JP2000312922A - Method of manufacturing thin-welded tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce roll adjusting time and reduce or control edge waving by setting a roll position and a roll caliber so as to make particular the relations between a formed shape of material tube just before the first-stage fin pass roll and formed shape of the first fin pass roll and between the formed shape of the first-stage fin pass roll and the formed shape of the next-stage fin pass roll. SOLUTION: The relations between the formed shape of the material tube just before the first-stage fin pass roll and the formed shape of the first-stage fin pass roll and between the formed shape of the first-stage fin pass roll and the formed shape of the next-stage fin pass roll are made so as to satisfy formulae I, II, III, and IV. In the formulae, c1 is 1/2 of maximum width in the formed shape of the material tube just before the first-stage fin pass roll, f1 is 1/2 of maximum width in the formed shape of the first-stage fin pass roll, f2 is 1/2 of maximum width in the formed shape of the next-stage fin pass roll, D is outside diameter of the tube, and t is wall thickness. The unit is mm for all.

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 a welded pipe by continuously forming a metal strip into an annular shape, and welding a butt portion of both ends of the pipe through a plurality of fin pass rolls. / D = 5% (t: wall thickness, D: pipe outer diameter) about or less.

[0002]

2. Description of the Related Art As shown in FIG. 1, a manufacturing process of a welded pipe includes a metal roll A, a breakdown roll 1 composed of a horizontal roll, and a cage roll or a vertical roll in which a large number of small-diameter rolls are arranged in the longitudinal and circumferential directions. Cluster role 2 consisting of roles
And formed into a U-shape by a plurality of subsequent fin pass rolls 3 and then sent to a high frequency welding machine 4 or a laser welding machine 5 in the form of an open pipe with an open seam. In the high-frequency welding machine 4, while only the edge portion a of the open pipe is rapidly and intensively heated, a side pressure is applied by the squeeze roll 6 to join to form a welded pipe P.
Alternatively, in order to obtain a higher quality welded portion, the laser welder 5 may be used in combination to melt-weld the edge a of the open pipe.

When a welded pipe is manufactured in the above-described manufacturing process, the trajectory l _1E of the metal band edge portion a is, as shown in FIG. Since the length is longer than l _1c , the edge part a is temporarily elongated, and edge stretching occurs. For this reason, in the fin pass forming process, a longitudinal compressive force acts on the edge portion a due to the imbalance in length between the edge portion a and the central portion. Particularly, in the production of a so-called thin-walled electric resistance welded steel pipe in which the ratio (t / D) of the wall thickness (t) to the outer diameter (D) is small, the edge portion a is easily buckled by this compressive force, so that an edge wave is generated. This causes welding defects such as seam steps and burn-through.

As a measure to eradicate the generation of such edge waves, a method of forming by adjusting the elongation amount of the metal band edge portion a and the central portion from the initial process, for example, a method of forming a roll at the most upstream side of the forming roll group A method of arranging a rolling roll with a variable crown amount to give a larger elongation deformation to the center of the metal band in advance than the edge (Japanese Patent Publication No. 64-4853). A method in which a central portion of a metal strip is rolled and formed by a breakdown roll so that the amount of stretching in the central portion is equal (Japanese Patent Laid-Open No. 4-84).
No. 626) has been attempted.

In Japanese Unexamined Patent Publication No. Sho 60-24220 or Japanese Unexamined Patent Publication No. Sho 60-108118, a u-shaped raw tube is formed by bending a central portion of a metal band only by a forming roll upstream of a fin pass roll. There has been proposed a technique for producing a welded pipe with good welding quality by preventing edge waves by successively extending the side portions of the raw pipe in the width direction using a subsequent fin pass roll.

[0006] However, in Japanese Patent Publication No. 64-4853, a roll having a variable roll crown amount must be arranged at the uppermost stream of a forming roll group, and remodeling of existing equipment requires a large amount of cost. Also, regarding the arrangement of the variable rolling rolls, the capital investment becomes large and the production cost increases. Furthermore, since the appropriate amount of pre-strain varies depending on the tube outer diameter, wall thickness, and material, detailed adjustment is required for all products, and the setting work becomes very complicated. Moreover, (t /
In a thin-walled tube with small D), there is a problem that edge buckling occurs in the initial stage of breakdown due to the introduction of prestrain.

In Japanese Patent Application Laid-Open No. 4-84626, it is necessary to finely adjust the rolling amount and the tension.
A control mechanism that immediately feeds back the roll rotation speed from the upstream to the downstream, the amount of rolling by the breakdown rolls, and the amount of advance of the material by rolling to all rolls while taking into account the thickness tolerance of the material is required, and it is structurally complicated. Is not practical. Moreover, Japanese Patent Publication No. 64-4
As in the case of No. 853, the appropriate amount of rolling differs depending on the tube outer diameter, wall thickness and material, so that a detailed adjustment is required for all products, and there has been a problem that the setting work becomes very complicated.

Further, in Japanese Patent Application Laid-Open No. 60-24220 or Japanese Patent Application Laid-Open No. 60-108118, an edge portion of a metal band is inserted into a fin pass roll without being formed, and the edge is formed by the fin pass roll. There is a problem that the overload of the finpass roll and the edge of the metal band are damaged by the finpass roll.

In order to solve such a problem, the present inventors tolerate the generation of the edge wave during molding to a certain extent, but to eliminate the edge wave once generated, the final fin pass roll 3 and the squeeze roll 6 are formed. A technique has been proposed in which a push-up roll device (not shown) for guiding the open pipe edge portion a while pushing it upward from the inside from the inside is provided (Japanese Patent Laid-Open No. Hei 5 (1994)).
-208213, JP-A-9-1232, etc.). This is because the elongation (excess material) corresponding to the longitudinal edge stretch generated at the edge portion a is continuously pushed upward, thereby correcting the imbalance of the trajectory and giving the tension to the edge portion a, and immediately before welding. This is to stabilize the edge while apparently eliminating the edge wave of the edge a. However, in this method, the effect is reduced with respect to the steep edge wave of the type shown in FIG. 3A, so that a molding method for suppressing and eliminating the edge wave at the time of molding is also required.

[0010]

As shown in FIG. 3, the edge wave includes a type (a) having a sharp peak and a type (b) having a gentle peak. In the case of the (b) type of edge wave generated when the wave height is relatively small, it can be easily suppressed by optimizing the lifting conditions by the lifting roll device, and a welded pipe without welding defects can be manufactured. is there. On the other hand, in the case of the (a) type of edge wave generated when the wave height is large, even if the push-up conditions are optimized, the sharp apex portion is plastically deformed at an acute angle, so that a trace of buckling remains. Poor welding may occur.

For this reason, when the edge wave as shown in the type (a) is generated, even if a push-up roll device is used, the operator can narrow down each fin pass roll based on many years of experience. Roll adjustment actions such as changing the amount and distribution and adjusting the position of cage rolls were performed alone or in combination to reduce edge waves. However, in the production of a thin-walled tube with a small t / D, the roll adjustment range is very narrow, so that a long time is required for the roll adjustment and the material yield is reduced.

The present invention has been made in view of such a situation, and provides a method of manufacturing a thin-walled welded pipe which is suitable for shortening and simplifying a roll adjustment time and for reducing or suppressing edge waves. The purpose is to do.

[0013]

Means for Solving the Problems The inventors of the present invention provide a method of manufacturing a welded pipe by continuously forming a metal strip into a roll, and welding a butt portion of both ends of the base pipe through a plurality of fin pass rolls. Intensive research on the roll adjustment method for suppressing the generation of edge waves, especially focusing on the shape of the shell just before the first-stage fin pass roll, that is, the relationship between the shape of the cage or cluster section 2 and the shape of the fin pass roll 3 Has been repeated. As a result, due to the maximum width change in the tube forming shape immediately before the first stage fin pass roll and the forming shape of the first stage fin pass roll, and by the maximum width change in the forming shape of the first stage fin pass roll and the forming shape of the next stage fin pass roll. It was clarified that the resulting deformation path was greatly involved in the generation of edge waves.

The present invention has been made based on the above findings, and the structure is as follows. (1) The method for manufacturing a thin-walled welded steel pipe according to the present invention is a method for manufacturing a thin-walled welded pipe by continuously forming a metal strip into a roll and welding a butt portion of both ends of the base pipe through a plurality of fin pass rolls. The relationship between the shape of the raw pipe immediately before the first-stage fin pass roll and the shape of the first-stage fin pass roll, and the relationship between the shape of the first-stage fin pass roll and the shape of the next-stage fin pass roll are represented by the following equation (1). ), (2),
The roll position and the roll caliber are set so as to satisfy (3) and (4).

[0015]

(Equation 2)

F ≦ D / 15 (2) C = c1−f1 (3) F = f1−f2 (4) c1: 1/2 of the maximum width in the tube forming shape immediately before the first-stage fin path roll ( mm) f1: 1/2 (mm) of the maximum width in the first-stage fin-pass roll forming shape f2: 1/2 (mm) of the maximum width in the next-stage fin-pass roll forming shape D: Tube outer diameter (mm) t: Meat Thickness (mm) The above equation (1) is an empirical equation (see FIGS. 7 and 8). (2) The method for producing a thin-walled welded steel pipe according to the present invention includes:
In the manufacturing method of the above (1), the forming radius of curvature RE of the raw pipe edge portion immediately before the first-stage fin pass roll is bent and formed within twice the upper roll forming radius of curvature RT of the first-stage fin pass roll.

When C (C = c1−f1) becomes larger than the value calculated on the right side of the equation (1), a large edge wave is generated and a welding defect is induced. When C is smaller than the value calculated on the left side of the equation (1), the front pipe of the first-stage fin path roll is formed into a folded shape instead of an annular shape. The forming load for forming is extremely high, and the roll is greatly worn.
In addition, a corner is formed in the vicinity of the bottom part (near the bottom part) of the raw tube when the sheet is folded in two, and this corner cannot be easily corrected even in the subsequent forming, so that not only the roundness of the product is reduced. In particular, that portion causes deterioration of the material.

If F is larger than the value calculated by the formula (2), the material is strongly aligned with the fin-pass roll even if no edge wave is generated because the width of the tube side portion (side portion) is large. It comes into contact, causing roll eaves and material to bite out.

When the forming radius of curvature RE of the pipe edge immediately before the first-stage fin path roll exceeds twice the upper roll forming radius of curvature RT of the first-stage fin path roll, the base pipe edge portion becomes the caliber of the fin path roll. As shown in FIG. 4 (a), it becomes difficult to conform to the shape, and as shown in FIG. 4 (a), the outer surface side of the raw tube edge portion is pressed against the fin path upper roll, and the inner surface side is pressed against the fin. 4 (b), the outer surface is sagged and the inner surface is crushed.

When the butt shape of the edge portion is as shown in FIG. 4B, there is not much problem in the case of normal high-frequency welding, but when laser welding is performed to obtain a higher quality welded portion. Has a laser spot diameter of 0.7mm
, So that unwelded defects occur particularly on the inner surface side.

From the above, equations (1), (2),
A molded shape that satisfies (3) and (4).
By setting the forming amount of the raw tube edge portion immediately before the fin pass within the range of the present invention, even in the roll forming of a thin-walled tube having a small t / D, the edge wave can be effectively reduced and suppressed by simple roll adjustment. And a welded pipe having excellent welding quality can be manufactured.

Japanese Patent Application Laid-Open (JP-A) Nos. 60-24220 and 60-108118 describe similar molding methods which define the shape of the above-mentioned raw tube. With the forming rolls, only the central part of the metal strip is bent and formed into a u-shape, and the subsequent first-stage fin pass roll suppresses the bending of the side parts of the tube. By overbending the edge part, and each boundary part of the raw pipe side part and the raw pipe bottom part more than the final formed pipe curvature, and applying a rolling reduction in a direction to reduce the raw pipe longitudinal diameter by a subsequent fin pass roll,
The tube side part is successively extended in the width direction, and the lateral diameter is gradually increased. The projecting part is bent to form the tube side, and the tube side and the tube edge are over-bent. The bending process is performed on the boundary portion and each boundary portion between the raw tube side portion and the raw tube bottom portion.
This technique is based on the fact that a base tube is stretched out and bent and bent back using a fin path roll, and a base tube and a fin that have been edge bent by a forming roll before the fin path roll as in the present invention. This is completely different from the technology that defines the maximum width of the pass roll. In particular, the molding shape of the region where the value of F represented by the above formula (4) is positive is described in JP-A-60-24220 and JP-A-60-10811.
No. 8 is completely different.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in detail below along with experimental results obtained. FIG. 5A is a schematic sectional view of the final stage of the cage roll according to the embodiment of the present invention, and FIG. 5B is a schematic sectional view of the final stage in the case of a cluster roll. 5A and 5B, the small roll 2
a roll moving device 2b for allowing a small roll to enter and exit
And a roll position detecting device 2c for detecting the position of the small roll 2a. The roll moving device 2b may be any of a manual screw type, an electric type, and a hydraulic type. Also,
The roll position detector 2c may be either a contact displacement meter or a non-contact laser displacement meter, and is not particularly limited as long as it can accurately detect the position of the small roll 2a. Note that a roll load detecting device (not shown) for detecting a load acting on the small roll 2a may be attached.

FIG. 6 is a schematic view of a shell shape according to the embodiment of the present invention. FIG. 6 (a) is a schematic view of the shape of a raw tube formed by a cage roll or a cluster roll, and FIG.
(B) is a schematic diagram of a tube shape formed by a fin pass roll. As shown in FIGS. 6 (a) and 6 (b), the maximum width in the shape of the raw tube is the width of a portion which is maximum in the width direction.

Usually, the fin pass roll caliber has a forming radius of curvature RT of the upper roll and a forming radius of curvature RB of the lower roll.
Is the maximum width / 2 in the raw tube forming shape of the fin pass roll, and the forming radius of curvature R of the lower roll is
Same as B.

The shape of the raw tube in the cage roll is as follows:
As shown in FIG. 5 (a), the shape is determined by the entrance and exit of the small rolls 2a arranged in the circumferential direction. However, when a plurality of pipe outer diameters are manufactured by the same cage roll device, the side portion is not required. Does not always match the maximum width of the tube. For this reason, it may not be possible to accurately measure the maximum width of the raw tube only by measuring the position of each small roll, and it is desirable to separately measure the vicinity of the maximum width using a laser shape meter or the like.
On the other hand, in the case of a cluster roll, the base tube has a maximum width at the caliber bottom of the roll (where the roll diameter becomes the narrowest). Therefore, the maximum width of the base tube can be easily calculated by measuring the width direction position of the small roll.

[0027]

EXAMPLE 1 FIG. 7 shows a pipe forming process immediately before a fin-pass roll caliber and a first-stage fin-pass roll under the following pipe-forming conditions (dimensions of a welded pipe, material of a welded pipe, configuration of a forming machine). Edge waves generated near the squeeze roll 6 when a welded pipe was manufactured using a model mill with various shapes were measured by a non-contact type edge wave meter having a laser displacement meter, and the results were measured for each molding condition. Classified and arranged.

Pipe making conditions Welded pipe outer diameter (mm) × wall thickness (mm): 101.6 × 1 t / D = 0.98% Material: Cold rolled steel plate (SPCC) Forming machine configuration: breakdown roll 3 steps + Cage roll + 2 steps of fin pass rolls (3 steps in part) + 1 step of squeeze roll However, the measuring position of the edge wave is 65 mm upstream from the center of the squeeze roll (fin pass roll side) and in the circumferential direction. The measurement position is in the vicinity of the edge tip.

In FIG. 7, the results of the edge wave measurement are shown.
mm: △, 2.0-5.0 mm: □, 5.0
Those exceeding are represented by ×. Arrows in FIG. 7 indicate the direction of roll adjustment. The edge wave height is 2.0
When the wave length exceeds mm, the edge wave of the type (a) having a sharp peak is often observed. As is clear from FIG. 7, it is understood that the edge wave can be effectively reduced or suppressed by adopting the maximum width forming shape according to the embodiment of the present invention.

[Example 2] FIG. 8 shows a fin-pass roll caliber and a first-stage fin-pass roll in the same manner as in Example 1 under the following pipe-forming conditions (dimensions of welded pipe, material of welded pipe, configuration of forming machine). The edge wave generated in the vicinity of the squeeze roll 6 when the welded tube was manufactured using a model mill while changing the shape of the tube immediately before was variously measured by a non-contact type edge wave meter having a laser displacement meter. The results are classified and arranged for each molding condition.

Pipe making conditions Welded pipe outer diameter (mm) × wall thickness (mm): 101.6 × 1.6 t / D = 1.57% 101.6 × 2.7 t / D = 2.66% Material: 1.6t Cold rolled steel plate (SPCC) 2.7t Hot rolled steel plate (equivalent to KME340) Forming machine configuration: 3 breakdown rolls + cage roll + 2 fin pass rolls (3 rolls in part) + 1 roll squeeze roll The measurement position of the edge wave is the same as that in the first embodiment.

The sign of the edge wave height in FIG.
In the same manner as above, the white symbols indicate the results at t1.6, and the middle symbols indicate the results at t2.7. As is clear from FIG. 8, it can be seen that the edge wave can be effectively reduced or suppressed by adopting the maximum width forming shape according to the embodiment of the present invention.

[Example 3] Table 1 shows the pipe forming conditions (the dimensions of the welded pipe, the material of the welded pipe, and the configuration of the forming machine) of the following actual machine.
Correlation showing the results of measuring the edge wave generated near the squeeze roll 6 when manufacturing the welded pipe by changing the tube forming shape immediately before the first-stage fin pass roll as the vertical movement of the high-frequency welding machine (contact shoe) 4. FIG. As a measuring method, an insulated extension part was attached to a contact shoe, and the vertical movement of the extension part was measured by a non-contact type edge wave meter having an eddy current displacement meter. In addition, in order to change the forming shape of the fin path in various ways as in the first embodiment, it is necessary to arrange the fin path rolls having different roll calipers on the actual machine, which is very costly. The change of edge wave was measured by changing the shape of the tube immediately before.

[0034]

[Table 1]

Pipe making conditions Welded pipe outer diameter (mm) × wall thickness (mm): 609.6 × 6.20 t / D = 1.02% 609.6 × 9.09 t / D = 1.49% Material: 6.20t hot-rolled steel plate (STK400) 9.09t hot-rolled steel plate (STPG370) Forming machine configuration: breakdown roll 3 + cage roll + fin pass roll 3 + squeeze roll 1 Is the case where the measurement position in the circumferential direction is 150 mm upstream from the squeeze roll center just above the center of the squeeze roll, and the measurement position in the circumferential direction is the position where the contact shoe comes into contact with the open pipe, that is, substantially near the edge portion.

As is evident from Table 1, even in the production of a large-diameter welded pipe, it is understood that the edge wave can be effectively reduced or suppressed by adopting the maximum width forming shape according to the embodiment of the present invention.

[Embodiment 4] Table 2 shows the pipe forming conditions (the dimensions of the welded pipe, the material of the welded pipe, and the configuration of the forming machine) of the following actual machine.
A non-contact type edge wave meter having a laser displacement meter was used to measure the edge wave generated near the squeeze roll 6 when a welded pipe was manufactured by changing the shape of the raw tube immediately before the first stage fin pass roll. FIG. In this case, too, as in the second embodiment, it takes a great deal of money to obtain various types of fin path rolls. Therefore, the shape of the shell immediately before the first-stage fin path roll is changed variously by adjusting the cluster roll to change the edge wave. Was measured.

[0038]

[Table 2]

Pipe making conditions Welded pipe outer diameter (mm) × wall thickness (mm): 114.3 × 1.2 t / D = 1.05% 114.3 × 4.5 t / D = 3.94% Material: 1.2t Hot rolled steel sheet (equivalent to KME340) 4.5t SUS304 Forming machine configuration: 5 breakdown rolls + 2 cluster rolls + 4 fin pass rolls + 1 squeeze roll

However, the measurement position of the edge wave is 100 mm upstream from the center of the squeeze roll (the side of the fin pass roll), and the measurement position in the circumferential direction is near the tip of the edge portion.

As is apparent from Table 2, even when the configuration of the molding machine is different, the edge wave can be effectively reduced or suppressed by forming the molding shape having the maximum width according to the embodiment of the present invention.

[0042]

As described above, according to the present invention, in the roll forming of a thin-walled welded pipe having a small t / D in which edge waves are likely to be generated, the shape of the base tube immediately before the first-stage fin pass roll and the shape of the first-stage fin pass roll are reduced. The relationship between the forming shape and the relationship between the forming shape of the first-stage fin-pass roll and the forming shape of the next-stage fin-pass roll were adjusted so as to satisfy a predetermined condition. Simplification is possible, and reduction or suppression of the edge wave is effectively performed. As a result, it is possible to improve welding quality, productivity, and reduce manufacturing costs.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a production line for a welded pipe.

FIG. 2 is an explanatory diagram showing edge stretching in roll forming.

FIG. 3 is an explanatory diagram showing types of edge waves generated in an open pipe when manufacturing a welded pipe.

FIG. 4A is a schematic diagram showing a state of insertion of the edge into the fin path roll when the amount of molding of the shell edge is insufficient, and FIG. It is a schematic diagram which shows the edge part butting part when it is insufficient.

FIG. 5A is a schematic diagram illustrating a configuration of a cage roll according to an embodiment of the present invention, and FIG. 5B is a schematic diagram illustrating a configuration of a cluster roll according to an embodiment of the present invention.

FIG. 6 (a) is a schematic view of a shell shape formed by a cage roll or a cluster roll according to the embodiment of the present invention,
(B) is a schematic diagram of the shape of the raw tube formed by the fin pass roll according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a correlation between a tube forming shape and a edge wave height.

FIG. 8 is an explanatory diagram showing a correlation between a tube forming shape and a edge wave height.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Breakdown roll group 2 Cage roll or cluster roll group 2a Cage roll or cluster roll 2b Cage roll or cluster roll roll moving device 2c Cage roll or cluster roll roll position detection device 3 Fin pass roll group 4 High frequency welding machine (contact Shoe) 5 Laser welding machine 6 Squeeze roll A Metal band a Edge part P Welded pipe RE Forming radius of curvature of raw tube edge just before first-stage fin path roll RT Upper roll forming radius of fin path roll RB Lower roll of fin path roll Forming radius of curvature c1 1/2 (mm) of the maximum width in the raw tube forming shape immediately before the first stage fin pass roll f1 1/2 (mm) of the maximum width in the first stage fin pass roll forming shape f2 In the second stage fin pass roll forming shape 1/2 of the maximum width (mm)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Ariizumi, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Akio Sato, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo F-term (reference) in Nippon Kokan Co., Ltd. 4E028 CA02 CA08 CA13 4E063 AA01 BB06 EA12 EA20 JA04

Claims (2)

[Claims] 1. A method for manufacturing a thin-walled welded pipe by continuously forming a metal strip in a roll and welding a butt portion of both ends of the pipe through a plurality of fin pass rolls, wherein the raw pipe is formed immediately before a first-stage fin pass roll. The relationship between the shape and the formed shape of the first-stage fin pass roll, and the relationship between the formed shape of the first-stage fin pass roll and the formed shape of the next-stage fin pass roll are expressed by the following equations (1), (2), (3) and (4) A method for producing a thin-walled welded pipe, wherein a roll position and a roll caliber are set so as to satisfy (4). (Equation 1) F ≦ D / 15 (2) C = c1−f1 (3) F = f1−f2 (4) c1: 1/2 (mm) f1 of the maximum width in the shell shape just before the first-stage fin path roll : 1/2 (mm) of the maximum width in the first-stage fin-pass roll forming shape f2: 1/2 (mm) of the maximum width in the next-stage fin-pass roll forming shape D: Tube outer diameter (mm) t: Wall thickness (mm) ) 2. The method according to claim 1, wherein a forming radius of curvature RE of the pipe edge portion immediately before the first-stage fin pass roll is bent within 2 · RT with respect to an upper roll forming radius of curvature RT of the first-stage fin pass roll. The method for producing a thin-walled welded pipe according to claim 1.