JPH07275954A - Production of electric resistance welded tube - Google Patents

Abstract

PURPOSE:To prevent the development of a linear flaw on the surface of a steel tube by making a hoop steel after bending almost the triangular steel tube constituted with three large arcs and three small arcs, in the mechanism for forming the steel tube from the hoop steel. CONSTITUTION:In the mechanism for forming the steel tube by gradually bending the hoop steel with forming rolls, the hoop steel after bending is formed to almost the triangular steel tube constituted with the three large arcs (d), (e), (f) and the three small arcs (a), (b), (c). By this method, the surface of the roll is not wholly brought into contact with each surface of the hoop steel rolled flower and the development of the linear flaw between the edge part and the surface of the steel tube caused by the difference with the peripheral velocity of the roll surface can be eliminated. Further, as this hoop steel is formed with almost the triangle having the three small arcs and the three large arcs, the change of a brake-down roll is made to be unnecessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for producing an electric resistance welded steel pipe by forming a steel strip into a steel tube by a forming roll and welding a butt portion.

[0002]

2. Description of the Related Art In the conventional continuous roll forming in the production of electric resistance welded steel pipes, the conventional forming process is as shown in FIG.
A steel tube was manufactured by forming the material into a nearly cylindrical shape and welding in the circular shape. That is, in FIG. 8 showing the conventional forming process, as shown in the figure, 10 sets of breakdown rolls 1 ′ to 10 ′ are arranged, and 5 sets of fin pass rolls 11 ′ to 15 ′ are arranged. A circular strip steel roll flower was constructed by these forming roll passes as shown in FIG. 9, and then welded and cooled.

After welding and cooling, the electric resistance welded steel pipe is straightened to a circular shape by a two-roll type sizing roll SR 'composed of several sets of upper and lower rolls or a pair of left and right rolls, and finally the turks head TH. The bend in the axial direction was corrected by ', the manufacturing process of the electric resistance welded steel pipe was completed, and then it was sent to the cutting process of the electric resistance welded steel pipe. Since the conventional technology is configured in this way, it is required that all the circumferences of the strip steel roll flower are arcs that match the desired pipe diameter, and the breakdown along the arcs is required. Rolls, fin pass rolls and bead cutters were required.

As a result of the above, a dedicated roll is required in the breakdown portion and the fin pass portion each time the diameter of the steel pipe is changed. Therefore, each time the diameter of the steel pipe is changed, the forming roll must be replaced. It had been done. Changing this molding roll is a laborious task,
When producing electric resistance welded steel pipes in high-mix low-volume production, there was a problem that it took time to replace the forming rolls.

[0005]

According to the present invention, as shown in FIG. 1, even a substantially triangular flower is molded, the abutting portion is welded in this substantially triangular state, and after welding and cooling, a sizing roll is used. Since it is shaped into a prescribed cylindrical shape, it is possible to use the forming rolls in common, and it is not necessary to replace the rolls in the breakdown part and the fin pass part.

[0006]

The problems to be solved by the present invention are as described above. Next, the means for solving the problems will be described. According to the first aspect of the present invention, in the mechanism for gradually bending the strip steel S by the forming roll to form the steel pipe, the strip steel S after bending has three large arcs d.e.f.
And a substantially triangular steel pipe composed of three small arcs a, b, and c.

According to the second aspect of the present invention, the steel strip is formed into a substantially triangular shape, and the abutting portions are welded together to form a steel pipe.

In the third aspect, the small arc c corresponding to the apex of the triangle is located in the lower center, and the large arc d corresponding to the base of the triangle is located in the upper center.
Small arcs a and b are arranged on both left and right sides of the large arc d forming the bottom side, and a portion connecting the small arcs a and b on the left and right and a small arc c at the lower center is a large arc on the left and right.
It is what

According to the present invention, the portion where the butt welding is performed after the steel tube is formed is the portion forming the large arc d at the upper portion.

In a fifth aspect of the present invention, the electric resistance welded steel pipe welded into a substantially triangular shape is sized by a sizing roll arranged in the next step to have a cylindrical shape.

In the sixth aspect, the sizing roll is a three-roll type stand.

According to a seventh aspect of the present invention, the diameter of the electric resistance welded steel pipe can be continuously produced by reducing the diameter of the pipe with a sizing roll.

[0013]

[Operation] Next, the operation will be described. According to the first aspect, unlike the conventional case where the entire circumference is formed into an arc, the surface of the roll does not come into contact with each surface of the strip steel roll flower, and the hem of the skirt is changed due to the difference in the peripheral speed of the roll surface. It was possible to eliminate the generation of linear scratches on the surface of the steel pipe, which was created between the part and the surface of the steel pipe. Also, three small arcs a
・ Bc and three large arcs d, e, and f form a substantially triangular shape, so it is no longer necessary to replace the breakdown roll. Further, in the conventional forming process, the bending of the end portion of the strip steel S was difficult, but in the forming process of the present method, the bending of the end portion of the strip steel is not performed in principle, so that the problem of occurrence of an edge wave is Resolved.

In the second aspect, since the arc shape of the large arc d portion is the same regardless of the pipe diameter, the shape of the large arc d portion, which is the welded portion, is the same regardless of the pipe diameter. You no longer need to change roles. Further, among the cutting tool shapes for cutting the weld bead on the outer surface, the cutting tool has the same arc shape, so that there is no need for cutting tools of different sizes. Further, adjustment of the bite position for cutting the weld bead on the inner surface was necessary in the conventional forming process due to the rolling of the strip steel, but in the present invention, it is configured and held in a substantially triangular shape. Since the steel pipe is conveyed while it is being conveyed, there is no occurrence of twisting of the steel pipe, and therefore the adjustment of the bite position is unnecessary.

In the third aspect, the welded portion can be a portion of a large arc d, and the substantially triangular holding portion can be a portion of a small arc a. It was possible to obtain a strip steel roll flower of a substantially triangular shape.

According to the present invention, the problem caused by poor welding due to unstable buttability due to bending of the end portions of the steel strip has been solved. Further, in the conventional circular forming, the method of restraining the edge portion was difficult as a measure for preventing the rolling of the strip steel, etc., but the triangular forming of the present method could not do so at all.

According to the present invention, it is not necessary to form a regular circular arc in the step of the breakdown roll, and the circular shape is first shaped into a circle in the final step of the sizing rolls SR1, SR2, SR3. Since the processing precision of was low, it was possible to reduce the precision of the forming process of the strip steel roll flower.

In the sixth aspect, a three-roll type sizing roll SR1 for straightening and driving an electric resistance welded steel pipe having a substantially triangular shape.
-The three roll type sizing rolls SR1 and S can be forcibly shaped into a circle by SR2 and SR3.
In the case of R2 and SR3, the accuracy can be improved,
Further, since the roll is shaped by dividing the circumference on three sides from three directions, there is no linear trace caused by the difference in peripheral speed of the contact position of the roll, as compared with the case where the roll is shaped or shaped into a circle with two rolls. You can do it.

According to the seventh aspect of the present invention, it was difficult to manufacture the electric resistance welded steel pipes having other diameters when the forming roll having the diameter is used for each pipe diameter as in the conventional case. In the case of, in the sizing rolls SR1, SR2, and SR3, it was possible to continuously reduce the diameter of the product round tube from the formed triangular tube of the same diameter, so the number of setup changes was further reduced and the productivity was improved. Has improved.

[0020]

EXAMPLES Next, examples will be described. FIG. 1 is a cross-sectional view showing a process of forming a strip steel roll flower into a substantially triangular shape according to the present invention, and FIG. 2 is a breakdown roll 1u.1d in which the upper side portion is bent with a constant arc regardless of the size of the steel pipe in the substantially triangular forming.
3 is a cross-sectional view showing the molding state of the portion of FIG. 3, FIG. 3 is a cross-sectional view showing the molding state of the breakdown rolls 4u and 4d that bend the small arcs a and b on the left and upper right sides of the substantially triangular shape, and FIG. Sectional view showing the forming state of the breakdown rolls 6u, 6d for bending the small arc c on the lower side, and FIG. 5 is a sectional view of the fin rolls 8u, 8d, 10u, 10d and the side rolls 7, 7, 9, 9 FIG. 6 is a drawing showing a process for forming a substantially triangular strip steel roll flower of the present invention, FIG. 7 is a sectional view of a bead cutter portion after welding, and FIG. 8 is a conventional forming of a strip steel roll flower having a circular shape. Drawing which shows a process, FIG. 9 is drawing which shows the forming process of the conventional circular strip steel roll flower.

In the present invention, the breakdown roll and the fin pass roll need not be exchanged, and even if they are exchanged, they can be replaced only when the diameter of the steel pipe is significantly changed. The electric resistance welded steel pipe is formed into a substantially triangular shape, and after welding, the substantially triangular shape is shaped into a circle by a three-roll type sizing roll SR. By adopting this method, the substantially triangular shape is composed of small arcs a, b, and c and large arcs d, e, and f, so it is formed into a strip steel roll flower that matches the desired circumferential shape of the electric resistance welded steel pipe. It is not necessary to form the strip steel S having an outer peripheral length corresponding to the diameter of the electric resistance welded steel pipe into a substantially triangular shape having a substantially similar shape, and thereafter, the sizing roll SR can be left to be formed into a circular shape. As a result, the small arc a
・ It is possible to use the same b and c for the breakdown roll and fin pass roll that make up the ERW steel pipe within a certain range of diameter, and when the ERW steel pipe diameters differ greatly. Only the breakdown rolls and the fin pass rolls need to be exchanged.

FIG. 6 shows the system steps of the method for manufacturing an electric resistance welded steel pipe of the present invention. Strip steel feeding part I
By G, the steel strip S is fed in the direction of the breakdown roll 1. The breakdown roll 1 is 1u · 1 vertically
It is composed of a pair of rolls in which the rolls of d are arranged. The breakdown rolls 1 and 2 are driven by the upper and lower rolls. Breakdown roll 3/4
In 5 and 6, only the lower roll is driven, and the upper roll is not driven. Next, in the fin pass portion formed by the side rolls 7 and 9 and the fin pass rolls 8 and 10, the abutting portion is finally formed and positioned, and is guided to the welding device.

After welding the butt portion with the welding device, the butt portion is cooled and then the three-roll type sizing roll SR1.
The shape of the electric resistance welded steel pipe is changed from a substantially triangular shape to a circular shape by SR2 and SR3. The sizing rolls SR1 and SR2
-SR3 is press-shaped from the direction in which the pressing direction of the roll is shifted by 60 degrees, and the sizing rolls SR1, SR2 and SR3 are driven respectively, so that a strong shaping force can be exerted. Of. After passing through the sizing rolls SR1, SR2, and SR3, final shaping is performed by a two-roll type sizing roll, and after bending in the axial direction by the turks head TH, the sizing roll is sent to a cutting device.

FIG. 2 shows the first forming process of the steel strip S. In the process of FIG. 2, the portion of the large arc d in the substantially triangular shape is broken down by the breakdown roll 1u.
It is molded by 1d. The breakdown rolls 1u and 1d are configured to be automatically controlled to move left and right and up and down depending on whether the diameter of the electric resistance welded steel pipe is small or large. When the diameter of the electric resistance welded steel pipe is small, the breakdown rolls 1u and 1d horizontally move to the side close to the pipe diameter center O, and move up and down in the direction close to the pipe diameter center O. vice versa,
When the pipe diameter is large, it moves left and right in the direction away from the pipe diameter center O, and moves up and down in the direction away from the pipe diameter center O.

The breakdown rolls 2 to 6 also have the breakdown rolls 2u and 2d to 6u and 6d.
And the upper and lower rolls. The breakdown rolls 1 and 2 are both driven up and down, but regarding the breakdown rolls 3 to 6, only the lower roll is driven and the upper roll is not driven.

FIG. 3 shows a process of forming left and right small circular arcs a and b of a substantially triangular shape. The breakdown rolls 4u and 4d are also configured to be automatically moved left and right and up and down according to the pipe diameter. In FIG. 4, breakdown rolls 6u and 6d forming a small circular arc c in the lower center portion of the substantially triangular shape are shown. Thus, in FIGS. 3 and 4, the small arcs a, b, and c are formed, and the radius R of the portion of the small arcs a, b, and c is equal to or smaller than the minimum radius of the pipe. Is configured as follows. That is, the pipe can be formed by the breakdown roll of the embodiment up to the range where the relationship of "radius R≤minimum pipe radius" is established.

The range in which the above-mentioned breakdown roll set can be formed is 20 to 60 mm for the small diameter roll set, 60 to 180 mm for the medium diameter roll set, and 180 to 540 mm for the large diameter roll set. If this range is exceeded,
Although it is necessary to change the roll set, when changing the diameter within the range of this roll set, the same breakdown roll set can be used.

In FIG. 5, the fin pass roll 8.1
0 and side rolls 7.9 are shown. The fin pass rolls 8 and 10 and the side rolls 7 and 9 correct the abutting portions to be welded and adjust the intervals of the abutting parts to a prescribed interval so that the abutting parts will not be distorted.

In the present invention, the abutting portion is located at the center of the large arc d, and the large arc d
Even if the pipe diameter is changed, the fin pass rolls 8 and 10 and the side rolls 7 and 9 can be the same since they are almost the same. The fin roll 8
Both the 10 and the side rolls 7 and 9 are automatically controlled by a computer to move left and right and up and down, and their positions are changed according to the pipe diameter.

FIG. 7 shows a mechanism for cutting the bead portion generated by welding by the bead cutter BC. Also in this case, since the shape of the circular arc of the large circular arc d is the same even if the pipe diameter is changed, the same bead cutter BC can be used regardless of the pipe diameter. Further, since the welded portion is formed at the center of the portion of the large arc d, and the shape of the large arc d is always formed to be the same, the shape of the weld abutting portion is the same regardless of the pipe diameter. Therefore, once adjusted, even if the pipe diameter is changed, it is possible to always weld in the same situation, and the occurrence of welding mistakes is small.

[0031]

Since the present invention is constructed as described above, it has the following effects. According to claim 1, the steel strip S
In the mechanism for forming a steel pipe by gradually bending the steel with a forming roll, the strip steel S after bending has three large arcs d · e.
・ Since the steel pipe has a substantially triangular shape made up of f and three small arcs a, b, and c, the surface of the roll is all made of strip steel roll flower, as in the conventional case where the entire circumference is formed into an arc. Since it did not come into contact with the surface, it was possible to eliminate the occurrence of linear scratches on the surface of the steel pipe, which were created between the skirt portion and the surface of the steel pipe due to the difference in peripheral speed of the roll surface. Further, since the three small arcs a, b, and c and the three large arcs d, e, and f are formed into a substantially triangular shape, it is not necessary to replace the breakdown roll. Further, in the conventional forming process, it was difficult to bend the end portion of the steel strip S, but in the forming process of this method,
Since the steel strip is not bent at the end in principle, the problem of occurrence of edge waves, etc. was solved.

Since the steel strip S is formed into a substantially triangular shape, the abutting portions are welded together to form a steel pipe.
Since the arc shape of the large arc d portion is the same regardless of the pipe diameter, the shape of the large arc d portion that is the welded portion is
It became the same regardless of the pipe diameter, eliminating the need to change the fin pass roll. Further, among the cutting tool shapes for cutting the weld bead on the outer surface, the cutting tool has the same arc shape, so that there is no need for cutting tools of different sizes. Further, the welding bead cutting on the inner surface was caused by the rolling of the strip steel in the conventional forming process, but since the present invention is configured to have a substantially triangular shape and is conveyed while being held, the twisting of the steel pipe, etc. Since there is no occurrence of, there is no need to adjust the bite position.

According to the third aspect, the small arc c corresponding to the apex of the triangle is located at the lower center, the large arc d corresponding to the bottom of the triangle is located at the upper center, and the large arc d forming the bottom is formed. A small arc a
b is arranged, and the portion connecting the left and right small arcs a and b and the lower center small arc c is defined as the left and right large arcs e and f, so that the welded portion can be the large arc d. The portion held by the substantially triangular shape could be the portion of the small arc a, and regardless of the pipe diameter, it was possible to make a substantially triangular strip steel roll flower of different shapes.

According to the fourth aspect, since the portion where the butt welding is performed after forming the steel tube is the portion forming the large arc d at the upper portion, the welding failure due to the unstable buttability due to the end bending of the strip steel is caused. The problem caused by is solved.
Further, in the conventional circular forming, the method of restraining the edge portion was difficult as a measure for preventing the rolling of the strip steel, etc., but the triangular forming of the present method could not do so at all.

Since the electric resistance welded steel pipe welded in a substantially triangular shape is sized by the sizing roll arranged in the next step to have a cylindrical shape, a regular arc is formed at the stage of the breakdown roll. There is no need to shape it into a circle for the first time in the final sizing roll SR1, SR2, and SR3 stages, so the processing precision of the breakdown roll and fin pass stages is low, so the precision of the strip steel roll flower forming process is low. I was able to do it.

Since the sizing roll is a three-roll type stand as in claim 6, a three-roll type sizing roll SR1 for straightening and driving an electric resistance welded steel pipe having a substantially triangular shape is provided.
-The three roll type sizing rolls SR1 and S can be forcibly shaped into a circle by SR2 and SR3.
In the case of R2 and SR3, the accuracy can be improved,
Further, since the roll is shaped by dividing the circumference on three sides from three directions, there is no linear trace caused by the difference in peripheral speed of the contact position of the roll, as compared with the case where the roll is shaped or shaped into a circle with two rolls. You can do it.

As described in claim 7, since the diameter of the electric resistance welded steel pipe can be manufactured steplessly by performing the work of reducing the diameter of the pipe by the sizing roll, as in the conventional case, the roll of the diameter is provided for each pipe diameter. However, in the case of the present invention, the diameter of the sizing rolls SR1, SR2, and SR3 is continuously reduced. As a result, it is possible to manufacture an electric resistance welded steel pipe having a desired diameter.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a process of forming a strip steel roll flower into a substantially triangular shape according to the present invention.

FIG. 2 is a breakdown roll 1u for bending the upper side of the substantially triangular shape with a constant arc regardless of the size of the steel pipe.
Sectional drawing which shows the shaping | molding state of the 1d part.

[FIG. 3] Similarly, a small arc a on the left and right sides of a substantially triangular shape
Sectional drawing which shows the shaping | molding state of the part of the breakdown rolls 4u * 4d which bends b.

FIG. 4 is a cross-sectional view showing a state where the breakdown rolls 6u and 6d that bend a small circular arc c on the lower side of the substantially triangular shape are formed.

FIG. 5: Fin pass roll 8u / 8d / 10u / 10d
And sectional drawing of a part of side rolls 7 * 7 * 9 * 9.

FIG. 6 is a drawing showing a process of forming the substantially triangular strip steel roll flower of the present invention.

FIG. 7 is a sectional view of a bead cutter portion after welding.

FIG. 8 is a view showing a forming process of a conventional strip steel roll flower having a circular shape.

FIG. 9 is a drawing showing a forming process of a conventional circular strip steel roll flower.

[Explanation of symbols]

 S band steel 1u, 1d Breakdown roll 2,3,4,5,6 Breakdown roll 7,9 Side roll 8,10 Fin pass roll SR1, SR2, SR3 Sizing roll

Claims (7)

[Claims] 1. A mechanism for gradually bending a strip steel S by a forming roll to form a steel pipe, wherein the strip steel S after bending is
3 large arcs d ・ e ・ f and 3 small arcs a ・
A method for manufacturing an electric resistance welded steel pipe, characterized in that the steel pipe has a substantially triangular shape constituted by b and c. 2. The method for manufacturing an electric resistance welded steel pipe according to claim 1, wherein the butt portions are welded to form a steel pipe in a state where the strip steel S is formed into a substantially triangular shape. . 3. The method for manufacturing an electric resistance welded steel pipe according to claim 2, wherein a small arc c corresponding to the apex of the triangle is located in the lower center, and a large arc d corresponding to the bottom of the triangle is located in the upper center. And a large arc d forming the bottom
Electric arc welding characterized by arranging small circular arcs a and b on both left and right sides and connecting the small circular arcs a and b on the left and right with a small circular arc c at the center of the bottom to form large circular arcs e and f on the left and right. Steel pipe manufacturing method. 4. The method of manufacturing an electric resistance welded steel pipe according to claim 3, wherein the butt-welding portion formed into a steel tube is a portion forming a large arc d at the top. Manufacturing method. 5. The method for manufacturing an electric resistance welded steel pipe according to claim 2, wherein the electric resistance welded steel pipe welded in a substantially triangular shape is sized by a sizing roll arranged in the next step to have a cylindrical shape. Manufacturing method of ERW steel pipe. 6. The method for manufacturing an electric resistance welded steel pipe according to claim 5, wherein the sizing roll is a three-roll type stand. 7. A method of manufacturing an electric resistance welded steel pipe, wherein the diameter of the electric resistance welded steel pipe can be manufactured steplessly by performing a work of reducing the diameter of the pipe with the sizing roll according to claim 5.