JP2008246555A - Blank for press forming and press forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy blank having an optimum intensity distribution corresponding to a forming object, which has improved its drawability and can produce a product without causing breakage even if the product is large-sized and complexly shaped. <P>SOLUTION: An aluminum alloy blank 1 is formed into a predetermined product shape by press forming. The intensity of the blank of a shrink flange deformation area 5, which is in the forming area having a drawing height highest in the product and subjected to shrink flange deformation in press forming, is previously made lower than that of a punch bottom contact area 6, with which the bottom of the punch comes into contact in press forming. Within a range 7, which is a wall part positioned between the shrink flange deformation area and the punch bottom contact area and corresponds to the drawing height, the intensity of the blank is made to continuously transit (vary). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides an aluminum alloy blank (meaning a cut plate material for press molding) in which press formability is improved by providing a strength distribution in the same plate when molding an automobile panel, an automobile part, an electric machine part or the like. And a press molding method using the blank.

  In recent years, automobiles have become more active in reducing the weight by using aluminum alloy plates instead of conventional steel plates for outer plate parts (hoods, doors, fenders, roofs, trunks, etc.) for the purpose of reducing fuel consumption. Yes. For this aluminum alloy plate, Al-Mg-based alloys that emphasize formability and Al-Mg-Si-based alloys whose strength is improved after painting and baking are applied.

  In general, press molding of automobile parts is performed by cutting a steel plate or an aluminum alloy plate from a sheet or coil state into a blank having a size appropriate for a pressed product (molded panel). Then, the blank is processed into a product (panelized) through processes such as drawing (drawing), restructuring, and piercing. However, in the case of an aluminum alloy plate, the formability is worse than that of a steel plate, so in the case of a part shape that requires high formability, cracks and wrinkles may occur during draw forming, and the product may not be formed successfully. is there.

  In the drawing, the load due to the material deformation resistance accompanying the shrinkage deformation of the flange portion of the blank is supported by the punch shoulder portion and formed. At this time, when the breaking resistance of the punch shoulder portion is larger than the deformation resistance of the flange portion, the punch shoulder can be formed without breaking. In addition, the deformation resistance and breaking resistance of the blank both depend on the material strength of each part.

For this reason, if the blank is in contact with the punch shoulder and the blank has a high yield strength and the flange has a low yield strength, the drawability during press molding will be lower than that of a blank with uniform material properties in the same plate. Will improve. As such a blank, there is a locally heated blank in which the material yield strength of the flange portion is locally reduced by heating, and it has been proved by tests that the formability is improved (see Patent Document 1 and Non-Patent Document 1). .
JP 2004-124151 A Outline of Light Metal Society 102nd Spring Meeting (2002), P283-284, “Improvement of deep drawability of 6061 aluminum alloy by local solution process”, Takeshi Nishiwaki, Naoyuki Kintake,

  As described above, a locally heated blank having a difference in strength within the same plate is effective for deep drawing, but the optimum strength distribution varies depending on the pressed product (molded panel) to be molded. And these optimal intensity distributions according to press products were not necessarily clear.

  For this reason, even if there is a difference in strength within the same plate, it is difficult to achieve an optimal strength distribution in a blank for forming an actual press product. The actual situation was that they could not be molded.

  The present invention has been made to solve such problems, and its purpose is to improve the deep drawability by giving the aluminum alloy blank an optimal strength distribution according to the object to be molded, It is to provide a blank capable of obtaining a product without breaking even in a large and complicated shape.

  The gist of the aluminum alloy blank of the present invention for achieving this object is an aluminum alloy blank which is formed into a predetermined product shape by press forming, and in the forming part where the drawing height is the highest among the products, press forming In some cases, the blank strength of the contracted flange deformed part that deforms the contracted flange is set lower in advance than the blank strength of the punched bottom contact part that the punch bottom contacts with at the time of press molding. It is assumed that the blank strength continuously changes (changes) in a range corresponding to the height of the diaphragm that becomes the wall portion sandwiched between the parts.

  Here, the blank strength in the range excluding the punch shoulder R contact portion in the range corresponding to the drawing height that becomes the wall portion sandwiched between both the contracted flange deformation portion and the punch bottom contact portion is continuous. It is preferable to make a transition (change). Moreover, it is preferable that the maximum height of the said wall part in a shaping | molding site | part with the highest said drawing height is 100 mm or more. Moreover, it is preferable to make the blank intensity | strength of the blank area | region used as the bottom of the said product lower than the said punch bottom contact part. Moreover, it is preferable that the material yield strength of the shrinkage flange deformation portion is 60 to 150 MPa, and the material yield strength of the punch bottom contact portion is 150 to 260 MPa.

  In order to achieve this object, the gist of the press molding method of the present invention is a press molding method using the press molding blank of any one of the gist described above, and has a strength distribution according to the shape of the product molded into the blank. This is provided in advance.

  According to the present invention, an optimum intensity distribution can be given to a blank according to a molding object. Therefore, even when a large and complicated shape is deep-drawn using an aluminum alloy blank, a good press-formed product can be obtained without breaking.

  Embodiments of the present invention will be described below in detail with reference to the drawings. First, with reference to FIGS. 1A to 1C, a blank and a forming method for press-molding into a square tube-shaped aluminum alloy product (formed product) will be described below.

  Fig.1 (a) is sectional drawing at the time of shape | molding the blank 1 in a simple square tube shape. In the molding method of FIG. 1A, the blank 1 is sandwiched between a die 3 (positioned on the lower side of the figure) and a blank holder 4 (positioned on the upper side of the figure), and the rectangular tube-shaped punch 2 is held on the die 3. On the other hand, they are moved relative to each other (in the figure, the punch 2 is lowered from the upper side) to form an aluminum alloy product having a rectangular tube shape.

  FIG.1 (b) is a top view of the blank 1 of Fig.1 (a). In the case of an aluminum alloy product (molded product) in the shape of a rectangular tube, assuming a plan shape of the product, when it is approximately superimposed on the plan view of the blank 1 in FIG. The flange deformation part 5 is at the peripheral edge of the blank outer peripheral side, and the contact part 6 with the punch bottom is at the central part on the blank inner side. The contracted flange deformed portion 5 corresponds to, for example, 12 in FIG. 2 described later although the shape is different, and the contact portion 6 with the punch bottom corresponds to 10 in FIG. 2 described later. A region 7 (length h) sandwiched between the two parts corresponds to a vertical wall portion of the product (hereinafter referred to as a wall equivalent portion 7), and a vertical wall portion of the product (for example, FIG. 2 described later). 8 and a height of about h).

  Here, the load generated in the blank 1 at the time of molding is mainly a load generated by the contraction flange deformation resistance at the contraction flange deformation portion 5, and the product is hardly broken by reducing this load. Since the shrinkage flange deformation resistance depends on the blank strength (more strictly speaking, the material yield strength), it is preferable to reduce the blank strength of the shrinkage flange deformation portion 5 in order to reduce the molding load.

  On the other hand, in the punch bottom contact portion 6, the load at the time of molding is supported in the vicinity of contact with the shoulder (shoulder R) of the punch 2. For this reason, it is preferable to increase the blank strength (more strictly speaking, the material proof stress) in the vicinity of contact with the shoulder (shoulder R) of the punch 2. If it does in this way, since blank intensity | strength differs in the outer peripheral part and inner peripheral part of the blank 1, the blank intensity | strength in the meantime will change.

  FIG.1 (c) shows the blank intensity | strength of the short side part of the wall equivalent part 7 of the product (molded article) of the blank 1 of FIG.1 (b). The actual strength distribution is measured by a tensile test or hardness measurement, and shows a hardness distribution that can be measured relatively easily. In the blank 1 for forming the product rectangular tube shape of the example of the present invention, the drawing height h of the wall equivalent portion 7 is constant over the entire area (the entire circumference) of the blank 1 (product). Any part of the wall equivalent part 7 (product wall part 8) is the maximum drawing height equivalent part. Here, the blank strength of the portion 5 that shrinks and deforms at the time of press molding is lower than the blank strength of the punch bottom contact portion 6 that the punch bottom contacts at the time of press molding, and is sandwiched between the both portions 5 and 6. In the wall equivalent part 7 which is the range, the blank intensity continuously changes (changes). In addition, the continuous transition (change) of the blank intensity | strength said by this invention means the blank intensity | strength in the meantime changes (changes) in steps.

  In the present invention, the molding part having the highest drawing height in the product means a whole of the molding part of the concave or convex part having the highest drawing depth among the irregularities in the product (press-molded product). Therefore, the part corresponding to the molding part with the highest drawing height in the product as the blank is the part corresponding to these product parts.

  In general, in the drawing, the higher the drawing height, the easier the breakage occurs, and the moldability becomes severe. Therefore, not only the maximum height portion is taken up, but a region where the strength transitions is provided in the entire region of the concave portion or convex portion including the molding portion having the highest drawing height. For example, in the case of a simple cylindrical shape, it refers to the entire surface of the outer peripheral vertical wall. Further, there may be a portion where the convex portion having the highest drawing depth is provided over the outer periphery of the product, and the drawing height is partially lower than other portions.

  Next, with reference to FIGS. 2A to 2C, blanks and molding for press forming into aluminum alloy product panels (molded product panels) having a relatively complicated rectangular tube shape as compared with the case of FIG. A method will be described. 2A is a plan view of the product, and FIG. 2B is a cross-sectional view of the AA ′ portion of FIG. 2A. FIG.2 (c) shows the blank intensity | strength of each blank site | part corresponded to the product cross section of FIG.2 (b).

  The product panel shape of the example of the invention has a convex portion 11 having the highest drawing depth at the outer peripheral portion of the panel, and the drawing height h is assumed to be 110 mm, which is about 100 mm or more. In addition, a relatively low bottom 10 is formed at the center of the panel. The bottom 10 has a convex portion in a recess, which is a depression, at a position shifted from the center toward the upper side of the figure. And the convex part 11 shape | molded by the comparatively low height which surrounds this bottom part 10 in the outer periphery edge part of this bottom part 10 of a center part.

  Here, as shown in FIG. 2C, the blank strength corresponding to the contracted flange deformation portion 12 is lower than the blank strength corresponding to the punch bottom contact portion that is the convex portion 11. And the blank intensity | strength is changing continuously in the range corresponded to the wall part 8 of the molded product pinched | interposed by these both site | parts. Moreover, in the blank area | region equivalent to the center bottom part 10, intensity | strength is made lower than the blank equivalent site | part 11 which contacts a punch shoulder (shoulder R) at the time of press molding. Therefore, even if it becomes a complicated shape which shape | molds a convex part in the center bottom part 10 by comparatively low height, the fracture | rupture of the blank during shaping | molding can be prevented.

  Next, the embodiment of the present invention shown in FIG. 2 will be described in more detail with reference to FIG. FIG. 3 is a partially enlarged view of only the portion B in FIG. 3A shows a cross-sectional view of the product panel as in FIG. 2B, and FIG. 3B shows the blank strength of each part corresponding to the product panel.

  In FIG. 3A, there are a contact portion 11 with the punch bottom, a wall portion 8, and a contracted flange deformed portion 12 from the center side of the panel, and the wall portion 8 has a contact portion 15 with the punch shoulder R. In the example of the present invention, the blank strength continuously changes (changes) even at the contact portion 15 with the punch shoulder R as indicated by a line 13 indicating that the strength changes (changes).

  When the blank is formed, the load is supported in the vicinity of the contact portion 15 with the punch shoulder R. Therefore, the contact portion 15 with the punch shoulder R is easily broken. Therefore, in the contact portion 15 with the punch shoulder R, the punch shoulder R contact portion has a blank strength comparable to that of the contact portion 11 with the punch bottom at the time of press molding, and out of the range corresponding to the drawing height to be the wall portion 8. The blank intensity in a range excluding 15 may be continuously changed.

  Therefore, the range of the punch shoulder R contact portion 15 may be excluded from the range in which the blank intensity continuously transitions, like the transition line 14 of the intensity due to the blank portion in FIG. Depending on the product shape, the punch shoulder R may break due to bending, so that the peripheral blank strength may be lower than the punch bottom contact portion 6 in order to improve the bending deformability. However, it is not always necessary to remove the punch shoulder R contact portion 15 in the range where the blank strength continuously changes.

  In the panel of the example of the present invention, as described above, the aperture height h that is the maximum height of the wall is assumed to be 110 mm. In the present invention, it is preferable that the maximum height h of the wall portion in the molding portion having the highest drawing height of the product is 100 mm or more. If the maximum height h of the wall portion is less than 100 mm, the present invention is unnecessary because a blank that does not provide a difference in strength can be formed in the same plate.

  Moreover, it is preferable that the blank material yield strength is 60 to 150 MPa, and the material yield strength is 150 to 260 MPa. If the strengths of these two parts are out of this range, molding may not be performed successfully.

(Means to give strength difference to blank)
The means for providing a difference in strength to the blank as in the present invention is basically performed by the partial annealing of the blank or artificial aging treatment in terms of the material of the aluminum alloy depending on whether or not the blank is partially heated. That is, referring to FIG. 1, for example, the portion 5 that shrinks and deforms during press molding is partially annealed by heating to a temperature selected up to 550 ° C. for a predetermined time, and is not heated (at room temperature). The blank strength is made lower than that of the punch bottom contact portion 6. The heating means is performed by pressing (pressing) from one side or both sides by high-frequency heating or a pressure heating body made of a metal block whose temperature can be adjusted to the predetermined temperature. Conversely, in age-hardening type aluminum alloys such as 6000 series, the punch bottom contact part 6 is partially artificially age-hardened by heating to a temperature up to 250 ° C. for a predetermined time, thereby increasing the strength and not heating (room temperature). It is also possible to make the strength higher than the portion 5 where the flange is deformed. Of course, the strength may be adjusted by combining cooling rate control such as rapid cooling (quenching treatment) by air cooling or water cooling.

  Moreover, in the wall equivalent part 7 which is the range sandwiched between these two parts 5 and 6, when the blank strength is changed (changed) continuously (stepwise), the heating temperature in the region of the wall equivalent part 7 is set. Using the heating means and the cooling means, the temperature is changed from site 5 to site 6 continuously (stepwise), for example, so as to decrease to room temperature. The heating time may be changed stepwise in combination with the heating temperature such as the high-frequency heating time or the pressing time of the metal block. These heating temperature and heating time are selected according to the type of aluminum alloy, the relationship between the tempering conditions and strength, and the blank strength selected according to the site.

(Applicable aluminum alloy plate)
For the blank of the present invention, aluminum alloy plates (rolled plates) such as 1000 series, 3000 series, 5000 series, and 6000 series that are standardized by JIS or equivalent to or close to JIS standards can be used. However, in order to have various properties such as basic strength, formability, and corrosion resistance necessary for automobile panels that are difficult to form such as hoods, doors, fenders, roofs, trunks, etc., it is Al-Mg-Si. It is preferable to use a 5000 series aluminum alloy which is a 6000 series or Al-Mg series.

(Blank manufacturing)
The aluminum alloy plate for the blank of the present invention is a plate of about 0.5 mm to 2.5 mm manufactured by a conventional method through the steps of melting, casting, homogenizing heat treatment, hot rolling, intermediate annealing, and cold rolling. Thick board can be applied. These plates are either cold-rolled or subjected to heat treatment (tempering) such as solution treatment or annealing in a batch-type or continuous-type annealing furnace to be in a state of a coil or sheet of an aluminum alloy plate. The blank of the present invention that is press-molded on a product panel is obtained by cutting into a blank having a size appropriate for the product (panel) from the state of these coils or sheets.

(Press molding)
The press forming itself is performed by a known method for forming a conventional aluminum alloy blank. That is, as shown in FIG. 1 described above, these blanks are commercialized (panelized) as the automobile panel or the like through three to four press processes such as drawing (redrawing), re-striking, and piercing. Since the present invention improves blank formability, known methods and conditions for press forming of conventional aluminum alloy blanks, or in some cases, known methods for press forming of steel plate blanks There is even an advantage that the conditions can be applied.

  According to the present invention, an optimal strength distribution can be given to an aluminum alloy blank according to the object to be formed. Therefore, even when a large and complicated shape is deep-drawn using an aluminum alloy blank, a good press-formed product can be obtained without breaking.

FIG. 1A is a sectional view showing a molding process, FIG. 1B is a plan view of a blank, and FIG. 1C is an intensity of each blank portion corresponding to each portion of a product. It is explanatory drawing which shows. FIG. 2A shows another embodiment of the present invention, FIG. 2A is a plan view of the product, FIG. 2B is a sectional view of the product, and FIG. 2C is the strength of each blank portion corresponding to each portion of the product. It is explanatory drawing which shows. 3B is a partially enlarged view of FIG. 2B, FIG. 3A is a cross-sectional view of the product, and FIG. 3C is an explanatory diagram showing the strength of each blank portion corresponding to each portion of the product.

Explanation of symbols

1: blank, 2: punch, 3: die, 4: blank holder, 5: shrinking flange deformation equivalent part, 6: punch bottom contact equivalent part, 7: wall equivalent part, 8: maximum drawing height equivalent part, h: Drawing height, 10: bottom part, 11: punch bottom contact part (convex part), 12: shrinking flange deformed part, 13: strength transition line, 14: strength transition line, 15: punch shoulder R contact part,

Claims (6)

  An aluminum alloy blank that is formed into a predetermined product shape by press molding, and presses the blank strength of the contracted flange deformed portion that undergoes contraction flange deformation at the time of press forming in the formed portion having the highest drawing height. A range corresponding to a drawing height that is lower than the blank strength of the punch bottom contact portion that is in contact with the punch bottom at the time of molding and becomes a wall portion sandwiched by both the shrinkage flange deformation portion and the punch bottom contact portion. The blank for press molding, wherein the blank strength continuously changes.   The blank strength of the range excluding the punch shoulder R contact portion in the range corresponding to the drawing height that becomes the wall portion sandwiched between both the contracted flange deformation portion and the punch bottom contact portion continuously transitions. The press-molding blank according to claim 1.   3. The press-molding blank according to claim 1, wherein the maximum height of the wall portion is 100 mm or more at a molding site where the drawing height is the highest.   The blank for press molding according to any one of claims 1 to 3, wherein a blank strength of a blank region serving as a bottom of the product is lower than a punch bottom contact portion.   The blank for press molding according to claim 1, wherein a material yield strength of the contracted flange deformation portion is 60 to 150 MPa, and a material yield strength of the punch bottom contact portion is 150 to 260 MPa.   A press molding method using the press molding blank according to any one of claims 1 to 5, wherein a strength distribution corresponding to the shape of a product molded into the blank is provided in advance. Molding method.

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