JP6389697B2 - Bending metal pipe manufacturing method, metal pipe bending apparatus and coil - Google Patents

Description

  The present invention relates to a bending metal tube manufacturing method, a metal tube bending apparatus, and a coil, and more particularly, to a heating coil suitable for hot bending a thick metal pipe.

  Metal pipes are used to transport liquid or gaseous substances in various industrial facilities such as factories, plants, pipelines, and power plants. In particular, metal pipes used in pipelines and power plants are increasingly being applied to harsher environments.

  For example, high-strength steel materials are used in pipelines that transport oil, natural gas, etc., and the need for large-walled thick pipes has increased in recent years due to the increase in pipelines for the deep sea. . In thermal power plants, pipes are being made thicker in order to improve power generation efficiency by increasing the temperature and pressure. Furthermore, instead of the conventional carbon steel, a material such as an alloy steel or a superalloy having a high high-temperature strength may be used as a constituent material of the metal tube.

  For such metal pipes, standardized and pre-shaped shaped pipes such as elbows and bends are used, while straight pipes are bent according to the construction object (“bending pipes”). Is widely used because it can flexibly meet the demands for various curvatures and pipe shapes.

  In order to manufacture a bent tube, generally, as shown in FIGS. 6 to 8, a part of a straight metal tube 11 to be processed is annularly heated by an induction heating coil 12 that is supplied with a high-frequency current. The metal tube 11 is pushed toward the induction heating coil 12 while holding the front end side (tube tip side) of the metal tube 11 with respect to the induction heating coil 12 by the clamp arm 31. The clamp arm 31 pivots around the support shaft 32 and restricts the path of the metal tube 11 in an arc shape. The clamp arm 31 propels the metal tube 11 while holding it, so that the induction heating coil 12 A bending moment is applied to the heated portion, and the metal tube 11 can be continuously plastically deformed so as to draw an arc having a radius R around the support shaft 32. FIG. 8 shows an example in which the induction heating coil 12 is configured by two coil portions (two-turn windings) 12c and 12d.

  Further, there is the following patent document as a technique for disclosing a technique related to the high-frequency bending of such a metal tube.

JP 2009-012062 A JP2013-010109A JP 2014-065072 A

  By the way, when performing high-frequency bending of a metal tube, if the tube thickness is increased, the inner surface temperature of the tube is less likely to increase with respect to the outer surface temperature of the tube, and the temperature difference between the inner and outer surfaces of the tube increases.

  This temperature difference between the inner and outer surfaces means that the average temperature of the tube cross-section is low even when heated so that the temperature of the tube outer surface is the same, which increases the deformation resistance of the tube and propels the metal tube during processing. A large thrust force is required, which causes a problem that the size of the tube that can be processed is limited. In particular, compression bending requires a very large thrust, which causes a problem that the size of a workable tube is greatly limited. In addition, high strength steel materials used for pipelines are secured by water cooling and quenching immediately after bending deformation, but when the inner surface temperature of the tube does not rise sufficiently, the strength of the tube is ensured. There may be situations where it is impossible.

  On the other hand, it is conceivable to increase the processing temperature in order to avoid such a situation. However, if the temperature of the inner surface of the tube is simply raised, the outer surface of the tube will be heated to a temperature higher than necessary, so that the soundness of the material may be impaired and the quality of the metal tube may be deteriorated. In addition, it is conceivable to slow down the processing speed (metal pipe propulsion speed) in order to raise the temperature of the pipe inner surface, but there is a limit to slowing down the feed speed of the pipe, and production is made as much as the speed is slowed down. Efficiency will decrease.

  Accordingly, it is an object of the present invention to provide a technique related to a new coil that performs high-frequency bending of a metal tube, particularly a heating coil that can favorably perform bending of a thick-walled tube.

  In order to solve the above problems and achieve the object, a method for manufacturing a bent metal tube according to the present invention heats a part of a metal tube in an annular shape with a coil, and can grip a position near a heating portion of the metal tube and The metal tube is gripped by a clamp arm that can be pivoted around a support shaft that is separated from the gripping portion by a certain distance, and the metal tube is propelled in the direction of the axis of the material, thereby rotating the gripping portion by the clamp arm and Bending metal that bends the metal tube by applying a bending moment to the heated portion of the metal tube by guiding it so as to curve in an arc and plastically deforming at least a part of the metal tube into a curved state continuously In the method of manufacturing a pipe, the coil includes a first coil part and a second coil part arranged so as to be arranged in order in the propelling direction of the metal pipe. Metal tube is driven at a higher output than the second coil portion of the first coil portion to be heated to a processing temperature by parts.

  In the conventional bending process, as shown in FIGS. 6 to 7 and Patent Documents 1 to 3, the portion of the metal tube immediately before the clamp arm is simply heated by a coil consisting of one turn of winding, or the above-mentioned Even when a coil having a plurality of coil portions (for example, a two-turn winding as shown in FIG. 8) is used as in the present invention, conventionally, the same power is applied to each coil portion without any particular change. It was usual to drive with output (equivalent power supply to each coil part).

  On the other hand, in the manufacturing method of the present invention, the coil includes the first coil portion and the second coil portion arranged so as to be sequentially arranged in the propelling direction of the metal tube as described above, and at the time of bending The first coil unit is driven with a larger output than the second coil unit so that the metal tube is heated to the processing temperature by the first coil unit. In other words, the coil according to the present invention is arranged in the first coil portion arranged on the rear side (the side far from the clamp arm) and in the front side (the side near the clamp arm) in the propulsion direction of the metal tube. A metal tube that includes the second coil portion, wherein the first coil portion is a main heating coil that raises the temperature of the metal tube to the processing temperature, and the second coil portion is raised by the first coil portion. Is maintained at the processing temperature (the metal tube is heated so that the temperature of the tube heating section heated to the processing temperature by the first coil section is maintained at the processing temperature).

  According to such a manufacturing method of the present invention, the metal tube that has advanced to the coil arrangement region is quickly heated so as to reach the processing temperature from the beginning, and this temperature is maintained. Bending can be performed with a small deformation resistance by sufficiently raising the temperature to the inner surface of the tube. In particular, the compression bending requires a very large thrust, and therefore the effect of suppressing the thinning is increased by making the deformation resistance small. Even when a crack is generated by receiving a tensile force at a high temperature, the tensile strain can be reduced and the crack can be suppressed by performing compression bending. Moreover, since the tube inner surface temperature can be sufficiently increased with respect to a material requiring high strength, sufficient strength can be ensured by quenching.

  In addition, the coil according to the present invention has the same coil width (width dimension in the traveling direction of the metal tube) as that of the conventional coil or the same peak temperature of the outer surface of the tube, compared with the conventional coil. Since the temperature difference can be reduced, the coil according to the present invention can of course be applied to a non-thick tube, but is particularly effective for a thick tube.

  The bending apparatus according to the present invention has the same characteristics as the above manufacturing method. Specifically, the bending apparatus includes a coil for heating a part of the metal tube in an annular shape, a propulsion device for propelling the metal tube in the material axis direction, a position near the heating part of the metal tube, and the A clamp arm pivotable about a support shaft that is spaced from the gripping part by a certain distance, grips the metal tube by the clamp arm, and pushes the metal tube toward the coil to pivot the gripping part by the clamp arm. By guiding at least a part of the metal tube so as to be curved, a bending moment is applied to the heated portion of the metal tube, and at least a part of the metal tube is continuously plastically deformed into a curved state, thereby A bending apparatus for bending, wherein the coil includes a first coil part and a second coil part arranged so as to be arranged in order in the propulsion direction of the metal tube, It is a main heating coil that heats the metal tube to the processing temperature by being driven with a larger output than the coil unit, and the second coil unit is a heat insulation coil for keeping the heating part of the metal tube at the processing temperature. is there.

  The coil according to the present invention also has the same characteristics as the manufacturing method described above, and is a coil that is provided in a bending apparatus for a metal tube and heats a part of the metal tube in an annular shape. A first coil portion and a second coil portion arranged so as to be arranged in order in the tube propulsion direction, and the first coil portion is driven with a larger output than the second coil portion, thereby This is a main heating coil that partially heats to the processing temperature, and the second coil portion is a heat retaining coil for maintaining the heating portion of the metal tube heated by the first coil portion at the processing temperature.

  According to the present invention, in hot bending of a metal tube, the metal tube can be quickly heated to the inner surface to prevent an increase in deformation resistance, and in particular, a thick tube can be favorably bent. Moreover, since the tube inner surface temperature can be sufficiently increased with respect to a material requiring high strength, sufficient strength can be ensured by quenching.

  Other objects, features, and advantages of the present invention will become apparent from the following description of embodiments of the present invention described with reference to the drawings. Note that the present invention is not limited to these embodiments, and it will be apparent to those skilled in the art that various modifications can be made within the scope of the claims. Moreover, in each figure, the same code | symbol shows the same or an equivalent part.

FIG. 1 is a plan view schematically showing a bending apparatus (initial state) according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing the bending apparatus (the state during processing) according to the embodiment. FIG. 3 is a cross-sectional view (A-A cross section of FIG. 1) of the coil placement portion (metal tube) of the bending apparatus according to the embodiment. FIG. 4 is a diagram showing the temperature change of the outer surface of the metal tube and the temperature change of the inner surface when processing is performed by the bending apparatus according to the embodiment. FIG. 5 is a diagram showing the temperature change of the outer surface of the metal tube and the temperature change of the inner surface when processing is performed by a conventional bending apparatus. FIG. 6 is a plan view schematically showing a conventional bending apparatus (initial state). FIG. 7 is a plan view schematically showing a conventional bending apparatus (state during processing). FIG. 8 is a plan view schematically showing another conventional bending apparatus (initial state).

  As shown in FIGS. 1 to 3, a bending apparatus according to an embodiment of the present invention includes an induction heating coil 12 that heats a part of a metal tube 11 to be processed in an annular shape, and a metal tube 11 facing the coil 12. A bending mechanism is applied to the metal tube 11 by rotating around the support shaft 32 as the metal tube 11 is propelled. A clamp arm 31 and a compression mechanism 21 that generates a pullback force that is a force in the direction opposite to the propulsion of the metal tube 11 and applies a compression force to the metal tube 11 are provided.

  1 to 3 show the front, back, left, right, up and down directions, and the present embodiment will be described based on these directions. Further, in the figure, symbol C is the center line of the metal tube 11, symbol R is the bending radius of the metal tube 11, symbol 11a is the inner surface of the metal tube 11, symbol 11b is the outer surface of the metal tube 11, and symbol t is the metal. Reference numeral 13 denotes a guide roller for guiding the metal tube 11.

  The propulsion mechanism 14 that propels the metal tube 11 includes a rear clamp 15 that holds the rear portion of the metal tube 11 and a propulsion drive unit 16 that applies a forward propulsive force to the metal tube 11 through the rear clamp 15. The propulsion drive unit 16 is constituted by, for example, a hydraulic cylinder.

  On the other hand, the compression mechanism 21 that applies a compression force to the metal tube 11 is fixed to the lower end portion of the clamp arm 31 and rotates together with the clamp arm 31 around the support shaft 32 of the clamp arm 31 (see arrow P4). The chain 23 meshes with the sprocket 24, and the compression drive unit 22 that generates a pulling back force P5 that pulls the chain 23 in the direction opposite to the propulsion direction of the metal tube 11 (rearward). The compression drive unit 22 may be constituted by, for example, a hydraulic cylinder.

  Note that the propulsion mechanism 14 and the compression mechanism 21 are not limited to specific structures, and the propulsion mechanism 14 in the present invention is capable of propelling the metal tube 11, and the compression mechanism 21 is a metal tube. Any structure can be used as long as it can apply a compressive force to 11 and is not limited to the illustrated structure. Further, if compression bending is not performed, the compression mechanism may not be provided.

  The coil 12 that heats the metal tube 11 is disposed behind the clamp arm 31. The coil 12 is composed of an induction heating coil, and a main heating coil portion 12a for raising the metal tube 11 to a processing temperature (a temperature for plastic deformation and a maximum temperature during processing), and also an induction heating coil and a main heating. And a heat retaining coil portion 12b that keeps the temperature of the metal tube 11 raised by the coil portion 12a at the processing temperature.

  Both of these coil parts 12a and 12b are driven by a drive part (not shown) including a power source for supplying high-frequency power, but the heating coil part 12a is supplied with high-frequency power compared to the heat retaining coil part 12b. Increase the amount. This is because the temperature of the metal tube 11 is quickly increased to the processing temperature by the main heating coil portion 12a, and the temperature is maintained by the heat retaining coil portion 12b to increase the average temperature of the tube cross section. Prevent increase in resistance (necessary thrust). Further, since the heat retaining coil portion 12b only needs to maintain the temperature raised by the main heating coil portion 12a, the power input amount may be smaller than that of the main heating coil portion 12a.

  To describe a specific example, in the apparatus of the present embodiment, for example, 70% of power is supplied to the first stage heating coil section 12a, and 30% of power is input to the second stage heating coil section 12b, for example. In the present invention, the first coil portion and the second coil portion can be driven in different ways by driving the first coil portion with a larger output than the second coil portion. It can also be said that the current is supplied to each coil part so that the current density of the coil part becomes larger than the current density of the second coil part. Further, in the present embodiment, the heating coil portion 12a and the heat retaining coil portion 12b are each provided with one coil portion (one turn winding), but each of the coil portions 12a and 12b is either One or both may be composed of a plurality of coil portions (windings of two or more turns).

  Further, a cooling mechanism capable of injecting cooling water so that the metal tube 11 can be cooled immediately after bending (the cooling mechanism itself is not shown, but the cooling water injected from the cooling mechanism is indicated by reference numeral 10 in FIG. 2). Is integrally formed with the coil 12 (the heat retaining coil portion 12b), and during processing, the cooling water 10 is sprayed toward the outer surface 11b of the metal tube 11 immediately in front of the coil 12 (the heat retaining coil portion 12b), and heated and bent. The obtained metal tube 11 is cooled.

  In processing, the rear portion of the metal tube 11 is held by the rear clamp 15 and the front portion of the metal tube 11 is held by the front clamp 33, and the metal tube 11 is pushed forward by the hydraulic cylinder 16 via the rear clamp 15 (arrow). P1).

  When the metal tube 11 is propelled forward (see arrow P2), the clamp arm 31 receives the propulsive force P2 and rotates horizontally around the support shaft 32 (see arrow P3) to grip the metal tube 11. The front clamp 33 is pivoted to draw an arc around the support shaft 32. Along with this, a bending moment is applied to the metal tube 11 held by the front clamp 33, the portions heated by the coil 12 are bent one after another, and the metal tube 11 is continuously plastically deformed in an arc shape (FIG. 2). reference).

  On the other hand, in order to reduce the tensile strain of the metal tube 11 (bending outer peripheral side) or prevent the thinning of the pipe outer peripheral side (thinning becomes thinner with bending), the following compression bending may be performed. .

  The sprocket 24 rotates and the chain 23 is taken up by the rotation of the clamp arm 31 accompanying the propulsion of the metal tube 11, and a force (retracting force backward) P <b> 5 is resisted by the compression drive unit 22. 23 and the sprocket 24, it is applied to the clamp arm 31. As a result, a compressive force in the material axis direction is applied to the metal tube 11 to reduce the tensile strain generated in the metal tube 11 during the bending process, or to suppress the thinning of the metal tube 11 on the outer peripheral side of the bending. I can do it.

  FIG. 4 shows the temperature change of the inner and outer surfaces 11a and 11b of the metal tube when the metal tube having a large thickness t is processed by the bending apparatus according to this embodiment. (Part) approaches the coil 12 as the metal tube 11 is propelled (as time elapses), enters the coil 12 and is heated, and then escapes from the coil 12 and is cooled by the cooling water 10. The temperature change up to is shown for each of the tube inner surface 11a (broken line) and the tube outer surface 11b (solid line). FIG. 5 shows the temperature change of the inner and outer surfaces 11a and 11b of the metal tube when the same metal tube is processed by a conventional apparatus, as in FIG.

  As can be seen from FIGS. 4 and 5, according to the apparatus (FIG. 4) of this embodiment, the temperature difference between the pipe outer surface 11b and the pipe inner surface 11a can be reduced as compared with the conventional apparatus (FIG. 5). A tube having a large wall thickness t does not have a particularly high temperature on the inner surface 11a compared to the outer surface 11b, and its deformation resistance increases compared to a tube having a smaller wall thickness t. Even for such a thick tube, the deformation resistance can be kept smaller than that of the conventional apparatus. In addition, even for high-strength steel materials that require high strength such as pipes for pipelines, the inner surface temperature of the pipe can be made sufficiently high, so that sufficient strength can be secured by quenching. .

C Center line of metal tube R Bending radius 11a Inner surface of metal tube 11b Outer surface of metal tube t Thickness of metal tube 11 Metal strip (metal tube)
12 Induction heating coil 12a Main heating coil portion 12b Thermal insulation coil portion 12c First stage coil portion (winding of the first turn)
12d 2nd stage coil (2nd turn winding)
13 Guide roller 14 Propulsion mechanism 15 Rear clamp 16 Propulsion drive unit 21 Compression mechanism 22 Compression drive unit 23 Chain 24 Sprocket 31 Clamp arm 32 Support shaft 33 Front clamp

Claims (3)

While heating a part of the metal tube in an annular shape by a coil,
The metal tube is gripped by a clamp arm that can pivot about a support shaft and can hold a position near the heating portion of the metal tube that is spaced from the support shaft by a certain distance ,
A bending moment is applied to the heating portion of the metal tube by propelling the metal tube in the direction of the material axis and pivoting the gripping portion by the clamp arm to guide at least a part of the metal tube to be curved in an arc. And bending the metal tube by continuously plastically deforming at least a part of the metal tube into a curved state, and manufacturing the bent metal tube,
The coil includes a first coil portion and a second coil portion arranged in order in the propulsion direction of the metal tube,
During the bending process,
While driving the first coil part with a larger output than the second coil part so that the metal tube is heated to the processing temperature by the first coil part ,
The temperature difference between the tube outer surface and the tube inner surface of the heating portion of the metal tube is reduced so that the temperature of the heating portion of the metal tube heated to the processing temperature by the first coil portion is maintained at the processing temperature. Thus, the metal tube is heated by the second coil portion as described above . A coil for heating a part of the metal tube in an annular shape;
A propulsion device for propelling the metal tube in the material axis direction;
A clamp arm capable of turning around a support shaft and gripping the vicinity of the heating portion of the metal tube at a certain distance from the support shaft;
The metal tube is gripped by the clamp arm, and the metal tube is propelled toward the coil so that the gripping portion by the clamp arm is turned and guided so that at least a part of the metal tube is curved in an arc. A bending device for a metal tube that applies a bending moment to the heating portion of the metal tube to bend the metal tube by plastically deforming at least a part of the metal tube into a continuously bent state,
The coil includes a first coil portion and a second coil portion arranged in order in the propulsion direction of the metal tube,
The first coil portion is a main heating coil that heats the metal tube to a processing temperature by being driven with a larger output than the second coil portion,
Said second coil part, characterized in that the heating portion of the metal tube is kept coils for reducing the temperature difference between the tube outer surface and the inner surface of the heating portion of the coercive Chi and the metal tube to the processing temperature Metal pipe bending machine. A coil that is provided in a bending apparatus for a metal tube and heats a part of the metal tube in an annular shape,
The coil includes a first coil portion and a second coil portion that are arranged in order in the propulsion direction of the metal tube,
The first coil part is a main heating coil that heats a part of the metal tube to a processing temperature by being driven with a larger output than the second coil part,
The second coil portion, in order to reduce the temperature difference between the tube outer surface and the inner surface of the heating portion of the coercive Chi and the metal tube to the working temperature of the heated portion of the metal pipe heated by the first coil portion A coil characterized by being a heat insulation coil.

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