JP5880175B2 - Electric heating method and hot press molding method - Google Patents

Description

  The present invention relates to an energization heating method for heating a conductive plate material having a predetermined electric resistance by energization heating, and a hot press forming method for press forming a plate material heated by the energization heating method.

  For example, a plate-like material (plate-like workpiece) such as a steel plate used for a car body such as an automobile is generally used after being formed into a predetermined shape by press molding. In addition, when using a plate-like workpiece such as a high-tensile steel plate in order to reduce the weight or increase the strength of the vehicle body, it is possible to perform hot press molding in which the workpiece is heated and press-molded after improving the formability. Molding is done.

  Thus, when press-molding by heating a board | plate material, in order to shorten a shaping | molding cycle time, it is calculated | required to heat a board | plate material rapidly. As a heating method that meets such demands, there is known an energization heating method in which electrodes are attached to both ends of a plate material and electricity is passed between both electrodes, whereby the plate material is rapidly heated by Joule heat generated in the plate material. When this energization heating method is adopted, generally, a rectangular plate is heated substantially uniformly.

  On the other hand, post-processing becomes easier when post-processing such as drilling is performed on a part of the molded product after hot press molding, or when the mechanical properties required for the final product differ depending on the part. Thus, for the purpose of lowering the hardness of the post-processed part or making the mechanical characteristics different depending on the part, it is required to heat the heated plate material before pressing at a predetermined non-uniform temperature distribution.

  In this regard, Patent Documents 1 and 2 disclose a technique for performing energization heating so that a heated plate material has a predetermined temperature distribution.

  Specifically, the technique of Patent Document 1 performs heating at a contact portion by performing energization heating in a state where a temperature control member controlled to be maintained at a predetermined temperature is in contact with a predetermined portion of a plate to be heated. By removing heat from the heated plate material inside, the heating temperature of this portion is lowered. According to the technique of this patent document 1, it is possible to heat a plate to be heated so as to have a desired temperature distribution by using a heating device in which temperature control members are appropriately arranged at various places where it is desired to lower the heating temperature. become.

  Moreover, the technique of patent document 2 makes the shape of a to-be-heated plate material into the shape where the dimension of the width direction orthogonal to an energization direction changes by a position of an energization direction in planar view, The current density flowing through the is changed depending on the position in the energization direction. According to the technique of Patent Document 2, the heated plate material is heated with a temperature distribution such that the higher the current density during energization heating in the heated plate material, the higher the temperature, and the lower the current density during energization heating, the lower the temperature. can do.

JP 2011-136342 A JP 2009-274122 A

  However, in the heating device used in the technique of Patent Document 1, the temperature control members are disposed at all locations where heat is removed from the heated plate material during energization heating, and each temperature control member is in contact with the heated plate material. In addition, since it is necessary to provide a drive mechanism that drives them to be separated from each other, the structure of the heating device becomes complicated, resulting in an increase in equipment cost.

  Moreover, when current heating is performed by the technique of Patent Document 2, there is a problem that the temperature distribution of the plate to be heated depends on the shape of the plate. Therefore, for example, it is impossible to increase the heating temperature of a portion having a large dimension in the width direction orthogonal to the energizing direction in a plan view, or to decrease the heating temperature of a portion having a small dimension in the width direction.

  Therefore, an object of the present invention is to enable heating with a simple configuration so as to have a predetermined temperature distribution, regardless of the shape of the plate material, when the plate material to be heated is heated by energization heating.

  In order to solve the above problems, the present invention is configured as follows.

First, the invention according to claim 1 of the present application is
An energization heating method of heating the heated plate material by attaching a pair of electrodes to a conductive heated plate material having a predetermined electrical resistance apart from each other and energizing,
Superposing the heated plate material and a conductive auxiliary heating plate material having a predetermined electrical resistivity;
A step of attaching a pair of electrodes to the heated plate material and the heating auxiliary plate material with the heated plate material and the auxiliary heating plate material being stacked,
Energizing between the electrodes, and
In each cross section orthogonal to the energization direction of the heated plate material and the heating auxiliary plate material, the sectional area of the heated plate material is S1, the electrical resistivity of the heated plate material is ρ1, and the sectional area of the heating auxiliary plate material is S2. When the electrical resistivity of the heating auxiliary plate material is ρ2,
As the heating auxiliary plate material,
In a state where the heated plate material and the heating auxiliary plate material are overlapped, the product (S1 / ρ1) of the cross-sectional area (S1) of the heated plate material and the reciprocal of the electrical resistivity (ρ1), and the heating auxiliary plate material So that the sum (S1 / ρ1 + S2 / ρ2) of the product (S2 / ρ2) of the cross-sectional area (S2) and the reciprocal of the electrical resistivity (ρ2) differs depending on the cross-section (S2) or the electrical resistivity ( It is characterized by using a heating auxiliary plate material having a heating adjustment part in which at least one of ρ2) is adjusted.

The invention according to claim 2 of the present application is the invention according to claim 1,
The heating adjustment portion is provided with a hole for reducing the cross-sectional area (S2).

Furthermore, the invention according to claim 3 of the present application is the invention according to claim 2,
The heating adjustment section includes a plurality of the hole portions, and is configured to adjust the cross-sectional area (S2) according to the size of the hole portions.

Furthermore, the invention according to claim 4 is the invention according to claim 2 or claim 3,
The hole has a shape with no corners in a peripheral edge in a plan view and an edge in a depth direction.

The invention according to claim 5 is the invention according to claim 1,
The heating auxiliary plate has a non-uniform thickness,
The heating adjustment unit is configured to adjust the cross-sectional area (S2) according to the thickness of the auxiliary heating plate in the heating adjustment unit.

Furthermore, the invention of claim 6 is the invention of claim 5,
One surface of the heating auxiliary plate is formed flat, and is configured such that the thickness of the heating adjustment portion is adjusted by the unevenness of the other surface,
In the step of superimposing the heated plate material and the auxiliary heating plate material, a flat surface of the auxiliary heating plate material is superimposed on the heated plate material.

Furthermore, the invention according to claim 7 is the invention according to claim 1,
A slit for reducing the cross-sectional area (S2) is provided in the heating adjustment section so as to extend in a direction orthogonal to the energization direction in plan view.

The invention according to claim 8 is the invention according to claim 7,
The slit is characterized in that it has a shape with no corners in a peripheral edge in a plan view and an edge in the depth direction.

Furthermore, the invention according to claim 9 is the invention according to claim 1,
In the heating adjustment part, a plating part for increasing the electrical resistivity (ρ2) is formed on at least one surface of the auxiliary heating plate.

Furthermore, the invention according to claim 10 is the invention according to any one of claims 1 to 9,
In the step of superimposing the heated plate material and the auxiliary heating plate material, an electric power smaller than that of the heated plate material and the auxiliary heating plate material is provided between the heated plate material and the auxiliary heating plate material in an attachment portion of the electrode. The heating target plate and the heating auxiliary plate are overlapped with a welding prevention plate having a resistivity interposed therebetween.

Moreover, the hot press molding method according to the invention of claim 11
The heated plate material is heated by the current heating method according to any one of claims 1 to 10, and the heated heated plate material is press-molded using a forming die.

  First, according to the energization heating method according to the first aspect of the present invention, since the heating heating is performed in a state in which the heating auxiliary plate having the heating adjustment portion is stacked on the heated plate, the heating temperature of the heated plate is The plate to be heated can be heated with a desired temperature distribution such that the heating temperature varies depending on the cross section orthogonal to the energization direction.

  Specifically, the heating auxiliary plate material is heated in the cross section provided with the heating adjustment section by adjusting at least one of the cross-sectional area (S2) or the electrical resistivity (ρ2) in the heating adjustment section. The product (S1 / ρ1) of the cross-sectional area (S1) of the plate material and the reciprocal of the electrical resistivity (ρ1), and the product (S2 / ρ1) of the cross-sectional area (S2) of the auxiliary heating plate material and the electrical resistivity (ρ2). ρ2) (S1 / ρ1 + S2 / ρ2), and consequently, the composition in the minute range when it is considered that the resistance of the heated plate material and the resistance of the auxiliary heating plate material in the minute range in the energizing direction are connected in parallel. The resistance can be adjusted, whereby the heating temperature of the heated plate material can be varied depending on the position in the energizing direction.

  Moreover, according to this invention, since the heating temperature of a to-be-heated plate material can be adjusted with the heating adjustment part of a heating auxiliary plate material as mentioned above, regardless of the shape of a to-be-heated plate material, desired temperature distribution is obtained. Can do.

  Furthermore, according to the present invention, the above-described effects can be obtained with a simple configuration in which the heating auxiliary plate having the heating adjustment unit as described above is simply superposed on the heated plate.

  According to the invention described in claim 2, since the hole is provided in the heating adjustment portion, the sectional area (S2) in the heating adjustment portion is adjusted so as to be reduced. It can adjust so that the heating temperature of a to-be-heated plate material may be increased in a cross section.

  Furthermore, when the invention according to claim 3 is applied to the invention according to claim 2, the cross-sectional area (S2) of the heating adjustment part is adjusted by the size of the hole provided in the heating adjustment part. Thereby, the heating temperature of the to-be-heated board | plate material in this cross section can be adjusted.

  Furthermore, when the invention according to claim 4 is applied to the invention according to claim 2 or claim 3, both the peripheral edge portion in the plan view and the edge portion in the depth direction of the hole portion are energized. Since there are no corners where heat generation tends to concentrate, damage to the auxiliary heating plate material due to local excessive heating can be prevented.

  According to the invention of claim 5, the cross-sectional area (S2) of the heating adjustment portion is adjusted by the thickness of the heating auxiliary plate material in the heating adjustment portion, so that the heated plate material at the position in the energization direction is adjusted. The heating temperature can be adjusted.

  Furthermore, when the invention according to claim 6 is applied to the invention according to claim 5, the plate to be heated and the plate to be heated at the time of energization are obtained by superimposing the flat surface of the plate to be heated on the plate to be heated. And the heating temperature of the plate to be heated can be adjusted with high accuracy.

  In addition, according to the invention described in claim 7, since the heating adjustment portion is provided with a slit, the cross-sectional area (S2) in the heating adjustment portion is adjusted to be reduced. It can adjust so that the heating temperature of a to-be-heated plate material may be reduced.

  Furthermore, when the invention according to claim 8 is applied to the invention according to claim 7, the corner where heat generation is likely to be concentrated at the time of energization in both the peripheral edge portion in the plan view and the edge portion in the depth direction of the slit. Since there is no portion, it is possible to prevent the heating auxiliary plate from being damaged due to local excessive heating.

  According to the invention described in claim 9, since the plating portion is formed on at least one surface of the auxiliary heating plate in the heating adjustment portion, the electrical resistivity (ρ2) in the heating adjustment portion is increased. It can adjust so that the heating temperature of a to-be-heated board | plate material may be increased in the position of this electricity supply direction by this.

  Furthermore, according to the invention described in claim 10, when the heated plate material and the heating auxiliary plate material are overlapped, in each attachment portion of the pair of electrodes for energization, between the heated plate material and the heating auxiliary plate material, By interposing the welding prevention plate material whose electric resistivity is smaller than that of the heated plate material and the auxiliary heating plate material, the heated plate material and the auxiliary heating plate material are locally heated excessively and welded to each other at the electrode mounting portion. Can be prevented. As a result, it is possible to avoid the problem that it becomes difficult to separate the heated plate material and the auxiliary heating plate material, or when the trace portion remains in the welded portion of the heated plate material, the trace portion cannot be used as a product. .

  Moreover, according to the hot press molding method according to the invention described in claim 11, the plate material to be heated can be quickly distributed in a desired temperature distribution by the electric heating method according to any one of claims 1 to 10. Since the heated plate material to be heated is press-molded using a molding die, it is possible to reduce the press molding cycle time, while partially reducing plate-shaped molded products having different mechanical properties depending on the part, or drilling, etc. It is possible to easily obtain a plate-like molded product that can be easily post-processed.

It is a top view which shows roughly the electric heating apparatus used with the electric heating method which concerns on 1st Embodiment. It is the side view which looked at the electric heating apparatus shown in FIG. 1 from the Y2A direction and Y2B direction of FIG. It is a top view which shows the plate-shaped workpiece | work heated by the electric heating apparatus shown in FIG. 1, and the heating auxiliary | assistant board | plate material used for this heating. It is the sectional view on the AA line of FIG.3 (b). It is a top view which shows the modification of the hole of a heating adjustment part. The product of the position in the energization direction of the plate-like workpiece and the heating auxiliary plate shown in FIG. 3 and the product (S1 / S2) of the cross-sectional area (S1, S2) of the plate-like workpiece and the heating auxiliary plate and the electrical resistivity (ρ1, ρ2). It is a graph which shows the relationship with (ρ1, S2 / ρ2). It is a side view which shows roughly an example of the press molding apparatus provided with the electric heating apparatus shown in FIG. It is a side view which shows the state by which the heating auxiliary plate material which concerns on a 1st modification was set to the electricity heating apparatus shown in FIG. It is a top view which shows the state by which the heating auxiliary plate material which concerns on a 2nd modification was set to the electricity heating apparatus shown in FIG. It is a top view which shows the state by which the heating auxiliary plate material which concerns on a 3rd modification was set to the electricity heating apparatus shown in FIG. It is a top view which shows roughly the electric heating apparatus used with the electric heating method which concerns on 2nd Embodiment. It is the side view which looked at the electric heating apparatus shown in FIG. 11 from the Y10A direction of FIG. It is a side view which shows roughly the electricity heating apparatus used with the electricity heating method which concerns on 3rd Embodiment. It is the top view and side view for demonstrating the temperature measurement conditions of an Example. It is the top view and side view for demonstrating the temperature measurement conditions of a comparative example. It is a graph which shows the measurement result of an Example and a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
First, the energization heating method according to the first embodiment will be described with reference to FIGS.

  FIG. 1 is a plan view schematically showing an electric heating apparatus 1 used in the electric heating method according to the first embodiment. 2A is a side view of the electric heating device 1 viewed from the Y2A direction in FIG. 1, and FIG. 2B is a side view of the electric heating device 1 viewed from the Y2B direction in FIG. is there. Further, FIG. 3A is a plan view showing a conductive plate-like workpiece (heated plate material) W heated by the energization heating device 1, and FIG. It is a top view which shows the electroconductive heating auxiliary plate material P1 used auxiliary to heating.

  2A and 2B, a part of a positioning member to be described later is indicated by a two-dot chain line, and this is shown in a transmissive state.

  As shown to Fig.3 (a), the plate-shaped workpiece W is an electroconductive board | plate material which has predetermined | prescribed electrical resistivity, such as a high tensile steel plate, for example. The plate-like workpiece W described in the present embodiment is a rectangular plate material having a substantially constant thickness, but the shape of the plate-like workpiece to which the present invention is applicable is not particularly limited thereto. The plate-like workpiece W is heated by energization heating and then press-formed into a predetermined shape, and unnecessary portions are removed by trimming, whereby various molded products such as vehicle body constituent members are obtained.

  On the other hand, as shown in FIG. 3B, the heating auxiliary plate P1 is a conductive plate having a predetermined electrical resistivity, such as a high-tensile steel plate, like the plate-like workpiece W, and has a substantially constant thickness. Have. Moreover, the heating auxiliary plate material P1 has substantially the same planar shape as the plate-like workpiece W, and is used by being overlapped with the end surfaces of the plate-like workpiece W and the heating auxiliary plate material P1 being aligned over the entire circumference. .

  In addition, as a material of the plate-like workpiece W and the heating auxiliary plate material P1, for example, a metal such as aluminum, stainless steel, magnesium, titanium, or a casting is used, but a material other than metal is used as long as it has conductivity. For example, a resin such as CFRP may be used. The material of the auxiliary heating plate P1 may be the same as or different from the material of the plate workpiece W. In particular, it is preferable to use stainless steel or cast iron as the material of the auxiliary heating plate P1, and this can suppress oxidation of the auxiliary heating plate P1. A more detailed configuration of the auxiliary heating plate P1 will be described later.

  As shown in FIGS. 1 and 2, the energization heating device 1 heats the plate-like workpiece W by Joule heat generated in the plate-like workpiece W by attaching electrodes 11 a and 11 b that are separated from each other to the plate-like workpiece W and energizing them. Therefore, in this embodiment, energization heating is performed in a state where the heating auxiliary plate material P1 is superimposed on the plate-like workpiece W.

  The energization heating device 1 includes an energization means 10 for electrically heating the plate-like workpiece W in a state where the heating auxiliary plate material P1 is superimposed on the plate-like workpiece W. The energization means 10 includes a pair of electrodes 11 that are spaced apart from each other in parallel, a power source 12 that supplies DC or AC power to the electrode 11, and a cable 13 that connects the power source 12 and the electrode 11. The plate-like workpiece W and the heating auxiliary plate P1 are heated by bringing the pair of electrodes 11 into contact with both ends of the overlapped plate-like workpiece W and the auxiliary heating plate P1, and energizing them. The pair of electrodes 11 are bar electrodes formed in a substantially rectangular parallelepiped shape using a material such as copper, for example, and one electrode 11a is used as a positive electrode and the other electrode 11b is used as a negative electrode.

  In the present embodiment, the energization heating is performed in a state where the pair of electrodes 11 are in contact with the plate-like workpiece W. However, the electrode 11 may be brought into contact with the heating auxiliary plate P1, and the energization heating may be performed. The electrode 11 may be brought into contact with both the work W and the auxiliary heating plate material P1 to perform energization heating.

  The electric heating device 1 also includes clamp members 15 disposed above the pair of electrodes 11. As shown in FIG. 2, the clamp member 15 is a pin having a substantially rectangular parallelepiped clamp base portion 16 extending substantially parallel to the length direction of the electrode 11, and a tip portion that contacts the plate-like workpiece W and the heating auxiliary plate material P <b> 1. And a spring 18 coupled to the clamp base 15 and the pin portion 17, and the clamp base 16 is connected to a clamp base moving means (not shown) so as to be movable in the vertical direction as indicated by an arrow Z1. Has been.

  The clamp member 15 is disposed on the opposite side of the electrode 11 with the plate-like workpiece W and the heating auxiliary plate P1 interposed therebetween, and is moved downward by moving the clamp base 16 downward by the clamp base moving means. When attaching the electrode 11 to the plate-like workpiece W and the auxiliary heating plate P1, the clamp member 15 is moved downward, and the plate-like workpiece W and the auxiliary heating plate P1 are sandwiched and attached by the electrode 11 and the clamp member 15. Can do. Thereby, the electrode 11 can be reliably attached to the plate-like workpiece W and the auxiliary heating plate P1 by a relatively simple method.

  In addition, the electric heating device 1 includes first and second positioning members 21 and 22 for holding the plate-like workpiece W at a predetermined position. The first positioning member 21 is formed in a substantially rectangular parallelepiped shape, and is disposed outside the pair of electrodes 11. As shown in FIG. 2A, the other electrode 11 is disposed in each of the pair of electrodes 11. It is coupled to the surface on the opposite side of the electrode 11 so as to protrude upward from the electrode 11.

  As a result, the first positioning member 21 is engaged with the positioning member 21 at a part of the peripheral edge of the plate-like workpiece W, specifically, the parallel opposite side Wa of the plate-like workpiece W, so The plate-like workpiece W can be held at a predetermined position in a direction orthogonal to the length direction of the electrode 11.

  The first positioning member 21 also engages the positioning member 21 with a part of the peripheral edge of the heating auxiliary plate P1 that is superimposed on the plate-like workpiece W, specifically, the parallel opposite side P1a of the heating auxiliary plate P1. Thus, the heating auxiliary plate material P1 can be held at a predetermined position in a direction orthogonal to the length direction of the electrode 11 in plan view.

  On the other hand, the second positioning member 22 is formed in a substantially rectangular parallelepiped shape and is disposed inside the pair of electrodes 11. As shown in FIG. 1, the second positioning member 22 extends in a direction perpendicular to the length direction of the electrode 11 in a plan view between the opposed end portions of the pair of electrodes 11. As shown by the dotted line, it protrudes above the electrode 11.

  As a result, the second positioning member 22 engages with the positioning member 22 at a part of the peripheral edge of the plate-like workpiece W, specifically, one side Wb perpendicular to the parallel opposite side Wa of the plate-like workpiece W. By combining, the plate-like workpiece W can be held at a predetermined position in the length direction of the electrode 11.

  The second positioning member 22 also has a part of the peripheral edge of the heating auxiliary plate P1 to be superimposed on the plate-like workpiece W, specifically, one side P1b perpendicular to the parallel opposite side P1a of the heating auxiliary plate P1. By engaging with the positioning member 22, the auxiliary heating plate P <b> 1 can be held at a predetermined position in the length direction of the electrode 11.

  The electric heating apparatus 1 is also provided with a control unit (not shown) that comprehensively controls the configuration related to the electric heating apparatus 1, and the control unit operates the energizing means 10, the clamp base moving means, and the like. Can be controlled. The control unit is preferably configured with a microcomputer as a main part.

  In the energization heating device 1 configured as described above, the plate-like workpiece W and the heating auxiliary plate material P1 are overlapped with each other with the positioning members 21 and 22 in a predetermined position while the clamp members 15 are moved upward. The clamp member 15 is moved downward with respect to the plate-like workpiece W and the heating auxiliary plate material P1, and the plate-like workpiece W and the heating auxiliary plate material P1 are held in close contact with each other by the electrode 11 and the clamp member 15. Then, the pair of electrodes 11 is attached to the plate-like workpiece W and the heating auxiliary plate material P1, and then the plate-like workpiece W and the heating auxiliary plate material P1 are heated by energizing the electrodes 11 between them.

  In the present invention, as shown in FIG. 7, the plate-like workpiece W is heated by the current heating device 1 using the press molding device 31 incorporating the current heating device 1, and then heated by using the molding die 30. The formed plate-like workpiece W may be press-molded to perform hot press molding. In this case, the press molding cycle time can be shortened.

  The press molding apparatus 31 shown in FIG. 7 includes a molding die 30 having a punch 40 having a projecting portion 41 projecting downward and a die 50 having a recess 51 formed in a concave shape corresponding to the projecting portion 41. The plate-like workpiece W can be formed in a predetermined shape by combining the protrusion 41 and the recess 51.

  The punch 40 is attached to a punch plate 44 via a spring 42 and a spring guide 43, and the punch plate 44 is attached to a punch holder 45. The punch holder 45 is connected to a punch moving mechanism (not shown), and the punch 40 is moved in the vertical direction by the punch moving mechanism, so that the punch 40 can be moved in the vertical direction. On the other hand, the die 50 is fixed to the die holder 52.

  The press molding apparatus 31 is also provided with the energization heating apparatus 1 having the above-described energization means 10, and the die 50 is provided with a pair of electrodes 11 on both sides of the recess 51 with the recess 51 of the die 50 interposed therebetween. . The pair of electrodes 11 is provided so as to protrude from the upper surface of the die 50, and is connected to the power source 12 by the cable 13. A clamp member 15 is attached above the pair of electrodes 11.

  In the press molding apparatus 31, the plate-like workpiece W and the heating auxiliary plate P <b> 1 that are superposed on each other as described above are sandwiched between the electrode 11 and the clamp member 15 while the punch 40 is moved upward. After the pair of electrodes 11 is attached to W and the heating auxiliary plate material P1, the plate-like workpiece W is heated by energizing between the electrodes 11.

  After the plate-like workpiece W is heated in this way, the clamp member 15 is moved upward, the heating auxiliary plate P1 is removed from the press molding apparatus 31 using a conveying means (not shown), and then the punch 40 is moved downward. The heated plate-shaped workpiece W is press-molded using the molding die 30, and the plate-shaped workpiece W is hot press-molded.

  The hot press forming is not limited to press-molding a plate-shaped workpiece by heating to a temperature higher than the quenching temperature, and includes hot-press molding that is performed by heating the plate-shaped workpiece to a temperature lower than the quenching temperature.

[Heating auxiliary plate]
The configuration of the auxiliary heating plate P1 will be described in detail with reference to FIG.

  The auxiliary heating plate P1 has a heating adjustment unit H (H1, H2, H3) for adjusting the heating temperature of the plate-like workpiece W at a predetermined position in the energization direction. In the present embodiment, a plurality of heating adjustment portions H are provided at intervals in the energization direction.

  Specifically, the heating temperature of the plate-like workpiece W is adjusted to be relatively low, and the heating temperature of the plate-like workpiece W is set to be higher than that of the first heating adjustment portion H1. A second heating adjustment unit H2 for adjusting the temperature to be high, and a third heating adjustment unit for adjusting the heating temperature of the plate-like workpiece W to be higher than that of the second heating adjustment unit H2. H3 is provided. More specifically, two first heating adjustment units H1, two second heating adjustment units H2, and two third heating adjustment units H3 are provided in order from the upstream side in the energization direction.

  As described above, since the auxiliary heating plate P1 includes the plurality of heating adjustment portions H, the plate-like workpiece W can be obtained by a simple configuration in which the heating auxiliary plate P1 is stacked on the plate-like workpiece W and heated by electricity as described above. The heating temperature is adjusted at each portion where the heating adjustment portions H are overlapped, so that the plate-like workpiece W can be heated with a desired temperature distribution. Further, this effect is not limited to the case where the plate-like workpiece W is rectangular, but can be obtained in the same manner when a plate-like workpiece having a shape other than the rectangle is energized and heated.

  In the present embodiment, three types of heating adjustment units H1, H2, and H3 are provided on the auxiliary heating plate P1, but the types of the heating adjustment units H may be the same, or two or four types. There may be more than one type. Further, in the present embodiment, two heating adjustment units H1, H2, and H3 are provided for each type in the energization direction, but only one location or three or more locations may be provided for each type. Furthermore, in this embodiment, although the heating adjustment part H is provided in six places in an electricity supply direction, in this invention, the setting number of the heat adjustment part H is not specifically limited, For example, 1 of an electricity supply direction is set. You may make it provide the heating adjustment part H only in a location.

  Then, the specific structure of the heating adjustment part H which concerns on this embodiment is demonstrated. In the description of the specific configuration of the heating adjustment unit H, the cross-sectional area of the plate-like workpiece W is S1 and the electric resistance of the plate-like workpiece W in each cross section orthogonal to the energizing direction of the plate-like workpiece W and the heating auxiliary plate material P1. The rate is ρ1, the cross-sectional area of the auxiliary heating plate P1 is S2, the electric resistivity of the auxiliary heating plate P1 is ρ2, the resistance of the plate-like workpiece W in the minute range ΔL in the energizing direction, the resistance of the auxiliary heating plate P1, and the plate-like workpiece The combined resistance of W and the heating auxiliary plate material P1 will be described as R1, R2, and R, respectively.

  In the present embodiment, holes 61, 62, 63 are provided in each heating adjustment portion H. More specifically, in each heating adjustment portion H, for example, two holes 61, 62, 63 are provided at intervals in a direction orthogonal to the energization direction in plan view. However, the number of the holes 61, 62, 63 in each heating adjustment section H is not necessarily two, but may be one or three or more.

  Thereby, in each heating adjustment part H, it adjusts so that cross-sectional area S2 of the cross section orthogonal to an electricity supply direction may decrease. Accordingly, in the state where the heating auxiliary plate material P1 is superimposed on the plate-like workpiece W as described above, the cross-sectional area S1 of the plate-like workpiece W and the reciprocal of the electrical resistivity ρ1 are obtained in each section provided with the heating adjustment unit H. And the sum (S1 / ρ1 + S2 / ρ2) of the product (S1 / ρ1) and the product (S2 / ρ2) of the cross-sectional area S2 of the auxiliary heating plate P1 and the reciprocal of the electrical resistivity ρ2 are adjusted. .

  Here, when energization heating is performed in a state where the plate-like workpiece W and the heating auxiliary plate P1 are overlapped with each other as described above, the resistance R1 (= ρ1 / 1 /) of the plate-like workpiece W in the minute range ΔL in the energization direction. It can be considered that S1) and the resistance R2 (= ρ2 / S2) of the auxiliary heating plate P1 are connected in parallel. Then, the following equation (1) is established for the combined resistance R of both plate materials W and P1 in the minute range ΔL.

  Therefore, it can be said that the combined resistance R in the minute range ΔL is inversely proportional to the above sum (S1 / ρ1 + S2 / ρ2). Therefore, in each cross section provided with the heating adjustment portion H, the above-mentioned sum (S1 / ρ1 + S2 / ρ2) is decreased by adjusting the cross-sectional area S2 to decrease, and the combined resistance is inversely proportional to the above. R increases. As a result, the heating temperature of the plate-like workpiece W is adjusted to be higher in each cross section where the heating adjustment unit H is provided and in the vicinity thereof. Therefore, the heating temperature of the plate-like workpiece W can be varied depending on the position in the energization direction, and the plate-like workpiece W can be heated with a desired temperature distribution.

  Further, in the present embodiment, the sizes of the holes 61, 62, 63 are different for each heating adjustment portion H, and the cross-sectional area S2 of the heating adjustment portion H is adjusted by the size of the holes 61, 62, 63. ing. Specifically, the sizes of the holes 61, 62, and 63 are adjusted to increase in the order of the first heating adjustment unit H1, the second heating adjustment unit H2, and the third heating adjustment unit H3. Thus, the size of the cross-sectional area S2 decreases in the order of the third heating adjustment unit H3, the second heating adjustment unit H2, and the first heating adjustment unit H1.

  Therefore, as shown by the line L2 in FIG. 6, the product (S2 / ρ2) of the cross-sectional area S2 of the auxiliary heating plate P1 and the reciprocal of the electrical resistivity ρ2 is the position of each hole 61, 62, 63 in the energization direction. The position of the holes 61, 62, 63 is greatly reduced as the size of the holes 61, 62, 63 increases. On the other hand, as shown by the line L1, the product (S1 / ρ1) of the cross-sectional area S1 of the plate-like workpiece W and the reciprocal of the electrical resistivity ρ1 is constant regardless of the position in the energization direction. Therefore, as indicated by the line L3, the sum (S1 / ρ1 + S2 / ρ2) of the products of the two plate materials W and P1 is greatly reduced as the positions of the hole portions 61, 62, and 63 are larger in the energizing direction. As a result, the position where the above sum (S1 / ρ1 + S2 / ρ2) greatly decreases, specifically, the position of the third heating adjustment unit H3, the position of the second heating adjustment unit H2 in the energization direction, the first The heating temperature of the plate-like workpiece W is adjusted so as to increase in the order of the position of the heating adjustment unit H1.

  However, since the heating temperature of the plate-like workpiece W is made uniform to some extent by heat conduction, the adjustment of the heating temperature of the plate-like workpiece W is realized over a certain range in the energizing direction. For example, in the case of the present embodiment, as indicated by reference numeral G1 in FIG. 1, the two first heating adjustment parts H1 allow the plate-like workpiece W to be formed in a range of the four hole parts 61 and its peripheral part in a plan view. The heating temperature is adjusted. Similarly, as indicated by reference numeral G2 in FIG. 1, the two second heating adjustment parts H2 adjust the heating temperature of the plate-like workpiece W in the range of the four hole parts 62 and its peripheral part in plan view. The two third heating adjustment parts H3 adjust the heating temperature of the plate-like workpiece W in the range of the four hole parts 63 and its peripheral part in plan view. Therefore, the plate-like workpiece W is heated with a temperature distribution that becomes high in the order of the range of the reference G3, the range of the reference G2, and the range of the reference G1.

  In this embodiment, each hole 61, 62, 63 in each heating adjustment part H is circular. Further, as shown in FIG. 4, each hole 61, 62, 63 is provided through the heating auxiliary plate P <b> 1, and both edges C <b> 1, C <b> 2 in the depth direction of each hole 61, 62, 63 are chamfered. It has a rounded shape. FIG. 4 shows the hole 62 of the second heating adjustment part H2, but the holes 61 and 63 of the first and third heating adjustment parts H1 and H3 have the same cross-sectional shape. Thus, since each hole 61, 62, 63 has a shape with no corners on either the peripheral edge in the plan view or the edge in the depth direction, concentration of heat generation during energization is suppressed in these portions. This can prevent damage to the auxiliary heating plate P1 due to local excessive heating.

  In the present embodiment, the holes 61, 62, and 63 are circular. However, the shape of the hole for reducing the cross-sectional area S2 in the heating adjustment unit H is not limited to this. For example, As shown in FIG. 5, a substantially rectangular slot 160 that is long in the energizing direction may be provided in the heating adjustment unit H. In this case, the cross-sectional area S2 of the auxiliary heating plate P1 can be made substantially constant in the length range of the long hole 160 in the energization direction. In this case, the corner portions C3, C4, C5, and C6 of the elongated hole 160 in a plan view are preferably rounded by chamfering, so that the corner portions C3, C4, C5, and C6 In addition, local excessive heating during energization can be prevented. Further, in this case, the edge in the depth direction of the long hole 160 is preferably rounded by chamfering like the hole 62 shown in FIG. Local excessive heating during energization can be prevented.

  In the above, although the structure using the heating auxiliary plate material P1 having the heating adjustment portion H that reduces the cross-sectional area S2 by providing the hole portion has been described, the present invention includes the heating auxiliary plate material according to various modified examples. Can be used.

[First Modification]
FIG. 8 is a side view showing the auxiliary heating plate P2 according to the first modification. As shown in FIG. 8, the auxiliary heating plate P2 has a non-uniform thickness. Specifically, the heating auxiliary plate P2 is formed so that the thickness varies depending on the position in the energization direction. As a method for producing the heating auxiliary plate P2 so as to change the plate thickness in this way, for example, a casting is used as the heating auxiliary plate P2, or the heating auxiliary plate P2 is formed by a tailor rolled foam or a tailored blank. It is possible to do.

  As a result, a plurality of heating adjustment portions H (H11, H12, H13) having different thicknesses are formed on the heating auxiliary plate material P2, and each heating adjustment portion H is provided on the heating auxiliary plate material P2 in the heating adjustment portion H. The cross-sectional area S2 is adjusted by the thickness. Therefore, even if the auxiliary heating plate P2 shown in FIG. 8 is used, the heating temperature of the plate-like workpiece W is adjusted to be higher as the thickness of the heating adjustment portion H is smaller at the position of the heating adjustment portion H in the energization direction. It is possible to obtain a desired temperature distribution.

  Further, the auxiliary heating plate P2 shown in FIG. 8 is configured such that one surface is formed flat and the thickness of the heating adjustment portion H is adjusted by the unevenness of the other surface. When the plate-like workpiece W and the heating auxiliary plate material P2 are overlapped with each other in the electric heating device 1, the flat surface of the heating auxiliary plate material P2 is overlapped with the plate-like workpiece W. Thereby, the clearance gap between the plate-shaped workpiece W at the time of electricity supply and the heating auxiliary plate material P2 can be excluded as much as possible, and the heating temperature of the plate-shaped workpiece W can be adjusted with high accuracy.

[Second Modification]
FIG. 9 is a plan view showing a state where the auxiliary heating plate P <b> 3 according to the second modification is set in the energization heating device 1. As shown in FIG. 9, the auxiliary heating plate P3 includes two first heating adjustment units H21, two second heating adjustment units H22, and two third heating adjustment units in order from the upstream side in the energization direction. H23 and slits 161, 162, 163, 164, 165, and 166 for reducing the cross-sectional area S2 in each of the heating adjustment portions H (H21, H22, and H23) are orthogonal to the energization direction in plan view. It is extended to. Even when the auxiliary heating plate P3 shown in FIG. 9 is used, the heating temperature of the plate-like workpiece W can be adjusted to increase at the position of the heating adjustment portion H in the energizing direction, and a desired temperature distribution can be obtained. Is possible.

  Each of the slits 161 to 166 is provided so as to penetrate the auxiliary heating plate P3 in the thickness direction. Like the circular holes 61, 62, 63 described above, the slits 161 to 166 have corners on the peripheral edge in the plan view and the edge in the depth direction. Thus, it is possible to prevent damage to the auxiliary heating plate P3 due to local excessive heating during energization.

  The slits 161 to 166 adjacent to each other in the energization direction are formed on opposite sides in a direction orthogonal to the energization direction in plan view, and the slits 161 to 166 are arranged in a staggered manner as a whole.

  In the example shown in FIG. 9, the slits 161 to 166 all have substantially the same width in the short direction, but are formed to have different lengths. Specifically, the lengths of the slits 161 to 166 are longer in the order of the first heating adjustment unit H21, the third heating adjustment unit H23, and the second heating adjustment unit H22, whereby the cross-sectional area S2 Is smaller in the order of the first heating adjustment unit H21, the third heating adjustment unit H23, and the second heating adjustment unit H22. Therefore, the heating temperature of the plate-like workpiece W is increased in the order of the position of the first heating adjustment unit H21, the position of the third heating adjustment unit H23, and the position of the second heating adjustment unit H22 in the energization direction. Adjusted. As a result, the plate-like workpiece W is heated in such a temperature distribution that the temperature becomes higher in the order of the range of G4, the range of G6, and the range of G5.

  The pitch of the slits 161 to 166 in the energization direction increases in the order of the first heating adjustment unit H21, the third heating adjustment unit H23, and the second heating adjustment unit H22 according to the length of the slits 161 to 166. Thus, a sufficient space is secured between the tip portions of the adjacent slits 161 to 166 to prevent local excessive heat generation, and fusing due to excessive heat generation can be prevented.

[Third Modification]
In the heating auxiliary plate materials P1, P2, and P3 described above, the cross-sectional area S2 is adjusted in the heating adjustment unit H. In the present invention, in the heating adjustment unit H, at least one of the cross-sectional area S2 or the electrical resistivity ρ2 is It only needs to be adjusted.

  Therefore, with reference to FIG. 10, a heating auxiliary plate P4 according to a third modification having the heating adjustment unit H in which the electrical resistivity ρ2 is adjusted will be described.

  In the heating auxiliary plate P4 shown in FIG. 10, the first heating adjustment unit H31 and the second heating adjustment unit H32 are provided at intervals in the energization direction. In each heating adjustment unit H (H31, H32), electric Plated portions F1 and F2 for increasing the resistivity ρ2 are formed on both surfaces. However, in each heating adjustment part H, plating part F1, F2 may be formed only in any one surface. Thus, by forming the plating parts F1 and F2 in the heating adjustment part H, the electrical resistivity ρ2 in the heating adjustment part H is adjusted so as to increase. The heating temperature of W can be adjusted to increase.

  The plating part F1 of the first heating adjustment part H31 has a larger thickness than the plating part F2 of the second heating adjustment part H32. Specifically, for example, the thickness of the plating part F1 is 300 μm, and the thickness of the plating part F2 is 100 μm. Thereby, in the 1st heating adjustment part H31, since it adjusted so that electrical resistivity (rho) 2 may become higher than the 2nd heating adjustment part H32, the heating temperature of the plate-shaped workpiece | work W is the 1st in the electricity supply direction. It adjusts so that it may become high temperature rather than the position of the 2nd heating adjustment part H32 in the position of the 1st heating adjustment part H31. Therefore, even if the auxiliary heating plate P4 shown in FIG. 10 is used, the plate-like workpiece W can be heated with a desired temperature distribution.

[Second Embodiment]

  11 and 12 are schematic views of an electric heating device 201 according to the second embodiment of the present invention. In FIG. 12, the positioning member 22 is indicated by a two-dot chain line, which is shown in a transparent state.

  Compared with the first embodiment, the energization heating device 201 according to the second embodiment is further provided with clamping means for clamping the plate-like workpiece W and the heating auxiliary plate material P1 between the electrodes 11. There are the same components as those in the first embodiment, and the description thereof will be omitted.

  Specifically, the energization heating device 201 is provided with clamping means 85 for clamping the plate-like workpiece W and the heating auxiliary plate material P1 at a substantially central portion between the electrodes 11, and the clamping means 85 includes the plate-like workpiece W and the heating auxiliary. The upper clamp member 91 clamps the plate material P1 from above, and the lower clamp member 95 clamps the plate-like workpiece W and the heating auxiliary plate material P1 from below.

  The upper clamp 91 is configured in the same manner as the clamp member 15 according to the first embodiment, and includes a substantially rectangular parallelepiped clamp base 92 extending substantially parallel to the length direction of the electrode 11, a stacked plate-like workpiece W, and A pin portion 93 having a tip portion that contacts the auxiliary heating plate P1, a clamp base 92, and a spring 94 coupled to the pin portion 93, the clamp base 92 being connected to an upper clamp moving means (not shown) As shown by the arrow Z2, it is configured to be movable in the vertical direction.

  On the other hand, the lower clamp 95 is a vertically inverted version of the upper clamp 91, a substantially rectangular parallelepiped clamp base 96 extending substantially parallel to the length direction of the electrode 11, the stacked plate-like workpiece W and heating assist. A pin portion 97 having a tip portion that comes into contact with the plate material P1, a clamp base portion 96, and a spring 98 coupled to the pin portion 97 are provided. The clamp base portion 96 is connected to a lower clamp moving means (not shown) and As shown by Z3, it is configured to be movable in the vertical direction.

  In the clamp means 85, the clamp base 91 is moved downward by the upper clamp moving means to move the upper clamp member 91 downward, and the clamp base 96 is moved upward by the lower clamp moving means. The lower clamp member 95 is moved upward. Thereby, the clamp means 85 can clamp the plate-like workpiece W and the heating auxiliary plate material P1 arranged on the electrodes 11 at the substantially central portion between the electrodes 11 by the upper clamp member 91 and the lower clamp member 95. It is like that.

  In the energization heating device 81, one clamping means 85 for clamping the plate-like workpiece W and the heating auxiliary plate material P1 is provided between the electrodes 11, and the plate-like workpiece W and the heating auxiliary plate material P1 are provided at one place between the electrodes 11. Although configured to clamp, a plurality of clamping means may be provided to clamp the plate-like workpiece W and the heating auxiliary plate material P1 at a plurality of locations between the electrodes 11.

[Third Embodiment]

  Next, an energization heating device 301 according to the third embodiment will be described with reference to FIG. Note that in the third embodiment, identical symbols are assigned to configurations similar to those in the first embodiment and descriptions thereof are omitted.

  In the energization heating device 301, the plate-like workpiece W and the heating auxiliary plate material P1 are overlapped between the plate-like workpiece W and the heating auxiliary plate material P1 in the attachment portion of the electrode 11 in a state where the plate-like workpiece W and the heating auxiliary plate material P1 are overlapped. A welding prevention plate material 14 having an electrical resistivity smaller than that of the auxiliary heating plate material P1 is interposed.

  In FIG. 14, the thickness of the welding prevention plate member 14 is greatly exaggerated, but the actual thickness of the welding prevention plate member 14 is extremely thin, and the plate-like workpiece W and the heating auxiliary plate member P <b> 1 are separated when energized. The thickness is small enough to allow contact with each other by Lorentz force and thermal expansion at a portion where the welding prevention plate member 14 is not interposed.

  As described above, in the third embodiment, the use of the welding prevention plate material 14 enables the materials and energization amounts of the plate-like workpiece W and the heating auxiliary plate material P1, the pressing force when the plate materials W and P1 are overlapped, or the like. Regardless of this, it is possible to prevent the plate-like workpiece W and the heating auxiliary plate material P1 from being excessively locally heated and welded to each other at the attachment portion of the electrode 11. Therefore, the problem that separation of the plate-like workpiece W and the auxiliary heating plate P1 becomes difficult, or when a trace remains in the welded portion of the plate-like workpiece W, the trace portion cannot be used as a product is avoided. Can do.

[Experiment]
Using the electric heating apparatus 1 according to the first embodiment, an example in which the heating auxiliary plate material P1 is superposed on the plate-like workpiece W to perform the electric heating, and the heating heating without superimposing the heating auxiliary plate material on the plate-like workpiece W is performed. An experiment for measuring the heating temperature of the plate-like workpiece W was performed for each of the comparative examples.

  FIG. 14 is an explanatory diagram for explaining the temperature measurement conditions of the example, and FIG. 15 is an explanatory diagram for explaining the temperature measurement conditions of the comparative example.

  In Examples and Comparative Examples, a cold rolled high-tensile steel plate SPFC440 having a thickness of 1.6 mm was used as the plate-like workpiece W and the heating auxiliary plate P1, and the length was 280 mm, as shown in FIGS. A rectangular shape having a width of 88 mm was prepared. Further, holes 61, 62, 63 are formed in each position shown in FIG. 14 in the auxiliary heating plate P1, and the diameter of the hole 61 of the first heating adjustment part H1 is 3.4 mm, so that the second heating adjustment is performed. The diameter of the hole 62 of the part H2 was 8 mm, and the diameter of the hole 63 of the third heating adjustment part H3 was 12 mm.

  In the example, as described in the first embodiment, the plate-like workpiece W and the heating auxiliary plate material P1 are set in the energization heating device 1, the current between the electrodes 11 is energized, and the plate-like workpiece W is heated. The energization was carried out for 10 seconds using a direct current power source and setting the current value to 4.2 kA. And immediately after heating the plate-like workpiece W for 10 seconds by energization heating, temperature measurement was performed at each measurement position of the plate-like workpiece W using a thermocouple. Specifically, as shown in FIG. 14A and FIG. 14B, the measurement was performed at each position indicated by T1 to T3 on the lower surface of the plate-like workpiece W. Simultaneously with the temperature measurement by the thermocouple, the temperature distribution of the plate-like workpiece W was confirmed using infrared thermography.

  On the other hand, in the comparative example, only the plate-like workpiece W was set in the energization heating device 1, the current between the electrodes 11 was energized, and the heating temperature of the plate-like workpiece W was measured. Except that the heating auxiliary plate material P1 is not overlapped on the plate-like workpiece W, energization heating was performed in the same manner as in the example, and the heating temperature of the plate-like workpiece W was measured. The energization heating conditions are the same as in the example. Immediately after the plate-like workpiece W is heated by energization heating for 10 seconds, as shown in FIGS. 15 (a) and 15 (b), T4˜ Measurement was performed at each position indicated by T6.

  The temperature measurement results of the plate-like workpiece W heated in the example are shown in Table 1 below, and the temperature measurement results of the plate-like workpiece W heated in the comparative example are shown in Table 2 below.

  As shown in Table 1, in the example, the plate-like workpiece W had a high heating temperature in the order of the measurement positions T3, T2, and T1. In addition, due to infrared thermography, the plate-like workpiece W has a substantially uniform temperature in each of the regions G1, G2, and G3 in FIG. 14, and heat is increased in the order of the region G3, the region G2, and the region G1. It was confirmed that the temperature was reached.

  On the other hand, as shown in Table 2, in the comparative example, the plate-like workpiece W had substantially the same heating temperature at the measurement positions T4, T5, and T6.

  From these results, the heating temperature of the plate-like workpiece W in the comparative example has a substantially uniform temperature distribution as shown by a line L11 in FIG. 16, whereas the heating temperature of the plate-like workpiece W in the example is It was confirmed that the temperature was appropriately adjusted by the heating adjustment unit H for each region in the energization direction as indicated by a line L12 shown in FIG. Therefore, according to said 1st Embodiment, it turns out that the plate-shaped workpiece | work W can be heated so that it may become a desired temperature distribution by energization heating.

  While the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments.

  For example, although the case where the heating auxiliary plate material P1 is used has been described in the second and third embodiments, the heating auxiliary plate material according to various modifications other than the heating auxiliary plate material P1 may be used in these embodiments. Good.

  As described above, according to the present invention, when a heated plate is heated by energization heating, it is possible to heat the plate to have a predetermined temperature distribution with a simple configuration regardless of the shape of the plate. There is a possibility of being suitably used in the manufacturing industry of vehicle body components such as pillars and impact bars.

1, 201, 301 Electric heating device 11, 11a, 11b Electrode 15, 91, 95 Clamp member 21, 22 Positioning member 30 Mold 31 Press molding device 61, 62, 63 Hole 85 Clamp means 161-166 Slit W Plate Workpiece (heated plate material)
P1, P2, P3, P4 Heating auxiliary plate

Claims (11)

An energization heating method of heating the heated plate material by attaching a pair of electrodes to a conductive heated plate material having a predetermined electrical resistance apart from each other and energizing,
Superposing the heated plate material and a conductive auxiliary heating plate material having a predetermined electrical resistivity;
A step of attaching a pair of electrodes to the heated plate material and the heating auxiliary plate material with the heated plate material and the auxiliary heating plate material being stacked,
Energizing between the electrodes, and
In each cross section orthogonal to the energization direction of the heated plate material and the heating auxiliary plate material, the sectional area of the heated plate material is S1, the electrical resistivity of the heated plate material is ρ1, and the sectional area of the heating auxiliary plate material is S2. When the electrical resistivity of the heating auxiliary plate material is ρ2,
As the heating auxiliary plate material,
In a state where the heated plate material and the heating auxiliary plate material are overlapped, the product (S1 / ρ1) of the cross-sectional area (S1) of the heated plate material and the reciprocal of the electrical resistivity (ρ1), and the heating auxiliary plate material So that the sum (S1 / ρ1 + S2 / ρ2) of the product (S2 / ρ2) of the cross-sectional area (S2) and the reciprocal of the electrical resistivity (ρ2) differs depending on the cross-section (S2) or the electrical resistivity ( An energization heating method using a heating auxiliary plate having a heating adjustment part in which at least one of ρ2) is adjusted.   The energization heating method according to claim 1, wherein a hole for reducing the cross-sectional area (S2) is provided in the heating adjustment unit.   The said heating adjustment part has two or more said hole parts, and is comprised so that a cross-sectional area (S2) may be adjusted with the magnitude | size of this hole part, The electric heating of Claim 2 characterized by the above-mentioned. Method.   The energization heating method according to claim 2, wherein the hole has a shape with no corners in a peripheral edge in a plan view and an edge in a depth direction. The heating auxiliary plate has a non-uniform thickness,
2. The energization heating method according to claim 1, wherein the heating adjustment unit is configured to adjust a cross-sectional area (S <b> 2) according to a thickness of the auxiliary heating plate in the heating adjustment unit. One surface of the heating auxiliary plate is formed flat, and is configured such that the thickness of the heating adjustment portion is adjusted by the unevenness of the other surface,
6. The energization heating method according to claim 5, wherein in the step of superimposing the heated plate material and the auxiliary heating plate material, a flat surface of the auxiliary heating plate material is superimposed on the heated plate material.   2. The energization heating method according to claim 1, wherein a slit for reducing the cross-sectional area (S <b> 2) is extended in the heating adjustment portion in a direction orthogonal to the energization direction in a plan view.   The current heating method according to claim 7, wherein the slit has a shape with no corners in a peripheral edge in a plan view and an edge in a depth direction.   2. The energization heating method according to claim 1, wherein a plating portion for increasing an electrical resistivity (ρ2) is formed on at least one surface of the auxiliary heating plate in the heating adjustment portion.   In the step of superimposing the heated plate material and the auxiliary heating plate material, an electric power smaller than that of the heated plate material and the auxiliary heating plate material is provided between the heated plate material and the auxiliary heating plate material in an attachment portion of the electrode. The energization heating method according to any one of claims 1 to 9, wherein the plate material to be heated and the heating auxiliary plate material are overlapped with each other with a welding prevention plate material having a resistivity interposed therebetween.   The hot plate material is heated by the electric heating method according to any one of claims 1 to 10, and the heated plate material is press-molded using a forming die. Press molding method.

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