JPH11209825A - Post-welding heat treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a post-welding heat treatment equipment capable of being attained by a small-scale equipment, causing no thermal adverse effect to ambiance, and capable of repaid and accurate application of heat treatment to a specific part of a weld zone. SOLUTION: The post-welding heat treatment equipment for application of heat treatment to a weld zone with the intention of removal of residual stress in the weld zone 3, softening, improvement of metallic structure, etc., has a high frequency induction heating means 10 provided in such a manner that heat treatment can be applied to the weld zone 3 by induction heating under respectively specified conditions of heating range, heating temperature, hating time, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to welding for heat-treating a welded portion between a heat transfer tube and a tube sheet of a multi-tube heat exchanger, which is widely used in power plants and petrochemical plants, after welding. The present invention relates to a post heat treatment (PWHT) apparatus.

[0002]

2. Description of the Related Art A heat transfer tube and a tube sheet of a multi-tube heat exchanger used in a power plant or a petrochemical plant, etc., are formed in a normal case so that high-temperature and high-pressure liquid or gas heat exchange can be performed. ,
Both are integrally joined by welding. However, when the heat transfer tube is made of carbon steel or low alloy steel, the welded portion exhibits a quench hardening phenomenon during welding. When a heat transfer tube made of carbon steel or low alloy steel is used, for example, in a corrosive atmosphere (liquid) while the quench hardening phenomenon is exhibited, so-called stress corrosion cracking (SCC) occurs in the welded portion. There is a possibility that. For this reason, generally, FIG.
Post-weld heat treatment is performed using post-weld heat treatment means as shown in FIG.

FIGS. 12A and 12B show two examples of conventional post-weld heat treatment means. In all cases, the entire weld between the heat transfer tube and the tube sheet of the multi-tube heat exchanger is subjected to heat treatment to remove the residual stress, soften the weld, and improve the metal structure of the weld. It is. 12A and 12B, 101 is a heat transfer tube, 102 is a tube sheet, 103 is a welded portion,
104 is a body of the heat exchanger body, 105 is a heat insulating material, 106
Is a furnace wall, 107 is a heating panel, and 108 is a heating furnace.

The post-weld heat treatment means shown in FIG. 12A shows a case where the entire welded portion is put into a heating furnace 108 and heat-treated. The post-weld heat treatment means shown in FIG. 12B shows a case in which a heating panel (nichrome wire panel) 107 is attached around or near the welded portion 103 and heat treatment is performed by heating the entire surface of the tube sheet 102. ing.

[0005] As a literature relating to this kind of heat treatment technology, there is, for example, "Pressure vessel local welding post heat treatment procedure manual" (published by the Japan Welding Association, Chemical Mechanical Welding Research Committee, local annealing subcommittee).

[0006]

The above prior art has the following problems. The method of heating the entire weld is not particularly problematic, for example, when the devices are not restrained at the time of manufacturing the devices. However, if these devices are completely assembled in the plant and, for example, the plant is temporarily stopped during operation and repair welding is performed, and then the entire weld is heat-treated after welding, the surrounding devices are Have a significant thermal effect on This will be described below.

[0007] For example, carbon steel and low alloy steel have the characteristic that their mechanical strength is determined according to the thermal history applied during the manufacturing process. Therefore, a member made of carbon steel or low alloy steel is used before being given a predetermined heat history so as to obtain appropriate strength.

Therefore, as described above, if post-weld heat treatment is performed by, for example, heating the entire weld after repair welding, the weld is formed of carbon steel or low alloy steel existing around the weld 103. Equipment or components will receive more heat history than originally planned. For this reason, a so-called mill sheet strength may not be able to be secured for the device or member newly receiving the heat history.

In the case where the entire weld is heated,
If the temperature rise rate and the temperature fall rate during the heat treatment after welding are large, a temperature difference occurs between the tube sheet surfaces and the like, and a large thermal stress is generated. For this reason, there is a possibility that cracks or breakage may occur in each part. Therefore, it is necessary to perform heat treatment after welding for a long time.

[0010] Further, if the entire weld of the heat exchanger installed in the plant is subjected to post-weld heat treatment, there is a possibility that peripheral devices or members may be deformed due to thermal expansion. Therefore, it is necessary to take measures to prevent deformation of peripheral devices and the like. It should be noted that even if the above deformation prevention measures are taken, slight thermal deformation cannot be avoided.

[0011] Thus, the conventional post-weld heat treatment means has problems such as requiring large-scale facilities, enormous construction cost and construction period, and is formed of carbon steel or low alloy steel existing around the welded portion. Adversely affect the devices or members that are in use, which may degrade the mechanical strength of those devices or members. Also, cracks or breaks are likely to occur in each part due to the generated thermal stress, and these are prevented. Therefore, it is necessary to perform heat treatment after welding for a long time,
As a result, there are drawbacks such as the inability to perform a rapid and accurate heat treatment, and the possibility that the devices or members around the welded portion may be deformed due to thermal expansion.

It is an object of the present invention to provide a post-weld heat treatment apparatus which can be realized with a small-scale facility, has no adverse thermal effect on the surroundings, and can perform a quick and accurate heat treatment at a specific portion of a weld.

[0013]

Means for Solving the Problems To solve the above problems and achieve the object, a post-weld heat treatment apparatus of the present invention is configured as follows. In the present invention, the hardness of the material is mentioned as an effective barometer of the metal structure improvement effect, and if the material is carbon steel, it is sufficient if the material is heated to 550 ° C. or more even if the heating time is short. Basically, the effect of heat treatment after welding is to be obtained. To avoid thermal adverse effects on surrounding equipment and members, heat treatment is performed by heating only a specific area of the welded part efficiently. It is. (1) The post-weld heat treatment apparatus of the present invention is a post-weld heat treatment apparatus for performing heat treatment on the above-described welded parts for the purpose of removing residual stress, softening, improving the metal structure, etc. of the welded parts, wherein the welded parts are specified. It is characterized by comprising high-frequency induction heating means provided so that heat treatment can be performed by induction heating under conditions such as a heating range, a heating temperature, and a heating time. (2) The post-weld heat treatment apparatus of the present invention removes residual stress from the welded portion to prevent stress corrosion cracking or the like from occurring at the welded portion between the heat transfer tube and the tube sheet of the multi-tube heat exchanger. In a post-weld heat treatment apparatus for performing heat treatment on the above-mentioned welded portion for the purpose of softening, improving the metal structure, etc., the welded portion is subjected to heat treatment by induction heating under specified conditions such as a heating range, a heating temperature, and a heating time. It is characterized by comprising high-frequency induction heating means provided as possible. (3) The post-weld heat treatment apparatus of the present invention is the apparatus according to the above (1) or (2), wherein the high-frequency induction heating means comprises:
The heating of the induction heating coil is controlled in a predetermined heating cycle according to a program control signal output from the temperature program controller, the heating temperature is detected by a temperature detector, and the detection signal is transmitted to a temperature monitoring and recording means through an optical fiber, and It is characterized by including a heater control unit for feeding back to the program controller. (4) The post-weld heat treatment apparatus of the present invention is the apparatus according to the above (1) or (2), wherein the high-frequency induction heating means comprises:
It is characterized by including frequency control means capable of high-frequency induction heating at a frequency of 10 KHz or more. (5) The post-weld heat treatment apparatus of the present invention is the apparatus according to the above (2), wherein the high-frequency induction heating means has a spiral shape as a whole, and a central portion protrudes in the axial direction, and the protruding portion is formed. Is provided with an induction heating coil in the form of a truncated cone wound with two or more steps so that it can be inserted into the opening of the heat transfer tube. (6) The post-weld heat treatment apparatus according to the present invention is the apparatus according to the above (2), wherein the holding apparatus includes a support arm having a structure that can be attached to and fixed to the surface of the tube sheet. A heater provided so as to be movable in parallel with the tube sheet surface, with the induction heating coil provided at the end portion being fixed at the end portion and being kept at a fixed distance from the surface of the tube sheet. It is characterized by: (7) The post-weld heat treatment apparatus according to the present invention is the apparatus according to the above (5), wherein the induction heating coil is formed by coating an insulating material having a high insulation property and a low thermal conductivity on the outer peripheral surface of the conductive tube member. It is characterized by having been done.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a first embodiment of the present invention. It is a figure which shows a structure, (a) is a schematic explanatory drawing, (b) is the same figure (a)
FIG. 4 is an enlarged cross-sectional view showing a portion surrounded by a circle. FIG. 3C is a perspective view of a modification of the heater shown in FIG.

As shown in FIG. 1A, one end of each of a plurality of heat transfer tubes 1 of the multi-tube heat exchanger passes through the tube sheet 2 from the back side to the front side. A portion between the end and the surface of the tube sheet 2 is welded to form a welded portion 3. Reference numeral 4 denotes an outer cylinder for protecting the heat transfer tube.

The post-welding heat treatment apparatus mainly includes a heater 10 and a temperature program controller 71.
The heating is controlled by a heater controller 70 including a high-frequency power supply 72 and the like.

As shown in FIG. 1 (b), the heater 10 is formed by spirally winding a part of a conductive pipe P through which cooling water can flow to form an induction heating coil 11. The induction heating coil 11 is provided so as to face the surface of the tube sheet 2 with a predetermined gap G therebetween, and to be able to smoothly move in parallel along the surface of the tube sheet 2.

By operating the heater control unit 70 in this manner, a high-frequency alternating magnetic flux φ is generated from the induction heating coil 11 of the heater 10, and the alternating magnetic flux φ causes
And a specified region in the vicinity thereof is subjected to high-frequency induction heating, and a heat treatment is performed on the welded portion 3 after welding.

At the time of performing the post-weld heat treatment, if the frequency of the high frequency power supply 72 is controlled by the temperature program controller 71, the thickness of the tube sheet 2 (the longitudinal direction of the heat transfer tube 1) can be increased.
Is adjusted, and it is possible to intensively heat portions required for improving the weld metal structure. At the time of heat treatment of the welded portion 3, the induction heating coil 11 of the heater 10 is set at a distance such that the induction heating coil 11 faces the surface of the tube sheet 2 with a certain gap G therebetween. There is no variation in the heating temperature due to 11 and uniform heat treatment can be performed. In this way, the heating efficiency can be improved, and the adverse thermal effects on the components due to the post-weld heat treatment can be avoided as much as possible.

The heater 10 'shown in FIG. 1 (c) is that the conductive pipe P through which the cooling water can flow is spirally wound to form an induction heating coil 11'. ), But the plane area of the induction heating coil 11 ′ is formed to a size that can simultaneously cover the open ends of the plurality of heat transfer tubes 1. In addition, 12 is a heat insulating material and 13 is a ferrite core.

Thus, according to the heater 10 ', the welded portions 3 of the plurality of heat transfer tubes 1 and the tube sheet 2 can be heated simultaneously while the heater 10' is stopped at a predetermined position. Therefore, even when there are many places where heat treatment is performed after welding, heat treatment can be efficiently performed. Except for the points described above, it is the same as the case (b).

(Second Embodiment) FIG. 2 is a view showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a second embodiment of the present invention. It is. As shown in FIG. 2, the heater 20 includes an induction heating coil 21 in which a part of a conductive pipe P through which cooling water can flow is spirally wound, and a heating coil holder 22 that holds the induction heating coil 21. Has become. Heating coil holder 2
2 is a short cylindrical heating coil housing 22 having one end opened.
a and a holding cylinder 22b integrally connected to the heating coil accommodating portion 22a and penetrating the conductive pipe P into a hollow portion thereof. A temperature detector 23 including a temperature sensor such as a radiation thermometer is attached to an outer peripheral portion of the heating coil housing portion 22a.

The heater control unit 70 includes a temperature program controller 71, a high frequency power supply 72 (comprising an AC commercial power supply 72a and a high frequency inverter 72b) controlled by a control signal from the controller 71, and a high frequency power supply of the high frequency power supply 72. An output transformer 73 for supplying the output of the inverter 72b to the induction heating coil 21;
3, the detected signal is displayed, and the detected temperature information is transmitted to the temperature program controller 71.
And a temperature recorder 75 for recording the display content of the thermometer 74.

Thus, the heater control unit 70 controls the induction heating coil 2 in a predetermined heating cycle in accordance with the program control signal output from the temperature program controller 71.
1 is controlled to be heated. Further, the thermometer 74 and the temperature recorder 75 constitute a temperature monitoring and recording unit.

In the present embodiment, the induction heating coil 2
1 and the closest distance between the welding portion 3 and the heating coil holder 22.
Cylindrical heating coil housing 2 provided at the tip of
It is regulated by the peripheral wall of 2a. For this reason, it is possible to avoid direct contact between the welded portion 3 and the induction heating coil 21, and furthermore, it is possible to keep the distance between the two constant. Further, since the induction heating coil 21 is controlled to be heated in a predetermined heating cycle, the welded portion 3 can be appropriately heat-treated. Since the temperature is controlled based on the detection signal fed back from the temperature detector 23, stable and highly accurate heat treatment is performed.

(Third Embodiment) FIG. 3 is a diagram showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a third embodiment of the present invention. It is. As shown in FIG. 3A, the heater 30 in the present embodiment has an induction heating coil 31 formed in a part of conductive pipes P1 and P2 through which cooling water W1 and W2 can flow, as shown in FIG. Has a frustoconical shape wound with two or more steps so that it has a spiral shape and its central part protrudes in the axial direction. Thus, as shown in FIG. 3A, the protruding end portion is formed so as to be inserted into the opening of the heat transfer tube 1 to a predetermined depth.

The length L of the induction heating coil 31 inserted in the opening of the heat transfer tube 1 in the axial direction of the heat transfer tube 1 is set so that the heat transfer tube 1 is not unnecessarily heated and softened and deteriorated. Influence depth D (depth dimension of weld zone d + 2.0mm)
It is set as follows. Numeral 33 in the figure denotes an infrared monitoring sensor as a radiation thermometer mounted in the heater 30, which monitors the temperature of the welded portion 3 and controls the heater controller 70 (FIG. (Not shown).

As shown in FIG. 3B, the induction heating coil 31 is formed by coating an insulating material 31b such as ceramics having a low thermal conductivity on the outer peripheral surface of a conductive tube member 31a. This insulating material 31b prevents erosion due to the conductive tube member 31a coming into contact with the welded portion 3, and
This is for always keeping an insulation distance of a certain value or more between the conductive tube member 31a and the welded portion 3.

Thus, in the present embodiment, the specified region including the heat transfer tube 1 and the welded portion 3 is heated by the three-dimensional heating surface by the frusto-conical induction heating coil 31, so that the uniform heating is performed. And it becomes possible to heat efficiently. In this case, since it is not necessary to pay particular attention to the fact that the induction heating coil 31 contacts the portion to be heated, the heat treatment operation can be performed efficiently.

Further, since the infrared monitoring sensor 33 is used as the temperature detecting means and the optical fiber is used as the detection signal transmitting means, the temperature of the welded portion 3, which is the object to be heated, can be detected in a non-contact manner and in real time, and furthermore, the electromagnetic wave can be detected. Signal transmission can be performed without interfering with noise. For this reason, high-precision temperature display and recording can be performed accurately, and even when the heat treatment in which the heating cycle is completed in a relatively short time is repeated many times, a temperature sensor such as a thermocouple is attached to the object to be heated each time. Since there is no need for operations such as replacement, there is an advantage that the setting operation of the heater 30 is simplified.

(Fourth Embodiment) FIG. 4 is a view showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a fourth embodiment of the present invention. is there. As shown in FIG. 4, the heater 40 in the present embodiment
A ferrite core 44 also having a truncated cone shape is disposed in a hollow portion of a heating coil 41 having a truncated cone shape, and a water cooling jacket 45 is provided at a base portion of the ferrite core 44 in order to prevent a temperature rise of the ferrite core 44. The water cooling jacket 45 is connected to cooling water circulation pipes Q1, Q2 disposed in parallel with the conductive pipes P1, P2. Note that, instead of the ferrite core 44, another high-permeability magnetic material having a similar shape may be inserted as a magnetic core.

In this embodiment, the ferrite core 4
Due to the magnetic concentration action of 4, the density of the magnetic flux passing through the welded portion 3 can be increased. For this reason, the heating efficiency is greatly improved.

(Fifth Embodiment) FIG. 5 is a view showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a fifth embodiment of the present invention. is there. As shown in FIGS. 5A to 5C, the heater 50 according to the present embodiment has a shape in which the heaters 50 are crushed flat so as to cover the open ends of the plurality of heat transfer tubes 1 over a predetermined width dimension H. Is formed, and a flat rectangular parallelepiped ferrite core 54 is inserted into the hollow portion of the induction heating coil 51 to prevent a temperature rise of the core 54 at both end surfaces of the ferrite core 54. A pair of water cooling jackets 55a and 55b are arranged closely.
The water cooling jackets 55a and 55b have cooling water circulation pipes Q arranged in parallel with the conductive pipes P1 and P2.
1 and Q2 are connected respectively.

Thus, in this embodiment, the width dimension H
It is possible to heat and heat-treat a plurality of welds 3 simultaneously by the induction heating coil 51. Therefore, work efficiency can be greatly improved.

(Sixth Embodiment) FIG. 6 is a view showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a sixth embodiment of the present invention. is there. As shown in FIG. 6, the heater 60 in the present embodiment
Is mounted on the holding device 80 and used. As shown in the figure, the holding device 80 has a pair of support arms 81 and 82, and by inserting the distal end portions of the support arms 81 and 82 into, for example, the opening of the heat transfer tube 1, the holding device 80 is stably mounted on the tube sheet 2. It can be set. Note that the holding device 80 may be suctioned to the surface of the tube sheet 2 using a vacuum suction means.

The base ends of the support arms 81 and 82 are
It is supported in a state where it is screwed to a pair of support shafts 83 and 84 each composed of a screw rod. Therefore, the support shaft 83,
Handles 85 and 86 respectively attached to 84
Is rotated to support arms 81 and 82.
Can be moved to any position along the support shafts 83 and 84. Thus, the above-described setting operation is facilitated, and the holding device 80 can be set at an arbitrary position on the tube sheet 2.

An output transformer 87 is mounted on the holding device 80. That is, the output transformer 87 is mounted in a state where a part of the case of the transformer 87 is slidably penetrated through the guide shaft 88 and the other part of the case is screwed to the moving shaft 89 formed of a screw rod. ing. The base of the heating coil holder 62 of the heater 60 is connected to the case of the transformer 87.

When the handle 90 attached to one end of the moving shaft 89 is rotated, the output transformer 8 is rotated.
7 is driven by the moving shaft 89 and moves along the guide shaft 88. Accordingly, while the heater 60 is kept at a fixed distance from the surface of the tube sheet 2 as shown in FIG. As shown by the arrow, it can move freely in parallel with the tube sheet surface. In this case, by setting the length of the guide shaft 88 and the moving shaft 89 to be sufficiently long, in a state where the holding device 80 is set at an arbitrary position, uniform heating of the plurality of welded portions 3 located in the vicinity thereof under the same conditions is performed. Processing can be performed.

By the way, when setting the tube sheet 2 by holding the heater 60 or the like by hand, for example,
It is difficult to keep the distance between the heating coil and the induction heating coil 61 constant, and the heating temperature distribution is not stable. However, in the present embodiment, since the heater 60 is used while being mounted on the holding device 80, the distance between the welding portion 3 and the induction heating coil 61 is kept constant, and the heating temperature distribution is stabilized.

Experimental Example 1 The eddy current penetration depth δ of high frequency induction heating as a heating condition is generally calculated by the following equation.

Δ = 5.03 × 10 ² (ρ / μf) ^1/2 (δ: eddy current penetration depth ρ: specific resistance of object to be heated μ:
(Relative magnetic permeability of the object to be heated) Therefore, when the physical properties of the welded portion 3 as the object to be heated are the same, the heating depth can be changed by controlling the frequency f.

FIG. 7 is a characteristic curve diagram showing the results of an experiment in which the heating depth (current density distribution with respect to the penetration depth δ of the eddy current) was changed by controlling the frequency f. As shown in FIG. 7, by controlling the frequency f, the heating depth changes as shown by characteristic curves A to D.

As can be seen from FIG. 7, for example, the magnetic flux is effectively concentrated only on the welded portion 3 located within a depth range of 2 to 3 mm from the tube sheet surface, and this portion is directly and rapidly cooled without relying on heat conduction. For heating, as shown in the characteristic curve D, 10 KHz
It is necessary to heat at the above high frequency.

Experimental Example 2 A heater 90 having an induction heating coil 91 corresponding to the induction heating coil shown in FIGS. 3 and 4 was manufactured, and the induction heating coil 91 is shown in FIG. 8A. 50kg / mm 2nd grade carbon steel heat transfer tube 1
After the heat treatment as shown in FIG. 8B, heat treatment is performed under the heating conditions shown in FIG. 8B, and the measurement shown in FIGS. 9A and 9B. Region X1, X
2, the temperature distribution was measured for Y1 and Y2, and an experiment for confirming the effectiveness of the post-weld heat treatment of the present embodiment was performed. The heating conditions shown in FIG. 8B are as follows.

(1) Heating cycle Temperature rise: (0 ° C. to 650 ° C.) / 60 seconds Holding temperature: 650 ° C. for 120 seconds Temperature decrease: (650 ° C. to 400 ° C.) / 60 seconds Natural cooling: 400 ° C. to normal temperature (2) Supply energy Output 5KW, voltage 90V, current 55A, frequency 14KHz FIG. 9 (c) to (f) show the measurement area X1 in the welded part 3 when the holding temperature in the heating cycle reaches 650 ° C. , X2, Y1, Y2 are diagrams showing the results of actual measurement of the heating temperature distribution.

As indicated by circles in FIGS. 9C to 9F, the temperature of the welded portion 3 is slightly lower than the set value of the program, but the temperature is 550 ° C. effective for reforming the welded portion 3. It can be seen that the above is sufficiently secured.

FIG. 10 is a view showing the results of measuring the micro-Vickers hardness of the welded portion 3 in the longitudinal direction of the tube in order to confirm the above-mentioned improvement effect. As shown by curve M in FIG.
While the hardness of the thermally affected region in the welded portion 3 in the as-welded state exceeds Hv400, the heat treatment was performed by the post-weld heat treatment apparatus according to the present embodiment as shown by the curve N in FIG. In this case, the hardness is reduced to Hv250 or less.

FIG. 11A shows the hardness distribution at the root between the heat transfer tube 1 and the tube plate 2 where stress corrosion cracking (SCC) and the like are problematic, in order to confirm the above-mentioned improvement effect. It is a figure which shows the result of having actually measured about the location shown to FIG.

As shown in FIG. 11 (a), according to the result of measurement at four sections (0 °, 90 °, 180 °, and 270 °) of the welded portion 3, after the heat treatment after the welding, The hardness distribution is considerably lower than the hardness distribution as it is and has less variation, and the effectiveness or improvement effect of the post-weld heat treatment of this embodiment is apparent. (Summary of Embodiment) [1] The post-weld heat treatment apparatus according to the embodiment includes a welded part (3).
For the purpose of removing residual stress, softening and improving the metal structure of
In the post-weld heat treatment apparatus for performing heat treatment on the welded portion (3), the welded portion (3) is provided so as to be capable of being heat-treated by induction heating under specified conditions such as a heating range, a heating temperature, and a heating time. High-frequency induction heating means (10 to 80).

In the above apparatus, the high-frequency induction heating means (1
0 to 80), the desired region can be locally and efficiently heated within a short time. [2] The post-weld heat treatment apparatus according to the embodiment prevents stress corrosion cracking or the like from occurring in the welded portion (3) between the heat transfer tube (1) and the tube sheet (2) of the multitubular heat exchanger. In order to eliminate residual stress, soften the weld, and improve the metallographic structure of the weld (3), a post-weld heat treatment apparatus for performing a heat treatment on the weld (3),
The welding part (3) is provided with a high-frequency induction heating means (10 to 80) provided so as to be capable of performing heat treatment by induction heating under conditions such as a specified heating range, a heating temperature, and a heating time. Features.

In the above apparatus, the heat transfer tube (1) made of carbon steel or low-alloy steel existing around the welded portion (3) has no adverse thermal effect on other devices and members.
It is possible to perform an accurate heat treatment on a predetermined welded portion (3). [3] The post-weld heat treatment apparatus according to the embodiment includes the [1].
Or the apparatus according to [2], wherein the high-frequency induction heating means (10 to 80) heats the induction heating coil (21) in a predetermined heating cycle according to a program control signal output from the temperature program controller (71). A heater for detecting the heating temperature with a temperature detector (23), transmitting the detection signal to the temperature monitoring and recording means (74, 75) through an optical fiber, and feeding it back to the program controller (71). It is characterized by including a control unit (70).

In the above apparatus, the induction heating coil (21)
Since heating is controlled by a predetermined heating cycle programmed in advance, it is possible to accurately heat-treat the welded part (1), and the detection signal fed back from the temperature detector (23) via an optical fiber. Temperature control is performed, so that stable and high-precision heat treatment can be performed. [4] The post-weld heat treatment apparatus according to the embodiment is the [1].
Or the apparatus according to [2], wherein the high-frequency induction heating means (10 to 80) includes frequency control means (71, 72) capable of high-frequency induction heating at a frequency of 10 KHz or more. Features.

In the above apparatus, for example, the magnetic flux can be effectively concentrated only in a depth range of several mm from the surface of the tube sheet, and this portion can be directly heated rapidly. [5] The post-weld heat treatment apparatus according to the embodiment is the [2].
The high-frequency induction heating means (10 to 80)
Are wound in two or more steps so that the whole is spiral and the central part protrudes in the axial direction, and the protruding part can be inserted into the opening of the heat transfer tube (1). It is characterized by having a frustoconical induction heating coil (31, 41).

In the above apparatus, the specified area including the heat transfer tube (1) and the welded portion (3) is three-dimensionally heated on the three-dimensional heating surface by the frusto-conical induction heating coils (31, 41). As a result, heating is performed uniformly and efficiently. [6] The post-weld heat treatment apparatus according to the embodiment is the [2].
A holding device comprising a support arm (81, 82) having a structure that can be attached and fixed to the surface of a tube sheet (2).
(80) and an induction heating coil (61) having a base end fixed to the holding device (80) and provided at a tip end thereof, while maintaining a constant distance from the surface of the tube sheet (2). A heater (60) provided so as to be movable in parallel with the surface.

In the above apparatus, the holding device (80) is attached to an arbitrary position on the tube plate by performing an operation such as inserting the tip of the support arm (81, 82) into the heat transfer tube (1). Can be fixed and positioned. That is, the holding device
(80) can be set at an arbitrary position on the tube sheet. In this state, by moving the heater (60) held by the holding device (80), the induction heating coil (6) is moved.
Move 1) to an arbitrary position on the tube sheet to obtain the required weld (3)
Heat treatment can be performed. Therefore, while the holding device (80) is fixed at a predetermined position, it is possible to perform a uniform heat treatment on the plurality of welded portions (3) located in the vicinity thereof under the same conditions. Further, since the distance between the welding portion (3) and the induction heating coil (61) is kept constant, the heating temperature distribution is stabilized. [7] The post-weld heat treatment apparatus according to the embodiment includes the [5].
The induction heating coil (31) is characterized in that an insulating material (31b) having high insulation properties and low thermal conductivity is coated on the outer peripheral surface of the conductive tube member (31a). And

In the above apparatus, even when the induction heating coil (31) inserted into the heat transfer tube (1) comes into contact with the object (3, 1) at the time of high-frequency induction heating, the outer surface of the coil does not change. Insulation (3
1b), it keeps a certain distance from the object to be heated (3,1), which prevents erosion and the like due to direct contact, and reduces the radiant heat from the object to be heated (3,1). Can be shut off. [8] The post-weld heat treatment apparatus according to the embodiment includes the above-mentioned [3].
Or the apparatus according to [5] or [6] or [7], wherein the induction heating coil (31 to 61) is formed of a conductive pipe (P) through which cooling water (W) can flow. It is characterized by.

In the above apparatus, by flowing cooling water (W) through the conductive pipe (P), it is possible to avoid melting of the induction heating coils (31 to 61) having a small heat capacity due to overheating of the object to be heated. can do. [9] The post-weld heat treatment apparatus according to the embodiment includes the [5].
An induction heating coil according to claim 1, wherein the induction heating coil is in the form of a truncated cone.
(31, 41) A high permeability magnetic material such as a ferrite core is inserted as a magnetic core into the hollow portion. In the above device, the magnetic flux φ is effectively concentrated, so that the heating efficiency is improved.

[0058]

According to the present invention, it is possible to provide a post-weld heat treatment apparatus having the following functions and effects. a. Since the heat treatment is performed only on the welded part and a specific area in the vicinity thereof, it can be realized with a small-scale facility, and the construction cost and construction period are short. b. Even if equipment or members made of carbon steel or low-alloy steel are present around the weld, the heating range is limited to the weld and a specific area near it, so avoid adverse thermal effects on the above equipment and members. Thus, the mechanical strength of the device or member can be kept stable. c. Even if the temperature rises or falls rapidly, the heating is applied only to the weld and the specific area in the vicinity, so that cracks and breaks due to thermal stress do not occur in each part,
Rapid and accurate heat treatment can be performed. d. Since the heat treatment is performed within a short time, there is no possibility that the devices and members around the welded portion are deformed or damaged by thermal expansion.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration of a post-weld heat treatment apparatus applied to a welded portion between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a first embodiment of the present invention. Figure, (b)
5A is a cross-sectional view showing, in an enlarged manner, a portion surrounded by a circle in FIG. 5A, and FIG. 5C is a perspective view showing a modification of the heater shown in FIG.

FIG. 2 is a diagram showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a third embodiment of the present invention, wherein (a) is a schematic diagram. Side sectional view,
(B) is sectional drawing of an induction heating coil.

FIG. 4 is a diagram showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a fifth embodiment of the present invention, wherein (a) is a front view. (B) is a side sectional view, and (c) is an explanatory view at the time of use.

FIG. 6 is a diagram showing a configuration of a post-weld heat treatment apparatus applied to a weld between a heat transfer tube and a tube sheet in a multi-tube heat exchanger according to a sixth embodiment of the present invention, wherein (a) is a plan view. (B) is a partially cutaway side view.

FIG. 7 is a characteristic curve diagram showing a result of an experiment of “Experimental example 1” according to the embodiment of the present invention.

FIGS. 8A and 8B are diagrams showing heating conditions and the like of “Experimental example 2” according to the embodiment of the present invention.

FIGS. 9A to 9F are diagrams showing measurement regions of “Experimental example 2” according to the embodiment of the present invention and measurement results of temperature distribution in each of the measurement regions.

FIG. 10 is a view showing the results of measuring the micro Vickers hardness of “Experimental example 2” according to the embodiment of the present invention.

FIGS. 11A to 11C are diagrams showing measurement results of a hardness distribution in a root portion between a heat transfer tube and a tube sheet in “Experimental example 2” according to the embodiment of the present invention.

12A and 12B are diagrams showing two examples of post-weld heat treatment means for a weld between a heat transfer tube and a tube sheet in a conventional multi-tube heat exchanger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Heat transfer tube 2 ... Tube plate 3 ... Welded part 10, 20, 30, 40, 50, 60 ... Heater 11, 21, 31, 41, 51, 61 ... Induction heating coil 44, 54 ... Ferrite core 70 ... Heating Container control unit 80 holding device 81, 82 support arm 87 output transformer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C21D 1/42 C21D 1/42 E 9/50 102 9/50 102A H05B 6/06 393 H05B 6/06 393 6/10 371 6 / 10 371 6/36 6/36 D

Claims (7)

[Claims] 1. A post-weld heat treatment apparatus for performing heat treatment on a welded portion for the purpose of removing residual stress, softening, improving a metal structure, etc. of the welded portion, comprising the steps of: A post-weld heat treatment apparatus comprising: a high-frequency induction heating means provided so as to be capable of performing heat treatment by induction heating under conditions such as time. 2. In order to prevent the occurrence of stress corrosion cracking or the like in a weld between a heat transfer tube and a tube sheet of a multi-tubular heat exchanger, residual stress removal, softening, metal structure improvement, and the like of the weld are performed. As an object, in a post-weld heat treatment apparatus for performing heat treatment on the welded portion, a high-frequency wave provided so that the welded portion can be heat-treated by induction heating under conditions such as a specified heating range, a heating temperature, and a heating time. A post-weld heat treatment apparatus comprising induction heating means. 3. A high-frequency induction heating means controls heating of the induction heating coil in a predetermined heating cycle in accordance with a program control signal output from a temperature program controller, detects a heating temperature by a temperature detector, and outputs the detected signal to a light source. The post-weld heat treatment apparatus according to claim 1 or 2, further comprising a heater control unit that transmits the data to a temperature monitoring and recording unit through a fiber and feeds back the data to the program controller. 4. The post-weld heat treatment apparatus according to claim 1, wherein the high-frequency induction heating means includes frequency control means capable of high-frequency induction heating at a frequency of 10 KHz or more. 5. The high-frequency induction heating means has two or more steps so that the whole has a spiral shape, the central portion protrudes in the axial direction, and the protruding portion can be inserted into the opening of the heat transfer tube. The post-weld heat treatment apparatus according to claim 2, further comprising an induction heating coil having a truncated conical shape wound and wound. 6. A holding device provided with a support arm having a structure which can be attached and fixed to the surface of a tube sheet, and an induction heating coil having a base end fixed to the holding device and provided at a tip end thereof, is provided on the tube sheet. The post-weld heat treatment apparatus according to claim 2, further comprising: a heater provided so as to be movable parallel to the tube sheet surface while maintaining a predetermined distance from the surface. 7. The post-weld heat treatment apparatus according to claim 5, wherein the induction heating coil is formed by coating an insulating material having high insulation properties and low heat conductivity on the outer peripheral surface of the conductive tube member. .