JP3355013B2 - Manufacturing method of deformed pipe with sharp recess - Google Patents

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 deformed tube having a concave portion having sharp corners.

[0002]

2. Description of the Related Art Steel pipes having various irregular cross-sections are used for decorative structural materials for building materials such as pillars, fences, handrails, sashes and the like, as well as for wheelchairs and chairs. Above all, as shown in FIG. 1, a deformed pipe 10 having a concave portion 11 formed at the center is used as a window or door frame by fitting a glass plate or the like into the concave portion 11. In the production of the deformed pipe 10, a method of rolling or bending a flat metal base material has been adopted.
In roll forming, bending forming, and the like, after a flat plate as a base material is formed into a predetermined cross-sectional shape, both ends in the width direction are butted or overlapped and welded.

[0003]

When a flat plate is formed into a closed tube, a portion into which another member is incorporated at the time of construction, that is, a recessed portion 11 protruding inside the tube, so that the welded portion does not impair the appearance. Place the welds on. At this time, superposition welding is generally adopted from the viewpoint of strength.
However, when the gap between the concave portion 11 and the side 13 facing the concave portion is small, welding is technically impossible, and thus, the shape and size of the deformable pipe that can be manufactured are restricted. Therefore, a method of manufacturing a deformed pipe by roll forming a cylindrical pipe so as to eliminate the need for welding has been partially studied. However, in the roll forming method using a cylindrical tube as a base material, it is difficult to obtain a deformed tube having a large radius of curvature at a corner portion and a sharp feel required for a decorative tube or the like. When the core is inserted into the deformed pipe and roll-formed, the radius of curvature of the corner can be reduced. However, the use of a cored bar introduces various problems, including a cored bar holding mechanism during the molding process. For this reason, the productivity is reduced, and this is not a practical solution for manufacturing a deformed pipe on an industrial level. The present invention has been devised in order to solve such a problem, and through a process of forming a concave portion having a corner angle smaller than a target angle, the radius of curvature of the corner portion is reduced to improve the design, An object of the present invention is to produce a deformed tube with improved discrimination by a roll forming method with high productivity.

[0004]

SUMMARY OF THE INVENTION In order to achieve the object, a method for manufacturing a deformed pipe according to the present invention is to roll-form a deformed pipe having a concave portion protruding inside the pipe on a part of a side face by using a multi-stage forming stand. At the time of reaching the final stage, after reducing the corner angle θ of the shoulder defining the concave portion from the target angle,
In the final stage, the shoulder is pushed open so that the corner angle θ becomes the target angle. The present invention can be applied to the manufacture of a deformed pipe having concave portions having various cross-sectional shapes such as a rectangular shape, a triangular shape, and a half hexagonal shape, as long as the shoulder is pushed open to a target angle in the final stage. However, in the following, for the sake of simplicity, description will be made by taking as an example the manufacture of a deformed pipe having a rectangular recess. In this case, the corner angle θ
After forming a concave portion having a shoulder of 40 to 70 degrees, it is preferable to push open the shoulder so that the corner angle θ is 90 degrees in the final stage.

[0005]

The process of forming a deformed pipe will be examined separately for the shoulder 12 and the side 13. The shoulder portion 12 is formed as a result of being greatly bent, and the degree of work hardening also depends on the side portion 13.
It is larger than that. Reducing the radius of the shoulder portion 12 causes the already hardened shoulder portion 12 to bend further. Under these conditions, even if the pressing force F by the roll is applied,
The deformation of the side portion 14 inside the deformed pipe 10 has priority over the reduction of the diameter of the shoulder portion 12. In a tube having a cross-sectional shape such as a rectangular tube having no concave portion protruding inward, deformation to the inside of the deformed tube is restrained by attaching a curvature that protrudes outward to the side. However, in the deformed pipe 10 having the concave portion 11 protruding inward, the pushing force applied to the shoulder portion 12 acts as a force for further deforming the concave portion 11 inward, and does not work to reduce the diameter of the shoulder portion 12.

The shoulder 12 has a metal flow during molding as shown in FIG. The pushing force F _d downward by upper roll 15 _u, when adding the pushing force F _l leftward in the right roll 15 _r base tube 16, specific metal flow to the shoulder portion 12 of the profiled pipe occurs. The metal flow 17 is a one-way flow from right to left and from top to bottom via the shoulder 12. On the other hand, the metal flow generated in the other corner portion 18 is caused by the two side portions 13 sandwiching the corner portion 18,
The flow is in two directions from 13 to the corner 18. The difference in the metal flow between the shoulder portion 12 and the other corner portion 18 has a great influence on the shapes of the shoulder portion 12 and the corner portion 18 after molding. That is, the diameter of the other corner portion 18 is easily reduced because the material flows in from both directions. On the other hand, since the material flows in the shoulder portion 12 in one direction, even if the concave portion 11 is rolled down, the metal flow 17 in one direction is promoted, but it does not effectively act to reduce the diameter of the shoulder portion 12. As a result, the concave portion 11 falls further downward, and the accuracy of the shape of the obtained deformed pipe 10 decreases.

In the course of investigating and studying various metal flows in the process of forming the deformed pipe 10 having such a concave portion 11, the present inventors have found that the corner angle θ of the shoulder 12 has a great effect on the behavior of the metal flow 12. To give. FIG. 3 shows shapes of the shoulder portions 12 having different corner angles θ before and after deformation. In this case, a tube manufactured from an unannealed stainless steel SUS304 was used as a raw tube. On the right end face of the upper side 11 _u defining the concave portion 11, a displacement toward the corner in the longitudinal direction was given while restraining the displacement in the vertical direction. Side 11 _v
The lower end face was restrained only in the horizontal direction without being restrained in the vertical direction. Under these conditions, the influence of the corner angle θ on the downsizing of the shoulder 12 and the vertical movement of the lower end face of the side 11 _V was investigated. Whether or not the lower end face of the side 11 _V moves in the vertical direction is to check the behavior of the metal flow 12.

In the shoulder 12 having a corner angle θ of 90 degrees, the diameter was not reduced. This indicates that the one-way metal flow 17 described in FIG. 2 is dominant.
On the other hand, the shoulder 12 having a corner angle θ of 60 degrees or 30 degrees
Had a small radius of curvature after deformation. From this, it is inferred that the metal flow 17 disappears as a one-way flow when the corner angle θ is reduced.
The speculation on the above-mentioned diameter reduction and metal flow is as follows.
This is supported by the experimental results in FIG. In FIG. 4, the value obtained by dividing the curvature radius R _g of the shoulder 12 by the initial thickness t ₀ to obtain a dimensionless value is plotted on the horizontal axis, and the movement distance Δ of the lower end surface of the side 11 _{V is taken} as Δ
Y is on the vertical axis. FIG. 4 shows the side 11 when the diameter is reduced.
_This shows that the vertical movement of the lower end surface of _V changes at the corner angle θ. If the corner angle θ is smaller than 60 degrees, the position of the lower end face of the side 11 _V increases as the diameter is reduced. When the corner angle θ is 60 degrees, the side 11
The lower end face position of _V does not change in the vertical direction. If the corner angle θ is larger than 60 degrees, the side 1
The position of the lower end face of 1 _V is lowered.

The movement of the lower end face of the side 11 _{V in} the vertical direction has a great effect on the reduction in diameter. That is, under the condition that the corner angle θ is close to 90 degrees, the movement of the lower end face of the side 11 _V moves downward, and the one-way flow 17 described with reference to FIG. 2 is generated. When the corner angle θ is 60 degrees, there is no movement of the lower end surface of the side 11 _V , and the behavior is as if the metal flow in the vertical direction is constrained. As a result, as shown in FIG.
Is reduced in diameter. Further, when the corner angle θ is smaller than 60 degrees, the lower end surface of the side 11 _V moves upward. As a result, a metal flow in two directions toward the shoulder portion 12 occurs like the other corner portions 18, and the diameter of the shoulder portion 12 is reduced. When the above model test result is applied to the deformed pipe 10 having the concave portion 11 shown in FIG. 1, when the base pipe is formed after the corner angle θ smaller than the target 90 degrees is attached to the shoulder 12, It can be seen that the shoulder 12 can be reduced in diameter.
However, when the corner angle θ is set to an angle smaller than 90 degrees, when the entire concave portion 11 moves up and down, that is, when the lower end face of the side 11 _V moves up and down, the amount of movement is Without proper roll design, product dimensions will be out of order. Therefore, the design becomes difficult. When the corner angle θ is extremely small, when the corner portion is pushed and opened thereafter, it does not spread to 90 degrees or cracks easily occur inside the corner portion. Therefore, in consideration of an appropriate range in which the diameter can be reduced at an industrial level, it is preferable to actually set the corner angle θ in a range of 40 to 70 degrees.

[0010]

EXAMPLES outer diameter 48.6mm made of stainless steel SUS304 annealed material, the cylindrical tube wall thickness 1.5mm and length 1 m, as shown in FIG. 5, profile pipe forming machine 2 as base pipe P ₀
Set to 0. The deformed tube forming machine 20 has a plurality of forming stands 21, 22,..., 2n in which forming rolls are incorporated. The base tube P ₀ is pushed into the forming stands 21, 22... 2 n by the hydraulic cylinder 25.
The raw tube P ₀ is roll-formed into a shape having a concave portion D _in (FIG. 6) at an intermediate stand, and then roll-formed into a shape having a concave portion D _fi (FIG. 7) at a final forming stand 2n. When forming the deformed tube having a recess D _fi from profiled tubes with recess D _in, it was investigated the effect of the shape of the intermediate stage has on the diameter of the shoulder portion D _sh recess D _fi. In the present embodiment, as shown in FIG.
This was used as a molding stand (a) of No. 1 and a molding stand (b) of the final stage n.

[0011] In forming stand of the final stage immediately preceding n-1, as shown in FIG. 8 (a), the upper roll 31 _u, the lower roll 3
_1d and the left and right rolls _31r , _31l . The upper roll _31u has a raised portion 31 _up formed at the center in the axial direction, and both sides of the raised portion 31 _{up in} the axial direction are inclined surfaces _31us , _31us . Inclined surface 31 _us , 31
_us was set such that the corner angle θ = 60 degrees with respect to the side surfaces 31 _uv and 31 _uv of the raised portion 31 _up . Uplift 31 _up
The surface _{31uf of} was flat. On the other hand, lower roll 31 _d
The left and right rolls 31 _r , 31 _l are provided with curved surfaces 31 _df , 31 _rf , 31 _lf with concave crowns having a predetermined curvature. When the raw tube fed from the forming stand on the upper side n-2 passes through the forming stand on the n-1 side immediately before the last stage, forming is partitioned by upper and lower rolls 31 _u and 31 _d and left and right rolls 31 _r and 31 _l. Following the space, it becomes an irregularly shaped tube P _n-1 having an intermediate shape. A concave portion d corresponding to the raised portion 31 _up is formed on the upper side of the deformed pipe P _n-1 , and both sides of the concave portion d are inclined surfaces 31 _us and 31.
_The slopes d _s and d _s correspond to _us . Slope 3
1 _us, 31 _us is the angle between the side walls d _v of recesses d 60
Degree. At this time, the diameter of the shoulder _Dsh was reduced. The right side, left side and lower side of the deformed pipe P _n-1 are concave curved surfaces 3
The shape slightly protruded outward following 1 _df , 31 _rf and 31 _lf .

The deformed pipe P _n-1 is roll-formed into a deformed pipe P _n having a target shape at a forming stand of the final stage n. Last stage n
Molding stand, as shown in FIG. 8 (b), the lower roll 32 _d and the lateral roll 32 _r, 32 using flat rolls as _l, on the raised portion 32 _{Stay up-formed} axially central roll 32 _u And combined. A raised portion 3 in the axial direction
The peripheral surfaces 32 _us , 32 _us on both sides of 2 _up are the raised portions 32 _up
Side surface 32 _uv , orthogonal to 32 _uv . When the concave portion d of the deformed pipe P _n-1 passes through the forming stand of the final stage n, the concave portion D is divided by the upper and lower rolls 32 _u , 32 _d and the left and right rolls 32 _r , 32 _l into planes orthogonal to each other. Become. At this time, the peripheral surfaces 32 _us and 32 _us and the side surfaces 32 _uv and 3
By 2 _uv , the corner portion of the deformed pipe P _n-1 is expanded to a corner angle θ = 90 degrees. Actually, when the shape of the obtained deformed pipe _Pn was measured, the radius of curvature of the shoulder portion _Dsh was only 0.8 times the wall thickness, and a sufficiently sharp concave portion Dn was obtained.
It had something.

For comparison, the molding stand shown in FIG. 9 was used immediately before the last stage n-1 and was combined with the molding stand of the last stage n (FIG. 8b). The forming stand in FIG. 9 uses a lower roll _33d and left and right rolls _33r , _33l with a convex crown so that the deformed pipe P _n-1 approaches the final shape of the deformed pipe _Pn. Combined with a caliber roll as roll 33 _u . Here, the side surfaces 33 _uv , 33 _{uv of} the raised portion 33 _up formed at the center of the upper roll 33 _{u in} the axial direction.
The angle between the _outer surface _33us and _33us was set to 90 degrees. In the obtained deformed pipe _Pn , a concave portion D in which the radius of curvature of the shoulder portion _Dsh was as large as 1.8 times the plate thickness was formed. As is apparent from this comparison, a deformed pipe P _n-1 having a concave portion d having an acute shoulder is formed by the n-1 forming stand immediately before the final stage, and the shoulder is pressed by the forming stand of the final stage n. By opening, the diameter of the shoulder _Dsh was reduced. As a result, the deformed tube manufactured according to the present invention gave a sharp impression, and was excellent in design and discernment. On the other hand, in the case where the molding stand shown in FIG. 9 was used immediately before the last stage n−1, the radius of curvature of the shoulder _Dsh was large, and the appearance was impaired.

In the above embodiment, the case where the deformed pipe _Pn having the rectangular concave portion D is roll-formed is taken as an example. However, the present invention is not restricted to this, and as long as the shoulder _Dsh is pushed open in the final stage to reach the target corner angle θ, the concave D
Can be changed arbitrarily. For example, when a concave portion having a triangular cross section is formed, the target corner angle θ is 120 degrees, so that the corner angle θ = 4 at an intermediate stage.
A recess with a 0-70 degree shoulder is formed. In addition, the corner angle θ smaller than the target angle is not limited to just before the last step,
It may be attached at any stage before reaching the final molding stand.

[0015]

As described above, according to the present invention, when a deformed pipe having a concave part protruding inside the pipe is manufactured by a roll forming method, a corner angle smaller than a target angle is added to a shoulder part of the concave part. Later, in the final stage, the corner is adjusted to the target angle by pushing the shoulder open. By this push-opening, the diameter of the shoulder portion is reduced, and a deformed pipe product excellent in design and distinction can be obtained.

[Brief description of the drawings]

Fig. 1 Deformed tube with a concave part protruding inside the tube

[Fig. 2] Metal flow during corner forming

Fig. 3 Model investigating metal flow during corner forming

FIG. 4 Relationship between material movement during molding and diameter reduction obtained from model experiments

FIG. 5 is a profiled tube molding machine used in an embodiment of the present invention.

FIG. 6 is a deformed tube having a recess formed therein.

FIG. 7: Deformed tube of final target shape

FIG. 8 shows the change in shape during roll forming according to the present invention.
It is shown by the shape of the deformed pipe in the molding stand (a) immediately before the final stage and the molding stand (b) in the final stage.

FIG. 9 shows a molding stand immediately before the last stage used for comparison.

[Explanation of symbols]

20: deformed tube forming machine 21, 22 · · · 22n: forming stand 25: hydraulic cylinder _{31 u, 32 u, 33 u} : upper roll 31 _r, 32
_r , 33 _r : right rolls 31 _l , 32 _l , 33 _l : left rolls 31 _d , 32
_d , 33 _d : Lower rolls 31 _up , 32 _up , 33 _up : Raised portions 31 _uv , 32 _uv , 33 _uv : Side surfaces of the raised portions 31 _us , 32 _us , 33 _us : Peripheral surfaces P _{n-1 on} both sides of the raised portions. : Deformed tube _Pn formed by the n-1 forming stand immediately before the last stage _Pn : Deformed tube formed by the last n forming stand d, D: recess _Dsh : shoulder of recess θ:
Corner angle

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Higashi 1 Tsurumachi, Amagasaki-shi, Hyogo Nisshin Steel Co., Ltd. Inside Processing Technology Laboratory (56) References JP-A-3-226311 (JP, A) JP-A Sho 54 JP-A-81156 (JP, A) JP-A-62-84831 (JP, A) JP-A-60-24414 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21C 37/15

Claims (2)

(57) [Claims] When a deformed pipe having a concave portion protruding into the inside of a pipe formed on a part of a side surface is roll-formed by a multi-stage forming stand, a corner angle θ of a shoulder section defining the concave portion at a stage reaching a final stage. Is smaller than the target angle, and then the shoulder is pushed open so that the corner angle θ becomes the target angle in the final stage. 2. After forming a concave portion having a shoulder having a corner angle θ of 40 to 70 degrees, the corner angle θ is 90 ° in the final stage.
The method for manufacturing a deformed pipe according to claim 1, wherein the shoulder is pushed open to a desired degree.