Full-field temperature-stress regulation method for primary side local heat treatment of steam generator tube sheet

Abstract

The application discloses a kind of steam generator tube plate primary side local heat treatment full-field temperature-stress regulation and control method, it includes the following steps: (1) determine the structure parameters of steam generator workpiece water chamber head and tube plate butt joint ring seam area;(2) determine the heating band width required by local heat treatment;(3) determine the holding band width required by local heat treatment;(4) determine the power of local heat treatment induction heating and the number of turns of induction heating cable arrangement;(5) determine the heating rate and cooling rate of local heat treatment, and arrange cooling device;(6) determine local heat treatment temperature measuring point, and arrange temperature measuring thermocouple and temperature control thermocouple;(7) implement heat treatment.The application determines the arrangement mode of heating band according to the size of workpiece, ensures the temperature uniformity of local heat treatment uniform temperature zone of weld, simultaneously ensures that the temperature at tube plate does not overheat, realizes weld micro residual stress regulation and control, and can also regulate and control inner wall stress, can greatly reduce inner wall residual stress.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat treatment, in particular to a full-field temperature-stress regulation method for local heat treatment of a steam generator tube plate primary side. BACKGROUND

[0002] The steam generator is an important equipment in the nuclear island, and is called the "lungs of nuclear power". The structure, design and manufacture of the steam generator are extremely complex. The primary side of the steam generator is connected with the reactor pressure vessel, and the medium is corrosive and radioactive, which is easy to cause stress corrosion cracking and cause leakage accidents, becoming a common problem faced by the world nuclear power industry. Accident investigation shows that the welding residual stress is one of the main causes of stress corrosion cracking. Due to the large thickness of the steam generator shell, the large number of welding beads and the strong restraint, a large amount of residual stress is generated after welding, which has a great influence on stress corrosion cracking, and it is required to use post-weld heat treatment to eliminate residual stress. Except for two ring seams: the upper cylinder and the cone butt joint ring seam, and the water chamber head and the tube plate butt joint ring seam requiring local heat treatment, all the remaining welds are subjected to integral heat treatment. At present, the integral heat treatment technology has been basically mature, but the local heat treatment of the water chamber head and the tube plate butt joint ring seam is the most difficult. The ring seam is connected with the head on one side and the tube plate on the other side, and the structure is complex and the tube plate has serious heat dissipation. The local heat treatment requires not only to ensure the temperature uniformity of the uniform temperature zone, but also to strictly control the temperature of the tube plate end face. The conventional local heat treatment process method cannot meet the special structure and strict process requirements. In addition, the water chamber head and the tube plate butt joint ring seam also need to be overlaid with a stainless steel overlay layer on the inner surface of the tube plate primary side after welding, and the base material is carbon steel. The restraint effect of the dissimilar materials makes it more difficult to eliminate the stress on the inner surface. Therefore, the local heat treatment of the water chamber head and the tube plate butt joint ring seam is still a key problem that has not been solved in the nuclear power technology. SUMMARY

[0003] To solve the above technical problems, the present application provides a full-field temperature-stress regulation method for local heat treatment of a steam generator tube plate primary side, which determines the arrangement mode of the local heat treatment induction heating belt according to the size of the workpiece, ensures the temperature uniformity of the weld local heat treatment uniform temperature zone, and can also ensure that the temperature of the tube plate does not overheat, realizes the micro residual stress regulation of the weld, and can also regulate the stress on the inner wall, which can greatly reduce the residual stress on the inner wall.

[0004] The technical solution adopted by the present application is:

[0005] The present application provides a full-field temperature-stress regulation method for local heat treatment of a steam generator tube plate primary side, comprising the following steps:

[0006] (1) Determine the structure parameters of the water chamber head and tube plate butt joint ring seam area of the steam generator workpiece, including the head side cylinder wall thickness δ1, the tube plate side cylinder wall thickness δ2, the tube plate side and the head side cylinder outer radius R, the distance L from the tube plate end face to the head side straight edge segment;

[0007] (2) Determine the heating band width required for local heat treatment according to the structure parameters determined in step (1), wherein the heating band width close to the head side with the weld center line as the boundary is W f = 4δ1, and the heating band width close to the tube plate side with the weld center line as the boundary is

[0008] (3) Determine the holding band width required for local heat treatment according to the structure parameters determined in step (1), wherein the outer wall holding band width close to the head side with the weld center line as the boundary is the outer wall holding band width close to the tube plate side with the weld center line as the boundary is the inner wall holding band width of the head side extending from the tube plate end face to the head side is the inner wall holding band width of the tube plate side in the tube plate diameter direction is

[0009] (4) Determine the heating mode of local heat treatment as induction heating, and determine the power of induction heating and the number of turns of induction heating cable according to the structure parameters determined in step (1);

[0010] The total power P of induction heating includes the power P1 required for heating the metal, the power P2 of radiation heat loss, the power P3 of convection heat loss, the power P4 of holding band heat loss, and other heat loss power P5, and P = P1 + P2 + P3 + P4 + P5;

[0011] The rated power P 额 of induction heating is: P 额 ≥ 2P;

[0012] The tube plate side cable turn number N1 and the head side cable turn number N2 are respectively:

[0013]

[0014] Wherein, I is the induction cable current, P is the total power, f is the induction heating frequency; μ is the relative magnetic permeability;

[0015] (5) Determine the local heat treatment heating rate and cooling rate according to the structure parameters determined in step (1), and arrange the cooling device;

[0016] (6) Determine the local heat treatment temperature measuring point, and arrange the temperature measuring thermocouple and the temperature control thermocouple;

[0017] (7) implement heat treatment, and record the heat treatment temperature curve.

[0018] Further, the thickness of the outer wall insulation zone of the head side and the tube sheet side in step (3) is H w = 50 + δ1 / 10; and the thickness of the inner wall insulation zone of the head side and the tube sheet side is H n = 60 + δ1 / 10.

[0019] Further, the calculation formulae of the heating zone metal heating required power P1, the radiation heat loss power P2, the convection heat loss power P3, the insulation zone heat loss power P4 and other heat loss power P5 in the step (4) are respectively:

[0020]

[0021]

[0022] P5 = 0.1·P1

[0023] Wherein, c is the specific heat capacity of the workpiece, (J / (kg·℃)); ρ is the density of the workpiece, kg / m 2 ; is the average heating rate of the workpiece after reaching 300℃, ℃ / h; T is the peak temperature of heat treatment; T e is the room temperature of heat treatment; ε is the blackness of the workpiece surface, usually taken as 0.8; h is the surface convection heat transfer coefficient, W / (m 2 ·K); L S is the distance from the edge of the insulation zone in the axial direction to the temperature of the room temperature in the axial direction, m; λ is the thermal conductivity of the insulation zone, kW / m·℃.

[0024] In the above technical solution, the arrangement mode of the local heat treatment induction heating zone and the selection of the induction heating power are determined according to the size of the workpiece, which facilitates the engineering personnel to select the appropriate power according to the actual workpiece and determine the appropriate heat treatment power, and the above power is not too large or too small, avoiding the additional energy loss and the adjustment of the power of the power supply in the engineering use process; the cable winding mode takes into account the particularity of the structure of the workpiece, fully considers the heat dissipation of the tube sheet and the special temperature requirement of the tube sheet end face, so that the heat treatment preparation work is done at one time, and the adjustment of the number of turns of the cable in the heat treatment process is avoided, thereby ensuring the uniformity of the temperature of the local heat treatment of the weld and the temperature of the tube sheet end face meeting the special process requirements.

[0025] Further, the heating rate in the step (5) is:

[0026] In the range below 300℃, the heating rate does not need to be controlled;

[0027] In the range of 300-400℃, the heating rate satisfies:

[0028]

[0029] In the range of 400-500℃, the temperature rising rate satisfies:

[0030]

[0031] In the range of 500-620℃, the temperature rising rate satisfies:

[0032]

[0033] Further, the temperature falling rate in the step (5) is:

[0034] In the range of 620-500℃, the temperature falling rate satisfies:

[0035]

[0036] In the range of 500-400℃, the temperature falling rate satisfies:

[0037]

[0038] In the range of 400-300℃, the temperature falling rate satisfies:

[0039]

[0040] In the range below 300℃, the temperature falling rate is not controlled.

[0041] In the above technical solution, in the temperature rising process, the thermal conductivity coefficient is small in the high temperature stage, and the temperature uniformity of the uniform temperature zone is further improved by controlling the multi-stage temperature rising rate; in the temperature falling process, the thermal stress generated in the heat treatment cooling stage is reduced by controlling the multi-stage temperature falling rate.

[0042] Further, the cooling device in the step (5) is arranged inside the head side cylinder, when the heat treatment is completed, the cooling device is opened, and the temperature falling is carried out according to the set temperature falling rate, and when the temperature of the center position of the weld outer wall is reduced to 300℃, the inner wall heat preservation belt near the weld is removed for temperature falling, and the temperature measuring thermocouple of the inner and outer walls is monitored, so that the temperature difference between the inner and outer walls satisfies:

[0043]

[0044] Wherein, σ y is the yield strength of the workpiece; v is the Poisson's ratio of the workpiece; E is the Young's modulus of the workpiece; and a is the thermal expansion coefficient of the workpiece.

[0045] In the technical scheme, the inner surface of the workpiece is entirely surfaced with a stainless steel surfacing layer, stress of the inner wall is difficult to eliminate due to the limitation of dissimilar material welding restraint, and if stress corrosion occurs, the corrosive medium enters the weld of the base material, so the area near the girth weld is the most vulnerable part, and the part is further treated. By controlling the temperature difference between the inner wall and the outer wall, the cooling rate of the inner wall is higher than that of the outer wall, a different distortion temperature field is generated in the inner wall than the traditional cooling mode without separately removing the inner wall heat preservation zone, the cooling rate of the inner wall is greater than that of the outer wall, reverse shrinkage deformation is generated, the residual stress of the inner wall is further regulated, and the risk of stress corrosion cracking caused by the contact of the high stress of the inner wall weld and the corrosive medium is reduced.

[0046] Further, in the step (3), the inner wall heat preservation zone near the weld is separately arranged, and the width of the inner wall heat preservation zone near the weld is

[0047] In the technical scheme, by separately arranging the inner wall heat preservation zone near the weld, the heat preservation zone can be removed during cooling, and the area near the weld is cooled.

[0048] Further, the working time of the cooling device in the step (5) satisfies:

[0049]

[0050] Wherein, k is the thermal diffusivity of the workpiece.

[0051] Further, in the step (6), 4n temperature measuring thermocouples are arranged, and n is greater than or equal to 2, wherein 2n temperature measuring thermocouples are arranged on the outer wall, and 2n temperature measuring thermocouples are arranged on the inner wall.

[0052] Among the 2n temperature measuring thermocouples arranged on the outer wall, n temperature measuring thermocouples are arranged at the center of the weld and uniformly distributed around the weld, and the remaining n temperature measuring thermocouples are arranged at the edge of the uniform temperature zone on both sides of the weld.

[0053] Among the 2n temperature measuring thermocouples arranged on the inner wall, n temperature measuring thermocouples are arranged at the center of the weld and uniformly distributed around the weld, and the remaining n temperature measuring thermocouples are arranged at the edge of the uniform temperature zone on both sides of the weld.

[0054] Further, in the step (6), at least two temperature control thermocouples are arranged, and the temperature control thermocouples are arranged at the connection between the tube plate and the straight edge section.

[0055] The temperature control thermocouples are connected with an induction power source of the induction heating power supply, and when the temperature monitored by the temperature control thermocouples exceeds 425 DEG C, the induction power source automatically reduces the heating power.

[0056] The present application has the following advantages:

[0057] The application provides a full-field temperature-stress regulation method for local heat treatment of a steam generator tube plate primary side, which determines the arrangement mode of a local heat treatment induction heating belt and the selection of a power supply power according to the size of a workpiece, facilitates an engineering personnel to select a proper power supply according to the actual workpiece, and can make the heat treatment preparation work in place at one time, avoids the adjustment of a cable in the heat treatment process, guarantees the temperature uniformity of the local heat treatment uniform temperature zone of a weld, and realizes the regulation of the microscopic residual stress of the weld; meanwhile, the method can not only guarantee that the temperature of the tube plate is not overheated, prevents the local heat treatment from causing the deflection deformation of the tube bundle on the tube plate side, but also can regulate the stress of the inner wall, can greatly reduce the residual stress of the inner wall, and reduces the risk of stress corrosion cracking caused by the contact between the high stress of the inner wall weld and corrosive medium. BRIEF DESCRIPTION OF DRAWINGS

[0058] In order to clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0059] Figure 1 It is a structural schematic diagram of a steam generator workpiece.

[0060] Figure 2 It is a schematic diagram of the arrangement of temperature measuring thermocouples and temperature control thermocouples.

[0061] Figure 3 It is an axial stress curve along the inner wall path.

[0062] Figure 4 It is a hoop stress curve along the inner wall path.

[0063] In the figure, 1 is a temperature measuring thermocouple of the outer wall; 2 is a temperature measuring thermocouple of the inner wall; and 3 is a temperature control thermocouple. DETAILED DESCRIPTION

[0064] The application provides a full-field temperature-stress regulation method for local heat treatment of a steam generator tube plate primary side, in order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0065] The application provides a full-field temperature-stress regulation method for local heat treatment of a steam generator tube plate primary side, comprising the following steps:

[0066] (1) Determine the structure parameters of the water chamber head and tube plate butt joint ring seam area of the steam generator workpiece, including the head side cylinder wall thickness δ1, the tube plate side cylinder wall thickness δ2, the tube plate side and the head side cylinder outer radius R, the distance L of the tube plate end face to the straight edge segment of the head side;

[0067] (2) Determine the heating band width required for local heat treatment according to the structure parameters determined in step (1), wherein the heating band width close to the head side is W f = 4δ1, and the heating band width close to the tube plate side is

[0068] (3) Determine the holding band width and thickness required for local heat treatment according to the structure parameters determined in step (1)

[0069] Wherein, the outer wall holding band width close to the head side is the outer wall holding band width close to the tube plate side is

[0070] the inner wall holding band width of the head side extending from the tube plate end face to the head side is the inner wall holding band width of the tube plate side in the tube plate diameter direction is In addition, the inner wall holding band near the weld is arranged separately, and can be fixed by using an easily removable tool, which is convenient for subsequent direct removal, and the inner wall holding band width near the weld is The holding band is symmetrically arranged with the weld center as the center line;

[0071] The outer wall holding band thickness of the head side and the tube plate side is H w = 50 + δ1 / 10; and the inner wall holding band thickness of the head side and the tube plate side is H n = 60 + δ1 / 10;

[0072] (4) The heating mode of local heat treatment is determined to be induction heating, and the power of induction heating and the number of turns of induction heating cable are determined according to the structure parameters determined in step (1);

[0073] The total power P of induction heating includes the power P1 required for the heating zone metal to be heated, the radiation heat loss power P2, the convection heat loss power P3, the holding band heat loss power P4, and other heat loss power P5, and P = P1 + P2 + P3 + P4 + P5;

[0074] The calculation formulas of the power P1 required for the heating zone metal to be heated, the radiation heat loss power P2, the convection heat loss power P3, the holding band heat loss power P4, and other heat loss power P5 are respectively:

[0075]

[0076] P5=0.1·P1

[0077] wherein c is the specific heat capacity of the workpiece, J / (kg·℃); ρ is the density of the workpiece, kg / m 2 ; is the average heating rate of the workpiece after the temperature reaches 300℃, ℃ / h, V1, V2, V3 are the heating rates in the ranges of 300-400℃, 400-500℃ and 500-620℃, respectively; T is the peak temperature of heat treatment; T e is the room temperature of heat treatment; ε is the blackness of the workpiece surface, usually taking the value of 0.8; h is the surface convection heat transfer coefficient, W / (m 2 ·K); L S is the distance from the edge of the insulation zone in the axial direction to the room temperature in the axial direction, m; λ is the thermal conductivity of the insulation zone, kW / m·℃.

[0078] The rated power P 额 of the induction heating is: P 额 ≥2P;

[0079] The number of turns of the cable on the tube plate side N1 and the number of turns of the cable on the head side N2 are respectively:

[0080] For electromagnetic induction, the magnetic field is an alternating magnetic field, and H satisfies:

[0081]

[0082] And H0 satisfies:

[0083]

[0084] The number of turns of the induction coil N is:

[0085]

[0086] Thus:

[0087]

[0088] wherein H is the magnetic field strength, L a is the effective magnetic path length, i.e. the coil winding width (heating zone width), I is the induction cable current, taking the value of 150A, P is the total power, f is the induction heating frequency, taking the value of 5000Hz; μ is the relative magnetic permeability, taking the value of 30; N1 and N2 are the upward integer numbers;

[0089] (5) determining the heating rate and the cooling rate of the local heat treatment according to the structure parameters determined in step (1), and arranging the cooling device;

[0090] The heating rate is:

[0091] In the range below 300℃, the heating rate is not controlled;

[0092] In the range of 300-400℃, the heating rate satisfies:

[0093]

[0094] In the range of 400-500℃, the heating rate satisfies:

[0095]

[0096] In the range of 500-620℃, the heating rate satisfies:

[0097]

[0098] The cooling rate is:

[0099] In the range of 620-500℃, the cooling rate satisfies:

[0100]

[0101] In the range of 500-400℃, the cooling rate satisfies:

[0102]

[0103] In the range of 400-300℃, the cooling rate satisfies:

[0104]

[0105] In the range below 300℃, the cooling rate is not controlled;

[0106] The cooling device is arranged inside the head-side cylinder, and the cooling device can adopt a cold air blower or spray dry ice. When the heat treatment is completed, the cooling device is started, and the temperature is lowered at the set cooling rate. When the temperature of the center position of the outer wall of the weld is reduced to 300℃, the inner wall insulation belt near the weld is removed, i.e. the inner wall insulation belt with a width of is removed near the weld, and the cooling device is started to lower the temperature. The temperature measuring thermocouple of the inner and outer walls of the center of the weld is monitored, so that the average temperature difference between the inner and outer walls satisfies:

[0107]

[0108] Wherein, σ y is the yield strength of the workpiece; v is the Poisson's ratio of the workpiece; E is the Young's modulus of the workpiece; and a is the thermal expansion coefficient of the workpiece;

[0109] The working time of the cooling device, i.e., the total time after the cooling device is turned on, satisfies:

[0110]

[0111] wherein k is the thermal diffusivity of the workpiece;

[0112] (6) Determine the local heat treatment temperature measurement points, and arrange the temperature measurement thermocouples and temperature control thermocouples;

[0113] The temperature measurement thermocouples are arranged in total 4n, n≥2, wherein 2n temperature measurement thermocouples are located on the outer wall, and 2n temperature measurement thermocouples are located on the inner wall;

[0114] Among the 2n temperature measurement thermocouples located on the outer wall, n are arranged at the center of the weld and uniformly distributed around the weld, and the remaining n temperature measurement thermocouples are arranged at the edges of the uniform temperature zone on both sides of the weld;

[0115] Among the 2n temperature measurement thermocouples located on the inner wall, n are arranged at the center of the weld and uniformly distributed around the weld, and the remaining n temperature measurement thermocouples are arranged at the edges of the uniform temperature zone on both sides of the weld;

[0116] The temperature control thermocouples are arranged at least 2, and the temperature control thermocouples are arranged at the connection between the tube sheet and the straight edge section;

[0117] The temperature control thermocouples are electrically connected with the induction power supply cabinet. When the temperature monitored by the temperature control thermocouples exceeds 425℃, the induction power supply automatically reduces the heating power, and can use the "cable lever" in an artificial assisted manner to appropriately increase the cable spacing at this place, so that the temperature at this place is lower than 425℃, without the worker touching the induction cable.

[0118] (7) Implement heat treatment, and record the heat treatment temperature curve.

[0119] Example 1

[0120] Referring to Figure 1 , this embodiment carries out local heat treatment on a workpiece of a steam generator water chamber head and tube plate butt joint ring seam, and detects the residual stress before and after the local heat treatment.

[0121] The related parameters of the above workpiece are as follows: the material is SA508-3, the outer radius R of the workpiece is 1768mm, the head side cylinder wall thickness δ1 is 180mm, the tube plate side cylinder wall thickness δ2 is 800mm, and the distance L from the tube plate end face to the straight edge section of the head side is 180mm.

[0122] The workpiece is subjected to local heat treatment according to the following steps:

[0123] (1) Determined workpiece parameters

[0124] The outer radius R of the workpiece is 1768mm, the wall thickness δ1 of the cylinder on the head side is 180mm, the wall thickness δ2 of the cylinder on the tube sheet side is 140mm, and the distance L from the tube sheet end face to the straight edge section on the head side is 180mm.

[0125] (2) Determined heating band width

[0126] Width W of the heating band on the end cap side f =720mm, width W of the heating band on the tube sheet side g =428mm;

[0127] (3) Determined insulation strip width and insulation strip thickness

[0128] The width of the outer wall insulation strip on the end cap side is The width of the outer wall insulation strip on the tube sheet side is The width of the inner wall insulation strip extending from the tube sheet end face towards the head side is: The width of the separately arranged inner wall insulation strip near the weld is The width of the insulation strip on the inner wall of the tube sheet side in the diameter direction is: The thickness of the outer wall insulation strip on the head side and tube sheet side is H w =68mm; the thickness of the inner wall insulation strip on the head side and tube sheet side is H n =78mm;

[0129] (4) Determine the power of induction heating and the number of turns of the induction heating cable.

[0130] Rated power P of induction heating 额 For: P 额 =2P=281.5kW;

[0131] The number of cable turns N1 on the tube sheet side is: N1 = 12 turns;

[0132] The number of cable turns N2 on the end cap side is: N2 = 10 turns;

[0133] (5) Determine the local heat treatment heating and cooling rates, and arrange the cooling device.

[0134] The heating rate is:

[0135] In the range below 300°C, there is no need to control the heating rate;

[0136] Within the temperature range of 300-400℃, the heating rate satisfies:

[0137] V1≤16.4℃ / h

[0138] In this embodiment, V1 is specifically set to 15℃ / h;

[0139] In the range of 400-500℃, the temperature rising rate satisfies:

[0140] V2≤11.4℃ / h

[0141] In this embodiment, V2 is specifically set to 10℃ / h;

[0142] In the range of 500-620℃, the temperature rising rate satisfies:

[0143] V3≤6.4℃ / h

[0144] In this embodiment, V3 is specifically set to 6℃ / h;

[0145] The temperature falling rate is:

[0146] In the range of 620-500℃, the temperature falling rate satisfies:

[0147] V3'≤6.4℃ / h

[0148] In this embodiment, V3' is specifically set to 6℃ / h;

[0149] In the range of 500-400℃, the temperature falling rate satisfies:

[0150] V2'≤11.4℃ / h

[0151] In this embodiment, V2' is specifically set to 10℃ / h;

[0152] In the range of 400-300℃, the temperature falling rate satisfies:

[0153] V2'≤16.4℃ / h

[0154] In this embodiment, V1' is specifically set to 15℃ / h;

[0155] In the range below 300℃, the temperature falling rate is not controlled;

[0156] The cooling device is arranged inside the head-side cylinder, and the cooling device uses multiple air coolers;

[0157] (6) Arranging temperature measuring thermocouples and temperature controlling thermocouples

[0158] Refer to Figure 2In the uniform temperature zone of the weld, i.e. the volume range of the heat treatment reaching the specified temperature at the surface area, generally 50 mm on each side of the weld, 16 temperature measuring thermocouples are arranged. Among them, 8 temperature measuring thermocouples are arranged on the outer wall, 4 of which are located at the center of the weld and are distributed at an interval of 90°, and the other 4 are located at the edge of the uniform temperature zone on each side of the weld (50 mm position on one side of the weld), and one is arranged at each of the 6 o'clock and 12 o'clock positions; 8 temperature measuring thermocouples are arranged on the inner wall, 4 of which are located at the center line of the weld and are distributed at an interval of 90°, and the other 4 are located at the edge of the uniform temperature zone on each side of the weld (50 mm position on one side of the weld), and one is arranged at each of the 6 o'clock and 12 o'clock positions; the above 8 temperature measuring thermocouples on the outer wall and the 8 temperature measuring thermocouples on the inner wall strictly implement the heat treatment process curve requirements; in addition to the above thermocouples, a separate temperature control thermocouple is arranged in the 6 o'clock and 12 o'clock directions at the connection between the tube sheet and the straight edge section, the thermocouple has a temperature feedback control function and is connected with an induction power supply cabinet, when the temperature at this position exceeds 425℃, the induction power supply automatically reduces the power to ensure that the temperature at this position is lower than 425℃;

[0159] (7) Implementing heat treatment, implementing heat treatment according to the heat treatment temperature and holding time specified in the heat treatment standard, the heat treatment holding temperature is 607±12℃, the holding time is 3.5h, the heating rate is implemented according to the calculated V1, V2, V3, and the heat treatment temperature curve is recorded

[0160] After the arrangement according to the above steps (1)-(6) is completed, the workpiece is subjected to heat treatment, and the temperature measuring data of the temperature measuring thermocouples are recorded to form a heat treatment temperature curve; after the heat treatment is completed, the cooling device is started, and the temperature is lowered according to the set cooling rate, and when the average temperature of the 4 temperature measuring thermocouples at the center position of the outer wall of the weld is reduced to 300℃, the inner wall heat preservation zone near the weld is removed, i.e. the separately arranged inner wall heat preservation zone with a width of of the weld is removed, and the temperature is lowered, and the 4 temperature measuring thermocouples at the center position of the inner and outer walls of the weld are monitored, so that the average temperature difference between the inner and outer walls satisfies ΔT'≥175℃, and the time of the cooling device is at least 35min.

[0161] Comparative Example 1

[0162] The workpiece of the present comparative example 1 is the same as that of Example 1, which adopts the traditional local heat treatment method, and the heat treatment holding temperature and holding time are the same as those of Example 1, and the heating rate is as follows: no control of the heating rate before 300℃, the heating rate is less than 55℃ / h after 300℃, and the heating rate is not changed until the heat treatment holding temperature is reached, after the holding is completed, the temperature is cooled to room temperature at a rate of less than 55℃ / h; in addition, the temperature difference between the inner and outer walls at the center position of the weld is not monitored, and no cold source is applied to the inner surface.

[0163] In the present comparative example, the inductive heating power is first selected as 1000 kW, and the power is adjusted according to the monitored temperature change of the temperature measuring thermocouple during the heat treatment process, which not only increases the workload, but also is difficult to ensure the temperature uniformity of the weld uniform temperature zone and the temperature at the tube plate.

[0164] In addition, in the present comparative example, the width and thickness of the heating band and the holding band are set to be the same as those in Example 1, and the arrangement of the temperature measuring thermocouple and the temperature control thermocouple is also set to be the same as that in Example 1.

[0165] The residual stress of the workpiece in the as-welded state and the residual stress after the heat treatment of Example 1 and the comparative example 1 are detected, as shown in Figure 3 and Figure 4 It can be seen from Figure 3 and Figure 4 that the average reduction of the axial residual stress of Example 1 is increased by 67.5% compared with that of the comparative example 1, and the average reduction of the circumferential residual stress of Example 1 is increased by 57.1% compared with that of the comparative example 1.

[0166] In addition, it can also be seen from Figure 3 and Figure 4 that after the local heat treatment, the axial residual stress and the circumferential residual stress of Example 1 are both reduced, and are distributed smoothly near the weld, avoiding stress concentration, that is, the residual stress of the weld and the surrounding weld is basically consistent, effectively reducing the sensitivity of stress corrosion cracking. In the comparative example 1, although the axial residual stress and the circumferential residual stress are both reduced after the local heat treatment, the tensile stress is still high, and the residual stress distribution near the weld is not uniform, especially the circumferential residual stress at the center of the weld is much higher than that around the weld, which is easy to cause stress concentration near the weld, increasing the risk of stress corrosion cracking.

[0167] It should be noted that the parts not mentioned in the present application can be realized by using or referring to the existing technology.

[0168] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples, and the changes, modifications, additions or replacements made by the person skilled in the art within the essential scope of the present application should also belong to the protection scope of the present application.

Claims

1. A method for full-field temperature-stress regulation of a once-through local heat treatment of a steam generator tube sheet, characterized in that, The method comprises the following steps: (1) determining the structure parameters of the water chamber head and tube plate butt joint ring seam area of the steam generator workpiece, including the head side cylinder wall thickness δ1, the tube plate side cylinder wall thickness δ2, the tube plate side and head side cylinder outer radius R, the distance L from the tube plate end face to the head side straight edge section; (2) determining the heating band width required for the local heat treatment according to the structure parameters determined in step (1), wherein the heating band width close to the head side with the weld center line as the demarcation line is W f = 4δ1, and the heating band width close to the tube sheet side with the weld center line as the demarcation line is (3) determining the holding zone width required for the local heat treatment according to the structure parameters determined in step (1), wherein the holding zone width of the outer wall close to the head side is the holding zone width of the outer wall close to the tube sheet side is the holding zone width of the inner wall of the head side extending from the tube sheet end face to the head side is the holding zone width of the inner wall of the tube sheet side in the tube sheet diameter direction is (4) determining that the heating mode of the local heat treatment is induction heating, and determining the power of the induction heating and the number of turns of the induction heating cable according to the structure parameters determined in step (1); The total power P of the induction heating includes the power P1 required for heating the metal in the heating area, the power P2 of the radiation heat loss, the power P3 of the convection heat loss, the power P4 of the heat loss in the heat preservation zone, and the power P5 of other heat losses, and P = P1 + P2 + P3 + P4 + P5; The rated power P of the induction heating 额 is: P 额 ≥ 2P; The number of turns N1 of the tube plate side cable and the number of turns N2 of the head side cable are respectively: Wherein, I is the current of the induction cable, P is the total power, f is the induction heating frequency; μ is the relative magnetic permeability; (5) determining the heating rate and the cooling rate of the local heat treatment according to the structure parameters determined in step (1), and arranging the cooling device; (6) determining the temperature measuring points of the local heat treatment, and arranging the temperature measuring thermocouples and the temperature control thermocouples; (7) implementing the heat treatment, and recording the heat treatment temperature curve.

2. The method of claim 1, wherein the method is characterized by: The thickness of the outer wall insulation zone of the head side and the tube sheet side in step (3) is H w = 50 + δ1 / 10; the thickness of the inner wall insulation zone of the head side and the tube sheet side is H n = 60 + δ1 / 10.

3. The method of claim 1, wherein the method is characterized by: The calculation formulas of the power P1 required for heating the metal in the heating area, the power P2 of the radiation heat loss, the power P3 of the convection heat loss, the power P4 of the heat loss in the heat preservation zone, and the power P5 of other heat losses in step (4) are respectively: P5 = 0.1·P1 Wherein, c is the specific heat capacity of the workpiece, J / (kg·℃); ρ is the density of the workpiece, kg / m 2 ; is the average heating rate of the workpiece after reaching 300℃, ℃ / h; T is the peak temperature of heat treatment; T e is the room temperature of heat treatment; ε is the blackness of the workpiece surface, usually 0.8; h is the surface convection heat transfer coefficient, W / (m 2 ·K); L S is the distance from the edge of the axial direction heat preservation zone to the axial direction temperature of room temperature, m; λ is the thermal conductivity of the heat preservation zone, W / m·℃.

4. The method of claim 1, wherein the method is characterized by: The heating rate in step (5) is: In the range below 300℃, the heating rate does not need to be controlled; In the range of 300-400℃, the heating rate satisfies: In the range of 400-500℃, the heating rate satisfies: In the range of 500-620℃, the heating rate satisfies:

5. The method of claim 1, wherein the method is characterized by: The cooling rate in step (5) is: In the range of 620-500℃, the cooling rate satisfies: In the range of 500-400℃, the cooling rate satisfies: In the range of 400-300℃, the cooling rate satisfies: In the range below 300℃, the cooling rate does not need to be controlled.

6. The method of claim 1, wherein the method is characterized by: The cooling device in step (5) is arranged inside the head side cylinder, after the heat treatment is completed, the cooling device is started, and the cooling is performed at the set cooling rate, and when the temperature of the center position of the weld outer wall is reduced to 300℃, the inner wall heat preservation zone near the weld is removed, the cooling device is started to cool, and the temperature measuring thermocouples of the inner and outer walls are monitored, so that the temperature difference between the inner and outer walls satisfies: where σ y is the yield strength of the workpiece; v is the Poisson's ratio of the workpiece; E is the Young's modulus of the workpiece; and a is the thermal expansion coefficient of the workpiece.

7. The method of claim 6, wherein the method is characterized by: In the step (3), the inner wall heat preservation zone near the weld is arranged separately, and the width of the inner wall heat preservation zone near the weld is 8. The method of claim 6, wherein the method is characterized by: The working time of the cooling device in step (5) satisfies: Wherein, k is the thermal diffusivity of the workpiece.

9. The method of claim 1, wherein the method is characterized by: In step (6), 4n temperature measuring thermocouples are arranged, n≥2, of which 2n temperature measuring thermocouples are arranged on the outer wall, and 2n temperature measuring thermocouples are arranged on the inner wall; Of the 2n temperature measuring thermocouples on the outer wall, n are arranged at the center of the weld and uniformly distributed around the weld, and the remaining n temperature measuring thermocouples are arranged at the edge of the uniform temperature zone on both sides of the weld; Of the 2n temperature measuring thermocouples on the inner wall, n are arranged at the center of the weld and uniformly distributed around the weld, and the remaining n temperature measuring thermocouples are arranged at the edge of the uniform temperature zone on both sides of the weld.

10. The method of claim 1, wherein the method is characterized by: The temperature control thermocouples in the step (6) are at least two, and are arranged at the connecting position between the tube plate and the straight edge section; The temperature control thermocouples are connected with the induction power source of the induction heating power supply, and when the temperature monitored by the temperature control thermocouples exceeds 425 ℃, the induction power source automatically reduces the heating power.

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