JP3351331B2 - A method of manufacturing a deformed metal tube and a method of manufacturing a bent metal tube. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

Variant present invention relates to the bulging portion using manufacturing <br/> method for producing profiled metal element tube for the metal tube manufacturing bending curved profile in the longitudinal direction, and the profile metal tube The present invention relates to a method for manufacturing a bent metal tube.

[0002]

2. Description of the Related Art Hydraulic bulging of a metal pipe (hereinafter, simply referred to as a pipe) is performed by injecting a working fluid into a pipe as a material, and appropriately applying a pressure (hereinafter, referred to as an internal pressure) and axial pushing from a pipe end. This is a processing method for obtaining various deformed metal tubular products (hereinafter referred to as products) having a bulging portion by adding them in combination.

[0003] Deformed metal tubular products are variously used for piping members, structural members and the like.

[0004] These products are broadly classified into those whose bulging portions are straight in the longitudinal direction and those which are bent.

FIG. 6 is a diagram showing one example of the former.
(A) is a longitudinal sectional view of the product 10, and (b) is a front view as viewed from a pipe end.

The product 10 comprises a bulging portion 10a and small-diameter portions 10b on both ends. Here, the case where the bulging portion 10a has a circular cross section is shown, but is not limited to this, and there are various shapes.

FIG. 7 is a view showing an example of a product in which the bulging portion is bent in the longitudinal direction. FIG. 7 (a) is a plan partial cross-sectional view of the product 1, and FIG. It is the front view seen.

The product 1 comprises a bulging portion 1a and small-diameter portions 1b on both ends of the tube, and A to A and CC of the bulging portion 30a.
Are bent in the longitudinal direction at a bending radius R and a bending angle θ. Here, the case of a circular cross section is shown, but it is of course not limited to this, and there may be a case of an irregular cross section. Further, FIG. 7 shows a case where the number of bending portions is one, but there may be a case where a plurality of portions bend. In addition, 2
It may be a double or triple layered tube.

First, a method of hydraulic bulging of the product 10 shown in FIG. 6 will be described.

FIG. 8A is a view for explaining the processing method, FIG. 8A is a longitudinal sectional view showing a state in which a raw tube is set between upper and lower dies, and FIG. It is a longitudinal cross-sectional view which shows the state after completion | finish of a processing bulge.

Bolster 1 of hydraulic bulging machine (not shown)
6. Set the raw tube on the lower mold 12 attached to 6,
The upper die 13 attached to the ram head 15 of the hydraulic bulging machine is lowered from above, and the upper die 13 is pressed against the lower die 12 by a pressing device (not shown). Then, the axial pushing tools 6 and 7 are advanced by an axial pushing device (not shown) of the hydraulic bulging machine, and the tip portions 6a and 7a of the axial pushing tools are pressed into the inner diameter portions of both ends of the raw tube 11. A working fluid 8 such as a water emulsion is introduced into the raw tube through the through hole 6b of the one axial pushing tool 6.
Is discharged from the through-hole 7b of the other axial pushing tool 7, and a valve (not shown) on the extension of the through-hole 7b is closed to fill the inside of the raw tube with the working fluid. FIG. 8 (a)
Indicates such a state.

The lower die 12 and the upper die 13 are provided with a die groove 1.
2a, 13a and guide grooves 12b, 13b are provided, and the die grooves 12a,
The inner shape of 3a is the same as the outer shape of the product bulging portion 10a. The guide grooves 12b and 13b have the same diameter as the base tube 11. The hydraulic bulging is performed by advancing the left and right axial pushing tools 6 and 7 while gradually increasing the pressure of the working fluid 8 by a pressure booster (not shown) in the state of FIG.

As the raw tube, the product small diameter portion 1 shown in FIG.
A tube having the same diameter as Ob and having a longer overall length than the product is used.

FIG. 8B shows a state in which the expansion has been completed in a shape along the die grooves 12a and 13a, and a product 10 shorter in length than the raw tube 11 is formed. When the molding is completed, the internal pressure of the working fluid 8 is reduced, the axial pushing tools 6 and 7 are retracted, the working fluid is discharged, the upper die 13 is raised, the product 10 is taken out, and the hydraulic bulging is completed.

Next, a method of processing the product 1 shown in FIG. 7 will be described.

FIG. 9 is a view showing a raw tube of the product 1, and FIG.
(A) is a partial cross-sectional view of a raw pipe, and (b) is a partial cross-sectional view of a bent pipe obtained by bending the raw pipe.

In order to manufacture the product 1, it is necessary to first bend the straight metal tube 2.

The straight metal pipe has an outer diameter d having the same diameter as that of the product small diameter part. The bending radius R and the bending angle θ of the bending part 30a of the bending pipe 3 are different from those of the bending part of the product 1. It is almost the same. The outer peripheral sides A 'to A' and the inner peripheral sides C 'to C' of the bent portion 30a substantially correspond to the outer peripheral sides A to A and the inner peripheral sides C to C of the bent portion of the product 1 shown in FIG. .

FIG. 10 is a view for explaining a hydraulic bulging method for the product 1. FIG. 10 (a) is a plan sectional view showing a state in which the bending tube is set in a mold, and FIG. 10 (b) is a bending tube. FIG. 4 shows a side view of a state in which an upper mold is pressed against a lower mold in which is set.

Bolster 1 of hydraulic bulging machine (not shown)
The bending pipe 3 is set between the lower die 4 attached to the hydraulic bulging machine 6 and the upper die 5 attached to the ram head 15 of the hydraulic bulging machine. The tip portions 6a and 7a of the axial pushing tools 6 and 7 are press-fitted into the inner diameter portions of both ends of the bending tube 3, and the inside of the bending tube is filled with the working fluid 8 in the same manner as described with reference to FIG.

The lower die 4 and the upper die 5 have a die groove 4a,
5a and guide grooves 4b, 5b are provided, and the inner shape of the dice grooves 4a, 5a in a state where both are brought into close contact with each other is the same as the outer shape of the product bulging portion.
b and 5b have the same diameter as both pipe end sides of the bending pipe 3.

From the state shown in FIG. 10, while the pressure of the working fluid 8 is gradually increased by a pressure booster (not shown), the left and right axial pushing tools 6 and 7 are advanced to perform bulging work.

FIG. 11 is a view showing a state in which the bulging is completed in a shape along the die groove by hydraulic bulging.
(A) is a plan sectional view, and (b) is a side view.

When the bulging process is completed, the internal pressure of the working fluid 8 is reduced, the axial pushing tools 6 and 7 are retracted, the working fluid is discharged, the upper die 4 is raised, and the product 1 is taken out.

[0025]

In the conventional hydraulic bulging described above, it is necessary to prevent breakage due to circumferential elongation due to the internal pressure of the product bulging portion and to reduce the wall thickness below a predetermined thickness. Is an important means for that.

In the hydraulic bulging of the product 10 in which the bulging portion is linear in the longitudinal direction shown in FIG. 8, the material is pushed from the guide grooves 12b, 13b into the die grooves 12a, 13a by axial pressing. , 13a, it is relatively easy to suppress the thickness reduction of the bulging portion by imparting the shrinking deformation in the axial direction to the bulging portion at the same time.

However, in hydraulic bulging of a product having a bent bulge as shown in FIGS. 10 and 11, it is difficult to positively push the shaft. The reason is that, in the initial stage of the axial pressing, the material is bent in the die groove, and buckling occurs inside the bent portion.

FIG. 12 is a sectional view showing a state in which buckling 11 has occurred during hydraulic bulging. Once in such a state, the buckling is further advanced by the axial pushing, and the shrinkage deformation in the axial direction cannot be given to the bulging portion.

That is, in the case of the product 1, since the axial pushing force is limited to a range where the buckling 11 does not occur, the outer peripheral surface of the bent portion is easily broken.

FIG. 13 is a view showing a broken state generated in a deformed bent pipe. The reason why the break 12 as shown in FIG. 9 is likely to occur is that the axial pushing is restricted and the pipe 2 shown in FIG. 9A is bent as shown in FIG. 9B. Is also relevant. That is, the bent portion 3 is formed by bending.
Oa is work-hardened and the ductility is reduced, so that it cannot withstand the expansion in the next hydraulic bulging process. Further, the thickness t0 ′ of the outer peripheral portion 30a in FIG. 9B is reduced by the bending process, while the thickness ti of the inner peripheral portion of the bent portion 30a is reduced.
The wall thickness increases. As a result, the circumferential elongation due to the expansion in the hydraulic bulging process causes the bent portion 3 having a small thickness.
There is a tendency to concentrate on the outer peripheral portion of Oa, and the portion is easily broken. The smaller the bend R, the greater the work hardening, the thinning of the outer peripheral part and the thickening of the inner peripheral part, so that the fracture is more likely to occur.

As a countermeasure against breakage, annealing is generally performed after bending. The purpose of this annealing is to eliminate the generated work hardening and restore the ductility of the material. However, there is a problem in that the cost of annealing and the efficiency decrease due to the discontinuity of bending and hydraulic bulging are reduced. In addition, even if annealing is performed, the circumferential elongation due to expansion by hydraulic bulging is concentrated at the outer peripheral portion of the thin bending wall, so it is a fundamental solution for preventing breakage. Not.

An object of the present invention is to solve the above-mentioned breakage problem which occurs in hydraulic bulging of a metal tube having a bulged portion bent in the longitudinal direction.
Specifically, there is provided a method of manufacturing a manufacturing <br/> production method and profile bending metal tube of irregular bending profiled metal element tube for the metal tube production.

[0033]

Means for Solving the Problems The gist of the present invention relating to a manufacturing method and profile bending pipe production method of the profiled element tube is as follows. (1) Bending metal obtained by bending a straight metal tube
Deformed bent metal that bulges at least the bent part of the pipe
There are few straight metal pipes, which are base pipes for the production of generic pipes.
The part on the bending outer peripheral side of the bent metal pipe is in the axial direction of the pipe.
The method for manufacturing a deformed metal tube which is bellow-shaped
The straight metal tube housed in the die groove of the mold
From inside and the shaft from both ends of the straight metal tube
By adding a pressing force, the straight metal tube
Expand the bellows-shaped part of the deformed metal tube and mold
Pressing pad with bellows shape housed inside
By pressing, the bulging part is formed into a bellows shape.
Manufacturing method of deformed metal tube.

(2) Obtained by the production method described in (1) above.
Bent bellows-shaped part becomes the outer peripheral part
To form a bent metal tube, and this bent metal tube
Stored in the die grooves of a pair of upper and lower molds, and
Pressure from the part, at least the bending of the bent metal pipe
Of a bent metal tube that bulges the bent part into a predetermined cross-sectional shape.
Construction method.

[0035]

The inventor of the present invention has made various attempts to eliminate breakage in hydraulic bulging which occurs when a product having a bulged portion bent in the longitudinal direction is produced by bending and subsequent hydraulic bulging. The experiment was studied. As a result, it is important to reduce the work hardening that occurs in the bending process of the raw tube and the thickness difference in the circumferential direction of the bent portion. It has been found that the use of a deformed pipe formed in a bellows shape can prevent the breakage.

Hereinafter, embodiments of the present invention will be described in detail.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION A description will be given of a deformed raw tube used for manufacturing the product 1 shown in FIG. 7, a method for manufacturing the same, and a deformed bent tube (product), but the shape of the product is not limited to this. However, the present invention can be applied to a deformed bent pipe having any cross-sectional shape as long as it is a deformed bent pipe.

(1) Deformed pipe and method of manufacturing the same FIG. 1 is a view showing an example of a deformed pipe used in the method of manufacturing a deformed bent metal pipe according to the present invention. FIG. FIG. 4B is a partial cross-sectional side view, and FIG.

FIG. 2 is a perspective view of the deformed pipe shown in FIG.

FIG. 3 is a sectional view of the bellows-shaped portion of the deformed raw tube shown in FIG.

FIG. 4 is a view showing one example of a bent tube 30 obtained by bending the deformed raw tube 20.

The deformed raw tube 20 shown in FIG.
0a and a straight portion 20b.
"a" is provided at a position corresponding to the bent portion 30a of the bending tube 30 shown in FIG. A section A "to A" passing through the bellows-shaped top portion B of the bellows-shaped portion 20a and a section C "to C" on the opposite side sandwiching the tube axis B are respectively the outer peripheral side A 'of the bent portion of the bending pipe 30 shown in FIG. ~ A 'section and the inner circumference side C' ~ C 'section.

Further, the bellows shape is not provided on the entire circumference of the pipe, and the area A ″ which is subjected to the axial tension in the bending process.
-A "is provided in the section A. The area which is subjected to the axial compression in the bending process is not provided in the section C" to C ". This is because it becomes difficult to eliminate the bellows shape even if the internal pressure expansion is performed in the subsequent bulge processing.

The shape of the bellows is not limited to the shape shown in FIG. 3, and it is sufficient if the following three conditions are satisfied.

The first condition is to make the bellows shape smooth, preferably connected by a curve, so that the bellows shape is easily elongated in the axial direction in the subsequent bending.

The second condition is that A ″-
A "Total length of section La" (length of surface including irregularities)
Is preferably as close to La 'as possible without exceeding the length La' of the outer peripheral portions A 'to A' of the bent portion 30a shown in FIG.

The third condition is that the circumferential length Ha ″ in the cross section of the bellows-shaped top part B shown in FIG. 2 is changed to the product bending part 30 shown in FIG.
It is preferable to set the range not to exceed the circumference Ha of a, and to make it as close as possible to Ha. These reasons will be described later.

FIG. 5 is a view for explaining a method of manufacturing a deformed pipe according to the present invention. FIG. 5 (a) is a cross-sectional view showing a state in which a straight metal pipe is housed between upper and lower molds, and FIG. FIG. 3C is a cross-sectional view showing a state where a bellows-shaped portion to be formed has been expanded, and FIG.
FIG. 4 is a cross-sectional view showing a state in which a bulging portion is formed in a bellows shape.

The deformed pipe 20 of the present invention can be manufactured by hydraulic bulging as shown in FIG. FIG.
(A) As shown in FIG.
And the upper die 41 are housed in a die groove, both ends of the pipe are sealed with axial pressing tools 6 and 7, and the working pipe 8 is filled with the working fluid 8. Upper mold 4
1, a pressing pad 60 is housed in a vertically movable state, and the pressing pad is provided with unevenness (bellows shape) 60a having the same shape as the bellows shape of the deformed raw tube 20 shown in FIG. ing. The pressure pad 60 is connected to a piston 50a of a hydraulic cylinder 50 housed and fixed in the upper die 41, and can be moved up and down by operating the hydraulic cylinder 50 by a hydraulic pump (not shown).

As shown in FIG. 5 (b), the pressure of the working fluid 8 is increased, and at the same time, the axial pushing tools 6, 7 are advanced to form the bulging portion 2a ″ in the space 41a in the upper die 41. The circumference of the protruding portion 2a ″ is set to be substantially equal to the circumference Ha ′ of the cross section passing through the bellows-shaped portion top portion b of the deformed raw tube 20 shown in FIG.

Next, by operating the hydraulic cylinder 50, the convex portion of the pressure pad unevenness 60a is pushed into the bulging portion 2a ″. As shown in FIG. The material of the bulging portion 2a "is formed by the pressure in accordance with the shape of the unevenness 60a of the pressure pad,
Is obtained.

In forming the deformed tube 20, it is necessary to minimize the thickness reduction of the bellows-shaped portion in order to secure the thickness t0 'of the bent outer peripheral portion of the bent tube 30 shown in FIG. For this purpose, the hydraulic bulging process shown in FIG. 5 in which the thickness of the bulging portion 2a ″ serving as the bellows-shaped portion is prevented and the circumference of the bulging portion 2a ″ is secured before the bellows shape is formed. Recommended.

In the bending process, the A "to A" lines and C "to C" lines of the deformed raw tube 20 shown in FIG. Side C '
.. C 'line. In the bending process, the section A ″ to A ″ of the deformed base tube 20 is subjected to tension in the axial direction, but the stretching that reduces the height difference of the bellows shape occurs preferentially. Therefore, the thickness reduction rate on the outer peripheral side of the bent portion 30a of the bending pipe 30 is smaller than the thickness reduction rate on the outer peripheral side of the bent portion 30a of the bending pipe 3 in FIG. Can be smaller. In the bending process, after the bellows shape has been stretched to a certain extent, the thinning due to bending starts. The larger the total length La "of the sections A" to A "of the bellows-shaped portion 20a is, the later the start of the wall thinning due to bending is delayed, so that the reduction rate of the wall thickness at the bending outer peripheral portion can be reduced. As a result, the axial compressive force acting on the inner circumferential side of the bending pipe is also reduced, and as a result, the rate of increase in the thickness of the inner circumferential side of the bending pipe 30 is reduced by the bending pipe formed by bending the straight pipe. It becomes smaller than the thickness increase rate on the inner peripheral side of 3. That is, the bent tube 30 obtained by bending the deformed raw tube 20 is:
The thickness difference in the circumferential direction of the bent portion can be made smaller than that of the bent tube 3 obtained by bending the straight tube 2.

Further, a small change in thickness due to bending means that work hardening due to bending is small, and a decrease in ductility due to bending is suppressed.

Even if the bellows shape cannot be completely erased by the bending process, there is no problem since the bellows shape can be erased by the subsequent finishing hydraulic bulging process.

The present invention can be applied to metal tubes of various materials such as carbon steel, stainless steel, copper and aluminum.

(2) Manufacturing Method of Deformed Bent Tube The manufacturing method of forming the bent tube 30 into the deformed bent tube 4 as a product may be the same as the method shown in FIGS. 10 and 11 described above. As described above, by using the deformed raw tube 20, work hardening due to bending is suppressed, and the difference in wall thickness due to a portion in the circumferential direction of the bent portion can be made smaller than that of the bent tube 3 obtained by bending the straight tube 2. Accordingly, circumferential elongation due to expansion in the hydraulic bulging process is likely to occur in the entire circumferential direction, and it is possible to avoid breaking at the bending outer peripheral portion as shown in FIG. Hereinafter, the effects of the present invention will be described with reference to examples.

[0059]

[Example] Outer diameter 50.8mm, wall thickness 1.6mm, length 3
A stainless steel electric resistance welded steel tube SUS304TKA (JIS G3446) for a machine structure of 00 mm was machined by hydraulic bulging to apply a maximum internal pressure of 350 atm shown in FIG.

The length Lc ″ of the sections C ″ to C ″ shown in FIG.
98.5 mm Total length La ″ of sections A ″ to A ″ = 137.1 mm Sectional circumference Ha ″ = 17 passing through the bellows-shaped top part B shown in FIG. 2
5.6 mm r1 = r2 = 5 mm shown in FIG. 3 Five bellows bellows shape of ψ1 = ψ2 = 155 ° Next, the deformed raw tube 20 is shown in FIG.
The bent tube 30 was bent at θ = 90 °. This bending tube 3
0, the outer peripheral portion has a thickness t0 '= 1.4 mm and a hardness HV =
270, bending inner peripheral wall thickness ti '= 1.8 mm, hardness H
V = 270.

The bent tube 30 is subjected to hydraulic bulging to apply a maximum internal pressure of 450 atm shown in FIGS. 10 and 11 so that R = 75 mm, θ = 90 °, and the bulging portion circumference Ha = 188. A 5 mm deformed bent tube 1 was obtained. The minimum thickness of the bending outer peripheral portion was 1.1 mm, and the minimum product thickness of 1 mm could be cleared.

On the other hand, a bent pipe was formed by a conventional method using stainless steel pipes of the same dimensions.

After bending the tube, the thickness and hardness of the bent portion were measured. As a result, the bending outer peripheral portion of the bending tube 3 shown in FIG. 9 had a thickness t0 = 1.2 mm and a hardness HV = 330, and the bending inner peripheral portion had a thickness ti = 2.0 mm and a hardness HV = 330.

When the hydraulic bulge processing shown in FIGS. 10 and 11 was performed on the bent pipe 3, the circumferential length of the bent portion was about 17
At the time when the distance reached 0 mm, the fracture 12 from the bending outer peripheral portion shown in FIG. 13 occurred. Breaking could be prevented by performing hydraulic bulging after annealing the bent tube 3, but the thickness of the bent outer peripheral portion was reduced to 0.9 mm, and in order to satisfy the minimum product thickness of 1.0 mm, It was necessary to increase the tube wall thickness to 1.8 mm.

[0065]

According to the method for producing a deformed metal tube of the present invention,
The deformed base tube is effective in preventing breakage of the bulged portion when a deformed bent pipe product in which at least the bulged portion is bent in the longitudinal direction is manufactured by hydraulic bulging, and the deformed base tube is formed by hydraulic bulging. It can be easily manufactured by the method.
Great effect on expanding the application range of hydraulic bulging, such as elimination of the intermediate annealing required by the conventional method, and the ability to reduce the wall thickness of the raw tube to secure the minimum thickness of the product compared to the conventional method. To play.

[Brief description of the drawings]

1 is a partial longitudinal sectional view of a different Katachimotokan.

FIG. 2 is a perspective view of a different Katachimotokan.

FIG. 3 is a sectional view of a bellows-shaped portion of a deformed raw tube.

4 is a partial cross-sectional view of a bent tube obtained by bending a different Katachimotokan.

FIG. 5 is a diagram for explaining an example of manufacturing a deformed pipe from a straight metal pipe according to the present invention.

FIG. 6 is a longitudinal sectional view of a hydraulic bulged product having a straight bulging portion.

FIG. 7 is a partial cross-sectional view of a hydraulic bulging product in which a bulging portion is bent in a longitudinal direction.

FIG. 8 is a longitudinal sectional view for explaining a hydraulic bulging state of a product having a straight bulging portion.

FIG. 9 is a partial cross-sectional view of a straight pipe and a bent pipe obtained by bending the straight pipe.

FIG. 10 is a cross-sectional view for explaining a state before a hydraulic bulging process is performed on a product whose bulging portion is bent using a bending tube.

FIG. 11 is a cross-sectional view for explaining a state after a product in which a bulging portion is bent using a bending tube is subjected to hydraulic bulging.

FIG. 12 is a cross-sectional view for explaining buckling that occurs when axial pressing is applied to a bent tube.

FIG. 13 is a view for explaining a state of breakage in hydraulic bulging of a product having a bent bulging portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Deformed metal tubular product in which bulging part was bent 15 Ram head 2 Straight base tube 16 Bolster 3 Bent tube 20 Deformed base tube 4, 12 Lower mold 20a Bellows-shaped part 5, 13 Upper mold 30a Bent part 6, 7 Axis pushing tool 50 Hydraulic cylinder 8 Working fluid 50a Piston 10 Linear product 60 Pressure pad 12a, 12a Dice groove 12b, 12b Guide groove

Claims (2)

(57) [Claims] 1. Obtained by bending a straight metal tube
A bent shape in which at least the bent part of the bent metal tube is bulged
For straight metal pipes, which are raw pipes for the production of
At least the part on the bending outer peripheral side of the bent metal pipe is
Manufacture of deformed metal tube with bellows in the axial direction
Method, straight shape housed in the die groove of the mold
Hydraulic pressure from inside the metal tube and both ends of the straight metal tube
By adding the axial pushing force, straight metal
Expand the bellows-shaped part of the deformed metal tube
And pressurized pad with bellows shape stored in the mold
By pressing against the bulging part, the bulging part is formed in a bellows shape.
A method for producing a deformed metal element tube, characterized by forming. 2. The method according to claim 1, wherein
The metal tube is bent so that the bellows-shaped part is bent
To form a bent metal tube.
Into the bent metal tube from inside the die groove of the mold.
Pressure so that at least the bent portion of the bent metal tube is
Unusual bending metal characterized by swelling into a constant cross-sectional shape
A method for producing a generic pipe.