Detection device for simulating and detecting shot blasting quality of outer wall of drill rod joint

Abstract

The invention discloses a detection device for simulating and detecting the shot blasting quality of the outer wall of a drill rod joint, and belongs to the field of machining quality detection.The detection device comprises a drill rod joint test piece, a sampling block and a fastener, a plurality of openings are formed in the outer wall of the drill rod joint test piece and located at the small-diameter end pipe opening, the middle section and the to-be-detected position of the outer wall of a circular bead of a conical external thread respectively; the opening form comprises a radial notch, an axial notch and a window structure, the sampling block is of a combined structure, is detachably fixed in the opening through a fastener, and is in the same shot blasting environment with the outer surface of a drill rod joint test piece, so that the shot blasting quality can be accurately simulated and detected. The material and the heat treatment process of the sampling block are consistent with those of the drill rod joint, the surface roughness, the size and the like meet the detection requirements, and the shot blasting effect can be truly reflected. The device can realize accurate quantitative detection for parts with complex shapes, obviously improves the detection precision and efficiency, reduces the detection cost, and is suitable for shot blasting quality detection of drill rod joints and other workpieces with complex shapes.

Description

Technical Field

[0001] The present invention relates to a technical solution belonging to the technical field of machining quality testing equipment, and in particular, to a testing device for testing the manufacturing quality of mechanical parts, and in particular, to a testing device for simulating the shot peening quality of the outer wall of a drill pipe joint. Background Art

[0002] From a structural point of view, oil drill pipe is a typical slender pipe with a standard length of about 10 meters and drill pipe joints at both ends. The oil drilling process is progressive, and the target drilling depth is usually several thousand meters or even more than 10,000 meters. Therefore, the matching oil drill pipe must be connected in sections to reach the drilling depth. During the drilling stage, the oil drill pipe must not only bear the extremely large torque, but also the accumulated weight formed by the series connection. Under this heavy-load working condition, the rotating oil drill pipe must have sufficient strength, especially the drill pipe joints at both ends, which have higher strength requirements.

[0003] In order to meet the supporting requirements of oil drilling projects, this industry usually uses high-quality alloy structural steel to manufacture oil drill pipes, and uses heat treatment and surface shot peening processes to further improve strength indicators. After the drill pipe joint is formed, its outer wall needs to be shot peened to significantly improve the structural strength and effectively reduce the thread galling phenomenon. Therefore, shot peening is an indispensable process for processing drill pipe joints.

[0004] Technicians in the field of mechanical manufacturing are well aware that the main technical parameters of the shot peening process include shot peening particle size, speed and spray angle. However, due to the irregular cylindrical structure of the outer wall of the drill pipe joint, under the same parameter conditions, there are certain differences in the shot peening impact force and shot peening quality of various parts of the joint. Especially in the tapered external thread section and the sealing shoulder, due to the irregular outer surface, the effect of the shot peening process is difficult to be uniform. This unevenness leads to large differences in the strength values ​​of various parts. The existing detection methods are mostly focused on the strength detection of relatively regular parts of the outer wall, which cannot comprehensively and objectively reflect the overall shot peening quality of the drill pipe joint.

[0005] The prior art patent CN116604474B discloses a drill pipe joint thread surface treatment process, which includes degreasing and oiling, shot peening and shot peening cleaning of the drill pipe joint thread surface, and the shot peening coverage rate reaches 100%, and the shot peening intensity ranges from 0.15mm·A to 0.38mm·A. This technology can significantly improve the strength and wear resistance of the drill pipe joint thread surface, and has the advantages of reducing pollution and reducing costs.

[0006] Although CN116604474B provides an effective method to improve the surface performance of threads, this technology does not provide a solution to the problem of shot peening quality detection of complex parts of the outer wall of drill pipe joints, especially for irregular structures such as tapered external thread sections and sealing shoulders. The shot peening uniformity and strength differences cannot be effectively quantitatively analyzed. In addition, its detection method is mainly based on the empirical inference of surface shot peening coverage, lacking more intuitive and accurate simulation detection methods. This defect makes it impossible for this technology to fully guide or optimize the shot peening process under complex working conditions. Therefore, the existing technology still has a lot of room for improvement in the field of simulation detection of shot peening quality of the outer wall of drill pipe joints. Summary of the invention

[0007] The present invention mainly aims at the problems that the existing technology is difficult to implement detection, and there are problems such as poor detection accuracy and high detection cost, difficulty in quantitative evaluation, and inability to cover complex structural parts. Therefore, a detection device for simulating the shot peening quality of the outer wall of the drill pipe joint is proposed. The main structure of the device is similar to the drill pipe joint to be inspected, and a detachable sampling block is preset at the inspection point. The preset sampling block is removed for quantitative detection after the shot peening process is implemented.

[0008] The present invention achieves the technical objectives through the following technical solutions.

[0009] A detection device for simulating the shot peening quality of the outer wall of a drill pipe joint, comprising a drill pipe joint specimen, a sampling block and a fastener, wherein the outer wall of the drill pipe joint specimen is provided with a plurality of openings for installing the sampling block, each opening corresponding to a position to be detected, including an opening arranged at the small diameter end pipe mouth of the tapered external thread on the outer wall of the drill pipe joint specimen, an opening radially penetrating the inner and outer walls opened at the middle section of the tapered external thread, and an opening opened on the outer wall of the shoulder, wherein the opening is a notch or window penetrating the inner and outer walls of the drill pipe joint specimen, and forms an open structure in at least one direction; the sampling block is a combined structure, and the sampling block is detachably fixed in the opening by a fastener, and the sampling block and the outer surface of the drill pipe joint specimen are in the same shot peening process environment, so as to simulate the shot peening quality detection.

[0010] Preferably, the opening of the drill pipe joint specimen includes a radial notch and an axial notch as well as a window A and a window B. The radial notch and the axial notch are arranged at the pipe mouth of the small diameter end of the tapered external thread and have a rectangular structure. The radial notch and the axial notch are used to locate the installation position of the sampling block. The window A is arranged at the middle section of the tapered external thread and has a rectangular structure. The window B is arranged on the outer wall of the shoulder and has a rectangular structure, which is used to accommodate the radial notch and the axial notch of the sampling block.

[0011] Preferably, the radial notch, axial notch, window A and window B built into the drill rod joint specimen are arranged in four equal parts on the cross section, so as to realize the simulated detection of shot peening quality at multiple key positions of the drill rod joint.

[0012] Preferably, the bottom edges of window A and window B built into the drill pipe joint specimen are axially inclined, and the inclination angle is equal to half the value of the tapered external thread angle of the drill pipe joint, and the inclination directions of the bottom edges of window A and window B are opposite to each other to correspond to the actual spray angle of the shot peening process. The bottom edges of window A and window B are designed to be inclined, and the inclination angle is set according to the thread tooth angle, which can better simulate the actual spray angle in the shot peening process, adapt to the inspection requirements of the outer wall of complex structure, adapt to the irregular outer wall structure, and effectively solve the problem that traditional technology is difficult to effectively analyze the shot peening effect of irregular outer wall.

[0013] Preferably, the radial notch, the axial notch, the bottom edges of window A and window B are all provided with screw holes, and the installed sampling block is locked with bolts and screw holes, thereby forming a detachable simulation detection structure for the drill pipe joint specimen with the sampling block.

[0014] Preferably, the sampling block comprises a template, a base and a fixing assembly, the base is an I-shaped boss structure, and the template is arranged on the upper end of the base and is locked and fixed by the fixing assembly.

[0015] Preferably, the fastener is a bolt and the fixing assembly is a screw.

[0016] Preferably, the template is a long thin strip with a thickness of 1.0 to 1.6 mm, a length of 15 to 20 mm, and a width of 3.0 to 5.0 mm.

[0017] Preferably, the sample material is the same as that of the drill pipe joint to be tested, and undergoes the same heat treatment to ensure that the results of the simulated test accurately reflect the effect of the shot peening process.

[0018] Preferably, the surface roughness of the sample is Ra3.2-1.6um.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention pre-places a detachable sampling block at the inspection point of the drill pipe joint test piece. This detachable structure is simple and reasonable, easy to manufacture, and convenient to operate. It can simulate the shot peening effect for different structural positions and realize quantitative detection, which fully reflects the shot peening process quality of each part of the joint. It effectively solves the problem that the existing technology mainly detects the shot peening coverage rate or thread surface performance of regular outer wall parts, and cannot objectively and accurately evaluate the shot peening quality of complex shape parts of the drill pipe joint.

[0020] The present invention presets openings of various forms on the outer wall of the drill pipe joint specimen, and the sampling block can be accurately positioned in the area to be tested, ensuring that it and the joint specimen are subjected to the same shot peening process environment. The measured data can accurately reflect the shot peening effect and improve the detection accuracy. Compared with the empirical inference method of the prior art, the detection method of the present invention is more intuitive and accurate.

[0021] The detachable sampling block design of the present invention is convenient for repeated testing of the shot peening effect, and can optimize the shot peening process parameters by comparing the test results of different parts, thereby providing a scientific basis for the shot peening process design of workpieces with complex structures.

[0022] The present invention can ensure the detection accuracy and avoid damage to the overall joint test piece by pre-setting a detachable sampling block, effectively reducing the detection cost and effectively solving the problem that the prior art often requires destructive testing for comprehensive evaluation of shot peening quality.

[0023] The material and heat treatment process of the sampling block of the present invention are consistent with those of the drill pipe joint to be tested, which can truly reflect the quality level of the point to be tested, ensure the reliability of the simulated test results, and enable it to truly reflect the impact of the shot peening process on the overall strength and durability of the drill pipe joint. In addition, the sampling block is detachable, which is convenient for using conventional inspection tools to detect the surface quality after shot peening, thereby significantly reducing the detection cost and greatly improving the detection accuracy and efficiency. The detachable sampling block of the present invention has a simple structure and is easy to install and disassemble. In actual application, its consumables are only the template configured for the sampling block, and the remaining parts can be reused. Therefore, the application cost of this inspection tool is very low, which is convenient for promotion and application in actual testing. In addition, this solution is not only suitable for shot peening quality inspection of drill pipe joints, but can also be extended to the field of shot peening quality inspection of other mechanical parts with complex surface shapes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a schematic structural stereoscopic diagram of a detection device for simulating and detecting the shot peening quality of the outer wall of a drill pipe joint.

[0025] Figure 2 for Figure 1 A three-dimensional schematic diagram of the structure of the drill pipe joint specimen is shown.

[0026] Figure 3 for Figure 1 Schematic diagram of the structure of the sampling block shown.

[0027] Figure 4 for Figure 3 Schematic diagram of the split body.

[0028] In the figure: 1-drill pipe joint specimen, 1.1-radial notch, 1.2-axial notch, 1.3-window A, 1.4-window B, 1.5-screw hole, 2-sampling block, 2.1-fixing assembly, 2.2-sample plate, 2.3-base, 3-fastener. DETAILED DESCRIPTION

[0029] The present invention will be further explained below in conjunction with the accompanying drawings and embodiments.

[0030] like Figure 1 As shown, the present invention provides a detection device for simulating the shot peening quality of the outer wall of a drill pipe joint, which includes a drill pipe joint test piece 1, a sampling block 2 and a fastener 3. Figure 3 and Figure 4 The sampling block 2 shown is a combination, which consists of a fixing component 2.1, a sample plate 2.2 and a base 2.3. The sampling block 2 is a combined structure, and the base 2.3 is an I-shaped boss structure, which is convenient for accurate positioning in the opening. The fixing component 2.1 adopts a screw structure, which cooperates with the base to fix the sample plate in the preset opening of the drill pipe joint specimen 1.

[0031] The drill joint test piece 1 is as follows Figure 2 As shown, the finished drill pipe joint to be inspected is used, and the conical external thread on its outer wall has been processed. In order to achieve the expected simulation detection function, preset openings are opened at multiple inspection points on the outer wall of the test piece, including: First, a rectangular radial notch 1.1 and an axial notch 1.2 are opened at the pipe mouth of the small diameter end of the tapered external thread, and a rectangular window A 1.3 which radially penetrates the inner and outer walls is opened at the middle section of the tapered external thread, and a window B 1.4 is opened on the outer wall of the shoulder. The radial notch 1.1, the axial notch 1.2, the window A 1.3 and the window B 1.4 for accommodating the sampling block 2 are all provided with screw holes 1.5 at the bottom edges. The installed sampling block 2 is locked with bolts 3 and the screw holes 1.5, thereby forming a detachable detection device for simulating the shot peening quality of the outer wall of the drill pipe joint.

[0032] The structural features of the present invention are mainly reflected in that the sampling block 2 is set in the drill pipe joint test piece 1 according to the position of the drill pipe joint to be inspected, and the sampling block 2 is detachable. In addition to the simple structure, easy production and convenient operation of this equiposition design, the most important thing is that the sampling block 2 is detachable, thereby directly simplifying the detection conditions, and the simulation is good and the detection accuracy is high. After the shot peening process, the sampling blocks 2 are removed from the drill pipe joint test piece 1 in turn, and the free sampling blocks 2 can be placed flat, and the flat sampling blocks 2 are convenient for inspection with conventional detection equipment. In this embodiment, the drill pipe joint specimen 1 is provided with four points to be inspected with the sampling block 2 as the carrier, the first point to be inspected is located at the end face of the small diameter end of the drill pipe joint specimen 1; the second point to be inspected is located at the outer wall of the small diameter end of the drill pipe joint specimen 1; the third point to be inspected is located at the middle section of the tapered external thread configured on the drill pipe joint specimen 1; the fourth point to be inspected is located on the outer wall of the shoulder, and the positions of the above four points to be inspected are determined by the radial notch 1.1, the axial notch 1.2, the A window 1.3 and the B window 1.4.

[0033] From the perspective of optimizing the structure, the four inspection points set above are as follows: Figure 1 As shown, the arrangement is uniformly distributed, that is, it is arranged in four equal parts on the cross section of the drill pipe joint specimen 1. In view of the fact that the tapered external thread of the drill pipe joint specimen 1 is a triangular tooth shape, that is, the two sides of the thread are inclined, the position of the spray gun should be tilted accordingly when the shot peening process is implemented in this section to achieve the expected requirements. In order to reduce the simulation detection error, the bottom edge of the window A 1.3 configured in the drill pipe joint specimen 1 is tilted by the same amount according to the bevel angle of the positive side of the thread. When the shot peening process is performed on the reverse side of the thread, the adjacent shoulder must be affected. Therefore, the bottom edge of the window B 1.4 located at the shoulder is tilted by the same amount according to the bevel angle of the reverse side of the thread. In short, the bottom edges of the window A 1.3 and the window B 1.4 are tilted in opposite directions along the axial direction, but the tilt angles are equal, and the tilt angle should be equal to half the value of the tooth angle of the matching tapered thread.

[0034] On the basis of completing the above-mentioned simulation detection structure design, the present invention proposes corresponding technical requirements for related supporting parts in order to obtain ideal detection accuracy. One of the technical requirements is that the sample 2.2 matched with the sampling block 2 is made of the same material as the drill rod joint to be tested, and it must undergo the same heat treatment process. The second technical requirement is that the size of the sample 2.2 matched with the sampling block 2 is a long thin plate with a thickness of 1.0-1.6mm, a length of 15-200mm, and a width of 3.0-5.0mm, and the plate surface roughness level is required to be the same as the level marked on the corresponding inspection point of the drill rod joint to be tested, and its roughness level is Ra3.2-1.6um, to ensure that the detection results are true and reliable; when used, the principle of selecting the size of the sample 2.2 is determined according to the size of the drill rod joint to be tested, that is, if the size of the drill rod joint to be tested is large, a sample 2.2 with a larger value is used, otherwise a sample 2.2 with a smaller size is used. The drill pipe joint to be inspected in this embodiment has a specification of 9 inches, which is medium to large, is a mainstream variety on the market, and is representative. The size of the sample 2.2 selected in this embodiment is 1.2 mm thick, 18 mm long, and 4.0 mm wide. The sample 2.2 of the sampling block 2 in the present invention is a disposable commodity, and a new piece is used for each inspection. Since the sample 2.2 is small in size, simple in shape, and low in manufacturing cost, the actual application cost is very small, which is conducive to further promotion and application.

[0035] In order to facilitate understanding of the above technical solutions of the present invention, the above technical solutions of the present invention are described in detail below through specific usage methods.

[0036] The specific working process is as follows: the drill pipe joint to be tested is used as the test piece 1, and its outer wall includes the tapered external thread section, the small diameter end face, the shoulder and other parts. These parts are the key parts of the shot peening process and need to be simulated. According to the position and characteristics of the area to be tested, multiple openings are opened on the outer wall of the test piece, including: radial notch 1.1 and axial notch 1.2, located at the small diameter end pipe mouth, used to detect the shot peening quality of the end face. Window A 1.3, located in the middle section of the tapered external thread, is used to detect the thread shot peening quality. Window B 1.4: located on the outer wall of the shoulder, used to detect the shoulder shot peening quality. Then position the sampling block 2 in the opening. The sampling block includes a base 2.3, a sample plate 2.2 and a fixing assembly 2.1. Use fasteners 3 to fix the sampling block in the corresponding opening of the drill pipe joint test piece so that the outer surface of the sampling block is consistent with the surface of the test piece. Ensure that all sampling blocks are installed firmly, the surface is flat, and they are in the same plane as the surface of the test piece to avoid affecting the shot peening process. Next, according to the process requirements of the drill pipe joint, set the parameters of the shot peening equipment, including the spray angle, shot particle size, speed, etc. The specimen equipped with the sampling block is shot peened. The material and heat treatment process of the sampling block are consistent with those of the specimen, ensuring that the stress and effect it bears during the shot peening process are consistent with the surface of the specimen. Then, use the tool to remove the fastener 3 and remove the sampling block 2 from the specimen. The removed sampling block remains intact and does not affect the surface of the sample 2.2. Separate the sample 2.2 from the sampling block, and the surface of the sample will be used for subsequent quality inspection. The sample is placed flat, and the roughness, hardening depth and other performance parameters of the sample surface are detected using conventional testing equipment such as microscopes and roughness measuring instruments. The actual effect of the shot peening process is evaluated based on the test data of the sample. By comparing the test data of each sampling block, the shot peening quality of the small diameter end face, tapered external thread, shoulder, etc. of each key part of the drill pipe joint is comprehensively evaluated. According to the test data, the parameters of the shot peening equipment such as the spray angle, speed, particle size, etc. are adjusted to optimize the shot peening process to meet the needs of different parts. The test data is recorded to provide a scientific basis for the subsequent shot peening process design of similar workpieces. In the future, the drill pipe joint test piece and the sampling block base and fixing components can be reused, and only the sample 2.2 is replaced to reduce the test cost. The disassembled sampling blocks are stored according to the position mark for subsequent analysis and recording.

[0037] Through the above process, the present invention can realize the simulated detection of the shot peening quality of complex shaped outer walls such as conical external thread sections, shoulders, etc., ensure the reliability and accuracy of the detection data, and at the same time optimize the shot peening process parameters, reduce the detection cost, and improve the detection efficiency.

[0038] In the description of the present invention, it should be noted that the terms "upper", "lower", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0039] It should be noted that, in the present invention, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0040] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features of the invention described herein.

Claims

1. A detection device for simulating the shot peening quality of the outer wall of a drill pipe joint, comprising a drill pipe joint test piece (1), a sampling block (2) and a fastener (3), characterized in that: The outer wall of the drill pipe joint specimen (1) is provided with a plurality of openings for installing a sampling block, each opening corresponding to a position to be tested, including an opening provided at the small diameter end pipe mouth of the tapered external thread on the outer wall of the drill pipe joint specimen (1), an opening radially penetrating the inner and outer walls opened at the middle section of the tapered external thread, and an opening opened on the outer wall of the shoulder, wherein the opening is a notch or window penetrating the inner and outer walls of the drill pipe joint specimen (1), and forms an open structure in at least one direction; the sampling block (2) is a combined structure, and the sampling block (2) is detachably fixed in the opening by a fastener (3), and the sampling block (2) and the outer surface of the drill pipe joint specimen (1) are in the same shot peening process environment, so as to simulate the shot peening quality test.

2. The detection device for simulating and detecting the shot peening quality of the outer wall of a drill pipe joint according to claim 1, characterized in that: The opening of the drill pipe joint test piece comprises a radial notch (1.1) and an axial notch (1.2) as well as a first window (1.3) and a second window (1.4); the radial notch (1.1) and the axial notch (1.2) are arranged at the pipe mouth of the small diameter end of the tapered external thread and are in a rectangular structure; the radial notch (1.1) and the axial notch (1.2) are used to locate the installation position of the sampling block; the first window (1.3) is arranged at the middle section of the tapered external thread and is in a rectangular structure; the second window (1.4) is arranged on the outer wall of the shoulder and is in a rectangular structure, and is used to accommodate the radial notch (1.1) and the axial notch (1.2) of the sampling block (2).

3. The detection device for simulating and detecting the shot peening quality of the outer wall of a drill pipe joint according to claim 2, characterized in that: The radial notch (1.1), the axial notch (1.2), the A window (1.3) and the B window (1.4) built into the drill pipe joint test piece (1) are arranged in four equal parts on the cross section, so as to realize the simulated detection of shot peening quality at multiple key positions of the drill pipe joint.

4. The detection device for simulating the shot peening quality of the outer wall of a drill pipe joint according to claim 3 is characterized in that: The bottom edges of the A window (1.3) and the B window (1.4) built into the drill pipe joint specimen (1) are axially inclined, with an inclination angle equal to half the value of the thread angle of the drill pipe joint conical external thread, and the bottom edges of the A window (1.3) and the B window (1.4) are inclined in opposite directions to correspond to the actual spray angle of the shot peening process.

5. The detection device for simulating the shot peening quality of the outer wall of a drill pipe joint according to claim 4, characterized in that: The bottom edges of the radial notch (1.1), the axial notch (1.2), the first window (1.3) and the second window (1.4) are all provided with screw holes (1.5), and the installed sampling block (2) is locked by the bolts (3) and the screw holes (1.5), thereby forming a detachable simulation detection structure for the drill pipe joint test piece (1) to carry the sampling block (2).

6. The detection device for simulating and detecting the shot peening quality of the outer wall of a drill pipe joint according to claim 1, characterized in that: The sampling block (2) comprises a template (2.2), a base (2.3) and a fixing assembly (2.1); the base (2.3) is an I-shaped boss structure; the template (2.2) is arranged on the upper end of the base (2.3) and is locked and fixed by the fixing assembly (2.1).

7. The detection device for simulating and detecting the shot peening quality of the outer wall of a drill pipe joint according to claim 6, characterized in that: The sample plate (2.2) is a long thin plate with a thickness of 1.0 to 1.6 mm, a length of 15 to 20 mm, and a width of 3.0 to 5.0 mm.

8. The detection device for simulating and detecting the shot peening quality of the outer wall of a drill pipe joint according to claim 6, characterized in that: The sample (2.2) is made of the same material as the drill pipe joint (1) to be tested and has undergone the same heat treatment, so as to ensure that the result of the simulated test accurately reflects the effect of the shot peening process.

9. The detection device for simulating and detecting the shot peening quality of the outer wall of a drill pipe joint according to claim 6, characterized in that: The surface roughness of the sample (2.2) is Ra3.2-1.6um.

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