JP2008161909A - Method of manufacturing uoe steel pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air press rolling method with an O press using a separate type bolster in the manufacture of a UOE steel pipe. <P>SOLUTION: This method is a method of manufacturing the UOE steel pipe by which the O press of a U-shaped steel plate is performed with the O press provided with the separate type bolster by an air press method, the step control and the inclination control of the separate type bolster are performed when performing the O press and the original point used in the inclination control is obtained by resetting an encoder fixed to the main frame to zero at the point of time when a set pressurizing force is obtained by preliminarily performing no-load pressurization of a lower die with the separate type bolster. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a UOE steel pipe manufacturing method, and more particularly to an O-press air press rolling method using a separate bolster.

  In the UOE pipe manufacturing method, a steel sheet is formed into a U shape by a U press, then converted into an O shape by an O press, subjected to vertical seam welding, and then expanded to a finished product shape.

  The U press and O press are mechanisms that sandwich a steel plate between the upper die and the lower die and raise and lower the upper die while the lower die is fixed. The upper die is a bolster attached to the lifting cylinder. It is incorporated.

  FIG. 5 schematically shows a state in which the steel plate 13 is rolled to a desired product diameter by an O press. The upper die incorporated in the bolster 1 is moved to the lower die by the pressure cylinder 2 with the shim 14 sandwiched therebetween. Pressurized (pressure molding method). The shim 14 is an inch-size die and is used so as to obtain a specified shape when a millimeter-size pipe is molded.

  In the pressure molding method, although excellent roundness can be obtained, the stress related to the main frame that receives the reaction force of the pressure cylinder 2 is high, and the time required for shim switching work is reduced to 20 H / month and the work efficiency is reduced.

  The applied pressure is calculated using the tensile strength, pipe thickness, and pipe length of the steel sheet, but it is set to a high value to account for variations in tensile strength, and cracks occur in the welds on the main frame. Damage such as occurs.

  Patent Document 1 reduces the burden on the main frame by O-pressing with the minimum necessary load in the pressure molding method. The electrical signal obtained by electrically measuring the amount of change in the die interval. O-press hydraulic control is described.

  Patent Document 2 describes that the load in the U press is detected, the material strength of the charged steel sheet is calculated from the obtained load, the optimum load of the O press is calculated, and used for control.

  The air press method was developed to solve the problem of the pressure molding method, and pressurization is terminated in a state where a gap is generated between the upper die and the lower die. Although the above-described drawbacks are solved, it has been pointed out that the roundness becomes unstable.

Patent Document 3 relates to a UOE steel pipe manufacturing method that performs O-molding while setting and adjusting the gap between the upper and lower dies, for each plate based on the output element of the U press, for example, the maximum value of the output load of the U press. It is described that the material strength of the upper and lower dies is set when performing O molding according to the material strength.
Japanese Patent Laid-Open No. 58-167024 JP 60-21124 A JP-A-61-67520

  By the way, the O press is roughly classified into an integrated bolster structure in which the entire length of the U-shaped steel plate is reduced by a single bolster and a separate bolster structure in which the steel plate is reduced by a few bolsters.

  1A and 1B are diagrams for explaining an O-press using a separate bolster, in which FIG. 1A shows an outline of the apparatus configuration, and FIG.

  Three pressure cylinders 2a, 3a, 4a are attached to the single bolster 1a in the tube length direction, and a U-pressed steel pipe (not shown) is pressurized with the lower die 10a.

  The position in the vertical direction at the start and end of the single bolster 1a in the pipe length direction is detected by the position detectors 9a and 9b, and the obtained position information is transmitted to the control device 8, and the control device 8 discharges oil to the servo pump 6. A control signal for controlling the amount is transmitted.

  In addition, kicker cylinders 31a are attached to both sides of the pressure cylinders 3a disposed at the center of the three pressure cylinders. The single bolsters 1b and 1c have the same structure.

  For the O-press with a separate bolster, the air press method or the pressure molding method can be applied. The hydraulic pipe shown by the solid line is the air press circuit used in the air press method, and the hydraulic pipe shown by the dotted line is added by contacting the upper and lower dies. A press-cut press circuit used in a pressure molding method for pressing is shown.

  In order to control the inclination of the single bolster 1a (1b, 1c), the air press circuit is provided with a servo valve 5 that adjusts the amount of oil entering each pressure cylinder 2a, 3a, 4a. The amount of oil supplied from the amplifier 6 to the pressure cylinders 2 a, 3 a, 4 a is ON / OFF controlled by the logic valve 7 without going through the servo valve 5.

  When performing the air press method using O-press with a separate bolster, “inclination” occurs when the vertical position is different at the start and end of one single bolster in the tube length direction, and “step difference” indicates that the vertical position differs between the left and right single bolsters. ”And a poorly shaped pipe such as an inclined pipe or a stepped pipe having a different peripheral length at the pipe end is manufactured (FIG. 1B).

  FIG. 2 is a diagram for explaining an air press method using an O-press with a separation-type bolster, and shows a state in which the single holster 1a is lowered toward the lower die 10a.

  In the air press method, first, the single holster 1a is lowered toward the lower die 10a while performing step control so as not to generate a step between adjacent single holsters (not shown) (a).

  In the step control, the amount of discharged oil is changed by changing the tilt angle of the servo amplifier 6, and the descending speed of each bolster is adjusted to correct the step between the bolsters. The descent is performed at the speed of the kicker cylinder 31.

  When the single bolster 1a is lowered to a position where it comes into contact with the U-bent steel plate, the pressure drop starts. Until the set pressure is obtained by the kicker cylinder 31 and the pressure cylinders 2a, 3a, 4a, the single holster 1a is The steel plate after U-bending is pressurized while the step is controlled (b).

  The single holster 1a starts tilt control (position control) from the position pressurized to the set pressure (dotted line 11), further descends to the lower limit set value (dotted line 12) (c), and reaches the lower limit set value. (D). The lower limit set value is set so that the distance d between the single bolster 1a and the lower die becomes the shim thickness.

  Inclination control (position control) is performed by correcting the inclination of the bolster detected by the position detectors 9a and 9b by changing the amount of oil entering the main cylinder by the displacement amount of the servo valve spool.

  With the step control and tilt control described above, it is possible to manufacture UOE steel pipes with the same dimensional accuracy as an O-press with an integrated bolster by using an O-press with a separate bolster, but in recent years the dimensional accuracy of line pipes has increased. There is a demand for an air press method that is stricter and that both the step and the inclination are ± 2 mm, and that a product dimension with higher accuracy can be obtained.

  Therefore, an object of the present invention is to provide an air press method in which a UOE steel pipe satisfying ± 2 mm in both step and inclination can be obtained by an O press using a separate bolster.

The object of the present invention can be achieved by the following means.
1. A method of manufacturing a UOE steel pipe in which a U-shaped steel plate is O-pressed by an air press method using an O-press equipped with a separation-type bolster. The origin used in the control is obtained in advance by resetting the encoder fixed to the main frame to zero when the set pressure is obtained by air-pressurizing the lower die with a separate bolster. Steel pipe manufacturing method.

  According to the present invention, by performing an air press with an O press using a separate bolster, the stress of the main frame is reduced by 7% compared to an O press using an O press using an integrated bolster, and the service life is shortened. It was extended for 8.7 years. Moreover, since the shim switching work is not required, the actual operation time of 270 H / year has increased.

  In addition, since the origin position is adjusted in consideration of the elongation of the main frame in the inclination control, a UOE steel pipe satisfying ± 2 mm in both step and inclination is obtained, which is extremely useful industrially.

Hereinafter, the present invention will be described in detail with reference to the drawings.
The manufacturing method of the UOE steel pipe according to the present invention is described in detail with reference to FIGS. 1 and 2, in the tilt control when performing O-press by the air press method, the origin in the position information is set in advance, and the lower die is previously set with a separation-type bolster. When the set pressure is obtained by air pressurization, the encoder fixed to the main frame 15 is obtained by resetting to zero.

  FIG. 4 is a side view for explaining the schematic structure of the separation-type bolster. When the single bolster 1a attached to the tip of the pressure cylinder 2a is contacted and pressed against the lower die 10a, the main frame 15 is caused by reaction force. It extends upward as shown by the dotted line.

  When an encoder is used as the position detector 9, the main body 92 of the encoder is fixed to the main frame 15, and the rack 91 that meshes with the pinion of the main body 92 is fixed to the single bolster 1a.

  When the single bolster 1a moves in the vertical direction, the pinion of the main body 92 rotates to detect the absolute position of the single bolster 1a in the vertical direction. When the main frame 15 is extended by the reaction force when the single bolster 1a is contacted and pressed to the lower die 10a, only the extended length is displayed on the minus side.

  Therefore, in the present invention, when pressurizing with the upper die, the upper and lower dies are brought into contact with each other in advance, air pressure is applied, and the encoder fixed to the main frame 15 is reset to zero when the set pressure is obtained, and is set as the origin.

  FIG. 3 is a diagram for explaining an air press method for securing a gap corresponding to the thickness of the shim when the press is completed according to the method of the present invention. The upper die 1a starts tilt control from the time when it is lowered to the dotted line 11. When the steel pipe 13 is pressurized with a set load, the descent is stopped when a gap d corresponding to the shim thickness is obtained above the lower die 10a.

  The position information in the tilt control is the reaction force due to the set load, and the extension amount generated in the main frame is corrected. Therefore, the upper die can be stopped with an accuracy of ± 0.5 mm.

It is a figure which shows an example of the separation holster suitable for application of the air press method which concerns on this invention, (a) is an apparatus structure, (b) is a figure explaining a shape defect (inclination, level | step difference). The figure explaining the air press method. The figure explaining an example of the air press method which concerns on this invention. The side view explaining the schematic structure of a separation-type bolster. The figure explaining the pressure molding method.

Explanation of symbols

1, 1a, 1b, 1c Single bolster 2, 2a, 2b, 2c, 3a, 3b, 3c, 4a, 4b, 4c Pressure cylinder 5 Servo valve 6 Servo amplifier 7 Logic valve 9 Position detector 91 Rack 92 Main body 10, 10a Lower die 11 position (dotted line)
12 Lower limit setting value (dotted line)
13 Steel pipe 14 Shim 15 Main frame 31a, 31b, 31c Kicker cylinder

Claims (1)

  A method of manufacturing a UOE steel pipe in which a U-shaped steel plate is O-pressed by an air press method using an O-press equipped with a separation-type bolster. The origin used in the control is obtained in advance by resetting the encoder fixed to the main frame to zero when the set pressure is obtained by air-pressurizing the lower die with a separate bolster. Steel pipe manufacturing method.

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