KR101983929B1 - Metal moldings including a tubular part having a slit, a method of manufacturing the same, and a manufacturing apparatus and a mold used therefor - Google Patents

Abstract

The manufacturing method disclosed is a manufacturing method for manufacturing a metal molded article including a tubular portion 1e having a slit 3. This manufacturing method comprises a step (i) of forming a U-shaped section having a U-shaped section and a molding step (20) having a protruding section (23) so that two ends of the U- (Ii) of forming the tubular portion 1e having a slit by deforming the U-shaped portion by using the above-mentioned U-shaped portion. In the step (ii), the peripheral length LH of the tubular portion 1e is made shorter than the sectional length LU of the U-shaped portion.

Description

Metal moldings including a tubular part having a slit, a method of manufacturing the same, and a manufacturing apparatus and a mold used therefor

The present invention relates to a metal molded article including a tubular portion having a slit, a method of manufacturing the same, and a manufacturing apparatus and a mold used for the same.

Tubular parts are widely used in automobile parts and household electric appliances. Therefore, development of a technique for manufacturing tubular parts is being promoted. UO molding is known as a typical method for manufacturing a tubular part from a metal plate (for example, Patent Documents 1 and 2).

Recently, in the field of automobiles, there is a demand for tubular parts having slits in the longitudinal direction. As a method of manufacturing such a tubular part, a method of performing bending processing several times has conventionally been used. However, this method has a problem that it is difficult to mold a component having a complicated shape and a problem that the process is troublesome. Therefore, application of UO molding is expected. However, general UO molding is a method for manufacturing a tubular part without a slit, and the butt of the formed tubular part is welded. For this reason, it is difficult to precisely fabricate tubular parts having a gap in the abutted portion by merely applying the conventional UO molding.

Patent Document 3 discloses a method of forming a hollow shape member having slots in the longitudinal direction. 3 and 4 of Patent Document 3 disclose a method using a core (core 11) having a blade for forming a slot. The manufacturing method of Patent Document 3 assumes that the slot is closed after forming to weld. Therefore, the accuracy of the interval of the slots and the accuracy of the shape before welding are not considered. In addition, when the material of the metal plate or the thickness of the metal plate changes, the amount of spring back also changes. Therefore, when changing the material and thickness of the metal plate, it is necessary to modify the metal mold to adjust the interval of the slots.

Patent Document 1 discloses a method of forming a tubular member having a square cross section by bending a plate member. The mold used in this method has a top mold, a bottom mold, and a side die. The side dice are dies for pressing the side portions of the plate material so as to bring the two end edges facing each other close to each other. The tubular member formed by this method is welded to the butt portion after molding. Therefore, the control of the interval between the two end edges is not considered sufficiently.

Roll forming is also known as a method of manufacturing a tubular part (for example, Patent Document 4). However, in the roll forming, it is difficult to produce a tubular part having a complicated shape such as a sectioned section tube whose sectional shape changes in the longitudinal direction.

BACKGROUND ART Press braking is known as bending of a metal plate (for example, Patent Document 5). It is also conceivable to form a tubular part having a gap in the butted portion by bending with a press brake. However, with press brake machining, it is difficult to reduce the gap between the butted portions.

Also, in the conventional UO molding, unintentional gaps may occur in the abutting portions of the tubular parts due to springback after molding. However, in the conventional UO molding, it is very difficult to control the gap between the butted portions.

Further, as described in, for example, Patent Documents 2 and 3, a core is sometimes used in O-molding. In this case, it is conceivable to form the tubular part having a gap in the abutted part by making the width of the metal plate shorter than the end peripheral length of the metal mold. However, in this method, since the molding is performed by simple bending, there is a problem that the spring back is large. Therefore, also in this case, it is difficult to control the interval of the gap of the abutted portion.

It is also conceivable to design the mold by trial and error, and to mold the tubular part having the gap at the abutting part by using the spring back. However, when mass production is considered, the material and plate thickness of the metal plate slightly change by lot change. In this case, since the spring back amount also changes, there is a variation in the gap between the butted portions and the shape of the tubular part. For this reason, it is difficult to continue mass production of the tubular part having a constant interval between the butted portions and good shape accuracy. Further, in the case of changing the material and the plate thickness of the metal plate, it is necessary to modify the metal mold in order to adjust the interval of the gap of the abutted portion, requiring a great deal of time and effort, resulting in high cost.

Patent Document 6 discloses a method of manufacturing a hollow release material from a cut blank using a UO molding technique. In the manufacturing method of Patent Document 6, a hollow release member is formed by abutting two opposed edge portions of the cut blank against each other. At this time, the length of the cut blank in the circumferential direction is made longer than the necessary forming length by a predetermined excess length. The surplus length is at least 1% to 10%. Patent Document 6 discloses that the region of the hollow release member abutting the edge joint is compressed at least partially in the circumferential direction. Patent Document 6 describes that the above-described manufacturing method is carried out by using a UO molding technique. However, Patent Document 6 does not specifically describe how to carry out the production method. That is, how to compress the hollow release material in the circumferential direction by using the UO molding technique is not disclosed in Patent Document 6. The method of Patent Document 6 does not assume that the width of the slit is arbitrarily controlled.

Japanese Patent Application Laid-Open No. 2001-191112 Japanese Patent Application Laid-Open No. 2004-25224 International Publication No. 2005/002753 pamphlet Japanese Patent Application Laid-Open No. 2000-616 Japanese Patent Application Laid-Open No. 2000-61551 Japanese Patent Specification No. 2014-516801

In the above situation, one of the objects of the present invention is to provide a manufacturing method capable of precisely molding a metal molded article including a tubular portion having a slit, and controlling the interval of the slit.

A method of an embodiment of the present invention is a manufacturing method of manufacturing a metal molded article including a tubular portion having a slit. This manufacturing method comprises the steps of: (i) forming a U-shaped section having a U-shaped section by deforming a metal plate; and (ii) forming a U-shaped section having the projecting section so that the two ends of the U- To form the tubular portion having the slit by deforming the U-shaped portion. In the step (ii), the end face circumferential length LH of the tubular portion is made shorter than the end face length LU of the U-shaped portion.

A metal molded article of an embodiment of the present invention is a metal molded article including a tubular portion having a slit. The average value of the deviation S in the circumferential direction is less than 0.4 when the deviation (S) of the Vickers hardness in the plate thickness direction in the cross section of the tubular portion is expressed by the following formula.

S = (Bmax-Bmin) / Bmax

Here, Bmin is the minimum value of the Vickers hardness in the plate thickness direction in the section. Bmax is a maximum value of the Vickers hardness in the plate thickness direction in the section.

A manufacturing apparatus of an embodiment of the present invention is a manufacturing apparatus for manufacturing a metal molded article including a tubular portion having a slit. The manufacturing apparatus includes a mold and a moving mechanism for moving the mold. The mold includes a first mold including a protrusion for forming the slit, and a second mold. Each of the first and second molds includes first and second pressing surfaces for deforming a U-shaped section having a U-shaped section to form a tubular section having a gap serving as the slit. The mold has a configuration for pressing the outer circumferential surface of the tubular portion so that a circumferential length of the tubular portion becomes shorter.

A metal mold of an embodiment of the present invention is a metal mold for manufacturing a metal molded article including a tubular portion having a slit. The mold includes a first mold including a protrusion for forming the slit, and a second mold. Each of the first and second molds includes first and second pressing surfaces for deforming a U-shaped section having a U-shaped section to form a tubular section having a gap serving as the slit. The mold has a configuration for pressing the outer circumferential surface of the tubular portion so that a circumferential length of the tubular portion becomes shorter.

According to the present invention, the interval between slits can be controlled by precisely shaping a metal molded article including a tubular portion having a slit. According to the present invention, a metal molded article including a tubular portion in which a slit is formed precisely is obtained. Further, according to the present invention, a production apparatus and a mold preferably used in the production method of the present invention are obtained.

Fig. 1 schematically shows a cross section of an example of a metal molded article of the present invention.
2A is a cross-sectional view schematically showing an example of one step of the manufacturing method of the present invention.
Fig. 2B is a cross-sectional view schematically showing an example of a process subsequent to Fig. 2A.
Fig. 2C is a cross-sectional view schematically showing a U-shaped portion formed by the process of Figs. 2A and 2B. Fig.
3A is a cross-sectional view schematically showing an example of a mold used in the production method of the present invention.
Fig. 3B is a cross-sectional view schematically showing an example of a manufacturing process using the mold of Fig. 3A.
FIG. 3C is a cross-sectional view showing an example of a process subsequent to the process of FIG. 3B.
3D is a cross-sectional view showing an example of a process subsequent to the process of FIG. 3C.
FIG. 3E is a cross-sectional view showing an example of a process subsequent to the process of FIG. 3D.
Fig. 3F is a cross-sectional view schematically showing an example of a metal molded article manufactured by the processes of Figs. 3B to 3E.
4A is a cross-sectional view schematically showing an example of a mold used in the production method of the present invention.
Fig. 4B is a cross-sectional view schematically showing an example of a manufacturing process using the mold of Fig. 4A. Fig.
4C is a cross-sectional view showing an example of a process subsequent to the process of FIG. 4B.
FIG. 4D is a cross-sectional view showing an example of a process subsequent to the process of FIG. 4C.
4E is a cross-sectional view showing an example of a process subsequent to the process of FIG. 4D.
Fig. 4F is a cross-sectional view schematically showing an example of a metal molded article manufactured by the processes of Figs. 4B to 4E.
5A is a cross-sectional view schematically showing an example of a mold used in the production method of the present invention.
Fig. 5B is a cross-sectional view schematically showing an example of a manufacturing process using the mold of Fig. 5A.
5C is a cross-sectional view showing an example of a process subsequent to the process of FIG. 5B.
5D is a cross-sectional view showing an example of a process subsequent to the process of FIG. 5C.
5E is a cross-sectional view showing an example of a process subsequent to the process of FIG. 5D.
5F is a cross-sectional view schematically showing an example of a metal molded article manufactured by the processes of Figs. 5B to 5E.
6A is a cross-sectional view schematically showing an example of a mold used in the production method of the present invention.
Fig. 6B is a cross-sectional view schematically showing an example of a manufacturing process using the mold of Fig. 6A.
FIG. 6C is a cross-sectional view showing an example of a process subsequent to the process of FIG. 6B.
FIG. 6D is a cross-sectional view showing an example of a process subsequent to the process of FIG. 6C.
FIG. 6E is a cross-sectional view showing an example of a process subsequent to the process of FIG. 6D.
FIG. 6F is a cross-sectional view schematically showing an example of a metal molded article manufactured by the processes of FIGS. 6B to 6E.
7 is a cross-sectional view schematically showing another example of a mold according to the present invention.
8 is a cross-sectional view showing another example of the mold of the present invention and an example of a tubular portion formed according to the mold.
FIG. 9A is a view schematically showing an example of a metal molded article of the present invention. FIG.
Fig. 9B is a diagram schematically showing another example of the metal molded article of the present invention. Fig.
9C is a diagram schematically showing another example of the metal molded article of the present invention.
FIG. 9D is a view schematically showing another example of the metal molded article of the present invention. FIG.
Fig. 9E is a diagram schematically showing another example of the metal molded article of the present invention. Fig.
Fig. 10A schematically shows a process of a manufacturing method of a tubular member of Comparative Example 1. Fig.
Fig. 10B schematically shows a process subsequent to Fig. 10A.
Fig. 11A schematically shows a process of a manufacturing method of a tubular member of Comparative Example 2. Fig.
Fig. 11B schematically shows a process subsequent to Fig. 11A.
12A is a graph showing the distribution of distortion in the plate thickness direction for the tubular members of Example 1, Comparative Example 1 and Comparative Example 2. Fig.
12B is a graph showing distortion distributions in the circumferential direction of the tubular members of Examples 2 to 4 and Comparative Example 2. Fig.
13 is a graph showing the relationship between the average value in the circumferential direction of the deviation S and the decreasing rate of the uniaxial compressive strength.
14A is a diagram showing an example of an operation of an example of the production apparatus of the present invention.
Fig. 14B is a diagram showing an example of the operation subsequent to Fig. 14A.
Fig. 14C is a diagram showing an example of an operation subsequent to Fig. 14B.
Fig. 14D is a diagram showing an example of an operation subsequent to Fig. 14C.
FIG. 15A is a diagram showing an example of an operation of another example of the manufacturing apparatus of the present invention. FIG.
Fig. 15B is a diagram showing an example of an operation subsequent to Fig. 15A.
Fig. 15C is a diagram showing an example of the operation subsequent to Fig. 15B.
15D is a diagram showing an example of an operation subsequent to Fig. 15C.

Hereinafter, embodiments of the present invention will be described. In the following, the embodiments of the present invention will be described by way of example, but the present invention is not limited to the examples described below. In the following description, specific numerical values and materials are exemplified, but other numerical values and materials may be applied as long as the effect of the present invention can be obtained.

(Manufacturing Method of Metal Molded Article)

The manufacturing method of the present invention is a method of manufacturing a metal molded article including a tubular portion having a slit. The matters described in the manufacturing method of the present invention can be applied to a metal molded article, a manufacturing apparatus, and a metal mold of the present invention.

The metal molded article may include a portion other than the tubular portion having the slit. Alternatively, the metal molded article may be constituted only by tubular portions having slits. In this case, the metal molded article is a tubular shaped article having slits. Examples of the metal moldings to be produced will be described later. The production method of the present invention includes the steps (i) and (ii) described below.

(Step (i))

In the step (i), the U-shaped section having a U-shaped section is formed by deforming the metal plate. The step (i) is not particularly limited, and the U-shape used in conventional UO molding may be applied. The U forming method is not particularly limited as long as it is a method capable of forming a metal plate so that its cross section is U-shaped. Examples of the U forming method include press forming, roll forming, and the like. The U-shaping may be performed by a plurality of processes. Further, before U molding, a process of bending the end of the metal plate (so-called C molding or the like) may be performed. After U molding, trimming (cutting) of the U-shaped portion may be performed.

Further, in this specification, unless otherwise specified, the section of the tubular section means the section in the circumferential direction of the tubular section. In other words, the section of the tubular section means a section in the direction perpendicular to the axial direction (usually the longitudinal direction) of the tubular section. The same is true for the cross section of the U-shaped section, the cross section of the tubular section, and the cross section of the press surface of the mold. Unless otherwise stated, the pressing surface of the mold means a surface in contact with the outer peripheral surface of the tubular portion (or tubular portion) of the metal mold. In the case where the mold is constituted by a plurality of members, the end face circumferential length of the pressing face of the mold means the sum of the cross-sectional lengths of the pressing faces of the plurality of members.

The metal plate to be formed in the manufacturing method of the present invention is hereinafter sometimes referred to as a " blank ". The metal plate (blank) is not particularly limited as long as it can be formed. Examples of the metal plate include a steel plate, for example, a hot-rolled steel plate, a cold-rolled steel plate, a coated steel plate, and the like. An example of the metal plate includes a metal plate (so-called tailed blank) obtained by laminating a plurality of metal plates. The tailored blank may have a plurality of metal plates joined together in the axial direction of the tubular portion to be obtained, or a plurality of metal plates may be joined to each other in the circumferential direction of the tubular portion to be obtained. Further, a steel sheet having a different thickness depending on the place may be used as a blank. Further, a so-called laminated plate may be used for the blank. Examples of the laminate include a polymer obtained by polymerizing a plurality of metal plates and a polymer obtained by polymerizing a metal base material. That is, the metal molded article may contain a material other than the metal plate.

The metal plate (blank) may be a thin metal plate or a high-strength steel plate (so-called high-tensile material). The present invention is particularly useful since they tend to increase springback. Examples of the thin metal plate include those in which the ratio of the plate thickness to the corresponding diameter of the metal plate is 10% or less. The diameter is a value obtained by dividing the peripheral length of the tubular portion by 3.14. The tensile strength of the high-tensile material is preferably 300 MPa or more, and may be 440 MPa or more (for example, 490 MPa or more or 780 MPa or more). The upper limit of the tensile strength is not particularly limited and may be 2000 MPa or less.

The material of the metal plate is not particularly limited as long as it is moldable. Examples of the material of the metal plate include metals such as Fe-based, Al-based, Cu-based, and Ti-based metals.

The thickness of the metal plate is not particularly limited and may be any thickness that can be formed. The thickness of the metal plate is selected in consideration of the material of the metal plate, the shape of the metal mold, the use of the metal mold, and the like. In one example, the thickness of the metal plate may be in the range of 0.4 to 5 mm (for example, in the range of 0.5 to 3 mm or in the range of 1 to 3 mm).

The shape of the metal plate is selected in accordance with the shape of the object metal mold product. As described later, in the manufacturing method of the present invention, the peripheral length LH of the tubular portion is made shorter than the sectional length LU of the U-shaped portion. The width W (the length in the circumferential direction in the tubular portion) of the portion of the metal plate that is tubular portion is determined in consideration of the compression ratio C to be described later.

(Step (ii))

In the step (ii), the tubular portion having the slit is formed by deforming the U-shaped portion by using a mold having the protruding portion so that the two ends of the U-shaped portion sandwich the protruded portion. In the step (ii), the peripheral length LH of the tubular portion is made shorter than the sectional length LU of the U-shaped portion. Thereby, the metal plate constituting the tubular portion is compressed in the circumferential direction. As a result, the springback of the tubular portion is suppressed, and the interval of the slits can be precisely controlled. The gap between the two end portions (the two end portions of the U-shaped portion) sandwiched between the protrusions becomes a slit. That is, by the step (ii), a metal molded article including a tubular portion having a slit is produced. Of course, the metal moldings obtained by the step (ii) may be further processed.

It is preferable that the difference between the peripheral edge length LH of the tubular portion and the sectional length LU of the U-shaped portion is 0.2% or more of the sectional length LU of the U-shaped portion. That is, it is preferable that the cross-sectional length (LU) of the U-shaped portion and the circumferential length (LH) of the tubular portion satisfy 0.2? 100? (LU-LH) / LU. If this difference is too small, the effect of suppressing springback and the effect of forming a tubular part accurately may not be obtained sufficiently. Hereinafter, the value of "100 × (LU-LH) / LU" may be referred to as the compression ratio C (%) of the tubular portion. The compression ratio (C) of the tubular portion may be 0.5% or more.

From the viewpoint of inhibiting buckling, the compression ratio C may be 2% or less, or less than 1%. By making the compression ratio (C) less than 1%, buckling can be further suppressed. Particularly, when the thickness of the metal plate is small, buckling tends to occur. Therefore, the compression ratio (C) is preferably less than 1%. In a preferred example, the expression 0.2? 100 × (LU-LH) / LU <1 is satisfied.

If the difference (LU-LH) between the end face circumferential length LH of the tubular portion and the end face length LU of the U-shaped portion is too large, buckling (folding of the metal plate) occurs or a metal plate is fitted to the abutment portion of the upper die and the lower die There is a concern. On the other hand, the thicker the metal plate, the less the buckling occurs even if the compression ratio C is increased. Further, the thinner the metal plate, the greater the effect obtained by the compression. From this point of view, it is preferable to determine the difference between the peripheral edge length LH and the cross-sectional length LU of the U-shaped portion in consideration of the thickness of the metal plate. For example, when the plate thickness of the metal plate constituting the tubular portion is t, the difference between the peripheral edge length LH of the tubular portion and the sectional length LU of the U-shaped portion may be 8t or less. In this case, the difference between the peripheral edge length LH of the tubular portion and the sectional length LU of the U-shaped portion may be 0.1 t or more.

In a preferred example, the compressibility (C) is 0.2% or more, and the difference between the peripheral length LH and the sectional length LU is 8 t or less. In another preferred example, the compressibility (C) is 0.2% or more and 2% or less. A metal plate of a thin plate having a plate thickness ratio of 5% or less to a corresponding diameter (corresponding diameter) of the metal plate is used as a blank. In this case, it is preferable that the compression ratio C is 0.2% or more and less than 1% (for example, 0.2% or more and less than 0.5%).

From the viewpoint of preventing buckling, the compression ratio C may be determined in consideration of the yield stress? (MPa) and the plate thickness t (mm) of the metal plate (blank) constituting the tubular portion. For example, the above-described compression ratio C (%) may satisfy the following expression. In this case, any one of the lower limit described above may be employed as the lower limit of the compression ratio C. The thickness of the metal plate when the following formula is satisfied is not limited, but it may be in the above-mentioned range (for example, in the range of 0.4 to 5 mm).

C? (1500 /?) Xt

The step (ii) may include the following steps (ii-1) and (ii-2). In the step (ii-1), the tubular portion is formed by deforming the U-shaped portion by using a metal so that the two ends of the U-shaped portion sandwich the projection. The tubular part is a precursor of the tubular part finally obtained in the step (ii), and can be referred to as a "first tubular part" or a "tubular part precursor". In step (ii-2), the peripheral length LT of the tubular portion is shortened by pressing the outer peripheral surface of the tubular portion with the two end portions sandwiching the protruding portions of the metal mold. By the step (ii-2), the end face peripheral length LH of the tubular portion is made shorter than the end face length LU of the U-shaped portion. That is, in the step (ii-2), the metal plate constituting the tubular portion is compressed in the circumferential direction. After the tubular part is formed in the step (ii-1), the tubular part is compressed in the circumferential direction in the step (ii-2), whereby the compression can be stably performed. Specifically, it is possible to suppress buckling or the like from occurring when the tubular portion is formed.

The three examples (Example (A), Example (B) and Example (C) of the step (ii) will be described below. Examples (A) and (B) are examples including the steps (ii-1) and (ii-2).

(Example (A) of the step (ii)) [

The mold (a) used in the example (A) has the following constitutions (a-1), (a-2) and (a-3).

(a-1) The mold (a) includes a first mold having a protrusion and a second mold.

(a-2) Each of the first and second molds includes first and second pressing surfaces for deforming the U-shaped portion to form the tubular portion.

(a-3) At least one mold selected from the first mold and the second mold is separable into a plurality of mold members.

With regard to the constitution (a-3), both of the first and second molds may be separable. Alternatively, only the first mold may be detachable, and only the second mold may be detachable. When the first and second molds are both detachable, it is easy to finely adjust the peripheral length LH of the tubular portion, and as a result, the deviation of the compressive stress acting on the tubular portion can be further reduced. As a result, the slit can be formed more precisely. In an example where the first mold is separable, the first mold is separable from the first mold member and the second mold member. In this case, the protruding portion may be constituted by the first protruding portion included in the first mold member and the second protruding portion included in the second mold member.

In the step (ii-1) of the example (A), the tubular portion is formed by deforming the U-shaped portion by using the mold (a) in which the plurality of mold members are separated. In the succeeding step (ii-2), the outer peripheral surface of the tubular portion is pressed by approaching the plurality of mold members, thereby shortening the peripheral length LT of the tubular portion. According to this configuration, the metal plate constituting the tubular portion is compressed in the circumferential direction.

In a preferred example of the example (A), the mold a moves only in the vertical direction in the step (ii-1) and the mold a only moves in the horizontal direction in the step (ii-2). For example, when only the upper mold out of the mold a moves in the vertical direction (press direction), the upper mold is moved to the bottom dead center in step (ii-1). Thereafter, in the step (ii-2), a plurality of separately separated mold members are moved in the horizontal direction.

(Example (B) of the step (ii))

The mold (b) used in the example (B) has the following structures (b-1), (b-2) and (b-3).

(b-1) The mold (b) includes a first mold having a protruding portion and a second mold.

(b-2) Each of the first and second molds includes first and second pressing surfaces for deforming the U-shaped portion to form the tubular portion.

(b-3) At least one mold selected from the first mold and the second mold includes a body portion and a movable portion relatively movable with respect to the body portion.

Regarding the structure (b-3), each of the first and second molds may include a movable portion. Alternatively, only the first mold may include the movable part, and only the second mold may include the movable part. In one example, the first and second dies include first and second movable parts movable in the pressing direction (vertical direction), respectively. In this case, the first movable part included in the first mold may include a protrusion for forming the slit. In another example, at least one of the first and second molds includes first and second movable parts movable in a direction orthogonal to the pressing direction. The first and second movable portions are arranged so as to face each other with the tubular portion interposed therebetween. The tubular portion can be compressed in the circumferential direction by pressing the outer peripheral surface of the tubular portion by the two movable portions (first and second movable portions). Here, the pressing direction means a direction in which the main body portion of the metal mold moves during molding.

In the step (ii-1) of the example (B), the U-shaped portion is deformed by using a metal mold in which the pressing surface of the movable portion does not protrude from the pressing surface of the main body. In the subsequent step (ii-2), the pressing surface of the movable portion is protruded from the pressing surface of the main body portion so as to press the outer peripheral surface of the tubular portion, thereby shortening the peripheral length LT of the tubular portion. According to this configuration, the metal plate constituting the tubular portion is compressed in the circumferential direction. In a typical process (ii-2), only the moving part is moved without moving the body part.

(Example (C) of the step (ii))

The mold (c) used in the example (C) has the following configuration.

(c-1) The mold (c) includes a first mold having a protrusion and a second mold.

(c-2) Each of the first and second molds includes first and second pressing surfaces for deforming the U-shaped portion to form the tubular portion.

(c-3) The peripheral length of the pressing surface of the mold (pressing surface of the first and second molds) is shorter than the sectional length (LU) of the U-shaped portion.

Different from the molds (a) and (b), the first and second molds constituting the mold (c) are in principle integrally formed. However, the projections of the first mold may be replaceable. In the example (C), the U-shaped portion is deformed only by bringing the first mold and the second mold close to each other in the step (ii), thereby forming the tubular portion having the slit. The example (C) has an advantage that the structure of the metal mold is simple and the production of the metal molded article is easy.

In the manufacturing method of the present invention, the mold may include a pressing surface corresponding to the outer circumferential surface of the tubular portion, and the circumferential length of the pressing surface may be shorter than the sectional length (LU) of the U-shaped portion. According to this configuration, the tubular peripheral length LH of the tubular portion can be made shorter than the sectional length LU of the U-shaped portion by pressing the outer peripheral surface of the U-shaped portion by the pressing surface of the mold to form the tubular portion. As described above, the mold (c) has this configuration, and the mold (a) has this configuration as a rule. The mold (b) may or may not have this structure. The end face circumferential length of the pressing surface of the mold means the sum of the sectional lengths of the pressing surfaces of the plurality of members constituting the mold.

In the case of using the molds (a) and (c), in the case of forming the tubular portion having the slit by completely closing the mold, the circumferential length of the pressing surface of the mold and the circumferential length LH of the tubular portion are It is thought that it does not differ greatly. In this case, in this specification, it is possible to replace the peripheral edge length LH of the tubular portion with the peripheral edge length of the pressing surface of the metal mold. For example, it is possible to replace the peripheral length LH of the tubular portion with the peripheral length of the pressing surface of the metal mold in the above-described expression of the compression ratio (C) or other formulas.

The step (ii) of the manufacturing method of the present invention is typically carried out without using a core, and for example, most of the inner peripheral surface of the tubular portion (or the cylindrical portion) Or more) of the present invention. By performing the step (ii) without using the core, the tubular part is likely to be uniformly compressed in the circumferential direction. When the core is used, the metal plate sandwiched between the mold and the core is less likely to be compressed in the circumferential direction. However, if necessary, the core may be used in the step (ii). By using the core, it is possible to stably form a metal molded article having a complicated sectional shape in the circumferential direction. For example, when the angle &amp;thetas; shown in Fig. 1, which will be described later, exceeds 180 DEG, it is also possible to use a core for stable molding. When the core is used, the core may be disposed on the entirety of the tubular part or only on a part of the tubular part.

In the production method of the present invention, after the step (ii), the metal molded article may be further processed. For example, a projection or a flat part may be added to the metal molded article, or a hole may be formed in the metal molded article.

A manufacturing method of the present invention aims to manufacture a metal molded article including a tubular portion having a gap in an abutted portion. Therefore, as a rule, after the step (ii), the welding of the slit (the butt portion having the gap) is not performed. However, a part of the abutting portion may be welded. For example, if a part of the abutting part has a gap (slit) and the other part does not have a gap, a part or all of the abutting part having no gap may be welded. Even in this case, it is preferable not to weld the butt portion having the gap. Further, when assembling a product using a metal molded article, a part of the abutting portion may be contacted with the abutting portion.

(Metal molding)

The metal molded article of the present invention includes a tubular portion having a slit. In one aspect, the tubular portion is a tubular portion having a gap in the abutting portion. The metal molded article of the present invention is produced by the production method of the present invention. In the case of the metal molded article, the description of the other parts may be omitted. The description of the metal molded article of the present invention can be applied to the manufacturing method, the manufacturing apparatus, and the mold of the present invention.

The metal molded article of the present invention may include a portion other than the tubular portion having the slit. Alternatively, the metal molded article may be constituted only by tubular portions having slits. In this case, the metal molded article is a tubular shaped article having slits. The slit is usually formed along the axial direction (usually the longitudinal direction) of the tubular portion. The slits may be formed over the entire tubular portion or only a part of the tubular portion. In other words, the metal molded article may have a slit over the entire length of the abutted portion, or may have a slit only in a part of the abutted portion.

The shape of the tubular portion having the slit is not particularly limited as long as it can be formed by the method of the present invention. The shape of the cross section of the tubular portion is not particularly limited and may be various shapes such as a circle, an ellipse, a quadrangle, a shape that is asymmetrical upside-down, or a shape that is asymmetric. The tubular part may have a round tubular shape or a tubular shape.

Examples of the shape of the tubular portion include a straight straight pipe, a bent pipe, a round wall having different outer diameters in the longitudinal direction, and a modified cross-sectional pipe having a different cross-sectional shape in the longitudinal direction. Specifically, examples of the tubular portion include the tubes (tubular portion 1e) shown in Figs. 9A, 9B, 9C, 9D, and 9E. In such a tube, a slit 3 is formed in the butted portion 2.

The tube shown in Fig. 9A is an intuitive tube having a circular cross-sectional shape in the circumferential direction. The tube shown in Fig. 9B is a circular tube whose sectional shape in the circumferential direction is circular. The pipe shown in Fig. 9C is a trumpet-shaped turning surface having a round cross-sectional shape in the circumferential direction. The tube shown in Fig. 9D is a modified cross section tube in which the cross-sectional shape in the circumferential direction changes from a circular shape to a tetragonal shape. The tube shown in Fig. 9E is a tube whose cross-sectional shape in the circumferential direction is a vertically asymmetric and asymmetrical shape. The tube shown in Fig. 9E is a tube formed by using a tailored blank in which different metal plates are connected to each other in the circumferential direction.

It is difficult to form a tube having a cross-sectional shape in the circumferential direction as a left-right asymmetric shape or a tube using the tailored blank shown in Fig. 9E by conventional UO molding. On the other hand, by appropriately selecting the mold of the present invention, it is possible to form tubes of various shapes and various blanks.

The metal molded article of the present invention is obtained by molding a metal plate (blank). Therefore, the material of the metal molded article is the same as the material of the blank. Further, the thickness of the metal molded article is almost the same as the thickness of the blank. Therefore, the plate thickness (plate thickness of the tubular portion) of the metal molded article may be within the range exemplified as the plate thickness of the blank. Some of the physical properties of the metal molded article change from the physical properties of the blank in the processing step. Particularly, in the metal molded article of the present invention, the tubular portion is compressed in the circumferential direction, and therefore the physical properties thereof are changed.

According to the production method of the present invention, the metal molded article of the present invention can be produced. When the deviation (S) of the Vickers hardness in the plate thickness direction in the cross section of the tubular part is expressed by the following formula, the average value of the deviation S in the circumferential direction is less than 0.4 (0 or more and less than 0.4 )to be.

S = (Bmax-Bmin) / Bmax

Here, Bmin is the minimum value of the Vickers hardness in the plate thickness direction in the section of the tubular portion. Bmax is a maximum value of the Vickers hardness in the plate thickness direction in the section.

The "average value of the deviation S in the circumferential direction" is an average value of the deviations S measured at three positions on one end face (circumferential end face) of the tubular portion. The three positions to be measured are a first position near the slit of the tubular portion, a second position farthest from the first position in the circumferential direction, and a third position intermediate the first position and the second position. The case where the tubular portion is in a circular tube shape and the slit is located at the uppermost portion of the tubular portion is considered. At this time, assuming that the bottom portion of the tubular portion is 0 deg. Centered on the center of the tubular portion, the first, second, and third positions are about 180 deg., 0 deg., And 90 deg. The first position is set so that the distance from the end facing the slit is, for example, in the range of 5 mm or less.

In the manufacturing method of the present invention, the peripheral length LH of the tubular portion is made shorter than the sectional length (LU) of the U-shaped portion. Therefore, compressive stress acts on the entire tubular portion in the thickness direction of the tubular portion, and the variation of compressive stress acting in the circumferential direction of the tubular portion is small. Therefore, by forming the tubular portion in the manufacturing method of the present invention, the Vickers hardness can be increased over the entire cross section of the tubular portion. As a result, it is possible to reduce the variation in Vickers hardness over the entire cross section of the tubular portion. Reducing the deviation of the Vickers hardness is effective for improving the durability and reliability of a metal molded article having a tubular portion.

In a preferred example, the deviations S measured at the three positions are all less than 0.4 (for example, less than 0.2). According to this configuration, improvement in durability and reliability can be expected particularly.

(Vickers hardness measurement method)

A method of measuring the Vickers hardness of the tubular portion will be described below. First, the tubular portion is cut in a circumferential direction, and the cut surface is mechanically polished until it becomes a mirror surface. Next, in order to eliminate the effect of work hardening by mechanical polishing, the cut surface is dissolved by chemical polishing or electrolytic polishing to a depth of 30 to 80 탆 from the surface of the cut surface. The Vickers hardness is measured for the cut surface thus obtained.

Vickers hardness is measured according to the test method of Vickers hardness test of JIS Z2244 of Japanese Industrial Standard (JIS). In the Vickers hardness test, depressions are formed in the test piece, and the diagonal length of the depressed portion is measured. When evaluating the deviation S of the cut surface of the tubular portion, a plurality of recesses are formed on the cut surface and the measurement is made. When the tubular portion is made of steel, copper or copper alloy, the distance between the centers of two adjacent recesses is set to 3d or more (d is a larger value in the diagonal length of the recess), and the distance between the centers of the recesses ) Should be 2.5d or more. In the case where the tubular portion is made of a light metal (including aluminum, aluminum alloy, titanium, titanium alloy, magnesium and magnesium alloy), the distance between the centers of two adjacent recesses is set to 6d or more and the distance from the center of the recess to the edge Make the distance more than 3d. Such a distance can be adjusted by a measurement interval of the Vickers hardness and a force to push the indenter.

Vickers hardness is measured at the above-mentioned first position at five points which are equally spaced on a straight line in the thickness direction. Then, the minimum value Bmin and the maximum value Bmax of the Vickers hardness are determined from the measured values of the five points, and the deviation S described above is obtained. With respect to the second and third positions, the Vickers hardness is similarly measured to obtain the deviation S described above. Then, by averaging the obtained three deviations S, an average value in the circumferential direction of the deviation S is obtained.

The metal molded article of the present invention can be used for various purposes. Examples of the use of the metal molded article include the parts of various vehicles (automobile, railroad car, other vehicles) (parts of wheels, parts of bodies, structures, etc.), parts of various machines, electronic devices, electronic products, , Aircraft), and the like.

(Manufacturing apparatus)

The manufacturing apparatus of the present invention is a manufacturing apparatus for manufacturing a molded metal article including a tubular portion having a slit. This production apparatus can be used in the production method of the present invention. The metal forming article of the present invention can be produced by this manufacturing apparatus. The manufacturing apparatus may be a press apparatus from another point of view, and a configuration of a known press apparatus may be applied to a configuration not described below. The description of other parts of this manufacturing apparatus may be omitted. The manufacturing apparatus of the present invention can be applied to the manufacturing method, the metal molded article, and the mold according to the present invention.

The manufacturing apparatus of the present invention includes a mold and a moving mechanism for moving the mold. The mold includes a first mold and a second mold. The first mold includes a protrusion for forming a slit. Each of the first and second molds includes first and second pressing surfaces for forming a tubular portion having a gap that becomes a slit by deforming a U-shaped portion having a U-shaped section. The mold has a configuration for pressing the outer peripheral surface of the tubular portion so that the peripheral length LT of the tubular portion becomes shorter.

Two examples (production apparatus (a) and production apparatus (b)) of the production apparatus of the present invention will be described below.

(Manufacturing apparatus (a))

The manufacturing apparatus (a) uses the above-described mold (a). As described above, the mold (a) has the following constitutions (a-1), (a-2) and (a-3).

(a-1) The mold (a) includes a first mold having a protrusion and a second mold.

(a-2) Each of the first and second molds includes first and second pressing surfaces for deforming the U-shaped portion to form the tubular portion.

(a-3) At least one mold selected from the first mold and the second mold is separable into a plurality of mold members.

The moving mechanism of the manufacturing apparatus (a) includes a first moving mechanism and a second moving mechanism. The first moving mechanism is a moving mechanism for moving the first mold and the second mold in a state in which the plurality of mold members are separated. Normally, the first moving mechanism brings the first mold and the second mold close to each other until the first mold and the second mold come in contact with each other with the plurality of mold members separated. The second moving mechanism is a moving mechanism for approaching a plurality of separated mold members. The first moving mechanism corresponds to the step (ii-1) of the above-described example (A). The second moving mechanism corresponds to the step (ii-2) of the example (A). According to the production apparatus (a), the step (ii) of the above-described example (A) can be carried out.

The first mold of the mold (a) may be separable from the first mold member and the second mold member. In this case, the protrusions for forming the slits may be constituted by the first protrusions included in the first mold member and the second protrusions included in the second mold member.

(Manufacturing apparatus (b))

The manufacturing apparatus (b) uses the mold (b) described above. As described above, the mold (b) has the following structures (b-1), (b-2), and (b-3).

(b-1) The mold (b) includes a first mold having a protruding portion and a second mold.

(b-2) Each of the first and second molds includes first and second pressing surfaces for deforming the U-shaped portion to form the tubular portion.

(b-3) At least one mold selected from the first mold and the second mold includes a body portion and a movable portion relatively movable with respect to the body portion.

The moving mechanism of the manufacturing apparatus (b) includes a first moving mechanism and a second moving mechanism. The first moving mechanism is a moving mechanism for approaching the first mold and the second mold. Normally, the first moving mechanism approaches the first mold and the second mold until the first mold and the second mold come in contact with each other so that the pressing surface of the movable portion does not protrude from the pressing surface of the main body. The second moving mechanism is a moving mechanism that moves the movable portion so that the pressing surface of the movable portion protrudes from the pressing surface of the body portion. The first moving mechanism corresponds to the step (ii-1) of the above-described example (B). The second moving mechanism corresponds to the step (ii-2) of the example (B). According to the production apparatus (b), the step (ii) of the above-mentioned example (B) can be carried out.

As long as the above operation is possible, the configuration of the moving mechanism of the manufacturing apparatuses (a) and (b) is not particularly limited, and a known moving mechanism used in a double-action type press apparatus may be applied. For example, each of the moving mechanisms of the manufacturing apparatuses (a) and (b) may be configured by a combination of a telescopic mechanism and a cam. Examples of the telescopic mechanism include a gas cylinder, a hydraulic cylinder, a spring, and the like.

The production apparatus for carrying out the step (ii) of the above-mentioned example (C) is not particularly limited except for using the mold (c). The step (ii) of the example (C) can be carried out in a general press apparatus.

(mold)

The mold of the present invention is a mold for producing a metal molded article including a tubular portion having a slit. This mold can be used in the production apparatus of the present invention. Further, this mold can be used in the production method of the present invention, specifically, in the step (ii) of the production method of the present invention. By using this mold, the metal molded article of the present invention can be produced. In regard to the mold, the description of the other parts may be omitted. The description of the mold of the present invention can be applied to the production method, the metal molded article, and the manufacturing apparatus of the present invention.

A mold of the present invention includes a first mold including a protrusion for forming a slit and a second mold. Each of the first and second molds includes first and second pressing surfaces for forming a tubular portion having a gap that becomes a slit by deforming a U-shaped portion having a U-shaped section. In the case where the outer periphery of the cross section forms a circular tubular section (or a tubular section), the second pressing surface has a semi-cylindrical shape and the first pressing surface has a semicircular shape except for the protrusions .

The mold of the present invention has a configuration for pressing the outer circumferential surface of the tubular portion so that the circumferential length of the tubular portion is shortened. In another aspect, the mold of the present invention has a configuration for compressing the tubular portion in the circumferential direction. Examples of the mold of the present invention include the above-mentioned mold (a) and mold (b).

The first mold having the projecting portion may be used as a top mold, and the second mold may be used as a bottom mold. Therefore, in this specification, the first mold may be changed to a top mold, and the second mold may be replaced with a bottom mold. The first mold may be replaced with a lower mold, and the second mold may be replaced with a top mold.

The protruding portion has a shape capable of forming a slit. The slit can be formed along the axial direction of the tubular portion by using the first mold having the plate-shaped protrusions arranged along the axial direction of the tubular portion. In a typical example, the projecting portion is a plate-like convex portion, and is provided at the uppermost position among the pressing surfaces of the upper half of the upper side. In other words, in a typical example, a protruding portion is provided at a central portion of a cross-section (cross-section in the circumferential direction) of the pressing surface of the upper mold. However, the projecting portion is not limited to the central portion but may be located at a position shifted from the center. For example, in the case of forming a tubular portion having a left-right asymmetry, the protruding portion may be located at a position shifted from the center portion. The position of the projection in the circumferential direction may change along the axial direction. The width of the projection may vary along the axial direction. By using the protruding portion changing in the axial direction, it is possible to form a slit that changes in the axial direction.

When the inner diameter of the tubular portion is Din and the plate thickness is t, the width of the slit may be t or more and (Din-2t) or less. If the width of the slit is less than t, there is a possibility that the strength of the projecting portion of the mold becomes insufficient. When the width of the slit is larger than (Din-2t), the effect of the invention may be reduced.

The width of the protruding portion is selected in accordance with the width of the slit (the gap of the abutted portion). The width of the protruding portion is preferably within ± 10% of the width of the slit.

As described above, in the mold (a), at least one mold selected from the first mold and the second mold can be separated into a plurality of mold members. If the number of the mold members is large, there is a possibility that the U-shaped portion tends to be sandwiched between the adjacent mold members at the time of molding. If the number of mold members is large, the structure of the mold and the apparatus using the same becomes complicated. Therefore, in a preferred example in which the first mold is divided into a plurality of mold members, the first mold is divided into two mold members. Similarly, in a preferred example in which the second mold is divided into a plurality of mold members, the second mold is divided into two mold members.

When the first mold and / or the second mold can be separated by a plurality of mold members, the position of the separation is not particularly limited. When the first mold is separable by the first mold member and the second mold member, the protrusions may be constituted by the first protrusions included in the first mold member and the second protrusions included in the second mold member. That is, the first mold may be divided at the protruding portion. According to this configuration, the two end portions of the U-shaped portion can be guided by the first and second projections, and the end of the U-shaped portion can be prevented from being pinched between the two mold members.

In the mold (a), by moving the plurality of mold members separately, the peripheral length LH of the tubular portion can easily be finely adjusted, and the deviation of the compressive stress acting on the tubular portion can be reduced. Therefore, according to the mold (a), the springback can be effectively suppressed, and as a result, the slit can be formed precisely.

As described above, in the mold (b), at least one mold selected from the first mold and the second mold includes a movable portion that is relatively movable with respect to the main body portion and the main body portion.

In the mold (b), only the first mold may have the main portion and the movable portion, and only the second mold may have the main portion and the movable portion. Alternatively, both of the first and second molds may have a body portion and a movable portion. When each of the two molds has the main body and the movable portion, the area of the pressing surface of the movable portion can be increased, and as a result, the pressure can be stably pressed when the cylindrical portion is pressed and compressed in the circumferential direction.

The position at which the movable portion is disposed is not particularly limited as long as it is a position where the peripheral edge length of the tubular portion can be adjusted by moving the movable portion. For example, the movable portion may be disposed at a position corresponding to a top portion and a bottom portion of the tubular portion, or may be disposed at a position corresponding to two side portions of the tubular portion. It is preferable that the movable portion is disposed so as to correspond to two positions facing each other with the center of the tubular portion sandwiched therebetween.

The movable portion is disposed at least in a region in which the step (ii) of Example (B) is performed. For example, the movable portion may be disposed over the entire length of the mold, or may be disposed only on a part of the mold.

In the case where the first mold has the main body portion and the movable portion, the number of the movable portions may be one or plural. In the case of a plurality of moving parts, it is easy to finely adjust the circumferential length of the tubular part as compared with the case where the movable part has one. Similarly, when the second mold has the main body portion and the movable portion, the number of the movable portions may be one or plural. When the movable part is plural, the movable part may be disposed at both the position corresponding to the top (or the bottom) of the tubular part and the position corresponding to the side part of the tubular part.

The movable portion can be moved by a cylinder, a cam mechanism, or the like so as to move relative to the body portion.

In the mold of the present invention, the protrusions for forming the slits may be replaceable. For example, in the above-mentioned molds (a), (b), and (c), the protrusions may be exchangeable. Since the projections are easy to consume, the lifetime of the mold can be prolonged by making the protrusions replaceable. Further, by changing the protruding portions, it is easy to adjust the width of the slit. When the physical properties (tensile strength, etc.) and thickness of the metal plate (blank) change, the amount of springback changes. Therefore, in the conventional method, it is necessary to change the entire metal mold every time the physical properties and the thickness of the metal plate change. However, by making the projection part replaceable, it is easy to adjust the width of the slit without changing the entire mold.

The shape of the mold is appropriately designed in accordance with the shape of the tubular portion to be aimed. For example, as shown in Fig. 8, the circumferential sectional shape of the pressing surface of the metal mold may be a vertically asymmetric shape or a left-right asymmetric shape. The cross-sectional shape of the pressing surface of the mold in the circumferential direction may be constant over the axial direction or may change in the axial direction. The pressing surface of the metal mold may be immediately in the axial direction or may be bent in the axial direction.

Each of the first mold and the second mold may be a single acting type. The first mold and the second mold may each be of a double-acting type, if necessary. In the molds (a) and (b), at least one selected from the first and second molds is a double-acting type. By using a double acting type mold, the peripheral length of the tubular portion can be finely adjusted, and the deviation of the compressive stress acting on the tubular portion can be reduced. Therefore, the springback can be suppressed particularly effectively and the precision of the shape of the metal molded article can be particularly enhanced. When the mold is a double-acting type, a device used in a double-action type press apparatus or a device using a cylinder, a cam, or the like is used for a manufacturing apparatus using the same.

When the material of the metal plate or the thickness of the metal plate changes, the springback amount changes accordingly. Therefore, in the conventional molding method using a metal mold, when the material and thickness of the metal plate are changed, it is necessary to change the metal mold accordingly. On the other hand, in the mold of the present invention, it is possible to change the compression ratio of the tubular portion without changing the mold. For example, in the mold (a), the compression ratio of the tubular portion can be changed by the distance between the plural mold members. In the mold (b), the compression rate of the tubular portion can be changed by changing the moving amount of the movable portion. Therefore, in the mold of the present invention, even when the material and the thickness of the metal plate change, it is possible to control the interval of the slit without changing the metal mold. Therefore, the mold of the present invention is suitable for mass production of the metal molded article of the present invention.

As will be described later, by using the mold of the present invention, the deviation of the hardness distribution in the plate thickness direction and the deviation of the hardness distribution in the circumferential direction of the tubular portion can be reduced. Therefore, by using the mold of the present invention, it is possible to produce a metal molded article having high fatigue strength.

Hereinafter, examples of embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals, and redundant description may be omitted.

(First Embodiment)

In the first embodiment, an example of the metal molded article of the present invention will be described. The metal molded article of the present invention includes a tubular portion having a slit. Fig. 1 schematically shows a cross section (a cross section in a circumferential direction) in a direction orthogonal to the axial direction of the tubular portion. The metal molded article 1 includes a tubular portion 1e on which a slit 3 is formed and typically comprises only a tubular portion 1e. In the slit 3, the two ends E1 and E2 abut against each other. In another aspect, the metal molded article 1 is a substantially closed end face part (tubular part having a substantially closed end face). Here, the term &quot; substantially closed end face &quot; refers to a cross section in which a gap exists between two end portions of metal plates formed in tubular form. The substantially closed end face component may have a gap over the entire length of the abutted portion, or may have a gap in a part of the abutted portion.

Here, it is assumed that points P1 and P2 are separated from the two ends E1 and E2 by 3 mm in the circumferential direction along the tubular portion 1e. Let O be the intersection between the tangent at point P1 and the tangent at point P2. The angle &amp;thetas; formed by the line OP1 and the line OP2 is preferably 30 DEG or more. If the angle &amp;thetas; is too small, there is almost no difference from the end face of the U-shaped portion, and there is a fear that the strength (bending strength) of the tubular portion after molding is lowered. A typical example angle? Is 150 degrees or more (e.g., 170 degrees or more). The angle &amp;thetas; is preferably 180 DEG or less. If the angle? Is too large, the molding may become unstable.

(Second Embodiment)

In the second embodiment, a manufacturing method of the present invention and an example of a mold used therefor will be described. In the following embodiments, an example of a case of manufacturing a metal molded article composed of only a tubular portion will be described. The manufacturing method of the second embodiment includes the steps (i) and (ii).

Process (i) is schematically shown in Figs. 2A and 2B. First, as shown in Fig. 2A, a metal plate (blank) 1a is disposed between the die 11 and the punch 12. The die 11 and the punch 12 are molds for U-molding. Next, as shown in Fig. 2B, the metal plate 1a is press-formed and a U-shaped portion 1b having a U-shaped cross section is formed. As shown in Fig. 2C, the U-shaped portion 1b has two end portions E1 and E2.

In step (i), the relationship between the width W of the portion to be the tubular portion (tubular portion 1e) of the metal plate and the sectional length (LU) of the U-shaped portion 1b is determined according to various conditions , The condition of the step (i), and the like). When the section length LU is longer than the width W, the section length LU is shorter than the width W, and both may be the same. In the manufacturing method of the present invention, it is important to form the tubular portion so that the peripheral length LH of the tubular portion in the step (ii) is shorter than the sectional length (LU) of the U-shaped portion. Therefore, the relationship between the width W and the section length LU in the step (i) is not particularly limited.

Fig. 3A schematically shows a mold used in the step (ii) of the second embodiment. The mold 20 of the second embodiment is an example of the above-described mold (a). The mold 20 includes a top mold (first mold) 21 and a bottom mold (second mold)

The upper die 21 has a plate-shaped protruding portion 23 for forming a slit. The upper mold 21 includes a first mold (first mold member) 21a and a second mold (second mold member) 21b which are separable in the horizontal direction. The protrusion 23 is constituted by a first protrusion 23a included in the first upper half 21a and a second protrusion 23b included in the second upper half 21b. The lower mold 22 includes a first lower mold (first mold member) 22a and a second lower mold (second mold member) 22b which are horizontally separable.

The upper die 21 has a first pressing surface 21p for pressing the outer peripheral surface of the U-shaped portion 1b to form the tubular portion 1d. The lower die 22 has a first pressing surface 22p for pressing the outer peripheral surface of the U-shaped portion 1b to form the tubular portion 1d (Fig. 3D). The projection 23 is a plate-like convex portion, and the length thereof is equal to or longer than the slit 3 to be formed. The end face circumferential length of the entire pressing surface (the first pressing surface 21p and the second pressing surface 22p) of the metal mold 20 is shorter than the sectional length LU of the U-shaped portion 1b.

The following step (ii) will be described with reference to Figs. 3B to 3E. The step (ii) of the second embodiment is the step of the above-described example (A), and includes the steps (ii-1) and (ii-2). According to the step (ii), the tubular portion 1e having a slit can be formed from the U-shaped portion 1b.

In the step (ii) of the second embodiment, first, the U-shaped portion 1b is arranged in the metal mold 20 as shown in Fig. 3B. Next, as shown in Fig. 3C and Fig. 3D, the mold 20 is moved in the state in which the end portion E1 and the end portion E2 (see Fig. 2C) of the U-shaped portion 1b sandwich the projection portion 23 To deform the U-shaped portion 1b (step (ii-1)). Specifically, the upper mold 21 and the lower mold 22 come close to each other until the upper mold 21 and the lower mold 22 come into contact with each other, and the outer peripheral surface of the U-shaped portion 1b is pressed on the pressing surface of the mold 20. In the step (ii-1), the first upper half 21a and the second upper half 21b are separated in the horizontal direction, and the first lower half 22a and the second lower half 22b are separated in the horizontal direction . In this state, the upper mold 21 and / or the lower mold 22 are moved in the vertical direction to bring them closer to each other. By the step (ii-1), the cylindrical portion 1d is formed. In the process of Fig. 3C, the U-shaped portion 1b is deformed to become the U-shaped portion 1c. At this time, the two end portions of the U-shaped portion 1c come into contact with the protruding portions 23 and stop, and a gap is formed between the two end portions. And the gap becomes the slit 3 of the tubular portion 1e. In the state of FIG. 3D, the end portion E1 and the end portion E2 are opposed to each other with the protruding portions 23 (protruding portions 23a and 23b sandwiched therebetween).

In the manufacturing method of the second embodiment, the sectional length of the U-shaped portion 1b and the peripheral length LT of the tubular portion 1d may be substantially the same in the state of FIG. 3D. This configuration can be realized by adjusting the interval between the first upper half 21a and the second half 21b and the interval between the first lower half 22a and the second lower half 22b. With this configuration, when the tubular portion 1d is formed by largely deforming the U-shaped portion 1b, it is possible to suppress the compression force in the circumferential direction. Therefore, it is possible to suppress buckling or the like from occurring when the tubular portion 1d is formed. Here, "substantially the same" means that the difference in length between both is shorter than, for example, 0.1% (for example, less than 0.05%) of the longer side.

Next, as shown in Fig. 3E, by pressing the outer circumferential surface of the tubular portion 1d with the end portions E1 and E2 of the U-shaped portion 1b sandwiching the projecting portion 23 therebetween, The peripheral length LT of the shape portion 1d is shortened (step (ii-2)). Concretely, the peripheral length LT is shortened by closing the divided metal mold 20. More specifically, the first upper mold 21a and the second upper mold 21b are moved in the horizontal direction so that the first lower mold 22a and the second lower mold 22b are moved in the horizontal direction, Close. In the example shown in Fig. 3E, the first upper half 21a and the second upper half 21b are in contact with each other, and the first lower half 22a and the second lower half 22b are brought close to each other. That is, in the example shown in Fig. 3E, the pressing surface of the metal mold 20 in a completely closed state corresponds to the outer peripheral surface of the tubular portion 1e. The peripheral length LH of the tubular portion 1e is set to be equal to the length of the U-shaped portion 1b in the step (ii-2) by shortening the peripheral length LT of the tubular portion 1d LU). Thus, the tubular portion 1e (metal molded article) shown in Fig. 3F is obtained. The butted portion 2 of the tubular portion 1e has a slit 3 formed therein.

Fig. 3E shows a case where the mold is completely closed at the final stage of molding. However, in the manufacturing method of the present invention, as long as the peripheral length LH of the tubular portion 1e is shorter than the sectional length LU of the U-shaped portion 1b, the mold is not completely closed at the final stage of molding do. It is possible to change the above-described compression ratio C depending on how close the mold is to be closed. Even when the thickness and the physical properties of the metal plate 1a change, there are cases where it is possible to cope with the degree of opening of the mold 30 in Fig. 3D and the degree of closing of the mold 20 in Fig. 3E . Therefore, even when the thickness and the physical properties of the metal plate 1a change, the desired tubular portion 1e can be produced without changing the metal mold. It is also possible to change the width of the slit 3 depending on how close the mold 20 is in Fig. 3E.

When a tubular part is manufactured by conventional UO molding, compressive stress acts on the inner circumferential side of the tubular part and tensile stress acts on the outer circumferential side of the tubular part. As a result, the springback becomes large and it becomes difficult to control the springback. In contrast, in the manufacturing method of the present invention, the peripheral length LH of the tubular portion 1e is made shorter than the sectional length LU of the U-shaped portion 1b. That is, in the manufacturing method of the present invention, the tubular portion 1d is compressed in the peripheral direction to obtain the tubular portion 1e. As a result, in the tubular portion 1e, compressive stress acts on both the inner peripheral side and the outer peripheral side. Therefore, the springback is suppressed, and the slit 3 can be precisely formed.

In the manufacturing method of the present invention, the tubular portion 1d is formed by compressing the tubular portion 1d in the circumferential direction. Therefore, in the tubular portion 1e, compressive stress acts on both the inner circumferential side and the outer circumferential side. Further, in the tubular portion 1e, the deviation in the circumferential direction of the compressive stress can be reduced. As a result, it is possible to reduce the deviation of the hardness distribution in the plate thickness direction and the hardness distribution in the circumferential direction of the tubular portion 1e. Therefore, according to the present invention, it is possible to obtain a tubular part having a high fatigue strength.

In the manufacturing method of the second embodiment, all of the mold members existing around the tubular portion 1d relatively move to compress the tubular portion 1d. Therefore, according to the manufacturing method and the mold of the second embodiment, it is possible to uniformly compress the cylindrical portion 1d in the circumferential direction. Therefore, springback can be effectively suppressed, and the shape accuracy of the tubular portion can be further improved.

(Third Embodiment)

In the third embodiment, a manufacturing method of the present invention and another example of a mold used therefor will be described. The manufacturing method of the third embodiment includes the steps (i) and (ii). Since the step (i) is the same as the step (i) described in the second embodiment, the overlapping description will be omitted.

Fig. 4A schematically shows a mold used in the step (ii) of the third embodiment. The mold 30 of the third embodiment is an example of the mold b described above. The mold 30 includes a top mold (first mold) 31 and a bottom mold (second mold)

The upper die 31 has a plate-shaped protrusion 33 for forming the slit 3. The upper die 31 includes a main body portion 31a and a movable portion 31b which is relatively movable with respect to the main body portion 31a. The movable portion 31b is disposed at the top of the pressing surface 31ap of the main body portion 31a and includes the protruding portion 33. [ The lower mold 32 includes a body portion 32a and a movable portion 32b that is relatively movable with respect to the body portion 32a. The movable portion 32b is disposed at the bottom of the pressing surface 32ap of the main body portion 32a. In the metal mold 30 of the third embodiment, both the movable portions 31b and 32b can be moved in the pressing direction (vertical direction). The movable portion 31b can be moved in the pressing direction in unison with the main body portion 31a. The movable portion 32b can be moved integrally with the body portion 32a in the pressing direction.

In the mold (b) of the present invention, as a rule, the body portion and the movable portion can be moved integrally in the press direction. In the mold (b) of the present invention, as a general rule, the end surface of the movable portion (the end surface facing the molding space) constitutes a part of the pressure surface, and no roll or the like is disposed. In the mold (b) of the present invention, as a general rule, the movable portion is movable in a state in which the first and second body portions are at the final position (dead point) of the molding.

The main body portion 31a and the main body portion 32a each include pressing surfaces 31ap and 32ap for pressing the outer peripheral surface of the U-shaped portion 1b to form the cylindrical portion 1d. The movable portions 31b and 32b include pressing surfaces 31bp and 32bp for pressing the outer peripheral surface of the U-shaped portion 1b. The pressing surface 31ap and the pressing surface 31bp constitute the pressing surface 31p of the upper die 31. [ The pressing surface 32ap and the pressing surface 32bp constitute the pressing surface 32p of the lower mold 32. [ In the example described in the third embodiment, the entire circumferential length of the entire pressing surface is longer than the circumferential length LH of the tubular portion 1e. The peripheral length of the entire pressing surface may be substantially the same as the sectional length (LU) of the U-shaped portion 1b.

The following step (ii) will be described with reference to Figs. 4B to 4E. The step (ii) of the third embodiment is the step of the above-described example (B), and includes the steps (ii-1) and (ii-2). According to the step (ii), the tubular portion 1e having a slit can be formed from the U-shaped portion 1b.

In the step (ii) of the third embodiment, first, the U-shaped portion 1b is arranged in the metal mold 20 as shown in Fig. 4B. Next, as shown in Fig. 4C and Fig. 4D, the end portion E1 and the end portion E2 (see Fig. 2C) of the U-shaped portion 1b are inserted into the mold 30 To deform the U-shaped portion 1b (step (ii-1)). Specifically, the upper mold 31 and the lower mold 32 approach each other until the upper mold 31 and the lower mold 32 come into contact with each other, and the outer peripheral surface of the U-shaped portion 1b is pressed by the pressing surface of the mold 30. The step (ii-1) is performed in a state in which the pressing surfaces 31bp and 32bp of the movable parts 31b and 32b do not protrude from the pressing surfaces 31p and 32p of the main body part. By the step (ii-1), the cylindrical portion 1d is formed. That is, in the example shown in Fig. 4D, the pressing surfaces 31p and 32p correspond to the outer peripheral surface of the cylindrical portion 1d. In the process of Fig. 4C, the U-shaped portion 1b is deformed to become the U-shaped portion 1c. At this time, the two end portions of the U-shaped portion 1c come into contact with the projecting portions 33 and stop, and a gap is formed between the two end portions. And the gap becomes the slit 3 of the tubular portion 1e. In the state of Fig. 4D, the end portion E1 and the end portion E2 are opposed to each other with the protruding portion 33 interposed therebetween.

In the manufacturing method according to the third embodiment, the end face peripheral length of the entire pressing surface of the metal mold 30 may be substantially equal to the end face length LU of the U-shaped portion 1b. In this case, when the tubular portion 1d is formed by largely deforming the U-shaped portion 1b, the compression force in the circumferential direction can be suppressed. Therefore, it is possible to suppress buckling or the like from occurring when the tubular portion 1d is formed.

4E, by pressing the outer peripheral surface of the cylindrical portion 1d with the end portions E1 and E2 of the U-shaped portion 1b sandwiching the protruding portions 33, The peripheral length LT of the tubular portion 1d is shortened (step (ii-2)). Specifically, the pressing surface of the movable portions 31b and 32b is pressed from the pressing surface of the body portions 31a and 32a to press the outer peripheral surface of the cylindrical portion 1d. In the third embodiment, the slit 3 and the position facing the slit 3 in the tubular portion 1d are pressed from above and below. The peripheral length LH of the tubular portion 1e is set to be equal to the length of the U-shaped portion 1b in the step (ii-2) by shortening the peripheral length LT of the tubular portion 1d LU). Thus, the tubular portion 1e (metal molded article) shown in Fig. 4F is obtained. The butted portion 2 of the tubular portion 1e has a slit 3 formed therein.

Also in the manufacturing method of the third embodiment, the tubular portion 1e is formed by compressing the tubular portion 1d in the circumferential direction. Therefore, as described in the second embodiment, the slit 3 can be formed precisely. In the manufacturing method of the third embodiment, the above-described compression ratio can be easily changed by changing the moving amount of the movable portion. Therefore, even when the thickness and the physical properties of the metal plate 1a change, there is a case that the desired tubular portion 1e can be manufactured without changing the metal mold. In the mold of the third embodiment, since the protrusion 33 can be replaced by replacing the movable portion 31b, the replacement of the protrusion 33 is easy.

In the manufacturing method of the third embodiment, since the cylindrical portion 1d is pressed and compressed by the movable portion, the cylindrical portion 1d is pressed with the contact area between the cylindrical portion 1d and the mold 30 small, Is compressed. In this case, the compressive force applied in the circumferential direction by the movable portion is liable to be applied to the entire cylindrical portion 1d. Therefore, according to the manufacturing method and the mold of the third embodiment, it is possible to more uniformly compress the cylindrical portion 1d in the circumferential direction.

An example of a manufacturing apparatus that can be used in the step (ii) of the third embodiment will be described with reference to Figs. 14A to 14E. Fig. This manufacturing apparatus includes a first support 141, a second support 142, an extensible mechanism 141a, and an extensible mechanism 142a. The first support base 141 is provided with a retracting mechanism 141a and a movable portion 31b. The extensible mechanism 141a is expandable and contractible in the press direction and presses the main body portion 31a. The extensible mechanism 142a and the movable portion 32b are disposed on the second support base 142. [ The stretching and shrinking mechanism 142a is stretchable in the press direction and supports the body portion 32a. The expansion and contraction mechanisms 141a and 142a are not limited, and may be a gas cylinder, a hydraulic cylinder, a spring, or the like.

In the step (ii) of the third embodiment, first, as shown in Fig. 14A, the U-shaped portion 1b is arranged in the metal mold 30. Next, as shown in Figs. 14B and 14C, the first support 141 and the second support 142 are brought close to each other. Thereby, the above-described step (ii-1) is carried out to obtain the tubular portion 1d. Next, as shown in Fig. 14D, the first supporting table 141 and the second supporting table 142 are brought closer to each other while reducing the expansion / contraction mechanism. 14D, the pressing surfaces of the movable portions 31b and 32b protrude from the pressing surfaces of the body portions 31a and 32a to press the outer peripheral surface of the cylindrical portion 1d. Thus, the step (ii-2) is carried out.

14A, a mechanism (not shown) for approaching the first and second support rods 141 and 142 and a stretching mechanism 141a and a stretching mechanism 142a, Corresponds to the first moving mechanism of the above-described manufacturing apparatus (b). A mechanism for bringing the first support 141 and the second support 142 close to each other and a second expansion mechanism 141a and an expansion and contraction mechanism 142a in the expansion and contraction state correspond to the second movement mechanism. As described above, in the molds (a) and (b), the same constituent members may also serve as the first moving mechanism and the second moving mechanism. Such a moving mechanism may be realized by using a moving mechanism of a known press apparatus in conformity with the manufacturing apparatus of the present invention.

(Fourth Embodiment)

In the fourth embodiment, a manufacturing method of the present invention and another example of a mold used therefor will be described. The manufacturing method of the fourth embodiment includes the steps (i) and (ii). Since the step (i) is the same as the step (i) described in the second embodiment, redundant description is omitted.

Fig. 5A schematically shows a mold used in the step (ii) of the fourth embodiment. The mold 30 of the fourth embodiment is an example of the mold b described above. The mold 30 includes a top mold (first mold) 31 and a bottom mold (second mold)

The upper die 31 has a plate-shaped protrusion 33 for forming the slit 3. The upper die 31 includes a body portion 31a and two movable portions 31b which are relatively movable with respect to the body portion 31a. The movable portion 31b is disposed at the lowermost portion of the pressing surface of the main body portion 31a. The lower mold 32 includes a body portion 32a and two movable portions 32b which are relatively movable with respect to the body portion 32a. The movable portion 32b is disposed at the top of the pressing surface of the main body portion 32a. In the metal mold 30 of the fourth embodiment, both of the movable parts 32a and 32b are movable in the horizontal direction. Further, the movable portion 31b can be moved in the vertical direction (press direction) in unison with the main portion 31a. Similarly, the movable portion 32b can be moved in the vertical direction integrally with the body portion 32a.

The main body portion 31a and the main body portion 32a each include pressing surfaces 31ap and 32ap for pressing the outer peripheral surface of the U-shaped portion 1b to form the cylindrical portion 1d. The movable portions 31b and 32b include pressing surfaces 31bp and 32bp for pressing the outer peripheral surface of the U-shaped portion 1b. In the example described in the fourth embodiment, the entire circumferential length of the entire pressing surface is longer than the circumferential length LH of the tubular portion 1e. The peripheral length of the entire pressing surface may be substantially the same as the sectional length (LU) of the U-shaped portion 1b.

The following step (ii) will be described with reference to Figs. 5B to 5E. The step (ii) of the fourth embodiment is the step of the above-described example (B), and includes the steps (ii-1) and (ii-2). According to the step (ii), the tubular portion 1e having a slit can be formed from the U-shaped portion 1b.

In the step (ii) of the fourth embodiment, first, the U-shaped portion 1b is arranged in the metal mold 30 as shown in Fig. 5B. Next, as shown in Figs. 5C and 5D, the mold 30 is placed in a state in which the end portion E1 and the end portion E2 (see Fig. 2C) of the U-shaped portion 1b sandwich the protrusion 33 To deform the U-shaped portion 1b (step (ii-1)). Specifically, the upper mold 31 and the lower mold 32 come close to each other until the upper mold 31 and the lower mold 32 come into contact with each other, and the outer peripheral surface of the U-shaped portion 1b is pressed by the pressing surface of the mold 30. In the step (ii-1), the pressing surfaces 31bp and 32bp of the movable portion are not protruded from the pressing surfaces 31ap and 32ap of the main body. By the step (ii-1), the cylindrical portion 1d is formed. In the process of Fig. 5C, the U-shaped portion 1b is deformed to become the U-shaped portion 1c. At this time, the two end portions of the U-shaped portion 1c come into contact with the projecting portions 33 and stop, and a gap is formed between the two end portions. And the gap becomes the slit 3 of the tubular portion 1e. In the state of Fig. 5D, the end portion E1 and the end portion E2 are opposed to each other with the protruding portion 33 interposed therebetween.

The peripheral length of the entire pressing surface of the metal mold 30 may be substantially the same as the sectional length LU of the U-shaped portion 1b in the manufacturing method of the fourth embodiment. In this case, when the tubular portion 1d is formed by largely deforming the U-shaped portion 1b, the compression force in the circumferential direction can be suppressed. Therefore, it is possible to suppress buckling or the like from occurring when the tubular portion 1d is formed.

5E, by pressing the outer peripheral surface of the cylindrical portion 1d with the end portions E1 and E2 of the U-shaped portion 1b sandwiching the protruding portion 33 therebetween, The peripheral length LT of the tubular portion 1d is shortened (step (ii-2)). More specifically, the pressing surfaces 31bp and 32bp of the movable portions 31b and 32b are protruded from the pressing surfaces 31ap and 32ap of the body portions 31a and 32b to press the outer peripheral surface of the cylindrical portion 1d do. In the fourth embodiment, the side surface of the cylindrical portion 1d is pressed from the left and right. The peripheral length LH of the tubular portion 1e is set to be smaller than the sectional length LU of the U-shaped portion 1b by reducing the peripheral length LT of the tubular portion 1d in the step (ii-2) ). Thus, the tubular portion 1e (metal molded article) shown in Fig. 5F is obtained. The butted portion 2 of the tubular portion 1e has a slit 3 formed therein.

Also in the manufacturing method of the fourth embodiment, the tubular portion 1e is formed by compressing the tubular portion 1d in the circumferential direction. Therefore, as described in the second and third embodiments, the slit 3 can be formed precisely. In the manufacturing methods of the third and fourth embodiments, the above-described compression ratio can be easily changed by changing the moving amount of the movable portion. Therefore, even when the thickness and physical properties of the metal plate 1a slightly change, there is a case that the desired tubular portion 1e can be manufactured without changing the metal mold.

An example of a manufacturing apparatus that can be used in the step (ii) of the fourth embodiment will be described with reference to Figs. 15A to 15E. Fig. This manufacturing apparatus includes a first support 151, two extensible mechanisms 141a, two shafts 153, and two cam units 154. The extensible mechanism 141a and the shaft 153 are disposed on the first support 151. The stretching and shrinking mechanism 141a is stretchable in the press direction and presses the main body portion 31a.

In the step (ii) of the fourth embodiment, first, the U-shaped portion 1b is arranged in the metal mold 30 as shown in Fig. 15A. Next, as shown in Figs. 15B and 15C, the first support table 151 is pressed down. Thereby, the above-described step (ii-1) is carried out to obtain the tubular portion 1d. Next, as shown in Fig. 15D, the first support table 151 is further pressed down while the expansion / contraction mechanism is reduced. At this time, the two cam units 154 are moved by the two shafts 153, and the movable units 31b and 32b are operated by the cam unit 154. [ As a result, as shown in Fig. 15D, the pressing surfaces of the movable portions 31b and 32b protrude from the pressing surfaces of the body portions 31a and 32a to press the outer peripheral surface of the cylindrical portion 1d. Thus, the step (ii-2) is carried out.

15A, a mechanism (not shown) for moving the first support 151 downward and a second expansion mechanism 141a in a state in which the expansion and contraction mechanism 141b are not in the contracted state, . The mechanism for moving the first support base 151 downward, the shaft 153, and the cam unit 154 constitute a second moving mechanism. Such a moving mechanism may be realized by using a moving mechanism of a known press apparatus in conformity with the manufacturing apparatus of the present invention.

(Fifth Embodiment)

In the fifth embodiment, a manufacturing method of the present invention and another example of a mold used therefor will be described. The manufacturing method of the fifth embodiment includes the step (i) and the step (ii). Since the step (i) is the same as the step (i) described in the second embodiment, repeated description is omitted.

Fig. 6A schematically shows a mold used in the step (ii) of the fifth embodiment. The mold 20 of the fifth embodiment includes a top mold (first mold) 21 and a bottom mold (second mold) 22.

The upper die 21 has a plate-shaped protruding portion 23 for forming the slit 3. The first upper mold 21 and the second lower mold 22 each include pressure surfaces 21p and 22p for pressing the outer peripheral surface of the U-shaped portion 1b to form the tubular portion 1d. In the metal mold 20 of the fifth embodiment, the entire peripheral surface of the pressing surface is shorter than the sectional length (LU) of the U-shaped portion 1b. The peripheral length LH of the tubular portion 1e can be made shorter than the sectional length LU of the U-shaped portion 1b by deforming the U-shaped portion 1b using the metal mold 20 .

The following step (ii) will be described with reference to Figs. 6B to 6E. The step (ii) of the fifth embodiment is the step of the above-described example (C). In the step (ii) of the fifth embodiment, first, the U-shaped portion 1b is arranged in the metal mold 20 as shown in Fig. 6B. Next, as shown in Figs. 6C and 6D, by using the mold 20 so that the end portions E1 and E2 of the U-shaped portion 1b sandwich the protrusions 23, the U- 1b are deformed to form the tubular portion 1d. Specifically, the upper die 21 and the lower die 22 come close to each other, and the outer peripheral surface of the U-shaped portion 1b is pressed by the pressing surface of the die 20. In the process of Fig. 6C, the U-shaped portion 1b is deformed to become the U-shaped portion 1c. At this time, the two end portions of the U-shaped portion 1c come into contact with the protruding portions 23 and stop, and a gap is formed between the two end portions. And the gap becomes the slit 3 of the tubular portion 1e.

6D shows an example of a state in which the peripheral length LT of the tubular portion 1d is substantially the same as the sectional length LU of the U-shaped portion 1b. The upper mold 21 and the lower mold 22 are not in contact with each other in the step of Fig. 6D because the peripheral edge length of the pressing surface of the mold 20 is shorter than the sectional length LU of the U-shaped portion 1b. That is, in the step of Fig. 6D, the mold 20 is not yet closed.

6D, the upper mold 21 and the lower mold 22 are brought close to each other to close the mold 20 as shown in Fig. 6E. For example, the upper die 21 is moved to the bottom dead center so that the upper die 21 and the lower die 22 are brought into contact with each other. In this process, the outer circumferential surface of the cylindrical portion 1d is pressed by the pressing surface of the mold 20 with the two end portions E1 and E2 sandwiching the protruding portion 23 therebetween. As a result, the tubular portion 1e having the slit 3 in the abutted portion 2 shown in Fig. 6F is formed. The peripheral edge length of the pressing surface of the metal mold 20 is shorter than the sectional length LU of the U-shaped portion 1b. Therefore, the tubular peripheral portion length LH of the tubular portion 1e becomes shorter than the sectional length LU of the U-shaped portion 1b. That is, in the process of Fig. 6E, the tubular portion 1d is compressed in the circumferential direction to become the tubular portion 1e.

When the end face circumferential length LH of the tubular portion 1e is shorter than the end face length LU of the U-shaped portion 1b before the mold 20 is completely closed, the mold 20 is completely closed It is also possible to finish the molding before. In this case, it is possible to adjust the compression rate of the tubular portion 1e by adjusting the degree to which the upper die 21 and the second lower die 22 are brought close to each other.

Also in the manufacturing method of the fifth embodiment, the tubular portion 1e is formed by compressing the tubular portion 1d in the circumferential direction. Therefore, as described in the second embodiment, the slit 3 can be formed precisely.

In the mold of the present invention, the protrusions may be exchangeable. An example of a mold capable of replacing the projection is shown in Fig. The mold 20 of Fig. 7 includes a top mold (first mold) 21 and a bottom mold (second mold) The upper die 21 has a portion 24 including the protruding portion 23. The portion 24 is fitted in the hole 25 of the upper die 21 and is exchangeable. The protruding portion 23 is a portion where the two end portions (the end portions E1 and E2) of the U-shaped portion are in contact with each other, and wear and deformation are likely to occur. Therefore, it is preferable to make the protruding portion 23 replaceable. Further, by making the protrusions 23 interchangeable, the above-described effect can be obtained.

In another aspect, the present invention provides a method of manufacturing a substantially closed end face part having a gap in an abutting portion. Hereinafter, the manufacturing method of this aspect is referred to as manufacturing method (S). The manufacturing method (S) includes a first step and a second step. In the first step, the metal plate is shaped into a U-shape to obtain a U-shaped article. This U-shaped article corresponds to a molded article including a U-shaped portion formed in the above-described step (i). In the second step, the U-shaped article is molded into a substantially closed end face by using a mold, and the peripheral circumferential length of the substantially closed end face component is made shorter than the peripheral circumferential length of the U-shaped article. The mold used has a protrusion corresponding to the abutted portion of the substantially closed end face component and has a mechanism capable of adjusting the circumferential length of the substantially closed end face component. Examples of the molds include the molds (a), (b), and (c) described above. The first step and the second step correspond to the above-mentioned steps (i) and (ii), respectively. The substantially closed end face part having a gap corresponds to the above-mentioned metal formed article including a tubular part having a slit. The term &quot; substantially closed end face part &quot; refers to a part having a substantially closed end face. The term &quot; substantially closed end face &quot; refers to a cross section in which a gap exists between two abutting ends of a metal plate formed in a tubular form. The substantially closed end face component may have a gap over the entire length of the abutted portion, or may have a gap in a part of the abutted portion.

In the manufacturing method (S), the peripheral edge length of the mold may be shorter than the peripheral edge length of the U-shaped article. Here, the &quot; peripheral edge length of the mold &quot; indicates the peripheral edge length of the mold when the mold is completely closed. The peripheral edge length of the substantially closed end face component can be made shorter than the peripheral edge length of the U-shaped article by making the peripheral edge length of the metal mold completely shorter than the peripheral edge length of the U-shaped article when the metal mold is completely closed. The mold having this configuration corresponds to the molds (a) and (c) described above.

In the manufacturing method (S), the mold has an upper mold and a lower mold having the protrusions, and at least one of the upper mold and the lower mold may have the main body and the movable part. The mold having this configuration corresponds to the above-described mold (b).

In another aspect, the present invention provides a mold for molding a U-shaped article into a substantially closed end face and manufacturing a substantially closed end face part having a gap in the abutted portion. Hereinafter, this mold is referred to as a mold T1. The mold T1 has an upper mold and a lower mold having projections corresponding to abutted portions of the substantially closed end face parts. The mold T1 has a mechanism capable of adjusting the circumferential length of the substantially closed end face component. At least one of the upper and lower molds is divided into a plurality. The mold T1 corresponds to the above-described mold (a). In the mold T1, the projections of the upper mold may be divided. An example of a mold having this configuration is the mold 20 shown in Fig. 3A.

In another aspect, the present invention provides another mold for molding a U-shaped article into a substantially closed end face and producing a substantially closed end face part having a gap in the abutted portion. Hereinafter, this mold is referred to as a mold T2. The mold T2 has an upper mold and a lower mold with the protruding portions corresponding to the abutting portions of the substantially closed end face parts. The mold T2 has a mechanism capable of adjusting the circumferential length of the substantially closed end face component. At least one of the upper mold and the lower mold has a body portion and a movable portion. The mold T2 corresponds to the mold b described above.

In the molds (T1) and (T2), the protrusions may be exchangeable.

Example

Hereinafter, the present invention will be described in detail with reference to Examples.

[Example 1]

In Example 1, U-shaped members (U-shaped members) were formed by the manufacturing method shown in FIGS. 2A to 2B, and tubular members (metal molded articles) having slits were produced by the manufacturing methods shown in FIGS. 3B to 3E . A hot-rolled steel sheet having a TS (tensile strength) of 590 MPa and a sheet thickness of 2.3 mm was used for the metal plate (blank). The outer diameter of the tubular member was 50 mm and the length was 200 mm. The width of the protrusion of the upper mold was 5 mm.

[Example 2]

In Example 2, the same metal sheet as in Example 1 was used to produce a tubular member having slits by the manufacturing method shown in Figs. 2A to 2B and Figs. 4B to 4E. The dimensions of the tubular member and the width of the projection of the upper mold were the same as those in Example 1. [

[Example 3]

In the third embodiment, a U-shaped part (U-shaped part) is formed by the manufacturing method shown in Figs. 2A to 2B by using the same metal plate as the first embodiment, and the slit is formed by the manufacturing method shown in Figs. 5B to 5E Made a tubular member. The dimensions of the tubular member and the width of the projection of the upper mold were the same as those in Example 1. [

[Example 4]

In the fourth embodiment, a U-shaped part (U-shaped part) is formed by the same manufacturing method as shown in Figs. 2A to 2B using the same metal plate as the first embodiment, and the slit is formed by the manufacturing method shown in Figs. 6B to 6E Made a tubular member. The dimensions of the tubular member and the width of the projection of the upper mold were the same as those of the first embodiment.

[Comparative Example 1]

In Comparative Example 1, U-molding was carried out by the method shown in Figs. 2A to 2B by using the same metal plate as in Example 1. Fig. Thereafter, as shown in Figs. 10A to 10B, the tubular member 50a was produced by O-molding using a mold (upper mold 51 and lower mold 52) having no protruding portion. The end face circumferential length of the pressing face of the mold when the mold was completely closed was the same as the sectional length of the U-shaped article (U-shaped portion).

[Comparative Example 2]

Using the same metal plate as in Example 1, U molding was carried out according to the method shown in Figs. 2A to 2B. Then, as shown in Figs. 11A and 11B, O molding was performed using a mold (upper mold 51 and lower mold 52) having no projection and a core 53. Fig. Thus, a tubular member 50b having slits was produced. The peripheral edge length of the pressing surface of the mold when the mold was completely closed was longer than the sectional length of the U-shaped product (U-shaped portion).

The compressibility (C) of Examples 1 to 4 was set to 0.99%. The compressibility (C) of Comparative Examples 1 and 2 was set at about 0%.

[evaluation]

For the tubular members of Example 1, Comparative Example 1 and Comparative Example 2, the distortion distribution in the plate thickness direction on the cross section was measured. The measurement results are shown in Fig. 12A. 12A shows the absolute value of the distortion. As shown in Fig. 12A, the tubular members of Example 1 had larger absolute values of distortion and smaller distortion distribution in the plate thickness direction than the tubular members of Comparative Examples 1 and 2. This result suggests that compressive stress is applied almost evenly to the entire plate thickness direction in the tubular member of the first embodiment.

In addition, for the tubular members of Examples 2 to 4 and Comparative Example 2, the distortion distribution in the circumferential direction on the cross section was measured. The measurement results are shown in Fig. 12B. The vertical axis in Fig. 12B indicates the absolute value of the distortion. In Fig. 12B, the bottom of the cross section of the tubular member was set at 0 DEG, and the butt portion was set at 180 DEG. As shown in FIG. 12B, the tubular members of Examples 2 to 4 had larger absolute values of distortion as compared with the tubular members of Comparative Example 2. These results suggest that large compressive stresses are generated in the entire circumferential direction in the tubular members of Examples 2 to 4.

As shown in Figs. 12A and 12B, according to the manufacturing methods of Examples 1 to 4, it is possible to make the compressive stress applied to the tubular member in the thickness direction and the circumferential direction more uniform. Therefore, according to the manufacturing methods of Examples 1 to 4, it is possible to suppress the spring back and to produce a metal molded article having high shape precision.

The distribution of the Vickers hardness of the tubular members of Example 1 and Comparative Examples 1 and 2 was determined by using the results of simulation by FEM (finite element method). From the distribution, the deviation (S) of the Vickers hardness in the plate thickness direction at the first position was obtained. Similarly, the deviation (S) of the Vickers hardness in the plate thickness direction was determined for the second and third positions. As a result, in the tubular member of Example 1, the deviation S was about 0.1 at any of the first, second, and third positions. That is, in the tubular member of Example 1, the average value of the deviation S in the circumferential direction was about 0.1. This result implies that the variation in Vickers hardness is small in either the plate thickness direction or the circumferential direction in the tubular member of the first embodiment. On the other hand, in Comparative Examples 1 and 2, the deviation S was about 0.7 at any of the first, second, and third positions. That is, in the tubular members of Comparative Examples 1 and 2, the average value of the deviation S in the circumferential direction was about 0.7.

13 shows a graph showing the relationship between the above-described average value in the circumferential direction of the deviation S and the decreasing rate of uniaxial compressive strength. The graph of Fig. 13 is a graph showing the results of simulating the results obtained when a plurality of round tubes in which the average value in the circumferential direction of the deviation S becomes a predetermined value is assumed and the uniaxial compression test is performed on such round tubes Graph. The ordinate of the graph of Fig. 13 is the reduction rate of the uniaxial compressive strength when a round tube having an average value of the deviation S in the circumferential direction is zero. Concretely, the results of simulating the uniaxial compression test on the circular pipe and determining the reduction rate (%) of the uniaxial compressive strength of the other round pipe on the basis of the uniaxial compressive strength at that time are shown in Fig. 13 And is shown on the vertical axis of the graph.

For reference, FIG. 13 shows two dashed lines showing the tendency of the variation of the decreasing rate of the uniaxial compressive strength. As shown in Fig. 13, when the average value of the deviation S in the circumferential direction was 0.4 or more, the rate of decrease of the uniaxial compressive strength greatly increased. On the other hand, when the average value of the deviation S in the circumferential direction was less than 0.4, the reduction rate of the uniaxial compressive strength was small. The results in FIG. 13 indicate that it is important to make the average value of the deviation S in the circumferential direction less than 0.4.

In the conventional O forming (O forming of Comparative Examples 1 and 2) in which the metal plate is not compressed in the circumferential direction, the spring back is large and it is difficult to form the slit precisely. On the other hand, according to the manufacturing method of the present invention, the interval of the slits can be precisely formed. Further, since the conventional O-molding is a simple bending, the work hardening at the center of the plate thickness is small, and the fatigue strength of the resulting molded article is low. On the other hand, according to the production method of the present invention, a metal molded article having high fatigue strength can be obtained. Further, in the conventional method for producing a tubular member having a slit, it has been necessary to bend the metal plate little by little and then to form a tubular shape, or to fasten the metal plate to form a tubular shape. Compared with such a conventional manufacturing method, according to the present invention, it is possible to reduce the number of steps, and as a result, cost reduction is possible.

Industrial availability

INDUSTRIAL APPLICABILITY The present invention can be used as a metal molded article including a tubular portion having a slit and a manufacturing method thereof. Further, the present invention can be applied to a production apparatus for producing the above molded article, and a mold used therefor.

1: metal molded article, 1a: metal plate,
1b, 1c: U-shaped portion, 1d: tubular portion,
1e: tubular portion, 2: abutment portion,
3: slit (gap), 11: die,
12: punch, 20, 30: mold,
21, 31: upper figure, 21a: first upper figure,
21b: second phase, 22, 32: bottom mold,
22a: first lower mold, 22b: second lower mold,
23, 33: projecting portion, 23a: first projecting portion,
23b: second projecting portion, 31a, 32a: main body portion,
31b, 32b: movable part, E1, E2: end part

Claims (15)

A manufacturing method for manufacturing a metal molded article including a tubular portion having a slit,
(i) forming a U-shaped portion having a U-shaped cross section by deforming a metal plate;
(ii) forming the tubular portion having the slit by deforming the U-shaped portion by using a mold having the protruding portion so that the two ends of the U-shaped portion sandwich the protruded portion,
In the step (ii), the peripheral length LH of the tubular portion is made shorter than the sectional length (LU) of the U-shaped portion,
The step (ii)
(ii-1) a step of forming the tubular portion by deforming the U-shaped portion using the mold so that the two ends of the U-shaped portion sandwich the protruded portion;
(ii-2) a step of shortening the peripheral edge length LT of the tubular portion by pressing the outer peripheral surface of the tubular portion with the two end portions sandwiching the protruding portion therebetween ,
Wherein the mold includes a first mold having the protruding portion and a second mold,
Wherein the first and second molds respectively include first and second pressing surfaces for deforming the U-shaped portion to form the tubular portion,
Wherein at least one mold selected from the first mold and the second mold is separable by a plurality of mold members,
In the step (ii-1), the tubular portion is formed by deforming the U-shaped portion by using the mold in which the plurality of mold members are separated,
In the step (ii-2), the outer peripheral surface of the tubular portion is pressed by approaching the plurality of metal mold members to thereby shorten the peripheral length LT of the tubular portion Gt; A manufacturing method for manufacturing a metal molded article including a tubular portion having a slit,
(i) forming a U-shaped portion having a U-shaped cross section by deforming a metal plate;
(ii) forming the tubular portion having the slit by deforming the U-shaped portion by using a mold having the protruding portion so that the two ends of the U-shaped portion sandwich the protruded portion,
In the step (ii), the peripheral length LH of the tubular portion is made shorter than the sectional length (LU) of the U-shaped portion,
The step (ii)
(ii-1) a step of forming the tubular portion by deforming the U-shaped portion using the mold so that the two ends of the U-shaped portion sandwich the protruded portion;
(ii-2) a step of shortening the peripheral edge length LT of the tubular portion by pressing the outer peripheral surface of the tubular portion with the two end portions sandwiching the protruding portion therebetween ,
Wherein the mold includes a first mold having the protruding portion and a second mold,
Wherein the first and second molds respectively include first and second pressing surfaces for deforming the U-shaped portion to form the tubular portion,
Wherein at least one mold selected from the first mold and the second mold includes a body portion and a movable portion relatively movable with respect to the body portion,
The tubular portion is formed by deforming the U-shaped portion by using the metal mold in a state in which the pressing surface of the movable portion does not protrude from the pressing surface of the main body portion in the step (ii-1)
The pressing surface of the movable portion is protruded from the pressing surface of the main body portion so as to press the outer peripheral surface of the tubular portion so that the peripheral length LT (LT) of the tubular portion in the step (ii-2) ) Is shortened. The method according to claim 1 or 2,
Wherein the cross-sectional length (LU) of the U-shaped portion and the peripheral length (LH)
(LU-LH) / LU &lt; 1. The method according to claim 1 or 2,
Wherein the mold includes a pressing surface corresponding to an outer circumferential surface of the tubular portion,
Wherein a peripheral edge length of the pressing surface is shorter than a sectional length (LU) of the U-shaped portion. A metal molded article comprising a tubular part having a slit, which is produced by the manufacturing method according to claim 1 or 2,
Wherein an average value of the deviation (S) in the circumferential direction is less than 0.4 when the deviation (S) of the Vickers hardness in the plate thickness direction in the cross section of the tubular portion is expressed by the following formula.
S = (Bmax-Bmin) / Bmax
Here, Bmin is the minimum value of the Vickers hardness in the plate thickness direction in the section. Bmax is a maximum value of the Vickers hardness in the plate thickness direction in the section. A manufacturing apparatus for manufacturing a metal molded article including a tubular portion having a slit,
A mold, and a moving mechanism for moving the mold,
Wherein the mold includes a first mold including a protrusion for forming the slit, and a second mold,
Wherein each of the first and second molds includes first and second pressing surfaces for deforming a U-shaped section having a U-shaped section to form a tubular section having a gap serving as the slit,
The mold has a configuration for pressing the outer peripheral surface of the tubular portion to shorten the peripheral edge length of the tubular portion,
At least one mold selected from the first mold and the second mold is separable into a plurality of mold members,
Wherein the moving mechanism comprises:
And a first moving mechanism for moving the first mold and the second mold in a state in which the plurality of mold members are separated from each other to form the tubular portion by deforming the U-shaped portion by the first and second pressing surfaces, Wow,
And a second moving mechanism for moving the plurality of separated mold members toward each other so as to press the outer peripheral surface of the tubular portion to shorten the peripheral edge length of the tubular portion. A manufacturing apparatus for manufacturing a metal molded article including a tubular portion having a slit,
A mold, and a moving mechanism for moving the mold,
Wherein the mold includes a first mold including a protrusion for forming the slit, and a second mold,
Wherein each of the first and second molds includes first and second pressing surfaces for deforming a U-shaped section having a U-shaped section to form a tubular section having a gap serving as the slit,
The mold has a configuration for pressing the outer peripheral surface of the tubular portion to shorten the peripheral edge length of the tubular portion,
Wherein at least one mold selected from the first mold and the second mold includes a body portion and a movable portion relatively movable with respect to the body portion,
Wherein the moving mechanism comprises:
A first moving mechanism for moving the first mold and the second mold in a state in which the movable part does not protrude from the first and second pressing surfaces,
And a second moving mechanism for moving the movable portion so as to protrude from the pressing surface. A metal mold for producing a metal molded article including a tubular portion having a slit,
A first mold including a protrusion for forming the slit, and a second mold,
Wherein each of the first and second molds includes first and second pressing surfaces for deforming a U-shaped section having a U-shaped section to form a tubular section having a gap serving as the slit,
And presses the outer circumferential surface of the tubular portion to shorten a circumferential length of the tubular portion,
Wherein at least one mold selected from the first mold and the second mold is separable by a plurality of mold members and the U and the second pressing surfaces are separated from each other by the first and second pressing surfaces, The cylindrical portion is deformed to form the tubular portion and the outer peripheral surface of the tubular portion is pressed by bringing the plurality of mold members closer to each other thereby to shorten the peripheral edge length of the tubular portion. The method of claim 8,
Wherein the first mold is separable into a first mold member and a second mold member,
Wherein the protruding portion is constituted by a first protruding portion included in the first mold member and a second protruding portion included in the second mold member. A metal mold for producing a metal molded article including a tubular portion having a slit,
A first mold including a protrusion for forming the slit, and a second mold,
Wherein each of the first and second molds includes first and second pressing surfaces for deforming a U-shaped section having a U-shaped section to form a tubular section having a gap serving as the slit,
And presses the outer circumferential surface of the tubular portion to shorten a circumferential length of the tubular portion,
Wherein at least one mold selected from the first mold and the second mold includes a body portion and a movable portion movable relative to the body portion, wherein a pressing surface of the movable portion protrudes from a pressing surface of the body portion Shaped portion by deforming the U-shaped portion with the first and second pressing surfaces in a state where the first and second pressing surfaces are not in contact with each other, and the pressing surface of the movable portion is protruded from the pressing surface of the main body portion, And presses the outer circumferential surface to thereby shorten the peripheral edge length of the tubular portion. The method according to any one of claims 8 to 10,
Wherein the protrusions are exchangeable. delete delete delete delete

Images