JPH03155478A - High-frequency resistance welded tube welding equipment - Google Patents

Abstract

PURPOSE:To improve welded joint quality of a thick-wall tube by providing the specified dimensional relation and frequency on an inductor arranged for preheating the edges on this side of a V-seam weld zone of high-frequency resistance welded tube welding equipment. CONSTITUTION:At the time of arranging the inductor 11 for preheating the facing edges on this side of the V-seam weld zone on the high-frequency resistance welded tube welding equipment to form tube raw material 1 in a tubular shape having a V-shaped gap and weld continuously the facing edges of the V-shaped gap, the inductor 11 has an edge heating conductor 14 and magnetic iron cores 17 and 18 are provided on the tubular body outer and inner periphery sides of the inductor and the relation of W>=S/2 (W and S denote dimensions where the outer and inner peripheral iron cores 17 and 18 lap on the one side edge and the interval between the facing edges, respectively) is maintained and electric power having <=50kHz frequency is supplied to the inductor 11. By this method, the generation of spatters, oxide contamination on the weld zone and the occurrence of pinholes can be prevented and welded joint quality can be improved.

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to a high frequency electric resistance welding pipe welding device.

B0 Summary of the Invention This invention is a high-frequency electric resistance welding device for thick inner tubes that is formed into a tube shape having a V-shaped gap, and that connects and welds opposite edges. and preheat the edges.An inductor is provided in front of the V-seam weld, and this 94-element I: 5
By supplying power with a frequency of 0 kHz or less, it is possible to perform good welding even when welding thick-walled pipes.

C6 Conventional technology For high-frequency electric resistance welding pipe welding, Japanese Patent Application No. 1983-45680 (
Japanese Patent Application Publication No. 62-203684) and Patent Application No. 5587/1983
No. 6 (Japanese Unexamined Patent Publication No. 62-176085) has been proposed. The former has a high frequency current of 0.1 m5ec ~ 0
．． The electromagnetic force induced by the high frequency current is eliminated or reduced at approximately constant intervals by periodically turning on and off or increasing and decreasing the current at intervals of 1 sec. On the other hand, in the latter case, there is a 20k
It is equipped with a coil that preheats with power at a frequency of Hz or less.

D9 Problems to be solved by the invention Since high-frequency ERW pipe welding equipment is generally applied to relatively thin-walled ERW pipes, the following problems arise when thick-walled ERW pipes are manufactured. .

(a) There is some difficulty in welding thick walls.

(b) The range of welding conditions for good welding is narrow.

(c) In particular, when the material of the pipe is a material containing alloy components such as Cr, Mo, Mn, etc., the tolerance range becomes narrow because these alloy components tend to become oxides.Next, the above (a) I will explain the reasons for this.

Edges that are heated and joined in ERW pipe welding
As shown in FIG. 14B, it is preferable that the heating is done flatly at the same depth from the tip. Then, when the tips are butted against each other by a squeeze roll section (pressure roll section) and joined together under pressure, the heated and melted portions of the image tips are pushed out toward the inner and outer circumferential sides, forming a sound welded portion. This is the basic condition for ERW pipe welding.

However, in the case of a thick-walled tube, the increase in wall thickness t makes it difficult to flatly heat the tips of both edges, as shown in FIG. 14A. In particular, while the inner and outer corner portions are heated, the central portion is heated, which tends to result in a heated portion as shown in FIG. 14A.

This uses the proximity effect of current to efficiently perform heat welding, so power at a high frequency of usually 100 to 400 kHz is used, and as a result, the edge effect is also strong and most of the current flows concentrated in one corner. It's for a reason. and,
When the heated parts of both edges are in the state shown in Fig. 14A (shaded area in the figure), the molten metal generated at the corners of the inner and outer peripheries becomes spatter due to electromagnetic force, is sputtered, and is ejected, or when the edges are butted together. During welding, as shown in Figure 14C, the molten metal from a portion of both corners (the shaded area in the figure) is not completely discharged and remains within the weld, resulting in pinholes and oxide entrainment. The integrity of the weld is lost. This is the first reason for welding thick-walled ERW pipes.
This is the problem.

In electric resistance welding pipe welding, a phenomenon as described in detail in Japanese Patent Application Laid-Open No. 62-203684 occurs. and,
In order to obtain a healthy weld, it is necessary to keep the amount of high-frequency power (welding heat input) supplied to the weld within an appropriate range.

The above publication describes a heat input range in which the period T satisfies O<T≦0.1 seconds. This applies to ERW pipe welding in general, but in particular, the thicker the pipe, the more likely it is that the high-frequency current will concentrate at the corners, so it is important to consider mechanical pressure contacts and current return. The adverse effects of vibration at the abutting point W become significant, and the range (width) of appropriate input conditions becomes narrower, making it more difficult to obtain a sound weld. This point is the second problem.

As described in detail in the ``Function'' section of the above-mentioned Japanese Unexamined Patent Publication No. 62-203684, molten metal is repeatedly discharged by electromagnetic force in the vicinity of the welding point, resulting in spatter. Moreover, in thick-walled pipes, some of the inner and outer corners are overheated as mentioned above, and the molten metal generated in these parts is discharged, which also causes a lot of spatter, which adheres to the pipe itself and squeeze rolls. It solidifies, causing eaves to form on the tube and damaging the roll. This point is the third problem.

Furthermore, since the frequency of the heating power is high as described above, only the tip portions of both edges are heated with a steep temperature gradient. Therefore, after welding, the amount of heat in the welded portion rapidly moves to both sides in the circumferential direction, and the welded portion is rapidly cooled. As a result, the hardness of the weld increases. Then, in order to restore the ductility of the welded part, annealing by reheating is required, which requires a large amount of electric power. This point is the fourth problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a high-frequency electric resistance welding pipe welding device that can perform good welding even when welding thick-walled pipes.

E1 Means for Solving the Problem This invention uses a high frequency electric resistance welding pipe welding line that forms a pipe material into a tubular shape having a V-shaped gap and continuously electrically welds opposing edges of this V-shaped gap. , ■ In an electric resistance welding pipe welding device in which an inductor is provided for preheating opposing edges in front of a seam welding part, the inductor has an edge heating conductor that is open and disposed between the opposing edges. The conductor is provided with magnetic cores on the outer circumferential side and the inner circumferential side of the tube body, and is equipped with WkS/
2 (W: the dimension in which the outer and inner cores overlap with one edge, S2 the distance between the opposing edges), and the inductor is supplied with power at a frequency of 50 kHz or less. It is characterized by preheating the edges.

Further, the present invention is a power supply device for preheating and welding, and is characterized in that it includes a power supply device that shares a forward conversion section and is provided in parallel with an inverse conversion section that can respectively adjust the output.

Further, a preheating means is provided for the opposite edge in front of the V-seam weld, and a post seam is provided adjacent to the V-seam weld at the rear of the V-seam weld. Install a heater,
This method is characterized in that the residual heat of the welded part is utilized to subsequently perform post-heat treatment of the welded part.

Furthermore, in addition to providing a preheating means for the opposite edge in front of the V-seam weld, the frequency of the welding power supplied to the V-seam weld is increased to 1.5, which is approximately three times the conventional frequency.
It is characterized by increasing the frequency to around 0.00 kHz.

F1 action Power with a frequency of 50 kHz or less is supplied to the inductor to preheat both edges of the material to a predetermined temperature below the melting point. Due to this preheating, both edges have little edge effect and are heated over a wide range in the circumferential direction.

Furthermore, since the preheating and welding power supplies are adjusted and delivered separately, power is saved.

Further, after welding is completed, reheating is performed to anneal the material to reduce the hardness of the weld and restore toughness.

In addition, by preheating both edges of the material and increasing the frequency of welding power supplied to the V-seam weld, electromagnetic repulsion at the V-seam weld is reduced and the quality of the weld is improved.

G. Embodiments Below, embodiments of the present invention will be described based on the drawings. First, an embodiment that solves the first problem will be described.

FIG. 1 is a perspective view of the embodiment, and in this FIG.
(2) is a tube material, 2a and 2b are pressure rolls, 4 is a V-seam welding point, 5 is a V-shaped gap, and 5a.

5b is both edges, 6a and 6b are contacts, 7 is a power source, and this portion becomes a V-seam weld. Opposing edges 1a of the tube material 1 in front of this seam weld.

An inductor 11 for preheating is provided between lb. This inductor 11
For example, a relatively low frequency power supply 19 of 50 kHz or less
Electric power is supplied to preheat the vicinity of the opposing edges 1a and lb. The inductor 11 is configured such that a one-turn coil is formed by an outer conductor 12.13 and a plate-shaped edge heating conductor 14 disposed between opposing edges 1a and lb. 1
5.16 is a pair of terminals for connection to the power source 19.

17 is a peripheral iron core.

The detailed structure of the inductor 11 is shown in FIGS. 2 to 4. FIG. 2 is a plan view, FIG. 3 is a side view, and FIG. 4 is an enlarged cross-sectional view taken along the Y-Y line in FIG. 3. It is. Figures 2 to 4
In the figure, an outer circumferential core 17 and an inner circumferential core 18 are arranged on the outer and inner circumferential sides of the edge heating conductor 14, respectively, and these cores 17 and 18 are formed, for example, by laminating silicon steel plates. 12a is a cooling water hole provided in the outer conductor 12, and cooling water holes are also provided in the outer conductor 13 and the edge heating conductor 14, respectively, from supply/drainage and water ports (not shown). Cooling water is passed through them.

In the inductor 11 configured as described above, the dimensional relationship of each part shown in FIG. 4 is set as shown in the following equation.

W≧S/2 However, S: the distance between opposing edges.

W: Dimension where the outer and inner cores overlap with one edge.

The equation is set as above because the magnetic flux generated by the alternating current flowing through the edge heating conductor 14 is
This is intended to increase the electrical efficiency of heating the edge by the edge heating conductor 14 by increasing the effective magnetic flux φ1 that crosses over the edges 1a and 1b to heat the edges 1a and lb, and conversely decreasing the ratio of the invalid magnetic flux φ2.

Here, the means for deriving the above equation W≧S/2 will be described. This formula is used to determine the conditions for magnetic resistance, and is used to effectively link magnetic flux to the material. Magnetic resistance R is proportional to the length (L) of the magnetic flux path and inversely proportional to the cross-sectional area A.

Rcc L/A R (valid) - (L/2 + L/2)/W -L/WR
(Invalid) - (L/2 + t + L/2) / (S-
B)/2-(2L+2t)/(S-B) Here, if R (valid) x R (invalid), the above equations become as follows.

L/W < (2L+2 t)/(S-B) Then, t<
<L, the above formula becomes (S-B)/2<W.

Also, if S>>B, S/2<W.

The inductor 11 is supplied with power at a low frequency of, for example, 50 kHz or less from a power source 19. The lower the frequency of the power, the smaller the edge effect and the deeper the induced current penetrates from the surface, so that the opposing edges 1a and lb are heated almost flat and evenly, as shown in Fig. 4. A wide range is heated in the circumferential direction from the end. Incidentally, FIG. 4 shows the heated portion.

After preheating both edges to a predetermined temperature below the melting point in this way, weld the V-seam as shown in Fig.
00kHz high frequency power is supplied to the edges 5a, 5b to further heat both edges 5a, 5b to a temperature equal to or higher than the melting point, and the pressure roll 2a is heated.

Welding is performed by pressing the edges together at 2b.

The temperature rise curves of the edges 5a and 5b at this time are shown in FIG. The temperature rise curve at the edge in the conventional case without preheating is a characteristic curve as shown in Figure 6 (A).
■, ■, ■ in the figure are parts a, b, c shown in Figure 6 (B)
This is the temperature distribution at . In addition, ■, ■ in Figure 5
, ■ also shows the temperature distribution at the same location as above.

Using the embodiment described above, within the edges of the blank 1.

The outer corner part a is not overheated, and the edge part is heated almost flat over the center part of corner part a1, so welding of thick inner pipes is as sound as welding of thin walled pipes. A welded part can be obtained. This also greatly alleviates the difficulty in welding thick-walled pipes due to the narrowness of the appropriate thermal conditions, making welding easier, and also greatly reducing the amount of spatter generated. This is also an embodiment that solves the second and third problems. Furthermore, since a wide range including the 0 part in FIG. 6(B) is heated, the rapid cooling of the welded part is relaxed and the hardness of the welded part is reduced. This makes it possible to omit annealing after welding depending on the material of the pipe. This is also an example for solving the fourth problem.

Next, the power supply 7.19 shown in FIG. 1 will be described. The power supplies 7 and 19 may be independent and separate power supplies, but as shown in the block diagram in FIG. It is preferable that the inverse conversion section 32 (150 to 450 kHz) is provided for both sites.

Fig. 16 is an example of a specific circuit diagram of the program diagram shown in Fig. 15. In Fig. 16, 30a is a transformer;
b is a rectifier circuit, 31a and 32a are electron tubes, 31b and 32
31c and 32c are matching transformers.

As described above, the output of the common forward converter 30 is supplied to the inverse converters 31 and 32 for preheating and welding, but the inverse converter 31.
The semiconductor switch circuits 31b and 32b provided in the grid circuits of the 32 electron tubes 31a and 32a perform PWM control on their respective oscillation outputs and adjust their on periods.
Each output can be controlled independently of the other.

By configuring a common forward converter 30 in this way, the power supply device can be made more compact than in the case where separate forward converters are provided, and the required commercial power can be significantly reduced. Can be done. For example, if 700 kW (30 kHz) is required for edge preheating and 500 kW (300 kHz) is required for V-seam welding, a configuration in which separate forward conversion sections are provided for each requires a total of approximately 2°4 Q. Q kVA of commercial power is consumed, but by adopting a configuration in which the forward converter 30 is shared as shown in Fig. 15, the commercial power consumption is reduced to 1.900 kVA as shown numerically in the figure. be able to.

Next is the second one. An embodiment that solves the third problem will be described.

As mentioned above, an edge preheating section equipped with an inductor is provided in front of the V-seam weld, and the opposing edges are preheated with power at a frequency of 50 kHz or less, and the tip of the edge is heated almost flat. By raising the temperature, the second. The third problem could be significantly improved.

However, as mentioned above, the second. The third problem is that
This is largely due to the phenomenon of movement of the welding point W at the seam weld part, as described in detail in Publication No. 2-203684. In welding thick-walled pipes, further effects were obtained by intermittent or reducing the welding current at a cycle that is at least twice as fast as the movement cycle of the welding point W.

Actually, using the power supply whose circuit diagram is shown in Figure 16,
Oscillation is performed by the semiconductor switch circuit 32b so that the moving length of the tube material at the V-seam part during the intermittent or high-low 1/2 cycle period of the welding current is 2I or less for each transport speed (line speed) of the tube material 1. Great effects were obtained by selecting the frequency of PWM control of the output and performing PWM control of the welding current. That is, in welding thick-walled pipes, the range of appropriate heat input conditions for obtaining a sound weld is expanded, the difficulty of welding is greatly alleviated, and the amount of spatter generated is greatly reduced.

Note that the PWM control frequency of the welding current may be selected according to the following equation.

pitch (travel length) -vii+/see X l
/2H<2V: Conveying speed of tube material (line speed)
.

H: PWM chopping frequency of high frequency welding current.

For example, v -60m/m1n (v -1000+am
/5ec), by setting H=500Hz, pi
tch= 1 0 0 0 X 1 /2
X500-I IImv= 180m/QIi
H=1500 when n (v=3000+I/5ec)
pitch -3000X 1/2X1500-
1 inch + both have a pitch (travel length) of 1 mm and are less than 2 irises.

Next, an embodiment for solving the fourth problem will be described. Conventionally, since the welded part is rapidly cooled after welding, the hardness increases and the toughness is not good as it is, so it has been necessary to perform reheating annealing in a post-process. FIG. 7 is a block diagram of a conventional welding-reheat annealing equipment, and FIG. 8 shows a temperature schedule characteristic curve of a welded part. In FIG. 7, TF is a matching transformer, and PH is a post pot seam Φ heater group.

Since only the tips of the opposing edges of the weld are heated and welded, the temperature drops rapidly after welding is completed, and the post seam 9 heater is used to reheat the weld from 200°C to perform annealing. Reduces hardness and restores toughness. Therefore, a large amount of electric power was required for reheating and annealing.

Conventionally, in this type of method, even if the post 0 seam heater PH was brought close to immediately after the pressure rolls 2a and 2b in order to utilize the residual heat of the welded part, the desired effect could not be obtained because the post-weld cooling cooled quickly. Ta. Post seam heater PH
Pressure roll 2a.

There are also difficulties in arranging the equipment to get it close to 2b. Therefore, even if you try to make it closer and look at it, the boss is 0.
It was difficult to obtain effects such as reducing the power consumption of the seam tatami heater PH.

However, in this embodiment, since the edges of the material are preheated at a low frequency, the opposing edges 1a and 1b are preheated not only at their tips but also over a wider range, and in addition, the average preheating is applied to part of the corner and the center. will be done. After welding is completed, the cooling rate of the welded area, including the central part, is much slower than in the conventional case without preheating.

Therefore, depending on the material (steel type) of the tube, annealing may be unnecessary. Also, if reheating is required after welding, the post seam heater is installed on the pressure roll 2 of the welding area.
By arranging them close to each other immediately after a and 2b, great effects such as a reduction in the power of the Bost fist seam ψ heater can be produced.

FIG. 9 shows an example of the equipment configuration of this embodiment method, and FIG. 1O shows a temperature schedule characteristic curve diagram of a welded part. As can be seen from Figure 10, the temperature of the welded part after welding is completed drops much more slowly than before, so in the case of steel, the residual heat of the welded part can be used to maintain the austenitic state at 850 to 900°C.
After heat retention is carried out for a predetermined period of time using a post seam O heater PH at a temperature such as 0.05 to 1.00, by cooling the welded part, it is possible to prevent an increase in hardness and a decrease in toughness of the welded part.

Therefore, unlike conventional heat treatment that involves reheating after the temperature of the weld zone has dropped (200°C), the residual heat of the weld zone can be used to replenish the amount of heat to prevent the temperature of the weld zone from decreasing using a post seam heater. Since the temperature is maintained at a predetermined temperature or the temperature is gradually cooled, the following effects can be obtained.

(1) As shown in the embodiments of FIGS.
-2,400kW (Figure 7) to 700kW (Figure 9)
can be significantly reduced.

In addition, the total power required for welding and post-heating as shown in the examples in Figures 7 and 9, including preheating the edge before the V-seam weld, is also Conventional 700+2.400-3.100kW (7th
) to 700 + 500 + 700 - 1,900 kW (Fig. 9).

(2) If the material of the pipe is steel, it can be continued to be heated with a post seam heater at the temperature of the austenitic state, so it is possible to apply constant temperature heat treatment etc. to give the welded part excellent strength and toughness. .

Next, we installed a preheating means for the opposite edge in front of the seam weld, and welded by setting the frequency of the welding power supplied from the power source to the V seam weld to be about three times higher than the conventional one. An example will be described.

In Figure 1, in order to perform welding at the V-seam weld, power is supplied from the power source 7 to the V-seam weld through the contacts 6a and 6b, and generally speaking, the higher the frequency, the more efficient the power for welding. It is preferable to be able to increase the However, as mentioned above, the higher the frequency, the stronger the edge effect becomes, and as shown in FIG.
A portion of the outer corner overheats, making it impossible to obtain flat heating from the end surface.

Furthermore, as the frequency becomes higher, the skin effect becomes stronger, and the current flows in a concentrated manner on the surface, making it impossible to obtain an effective heating depth from the end face. For these reasons, if the frequency is too high, good welding results cannot be obtained, so conventionally, electric power with a frequency of 100 kHz to about 450 kHz has been used.

FIG. 11 illustrates the relationship between the capacity and frequency of the welding power supplied to the V-seam weld. In the diagram■
The −■−■ curve is an induction type using an induction heating coil.
Moreover, the curves (■-■-〇) show examples of the conventional contact type shown in FIG. The reason why the frequency is low in the range of large capacity for both curves is mainly because as the capacity increases, it becomes difficult to effectively input power to the welding part at a high frequency due to the circuit configuration. be.

By the way, when the opposite edge is preheated by supplying power with a frequency of 50 kHz or less with a preheating means before the V-seam weld as described above, the welding power supplied to the V-seam weld The frequency of the power used for this purpose can be made much higher than in the past.

Fig. 12 shows an example of the equipment configuration of this embodiment method, and Fig. 13 shows a temperature schedule characteristic curve diagram of the welded part. Power is supplied. 7 is a power source for welding, and 1.100 through a matching transformer TF.
Power at a frequency of kHz is supplied to the V-seam weld.

As shown in FIG. 13, the temperature of the edge of the tube material is heated to 900° C. by the preheating means 11. Since the frequency of the heating power at this time is as low as 50 kHz or less, as mentioned above, heating is performed in a nearly flat manner over some of the corners and the center of the edges, and heating is performed to a deep range from the end surface. . Further, since the V-seam welded part is welded by additionally heating and raising the temperature to the melting temperature, the above-mentioned problems are much less likely to occur even if the frequency of the electric power for welding is increased. In addition, if the pipe material is a steel pipe, the temperature at the edge has already risen to a temperature in the non-magnetic region above the Curie point due to preheating, so even if the frequency of welding power is increased, the current Penetration depth: △ (cm) -5,03J p/μ・f (where p: specific resistivity of tube material (μΩ-cm), μ: relative magnetic permeability, f: frequency (Hz)) is magnetic Since it is large compared to the area, it is difficult to be influenced by the skin effect. Therefore, the frequency of electric power for welding can be made much higher than in the past.

As a result of welding by changing the frequency of the electric power for welding, we found that the frequency was 1, which corresponds to more than three times the conventional frequency.
Even at 500 kHz we were able to obtain better welding results than before. The curve ■-■-■ shown in Fig. 11 shows an example of the case where edge preheating is performed according to the method of this embodiment in comparison with the conventional example, and the frequency range is within the shaded range ■. Good welding results were obtained in all cases.

Note that the reason why the frequency is lower in the range where the capacitance is large is due to the same reason as mentioned above.

By increasing the frequency of electric power for welding in this way, it was possible to increase electrical efficiency and reduce the capacity of the power source. Also, when the frequency is increased, the voltage value of the welding power supplied to the V-seam weld is increased and the current value is decreased (
can do.

This reduces the value of the welding current flowing through the V-seam portion, thereby reducing electromagnetic repulsion. Therefore, it reduces the repeated ejection of molten metal and spatter caused by electromagnetic force near the welding point, reduces pulsation in the weld, prevents oxide entrainment and penetrator defects, and smooths the weld bead. This had a great effect on obtaining good welding results. These things greatly contribute to solving the third problem mentioned above.

H1 Effects of the invention As described above, according to the invention, the following effects can be obtained in welding thick-walled pipes.

(a) Since the generation of spatter during welding is drastically reduced, it is possible to prevent the generation of eaves at the pipe mouth body, improve the quality of the pipe, and protect the pressure roll etc. from damage and insulation deterioration.

(b) The inclusion of oxides in the weld zone and the occurrence of defects such as pinholes can be prevented, and the quality of the weld zone can be improved by smoothing the weld bead.

(c) Since the range of allowable welding heat input conditions for sound welding is expanded, the difficulty in welding thick-walled pipes is greatly alleviated, making welding work easier and reducing the defective rate.

(d) The heating area at the edge of the material becomes nearly flat, and the temperature at the center becomes sufficient for welding. Therefore, in order to obtain a good weld, it is difficult to use an excessive pressure roll as in the conventional method. There is no need to apply pressure.

(e) The hardness of the welded part is reduced, resulting in a welded part with excellent toughness, and damage to the cutting machine when cutting the pipe can be reduced.

(f) When the material of the pipe is steel, the welded part can be post-heated (post-heat treated) from the austenitic state, so it is possible to apply constant temperature heat treatment such as aus tempering to impart excellent strength and toughness.

(g) It is possible to significantly reduce the amount of power required for post-heating (post-heat treatment) of the welded part, and furthermore, the amount of power required for the entire amount of power including welding.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing an embodiment of the invention, Figures 2 to 4 show details of the inductor in the embodiment of Figure 1, Figure 2 is a plan view, and Figure 3 is a side view. 4 is an enlarged cross-sectional view taken along the Y-Y line in FIG. Temperature rise curve diagram, Figure 6 (B) is an explanatory diagram showing the heating temperature distribution at the edge of the material, Figure 7 is a configuration diagram showing a conventional example when a post heater is combined, and Figure 8 is a diagram showing the heating temperature distribution at the edge of the material. Figure 9 is a temperature schedule characteristic curve diagram, Figure 9 is a configuration diagram showing another embodiment of the present invention when a post heater is combined,
FIG. 10 is a temperature schedule characteristic curve diagram in FIG. 9, FIG. 11 is a diagram of the relationship between output power and frequency of the V-seam weld, FIG. 12 is a configuration diagram showing another embodiment of the present invention, and FIG. 13 is a temperature schedule characteristic diagram in FIG. 12, FIGS. 14A, B, and C are explanatory diagrams showing the heating temperature distribution state of the edge portion of the material, and FIG. 15 is a block diagram showing another embodiment of the present invention. , FIG. 16 is a specific circuit diagram of FIG. 15. 11...Inductor, 12.13...Outer conductor, 14.
...Edge heating conductor, 15.16...Terminal, 17.18
... Iron core, 19... Power supply. 2 people outside 14 Figure 2 Figure 3 Figure 4 (Y-Y Yue Yue) Figure 5 (text) 500 1000 1500 Capacity (W)

Claims (4)

[Claims] (1) Forming the tube material into a tube shape with a V-shaped gap,
In a high-frequency ERW pipe welding line that continuously electrically welds the opposing edges of this V-shaped gap, welded ERW pipes with an inductor installed to preheat the opposing edges in front of the V-seam weld. In the device, the inductor has an edge heating conductor that is open and disposed between opposing edges, and has magnetic cores on the outer and inner circumferential sides of the tube body of the conductor, and W≧S/2 (
W: the dimension in which the outer and inner cores overlap with one edge; S: the distance between the opposing edges), and by supplying power at a frequency of 50 kHz or less to the inductor, A high-frequency electric resistance welding pipe welding device characterized by preheating. (2) A power supply device for preheating and welding, characterized in that the power supply device is equipped with a power supply device that shares a forward conversion section and is provided in parallel with an inverse conversion section whose output can be adjusted. High frequency electric resistance welding pipe welding equipment. (3) Forming the tube material into a tube shape with a V-shaped gap,
In a high frequency electric resistance welding pipe welding line that continuously electrically welds the opposite edges of this V-shaped gap, a preheating means for the opposite edges is provided in front of the V-seam weld, and a means for preheating the opposite edge is provided in the rear of the V-seam weld. A high-frequency electric resistance welding pipe welding device characterized in that a post seam heater is disposed close to the V-seam welding part, and the residual heat of the welding part is used to continuously perform post-heat treatment of the welding part. (4) Forming the tube material into a tube shape with a V-shaped gap,
A high frequency electric resistance welding pipe welding device that continuously electrically welds the opposing edges of this V-shaped gap is equipped with a means for preheating the opposing edges in front of the V-seam welding part, and uses electric power with a frequency of 50 kHz or less. A high-frequency electric resistance welding pipe welding device is characterized in that the frequency of the welding power supplied from the power source to the V-seam welding area is increased to a high frequency of around 1,500kHz at the highest. .