JPH05212464A - Method for forming metal sheet by using hydraulic pressure with metal die - Google Patents

Abstract

PURPOSE:To facilitate the forming of materials with low formability by performing an intermediate forming through a hydraulic pressure while fixing the periphery of a plate material with a blank holder, and then forming a final article to be formed by means of punch and die in accordance with the final shape. CONSTITUTION:The periphery of the plate material is fixed with the blank holder, a hydraulic pressure is applied from the punch side and the intermediate forming is performed. Then, the punch is lowered, the forming is performed between punch and die and the final shape is made. Thus, the forming of materials with low formability by a conventional metal die method, is facilitated, and also, the shapeability of a formed article, which is a problem with the conventional hydraulic forming, is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is for processing a blank material such as a thin metal plate to obtain automobile parts, electric parts, etc.
The present invention relates to a molding method in which both hydraulic molding and die molding are used and the advantages of both are utilized.

[0002]

2. Description of the Related Art Conventionally, a press molding method for a thin metal plate using a pair of upper and lower molds has been widely used as a known technique. Further, regarding the hydraulic forming, Japanese Patent Application Laid-Open No. 48-4359,
This is a known technique as disclosed in JP-A-48-57881. However, for low-formability materials such as high-strength steel plates and aluminum, press forming with a die has a limit of application, and hydraulic forming is limited to special applications due to the problem of shape and dimension accuracy of products.

[0003]

SUMMARY OF THE INVENTION The present invention facilitates the molding of low-formability materials such as aluminum and high-strength steel sheets, which were difficult to form by the conventional molding method using a die, and also uses conventional hydraulic forming. It is a new molding method that improves the shape of a molded product in question, and an object thereof is to provide a new molding method that can eliminate the drawbacks of both molding methods.

[0004]

The present invention has been made by research to solve the problems of the above-mentioned prior art. In the present invention, in the first step, while fixing the periphery of the material by the upper mold wrinkle holding mold and the lower mold,
A liquid, which is a pressure medium, is fed from the punch side of the upper die to perform hydraulic forming, and in a second step, the end portion of the hydraulically formed material is fixed by a wrinkle holding die and a lower die of the upper die. However, after the liquid is discharged, or while the liquid is being discharged, the material is pushed downward by the punch of the upper mold and brought into close contact with the bottom surface of the molding lower mold, thereby performing the mold molding.

[0005]

The present invention eliminates the drawbacks of hydraulic molding and mold molding,
This is a molding method that takes advantage of the advantages of both, and is a molding method that facilitates the molding of low-strength materials such as high-strength steel sheets and aluminum.
The molding mechanism is explained below.

The first problem in press molding is breakage. In the usual die forming, the point where the strain is concentrated is mainly determined by the target shape, and especially in the case of high-strength steel sheets and low-ductility materials such as aluminum, fracture occurs at such places and molding failure occurs. It will be possible. In the example shown in FIG. 1, the fracture occurs at the punch shoulder portion A. On the other hand, in hydraulic forming, since there is no frictional force, breakage occurs at the portion B in FIG. In the present invention, as shown in FIG. 3A, in the hydraulic forming of the first step, the strain is developed in the C portion, and in the second step shown in FIG. By dispersing the concentrated points of the above and uniformly deforming the entire molded product, the molding limit of a low ductility material such as a high strength steel plate or aluminum is improved.

The next problem is shape. Even if it can be molded without breaking, it cannot be a product unless the desired shape is obtained. In particular, a high-strength steel sheet has a high yield stress, and aluminum has a low Young's modulus, which makes it impossible to obtain a desired shape of a molded product due to springback after forming. From the viewpoint of the molding method, it is possible to eliminate such a shape defect by increasing the amount of deformation at the place where such a shape defect occurs. That is, the springback corresponds to the ratio of the amount of deformation given by processing and the amount of elastically recovered deformation, and the amount of elastically recovered deformation decreases as the amount of deformation by processing increases. However, for example, in the case of die molding shown in FIG. 1, the deformation amount of the E portion is at most several percent due to the frictional force between the punch and the material. On the other hand, in the present invention, in the hydraulic forming of the first step shown in FIG. 3 (a), a sufficient molded product shape is obtained by sufficiently deforming the C portion, which cannot be deformed by the usual die molding. It becomes possible.

Further, in the conventional hydraulic molding, there is a limit to the hydraulic pressure that can be industrially added, so when it is necessary to obtain a molded product having a small radius of curvature as shown in F part of FIG.
Cannot obtain a sufficient shape. However, according to the present invention, it is possible to obtain a molded product having such a small radius of curvature because the molding is performed in the second step. As described above, the present invention eliminates the drawbacks of conventional hydraulic molding and mold molding,
This is a revolutionary new molding method that takes advantage of its advantages.

[0009]

【Example】

(Example 1) 5000 having mechanical property values shown in Table 1
An aluminum alloy of the system and a high-tensile steel plate having a high tension of 60 kgf / mm ² were used for the test. As a molding test, as shown in FIG.
As a comparison with the molding method according to the present invention shown in FIG.
The hydraulic molding shown in and the molding with the die punch were performed. The target molded product is a cylindrical molded product having a diameter of 100 mm. Hydraulic forming has a wrinkle holding force of 10 tons, die forming has a wrinkle holding force of 0.5 tons to 4 tons with a 0.5 ton pitch, and blank diameter varies from 160 to 180 mm with a 5 mm pitch, and deep cylinder forming is performed for maximum. The molding height of was determined. The molding conditions of the present invention are that the wrinkle holding force is 10 tons and the height is 25 mm.
Hydroforming was performed up to, and thereafter, die molding was performed up to 40 mm. The results are shown in Table 2.

With respect to the 5000 series aluminum alloy, in hydraulic forming, it fractured at a forming height of 28 mm at a portion B in FIG. In mold forming, wrinkle holding force is 1 ton, blank plate size is 170
Maximum molding height of 35 mm was obtained in mm, but if the blank size or wrinkle holding force is increased further, fracture occurs at part A in Fig. 1, and if the wrinkle holding force is reduced, wrinkles occur and normal molded products are obtained. Was not obtained. On the other hand, according to the molding method of the present invention, a molded product having a molding height of 40 mm could be obtained. The result was the same for the high-tensile steel plate having a high tensile strength of 60 kgf / mm ² .
The results are shown in Table 2.

5 to 7 show the results of examining the strain distribution of molded articles of 5000 series aluminum alloys by the three molding methods including the present invention. 5 shows the strain distribution of the die-molded product, FIG. 6 shows the strain distribution of the hydraulic molded product, and FIG. 7 shows the strain distribution of the molded product of the present invention. The molded product molded according to the present invention is deformed more uniformly than the other two conventional molding methods, and the above-mentioned good results are obtained by this effect. As described above, the present invention is an unprecedented and revolutionary new molding method that makes the most of the deformability of the material.

[0012]

[Table 1]

[0013]

[Table 2]

Example 2 Using a 5000 series aluminum alloy and SPCE steel having the mechanical property values shown in Table 3, FIG.
Using the die punch shown in FIG. 1, conventional die molding and molding according to the present invention were performed. In the present invention, in order to obtain the desired radius of curvature and to secure the shape by obtaining the distortion of the G portion of FIG. 8, the molding is performed by hydraulic pressure up to the molding height of 30 mm, and then the molding is performed by the die punch. It was The result of measuring the radius of curvature of the G portion is shown in FIG. For comparison, the figure shows the result of molding SPCE by ordinary mold molding. Since the aluminum alloy has a low Young's modulus, the desired shape cannot be obtained by ordinary mold forming as compared with steel. In general, it is possible to strengthen the wrinkle holding force to make the distortion of the G part in FIG. 8 closer to the desired shape, but since aluminum has low ductility, breakage occurs at the H part in FIG. 8 and molding failure occurs. It will be possible. On the other hand, according to the present invention, when molding is performed, it becomes possible to obtain a target shape by controlling the amount of strain in the G portion in the hydraulic molding in the first step.

[0015]

[Table 3]

(Example 3) Using the SPCE steel used in Example 2, the truncated cone shape shown in FIG. 10 is formed and the radius of curvature of the I portion is formed by various hydraulic pressures. In hydraulic forming, it is possible to obtain a molded product having a small radius of curvature as the hydraulic pressure is increased, but it is difficult to obtain a radius of curvature of 10 mmR or less. However, in the present invention, since the molding is performed by the mold in the second step, it is possible to obtain a molded product having a radius of curvature substantially equal to the punch shoulder radius of 3 mm which is the main test.

[0017]

INDUSTRIAL APPLICABILITY The present invention relates to a molding method for processing a blank material such as a metal thin plate to obtain an automobile part, an electric part, etc., which is difficult to form by a conventional molding method using a die. It is an epoch-making new molding method that facilitates the molding of low-formability materials such as high-strength steel sheets and improves the formability of molded products, which is a problem in conventional hydraulic forming. Therefore, an extremely large effect is expected in the industry.

[Brief description of drawings]

FIG. 1 shows an example of die molding.

FIG. 2 shows an example of hydraulic forming.

FIG. 3 (a) shows hydraulic molding which is the first step of the present invention, and (b) shows mold molding which is the second step of the present invention.

FIG. 4 shows an example of a molded product having a low radius of curvature.

FIG. 5 shows a strain distribution of a die-molded product.

FIG. 6 shows the strain distribution of a hydroformed product.

FIG. 7 shows the strain distribution of a molded product according to the present invention.

FIG. 8 shows the punch shape used.

FIG. 9 shows the relationship between the wrinkle holding pressure and the radius of curvature.

FIG. 10 shows a truncated cone tool.

FIG. 11 shows the relationship between the radius of curvature and the hydraulic pressure.

Claims (1)

[Claims] 1. When manufacturing various molded products from a thin metal plate, intermediate molding is performed by hydraulic pressure while fixing the periphery of the blank plate with a blank holder, and then the final shape of the product is maintained with the periphery of the blank plate fixed. A molding method characterized by obtaining a final molded product with a corresponding punch and die.