JP4133465B2 - Hydroform processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is used in the manufacture of exhaust system parts and suspension system parts for automobiles. The metal pipe is placed in a divided mold, and after the mold is clamped, the internal pressure and the axial direction of the pipe are in the metal pipe. The present invention relates to a hydroform processing method for forming a predetermined shape by applying a pressing force.
[0002]
[Prior art]
In recent years, hydroform technology has been attracting attention in the automobile field as one of the means for reducing costs and reducing weight by reducing the number of parts. In Europe and the United States, it has already been used in actual vehicles for several years, and in Japan it has been changed from 1999 to actual vehicles. Started to apply. Since then, the number of applicable parts for hydroforming has increased year by year, and the market size has greatly expanded.
[0003]
[Problems to be solved by the invention]
When hydroforming and pressing are compared, one of the technical advantages of hydroforming is that large deformation is possible. Fig. 1 shows a diagram of the state of strain that occurs during hydroforming (marked with ●) and pressing (marked with □). In general, in press working, deformation is performed in a region from an equibiaxial tension state to a plane strain state to a uniaxial tension state. The equibiaxial tension state is a state in which the tensile strain in the X direction works equal to the tensile strain in the direction perpendicular to the X direction, and the plane strain state is a strain in the X direction that is zero and the tensile force in the direction perpendicular to the X direction. A state in which only strain is applied is referred to, and the uniaxial tensile state is a state in which the tensile stress in the X direction is 0 and only the tensile stress in the direction perpendicular to the X direction works. Therefore, in the press working, deformation occurs in a region where the deformability is small from the viewpoint of the molding limit of the material, and particularly, when the strain progresses in a plane strain state, it tends to break. On the other hand, in the hydroforming process, the inner pressure is applied and the axial push is applied at the same time, so that the material can be subjected to shear deformation, and the deformation progresses in the region of uniaxial tension to pure shear. The pure shear state means a state in which the compressive strain in the X direction works equally as the tensile strain in the direction perpendicular to the X direction. Accordingly, when viewed from the molding limit of the material, the deformation is performed in a very wide region, and as a result, large deformation is possible. In other words, it is no exaggeration to say that it depends on how to bring the strain state to the pure shear side in order to realize large deformation by hydroforming.
[0004]
Needless to say, in order to deform on the pure shear side, it is effective to simply apply a positive axial push. However, if the axial push is simply increased, the problem of buckling naturally occurs. Increasing the internal pressure is effective in preventing this buckling. However, increasing the internal pressure means that the strain state moves from the shearing side to the plane strain side, so that it tends to break. Therefore, a free bulge without a mold as shown in FIG. 2 can be molded only on the plane strain side of the uniaxial tension state in order to prevent buckling (extracted from Non-Patent Document 1).
[0005]
The reason why the shear deformation can be realized by the T-molding (hydroforming process) as shown in FIG. 1 is because of the effect of restraint of the mold. Since there is a mold around, buckling can be suppressed more than in the case of a free bulge. Further, since there is a mold, it becomes possible to make the internal pressure higher than in the case of a free bulge, thereby further increasing the close contact with the mold and effectively suppressing buckling. As described above, in the T-molding, the shear deformation can be realized while suppressing buckling due to the presence of the mold, so that a large deformation is possible.
[0006]
In addition to T-molding, there is an example as shown in FIG. However, what is common to these examples is that both pipes are expanded or branch pipes are extended on one surface. For example, in the example of the rectangular tube expansion, the tube is expanded only in the Y direction on the YZ plane, and is not expanded in the Z direction.
[0007]
On the other hand, in the example of FIG. 4, the direction of tube expansion is not limited to one surface. For example, in the case of square tube expansion or hemispherical tube expansion, the elementary tube is expanded not only in the Y direction but also in the Z direction on the YZ plane. In such an example, until a part of the raw tube comes into contact with the mold, it becomes the same state as the free bulge, so that shear deformation cannot be realized without causing buckling. Could not be bigger.
[0008]
As described above, an object of the present invention is to provide a hydroform processing method that enables a part having a shape in which the direction of pipe expansion in a plane is not limited to one direction to be processed by hydroform.
[0009]
[Non-Patent Document 1]
Plasticity and processing, Mori et al .: vol.29 no.325 (1988) p.131
[0010]
[Means for Solving the Problems]
In order to solve the problem, the gist of the present invention is as follows.
(1) In a hydroforming method in which an internal pressure and a pushing force in the axial direction of the tube are loaded on the metal tube after the metal tube is mounted on a divided mold and clamped, in the first hydroforming step, the metal tube while tube expanding said metal pipe in one direction of the cross section, to be smaller than the expansion ratio in the one direction, the double-base pipe diameter of the plate thickness of the diameter of the metal tube in the one direction perpendicular to the direction 1. After the deformation to 4 times (excluding 1 times the diameter of the raw tube), in the second hydroforming step, the metal tube is expanded in a direction perpendicular to the one direction in the cross section of the metal tube. The diameter of the metal tube is formed to be twice the plate thickness to 1.4 times the width after the deformation in the one direction so as to be smaller than the tube expansion rate in the perpendicular direction in the foam process. Hydroform processing method.
However, the expansion ratio = the diameter (width) of the tube after forming / the diameter (width) of the tube before forming.
(2) In the first hydroforming step, while expanding the metal tube in one direction of the metal tube, the diameter of the metal tube is set in a direction perpendicular to the one direction so as to be smaller than the tube expansion rate in the one direction. After deforming from twice the thickness to 1.4 times the tube diameter (excluding 1 times the tube diameter), in the second hydroforming step, the metal tube is mounted on the final product shape mold. While expanding the metal tube in a direction perpendicular to the one direction in the cross section, the diameter of the metal tube in the one direction is set to a thickness of 2 so as to be smaller than the tube expansion rate in the perpendicular direction in the second hydroforming step. (1) The hydroforming method according to (1), wherein the forming is performed at a magnification of 1.4 times the width after deformation.
(3) In a hydroforming method in which an internal pressure and a pushing force in the axial direction of the tube are applied to the metal tube after the metal tube is mounted on a divided mold and clamped, the metal tube is a first hydroforming step. While expanding the metal tube in one direction of the cross section, the diameter of the metal tube in the direction perpendicular to the one direction is set to be twice the plate thickness to 1. After deforming to 4 times (excluding 1 times the raw tube diameter), in the second hydroforming step, expanding the metal tube in the direction perpendicular to the one direction in the cross section of the metal tube, the second hydroform The diameter of the metal tube in one direction is formed to be twice the plate thickness to 1.4 times the width after the deformation so as to be smaller than the tube expansion rate in the right-angle direction in the process. Hydroform process, intermediate production It was attached to a mold of the final product shape, hydroforming method characterized by hydroforming.
However, the expansion ratio = the diameter (width) of the tube after forming / the diameter (width) of the tube before forming.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In the example of FIG. 5, first, the metal tube 1 is mounted on the lower mold 2 and the upper mold 3 is closed. At this time, the shape of the cavity of the molds 2 and 3 is expanded in the horizontal direction with respect to the diameter of the metal tube 1 and the diameter of the metal tube is set in the vertical direction so that the expansion rate in the horizontal direction is smaller. In addition, the shape is set so that the pipe is expanded to a maximum of 1.4 times the original pipe diameter (width), which is greater than one time the diameter of the pipe. The material can be subjected to shear deformation to some extent as long as it is up to 1.4 times the original tube diameter (width). Next, an internal pressure is applied to the inside of the set pipe 1 and at the same time the left and right ends are pushed in the pipe axis direction by the axial push punches 4 and 5 to finish the shape of the intermediate product 6. This is the first hydroforming step.
[0012]
Next, the intermediate product 6 is taken out from the first hydroform molds 2 and 3 and mounted on another lower mold 7 corresponding to the final product shape, and another upper mold 8 is closed. At this time, the shape of the cavity of the molds 7 and 8 is expanded in the vertical direction with respect to the shape of the intermediate product 6, and also in the horizontal direction from the expansion rate in the vertical direction in the second hydroforming step. In order to reduce the diameter , the metal pipe has a maximum diameter of 1 to 1.4 times the diameter (width) of the pipe after the first hydroform molding. This is because if the shape (height) of the hollow portion in the vertical direction exceeds 1.4 times the diameter (width) of the tube after the first hydroform molding, it is difficult to apply shear deformation to the material. Next, an internal pressure is applied to the inside of the set intermediate product 6 and at the same time, the left and right ends are pushed in the direction of the tube axis by the axial push punches 9 and 10 to finish the shape of the final product 11. As a result, the final product 11 expanded in both the horizontal direction and the vertical direction with respect to the tube 1 is finally completed.
[0013]
In the above example, the pipe was expanded mainly in the horizontal direction in the first hydroforming process, and expanded mainly in the vertical direction in the second hydroforming process. Even if the pipe is expanded in the vertical direction and mainly in the horizontal direction in the second hydroforming step, the effect of the present invention can be obtained similarly.
Moreover, when setting the intermediate product shape | molded by the 1st hydroforming process to the 2nd hydroforming process, it is not necessary to put in the same direction, for example, you may set an intermediate product in the direction inclined 90 degrees. In this case, the direction of the mold cavity in the second hydroforming process is the same as the direction of the mold cavity in the first hydroforming process.
[0014]
Further, the same effect can be obtained even if the tube is expanded after the cross section is flattened in the clamping direction at the time of clamping. In the example of FIG. 6, first, the metal tube 1 is mounted on the lower mold 2 and the upper mold 3 is closed. At this time, the shapes of the cavities of the molds 2 and 3 are expanded in the horizontal direction with respect to the diameter of the metal tube 1 and the diameter of the metal tube in the vertical direction is more than twice the plate thickness. The shape is made smaller than the raw tube diameter (width). Shear deformation can be imparted by reducing the plate thickness (width) from 2 times or more of the plate thickness to less than the original tube diameter (width). However, since adhesion to the mold is increased, a highly lubricated lubricant is applied, etc. It is preferable that the lubrication between the pipe 1 and the upper and lower molds 2 and 3 is improved. Next, an internal pressure is applied to the inside of the set pipe 1 and at the same time the left and right ends are pushed in the pipe axis direction by the axial push punches 4 and 5 to finish the shape of the intermediate product 6. This is the first hydroforming step.
[0015]
Next, the intermediate product 6 is taken out from the first hydroform molds 2 and 3 and mounted on another lower mold 7 corresponding to the final product shape, and another upper mold 8 is closed. In the example of FIG. 6, when setting the intermediate product formed in the first hydroforming step in the second hydroforming step, the intermediate product was set in a direction inclined by 90 °.
That is, in this case, the shape of the cavity of the molds 7 and 8 is expanded in the horizontal direction with respect to the shape of the intermediate product 6 and is perpendicular to the direction of expansion (in the case of FIG. 6, the vertical direction). ) Is smaller than the horizontal tube expansion rate in the second hydroforming step, so that the diameter of the metal tube is twice the plate thickness to the width after deformation in the first hydroforming step (in the case of FIG. 6, The height was made up to 1.4 times (see FIG. 6). This is because if the mold clamping is smaller than twice the plate thickness, it is difficult to impart shear deformation. Moreover, it is because it will become difficult to load a material with shear deformation if it exceeds 1.4 times the width after deformation.
[0016]
Next, an internal pressure is applied to the inside of the set intermediate product 6 and at the same time, the left and right ends are pushed in the direction of the tube axis by the axial push punches 9 and 10 to finish the shape of the final product 11. As a result, the final product 11 expanded in both the horizontal and vertical directions with respect to the tube 1 is finally completed.
[0017]
In the above example, the intermediate product formed in the first hydroforming process is tilted by 90 ° when set in the second hydroforming process. However, the intermediate product may be set without tilting. In this case, the direction of the mold cavity in the second hydroforming process is perpendicular to the direction of the mold cavity in the first hydroforming process. At this time, the tube may be expanded in the horizontal direction in the first hydroforming step, and may be expanded in the vertical direction in the second hydroforming step, or vice versa. That is, the effects of the present invention can be obtained in the same manner even when the pipe is expanded mainly in the vertical direction in the first hydroforming step and in the horizontal direction in the second hydroforming step.
[0018]
To sum up the invention described in FIGS. 5 and 6, is deformed in the direction perpendicular to the direction in which tube expansion, so that less than the expansion ratio in the direction tube expansion, the reduction in the diameter of the metal tube up to twice the sheet thickness The effect of the present invention can be obtained in the same manner as long as the expansion is up to 1.4 times the original diameter (width) of the process (except for the diameter of the raw pipe in the first hydroforming process).
[0019]
In addition, there are counter punches as shown in Fig. 7 and movable molds that can move in the direction of the tube axis, etc. (extracted from Schuler's Metal Forming Handbook). When this method is used for each hydroforming step, the tube expansion rate in each step can be further increased, and the final tube expansion rate can be further improved.
[0020]
Further, the example of FIG. 8 is an example in which the counter punches 12 and 13 are used in the first hydroforming process and the movable dies 14, 15, 16 and 17 are used in the second hydroforming process.
[0021]
Moreover, the example which processed the 1st hydroforming process and the 2nd hydroforming process in the same metal mold | die 20 and 21 is FIG. The pair of molds 20 and 21 has a hollow portion in the horizontal direction in which the metal tube 1 can be expanded, and has a final shape from the outer surface of the metal tube at the initial stage of forming in the direction perpendicular to the tube expansion direction corresponding to the cavity portion (vertical direction). It has movable molds 24 and 25 whose positions can be controlled up to the outer surface of the metal tube. In this way, the mold mechanism is complicated, but the number of molds can be reduced, which is advantageous in terms of cost.
Also, in the case of an integral mold, when a counter punch or a movable mold as in the example of FIG. 7 is used in combination, it is possible to mold to a larger tube expansion rate, which is advantageous.
[0022]
Moreover, the example of FIG. 8, FIG. 9 is an example which does not deform | transform at all in the direction perpendicular | vertical to the direction of pipe expansion also in a 1st hydroforming process and a 2nd hydroforming process. However, it goes without saying that almost the same effect can be obtained if the deformation is up to 1.4 times the original diameter (width) of the process (see FIG. 5).
[0023]
In any of the above examples, when expanding in the horizontal direction, the expansion in the vertical direction is limited, and when expanding in the vertical direction, the expansion in the horizontal direction is limited. The final product shape often becomes a simple shape. Therefore, it is effective to add one more step to finish a complicated shape like an automobile part. That is, the pipe is expanded to the expansion ratio corresponding to the final product by the first and second hydroforming processes (or the processing process using the integrated mold), and the intermediate product 26 is obtained. A hydroforming process is performed so that only the shape is mounted (see FIG. 10). By this method, it is possible to hydroform a part having a complicated shape and a large pipe expansion rate. In forming the intermediate product 26, the first and second hydroforming steps may be performed using the same mold.
As the metal pipe, a steel pipe, a stainless steel pipe, an aluminum pipe, a titanium pipe, or the like can be used.
[0024]
【Example】
Examples of the present invention are shown below.
The raw pipe used was an outer diameter of 63.5 mm, a plate thickness of 2.3 mm, a length of 500 mm, and a material JIS standard STKM11A (carbon steel pipe for machine structure). As shown in FIG. 5, the product shape to be processed was a shape that expanded into a square, the length of one side of the square was 150 mm, the corner R was 8 mm, and the length in the tube axis direction of the expanded portion was 100 mm.
[0025]
First, in the first hydroforming step, the tube was expanded in the horizontal direction and expanded in the vertical direction to obtain an intermediate product. At that time, the shaft pressing amount was 50 mm for both left and right, and the internal pressure was 30 MPa at maximum. By this first hydroforming step, the diameter of the metal tube was expanded to about 1.9 times in the horizontal direction and about 1.1 times in the vertical direction with respect to the diameter of the raw tube.
Next, the intermediate product molded as described above was attached to a second hydrofoam mold having a final product shape and expanded in the vertical direction. At that time, the axial pressing amount was 40 mm on both the left and right sides, and the internal pressure was 30 MPa at maximum. By this second hydroforming step, the diameter of the metal tube was expanded about 1.2 times in the horizontal direction and about 2.1 times in the vertical direction with respect to the diameter (width) of the tube after the first hydroforming. .
[0026]
For comparison, molding was also performed by a conventional method that is not the method of the present invention. That is, the first hydroforming step was omitted, and the raw tube was directly inserted into the mold of the second hydroforming step and molded. As a result, no matter how the axial push and the internal pressure were adjusted, the mold at the expanded portion was not contacted, and burst or buckling occurred and molding could not be performed.
[0027]
【The invention's effect】
According to the present invention, it becomes possible to perform hydroforming with a large expansion ratio, which could not be processed due to a conventional burst or buckling, and as a result, the range of hydroform application parts is expanded. Thereby, it can contribute to the cost reduction and weight reduction effect of the automobile parts as described at the beginning.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a strain state in press working and hydroforming.
FIG. 2 is an explanatory diagram of a forming limit in free bulge processing.
FIG. 3 is an explanatory diagram of a hydroform shape example suitable for shear deformation.
FIG. 4 is an explanatory diagram of a hydroform shape example when shear deformation is difficult.
FIG. 5 is an explanatory diagram of the present invention when the deformation in the direction perpendicular to the direction of tube expansion is 1 to 1.4 times the original diameter (width).
FIG. 6 is an explanatory diagram of the present invention when the deformation in the direction perpendicular to the direction in which the pipe is expanded is from twice the plate thickness to one times the original diameter (width).
FIG. 7 is an explanatory view of a counter punch and a movable mold.
FIG. 8 is an explanatory diagram when a counter punch or a movable die is used in combination with the hydroform processing method.
FIG. 9 is an explanatory diagram of an example of a hydroforming processing method using an integral mold.
FIG. 10 is an explanatory diagram of an example of a hydroforming processing method to which a third hydroforming step of the present invention is added.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Metal pipe 2 ... 1st hydroforming process lower metal mold 3 ... 1st hydroforming process upper metal mold 4 ... 1st hydroforming process left axis pushing punch 5 ... 1st hydroforming process right axis pushing Punch 6 …… Intermediate product 7 after the first hydroforming process ............ Second hydroforming process lower mold 8 …… Second hydroforming process upper mold 9 …… Second hydroforming process left axis push punch 10 …… 2nd hydroforming process right axis push punch 11 ... final product 12 ... 1st hydroforming process front counter punch 13 ... 1st hydroforming process rear counter punch 14 ... 2nd hydroforming process lower left side movable mold 15 …… Second hydroform process lower right movable mold 16 …… Second hydroform process upper left movable mold 17 …… Second hydroform process Upper movable mold 18 ... second hydroforming process left mold shaft pressing tool 19 ... second hydroforming process right mold axial pressing tool 20 ... first second process integrated mold lower mold 21 ... first Second process integrated upper die 22 ... 1st 2nd process integrated left shaft push punch 23 ... 1st 2nd process integrated right shaft push punch 24 ... 1st 2nd process integrated front counter punch ( (Movable mold)
25 …… First counter and second process integrated front counter punch (movable mold)
26 …… Intermediate product 27 after the second hydroforming step 27 ...... Third hydroforming step lower die 28 …… Third hydroforming step upper die 29 …… Third hydroforming step left axis push punch 30 …… No. 3 Hydroforming process right axis push punch

Claims (3)

In a hydroforming method in which an internal pressure and a pushing force in the axial direction of the tube are loaded on the metal tube after the metal tube is mounted on a divided mold and clamped, one cross section of the metal tube is formed in a first hydroforming step. While expanding the metal tube in the direction, the diameter of the metal tube in the direction perpendicular to the one direction is reduced from twice the plate thickness to 1.4 times the raw tube diameter so as to be smaller than the tube expansion rate in the one direction ( In the second hydroforming step, the metal tube is expanded in a direction perpendicular to the one direction in the cross section of the metal tube in the second hydroforming step. The diameter of the metal tube is formed in the one direction to be twice the plate thickness to 1.4 times the width after the deformation so as to be smaller than the tube expansion rate in the perpendicular direction. Method.
However, the expansion ratio = the diameter (width) of the tube after forming / the diameter (width) of the tube before forming. In the first hydroforming step, while expanding the metal tube in one direction of the cross section of the metal tube, the diameter of the metal tube in the direction perpendicular to the one direction is set to a thickness of 2 so as to be smaller than the tube expansion rate in the one direction. After deformation to 1.4 times the tube diameter (excluding 1 times the tube diameter), in the second hydroforming step, it is attached to the final product shape mold, While expanding the metal tube in a direction perpendicular to one direction, the diameter of the metal tube in the one direction is set to be twice the plate thickness to be smaller than the tube expansion rate in the perpendicular direction in the second hydroforming step. The hydroforming method according to claim 1, wherein the hydroforming method is formed to be 1.4 times the width after deformation. In a hydroforming method in which an internal pressure and a pushing force in the axial direction of the tube are loaded on the metal tube after the metal tube is mounted on a divided mold and clamped, one cross section of the metal tube is formed in a first hydroforming step. while tube expanding said metal pipe in a direction, to be smaller than the expansion ratio in the one direction, 1.4 times the double-raw tube diameters of the diameter thickness of the metal tube in the one direction perpendicular to the direction ( In the second hydroforming step, the metal tube is expanded in a direction perpendicular to the one direction in the cross section of the metal tube in the second hydroforming step. A third hydroforming step in which the diameter of the metal tube is formed in the one direction so as to be smaller than twice the plate thickness to 1.4 times the deformed width in one direction so as to be smaller than the tube expansion rate in the perpendicular direction; The intermediate product Hydroforming method characterized by mounting the mold product shape, for hydroforming.
However, the expansion ratio = the diameter (width) of the tube after forming / the diameter (width) of the tube before forming.

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