JPS59169631A - Forming of assymmetrical stretch flange - Google Patents

Abstract

PURPOSE:To obtain a formed product of titled flange having high work accuracy and large draft by giving initial distribution of strain necessary to obtain uniform working strain at the hole edge to a material after working and then forming the stretch flange to obtain specified shape in the next stage. CONSTITUTION:As the first stage of working, an elliptic hole 41 is formed by blanking or cutting in the material (k) to make the direction of minor axis of an oblong punch a major axis, and bulged as shown by l. As the second stage of work, an oblong prepared hole 42 is worked by blanking or cutting to make the major axis conform to the direction of major axis of above-mentioned oblong punch or desired final shape. Then, this is worked to stretch flange using above- mentioned oblong punch and a product (n) of final shape is obtained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to the elongation 7-lunge forming method for metal sheet materials, and in particular to the elongation 7-lunge forming process for non-axisymmetric elongation 7-lunge processed products that require high processing accuracy and large processing rate. This invention relates to a non-axisymmetric stretch 72-inch molding method suitable for molding.

[Background technology]

A product with a hole 2 in the bottom 1 of an elliptical or long cylindrical container as shown in Fig. 1a, and a product with a slanted cylinder or an elongated cylinder 3 without a bottom as shown in Fig. 1b. To process the material, as shown in Fig. 2, a pilot hole 12 is made in the metal plate material 11, and a non-axisymmetric elongation 7 lunge process is applied, in which a pilot hole 12 is made in the metal plate material 11 and the hole is stretched out using an elliptical or long cylindrical punch 13. Common. However, in such non-axisymmetric elongation 7 lunge machining, there are parts where deformation is locally larger than in axisymmetric machining, so deformation at the hole edge becomes non-uniform. Generally, the thickness of the plate after forming becomes uneven due to the cracks, and cracks 4 occur at the flange part at the longitudinal hole edge where deformation is concentrated during processing, as shown by C in Figure 1. The disadvantage was that product defects were likely to occur. Additionally, in order to prevent such cracks from propagating to the flange, a technique has been reported in which a pilot hole 5 is drilled in the material as shown in FIG. It limits and promotes the occurrence of
For this reason, the holes in the vJ stage are connected,
There was a drawback that the machining limit was low because the machining was completed.

As mentioned above, conventional non-axisymmetric stretch 7-lunge machining has limitations in machining accuracy and machining rate. For example, parts that make up the heart of electronic equipment require high precision and large machining rate. It could not be applied to those who

[Purpose of the invention]

The present invention has been made with attention to this point, and it is an object of the present invention to provide a non-axisymmetric elongation 7-lunge forming method that has uniform processing strain at the hole edge after processing, has high processing accuracy and large processing rate. The purpose is to

[Summary of the invention]

In order to achieve the above object, in the present invention, elongation 7
Lunge forming 1: Divided into a two-stage processing process, the first stage processing process gives the material the initial strain distribution necessary to achieve uniform processing strain at the hole edge after processing, and the second stage processing process It is constructed so that it can be stretch flanged into a predetermined shape.

That is, in non-axisymmetric stretch flange forming, in order to achieve a uniform processing strain distribution at the hole edge after processing, the present inventors have determined that in order to achieve a uniform processing strain distribution at the hole edge after processing, it is necessary to The need for a material with a large initial machining strain distribution at the hole edge in the direction, and in order to give such a material the necessary machining strain distribution, K is, for example, a circular shape or a non-axisymmetric punch to be used or the desired shape. A prepared hole is formed in a non-axisymmetric shape (for example, an elliptical shape) such that the long axis coincides with the short axis direction of the final product shape,
It has been found that this can be obtained by stretch molding using the punch described above.

Based on this knowledge, first, a material with a predetermined pilot hole drilled as described above is stretch-formed using the non-axisymmetric punch, and then the non-axisymmetric punch is used to form the material in the longitudinal direction of the desired final shape. After machining a pilot hole with a shape (for example, an elliptical hole or an oblong hole) whose long axes coincide with each other, the non-axially symmetrical punch is used to form the hole into the final shape, so it is possible to use this method. This makes it possible to obtain a non-axisymmetric stretch flange molded product that exhibits uniform processing strain at the hole edge after processing.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 3 to 6.

FIG. 3 shows, as an example, an elongated 7-range lunge forming process using an austenitic stainless steel plate having a thickness of 0.4 m. Material e with an oblong prepared hole 21
The distribution of strain in the plate thickness of the flange portion 22 of the semi-finished product f which was stretch-formed using an oblong punch was actually measured, and this is shown in a contour diagram (indicated by a dashed-dotted line in the figure) g. The plate thickness strain is the logarithm of the ratio between the plate thickness after processing and the material plate thickness, and the larger the absolute value, the greater the reduction in plate thickness. As is clear from g in the figure, in the oval stretch flange molded product, the amount of plate thickness strain is large at the circular arc hole edge 23, and the plate thickness strain is small at the straight hole edge 24.

Therefore, the present inventors found that, contrary to the thickness strain distribution shown in Fig. 3, the amount of thickness strain is small at the hole edge of the circular part, and the amount of thickness strain is small at the edge of the hole in the straight part, and It has been found that if a material with a large amount of thickness strain is prepared in advance at the hole edge, a processed product with uniform thickness strain at the hole edge can be obtained by stretching and 7 lunging the material. Furthermore, for materials with a small thickness strain at the arcuate hole edge and a large thickness strain at the straight hole edge, insert an elliptical prepared hole so that the long axis coincides with the short axis direction of the oval punch. It has been found that this can be obtained by forming the material in advance and punching it out using an oblong punch.

As an example of this, in Fig. 4, a material with an elliptical pilot hole 31 with a ratio of major axis to minor axis of 6:5 is machined so that the minor axis direction of the pilot hole and the major axis direction of the oval punch match. The processed product i was stretch-formed, and the plate thickness strain distribution of the flange portion 32 of the processed product i is shown in a contour diagram (indicated by a dashed line in the figure) j. i in the figure.

As is clear from j, there is no large plate thickness strain at the hole edge 35 in the direction of the straight part 34 of the outer periphery of the flange part, that is, the hole edge in the short axis direction, and the hole edge 36 in the direction of the circular arc part 33, that is, the hole edge in the long axis direction. It can be seen that the plate thickness strain is small. The present inventors removed the oval part indicated by the broken line in Fig. j from the 7th rank part 32 of the molded product i by punching, etc., and after stretching it with an oval punch, punched a hole. It has been found that a material can be obtained in which the thickness strain is uniform at the edges, that is, the thickness strain is small in the circular arc portion and the thickness strain is large in the straight portion.

FIG. 5 shows an example of the processing process for elongation 7 lunge forming of an oval shape in which the thickness strain is uniform at the edge of the hole after processing, according to the present invention developed based on the above findings. That is, in the first step of processing, the material k is formed by punching or cutting an elliptical prepared hole 41t such that the short axis direction of the oval punch (not shown) becomes the long axis, and then Stretch forming is performed as shown in t, and then, in the second stage of processing, as shown in the figure m, an elliptical pilot hole is formed so that the long axis of the oval punch or the long axis of the desired final shape coincides with the long axis direction. 42 is processed by punching or cutting,
Thereafter, this is subjected to elongation 7 lunge forming using the oval punch to form a final product as shown by n in the figure.

In this example, we have shown a case where an elliptical pilot hole is formed in the material in the first step of the above processing as a desirable example, but basically, the hole is not limited to this, and it is also possible to form a circular (or oval) hole. It is also applicable even if a pilot hole is formed.

Figure 6 shows the distribution of thickness strain at the hole edge of the elongation 7 lunge formed product obtained by the above-mentioned present invention (A) and the plate thickness at the hole edge of the molded product obtained by normal elongation 7 lunge forming. The characteristic diagram (lower figure) shows the distribution of strain amount (b), the vertical axis shows the plate thickness strain II (purple), and the horizontal axis shows the position of the hole edge (in the upper figure, θ: )2 51 Position of arc part, t: 7 lunge 5
1). As is clear from the figure, according to the present invention, it is possible to significantly reduce the non-uniformity of the plate thickness strain at the edge of the hole (approximately 173 or less) that occurs during elongated elliptical 72-inch forming. Furthermore, the thickness strain of the metal material used in this example at the time of rupture is approximately 0.4 (indicated by the dashed line in the figure), but the normal elongation of the oval shape is 7.
In lunge machining, the plate thickness strain reaches the amount at breakage at the circular arc hole edge, whereas according to the present invention, the plate thickness strain jiFi
o.28, which is approximately 70% of the amount of strain in the plate thickness at the time of rupture, and can further deform by 0.12 in terms of the amount of strain in the plate thickness. From this, it can be seen that, compared to normal oval stretch flange processing, according to the present invention, processing stability is increased by approximately 30%.

In addition, in the above example, even if the oval elongation 7 lunge processing is performed,
It goes without saying that the present invention is applicable. Also, the type of metal material used in the above example.

It goes without saying that the plate thickness, the shape and size of the pilot hole, the punch size, etc., are not limited to these, and can be appropriately selected and set depending on the desired product.

〔Effect of the invention〕

As described above, according to the present invention, non-axisymmetric elongation 7-lunge forming with uniform processing strain distribution at the hole edge after processing is possible. A lung molded product with an elongation of 7 was obtained, and its effectiveness is remarkable when used in practical applications such as electronic devices.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of a non-axisymmetric elongation 7 lunge molded product;
Fig. 2 is a schematic diagram illustrating normal non-axisymmetric elongation 7-lunging process, Fig. 3 is a contour diagram of the thickness strain caused in elliptical elongation 7-lunging process, and Fig. 4 is an elliptical shape according to the present invention. FIG. 5 is a contour diagram of the plate thickness strain that occurs when the prepared hole is stretched out with an oblong punch.
FIG. 6 is a characteristic diagram showing the distribution of thickness strain at the hole edge of the non-axisymmetric elongation 7 lunge molded product obtained by the present invention and the conventional molded product. k...Material with an oval prepared hole, t...Extrusion molded product with an oval prepared hole, m...Product with an oval f hole processed, n.
・Stretch 7 lunge molded product. 'fJ 1 Fig.￥-J 2 Fig. 2 3rd drawing 4 Fig. 5 Fig. 1 ] Fig. 6 (b)

Claims (1)

[Claims] 1. In elongation 7 langing of a metal plate using a non-axisymmetric punch, the first stage of processing is to drill a circular or non-axisymmetric pilot hole so that the short axis of the punch is the long axis. After that, stretch forming is carried out, and in the second stage of processing, an elliptical pilot hole is machined so that the long axis coincides with the long axis direction of the punch, and this is stretched and formed. Axisymmetric elongation 7 lunge forming method.