JPH0514472Y2 - - Google Patents

Description

[Detailed explanation of the idea]

A. Industrial Application Field The present invention relates to the arrangement of an inductor in an electric resistance welded tube local heat treatment device. B. Summary of the invention This invention is a device that locally heats the vicinity of the welded part of a running electric resistance welded pipe by induction heating, in which at least three inductors are sequentially arranged along the heat treatment line, and at least one of them is The inductor is arranged to face the center of the heat-treated part in the circumferential direction, and at least one other inductor is arranged near the opposite end of the heat-treated part in the circumferential direction. By induction heating the part to be heat-treated, the welded part to be heat-treated and the heat-affected zone around it can be uniformly heated.This allows for energy-saving and smooth heat treatment, and the overall length of the equipment can be shortened. It was possible to do so. C. Prior Art It has already become common practice to provide an inductor in an ERW tube welding line to anneal or normalize the ERW tube welded portion to improve the quenched structure and hardened portion. Furthermore, in recent years, quenching and tempering heat treatments have been applied to welded parts to improve low-temperature embrittlement. For example, referring to FIGS. 7 and 8, reference numeral 1 indicates an electric resistance welded tube running in the direction of the arrow, and a V-seam portion formed by gradually bending the band plate on the left side of the figure as it runs. 2 is supplied with high frequency power by an induction coil 3, and a welding point 5 at the tip of the V-seam portion is welded by squeeze rolls 4, 4. 6 is a high frequency power source. Further, 7, 7, . . . are a plurality of inductors for annealing or normalizing provided facing the welding portion 8 and on a straight line. In this way, inductors 7, 7...
ERW pipe 1 is provided with multiple at intervals.
This is to reduce the temperature difference between the inner and outer surfaces when the outer surface of the welded portion 8 is heated by induction while running, and the temperature is further increased to the inner diameter surface by heat conduction in the thickness direction. By the way, the inductor 7 is a conductor 1 through which current flows, as shown in FIGS.
0 (excluding the surface facing the welded part 8) is surrounded by an iron core 9. Further, the conductor 10 is made of a rectangular cross-section pipe having a hole through which cooling water passes. Then, as shown in Fig. 9, the conductor 1
Both ends of the conductor 10 are connected to a power source, and an induced current induced by the alternating current flowing through the conductor 10 flows into the electric resistance welded tube 1, and this induced current is particularly applied to the welded part 8 where the inductor 7 is opposed. Since the flow is concentrated, the temperature of the weld zone increases. Figure 6A shows the temperature in the circumferential direction of the ERW tube 1 when heated by a single inductor 7 while changing the gap G between the ERW tube 1 and the inductor 7 (see Figures 9 and 10). An example of the distribution is shown, and as can be seen from the figure, the electric resistance welded tube 1 is heated within a range approximately corresponding to the conductor width Wc of the inductor 7. and inductor 7
A temperature peak occurs at a portion facing the widthwise center of the conductor 10, and the gap G between the ERW tube 1 and the inductor 7 increases to G ₁ , G ₂ , and G ₃ . The temperature peak becomes gentle. however,
Of course, the heating efficiency deteriorates. FIG. 6B is a diagram showing an example of temperature distribution in a cross section of the electric resistance welded tube 1 using isothermal lines. D Problems to be solved by the invention By the way, the area to be heat treated is the welded part of the ERW tube and the heat-affected zone on both sides, but in order to completely cover this part, the actual heat treatment area is further circumferential. The area is rather wide on both sides of the direction. As the wall thickness of the pipe increases, the heat-affected zone also expands on both sides of the weld, and the range of heat treatment becomes correspondingly wider. Furthermore, in the quenching and tempering heat treatments, the quenching range is similarly wider than the heat-affected zone, and in order to completely cover this quenching range, the tempering range is wider in the circumferential direction. These heat-treated ranges are graphically shown in FIG. 10 as the welded portion 8 and the heat-treated portions 12 indicated by diagonal lines on both sides of the welded portion 8, which must be heated within a predetermined temperature range. The reason for this is that in order to perform heat treatment, the temperature of the heat-treated portion 12 must be raised to a predetermined heat treatment temperature or higher, but on the other hand, if the temperature is too high, the crystal grains will become coarse, which is inappropriate. Therefore, the temperature at point a, the center of the outer surface where the temperature rises most easily (this is referred to as T ₁ ), is kept below the upper limit temperature for proper heat treatment, and from the center on the inner diameter side, where the temperature rise is the slowest. The temperature at distant points _d1 and _d2 (these are referred to as _T2 ) needs to be lower than the lower limit temperature for proper heat treatment ( _T1 > _T2 ). Nahoko's
It is desirable that the temperature difference between T ₁ and T ₂ be as small as possible. Therefore, temperature distribution not only in the thickness direction but also in the circumferential direction is important. However, in a heating device using conventionally arranged inductors 7, as shown in FIG. It is within the range corresponding to the width of . Therefore, the conductor width of the inductor in Fig. 10
It was necessary for Wc to satisfy Wc≧Wh with respect to the width Wh of the heat-treated portion 12 in the circumferential direction. Furthermore, a sharp temperature peak occurs at the circumferential center of the heated portion of the ERW tube 1, and such an inductor 7
Since multiple units are arranged in a straight line along the running direction of the ERW pipe 1, that is, along the heat treatment line, if point a in Fig. 10 is heated to the appropriate temperature, the heating temperature at points d _{1 and 2} will be insufficient. , Conversely, if points d ₁ and d ₂ are heated to the appropriate temperature, point a will be heated excessively,
On the other hand, there was a delay in the temperature rise at points _A1 and _A2 . In this way, in order to uniformly heat the heat-treated area 12 which is wide in the circumferential direction due to an increase in the wall thickness of the electric resistance welded tube 1, quenching near the welded part, tempering heat treatment, etc., the inductor 7 is required.
As the conductor width Wc becomes larger, the device becomes larger and heavier, and it is difficult to uniformly heat the device, making conventional heating devices unsuitable. In addition, conventionally, in order to compensate for the above-mentioned drawbacks, the only way to make the temperature uniform is through heat conduction in both the width direction and the wall thickness direction. A plurality of inductors 7, 7, etc. are provided at large intervals in the running direction, but with this, it takes time to equalize the temperature in both the width direction and the wall thickness direction, and it is difficult to make the temperature uniform. This was difficult, and the amount of heat dissipated during that time also increased, making it difficult to improve thermal efficiency. Furthermore, as shown in FIG. 7, since a plurality of inductors 7, 7, . . . are used at large intervals, the line of the device becomes long. However, as mentioned above, one of the reasons why the heating of the heat-treated part 12 is uneven is that the electric current penetration depth is shallow while the wall thickness of the ERW tube 1 is thick (for example, 16 mm or more). However, if the frequency is lowered in order to increase the penetration depth, it becomes difficult for the inductor 7 to effectively supply power to the electric resistance welded tube 1. In other words, there is a problem that the heating efficiency deteriorates. An object of the present invention is to provide a local heating device for an electric resistance welded tube that solves the above-mentioned drawbacks. E. Means for Solving the Problems The present invention is a device for locally heating the vicinity of the welded part of a running electric resistance welded pipe by induction heating, in which at least three inductors are sequentially arranged along the heat treatment line. At least one inductor is disposed facing the center of the heat-treated portion in the circumferential direction, and at least one other inductor is disposed at each opposite end of the heat-treated portion in the circumferential direction. It is characterized in that it is arranged closer to the side and the part to be heat treated is heated by induction. F Example The present invention will be described below with reference to FIGS. 1 to 5. 1, 2, and 3 are plan views showing a first embodiment, a second embodiment, and a third embodiment of the present invention. That is, in FIG. 1, an example of the arrangement of three inductors 7 is shown, and the first stage inductor 7 located furthest in the direction of movement of the ERW tube 1 is placed in the heat-treated portion 12.
The second stage inductor 7 and the third stage inductor 7 are arranged opposite to the circumferential center (that is, the welding part 8) of the heat-treated part 12 at the left and right ends in the circumferential direction. An example is shown in which it is placed closer to the side. FIG. 2 shows an example of the arrangement of four inductors 7. The arrangement of the inductors 7 in the first to third stages is the same as that in FIG. 1, and the inductor 7 in the fourth stage is Like those in the second stage, they are disposed to face the center of the heat-treated portion 12 in the circumferential direction. FIG. 3 shows an example of the arrangement of five inductors 7, with the first stage inductor 7 placed in the heat-treated area 1.
The inductors 7, 7 of the second and third stages are arranged to face each other at the center in the circumferential direction of the two, and the inductors 7, 7 of the second and third stages are arranged largely left and right from the center. 7
shows an example of placement slightly to the left and right from the center. Although not shown in the figure, the number of inductors 7 may be six or more, but in any case, each inductor 7...as a whole is arranged in a well-balanced manner on the left and right sides with respect to the center of the heat-treated portion 12. It's good. Therefore, FIG. 4 shows the temperature rising process of the heat-treated part 12 by the inductor arrangement of the first embodiment of the present invention shown in FIG. 1, and FIG. The figure shows the process of increasing the temperature of the heat-treated part 12 due to the conventional linear arrangement of inductors on the welded part, and will be explained below by comparing each figure. In each figure, t ₁ indicates the upper limit temperature for heat treatment of the part to be heat treated, and t ₂ indicates the lower limit temperature for heat treatment.
(The figure shows an example in which three inductors are arranged _, so the third _stage inductor) ，
If the temperatures of c ₁ , d ₁ , d ₂ ) are within the range of t ₁ and t ₂ above, the entire area to be heat treated has been heated within the appropriate heat treatment temperature range, and good heat treatment has been performed. be done. However, according to the conventional inductor arrangement shown in FIG. 5, as can be seen from the temperature curve shown in the same figure,
The temperatures at each point a, a ₁ , b, c ₁ of the heat-treated portion 12 after being heated by the inductor 7 of the third stage, which is the final stage, are t ₁ (heat treatment upper limit temperature) and t ₂ (heat treatment upper limit temperature). The temperature at point a has already reached t ₁ , but the temperature at point d ₁ and d ₂ (d ₁ = d ₂ ) farthest from the center is within the temperature range between The temperature is below t ₂ . In other words, when heating the heat-treated portion 12 which is wide in the circumferential direction, it is difficult to enter the appropriate heat treatment temperature range near d ₁ and d ₂ . Therefore, in the case of such a conventional heating device, in order to heat the points d ₁ and d ₂ to a temperature higher than t ₂ , it is necessary to increase the temperature of each inductor 7.
It is necessary to take measures such as further increasing the conductor width Wc at , further widening the interval between each inductor 7, or further increasing the number of inductors 7 to four or more. However, all of these problems include an increase in the size and weight of the device due to the increase in the width of the inductor 7, an increase in the length of the heat treatment line, and an increase in the manufacturing cost of the device.
This results in an increase in power consumption for heating. On the other hand, according to the inductor arrangement of the present invention shown in FIG.
The area near point b is heated mainly, and by shifting the second stage inductor 7 to the right, the area near points a _{1 and} d is mainly heated, and the third stage inductor 7 is shifted to the left. Due to the staggered arrangement, the area around the _two points a ₂ and d is mainly heated. As a result, when the heat-treated portion 12 passes through the third stage inductor 7, which is the final stage, as can be seen from the temperature curve in the same figure, d ₁ , which is least likely to be heated,
It can be seen that the temperature difference between point _d and point a, which is easy to heat, is small, and it is easy to raise the temperature of the entire heat-treated part to within the appropriate heat treatment temperature range. Furthermore, in the heating using the inductor arrangement of the present invention, a plurality of inductors 7 on the heat treatment line are arranged alternately toward the center and both ends of the heat-treated portion 12 of the ERW tube 1 in the circumferential direction. Since heating is performed, the conductor width Wc of the inductor 7 may be smaller than the width Wh of the heat-treated portion. Therefore, the device including the inductor 7 can be made smaller and lighter. Furthermore, when comparative experiments were conducted using the respective inductor arrangements shown in FIG. 1 and FIG. 8, the following results were obtained. For the experiment, an electric resistance welded tube with a wall thickness of 16 mm was used.
The line was run at a line speed of 13 m/mm, and the power consumption required to heat the heat-treated area 12 near the weld to a predetermined temperature range centered around 560°C was investigated.

[Table] From the above comparative experiment, it was found that the heating device with the inductor arrangement of the present invention provides the following effects compared to the conventional one. The heat treatment target area can be uniformly heated over a wide range, and the width of the heating range can be adjusted. Total power consumption reduced to 1110kw compared to before.
→630kw, approximately 43% reduction, which is a great energy saving effect. Since it is not necessary to make the conductor width Wc of each inductor 7 larger than the width Wh of the heat-treated part, the weight of the heating device can be reduced from 2.4 to 1.0 compared to the previous one due to miniaturization.
(weight ratio) can be reduced to approximately 42%, reducing the device weight and manufacturing cost. The heat treatment line length can be shortened. G. Effects of the invention As described above, according to the heating device of the invention,
at least three arranged sequentially along the heat treatment line.
At least one of the inductors on the stand is placed in the center of the heat-treated area in the circumferential direction, and at least one other inductor is placed toward the opposite end of the center. Since each inductor is installed in the welded section of the ERW tube and its heat-affected zone, the area to be heat-treated can be uniformly heated in a short time, and the heat treatment of this area can be carried out smoothly. , and the width of the heating range can be easily adjusted. In addition, since heat can be soaked in a short time, less heat is radiated to the outside, making it possible to perform heat treatment with less energy. For example, when an electric resistance welded pipe with a wall thickness of 16 mm is run at a line speed of 13 m/mm and the area near the welded part is heated to a predetermined temperature range centered around 560 degrees Celsius, the proposed inductor arrangement is more effective than the conventional inductor arrangement. The total power used by the inductor can be reduced by more than 40%, resulting in energy savings. Furthermore, the present invention has the effect of making it possible to downsize the heating device, reduce its weight by more than 50%, and reduce manufacturing costs accordingly. Furthermore, by using the inductor of the present invention, as mentioned above, it is possible to uniformize the temperature near the welded part of the ERW pipe in a short time, so it is possible to uniformly heat the area near the welded part of the ERW pipe. Since it is possible to shorten the interval between the two or to reduce the number of installed inductors, the total length of the heat treatment equipment line can be shortened.

[Brief explanation of the drawing]

1A, 2, and 3 are plan views showing examples of inductor arrangement according to the first, second, and third embodiments of the present invention, and FIG. 1B is a side view of the tube. , Figure 4A
FIG. 4B is an explanatory diagram showing the inductor arrangement according to the present invention and the temperature increase process at each point of the heat-treated portion of the tube due to the inductor arrangement according to the present invention.
is a side view of the tube in FIG. 4A, FIGS. Figure A is an explanatory diagram showing the conventional inductor arrangement and the temperature increase process at each point in the heat-treated portion of the tube, Figure 5B is a side view of the tube in Figure A, Figures 5C, D, and E. are the knee line and hole in figure A.
An explanatory diagram showing the heating area of the tube at the E line and the Hee line, FIG. A diagram showing an example of temperature distribution in the cross section of the tube corresponding to Figure A using isothermal lines, Figures 7A and 8 are front and plan views of a heat treatment apparatus with a conventional inductor arrangement, and Figure 7B is an electric resistance welding A cross-sectional view of the tube, Figure 9 is a perspective view of the main parts of the heat treatment equipment with arrows indicating the current flowing in the inductor and the induced current flowing in the ERW tube, and Figure 10 is the welded part of the tube heated by the inductor. FIG. 3 is an explanatory diagram showing a nearby heat-treated portion. 1... ERW pipe, 7... Inductor, 8... Welded part,
9... Iron core, 10... Conductor, 12... Part to be heat treated.

Claims (1)

[Scope of utility model registration request] An inductor is installed opposite the welded part of a traveling ERW pipe with a predetermined distance from the ERW pipe, and the apparatus locally heats the vicinity of the welded part by induction heating using the inductor. Three inductors are sequentially arranged at predetermined intervals, at least one of them is arranged facing the center in the circumferential direction of the heat-treated part near the welding part, and at least each 1. A local heating device for an ERW tube, characterized in that each inductor is disposed closer to the opposite end of the heat-treated portion in the circumferential direction to inductively heat the heat-treated portion.