JPH07241619A - Manufacture of special shaped tube having sharp recessed part - Google Patents

Abstract

PURPOSE:To manufacture by a roll forming method a special shaped tube which is provided with a recess with a small radius part on the shoulder and which enhances design and discrimination characteristics. CONSTITUTION:In roll-forming a special shaped tube Pn in which a recessed part D projecting inside the tube is formed on a part of the side, a corner angle theta at a shoulder is made smaller than a target angle, and also, after it is made to be small, a shoulder part Dsh is flared so that the corner angle thetabecomes the target angle in the last stage. In manufacturing a special shaped tube with a rectangular recessed part D, the corner angle theta in an intermediate stage is set in the range of 40 to 70 deg.C When the corner angle theta is made the target angle by flaring, the radius of shoulder part Dsh is made to be small, which gives an ingenious impression and also facilitates the manufacture of a special shaped tube Pn superior in design and discrimination characteristics.

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 profiled tube having a recess having sharp corners.

[0002]

2. Description of the Related Art Steel pipes having various cross-sections are used as decorative structural materials for building materials such as columns, fences, handrails, sashes, car stops, chairs and the like. Among them, as shown in FIG. 1, a deformed tube 10 having a recess 11 formed in the center is used as a window or door frame by fitting a glass plate or the like into the recess 11. For manufacturing the deformed pipe 10, a method of roll-forming or bending-forming a flat metal base material has been adopted.
In roll forming, bending forming, etc., a flat plate as a base material is formed into a predetermined cross-sectional shape, and then both widthwise end portions are butted or overlapped and welded.

[0003]

When a flat plate is formed into a closed pipe, a portion where another member is incorporated at the time of construction, that is, a recessed portion 11 which is projected to the inside of the pipe so that the welded portion does not spoil the appearance. Place the weld on. At this time, superposition welding is generally adopted from the viewpoint of strength.
However, if the gap between the concave portion 11 and the side 13 facing the concave portion is small, it is technically impossible to perform welding, so that 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 of a cylindrical pipe so as to eliminate the need for welding is being studied by some. However, in the roll forming method using a cylindrical tube as a base material, it is difficult to obtain a deformed tube having a sharp feel required for a decorative tube or the like because the radius of curvature of the corner portion is large. When a cored bar is inserted into the profiled tube for roll forming, the radius of curvature of the corner can be reduced. However, the use of cored bar introduces various problems including cored bar retention mechanism during the molding process. Therefore, the productivity is lowered, and it is not a practical solution for manufacturing the deformed pipe on an industrial level. The present invention has been devised to solve such a problem, and by performing a step of forming a recess having a corner angle smaller than the target angle, the radius of curvature of the corner portion can be reduced to improve the designability. The purpose of this invention is to manufacture a deformed pipe with improved distinctiveness by a roll forming method with high productivity.

[0004]

In order to achieve the object, the method for manufacturing a profiled pipe of the present invention is to roll-form a profiled pipe having a concave portion projecting inside the pipe on a part of its side surface by a multi-stage molding stand. At the time of reaching the final stage, after the corner angle θ of the shoulder portion that defines the recess is made smaller than the target angle,
In the final stage, the shoulder portion is pushed open so that the corner angle θ becomes a target angle. INDUSTRIAL APPLICABILITY The present invention can be applied to the manufacture of a deformed pipe in which concave portions having various cross-sectional shapes such as a rectangular shape, a triangular shape, and a half-hexagonal shape are formed as long as the shoulder portion is pushed open to the target angle at the final stage. However, in the following, for simplification of the description, manufacturing of a deformed tube in which a rectangular recess is formed will be described as an example. In this case, the corner angle θ
It is preferable that after forming a recess having a shoulder of 40 to 70 degrees, the shoulder is pushed open at the final stage so that the corner angle θ becomes 90 degrees.

[0005]

The process of forming the deformed pipe will be examined separately for the shoulder portion 12 and the side portion 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.
Is larger than. Reducing the radius of the shoulder portion 12 as described above further bends the shoulder portion 12 which has already been work hardened. Even if the pushing force F by the roll is applied under this condition, unless some restraint is applied,
Deformation of the side portion 14 inside the deformed tube 10 has priority over reduction of the diameter of the shoulder portion 12. In the case of a tube having a cross-sectional shape such as a rectangular tube that does not have a recess projecting inward, the deformation to the inside of the deformed tube is constrained by providing the side with a curvature that is convex outward. However, in the deformed tube 10 having the recess 11 protruding inward, the pushing force applied to the shoulder 12 acts as a force to further deform the recess 11 inward, and does not work to reduce the diameter of the shoulder 12.

At the shoulder portion 12, there is a metal flow as shown in FIG. 2 at the time of molding. When a downward pushing force F _d is applied by the upper roll 15 _u and a left pushing force F _l is applied by the right roll 15 _r to the raw pipe 16, a metal flow peculiar to the shoulder portion 12 of the deformed pipe is generated. The metal flow 17 is a one-way flow from the right to the left and further from the top to the bottom via the shoulder portion 12. On the other hand, the metal flow generated in the other corner portion 18 is caused by the both side portions 13 sandwiching the corner portion 18,
There are two directions of flow from 13 toward the corner portion 18. The difference in 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 other corner portions 18 are likely to have a smaller diameter because the material flows in from both directions. On the other hand, since the material flows in one direction in the shoulder portion 12, even if the recess 11 is rolled down, the metal flow 17 in one direction is promoted, but the diameter of the shoulder portion 12 is not effectively reduced. As a result, the recess 11 is further lowered, and the shape accuracy of the obtained deformed tube 10 is reduced.

The inventors of the present invention, in the process of variously investigating and studying the metal flow in the forming process of the deformed pipe 10 having such a recess 11, the corner angle θ of the shoulder 12 has a great influence on the behavior of the metal flow 12. Found to give. FIG. 3 shows the shape of the shoulder 12 with different corner angles θ before and after deformation. In this case, a tube material manufactured from an unannealed material of stainless steel SUS304 was used as a raw tube. On the right side end surface of the upper side 11 _u that defines the recessed portion 11, the displacement in the longitudinal direction was applied toward the corner 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 reduction of the diameter of the shoulder 12 and the vertical movement of the lower end surface of the side 11 _V was investigated. Whether or not the lower end face of the side edge 11 _V moves in the vertical direction is for observing the behavior of the metal flow 12.

The shoulder portion 12 having the corner angle θ of 90 degrees did not have a smaller diameter. This indicates that the unidirectional 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 smaller radius of curvature after deformation. From this, it is presumed that the metal flow 17 disappears in one direction when the corner angle θ is reduced.
The above conjecture regarding the diameter reduction and metal flow is
This is supported by the experimental results shown in FIG. In FIG. 4, the horizontal axis represents a dimensionless value obtained by dividing the radius of curvature R _g of the shoulder portion 12 by the initial wall thickness t ₀ , and the moving distance Δ of the lower end face of the side 11 _V.
The vertical axis is Y. FIG. 4 shows the side edge 11 when the diameter is reduced.
It shows that the movement of the lower end surface of _V in the vertical direction changes with the corner angle θ. If the corner angle θ is smaller than 60 degrees, the position of the lower end face of the side edge 11 _V rises as the diameter decreases. When the corner angle θ is 60 degrees, the side edge 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 moves down.

The movement of the lower end face of the side edge 11 _{V in} the vertical direction has a great influence 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 edge 11 _V is downward, and the unidirectional flow 17 described in 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 restricted. As a result, as shown in FIG.
Is reduced in diameter. Further, when the corner angle θ is made smaller than 60 degrees, the lower end face of the side edge 11 _V moves upward. As a result, similar to the other corner portions 18, a metal flow in two directions toward the shoulder portion 12 is generated, and the diameter of the shoulder portion 12 is reduced. When the above model experiment results are applied to the deformed pipe 10 having the recessed portion 11 shown in FIG. 1, when forming a blank pipe after attaching a corner angle θ smaller than 90 degrees to the target to the shoulder portion 12, It can be seen that the diameter of the shoulder portion 12 can be reduced.
However, when the corner angle θ is set to an angle smaller than 90 degrees, when the entire concave portion 11 moves vertically, that is, when the lower end face of the side 11 _V moves vertically, the movement amount is changed. If the roll design is not planned, the product dimensions will be incorrect. Therefore, design becomes difficult. Further, if the corner angle θ is extremely small, then when the corner portion is pushed open, the corner angle θ does not spread to 90 degrees, or cracks easily occur inside the corner portion. Therefore, it is preferable to actually set the corner angle θ in the range of 40 to 70 degrees in consideration of the appropriate range in which the diameter can be reduced at the industrial level.

[0010]

EXAMPLE A cylindrical tube made of stainless steel SUS304 annealed material and having an outer diameter of 48.6 mm, a wall thickness of 1.5 mm and a length of 1 m was used as a base pipe P ₀ as shown in FIG.
I set it to 0. The profiled pipe forming machine 20 has a plurality of forming stands 21, 22 ... 2n in which forming rolls are incorporated. The raw pipe P ₀ is pushed into the molding stands 21, 22 ... 2n by the hydraulic cylinder 25.
The raw pipe P ₀ is roll-formed into a shape having a recess D _in (FIG. 6) by an intermediate stand, and then roll-formed into a shape having a recess D _fi (FIG. 7) by 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 this embodiment, a combination of molding rolls as shown in FIG.
1 was used as the molding stand (a) and the final stage n of the molding stand (b).

In the n-1 forming stand immediately before the final stage, as shown in FIG. 8A, the upper roll 31 _u and the lower roll 3 are
_1d and right and left rolls 31 _r and 31 _l are combined. The upper roll 31 _u is formed with a ridge 31 _{up at the} center in the axial direction, and both sides of the ridge 31 _{up in} the axial direction are inclined surfaces 31 _us , 31 _us . Inclined surface 31 _us , 31
_Us was set so that the corner angle θ = 60 degrees with respect to the side surfaces 31 _uv and 31 _uv of the raised portion 31 _up . Raised part 31 _up
The surface 31 _{uf of} was made flat. On the other hand, the lower roll 31 _d
The left and right rolls 31 _r and 31 _l are provided with curved surfaces 31 _df , 31 _rf , and 31 _lf with concave crowns having a predetermined curvature. When the blank pipe fed from the forming stand on the upper stage side n-2 passes through the forming stand on the stage n-1 immediately before the final stage, it is divided into upper and lower rolls 31 _u and 31 _d and left and right rolls 31 _r and 31 _l. Following the space, a deformed pipe P _n-1 having an intermediate shape is formed. 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 , 31.
_The inclined surfaces d _s and d _s correspond to _us . Slope 3
1 _us and 31 _us have an angle of 60 with the side wall d _{v of the} recess d.
It was degree. At this point, the diameter of the shoulder D _sh is reduced. The right side, the left side and the lower side of the deformed pipe P _n-1 are concave curved surfaces 3
The shape was a little overhanging, 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 the forming stand at 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 Combined with. Protrusion 3 in the axial direction
Peripheral surfaces 32 _us , 32 _us on both sides of 2 _up are raised parts 32 _up
The side _faces of 32 _uv and 32 _uv were orthogonal to each other. When passing through the forming stand of the final stage n, the recessed portion d of the deformed pipe P _n-1 becomes a recessed portion D partitioned by the upper and lower rolls 32 _u and 32 _d and the left and right rolls 32 _r and 32 _l in mutually orthogonal planes. Become. At this time, the peripheral surfaces 32 _us , 32 _us and the side surfaces 32 _uv , 3
By 2 _uv , the corner portion of the deformed pipe P _n-1 is expanded to the corner angle θ = 90 degrees. In fact, when the shape of the obtained deformed pipe P _n was measured, the radius of curvature of the shoulder portion D _sh remained 0.8 times the wall thickness, and the sufficiently sharp recess D was obtained.
It was one with.

For comparison, the molding stand shown in FIG. 9 was used immediately before the final stage n-1 and was combined with the molding stand of the final stage n (FIG. 8b). The forming stand of FIG. 9 uses a roll having a convex crown on the lower roll 33 _d and the left and right rolls 33 _r and 33 _l so that the deformed pipe P _n-1 approaches the deformed pipe P _n of the final shape. Combined with caliber roll as roll 33 _u . Here, the upper roll 33 _u
Side surface 33 _uv , 3 of the ridge 33 _up formed in the axial center of the
The angle between 3 _uv and the peripheral surfaces 33 _us , 33 _us was set to 90 degrees. In the obtained deformed pipe P _n , a recess D having a large radius of curvature of the shoulder D _sh of 1.8 times the plate thickness was formed. As is clear from this comparison, a deformed pipe P _n-1 having a concave portion d having an acute shoulder is formed by the forming stand n-1 immediately before the final stage, and the shoulder is pushed by the forming stand at the final stage n. By opening, the diameter of the shoulder portion D _sh was reduced. As a result, the deformed tube manufactured according to the present invention gave a sharp impression and was excellent in designability and distinguishability. On the other hand, in the case where the molding stand shown in FIG. 9 was used immediately before the final stage n−1, the radius of curvature of the shoulder D _sh was large and the appearance was spoiled.

In the above embodiments, the case where the deformed pipe P _n having the rectangular recess D is roll-formed is taken as an example. However, the present invention is not restricted by this, and as long as the shoulder D _sh is pushed open at the final stage to reach the target corner angle θ, the concave D
The cross-sectional shape of can be changed arbitrarily. For example, when forming a recess having a triangular cross section, since the target corner angle θ is 120 degrees, the corner angle θ = 4 at the intermediate stage.
Form a recess with a shoulder between 0 and 70 degrees. Also, the corner angle θ smaller than the target angle is not limited to just before the final stage,
It may be attached at any stage before reaching the final forming stand.

[0015]

As described above, in the present invention, when a deformed pipe having a concave portion protruding inside the pipe is manufactured by the roll forming method, a corner angle smaller than the target angle is attached to the shoulder portion of the concave portion. Later, at the final stage, the shoulder angle is pushed open to adjust the corner angle to the target angle. Due to this push-opening, the diameter of the shoulder portion is reduced, and a deformed pipe product excellent in design and distinctiveness can be obtained.

[Brief description of drawings]

FIG. 1 Deformed tube having a recess protruding inside the tube

[Fig. 2] Metal flow during corner molding

[Figure 3] Model investigating metal flow during corner forming

Fig. 4 Relationship between material movement during forming and diameter reduction obtained from model experiments

FIG. 5: Deformed tube forming machine used in the embodiment of the present invention

[FIG. 6] Deformed tube having a recess

[Figure 7] Deformed tube with the final target shape

FIG. 8 shows the shape change during roll forming according to the present invention,
The shapes of the deformed tubes in the forming stand (a) immediately before the final stage and the forming stand (b) in the final stage are shown.

FIG. 9: Molding stand just before the final stage used for comparison

[Explanation of symbols]

20: Deformed tube forming machines 21, 22 ... 22n: Forming stand 25: Hydraulic cylinders 31 _u , 32 _u , 33 _u : Upper rolls 31 _r , 32
_r , 33 _r : right roll 31 _l , 32 _l , 33 _l : left roll 31 _d , 32
_d , 33 _d : lower roll 31 _up , 32 _up , 33 _up : raised portion 31 _uv , 32 _uv , 33 _uv : side surface of raised portion 31 _us , 32 _us , 33 _us : peripheral surfaces on both sides of raised portion P _n-1 : Deformed pipe formed by the forming stand n-1 immediately before the final stage P _n : Deformed pipe formed by the forming stand of the final stage n d, D: Recess D _sh : Shoulder of the recess θ:
Corner angle

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tsutomu Higashi 1 Tsurumachi, Amagasaki City, Hyogo Prefecture Nisshin Steel Co., Ltd.

Claims (2)

[Claims] 1. A corner angle θ of a shoulder that defines the recess at the final stage when roll-forming a deformed pipe having a recess protruding inward of the pipe on a part of its side surface by a multi-stage forming stand. Is made smaller than the target angle, and then the shoulder portion is pushed open so that the corner angle θ becomes the target angle in the final stage. 2. After forming a recess having a shoulder with a corner angle θ of 40 to 70 degrees, the corner angle θ is 90 at the final stage.
The method for manufacturing a deformed pipe according to claim 1, wherein the shoulder portion is pushed open so as to have a certain degree.