JP2002283063A - Seam guide stand and high frequency induction welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seam guide stand which has the ability to prevent a V shape from changing and to provide high frequency induction welding equipment in which this seam guide stand is incorporated. SOLUTION: In the seam guide stand 4, a base 10 is installed on a frame 9, a post 11 is provided on the base 10, a holder 12 is attached to the post 11, and a seam guide 5 is fixed on the holder 12. In addition, a bar stock supporter 13 for supporting a metallic bar stock 2 is built on the base 10. The base 10, post 11, holder 12, bar stock supporter 13, and bolts 15, 16 are all composed of an insulating resin. This resin has a linear expansion coefficient of 6×10<-5> or less, tensile breaking elongation of 3% or more, Izod impact strength of 30 J/m or higher, and tensile strength of 70 MPa or above. For the resin, there are used polyamide-imide, peak or ultra-high-molecular-weight polyethylene, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seam guide stand for holding a seam guide of a high-frequency induction welding apparatus for producing a welded pipe, and a high-frequency induction welding apparatus incorporating the seam guide stand. The present invention relates to a stabilized seam guide stand and a high-frequency induction welding device.

[0002]

2. Description of the Related Art Conventionally, a high frequency induction welding apparatus for producing a welded pipe by high frequency induction welding of a metal strip is provided with a high frequency induction heating apparatus having a coil for high frequency induction heating of a metal strip bent in the width direction. And a squeeze roll for welding the heated metal strips by butt-welding the edges in the width direction. With such a high-frequency induction welding apparatus, a welded pipe having the longitudinal direction of the metal strip material as the pipe axis direction can be continuously manufactured. This welded tube is used, for example, as a heat exchanger tube of a heat exchanger.

In the method of manufacturing a welded pipe by such a high-frequency induction welding apparatus, the shape of the welded portion of the metal strip, that is, the portion where the edges in the width direction of the metal strip are butted, is always constant. It is important that there is. As described above, the welded pipe is formed by rolling the strip in the width direction and joining the edges in the width direction to each other and joining them together. Tube) V-shaped toward the upstream side in the traveling direction. This V
It is important that the character shape (V shape) always has a constant shape (opening degree).

In the continuous production of a welded pipe, if this V shape fluctuates, the butting condition of the edges changes, and the relative positions of the butting edges are shifted. Thereby, on the inner surface of the welded portion of the welded pipe,
A step is generated. FIG. 4 is a partial cross-sectional view showing the shape of the welded pipe in which a step is formed on the inner surface of the welded portion, in a section orthogonal to the pipe axis. In addition, after cutting a bead from a welding part with a bead cutter after welding, observation is performed. As shown in FIG. 4, on the inner surface of the weld portion 22 of the weld pipe 21, an edge step 24 occurs in the same plane as the weld surface 23.

[0005] A welded pipe having a step at the welded portion has reduced pressure resistance. In addition, when the relative positional deviation between the two ends of the metal strip described above is remarkable, the edges cannot be abutted with each other, and the width direction ends of the metal strip overlap, resulting in poor welding. Is generated. Further, when the V shape fluctuates, the abutting state of the edges changes. For this reason, the heating state at the welded portion changes, and the metal strip material is partially melted, and spatter occurs frequently.

In order to prevent such a V-shape fluctuation, a high frequency induction welding apparatus is provided with a ceramic tool called a seam guide upstream of the high frequency induction heating apparatus. The seam guide is a plate-shaped or roll-shaped tool, is held by a seam guide stand, and the end of the seam guide is inserted between the edges of the strip curved in the width direction. With this seam guide, the distance between the edges of the metal strip can be kept constant at a predetermined position on the upstream side of the high-frequency induction heating device. Thereby, the V shape of the welded portion can be kept constant. Further, the seam guide stand can move the position of the seam guide in the plate width direction and the vertical direction of the metal strip. Thus, the V shape can be controlled.

[0007]

However, the above-mentioned prior art has the following problems. In the above-described manufacturing process of the welded pipe, the thickness and width of the edge portion of the metal strip are made constant, the bending in the longitudinal direction of the metal strip is reduced, and the position of the seam guide is fixed by the seam guide stand, Even if the heating condition of the metal strip by the coil of the high-frequency induction heating device is kept constant and the butting condition by the squeeze roll is kept constant, the V shape may still fluctuate. For this reason, there is a problem that a step is generated in the welded portion of the welded pipe, welding failure occurs, and spatter occurs frequently.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a seam guide stand capable of preventing a change in V shape and a high-frequency induction welding apparatus incorporating the seam guide stand. With the goal.

[0009]

According to the present invention, there is provided a seam guide stand, wherein a widthwise edge of a metal strip is supplied with high-frequency induction heating by a coil supplied with a metal strip bent in a width direction and through which a high-frequency current flows. At least a part of a seam guide stand used for a high-frequency induction welding device that welds the edges by butt welding with a squeeze roll and that holds a seam guide inserted between the edges to adjust the distance between the edges. Is made of an insulating material.

In the present invention, by forming the seam guide stand from an insulating material, it is possible to prevent the seam guide stand from being inductively heated by the high frequency induction magnetic field generated by the coil. This allows
Thermal expansion of the seam guide stand can be prevented, and the position of the seam guide can be kept constant. As a result, it is possible to prevent a change in the shape of the metal strip at the welded portion, that is, the V shape.

Further, the insulating material may be a resin material. Thereby, while ensuring the strength of the seam guide stand, the seam guide stand can be easily formed.

Further, the insulating material has a linear expansion coefficient of 6 ×.
It is preferably at most 10 ⁻⁵ . Accordingly, even when the coil is heated and the seam guide stand is heated by radiant heat or the like from the coil, the thermal expansion of the seam guide stand can be suppressed, and the position of the seam guide can be prevented from changing. Can be. The edge expansion coefficient is a value at 20 ° C.

Further, it is preferable that the insulating material has a tensile elongation at break of 3% or more and an Izod impact strength of 30 J / m or more. Thereby, the impact resistance of the seam guide stand can be improved. In addition, the Izod impact strength is a value in a case with notch. Further, the insulating material preferably has a tensile strength of 70 MPa or more. Thereby, the strength and rigidity of the seam guide stand can be improved, the seam guide can be firmly supported, and the position of the seam guide can be further stabilized.

A high-frequency induction welding apparatus according to the present invention is provided with a seam guide inserted between widthwise edges of a metal strip curved in a width direction to adjust a distance between the edges, and holds the seam guide. A seam guide stand, and a coil for high-frequency induction heating of the metal strip, and a squeeze roll for manufacturing a welded pipe by butt welding the widthwise edges of the heated metal strip to each other, The seam guide stand is characterized in that at least a part thereof is made of an insulating material.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive experimental research to solve the above-mentioned problems. As a result, in a conventional high frequency induction welding apparatus, a seam guide stand is made of a metal such as a bronze casting having a high conductivity. , An induction current is generated in the seam guide stand by the high-frequency induction magnetic field oscillated from the coil of the high-frequency induction heater arranged near the seam guide stand, and the seam guide stand itself generates heat and thermally expands. Was found to have occurred. As a result, the size and shape of the seam guide stand were out of order, the position of the seam guide was changed, and the shape of the welded portion of the metal strip, that is, the V shape was changed.
Therefore, in the present invention, this problem is solved by forming the seam guide stand from an insulating material.

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a side view showing the configuration of the high frequency induction welding apparatus according to the embodiment of the present invention. As shown in FIG. 1, in the high-frequency induction welding apparatus 1, a seam guide stand 4, a high-frequency induction heater 6, and a pair of squeeze rolls 7 are arranged in order from the upstream side along a path along which the metal strip 2 flows. I have. A roll forming device 3 is arranged on the upstream side of the high frequency induction welding device 1. The high-frequency induction heater 6 has a high-frequency coil 6a through which the metal strip 2 is inserted. A seam guide 5 is attached to the seam guide stand 4. The welded portion 2c of the metal strip 2, that is, the portion where the edges of the metal strip 2 meet each other is located between the squeeze rolls 7, and the metal strip 2 is welded by the squeeze rolls 7 and formed into a welded pipe 8. You.

FIG. 2A is a front view showing the structure of the seam guide stand 4 according to the present embodiment, and FIG. 2B is a partial cross-sectional view showing the structure near the seam guide 5 in the seam guide stand 4. As shown in FIG. 2A, the seam guide stand 4 is provided on a gantry 9. In the seam guide stand 4, a base 10 arranged on a gantry 9 is provided, and the base 10 is fixed on the gantry 9 by bolts 14. A column 11 is erected on the base 10, and the column 11 is fixed to the base 10 by bolts 16. The holding part 12 is attached to the pillar part 11 by a bolt 15. The vertical position of the holding part 12 can be adjusted by the bolt 15. On the other hand, a strip support 13 is provided on the base 10. Strip support 13
Is fixed to the gantry 9 by bolts 17 through the through holes 10 a of the base 10. The seam guide stand 4 is constituted by the base 10, the pillar 11, the holder 12, the strip support 13, and the bolts 15 and 16. The seam guide 5 is fixed to the holding portion 12 of the seam guide stand 4. The seam guide 5 is made of ceramics and has a plate shape. The roll forming device 3 (see FIG. 1) is provided on the strip support portion 13.
The metal strip 2 curved in the width direction is disposed. The seam guide stand 4 is also provided with an adjustment mechanism (not shown) for adjusting the position of the seam guide 5 in the width direction of the metal strip 2.

As shown in FIG. 2 (b), the lower end 5a of the seam guide 5 is thinner toward the edge. The lower end 5a is the edge 2a and 2b of the metal strip 2.
It is located between.

Parts constituting the seam guide stand 4;
That is, the base 10, the pillar 11, the holding part 12, and the strip support 1
3. The bolts 15 and 16 are all made of resin. The bolts 14 and 17 are also made of resin. The linear expansion coefficient of this resin at 20 ° C. is 6 × 1
0 is ^-5 or less. The volume resistivity of this resin is about 1 to 10 × 10 ⁻¹⁴ Ωm. Further, the resin has a tensile elongation at break of 3% or more and an Izod impact strength of 30 J.
/ M or more, and the tensile strength is 70 MPa or more. As the resin, for example, polyamide imide, Peak or Ulmora can be used.

The material constituting the seam guide stand will be described in more detail. Table 1 shows the characteristics when the seam guide stand is made of each type of material.

[0021]

[Table 1]

The main characteristics required for the material forming the seam guide are that it is not induction-heated, that a strong and strong seam guide stand can be formed, and that machinability such as machinability and machinability is excellent. It is. As shown in Table 1, the resin does not conduct electricity except for the conductive resin, so that the resin is not subjected to induction heating even when a high-frequency induction magnetic field is applied. Further, since it has high strength and excellent workability, it is optimal as a material for forming a seam guide stand. Ceramics are not induction-heated and have high strength, so they can be used as a material for seam guide stands. However,
Ceramics are somewhat difficult to process because their workability is inferior to resins. Further, since ceramics are generally brittle, they are easily damaged by externally applied shocks when using and handling the seam guide stand. Since wood has low strength, if the seam guide stand is made of wood, the seam guide cannot be firmly fixed. Metal is the material that makes up the conventional seam guide stand. Metals are excellent in strength and workability, but generate heat when placed near a high-frequency coil due to induction heating. For this reason, the seam guide stand made of metal thermally expands, and the position of the seam guide changes. Therefore, wood and metal are unsuitable materials for the seam guide stand.

Next, the operation of the high-frequency induction welding apparatus 1 according to the present embodiment will be described with reference to FIGS. 1, 2A and 2B. The metal strip 2 shown in FIG.
Copper, a copper alloy, aluminum or an aluminum alloy can be used. The metal strip 2 may have a groove formed on one side, or both sides may be smooth. Metal strip 2
Is curved in the width direction by the roll forming device 3 and rounded into a substantially arc shape.

At this time, the variation in the thickness of the edge portion of the metal strip 2 is preferably ± 0.01 mm or less, and the variation in the width is preferably ± 0.05 mm or less. The bending is preferably 1.0 mm / m or less. Thereby, the shape of the welded portion (V shape)
Can be further suppressed.

Next, as shown in FIGS. 2A and 2B, the metal strip 2 passes over the strip support 13. At this time, the lower end 5a of the seam guide 5 is inserted between the both ends 2a and 2b in the width direction of the metal strip 2, and the distance between the both ends 2a and 2b in the width direction of the metal strip 2 is fixed. To

Thereafter, as shown in FIG. 1, the metal strip 2 passes through the high-frequency coil 6a of the high-frequency induction heater 6.
At this time, when the high-frequency coil 6a oscillates a high-frequency induction magnetic field, an induction current flows in the metal strip 2, and the metal strip 2, particularly the edges 2a and 2b are induction-heated. next,
The metal strip 2 is pressed from both sides by a pair of squeeze rolls 7, and the edges 2a and 2b abut against each other. At this time, a V-shape is formed in the welded portion 2c of the metal strip 2. The edge 2a is welded to the edge 2b, and the welded pipe 8 is manufactured.

In the high frequency induction welding apparatus 1 of this embodiment, the seam guide stand 4 is made of an insulating resin, and the bolts 14 and 17 are also made of an insulating resin. Is installed near the high frequency coil 6a of the high frequency induction heater 6, no induction current is generated in the seam guide stand 4, the bolts 14 and 17. Therefore, the seam guide stand 4, the bolts 14 and 17 are not heated by the high frequency coil 6a. Further, since the linear expansion coefficient of the resin constituting the seam guide stand 4 is 6 × 10 ^-5 or less, even seam guide stand 4 is heated by the radiant heat such as a high-frequency coil 6a itself generates heat, seam guide The stand 4 hardly undergoes thermal expansion, and the seam guide 5 can be kept fixed at a fixed position. Furthermore, since the tensile strength of this resin is 70 MPa or more, the seam guide stand 4 has excellent strength and rigidity, and can strongly support the seam guide 5. As a result, the seam guide stand 4 can hold the seam guide 5 at a fixed position. Thereby, the variation of the V shape in the welded portion 2c is suppressed. Therefore, the metal strip 2 can be stably welded, and the occurrence of poor welding and spatter during welding can be prevented, and the occurrence of an edge step in the welded portion in the welded pipe 8 can be prevented.

Further, since the resin constituting the seam guide stand 4 has a tensile elongation at break of 3% or more and an Izod impact strength of 30 J / m or more, the seam guide stand 4 has excellent impact resistance.

The seam guide stand 4 may be made of a resin reinforced by glass fiber in order to further reduce the coefficient of linear expansion and improve the strength. However, the resin reinforced with carbon fiber is
Since the carbon fiber is induction-heated, it is not preferable as a constituent material of the seam guide stand 4.

The material constituting the seam guide stand 4 does not need to be limited to one kind, and a plurality of kinds of materials may be used as long as they satisfy the above-mentioned required characteristics. For example, a material having good machinability may be used for a portion requiring precise shape, and a material having higher strength may be used for other portions.

Further, in this embodiment, all the parts constituting the seam guide stand 4 are made of resin, and the bolts 14 for fixing the seam guide stand 4 to the gantry 9 and the bolts for fixing the strip support 13 to the gantry 9 are provided. In the present invention, at least a part of the part constituting the seam guide stand 4 which is affected by the high-frequency induction magnetic field oscillated by the high-frequency coil 6a is made of an insulating material. With this configuration, a certain effect can be obtained.

Further, in the present embodiment, an example is shown in which the shape of the seam guide 5 is plate-shaped. However, in the present invention, the shape of the seam guide 5 is not limited to a plate shape. It may be configured to rotate according to the passing plate of the metal strip 2. Thereby, the movement of the metal strip 2 can be made smoother.

[0033]

The effects of the embodiment of the present invention will be specifically described below in comparison with a comparative example outside the scope of the claims. There are two types of high-frequency induction welding devices, a high-frequency induction welding device of the present invention using a polyamide-imide seam guide stand, and a conventional high-frequency induction welding device using a bronze casting (AlBC2) seam guide stand. Prepared.

A welded pipe was manufactured using these two types of high frequency induction welding equipment. First, a raw material made of phosphorus deoxidized copper, having a hydrogen content of 0.4 ppm, an oxygen content of 30 ppm, a plate width of 25 mm, a plate thickness of 0.50 mm, and a surface oxide film thickness of 7 nm was prepared. . This strip was subjected to groove rolling using a grooved roll composed of one grooved ring and two tapered edge rolls arranged on both sides of the grooved ring. The outer peripheral surface of the tapered edge roll has a shape such that the strip becomes thinner toward both ends in the width direction,
The width of the area where this shape was formed at both ends of the strip was 0.8 mm. The rolling speed was 200 m / min. Thus, a metal strip having a spiral groove formed on one surface was manufactured.

Next, this metal strip was rounded in the width direction by a forming roll. Next, the distance between both edges (edges) in the width direction of the metal strip was made constant by the seam guide held by the seam guide stand.

Thereafter, the metal strip was passed through a high-frequency induction heater and heated by a high-frequency induction magnetic field having a frequency of 600 kHz. Thereafter, both edges were butted and pressed against each other by a squeeze roll and welded to produce a welded pipe. At this time, the welding speed was 150 m / min. The manufacturing conditions such as the position of the forming roll, the position of the seam guide, the distance between the edges of the metal strip, the input power of the high-frequency induction heater and the pressing load of the squeeze roll are 1.4 times the outer diameter of the welded pipe. A spread test was performed on 20 welded pipes, and the conditions were such that cracks did not occur. The outer diameter of the welded pipe after welding was about 8 mm.

After welding, the diameter of the welded pipe was reduced by a sizing roll until the outer diameter became 7 mm. The inner groove shape of the welded pipe after sizing has a lead angle of 20 °, an average groove depth of 0.20 mm, an average bottom thickness of 0.25 mm, and a peak angle of 3
A spiral groove having 0 ° and a groove pitch of 0.4 mm was used. In addition, the bottom wall thickness is the intersection between the intersection where the straight line perpendicular to the pipe radial direction from the midpoint of the line connecting the fin tops on both sides of the groove with the tangent line intersects the pipe inner surface and the intersection where this straight line intersects the pipe outer surface Distance. As for the average bottom thickness, when the number of divisions of the groove in the cross section orthogonal to the pipe axis is n, the bottom thickness of n or more portions other than the welded portion was measured, and the average value of the measured values was used. The groove depth, that is, the fin height, is the distance between the midpoint of the line connecting the fin tops on both sides of the groove with the tangent line and the intersection point where a straight line perpendicular to the pipe radial direction from this midpoint intersects the pipe inner surface. did. The average groove depth (average fin height) is obtained by measuring the fin heights of n or more parts other than the welded parts when the number of divisions of the groove is n in the cross section orthogonal to the pipe axis, and averaging the measured values. Value.

Thereafter, the edge displacement at the welded portion of the welded pipe was evaluated. From the tip of the welded pipe manufactured as described above, that is, from the welding start side, to a length of 10,000 m,
Welded pipes were sampled every 2000 m. Thereafter, the collected welded pipe was cut in a direction perpendicular to the pipe axis to expose a cross section perpendicular to the pipe axis, and the cross section was polished. Next, the welded portion was observed on the cross section at a magnification of 100 times with an optical microscope, and the size of the edge shift on the inner surface of the welded portion, that is, the edge step 24 (see FIG. 4) was measured. The result is shown in FIG.

FIG. 3 is a graph showing the effect of the material of the seam guide stand on the edge step of the welded pipe, with the horizontal axis indicating the welding length and the vertical axis indicating the measured value of the edge step. The measurement result 18 shown in FIG. 3 is the measurement result of the edge step in the welded pipe according to the embodiment of the present invention. Since this welded pipe was manufactured by a high-frequency induction welding apparatus using a seam guide stand made of polyamideimide, no edge step was observed over the entire length of the welded pipe.

On the other hand, the measurement result 19 is a measurement result of the edge step in the welded pipe of the comparative example. Since this welded pipe was manufactured from a high-frequency induction welding apparatus using a conventional bronze casting (AlBC2) seam guide stand, no edge step was generated at the initial stage of welding, but the seam guide stand was heated as welding progressed. As a result, the seam guide was displaced, and an edge step was generated. At a position of 10,000 m after the start of welding, an edge step of about 0.05 mm was generated.

[0041]

As described in detail above, according to the present invention,
It is possible to obtain a seam guide stand that can prevent the V shape from changing. Thereby, it is possible to prevent the occurrence of poor welding and spatter during the production of the welded pipe, and to prevent the occurrence of an edge step at the welded portion in the welded pipe.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of a high-frequency induction welding apparatus according to an embodiment of the present invention.

FIG. 2A is a front view illustrating a configuration of a seam guide stand according to the present embodiment, and FIG. 2B is a partial cross-sectional view illustrating a configuration near a seam guide in the seam guide stand.

FIG. 3 is a graph showing the effect of the material of the seam guide stand on the edge step of the welded pipe, with the horizontal axis indicating the welding length and the vertical axis indicating the measured value of the edge step.

FIG. 4 is a partial cross-sectional view showing a shape of a welded pipe in which a step is formed on an inner surface of a welded portion in a cross section orthogonal to the pipe axis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; High frequency induction welding device 2; Metal strip 2a, 2b; Edge 2c; Welding part 3: Roll forming device 4: Seam guide stand 5; Seam guide 6; High frequency induction heater 6a; High frequency coil 7; Squeeze roll 8 Welded pipe 9; Stand 10; Base 10a; Through hole 11; Column part 12; Holding part 13; Comparative Example) 21; welded pipe 22; welded part 23; welded surface 24; edge step

Claims (6)

[Claims] 1. A high-frequency induction heating method in which a widthwise edge of a metal strip is supplied with a coil to which a high-frequency current flows and a high-frequency current flows, and the widthwise edge of the metal strip is heated by a squeeze roll. In a seam guide stand used for a welding device and holding a seam guide inserted between the edges to adjust a distance between the edges, at least a part of the seam guide stand is made of an insulating material. Seam guide stand. 2. The seam guide stand according to claim 1, wherein the insulating material is a resin material. 3. The insulating material has a linear expansion coefficient of 6 × 10.
The seam guide stand according to claim 1, wherein the value is ⁻⁵ or less. 4. The insulating material according to claim 1, wherein a tensile elongation at break is 3% or more.
Seam guide stand as described in section. 5. An insulating material having an Izod impact strength of 30 J / m or more.
The seam guide stand according to any one of the above. 6. A seam guide inserted between widthwise edges of a metal strip curved in the width direction to adjust a distance between the edges, a seam guide stand for holding the seam guide, and the metal. A coil for high-frequency induction heating of the strip material, and a squeeze roll for manufacturing a welded pipe by butt welding the width-direction edges of the heated metal strip material, and the seam guide stand is at least partially provided. Is formed of an insulating material.