JP3704206B2 - Induction heating work coil and induction heating method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating work coil and an induction heating method used for heating when a long metal material such as a metal tube or a metal rod is joined in a lengthwise direction.
[0002]
[Prior art]
As means for butt-joining metal pipes such as steel pipes or metal bars such as steel bars in the length direction, welding such as MIG welding and TIG welding, pressure welding, diffusion bonding, and the like are known. In diffusion bonding, there is also a method in which an insert metal made of an amorphous metal foil is sandwiched between both materials to be bonded, and the elements contained in the metal are diffused into both materials by heating under pressure.
[0003]
In this diffusion bonding method, since the amorphous metal element in the insert metal is easily diffused, it is possible to perform heating and bonding in the atmosphere. Therefore, it has been attracting attention as an inexpensive and simple joining means to replace MIG welding and TIG welding in field construction of oil well steel pipes.
[0004]
The present inventors have proposed a brazing material for a truncated cone ring made of a rapidly solidified foil and a method for producing the same in Japanese Patent Application Laid-Open No. 5-123890 as an insert metal for butt joining such as a steel pipe. As shown in FIG. 10, the end face of the pipe 13 and the pipe 14 to be joined is processed, and one pipe 13 has a concave taper, and the other pipe 14 has a conical taper ring. A convex taper is formed, and the truncated cone ring bonding material 12 is sandwiched between the two tapers and heated under pressure.
[0005]
In these joints, in the case of welding, heating for heat treatment after welding is necessary depending on the material. In the case of pressure welding or diffusion bonding, heating for bonding is required. As the heating means, induction heating is widely adopted, and an appropriate frequency is selected according to the required heating depth of the material to be heated. By the way, there is a problem that when the base material other than the joint is heated at the time of heating at the time of joining or heat treatment after joining, there is a problem that material deterioration such as strength reduction occurs, so the heating part is necessary on both sides of the joint. It is desirable to limit to a minimum narrow range.
[0006]
Conventional induction heating uses a coil that surrounds the material to be heated. Therefore, in order to narrow the heated portion, it is necessary to close the coil or reduce the number of turns. However, in order to increase the winding density of the coil, there is a restriction in terms of maintaining insulation between the windings. When the number of turns is reduced, it is necessary to pass a large current through the coil in order to heat the heating part to a predetermined temperature. The power supply must be large and large. Moreover, when using the coil which surrounds the to-be-heated material like the past, since the magnetic flux leaks except the part enclosed by the coil, the efficiency of heating falls.
[0007]
JP-A-5-69024 discloses a plate edge heater and a heating device for butt joining, in which an induction heater composed of a coil and an iron core is disposed in a heating portion. However, the technique of this publication cannot be applied to heating of a limited part in the length direction of a metal tube or a metal rod.
[0008]
[Problems to be solved by the invention]
In the present invention, when metal pipes such as steel pipes or metal bars such as steel bars are butt-joined in the length direction, a part limited in the length direction, such as heating at the time of joining or heat treatment after joining, is induced. A first object of the present invention is to provide a work coil and a heating method for heating, which do not have a problem in maintaining insulation of the coil, and do not require an increase in capacity and size of a power source.
[0009]
In addition, in the above-described joining or the like, in order to perform induction heating using a coil surrounding the heated material, the heated material 1 is inserted into each coil 4 of the work coil as shown in FIG. Must be mounted at the center in the length direction of the work coil.
In field construction such as oil well pipes, a work coil can be easily attached before joining, but after joining, it may be difficult to move the work coil over a long distance in order to remove it from a long steel pipe, etc. is there.
[0010]
In view of this, the present invention provides an arbitrary material to be heated at the time of heating such as when joining a long metal material such as a metal tube or a metal rod in the length direction with an insert metal sandwiched and heating under pressure to perform diffusion bonding. It is a second object of the present invention to provide a work coil for induction heating and a heating method that can be divided in the circumferential direction, which can be easily attached and detached at the position.
[0011]
[Means for Solving the Problems]
The present invention apparatus for achieving the above object, and arranged in a ring surrounding the core and coil are both on the same circumferential of the material to be heated, the core-side is an end of the center iron with allowed to position inside of the ring The induction heating work coil is characterized in that both ends of the core side are close to each other with a shielding plate in between, and the coil is wound around an iron core . And it is preferable that an iron core is divided | segmented into the circumferential direction of a to-be-heated material, and the coil is formed for every divided | segmented iron core.
[0012]
In addition, the method of the present invention for achieving the above object is that the work coil of the present invention forms a circuit of magnetic flux passing through the entire cross section of the heated portion of the heated material, and induces an induced current in the heated material facing each other. Is an induction heating method characterized in that
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The work coil of the present invention will be described with reference to an example shown in the drawings. FIG. 1 is a perspective view showing a state in which the material 1 is mounted on a material to be heated 1. FIG. 2 is a longitudinal sectional view thereof and FIG. 4 is a transverse sectional view thereof. As shown in FIGS. 1 and 4, the work coil of the present invention has a ring shape in which both the iron core 3 and the coil 4 surround the same circumference of the heated material 1. As shown in FIG. 2, the core 3 has the core side 7 positioned on the inner side of the ring and is close to the shield plate 5 with the shielding plate 5 interposed therebetween. The core side 7 is an end portion of the iron core 3 shown in FIG.
[0014]
The shielding plate 5 is configured by sandwiching plates made of a magnetic shielding material such as copper, copper alloy, aluminum or the like with an insulating plate 6 as shown in FIG. As the insulating plate 6, a glass cloth or the like can be employed. Further, the shielding plate 5 may have a structure in which cooling water is cooled inside to prevent heating. The shielding plate 5 may be inclined as shown in FIG. 5, for example, in addition to being perpendicular to the surface of the heated material 1 as shown in FIG.
[0015]
When such a work coil of the present invention is mounted on the material to be heated 1 and the coil 4 is connected to the power source 16 and a current such as high frequency is passed through, the magnetic flux 8 is generated from the end of the iron core 3 as shown in FIG. Since a circuit that passes through the restricted portion of the material to be heated 1 is formed, an induced current is generated in the restricted portion and heated. By positioning, for example, the joint portion 2 in the center of the restricted heating portion, the joint portion 2 and necessary portions on both sides thereof can be selectively heated.
[0016]
And, according to the work coil of the present invention, the core side 7 of the iron core 3 is close to each other, so that a circuit in which the magnetic flux 8 passes through the entire cross section of the heated portion of the heated material 1 as shown in FIG. And the entire thickness range of the material to be heated 1 is heated. On the other hand, as shown in FIG. 6B, when the core side 7 is separated, a portion where the magnetic flux 8 does not pass in the heated portion of the heated material 1 is generated. It becomes insufficient.
[0017]
The iron core 3 can be made of electromagnetic steel, soft ferrite, or the like. The coil 4 may be a single turn as shown in the example of FIG. 2 or a plurality of turns as necessary. In addition, the coil 4 is heated by passing an electric current, and further heated by heat transfer from the heated material 1 to be hollow and water-cooled when there is a risk of deformation or melting. And it is preferable to interpose the heat insulating material 11 between the to-be-heated material 1 and the iron core 3. FIG. The heat insulating material 11 may be attached to the heated material 1 side of the iron core 3.
[0018]
In a preferred embodiment of the work coil of the present invention, as shown in FIG. 7, the iron core 3 is divided in the circumferential direction of the material to be heated 1, and a coil 4 is formed for each of the divided iron cores 3. In the example of FIG. Each of the divided iron cores 3 and 3 is locked by a hinge 9 and a stopper 10 and mounted in a ring shape surrounding the same circumference of the heated material 1. Hinges 9 and fasteners 10 are magnetically insulated from the iron core 3 and are electrically insulated from the coil 4. Like the shielding plate 5, a magnetic shielding material such as copper is sandwiched between insulating plates such as glass cloth. It is preferable to shield with an object.
[0019]
When joining a long metal material using the work coil of this preferred aspect, after attaching the part where the divided portions are connected in advance to one metal material and joining the other metal material before joining Then, the position is adjusted so that the joint becomes the center, and a current such as a high-frequency current is passed through each of the coils 4 and 4 to perform induction heating. After the heating is finished and the joining portion is joined, the work coil can be easily removed by removing the stopper 10 and opening the hinge 9. Further, the divided portions can be connected and mounted at a required heating site of the material to be heated 1, or can be mounted at an arbitrary site and moved to the required heating site. Removal can also be performed at any position.
[0020]
During heating, for example, in diffusion bonding of steel via an insert metal made of an amorphous metal foil, the temperature of the heated material 1 is as high as about 1200 ° C. Therefore, in order to protect the work coil, the heated material A heat insulating material 11 is wound around 1. The number of turns of the coil 4 is appropriately determined according to the material of the material to be heated 1 and heating conditions. In the case of a plurality of windings, a distance is maintained such that each coil 4 is not short-circuited, and an insulator is interposed as necessary.
[0021]
Diffusion bonding with an amorphous metal foil as in the above example can be performed cheaply and easily compared to other bonding means such as MIG welding, TIG welding, or pressure welding. Suitable for joining steel pipes and bars in various construction work sites. By adopting the present invention, it is possible to easily attach and detach and join even in places where it has been difficult or impossible to attach and detach the work coil.
[0022]
The work coil of the present invention can be applied to diffusion bonding between metal bars in addition to the above-described example of the metal tube. Further, the present invention is not limited to diffusion bonding, and can also be applied to heating when heat-welding metal pipes, metal rods or metal wires, heat treatment after welding, and the like. Further, the split work coil 15 can be mounted on the ring-shaped heated material 1 as shown in FIG. 8 and heated. In this case, the to-be-heated material 1 is not restricted to a joining part, As shown by the arrow, heating, such as heat processing, can also be performed over the full length, running the to-be-heated material 1.
[0023]
In addition, the workpiece coil or the material to be heated 1 of the present invention can be provided with a rotation mechanism and rotated in the circumferential direction to uniformly heat the material to be heated 1 in the circumferential direction.
The work coil of the present invention is not limited to the material to be heated 1 having a circular cross section as described above, but can be applied to various shapes such as a square. In this case, the shapes of the ring-shaped iron core 3 and coil 4 are set to match the shape of the material 1 to be heated.
Furthermore, it is good also as a structure which provides a cooling device in the edge part of the work coil of this invention, and prevents that except a heating site | part is heated by heat conduction.
[0024]
Next, according to the method of the present invention, the work coil of the present invention forms a circuit of magnetic flux 8 that passes through the entire cross section of the heated portion of the material to be heated 1, and causes an induced current to be generated in the material to be heated 1 facing. It is the induction heating method characterized. As shown in FIG. 6A, the induced current is generated by the magnetic flux 8 that concentrates from the core side 7 of the iron core 3 to the limited part of the heated material 1 and passes through the entire cross section. The part is selectively heated uniformly.
Then, according to the method of the present invention, the distance between the material to be heated 1 and the work coil is maintained at an appropriate interval, and the temperature of the material to be heated is detected and the power is controlled as necessary, thereby meeting the purpose of the material to be heated 1. High-precision heating can be performed.
[0025]
【Example】
Steel pipes were diffusion-bonded using the work coil of the present invention as shown in FIG. The steel pipe has STK400 defined in JIS G 3444, an outer diameter of 264.4 mm, an inner diameter of 228.8 mm, and a wall thickness of 17.8 mm. A convex taper and a concave taper with an inclination angle α = 45 ° as shown in FIG. 10 are processed at the pipe ends of both steel pipes, and fitted with the frustoconical ring bonding material 12 as an insert metal of amorphous metal foil. And heated under a load of about 900 kg. The insert metal is an amorphous alloy foil having a composition composed of Fe-9 wt% Si-1.5 wt% B and has a thickness of 30 μm.
[0026]
The work coil is a two-divided type with an inner diameter of 330 mmφ, and each iron core 3 and 3 is formed of soft ferrite. The width of the heated material 1 in the length direction (a in FIG. 2) is 40 mm. The number of turns of each coil 4, 4 is two. Each of the coils 4 and 4 is a copper pipe having an outer diameter of 10 mmφ, water-cooled through the inside, and covered with a glass cloth to prevent a short circuit due to contact between the coils. The interval between the end portions of the iron cores 3 and 3 was 10 mm, and a copper plate shielding plate 5 sandwiched between glass cloth insulating plates 6 was interposed. Further, a cylindrical ceramic fiber having an initial thickness of 15 mm was wound around the material to be heated 1 as the heat insulating material 11.
[0027]
The power source 16 connected to each of the coils 4 and 4 is a small high-frequency power source with a maximum output of 50 kW and a frequency of 8 kHz. With this power source, the secondary power was induction-heated at 40 kW, heated to 1200 ° C. at a rate of temperature increase of approximately 8 ° C./second, held for 5 minutes, then turned off and allowed to cool. After cooling, the fastener 10 was removed, the hinge 9 was opened, and the work coil was removed. The removed work coil was sufficiently usable for the next joining. Further, the strength and toughness of the joint were sufficient as a structural member.
[0028]
【The invention's effect】
In the present invention, when a long metal material such as a metal tube or a metal rod is butt-joined in the length direction, the portion limited in the length direction is induction-heated, such as heating of the joint or heat treatment after joining. Thus, a limited and narrow range of heating part can be heated to a predetermined temperature over the entire cross section, and material deterioration such as a decrease in strength of the base material can be suppressed at a part outside the heating part. Further, there is no problem in maintaining the insulation of the coil, and it is not necessary to increase the capacity and size of the power source.
[0029]
Moreover, since the preferable aspect of this invention is made into the structure which can divide | segment the induction heating work coil in the circumferential direction of a to-be-heated material, long metal materials, such as a metal pipe, a metal bar, or a metal wire, insert metal is used. It is easy to attach and detach during heating, such as when joining in the length direction, heating under pressure and diffusion bonding, etc., and heating easily even in places where induction heating was difficult or impossible in the past be able to.
Therefore, it is suitable for on-site construction of oil well pipes or for joining and heat treatment of steel pipes and bars in various construction works.
[0030]
Moreover, it is applicable not only to diffusion bonding but also to heat treatment and heat treatment after welding when metal tubes, metal rods, or metal wires are pressed together. Further, both ends of a metal wire or the like can be abutted and joined into a ring shape, or can be applied to heat treatment or processing of a ring-shaped material.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an application example of a work coil of the present invention.
FIG. 2 is a longitudinal sectional view showing an example of a work coil of the present invention.
FIG. 3 is a cross-sectional view showing an example of a shielding plate in the work coil of the present invention.
FIG. 4 is a cross-sectional view showing an example of the work coil of the present invention.
FIG. 5 is a longitudinal sectional view showing another example of the work coil of the present invention.
6A and 6B are cross-sectional views showing the operation of a work coil, in which FIG. 6A is an example of the present invention, and FIG. 6B is a comparative example.
FIG. 7 is a cross-sectional view showing another example of the work coil of the present invention.
FIG. 8 is a perspective view showing another application example of the work coil of the present invention.
FIG. 9 is a perspective view showing an example of a conventional work coil.
FIG. 10 is an explanatory view of a method for diffusion bonding metal tubes with an insert metal interposed therebetween.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heated material 2 ... Joining part 3 ... Iron core 4 ... Coil 5 ... Shielding board 6 ... Insulating plate 7 ... Core side 8 ... Magnetic flux 9 ... Hinge 10 ... Stopper 11 ... Heat insulating material 12 ... Frustum ring joining material 13,14 ... Pipe 15 ... Work coil 16 ... Power supply

Claims (3)

Configured in a ring shape surrounding the core and coil are both on the same circumferential of the material to be heated, the core-side is an end of the center iron with allowed to position inside of the ring, close across the shield plate between the core-side ends The induction heating work coil is characterized in that the coil is wound around an iron core . The induction heating work coil according to claim 1, wherein the iron core is divided in a circumferential direction of the material to be heated, and a coil is formed for each of the divided iron cores. An induction heating method characterized by forming a circuit of magnetic flux passing through the entire cross section of the heated portion of the heated material by the work coil according to claim 1 or 2 and generating an induced current in the heated heated material facing each other. .

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