JP2008093717A - Forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique by which the thickness of formed product which is obtained by superplastic forming can be simply controlled and the superplastic forming can be simply performed. <P>SOLUTION: A forming method is for forming a material composed of superplastic metal into the formed product having a prescribed shape, and this forming method includes: a stage of losing superplastic deformability for losing the superplastic deformability in a region by giving working stress by applying cold rolling to a part of the region of a material composed of the superplastic metal and a stage of forming superplastic for applying the superplastic forming to the material composed of the superplastic metal after the stage of losing superplastic deformability. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a superplastic metal molded product. In particular, the molding used to regulate the thickness of the molded product to a desired thickness, for example, the thickness of the molded product is thick only at a specific location, or is generally uniform. Regarding the method. Examples of the molded product include bodies of transportation equipment such as airplanes and automobiles, structures such as building materials and bridges, and various types of pipes and the like.

  Superplastic materials are known. That is, if the polycrystalline metal material has a crystal grain of about 10 μm or less and has a two-phase structure or finely dispersed particles to prevent crystal grain growth during high-temperature deformation, it is A phenomenon of stretching like a wrinkle has been found in over 100%, and superplastic alloys (see JIS H7007) that cause such superplastic deformation are attracting attention. And superplastic alloys can be roughly classified into fine grain superplastic alloys and transformation superplastic alloys. What is generated by refining crystal grains is called a fine grain superplastic alloy, and what is generated by applying a temperature cycle near the transformation point peculiar to a metal is called a transformation superplastic alloy. The transformation is a phenomenon in which the crystal structure, that is, the arrangement of atoms changes as the temperature rises or falls, resulting in different properties. And in order to refine | miniaturize a crystal grain, the method performed in a solid-liquid coexistence area | region and the method performed in a solid phase area | region, ie, a solid state, are known.

  As an alloy exhibiting superplasticity as described above, for example, Al-78% Zn, Al-33% Cu, Al-6% Cu-0.4% Zr (SUPURAL), Al-Zn-Mg-Cu alloy. (7475, 7075), Al-Zn alloys such as Al-4.5% Mg-0.7% Mn-0.15% Cr (5083), Al-Cu alloys, Al-Mg alloys, Al- Known are Al alloys such as Zn-Mg alloys, Al-Zn-Mg-Cu alloys, Al-Li alloys, Al-Si alloys, and Al-Mg-Si alloys. In addition, T-based alloys and Ni-based alloys are also known.

  The superplastic material that causes superplastic deformation is generally a metal material as described above, but recently, it is not limited to a metal system, but is difficult to process materials such as ceramics, intermetallic compounds, and others. Is also known to cause superplastic deformation even in composite materials.

Since these superplastic alloys exhibit a phenomenon that stretches like several hundred% or more like a wrinkle, complicated shaped bodies and structures based thereon are proposed and put into practical use. The superplastic molding is characterized by being molded at a high temperature, so that it can be deformed with low stress, and is generally molded by gas blow molding. That is, forming is performed by adding an inert gas such as air, nitrogen gas, or Ar to a heated superplastic alloy plate, applying a hydrostatic pressure, and pressing the superplastic alloy plate against a female die or a male die. For this reason, there are many cases where the die is only a female die or a male die, and the die material is not required to be a high-strength super hard material like a general cold press, and the die cost is low ( For example, about 1/2 is sufficient). Therefore, such a feature is highly effective when applied to a small-sized product having a relatively small number of products and a large molded product having a high die cost. It is particularly suitable for molded products in the aerospace sector.
JP-A 63-56317 JP-A-5-177266 JP-A-8-67992 JP 2000-237882 A

  As described above, superplastic forming has a number of advantages.

  However, the following problems remain unsolved.

  For example, when it is desired to increase the thickness only at a predetermined location (conversely, when it is desired to reduce the thickness only at a predetermined location), it cannot be handled only by superplastic forming. Therefore, in such a case, it is proposed to partially etch the superplastic alloy plate, set the plate thickness to be different depending on the location by this etching, and then perform superplastic forming (Cited document 3). Has been.

  However, it is difficult to implement the technique of regulating the plate thickness by an etching technique in advance before superplastic forming. For example, the selection and management of the etching solution, the execution of the etching, and the waste solution treatment of the etching solution are very difficult. In particular, the etching itself is very troublesome. Furthermore, the work process for etching and the work process for forming are too far apart from each other, and the cooperation between the two is not smooth, and the work efficiency is poor. For example, it is difficult to perform etching work and superplastic forming work in the same building.

  Therefore, the first problem to be solved by the present invention is to provide a technique capable of easily controlling the thickness of a superplastic molded product.

  The second problem to be solved by the present invention is to provide a technique that can easily provide a superplastic molded product having a desired plate thickness.

  While eagerly pursuing the study for solving the above-mentioned problems, the present inventor, in one superplastic alloy plate, does not superplastically deform with a portion that can be superplastically deformed (superplastic deformability is lost). I came to think that it would be good if there was a part. If no treatment is applied to the superplastic alloy plate, the portion (region) is a portion that can be superplastically deformed, whereas a working strain (plastic deformation) is caused by cold working or the like. When given, I noticed that the part (region) was recrystallized at the superplastic forming temperature during superplastic forming, the crystal grains became coarse, and the superplastic deformability was lost during superplastic forming. . Moreover, cold working before superplastic deformation can be performed much more easily than when etching is performed, and in particular, both cold working and superplastic working are of the same type. It has been found that cold working is suitable as a preforming performed before superplastic forming, and that it is also suitable for superplastic forming because it can also be preformed to some extent. I came.

  The present invention has been made based on such findings.

That is, the first and second problems are as follows:
A molding method for molding a material made of a superplastic metal into a molded product having a predetermined shape,
A superplastic deformability loss step of losing the superplastic deformability in the region by giving a working strain to a region of a part of the material made of the superplastic metal;
This is solved by a molding method comprising a superplastic forming step of performing superplastic forming on the material made of the superplastic metal after the superplastic deformability loss step.

In particular, a molding method for molding a material made of a superplastic metal into a molded product with a desired thickness and a predetermined shape,
A superplastic deformability loss step of losing the superplastic deformability in the region by giving a working strain to a region of a part of the material made of the superplastic metal;
This is solved by a molding method comprising a superplastic forming step of performing superplastic forming on the material made of the superplastic metal after the superplastic deformability loss step.

Furthermore, in the above molding method,
This is solved by a forming method characterized in that the superplastic deformability loss process is performed by cold working. Above all, it is solved by a molding method characterized in that the superplastic deformability loss process is based on incremental forming.

  In the present invention, the superplastic metal is in particular a superplastic Al-based alloy. The superplastic metal plate is not, for example, two superplastic metal plates joined by welding or the like, and one superplastic metal plate has superplastic deformability in all regions. That is, by performing cold working (preliminary forming) such as incremental forming, the portion (region) is a superplastic metal plate that first loses superplastic deformability.

  According to the present invention, prior to superplastic forming (deformation) of a superplastic Al-based alloy plate, cold forming (preliminary forming) such as incremental forming is performed. Almost no superplastic deformation even when molded. Therefore, the pre-formed part (cold working region: the part not superplastically deformed) does not become thin even after superplastic forming, and is thicker than the superplastically deformed part (non-cold working region). Is thick. In other words, when it is desired to prevent the plate thickness from becoming excessively thin (to adjust the plate thickness), the part should be subjected to cold forming (preliminary forming) such as incremental forming prior to superplastic forming. In this way, a molded product with the desired thickness can be easily obtained. Moreover, since the preforming is only cold working such as incremental forming, it is very easy to implement.

  Now, a product manufactured by pressing from a plate material is generally manufactured by producing a dedicated die and pressing it. However, in recent years, there has been a tendency to produce a variety of products in small quantities, and the required products tend to be made to order. Therefore, if a dedicated mold is remade in accordance with that, it is too costly and the efficiency is poor. From such a viewpoint, incremental forming (sequential stretch forming method) has been proposed in recent years. This incremental forming (sequential stretch forming method) is a method of forming a desired shape while pressing a tool against a plate and locally plastically deforming it. Therefore, a mold is not necessary for incremental forming.

  If incremental forming technology is used as a pre-molding prior to superplastic forming (deformation), the base plate support (seal surface) during superplastic forming remains flat (flat) in incremental forming. it can. That is, in superplastic molding (blow molding), the flat surface (flat surface) can be used as a seal surface (airtight surface), and superplastic molding is facilitated. In addition, the incremental forming is easy to accurately adjust the quantitative processing degree, and is advantageous as a preforming prior to superplastic forming. That is, in incremental forming, the amount of distortion (cold working amount) can be quantitatively grasped as the angle of the molding surface, and the degree of working for losing superplastic deformability becomes easy. Furthermore, since some three-dimensional molding is performed by incremental forming, the degree of deformation by subsequent superplastic molding can be reduced (for example, three-dimensional molding is performed only by superplastic molding on flat plates having different thicknesses. Compared to the case, the degree of deformation at the time of superplastic forming may be small), so that it is difficult to form a cavity and the decrease in mechanical strength is considered to be small. In addition, since a dedicated mold for incremental forming is not required, it is advantageous in terms of cost.

  By the way, cold working techniques such as incremental forming and superplastic forming techniques are already known.

  However, the technical idea that the thickness of the molded product can be controlled if cold working such as incremental forming is performed prior to superplastic forming is not known and unthinkable. Met. In addition, even if cold working such as incremental forming is performed after superplastic forming, the characteristics as achieved by the present invention cannot be obtained. In other words, the invention of the present application that performs cold forming such as incremental forming and then superplastic forming to control the thickness of the molded product is convinced that it is a novel and inventive invention. .

  Further, for example, a vertical wall cannot be formed only by incremental forming. That is, only an inclined state can be formed. However, if superplastic forming is performed after performing cold working such as incremental forming, vertical walls can be formed, and the degree of freedom of modeling is high.

  In addition, only incremental forming may cause springback, which may deteriorate the molding accuracy of the molded product. However, if superplastic forming is performed after incremental forming, the occurrence of springback can be suppressed, and a molded product can be obtained with high accuracy.

  In the above case, after superplastic forming, the portion where the preforming (cold processing: incremental forming) is thick is thick, and the portion where the pre-forming (cold processing: incremental forming) is not performed is thin. explained.

  However, in the previous stage of superplastic forming, comparing the thickness of the cold-worked part (cold-worked part) with the thickness of the non-cold-worked part (non-cold-worked part), It is only natural that (thickness of cold-worked portion) <(thickness of non-cold-worked portion). Therefore, if the degree of elongation in superplastic forming is taken into account, it is also possible to control after superplastic forming so that (thickness of non-cold working location) ≒ (thickness of cold working location). is there. In other words, if the area of the cold-worked portion where the plate thickness is thin in the previous stage of superplastic forming is taken large and the region of the non-cold-worked portion (place where superplastic deformation is possible) is made small, the plate after superplastic forming The thickness can be made approximately the same. That is, in superplastic forming, not everyone uniformly superplastically deforms, but it is difficult to superplastically deform at a point where it begins to contact the male or female mold. Therefore, in such a case, thickness variation occurs in the superplastic molded product. Therefore, when such a phenomenon is expected, if a place is determined in advance and cold forming such as incremental forming is performed, and then superplastic forming is performed, a molded product having a uniform thickness can be obtained only by superplastic forming. Even in such a case, it is possible to obtain a superplastic molded product having the same thickness in all regions. In such a case, since the area of superplastic deformation is small, that is, the ratio of superplastic deformation is low, the generation of cavities associated with superplastic forming is reduced, and the mechanical strength is reduced. Can be prevented.

  The method of the present invention is a forming method for forming a material made of a superplastic metal (particularly, a superplastic Al-based alloy plate) into a molded product having a predetermined shape. Among them, a molding method for molding a material made of a superplastic metal (particularly, a superplastic Al-based alloy plate) into a molded product having a desired thickness and a predetermined shape. And it has the superplastic deformability loss process of losing the superplastic deformability in the said area | region by giving a working strain with respect to the partial area | region of the material which consists of the said superplastic metal. Furthermore, after the superplastic deformability loss step, there is a superplastic forming step in which superplastic forming is performed at a superplastic temperature on the material made of the superplastic metal. The process of losing the superplastic deformability is in particular by cold working, especially by incremental forming. For example, by cold working at room temperature (0 to 40 ° C.) with an elongation of 4 to 25% (in particular, 4% or more and 15% or less).

  This will be described in more detail below.

  FIGS. 1A, 1B, 1C and 1D are explanatory views showing a first embodiment of a forming method according to the present invention using 5083 alloy as a superplastic Al-based alloy material. 1A is a cross-sectional view at a stage where a preformed (incremental forming: cold work) body is disposed on a superplastic mold, and FIG. 1B is a cross-sectional view after superplastic forming. 1 (c) is a cross-sectional view at a stage where unnecessary portions are trimmed after superplastic forming, and FIG. 1 (d) is a perspective view of the superplastic formed body.

  First, incremental forming (cold working (elongation rate at 20 ° C.) is not applied to a single superplastic Al-based alloy flat plate 1 of a predetermined size, which is not said that two plates are joined by welding or the like. 4% cold working): preforming) is performed to obtain a preformed body 2 as shown in FIG.

  In FIG. 1 (a), the part subjected to incremental forming (incremental forming part: cold-worked part) 1a has an inclined surface, and the thickness of the part 1a corresponding to the part subjected to the pre-forming is as follows. It is thinner than the plate thickness of the portion that is not subjected to incremental forming (non-incremental forming portion: non-cold working portion) 1b. That is, with reference to FIG. 1A, it is understood that the plate thickness of the incremental forming portion 1a is thinner than the plate thickness of the non-incremental forming portion 1b. And the incremental forming part 1a becomes only an inclined surface until it turns. Since incremental forming is well known from the past, other details are omitted.

  Then, the preformed body 2 having a predetermined shape is disposed in the superplastic mold 3 and superplastic forming is performed by gas blow molding at a temperature higher than the recrystallization temperature (superplastic temperature). Since superplastic forming is well known from the past, details are omitted.

  Then, a molded product 4 as shown in FIG. 1B is obtained by superplastic molding following incremental forming. In addition, since the incremental forming part 1a has lost superplastic deformability, it does not undergo superplastic deformation even by superplastic forming, and the plate thickness hardly changes. On the other hand, the non-incremental forming portion 1b has not lost its superplastic deformability, undergoes superplastic deformation by superplastic forming, and its elongation is remarkable, so the thickness is further reduced. .

  Therefore, as can be seen from the above description, the thickness of the molded product 4 is controlled depending on the location. On the other hand, when superplastic forming is performed on the flat plate 1 without performing the incremental forming, a thick plate portion as shown in FIG. 1B cannot be obtained. In other words, the plate thickness at the target location cannot be restricted to a specific one.

  FIGS. 2A, 2B, 2C and 2D are explanatory views showing a second embodiment of the forming method according to the present invention using 5083 alloy as a superplastic Al-based alloy material. 2A is a cross-sectional view at a stage where a preformed (incremental forming: cold work) body is disposed on the superplastic forming die, and FIG. 2B is a cross-sectional view after superplastic forming. 2 (c) is a sectional view at a stage where unnecessary portions are trimmed after superplastic forming, and FIG. 2 (d) is a perspective view of the superplastic formed body.

  First, incremental forming (cold working (elongation rate at 20 ° C.) is not applied to a single superplastic Al-based alloy flat plate 5 of a predetermined size, which is not said that the two plates are joined by welding or the like. 4.5% cold working): preforming) is performed to obtain the preform 6.

  As can be seen from FIG. 2 (a), in this embodiment, the portion 5a subjected to incremental forming (incremental forming portion: cold-worked portion) 5a has an inclined surface, and has undergone preforming. Accordingly, the thickness of the portion 5a is thinner than the thickness of the portion 5b that is not subjected to incremental forming (non-incremental forming portion: non-cold working portion) 5b.

  Next, the preform 5 having a predetermined shape is disposed in a superplastic mold, and superplastic forming is performed by gas blow molding.

  Then, a molded product 7 as shown in FIG. 2B is obtained by superplastic molding following incremental forming. In addition, as can be seen from FIG. 2B, in the molded product 7 in this embodiment, the plate thickness in the incremental forming portion 5a and the plate thickness in the non-incremental forming portion 5b are almost the same. . And even in such a case, it is said that the plate | board thickness of the target location can be controlled to the specific thing. That is, the present invention can be applied not only when the thicknesses are made different but also when the thicknesses are made uniform.

  In the above embodiment, the case where the 5083 alloy is used has been described. However, in the case where the 7475 alloy or the like is used, a similar molded product is obtained through the same process.

Explanatory drawing which shows 1st Embodiment of the shaping | molding method which becomes this invention. Explanatory drawing which shows 2nd Embodiment of the shaping | molding method which becomes this invention.

Explanation of symbols

1,5 Superplastic Al alloy flat plate 1a, 5a Incremental forming part (cold working part)
1b, 5b Non-incremental forming part (non-cold working part)
2,6 Preliminary molded body 3a, 3b Superplastic mold 4,7 Superplastic molded product

Patent applicant Japan Airplane Co., Ltd.
Representative Katsumi Udaka

Claims (5)

A molding method for molding a material made of a superplastic metal into a molded product having a predetermined shape,
A superplastic deformability loss step of losing the superplastic deformability in the region by giving a working strain to a region of a part of the material made of the superplastic metal;
And a superplastic forming step of performing superplastic forming on the material made of the superplastic metal after the superplastic deformability loss step.   2. The molding method according to claim 1, wherein the molding method is used for making the thickness of the molded product a desired thickness.   The molding method according to claim 1 or 2, wherein the superplastic deformability loss step is performed by cold working.   The molding method according to claim 1, wherein the superplastic deformability loss step is performed by incremental forming. The forming method according to claim 1, wherein the superplastic metal is a superplastic Al-based alloy.

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