WO1997032676A1 - Method of manufacturing thin-walled pipe or product having similar cross section - Google Patents

Abstract

A method of manufacturing thin-walled pipes or products having a similar cross section with improved formability at a high speed without damaging or deforming their edges. Ordinary cold rolling units B1, B2-B4, CL, FS, SQ are used with which a belt conveyor comprising a flexible flat belt (1) is combined. A raw material (10) is placed on the flat belt (1) and passed through forming rolls, whereby the raw material (10) is cold rolled so as to be covered with the flat belt (1). This method can reduce the ratio of the wall thickness to the outer diameter (t/D x 100) of a pipe to less than 1%, and it also improves formability and speed without damaging or deforming pipe edges.

Description

 Specification

 Manufacturing method for thin-walled pipes and products with cross-sectional shapes similar to pipes

 The present invention relates to an improvement in a method of cold-roll forming a thin-walled strip continuously into a required closed cross-sectional shape like a tube by, for example, using a normal cold-roll forming apparatus. Combining a belt conveyor with a sinterable flat belt, placing the strip on a flat belt and passing it between the forming ports to form a cold port so that the strip is covered with the flat belt. Even with welded pipes with a thickness / outer diameter (t / DX 100) of 1% or less, thin-walled pipes that can be formed with good formability and high speed without causing so-called buckling or edge waves at the edge The present invention relates to a method for producing a product having a sectional shape similar to a pipe.

 Background art

 The cold roll forming method has been developed as a method for forming a relatively thin strip continuously and forming it into a required closed cross-sectional shape like a tube. However, various problems occur when the thickness of the strip is reduced compared to the dimensions of the configured cross section.

 For example, in the case of forming a welded pipe, if the thickness / outer diameter (t / Dx100) is 1% or less, the material constituting the seam is thin, so the buckling strength is low, and the edge It buckles and becomes wavy, making it impossible to form a uniform seam and causing poor welding. Similarly, in a general molding material, a so-called “wave” at an edge portion and a pocket wave at a flat portion are generated.

 The cause is related to the material properties and residual stress of the base material, but the direct cause is considered to be the suitability of the molding method.

Phenomenologically speaking, at each stage of forming, the edge of the material elongates in the longitudinal direction because it draws a very long trajectory compared to the center, so that during the final forming stage, The difference between the two appears as a twist in the product in the longitudinal direction. If the longitudinal direction is straightened, compressive stress will be generated in the stretched part, and if the buckling limit is exceeded, a buckling phenomenon, that is, edge waves will be generated at the edges.

 Therefore, the following technology has been adopted in the conventional roll forming method as a countermeasure against the edge wave of the buckling phenomenon.

 1. To reduce the elongation of the edge, configure a roll flower such as a downhill that has a shorter trajectory at the edge.

 2. Shorten the stand interval to reduce the return of the edge position due to spring back at each molding stage.

 3. Avoid the concentration of stress caused by the force applied near the edge, increase the contact area, and keep the longitudinal extension of the edge within the elastic limit. That is, the forming load is reduced and the roll diameter is increased.

 4. To ensure that the stress generated at the edge is always on the pull side, a tension is applied to the entire material, the center is particularly elongated, and the tension is controlled so as to reduce the difference between the extension and the edge.

 Despite the measures described above, roll forming has been particularly difficult for steel pipes when t / D is less than 1%.

 Therefore, instead of the roll forming method, a single forming was considered. In other words, instead of a roll, a hole-type shoe (Shoe) that forms the required forming cross section is installed, and the strip is formed by pulling it from the downstream side. Therefore, steel pipe with t / D of 1% or less can be formed sufficiently.

However, in shear forming, a large friction occurs between the material and the shoe, which may cause a scratch, and a large braking force is generated by the friction, which impairs the shape of the molded product. However, there is a drawback that a mechanism that generates large pulling rim is required. In addition, since this shoe is so worn that it cannot withstand long-term use, the machines actually operated are inefficient at low speeds of about 4 to 5 m / min, and The adjustment technique had the drawback that it had to rely on the skill of the operator. On the other hand, in the sizing process in pipe forming, a caterpillar method is used to generate sufficient tensile lica. In other words, half the segments are mounted on the surface of the flat belt, and the pipe is pulled out by the belt driving force while holding the pipe with the upper and lower segments via the slide guide.

 Disadvantages of this method are that the segments must be manufactured and used for each size of pipe, which requires a great deal of effort to change the size, and that the preparation of segments of various sizes requires a great deal of time. There are also problems that require cost. In addition, since a braking force is generated by friction between the slide guide and the belt, it is necessary to use a high torque type for the drive motor.

 The present invention solves the above-mentioned problems in the manufacture of thin-walled pipes, and manufactures thin-walled pipes and cross-sectional products similar to pipes that can be formed with good formability and at high speed without generating buckling or edge waves at edges. It is intended to provide a method. Disclosure of the invention

 The present invention relates to a forming device for forming a tube or a product having a sectional shape similar to a tube by using a plurality of pairs of rolls and / or shoes, and rotationally driving a pair of drive ports with a predetermined tension. The rotatable roll is rotatable together with the belt through the roll and / or the belt, and the flat belt deformed into a predetermined cross-sectional shape by the rotating roll and / or the contacting belt. This is a method for producing a thin-walled tube and a product having a cross-sectional shape similar to the tube, characterized by forming a band through the belt.

The operation of the present invention will be described by taking the forming of the breakdown portion as an example. Here, a flat belt having a width approximately equal to the width of the material is used to drive and idle rollers and a tensioner. This is the case where the apparatus shown in Fig. 1 of the embodiment in which the apparatus is combined with a forming roll stand and a forming roll stand is used. The combination of the holding roll (upper roll) and the guide roll (lower roll) is a normal roll forming roll flower. All rolls use idler rolls (non-driving rolls) in principle. Therefore, the roll regulates the cross-sectional shape of the belt, but rotates at a speed matching the belt speed due to contact with the belt.

 On the other hand, the material is formed between the guide roll, belt, and presser roll and travels at the same speed as the belt (see Figs. 3 and 4). Separation due to the difference between the belt and the spring back of the material is achieved by appropriately arranging guide rolls to maintain contact as much as possible, and by forming the material at the position of the holding roll while restraining the spring bag of the material. The belt is deformed and deformed at the location of the holding hole.Because the springback is constrained and the contact is made via the belt, it changes suddenly just before the roll, as in conventional roll forming. Smooth forming without bending.

 In other words, the external force for molding is dispersed by the belt, and local deformation, which is a distributed load, is less likely to occur. In addition, since the outer surface of the material is not in direct contact with the roll but through the belt, no slippage occurs due to the rotation of the roll. Therefore, roll marks do not occur on the outer surface. Description of the drawings

 FIG. 1 is an explanatory diagram viewed from a pass line, showing a configuration of a pipe mill to which the method for manufacturing a thin-walled pipe according to the present invention is applied.

 Fig. 2 is a vertical cross-sectional view of the forming roll at the first stage of the breakdown viewed from the downstream side of the material pass line.

 FIG. 3 is an explanatory longitudinal sectional view of a second-stage molding port using a flat belt according to the present invention, as viewed from the downstream side of a material path line.

Claims

 FIG. 4 is an explanatory longitudinal sectional view of a third-stage forming roll using a flat belt according to the present invention as viewed from the downstream side of a material pass line.  FIG. 5 is an explanatory longitudinal sectional view of a forming roll at one stage of a cluster using the flat belt according to the present invention as viewed from the downstream side of a material pass line.  FIG. 6 is an explanatory longitudinal sectional view of another forming roll in one stage of the cluster using the flat belt according to the present invention, as viewed from the downstream side of the material pass line.  FIG. 7 is an explanatory longitudinal sectional view of the forming roll in the fin pass stage using the flat belt according to the present invention, as viewed from the downstream side of the material pass line.  FIG. 8 is a longitudinal sectional view of a forming roll in a squeeze stage using a flat belt according to the present invention, as viewed from the downstream side of a material pass line.  FIG. 9 is an explanatory longitudinal sectional view of the forming roll in the sizing stage using the flat belt according to the present invention viewed from the downstream side of the material pass line. BEST MODE FOR CARRYING OUT THE INVENTION  In the present invention, a belt for forming a band material to be wrapped by being deformed or wrapped with the shape of the forming roll in a contact or abutment manner is formed by a plurality of forming belts on which a band material to be formed is placed and which is paired up and down or left and right Since it is necessary to rotate the idle roll passing through the gap between the pair of drive rolls, the idle roll is rotated with a predetermined tension over a span longer than the length of the forming roll group. In addition, the flat belt itself deforms with the shape of the forming roll, and is required to have excellent flammability because it can be bent to the same size as the specified pipe outer diameter in the fin pass, squeeze, or sizing process. At the same time, it is rotated and driven as described above, so it retains the bending strength required for molding when a predetermined tension is applied, and furthermore, it only returns to the flat belt at the pair of drive ports. It is necessary to have elasticity, and if such conditions are satisfied, the base fabric material and lining structure of the belt The composition, surface material, lamination state, material combination, etc., must be appropriately selected according to the type and physical properties of the strip to be molded.  It is desirable that the flat belt having flammability has excellent bending strength when a driving tension is applied, and has a bending strength at least equal to or higher than the band to be molded. It is desirable that the material has a large limit and the elongation is large in that range. However, the bending strength is only required to be able to hold the predetermined shape by suppressing the force of the molded material to return by springback. The belt strength is determined not only by the strength of the flat belt itself but also by factors such as the driving tension, the type of roll used, and the mechanical system such as reinforcement with rolls, etc., and these factors need to be considered comprehensively. is there.  In addition, in order to obtain such characteristics, as a flat belt, it is necessary to specify the weaving and weaving of the base fabric, to reinforce various fibers in the base fabric, or to laminate a plurality of resins and fibers. Techniques such as reinforcement and coating to obtain a predetermined coefficient of friction can be adopted. Any known material such as cloth, synthetic resin, rubber, and metal can be appropriately selected as the material of the belt.  In the present invention, a roll forming apparatus such as a conventionally known pipe mill or a cold roll forming apparatus used for forming a closed profile conforming to a pipe can be used as the forming apparatus. It is also possible to bend the belt to the required cross-sectional shape by bending the belt by appropriately combining a combination of flat rolls or arranging or shaping as well as forming rolls.The inventor has already proposed (Japanese Patent Publication No. 3-12975- 7) The use of a pipe mill with a forming port having an involute curve on the surface, which can produce pipes of the required diameter within the required range without changing rolls, will result in a flat bell of the width selected by the strip width. By simply exchanging the rolls, it is possible to form thin-walled tubes without changing rolls. Further, in the present invention, the flat belt has a simple configuration in which a span longer than the length of the forming roll group to be applied is rotated between a pair of drive rolls with a predetermined tension. It is easy to replace the belt, but even if the flat belt is wider than the belt material, it can be rotated and driven by overlapping the belt edge. It is possible to have versatility such as molding. Example 1  Fig. 1 is an explanatory view of the configuration of a pipe mill to which the method for manufacturing a thin-walled pipe according to the present invention is applied, as viewed from the path line.First, the first stage of the breakdown Bi is the conventional one shown in FIG. An intermediate opening 13 is disposed between the rollers 11 and 12, and the material 10 is sandwiched and formed by the upper rolls 14 and 15. Breakdown 2 stage B ₂ ~ the four stages B ₄ and cluster one step C _L, is applied to the molding method according to the belt of the present invention. The flat belt 1 is driven by a span longer than the above-mentioned forming rolls so as to pass between the above-mentioned forming ports while applying a predetermined tension to the driving rollers 1 and 3 and the tension roller 14. Each molding port of the drive is rotated in contact with the flat belt 1 and the material 10 placed on the flat belt 1. Breakdown stage B _2, as shown in FIG. 3, although the material 10 placed on the flat belt 1 passing between the upper and lower rolls 20 and 21, the lower roll 20 flat belt 1 is pressed to Kamiguchi one Honoré 21 The material 10 which is deformed along and placed thereon is also deformed and formed together with the flat belt 1. Moreover, breakdown four stages B ₄ also, as shown in FIG. 4, although the material 10 placed on the flat belt 1 passes between the upper and lower openings Ichiru 22 and 23, the flat belt 1 is kept to Kamiguchi Lumpur 23 The material 10 placed along the lower roll 22 after being deformed along the lower roll 22 is deformed and formed together with the flat belt 1. Here, normal solid rolls were used for the upper rolls 21 and 23 of the breakdown, but a configuration in which rubber tires can be used to change the amount of air or change the width of the tread using a pressing plate can also be used. Cluster part C _L, as shown in FIG. 5, to deform the flat belt 1 and the lower roll 30 at the left and right side rolls 31, 32 in an arc to forming shape the material 10 at upper roll 33 of the press. In addition, a configuration in which the roll 33 is not used may be adopted.  Subsequent fin pass section FS and squeeze section SQ are performed by conventional forming and welding equipment.  As shown in Fig. 9, the sizing part SZ is composed of upper and lower rolls 73 and 83 with the same upper and lower roll shape, and two sets of flat belts 70 and 80, which are divided into upper and lower parts. The upper and lower rolls 73 and 83 are driven to rotate by drive rollers 71, 72, 81, and 82 over a longer span than the group of upper and lower rolls. The belt is adjusted by adjusting the rolls to wrap the forming machine and the formed material 10. 9A shows the case of a large-diameter pipe, and FIG. 9B shows the case of a small-diameter pipe. However, the belt between the upper and lower rolls 73 and 83 is driven while being in contact with the molding machine, and is formed. The material 10 is pulled by a frictional force, and acts as a tension forming force on a formed portion.  As the guide rolls, right and left rolls of the same shape can be used, and two sets of belts with flat belts separated into left and right can be used.  Example 2  The fin path portion FS shown in FIG. 6 is formed by using the belt according to the present invention, and the guide belts 40 and 41 having the same shape on the left and right sides are used. The material 10 is formed into a substantially circular shape. Further, the fin pass portion FS shown in FIG. 7 uses guide rolls 50 and 51 having the same shape on the left and right, and uses the fin pass roll 52 which comes into contact with the opposed edge portion. The raw material 10 is formed by being held by guide rollers 50 and 51 on a flat belt 10 that has been deformed into a predetermined substantially circular shape, with the edge portion thereof abutting on a fin pass roller 52.  Example 3 The squeeze part SQ shown in FIG. 8 is formed by using the belt according to the present invention, and is used to deform the flat belt 10 into a circular shape with the same squeeze shoes 60, 61 on the left and right sides. The flat belt 10 is held in a predetermined circular shape by the pressing of the discs 60, 61 themselves and the injection from the apertures 62 provided on the inner surface of the arc of each squeeze disc 60, 61, and the material is held in the flat belt 10. The welding torch 63 is used for welding. Industrial applicability  In the present invention, as in the embodiments, a normal cold-hole forming apparatus is used, and a belt conveyer using a flammable flat belt is combined with the apparatus. Cold roll forming so that the band material is covered with a flat belt by passing it through allows localized concentrated loads to become distributed loads, without causing buckling or edge waves at the edges, and with good formability. It has the advantages of high speed molding, no scratches due to friction, and little wear on the tool.It also withstands high-speed operation for a long time without the need for adjustment technology due to wear. It is possible to efficiently manufacture a product having a similar sectional shape.