JP3185612B2 - ERW pipe manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electric resistance welded tube whose sectional shape is gradually made circular from a metal strip or coil, and a thin-walled electric resistance welded tube having a t / d of about 5% or less. The present invention relates to a production method suitable for the production of

[0002]

2. Description of the Related Art Breaking rolls, cage rolls, fin pass rolls,
An apparatus provided with squeeze rolls in order from the upstream side is known. Usually, in such a manufacturing apparatus, FIGS.
A seam guide roll c for restraining the edge from the outside of the pipe is disposed between the final fin pass roll a and the squeeze roll b as shown in FIG. ing. By the way, in forming an electric resistance welded tube, as shown in FIG. 9, since the trajectory of the strip edge is longer than the center, the edge is temporarily elongated, and edge stretching occurs. Due to the length imbalance between the edge portion and the central portion during the molding, a longitudinal tensile stress and a compressive stress act on the edge. When the compressive stress excessively acts on the edge, the edge portion buckles and a waving phenomenon occurs. This is a so-called edge wave. If an edge wave is generated at the edge portion before the electric resistance welding, not only stable welding is not performed, but also the phase of the edge wave at both edge ends is generally not synchronized. Therefore, as shown in FIG. There is a case where the peers do not meet, a gap G occurs, and the welding itself becomes impossible. In the ERW pipe manufacturing apparatus as described above, the cage roll,
By arranging the fin pass rolls, the occurrence of edge stretch is minimized, and the reduction in the fin pass rolls absorbs the edge stretch, thereby stabilizing the thin-wall forming when the thickness ratio is small. I have to. Also, as one of the methods of suppressing the longitudinal extension of the edge portion and conversely giving the bottom portion an extension,
A method of giving a downhill to the entire line has been used (JP-A-61-165225, JP-A-61-165226). However, even if such measures are taken, t / D =
1.6% (t: pipe wall thickness, D: pipe outer diameter) is the limit of stable molding.

To cope with such a problem, the generation of edge waves during the formation of a thin-walled tube is tolerated to some extent, and the edge of the tube is pressed between the fin pass roll and the squeeze roll so as to eliminate the once generated edge waves. A technique has been proposed in which a lower seam guide roll for guiding while raising is installed. This focuses on the fact that the surplus material is embodied as edge waves due to the elongation in the longitudinal direction of the edge, and this surplus material is continuously pushed upward to give tension to the edge. Thus, apparent waves are eliminated. As such a technique, Japanese Patent Publication No. 61-34908 discloses a lower seam guide roll 8 supported by a pair of right and left adjustment rods having a turnbuckle 14 as shown in FIG. 11 to adjust the pressing amount of the edge. It has a structure. Therefore, according to the prior art, it is stated that the forming at the time of butt welding can be stabilized even in the thin-wall forming in which a wave is generated at the edge exceeding the forming stability limit. However, since the lower seam guide roll is provided independently, there is a problem that it is difficult to hold the lower seam guide roll at a fixed position between the fin pass roll and the squeeze roll. Although the same publication discloses that the lower seam guide device may be mounted on the rod 10 if the rigidity of the inner bead cutter rod 10 permits, such a structure reduces the rigidity of the inner bead cutter rod. Feasibility is poor when considered. In addition, although the adjustment of the pressing amount of the lower seam guide roll is performed independently on the left and right by a turn buckle, it is difficult to remotely control this, and it is difficult to adjust the lower seam guide roll at any time during operation. . Furthermore, it is also difficult to hold at a fixed position.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present applicant has strengthened the mechanism for holding the position of the push-up roll at the edge of the molding material, and has also been able to remotely control the amount of push-up of the roll. It has been proposed that the structure is operable (Japanese Patent Laid-Open No. 5-208213). According to this technique, it is possible to form even a large-diameter thin-walled pipe (t / D of 1.6% or less) in which stable pipe production cannot be expected. However, as shown in FIG. 12, the state shown in FIG. When the amount of pushing up to the state shown in the figure is large, the cross-sectional shape becomes an upwardly convex squash-like shape, and by performing ERW welding in this state, the roundness may be reduced as shown in FIG. Yes, further improvement of the technology was desired.

The present invention has been made in view of the above-mentioned problems and the like, and identifies a push-up position effective for eliminating edge waves and a necessary push-up force, and pushes up an edge portion based on this. An object of the present invention is to provide a method for manufacturing an electric resistance welded tube free from a shape defect.

[0006]

In order to achieve such an object, a method for manufacturing an electric resistance welded tube according to the present invention comprises the steps of sequentially forming a strip or a coil into a circular shape in a step of forming a final fin pass roll and a squeeze roll. When the distance between the final fin pass roll and the squeeze roll is set to 100% by the push-up rolls disposed between
% To 43%, wherein the edge portion of the molded material is pushed up by a push-up roll at a push-up rate of 2 to 5 and stretched.

[0007]

In the invention of the method for manufacturing an electric resistance welded pipe according to the present invention, the edge of the formed material is stretched between the final fin pass roll and the squeeze roll so that the edge is formed between the final fin pass roll and the squeeze roll. If the push-up position of the placed push-up roll is too far from the squeeze stand, the edge wave once extended occurs again before entering the squeeze stand,
If the squeeze stand is too close to the squeeze stand, the edge is pressed into the squeeze stand, and a sufficient amount of pushing up cannot be secured. Assuming that the distance between the final fin pass roll and the squeeze roll is 100%, the distance from the upstream side of the squeeze roll is 43%.
By setting the percentage to less than or equal to%, the edge wave once stretched will not be generated again before entering the squeeze stand. Therefore, the upper limit of the push-up position of the push-up roll is set to 43%. When the distance between the final fin pass roll and the squeeze roll is 100%, the distance from the upstream side of the squeeze roll is 28%.
% Or more, the edge portion is not pressed down by the squeeze stand, and a sufficient amount of push-up can be secured. Within this position range, another device for the pipe-making line, for example, a contact tip for high frequency electric resistance welding It is possible to manufacture an ERW pipe of excellent quality without causing any interference with the installation.

Further, the edge wave is lifted up by a push-up roll disposed between the final fin pass roll and the squeeze roll so as to extend the edge of the formed material between the final fin pass roll and the squeeze roll. In the case of erasing, in principle, it should be sufficient to push up the push-up roll by the height of the wave, but in actuality, by pushing up at one place, the peripheral edge also moves upward in parallel as shown in FIG. Pushed up,
Not all of the boosted amounts work effectively for edge cancellation. Unless the height of the generated edge wave is twice or more, that is, the lifting rate is 2 or more, the edge wave canceling effect is not exhibited. By setting the lower limit of the push-up rate to 2 or more, the edge wave becomes 50%
The above is suppressed. On the other hand, if the push-up amount is too large, in addition to the original edge stretching of the ERW pipe due to the difference between the trajectory of the pipe center and the edge, further edge stretching is added and the edge wave height increases. Therefore, the upper limit of the pushing amount is 5 times or less of the generated edge wave height, that is, the pushing rate is 5 times.
The following are appropriate, and a high quality electric resistance welded tube can be manufactured.

[0009]

【Example】

Embodiment 1 FIG. FIG. 1 is a conceptual diagram showing a configuration of a verification example to which an electric resistance welded pipe manufacturing method according to the present invention is applied. In the figure, a molding material P is a distance l from a squeeze roll b as an intermediate portion of a distance L between a fin pass roll a and a squeeze roll b.
Is lifted up by the height H, and tension is applied to the edge of the formed material to extend it. The purpose of the structure of the push-up roll 3 can be achieved, for example, by employing the technique disclosed in Japanese Patent Application Laid-Open No. 5-208213 filed earlier. According to the technique disclosed in Japanese Patent Application Laid-Open No. 5-208213 filed earlier, as shown in FIG. 2, the edge push-up device 1 supports the push-up roll 3 with respect to the device main body 100 by the elevating device 5 so as to be able to move up and down. ing. The edge push-up device 1 is structured to slide on the inner surface with a bottom roll 4 provided at a lower portion. Further, an edge wave meter is installed at a predetermined position m in front of the center of the squeeze roll b. In order to confirm the effects of the initial edge wave height and the edge wave elimination, it is preferable to install a laser displacement meter, an optical cutting device, or the like, and based on the measured edge wave height data, the edge push-up device 1 It is better to perform feedback control.

With the above configuration, the edge of the molding material P
By pushing up from the edge line shown by the dashed line in FIG. 1 to the upper portion shown by the solid line by the push-up roll 3 and applying a tension to the edge portion to suppress the waving while guiding the welded portion, it is favorable in the electric resistance welded portion. It is possible to perform complete electric resistance welding in a state of meeting. As described above, when erasing the edge wave height, in principle, the push-up roll should be pushed up by the wave height, but in practice, by raising it one place, the peripheral edge is also pushed up in parallel However, not all of the pushed-up amount works effectively for edge wave elimination, and the edge wave elimination effect does not appear unless it is pushed up beyond the generated edge wave height. However, if the pushing amount is too large, on the other hand, in addition to the original edge stretch of the ERW pipe due to the difference in the trajectory between the pipe center and the edge, further edge stretch is added and the edge wave height increases. If the push-up roll is installed too far from the squeeze stand, the stretched edge wave will be generated again before entering the squeeze stand, and if it is too close to the squeeze stand, the edge will be And a sufficient amount of pushing up cannot be secured. In an ERW pipe forming line consisting of three steps of breakdown stand, three sections of cage section, three steps of fin pass stand, and one step of squeeze stand, an ERW pipe having an outer diameter of 101.6 mm is formed from a steel plate having a thickness of 1.0 mm x 323 mm width. The effect of the position of the push-up roll was investigated in the case of performing. In this case, t / D is about 1%, which is a tube-making size in which edge waves are easily generated even when the roll gap setting is optimized. The distance between the final fin pass stand and the squeeze stand is 400mm.
It is. The push-up position is 40 mm, 80 mm, 160 mm, 240 mm, 280 mm upstream from the squeeze stand.
The measurement was made at five locations of mm. This is when the distance between the Finpass # 3 stand and the squeeze stand is 100%,
10% and 20% respectively upstream of the squeeze stand
%, 40%, 60%, 70%. The height of the edge wave was measured 20 mm upstream of the squeeze stand.
Non-contact measurement is performed by laser displacement meter at the position. The push-up rate was kept constant at 3.0. Here, the lifting rate means a value obtained by dividing the lifting amount (mm) by the initial wave height (mm). The lifting amount is a rising amount H when the edge line shown by the broken line in FIG. 1 is changed to the position of the solid line edge line, and more specifically, from the position where the lifting roller contacts the bottom of the edge line. Is the amount that was raised. FIG. 4 shows the relationship between the position of the push-up roll and the edge wave height change rate (wave height at the time of push-up (mm) / initial wave height (mm) [wave height at the time of no push-up]). If the effect of the push-up roll is to suppress the edge wave height change rate to 0.5 or less, the position of the push-up roll at which the wave height satisfies this condition is 18% from the squeeze stand to the upstream side.
４６46%. In the above range, there is a low possibility of interference with other devices of the pipe-making line, for example, a contact tip for high-frequency electric resistance welding in all sizes of the pipe to be manufactured, which is advantageous.

Example 2 FIG. 5 shows the results when the position of the push-up roll is fixed at 28% and 43% upstream of the squeeze stand and the amount of push-up is changed under the above-mentioned tube forming conditions. . The pushing ratio on the horizontal axis is a value obtained by dividing the pushing amount (mm) by the initial wave height (mm). When aiming to suppress the edge wave height change rate to 0.5 or less as an effect of the push-up roll, the push-up rate of the push-up roll at which the wave height satisfies this condition is 2 to 5.
It turns out that it is. This tendency does not change significantly even if the position of the push-up roll is slightly changed, and the edge wave height is smaller than when no push-up is performed outside this range, but no great effect is recognized.

Example 3 Under the above pipe making conditions, the position of the push-up roll was fixed at a position of 33% upstream of the squeeze stand, the push-up rate was fixed at 3.0, and the pipe forming size was changed. FIG. 6 shows the results. Specifically, t / D (t: plate thickness of the base plate, D: pipe forming outer diameter) was changed by changing only the plate thickness without changing the outer diameter of the pipe to be formed. The data of the conventional method without using the lifting device is also shown in the figure. It is said that if the edge wave steepness exceeds 0.01 in the actual pipe-making process, the accuracy of the butting will deteriorate, and stable electric resistance welding and laser welding cannot be performed. As shown in FIG. 6, the edge wave steepness exceeds 0.01 when t / D is 1.6 or less in the conventional method, but in the present invention, t / D does not exceed t / D in the present invention.
It can be seen that the edge wave steepness does not exceed 0.01 until D is 0.8. The welding method is not restricted by any method such as high-frequency electric resistance welding, Tig welding and laser welding. Naturally, when high-frequency electric resistance welding is performed, it is necessary to sandwich an insulator between the left and right of the push-up roll 3 so that high-frequency current does not flow through the push-up roll.

[0013]

As described above, according to the present invention, in the step of sequentially forming a strip or a coil into a circular shape, the push-up roll disposed between the final fin pass roll and the squeeze roll allows the final fin pass roll to be formed. When the distance from the squeeze roll is set to 100%, the edge of the formed material is pushed up and stretched by the push-up roll at a push-up rate of 2 to 5 between 28% to 43% on the upstream side of the squeeze roll.
The waving of the edge portion at the time of forming a thin-walled electric resistance welded tube can be appropriately suppressed, and the forming at the time of butt welding can be stabilized. As a result, not only can the production range be expanded in the same production line, but also when the feedback control is performed by continuously monitoring the edge wave height, the push-up amount can be increased even when the material of the material or the pipe size is changed. It is also worth noting that there is no need to reset the settings. For the same reason, it is also useful for early detection of occurrence of irregular molding or unstable molding.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a verification example to which an electric resistance welded pipe manufacturing method according to the present invention is applied.

FIG. 2 is an explanatory cross-sectional view showing a state where a molding material edge portion shown in FIG. 1 is pushed up.

FIG. 3 is an explanatory diagram showing a change caused by pushing up a molding material edge portion.

FIG. 4 is a graph showing a relationship between a pushing-up position of a molding material and a rate of change in edge wave height.

FIG. 5 is a graph showing a relationship between a pushing-up rate of a molding material and a rate of change in edge wave height.

FIG. 6 is a graph showing changes in t / D and the steepness of edge waves at the edge of a formed material.

FIG. 7 is a side view showing a conventional seam guide roll.

FIG. 8 is a front view showing the seam guide roll of FIG. 7;

FIG. 9 is an explanatory view showing edge stretch in the electric resistance welded tube molding.

FIG. 10 is an explanatory view showing a staggered state of a molding material edge portion.

FIG. 11 is an explanatory diagram showing a main part configuration of a conventional seam guide roll.

FIG. 12 is an explanatory diagram showing a relationship between a pushing amount by a seam guide roll and a change in shape of a molding material edge portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Edge push-up apparatus 3 Push-up roll a Fin pass roll b Squeeze roll

Continuation of the front page (56) References JP-A-5-208213 (JP, A) JP-B-61-34908 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21C 37 / 08

Claims (1)

(57) [Claims] In the step of sequentially forming a strip or a coil into a circular shape, the distance between the final fin pass roll and the squeeze roll is set to 100% by a push-up roll disposed between the final fin pass roll and the squeeze roll. When
A method for manufacturing an electric resistance welded pipe, wherein an edge portion of a formed material is pushed up by a push-up roll at a push-up rate of 2 to 5 and stretched between 28% to 43% on an upstream side of a squeeze roll.