JP2019098376A - Method for manufacturing press molding - Google Patents

Abstract

To manufacture a press molding having a flange subjected to stretch-flange molding, in one process and at low costs, without changing a design of a shape of the flange, without depending on a punching condition and without causing cracking of the stretch-flange due to decrease in plate thickness caused by a concentration of tensile strain.SOLUTION: A press molding 31 having a stretch flange 32 is manufactured by performing press molding after forming a hole penetrating in a plate thickness direction in a specific region of a blank 30. The specific region is a region which is press-molded on a top plate 33 led through a ridge line 34 to a curved line of a vertical wall 32 in which cracking of a stretch flange is caused by press molding in a planar view orthogonal to the top plate 33 in the planar view, which includes a position separated by a distance of 0-10 mm (preferably 0-5 mm) from an arbitrary one point in a direction crossing a contact line m in the arbitrary one point P on a first R stop 35.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a press-formed product.

  For example, in the case of manufacturing a floor cross member which is a component of a car body by press forming, stretch flange forming is used. As a method of improving stretch flange formability, a method of devising the shape of the blank, a method of improving the properties of the end face of the stretch flange formed flange, and further disperse the strain of the end of the stretch flange formed flange Methods etc. are known.

  In recent years, in order to improve the fuel efficiency of a car and the safety at the time of a collision, component parts of a car body are being promoted to reduce the thickness by increasing the strength. For this reason, a high tensile steel plate having a tensile hardness of 590 MPa or more, and further 980 MPa or more is used as a material of a component of an automobile body. Stretch flange formability falls with such high strengthening.

  FIG. 6 (a) is an explanatory view showing an example of the blank 11 of the press-formed product 10 having the extension flange-formed flange 12, and FIG. 6 (b) is an explanatory view showing the press-formed product 10. A case is considered in which the flange 12 and the top plate 14 are formed on the blank 11 by press forming, and the press-formed product 10 shown in FIG. 6B is manufactured.

  For example, as shown in FIG. 6 (b), when forming the flange 12 bent and formed along the concave outer periphery by press forming, the portion of the blank 11 formed into the flange 12 is subjected to tensile deformation during processing The tensile stress acts on this part. For this reason, in a portion formed in the center of the concavely curved flange 12, tensile stress is concentrated to cause tensile strain, and therefore, the plate thickness is reduced. When the plate thickness is greatly reduced, machining cracks occur at the end of the flange 12.

  FIG. 7 is an explanatory view showing an apparatus 20 for manufacturing a press-formed product 10 having a flange 12 according to the prior art.

  As an example of forming the flange 12 by press forming, as shown in FIG. 7, the blank 21 is stretch flanged using the punch 22, the die 23 and the blank holder 24. The blank holder 24 holds the blank 21 together with the die 23 to adjust the inflow of the material, and also prevents the occurrence of wrinkles.

  The blank holder 24 does not necessarily have to be in close contact with the blank 21, and a gap may be present between the blank holder 24 and the blank 21. Using this apparatus 20, the flanges 12 are formed by stretch-flanging by relatively moving the punch 22 and pushing the blank 21 fixed by the die 23.

  In the press-formed product 10 in which the flange 12 and the top plate 14 are formed, the top plate portion 14 has a concave outer peripheral portion recessed inward, and the concave outer peripheral portion becomes a bending line 13. When molding the flange 12, relative to the direction of the straight line A, that is, in the direction normal to the center of the end of the flange in general, relative to the direction of the straight line B, that is, the normal direction to the end of the flange Compression occurs. As a result, in the end portion C which is the central portion of the flange 12, the tensile strain is concentrated generally in the tangential direction of the flange 12, so that the plate thickness may be reduced and a crack may occur.

  FIG. 8 is a contour view showing increase and decrease of the plate thickness of the press-formed product 10 having the flange 12 manufactured by the conventional method.

  As shown in the contour diagram of FIG. 8, it can be seen that the plate thickness is greatly reduced near the center of the formed flange 12. This phenomenon is particularly likely to occur in high strength steel plates having a tensile strength of 590 Mpa or more, and the tendency becomes remarkable as the tensile strength increases.

  Patent Document 1 has a substantially grooved cross section having a top plate, a ridge line and a vertical wall, and a flange which is stretch flanged over the ridge line and the top plate and the vertical wall positioned on both sides of the ridge line among longitudinal ends. There is disclosed a method of manufacturing a press-formed product made of high-tensile steel sheet having the In this manufacturing method, by dispersing strain concentration of the flange, stretch flange formability is improved without providing a notch in the flange or reducing the yield of the material.

  Patent Document 2 discloses a press-forming method of a press-formed product in which a vertical wall having a curve that is convexly curved toward the base side is formed. In this method, the part on the boundary side with the deformation part of the base and the outer part of the deformation part are separately restrained. And the part which becomes the vertical wall of a deformation | transformation part is shear-deformed in a plate surface. This causes a flow of material from the bend towards the part away from the bend.

  Further, Patent Document 3 discloses a method of manufacturing a press-formed product having a stretch-flanged flange. In this method, a ridge is extended at the outer peripheral edge of the end of the flange so as to surround the outer peripheral edge, and a step-shaped portion bent in the thickness direction is formed to suppress stretch flange cracking.

International Publication No. 2013/191256 brochure International Publication No. 2016/031159 brochure Patent No. 6052478 specification

  In the invention disclosed by Patent Document 1, the molding site of the first process and the molding site of the second process have to be changed, and two processes are essential. For this reason, the manufacturing cost of the press-formed product is increased.

  The invention disclosed by Patent Document 2 requires two restraints, and the movement of one restraint during pressing becomes complicated. For this reason, the manufacturing cost of the press-formed product is increased.

  Furthermore, the invention disclosed by Patent Document 3 requires a step of forming a step-shaped portion and a step of forming a vertical wall and a flange, and the two steps are essential. For this reason, the manufacturing cost of the press-formed product is increased.

  An object of the present invention is to provide a method for producing a press-formed product, and in particular, it is possible to reduce the thickness of a flange of a stretch-flanged press-formed product, in particular, without changing the shape of the flange end. It is an object of the present invention to provide a method of manufacturing a restricted stretch flanged press-formed product.

  In order to solve the above-mentioned problems, the inventor of the present invention has intensively studied, and by forming a hole in a part of a portion of a blank formed on a top plate and performing press forming, the top plate in stretch flange forming is formed. Can improve the stretch flange formability (it can improve the forming limit by suppressing the crack), because it is possible to release the minimum principal stress (compression) of the portion to be reduced and thereby to reduce the maximum principal stress (tension) in stretch flange forming. The present invention has been completed in consideration of what can be done). The present invention is as listed below.

(1) A method for producing a press-formed product by performing press forming on a blank using a punch and a die,
The press-formed product is connected to a top plate having a first radiused end (first bending corner), a ridge line continuous with the first radiused end, a ridge line having a second radiused end (second bending corner), and a second radiused end. Has a cross section with a vertical wall, and
The first R-stop, the ridgeline, the second R-stop, and the vertical wall are convex toward the inside of the cross section in a part or all of the extending directions in a plan view seen from the direction orthogonal to the top plate Make a curve of
A method for producing a press-formed product, wherein the press-forming is performed after providing a hole penetrating in a thickness direction in the following specific region of the blank;
Specific area: an area which is press-formed on the top plate continuous to the curved portion of the vertical wall via the ridge line in the plan view, and a tangent m at any one point on the first R stop An area including a position at which the distance a from the arbitrary one point is separated by 0 to 10 mm (preferably 0 to 5 mm) in the intersecting direction.

  (2) The method for producing a press-formed product according to any one of the items (1), wherein the length L of the hole in the direction intersecting the tangent m is 20 mm or more in the plan view.

  (3) The manufacturing method of the press-formed article according to 1 or 2, wherein the length W of the hole in the direction parallel to the tangent line m is 6 mm or more in the plan view.

  (4) The crossing direction is a direction included in two directions which make an acute angle of ± 15 ° with respect to the direction orthogonal to the tangent line in the plan view, according to any one of 1 to 3 Of the press-formed product of

(5) Assuming that the radius of curvature in plan view of the first R end is R (mm) and the height of the vertical wall is h (mm), the stretch flange ratio (%) = {h / (R) -H)} × 100
The manufacturing method of the press-formed article according to any one of the items 1 to 4, wherein is 50% or more.

  (6) The method for producing a press-formed product according to any one of Items 1 to 5, wherein the blank is a steel plate having a tensile strength of 590 to 1870 MPa.

  (7) The method for producing a press-formed product according to any one of the items 1 to 6, wherein the blank is a steel plate having a thickness of 0.7 to 3.5 mm.

  According to the present invention, a press-formed product having a stretch-flanged flange is formed into a plate thickness by concentration of tensile strain at a low cost by one process without redesigning the shape of the flange and without relying on punching conditions. Can be manufactured without causing stretch flange cracking due to the reduction of

FIG. 1 (a) is an explanatory view showing a press-formed product having a stretch-flange-formed longitudinal wall manufactured according to the present invention, and FIG. 1 (b) is a press-formed product by pressing a blank. It is explanatory drawing which shows the condition which manufactures notionally. FIG. 2A is an explanatory view showing a press-formed product, and FIG. 2B is a plan view showing the hole 37 in the specific region B in an enlarged manner. FIG. 3 (a) is a plan view showing the shape of the punch used in this example, and FIG. 3 (b) is a side view of the mold used in this example. ) Is a plan view showing the shape of the blank used in this example. FIG. 4 is a plan view showing the installation position of the hole in the embodiment. FIG. 5 is a contour diagram showing an analysis result. Fig.6 (a) is explanatory drawing which shows an example of the blank of the press-formed product which has the longitudinal wall by which extension flange formation was carried out, and FIG.6 (b) is explanatory drawing which shows a press-formed product. FIG. 7 is an explanatory view showing an apparatus for manufacturing a press-formed product having a stretch-flanged flange according to the prior art. FIG. 8 is a contour view showing increase and decrease in thickness of a press-formed product having a stretch flange-formed longitudinal wall manufactured by a conventional method.

The invention will be described with reference to the accompanying drawings.
FIG. 1 (a) is an explanatory view showing a press-formed product 31 having a stretch flange-formed vertical wall 32 manufactured according to the present invention, and FIG. FIG. 10 is an explanatory view conceptually showing the situation of manufacturing the press-formed product 31.

  As shown in FIGS. 1 (a) and 1 (b), in the present invention, the blank 30 is stretch-flanged by pressing using a punch and die (not shown) and, if necessary, a die pad. The press-formed product 31 having the vertical wall 32 is manufactured.

  The press-formed product 31 has a cross section having a top plate 33, a ridgeline 34, and a vertical wall 32. The top plate 33 is flat and has a first radiused end 35 (first bending corner). The ridge 34 has a curved surface shape, and is continuous with the first R stop 35 and has a second R stop (second bending corner) 36. The vertical wall 32 is flat and continues to the second R stop 36.

  Furthermore, the first R stop 35, the ridgeline 34, the second R stop 36, and the vertical wall 32 extend in the respective extending directions in plan view (view A in FIG. 1A) viewed from the direction orthogonal to the top plate 33. In a part or all of (longitudinal direction), a convex curve directed to the inside of the cross section of the press-formed product 31 is formed.

2 (a) is an explanatory view showing the press-formed product 31, and FIG. 2 (b) is a plan view (enlarged view in the direction of arrow A in FIG. 1 (a)) showing the hole 37 in the specific region B in an enlarged manner. is there.
In the present invention, after the hole 37 penetrating in the thickness direction is provided in a specific area of the blank 30, the above-described press forming is performed.

  Here, as shown in FIG. 1 (a) and FIG. 2 (b), the specific region B is a ridgeline 34 in the range C of the curved portion of the vertical wall 32 in which stretch flange cracking occurs by press forming in the plan view. 0 through a distance a from an arbitrary one point P in a direction intersecting a tangent m at an arbitrary one point P on the first R stopper 35 in a region which is press-formed on a continuous top plate 33 through It means an area including a position Q separated by 10 mm, preferably 0-5 mm. That is, the distance a in FIG.2 (b) is 0-10 mm, Preferably it is 0-5 mm.

  A hole 37 is opened in a specific area B which is a part of a portion to be formed on the top plate 33 of the blank 30 and press forming is performed, thereby releasing the minimum principal stress (compression) of the portion to be formed on the top plate 33 Thus, the maximum principal stress (tension) of the vertical wall 32 can be reduced. For this reason, the forming limit can be increased to suppress stretch flange cracking, and stretch flange formability can be improved.

  According to the present invention, without changing the design of the shape of the vertical wall 32 for the press-formed product 31 having the stretch flange 32, the plate thickness due to concentration of tensile strain can be achieved at low cost by one process without relying on punching conditions. Can be manufactured without causing stretch flange cracking due to the reduction of

Next, preferred embodiments of the present invention will be described.
(I) Length L in a direction intersecting the tangent m of the hole 37
As shown in FIG. 2 (b), it is preferable that the length L of the hole 37 in the direction intersecting with the tangent m is 20 mm or more in the plan view (arrow A). If the length L is less than 20 mm, the effect of reducing the minimum principal stress (compression) of the portion formed on the top plate 33 and reducing the maximum principal stress (tension) of the vertical wall 32 can not be sufficiently obtained.

  The upper limit of the length L is not particularly limited from the viewpoint of the above effects, but it is preferably 60 mm or less because it may affect the rigidity of the press-formed product 31 if it is too long.

(Ii) A length W in a direction parallel to the tangent m of the hole 37 (also referred to as a “width” in the present specification)
As shown in FIG. 2B, it is preferable that the length W of the hole 37 in the direction parallel to the tangent m is 6 mm or more in the plan view (arrow A).

If the width W is less than 6 mm, the minimum principal stress (compression) of the portion formed on the top plate 33 is released, and the effect of reducing the maximum principal stress (tension) of the vertical wall 32 can not be sufficiently obtained.
The upper limit of the width W does not have to be particularly defined from the viewpoint of the above effects, but it is preferably 30 mm or less because if it is too wide, the rigidity of the press-formed product 31 may be affected.

(Iii) Installation direction of hole 37 (direction intersecting tangent m)
As shown in FIG. 2 (b), the direction intersecting with the tangent line m is an acute angle of ± 15 ° with respect to the direction orthogonal to the tangent line m (in the present specification, “a deflection angle It is preferable that the direction is included between two directions forming θ.

  If the hole 37 is installed in a direction not included between these two directions, the minimum principal stress (compression) of the portion formed on the top plate 33 is released and the maximum principal stress (tension) of the vertical wall 32 is reduced. You can not get enough.

(Iv) Stretch flange ratio {h / (R−h)} × 100
When the radius of curvature of the first R stop 34 in a plan view (viewed by an arrow A) is R (mm) and the height of the vertical wall 32 is h (mm), it indicates how much the part is extended The stretch flange ratio {h / (R−h)} × 100 is preferably 50% or more. If the stretch flange ratio is less than 50%, the radius of curvature R is large or the height h is small, and the rigidity of the press-formed product 31 may be reduced.

(V) Shape of Longitudinal End of Hole 37 The shape of the longitudinal end of the hole 37 is preferably semicircular with a single radius of curvature that matches the width of the hole 37.

(Vi) Shape of Hole 37 The hole 37 is not limited to the oval shown in FIGS. 2 (a) and 2 (b), and may be an oval, a rectangle, or a rhombus.

(Vii) Installation range of the hole 37 The installation range of the hole 37 is included in the top plate 33 continuous to the range C of the vertical wall 32 via the ridgeline 34, and the plane view R of the ridgeline 34 of the range C It is preferable that the region is included between vertical lines extending to the plate 33 side.

(Viii) Protruding Length It is preferable that the flange length to be formed (protruding length) has a flange length of 7 mm or more, for example, when joining with other members is required.

(Ix) Strength of Blank 31, Thickness of Plate The blank 31 is exemplified as a steel plate having a tensile strength of 590 to 1870 MPa and a thickness of 0.7 to 3.5 mm.

  In the above description, the case where the longitudinal wall (stretch flange) 32 is stretch-flanged on one side of the press-formed product 31 is taken as an example, but the longitudinal wall (stretch flange) is also on the other side facing the one side 32 may be stretch flanged.

  Furthermore, the press-formed product 31 may have an outward facing flange continuous with the vertical wall (stretching flange) 32. When the vertical wall 32 and the two outward flanges are provided, the press-formed product 31 has a hat cross section.

The invention will be described with reference to the examples.
As shown in FIGS. 1A and 1B, the blank 30 was press-formed using a punch, a blank holder and a die to produce a press-formed product 31 having a stretch flange 32.

  FIG. 3 (a) is a plan view showing the shape of the punch used in this embodiment, FIG. 3 (b) is a side view of the mold used in this embodiment, and FIG. 3 (c) is a plan view It is a top view which shows the shape of the blank 30 used by the present Example.

  The unit of the dimension in FIG. 3 (a)-FIG.3 (c) is mm. The plate thickness of the blank 30 was three levels of 0.7, 1.6, and 3.5 mm.

FIG. 4 is a plan view showing the installation position of the hole 37 in the present embodiment.
As shown in FIG. 4, the first R end (first bending corner) 35 of the press-formed product 31 has two curvature radii of R60 and R30. The installation positions of the holes 37 are the center (c) of R30, the straight line (a) on the R30 side, the border (b) with the straight line with R30, the border (d) with R30 and R60, the center (e) of R60, and the straight line Six levels of boundary (f).

  In Table 1, the distance a of the hole 37, the width W, the length L, the deflection angle θ, the installation position, the height h of the vertical wall 32, and the radius of curvature of the first R blind 34 in plan view (view from arrow A). R, stretch flange ratio λ, presence or absence of the hole 37, strength of the blank 30, thickness of the plate, and molding results are collectively shown.

Table 1 No. By contrasting 1 to 7, it can be seen that if the distance a is 0 to 6 mm, the press-formed product 31 can be manufactured without stretch flange cracking.
Table 1 No. By comparing 1, 11, 5 and 12, it can be seen that if the length L is 20 mm or more, the press-formed product 31 can be manufactured without the stretch flange cracking.

Table 1 No. By comparing 1, 8, 5, 9, 10, it can be seen that if the width W is 6 m or more, the press-formed product 31 can be manufactured without causing stretch flange cracking.
Table 1 No. By comparing 1,13,14,15,16,5,17,18,19,20, if the deflection angle θ is within ± 15 °, the press-formed product 31 is manufactured without causing stretch flange cracking. I know what I can do.

  Table 1 No. If the installation position of the hole 37 is on a curve in plan view by comparing 1, 12, 22, 5, 23, 24, and 25, it is possible to manufacture the press-formed product 31 without causing stretch flange cracking. I understand.

  Table 1 No. By comparing 5, 1, 26, 27 with each other, it is understood that the press-formed product 31 can be manufactured without stretch flange cracking if the stretch flange ratio λ is 50% or more.

  Table 1 No. By contrasting 28, 29, 30, 31, 5, 1, 32, 32 with each other, it can be seen that the present invention has the effect of preventing stretch flange cracking with a tensile strength of 590 to 1760 MPa of the blank.

  Furthermore, in Table 1, No. By contrasting 34, 35, 55, 1, 36 and 37, it can be seen that the present invention has the effect of preventing stretch flange cracking with a blank thickness of 0.7 to 3.5 mm.

FIG. 3 (invention examples), no. It is a contour figure which shows the analysis result of 1 (comparative example).
According to the present invention, it can be seen that the maximum thickness reduction rate of the vertical wall (stretch flange) 32 can be reduced by about 3%.

30 Blank 31 Press-formed product 32 Stretch flange (vertical wall)
33 top plate 34 ridge line 35 1st R stop (1st bending corner)
36 Stop at 2nd R (2nd bending corner)
37 hole m tangent P 0 to 10 mm away from any one point Q P

Claims (7)

A method of producing a press-formed product by performing press forming on a blank using a punch and a die,
The press-formed product is connected to a top plate having a first radiused end (first bending corner), a ridge line continuous with the first radiused end, a ridge line having a second radiused end (second bending corner), and a second radiused end. Has a cross section with a vertical wall, and
The first R-stop, the ridgeline, the second R-stop, and the vertical wall are convex toward the inside of the cross section in a part or all of the extending directions in a plan view seen from the direction orthogonal to the top plate Make a curve of
A method for producing a press-formed product, wherein the press-forming is performed after providing a hole penetrating in a thickness direction in the following specific region of the blank;
Specific region: a region which is press-formed on the top plate continuous to the curved portion of the vertical wall via the ridge line in the plan view, and intersects a tangent at any one point on the first R stop An area including a position at which the distance a from the arbitrary one point is 0 to 10 mm in the direction to be.   The method for manufacturing a press-formed product according to claim 1, wherein a length of the hole in a direction intersecting the tangent line is 20 mm or more in the plan view.   The method for manufacturing a press-formed product according to claim 1, wherein a length of the hole in a direction parallel to the tangent in the plan view is 6 mm or more.   The press according to any one of claims 1 to 3, wherein the intersecting direction is a direction included between two directions forming an acute angle of ± 15 ° with respect to the direction orthogonal to the tangent line in the plan view. Method of producing a molded article.   Assuming that the radius of curvature in plan view of the first R end is R (mm) and the height of the vertical wall is h (mm), the stretch flange ratio {h / (R−h)} × 100 The method for producing a press-formed product according to any one of claims 1 to 4, which is 50% or more.   The method for manufacturing a press-formed product according to any one of claims 1 to 5, wherein the blank is a steel plate having a tensile strength of 590 to 1870 MPa.   The method for producing a press-formed product according to any one of claims 1 to 6, wherein the blank is a steel plate having a thickness of 0.7 to 3.5 mm.

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