A method for controlling quality of pipe joint weld

Abstract

The present invention proposes a pipe interface weld quality control method, the method comprises the steps of initializing welding parameters, preprocessing and forming the pipe joint, monitoring the welding process, detecting the welding quality, and recording and reporting. By cutting an annular step on the pipe joint to be plugged with the pipe interface opened on the pipeline, and arranging a limiting boss on the annular step to limit the welding height, the method can also be used as a welding material to participate in the self-melting welding process to complete the fixation of the pipeline and the pipe joint. By establishing a control formula for the size of the limiting boss and the welding heat, the mechanical property requirements of the weld and the uniformity of the weld, the adjustment of the size of the limiting boss has a basis to rely on, and effectively avoids the problems of uneven welds and substandard strength caused by insufficient experience judgment in traditional welding. The present invention significantly improves the stability and reliability of the welding process and improves the overall welding quality of the pipeline connection by accurately controlling the size of the limiting boss.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a method for controlling the quality of a pipe interface weld. Background Art

[0002] The quality of welds in pipeline systems is directly related to the safety of the entire system. If there are defects in the welds, serious accidents such as leakage and rupture may occur. Especially in the transportation of high-pressure, high-temperature or toxic media such as oil, natural gas, and chemicals, the quality of welds is particularly important. In existing pipeline systems, through holes are usually opened in the side walls of the pipeline to achieve the insertion of pipe joints. When welding, spot welding is first performed at the insertion point to temporarily fix the position of the pipe joint to prevent relative displacement during the welding process. Then, wire welding is performed to fill the gap between the pipe joint and the pipeline. The heat of the arc fuses the welding wire and the pipeline material to form a weld, thereby completing the welding of the pipeline and the pipe joint. However, relying solely on spot welding to fix the pipe joint may not provide sufficient limiting function. Especially during the welding process, due to the effects of thermal expansion and welding stress, the previously performed spot welding points may melt, which may cause the position of the pipe joint to shift, affecting the welding quality and the sealing of the pipeline. This requires high skills of the welder, and the welding quality depends to a large extent on the operator's experience and technical level.

[0003] Secondly, the filler wire welding process requires the addition of additional welding wire materials. The welding process is relatively complicated. It is necessary to accurately control the addition of filler wire and the wire feeding speed to ensure the quality of the weld. The interaction between the welding wire and the molten pool can easily make it difficult for gas to escape, which can easily increase the risk of porosity and make welding more difficult. Compared with the filler wire welding process, the autogenous welding process has more advantages in these aspects. Since there is no addition of welding wire, the appearance of the weld is smoother and more uniform, which reduces the problem of gas difficulty escaping. No additional welding wire and wire feeding system are required. The welding process is relatively simple and does not need to consider the addition of welding wire and the control of wire feeding speed. However, the existing autogenous welding process also has some challenges. Since the size of the materials involved in autogenous welding often relies on experience and trial and error methods, rather than on precise scientific calculations or simulations, there is a lack of in-depth understanding of the effects of welding heat and the melting behavior of materials. The welding quality is difficult to accurately control, and welding metal accumulation or insufficient weld strength is prone to occur, affecting the connection strength of the pipeline and the pipe joint.

[0004] Therefore, there is an urgent need to provide a welding quality control method that provides a reliable positioning mechanism and accurately controls the size of the self-fluxing welding material to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a pipe joint weld quality control method to solve the above-mentioned problems of the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A pipe joint weld quality control method comprises the following steps:

[0008] S1. Initialize welding parameters: set the initial welding parameters according to the material properties and welding process requirements, including the initial current I, the initial voltage U and the initial welding speed v;

[0009] S2. Pretreatment and molding of the pipe joint: according to the processing requirements, a pipe interface for plugging the pipe joint is opened on the pipeline, and an annular step is cut out at one end of the pipe joint plugged into the pipeline according to the processing requirements. The outer diameter of the annular step is matched with the inner diameter of the pipe interface, and a limiting boss is provided in the circumferential direction of the annular step; after the molding is completed, the surface of the pipe interface and the annular step is polished to remove burrs, unevenness, oil stains and chip impurities;

[0010] The upper limit of the size of the limiting boss is determined by the welding heat Q and satisfies the following formula:

[0011]

[0012] The lower limit of the size of the limiting boss is determined by the mechanical property requirements of the weld and satisfies the following formula:

[0013]

[0014] Wherein, c is the specific heat capacity of the limiting boss, ΔT is the temperature difference before and after the limiting boss is melted, I is the starting current, U is the starting voltage, η is the heat conduction efficiency of the limiting boss, v is the welding speed, ρ is the density of the limiting boss, R is the outer diameter of the annular step, h is the height of the limiting boss, b is the width of the limiting boss, F is the designed tensile load of the weld, and σ is the tensile strength of the weld;

[0015] The size of the limit boss directly affects the demand for welding heat. Larger materials require more heat to ensure that the welding area is fully melted and the welding is thorough. Secondly, the higher the specific heat capacity of the material, the more heat it needs to absorb during the heating process to reach its melting point. Therefore, the input welding heat must be sufficient and exceed the heat threshold required for the melting of the limit boss material to ensure the thoroughness of the welding and the reliability of the joint.

[0016] In actual welding operations, the welding heat is usually adapted by adjusting the size of the limiting boss, because the welding heat input is usually fixed within a certain range, and excessive welding heat will cause the pipe and pipe joint materials to overheat and melt excessively, thereby affecting the performance of the pipe and pipe joint; while insufficient welding heat will cause defects such as unfused welds and cold cracks. Therefore, the present invention mainly determines the upper limit of the size of the limiting boss based on the welding heat.

[0017] The lower limit of the size of the limiting boss is usually determined by the mechanical performance requirements of the weld, because the weld must meet certain mechanical performance standards to ensure the reliability of the welded joint. If the size of the limiting boss is too small, the mechanical properties of the weld will be insufficient, such as insufficient strength and toughness, thereby affecting the safety and durability of the welded structure. Therefore, in order to ensure the mechanical properties of the weld, the present invention mainly determines the lower limit of the size of the limiting boss according to the mechanical performance requirements of the weld.

[0018] S3, monitoring of the welding process: starting the welding gun to melt the limiting boss, fixing the pipe joint and the pipe interface of the pipeline, using a machine vision system to monitor the shape and flow of the welding molten pool in real time during the whole welding process, and transmitting the monitoring results to an external control system, and the control system dynamically adjusts the welding parameters according to the monitoring results;

[0019] S4. Welding quality inspection: non-destructive inspection is performed on the weld quality of all the pipes and the pipe joints, several groups of weld samples are selected for mechanical property testing, and an inspection report is generated;

[0020] S5. Record and report: record all parameters and test results in the welding process, prepare a welding quality test report, and the control system optimizes the welding parameters and the size of the limit boss in real time according to the test report.

[0021] As a preferred technical solution of the present invention, the annular step and the limiting boss are integrally formed, and the cross section of the limiting boss is rectangular.

[0022] As a preferred technical solution of the present invention, the limiting boss is arranged on the annular step close to one side of the pipe joint, and a gap is formed between the limiting boss and the pipe joint.

[0023] As a preferred technical solution of the present invention, when the material of the limiting boss is stainless steel, the value of h·b is 0.8 mm. 2 ~1.50mm 2 .

[0024] As a preferred technical solution of the present invention, the pipe interface is an outward-turned hole.

[0025] Furthermore, an inverted cone-shaped welding groove is provided at the opening of the outward-turned hole.

[0026] As a preferred technical solution of the present invention, the larger the aspect ratio of the limiting boss is, the better the uniformity of the weld is. Therefore, the size of the limiting boss is also determined by the uniformity of the weld, satisfying the following formula:

[0027]

[0028] Among them, γ1, γ2, and γ3 are adjustment coefficients, k is the uniformity of the weld, v is the welding speed, h is the height of the limiting boss, and b is the width of the limiting boss.

[0029] The size of the limiting boss has a significant impact on the quality of the weld. The height h and width b of the limiting boss determine the contact area and heat distribution in the welding area, thus affecting the formation and quality of the weld. When the cross-sectional area of ​​the limiting boss remains constant, that is, the product of h·b remains unchanged, adjusting the ratio of h to b will change the heat distribution and mechanical properties during welding, thereby affecting the quality of the weld.

[0030] When the width b of the limiting boss is large, the heat will be distributed over a larger area during welding, and the current and welding pressure will be distributed more evenly, forming a more uniform weld, which helps to reduce the heat concentration in the weld area, thereby reducing the risk of overheating and burn-through. It also helps the lateral flow of metal, promotes uniform filling of weld metal, and improves the density and strength of the weld. On the contrary, if the height h of the limiting boss is large and the width b is small, it will cause heat to be concentrated in a smaller area, increasing the risk of defects in the welding process, such as metal accumulation in the center area of ​​the weld, resulting in a decrease in weld strength. Therefore, in order to optimize the welding quality, a wider design should be considered when designing the limiting boss to promote uniform distribution of heat, current and pressure.

[0031] As a preferred technical solution of the present invention, the machine vision system in step S3 includes a dynamic camera and an image processing device. The dynamic camera captures the image of the welding pool during the welding process in real time and transmits it to the image processing device. The image processing device performs denoising, edge detection and feature extraction, identifies and analyzes the shape changes and flow dynamics of the welding pool at each moment, and transmits the analysis results to the control system.

[0032] As a preferred technical solution of the present invention, the nondestructive testing in step S4 includes radiographic testing, ultrasonic testing, magnetic particle testing, penetration testing, and eddy current testing.

[0033] As a preferred technical solution of the present invention, the mechanical properties test in step S4 includes a tensile test, a hardness test, a bending test, a fatigue test, an impact test,

[0034] The beneficial effects of the present invention are:

[0035] 1. The present invention provides space for the weld by cutting an annular step at the connection between the pipe joint and the pipeline, and sets a limiting boss on the annular step to limit the height of the weld to prevent relative displacement during the welding process. Compared with the traditional electric welding method, the limiting boss of the present invention provides a more stable and firm limiting function. Secondly, the limiting boss itself participates in the self-melting welding process as a welding material, reducing the need for additional welding wire and avoiding the common gas escape problem in filler wire welding, thereby improving the efficiency of the welding process and the quality of the weld.

[0036] 2. The present invention introduces the control relationship between welding heat, weld mechanical property requirements, weld uniformity index and limit boss size, and deeply understands the influence of limit boss size on welding heat and material melting behavior, so that the adjustment of limit boss size can be based on a basis, ensuring that the welding area is fully melted while ensuring sufficient tensile strength between the pipeline and the pipe joint. By accurately controlling the size of the limit boss, the problems of uneven welds and substandard strength caused by insufficient experience in traditional welding are effectively avoided, and the stability of the welding process and the uniformity of the weld are effectively improved, thereby improving the overall welding quality.

[0037] 3. The shape and flow of the welding pool are monitored in real time by a machine vision system, and the welding parameters are optimized in real time in combination with a control system. The present invention realizes precise control of the welding process, reduces welding defects, and improves production efficiency and welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A flow chart of a pipe joint weld quality control method according to the present invention;

[0039] Figure 2 This is a schematic diagram of the welding of a pipeline and a pipe joint of the present invention;

[0040] Figure 3 for Figure 2 A partial enlarged view of A in FIG.

[0041] Figure 4 for Figure 3 Stereoscopic image of

[0042] Figure 5 is a schematic diagram of a pipe joint;

[0043] Figure 6 is a schematic diagram of the welding groove;

[0044] Figure 7 is a curve diagram of the aspect ratio b / h of the limiting boss and the weld uniformity k of the present embodiment;

[0045] In the figure, 1-pipe, 11-pipe interface, 12-welding groove, 2-pipe joint, 21-annular step, 22-limiting boss, 23-notch. DETAILED DESCRIPTION

[0046] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given here are only used to illustrate and explain the present invention, and cannot be used to limit the present invention.

[0047] It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may also have other implementations and variations thereof. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0048] like Figures 1 to 6 As shown, a pipe interface weld quality control method implemented in this embodiment includes the following steps:

[0049] S1. Initialize welding parameters: It is planned to weld a section of 304 stainless steel pipe joint 2 with a wall thickness of 2 mm and an outer diameter of 28 mm on a 304 stainless steel pipe 1 with a wall thickness of 1.5 mm for drainage. Based on the above material properties and welding process requirements, the initial welding parameters are set, including the initial current I, the initial voltage U and the initial welding speed v, which are 180A, 25V, and 3mm / s respectively;

[0050] S2. Pretreatment and forming of pipe joint 2: according to the processing requirements, a pipe interface 11 for plugging in pipe joint 2 is opened on pipe 1. Pipe interface 11 is an outward-turned hole with an inner diameter of 27 mm and a wall thickness of 1.5 mm. An inverted cone-shaped welding groove 12 is provided at the opening of the outward-turned hole. The welding groove 12 can ensure that the root of the weld can be fully melted through, so that the weld metal can better fill and penetrate into the root, avoiding defects such as incomplete fusion and incomplete penetration, thereby ensuring the quality and performance of the welded joint; according to the processing requirements, a circular step 21 with an outer diameter of 26 mm is cut out at one end of pipe joint 2 plugged into pipe 1. The circular step 21 with an outer diameter of 26 mm is cut out at the end of pipe joint 2 plugged into pipe 1. 21 is adapted to the pipe interface 11 with an inner diameter of 27 mm, and a limiting boss 22 with a rectangular cross section is provided in the circumferential direction of the annular step 21. The annular step 21 and the limiting boss 22 are integrally formed, and the limiting boss 22 is arranged on the annular step 21 close to the side of the pipe joint 2. A gap 23 with a width of 2 mm is formed between the limiting boss 22 and the pipe joint 2. The existence of the gap 23 is mainly to ensure that the welding gun can smoothly reach the welding area and ensure the accessibility of the welding gun; after the molding is completed, the surface of the pipe interface 11 and the annular step 21 is polished to remove burrs, unevenness, oil stains and chip impurities;

[0051] The upper limit of the size of the limiting boss 22 is determined by the welding heat Q and satisfies the following formula:

[0052]

[0053] The lower limit of the size of the limiting boss 22 is determined by the mechanical property requirements of the weld and satisfies the following formula:

[0054]

[0055] Wherein, c is the specific heat capacity of the limiting boss 22, ΔT is the temperature difference before and after the limiting boss 22 melts, I is the starting current, U is the starting voltage, η is the heat conduction efficiency of the limiting boss 22, v is the welding speed, ρ is the density of the limiting boss 22, R is the outer diameter of the annular step 21, h is the height of the limiting boss 22, b is the width of the limiting boss 22, F is the design tensile load of the weld, and σ is the tensile strength of the weld;

[0056] Based on the specific heat capacity of pipe joint 2 being 500 J / kg·K and the density being 7930 kg / m 3 , the melting point is 1400°C, and the pipe joint 2 and the limiting boss 22 are integrally formed, so the specific heat capacity c of the limiting boss 22 is 500 J / kg·K, and the density ρ is 7930 kg / m 3 , the temperature difference ΔT before and after the limiting boss 22 melts is the melting point minus the room temperature, that is, 1400°C-25°C=1375°C. Since the limiting boss 22 is directly welded by laser self-melting welding technology, the heat conduction efficiency is 0.89, and the upper limit of the size of the limiting boss 22 satisfies the following formula:

[0057]

[0058] That is, based on the above welding process requirements, the upper limit of the product of the height h and the width b of the limiting boss 22 is 1.50 mm. 2 ; Secondly, this embodiment requires that the design tensile load F of the weld is 400N, and the tensile strength σ of the 304 stainless steel limiting boss 22 after melting into the weld is 500MPa, so the lower limit of the size of the limiting boss 22 satisfies the following formula:

[0059]

[0060] In summary, the product of the height h and the width b of the limiting boss 22 should be greater than or equal to 0.80 mm. 2 , and less than or equal to 1.50mm 2 , in order to ensure that the welding area is fully melted and welded thoroughly, while ensuring that there is sufficient tensile strength between the pipeline 1 and the pipe joint 2, and the strength and toughness of the weld meet the requirements.

[0061] In addition to the product of the height h and the width b of the limiting boss 22 affecting the quality of the weld, the ratio of the width b to the height h of the limiting boss 22 will also affect the quality of the weld, mainly by affecting the contact area and heat distribution of the welding area, thereby affecting the formation and quality of the weld. When the cross-sectional area of ​​the limiting boss 22 remains constant, that is, the product of h·b remains unchanged, the larger the aspect ratio of the limiting boss 22, the more conducive it is to the lateral flow of the metal, promote the uniform filling of the weld metal, and the better the uniformity of the weld. Therefore, the size of the limiting boss 22 is also determined by the uniformity of the weld, satisfying the following formula:

[0062]

[0063] Among them, γ1, γ2, and γ3 are adjustment coefficients, k is the uniformity of the weld, v is the welding speed, h is the height of the limiting boss 22, and b is the width of the limiting boss 22.

[0064] like Figure 7 As shown, this embodiment studies the influence of the aspect ratio of the limiting boss 22 on the uniformity of the weld under the process requirements of current I, voltage U and welding speed v of 180A, 25V and 3mm / s respectively. By changing the aspect ratio of the limiting boss 22, multiple groups of test data of the uniformity of the weld are obtained, and a comparative analysis is performed. Through statistics and fitting of these data, it can be determined that the adjustment coefficients γ1, γ2 and γ3 are 0.223, 10.43 and 0.31 respectively. Therefore, the uniformity of the weld and the aspect ratio b / h satisfy the following formula:

[0065]

[0066] According to the above formula, in order to ensure that the uniformity of the weld reaches 90% or higher, the aspect ratio b / h of the limiting boss 22 needs to be greater than or equal to 0.91. Therefore, in this embodiment, the width b of the limiting boss 22 is 1 mm, the height h is 1 mm, and the cross-section is in the positive direction. The size of the limiting boss 22 is precisely controlled by welding heat, weld mechanical property requirements and weld uniformity, which can effectively improve the stability of the welding process and the uniformity of the weld, thereby improving the overall welding quality.

[0067] S3, monitoring of the welding process: starting the welding gun to melt the limiting boss 22, fixing the pipe joint 2 and the pipe interface 11 of the pipeline 1, and using the machine vision system to monitor the shape and flow of the welding pool in real time during the whole welding process, and transmitting the monitoring results to the external control system, and the control system dynamically adjusts the welding parameters according to the monitoring results;

[0068] The real-time monitoring and adjustment mechanism ensures the stability of the welding process and the uniformity of the weld, thereby improving the overall performance and reliability of the weld. The state of the molten pool during the welding process can be continuously and accurately monitored, minimizing welding defects to ensure the best welding quality, optimize welding efficiency, and realize automated welding operations.

[0069] S4. Welding quality inspection: Perform nondestructive inspection on the weld quality of all pipes 1 and pipe joints 2, select several groups of weld samples for mechanical property testing, and generate an inspection report;

[0070] S5. Recording and reporting: Record all parameters and test results during the welding process, prepare a welding quality test report, and provide data support for tracking and future optimization of welding quality. The control system optimizes the welding parameters and the size of the limit boss 22 in real time according to the test report to achieve continuous improvement of the welding process.

[0071] As a preferred embodiment of the present invention, the machine vision system in step S3 includes a dynamic camera and an image processing device. The dynamic camera captures the image of the welding pool during the welding process in real time and transmits it to the image processing device. The image processing device performs denoising, edge detection and feature extraction, identifies and analyzes the shape changes and flow dynamics of the welding pool at each moment, and transmits the analysis results to the control system.

[0072] As a preferred embodiment of the present invention, the nondestructive testing in step S4 includes radiographic testing, ultrasonic testing, magnetic particle testing, penetration testing, and eddy current testing.

[0073] As a preferred embodiment of the present invention, the mechanical property test in step S4 includes a tensile test, a hardness test, a bending test, a fatigue test, and an impact test.

[0074] Through non-destructive testing and mechanical property testing, the quality of welds can be comprehensively evaluated to ensure that the welds meet design and safety requirements. These testing methods can detect internal and external defects and ensure the reliability and safety of welded structures.

[0075] It should be understood that the above-mentioned embodiments are one or more embodiments of the present invention, and there are many other embodiments and variations thereof based on the present invention; the variations and modifications made by ordinary technicians in this industry through the present invention without making pioneering innovations all fall within the scope of protection of the present invention.

Claims

1. A method for controlling the quality of pipe joint welds, characterized in that: The following steps are involved: S1. Initialize welding parameters: set the initial welding parameters according to the material properties and welding process requirements, including the initial current I, the initial voltage U and the initial welding speed v; S2. Pretreatment and molding of the pipe joint: according to the processing requirements, a pipe interface for plugging the pipe joint is opened on the pipeline, and an annular step is cut out at one end of the pipe joint plugged into the pipeline according to the processing requirements. The outer diameter of the annular step is matched with the inner diameter of the pipe interface, and a limiting boss is provided in the circumferential direction of the annular step; after the molding is completed, the surface of the pipe interface and the annular step is polished to remove burrs, unevenness, oil stains and chip impurities; The upper limit of the size of the limiting boss is determined by the welding heat Q and satisfies the following formula: The lower limit of the size of the limiting boss is determined by the mechanical property requirements of the weld and satisfies the following formula: Wherein, c is the specific heat capacity of the limiting boss, ΔT is the temperature difference before and after the limiting boss is melted, I is the starting current, U is the starting voltage, η is the heat conduction efficiency of the limiting boss, v is the welding speed, ρ is the density of the limiting boss, R is the outer diameter of the annular step, h is the height of the limiting boss, b is the width of the limiting boss, F is the designed tensile load of the weld, and σ is the tensile strength of the weld; S3, monitoring of the welding process: starting the welding gun to melt the limiting boss, fixing the pipe joint and the pipe interface of the pipeline, using a machine vision system to monitor the shape and flow of the welding molten pool in real time during the whole welding process, and transmitting the monitoring results to an external control system, and the control system dynamically adjusts the welding parameters according to the monitoring results; S4. Welding quality inspection: non-destructive inspection is performed on the weld quality of all the pipes and the pipe joints, several groups of weld samples are selected for mechanical property testing, and an inspection report is generated; S5. Record and report: record all parameters and test results in the welding process, prepare a welding quality test report, and the control system optimizes the welding parameters and the size of the limit boss in real time according to the test report.

2. A pipe joint weld quality control method according to claim 1, characterized in that: The annular step and the limiting boss are integrally formed, and the cross section of the limiting boss is rectangular.

3. A pipe joint weld quality control method according to claim 1, characterized in that: The limiting boss is arranged on the annular step close to one side of the pipe joint, and a gap is formed between the limiting boss and the pipe joint.

4. A pipe joint weld quality control method according to claim 1, characterized in that: When the limiting boss is made of stainless steel, the value of h·b is 0.8 mm. 2 ~1.50mm 2 .

5. A pipe joint weld quality control method according to claim 1, characterized in that: The pipe interface is an outward-turned hole.

6. A pipe joint weld quality control method according to claim 5, characterized in that: An inverted cone-shaped welding groove is provided at the opening of the outward-turned hole.

7. A pipe joint weld quality control method according to claim 1, characterized in that: The larger the aspect ratio of the limiting boss is, the better the uniformity of the weld is. Therefore, the size of the limiting boss is also determined by the uniformity of the weld, satisfying the following formula: Among them, γ1, γ2, and γ3 are adjustment coefficients, k is the uniformity of the weld, v is the welding speed, h is the height of the limiting boss, and b is the width of the limiting boss.

8. A pipe joint weld quality control method according to claim 1, characterized in that: The machine vision system in step S3 includes a dynamic camera and an image processing device. The dynamic camera captures the image of the welding pool during the welding process in real time and transmits it to the image processing device. The image processing device performs denoising, edge detection and feature extraction, identifies and analyzes the shape changes and flow dynamics of the welding pool at each moment, and transmits the analysis results to the control system.

9. A pipe joint weld quality control method according to claim 1, characterized in that: The nondestructive testing in step S4 includes radiographic testing, ultrasonic testing, magnetic particle testing, penetration testing, and eddy current testing.

10. A pipe joint weld quality control method according to claim 1, characterized in that: The mechanical property test in step S4 includes a tensile test, a hardness test, a bending test, a fatigue test, and an impact test.

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