Weldment welding joint microstructure component analysis method

Abstract

The invention discloses a method for analyzing the microstructure of a welding joint of a weldment. The method comprises the following steps: setting a temperature detection point on the surface of a base metal of the weldment; the weldment base material is welded, and a detection point temperature field is obtained; establishing a weldment model which is the same as a weldment base material, and solving a simulated temperature field T1 (x, y, z, t) on the surface of the weldment model; determining an effective simulated temperature field T1 (x, y, z, t) based on the solved simulated temperature field T1 (x, y, z, t); simulating a simulated microstructure component F1 (f, x, y, z) of a welding seam area (12) of the weldment model by combining phase change CCT curve parameters; based on the simulated microstructure components F1 (f, x, y, z), effective simulated microstructure components F1 (f, x, y, z) are determined; after the to-be-welded piece base metal is welded, a metallographic detection point is arranged in a welding seam area of the cross section of the to-be-welded piece base metal; and observing and recording microstructure components at each metallographic detection point. The analysis method provided by the invention can accurately simulate the microstructure phase change content and distribution condition of the same weldment in different welding processes.

Description

Technical Field

[0001] The present invention relates to the technical field of welding phase transformation microstructure analysis, and in particular to a method for analyzing the microstructure composition of welded joints. Background Art

[0002] Thick plate structural components play a crucial role in the welding industry and are widely used in heavy industries such as defense, construction, water conservancy, transportation, shipbuilding, and large-scale pressure pipelines. Due to the limitations of weld penetration and weld width, multi-layer, multi-pass welding is typically used in thick plate welding.

[0003] Currently, numerical simulations of stress distribution in multi-layer, multi-pass welds mostly focus on the coupled analysis of the welding temperature and stress fields. However, the actual welding process also involves phase transformations in the microstructure. A more comprehensive numerical simulation of multi-layer, multi-pass welds should involve a three-field coupled analysis, where the temperature field, phase transformation field, and stress field are coupled. Accurately simulating the stress distribution in thick plates during multi-layer, multi-pass welds requires not only considering the temperature field but also analyzing the changes in the phase transformation field. Therefore, it is imperative to design a solid-state phase transformation analysis method that can be closely integrated with actual microstructure metallographic testing. This will provide R&D and engineering personnel with a better means of simulating the welding of thick plate structures and improve the technical level of thick plate welding manufacturing. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for analyzing the microstructure composition of welded joints of weldments. The method is based on a solid-state phase change analysis method combining weld metallographic testing with welding numerical simulation, which can accurately simulate the microstructure composition and content of the welding area of ​​the welded component and can be used in phase change analysis of different welding processes.

[0005] To achieve the above object, the present invention is specifically achieved as follows:

[0006] A method for analyzing the microstructure of a welded joint of a weldment comprises: setting temperature detection points on the surface of a weldment base material, numbering the temperature detection points in sequence as integers of 1, 2, 3, ..., m, where m≥1; welding the weldment base material, obtaining a temperature field at the detection points, arranging the temperature field at the detection points into a form T0(m, t) of the detection point number m and time t, and arranging the welding direction M(t), the number of welding layers N(t), the welding current A(t), and the welding voltage V(t) during the welding process into a form related to time t; establishing a weldment model identical to the weldment base material, and solving a simulated temperature field T1(x, y, z, t) on the surface of the weldment model, wherein the simulated temperature field T1(x, y, z, t) is associated with the welding direction M(t), the number of welding layers N(t), the welding current A(t), and the welding voltage V(t); Based on the solved simulated temperature field T1(x, y, z, t), an effective simulated temperature field T1(x, y, z, t) is determined; in combination with the phase transformation CCT curve parameters, a simulated microstructure composition F1(f, x, y, z) of the weld area of ​​the weldment model is simulated; based on the simulated microstructure composition F1(f, x, y, z), an effective simulated microstructure composition F1(f, x, y, z) is determined to verify the phase transformation CCT curve parameters; after the welding of the weldment base material is completed, metallographic inspection points are set in the weld area of ​​the weldment base material cross section, and the metallographic inspection points are numbered and marked in sequence as integers of 1, 2, 3...n, where n≥1; the microstructure composition at each metallographic inspection point is observed and recorded, and the recorded microstructure composition is organized into a form F0(f, n) related to the microstructure composition f and the inspection point number n.

[0007] In some embodiments, the welding direction M(t), number of welding layers N(t), welding current A(t), and welding voltage V(t) during the welding process are all organized into a form relative to time t as follows:

[0008]

[0009] In the table, A1 and V1 are the welding current and voltage from t0 to t1, A2 and V2 are the welding current and voltage from t1 to t2, and t0, t1, and t2 are the welding time recording points.

[0010] In some embodiments, the temperature detection points are arranged in two rows, and the temperature detection points in the two rows are 5 cm apart both horizontally and vertically, and are 5 cm away from the weld area.

[0011] In some embodiments, the metallographic detection points are in two rows, one row is located at the center line of the center cross section of the weld base material in the height direction, and the other row is located near the upper surface of the center cross section of the weld base material in the height direction.

[0012] In some embodiments, three metallographic inspection points are arranged in each row, the spacing between adjacent metallographic inspection points is 5 cm, the middle metallographic inspection point is located in the heat affected zone of the weld, and the two metallographic inspection points on both sides are symmetrically distributed in the weld area and the weldment base material area.

[0013] In some embodiments, a weldment model identical to the weldment base material is established, and heat source formulas regarding the welding direction M(t), number of welding layers N(t), welding current A(t), and welding voltage V(t) are written to solve the simulated temperature field T1 (x, y, z, t) on the surface of the weldment model.

[0014] In some embodiments, the heat source formula is obtained by using a moving heat source subroutine. The moving mode of the moving heat source of the moving heat source subroutine is consistent with the welding direction M(t). The activation direction of the life and death unit is consistent with the welding direction M(t). The activation order and time of the life and death units are determined according to the number of welding layers N(t). When activating the life and death units, the layers with a smaller number of layers are activated first, and the layers with a larger number of layers are activated later. The activation time of the life and death unit of each layer corresponds one-to-one to the start welding time of each layer.

[0015] In some embodiments, determining the valid simulated temperature field T1 (x, y, z, t) includes: in the simulated temperature field T1 (x, y, z, t), finding the detection point temperature field T0 (m, t) corresponding to the temperature detection point according to the x, y, z coordinates, comparing the simulated temperature field T1 (x, y, z, t) with the detection point temperature field T0 (m, t), if the temperature difference between the two at the same time does not exceed a predetermined value, then the simulated temperature field T1 (x, y, z, t) is valid; if the temperature difference between the two at the same time is greater than the predetermined value, then adjusting the temperature in the weldment model until the temperature difference between the simulated temperature field T1 (x, y, z, t) and the detection point temperature field T0 (m, t) at the same time does not exceed the predetermined value.

[0016] In some embodiments, simulating the simulated microstructure composition F1 (f, x, y, z) of the weld area of ​​the weldment model includes: first calibrating the simulated temperature field T1 (x, y, z, t) according to the detection point temperature field T0 (m, t); and then calibrating the simulated microstructure composition F1 (f, x, y, z), wherein the simulated microstructure composition F1 (f, x, y, z) is calibrated by phase transformation CCT curve parameters, and the phase transformation CCT curve parameters are determined by chemical composition, grain size, austenite transformation temperature and T8 / 5 cooling rate parameters.

[0017] In some embodiments, determining the effective simulated microstructure composition F1 (f, x, y, z) includes: finding the measured microstructure composition F0 (f, n) corresponding to the metallographic inspection point in the simulated microstructure composition F1 (f, x, y, z) according to the x, y, z coordinates; comparing the simulated microstructure composition F1 (f, x, y, z) with the measured microstructure composition F0 (f, n); if the compositions of the two are consistent at the same position, then the phase transformation CCT curve parameters are reasonable; if the compositions of the two are inconsistent at the same position, then adjusting the phase transformation CCT curve parameters until the compositions of the two are consistent at the same position, then the phase transformation CCT curve parameters are reasonable.

[0018] The beneficial effects of the present invention over the prior art are as follows: the present invention provides a method for analyzing the microstructure composition of welded joints of welds, which obtains the microstructure composition of the actual weld by metallographic testing, and then uses finite element numerical simulation to approximate the actual microstructure composition, with the aim of calibrating the phase change CCT curve parameters. Finally, the calibrated CCT curve is added to professional welding analysis software, which can be directly used in the phase change analysis of different welding processes, and the distribution law of the microstructure composition of welds under different welding processes is studied, which can accurately simulate the microstructure phase change content and distribution of the same weld under different welding processes.

[0019] It should be understood that the implementation of any embodiment of the present invention does not mean that multiple or all of the above-mentioned beneficial effects must be possessed or achieved at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0021] The structures, proportions, sizes, etc. illustrated in this specification are intended solely to complement the contents disclosed herein and to facilitate understanding and reading by persons skilled in the art. They are not intended to limit the conditions under which the present invention may be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in sizes, provided they do not affect the efficacy and objectives of the present invention, shall remain within the scope of the technical contents disclosed herein.

[0022] Figure 1 This is a front view of the central cross section of the flat plate butt weld disclosed in the embodiment of the present application;

[0023] Figure 2 is a side view of a flat plate butt weld disclosed in an embodiment of the present application;

[0024] Figure 3 This is a flow chart of the method for analyzing the microstructure composition of welded joints of weldments disclosed in the embodiments of the present application;

[0025] Figure 4 This is a distribution diagram of ferrite and pearlite content in the numerical simulation microstructure disclosed in the examples of this application.

[0026] The above drawings include the following reference numerals:

[0027] 10. Weldment base material; 11. Heat-affected zone; 12. Weld seam area; 21. Temperature detection point; 22. Metallographic detection point. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0029] In the description of the present invention, the terms "comprises / comprising", "consisting of" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product, apparatus, process or method comprising a list of elements includes not only those elements but also, if necessary, other elements not explicitly listed, or elements inherent to such product, apparatus, process or method. In the absence of further limitations, elements defined by the phrases "comprises / comprising..." or "consisting of..." do not exclude the presence of additional identical elements in the product, apparatus, process or method comprising the elements.

[0030] It should be understood that, unless otherwise expressly specified or limited, terms such as "disposed," "installed," "connected," "connected," and "fixed" should be interpreted broadly. For example, they may refer to any suitable disposition, such as a fixed connection, a detachable connection, or an integral connection; they may be mechanically connected or electrically connected; they may be directly connected or indirectly connected through an intermediate medium; they may refer to internal communication between two elements or an interaction between two elements. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0031] It should also be understood that terms such as "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", and "center" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device, component or structure referred to must have a specific direction, be constructed or operate in a specific direction, and should not be understood as limiting the present invention.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0033] See also Figures 1 to 4 As shown, according to an embodiment of the present invention, a method for analyzing the microstructure composition of a welded joint of a weldment is provided. The method mainly includes six steps: setting a temperature detection point 21 on the surface of a weldment base material 10, welding the weldment base material 10, and obtaining a temperature field at the detection point; after the welding of the weldment base material 10 is completed, setting a metallographic detection point 22 in the weld seam area 12 of the cross section of the weldment base material 10, observing and recording the microstructure composition at each metallographic detection point 22; establishing a weldment model identical to the weldment base material 10, solving a simulated temperature field T1 (x, y, z, t) on the surface of the weldment model, and obtaining a simulated temperature field T1 (x, y, z, t) on the surface of the weldment model. y, z, t) is associated with the welding direction M(t), the number of welding layers N(t), the welding current A(t) and the welding voltage V(t); based on the solved simulated temperature field T1(x, y, z, t), the effective simulated temperature field T1(x, y, z, t) is determined; combined with the phase transformation CCT curve parameters, the simulated microstructure composition F1(f, x, y, z) of the weld area 12 of the weldment model is simulated; based on the simulated simulated microstructure composition F1(f, x, y, z), the effective simulated microstructure composition F1(f, x, y, z) is determined to obtain reasonable phase transformation CCT curve parameters.

[0034] The following describes in detail the various steps of the analysis method in combination with preferred implementations and specific diagrams.

[0035] See also Figure 1 、 Figure 2 The left and right weldment base materials 10 are butt-welded, forming a weld region 12 in the middle. The heat-affected zone 11 is formed between the weld region 12 and the two weldment base materials 10. This welded structure is used as an example for the following description, but it should be understood that this type of welded structure is not the only type and should not be interpreted as limiting the analysis method of the embodiments of the present invention.

[0036] S10, setting temperature detection points 21 on the surface of the weldment base material 10, and numbering the temperature detection points 21 in the form of integers 1, 2, 3, ..., m, where m≥1.

[0037] Since the simulation process of the weld temperature field requires the current and voltage values ​​of the entire welding process, it is necessary to record the current and voltage values ​​during the welding process, and the current and voltage values ​​during the welding process are related to the temperature detection point 21. Therefore, in this embodiment, after the temperature detection point 21 is set on the surface of the weld base material 10, the temperature detection point 21 is numbered for easy input into the mobile heat source subroutine of the welding simulation.

[0038] like Figure 2 As shown, in this embodiment, the temperature detection points 21 are set on the weldment base material 10 on the left and right sides of the weld area 12 and are arranged symmetrically with respect to the weld area 12 .

[0039] Preferably, there are two rows of temperature detection points 21 on each side of the weldment base material 10, and the two rows of temperature detection points 21 are evenly spaced on the surface of the weldment base material 10. Considering the feasibility of the welding operation, too small a spacing will affect the welding, and too large a spacing will result in inaccurate data. In the present invention, the longitudinal spacing distance c and the transverse spacing distance d are both 5 cm, and the closest distance b from the weld area 12 is 5 cm.

[0040] As shown in the figure, the temperature detection points 21 on each side of the weld base material 10 are arranged in two columns and three rows, that is, three temperature detection points 21 are set in each column, the middle temperature detection point 21 is located on the plane center line of the surface of the weld base material 10, and the other two are arranged symmetrically with the middle temperature detection point 21.

[0041] S20, weld the weldment base material 10, obtain the temperature field of the detection point, and organize the temperature field of the detection point into the form of detection point number m and time t T0 (m, t). At the same time, the welding direction M (t), number of welding layers N (t), welding current A (t) and welding voltage V (t) in the welding process are all organized into the form of time t.

[0042] Since the simulation process of the weld temperature field requires the current and voltage values ​​of the entire welding process, it is necessary to record the current and voltage values ​​during the welding process, and the current and voltage values ​​during the welding process are related to the temperature detection point 21, in this embodiment, after obtaining the detection point temperature field, the detection point temperature field is further organized into the form of detection point number m and time t T0 (m, t), and at the same time, the welding direction M (t), number of welding layers N (t), welding current A (t) and welding voltage V (t) in the welding process are all organized into a form related to time t, so as to facilitate input into the mobile heat source subroutine of the welding simulation.

[0043] In this embodiment, the welding direction M(t), number of welding layers N(t), welding current A(t), and welding voltage V(t) during the welding process are all organized into the form of time t as follows:

[0044] Table 1

[0045]

[0046] It is easy to understand that the ellipsis “…” in the formula represents multiple layers and multiple passes of welding, which means that there may be multiple welding layers and multiple passes of welding.

[0047] Where A1 and V1 are the welding current and voltage at time t0~t1, A2 and V2 are the welding current and voltage at time t1~t2, and t0, t1, and t2 are the welding time recording points.

[0048] S30, establishing a weldment model identical to the weldment base material 10, and solving a simulated temperature field T1 (x, y, z, t) on the surface of the weldment model. The simulated temperature field T1 (x, y, z, t) is associated with the welding direction M(t), the number of welding layers N(t), the welding current A(t), and the welding voltage V(t);

[0049] In this embodiment, professional welding analysis software, such as Simufact Welding, is used to substitute the recorded welding direction M(t), number of welding layers N(t), welding current A(t), and welding voltage V(t) into the professional welding analysis software to obtain a simulated temperature field T1 (x, y, z, t).

[0050] A weldment model identical to the weldment base material 10 is established in professional welding analysis software. At the same time, heat source formulas regarding the welding direction M(t), number of welding layers N(t), welding current A(t), and welding voltage V(t) are compiled. The simulated temperature field T1 (x, y, z, t) on the surface of the weldment model is solved using the professional welding analysis software.

[0051] Preferably, the heat source formula is obtained by using the mobile heat source subroutine. It is easy to understand that the heat source formula is a basic theory in this field, and only the detected current and voltage need to be input. The present invention exemplarily provides the following heat source formula:

[0052] The heat source distribution expression in the front half of the ellipsoid is:

[0053]

[0054] The heat source distribution expression in the second half of the ellipsoid is:

[0055]

[0056] Where: Q = ηUI, η is the heat source efficiency, U is the welding voltage, and I is the welding current; a1, a2, b, and c are the ellipsoid shape parameters; f1 and f2 are the front and rear ellipsoid heat distribution functions, and f1 + f2 = 2.

[0057] The movement mode of the mobile heat source of the mobile heat source subroutine is consistent with the welding direction M(t), the activation direction of the life and death unit is consistent with the welding direction M(t), and the activation order and time of the life and death units are determined by the number of welding layers N(t). When activating the life and death units, the layers with smaller numbers are activated first and the layers with larger numbers are activated later. The activation time of the life and death units of each layer corresponds to the start welding time of each layer.

[0058] S40, determining a valid simulated temperature field T1 (x, y, z, t) based on the solved simulated temperature field T1 (x, y, z, t);

[0059] In this embodiment, the effective simulated temperature field T1 (x, y, z, t) can be determined in the following manner:

[0060] In the solved simulated temperature field T1 (x, y, z, t), find the detection point temperature field T0 (m, t) corresponding to the temperature detection point 21 according to the x, y, z coordinates.

[0061] Compare the simulated temperature field T1 (x, y, z, t) with the detection point temperature field T0 (m, t). If the temperature difference between the two at the same time does not exceed the predetermined value, the simulated temperature field T1 (x, y, z, t) is valid; if the temperature difference between the two at the same time is greater than the predetermined value, adjust the temperature in the weldment model until the temperature difference between the simulated temperature field T1 (x, y, z, t) and the detection point temperature field T0 (m, t) at the same time does not exceed the predetermined value.

[0062] In this embodiment, the so-called predetermined temperature difference value may be, for example, 10° C., which meets the determination requirement.

[0063] Specifically, the temperature in the weldment model can be adjusted by adjusting the output thermal efficiency in the heat source formula to control the temperature.

[0064] S50, after the simulated temperature field T1 (x, y, z, t) is determined, the simulated microstructure composition F1 (f, x, y, z) of the weld region 12 of the weldment model is simulated by further combining the phase transformation CCT curve parameters;

[0065] In this embodiment, the simulated microstructure composition F1 (f, x, y, z) of the weld region 12 of the weldment model can be simulated in the following manner:

[0066] Using professional welding analysis software, first calibrate the simulated temperature field T1 (x, y, z, t) according to the temperature field T0 (m, t) of the detection point;

[0067] The simulated microstructure composition F1 (f, x, y, z) is then calibrated, where the simulated microstructure composition F1 (f, x, y, z) is calibrated by the phase transformation CCT curve parameters. The phase transformation CCT curve parameters are determined by the chemical composition, grain size, austenite transformation temperature and T8 / 5 cooling rate parameters, which determine the shape of the CCT curve.

[0068] S60 , based on the simulated simulated microstructure composition F1 (f, x, y, z), determining an effective simulated microstructure composition F1 (f, x, y, z) to obtain reasonable phase transformation CCT curve parameters.

[0069] In this embodiment, the effective simulated microstructure component F1 (f, x, y, z) can be determined as follows:

[0070] In the simulated microstructure composition F1 (f, x, y, z), find the measured microstructure composition F0 (f, x, y, z) corresponding to the metallographic inspection point 22 according to the x, y, z coordinates;

[0071] Compare the simulated microstructure composition F1 (f, x, y, z) and the measured microstructure composition F0 (f, x, y, z). If the compositions of the two are consistent at the same position, it means that the previously selected phase transformation CCT curve parameters are accurate and effective, and the phase transformation CCT curve parameters can be directly used in the phase transformation analysis of different welding processes. If the compositions of the two are inconsistent at the same position, adjust the phase transformation CCT curve parameters until the compositions of the two are consistent at the same position. The calibrated phase transformation CCT curve parameters are also accurate and effective, and the calibrated phase transformation CCT curve parameters can also be directly used in the phase transformation analysis of different welding processes.

[0072] S70, after the welding of the weldment base material 10 is completed, metallographic detection points 22 are set in the weld area 12 of the cross section of the weldment base material 10, and the metallographic detection points 22 are numbered in sequence as integers 1, 2, 3...n, where n≥1.

[0073] In this embodiment, the metallographic inspection points are preferably arranged in order of number, or they can be organized in the form of coordinates F0 (f, x, y, z), primarily considering the correspondence with the actual temperature detection field. Therefore, after the metallographic inspection points 22 are set, they are numbered in the form of integers 1, 2, 3, ..., n, where n ≥ 1.

[0074] like Figure 1As shown, in this embodiment, the metallographic inspection points 22 are arranged in two rows, one above the other. The upper row is located at the centerline of the central cross section of the weldment base material 10 in the height direction, and the lower row is located near the upper surface of the central cross section of the weldment base material 10 in the height direction. This facilitates welding quality assessment. It should be noted that the centerline position should not be understood as necessarily or strictly located at the centerline position. The upper row of metallographic inspection points 22 can be located exactly at the centerline position of the central cross section, or there can be a certain deviation between the upper and lower rows.

[0075] Preferably, three metallographic inspection points 22 are arranged in each row, the horizontal spacing between adjacent metallographic inspection points 22 is 5 cm, the middle metallographic inspection point 22 is located in the weld heat affected zone 11, and the two metallographic inspection points 22 on both sides are symmetrically distributed in the weld area 12 and the weldment base material 10 area.

[0076] S80 , observing and recording the microstructure components at each metallographic detection point 22 , and organizing the recorded microstructure components into a form F0 (f, n) of microstructure components f and numbers n.

[0077] In this embodiment, an optical microscope is used for observation, and the microscopic tissue components at each detection point are recorded, and the recorded microscopic tissue components are organized into a form F0 (f, n) with respect to the microscopic tissue component f and the number n.

[0078] In this embodiment, the microstructure component f is mainly pearlite, ferrite and bainite.

[0079] Welding simulation analysis software calculates the microstructure composition of each area of ​​the weld based on an accurate temperature field and CCT curve. After obtaining an accurate temperature field, an accurate CCT curve is one of the important conditions for simulating the microstructure. By calibrating the phase change CCT curve parameters and finally adding the calibrated CCT curve to professional welding analysis software, the microstructure composition distribution pattern of the weld under different welding processes can be studied.

[0080] The above simulated microstructure composition F1 (f, x, y, z) and the measured microstructure composition F0 (f, n) have the same composition at the same position, that is, the pearlite, ferrite and bainite compositions are consistent.

[0081] From the above description, it can be seen that the analysis method of the present invention can be summarized as follows: the first step is to organize the temperature field of the detection point into the form of number and time, and organize the recorded welding sequence, number of welding layers, welding current and welding voltage into the form of time; the second step is to organize the microstructure components obtained from the metallographic test into the form of microstructure components and numbers; the third step is to substitute the recorded welding sequence, number of welding layers, welding current and welding voltage parameters into professional welding analysis software to obtain a simulated temperature field, and compare the simulated temperature field with the temperature field of the detection point. If the difference is not large, it can be proved that the numerical simulation temperature field is effective and can be directly used for subsequent phase change analysis, such as If the difference is large, the relevant parameters can be adjusted appropriately to approach the measured temperature field until the error between the two is within the allowable range. Then the adjusted simulated temperature field can also be used for subsequent phase change analysis. The fourth step is to add the initial phase change CCT curve parameters to the calibrated numerical simulation temperature field, and perform phase change analysis in professional welding analysis software. The simulated microstructure composition is compared with the measured microstructure composition. If the composition is consistent, it proves that the initial phase change CCT curve parameters are reasonable and effective. If the microstructure composition is inconsistent, the phase change CCT curve parameters can be further adjusted until the microstructure composition of the two is consistent. Then the calibrated phase change CCT curve is also accurate and effective. In other words, the present invention can use metallographic tests to obtain the microstructure composition of the actual weldment, and then use the finite element numerical simulation method to approximate the actual microstructure composition. The purpose is to calibrate the phase change CCT curve parameters. Finally, the calibrated CCT curve is added to the professional welding analysis software to study the distribution law of the microstructure composition of the weldment under different welding processes. Figure 4 As shown in the figure, the effect of numerical simulation is good, and it is completely feasible to use it to study the distribution law of microstructure components of weldments.

[0082] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above preferred solutions can be freely combined and superimposed.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing the microstructure of a welded joint, characterized in that: include: Setting temperature detection points (21) on the surface of the weldment base material (10), and numbering the temperature detection points (21) in the form of integers 1, 2, 3, ..., m, where m≥1; Welding the weldment base material (10) to obtain the temperature field of the detection point, organizing the temperature field of the detection point into the form of detection point number m and time t T0 (m, t), and at the same time organizing the welding direction M (t), the number of welding layers N (t), the welding current A (t) and the welding voltage V (t) in the welding process into the form of time t; Establishing a weldment model identical to the weldment base material (10), solving a simulated temperature field T1 (x, y, z, t) on the surface of the weldment model, wherein the simulated temperature field T1 (x, y, z, t) is associated with the welding direction M(t), the number of welding layers N(t), the welding current A(t), and the welding voltage V(t); Determine an effective simulated temperature field T1 (x, y, z, t) based on the solved simulated temperature field T1 (x, y, z, t); Combined with the phase transformation CCT curve parameters, the simulated microstructure composition F1 (f, x, y, z) of the weld region (12) of the weldment model is simulated; Determining an effective simulated microstructure composition F1 (f, x, y, z) based on the simulated microstructure composition F1 (f, x, y, z) to verify phase transformation CCT curve parameters; After the welding of the weldment base material (10) is completed, metallographic detection points (22) are set in the weld seam area (12) of the cross section of the weldment base material (10), and the metallographic detection points (22) are numbered in the form of integers 1, 2, 3, ..., n, where n≥1; The microstructure composition at each metallographic inspection point (22) is observed and recorded, and the recorded microstructure composition is organized into a form F0 (f, n) with respect to the microstructure composition f and the inspection point number n.

2. The method according to claim 1, characterized in that The welding direction M(t), number of welding layers N(t), welding current A(t) and welding voltage V(t) in the welding process are all organized into the form of time t as follows: ； In the table, A1 and V1 are the welding current and voltage from t0 to t1, A2 and V2 are the welding current and voltage from t1 to t2, and t0, t1, and t2 are the welding time recording points.

3. The method according to claim 1, characterized in that The temperature detection points (21) are arranged in two rows, and the temperature detection points (21) in the two rows are spaced 5 cm apart in both the horizontal and vertical directions, and are 5 cm away from the weld area (12).

4. The method according to claim 1, wherein The metallographic detection points (22) are in two rows, one row being located at the center line of the center cross section of the weldment base material (10) in the height direction, and the other row being located near the upper surface of the center cross section of the weldment base material (10) in the height direction.

5. The method according to claim 4, characterized in that Three metallographic inspection points (22) are arranged in each row of metallographic inspection points (22), and the spacing between adjacent metallographic inspection points (22) is 5 cm. The middle metallographic inspection point (22) is located in the weld heat affected zone (11), and the two metallographic inspection points (22) on both sides are symmetrically distributed in the weld area (12) and the weldment base material (10) area.

6. The method according to claim 1, characterized in that A weldment model identical to the weldment base material (10) is established, and heat source formulas regarding the welding direction M(t), number of welding layers N(t), welding current A(t) and welding voltage V(t) are compiled to solve the simulated temperature field T1 (x, y, z, t) on the surface of the weldment model.

7. The method according to claim 6, characterized in that The heat source formula is obtained by using a mobile heat source subroutine. The movement mode of the mobile heat source of the mobile heat source subroutine is consistent with the welding direction M(t). The activation direction of the birth and death units is consistent with the welding direction M(t). The activation order and time of the birth and death units are determined by the number of welding layers N(t). When activating the birth and death units, the layers with a smaller number are activated first, and the layers with a larger number are activated later. The activation time of the birth and death units of each layer corresponds to the start time of welding of each layer.

8. The method according to claim 1, characterized in that The determining of the effective simulated temperature field T1 (x, y, z, t) includes: In the simulated temperature field T1 (x, y, z, t), the detection point temperature field T0 (m, t) corresponding to the temperature detection point (21) is found according to the x, y, z coordinates. Compare the simulated temperature field T1 (x, y, z, t) with the detection point temperature field T0 (m, t). If the temperature difference between the two at the same time does not exceed a predetermined value, the simulated temperature field T1 (x, y, z, t) is valid. If the temperature difference between the two at the same time is greater than the predetermined value, adjust the temperature in the weldment model until the temperature difference between the simulated temperature field T1 (x, y, z, t) and the detection point temperature field T0 (m, t) at the same time does not exceed the predetermined value.

9. The method according to claim 8, characterized in that The simulated microstructure composition F1 (f, x, y, z) of the weld area (12) of the weldment model includes: First, calibrate the simulated temperature field T1 (x, y, z, t) according to the temperature field T0 (m, t) at the detection point; Then the simulated microstructure composition F1 (f, x, y, z) is calibrated, wherein the simulated microstructure composition F1 (f, x, y, z) is calibrated by the phase transformation CCT curve parameters, and the phase transformation CCT curve parameters are determined by the chemical composition, grain size, austenite transformation temperature and T8 / 5 cooling rate parameters.

10. The method according to claim 1, characterized in that The determination of the effective simulated microstructure component F1 (f, x, y, z) includes: In the simulated microstructure composition F1 (f, x, y, z), the measured microstructure composition F0 (f, n) corresponding to the metallographic detection point (22) is found according to the x, y, z coordinates; Compare the simulated microstructure composition F1 (f, x, y, z) and the measured microstructure composition F0 (f, n). If the compositions of the two are consistent at the same position, the phase change CCT curve parameters are reasonable. If the compositions of the two are inconsistent at the same position, adjust the phase change CCT curve parameters until the compositions of the two are consistent at the same position, and the phase change CCT curve parameters are reasonable.

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