A method for preparing a weld specimen with cracks

Abstract

The present invention provides a method for preparing a weld specimen with a crack, which relates to the technical field of weld specimen preparation. The method comprises the following steps: S1: Process the bevels at the welding ends of two base metals. The main weld is located between the two bevels, and the two base metals are welded at the main weld; S2: Process a first groove on the outer side wall of the base metal, and the first groove penetrates through the main weld; S3: Weld in the first groove to form an induced layer; S4: Process a second groove on the surface of the induced layer, and perform welding in the second groove by means of fusion welding. After welding, perform a cooling treatment to generate cracks; S5: Complete the welding of the cover layer of the main weld, and cover the crack inside the welding material during welding. By adopting the present invention, the crack morphology is realistic, and the position and depth of the crack are easy to control during the preparation process. It can be detected and verified in ultrasonic testing to ensure the reliability of the simulation test results. Compared with the fatigue loading method, this method effectively saves the production cost and time of cracks.

Description

Technical Field

[0001] This invention relates to the field of weld specimen preparation technology, and more specifically, to a method for preparing weld specimens with cracks. Background Technology

[0002] In the manufacturing and in-service inspection of pressure vessels, pipelines, and other pressure-bearing equipment, non-destructive testing (such as radiographic testing and ultrasonic testing) is a crucial step in detecting internal weld cracks and ensuring safety. The skills training of testing personnel and the accuracy calibration of testing equipment both require the use of specimens containing known artificial defects. Among these, specimens simulating real-world working conditions with transverse weld cracks are particularly important.

[0003] Currently, the methods for creating artificial crack specimens are mostly machining (such as wire cutting) or fatigue loading. Cracks produced by machining have regular shapes and smooth edges, which differ significantly from natural cracks generated during actual welding due to stress and metallurgical factors in terms of morphology and tip sharpness, making it difficult to accurately reflect the characteristics of the detection signal. Fatigue loading methods involve expensive equipment, long cycles, and precise control of crack depth and location. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing weld crack specimens, which is simple to operate, low in cost, produces realistic crack morphology, and facilitates control of crack location and depth during preparation. Cracks prepared by this method can be detected and verified in ultrasonic testing to ensure the reliability of simulation test results. The specimens can be reused. Compared with the fatigue loading method, this method effectively saves the cost and time of crack preparation.

[0005] The technical solution adopted in this invention is as follows: This application provides a method for preparing a weld specimen with cracks, comprising the following steps: S1: Process the bevels at the two base materials to be welded. The main weld is between the two bevels. Weld the two base materials at the main weld until the welding stops before reaching the cover layer. S2: A first groove is machined on the outer wall of the base material, and the first groove passes through the main weld along the axial direction of the base material; S3: Add welding wire into the first groove to form an induction layer; S4: A second groove is machined from the surface of the induction layer inward into the induction layer. Welding is carried out in the second groove by fusion welding. After welding is completed, the welded part is immediately subjected to rapid cooling to cause cracks in the welded part. S5: Complete the cover layer welding of the main weld, covering the cracks inside the welding material during welding.

[0006] Furthermore, in this invention, in step S5, before welding the cover layer of the main weld, the length of the crack is trimmed so that the crack reaches the set length.

[0007] Furthermore, in this invention, after the crack is repaired, the first groove is filled by welding inside the first groove, and then the welding material at the opening of the first groove is ground to make it flush with the outer wall of the base material.

[0008] Furthermore, in this invention, when welding to fill the first groove, manual tungsten inert gas welding is used, and the welding material is the same as the base material.

[0009] Furthermore, in this invention, the base material is austenitic stainless steel.

[0010] Furthermore, in this invention, in step S2, the depth of the first groove is greater than the set depth of the crack.

[0011] Furthermore, in this invention, in step S2, the width of the first groove opening is smaller than the width of the main weld opening.

[0012] Furthermore, in this invention, during step S3, when welding is performed in the first groove, a cobalt-based welding wire is used.

[0013] Compared with the prior art, the present invention has at least the following advantages or beneficial effects: The method for preparing weld crack specimens provided by this invention is simple to operate, low in cost, produces realistic crack morphology, and facilitates control of crack location and depth during preparation. Cracks prepared by this method can be detected and verified in ultrasonic testing to ensure the reliability of simulation test results. The specimens can be reused. Compared with the fatigue loading method, this method effectively saves the cost and time of crack preparation. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a cross-sectional view of the specimen after it has been fabricated according to the present invention; Figure 2 This is a top view showing the completion of the main weld in step S1 of the present invention. Figure 3 This is a top view of the first groove after it has been machined in step S2 of the present invention; Figure 4 This is a top view of the welded induction layer formed in step S3 of the present invention; Figure 5 This is a top view of the second groove after it has been machined in step S4 of the present invention; Figure 6 This is a top view of the crack after it is generated in step S4 of the present invention; Figure 7 This is a top view of the crack after its length has been adjusted in this invention; Figure 8 This is a top view of the first groove after it has been leveled in this invention; Figure 9 This is a top view of the first groove leveling area after grinding in this invention; Figure 10 This is a top view of the specimen after it has been fabricated according to the present invention.

[0016] Icons: 1-Base material; 2-Main weld. Detailed Implementation

[0017] The embodiments of this application will now be described in detail with reference to the accompanying drawings. Example

[0018] Please refer to Figures 1-10 This embodiment provides a method for preparing a weld specimen with a crack, which is mainly used to prepare transverse cracks, and includes the following steps: S1: The two base materials 1 to be welded are machined to form bevels. The two base materials 1 are preferably austenitic stainless steel pipes of the same size. The use of austenitic stainless steel as the base material is due to its low thermal conductivity and high coefficient of linear expansion, which generates greater tensile stress during welding cooling, thus increasing the probability of crack formation. The two base materials 1 are positioned opposite each other, with their bevels close together and spaced a certain distance apart. The main weld 2 is located between the two bevels. The bevels are first cleaned by grinding with a grinding wheel. At the main weld 2, conventional welding techniques are used, and ER308 welding wire is used to weld the two base materials 1 until the capping layer is reached (the capping weld is the final surface layer welding step in the welding process, mainly including the root pass, filler layer, and capping layer; in this embodiment, stopping before the capping layer means welding the root pass and filler layer first). At this point, if... Figure 2 As shown.

[0019] S2: As Figure 3As shown, a first groove is machined on the outer wall of the base material 1. This first groove can be machined using an angle grinder. The machined first groove passes through the main weld 2 along the axial direction of the base material 1. The depth of the first groove is greater than the set depth of the crack, and the width of the opening of the first groove is less than the width of the opening of the main weld 2. The machined first groove is a transverse groove, which can control the direction of the crack. The first groove can create a window effect, forming stress concentration, which is conducive to the formation of subsequent cracks, while ensuring the fusion effect of subsequent welding. The bottom of the first groove can be widened during machining to ensure good fusion during welding and avoid incomplete fusion defects.

[0020] S3: As Figure 4 As shown, welding wire is added to the first groove to form an induced layer. Manual tungsten inert gas welding is used with high current welding. The high current range for welding is 200A-250A, which makes the cobalt-based welding wire and the base material 1 fuse and facilitates the subsequent formation of cracks. High current, narrow weld bead, and rapid cooling ensure the formation of subsequent cracks. In addition, since the density difference between the cobalt-based welding wire and the base material austenitic stainless steel is not large, a small amount added to the weld has almost no color difference on the film during radiographic inspection, which can meet the technical requirements.

[0021] S4: As Figure 5 As shown, a second groove is machined from the surface of the induction layer inwards into the induction layer. Welding is performed in the second groove using a fusion welding method without adding welding wire. The machined second groove can further create a window effect, increase stress concentration, and ensure the subsequent welding fusion effect, preventing the stainless steel material from cracking. Immediately after welding, the welded area is subjected to rapid cooling to cause the welded area to shrink sharply, generating tensile stress, which ultimately causes cracks in the welded area. At this time, as shown... Figure 6 As shown, during cooling, simply spray the welded area with cooling water. Since the standard specifies requirements for crack depth, the crack thickness generated by the first groove may not meet the detailed requirements. Therefore, a second groove is created. While controlling the groove depth and retaining a certain amount of the original weld metal composition, high-current fusion welding without welding wire is used to further concentrate and increase the welding stress. Fusion welding serves to achieve instantaneous cooling during the welding process, further making the crack more prominent and achieving the required thickness. To ensure maximum instantaneous stress concentration and release, and that the resulting crack length and depth meet the technical requirements, cold water must be poured onto the weld immediately after welding to induce cracking.

[0022] S5: As Figure 7 As shown, the length of the crack is trimmed to achieve the desired length. During trimming, the ends of the crack can be ground with a grinding wheel to shorten the crack length and achieve the desired result. After trimming, as shown... Figure 8As shown, the first groove is filled by welding within it. During filling, manual tungsten inert gas welding is used, and the welding material is the same as that of the base material 1. Figure 9 As shown, the welding material at the opening of the first groove is then ground to be flush with the outer wall of the base material 1. Finally, the cover layer welding of the main weld 2 is completed. During welding, the crack is covered inside the welding material. The finished specimen formed after welding is shown in the figure. Figure 10 As shown.

[0023] The method for preparing weld crack specimens provided in this application can quickly and effectively form a continuous transverse crack while ensuring the integrity of the specimen, and the crack morphology matches the actual crack morphology in the product weld. The crack prepared by this method can be detected and verified in ultrasonic testing to ensure the reliability of the simulation test results. The specimen preparation method is simple and reusable, and compared with the fatigue loading method, this method effectively saves the preparation cost and time of the specimen. The successful preparation of this specimen brings high economic benefits and technical value to the application of advanced non-destructive testing technology in production.

[0024] One specific implementation is as follows, which is used to prepare ultrasonically tested transverse crack specimens for training purposes: S1: As Figure 2 As shown, two 304 austenitic stainless steel pipes with a length of 350mm, a thickness of 20mm, and an outer diameter of 200mm are selected, and V-shaped bevels are machined at the ends. After cleaning the bevels, manual tungsten inert gas welding is used, and ER308 welding wire is used to complete the root pass and filler pass welding of the main weld.

[0025] S2: As Figure 3 As shown, in the middle of the main weld, an angle grinder is used to grind a first groove with a depth of about 10 mm and a width of about 8 mm, and the bottom of the groove is widened.

[0026] S3: As Figure 4 As shown, tungsten inert gas welding is performed in the first groove using parameters of 220A current and 16V voltage, and ERCoCr-A cobalt-based welding wire is added to complete the welding of the induced layer.

[0027] S4: As Figure 5 As shown, a second groove is ground into the surface of the induced layer using an angle grinder. No welding wire is added into the second groove. Self-fusion welding is performed using spot welding at a slow welding speed. Immediately after welding, the weld area is rapidly cooled with cold water. Figure 6 As shown, the inspection revealed a transverse crack approximately 20 mm long.

[0028] S5: As Figure 7 As shown, after trimming the crack ends with a grinding wheel, the required crack length is retained, such as... Figure 8 and Figure 9 As shown, fill the remaining grooves to achieve the same thickness as the original parent material, such as... Figure 10 As shown, the final weld bead of the main weld seam was completed. Radiographic testing revealed that the internal crack morphology was natural and met all technical requirements.

[0029] Furthermore, unless otherwise explicitly specified or limited, the terms "installation" and "connection" in this application embodiment should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. The terms "upper," "lower," "left," "right," "inner," "outer," and "side," etc., are merely for reference to the direction in the accompanying drawings or the usual placement of the product during use. They are only for clearly describing this application and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limitations on this application. The terms "first," "second," etc., are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance; "multiple" refers to at least two. In this application embodiment, the limitations on relative positional relationships such as parallel, perpendicular, and aligned are all relative to the current technological level and are not absolutely strict limitations. Slight deviations are allowed; approximations of parallel, perpendicular, and aligned are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 degrees and 10 degrees.

[0030] The above are only some embodiments and implementation methods of this application. The protection scope of this application is not limited thereto. In the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other. Any combination of features in different embodiments is also within the protection scope of this application. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.

Claims

1. A method for preparing a weld specimen with cracks, characterized in that, Includes the following steps: S1: Make bevels at the ends of the two base materials (1) to be welded, and the main weld (2) is between the two bevels. Weld the two base materials (1) at the main weld (2) until the welding stops before the cover layer. S2: A first groove is machined on the outer wall of the base material (1), and the first groove passes through the main weld (2) along the axial direction of the base material (1). S3: Add welding wire into the first groove to form an induction layer; S4: A second groove is machined from the surface of the induction layer inward into the induction layer. Welding is carried out in the second groove by fusion welding. After welding is completed, the welded part is immediately subjected to rapid cooling to cause cracks in the welded part. S5: Complete the cover layer welding of the main weld (2), and cover the crack inside the welding material during welding.

2. The method for preparing a weld crack specimen according to claim 1, characterized in that, In step S5, before welding the cover layer of the main weld (2), the length of the crack is trimmed so that the crack reaches the set length.

3. The method for preparing a weld crack specimen according to claim 2, characterized in that, After repairing the cracks, the first groove is filled by welding inside the first groove, and then the welding material at the opening of the first groove is ground to make it flush with the outer wall of the base material (1).

4. The method for preparing a weld crack specimen according to claim 3, characterized in that, Welding is performed inside the first groove to fill the first groove. Manual tungsten inert gas welding is used for welding, and the welding material is the same as that of the base material (1).

5. The method for preparing a weld crack specimen according to claim 1, characterized in that, The base material (1) is austenitic stainless steel.

6. The method for preparing a weld crack specimen according to claim 1, characterized in that, In step S2, the depth of the first groove is greater than the set depth of the crack.

7. The method for preparing a weld crack specimen according to claim 1, characterized in that, In step S2, the width of the first groove opening is smaller than the width of the main weld (2) opening.

8. The method for preparing a weld crack specimen according to claim 1, characterized in that, In step S3, when welding is performed in the first groove, cobalt-based welding wire is used.

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