JP2011230141A - Apparatus and method for forming steel pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method capable of stably forming a high-quality steel pipe by preventing variation in the outer peripheral length of a material to be formed even in high-speed welding in forming the steel pipe.SOLUTION: The apparatus for forming a steel pipe has rolls 2-4 disposed at least two points with the material 1 to be formed sandwiched, and forms the steel pipe by the rolls 2-4. The apparatus further includes a position correcting means for always correcting the positions of the respective rolls 2-4 which vary due to a repulsive force imposed from the material 1 to be formed during forming by pushing back the rolls to predetermined positions so that the outer peripheral length is prevented from varying. The position correcting means has a monitoring means for always monitoring the positional variation of the respective rolls 2-4, and a moving means for sequentially moving the respective rolls 2-4 to the predetermined positions on the basis of the output of the corresponding monitoring means.

Description

  TECHNICAL FIELD The present invention relates to a steel pipe forming apparatus and a forming method, and more particularly to an apparatus suitable for forming a steel pipe in which a butt portion is welded by various welding methods such as laser welding and welding by electric resistance.

For example, in the manufacture of welded pipes by electro-sewing, usually, a plate-shaped coil is formed by a forming roll by applying a bending moment in the circumferential direction, and both edges of the material to be formed are made to face each other. The forming material is pressurized by a forming stand called a squeeze roll, and a butt portion of both edges is formed at the position of the welding machine arranged immediately before the SQ roll, while the heated and melted butt portion is formed with a roll. Crimp and weld.
The SQ roll forming stand uses two or more rolls sandwiching the material to be molded, and the position of each roll can be moved manually with a screw jack before the start of molding, Usually, it is moved in advance by the driving force of the electric motor using the count, and is adjusted in advance to a position corresponding to the outer peripheral length of the steel pipe to be formed.

  However, if the butt portion of the material to be molded is welded using such an SQ roll, the position of the butt portion and the welding upset position will deviate from the normal position, and the welding will not be stabilized. Variations in quality sometimes occurred. In particular, this tendency was remarkable when the material to be molded was allowed to pass through at a high speed.

JP 59-7428 A

Therefore, the inventors have examined the cause of variations in the position of the butt portion of the molding material and the welding upset position. Such variations in the position of the butt portion and welding upset position are It often occurs when there is strength fluctuation of the material, thickness fluctuation of the material, and during molding, each roll receives unexpected reaction force from the molding material due to strength fluctuation of the material of the molding material, etc. Along with this, it was found that the position of each roll changed in the direction of escaping from the initial position due to bending of the stand or the like.
Therefore, further verification was made on the relationship between the position fluctuation of each roll and the position fluctuation of the butt section and welding upset. If the position of the forming roll fluctuated, appropriate pressurization could not be applied to the workpiece. Since the outer peripheral length of the steel pipe after welding at the butt portion fluctuates, it has been found that the positions and intervals of both edges of the molding material before welding fluctuate. As a result, it was found that the position of the butting portion was shifted from the appropriate position to the front, rear, left and right, so that heating and melting at an appropriate position and range were not performed on the butting portion. Further, it was also found that when the outer peripheral length of the steel pipe after welding at the butt portion fluctuates, the discharge amount of the molten steel fluctuates when the weld portion is pressurized, so that the size of the weld bead fluctuates and the welding quality varies.
From the results of these verifications, the inventors have determined that the outer peripheral length of the steel pipe should be as constant as possible by suppressing the positional fluctuation of each roll during molding, regardless of the strength fluctuation or thickness fluctuation of the material of the molding material. By doing so, the displacement of the butt portion can be suppressed, proper welding can be performed stably, and fluctuations in the amount of molten steel discharged after butt portion welding can also be suppressed to suppress variations in welding quality. I have come to know that I can do it.

By the way, in order to cope with the strength fluctuation and plate thickness fluctuation of the material of the material to be molded, for example, as disclosed in Patent Document 1, the caliber-equipped molding roll is used as a work roll, and the load of these work rolls is reduced. It is conceivable to prevent bending and position fluctuation of the forming roll by arranging the receiving backup rolls respectively.
However, when the apparatus of Patent Document 1 is used, the edge of the material to be molded, the oxide scale generated during welding, welding spatter, etc. enter between the rolls, and the gap between the rolls and seizure due to the biting. In addition, there is a drawback that the entire apparatus is enlarged by the provision of the backup roll, and the practicality is poor. In particular, if the gap between the rolls is wide, it is difficult to take measures such as adjusting the gap during molding. Becomes unstable.

  In view of the above, the technical problem of the present invention is to enable stable forming of a high-quality steel pipe by suppressing fluctuations in the outer peripheral length of the material to be formed even during high-speed welding when forming the steel pipe. There is.

  In order to solve the above-mentioned problems, a steel pipe forming apparatus according to the present invention is a steel pipe forming apparatus having rolls arranged at least at two locations sandwiching a material to be formed, and roll forming the steel pipe with these rolls. The position of each roll that has fluctuated due to the reaction force received from the molding material during molding is constantly corrected by pushing it back to a predetermined position, thereby having position correction means for suppressing fluctuations in the outer peripheral length of the steel pipe. It is a feature.

  In this case, the position correction means includes a monitoring means for constantly monitoring the position fluctuation of each roll, and a moving means for sequentially moving the position of each hole-type roll to a predetermined position based on the output from the monitoring means. And can be provided.

  On the other hand, in order to solve the above-mentioned problems, a method for forming a steel pipe according to the present invention is a method for forming a steel pipe by roll-forming a steel pipe by means of rolls arranged at least at two positions sandwiching the material to be formed. The position of each roll fluctuated by the reaction force received is always corrected by pushing it back to a predetermined position, and forming is performed while suppressing fluctuations in the outer peripheral length of the steel pipe.

  According to the present invention, during molding, in order to constantly correct the position of each roll that has fluctuated due to the reaction force from the molding material to a predetermined position and suppress fluctuations in the outer peripheral length of the steel pipe, Even if the material has strength fluctuations and plate thickness fluctuations, the outer peripheral length of the steel pipe can be kept almost constant in response to the fluctuations at an early stage. Therefore, particularly when employed in SQ rolls, the position of the butt portion and the welding upset position can be held at a fixed position, so that the workability of the butt portion is improved and welding is performed at a high speed. However, it can be carried out stably and reliably, and it is possible to stabilize by suppressing variations in the quality of the welded portion.

1 is a front view schematically showing a steel pipe forming apparatus according to the present invention. It is a principal part enlarged view which shows typically the state which heated and fuse | melted the to-be-molded material. However, (a) is a state in which heating and melting are normal, (b) is a state in which the distance between both edges is too wide and heating / melting is poor, and (c) is a position in which both edges are displaced from each other. The state where the heating / melting is defective is shown. It is a principal part enlarged view which shows the state of the welding part of a to-be-formed material typically. However, (a) shows a state where the discharge amount of molten steel is normal, and (b) shows a case where the discharge amount of molten steel is bad. It is a principal part enlarged view which shows typically the state by which the position fluctuation | variation of each roll is correct | amended by the position correction means which concerns on this invention. In addition, about each roll and each bearing member, it is set as the simplified aspect, respectively. It is explanatory drawing which shows typically other embodiment of the monitoring means of the position correction means which concerns on this invention. However, (a) is a figure which shows the outline | summary of a monitoring means, (b) is a figure which shows the state before the position fluctuation | variation of a roll arises, (c) is a figure which shows the state after the position fluctuation | variation of a roll arises. . It is explanatory drawing which shows typically other embodiment of the monitoring means of the position correction means which concerns on this invention. It is a graph which each shows the relationship between the load loaded on the roll, and the displacement of this roll about the case where it does not use the case where the position correction means of the shaping | molding apparatus which concerns on this invention is used.

FIG. 1 shows an embodiment of a steel pipe forming apparatus according to the present invention. The forming apparatus of this embodiment is opposed to a material 1 formed in a substantially cylindrical shape from a plate-like coil. A pair of left and right side rolls 2 and 3 disposed at the left and right positions, and a pair of top rolls 4 and 4 disposed on the upper side of the material to be molded.
Also, left and right side roll bearing members 5 and 6 that rotatably support the rotation shafts of the pair of side rolls 2 and 3, and left and right bearing base portions 7 and 8 to which the bearing members 5 and 6 are fixed, The top roll bearing member 9.9 that rotatably supports the rotation shafts of the pair of top rolls 4 and 4 and the single upper bearing base portion 10 to which the top roll bearing members 9 and 9 are fixed. And an elevating member 11 to which the upper bearing base 10 is attached, a stand 12 provided so as to surround the left and right bearing base portions 6 and 7 and the outer side of the elevating member 11, and the stand 12 is attached The base 13 is provided.
In addition, the shaping | molding apparatus of this embodiment has shown the example used as an SQ roll used when carrying out electro-welding with respect to the butt | matching part 14 located in the upper part of the to-be-molded material 1, and this shaping | molding is shown. A welding means (not shown) is disposed in the vicinity of the upstream side in the pipe passing direction of the apparatus.

The pair of side rolls 2 and 3 are perforated rolls each having a groove-shaped caliber (hole mold) formed with a predetermined curvature on the outer peripheral surface, and pressurize the molding material 1 from the left and right. Then, it roll-forms into a cylindrical shape with a predetermined outer peripheral length together with the pair of top rolls 4 and 4. The left and right side rolls 2 and 3 have the same shape.
Further, the pair of top rolls 4 and 4 pressurize both the left and right edges 1a and 1b of the material 1 so that the both edges 1a and 1b face each other at the same height. . The pair of top rolls 4 and 4 have the same shape.

The left and right bearing base portions 7 and 8 are mounted on a guide member 16 provided on the base 13 so as to be movable substantially horizontally in the left-right direction, and the other bearing base portion at the upper end portion. The side roll bearing members 5 and 6 are fixed in a fixed position at positions facing each other. Therefore, the left and right side rolls 2 and 3 are integrated and linear with the bearing base portions 7 and 8 via the side roll bearing members 5 and 6 as the respective bearing base portions 7 and 8 move to the left and right. It is the structure which moves to the left-right direction.
Note that the guide member 16 is adapted to accurately transmit the driving force by the moving means of the position correcting means, which will be described later, so that the position correction of the side rolls 2 and 3 can be performed with high accuracy, and by the load cells 20 and 20 that are monitoring means. In order to reduce the load detection error as much as possible, the bearing base portions 7 and 8 can be smoothly slid only in the left-right direction. For example, a linear guide mechanism with low friction is used. .

The upper bearing base portion 10 has the pair of top roll bearing members 9 and 9 attached to the lower surface side in a state where the inclination of the top rolls 4 and 4 is maintained, and the upper and lower bearing members 10 are attached to the lifting member 11 on the upper surface side. It is connected.
The elevating member 11 is integrally moved up and down in the vertical direction in synchronism with the vertical movement of the piston rods 24a and 24a of the hydraulic cylinders 24 and 24, which are moving means of the position correcting means to be described later. The top rolls 4, 4 are configured to move up and down integrally and linearly via the upper bearing base 10 and the top roll bearing members 9, 9 as the elevating member 11 moves up and down.

The elevating member 11 has a face plate portion 11a having a substantially horizontal plate surface, and left and right side plate portions 11b and 11b extending in a substantially vertical direction attached at right angles to the lower surface sides of the left and right ends of the face plate portion 11a. ing. An elevating guide member 17 is disposed between a surface of the left and right side plate portions 11 b and 11 b facing the inner surface of the stand 12 and the inner surface of the stand 12.
The raising / lowering guide member 17 smoothly moves the raising / lowering member up and down smoothly so that the position of the top roll 4 can be corrected by the moving means of the position correcting means, which will be described later, and the load detection of the load cells 21, 21 as the monitoring means can be accurately performed. For example, a linear guide mechanism having a small friction is used.
The upper bearing base portion 10 is connected to the lower surface side of the face plate portion 11 a of the elevating member 11.

By the way, as already described, when the steel pipe is formed, when the strength fluctuation and the plate thickness fluctuation occur in the material of the material 1, each roll is assumed from the material 1 during the forming of the steel pipe. In the direction that each roll escapes from the initial position, specifically, the left side roll 2 is to the left, the right side roll is to the right 3, and the top rolls 4 and 4 are upward. Respectively.
Then, since the roll pushes the stand 12 and bends the stand 12, as a result, the roll is displaced from the initial position, and if nothing is dealt with, a steel pipe having an initially planned outer peripheral length can be formed. Disappear.

In particular, in the case of an SQ roll, the butt portion is heated and melted immediately before, so that the position of the butt portion fluctuates if the molding material 1 does not have a desired outer peripheral length when pressed by each roll. As shown in FIG. 2B, the width between both edges 1a and 1b widens, or the positions of both edges 1a and 1b shift as shown in FIG. And the heating / melting failure occurs (FIG. 2 (a) shows the case where the heating / melting is performed stably).
Alternatively, as shown in FIG. 3 (b), the discharge amount of the molten steel 19 is reduced when the two edges 1a and 1b are pressed together, and there is a possibility that the strength of the welded portion may be deteriorated (note that FIG. 3 (a) The case where the discharge amount of the molten steel 19 is normal is shown.).

  In order to solve this problem, as shown in FIG. 4, an appropriate force (in FIG. 4) that pushes the roll against the roll against the material to be molded against an unexpected reaction force from the material to be rolled 1. In order to increase the so-called mill rigidity, the forming apparatus according to the present invention has the position of each roll fluctuated by the reaction force from the forming material during the forming of the steel pipe. Position correction means is provided that constantly corrects each by pushing back to a predetermined position and suppresses fluctuations in the outer peripheral length of the molding material.

Here, in the present invention, correcting each roll to “predetermined predetermined position” means correcting each roll to a position necessary for forming a steel pipe having a target outer peripheral length. . Usually, the “predetermined predetermined position” is the initial position of each roll for setting the target outer peripheral length, that is, the position of each roll before the position is changed by the reaction force from the molding material. In this embodiment, the position correction of each roll performed by the position correction means will be described for a case where each roll is pushed back to the initial position.
In the present invention, the “mill rigidity” means a strength capable of resisting the reaction force of the material to be molded without causing the roll to change its position. Therefore, when the mill rigidity is increased, the roll position fluctuation is suppressed, and the fluctuation of the outer peripheral length of the steel pipe (the fluctuation of the upset amount during welding) is also suppressed.

The position correcting unit includes a monitoring unit that constantly monitors the position variation of each roll, and a moving unit that sequentially moves the position of each roll to a predetermined position based on an output from the monitoring unit. .
In the present embodiment, the monitoring means employs a configuration in which the load acting on each roll is measured by the load cell, and the variation in the position of each roll is constantly monitored based on the load variation. The result is output to a control means (not shown), which will be described later, and used for controlling the moving means.

Specifically, with respect to the side rolls 2 and 3, load cells 20.20 are respectively disposed between the surfaces of the left and right bearing base portions 7 and 8 that face the stand 12 and the inner surface of the stand 12. The load acting on the left and right side rolls 2 and 3 is constantly and individually measured. The load cells 20 and 20 for the side rolls are disposed at substantially the same height as the side rolls 2 and 3, are made as small as possible by the bearing base portions 6 and 7, and operate in the horizontal direction acting on the side rolls 2 and 3. The load can be measured as accurately as possible.
For the top rolls 4, 4, the upper end portions of the top roll bearing members 9, 9 and the surfaces of the upper bearing base portion 10 facing the upper end portions of the top roll bearing members 9, 9. The load cells 21 and 21 are respectively disposed between the top and the top rolls 4 and 4 so that the loads acting on the top rolls 4 and 4 are always and individually measured. Thus, by providing the load cells 21 and 21 for the top rolls in the vicinity of the top rolls 4 and 4, the accuracy of measurement of the load acting on the top rolls 4 and 4 is improved.

On the other hand, the moving means is provided on the left and right side surfaces of the stand 12, and is mounted on the left and right hydraulic cylinders 22 and 23 in which the piston rods 22 a and 23 a move back and forth in the horizontal direction, and on the upper surface of the stand 12. The piston rods 24a, 24a are provided with two upper hydraulic cylinders 24, 24 that move up and down in the vertical direction.
Specifically, each of the left and right hydraulic cylinders 22 and 23 has cylinder bodies 22b and 23b fixed to the outer surface of the stand 12, and piston rods 22a and 23a passing through the stand 12 and bearings. It is led out substantially horizontally to the inner surface side of the base portion side, and the rod tip side is connected to the left and right bearing base portions 7 and 8 (strictly, the load cell portions 20 and 20). Then, based on the output signal from the monitoring means, the piston rods 22a and 23a are moved back and forth in the horizontal direction by moving the piston (not shown) back and forth, so that the left bearing base 7 is moved in the right and left direction and the right side. The bearing base 8 can be moved linearly in the left-right direction.
Accordingly, the driving forces of the hydraulic cylinders 22 and 23 are transmitted to the left and right side rolls 3 and 4 via the corresponding bearing base portions 7 and 8 and can be moved freely in the left and right directions.

The two upper hydraulic cylinders 24, 24 have the same shape. The cylinder bodies 24b, 24b are fixed to the upper surface of the stand 12, and the piston rod 24a passes through the stand 12. It is led out substantially vertically to the upper surface side of the face plate portion 11 a of the elevating member 11, and the tip end side of the rod is connected to the upper surface of the face plate portion 11 a of the elevating member 11. Then, based on the output signal from the monitoring means, the pistons (not shown) of both hydraulic cylinders 24, 24 are moved up and down simultaneously and with the same stroke, so that the piston rods 24a and 24a move simultaneously and with the same stroke in the vertical direction. Thus, the entire lifting member 11 can be moved up and down linearly while the horizontal state of the face plate portion 11a is maintained.
Accordingly, the driving forces of the hydraulic cylinders 24 and 24 are transmitted to the two top rolls 4 and 4 through the elevating member 11 and can be freely moved in the vertical direction.
Note that the piston rods 24a, 24a of the hydraulic cylinders 24, 24 are arranged from the center of the face plate portion 11a of the elevating member 11 so that the two upper hydraulic cylinders 24, 24 are loaded with an equivalent load. It arrange | positions so that it may each be connected with the position of distance.

Further, a position sensor (not shown) for detecting the position of the piston or the position of the piston rods 22a to 24a is attached to each of the hydraulic cylinders 22 to 24, and the position of the piston or the piston rods 22a to 24a is always accurately determined. To be able to grasp.
Each hydraulic cylinder 22 to 24 of the moving means is provided with a digital servo valve 25 excellent in responsiveness and accuracy, and output from a control means described later based on the output from the monitoring means. In accordance with the control signal, the amount of oil in the pressure chambers on the piston head side and the piston rod side in the hydraulic cylinders 22 to 24 is appropriately adjusted within a short time, and the position of the piston, and thus the piston rods 22a to 24a. Each position can be controlled accurately and quickly.
In this embodiment, the servo valve 25 is directly attached to the cylinder bodies 22b to 24b of the hydraulic cylinders 22 to 24 in order to realize a high response, and the piping distance between the hydraulic cylinders 22 to 24 is provided. Is shortened as much as possible.
In this embodiment, the initial positions of the respective rolls determined to obtain the target outer peripheral length can be set by the hydraulic cylinders 22 to 24 of the moving means.

Here, in the position correction means, the roll position correction amount (movement amount) determined based on the load data from the load cell as the monitoring means is used to control the position of the piston and piston rod of the hydraulic cylinder of the movement means. More specifically, in this embodiment, each load data output from each load cell is sequentially sent to a control means (not shown), and in this control means, the position correction of each roll is sequentially performed by feedback. The roll to be position-corrected is determined according to the obtained load data, and the position correction amount (movement amount) necessary for the roll to be position-corrected is calculated. At this time, the relationship between the load acting on the roll and the position variation of the roll due to the load (that is, how much the position of the roll fluctuates when the load is applied) is previously stored as data for each roll. The position correction amount is calculated from this data and the load data.
Then, by outputting a control signal related to the position correction amount to the hydraulic cylinder to be position-corrected (in this case, strictly a servo valve), the positions of the pistons and piston rods of the hydraulic cylinders are detected by the position sensor. The position is detected successively and accurately controlled, and the rolls are constantly corrected so that each roll is quickly returned to the initial position.

When a steel pipe is formed using the forming apparatus having the above-described configuration, the target outer peripheral length is the target material 1 in which both edges 1a and 1b are heated and melted by the welding means disposed immediately before the forming apparatus. The left and right side rolls 2 and 3 and the two top rolls 4 and 4 that have been adjusted in advance to the position (initial position) for forming the steel pipe are pressed to weld the butt portion 14.
At this time, when the material of the molding material 1 has strength fluctuation and plate thickness fluctuation, each roll of the molding apparatus receives an unexpected reaction force from the molding material 1 to cause position fluctuation. During the molding, the roll position correcting means functions, and each roll whose position is changed by the reaction force received from the molding material 1 is always pushed back to the initial position, and the outer peripheral length of the molding material 1 is changed. The molding is proceeded in a state where is always suppressed.
That is, the position change of each roll is constantly monitored by the monitoring means, and when the position change occurs, the position of each roll is moved by sequentially pushing the roll back to the initial position based on the output from the monitoring means. Is always corrected, and fluctuations in the outer peripheral length of the steel pipe can be suppressed regardless of fluctuations in material strength and plate thickness.

In this way, during the formation of the steel pipe, the position of each roll is constantly corrected to a predetermined position, so that the mill rigidity is increased and the fluctuation of the outer peripheral length of the molding material is suppressed, so that the butt portion is at a fixed position. Thus, the position and range of the heating / melting portion by the welding means performed immediately before can be kept almost constant, and variations in the position of the butting portion and the upset position can be suppressed. Moreover, since the fluctuation | variation of the outer periphery length of a to-be-molded material was suppressed, since appropriate pressurization can always be performed with respect to a butt | matching part, the discharge amount of the molten steel at the time of welding can also be kept substantially constant.
As a result, the weldability of the butt joint is dramatically improved, so that welding can be performed stably even at high speeds, and high quality steel pipes can be formed while suppressing variations in weld quality. It becomes possible to do.

In the above embodiment, a forming apparatus having a total of four forming rolls, that is, the left and right side rolls 2 and 3 and the two top rolls 4 and 4, is used. 2, 3, or 5, and can be arbitrarily selected.
Furthermore, in the said embodiment, although the case where the butt | matching part is welded by electro-welding welding is shown, you may make it weld by arbitrary welding methods, such as welding by a laser other than this.

In the above embodiment, as the monitoring means of the position correction means, a configuration is adopted in which the load acting on each roll is measured and the fluctuation of the position of each roll is constantly monitored based on the load fluctuation. However, any other means can be used as the monitoring means.
For example, as shown in FIG. 5 (a), the light emitting means 30 for irradiating the roll with light in the direction of the tube before and after each roll (upstream and downstream in the direction of the tube), and the light emitting means 30 A so-called light cutting method may be used in which a light receiving means 31 is provided for receiving the light from the light, and the position variation of each roll is detected and the amount of displacement is measured based on the shape grasped based on the received light. .
In this case, as shown in FIG. 5B, the maximum width δ _{1 of the} shape obtained before the position change of the roll (in the case of FIG. 5, the right side roll 3 is shown) and the position change of the roll. Since the difference from the maximum width δ _{2 of the} shape obtained later is the amount that the position of the roll is fluctuated by the reaction force of the material to be molded as shown in FIG. 5C, the position correction for eliminating this fluctuation amount is performed. Just do it.
It is important to provide the light emitting means 30 and the light receiving means 31 in a place that is not affected by the bending of the stand 12.

Alternatively, as shown in FIG. 6, a so-called non-contact displacement meter 32 such as a laser displacement meter or an optical displacement meter is used, and each roll (the right side roll 3 is shown in FIG. 6). On the other hand, the position variation amount of the roll may be constantly measured by irradiating a laser or the like from a horizontal direction orthogonal to the tube passing direction. (FIG. 6 shows a case where the displacement amount of the right side roll 3 is measured.)
In this case, the displacement meter 32 is attached to an arm 33 installed in a place not affected by the bending of the stand, and the displacement amount of the roll is accurately measured in the space between the roll and the bearing member. Is essential.

Furthermore, in the said embodiment, although the case where the shaping | molding apparatus and shaping | molding method of this invention are used as a SQ roll is described, besides this, as a sizer roll which adjusts the outer diameter of a steel pipe in the next shaping process, or Each can be used as a fin pass roll used for adjusting the outer peripheral length of the steel pipe before the material to be molded is heated and melted by the welding machine.
In any case, even if an unexpected reaction force due to material strength fluctuation or plate thickness fluctuation is applied to the roll during molding, each roll changed due to the reaction force from the molding material. Since the position can always be corrected to a predetermined position and the outer peripheral length of the steel pipe can always be kept constant, the dimensional accuracy and the like of the formed steel pipe can be improved.

In order to confirm the effect of the present invention, a performance comparison experiment was performed between the molding apparatus of FIG. 1 used in the above embodiment and a conventional molding apparatus having no roll position correcting means as in the present invention. It was. Specifically, a load was applied to the roll of the forming apparatus, and the amount of positional fluctuation of the roll was measured.
The conventional forming apparatus is basically the same as the forming apparatus of the present invention except that there is no roll position correcting means and the initial position of the roll can be manually adjusted by a screw jack.
The result of this experiment is shown in FIG.

As can be seen from FIG. 7, in the case of the molding apparatus of the present invention, even when a load equivalent to that of the conventional molding apparatus was applied to the roll, the displacement of the roll was about 1/10 or less.
Therefore, it was found that the mill rigidity of the molding apparatus of the present invention is improved by 10 times or more compared with the conventional apparatus.

Next, in order to confirm the effect of suppressing the fluctuation of the outer peripheral length of the molding material by the position correction means in the present invention, the same molding apparatus as that of the above embodiment is used, and the position correction means is used. When not used, a steel pipe is formed from the material to be molded under the same conditions from a material with a difference in strength, and the outer circumference of the welded steel pipe is measured with an outer diameter measuring device that can measure the absolute value of the radius method. Then, the average radius of each material was measured.
As the material of the material to be molded, a steel plate having a tensile strength of 300 MPa and 500 MPa was used, and the material was molded and welded with an outer diameter of 60.5 mm and a plate thickness of 2.0 mm. For welding, both the present invention and the conventional example used work coil type high frequency electric resistance welding (ERW) 250 KHz.
In the molding apparatus according to the present invention, the pressure of the used hydraulic servo is 15 MPa, the rod head pressure receiving area of the servo cylinder is 22 cm ² rod, the head is 32 cm ² , and the servo flap is a nozzle flapper type (180 Hz, −3 dB). .
In addition, the response frequency of the control system was 25 Hz and −3 dB at a control period of 1 ms.
The results are shown in Table 1.

As a result of this experiment, when the position correction means was not used, a difference of 50 μm or more was generated in the difference in average radius, and a step was generated at a position where the intensity changed.
On the other hand, when the position correction means was used, welding could be performed while suppressing the difference in average radius to 20 μm or less.
As a result, even if the material of the molding material has strength fluctuations (including strength fluctuations due to plate thickness fluctuations), the outer diameter fluctuations at the tip, center, and rear end portions of the coil to be molded (by extension) It was found that the fluctuation of the outer peripheral length) can be suppressed. Therefore, it was proved that variations in the position of the butt portion and upset during welding and variation in the dimensions of the final product can be suppressed.

1: Material to be molded 2: Left side roll 3: Right side roll 20: Load cell for side roll 21: Load cell for top roll 22 to 24: Hydraulic cylinder 25: Servo valve

Claims (3)

It has a roll arranged at least at two locations sandwiching a material to be molded, and is a steel pipe forming apparatus for roll forming a steel pipe with these rolls,
It has a position correction means that constantly corrects the position of each roll changed by the reaction force received from the molding material during forming by pushing it back to a predetermined position and suppresses fluctuations in the outer peripheral length of the steel pipe. Steel pipe forming equipment.   The position correcting unit includes a monitoring unit that constantly monitors the position variation of each roll, and a moving unit that sequentially moves the position of each roll to a predetermined position based on an output from the monitoring unit. The steel pipe forming apparatus according to claim 1. A method of forming a steel pipe, in which a steel pipe is roll-formed with at least two rolls sandwiching a material to be formed,
A steel pipe characterized in that molding is performed while suppressing fluctuations in the outer peripheral length of the steel pipe by constantly correcting the position of each roll, which has been fluctuated by the reaction force received from the material to be molded, by pushing it back to a predetermined position. Molding method.

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