JP2003220420A - Method and device for forming plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for forming a plate capable of achieving a constant YR rising rate on YR rising section of the plate to prevent extremely-high YR generation after the plate is formed by pressing forming rolls. <P>SOLUTION: The method and the device for forming the plate by pressing the forming rolls with circular arc shape surface on both surfaces of the plate, are characterized by that a hydraulic cylinder of a hydraulic power unit provides a thrust power between upper and lower forming rolls and the hydraulic power unit maintains the thrust power applied by the hydraulic cylinder during forming within a constant range. Especially they are those for manufacturing an electric resistance melded steel pipe, and the rolls with the thrust power between two forming rolls given by the hydraulic power unit are breakdown rolls for bending and correcting a central part in width of a coiled steel sheet. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forming method and a forming apparatus for pressing a forming roll having a surface arc shape on the upper and lower surfaces of a plate, and more particularly to a method and an apparatus for manufacturing electric resistance welded steel pipe, The present invention relates to a plate forming method and a forming apparatus capable of producing a low YR molded product.

[0002]

2. Description of the Related Art ERW steel pipes, TIG welded steel pipes, laser welded pipes and other formed steel pipes, square columns formed by roll forming, aluminum pipes and aluminum columns formed by the same method, have surface arcs on the upper and lower surfaces of the plate. It is formed by using a forming roll which is formed by pressing a roll having a shape.

For example, an electric resistance welded steel pipe is manufactured by continuously forming a raw material steel strip into a cylindrical open pipe by a group of forming rolls, and then joining the joints by an electric resistance welding method. The forming roll is usually composed of a roll group of dozens of stages. The breakdown roll is a driven horizontal roll that performs the initial forming up to a half circle including the forming of the steel strip edge. The side rolls are non-driven vertical rolls,
Deployed between breakdown rolls or as a cluster. After the strip steel is formed by the breakdown rolls and the side rolls, it is finish-formed by the fin pass rolls, and the butt shape of the steel strip edges in the welding process is controlled by the squeeze roll.

The breakdown rolls are usually formed as a roll group of 3 to 5 sets, and are formed by continuously straightening and straightening the strip steel. A type in which rolls are arranged so that the radius of curvature of the roll shape gradually decreases from the front stage to the rear stage of the roll group, and a type in which a W bend roll for forming the steel strip into a W shape is arranged in the front stage of the roll group (Fig. 5
(C)) (for example, Japanese Unexamined Patent Publication No. 62-50019), a type in which a roll for rectifying a portion other than the central portion of the strip is arranged in the front stage of the roll group (for example, Japanese Unexamined Patent Publication No. 63-2).
81713). In both types, since the break roll group is formed from a semi-circular shape to a shape close to a cylinder including the widthwise central portion of the strip steel, the widthwise central portion of the strip steel is straightened inward at the subsequent stage of the roll group. A breakdown roll (FIGS. 5A and 5B) is arranged. Further, since the breakdown roll functions as a driving roll for advancing the strip steel, the strip steel is pressed by the upper and lower rolls to give a pressing force, and then a driving rotational force is given to the roll.

The opening setting of the breakdown upper and lower rolls is
As shown in FIG. 4, usually, a manual method such as a screw nut method is used, and the opening degree between the upper and lower rolls is adjusted by the manual lifting device 10 that rotates the screw nut 11 manually. It is constant. When the upper and lower rolls receive a repulsive force from the steel strip during pipe forming, the roll spacing increases by a predetermined amount with respect to a predetermined repulsive force due to elastic deformation of the roll stand and the roll itself. Therefore,
By setting the set opening between the rolls to a predetermined amount that is smaller than the thickness of the steel strip of the material, the roll interval is expanded to the thickness of the steel strip during pipe making, and the roll pressing force at that time is desired. It can be a value.

In the roll for forming ERW steel pipe,
The same electric resistance welded steel pipe to minimize the frequency of replacement
About the outer diameter About the total thickness of the strip steel from thin to thick
Uses common rolls. Therefore, the breakdown
Radius of the lower roll surface shape is R_LIf so, above
Curvature radius R of roll surface shape_UIs the lower roll radius of curvature R _L
To the maximum thickness t of the steel strip_maxIs the value obtained by subtracting. Furthermore
In addition, even for different ERW pipe outer diameters, breakdown is possible.
Sometimes used as a roll. In this case, below
The radius of curvature of the roll is adjusted to match the ERW steel pipe with a large outer diameter.
The radius of curvature of the roll is set according to the ERW steel pipe with a small outer diameter.
Meru. As a result, the radius of curvature R of the upper roll surface shape_UAnd below
Roll curvature radius R_LIs the maximum wall thickness t of the steel strip._maxThan
May be a large value.

ERW steel pipes used as structural materials for buildings are required to have a low YR in order to prevent breakage of the ERW steel pipe structural portion when an earthquake occurs. or,
In the case of line pipes, when the pipes are laid while bending deformation from the ship to the seabed, low YR is required due to the deformability in the longitudinal direction of the pipe, and in the circumferential direction when abnormal pressure is applied from the transport fluid. In some cases, low YR is required to secure the deformability.

[0008] For automobile parts and the like, products formed by forming an electric resistance welded steel pipe by a hydroforming method have begun to be adopted. The hydroforming method is a cylinder for pushing from both sides by inserting a raw pipe into the split mold whose internal shape is the final product shape, introducing liquid from the end of the raw pipe into the raw pipe, applying internal pressure. In this method, a compressive load is applied in the axial direction of the tube by-and pushed in to process the raw tube into its final shape.

[0009] By the hydroform method, it is possible to form a complex shape that is lightweight and has a high degree of processing that cannot be obtained by conventional methods. Furthermore, the axial force and internal pressure during processing can be controlled with high precision. By doing so, since it is possible to integrally mold the parts having complicated shapes and to improve the accuracy, it is expected as a technology for realizing a vehicle body structure that enables weight reduction and cost reduction of an automobile.

Excellent formability is required for the raw tube for hydroforming. When hydroforming is performed using an electric resistance welded steel pipe as a raw pipe, if the workability is increased, the elongation may locally exceed the limit of elongation and fracture may occur. Therefore, in order to hydroform a product with a complicated shape,
It is required to have a low YR and good ductility in any part of the electric resistance welded steel pipe.

The electric resistance welded portion of the electric resistance welded steel pipe can be subjected to strain relief annealing by a local heat treatment apparatus called a post annealer, whereby the ductility of the electric resistance welded portion can be improved and the YR can be reduced.

[0012]

In the electric resistance welded steel pipe after the electric resistance welding, except for the electric resistance welded portion, FIG.
As shown in (a), there is a portion having a higher YR and a lower ductility than the other portions on the opposite side in the circumferential direction of the electric resistance welded portion, that is, the portion corresponding to the width center portion of the strip steel. I understood. This part is called the YR rising part. Also,
When the variation of YR in this portion in the longitudinal direction of the manufactured electric resistance welded steel pipe is examined, as shown in FIG. 8 (a), the degree of increase of YR in the YR rising portion is not constant and sometimes a very large YR increase occurs. It turned out that there is a part to show.
If there is a particularly large YR rise part, when electric resistance welded steel pipe is used as a structural material for buildings, it will be
The portion with high R tends to be the starting point of fracture. Further, when the electric resistance welded steel pipe is used as a raw pipe for hydroforming, if the workability is increased, the elongation also exceeds the limit of elongation in the portion where YR is high, and fracture occurs. In addition to the conventional post anneal applied to the electric resistance welded part, if you try to carry out post annealing to the part on the opposite side of the welded part, it is necessary to install new post anneal equipment.
It will also deteriorate the productivity of pipe making.

The present invention is a roll forming process for pressing an electric resistance welded steel pipe to press a roll having a surface arc shape on the upper and lower surfaces of the plate to form the YR at the YR rising portion of the plate.
An object of the present invention is to provide a technique capable of making the amount of rise constant in the longitudinal direction of the steel pipe and preventing the occurrence of extremely high YR.

[0014]

In a forming roll in which a roll having a surface arc shape is pressed against the upper and lower surfaces of a plate to form, the curvature radius R _U of the upper roll surface shape of the forming roll.
Is the value obtained by subtracting the maximum thickness t _max of the plate from the lower roll curvature radius R _L as described above. Therefore, when the thickness of the plate to be formed is smaller than the maximum thickness t _max , as shown in FIG. 6, the portion where the upper roll 1 and the lower roll 2 press the plate 3 from the front and back sides is the pressing center portion. Only 20.
Further, in the production of electric resistance welded steel pipe, in the case where the breakdown rolls are also used for different outer diameters of the electric resistance welded pipe, the difference between the curvature radius R _U of the upper roll surface shape and the curvature radius R _L of the lower roll is: The value may be larger than the maximum thickness t _{max of the} plate. In this case, even if the thickness of the plate to be formed is the maximum thickness t _max , the upper roll 1 and the lower roll 2 press the plate 3 from both front and back sides only at the pressing center portion 20. Then, it was found that the YR rising portion was generated in coincidence with the pressing center portion 20 where the plate was pressed by the upper and lower rolls.

Since the forming roll is a drive roll for moving the plate, it is necessary to secure a predetermined pressing force. Therefore, it has been clarified that in the pressing center portion 20, the plate undergoes plastic deformation due to an excessive rolling force by the rolls, which causes YR of the pressing center portion 20 to rise.

A plate as a forming material is generally manufactured by hot rolling, and the plate thickness is not always constant. Regarding the longitudinal direction of the hot-rolled coil, since the tip of the hot-rolled coil is rolled by being pushed in from the rear, stress in the compressive direction is easily applied and the plate thickness becomes thicker. The stress tends to reduce the plate thickness. Further, the thickness of the skid marks at the time of extraction from the heating furnace for hot rolling becomes thick, and the thickness also fluctuates due to the eccentricity of the backup roll for hot rolling.
Further, since the plate thickness of the center of the width of the hot rolled coil is often 0.3 mm due to the crown, the plate thickness of the strip steel taken from the center of the width of the hot rolled coil by trimming becomes thick.

As described above, the pressing force of the upper and lower rolls of the forming roll is adjusted by setting the set opening to a constant value smaller than the plate thickness and pressing the reaction force when the roll interval extends to the plate thickness. It is adjusted by using it as force. In such an adjusting method, if the plate thickness of the plate to be formed changes, the pressing force of the forming roll also changes accordingly, and if the plate thickness of the passing plate is thicker than the set plate thickness, the pressing force will naturally be applied. The force also becomes higher than the set pressing force.

In this case, the pressing force of the forming roll is adjusted by controlling the pressing force by a hydraulic device so as to keep the hydraulic pressure constant, instead of keeping the set opening constant as in the conventional case. For example, the pressing force can always be maintained at a constant value even if the distance between the upper and lower rolls changes due to the change in plate thickness. As a result, the pressing force can be maintained at a constant value regardless of the variation in the plate thickness of the plate, and by preventing the occurrence of extremely high YR in the pressing center part 20, the YR rise amount in the pressing center part 20 can be increased. It becomes possible to make constant in the longitudinal direction.

The present invention has been made based on the above findings, and its gist is as follows.

(1) In a forming method in which a forming roll having an arcuate surface shape is pressed against the upper and lower surfaces of a plate to form the pressing roll, the pressing force between the upper and lower rolls of the forming roll is applied by a hydraulic cylinder of the hydraulic device. A method of forming a plate, characterized in that the pressing force of a hydraulic cylinder is kept constant during forming. (2) The plate forming method as described in (1) above, wherein the hydraulic device has a relief valve. (3) The plate forming method according to (1) above, wherein the hydraulic device has a constant pressure source circuit using an accumulator. (4) A method for manufacturing an electric resistance welded steel pipe using the plate forming method according to any one of (1) to (3), wherein the roll that applies a pressing force between the upper and lower rolls by a hydraulic device is a belt. A method for producing an electric resistance welded steel pipe, which is a breakdown roll for straightening the center of the width of the steel.

(5) In a forming apparatus for pressing a forming roll having a surface arc shape on the upper and lower surfaces of a plate to form a plate, a hydraulic device for applying a pressing force between upper and lower rolls of the forming roll by a hydraulic cylinder is used. The device is a plate forming device characterized in that the pressing force by the hydraulic cylinder during forming can be kept constant. (6) The plate forming apparatus as described in (5) above, wherein the hydraulic device has a relief valve. (7) The plate forming apparatus as described in (5) above, wherein the hydraulic device has a constant pressure source circuit using an accumulator. (8) An electric resistance welded steel pipe manufacturing apparatus using the plate forming apparatus according to any one of (5) to (7), wherein the roll has a hydraulic device that applies a pressing force between the upper and lower rolls, An ERW steel pipe manufacturing apparatus, which is a breakdown roll that straightens and straightens the width center of a strip steel.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to forming steel plates such as electric resistance welded steel pipes, TIG welded steel pipes, laser welded pipes and the like, square columns formed by roll forming, aluminum pipes and aluminum columns formed by a similar method, and the like. It can be applied to all types of plate forming methods and forming devices in which rolls having surface arc shapes are pressed against the upper and lower surfaces. Hereinafter, the case where the forming roll is a breakdown roll of an electric resistance welded steel pipe will be described as an example, but it goes without saying that the present invention is not limited to the method and the apparatus for manufacturing the electric resistance welded steel pipe.

In the breakdown roll having the hydraulic system of the present invention, one of the upper roll 1 and the lower roll 2 is usually fixed and the other is movable in the vertical direction. of course,
Both the upper and lower rolls may be movable rolls. Hereinafter, a case where the upper roll 1 is a movable roll will be described with reference to FIG.

The bearings 5 arranged on both sides of the upper roll 1 are
It is arranged so that it can be raised and lowered by a hydraulic cylinder 6 of a hydraulic device. Normally, not only the hydraulic cylinder 6 but also the manual lifting device 10 is used together to lift and lower the bearing 5. Either the hydraulic cylinder 6 or the piston rod 9 connected to it is the fixed side, and the other is moved up and down by the operation of hydraulic pressure. In FIG. 1, the piston rod 9
Is fixed to the screw nut 11 of the manual lifting device 10, the hydraulic cylinder 6 is fixed to the bearing 5, and the bearing 5 moves up and down as the hydraulic cylinder 6 moves up and down. Before the strip steel of the material is bitten, the hydraulic cylinder 6 is at the lower limit position for raising and lowering by the action of hydraulic pressure, and the screw nut 11 is raised and lowered by the operation of the manual raising and lowering device 10.
The opening degree between the upper and lower rolls can be set to a predetermined value. Instead of the manual lifting device 10, another means such as an electric lifting device may be adopted. Further, the lifting / lowering by the manual lifting / lowering device 10 may be carried out on the upper roll 1 as usual, and the lifting / lowering by the hydraulic cylinder 6 of the present invention may be carried out on the lower roll 2.

The bearing 5 may be lifted and lowered only by the hydraulic cylinder 6 without using a manual lifting device or the like.
In that case, the set opening between the upper and lower rolls before the strip steel bites can be set by, for example, disposing a stopper having a predetermined thickness between the upper and lower bearings. Change the set opening by changing the thickness of the stopper.
When the hydraulic pressure of the hydraulic cylinder is activated, the bearing of the upper roll descends and stops at the position where it hits the stopper,
The opening between the upper and lower rolls is set to the set value.

The set opening between the upper and lower rolls is set to be slightly narrower than the thickness of the steel strip, usually about 3 mm.

The present invention relates to a molding method and a manufacturing apparatus for pressing a forming roll having a surface arc shape onto the upper and lower surfaces of a plate, wherein the pressing force between the upper and lower rolls of the forming roll is controlled by a hydraulic cylinder of a hydraulic device. The hydraulic device is characterized in that the pressing force by the hydraulic cylinder is kept constant during pipe making.

A circuit having a relief valve 8 as shown in FIG. 1 as a hydraulic circuit for keeping the pressing force of the hydraulic cylinder constant, and the relief valve 8 is arranged in the hydraulic system supplied to the hydraulic cylinder 6. Can be adopted. Due to the action of the relief valve 8, the hydraulic pressure supplied to the hydraulic cylinder 6 is maintained at the set pressure of the relief valve 8. Before the strip steel bites in, there is no reaction force to the rolls, so the interval between the upper and lower rolls maintains the set opening, that is, the narrowest opening. When the strip steel bites into the breakdown roll, the strip thickness of the strip steel is thicker than the set opening, so that the breakdown roll receives a repulsive force in the direction of expanding the vertical roll interval. At this time, since the pressure in the hydraulic cylinder is kept constant by the action of the relief valve 8, the repulsive force by the strip steel exceeds the pressing force by the hydraulic pressure, and the hydraulic cylinder 6 or the piston rod 9 retracts and the upper roll 1 A balance is achieved at a position where the rebound force of the steel strip rises and the pressing force of the hydraulic pressure is balanced. Since the pressing force by hydraulic pressure is always constant regardless of the position of the upper roll 1, even if the strip thickness is thicker or thinner than the set strip thickness, the roll pressing force to the strip is high. Can be held constant.

As another hydraulic circuit for keeping the pressing force of the hydraulic cylinder constant, as shown in FIG. 2, a constant pressure source circuit using an accumulator can be adopted. The accumulator 12 operates in principle as a constant pressure source. 2A shows whether the pressure inside the accumulator 12 is higher or lower than a predetermined pressure.
When it is low, the motor 15 is rotated to drive the hydraulic pump 7, and when it is high, the rotation of the motor 15 is stopped to control the discharge pressure within a certain range. Further, in FIG. 2B, the hydraulic pump 7 remains rotating,
When the pressure in the accumulator 12 exceeds a required value, the unload valve 13 on the pump discharge side operates, the discharge oil of the pump is returned to the tank, and the oil supply to the accumulator is cut off. As a result, the hydraulic pressure in the accumulator can be kept constant.

In the prior art, as described above, the pressing force increases as the deviation between the roll distance expanded by the repulsive force of the strip steel and the set opening increases, and the pressing force decreases when the deviation is small. Therefore, when the plate thickness of the strip steel becomes thicker than the set value, the roll pressing force increases, and as a result, the phenomenon that YR of the pressing center part 20 extremely increases at the portion where the plate thickness becomes thicker is observed. However, in the present invention, since the roll pressing force can be kept constant regardless of the plate thickness of the strip steel, YR of the pressing center portion 20 should be kept constant regardless of the plate thickness of the strip steel. Therefore, it is possible to prevent the phenomenon that YR of the pressing center portion 20 extremely increases.

When the plate forming method and the forming apparatus of the present invention are applied to the electric resistance welded pipe manufacturing method and manufacturing apparatus, particularly preferable results can be obtained. The application of the pressing force between the upper and lower rolls by the hydraulic device of the present invention can be applied to all the rolls in the breakdown roll group. Among the breakdown rolls, as described in the above (4) and (8) of the present invention, particularly high effects can be obtained when applied to the breakdown rolls for straightening the width center of the steel strip. The breakdown roll for inwardly straightening the width center portion of the steel strip is a roll of the type shown in FIGS. 5A and 5B, and the pressing force of the upper and lower rolls is narrow as shown in FIG. Y in this part concentrated on the area
This is because R is increased, so that the effect of the present invention can be particularly exerted.

Therefore, in the break roll for forming the electric resistance welded steel pipe, in the type in which the rolls are arranged such that the radius of curvature of the roll shape gradually decreases from the front stage to the rear stage of the breakdown roll group, the break of each stage is broken. Down rolls are the subject of the present invention. Further, in the front stage of the roll group, a type in which a W bend roll for forming a W-shaped strip steel as shown in FIG. 5 (c) is arranged, and in the front stage of the roll group, a portion excluding the central portion of the strip steel is used. In the type in which the rolls for straightening are arranged, only the breakdown rolls for straightening the inner center of the width of the strip steel as shown in FIGS. May be the target of.

On the other hand, in the W bend roll shown in FIG. 5 (c), the portion to which the pressing force is applied covers a wide range of the strip steel, and the pressing force is not locally applied.
When the strip thickness is equal to the set strip thickness, the strip steel is pressed from the upper and lower rolls by an appropriate pressing force, and YR does not rise. However, even in the W bend roll, when the strip thickness is thicker than the set strip thickness, in the conventional type roll, the gap between the upper and lower rolls is excessively widened, and the pressing force increases, and An increase in YR will occur over a wide range. Therefore,
The effect of applying the present invention can be exhibited also in the W bend roll.

[0034]

EXAMPLES (Conventional example) In a 24-inch cage mill,
When manufacturing an electric resistance welded steel pipe having a diameter of 609.6 mm, a wall thickness of 22.0 mm, and a grade of 50 k, the conventional electric resistance welded steel pipe manufacturing method was used. The breakdown roll group has a total of six rolls, and the first two rolls are W bend type rolls (see FIG. 5) as described in JP-A-62-50019.
(C)) and the latter four units use rolls of a type (FIGS. 5 (a) and 5 (b)) that straightens and straightens the width center of the steel strip.
Regarding the rolls of the last four rolls (# 3 to # 6 rolls), the radius of curvature of the roll surface shape in the width center portion is the lower roll 2
Are # 3: 2476 mm, # 4: 1121 mm,
# 5: 648 mm, # 6: 466 mm, and the upper roll 1 has # 3: 2498 mm, # 4: 889 mm, # 5:
It is 405 mm and # 6: 285 mm. The wall thickness manufacturing range of ERW steel pipe using this roll is 6.3 mm to 22.0 m.
m. The interval between the upper and lower rolls can be adjusted by a screw nut type manual method.

The upper and lower roll intervals of the rolls were set so that the vertical load of the # 3 to # 6 rolls during forming was 110 tons. For example, for the # 4 roll, the set value of the roll interval is set to 3.0 mm from the wall thickness of the strip steel of 22.0 mm.
It was set to a narrow 19.0 mm. When the strip steel having a plate thickness of 22.0 mm is bitten into this, a roll pressing force of 110 tons is generated by expanding the roll interval by 3 mm.

FIG. 7 (a) shows the YR distribution in the circumferential direction of the steel pipe after pipe making when a steel strip having a plate thickness of 22.0 mm and a set plate thickness is produced. Moreover, the result of having calculated | required the equivalent plastic strain in the circumferential direction of the steel pipe by calculation is shown in FIG.7 (b). As you can see from these figures,
At the width center portion of the strip steel in the direction opposite to the circumference of the welded portion, that is, at the pressing center portion 20, locally high YR is shown and the equivalent plastic strain is high at the same portion. From this, the pressing center portion 20 is locally pressed down during molding, particularly during molding with # 3 to 6 breakdown rolls,
It can be seen that due to this, the YR is high in the relevant part.

The maximum wall thickness t _max within the manufacturable range of the pipe wall thickness
However, the pressing center portion 20 is locally pressed. It is assumed that the breakdown rolls used in this embodiment are also used for different ERW pipe outer diameters. For example, # 6 roll is 609.6
It is also used for the outer diameter of ~ 457.2 mmφ. As a result, the difference between the radius of curvature R _U of the surface shape of the upper roll and the radius of curvature R _L of the lower roll is larger than the maximum thickness t _max of the strip steel, and the thickness of the strip steel is the maximum thickness t _max. This is because the upper roll 1 and the lower roll 2 press the strip steel from both front and back sides only at the pressing center portion 20.

Next, in the case where pipes are manufactured by a conventional electric resistance welded steel pipe manufacturing apparatus using a strip steel whose plate thickness varies in the longitudinal direction of the strip steel, the YR steel pipe longitudinal direction in the pressing center portion 20 after pipe forming. The distribution is shown in FIG. 8 (a), and the plate thickness distribution of this strip steel is shown in FIG. 8 (b). YR fluctuates according to the distribution of the plate thickness of the coil. Particularly, the plate thickness is the thickest at a position 10 m from the tip of the coil, and YR is the highest at that portion at 91%.

(Examples of the present invention) In producing the same electric resistance welded steel pipe as described above, the production was performed using the electric resistance welded steel pipe manufacturing method of the present invention. The basic specifications of the group of six breakdown rolls were the same as in the conventional method described above, and the pressing force control of the upper rolls was performed for the # 3 to # 6 rolls by using the hydraulic device of the present invention.

As the lifting device for the # 3 to # 6 upper rolls, a manual lifting device 10 and a hydraulic cylinder 6 are used together as shown in FIG. The hydraulic device has a relief valve 8, and by adjusting the relief valve 8, the pressure in the hydraulic cylinder is kept constant so that the pressing force of the upper roll 1 becomes 110 tons. By operating the manual lifting device 10 with the hydraulic cylinder 6 at the lower limit position, the interval between the upper and lower rolls is adjusted to the set opening degree. The set opening was 19.0 mm, which was 3.0 mm narrower than the set plate thickness 22.0 mm of the steel strip.

When the strip steel bites into the breakdown rolls during pipe making, when the upper roll 1 rises due to the repulsive force of the strip steel and the hydraulic cylinder rises, the hydraulic pressure in the hydraulic cylinder 6 acts on the relief valve 8. Since it is kept constant by the pressing force of the strip steel by the upper and lower rolls is always 1
It can be kept constant at 10 tons. The pressing force is constant even if the strip thickness of the strip changes in the longitudinal direction.

FIG. 3 shows the distribution of YR in the longitudinal direction of the steel pipe in the pressing center portion 20 after pipe making when the pipe is made by the method of the present invention using the steel strip whose plate thickness varies in the longitudinal direction of the steel strip. , Together with the strip thickness distribution of the steel strip. Despite the plate thickness fluctuating between 21.92 and 22.26 mm in the longitudinal direction, YR in the pressing center portion 20 is kept constant and is 88.0% or less, which is a comparison with the conventional method. Then, it is clear that the occurrence of the extreme rise of YR can be eliminated.

[0043]

INDUSTRIAL APPLICABILITY The present invention is a molding method and a molding apparatus for pressing a molding roll having a surface arc shape on the upper and lower surfaces of a plate, for example, a manufacturing method and a manufacturing apparatus of an electric resistance welded steel pipe. The pressing force between the upper and lower rolls is applied by the hydraulic cylinder of the hydraulic device, and the pressing force of the hydraulic cylinder during molding is kept constant. Therefore, even when the plate thickness of the plate changes, the pressing force of the plate by the upper and lower rolls can be kept constant, and an extreme rise in YR at the pressing center can be prevented.
Accordingly, when the electric resistance welded steel pipe is used as a structural material of a building or a line pipe, the electric resistance welded steel pipe can have excellent fracture resistance. In addition, when the electric resistance welded steel pipe is used as a material for hydroforming, the electric resistance welded steel pipe can have good workability. The present invention is not limited to ERW steel pipe,
Molded steel pipes such as TIG welded steel pipes and laser welded pipes, square columns formed by roll forming, aluminum pipes and aluminum columns formed by the same method, etc., by pressing rolls with a surface arc shape on the upper and lower surfaces of the plate The same effect can be obtained in the forming method and forming apparatus for all kinds of metal plates.

[Brief description of drawings]

FIG. 1 is a view showing a breakdown roll of an electric resistance welded steel pipe of the present invention, (a) is a schematic view of the breakdown roll,
(B) is a schematic diagram of a hydraulic device.

FIG. 2 is a schematic view showing a hydraulic device of the present invention.

FIG. 3 shows the longitudinal quality of an electric resistance welded steel pipe produced by the method of the present invention, (a) showing the YR distribution at the center of pressing, and (b) showing the plate thickness distribution of the strip steel.

FIG. 4 is a view showing a breakdown roll of a conventional electric resistance welded steel pipe.

FIG. 5 is a view showing a breakdown roll shape of an electric resistance welded steel pipe, wherein (a) and (b) are breakdown rolls for straightening inward bending on both sides of a pressing center portion, and (c) is a W-shaped strip steel. It is W bend roll.

FIG. 6 is a diagram showing a contact state in the vicinity of a pressing center portion of a forming roll.

FIG. 7 shows the circumferential quality of an electric resistance welded steel pipe manufactured by a conventional method, (a) showing a YR distribution and (b) showing a distribution of an equivalent plastic strain.

FIG. 8 shows the longitudinal quality of an electric resistance welded steel pipe manufactured by a conventional method. (A) shows the YR distribution at the center of pressing and (b) shows the strip thickness distribution of the strip steel.

[Explanation of symbols]

1 upper roll 2 Lower roll 3 band steel 4 stand 5 bearings 6 hydraulic cylinder 7 hydraulic pump 8 relief valve 9 Piston rod 10 Manual lifting device 11 screw nuts 12 Accumulator 13 Unload valve 14 Pressure switch 15 motor 20 Center of pressing

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshihiro Ishibashi             20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd.             Inside the surgical development headquarters (72) Inventor Takeyuki Sato             2-12-2 Mikunihonmachi, Yodogawa-ku, Osaka-shi, Osaka             Issue Nakata Manufacturing Co., Ltd. F-term (reference) 4E028 CA02 CA07                 4E063 AA01 BA06 EA10

Claims (8)

[Claims] 1. A molding method in which a molding roll having an arcuate surface shape is pressed against the upper and lower surfaces of a plate to form a pressing force between the upper and lower rolls of the molding roll by a hydraulic cylinder of the hydraulic device, and the hydraulic device forms A method for forming a plate, characterized in that the pressing force by a hydraulic cylinder is kept constant inside. 2. The plate forming method according to claim 1, wherein the hydraulic device has a relief valve. 3. The plate forming method according to claim 1, wherein the hydraulic device has a constant pressure source circuit using an accumulator. 4. A method for manufacturing an electric resistance welded steel pipe using the plate forming method according to claim 1, wherein the roll for applying a pressing force between the upper and lower rolls by a hydraulic device is a strip steel. A method for manufacturing an electric resistance welded steel pipe, which is a breakdown roll for straightening the center portion of the width of the wire. 5. A forming apparatus for pressing a forming roll having an arcuate surface shape to the upper and lower surfaces of a plate to form a press, the hydraulic device having a hydraulic cylinder for applying a pressing force between upper and lower rolls of the forming roll. Is a plate forming device characterized by being able to maintain a constant pressing force by a hydraulic cylinder during forming. 6. The plate forming apparatus according to claim 5, wherein the hydraulic device has a relief valve. 7. The plate forming apparatus according to claim 5, wherein the hydraulic device has a constant pressure source circuit using an accumulator. 8. An electric resistance welded steel pipe manufacturing apparatus using the plate forming apparatus according to claim 5, wherein the roll having a hydraulic device for applying a pressing force between the upper and lower rolls is a strip. An electric resistance welded pipe manufacturing apparatus, which is a breakdown roll for straightening the center of the width of steel.