JPH07204736A - Method for forming welded pipe and forming stand - Google Patents

Abstract

PURPOSE:To enable torsion-free forming without impairing the precision of thickness by making the axial centers of side rolls adjustable in inclination within a specific range against the vertical axis in a line advancing direction. CONSTITUTION:Upper and lower horizontal rolls 1, 2 and side vertical rolls 3, 3 are arranged in a four-roll breakdown stand. Or a lower horizontal roll and side rolls are arranged in a three-roll stand. Roll group are center-bent carried out in initial and middle stages of a manufacturing line for a welded pipe for which a prescribed metallic strip 4 is roll-formed and welded by using of these roll stands. Therefor, the axial center of the side roll 3 is made adjustable in inclination within the range of 0 to 45 deg. against the vertical axis in the line advancing direction. Consequently, a welded pipe superior in the dimensional precision is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is intended for a center bend of a welded pipe manufacturing line for continuously forming and welding a metal strip having a predetermined width by an electric resistance welding method or another welding method. In the first and mid-term roll forming group,
The present invention relates to a forming method and a forming stand for forming a welded pipe having no twist and excellent dimensional accuracy.

[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 steel strip having a predetermined width is formed into a group of forming rolls including a plurality of breakdown rolls, side rolls, fin pass rolls and the like. Continuously supplied,
After that, it is manufactured by performing high frequency welding and other welding with a squeeze roll. Since this method can be manufactured continuously, it is a great advantage that it is highly efficient and low in cost. For this reason, they are widely used for machine structure pipes, boiler pipes, oil well pipes, various pipes, etc., and recently, demands for thick-walled pipes, high-tensile pipes, etc. are increasing. Further, it is strongly desired to secure high dimensional accuracy for high-grade pipes.

This method is conventionally performed by forming a plurality of edge bend rolls having a hole shape and a breakdown roll,
2-roll type vertical side roll 3 as shown in FIG.
Therefore, there is a problem that twisting occurs during threading or molding, especially in the production of thick-walled pipes and high-strength pipes. On the other hand, there is also a strong demand for roll-sharing technology for reducing roll costs by reducing the number of rolls held by hand and improving the line operation rate by reducing the frequency of roll changes.

On the other hand, the inventors of the present invention disclosed in Japanese Patent Laid-Open No. 3-2
In Japanese Patent No. 91116, horizontal top and bottom rolls and vertical side rolls for the purpose of center bend are arranged.
A method of sharing a roll is provided by adjusting the stand position of the roll breakdown stand and optimizing the deformation curvature in the roll unrestrained region to the molding size.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
By applying the publication No. 6, it has become possible to share the rolls in the welding pipe forming line. Further, it has an advantage that it is less likely to be twisted due to the restraint in the vertical direction, as compared with the forming by the two-roll vertical side roll stand for the normal center bend. On the other hand, especially
The following problems are expected when forming thick materials and high tensile strength materials. That is, when attempting to form a thick material or a high tensile strength material, the reaction force of the side rolls becomes large, and the deformation is concentrated in the roll unrestrained region as shown in FIG. There is a problem in that the compression force acts to increase the thickness, which may cause uneven thickness. Further, in the case of a structure in which the vertical side rolls are contacted before the horizontal upper and lower rolls are contacted with each other, there is a problem that the occurrence of twist becomes large.

[0006]

The first aspect of the present invention is to provide a horizontal bend in the horizontal and vertical directions for the purpose of a center bend in a roll group in the first and middle stages of a welded pipe manufacturing line for roll forming and welding a metal strip having a predetermined width. In a 4-roll breakdown stand in which rolls and side rolls are arranged or in a 3-roll stand in which horizontal lower rolls and side rolls are arranged, the axis of the side rolls is 0 ° to 45 ° in the line advancing direction with respect to the vertical axis. A method for forming a welded pipe is characterized in that it is formed by a roll stand whose inclination can be adjusted arbitrarily within a range.

The second aspect of the present invention is to arrange horizontal upper and lower rolls and side rolls for the purpose of center bend in roll groups in the first and middle stages of a welded pipe manufacturing line for roll forming and welding a metal strip having a predetermined width. In the four roll breakdown stand or the three roll stand in which the lower horizontal roll and the side roll are arranged, the axis of the side roll is 0 ° to 45 in the line traveling direction with respect to the vertical axis.
This is a method for forming a welded pipe, which is characterized in that the welding is performed while adjusting the inclination arbitrarily within the range of °.

The third item of the present invention aims at the center bend in the roll group of the first and middle stages of the welded pipe production line for roll forming and welding a metal strip having a predetermined width, and arranging horizontal upper and lower rolls and side rolls. In the 4-roll breakdown stand or the 3-roll stand in which the horizontal lower roll and the side roll are arranged, the axis of the side roll is 0 ° to 45 ° in the line traveling direction with respect to the vertical axis.
It is a stand for forming a welded pipe, which is provided so that its inclination can be arbitrarily adjusted within the range.

[0009]

The present invention realizes the commonality of rolls by adjusting the roll positions of the horizontal rolls and the side rolls in the 4-roll breakdown stand or the 3-roll stand for the purpose of center bend in the forming region of the welded pipe. is doing. Further, by forming the side roll shaft core in a state in which it is inclined in the line advancing direction with respect to the vertical axis, the area of the roll unrestrained region is increased, and local thickening due to width direction rolling reduction is suppressed. ing. Further, since the side roll is inclined, the contact is started from a portion other than the edge portion of the metal strip to be formed, so that the twist is less likely to occur. In order to maximize these effects,
It is desirable that the inclination of the side roll axis is 5 ° or more. When the angle is 45 ° or more, the thrust force in the vertical direction becomes excessive and causes roll marks and the like, so the upper limit of the angle was set.

Further, in the second aspect of the present invention, when twist occurs during molding, the angle of inclination of the side roll is adjusted according to the amount of twist to generate a twist moment opposite to the twist. It is possible to correct the twist. In addition, in the present invention, even when the rolls are adjusted by adjusting the position of the rolls, a 4-roll breakdown or a 3-roll side roll that changes rolls for each molding outer diameter is used as a center bend that does not perform roll sharing. Even in the case where one stage or several stages are installed, the same great effect is exerted in improving the dimensional accuracy and suppressing the twist.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in FIGS. FIG. 1 is a front view of a 4-roll breakdown example to which the present invention is applied, and FIG. 2 is a side view of FIG. In the figure, 1: horizontal upper rolls, 2: horizontal lower rolls, 3, 3: side rolls, 4: strips to be molded are shown. The shaft cores of the side rolls 3, 3 which are symmetrically arranged are arranged so that the inclination can be adjusted with respect to the line direction. When applied to twist control, for example, a metal band edge is detected by a detector (not shown) installed downstream of this stand, and the controller is operated according to this twist amount to set the roll angle. The tilt angle of the roll is changed and controlled according to the instructions of the vessel.

Table 1 shows the yield stress of 279 N / mm ² , φ50.
In the forming of a steel pipe equivalent to 8 × t8 (mm), the amount of twist on the fin pass roll entrance side when the present invention is applied to the center bend region and when formed by a conventional 2-roll vertical side roll is shown. By applying the present invention, it can be seen that there is a remarkable twist suppressing effect even during molding and threading.

[0013]

[Table 1]

[0014]

According to the present invention, when a metal pipe is continuously roll-formed and welded to produce a welded pipe, the center-bend region can be formed without twisting, without impairing wall thickness accuracy. It is possible.

[Brief description of drawings]

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

FIG. 2 is a side view of FIG.

FIG. 3 is an explanatory view showing a 2-roll type vertical side roll for a center bend in a conventional method.

FIG. 4 is a schematic diagram of a situation of a thickness increase occurring in a conventional 4-roll breakdown method.

[Explanation of symbols]

 1 Horizontal upper roll 2 Horizontal lower roll 3 Vertical side roll 4 Formed strip 5 2 Roll type side roll 6 Thickness increase area 7 Compressive force 8 Width direction rolling force

Claims (3)

[Claims] 1. A 4-roll breakdown stand in which horizontal upper and lower rolls and side rolls are arranged for the purpose of center bend in roll groups in the first and middle stages of a welded pipe manufacturing line for roll forming and welding a metal strip having a predetermined width. ,
Or 3 with horizontal lower roll and side roll
A method for forming a welded pipe, characterized in that, in a roll stand, the axis of the side roll is formed by a roll stand whose inclination can be arbitrarily adjusted within a range of 0 ° to 45 ° in a line advancing direction with respect to a vertical axis. 2. A 4-roll breakdown stand in which horizontal upper and lower rolls and side rolls are arranged for the purpose of center bending in the first and middle roll groups of a welded pipe manufacturing line for roll forming and welding a metal strip having a predetermined width. ,
Or 3 with horizontal lower roll and side roll
A method for forming a welded pipe, which comprises forming an axis of a side roll in a roll stand while adjusting an inclination of the side roll in a line traveling direction within a range of 0 ° to 45 °. 3. A 4-roll breakdown stand in which horizontal upper and lower rolls and side rolls are arranged for the purpose of center bending in the first and middle roll groups of a welded pipe manufacturing line for roll forming and welding a metal strip having a predetermined width. Or, in a three-roll stand in which a horizontal lower roll and a side roll are arranged, the axis of the side roll is provided so that the inclination can be arbitrarily adjusted within the range of 0 ° to 45 ° in the line advancing direction with respect to the vertical axis. Characteristic welded pipe forming stand.