JPH0394910A - Method for forming one seam large diameter angular steel pipe - Google Patents

Abstract

PURPOSE:To manufacture a one seam angular steel pipe of high dimensional accuracy by passing through the space between forming rolls in plural steps after welding a bevel part without any discrepancy in the case of forming a steel plate in a specified width in the shape approximate to an angular steel pipe at its section. CONSTITUTION:While a steel plate 1 having a specified width is transferred in the length direction, beveling is executed on both side edges thereof and also an end bending 2 is performed by a roll forming means 3, 4. In the case of forming the section in the shape approximate to an angular steel pipe by abutting the beveling parts, the abutment is executed just as holding the shape of expanding each side of the section slightly to the outside and the beveling face is subjected to tack welding without any discrepancy. After executing a normal welding, it is passed through the space between forming rolls in plural steps, the bulge of the four faces, the roundness of each corner part and the squareness are shaped gradually, and a one seam large diameter angular steel pipe of high quality with the high flatness of each side and whose R of the corner part is uniform can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a technology related to a new forming method for one-seam large-diameter rectangular steel pipes used for construction and other purposes.

[Conventional technology]

Large diameter rectangular steel pipes used for construction and other purposes have conventionally been manufactured by bending two elongated members into a U-shaped cross section, facing each other, and welding the side edges together. This method involves a large number of forming materials, which requires double the man-hours to process, and two weld lines are created on the formed square steel pipe, which increases the welding materials, processing time, and man-hours, or the welding process requires double the man-hours. The disadvantage of this method is that it is not economical, as the work to correct distortions caused by this process accounts for a large proportion of the manufacturing cost of steel pipes.

Therefore, recently, the parts corresponding to the llv corners of a belt-shaped single steel plate are bent in the longitudinal direction one by one by press working, and the cross section is shaped into a shape that approximates a square steel pipe. After that, the material is transferred between multiple stages of forming rolls to shape it into an accurate square cross section, and after the butt portions of the steel plates are permanently welded or temporarily attached, the butt portions are welded from the inner and outer surfaces of the steel pipe. Construction methods such as main welding of parts began to be adopted.

According to this method, the process is relatively short, and since there is only one weld line on one steel pipe, work efficiency is improved, less welding materials are required, and the problem of distortion is easily solved. Since it can be removed using a straightening process, it is possible to significantly reduce costs. In addition, a coiled steel plate is rolled in the width direction to form a round steel pipe in cross section, and then the round steel pipe is passed between multiple stages of large rolls to form a square steel pipe. There are also construction methods in place.

However, there are limits to the plate thickness and size of large-diameter square steel pipes made using the above-mentioned method, and for this reason, large-diameter square steel pipes that are used in high-rise buildings are manufactured using traditional methods, and problems such as cost and distortion are avoided. still unresolved.

By the way, in the method for manufacturing one-seam large-diameter rectangular steel pipes described above, the bending process by pressing of the portion corresponding to the corner of the III tube of the single sheet steel pipe is performed by bending the corner portion on the side closer to the weld line (also referred to as R). ) and the roundness of the corners on both sides (bottom or side) that do not include the weld line do not match, and even if R correction processing is performed after forming the steel pipe, the error can be corrected in the cross section of the square steel pipe. The problem is that it is difficult to meet the standards.

That is, in the final step of bending, the press bending die must be extracted from the gap formed by the beveling of the material. The bottom corner is bent at an angle of 100° to 115°, and the beveled part is not welded during the forming process. This is because even if an attempt is made to form a rectangular steel tube with an accurate cross section by passing it through a corrugated round roll, it is not possible to apply a large load, and the influence of unbalanced corner processing cannot be completely eliminated. The material is therefore subjected to an upward force within the forming rolls, causing a tendency for the bottom edge to curve outward, with the radius of the corner being greater than the radius of the corner of the side where the weld line is located. The curves are generally largely oval shaped, and the end of the radius is not clear.

In order to prevent this situation from occurring, there is a method of inserting a core roll inside the tube, facing the forming roll and suppressing the bottom of the material, but there is a problem in terms of strength even if the roll is applied in a narrow space. However, the necessary effect cannot be obtained and it is not practical.

For this reason, it is difficult to reduce the machining error in R between each corner of a one-seam large-diameter rectangular steel pipe, and if the column cross-section specifications are made stricter, there is a high risk of producing defective products.

[The problem that the invention attempts to solve]

The present invention is a method for manufacturing one-seam large-diameter square steel pipes that stably produces steel pipes that have a rectangular cross section with good uniformity of the radius applied to each corner of the cross section, good flatness of each side, and high dimensional accuracy. The purpose of this project is to develop a method to obtain a cylindrical shape and to provide uniform, high-quality products.

[Means for resolving issues]

In order to achieve the above-mentioned object, the present invention includes each of the constituent elements as described below.

(1) In a method for manufacturing a large-diameter one-seam rectangular steel pipe, while a steel plate having a certain width is being transferred in the length direction, beveling is performed on both edges of the steel plate, and both edges are beveled along the side edges. After shallowly curving the vicinity inward, the portions of the steel plate corresponding to the steel pipe corner portions are bent inward along the length direction, and the edge-processed portions are brought into butt contact, and the cross section is shaped into a square steel pipe. When forming into a shape similar to the above, each side of the cross section is tack welded on the groove surface without any butting points while maintaining the slightly outwardly bulging shape, and then the inner and outer surfaces of the groove are permanently welded. A method of forming one-seam large-diameter rectangular steel pipes, which consists of the process of gradually shaping the bulges on all four sides and the roundness and squareness of each corner by passing them between multiple stages of forming rolls.

[For production]

In the pre-process of bending the steel plate at the corner portion of the square steel pipe,
The reason for performing the edge bending process inward near both edges of the steel plate is as follows.
The fR plate is formed into a shape similar to a rectangular steel pipe, the tips of which are tack-welded, and when performing main welding, each side of the steel pipe is left slightly bulged outward, and the tack welding is performed at this time. This is to make the edge with the line a flat surface with a gentle curve.

If the edge is bent without being bent, the cross section of the side where the tack groove exists will be formed into a chevron-shaped cross section, and even if it is subsequently welded or passed between forming rolls, the same part will not be the same. , because it does not return to a flat edge.

In the method of the present invention, after each corner is bent, each side is passed through a forming step using a slightly concave shaped roll, and each side of the cross section is slightly expanded to a shape similar to a square steel pipe. At the same time, tack welding of the groove part is performed in a state of metal touch while holding down the vicinity of the butt end faces from the outside with a press roll to prevent misalignment of the end faces.

After welding the temporarily attached parts, a square steel pipe whose cross section has a slight outward bulge on each side is passed between multiple stages of forming rolls, and the cross section is gradually shaped into a precise square shape. It is a completed material for steel pipes, and the forming conditions are such that it is symmetrical around the longitudinal axis and sufficient load can be applied, so the product after forming is made up of the four corners of a 1L pipe. Not only can R be made the same, but also forming processing can be easily performed to ensure flatness on each side.

Furthermore, the final cold forming process ensures that the cross-sectional shape of the product is always uniform within a certain margin of error.

〔Example〕

The construction method of the present invention will be explained below with reference to the drawings, but since there may be various modifications to this embodiment that can be considered by those skilled in the art based on the technical level at the time of filing of the present invention, no particular reason will be given. The gist of the present invention should not be interpreted in a limited manner based on the description of examples only. Figure 1 shows a hot-rolled coil that is unrolled and roll-formed, then width determined and beveled on both sides.
This figure shows a step of performing an end bending process 2 on a single steel plate cut into a predetermined length in the longitudinal direction, while being transferred in the longitudinal direction, and loosely inwardly bending the vicinity of both ends thereof. In this embodiment, the end bending process of the steel plate is performed by roll forming means 3 and 4, but the bending process may also be performed using a press.

FIG. 2 shows the process of bending the above-mentioned steel plate with approximately the same radius at four locations corresponding to the corners of a square steel pipe, so that the cross section thereof approximately has a shape approximately similar to that of a square steel pipe.

In the figure, the bending angles of the corners a and d, that is, the corners near the abutting surfaces, are 95° to 100°, and the bending angles of the corners a and d are 95° to 100°;
The bending angle of the corners of and C, that is, the corners close to the base, is 100° to 110°. Note that the opening gap between the beveled edges needs to be wide enough to allow the upper mold to be bent through the gap.

Figure 3(a) shows the intermediate product of the square steel pipe that has gone through the above process.
The pipe is passed between multiple stages of skew-type forming rolls 5 and 6 to form a square cross-section steel pipe with a cross section in which the middle part of each side slightly bulges outward. The figure shows how to perform tack welding 9 on the same part while guiding the butt surface 8 to avoid any misalignment and maintaining the metal touch.
At this time, it is advantageous for the subsequent roll forming process to form the bending angles of each corner portion to be the same or nearly the same throughout.

The above tack welding process may include spot welding and continuous tack welding in the longitudinal direction.

FIG. 3(b) shows an enlarged view of the above-mentioned tacking process. When tacking the butt parts of the raw steel plates, the welding surface is held down from the outside by the roll guide 7 so that it becomes flat, and then opened. The leading surfaces form a metal touch with each other, and the abutting surfaces 8
It is held in such a way that it does not cause any problem even if pressure is applied to it.

At this stage, the steel pipe has a rectangular cross section with the middle part of each side slightly bulging outward, and each corner has been deformed to have approximately the same radius.

Next, the above-mentioned tack welded portions were welded from the inside and outside of the steel pipe, and the welded joint of the butt end faces was completed (see Figure 4). A one-seam large-diameter rectangular steel pipe having a rectangular cross section as shown in FIG. 5 is formed by passing through the tube.

At this stage, the processing conditions for all four sides of the steel pipe are the same, so if the number of stages of the forming rolls is appropriately selected and the bulges of the sides are evenly and gradually corrected so that they approach a flat surface, After shaping, the square steel pipe can be formed with uniformity in the radius of each corner and with the same level of flatness on all sides. Furthermore, obtaining a final product by passing the steel pipe through a strain relief straightening machine in the longitudinal axis direction is the same as the manufacturing process of a known one-seam large diameter rectangular steel pipe.

Figure 6 shows the cross-sectional shape of a one-seam rectangular steel pipe after completion of a weld line joint in the case where the end bending process is omitted in this embodiment method. It is shaped like a mountain.

Therefore, when the side where the same line exists is roll-formed, the initial chevron-shaped cross-section remains during the work, and the side with the wave-shaped cross-section as shown in FIG. 7 is formed.

From this, it can be seen that the preliminary edge bending of the steel plate in the method of the present invention is an essential requirement for the structure of the method of the present invention.

Figures 8 and 9 show part of the process of manufacturing a one-seam large-diameter square steel pipe using a known construction method.
Figure 8 shows the process of sequentially bending or shaping the portions of the steel plate corresponding to the corners of the steel pipe by press working to create a cross-sectional shape similar to that of a square steel pipe, and Figure 9 shows the process of the next step. This shows the forming process.

A slightly exaggerated cross-section of the large-diameter rectangular steel pipe formed according to the above process is shown in Figure 10, with the corners a. As shown in FIG. 11(a), each R of d is sharp and has a fixed shape, but the corners b.d on both sides of the base. For c, R'>R as shown in Figure 11(b), and R
The stop is not certain, as explained in the [Prior Art] section.

〔Effect of the invention〕

As described above, according to the construction method of the present invention, a new construction method can be implemented simply by making improvements to conventionally installed equipment, and the one-seam large-diameter square steel pipe processed according to the construction method of the present invention can be Unlike conventional products, we manufacture high-quality one-seam large-diameter square #l pipes with uniform corner radius and fewer manufacturing errors, high flatness on each side, and less variation in products. It is possible to do so.

[Brief explanation of drawings]

Figure 1 shows an example of the end bending process of the method of the present invention, and Figure 2 shows a cross section of a single steel plate formed by bending the corners corresponding to each corner and forming it into a shape approximating a square steel pipe. Figure 3 is a cross-sectional view showing the process of tack welding the beveled butt end faces by passing through a preform roll, and Figure 4 shows the process of tack welding the tack welded part from its inner and outer surfaces. Figure 5 is a cross-sectional view of a rectangular approximate steel pipe that has been welded into a joint, and Figure 6 is a cross-sectional view of a product formed through final forming rolls so that the radius of each side and corner is within a predetermined error range. Fig. 7 is a cross-sectional view of a defective square steel pipe showing defects after forming due to the omission of one step in the construction method of the present invention, and Fig. 8 is a sectional view of a defective square steel pipe produced by a conventional one-seam large diameter square steel pipe. FIG. 9 is a cross-sectional view showing the bending process of the steel plate in the method, and the next step, the roll forming process, is shown, and FIG. 10 is a typical one-seam large-diameter rectangular steel pipe formed as a result. FIG. 11, which is a slightly exaggerated cross-sectional view, shows an enlarged sectional view of each corner of the square steel pipe. l. ．． ．． Single sheet steel plate, 3, 4. , end bending roll, 7. ．． ．． Guide roll, 9. ．． ．． Tack welding. 2. ．． ．． End bending, 5, 6. ．． Shaped roll, 8. ．． ．． Butt surface,

Claims (1)

[Claims] (1) In a method for manufacturing a large-diameter one-seam rectangular steel pipe, while a steel plate having a certain width is being transferred in the length direction, beveling is performed on both edges of the steel plate, and both edges are beveled along the side edges. After shallowly curving the vicinity inward, the portions of the steel plate corresponding to the steel pipe corners are bent inward along the length direction, the grooved portions are brought into butt contact, and the cross section is made into a square steel pipe. When forming into a shape similar to the above, each side of the cross section is tack welded on the groove surface without any butting points while maintaining the slightly outwardly bulging shape, and then the inner and outer surfaces of the groove are permanently welded. A method for forming one-seam large-diameter rectangular steel pipes, which consists of the process of gradually shaping the bulges on all four sides, the roundness and squareness of each corner by passing the pipe between multiple stages of forming rolls.