JP6448587B2 - Hot press apparatus and hot press method - Google Patents

Description

The present invention relates to a hot pressing apparatus and a hot pressing method for bending a steel plate into a predetermined shape.

  In parts for vehicles, both safety and economy are achieved by using a member having a thin thickness and high strength. For this purpose, so-called hot press forming is known in which a steel plate heated to a high temperature is cooled by a low-temperature press mold and quenched. In this method, the steel sheet is heated to the austenitizing temperature or higher, and quenched and quenched at the same time as press forming.

  For example, a vehicle component such as a pillar reinforcement constituting the vehicle side structure is formed by bending a steel plate into a desired shape using a hot press device. The pillar reinforcement is arranged between the pillar outer panel and the pillar inner panel of the center pillar, and controls the deformation shape of the center pillar at the time of a vehicle collision, and prevents the center pillar from interfering with the passenger. This is a vehicle component for protecting an occupant.

  FIG. 5 is a diagram showing the configuration of the pillar reinforcement, FIG. 5A is a plan view thereof, and FIG. 5B is a cross-sectional view taken along the line AA of FIG. 5A. The pillar reinforcement 50 is U-shaped when viewed in a cross-sectional view along the line AA. Further, the pillar reinforcement 50 has a bottom 51 and side walls 52 and 53 that are bent up from the bottom 51, and in the vicinity of the bent portion (corner portion of the bottom 51) in the event of a vehicle collision. In order to control the deformed shape of the center pillar, a groove 54 that is recessed from the main surface of the bottom 51 is formed along the longitudinal direction.

  FIG. 6 is a cross-sectional view of the hot press apparatus 100 and corresponds to the apparatus cross-sectional structure for forming the U-shaped cross section of the pillar reinforcement 50 in FIG. This hot press apparatus 100 is disposed adjacent to a lower mold 12 having a step 11 for bending a steel plate 10 to be pressed, and a horizontal direction with respect to the lower mold 12, and is urged by a spring or the like. The pad portion 13 is supported by means (not shown) so as to be movable up and down, and the upper mold 14 is disposed so as to face the pad portion 13 in the vertical direction.

  In this case, the lower mold 12 has an opening with a U-shaped cross section, and a step 11 is formed between the press molding surface (upper surface) of the upper mold 14 and the bottom of the opening. The pad portion 13 is configured to move up and down within the opening. The upper die 14 has a convex portion 14 a that fits into the lower die 12 in order to hold the steel plate 10 between the pad portions 13 and push it into the step 11.

  Further, in order to form the groove 52 of the pillar reinforcement 50, a protruding portion 14b protruding in the vertical direction is formed at the end of the press molding surface of the upper mold 14 convex portion 14a, and the pressing of the opposing pad portion 13 is performed. A notch 13a corresponding to the protrusion 14b is formed at the end of the molding surface.

  A hot press forming process using the hot press apparatus 100 will be described with reference to FIG. First, as shown in FIG. 6A, a preheated steel plate 10 is set on the lower mold 12 and the pad portion 13 by an automatic transport mechanism. In this case, the press molding surface of the lower die 12 and the press molding surface of the pad portion 13 are located on substantially the same plane. In this state, the upper mold 14 moves downward toward the pad portion 13.

  Next, as shown in FIG. 6B, before the U-shaped bending of the steel plate 10, the steel plate 10 is sandwiched between the upper mold 14 and the pad portion 13 and held (held). At this time, the protruding portion 14b of the upper mold 14 hits the steel plate 10 and is pushed into the notched portion 13a of the pad portion 13, whereby a portion to be the groove portion 54 of the pillar reinforcement 50 is formed in advance. The steel plate 10 is cooled by being in contact with the lower mold 12, the pad portion 13, and the upper mold 14.

  Thereafter, when the upper die 14 is further moved downward, the steel plate 10 is pushed into the step 11 of the lower die 12 while being held between the upper die 14 and the pad portion 13, and the bending process proceeds. To go. When the upper die 14 and the pad portion 13 reach the bottom dead center, a pillar reinforcement 50 bent into a U-shaped cross section is formed.

JP2015-142928A

  However, as shown in FIG. 5, there has been a problem that cracks and molding defects such as necking occur in the vicinity of the bent portion of the steel sheet 10 during the hot press forming process. Further, there is a problem that such a molding defect is likely to occur in the vicinity of the bent portion where the groove 54 is formed.

In view of the above-described problems, the hot pressing device of the present invention is adjacent to the lower mold (12) having a step (11) for bending the steel plate (10) in the horizontal direction with respect to the lower mold (12). And a pad part (13) supported so as to be movable up and down, and an upper mold (14) arranged to face the pad part (13) in the vertical direction. 13) and an upper mold (14) disposed vertically opposite to each other, and the upper mold (14) is moved downward to push the steel plate (10) into the step (11) and bend it. On the way, the steel material (10) is held between the upper die (14) and the pad portion (13) to perform hot press molding, and the steel material (10) is held in the upper die. (14) There is no clearance margin between the press molding surfaces of the pad portion (13) .

Further, the hot pressing method of the present invention is disposed adjacent to the lower mold (12) having a step (11) for bending the steel plate (10) in the horizontal direction with respect to the lower mold (12). A hot press apparatus comprising a pad portion (13) supported so as to be movable up and down, and an upper die (14) arranged to face the pad portion (13) in the vertical direction is prepared. Setting the preheated steel plate (10) on the lower die (12) and waiting the pad portion (13) below the lower die (12) without contacting the steel plate (10); Lowering the upper mold (14) and pushing the steel plate (10) into the step (11) to start the bending process of the steel sheet (10), and in the middle of the bending process, the steel material (10) is Holding between the mold (14) and the pad (13), and holding the steel (10) The upper die (14) and the pad portion (13) are further moved downward in the state to continue the bending process, and the upper die (14) and the pad portion ( 13) There is no clearance margin between the press-molding surfaces .

  ADVANTAGE OF THE INVENTION According to this invention, when bending a steel plate with a hot press, the crack of the bending part vicinity of a steel plate, forming defects, such as necking, can be prevented.

It is a top view of the hot press apparatus in the embodiment of the present invention. It is a 1st sectional view explaining the hot press machine in the embodiment of the present invention, and its operation. It is a 2nd sectional view explaining the hot press machine in the embodiment of the present invention, and its operation. It is a 3rd sectional view explaining the hot press machine in the embodiment of the present invention, and its operation. It is a figure which shows the structure of a pillar reinforcement. It is sectional drawing explaining the hot press apparatus of a prior art example, and its operation | movement.

<Causes of steel sheet forming defects>
Before explaining the details of the embodiment of the present invention, in the conventional example, in the process of hot press forming, in the vicinity of the bent portion of the steel plate 10 (for example, near the corner portion of the bottom 51 of the pillar reinforcement 50), The cause of molding defects such as cracking and necking will be described.

  As shown in FIG. 6B, before the U-shaped bending process of the steel plate 10, the steel plate 10 is sandwiched between the upper mold 14 and the pad portion 13 and held. At this time, since the gap G exists between the pad portion 13 and the opening side wall of the lower mold 12, the steel plate 10 in the vicinity of the bent portion floats in the air, and a narrow non-contact region where the mold or the like does not contact is formed. The cross-sectional length L1 of this region corresponds to the distance from the end of the press molding surface of the pad portion 13 of the pad portion 13 to the end of the press molding surface of the lower mold 12.

  Then, at this time, the non-contact area of the steel plate 10 is not rapidly cooled by a mold or the like, and the contact areas on both sides thereof are rapidly cooled by the mold or the like, so that a large temperature difference occurs locally. Thus, the non-contact area is locally stretched due to the tensile stress from the adjacent contact area contracted by the rapid cooling. Since the steel plate 10 is pushed into the step 11 of the lower mold 12 in a state where this local elongation has occurred, the local elongation is promoted in the process of the bending process, and in the vicinity of the bent portion of the steel plate 10. It is considered that molding defects such as cracks occur.

  In particular, when the groove 54 is formed in the vicinity of the bent portion, this portion is strongly pushed by the protruding portion 14b of the upper mold 14, and therefore it is considered that molding defects such as cracks are likely to occur.

<Principle of the present invention>
Therefore, according to the present invention, as shown in FIG. 2, before the U-shaped bending of the steel plate 10,
The stroke of the pad portion 13 is reduced so that the steel plate 10 is held in the middle of the bending process after the bending process is started without holding the steel plate 10 between the upper die 14 and the pad portion 13 and held. Has been.

Specifically, as shown in FIG. 2 (a), in a state where the steel plate 10 is set in the hot press apparatus 100 </ b> A, the pad portion 13 does not contact the steel plate 10 and is below the press molding surface of the lower mold 12. Waiting. For this reason, when the upper mold 14 is moved downward, first, the upper mold 14 comes into contact with the upper surface of the steel plate 10, and the steel plate 10 is pushed into the step 11 of the lower mold 12.

  Then, as shown in FIG. 2 (b), the steel plate 10 is held between the upper mold 14 and the pad portion 13 in the middle of the bending process. Therefore, the stroke of the pad portion 13 is reduced as compared with the conventional example.

  When the steel plate 10 is held, a non-contact area where the mold or the like does not contact is formed, and the tensile stress is applied from the contact area adjacent to the non-contact area. However, the length L2 of the non-contact area in this case is considerably longer than the conventional non-contact area of FIG. 6 because the steel plate 10 is pulled into the step 11 to some extent, and the contracted contact accordingly. The effect of tensile stress from the region is mitigated.

  That is, in the conventional example, a tensile stress is applied to a narrow non-contact region. However, according to the present invention, a tensile stress is applied to a relatively wide non-contact region, so that the local elongation is reduced accordingly. For this reason, according to this invention, formation defects, such as a crack of the steel plate 10 in hot press forming, can be prevented.

<Detailed Description of Embodiment of the Present Invention>
Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a hot press apparatus 100A according to an embodiment of the present invention. To make the diagram easier to see,
FIG. 1A shows the lower mold 12 and the pad part 13, and FIG. 1B shows the pad part 13 and the upper mold 14 separately. 2 is a cross-sectional view taken along line BB in FIG. 1, FIG. 3 is a cross-sectional view taken along line CC in FIG. 1, and FIG. 4 is a cross-sectional view taken along line DD in FIG.

  1 to 5, the shapes of the lower mold 12, the pad portion 13, and the upper mold 14 are shown in a simplified manner. Actually, since the vehicle parts such as the pillar reinforcement 50 have a complicated shape as shown in FIG. 5, the lower mold 12, the pad portion 13, and the upper mold 14 are adjusted accordingly. It has a complicated shape.

  As shown in FIG. 1, the pad portion 13 includes a first pad 131, a second pad 132, and a third pad 133 that are arranged in this order in the horizontal direction. Further, as shown in FIG. 4, the first pad 131, the second pad 132, and the third pad 133 are respectively composed of a first biasing means 151, a second biasing means 152, and a third biasing. It is supported by means 153 so as to be movable up and down. The biasing means can be constituted by, for example, a spring or a cylinder.

  Then, when the upper die 14 is moved downward and the steel material 10 is held between the upper die 14 and the pad portion 13 and hot press forming is performed, the second pad 132 is delayed from the upper die 14 and the steel plate 10, the stroke of the second pad 132 is set to be smaller than the strokes of the first and third pads 131 and 133.

That is, according to the hot press apparatus 100A, the pad portion 13 is divided into three pads, and the first and third pads 131 and 133 located at both ends of the pad portion 13 are the same as in the conventional example. Before the U-shaped bending process of the steel plate 10, the steel plate 10 is sandwiched and held between the upper mold 14 and the first and third pads 131 and 133, but the second pad 132 located at the center of the pad portion 13. As for No. 1, the steel plate 10 is not sandwiched between the upper mold 14 and the second pad portion 132 and held, and the folding process is started and the steel plate 10 is held in the middle of the folding process. The stroke of the second pad portion 132 is reduced.

  Thereby, about the part corresponding to the 2nd pad 132, the shaping | molding defects, such as a crack near the bending part of the steel plate 10, can be prevented by the principle of this invention mentioned above. In addition, the first and third pads 131 and 133 located at both ends of the pad portion 13 hold the steel plate 10 before the U-shaped bending process of the steel plate 10, so It can prevent and perform stable hot pressing. In particular, when the groove 54 is formed in the vicinity of the bent portion of the steel plate 10 corresponding to the second pad 132, the effect of preventing molding defects such as cracking is great.

Next, a hot press forming process using the hot press apparatus 100A will be described with reference to FIGS. 2 shows a portion corresponding to the second pad 132, FIG. 3 shows a portion corresponding to the first and third pads 131 and 133, and FIG.
In addition, illustration of the steel plate 10 is abbreviate | omitted in FIG.

  First, the preheated steel plate 10 is set on the lower mold 12 and the pad portion 13 by an automatic conveyance mechanism. In this case, as shown in FIGS. 2 (a) and 4 (a), the second pad 132 does not contact the steel plate 10 and is waiting below the press molding surface of the lower mold 12. On the other hand, as shown in FIGS. 3A and 4A, the steel plate 10 is placed on the first and third pads 131 and 133.

Then, when the upper mold 14 is moved downward, before the U-shaped bending process of the steel plate 10,
The steel plate is held at the first and third pads 131 and 133, but the steel plate 10 is not held at the second pad 132 located in the center.

  Next, when the upper die 14 is further moved downward, the upper die 14 comes into contact with the upper surface of the steel plate 10 and the steel plate 10 is pushed into the step 11 of the lower die 12. And as shown in FIG.2 (b), the steel plate 10 is hold | maintained in the place of the 2nd pad 13 in the middle of a bending process. On the other hand, as shown in FIG. 3 (b), at the first and third pads 131 and 133, the bending process proceeds while the steel plate 10 is held.

  In this case, as shown in FIG. 4, the strokes S1, S2, and S3 of the vertical movements of the first to third pads 131, 132, and 133 have a magnitude relationship of S2 <S1, S3, and S2 = S3. . In order to reduce the stroke S <b> 2 of the second pad 132, a stopper portion 12 a for stopping the second pad 132 is formed below the second pad 132.

  Based on FIG. 4, the movement of the first to third pads 131, 132, 133 will be described. First, as shown in FIG. 4A, when the first to third pads 131, 132, 133 are located at the top dead center, the press molding surface of the second pad 132 is a relatively low position. It is in.

  Next, as shown in FIG. 4B, when the upper mold 14 is moved downward, the first and third pads 131 and 133 are first pushed down, and then the second pad 132 is moved. In addition, the entire pad portion 13 is pushed down while maintaining the press molding surface having the same height. And as shown in FIG.4 (c), the 1st thru | or 3rd pad 131,132,133 stops at the time of reaching those bottom dead centers.

  In the hot press apparatus 100A described above, the pad portion 13 is divided into first to third pads 131 to 133. However, the pad portion is further divided into more pads, and a stroke is made between adjacent pads. It may be different.

  Alternatively, the pad portion 13 may be configured with only one pad, and the entire pad portion 13 may be configured to contact the steel plate 10 with a delay from the upper mold 14. Even in this case, molding failure such as cracking of the steel sheet 10 in hot press molding can be prevented by the principle of the invention described above.

DESCRIPTION OF SYMBOLS 10 Steel plate 11 Step 12 Lower mold 13 Pad part 13a Notch part 14 Upper mold 14a Projection part 14b Projection part 100, 100A Hot press apparatus 131 1st pad 132 2nd pad 133 3rd pad 151 1st Urging means 152 second urging means 153 third urging means

Claims (5)

A lower mold (12) having a step (11) for bending the steel plate (10);
A pad portion (13) disposed adjacent to the lower mold (12) in the horizontal direction and supported so as to be movable up and down;
An upper mold (14) disposed perpendicularly to the pad portion (13),
While the upper die (14) is moved downward and the steel plate (10) is pushed into the step (11) and bent, the steel material (10) is held between the upper die (14) and the pad portion (13). It is configured to perform hot press forming and is characterized in that there is no clearance margin between the press forming surfaces of the upper mold (14) and the pad portion (13) in a state where the steel material (10) is held. Hot press machine to do. A protrusion (14b) protruding vertically is formed at the end of the press molding surface of the upper mold (14), and corresponds to the protrusion (14b) at the end of the press molding surface of the pad (13). The hot press apparatus according to claim 1, wherein a notch (13a) is formed. A lower mold (12) having a step (11) for bending the steel plate (10);
A pad portion (13) disposed adjacent to the lower mold (12) in the horizontal direction and supported so as to be movable up and down;
An upper mold (14) disposed perpendicularly to the pad portion (13),
The pad portion (13) has a first pad (131), a second pad (132), and a third pad (133) arranged in this order in the horizontal direction.
Lower the upper die (14), push the steel plate (10) into the step (11) and bend it
On the way, the stroke of the second pad (132) is the first so that the hot press molding is performed by holding the steel material (10) between the upper die (14) and the second pad portion (132). And the stroke of the third pad (131, 133) is set smaller than the steel material (10)
In the held state, the upper mold (14) and the press molding surface of the second pad part (132)
A hot press machine characterized by having no clearance between them .   A protrusion (14b) protruding vertically is formed at the end of the press molding surface of the upper mold (14), and the protrusion (14b) is formed at the end of the press molding surface of the second pad (132). The hot press apparatus according to claim 3, wherein a notch (13 a) corresponding to is formed. A lower mold (12) having a step (11) for bending the steel plate (10), and a pad portion (which is disposed adjacent to the lower mold (12) in the horizontal direction and supported so as to be movable up and down) 13) and an upper mold (14) arranged to face the pad portion (13) in the vertical direction, and a hot press device is prepared,
Setting the preheated steel plate (10) on the lower die (12) and waiting the pad portion (13) below the lower die (12) without contacting the steel plate (10);
Lowering the upper mold (14) and pushing the steel plate (10) into the step (11) to start bending the steel plate (10);
In the middle of the bending process, holding the steel material (10) between the upper mold (14) and the pad portion (13);
A step of further lowering the upper die (14) and the pad portion (13) while holding the steel material (10) and continuing the bending process,
A hot pressing method characterized in that there is no clearance margin between the press molding surfaces of the upper die (14) and the pad portion (13) in a state where the steel material (10) is held .

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