Method and facility for manufacturing cold roll molding square steel tube

Abstract

To provide a method and a facility for manufacturing a cold roll molding square steel tube, which can improve feeding forces applied to respective thick steel plates during molding of the square steel tube from various rolls and a molding device.SOLUTION: The method for manufacturing the cold roll molding square steel tube uses a thick steel plate 90 as a base material, conveys the thick steel plate 90 in a conveying direction H to mold it into a cylindrical shape through cold roll molding, and then molds it into a square shape to manufacture a square steel tube 95. In a plurality of thick steel plates 90 continuously conveyed in the conveying direction H, the rear end of the thick steel plate 90 positioned on the front side in the conveying direction H and the front end of the thick steel plate 90 positioned on the rear side in the conveying direction H are connected, and the thick steel plate 90 positioned on the front side in the conveying direction H is conveyed in the conveying direction H by conveying, in the conveying direction H, the thick steel plate 90 positioned on the rear side in the conveying direction H and connected to the thick steel plate 90 positioned on the front side in the conveying direction H.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a manufacturing method and equipment for cold roll-formed square steel pipes, which use a thick steel plate as a base material and form the thick steel plate into a cylindrical shape by cold roll forming while transporting the steel plate in a predetermined transport direction, and then form the steel plate into a square shape to produce a square steel pipe. [Background technology]

[0002] Conventionally, as this type of cold roll-formed square steel pipe manufacturing equipment, there is equipment as shown in Patent Document 1. In the steel pipe manufacturing equipment of Patent Document 1, a coil (roll)-shaped steel plate having a plate thickness and width corresponding to the square steel pipe to be manufactured is prepared as a base material for the square steel pipe. Then, the coil-shaped steel plate is continuously discharged and passed through various rolls such as breakdown rolls in sequence to form a cylindrical steel pipe. Furthermore, a square steel pipe is formed by passing the cylindrically formed steel pipe through a sizing device or the like. In the steel pipe manufacturing equipment of Patent Document 1, the coil-shaped steel plate is formed into a square steel pipe by being conveyed toward the downstream side of the steel pipe manufacturing line while being fed by the feeding force of various rolls and forming devices. Here, the feeding force of various rolls and forming devices is integrally applied to the entire coil-shaped steel plate on the steel pipe manufacturing line.

[0003] However, in the steel pipe manufacturing equipment of Patent Document 1, the coiled steel sheet is flattened while tension is applied by a leveling device before passing through various rolls, which generates residual stress in the coiled steel sheet after flattening. Therefore, when forming a square steel pipe from the coiled steel sheet after flattening, the flat and corner parts are significantly work-hardened, which causes a problem that the ductility and toughness of the flat and corner parts are reduced.

[0004] Therefore, a cold roll-formed square steel pipe manufacturing facility has been developed that uses thick steel plates as the base material for square steel pipes, which do not require leveling by a leveling device. In this cold roll-formed square steel pipe manufacturing facility, by using thick steel plates as the base material for square steel pipes, work hardening of the flat plate parts and corner parts during the formation of the square steel pipes is suppressed, and square steel pipes with high ductility and toughness of the flat plate parts and corner parts can be manufactured. In addition, by using thick steel plates as the base material for square steel pipes, square steel pipes with large plate thicknesses that cannot be manufactured from coiled steel plates can be manufactured. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7306494 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in a cold roll forming square steel pipe manufacturing facility that uses a thick steel plate as the base material for a square steel pipe, a thick steel plate of a predetermined length is conveyed one by one to form a square steel pipe, and the delivery force from various rolls and forming devices is distributed and applied to each thick steel plate in the facility. Therefore, the delivery force applied to each thick steel plate is smaller than the delivery force applied to the coiled steel plate. Therefore, the thick steel plate being formed into a square steel pipe may stop or progress poorly in the various rolls or forming devices, and the thick steel plate may not be conveyed downstream of the steel pipe manufacturing line.

[0007] Therefore, the present invention aims to provide a manufacturing method and cold roll-formed square steel pipe manufacturing equipment that can improve the feed-out force applied by the various rolls and forming devices to each thick steel plate being formed into a square steel pipe. [Means for solving the problem]

[0008] The problem to be solved by the present invention has been described above. Next, the means for solving this problem will be described.

[0009] In other words, the manufacturing method for cold-roll-formed square steel pipes of the present invention is a manufacturing method for cold-roll-formed square steel pipes in which a thick steel plate is used as a base material, and the thick steel plate is cold-roll-formed into a cylindrical shape while being transported in a predetermined transport direction, and then formed into a square shape to produce a square steel pipe, in which, for a plurality of thick steel plates that are continuously transported in the transport direction, the rear ends of the thick steel plates located on the front side of the transport direction are connected to the front ends of the thick steel plates located on the rear side of the transport direction, and the thick steel plates located on the rear side of the transport direction that are connected to the thick steel plates located on the front side of the transport direction are transported in the transport direction, thereby transporting the thick steel plates located on the front side of the transport direction in the transport direction.

[0010] The manufacturing method for cold roll-formed square steel pipe of the present invention is a method of connecting the thick steel plate located on the rear side of the conveying direction with the thick steel plate located on the front side of the conveying direction in a process before forming the thick steel plate located on the rear side of the conveying direction into a square shape.

[0011] The manufacturing method of cold roll-formed square steel pipes of the present invention is a method in which the thick steel plate located at the front side of the conveying direction is pushed by the thick steel plate located at the rear side of the conveying direction, thereby conveying in the conveying direction.

[0012] The cold roll-formed square steel pipe manufacturing equipment of the present invention is a cold roll-formed square steel pipe manufacturing equipment that uses a thick steel plate as a base material, and manufactures square steel pipes by cold roll-forming the thick steel plate into a cylindrical shape while transporting the thick steel plate in a predetermined transport direction, and then forming the thick steel plate into a square shape.The equipment is equipped with a transport mechanism that transports the thick steel plate in the predetermined transport direction, and a connecting mechanism that connects the rear ends of the thick steel plates located on the front side of the transport direction to the front ends of the thick steel plates located on the rear side of the transport direction for multiple thick steel plates that are continuously transported by the transport mechanism, and the transport mechanism transports the thick steel plate located on the rear side of the transport direction that is connected to the thick steel plate located on the front side of the transport direction by the connecting mechanism in the transport direction, thereby transporting the thick steel plate located on the front side of the transport direction in the transport direction.

[0013] The cold roll-formed square steel pipe manufacturing equipment of the present invention is equipped with an angle forming device that forms the thick steel plate formed into a cylindrical shape into an angular shape, and the connecting mechanism connects the thick steel plate located at the rear side of the conveying direction to the thick steel plate located at the front side of the conveying direction before the angle forming device forms the thick steel plate located at the rear side of the conveying direction into an angular shape.

[0014] In the cold roll-formed square steel pipe manufacturing equipment of the present invention, the conveying mechanism conveys the thick steel plate located at the rear of the conveying direction and pushes the thick steel plate located at the front of the conveying direction, thereby conveying the thick steel plate located at the front of the conveying direction. Effect of the Invention

[0015] According to the manufacturing method and manufacturing equipment for cold roll-formed square steel pipes of the present invention, the sending force from the various rolls and forming devices is integrally applied to each thick steel plate being formed into a square steel pipe, so that the sending force applied to each thick steel plate in the equipment is improved. Therefore, each thick steel plate being formed into a square steel pipe can be smoothly transported toward the downstream side of the steel pipe manufacturing line without being stopped within the various rolls or forming devices. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing a first embodiment of a cold roll-formed square steel pipe manufacturing facility according to the present invention. FIG. [Figure 2A] FIG. 4 is a schematic view showing a first connecting method of thick steel plates in the cold roll-formed square steel pipe manufacturing equipment. [Figure 2B] FIG. 11 is a schematic view showing a second connecting method of steel plates in the cold roll-formed square steel pipe manufacturing equipment. [Diagram 3] FIG. 4 is a schematic diagram showing a second embodiment of the cold roll-formed square steel pipe manufacturing equipment according to the present invention. [Figure 4] FIG. 2 is a schematic diagram showing a method of connecting thick steel plates in the cold roll-formed rectangular steel pipe manufacturing equipment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a cold roll-formed square steel pipe manufacturing equipment 10, which is a first embodiment of the cold roll-formed square steel pipe manufacturing equipment according to the present invention, will be described.

[0018] As shown in Figure 1, the cold roll-forming square steel pipe manufacturing equipment 10 uses a thick steel plate 90 as a base material, and while transporting the thick steel plate 90 in a transport direction H, it cold rolls it to form it into a cylindrical shape, and then forms it into a square shape to manufacture a square steel pipe 95.

[0019] In the cold roll-formed square steel pipe manufacturing equipment 10, a thick steel plate 90 is prepared as a base material for manufacturing a square steel pipe 95. The thick steel plate 90 is a single steel plate having a predetermined plate thickness (9 mm to 40 mm) and width suitable for the square steel pipe 95 to be manufactured.

[0020] The square steel pipe 95 manufactured in the cold roll-formed square steel pipe manufacturing facility 10 has an outer diameter of 400 mm to 700 mm, a plate thickness of 9 mm to 40 mm, and a curvature radius of the outer corner of 2.5t±0.5t. The square steel pipe 95 has a yield point or strength of 295 N / mm 2 from 535N / mm2 , tensile strength is 400N / mm 2 from 670N / mm 2 The yield ratio is 90% or less, and the Charpy absorbed energy is 70J or more (flat plate and corners).

[0021] As shown in Fig. 1, in a cold roll-formed rectangular steel pipe manufacturing facility 10, a thick steel plate 90 is placed on a conveying device 15 and conveyed in a conveying direction H. The thick steel plate 90 conveyed by the conveying device 15 has edge portions 90f on both sides in the width direction cut and removed by a trimming device 16. Next, the thick steel plate 90 is formed into a gentle R-shape by a preforming device 17 so that the edge portions 90f on both sides in the width direction face each other, and is then gradually curved into an arc by a breakdown device 18 consisting of multiple breakdown rolls 18A.

[0022] The thick steel plate 90 curved into an arc is bent inward at a pair of vertical plate portions at the top in a cluster device 19 consisting of multiple cluster rolls 19A. The thick steel plate 90 curved into an arc is gradually formed into a circular tube by a fin pass device 20 consisting of multiple fin pass rolls 20A, and a cylindrical steel pipe 94 is press-formed with both edge portions 90f of the steel pipe 90 abutted against each other in the width direction. The steel pipe 94 enters a high-frequency resistance welding machine 21, where it is welded by a fusion method using heat, and then the outer bead is cut by a cutting device 22. The steel pipe 94 from which the outer bead is cut enters a sizing device 23, which is a square forming device that forms the thick steel plate 90 (steel pipe 94) into a square shape, and is reduced in diameter while still in a cylindrical shape by multiple rolls, and is then successively formed into a square shape by other multiple rolls. The steel pipe 94 is then cut to a predetermined length by a traveling cutting device 24 using a milling method, to become a square steel pipe 95 as a product.

[0023] In the cold roll-formed square steel pipe manufacturing equipment 10, the conveying device 15, various rolls (breakdown roll 18A, cluster roll 19A, fin pass roll 20A) and sizing device 23 form a conveying mechanism that conveys the thick steel plate 90 in the conveying direction H.

[0024] As shown in Figure 2A, a thick steel plate 90, which is the base material of a square steel pipe 95, has a first connecting portion 91 and a second connecting portion 92, which are connecting mechanisms, and is configured to be connectable to other thick steel plates 90 at both longitudinal ends of the thick steel plate 90.

[0025] The first connecting portion 91 is an uneven portion extending in a substantially hook-like shape in the width direction of the thick steel plate 90. The first connecting portion 91 is formed on one surface of the thick steel plate 90 and at one end of the thick steel plate 90 in the longitudinal direction so as to be the lower surface of the thick steel plate 90 and the front end of the thick steel plate 90 in the conveying direction H when the thick steel plate 90 is conveyed on the steel pipe manufacturing line of the cold roll-formed rectangular steel pipe manufacturing equipment 10. The first connecting portion 91 is composed of a concave portion 91a extending in the width direction of the thick steel plate 90 and a convex portion 91b extending in the width direction of the thick steel plate 90.

[0026] The second connecting portion 92 is a protruding portion extending in a generally hook-like shape in the width direction of the thick steel plate 90. The second connecting portion 92 is formed on the other surface of the thick steel plate 90 and on the other end portion in the longitudinal direction of the thick steel plate 90 so as to be the upper surface of the thick steel plate 90 and the rear end portion of the thick steel plate 90 in the conveying direction H when the thick steel plate 90 is conveyed on the steel pipe manufacturing line of the cold roll-formed rectangular steel pipe manufacturing equipment 10. The second connecting portion 92 is composed of a concave portion 92a extending in the width direction of the thick steel plate 90 and a convex portion 92b extending in the width direction of the thick steel plate 90.

[0027] The thick steel plate 90 is connected to another thick steel plate 90 by fitting the first connecting portion 91 into the second connecting portion 92 of the other thick steel plate 90 from above and below. Specifically, the thick steel plate 90 is connected to another thick steel plate 90 by fitting the concave portion 91a of the first connecting portion 91 into the convex portion 92b of the second connecting portion 92 of the other thick steel plate 90 and by fitting the convex portion 91b of the first connecting portion 91 into the concave portion 92a of the second connecting portion 92 of the other thick steel plate 90. 2A, when a plurality of thick steel plates 90 are continuously transported in the transport direction H, the second connecting portion 92, which is the rear end of the thick steel plate 90 located at the front side of the transport direction H, and the first connecting portion 91, which is the front end of the thick steel plate 90 located at the rear side of the transport direction H, are fitted together to connect the rear end of the thick steel plate 90 located at the front side of the transport direction H to the front end of the thick steel plate 90 located at the rear side of the transport direction H. In other words, the first connecting portion 91 and the second connecting portion 92 act as a connecting mechanism that connects two thick steel plates 90 that are continuously transported.

[0028] As shown in Fig. 1, in the cold roll-formed rectangular steel pipe manufacturing equipment 10, a thick steel plate 90 is connected to a thick steel plate 90 preceding it in the conveying direction H before being conveyed to the trimming device 16. Specifically, when the thick steel plate 90 suspended by a hanging conveying device (not shown) is lowered from above to below and placed on the conveying device 15, a first connecting portion 91 of the thick steel plate 90 suspended by the hanging conveying device and a second connecting portion 92 of the thick steel plate 90 conveyed preceding the trimming device 16 are fitted together, thereby connecting the two thick steel plates 90 conveyed consecutively.

[0029] In this way, two thick steel plates 90 that are transported in succession are connected, so that when the thick steel plate 90 located at the rear side of the transport direction H is transported in the transport direction H, the thick steel plate 90 located at the front side of the transport direction H is transported in the transport direction H. At this time, the thick steel plate 90 on the transport device 15 is transported to push the thick steel plate 90 located at the trimming device 16, thereby transporting the thick steel plate 90 located at the trimming device 16. In addition, the sending force of the transport device 15 is applied integrally to the multiple connected thick steel plates 90.

[0030] Furthermore, as the succeeding thick steel plate 90 is connected to the preceding thick steel plate 90, when the thick steel plate 90 is transported, in addition to the sending force by the transport device 15, the sending forces by the various rolls (breakdown roll 18A, cluster roll 19A, fin pass roll 20A) on the downstream side of the steel pipe production line and the sizing device 23 are integrally applied to the thick steel plate 90. Therefore, compared with the case where one thick steel plate 90 is transported, the sending force applied to each thick steel plate in the facility is improved. Therefore, each thick steel plate 90 being formed into a square steel pipe 95 can be smoothly transported toward the downstream side of the steel pipe production line without stopping, etc., in the various rolls or the forming device.

[0031] In addition, the configuration for connecting the thick steel plate 90 to other thick steel plates 90 at both longitudinal ends of the thick steel plate 90 may be a configuration in which thick steel plates 90A having third connecting portions 91A and fourth connecting portions 92A as shown in Figure 2B are connected to each other.

[0032] The third connecting portion 91A is a protruding portion extending in a rectangular column shape in the width direction of the thick steel plate 90A. The third connecting portion 91A is formed at one end of the thick steel plate 90A in the longitudinal direction so as to protrude from the front end face of the thick steel plate 90A in the conveying direction H when the thick steel plate 90A is conveyed on the steel pipe manufacturing line of the cold roll-formed rectangular steel pipe manufacturing equipment 10. The third connecting portion 91A is composed of a rectangular column portion 91c extending in the width direction of the thick steel plate 90A and a support portion 91d protruding in a flat plate shape from the end face on one side of the thick steel plate 90A to support the rectangular column portion 91c.

[0033] The fourth connecting portion 92A is a hole portion extending in the width direction of the thick steel plate 90A. The fourth connecting portion 92A is formed at the other end of the thick steel plate 90A in the longitudinal direction so as to be the rear end of the thick steel plate 90A in the conveying direction H when the thick steel plate 90A is conveyed on the steel pipe manufacturing line of the cold roll-formed rectangular steel pipe manufacturing equipment 10. The fourth connecting portion 92A is composed of a rectangular hole portion 92c formed in a rectangular shape and a flat hole portion 92d formed in a flat shape continuous with the rectangular hole portion 92c.

[0034] The thick steel plate 90A is connected to another thick steel plate 90A by fitting the third connecting portion 91A into the fourth connecting portion 92A of the other thick steel plate 90A from the left and right direction. Specifically, the thick steel plate 90A is connected to another thick steel plate 90A by fitting the rectangular column portion 91c of the third connecting portion 91A into the rectangular hole portion 92c of the fourth connecting portion 92A of the other thick steel plate 90A and by fitting the support portion 91d of the third connecting portion 91A into the flat hole portion 92d of the fourth connecting portion 92A of the other thick steel plate 90A. Here, as shown in Figure 2B, when multiple thick steel plates 90A are transported continuously in the transport direction H, the fourth connecting portion 92A of the thick steel plate 90A located on the front side of the transport direction H and the third connecting portion 91A of the thick steel plate 90A located on the rear side of the transport direction H are fitted together to connect the rear end of the thick steel plate 90A located on the front side of the transport direction H and the front end of the thick steel plate 90A located on the rear side of the transport direction H.

[0035] In the case of thick steel plate 90A, when the thick steel plate 90A is placed on the conveying device 15, the thick steel plate 90A is slid laterally from the side of the conveying device 15 to be conveyed, so that the third connecting portion 91A, which is the front end of the thick steel plate 90A being slid and conveyed, and the fourth connecting portion 92A, which is the rear end of the thick steel plate 90A preceding in the conveying direction H, are fitted together to connect the two thick steel plates 90A being conveyed in succession.

[0036] Furthermore, in the cold roll-formed square steel pipe manufacturing equipment 10, two thick steel plates 90 or thick steel plates 90A that are continuously transported are connected at the transport device 15 (upstream side of the trimming device 16), but as in the cold roll-formed square steel pipe manufacturing equipment 10A (second embodiment of the cold roll-formed square steel pipe manufacturing equipment according to the present invention) shown in Fig. 3, they may be connected downstream of the cutting device 22 and upstream of the sizing device 23 after welding by the high-frequency resistance welding machine 21. That is, in a process before forming the thick steel plate 90B (cylindrical steel pipe 94) located at the rear side of the transport direction H into a square shape among a plurality of thick steel plates 90B (a plurality of cylindrical steel pipes 94) continuously transported in the transport direction H, the thick steel plate 90B (cylindrical steel pipe 94) located at the rear side of the transport direction H may be connected to the thick steel plate 90B (cylindrical steel pipe 94) located at the front side of the transport direction H.

[0037] In the cold roll-formed square steel pipe manufacturing equipment 10A, the distance between the cutting device 22 and the sizing device 23 is larger than the distance in other rolls and forming devices. Therefore, when a square steel pipe 95 is manufactured by conveying one thick steel plate 90B without connecting it to other thick steel plates 90B, the cylindrical steel pipe 94 is difficult to convey toward the downstream side of the steel pipe manufacturing line when conveyed to the sizing device 23 by only the delivery force of the sizing device 23, and may stop or progress poorly in the sizing device 23.

[0038] Therefore, when the preceding cylindrical steel pipe 94 is transported to the sizing device 23, the front end of the following cylindrical steel pipe 94 is connected to the rear end of the preceding cylindrical steel pipe 94, and the preceding cylindrical steel pipe 94 is pushed by the following cylindrical steel pipe 94, thereby transporting the preceding cylindrical steel pipe 94 in the transport direction H. That is, in the process before the sizing device 23, which is a square forming device, forms the following cylindrical steel pipe 94 into a square shape, the following cylindrical steel pipe 94 located at the rear side of the transport direction H is connected to the preceding cylindrical steel pipe 94 located at the front side of the transport direction H, and the following cylindrical steel pipe 94 pushes the preceding cylindrical steel pipe 94.

[0039] In addition, by connecting the leading cylindrical steel pipe 94 to the following cylindrical steel pipe 94, the feeding force from the sizing device 23 and the feeding force from the squeeze roll 21A of the high-frequency resistance welding machine 21 are applied integrally to the leading cylindrical steel pipe 94, so that the leading cylindrical steel pipe 94 is smoothly transported toward the downstream side of the steel pipe production line without stopping or slowing down within the sizing device 23.

[0040] When two thick steel plates 90B (two cylindrical steel pipes 94) that are transported continuously are connected in a process before being formed into a rectangular shape (at a position upstream of the sizing device 23), a front protrusion 90t and a rear hole 90h are formed in the thick steel plate 90B, as shown in Figures 3 and 4.

[0041] The front protrusions 90t are a pair of angular protrusions provided on one end surface in the longitudinal direction of the thick steel plate 90, protruding from both ends in the width direction. The front protrusions 90t are formed on one end surface in the longitudinal direction of the thick steel plate 90B so as to protrude from the front end surface of the thick steel plate 90B when the thick steel plate 90B is transported on the steel pipe production line of the cold roll-formed rectangular steel pipe production equipment 10A. When the thick steel plate 90B is formed into a cylindrical steel pipe 94, the pair of front protrusions 90t abut against each other at the welded portion of the steel pipe 94 to form one angular protrusion.

[0042] The rear hole portion 90h is a pair of holes opened in a substantially rectangular shape at both ends in the width direction on the other end surface in the longitudinal direction of the thick steel plate 90B. The rear hole portion 90h is formed on the other end surface in the longitudinal direction of the thick steel plate 90B so as to be formed on the rear end surface of the thick steel plate 90B when the thick steel plate 90B is transported on the steel pipe production line of the cold roll-formed rectangular steel pipe production equipment 10A. When the thick steel plate 90B is formed into a cylindrical steel pipe 94, the pair of rear hole portions 90h abut against each other at the welded portion of the steel pipe 94, forming one hole portion into which the pair of front protrusions 90t can be fitted.

[0043] In the thick steel plates 90B, the rectangular protruding portions formed by the pair of front protruding portions 90t are fitted into the substantially rectangular hole portions formed by the pair of rear hole portions 90h, thereby connecting the cylindrical thick steel plates 90B together. Here, as shown in Fig. 4, when a plurality of thick steel plates 90B are formed into cylindrical steel pipes 94 and continuously transported in the conveying direction H, the pair of rear hole portions 90h of the steel pipe 94 located on the front side of the conveying direction H are fitted into the pair of front protruding portions 90t of the steel pipe 94 located on the rear side of the conveying direction H, thereby connecting the rear end of the steel pipe 94 located on the front side of the conveying direction H to the front end of the steel pipe 94 located on the rear side of the conveying direction H.

[0044] As described above, according to the manufacturing method of the square steel pipe 95 and the cold roll-forming square steel pipe manufacturing equipment 10, 10A, the sending force by the various rolls and forming devices is integrally applied to each of the thick steel plates 90, 90A, 90B being formed into the square steel pipe 95, so that the sending force applied to each of the thick steel plates 90, 90A, 90B in the equipment is improved. Therefore, each of the thick steel plates 90, 90A, 90B being formed into the square steel pipe 95 can be smoothly transported toward the downstream side of the steel pipe manufacturing line without being stopped within the various rolls or forming devices.

[0045] In addition, in the manufacturing method of the square steel pipe 95 and the cold roll-formed square steel pipe manufacturing equipment 10, 10A, the two thick steel plates 90, 90A, 90B that are transported continuously are connected by fitting the connecting portions of the thick steel plates 90, 90A, 90B together, but the two thick steel plates may also be connected by welding.

[0046] In the cold roll-formed square steel pipe manufacturing equipment 10, the thick steel plate 90 suspended by the hanging transport device is connected to the thick steel plate 90 transported in advance to the trimming device 16, but the thick steel plate 90 suspended by the hanging transport device may also be connected to the thick steel plate 90 before it is transported to the trimming device 16. [Explanation of symbols]

[0047] 10. Cold roll forming square steel pipe manufacturing equipment 10A Cold roll forming square steel pipe manufacturing equipment 90 thick steel plate 90A thick steel plate 90B thick steel plate 95 Square steel pipe H Transport direction

Claims

1. A method for manufacturing a cold roll-formed rectangular steel pipe, comprising the steps of: using a thick steel plate as a base material, forming the thick steel plate into a cylindrical shape by cold roll forming while conveying the thick steel plate in a predetermined conveying direction, and then forming the thick steel plate into a rectangular shape to manufacture a rectangular steel pipe, In the plurality of thick steel plates continuously transported in the transport direction, a rear end of the thick steel plate located on a front side in the transport direction is connected to a front end of the thick steel plate located on a rear side in the transport direction, The thick steel plate located on the rear side in the conveying direction and connected to the thick steel plate located on the front side in the conveying direction is conveyed in the conveying direction, so that the thick steel plate located on the front side in the conveying direction is conveyed in the conveying direction. A manufacturing method of cold roll-formed square steel pipes, characterized by the above.

2. In a process before forming the thick steel plate located on the rear side in the conveying direction into an angular shape, the thick steel plate located on the rear side in the conveying direction is connected to the thick steel plate located on the front side in the conveying direction. The method for manufacturing a cold roll-formed square steel pipe according to claim 1,

3. The thick steel plate located at the front side in the conveying direction is pushed by the thick steel plate located at the rear side in the conveying direction, and is conveyed in the conveying direction.

3. The method for producing a cold roll-formed square steel pipe according to claim 1 or 2,

4. A cold roll-forming square steel pipe manufacturing facility that uses a thick steel plate as a base material, transports the thick steel plate in a predetermined transport direction, forms the thick steel plate into a cylindrical shape by cold roll forming, and then forms the thick steel plate into a square shape to manufacture a square steel pipe, A conveying mechanism that conveys the thick steel plate in a predetermined conveying direction; A connecting mechanism is provided to connect a rear end of the thick steel plate located on the front side of the conveying direction to a front end of the thick steel plate located on the rear side of the conveying direction in the plurality of thick steel plates continuously conveyed by the conveying mechanism, The conveying mechanism conveys, in the conveying direction, the thick steel plate located on the rear side in the conveying direction and connected to the thick steel plate located on the front side in the conveying direction by the connecting mechanism, thereby conveying, in the conveying direction, the thick steel plate located on the front side in the conveying direction. This cold roll forming square steel pipe manufacturing equipment is characterized by:

5. A corner forming device is provided for forming the cylindrically shaped thick steel plate into a corner shape, The connecting mechanism connects the thick steel plate located on the rear side in the conveying direction to the thick steel plate located on the front side in the conveying direction before the corner forming device forms the thick steel plate located on the rear side in the conveying direction into an angular shape.

5. The cold roll-formed square steel pipe manufacturing facility according to claim 4,

6. The conveying mechanism conveys the thick steel plate located on the rear side in the conveying direction, and pushes the thick steel plate located on the front side in the conveying direction, thereby conveying the thick steel plate located on the front side in the conveying direction.

6. The cold roll-formed square steel pipe manufacturing facility according to claim 4 or 5,

Images