JP5151784B2 - Center pillar outer panel manufacturing method and center pillar outer panel blank - Google Patents

Description

  The present invention relates to a method for manufacturing a center pillar outer panel by hot press molding and a blank for a center pillar outer panel. In particular, the present invention relates to a method for manufacturing a center pillar outer panel excellent in trim properties and surface quality after hot press molding, and a blank for a center pillar outer panel.

  In recent years, structural members for automobiles are required to be thin and have high strength from the viewpoint of global environmental problems and collision safety performance. In order to satisfy these conflicting requirements, the application of high-strength steel sheets is expanding. However, as one of the problems when using a high strength steel sheet, there is a forming defect including wrinkles, which is an obstacle to expanding the application of the high strength steel sheet.

  As a technique for solving these problems, heat for manufacturing a high-strength molded product by press-molding a workpiece (blank) heated to a high temperature of 700 ° C. or higher and then quenching in the mold or outside the mold. Inter-press forming methods are known.

  Since hot press forming is performed in a high temperature range where the tensile strength of the steel sheet is reduced, forming defects can be easily suppressed or eliminated. In addition, since high strength is achieved by quenching after molding, an ultra-high strength product having a tensile strength of 1500 MPa class can be manufactured.

  However, since the tensile strength of the molded product quenched by this hot press molding is extremely large, for example, about 1500 MPa, there are various problems when trimming the molded product into a product shape. For example, a case where a center pillar outer panel (hereinafter simply referred to as “center pillar outer”) is hot press-molded by drawing (hereinafter also simply referred to as “drawing”) will be described.

  In drawing, a die comprising a die, a blank holder, a punch and a pad is used, a blank heated to a predetermined temperature is sandwiched between the punch and the pad, and a cut-off portion provided around the blank is formed between the die and the blank holder. Molding is performed in a state of being constrained by the above, and the blank is quenched by contact with the mold at the bottom dead center of molding to obtain a drawn product. The cut-off portion around the drawn product is removed by trimming after the drawing.

  However, if the trim processing after drawing is performed by shearing, the drawn product has high strength, so the service life of the tool used for shearing is shortened and the cost is increased. When trimming is performed by laser cutting, the trim line, which is the boundary between the product part and the cut-off part, surrounds the periphery of the product part inside the drawn product, so the trim distance is long. Therefore, the time and cost required for trimming increase, and productivity decreases. For these reasons, drawing forming that requires trimming generally tends to be avoided.

  For example, Patent Documents 1 and 2 disclose a method of hot pressing a bumper beam or a bumper reinforcing material by hot bending forming (hereinafter also simply referred to as “bending forming”) that does not require trimming after forming. Has been.

Bending is performed by using a die consisting of a die, a punch and a pad, sandwiching a blank heated to a predetermined temperature between the punch and pad, and lowering the die. Quenched by contact with The shape of the blank used for bending is adjusted in advance so that the shape of the bent product obtained by bending is the same as the product shape, that is, the shape of the bent product developed. For this reason, the bending molded product obtained by bending molding does not have a cut-off part like a drawing molded product, and trim processing is unnecessary after bending molding.
JP 2007-38756 A JP 2004-217041 A

  However, when an attempt is made to produce the center pillar outer by bending, a surplus occurs during bending due to the curved shape of the center pillar outer in the longitudinal direction. This surplus is generated as wrinkles in the wall or flange at the location where the wall height located at the center in the longitudinal direction changes suddenly.

  The wrinkles of the center pillar outer having a general shape are generated in a region within approximately 30% of the length of the center pillar outer from the center in the longitudinal direction to the both sides in the longitudinal direction, that is, approximately 20% from both ends. It exists in the area | region within 60% except the area | region of. The wrinkles may be wrinkled on the wall before forming the flange, and even the formation to the bottom dead center is obstructed, which is a great obstacle to bending the center pillar outer.

  In other words, when manufacturing the center pillar outer by hot press forming, when performing hot press forming by drawing, the cost and man-hours required for trim processing after drawing are increased, while the heat by bending is increased. In the case of performing the intermediate press forming, wrinkles are generated in the above-described region during the bending forming.

  The object of the present invention is to suppress or eliminate the generation of wrinkles without increasing the cost and man-hour required for trim processing after molding, and to improve the trim properties and surface quality after hot press molding by hot press molding. It is to produce an excellent center pillar outer panel.

  As a result of intensive studies in order to solve this problem, the inventors have performed hot press forming that combines drawing forming performed on a part of the blank and bending forming performed on the remaining part other than this part. Can suppress or eliminate the generation of wrinkles without increasing the cost and man-hours required for trimming after molding, which results in excellent trim properties and surface quality after hot press molding and high strength. The present invention has been completed by discovering that it is possible to provide a center pillar outer having high collision safety performance by realizing high speed and high rigidity.

The present invention is a method of manufacturing a center pillar outer panel by inserting a blank heated to a predetermined temperature into a mold and hot press-molding the molded product, and trimming the molded product. Press forming is performed on a part of the blank including at least a part of a region of 30% or less of the length of the blank from the longitudinal center of the blank to both sides in the longitudinal direction, and at least both ends in the longitudinal direction excluding this part. The center pillar outer panel manufacturing method is characterized in that the center pillar outer panel is formed by a combination with bending in the remaining portion including a region of 10% or less of the length of the blank in the longitudinal direction .

In the case of this, a portion of 30 percent or less of the area of the length of the blank, it is desirable that all of the more than 20% area of the length of the blank.

  In the manufacturing method of the center pillar outer panel according to the present invention, it is desirable that the molded product includes a groove portion extending in the longitudinal direction at least in a part of the molded product in the longitudinal direction. In this case, it is desirable that the groove portion has a depth equal to or less than the wall height in the cross section of the molded product in which the groove portion is formed.

  In the manufacturing method of the center pillar outer panel according to the present invention, the blank is constrained by a die and a blank holder used in the drawing and has a cut-off portion that is removed by trim processing, and the remaining part of the blank. It is desirable that at least a part of the portion does not have a cut-off portion that is removed by trimming.

In particular, it is further desirable that at least a portion of the remaining portion has the shape of the final product and does not need to be removed by trimming. From another aspect, the present invention is subjected to hot pressing, and at least In addition to having a cut-out portion in the entire area of 20% or less of the length of the blank on both sides in the longitudinal direction from the center in the longitudinal direction of the blank, at least 10% or less of the length of the blank in the longitudinal direction from both ends in the longitudinal direction The center pillar outer is characterized in that there is no cut-out portion in the region of the above , and that the region having the cut-out portion is subjected to drawing and the region not having the cut-out portion is subjected to bending molding. Panel blank.

  According to the present invention, the occurrence of wrinkles is suppressed or eliminated without increasing the cost and man-hours required for trim processing after molding, and the hot press molding improves the trim properties and surface quality after hot press molding. An excellent center pillar outer panel can be manufactured, and can greatly contribute to the reduction in thickness and strength of the center pillar outer panel, which is a structural member for automobiles.

(Embodiment 1)
The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

Before describing the embodiment of the present invention, first, a conventional method of manufacturing a center pillar outer by hot press forming using drawing or bending will be described.
(I) Hot press forming using drawing FIG. 1A and FIG. 1B are explanatory views showing an outline of a hot press forming die of the center pillar outer. Moreover, FIG. 2 is explanatory drawing which shows the outline of the various shapes of the blank of a center pillar outer, Comprising: Fig.2 (a) shows the blank for drawing, FIG.2 (b) shows the blank for bending, FIG. 2 (c) shows a blank for bending and drawing according to the present invention.

  For drawing, a die composed of a die 1, a blank holder 2, a punch 3 and a pad 4 shown in FIGS. 1 (a) and 1 (b) and a drawing blank 5 shown in FIG. 2 (a) are used. Use. The blank for drawing 5 is a portion 5a to be a product after drawing and the periphery of the portion 5a is restricted by the die 1 and the blank holder 2 at the time of drawing and is removed by trimming after drawing. Part 5b.

  3 (a) to 3 (e) are explanatory diagrams showing the hot pressing process, and FIGS. 3 (a) and 3 (b) are respectively the before-molding start and the bottom dead center of molding in drawing. FIGS. 3 (c) and 3 (d) show the respective states before the start of molding and at the bottom dead center of molding.

In the drawing, first, a drawing blank 5 heated to a predetermined temperature equal to or higher than the Ac ₁ transformation point is arranged at a predetermined position on the blank holder 2. Next, as shown in FIG. 3A, the die 1 and the pad 4 are lowered at the same time, the die 1 and the blank holder 2 restrain the cut-out portion 5b of the drawing blank 5, and the punch 3 and the pad 4 Thus, the portion 5a to be a product of the drawing blank 5 is sandwiched.

  Next, as shown in FIG. 3B, the die 1 and the blank holder 2 are lowered while the cut-off portion 5b of the drawing blank 5 is constrained by the die 1 and the blank holder 2, and the drawing molding blank is lowered. 5a is pressed against the punch 3, and a three-dimensional shape is created by the elongation and inflow of the material to obtain a molded product 5c.

  The draw blank 5 is quenched by contact with the mold at the bottom dead center. The molded product 5c has a product portion and a cut-out portion restrained by the die 1 and the blank holder 2 on the outer periphery of the product portion. The trimmed portion is removed by being sheared along a trim line that is a boundary line between the product portion and the trimmed portion in the trim processing after molding. In this way, the center pillar outer is manufactured.

  FIG. 4 shows an angle (hereinafter also referred to as a shear angle) formed by a direction (shown by a broken line) perpendicular to the moving direction (shear direction) of the blade of the shearing die in trim processing of the molded product 5c and the trim line. It is explanatory drawing shown typically. When trim processing is performed by shearing, if the shear angle is large, the blade passing distance, that is, the shear width increases, so that the shearing mold is easily damaged, and trim processing becomes difficult. On the other hand, when this shear angle is small, trim processing becomes easy.

  Usually, when trimming of the molded product 5c is performed by shearing, the molded product 5c is horizontally arranged and sheared as shown in FIG. At this time, the shear angle is different in each part of the molded product 5c.

  That is, the shear angle 10 in the central portion in the longitudinal direction is larger than the shear angles 11U and 11L in the T-shaped part wall portions 12U and 12L existing on the upper side where the wall height is small and the lower side where the wall height is large. ,small.

For example, the shear angle 10 at the central portion in the longitudinal direction is usually about 20 ° or less, whereas the shear angles 11U and 11L at the T-shaped part wall portions 12 existing on the upper side and the lower side are usually 60 °. More than about. Therefore, in particular, it is difficult to trim the T-shaped part wall portions 12U and 12L. Usually, the T-shaped part wall portions 12U and 12L are present in an area of approximately 10% or less of the length of the center pillar outer in the longitudinal direction from both ends in the longitudinal direction of the center pillar outer.
(Ii) Hot press forming using bend forming As shown in FIGS. 1 (a) to 1 (b), bend forming is performed using a die composed of a die 1, a punch 3 and a pad 4, and FIG. 2 (b). A blank 6 for bending is used. Generally, the blank holder 2 is not used in bending. The bending blank 6 has a shape adjusted in advance so that a product shape can be obtained as it is after hot bending.

In bending, a bending blank 6 heated to a predetermined temperature equal to or higher than the Ac ₁ transformation point is placed at a predetermined position on the punch 3. Next, as shown in FIG. 3 (c), the pad 4 and the die 1 are lowered at the same time, the blank 6 for bending is sandwiched between the punch 3 and the pad 4, and the blank 6 is placed as shown in FIG. 3 (d). A bent molded product 6a is obtained by creating a bent solid shape.

  The bending blank 6 is quenched by contacting the mold at the bottom dead center. As described above, since the shape of the bending-molded blank 6 is adjusted in advance so that the shape of the bent-molded product 6a matches the product shape, the bent-molded product 6a has a cut-off portion of the draw-molded product 5c. There is no need to trim after bending.

  However, when the center pillar outer is formed by bending as described above, the bent product has a curved shape in the longitudinal direction as shown in FIG. This surplus is generated as wrinkles in the wall and flange of the portion 14 located at the center in the longitudinal direction where the wall height on the upper side and the lower side changes abruptly.

  Usually, the places where the wall heights on the upper side and the lower side change abruptly exist in the region of approximately 30% or less of the length of the center pillar outer from the center in the longitudinal direction of the center pillar outer to both sides in the longitudinal direction. That is, wrinkles are likely to occur in a region of approximately 60% or less in the longitudinal direction excluding a region of approximately 20% or less from both ends.

This wrinkle may be wrinkled on the wall before forming the flange, which is a major obstacle to bending the center pillar outer.
(Iii) Hot press molding using bending and drawing according to the present embodiment Next, an embodiment of the present invention will be described.

Also in the present embodiment, a blank having a steel composition heated to a predetermined temperature equal to or higher than the Ac ₁ transformation point, preferably equal to or higher than the Ac ₃ transformation point, is charged into a mold and hot pressed into a molded product. The center pillar outer is manufactured by trimming the.

  At this time, this hot press molding is performed on a part of the blank, specifically, at least a part of a region of 30% or less of the length of the blank from the center in the longitudinal direction to both sides in the longitudinal direction. Hot press molding that combines molding and bending that is performed on the remaining portion excluding this part, specifically, bending at least 10% of the length of the blank in the longitudinal direction from both ends in the longitudinal direction ( Hereinafter, the center pillar outer is manufactured by simply performing “bending and drawing”.

  As described above, in the region of approximately 60% or less in the longitudinal direction excluding the region of approximately 20% or less in the longitudinal direction from both ends in the longitudinal direction of the center pillar outer (hereinafter also referred to as “center portion”), bending is performed. I am prone to wrinkles. Therefore, wrinkle generation can be suppressed by drawing the partial region. At least the entire region of 20% or less of the length of the blank from the center in the longitudinal direction to both sides in the longitudinal direction, that is, the entire region of 40% excluding the region of 30% or less from the both end surfaces in the longitudinal direction is drawn. It is desirable to prevent the generation of wrinkles. At least the center of the longitudinal direction and at least 30% or less of the length of the blank in the longitudinal direction on both sides, that is, the entire region of 60% excluding the region of 20% or less in the longitudinal direction from at least both end faces Is more desirable.

  When drawing is performed in an area of 10% or less of the length of the blank in the longitudinal direction from both ends in the longitudinal direction, in the trim processing after molding, the direction perpendicular to the moving direction of the trim line and the blade of the shearing mold Since the angle formed, i.e., the shear angle becomes large, the shear width becomes large and the tool is easily damaged, but in this embodiment, since this region is bent, trimming is not necessary, The problem with trim processing is solved.

  For bending and drawing, a die composed of a die 1, a blank holder 2, a punch 3 and a pad 4 shown in FIGS. 1 (a) and 1 (b) and a bending according to the present invention shown in FIG. 2 (c) are used. And a drawing blank 7 are used.

  The bending and drawing blank 7 is a center pillar outer used for hot press forming that combines drawing forming for a portion 7-1 and bending forming for the remaining portions 7-2 and 7-2 excluding this portion. Blank. The bending and drawing blank 7 is constrained (held) by the part 8a that becomes the product part after bending and drawing, the die 1 and the blank holder 2, and is subjected to trim processing along the trim line 9 after bending and drawing. The cut-off portion (hereinafter also referred to as “blank hold”) 8b and 8b to be removed.

  The cut-off portion 8b is provided in a portion 7-1 where drawing is performed. Further, in the present embodiment, the remaining portions 7-2 and 7-2 are configured not to be provided with a cut-off portion that is removed by trimming. It is sufficient that the cut-off portion is not provided. In other words, at least a part of the remaining portion 7-2 may be configured not to have a cut-off portion that is removed by trimming. Thereby, the length of the trim line 9 can be significantly reduced as compared with the drawing blank 5 shown in FIG.

  As shown in FIG. 2 (c), the bending and drawing blank 7 is cut off at least in the entire area of 20% or less of the length of the blank 7 from the longitudinal center of the blank 7 to both sides of the longitudinal direction. In addition to having the portion 8b, it is desirable that at least a region not longer than 10% of the length of the blank in the longitudinal direction from both ends in the longitudinal direction does not have a cut-off portion.

First, the bending and drawing blank 7 heated to a predetermined temperature not lower than the Ac ₁ transformation point is arranged at a predetermined position on the blank holder 2. Next, as shown in FIG. 3E (cross section AA ′ in FIG. 1A) and FIG. 3A (cross section BB ′ in FIG. 1A), the die 1 and the pad 4 is simultaneously lowered, the two blank holding margins 8 b are restrained by the die 1 and the blank holder 2, and the blank 7 is sandwiched by the punch 3 and the pad 4.

  Next, as shown in FIG. 3D (cross section AA ′ in FIG. 1A) and FIG. 3B (cross section BB ′ in FIG. 1A), bending and drawing are performed. The die 1 and the blank holder 2 are lowered while the blank 7 is restrained. The portion where the tension is generated by the restriction of the cut-off portion 8b is drawn, and the other portions are bent. The bending and drawing blank 7 is quenched by contacting the mold at the bottom dead center.

  Thus, when the center pillar outer is formed by hot bending and drawing using the bending and drawing blank 7, the cut-off portion 8 b is restrained by the die 1 and the blank holder 2. Thereby, since tension is generated in the width direction of the bending and drawing blank 7, the generation of wrinkles is suppressed or eliminated.

  Since the bending and drawing blank 7 of the present embodiment has a cut-off portion 8b, it is necessary to perform trim processing for removing the cut-out portion 8b after bending and drawing. At this time, when trimming is performed by shearing, as shown in FIG. 4, bending and drawing products are horizontally arranged, but the cut-off portion 8b is arranged in the longitudinal direction of the bending and drawing products. Since it exists in the part 7-1 located in the center and basically does not exist in the remaining part 7-2, in the part where the cut-off part 8b exists, the shear angle 10 is small, for example, 20 ° or less, and the shear width is small. Trimming is easy because it is short. Even in the case of performing trim processing by laser, since the trim line is short, the cost and man-hour required for trim processing are reduced, and at the same time, the processing time is shortened.

As described above, according to the present embodiment, the center pillar outer panel is formed by hot press forming while suppressing or eliminating the generation of wrinkles while suppressing the increase in cost and man-hour required for trim processing after forming as much as possible. Can be manufactured.
(Embodiment 2)
Next, a second embodiment will be described. In the following description, parts that are different from the above-described first embodiment will be described, and the same parts will be denoted by the same reference numerals, and redundant description will be omitted.

  FIG.1 (c) and FIG.1 (d) are explanatory drawings which show the outline of the die for hot press moldings of the center pillar outer used in this Embodiment. 3 (f) to 3 (i) are explanatory views showing the hot pressing process in the present embodiment, and FIGS. 3 (f) and 3 (g) show the drawing, and FIG. (H) and FIG. 3 (i) show bending.

This embodiment is different from the first embodiment in that a groove 18 extending in the longitudinal direction is provided in a part of a bent and drawn product by bending and drawing.
In the present embodiment, a die comprising the die 1, the blank holder 2, the punch 15 having a concave shape, and the pad 16 having a convex shape shown in FIGS. 1C and 1D, and FIG. And a bending and drawing blank 7 shown in FIG. As described above, the bending and drawing blank 7 is constrained (held) by the portion 8a that becomes the product part after bending and drawing, the die 1 and the blank holder 2, and is removed by trimming after bending and drawing. The cut-out portions 8b and 8b are provided.

First, as shown in FIG. 3 (f), the bending and drawing blank 7 heated to a predetermined temperature range equal to or higher than the Ac ₁ transformation point is arranged at a predetermined position on the blank holder 2. Next, the die 1 and the pad 16 are lowered simultaneously, the cut-off portion 8b is restrained by the die 1 and the blank holder 2, and the bending and drawing blank 7 is sandwiched between the punch 15 and the pad 16. FIG. 3F shows the AA ′ cross section in FIG.

  Next, as shown in FIG. 3G, the die 1 and the blank holder 2 are lowered while the bending and drawing blank 7 is restrained. As a result, tension is generated in the portion 7-1 having the cut-off portion 8b, resulting in drawing. On the other hand, no tension is generated in the remaining portion 7-2 that does not have the cut-off portion 8b, and bending is performed. FIG. 3G is a cross-sectional view taken along the line A-A ′ of FIG. The bending and drawing blank 7 is quenched by contact with the mold at the bottom dead center of molding, and the cut-off portion 8b is removed by trim processing after molding, and a center pillar outer as a product is obtained.

  This product is provided with a groove portion 17 extending in the longitudinal direction at least in a part in the longitudinal direction, that is, in a portion where drawing is performed. For this reason, this center pillar outer has high bending strength, and collision safety performance improves. The groove portion 17 is desirably provided in an upper side region having a smaller wall height than the lower side. The depth of the groove portion 17 is not particularly limited. However, due to restrictions when the center pillar outer is mounted on the vehicle body, it may be practically set to a depth equal to or lower than the wall height in the cross section of the molded product in which the groove portion 17 is formed. desirable. From the viewpoint of high strength, the depth of the groove portion 17 is desirably 25% or more of the wall height in the cross section of the molded product in which the groove portion 17 is formed.

  According to the present embodiment, generation of wrinkles is suppressed or eliminated without increasing the cost and man-hours required for trim processing after molding, and hot press molding provides high bending strength and high collision safety performance. An improved center pillar outer panel can be produced.

  Next, the present invention will be described more specifically with reference to examples.

  In the example of the present invention, the bending and drawing blank 7 shown in FIG. 2 (c) having the steel composition shown in Table 1 (remainder: Fe and impurities) is shown in FIGS. 1 (a) and 1 (b). A center pillar outer was manufactured by performing hot bending and drawing press molding using a press apparatus having a die consisting of a die 1, a blank holder 2, a punch 3 and a pad 4 shown. And the generation | occurrence | production condition of wrinkles and trim workability were evaluated.

  The dimensions of the manufactured center pillar outer are a longitudinal length of 1200 mm, an upper side end width of 200 mm, a lower side end width of 440 mm, and a longitudinal center width of 160 mm. Further, the molding depth (wall height) on the upper side is 30 mm, the molding depth (wall height) on the lower side is 75 mm, and the wall height is from 400 mm to 600 mm from the end on the upper side. Changes rapidly. As for the dimensions of the blank, the length in the longitudinal direction is 1210 mm, the end width on the upper side is 200 mm, the end width on the lower side is 440 mm, and the length from the end on the upper side to the position of 350 mm to 750 mm in the longitudinal direction. A cut-off portion 8b having a width of a maximum of 25 mm is provided in an area of 400 mm.

  Moreover, with respect to the bending blank 6 shown in FIG. 2 (b) as a comparative example 1 and having a shape adjusted in advance so as to have a product shape after molding, it is shown in FIG. 1 (a) and FIG. 1 (b). Using a press device having a die consisting of a die 1, a punch 3 and a pad 4, a blank molded product is obtained by performing hot press molding by bending without using the blank holder 2, and this is similarly evaluated. did.

  Further, as shown in FIG. 2 (a) as Comparative Example 2, an aperture comprising a part 5a that becomes a product shape after molding and a part 5b (cut-off part) constrained (held) by a die 1 and a blank holder 2 on the entire periphery thereof. Hot drawing press molding is performed on a molding blank 5 using a press device having a die composed of a die 1, a blank holder 2, a punch 3, and a pad 4 shown in FIGS. 1 (a) and 1 (b). To obtain a draw-formed product and evaluated in the same manner.

Bending and drawing, which are examples of the present invention, were performed according to the following procedure.
(1) The bending and drawing blank 7 is heated to 920 ° C. at a heating rate of 6 ° C./second in a heating furnace, and then held at this temperature for 100 seconds.
(2) The heated bending and drawing blank 7 is quickly transported into the mold shown in FIGS. 1 (a) and 1 (b) by the transport device and placed at a predetermined position on the blank holder 2. To do.
(3) The die 1 and the pad 4 are lowered simultaneously, the die 1 and the blank holder 2 restrain the cut-off portion 8b of the bending and drawing blank 7, and the punch 3 and the pad 4 are used for bending and drawing. Insert the blank 7. The state of the AA ′ cross section of FIG. 1A at this time is shown in FIG. Further, FIG. 3A shows the state of the BB ′ cross section.
(4) The die 1 and the blank holder 2 are lowered while the cut-off portion 8b is restrained. Tension is generated in the portion having the cut-off portion 8b and drawing is performed, and the portion not having the cut-out portion 8b is bending. The state of the AA ′ cross section of FIG. 1A at this time is shown in FIG. 3D, and the state of the BB ′ cross section is shown in FIG. 3B. The bending and drawing blank 7 is quenched by contacting the mold at the bottom dead center.

Moreover, the bending which is the comparative example 1 was performed in the following procedure.
(1) The bending blank 6 is heated to 920 ° C. at a heating rate of 6 ° C./second in a heating furnace, and then held at this temperature for 100 seconds.
(2) The heated bending blank 6 is quickly conveyed into the mold shown in FIGS. 1 (a) and 1 (b) by the conveying device and placed at a predetermined position on the punch 3.
(3) The die 1 and the pad 4 are lowered simultaneously, and the bending blank 6 is sandwiched between the punch 3 and the pad 4. FIG. 3C shows the state of the AA ′ cross section and the BB ′ cross section in FIG.
(4) While sandwiching the bending blank 6, the bending blank 6 is bent by the die 1 to form a three-dimensional shape to obtain a molded product. FIG. 3D shows the state of the AA ′ cross section and the BB ′ cross section in FIG. The bending blank 6 is quenched by contacting the mold at the bottom dead center.

Furthermore, the draw forming as Comparative Example 2 was performed according to the following procedure.
(1) The draw blank 5 is heated to 920 ° C. at a heating rate of 6 ° C./second in a heating furnace, and then held at this temperature for 100 seconds.
(2) The heated drawing blank 5 is quickly transported into the mold shown in FIGS. 1A and 1B by the transport device, and is placed at a predetermined position on the blank holder 2.
(3) The die 1 and the pad 4 are lowered at the same time, and the die 1 and the blank holder 2 restrain a part of the drawing blank 5 (the cut-off portion 5b), and the punch 3 and the pad 4 hold the drawing blank 5 Pinch. FIG. 3A shows the state of the AA ′ cross section and the BB ′ cross section in FIG.
(4) The die 1 and the blank holder 2 are lowered while a part of the drawing blank 5 (cut-off portion 5b) is constrained, the drawing blank 5 is pressed against the punch 3, and the three-dimensional shape is formed by the elongation and inflow of the material. A molded product is obtained by making. FIG. 3B shows the state of the AA ′ cross section and the BB ′ cross section in FIG. The draw blank 5 is quenched by contact with the mold at the bottom dead center.

The Vickers hardness of each of the molded products of the present invention and Comparative Examples 1 and 2 was about 450.
About the inventive product and the molded products of Comparative Examples 1 and 2,
(I) Sensory evaluation of wrinkles generated in the region of 400 to 600 mm in the longitudinal direction from the upper side where the wall height changes rapidly,
(Ii) Measurement of the length of the trim line, and (iii) Angle formed between the trim line and the direction perpendicular to the moving direction of the blade of the shearing mold, that is, the angle and distance of the portion where the shear angle is 60 ° or more Was measured.

  The length of the trim line affects the processing time in the laser trim processing, and the processing time becomes longer as the trim line becomes longer. Further, the shear angle affects the processing difficulty in the trim processing by the shear method, and if this angle is large, the shear processing becomes difficult.

  The evaluation results are summarized in Table 2.

  As shown in Table 2, it can be seen that the molded product of the example of the present invention was free of wrinkles that would be a problem in hot bending molding, and was able to solve the wrinkle problem. In addition, since the trim line is short, the cost for trim processing by the laser method is reduced and the processing time is shortened. Further, even in the trim processing which is a problem in the drawing, the shear angle is about 20 °, and the shear width is short and the trim processing is easy as compared with the case where the drawn product is trimmed into the product shape.

  On the other hand, in the molded product of Comparative Example 1, the wall portion overlapped during bending and wrinkles occurred, and there was a risk of damage to the mold. Further, in Comparative Example 2, although the generation of wrinkles did not occur, a trim line was long and a region where the shear angle was 60 ° or more occurred, and the problem of trim processing could not be solved.

Next, an embodiment in which grooves extending in the longitudinal direction are formed will be described.
Inventive Example 2, as in Inventive Example 1, has the steel composition shown in Table 1 (remainder: Fe and impurities) and is restrained by die 1 and blank holder 2 in addition to part 8a that becomes a product shape after molding. Bending and drawing blank 7 composed of a portion to be held (cut-off portion 8b) is prepared, and die 1, blank holder 2, and punch having a concave shape shown in FIGS. 1 (c) and 1 (d) The center pillar outer was subjected to hot bending and drawing press molding using a press apparatus having a die composed of 15 and a pad 16 having a convex shape. Thereafter, the wrinkle generation state and trim processability of this molded product were evaluated in the same manner as in Example 1.

  The dimensions of the manufactured center pillar outer are a longitudinal length of 1200 mm, an upper side end width of 200 mm, a lower side end width of 440 mm, and a longitudinal center width of 160 mm. Further, the molding depth (wall height) on the upper side is 30 mm, the molding depth on the lower side is 75 mm, and the wall height changes abruptly in the region from 400 mm to 600 mm in the longitudinal direction from the end on the upper side. .

  In addition, as shown in FIG. 1 (c), a length of 400 mm, a width of 25 mm, and a depth in a region from 100 mm to 500 mm in the longitudinal direction from the end on the upper side in the longitudinal direction of the center pillar outer, A groove 17 having a uniform trapezoidal cross section in the longitudinal direction of 25 mm was formed. The wall height in the region from the position of 100 mm to the position of 500 mm in the longitudinal direction from the end on the upper side is 30 mm or more and 50 mm or less. As for the dimensions of the blank, the length in the longitudinal direction is 1210 mm, the end width on the upper side is 200 mm, the end width on the lower side is 440 mm, and the length from the end on the upper side to the position of 350 mm to 750 mm in the longitudinal direction. A cut-off portion 8b having a maximum width of 30 mm is provided in an area of 400 mm.

  Moreover, it shows to FIG.1 (c) and FIG.1 (d) with respect to the blank 6 for bending molding shown in FIG.2 (b) as a comparative example 3 and which shape was adjusted previously so that it might become a product shape after shaping | molding. Using a press apparatus having a die composed of a die 1, a punch 15 having a concave shape, and a pad 16 having a convex shape, the blank holder 2 is bent without using it to obtain a molded product. Evaluation was performed.

The molding of Invention Example 2 was performed according to the following procedure.
(1) The bending and drawing blank 7 is heated to 920 ° C. at a heating rate of 6 ° C./second in a heating furnace, and then held at this temperature for 100 seconds.
(2) The heated bending and drawing blank 7 is quickly transported into the mold shown in FIGS. 1 (c) and 1 (d) by the transport device and placed at a predetermined position on the blank holder 2. To do.
(3) The die 1 and the pad 16 are lowered at the same time, the cut-off portion 8b of the blank 7 is restrained by the die 1 and the blank holder 2, and the bending and drawing blank 7 is sandwiched between the punch 15 and the pad 16. FIG. 3F shows the state of the AA ′ cross section in FIG.
(4) The die 1 and the blank holder 2 are lowered while the cut-off portion 8b is restrained. Locations where tension is generated by the cut-off portion 8b are drawn, and locations where no other tension is generated are bending. The state of the AA ′ cross section in FIG. 1C at this time is shown in FIG.

The molding of Comparative Example 3 was performed according to the following procedure.
(1) The bending blank 6 is heated to 920 ° C. at a heating rate of 6 ° C./second in a heating furnace, and then held at this temperature for 100 seconds.
(2) The heated blank 6 for bending is quickly conveyed into the mold shown in FIGS. 1C and 1D by the conveying device, and is arranged at a predetermined position on the punch 15.
(3) The die 1 and the pad 16 are lowered simultaneously, and the bending blank 6 is sandwiched between the punch 15 and the pad 16. The state of the AA ′ cross section of FIG. 1C at this time is shown in FIG.
(4) A molded product is obtained by sandwiching the bending blank 6 with the die 1 and bending it to create a three-dimensional shape. FIG. 3I shows the state of the AA ′ cross section in FIG. The bending blank 6 is quenched by bringing it into contact with the mold at the bottom dead center of molding to increase the strength.

About Invention Example 2 and Comparative Example 3,
(Iv) The sensory evaluation of wrinkles generated in the region from the position of 400 mm to the position of 600 mm from the end on the upper side where the wall height changes rapidly was performed.

As a result, in the example of the present invention, even in the evaluation (iv), the wrinkles were eliminated, and there was no problem in the surface quality.
In contrast, in Comparative Example 3, wrinkles occurred in the evaluation (iv). That is, in the region from the 400 mm position to the 600 mm position from the end on the upper side, the wall portion overlaps during bending and there is a risk of damage to the mold, so the molding must be stopped halfway. .

1 (a) and 1 (b) are explanatory views showing the outline of a center pillar outer hot press-molding die used in Embodiment 1, and FIG. 1 (c) and FIG. 1 (d). ) Is an explanatory view showing an outline of a hot press-molding die for the center pillar outer used in the second embodiment. 2A and 2B are explanatory views showing outlines of various blank shapes of the center pillar outer, in which FIG. 2A shows a drawing blank, FIG. 2B shows a bending blank, and FIG. (C) shows the blank for bending and drawing according to the present invention. 3 (a) to 3 (i) are explanatory views showing a hot pressing process, and FIGS. 3 (a) and 3 (b) show drawing, and FIGS. 3 (c) to (e). ) Shows bending, FIG. 3 (f) and FIG. 3 (g) show cases where grooves are formed by drawing, and FIGS. 3 (h) and 3 (i) show cases where grooves are formed by bending. Indicates. It is explanatory drawing which shows the outline of the angle which the direction perpendicular | vertical to the moving direction of the blade of a shear metal mold | die and the trim line of a center pillar outer in the case of performing trim processing by shearing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Die 2 Blank holder 3 Punch 4 Pad 5 Drawing molding blank 5a Product part 5b Cut-off part 5c Molded product 6 Bending molding blank 7 Bending and drawing molding blank 7-1 According to the present invention Part 7-2 Remaining Part 8a Product part 8b Cut-out part 9 Molded trim line 10 Angle 11 formed by the trim line in the longitudinal center of the molded product and the direction perpendicular to the moving direction of the blade of the shearing die Angle formed by the trim line on the part wall and the direction perpendicular to the moving direction of the blade of the shearing mold 12 T-shaped part part wall 13 Trim line 14 of the drawn product Position 15 where the wall height changes suddenly Concave shape Punch 16 having a pad 17 having a convex shape groove shape (concave shape)
18 Groove shape (convex shape)

Claims (5)

A method of manufacturing a center pillar outer panel by inserting a blank heated to a predetermined temperature into a mold and hot-pressing the molded product, and trimming the molded product, wherein the hot-press molding is performed At least both ends in the longitudinal direction excluding drawing and forming the portion of the blank including at least a part of a region of 30% or less of the length of the blank on both sides in the longitudinal direction from the longitudinal center of the blank. A method of manufacturing a center pillar outer panel, characterized in that the center pillar outer panel is formed by a combination with bending in the remaining portion including a region of 10% or less of the length of the blank in the longitudinal direction . Said portion of the length of 30% or less of the area of the blank, method of manufacturing the center pillar outer panel according to claim 1 which is all of 20% or less of the area of the length of the blank. The method of manufacturing a center pillar outer panel according to claim 1 , wherein the molded product includes a groove portion that extends in the longitudinal direction at least in a part of the longitudinal direction of the molded product. The blank has a cut-off portion that is constrained by the die and blank holder used in the drawing and is removed by the trim processing, and the trim processing is performed on at least a part of the remaining portion. The manufacturing method of the center pillar outer panel of any one of Claim 1 to Claim 3 which does not have the truncation part removed by this. It is subjected to hot press molding, and has cut-off portions in all regions of 20% or less of the length of the blank on both sides in the longitudinal direction from the center in the longitudinal direction of the blank, and at least from both ends in the longitudinal direction. The region having 10% or less of the length of the blank in the longitudinal direction does not have a cut-off portion , and the region having the cut-out portion is subjected to drawing, and the region having no cut-out portion is A blank for a center pillar outer panel, which is used for bending .

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