Method for obtaining tempering temperature interval, application thereof, method for evaluating applicability of tempering weld bead technology, and implementation method for tempering weld bead technology

Abstract

The present application discloses a method for obtaining a tempering temperature interval, an application thereof, a method for evaluating the applicability of a tempering weld bead technology, and an implementation method for the tempering weld bead technology. The method for obtaining the tempering temperature interval comprises: determining a judgment criterion for the structure and performance obtained after a tempering weld bead of a steel grade is welded; determining a temperature Ac1 at which the steel grade starts to be formed or transformed into austenite in a welding and heating process; obtaining a temperature field distribution in the welding process, and determining a thermal cycle curve and the size distribution of a temperature field at different temperature intervals; adopting different peak tempering temperatures to conduct simulation and performance testing on a thermal cycle curve of the structure of a welded coarse grain area, and determining a lowest peak temperature Tw and a highest peak temperature Tp meeting the judgment criterion; and obtaining, on the basis of the highest peak temperature Tp and the lowest peak temperature Tw of the steel grade, a tempering temperature interval △Tw, wherein Tp = Ac1 for some steel grades.

Description

Methods for obtaining the tempering temperature range and its application, evaluation methods for the applicability of tempering weld technology, and implementation methods of tempering weld technology Technical Field

[0001] The present application specifically relates to a method for obtaining a tempering temperature range and its application, a method for evaluating the applicability of a tempering weld bead technology based on the tempering temperature range, and a method for implementing the tempering weld bead technology. Background Art

[0002] Pressure-bearing special equipment inevitably develops damage or even defects during service. Welding repairs or replacement parts are often used to eliminate these damages and defects to maintain the structural integrity of the equipment. The weld thermal cycle during the repair process increases residual stress, hardness, and toughness in the heat-affected zone (HAZ). Post-weld heat treatment (PTW) is often required to improve performance. However, certain objective conditions limit the application of PTW, leading to the development of a PT-free weld repair technology: tempered bead welding (TBW).

[0003] ASME (2004 Edition), Section IX, QW490, defines tempering bead welding technology as "the application of a weld bead to a specific location or weld surface to affect the metallurgical properties of the heat-affected zone (HAZ) or the previously deposited weld metal." Tempering bead welding technology effectively improves the microstructure and properties of the HAZ of steel grades during multi-layer, multi-pass welds by properly controlling weld bead geometry, weld overlap, and welding heat input.

[0004] With the maturity and development of tempering bead welding technology, it is increasingly being applied to the weld repair of thick-walled components in the thermal power, nuclear power, and petrochemical industries. Furthermore, various tempering bead welding techniques, such as half-bead tempering, controlled deposition, uniform weld layer, double-layer tempering, and toe tempering, have been developed, eliminating the need for post-weld heat treatment. The American American Society of Mechanical and Electrical Engineers (ASME) and French Royal Society of Mechanical and Electrical Engineers (RCCM) standards have also gradually incorporated tempering bead welding technology into their standards systems. ASME Standards, Volume IX, Chapter II, "Welding Procedure Qualification," QW-290, and Volume XI, "Rules for In-Service Inspection of Nuclear Power Plant Components," respectively, set forth requirements for tempering bead welding technology, including welding procedure qualification, defect removal, welding method selection, electrode selection, and tempering bead repair dimensions. French RCC-M, Volume IV, S7600, "Welding Repair," also provides standards for tempering bead welding technology. Unlike the American ASME Standards, the French RCC-M requires additional analysis of the impact of the weld repair area on overall component stress.

[0005] In recent years, many domestic scholars have also done a lot of work on the application research of tempering weld technology for low-alloy steel materials. For example, Shanghai Jiao Tong University uses double-layer tempering laser cladding repair technology, which can achieve the process of eliminating subsequent tempering heat treatment by fully utilizing the tempering effect of the subsequent cladding layer on the previous cladding layer; Harbin Welding Research Institute systematically studied the weld size, heat-affected zone structure, performance and welding thermal cycle changes of SA508-3 steel tempering weld; Suzhou Thermal Engineering Research Institute analyzed the microstructure and properties of 16MnD5 steel tempered welds with 690 nickel-based welding wire; China General Nuclear Power Engineering Company completed the exploration of the simulated tempering weld repair process of 18MnD5 forgings using nickel-based alloy welding materials.

[0006] The US ASME standard specifies that tempering weld bead technology is applicable to carbon steels and low-alloy steels such as P-1, 3, 12A, 12B, and 12C, but does not explain the reasons or whether other steel grades are also suitable for this technology. The US ASME standard QW-290 specifies that tempering weld bead technology is limited to manual metal arc welding (SMAW), tungsten inert gas welding (GTAW), submerged arc welding (SAW), gas metal arc welding (GMAW), and plasma arc welding (PAW) welding methods. Among them, gas metal arc welding includes flux cored arc welding (FCAW). Similarly, the reason is not explained or why other welding methods are not suitable for this technology. Moreover, most of these studies at home and abroad focus on the process exploration and engineering application of tempering welds. Currently, there is a lack of research on the applicability of tempering weld technology in materials and welding methods, which limits the application of tempering weld technology, especially in pressure-bearing special equipment.

[0007] Application Contents

[0008] In view of this, in order to overcome the defects of the prior art, the purpose of this application is to provide a method for obtaining the tempering temperature range, and apply it to the evaluation of the applicability of the tempering weld technology and the implementation of the tempering weld technology.

[0009] In order to achieve the above objectives, this application adopts the following technical solutions:

[0010] A method for obtaining a tempering temperature range comprises the following steps:

[0011] Determine the criteria for determining the effect of tempering welds on steel grades;

[0012] Determine the temperature Ac1 at which the steel begins to form or transform into austenite during welding heating;

[0013] Obtain the temperature field distribution during welding, and determine the thermal cycle curves and temperature field size distribution in different temperature ranges;

[0014] The thermal cycle curve under the coarse grain zone is used to simulate the steel grade, and the sample with the coarse grain zone structure is obtained and the performance test is carried out;

[0015] Take samples of the coarse-grained zone of the weld and simulate the thermal cycle curve and perform performance tests using different peak tempering temperatures to determine the minimum peak temperature Tw and the maximum peak temperature Tp that meet the judgment criteria;

[0016] The tempering temperature range ΔTw is obtained according to the highest peak temperature Tp and the lowest peak temperature Tw.

[0017] Optionally, the lower limit of the tempering temperature range ΔTw is the lowest peak temperature Tw, and the upper limit is the highest peak temperature Tp.

[0018] Optionally, the minimum peak temperature Tw is the minimum tempering temperature of the steel grade having the tempering effect of the tempering weld.

[0019] Optionally, the maximum peak temperature Tp is the highest tempering temperature of the steel grade having the tempering effect of the tempering weld.

[0020] Optionally, when the steel grade is nuclear-grade 18MnD5 low-alloy steel, the corresponding criteria for determining the effect of the tempering weld are: impact energy ≥40J at -20°C and ≥72J at 20°C, the hardness value is the steel grade hardness + 100HB, the yield strength is ≥420MPa at 20°C and ≥380MPa at 350°C, and the tensile strength is 580-720MPa at 20°C and ≥540MPa at 350°C.

[0021] Optionally, the temperature field distribution during the welding process is obtained by the following steps: establishing a calculation model of the welding process through finite element analysis calculation method, verifying the calculation model through experiments or temperature acquisition methods, and then obtaining the temperature field distribution during the welding process.

[0022] Optionally, when the steel type is nuclear-grade 18MnD5 low-alloy steel, the size distribution of the thermal cycle curve and the temperature field is set as follows: melting zone >1504°C, corresponding to the size W1; coarse grain zone 1100°C~1504°C, corresponding to the size W2; fine grain zone / complete recrystallization zone Ac3~1100°C, corresponding to the size W3; critical zone Ac1~Ac3, corresponding to the size W4; tempering temperature zone Tw~Ac1, corresponding to the size W5, and Tp=Ac1 of 18MnD5 low-alloy steel.

[0023] Optionally, when the steel type is nuclear-grade 18MnD5 low-alloy steel, the Ac1 temperature of the steel type is 721°C, the minimum tempering peak temperature Tw with a tempering weld effect is 500°C, the maximum tempering peak temperature Tp with a tempering weld effect is Ac1, and the corresponding tempering temperature range ΔTw is 500°C to 721°C.

[0024] The present application also provides a method for obtaining a tempering temperature range according to the acquisition method described above, thereby realizing the application of the "tempering temperature range" in a method for evaluating the suitability of tempering weld technology.

[0025] Specifically, a method for evaluating the suitability of tempering weld technology includes the following steps:

[0026] According to the acquisition method described above, the tempering temperature interval ΔTw is obtained, and the size corresponding to the tempering temperature interval ΔTw is W5;

[0027] If the W5 obtained under a certain welding process parameter can cover the size W2 of the coarse grain zone of the previous weld bead, the tempering weld bead technology is suitable for this steel grade;

[0028] If the welding parameters cannot be adjusted so that W5 covers the size W2 of the coarse-grained area of ​​the previous weld, the tempering weld technology is not suitable for this steel grade.

[0029] According to the tempering temperature range △Tw size of the obtained steel grade, it can be judged that the wider the tempering temperature range △Tw temperature range is, the easier it is to achieve the effect of improving the microstructure and performance by adopting the tempering weld technology, and vice versa.

[0030] For welding under a specific welding method, the tempering temperature range △Tw is combined with the size of the tempering temperature zone W5 in the temperature field during welding to determine whether the tempering weld bead technology is suitable for welding this type of steel with this welding method, and then adjust the welding parameters to meet the implementation of the tempering weld bead technology.

[0031] Optionally, the welding parameters include heat input, current, voltage, rate, overlap, and grinding amount.

[0032] Based on the above-mentioned method for obtaining the tempering temperature range and the method for evaluating the technical applicability of the tempering weld bead, the present application also provides a tempering weld bead welding method, comprising the following steps:

[0033] According to the acquisition method described above, the tempering temperature range ΔTw of the steel grade is obtained, and the size corresponding to the tempering temperature range ΔTw is W5;

[0034] If the W5 obtained under a certain welding process parameter can cover the size W2 of the coarse grain zone of the previous weld bead, then the welding process parameter is used for the tempering weld bead;

[0035] If W5 obtained under the welding process parameters cannot cover the size W2 of the coarse grain zone of the previous weld bead, the welding parameters are adjusted so that W5 covers the size W2 of the coarse grain zone of the previous weld bead, and the tempering weld is welded using the adjusted welding process parameters.

[0036] As described above, the present application provides a method for obtaining a tempering temperature range and its application, a method for evaluating the applicability of a tempering weld bead technology based on the tempering temperature range, and an implementation method for the tempering weld bead technology. By obtaining the tempering temperature range, the obtained tempering temperature range can effectively characterize the welding effect of the tempering weld bead technology and be used in the evaluation of the applicability of the tempering weld bead technology. It can easily determine the steel type and welding method applicable to the tempering weld bead technology, avoid unnecessary losses due to improper selection, and provide a reasonable criterion for whether the tempering weld bead technology can be effectively applied. It has universal applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0038] FIG1 is a schematic diagram showing the determination of the tempering temperature range under the corresponding temperature field in the iron-carbon phase diagram in one embodiment of the present application.

[0039] FIG2 shows the tempering temperature range determination given in combination with the determination criteria for the tempering weld effect in one embodiment of the present application.

[0040] FIG3 is a schematic diagram of the process of obtaining and promoting the “tempering temperature range” in one embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0042] Many parameters affect the microstructure and performance of tempered welds, such as electrode diameter, heat input, weld overlap, and weld grinding. Heat input and weld overlap directly affect the geometric size distribution of the weld bead, which in turn affects the distribution of the hardened microstructure between adjacent welds, directly determining the success of tempered weld technology.

[0043] However, there is no unified criterion to judge whether different metal materials and different welding methods are suitable for tempering weld technology. Based on this, this application proposes a "tempering temperature range" △Tw that affects the effect of tempering weld, and defines this criterion: △Tw is the width of the tempering temperature range for steel with a tendency to harden (easy to harden steel) to obtain high-quality microstructure and performance under the welding heat cycle implemented by tempering weld technology, △Tw = Tp-Tw, where Tw is the lowest tempering temperature of the steel with the tempering weld tempering effect, and Tp is the highest tempering temperature of the steel with the tempering weld tempering effect. The Tp obtained for certain steels is the temperature Ac1 at which austenite begins to form or transform into austenite during the welding heating process. At the same time, a method for obtaining the "tempering temperature range" is proposed; and then the "tempering temperature range" is derived and applied to other steels and welding methods, expanding the application of tempering welds.

[0044] The method for evaluating the suitability of tempering weld technology using the tempering temperature range ΔTw in this application specifically includes the following steps:

[0045] Step 1: Determine the judgment criteria

[0046] When determining the criteria, the industry standards or regulations for the corresponding steel grade are selected based on the steel grade's material quality, and the criteria for determining the effectiveness of the tempering weld bead are determined. In this embodiment, when the steel grade is nuclear-grade 18MnD5 low-alloy steel, the criteria are determined based on the requirements specified in the French RCC-M2000 standard. The determined criteria for determining the effectiveness of the tempering weld bead are: impact energy ≥ 40J at -20°C and ≥ 72J at 20°C, hardness value is the steel grade hardness + 100HB, yield strength ≥ 420MPa at 20°C and ≥ 380MPa at 350°C, and tensile strength 580-720MPa at 20°C and ≥ 540MPa at 350°C. In other embodiments, when other steel grades are selected, the criteria for determining the effectiveness of the tempering weld bead can be determined based on the corresponding industry standards or regulations for the steel grade.

[0047] Step 2: Determine Ac1

[0048] Determine the temperature Ac1 at which the steel begins to form or transform into austenite during welding heating.

[0049] In this application, the Ac1 of different steel grades can be obtained by experimental testing. In this application, for example, with reference to the Chinese standard YB / T 5128-1993 "Measurement Method of Continuous Cooling Transformation Curve of Steel (Dilatation Method)", the Ac1 of the steel grade is determined by experimental methods.

[0050] In this embodiment, when the steel type is nuclear-grade 18MnD5 low-alloy steel, the Ac1 temperature of the steel type is obtained by the following steps: referring to the Chinese standard YB / T 5128-1993 "Measurement method of continuous cooling transformation curve of steel (expansion method)", the Ac1 temperature of the steel type is determined by experimental method.

[0051] Step 3: Obtain temperature field distribution

[0052] Obtain the temperature field distribution during the welding process, and determine the thermal cycle curve and temperature field size distribution in different temperature ranges.

[0053] The temperature field distribution during welding can be obtained through the following steps: establish a calculation model of the welding process through finite element analysis calculation method, verify the calculation model through experiments or temperature acquisition methods, and obtain the temperature field distribution during welding.

[0054] During the welding process, after setting the welding conditions, the temperature field distribution under the welding conditions is obtained. In this application, the welding process is divided into, for example, a melting zone > T1 (size W1), a coarse grain zone T2 to T1 (size W2), a fine grain zone / complete recrystallization zone T3 to T2 (size W3), a critical zone T4 to T3 (size W4), and a tempering temperature zone T5 to T4 (size W5). Among them, T1 is the solidus temperature of the steel, T2 is the temperature at which the grains grow rapidly, for example, around 1100°C, T3 is the temperature at which the steel stops forming or transforming into austenite during the heating process, i.e., Ac3, T4 is the highest peak temperature that meets the judgment criteria during the welding process, and T5 is the lowest peak temperature that meets the judgment criteria during the welding process.

[0055] In this embodiment, when the steel grade is nuclear-grade 18MnD5 low-alloy steel, the thermal cycle curve and temperature field size distribution are set as follows: melting zone > 1504°C (size W1), coarse grain zone 1100°C to 1504°C (size W2), fine grain zone / complete recrystallization zone Ac3 to 1100°C (size W3), critical zone Ac1 to Ac3 (size W4), and tempering temperature zone Tw to Ac1 (size W5). When the steel grade is nuclear-grade 18MnD5 low-alloy steel, Ac1 is the same as the highest peak temperature that meets the judgment criteria during welding, and Ac1 is the temperature at which the steel begins to form or transform into austenite during the heating process.

[0056] Step 4: Obtain the lowest peak temperature Tw and the highest peak temperature Tp

[0057] The steel grade was simulated using a thermal cycle curve within the coarse-grained zone to obtain weld specimens with the coarse-grained zone structure and perform performance testing. This step aims to obtain specimens with the coarse-grained zone structure, specifically those within the W2 range. Since the coarse-grained zone exhibits the poorest performance during welding, this structure was selected as the specimen to confirm whether the coarse-grained zone meets the criteria after simulating the thermal cycle curve at the tempering temperature, ensuring that the performance of the welded area meets the required performance requirements.

[0058] For samples in the coarse-grained zone, thermal cycle curve simulation and performance testing are performed using different peak tempering temperatures to determine the minimum peak temperature Tw and the maximum peak temperature Tp that meet the judgment criteria. This step is to re-process the samples in the coarse-grained zone for a second thermal cycle or tempering to obtain Tw and Tp.

[0059] The minimum peak temperature Tw is defined as the lowest tempering temperature of the steel grade at which the tempering weld bead has a tempering effect.

[0060] The maximum peak temperature Tp is defined as the highest tempering temperature at which the steel grade has the tempering effect of the tempering weld.

[0061] In this application, the Tp of certain steel grades is the temperature Ac1 at which austenite begins to form or transform during the welding heating process, such as the nuclear-grade 18MnD5 low-alloy steel provided in this embodiment. In other embodiments, when other steel grades are selected, the Tp obtained may be different from Ac1, or higher than Ac1.

[0062] Step 5: Obtain the tempering temperature range △Tw

[0063] The tempering temperature range ΔTw is determined based on the maximum peak temperature Tp and the minimum peak temperature Tw of the steel grade. ΔTw is defined as the width of the tempering temperature range required to achieve high-quality microstructure and properties in a steel grade with a hardening tendency (easily hardenable steel) using a tempering weld bead technique during the welding thermal cycle.

[0064] The tempering temperature interval ΔTw=Tp-Tw, that is, the lower limit of the tempering temperature interval ΔTw is the lowest peak temperature Tw, and the upper limit is the highest peak temperature Tp.

[0065] Step 6. Application of tempering temperature range △Tw in the evaluation of the suitability of tempering weld technology and tempering weld technology welding

[0066] Based on the tempering temperature interval ΔTw and the tempering temperature zone size W5 in the temperature field during welding, the suitability of the tempering weld bead technology for this welding method and steel grade can be determined. The welding parameters can then be adjusted to ensure the implementation of the tempering weld bead technology. Welding parameters primarily include welding process parameters (including heat input, current, voltage, and rate), overlap, and grinding.

[0067] The above steps 1 to 5 are the methods for obtaining the tempering temperature range ΔTw. The obtained tempering temperature range ΔTw is combined with the above step 6, that is, the tempering temperature range ΔTw is applied to the evaluation of the technical applicability of the tempering weld bead, thereby obtaining the evaluation method of the technical applicability of the tempering weld bead.

[0068] Specifically, the evaluation method for the suitability of tempering weld technology includes the following steps:

[0069] According to the acquisition method described above, the tempering temperature interval ΔTw is obtained, and the size corresponding to the tempering temperature interval ΔTw is W5;

[0070] If the W5 obtained under a certain welding process parameter can cover the size W2 of the coarse grain zone of the previous weld bead, the tempering weld bead technology is suitable for this steel grade;

[0071] If the welding parameters cannot be adjusted so that W5 covers the size W2 of the coarse-grained area of ​​the previous weld, the tempering weld technology is not suitable for this steel grade.

[0072] The implementation method of the tempering weld technology includes the following steps:

[0073] According to the acquisition method described above, the tempering temperature range ΔTw of the steel grade is obtained, and the size corresponding to the tempering temperature range ΔTw is W5;

[0074] If the W5 obtained under a certain welding process parameter can cover the size W2 of the coarse grain zone of the previous weld bead, then the welding process parameter is used for the tempering weld bead;

[0075] If W5 obtained under the welding process parameters cannot cover the size W2 of the coarse grain zone of the previous weld bead, the welding parameters are adjusted so that W5 covers the size W2 of the coarse grain zone of the previous weld bead, and the tempering weld is welded using the adjusted welding process parameters.

[0076] Example

[0077] The suitability of tempering temperature ranges for different steel grades and welding methods varies. This case study uses the SMAW welding method for welding nuclear-grade 18MnD5 low-alloy steel using tempering weld technology to illustrate the process of obtaining the tempering temperature range and use it to evaluate the suitability of tempering weld technology.

[0078] Step 1: Refer to the French RCC-M2000 standard for the standard requirements of nuclear-grade 18MnD5 low-alloy steel, and design the judgment criteria for the microstructure and performance obtained after tempering weld of nuclear-grade 18MnD5 low-alloy steel as follows: impact energy ≥40J (-20℃), ≥72J (20℃), hardness value is the steel grade hardness + 100HB, yield strength ≥420MPa (20℃), ≥380MPa (350℃), tensile strength 580~720MPa (20℃), ≥540MPa (350℃).

[0079] Step 2: Referring to the Chinese standard YB / T 5128-1993, the Ac1 temperature of nuclear-grade 18MnD5 low-alloy steel was determined experimentally, Ac1 = 721°C.

[0080] Step 3: Using finite element analysis, a computational model for the SMAW welding process of nuclear-grade 18MnD5 low-alloy steel was established. After validating the model through experiments and temperature acquisition, the temperature field distribution of the welding process was obtained, and the thermal cycle curves and size distribution in different temperature ranges were determined.

[0081] As shown in Figures 1 and 2, the size distribution of the thermal cycle curve and temperature field is set as: melting zone > 1504°C (size W1), coarse grain zone 1100°C ~ 1504°C (size W2), fine grain zone / complete recrystallization zone Ac3 ~ 1100°C (size W3), critical zone Ac1 ~ Ac3 (size W4), tempering temperature zone Tw ~ Ac1 (size W5).

[0082] Step 4: Through Gleeble thermal simulation test or other testing methods, use different peak tempering temperatures to simulate the thermal cycle curve and performance test of the coarse grain zone structure to determine the "minimum peak temperature" Tw and "maximum peak temperature" Tp that meet the judgment criteria specified in step 1.

[0083] Where Tw is defined as the minimum tempering temperature at which a tempering weld bead is effective, and Tp is defined as the maximum tempering temperature at which a tempering weld bead is effective. In this case, the measured Tw for 18MnD5 low-alloy steel is 500°C and Tp is Ac1.

[0084] Step 5: Using Tw and Tp obtained in step 4, calculate the "tempering temperature range" ΔTw according to the formula ΔTw = Tp - Tw, as shown in Figures 1 and 2.

[0085] ΔTw is defined as the width of the tempering temperature range within which high-quality microstructure and properties are achieved in a tempering weld heat cycle for a steel with a hardening tendency (easily hardenable steel). In this case, the calculated ΔTw for nuclear-grade 18MnD5 low-alloy steel is 221°C.

[0086] Step 6: Based on the △Tw obtained in step 5 and the size distribution of the temperature field obtained in step 3, the tempering temperature zone size W5 is determined, and the weld arrangement of the subsequent welds is determined so that the tempering effect of the previous welds can be achieved. By changing the overlap amount, grinding amount, welding heat input and other parameters, comprehensive control can be performed to obtain a tempering weld microstructure with excellent performance.

[0087] The "tempering temperature range △Tw" obtained according to the above steps can be extended and applied to any type of steel and different welding methods. If the △Tw of a specific metal material under a certain welding method is large enough, a high-quality weld joint can be obtained through the tempering weld bead technology, otherwise it is not easy to achieve: if the tempering temperature zone size range W5 of the subsequent weld bead just covers the coarse-grained zone W2 of the previous weld bead, then the tempering weld bead technology under this welding process is applicable, otherwise it is not applicable; if it is not applicable, the tempering weld bead temperature field size distribution can be comprehensively controlled by changing parameters such as overlap, grinding amount, and welding heat input, so that the W5 size of the subsequent weld bead obtained after adjusting the parameters covers the W2 size of the previous weld bead, and an excellent performance tempering weld bead structure can also be obtained, thereby meeting the use conditions of the tempering weld bead technology; if after changing the welding process parameters, the W5 size of the subsequent weld bead obtained after adjusting the parameters still cannot cover the W2 size of the previous weld bead, then the tempering weld bead technology is not suitable for welding this steel type under this welding method.

[0088] As shown in Figure 3, different materials have different microstructures and properties after welding thermal cycles. This application selected representative steel grades, such as 20G, 18MnD5, BHW35, 410S, P22, P91, WC6, WC9, etc., to obtain the "tempering temperature range" and explore the influence of tempering weld technology on the heat-affected zone of steel grades. The following conclusions were drawn: the tempering temperature range △Tw of carbon steel and low alloy steel is 150℃ or even above 200℃, while the tempering temperature range △Tw of medium alloy steel and high alloy steel is less than 100℃ or even 0℃. The tempering temperature zone size W5 of carbon steel and low alloy steel is also larger than that of medium alloy steel and high alloy steel. Therefore, it is easier for carbon steel and low alloy steel to achieve the purpose of optimizing microstructure and performance through tempering weld technology, while it is not easy for medium alloy steel and high alloy steel to achieve this.

[0089] Based on the above method, 18MnD5, BHW35, and WC6 steels represented by deaerators, steam drums, and valves were selected. According to the requirements of the American ASME and French RCCM standards, the welding thermal cycle of the welding temperature field was first verified by finite element simulation calculation, and the performance change law of the coarse-grained zone organization was simulated and verified by combining GLEEBLE thermal simulation. Then, by comparing the hardness with normal welded specimens with / without heat treatment, the change law of the tempering weld bead in improving the organizational properties was analyzed. Finally, through the confirmatory test of the tempering process assessment, the final qualified weld joint was obtained, and the results were applied to the heat treatment-free tempering weld bead repair of deaerators, steam drums, valve bodies, cylinders, and pipelines.

[0090] On key special equipment that is difficult to heat treat, the evaluation method and welding method in this application can be used to easily determine the steel type and welding method that are suitable for the tempering weld technology, avoiding unnecessary losses due to improper selection. The evaluation method of this application can provide a reasonable criterion for whether the tempering weld technology can be effectively applied, and it has universal applicability and can be extended to the fields of welding manufacturing and welding repair in different industries. This achievement has been successfully applied to pressure-bearing special equipment in nuclear power and thermal power, such as the repair of deaerators, steam drums, valve bodies, cylinders, and pipelines, ensuring the safe and reliable operation of the units. The research results can ensure the safety of special equipment components after repair, and realize green repair technology that saves materials, saves energy, shortens construction period, and is green and environmentally friendly. It provides customers with a solution for restoring the functional performance of equipment components after failure, and has the value of promoting the application of welding repair of similar equipment in domestic power plants or other industries, improving safety and reliability, and improving economic and social benefits.

[0091] The above embodiments are intended only to illustrate the technical concepts and features of this application. Their purpose is to enable those familiar with the art to understand the content of this application and implement it accordingly. They are not intended to limit the scope of protection of this application. Any equivalent changes or modifications made in accordance with the spirit of this application shall be included in the scope of protection of this application.

Claims

1. A method for obtaining a tempering temperature range, comprising the following steps: Determine the criteria for judging the effect of tempering welds on steel grades; Determine the temperature Ac1 at which the steel begins to form or transform into austenite during welding heating; Obtain the temperature field distribution during welding, determine the thermal cycle curves and size distribution of the temperature field in different temperature ranges; The thermal cycle curve in the coarse grain zone is used to simulate the steel type, and the sample with the structure of the coarse grain zone is obtained and the performance test is carried out; Take the sample of the coarse grain zone of welding, use different peak tempering temperatures to simulate the thermal cycle curve and perform performance tests, and determine the minimum peak temperature Tw and the maximum peak temperature Tp that meet the judgment criteria; The tempering temperature range ΔTw is obtained according to the highest peak temperature Tp and the lowest peak temperature Tw.

2. The acquisition method according to claim 1, wherein the lower limit value of the tempering temperature interval ΔTw is the lowest peak temperature Tw, and the upper limit value is the highest peak temperature Tp.

3. The acquisition method according to claim 1, wherein the minimum peak temperature Tw is the minimum tempering temperature of the steel grade having the tempering effect of the tempering weld.

4. The acquisition method according to claim 1, wherein the maximum peak temperature Tp is the maximum tempering temperature of the steel having the tempering effect of the tempering weld.

5. The acquisition method according to claim 1, wherein when the steel grade is nuclear grade 18MnD5 low alloy steel, the corresponding judgment criteria for the tempering weld effect are: impact energy ≥40J at -20°C, ≥72J at 20°C, hardness value is the steel grade hardness + 100HB, yield strength ≥420MPa at 20°C, ≥380MPa at 350°C, tensile strength 580-720MPa at 20°C, ≥540MPa at 350°C.

6. The acquisition method according to claim 1, wherein the temperature field distribution during the welding process is acquired by the following steps: a calculation model of the welding process is established by a finite element analysis calculation method, and the temperature field distribution during the welding process is obtained after the calculation model is verified by an experiment or a temperature acquisition method.

7. The acquisition method according to claim 6, wherein when the steel type is nuclear grade 18MnD5 low alloy steel, the size distribution of the thermal cycle curve and the temperature field is set as follows: melting zone>1504°C, corresponding to the size W1; coarse grain zone 1100°C~1504°C, corresponding to the size W2; fine grain zone / complete recrystallization zone Ac3~1100°C, corresponding to the size W3; critical zone Ac1~Ac3, corresponding to the size W4; tempering temperature zone Tw~Ac1, corresponding to the size W5, 18MnD5 low alloy steel Tp=Ac1.

8. The acquisition method according to claim 1 or 7, wherein when the steel type is nuclear grade 18MnD5 low alloy steel, the Ac1 temperature of the steel type is 721°C, the minimum tempering peak temperature Tw with the tempering weld effect is 500°C, the maximum tempering peak temperature Tp with the tempering weld effect is Ac1, and the corresponding tempering temperature range △Tw is 500°C to 721°C.

9. An application of the tempering temperature range obtained by the acquisition method according to any one of claims 1 to 8 in a method for evaluating the suitability of tempering weld technology.

10. A method for evaluating the suitability of tempering weld technology, comprising the following steps: The tempering temperature interval ΔTw of the steel grade is obtained according to the acquisition method according to any one of claims 1 to 8, wherein the size corresponding to the tempering temperature interval ΔTw is W5; If W5 obtained under a certain welding process parameter can cover the size W2 of the coarse grain area of ​​the previous weld, then the tempering weld technology is suitable for this steel grade; If the welding parameters cannot be adjusted so that W5 covers the size W2 of the coarse-grained area of ​​the previous weld, the tempering weld technology is not suitable for this type of steel.

11. The evaluation method according to claim 10, wherein the welding parameters include heat input, current, voltage, speed, overlap, and grinding amount.

12. A method for implementing the tempering weld technology, comprising the following steps: The tempering temperature interval ΔTw of the steel grade is obtained according to the acquisition method according to any one of claims 1 to 8, wherein the size corresponding to the tempering temperature interval ΔTw is W5; If W5 obtained under a certain welding process parameter can cover the size W2 of the coarse grain zone of the previous weld, then the welding process parameter is used for tempering weld; If W5 obtained under the welding process parameters cannot cover the size W2 of the coarse grain zone of the previous weld, the welding parameters are adjusted so that W5 covers the size W2 of the coarse grain zone of the previous weld, and the tempering weld is welded using the adjusted welding process parameters.

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