JP2671687B2 - Deep drawing method for metal clad plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep drawing method for a metal clad plate which suppresses cracking at a bending portion.

[Prior art and its problems]

[0002] A clad plate obtained by joining dissimilar metals to each other by bombarding or rolling to have the characteristics of both has been used for various industrial purposes for a long time, but in recent years, it is a material for high-grade houseware such as a pot. Even so, the demand for clad plates is increasing steadily.

However, when a container such as a pot is manufactured from a plate-shaped material, deep drawing is an essential step. However, if a clad plate is deep drawn, the following problems occur. It was

That is, in the case of a clad plate or the like in which mild steel and stainless steel are combined, it is possible to perform heat treatment after clad bonding to soften both layers to the same degree, so that "solid forming (stainless steel or mild steel The press formability is good as in the case of the "single material forming)", and no particular problem occurs in deep drawing. However, recently, "aluminum / stainless steel" and "stainless steel / aluminum /" have attracted attention as houseware materials for electromagnetic cookers.
In the clad plate that is a combination of "stainless steel",
Since the softening heat treatment temperature is greatly different between the two materials, it is virtually impossible to carry out the softening heat treatment after clad joining.Therefore, the formability of the clad plate of such a combination is remarkably inferior to that of the case of solid forming, When deep drawing is performed, it often becomes a problem that "bending cracks" occur at the bent portion of the flange. This problem is particularly noticeable when performing deep drawing in two stages with different drawing diameters in order to provide a "step for fitting a lid" at the mouth of a container for deep drawing. It was apt to appear, and often caused fatal cracks as a product in the process of "bending" and "bending back" performed at the transition part from the flange part to the side wall part.

Therefore, attempts have been made to increase the bending radius R or to reduce the forming depth in order to prevent "bending cracks" during the deep drawing, but the effect was not sufficient.

Therefore, the object of the present invention is that a softening heat treatment after clad bonding such as a clad plate in which dissimilar metal layers are combined, especially "combination of aluminum and stainless steel" is impossible. It was also to establish a deep-drawing forming method that can perform stable forming without causing "bending cracks" even when using a clad plate that has a significant difference in deformation resistance of each layer. .

[0006]

Means for Solving the Problems The inventors of the present invention have obtained the following findings as a result of earnest studies while repeating many experiments to achieve the above object. a) In general deep-drawing when the material (blank) is a solid material, it was said that the bending property deteriorates as the tensile force is applied to the material. In the case of deep drawing using as a material, completely different forming behavior is exhibited, and the "bendability" and "bend backability" show a great improvement when a tensile force within a certain range is applied. b) Therefore, in order to improve the deep drawability of the clad plate, the resistance against the material inflow into the die at the flange is strengthened and the tensile force applied to the material during the "bending" and "bending back" processes is increased. , It suffices to try to keep this within a specific range.

The present invention has been completed on the basis of the above-mentioned findings and the like. "When performing deep drawing of a clad plate in which dissimilar metal layers are combined, a material drawing portion (a bending portion between a flange and a container side wall portion is formed). specific hand or unbending site)
By performing deep drawing while applying a tensile force adjusted to a specific value depending on the step, it is possible to perform smooth deep drawing while suppressing "bending cracks" at the bent part of the flange as much as possible. " It has a great feature.

The type of the "clad plate in which different metal layers are combined", which is a deep-drawing material, is not particularly limited, and any of the clad plates in which different metals are joined by bombardment or rolling is used. Although a corresponding effect can be obtained as a material, for softening heat treatment after clad joining is not possible because the softening heat treatment temperatures of the dissimilar metal layers composing the clad plate are greatly different, and there is a difference in deformation resistance. It goes without saying that significant advantages are exhibited.

[0009]

As described above, according to the present invention, in the deep drawing of a metal clad plate, the inflow of the material of the flange portion into the deep drawing die is suppressed to a lesser extent than in the case of using a solid material. "Strengthen the tensile force of the material in the bending or bending back forming between the flange and the side wall of the container" to prevent bending cracks and improve the deep drawability. When a suitable tensile force is applied to the material at the time of molding, the bending process following the punch R is done without difficulty and the "bending or bending back formability between the flange and the side wall of the container" becomes better, improving the deep drawability. No more cracking will occur. "

The tensile force applied to the narrowed portion (bent portion) of the material is preferably "a value corresponding to the case where the flange pressing force is adjusted to 3 to 20% of the tensile strength of the material". This is because when the applied tensile force is smaller than the above value, a bending R smaller than the punch R, a so-called "overbend phenomenon", occurs in the bending portion and the bending back portion, and cracking occurs, while If the tensile force to be applied is larger than the above value, the material strength limit of the clad plate is exceeded, which may lead to fracture of the material.

[0011] And, the material narrowing portion (bending portion)
The simplest way to add tensile force to the flange is by "a method of strengthening the flange pressing force", but in addition, "adding a bead to the flange of the material to increase the resistance to the material inflow into the die. A "strengthening method" or "a method of increasing the flange width of the material to enhance the resistance to material inflow into the die" is also practical.

Next, the present invention will be described more specifically by way of examples.

Example 1 Three-layer clad plate (2.0 mm thick, tensile strength: 36 kgf / mm ² ) of a combination of “NAR160 (trade name: Nippon Stainless Steel Co., Ltd.) / Al / SUS304L” obtained by rolling joining
The plate was prepared, and the "bending-bending back property" at 90 ° of tensile bending was evaluated. In this case, the bending R in the first bending process is set to each value of 8 mm, 10 mm or 12 mm, and the bending R in the second bending back process is 3 mm,
The evaluation was performed by setting each value to 5 mm or 7 mm and varying the tensile force applied to the material during the second bending back processing. These evaluation results are summarized and shown in FIG.

The tensile force applied to the material during the double-bending process was evaluated by the flange pressing force (plate pressing force). As a matter of course, when the plate pressing force increases, the tensile force also increases. In addition, “bending property evaluation result” in FIG.
Is indicated by ○: no cracking occurs, △: constriction occurs, ×: slight cracking occurs, ××: cracking occurs by division .

From the results shown in FIG. 1, the following is clear. That is, when the second bending R in bending-bending back processing is very small (when R = 3 mm), cracks occur in the bending portion even if the plate pressing force is changed, and
If the bending R is very large, no cracks will occur in a wide range of the plate pressing force, but in the vicinity of the bending R of 5 mm and the limit bending R of the material, the region where the plate pressing force is 1.5 kgf / mm ² or less and 7.5 kgf / If it enters the area of mm ² or more, cracks will occur in the bent part. However, when the plate pressing force is in the range of 1.5 to 7.5 kgf / mm ² , bending does not occur at all. This "plate pressing force: 1.5 to 7.5 kgf / mm ² " is 3 to 20% of the tensile strength of the material.
Is equivalent to

FIG. 2 shows an example of a cross-sectional observation of the test piece after the above-mentioned "bending-bending back test" (magnification: 7 times). The following can be confirmed from this FIG. That is, cracks with a small plate pressing force are smaller than the actual bending R (punch bending R), and cracks with a too large plate pressing force reduce the plate thickness of the entire clad plate. It shows that the tensile force applied to the material exceeds the strength limit of the material. On the other hand, a material in which an appropriate tensile force is applied to the material by an appropriate plate pressing force is uniformly deformed following the bending punch R, and is not cracked.

Example 2 "SUS430 / Al / SUS30" obtained by rolling bonding
Prepare a 3 layer clad plate (2.0 mm thick, tensile strength: 42 kgf / mm ² ) in a combination of 4 ”and use this to change the flange pressing force (plate pressing force) variously in the actual press. Deep drawing was carried out and the deep drawability at that time was evaluated, and the results are shown in Table 1.

[0017]

Also from Table 1 above, in the deep drawing of the clad material, if the flange pressing force is adjusted to a range of 3 to 20% of the tensile strength of the material, the formation of cracks is suppressed. I can confirm that.

[0019]

As described above, according to the present invention, a "clad plate having inferior deep drawability because a softening heat treatment after joining cannot be performed" such as a combination of aluminum and stainless steel is provided. Has the deep drawability equivalent to that of the solid material, and can greatly contribute to the improvement of press molding technology for the clad material, which is strongly demanded today, and brings industrially useful effects.

[Brief description of the drawings]

FIG. 1 is a graph showing evaluation results of “bending-bending back property” of a three-layer clad plate by deep drawing.

FIG. 2 is an explanatory diagram comparing the results of cross-section observation of test pieces after “bending-bending back test”.

Claims (3)

(57) [Claims] 1. When performing deep drawing of a clad plate in which dissimilar metal layers are combined, a "flange pressing" is applied to a material narrowing portion.
Even adjusting the force to 3-20% of the tensile strength of the material
Therefore, the deep drawing is performed while adding the " tensile force obtained " to prevent the occurrence of cracks in the bent portion of the metal clad plate.
A deep drawing method that has been suppressed . 2. A clad plate in which dissimilar metal layers are combined.
For deep drawing, a bead was attached to the flange of the material.
Materials to refine site adds a "flange pressing force tensile force corresponding to a value obtained Ri by <br/> to be adjusted to 3-20% of the tensile strength of the material" being deep drawing by previously
At the bending portion of the metal clad plate , which is characterized by
Deep drawing method that suppresses cracking . 3. A clad plate in which dissimilar metal layers are combined.
Before deep drawing, increase the flange width of the material
Obtained by adjusting the "flange pressing force to refine site materials 3-20% of the tensile strength of the material by
Deep drawing while adding a tensile force equivalent to the value
Which is characterized by the fact that cracking occurs at the bending part of the metal clad plate.
Deep-drawing molding method that suppresses rawness.