JP5136998B2 - Hydraulic bulge method and hydraulic bulge product - Google Patents

Description

  The present invention relates to a hydraulic bulge for producing a closed cross-section product having a flange that joins other parts, and more particularly, the formed flange width satisfies a desired dimension, has less variation, and further has a hydraulic pressure. Hydraulic bulge method capable of increasing the bulge expansion rate and reducing the crack at the flange tip and obtaining excellent fatigue strength, the hydraulic bulge product produced by the method, and the hydraulic bulge mold It is about.

  In recent years, the hydraulic bulge of metal pipes has been evaluated for its excellent features and has been actively applied in various processing fields including automobile parts. Normally, when manufacturing automotive parts using a hydraulic bulge, a straight metal tube with a uniform circular cross-section in the longitudinal direction (hereinafter sometimes simply referred to as “element tube”) is used as a processing material. In addition, after applying a so-called preform such as bending or crushing, pressure is applied to the liquid introduced into the metal tube to finish the product having a closed cross section.

  This hydraulic bulge has various features compared to ordinary molding methods. For example, (a) a complex shape product having a different cross-sectional shape in the longitudinal direction can be manufactured, so that parts that have been assembled by welding in the past can be processed by integral molding, and (b) work hardening is performed over the entire product. Since it is easy to obtain, a high-strength product can be manufactured even using a soft metal material, and (c) the product has a small spring back, a good dimensional accuracy of the product, a good shape freezing property, and a rework process. Features that can be omitted.

  FIG. 1 is a diagram for explaining a hydraulic bulge method that has been conventionally adopted as a general processing method for automobile parts and the like. FIG. 1 (a) shows that a metal pipe P1 is accommodated in upper and lower molds 1,2. (B) shows a state in which the product P4 is obtained by applying hydraulic pressure to the inside of the metal tube.

  As shown in FIG. 1, the hydraulic bulge method is such that the machining liquid is injected into the metal pipe P1 accommodated in the upper and lower hydraulic bulge molds 1 and 2 through the injection hole 3, and the pressure of the machining liquid (hereinafter referred to as the working liquid pressure) , Referred to as “hydraulic pressure”), and a product P4 having various cross-sectional shapes is manufactured. At this time, in the hydraulic bulge method, it is also possible to push in the axial direction of the metal pipe P1 from both pipe ends by the axial pressing tools 4 and 5 also serving as a sealing tool (hereinafter referred to as “axial pressing”).

  Usually, the shaft pushing tools 4 and 5 that also serve as the sealing tool are connected to a hydraulic cylinder (not shown), and the axial position and the shaft pushing force in the hydraulic bulge are controlled.

  The axial push described above is an extremely important step in the hydraulic bulge method because it has the effect of promoting the metal flow during expansion of the metal tube in the hydraulic bulge and improving the expansion limit. For example, when hydraulic bulging is performed without applying axial push, the plate thickness may decrease significantly in response to the swelling of the metal material, in which case the metal tube breaks from the initial processing stage, Processing is possible only with a limited expansion limit, and a complicated cross-sectional shape cannot be secured.

  By the way, products finished by this hydraulic bulge method (hereinafter referred to as “hydraulic bulge products”) may be used as a single product, but are often used in combination with other parts. . In this case, there are welding joining and bolt fastening as typical joining methods between parts.

  FIG. 2 is a perspective view showing an example of a flanged part manufactured by press-molding a metal plate. FIG. 2A shows an example in which another part 8 is joined by spot welding 9b, and FIG. An example of fastening is shown.

  When a part having a closed cross-section structure is manufactured by press molding, the two members 6a and 6b that are press-molded can be combined by spot welding 9a, and the flanges 7 can be joined together to fix the two members. The flange 7 can be used for joining with other parts 8 by spot welding 9b as shown in FIG. 2 (a) and by bolt fastening 10 as shown in FIG. 2 (b).

  However, normally, the hydraulic bulge product has a closed cross-sectional structure without a flange, and when joining other parts, a method such as arc welding is employed.

  FIG. 3 is a perspective view showing a configuration example in which other parts are coupled to a hydraulic bulge product, where (a) shows an example of joining by arc welding 11 and (b) shows an example of fastening by bolt 10. Yes. That is, as shown in FIG. 3A, when directly connecting the other part 8 to the hydraulic bulge product P4, it is necessary to connect the other part 8 and the hydraulic bulge product P4 by arc welding 11. Further, as shown in FIG. 3B, when the other component 8 is fastened with the bolt 10, the bracket 12 must first be joined to the hydraulic bulge product P4 by the arc welding 11. However, arc welding has lower productivity than spot welding, and further has a problem that the dimensional accuracy of the product deteriorates due to heat during welding.

  In this way, when a flange is provided on a hydraulic bulge product using arc welding, a large number of man-hours are required for welding and dimensional accuracy cannot be ensured. Attempts have also been made to provide a flange on the hydraulic bulge product itself.

  For example, Patent Document 1 discloses manufacturing a flanged tubular member by hydraulic molding (hydraulic bulge). However, the flanged tubular member disclosed in Patent Document 1 does not process the flange by a hydraulic bulge. The flange in the flanged tubular member disclosed in Patent Document 1 has a structure that is already provided before hydraulic bulging.

  That is, as described in paragraph [0025] of Patent Document 1, the hydraulic bulge disclosed in Patent Document 1 rounds the central part of a metal plate to form a cylindrical part and overlaps both ends. Thus, a tubular material having a cylindrical portion and an overlapping portion of plate members extending outward from the cylindrical portion is used as a material for a hydraulic bulge. For this reason, the overlapping portion of the plate material of the tubular material becomes the flange of the hydraulic bulge product as it is.

  In Patent Document 2, as described in paragraph [0012], fins are integrally formed by extrusion molding or the like in the longitudinal direction of the outer surface of a round pipe material, and this is placed in a bulge mold and placed in a hydraulic pressure. It is disclosed to produce a flanged component (a flanged hydraulic bulge product) by bulging. However, the flange in the hydraulic bulge product with a flange disclosed in Patent Document 2 is not formed by the hydraulic bulge as in the case of Patent Document 1, and before performing the hydraulic bulge substantially, It is a flange formed by extrusion molding or the like.

  Patent Document 3 relates to a method of joining a hydroform component (hydraulic bulge product) and another component by welding, punching out a wall portion of a predetermined portion of the hydroform component in a partially connected state, and bending it outward. To form a flange.

  Further, paragraph [0004] of Patent Document 3 discloses that a technology for forming a flange on a hydroform component by hydroform (hydraulic bulge) already exists. That is, paragraph [0004] of Patent Document 3 discloses a technique for forming a flange while simultaneously forming a hydroform part by hydroform.

  However, according to the study by the present inventors, as shown in paragraph [0004] of Patent Document 3, if the formation of the hydroform part and the formation of the flange are performed only by the hydroform and simultaneously, It has been found that it is difficult to apply when a variation in dimensional shape becomes large and a highly accurate dimensional shape flange is required.

  In Patent Document 4, the metal tube is bulged into a product shape, and a flange forming scheduled portion of the metal tube is expanded, and after the expansion, the expanded portion is crushed with a punch to form a flange. It is disclosed.

  In the investigation by the present inventors, the flange forming method disclosed in paragraph [0004] of Patent Document 3 uses only hydroforming (hydraulic bulge), whereas the flange forming method disclosed in Patent Document 4 is Since the hydraulic bulge and crushing with a punch are used together, the accuracy of the dimensional shape of the flange has been improved.

  In general, the hydraulic bulge forming has a problem that the processing time is long and the productivity is low. In the method disclosed in Patent Document 4, after the internal pressure is raised before flange molding, the flange molding part is crushed with a punch, and the internal pressure is further raised to perform finish molding into a product shape. For this reason, compared with the normal hydraulic bulge forming, the number of times of pressurization is large, and crushing forming with a punch is added, so that the processing time becomes long.

  Therefore, in order to improve productivity, that is, in order to shorten the processing time, if the absolute value of the pressure before flange forming is reduced or the timing of punch lowering is advanced to shorten the overall cycle time, flange forming It has been found that there is a case where a variation in the bulging amount of the portion becomes large, and as a result, a flange having a desired size and shape cannot be obtained.

  In Patent Document 4, the paragraph [0016] describes a method of forming a flange at the time of hydraulic bulge processing, and includes a biting portion where the material buckled or buckled while the upper die is further lowered. The method of using is disclosed.

  Although the method of using the material biting phenomenon is different from the method of forming the flange by crushing the bulging portion disclosed in Patent Document 4 with a punch, the flange width is limited, the strength of the material and the mold This includes problems such as variations in flange width due to friction, and restrictions on product shape due to provision of a flange (see paragraphs [0018] to [0020]).

JP 2002-273528 A (Claims, paragraph [0025]) JP-A-6-226339 (Claims, paragraphs [0012] and [0013]) Japanese Patent Laid-Open No. 11-170060 (Claims, paragraph [0004]) JP 2001-259754 A (Claims, FIG. 6)

  The present invention has been made in view of the above-mentioned problems of the prior art, and when manufacturing a hydraulic bulge product having a flange necessary for fastening with other parts, a dimension in which a formed flange width is desired. The hydraulic bulge method, which can satisfy the above, has little variation, can increase the pipe expansion rate of the hydraulic bulge if necessary, and can effectively prevent the crack at the flange tip, and is manufactured by the method. It is an object to provide a hydraulic bulge product and a hydraulic bulge mold.

  In order to solve the above-mentioned problems, the present inventors have made various studies, and as a result, when manufacturing a closed cross-sectional product having a flange by a hydraulic bulge method, a metal tube pre-formed with a rough flange is used. We focused on the fact that it is effective to mold the finished flange in a hydraulic bulge mold.

  Specifically, the inventors have made various studies and formed a rough flange with a preform that is a pre-stage of a hydraulic bulge, and then formed a finished flange with a hydraulic bulge, or an intermediate flange and It has been found that if a finished flange is formed, a flange having a predetermined width can be formed without variation.

  As described above, the axial pushing is an extremely important step in the hydraulic bulge method. However, when the finished flange is formed by crushing the flange portion, the axial pushing is constrained by the finished flange and the action is not exhibited. Here, the intermediate flange is formed before the finish flange is formed. After the rough flange processing is performed in the preform in the previous stage of the hydraulic bulge, the intermediate flange, that is, the rough flange is formed in the hydraulic bulge. This is because it has been found that axial pressing can be effectively performed by forming a flange that is thinner than the thickness but thicker than the finished flange.

  In addition, when forming a rough flange with a preform and then forming a finished flange with a hydraulic bulge, or when forming an intermediate flange and a finished flange, the preformed metal tube moves in the hydraulic bulge mold. It was clarified that the flange with a predetermined width can be reliably formed without variation by not doing so.

  For example, in a hydraulic bulge, in order to prevent the preformed metal tube from moving in the mold, in the preform that is the previous stage, the processing width of the preformed metal tube is that of the portion having the flange. It is effective to process to the finished product width.

  Further, it has been found that by changing the mold shape of the flange contact portion, biting can be suppressed and cracking of the flange tip portion can also be prevented.

The present invention has been completed based on the above study results, and the gist hydraulic bulging method, and a hydraulic bulging product of (5) below (1) to (4).

Although not the gist of the present invention, the present invention is a hydraulic bulge for manufacturing a closed section product having a main body portion and a flange in the longitudinal direction thereof by performing a preform and a subsequent hydraulic bulge on a metal pipe as a material. In the preform, a rough flange thicker than a finish flange thickness of the flange is formed in the preform, a finish flange is formed in the hydraulic bulge, and then a body portion of the closed section product is finished. The characteristic hydraulic bulge method (hereinafter referred to as “first bulge method”) can be targeted .

(1) Although not the gist of the present invention, the present invention manufactures a closed-section product having a main body portion and a flange in the longitudinal direction thereof by performing a preform and a subsequent hydraulic bulge on a metal tube as a material. A hydraulic bulge method, wherein a rough flange thicker than a finished flange thickness of the flange is formed in the preform, and an intermediate flange thinner than the rough flange thickness but thicker than a finished flange thickness is formed in the hydraulic bulge. The hydraulic bulge method is characterized by performing axial pressing for compressing the metal tube in the longitudinal direction, then forming a finished flange, and then finishing the main body of the closed cross-section product (hereinafter referred to as a hydraulic bulge method) , it can be directed to a) referred to as a "second bulge method".

(2) A hydraulic bulge method for manufacturing a closed section product having a main body portion and a flange in the longitudinal direction thereof by performing a preform and a subsequent hydraulic bulge on a metal pipe as a material, wherein the preform A rough flange thicker than a finish flange thickness of the flange is formed, and an intermediate flange thinner than the rough flange thickness but thicker than the finish flange thickness is formed in the hydraulic bulge, and the metal tube is compressed in the longitudinal direction. This is a hydraulic bulge method characterized in that after finishing the main body of the closed section product and then finishing the main body, a finished flange is formed (hereinafter referred to as “third bulge method”).

(3) In the above SL third bulge method, in the hydraulic bulge, so that the metal tube is preform does not move in the mold, for example, preformed processing width of the metal tube a flange closed cross product It is desirable to perform processing so as to have a finished processing width.

(4) In the hydraulic bulge method described in (2 ) above, it is desirable to perform the preform and the subsequent hydraulic bulge using a single mold.
(5) By the hydraulic bulge method described in the above (1) and (2), the main body manufactured using the upper and lower hydraulic bulge molds having a gap at the portion corresponding to the flange tip and the longitudinal direction thereof A closed-section product provided with a flange, wherein the radius (R) of the flange tip is 0.6 times or more the flange thickness (t).

  Normally, a hydraulic bulge is composed of upper and lower mold clamping, low pressure water supply, high pressure application, shaft pushing, pressure release, and upper and lower mold opening (mold raising) processing steps. In the description of this specification, “hydraulic bulge” When it prescribes | regulates, it shall mean the shaping | molding process including these processes. Further, “preform” indicates preliminary processing that is a pre-stage of the hydraulic bulge.

  According to the hydraulic bulge method of the present invention, a closed cross-section product having a main body portion and a flange in the longitudinal direction is manufactured using a preformed metal tube, so that the flange width has a desired dimension and variation. Can be processed less. Furthermore, since the intermediate flange is formed in the hydraulic bulge, the shaft can be pushed. And since the crack which generate | occur | produces in the crushing-processed flange front-end | tip part can be reduced, the manufactured closed cross-section product can exhibit the outstanding fatigue strength.

  Furthermore, if the hydraulic bulge mold of the present invention is used, it is possible to prevent biting of the flange tip. Accordingly, the hydraulic bulge product of the present invention is most suitable for automobile parts and the like having a flange for coupling with other parts, and can be widely applied for processing automobile parts and the like for the same application.

  In the hydraulic bulge method of the present invention, a rough flange is formed in a preform that is a preliminary stage of the hydraulic bulge, and then a finished flange is formed by a hydraulic bulge, or an intermediate flange and a finished flange are formed, and thereafter It is characterized by finishing a closed section product having a frangipani.

  FIG. 4 is a diagram showing a cross-sectional configuration example of a hydraulic bulge product manufactured by the hydraulic bulge method of the present invention, (a) shows a cross-sectional configuration of a product P4 having a flange only on one side, and (b) Shows a cross-sectional configuration of a product P4 having flanges on both sides. The product P4 includes a main body portion and a flange formed in the longitudinal direction of the main body portion. The main body portion is constituted by a closed section indicated by a width W and a height H, and the shape of the flange 7 is indicated by a (finish) flange width f and a (finish) flange thickness t. Furthermore, the cross-sectional width of the product P4 is indicated by the product finish width SWf of the portion having the flange.

  Hereinafter, the contents of the present invention will be described separately for the hydraulic bulge method, the hydraulic bulge mold, and the hydraulic bulge product.

1. Hydraulic bulge method 1-1 About the first bulge method In the first bulge method, in the preform, a rough flange thicker than the finished flange thickness t is formed in the longitudinal direction of the raw tube, and then in the hydraulic bulge, After forming the finished flange, the body of the closed section product is finished.

  FIG. 5 is a view showing a method of forming a rough flange on one side of a raw tube with a preform. (A) shows a state in which the raw tube P1 is accommodated in the preform molds 1a and 2a, and (b) The state where the rough flange 7r is formed in the preform pipe P2 is shown.

  As shown in FIG. 5 (a), the preform P1 is accommodated between the upper preform mold 1a and the lower preform mold 2a, and the upper and lower preform molds are used in the preform that is the previous stage of the hydraulic bulge. By closing the mold, as shown in FIG. 5 (b), the rough flange 7r is formed at the site where the finished flange of the product is to be formed.

  As shown in FIG. 5B, the thickness tr of the rough flange is larger than the finished flange thickness t formed on the product, and the length fr of the rough flange is the length of the flange formed on the product. It is desirable to ensure a length substantially equal to f. The preform pipe P2 on which the rough flange 7r is formed is supplied to a hydraulic bulge.

  FIG. 6 is a diagram for explaining a method of processing a hydraulic bulge product using a preform tube by the first bulge method. FIG. 6A shows a preform tube P2 accommodated in hydraulic bulge molds 1b and 2b. (B) shows a state where the finish flange 7 is formed with the upper and lower hydraulic bulge molds closed, and (c) shows that the hydraulic bulge product P4 is finished by increasing the hydraulic pressure. Indicates the state.

  After the preform tube P2 is accommodated in the hydraulic bulge dies 1b and 2b because of the hydraulic bulge, the finishing flange 7 is closed in the process of closing the upper and lower hydraulic bulge dies 1b and 2b as shown in FIG. 6 (b). However, since it is an initial stage of the hydraulic bulge, the machining liquid is not injected into the preform pipe P2 or the pressure of the machining liquid is low.

  Thereafter, as shown in FIG. 6C, the hydraulic pressure inside the preform pipe P2 is increased, and the hydraulic bulge product P4 having the flange 7 is finished. The shape of the flange 7 to be formed is designed according to the shape of other parts to be joined.

  Again, as can be seen from FIG. 6, since the rough flange length 7r is sufficiently secured in the preform pipe P2, the final flange width f can be easily obtained. That is, as shown in FIG. 6 (a), if the rough flange length 7r of the preform pipe P2 is sufficiently secured, the flange tip end in the process of closing the vertical hydraulic bulge mold shown in FIG. 6 (b). Since the flange is crushed while the portion is in contact with the vertical wall of the lower hydraulic bulge mold 2b, the flange width f can be reliably ensured.

  FIG. 7 is a view showing a state in which a gap is generated on the opposite side of the preform tube from the flange forming portion in the hydraulic bulge mold in the hydraulic bulge. As shown in FIG. 7, when a finish flange or an intermediate flange is formed on the preform pipe P2 with the gap L formed, the preform pipe P2 moves in a direction opposite to the flange forming portion when the mold is lowered. The crushing length of the flange may become unstable. When such unstable machining is performed, the flange width f may vary.

  For this reason, when forming a rough flange with a preform and then forming a finish flange with a hydraulic bulge, or when forming an intermediate flange and a finish flange, the preform pipe P2 is connected to the upper and lower hydraulic bulge molds 1b and 2b. It is desirable not to move within.

  In order to prevent the preform pipe P2 from moving in the hydraulic bulge mold, various means can be adopted. For example, in the preform which is the previous stage, the processing width of the preform pipe P2 is small. It is effective to perform processing so that the product finish width SWf of the portion having the flange is obtained.

  FIG. 8 is a view for explaining a method of processing so that the processing width of the preform tube in the preform is the product finishing width SWf of the portion having the flange. FIG. 2B shows a state accommodated in 2a, and (b) shows a state where the processing width of the preform pipe P2 is processed so as to be the product finishing width SWf of the portion having the flange.

  As shown in FIG. 8B, in the preform, the rough flange 7r is processed in the preform pipe P2, and the processing width is set to a length corresponding to the product finishing width SWf of the portion having the flange. The preform pipe P2 in which the rough flange 7r is formed and the processing width is secured is supplied to the hydraulic bulge.

  FIG. 9 is a view for explaining a method of processing a hydraulic bulge product using a preform tube having a secured processing width. FIG. 9A shows a preform tube P2 accommodated in hydraulic bulge molds 1b and 2b. (B) shows a state where the finish flange 7 is formed with the upper and lower hydraulic bulge molds closed, and (c) shows that the hydraulic bulge product P4 is finished by increasing the hydraulic pressure. Indicates the state.

  As shown in FIGS. 9 (a) to 9 (b), if the processing width of the preform pipe P2 is processed so as to be the product finishing width SWf of the portion having the flange, the upper and lower liquids for forming the finishing flange 7 are formed. In the process of closing the pressure bulge molds 1b, 2b, the preform pipe P2 is stably held without moving in the hydraulic bulge molds 1b, 2b, so that the flange width f can be reliably ensured. .

  In the present invention, when processing is performed so that the processing width of the preform pipe P2 is equal to the product finishing width SWf of the portion having the flange, the processing width is considered in consideration of the ability to insert into the hydraulic bulge molds 1b and 2b. Cannot exceed the product finish width SWf. Therefore, it is necessary to process the preform tube P2 so that the processing width is equal to or slightly smaller than the product finishing width SWf.

  In order to prevent the preform tube P2 from moving in the hydraulic bulge mold, a bead portion 2c is provided on the lower hydraulic bulge mold 2b as shown in FIG. As described above, a concave portion may be provided in a corresponding portion of the preform tube P2. Furthermore, as shown in FIG. 11, a groove portion may be provided in the lower hydraulic bulge mold, and a convex portion may be provided at a corresponding portion of the preform pipe P2 along the groove portion.

(When using double acting mold for hydraulic bulge mold)
By using a double-action die for the hydraulic bulge die, it is possible to form the rough flange and the finished flange, or the rough flange, the intermediate flange and the finished flange with the same hydraulic bulge die.

  FIG. 12 is a diagram for explaining a method of forming a rough flange and a finished flange with a hydraulic bulge mold using a double-acting mold. FIG. (B) shows a state in which a rough flange 7r is formed, (c) shows a state in which a double-acting mold (punch) 1c is operated to form a finished flange 7, and (d) shows a liquid state. A state is shown in which the pressure is increased and the hydraulic bulge product P4 is processed.

  In the hydraulic bulge molds 1 and 2 shown in FIG. 12, by providing a punch as a double-acting mold 1 c in the upper mold 1, the rough flange 7 r and the finishing flange 7 can be replaced with the same hydraulic bulge molds 1 and 2. It becomes possible to form. Specifically, the upper molds 1 and 1c are raised to accommodate the raw pipe P1 in the hole mold of the lower mold 2 and the upper molds 1 and 1c are lowered as shown in FIG. A rough flange 7r is formed.

  Thereafter, as shown in FIG. 12 (c), the punch 1 c in the upper mold 1 is lowered to form the finished flange 7. Further, as shown in FIG. 12 (d), the hydraulic pressure is increased in a state where the flange 7 is pressed by the punch 1c, and the hydraulic bulge product P4 is finished.

1-2 About the 2nd and 3rd bulge methods Below, in order to make an understanding easy, the contents of the 3rd bulge method are explained first, and then the contents of the 2nd bulge method are explained. First, in the third bulge method, a rough flange that is thicker than the finished flange thickness t is formed in the preform in the longitudinal direction of the preform, and then in the hydraulic bulge, the finished flange is thinner than the coarse flange thickness tr. After forming an intermediate flange thicker than the thickness t and increasing the hydraulic pressure, axially compressing the entire raw tube in the longitudinal direction, and then finishing the body of the closed section product, Form a finished flange.

  As shown in FIG. 13, which will be described later, in the third bulge method, processing can be performed with a pair of upper and lower hydraulic bulge molds until the intermediate flange is formed with the hydraulic bulge. Thereafter, the hydraulic pressure is increased and the shaft is pushed. In order to form a finished flange by processing, it is desirable to use a double-action die provided with a punch. It is also possible to form the finished flange by using another press machine or the like.

  On the other hand, in the second bulge method, after the finish flange is formed, the main body of the hydraulic bulge product is finished. In the second and third bulge methods as well, the preform process shown in FIG. 5 is adopted as a pre-stage of the hydraulic bulge. For this reason, the preform pipe in which the rough flange is formed at the portion where the flange is formed by the preform is similarly supplied to the hydraulic bulge.

  FIG. 13 is a diagram for explaining a method of processing a hydraulic bulge product using a preform tube by the third bulge method. FIG. 13A is a diagram illustrating how the preform tube P2 is accommodated in the hydraulic bulge molds 1b and 2b. (B) shows the state in which the intermediate flange 7m is formed with the upper and lower hydraulic bulge molds closed, and (c) shows the intermediate product P3 by increasing the hydraulic pressure and carrying out the shaft pressing process. (D) shows a state in which the hydraulic pressure is further increased to finish the main body of the hydraulic bulge product, and (e) shows a state in which the punch 1c is lowered and the finishing flange 7 is processed. ing.

  After the preform tube P2 is accommodated in the hydraulic bulge molds 1b and 2b, the flange portion is removed in the process of closing the upper and lower hydraulic bulge molds at the initial stage of the hydraulic bulge as shown in FIG. 13 (b). Without the contact, an intermediate flange 7m that is thinner than the rough flange thickness tr but thicker than the finished flange thickness t is formed. At this time, the inside of the preform pipe P2 is in a state where the machining liquid is not injected or the hydraulic pressure is low.

  After that, as shown in FIGS. 13C to 13D, the hydraulic pressure is increased and the shaft is pushed. At this stage, the shaft can be pushed without the flange portion being restrained by the vertical hydraulic bulge mold. Therefore, thickness reduction due to tube expansion can also be suppressed by pushing the shaft. That is, in the intermediate product P3, the restriction on the tube expansion rate is relaxed, and even a component having a relatively complicated shape can be processed.

  Until the intermediate product P3 in which the intermediate flange 7m is formed in FIGS. 13 (a) to 13 (d) described above can be processed with a pair of upper and lower hydraulic bulge dies, as shown in FIG. 13 (e), In order to process the finished flange 7 by crushing the intermediate flange 7m, it is desirable to use a double-action die 1c in which a punch or the like is operably installed as a hydraulic bulge die. In addition, although the process shown in FIG.13 (e) can be processed using another press machine etc., when processing the product which has a partial flange as shown in below-mentioned FIG.22 (b), The processing of a pair of upper and lower hydraulic bulge molds shown in FIGS. 13 (a) to (c) is sufficient.

  FIG. 14 is a diagram for explaining a method of processing a hydraulic bulge product using a preform pipe by the second bulge method. FIG. 14A shows a preform pipe P2 accommodated in hydraulic bulge molds 1b and 2b. (B) shows the state in which the intermediate flange 7m is formed with the upper and lower hydraulic bulge molds closed, and (c) shows the intermediate product P3 by increasing the hydraulic pressure and carrying out the shaft pressing process. (D) shows the state where the punch 1c is lowered and the finishing flange 7 of the intermediate product is machined. (E) shows the state where the punch 1c is lowered and the hydraulic pressure is maintained or increased. The main body of the hydraulic bulge product P4 is shown in a finished state.

  In the second bulge method, it is desirable to use a double-action mold 1c provided with a punch or the like as the hydraulic bulge molds 1b and 2b. By using this double-acting die, the hydraulic bulge shown in FIGS. 14A to 14E can be performed on the same production line as a series of operations without taking out the material.

  As shown in FIG. 14 (d), when the punch 1 c is lowered and the flange portion is crushed to form the finished flange 7, the hydraulic pressure may be decreased or increased. In any case, at the stage of finishing the hydraulic bulge product P4 shown in FIG. 14 (e), it is necessary to increase the hydraulic pressure to a predetermined pressure.

(When using double acting mold for hydraulic bulge mold)
The second and third bulge methods use a preform mold and a hydraulic bulge mold in order to perform a hydraulic bulge after forming the preform tube. However, by using a double-action mold for the hydraulic bulge mold, the rough flange, the intermediate flange and the finishing flange can be formed with the same hydraulic bulge mold. Next, an application example of the double-action mold to the second bulge method will be described.

  FIG. 15 is a diagram showing a method of forming a rough flange, an intermediate flange, and a finished flange with a hydraulic bulge mold using a double-action mold by the second bulge method. FIG. FIG. 2 shows a state in which the pressure bulge molds 1 and 2 are accommodated, FIG. 3B shows a state in which a rough flange 7r is formed, and FIG. (D) shows a state in which the intermediate pressure P3 is processed by increasing the hydraulic pressure, (e) shows a state in which the punch 1c is lowered and the finishing flange 7 is processed, and (f) shows an application of the hydraulic pressure. The state where the hydraulic bulge product P4 is finished is shown.

  In the hydraulic bulge molds 1 and 2 shown in FIG. 15, the rough flange 7r, the intermediate flange 7m, and the finishing flange 7 are made of the same hydraulic bulge mold by providing a punch as a double acting mold 1c in the upper mold. Can be formed. The operation at each stage in FIGS. 15A to 15E is as described above.

  The application of the double-action mold to the third bulge method can also be designed in the same manner as the application example to the second bulge method.

2. Hydraulic bulge mold The hydraulic bulge mold of the present invention is a mold used in a hydraulic bulge for manufacturing a closed cross-sectional product having a flange from a preformed metal tube. Includes molds. As a specific configuration, the surface facing the flange formed in the element pipe to be accommodated is configured by a vertical wall, and at least when the finished flange is formed, the end of the finished flange contacts the vertical wall. It is characterized by being touched.

  FIGS. 16 and 17 are diagrams for explaining the configuration of the hydraulic bulge mold of the present invention used when processing a hydraulic bulge product having flanges on both sides.

  FIG. 16 is a diagram for explaining a configuration when used as a preform mold, in which (a) shows a state in which the raw tube P1 is accommodated between the upper and lower preform molds 1a, 2a, and (b). Indicates a state in which the rough flange 7r is formed. By the preform dies 1a and 2a of the present invention, the raw pipe P1 is formed with a rough flange 7r to become a preform pipe P2, which is supplied to the hydraulic bulge.

  FIG. 17 is a diagram for explaining a configuration when used as a hydraulic bulge mold. FIG. 17A shows a state in which the preform pipe P2 is accommodated in the hydraulic bulge molds 1b and 2b, and FIG. The state which formed the finishing flange 7 is shown, (c) has shown the state which increased the hydraulic pressure and finished the hydraulic bulge product P4.

  The “vertical wall” defined in the present invention is provided to prevent the flange tip from biting out of the mold when the flange is formed, and is indicated by Vp in the preform mold 2a shown in FIG. It corresponds to a part and corresponds to a part indicated by Vb in the hydraulic bulge mold 2b shown in FIG.

  These vertical walls Vp and Vb are provided on the surface facing the flange formed in the raw tube. Therefore, as shown in FIGS. 16 and 17, when a product having flanges on both sides is processed, it is provided on both sides. The vertical walls Vp and Vb need only be high enough to prevent the flange tip from biting out. However, in order to fully demonstrate the effect, the vertical walls Vp and Vb should be equal to or higher than the product body height H. It is desirable to do.

  FIG. 18 is a diagram for explaining a biting situation that occurs when a hydraulic bulge mold that does not constitute a vertical wall is used. FIG. 18A shows that the preform pipe P2 is accommodated in the hydraulic bulge molds 1b and 2b. (B) has shown the state which the biting part 14 generate | occur | produced in the flange front-end | tip part.

  When the preform pipe P2 having the rough flange 7r formed in the preform process is accommodated in the hydraulic bulge molds 1b and 2b and the upper and lower molds are closed, no vertical wall is formed on the surface facing the flange. Therefore, the biting portion 14 is generated at the flange tip portion. If the biting portion 14 is generated in the hydraulic bulge, it not only causes a product defect but also may damage the mold itself.

  On the other hand, as shown in FIG. 17, by forming the vertical wall Vb in the hydraulic bulge mold 2b, the front end of the flange can be brought into contact with the vertical wall Vb and the biting can be surely prevented. In addition, the flange length can be adjusted by bringing the front end of the flange into contact with the vertical wall Vb.

  As described above, the vertical wall with which the flange tip abuts can regulate the flange length and prevent biting, so it is most effective when forming a finished flange, but forms a rough flange or an intermediate flange. It is also effective to make it abut against the vertical wall.

  Furthermore, the hydraulic bulge mold according to the present invention has both side positions facing each other across the processing width of the preform tube when the processing width of the preform tube is processed to be the product finishing width SWf of the portion having the flange. A "vertical wall" can be provided in For example, when processing a preform tube using this hydraulic bulge mold, if both end portions of the processing width of this preform tube are brought into contact with the vertical walls provided at both side positions, it is simple. Processing can be performed so that the processing width of the preform tube is equal to the finished product width of the portion having the flange.

3. Hydraulic bulge product The hydraulic bulge product of the present invention is preferably characterized in that the radius (R) of the flange tip is 0.6 times or more the flange thickness (t). By defining the radius (R) of the front end of the flange, cracks at the front end can be reduced, stress concentration can be relaxed, and fatigue strength can be improved.

  Usually, in the flange formation part by the hydraulic bulge, in addition to the 180 ° bending of the metal material, the circumferential pressure is applied because the hydraulic pressure is applied, but such flange processing does not apply the internal pressure. The processing conditions are harsher than the tight bending process, and the frequency of occurrence of cracking is increased.

  In the hydraulic bulge product of the present invention, the shape of the flange tip is further improved to prevent cracking and to improve the fatigue strength.

  19 and 20 are diagrams showing examples of the shape of the flange tip in the hydraulic bulge product of the present invention. FIGS. 19A to 20C show the shape of the tip of the flange 7 and the vertical hydraulic bulge mold 1. 2 shows the relationship with the cross-sectional shape. As shown in FIGS. 19 and 20, the crack can be prevented by adjusting the radius (R) of the tip of the flange 7.

  FIG. 21 is a diagram showing the influence of the shape of the flange tip portion {the radius (R) of the flange tip portion / the flange thickness (t)} on the occurrence of cracks in the flange tip portion. A steel pipe having an outer diameter of 54 mm and a wall thickness of 2.0 mm was used as a specimen tube, and the material was made of four types of A material, B material, C material, and D material, and the results of each JIS12B arc tensile test are shown in Table 1. Show.

  When a hydraulic bulge product having a one-side flange having a main body width W of 35 mm, a main body height of 26 mm, and a flange width f of 34 mm is used in the test specimen tube shown in Table 1, The radius (R) was variously changed, 100 to 200 tests were performed for each molding condition, and the occurrence rate of cracks (microcracks) at the flange tip portion was investigated. The maximum pressure in the hydraulic bulge was 170 MPa.

  As is clear from the results shown in FIG. 21, there is a difference in the crack occurrence rate depending on the material, but the crack (by increasing the radius (R) of the flange tip to 0.6 times the flange thickness (t) ( The occurrence of micro cracks can be greatly reduced.

  Generally, fatigue strength is often required for industrial products such as automobile parts. Therefore, even in a hydraulic bulge product having a flange, the stress concentration is reduced and the fatigue strength of the product is improved as the radius (R) of the flange tip is increased. For this reason, the shape improvement of the flange tip is an industrially useful improvement as a hydraulic bulge product used for automobile parts.

  FIG. 22 is a perspective view showing a flange shape formed in the hydraulic bulge product of the present invention, wherein (a) shows a state in which the contact crushing process at the flange 7 is linearly applied, (b) Shows a state in which the contact crushing process at the flange 7 is performed in a spot shape. The close-contact crushing portion is indicated by a hatched portion, and in each case, an R at the tip of the flange is provided, indicating that an outer peripheral bending radius of 0.6 times or more of the flange thickness t is secured.

The effects of the hydraulic bulge method and hydraulic bulge product of the present invention will be described below based on specific examples.
Example 1
A hydraulic bulge product having a one-side flange and having a main body width W of 35 mm, a main body height H of 26 mm, and a flange width f of 34 mm as shown in FIG.

  As the raw tube, a structural steel pipe STKM-11A (tensile strength in JIS No. 12B arc tensile test: 380 MPa, elongation 34%) having an outer diameter of 54 mm and a wall thickness of 2.0 mm was used. The flange tip was crushed, and the flange tip R was 3 mm (0.75 times the flange thickness t).

  As Comparative Example 1, a preformed flange is formed in the process of closing the upper and lower hydraulic bulge molds after the raw tube is accommodated in the hydraulic bulge mold shown in FIG. processed. Thereafter, the hydraulic pressure was increased to 170 MPa to produce a hydraulic bulge product.

  As Invention Example 1, rough flange processing was performed with the preform shown in FIG. Next, the preform product thus obtained was accommodated in the hydraulic bulge mold shown in FIG. 6, and a finished flange was formed in the process of closing the upper and lower molds, and crushed to the tip of the flange. Thereafter, the hydraulic pressure was increased to 170 MPa to produce a hydraulic bulge product.

  As Invention Example 2, using the double-action mold provided with the punch shown in FIG. 12, rough flange processing is formed in the same hydraulic bulge mold, and the finish flange is formed by operating the punch. Until crushing. Thereafter, the hydraulic pressure was increased to 170 MPa to produce a hydraulic bulge product.

  As Invention Example 3, rough flange processing was performed with the preform shown in FIG. Next, the obtained preform product was accommodated in the hydraulic bulge mold shown in FIG. 9, and a finished flange was formed in the process of closing the upper and lower molds and crushed to the tip of the flange. Thereafter, the hydraulic pressure was increased to 170 MPa to produce a hydraulic bulge product.

  In Invention Examples 1 to 3, the finished product width SWf of the portion having the flange was secured in any of the preforms.

  In any case, as a result of producing about 2000 products, no cracks occurred in the flange tip in Comparative Example 1, Invention Examples 1, 2, and 3.

  However, in Comparative Example 1, there are many products in which the flange width f does not reach the predetermined 34 mm, the average value of the product flange width f is 32 mm, and 1523 products whose flange width is 33 mm or less are rejected. . In contrast, in Invention Examples 1, 2, and 3, all the flange widths f satisfied the target of 34 mm, and all passed.

(Example 2)
A hydraulic bulge product having a one-side flange shown in FIG. 4A and having a main body width W of 38 mm, a main body height H of 29 mm, and a flange width f of 34 mm was manufactured by a hydraulic bulge. The main body dimensions W and H are different from those of the first embodiment. Compared with the first embodiment, the flange width f is the same, but the main body dimensions W and H are larger. In this case, axial pressing is an important process in the hydraulic bulge.

  As the raw tube, a structural steel pipe STKM-11A (tensile strength in JIS No. 12B arc tensile test: 380 MPa, elongation 34%) having an outer diameter of 54 mm and a wall thickness of 2.0 mm was used. The flange tip was crushed, and the flange tip R was 3 mm (0.75 times the flange thickness t).

  As Comparative Example 2, the preformed flange was formed in the process of closing the upper and lower molds after the raw tube was accommodated in the hydraulic bulge mold shown in FIG. . Thereafter, the hydraulic pressure was increased to 170 MPa to produce a hydraulic bulge product.

  As Invention Example 4, rough flange processing was performed with the preform shown in FIG. Next, the obtained preform product was accommodated in the hydraulic bulge mold shown in FIG. 14, and an intermediate flange was formed with a flange thickness of 6 mm in the process of closing the upper and lower molds. Here, as the hydraulic bulge mold shown in FIG. 14, a double-action mold having a punch operable for crushing the flange portion was used. Next, the hydraulic pressure is adjusted to 100 to 170 MPa and axial pressing is performed. Thereafter, the punch is moved while maintaining the hydraulic pressure to crush to the tip of the flange to form a finished flange, and further increased to a hydraulic pressure of 170 MPa. A hydraulic bulge product was manufactured.

  As Invention Example 5, rough flange processing was performed with the preform shown in FIG. Next, the obtained preform product was accommodated in the hydraulic bulge mold shown in FIG. 14, and an intermediate flange was formed with a flange thickness of 6 mm in the process of closing the upper and lower molds. Next, the hydraulic pressure is adjusted to 100 to 170 MPa and axial pressing is performed. Thereafter, the hydraulic pressure is temporarily reduced, the punch is moved and crushed to the tip of the flange to form a finished flange, and further increased to a hydraulic pressure of 170 MPa. A hydraulic bulge product was manufactured.

  As Invention Example 6, rough flange processing was performed with the preform shown in FIG. Next, the obtained preform product was accommodated in the hydraulic bulge mold shown in FIG. 13, and an intermediate flange was formed with a flange thickness of 6 mm in the process of closing the upper and lower molds. Next, the hydraulic pressure was adjusted to 100 to 170 MPa and axial pressing was performed. Thereafter, the intermediate product shown in FIG. 13 (d) was taken out and crushed to the flange tip in another production line to form a finished flange to produce a hydraulic bulge product.

  In either case, as a result of manufacturing about 2000 products, no cracks occurred at the flange tip in both Comparative Example 2 and Invention Examples 4-6.

  However, in Comparative Example 2, there are many products in which the flange width f does not reach the predetermined 34 mm, the average value of the product flange width f is 32 mm, and 1750 products whose flange width is 33 mm or less are rejected. . In contrast, in Invention Examples 4 to 6, all the flange widths f satisfied the target of 34 mm, and all passed.

  Further, Invention Examples 4 and 5 had good dimensional accuracy of the product, and the total number was within ± 0.05 mm with respect to the target value. Invention Example 6 was within ± 0.1 mm in total with respect to the target value, and was slightly inferior in dimensional accuracy to Invention Examples 4 and 5. However, since it satisfies the required accuracy, it was all passed.

(Example 3)
A hydraulic bulge product having a flange on one side as shown in FIG. 4 (a) and having a main body width W of 35 mm, a main body height H of 26 mm, and a flange width f of 34 mm to 37 mm is manufactured by a hydraulic bulge. did. The form of the flange crushing process is as shown in FIG.

  As the raw tube, a structural steel pipe STKM-20A (tensile strength in JIS No. 12B arc tensile test: 590 MPa, elongation 23%) having an outer diameter of 54 mm and a wall thickness of 1.8 mm was used.

  When manufacturing a hydraulic bulge product, rough flange processing is performed with the preform shown in FIG. 5, and the resulting preform is placed in the hydraulic bulge mold shown in FIG. 6 and finished in the process of closing the upper and lower molds. A flange was formed, after which the hydraulic pressure was increased to produce a hydraulic bulge product. At this time, the R shape and the hydraulic pressure at the flange tip were changed.

  In Invention Example 7, the hydraulic pressure of the hydraulic bulge is 170 MPa, the flange width of the mold is 37 mm, the flange is crushed to the tip, and R at the tip is 1.8 mm (0.5 times the flange thickness t). It was.

  In Invention Example 8, the hydraulic pressure of the hydraulic bulge is 200 MPa, the flange width of the mold is 37 mm, the flange is crushed to the tip, and R at the tip is 1.8 mm (0.5 times the flange thickness t). It was.

  In Invention Example 9, the hydraulic pressure of the hydraulic bulge is 170 MPa, the flange width of the mold is 35 mm, the flange is crushed to the tip, and R at the tip is 1.8 mm (0.5 times the flange thickness t). It was.

  In Invention Example 10, the hydraulic pressure of the hydraulic bulge is 170 MPa, the flange width of the mold is 35 mm, the flange is crushed to the tip, and R at the tip is 2.7 mm (0.75 times the flange thickness t). It was.

  In either case, about 2000 products were produced. In Invention Example 7, cracks at the flange tips occurred in 82% (1640) of products. Similarly, in Invention Example 8, a crack at the flange tip occurred in 93% (1865 pieces) of the molded product. When observing the processing steps of Invention Examples 7 and 8, the tightly bent portion was not in contact with the vertical wall of the mold at the stage of applying hydraulic pressure with a hydraulic bulge.

  In Invention Example 9, cracks at the flange tip occurred in 1.8% of the products. When the molding process was observed, the tightly bent portion was in contact with the vertical wall of the mold at the stage of applying the hydraulic pressure with the hydraulic bulge. In Invention Example 10, no cracks at the flange tips occurred in all products.

Example 4
A hydraulic bulge product having both flanges shown in FIG. 4 (b) and having a main body width W of 67 mm, a main body height H of 33 mm, and a flange width f of 15 mm was manufactured by a hydraulic bulge. And the form of the crushing process of the flange was made into the thing of about 8 mm in diameter shown in the said FIG.22 (b) except the invention example 11. FIG. The obtained product was subjected to a fatigue test, and each fatigue strength was evaluated.

Specifically, a load is applied so that a tensile force in the direction in which the flange tip opens is applied, and the ratio between the maximum load Pmax and the minimum load Pmin is set to 0.05. Maximum load Pmax level cyclic loading the pulsating load of varying the, the load when the life becomes 10 ⁷ times was fatigue strength.

  As the raw pipe, a structural steel pipe STKM-11A having an outer diameter of 89.1 mm and a wall thickness of 2.0 mm (tensile strength of 380 MPa and elongation of 34% in a JIS No. 12B arc-shaped tensile test) was used.

  In the process of manufacturing the hydraulic bulge product, rough flange processing is performed with the preform shown in FIG. 16, and the obtained preform is accommodated in the hydraulic bulge mold shown in FIG. 17, and the upper and lower molds are closed. A finished flange was formed, and then the hydraulic pressure was increased to 170 MPa to produce a hydraulic bulge product.

  In Invention Example 11, R at the front end of the flange was 2 mm (0.5 times the flange thickness t). In Invention Example 12, R at the front end of the flange was 3 mm (0.75 times the flange thickness t), and a portion having a diameter of about 8 mm was crushed. Further, in Invention Example 13, the flange tip R was 7 mm (1.0 times the flange thickness t), and the portion having a diameter of about 8 mm was crushed.

  In Invention Examples 11 to 13, no crack occurred at the tip. The fatigue strength of Invention Example 11 was about 1.2 times that of Invention Example 10, and Invention Example 12 was about 1.3 times that of Invention Example 10.

  According to the hydraulic bulge method and the hydraulic bulge mold of the present invention, a closed cross-section product having a main body portion and a flange in the longitudinal direction thereof is manufactured using a preformed metal tube, so that the flange width is desired. In addition, since the intermediate flange is formed in the hydraulic bulge, it is possible to push the shaft and reduce the cracks that occur at the flange tip that has been crushed in close contact. Can exhibit excellent fatigue strength.

  Therefore, the hydraulic bulge product manufactured according to the present invention is most suitable for automobile parts and the like having a flange that joins other parts.

It is a figure explaining the hydraulic bulging method employ | adopted as a general processing method conventionally, such as a motor vehicle part. It is a perspective view which shows an example of the parts with a flange which produced by press-molding a metal plate for automobile parts. It is a perspective view which shows the structural example which couple | bonded other parts with the hydraulic bulge product for motor vehicle parts. It is a figure which shows the cross-sectional structural example of the hydraulic bulge product manufactured by the hydraulic bulge method of this invention. It is a figure which shows the method of forming a rough flange in the single side | surface of a raw tube with a preform by the method of this invention. It is a figure explaining the method of processing a hydraulic bulge product using a preform pipe by the 1st bulge method of the present invention. FIG. 7 is a view showing a state in which a gap is generated on the opposite side of the preform tube from the flange forming portion in the hydraulic bulge mold in the hydraulic bulge. It is a figure explaining the method to process so that the processing width | variety of a preform pipe may become the product finishing width SWf of the part which has a flange in a preform. It is a figure explaining the method of processing a hydraulic bulge product using the preform pipe with which processing width was secured. It is a figure explaining embodiment for preventing a preform pipe from moving within a hydraulic bulge metal mold. It is a figure explaining other embodiment for preventing a preform pipe from moving within a hydraulic bulge metal mold. It is a figure explaining the method of forming a rough flange and a finishing flange with the hydraulic bulge die using a double acting die by the 1st bulge method of the present invention. It is a figure explaining the method of processing a hydraulic bulge product using a preform pipe by the 3rd bulge method of the present invention. It is a figure explaining the method of processing a hydraulic bulge product using a preform pipe by the 2nd bulge method of the present invention. It is a figure which shows the method of forming a rough flange, an intermediate | middle flange, and a finishing flange with the hydraulic bulge metal mold | die using a double acting metal mold | die by the 2nd bulge method of this invention. It is a figure explaining the structure at the time of using the hydraulic bulge metal mold | die of this invention as a preform metal mold | die. It is a figure explaining the structure at the time of using the hydraulic bulge metal mold | die of this invention as a hydraulic bulge metal mold | die. It is a figure explaining the biting condition which generate | occur | produces when using the hydraulic bulge die which does not comprise a vertical wall. It is a figure which shows the example of a shape of the flange front-end | tip part in the hydraulic bulge product of this invention. It is a figure which shows the other example of a shape of the flange front-end | tip part in the hydraulic bulge product of this invention. It is a figure which shows the influence which the shape of the flange front-end | tip part {the radius (R) of the flange front-end | tip part / flange thickness (t)} exerts on the crack generation | occurrence | production of a flange front-end | tip part. It is a perspective view which shows the flange shape formed in the hydraulic bulge product of this invention.

Explanation of symbols

1: upper mold, upper hydraulic bulge mold, 1a: upper preform mold 1b: upper hydraulic bulge mold, 1c: double acting mold, punch 2: lower mold, lower hydraulic bulge mold 2a : Lower preform mold 2b: Lower hydraulic bulge mold, 2c: Bead part, 3: Injection hole 4, 5: Shaft pushing tool, 6a, 6b: Members 7, 7r, 7m: Flange, coarse flange, intermediate flange 8: Other parts, 9a, 9b: Spot welding 10: Bolt fastening, 11: Arc welding 12: Bracket, 14: Biting part P1: Metal pipe, raw pipe, P2: Preform pipe P3: Intermediate product, P4: Liquid Pressure bulge products, products

Claims (6)

A hydraulic bulge method for manufacturing a closed section product having a main body portion and a flange in the longitudinal direction by performing a preform and subsequent hydraulic bulge on a metal pipe as a material,
In the preform, forming a rough flange thicker than the finished flange thickness of the flange,
In the hydraulic bulge, an intermediate flange that is thinner than the rough flange thickness but thicker than the finished flange thickness is formed, axial pressing is performed to compress the metal tube in the longitudinal direction, and then the body portion of the closed section product is A hydraulic bulge method characterized by forming a finished flange after finishing. 2. The hydraulic bulge method according to claim 1, wherein the preformed metal tube does not move horizontally in the mold in the hydraulic bulge. The hydraulic bulge method according to claim 1, wherein the preform is processed so that a processing width of the preformed metal tube becomes a finishing width having a flange of the closed section product. The hydraulic bulge method according to any one of claims 1 to 3 , wherein the preform and the subsequent hydraulic bulge are performed using a single mold. The main body part manufactured using the upper and lower hydraulic bulge mold which has a gap | interval in the site | part equivalent to a flange front-end | tip by the hydraulic bulge method in any one of Claims 1-4 , and a flange in the longitudinal direction A closed section product with
A hydraulic bulge product characterized in that the radius (R) of the flange tip is 0.6 times or more the flange thickness (t). By performing the preform and hydraulic bulge subsequent to the metal pipe which is a material, in producing a closed cross section product having a flange in the longitudinal direction and the main body portion and have contact with the preform, finish of the flange Form a rough flange thicker than the flange thickness,
In the hydraulic bulge, an intermediate flange that is thinner than the rough flange thickness but thicker than the finished flange thickness is formed, axial pressing is performed to compress the metal tube in the longitudinal direction, and then the finished flange is formed. A hydraulic bulge method for finishing the main body of a closed cross-section product is provided with a main body manufactured using an upper and lower hydraulic bulge mold having a gap at the portion corresponding to the flange tip and a flange in the longitudinal direction. A closed cross-section product ,
Hydraulic bulging product to feature the radius of the flange tip portion (R) is not less than 0.6 times the flange thickness (t).

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