JPH02104419A - Manufacture of welded pipe - Google Patents

Abstract

PURPOSE:To sufficiently form both edges by constituting lower caliber rolling roll of horizontal roll on at least one stand on the forming groups with two rolls, tilting in the progressing direction of the metallic pipe and making the crossing angle on the vertical plate possible to adjust. CONSTITUTION:On the one horizontal stand, the lower roll 3 is composed of two rolls 5, 5 having an inclination beta (tilt angle) for the feeding direction of a metallic band 4 and having an inclination alpha (crossing angle) for the cross direction of the metallic band 4 in the vertical plane for the feeding direction of the metallic band 4. The tilt angle beta means the angle on the plane for the feeding direction of the metallic band 4, the cross angle alpha means the angle on the side face. The right end is the normal cross section when the metallic band 4 starts to contact with the upper roll 2 and one of the lower roll 5. The left end is the section at the center position of the upper roll 2 and the normal cross section when the bending of the edge is completed. The contact point of the lower roll 5 with the metallic band 4 is moved with progressing the bending forming for the angles alpha, alpha the bending forming is performed sufficiently to the edge of the metallic band 4 without generating roofing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a welded pipe manufacturing apparatus incorporating a forming roll group for continuously forming a metal strip into a cylindrical shape.

(Prior art) For example, welded pipes such as electric resistance welded pipes are made by first forming the metal from a flat state into a circular arc cross section in a roll forming process, and then forming it into a tubular shape in the final stage before forming the butt edges. It is manufactured by melt-welding. In this step of forming into a tubular shape, so-called roll bending is performed.
Generally, the first step is forming into an arc shape called breakdown, then the arc is further formed into a tubular body with a smaller radius, and the final stage is called fin bath, where the butt edges of the tubular body are formed. It is used to mold.

In the roll forming of such welded pipes, the bending applied to both edges of the metal strip is extremely important, and if this bending is poor, the shape quality of the weld will deteriorate and the material yield will decrease. Cause.

Nowadays, the performance of welded pipes has improved, and because they are easy to manufacture, their uses are expanding, and attempts are being made to manufacture welded pipes not only for thin-walled materials but also for considerably thick-walled materials. Ta. For example, in the case of a thick material, as the plate thickness increases, it becomes difficult to form the edge portion, leaving an unformed portion where no bending has been performed. This results in irregular welding contact and deteriorates welding quality.

FIG. 1 is a schematic cross-sectional view showing a typical example, and in particular, the vicinity of 1° of the welded portion inside the steel pipe 1 remains as an unformed straight portion a, resulting in a so-called roofing phenomenon. The straight parts that are not bent are welded and left as a roof.

In addition, since thin to thick metal strips are usually formed using the same roll, for example, thin metal strips caught between the upper roll 2 and the lower roll 3, as shown in FIG. The edges of the metal band 4 cannot be bent. On the contrary, with thin walls, the edges tend to stretch a little compared to the center of the metal band.
These elongated edges bend and become wavy, making the weld unstable. When the material is thin, for example, when the ratio of wall thickness t/outer diameter is less than 1.5%, undulations occur at the side edges of the metal strip during forming. This is so-called edge buckling.

On the other hand, as shown in FIG. 2(b), when the wall is thick, it becomes difficult to form the edges, and roofing occurs.

Therefore, since one roll has an optimum forming range, the current situation is to limit the wall thickness of the metal strip and to change the roll to an appropriate roll according to the wall thickness for rolling forming.

Conventionally, there is a W-bend method shown in Japanese Patent Publication No. 59-27654 as a method for bending edges for manufacturing welded pipes, but even with this W-bend method, the thinning of the edge that occurs when bending the edges can be avoided. I can't. Also, since it is not possible to form from thin to thick walls using the same roll, the rolls are changed for each thickness range.

FIG. 3 is a schematic diagram showing the state of contact between the roll and the material when bending an edge using a normal horizontal roll stand. Here, the contact between the lower roll 3, which is a grooved roll, and the metal strip 4 begins at both edges of the metal strip 4 (points A and B) at the roll entrance.
) is correct. Then, the lower roll pushes the metal strip 4 at points A and B, the metal strip 4 is wound around the upper roll 2, and the edge of the metal strip 4 is bent. Therefore, the portions of the metal strip 4 corresponding to points A and B at the intermediate point leading to the roll center receive concentrated stress and thinning occurs. Then, bending is performed at the roll center in a state where the thickness is reduced. Such thinning of the edge of the metal band is the same in the case of forming by the W-bend method, which is limited to the edge bend type forming shown in FIG.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to sufficiently bend both edges of a metal strip in roll forming of a welded pipe, and to perform edge bending even when forming a thick material. Forming is possible without edge thinning, that is, no roofing occurs even after welding, and even thin materials are formed without edge buckling, and the same roll can be used for both thin and thick materials. An object of the present invention is to provide a welded pipe manufacturing device incorporating a roll forming device capable of sufficiently performing edge bending.

(Means for Solving the Problem) The present inventors have studied to solve the problem and found that the cause of edge thinning that occurs during edge forming of thick-walled materials is that concentrated stress is applied to the metal strip by the rolls. By continuously changing the contact point between the roll and the metal strip,
We believe that this will prevent concentrated loads, and when forming from thick to thin walls using the same roll, the edges of thin materials cannot be bent with conventional gap settings alone. It is necessary to find a way to adjust the distance between the upper and lower rolls at the edge and the center depending on the situation, and after conducting various experiments, we found that such a measure was effective. The present invention was completed after learning that the crossing angle could be made freely adjustable.

Here, the gist of the present invention is a welding method comprising a group of forming rolls for continuously forming a metal strip into a cylindrical shape, and a welding means for joining the seams of the cylindrical metal band thus formed. In the pipe manufacturing apparatus, in the breakdown stand of the forming roll group, the pilot hole type rolls of the horizontal rolls of at least l stands are composed of two rolls, and are inclined in the metal band traveling direction, and the metal band This welded pipe manufacturing apparatus is characterized in that the intersecting angle can be adjusted within a plane perpendicular to the direction of travel.

Here, "at least one stand in the breakdown stand" is set to the lower 20 roll method, which means that among the rolls that are mainly responsible for bending the edges in the process of forming a flat metal strip on the breakdown stand. One stand always consists of two pilot hole type rolls (hereinafter simply referred to as "lower rolls"), and if necessary, two stands,
This means that two rolls may be used on the lower side in three stands and multiple stands.

The bending of the edge of the metal band in the breakdown stand is usually the largest in the first stand, decreases downstream in the second and third stands, and almost disappears in the fourth stand. Therefore, if at least the first stand is of the lower 20-level type, the effect will be great. In addition, the amount of molding in the first stand was reduced, and the amount of molding in the second stand was reduced.
It is also possible to increase the amount of molding of the stand, and in such a case, it is preferable that the second stand also be of the lower 20-hole type.

As described above, according to the present invention, in the roll forming apparatus for welded pipes, the lower roll is divided into two parts in at least one horizontal roll stand which is mainly responsible for bending the edges at the initial stage of the roll forming process. The metal strip is tilted with respect to the feeding direction of the metal strip, and the intersecting angle can be adjusted within a plane perpendicular to the metal strip traveling direction.

Although the present invention is not limited to a specific value, the intersection angle in a plane perpendicular to the metal strip traveling direction of the lower roll (hereinafter simply referred to as "intersection angle") is defined as If the material is large and thick, it is preferable to make it small.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 4 (al, tb>) is a schematic illustration of the roll arrangement of the apparatus according to the invention. In at least one horizontal stand, which is primarily responsible for edge bending, the lower roll 3 is connected to two rolls. 5.5, has an inclination β (angle of inclination) with respect to the feeding direction of the metal band 4, and has an inclination α with respect to the width direction of the metal band in a plane perpendicular to the feeding direction of the metal band 4.
(cross angle). Here, the inclination angle (β) refers to the angle on the plane with respect to the feeding direction of the metal strip 4 in FIG. 4, and the crossing angle (α) refers to the angle on the side surface.

FIG. 4 also shows a normal cross section perpendicular to the feeding direction when the metal strip 4 is fed to this stand.

In the figure, the cross section ■ is the normal cross section of the metal strip 4 when the fed metal strip 4 starts contacting the upper roll 2 and one of the lower rolls 5, and the cross section ■ is the cross section at the center position of the upper roll 2. This is a normal cross section at the time when the edge bending of the metal band 4 is completed. Also, the ■ cross-section is a normal cross-section at an intermediate position between the ■ cross-section and the ■ cross-section. As is clear from Fig. 4, the lower roll 5
Since each lower roll 5 has an inclination angle β and an intersecting angle α, the contact point between the metal strip 4 and the lower roll 5 moves as the bending of the metal strip 4 progresses, and the contact point between the metal strip 4 and the metal strip 4 changes and does not receive concentrated stress at the − point. . Therefore, thinning of the edge of the metal band 4 does not occur, and bending can be sufficiently performed up to the edge of the metal band 4, so that roofing does not occur.

Next, in the case of metal strips with different wall thicknesses, the edge of the metal strip 4 is adjusted by adjusting the rolling reduction of the upper roll 2 and the crossing angle α of each lower roll 5.5 so that the crossing angle of the thin material becomes larger. The arrangement can be such that sufficient molding is possible.

For thin materials, bending the edges increases the rigidity of the edges and is effective in preventing edge buckling.

As described above, according to the present invention, by adjusting the intersecting angle according to the plate thickness each time, edge bending from thin to thick walls can be performed sufficiently with the same roll, and the edge bending during thin wall forming can be It is possible to effectively prevent the occurrence of buckling and roofing during thick-walled molding.

It should be noted that the relationship between the plate thickness and the intersecting angle at this time cannot necessarily be stated unambiguously because it is also related to the radius of curvature of the pilot hole type roll, but a person skilled in the art can understand it from the description of the examples described below. You can also set it as appropriate.

Next, the present invention will be explained in more detail with reference to examples thereof.

(Example) Two types of steel plates with wall thicknesses of 10 mm and 0.7 mm were roll-formed using a conventional method and the method of the present invention using a single stand, and their formability was compared.

FIG. 5 is a schematic explanatory diagram showing the roll shape of the conventional example at this time, and the radius of curvature R of the upper roll was 20I.

On the other hand, that of the lower roll was R=301!111.

In the case of this example, as shown in the same schematic diagram in Fig. 6,
The lower roll was divided into two parts, and the inclination angle (β) was 30°, and the intersection angle (α) of each was 20″ for a plate thickness of 1OIIIl and 45° for a plate thickness of 0.7mm.

The wall thickness distribution of the edge after passing through a single stand in the case of a steel plate with a wall thickness of l10l1 is shown graphically in FIG. In the conventional method, 21,111 times of edge thickness loss occurred, but in the present invention, edge thickness loss hardly occurred.

Next, FIG. 8 shows the inner surface curvature after single stand molding. In the conventional method, when the wall is thick, that is, when the wall thickness is 10 m+*, the inner surface is not bent due to thinning at the edges.

Even with a wall thickness of 0.7 mm, the edges could not be bent.

In comparison, with the method of the present invention, even if the thickness is 10 mm, the wall thickness is 0.7+
In all cases, it was possible to sufficiently bend the edge to the edge. In addition, in the figure, the inner curvature (1/R) of 0.05 is a value when R=20 of the upper roll.

Here, the method of the present invention is incorporated into the first stage roll stand of a roll forming device of a normal electric resistance welded pipe manufacturing device, and the outer diameter is 50 mm.
．． hs, wall thickness 101% 11 and 0.7+nm "t" welded pipes were manufactured. Welding was performed by electric resistance welding. As a result, with a wall thickness of 10Ila+, no edge thinning occurred and no roofing was observed. There was no. 0, 7 again
In the case of a steel plate having an o111 thickness, edge bank ring occurred in the conventional method, but in the method of the present invention, edge buckling was not observed because the edges were sufficiently bent.

(Effects of the Invention) As described in detail above, according to the present invention, both edges can be formed satisfactorily regardless of whether it is a J7 wall material or a thin wall material. Roofing of materials can be effectively prevented8, and edge bank ringing of thin materials can also be prevented, which is of great significance in terms of quality control.

In addition, by adjusting the thickness of each lower roll, changes in plate thickness can be accommodated, and there is no need to rearrange the rolls as in the past, so there are great benefits in terms of production technology.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view showing defects in welded pipes produced by conventional methods; Fig. 2 (al and mountains) is a schematic explanatory drawing showing roll-biting states of thin-walled and thick-walled materials, respectively; Fig. 3 is A schematic diagram of the contact state between the roll and the forming material: FIG. 4 (al and Tb) is a schematic explanatory diagram illustrating the arrangement of the upper and lower rolls of the forming device of the welded pipe manufacturing device according to the present invention; FIG. 6 is a schematic explanatory diagram of the example; and FIGS. 7 and 8 are graphs collectively showing the results of the example. l: Welded steel pipe 2: Upper roll 3: Lower roll 4: Metal strip 5: Split lower roll

Claims (1)

[Claims] A welded pipe manufacturing apparatus comprising a forming roll group for continuously forming a metal strip into a cylindrical shape, and a welding means for joining the joints of the cylindrical metal band thus formed, the forming roll group comprising: at least 1 in the breakdown stand of
The horizontal roll of the stand is composed of two rolls, and is tilted in the direction of movement of the metal band, so that the intersecting angle can be adjusted in a plane perpendicular to the direction of movement of the metal band. Welded pipe manufacturing equipment.