JP4442758B2 - ERW pipe manufacturing method - Google Patents

Description

The present invention, the plate thickness is thin walled electric-resistance-welded pipe with respect to the outer diameter, relates to a process for the production of so-called low t / D ERW pipe suitable electric-resistance-welded pipe is applied to the production of, in particular of both edges butt welding The present invention relates to a squeeze roll that provides a circumferential compressive force.

  The electric sewing tube manufacturing apparatus is generally configured as shown in FIG. 6 which is common to the present invention and the conventional example, and a strip-shaped metal plate 1 is passed through an inlet guide roll 13 and a plurality of breakdown rolls 2. Is formed into a substantially semicircular shape in a breakdown roll region 3 and then formed into a substantially circular shape in which both edges are close in a fin pass roll region 5 composed of a plurality of stages of fin pass rolls 4 and at the same time an outer diameter drawing In a welded portion 8 that includes a squeeze roll 6 (6 ′) that applies a processing and then applies a circumferential compressive force for butt welding of both edges and a welding machine 7 that electrically heats the edge portion. Both edges of the material (molded material) are heated while being energized by the welding machine 7, and both edges of the material are brought into contact with each other by the squeeze roll 6 (6 ') to form a tube. In the illustrated example, a cluster roll 11 including a plurality of side rolls 10 that press the material from the side is installed between the breakdown roll area 3 and the fin pass roll area 5.

The squeeze roll 6 (6 ′) includes a two-roll type consisting only of left and right side rolls, a three-roll type consisting of both left and right side rolls and one lower lower roll, There are four roll types consisting of side rolls and a pair of upper left and right head rolls, and five roll types consisting of left and right side rolls, a pair of upper left and right head rolls and one lower roll.
FIGS. 10 (a) and 10 (b) show a conventional example of a five-roll type comprising a side roll 21 on both left and right sides, a pair of left and right head rolls 22 ', and a lower roll 23 on the lower side. In the conventional squeeze roll of the type having 22 ′, as shown in FIG. 10B, the axis 21a of the side roll 21 and the axis 22′a of the head roll 22 ′ are on the same vertical plane, that is, the material. It was at the same position in the feed direction. The material feed direction position of the axis 22′a of the head roll 22 ′ is indicated by a vertical line M ′. In FIG. 10, reference numeral 1 indicates a tubular material that is butt-welded with a squeeze roll, and A indicates a butt point (edge contact point) at both edges of the material.

  By the way, in the case of a low t / D ERW pipe having a thin plate thickness t with respect to the outer diameter D, a welding failure tends to occur during butt welding of the edge portion of the squeeze roll of the welded portion. Manufacture of the tube is difficult, and conventionally, the low t / D was limited to 1%.

As a cause of the welding failure, there is a cause due to a butt shape defect (edge shape defect) at the time of butt welding, which is caused in a broad forming process until it is introduced into a squeeze roll. It is a welding failure due to a mechanical cause. There are cases where the shape of the edge part is asymmetric and the steps are asymmetric, and there are cases where the edge part itself is unsuitable for butt welding even though it is symmetrical. As a cause of the occurrence of such a defective shape of the edge portion, there are the following causes.
(1) In breakdown molding (molding in the breakdown roll region), an edge wave 16 may occur at the edge portion as shown in FIG. In the case of low t / D, the edge wave of the edge portion is particularly likely to occur. When the edge wave is generated, a step 17 is generated between the two edges at the time of abutting of both edges in the welded portion as shown in FIG.
(2) In the fin pass molding (molding in the fin pass roll region), an outer diameter drawing process (hoop compression) is performed, but the edge portion of the material may be buckled by the applied pressure of the outer diameter drawing process. This buckling is also particularly likely to occur at low t / D.
In addition, the edge part of the fin pass roll is bent to a predetermined curvature, but the curvature radius of the edge part becomes large due to the springback of the material after passing through the fin pass roll (the phenomenon that the bending returns), and both edges May be a V groove 18 as shown in FIG. 9B instead of the original I groove. In this case, of course, welding failure occurs.

  The welding failure caused by the step between the two edges is due to the essence of high-frequency welding that uses the skin effect and proximity effect of the high-frequency current to heat the opposing edges evenly. The part where the upper part is not heated toward the center of the plate thickness and the lower part is heated is excessive heat input, and the butt part is welded with heat input over and cold welding mixed together, resulting in a decrease in welding strength. It is a phenomenon. Further, when both edges become V grooves, the circumferential compressive force is not generated correctly, so that good welding is not performed.

  In contrast to the welding failure caused by the shape defect of the edge portion, there is also a welding failure caused by forge welding that occurs in the butt welding process, that is, in the forge welding process, although there is no problem in the butt shape of the edge part. That is, although the material is introduced into the squeeze roll without any inconvenience, there is a case where plastic buckling occurs at the edge portion of the material due to the upset pressure (circumferential compression force) in the squeeze roll during welding. This buckling is also particularly likely to occur at low t / D.

  The weld failure due to forge welding is the case where the edge that has been welded normally is suddenly seated when the heat input is increased by one degree or when the upset amount (circumferential compression amount) is adjusted. This is a phenomenon in which the vicinity of the heat-softened welded part cannot withstand the circumferential compressive force for pressure welding and is plastically buckled. Once buckling occurs, the same is true for poor welds due to mechanical causes, but it does not return to the original normal butting condition. It is necessary to reduce.

Conventionally, as a measure for preventing the weld failure caused by the forge welding, a measure for mainly increasing the V seam angle has been taken. The V seam angle refers to an angle (angle θ in FIG. 2) formed by both edges toward an edge abutting point (a butt point of both edges) when the butt weld is viewed from above.
For example, as disclosed in Japanese Patent Application Laid-Open No. 5-42376 (Patent Document 1), the rotation axis of the side roll is inclined in the traveling direction of the tube, and the squeeze roll hole shape is an elliptical projection hole shape in the traveling direction of the tube. There has been proposed a method of forming a vertical ellipse shape having a major-minor-diameter ratio as close as possible to a perfect circle as long as it does not enter the inside of a perfect circle whose diameter is the minor axis.
In addition, as disclosed in Japanese Patent Application No. 5-277757 (Patent Document 2), it is also proposed to provide an inner roll inside the pipe so as to be bitten by the head roll while lifting both edge portions.
Further, as disclosed in JP-A-62-156082 (Patent Document 3), a dedicated V seam angle adjusting device is provided on the upstream side of the squeeze roll to increase the V seam angle by applying a mechanical pressing force in the cross-sectional direction of the material. Some are installed.
Further, as in Japanese Patent No. 2788911 (Patent Document 4), the edge of the material is formed in the squeeze roll of the weld by reducing the radius of curvature in the vicinity of both edges of the material by forming the material into an elliptical shape by fin pass molding. There is also a method of increasing the rigidity with respect to the circumferential compressive force at the time of abutment, thereby preventing the edge portion from buckling by the circumferential compressive force.
Summary of JP-A-5-42376, paragraph numbers 0004 to 0008, etc. JP-A-5-277757 JP-A-62-156082 Japanese Patent No. 2788911

In the method of the above-mentioned Patent Document 1, it seems that it is not always easy to appropriately set the inclination angle of the axis of the side roll and to design an appropriate squeeze roll hole shape. Moreover, the methods of Patent Document 2 and Patent Document 3 have complicated mechanisms. Further, even if a method of forming a vertically long ellipse by fin pass molding as in Patent Document 4 is adopted, it is desired to further increase the high buckling prevention effect.
The present invention has been made based on the above background, and when adopting a method of forming a vertically long ellipse by fin pass molding, mainly forged welding that occurs at the time of butt welding although there is no edge butt shape defect. It is an object of the present invention to provide a method for manufacturing an electric resistance welded tube that can effectively prevent a defective welding due to a simple configuration.

The present invention that solves the above problems is to form a strip-shaped metal plate in a substantially arc shape in the breakdown roll region, and in the fin pass roll region to form an oblong shape with both edges approaching, and at the same time, outer diameter drawing Then, both edges are butt-welded and welded at a welded portion having a squeeze roll having at least left and right side rolls and an upper pair of left and right head rolls, and a welding machine for energizing and heating the edge portions. In the method of manufacturing an electric sewing tube for manufacturing a sewing tube,
The axis of the head roll in the squeeze roll is eccentric to the upstream side with respect to the axis of the side roll, and the contact start point B between the head roll and the material is located upstream from the butt position A of both edges. Thus, butt welding of both edges is performed.

At the time of butt welding with a squeeze roll, the butt position A of both edges is upstream from the contact start point B ′ between the head roll 22 ′ and the material 1 as shown in FIG. At the right side), the abutment in the air is not constrained to the edge part, and when the circumferential compression force by the side roll, which is the main part of the squeeze roll, is applied, the side roll material feed direction center (side As a result, plastic buckling is likely to occur at the edge portion on the upstream side of the side roll axis 21a.
However, in the present invention, as shown in FIG. 3A, the axis of the head roll 22 (the position in the material feed direction is indicated by M) is positioned upstream of the axis 21a of the side roll. The contact start point B between the material 22 and the material 1 can be positioned upstream from the abutting position A of both edges, and therefore, the tension force of the material edge portion on the head roll can be increased. For this reason, when the restraint with respect to an edge part is ensured and the circumferential direction compressive force by the side roll which is the main part of a squeeze roll acts, the material feed direction center position (position of the side roll axis 21a seeing from the side) of a side roll ) The occurrence of plastic buckling at the edge portion on the upstream side is suppressed.
In addition, the head roll 22 positioned on the upstream side of the side roll also serves to correct a butt shape defect that has occurred until the head roll 22 contacts the head roll 22.

  Hereinafter, an embodiment of an electric sewing tube manufacturing apparatus according to the present invention will be described with reference to FIGS.

The overall configuration of the electric sewing tube manufacturing apparatus according to the embodiment of the present invention is as schematically shown in FIG. 6 which is common to the above-described present invention and the conventional example. In the breakdown roll region 3 composed of the breakdown roll 2, a curve is formed in a substantially semicircular shape, and then in the fin pass roll region 5 composed of a plurality of stages of fin pass rolls 4, the both edges are formed in a substantially circular shape. At the same time, the outer diameter drawing process is performed, and then, in a welded portion 8 including a squeeze roll 6 that gives a circumferential compressive force for butt welding of both edges and a welding machine 7 that electrically heats the edge portion. Both edges of the material 1 are heated while being energized by the welding machine 7, and both edges of the material 1 are butted against each other with a squeeze roll 6 to form a pipe. Then, the product is shaped into a final product shape by a plurality of subsequent sizing rolls 9. In the illustrated example, a cluster roll 11 composed of a plurality of side rolls 10 for pressing the material from the side is installed between the breakdown roll area 3 and the fin pass roll area 5. In addition, the thing including the flame | frame which supports each roll 2, 4, 10 is called a roll stand (or only a stand).
In the figure, 12 is an uncoiler, and 13 is an inlet guide roll. Normally, a pinch roll, a leveler, a material shearing machine and a relay welding machine, a looper, etc. are installed between the uncoiler 12 and the inlet guide roll 13, but these are omitted (14 indicates the inlet portion of the looper. )is doing. As the welding machine 7, a high frequency induction welding machine, a high frequency resistance welding machine or the like is generally used.

An example of the hole shape of each roll in FIG. 6 is shown in FIG. In the illustrated example, the flat metal plate 1 passes through an inlet guide roll 13 that constrains at least the lower surface of the material 1, and is roughly arc-shaped with three breakdown rolls 2 (BDR # 1, BDR # 2, BDR # 3). in the rough-molded, while pressing the material in the side roll 10 in two stages from both sides is guided in the fin pass roll 4, by the two-stage fin pass roll 4 (FPR # 1, FPR # 2), elongated both edges are close Finished into an elliptical shape . The fin pass roll 4 has a fin roll 4f with which the edge of the material hits in the center of the upper roll 4a.

1A and 1B show a squeeze roll 6 of a welded portion in an apparatus for manufacturing an ERW pipe according to the present invention. FIG. 1A is a schematic front view, FIG. 1B is a schematic side view of FIG. FIG. 2 is a plan view of FIG. The squeeze roll 6 according to the present invention has at least side rolls 21 on both the left and right sides and a pair of upper left and right head rolls 22 as shown in the figure, but in the example shown in the figure, a five roll type having one lower roll 23 on the lower side. It is. Since FIG. 1 is a schematic diagram, the hole shape of the squeeze roll 6 is circular, and the cross-sectional shape of the material 1 passing through is circular. In the present invention, the material 1 is a fin as shown in FIG. Since it is formed into a vertically long elliptical shape by a pass roll, the hole shape of the squeeze roll 6 is a vertically long elliptical shape, and the cross-sectional shape of the material 1 passing through is actually a vertically long elliptical shape. Similarly, the schematic diagram of FIG. 4 described later has a vertically long elliptical shape. The same applies to the schematic diagram of FIG. 10A of the conventional example, and assumes a vertically long elliptical shape.
As shown in the drawing, in the present invention, the axis 22a of the head roll 22 is eccentric to the upstream side with respect to the axis 21a of the side roll 21. The material feed direction position of the axis 22a of the head roll 22 is indicated by a vertical line M. In that case, since the head roll 22 has a function of giving the material a circumferential compressive force required for butt welding together with the side roll 21, the eccentric amount L of the head roll axis 22a with respect to the side roll axis 21a is required. The circumferential compression force is kept within a range that can be secured. The appropriate amount of eccentricity L varies depending on various conditions such as the tube diameter, the plate thickness, the diameter of the side roll 21 and the diameter of the head roll 22, and may be determined experimentally.

At the time of butt welding with a squeeze roll, the butt position A of both edges is upstream from the contact start point B ′ between the head roll 22 ′ and the material 1 as shown in FIG. At the right side), the abutment is performed in the air without restriction on the edge portion, and when the circumferential compression force by the side roll 21 which is the main part of the squeeze roll 6 'is applied, the material feed direction center of the side roll is applied. Plastic buckling is likely to occur at the edge portion on the upstream side (position of the side roll axis 21a when viewed from the side). Arrow a indicates the material traveling direction.
However, in the present invention, as shown in FIG. 3A, the axis 22a of the head roll 22 is positioned upstream of the axis 21a of the side roll 21, so that the contact start point between the head roll 22 and the material 1 is reached. B can be positioned upstream of the abutting position A of both edges, and therefore, the force of the edge portion to the head roll 22 can be increased. For this reason, restraint with respect to the edge portion is ensured, and when a circumferential compressive force is exerted by the side roll 21 which is the main part of the squeeze roll 6, the center position of the side roll 21 in the material feeding direction (side roll axis as viewed from the side). The occurrence of plastic buckling at the edge portion upstream from the position 21a) is suppressed.
In addition, the head roll 22 positioned on the upstream side of the side roll 21 also serves to correct a butted shape defect that has occurred until the head roll 22 comes into contact.
FIG. 1 (b) simply shows that the axial center of the head roll 22 is eccentric to the upstream side, and the axial center position M of the head roll 22 and the material butting position A start to contact each other. The relationship with the point (B) is not accurate but is a schematic diagram, and more precisely, the positional relationship is as shown in FIG.

  The squeeze roll 6 in the above embodiment is a 5-roll type that also includes a lower roll 23, but as shown in FIG. 4, there are no lower rolls, and the left and right side rolls 21 and the upper left and right pair of head rolls 22 A 4-roll type squeeze roll 6A may be used.

FIG. 5 correctly shows the shape of the roll hole of the squeeze roll according to the present invention because it is actually a vertically long elliptical shape, and the cross-sectional shape of the material 1 passing through is actually a vertically long elliptical shape. That is, as the roll groove shape shown in FIG. 7, elongated elliptic shape as so to shape the material into elongated oval fin pass roll 4, a squeeze roll 6B of the hole-shaped squeeze rolls, shown in FIG. 5 To. By forming the material into an oblong shape, the radius of curvature in the vicinity of both edges of the material is reduced. Therefore, the rigidity against the circumferential compressive force when the edge of the material is abutted in the squeeze roll 6B of the welded portion is high. Become. Therefore, coupled with the effect of decentering the head roll upstream, the effect of preventing the edge portion from buckling due to the circumferential compressive force is further enhanced.

The squeeze roll in the manufacturing apparatus of the ERW pipe of one Example of this invention is shown, (A) is a typical front view, (B) is a typical side view of (A). FIG. 2 is a plan view of FIG. It explains the butt-matching situation of the material in the squeeze roll, (A) corresponds to FIG. 2 of the present invention, (B) corresponds to FIG. 10 of the conventional example, (C) is for comparison of both. (I) and (b) are both drawn together. The other type of squeeze roll in this invention is shown, and it is a schematic diagram corresponding to FIG . FIG. 2 is a view corresponding to FIG. 1A, which correctly shows that the hole shape of the squeeze roll in the present invention is a vertically long elliptical shape and the cross-sectional shape of the passing material 1 is actually a vertically long elliptical shape . It is a principal part block diagram for demonstrating the whole structure of the manufacturing apparatus of the ERW pipe to which this invention is applied. It is the figure which showed an example of the roll hole shape of each step | level to the fin pass roll in FIG. It is a figure explaining the mechanism in which an edge wave generate | occur | produces in material at the time of pipe forming. The aspect of the butt shape defect of the material in the welded portion will be described, where (A) is a case of a butt step and (B) is a case of insufficient edge portion molding. The squeeze roll in the manufacturing apparatus of the conventional electric sewing pipe is shown, (A) is a schematic front view, (B) is a schematic side view of (A).

Explanation of symbols

1 Material (metal plate or molding material)
6, 6A, 6B Squeeze roll 21 Side roll 21a Side roll axis 22 Head roll 22a Head roll axis 23 Lower roll L Eccentricity of head roll axis with respect to side roll axis M Head roll axis material feed direction Position A Edge collision point (matching point of both edges)
B Contact start point between head roll and material θ V seam angle

Claims (1)

A strip-shaped metal plate is formed into a generally arcuate shape in the breakdown roll region, and is formed into an oblong shape with both edges approaching in the fin pass roll region, and at the same time subjected to outer diameter drawing, and then at least on both the left and right sides. An electric resistance welded tube for manufacturing an electric resistance welded tube by butt-welding both edges at a welded portion having a squeeze roll having a side roll and a pair of left and right head rolls and a welding machine for energizing and heating the edge portion . In the manufacturing method,
The axis of the head roll in the squeeze roll is eccentric to the upstream side with respect to the axis of the side roll, and the contact start point B between the head roll and the material is located upstream from the butt position A of both edges. A method of manufacturing an electric resistance welded tube characterized by performing butt welding of both edges.

Images