US20210229153A1 - Method for bend straightening - Google Patents

Method for bend straightening Download PDF

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Publication number
US20210229153A1
US20210229153A1 US17/054,031 US201917054031A US2021229153A1 US 20210229153 A1 US20210229153 A1 US 20210229153A1 US 201917054031 A US201917054031 A US 201917054031A US 2021229153 A1 US2021229153 A1 US 2021229153A1
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United States
Prior art keywords
bend
amount
pressing
load value
steel pipe
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US17/054,031
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English (en)
Inventor
Koichi Kuroda
Shuji OTAO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
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Nippon Steel Corp
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Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Assigned to NIPPON STEEL CORPORATION reassignment NIPPON STEEL CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: OTAO, Shuji, KURODA, KOICHI
Publication of US20210229153A1 publication Critical patent/US20210229153A1/en
Abandoned legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D3/00—Straightening or restoring form of metal rods, metal tubes, metal profiles, or specific articles made therefrom, whether or not in combination with sheet metal parts
    • B21D3/10—Straightening or restoring form of metal rods, metal tubes, metal profiles, or specific articles made therefrom, whether or not in combination with sheet metal parts between rams and anvils or abutments

Definitions

  • the present invention relates to a method for bend straightening.
  • Patent Document 1 and Patent Document 2 disclose straightening methods for straightening bends of a pipe or a bar material.
  • FIG. 7 is a graph used for describing a principle of a conventional method for bend straightening.
  • the straightening methods described in Patent Documents 1 and 2 present a method in which a load and a deflection in press straightening are measured continuously over time, and the load is removed when a limit within which the load increases in proportion to the deflection is exceeded and a value of (deflection ⁇ straightening load ⁇ proportionality coefficient) reaches a preset amount of straightening.
  • a bend of a pipe is straightened by measuring an amount of bend in advance before applying the straightening load, determining a deflection ⁇ 1 of a material in pressing for giving unbending deformation necessary to straighten the bend by a predetermined method, performing press bending until the deflection ⁇ 1 is reached, and then removing the load.
  • an initial bend ⁇ 0 of a material placed on two supports separated by a span L is measured before straightening.
  • an amplitude of a mid-span portion of the material is measured with a measuring instrument such as a dial gauge installed below the material.
  • Half of the amplitude of the mid-span portion is considered to be a target value ⁇ 0 for an amount of the bending by which the bend straightening is to be performed.
  • the material is placed on the supports such that a direction of the bend of the material becomes a vertically upward direction, and a center portion of the material is bent downward with a press head attached to an end of a hydraulic cylinder.
  • deformation of the material is in an elasticity region in an initial stage being a beginning of pressing, where a P- ⁇ curve has an inclination of X 1 .
  • Patent Documents 1 and 2 are characterized in that a bending amount ⁇ 1 up to a pressing bottom dead center position described above is determined with consideration given to a difference between the inclination ⁇ 1 in the elasticity region when a bending load is applied initially and an inclination ⁇ 2 when the load is removed after the pressing bottom dead center position is reached and the elastic deformation is released, that is at so-called spring back, on a load-displacement curve.
  • an amount of pressing operation is determined, focusing on the fact that the inclination in loading and the inclination in unloading are ⁇ 1 and ⁇ 2 , respectively, both of which do not match in general.
  • the present inventors consider that a reason for this is due to Bauschinger effect and residual stress associated with a history of a straightened material.
  • Patent Document 1 JP63-199025A
  • Patent Document 2 JP10-5872A
  • the press bending amount ⁇ 1 is determined with reference to behavior of the relationship between the load and the displacement illustrated in FIG. 7 . This is effective in a case where behavior of the plastic deformation is clear, for example, in a case where a large bend is to be straightened.
  • the present inventors found that the following problem occurs if the methods described in Patent Documents 1 and 2 are used in a case where a minute bend is to be straightened.
  • the present inventors conducted detailed studies about a flaw of prior art and found that the straightening with high accuracy to perform needs slight adjustment in amount of bend in its final stage, that is, finish straightening; however, this case requires straightening working in a light load region where no clear transition to the plasticity region can be read even when a load-displacement curve is observed by on-line measurement. In other words, as illustrated in FIG.
  • FIG. 8 is a diagram illustrating relation between load and amount of bend in pressing operation with various amounts of press stroke.
  • pressing bottom dead center positions B 3 and B 4 correspond to a case where press working is performed beyond the point B in FIG. 7 .
  • Pressing bottom dead center positions B 1 and B 2 correspond to press working in the light load region that is seemingly considered as the elastic deformation region.
  • inclinations at times of unloading at B 1 , B 2 , B 3 , and B 4 are illustrated as ⁇ 21 , ⁇ 22 , ⁇ 23 , and ⁇ 24 ; ⁇ 23 and ⁇ 24 are equal to each other as in prior art, while ⁇ 21 and ⁇ 22 in the light load region are different from each other.
  • the present inventors found that determining an operation amount of pressing control to be a target load value to be applied to a steel material in a region that is not used in conventional practice makes the pressing control easy, which can increase an accuracy of the bend straightening as compared with the case of Patent Documents 1 and 2 where a displacement of the steel material in pressing is determined as the operation amount of the pressing control.
  • An objective of the present invention is to provide a method for bend straightening that includes determining a target load value, and performing pressing control using the target load value to increase the accuracy of the bend straightening.
  • the present invention is a method for bend straightening in which a pipe body having a bend is placed in a state where the pipe body is convex upward, the pipe body is pressed from above by a press unit at a target load value, whereby the pipe body is straightened, the method including: (a) a step of measuring a bottom-dead-center load value when the press unit is at a bottom dead center in the pressing; (b) a step of measuring an amount of change in amount of bend between an amount of bend of the pipe body before the pressing in the step (a) and an amount of bend of the pipe body after the pressing in the step (a); (c) a step of repeating the step (a) and the step (b) a plurality of times to create a relation between the bottom-dead-center load value and the amount of change in the amount of bend; and (d) a step of determining a target load value for next pressing from the relation.
  • the bottom-dead-center load value and the amount of change in amount of bend are collected to create a relation between the bottom-dead-center load value and the amount of change in amount of bend, and from the relation, the target load value used for pressing the pipe body is determined.
  • the target load value as an operation amount of pressing control, the pressing control can be made easy to perform, and an accuracy of bend straightening can be increased.
  • FIG. 1 is a diagram used for describing a press straightener that performs press straightening on a steel pipe.
  • FIG. 2 is a diagram used for describing an amount of bend of a steel pipe.
  • FIG. 3 is a diagram used for describing the rotation amplitude value measured by the displacement gauge.
  • FIG. 5 is a flowchart illustrating a procedure of a method for bend straightening.
  • FIG. 7 is a graph used for describing a conventional method for bend straightening.
  • FIG. 8 is a diagram illustrating a relation between load and amount of bend in pressing operation with various amounts of press stroke.
  • a method for bend straightening to be described below is a method for straightening a steel pipe being a pipe body by pressing a bend portion that occurs in the steel pipe using a press straightener.
  • FIG. 1 is a diagram used for describing a press straightener 1 that performs press straightening on a steel pipe 100 .
  • the steel pipe 100 that is to be subject to the press straightening by the press straightener 1 has, for example, a curve-like bend.
  • the bend of the steel pipe 100 occurs in, for example, hot or cold working in a producing process of the steel pipe 100 .
  • the press straightener 1 includes a two-point support 2 .
  • the two-point support 2 supports the steel pipe 100 at two points, with its axis direction set to be a horizontal direction.
  • the steel pipe 100 is placed on the two-point support 2 to be convex upward.
  • the press straightener 1 includes a press unit 3 .
  • the press unit 3 includes a press cylinder 31 and a press plate 32 .
  • the press unit 3 presses the steel pipe 100 placed on the two-point support 2 to apply a load to the steel pipe 100 .
  • the press cylinder 31 includes a rod not illustrated, which has a rod end provided with the press plate 32 .
  • the press cylinder 31 is coupled to a hydraulic unit 33 and expands and contracts the rod via working of the hydraulic unit 33 to perform ascending and descending operation of the press plate 32 and the pressing control on the steel pipe 100 .
  • the press plate 32 ascends and descends via the expansion and contraction of the press cylinder 31 .
  • the press plate 32 presses the steel pipe 100 placed on the two-point support 2 from above, applying the load to the steel pipe 100 .
  • the press cylinder 31 is provided with a load cell 34 .
  • the load cell 34 measures a load value P with which the press plate 32 presses the steel pipe 100 .
  • the load cell 34 measures the load value P as appropriate and outputs a value of the measurement to a controller 10 described below.
  • the press straightener 1 is provided with a displacement gauge 4 .
  • the displacement gauge 4 measures an amount of bend ⁇ of the steel pipe 100 being pressed by the press unit 3 .
  • FIG. 2 is a diagram used for describing the amount of bend ⁇ of the steel pipe 100 .
  • the amount of bend ⁇ is an amount of displacement from a reference level that is set at support points of the steel pipe 100 provided by the two-point support 2 .
  • the displacement gauge 4 measures an amount of bend ⁇ of the steel pipe 100 by the press unit 3 with respect to the axis direction of the steel pipe 100 .
  • the displacement gauge 4 outputs a value of the measurement to the controller 10 described below.
  • the displacement gauge 4 may be of a contact type that comes in contact with the steel pipe 100 to measure the amount of bend ⁇ or may be of a noncontact type that measures the amount of bend ⁇ without contact with the steel pipe 100 .
  • the press straightener 1 includes a pair of rotating rollers 51 and the displacement gauge 4 .
  • the pair of rotating rollers 51 rotates while sandwiching one end of the steel pipe 100 to hold the steel pipe 100 .
  • the press straightener 1 causes the press unit 3 to press the steel pipe 100 , lifts up the steel pipe 100 from the two-point support 2 after unloading, and causes the pair rotating rollers 51 to rotate the steel pipe 100 .
  • the displacement gauge 4 measures a rotation amplitude value S of the steel pipe 100 rotated by the pair rotating rollers 51 .
  • the rotation amplitude value S is measured by the displacement gauge 4 , and half of the rotation amplitude value can be measured as a residual amount of bend ⁇ a of the steel pipe 100 after the pressing.
  • the displacement gauge 4 is, for example, a dial gauge.
  • FIG. 3 is a diagram used for describing the rotation amplitude value S measured by the displacement gauge 4 .
  • the steel pipe 100 deforms elastically, and as the pressing further continues, the steel pipe 100 deforms plastically.
  • the steel pipe 100 When the steel pipe 100 is unloaded being bent in the plastic deformation region, the steel pipe 100 maintains its bent state. In the state where the steel pipe 100 is deformed plastically after the unloading, the amount of bend ⁇ from the reference level described above is the residual amount of bend ⁇ a.
  • the displacement gauge 4 measures the rotation amplitude value S of the steel pipe 100 rotated by the pair rotating rollers 51 when the steel pipe 100 is bent downward. In other words, the residual amount of bend ⁇ a of the steel pipe 100 after the pressing is obtained by halving the rotation amplitude value S measured by the displacement gauge 4 .
  • the press straightener 1 includes the controller 10 .
  • the controller 10 is, for example, a control circuit using a PC or the like.
  • the controller 10 drives and controls the hydraulic unit 33 to press the steel pipe 100 .
  • the controller 10 drives and controls the pair of rotating rollers 51 to rotate the steel pipe 100 about a rotation axis Ax.
  • the controller 10 acquires results of the measurement from the load cell 34 and the displacement gauge 4 .
  • the controller 10 uses the value of the measurement by the load cell 34 to perform feedback control on the hydraulic unit 33 and perform the pressing control on the press unit 3 .
  • the controller 10 measures a bottom-dead-center load value Pk when the press unit 3 is at its bottom dead center.
  • Pk a bottom-dead-center load value
  • the controller 10 measures an amount of change M between the amount of bend ⁇ of the steel pipe 100 before the pressing and the amount of bend ⁇ of the steel pipe 100 after the pressing.
  • the pressing means a state where the load of the pressing is removed, and no load is applied to the steel pipe 100 by the press unit 3 .
  • controller 10 measures the residual amount of bend ⁇ a of the steel pipe 100 from the rotation amplitude value S measured by the displacement gauge 4 , as described with reference to FIG. 3 .
  • black dots each indicate a bottom-dead-center load value Pk and an amount of change ⁇ measured in one press.
  • FIG. 4 illustrates data in a case where carbon steel pipes each of which has an outer diameter of 34 mm and a wall thickness of 2.6 mm are supported at a press span of 1500 mm and pressed by the press unit 3 .
  • the press span is a distance between the two support points with which the two-point support 2 supports the steel pipe 100 .
  • the amount of change M in the amount of bend ⁇ of the steel pipe 100 before and after the pressing is about 0.4 [mm]. In this case, the steel pipe 100 is deformed plastically.
  • the amount of change M in the amount of bend ⁇ of the steel pipe 100 before and after the pressing is about 0 [mm].
  • the steel pipe 100 is deformed elastically.
  • Formula (1) is updated whenever a bottom-dead-center load value Pk and an amount of change M are measured.
  • the controller 10 determines a load value for the next pressing (hereinafter, referred to as target load value Pa).
  • target load value Pa a load value necessary to perform the bend straightening by deforming the steel pipe 100 plastically by the residual amount of bend ⁇ a.
  • a load value necessary to deform the steel pipe 100 plastically by about 1.8 mm is about 3.0 kN (see FIG. 4 ).
  • the controller 10 sets a target load value Pa at about 3.0 kN to press the steel pipe 100 .
  • the controller 10 When performing the pressing at the target load value Pa, the controller 10 performs feedback control on the hydraulic unit 33 to press the steel pipe 100 with reference to the result of the measurement by the load cell 34 . The controller 10 then repeats the pressing of the steel pipe 100 until the residual amount of bend ⁇ a becomes not more than a threshold value, so as to straighten the steel pipe 100 .
  • the threshold value is preferably 1 mm, more preferably 0.5 mm.
  • FIG. 5 is a flowchart illustrating a procedure of the method for bend straightening.
  • the controller 10 causes the press unit 3 to press the steel pipe 100 (S 1 ). Specifically, the controller 10 operates the hydraulic unit 33 to expand the rod of the press cylinder 31 . The controller 10 then uses the press plate 32 to press the steel pipe 100 placed on the two-point support 2 . At this time, the controller 10 controls the hydraulic unit 33 such that the load value P becomes the target load value Pa while acquiring the result of the measurement by the load cell 34 .
  • the controller 10 may start the operation based on a material strength level of the material and a simple elastic bending deformation prediction formula.
  • the pressing may be performed according to an empirical rule of a worker or a load value determined by another method.
  • the controller 10 measures the bottom-dead-center load value Pk (S 2 ). Thereafter, the controller 10 performs unloading (S 3 ) and measures the amount of change M (S 4 ).
  • the amount of change M is measured as the difference between the amount of bend ⁇ of the steel pipe 100 before the pressing and the amount of bend ⁇ of the steel pipe 100 after the pressing, as described above.
  • the controller 10 controls the rotation of the pair of rotating rollers 51 to rotate the steel pipe 100 (S 6 ).
  • the controller 10 causes the displacement gauge 4 to measure the rotation amplitude value S (S 7 ).
  • the controller 10 determines the residual amount of bend ⁇ a of the steel pipe 100 from the measured rotation amplitude value S (S 8 ).
  • the controller 10 determines whether the residual amount of bend ⁇ a of the steel pipe 100 after the straightening is not more than the threshold value (e.g., 1 mm or 0.5 mm) (S 9 ). When the residual amount of bend ⁇ a is not more than the threshold value (S 9 : YES), the controller 10 determines that the steel pipe 100 is straight. The method for bend straightening is thus finished.
  • the threshold value e.g. 1 mm or 0.5 mm
  • the controller 10 determines that the steel pipe 100 is not straight.
  • the controller 10 determines the calculated load value Pk as the target load value Pa.
  • the controller 10 returns to step ⁇ 1 to press the steel pipe 100 with the determined target load value Pa.
  • the steel pipe 100 is convex downward before being pressed in step S 1 , the steel pipe 100 is rotated to be convex upward.
  • Path means the process for performing the pressing by the press unit 3 .
  • Path No of “1” means that the steel pipe 100 is pressed once, and “Path No” of “2” means that the steel pipe 100 is pressed twice.
  • Actual load value is a load value P measured by the load cell 34 when the controller 10 controls the hydraulic unit 33 to perform the pressing with the “Target load value Pa”.
  • the pressing control is performed using only the target load value Pa without measuring the amount of bend of the steel pipe 100 being pressed. Furthermore, as shown in FIG. 6 , the actual load value substantially matches the target load value Pa. In other words, in the present embodiment, the pressing control is performed accurately. As a result, as read from FIG. 6 , the amount of bend ⁇ of the steel pipe 100 is 0.5 mm or less at fourth pressing. As seen from the above, the method for bend straightening of the present embodiment provides results of high accuracy.
  • the bend straightening is performed while observing a displacement of a steel pipe being pressed in the plastic deformation region using the inclination ⁇ 2 of an unload curve created in the plastic deformation region, as illustrated in FIG. 7 ; in contrast, in the present embodiment, the relation expressed by Formula (1) shown above is created in (the region where the load increases with the inclination ⁇ 1 ), which is seemingly observed as the elastic deformation region immediately after starting the press loading illustrated in FIG. 7 . Then, in the region, the bend straightening is performed at the target load value Pa determined from the relation expressed by Formula (1).
  • the present embodiment is effective when a quality level of 1 mm to 0.5 mm or less per length of 1 m in terms of the bend displacement is required.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Straightening Metal Sheet-Like Bodies (AREA)
  • Bending Of Plates, Rods, And Pipes (AREA)
US17/054,031 2018-08-09 2019-08-06 Method for bend straightening Abandoned US20210229153A1 (en)

Applications Claiming Priority (3)

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JP2018150091 2018-08-09
JP2018-150091 2018-08-09
PCT/JP2019/030998 WO2020032070A1 (ja) 2018-08-09 2019-08-06 曲がり矯正方法

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US (1) US20210229153A1 (zh)
EP (1) EP3834956A4 (zh)
JP (1) JP7036215B2 (zh)
CN (1) CN112543683A (zh)
WO (1) WO2020032070A1 (zh)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114192611A (zh) * 2020-09-17 2022-03-18 宝山钢铁股份有限公司 一种用于无缝钢管无损探伤样管全长校直的装置及其方法
CN114210770A (zh) * 2021-11-24 2022-03-22 栋梁铝业有限公司 一种型材矫直机

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114309147A (zh) * 2021-12-31 2022-04-12 徐州徐工液压件有限公司 一种拉弯组合的校直方法

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JPS5341631B2 (zh) * 1973-04-20 1978-11-06
JPS6146320A (ja) * 1984-08-10 1986-03-06 Nissan Motor Co Ltd 自動歪取りプレス装置
JPS63144822A (ja) * 1986-12-05 1988-06-17 Nippon Steel Corp 長尺材の曲がり矯正方法
JPS63199026A (ja) * 1987-02-12 1988-08-17 Toyota Central Res & Dev Lab Inc ワ−クの歪矯正方法及び装置
JPS63199025A (ja) 1987-02-14 1988-08-17 Sumitomo Metal Ind Ltd 管・棒材の曲り矯正方法
JPH02192820A (ja) * 1989-01-19 1990-07-30 Sumitomo Metal Ind Ltd 管・棒材の曲がり矯正方法
JPH0829354B2 (ja) * 1990-01-30 1996-03-27 株式会社クボタ 管矯正方法
JPH105872A (ja) * 1996-06-26 1998-01-13 Nippon Seiko Kk 長尺部材の曲がり矯正方法
JP2006281228A (ja) * 2005-03-31 2006-10-19 Sumitomo Metal Ind Ltd ロール式管矯正機の制御方法
CN101421059B (zh) * 2006-04-14 2010-08-18 住友金属工业株式会社 管的矫正方法及使用该矫正方法的管的制造方法
JP2008030090A (ja) * 2006-07-28 2008-02-14 Jfe Steel Kk 形鋼の曲がり矯正方法および形鋼用矯正装置
KR101876265B1 (ko) * 2012-12-27 2018-07-10 재단법인 포항산업과학연구원 관형소재 교정장치

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114192611A (zh) * 2020-09-17 2022-03-18 宝山钢铁股份有限公司 一种用于无缝钢管无损探伤样管全长校直的装置及其方法
CN114210770A (zh) * 2021-11-24 2022-03-22 栋梁铝业有限公司 一种型材矫直机

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WO2020032070A1 (ja) 2020-02-13
EP3834956A1 (en) 2021-06-16
EP3834956A4 (en) 2022-07-06
JPWO2020032070A1 (ja) 2021-04-30
JP7036215B2 (ja) 2022-03-15
CN112543683A (zh) 2021-03-23

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