WO2003082495A1

WO2003082495A1 - Cold diameter reduction press molding method of metal pipe and metal pipe molded by that method

Info

Publication number: WO2003082495A1
Application number: PCT/JP2003/004269
Authority: WO
Inventors: Tsuyoshi Ishikawa
Original assignee: Nakayama Corporation
Priority date: 2002-04-03
Filing date: 2003-04-03
Publication date: 2003-10-09
Also published as: JP2003290849A; AU2003236357A1

Abstract

A cold diameter reduction press molding method of a metal pipe comprising a diameter reduction molding process for reducing the outer circumferential length of an original metal pipe having a noncircular transverse section as compared with the original outer circumferential length while press molding the original pipe to have a transverse section different from that of the original pipe; and a cold diameter reduction press molding method characterized by comprising a process for premolding an original metal pipe having a circular transverse section into a pipe having a transverse section different from that of the original pipe by roll molding using a premolding roll or first press molding using a premolding die, and a diameter reduction molding process for reducing the outer circumferential length of a premolded metal pipe as compared with that of the original metal pipe while remolding the premolded metal pipe to have a transverse section different from that of the premolded metal pipe by second press using a molding die.

Description

Specification

TECHNICAL FIELD The present invention relates to a cold-diameter breathing method for forming a metal tube and a metal tube formed thereby.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cold reducing a diameter of a metal tube, and a metal tube formed by reducing the diameter. In particular, the present invention relates to a method for reducing the diameter of a metal tube by press molding and a tube formed by the method. Background art

Conventionally, the following cold roll forming technology has been proposed for cold reduction of metal pipes.

For example, a steel pipe is cold-drawn by a three-roll reducer (Japanese Patent Laid-Open No. 7-51707). This is intended to suppress uneven thickness of the weld. The aim is to achieve this object by using a drawing process using three or more reducers and a two-roll type constant diameter machine with two or more stands.

Also, there has been proposed a method of manufacturing a steel pipe in which a predetermined shape is provided on an inner peripheral surface of a die and the die is drawn out using the predetermined shape to form a ridge-shaped uneven shape on the surface (Japanese Patent Application Laid-Open No. H07-19764). — 3 1 4 0 3 1). This is an invention in which the effect is enhanced by applying a strong compressive force and compressive deformation to the pipe wall thickness by combining a die with a gear-like shape on the inner peripheral surface and a plug for reducing the thickness of the raw pipe. It is.

Further, there has been proposed a cold roll forming method of an electric resistance welded steel pipe in which only the roll hole formed by the roll profile of the final roll stand located at the most downstream side is a perfect circle (Japanese Patent Application Laid-Open No. 6-1 / 1990). 4 2 7 18).

Each of the above-mentioned conventional technologies achieves each processing purpose, but the use of each device is limited to a specific one, and the size (angle) that can be processed is restricted. There was a problem that the number increased. The applicant of the present application has proposed a method of cold-diameter forming of a metal tube by cold-hole forming, in which an original tube made of a metal pipe is traversed in an elliptical shape, an elliptical shape, or a square shape by a preforming roll. A preforming step of forming a metal tube having a surface, and subsequently, using a reduced-diameter forming roll disposed downstream of the preforming roll, reducing the cross-sectional shape of the preformed metal tube. A diameter reduction forming step is performed in which the outer peripheral length is reduced from the outer peripheral length of the original tube while reshaping into a circular shape or another cross sectional shape different from the cross sectional shape of the preformed metal tube. A cold reduction roll forming method for metal pipes characterized by the above features and a metal pipe formed by this method have been proposed (PC TZJ P01 / 08310). Disclosure of the invention

According to the cold-diameter forming method for metal pipes by cold-hole molding proposed in the earlier patent application by the applicant of the present invention, a long product is produced and then cut to obtain a product. However, even if only short products are required, large roll forming machines and other equipment are required.

The present invention is based on the cold roll forming method of a metal pipe by cold roll forming proposed in the earlier patent application by the applicant of the present invention, and a metal pipe reduced in diameter from an original pipe made of a metal pipe. A metal tube reduced in diameter from the original tube and having irregularities formed on the inner and / or outer periphery, or an inner / outer double tube reduced in diameter from the original tube is easily and reliably formed. It is an object of the present invention to provide a cold diameter reduction forming method which can be carried out with smaller equipment and machines by using a cold reduction diameter forming method, and a metal pipe formed thereby.

In order to solve the above-mentioned problems, a cold-diameter forming method of a metal tube proposed by the present application is to press-mold a raw tube made of a metal pipe having a non-circular cross-sectional shape by using a forming die. A metal pipe having a cross-sectional shape different from the cross-sectional shape of the original pipe, and a diameter reducing step of reducing the outer peripheral length from the outer peripheral length of the raw pipe is performed. This is a diameter reduction press molding method.

In the above, having a non-circular cross-sectional shape by press molding using a molding die The diameter reduction forming step of reducing the outer peripheral length from the outer peripheral length of the original tube while forming the original tubes to have different cross-sectional shapes can be repeated a plurality of times until a desired diameter is obtained.

In this case, the forming die used in the diameter reducing forming step repeated a plurality of times is configured such that the cross-sectional shape of the metal tube formed by the immediately preceding press forming is changed to a different cross-sectional shape by the next press forming. The arrangement is adjusted and used.

This adjustment is performed, for example, by changing the arrangement position of the molding die used for the next press molding with respect to the arrangement position of the molding die used for the immediately preceding press molding, by using a metal pipe to be reduced in diameter. The position of the molding die used for the immediately preceding press molding and the arrangement of the molding die used for the next press molding, such as by rotating the shaft at a predetermined angle with respect to the center axis of the The position is displaced relatively each time.

The molding dies used for press molding in the above-described diameter reducing molding step may each be composed of a plurality of dies. By doing so, it is possible to prevent the pipe from sticking out due to the reduction in diameter and the occurrence of scratches and the like.

In this way, the number of dies and the shape of the dies used in the press forming in the diameter reduction forming process, each of which includes a plurality of dies, are variously determined, and the forming by the immediately preceding press forming is also possible. The cross-sectional shape of the metal tube to be formed can be formed into a different cross-sectional shape by the next press forming.

Further, another cold reduction forming method of a metal pipe proposed by the present application is to perform a roll forming using a preforming roll or a preforming die for a raw pipe made of a metal pipe having a circular cross-sectional shape. A preforming step of preforming a tube having another cross-sectional shape different from the cross-sectional shape of the original tube by the first press forming used, followed by a second press forming using a forming die In this way, the preformed metal tube is reformed into another cross sectional shape different from the cross sectional shape of the preformed metal tube, and the outer peripheral length is reduced from the outer peripheral length of the original tube. And a cold reduction press forming method for a metal tube.

In such a cold-diameter press-forming method for a metal tube, in the preforming step, the cross-sectional shape of the raw tube is polygonal, and the longitudinal tube extending from one end to the other end of the raw tube. After preforming into a polygonal shape in which the R of each corner in each successive cross section gradually changes from one end of the original tube to the other end, the second press molding using a molding die Thus, a cold reduction press forming method for a metal tube characterized in that a tapered tube is formed can be provided.

In either method, the preforming step (roll forming or first press forming using a preforming die) and the second press forming step can be alternately repeated until a desired diameter is obtained.

After repeating the preforming step (roll forming or first press forming using a preforming die) once or plural times, the second press forming step for diameter reduction forming is performed once or plural times. Can be repeated.

Even if the preforming step and the second press forming step are alternately repeated, the preforming step is performed once or more than once, and then the second press forming step for diameter reduction is performed once. Or, even if it is performed multiple times, in the forming process after the second breath forming process is first performed, the cross-sectional shape of the metal tube obtained by the immediately preceding forming differs depending on the next forming. It is desirable to be formed into a.

The first preforming step (roll forming or first press forming using a preforming die), the first second breath forming step, and the second preforming step (roll forming or preforming). First press forming using mold) Second second press forming step 1 Third preforming step (Roll forming or first press forming using preforming mold) 13th second press forming step Even if the pre-forming step and the second press-forming step are repeated alternately as in the press-forming step, the pre-forming step (roll forming or first press forming using a pre-forming die) Is performed once or more than once, and then even if the second press forming step for diameter reduction is performed once or more than once, the forming after the second press forming step is performed first In the process, the cross-sectional shape of the metal Arbitrary desirable to be formed into cross-sectional shape that is different depending on the shape.

In order for the cross-sectional shape of the metal tube formed by the immediately preceding molding to be formed into a different cross-sectional shape by the next molding, for example, the preforming roll or press used in the immediately preceding molding is used. The next pre-molding port with respect to the position of the molding die —The pre-forming or press-forming process can be performed by rotating the position of the metal mold for press forming or press forming by a predetermined angle with respect to the center axis of the metal pipe to be reduced in diameter. It is performed by displacing the used preforming rolls or press forming dies and the next preforming rolls or press forming dies each time. be able to. Even when the preforming step and the second press forming step are alternately repeated, the preforming step is performed once or more than once, and then the second press forming step for diameter reduction forming is performed. Even when performing one or more times, the preforming rolls or preforming dies used in the preforming process and the press forming dies used in the diameter reduction forming process are each of multiple It may be composed of a preforming roll or a plurality of preforming dies and a plurality of forming dies. By doing so, it is possible to prevent the pipe from sticking out due to the reduction in diameter, and the occurrence of scratches and the like.

As described above, each of the plurality of pre-forming rolls or the plurality of pre-forming dies, and the pre-forming roll or the pre-forming dies used in the pre-forming step composed of the plurality of the forming dies, and the diameter reducing forming step. Even if the number and shape of the dies used in the press forming dies are determined in various ways, the cross-sectional shape of the metal tube obtained by the immediately preceding molding differs depending on the next molding. It can be made to be molded. For example, when preforming a cross section 1a of a metal tube into a square shape in one preforming step, two preforming rolls 2a and 2b can be used as shown in Fig. 1 (a). However, as shown in FIG. 1 (b), four preforming rolls 2a, 2b, 2c and 2d can be used. In addition, a preformed metal pipe having the cross-sectional shape shown in FIGS. 1 (a) and (b) can be obtained by press forming instead of a preforming die for press forming.

In the above case, the plurality of preforming rolls used in the preforming step rotate partly or entirely in conjunction with each other, so that the metal pipe to be preformed moves with respect to the preforming rolls. Can be used.

Alternatively, the plurality of preforming rolls used in the preforming step are idle rollers, some or all of which are not receiving the driving force from the driving means, and the metal pipe to be subjected to the preforming is pushed in. By means of pressing from upstream into the hole of the preforming roll. Into the hole of the pre-formed roll by the punching means or by pulling it out of the hole of the pre-formed roll by the punching means, or from the upstream side into the hole of the pre-formed roll by the pushing means. It is possible to adopt a method in which the metal pipe to be preformed is moved with respect to the preforming roll by being pushed in and being drawn out from the hole shape of the preforming port to the downstream side by the drawing means. Wear.

In the case of roll forming, there are roll-driven roll forming method, roll-less driven draw forming method, and next-roll forming method, and all methods can realize preforming.

It should be noted that pipes formed by a cold drawing method may be used instead of preforming into a square shape.

In order to obtain a preformed metal tube having an elliptical or elliptical cross section 1a by a single preforming by roll forming or press forming, as shown in Fig. 1 (a), A single preforming roll or a preforming die for press forming is used.

In order to obtain a preformed metal pipe with a triangular polygonal cross section by one preforming by roll forming or press forming, two or three preformed rolls or presses are required. A preforming mold for molding is used.

Further, in order to obtain a preformed metal pipe having a pentagonal polygonal cross section by one preforming by roll forming or press forming, two, four or five preforming rolls or A preforming die for press forming is used.

In order to obtain a preformed metal pipe having a hexagonal cross-sectional shape by one preforming by roll forming or press forming, two, four or six preforming rolls or A preforming die for press forming is used.

As described above, in the cold reduction press forming method for a metal pipe according to the present invention, when the raw pipe made of a metal pipe has a circular cross-sectional shape, a roll using a preformed roll is used. The first press forming using a forming or preforming mold first requires a preforming step of preforming so as to have another cross sectional shape different from the cross sectional shape of the original tube.

On the other hand, when the cross section of the original pipe made of metal pipe is other than circular ( That is, in the case of a non-circular cross-sectional shape), the pre-forming step is not performed, and the cross-sectional shape is different from the cross-sectional shape of the original tube by press forming using a forming die. By reducing the outer peripheral length from the outer peripheral length of the original tube while forming, it is possible to perform the cold reduction press forming of the metal tube according to the present invention.

Here, the circular cross-sectional shape includes the case where the cross-sectional shape of a metal pipe subjected to diameter reduction processing, that is, the original pipe, is not only a perfect circle but also a substantially circular shape close to a perfect circle. is there. The non-circular cross-sectional shape refers to a metal pipe that undergoes diameter reduction processing, that is, the cross-sectional shape of the original pipe is square or polygonal, such as rectangular, square, pentagonal, hexagonal, or polygonal. Or, it refers to a shape that is not included in the concept of the above-mentioned circular cross-sectional shape, such as an elliptical shape and an elliptical shape.

According to the cold-diameter press forming method for a metal tube according to the present invention described above, the diameter can be easily reduced using a small press machine as compared with a roll forming machine. This press machine can use the press machine conventionally used for press forming, and can perform diameter reduction forming without requiring any specific mechanical equipment for swaging, heating, etc. .

In the above, each of the forming dies used for press forming in the diameter reducing step has an uneven portion on its surface, and the outer periphery of a predetermined position of the metal tube subjected to the diameter reducing by the forming die. On the surface, it is possible to form projections and depressions corresponding to the irregularities on the surface of the molding die.

That is, according to the cold diameter reduction press forming method of the present invention, the diameter reduction forming step including the outer peripheral surface of the preformed metal tube and the concave and convex portions such as a desired pattern dug into the surface in advance. Due to the contact with the surface of the molding die for press molding, it is possible to provide a convex or concave portion such as a desired pattern on the outer peripheral surface of the metal tube subjected to the diameter reduction simultaneously with the diameter reduction. For example, the metal pipe (round pipe 1b) shown in FIG. 3 (a) shows a part of a metal pipe formed by the method of the present invention, but has a concave and convex portion on the surface. By using a press forming die in the diameter forming step, a metal tube having a groove 1c formed in a part of the outer circumferential direction in the direction parallel to the axis is formed.

In the above-described drawing method using a die in the conventional cold reduction method for metal pipes, it is only possible to provide the same pattern in the longitudinal direction of the surface of the metal pipe. You. However, according to the method of the present invention, as described above, a desired pattern is dug into the surface of a molding die used for press molding in the diameter reduction forming step, so that the metal tube after the diameter reduction molding is formed. The desired shape / pattern can be provided at a desired position, for example, over the entire length in the circumferential direction or at a part in the long direction.

Further, in the above, the press forming step for the diameter reduction forming or the second press forming step can be performed in a state where the mold is inserted into the original tube.

This mold material is used by inserting it into the inside of the original pipe, that is, inside the metal pipe to be the original pipe when performing the diameter reducing step after the preforming step.

This mold material serves to support and fix the original tube during the press forming in the diameter reducing process, and also plays a role in preventing the original tube from being displaced during the diameter reducing forming. .

Further, by inserting the shape member into the original pipe, it is possible to prevent buckling from occurring inside the metal pipe even when the thickness of the original pipe is thin. In particular, when the cross-sectional shape of a metal pipe made of a metal pipe is non-circular, a mold material is inserted into the raw pipe during the diameter-reduction forming step by press forming using a forming die. This effectively prevents buckling inside the metal pipe.

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In addition, by appropriately adjusting the size of the outer peripheral length of the mold material, or by using mold materials having different outer peripheral lengths, the inner peripheral length can be reduced without changing the press forming die in the diameter reducing process. It is possible to form a metal tube having a reduced diameter and a metal tube having a reduced diameter.

Here, by using a mold material having predetermined irregularities on its outer peripheral surface as the mold material, a concave and convex portion is formed on the inner peripheral surface at a predetermined position of the metal tube at the same time as the diameter reduction molding. I can do it.

For example, on the inner peripheral wall of the metal tube whose diameter has been reduced, straight ridges and valleys extending in the longitudinal direction, that is, extending parallel to the central axis of the metal tube can be formed. Also

By arbitrarily changing the position where the mold material is placed in the metal pipe after preforming, the desired shape and pattern of irregularities are formed on the inner peripheral wall at the desired position of the metal pipe. You can also. In addition, by providing the desired shape and pattern irregularities on a part of the outer periphery of the mold material, the desired shape and pattern of the desired shape and pattern can be formed only on the desired portion of the inner peripheral wall of the metal tube having a reduced diameter. It can also be formed.

In this way, it is possible to form a reduced diameter metal pipe having a different inner circumference or a reduced diameter metal pipe having a different wall thickness, and to form the inner circumference wall at a desired position of the reduced diameter metal pipe. The desired shape and pattern can be formed at the same time by using the above-mentioned mold material.

Here, if a molding die for press forming in the diameter reducing step in which the above-mentioned surface is provided with the concave and convex portions is used, each of the inner peripheral wall and the outer peripheral wall of the metal tube to be reduced in diameter is used. It is possible to form the desired shape and pattern at the desired position at the same time.

For example, the arrangement position of the molding die for press molding in the diameter reduction molding step in which the concave and convex portions are provided on the surface, the position of the concave and convex portion provided on the surface of the molding die, The shape of the pattern formed on the inner periphery is adjusted by appropriately adjusting the arrangement position of the mold material inserted inside the original pipe and the position of the concave and convex portions provided on the outer peripheral surface of the mold material. And the shape and pattern formed on the outer periphery can be given a specific relationship.

In the above, the mold is a split mold, and a tapered pin that can slide in the axial direction of the split mold is disposed at the center of the split mold, and the tapered bin is a split mold. By sliding in the axial direction, the size of the outer diameter of the split mold can be adjusted.

For example, as shown in FIGS. 4 (a) and (b), the mold 50 is divided into four split molds 5 1 a

, 5 1b, 5 1c, 5 Id, with a tapered pin 53 inserted in the center, with bin 53 and split 5 1a, 5 1b, 5 1c, 5 1 d can be slid by keys 52a, 52b, 52c, 52d.After the diameter reduction process is completed, pin 53 is moved to 0 can be loosened so that it can be pulled out of the reduced-diameter molded tube.

By keeping the mold material in such a configuration, for example, after the diameter reduction forming process is completed, the tapered pin is slid in the axial direction of the split die to loosen the split die. Thus, the split mold (mold material) can be extracted from the reduced-diameter molded pipe. Also, by sliding the tapered pin in the axial direction of the split die, the outer diameter of the die (split die) can be arbitrarily adjusted, thereby reducing the diameter of the reduced-diameter tube having a desired inner diameter. Can be molded.

According to the cold-diameter press forming method of the present invention described above, the cross-sectional shape of the metal tube whose diameter has been reduced can be any shape such as a circle, an ellipse, an oval, a square, and a polygon. It is possible. The various cross-sectional shapes described above can be obtained by variously determining the number of dies used for the dies of each diameter reducing press and the shape of the dies.

In any of the cold reduction press forming methods for a metal tube according to the present invention, the metal tube which has been subjected to the diameter reduction over the entire length of the preformed metal tube is formed. You can also get.

In addition, it is possible to obtain a metal tube having only a part with a different outer peripheral length, in which only a part is reduced in diameter and the remaining part is simply formed. For example, it is possible to obtain a metal pipe having a stepped portion having a partly rectangular tube and a partly round tube having different peripheral lengths.

Further, it is possible to obtain a tapered metal pipe having a step-shaped outer peripheral length that changes smoothly in the longitudinal direction.

In addition, two types of pipes having two different shapes, in which the end of one pipe can be inserted into the end of the other pipe, are used, and the end of one pipe is connected to the other pipe. With the tube inserted into the end of the body, or with a tube of the same shape, the end of one tube is reduced in diameter, and the end of one tube is connected to the end of the other tube. With the other tube inserted,

The two tubes can also be joined by reducing the diameter by the cold-diameter press forming method of the present invention and crimping.

Furthermore, according to the cold reduction press forming method for a metal tube of the present invention, a reduction ratio of 3% or more can be achieved in the reduction forming step using a forming die. In addition, a diameter reduction ratio of 3% or more can be achieved by a preforming step and a subsequent diameter reduction step using a molding die.

In particular, a raw tube having a non-circular cross-sectional shape is formed by breath molding using a molding die. When the process of reducing diameter is repeated several times to reduce the outer peripheral length from the outer peripheral length of the original tube while forming it into different cross-sectional shapes, the cross-sectional shape of the metal tube formed by the immediately preceding press forming is By forming into a different cross-sectional shape by the next breath forming, when the preforming step and the second press forming step are alternately repeated, or the preforming step is performed once or multiple times After that, when performing the second press forming step for reducing the diameter once or more times, in the forming step after the first press forming step is performed, the metal pipe formed by the immediately preceding forming step is formed. By forming the cross-sectional shape into a different cross-sectional shape depending on the subsequent molding, the above-described diameter reduction ratio of 3% or more can be more reliably and easily achieved.

Next, in order to solve the above-mentioned problem, another cold reduction brace forming method for a metal pipe proposed by the present invention is as follows. The small-diameter inner pipe comprises a large-diameter metal pipe having a non-circular cross-sectional shape. The inner and outer double original tubes inserted into the outer tube are formed by press molding using a molding die so that the outer tube has another cross-sectional shape different from that of the outer tube. By a diameter reduction forming step of reducing the outer peripheral length of the outer tube from the initial outer peripheral length of the outer tube, a structure in which part or all of the inner peripheral surface of the outer tube is in close contact with the outer peripheral surface of the inner tube is provided. It is characterized by forming a double tube having the same.

Even in the case of forming this double tube, at least the outer peripheral length of the outer tube is formed by press molding using a molding die so that the outer tube has another cross-sectional shape different from that of the outer tube. In the diameter-reducing forming, the diameter of the outer tube is reduced from the initial outer length by a plurality of times until a part or the whole of the inner surface of the outer tube comes into close contact with the outer surface of the inner tube to form a double tube having a desired diameter. Can be repeated.

Also in this case, the molding die used in the diameter reduction molding process repeated a plurality of times is such that the cross-sectional shape of the outer tube formed by the immediately preceding press forming has a different cross-sectional shape due to the next press forming. It is desirable that the layout be adjusted and used. The method of this adjustment can be the same as in the case of the single tube described above.

In addition, as in the case of the single tube described above, in this case, each of the molding dies used in the diameter reducing molding step can be made up of a plurality of dies. In this way, the number and shape of the molds are determined in various ways, so that the outer tube formed by the immediately preceding press molding The cross-sectional shape can be made to have a different cross-section 开 K by the next breath forming as in the case of the single tube described above.

The number of times press forming for diameter reduction is performed depends on the material and thickness of the metal tube to be diameter reduced, for example, the material, wall thickness, ratio of diameter reduction, and diameter reduction of the outer tube and the inner tube. It can be determined according to the use of the formed metal tube.

Further, still another cold reduction press forming method for metal pipes proposed by the present application is that a small-diameter inner pipe is inserted into an outer pipe composed of a large-diameter metal pipe having a circular cross-sectional shape. A heavy original pipe is pre-formed by roll forming using a pre-forming roll or first press forming using a pre-forming die so that the outer pipe has a different cross-sectional shape. A preforming step, followed by a second press forming using a forming die, causes the preformed outer pipe to be crossed to another cross section having a different cross-sectional shape from that of the preformed outer pipe. A step of reducing the diameter of at least the outer peripheral length of the outer tube from the initial outer peripheral length of the outer tube while reshaping the outer tube into a planar shape; When forming an outer tube, press forming using a molding die The diameter-reducing forming at least reducing the outer circumferential length of the outer tube from the initial outer circumferential length of the outer tube while forming the cross-sectional shape to have another different cross-sectional shape is performed by a preforming step (roll forming or preforming). The first press molding using a molding die) and the second press molding step can be alternately repeated.

After the preforming step (roll forming or first breath forming using a preforming mold) is performed once or repeated plural times, the second press forming step is performed once or multiple times It can be repeated.

The number of times the pre-forming step and the second press-forming step are alternately repeated. One or more pre-forming steps, followed by one or more second press-forming steps. The number of times of the second press forming process depends on the material of the metal tube to be reduced in diameter.

The thickness can be determined according to, for example, the material of each of the outer tube and the inner tube, the wall thickness, the ratio of reducing the diameter, the use of the metal tube having the reduced diameter, and the like.

Even when the preforming step and the second press forming step are alternately repeated, after the preforming step is performed once or a plurality of times, the second press forming step is repeated. Even if it is repeated or repeated a number of times, in the forming step after the second press forming step is first performed, the cross-sectional shape of the outer tube formed by the immediately preceding forming depends on the next forming Desirably, it is formed into a different cross-sectional shape as in the case of the single tube described above.

Here, the preforming rolls or preforming dies used in the preforming process and the press forming dies used in the diameter reduction forming process are respectively a plurality of preforming holes or a plurality of preforming rollers. The second press forming process can be performed first by setting the number and shape of the dies in a variety of ways, including the pre-forming dies and a plurality of forming dies. In the case of a single pipe as described above, the outer pipe formed by the immediately preceding molding in the subsequent molding step can be formed into a different cross sectional shape by the next molding. Is the same as

Further, here, the plurality of preforming rolls used in the preforming step are such that the original tube which receives the preforming by partially or entirely rotating in conjunction with the preforming roll is connected to the preforming roller. The same method as that of the single pipe described above can be used for the moving method. Further, the plurality of pre-forming rolls used in the pre-forming step are idle rollers, some or all of which are not receiving the driving force from the driving means, and the original tube receiving the pre-forming is By being pushed into the hole of the preforming roll from the upstream side by pushing means, or by being pulled out from the hole of the preforming roll to the downstream side by the bow I punching means. Alternatively, the preform is received by being pushed into the hole of the preforming roll from the upstream side by pushing means and pulled out from the hole of the preforming roll to the downstream side by drawing means. The method in which the original tube is moved with respect to the preforming roll can be adopted in the same manner as in the case of the single tube described above.

Regardless of the single tube or double tube described above, in the case of performing preforming by roll forming in the preforming step in the cold reducing press forming method of the metal tube of the present invention.

As a method of moving the metal tube or the original tube relatively in the axial direction, either a method of moving the metal tube or the original tube, or a method of moving a molding machine having a preforming roll can be adopted. .

When performing preforming by roll forming in the preforming process, the metal pipe or raw In the case of moving the pipe, the following method can be adopted. For example, the preforming roll is composed of a plurality of rolls, and a metal tube or a raw tube which receives the preforming by rotating part or all of the plurality of rolls in each preforming roll in conjunction with each other. However, the method moves with respect to the preforming roll.

This is called a roll forming method (roll driving method), an example of which is shown in FIG. 2 (c). FIG. 2 (c) In the illustrated embodiment, reference numerals 41a, 41b, and 41c denote preforming rolls, respectively, in which the preforming rolls are continuously formed. It is repeated several times. If a roll having a plurality of preforming stands is arranged in tandem in this way, it is also possible to adopt a method in which only some of the stands are forcibly driven. For example, if a set of four rolls is used, only the set of two rolls can be forcibly driven. FIG. 2 (c) In the example shown, only two rolls of the preforming roll 4la and only the rolls 2a and 2c of the preforming roll 41c are forcibly driven.

In addition, the preforming rolls are each composed of a plurality of rolls, and some or all of the plurality of rolls in each preforming roll are idler rolls that have not received the driving force from the driving means. , One of the following methods could be used.

The first method is that a raw tube to be preformed is pushed from the upstream side into a hole shape of a preforming roll and a hole shape of a reduced-diameter forming roll by a pushing means, whereby a preforming roll of the original tube is formed. Is moved. This is called the next roll forming method (roll non-drive pipe pushing method), an example of which is shown in FIG. 2 (a). As the pushing means, a hydraulic cylinder or a hydraulic jack can be used. In the embodiment shown in FIG. 2 (a), the rod 5 of the hydraulic cylinder 4 is pushed out, whereby the round steel pipe 1 as the original pipe moves and is preformed by the preforming roll.

In the second method, the round steel pipe 1, which is the raw pipe to be preformed, is drawn out to the downstream side from the hole shape of the preforming roll 31 and the hole shape of the reduced diameter forming roll by a drawing means. The original tube is moved with respect to the preforming roll. You. This is called the draw forming method (roll-driven pipe pulling method), an example of which is shown in Fig. 2 (b). As the bow I punching means, a chuck for gripping the distal end side of the metal tube, a hydraulic jack for holding and pulling the chuck, or a chain for pulling the chuck while being driven in rotation can be used.

The third method is a combination of the first method and the second method, wherein the original tube to be preformed is pushed into the hole shape of the preforming roll from the upstream side by a pushing means, and is pulled out. By pulling out from the hole shape of the preforming roll to the downstream side by means, the original pipe is moved with respect to the preforming roll. Regarding the method of moving the metal tube, a preferable method can be selected from the above-mentioned methods according to the relationship of the diameter, wall thickness, length, molding speed, etc.

However, since the length of the hydraulic cylinder tends to be long in the next-roll forming method, it is necessary to devise ways to reduce this as much as possible. In the case of the draw forming method, it is necessary to devise a method that does not deform the tensile end. Furthermore, in the roll forming method, it is necessary to devise a method of driving the roll. The embodiment shown in FIGS. 2 (a) and 2 (b) describes a case where only one set of preforming steps is required. However, as shown in FIG. 2 (c), a plurality of tandemly arranged It is also possible to adopt a form in which preforming is performed a plurality of times by using the preforming hole.

In any of the above methods, the method of preforming a metal tube by a roll forming method in the preforming step has been described.However, the same effect can be obtained by a method using a press and a cold drawing method. It is possible to reduce the diameter of the preformed pipe formed by the above method.

In the cold-diameter press-forming method for a metal tube according to the present invention used for forming the above-mentioned double tube, the inner tube may be inserted over the entire length of the outer tube or only a part of the outer tube. Further, it is also possible to adopt a form in which the outer pipe is mounted on a part of the inner pipe.

If the inner tube is inserted over the entire length of the outer tube, the inner / outer double is formed over the entire length by the cold reduction press forming method applied to the formation of the double tube of the present invention described above. A double tube can be formed. In addition, if the inner pipe is inserted only in a part of the outer pipe, a double pipe in which only the portion where the inner pipe is inserted is formed thicker can be formed. Further, if the outer tube is provided around a part of the inner tube, it is possible to form a double tube in which only the portion where the outer tube is provided is thick. Further, in the cold reduction press forming method of the metal tube of the present invention used for forming the double tube, similarly to the case of the single tube described above, the forming dies used for the diameter reduction are each respectively. Since the surface of the metal tube is provided with projections and depressions, the diameter of the metal tube can be reduced while forming the depressions and projections on the surface of the metal tube whose diameter has been reduced by the molding die.

Further, the press forming step or the second press forming step for diameter reduction forming can be performed in a state where the mold material is inserted into the inner tube.

Here, a predetermined irregularity is formed on the outer peripheral surface of the mold material, and the irregularity can be formed on the inner peripheral surface at a predetermined position of the inner tube simultaneously with the diameter reduction molding.

In addition, tapered bins that are slidable in the axial direction of the split mold are arranged at the center of the split mold, and the tapered bins slide in the axial direction of the split mold. By moving the arm, the size of the outer diameter of the split mold can be adjusted.

The functions and effects obtained by adopting these embodiments are the same as those of the above-described single pipe.

As described above, according to the cold reduction press forming method for a metal tube of the present invention, an internal / external double tube can be easily manufactured.

In this method of forming a double pipe, for example, it is possible to form an inner / outer double pipe in which the inner pipe has a triangular cross section and the outer pipe has a circular cross section.

Further, in the diameter reduction forming step, the inner circumference of the outer pipe is reduced in diameter so that the inner circumference of the outer pipe is smaller than the outer circumference of the inner pipe, whereby the inner circumference of the outer pipe and the outer circumference of the inner pipe are formed. A double tube with a close-fitting structure can also be formed. In the double pipe manufactured by this method, the outer pipe of the inner pipe and the inner pipe of the outer pipe are in direct contact with uniform pressure, and the heat characteristics become uniform. Therefore, in any of the above-described methods for forming a double pipe, which can provide a double pipe product with significantly improved reliability, the same as described above, the circular shape Is a concept that includes not only a perfect circular shape but also a substantially circular shape close to a perfect circle. In addition, the non-circular shape means that the cross section of the outer tube has a rectangular shape such as a triangular shape, a square shape, a pentagonal shape, a hexagonal shape or a polygonal shape, or an elliptical shape, an oval shape, A shape that is not included in the concept of a circular shape.

According to the cold reduction press forming method of the metal tube used for forming the double tube of the present invention described above, it is not necessary to use an adhesive or the like at all. Therefore, according to the method of the present invention, it is possible to provide a double pipe product whose reliability is dramatically improved.

The inner tube may be made of the same material as the metal tube constituting the outer tube or a metal tube of a different material. Further, a non-metallic tube made of a different material from the metal tube constituting the outer tube may be used. For example, when the outer tube is a steel tube, the inner tube may be a tube made of aluminum, titanium, or a synthetic resin.

For example, the double pipe 10 shown in FIG. 3 (b) is manufactured by the method of the present invention, and the synthetic resin pipe 8 is disposed inside the round steel pipe 7. Since the round steel pipe 7 is reduced in diameter by the diameter reducing step by press forming, the inner peripheral wall of the round steel pipe 7 and the outer peripheral wall of the synthetic resin pipe 8 abut uniformly and at equal pressure to form an integral double pipe. Tubes are being manufactured.

Further, the inner tube is made of the same material as the metal tube forming the outer tube, a metal tube of the same material as the outer tube, or a non-metal tube of a different material from the metal tube forming the outer tube. After forming the inner and outer double pipes by the cold diameter reduction press forming method applied to the formation of double pipes, the formed pipes are used as inner pipes, which are inserted into large diameter metal pipes. By performing the cold reduction press forming method applied to the formation of the double tube according to the present invention, the inner and outer triple tubes can be formed. Similarly, it is possible to form multiple tubes such as a quadruple tube and a quintuple tube.

In any of the cold reduction press forming methods of the present invention applied to the formation of a double pipe, when the outer pipe is reduced in diameter by using the reduced diameter press forming, the gap between the reduced diameter press forming dies is reduced. It is possible to reduce the diameter of the outer tube without extruding the outer tube into the tube.

According to the cold reduction press forming method of the metal pipe used for forming the double pipe of the present invention described above, the double pipe can be formed using the reduced-diameter forming die. It is only necessary to clean the inner and outer tubes by washing. That is, it is not necessary to perform pretreatment such as heat treatment and mechanical treatment on the inner pipe and the outer pipe.

In addition, since a double tube can be formed using a reduced-diameter forming die, a special material is not required as a press die material, and surface treatment of the die is not required, so that it is inexpensive and efficient. A heavy tube can be formed.

In the above-described preforming step of the cold reduction press forming method for the metal pipe used for forming the double pipe of the present invention, at least a part of the inner peripheral wall of the outer pipe abuts on the outer peripheral wall of the inner pipe. By doing so, it is possible to fix the inner tube at a desired position and perform the diameter-reduction molding without causing displacement. Therefore, when the inner pipe is inserted only into a part of the outer pipe, and only the inserted part is to be formed to be thick, by doing so, only the target part can be accurately and thickly formed. Meat can be formed.

According to the cold reduction press forming method of the present invention described above, when the cross-sectional shape of the original pipe or outer pipe made of a metal pipe is circular, the preforming step and the subsequent reduction press forming once are performed. A diameter reduction ratio of 3% or more was achieved. In addition, when the cross-sectional shape of the original pipe or outer pipe made of metal pipe was other than circular, a diameter reduction rate of 3% or more could be achieved in one round of diameter reduction breath forming.

According to experiments conducted by the inventors, these diameter reduction rates were sufficiently possible up to 22%.

. The diameter reduction rate can be varied between 3% and 22% depending on the preforming step to be used and the form of the diameter reduction press mold.

For example, in the case of an iron metal tube with a wall thickness of 1.6 mm and an outer diameter of 42.7 mm, a pre-forming die equipped with three pre-forming dies is preformed into a triangular cross-section, and then Then, with a press molding machine equipped with three molding dies, a mold material is inserted into the preformed metal tube, and the apex of the triangle of the preformed metal tube is directed inward. By reducing the diameter in the compression direction, a reduction rate of 22% was achieved.

In addition, while using the same three pre-forming dies, only the relative position is changed, and by changing the pressing dies for the press forming in the reducing process, the diameter reduction ratio can be reduced.

% Round steel pipe with an outer diameter of 39.2 mm.

In the case of an iron metal pipe with a wall thickness of 1.2 mm and an outer diameter of 42.7 mm, Preforming into a rectangular cross section with a preforming stand equipped with four metal molds, and subsequently, a press forming machine equipped with four molding dies puts the mold material inside the preformed metal tube. After insertion, the diameter of the preformed metal tube was reduced in the direction of compressing the square apex toward the inside, achieving a diameter reduction ratio of 11.8%.

Also, while using the same four pre-forming rolls, only the relative position is changed, and by changing the press forming die in the diameter reducing step, the outer diameter at which the diameter reduction ratio becomes 5% can be obtained. A 0.5 mm round steel pipe was obtained.

Furthermore, in the case of an iron metal tube having a wall thickness of 2.3 mm and an outer diameter of 63.5 mm, a preforming stand equipped with four preforming rolls is preformed into a pentagonal cross section, and subsequently, With a press forming machine equipped with five forming dies, a mold is inserted into the preformed metal tube, and the pentagonal apex of the preformed metal tube is pressed inward. A diameter reduction ratio of 7.2% was achieved by reducing the diameter in the direction of reduction.

Also, while using the same four pre-forming rolls, only changing the relative position, and replacing the press forming die in the diameter reducing process, the outer diameter at which the diameter reduction ratio becomes 3% can be improved. A 1.4 mm round steel pipe was obtained.

Furthermore, even in the method of manufacturing a double pipe, the outer pipe is reduced in diameter by a combination of a single preforming step and a single press forming step using a forming die for press forming. Rates of 3% to 22% were possible.

When the metal pipe of the present invention manufactured by the method of the present invention was examined, when the cross-sectional shape of the original pipe was circular and the cross-sectional shape of the metal pipe after diameter reduction was circular, The result was that the diameter accuracy was equivalent to the outer diameter accuracy of the original tube before diameter reduction molding. Further, when the metal pipe of the present invention manufactured by the method of the present invention was cut and tested, it was found that the outer diameter of the cut surface was almost the same as before cutting.

The cold reduction press forming method for metal tubes proposed by the present invention has been described above. The metal pipe proposed by the present invention is formed by any of the above-described cold reduction press forming methods of the metal pipe of the present invention. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 (a) is a schematic sectional view illustrating a preforming step of the present invention, and FIG. 1 (b) is another schematic sectional view explaining a preforming step of the present invention.

FIG. 2 (a) is a perspective view illustrating an embodiment of an extrusion forming method employed in the preforming step of the present invention, and FIG. 2 (b) is employed in the preforming step of the present invention. FIG. 2 (c) is a perspective view illustrating an embodiment of a roll forming method employed in the preforming step of the present invention.

FIG. 3 (a) is a perspective view showing a metal tube of the present invention, which is a reduced-diameter tube formed by the method of the present invention and has a groove formed in a direction parallel to the axis on the outer periphery, (B) is a perspective view in which a part of the double pipe formed by the method of the present invention is cut and represented.

FIG. 4 (a) is a side view of a mold used when press molding is performed in the method of the present invention, and FIG. 4 (b) is a cross-sectional view of the mold shown in FIG. 4 (a). . FIG. 5 is a schematic cross-sectional view illustrating a step of reducing the diameter of a square steel pipe into a round steel pipe by press molding.

FIG. 6 is a schematic cross-sectional view illustrating a step of performing diameter reduction forming from a pipe having a circular cross-sectional shape. FIG. 6 (a) is a schematic cross-sectional view illustrating a preforming step by roll forming. FIG. 7 (b) is a schematic cross-sectional view for explaining a diameter reduction forming step by press molding. FIG. 7 is a schematic cross-sectional view for explaining a step of performing diameter reduction forming from a tube having a rectangular cross section. Figure (a) is a schematic cross-sectional view illustrating the process of reducing the diameter of a rectangular tube into an octagonal cross-section by a press die. Figure 7 (b) is a diagram of reducing the diameter to an octagonal cross-section. FIG. 3 is a schematic cross-sectional view illustrating a step of reducing the diameter of a press-formed pipe into a round steel pipe by press forming.

FIG. 8 is a schematic sectional view illustrating a step of forming a double pipe according to the present invention.

Fig. 8 (a) is a schematic cross-sectional view for explaining a step of preforming the outer tube into a rectangular cross-sectional shape by roll forming, and Fig. 8 (b) is reducing the diameter of the outer tube by press forming; It is an outline sectional view explaining a process of forming a double pipe (round steel pipe). BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. However, the respective configurations, shapes, and arrangements are only schematically shown to the extent that the present invention can be understood. The material of each configuration is merely an example. Therefore, the present invention is not limited to the embodiments described in the following embodiments, and can be changed to various embodiments within the technical scope understood from the description of the claims.

[Example 1]

A 4 Omm x 4 Omm square steel pipe 60 (thickness: 1.6 mm, outer circumference: 134 mm, length: 150 mm) is formed into a round steel pipe 63 by press forming. Fig. 4 (a), (b) Inserting the four-piece mold 50 shown in the figure into the square steel pipe 60, and reducing the diameter of the tape-shaped bin 53 while sliding it in the direction of the arrow 54. Went. Using four molding dies 61a, 61b, 61c, and 6Id shown in Fig. 5, press-mold in the directions of arrows 62a, 62b, 62c, and 62d to form round steel pipe 63 with an outer diameter of 4 Omm. The diameter was reduced. After the completion of the diameter-reduction forming, the bin 53 of the mold 50 was slid in the direction of the arrow 55 to loosen the mold 50 and pulled out from the round steel pipe 63. The outer circumference of the round steel pipe 63 was 125.7 mm, and was reduced in diameter by about 6.2%.

[Example 2]

Into a 4 Ommx 4 Omm square steel pipe (thickness: 1.6 mm, outer circumference: 134 mm, length: 15 Omm), insert a four-piece mold as shown in Figs. 4 (a) and (b) Then, diameter reduction was performed by press molding using four molding dies to form a regular octagonal cross-sectional shape. In this regular octagonal shape, the outer diameter was reduced to 129.8 mm.

After this, the above-mentioned four-piece mold material was extracted, and instead, eight-piece mold materials were inserted, press-formed using eight molding dies, and reduced in diameter to a round steel pipe with an outer diameter of 4 Omm. Was. The outer diameter of the reduced-diameter round steel pipe was 125.6 mm, which was reduced by approximately 6.2% from the square steel pipe with a non-circular cross-sectional shape as the original pipe.

[Embodiment 3]

JIS standard STK400-E—G (outer diameter: 42.7mmx thickness: 1.6mm, length: 150mm) is used as a raw tube, and four preforming rolls 71a, 71b, Preforming was performed using 71c and 71d.

Set the four preforming rolls 71a, 71b, 71c, 71d at the desired positions in the directions indicated by arrows 72a, 72b, 72c, 72d in Fig. 6 (a), and remove the original tube. Fig. 1 (b) was passed through the state shown in the figure, and preformed into a square tube 73 (Fig. 6 (b)) with a cross section of 39.5mm x 39.5mm.

Next, using four molding dies 74a, 74b, 74c, and 74d, press forming was performed from the directions of arrows 75a, 75b, 75c, and 75d to reduce the diameter to a round steel pipe 76 having an outer diameter of 40 mm. After the completion of the diameter reduction molding, the mold material was extracted from the round steel pipe 76. The diameter reduction rate from the original tube was 6.3%.

[Example 4]

JIS standard STK400—E-G (outer diameter: 42.7mmx thickness: 1.6mm, length: 150mm) is used as the original tube, and four of them are shown in Fig. 4 (a) and (b). Inserting the split mold material and preforming by press molding using four molding dies, the cross section indicated by reference numeral 73 in FIG. 6 (b) is 39.5 mm x 39.5 mm Was preformed into a square tube. Next, insert the four-piece mold material as shown in Figs. 4 (a) and (b) into the preformed tube, press-mold using four molding dies, and make an outer diameter of 40mm. Of a round steel pipe. The diameter reduction rate from the original tube was 6.3%.

[Example 5]

JIS standard STK400-E-G (outer diameter: 42.7 mm x thickness: 1.6 mm, length: 150 mm) was used as a raw tube, and preforming was performed using four preforming rolls. The four pre-formed rolls are set at desired positions in the directions indicated by arrows 72a, 72b, 72c and 72d in FIG. 6 (a), and the original tube is set as shown in FIG. 1 (b). It was preformed into a square tube 80 (Fig. 7 (a)) with a cross section of 39.5mm x 39.5mm.

Next, a four-piece mold as shown in FIGS. 4 (a) and (b) is inserted into this tube 80, and four molds 81a, 81b, 81c and 81d are used. , Arrow 82a,

It was press-formed from directions 82b, 82c and 82d, and reduced in diameter to an octagonal tube 83 having an outer diameter of 137 mm. After the completion of the diameter reduction molding, the mold material was extracted from the tube 83. Next, an eight-piece mold is inserted into this tube 83, and eight molding dies 84a, 84b, 84c, 84d, 84e, 84f, 84g, and 84h are used. (B) Press forming was performed in the direction of the arrow in the middle to reduce the diameter to a round steel pipe 85 having an outer diameter of 39 mm. After the completion of the diameter reduction molding, the mold material was extracted from the round steel pipe 85. The diameter reduction ratio was about 8.7%.

[Example 6]

JIS standard STK400-E—G (outer diameter: 42.7 mm x thickness: 1.6 mm, length: 150 mm) is used as the original tube, and four pre-formed rolls are used as shown in Fig. 1 (b). As a result, the original tube was preformed into a square tube having a cross section of 39.5 mm x 39.5 mm as shown by reference numeral 73 in Fig. 6 (b).

Furthermore, a second preforming was performed with four rolls to form a square tube having a cross section of 39. Ommx 39. Omm as shown by reference numeral 73 in FIG. 6 (b).

Then, it was press-formed using four molding dies, and the diameter was reduced to an octagonal tube with an outer diameter of 137 mm.

Next, it was press-formed using eight forming dies, and reduced in diameter to a round steel pipe with an outer diameter of 39 mm. The diameter reduction ratio was about 8.7%.

[Example 7]

JIS standard STK400-E—G (outer diameter: 42.7 mm x thickness: 1.6 mm, length: 15 Omm) is used as the original tube, and four pre-formed as shown in Fig. 1 (b) By mouth, this original tube was preformed into a square tube with a cross section of 39.5 mm x 39.5 mm as shown by reference numeral 73 in Fig. 6 (b).

Next, press molding was performed using four molding dies to form a round steel tube with an outer diameter of 39 mm. The diameter reduction ratio was about 8.7%.

[Embodiment 8]

J IS STK400-E—G (outer diameter: 42.7 mm x thickness: 1.6 mm, (Length: 150 mm) as the original tube, and as shown in Fig. 6 (a), this original tube is represented by reference numeral 73 in Fig. 6 (b) by four pre-formed rolls. Such a cross section was preformed into a 39.5 mm x 39.5 mm square tube.

Next, insert a four-piece mold as shown in Figs. 4 (a) and (b) into this tube, press-mold using four molding dies, and reduce to a round steel tube with an outer diameter of 40 mm. Diameter molded. After the completion of the diameter reduction molding, the mold material was extracted from the round steel pipe.

As shown in Fig. 6 (a), this round steel pipe is formed by four preforming rolls with a cross section of 37. Ommx 37. Omm as indicated by reference numeral 73 in Fig. 6 (b). Preformed into square tubes.

Next, insert a four-piece mold as shown in Figs. 4 (a) and (b) into this tube and press-form it with four molding dies to form a round steel tube with an outer diameter of 37 mm. Reduced diameter molding. After the completion of the diameter reduction molding, the mold material was extracted from the round steel pipe. The final diameter reduction was about 13.3%.

[Embodiment 9]

Fig. 4 (a), (b) 4 pieces as shown in the square steel pipe 60 of 40 mm x 40 mm square (thickness: 1.6 mm, outer circumference: 134 mm, length: 15 Omm) Pressing the four molds as shown in Fig. 5 with a split mold material having a concave-convex pattern on the surface, and press-molding it into a round shape with an outer diameter of 4 Omm The diameter was reduced and formed into a steel pipe. After the completion of the diameter reduction molding, the mold material was extracted from the round steel pipe. The outer circumference of the round steel pipe was 125.7 mm, and the inner wall of the round steel pipe had a pattern with a depth of about 0.2 mm corresponding to the uneven pattern formed on the surface of the section.

[Example 10]

4 Ommx 40 mm square steel pipe 60 (thickness: 1.6 mm, outer circumference: 134 mm, length: 15 Omm), 4 pieces as shown in Fig. 4 (a) and (b) Pressing the four molds, each with a vertical stripe pattern on the surface, as shown in Fig. 5, with the split mold material inserted, and reducing the diameter to a round steel pipe with an outer diameter of 4 Omm did. After the completion of the diameter reduction molding, the mold material was extracted from the round steel pipe. The outer circumference of the round steel pipe is 125.

At 7 mm, a vertical stripe pattern with a depth of about 0.2 mm was formed on the outer peripheral wall of the round steel pipe, corresponding to the concavo-convex pattern formed on the surface of the forming die. [Example 11]

JIS standard STK400—E—G (outer diameter: 42.7 mm x thickness: 1.2 mm, length: 150 mm) is used as a raw tube, which is used as four preforming rolls as shown in Fig. 1 (b). Was preformed into a square tube having a cross section of 37. Ommx 37.0 mm as shown by reference numeral 73 in Fig. 6 (b). Next, we tried to reduce the diameter of the round steel pipe to a round steel pipe with an outer diameter of 37 mm by press forming using four forming dies.However, during the diameter reduction process, buckling occurred inside and a round steel pipe was formed. Did not become.

Using the same original tube and preforming in the same process, insert the four-piece mold as shown in Fig. 4 (a) and (b) inside the preformed tube, When we tried to reduce the diameter of a round steel pipe with an outer diameter of 37 mm by press forming using four molds, we obtained a round steel pipe (outer diameter of 37 mm) without buckling.

[Example 12]

4 Ommx 40 mm square steel pipe 60 (thickness: 1.6 mm, outer circumference: 134 mm, length: 15 Omm), 4 pieces as shown in Fig. 4 (a) and (b) As shown in Fig. 5, four molding dies, each of which has a vertical stripe pattern on its surface, are inserted in a state where a molding material having a concave and convex pattern on the surface is inserted. And then reduced in diameter to a round steel tube with an outer diameter of 4 Omm. After the completion of the diameter reduction, the mold was removed from the round steel pipe. The outer circumference of the round steel pipe was 125.7 mm, and a pattern with a depth of about 0.2 mm corresponding to the concavo-convex pattern formed on the surface of the section was formed on the inner peripheral wall. Also, on the outer peripheral wall, a vertical stripe pattern having a depth of about 0.2 mm corresponding to the uneven pattern formed on the surface of the molding die was formed.

[Example 13]

53.5mmx 53.5mm square steel pipe (thickness: 1.2mm, outer circumference: 19 Omm, length: 15 Omm) to be the inner tube, JIS standard STK 400 -EG to be the inner tube (Outer diameter: 50.8mm x thickness: 1.2mm, length: 15 Omm) A round steel pipe was inserted and used as the original pipe.

As shown in Fig. 5, press forming was performed using four forming dies, and the outer tube (square steel tube) was reduced to an octagonal shape with an outer circumference of 187 mm. The diameter of the outer pipe (square steel pipe) was reduced to a double pipe where the center of each side of the inner pipe (square steel pipe) and a part of the inner pipe (round steel pipe) were in contact. [Example 14]

The double tube obtained in Example 13 was used as the original tube, and as shown in FIG. 7 (b), the diameter of the outer tube was reduced to 54 mm by press forming using eight forming dies. A double round tube was obtained.

[Example 15]

JIS standard STK400-EG (outer diameter: 63.5mmx thickness: 1.2mm, length: 150mm) round steel pipe 90 that becomes the inner pipe A round steel pipe 91 (diameter: 60.5 mm x thickness: 1.2 mm, length: 150 mm) was inserted and used as the original pipe.

As shown in Fig. 8 (a), the preforming using four preforming rolls 92a, 92b, 92c, and 92d results in a 60 mm x 60 mm Preformed into square tubes.

Subsequently, diameter reduction by press molding using four molding dies 94a, 94b, 94c, 94d is performed, and the outer diameter of the outer pipe 95 is 6 Omm, and the inner pipe (round steel pipe) 9 1) A double tube with the outer periphery closely adhered was obtained.

[Example 16]

The double pipe of Example 15 was used as a raw pipe, and as shown in FIG. 6 (a), four preformed holes were used to traverse the cross section indicated by reference numeral 73 in FIG. 6 (b). It was preformed into a square double tube with a face of 58.0 mm mx 58. Omm.

Then, press molding was performed using four molding dies to obtain a double tube having an outer diameter of 58.5 mm and a thickness of 2.4 mm.

[Example 17]

The double tube of Example 15 was used as a raw tube, and as shown in FIG. 6 (a), four preformed holes were used to traverse the cross section indicated by reference numeral 73 in FIG. 6 (b). It was preformed into a square double tube with a face of 57.0 m mx 57. Omm.

Next, press forming is performed using four forming dies, the outer diameter is reduced to an octagonal cross section of 197.5 mm, and then press forming is performed using eight forming dies. I got a tube.

[Example 18] The double pipe of Example 15 was used as a raw pipe, and as shown in FIG. 6 (a), four preformed holes were used to traverse the cross section as indicated by reference numeral 73 in FIG. 6 (b). The surface is preformed into a square double tube with a surface of 57. Om mx 57. Omm, and then, similarly, by four preforming rolls, as indicated by reference numeral 73 in FIG. 6 (b). It was preformed into a square double tube with a cross section of 55.0 mm x 55.0 mm.

Next, a pressurized mold was used to form a double tube having an outer diameter of 55. Omm.

[Example 19]

The double tube of Example 15 was used as a raw tube, and as shown in FIG. 6 (a), four pre-formed holes were used to traverse the cross section indicated by reference numeral 73 in FIG. 6 (b). The surface is preformed into a square double tube with a surface of 57. Om mx 57. Omm, and then, similarly, by four preforming rolls, as indicated by reference numeral 73 in FIG. 6 (b). It was preformed into a square double tube with a cross section of 55.0 mm x 55.0 mm.

Next, press forming is performed using four forming dies, the outer diameter is reduced to an octagonal cross section of 190.Omm, and then press forming is performed using eight forming dies, and the outer diameter is 55. I got a tube.

[Example 20]

JIS standard STK400—E—G (outer diameter: 60.5 mm, thickness: 1.2 mm, length: 15 Omm) was used as the original tube.

By using three preforming dies and press forming, the cross section of the raw tube is triangular, and in each continuous cross section in the longitudinal direction from one end of the raw tube to the other end. The shape was preformed in such a manner that the R at each vertex (corner) of the triangular shape gradually changed from one end of the original tube to the other end. At one end of the original tube, a triangular cross section with a side of 61 mm was formed. became.

One end is a round shape with an outer diameter of 6 Omm, the outer diameter gradually decreases toward the other end, and the other end has a round shape with an outer diameter of 49 mm. Using a mold, the preformed tube is reduced in diameter by press forming, and the one end A round taper tube having an outer diameter of 60 mm and an outer diameter of the other end of 49 mm was obtained. In the case of diameter reduction by press molding, a mold material as shown in Figs. 4 (a) and (b), which is tapered from one end to the other end, is preliminarily used. The tube was inserted into the formed tube to reduce the diameter. The cold-reducing press forming method for metal pipes according to the present invention includes various methods for forming a raw metal pipe by roll forming using a pre-forming roll or pre-forming by press forming using a pre-forming die. A preforming step of forming a metal tube having a cross-sectional shape of the following, followed by press forming using a forming die, thereby changing the cross-sectional shape of the preformed metal tube to a circular shape or the preforming. A diameter reducing step of reducing the outer peripheral length from the outer peripheral length of the original tube while reshaping the metal tube into another cross sectional shape different from the cross sectional shape of the metal tube.

Therefore, a reduced-diameter metal tube, a reduced-diameter metal tube having irregularities formed on the inner and / or outer circumference, or a reduced-diameter inner / outer double tube can be simply and Molding can be performed reliably.

According to the method of the present invention, it is possible to provide a metal tube having a very large thickness and a metal tube having a partly thick wall easily at a very low price as compared with the related art.

In the conventional press method, it was necessary to prepare and use mechanical equipment completely different from breath forming and diameter reduction forming. However, according to the present invention, it is particularly necessary to prepare new equipment and equipment. Therefore, a metal pipe having a desired outer diameter and wall thickness can be easily manufactured at low cost.

Also, in the case of metal pipes that require high strength in some parts, conventionally, it was necessary to use not only the part where this strength was insufficient but also the whole metal pipe with a thicker wall and a stronger metal pipe. . However, according to the present invention, it is possible to make only a portion requiring high strength a double tube, and to compensate for the lack of strength at that portion. Moreover, this can be realized at a very low cost as compared with the case where the whole is made of a thick metal tube or a high-strength metal tube.

By adjusting the position of the inner tube inserted into the outer tube, only the desired portion of the double tube manufactured by the method of the present invention can be accurately formed into a double tube. Conventionally, tailored structural steel pipes manufactured by welding pipes with the same outer diameter and different wall thickness have been used to compensate for some insufficient strength. Since the double pipe manufactured by the method proposed by the present invention can be formed into a double pipe only at a portion where the wall thickness is desired to be increased, it is necessary to provide an inexpensive alternative to such a steel pipe for tailored structure. Can be.

In addition, it is possible to simply and inexpensively provide a thick metal tube in which only a portion corresponding to a portion to be reduced in thickness by bending, paddle processing, hydroforming or the like is formed as a double tube.

Further, the metal pipe of the present invention (reduced diameter pipe or reduced diameter double pipe) manufactured by the method of the present invention is used as a raw pipe, and is again converted into a metal pipe having a circular, square or other irregular cross section. By forming, it is possible to easily, reliably, and inexpensively provide multiple steel pipes having circular, square, and other irregular cross-sections, which were conventionally very expensive.

Claims

The scope of the claims

1. A metal pipe having a non-circular cross-sectional shape is formed into a cross-sectional shape different from the cross-sectional shape of the raw tube by press molding using a molding die, A cold-diameter press forming method for a metal pipe, wherein a diameter-reducing step of reducing the outer peripheral length from the outer peripheral length of the original pipe is performed.

2. By the press molding using the molding die, the original tube having a non-circular cross-sectional shape is formed so as to have a different cross-sectional shape, and the outer peripheral length is reduced from the outer peripheral length of the original tube. 2. The cold-diameter press-molding method for metal tubes according to claim 1, wherein the diameter-forming step is repeated a plurality of times.

3. The molding die used for the diameter reduction molding step repeated a plurality of times is formed by forming the metal pipe formed by the immediately preceding press molding into a different cross-sectional shape by the next press molding. 3. The cold-diameter press-molding method for a metal tube according to claim 2, wherein the arrangement is adjusted so that the metal tube is used.

4. The molding die used in the press forming in the diameter reducing forming step is formed of a plurality of dies, respectively, any one of claims 1 to 3 characterized by the above-mentioned. The cold reduction press forming method for a metal tube according to the above.

5. The original pipe made of a metal pipe having a circular cross-sectional shape is roll-formed using a preforming hole or first press-formed using a preforming die, and the cross section of the raw pipe is formed. A preforming step of preforming into a tube having another cross-sectional shape different from the shape, and subsequently, the metal tube preformed by the second press forming using a forming die is subjected to the preforming. A metal forming step of reducing the outer circumferential length from the outer circumferential length of the original tube while reshaping the metal tube into another cross-sectional shape different from the cross-sectional shape of the drawn metal tube. Cold-reducing press forming method for tubes.

6. In the preforming step, the cross section of the raw pipe is polygonal, and the R of each corner in each of the continuous cross sections in the longitudinal direction from one end to the other end of the raw pipe is obtained. Is preformed into a polygonal shape that gradually changes from one end to the other end of the original tube, and then a tapered tube is formed by a second press molding using the molding die. 6. The cold reduction press forming method of a metal tube according to claim 5, wherein the method is performed.

7. The method according to claim 5 or 6, wherein the preforming step and the second press forming step are alternately repeated.

8. The method according to claim 5, wherein after the preforming step is performed one or more times, the second press forming step for reducing the diameter is performed one or more times. 7. The cold-diameter press-forming method for a metal tube according to claim 6.

9. In the forming step after the second press forming step is first performed, it is required that the cross-sectional shape of the metal tube formed by the immediately preceding forming be formed into a different cross-sectional shape by the next forming. 9. The cold-diameter press-forming method for a metal pipe according to claim 7 or 8, wherein

10. The preforming rolls or preforming dies used in the preforming step and the press forming dies used in the diameter reducing forming step include a plurality of preforming rolls or a plurality of preforming dies, respectively. 10. The cold reduction press forming method for a metal tube according to claim 9, wherein the method comprises a mold and a plurality of molding dies.

11. A plurality of the preforming rolls used in the preforming step rotate part or all of them in conjunction with each other, so that the metal pipe to be subjected to the preforming is formed on the preforming roll. The cold-diameter press-molding method for a metal tube according to claim 10, wherein the metal tube is moved with respect to the metal tube.

12. A plurality of the pre-forming rolls used in the pre-forming step are idle rollers, some or all of which do not receive the driving force from the driving means, and receive the pre-forming. By pushing the metal pipe from the upstream side into the hole of the preforming roll by pushing means, or by drawing out the hole from the hole of the preforming roll to the downstream by drawing means, or The preforming roll is pushed from the upstream side into the hole shape of the preforming roll by the pushing means, and is drawn out from the hole shape of the preforming roll to the downstream side by the drawing means, so that the preforming roll is received. 10. The cold-diameter press-forming method for metal pipes according to claim 10, wherein the metal pipe is moved with respect to the preforming roll.

13. The molding dies used in the diameter reducing step each have an uneven portion on the surface thereof, and the outer periphery of a predetermined position of the metal tube subjected to the diameter reducing by the molding die. The metal tube according to any one of claims 1 to 12, wherein projections and depressions corresponding to the projections and depressions on the surface of the molding die are formed on the surface. Cold reduction press forming method.

14. The press forming step for the diameter reduction forming or the second press forming step is performed in a state where a mold is inserted into the original tube. 13. The cold reduction breath forming method for a metal tube according to any one of the above items 3.

15. The mold member is provided with a predetermined uneven portion on its outer peripheral surface, and at the same time as the diameter reduction molding, a convex and concave portion is formed on the inner peripheral surface at a predetermined position of the metal tube. The method for cold-diameter breathing of metal tubes according to claim 14.

16. The mold is a split mold, and a taper-like bin slidable in the axial direction of the split mold is disposed at the center of the split mold, and the tapered bin is The metal pipe according to claim 14 or 15, wherein the outer diameter of the split die is adjusted by sliding the split die in the axial direction. Cold press forming method.

17. The method according to any one of claims 1 to 16, wherein a diameter reduction ratio in a diameter reduction step in press molding by the molding die is 3% or more. Cold reduction press forming method for metal tubes.

18. The diameter reduction ratio of the preforming step and the diameter reduction step of the subsequent diameter reduction step in press molding by a molding die is 3% or more, wherein the diameter reduction rate is 3% or more. 18. The cold reduction press forming method for a metal tube according to any one of items 16 to 16.

1 9. The inner / outer double original tube in which the small-diameter inner tube is inserted into the outer tube composed of a large-diameter metal tube having a non-circular cross-sectional shape is formed by press molding using a molding die. By forming at least the outer peripheral length of the outer tube to be smaller than the initial outer peripheral length of the outer tube while forming the outer cross-sectional shape of the tube so as to have another different cross-sectional shape, A cold-diameter press forming method for a metal tube, comprising forming a double tube having a structure in which a part or the whole of an inner peripheral surface of the outer tube is in close contact with an outer peripheral surface of the inner tube.

20. By the press molding using the molding die, the outer tube is formed so as to have another cross-sectional shape having a different cross-sectional shape. 20. The cold-diameter press-molding method for a metal tube according to claim 19, wherein the diameter-reducing forming to reduce the outer peripheral length of the outer tube from the initial outer length is repeated a plurality of times.

21. In the molding die used in the diameter reducing molding step repeated a plurality of times, the cross-sectional shape of the outer tube formed by the immediately preceding press molding differs depending on the next press molding. 20. The cold-diameter press-molding method for a metal tube according to claim 20, wherein an arrangement thereof is adjusted so as to obtain a planar shape.

22. The method according to any one of claims 19 to 21, wherein each of the molding dies used in the diameter reducing molding step comprises a plurality of dies. Cold reduction press forming method for metal tubes.

2 3. The inner / outer double original tube, in which a small-diameter inner tube is inserted into an outer tube composed of a large-diameter metal tube having a circular cross-sectional shape, is roll-formed using a pre-formed roll or preformed metal. A preforming step of preforming the outer tube into another cross sectional shape having a different cross sectional shape by a first press forming using a mold; and a second forming using a forming die. By breath forming, the preformed outer tube is reshaped into another cross-sectional shape different from the cross-sectional shape of the preformed outer tube, and at least the outer peripheral length of the outer tube is The step of reducing the diameter of the outer tube from the initial outer length to form a double tube having a structure in which part or all of the inner surface of the outer tube is in close contact with the outer surface of the inner tube. A method for cold reduction press forming of metal tubes.

24. While the outer tube is formed by press molding using the molding die so that the outer tube has a different cross-sectional shape, at least the outer peripheral length of the outer tube is set to the outer tube length. 24. The cold-shrinking of a metal tube according to claim 23, wherein said diameter-reducing forming to reduce the diameter from an initial outer peripheral length is performed by alternately repeating the preforming step and the second press forming step. Diameter breath molding method.

25. The method according to claim 23, wherein the second press-forming step is performed once or repeated a plurality of times after performing the pre-forming step once or after repeating the plurality of times. Cold reduction press forming method for metal pipes.

26. In the forming step after the second press forming step is first performed, the cross-sectional shape of the outer tube formed by the immediately preceding forming is changed so as to be different by the next forming. The gold according to claim 24 or 25, characterized by being molded Cold reduction press forming method for pipes.

27. The preforming rolls or preforming dies used in the preforming step and the press forming dies used in the diameter reducing forming step include a plurality of preforming rolls or a plurality of preforming dies, respectively. 27. The cold reduction press forming method for a metal tube according to claim 26, comprising a mold and a plurality of molds.

28. A plurality of pre-forming rolls used in the pre-forming step rotate a part or all of them in conjunction with each other, so that the original tube receiving the pre-forming moves with respect to the pre-forming rolls. 28. The method for cold reduction press forming of a metal tube according to claim 27, wherein:

29. The plurality of pre-forming rolls used in the pre-forming step are idle rollers, some or all of which are not receiving the driving force from the driving means, and The pipe is pushed from the upstream side into the hole shape of the preforming port by the sinking means, or is drawn out from the hole shape of the preforming roll to the downstream side by the drawing means. Or by being pushed into the hole of the preforming roll from the upstream side by a pushing means and being pulled out from the hole of the preforming roll to the downstream by a drawing means, 28. The cold-diameter press-molding method for a metal tube according to claim 27, wherein the original tube subjected to the preforming is moved with respect to the preforming roll.

30. The inner pipe is inserted over the entire length of the outer pipe or only in a part of the outer pipe, or the outer pipe is wrapped around a part of the inner pipe. The method for cold-pressing a metal tube according to any one of claims 19 to 29.

31. Each of the molding dies used for the diameter reduction molding has a convex and concave portion on its surface, and a concave portion and a convex portion are formed on the surface of the metal tube formed by the diameter reduction by the molding die. 30. The method for cold-diameter press-forming of a metal tube according to claim 19, wherein the diameter-reducing forming is performed.

32. The press forming step or the second press forming step for diameter reduction forming is performed in a state where a mold material is inserted into the inner tube.

30. The cold reduction press forming method for a metal tube according to any one of items 9 to 31.

33. The mold material has a predetermined uneven portion formed on the outer peripheral surface thereof, and the concave and convex portion is formed on the inner peripheral surface at a predetermined position of the inner tube simultaneously with the diameter reduction molding. 33. The cold-diameter press-forming method for metal tubes according to item 32.

3 4. The mold is a split mold, and a tape-shaped bin that can slide in the axial direction of the split mold is disposed at the center of the split mold, and the tapered bin is The metal tube according to claim 32 or 33, wherein the outer diameter of the split die is adjusted by sliding in the axial direction of the split die. Cold press forming method.

35. The metal tube according to any one of claims 19 to 34, wherein a diameter reduction ratio in a diameter reduction forming step using the molding die is 3% or more. Reduced diameter press forming method.

36. The diameter reduction ratio of the preforming step and the subsequent diameter reduction step of the molding die performed by the molding die is 3% or more, wherein the diameter reduction rate is 3% or more. 6. The cold-reducing press forming method for a metal tube according to any one of the above items 5.

37. A metal tube formed by a cold-diameter press molding method of the metal tube according to any one of claims 1 to 36.