JP2000094042A - Bent pipe and manufacture of bent tube by plastic working - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a pipe which is hard to leave chips and sand on the inner wall-surface of a hole by forming an expanded part on the pipe by plastic working and bending that part at a prescribed angle. SOLUTION: A piece 31 of a solid base stock is formed into a thing having a blind hole 33 whose cross section is circular in a round bar 32. Two holes 35, 36 having different diameters are formed inside a cylindrical base stock 34 by forging the round bar 32. A pipe stock 37 having the same outside diameter, inside diameter and thickness is made by cold forging the cylindrical base stock 34. Using six dies 38-43, the pipe 44 is formed. The pipe 44 has the expanded part 44a formed by plastic working in the middle part and linear parts 44b, 44c on both sides. In the expanded part 44a, the shape and thickness on the upper and lower sides are different. By bending the pipe 44 having the expanded part 44a with bending dies 51-56, a bent part is formed. It is preferable to form the bent part in a state where the part is heated to 650-800 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bent pipe used in various technical fields and a method for manufacturing a bent pipe by plastic working.

[0002]

2. Description of the Related Art As a method of manufacturing a bent pipe (a typical example of which is called an elbow pipe), a drill cutting method and a casting method of manufacturing from a hot forged solid element are well known. .

[0003] An elbow pipe used for a pump, a valve, a cylinder and the like will be described as an example.

The elbow tube has a bent portion and straight portions extending on both sides thereof, and a through hole is formed through the bent portion and the straight portion. The hole is turned at an angle of 45 ° or 90 °.

[0005] This hole is formed by drilling two holes separately from both ends of a solid bending member that is turned at an angle of 45 ° or 90 °, and cutting the holes until they intersect. Is common.

[0006] Elbow tubes are also manufactured by an automatic casting process using a mold that forms a hole that is turned at an angle of 45 ° or 90 °.

[0007]

In the case of the drill cutting method,
Cutting burrs tend to remain at the intersection of the two holes. In addition, if cutting dust or cutting powder adheres to the inner wall surface of the hole, it is difficult to remove it even when washing. Such burrs, cutting debris,
Powder and the like tend to increase the rate of failure of equipment.

[0008] In the case of the casting method, sand and dust easily adhere to the inner wall surface of the hole. In this case, it is not easy to remove them, and an elbow pipe is often used with sand or dust remaining on the inner wall surface of the hole. As a result, the failure occurrence rate of the devices is increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bent pipe in which cutting waste, sand and the like are unlikely to remain on the inner wall surface of the hole, and a method of manufacturing such a bent pipe.

[0010]

One of the solutions of the present invention is a curved pipe having a straight section and a curved section, wherein the curved section has a flow of plastically processed metal fibers. It is. In particular, it is preferable that the bent portion is forged and bent.

There are various relationships between the thickness of the outside of the bent portion and the thickness of the straight portion, but it is preferable that the thickness of the outside of the bent portion is substantially the same as the thickness of the straight portion. Speaking of the difficulty of plastic working, as the bending angle of the bent portion is closer to 90 degrees, it is relatively easy to process so that the thickness outside the bent portion is smaller than the thickness of the straight portion. It is relatively difficult to work so that the thickness of the outside is larger than the thickness of the straight part.

Another solution of the present invention is a method of manufacturing a bent tube having a straight portion and a bent portion, wherein a bulged portion is formed in a part of the tube by plastic working, and at the same time or thereafter. A method of manufacturing a bent pipe by plastic working, wherein a bent portion is formed by bending a pipe at a bulging portion to a predetermined angle by plastic working.

Preferably, before the bending process, a bulging portion is formed in a part of the pipe by plastic working so that the thickness of the bulging portion is larger than the thickness of the other portions. In this way, when forming the bent portion, it becomes easy to manufacture a bent tube in which the thickness outside the bent portion is almost the same as the thickness of the straight portion.

Depending on the purpose of use of the pipe, when a bulged portion is formed in a part of the pipe by plastic working, it is preferable that the thickness of the bulged portion is substantially the same as the thickness of other portions.

In another embodiment of the present invention, a bulged portion is formed in a part of the pipe by plastic working before bending, and the bulged portion at a position corresponding to the outside of the bent portion is bent. It is preferable to make it larger than the bulging portion at a position corresponding to the inside of the portion. .

Further, before forming the bent portion, a bulged portion is formed in a part of the pipe by plastic working so that the bulged portion corresponding to the outside of the bent portion is located at the position corresponding to the inside of the bent portion. The bulging portion is substantially the same as the bulging portion, or conversely, a bulging portion is provided at a position corresponding to the outside of the bent portion, and substantially no bulging portion is provided at a position corresponding to the inside of the bent portion, Thereafter, the pipe may be bent at a predetermined angle by plastic working at the bulging portion to form a bent portion,
This is one of preferred embodiments of the present invention.

Further, the bent portion is formed in a cold state,
It is formed while being heated to 50 to 800C.

From the viewpoint of manufacturing cost, it is preferable to use a solid wire and perform forging in a plurality of continuous steps.

[0019]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a bent portion of a pipe is formed by plastic working, particularly, forging.

If the bent portion is formed by plastic working, unlike the drill cutting method and the casting method, it is possible to prevent cutting chips, cutting powder, sand and the like from adhering to the inner wall surface of the hole of the pipe.

In addition, when the bent portion is formed by plastic bending, the bent portion is likely to be substantially rounded, and the hole tends to have a shape in which fluid (particularly liquid) flows smoothly. Therefore, the cavitation occurrence rate of the fluid is reduced.

Further, in the case of plastic working, especially forging, waste of material is reduced. Compared to drill cutting method,
Raw material usage can be reduced by about 30%.

In the case where a bent portion is formed by automatic forging, the production speed is remarkably improved as compared with a casting method or a drill cutting method. As a result, manufacturing costs can be significantly reduced.

Various raw materials can be used for the method for producing a bent tube of the present invention. A typical example of low material costs is very long solid coil material. Such coiled material is sheared at predetermined lengths to first form short solid round bars. Thereafter, each round bar is plastically worked to form a short circular tube. For example, using a solid round bar, 4
A short circular tube is formed by a cold forging machine of a 6-stage forming type (a typical example is a part former).

Although the material cost is higher than that of a solid coil material, a circular tube can be used as a raw material from the beginning.

The bent pipe according to the present invention has various features by plastic working, especially forging, unlike those manufactured by a conventional casting method or drill cutting method. One of the features of the bent tube according to the present invention is that the flow of the metal fiber becomes unique to forging. For example, in the bent portion, the metal fibers flow smoothly along the bend. In other words, the metal fibers are arranged so as to flow with roundness along the shape of the hole.

In forming a bent portion according to the present invention, a bulge is formed on one side of a straight circular tube material so that the flow path area of the bent portion is not reduced by forging and bending. Bend so that it is outside of.

In another embodiment of the present invention, a bulge is formed on both sides of a straight circular tube material, and the bulge is formed. When bulging on both sides in this way, both bulges can be made almost the same shape, but the bulge on the part outside the bent part is increased, and the bulge on the part inside the bent part is reduced. You can also. By doing so, it is easy to make the thickness of the bent portion not much different between the outside and the inside.

The bending angle of the bending portion is arbitrarily determined according to the purpose of use. When the bending angle is set to 45 to 90 degrees, the effect of the present invention becomes remarkable.

The bent tube according to the present invention can be formed with a screw at both ends or can be cut on the outer surface.

The bend radius of the bend is 0.5 of the hole diameter at the end.
It is preferable to set it to 2.5 times. When a screw is formed at the end, the bending radius is 0.5 to 2.5 times the nominal screw diameter, and when the screw diameters at both ends are different, 0.5 to the average of both screw diameters is 0.5 to 2.5 times. It is preferably 2.5 times.

[0032]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an example of a method for manufacturing a bent pipe of the present invention from a pipe material (not shown) having the same outer diameter, inner diameter, and wall thickness over the entire length.

First, a long pipe material is cut into predetermined lengths. As a cutting method, a shearing method or a cutting method can be adopted. Thereby, many short pipe pieces are made.

Next, as shown in FIG. 1A, the short pipe pieces are cold forged using six molds 1 to 6 for cold forging. Thereby, the tube 7 is formed.

The mold 1 is arranged outside the both ends of the pipe piece or the pipe 7, and has a substantially sleeve shape as a whole. The mold 2 is arranged inside the mold 1, and is configured such that the tip end surface of the mold 2 contacts one end surface of the tube 7. The mold 3 is a round bar-shaped mold generally called a core metal, and is arranged so as to penetrate through the hole inside the tube 7 and the hole inside the mold 2 described above.
The dies 4, 5 and 6 have substantially the same shape as the dies 1, 2 and 3, and are arranged symmetrically with the dies 1, 2 and 3.

After arranging short pipe pieces at predetermined positions in a ring-shaped space formed by these six dies 1 to 6, the right dies 1, 2 and 3 and / or the left dies 4, The pipes 5 and 6 are moved in the direction of each other in conjunction with each other, whereby the pipe pieces are cold-cast to form the pipe 7. Tube 7
It has an outwardly bulging portion 7a at its center.

FIG. 1 (B) shows the tube 7 in FIG. 1 (A).
XX section of FIG.

Comparison between before and after cold forging is as follows.
The outer diameter of the bulging portion 7a of the pipe 7 after processing is about 1.0 to 1.2 times the outer diameter of the pipe piece before processing. The outer diameter of the straight portions 7b and 7c of the pipe 7 after processing is about 0.6 to 0.7 times the outer diameter of the pipe piece before processing. That is, tube 7
The outer diameters of the straight portions 7b and 7c are smaller than those of the pipe pieces by forging. On the other hand, the bulging portion 7a of the pipe 7 has the same or larger outer diameter by forging than the pipe piece. Also, the length of the pipe piece becomes smaller after processing. As a result, the bulging portion 7a of the tube 7
Is thicker than the pipe piece before processing.

However, when the pipe piece and the pipe 7 are compared, a change in the length before and after the processing, a change in the outer diameter of the bulging portion, a change in the thickness of the bulging portion, and a change in the outer diameter and thickness of the straight portions 7b and 7c. The change in thickness can be freely selected according to the use of the bent tube.

According to the present invention, a pipe 7 having a bulging portion 7a as shown in FIG. 1 is bent at a predetermined angle by plastic working to form a bent portion as described later.

FIG. 2 shows another example of the tube.

First, similarly to the example of FIG. 1, a long pipe material is cut to produce a short pipe material. Next, eight dies 10
13 (the molds at the center and both ends are not shown), the pipe material is cold-forged into a shape as shown in FIGS. The pipe material moves the plurality of molds 10 to 13 as described above so as to approach each other.
4 is pressed. The tube 14 has straight sections 14 at both ends.
b, 14c, and a bulging portion 14a at the center.

In the example shown in FIG. 2, when the pipe 14 is further bent, the flow path cross-sectional area of the hole at the bent portion is made to be closer to the flow path cross-sectional area of the hole at the straight portion. 2
(B), the hole 14d has an elongated cross-sectional shape. The upper side of the hole 14d is largely rounded to have a substantially arc shape, the lower side is a flat surface, the both sides are flat surfaces, and a small round is formed at the intersection of the flat surfaces.

The pipe of FIG. 2 is also an intermediate material before further bending, as in the example of FIG.

Further, the tube 7 having the bulging portion 7a as shown in FIG. 1 is cold forged to form a tube 14 as shown in FIG.
It is also possible to take the shape of

FIG. 3 shows that after cutting a solid wire into a predetermined length, cut pieces 31 shown in FIG. 3 (A) are formed, and each cut piece 31 is continuously connected to each of FIG. This shows a series of steps of manufacturing a bent tube 57 by forging as shown in FIG. 3E and then bending as shown in FIG. 3F.

First, FIG. 3A shows a solid material piece 31 cut into a predetermined short length. This piece of material 3
As shown in FIG. 3B, 1 is formed in a round bar 32 with a circular hole 33 having a circular cross section. When the material piece 31 is cold forged into the round bar 32 as described above, the outer diameter is small, but the length is long. The mass of the material piece 31 and the round bar 32 is
It is substantially the same as in normal forging.

Further, as shown in FIG.
Is forged to form 2 having different diameters inside the cylindrical material 34.
Two holes 35 and 36 are formed. The outer diameter is further reduced by the cold forging from the round bar 32 shown in FIG. 3B to the cylinder 34 shown in FIG. 3C, but the length is further increased. There is no change in mass.

FIG. 3D shows the cylinder 34 shown in FIG.
Further cold forging, the same outer diameter over the entire length,
This shows a state in which a pipe material 37 having an inner diameter and a wall thickness is formed. The length of the pipe member 37 is substantially the same as the length of the cylinder 34 described above.

Further, as shown in FIG. 3E, the pipe material 37 is cold forged using six molds 38 to 43 to form a pipe 44. This tube 44 has a bulge portion 44a at the center and straight portions 44b, 4
4c. In the illustrated example, the inner diameter and the outer diameter of the straight portions 44b and 44c are 0.6 times and 0.9 times the inner diameter and the outer diameter of the pipe member 37 in FIG. 3D, respectively. Also, a mode without change is possible.

The shape and thickness of the bulging portion 44a are different between the upper side and the lower side in the figure. That is, the shape of the bulge is larger on the upper side of the bulge portion 44a than on the lower side, and the wall thickness is thicker. Bulge 44a
The shape and thickness of the sleeve-shaped mold 3 arranged on the outside
8 and 41 can be formed by having shapes that are not symmetrical in the vertical direction. The outer dimensions of the bulging portion 44a are 1.05 to 1.10 times the outer diameter of the pipe member 37 in FIG.

FIG. 3F shows a state in which the tube 44 having the bulge portion 44a shown in FIG. 3E is bent 90 ° by bending dies 51 to 56 of a bending machine. .

First, the mold 38 shown in FIG.
The tube 44 is taken out of the mold 43 of the bending machine.
To 56. At this time, the molds 51 to 53 constituting one unit and the molds 54 to 56 constituting the other unit are arranged in a plane-symmetric manner on the left and right. In other words, the center axes of the core-shaped molds 53 and 56 at the center on both sides are aligned. Thereafter, the dies 53 and 56 are gradually rotated with respect to each other, and at the same time, at least one of the two dies 53 and 56 is gradually shifted outward with respect to the other. That is, the pipe 44 is bent while moving these two molds 53 and 56 little by little. As a result, the tube 44 is bent to a bending angle of 90 °. Thus, a bent tube 57 having a bent portion 57a is formed.

Depending on the material of the pipes 44 and 57, the bulged portion 44a and the bent portion 57a are heated at a high frequency, and are bent as described with reference to FIG.
At this time, it is preferable that the bulging portion 44a and the bent portion 57a are heated to 650 ° C. to 800 ° C. by a high frequency heating device.

Finally, the bent tube 57 has a bending angle of 90 ° at the bending portion 57a in the example shown in FIG. 3F, but this bending angle is much smaller than 90 °, for example, 45 °. If it is less than 0 °, no inconvenience will occur during the bending process even if the heating temperature of the bulging portion 44a is lowered or a cold state where no heating is performed.

FIGS. 4 to 6 show an example of manufacturing a bent pipe having a bent angle of 45 ° from a pipe material having a predetermined length.

FIGS. 4A and 4B show a tubular pipe member 6 having the same outer diameter, inner diameter and wall thickness over the entire length.
1 is shown.

FIG. 5 shows a pipe 62 formed by cold forging the pipe member 61 shown in FIG. 4 and having a bulged portion 62a and straight portions 62b and 62c on both sides thereof.

As shown in FIG. 5A, a pipe 62 is formed by preforming the pipe member 61 of FIG. 4 using at least four dies 63 to 66. As described above, this tube 62 has a bulging portion 62a and straight portions 62b and 62c on both sides thereof, and the bending of the two straight portions 62b and 62c is two.
It is between 5 ° and 30 °. The tube 62 has a bulge 62 only on the upper side, does not exist on the lower side 62a and the left and right sides 62b and 62c, and has a flat outer surface. Moreover, the degree of bulging of the bulging portion 62 is small.
The width of the hole of the bulging portion 62a is 0.6 to 0.8 times the diameter of the hole in FIG.

FIG. 6 shows a bent pipe 71 formed by further bending the pipe 62 shown in FIG. 5 by a bending machine.

The bending machine shown in FIG. 6B has three dies 72, 73 and 74 on one side and three dies 75, 76 and 77 on the other side. Straight section 6 of tube 62
While holding 2b and 62c, the two center molds 74 and 77 gradually turn so as to have an angle with each other, and stop at 45 °.

As shown in FIG. 6A, the bent portion 71a of the bending tube 71 thus formed is
In the figure, the upper side 71b of the bent portion 71a is rounded, the lower side 71c of the bent portion 71a is flat, and both sides 71d and 71e are flat surfaces. However, the connecting portions 71f and 71g between the flat surfaces of both sides 71d and 71e and the lower flat surface are small rounded.

After the bending, the thickness of the upper side 71b and the lower side 71c of the bent portion 71a is 0.7 to 0.7, respectively, as compared with the thickness of the pipe member 61 of FIG. 4 before the bending.
The height of the hole in the bent portion 71a in the vertical direction is 0.6 to 0.5 times as large as the inner diameter of the pipe member 61 in FIG. It is twice.

The present invention is not limited to the above embodiment. For example, while the tube 14 of FIG. 2 has been described as an intermediate material for making a final bent tube, the tube of FIG. 2 may fall within the scope of the bent tube according to the present invention. Similarly, the tube 62 shown in FIG. 5 is within the scope of the present invention. Also, using the bending machine shown in FIG. 3 (F) or FIG. 6 (B), the pipe 7 shown in FIG. 1, the pipe 14 shown in FIG. 2, and other pipes (those having a bulging portion) Can be forged and bent.

[Brief description of the drawings]

FIG. 1A shows a state in the course of manufacturing a bent tube according to the present invention. (B) shows an XX cross section of the tube shown in (A).

FIG. 2 (A) shows another embodiment halfway through a bent tube or intermediate according to the present invention. (B) shows an XX cross section of the tube shown in (A) and a mold for forming the same.

FIGS. 3A to 3F show a series of manufacturing steps for manufacturing a bent tube according to the present invention from a solid material.

FIG. 4 shows a pipe material as an example of a starting material for manufacturing the bent pipe of the present invention. (A) is XX sectional drawing of the pipe material of (B).

5 (A) is a shoulder for processing the pipe material of FIG. 4;
The XX section of the tube of (B) is shown. (B) is (A)
The tube is shown.

6 (A) shows a bulged portion of the bent tube according to the present invention, and FIG. 6 (B) shows a state where the tube having the bulged portion shown in FIG. 5 is further bent to plastically process the bent tube of the present invention. Is shown. (A) is XX sectional drawing of the tube of (B).

[Explanation of symbols]

 1, 2, 3 Mold 4, 5, 6 Mold 7 Tube 7a Bulging portion 7b, 7c Pipe material linear portion 10, 11, 12, 13 Mold 14 Tube 14a Bulging portion 14b, 14c Linear portion 14d Bulging portion 14a Hole 31 Material piece 32 Round bar 33 Hole 34 Cylindrical material 35, 36 Hole 37 Pipe material 38, 39, 40, 41, 42, 43 Mold 44 Tube 44a Swelling portion 44b, 44c Linear portion 51, 52, 53, 54, 55 , 56 type 57 bent pipe 57a bent section 61 pipe material 62 pipe 62a bulging section 62b, 62c linear section 63, 64, 65, 66 type 71 bent pipe 71a bent section 72, 73, 74 type 75, 76, 77 type

Claims (13)

[Claims] 1. A method for manufacturing a bent tube having a straight portion and a bent portion, wherein a bulged portion is formed in a part of the tube by plastic working, and the bulged portion is bent at a predetermined angle by plastic working. A curved pipe manufacturing method by plastic working, wherein a bent portion is formed by bending. 2. The method according to claim 1, wherein a bulging portion is formed in a part of the tube by plastic working before forming the bent portion, and the bulging portion has a greater thickness than other portions. 2. A method for manufacturing a bent pipe by plastic working according to 1. 3. A bulged portion is formed in a part of the pipe by plastic working before forming a bent portion, and a thickness of the bulged portion is substantially the same as a thickness of other portions. A method for manufacturing a bent pipe by plastic working according to claim 1. 4. A bulge portion is formed in a part of the pipe by plastic working before forming the bent portion, and the bulge portion at a position corresponding to the outside of the bent portion is bulged at a position corresponding to the inside of the bent portion. 4. The method according to claim 1, wherein the first part is larger than the first part.
A method for manufacturing a bent pipe by plastic working according to any one of the above items. 5. A bulging portion is formed in a part of the tube by plastic working before forming the bent portion, and the bulging portion at a position corresponding to the outside of the bent portion is bulged at a position corresponding to the inside of the bent portion. The method for manufacturing a bent pipe by plastic working according to any one of claims 1 to 3, wherein the bent pipe is substantially the same as the portion. 6. A method for manufacturing a bent tube having a straight portion and a bent portion, wherein a bulging portion is provided at least at a position corresponding to the outside of the bent portion, and thereafter, the tube is bent to a predetermined angle by plastic working. And a method of manufacturing a bent pipe by plastic working, wherein a bulged portion becomes a part of a bent portion. 7. The bent portion is formed in a cold state.
7. The method for producing a bent pipe by plastic working according to any one of 6. 8. The method for producing a bent pipe by plastic working according to claim 1, wherein the bent portion is formed while being heated to 650 ° C. to 800 ° C. 9. The method according to claim 1, wherein the pipe is formed by a plurality of forging processes from a solid coil material. 10. A bent tube having a straight portion and a bent portion, wherein the bent portion has a flow of plastically processed metal fibers. 11. The method according to claim 1, wherein the thickness of the outside of the bent portion is substantially equal to or greater than the thickness of the straight portion.
Bent tube according to 0. 12. The bent pipe according to claim 10, wherein the thickness of the outside of the bent portion is smaller than the thickness of the straight portion. 13. The bent pipe according to claim 10, wherein the bent portion is formed by forging and bending.