JP7116009B2 - Press molding method - Google Patents

Description

The present invention relates to a press molding method. In particular, the present invention relates to improvement of a press forming method including a step of heating a high-strength steel plate as a work.

2. Description of the Related Art Conventionally, in the production of automobile bodies, a metal plate (for example, a high-strength steel plate) forming the body is formed into a predetermined shape by press working. Moreover, in this type of press working, as disclosed in Patent Document 1, a metal plate is also heated. In this patent document 1, a hot press forming method for obtaining a quenched press-formed product by performing press working with a mold while the entire metal plate is heated and cooling the metal plate while the mold is clamped. is disclosed.

JP 2005-205416 A

However, in Patent Document 1, since press working is performed using a forming die while the metal plate is heated, it is necessary to have a configuration in which a heating device such as a furnace is directly connected to or built into the press working device. (Press equipment) manufacturing costs will rise. In addition, since the entire metal plate is heated, there is concern that the tempering of the entire metal plate may reduce the strength of the entire press-formed product.

The present invention has been made in view of this point, and an object of the present invention is to provide a press forming method including a step of heating a high-strength steel sheet, which can suppress the increase in the manufacturing cost of the press working apparatus, and Another object of the present invention is to provide a press-molding method capable of suppressing a decrease in the strength of the entire press-molded product.

A solution of the present invention for achieving the above object is a press forming method in which a pressing portion of a press working device is pressed against a high-strength steel plate so as to press the high-strength steel plate along the shape of the pressing portion. is assumed. The pressing portion has a central portion that first comes into contact with the high-strength steel plate in the press working, a shoulder that is an end of the central portion, and a vertical wall that extends continuously from the shoulder. ing. Then, this press forming method includes a partial heating step of heating only at least a part of an outer region located outside a contact portion where the central portion and the shoulder portion of the pressing portion contact each other in the high-strength steel plate; After the partial heating step, the cooling air blown from the cooling air nozzle is relatively moved along the extending direction of the heated region, and is passed through the movement trajectory a plurality of times. A cooling step of cooling and tempering the heated region by blowing the cooling air to the region a plurality of times, and after the cooling step, the high-strength steel plate is placed in the press working device. a pressing step of setting and pressing the high-strength steel plate by the pressing portion, and forming the high-strength steel plate along the shapes of the central portion, the shoulder portion, and the vertical wall portion of the pressing portion; It is characterized by having

According to this specific matter, in the press forming of the high-strength steel sheet, first, at least one of the outer regions located outside the contact portion where the central portion and the shoulder portion of the pressing portion of the press working device contact in the high-strength steel plate Only the part is heated (partial heating step). This results in partial material softening in high-strength steel sheets. After that, the cooling air blown out from the cooling air nozzle is relatively moved along the extending direction of the heated area, and is caused to pass through the moving trajectory a plurality of times. The heated region is cooled and tempered by blowing cooling air a plurality of times (cooling step). This improves the ductility of the material in addition to localized material softening. After such processing is performed, the high-strength steel plate is set in a press working device, and a press working step is performed in which the high-strength steel plate is pressed by a pressing portion. As described above, the partial heating process and the cooling process are performed to soften the material and improve the ductility of the material. It will be molded into a predetermined shape along the shape of 1 with high precision, and the occurrence of cracks and wrinkles will be suppressed. In addition, since only a portion of the high-strength steel sheet is heated in the partial heating process, the strength of the entire press-formed product can be increased compared to heating the entire high-strength steel sheet. In addition, since the partial heating process and the cooling process are performed before the press working process, there is no need to directly connect or incorporate a device for heating or cooling the high-strength steel sheet to the press working equipment. It is possible to suppress an increase in the manufacturing cost of the press working device.
In addition, the outer edge shape of the high-strength steel plate includes a first edge extending in one direction, a second edge extending in a direction orthogonal to the extending direction of the first edge, and the first edge A third edge curved with a predetermined curvature from one end in the extending direction of the second edge to one end in the extending direction of the second edge, the second edge from the other end in the extending direction of the first edge It is composed of a fourth edge curved with a predetermined curvature over the other end in the extending direction, and in the pressing step, the third edge has a predetermined dimension from the third edge A range to an inner line, a first range along the extending direction of the third edge, and a range from the fourth edge to an inner line having a predetermined dimension with respect to the fourth edge Each of the second ranges along the extending direction of the fourth edge portion is bent, and the shoulder portion of the pressing portion is formed in a circular shape along each of the inner lines. arc-shaped,
In the partial heating step, at least a partial area of the first range and an arc-shaped area along the extending direction of the third edge and at least a partial area of the second range and only the arc-shaped region along the extending direction of the fourth edge portion is heated.

In the present invention, the outer region located outside the contact portion where the central portion and the shoulder portion of the pressing portion of the high-strength steel plate are in contact in the pre-step of the pressing step of pressing the high-strength steel plate with the pressing portion of the pressing device. and a cooling step of cooling and tempering the heated region. Therefore, the strength of the entire press-formed product can be increased as compared with a method in which the entire high-strength steel plate is heated. In addition, there is no need to directly connect or incorporate a device for heating or cooling the high-strength steel sheet to the press working device, and it is possible to suppress an increase in the manufacturing cost of the press working device.

It is a figure for demonstrating each process of the press molding which concerns on 1st Embodiment. FIG. 4 is a diagram for explaining heating regions of the high-strength steel sheet in the partial heating process of the first embodiment; It is a cross-sectional view taken along line III-III in FIG. 1(d). It is a figure which shows the modification of a press processing apparatus. It is a figure for demonstrating the press molding which concerns on 2nd Embodiment. FIG. 5B is a cross-sectional view taken along the line VI-VI in FIG. 5B; It is a perspective view which shows the punch of the press working apparatus used by 2nd Embodiment. It is a figure for demonstrating the pressing process in 2nd Embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case will be described where the present invention is applied as a press forming method for forming a high-strength steel plate that constitutes a vehicle body into a predetermined shape by press working in the production of a vehicle body.

<First Embodiment>
-Each process of press molding-
FIG. 1 is a diagram for explaining each step of press molding according to the present embodiment. In this press-forming, a substantially circular high-strength steel plate 1 shown in FIG. 2 is molded. The high-strength steel sheet 1 is, for example, a high-strength steel sheet having a tensile strength of 980 MPa or more.

The steps for molding this press-formed product 2 include a partial heating step (see FIG. 1(a)), a cooling step (see FIG. 1(b)), and a pressing step (see FIG. 1(c). ) are performed in sequence.

Each step will be described below.

(Partial heating process)
The partial heating step is a step of heating only the outer peripheral portion 11 of the high-strength steel plate 1 . Specifically, only the outer region (the outer peripheral portion) 11 located outside the contact portion where the central portion 31b and the shoulder portion 31a, which are the upper surfaces of the punch (pressing portion) 31 of the press working device 3 to be described later, is in contact. heat up.

In this embodiment, as described above, the punch 31 has a substantially columnar shape in order to mold the press-formed product 2 having a substantially cylindrical shape with a bottom. The circular upper surface of the punch 31 corresponds to the central portion 31b, and the end (outer edge) of the central portion 31b corresponds to the shoulder portion 31a. The central portion 31b is the portion that first comes into contact with the high-strength steel plate 1 in the pressing process. A cylindrical portion continuously extending from the shoulder portion 31a serves as a vertical wall portion 31c. Therefore, the contact portion of the high-strength steel plate 1 is the center portion of the high-strength steel plate 1 and has a circular shape with which the center portion 31b and the shoulder portion 31a of the punch 31 come into contact.

FIG. 2 is a diagram for explaining the heating region (outer region) 11 of the high-strength steel sheet 1 in the partial heating process of this embodiment. A circle indicated by a dashed line in FIG. 2 is a portion with which the shoulder portion 31a of the punch 31 contacts. In the partial heating step, an annular region that is slightly on the outer peripheral side of the contact portion (the portion where the central portion 31b and the shoulder portion 31a contact) and extends over the outer edge of the high-strength steel plate 1 is A heating area (dotted area in FIG. 2) is defined as 11, and only this heating area 11 is heated. In other words, the circular region (the region not marked with dots in FIG. 2 ) that is the central portion of the high-strength steel plate 1 is the non-heating region 12 , and the other region is the heating region 11 .

The portion of the punch 31 with which the shoulder portion 31a contacts (the circular portion indicated by the dashed line) may be aligned with the inner edge of the heating region 11 (the circular portion indicated by the broken line).

A laser irradiation device 4 (see FIG. 1(a)) is provided as an example of device configuration for carrying out this partial heating step. This laser irradiation device 4 is arranged above a base (not shown) on which the high-strength steel plate 1 is placed, and incorporates a laser oscillator. A laser beam generated by this laser oscillator is guided to a laser scanner (not shown) and irradiated toward the high-strength steel plate 1 (see the dashed line in FIG. 1(a)). Since the configurations of the laser oscillator and the laser scanner are well known, their description is omitted here. As the laser beam, for example, a carbon dioxide laser, a YAG laser, a fiber laser, or the like can be used.

More specifically, the outer diameter dimension (dimension D in FIG. 2) of the high-strength steel plate 1 in this embodiment is 100 mm, and the outer diameter dimension of the punch 31 (dimension d1 in FIG. 2; the outer diameter dimension of the contact portion) is 50 mm, and the width dimension of the heating area 11 (dimension d2 in FIG. 2) is 20 mm. These dimensions and dimension ratios are not limited to these, and may be set as appropriate.

Moreover, in this partial heating step, the heating region 11 of the high-strength steel plate 1 is heated to, for example, about 500°C. Therefore, the laser beam irradiated from the laser scanner toward the high-strength steel plate 1 is set at a position where the focal point is deviated from the surface of the high-strength steel plate 1, for example, at a position below the high-strength steel plate 1. It will be. For example, the focus of the laser beam is set so that the irradiation range of the laser beam on the upper surface of the high-strength steel plate 1 coincides with the width dimension d2 of the heating region 11, and in this state, the irradiation position of the laser beam is along the heating region. The laser beam is scanned so as to move along a circular trajectory. In addition, a rotating mechanism (a so-called turntable) that rotates the base on which the high-strength steel plate 1 is placed is provided, and the base is rotated while the irradiation position of the laser beam is fixed, whereby the heating region 11 is changed. Heating may be performed in order along the circumferential direction. When the heating region 11 is heated in this way, the laser beam is irradiated several times in the circumferential direction of the heating region 11 so that a temperature difference (temperature gradient) does not occur in the entire heating region 11 . It is preferable to continue (to complete the partial heating step with multiple rotations).

By performing such a partial heating process, the material of the outer peripheral portion (the heating region) 11 of the high-strength steel sheet 1 is softened.

(Cooling process)
The cooling step is a step of cooling and tempering the region (heating region) 11 heated in the partial heating step.

A cooling air nozzle 5 (see FIG. 1(b)) is provided as an apparatus configuration for carrying out this cooling process. The cooling air nozzle 5 cools the heating area 11 of the high-strength steel plate 1 placed on the base by blowing cooling air onto the heating area 11 .

More specifically, the cooling air nozzle 5 is connected to a blower (not shown), and the airflow generated by the operation of this blower is blown toward the heating area 11 in the high-strength steel plate 1 through the cooling air nozzle 5. It will be. Although the air volume and cooling time in this case can be set arbitrarily, they are set through experiments and simulations as values at which tempering is performed by slow cooling. For example, as described above, the heating region 11 heated to about 500° C. is set to cool down to a temperature of less than 200° C. in a period of several tens of seconds. These time and temperature are not limited to these, and are set as appropriate.

Further, since the heating region 11 in the high-strength steel plate 1 is annular, the moving mechanism is arranged so that the outlet of the cooling air nozzle 5 moves along the heating region 11 (moves on a circular trajectory). are provided. In addition, a rotation mechanism is provided to rotate the base on which the high-strength steel plate 1 is placed, and the base is rotated while the outlet of the cooling air nozzle 5 faces the heating area 11, whereby the heating area is heated. 11 may be cooled in order. In this case as well, the cooling air is blown a plurality of times in the circumferential direction of the heating region 11 so that the temperature difference (temperature gradient) in the entire heating region 11 does not increase (a cooling process is performed by a plurality of rotations). completed) is preferred.

By performing such a cooling process, the outer peripheral portion (the heating region) 11 of the high-strength steel sheet 1 is cooled and tempered.

(Pressing process)
In the press working process, the high-strength steel sheet 1 that has undergone the partial heating process and the cooling process described above is moved (set) from the base to the press working device 3, and the high-strength steel plate 1 is formed into a predetermined shape by the press working device 3. It is a process that

As shown in FIG. 1(c), the press working device 3 has a configuration in which a plurality of dies 32, 32, . . . and punches 31, 31, . By clamping the molds with the high-strength steel plate 1 placed between the die 32 and the punch 31, the press-formed product 2 along the shape of the space formed between the die 32 and the punch 31 is formed. will be As a result, the high-strength steel plate 1 is formed along the shapes of the central portion 31b, the shoulder portion 31a, and the vertical wall portion 31c of the punch 31. As shown in FIG. , and punches 31, 31, . Obtainable.

－Press molded product－
FIG. 1(d) shows a press-formed product 2 formed by the press working device 3. As shown in FIG. FIG. 3 is a cross-sectional view taken along line III--III in FIG. 1(d).

The press-formed product 2 includes a disk portion 21 formed between the central portion 31b of the punch 31 and the bottom surface of the die 32, and formed between the vertical wall portion 31c of the punch 31 and the inner peripheral surface of the die 32. and a flange portion 23 formed between the outer edge of the punch 31 (blank holder) and the outer edge of the die 32 .

- Effects of Embodiment -
As described above, in this embodiment, the material of the outer peripheral portion (the heating region) 11 of the high-strength steel plate 1 is softened by the partial heating process. In addition, the heating region is cooled and tempered by the subsequent cooling process. As a result, in the outer peripheral portion 11 of the high-strength steel plate 1, the ductility of the material is improved in addition to the material softening. Since the press working process is performed after such a process is performed, even the high-strength steel plate 1, which is difficult to be press-worked into a complicated shape, is formed into a predetermined shape along the shape of the punch 31 with high accuracy. Also, the occurrence of cracks and wrinkles is suppressed. In particular, in the conventional technology (without the partial heating process and the cooling process), cracks occurred in the cylindrical part of the press-formed product, and wrinkles occurred in the flange part. In the embodiment, the occurrence of these cracks and wrinkles can be suppressed.

In addition, since only a part of the high-strength steel plate 1 is heated in the partial heating step, the strength of the entire press-formed product 2 can be increased compared to a method in which the entire high-strength steel plate 1 is heated.

In addition, a partial heating process and a cooling process are performed in the previous stage of the pressing process, and after these processes, the high-strength steel sheet 1 is set in the press working device 3, so the high-strength steel sheet 1 is heated and cooled. Since there is no need to directly connect or incorporate a device for pressing to the press working device 3, it is possible to suppress an increase in the manufacturing cost of the press working device 3.

Furthermore, in the prior art, in the case where the high-strength steel sheet is entirely heated and press-worked by a press-working device, the die and the punch are in sliding contact with the high-strength steel sheet in a high-temperature environment. The surface of the die and punch could be damaged. On the other hand, in the present embodiment, since the pressing process is performed after the cooling process, the die 32 and the punch 31 are in sliding contact with the high-strength steel sheet 1 while the temperature of the high-strength steel sheet 1 is relatively low. Become. Therefore, the possibility of damage to the surfaces of the die 32 and the punch 31 is reduced, and the life of the press machine 3 can be extended and maintenance costs can be reduced.

<Modified example of press working device>
FIG. 4 is a diagram showing a modification of the press working device 3. As shown in FIG. The press working device 3 shown in FIG. 4 includes a blank holder 33 in addition to a die 32 and a punch 31 . The blank holder 33 clamps the outside of the outer peripheral portion (heating region) 11 of the high-strength steel plate 1 between itself and the die 32 . By clamping the molds with the heating region 11 sandwiched between the blank holder 33 and the die 32 in this manner, the press-formed product 2 described above is formed.

Even when such a press working apparatus 3 is used, the partial heating process and the cooling process are performed in the previous stage of the press working process, so that the outer peripheral portion 11 of the high-strength steel sheet 1 is softened and ductile. will improve. Therefore, even the high-strength steel plate 1, which is difficult to press into a complicated shape, can be formed into a predetermined shape along the shape of the punch 31 with high accuracy, and the occurrence of cracks and wrinkles is suppressed. will be Further, after the partial heating process and the cooling process, the high-strength steel plate 1 is set in the press working device 3, so a device for heating or cooling the high-strength steel plate 1 is directly connected to the press working device 3. Since there is no need to incorporate it, it is possible to suppress an increase in manufacturing cost of the press working device 3 .

<Second embodiment>
Next, a second embodiment will be described. This embodiment differs from the above-described embodiment in the shape of the press-formed product 2 to be molded. FIG. 5 is a diagram for explaining press molding according to this embodiment. In the press forming of this embodiment, a substantially strip-shaped (substantially fan-shaped) high-strength steel plate 1 as shown in FIG. )) is to be molded. FIG. 6 is a cross-sectional view taken along the line VI--VI in FIG. 5(b).

In the present embodiment, the steps for forming the press-formed product 2 are the partial heating step, the cooling step, and the pressing step, which are performed in this order, as in the case of the above-described embodiments.

As the shape of the high-strength steel plate (high-strength steel plate before press working) 1 shown in FIG. a second edge portion 14 extending in a direction to extend, a third edge portion 15 curving with a predetermined curvature from one end of the extending direction of the first edge portion 13 to one end of the extending direction of the second edge portion 14; A fourth edge portion 16 that curves with a predetermined curvature (a larger curvature than the third edge portion 15) from the other end in the extending direction of the first edge portion 13 to the other end in the extending direction of the second edge portion 14 is the outer edge shape. Then, in the press working step, a predetermined width dimension range from the outer edge of the third edge portion 15 and a predetermined width dimension range from the outer edge of the fourth edge portion 16 are bent. That is, by bending a predetermined width from the outer edge of the third edge portion 15, this region is made into a stretch flange. Further, a range of a predetermined width dimension from the outer edge of the fourth edge portion 16 is bent to form a contraction flange.

In this embodiment, in order to form the press-formed product 2 having the shape shown in FIG. 5(b), as shown in FIG. It has a convex shape corresponding to the edges 13-16. The outer edge of the central portion 31b, which is the upper surface of the punch 31, corresponds to the shoulder portions 31a, 31a. Therefore, the contact portion of the high-strength steel plate 1 has a substantially arcuate shape with which the center portion 31b and the shoulder portions 31a, 31a of the punch 31 come into contact.

The circular arc indicated by the dashed line in FIG. 5(a) is the portion with which the shoulder portion 31a of the punch 31 contacts. In the partial heating step, the outer edge of the high-strength steel plate 1 (the third edge 15 and the fourth edge) is a region slightly outside the contact portion where the central portion 31b and the shoulder portions 31a, 31a contact. Circular regions extending over the portion 16) are heating regions (dotted regions in FIG. 5A) 11, 11, and only these heating regions 11, 11 are heated.

The portion (arc portion indicated by the dashed line) with which the shoulder portion 31a of the punch 31 contacts may coincide with the inner edge of the heating regions 11 (arc portion indicated by the dashed line).

As an example of the device configuration for carrying out this partial heating step, a laser irradiation device is provided as in the case of the above-described embodiment. That is, the laser beam generated by this laser irradiation device is irradiated toward the heating region 11 of the high-strength steel plate 1 .

More specifically, the width dimension of the high-strength steel plate 1 in the present embodiment (dimension D in FIG. 5(a)) is 150 mm, and the width dimension of the punch 31 (dimension d1 in FIG. 5(a); The width dimension) is 100 mm, and the width dimension of the heating region 11 (dimension d2 in FIG. 5(a)) is 20 mm. These dimensions and dimension ratios are not limited to these, and may be set as appropriate.

Moreover, in this partial heating step, the heating regions 11, 11 of the high-strength steel plate 1 are heated to, for example, about 600°C. Then, in the cooling step, the heating regions 11, 11 heated to about 600° C. are cooled to a temperature of less than 200° C. in a period of several tens of seconds.

FIG. 8 is a diagram for explaining the press working process in this embodiment. The press working device 3 shown in FIG. 8 has a pad 34 in addition to a die 32 and a punch 31 . The pad 34 sandwiches the central portion (unheated area) 12 of the high-strength steel plate 1 between itself and the punch 31 . In this manner, the die 32 is lowered while the non-heating region 12 is held between the pad 34 and the punch 31, and the die is clamped, thereby forming the press-formed product 2 described above.

Also in this embodiment, by performing the partial heating process and the cooling process in the previous stage of the pressing process, the outer parts (heating regions) 11, 11 in the high-strength steel sheet 1 are softened and the ductility of the material is improved. will do. Therefore, even the high-strength steel plate 1, which is difficult to press into a complicated shape, can be formed into a predetermined shape along the shape of the punch 31 with high accuracy, and the occurrence of cracks and wrinkles is suppressed. will be

Further, after the partial heating process and the cooling process, the high-strength steel plate 1 is set in the press working device 3, so a device for heating or cooling the high-strength steel plate 1 is directly connected to the press working device 3. Since there is no need to incorporate it, it is possible to suppress an increase in manufacturing cost of the press working device 3 .

-Other embodiments-
The present invention is not limited to the above-described embodiments and modifications, and all modifications and applications within the scope of the claims and their equivalents are possible.

For example, in each of the above-described embodiments and modifications, the partial heating process and the cooling process are performed by placing the high-strength steel plate 1 on the same substrate. The present invention is not limited to this, and the partial heating process and the cooling process may be performed by placing the high-strength steel plate 1 on different substrates.

Further, in each of the above-described embodiments and modifications, laser light is used as the heat source in the partial heating process. The present invention is not limited to this, and it is also possible to use IH (Induction Heating), near-infrared rays, or the like as a heat source.

Further, in the first embodiment, the heating region 11 of the high-strength steel plate 1 is heated to about 500° C. in the partial heating step. Further, in the second embodiment, the heating regions 11, 11 of the high-strength steel plate 1 are heated to about 600° C. in the partial heating step. These values are not limited to these, and are appropriately set to values between 200° C. and 700° C., for example.

Moreover, the press working device 3 used in the press forming method according to the present invention is not particularly limited, and a transfer type, a tandem type, or the like can be used.

Further, in each of the above-described embodiments and the above-described modifications, an example of press working in which the punch 31 is pressed against the central portion of the high-strength steel plate 1 has been described. The present invention is not limited to this, and can be applied to press working in which the punch 31 is pressed against a region other than the central portion of the high-strength steel plate 1 (for example, the outer edge portion of the high-strength steel plate 1).

INDUSTRIAL APPLICABILITY The present invention can be applied to a press forming method in which a step of heating a high-strength steel plate is performed prior to a press forming step.

1 High-strength steel plate 11 Peripheral portion, outer region, heated region 12 Non-heated region 2 Press-formed product 3 Pressing device 31 Punch (pressing portion)
31a shoulder portion 31b central portion 31c vertical wall portion 4 laser irradiation device

Claims (2)

In the press forming method for pressing the high-strength steel plate along the shape of the pressing portion by pressing the pressing portion of the press working device against the high-strength steel plate,
The pressing portion has a central portion that first comes into contact with the high-strength steel plate in the press working, a shoulder that is an end of the central portion, and a vertical wall that extends continuously from the shoulder. ,
a partial heating step of heating only at least a portion of an outer region located outside a contact portion where the central portion and the shoulder portion of the pressing portion are in contact with each other in the high-strength steel plate;
After the partial heating step, the cooling air blown from the cooling air nozzle is relatively moved along the extending direction of the heated region, and is passed through the movement trajectory a plurality of times. a cooling step of cooling and tempering the heated region by blowing the cooling air to the region a plurality of times ;
After the cooling step, the high-strength steel plate is set in the press working device, and the high-strength steel plate is pressed by the pressing portion, and the high-strength steel plate is subjected to the central portion, the shoulder portion, and the and a press forming step of forming along the shape of the vertical wall portion. In the press molding method according to claim 1,
The outer edge shape of the high-strength steel plate includes a first edge extending in one direction, a second edge extending in a direction orthogonal to the extending direction of the first edge, and an extension of the first edge. a third edge curved with a predetermined curvature from one end in the extension direction of the second edge to one end in the extension direction of the second edge; a fourth edge curving with a predetermined curvature over the other end in the direction in which the
In the pressing step, a first range extending from the third edge to an inner line having a predetermined dimension with respect to the third edge along the extending direction of the third edge; and a range from the fourth edge to an inner line having a predetermined dimension with respect to the fourth edge, and each second range along the extending direction of the fourth edge is bent. and
The shoulder portion of the pressing portion is arc-shaped along each of the inner lines,
In the partial heating step, at least a partial area of the first range and an arc-shaped area along the extending direction of the third edge and at least a partial area of the second range A press molding method, wherein only an arc-shaped region along the extending direction of the fourth edge portion is heated.

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