JP2687536B2 - Press forming method for bonded materials - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to sheet metal stamping, and more particularly to a method for press-forming a joining material of plates having different thicknesses.

[Prior Art] Conventionally, a metal plate (a steel plate, a stainless steel plate, an aluminum alloy plate, etc.) having a uniform plate thickness or a gradual plate thickness change is used as a forming material in a drawing press process. Was limited to.

On the other hand, due to the practical use of laser welding technology, press forming with laser welded joint materials has also been performed to improve product yield from the viewpoint of effective use of materials, but it is limited to metal plate combinations with the same plate thickness. Has been done.

[Problems to be solved by the invention]

In order to improve product yield and reduce product weight,
It is required to develop a press-formed product made of a material obtained by laser-welding plates having different thicknesses. However, in the drawing press, it is necessary to have a clearance equal to the plate thickness of the material between the upper die and the lower die, and the die corresponding to the step (step) according to the sheet thickness difference at the material joining part. It is very difficult to introduce the step change of the clearance into the mold due to the variation in the injection of the bonding material into the mold and the variation in the behavior (deformation / movement) of the bonding material in the drawing process. Therefore, it is considered that the deterioration of product quality is inevitable when the laser-bonded materials having different plate thicknesses are applied to press molding.

FIG. 3 shows an example of the material 1 in which plates having different thicknesses are combined (for example, laser-welded). In this case, the plates 2,3,
4 and 5 have thicknesses of t ₂ , t ₃ , t ₄ and t ₅ , respectively,
(Laser welding) The plate 2 is joined at the joining portion 6.
(T ₂ ) or plate 4 (t ₄ ) and plate 3 (t ₃ ) and plate 5 (t ₅ ) have different thicknesses. 4A and 4B show the shape of the strain generated in the material (product) when the material 1 is press-molded with a press die having a step (step) clearance change equal to the plate thickness difference. Show. FIG. 4A and FIG. 4B show a processing situation in the vicinity of the joint portion 6 between the plate 2 and the plate 3,
The lower die 7 of the die is provided with a clearance step 8.
The height difference Δt at the clearance step 8 is determined by the connecting plates 2 and 3
Is equal to the plate thickness difference t ₂ −t ₃ = Δt. The upper mold of the mold is omitted in the drawing. FIG. 4A shows the case where the joint portion 6 of the joint material is displaced from the clearance step 8 toward the thin plate (3) side, and FIG. 4B is the case where it is displaced toward the thick plate (2) side. The amount of deviation is 1, the strain height (depth) of the plate is H,
The strain range is indicated by L. According to an experiment conducted by the present inventor using a pressed steel sheet for automobiles, the relationship between the strain amount ratio (shown by H / L) and the shift amount 1 shown in FIG. 5 was obtained. Considering that the total variation (variation range) of the joining material into the mold and the variation in material behavior during the drawing process is ± 10 mm, the strain amount ratio H / L generated in the product is within ± 0.01. It can be seen from Fig. 5 that there are variations and the product quality is not stable.

Therefore, it is an object of the present invention to provide a method for forming a high quality product by reducing the amount of strain in the vicinity of a joint portion when press-forming joint materials for plates having different thicknesses.

[Means for solving the problem]

In the method in which the above-mentioned object is press-molding the joining material in which the plates having different thicknesses are welded by the upper die and the lower die,
One side surface of the bonding material is flat and contacts the upper or lower mold of the mold, while the opposite side surface has a step at the material bonding part due to the difference in plate thickness, and the lower or upper mold of the mold This is achieved by a press-molding method of a bonding material, characterized in that an inclined surface made of a difference in plate thickness and a length of 50 times or more thereof is provided, and a material coupling portion is located on the inclined surface.

(Operation)

A relatively long (slow) inclined surface is provided on the lower die (or upper die) of the press die, and the material joining part is located on the inclined surface so that the material can easily slide on the inclined surface during molding. , Strain height (depth) and strain amount H / L are reduced.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to an example of press-molding a bonding material having a plate thickness difference including the case according to the present invention.

Fig. 2 shows the clearance difference in the lower die 11 of the press die.
12 shows a partial cross section with 12. The clearance step 12 is an inclined surface, and its height difference Δt is equal to the plate thickness difference in the joint material to be pressed, and its length S is made considerably larger than Δt. The upper die (not shown) of the press die is flat and contacts the flat surface of the bonding material. Therefore, conversely, a clearance step may be provided on the upper mold so that the lower mold has a flat surface.

Press the plate joining (laser welding) material having the same thickness as the conventional one with the lower die 11 and the flat upper die in FIG. 2 so that the joining portion with the step comes to the clearance step (sloping surface) 12. Mold. At that time, the ratio of the length to the height difference (S / Δt) at the clearance step of the lower mold 11 is 50 to 14
The strain amount ratio H / L between the strain height (depth) H and the strain range L near the joint was determined by changing the strain in the range of 0, and the results shown in FIG. 1 were obtained. As the ratio (S / Δt) increases, the strain amount ratio (H / L) decreases.

If the strain amount ratio H / L is 0.005 or less, for example, the strain height (depth) in the strain range of 20 mm is 0.1 mm or less, the quality of the product is acceptable in automobile parts. From this, it can be seen from FIG. 1 that the ratio S / Δt at the clearance step is 90 or more. This amount does not change in the strain amount ratio even when considering that the range of variation of the input of the bonding material and the behavior is ± 10 mm (total 20 mm).

Therefore, the metal mold for press-molding the material in which the plates having different thicknesses are combined has a height difference corresponding to the plate thickness difference Δt at the portion of the upper mold or the lower mold where the joint portion of the joint material abuts. By providing a gentle inclined surface that changes the clearance step by 90 times or more of Δt, it is possible to reduce the processing distortion and obtain a pressed product of stable quality. The range of the inclined surface is determined in the range of the strain amount ratio of 50 to 140 according to the required quality of the pressed product according to FIG.

〔The invention's effect〕

According to the present invention, since the inclined surface having a long length is formed in the press die, the joint portion of the joint material can be located on the inclined surface even if there is variation, and the pressing material can be formed during the press molding. Since the deformation is gentle on the inclined surface, the clearance step corresponding to the difference in plate thickness does not hinder the forming. As a result, conventionally, the bonding material having a difference in thickness is limited to the shallow drawing product, but it can be applied to the deep drawing product.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the ratio of the length to the height difference in the clearance step of the inclined surface provided in the mold and the strain amount ratio generated in the bonding material of the press-formed product, and FIG. FIG. 4 is a partial cross-sectional view of a lower mold having an inclined surface provided in the mold, FIG. 3 is a perspective view of a joining material of plates having different thicknesses, and FIGS. 4A and 4B are conventional molds. FIG. 5 is a partial cross-sectional view of the joining material and the lower die near the joining portion when the joining material is press-molded, and FIG. 5 is a deviation when the joining material having a plate thickness difference is press-formed with a conventional die. It is a graph which shows the relationship between the amount and the strain amount ratio. 1 ... Coupling material, 2-5 ... Plate, 6 ... Coupling part, 11 ... Lower mold, 12 ... Slope, Δt ... Clearance step (plate thickness difference), S ... Length at slope It is.

Claims (1)

(57) [Claims] 1. A method of press-molding a joining material, which is obtained by welding plates having different thicknesses, with an upper die and a lower die, wherein one side surface of the joining material is flat and the upper die or the lower die of the die. On the other hand, there is a step on the opposite side surface at the material joining part due to the difference in plate thickness, and the lower mold or upper mold of the mold is made with the difference in plate thickness and 50 times or more of that difference. A method for press-molding a joining material, comprising providing an inclined surface and arranging the material joining portion on the inclined surface.