JPH10249444A - Method for forming different cross section bending tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the buckling caused on bending and to form in a well shape even in a different shaped cross-section bending tube by using a die of installing a projection part at an initial contact place to a tube as the raw material and locally enlarging the tensile strain of the contact place of the forming die in bending the bending tube. SOLUTION: An upper die 11 supported with an upper holder 14a and having a projection 11a is arranged freely moving up and down making a post 8 as a guide, it is matched to a lower die 12 at the lowest point and these are closed. A bending tube 1 is formed by pressing the axial direction load 13a of a pressing rod 13 into both ends of a raw material tube supported with an upper holder 14a and a lower holder 14b, machining in a taper like, loading a pressing post 9 with a pressing load 9a in the state of loading an inside pressure 10 in the raw material tube, and bending with pressing with the upper die 11 and the lower die 12. A dimple is generated at the place of the projection 11a made in contact with the bending tube 1, with this dimple, the axial direction tensile strain is made large even nearby the point of inflection, so buckling is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pipe having a curved section.

[0002]

2. Description of the Related Art Conventionally, a method of forming a curved pipe having a deformed cross section has been disclosed in Japanese Patent Application Laid-Open No. H8-90097, in which an internal pressure is applied to a material pipe having a circular cross section, and press bending is performed using upper and lower dies. Was. Buckling, which is likely to occur due to press bending, has been prevented by applying an internal pressure to the material pipe during press bending to generate tensile strain in the circumferential direction of the material pipe. Also,
At the time of press bending, an internal pressure equal to or lower than the yield pressure over the entire area of the material pipe is applied to the material pipe in order to prevent a forming defect in which the material pipe expands due to an excessive internal pressure load.

[0003]

SUMMARY OF THE INVENTION In the above conventional technique,
When forming a curved pipe having a deformed section having a large amount of bending deformation, buckling occurs near the inflection point of the shape of the deformed section only by the circumferential tensile strain of the material pipe caused by the above-mentioned internal pressure load.

[0004] It is an object of the present invention to add a locally increased tensile strain in the axial direction of a material pipe to a circumferential tensile strain of the material pipe generated by applying a conventional internal pressure, thereby forming a curved pipe having a modified cross section. Is to prevent buckling, which is likely to occur near an inflection point at which the cross-sectional shape changes from an elliptical shape to a rectangular shape, and to obtain a molded article having a good curved cross-section.

[0005]

In order to achieve the above-mentioned object, the present invention provides a method of forming a material by using a metal mold having a projection at a central portion inside the metal mold, that is, a position where the metal pipe comes into contact first. By press-bending the tube while applying an internal pressure to the tube, the tensile strain in the axial direction of the material tube is locally increased.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1] FIG. 1 is a perspective view of a curved tube 1 having an irregular cross section formed by the forming method of the present invention. Curved pipe 1
Has a shape in which two pipe members used as a flow path of a fluid such as gas are connected in the axial direction, and has a circular cross section at the end and a rectangular cross section at the center. The curved tube 1 has a shape in which the section between the end and the center is bent in the axial direction, and the cross-sectional shape is continuously changed to a circle, an ellipse, or a rectangle.

FIG. 2 is a perspective view of a tube before bending, that is, a blank tube 2 according to an embodiment of the present invention. Material pipe 2
The central portion is preliminarily formed by overhang so as to correspond to the peripheral length of the bent tube 1 formed by bending.

FIG. 3 is a longitudinal sectional view of an apparatus for overhanging and forming the material pipe 2. This apparatus comprises an overhanging mold 4a and an overhanging lower mold 4b for overhanging the central portion of the straight pipe 3, and a seal for internal pressure and a load applied in the axial direction of the straight pipe 3. The overhanging pressure rod 5, the overhanging upper holder 6a for supporting and restraining the straight pipe 3, the overhanging lower holder 6b, and the upper die set 7 for supporting the overhanging upper mold 4a.
a, a lower die set 7b that supports the lower overhanging die 4b and the lower overhanging holder 6b, a post 8 that guides the upward and downward movement of the upper overhanging die 4a, and a press load for restraining the die. It is composed of a pressure post 9. The overhanging pressure rods 5 are arranged at both ends of the straight tube 3 supported by the overhanging holder 6, and are arranged to move back and forth in the same direction as the axial direction of the straight tube 3. The overhanging upper mold 4a supported by the upper die set 7a is arranged to move up and down with the post 8 as a guide, and is closed with the overhanging lower mold 4b.

FIG. 4 is a longitudinal sectional view showing a state in which the central portion of the material pipe 2 is being formed by the overhanging apparatus shown in FIG. In the raw material tube 2, the pressurizing rods 5 for extending are pushed into both end surfaces of the raw material tube of the straight tube 3 supported by the upper holder 6a and the lower holder 6b with an axial load 5a, and an internal pressure 10 is applied to the straight tube 3. In this state, a molding is performed by applying a press load 9a to the pressing post 9 to constrain the die and projecting it in the overhanging die 4.

FIG. 5 is a longitudinal sectional view of a bending device for forming the curved tube 1. As shown in FIG. This apparatus comprises an upper mold 11 and a lower mold 12 for press-bending the material tube 2 and a pressure rod 1 for sealing the internal pressure.
3. Upper holder 14a and lower holder 14b for supporting and restraining material tube 2, upper die set 7a for supporting upper mold 11,
Lower die set 7 supporting lower mold 12 and lower holder 14b
b, a post 8 for guiding the vertical movement of the upper mold 11 and a pressure post 9 for applying a press load. The pressure rods 13 are arranged at both ends of the material tube 2 supported by the holder 14 and are arranged so as to move back and forth in the same direction as the axial direction of the material tube 2. The upper mold 11 supported by the upper holder 14a and having the protrusion 11a is arranged to move up and down with the post 8 as a guide, and the lower mold 12 is positioned at the lowest point.
And is closed.

FIG. 6 shows an embodiment of the present invention, in which a longitudinal section of a bending apparatus in a state in which an internal pressure is applied to the material pipe 2 and press-bending is performed using a mold provided with a projection 11a. . The curved tube 1 is formed by pressing a pressure rod 13 into both ends of a raw tube 2 supported by an upper holder 14a and a lower holder 14b with an axial load 13a to form a tapered shape, and applying an internal pressure 10 to the raw tube 2. And press load 9a on the pressure post 9.
, And press-bending with the upper mold 11 and the lower mold 12 to be formed.

FIG. 7 is a perspective view of the curved tube 1 when press-bending with the upper mold 11 having no projection 11a. Buckling 15 occurs near the inflection point where the cross-sectional shape of the curved tube 1 changes from elliptical to rectangular. The feature of the present invention is that the upper mold 11 is press-bent using the upper mold 11 provided with a projection 11 a at a position where it comes into contact with the material pipe 2 first, that is, crosses the curved pipe 1. An object of the present invention is to prevent buckling 15 which is likely to occur near an inflection point where the surface shape changes from an elliptical shape to a rectangular shape.

FIG. 8 is a perspective view of the curved tube 1 when the upper tube 11 provided with the projections 11a is press-bent formed. Curved pipe 1
A depression 16 is generated at a position where the projection 11a contacts the surface of the tube, and the forcibly generated depression 16 locally increases the tensile strain in the outer surface of the curved tube 1 in the axial direction and has an elliptical cross-sectional shape. Even near the inflection point where the shape changes to a rectangular shape, the tensile strain in the axial direction of the outer surface is increased, and buckling 15 that is likely to occur at this location can be prevented, and a curved pipe having a good shape 1 can be molded.

Embodiment 2 FIG. 9 is a perspective view of an example in which a final molded product is cut in order to take out necessary parts from a bent tube 1 as a bent molded product. In this embodiment, the central part 1 of the molded article is used.
By cutting and removing b, it is possible to obtain two deformed cross-sectionally curved tubes 1a which are required by a single bending process. The deformed cross-section curved pipe 1a is a piping member used as a flow path of a fluid such as a gas, and a circular cross-section side is a fluid inlet and a rectangular cross-section side is a fluid outlet.

FIG. 10 is a perspective view of a bent pipe 1a of a modified cross section used for a pipe member of a gas turbine. The approximate dimensions of the irregular-shaped curved tube 1a are as follows: a fluid inlet side is a circle having an outer diameter of 380 mm; a fluid outlet side is a rectangle having a width of 550 mm and a height of 180 mm;
The thickness is 0 mm and the thickness is 5 mm. The perimeter of the curved tube 1a with an irregular cross section increases from the inlet side of the fluid toward the outlet side, and at the rectangular cross section on the outlet side of the fluid, it becomes about 1.2 times the perimeter of the circular section on the inlet side. . This modified cross-section curved tube 1 a
It was formed from a 0 mm stainless steel straight tube 3. First, FIG.
And the overhanging device shown in FIG.
The inner pressure 10 was applied, and the central portion was extended as shown in FIG. Thereafter, the bent tube 1 was formed by the bending apparatus shown in FIGS. 5 and 6 using the raw tube 2 according to the following process. First, in order to prevent buckling in the process of press-bending the material pipe 2, the material pipe 2 is subjected to a pressure of approximately 6 MPa which is equal to or less than the entire internal pressure of the material pipe 2.
Is applied. In this state, the upper mold 11 was lowered, and a press load 9a of about 9 MN was applied to bend the material tube 2 to form each cross section into a different shape. Thereafter, the internal pressure 10 in the tube was increased to about 25 MPa, and the material tube 2 was formed along the closed upper mold 11 and lower mold 12 to complete the molding. Then, as shown in FIG.
From above, a modified-shaped curved tube 1a was cut out.

Example 3 A deformed curved tube 1a having the approximate dimensions shown in FIG. 10 was formed from a nickel-based alloy straight tube 3 having an outer diameter of 380 mm by the procedure shown in Example 2 under the following conditions. First, with the overhanging device shown in FIGS.
An internal pressure 10 of about 45 MPa was applied to the raw material tube to protrude the central portion as shown in FIG. afterwards,
With the bending device shown in FIGS.
The internal pressure 10 of a is applied. In this state, the upper mold 11 was lowered, and a press load 9a of about 16 MN was applied to bend the material tube 2 to form each section into a different shape. Thereafter, the internal pressure 10 in the pipe is increased to about 45 MPa, and the material pipe 2 is closed in the shapes of the closed upper mold 11 and lower mold 12.
And the molding was completed. After that, as shown in FIG.

Example 4 A deformed curved tube 1a having the approximate dimensions shown in FIG. 10 was formed by a method shown in Example 3 using a straight tube 3 of an aluminum-based alloy having an outer diameter of 380 mm.

[Embodiment 5] A curved tube 1a having an irregular cross section having the approximate dimensions shown in FIG. 10 was formed by a method shown in Embodiment 3 using a copper-base alloy straight tube 3 having an outer diameter of 380 mm.

[Embodiment 6] FIG. 11 shows a gas turbine 1 provided with a modified cross-section pipe 1a formed by the forming method of the present invention.
In the overall view of FIG. 7, a part of the turbine 17 is cut away for explanation of the installation state of the curved pipe 1 a having a modified cross section. The modified cross-section curved pipe 1 a is used as a flow pipe for guiding the high-temperature and high-pressure gas burned in the combustor 18 to the turbine blade 19, and 10 to 14 pipes are provided on the outer periphery of the gas turbine 17. .

[0021]

According to the present invention, when bending a curved tube having an irregular cross section, the tensile strain in the axial direction at the contact point of the bending mold can be locally increased. Buckling due to bending that can be easily performed can be prevented, and even a deformed curved pipe having a large bending deformation amount can be formed into a favorable shape.

Further, since the deformed cross-section curved pipe can be formed with high precision and in accordance with the final shape, a flow path member such as a gas turbine can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a curved tube formed by the present invention.

FIG. 2 is a perspective view of a material pipe showing a state before bending a bent pipe;

FIG. 3 is a cross-sectional view of the forming apparatus showing a state before the stretch forming of the material pipe.

FIG. 4 is a cross-sectional view of a forming apparatus showing a state of overhang forming of a material pipe.

FIG. 5 is a cross-sectional view of a forming apparatus showing a state before bending a bent pipe.

FIG. 6 is a cross-sectional view of an apparatus for forming a curved tube according to an embodiment of the present invention.

FIG. 7 is a perspective view of a bent tube formed without applying the present invention.

FIG. 8 is a perspective view of a curved tube showing features formed by the present invention.

FIG. 9 is a perspective view of a curved tube having a deformed cross section having a final shape formed by the present invention.

FIG. 10 is a perspective view of a curved pipe having a modified cross section used in the gas turbine formed by the present invention.

FIG. 11 is a side view of a gas turbine in which a deformed curved pipe formed according to the present invention is installed.

[Explanation of symbols]

1 ... curved pipe, 7 ... die set, 7a ... upper die set, 7b
... Lower die set, 8 ... Post, 9 ... Pressing post, 9a ...
Press load, 10 ... internal pressure, 11 ... upper mold, 11a ... protrusion,
12: Lower mold, 13: Pressure rod, 13a: Axial load, 14: Holder, 14a: Upper holder, 14b: Lower holder.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Tanaka 502 Kandachi-cho, Tsuchiura-shi, Ibaraki Machinery Research Laboratory, Hitachi, Ltd. Hitachi, Ltd.Hitachi Plant (72) Inventor Yoshiro Uchinuma 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Prefecture Hitachi, Ltd.Hitachi Plant (72) Inventor, Takeo Kurokawa 3-1-1, Sachimachi, Hitachi-shi, Ibaraki No. 1 Inside Hitachi, Ltd. Hitachi Plant

Claims (1)

[Claims] 1. A method for forming a curved tube having a deformed cross section by bending under a condition that an internal pressure is applied to the material tube, wherein a projection is provided at a central portion of a mold that first comes into contact with the material tube. Press bending to locally increase the tensile strain in the axial direction, and to prevent buckling, which is likely to occur near the inflection point where the cross-sectional shape of the above-mentioned curved pipe changes from elliptical to rectangular. A method for forming a curved pipe having an irregular cross section.