Method for testing liquefaction cracks in welding heat affected zone of high-temperature alloy

Abstract

The invention provides an inspection method for liquefaction cracks in a welding heat affected zone of a high-temperature alloy, and belongs to the technical field of material welding. The problems of inaccurate detection technology, low efficiency and high cost are solved. The method comprises the steps of inspection surface determination, bending sample preparation and test method and result evaluation. The method can effectively identify the liquefied crack and quantitatively evaluate the sensitivity of the liquefied crack. The detection method is suitable for various welding structures, can effectively detect the welding quality, is also suitable for various welding methods of single-pass welding and multi-layer multi-pass welding and covers common welding joint forms, and base metal can be pipes or plates. The beveled sample prepared by the method comprises all sections which are easy to generate heat affected zone liquefaction cracks in the length and depth directions of a welding seam; the inspection and detection method provided by the invention can be used for qualitatively and quantitatively characterizing the liquefaction cracking degree, is simple to operate and rapid to inspect, and has lower requirements on professional skills of inspectors.

Description

Technical Field

[0001] The present invention belongs to the technical field of material welding, and particularly focuses on the detection and analysis technology of liquation cracks after the welding of superalloys, aiming to provide accurate and efficient inspection means for the quality control and reliability evaluation of superalloy welded structural parts widely used in the fields of aerospace, energy power, etc. Background Art

[0002] Superalloys play a crucial role in the manufacturing of key components serving in high-temperature, high-pressure and harsh environments in the fields of aerospace, energy, etc. However, during the welding process, due to their special chemical composition and microstructural characteristics, liquation crack defects with small sizes and multi-source characteristics are extremely likely to occur in the heat-affected zone. For such liquation cracks, traditional inspection means have shown significant limitations: First, the accuracy of ultrasonic testing and radiographic testing is limited, and their sensitivity and accuracy are difficult to meet the requirements when facing small liquation cracks; Second, although industrial CT has high-precision detection capabilities, the equipment purchase cost is extremely high; Third, although the detection accuracy of penetrant testing and macro-microstructure inspection is higher than that of conventional non-destructive testing methods, some small-sized cracks will still be missed, and the randomness of the sampling position is relatively large, resulting in limited representativeness of the detection results; Fourth, micro-microstructure inspection can achieve accurate detection, but its operation is cumbersome, time-consuming and laborious, and it is also affected by the insufficient representativeness of the sampling position.

[0003] Therefore, the traditional inspection methods can no longer meet the requirements of the detection accuracy and accuracy of liquation cracks in superalloy welding, and there are also obvious deficiencies in quantitative evaluation. Therefore, there is an urgent need to develop an innovative inspection method that can not only accurately reflect the cracking degree of liquation cracks in superalloy welding, effectively improve the detection accuracy and efficiency, but also quantitatively evaluate the sensitivity of superalloy welded structures to liquation cracks.

[0004] In high-temperature alloys, as the manufacturing materials for key components in high-temperature, high-pressure, and harsh environments in the fields of aerospace and energy, they occupy a crucial position. However, during the welding process, due to the special chemical composition and microstructural characteristics of high-temperature alloys, liquation crack defects that are small in size and have multi-source characteristics are prone to occur in the heat-affected zone. Regarding liquation cracks, the existing traditional inspection methods have significant limitations: First, the accuracy of ultrasonic testing and radiographic testing is limited, and the sensitivity and accuracy for detecting small liquation cracks are difficult to meet the actual requirements; Second, although industrial CT has high-precision detection capabilities, its equipment purchase cost is extremely high and it is not easy to popularize; Third, the accuracy of penetrant testing and macroscopic metallographic inspection is higher than that of conventional non-destructive testing methods. However, some small cracks may still be missed, limiting the representativeness of the test results; Fourth, although microscopic metallographic inspection can achieve accurate detection, its operation process is cumbersome, time-consuming, and laborious, and it is also affected by the lack of representativeness of the sampling position, affecting the accuracy of the results. Traditional inspection methods can no longer meet the requirements of high-temperature alloy welding liquation cracks in terms of detection accuracy and accuracy, and there are also obvious deficiencies in quantitative evaluation. Therefore, there is an urgent need to develop an innovative inspection method that can not only accurately detect the cracking degree of liquation cracks but also effectively improve the quantitative evaluation method of detection accuracy and efficiency. Summary of the Invention

[0005] In view of this, in order to solve the problems of inaccurate detection technology, low efficiency, and high cost, the present invention proposes an inspection method for liquation cracks in the heat-affected zone of high-temperature alloy welding, which can effectively identify liquation cracks and quantitatively evaluate the liquation crack sensitivity. This detection method is applicable to a variety of welding structures, can effectively detect welding quality, and is also applicable to a variety of welding methods such as single-pass welding and multi-layer multi-pass welding, covering common welding joint forms. The base material can be a pipe or a plate.

[0006] To achieve the above object, the present invention adopts the following technical solutions: An inspection method for liquation cracks in the heat-affected zone of high-temperature alloy welding, specifically including the following steps:

[0007] Step 1: Determination of the inspection surface

[0008] In order to obtain a specimen that can fully characterize the degree of liquation cracking, it is necessary to first determine the detection depth l.

[0009] For surfacing inspection on the plate surface, one end of the inspection surface should include the material surface, and the other end should include part of the heat-affected zone, so that the transition region between the two ends of the inspection surface can include most liquation cracks at different positions. During the specific operation process, before sampling, it is necessary to measure the weld penetration depth d according to the macrostructure inspection, or the maximum value of d can also be obtained through reasonable estimation. The detection depth l = d + 1 - 3 mm.

[0010] For the butt joint inspection of plates or tubes, both ends of the inspection surface should respectively include the upper and lower (or inner and outer) surfaces, so that the transition area between both ends of the inspection surface can include liquation cracks at different positions. During the operation, the thickness of the plate (wall) needs to be measured, that is, the inspection depth l = t, where t is the thickness of the plate (wall).

[0011] For the corner joint inspection of plates, the surfacing and butt joint sampling methods can be referred to.

[0012] Step 2: Dimensions of the bending specimen:

[0013] The inspection length L, the indenter radius R, and the specimen length a should satisfy the following relationship:

[0014] 2R < L ≤ 2.5R

[0015] 0.7a ≤ L ≤ a (L ≥ 50 mm)

[0016] According to the severity of the assessment of liquation cracks, different indenter radii R can be selected. The following three specimen dimensions are recommended in descending order:

[0017] (1) When R = 30 mm, the specimen length a = 75 mm, and the thickness t = 3 mm (severe);

[0018] (2) When R = 50 mm, the specimen length a = 120 mm, and the thickness t = 2.5 or 3 mm (general);

[0019] (3) When R = 80 mm, the specimen length a = 180 mm, and the thickness t = 2.5 mm (lenient).

[0020] During sampling, the starting and ending positions of the welding specimen or the actual product should be avoided. The specimen width b ≥ w + 20, where w is the weld width. According to the determined specimen dimensions, the specimen length direction is consistent with the welding direction. When the inspection length is insufficient due to the small pipe diameter and wall thickness, for example, L < 50 mm, multiple specimens can be taken to make the total inspection length meet the requirements, and the minimum length of each specimen is 30 mm.

[0021] Step 3: Test method and result evaluation

[0022] Use a bending testing machine and a supporting bending fixture to bend the inspection surface of the specimen. After bending, with the help of a magnifying glass with a magnification of more than 10× and a vernier caliper, or a stereomicroscope, count the number of cracks and the maximum length and total length of a single crack to achieve a quantitative evaluation of the liquation crack sensitivity.

[0023] Furthermore, in Step 1, for the surfacing inspection of the plate surface, before sampling, the weld penetration depth d needs to be measured according to the macrostructure inspection, or the maximum value of d is estimated, and the inspection depth l = d + 1 - 3 mm.

[0024] Furthermore, in step 1, for the butt joint inspection of plates or pipes, the plate thickness or wall thickness is measured, and the inspection depth is the plate thickness or wall thickness.

[0025] Furthermore, in step 2, when sampling, avoid the starting and ending arc positions of the welded specimen or the actual product. The specimen width b ≥ w + 20, where w is the fusion width.

[0026] Furthermore, in step 2, according to the determined specimen size, the specimen length direction is consistent with the welding direction. When the inspection length is insufficient, multiple specimens can be taken to make the total inspection length meet the requirements, and the minimum length of each specimen is 30 mm.

[0027] Furthermore, in step 3, the quantitative evaluation criteria for liquation crack sensitivity are as follows: when the number of cracks is 0, there is no liquation tendency; when the number of cracks is 1 - 3, the maximum crack length ≤ 1.0 mm and the total crack length ≤ 2.0 mm, the liquation tendency is low; when the number of cracks > 3 or the maximum crack length > 1.0 mm or the total crack length > 2.0 mm, the liquation tendency is high.

[0028] Compared with the prior art, the beneficial effects of the method for inspecting liquation cracks in the heat - affected zone of superalloy welding of the present invention are as follows:

[0029] 1. The bevel - cut specimen prepared by the present invention includes all cross - sections prone to heat - affected zone liquation cracks in the weld length and depth directions. The present invention creatively adopts a three - dimensional bevel - cut sampling technique to completely retain the key cross - section features of the heat - affected zone in the weld length and depth directions. By constructing a detection plane at a specific angle, it ensures the comprehensive detection of surface and buried cracks in the bending inspection.

[0030] 2. The inspection method of the present invention is simple and fast, and has low requirements for the professional skills of inspectors.

[0031] 3. The inspection and detection method provided by the present invention can quickly qualitatively and quantitatively characterize the degree of liquation cracking. This method effectively solves the technical problem of low crack detection rate in traditional detection methods, and significantly improves the accuracy and reliability of welding quality evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 is a sampling schematic diagram of the surfacing test plate;

[0034] Figure 2 is a schematic diagram of the specimen taken from the surfacing test plate

[0035] Figure 3 Schematic diagram of sampling for butt test plate

[0036] Figure 4 Schematic diagram of specimen taken from butt test plate

[0037] Figure 5 Schematic diagram of sampling for single specimen of butt pipe

[0038] Figure 6 Schematic diagram of sampling for multiple specimens of butt pipe

[0039] Figure 7 Schematic diagram of bending fixture and bending process

[0040] Figure 8 Liquation crack in heat - affected zone on bending surface Specific implementation mode

[0041] The following will clearly and completely elaborate on the technical solutions in the embodiments of the present invention in combination with the accompanying drawings in the embodiments of the present invention. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0042] See Figure 1-8 Describing this implementation mode, a method for inspecting liquation cracks in the heat - affected zone of superalloy welding specifically includes the following steps:

[0043] Step 1: Determination of inspection surface

[0044] To obtain specimens that can fully characterize the degree of liquation cracking, it is necessary to first determine the detection depth l.

[0045] For the detection of surfacing on the plate surface, one end of the inspection surface should include the material surface, and the other end should include part of the heat - affected zone, so that the transition region between the two ends of the inspection surface can contain most liquation cracks at different positions. In the specific operation process, before sampling, it is necessary to measure the weld penetration depth d (mm) according to the macrostructure inspection, or the maximum value of d can also be obtained through reasonable estimation. The detection depth l = d + 1 - 3 mm.

[0046] For the detection of butt joint of plate or pipe, both ends of the inspection surface should respectively include the upper and lower (or inner and outer) surfaces, so that the transition region between the two ends of the inspection surface can contain liquation cracks at different positions. During the operation process, it is necessary to measure the thickness of the plate (wall), that is, the detection depth l = t, where t is the thickness of the plate (wall).

[0047] For the detection of corner joint of plate, the sampling methods of surfacing and butt joint can be referred to.

[0048] Step 2: Dimensions of bending specimen

[0049] The inspection length L, indenter radius R, and specimen length a should satisfy the following relationship:

[0050] such as Figure 5 shown.

[0051] According to the severity of the assessment of liquation cracking, different indenter radii R can be selected. The following three specimen sizes are recommended in descending order:

[0052] (1) When R = 30 mm, the specimen length a = 75 mm, and the thickness t = 3 mm (severe);

[0053] (2) When R = 50 mm, the specimen length a = 120 mm, and the thickness t = 2.5 or 3 mm (general);

[0054] (3) When R = 80 mm, the specimen length a = 180 mm, and the thickness t = 2.5 mm (lenient).

[0055] During sampling, the starting and ending positions of the welding specimen or the actual product should be avoided. The specimen width b ≥ w + 20, where w is the weld width. According to the determined specimen size, the specimen length direction should be consistent with the welding direction. When the inspection length is insufficient due to the small pipe diameter and wall thickness, multiple specimens can be taken to make the total inspection length meet the requirements, and the minimum length of each specimen is 30 mm, such as Figure 6 shown.

[0056] Step 3: Test method and result evaluation

[0057] Use a bending testing machine and a supporting bending fixture to bend the inspection surface of the specimen. After bending, with the help of a magnifying glass with a magnification of more than 10× and a vernier caliper, or a stereomicroscope, count the number of cracks, the maximum length and the total length of a single crack, and through comparison with Table 1, achieve a quantitative evaluation of the liquation cracking sensitivity.

[0058] The quantitative evaluation standard for liquation cracking sensitivity is as follows: 9. The quantitative evaluation standard for liquation cracking sensitivity is: when the number of cracks is 0, there is no tendency for liquation; when the number of cracks is 1 - 3, the maximum crack length ≤ 1.0 mm and the total crack length ≤ 2.0 mm, the liquation tendency is low; when the number of cracks > 3 or the maximum crack length > 1.0 mm or the total crack length > 2.0 mm, the liquation tendency is high, that is, as long as any one of the high - tendency criteria is met, it indicates a high liquation tendency.

[0059] Table 1 Evaluation standard for liquation cracking sensitivity

[0060]

[0061] Example 1:

[0062] A method for inspecting liquation cracks in the heat affected zone of superalloy welding, specifically including the following steps:

[0063] Step 1: Determination of inspection surface

[0064] Select an Inconel 617 nickel-based welding wire with a diameter of Φ1.2mm and a HT700C iron-nickel-based superalloy base material with a thickness of δ10mm, and prepare a single-pass surfacing test plate by TIG welding method. The welding process is shown in Table 2:

[0065] Table 2 Welding process

[0066]

[0067] Measure the weld penetration depth d = 0.8mm, the weld width w = 1.2mm, and determine the detection depth l = 3.8mm.

[0068] Step 2: Detection method

[0069] Determine the indenter radius R = 30mm, sample without including the starting and ending arc positions, the detection length L = a, the sample length a = 75mm, the sample width b = 3.2mm, and the thickness t = 3mm.

[0070] Step 3: Result evaluation

[0071] Use a bending testing machine and a supporting bending fixture to bend the inspection surface of the sample. After bending, count the number of cracks, the maximum length of a single crack, and the total length with the aid of a stereomicroscope, and compare with Table 1. The test results are shown in Table 3. The liquation cracks on the bending surface are shown in Figure 5 .

[0072] Table 3 Test results

[0073]

[0074] The above disclosed embodiments of the present invention are only used to help explain the present invention. The embodiments do not describe all details in detail, nor limit the invention to the specific embodiments described. According to the content of this specification, many modifications and changes can be made. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention.

Claims

1. A method for inspecting liquefaction cracks in a high-temperature alloy welding heat-affected zone, characterized in that: The specific steps include: Step 1: Inspection surface determination: First, determine the detection depth l. For plate surface cladding detection, one end of the detection surface includes the material surface, and the other end includes part of the heat affected zone. For plate or tube butt testing, the two ends of the test surface include upper and lower surfaces or inner and outer surfaces respectively, so that the transition area between the two ends of the test surface can contain liquefaction cracks at different positions; For corner joint inspection, refer to the cladding and butt joint sampling methods; Step 2: Bend specimen preparation: Bending specimen size requirements: The test length L, the indenter radius R and the specimen length a satisfy the following relationship, where L ≥ 50 mm: Step 3: Test methods and result evaluation: Use a bending test machine and a matching bending fixture to bend the test surface of the sample. After bending, use a magnifying glass with a magnification of more than 10× and a vernier caliper or a stereo microscope to count the number of cracks and the maximum and total lengths of a single crack to achieve quantitative evaluation of liquefaction crack sensitivity.

2. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 1, for plate surface cladding detection, before sampling, the weld penetration d needs to be measured based on low-power structure inspection, or the maximum value of d needs to be estimated, and the detection depth l = d + 1 ~ 3mm.

3. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 1, for plate or tube butt detection, the plate thickness or wall thickness is measured, and the detection depth is the plate thickness or wall thickness.

4. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 2, when the indenter radius R = 30 mm, the sample length a = 75 mm and the thickness t = 3 mm.

5. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 2, when the indenter radius R = 50 mm, the sample length a = 120 mm and the thickness t = 2.5 or 3 mm.

6. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 2, when the indenter radius R = 80 mm, the sample length a = 180 mm and the thickness t = 2.5 mm.

7. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 2, when taking samples, avoid the arc starting and arc ending positions of the welding specimen or actual product. The sample width b≥w+20, where w is the weld width.

8. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 2, according to the determined sample size, the sample length direction is consistent with the welding direction. When the inspection length is insufficient, multiple samples can be taken to make the total inspection length meet the requirements, and the minimum length of each sample is 30mm.

9. The method for inspecting liquefaction cracks in the heat affected zone of high temperature alloy welding according to claim 1, characterized in that: In step 3, the quantitative evaluation standard of liquefaction crack sensitivity is: when the number of cracks is 0, there is no liquefaction tendency; when the number of cracks is 1 to 3, the longest crack length is ≤1.0 mm and the total crack length is ≤2.0 mm, the liquefaction tendency is low; when the number of cracks is >3 or the longest crack length is >1.0 mm or the total crack length is >2.0 mm, the liquefaction tendency is high.

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