JP5569429B2 - Hat channel member press molding method - Google Patents

Description

  The present invention relates to a press forming method for a hat channel member using a metal plate, and more particularly to a press forming method for a hat channel member having excellent dimensional accuracy.

  It is well known that when a metal plate such as a steel plate is press-formed, the molded product after mold release undergoes springback or twist due to elastic recovery, resulting in failure to obtain a predetermined dimensional accuracy, that is, a defective shape. Yes.

  In recent years, in car body members for automobiles where the strength of steel plates as materials has been increasing, such problems of shape defects have been highlighted, and several metal sheet press forming methods that are less likely to cause shape defects have been proposed. Among them, as a countermeasure against the slant of the vertical wall portion and the angle defect of the hat head corner that occur when drawing a hat channel member having a hat-shaped cross section as shown in FIG. Is a hat-shaped metal part (hat channel member) that is formed of a ceiling portion (hat head), a vertical wall portion, and a flange portion, and is press-formed into a U-shaped or C-shaped cross-sectional shape, A hat-type metal part having a plurality of holes with a width of 10 mm or less in which a residual stress after press forming is relaxed at least in a part of a vertical wall part and a manufacturing method thereof are disclosed. Further, Patent Document 2 includes a punch and a die, and a convex portion extending in the die direction is provided in the vicinity of the punch head. The clearance between the convex portion and the die, and the punch side wall portion where the convex portion is not provided There is disclosed a press die for a hat channel member that is set so as to satisfy a specific relationship between the clearance and the clearance.

JP 2008-778 Japanese Unexamined Patent Publication No. 2009-23000

  However, the hat-type metal part described in Patent Document 1 has a problem in that strength is reduced because the vertical wall portion has a plurality of holes (voids) having a width of 10 mm or less. Further, when the press mold for the hat channel member described in Patent Document 2 is used, there are problems such as a decrease in mold rigidity and an increase in the number of steps for manufacturing the mold.

  The present invention is capable of preventing strength reduction without causing problems such as reduction in mold rigidity and increase in the number of manufacturing steps, and press molding of a hat channel member in which warpage of a vertical wall portion and angle failure of a head corner are unlikely to occur. It aims to provide a method.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that the hat is positioned at two positions separated by a predetermined length along the longitudinal direction of the hat head of the hat channel member. It has been found that it is effective to trim the convex part to a predetermined length after drawing so that a convex part having a predetermined height is formed over the width direction of the head.

The present invention has been made based on such knowledge, the metal plate having a hat-shaped cross-sectional shape, when the hat is drawn to a hat channel member having a length L in the longitudinal direction of the hat head, the hat Convex portions having a height D satisfying the following formula (1) are formed over the width direction of the hat head at two positions separated by a length L along the longitudinal direction of the head. Thus, after the drawing, there is provided a press forming method of a hat channel member, wherein the convex portion is trimmed to make the length of the hat head in the longitudinal direction L.
D × (1 / sinθ-1.1 / tanθ) ≧ 0.05 × L + 0.1 × S ... (1)
Where θ is the angle (°) between the inclined part of the convex part and the horizontal part of the hat head, S is the distance from the starting point of the inclined part of the convex part to the latest trim position, and 30 ° ≦ θ ≦ 90 °.

  The press molding method of the present invention has a hat-shaped cross-sectional shape, and the above-described width direction of the hat head at two positions separated by a length L along the longitudinal direction of the hat head. This can be realized by drawing using a punch provided with a convex portion having a height D that satisfies Equation (1).

  The press forming method of the hat channel member according to the present invention can prevent a decrease in strength without causing problems such as a decrease in the rigidity of the mold and an increase in the number of manufacturing steps, and can prevent a vertical wall warp and a head corner angle defect. It became possible to form hat channel members that are difficult to generate. The hat channel member press molding method of the present invention is suitable for manufacturing a vehicle body member of an automobile.

It is a figure which shows an example of a hat channel member. It is a figure which shows typically an example of the press molding method of this invention. FIG. 3 is a view showing a longitudinal section of the hat channel member before trim shown in FIG. 2 (a). It is the figure which compared the opening amount W of the hat channel member shape | molded by the press molding method of this invention, and the conventional method.

  FIG. 2 schematically shows an example of the press molding method of the present invention.

  First, as shown in FIG. 2 (a), at two positions separated by a length exceeding the target length L along the longitudinal direction of the hat head, a predetermined height is provided across the width direction of the hat head. Drawing is performed so that a convex portion of length D is formed. At this time, the height D is the angle θ (°) between the inclined part of the convex part defined in FIG. 3 showing the longitudinal section of the hat channel member before trim and the horizontal part of the hat head, and the inclination of the convex part It is necessary to satisfy the relationship of the above formula (1) between the position where the part starts and the distance S to the latest trim position. However, 30 ° ≦ θ ≦ 90 °.

  In this way, when convex portions having a height D satisfying the above equation (1) are formed at both end portions exceeding the length L across the width direction of the hat head, the thickness is increased in the region between the convex portions. The excess state becomes large, and the difference between the tensile stress on the outer surface side and the compressive stress on the inner surface side at the punch shoulder is reduced, that is, the bending stress is reduced, so that the vertical wall warp and head corner angle defect after molding Can be suppressed. On the other hand, if the height D does not satisfy the relationship of the above formula (1), the surplus state is not sufficiently increased in the region between the convex portions, and the bending stress at the punch shoulder cannot be reduced. Occurrence of the sled of the wall and the angle defect of the head corner cannot be sufficiently suppressed.

  After molding, if the convex portions at both ends are trimmed so as to have a predetermined length L, a hat channel member having a target dimensional accuracy as shown in FIG. In addition, since the bending stress at the punch shoulder is small, there is no occurrence of warping of the vertical wall portion or angle failure of the head corner during trimming.

  Such an effect of the present invention can also be obtained by forming a concave portion instead of the convex portion. In this case, the depth D of the concave portion needs to satisfy the relationship of the above formula (1).

  Actually, using a high strength steel plate having a tensile strength of 980 MPa and a plate thickness of 1.6 mm, a hat channel member was manufactured by the press forming method of the present invention and the conventional method, and the opening amount W of the hat was measured. Thus, it can be seen that in the method of the present invention, W is small and higher dimensional accuracy can be obtained. At this time, in order to make the molding conditions uniform, the wrinkle restraining force (BHF) was adjusted so that the plate thickness strains of the vertical wall portions were equal.

Claims (2)

When drawing a metal plate into a hat channel member having a hat-shaped cross-sectional shape and having a length L in the longitudinal direction of the hat head, the metal plate is separated by more than a length L along the longitudinal direction of the hat head. After drawing, so as to form a convex portion having a height D satisfying the following formula (1) over the width direction of the hat head at two positions, the convex portion is trimmed and the hat is trimmed A press forming method of a hat channel member, wherein the length of the head in the longitudinal direction is L;
D × (1 / sinθ-1.1 / tanθ) ≧ 0.05 × L + 0.1 × S ... (1)
Where θ is the angle (°) between the inclined part of the convex part and the horizontal part of the hat head, S is the distance from the starting point of the inclined part of the convex part to the latest trim position, and 30 ° ≦ θ ≦ 90 °. A hat having a hat-shaped cross-sectional shape, at two positions separated by a length L exceeding the longitudinal direction of the hat head, and satisfying the following formula (1) over the width direction of the hat head 2. The press forming method of a hat channel member according to claim 1, wherein the press forming is performed using a punch provided with a convex portion having a height D;
D × (1 / sinθ-1.1 / tanθ) ≧ 0.05 × L + 0.1 × S ... (1)
Where θ is the angle (°) between the inclined part of the convex part and the horizontal part of the hat head, S is the distance from the starting point of the inclined part of the convex part to the latest trim position, and 30 ° ≦ θ ≦ 90 °.

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