JP2001340922A - Manufacturing method of t joint part and hydroform die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a T joint part capable of preventing wrinkles at an opposite side of a bulged portion during an axial extrusion and a hydroform die. SOLUTION: In a manufacturing method, of a T joint part forming a predetermined profile of a bulged portion 11 at a periphery and at a selected portion of an axial direction of a pipe 1 while applied hydraulic pressure and an axial extrusion into the pipe after inserted the pipe in the die, a rib-like convex portion 1A is first formed at first at an opposite side (anti-bulged portion 12) of the above-described bulged portion. Then, the bulged portion is formed at a predetermined profile. The die, in which a rib-like groove 2A or a movable wall 2W is provided for constructing a die having a rib-like convex portion, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a T-joint part and a mold for hydroforming.

[0002]

2. Description of the Related Art Hydroforming is a processing method in which a pipe is adapted to a mold by hydraulic pressure and is formed. In many cases, material inflow is assisted by pushing in a pipe axial direction (referred to as axial pushing). Hydroformed parts are: 1) Since complex shapes can be integrally molded, weight reduction and mold cost reduction by integrating parts 2)
There is an advantage that the weight is reduced and the rigidity is increased by making the hollow closed section, 3) the weight is reduced because the assembly welding flange is not required, and 4) the whole is plastically deformed, so that the spring back is small and the dimensional accuracy is good. (Kuriyama: Plasticity and Processing: Vol. 39, No. 453, No. 1011)
(Page (1998)) A conventional example of a method for manufacturing a T-joint part by hydroforming will be described with reference to FIG. In FIG. 4, 1 is a tube,
2 is a lower mold, 3 is an upper mold, 4 is an overhang provided in the upper mold 3,
5 is a piston that controls the overhang height by pressing the overhang end of the tube 1, 6 and 6 ′ are axial presses that axially push the tube 1 from both ends,
Reference numerals 7 and 7 'denote liquid passage holes provided in the shaft pushers 6 and 6'. In this example, the mold inner surface of the lower mold 2 is circular in the circumferential direction and linear in the longitudinal direction, and the mold inner surface of the upper mold 3 is circular in the circumferential direction except for the overhanging hole 4 and has a longitudinal shape. Although the inner shape of the upper and lower dies is not limited to this, there are various types such as those having a bend in the longitudinal direction and those having an elliptical arc in the circumferential direction.

[0003] In the method of hydroforming, a pipe 1 is loaded into a lower mold 2 and an upper mold 3, and both ends of the pipe are pressed with shafts 6, 6 '.
Then, the liquid passage hole 7 'is closed 9 and the high-pressure liquid 8 is injected into the tube 1 from the liquid passage hole 7 to increase the liquid pressure in the tube. A force 10 is applied to help the material flow into the overhang 11 that overhangs by hydraulic pressure. The piston 5 is gradually raised while opposing the hydraulic pressure, and is fixed at a height where the thickness reduction of the overhang portion 11 reaches the allowable upper limit.

[0004]

However, according to the above-mentioned conventional method, when the shaft is pushed, wrinkles are easily generated on the opposite side of the overhanging portion 11 (reverse overhanging portion 12). The height (overhang height) of the portion 11 must be set to a level that is considerably lower than the height at which the thickness of the overhang portion 11 is at an allowable lower limit, and there is a problem that the manufacturable dimensional range is narrow.

Accordingly, an object of the present invention is to provide a method of manufacturing a T-joint part and a mold for hydroforming, which can effectively suppress the generation of wrinkles at the projecting portion when the shaft is pushed.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a pipe is placed in a mold, and the pipe is hydraulically and axially pushed to form a projecting part having a predetermined shape in a circumferential direction and a longitudinal direction of the pipe. In the method of manufacturing a T-joint part forming a part, first, a rib-like convex part is formed on the opposite side of the overhang part, and then the overhang part is formed into a predetermined shape. It is a manufacturing method.

[0007] The present invention also provides a hydroforming metal in which an upper die having an overhanging hole in a part of the die is combined with a lower die, and a piston for controlling the overhang height is provided in the overhanging hole. A mold for hydroforming, wherein the lower mold has a rib-shaped groove in a portion facing the overhanging hole. Further, the present invention provides a hydroform mold in which an upper mold having an overhanging hole in a part of the mold is combined with a lower mold, and a piston for controlling the overhang height is installed in the overhanging hole. A mold for hydroforming, wherein the lower mold has a movable wall that can move forward and backward at a portion facing the overhanging hole.

[0008]

FIG. 1 is a sectional view showing a first example of a mold of the present invention and a first example of a method of the present invention performed using the mold. In this mold, an upper mold 3 having an overhang 4 in a part of the mold is combined with a lower mold 2 and a piston 5 for controlling an overhang height is installed in the overhang 4. The mold 2 has a rib-shaped groove 2 </ b> A at a position facing the overhang hole 4.
The depth of the rib-shaped groove 2A depends on the outer diameter and thickness of the material of the tube 1, but is preferably approximately 1/4 or more of the wall thickness and 1/5 or less of the outer diameter.

In order to carry out the method of the present invention by using this mold, after the tube 1 is inserted into the mold, first, the hydraulic pressure P1 is applied and the anti-extension portion 12 (the side opposite to the extension portion 11) is applied. The rib-shaped convex portion 1A is formed on the projecting portion 12 by being adapted to the rib-shaped groove 2A. At this time, if the height of the piston 5 (the distance between the lower end surface of the piston and the lower end surface of the overhanging hole 4) is set to be substantially the same as the depth of the rib-shaped groove 2A, the overhanging portion 11 fits into the overhanging hole 4. This is preferable because the material flows smoothly by the axial pushing after that (FIG. 1A).

Next, the hydraulic pressure is switched to P2 higher than P1, and the piston 5 is raised to the upper limit height at which the wall thickness of the overhang portion 11 becomes the allowable lower limit while applying the shaft pressing force 10 (FIG. 1).
(B)). FIG. 2 is a cross-sectional view illustrating a second example of the mold of the present invention and a second example of the method of the present invention performed using the mold. In this mold, an upper mold 3 having an overhang 4 in a part of the mold is combined with a lower mold 2 and a piston 5 for controlling an overhang height is installed in the overhang 4. The mold 2 has a movable wall 2W which can move forward and backward at a position facing the overhanging hole 4. The mold of the second example has an advantage that the depth of the rib-shaped groove can be freely changed as compared with the mold of the first example.

In order to carry out the method of the present invention using this mold, the tube 1 is inserted into the mold, and the movable wall 2W is first retracted to a predetermined position while applying the hydraulic pressure P1. The ribs 12 are fitted into the grooves, and the rib-shaped protrusions 1
Form A. Piston 5 in accordance with retreat of movable wall 2W
Is retracted (elevated) by the same distance as the movable wall 2W, since the overhanging portion 11 expands to such an extent that the overhanging hole 4 is adapted to the overhanging hole 4, and the subsequent inflow of material by axial pressing smoothly proceeds (FIG. 2). (A)). The retreat distance of the movable wall 2W (depth of the rib-shaped groove = height of the rib-shaped protrusion) depends on the material outer diameter and the wall thickness of the tube 1, but is approximately 1/4 or more of the wall thickness, and 1/4 of the outer diameter. / 5 or less is preferable.

Next, the movable wall 2W is fixed to the current position (the predetermined position), the hydraulic pressure is switched to P2 higher than P1, and the axial pressure is applied to the piston 5 and the piston 5 is made thicker. Is raised to the upper limit height at which the allowable lower limit is reached (FIG. 2B).
In the method of the present invention, as shown in the first and second examples,
Since the rib-shaped convex portion is formed in the projecting portion at the initial stage of molding, the rigidity of the tube is increased, and the upper limit of the axial pressing force range where no wrinkles occur is increased. Therefore, it is possible to apply a larger axial pressing force than before, and the flow of material into the overhanging portion is further promoted. As a result, the decrease in the wall thickness of the overhanging portion is suppressed to be smaller, and the upper limit height of the piston, that is, The overhang height can be made higher than before, and an industrially advantageous effect of expanding the manufacturable dimension range can be obtained.

As shown in FIG. 3, for example, one or more rib-shaped convex portions 1A are provided on the lower surface side of the T-shaped portion where buckling is likely to occur, preferably within a range of a central angle ± 60 ° with respect to the center point of the tube. (FIG. 3 (c)). The cross-sectional shape of the rib-shaped protrusion may be a curved shape or a linear shape. In addition, the rib-shaped convex portion 1A
Although the above effect can be exerted even if one is provided, it is preferable to provide a plurality of pipes in parallel in the circumferential direction of the pipe as shown in FIG. 3 because the rigidity of the pipe becomes larger. Correspondingly, it is preferable to provide a plurality of rib-shaped grooves or movable walls in parallel in the circumferential direction of the lower die.

[0014]

EXAMPLE A T-joint part was manufactured by hydroforming using an electric resistance welded steel pipe made of ordinary steel equivalent to JIS STKM11A, and the overhang height was investigated. Table 1 shows the survey results of the material dimensions, the types of the hydroforming method, and the corresponding overhang heights corresponding to the survey. The overhang height is indicated by an index defined by the following equation.

Critical overhang height (index) = H / DH H: Overhang height at the start of wrinkling, D: Outer diameter of material (see FIG. 5 for measurement site) According to the present invention, it is larger than before. It is clear that a marginal overhang height is obtained.

[0016]

[Table 1]

[0017]

As described above, according to the present invention, the rigidity of the pipe is improved and the generation of wrinkles is suppressed, so that the overhang height can be made larger than before, and the T
This has an industrially beneficial effect in that the range of manufacturable dimensions of the joint component is expanded.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first example of a mold of the present invention and a first example of a method of the present invention performed using the mold.

FIG. 2 is a cross-sectional view illustrating a second example of the mold of the present invention and a second example of the method of the present invention performed using the mold.

FIG. 3 is an explanatory view showing an example in which a plurality of rib-shaped protrusions are formed.

FIG. 4 is a cross-sectional view showing a conventional example of a method for manufacturing a T-joint part by hydroforming.

FIG. 5 is a schematic view showing a measurement site of a factor (H, D) of a critical overhang height (index).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tube 1A Rib-shaped convex part 2 Lower mold 2A Rib-shaped groove 2W Movable wall 3 Upper mold 4 Overhanging hole 5 Piston 6, 6 'Shaft pressing tool 7, 7' Liquid passage hole 8 High-pressure liquid 9 Sealing 10 Shaft pressing force 11 Overhang 12 Overhang

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Ito 1-1 1-1 Kawasaki-cho, Handa-shi, Aichi F-term (reference) in Chita Works, Kawasaki Steel Corporation 3H019 BA02 BB01 BD03 4E050 AA14

Claims (3)

[Claims] 1. A T-joint part in which a pipe is inserted into a mold and hydraulically and axially pressed on the pipe to form a projection of a predetermined shape in a part of the pipe in a circumferential direction and a longitudinal direction thereof. A method for manufacturing a T-joint component, comprising: first, forming a rib-shaped convex portion on the opposite side of the overhang portion, and then forming the overhang portion into a predetermined shape. 2. A hydroforming mold in which an upper mold having an overhanging hole in a part of the mold is combined with a lower mold and a piston for controlling an overhang height is installed in the overhanging hole. A mold for hydroforming, wherein the lower mold has a rib-shaped groove at a portion facing the overhang hole. 3. A hydroforming mold in which an upper mold having an overhanging hole in a part of the mold is combined with a lower mold and a piston for controlling an overhang height is installed in the overhanging hole. A mold for hydroforming, wherein the lower mold has a movable wall that can move forward and backward at a portion facing the overhanging hole.