JPH0910829A - Manufacture of welded pipe - Google Patents

Abstract

PURPOSE: To provide manufacture of a welded pipe whereby thin walled pipe, especially extremely thin walled pipe is able to be manufactured. CONSTITUTION: At least two means 11, 13 for restraining the welded pipe after butt welding are provided at downstream from a squeeze roll 6 and only pass line height Hg of the means for restraining the pipe at upstream is provided lower than pass line height Hf of the reference pass line height, that is, an end fin pass roll 5B. On the one hand, the squeeze roll 6 is arranged at the position wherein distance J from the end fin pass roll satisfies a certain condition and the pass line height Hs and an inclined angle θ are adjusted and set so as to run along a shape of metal strip H settled by the two means for restraining the pipe and the end fin pass roll 5B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a welded pipe, and in particular, an extremely thin welded pipe having a wall thickness outer diameter ratio (t / D) of 1% or less is manufactured by using a high frequency heating means. The present invention relates to a suitable manufacturing method.

[0002]

2. Description of the Related Art FIG. 10 is a diagram showing a general prior art example for manufacturing a welded pipe from a metal band by a roll forming method using a high frequency heating means.

In FIG. 1, H is a metal strip H, which is rewound by an uncoiler and a leveler (not shown), straightened, and continuously fed to the roll forming machine 1.

The roll forming machine 1 includes a guide roll 2 consisting of a pair of left and right vertical rolls, a breakdown roll 3, 3 consisting of a pair of upper and lower horizontal rolls, and a side cluster roll 4, 4 consisting of a pair of left and right vertical rolls. ... and fin pass rolls 5, 5, 5B consisting of a pair of upper and lower horizontal rolls
The metal strip H is sequentially bent in the width direction and is formed into an open pipe shape having a circular cross section with both edge portions facing each other. After that, as shown in FIG. 11, the metal strip H formed into an open pipe shape is heated by the induction heating coil 10 of the high-frequency heating means until both edge portions 7, 7 are melted, and then a pair of left and right vertical rolls. Lateral pressure is applied by the squeeze rolls 6, 6
Abutting welding is performed while discharging molten metal from between the end faces of 7 as much as possible (hereinafter, this is referred to as a high frequency welding method).

Further, when performing complex heat source welding using high frequency heating means, high frequency heating means 12 (see FIG. 10)
After preheating both edge portions 7, 7 to a predetermined temperature by
TIG and MI provided near and above the squeeze roll 6
Both edges 7, 7 are melted by using an appropriate melting welding means (not shown) such as G or laser, and side pressure is applied by the squeeze roll 6 to perform butt welding (hereinafter, this is combined with high frequency preheating and melting. Welding method).

In any of the above welding methods, both edge portions 7 of the metal strip H are formed during the forming process by the roll forming machine 1.
In the vicinity of 7, a tensile force larger than that of the other portion 8 acts, and it is elongated and deformed in the longitudinal direction. That is, the breakdown rolls 3, 3, ... And the side cluster rolls 4,
In Nos. 4, ..., Tensile stress is generated in the vicinity of both edge portions 7, 7 and stretches in the longitudinal direction, and compressive stress is generated in the other portion 8 and contracts in the longitudinal direction. Further, in the fin-pass rolls 5, 5, 5B, since a pair of upper and lower rolls act so that the longitudinal elongation of the metal strip H becomes constant in the width direction, compressive stress is applied in the vicinity of both edge portions 7, 7. Occurs,
The amount of elongation in the longitudinal direction becomes smaller than the average amount of elongation and contracts in the longitudinal direction, and tensile stress occurs in the other portion 8,
The elongation in the longitudinal direction becomes larger than the average elongation and the film is stretched in the longitudinal direction.

Due to repeated stretching and contraction of both edge portions during this forming process, the buckling strength of the material is small, for example, a thin-walled tube having a wall thickness / outer diameter ratio (t / D) of more than 1% and 2% or less. In the case of molding, both edge portions buckle during the molding process, so-called edge waves are generated.

As a method for preventing the generation of the edge wave, a downhill forming method for adjusting the forming height or a plurality of rolls arranged at a short pitch in the longitudinal direction in order to increase the buckling strength of both edge portions. There is a cage forming method in which both edge portions are pressed and restrained. Further, there is a method (Japanese Patent Publication No. 61-61914) in which the difference in strain between the two edge portions and the other portion generated in the molding process is locally heated or cooled after the local heating to adjust the difference in thermal strain. Furthermore, there is also a method in which the above-mentioned methods are combined to eliminate the difference in strain between the two edge portions of the metal strip and the other portions to prevent the generation of edge waves.

[0009]

When a welded pipe is manufactured by the above-mentioned high-frequency welding method or a simple fusion welding method using only appropriate fusion welding means such as TIG, MIG or laser, the above t / D exceeds 1%, When a thin-walled tube having a thickness of 2% or less is targeted, it is possible to sufficiently prevent the generation of edge waves by each of the conventional methods described above.

However, when an extremely thin thin-walled tube having a t / D of 1% or less is to be produced by the high-frequency welding method or the high-frequency preheating combined melting welding method, even if the conventional welding methods described above are used, Although no edge wave was generated on the exit side of the fin-pass roll, there was a problem that an edge wave was generated immediately before the squeeze roll, resulting in frequent welding defects. This is for the following reason.

FIG. 12 shows an induction method as an example of the flow of the high frequency current when a high frequency current is passed through the metal band H in order to melt or preheat both edges 7, 7 of the metal band H. FIG. 1A is a schematic view, and FIG. 1A is a plan view, and FIG. 1B is a side view.

FIG. 13 is a schematic view showing a deformation mode of the metal strip H which occurs in correspondence with the flow of the high frequency current.
FIG. 1A is a plan view, and FIG. 1B is a side view.

As is apparent from FIG. 12, the high-frequency current indicated by the arrow in the drawing, which is generated by the magnetism given by the induction heating coil 10, is a circle of the metal strip H formed in the shape of an open pipe near the induction heating coil 10. It flows in the circumferential direction and concentrates on both edge portions 7, 7. Corresponding to this current distribution, both edge parts 7, 7 are heated to a high temperature, but the other part 8 is hardly heated, so that a significant temperature difference occurs between the both edge parts 7, 7 and the other part 8, The thermal strain of both edge portions 7, 7 becomes large.

Therefore, as shown in FIG. 13, both edge portions 7, 7 are in a direction indicated by an arrow in the figure with respect to the bottom portion 9 which is 180 ° in the circumferential direction with respect to this, that is, the metal strip H.
Greatly extends in the longitudinal direction. As a result, for example, FIG.
As shown in (a), the edges 7 and 7 undergo a mouth-opening deformation in which the gap between them is wide, and as shown in FIG. 14 (b), both edges 7 and 7 cause a warp deformation in which they are curved upward.

In each of the above deformations, the metal strip H is constrained by the squeeze roll 6 and the final fin pass roll 5B (see FIG. 10) in front of and behind the deformed portion, so that the metal strip H cannot be deformed more than a certain amount. A portion to which compressive stress is applied is generated on both edge portions 7, 7, and this portion locally buckles and deforms to generate an edge wave. The above phenomenon is the same when the resistance type high frequency heating means is used.

Therefore, even when an ultra-thin wall tube having a t / D of 1% or less is produced by the above-mentioned high frequency welding method or high frequency preheating fusion welding method, an edge wave is not generated. Development was desired.

The object of the present invention has been made in view of the above situation, and a high-frequency heating means capable of producing an extremely thin tube having a t / D of 1% or less without generating an edge wave. An object of the present invention is to provide a method for manufacturing a welded pipe by the high-frequency welding method or the high-frequency preheating combined melting welding method used.

[0018]

Means for Solving the Problems The inventors have conducted various studies on the phenomenon of generation of the above-mentioned edge wave and a means for preventing it, and have found the following (1) to (3).

(1) Edge waves generated when an ultra-thin wall tube having a t / D of 1% or less is produced by a high-frequency welding method using a high-frequency heating means or a high-frequency preheating combined melting welding method. The high-frequency current that flows in the metal band for high-frequency melting heating or high-frequency preheating mainly heats both edges, not due to the strain difference that occurs due to the difference in the amount of molding between both edges of the band and other parts. Therefore, a difference in thermal strain is generated between the two edge portions and the other portion, and as a result, both edge portions are stretched in the longitudinal direction of the metal strip to generate edge waves. However, by controlling the shape of the open pipe-shaped metal strip on the entrance side of the squeeze roll so as to draw an upward convex arc, it is possible to prevent edge waves from occurring at both edge portions.

(2) In this case, it is useless to set the pass line height of the squeeze roll above the pass line height of the final fin pass roll, which is the reference pass line height.
On the downstream side of the squeeze roll, the height of the pass line is set lower than the height of the pass line of the final fin pass roll. What you need to do.

(3) In the metal strip formed into the open pipe shape before the abutting welding by the squeeze roll, both edge portions are not deformed and restrained by the rolls.
Since it is relatively freely deformable, when a compressive force acts on both edge portions, it is deformed with a small force, and edge waves are extremely easily generated. However, since the metal strips after abutting welding are welded to each other at their edge portions and are constrained in shape in the circumferential direction, it is difficult for both edge portions to deform. Even if a force equivalent to the level at which the edge wave is generated is generated, the edge wave does not occur, and by providing the pipe restraining means on the downstream side of the squeeze roll, both edges of the metal strip after abutting welding are provided. There should be no problem even if the compressive force comes into play.

The present invention was made on the basis of the above findings, and its gist resides in the following method for manufacturing a welded pipe.

The metal strip is passed through a roll forming machine to be formed into an open pipe shape, and the opposite edge portions are melted and heated by a high frequency heating means and then butt-welded by a squeeze roll, or preheated by a high frequency heating means. Then, in the welding method of the welded pipe, which is then subjected to abutting welding with a squeeze roll after being melt-heated using a melt welding means, at least a pipe restraining means for restraining the welded pipe after the abutting welding to the downstream side of the squeeze roll. Two of them are provided, and the pass line height of the upstream pipe restraining means of these pipe restraining means is set lower than the pass line height of the final fin pass roll of the roll forming machine, while the squeeze roll is of the following formula. A metal which is placed at a position satisfying the above conditions and whose pass line height and inclination angle are determined by the two pipe restraining means and the final fin pass roll. Method for producing a welded pipe, characterized by adjusting set along the orientation of the strip.

L (G + L) / (G + 3L) ≧ J where J: distance between final fin pass roll and squeeze roll (mm) L: distance between final fin pass roll and upstream pipe restraining means (mm) G: Distance between upstream pipe restraining means and downstream pipe restraining means (mm)

[0025]

As shown in FIG. 1, the edge buckling, that is, the edge wave, which is generated due to the amount of thermal strain generated when the both edge portions are heated by the above-mentioned high frequency heating means, enters the squeeze roll 6 as shown in FIG. It is possible to prevent the posture of the metal strip H formed in the shape of an open pipe on the side by controlling the posture so as to draw an upward convex arc.

The basic principle is as follows.

As shown in FIG. 1, when the side view of the metal strip H on the entrance side of the squeeze roll 6 is in the shape of an upward convex arc, the squeeze roll 6 and a final fin pass (not shown). Both edge parts 7, between the area with the roll,
Since the shape of 7 is extended from that of the bottom portion 9, tensile stress acts on both edge portions 7 in the direction indicated by the solid arrow. As a result, the compressive stress acting on both edge portions 7, 7 due to the thermal strain due to local heating of both edge portions 7, 7 in the high frequency heating means 10 is canceled by the tensile stress, Both edge parts 7, 7
Since the compressive stress does not act on the edge, the edge wave does not occur.

Here, the simplest and simplest method for controlling the attitude of the metal strip H on the entrance side of the squeeze roll 6 so as to draw an upward convex arc is the final fin pass of the roll forming machine 1. This is a method in which the pass line height of the roll 5B is set higher than the reference pass line height, or the pass line height of the squeeze roll 6 is set lower or higher than the reference pass line height. However, the former method involves deformation in which compressive stress acts on both edge portions 7 on the exit side of the fin pass roll 5 in the immediately preceding stage of the final fin pass roll 5B, so edge waves are generated at this portion. It cannot be adopted because it will be lost. Further, the latter method cannot be adopted for the following reason.

In this type of pipe mill, usually, as shown in FIG. 2, a bead cutting device for removing an outer bead formed by arranging a plurality of support rollers 13 'and a cutting tool 14 facing each other is a squeeze roll. 6 is provided on the downstream side. This bead cutting device has a plurality of support rollers 13 'and a cutting tool 1.
4 are arranged so as to face each other and have a function of restraining the rotation of the metal strip H in the longitudinal direction, so that they can be treated as fixed support points.

Further, in the final fin pass roll 5B, the cross-sectional shape of the metal strip H in this portion is usually formed into a desired final tube shape, and substantially the entire circumference thereof is formed into a hole shape of the final fin pass roll 5B. Since it has a function of restraining the rotation of the metal strip H in the longitudinal direction, it can also be regarded as a fixed support point.

Therefore, the metal strip H before and after the squeeze roll 6
Can be regarded as a horizontal elastic beam, one end of which is fixed by the final fin pass roll 5B and the other end of which is fixed or simply supported by the first pipe restraining means 13 including a bead cutting device. When the load W application point is at the squeeze roll 6 position, the relationship between each support point and load point and the bending moment generated in the metal strip is as follows.

FIG. 5 shows a metal strip H before and after the squeeze roll 6.
Is a diagram showing a relationship between each supporting point and a load point and the generated bending moment M when the elastic beam is regarded as a horizontal elastic beam. FIG. 7A shows each supporting point of the metal strip H and a load W applying point. Regarding the positional relationship, in the same figure (b), the point of load W is set to the squeeze roll 6 position and the generated bending moment when the pass line height is set above the reference pass line height is shown in the same figure (c). ) Is a bending moment diagram when the applied point of the load W is at the squeeze roll 6 position and the pass line height is set lower than the reference pass line height. And the relationship between the positive and negative of the generated bending moment are shown respectively.

The first pipe restraining means 13 is shown in FIG.
As shown in (a), instead of the bead cutting means, one having a pair of upper and lower hole type rolls may be provided.

As can be seen from FIG. 5B, when the pass line height of the squeeze roll 6 is set higher than the reference pass line height, the bending moment M generated in the vicinity of the entrance side of the squeeze roll 6 becomes a positive value. Thus, the metal strip H has a shape in which an upward convex arc is drawn.

However, in the vicinity of the exit side of the final fin pass roll 5B, the generated bending moment M becomes a negative value and the metal strip H
Becomes a shape that forms a downward convex arc, and compressive stress acts on both edge portions of this portion, and an edge wave is generated.

Further, as can be seen from FIG. 5C, when the pass line height of the squeeze roll 6 is set lower than the reference pass line height, the final fin pass roll 5B of the final fin pass roll 5B is reversed, contrary to the above. Although the bending moment M generated in the vicinity of the outlet side has a positive value, the bending moment M generated in the vicinity of the inlet side of the squeeze roll 6 becomes a negative value, and the metal strip H in this portion has a downward convex arc shape. Therefore, compressive stress acts on both edge portions of this portion, and an edge wave is generated.

From the above, it can be seen that even if the height of the pass line of the squeeze roll 6 is adjusted, the generation of edge waves cannot be prevented.

However, as shown in FIG. 3, the distance between the center of the final fin pass roll 5B between the first pipe restraining means 13 and the squeeze roll 6 is L, and the first pipe restraining means is L. The second tube restraint means 11 is arranged at a position where the distance from the center of the roller 13 is G, and the pass line height Hf of the final fin pass roll 5B and the first tube restraint means 13 are arranged.
The pass line height Hg of the second pipe restraining means 11 is set so that the squeeze roll 6 does not serve as a load applying point and a fixed fulcrum.
Final fin pass roll 5 where g is the reference pass line height
When the load W is applied by setting it below the pass line height Hf of B, the relationship between each supporting point and the applying point of the load W and the generated bending moment M is as shown in FIG.

As shown in FIG. 6 (b), refer to the formula of curved beams with both ends fixed (for example, Sanseido Co., Ltd., 5th edition of the mechanical engineering indispensable new edition, issued February 1, 1949, page 176). ) Final fin roll 5B as required from
From the final fin pass roll 5B is "L
The generated bending moment M up to the position of (G + L) / (G + 3L) ”has a positive value.

Therefore, this final fin pass roll 5B
And the metal band H between the regions up to the above “L (G + L) / (G + 3L)” position has an upward convex arc shape, and both edge portions 7, 7 are extended, The compressive stress does not act on the edge portions 7, 7. On the other hand, in the region from the position of “L (G + L) / (G + 3L)” to the second pipe restraining means 11, the generated bending moment M is generated.
Becomes a negative value, and the metal strip H has a shape in which a downward convex arc is drawn, and a compressive stress acts on both edge portions 7, 7.

On the other hand, the pass line height Hg of the second pipe restraining means 11 is set above the pass line height Hf of the final fin pass roll 5B, which is the reference pass line height, and the load W is set. When applied, as shown in FIG. 6 (c), the bending moment M generated on the exit side of the final fin pass roll 5B becomes a negative value, and the metal strip H becomes a downward convex arc. Compressive stress acts on both edge portions 7, 7.

Therefore, the bending moment M generated on the exit side of the final fin pass roll 5B becomes a positive value, and the metal strip H has a shape which forms an upward convex arc, and a compressive stress acts on both edge portions 7, 7. To prevent this, the second pipe restraining means 1
It can be seen that it is necessary to set the pass line height Hg of 1 below the reference pass line height Hf.

Further, as described above, since the edge portion 7 of the metal strip H before the butt welding is not restrained at all, it deforms relatively freely, and easily deforms even when a small compressive stress acts. Edge waves are generated, but both edge parts 7, 7 after butt welding
Is welded and shape-constrained in the circumferential direction of the pipe, and thus is unlikely to be deformed, and edge waves are less likely to be generated even if a compressive stress equivalent to the level at which edge waves are generated in the metal band H before the abutting welding is applied.

From this fact, the second pipe restraining means 11 is provided.
The height Hg of the pass line is set lower than the reference pass line Hf, and the distance J (see FIG. 4) from the final fin pass roll 5B is set to "L (G + L) / (G
+ 3L) ”= Q, if the squeeze roll 6 is arranged at a position satisfying Q ≧ J so as not to be the load applying point or the fixed fulcrum of the elastic beam, before the abutting welding on the entry side of the squeeze roll 6. Since a compressive stress does not act on both edge portions 7 and 7 to generate an edge wave, normal welding can be performed. Further, even if a compressive stress is applied to the edge portion 7 on the downstream side of the squeeze roll 6, it is difficult to deform due to abutting welding. It will be extremely minor.

In the above, the reason why the squeeze roll 6 is arranged so as not to be the load applying point and the fixed fulcrum of the elastic beam is as follows. That is, the second pipe restraining means 1
When the attitude of the metal strip H is controlled in a shape that draws an upward convex arc by setting the pass line height Hg of 1 below the reference pass line height Hf, the pass line height Hs of the squeeze roll 6 is controlled. Unless the tilt angle θ (see FIG. 4 to be described later) is adjusted, the squeeze roll 6 constrains the metal strip H almost all around in the circumferential direction. Therefore, the fulcrum of the elastic beam (the load application fulcrum or / and Fixed fulcrum), a bending moment is generated in this portion, and both edge portions 7, 7 of the metal strip H between the final fin pass roll 5B and the squeeze roll 6 are formed.
The compressive stress acts on a part of the.

FIG. 7 shows that when the squeeze roll 6 is arranged at a position where the distance J from the final fin pass roll 5B is "L / 4", the height Hs of the pass line is changed and the load of the elastic beam is changed. It is a figure which shows the relationship between each support point and a load point, and a bending moment which generate | occur | produce when it is made to act as a provision fulcrum.

As shown in FIG. 7B, the pass run height Hs of the squeeze roll 6 is controlled to the upward convex shape at the squeeze roll 6 position. (See FIG. 4) and acts as a point to which the upward load W is applied, a bending moment M '(shown only on the upstream side of the squeeze roll 6) shown by the alternate long and short dash line in the drawing is generated, The bending moment M shown by the solid line in the figure when the second pipe restraining means 11 is set downward becomes the bending moment M ″ shown by the dotted line in the figure, and the bending moment M ″ on the exit side of the final fin pass roll 5B. Becomes a negative value.

Further, as shown in FIG. 7C, the pass-run height Hs of the squeeze roll 6 is determined from the open pipe axis PC of the metal body H whose posture is controlled in the upward convex shape at the position of the squeeze roll 6. Is also set downward and is acted as a point of application of the downward load W, a bending moment M ′ (only shown upstream of the squeeze roll 6) is generated in the figure, and the second pipe restraining means is generated. The bending moment M shown by the solid line in the drawing when 11 is set downward becomes the bending moment M ″ shown by the dotted line in the drawing, and the bending moment M ″ on the entry side of the squeeze roll 6 has a negative value.

As a result, the metal strip H on the entry side of the squeeze roll 6 forms a downward convex arc, and the edge portion 7 before the butt welding is performed.
A compressive stress acts on the edge to generate an edge wave, which prevents normal welding.

Further, as described above, since the squeeze roll 6 restrains the metal pair H almost all around in the circumferential direction, it serves as a fixed end fulcrum of the curved beam. Therefore, if the inclination angle θ (see FIG. 4 described later) is different from the inclination angle along the upward convex shape of the metal strip H determined by the second pipe restraining means 11 and the final fin pass roll 5B, A new bending moment is generated with this as a fixed fulcrum.

FIG. 8 shows the separation distance J as in the case of FIG.
Squeeze roll 6 is arranged at a position of "L / 4" and the pass line height Hs thereof is matched with the open pipe axis PC of the upwardly convex metal body H. FIG. 7 is a diagram showing a relationship between each supporting point and a load point and a generated bending moment when the inclination angle θ of is changed to act as a fixed fulcrum of the elastic beam.

As shown in FIG. 8B, the pass line height Hg of the second pipe restraining means 11 is set to the reference pass line height Hf.
If the tilt angle θ of the squeeze roll 6 is set smaller than the tilt angle of the metal body H whose posture is controlled to be upwardly convex by setting the tilt angle θ downward, a negative bending moment is generated in the squeeze roll 6. The bending moment M shown by the solid line in the figure when the pipe restraining means 11 of No. 2 is set downward becomes the bending moment M'shown only by the dotted line in the figure (only shown on the upstream side of the squeeze roll 6). Bending moment M ′ on the entry side of 6 becomes a negative value.

Further, as shown in FIG. 8C, when the inclination angle θ of the squeeze roll 6 is set to be larger than the inclination angle of the metal body H whose attitude is controlled to have an upward convex shape in the same manner as above. Since a positive bending moment is generated in the squeeze roll 6, the bending moment M shown by the solid line in the figure when the second pipe restraining means 11 is set downward is the bending moment M '(squeeze line) shown by the dotted line in the figure. Only the upstream side of the roll 6 is shown), which is preferable from the viewpoint of preventing edge wave generation. However, in this case, squeeze roll 6
The metal body H is rapidly deformed in the vicinity of the entrance side of the metal body H, and the metal body H is rubbed by the lower flange 6a of the squeeze roll 6 (see FIG. 4, which will be described later) to cause roll flaws.

As a result, in both cases shown in FIGS. 7 and 8, the metal strip H on the entrance side of the squeeze roll 6 forms a downward convex arc, and a compressive stress acts on the edge portion 7 before butt welding. However, edge waves occur and normal welding cannot be performed, or roll flaws occur.

Therefore, the squeeze roll 6 is inclined along its pass line height Hs so as to follow the upward convex shape of the metal strip H determined by the second pipe restraining means 11 and the final fin pass roll 5B. It is necessary to adjust the angle θ so that the elastic beam, that is, the load applying fulcrum and the fixed fulcrum of the metal body H are not provided.

FIG. 4 is a schematic diagram showing an adjusting mode for preventing the squeeze roll 6 from becoming a load applying point or a fixed fulcrum of the elastic beam. Depending on the shape, the pass line height Hs of the squeeze roll 6 is different from the reference pass line Hf, in other words, the open pipe axis center of the metal strip H formed in the open pipe shape at the position of the squeeze roll 6. The tilt angle θ is set so as to match the PC and the tilt of the metal strip H is matched. This makes it possible to prevent the squeeze roll 6 from becoming a load applying point or a fixed fulcrum of the elastic beam.

The positions where edge waves are likely to occur between the exit side of the final fin pass roll 5B and the entrance side of the squeeze roll 6 are the preheating temperature of both edge portions, welding conditions (welding speed, upset amount, etc.). However, in this case, the position of the squeeze roll 6 in the mill line direction may be finely adjusted and the height Hs of the pass line may be adjusted.
And the tilt angle θ should be finely adjusted at the same time.

Further, the setting position of the squeeze roll 6 in the mill line direction is determined by setting the second fin restraint means 11 on the basis of the final fin pass roll 5B and / or the first fin restraint means 13 (a bead cutting device may be used). After installing in the appropriate position,
There is no problem in determining by either the experiment or the curved beam calculation method. When applied to an existing pipe mill, the second fin restraint roll 5B, the squeeze roll 6, and the first pipe restraining means 13 (a bead cutting device is also possible) are used as the second pipe restraint with reference to the mutual separation distance. Means 11
The arrangement position may be determined by the same method as described above.
However, since it takes a lot of time to determine the position by the experiment, it is preferable to determine the position by bending beam calculation and then adjust the experiment to determine the final arrangement position.

Further, since the second pipe restraining means 11 constituting the above-mentioned simple supporting point can achieve its purpose by simply pressing the metal strip H from above, only the upper roll having the hole shape is formed. May be included.
Further, the hole type may be formed into a hole type having a curvature that is the same as or slightly larger than the pipe outer diameter of the maximum outer diameter to be shared so as to be shared by various pipe outer diameters. Further, instead of the upper roll, a concave surface having a curvature R is formed in the lower surface longitudinal direction so as to follow the curvature R (see FIG. 1) of the metal strip H whose posture is controlled so as to draw an arc in an upward convex shape. A block body having an appropriate shape may be used.

[0060]

The method of the present invention will be described in detail below with reference to its examples.

FIG. 9 is a schematic diagram showing the entire apparatus configuration for carrying out the present invention. In the figure, 1 is a roll forming machine, 6 is a squeeze roll, 11 is a second tube restraining means, 1
Reference numeral 3 is a first tube restraining means, 12 is an induction type high frequency heating means including the induction heating coil 10, and H is a metal body.

The roll forming machine 1 is similar to the conventional apparatus, and includes a guide roll 2 and a plurality of breakdown rolls 3, 3.
, Side cluster rolls 4, 4, ..., Fin pass rolls 5 and 5 and final fin pass roll 5B. The height of the pass line is determined by the final fin pass roll 5B.
Are arranged so as to match the height Hf of the pass line (see FIG. 3).

On the downstream side of the final fin pass roll 5B constituting the roll forming machine 1, as shown in FIG. 3 described above, a second pipe restraining means is provided with a separation distance L therebetween.
Further, on the downstream side of the second pipe restraining means 13, a first pipe restraining means is provided with a separation distance G. Also,
The squeeze roll 6 is provided between the final fin pass roll 5B and the second tube restraining means 13 at a position where the distance J from the final fin pass roll 5B is equal to or less than “L (G + L) / (G + 3L)”. ing.

The pass line height Hk of the first pipe restraining means 11 is made to coincide with the pass line height Hf of the final fin pass roll 5B, which is the reference pass line height, while the pass line height Hk of the second pipe restraining means 11 is adjusted. The pass line height Hg is set lower than the reference pass line height Hf.

The squeeze roll 6 is the same as that shown in FIG.
As shown in FIG. 7, the metal pipe H is formed in the shape of an open pipe whose posture is controlled to draw an upward convex arc defined by setting the pass line height Hg of the second pipe restraining means 11 low. As described above, the pass line height Hs is matched with the open pipe axis PC of the attitude-controlled metal body H, and the inclination angle θ is set.

The metal body H is continuously formed into an open pipe shape by the roll forming machine 1, the squeeze roll 6, the second pipe restraining means 13 and the first pipe restraining means 11 set as described above, and Both edge portions 7, 7 are heated to a melting temperature by using a high frequency heating means 12 and post-butt welded, or after being preheated to a predetermined temperature, TIG, M (not shown).
In the case of fusion butt welding by fusion welding means such as IG or laser, the attitude of the metal body H is controlled between the final fin-pass roll 5B and the squeeze roll 6 so as to draw an upward convex arc. .

As a result, the compressive stress does not act on the both edge portions 7, 7 and the edge wave does not occur before the abutting welding, and the abutting welding can be continuously carried out without any problems. . Further, even if a compressive stress is applied to both edge portions 7, 7 after the abutting welding on the exit side of the squeeze roll 6, since the rigidity against the deformation is increased by the abutting welding, the edge wave does not occur. Further, even if an edge wave is generated, it becomes extremely small.

Experimental Example 1 Outer diameter 50.8 mm made of ferritic stainless steel (corresponding to JIS-SUS420)
Then, for thin-walled tubes having various wall thicknesses (0.5 to 1.6 mm), an induction heating coil that constitutes induction-type high-frequency heating means is placed at a position 120 mm upstream from the squeeze roll center to the coil width center. Are arranged so that the temperature of both edges at the center position of the squeeze roll is 1400.
In order to manufacture an electric resistance welded pipe by the electric resistance welding method in which the temperature is adjusted to ℃ and the squeeze roll is used to apply an upset amount of 0.4 mm, the welding is performed by butt welding at a pipe forming speed of 40 m / min. The feasibility of manufacturing using the method and the conventional method was investigated.

In the squeeze roll, the separation distance J from the final fin pass roll is 500 mm, and in the second pipe restraining means (only the upper roll), the separation distance L from the final fin pass roll is 1000 mm. In addition, the first pipe restraining means (having upper and lower rolls) was arranged at a position where the distance G from the second pipe restraining means was 200 mm. Further, in the conventional method, the pass line heights of the rolls and the pipe restraining means are all the same (Hf =
Hs = Hg = Hk), and in the method of the present invention, the pass line heights of the final fin pass roll and the first pipe restraining means are matched (Hf = Hk), and the pass of the second pipe restraining means. The line height Hg is "Hg = Hf-20mm", and the squeeze roll pass line height Hs is "Hs = Hf-18m".
m ”was set to a proper value, and the squeeze roll inclination angle θ was set to a proper value of 3 °. The experimental results
The results are shown in Table 1.

[0070]

[Table 1]

As is clear from Table 1, in the case of the method of the present invention, no edge wave is generated at both edges before the abutting welding with any thickness, and the abutting without any problem. Could be welded.

On the other hand, in the conventional method, the wall thickness is 0.
At 8 mm (t / D = 1.57%) or more, since the material itself is rigid, edge waves do not occur at both edges before the butt welding, and butt welding can be performed without any problems. Met. When the wall thickness was 0.6 mm (t / D = 1.18%), a small edge wave was generated at both edges before the abutting welding, and the abutting welding became unstable. It was possible to tentatively manufacture by removing. However, the wall thickness is 0.6 mm
At (t / D = 0.98%), edge waves frequently occurred at both edge portions, and butt welding could not be performed at all. When both edge portions were not heated by the high frequency heating means, no edge wave was generated at all thicknesses in both the conventional method and the method of the present invention.

Experimental Example 2 An outer diameter of 50.8 mm made of ferritic stainless steel (corresponding to JIS-SUS420),
For a thin-walled tube (t / D = 0.98%) having a wall thickness of 0.5 mm, an induction heating coil constituting an induction-type high-frequency heating unit is placed 120 mm upstream from the center of the squeeze roll and has its coil width center. Are placed so that the temperature of both edges at the center position of the squeeze roll is 1400 ° C., and the squeeze roll gives an upset amount of 0.4 mm while abutting at a pipe-making speed of 40 m / min. When manufacturing an electric resistance welded pipe by the electric resistance welding method of welding, the separation distance J from the final fin pass roll is 500 m.
The squeeze roll is fixed at a position m, and the first pipe restraining means is fixed at a position where the distance "L + G" from the final fin pass roll is 1900 mm, while the pass line height Hg is set to an appropriate value "Hg = Hf". The separation distance L from the final fin pass roll of the second pipe restraining means set to "-20 mm" is changed variously, in other words, the final fin pass roll and the second fin pass roll are separated from each other.
The distance L from the pipe restraining means and the distance G between the pipe restraining means are changed variously, and the pass line height Hs and the inclination angle θ of the squeeze roll are changed variously, and the feasibility of manufacturing under each condition is investigated. did. The experimental results are shown in Table 2.
Is also shown together with each setting condition.

In the experiment, the position of the second pipe restraining means in the mill line direction was changed for the convenience of the apparatus, but this may be fixed and the squeeze roll arrangement position may be changed. Is as described above.

[0075]

[Table 2]

As is apparent from Table 2, the position of the squeeze roll relative to the second pipe restraining means, the pass line height Hg of the second pipe restraining means, the pass line height Hs of the squeeze roll and the inclination angle θ are shown. In the examples of the present invention (Nos. 1 to 3) set to appropriate values, generation of edge waves was not observed at both edge portions before the butt welding.

On the other hand, the height Hs of the pass line of the squeeze roll and the inclination angle θ are proper values, but the installation position is “J> Q = L (G + L) / (G + 3L)”, which is an inappropriate comparative example. In (No. 4), edge waves were generated at both edge portions from near the entrance side of the squeeze roll to the downstream side. In addition, the installation position of the squeeze roll and the inclination angle θ are proper, but the height Hs of the pass line is too high.
In 5), edge waves were generated at both edge portions near the exit side of the final fin pass roll. Furthermore, the installation position of the squeeze roll and the inclination angle θ are proper, but the height Hs of the pass line is too low and the comparison example is inappropriate (No. 6), and the installation position of the squeeze roll and the height Hs of the pass line are It is appropriate, but its inclination angle θ is too small and is inappropriate.
With o. 7), edge waves occurred at both edges near the entrance side of the squeeze roll. In addition, although the installation position of the squeeze roll and the height Hs of the pass line are proper, roll flaws occurred in Comparative Example (No. 8) in which the inclination angle θ was large and inappropriate.

Each of the above experiments is based on the electric resistance welding method, and although the data display is omitted, both edge portions of the metal body are preheated to a predetermined temperature by the high frequency heating means, Similar results are obtained when applied to the so-called high frequency preheating combined welding method, in which both edge parts preheated by melting welding means such as TIG, MIG, and laser are then heated to the melting temperature and subjected to butt welding. It goes without saying that it was done.

[0079]

According to the method of the present invention, when the existing electric resistance welded pipe manufacturing apparatus is provided with the outer bead cutting device, only the second pipe restraining means is provided and the outer bead cutting device is provided. If not, the first and second pipe restraining means are arranged at proper positions in association with the squeeze rolls, while the squeeze rolls are simply modified so that the vertical position and the tilt angle can be adjusted. It becomes possible to manufacture an ultra-thin electric resistance welded pipe having a t / D of 1% or less, which could not be manufactured by the method. Further, when the fusion welding means is additionally provided, it becomes possible to manufacture a thin-walled welded pipe which could not be produced by the conventional high frequency preheating combined welding method, which is an extremely significant contribution to the industry.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the principle of edge wave generation prevention according to the present invention.

FIG. 2 is a schematic view showing an example of a first pipe restraining means in the present invention.

FIG. 3 is a diagram for explaining the positional relationship between each roll and the tube restraint means and the relationship between the pass line height in the present invention.

FIG. 4 is a diagram illustrating a posture control mode of a squeeze roll according to the present invention.

FIG. 5 is a diagram for explaining a bending moment that occurs when a load is applied by vertically moving the squeeze roll to a metal strip whose both ends are fixed horizontally before and after the squeeze roll, and FIG. 5A shows the position of each fulcrum. As for the relationship, (b) in the figure shows the bending moment generated when an upward load is applied, (c) shows the bending moment generated when a downward load is applied, and (d) shows the bending deformation direction of the metal strip and the generated bending moment. It is a figure which shows the relationship with the positive / negative of a moment.

6A and 6B are views for explaining a bending moment generated when a load is applied to a metal strip by the method of the present invention. FIG. 6A shows the positional relationship of each fulcrum, and FIG. 6B shows an upward load application. FIG. 6C is a diagram showing a bending moment generated at the time of applying a downward load, and FIG. 7D is a diagram showing a relationship between the bending deformation direction of the metal strip and the positive / negative of the generated bending moment. .

FIG. 7 is a view for explaining a bending moment generated when a load is applied by a squeeze roll when a load is applied to a metal strip by the method of the present invention. FIG. The figure (b) shows the bending moment generated when an upward load is applied, the figure (c) shows the bending moment generated when a downward load is applied, and the figure (d) shows the bending deformation direction of the metal band and the positive and negative of the generated bending moment. It is a figure which shows the relationship with.

FIG. 8 is a view for explaining a bending moment generated when a squeeze roll is used as a fixed fulcrum when a load is applied to a metal strip by the method of the present invention, and FIG. 8A shows a positional relationship between the fulcrums. The figure (b) shows the bending moment generated when the inclination angle θ of the squeeze roll is small, the figure (c) shows the bending moment generated when the inclination angle θ of the squeeze roll is large, and the figure (d) shows the metal strip. It is a figure which shows the relationship between the bending deformation direction and positive / negative of the generated bending moment.

FIG. 9 is a schematic diagram showing the overall configuration of an apparatus for carrying out the method of the present invention.

FIG. 10 is a schematic diagram showing an overall configuration of a conventional welded pipe manufacturing apparatus.

FIG. 11 is a schematic diagram showing a main part in a method for manufacturing a welded pipe using a high-frequency heating means.

FIG. 12 is a diagram for explaining a high frequency current path when heating the metal strip by the high frequency heating means.

FIG. 13 is a diagram for explaining the action direction of stress generated when the metal band is heated by the high frequency heating means.

14A and 14B are schematic diagrams showing a deformation mode of the metal band generated when the metal band is heated by the high-frequency heating means. FIG. 14A is a diagram showing a mouth opening deformation, and FIG. 14B is a diagram showing a warp deformation. .

[Explanation of symbols]

1: Roll forming machine, 2: Guide roll, 3: Breakdown roll,
4: side cluster roll, 5: fin pass roll,
5B: final fin roll, 6:
Squeeze roll, 7: edge part, 8: part other than edge part, 9:
Bottom part, 10: high frequency heating coil,
11: second pipe restraining means, 12: high frequency heating means,
13: 1st pipe restraint means, 14: cutting tool, 13 ': support roller, H: metal strip.

Claims (1)

[Claims] 1. A metal strip is passed through a roll forming machine to be formed into an open pipe shape, and opposite edge portions are melted and heated by a high frequency heating means and then butt-welded by a squeeze roll, or a high frequency heating means. In a method for welding a welded pipe, which is preheated by means of melt welding and then melt-heated by means of melt-welding means and then butt-welded by a squeeze roll, a pipe restraining means for restraining the welded pipe after the butt-welding on the downstream side of the squeeze roll. At least two of these pipe restraining means are provided, and the pass line height of the upstream pipe restraining means of these pipe restraining means is set lower than the pass line height of the final fin pass roll of the roll forming machine, while the squeeze roll is A metal which is placed at a position satisfying the following formula and whose pass line height and inclination angle are determined by the two pipe restraining means and the final fin pass roll. Method for producing a welded pipe, characterized by adjusting set along the orientation of the strip. L (G + L) / (G + 3L) ≧ J where J: distance between final fin pass roll and squeeze roll (mm) L: distance between final fin pass roll and upstream pipe restraining means (mm) G: upstream Separation distance between the side pipe restraining means and the downstream side pipe restraining means (mm)