JP2003220419A - Forming rolls and forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide forming rolls and a forming method capable of manufacturing a molded article having a sufficiently low YR in all other parts than the welded part after forming in the roll forming to force and form rolls having a surface circular arc shape on the upper and lower surface of the steel plate such as an electric resistance welded tube. <P>SOLUTION: By forming a concave portion 4 in the width center portion of the lower roll 1 of the forming rolls, circumstances where the upper and lower roll force the steel plate in the forcing center portion 10 are removed, which leads to prevent local area drafting of the forcing center portion 10, enabling low YR molded articles to be manufactured by preventing a YR increase of the region. When the roll configuration of forcing center portion of both sides of the lower roll 1 is radius of curvature R<SB>1</SB>and a virtual circle 11 of the radius R<SB>1</SB>contacting the roll configuration in the center portion of both sides is described, the roll surface position C of the width center portion is situated in the roll center side rather than the position of the virtual circle 11. <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 roll for pressing a roll having an arcuate surface shape onto the upper and lower surfaces of a plate, and more particularly to a breakdown roll for forming an electric resistance welded steel pipe. The present invention relates to a forming roll capable of producing

[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 a forming roll that is formed by pressing a shaped roll.

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. 6
(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. 6 (a) and 6 (b)) is arranged. Further, since the breakdown roll functions as a drive roll for advancing the strip steel, the roll steel is pinched by the upper and lower rolls and then a driving torque is applied to the roll.

In the roll for forming the electric resistance welded 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.

[0007] For automobile parts and the like, products formed by forming an electric resistance welded steel pipe by a hydroforming method have begun to be used. 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.

[0008] By the hydroform method, it is possible to form a complex shape having a light weight and a high degree of processing that cannot be obtained by the conventional method. Further, the axial force and the internal pressure during processing can be controlled with high accuracy. 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.

[0011]

Regarding the portion of the electric resistance welded steel pipe after electric resistance welding other than the electric resistance welding portion, it corresponds to the opposite side in the circumferential direction of the electric resistance welding portion, that is, the width center portion of the strip steel. It was found that there is a portion in which the YR is high and the ductility is low in the portion to be filled as compared with the other portions. When such a portion is present, when an electric resistance welded steel pipe is used as a structural material for a building, a portion having a high YR tends to be a starting point of fracture during an earthquake. 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-annealer applied to the electric resistance welded part, if post-annealing is attempted to reach the part on the opposite side of the welded part, it becomes necessary to install new post-annealer equipment, which deteriorates the productivity of pipe making. It will be different.

The present invention is a roll forming process for pressing an electric resistance welded steel pipe and pressing a roll having a surface arc shape on the upper and lower surfaces of the plate to form a roll. It is an object of the present invention to provide a technique capable of producing a molded product having extremely low YR.

[0013]

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 wall thickness of the plate to be formed is smaller than the maximum wall thickness t _max , as shown in FIG. 7, the portion where the upper roll 2 and the lower roll 1 press the plate 3 from both front and back sides is the pressing center portion. Only 10.
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 2 and the lower roll 1 press the plate 3 from both front and back sides only at the pressing center portion 10.

Since the forming roll is a drive roll for moving the plate, it is necessary to secure a predetermined pressing force. Therefore, in the pressing center portion 10, the plate is plastically deformed by an excessive rolling force by the rolls, which causes the YR of the pressing center portion 10 to increase, the ductility to decrease, and the hardness to increase further. Became.
Especially in the width center of the hot rolled coil, the plate thickness is 0.
Since the thickness is often about 3 mm, the thickness of the plate taken from the width center of the hot-rolled coil by trim is large, and therefore the rolling force is increased to increase the Y of the pressing center portion 10.
The degree of R rise becomes larger.

As shown in FIG. 1, by forming a recess 4 in the pressing center portion 10 at the center of the width of the lower roll 1, the situation in which the upper and lower rolls press the plate at the pressing center portion 10 is eliminated, and the rolling force of the roll is reduced. Are distributed on both sides of the pressing center part 10. As a result, it is possible to prevent local reduction of the pressing center portion 10 and to prevent YR rise of the relevant portion, so that it is possible to manufacture a metal molded product of low YR.

The present invention was made on the basis of the above findings, and the gist thereof is as follows. (1) 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 a lower roll 1 of the forming roll, the shape of the rolls on both sides of the pressing center portion has a radius of curvature R ₁ . When a virtual circle 11 having a radius R ₁ that touches the roll shape on both sides of the pressing center portion is drawn, the roll surface position C of the pressing center portion is located closer to the roll center than the position of the virtual circle 11. Forming roll. (2) a second imaginary circle 12 is the thinnest thickness value obtained by adding a surface curvature radius R _U in the center pressing the upper roll t _{m in} of the strip in which the radius R ₂ is molded, the second Virtual circle 1
When 2 is arranged so as to contact the lower roll surface on both sides of the pressing center part, the roll surface position C of the pressing center part is located at the same position as the position of the second virtual circle 12 or on the roll center side from that position. The forming roll according to (1) above, which is characterized in that (3) In a forming roll formed by pressing a roll having a surface arc shape on the upper and lower surfaces of the plate, the lower roll 1 of the forming roll has a shape in which the roll surface radius of curvature R ₃ of the pressing center portion 10 is the pressing center. A forming roll characterized by being smaller than the roll surface curvature radius R _L on both sides of the part. (4) The lower roll surface curvature radius R ₃ of the pressing center part is
The forming roll according to (3) above, which is equal to or less than a value obtained by adding the thinnest plate thickness t _min among the plates to be formed to the upper roll surface curvature radius R _U of the pressing center portion. (5) The forming roll according to any one of (1) to (4) above, wherein the forming roll is a breakdown roll for forming an electric resistance welded steel pipe.

(6) A plate forming method using the forming roll described in any one of (1) to (4) above. (7) A method for manufacturing an electric resistance welded steel pipe, which comprises using the breakdown roll described in (5) above.

(8) A plate forming apparatus comprising the forming roll described in any one of (1) to (4) above. (9) An electric resistance welded steel pipe manufacturing apparatus having the breakdown roll described in (5) above.

In the present invention, the upper roll has a convex arc shape on the roll surface, and the lower roll has a concave arc shape on the roll surface.

[0020]

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 kinds of roll forming in which rolls having arcuate surface shapes are pressed against the upper and lower surfaces. Hereinafter, the breakdown roll of the 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 breakdown roll of the electric resistance welded steel pipe.

In the break roll for forming the electric resistance welded steel pipe, in the type in which the 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 breakdown roll group, the breakdown rolls of each stage 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. 6 (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, both sides of the pressing center portion 10 located in the width center portion of the strip steel as shown in FIGS. Breakdown rolls for are subject of the present invention.
The pressing center portion 10 is located at the center of the width of the roll.

The sectional shape of the breakdown roll for straightening both sides of the pressing center portion of the strip steel is to have a constant radius of curvature in the entire width of the roll as shown in FIG. 6 (a), and FIG. 6 (b). There are rolls having different radii of curvature on the width center and on both sides of the width. In the case where the roll width center and the width sides have different curvature radii, conventionally, a constant radius of curvature R _L or R _U is often used in a region of a certain range including the roll width center portion. The region in which the radius of curvature of the roll shape is constant in the width center of the upper and lower rolls is referred to as "central constant radius of curvature region 15" here.
Call. The relationship of the radii of curvature between the upper roll 2 and the lower roll 1 is, for example, in the width center of the roll, the upper roll 2
The radius of curvature R _U is defined as a value obtained by subtracting the maximum plate thickness t _max of the strip steel from the radius of curvature R _L of the lower roll 1.

In the above (1) of the present invention, FIG.
As shown in (b), the shape of the lower roll 1 is such that the roll shape on both sides of the pressing center portion 10 has a radius of curvature R ₁ (= _RL ), and the radius R in contact with the roll shape on both sides of the pressing center portion is R.
_{When one} virtual circle (first virtual circle 11) is drawn, the roll surface position C at the center of pressing is located closer to the roll center than the position of the first virtual circle 11. Center of pressing 1
The roll shape on both sides of 0 has a radius of curvature R ₁ means that the radius of curvature _RL of the lower roll cross-sectional shape in the central constant radius of curvature region 15 is R ₁ . Then, in the case of the conventional lower roll 1, the roll surface position C at the pressing center portion coincides with the position of the first virtual circle 11. In the present invention, the fact that the roll surface position C of the pressing center portion is located closer to the roll center side than the position of the first virtual circle 11 means that the concave portion 4 is formed in the width center portion of the lower roll 1. Is to say.

As for the upper roll 2, the radius of curvature R _{U of the} cross-sectional shape is constant in the central constant radius of curvature region 15, as is conventional. Usually, the lower roll 1 has a radius of curvature R _U of a value obtained by subtracting the maximum plate thickness t _max of the strip steel from the radius of curvature R _L of the lower roll 1. Therefore, as a result of forming the concave portion 4 in the width center of the lower roll 1, when the lower roll 1 is used as a breakdown roll to form a strip steel, the lower roll 1 and the lower roll 1 are pressed. The parts are not locally concentrated on the pressing center part 10, and are dispersed on both sides of the pressing center part or in a wide area including the pressing center part. As a result, the compressive stress received by the strip steel due to the rolling reduction is naturally small, and the deformation strain of the pressing center portion due to the compression is reduced, so that the local increase of YR can be suppressed.

Next, in order to define the shape of the recess of the present invention (1), a second virtual circle 12 as shown in FIG. 2 is assumed here. The radius R ₂ of the second virtual circle 12 is a value obtained by adding the surface curvature radius R _U at the center of the upper roll width to the thinnest plate thickness t _min of the band steel to be formed. The second virtual circle 12 represents the radius of curvature of the lower surface of the strip steel 3 when it is assumed that the strip steel 3 is in close contact with the upper roll 2 when the strip steel 3 having the thinnest plate thickness t _min is formed. ing. As above, usually R _U =
Since R ₁ −t _max , R ₂ = R _U + t _min = R ₁ − (t
_max −t _min ), and the radius R ₂ of the _second virtual circle 12 is smaller than the radius R ₁ of the first virtual circle 11.

In the above (1) of the present invention, when the second virtual circle 12 is arranged so as to contact the lower roll 1,
When the imaginary circle 12 is in contact with the width center of the lower roll 1, the degree of depression of the concave portion 4 at the width center of the lower roll is still small, and there is a reduction at the width center. However, since the radius of curvature at the center of the width of the lower roll 1 is smaller than that of the conventional one, the rolling-down region at the center of the width is widened in the width direction, and the stress locally received by the steel strip is reduced. It is possible to enjoy the effect of lowering YR in.

In the above (2) of the present invention, as shown in FIG. 2, when the second virtual circle 12 is arranged so as to contact the lower roll 1, the second virtual circle 12 is located on both sides of the pressing center portion. It contacts the surface of the lower roll at point P. The roll surface position C at the center of the width is at the same position as the position of the second virtual circle 12 (FIG. 2B) or on the roll center side from the position of the second virtual circle 12 (FIG. 2A). Is located in. Second
That the imaginary circles 12 contact the surface of the lower roll at points P on both sides of the pressing center means that the concave portion 4 at the center of the lower roll
It means that the degree of depression of the is larger. Then, at the same time, when the roll surface position C at the center of the width becomes the same position as the position of the second virtual circle 12 (FIG. 2 (b)), the width in the case of forming the strip steel 3 having the minimum wall thickness t _min It corresponds to the position where the local reduction in the central part is just resolved. Further, when the roll surface position C at the width center is located closer to the roll center than the position of the second virtual circle 12 (FIG. 2 (a)).
In the case where the strip steel 3 having the minimum wall thickness t _min is formed, the width center portion is not pressed by the upper and lower rolls.
When the degree of depression of the concave portion 4 is increased to this extent, the local reduction of the pressing center portion 10 can be almost eliminated even when the deflection of the roll and the roll shaft is taken into consideration, and any thickness of steel strip can be used. Even in such a case, the YR distribution in the circumferential direction of the steel pipe after pipe making is almost uniform except for the welded portion, and there is no region where the YR is locally high.

In the present invention (2), since the second virtual circle is in contact with the surface of the lower roll at the points P on both sides of the pressing center portion, the strip steel 3 is highly rolled at the two points P in contact with each other. You will receive power. Conventionally, the pressure was applied only at one point on the pressing center portion 10, whereas
The local rolling force is reduced because the rolling force is received at two points. However, in order to make the local rolling force as small as possible and realize the uniform distribution of YR, the second virtual circle 12
It is preferable that the surface shape of the lower roll is as smooth as possible in the vicinity of the point P on both sides of the width center portion in contact with the lower roll 1. Specifically, as shown in FIG. 4, it is preferable to have a cross-sectional shape in which the radius of curvature R ₄ of the fourth virtual circle 14 that is in contact with the relevant portion is as large as possible.

The distance between the points P where the second imaginary circle 12 is in contact with the lower roll surface on both sides of the pressing center is d _P as shown in FIG. If the value of d _P is too large, the function of forming the breakdown roll that straightens the inner center of the pressing core 10 cannot be fully exerted, and if the value of d _P is too small, local reduction of the pressing center part 10 is prevented. The effect of the present invention is reduced. When the total width of the steel strip is 200%,
Press the position of point P against the central part 10 ± 5% to ± 30
% Is preferable. At this time, the value of d _P is 10
~ 60%. The reason why the position of the point P is within the above range is
This is because at least ± 5% or more is desirable because the widthwise center position may move about ± 5% in consideration of meandering in the width direction of the coil passing through. Further, in the case of a plurality of center bends, it is necessary to shift the position (point P) to receive the rolling reduction. For example, in the case of four stages, considering the meandering of the coil, the first stage ± 25%, the second stage ± 20%, 3rd stage ± 15%, 4th stage ±
Because it is necessary to set the pitch to 10%, it is preferable to set the pitch to about 30% at the maximum.

[0030] When the breakdown rolls for the inner bend straightening the sides of the central portion 10 pressed into the breakdown rolls are more disposed, as d _P of each roll is not the same value as much as possible different values It is preferable to determine the roll shape so that When the values of d _P are substantially the same in a plurality of rolls, the same part of the strip steel 3 is subjected to multiple reductions, but if the d _{p of} each roll is different, the same part of the strip steel is It is not subject to multiple reductions. As a result, the local abnormality of YR due to local pressure reduction is further eliminated. Normally, it is convenient to make d _P smaller as the radius R _{1 of} the first virtual circle 11 becomes smaller.

As shown in FIG. 3, in the present invention, as the shape of the concave portion 4 formed in the width center of the lower breakdown roll 1, as described in the above (3) of the present invention, the radius of curvature of the roll surface at the center of the pressing. It can be expressed that R ₃ is smaller than the roll surface radius of curvature R ₁ (= _RL ) on both sides of the pressing center portion. As a result, similarly to the present invention (1), it is possible to reduce or eliminate the local reduction in the pressing center portion.

Further, as in the above (4) of the present invention,
The lower roll surface curvature radius R ₃ of the pressing center portion is equal to or less than a value (R ₂ ) obtained by adding the thinnest plate thickness t _min of the strip steel to the upper roll surface curvature radius R _U of the pressing center portion. By expressing it, it is possible to make the invention almost equivalent to the invention (2). FIG. 3A shows the case where R ₃ has a smaller value than R ₂ , and FIG. 3B shows the case where R ₃ has a value equal to R ₂ . Since the value obtained by adding the thinnest plate thickness t _min of the band steel to be formed to the upper roll surface radius of curvature R _U of the pressing center part is the radius R ₂ of the second virtual circle 12, the present invention ( 4) When the second virtual circle 12 is arranged so as to contact the lower roll 1 in the lower roll shape, the contacting position is not the center of the roll width, but the positions P on both sides of the width center part.
Becomes

Also in the present inventions (3) and (4), the point where the roll shape should be made as smooth as possible in the portion where the radius of curvature of the central portion of the lower roll width transitions to the radius of curvature on both sides thereof is the present invention ( 1) Same as (2). Further, regarding the distance d _P of the point P where the second virtual circle is in contact with the lower roll in the present inventions (3) and (4), more preferable results can be obtained by the same consideration as in the present inventions (1) and (2). Can be obtained.

The above (5) of the present invention is the same as the present invention (1) to (1).
The forming roll of (4) is limited to a breakdown roll for forming electric resistance welded steel pipe.

As described in the above item (6) of the present invention, by using the forming rolls of the present invention (1) to (4), it is possible to prevent the local reduction of the pressing center portion 10 and to prevent the YR of the relevant portion. Since the rise can be prevented, it becomes possible to manufacture a low YR molded product. Further, the present invention (7)
By manufacturing an electric resistance welded steel pipe using the breakdown roll of the present invention (5), it is possible to prevent local reduction of the pressing central portion 10 and prevent YR rise of the relevant portion. It becomes possible to manufacture a low YR electric resistance welded steel pipe.

Further, as described in the above item (8) of the present invention, the plate forming apparatus having the forming rolls of the present inventions (1) to (4) is formed by using this apparatus to form a plate. Since it is possible to prevent local reduction of the pressing center portion 10 and prevent YR rise of the relevant portion,
It becomes possible to manufacture low YR molded products. The present invention (9) having the breakdown roll of the present invention (5)
By manufacturing the electric resistance welded steel pipe using this device, the local reduction of the pressing center portion 10 can be prevented and the YR rise of the relevant part can be prevented. , It becomes possible to manufacture low YR ERW steel pipe.

[0037]

EXAMPLE A diameter of 60 in a 24-inch cage mill
When producing an electric resistance welded steel pipe of 9.6 mm, a wall thickness of 22.0 mm, and a product type of 50 k class, the production was performed using a conventional electric resistance welded steel pipe production method. The breakdown roll group has a total of six rolls, and the first two rolls are W bend type rolls (see FIG. 6) as described in JP-A-62-50019.
(C)), the latter four use rolls of a type (FIGS. 6 (a) and 6 (b)) that press and rectify both sides of the center portion. For the last four rolls (# 3 to # 6 rolls),
Regarding the radius of curvature of the roll surface shape in the central constant radius of curvature region 15, the lower roll 1 has # 3: 2476 m, respectively.
m, # 4: 1121 mm, # 5: 648 mm, # 6: 4
66 mm, the upper roll 2 is # 3: 2498 mm,
# 4: 889 mm, # 5: 405 mm, # 6: 285 m
m. The wall thickness production range of the electric resistance welded steel pipe using this roll is 6.3 mm to 22.0 mm.
The vertical load of the 3 to # 6 rolls is about 110 tons.

The distribution of YR in the circumferential direction of the steel pipe after pipe making is shown in FIG. 9 (a). Further, FIG. 9B shows the result of calculation of the equivalent plastic strain in the circumferential direction of the steel pipe. As is clear from these figures, in the width center portion of the steel strip located in the direction opposite to the circumference of the welded portion, that is, the pressing center portion 10, a locally high YR and a high equivalent plastic strain in the same portion are obtained. Has become. From this,
It can be seen that at the time of forming, particularly at the time of forming with the # 3 to 6 breakdown rolls, the width center part of the strip steel is locally rolled down, which causes a high YR at that part.

The maximum wall thickness t _max within the manufacturable range of the pipe wall thickness
However, the central width portion of the steel strip is locally compressed. 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 609.6-4
It is also used for the outer diameter of 57.2 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. Even if there is upper roll 2
This is because the lower roll 1 presses the strip steel from both front and back sides only at the width center portion of the strip steel. When the pipe wall thickness is smaller than the maximum wall thickness t _max , the increase in YR at the width center portion of the steel strip, that is, the pressing center portion 10, becomes more severe.

Next, the present invention was applied to a breakdown roll for producing the same electric resistance welded steel pipe. # 3 to 6 A recess 4 was formed in the center of the lower roll width of the breakdown roll. The shape of the recess 4 of the lower roll 1 is determined as follows. First, as shown in FIG. 8, when a first virtual circle 11 having a radius R ₁ that is in contact with the roll shape on both sides of the central portion is drawn, the roll surface position C in the width central portion and the position of the first virtual circle 11 are drawn. Distance z ₁
far. If z ₁ is negative, the roll surface position C at the center of the width is located closer to the roll center than the position of the first virtual circle 11, as shown in FIG. Next, the second virtual circle 1
When 2 is arranged so as to be in contact with the lower roll surface on both sides of the pressing center part, the distance between the second virtual circle 12 and the roll surface position at the center of the width is set to z ₂ . If z ₂ is negative, the roll surface position at the center of the width is the second as shown in FIG.
Is located closer to the center of the roll than the position of the virtual circle. Further, the radius of curvature of the lower roll surface in the central portion of the width is set to R ₃ . #
3 to 6 breakdown rolls R _L , R _U , R ₃ , z ₁ , z
₂ and d _P are shown in Table 1.

[0041]

[Table 1]

When the above recessed portion 4 was formed in the breakdown lower roll 1 and an electric resistance welded steel pipe of the same type as the above-mentioned conventional example was pipe-formed, Y in the circumferential direction of the steel pipe after pipe-making was obtained.
The distribution of R is as shown in FIG. 10 (a), and the result of calculating the equivalent plastic strain in the circumferential direction of the steel pipe by calculation is as shown in FIG. 10 (b). That is, the local YR rising portion and the local strain portion of the pressing center portion 10 generated in the conventional pipe making method are eliminated, and a steel pipe having a low YR having a uniform quality in the entire circumference in the circumferential direction except the welded portion is manufactured. I was able to.

[0043]

INDUSTRIAL APPLICABILITY The present invention is a forming roll for pressing and forming a roll having a surface arc shape on the upper and lower surfaces of a plate, for example, a breakdown roll for forming electric resistance welded steel pipe, in which both sides of the pressing center portion are internally bent. In the breakdown roll to be straightened, a recessed portion is formed at the center of the width of the breakdown lower roll, so that after the electric resistance welded steel pipe is made, the electric resistance welded steel pipe having a sufficiently low YR in any portion except the electric resistance welded portion. Can be manufactured. Thereby, in the electric resistance welded steel pipe used as the structural material of the building, it is possible to prevent the electric resistance welded steel pipe structure from breaking when an earthquake occurs. Further, in the case of performing hydroforming by using an electric resistance welded steel pipe as a raw pipe, it becomes possible to hydroform a product having a complicated shape without causing breakage of the steel pipe. INDUSTRIAL APPLICABILITY The present invention is not limited to electric resistance welded steel pipes, but also formed 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, and surface arcs on the upper and lower surfaces of the plate. The same effect can be obtained in roll forming of all kinds of metal plates which are formed by pressing a shaped roll.

[Brief description of drawings]

1A and 1B are views showing a forming roll of the present invention, in which FIG. 1A is a schematic sectional view, and FIG. 1B is a partial sectional view in the vicinity of a recess of a lower roll.

FIG. 2 is a partial cross-sectional view of a lower roll of the present invention near a recess.

FIG. 3 is a partial cross-sectional view of the lower roll of the present invention near a recess.

FIG. 4 is a partial cross-sectional view of the lower roll of the present invention near a recess.

FIG. 5 is a partial cross-sectional view of the lower roll of the present invention near a recess.

FIG. 6 is a view showing a conventional forming roll, (a)
(B) is a forming roll for inwardly straightening both sides of the pressing center portion, and (c) is a W bend roll for forming the plate into a W shape.

FIG. 7 is a diagram showing a contact situation in the vicinity of a width center portion of a conventional forming roll.

FIG. 8 is a diagram showing a positional relationship in the vicinity of a recess in the lower roll of the present invention.

FIG. 9 shows the circumferential quality of an electric resistance welded steel pipe manufactured by a conventional method, where (a) shows a YR distribution and (b) shows an equivalent plastic strain distribution.

FIG. 10 shows circumferential quality of an electric resistance welded steel pipe manufactured by the method of the present invention, (a) showing YR distribution, and (b) showing distribution of equivalent plastic strain.

[Explanation of symbols]

1 Lower Roll 2 Upper Roll 3 Plate (Steel) 4 Recess 10 Pressing Center 11 First Virtual Circle 12 Second Virtual Circle 13 Third Virtual Circle 14 Fourth Virtual Circle 15 Central Constant Radius of Curvature R ₁ First virtual circle radius R ₂ Second virtual circle radius R ₃ Third virtual circle radius R ₄ Fourth virtual circle radius R _L Lower roll radius of curvature R _U Upper roll radius of curvature t _max Maximum wall thickness of strip steel t _min Minimum thickness of strip steel

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Eiji Tsuru             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 CA07                 4E063 AA01 BB06 EA01 JA02 MA10                       MA18

Claims (9)

[Claims] 1. A forming roll in which a roll having an arcuate surface shape is pressed against the upper and lower surfaces of a plate to form a lower roll of the forming roll having a radius of curvature R ₁ on both sides of the pressing center portion. When a virtual circle having a radius R ₁ that is in contact with the roll shapes on both sides of the pressing center portion is drawn, the roll surface position of the pressing center portion is located closer to the roll center than the position of the virtual circle. Forming roll. 2. The second imaginary circle is a value obtained by adding the surface curvature radius of the center portion of the upper roll pressing to the thinnest plate thickness of the plates to be formed, and the second imaginary circle is pressed to the center. When arranged so as to contact the lower roll surface on both sides of the part, the roll surface position of the pressing center portion is located at the same position as the position of the second virtual circle or on the roll center side with respect to that position. The forming roll according to claim 1. 3. A forming roll formed by pressing a roll having an arcuate surface shape on the upper and lower surfaces of a plate, wherein the lower roll of the forming roll has a roll surface curvature radius of the pressing center portion on both sides of the pressing center portion. Forming roll having a radius of curvature smaller than that of the roll surface. 4. The radius of curvature of the lower roll surface of the pressing center portion is less than or equal to a value obtained by adding the thinnest plate thickness of the plates to be formed to the radius of curvature of the upper roll surface of the pressing center portion. The molding roll described in 1. 5. The forming roll according to claim 1, wherein the forming roll is a breakdown roll for forming an electric resistance welded steel pipe. 6. A method for forming a plate, which comprises using the forming roll according to any one of claims 1 to 4. 7. A method for manufacturing an electric resistance welded steel pipe, characterized in that the breakdown roll according to claim 5 is used. 8. A plate forming apparatus comprising the forming roll according to any one of claims 1 to 4. 9. An electric resistance welded steel pipe manufacturing apparatus comprising the breakdown roll according to claim 5.