower iron core 2, but the case where the cross-sectional area of the object to be heated 6 is larger than those of the upper iron core 1 and the lower iron core 2. Needless to say, the auxiliary iron cores 14 and 15 are made in accordance with the cross-sectional shape of the article 6 to be heated, as shown in FIG.

Moreover, as shown in FIG. 6, when the diameters of the upper end surface and the lower end surface of the object to be heated 6 are different, the auxiliary iron cores 14 and 15 are matched to the cross-sectional shapes of the upper end surface and the lower end surface of the object to be heated 6, respectively. The magnetic flux Φ ₁ entering from the auxiliary iron cores 14 and 15 is allowed to enter the object to be heated 6 in parallel by being manufactured and arranged in a shape. Therefore, the heated object 6 can be heated uniformly even if there is a difference in diameter between the upper end and the lower end.

  Here, the heating operation of the magnetic heating apparatus according to the first embodiment will be described. The controller 8 shown in FIG. 1 is inputted in advance with the dimensions of the object 6 to be heated, the magnetic material (a type for classifying ferromagnetic material, paramagnetic material, and other metal materials), and a predetermined heating target temperature. Yes. At the time of starting the magnetic heating device, the control device 8 determines the frequency and voltage of alternating current applied to the upper coil 4 and the lower coil 5 in accordance with the shape and material of the article 6 to be heated in the following judgment process.

(1) The total magnetic resistance of the magnetic circuit is obtained by adding the expected magnetic resistance of the object to be heated 6 to the magnetic resistance of the entire core calculated by the upper iron core 1, the lower iron core 2, the rear iron core 3, and the auxiliary iron cores 14 and 15. Resistance is calculated. In practice, since the magnetic path lengths of the upper iron core 1, the lower iron core 2, and the rear iron core 3 occupy most of the magnetic cores, the auxiliary iron cores 14 and 15 and the object to be heated 6 are not greatly affected in this calculation.

The frequency is between 50 and 100 Hz as a reference, the impedance of the upper coil 4 and the lower coil 5 (determined by the frequency, magnetic resistance, and number of turns of the coil) obtained from the total magnetic resistance described above, and the rated voltage that can be generated by the power supply device And an appropriate frequency and voltage are determined so as to approach the rated current.
The frequency standard is 50 to 100 Hz, which is a general frequency (maximum 400 Hz) that can be output by a general-purpose type used as an inverter, and there is a margin for adjustment in the upper and lower frequency ranges. Because.

(2) The starting voltage is set low. This is to prevent an overcurrent trip of the power supply device 7 due to a large current flowing through the upper coil 4 and the lower coil 5 during startup. After starting the heating device, the current detector 11 measures the current flowing through the upper coil 4 and the lower coil 5 and inputs it to the control device 8, calculates the difference from the allowable current of the power supply device 7, and determines the degree of increase or decrease in voltage. The voltage is commanded to the power supply device 7. As the temperature of the article to be heated 6 rises, its resistivity and relative permeability change, and the magnetic resistance also changes slightly. Therefore, the current changes, and the voltage is constantly changed in the determination process.

  The set frequency and voltage are commanded from the control device 8 to the power supply device 7, and a predetermined alternating current is applied to the upper coil 4 and the lower coil 5. The temperature of the article 6 to be heated is constantly measured by a thermometer 10. Further, the magnetic flux penetrating the heated object 6 is measured by the annular magnetic flux detector 17 disposed around the heated object 6.

  The magnetic flux detector 17 is an annular conductor, and the voltage generated at both ends of the conductor is measured by using the principle that the voltage generated at the annular conductor is proportional to the magnetic flux penetrating through the inside of the conductor. Can be calculated, that is, the magnetic flux penetrating the article 6 to be heated. Moreover, if the cross-sectional area of the to-be-heated material 6 is known, the magnetic flux density of the to-be-heated material 6 can be calculated.

  During startup of the magnetic heating device, the voltage generated by the magnetic flux detector 17 is always input to the control device 8, and the following judgment and command are automatically made based on the magnetic flux density of the heated object 6 calculated by the control device 8. To be done.

(1) When the heated object 6 is a ferromagnetic material (iron, cobalt, nickel, etc.):
When the magnetic flux density exceeds the saturation magnetic flux density of the article 6 to be heated, heat generation due to magnetic hysteresis is remarkably reduced, and therefore it is necessary to heat the magnetic flux with a magnetic flux density smaller than the saturation magnetic flux density.
The magnetic flux density of the upper iron core 1 and the lower iron core 2 is substantially determined by the voltage and frequency applied from the power supply device 7, which also determines the penetration magnetic flux of the article 6 to be heated. Accordingly, the voltage and frequency are set so that the magnetic flux density of the article 6 to be heated is as high as possible within a range not exceeding the expected saturation magnetic flux density (about 1.0 Tesla). Note that the magnetic flux density is substantially proportional to the voltage of the supplied power source and is almost inversely proportional to the frequency.

(2) When the heated object 6 is a paramagnetic material (aluminum, etc.):
Since the magnetic susceptibility is significantly smaller than that of a ferromagnetic material, the rate of heat generation due to eddy current is large, and the heat generation due to magnetic hysteresis is small. Therefore, a low frequency and a high voltage are required so that the highest possible magnetic flux density can be generated.

  However, since the penetration depth of the eddy current calculated by the following equation (1) is generally 1/3 to 1/7 of the diameter of the object 6 to be heated, there is a lower limit frequency that can be supplied. Therefore, a frequency higher than the lower limit frequency is set according to the monster of the article 6 to be heated. Note that the resistivity of the object to be heated shown in the following formula (1) needs to be input to the control device 8 as information on the object to be heated 6 in advance.

(3) When the heated object 6 is a metal other than the above:
Since it has almost no magnetism, the proportion of heat generated by eddy currents occupies the majority. Similar to the paramagnetic material, the frequency is set so that the penetration depth of the eddy current becomes an appropriate value. Similarly to the above (2), the resistivity of the object to be heated 6 shown in the equation (1) needs to be input to the control device 8 as information on the object to be heated 6 in advance.

  As the temperature of the object to be heated 6 increases, its resistivity increases and the relative permeability also changes, so that the magnetic resistance combined with the iron core also changes slightly, and even if the frequency and voltage are constant, the magnetic flux density changes at any time. However, the magnetic flux density of the article 6 to be heated is constantly measured by the magnetic flux detector 17, and the frequency and voltage are adjusted so that the magnetic flux density always becomes an optimum value by the above-described determination process.

  A control block for determining these voltages and frequencies is shown in FIG. That is, each information of A, B, C, D, and E is input to the control device 8. A is information on the object 6 to be heated, and the dimensions, mass, material, heating target temperature and resistivity of the object to be heated are input.

B is information on the number of turns of the upper coil 4 and the lower coil 5 and the magnetic resistance of the iron core, and the circuit impedance is calculated by F based on these information.
C is a measurement result of the current detector 11. Further, D is a measurement result of the magnetic flux detector 17, and the magnetic flux density of the article to be heated 6 is calculated by G based on this result.

E is a measurement result of the thermometer 10, and when the object 6 to be heated is a ferromagnetic material, it is determined based on this result whether H is equal to or higher than the magnetic transformation point.
The AC voltage and frequency supplied from the power supply device 7 are calculated in J based on the above information, and the end of heating is determined according to the measurement result from the thermometer 10, and the power supply device in K. 7 is commanded.

  In the object to be heated 6 having a difference in diameter between the upper end and the lower end as shown in FIG. 6, the magnetic flux detector 17 is arranged so as to correspond to a portion having a small diameter. By monitoring a portion having a small diameter where the magnetic flux density is higher than that of a portion having a large diameter, the above-described determination based on the magnetic flux density is accurately performed. Further, since the magnetic flux detector 17 is coupled to the upper iron core 1 and the upper auxiliary iron core 14 via a bracket (not shown) or the like, the magnetic flux detector 17 moves up and down simultaneously when the upper iron core 1 is raised and lowered, and does not interfere with the object 6 to be heated. It is like that.

  Moreover, it is judged from the measurement signal of the thermometer 10 that the temperature of the article 6 to be heated has reached a predetermined value, and the power supply device 7 is stopped.

  In the example of FIG. 1, the connection of the upper coil 4 and the lower coil 5 is in series, but this can be expected to have the same effect as described above even when connected in parallel to the power supply device 7. In this case, if the upper coil 4 and the lower coil 5 are manufactured with the same number of turns, the impedances thereof are almost equal and the flowing currents are also substantially the same. Therefore, the current detector 11 is either the upper coil 4 or the lower coil 5. Just put it on one side.

  Since the first embodiment is configured as described above, the temperature of the object to be heated 6 can be increased uniformly by the effect of the auxiliary iron cores 14 and 15, and is optimal according to the magnetic material of the object to be heated 6. In addition, since the magnetic flux density of the object to be heated 6 is constantly monitored, the maximum voltage possible without saturation of the magnetic flux density regardless of the magnetic material of the object to be heated 6 Current can be supplied, and the temperature can be rapidly raised to a predetermined temperature.

Embodiment 2.
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 8 shows a voltage setting pattern when the power supply of the magnetic heating apparatus according to the second embodiment is stopped, and is intended for the case of processing a ferromagnetic material as an object to be heated.

  Since the ferromagnetic material has a magnetic hysteresis curve as shown in FIG. 9, if the power supplied to the upper coil 4 and the lower coil 5 is shut off while the object 6 is heated, the residual magnetic flux density (residual magnetism) ) Since the magnetic flux density is substantially proportional to the supplied voltage, the magnetic hysteresis curve becomes smaller and the residual magnetic flux density becomes smaller as the supplied voltage becomes smaller.

In the second embodiment, as shown in FIG. 8, a setting pattern is set such that the voltage decreases with time and becomes zero based on a command from the control device 8 after a command to stop the power supply device.
Since the magnetic flux density is substantially proportional to the supplied voltage, if the voltage is reduced as described above, the magnetic flux density of the object to be heated decreases, the magnetic hysteresis curve shown in FIG. The residual magnetic flux density of 6 can be made almost zero.

  Since the second embodiment is configured as described above, it is possible to reduce the residual magnetism of the heated object 6 that is a ferromagnetic body when the magnetic heating device is stopped.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 10 shows a frequency setting pattern of the magnetic heating device according to the third embodiment. When the object 6 to be heated, which is a ferromagnetic material, is heated below the magnetic transformation point (about 770 ° C.), the magnetism disappears above the magnetic transformation point, so there is no heat generation due to magnetic hysteresis, only heat generation due to eddy currents. It becomes.

Further, when the magnetism disappears, the relative permeability μ _s in the formula (1) becomes approximately 1, so that the penetration depth of the eddy current becomes remarkably large, and if this value becomes larger than the diameter of the object to be heated, the heating is performed. It causes a decrease in efficiency. As described above, the penetration depth of the eddy current is preferably 1/3 to 1/7 of the diameter of the object to be heated. However, in order to reduce the penetration depth, it is necessary to increase the frequency.

  Since the third embodiment corresponds to this, based on the measurement result from the thermometer 10, a predetermined frequency is instructed by the control device 8 in the region where the temperature of the heated object 6 is equal to or lower than the magnetic transformation point, and the heated object 6 The frequency is increased when the temperature reaches the magnetic transformation point.

For example, if the diameter of the article 6 to be heated is about 100 mm, the frequency below the magnetic transformation point is set to about 100 Hz, and is set to about 300 to 400 Hz above the magnetic transformation point.
In this frequency range of 300 to 400 Hz, the penetration depth of the eddy current calculated by the equation (1) is about 25 to 30 mm.

  Since Embodiment 3 is configured as described above, even when the object to be heated 6 is heated to a temperature above the magnetic transformation point, it can be efficiently heated.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 11 (a) shows the relationship between the carbon content of the magnetic heating device according to Embodiment 4 and the target heating temperature. For example, the pre-heating before the welding process (not shown) is a ferromagnetic material. It is assumed that the heated object is heat-treated.

  In the process of welding a ferromagnetic material, particularly carbon steel, the welded portion is harder than other portions because of thermal effects. That is, since a hardness difference can be generated in the material, cracking is likely to occur when the temperature is lowered after welding. Therefore, preheating of an object to be heated is performed before the welding process.

  Here, in the cooling process after heating the carbon steel as a heated object to a high temperature such as a welding process, the carbon content of the carbon steel and the martensitic transformation start temperature have a relationship as shown in FIG. Generally (see “Heat Treatment Guidebook” published by Japan Heat Treatment Technology Association), the higher the carbon content, the lower the martensitic transformation start temperature.

  It is generally accepted as a means for preventing cracking of the object to be heated that it is gradually cooled from the martensite transformation start temperature to a low ordinary temperature in the cooling process. Therefore, if the object to be heated is heated to the martensite transformation start temperature in the welding process, it can be gradually cooled without being rapidly cooled from near the martensite transformation start temperature to room temperature.

  In the fourth embodiment, the object to be heated is preheated to the martensitic transformation start temperature corresponding to the carbon content of the object to be heated, and then the welding process is performed.

  In the magnetic heating device, when the object to be heated 6 is a ferromagnetic material, the carbon content of the object to be heated 6 is also input to the control device 8 in advance. Since the carbon content and the heating target temperature are set in the control device 8 with the relationship shown in FIG. 11 (a), the martensitic transformation start temperature corresponding to the carbon content is shown in FIG. 11 (b). Is calculated and set as the heating target temperature.

  When the measurement signal of the thermometer 10 reaches the heating target temperature after the magnetic heating device starts heating the article 6 to be heated, the heating is ended according to the judgment of the control device 8. With this temperature setting, the object to be heated, which is carbon steel, is heated to a predetermined temperature and then transported to a welding process (not shown), so that cracking defects can be reduced even after welding.

  In the above example, the carbon content of the object to be heated was taken as an example, but the alloy steel containing components such as manganese, nickel, cobalt, etc. also has a higher martensitic transformation start temperature as the alloy content increases. Since it becomes low, the defect of the crack after welding can be reduced by previously determining the heating target temperature according to the alloy content.

  In the above description, an example in which the magnetic heating device is used as a preheating means for the welding process is shown. Slow cooling without rapid cooling is possible, and the same effect as in the case of preheating can be obtained.

It is the schematic which shows the structure of the magnetic heating apparatus by Embodiment 1 of this invention. It is explanatory drawing which expands and shows the structure of the space | gap part vicinity in FIG. It is explanatory drawing which expands and shows the structure of the space | gap part vicinity in FIG. It is the schematic which shows the cooling structure of the auxiliary iron core in FIG. It is explanatory drawing which shows the condition in case the cross-sectional areas of to-be-heated material differ. It is explanatory drawing which shows the condition in case the cross-sectional areas of to-be-heated material differ. It is a control block diagram which shows the process for determining the voltage and frequency of a power supply device. It is a figure which shows the voltage setting pattern in Embodiment 2 of this invention. It is a figure which shows a magnetic hysteresis curve. It is a figure which shows the frequency setting pattern in Embodiment 3 of this invention. It is a figure which shows the relationship between the carbon content and heating target temperature in Embodiment 4 of this invention.

Explanation of symbols

1 Upper iron core, 2 Lower iron core, 3 Rear iron core, 4 Upper coil, 5 Lower coil,
6 heated object, 7 power supply, 8 control device, 10 thermometer,
DESCRIPTION OF SYMBOLS 11 Current detector, 12 Elevating mechanism, 13 Moving mechanism, 14, 15 Auxiliary iron core, 17 Magnetic flux detector, 18 Cooling pipe, 20 Air gap part.

Claims (14)

  In a magnetic heating device that heats an object to be heated up to a predetermined temperature by heat generation due to iron loss and is heat-bonded to a main core having a gap portion that is magnetically coupled with laminated electromagnetic steel plates, and attached to the main core in a circular fashion Heating coil, an object to be heated disposed in an air gap of the main iron core via an auxiliary iron core, a power supply device for applying an alternating current to the heating coil, and a control device for setting a voltage and a frequency generated by the power supply device A current detector for measuring the current supplied to the heating coil, a magnetic flux detector for detecting the amount of magnetic flux passing through the heated object, and a temperature detecting means for detecting the temperature of the heated object. A magnetic heating device.   In a magnetic heating device that heats to a predetermined temperature by heat generated by iron loss before welding the object to be heated, a main iron core that is magnetically coupled with laminated electromagnetic steel sheets and has a gap, and circulates around the main iron core The attached heating coil, the object to be heated disposed in the gap of the main iron core via the auxiliary iron core, the power supply device for applying alternating current to the heating coil, and the control for setting the voltage and frequency generated by the power supply device An apparatus, a current detector for measuring the current supplied to the heating coil, a magnetic flux detector for detecting the amount of magnetic flux penetrating the heated object, and a temperature detecting means for detecting the temperature of the heated object Magnetic heating device characterized by   In a magnetic heating device that heats to-be-heated object to a predetermined temperature by heat generation due to iron loss, a main core that is magnetically coupled with laminated electromagnetic steel plates and has a gap, and is attached to the main core in a circular fashion Heating coil, an object to be heated disposed in an air gap of the main iron core via an auxiliary iron core, a power supply device for applying an alternating current to the heating coil, and a control device for setting a voltage and a frequency generated by the power supply device A current detector for measuring the current supplied to the heating coil, a magnetic flux detector for detecting the amount of magnetic flux passing through the heated object, and a temperature detecting means for detecting the temperature of the heated object. A magnetic heating device.   The main iron core is disposed opposite to the fixed second iron core via the gap portion with respect to the second iron core, and is configured to be movable to adjust the height of the gap portion. 4. The structure according to claim 1, wherein the first iron core and the second iron core are magnetically coupled to the first iron core and the second iron core to be movable. A magnetic heating apparatus according to claim 1.   The magnetic heating device according to any one of claims 1 to 4, wherein the auxiliary iron core is made of the same magnetic material as the object to be heated.   The said auxiliary iron core has the same cross-sectional shape as the said to-be-heated material with respect to the direction orthogonal to the penetration direction of the magnetic flux which penetrates the said to-be-heated material. The magnetic heating device according to item.   The said auxiliary iron core has a water cooling pipe for cooling, The magnetic heating apparatus of any one of Claims 1-6 characterized by the above-mentioned.   The magnetic heating apparatus according to claim 1, wherein the object to be heated is a ferromagnetic material.   The magnetic heating apparatus according to claim 1, wherein the object to be heated is a paramagnetic material.   The said control apparatus determines and instruct | indicates the voltage and frequency supplied from the said power supply device according to the magnetic material of the said to-be-heated object, The any one of Claims 1-9 characterized by the above-mentioned. Magnetic heating device.   The magnetic heating device according to any one of claims 1 to 8, wherein the control device issues a command to change the frequency when the temperature of the object to be heated reaches a magnetic transformation point. .   The voltage applied to the heating coil is decreased stepwise at the end of heating to reduce the residual magnetism of the object to be heated, or any one of claims 1 to 8 or claim 10. Or the magnetic heating apparatus of Claim 11.   The magnetic heating apparatus according to claim 2 or 3, wherein a heating target temperature of the object to be heated is determined according to a carbon content of the object to be heated. 4. The magnetic heating apparatus according to claim 2, wherein a heating target temperature of the object to be heated is determined in accordance with an alloy content of the object to be heated.

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