Liquefied natural gas ship pipe fitting welding quality detection method and system

Abstract

The invention provides a liquefied natural gas ship pipe fitting welding quality detection method and system. The method comprises the steps that reactivation electric quantity in a potentiodynamic reactivation test is collected; determining the deadline of complete sensitization of the pipe fitting samples at each sensitization temperature and the critical sensitization time when a chromium-poor area is formed according to the reactivation electric quantity and sensitization time change of all the pipe fitting samples at each sensitization temperature; according to the reactivation electric quantity and the sensitization temperature change of the pipe fitting sample of which the sensitization time is greater than the deadline, extracting a precipitation constraint condition when the network carbide is precipitated from the pipe fitting sample; and according to the precipitation constraint condition and all the critical sensitization time, establishing a temperature-time model when intergranular corrosion occurs to the pipe fitting base material, and identifying all the welding defect points on the liquefied natural gas ship pipe fitting by combining the temperature-time model with the heating curve at each welding point in the welding process on the liquefied natural gas ship pipe fitting. By adopting the scheme of the invention, the welded pipe fitting can be quickly subjected to nondestructive intergranular corrosion detection.

Description

Technical Field

[0001] The present application relates to the technical field of quality inspection, and more specifically, to a method and system for inspecting the welding quality of liquefied natural gas ship pipe fittings. Background Art

[0002] Liquefied Natural Gas (LNG) ship pipe welding requires the use of cryogenically resistant materials and high-precision processes to control heat input to ensure weld tightness at ultra-low temperatures of -162°C. However, defects such as cracks and pores are easily generated during the welding process, directly threatening the safety of LNG transportation. Therefore, non-destructive testing is essential to thoroughly identify weld hazards and verify whether the welding quality meets standards. This is essential to eliminate the risk of cryogenic leakage, ensure ship navigation safety, and protect the lives and property of personnel. Since the storage temperature of LNG is as low as -162°C, the base material of pipe fittings is mostly made of low-temperature resistant austenitic stainless steel. The heat input during welding can easily lead to defects such as intergranular corrosion and σ phase precipitation. In ultra-low temperature environments, the stress structure changes inside the weld and the superposition of intergranular corrosion can easily cause leakage. The detection of intergranular corrosion in existing technologies is usually a destructive test (such as the test schemes proposed in GB / T4334-2020 and GB / T 29088-2012). There is a lack of technical solutions for non-destructive intergranular corrosion detection of welded pipe fittings. Therefore, how to quickly and non-destructively detect intergranular corrosion of welded pipe fittings has become a difficult problem facing the industry. Summary of the Invention

[0003] The present application provides a method and system for detecting the welding quality of liquefied natural gas ship pipe fittings, which can quickly perform non-destructive intergranular corrosion detection on welded pipe fittings.

[0004] In a first aspect, the present application provides a method for inspecting the welding quality of liquefied natural gas ship pipe fittings, wherein a plurality of pipe fitting samples at different sensitization temperatures and different sensitization times are prepared in advance, and the method comprises: All pipe fitting samples were subjected to a potentiodynamic reactivation test, and the reactivation quantity of each pipe fitting sample during the potentiodynamic reactivation test was collected by an electrochemical sensor; According to the response characteristics between the reactivation charge and sensitization time of all pipe fitting samples at each sensitization temperature, the cutoff time for complete sensitization of pipe fitting samples at each sensitization temperature and the critical sensitization time for the formation of chromium-depleted zone are determined; Selecting all pipe fitting samples whose sensitization time is greater than the cut-off time, and extracting the precipitation constraint conditions when the pipe fitting samples precipitate network carbides based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe fitting sample; A temperature-time model for intergranular corrosion of the pipe base material is established based on the precipitation constraint conditions and all critical sensitization times, and the intergranular corrosion index of each weld point on the LNG ship pipe fitting is determined by combining the temperature-time model with the heat curve of each weld point during welding on the LNG ship pipe fitting; Identify all weld defects on the LNG ship fittings based on all intergranular corrosion indices In some embodiments, collecting the reactivation power of each pipe sample during the potentiodynamic reactivation test using an electrochemical sensor specifically includes: The reactivation current sequence of each pipe sample during the potentiodynamic reactivation test is collected in real time by an electrochemical sensor; The reactivation charge of each pipe fitting sample during the potentiodynamic reactivation test was determined based on the reactivation current sequence of each pipe fitting sample.

[0005] In some embodiments, determining the cutoff time for complete sensitization of the pipe sample at each sensitization temperature and the critical sensitization time for forming the chromium-depleted zone based on the response characteristics between the reactivation charge and the sensitization time of all pipe samples at each sensitization temperature specifically includes: Selecting a sensitization temperature as the selected sensitization temperature, and screening out all pipe fitting samples corresponding to the selected sensitization temperature; Determine the response characteristics between the reactivation electricity and the sensitization time of all pipe fitting samples at the selected sensitization temperature according to the reactivation electricity of all pipe fitting samples and the sensitization time of all pipe fitting samples; According to the response characteristics between the reactivation charge and sensitization time of all pipe fitting samples, the trigger threshold for the formation of chromium-depleted zone in the pipe fitting samples at the selected sensitization temperature is determined; Determining, based on the trigger threshold, a critical sensitization time when a chromium-depleted zone is formed in the pipe sample at a selected sensitization temperature and a cutoff time when the pipe sample is completely sensitized; Continue to determine the cutoff time for complete sensitization of the pipe sample at the residual sensitization temperature and the critical sensitization time for the formation of chromium-depleted area.

[0006] In some embodiments, the precipitation constraint conditions for the precipitation of network carbides in the pipe sample are extracted based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample, specifically including: Determine the response characteristics between the reactivation electricity and the sensitization temperature of all the pipe fitting samples according to the reactivation electricity and the sensitization temperature of all the pipe fitting samples selected; Based on the response characteristics between the reactivation charge and the sensitization temperature of all pipe fitting samples, the precipitation threshold at which precipitation begins at the grain boundary in the base material of the pipe fitting samples and the fracture threshold at which the precipitated crystals begin to fracture are determined; The precipitation constraint conditions when network carbides are precipitated in the pipe sample are determined based on the precipitation threshold and the fracture threshold.

[0007] In some embodiments, establishing a temperature-time model for intergranular corrosion of a pipe base material based on the precipitation constraint conditions and all critical sensitization times specifically includes: determining a temperature asymptotic domain according to the precipitation constraint condition; A temperature-time model when intergranular corrosion occurs in the pipe base material is determined according to the temperature asymptotic domain and all critical sensitization times.

[0008] In some embodiments, determining the intergranular corrosion index at each weld point on the LNG ship pipe fitting by using the temperature-time model in combination with the heat curve at each weld point during welding on the LNG ship pipe fitting specifically includes: Obtain the heat curves at each weld point during the welding process on liquefied natural gas ship pipe fittings; Selecting a solder point as a selected solder point, and determining a residence time distribution of heat at the selected solder point according to a heat curve of the selected solder point; Inputting the dwell time distribution into the temperature-time model to obtain an intergranular corrosion index at a selected solder joint; Continue to determine the intergranular corrosion index of the remaining welds on LNG vessel fittings.

[0009] In some embodiments, the base material of the liquefied natural gas ship pipe fitting is austenitic stainless steel.

[0010] In a second aspect, the present application provides a liquefied natural gas ship pipe welding quality inspection system, comprising: The acquisition module is used to perform a dynamic potentiodynamic reactivation test on all pipe fitting samples and collect the reactivation electricity of each pipe fitting sample during the dynamic potentiodynamic reactivation test through an electrochemical sensor; A processing module is used to determine the cutoff time for complete sensitization of the pipe fitting samples and the critical sensitization time for forming a chromium-depleted zone at each sensitization temperature based on the response characteristics between the reactivation quantity and the sensitization time of all pipe fitting samples at each sensitization temperature; The processing module is further configured to select all pipe samples whose sensitization time is greater than the cutoff time, and extract precipitation constraint conditions for the precipitation of network carbides in the pipe samples based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample; The processing module is further configured to establish a temperature-time model for intergranular corrosion of the pipe base material based on the precipitation constraint conditions and all critical sensitization times, and then determine the intergranular corrosion index of each weld point on the liquefied natural gas ship pipe fitting by combining the temperature-time model with the heat curve of each weld point during welding on the liquefied natural gas ship pipe fitting; The execution module is used to identify all welding defects on the liquefied natural gas ship pipe fittings according to all intergranular corrosion indexes.

[0011] In a third aspect, the present application provides a computer device comprising a memory and a processor, wherein the memory stores a code, and the processor is configured to obtain the code and execute the above-mentioned method for detecting welding quality of liquefied natural gas ship pipe fittings.

[0012] In a fourth aspect, the present application provides a computer-readable storage medium storing a computer program, which implements the above-mentioned method for detecting welding quality of liquefied natural gas ship pipe fittings when executed by a processor.

[0013] The technical solutions provided by the embodiments disclosed in this application have the following beneficial effects: In the LNG ship pipe welding quality inspection method and system provided in the present application, first, a dynamic potentiodynamic reactivation test is performed on all pipe samples, and the reactivation charge of each pipe sample during the dynamic potentiodynamic reactivation test is collected by an electrochemical sensor; the cutoff time for complete sensitization of the pipe sample and the critical sensitization time for the formation of a chromium-depleted zone at each sensitization temperature are determined based on the response characteristics between the reactivation charge and the sensitization time of all pipe samples at each sensitization temperature; all pipe samples with a sensitization time greater than the cutoff time are selected, and the precipitation constraint conditions for the precipitation of network carbides in the pipe samples are extracted based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample; based on the precipitation constraint conditions and all critical sensitization times, a temperature-time model for the occurrence of intergranular corrosion of the pipe base material is established, and then the intergranular corrosion index at each weld point on the LNG ship pipe is determined by combining the temperature-time model with the heat curve of each weld point during the welding process on the LNG ship pipe; and all welding defects on the LNG ship pipe are identified based on all the intergranular corrosion indices.

[0014] It can be seen that the present application obtains the reactivation charge through the potentiodynamic reactivation test, determines the cutoff time for complete sensitization and the critical sensitization time for the start of sensitization by combining the response characteristics of sensitization temperature and time, and screens out the fully sensitized pipe samples based on the cutoff time, and then extracts the constraint conditions (i.e., precipitation constraint conditions) for the continuous precipitation of network carbides in the pipe parent material. By limiting the range of the precipitation constraint conditions and combining the critical sensitization time, a temperature-time model for the occurrence of intergranular corrosion in the pipe parent material is established, which realizes the quantitative evaluation of the intergranular corrosion of the pipe parent material, and then combines the heat curve of the weld during the welding process to calculate the intergranular corrosion index, thereby quickly and non-destructively identifying welding defects. In summary, the solution of the present application can quickly and non-destructively detect intergranular corrosion of welded pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram of an application scenario of a method for detecting welding quality of liquefied natural gas ship pipe fittings according to some embodiments of the present application; Figure 2 is an exemplary flow chart of a method for inspecting welding quality of liquefied natural gas vessel pipe fittings according to some embodiments of the present application; Figure 3 is an exemplary flow chart for determining precipitation constraints according to some embodiments of the present application; Figure 4 is a schematic structural diagram of a liquefied natural gas ship pipe welding quality inspection system according to some embodiments of the present application; Figure 5 It is a structural schematic diagram of a computer device for implementing a method for detecting welding quality of liquefied natural gas ship pipe fittings according to some embodiments of the present application. DETAILED DESCRIPTION

[0016] In order to better understand the technical solution of the present application, the technical solution of the present application will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0017] In some embodiments, reference Figure 1 , which is an application scenario diagram of the liquefied natural gas ship pipe welding quality inspection method shown in some embodiments of the present application, specifically including: Pipe fitting samples, pre-prepared pipe fitting samples for potentiodynamic reactivation testing; In electrochemical work, it is used to perform potentiodynamic reactivation tests on pipe samples; Infrared temperature sensors are used to collect real-time data on the heating conditions of LNG ship pipes during welding; The data processing center is used to process and analyze the test data of the electrochemical workstation and the data collected by the infrared temperature sensor, and output the location of the welding defect point; Welding quality inspection database, used to archive data output from the data processing center; The visualization module is used to visualize the data output by the data processing center.

[0018] It should be noted that the base material of the liquefied natural gas ship pipe fittings in this application is austenitic stainless steel.

[0019] refer to Figure 2 , which is an exemplary flow chart of a method for inspecting the welding quality of liquefied natural gas ship pipe fittings according to some embodiments of the present application. The method 100 for inspecting the welding quality of liquefied natural gas ship pipe fittings mainly includes the following steps: In step 101, a potentiodynamic reactivation test is performed on all pipe fitting samples, and the reactivation quantity of each pipe fitting sample during the potentiodynamic reactivation test is collected by an electrochemical sensor.

[0020] In some embodiments, before performing the potentiodynamic reactivation test on all pipe samples, the method further includes: pre-preparing a plurality of pipe samples at different sensitization temperatures and different sensitization times.

[0021] In a specific implementation, the following method can be used to pre-prepare multiple pipe fitting samples at different sensitization temperatures and different sensitization times, namely: multiple φ25mm×100mm pipe sections are cut from liquefied natural gas ship pipe fittings, and all the cut pipe sections are surface treated (each pipe section can be sanded, ultrasonically cleaned with ketone in the liquefied natural gas ship pipe fitting welding quality inspection system, rinsed with deionized water and dried in turn). Then, all the surface-treated pipe sections are placed in a tube furnace for sensitization, wherein the sensitization temperature and sensitization time of each pipe section are different, and the sensitization temperature and sensitization time can be preset according to actual needs. For example, in this application, 10 sensitization temperatures (sampling at equal intervals from 350°C to 850°C) and 10 sensitization times (sampling at equal intervals from 30 minutes to 530 minutes) are set, that is, a total of 100 (10x10) pipe fitting samples are obtained.

[0022] In specific implementation, the potentiodynamic reactivation test for all pipe fitting samples can be achieved in the following manner, namely: all pipe fitting samples are tested according to the experimental steps in GB / T 29088-2012 "Double-ring electrochemical potentiodynamic reactivation method for corrosion of metals and alloys".

[0023] In some embodiments, collecting the reactivation electricity of each pipe sample during the potentiodynamic reactivation test using an electrochemical sensor can be achieved in the following manner, namely: The reactivation current sequence of each pipe sample during the potentiodynamic reactivation test is collected in real time by an electrochemical sensor; The reactivation charge of each pipe fitting sample during the potentiodynamic reactivation test was determined based on the reactivation current sequence of each pipe fitting sample.

[0024] In specific implementation, the real-time collection of the reactivation current sequence of each pipe sample during the potentiodynamic reactivation test by an electrochemical sensor can be achieved in the following manner, namely: for each pipe sample, the reactivation current of each pipe sample during the potentiodynamic reactivation test is collected by the electrochemical sensor according to a preset sampling interval, and all the reactivation currents collected for each pipe sample are arranged in the order of sampling, and each sequence obtained by the arrangement is used as the reactivation current sequence of each pipe sample during the potentiodynamic reactivation test. The reactivation current of each pipe sample during the potentiodynamic reactivation test can be collected according to the experimental steps in GB / T29088-2012 "Double-ring Electrochemical Potentiodynamic Reactivation Measurement Method for Corrosion of Metals and Alloys". The sampling interval can be preset according to actual needs. For example, the sampling interval is preset to 0.5 seconds in this application.

[0025] In specific implementation, the reactivation amount of each pipe fitting sample during the potentiodynamic reactivation test can be determined based on the reactivation current sequence of each pipe fitting sample. This can be achieved in the following manner: for each pipe fitting sample, the reactivation current sequence of each pipe fitting sample is fitted into a corresponding curve by the Lagrange interpolation method, and the curve corresponding to each pipe fitting sample is integrated, and the value obtained by integrating the curve of each pipe fitting sample is used as the reactivation amount of each pipe fitting sample during the potentiodynamic reactivation test.

[0026] It should be noted that the reactivation charge in this application refers to the total charge released during the activation and dissolution process of the base material of the liquefied natural gas ship pipe fittings due to the precipitation of chromium-deficient areas or brittle phases.

[0027] In step 102, the cutoff time for complete sensitization of the pipe samples and the critical sensitization time for forming the chromium-depleted zone at each sensitization temperature are determined based on the response characteristics between the reactivation quantity and the sensitization time of all pipe samples at each sensitization temperature.

[0028] In some embodiments, the following steps may be used to determine the cutoff time for complete sensitization of the pipe sample and the critical sensitization time for forming the chromium-depleted zone at each sensitization temperature based on the response characteristics between the reactivation charge and the sensitization time of all pipe samples at each sensitization temperature: Selecting a sensitization temperature as the selected sensitization temperature, and screening out all pipe fitting samples corresponding to the selected sensitization temperature; Determine the response characteristics between the reactivation electricity and the sensitization time of all pipe fitting samples at the selected sensitization temperature according to the reactivation electricity of all pipe fitting samples and the sensitization time of all pipe fitting samples; According to the response characteristics between the reactivation charge and sensitization time of all pipe fitting samples, the trigger threshold for the formation of chromium-depleted zone in the pipe fitting samples at the selected sensitization temperature is determined; Determining, based on the trigger threshold, a critical sensitization time when a chromium-depleted zone is formed in the pipe sample at a selected sensitization temperature and a cutoff time when the pipe sample is completely sensitized; Continue to determine the cutoff time for complete sensitization of the pipe sample at the residual sensitization temperature and the critical sensitization time for the formation of chromium-depleted area.

[0029] In specific implementation, the response characteristics between the reactivation electricity and sensitization time of all pipe fitting samples at the selected sensitization temperature are determined based on the reactivation electricity of all pipe fitting samples and the sensitization time of all pipe fitting samples. The following method can be used, namely: first, the reactivation electricity of all pipe fitting samples screened out is arranged in ascending order according to the size of the sensitization time, and then the autocorrelation coefficients of the arranged sequence at different lag times are calculated, and all the autocorrelation coefficients are arranged in ascending order according to the size of the lag time, and the obtained sequence is used as the response characteristics between the reactivation electricity and sensitization time of all pipe fitting samples at the selected sensitization temperature, wherein the lag time can be set according to the total number of pipe fitting samples screened out and actual needs. For example, in this application, 5 times obtained by sampling at equal intervals between 30 minutes and 280 minutes are used as lag times.

[0030] It should be noted that the response characteristics between the reactivation charge and the sensitization time of all pipe fitting samples in this application are a sequence describing the correlation between the change of the reactivation charge and the sensitization time.

[0031] In specific implementation, the trigger threshold for the formation of a chromium-depleted zone in the pipe sample at the selected sensitization temperature is determined based on the response characteristics between the reactivation charge and the sensitization time of all pipe samples. This can be achieved in the following manner, namely: each autocorrelation coefficient in the response characteristics is compared with a preset trigger threshold in turn, and the lag time of the first autocorrelation coefficient that is smaller than the trigger threshold is recorded. The recorded lag time is used as the trigger threshold for the formation of a chromium-depleted zone in the pipe sample at the selected sensitization temperature. The trigger threshold can be preset according to actual needs. For example, in this application, the trigger threshold is preset to 0.1.

[0032] It should be noted that the trigger threshold in this application refers to the sensitization time when the chromium-depleted area begins to form in the base material of the pipe.

[0033] In specific implementation, the critical sensitization time when the pipe sample forms a chromium-depleted zone at the selected sensitization temperature and the cutoff time when the pipe sample is completely sensitized are determined based on the trigger threshold, which can be achieved in the following manner, namely: first, for all screened pipe samples, the pipe samples with a sensitization time less than the trigger threshold are used as pre-trigger samples, and the pipe samples with a sensitization time greater than or equal to the trigger threshold are used as post-trigger samples. Subsequently, the autocorrelation coefficients of the reactivation power of all post-trigger samples to the sensitization time at different lag times are calculated, and the autocorrelation coefficients of all post-trigger samples are compared with the trigger threshold in turn according to the size of the lag time, and the lag time of the first autocorrelation coefficient less than the trigger threshold is recorded, and the lag time is used as the cutoff threshold. Secondly, for all triggered samples, After the triggering, the pipe fitting samples with a sensitization time less than the cut-off threshold are taken as the pre-cut-off samples, and the pipe fitting samples with a sensitization time greater than or equal to the cut-off threshold are taken as the post-cut-off samples. Finally, the least squares method in the prior art is used to perform curve fitting on all pre-triggering samples, all pre-cut-off samples and all post-cut-off samples respectively, wherein the dependent variable is the reactivation charge, and the independent variable is the sensitization time. The horizontal coordinate corresponding to the intersection of the curve fitted by all pre-triggering samples and the curve fitted by all pre-cut-off samples is used as the critical sensitization time when the chromium-depleted zone is formed in the pipe fitting sample at the selected sensitization temperature, and the horizontal coordinate corresponding to the intersection of the curve fitted by all pre-cut-off samples and the curve fitted by all post-cut-off samples is used as the cut-off time for the pipe fitting sample to be completely sensitized at the selected sensitization temperature.

[0034] It should be noted that the critical sensitization time in this application refers to the shortest sensitization time required for the base material of the pipe sample to begin to form a chromium-depleted zone at a specific sensitization temperature.

[0035] It should be noted that the cut-off time in this application refers to the shortest time required for the pipe sample to reach a fully sensitized state at a specific sensitization temperature.

[0036] In step 103, all pipe samples with sensitization time greater than the cut-off time are selected, and precipitation constraint conditions for precipitation of network carbides in the pipe samples are extracted based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample.

[0037] In some embodiments, reference Figure 3 This figure is an exemplary flow chart for determining precipitation constraints according to some embodiments of the present application. In this application, the precipitation constraints for the precipitation of network carbides in the pipe samples are extracted based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample. The following steps can be used to achieve this: In step 1031, the response characteristics between the reactivation electricity and the sensitization temperature of all the pipe fitting samples are determined based on the reactivation electricity of all the pipe fitting samples and the sensitization temperature of all the pipe fitting samples selected; In step 1032, the precipitation threshold at which precipitation begins at the grain boundary in the mother material of the pipe sample and the fracture threshold at which the precipitated crystals fracture are determined based on the response characteristics between the reactivation charge and the sensitization temperature of all pipe samples; In step 1033, the precipitation constraint conditions for precipitating network carbides in the pipe sample are determined based on the precipitation threshold and the fracture threshold.

[0038] In specific implementation, the response characteristics between the reactivation electricity and the sensitization temperature of all pipe fitting samples are determined based on the reactivation electricity of all pipe fitting samples and the sensitization temperature of all pipe fitting samples. The following method can be used, namely: first, the reactivation electricity of all pipe fitting samples are arranged from small to large according to the size of the sensitization temperature, and then the Pearson correlation coefficient of the arranged sequence at different lag orders is calculated, and all Pearson correlation coefficients are arranged from small to large according to the size of the lag order, and the obtained sequence is used as the response characteristics between the reactivation electricity and the sensitization temperature of all pipe fitting samples. The lag order can be preset according to the total number of selected pipe fitting samples and actual needs. For example, a total of 50 pipe fitting samples are selected in this application, and the lag order can be set to all integers between 1 and 25.

[0039] It should be noted that the response characteristics between the reactivation charge and the sensitization temperature of all pipe fitting samples in this application are a sequence describing the correlation between the reactivation charge and the sensitization temperature change.

[0040] In specific implementation, the precipitation threshold at which grain boundaries in the mother material of the pipe fitting samples begin to precipitate and the fracture threshold at which the precipitated crystals fracture based on the response characteristics between the reactivation charge and the sensitization temperature of all pipe fitting samples can be determined in the following manner, namely: each autocorrelation coefficient in the response characteristics between the reactivation charge and the sensitization temperature of all pipe fitting samples is compared with a preset precipitation threshold threshold in turn, and the lag order N of the autocorrelation coefficient that is first less than the precipitation threshold threshold is recorded. Subsequently, the Nth sensitization temperature of all pipe fitting samples (sensitization temperatures are arranged in ascending order) is used as the precipitation threshold. Subsequently, the autocorrelation coefficients of all pipe fittings with a sensitization temperature greater than the precipitation threshold at different lag orders are recalculated (arranged in ascending order of sensitization temperature), and the lag order M of the recalculated autocorrelation coefficient that is first less than the preset truncation threshold threshold is recorded. Finally, the (N+M)th sensitization temperature of all pipe fitting samples (sensitization temperatures are arranged in ascending order) is used as the precipitation threshold.

[0041] It should be noted that the precipitation threshold in this application is the sensitization temperature at which carbide precipitation begins to appear at the grain boundaries of the pipe base material.

[0042] It should be noted that the fracture threshold in the present application is the sensitization temperature at which the fracture of the precipitation crystal structure of the pipe base material is detected.

[0043] In specific implementation, the precipitation constraint conditions for the precipitation of network carbides in pipe fitting samples based on the precipitation threshold and the fracture threshold can be achieved in the following manner, namely: first, all selected pipe fitting samples are divided into three groups of samples according to the sensitization temperature through the precipitation threshold and the fracture threshold (namely, the first group is pipe fitting samples with a sensitization temperature less than or equal to the precipitation threshold, the second group is pipe fitting samples with a sensitization temperature between the precipitation threshold and the fracture threshold, and the third group is pipe fitting samples with a sensitization temperature greater than or equal to the fracture threshold). Then, the three groups of samples are fitted separately by the least squares method, wherein the dependent variable is the reactivation charge of the pipe fitting sample, the independent variable is the sensitization temperature, and the abscissa of the intersection of the first group and the second group of curves is used as the lower limit, and the abscissa of the intersection of the second group and the third group of curves is used as the upper limit. The range formed by the lower limit and the upper limit is used as the precipitation constraint conditions for the precipitation of network carbides in pipe fitting samples.

[0044] It should be noted that the precipitation constraint condition in this application is the sensitization temperature range within which the pipe base material will continue to precipitate network carbides.

[0045] In step 104, a temperature-time model is established when intergranular corrosion occurs in the pipe base material based on the precipitation constraint conditions and all critical sensitization times. Then, the intergranular corrosion index at each weld point on the LNG ship pipe fitting is determined by combining the temperature-time model with the heat curve of each weld point during the welding process on the LNG ship pipe fitting.

[0046] In some embodiments, establishing a temperature-time model for intergranular corrosion of a pipe base material based on the precipitation constraints and all critical sensitization times can be achieved by the following steps: determining a temperature asymptotic domain according to the precipitation constraint condition; A temperature-time model when intergranular corrosion occurs in the pipe base material is determined according to the temperature asymptotic domain and all critical sensitization times.

[0047] In a specific implementation, determining the temperature asymptotic domain according to the precipitation constraint condition can be achieved in the following manner: drawing two straight lines on the temperature-time coordinate axis, one being the lower limit where the temperature is equal to the precipitation constraint condition, and the other being the upper limit where the temperature is equal to the precipitation constraint condition; using these two straight lines as asymptotes of the function, and using the range enclosed by these two asymptotes as the temperature asymptotic domain.

[0048] It should be noted that the temperature asymptotic domain in this application is a region enclosed by two straight lines used to limit the asymptotic range of the temperature-time model.

[0049] In a specific implementation, the temperature-time model when intergranular corrosion occurs in the pipe base material is determined according to the temperature asymptotic domain and all critical sensitization times. This can be achieved in the following manner: all critical sensitization times are fitted into a curve by the least squares method, wherein the dependent variable is the critical sensitization time, the independent variable is the sensitization temperature, and the two asymptotes in the temperature asymptotic domain are used as the asymptotes of the curve. Finally, the fitted curve is used as the temperature-time model when intergranular corrosion occurs in the pipe base material.

[0050] It should be noted that the temperature-time model in this application is a function curve that quantifies the minimum sensitization time threshold required for intergranular corrosion of the pipe base material at different temperatures.

[0051] In some embodiments, determining the intergranular corrosion index at each weld point on a liquefied natural gas vessel pipe fitting by combining the temperature-time model with the heat curve of each weld point during welding on the liquefied natural gas vessel pipe fitting can be achieved by the following steps: Obtain the heat curves at each weld point during the welding process on liquefied natural gas ship pipe fittings; Selecting a solder point as a selected solder point, and determining a residence time distribution of heat at the selected solder point according to a heat curve of the selected solder point; Inputting the dwell time distribution into the temperature-time model to obtain an intergranular corrosion index at a selected solder joint; Continue to determine the intergranular corrosion index of the remaining welds on LNG vessel fittings.

[0052] In specific implementation, the following method can be used to obtain the thermal curve of each weld point during the welding process on the LNG ship pipe fittings, namely: infrared temperature sensors are arranged near each weld point on the LNG ship pipe fittings, and the temperature changes of each weld point during welding are recorded in real time through a multi-channel data acquisition system, and finally a thermal curve of the temperature change of each weld point over time is generated.

[0053] In a specific implementation, the residence time distribution of the heat at the selected solder point can be determined according to the heat curve of the selected solder point in the following manner: based on the heat curve (temperature-time data), the temperature range is divided into fixed intervals (such as each 10°C as an interval), the curve data points are traversed and the cumulative residence time in each temperature interval is recorded; the sum of the time of each interval is counted through programming (such as Python's Pandas library or MATLAB script) or data processing software (such as Excel), and a temperature-time histogram is generated, and the temperature-time histogram is used as the residence time distribution of the heat at the selected solder point.

[0054] It should be noted that the dwell time distribution in this application is a histogram describing the distribution of the cumulative dwell time of a soldering point in different temperature ranges.

[0055] In a specific implementation, the dwell time distribution is input into the temperature-time model, and the intergranular corrosion index at the selected solder joint is obtained by superimposing the temperature-time histogram data points of the dwell time distribution with the curve of the temperature-time model, screening out all data points located to the right of the curve of the temperature-time model (i.e., right points), calculating the vertical distances from the temperature-time coordinates of these data points to the curve of the temperature-time model by a numerical integration method, and taking the sum of all vertical distances as the intergranular corrosion index at the selected solder joint. In order to eliminate the influence caused by the different dimensions between temperature and time, a normalization operation can be added to the process of calculating the vertical distance, and the temperature and time can be normalized to between [0,1].

[0056] It should be noted that the intergranular corrosion index in this application is a cumulative risk value that reflects the critical sensitization condition exceeded during the heating process of the welding point.

[0057] In step 105, all welding defects on the liquefied natural gas ship pipe are identified according to all intergranular corrosion indices.

[0058] In some embodiments, identifying all welding defects on the liquefied natural gas vessel pipe fittings according to all intergranular corrosion indices can be achieved by the following steps: Preset intergranular corrosion threshold; All welds with an intergranular corrosion index greater than the intergranular corrosion threshold are regarded as weld defect points on the liquefied natural gas ship pipe fittings.

[0059] It should be noted that the intergranular corrosion threshold in this application can be preset according to actual needs. For example, multiple φ25mm×100mm pipe sections can be cut from the same batch of liquefied natural gas ship pipe fittings for welding, and the intergranular corrosion index of multiple pipe sections can be determined by the heat curve during the welding process and the temperature-time model in this application. Subsequently, the corrosion conditions of each pipe section are detected according to the steps of GB / T4334-2020, and they are divided into defective pipe sections with intergranular corrosion and intact pipe sections without intergranular corrosion. The average intergranular corrosion index of all defective pipe sections is calculated, and the average intergranular corrosion index of all intact pipe sections is calculated, and the median of the two average values ​​is used as the intergranular corrosion threshold.

[0060] In some embodiments, after identifying all welding defects on the liquefied natural gas vessel pipe according to all intergranular corrosion indices, the method further includes: Visualize all welding defects; The intergranular corrosion index and location information of all welding defects are transmitted to the welding quality inspection database for storage.

[0061] In addition, in another aspect of the present application, in some embodiments, the present application provides a liquefied natural gas ship pipe welding quality detection system, referring to Figure 4 This figure is a schematic diagram of the structure of a liquefied natural gas ship pipe fitting welding quality detection system according to some embodiments of the present application. The liquefied natural gas ship pipe fitting welding quality detection system 400 includes: an acquisition module 401, a processing module 402 and an execution module 403, which are described as follows: Acquisition module 401, in this application, acquisition module 401 is mainly used to perform a dynamic potentiodynamic reactivation test on all pipe fitting samples, and collect the reactivation electricity of each pipe fitting sample during the dynamic potentiodynamic reactivation test through an electrochemical sensor; Processing module 402, in this application, is mainly used to determine the cutoff time for complete sensitization of the pipe fitting samples at each sensitization temperature and the critical sensitization time for forming a chromium-depleted zone based on the response characteristics between the reactivation charge and the sensitization time of all pipe fitting samples at each sensitization temperature; It should be noted that the processing module 402 in the present application is also used to select all pipe samples whose sensitization time is greater than the cut-off time, and extract the precipitation constraint conditions for the precipitation of network carbides in the pipe samples based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample; It should be noted that the processing module 402 in the present application is further configured to establish a temperature-time model for the occurrence of intergranular corrosion of the pipe base material based on the precipitation constraint conditions and all critical sensitization times, and then determine the intergranular corrosion index at each weld point on the LNG ship pipe fitting by combining the temperature-time model with the heat curve at each weld point during the welding process on the LNG ship pipe fitting; The execution module 403 in this application is mainly used to identify all welding defects on the liquefied natural gas ship pipe according to all intergranular corrosion indices.

[0062] In addition, the present application also provides a computer device, which includes a memory and a processor, the memory storing a code, and the processor being configured to obtain the code and execute the above-mentioned liquefied natural gas ship pipe welding quality detection method.

[0063] In some embodiments, reference Figure 5 , which is a schematic diagram of the structure of a computer device for implementing a method for detecting welding quality of liquefied natural gas ship pipe fittings according to some embodiments of the present application. The method for detecting welding quality of liquefied natural gas ship pipe fittings in the above embodiment can be performed by Figure 5 The computer device 500 shown in FIG. 5 is implemented as shown in FIG. 5 . The computer device 500 includes at least one processor 501 , a communication bus 502 , a memory 503 , and at least one communication interface 504 .

[0064] The processor 501 may be a general-purpose central processing unit (CPU) or an application-specific integrated circuit (ASIC).

[0065] The communication bus 502 may be used to transmit information between the aforementioned components.

[0066] The memory 503 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, a random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), a magnetic disk or other magnetic storage device, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto. The memory 503 may be independent and connected to the processor 501 via the communication bus 502. The memory 503 may also be integrated with the processor 501.

[0067] Memory 503 is used to store program code for implementing the present invention, and is controlled by processor 501 for execution. Processor 501 is used to execute the program code stored in memory 503. The program code may include one or more software modules. The above-described method for inspecting the welding quality of liquefied natural gas vessel pipe fittings can be implemented by processor 501 and one or more software modules in the program code stored in memory 503.

[0068] The communication interface 504 uses any device such as a transceiver to communicate with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area network (WLAN), etc.

[0069] In a specific implementation, as an example, a computer device may include multiple processors, each of which may be a single-core (single-CPU) processor or a multi-core (multi-CPU) processor. A processor herein may refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0070] The aforementioned computer device can be a general-purpose computer device or a dedicated computer device. In a specific implementation, the computer device can be a desktop computer, a portable computer, a network server, a personal digital assistant (PDA), a mobile phone, a tablet computer, a wireless terminal device, a communication device, or an embedded device. The embodiments of this application do not limit the type of computer device.

[0071] In addition, the present application also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the above-mentioned liquefied natural gas ship pipe welding quality detection method.

[0072] In summary, in the LNG ship pipe welding quality detection method and system disclosed in the embodiment of the present application, first, a dynamic potential reactivation test is performed on all pipe samples, and the reactivation charge of each pipe sample during the dynamic potential reactivation test is collected by an electrochemical sensor; the cutoff time for complete sensitization of the pipe sample at each sensitization temperature and the critical sensitization time when the chromium-depleted zone is formed are determined according to the response characteristics between the reactivation charge and the sensitization time of all pipe samples at each sensitization temperature; all pipe samples with a sensitization time greater than the cutoff time are selected, and the precipitation constraint conditions when the pipe sample precipitates network carbides are extracted according to the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample; based on the precipitation constraint conditions and all critical sensitization times, a temperature-time model is established when intergranular corrosion occurs in the pipe base material, and then the intergranular corrosion index at each weld point on the LNG ship pipe is determined by combining the temperature-time model with the heat curve at each weld point during the welding process on the LNG ship pipe; all welding defects on the LNG ship pipe are identified according to all the intergranular corrosion indices.

[0073] It can be seen that the present application obtains the reactivation charge through the potentiodynamic reactivation test, determines the cutoff time for complete sensitization and the critical sensitization time for the start of sensitization by combining the response characteristics of sensitization temperature and time, and screens out the fully sensitized pipe samples based on the cutoff time, and then extracts the constraint conditions (i.e., precipitation constraint conditions) for the continuous precipitation of network carbides in the pipe parent material. By limiting the range of the precipitation constraint conditions and combining the critical sensitization time, a temperature-time model for the occurrence of intergranular corrosion in the pipe parent material is established, which realizes the quantitative evaluation of the intergranular corrosion of the pipe parent material, and then combines the heat curve of the weld during the welding process to calculate the intergranular corrosion index, thereby quickly and non-destructively identifying welding defects. In summary, the solution of the present application can quickly and non-destructively detect intergranular corrosion of welded pipes.

[0074] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0075] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A method for detecting welding quality of liquefied natural gas ship pipe fittings, characterized in that: include: All pipe fitting samples were subjected to a potentiodynamic reactivation test, and the reactivation quantity of each pipe fitting sample during the potentiodynamic reactivation test was collected by an electrochemical sensor; According to the response characteristics between the reactivation charge and sensitization time of all pipe fitting samples at each sensitization temperature, the cutoff time for complete sensitization of pipe fitting samples at each sensitization temperature and the critical sensitization time for the formation of chromium-depleted zone are determined; Selecting all pipe fitting samples whose sensitization time is greater than the cut-off time, and extracting the precipitation constraint conditions when the pipe fitting samples precipitate network carbides based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe fitting sample; A temperature-time model for intergranular corrosion of the pipe base material is established based on the precipitation constraint conditions and all critical sensitization times, and the intergranular corrosion index of each weld point on the LNG ship pipe fitting is determined by combining the temperature-time model with the heat curve of each weld point during welding on the LNG ship pipe fitting; All welding defects on the liquefied natural gas ship pipe fittings are identified according to all intergranular corrosion indices.

2. The method according to claim 1, wherein The reactivation electricity of each pipe sample collected by the electrochemical sensor during the potentiodynamic reactivation test specifically includes: The reactivation current sequence of each pipe sample during the potentiodynamic reactivation test is collected in real time by an electrochemical sensor; The reactivation charge of each pipe fitting sample during the potentiodynamic reactivation test was determined based on the reactivation current sequence of each pipe fitting sample.

3. The method according to claim 1, wherein According to the response characteristics between the reactivation charge and sensitization time of all pipe fitting samples at each sensitization temperature, the cutoff time for complete sensitization of pipe fitting samples at each sensitization temperature and the critical sensitization time for the formation of chromium-depleted zone are determined. Specifically, the following are included: Selecting a sensitization temperature as the selected sensitization temperature, and screening out all pipe fitting samples corresponding to the selected sensitization temperature; Determine the response characteristics between the reactivation electricity and the sensitization time of all pipe fitting samples at the selected sensitization temperature according to the reactivation electricity of all pipe fitting samples and the sensitization time of all pipe fitting samples; According to the response characteristics between the reactivation charge and sensitization time of all pipe fitting samples, the trigger threshold for the formation of chromium-depleted zone in the pipe fitting samples at the selected sensitization temperature is determined; Determining, based on the trigger threshold, a critical sensitization time when a chromium-depleted zone is formed in the pipe sample at a selected sensitization temperature and a cutoff time when the pipe sample is completely sensitized; Continue to determine the cutoff time for complete sensitization of the pipe sample at the residual sensitization temperature and the critical sensitization time for the formation of chromium-depleted area.

4. The method according to claim 1, wherein Based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample, the precipitation constraint conditions for the precipitation of network carbides in the pipe sample are extracted, including: Determine the response characteristics between the reactivation electricity and the sensitization temperature of all the pipe fitting samples according to the reactivation electricity and the sensitization temperature of all the pipe fitting samples; Based on the response characteristics between the reactivation charge and the sensitization temperature of all pipe fitting samples, the precipitation threshold at which precipitation begins at the grain boundary in the base material of the pipe fitting samples and the fracture threshold at which the precipitated crystals begin to fracture are determined; The precipitation constraint conditions when network carbides are precipitated in the pipe sample are determined based on the precipitation threshold and the fracture threshold.

5. The method according to claim 1, wherein The temperature-time model for intergranular corrosion of the pipe base material is established based on the precipitation constraint conditions and all critical sensitization times, specifically including: determining a temperature asymptotic domain according to the precipitation constraint condition; A temperature-time model when intergranular corrosion occurs in the pipe base material is determined according to the temperature asymptotic domain and all critical sensitization times.

6. The method according to claim 1, wherein Determining the intergranular corrosion index of each weld point on the LNG ship pipe fitting by using the temperature-time model in combination with the heat curve of each weld point during the welding process of the LNG ship pipe fitting specifically includes: Obtain the heat curves at each weld point during the welding process on liquefied natural gas ship pipe fittings; Selecting a solder point as a selected solder point, and determining a residence time distribution of heat at the selected solder point according to a heat curve of the selected solder point; Inputting the dwell time distribution into the temperature-time model to obtain an intergranular corrosion index at a selected solder joint; Continue to determine the intergranular corrosion index of the remaining welds on LNG vessel fittings.

7. The method according to claim 1, wherein The base material of the liquefied natural gas ship pipe fittings is austenitic stainless steel.

8. A liquefied natural gas ship pipe welding quality inspection system, characterized in that: include: The acquisition module is used to perform a dynamic potentiodynamic reactivation test on all pipe fitting samples and collect the reactivation electricity of each pipe fitting sample during the dynamic potentiodynamic reactivation test through an electrochemical sensor; A processing module is used to determine the cutoff time for complete sensitization of the pipe fitting samples and the critical sensitization time for forming a chromium-depleted zone at each sensitization temperature based on the response characteristics between the reactivation quantity and the sensitization time of all pipe fitting samples at each sensitization temperature; The processing module is further configured to select all pipe samples whose sensitization time is greater than the cutoff time, and extract precipitation constraint conditions for the precipitation of network carbides in the pipe samples based on the response characteristics between the reactivation charge and the sensitization temperature of each selected pipe sample; The processing module is further configured to establish a temperature-time model for intergranular corrosion of the pipe base material based on the precipitation constraint conditions and all critical sensitization times, and then determine the intergranular corrosion index of each weld point on the liquefied natural gas ship pipe fitting by combining the temperature-time model with the heat curve of each weld point during welding on the liquefied natural gas ship pipe fitting; The execution module is used to identify all welding defects on the liquefied natural gas ship pipe fittings according to all intergranular corrosion indexes.

9. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores codes, and the processor is configured to obtain the codes and execute the method for detecting welding quality of liquefied natural gas ship pipe fittings according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for detecting welding quality of liquefied natural gas ship pipe fittings according to any one of claims 1 to 7 is implemented.

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