JP2005324255A - Method for manufacturing round steel tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a round steel tube, which can manufacture a round steel tube without performing manual conditioning work even when the round steel tube has a thick wall and a large diameter, can improve the quality of weld zone, and can easily and securely manufacture the round steel tube having no residual stress and sufficient toughness. <P>SOLUTION: A steel plate 1 with a specified width having grooves 2 at its both ends in a width direction is bent by press forming at a plurality of places across the width so that straight portions 3a and 3b with a desired length remain and the portion between the straight portions is bent to an arc 3c, at both ends and intermediate specific portions across the width. The bent steel plate 3 is formed to a semi-finished round steel tube 5 by welding the groove portions of the bent steel plate 3 while the groove portions are made to butt against each other. After the whole semi-finished round steel tube is heated, faces 22 and 25 to be formed are passed for hot forming between a plurality of forming rolls 21 and 24 with a semicircular shape corresponding to the final radius. This enables the semi-finished round steel tube to be formed by a few times of press forming and welding, and the round steel tube can be manufactured easily, securely and efficiently by passing the semi-finished round steel tube between a plurality of forming rolls for hot forming. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a round steel pipe employed to obtain a large-diameter, thick-walled round steel pipe used for, for example, a building pillar.

Conventionally, this type of round steel pipe has been manufactured by the following method. That is, a pipe original plate having a predetermined width and a predetermined length is prepared, and end bending of a predetermined width is performed by pressing on an end portion in the width direction of the pipe original plate. Next, the end portion of the pipe original plate that has been bent is further pressed so as to be bent so that the cross-sectional shape is substantially U-shaped. And it shape | molds so that a cross-sectional shape may become a substantially circular shape by the press work means which consists of a pair of shaping | molding die which has a semicircular shaping | molding surface. At this time, the concave portion and the convex portion are engaged. There is also a method in which the cross-sectional shape is formed into a substantially circular shape and then welded between end portions (joint portions) (see, for example, Patent Document 1).
JP-A-9-234511 (page 3-5, FIGS. 1 and 2)

  However, according to the above-described conventional method, the manufactured pipe has a substantially circular cross-sectional shape and hardly forms a perfect circle. To make a perfect circle, manual refining work must be performed for a long time. I must. In addition, tensile and compressive residual stresses are generated by bending, resulting in low buckling strength. Therefore, when performing welding, cutting or hot dip galvanizing, etc., these residual stresses can be released. There is a risk of causing cracks and deformations that cannot be controlled. Furthermore, apart from the production of thin-walled pipes, the above-mentioned problems become noticeable when producing thick-walled pipes.

  For example, as a thick bending method, there is a method of forming a substantially circular shape by pressing a large number of locations in the width direction (for example, 40 to 50 locations when the diameter is 600 mm). In this case, the manufacturing time is increased by pressing at a large number of places, and in order to obtain a perfect circle, a manual refining operation must be performed for a long time.

  Therefore, the invention described in claim 1 of the present invention can be obtained without performing manual refining work, even if it is thick and large in diameter, and can improve the quality of the welded portion, and can further reduce residual stress. It is an object of the present invention to provide a method of manufacturing a round steel pipe that can easily and reliably manufacture a round steel pipe having no toughness.

  In order to achieve the above-described object, a method for manufacturing a round steel pipe according to claim 1 of the present invention is a method of press forming a steel plate having a predetermined width with grooves formed at both ends in the width direction, at a plurality of intermediate positions in the width direction. Thus, a straight portion having a desired length remains at both end portions in the width direction and a specific portion in the middle, and the straight portion is bent as an arc portion, and the bent portion is formed at the groove portion. A semi-formed round steel pipe is formed by welding and joining in the state of considerable contact, and after heating the entire semi-formed round steel pipe, the forming surface is formed between a plurality of forming rolls having a semicircular shape corresponding to the final radius. It is characterized by hot forming through.

  Therefore, according to the invention of claim 1, a semi-formed round steel pipe can be formed by a small number of press forming and welding joints, and a round steel pipe can be produced by hot forming through a plurality of forming rolls. And even if the round steel pipe is thick and large diameter, it can be obtained without manual refining work, the quality of the weld can be improved, there is no residual stress, and sufficient toughness It will have.

  Moreover, the manufacturing method of the round steel pipe of Claim 2 of this invention WHEREIN: The structure of Claim 1 mentioned above WHEREIN: The steel plate of the width | variety corresponding to a half-round steel pipe is formed by press molding of the middle two places in the width direction, A straight portion having a desired length remains at each of both end portions and the central portion in the width direction and is bent into a U shape with an arc portion between the straight portions, and a pair of U-shaped bodies are It is characterized in that a semi-formed round steel pipe is formed by welding in a state where the portions are substantially in contact with each other.

  Therefore, according to the invention of claim 2, a semi-formed round steel pipe can be formed by four press moldings and two welding joints, and a round steel pipe is manufactured by hot forming through a plurality of forming rolls. obtain.

  And the manufacturing method of the round steel pipe of Claim 3 of this invention WHEREIN: The structure of Claim 1 mentioned above WHEREIN: The width direction is performed by press-forming the steel plate of the width | variety corresponding to a round steel pipe in the middle four places in the width direction. A straight portion of a desired length remains at each of both end portions and the middle three portions, and the straight portion is bent into a substantially circular shape with an arc portion between the straight portions, and the groove portion of this circular body is brought into substantial contact. In this state, a semi-formed round steel pipe is formed by welding and joining.

  Therefore, according to the invention of claim 3, a semi-formed round steel pipe can be formed by four press moldings and one weld joint, and a round steel pipe is manufactured by hot forming through a plurality of forming rolls. obtain.

  According to claim 1 of the present invention described above, a semi-formed round steel pipe can be formed by a small number of press forming and welding joints, and the round steel pipe can be easily and reliably formed by hot forming through a plurality of forming rolls. And can be manufactured efficiently. And even if a round steel pipe is thick and has a large diameter, it can be efficiently obtained in a short time without performing manual refining work. Furthermore, the quality of the weld can be improved, and there is almost no residual stress, high buckling strength can be obtained, excellent secondary weldability and sufficient toughness, especially for building columns. A suitable round steel pipe can be provided.

  According to claim 2 of the present invention described above, a semi-formed round steel pipe can be formed by four press moldings and two welded joints, and hot forming by passing between a plurality of forming rolls. Can be manufactured easily and reliably and efficiently.

  According to the third aspect of the present invention described above, a semi-formed round steel pipe can be formed by four press moldings and one welding joint, and hot forming by passing between a plurality of forming rolls. Can be manufactured easily and reliably and efficiently.

[Embodiment 1]
Below, Embodiment 1 of this invention is demonstrated based on FIGS. 1-4.
First, as shown in FIG. 1A, a steel plate 1 having a width (an example of a predetermined width) W and a predetermined length corresponding to a half round steel pipe is prepared. Here, the groove | channel 2 for welding is formed in the both ends of the width direction in the steel plate 1. As shown in FIG. Next, the steel plate 1 is bent and formed into a U shape by press forming with a pressing means. As shown in FIG. 1B, the pressing means 30 includes a fixed lower mold 31 and an upper mold 33 that can move toward and away from the lower mold 31. An upward concave molding surface 32 is formed on the lower die 31, and a downward convex molding surface 34 is formed on the upper die 33.

  Therefore, as shown in FIG. 1B, after the upper mold 33 is moved away from the lower mold 31 and one end side of the steel plate 1 is set on the lower mold 31, the upper mold 33 is moved with respect to the lower mold 31. As shown in FIG. 1C, the one end side of the steel plate 1 can be bent and formed by the first press forming by the pressing means 30. Next, the upper mold 33 is moved away from the lower mold 31 and the other end side of the steel plate 1 is set on the lower mold 31, and then the upper mold 33 is moved closer to the lower mold 31 as shown in FIG. As shown in (d), the other end side of the steel plate 1 can be bent by the second press forming by the pressing means 30.

  Thus, the steel plate 1 can be made into a U-shaped body (an example of a bending formed body) 3 by press forming at two intermediate positions (twice) in the width direction of the steel plate 1. When press forming in this way, when the steel plate 1 is set on the lower mold 31, the U-shaped body 3 is placed at both end portions in the width direction by leaving both end portions out of the press forming range. The straight part 3b having a desired length remains. In addition, when the press forming is performed twice on the steel plate 1, the U-shape is adjusted by adjusting the press width with respect to the width W of the steel plate 1 so that an unpressed range is generated in the central portion of the steel plate 1. In the body 3, the straight portion 3a having a desired length remains in the central portion. And it will be in the state by which the circular arc part 3c was bent and formed between the straight part 3a and both the straight parts 3b (an example of a specific part). Here, the arc portion 3c is bent and formed with a radius r smaller than the final radius (diameter of the round steel pipe) R, and the concave molding surface 32 and the convex molding surface 34 are formed corresponding thereto.

  Then, as shown in FIG. 1 (e), the end portions of the pair of U-shaped bodies 3, that is, the portions of the groove 2 are brought into substantial contact, and then welding means (not shown) acts between the grooves 2. By doing so, as shown in FIG. 1 (f), the grooves 2 are joined by welding 4 to form a semi-formed round steel pipe 5. Here, the semi-formed round steel pipe 5 includes a pair of straight portions 5a located between the welds 4 and a pair of straight shapes located between the welds 4 as shown by phantom lines in FIG. 1 (f) and FIG. A state is formed by the portion 5b and a total of four arc portions 5c located between the straight portions 5a and 5b. Each arc portion 5c has a radius r smaller than the radius R of the round steel pipe 6 shown in FIG.

Next, as shown in FIG. 2, the semi-formed round steel pipe 5 is put into a heating furnace (an example of heating means) 18 and heated. The heating furnace 18, a high frequency, the gas is such as by heating form oil, heating the entire Te than the (. Containing _{A 3} transformation point) 600 to 1000 ° C..

  Then, the semi-formed round steel pipe 5 is taken out of the heating furnace 18 and hot-formed by the forming means 20. The forming means 20 is a roll forming system, and is constituted by a pair of upper and lower forming rolls 21 and 24, for example. As shown in FIG. 3, both the forming rolls 21, 24 have semi-circular shapes 22, 25 corresponding to the final radius R. The drive shafts (not shown) of the roll axes 23, 26 are provided. It is configured to be able to drive and rotate in directions opposite to each other around. At that time, the forming rolls 21 and 24 are formed and arranged so that the distance between the forming surfaces 22 and 25 is equal to the distance L between the outer surfaces of the opposed straight portions 5a, 5a, 5b and 5b. Thus, the outer surface of each arc portion 5c protrudes outward with respect to the molding surfaces 22 and 25.

  Accordingly, by passing the heated semi-formed round steel pipe 5 between the forming rolls 21 and 24, the semi-formed round steel pipe 5 has the straight portions 5a and 5b formed in an arc shape and an arc portion by both forming surfaces 22 and 25. Hot forming can be performed in a state where 5c is pushed. As a result, as shown in FIG. 4, the forming means 20 can weld two places 4 and hot form a round steel pipe 6 having a predetermined radius R and a predetermined length.

By the above, for example, even a round steel pipe 6 having a thickness of 25 to 120 mm, a diameter of 1200 mm or more, and a length of 7000 mm or more, that is, a large diameter and extremely thick round steel pipe 6 can be suitably manufactured.
[Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. 2 to 4, 5, and 6.

  First, as shown in FIG. 5A, a steel plate 1 having a width (an example of a predetermined width) WA corresponding to a round steel pipe and a predetermined length is prepared. Here, the groove | channel 2 for welding is formed in the both ends of the width direction in the steel plate 1. As shown in FIG. Next, the steel plate 1 is bent and formed in a substantially circular shape by press forming by the press means 30 similar to that of the first embodiment.

  5B, first, the upper mold 33 is moved away from the lower mold 31, and one end side of the steel plate 1 is set on the lower mold 31, and then the lower mold 31 is moved. By moving the upper die 33 closer, the one end side of the steel plate 1 can be bent and formed by the first press forming by the pressing means 30 as shown by the solid line in FIG. Next, the upper die 33 is moved away from the lower die 31, and an intermediate portion near one end of the steel plate 1 is set on the lower die 31, and then the upper die 33 is moved closer to the lower die 31. As shown in FIG. 5C, the intermediate portion near one end of the steel plate 1 can be bent and formed by the second press forming by the pressing means 30.

  Then, the upper mold 33 is moved away from the lower mold 31 and the other end side of the steel plate 1 is set on the lower mold 31, and then the upper mold 33 is moved closer to the lower mold 31 as shown in FIG. As shown to (a), the other end side of the steel plate 1 can be bent by the third press forming by the pressing means 30. Next, the upper die 33 is moved away from the lower die 31, and an intermediate portion near the other end of the steel plate 1 is set on the lower die 31, and then the upper die 33 is moved closer to the lower die 31. Thus, as shown in FIG. 6 (b), the intermediate portion near the other end of the steel plate 1 can be bent and formed by the fourth press forming by the pressing means 30.

  In this way, the pressing means 30 bends the steel plate 1 into a substantially circular shape by press forming at four intermediate positions (four times) in the width direction of the steel plate 1, and thus a circular body (an example of a bending formed body) 8. It can be.

  When press forming is performed in this way, when both ends of the steel plate 1 are set on the lower die 31, the circular body 8 is formed at both ends in the width direction by removing both end portions from the press forming range. The straight portion 8b having a desired length remains in the portion. In addition, when the press forming is performed four times on the steel plate 1, the press width is adjusted with respect to the width WA of the steel plate 1 so that there is a range where the press forming is not performed in the middle three places of the steel plate 1. In the body 8, straight portions 8 a having a desired length remain at three intermediate positions. And the state where the circular arc portion 8c is bent at a total of four places such as between the straight portion 8a and the straight portion 8b (an example of the specific portion) and between the straight portions 8a and 8a (an example of the specific portion) Become. Here, the arc portion 8c is bent and formed in a substantially circular shape with a radius r smaller than the final radius (diameter of the round steel pipe) R, and the concave molding surface 32 and the convex molding surface 34 are formed correspondingly. Yes.

  Then, as shown in FIG. 6 (c), a pressure is applied to the circular body 8 from the outside so that the pair of end portions (both end portions), that is, the groove 2 portions are substantially in contact with each other, and then the opening is opened. By applying a welding means (not shown) between the tips 2, the gaps 2 are joined by welding 4 to form a semi-formed round steel pipe 5 as shown in FIG. 6 (d). Here, the semi-formed round steel pipe 5 has the same configuration as that of the first embodiment except that the above-described first embodiment welds two places (two seams), but welds one place (one seam). Then, in the same manner as in the first embodiment, that is, in the same manner as in FIGS. 2 to 4, it is heated in the heating furnace 18, and one place is welded 4 by the forming means 20 and a predetermined radius R, It is hot-formed into a round steel pipe 6 having a predetermined length.

  In the above-described embodiment, a single-stage forming method including a pair of forming rolls 21 and 24 is shown as the forming means 20, but this may be gradually hot formed by a multi-step forming method.

  In the above-described embodiment, as the forming means 20, a form consisting of a pair of forming rolls 21 and 24 is shown, but this is a form consisting of three forming rolls or a form consisting of four forming rolls. There may be.

  In the above-described embodiment, the semi-formed round steel pipe 5 is hot-formed in a state where the straight portion 5b is opposed to the gap between the pair of forming rolls 21 and 24 in the forming means 20, but this is not the case. Hot forming may be performed in a state where the straight portions 5a are opposed to each other. Alternatively, hot forming may be performed with the arc portion 5c facing the gap.

  In the above-described embodiment, press molding is performed four times. However, depending on the shape of the molding surface of the press means 30, three press moldings or five or more press moldings can be performed.

In the above-described embodiment, the push-off type is shown as the pressing means 30, but the pressing means may be an air bend type.
In the above-described embodiment, after bending the steel plate 1 by press forming, the end portions that are in close contact with each other are welded to each other, so that the straight portions 5a and 5b remain in the end portion and the specific portion, and the arc The portion 5c forms a semi-formed round steel pipe 5 having a radius r smaller than the final radius R. This is because the straight portions 5a and 5b remain at the end portion and the specific portion, and the arc portion between the straight portions. A semi-formed round steel pipe 5c having a radius slightly larger than the final radius R is formed, and this semi-formed round steel pipe is hot-formed by the forming means 20 so that the entire circumference (entire area) is lightly pressed to obtain the round steel pipe 6. You may do it.

It is explanatory drawing which shows Embodiment 1 of this invention and manufactures a semi-formed round steel pipe from a steel plate. It is explanatory drawing which manufactures a round steel pipe from the same semi-formed round steel pipe. It is a front view before shaping | molding in the shaping | molding means. It is a front view at the time of shaping | molding in the shaping | molding means. It is Embodiment 2 of this invention, and is explanatory drawing of the front | former stage process which manufactures a semi-formed round steel pipe from a steel plate. It is explanatory drawing of the back | latter stage process which manufactures a semi-formed round steel pipe from the steel plate.

Explanation of symbols

1 Steel plate 2 Groove (edge part)
3 U-shaped body (bending body)
3a Straight part 3b Straight part 3c Arc part 4 Welding 5 Semi-formed round steel pipe 5a Straight part 5b Straight part 5c Arc part 6 Round steel pipe 8 Circular body (bending body)
8a Straight portion 8b Straight portion 8c Arc portion 18 Heating furnace (heating means)
20 Forming means 21 Forming roll 22 Forming surface 24 Forming roll 25 Forming surface 30 Pressing means 31 Lower mold 32 Concave forming surface 33 Upper mold 34 Convex forming surface W Width of steel plate 1 (predetermined width)
WA Width of steel plate 1 (predetermined width)
R radius of round steel pipe (final radius)
r Small radius L Distance between straight surfaces

Claims (3)

  A steel sheet having a predetermined width formed with grooves at both ends in the width direction is subjected to press forming at a plurality of intermediate positions in the width direction so that straight portions of desired lengths are respectively formed at both end portions in the width direction and intermediate specific portions. The remaining straight part is bent and formed as an arc part, and the bend formed body is welded and joined in a state where the groove part is substantially in contact with each other to form a semi-formed round steel pipe. A method for producing a round steel pipe, characterized in that after the whole is heated, the forming surface is hot-formed by passing between a plurality of forming rolls having a semicircular shape corresponding to the final radius.   A steel plate having a width corresponding to a half round steel pipe is subjected to press forming at two intermediate positions in the width direction so that straight portions of a desired length remain at both end portions and the central portion in the width direction and between the straight portions. A semi-formed round steel pipe is formed by bending a pair of U-shaped bodies into a U-shape as a circular arc portion, and welding and joining a pair of U-shaped bodies with their groove portions substantially in contact with each other. The manufacturing method of the round steel pipe of 1 description. A steel plate having a width corresponding to a round steel pipe is subjected to press forming at four intermediate positions in the width direction, so that straight portions having desired lengths remain at both end portions and three intermediate positions in the width direction, and between the straight portions. 2. A round steel pipe according to claim 1, wherein a semi-formed round steel pipe is formed by bending in a substantially circular shape as an arc portion, and welding and joining in a state in which the groove portions of the circular body are substantially in contact with each other. Manufacturing method.

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