JP2674797B2 - High frequency induction heating device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-frequency induction heating device for pipes, and more particularly to a high-frequency induction heating device suitable for bending pipes.

[Prior Art] Conventionally, in this type of high-frequency induction heating device, as shown in Fig. 5, there is a heating coil 18 having a rectangular cross section surrounding a pipe P, and a cooling ring 19 having a trapezoidal cross section on the front side thereof. Yes, a high-frequency current is passed through the heating coil 18 to heat the pipe P, while the cooling liquid passed through the heating coil 18 is cooled by a cooling ring.
The pipe P is cooled by injecting from the hole of 19 as shown by reference numeral 7, and the width of the heating portion 14 is controlled. In the figure, the pipe P is gradually moved to the left relative to the heating coil 18 and the cooling ring 19. As a known example of this type, there is JP-A-58-93516.

[Problems to be Solved by the Invention] However, in the above-described conventional technique, the heating coil 18 having a rectangular cross section is used.
Therefore, since the coil surface on the side of the pipe P is widened, the heating portion 14 of the pipe is widened, and it is difficult to handle the small radius bending of the pipe. Further, the width of the heating portion 14 is controlled by injecting the cooling liquid 7 onto the pipe surface from the cooling ring 19 on the front side of the heating coil 18 at a constant angle, but the pipe heating plate is controlled by the collision pressure of the cooling liquid on the pipe P. The return of the cooling liquid to 14 occurs, the return amount is not constant in the circumferential direction of the pipe, and
Since the connection between the heating coil and the conductor that supplies current to the heating coil is wide, the temperature of the heating section 14 is uneven in the circumferential direction of the piping due to the local decrease in the magnetic flux density on the piping side. Therefore, there is a problem that the bent pipe has a large thickness reduction rate and a large ovalization rate.

As described above, in the conventional technology, the width of the pipe heating part is widened, the return of the cooling liquid to the heating part cannot be prevented, and the uniform magnetic flux density in the circumferential direction cannot be obtained. There was a problem that it was difficult to cope with small radius bending due to.

The object of the present invention is to prevent the return of the coolant to the pipe heating part, to impart a uniform magnetic flux density in the circumferential direction, to narrow the width of the pipe heating part, thereby making the pipe uniform in a narrow width. The purpose of this is to make it possible to reduce the ovalization rate of pipes and the wall thinning rate during heating and high-frequency induction heating bending, and to cope with bending with a small radius.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a high-frequency induction heating device according to each of the claims.

[Operation] Cooling liquid is injected to the pipe while high-frequency induction heating is performed by the ring coil, and immediately after that, the purge gas is obliquely injected to the pipe from the purge gas ring. The gas that collided with the pipe and flowed forward prevents the coolant injected from the ring coil from colliding with the pipe and trying to return to the pipe heating area, preventing the return of the cooling liquid to the heating area. To do. The inside of the ring coil is divided into two chambers, and a large number of holes are appropriately formed in the partition wall, and the cooling liquid injected from the injection port into the first chamber is equalized and ejected from the second chamber. All of the cooling liquid is at a constant pressure when it collides with the pipe. By making the joint of the conductor supplying the high-frequency current to the coil thin with the coil, it is possible to prevent a decrease in the magnetic flux density at the coil end. Since the coil has a cross-sectional shape with corners protruding toward the piping side, the width facing the piping becomes narrower even though the coil surface area can be increased and the current capacity of the coil can be increased, thus reducing the heating width of the piping. It becomes possible. By these, the temperature of the pipe heating region becomes uniform in the pipe circumferential direction, the deformation resistance of the pipe material to be processed becomes uniform, and the processing force in the pipe circumferential direction becomes constant. Further, since the heating width is narrow, the working area is narrowed, so that it is possible to prevent buckling on the inside of the pipe bending during pipe bending, reduce the wall thinning rate on the outside of the pipe bending, and reduce the ovalization rate.

[Examples] One example of the present invention will be described below in order from the drawings.

FIG. 2 is a schematic view of the apparatus of this embodiment as seen in the axial direction, in which the pipe P to be bent is set inside the coil ring 3. The coil ring 3 has current supply conductors 2 and 2 ', a coolant injection pipe 1, and a purge gas injection pipe 4
Are combined.

FIG. 1 shows a cross section of the coil ring 3 as seen in FIG. 2A-A. In FIG. 1, the pipe P is gradually moved to the left relative to the coil ring 3.
The coil ring 3 is made of copper and has a structure in which the hollow purge gas ring 5 and the cooling ring coil 8 are integrated. The coil ring 3 high-frequency induction-heats the pipe P by the high-frequency current flowing through it. At the same time, the purge gas is injected from the purge gas injection pipe 4 into the purge gas ring 5, the purge gas cools the coil ring 3, and the reference numeral 6 is applied to the surface of the pipe P from the numerous holes 5 ′ of the purge gas ring coil 5. It is jetted diagonally as shown. On the other hand, a cooling liquid (for example, water) is injected into the first chamber 81 of the cooling ring coil 8 from some cooling liquid injection pipes 1 and then passes through the multiple holes 9 to the second chamber 82 of the cooling ring coil 8. As a result, the cooling liquid in the second chamber 82 has a uniform pressure and is jetted obliquely from the multiple holes 8'of the second chamber 82 onto the surface of the pipe P as indicated by reference numeral 7. Thereby, the heating part of the pipe P is cooled and the width of the heating part is controlled. When the injected cooling liquid 7 collides with the pipe P, a part of the liquid tries to return to the heating portion of the pipe P (that is, rightward in FIG. 1). Gas 6
Is blocked at any position in the circumferential direction of the pipe.
When the cooling liquid flows in the cooling ring coil 8,
The cooling ring coil 8 is cooled, and the purge gas ring 5 integrated with the cooling ring coil 8 is also cooled by heat conduction.

FIG. 4 shows the heating / cooling status of the pipe P according to this embodiment. The pipe P gradually moves to the left relative to the coil ring 3. By the high-frequency current flowing through the coil ring 3 via the current supply conductors 2 and 2 ′, the portion of the pipe P facing it is heated (in the figure, reference numeral 14 indicates the heating portion) and subsequently cooled. It is cooled with liquid 7. FIG. 4 shows how the purge gas 6 prevents a part of the cooling liquid that has collided with the pipe P from returning to the heating portion 14.

Next, FIG. 3 shows the connection between the coil ring 3 and the current supply conductors 2, 2'in the above device. The current passage is forcibly restricted by making the connecting portion 10 a thin current passage restricting portion as shown in the drawing. As a result, the current is applied to the coil ring 3
Since it passes near the gap between the two ends of the pipe, it is possible to prevent the decrease in magnetic flux density at the position near the gap 12 where the conventional magnetic flux density decreased and the temperature rise effect on the pipe was not good. Since it is possible to give a magnetic flux density of, it is possible to obtain a uniform temperature distribution in the circumferential direction of the pipe. In order to prevent reduction in mechanical strength due to narrowing of the current passage restricting portion 10, a reinforcing plate 11 made of an insulating material is connected to the coil ring 3 and the current supply conductors 2 and 2'to provide mechanical strength. is there. The gap 12 may be filled with an appropriate insulating plate.

In the prior art, since the portion corresponding to the current connection portion 10 is widened, there was a problem that the current mainly passes through that portion, and the magnetic flux density decreases at the inner position near the gap 12, but in the embodiment of the present invention. The problem is solved by forming the narrow current passage restricting portion as described above.

In the prior art shown in FIG. 5, the cooling ring 8 is provided in front of the heating coil 5 having a rectangular cross section, and the heating coil 5 is connected to the pipe P.
Is heated, the cooling liquid 7 is sprayed to cool the pipe P, and the heating area
14 is formed in the pipe P. Therefore, the width of the heating area becomes wide, and the return of the cooling liquid 7 to the heating area 14 becomes large,
It is difficult to obtain a uniform temperature distribution.

On the other hand, in the apparatus according to the embodiment of the present invention, as shown in FIG.
Since it is injected at the same angle as, the heating part (heating area) of the cooling liquid 7
It is possible to prevent the return to 14. Further, the purge gas ring 5 and the cooling ring coil 8 have a one-piece structure to improve heat conduction and prevent the temperature rise of the coil ring 3 due to radiant heat of the pipe and self-heating. In addition, as shown in FIGS. 1 and 4, the cross-sectional shape of the coil ring 3 has a pipe P
Since the coil ring area on the pipe P side is reduced by forming the shape with corners protruding toward the pipe P,
The width of the heating area 14 is narrowed to reduce the wall thinning rate and the ellipticity rate of the pipe bending portion.

FIG. 6 shows the processing temperature distribution of the pipe by the conventional device and the device of the present invention, and FIG. 7 shows the ellipticity and the wall thinning rate of the pipe bending part. White circles indicate the case of the embodiment of the present invention, and black circles indicate the case of the conventional device. When the embodiment of the present invention is used for the line shown in FIG. 6, a uniform temperature distribution can be made in the circumferential direction, and as shown in FIG. 7, the ellipticity and the wall thinning rate can be improved. It is possible.

FIG. 8 shows another embodiment of the present invention, in which the cooling liquid 7 is sprayed substantially at right angles to the pipe to narrow the pipe heating region, and gas is purged from behind to cool the cooling liquid back into the heating region. It was designed to prevent it.

FIG. 9 shows still another embodiment, which is a cooling ring coil 16
A high-frequency current is applied to the pipe P to heat the pipe P, the cooling ring coil 16 is cooled with a cooling liquid, and the cooling liquid 7 is jetted from the cooling ring coil 16 to the pipe P. The purge gas 6 is sprayed from the gas ring 17 to the pipe to prevent the cooling liquid 7 from returning to the pipe heating area.

EFFECTS OF THE INVENTION According to the present invention, by injecting the purge gas from the rear of the injection cooling liquid that controls the heating area of the pipe, it is possible to apply a uniform processing temperature in the pipe circumferential direction, and to bend the pipe. It is possible to reduce the thinning rate and ellipticity rate of the processed part. In addition, by providing a current path restriction part to the coil ring, it is possible to prevent local decrease in magnetic flux density and to achieve high-frequency induction heating that is uniform in the circumferential direction. By making it have a shape and reducing the coil ring area on the pipe side, the width of the heating area of the pipe can be narrowed and it becomes possible to handle small diameter bending of the pipe. Therefore, it is possible to perform high-quality pipe bending with a low ovalization rate and a low wall thickness reduction rate.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an apparatus of the present invention, FIG. 2 is a schematic front view of the apparatus, FIG. 3 is a view showing a current supply conductor connecting portion in the apparatus, and FIG. 4 is heating / cooling of the apparatus. FIG. 5 shows a state, FIG. 5 shows a heating / cooling state of a conventional device, FIG.
FIG. 7 is a diagram showing machining temperature distributions of the conventional example and the embodiment of the present invention, FIG. 7 is a diagram showing an ellipticity rate and a wall thinning rate diagram of the pipe bending process, FIG. 8 and FIG. 9 are other examples. FIG. 1 ... Coolant injection pipe, 2, 2 '... Current supply conductor, 3 ... Ring coil, 4 ... Purge gas injection pipe, 5 ... Purge gas ring, 6 ... Purge gas, 7 ... Coolant , 8 ... Cooling ring coil, 9 ... Hole, 10 ... Current passage control part, 11 ... Insulating plate reinforcing plate, 14 ... Heating area, P ... Piping.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Kanazawa 3-1-1, Sachimachi, Hitachi, Ibaraki Hitachi, Ltd., Hitachi Works, Ltd. (56) References JP 61-273220 (JP, A) Actual Kai 61-143711 (JP, U)

Claims (4)

(57) [Claims] 1. A high-frequency induction heating apparatus for surrounding a pipe with a ring coil through which a high-frequency current flows, and axially moving the pipe relative to the ring coil to heat a sequential portion of the pipe. The coil is hollow, and the cooling liquid is caused to flow inside and the cooling liquid is jetted from the ring coil to the downstream side of the heating area as viewed in the pipe moving direction, and the pipe is formed by collision of the cooling liquid with the pipe. A purge gas ring for obliquely injecting a purge gas is provided upstream of the collision position of the cooling liquid and the pipe so as to prevent the pipe from returning to the heating region, and the ring coil has a sectional shape facing the pipe. A high-frequency induction heating device, characterized in that the side forms a corner protruding with respect to the pipe. 2. The high frequency induction heating device according to claim 1, wherein a joint portion of the conductor supplying the high frequency current to the ring coil and the ring coil is thinly constricted. 3. The ring coil has a ring-shaped first chamber in which a cooling liquid is injected from a cooling liquid injection pipe, and a ring-shaped second chamber communicating with the first chamber by a large number of holes. The high frequency induction heating device according to claim 1 or 2, wherein the cooling liquid is injected from the second chamber to a pipe. 4. The high frequency induction heating device according to claim 1, wherein the ring coil and the purge gas ring are in contact with each other and integrally formed.