JPH07284971A - Solid shaped body for press forming and production therefor - Google Patents

Abstract

PURPOSE:To avoid a forming failure, rationalize the pressing process, strengthen a member and lighten the member by using a solid shaped body of a near net shape made in one body by laser welding. CONSTITUTION:A metal plate is cut into plural specific flat plane like pieces, plural specific solid shaped metal shells are formed by pressing or rolling, and these metal plates and metal shells are assembled into a solid shaped body for press forming to be obtained. For example, a raw material of bottom part 10 and parts of a side wall 11 are assembled. They are assembled into a solid shape, and joined integrally by laser welding. Using this solid shaped body for press forming, a press formed product is produced in which the maximum strain in welding part is regulated to <=10%. Therefore, in the case of pressing a hard-to-work material, the forming failure can be avoided with a comparatively few pressing processes, and the hard-to-work material such as a high-strength steel plate can effectively be utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a press-formed product of parts such as automobiles and home electric appliances.

[0002]

2. Description of the Related Art In recent years, in the manufacture of automobile body parts, the number of press molding processes has been reduced and the manufacturing process has been simplified by integral molding.
Continuity is an indispensable technological element in reducing manufacturing costs. When a three-dimensional shaped part is manufactured by press molding from a flat metal plate, the more complicated the shape of the final product is, the more easily press molding defects such as breakage and defective shape occur. It becomes difficult to perform press molding in a small number of steps. In order to avoid problems with press molding, a multi-step press molding process is provided, and press molding is performed little by little to finally obtain the desired product shape, and small divided parts are individually manufactured by press molding. However, a general method is to join them to obtain the final product. However, these methods have problems such as an increase in the number of pressing steps and an increase in equipment / die costs, which are against the modernization of the manufacturing process such as omission of processes and integral molding. Therefore, although press forming is performed using a steel sheet having extremely excellent press formability, the cost of the raw material increases significantly. JP-A-59-220229 and JP-B-3-625
No. 16 discloses a method of integrally manufacturing a press-formed product using a flat blank in which a plurality of metal plates are joined by laser welding. This is advantageous in terms of the number of pressing steps and die cost, and the material yield can be improved by devising the method of cutting the material. However, due to the combination of the welded portion and the material, the press-forming material is inhomogeneous in the plate surface, so that it is more disadvantageous than the conventional homogeneous material in terms of formability. That is, the problem is widening in terms of avoiding press-molding defects.

[0003]

When a product having a three-dimensionally complicated shape is obtained by press molding from a flat material, the material during the molding is broken (including the reduction of the plate thickness due to the constriction) and the shape of the product is defective (wrinkles). , Flaws, warpage, twisting, etc., become problems. In particular, low-priced steel plates, high-strength steel plates, aluminum alloy plates, etc. are characterized by material properties such as insufficient ductility, in-plane plastic anisotropy, high yield strength, and low elastic modulus.
The above-mentioned press-molding defects are likely to become noticeable. On the other hand, in the flat blank obtained by laser bonding, the ductility of the welded portion is significantly lower than that of the base metal, and thus cracks are also likely to occur during press forming. In addition, when using flat plate laser bonding blanks that combine different materials in the right place for the purpose of weight reduction, strength enhancement, corrosion resistance improvement, material cost reduction, etc., since the deformation behavior during processing differs depending on the material, single plate Shape defects that did not occur may occur.

The present invention has problems such as breakage during production, wrinkles, or defective product shape in the press forming of relatively low-priced steel plates, laser-bonded steel plates, high-strength steel plates, and aluminum alloy plates. The purpose is to make it easier to avoid.

[0005]

In order to solve the above problems, according to the present invention, a plurality of metal plates joined by laser welding into a three-dimensional shape close to the shape of the press-formed product to be obtained is used for press-forming. It is characterized by being used as a material, and its gist is as follows.

(1) A metal plate cut into a plurality of predetermined plane shapes or a three-dimensional metal shell processed into a shape having a curved surface is welded to a three-dimensional shape close to the shape of the press-formed product to be obtained. The three-dimensional product for press molding is characterized by being combined.

(2) A metal plate is cut into a plurality of predetermined plane shapes, and / or the further cut plane shape metal plate is formed into a plurality of predetermined three-dimensional shape metal shells by press molding or roll forming, and these metal plates are formed. And a press molding characterized by combining with a three-dimensional shape close to the shape of a press-formed product to obtain a metal shell and performing end face processing or not end face processing so that they can be butt-welded to each other and joined by laser welding. For manufacturing three-dimensional products for automobiles.

(3) Press molding wherein the maximum distortion of the welded portion is 10% or less is performed by using the three-dimensionally shaped product for press molding described in (1) or (2) above. Method of manufacturing goods.

[0009]

The present invention will be described in detail below.

Conventionally, the press forming of a metal plate that has been carried out uses a flat plate as a material for press forming. In such press forming, various deformations are applied to the product depending on the mechanical properties of the blank material and the press forming conditions, and a strain distribution is generated. Press molding defects such as breakage and defective shape,
This is because a large strain is locally concentrated, a non-uniform deformation mode is generated, and the deformation mode is distributed depending on places. Generally, in deep drawing and press forming of a complicated part shape, the larger the deformation applied, the larger the distribution of the deformation modes and the higher the non-uniformity.

In order to reduce such nonuniformity of deformation, it is desirable to suppress the deformation given to each part of the material during press forming as much as possible. For that purpose, a material having a shape close to the shape of the final product may be used as the material for press molding. However, if press molding is used to obtain such a material, naturally, the equipment cost of the mold and the like increases and the number of steps increases, but a great effect cannot be expected. Therefore, the present invention proposes a method of assembling a three-dimensional shape using laser welding as a method of embodying the near net shape. With the recent development of laser processing technology, laser welding in which the position in three-dimensional space coordinates is controlled is possible. In particular, welding with a YAG laser is relatively easy to control. By using this technique, it is possible to three-dimensionally combine a plurality of metal plates processed into a predetermined shape with their ends abutted and join them by laser welding. If necessary, a filler wire may be supplied at the time of welding to prevent welding failure due to poor matching accuracy. The metal plates to be combined may have the same composition, metal structure, mechanical properties, plate thickness, surface treatment, lubrication, etc., but with respect to weldability, press formability, corrosion resistance, strength, rigidity, fatigue durability required for products, etc. Depending on the type, two or more types may be used together.

Part or all of the metal plates to be combined may have a curved surface by a simple preliminary process such as bending. The preliminary processing refers to a deformation given when the metal plates are fixed when they are combined and welded. The processing may be processing up to plastic deformation or elastic deformation alone.

By subjecting the three-dimensional press-molded article obtained as described above to press-molding, it becomes easy to avoid press-molding defects even with difficult-to-mold materials. Also,
In many cases, the ductility of the weld is lower than that of the base metal, but since the material used for press forming is assembled in a three-dimensional shape, it is possible to suppress the strain received by the press during welding. . The fracture limit strain of the welded part is determined by the material and welding conditions, but if the strain of the welded part due to press forming is smaller than the limit value, a sound product can be obtained. As a result of investigating the breaking limit strain of various steel plates and aluminum alloy plates shown in the examples, it was possible to secure a breaking limit strain of more than 10% in any combination of materials. The upper limit of the strain received was 10%. That is, if a three-dimensional product is manufactured so that the strain applied to the welded portion during press forming is 10% or less, breakage of the welded portion can be avoided.

[0014]

EXAMPLES Next, the present invention will be specifically described with reference to Examples.

Example 1 When manufacturing a spherical frustoconical product having a bottom of 40 mm in radius as shown in FIG. 1, generally, the punch 1, the die 2 and the blank holder 3 shown in FIG. Using one tool, deep drawing is performed using the circular blank 4 shown in FIG. In this case, the molding defects that are likely to occur are breakage 7 near the punch shoulder, wrinkles 8 at the side wall portion, and blemishes 9 at the opening end of the cup as shown in FIG.

Here, the metal plate shown in Table 1 was cut into the joining base plates 10 and 11 shown in FIG. The combinations shown in Table 2 were joined by laser welding, the parts shown in FIG. 5 were assembled, and the parts were subjected to press molding. At this time, the joining base plate 11 is deformed and fixed in a shape having a curved surface at the time of joining, as shown in FIG. The size of this press-molding material was set to be slightly smaller than the product size so that the minimum plastic deformation necessary for producing the shape during press-molding is added. The press molding at this time is performed by the convex mold 1 shown in FIG.
Two tools, 2 and concave 13, were used. For comparison, one flat metal plate shown in Table 1 was used as a blank for press forming with the tool of FIG. 2 and two types of metal plates cut into shapes 5 and 6 as shown in FIG. Press molding was also carried out using the tool shown in FIG. 2 (a) in which a flat laser-bonded product was used as a blank. The results are shown in Table 2.

[0017]

[Table 1]

[0018]

[Table 2]

This part is shown in FIG. 2 (b) with the tool of FIG. 2 (a).
When the blank of No. 1 is used for forming, as shown in Example g, the metal plate A has breakage, wrinkles, and imperfections in molding. However, even if the same metal plate is used as shown in Example a, molding defects can be avoided. And you can get the product. If the laser-bonded blank shown in FIG. 2 (c) is used as in Example j, a wrinkle-free product can be obtained from a flat plate by deep drawing. Causes the weld to break.

Since the stains can be removed by post-treatment after press molding, even if excluded from defective molding, a material of metal plate C or higher is required for molding from a single plate as shown in Example i. However, such a material is not preferable because of its high price. In particular, when corrosion resistance is a problem for a part of the product, surface treatment such as plating is required, which further increases the material cost. For example, when the spherical bottom of the product of FIG. 1 requires corrosion resistance, it is necessary to use a material having both corrosion resistance and moldability in the method of deep drawing from a single plate, as shown in Example j, It is disadvantageous in terms of material cost. However, as shown in Example b, according to the present invention, the plating material may be used only on the bottom portion of the product requiring corrosion resistance, and even a low-grade material can be formed, so that the material cost can be significantly reduced. .

When strength and weight reduction of the product are required, it is necessary to use a high-strength steel plate or an aluminum alloy plate as the metal plate. However, since such a material is inferior in formability, it is possible to form a single plate by deep drawing. When performing, molding defects are likely to occur. Example h is an example thereof, and even if a solid lubricant is used, molding defects such as breakage and wrinkles occur. However, as shown in examples c and e,
According to the present invention, a product can be obtained while avoiding molding defects even when such a material is used. In addition, as in Examples d and f, it is possible to balance the strength or weight with the cost by using a low-priced material in part.

Embodiment 2 Since deep-drawing parts such as a wheel house of automobile parts, fuel tanks, and fenders have problems of breakage and wrinkling, many steps are required for press molding. Here, the present invention will be described by taking the wheel house inner shown in FIG. 7 as a typical example. In the conventional method of press-forming from one flat plate, an expensive metal plate C having good formability was used to obtain the shape shown in FIG. 7, but wrinkles occurred at the 14th part and breakage occurred at the 15th part. In order to achieve this, three stages of pressing processes are provided for molding. As an application example of the present invention, here, the components shown in FIG. 8 were assembled by laser bonding and subjected to press molding. The materials for assembly at this time are 16 and 1 shown in FIG.
The metal plate C was used only for 18, and the metal plate D of relatively low cost was applied to 16 and 17. When the three-dimensionally shaped product for press molding shown in FIG. 8 is used, the pressing step has only one step, the maximum value of strain applied to the welded portion is 9%, and the shape shown in FIG. 7 can be obtained without molding defects. In this case, it is possible to omit the pressing process and reduce the material cost.

Embodiment 3 Frames such as members of automobile parts, pillars, and sill have a problem of shape freezing failure due to spring back (elastic recovery, rebound) during press molding. In recent years, a high-strength steel plate such as the metal plate E and an aluminum alloy plate such as the metal plate G have been applied from the viewpoints of collision safety and weight reduction of a vehicle body. Since it is large, the pressing process for shape correction is increased.
Here, the present invention is applied to a side member of an automobile part having a shape shown in FIG. 10 as a typical example of such a product. The shape freezing failure in this case is mainly called “sledding” shown in FIG. 11, and is a phenomenon in which the vertical wall portion has a curvature and the end portion is wide open. This is a phenomenon of shape freezing failure due to residual stress after bending deformation at the punch shoulder and bending / bending back deformation at the die shoulder. In order to avoid the warpage, the above bending deformation should be avoided. Here, the three-dimensional press-molded product shown in FIG. 12 was assembled using the metal plate G and the metal plate E as raw materials, and press-molded in one step. As a result, the product in FIG. 10 could be manufactured without causing warpage. Further, the maximum value of strain that the welded part receives is 6%, and no fracture of the welded part occurs.

[0024]

EFFECTS OF THE INVENTION By using the three-dimensionally shaped product for press molding according to the present invention, it becomes easy to avoid molding defects with a relatively small number of pressing steps in pressing of difficult-to-mold materials, so that it is possible to reduce the molding material. It is extremely effective for cost reduction, rationalization and efficiency of the pressing process, and strength and weight reduction of parts.

[Brief description of drawings]

FIG. 1 is a perspective view of a press-formed product according to a first embodiment of the present invention.

2A is a sectional view of a tool for obtaining the product of FIG. 1 from a flat plate by deep drawing, FIG. 2B is a plan view of a single plate blank, and FIG. 2C is a plan view of a laser-bonded blank.

FIG. 3 is a perspective view of a molded product when press-molded by the method of FIG. 2, and an explanatory view of an example of molding failure.

FIG. 4 is a development view of the joining material of the present invention.

FIG. 5 is a perspective view of a three-dimensional product for press molding of the present invention.

6 is a cross-sectional view of a tool used for the press-molding material of FIG.

FIG. 7 (a) is a perspective view of an automobile part wheel house inner drawing process completed product (simultaneous left and right molding), and FIG.
-A 'sectional view.

FIG. 8A is a perspective view of a three-dimensionally shaped product for press molding of the present invention, and FIG. 8B is a cross-sectional view taken along the line BB ′.

9 (a), (b) and (c) are explanatory views of a joining material constituting the three-dimensional press-formed product of FIG.

FIG. 10 is a perspective view of an automobile part side member.

FIG. 11 is a cross-sectional view of a side member for explaining the warpage.

FIG. 12 is a perspective view of a three-dimensional press-formed product for a side member of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Punch 2 ... Die 3 ... Blank holder 4 ... Single plate circular blank 5 ... Laser joining material (bottom) for obtaining a flat plate press-forming material 6 ... Laser for obtaining a flat plate press-forming material Joining material (side wall) 7 ... Breakage 8 ... Wrinkle 9 ... Stain 10 ... Laser joining material (bottom) 11 for obtaining a three-dimensional press-formed three-dimensional product 11 ... Three-dimensional press-formed three-dimensional product Material for laser bonding for obtaining (side wall portion) 12 ... Convex type 13 ... Recessed type 14 ... Wrinkled portion 15 ... Breakage portion 16, 17, 18 ... Configure the three-dimensional press-molded article of FIG. Material for assembly

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasunobu Miyazaki 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (3)

[Claims] 1. A metal plate cut into a plurality of predetermined plane shapes or a three-dimensional metal shell processed into a shape having a curved surface is combined with a three-dimensional shape close to the shape of a press-formed product to be obtained through a weld. A three-dimensional product for press molding, which is characterized by being 2. A metal plate is cut into a plurality of predetermined plane shapes,
And / or a plurality of three-dimensional metal shells having a predetermined three-dimensional shape are formed by press-molding or roll-molding a flat-shaped metal plate that has been further cut, and these metal plates and metal shells are combined into a three-dimensional shape close to the shape of the press-formed product to be obtained , End-face processed or not end-face processed so that they can be butt welded to each other,
A method for manufacturing a three-dimensionally shaped product for press molding, which comprises integrally joining by laser welding. 3. The maximum strain of the welded portion is 10% when using the press-formed three-dimensionally shaped product according to claim 1 or 2.
A method for producing a press-formed product, which comprises performing the following press-forming.