JPH05317979A - Method and stand for forming welded tube - Google Patents

Abstract

PURPOSE:To precisely bend a metallic product by adjusting the position in a breadthwise direction of a couple of upper and lower horizontal forming roll bisected in a breadthwise direction of a metallic plate and turning and fixing each of bisected upper rolls having a perpendicular axis. CONSTITUTION:In a manufacturing line in which a strip metal 9 is formed by rolling and welded into a welded tube, the horizontal forming upper roll for bending the end part of the strip metal bisected in the breadthwise direction of the strip metal is turned and fixed having the perpendicular axis and, in this state, the strip metal is formed. The turning angle of the metal forming upper roll alphaU is set within the range of alphaU<=45 deg. (alphaU is an angle formed by the axis in the breadthwise direction of the strip metal and the rolling axis of the horizontal forming upper roll). Thus, in a break-down rolling device used in an initial forming process, the edge is bent without a hindrance on the precision of thickness of the strip metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dimensional accuracy in a welded pipe production line, in which a metal strip having a predetermined width is continuously roll-formed and welded by an electric resistance welding method or another welding method. The present invention relates to a forming method and a forming stand for forming a good welded pipe.

[0002]

2. Description of the Related Art Generally, in a manufacturing process for manufacturing a welded pipe such as an electric resistance welded steel pipe, a metal strip having a predetermined width is
It is manufactured by being continuously supplied to a forming roll group including a plurality of breakdown rolls, side rolls, fin pass rolls, and the like, and then subjected to welding such as high frequency welding with a squeeze roll.

Since this method can be continuously manufactured, its high efficiency and low cost are major advantages. For this reason, they are widely used for machine structure pipes, boiler pipes, oil well pipes, various pipes, etc., and recently, demands for thin-walled pipes, thick-walled pipes, high-tensile pipes, etc. are increasing. Further, there is a strong demand for ensuring high dimensional accuracy for high-grade pipes.

However, when these thin-walled pipes, thick-walled pipes and high-strength pipes are molded by the conventional method, defective shapes will occur. That is, as shown in FIG. 9, in forming with the pair of upper and lower breakdown rolls in the initial forming process of edge forming, there arises a problem such as insufficient bending of the edge portion of the material to be formed.

On the other hand, at the time of edge forming as shown in FIG. 10, the so-called W bend is formed by bending the vicinity of the center of the material to be molded into a curvature opposite to that of the product and bending both ends to the same side as the product. The method has been put to practical use. The effect of this method is introduced, for example, in p. 519, Proc.

[0006] Further, Japanese Patent Laid-Open No. 1-44217 discloses that
By forming the lower hole type roll of the horizontal roll of the forming stand for edge forming from two rolls and adjusting the inclination angle in the metal strip advancing direction, edge parts of thick and thin materials can be A method is described which makes it possible to sufficiently perform the molding of

[0007]

DISCLOSURE OF THE INVENTION As described above,
In the case of a breakdown roll that performs edge forming in the conventional forming method, a problem of defective shape occurs particularly when forming a thin-walled tube, a thick-walled tube, or a high-strength tube. In addition, in order to eliminate this shape defect, when the edge forming is attempted to be strengthened by the fin pass roll in the subsequent stage, the thickness increase 13 of the edge portion as shown in FIG. Becomes

Further, in the W-vent type breakdown roll shown in FIG. 10, since the bending force of the edge portion can be sufficiently secured, the edge portion can be bent as compared with the conventional method. In the molding process from the contact start point between the material to be molded and the upper roll to just below the roll,
Since the upper roll and the material to be molded are locally in contact with each other, as shown in FIG.
The indentation 14 as shown in (3) is likely to occur, which is a factor that hinders the wall thickness accuracy. Further, even in this method, it is not possible to fundamentally solve the shape defect when molding a thick or thin pipe having a thickness larger or smaller than the design wall thickness of the upper roll to some extent, and it is possible to form a common wall thickness. Has not yet expanded.

On the other hand, the above-mentioned JP-A-1-44217 has been proposed.
In the publication, compared to the usual edge forming method, contact between the material to be molded and the rolls changes continuously, so it is expected to reduce indentations, but due to the structure in which the lower roll intersects and is inclined, commonality The range of is limited.

The present invention has been made to solve the above-mentioned problems of the prior art, and it is possible to form a welded pipe having good dimensional accuracy in a welded pipe manufacturing line. An object of the present invention is to provide a molding method and a molding stand capable of accurately bending an end portion.

[0011]

According to a first aspect of the present invention, in a welded pipe manufacturing line in which a metal strip having a predetermined width is roll-formed and welded, a metal strip end portion bent in the width direction of the metal strip is bent. A method for forming a welded steel pipe, characterized in that the above-mentioned metal strip is formed in a state in which a horizontal forming upper roll for use in the vertical direction is rotated and fixed about a rotating shaft. According to a fourth aspect of the present invention, in a welded pipe manufacturing line for initializing and welding a metal strip having a predetermined width, in a group of initial forming rolls, a horizontal forming upper roll for bending a metal strip end is a metal strip width. It is divided into two parts and is arranged on both sides of the line, and the upper roll can adjust the roll position setting with the vertical direction as the pivot axis, and can adjust the position in the plate width direction. In addition, the horizontal forming lower roll can be divided into two in the width direction of the metal strip to adjust the position in the width direction.

Further, claim 2 of the present invention is for maximizing the effect of the present invention, and the turning angle α _u of the horizontal forming upper roll divided into two in the metal band width direction is α _u ≤ 45
2. The method for forming a welded pipe according to claim 1, wherein the range is set to be ° (where α _{u is the} angle formed by the axis of the metal band width direction and the roll axis of the horizontal forming upper roll).

Further, claim 3 of the present invention is a means for making the present invention effective regardless of the setting accuracy of the forming stand, and is a roll stand in a horizontal forming upper roll divided into two in the metal band width direction. 3. The method for forming a welded pipe according to claim 2, wherein the swivel angle is set so that the inlet side of the metal strip is directed to the edge side of the metal strip and the outlet side of the roll stand is directed to the center side of the metal strip.

[0014]

In the present invention, in the breakdown stand for the purpose of edge forming, the metal strip as the material to be molded is divided into two in the plate width direction and arranged on both sides.
Forming horizontal upper roll for the purpose of edge forming,
By forming the metal strip in a state in which the metal strip is swung and fixed with the vertical direction as the swivel axis, it is possible to form thin-walled pipes to thick-walled pipes with high dimensional accuracy. This is done by rotating the upper forming horizontal roll as shown in FIG.
Since the upper roll 1 is formed by contacting continuously from both sides of the bent portion of the metal strip to be formed in the vicinity immediately below the roll, local contact does not occur unlike the conventional method in the forming process. is there. Further, as shown in FIGS. 2A to 2C, when the turning angle of the upper roll 1 is changed, the curvature formed by the history of the upper roll in the vicinity immediately below the roll is changed, and thus the material to be molded. A gap history corresponding to the wall thickness of the metal strip 9 can be configured, and it is possible to perform accurate molding in a wall thickness range from a thin material to a thick material. Further, by dividing the upper and lower rolls into two in the width direction and making the position of the metal strip in the width direction variable, it is possible to adjust the position according to the wall thickness, the plate width, and the bending length.

Generally, the swivel angle of the upper roll is determined by the shape of the hole of the upper roll, the outer diameter of the metal strip, the thickness of the metal strip,
Although it is determined by the diameter of the upper roll and the like, in claim 2 of the present invention, in order to maximize the effect of the present invention, the turning angle direction of the upper roll is limited as follows.

The thinner the forming thickness of the metal strip, the larger the swivel angle of the upper roll must be. However, if the swiveling angle is excessive, the slip between the upper roll and the metal strip becomes excessive, resulting in forming scratches, seizure of the roll, and rolling. The roll life is shortened, so the upper limit of the turning angle is set to 45 ° in consideration of the common range of the thickness of the metal strip.

On the other hand, when the upper roll is rotated, a force may be applied to the roll in the width direction of the metal band due to the slip relationship between the roll and the metal band, causing a runout. For example, in FIG.
As shown in (a), the upper roll is set so that the entrance side of the roll stand faces the edge side of the metal strip and the exit side faces the center side of the metal strip, and the lower roll has its turning direction set in the opposite direction. When the upper and lower rolls are crossed (in this case,
Since the contact point of the upper roll moves from the edge portion of the metal strip to the inside, the upper roll is hereinafter referred to as an inward forming die. ), The upper roll has a widthwise outward deflection, and the lower roll has a widthwise inward deflection. On the other hand, as shown in FIG. 7B, the upper roll is set so that the entrance side of the roll stand faces the center side of the metal strip and the exit side faces the edge side of the metal strip, and the lower roll turns its turning direction in the opposite direction. When the upper and lower rolls are crossed by setting (in this case, since the contact point of the upper roll moves from the inside of the metal strip to the edge portion, the upper roll is hereinafter referred to as an outward forming die). In the width direction, and in the lower roll, there is a shake in the width direction. Here, in the case of the outward forming die, the edge portion is insufficiently bent because the upper roll does not come into contact with the outermost edge, and as shown in FIG. 8, when the present invention is applied to the W bend method, the gap due to the runout is generated. Local thinning may occur due to narrowing.

On the other hand, in the inward molding die, there is no fear of the above-mentioned problems, and the deflection generating force of the upper roll acts in a direction advantageous to the edge forming, and it is expected that advantages such as reduction of the pressing force of the upper and lower rolls can be expected. .. Therefore, it is preferable to use the inward molding die according to the third aspect of the present invention, particularly in the case of a stand in which the shake easily occurs due to the rigidity of the stand.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in FIGS. FIG. 1 shows a front view and a plan view of an example of a roll to which the present invention is applied. Here, in the lower roll 2, the positions in the upper and lower roll width directions on both sides are determined according to the plate width and bending length of the metal strip 9 to be formed. Further, the turning angle α _u of the upper roll 1 is determined according to the wall thickness of the metal strip 9. Reference numeral 16 indicates the central portion of the metal strip.

FIG. 2 shows an example of the history of the roll gap immediately below the roll when the turning angle is set according to the wall thickness and bending curvature of the metal strip. In addition, FIG. 3 shows an example of the deformation state of the metal strip according to the history of the roll gap. 1 is an upper roll, 2 is a lower roll, and 9 is a metal strip.

FIG. 4 is a front view of an example of an edge bend stand to which the present invention is applied. The roll supporting beam member 7 vertically holds the upper roll bearing member 3, and the upper roll supporting beam member 7 has a structure that can be moved and fixed in the vertical direction by a screwing screw shaft 8. The upper roll support base 5 has a structure that can be moved and fixed in the width direction by screw shaft rotation (not shown) installed in the beam member 7 or sliding of a slide bracket on a rail (not shown). ing. Further, the upper roll support base 5 is rotated around the vertical axis by a method such as gear drive (not shown),
It has a structure that can be fixed. On the other hand, the lower roll 2
It can be rotated by the lower roll shaft 6 via the lower roll bearing member 4, and further, a screw mechanism (not shown), or
The structure allows the position to be changed and fixed in the width direction by a hydraulic mechanism.

If necessary, as shown in FIG.
It is also possible to adopt a structure in which the bearing material 12 supporting the central upper roll 10 is fixed to the upper roll supporting beam member 7 at the central portion in the plate width direction. 11 is a central lower roll at that time. Fig. 6 shows the yield stress of 294 N / mm ² , φ50.8 × t
For edge forming of strip steel equivalent to 2,10 mm,
3A and 3B respectively show a curvature distribution and a wall thickness distribution after single stand molding when the present invention is applied and when the present invention is not applied. In the conventional method, bending of the thin material is insufficient and indentation of the bent portion is generated in the thick material, but with the application of the present invention, a very good shape is obtained.

Table 1 shows the actual results of the curvature and the thickness reduction allowance when the same roll is used to perform forming by changing the turning angle of the upper roll for various forming thicknesses. By applying the present invention, it can be seen that the edge formability is improved and the thickness reduction amount is reduced. Furthermore, it is understood that the effect of the present invention can be maximized by applying the turning angle setting conditions to the second and third aspects of the present invention.

[0024]

[Table 1]

[0025]

As described above, according to the present invention, when manufacturing a welded pipe by continuously roll-forming and welding a metal strip, a breakdown roll device in an initial forming process for edge forming is provided. Thus, there is an effect that edge bending can be performed without impairing the wall thickness accuracy of the material to be molded.

[Brief description of drawings]

FIG. 1 is a front view and a plan view of a roll example to which the present invention is applied.

FIG. 2 is a diagram showing an example of upper and lower roll gaps set according to respective molding curvatures and wall thicknesses when the present invention is applied.

FIG. 3 is a diagram showing the progress of metal band forming in the vicinity of just below a roll.

FIG. 4 is a diagram showing an example of a molding apparatus to which the present invention is applied.

FIG. 5 is a diagram showing another example of the molding apparatus.

FIG. 6 is an example of curvature and wall thickness distribution after single stand molding with and without application of the present invention.

FIG. 7A is an example of an inward molding die according to the present invention,
(B) is an example of the outward mold according to the present invention.

FIG. 8 is an example of a case where inward deflection of the upper roll occurs when the outward forming die according to the present invention is applied to the W bend method.

FIG. 9 is a cross-sectional view of a conventional edge bend roll.

FIG. 10 is an example of a W bend type breakdown roll.

FIG. 11 is a cross-sectional view of a metal band showing an example of edge thickening in which dimensional accuracy is deteriorated.

FIG. 12 is a cross-sectional view of a metal strip showing an example of an indentation at a bent portion where the dimensional accuracy is deteriorated.

[Explanation of symbols]

 1 Upper Roll 2 Lower Roll 3 Upper Roll Bearing Material 4 Lower Roll Bearing Material 5 Upper Roll Support Stand 6 Lower Roll Shaft 7 Upper Roll Support Beam Member 8 Reduction Screw Shaft 9 Metal Band (Forming Material) 10 Center Upper Roll 11 Center Sub rolls 12 Central upper roll bearing material 13 Edge thickening 14 Bend indentation 15 Edge 16 Metal band center 17 Fin pass roll

Claims (4)

[Claims] 1. In a welded pipe manufacturing line for roll-forming and welding a metal strip having a predetermined width, a horizontal forming upper roll for bending the end of the metal strip divided into two in the width direction of the metal strip is provided in the vertical direction. A method for forming a welded pipe, which comprises forming the metal strip in a state of being swiveled and fixed as a swivel axis. Wherein the turning angle alpha _u of the horizontal molded on rolls halving the metal strip width direction α _u ≦ 45 ° where, alpha _u: the angle of the roll shaft of the metal strip width axis and a horizontal molding on a roll The method for forming a welded pipe according to claim 1, wherein the range is set. 3. In a horizontal forming upper roll divided into two in the width direction of the metal strip, the swivel angle is set so that the entrance side of the roll stand faces the edge side of the metal strip and the exit side of the roll stand faces the center side of the metal strip. The method for forming a welded pipe according to claim 2, wherein 4. A welded pipe manufacturing line for roll forming and welding a metal strip having a predetermined width. In a group of initial forming rolls, a horizontal forming upper roll for bending the end portion of the metal strip is divided into two in the width direction of the metal strip. Are arranged on both sides of the line, the upper roll can adjust the roll position setting with the vertical direction as the pivot axis, and can adjust the position in the plate width direction. A forming stand for a welded pipe, wherein the lower forming roll is divided into two in the width direction of the metal strip, and the position can be adjusted in the width direction.