JPH0312977B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a forming method and apparatus in the forming area of the end of a steel strip called breakdown in the manufacture of electric resistance welded steel pipes, that is, the manufacture of steel pipes by continuous roll forming. Accordingly, it is possible to bend the end of a steel strip suitable for manufacturing steel pipes of a wide range of diameters and wall thicknesses, from small diameter pipes to large diameter pipes, with one set and one type of forming rolls without replacing the forming rolls. ,
It also reduces the influence of spring back at the ends of the strip, significantly improving the formability in the initial stage of forming in the pipe mill, and reducing defects at the ends, which improves the forming area and fin pass area of the subsequent center of the strip. The present invention relates to a method and apparatus for forming the end of a steel strip, which reduces the amount of forming and enables continuous roll forming with excellent forming distribution and formability.

Conventional technology Currently, straight seam welded steel pipes are manufactured by continuous roll forming, in which the strip is continuously formed by using forming rolls suitable for forming the required diameter and wall thickness, and arranging the forming rolls according to the diameter. So-called electric resistance welded steel pipes have become mainstream, and are ideal for mass production of small quantities.

As shown in FIG. 8, the entire process of pipe making by continuous roll forming is roughly divided into forming areas I for the ends of the steel strip, forming areas for the center of the steel strip, and fin pass areas.

That is, first, the breakdown roll (same b
Initial forming from bending the end of the steel strip to a semicircle is carried out using a non-driving side roll cluster (see Fig. c) and/or horizontal rolls to form a substantially circular shape. Fin pass roll (Figure d)
The angle of the edge surface is adjusted, reduced, finished formed, and centered, and then the welding process is started using a squeeze roll.

In addition, in the above process, the forming rolls are usually formed by arranging various combinations of horizontal and side rolls, and furthermore, in order to prevent buckling and edge waves due to edge stretching that occurs when forming thin-walled pipes, A cage forming method in which a large number of small flat rolls called cage rolls are arranged is also used.

In all conventional continuous roll forming methods, the main process is to form a semicircular shape at the initial stage of forming, which is the most difficult process, but the bending of the end of the strip is a major factor that affects the roundness of the tube and the quality of the welding process. is insufficient.

Generally, there is a lot of spring back after passing through the rolls due to insufficient bending of the ends of the strip, but mainly due to manufacturing cost requirements, the number of forming stages is increased and the ends of the strip are not completely bent, and the next forming area is The idea is to form the central part of the steel strip and correct any formability defects in the early and middle stages of forming at once in the fin pass area.

For example, for the purpose of sufficient initial forming, a technique has been proposed in which the central part of the steel strip is back-bent, both ends are bent inward, and then the back-bend is returned to its original state (Japanese Patent Publication No. 59-27654, 59-150620), but
It cannot be said that the initial forming is still sufficient to eliminate the need for the above-mentioned corrections, and the forming rolls have almost no commonality with respect to changes in pipe diameter and wall thickness.

Therefore, an increase in the amount of molding in the fine pass region due to poor formability in the initial and middle stages of molding is undesirable from the perspective of the distribution of molding amount in the entire process, considering product accuracy, manufacturability, and economical efficiency of the molding equipment. .

In addition, insufficient bending of the strip end face and so-called angularity during the middle stage of forming affect the circularity of the pipe and the quality of the welding process, so it is possible to perform sufficient forming at the stage of bending the end of the strip steel, or in the next stage. There has been a strong need for a forming method or forming device that can compensate for the lack of edge bending and prevent angular formation.

Furthermore, as mentioned above, manufacturing welded steel pipes by continuous roll forming requires the use of forming rolls suitable for forming the required diameter and wall thickness, the formation roll arrangement according to the diameter, and the width of the steel strip to be formed. It is necessary to replace the forming rolls depending on the size of the product, and it is not desirable from the viewpoint of manufacturing efficiency to prepare and replace a large number of forming rolls for each required diameter. Although it has been used for mass production, today there is a need to efficiently manufacture a wide variety of products using a single machine, and continuous rolls are suitable not only for mass production of a small number of products, but also for production of a wide variety of products in small quantities. A molding method or molding device is required.

In addition, in double radius forming, if the pipe diameter changes, the curvature of the bent end changes, so if the roll is shared, the bent end cannot be rolled down, and the circular part should be rolled with a straight roll or relatively Since the roll is rolled down while making point contact with a roll having a large radius of curvature, there is a problem that the formability into a circular shape deteriorates and angularity tends to occur.

Furthermore, when a large number of cage rolls are used in common, it is necessary to use a flat roll as well, which poses a problem in that the strip material to be formed tends to roll.

On the other hand, Japanese Patent Publication No. 57-46926 describes a forming roll for rough forming (breakdown) for the purpose of sharing the roll for several types of pipe diameters, for bending the ends of the strip steel of the planned maximum diameter pipe. Required curved surface R ₃ , the curved surface required for bending the end of the strip of pipe with the planned minimum diameter
R ₁ , curved surface R ₂ of the bending radius necessary for rough forming of the inner curved surface following the end of the strip steel of the pipe with the minimum diameter, from the outside of the roll surface to the inside in the order of curved surface R ₃ , curved surface R ₁ , and curved surface R ₂ Rough forming rolls have been proposed that have roll surfaces aligned in the .

Forming using this rough forming roll is basically edge forming, and the purpose is to share the roll within several types of pipe diameter ranges, and three types of roll curved surfaces are used based on the maximum and minimum pipe diameters in the shared range. As in the conventional method, multi-stage molding is essential in order to determine , the idea is to make corrections all at once in the fine path area.

Therefore, a large amount of forming in the fin pass area is unfavorable from the viewpoint of forming amount distribution in the entire process, considering product accuracy, manufacturability, and economic efficiency of the forming equipment. Since such end defects affect the roundness of the tube and the quality of the welding process, there has been a strong need for a forming method and forming apparatus that can sufficiently and completely bend the ends of the steel strip.

Furthermore, as mentioned above, manufacturing welded steel pipes by continuous roll forming requires the use of forming rolls suitable for forming the required diameter and wall thickness, and the formation roll arrangement according to the diameter, and the width of the strip to be formed. Accordingly, it is necessary to replace the forming rolls, and it is not desirable from the viewpoint of manufacturing efficiency to prepare and replace a very large number of forming rolls for each required diameter. However, today there is a need to efficiently manufacture a wide variety of products with a single machine, and continuous roll forming is suitable not only for mass production of a small number of products, but also for production of a wide variety of products in small quantities. A method is needed.

Problems with the conventional technology Therefore, as a result of examining the conventional technology for the purpose of forming pipes with a certain range of outer diameter and wall thickness using a common roll in continuous roll forming, we found that there is no forming method that has the same purpose. There are the following methods.

1) Cage roll forming method 2) Linear forming method 3) VRF method 4) CTA method In each of the conventional methods, the roll used to form a semicircular arc shape based on a roll flower is, in the case of 1), a circular In case 2), forming is the basic method and many flat rolls are used. In case 3), UO forming and center forming are the basic methods and many flat rolls are used. In case 3), circular forming is the basic method. In the case of 4), circular forming is used as the basic method, and instead of the flat roll in 1, a combination of concave arc rolls is used.

In either method, edge bending is basically not performed at the initial stage of molding, and when edge bending is required, it is carried out using a dedicated roll set.

Therefore, both conventional forming methods
It has not been possible to bend the ends of a steel strip suitable for manufacturing steel pipes of a wide variety of diameters and wall thicknesses, from small diameter pipes to large diameter pipes, with a single type of forming roll.

Purpose of the Invention In view of the current situation, the present invention aims to bend the end of a strip steel, which is the most difficult to form, in the production of welded steel pipes by continuous roll forming, by using one set and one type of forming rolls, without replacing the forming rolls. A strip for pipe mills that can bend the ends of steel strips suitable for manufacturing steel pipes of a wide range of diameters and wall thicknesses, from small diameter pipes to large diameter pipes, and that can reduce the effects of spring back on the ends of the steel strip. The purpose of this paper is a method and apparatus for forming steel ends.

Summary of the Invention This invention provides a method for forming steel pipes with various outside diameters in which part or all of the cross-sectional curve of the roll surface of a forming roll forms steel pipes with various predetermined outer diameters in forming the forming area of the end of a steel strip in the production of steel pipes by continuous roll forming. Using a forming roll whose cross section is an elongation curve set in advance to include each curved surface of the end of the steel strip in the rolled flower of each steel pipe, both ends of the steel strip are shaped like the elongation curve. A pair of upper and lower forming rolls each having a cross-sectional shape of Accordingly, the rolling direction of at least the upper forming roll of each forming roll set is changed using a roll that raises the center part of the strip upward, and the forming roll is set in advance according to the width of the strip to be formed and the required end bending stage. A method for forming a steel strip end in a pipe mill, which is characterized by forming on a part or the entire surface of the expansion curve of a cross-sectional shape; In forming the area, the forming rolls for forming both ends of the steel strip are formed by a pair of upper and lower male rolls and female lower rolls that are pivotally supported with variable vertical spacing, and a part of the cross-sectional curve of the roll surface. Or, all of the forming rolls have a cross-sectional shape of an elongation curve elongation curve set in advance to include each curved surface of the end of the steel strip in the roll flower of each steel pipe for forming steel pipes of various planned outer diameters. None, the above pair of upper and lower forming rolls are individually supported in the width direction of the strip so that they can move in the direction of the strip, and the interval between the pair of forming rolls at both ends of the strip is adjusted according to the width of the strip. Depending on the width of the strip to be formed and the required end bending stage, the upper roll can be bent to the edge of the strip on a part or the entire surface of the elongation curve of the preset cross-sectional shape of the forming roll. An intermediate roll whose roll surface supports the steel strip so that it can swing in an arc in the width direction of the steel strip, or can be further divided into two parts so as to be able to approach and separate from each other in the width direction of the steel strip, so that the central part of the shaft-fixed steel strip can be made protruding, flat, or concave. This is an apparatus for forming a steel strip end in a pipe mill, characterized in that the shaft is fixed between a pair of lower rolls.

Structure and Effect Forming Method of the Invention In the present invention, as shown in FIG.
In the drawing, the end bending of the wide band steel 31 is done so that part or all of the cross-sectional curve of the roll surface matches the preset curve of the end of the steel band 10 in each roll flower of various outer diameter steel pipes. , forming roll 3
0, and when bending the end of the narrow strip steel 32, the roll surface should match the upper curved surface of the forming roll 30. The forming rolls are moved so that the curved surface is at a predetermined position.In addition to moving the pair of upper and lower forming rolls that bend the ends of the strip in the width direction of the strip, changing the orientation of the roll surface is also possible. At least it is necessary to change the direction of only the upper roll, and in the case of the drawing, it is necessary to change the direction of the roll surfaces of both the upper and lower rolls 18 and 30.

As mentioned above, in order to expand the range of common use, the forming roll of the present invention has a roll surface of a specific shape, and a required curved surface is appropriately selected according to the diameter of the roll surface, that is, the forming roll side is moved. hand,
The idea is to match the edge of the steel strip to be formed.

Forming roll To be more specific, in the process of forming pipes of many different diameters, for example, in the step of forming the ends of a steel strip, a roll that contains all the many types of circular arcs necessary for forming the ends of various steel strips and is continuous and smooth. In order to give a curved surface to the roll surface,
As a result of various studies, we found that a so-called expansion curve is appropriate.

In other words, a conventional forming roll with a curved surface such as a double radius cannot be used as a common roll, but if the roll surface is given an expansion curve based on a circle, the forming roll can be used in a much wider range of common uses. Furthermore, as shown in the examples, as a result of further studies in search of a forming roll that can be used in a wide range of applications, and which can be used to form pipes of dozens of different diameters, we found that the necessary radius and length as described above were obtained. In order to obtain a continuous circular arc surface that includes many different types of circular arcs, for example, it must be an expansion and expansion curve based on polygons assuming the circular arcs, as shown in Figure 2 a, b, and c. This knowledge led to the completion of this invention.

To explain in more detail, first, assuming that the forming method in which plastic deformation of the steel strip is the most natural, then in order to continuously form the steel strip into a tube with a predetermined outer diameter by continuous roll forming, the forming method is the most difficult to form. The ends of the steel should be bent to fit the specified outer diameter from the beginning, but it is more natural to gradually bend and form the parts other than the ends of the steel strip, that is, from the ends to the center. It was considered that the most preferable roll curved surface of a forming roll suitable for forming is one in which the curvature becomes gradually gentler from the point where it abuts the end of the steel strip.

On the other hand, if we assume that the roll surface of the forming roll is composed of curved surfaces with multiple curvatures for the purpose of sharing the roll for forming pipes of different diameters, it will be possible to form any pipe diameter without difficulty. It needs to be well bent and formed.

In addition, since the ends of the strip steel are the most difficult to form,
As mentioned above, all conventional continuous roll forming methods are based on the premise of using forming rolls exclusively for the ends of the steel strip according to the target outer diameter, but the forming of the ends of the steel strip is performed in the initial stage of forming using the common roll. If this could be done, the central part of the steel strip could be formed relatively easily in the middle stage of forming by using the forming curved surface of the end of the steel strip of this shared roll.

Therefore, there are various questions as to whether the roll surface of the forming roll, which has a continuous gentle curvature from the point where it contacts the end of the steel strip to the center, which is considered the most natural forming method, can be applied to the above-mentioned purpose of sharing the roll. As a result of our investigation, we found that a roll surface consisting of a curved surface with multiple or innumerable groups of curvatures with a certain relationship selected according to the common range and a continuous gentle curvature is the best, and this idea is based on the above idea. It has been found that the present invention can be applied not only to the forming stage of the end of the steel strip, but also to any forming roll used in any forming area of continuous roll forming.

Generally, the curvature of the end of a steel strip cannot be formed into a uniform radius even if it is formed by a roll having an arcuate surface due to the influence of spring back. That is, since the moment arm becomes shorter as it approaches the edge, the shape of the edge bending after springback becomes gentler in curvature as it approaches the edge.

Therefore, it has been found that if the curved surface is formed with a radius of curvature that becomes smaller as it approaches the end, the curvature will be close to uniform after springback.

When performing edge bending to form tubes with different outer diameters using a shared roll, it is possible to use an involute curved roll with a radius of curvature within a certain range.
The molding curvature can be changed by changing the location in contact with the molding material. In other words, it is possible to perform molding with different curvatures using a shared roll.

According to the above knowledge, the roll surface consisting of a curved surface with a plurality of curvatures or innumerable groups of curvatures whose curvature changes continuously refers to steel pipes of various outside diameters as defined in this invention, as shown in Fig. 2 a, b, and c. This is a roll surface consisting of an expansion curve set in advance to include each curved surface of the end of the steel strip in the roll flower of each steel pipe to be formed.

Such an expansion curve is one in which a large number of continuous curvatures are formed so that part or all of the cross-sectional curve of the roll surface includes the curve of the required part of the strip steel of each roll flower of steel pipes with various outside diameters in the forming area. changing curved surface,
That is, it consists of an expansion curve using a circle, curve, polygon, etc. as an evolute, which is assumed to change the curvature of the roll surface continuously at a preset rate of change.

Therefore, for example, in addition to actually obtaining it from a roll flower diagram, it may be a regular expansion curve based on a certain base circle, or it may include a expansion curve based on the above-mentioned circle or ellipse. It may be a curve.

To explain an example of actually finding such a stretching curve, as shown in Fig. 2c, a number of sides consisting of various required opening angles θ _o are set, and the stretching curve is found by evoluting based on this. Depending on the type of diameter required, wall thickness, bending location, stage, etc., there are a variety of cases, from using only two sides to finding an expansion curve based on an arc or circle. be.

The roll surface of the forming roll will be described in detail with reference to the upper and lower rolls in FIG.
Furthermore, depending on the end bending stage, the cross-sectional shape of the roll surface is set to an expansion curve based on a preset polygon (portion α in the drawing), and the roll surface is based on this specific expansion curve. This makes it possible to match the curve of the steel strip end of the roll flower of steel pipes of various outside diameters and wall thicknesses in roll forming from small diameter pipes to large diameter pipes, and to bend the steel band ends.

Furthermore, it has been found that the forming roll according to the present invention in which the cross-sectional shape of the roll surface is an expansion curve can prevent spring back at the end of the steel band.

To explain the mechanism in detail, in general, even if forming is performed using a roll with a curved surface of a constant curvature, the plate that curves along the roll curved surface during rolling will not be able to form. After passing through the roll,
It is shaped into a continuously changing curvature due to spring back.

In other words, with a forming roll having a curved surface of a constant curvature, the bending moment arm changes near the end of the strip during rolling and becomes close to 0, so the stress applied to the material changes depending on the strip position. , it can be said that molding with a constant curvature is practically impossible.

However, if the curved surface is made to have a smaller radius as it approaches the end of the steel strip, even if spring back occurs, bending to a required constant radius becomes possible. As shown in FIG. 2, the cross-sectional shape of the roll surface of the forming roll of this invention is an expansion curve based on a preset polygon, so that the closer it is to the end of the steel strip, the smaller the The radius can be a curved surface, and the end of the steel strip can be formed into a curved surface with a substantially constant radius.

Effects Therefore, the band steel end bending method according to the present invention can be used to manufacture steel pipes of various diameters and wall thicknesses over a wide range from small diameter pipes to large diameter pipes using a single forming roll without replacing the forming rolls. It is possible to bend the ends of the steel strip in a suitable manner, reduce the influence of spring back on the ends of the steel strip, and significantly improve the formability at the initial stage of forming in the pipe mill. By reducing the amount of forming in the forming area and fin pass area at the center of the steel strip, continuous roll forming with excellent forming distribution and formability is possible.

Forming Apparatus The upper and lower sets of forming rolls in this invention are configured such that the interval between the pair of forming rolls at both ends of the steel strip is changed according to the width of the steel strip, and is set in advance according to the width of the steel strip to be formed and the required end bending stage. At least the upper roll is supported so that its roll surface can swing in an arc in the width direction of the steel strip, so that it can come into contact with the end of the steel strip on a part or the entire surface of the expansion curve of the cross-sectional shape of the forming roll. For example, any shaft support or arrangement method may be used.

In addition, in this invention, an intermediate roll is used between a pair of lower rolls in the width direction of the steel strip to raise the center part of the steel strip upward, and the steel strip is made into a bow shape as opposed to a semicircle, thereby improving the formability of both ends. In this case, it is necessary to return the central part of the steel strip to a semicircular shape in the next stage, but it is also good to correct it with a so-called inner roll placed in the next stage, and the forming area of the central part of the steel strip It is also good to do both at the same time.

The intermediate roll can also hold the central part of the steel strip flat or concave, depending on various conditions such as the required diameter, wall thickness, end bending stage, and forming distribution on the forming line. It is advisable to select it appropriately.

Further, in the forming method according to the present invention, the forming rolls may be free or driven. For example, both the upper and lower rolls may be driven, or a free roller or an upper roll-driven type may be installed next to a forming stand in which only the lower roll is driven. Required caliber, such as placement,
It may be selected appropriately depending on various conditions such as wall thickness, end bending stage, and molding distribution on the molding line.

Further, in the present invention, the material to be formed is not limited to steel strips, but can be applied to pipe making of various metals and alloys.

Disclosure Based on Drawings of the Invention Figures 3 and 4 are a front view and a side view of the steel strip end forming device according to the present invention, and Figures 5 and 6 are front explanatory views showing details of the upper roll. and a longitudinal side view. FIG. 7 is an explanatory diagram of the forming roll showing the forming roll closest to the forming roll in the width direction of the strip steel.

Configuration The forming apparatus consists of a normal roll stand in which a lower roll shaft 3 and an upper roll support shaft 4 are arranged between U-shaped roll stands 2 erected on a base 1 at predetermined intervals.

The lower roll shaft 3 includes a pair of lower rolls 5, 5 and a two-part intermediate roll 6, 6 disposed between them.
It is positioned and fixed at a predetermined position in the axial direction via spacers 7 of various widths. This lower roll shaft 3 serves as a drive shaft here, and is driven by an electric motor (not shown).

The upper roll support shaft 4 is connected to a pair of non-driven upper rolls 1.
8 and 18 vertically, and is screwed onto the upper end of the roll stand 2 in order to adjust the facing distance to the lower roll shaft 3 to cope with the thickness of the steel strip 10 and to increase or decrease the amount of rolling. A support shaft body 12 is connected to the screw shaft 11, which is clamped by a roll stand 2, so as to be movable in the vertical direction.

The upper roll support shaft 4 has a pair of beam members 13 arranged between a support shaft main body 12 which is held between the roll stands 2, and a rail 14 is attached to the lower surface of each beam member 11.

A saddle-shaped upper roll holding seat 16 is mounted on the rail 14 via a slide bracket 15 that can fit and slide on the rail 14, and is vertically held with its head inserted between the pair of beam members 13. ing.

The upper roll holding seat 16 has a downwardly facing inner surface forming a cylindrical seat surface 17 facing toward the rail 14 . Further, a U-shaped bearing member 1 that pivotally supports the upper roll 18 is provided.
A fan-shaped contact member 20 that contacts the cylindrical seat surface 17 is installed on the upper part of the upper roll support seat 16.
A fan-shaped receiving member 21 fixed to the cylindrical seat surface 17
It is slidably held in between.

A fan-shaped tooth surface 22 is provided on the upper surface of the bearing member 19, and a gear 24 is attached to a small shaft 23 which is fixed in the head of the saddle-shaped upper roll holding seat 16 in the traveling direction of the steel strip 10. In addition, the worm gear 25 that penetrates the small shaft 23 meshes with the worm shaft 26 disposed between the spindle bodies 12, and the rotation of the worm shaft 26 causes the bearing member 19 of the upper roll 18 to rotate in an arc. It is configured so that the roll surface of the upper roll 18 can change the direction of contact with the steel strip 10 in the width direction thereof.

In the drawing, the tooth surfaces of the worm gears 25 are carved in opposite directions so that the circular arc swings of the pair of left and right upper rolls 18 are opposite to each other.

In addition, a nut member 27 is fixed to the head of the saddle-shaped upper roll holding seat 16, and is screwed into a screw shaft 28 disposed between the support shaft bodies 12, and rotates as the screw shaft 28 rotates. , the upper roll holding seat 16 moves in the width direction of the steel strip 10, and the upper roll 18 moves in the width direction of the steel strip 10, and the saddles are arranged so that the left and right pair of upper rolls 18 approach and separate in the drawing. Nut member 2 fixed to the head of the upper roll holding seat 16 of the mold
7 and the threaded shaft 28 are opposite to each other.

On the other hand, the lower rolls 5, 5 and the intermediate rolls 6, 6
As mentioned above, the spacer 7 is attached to the lower roll shaft 3.
The upper rolls 18 and 18 are also configured to be able to change the width direction and the contact direction of the roll surfaces with respect to the steel strip 10.

Furthermore, upper rolls 18, 18, lower rolls 5, 5
And the intermediate rolls 6, 6 each have a roll surface with a required steel pipe outer diameter width, for example, 89.1φ.
Assuming that various steel pipes of 241.8φ will be formed,
This is an evolutive elongation of a polygon consisting of many sides, which is assumed to continuously change the curvature of the roll surface at a preset rate of change to include each curved surface of the end of the strip in each roll flower of various outer diameter steel pipes. It consists of a forming roll whose cross section is an open curve.

Effects The forming apparatus according to the present invention having the above configuration can be used, for example, when bending the ends of a steel strip in forming a steel pipe with a relatively large diameter, as shown in FIG. In other words, the spacing between the forming rolls is changed according to the width of the steel strip 10 so that a pair of upper roll 18 and lower roll 95) are positioned, and further, the rolling direction of the upper roll 18 is
The direction of contact with the forming roll is changed, and the required extension curve of the preset forming roll cross-sectional shape is determined depending on the width of the steel strip 10 to be formed and the required end bending stage, that is, whether the end bending is completed in one stage or divided into multiple stages. The end of the steel strip 10 is formed into a desired shape at the curved surface portion, here the central curved surface portion.

In this case, intermediate rolls 6 are used to raise the central part of the steel strip and improve formability at both ends, but the interval between the pair of intermediate rolls 6, 6 also depends on the width of the steel strip and the forming stage. The selection will be made accordingly.

In addition, in the case of the smallest diameter of the assumed diameter, the sixth
As shown in the figure, the lower rolls 5, 5 and the intermediate rolls 6, 6 are arranged integrally without intervening spacers, and the contact direction of the upper rolls 18, 18 is also changed to the opposite direction from the previous one, and set in advance. The end of the steel strip 10 is formed into a desired shape at a desired curved surface portion of the expansion curve of the forming roll cross-sectional shape, here the outermost curved surface portion.

As described in detail, the molding device according to the present invention has the following features:
With one set and one type of forming rolls, it is possible to bend the ends of a steel strip suitable for manufacturing steel pipes of a wide range of diameters, from small diameter pipes to large diameter pipes, without replacing the forming rolls.

In addition, the roll surface shape of the lower roll is an evolved polygon with many sides, which is assumed to change the curvature of the roll surface continuously at a preset rate of change to include each curved surface at the end of the steel strip. By making the expansion curve the cross-sectional shape, it matches the curve of the steel strip end in each roll flower of various outer diameter steel pipes,
In addition, the edge of the strip can be set to a shape that allows for slight overbending, and the central part of the strip is raised with an intermediate roll to make it easier to form the edge. This reduces the influence of spring back and significantly improves the formability in the initial stage of forming in the pipe mill, reducing defects at the edges and reducing the amount of forming in the subsequent forming area and fin pass area of the center of the strip. This enables continuous roll forming with excellent forming distribution and formability.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a forming roll and a steel band roll flower showing forming rolls used in the forming method of the present invention. FIGS. 2a and 2b are explanatory cross-sectional views of a forming roll according to the present invention, and FIG. 2c is an explanatory view showing an expansion curve based on a preset polygon α in FIG. 2b. 3 and 4 are a front view and a side view of a steel strip end forming device according to the present invention,
FIG. 5 and FIG. 6 are a front explanatory view and a vertical side view showing details of the upper roll. FIG. 7 is an explanatory diagram of the forming roll showing the forming roll closest to the forming roll in the width direction of the strip steel. FIGS. 8a to 8d are explanatory diagrams of a pipe mill and forming rolls showing a conventional continuous roll forming method. 1...Base, 2...Roll stand, 3...Lower roll shaft, 4...Upper roll support shaft, 5...Lower roll, 6...Intermediate roll, 7...Spacer, 10
... Steel band, 11 ... Screw shaft, 12 ... Support shaft body, 13 ... Beam member, 14 ... Rail, 15 ...
...Slide bracket, 16...Top roll holding seat, 17...Cylindrical bearing surface, 18...Top roll, 19
... Bearing member, 20 ... Contact member, 21 ... Sector-shaped receiving member, 22 ... Sector-shaped tooth surface, 23 ... Small shaft, 2
4...Gear, 25...Worm gear, 26...Worm shaft, 27...Nut member, 28...Screw shaft, 30...Forming roll, 31, 32...Strip steel.

Claims (1)

[Claims] 1. In forming the forming area of the end of a steel strip in the manufacture of steel pipes by continuous roll forming, part or all of the cross-sectional curve of the roll surface of the forming roll forms steel pipes with various predetermined outer diameters. Using a forming roll whose cross-sectional shape is an elongation curve set in advance to include each curved surface of the end of the steel strip in the roll flower of each steel pipe, the cross-sectional shape of both ends of the steel strip is formed using the elongation curve. Each is molded using a pair of upper and lower molding rolls,
When forming this in one stage or in multiple stages, the interval between the pair of forming rolls at both ends of the strip is changed according to the width of the band, and at least the rolling direction of the upper forming roll of each forming roll set is changed, and the forming roll is A method for forming a steel strip end in a pipe mill, which comprises forming on a part or the entire surface of the expansion curve of a preset forming roll cross-sectional shape, depending on the steel width and the required end bending stage. 2. In the forming of the forming area of the end of a steel strip in the manufacture of steel pipes by continuous roll forming, part or all of the cross-sectional curve of the roll surface of the forming roll is the same as that of each steel pipe for forming steel pipes of various planned outer diameters. Using a forming roll whose cross section is an elongation curve set in advance to include each curved surface of the end of the steel strip in a roll flower, both ends of the steel strip are formed into a pair of upper and lower sections whose cross section is an elongation curve. Each is molded with a molding roll,
When forming this in one stage or in multiple stages, the interval between a pair of forming rolls at both ends of the strip is changed according to the width of the steel band, and rolls that raise the center part of the steel band upward are used, and at least each forming roll is The rolling direction of the upper forming roll of the set is changed, and forming is performed on a part or the entire surface of the stretching curve of the forming roll cross-sectional shape set in advance, depending on the width of the strip to be formed and the required end bending stage, and then the next step is performed. A method for forming an end portion of a steel strip in a pipe mill, characterized in that the center portion of the steel strip is formed into a cylindrical shape. 3. In forming the forming area of the end of a steel strip in the manufacture of steel pipes by continuous roll forming, the forming rolls for forming both ends of the steel band are supported by a male upper roll and a female lower roll that are pivotally supported with variable vertical spacing. set in advance so that part or all of the cross-sectional curve of the roll surface includes each curved surface of the end of the steel strip in the roll flower of each steel pipe for forming steel pipes of various planned outside diameters. The above-mentioned pair of upper and lower forming rolls and a pair of forming rolls in the width direction of the strip are individually supported so as to be movable in the direction of the strip. The interval between the pair of forming rolls is changed according to the strip width, and the strip is formed on one side or the entire surface of the elongation curve of the preset forming roll cross-sectional shape, depending on the width of the band to be formed and the required end bending stage. The upper roll is supported so that its roll surface can swing in an arc in the width direction of the steel strip so as to be able to come into contact with the steel end, and the center part of the steel strip is divided into two parts so as to be able to approach and separate from each other in the width direction of the steel strip. 1. An apparatus for forming a steel strip end in a pipe mill, characterized in that an intermediate roll for obtaining a raised, flat or concave shape is pivoted between a pair of lower rolls. 4. The upper roll was pivoted by a bearing member having a fan-shaped tooth surface provided at the center of the fan-shaped upper surface, the bearing member was received by the bearing surface of a support member having a cylindrical inner seat, and the steel strip was placed on a forming stand in the width direction of the steel strip. The support member is slidably connected to the slide rail, and the circular swing of the upper roll roll surface is controlled by rotation of a gear that meshes with the fan-shaped tooth surface, and the distance between the pair of upper rolls is adjusted by sliding the support member. 4. A device for forming a steel strip end in a pipe mill according to claim 3, wherein the device controls: