Tube flanging method

Abstract

A tube flanging method includes the steps of: disposing a tube such that an edge thereof is exposed to the outside of a forming mold while the tube is inserted into the forming mold; applying an external force to the exposed edge of the tube to expand the exposed edge of the tube; applying an external force to the expanded edge to bend the expanded edge toward an outer surface of the forming mold; and applying an external force to the bent edge to form a flange, the flange having a linearly integrated cross section and being perpendicular to the longitudinal direction of the tube. With this configuration, it is possible to bend the tube to form the flange at a uniform thickness.

Claims

1. A tube flanging method comprising: disposing a tube such that an edge thereof is exposed to an outside of a forming mold while the tube is inserted into the forming mold; expanding the exposed edge of the tube to have a first bend with a spinning tool; bending the expanded edge of the tube to have a second bend by the spinning tool, the second bend being bent toward an outer surface of the forming mold, wherein the first bend and the second bend face each other; and forming a flange by friction stir welding the first and the second bends, wherein the flange is flat and perpendicular to a longitudinal direction of the tube, wherein a thickness of the flange formed by the friction stir welding is the same as a thickness of the tube.

2. The tube flanging method according to claim 1, wherein the first bend and the second bend are integrated by the friction stir welding.

3. The tube flanging method according to claim 2, wherein, when the edge is expanded and bent or when the flange is formed, the forming mold or the tube is rotated.

4. The tube flanging method according to claim 1, wherein a length (L) of the edge of the tube which is exposed to the outside of the forming mold is expressed as L=(0.25d)(D.sup.2d.sup.2)/(d+t), wherein an inner diameter of the tube is d, a diameter of the flange is D, and a thickness of the tube is defined as t.

5. The tube flanging method according to claim 1, wherein the forming mold comprises: a tube seating hole into which the tube is inserted and fixed; a circular processing face that exposes the edge of the tube to bend the exposed portion and is provided around the seating hole; and a restriction mold that restricts a processing length of the tube to within an outer circumference of the processing face.

6. The tube flanging method according to claim 5, wherein, when an inner diameter of the tube is defined as d, a length of the exposed portion is defined as L, a thickness of the tube is defined as t, and an inner diameter (D) of the restriction mold is expressed as D={square root over (4L(d+t)+d.sup.2)}.

7. The tube flanging method according to claim 5, wherein the forming mold is rotatable.

8. The tube flanging method according to claim 5, wherein the restriction mold is detachable from the forming mold.

Description

DESCRIPTION OF DRAWINGS

(1) FIGS. 1a and 1b are view for describing a flange structure and flange processing based on a bending process.

(2) FIG. 2 is a flowchart showing processes of a tube flanging method according to the present invention.

(3) FIGS. 3a and 3b are schematic views showing a process of bending a tube using a spinning process.

(4) FIG. 4 is a schematic view showing a process of forming a flange using a friction stir process.

(5) FIGS. 5a and 5b are schematic views showing process conditions for flange processing.

MODE FOR INVENTION

(6) The present invention is directed to a tube flanging technique, and proposes a method in which, in expanding an edge of a tube to form a flange, the edge (i.e. portion to be flanged) of the tube exposed to the outside of a forming mold is expanded under an external force using a spinning tool or the like, subsequent processing proceeds such that the expanded edge is rolled inward, the rolled edge is linearly integrated by friction stirring to form a flange bent at right angles such that an original thickness of the tube and a thickness of the flange are maintained constant.

(7) Particularly, in the present invention, when the flange is formed by bending, process conditions having excellent reproducibility are presented. Thereby, it is possible to make the thickness of the flange identical to the original thickness of the tube. For example, in the tube for flanging, the length exposed to the outside of the forming mold may be specified to adjust a size of the forming mold, or a length of the exposed portion of the tube may be adjusted when the forming mold is determined on a predetermined scale

(8) Hereinafter, technical configurations and effects of the present invention will be described in greater detail using an exemplary embodiment of the invention with reference to the drawings.

(9) FIG. 2 shows processes for a tube flanging method according to the present invention. First, a tube is placed in a forming mold (S110).

(10) As shown in a sectional schematic view of FIG. 3a, the forming mold 200 is formed with a cylindrical seating hole into which the tube 100 can be inserted and fixed. Further, a portion of the tube is exposed, and then the exposed portion is bent. To this end, a circular processing face 202 (FIG. 3b) is provided around the seating hole. In addition, the forming mold is preferably provided with a restriction mold 210 (FIG. 4) that restricts a processing length of the tube to within an outer circumference of the processing face.

(11) An edge of the tube (FIG. 3a) is exposed to the outside of the forming mold when the tube is inserted into the forming mold.

(12) An external force is applied to the exposed edge of the tube, thereby expanding the edge as shown in FIG. 3a. Due to the expansion, a first bend 110a is formed at the edge. The expanding process may be performed using a bending tool 310, for instance, in a spinning process (first spinning process, S120).

(13) Next, an external force is applied to the edge in a step-by-step way or in a continuous way after the expansion, thereby bending the edge toward an outer face of the forming mold. In this process, a second bend 110b is formed at the edge. The second bend 110b is bent toward the processing face 202 of the forming mold, and the edge is in a rolled state like a spherical shape on the whole. In this state, the first bend 110a and the second bend 110b face each other.

(14) Like the aforementioned expanding process, this bending process may also be performed using the bending tool 310 in the spinning process (second spinning process, S130).

(15) An external force is applied to the bent edge using a pressing tool 320, thereby forming a flange that has a linearly integrated cross section and is perpendicular to a longitudinal direction of the tube, as shown in FIG. 4.

(16) The bent edge may be formed into the flange having the linearly integrated cross section by a friction stir process (friction stir process, S140).

(17) The friction stir process is a simple unique continuous process in which substrates to be joined are fixed, a portion of a non-consumable rotating tool harder than the substrates is inserted along a butt joint, and a frictional heat is generated by relative movement between the tool and the substrates and reduces resistance to deformation of the substrates to heat the joint adjacent to the tool. Thus, a softened zone is generated around a probe that is the inserted portion of the tool. As the probe moves along a joint line under a mechanical force, the heated zone is extruded backward in front of the probe. A solid state joint is made by a combination of the frictional heat and the mechanical processing.

(18) In the present invention, the bent edge is linearly processed using this friction stir process, and the first bend 110a and the second bend 110b are integrated to improve a strength using friction stir welding, forming the flange perpendicular to the longitudinal direction of the tube. The thickness of the flange is identical to the original thickness of the tube due to the friction stir process, and an increase in horizontal length, i.e. diameter, of the flange is restricted by the restriction mold 210 at the outer circumference of the processing face of the forming mold.

(19) In the present invention, when the edge is expanded and bent or when the flange is formed, the forming mold or the tube can be rotated. In this way, by rotating the tube itself or the forming mold (along with the tube), it is possible to increase process efficiency of the spinning process and the friction stir process and uniformly form a shape of the processed flange, and it is easy to control the thickness of the flange.

(20) Further, in the present invention, the process conditions for the bent flange can be controlled such that the thickness of the flange is identical to that of the tube.

(21) Referring to FIG. 5a, in the forming mold 200 for the tube flanging according to the present invention, the tube 100 is inserted into and fixed in the seating hole, and in this state, a portion 110 of the tube is exposed. When the inner diameter of the tube is defined as d, the thickness of the tube is defined as t, and the length of the edge of the tube which is exposed to the outside of the forming mold is defined as L, a volume V.sub.E of the exposed tube is as follows.
V.sub.E=Lt(d+t)

(22) Also, referring to FIG. 5b, the flange 10 is formed by the tube flanging. When the inner diameter of the tube is defined as d, the diameter of the flange is defined as D, and the thickness of the flange is defined as t that is the same as the tube, a volume V.sub.E of the flanged end is as follows.
V.sub.E=(0.25)(D.sup.2d.sup.2)(t)

(23) In the tube flanging according to the present invention, when the inner diameter of the tube is defined as d and the diameter of the flange is defined as D, the length L of the edge of the tube exposed to the outside of the forming mold is determined from such a relation as follows.
L=(0.25)(D.sup.2d.sup.2)/(d+t)

(24) That is, if the size of the forming mold is constant, the thickness of the flange which is identical to the original thickness of the tube can be obtained by restricting the length of the edge which is exposed to the outside of the forming mold.

(25) Further, when the inner diameter of the tube is defined as d and the length of the exposed edge is defined as L, the inner diameter D of the restriction mold can be determined as follows.
D={square root over (4L(d+t)+d.sup.2)}

(26) That is, even if the length of the edge exposed to the outside is changed, the flange having the same thickness as the tube can be formed by a change in the inner diameter of the restriction mold provided for the forming mold.

(27) In the present invention, the forming mold and the restriction mold are preferably rotatable, and the restriction mold is preferably detachable from the forming mold in order to use various molds having different inner diameters.

(28) In the above description, the embodiment of the present invention has been disclosed for illustrative purposes, the present invention is not limited to these specific embodiments. It is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.

LIST OF SYMBOLS OR NUMERALS

(29) 100: pipe 110: edge 110a, 110b: bend 120: flange 200: forming mold 202: processing face 210: restriction mold 310: bending tool 320: pressing tool