Method for improving low-temperature toughness of multi-pass welding joint and application of method

Abstract

The invention belongs to the technical field of welding processes, and particularly relates to a method for improving the low-temperature toughness of a multi-pass welding joint and application of the method. According to the method, through a thermal simulation test, an ICCGHAZ structure containing chain martensite-austenite (M-A) is obtained through secondary thermal circulation, then a target peak temperature interval is determined through third thermal circulation, an initial interlayer cladding amount interval is further determined through a heat conduction simulation test and a welding pre-test, and parameter correction is conducted on the initial interlayer cladding amount interval; and finally, formal multi-pass welding is conducted according to the basic technological parameters of the workpiece to be welded, the target peak temperature interval and the target interlayer cladding amount interval. When the method is adopted for welding, directional toughening of an ICCGHAZ structure can be achieved, the low-temperature toughness of a joint is remarkably improved, the method is achieved based on existing welding equipment, the cost is controllable, and the method is suitable for various low-alloy high-strength steel, stable in technological performance and good in application prospect in the fields of petrochemical engineering, ocean engineering and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding process, and particularly relates to a method for improving low-temperature toughness of a multi-pass welding joint and application thereof. BACKGROUND

[0002] In a welding structure (such as a liquefied natural gas storage tank, a deep-sea pipeline and a low-temperature pressure container) operating in a low-temperature service environment, the low-temperature toughness of a welding joint is a key performance index affecting the overall safety and reliability of the structure. Multi-pass welding is a mainstream process in the manufacture of thick-walled components, and the joint performance thereof is greatly affected by a thermal cycle process. In actual welding, due to the influence of factors such as the thickness of a steel plate and welding process, multi-layer and multi-pass welding is often required, and a coarse-grained heat-affected zone (CGHAZ) formed by a previous pass welding will again undergo a thermal cycle in the process of subsequent pass welding, thereby causing more complex microstructure changes, such as the formation of an intercritical coarse-grained heat-affected zone (ICCGHAZ), and causing fluctuations in the performance of the welding joint.

[0003] The ICCGHAZ region undergoes a complex thermal cycle of "high-temperature austenitization-rapid cooling", which causes a large number of chain-shaped martensite-austenite (M-A) components to be precipitated in the microstructure thereof. Such a structure has the characteristics of high hardness and poor plasticity, and the bonding interface between the structure and the matrix is prone to stress concentration, which becomes the core region of crack initiation and propagation, so that the ICCGHAZ region becomes a weak toughness region in the welding joint, and seriously deteriorates the anti-fracture ability of the joint in a low-temperature environment.

[0004] At present, the technical means for improving the performance of the ICCGHAZ mainly include optimizing the single-pass welding heat input, adjusting the welding material alloy system and implementing post-welding quenching and tempering. However, only optimizing the single heat input can only control the secondary thermal cycle parameters, and it is difficult to realize the directional thermal action control of the ICCGHAZ region; adjusting the chemical composition of the welding material requires the development of special welding materials, which is high in cost and limited in material applicability; although the post-welding heat treatment can improve the microstructure to some extent, it introduces an additional production link, increases energy consumption, and easily causes welding deformation and residual stress in thick-walled components, affecting the dimensional stability and service performance of the structure. SUMMARY

[0005] In a first aspect, the application provides a method for improving the low-temperature toughness of a multi-pass welding joint, comprising the following steps:

[0006] S1, determining welding basic process parameters according to the material of a workpiece to be welded;

[0007] S2, determining a target peak temperature range through a thermal simulation test;

[0008] The thermal simulation test comprises: performing secondary thermal cycle on the workpiece sample to be welded to obtain an ICCGHAZ simulation sample containing chain M-A, and then performing third thermal cycle on the ICCGHAZ simulation sample at different peak temperatures, and the thermal cycle peak temperature interval at which the chain M-A is decomposed into cementite is defined as the target peak temperature interval; in the target peak temperature interval, the decomposition rate of the chain M-A is greater than or equal to 70%;

[0009] S3, determining an initial interlayer deposition amount interval through a thermal conduction simulation test;

[0010] S4, performing multi-pass pre-welding test on the workpiece sample to be welded by using the initial interlayer deposition amount interval obtained in step S3, monitoring the peak temperature of the pass subjected to the third thermal cycle in real time during the welding process, and if the peak temperature of the pass subjected to the third thermal cycle deviates from the target peak temperature interval, performing parameter correction on the initial interlayer deposition amount interval to obtain a target interlayer deposition amount interval;

[0011] S5, performing multi-pass welding on the workpiece to be welded according to the basic process parameters determined in step S1, the target peak temperature interval determined in step S2, and the target interlayer deposition amount interval determined in step S4.

[0012] The present application obtains the ICCGHAZ structure containing chain M-A by heat simulation test, adopts secondary heat cycle, and then determines the key peak temperature interval (i.e. target peak temperature interval) through the third heat cycle. In the temperature interval, chain M-A can be fully decomposed into fine cementite, and grain overgrowth or new brittle phase can be avoided, so that the adverse structure in the ICCGHAZ structure can be well controlled, thereby realizing the directional toughening of the ICCGHAZ structure, and significantly improving the low-temperature toughness of the joint. Taking 4-pass filling welding as an example, the welding temperature of each pass is between 1300℃-1400℃ in the actual welding process. After welding the first pass, the coarse grain heat affected zone is formed. Due to the effect of heat conduction, the first pass is inevitably subjected to secondary heat cycle when welding the second pass, so that the critical coarse grain heat affected zone (ICCGHAZ) is easily formed in the first pass. The critical coarse grain heat affected zone is the heat affected zone formed after the coarse grain heat affected zone is heated again in the (α+γ) dual-phase zone at the peak temperature, which will significantly affect the toughness of the welded joint. In step S2 of the present application, the target peak temperature interval is obtained by performing the third heat cycle on the sample (i.e. ICCGHZA simulation sample containing chain M-A) subjected to twice heat cycle. If the heat conduction temperature to the first pass falls within the target peak temperature interval when welding the third pass of filling welding in the actual welding process, the chain M-A generated in the first pass in the secondary heat cycle can be well eliminated, and the performance of the multi-pass welded joint can be improved. Similarly, when welding the fourth pass, the heat conduction temperature to the second pass falls within the target peak temperature interval, so that the chain M-A generated in the second pass in the secondary heat cycle can be well eliminated.

[0013] In the multi-pass welding process, the inter-pass deposition amount directly determines the heat conduction efficiency and heat action intensity of the subsequent welding pass heat input to the ICCGHAZ structure. Through heat conduction simulation test and parameter correction, the present application can accurately control the deposition amount to match the target peak temperature interval, provide the optimal thermal environment for the decomposition of ICCGHAZ chain M-A, and well solve the brittleness problem of ICCGHAZ. Taking 4-pass filling welding as an example, in step S3 of the present application, the initial inter-pass deposition amount interval is determined by the heat conduction simulation test. Since the actual welding temperature of each pass is 1300-1400℃, when the inter-pass deposition amount falls within the initial inter-pass deposition amount interval, the temperature conducted to the first pass when welding the third pass falls within the target peak temperature interval, reducing the chain M-A content in the first pass. In this way, the temperature conducted to the second pass when welding the fourth pass falls within the target peak temperature interval, reducing the chain M-A content in the second pass, thereby significantly improving the toughness of the welded joint. In step S4 of the present application, welding pre-test is carried out on the welded workpiece sample, and the welding temperature of each pass during the pre-welding process is 1300-1400℃, and the inter-pass deposition amount falls within the initial inter-pass deposition amount interval. In the third pass of welding, the peak temperature of the first pass (ICCGHAZ region) is monitored in real time by an infrared thermal imager (accuracy ±2℃), to verify whether the third heat cycle temperature of the first pass falls within the target peak temperature interval [Ts, Te], and if there is a deviation, the deposition amount parameter is corrected immediately. When the third heat cycle peak temperature of the first pass is lower than Ts, the inter-pass deposition amount is increased to increase the heat conduction efficiency; when the third heat cycle peak temperature of the first pass is higher than Te, the deposition amount is reduced to reduce the heat input intensity, so that the third heat cycle peak temperature of the first pass falls within the target peak temperature interval. In this way, when welding the fourth pass, the peak temperature of the second pass (the second pass has experienced two heat cycles when welding the fourth pass, the first heat cycle occurs when welding the second pass, and the second heat cycle occurs when welding the third pass) is monitored in real time by an infrared thermal imager (accuracy ±2℃), to verify whether the third heat cycle temperature of the second pass falls within the target peak temperature interval [Ts, Te], and if there is a deviation, the deposition amount parameter is corrected immediately. When the third heat cycle peak temperature of the second pass is lower than Ts, the inter-pass deposition amount is increased to increase the heat conduction efficiency; when the third heat cycle peak temperature of the second pass is higher than Te, the deposition amount is reduced to reduce the heat input intensity, so that the third heat cycle peak temperature of the second pass falls within the target peak temperature interval [Ts, Te]. The finally corrected deposition amount parameter interval is defined as the target inter-pass deposition amount interval.

[0014] In view of the defect that the chain-like M-A in the ICCGHAZ cannot be decomposed by heat cycle regulation in the prior art multi-pass welding, the application provides a method based on precise control of interlayer cladding amount, which induces three heat cycles and controls the peak temperature range of the third heat cycle to promote the decomposition of the chain-like M-A in the ICCGHAZ to form cementite, thereby achieving the brittle toughening of the ICCGHAZ and significantly improving the low-temperature toughness of the joint.

[0015] In some embodiments, in step S1, the base process parameters of the multi-pass welding are determined according to the material, thickness and groove form of the workpiece to be welded, and the base process parameters specifically include: welding method, welding parameter, heat input parameter, heat conduction coefficient, workpiece thickness to be welded and weld arrangement.

[0016] In some embodiments, the material of the workpiece to be welded includes but is not limited to Q500-grade steel, E500-grade steel and Q355-grade steel, and also includes other materials of low-alloy high-strength steel disclosed in the art, such as X80 pipeline steel and Q460 bridge steel.

[0017] In some embodiments, the groove form of the workpiece to be welded includes but is not limited to X-type, V-type and K-type.

[0018] In some embodiments, in step S1, the welding includes welding a backing layer and a filling layer, the backing layer is welded by a gas shielded welding process, and the filling layer is welded by a submerged arc welding process.

[0019] In some embodiments, the base process parameters include welding parameters, heat input parameters, heat conduction coefficient of the workpiece to be welded and thickness of the workpiece to be welded.

[0020] In some embodiments, the welding parameters include wire diameter, type of protective gas and gas flow.

[0021] In some embodiments, the heat input parameters include welding current, welding voltage and welding speed, which ensure that a single weld is well formed without defects such as incomplete fusion, porosity and the like.

[0022] In some embodiments, the process parameters of the gas shielded welding (MIG) include: wire diameter of 1.0 mm, 1.2 mm and 4.0 mm, welding current of 150-250 A, welding voltage of 22-30 V, welding speed of 20-45 cm / min, protective gas of argon and carbon dioxide, and gas flow of 15-20 L / min. In some embodiments, the cladding amount of the backing layer welded by the gas shielded welding process is 5-10 g / 10 mm.

[0023] In some embodiments, the process parameters of the submerged arc welding (SAW) include: a welding wire diameter including but not limited to 1.0 mm, 1.2 mm and 4.0 mm, a welding current of 450-600 A, a welding voltage of 25-36 V, a welding speed of 20-45 cm / min, and an interlayer cladding amount interval of the filler layer welded by the submerged arc welding process being the target interlayer cladding amount interval determined in step S4.

[0024] In some embodiments, in step S2, the secondary thermal cycle includes a first thermal cycle and a second thermal cycle, the peak temperature of the first thermal cycle being 1300-1400℃, and the peak temperature interval of the second thermal cycle being [Ac1, Ac3], wherein the Ac1 is a temperature at which the workpiece to be welded starts to form austenite, and the Ac3 is a temperature at which the workpiece to be welded is completely converted into austenite.

[0025] In some embodiments, the heating rate of the first thermal cycle and the second thermal cycle is 80-150℃ / s, and the cooling rate is 10-30℃ / s.

[0026] In some embodiments, in step S2, the conditions for performing a third thermal cycle on the ICCGHAZ simulation sample at different peak temperatures include: heating the ICCGHAZ simulation sample to a third thermal cycle peak temperature at a heating rate of 80-150℃ / s, and then cooling the ICCGHAZ simulation sample to room temperature at a cooling rate of 10-30℃ / s; the third thermal cycle peak temperature interval is [400℃, 750℃], and the ICCGHAZ simulation sample is subjected to a third thermal cycle at intervals of 5-50℃ within the interval. For example, when the interval is 20℃, the operation of the third thermal cycle is: heating the ICCGHAZ simulation sample from room temperature to 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, respectively, at a heating rate of 80-150℃ / s, and then cooling the ICCGHAZ simulation sample to room temperature at a cooling rate of 10-30℃ / s. For example, when the interval is 50℃, the operation of the third thermal cycle is: heating the ICCGHAZ simulation sample from room temperature to 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, respectively, at a heating rate of 80-150℃ / s, and then cooling the ICCGHAZ simulation sample to room temperature at a cooling rate of 10-30℃ / s. The interval can be selected and adjusted according to actual conditions.

[0027] In some embodiments, in step S2, the content of chain M-A after the second and third thermal cycles is observed and measured under a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the decomposition rate of the chain M-A is calculated, the decomposition rate of the chain M-A (%) = [(M-A content after the second thermal cycle - M-A content after the third thermal cycle) / M-A content after the second thermal cycle] * 100%. To ensure statistical significance, multiple images are taken at different positions of the sample and the decomposition rate of the chain M-A is calculated and averaged.

[0028] In some embodiments, in step S2, the thermal simulation test is performed using a Gleeble thermal simulation machine.

[0029] The interpass deposition amount of the present application refers to the deposition metal mass of a single layer of weld (unit: g / 10 mm of weld length). In some embodiments, the interpass deposition amount refers to the deposition metal mass of a single layer of weld of a filler layer.

[0030] In some embodiments, in step S3, the thermal conduction simulation test comprises: inputting the base process parameters, the peak temperature of each pass and the target peak temperature interval into a thermal analysis software to obtain an initial interpass deposition amount interval; the welding temperature of each pass is 1300-1400℃.

[0031] In some embodiments, the thermal analysis software comprises at least one of ANSYS and ABAQUS.

[0032] In some embodiments, in step S4, the parameter correction method is:

[0033] If the peak temperature of the pass that has undergone the third thermal cycle is lower than the minimum value of the target peak temperature interval, the interpass deposition amount is increased; if the peak temperature of the pass that has undergone the third thermal cycle is higher than the maximum value of the target peak temperature interval, the deposition amount is decreased, so that the peak temperature of the pass that has undergone the third thermal cycle falls within the target peak temperature interval, and the corrected interpass deposition amount interval is defined as the target interpass deposition amount interval.

[0034] In some embodiments, when the material of the workpiece to be welded is Q500 grade steel, the target peak temperature interval determined by the thermal simulation test is [500℃, 660℃], the target interpass deposition amount interval determined by the thermal conduction simulation test and parameter correction is [10g / 10mm, 12g / 10mm], and the corresponding deposition layer thickness interval is [3.0mm, 3.5mm].

[0035] In some embodiments, when the material of the workpiece to be welded is E500 grade steel, the target peak temperature interval determined by the thermal simulation test is [480℃, 640℃], the target interlayer cladding layer interval determined by the thermal conduction simulation test and parameter correction is [9g / 10mm, 11g / 10mm], and the corresponding cladding layer thickness interval is [2.8mm, 3.3mm].

[0036] In some embodiments, when the workpiece to be welded is Q355 grade steel, the target peak temperature interval determined by the thermal simulation test is [580℃, 700℃], the target interlayer cladding layer interval determined by the thermal conduction simulation test and parameter correction is [12g / 10mm, 14g / 10mm], and the corresponding cladding layer thickness interval is [3.1mm, 3.6mm].

[0037] In the second aspect of the present application, the above method is applied in petrochemical industry and marine engineering.

[0038] In some embodiments, the application includes multi-pass welding of thick-walled components such as wind turbine towers and offshore platforms in marine engineering.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] (1) Through thermal simulation test, the ICCGHAZ structure containing chain M-A is obtained by adopting secondary thermal cycle, and then the key peak temperature interval (i.e. the target peak temperature interval) is determined by the third thermal cycle. In this temperature interval, the chain M-A can be fully decomposed into fine cementite, and the grain can be prevented from growing excessively or generating new brittle phase, so that the adverse structure in the ICCGHAZ structure can be well controlled, thereby realizing the directional toughening of the ICCGHAZ structure and significantly improving the low-temperature toughness of the joint.

[0041] (2) Through thermal conduction simulation test and parameter correction, the cladding amount is precisely controlled to match the target peak temperature interval, providing an optimal thermal environment for the decomposition of ICCGHAZ chain M-A, and well solving the brittleness problem of ICCGHAZ, meeting the requirements of low-temperature service environment of the joint.

[0042] (3) The process has strong compatibility and wide applicable material range: the method provided by the present application can be realized by using existing welding equipment (such as MIG welder and submerged arc welder), and only needs to determine the target peak temperature interval and the target interlayer cladding amount through simulation test, so the cost is controllable; it can be adapted to various low-alloy high-strength steels, has high control precision and excellent process stability, and has good application prospect in the fields of petrochemical industry, marine engineering and the like. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1For comparative example 1B ICCGHAZ tissue, SEM and TEM images are shown: (a) SEM image, (b) TEM image.

[0044] Figure 2 SEM and TEM images of ICGHAZ tissue in Example 1, (a) SEM image, (b) TEM image. Detailed Implementation

[0045] The following detailed embodiments further illustrate the content of the present invention. These embodiments do not constitute a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention. In the following embodiments and comparative examples, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0046] Example 1: Multi-pass welding of Q500 class wind turbine tower circumference

[0047] I. Multi-pass welding of Q500 class wind turbine tower

[0048] Workpiece to be welded: 26mm thick, X-groove type, 9 weld passes.

[0049] S1. Determine the basic process parameters for multi-pass welding based on the workpiece material.

[0050] Number of weld passes: 9 (1 root pass + 8 filler passes);

[0051] Welding method: Gas shielded welding (MIG) for the root pass + submerged arc welding (SAW) for the fill pass;

[0052] Root pass welding wire: diameter 1.2mm; shielding gas: Ar+CO2 (volume ratio 80%+20%); flow rate 20L / min; welding current: 180-220A; welding voltage: 24-27V; welding speed: 35-40cm / min; root pass welding cladding amount is 5g / 10mm weld length.

[0053] Filler wire: 4.0mm diameter; Welding current: 480-510A; Welding voltage: 26-30V; Welding speed: 30-35cm / min.

[0054] S2. Determine the target peak temperature range [Ts, Te] through thermal simulation experiments.

[0055] A Gleeble-3500 thermal simulator was used to simulate a secondary thermal cycle on the workpiece sample to be welded. The conditions of the secondary thermal cycle included: heating from room temperature to the peak temperature (1300℃) at a rate of 130℃ / s, then cooling to room temperature at a rate of 15.3℃ / s, then heating to the two-phase region temperature [Ac1, Ac3] (750℃ in this example) at a rate of 130℃ / s, and then cooling to room temperature at a rate of 15.3℃ / s, resulting in an ICCGHAZ simulated sample containing chain-like MA. Ac1 and Ac3 temperatures are the key phase transformation temperatures in steel heat treatment, referring to the temperatures at which austenite begins to form and completely transforms into austenite, respectively. The Ac1 temperature for Q500 steel is 693℃, and the Ac3 temperature is 825℃.

[0056] The ICCGHAZ simulated sample was subjected to a third thermal cycle at different peak temperatures, with the peak temperature of the third thermal cycle ranging from 400 to 750℃, and the tests were conducted at 20℃ intervals. Specifically, the ICCGHAZ simulated sample was heated from room temperature to 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, and 760℃ respectively at a heating rate of 130℃ / s, and then cooled back to room temperature at a cooling rate of 15.3℃ / s. After three thermal cycles, the sample was obtained. Through SEM observation and calculation, the peak temperature range of the third thermal cycle in the ICCGHAZ region of Q500 steel was found to be [500℃, 660℃], which is the target peak temperature range [Ts, Te].

[0057] The purpose of determining the target peak temperature range: Taking the 8-pass filler weld in this embodiment as an example, in the actual welding process, the welding temperature of each pass is 1300℃. After welding the first pass, a coarse-grained heat-affected zone is formed. Due to heat conduction, the first pass will inevitably undergo another heat cycle during the second pass, which easily leads to the formation of a critical coarse-grained heat-affected zone (ICCGHAZ) in the first pass. The critical coarse-grained heat-affected zone is the heat-affected zone formed after the coarse-grained heat-affected zone is heated to the (α+γ) two-phase region at a second peak temperature, which will significantly affect the toughness of the weld joint. Step S2 obtains the target peak temperature range by performing a third heat cycle on the sample that has undergone two heat cycles (i.e., the ICCGHZA simulated sample containing chain-like MA). During the actual welding of the third pass (the temperature of the third pass is still 1300℃), the temperature of the heat conducted to the first pass can fall within the target peak temperature range. Therefore, the chain-like MA generated in the first pass during multiple heat cycles can be effectively eliminated, improving the performance of the multi-pass weld joint. Similarly, when welding the fourth pass, if the temperature at which heat is transferred to the second pass falls within the target peak temperature range, then the chain-like MA generated during multiple thermal cycles in the second pass can be effectively eliminated. Furthermore, by analogy, when welding the eighth pass, if the temperature at which heat is transferred to the sixth pass falls within the target peak temperature range, then the chain-like MA generated during multiple thermal cycles in the sixth pass can be effectively eliminated.

[0058] S3. Determine the initial interlayer cladding range [C1min, C1max] through thermal conduction simulation experiments.

[0059] The basic process parameters (filler wire: diameter 4.0mm; welding current: 480-510A; welding voltage: 26-30V; welding speed: 30-35cm / min; thermal conductivity: 45W / (m·K); plate thickness: 26mm; welding temperature per pass: 1300℃) and the target peak temperature range [Ts, Te] obtained in step S2 are input into the thermal analysis software ANSYS to establish a heat conduction model and obtain the initial interlayer cladding amount range [10g / 10mm, 12g / 10mm], with a corresponding cladding layer thickness of 3.0-3.5mm.

[0060] The purpose of determining the initial interlayer cladding range: Step S3 determines the initial interlayer cladding range through heat conduction simulation experiments. Taking the 8-pass filler weld in this embodiment as an example, since the welding temperature of each pass is 1300℃, when the interlayer cladding falls within the initial interlayer cladding range, the temperature conducted to the first pass during the third pass falls within the target peak temperature range, reducing the chain MA content in the first pass. Similarly, the temperature conducted to the second pass during the fourth pass falls within the target peak temperature range, reducing the chain MA content in the second pass. Further, this process continues, ensuring that the temperature conducted to the sixth pass during the eighth pass falls within the target peak temperature range, reducing the chain MA content in the sixth pass, thereby significantly improving the weld joint toughness.

[0061] S4. Determine the target interlayer cladding amount range [C2min, C2max] by adjusting parameters through process experiments.

[0062] Pre-welding tests were conducted on the welded workpiece samples. During the welding process, the welding temperature for each pass was 1300℃, and the interlayer cladding amount was within the initial interlayer cladding amount range [C1min, C1max]. At the third pass, the peak temperature of the first pass (ICCGHAZ region) was monitored in real time using an infrared thermal imager (accuracy ±2℃) to verify whether the third thermal cycle temperature of the first pass fell within the target peak temperature range [Ts, Te]. If a deviation occurred, the cladding amount parameters were immediately corrected. When the peak temperature of the third thermal cycle of the first pass was lower than Ts, the interlayer cladding amount was increased to improve heat transfer efficiency; when the peak temperature of the third thermal cycle of the first pass was higher than Te, the cladding amount was reduced to decrease heat input intensity, ultimately ensuring that the peak temperature of the third thermal cycle of the first pass fell within the target peak temperature range [Ts, Te].

[0063] Similarly, when the filler pass reaches the fourth pass, the peak temperature of the second pass (which has undergone two thermal cycles by the fourth pass – the first occurring during the second pass and the second during the third pass) is monitored in real time using an infrared thermal imager (accuracy ±2℃). This verifies whether the temperature of the third thermal cycle of the second pass falls within the target peak temperature range [Ts, Te]. If a deviation occurs, the cladding amount parameter is adjusted immediately. If the peak temperature of the third thermal cycle of the second pass is lower than Ts, the interlayer cladding amount is increased to improve heat transfer efficiency; if the peak temperature of the third thermal cycle of the second pass is higher than Te, the cladding amount is reduced to decrease heat input intensity, ultimately ensuring that the peak temperature of the third thermal cycle of the second pass falls within the target peak temperature range [Ts, Te].

[0064] Furthermore, following this principle, when the filler pass reaches the eighth pass, the peak temperature of the sixth pass (which has undergone two thermal cycles by the eighth pass – the first occurring during the sixth pass and the second during the seventh pass) is monitored in real time using an infrared thermal imager (accuracy ±2℃). This verifies whether the third thermal cycle temperature of the sixth pass falls within the target peak temperature range [Ts, Te]. If a deviation occurs, the cladding amount parameter is adjusted immediately. If the peak temperature of the third thermal cycle of the sixth pass is lower than Ts, the interlayer cladding amount is increased to improve heat transfer efficiency; if the peak temperature of the third thermal cycle of the sixth pass is higher than Te, the cladding amount is reduced to decrease heat input intensity, ultimately ensuring that the peak temperature of the third thermal cycle of the sixth pass falls within the target peak temperature range [Ts, Te].

[0065] The final corrected cladding amount parameter range is defined as the target interlayer cladding amount range [C2min, C2max].

[0066] In this embodiment, during the welding test, the infrared thermal imager showed that the peak temperature of the third thermal cycle of the first to sixth passes of filler welding all fell within the target peak temperature range [Ts, Te], which met the requirements. Therefore, there was no need to correct the parameters of the interlayer cladding amount, and the target interlayer cladding amount range remained [10g / 10mm, 12g / 10mm].

[0067] S5. Perform formal welding on the workpiece to be welded.

[0068] Preheating before welding: 80℃, with a preheating range of 50mm on each side of the bevel;

[0069] Welding process: Input the basic process parameters and interlayer cladding amounts [C2min, C2max] determined in step S1 into the welding equipment. Specifically:

[0070] Root pass welding wire: diameter 1.2mm; shielding gas Ar+CO2 (volume ratio 80%+20%), flow rate 20L / min; welding current: 200A; welding voltage: 25V; welding speed: 36cm / min; root pass cladding amount is 5g / 10mm weld length; number of root pass welds is 1.

[0071] Filler wire: 4.0mm diameter; welding current: 500A; welding voltage: 28V; welding speed: 32cm / min; filler weld: interlayer cladding amount is stably controlled at 10.8g / 10mm weld length (falling into the target interlayer cladding amount range); the welding temperature of each pass is 1300℃; the number of filler weld passes is 8.

[0072] II. Proportion Setting:

[0073] (1) Comparative Example 1A (interlayer cladding amount less than C2min): When welding the workpiece to be welded, the only difference from step S5 of Example 1 is that the interlayer cladding amount is controlled at 8.9g / 10mm, and the other parameters are exactly the same as step S5 of Example 1.

[0074] (2) Comparative Example 1B (interlayer cladding amount is higher than C2max): When welding the workpiece to be welded, the only difference from step S5 of Example 1 is that the interlayer cladding amount is controlled at 14.2g / 10mm, and the other parameters are exactly the same as step S5 of Example 1.

[0075] III. Performance Testing

[0076] (1) Low-temperature impact test (-20℃):

[0077] According to GB / T 229-2020, three sets of samples were taken from the ICCGHAZ region of the welded joint and subjected to Charpy pendulum impact tests at a target low-temperature environment (-20℃). The impact absorption energy Akv (in J) was measured, and the average value of the test results was taken. The larger the value of the impact absorption energy, the better the toughness of the material and the less sensitive it is to notches or other stress concentrations in the structure. The test results are the average value of the three sets of samples, and the results are shown in Table 1.

[0078] Table 1

[0079] Group Interlayer melt volume (g / 10 mm) Impact absorption work average Akv (J) Example 1 10.8 96 Comparative Example 1A 8.9 67 Comparative Example 1B 14.2 58

[0080] The results show that the method provided by the present invention can significantly improve the toughness of the welded joint.

[0081] (2) Microstructural analysis:

[0082] The microstructure of the ICCGHAZ region was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to examine whether the chain-like MA decomposed into fine, dispersed cementite, and whether the grain size increased significantly. Observations showed that the chain-like MA decomposition rate in the ICCGHAZ region of Example 1 was 85%, and the cementite size was less than 200 nm.

[0083] Figure 1 Here are the SEM and TEM images for Comparative Example 1B. Figure 2 The images shown are SEM and TEM images of Example 1.

[0084] Example 2: Multi-pass welding of E500 grade offshore platform steel

[0085] I. Multi-pass welding of steel for E500 class offshore platforms

[0086] Workpiece to be welded: 36mm thick, X-groove type, 15 weld passes.

[0087] S1. Determine the basic process parameters for multi-pass welding based on the workpiece material.

[0088] Number of weld passes: 15 passes (1 pass for root pass + 14 passes for fill pass);

[0089] Welding method: Gas shielded welding (MIG) for the root pass + submerged arc welding (SAW) for the fill pass;

[0090] Root pass welding wire: diameter 1.2mm; shielding gas: Ar+CO2 (volume ratio 80%+20%); flow rate 18L / min; welding current: 180-210A; welding voltage: 25-30V; welding speed: 35-45cm / min; root pass welding cladding amount is 6g / 10mm weld length.

[0091] Filler wire: 4.0mm diameter; Welding current: 450-520A; Welding voltage: 28-33V; Welding speed: 28-32cm / min.

[0092] S2. Determine the target peak temperature range [Ts, Te] through thermal simulation experiments.

[0093] A Gleeble-3500 thermal simulator was used to simulate a secondary thermal cycle on the workpiece sample to be welded. The conditions of the secondary thermal cycle included: heating from room temperature to the peak temperature (1300℃) at a rate of 130℃ / s, then cooling to room temperature at a rate of 15.3℃ / s, then heating to the two-phase region temperature [Ac1, Ac3] (760℃ in this example) at a rate of 130℃ / s, and then cooling to room temperature at a rate of 15.3℃ / s, resulting in an ICCGHAZ simulated sample containing chain-like MA. Ac1 and Ac3 temperatures are the key phase transformation temperatures in steel heat treatment, referring to the temperatures at which austenite begins to form and completely transforms into austenite, respectively. The Ac1 temperature for E500 steel is 736℃, and the Ac3 temperature is 830℃.

[0094] The ICCGHAZ simulated sample was subjected to a third thermal cycle at different peak temperatures, with the peak temperature of the third thermal cycle ranging from 400 to 750℃, and the tests were conducted at 20℃ intervals. Specifically, the ICCGHAZ simulated sample was heated from room temperature to 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, and 760℃ respectively at a heating rate of 130℃ / s, and then cooled back to room temperature at a cooling rate of 15.3℃ / s. After three thermal cycles, the sample was obtained. Through SEM observation and calculation, the peak temperature range of the third thermal cycle in the ICCGHAZ region of E500 steel was found to be [480℃, 640℃], which is the target peak temperature range [Ts, Te].

[0095] S3. Determine the initial interlayer cladding range [C1min, C1max] through thermal conduction simulation experiments.

[0096] The basic process parameters (filler wire: diameter 4.0mm; welding current: 450-520A; welding voltage: 28-33V; welding speed: 28-32cm / min; thermal conductivity: 45W / (m·K); plate thickness: 36mm; welding temperature per pass: 1300℃) and the target peak temperature range [Ts, Te] obtained in step S2 were input into the thermal analysis software ANSYS to establish a heat conduction model and obtain the initial interlayer cladding amount range [9g / 10mm, 11g / 10mm], with a corresponding cladding layer thickness of 2.8-3.3mm.

[0097] S4. Determine the target interlayer cladding amount range [C2min, C2max] by adjusting parameters through process experiments.

[0098] Welding pre-tests were conducted on the welded workpiece samples. During the welding process, the welding temperature for each pass was 1300℃, and the interlayer cladding amount was within the initial interlayer cladding amount range [C1min, C1max]. At the third pass, the peak temperature of the first pass (ICCGHAZ region) was monitored in real time using an infrared thermal imager (accuracy ±2℃) to verify whether the third thermal cycle temperature of the first pass fell within the target peak temperature range [Ts, Te]. If a deviation occurred, the cladding amount parameters were immediately corrected. When the peak temperature of the third thermal cycle of the first pass was lower than Ts, the interlayer cladding amount was increased to improve heat transfer efficiency; when the peak temperature of the third thermal cycle of the first pass was higher than Te, the cladding amount was reduced to decrease heat input intensity, ultimately ensuring that the peak temperature of the third thermal cycle of the first pass fell within the target peak temperature range [Ts, Te].

[0099] Similarly, when the filler welding reaches the fourteenth pass, the peak temperature of the twelfth pass (ICCGHAZ region) is monitored in real time using an infrared thermal imager (accuracy ±2℃) to verify whether the temperature of the third thermal cycle of the twelfth pass falls within the target peak temperature range [Ts, Te]. If a deviation occurs, the cladding amount parameter is adjusted immediately. When the peak temperature of the third thermal cycle of the twelfth pass is lower than Ts, the interlayer cladding amount is increased to improve heat transfer efficiency; when the peak temperature of the third thermal cycle of the twelfth pass is higher than Te, the cladding amount is reduced to decrease heat input intensity, ultimately ensuring that the peak temperature of the third thermal cycle of the twelfth pass falls within the target peak temperature range [Ts, Te].

[0100] The final corrected cladding amount parameter range is defined as the target interlayer cladding amount range [C2min, C2max].

[0101] In this embodiment, during the welding test, the infrared thermal imager showed that the peak temperature of the third thermal cycle of the first to twelfth filler welds all fell within the target peak temperature range [Ts, Te], which met the requirements. Therefore, there was no need to correct the parameters of the interlayer cladding amount, and the target interlayer cladding amount range remained [9g / 10mm, 11g / 10mm].

[0102] S5. Perform formal welding on the workpiece to be welded.

[0103] Preheating before welding: 100℃, with a preheating range of 50mm on each side of the bevel;

[0104] Welding process: Input the basic process parameters and target interlayer cladding amounts [C2min, C2max] determined in step S1 into the welding equipment. Specifically:

[0105] Root pass welding wire: diameter 1.2mm; shielding gas Ar+CO2 (volume ratio 80%+20%), flow rate 18L / min; welding current: 190A; welding voltage: 27V; welding speed: 40cm / min; root pass cladding amount is 6g / 10mm weld length; number of root pass welds is 1.

[0106] Filler wire: 4.0mm diameter; welding current: 480A; welding voltage: 30V; welding speed: 30cm / min; filler weld: interlayer cladding amount is stably controlled at 9.7g / 10mm weld length (falling into the target interlayer cladding amount range); the welding temperature of each pass is 1300℃; the number of filler weld passes is 14.

[0107] II. Proportion Setting:

[0108] (1) Comparative Example 2A (interlayer cladding amount less than C2min): When welding the workpiece to be welded, the only difference from step S5 of Example 2 is that the interlayer cladding amount is controlled at 7.4g / 10mm, and the other parameters are exactly the same as step S5 of Example 1.

[0109] (2) Comparative Example 2B (interlayer cladding amount is higher than C2max): When welding the workpiece to be welded, the only difference from step S5 of Example 2 is that the interlayer cladding amount is controlled at 11.7g / 10mm, and the other parameters are exactly the same as step S5 of Example 1.

[0110] III. Performance Testing

[0111] (1) Low-temperature impact test (-20℃):

[0112] According to GB / T 229-2020, three sets of samples were taken from the ICCGHAZ region of the welded joint and subjected to Charpy pendulum impact tests at a target low-temperature environment (-20℃). The impact absorption energy Akv (unit: J) was measured, and the average value of the test results was taken. The larger the value of the impact absorption energy, the better the toughness of the material and the less sensitive it is to notches or other stress concentrations in the structure. The test results are the average value of the three sets of samples, and the results are shown in Table 1.

[0113] Table 2

[0114]

[0115] The results show that the method provided by the present invention can significantly improve the toughness of the welded joint.

[0116] (2) Microstructural analysis:

[0117] The microstructure of the ICCGHAZ region was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to examine whether the chain-like MA decomposed into fine, dispersed cementite, and whether the grain size increased significantly. Observations showed that the chain-like MA decomposition rate in the ICCGHAZ region was 82%, and the cementite size was less than 220 nm.

[0118] Example 3: Multi-pass welding of Q355 grade wind power steel

[0119] I. Multi-pass welding of Q355 grade wind power steel

[0120] Workpiece to be welded: 50mm thick, X-groove type, 21 weld passes.

[0121] S1. Determine the basic process parameters for multi-pass welding based on the workpiece material.

[0122] Number of weld passes: 21 passes (1 pass for root pass + 20 passes for fill pass);

[0123] Welding method: Gas shielded welding (MIG) for the root pass + submerged arc welding (SAW) for the fill pass;

[0124] Root pass welding wire: diameter 1.2mm; shielding gas: Ar+CO2 (volume ratio 80%+20%); flow rate 18L / min; welding current: 180-210A; welding voltage: 25-30V; welding speed: 35-45cm / min; root pass welding cladding amount is 7g / 10mm weld length.

[0125] Filler wire: 4.0mm in diameter; Welding current: 500-580A; Welding voltage: 32-36V; Welding speed: 26-31cm / min.

[0126] S2. Determine the target peak temperature range [Ts, Te] through thermal simulation experiments.

[0127] A Gleeble-3500 thermal simulator was used to simulate a secondary thermal cycle on the workpiece sample to be welded. The conditions of the secondary thermal cycle included: heating from room temperature to the peak temperature (1300℃) at a rate of 130℃ / s, then cooling to room temperature at a rate of 15.3℃ / s, then heating to the two-phase region temperature [Ac1, Ac3] (780℃ in this embodiment) at a rate of 130℃ / s, and then cooling to room temperature at a rate of 15.3℃ / s, resulting in an ICCGHAZ simulated sample containing chain-like MA. Ac1 and Ac3 temperatures are the key phase transformation temperatures in steel heat treatment, referring to the temperatures at which austenite begins to form and completely transforms into austenite, respectively. The Ac1 temperature for Q355 steel is 730℃, and the Ac3 temperature is 858℃.

[0128] The ICCGHAZ simulated sample was subjected to a third thermal cycle at different peak temperatures, with the peak temperature of the third thermal cycle ranging from 400 to 750℃, and the tests were conducted at 20℃ intervals. Specifically, the ICCGHAZ simulated sample was heated from room temperature to 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, and 760℃ respectively at a heating rate of 130℃ / s, and then cooled back to room temperature at a cooling rate of 15.3℃ / s. After three thermal cycles, the sample was obtained. Through SEM observation and calculation, the peak temperature range of the third thermal cycle in the ICCGHAZ region of Q355 steel was found to be [580℃, 700℃], which is the target peak temperature range [Ts, Te].

[0129] S3. Determine the initial interlayer cladding range [C1min, C1max] through thermal conduction simulation experiments.

[0130] The basic process parameters (filler wire: diameter 4.0mm; welding current: 500-580A; welding voltage: 32-36V; welding speed: 26-31cm / min; thermal conductivity: 45W / (m·K); plate thickness: 50mm; welding temperature per pass: 1300℃) and the target peak temperature range [Ts, Te] obtained in step S2 were input into the thermal analysis software ANSYS to establish a heat conduction model and obtain the initial interlayer cladding amount range [12g / 10mm, 14g / 10mm], with a corresponding cladding layer thickness of 3.1-3.6mm.

[0131] S4. Determine the target interlayer cladding amount range [C2min, C2max] by adjusting parameters through process experiments.

[0132] Welding pre-tests were conducted on the welded workpiece samples. During the welding process, the welding temperature for each pass was 1300℃, and the interlayer cladding amount was within the initial interlayer cladding amount range [C1min, C1max]. At the third pass, the peak temperature of the first pass (ICCGHAZ region) was monitored in real time using an infrared thermal imager (accuracy ±2℃) to verify whether the third thermal cycle temperature of the first pass fell within the target peak temperature range [Ts, Te]. If a deviation occurred, the cladding amount parameters were immediately corrected. When the peak temperature of the third thermal cycle of the first pass was lower than Ts, the interlayer cladding amount was increased to improve heat transfer efficiency; when the peak temperature of the third thermal cycle of the first pass was higher than Te, the cladding amount was reduced to decrease heat input intensity, ultimately ensuring that the peak temperature of the third thermal cycle of the first pass fell within the target peak temperature range [Ts, Te].

[0133] Similarly, when the filler welding reaches the twentieth pass, the peak temperature of the eighteenth pass (ICCGHAZ region) is monitored in real time using an infrared thermal imager (accuracy ±2℃) to verify whether the temperature of the third thermal cycle of the eighteenth pass falls within the target peak temperature range [Ts, Te]. If a deviation occurs, the cladding amount parameter is adjusted immediately. When the peak temperature of the third thermal cycle of the eighteenth pass is lower than Ts, the interlayer cladding amount is increased to improve heat transfer efficiency; when the peak temperature of the third thermal cycle of the eighteenth pass is higher than Te, the cladding amount is reduced to decrease heat input intensity, ultimately ensuring that the peak temperature of the third thermal cycle of the eighteenth pass falls within the target peak temperature range [Ts, Te].

[0134] The final corrected cladding amount parameter range is defined as the target interlayer cladding amount range [C2min, C2max].

[0135] In this embodiment, during the welding test, the infrared thermal imager showed that the peak temperature of the third thermal cycle of the first to eighteenth filler welds all fell within the target peak temperature range [Ts, Te], which met the requirements. Therefore, there was no need to correct the parameters of the interlayer cladding amount, and the target interlayer cladding amount range remained [12g / 10mm, 14g / 10mm].

[0136] S5. Perform formal welding on the workpiece to be welded.

[0137] Preheating before welding: 120℃, with a preheating range of 50mm on each side of the bevel;

[0138] Welding process: Input the basic process parameters and target interlayer cladding amounts [C2min, C2max] determined in step S1 into the welding equipment. Specifically:

[0139] Root pass welding wire: diameter 1.2mm; shielding gas Ar+CO2 (volume ratio 80%+20%), flow rate 18L / min; welding current: 205A; welding voltage: 28V; welding speed: 38cm / min; root pass cladding amount is 7g / 10mm weld length; number of root pass welds is 1.

[0140] Filler wire: 4.0mm diameter; welding current: 540A; welding voltage: 34V; welding speed: 28cm / min; filler weld: interlayer cladding amount is stably controlled at 13.4g / 10mm weld length (falling into the target interlayer cladding amount range), the welding temperature of each pass is 1300℃, and the number of filler weld passes is 20.

[0141] II. Proportion Setting:

[0142] (1) Comparative Example 3A (interlayer cladding amount less than C2min): When welding the workpiece to be welded, the only difference from step S5 of Example 3 is that the interlayer cladding amount is controlled at 10.5g / 10mm, and the other parameters are exactly the same as step S5 of Example 1.

[0143] (2) Comparative Example 3B (interlayer cladding amount is higher than C2max): When welding the workpiece to be welded, the only difference from step S5 of Example 3 is that the interlayer cladding amount is controlled at 16.3g / 10mm, and the other parameters are exactly the same as step S5 of Example 1.

[0144] III. Performance Testing

[0145] (1) Low-temperature impact test (-20℃):

[0146] According to GB / T 229-2020, three sets of samples were taken from the ICCGHAZ region of the welded joint and subjected to Charpy pendulum impact tests at a target low-temperature environment (-20℃). The impact absorption energy Akv (unit: J) was measured, and the average value of the test results was taken. The larger the value of the impact absorption energy, the better the toughness of the material and the less sensitive it is to notches or other stress concentrations in the structure. The test results are the average value of the three sets of samples, and the results are shown in Table 1.

[0147] Table 3

[0148]

[0149] The results show that the method provided by the present invention can significantly improve the toughness of the welded joint.

[0150] (2) Microstructural analysis:

[0151] The microstructure of the ICCGHAZ region was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to examine whether the chain-like MA decomposed into fine, dispersed cementite, and whether the grain size increased significantly. Observations showed that the chain-like MA decomposition rate in the ICCGHAZ region was 79%, and the cementite size was less than 240 nm.

[0152] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for improving the low-temperature toughness of multi-pass welded joints, characterized in that, Includes the following steps: S1. Determine the basic welding process parameters based on the material of the workpiece to be welded; S2. Determine the target peak temperature range through thermal simulation experiments; The thermal simulation test includes: performing a second thermal cycle on the workpiece sample to be welded to obtain an ICGHAZ simulated sample containing chain MA; then performing a third thermal cycle on the ICGHAZ simulated sample at different peak temperatures; the thermal cycle peak temperature range in which the chain MA decomposes into cementite is defined as the target peak temperature range; within the target peak temperature range, the decomposition rate of chain MA is ≥70%. S3. Determine the initial interlayer cladding range through thermal conduction simulation experiments; S4. Using the initial interlayer cladding range obtained in step S3, perform a multi-pass pre-welding test on the workpiece sample to be welded. During the welding process, monitor the peak temperature of the pass that has undergone the third thermal cycle in real time. If the peak temperature of the pass that has undergone the third thermal cycle deviates from the target peak temperature range, then correct the parameters of the initial interlayer cladding range to obtain the target interlayer cladding range. S5. Based on the basic process parameters determined in step S1, the target peak temperature range determined in step S2, and the target interlayer cladding range determined in step S4, perform multi-pass welding on the workpiece to be welded.

2. The method as described in claim 1, characterized in that, In step S1, the welding includes welding the root pass and the fill pass. The root pass is welded using a gas shielded welding process, and the fill pass is welded using a submerged arc welding process.

3. The method as described in claim 1, characterized in that, The basic process parameters include welding parameters, heat input parameters, thermal conductivity coefficient of the workpiece to be welded, and thickness of the workpiece to be welded.

4. The method as described in claim 1, characterized in that, In step S2, the secondary thermal cycle includes a first thermal cycle and a second thermal cycle. The peak temperature of the first thermal cycle is 1300-1400℃, and the peak temperature range of the second thermal cycle is [Ac1, Ac3]. Ac1 is the temperature at which the workpiece to be welded begins to form austenite, and Ac3 is the temperature at which the workpiece to be welded is completely transformed into austenite. The heating rate of the first thermal cycle and the second thermal cycle is 80-150℃ / s, and the cooling rate is 10-30℃ / s.

5. The method as described in claim 1, characterized in that, In step S2, the conditions for subjecting the ICGHAZ simulated sample to a third thermal cycle at different peak temperatures include: heating the ICGHAZ simulated sample to the peak temperature of the third thermal cycle at a heating rate of 80-150℃ / s, and then cooling it to room temperature at a cooling rate of 10-30℃ / s; the peak temperature range of the third thermal cycle is [400℃, 750℃], and the ICGHAZ simulated sample is subjected to a third thermal cycle at test intervals of 5-50℃ within this range.

6. The method as described in claim 1, characterized in that, In step S2, the thermal simulation test is conducted using a Gleeble thermal simulator.

7. The method as described in claim 1, characterized in that, In step S3, the heat conduction simulation test includes: inputting the basic process parameters, the peak welding temperature of each pass and the target peak temperature range into the thermal analysis software to obtain the initial interlayer cladding range; the welding temperature of each pass is 1300-1400℃.

8. The method as described in claim 7, characterized in that, The thermal analysis software includes at least one of ANSYS and ABAQUS.

9. The method as described in claim 1, characterized in that, In step S4, the method for parameter correction is as follows: If the peak temperature of the pass undergoing the third thermal cycle is lower than the minimum value of the target peak temperature range, the interlayer cladding amount is increased; if the peak temperature of the pass undergoing the third thermal cycle is higher than the maximum value of the target peak temperature range, the cladding amount is reduced, so that the peak temperature of the pass undergoing the third thermal cycle falls into the target peak temperature range. The corrected interlayer cladding amount range is defined as the target interlayer cladding amount range.

10. The application of the method as described in any one of claims 1-9 in petrochemical and marine engineering.

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