Method and equipment for improving ultrasonic peening effect of weld joint in pipeline

Abstract

The invention discloses a method for improving the ultrasonic impact effect of a weld joint in a pipeline. The method comprises the following steps: testing material parameters and processing a welding test plate; surface cleaning and hardness measurement; characterizing welding seam residual stress of the welding test panel; a simulation result is verified, and simulation parameters are corrected; performing ultrasonic impact on the welding test plate to obtain an influence rule of impact time and impact power on the material; performing subzero treatment on the welding seam part of the welding test plate to obtain an influence rule of cooling time on residual stress reduction by ultrasonic treatment; cleaning weld joints on the inner surface of the structure; carrying out subzero treatment and ultrasonic peening on the on-site welding seam, and carrying out surface cleaning after treatment; field equipment runs for a period of time after weld joint treatment, and the application effect is observed. By means of the mode of local subzero treatment and ultrasonic peening, the problem that stress of on-site large equipment components is difficult to reduce through overall heat treatment is solved, the surface layer residual tensile stress is effectively reduced, the ultrasonic peening effect is improved, and the service life of equipment is prolonged.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and specifically to a method and equipment for improving the ultrasonic impact effect of welds inside pipelines. Background Technology

[0002] Welding is a key technology for connecting pipes and assembling equipment. However, welding results in high stress at the joints, especially tensile stress, which can lead to premature failures such as stress corrosion cracking and fatigue. Ultrasonic impaction is one method of stress relief. It can effectively reduce surface stress at welded joints, introduce compressive stress, and strengthen the surface. The principle of ultrasonic impaction for eliminating residual stress is to convert ultrasonic oscillations into impact pulses. The mechanical vibration converted from electrical signals drives the impact head to strike the welded joint, which can greatly improve the surface morphology and mechanical properties of the impacted area, adjust the concentration distribution of residual stress in the weld zone, generate compressive stress beneficial to structural integrity, and effectively improve the fatigue strength of the welded joint. Compared with shot peening, ultrasonic impaction is less efficient, but it still has its advantages. The actuator is compact, lightweight, and portable, easy to install and transport, and convenient to operate. It is not limited by site or welded structure. Compared with traditional shot peening and waterjet shot peening, it does not require the addition and cleaning of sprayed particles. Regarding the improvement of weld joint quality and reduction of residual stress by ultrasonic impact, patent CN104862454B discloses a method and apparatus for surface treatment of high-hardness materials. This method heats the workpiece surface using an induction coil and simultaneously impacts the surface with an ultrasonic impact needle at high frequency, thereby forming a plastic deformation layer on the workpiece surface. This alters the stress field distribution, eliminates harmful residual tensile stress, introduces beneficial residual compressive stress, improves the fatigue strength and performance of the workpiece, and refines its surface microstructure, resulting in surface strengthening. Patent CN110860808A discloses an inductively coupled ultrasonic-assisted pulsed laser welding device and method, which couples the temperature field of inductive heating with the wave field of ultrasonic vibration. Heating should be used to slow down the solidification rate of molten metal, while simultaneously applying ultrasound to impact and stir the molten pool. This reduces internal porosity and inhibits crack initiation, thereby reducing both micro and macro cracks. Patent CN113278788A proposes a composite device and method for eliminating residual stress in welds. This involves heating components with heating plates and a hot air gun, while an ultrasonic impact gun operates simultaneously to eliminate residual stress on the weld surface. Patent CN116803587A discloses a device that combines external ultrasonic impact with electromagnetic auxiliary heating to optimize weld quality. This addresses issues such as grain coarsening, residual stress, and welding defects during welding, thereby strengthening the weld microstructure and mechanical properties and extending the service life of the welded structure. The aforementioned existing technologies mostly employ heat treatment to reduce welding stress. However, large-scale equipment in the field cannot perform overall heat treatment or cold treatment, and can only adopt localized treatment methods. Current ultrasonic impact methods introduce residual compressive stress near the surface, and due to its plastic rebound, tensile stress occurs on the surface. Summary of the Invention

[0003] The purpose of this invention is to address the residual stress treatment of welds in large-scale equipment and pipelines on-site, overcome the shortcomings of the existing background technology, and provide a method and equipment for improving the ultrasonic impact effect of welds in pipelines.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for improving the ultrasonic impact effect of welds inside pipelines includes the following steps:

[0006] S1. Material parameter testing and welding test plate processing: First, tensile tests of equipment materials are carried out to select simulation test plates. Then, the simulation test plates are welded using the same process method as the on-site welding equipment.

[0007] S2. Surface cleaning and hardness measurement: Remove protrusions and impurities, reduce surface roughness, and perform hardness measurement at the same time.

[0008] S3. Characterization of residual stress in weld seams of welding test plates: Residual stress is tested on welding test plates by drilling method.

[0009] S4. Verify the simulation results, conduct simulation analysis on the welding test plate and the actual structure, and correct the simulation parameters of the welding test plate.

[0010] S5. Perform ultrasonic impact on the welding test plate to obtain the influence of impact time and impact power on the material.

[0011] S6. Perform deep cryogenic treatment on the weld seam of the welding test plate; obtain the influence law of cooling time on the reduction of residual stress by ultrasonic treatment;

[0012] S7. Clean the weld seams on the inner surface of the structure, using the same cleaning method as in step S2.

[0013] S8. Combine the parameters obtained in the above steps to perform cryogenic treatment and ultrasonic impact on the field weld. The ultrasonic impact is performed immediately after the cryogenic treatment, which has continuity.

[0014] S9. Clean the surface after processing;

[0015] S10. After the on-site equipment has been processed, run it for a period of time, observe its application effect, and provide feedback.

[0016] Furthermore, in step S1, the thickness of the simulation test plate is equal to the wall thickness of the field equipment, the welding method is V-groove welding, the groove is on the outside of the equipment, and the root cleaning welding is performed inside. The size of the welding test plate is 300×300mm.

[0017] Furthermore, in step S2, a thousand-blade grinding tool is used to grind the weld and heat-affected zone, with the grinding direction perpendicular to the weld; the hardness of the weld, heat-affected zone, and base material is measured using a portable hardness tester.

[0018] Furthermore, if the weld hardness is significantly greater than that of the heat-affected zone and the base metal, it indicates that the residual stress at the weld is relatively large, and the weld reinforcement should be as flush as possible with the base metal during grinding and polishing; if the weld hardness is less than that of the heat-affected zone and the base metal, it indicates that the residual stress at the weld is relatively small, and the weld reinforcement can be appropriately higher than that of the base metal during grinding and polishing.

[0019] Further, the residual stress test using the drilling method in step S3 includes steps such as parameter calibration, strain gauge attachment, drilling test, and data processing; wherein the strain gauges are attached to one side of the welded plate sample, perpendicular to the weld direction, and evenly distributed; a certain load is applied, the strain of the strain gauges is recorded, and then a hole is drilled at the geometric center of the strain gauge, the released strain is recorded, and the stress release coefficients A and B are further checked by strain difference; through data fitting, the residual stress distribution law of the welded test plate is obtained, and the range of tensile stress of the welded test plate is recorded as the range of ultrasonic impact.

[0020] Furthermore, the strain gauges are arranged symmetrically, totaling 10 gauges, with each side including 3 gauges on the base material, 1 gauge in the heat-affected zone, and 1 gauge on the weld.

[0021] Furthermore, the simulation parameters in step S4 include voltage, current, welding speed, and cooling time.

[0022] Furthermore, step S5 specifically involves first using an ultrasonic impact head to process the welding test plate, with the voltage controlled at 20V, the current controlled at 2A, and the impact time at 2 minutes.

[0023] Furthermore, in step S9, a multi-blade grinding wheel is used to polish the weld area. The polishing path is perpendicular to the weld to avoid introducing scratches parallel to the weld.

[0024] The technical solution of this invention also provides equipment for improving the ultrasonic impact effect of welds inside pipelines. Applied to the aforementioned method for improving the ultrasonic impact effect of welds inside pipelines, it includes an ultrasonic impact power source, an ultrasonic impact head, a liquid nitrogen container, and a cryogenic treatment head connected to the liquid nitrogen container. The ultrasonic impact power source is connected to the ultrasonic impact head via a circuit. The ultrasonic impact head includes an impact head, connecting rods symmetrically arranged on both sides of the impact head, and universal wheels installed at the lower ends of the connecting rods. The upper end of the connecting rod is hinged to the upper part of the impact head, and the middle part is hinged to the lower middle part of the impact head via a support rod. A spring is fitted onto the lower end of the connecting rod near the universal wheels. The cryogenic treatment head includes a support frame and an insulation layer inside it. The support frame has a through-hole for liquid nitrogen at its center. The upper end of the liquid nitrogen through-hole is sealed and connected to a gas supply pipe. A valve is installed on the gas supply pipe, and the other end of the gas supply pipe is connected to the liquid nitrogen container.

[0025] Compared with the prior art, the present invention has the following beneficial effects: The present invention solves the problem of the difficulty in overall heat treatment of large equipment components on site by adopting local deep cryogenic treatment + ultrasonic impact. After ultrasonic impact, the residual tensile stress on the surface caused by surface springback is effectively reduced, so that the weld is in a state of compressive stress, which further improves the ultrasonic treatment effect of the weld, improves the corrosion resistance and fatigue resistance of the equipment, and thus improves the service life of the equipment. Attached Figure Description

[0026] The accompanying drawings, which are provided to further illustrate the invention and form part of this application, are intended to help you understand the invention and do not constitute an undue limitation of the invention.

[0027] Figure 1 This is a schematic diagram of an equipment structure for improving the ultrasonic impact effect of welds inside pipelines according to the present invention.

[0028] Figure 2 This is a schematic diagram of the cryogenic treatment head in the equipment of the present invention;

[0029] Figure 3 This is a schematic diagram of the ultrasonic impact head in the equipment of the present invention;

[0030] Figure 4 This is a curve showing the mechanical property parameters of a certain P91 material at different temperatures in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the weld seam cross-section of the present invention;

[0032] In the diagram: 1. Ultrasonic impact power source, 2. Liquid nitrogen container, 3. Ultrasonic impact head, 4. Cryogenic treatment head, 5. Welding test plate, 6. Weld seam, 7. Valve, 8. Gas supply pipe, 31. Impact head, 32. Connecting rod, 33. Caster wheel, 34. Support rod, 321. Outer sleeve rod, 322. Inner sleeve rod, 323. Spring, 41. Bracket, 42. Liquid nitrogen through hole. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] It should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] Example 1,

[0036] A method for improving the ultrasonic impact effect of welds inside pipelines, taking a certain type of horizontal roasting furnace as an example, specifically includes the following steps:

[0037] S1. Material parameter testing and welding test plate fabrication. Material parameter testing provides support for test plate simulation and scaling simulation. First, tensile tests are conducted on the equipment material at different temperatures using a universal testing machine to obtain parameters such as elastic modulus and yield stress at different temperatures. The selected simulation test plate material is P91 material, referring to… Figure 4 The curve shown is used for optimal selection; subsequently, the simulation test plate is welded using the same process method as the on-site welding equipment. The thickness of the simulation test plate is the same as the wall thickness of the corresponding on-site welding equipment, which is 28mm. Due to the treatment of the catalyst medium material inside the equipment, which contains corrosive components such as chlorine, it has a significant impact on equipment corrosion. Therefore, the welding method used is V-groove welding, with the groove on the outside of the equipment and root cleaning welding inside. Correspondingly, the welding of the above-mentioned simulation test plate is equivalent to the unfolded diagram of the pipeline. The V-groove is located on the lower side of the welding test plate, and root cleaning welding is performed on the upper side. The specific welding process used is the same as the welding process of the corresponding equipment, such as... Figure 5 As shown, the corresponding welding test plate has dimensions of 300×300mm.

[0038] S2. Surface cleaning and hardness measurement: Remove protrusions and impurities to reduce surface roughness, and simultaneously perform hardness measurements. First, use a blade grinder to polish the weld and heat-affected zone, with the final grinding direction perpendicular to the weld to avoid introducing minor defects. Then, use a portable hardness tester to measure the hardness of the weld, heat-affected zone, and base material. If the weld hardness is significantly greater than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is large, and the polishing height should be as flush as possible with the base material. If the weld hardness is smaller than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is small, and the polishing height of the weld can be appropriately higher than that of the base material.

[0039] S3. Characterization of Residual Stress in Welded Test Plates: Residual stress testing of welded test plates was conducted using the drilling method, including parameter calibration, strain gauge attachment, drilling testing, and data processing. For P91 material parameter calibration, standard plate samples were fabricated, strain gauges were attached to one side, and the plates were subjected to tension on a universal testing machine under a given load. The strain of the strain gauges was recorded, and then a hole was drilled at the geometric center of each strain gauge to record the released strain. The stress release coefficients A and B were further verified using the strain difference. On the welded test plate, strain gauges were evenly distributed perpendicular to the weld direction: three for the base material, one for the heat-affected zone, and one for the weld, arranged symmetrically, for a total of ten gauges. Through data fitting, the residual stress distribution pattern of the welded test plate was obtained, and the range of tensile stress in the welded test plate was recorded as the range for ultrasonic impact. This residual stress testing method—the drilling method—is a destructive approach and cannot be applied to field equipment. The purpose of using welded test plates is to determine the range of ultrasonic impact. Compared to residual stress characterization methods such as X-rays, drilling can overcome problems such as excessively large grain size. In addition, the residual tensile stress distribution area at the weld may be larger than the weld itself.

[0040] S4. The simulation results were verified through residual stress testing of the welding test plate. Simulation analysis was performed on the welding test plate and the actual equipment structure, and the simulation parameters of the welding test plate, including voltage, current, welding speed, and cooling time, were corrected. The purpose of the simulation verification of the welding test plate was to provide support for the simulation of ultrasonic impact and the actual equipment structure. Further simulation of the actual equipment structure was conducted to obtain the residual stress distribution law of the weld and further determine the range and amplitude of the residual tensile stress. Comparison revealed that the main difference between the residual stress in the actual structure and the welding test plate lies in the amplitude; however, the residual stress distribution law is consistent. The external constraints in the actual structure increase the amplitude of the residual stress.

[0041] S5. Ultrasonic impact was applied to the welded test plate to investigate the effects of impact time and power on the material. First, an ultrasonic impact head was used to treat the welded test plate. The impact head was made of tungsten-titanium alloy, which has high hardness. Due to the hardness of P91 material, after controlling the voltage to 20V and the current to 2A, it was observed that significant impact marks appeared on the weld surface after an impact time of 2 minutes. Measurement of the residual stress after impact revealed the introduction of substantial residual stress in the surface layer. Insufficient impact power had limited impact on the surface of the P91 welded joint. Excessive impact time resulted in limited change in the surface residual compressive stress. Furthermore, surface damage inspection using a 3D profilometer revealed that prolonged impact time led to significant plastic damage to the surface. Therefore, the ultrasonic impact voltage, current, and impact time parameters were determined to be 20V, 2A, and 2 minutes.

[0042] S6. Perform cryogenic treatment on the weld seam of the welded test plate; obtain the influence of cooling time on the reduction of residual stress by ultrasonic treatment. Based on the tensile stress range determined by residual stress testing and simulation, determine the range requiring cooling + ultrasonic impact. Perform cryogenic treatment on the weld surface within this range, using liquid nitrogen for cooling for 5 seconds, followed by ultrasonic impact treatment. Perform residual stress testing and surface observation on the ultrasonically treated test plate, finally obtaining the cryogenic treatment + ultrasonic impact process, and applying it to actual equipment structures.

[0043] S7. Clean the weld seams on the inner surface of the structure, using the same cleaning method as in step S2. Use a thousand-blade grinder to grind the weld seams and heat-affected zone. The final grinding direction should be perpendicular to the weld seams to avoid introducing minor defects.

[0044] S8. Combining the parameters obtained in the above steps, the on-site weld is subjected to cryogenic treatment and ultrasonic impact. Due to the gravitational effect of liquid nitrogen, the roasting furnace is rotated during the cryogenic treatment to ensure that the weld remains horizontal throughout the process. Ultrasonic impact is then performed immediately after the cryogenic treatment, ensuring a continuous process. Equipment to enhance the ultrasonic impact effect on welds inside pipelines is used in this process, such as… Figures 1 to 3As shown, the equipment includes an ultrasonic impact power source 1, an ultrasonic impact head 3, a liquid nitrogen container 2, and a cryogenic treatment head 4 connected to the liquid nitrogen container 2. The ultrasonic impact power source 1 is connected to the ultrasonic impact head 3 via a circuit. The ultrasonic impact head 3 includes an impact head 31, two connecting rods 32 symmetrically arranged on both sides of the impact head 31, and casters 33 mounted on the lower ends of the connecting rods 32. The connecting rods 32 include an outer rod 321, an inner rod 322, and a spring 323, wherein the outer rod 321 is coaxially fitted onto the inner rod 322. On the outside, the upper end of the inner sleeve rod 322 is hinged to the upper part of the impact head 31 via a movable button. A support rod 34 is hinged to the middle of the side wall of the outer sleeve rod 321 via a movable button. The other end of the support rod 34 is hinged to the lower middle part of the impact head 31 via a movable button. The spring 323 is installed inside the outer sleeve rod 321, with one end abutting against the lower end of the inner sleeve rod 322 and the other end abutting against the bottom of the inner side of the outer sleeve rod 321. By changing the length of the connecting rod 32, the lower end of the impact head 31 is always aligned with the weld 6. The liquid nitrogen container 2 is connected to the cryogenic treatment head 4 via a gas supply pipe 8. A regulating valve 7 is installed on the gas supply pipe 8 to control the flow and interruption of liquid nitrogen. The cryogenic treatment head 4 includes a support 41 and an insulation layer inside it. A through-hole 42 for liquid nitrogen is located at the center of the support 41. The upper end of the liquid nitrogen through-hole 42 is sealed to the gas supply pipe 8, and the lower end of the cryogenic treatment head 4 is rounded to facilitate full contact with the weld 6. In use, the weld 6 is first cryogenically treated, followed by ultrasonic impact from the ultrasonic impact head 3.

[0045] S9. After the treatment is completed, the surface is cleaned. Since ultrasonic impact is difficult to achieve uniform impact and some areas may have been damaged, a multi-blade grinding wheel is used to polish the weld area. The polishing path is perpendicular to the weld to avoid introducing scratches parallel to the weld, which could become crack sources.

[0046] S10. After the on-site equipment has been treated, its application effect is observed and feedback is provided. For different weld locations of a single piece of equipment, no treatment, ultrasonic impact treatment, and cryogenic + ultrasonic impact treatment are performed respectively. After one cycle of equipment operation, approximately three months later, the corrosion of the internal welds is observed. It can be found that the cryogenic + ultrasonic treatment method has a better treatment effect, with less surface corrosion. This proves that cryogenic + ultrasonic treatment has a better stress relief and corrosion resistance effect.

[0047] Example 2,

[0048] A method for improving the ultrasonic impact effect of welds inside pipelines, taking a certain type of horizontal roasting furnace as an example, specifically includes the following steps:

[0049] S1. Material parameter testing and welding test plate fabrication. Material parameter testing provides support for test plate simulation and scaling simulation. First, tensile tests are conducted on the equipment material at different temperatures using a universal testing machine to obtain parameters such as elastic modulus and yield stress at different temperatures. The selected simulation test plate material is P91 material, referring to… Figure 4 The curve shown is used for optimal selection; subsequently, the simulation test plate is welded using the same process method as the on-site welding equipment. The thickness of the simulation test plate is the same as the wall thickness of the corresponding on-site welding equipment, which is 28mm. Due to the treatment of the catalyst medium material inside the equipment, which contains corrosive components such as chlorine, it has a significant impact on equipment corrosion. Therefore, the welding method used is V-groove welding, with the groove on the outside of the equipment and root cleaning welding inside. Correspondingly, the welding of the above-mentioned simulation test plate is equivalent to the unfolded diagram of the pipeline. The V-groove is located on the lower side of the welding test plate, and root cleaning welding is performed on the upper side. The specific welding process used is the same as the welding process of the corresponding equipment, such as... Figure 5 As shown, the corresponding welding test plate has dimensions of 300×300mm.

[0050] S2. Surface cleaning and hardness measurement: Remove protrusions and impurities to reduce surface roughness, and simultaneously perform hardness measurements. First, use a blade grinder to polish the weld and heat-affected zone, with the final grinding direction perpendicular to the weld to avoid introducing minor defects. Then, use a portable hardness tester to measure the hardness of the weld, heat-affected zone, and base material. If the weld hardness is significantly greater than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is large, and the polishing height should be as flush as possible with the base material. If the weld hardness is smaller than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is small, and the polishing height of the weld can be appropriately higher than that of the base material.

[0051] S3. Characterization of Residual Stress in Welded Test Plates: Residual stress testing of welded test plates was conducted using the drilling method, including parameter calibration, strain gauge attachment, drilling testing, and data processing. For P91 material parameter calibration, standard plate samples were fabricated, strain gauges were attached to one side, and the plates were subjected to tension on a universal testing machine under a given load. The strain of the strain gauges was recorded, and then a hole was drilled at the geometric center of each strain gauge to record the released strain. The stress release coefficients A and B were further verified using the strain difference. On the welded test plate, strain gauges were evenly distributed perpendicular to the weld direction: three for the base material, one for the heat-affected zone, and one for the weld, arranged symmetrically, for a total of ten gauges. Through data fitting, the residual stress distribution pattern of the welded test plate was obtained, and the range of tensile stress in the welded test plate was recorded as the range for ultrasonic impact. This residual stress testing method—the drilling method—is a destructive approach and cannot be applied to field equipment. The purpose of using welded test plates is to determine the range of ultrasonic impact. Compared to residual stress characterization methods such as X-rays, drilling can overcome problems such as excessively large grain size. In addition, the residual tensile stress distribution area at the weld may be larger than the weld itself.

[0052] S4. The simulation results were verified through residual stress testing of the welding test plate. Simulation analysis was performed on the welding test plate and the actual equipment structure, and the simulation parameters of the welding test plate, including voltage, current, welding speed, and cooling time, were corrected. The purpose of the simulation verification of the welding test plate was to provide support for the simulation of ultrasonic impact and the actual equipment structure. Further simulation of the actual equipment structure was conducted to obtain the residual stress distribution law of the weld and further determine the range and amplitude of the residual tensile stress. Comparison revealed that the main difference between the residual stress in the actual structure and the welding test plate lies in the amplitude; however, the residual stress distribution law is consistent. The external constraints in the actual structure increase the amplitude of the residual stress.

[0053] S5. Ultrasonic impact was applied to the welded test plate to investigate the effects of impact time and power on the material. First, an ultrasonic impact head was used to treat the welded test plate. The impact head was made of tungsten-titanium alloy, which has high hardness. Due to the hardness of P91 material, after controlling the voltage to 10V and the current to 2A, it was observed that after 5 minutes of impact, noticeable impact marks appeared on the weld surface. Measurement of residual stress after impact revealed the introduction of significant residual stress in the surface layer. Insufficient impact power had limited impact on the surface of the P91 welded joint. Excessive impact time resulted in limited change in surface residual compressive stress. Furthermore, surface damage inspection using a 3D profilometer revealed that prolonged impact time led to significant plastic damage to the surface. Therefore, the ultrasonic impact voltage, current, and impact time parameters were determined to be 10V, 2A, and 5 minutes.

[0054] S6. Perform cryogenic treatment on the weld seam of the weld test plate; obtain the influence of cooling time on the reduction of residual stress by ultrasonic treatment. Based on the tensile stress range determined by residual stress testing and simulation, determine the range requiring cooling + ultrasonic impact. Perform cryogenic treatment on the weld surface within this range, using liquid nitrogen for cooling for 10 seconds, followed by ultrasonic impact treatment. Perform residual stress testing and surface observation on the ultrasonically treated test plate, finally obtaining the cryogenic treatment + ultrasonic impact process, and applying it to actual equipment structures.

[0055] S7. Clean the weld seams on the inner surface of the structure, using the same cleaning method as in step S2. Use a thousand-blade grinder to grind the weld seams and heat-affected zone. The final grinding direction should be perpendicular to the weld seams to avoid introducing minor defects.

[0056] S8. Combining the parameters obtained in the above steps, the on-site weld is subjected to cryogenic treatment and ultrasonic impact. Due to the gravitational effect of liquid nitrogen, the roasting furnace is rotated during the cryogenic treatment to ensure that the weld remains horizontal throughout the process. Ultrasonic impact is then performed immediately after the cryogenic treatment, ensuring a continuous process. Equipment to enhance the ultrasonic impact effect on welds inside pipelines is used in this process, such as… Figures 1 to 3 As shown, the equipment includes an ultrasonic impact power source 1, an ultrasonic impact head 3, a liquid nitrogen container 2, and a cryogenic treatment head 4 connected to the liquid nitrogen container 2. The ultrasonic impact power source 1 is connected to the ultrasonic impact head 3 via a circuit. The ultrasonic impact head 3 includes an impact head 31, two connecting rods 32 symmetrically arranged on both sides of the impact head 31, and casters 33 mounted on the lower ends of the connecting rods 32. The connecting rods 32 include an outer rod 321, an inner rod 322, and a spring 323, wherein the outer rod 321 is coaxially fitted onto the inner rod 322. On the outside, the upper end of the inner sleeve rod 322 is hinged to the upper part of the impact head 31 via a movable button. A support rod 34 is hinged to the middle of the side wall of the outer sleeve rod 321 via a movable button. The other end of the support rod 34 is hinged to the lower middle part of the impact head 31 via a movable button. The spring 323 is installed inside the outer sleeve rod 321, with one end abutting against the lower end of the inner sleeve rod 322 and the other end abutting against the bottom of the inner side of the outer sleeve rod 321. By changing the length of the connecting rod 32, the lower end of the impact head 31 is always aligned with the weld 6. The liquid nitrogen container 2 is connected to the cryogenic treatment head 4 via a gas supply pipe 8. A regulating valve 7 is installed on the gas supply pipe 8 to control the flow and interruption of liquid nitrogen. The cryogenic treatment head 4 includes a support 41 and an insulation layer inside it. A through-hole 42 for liquid nitrogen is located at the center of the support 41. The upper end of the liquid nitrogen through-hole 42 is sealed to the gas supply pipe 8, and the lower end of the cryogenic treatment head 4 is rounded to facilitate full contact with the weld 6. In use, the weld 6 is first cryogenically treated, followed by ultrasonic impact from the ultrasonic impact head 3.

[0057] S9. After the treatment is completed, the surface is cleaned. Since ultrasonic impact is difficult to achieve uniform impact and some areas may have been damaged, a multi-blade grinding wheel is used to polish the weld area. The polishing path is perpendicular to the weld to avoid introducing scratches parallel to the weld, which could become crack sources.

[0058] S10. After the on-site equipment has been treated, its application effect is observed and feedback is provided. For different weld locations of a single piece of equipment, no treatment, ultrasonic impact treatment, and cryogenic + ultrasonic impact treatment are performed respectively. After one cycle of equipment operation, approximately three months later, the corrosion of the internal welds is observed. It can be found that the cryogenic + ultrasonic treatment method has a better treatment effect, with less surface corrosion. This proves that cryogenic + ultrasonic treatment has a better stress relief and corrosion resistance effect.

[0059] Example 3,

[0060] A method for improving the ultrasonic impact effect of welds inside pipelines, taking a certain type of horizontal roasting furnace as an example, specifically includes the following steps:

[0061] S1. Material parameter testing and welding test plate fabrication. Material parameter testing provides support for test plate simulation and scaling simulation. First, tensile tests are conducted on the equipment material at different temperatures using a universal testing machine to obtain parameters such as elastic modulus and yield stress at different temperatures. The selected simulation test plate material is P91 material, referring to… Figure 4 The curve shown is used for optimal selection; subsequently, the simulation test plate is welded using the same process method as the on-site welding equipment. The thickness of the simulation test plate is the same as the wall thickness of the corresponding on-site welding equipment, which is 28mm. Due to the treatment of the catalyst medium material inside the equipment, which contains corrosive components such as chlorine, it has a significant impact on equipment corrosion. Therefore, the welding method used is V-groove welding, with the groove on the outside of the equipment and root cleaning welding inside. Correspondingly, the welding of the above-mentioned simulation test plate is equivalent to the unfolded diagram of the pipeline. The V-groove is located on the lower side of the welding test plate, and root cleaning welding is performed on the upper side. The specific welding process used is the same as the welding process of the corresponding equipment, such as... Figure 5 As shown, the corresponding welding test plate has dimensions of 300×300mm.

[0062] S2. Surface cleaning and hardness measurement: Remove protrusions and impurities to reduce surface roughness, and simultaneously perform hardness measurements. First, use a blade grinder to polish the weld and heat-affected zone, with the final grinding direction perpendicular to the weld to avoid introducing minor defects. Then, use a portable hardness tester to measure the hardness of the weld, heat-affected zone, and base material. If the weld hardness is significantly greater than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is large, and the polishing height should be as flush as possible with the base material. If the weld hardness is smaller than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is small, and the polishing height of the weld can be appropriately higher than that of the base material.

[0063] S3. Characterization of Residual Stress in Welded Test Plates: Residual stress testing of welded test plates was conducted using the drilling method, including parameter calibration, strain gauge attachment, drilling testing, and data processing. For P91 material parameter calibration, standard plate samples were fabricated, strain gauges were attached to one side, and the plates were subjected to tension on a universal testing machine under a given load. The strain of the strain gauges was recorded, and then a hole was drilled at the geometric center of each strain gauge to record the released strain. The stress release coefficients A and B were further verified using the strain difference. On the welded test plate, strain gauges were evenly distributed perpendicular to the weld direction: three for the base material, one for the heat-affected zone, and one for the weld, arranged symmetrically, for a total of ten gauges. Through data fitting, the residual stress distribution pattern of the welded test plate was obtained, and the range of tensile stress in the welded test plate was recorded as the range for ultrasonic impact. This residual stress testing method—the drilling method—is a destructive approach and cannot be applied to field equipment. The purpose of using welded test plates is to determine the range of ultrasonic impact. Compared to residual stress characterization methods such as X-rays, drilling can overcome problems such as excessively large grain size. In addition, the residual tensile stress distribution area at the weld may be larger than the weld itself.

[0064] S4. The simulation results were verified through residual stress testing of the welding test plate. Simulation analysis was performed on the welding test plate and the actual equipment structure, and the simulation parameters of the welding test plate, including voltage, current, welding speed, and cooling time, were corrected. The purpose of the simulation verification of the welding test plate was to provide support for the simulation of ultrasonic impact and the actual equipment structure. Further simulation of the actual equipment structure was conducted to obtain the residual stress distribution law of the weld and further determine the range and amplitude of the residual tensile stress. Comparison revealed that the main difference between the residual stress in the actual structure and the welding test plate lies in the amplitude; however, the residual stress distribution law is consistent. The external constraints in the actual structure increase the amplitude of the residual stress.

[0065] S5. Ultrasonic impact was applied to the welded test plate to investigate the effects of impact time and power on the material. First, an ultrasonic impact head was used to treat the welded test plate. The impact head was made of tungsten-titanium alloy, which has high hardness. Due to the hardness of P91 material, after controlling the voltage to 20V and the current to 2A, it was observed that significant impact marks appeared on the weld surface after an impact time of 2 minutes. Measurement of the residual stress after impact revealed the introduction of substantial residual stress in the surface layer. Insufficient impact power had limited impact on the surface of the P91 welded joint. Excessive impact time resulted in limited change in the surface residual compressive stress. Furthermore, surface damage inspection using a 3D profilometer revealed that prolonged impact time led to significant plastic damage to the surface. Therefore, the ultrasonic impact voltage, current, and impact time parameters were determined to be 20V, 2A, and 2 minutes.

[0066] S6. Perform cryogenic treatment on the weld seams of the weld test plate; determine the effect of cooling time on the reduction of residual stress by ultrasonic treatment. Based on the tensile stress range determined by residual stress testing and simulation, determine the range requiring cooling + ultrasonic impact. Perform cryogenic treatment on the weld surface within this range using liquid nitrogen for cooling for 15 seconds, followed by ultrasonic impact treatment. Perform residual stress testing and surface observation on the ultrasonically treated test plate to finally obtain the cryogenic treatment + ultrasonic impact process, and apply it to actual equipment structures. When the cooling time is 15 seconds or longer, the introduction of residual compressive stress no longer increases; the compressive stress amplitude is higher than that without cryogenic treatment.

[0067] S7. Clean the weld seams on the inner surface of the structure, using the same cleaning method as in step S2. Use a thousand-blade grinder to grind the weld seams and heat-affected zone. The final grinding direction should be perpendicular to the weld seams to avoid introducing minor defects.

[0068] S8. Combining the parameters obtained in the above steps, the on-site weld is subjected to cryogenic treatment and ultrasonic impact. Due to the gravitational effect of liquid nitrogen, the roasting furnace is rotated during the cryogenic treatment to ensure that the weld remains horizontal throughout the process. Ultrasonic impact is then performed immediately after the cryogenic treatment, ensuring a continuous process. Equipment to enhance the ultrasonic impact effect on welds inside pipelines is used in this process, such as… Figures 1 to 3As shown, the equipment includes an ultrasonic impact power source 1, an ultrasonic impact head 3, a liquid nitrogen container 2, and a cryogenic treatment head 4 connected to the liquid nitrogen container 2. The ultrasonic impact power source 1 is connected to the ultrasonic impact head 3 via a circuit. The ultrasonic impact head 3 includes an impact head 31, two connecting rods 32 symmetrically arranged on both sides of the impact head 31, and casters 33 mounted on the lower ends of the connecting rods 32. The connecting rods 32 include an outer rod 321, an inner rod 322, and a spring 323, wherein the outer rod 321 is coaxially fitted onto the inner rod 322. On the outside, the upper end of the inner sleeve rod 322 is hinged to the upper part of the impact head 31 via a movable button. A support rod 34 is hinged to the middle of the side wall of the outer sleeve rod 321 via a movable button. The other end of the support rod 34 is hinged to the lower middle part of the impact head 31 via a movable button. The spring 323 is installed inside the outer sleeve rod 321, with one end abutting against the lower end of the inner sleeve rod 322 and the other end abutting against the bottom of the inner side of the outer sleeve rod 321. By changing the length of the connecting rod 32, the lower end of the impact head 31 is always aligned with the weld 6. The liquid nitrogen container 2 is connected to the cryogenic treatment head 4 via a gas supply pipe 8. A regulating valve 7 is installed on the gas supply pipe 8 to control the flow and interruption of liquid nitrogen. The cryogenic treatment head 4 includes a support 41 and an insulation layer inside it. A through-hole 42 for liquid nitrogen is located at the center of the support 41. The upper end of the liquid nitrogen through-hole 42 is sealed to the gas supply pipe 8, and the lower end of the cryogenic treatment head 4 is rounded to facilitate full contact with the weld 6. In use, the weld 6 is first cryogenically treated, followed by ultrasonic impact from the ultrasonic impact head 3.

[0069] S9. After the treatment is completed, the surface is cleaned. Since ultrasonic impact is difficult to achieve uniform impact and some areas may have been damaged, a multi-blade grinding wheel is used to polish the weld area. The polishing path is perpendicular to the weld to avoid introducing scratches parallel to the weld, which could become crack sources.

[0070] S10. After the on-site equipment has been treated, its application effect is observed and feedback is provided. For different weld locations of a single piece of equipment, no treatment, ultrasonic impact treatment, and cryogenic + ultrasonic impact treatment are performed respectively. After one cycle of equipment operation, approximately three months later, the corrosion of the internal welds is observed. It can be found that the cryogenic + ultrasonic treatment method has a better treatment effect, with less surface corrosion. This proves that cryogenic + ultrasonic treatment has a better stress relief and corrosion resistance effect.

[0071] Example 4,

[0072] A method for improving the ultrasonic impact effect of welds inside pipelines, taking a certain type of horizontal roasting furnace as an example, specifically includes the following steps:

[0073] S1. Material parameter testing and welding test plate fabrication. Material parameter testing provides support for test plate simulation and scaling simulation. First, tensile tests are conducted on the equipment material at different temperatures using a universal testing machine to obtain parameters such as elastic modulus and yield stress at different temperatures. The selected simulation test plate material is P91 material, referring to… Figure 4 The curve shown is used for optimal selection; subsequently, the simulation test plate is welded using the same process method as the on-site welding equipment. The thickness of the simulation test plate is the same as the wall thickness of the corresponding on-site welding equipment, which is 28mm. Due to the treatment of the catalyst medium material inside the equipment, which contains corrosive components such as chlorine, it has a significant impact on equipment corrosion. Therefore, the welding method used is V-groove welding, with the groove on the outside of the equipment and root cleaning welding inside. Correspondingly, the welding of the above-mentioned simulation test plate is equivalent to the unfolded diagram of the pipeline. The V-groove is located on the lower side of the welding test plate, and root cleaning welding is performed on the upper side. The specific welding process used is the same as the welding process of the corresponding equipment, such as... Figure 5 As shown, the corresponding welding test plate has dimensions of 300×300mm.

[0074] S2. Surface cleaning and hardness measurement: Remove protrusions and impurities to reduce surface roughness, and simultaneously perform hardness measurements. First, use a blade grinder to polish the weld and heat-affected zone, with the final grinding direction perpendicular to the weld to avoid introducing minor defects. Then, use a portable hardness tester to measure the hardness of the weld, heat-affected zone, and base material. If the weld hardness is significantly greater than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is large, and the polishing height should be as flush as possible with the base material. If the weld hardness is smaller than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is small, and the polishing height of the weld can be appropriately higher than that of the base material.

[0075] S3. Characterization of Residual Stress in Welded Test Plates: Residual stress testing of welded test plates was conducted using the drilling method, including parameter calibration, strain gauge attachment, drilling testing, and data processing. For P91 material parameter calibration, standard plate samples were fabricated, strain gauges were attached to one side, and the plates were subjected to tension on a universal testing machine under a given load. The strain of the strain gauges was recorded, and then a hole was drilled at the geometric center of each strain gauge to record the released strain. The stress release coefficients A and B were further verified using the strain difference. On the welded test plate, strain gauges were evenly distributed perpendicular to the weld direction: three for the base material, one for the heat-affected zone, and one for the weld, arranged symmetrically, for a total of ten gauges. Through data fitting, the residual stress distribution pattern of the welded test plate was obtained, and the range of tensile stress in the welded test plate was recorded as the range for ultrasonic impact. This residual stress testing method—the drilling method—is a destructive approach and cannot be applied to field equipment. The purpose of using welded test plates is to determine the range of ultrasonic impact. Compared to residual stress characterization methods such as X-rays, drilling can overcome problems such as excessively large grain size. In addition, the residual tensile stress distribution area at the weld may be larger than the weld itself.

[0076] S4. The simulation results were verified through residual stress testing of the welding test plate. Simulation analysis was performed on the welding test plate and the actual equipment structure, and the simulation parameters of the welding test plate, including voltage, current, welding speed, and cooling time, were corrected. The purpose of the simulation verification of the welding test plate was to provide support for the simulation of ultrasonic impact and the actual equipment structure. Further simulation of the actual equipment structure was conducted to obtain the residual stress distribution law of the weld and further determine the range and amplitude of the residual tensile stress. Comparison revealed that the main difference between the residual stress in the actual structure and the welding test plate lies in the amplitude; however, the residual stress distribution law is consistent. The external constraints in the actual structure increase the amplitude of the residual stress.

[0077] S5. Ultrasonic impact was applied to the welded test plate to investigate the effects of impact time and power on the material. First, an ultrasonic impact head was used to treat the welded test plate. The impact head was made of tungsten-titanium alloy, which has high hardness. Due to the hardness of P91 material, after controlling the voltage to 20V and the current to 2A, it was observed that significant impact marks appeared on the weld surface after an impact time of 2 minutes. Measurement of the residual stress after impact revealed the introduction of substantial residual stress in the surface layer. Insufficient impact power had limited impact on the surface of the P91 welded joint. Excessive impact time resulted in limited change in the surface residual compressive stress. Furthermore, surface damage inspection using a 3D profilometer revealed that prolonged impact time led to significant plastic damage to the surface. Therefore, the ultrasonic impact voltage, current, and impact time parameters were determined to be 20V, 2A, and 2 minutes.

[0078] S6. Perform cryogenic treatment on the weld seams of the weld test plate; determine the effect of cooling time on the reduction of residual stress by ultrasonic treatment. Based on the tensile stress range determined by residual stress testing and simulation, determine the range requiring cooling + ultrasonic impact. Perform cryogenic treatment on the weld surface within this range using liquid nitrogen for cooling for 20 seconds, followed by ultrasonic impact treatment. Perform residual stress testing and surface observation on the ultrasonically treated test plate to finally obtain the cryogenic treatment + ultrasonic impact process, and apply it to actual equipment structures. When the cooling time is 20 seconds or longer, the introduction of residual compressive stress no longer increases; the compressive stress amplitude is higher than that without cryogenic treatment.

[0079] S7. Clean the weld seams on the inner surface of the structure, using the same cleaning method as in step S2. Use a thousand-blade grinder to grind the weld seams and heat-affected zone. The final grinding direction should be perpendicular to the weld seams to avoid introducing minor defects.

[0080] S8. Combining the parameters obtained in the above steps, the on-site weld is subjected to cryogenic treatment and ultrasonic impact. Due to the gravitational effect of liquid nitrogen, the roasting furnace is rotated during the cryogenic treatment to ensure that the weld remains horizontal throughout the process. Ultrasonic impact is then performed immediately after the cryogenic treatment, ensuring a continuous process. Equipment to enhance the ultrasonic impact effect on welds inside pipelines is used in this process, such as… Figures 1 to 3As shown, the equipment includes an ultrasonic impact power source 1, an ultrasonic impact head 3, a liquid nitrogen container 2, and a cryogenic treatment head 4 connected to the liquid nitrogen container 2. The ultrasonic impact power source 1 is connected to the ultrasonic impact head 3 via a circuit. The ultrasonic impact head 3 includes an impact head 31, two connecting rods 32 symmetrically arranged on both sides of the impact head 31, and casters 33 mounted on the lower ends of the connecting rods 32. The connecting rods 32 include an outer rod 321, an inner rod 322, and a spring 323, wherein the outer rod 321 is coaxially fitted onto the inner rod 322. On the outside, the upper end of the inner sleeve rod 322 is hinged to the upper part of the impact head 31 via a movable button. A support rod 34 is hinged to the middle of the side wall of the outer sleeve rod 321 via a movable button. The other end of the support rod 34 is hinged to the lower middle part of the impact head 31 via a movable button. The spring 323 is installed inside the outer sleeve rod 321, with one end abutting against the lower end of the inner sleeve rod 322 and the other end abutting against the bottom of the inner side of the outer sleeve rod 321. By changing the length of the connecting rod 32, the lower end of the impact head 31 is always aligned with the weld 6. The liquid nitrogen container 2 is connected to the cryogenic treatment head 4 via a gas supply pipe 8. A regulating valve 7 is installed on the gas supply pipe 8 to control the flow and interruption of liquid nitrogen. The cryogenic treatment head 4 includes a support 41 and an insulation layer inside it. A through-hole 42 for liquid nitrogen is located at the center of the support 41. The upper end of the liquid nitrogen through-hole 42 is sealed to the gas supply pipe 8, and the lower end of the cryogenic treatment head 4 is rounded to facilitate full contact with the weld 6. In use, the weld 6 is first cryogenically treated, followed by ultrasonic impact from the ultrasonic impact head 3.

[0081] S9. After the treatment is completed, the surface is cleaned. Since ultrasonic impact is difficult to achieve uniform impact and some areas may have been damaged, a multi-blade grinding wheel is used to polish the weld area. The polishing path is perpendicular to the weld to avoid introducing scratches parallel to the weld, which could become crack sources.

[0082] S10. After the on-site equipment has been treated, its application effect is observed and feedback is provided. For different weld locations of a single piece of equipment, no treatment, ultrasonic impact treatment, and cryogenic + ultrasonic impact treatment are performed respectively. After one cycle of equipment operation, approximately three months later, the corrosion of the internal welds is observed. It can be found that the cryogenic + ultrasonic treatment method has a better treatment effect, with less surface corrosion. This proves that cryogenic + ultrasonic treatment has a better stress relief and corrosion resistance effect.

[0083] Example 5,

[0084] A method for improving the ultrasonic impact effect of welds inside pipelines, taking a certain type of horizontal roasting furnace as an example, specifically includes the following steps:

[0085] S1. Material parameter testing and welding test plate fabrication. Material parameter testing provides support for test plate simulation and scaling simulation. First, tensile tests are conducted on the equipment material at different temperatures using a universal testing machine to obtain parameters such as elastic modulus and yield stress at different temperatures. The selected simulation test plate material is P91 material, referring to… Figure 4 The curve shown is used for optimal selection; subsequently, the simulation test plate is welded using the same process method as the on-site welding equipment. The thickness of the simulation test plate is the same as the wall thickness of the corresponding on-site welding equipment, which is 28mm. Due to the treatment of the catalyst medium material inside the equipment, which contains corrosive components such as chlorine, it has a significant impact on equipment corrosion. Therefore, the welding method used is V-groove welding, with the groove on the outside of the equipment and root cleaning welding inside. Correspondingly, the welding of the above-mentioned simulation test plate is equivalent to the unfolded diagram of the pipeline. The V-groove is located on the lower side of the welding test plate, and root cleaning welding is performed on the upper side. The specific welding process used is the same as the welding process of the corresponding equipment, such as... Figure 5 As shown, the corresponding welding test plate has dimensions of 300×300mm.

[0086] S2. Surface cleaning and hardness measurement: Remove protrusions and impurities to reduce surface roughness, and simultaneously perform hardness measurements. First, use a blade grinder to polish the weld and heat-affected zone, with the final grinding direction perpendicular to the weld to avoid introducing minor defects. Then, use a portable hardness tester to measure the hardness of the weld, heat-affected zone, and base material. If the weld hardness is significantly greater than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is large, and the polishing height should be as flush as possible with the base material. If the weld hardness is smaller than that of the heat-affected zone and base material, it indicates that the residual stress at the weld is small, and the polishing height of the weld can be appropriately higher than that of the base material.

[0087] S3. Characterization of Residual Stress in Welded Test Plates: Residual stress testing of welded test plates was conducted using the drilling method, including parameter calibration, strain gauge attachment, drilling testing, and data processing. For P91 material parameter calibration, standard plate samples were fabricated, strain gauges were attached to one side, and the plates were subjected to tension on a universal testing machine under a given load. The strain of the strain gauges was recorded, and then a hole was drilled at the geometric center of each strain gauge to record the released strain. The stress release coefficients A and B were further verified using the strain difference. On the welded test plate, strain gauges were evenly distributed perpendicular to the weld direction: three for the base material, one for the heat-affected zone, and one for the weld, arranged symmetrically, for a total of ten gauges. Through data fitting, the residual stress distribution pattern of the welded test plate was obtained, and the range of tensile stress in the welded test plate was recorded as the range for ultrasonic impact. This residual stress testing method—the drilling method—is a destructive approach and cannot be applied to field equipment. The purpose of using welded test plates is to determine the range of ultrasonic impact. Compared to residual stress characterization methods such as X-rays, drilling can overcome problems such as excessively large grain size. In addition, the residual tensile stress distribution area at the weld may be larger than the weld itself.

[0088] S4. The simulation results were verified through residual stress testing of the welding test plate. Simulation analysis was performed on the welding test plate and the actual equipment structure, and the simulation parameters of the welding test plate, including voltage, current, welding speed, and cooling time, were corrected. The purpose of the simulation verification of the welding test plate was to provide support for the simulation of ultrasonic impact and the actual equipment structure. Further simulation of the actual equipment structure was conducted to obtain the residual stress distribution law of the weld and further determine the range and amplitude of the residual tensile stress. Comparison revealed that the main difference between the residual stress in the actual structure and the welding test plate lies in the amplitude; however, the residual stress distribution law is consistent. The external constraints in the actual structure increase the amplitude of the residual stress.

[0089] S5. Ultrasonic impact was applied to the welded test plate to investigate the effects of impact time and power on the material. First, an ultrasonic impact head was used to treat the welded test plate. The impact head was made of tungsten-titanium alloy, which has high hardness. Due to the hardness of P91 material, after controlling the voltage to 20V and the current to 2A, it was observed that significant impact marks appeared on the weld surface after an impact time of 2 minutes. Measurement of the residual stress after impact revealed the introduction of substantial residual stress in the surface layer. Insufficient impact power had limited impact on the surface of the P91 welded joint. Excessive impact time resulted in limited change in the surface residual compressive stress. Furthermore, surface damage inspection using a 3D profilometer revealed that prolonged impact time led to significant plastic damage to the surface. Therefore, the ultrasonic impact voltage, current, and impact time parameters were determined to be 20V, 2A, and 2 minutes.

[0090] S6. Perform cryogenic treatment on the weld seam of the welded test plate; obtain the influence of cooling time on the reduction of residual stress by ultrasonic treatment. Based on the tensile stress range determined by residual stress testing and simulation, determine the range requiring cooling + ultrasonic impact. Perform cryogenic treatment on the weld surface within this range, using liquid nitrogen for cooling for 30 seconds, followed by ultrasonic impact treatment. Perform residual stress testing and surface observation on the ultrasonically treated test plate, finally obtaining the cryogenic treatment + ultrasonic impact process, and applying it to actual equipment structures.

[0091] S7. Clean the weld seams on the inner surface of the structure, using the same cleaning method as in step S2. Use a thousand-blade grinder to grind the weld seams and heat-affected zone. The final grinding direction should be perpendicular to the weld seams to avoid introducing minor defects.

[0092] S8. Combining the parameters obtained in the above steps, the on-site weld is subjected to cryogenic treatment and ultrasonic impact. Due to the gravitational effect of liquid nitrogen, the roasting furnace is rotated during the cryogenic treatment to ensure that the weld remains horizontal throughout the process. Ultrasonic impact is then performed immediately after the cryogenic treatment, ensuring a continuous process. Equipment to enhance the ultrasonic impact effect on welds inside pipelines is used in this process, such as… Figures 1 to 3 As shown, the equipment includes an ultrasonic impact power source 1, an ultrasonic impact head 3, a liquid nitrogen container 2, and a cryogenic treatment head 4 connected to the liquid nitrogen container 2. The ultrasonic impact power source 1 is connected to the ultrasonic impact head 3 via a circuit. The ultrasonic impact head 3 includes an impact head 31, two connecting rods 32 symmetrically arranged on both sides of the impact head 31, and casters 33 mounted on the lower ends of the connecting rods 32. The connecting rods 32 include an outer rod 321, an inner rod 322, and a spring 323, wherein the outer rod 321 is coaxially fitted onto the inner rod 322. On the outside, the upper end of the inner sleeve rod 322 is hinged to the upper part of the impact head 31 via a movable button. A support rod 34 is hinged to the middle of the side wall of the outer sleeve rod 321 via a movable button. The other end of the support rod 34 is hinged to the lower middle part of the impact head 31 via a movable button. The spring 323 is installed inside the outer sleeve rod 321, with one end abutting against the lower end of the inner sleeve rod 322 and the other end abutting against the bottom of the inner side of the outer sleeve rod 321. By changing the length of the connecting rod 32, the lower end of the impact head 31 is always aligned with the weld 6. The liquid nitrogen container 2 is connected to the cryogenic treatment head 4 via a gas supply pipe 8. A regulating valve 7 is installed on the gas supply pipe 8 to control the flow and interruption of liquid nitrogen. The cryogenic treatment head 4 includes a support 41 and an insulation layer inside it. A through-hole 42 for liquid nitrogen is located at the center of the support 41. The upper end of the liquid nitrogen through-hole 42 is sealed to the gas supply pipe 8, and the lower end of the cryogenic treatment head 4 is rounded to facilitate full contact with the weld 6. In use, the weld 6 is first cryogenically treated, followed by ultrasonic impact from the ultrasonic impact head 3.

[0093] S9. After the treatment is completed, the surface is cleaned. Since ultrasonic impact is difficult to achieve uniform impact and some areas may have been damaged, a multi-blade grinding wheel is used to polish the weld area. The polishing path is perpendicular to the weld to avoid introducing scratches parallel to the weld, which could become crack sources.

[0094] S10. After the on-site equipment has been treated, its application effect is observed and feedback is provided. For different weld locations of a single piece of equipment, no treatment, ultrasonic impact treatment, and cryogenic + ultrasonic impact treatment are performed respectively. After one cycle of equipment operation, approximately three months later, the corrosion of the internal welds is observed. It can be found that the cryogenic + ultrasonic treatment method has a better treatment effect, with less surface corrosion. This proves that cryogenic + ultrasonic treatment has a better stress relief and corrosion resistance effect.

[0095] This invention can be applied to the assembly and post-processing of large-scale petrochemical equipment. Currently, large-scale equipment on-site is difficult to heat or cold treat as a whole, and can only be treated locally. Therefore, this invention uses local deep cryogenic treatment combined with ultrasonic impact to bring the weld seam under compressive stress, thereby improving the equipment's performance and showing broad application prospects.

[0096] It should be noted that in the description of this invention, terms such as "upper," "lower," "left," "right," "inner," "outer," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are only used to facilitate the description of the structural relationship between the components of this invention and do not specifically mean that any component in this invention must have a specific orientation, be constructed and operated in a specific orientation, or be construed as a limitation of this invention.

[0097] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for improving the ultrasonic impact effect of welds inside pipelines, characterized in that, Includes the following steps: S1. Material parameter testing and welding test plate processing: First, tensile tests of equipment materials are carried out to select simulation test plates. Then, the simulation test plates are welded using the same process method as the on-site welding equipment. S2. Surface cleaning and hardness measurement: Remove protrusions and impurities, reduce surface roughness, and perform hardness measurement at the same time. S3. Characterization of residual stress in weld seams of welding test plates: Residual stress is tested on welding test plates by drilling method. S4. Verify the simulation results, conduct simulation analysis on the welding test plate and the actual structure, and correct the simulation parameters of the welding test plate. S5. Perform ultrasonic impact on the welding test plate to obtain the influence of impact time and impact power on the material. S6. Perform deep cryogenic treatment on the weld seam of the welding test plate; obtain the influence law of cooling time on the reduction of residual stress by ultrasonic treatment; S7. Clean the weld seams on the inner surface of the structure, using the same cleaning method as in step S2. S8. Combine the parameters obtained in the above steps to perform cryogenic treatment and ultrasonic impact on the field weld. The ultrasonic impact is performed immediately after the cryogenic treatment, which has continuity. S9. Clean the surface after processing; S10. After the on-site equipment has been processed, run it for a period of time, observe its application effect, and provide feedback.

2. The method for improving the ultrasonic impact effect of weld seams inside pipelines according to claim 1, characterized in that: In step S1, the thickness of the simulation test plate is equal to the wall thickness of the field equipment. The welding method is V-groove welding, with the groove on the outside of the equipment and the root cleaning welding inside. The size of the welding test plate is 300×300mm.

3. The method for improving the ultrasonic impact effect of weld seams inside pipelines according to claim 1, characterized in that: In step S2, the weld and heat-affected zone are ground with a thousand blades, and the grinding direction is perpendicular to the weld. The hardness of the weld, heat-affected zone and base material is measured by a portable hardness tester.

4. The method for improving the ultrasonic impact effect of weld seams inside pipelines according to claim 3, characterized in that: If the weld hardness is significantly greater than that of the heat-affected zone and the base metal, it indicates that the residual stress at the weld is large, and the weld reinforcement should be flush with the base metal during grinding and polishing. If the weld hardness is smaller than that of the heat-affected zone and the base metal, it indicates that the residual stress at the weld is small, and the weld reinforcement can be appropriately higher than the base metal during grinding and polishing.

5. The method for improving the ultrasonic impact effect of weld seams inside pipelines according to claim 1, characterized in that: The residual stress test using the drilling method in step S3 includes parameter calibration, strain gauge application, drilling test, and data processing. Strain gauges are applied to one side of the welded plate sample, perpendicular to the weld direction, and evenly distributed. A certain load is applied, and the strain of the strain gauges is recorded. Then, a hole is drilled at the geometric center of the strain gauge, and the released strain is recorded. The stress release coefficients A and B are further verified through strain difference. Through data fitting, the residual stress distribution law of the welded test plate is obtained, and the range of tensile stress in the welded test plate is recorded as the range of ultrasonic impact.

6. The method for improving the ultrasonic impact effect of welds inside pipelines according to claim 5, characterized in that: The strain gauges are arranged symmetrically, totaling 10 gauges, with each side including 3 gauges on the base material, 1 gauge in the heat-affected zone, and 1 gauge on the weld.

7. The method for improving the ultrasonic impact effect of weld seams inside pipelines according to claim 1, characterized in that: The simulation parameters in step S4 include voltage, current, welding speed, and cooling time.

8. The method for improving the ultrasonic impact effect of welds inside pipelines according to claim 1, characterized in that: The specific content of step S5 is as follows: firstly, the welding test plate is treated with an ultrasonic impact head, the voltage is controlled at 20V, the current is controlled at 2A, and the impact time is 2 minutes.

9. The method for improving the ultrasonic impact effect of weld seams inside pipelines according to claim 1, characterized in that: In step S9, a multi-blade grinding wheel is used to polish the weld area. The polishing path is perpendicular to the weld to avoid introducing scratches parallel to the weld.

10. An apparatus for improving the ultrasonic impact effect of welds inside pipelines, applied to the method for improving the ultrasonic impact effect of welds inside pipelines as described in any one of claims 1-9, characterized in that, The device includes an ultrasonic impact power source, an ultrasonic impact head, a liquid nitrogen container, and a cryogenic treatment head connected to the liquid nitrogen container. The ultrasonic impact power source is connected to the ultrasonic impact head via a circuit. The ultrasonic impact head includes an impact head, connecting rods symmetrically arranged on both sides of the impact head, and casters mounted on the lower ends of the connecting rods. The upper end of the connecting rod is hinged to the upper part of the impact head, and the middle part is hinged to the lower middle part of the impact head via a support rod. A spring is fitted on the lower end of the connecting rod near the casters. The cryogenic treatment head includes a support frame and an insulation layer inside it. The support frame has a through-hole for liquid nitrogen at its center. The upper end of the liquid nitrogen through-hole is sealed and connected to a gas supply pipe. A valve is installed on the gas supply pipe, and the other end of the gas supply pipe is connected to the liquid nitrogen container.

Images