Welding method

Abstract

The invention relates to the technical field of welding, in particular to a welding method which comprises the steps that S1, the service life t0 of a repaired part is determined according to the operation temperature T of the repaired part; s2, according to the operation temperature T and the planned operation time H, the feasibility of the nickel-based welding material repairing process is judged; s3, judging the stability of the nickel-based repair process; s4, according to the wall thickness delta and the outer diameter D of the pipeline, the effective thickness range of a weld joint is calculated, and the low-temperature tempering heat treatment frequency is determined; s5, welding is carried out, and low-temperature tempering heat treatment is carried out after the thickness of a newly-added welding seam reaches the effective welding seam thickness; s6, heat treatment; s7, carrying out nondestructive testing; s8, a nickel-based welding material is adopted for welding repair; s9, after no crack is found through nondestructive testing, nondestructive testing is carried out every 12 hours, 24 hours and 48 hours, and if no crack is detected through nondestructive testing after 48 hours, welding repair is completed; the method has the effects of improving the welding seam quality of the nickel-based welding seam and reducing the use hidden danger of the repaired part.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a welding method. BACKGROUND

[0002] For welding repair of weld cracks, the welding process is generally based on the original welding process evaluation, so when repairing reheat cracks, the requirements of the process evaluation are preferentially implemented, but for iron-based alloy steel large-diameter thick-wall pipes with a wall thickness exceeding 40 mm, especially pipes, cylinders or valve bodies, tees and irregular-shaped parts that are prone to cracks, if the original welding process is used for welding repair, cracks are likely to occur near the fusion line and the heat-affected zone during welding or post-weld heat treatment, and most of these cracks are reheat cracks, which have strong delay, and the success rate of repair is low and the repair effect is poor if the original welding process evaluation is used to repair cracks that occur during post-weld heat treatment.

[0003] In the prior art, for welding of iron-based large-diameter thick-wall pipes, iron-based welding materials are used from the backing layer without interruption until the final welding is completed, but during the welding process, a large amount of cumulative stress is generated, and when the cumulative stress reaches a certain level, especially after the final welding is completed, due to the excessive cumulative stress in the welding area and the rapid release of accumulated stress during low-temperature transformation, low-temperature tempering heat treatment and post-weld heat treatment, cracks are likely to occur at the weak position of the weld, thereby affecting the quality of the weld; for repair of weld cracks, the cracks are polished and removed, and then nickel-based welding materials ERNiCr-3 or ERNiCrFe-3 are used for welding repair, but since nickel-based welding materials are extremely sensitive to operating temperatures, the service life of the welding repair part has a large variation range, and if the service life of the repair part repaired by nickel-based welding is shorter than the planned operating time of the repair part, there is a great safety hazard. SUMMARY

[0004] In order to improve the overall welding quality and the welding quality of the nickel-based weld and reduce the use of the repair site, the present application provides a welding method.

[0005] The welding method provided by the present application adopts the following technical scheme: A welding method, comprising: S1: determining the service life t0 of the repair site according to the operating temperature T of the repair site, wherein the unit of the operating temperature T is ℃ and the unit of the service life t0 is month; S2: determining the feasibility of the nickel-based welding repair process under the condition that H < t0, according to the operating temperature T and the planned operating time H, wherein the unit of the planned operating time H is month; S3: judge the stability of the nickel-based repair process; S4: according to the pipe wall thickness δ and the outer diameter D, the effective weld thickness range which should be subjected to low-temperature tempering heat treatment is calculated, and the number of low-temperature tempering heat treatment is determined according to the pipe wall thickness δ and the effective weld thickness; S5: welding is implemented to obtain new welds, and after the thickness of the new welds reaches the effective weld thickness, low-temperature tempering heat treatment is performed, after the low-temperature tempering heat treatment is completed, non-destructive testing is passed, and then welding is continued until the final welding is completed and cooled to below 100℃, and then post-weld non-destructive testing is performed; S6: after the post-weld non-destructive testing is passed, heat treatment is performed; S7: after the heat treatment is completed, non-destructive testing is performed to determine the position of the weld cracks, and the cracks are removed; S8: nickel-based welding material is used to weld and repair the part where the cracks are removed until all the crack defects are repaired, and then non-destructive testing is performed again; S9: after non-destructive testing does not find cracks, non-destructive testing is performed at intervals of 12 hours, 24 hours and 48 hours respectively, and if non-destructive testing after 48 hours does not detect cracks, the welding repair is completed.

[0006] By adopting the above technical scheme, after low-temperature tempering heat treatment, the accumulated stress generated by welding can be reduced to the maximum extent, the probability of cracks after the final welding is completed and after the heat treatment is completed is greatly reduced, and the welding quality is significantly improved, but during the subsequent slow cooling, low-temperature transformation, low-temperature tempering heat treatment and heat treatment of the weld, the redistribution and concentrated release of stress may cause micro-cracks on the surface of the weld which are almost impossible to be found by non-destructive testing. When cooled to ambient temperature, these micro-cracks, whether in length or depth, are rapidly expanded, and the expanded cracks can be accurately located by non-destructive testing technology. In order to well cope with the cracks that occur when the weld is cooled to room temperature after slow cooling, low-temperature transformation, low-temperature tempering heat treatment and heat treatment, therefore, before welding preparation and welding operation, a coping method should be proposed for the treatment technology of such cracks to prevent the cracks from rapidly expanding after appearing. The inventor believes that nickel-based welding materials ERNiCr-3 and ERNiCrFe-3 can be used for welding repair of the part where the cracks are removed, which can be used as an effective coping method. However, for the pipe or welded part repaired by nickel-based welding material, since the service life of nickel-based welding material is greatly affected by temperature, before considering nickel-based welding material as a coping method, the feasibility and stability of the nickel-based repair process must be strictly evaluated to achieve the final goal of ensuring good welding quality.

[0007] The skilled person determines the service life t0 of the repair site according to the operating temperature T of the repair site, and then determines the feasibility of the nickel-based repair process according to the operating temperature T and the planned operating time H, under the condition that the maximum value of H < t0, if the nickel-based repair process is determined to be feasible, the stability of the nickel-based repair process is determined again, so that the security department can select the appropriate maintenance period or perform the re-welding operation after shutdown in advance according to the feasibility and stability, thereby reducing the safety hidden danger of the repair site and providing an important reference for the decision-making of the security department. When the nickel-based repair process is feasible or stable, the welder prepares for the welding operation in advance. With the welding operation, especially for the pipeline or weldment with a wall thickness of more than 40 mm, the weld thickness of the weld stack gradually increases, and the internal stress of the corresponding welding site also gradually increases. When the internal stress accumulates to a certain extent, in order to prevent cracks from occurring at the weak part of the weld, when the weld is welded to the effective thickness, the welding site of the pipeline or weldment is subjected to low-temperature tempering heat treatment, which can reduce the internal stress of the welding site to a certain extent, thereby reducing the possibility of cracks occurring during welding. After the low-temperature tempering heat treatment is completed, non-destructive testing is performed. The non-destructive testing here usually uses PT detection technology to check the crack defects on the surface of the weld. After the non-destructive testing is qualified, the welding continues until the welding operation is finally completed. Then, low-temperature tempering heat treatment or low-temperature transformation is performed, and then post-weld non-destructive testing is performed. The post-weld non-destructive testing here usually uses MT detection technology to check the crack defects on the surface of the weld. After the post-weld non-destructive testing is qualified, the pipeline is subjected to heat treatment again, and non-destructive testing is performed after the heat treatment is completed. In the non-destructive testing, ultrasonic detection technology or phased array detection technology is used for internal quality detection of the weld, and MT detection technology is used for surface crack defect detection. When the non-destructive testing accurately locates the position of the crack, the crack is removed using a tool, and the repaired site is welded using nickel-based welding material. Non-destructive testing is performed at three time nodes of 12 hours, 24 hours and 48 hours, respectively. If no cracks are found during the three times of non-destructive testing, the pipeline welding repair work is completed.

[0008] In one specific implementation, in the step S1, When T < 570℃, the service life t0 of the repair site is in the range of 16.1 months ≤ t0 ≤ 72 months; when 570℃ ≤ T < 590℃, the service life t0 of the repair site is in the range of: When 590℃ ≤ T ≤ 630℃, the service life t0 of the repair site is in the range of: Wherein, the temperature influence coefficient a0 of the nickel-based welding material repair site ranges between 6% and 12%, the time influence coefficient a1 of the nickel-based welding material repair site ranges between 0.75 and 0.85, and the time influence coefficient b of the iron-based alloy welding material ranges between 7% and 10%.

[0009] By adopting the technical scheme, when the welding repair site fails during operation, there are three failure conditions, the first one is that the failure site appears in the middle region of the nickel-based weld, i.e. the failure site is between nickel-based and nickel-based, and the iron-based alloy component is extremely low; the second one is that the failure site appears between nickel-based and iron-based, tends to the nickel-based side, and the failure site has a certain concentration of iron-based alloy component, resulting in that the metal structure of the weld is relatively complex, which is a structural weak point; the third one is that the failure site appears on the iron-based and iron-based side outside the fusion line, i.e. the failure site appears in the welding heat affected zone, because the metallographic structure of the welding heat affected zone is abnormal, there are coarse and overheated structures, and the fracture condition is relatively easy to appear. Because of the above three conditions, the relationship between the repair site service life and the repair site operating temperature, the nickel-based welding material repair site temperature influence coefficient, the nickel-based welding material repair site time influence coefficient and the iron-based alloy welding material repair site time influence coefficient is given, thereby a calculation method of the repair site service life t0 under each operating temperature condition is provided, so as to realize the purpose of accurately judging the repair service life of the welding site.

[0010] In a specific implementable scheme, in the step S2, When T<570℃, it is determined that the nickel-based welding material repair process has feasibility; When 570℃≤T<590℃, if it is determined that the nickel-based welding material repair process has feasibility; When 590℃≤T≤630℃, the risk coefficient of the nickel-based welding material repair region is the risk coefficient of the iron-based alloy welding material repair region is If A Wherein, the temperature influence coefficient a0 of the nickel-based welding material repair site ranges between 6% and 12%, the time influence coefficient a1 of the nickel-based welding material repair site ranges between 0.75 and 0.85, the time influence coefficient b of the iron-based alloy welding material ranges between 7% and 10%, and the risk factor θ ranges between 0 and 20%.

[0011] By adopting the technical scheme, a calculation and evaluation method for judging whether the pipe material adopts the nickel-based welding material repair process under each temperature condition is provided.

[0012] In a specific implementable scheme, in the step S3, When T < 570℃, and the planned operation time H < 16.1 months, it belongs to the stable period, and when the planned operation time H ≥ 16.1 months, it belongs to the unstable period; When 570℃ ≤ T < 590℃, it belongs to the stable period, and when 590℃ ≤ T ≤ 630℃, it belongs to the unstable period; When 570℃ ≤ T < 590℃, it belongs to the stable period, and when 590℃ ≤ T ≤ 630℃, it belongs to the unstable period.

[0013] By adopting the above technical scheme, on the basis of judging that the nickel-based welding material repair process is feasible, a nickel-based welding material repair process stability evaluation method is further provided, thereby reminding the safety department to perform key monitoring, shutdown and re-welding, and advance the planned operation time on the welding repair part in the unstable period and the like.

[0014] In a specific implementable scheme, in the step S4, The calculation method of the effective weld thickness is as follows: The calculation method of the low-temperature tempering heat treatment times is as follows: δ / effective weld thickness is taken as a positive integer, if there is a remainder and the remainder is greater than effective weld thickness / 2, then the low-temperature tempering heat treatment times is increased by one.

[0015] By adopting the above technical scheme, a weld effective thickness calculation method based on the pipe outer diameter and the pipe wall thickness is provided, thereby facilitating reminding the operator to perform low-temperature tempering heat treatment when the newly added weld depth reaches the effective weld thickness, and the calculation method of the low-temperature tempering heat treatment times is given.

[0016] In a specific implementable scheme, the step S5 includes: S51: immediately performing low-temperature tempering heat treatment after welding to the newly added weld thickness reaches the effective weld thickness, wherein the constant temperature temperature of the low-temperature tempering heat treatment is 300℃-400℃, and the constant temperature time is 2-4 hours; S52: after naturally cooling to below 50℃, performing nondestructive testing again.

[0017] S53: after the nondestructive testing is qualified, repeating the steps S51 and S52 until the weld is finally completed and cooled to below 100℃, and then performing post-weld nondestructive testing.

[0018] By adopting the above technical scheme, low-temperature tempering heat treatment can be immediately performed after welding to the newly added weld thickness reaches the effective weld thickness to release the internal stress generated by welding, thereby obviously reducing the probability of cracks, and nondestructive testing is performed after cooling, which can guarantee that the welded layer that has been welded does not have crack defects, thereby avoiding the operation difficulty caused by detecting and repairing after the welding is completely performed.

[0019] In one specific implementation, the step S6 comprises: S61: first heat the weld joint to 300-400℃, and keep the temperature for 2 hours; S62: then increase the heat treatment temperature to the temperature determined by the original heat treatment process, and heat treat for the time determined by the original heat treatment process.

[0020] By using the above technical solution, the quality of the weld can be effectively improved.

[0021] In one specific implementation, in the step S53, the positive integer is taken after the δ / weld effective thickness, if there is a remainder and the remainder is not greater than the weld effective thickness / 2, then low temperature transformation is performed after the final welding is completed, the low temperature transformation temperature is between 80-100℃, the temperature keeping time is 1-2 hours, and after the low temperature transformation is completed, post-weld non-destructive testing is performed.

[0022] By using the above technical solution, for the case that there is a remainder and the remainder is less than or equal to the weld effective thickness / 2, since no low temperature tempering heat treatment is performed at this time, but the weld thickness obtained by the last welding still generates internal stress, the welding internal stress needs to be removed, and the low temperature transformation processing can reduce the size of the internal stress. In addition, the low temperature transformation can prevent the weld from having abnormal metal organization due to too fast cooling speed, which affects the performance.

[0023] In one specific implementation, the step S8 comprises: S81: first preheat the part where the crack is removed, and the preheating temperature is between 100-250℃; S82: use nickel-based welding material to perform welding repair, and control the interlayer temperature of the weld to be between 150-300℃; S83: repeat the step S81 and the step S82 until all the crack parts are welded, then slowly cool to room temperature, and then perform non-destructive testing.

[0024] By using the above technical solution, by performing preheating before welding and controlling the interlayer temperature of the weld, the generation of welding internal stress can be effectively reduced, and the welding quality can be improved.

[0025] In summary, the present application includes at least one of the following beneficial technical effects: 1. The designed welding method enables the security department to select the appropriate overhaul period according to stability or to perform shutdown and re-welding operation in advance, thereby reducing the safety hazard of the repair site in use; for the pipeline or welded part with a wall thickness exceeding 40 mm, as the welding operation is performed, the stacked weld thickness at the weld gradually increases, and the internal stress generated by the welding also gradually increases, when the internal stress accumulates to a certain extent, cracks are easily generated at the weak part of the weld, therefore, when the weld is welded to the effective thickness, low-temperature tempering heat treatment is performed on the pipeline or welded part to reduce the internal stress, thereby reducing the possibility of crack generation in the welding process and improving the weld quality of the nickel-based weld, even if a crack is generated after the welding is completed, after the nickel-based welding material is used for crack repair, due to the low-temperature tempering heat treatment in the early stage, the internal stress at the weld is reduced, and the weld quality of the repair site of the nickel-based welding material is also improved to a certain extent compared with the conventional nickel-based repair process.

[0026] 2. The designed welding method gives the relationship among the service life of the repair site, the operating temperature of the repair site, the temperature influence coefficient of the nickel-based welding material repair site, the time influence coefficient of the nickel-based welding material repair site, and the time influence coefficient of the iron-based alloy welding material repair site, thereby providing a calculation method of the service life t0 of the repair site under each operating temperature condition, to realize the purpose of accurately judging the repair service life of the welded site.

[0027] 3. The designed welding method further provides an evaluation method of the stability of the nickel-based welding material repair process on the basis of judging that the nickel-based welding material repair process is feasible, thereby reminding the security department to perform key monitoring or shutdown and re-welding operation on the welded repair site in the unstable period.

[0028] 4. The designed welding method can immediately perform low-temperature tempering heat treatment to release the internal stress generated by the welding after the welding is performed to the newly added weld thickness to reach the effective thickness of the weld, and perform nondestructive testing after cooling, which can guarantee that the welded layer that has been welded does not have crack defects, to avoid the increase in operation difficulty caused by detection and repair after the welding is completely performed. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flowchart of the welding method of the embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will be described in detail with reference to the accompanying drawings. Figure 1 The present application will be further described in detail.

[0031] The embodiment of the present application discloses a welding method.

[0032] Reference Figure 1 , a welding method comprises: S1: determining the service life t0 of the repaired part according to the operating temperature T of the repaired part, wherein the unit of the operating temperature T is ℃ and the unit of the service life t0 is month; S2: determining the feasibility of the repair process using nickel-based welding material according to the operating temperature T and the planned operating time H under the condition that the maximum value of H < t0, wherein the unit of the planned operating time H is month; S3: judging the stability of the nickel-based repair process; S4: calculating the effective weld thickness range that should be subjected to low-temperature tempering heat treatment according to the pipe wall thickness δ and the outer diameter D, and determining the number of low-temperature tempering heat treatments according to the pipe wall thickness δ and the effective weld thickness; S5: implementing welding to obtain new welds, and after the thickness of the new welds reaches the effective weld thickness, performing low-temperature tempering heat treatment, and after the low-temperature tempering heat treatment is completed, continuing welding until the final welding is completed and cooled to below 100℃, and then performing post-welding non-destructive testing; S6: performing heat treatment after the post-welding non-destructive testing is qualified; S7: performing non-destructive testing after the heat treatment is completed, determining the position of the weld cracks, and removing the cracks; S8: welding and repairing the part where the cracks are removed using nickel-based welding material until all crack defects are repaired, and then performing non-destructive testing again; S9: after no cracks are found through non-destructive testing, performing non-destructive testing at intervals of 12 hours, 24 hours and 48 hours respectively, and if no cracks are detected through non-destructive testing after 48 hours, the welding repair is completed.

[0033] Further, in step S1, when T < 570℃, the service life t0 of the repaired part ranges from 16.1 months to 72 months; when 570℃ ≤ T < 590℃, the service life t0 of the repaired part ranges from: when 590℃ ≤ T ≤ 630℃, the service life t0 of the repaired part ranges from: wherein the temperature influence coefficient a0 of the nickel-based welding material repaired part ranges from 6% to 12%, the time influence coefficient a1 of the nickel-based welding material repaired part ranges from 0.75 to 0.85, and the time influence coefficient b of the iron-based alloy welding material repaired part ranges from 7% to 10%.

[0034] Specifically, in step S2, when T < 570℃, it is determined that the repair process using nickel-based welding material is feasible; when 570℃ ≤ T < 590℃, if determining that the nickel-based welding material repair process is feasible; when 590℃≤T≤630℃, the nickel-based welding material repair area risk coefficient is iron-based alloy welding material repair area risk coefficient if A < B, it is determined that the nickel-based welding material repair process is feasible; wherein the nickel-based welding material repair site temperature influence coefficient a0 ranges between 6% and 12%, the nickel-based welding material repair site time influence coefficient a1 ranges between 0.75 and 0.85, the iron-based alloy welding material time influence coefficient b ranges between 7% and 10%, and the risk factor θ ranges between 0 and 20%.

[0035] Further, in step S3, when T < 570℃, the planned operation time H < 16.1 months belongs to the stable period, and the planned operation time H ≥ 16.1 months belongs to the unstable period; when 570℃≤T<590℃, belongs to the stable period, belongs to the unstable period; when 590℃≤T≤630℃, belongs to the stable period, belongs to the unstable period.

[0036] In some embodiments of the present application, in step S4, The calculation method of the effective weld thickness is: The calculation method of the low-temperature tempering heat treatment times is: δ / effective weld thickness is taken as a positive integer, and if there is a remainder and the remainder is greater than effective weld thickness / 2, the low-temperature tempering heat treatment times is increased by one.

[0037] Further, step S5 includes: S51: immediately performing low-temperature tempering heat treatment after welding to the newly added weld thickness reaches the effective weld thickness, wherein the constant temperature temperature of the low-temperature tempering heat treatment is 300℃-400℃, and the constant temperature time is 2-4 hours; S52: after natural cooling to below 50℃, performing non-destructive testing.

[0038] S53: after the non-destructive testing is qualified, repeating steps S51 and S52 until the weld is finally welded and cooled to below 100℃, and then performing post-weld non-destructive testing.

[0039] It needs to be further explained that in step S53, the δ / weld effective thickness is taken as a positive integer, and if there is a remainder and the remainder is not greater than the weld effective thickness / 2, then after the welding is finally completed, low temperature transformation is carried out, the low temperature transformation temperature is between 80℃ and 100℃, the constant temperature time is 1 hour-2 hours, and after the low temperature transformation is completed, post-weld nondestructive testing is carried out.

[0040] In addition, step S6 includes: S61: first, the weld position is heated to 300℃-400℃, and the constant temperature time is 2 hours; S62: then, the heat treatment temperature is raised to the constant temperature temperature determined by the original heat treatment process, and heat treatment is carried out according to the constant temperature time determined by the original heat treatment process.

[0041] More specifically, step S8 includes: S81: first, the crack-removed part is preheated, and the preheating temperature is between 100℃ and 250℃; S82: nickel-based welding material is used for welding repair, and the interlayer temperature of the weld is controlled to be between 150℃ and 300℃; S83: repeat steps S81 and S82 until all crack parts are welded, then slowly cool to room temperature, and then perform nondestructive testing.

[0042] In summary, a welding method includes: S1: according to the operating temperature T of the repair part, the service life t0 of the repair part is determined; When T<570℃, the service life t0 of the repair part ranges from 16.1 months to 72 months; when 570℃≤T<590℃, the service life t0 of the repair part ranges from: When 590℃≤T≤630℃, the service life t0 of the repair part ranges from: Wherein, the unit of operating temperature T is ℃, the unit of service life t0 is month, the temperature influence coefficient a0 of the nickel-based welding material repair part ranges from 6% to 12%, the time influence coefficient a1 of the nickel-based welding material repair part ranges from 0.75 to 0.85, and the time influence coefficient b of the iron-based alloy welding material repair part ranges from 7% to 10%; S2: according to the operating temperature T and the planned operating time H, the feasibility of the nickel-based welding material repair process is determined under the condition that H<t0 is the maximum; When T<570℃, it is determined that the nickel-based welding material repair process is feasible; When 570℃≤T<590℃, if It is determined that the nickel-based welding material repair process is feasible; When 590℃≤T≤630℃, the nickel-based welding material repair area risk coefficient is Iron-based alloy welding material repair area risk coefficient If A Wherein, the planned operation time H is in month, the nickel-based welding material repair site temperature influence coefficient a0 ranges between 6% and 12%, the nickel-based welding material repair site time influence coefficient a1 ranges between 0.75 and 0.85, the iron-based alloy welding material time influence coefficient b ranges between 7% and 10%, and the risk factor θ ranges between 0 and 20%; S3: judge the stability of the nickel-based repair process; When T<570℃ and the planned operation time H<16.1 months, it belongs to the stable period, and when the planned operation time H≥16.1 months, it belongs to the unstable period; When 570℃≤T<590℃, It belongs to the stable period, It belongs to the unstable period; When 590℃≤T≤630℃, It belongs to the stable period, It belongs to the unstable period; S4: according to the pipe wall thickness δ and the outer diameter D, the effective weld thickness range which should be subjected to low-temperature tempering heat treatment is calculated, and the low-temperature tempering heat treatment times are determined according to the pipe wall thickness δ and the effective weld thickness; The calculation method of the effective weld thickness is: The calculation method of the low-temperature tempering heat treatment times is: δ / effective weld thickness is taken as a positive integer, if there is a remainder and the remainder is greater than effective weld thickness / 2, then the low-temperature tempering heat treatment times increase once.

[0043] It should be noted that in multiple welding of the same pipeline, each welding can adopt the same effective weld thickness value, or different effective weld thickness values, and when different effective weld thickness values are adopted, (δ-first effective weld thickness-second effective weld thickness-…-Nth effective weld thickness) / Nth effective weld thickness is taken as a positive integer, if there is a remainder and the remainder is greater than Nth effective weld thickness / 2, then the low-temperature tempering heat treatment times increase once, if there is a remainder and the remainder is not greater than Nth effective weld thickness / 2, then low-temperature conversion is carried out after the final welding is completed, the low-temperature conversion temperature is between 80℃ and 100℃, and the constant temperature time is 1 hour to 2 hours; S5: welding is implemented to obtain a new weld, and after the thickness of the new weld reaches the effective weld thickness, low-temperature tempering heat treatment is performed, after the low-temperature tempering heat treatment is completed, nondestructive testing is performed after the welding is completed and cooled to below 100℃, and then post-weld nondestructive testing is performed; S51: immediately after welding to a thickness of the new weld reaches the effective weld thickness, low-temperature tempering heat treatment is performed, wherein the constant temperature temperature of the low-temperature tempering heat treatment is 300-400℃, and the constant temperature time is 2-4 hours; S52: after natural cooling to below 50℃, nondestructive testing is performed.

[0044] S53: after the nondestructive testing is qualified, steps S51 and S52 are repeated, and then post-weld nondestructive testing is performed after the welding is completed and cooled to below 100℃; and δ is a positive integer, if there is a remainder and the remainder is not greater than the effective weld thickness / 2, then low-temperature transformation is performed after the welding is completed, the low-temperature transformation temperature is between 80-100℃, the constant temperature time is 1-2 hours, and post-weld nondestructive testing is performed after the low-temperature transformation is completed; if there is a remainder and the remainder is greater than the effective weld thickness / 2, then low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 300-400℃, and the constant temperature time is 2-4 hours; S6: after the post-weld nondestructive testing is qualified, heat treatment is performed; S61: first, the weld portion is heated to 300-400℃, and the constant temperature time is 2 hours; S62: then, the heat treatment temperature is increased to the constant temperature temperature determined by the original heat treatment process, and heat treatment is performed according to the constant temperature time determined by the original heat treatment process; S7: after the heat treatment is completed, nondestructive testing is performed to determine the position of the weld cracks, and the cracks are removed; S8: the portion where the cracks are removed is welded and repaired using nickel-based welding material, until all crack defects are repaired, and then nondestructive testing is performed again; S81: first, the portion where the cracks are removed is preheated, and the preheating temperature is between 100-250℃; S82: welding and repair is performed using nickel-based welding material, and the interlayer temperature of the weld is controlled to be between 150-300℃; S83: steps S81 and S82 are repeated, until all crack portions are welded, then slow cooling to room temperature is performed, and then nondestructive testing is performed; S9: after the nondestructive testing does not find cracks, nondestructive testing is performed at intervals of 12 hours, 24 hours, and 48 hours, respectively, and if the nondestructive testing after 48 hours does not detect cracks, the welding and repair is completed.

[0045] In this embodiment, in order to better understand the technical solutions disclosed in this embodiment, the welding method is described in detail in combination with a specific application scenario. It should be noted in advance that since there will be errors in the weld thickness obtained after the welding worker welds in actual operation, in the following specific application examples, the weld thickness values are calculated based on theoretical data, and the data errors in actual operation are not considered.

[0046] Application Example 1 Precondition: The operating temperature of the repaired part is 569℃, the planned operating time is 16 months, the welding material is 12Cr1MoVG and 12Cr1MoVG butt welding, the outer diameter is D = 450mm, the wall thickness δ = 80mm, the heat treatment constant temperature of the original welding process evaluation is 720℃-750℃, and the constant temperature time is 4 hours.

[0047] S1: According to the operating temperature T of the repaired part: 569℃, determine the service life t0 of the repaired part: 16.1 months-72 months; S2: According to the operating temperature T: 569℃ and the planned operating time H: 16 months, the maximum value of H < t0 is satisfied, since the operating temperature of the repaired part is 569℃, which is less than 570℃, therefore the nickel-based repair process is feasible; S3: Judge the stability of the nickel-based repair process, since the planned operating time is 16 months, which is less than 16.1 months, therefore it belongs to the stable period; S4: According to the pipe wall thickness δ and the outer diameter D, the effective weld thickness range of low temperature tempering heat treatment should be calculated, and the number of low temperature tempering heat treatment is determined according to the pipe wall thickness δ and the effective weld thickness, specifically, The effective weld thickness is 1.0*33.7mm = 33.7mm, 80 / 33.7 equals 2 with a remainder, but the remainder is less than 33.7 / 2, so the low temperature tempering heat treatment is 2 times; S5: Implement welding to obtain new weld, and after the thickness of the new weld reaches the effective weld thickness 33.7mm, the first low temperature tempering heat treatment is carried out, the low temperature tempering heat treatment constant temperature is 300℃, the constant temperature time is 3 hours, after the low temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, and nondestructive testing is carried out, after the nondestructive testing is qualified, welding is carried out again until the thickness of the new weld reaches the effective weld thickness 33.7mm, and the second low temperature tempering heat treatment is carried out, the low temperature tempering heat treatment constant temperature is 300℃, the constant temperature time is 3 hours, after the low temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, and after the nondestructive testing is qualified, welding is continued, until the welding is completed, low temperature transformation is carried out, the low temperature transformation temperature is 80℃, the constant temperature time is 1 hour, and after the low temperature transformation is completed, post-weld nondestructive testing is carried out; S6: After the non-destructive testing after welding is qualified, heat treatment is carried out, and the heat treatment process is: first heated to 300℃, constant temperature time 2 hours, then heated to 740℃, constant temperature, constant temperature time 4 hours, after constant temperature, cooling and slow cooling; S7: After the heat treatment is completed, non-destructive testing is carried out to determine the position of the weld crack, the crack length is 70mm, the maximum depth is 20mm, and the crack is polished and removed; S8: For the part where the crack is removed, nickel-based welding material is used for welding repair, the preheating temperature is 100℃, the interlayer temperature is 200℃, the welding surface is polished after welding is completed, until all the crack defects are repaired, and non-destructive testing is carried out again; S9: After non-destructive testing does not find cracks, non-destructive testing is carried out at intervals of 12 hours, 24 hours and 48 hours respectively, and no cracks are detected in three times of non-destructive testing, and the welding repair is completed.

[0048] Application example 2 Precondition: The operating temperature of the repair part is 540℃, the planned operating time is 16.1 months, the welding part material is 12Cr1MoVG and 12Cr1MoVG butt welding, the outer diameter is D = 810mm, the wall thickness δ = 90mm, the original welding process evaluation heat treatment constant temperature is 720℃-750℃, and the constant temperature time is 4 hours.

[0049] S1: According to the operating temperature T of the repair part: 540℃, the service life t0 of the repair part is determined: 16.1 months-72 months; S2: According to the operating temperature T: 540℃ and the planned operating time H: 16.1 months less than 72 months, it meets the maximum value of H < t0, since the operating temperature of the repair part is 540℃, which is less than 570℃, therefore the nickel-based repair process is feasible; S3: Evaluate the stability of the nickel-based repair process, since the planned operating time is 16.1 months, which is equal to 16.1 months, therefore it belongs to the unstable period; S4: According to the pipe wall thickness δ and the outer diameter D, the effective thickness range of the weld which should be subjected to low temperature tempering heat treatment is calculated, and the number of low temperature tempering heat treatment is determined according to the pipe wall thickness δ and the effective thickness of the weld, specifically, The effective thickness of the weld is 2.0*30mm = 60mm, 90 / 60 is equal to 1 with a remainder, but the remainder is equal to 60 / 2, so the low temperature tempering heat treatment is 1 time; S5: after the welding is implemented to obtain the new weld, and the thickness of the new weld reaches the effective weld thickness of 60 mm, low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 350℃, the constant temperature time is 3 hours, after the low-temperature tempering heat treatment is completed, the temperature is reduced to below 50℃, after the non-destructive testing is qualified, the welding is continued until the low-temperature transformation is performed after the welding is completed, the low-temperature transformation temperature is 90℃, and the constant temperature time is 2 hours, and after the low-temperature transformation is completed, the post-weld non-destructive testing is performed; S6: after the post-weld non-destructive testing is qualified, heat treatment is performed, and the heat treatment process is: first, the temperature is increased to 350℃, the constant temperature time is 2 hours, then the temperature is increased to 735℃, and the constant temperature is performed, the constant temperature time is 4 hours, after the constant temperature is completed, the temperature is reduced and the temperature is slowly cooled; S7: after the heat treatment is completed, the non-destructive testing is performed to determine the position of the weld crack, the crack length is 130 mm, the maximum depth is 24 mm, and the crack is polished and removed; S8: for the part where the crack is removed, nickel-based welding material is used for welding repair, the preheating temperature is 175℃, the interlayer temperature is 225℃, after the welding is completed, the surface of the weld is polished until all the crack defects are repaired, and the non-destructive testing is performed again; S9: after the non-destructive testing does not find cracks, the non-destructive testing is performed at intervals of 12 hours, 24 hours and 48 hours respectively, and the non-destructive testing does not detect cracks for three times, and the welding repair is completed.

[0050] Application Example 3 Precondition: the operating temperature of the repair part is 505℃, the planned operating time is 71.5 months, the welding material is 12Cr1MoVG and 15CrMoG butt welding, the outer diameter is D = 540 mm, the wall thickness δ = 125 mm, and the heat treatment constant temperature temperature of the original welding process evaluation is 700℃, and the constant temperature time is 2.75 hours.

[0051] S1: according to the operating temperature T of the repair part: 505℃, the service life t0 of the repair part is determined: 16.1 months to 72 months; S2: according to the operating temperature T: 505℃ and the planned operating time H: 71.5 months less than 72 months, H < t0 is satisfied, and since the operating temperature of the repair part is 505℃, which is less than 570℃, the nickel-based repair process is feasible; S3: judge the stability of the nickel-based repair process, since the planned operating time 71.5 months is greater than 16.1 months, it belongs to the unstable period; S4: according to the pipe wall thickness δ and the outer diameter D, the effective weld thickness range of the low-temperature tempering heat treatment should be calculated, and the number of low-temperature tempering heat treatments is determined according to the pipe wall thickness δ and the effective weld thickness, specifically, The effective thickness of the first weld is 0.5*60.1mm=30.05mm, the effective thickness of the second weld is 1*60.1mm=60.1mm, and the remaining weld thickness is greater than the effective thickness of the second weld / 2, so the low-temperature tempering heat treatment is performed 3 times; S5: welding is performed to obtain new welds, and after the first new weld thickness reaches the effective weld thickness of 30.05mm, the first low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 400℃, and the constant temperature time is 2 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, after passing the non-destructive testing, the second welding is performed until the new weld thickness reaches the effective weld thickness of 60.1mm, and the second low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 300℃, and the constant temperature time is 4 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, after passing the non-destructive testing, the third welding is performed until the welding is completed, and the third low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering is 300℃, and the constant temperature time is 4 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 100℃, and the post-weld non-destructive testing is performed; S6: after the post-weld non-destructive testing is passed, the heat treatment is performed, and the heat treatment process is: first heated to 400℃, constant temperature time 2 hours, then heated to 700℃ and kept constant temperature, constant temperature time 2.75 hours, after the constant temperature is completed, the temperature is lowered and the temperature is slowly cooled; S7: after the heat treatment is completed, the non-destructive testing is performed to determine the position of the weld crack, the crack length is 170mm, the maximum depth is 26mm, and the crack is polished and removed; S8: for the part where the crack is removed, nickel-based welding material is used for welding repair, the preheating temperature is 250℃, the interlayer temperature is 300℃, the welding surface is polished after the welding is completed, until all the crack defects are repaired, and the non-destructive testing is performed again; S9: after the non-destructive testing does not find cracks, the non-destructive testing is performed at intervals of 12 hours, 24 hours and 48 hours respectively, and no cracks are detected in the three non-destructive testings, and the welding repair is completed.

[0052] Application Example 4 Precondition: the operating temperature of the repair part is 570℃, the planned operating time is 15.8 months, the welding part material is 12Cr1MoVG and P91 butt welding, the outer diameter is D=790mm, the wall thickness is δ=82mm, and the heat treatment constant temperature temperature of the original welding process evaluation is 750℃, and the constant temperature time is 4 hours.

[0053] S1: according to the operating temperature T of the repair part: 570℃, the service life t0 of the repair part is determined: After calculation, the service life t0 is 15.93 months-38.93 months; S2: According to the operating temperature T: 570℃ and the planned operating time H: 15.8 months less than 38.93 months, the maximum value of H < t0 is met, when the operating temperature T falls between 570℃-590℃, calculate Therefore, the nickel-based welding material repair process is feasible; S3: judge the stability of the nickel-based repair process, since the planned operating time 15.8 months is less than 15.93 months, it belongs to the stable period; S4: according to the pipe wall thickness δ and the outer diameter D, calculate the effective weld thickness range that should be subjected to low-temperature tempering heat treatment, and determine the number of low-temperature tempering heat treatments according to the pipe wall thickness δ and the effective weld thickness, specifically, The effective weld thickness is 1.2 x 26.42 mm = 31.70 mm, since 82 / 31.70 is equal to 2 with a remainder, and the remainder is greater than the effective weld thickness / 2, so the low-temperature tempering heat treatment is performed 3 times; S5: perform welding to obtain new welds, and after the first new weld thickness reaches the effective weld thickness 31.70 mm, perform the first low-temperature tempering heat treatment, the low-temperature tempering heat treatment constant temperature is 400℃, the constant temperature time is 3 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, after the non-destructive testing is qualified, the second welding is performed, until the new weld thickness reaches the effective weld thickness 31.70 mm, the second low-temperature tempering heat treatment is performed, the low-temperature tempering heat treatment constant temperature is 400℃, the constant temperature time is 3 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, after the non-destructive testing is qualified, the third welding is performed, until the welding is completed, the third low-temperature tempering heat treatment is performed, the low-temperature tempering heat treatment constant temperature is 400℃, the constant temperature time is 3 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 100℃, and then the post-weld non-destructive testing is performed; S6: after the post-weld non-destructive testing is qualified, perform heat treatment, the heat treatment process is: first rise to 400℃, constant temperature time 2 hours, then rise to 750℃ and constant temperature, constant temperature time 4 hours, after the constant temperature is completed, perform cooling and slow cooling; S7: after the heat treatment is completed, perform non-destructive testing to determine the position of the weld crack, the crack length is 270 mm, the maximum depth is 21 mm, polish and remove the crack; S8: for the part where the crack is removed, use nickel-based welding material to perform welding repair, the preheating temperature is 250℃, the interlayer temperature is 150℃, after the welding is completed, polish the weld surface until all crack defects are repaired, and then perform non-destructive testing again; S9: after the non-destructive testing does not find cracks, perform non-destructive testing at intervals of 12 hours, 24 hours and 48 hours respectively, and no cracks are detected in the three non-destructive testing, the welding repair is completed.

[0054] Application Example 5 Precondition: the running temperature of the repair site is 580℃, the planned running time is 15.04 months, the welding material is 12Cr1MoVG and 12Cr1MoVG butt welding, the outer diameter is D=759mm, the wall thickness is δ=40mm, the original welding process evaluation heat treatment constant temperature is 740℃, and the constant temperature time is 2 hours.

[0055] S1: according to the running temperature T of the repair site: 580℃, determine the service life t0 of the repair site: The calculated service life t0 is 15.04 months-35.21 months; S2: according to the running temperature T: 580℃ and the planned running time H: 15.04 months, which is less than 35.21 months, it meets the maximum value of H Therefore, the nickel-based repair process is feasible; S3: judge the stability of the nickel-based repair process, since the planned running time 15.04 months is equal to 15.04 months, it belongs to the unstable period; S4: according to the pipe wall thickness δ and the outer diameter D, calculate the effective weld thickness range that should be subjected to low temperature tempering heat treatment, and determine the number of low temperature tempering heat treatment according to the pipe wall thickness δ and the effective weld thickness, specifically, The effective weld thickness is 2*9.18mm=18.36mm, since 40 / 18.36 is equal to 2 with a remainder, but the remainder is less than the effective weld thickness / 2, so the low temperature tempering heat treatment is 2 times; S5: implement welding to obtain new welds, and after the first new weld thickness reaches the effective weld thickness 18.36mm, perform the first low temperature tempering heat treatment, the low temperature tempering heat treatment constant temperature is 330℃, and the constant temperature time is 2 hours, after the low temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, and after the non-destructive testing is qualified, the second welding is performed, until the new weld thickness reaches the effective weld thickness 18.36mm, the second low temperature tempering heat treatment is performed, the low temperature tempering heat treatment constant temperature is 330℃, and the constant temperature time is 2 hours, after the low temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, and after the non-destructive testing is qualified, the third welding is performed, until the welding is completed, and then the low temperature transformation is performed, the low temperature transformation temperature is 90℃, and the constant temperature time is 2 hours, after the low temperature transformation is completed, the post-weld non-destructive testing is performed; S6: after the post-weld non-destructive testing is qualified, heat treatment is performed, the heat treatment process is: first, the temperature is raised to 330℃, the constant temperature time is 2 hours, then the temperature is raised to 740℃ for constant temperature, the constant temperature time is 2 hours, after the constant temperature is completed, the temperature is lowered and the temperature is slowly cooled; S7: after the heat treatment is completed, the non-destructive testing is performed to determine the position of the weld crack, the crack length is 258mm, the maximum depth is 15mm, the crack is polished and removed; S8: The site of the crack is repaired by welding with nickel-based welding material, the preheating temperature is 100℃, the interpass temperature is 300℃, and after welding, the weld surface is polished until all the crack defects are repaired, and then non-destructive testing is performed again; S9: After non-destructive testing does not find cracks, non-destructive testing is performed at intervals of 12 hours, 24 hours and 48 hours, respectively, and no cracks are detected in three non-destructive tests, and the welding repair is completed.

[0056] Application Example 6 Precondition: The operating temperature of the repair site is 589℃, the planned operating time is 31 months, the welding material is P91 and P91 butt welding, the outer diameter is D = 535mm, the wall thickness δ = 105mm, the original welding process evaluation heat treatment constant temperature is 740℃, and the constant temperature time is 8 hours.

[0057] S1: According to the operating temperature T of the repair site: 589℃, the service life t0 of the repair site is determined: After calculation, the service life t0 is 14.22 months to 32.05 months; S2: According to the operating temperature T: 589℃ and the planned operating time H: 31 months less than 32.05 months, it meets H < t0, the maximum value, when the operating temperature T falls between 570℃ and 590℃, calculate Therefore, the nickel-based welding material repair process is feasible; S3: Judge the stability of the nickel-based repair process, since the planned operating time 31 months is greater than 14.22 months, it belongs to the unstable period; S4: According to the pipe wall thickness δ and the outer diameter D, the effective weld thickness range of low temperature tempering heat treatment is calculated, and the number of low temperature tempering heat treatment is determined according to the pipe wall thickness δ and the effective weld thickness, specifically, The effective weld thickness of the first welding is 0.5 x 46.52mm = 23.26mm, and the effective weld thickness of the second welding is 1.6 x 46.52mm = 74.43mm, since the remainder is less than the second effective weld thickness / 2, the low temperature tempering heat treatment is 2 times; S5: welding is implemented to obtain new welds, and after the first new weld thickness reaches the effective weld thickness 23.26mm, the first low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 300℃, the constant temperature time is 4 hours, after the low-temperature tempering heat treatment is completed, the temperature is reduced to below 50℃, after the non-destructive testing is qualified, the second welding is performed, until the new weld thickness reaches the effective weld thickness 74.43mm, the second low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 300℃, the constant temperature time is 4 hours, after the low-temperature tempering heat treatment is completed, the temperature is reduced to below 50℃, after the non-destructive testing is qualified, the third welding is performed, until the welding is completed, the low-temperature transformation is performed, the low-temperature transformation temperature is 100℃, the constant temperature time is 1.5 hours, after the low-temperature transformation is completed, the post-weld non-destructive testing is performed; S6: after the post-weld non-destructive testing is qualified, the heat treatment is performed, the heat treatment process is: first, the temperature is raised to 300℃, the constant temperature time is 2 hours, then the temperature is raised to 740℃, the constant temperature is performed, the constant temperature time is 8 hours, after the constant temperature is completed, the temperature is reduced and the slow cooling is performed; S7: after the heat treatment is completed, the non-destructive testing is performed to determine the position of the weld crack, the crack length is 265mm, the maximum depth is 28mm, the crack is polished and removed; S8: for the part where the crack is removed, nickel-based welding material is used for welding repair, the preheating temperature is 150℃, the interlayer temperature is 230℃, after the welding is completed, the weld surface is polished until all the crack defects are repaired, and the non-destructive testing is performed again; S9: after the non-destructive testing does not find cracks, the non-destructive testing is performed at intervals of 12 hours, 24 hours and 48 hours respectively, and no cracks are detected in the three non-destructive testings, and the welding repair is completed.

[0058] Application example 7 Precondition: the operating temperature of the repair part is 590℃, the planned operating time is 31.5 months, the welding part material is P91 and P91 butt welding, the outer diameter is D = 675mm, the wall thickness δ = 50mm, the heat treatment constant temperature temperature of the original welding process evaluation is 750℃, and the constant temperature time is 5 hours.

[0059] S1: according to the operating temperature T of the repair part: 590℃, the service life t0 of the repair part is determined: Wherein: the temperature influence coefficient a0 of the nickel-based welding material repair part is 6%, the time influence coefficient a1 of the nickel-based welding material repair part is 0.75, the time influence coefficient b of the iron-based alloy welding material repair part is 7%, after calculation, the service life t0 is 14.08 months-31.96 months; S2: According to the operating temperature T: 590℃ and the planned operating time H: 31.5 months less than 31.96 months, the maximum value of H < t0 is met, when 590℃ ≤ T < 630℃, the risk coefficient of the nickel-based welding material repair area is The risk coefficient of the iron-based alloy welding material repair area Wherein the temperature influence coefficient a0 of the nickel-based welding material repair site is 6%, the time influence coefficient a1 of the nickel-based welding material repair site is 0.75, the time influence coefficient b of the iron-based alloy welding material is 7%, and the risk factor θ is 0. After calculation: A = 4.61%, B = 10.63%, A < B is met, it is determined that the nickel-based repair process has feasibility; S3: Judge the stability of the nickel-based repair process. Since the planned operating time 31.5 months is greater than 14.08 months, it belongs to the unstable period. It is suggested that after the operating time exceeds 14.1 months, the non-periodic non-destructive testing of the repair site should be increased to ensure the safe operation of the repair site; S4: According to the pipe wall thickness δ and the outer diameter D, the effective weld thickness range which should be subjected to low-temperature tempering heat treatment is calculated, and the number of low-temperature tempering heat treatment is determined according to the pipe wall thickness δ and the effective weld thickness. Specifically, The effective weld thickness is 1.6 x 13.61 mm = 21.78 mm. Since the remainder is less than the effective weld thickness / 2, the low-temperature tempering heat treatment is performed twice; S5: Perform welding to obtain new welds. After the first new weld thickness reaches the effective weld thickness 21.78 mm, perform the first low-temperature tempering heat treatment. The constant temperature temperature of the low-temperature tempering heat treatment is 300℃, and the constant temperature time is 2 hours. After the low-temperature tempering heat treatment is completed, the temperature is reduced to below 50℃. After passing the non-destructive testing, the second welding is performed. After the second new weld thickness reaches the effective weld thickness 21.78 mm, the second low-temperature tempering heat treatment is performed. The constant temperature temperature of the low-temperature tempering heat treatment is 300℃, and the constant temperature time is 2 hours. After the low-temperature tempering heat treatment is completed, the temperature is reduced to below 50℃. After passing the non-destructive testing, the third welding is performed. After the third welding is completed, the low-temperature transformation is performed. The low-temperature transformation temperature is 100℃, and the constant temperature time is 2 hours. After the low-temperature transformation is completed, the post-weld non-destructive testing is performed; S6: After the post-weld non-destructive testing is passed, the heat treatment is performed. The heat treatment process is: first, the temperature is raised to 300℃, and the constant temperature time is 2 hours. Then, the temperature is raised to 750℃ for constant temperature, and the constant temperature time is 5 hours. After the constant temperature is completed, the temperature is reduced and the temperature is slowly cooled; S7: After the heat treatment is completed, the non-destructive testing is performed to determine the position of the weld crack. The crack length is 300 mm, and the maximum depth is 19 mm. The crack is polished and removed; S8: The site of the crack is repaired by welding with nickel-based welding material, the preheating temperature is 250℃, the interlayer temperature is 150℃, and the weld surface is polished after welding to repair all the crack defects, and then nondestructive testing is performed again; S9: After nondestructive testing does not find cracks, nondestructive testing is performed at intervals of 12 hours, 24 hours and 48 hours respectively, and no cracks are detected in three nondestructive tests, and the welding repair is completed.

[0060] Application Example 8 Precondition: The operating temperature of the repair site is 610℃, the planned operating time is 9.33 months, the welding material is P91 and P91 butt welding, the outer diameter is D = 505mm, the wall thickness is δ = 122mm, the original welding process evaluation heat treatment constant temperature is 760℃, and the constant temperature time is 8 hours.

[0061] S1: According to the operating temperature T of the repair site: 610℃, the service life t0 of the repair site is determined: Wherein: the temperature influence coefficient a0 of the nickel-based welding material repair site is 9%, the time influence coefficient a1 of the nickel-based welding material repair site is 0.80, and the time influence coefficient b of the iron-based alloy welding material repair site is 8.5%, and the calculated service life t0 is 9.33 months-16.98 months; S2: According to the operating temperature T: 610℃ and the planned operating time H: 9.33 months equal to 9.33 months, it satisfies H < t0, when 590℃ ≤ T < 630℃, the risk coefficient of nickel-based welding material repair area is Risk coefficient of iron-based alloy welding material repair area Wherein: the temperature influence coefficient a0 of the nickel-based welding material repair site is 9%, the time influence coefficient a1 of the nickel-based welding material repair site is 0.80, and the time influence coefficient b of the iron-based alloy welding material is 8.5%, and the risk factor θ is 10%, and the calculation: A = 14.16%, B = 19.40%, satisfies A < B, it is determined that the nickel-based repair process is feasible; S3: Judge the stability of nickel-based repair process, since the planned operating time 9.33 months is equal to 9.33 months, it belongs to unstable period, it is suggested that after the operating time exceeds 9.33 months, the non-periodic nondestructive testing of the repair site is increased to ensure the safe operation of the repair site; S4: According to the pipe wall thickness δ and the outer diameter D, the effective thickness range of the weld which should be subjected to low temperature tempering heat treatment is calculated, and the number of low temperature tempering heat treatment is determined according to the pipe wall thickness δ and the effective thickness of the weld, specifically, The effective thickness of the first weld is 0.5*60.0mm=30.0mm, and the effective thickness of the second weld is 1.0*60.0mm=60.0mm. Since the remainder is greater than the effective thickness of the second weld / 2, the low-temperature tempering treatment is performed three times; S5: welding is performed to obtain new welds, and after the first new weld thickness reaches the effective weld thickness 30.0mm, the first low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 350℃, and the constant temperature time is 3 hours. After the low-temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, and after passing the non-destructive testing, the second welding is performed until the new weld thickness reaches the effective weld thickness 60.0mm, and the second low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 350℃, and the constant temperature time is 3 hours. After the low-temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, and after passing the non-destructive testing, the third welding is performed, and after the welding is completed, the third low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 350℃, and the constant temperature time is 3 hours. After the low-temperature tempering heat treatment is completed, the temperature is lowered to below 100℃, and the post-weld non-destructive testing is performed; S6: After the post-weld non-destructive testing is completed, heat treatment is performed, and the heat treatment process is: first, the temperature is raised to 350℃, and the constant temperature time is 2 hours. Then, the temperature is raised to 760℃ and kept constant, and the constant temperature time is 8 hours. After the constant temperature is completed, the temperature is lowered and the temperature is slowly cooled; S7: After the heat treatment is completed, non-destructive testing is performed to determine the position of the weld crack, the crack length is 317mm, the maximum depth is 34mm, and the crack is polished and removed; S8: For the part where the crack is removed, nickel-based welding material is used for welding repair, the preheating temperature is 100℃, the interlayer temperature is 300℃, and after the welding is completed, the weld surface is polished until all the crack defects are repaired. Non-destructive testing is performed again; S9: After non-destructive testing does not find cracks, non-destructive testing is performed at intervals of 12 hours, 24 hours and 48 hours respectively, and no cracks are detected in the three non-destructive tests, and the welding repair is completed.

[0062] Application Example 9 Precondition: The operating temperature of the repair part is 630℃, the planned operating time is 6.9 months, the welding part material is P92 and P92 butt welding, the outer diameter is D=635mm, the wall thickness δ=48mm, and the heat treatment constant temperature temperature of the original welding process evaluation is 765℃, and the constant temperature time is 6 hours.

[0063] S1: According to the operating temperature T of the repair part: 630℃, the service life t0 of the repair part is determined: Wherein: the temperature influence coefficient a0 of the nickel-based welding material repair site is 12%, the time influence coefficient a1 of the nickel-based welding material repair site is 0.85, the time influence coefficient b of the iron-based alloy welding material repair site is 10%, and the service life t0 calculated is 6.95 months to 11.85 months; S2: According to the operating temperature T: 630℃ and the planned operating time H: 6.9 months less than 11.85 months, the maximum value of H < t0 is satisfied, when 590℃ ≤ T ≤ 630℃, the risk coefficient of the nickel-based welding material repair area is The risk coefficient of the iron-based alloy welding material repair area Wherein: the temperature influence coefficient a0 of the nickel-based welding material repair site is 12%, the time influence coefficient a1 of the nickel-based welding material repair site is 0.85, the time influence coefficient b of the iron-based alloy welding material repair site is 10%, and the risk factor θ is 20%, the calculation result is A = 31.37% and B = 32.12%, which satisfies A < B, and it is determined that the nickel-based welding material repair process has feasibility; S3: The stability of the nickel-based repair process is judged, since the planned operating time 6.9 months is less than 6.95 months, it belongs to the stable period; S4: According to the pipe wall thickness δ and the outer diameter D, the effective weld thickness range which should be subjected to low-temperature tempering heat treatment is calculated, and the low-temperature tempering heat treatment frequency is determined according to the pipe wall thickness δ and the effective weld thickness, specifically, The effective weld thickness is 2 × 13.20mm = 26.4mm, since the remainder is greater than the effective weld thickness / 2, the low-temperature tempering heat treatment is performed twice; S5: Welding is performed to obtain new welds, and after the first new weld thickness reaches the effective weld thickness 26.4mm, the first low-temperature tempering heat treatment is performed, the constant temperature temperature of the low-temperature tempering heat treatment is 380℃, and the constant temperature time is 2 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 50℃, and after the non-destructive testing is qualified, the second welding is performed, until the second low-temperature tempering heat treatment is performed after the welding is completed, the constant temperature temperature of the low-temperature tempering heat treatment is 380℃, and the constant temperature time is 2 hours, after the low-temperature tempering heat treatment is completed, the temperature is lowered to below 100℃, and the post-weld non-destructive testing is performed; S6: After the post-weld non-destructive testing is qualified, heat treatment is performed, and the heat treatment process is: first heating to 380℃, constant temperature time 2 hours, then heating to 765℃ for constant temperature, constant temperature time 6 hours, after the constant temperature is completed, cooling and slow cooling are performed; S7: After the heat treatment is completed, non-destructive testing is performed to determine the position of the weld crack, the crack length is 293mm, and the maximum depth is 11mm, the crack is polished and removed; S8: The site of the crack is repaired by welding with nickel-based welding material, the preheating temperature is 200℃, the interlayer temperature is 200℃, the weld surface is polished after welding, until all the crack defects are repaired, and then nondestructive testing is performed again; S9: After nondestructive testing does not find cracks, nondestructive testing is performed at intervals of 12 hours, 24 hours and 48 hours respectively, and no cracks are detected in three nondestructive tests, and the welding repair is completed.

[0064] The inventors have statistically analyzed the probability of cracks in the welding seams of the above-mentioned parts, especially the parts with a thickness of more than 40 mm, such as valves, tees and irregular-shaped parts, etc., which are prone to cracks, and analyzed the causes of the cracks: 1. According to the research results, if the original welding process is followed: iron-based alloy welding material bottoming-filling-welding completion-low temperature transformation-welding heat treatment, it is statistically found that the probability of obvious cracks during welding is more than 10% to 20%, the probability of cracks before welding heat treatment is 15% to 25%, and the probability of cracks after slow cooling to ambient temperature after welding heat treatment is more than 30%, and the probability of cracks in the welding seams of iron-based alloy heat-resistant steel is about 40%. This is because the stress generated during welding is very large, and the accumulated stress is easily released at weak parts during the welding process, after welding completion and during welding heat treatment, resulting in the occurrence of cracks.

[0065] 2. For part of the welding process: iron-based alloy welding material bottoming-filling-welding completion-low temperature tempering treatment-welding heat treatment, it is statistically found that the probability of obvious cracks during welding is more than 10% to 15%, the probability of cracks before welding heat treatment is about 12% to 18%, and the probability of cracks after slow cooling to ambient temperature after welding heat treatment is more than 23%, and the probability of cracks in the welding seams of iron-based alloy heat-resistant steel is about 30%. The main reason for the cracks during welding is that the accumulated stress is too large, and the stress is easily released at weak parts, resulting in cracks; the internal stress after welding completion is usually too large, and when it is reduced to below 100℃ after low temperature tempering heat treatment, although low temperature tempering heat treatment has limited effect on stress relief, and the internal stress is released too quickly, cracks are easily generated at weak parts; during welding heat treatment, the accumulated stress is released at weak parts, and the probability of cracks is relatively large.

[0066] 3. The welding process proposed in this invention consists of the following steps: applying the root pass with iron-based welding materials, filling the weld, alternating between low-temperature tempering and welding, completing the welding, performing low-temperature tempering or low-temperature transformation treatment, and post-weld heat treatment. According to statistics, the probability of cracks appearing during the welding process is only about 2% to 4%, the probability of cracks appearing before post-weld heat treatment is less than 5% to 7%, and the probability of cracks appearing after slow cooling to ambient temperature after post-weld heat treatment is less than 10%. The probability of cracks appearing in iron-based alloy heat-resistant steel welds can be effectively controlled to less than 12%.

[0067] Statistical data comparison shows that, in terms of welding heat treatment quality, the welding method disclosed in this application significantly improves the quality of the weld.

[0068] Based on the above statistics, regarding the repair of cracks after heat treatment, the inventors have tracked the situation of the repaired parts with nickel-based welding materials in actual operation for many years, and have statistically analyzed the failure situation during the stable period and the unstable period.

[0069] 1. The process is as follows: iron-based welding material for root pass ~ fill pass ~ welding completion ~ low temperature transition ~ post-weld heat treatment. After repairing the cracks that appear in the post-weld heat treatment with nickel-based welding material, the probability of failure in the stable period is 15% to 40%, and the probability of cracks appearing in the unstable period is 25% to 90%. 2. The process is as follows: iron-based welding material for root pass ~ fill pass ~ welding completion ~ low temperature tempering treatment ~ post-weld heat treatment. After repairing the cracks that appear in the post-weld heat treatment with nickel-based welding material, the probability of failure in the stable period is 10% to 25%, and the probability of cracks appearing in the unstable period is 15% to 60%. 3. The welding process proposed in this invention consists of the following steps: applying iron-based welding materials for the root pass, filling the hole, alternating between low-temperature tempering and welding, completing the welding, applying low-temperature tempering or low-temperature transformation treatment, and post-weld heat treatment. After repairing the cracks that appear during the post-weld heat treatment with nickel-based welding materials, the probability of failure during the stable period is 2% to 4%, and the probability of cracks appearing during the unstable period is 7% to 20%.

[0070] The reasons for the above situations are mainly related to the magnitude of the internal stress generated by welding and the degree of release of internal stress through post-heat treatment, low-temperature transition, and post-weld heat treatment. In addition, through the above comparison, the present invention significantly improves the quality effect of nickel-based welding material repair and significantly reduces the occurrence of quality and safety hazards during the stabilization period. This indicates that the welding process described in this invention has good reliability in terms of welding quality and operational safety for easily cracked areas, and has significant advantages compared to other processes.

[0071] Further, according to years of practical experience, in order to effectively improve the implementation effect of low-temperature tempering heat treatment during welding and the stress relief effect of post-weld heat treatment, the following operation experience is proposed: according to the calculation of the effective thickness of the weld, when welding layer by layer, the thickness range of each layer of the weld is reasonably planned, when welding to within 3mm from the effective thickness of the weld, the local thickness of the weld can be repaired by welding, and the local thickness of the weld can be polished on the surface, the thickness of the weld should not exceed the calculated value of the effective thickness of the weld, at this time, the low-temperature tempering heat treatment process is used, which also does not affect the implementation effect; after post-weld heat treatment, when the cooling speed is controlled at 60℃ / h-150℃ / h, the stress relief effect is not affected.

[0072] Regarding non-destructive testing, the inventor believes through practical experience that after low-temperature tempering heat treatment before the final welding is completed, when the temperature is reduced to below 50℃, the PT detection technology is preferred for surface detection of the weld area, and after detection, the next process is carried out; after low-temperature transformation and low-temperature tempering heat treatment after the final welding is completed, when the temperature is below 100℃, the MT detection technology is preferably used for detection of the weld surface, and after detection, the subsequent post-weld heat treatment is carried out; after post-weld heat treatment is completed, when the temperature is reduced to below 100℃, the MT detection technology is preferred for detection of the weld area. Internal crack detection of the weld is usually based on ultrasonic detection and phased array detection technology. If cracks are detected before post-weld heat treatment, the crack area can be polished and eliminated for repair welding; if cracks are detected after post-weld heat treatment, the nickel-based welding material repair process described in the present application can be used to repair the crack removal area.

[0073] Regarding the feasibility and stability of the nickel-based welding material repair process, according to implementation experience, since the operating temperature of the repair area remains stable and does not change significantly during operation, the inventor believes that if the evaluation result value is ≥5% when 570℃≤T<590℃ or the nickel-based welding material repair area risk coefficient A is ≥ the iron-based alloy welding material repair area risk coefficient B when 590℃≤T≤630℃, it is extremely likely that the planned operation time H established by the security department or the operation department is unreasonable. In order to avoid the above problems, improve the reliability of the welding quality of the nickel-based repair area, and greatly reduce the quality safety hidden danger, the inventor believes that the most effective way to reduce the quality safety hidden danger is to shorten the planned operation time or adjust the planned operation time to a controllable range.

[0074] The implementation principle of the welding method in the embodiment of the application is as follows: for a pipeline or a welded part repaired by using nickel-based welding material, since the service life of the nickel-based welding material is greatly affected by temperature, when the repaired part appears failure again, there are three failure conditions, the first condition is that the failure part appears in the middle region of the nickel-based weld, that is, the failure part is between nickel-based materials and there is basically no iron-based alloy composition; the second condition is that the failure part appears between the nickel-based material and the iron-based material and tends to the nickel-based side, and the failure part has a certain concentration of iron-based alloy composition, which causes the metal structure of the weld to be relatively complex and belongs to a weak structure; the third condition is that the failure part appears on the iron-based side outside the fusion line, that is, the failure part appears in the welding heat affected zone, because the metallographic structure of the welding heat affected zone is abnormal, there are coarse and overheated structures, and the failure part is relatively prone to fracture. Therefore, the relationship among the service life of the repaired part, the operating temperature of the repaired part, the temperature influence coefficient of the nickel-based repaired part, the time influence coefficient of the nickel-based repaired part, and the time influence coefficient of the iron-based alloy repaired part is provided, so as to provide a calculation method of the service life t0 of the repaired part under each operating temperature condition, so as to accurately judge the service life of the repaired part.

[0075] Then, according to the operating temperature T and the planned operating time H, the feasibility of the nickel-based welding material repair process is determined under the condition that H is less than the maximum value of t0, and on the basis of judging that the nickel-based welding material repair process is feasible, an evaluation method of the stability of the nickel-based welding material repair process is further provided, so as to remind the safety department to focus on monitoring or stopping and rewelding the welding repaired part in the unstable period, so that the safety department can select a suitable maintenance period or perform the stopping and rewelding operation in advance according to the stability, so as to reduce the safety hidden danger of the repaired part.

[0076] For the pipeline or the welded part with a wall thickness greater than 40 mm, the thickness of the stacked weld at the weld gradually increases with the welding operation, and the internal stress generated by the welding also gradually increases, when the internal stress accumulates to a certain degree, cracks are easily generated at the weak part of the weld, therefore, when the weld is welded to the effective thickness, the pipeline or the welded part is subjected to low-temperature tempering treatment to reduce the internal stress, so as to reduce the possibility of generating cracks in the welding process and improve the weld quality of the nickel-based weld, and after the low-temperature tempering heat treatment is completed, nondestructive testing is performed, a weld effective thickness calculation method based on the pipe outer diameter and the pipe wall thickness is provided, so as to facilitate reminding the operator to perform low-temperature tempering heat treatment when the newly added weld depth reaches the effective weld thickness, and a calculation method of the number of low-temperature tempering heat treatments is provided.

[0077] After the welding operation is completed, the pipeline is again subjected to heat treatment, and after the heat treatment is completed, nondestructive testing is performed to determine the location of the cracks at the weld, and the cracks are removed using a tool, and nondestructive testing is performed three times at three time nodes of 12 hours, 24 hours and 48 hours apart, respectively, and if no cracks are found in the three nondestructive testing processes, it means that the pipeline welding repair work is completed.

[0078] The above are preferred embodiments of the present application, and do not limit the protection scope of the present application, so: any equivalent changes made in structure, shape, principle, etc. according to the present application should be covered within the protection scope of the present application.

Claims

1. A welding method, characterized in that: include: S1: Determine the service life t0 of the repaired part based on the operating temperature T of the repaired part, where the operating temperature T is in °C and the service life t0 is in months. S2: Based on the operating temperature T and the planned operating time H, under the condition that H < t0 at its maximum value, the feasibility of using nickel-based welding materials for repair is determined. The planned operating time H is in months. S3: Evaluate the stability of the nickel-based repair process; S4: Calculate the effective thickness range of the weld that should undergo low-temperature tempering heat treatment based on the pipe wall thickness δ and the outer diameter D, and determine the number of low-temperature tempering heat treatments based on the pipe wall thickness δ and the effective weld thickness. S5: Welding is carried out to obtain a new weld. After the thickness of the new weld reaches the effective weld thickness, low-temperature tempering heat treatment is performed. After the low-temperature tempering heat treatment is completed and the non-destructive testing is qualified, welding continues until the welding is finally completed and cooled to below 100°C. Then, post-weld non-destructive testing is performed. S6: Heat treatment is performed after the non-destructive testing of the weld is qualified. S7: After heat treatment, perform non-destructive testing to determine the location of weld cracks and remove them; S8: For areas where cracks have been removed, repair them by welding with nickel-based welding materials until all cracks and defects have been repaired, and then perform non-destructive testing again; S9: If no cracks are found during non-destructive testing, non-destructive testing is performed at intervals of 12 hours, 24 hours and 48 hours. If no cracks are detected during non-destructive testing after 48 hours, the welding repair is complete.

2. The welding method according to claim 1, characterized in that: In step S1 When T < 570℃, the service life t0 of the repaired part ranges from 16.1 months to 72 months; when 570℃ ≤ T < 590℃, the service life t0 of the repaired part ranges from: When 590℃≤T≤630℃, the service life t0 of the repaired part is within the range of: Among them, the temperature influence coefficient a0 of the nickel-based welding material repaired part ranges from 6% to 12%, the time influence coefficient a1 of the nickel-based welding material repaired part ranges from 0.75 to 0.85, and the time influence coefficient b of the iron-based alloy welding material repaired part ranges from 7% to 10%.

3. The welding method according to claim 1, characterized in that: In step S2 When T < 570℃, it is determined that the repair process using nickel-based welding materials is feasible; When 570℃≤T<590℃, if The feasibility of using nickel-based welding materials for repair was determined. When 590℃≤T≤630℃, the risk coefficient of the nickel-based welding material repair zone is: Risk coefficient of iron-based alloy welding materials in the repair area If A < B, then the repair process using nickel-based welding materials is deemed feasible. Among them, the temperature influence coefficient a0 of the repaired part of nickel-based welding material ranges from 6% to 12%, the time influence coefficient a1 of the repaired part of nickel-based welding material ranges from 0.75 to 0.85, the time influence coefficient b of iron-based alloy welding material ranges from 7% to 10%, and the risk factor θ ranges from 0 to 20%.

4. The welding method according to claim 1, characterized in that: In step S3 When T < 570℃ and the planned operating time H < 16.1 months, it is considered a stable period; when the planned operating time H ≥ 16.1 months, it is considered an unstable period. When 570℃≤T<590℃ This is a period of stability. This period is considered an unstable time. When 590℃≤T≤630℃ This is a period of stability. This period is considered an unstable time.

5. The welding method according to claim 3, characterized in that: In step S4 The method for calculating the effective thickness of the weld is as follows: The calculation method for the number of low-temperature tempering heat treatments is as follows: δ / effective weld thickness, rounded to a positive integer. If there is a remainder and the remainder is greater than the effective weld thickness / 2, then the number of low-temperature tempering heat treatments is increased by one.

6. The welding method according to claim 5, characterized in that: In step S4, δ / effective weld thickness is taken as a positive integer. If there is a remainder and the remainder is not greater than the effective weld thickness / 2, then a low-temperature transition is performed after the welding is finally completed. The low-temperature transition temperature is between 80℃ and 100℃, and the holding time is 1 hour to 2 hours. After the low-temperature transition is completed, post-weld non-destructive testing is performed.

7. The welding method according to claim 6, characterized in that: Step S5 includes: S51: After each weld reaches the effective thickness of the new weld, a low-temperature tempering heat treatment shall be performed immediately. The constant temperature of the low-temperature tempering heat treatment shall be 300℃~400℃ and the constant temperature time shall be 2~4 hours. S52: Allow the temperature to cool naturally to below 50°C before performing non-destructive testing. 8.S53: After passing the non-destructive testing, repeat steps S51 and S52 until the weld is finally completed and the temperature drops below 100℃ before performing post-weld non-destructive testing.

9. The welding method according to claim 1, characterized in that: Step S6 includes: S61: First, heat the weld area to 300℃~400℃ and keep it at that temperature for 2 hours; S62: Then raise the heat treatment temperature to the constant temperature determined by the original heat treatment process, and perform heat treatment according to the constant temperature time determined by the original heat treatment process.

10. The welding method according to claim 1, characterized in that: Step S8 includes: S81: First, preheat the area where the cracks have been removed. The preheating temperature should be between 100℃ and 250℃. S82: Use nickel-based welding materials for welding repair and control the interpass temperature of the weld between 150℃ and 300℃; S83: Repeat steps S81 and S82 until all cracked areas are welded, then slowly cool to room temperature and perform non-destructive testing.

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