JPH05277757A - Manufacture of resistance welded tube - Google Patents

Abstract

PURPOSE:To provide the manufacturing method of the electro-resistance-welded tube capable of always forming a V-shape with the same size without exchang ing rolls and further, suppressing the generation of a lap which is a weld defect. CONSTITUTION:A steel strip H bent into an open pipe (h), heated on both edges by resistance heat generation of a high-frequency current and while both edge parts are raised by an inner roll 8 given the vertical upward pressure by a hydraulic cylinder 10, these edge parts are bitten into top pressure rolls 7 and 7. Since both edge parts are given the steep movement in the vertical direction right before the top pressure rolls 7 and 7 in this way, a V angle formed between both edge parts and a welding point is enlarged and both edge parts are carried to the top pressure roll 7 and 7 sides and butt-welded together.

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 pipe in which metal strips are sequentially formed into a cylindrical shape by a forming roll group and welded by a high frequency current.

[0002]

2. Description of the Related Art FIG. 4 is a schematic perspective view showing a process of manufacturing an electric resistance welded pipe from a steel strip by a conventional roll forming method.
In the figure, H is a steel strip. The rolled steel strip H is fed from the uncoiler 1 to the leveler 2, flattened by the leveler 2 and fed to the roll forming machine. The roll forming machine is provided with breakdown rolls 3, 3, ..., Which are horizontal rolls, cluster rolls 4, 4, ..., Which are vertical rolls, and fin pass rolls 5, 5 ,. The steel strips H are arranged in pairs and are sequentially arranged in series in the conveying direction of the steel strips H. Here, the steel strip H is sequentially bent into an open pipe h having a circular cross section so that both side edges thereof, that is, the edge portions face each other. After that, both edges of the open pipe h are heated by a welding machine (not shown), lateral pressure is applied by the squeeze rolls 6 and 6, and both edges are constrained by the top pressure rolls 7 and 7. In this way, the opposite edge portions are butt welded to each other to manufacture the electric resistance welded pipe.

FIG. 5 is a plan view of a welding process of an electric resistance welded pipe manufacturing line, that is, a process in which a steel strip H which has become an open pipe h is heated through a fin pass roll 5 and lateral pressure is applied by a squeeze roll 6. (Top pressure roll omitted). Both edge portions e, e to be abutted and welded together form a V angle with the abutted welding point c.

Generally, the welded state of an electric resistance welded pipe has a speed (Va) in which both edges approach each other along the V angle and a speed (a) in which the edge surface is scraped off because the molten steel generated by heating is discharged by electromagnetic force. Vr) depends on the magnitude relationship with Vr). When the welding speed is slowed down and the welding energy is increased, Va <Vr is satisfied, and the molten steel slit repeatedly grows and disappears in the welded portion, and flashes or penetrators are frequently generated. On the other hand, when the welding speed is high and the welding energy is small, Va> Vr is satisfied, and no slit growth is observed, but cold welding is likely to occur. Therefore, in order to obtain stable welding quality, Va needs to be slightly larger than Vr. For this purpose, it is conceivable to increase the welding speed or increase the above-mentioned V angle. With regard to the former, the upper limit of the welding speed is defined by the capacity of each equipment of the mill line, and therefore the welding quality is usually improved by increasing the V angle of the latter.

[0005]

When steel strips having different deformation resistances due to the strength or wall thickness of steel strips are manufactured into electric resistance welded pipes having the same outer diameter, the V angle is different. Sometimes When a steel strip with a large deformation resistance, that is, a steel strip with a high strength or a thick wall is manufactured as an electric resistance welded pipe, the V angle becomes smaller than when a steel strip with a small deformation resistance is manufactured with the same outer diameter. .. In order to adjust the size of the V angle, the fin plate in the central portion of the final fin pass roll 5 (Fig. 5) is used.
51 The width must be increased, and when continuously manufacturing ERW pipes with the same outer diameter, if the deformation resistance of the steel strip is different, V
I had to replace Finpass Roll 5 just to adjust the corners.

As shown in FIG. 4, after welding both edges of the steel strip, a squeeze rolls 6 and 6 and top pressure rolls 7 and 7 perform abutting welding. Used in the manufacture of ERW pipes. In this 4-roll type, since there are many roll adjustment points and skill is required for proper adjustment, exchanging the roll only for adjusting the V angle consumes wasteful time and lowers manufacturing efficiency. There was a problem of inviting.

When the steel strip has a large number of cambers, the steel strip is apt to meander during the forming, and many defects and laps in which the welded portion is stepped are generated. In order to solve this, a method of controlling the adjustment of the roll by measuring the amount of camber (Japanese Patent Laid-Open No. 61-115685), or a step of the quantity edge of the steel strip before welding is detected, and based on this To control the height of the top pressure roll (Japanese Patent Laid-Open No. 618602)
No. 7, JP-A-1-40185) have been proposed. However, when the degree of lap changes, these methods have a problem that the control system is apt to cause hunting, and in that case, the welding quality is rather deteriorated.

The present invention has been made in view of the above circumstances, and when metal bands having different deformation resistances are formed into an electric resistance welded pipe having the same outer diameter, the same large V-shape can be formed without replacing the roll. It is an object of the present invention to provide a method for manufacturing an electric resistance welded pipe, which can be formed by molding and can suppress the generation of a lap that is a welding defect.

[0009]

A method of manufacturing an electric resistance welded pipe according to the present invention conveys a metal strip in the length direction thereof, and at the same time, a plurality of roll forming stands oppose each other on both side edges in the width direction. After molding into an open pipe like that, in the method of manufacturing the electric resistance welded pipe by melting both side edge parts by electric energy and pressure contact with a squeeze roll,
On the upstream side of the squeeze roll, the both side edge portions are pressed from the inner side to the outer side of the open pipe by an inner roll.

[0010]

In the method of manufacturing the electric resistance welded pipe of the present invention, the inner rolls press both side edge portions from the inner side to the outer side immediately before pressing the metal strip. As a result, the movement of the edge portions on both sides becomes steep in the direction orthogonal to the conveying direction, and the V angle formed by the edge portions is determined by which metal strip in the case of manufacturing an electric resistance welded pipe having the same outer diameter. Also make the same angle. Immediately before pressing the metal strip, both side edge portions are simultaneously pressed by the inner roll, so that both side edge portions are restrained in the direction orthogonal to the axial direction of the electric resistance welded pipe, and the step difference between the both side edge portions is alleviated. ..

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. FIG. 1 is a schematic perspective view showing an implementation state in the case of manufacturing an electric resistance welded pipe according to the present invention, FIG. 2 is an enlarged sectional view taken along the line II-II, and FIG. 3 is an enlarged sectional view taken along the line III-III. .. In the figure, H is a steel strip as a material metal strip of an electric resistance welded pipe, which is sequentially bent into an open pipe h by a forming roll (not shown). A power source (not shown) is connected to the downstream side of the conveyance where the fin pass rolls 5, 5, ... Are arranged to heat both edge portions. As shown in FIGS. 2 and 3, on the downstream side thereof, a hydraulic cylinder 10 is arranged inside the open pipe h with the radial direction of the open pipe h facing the edge portion as the axial direction. On the edge side of the hydraulic cylinder 10, an inner roll 8 made of a non-conductor is brought into contact with the edge portion, and on the opposite side, a reaction force roll 9 is brought into contact with the inside of the open pipe h, so that the hydraulic cylinder 10 is mutually in contact. Is installed via a hydraulic cylinder
The pressure of 10 can be effectively transmitted to the edge part. The pressure of the hydraulic cylinder 10 is adjusted to an appropriate value by the deformation resistance of the steel strip H.

At this time, the position of the center of the inner roll 8 in the axial direction of the open pipe h is at a position separated from the center of the squeeze rolls 6, 6 upstream by the radial length of the top pressure rolls 7, 7 and the inner roll 8 Is smaller than the radius of the top pressure rolls 7, 7. This is the thickness of the electric resistance welded pipe G to be manufactured, or the steel strip H.
Is determined by the strength of. Further, the material of the inner roll 8 is made of a non-conductive material in order to prevent the welding current from being short-circuited by the inner roll 8 when the edge portion is heated. Further, it is desirable that the material has heat resistance and toughness.

The squeeze rolls 6, 6 are arranged on both sides of the open pipe h on the downstream side of the inner roll 8, and the top pressure rolls 7, 7 are provided outside the open pipe h facing the edge portion. It is arranged.
Further on the downstream side, a bead cutting mandrel 11 equipped with a cutter is disposed so as to face the inside of the welded portion of the electric resistance welded pipe G, and the shaft thereof penetrates through the central portion of the open pipe h and the fin It is fixed on the upstream side of the pass rolls 5, 5, ....

In the electric resistance welded pipe manufacturing line constructed as described above, the steel strip H is bent by the fin pass rolls 5, 5, ... into an open pipe h whose edge portion abuts at the upper position, Both edge portions are heated by the resistance heating of the high frequency current. The inner roll 8 which is vertically upwardly pressed by the hydraulic cylinder 10 conveys and rotates while lifting both edge portions, and both edge portions are top pressure rolls 7 that restrain downward from the outside of the open pipe h.
It is bitten by 7, and at the same time, lateral pressure is applied by squeeze rolls 6, 6. In this way, both edge portions are provided with a sharp vertical movement immediately before the squeeze rolls 6 and 6, so that the V angle formed between both edge portions and the welding point becomes large, and the squeeze rolls 6 and 6 are formed. 6 or the top pressure rolls 7 and 7 are conveyed and abutted and welded. After that, the inner surface bead generated due to the butt welding is cut off by the bead cutting mandrel 11, and the outer surface bead is removed by the outer surface bead cutting tool to manufacture the electric resistance welded pipe G.

Next, under the following conditions, the size of the V angle and the state of lap generation when an electric resistance welded pipe having an outer diameter of 508.0 mm, a wall thickness of 6.35 mm and 12.7 mm is manufactured by the method of the present invention and the conventional method. Table 1 shows the results of the comparison. Metal band, strength (tensile strength) of 42.0 kg / mm ^2, using a strip of 57.0kg / mm ^2. Top pressure roll outer diameter: φ300mm Inner roll outer diameter, radius, width: φ100mm, R150mm, 80mm Inner roll center position: 150m from squeeze roll center
m Hydraulic cylinder inner diameter: φ100mm Steel strip: Strength (tensile strength kg / mm ² ) is 42.0, 57.0

[0016]

[Table 1]

As is clear from Table 1, when steel strips having different strengths are manufactured into electric resistance welded pipes having the same outer diameter, the V angle changes in the conventional method, whereas the V angle changes in the present invention. In the case where steel strips having the same strength and different strengths are manufactured into ERW pipes having the same outer diameter, the V angle changes in the conventional method, whereas the V angle changes in the present invention. is doing. Further, when steel strips having different strengths are manufactured with different wall thicknesses into electric resistance welded pipes having the same outer diameter, the V angle changes in the conventional method, whereas the V angle changes in the present invention. From this, it can be said that in the present invention, the strength and wall thickness of the steel strip do not affect the V angle. Further, it can be seen that the present invention suppresses the occurrence of lapping.

Although a four-roll type welded portion is used in this embodiment, it can be applied to a two-roll type.

[0019]

As described above, according to the method of manufacturing an electric resistance welded pipe of the present invention, when metal bands having different deformation resistances are manufactured into an electric resistance welded pipe having the same outer diameter, inner edges of both side edges are formed by inner rolls. Since the same V angle is formed in any of the metal strips by pressing from the outside toward the outer side, it is possible to manufacture the electric resistance welded pipe having the same outer diameter without exchanging the roll. Further, the present invention has excellent effects such that the step of both side edge portions can be alleviated by simultaneously pressing both side edge portions by the inner roll and the occurrence of wrap can be suppressed.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an implementation state in the case of manufacturing an electric resistance welded tube according to the present invention.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged sectional view taken along line III-III in FIG.

FIG. 4 is a schematic perspective view showing a process of manufacturing an electric resistance welded pipe from a steel strip by a conventional roll forming method.

FIG. 5 is a plan view of a welding process of the electric resistance welded pipe manufacturing line.

[Explanation of symbols]

 1 Uncoiler 2 Leveler 3 Breakdown roll 4 Cluster roll 5 Fin pass roll 6 Squeeze roll 7 Top pressure roll 8 Inner roll 9 Reaction roll 10 Hydraulic cylinder 11 Mandrel for bead cutting H Steel strip G ERW pipe

Claims (1)

[Claims] 1. A metal strip is conveyed in its length direction, and is formed into an open pipe by a plurality of roll forming stands so that both side edges in the width direction face each other, and then both edges are formed by electric energy. In the method for manufacturing an electric resistance welded pipe by melting a part and pressing it with a squeeze roll, pressing both side edge parts from the inside of the open pipe to the outside by an inner roll on the upstream side of the squeeze roll. And a method for manufacturing an electric resistance welded pipe.