An ultra-long pipeline inner wall global laser cladding process and equipment

Abstract

The application relates to a kind of ultra-long pipeline inner wall global laser cladding process and equipment, first, the inner wall of pipeline is divided into starting zone, stable zone and termination zone along the axial direction, and reference working distance is set in each zone;During the cladding process, the real-time working distance from the surface of cladding layer to the cladding head is monitored synchronously, and the characteristic cooling temperature of the solidified area behind the molten pool is monitored;Based on the comparison of real-time working distance and reference working distance, the first control signal is generated to adjust the laser power and wire feeding rate simultaneously;At the same time, based on the comparison of characteristic cooling temperature and preset partition temperature threshold, the second control signal is generated, and asymmetric control logic is used in starting zone and termination zone: when the temperature in starting zone is too low, the power is reduced or the speed is increased to prevent supercooling, and when the temperature in termination zone is too high, the power is increased or the speed is reduced to improve the organization. By combining the two types of signals, the axial thickness and microstructure uniformity of the cladding layer are controlled, and the overall consistency of the cladding quality of the inner wall of the ultra-long pipeline is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser cladding, in particular to a kind of super-long pipeline inner wall global laser cladding process and equipment. BACKGROUND

[0002] In the industrial fields of oil and gas chemical industry, energy storage and transportation, super-long pipeline is a crucial infrastructure, to ensure its long-term safe operation in harsh environment, often needs to be cladded with a layer of corrosion-resistant, wear-resistant alloy layer on its inner wall.Laser cladding technology is considered as an ideal choice to realize the high-performance addition of pipeline inner wall due to its low heat input, small dilution rate, high bonding strength and other advantages.However, when the length of the pipeline exceeds ten meters, it is a serious challenge to achieve the consistency of the quality of the cladding layer in the entire length range of the inner wall.

[0003] The control idea of the prior art relies on visual detection for parameter feedback adjustment, for example, by monitoring the distance between the cladding head and the inner wall of the pipeline (working distance) in real time, and comparing it with a preset reference working distance, and then generating a control signal to adjust the laser power or wire feeding rate, so as to obtain uniform cladding layer thickness.However, practice shows that this control method relying only on working distance feedback is not ideal in the actual application of super-long pipeline, although it can compensate for the thickness, but due to the pipeline process, the compensation effect is limited, resulting in poor consistency of the overall quality of the cladding layer, and the front and rear sections of the cladding layer still have uneven axial thickness compared with the middle section, and the surface quality and microstructure of the cladding layer located in the front and rear sections also often have serious defects. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the poor consistency of the quality of the cladding layer on the inner wall of the super-long pipeline in the prior art, and to provide a super-long pipeline inner wall global laser cladding process and equipment, which can realize the homogenization of the cladding layer in the entire length range not only in thickness but also in microstructure and service performance through the dual-mode coordinated control of geometry and metallurgical quality.

[0005] To solve the above technical problems, the present application provides a super-long pipeline inner wall global laser cladding process, comprising the following steps:

[0006] Divide the entire inner wall of the pipeline into a starting zone, a stable zone and a termination zone along the axial direction, and select at least one reference point in each zone, and perform a standard cladding process to determine the reference working distance of each reference point in the zone;

[0007] The rotation of the pipe and the axial feeding of the laser cladding head are started to perform laser cladding on the inner wall; during the cladding process, the real-time working distance from the surface of the cladding layer to the laser cladding head is monitored in real time, and the feature cooling temperature of the solidified area behind the molten pool is monitored in real time through the infrared thermal imager;

[0008] The real-time working distance is compared with the reference working distance at the current axial position to generate a first control signal for first-level coordinated adjustment of the laser power and the wire feeding rate; meanwhile, based on the comparison of the feature cooling temperature with a preset temperature threshold value dependent on the axial zone, a second control signal is generated;

[0009] In the starting zone, if the feature cooling temperature is lower than the temperature threshold value, the second control signal instructs to reduce the laser power or increase the wire feeding power; in the termination zone, if the feature cooling temperature is higher than the temperature threshold value, the second control signal instructs to increase the laser power or reduce the wire feeding power.

[0010] The first control signal and the second control signal are fused to jointly act on the current cladding process to realize compound control of the axial thickness of the cladding layer and the uniformity of the microstructure.

[0011] In an embodiment of the present application, the division into the starting zone, the stable zone and the termination zone along the axial direction includes:

[0012] Before starting the cladding formally, the laser cladding head is controlled to scan along the inner wall of the pipe at a preset scanning power at a constant speed in a wireless state;

[0013] During the scanning process, the axial temperature distribution curve of the inner wall of the pipe is monitored and recorded synchronously through the infrared thermal imager;

[0014] Two feature inflection points on the axial temperature distribution curve are identified: the first inflection point is the turning point at which the temperature changes from rapid rise to slow rise, and the second inflection point is the turning point at which the temperature changes from slow rise to accelerated rise again;

[0015] The axial zone between the pipe opening and the first inflection point is defined as the starting zone; the axial zone between the first inflection point and the second inflection point is defined as the stable zone; and the axial zone between the second inflection point and the end of the pipe is defined as the termination zone.

[0016] In an embodiment of the present application, the preset temperature threshold value dependent on the axial zone is determined synchronously through the axial scanning process in the wireless state, and specifically includes:

[0017] After identifying the axial boundaries of the starting zone, the stable zone and the termination zone in the wireless scanning process, the average values of the corresponding data of the recorded axial temperature distribution curves in the starting zone, the stable zone and the termination zone are calculated respectively;

[0018] The calculated average of the starting zone temperature, the average of the stable zone temperature and the average of the termination zone temperature are directly set as the characteristic cooling temperature threshold of the starting zone, the stable zone and the termination zone respectively.

[0019] In an embodiment of the present application, when multiple reference points are selected in each of the starting zone, the stable zone and the termination zone, after the standard cladding process is performed on each reference point in the zone, the initial reference working distance of the point is measured and recorded, the arithmetic mean of multiple initial reference working distances in the same zone is calculated, and the final reference working distance of the zone is determined.

[0020] In an embodiment of the present application, the first regulation signal is used to perform first-level coordinated adjustment on the laser power and the wire feeding rate, which includes:

[0021] According to the deviation value of the real-time working distance from the reference working distance, the laser power compensation value required to maintain the energy density per unit area constant is calculated;

[0022] Based on the adjustment direction and amplitude of the laser power compensation value, the adjustment value of the wire feeding rate is calculated synchronously according to the preset wire feeding rate-laser power matching ratio; when the laser power is adjusted upward, the wire feeding rate is adjusted upward synchronously according to the ratio; when the laser power is adjusted downward, the wire feeding rate is adjusted downward synchronously according to the ratio;

[0023] The laser power compensation value and the wire feeding rate adjustment value are encapsulated together to generate the first regulation signal.

[0024] In an embodiment of the present application, the wire feeding rate-laser power matching ratio is different in the starting zone, the stable zone and the termination zone, wherein: the wire feeding rate-laser power matching ratio adopted in the termination zone is greater than the matching ratio adopted in the stable zone; the wire feeding rate-laser power matching ratio adopted in the stable zone is greater than the matching ratio adopted in the starting zone.

[0025] In an embodiment of the present application, the first regulation signal and the second regulation signal are fused to jointly act on the current cladding process, which includes:

[0026] The first regulation signal is used as a basic execution instruction to perform basic adjustment on the laser power and the wire feeding rate;

[0027] While the adjustment based on the first regulation signal is being performed, the trigger state of the second regulation signal is judged in real time; when the characteristic cooling temperature continuously exceeds the temperature threshold of the axial sub-zone to which it belongs and reaches a stable duration, it is determined that the second regulation signal is activated.

[0028] The second regulation signal and the instructions about the laser power and the wire feeding speed in the first regulation signal are superimposed to form a comprehensive laser power instruction, which is output as the final coordinated control instruction to the execution mechanism.

[0029] In one embodiment of the present application, when the second control signal is activated, a dynamic laser power adjustment amount and a dynamic wire feeding rate adjustment amount are generated synchronously according to the extent to which the current characteristic cooling temperature deviates from the temperature threshold value;

[0030] The laser power instruction in the first control signal is superimposed with the laser power adjustment amount to form a comprehensive laser power instruction; meanwhile, the wire feeding rate instruction in the first control signal is superimposed with the wire feeding rate adjustment amount to form a comprehensive wire feeding rate instruction;

[0031] The comprehensive laser power instruction and the comprehensive wire feeding rate instruction are combined as the final cooperative control instruction output.

[0032] In one embodiment of the present application, when the pipe rotation and the axial feeding of the laser cladding head are started to perform the inner wall laser cladding, the rotation speed of the pipe is 0.1-5 RPM, the wire feeding rate of the laser cladding head is 3000-4000 mm / min, and the laser power of the laser cladding head is 8-12 kw.

[0033] To solve the above technical problems, the present application further provides a kind of ultra-long pipe inner wall global laser cladding equipment for executing process, comprising:

[0034] Laser cladding mechanism, including laser, laser cladding head and wire feeder;

[0035] Motion execution mechanism, including numerical control roller frame for driving pipe rotation around its axis, and linear guide mechanism for driving laser cladding head axial feeding along pipe;

[0036] Integrated on-line monitoring mechanism on the laser cladding head, including optical distance measuring module for measuring the distance from cladding layer surface to laser cladding head in real time, and infrared thermal imager for monitoring the temperature of solidified area behind molten pool;

[0037] Central control system, which is communicatively connected with the motion execution mechanism, on-line monitoring mechanism, laser and wire feeder;The central control system is configured to:

[0038] Receive real-time working distance data sent by the optical distance measuring module, and compare it with the pre-stored reference working distance of the current axial position, to generate a first control signal for cooperatively adjusting the power of the laser and the rate of the wire feeder;

[0039] receive the characteristic cooling temperature data sent by the infrared thermal imager, and compare it with the pre-stored temperature threshold value dependent on the axial region to generate a second control signal; wherein when the characteristic cooling temperature in the starting region is lower than the threshold value, it is instructed to reduce the laser power or increase the wire feeding speed, and when the characteristic cooling temperature in the termination region is higher than the threshold value, it is instructed to increase the laser power or reduce the wire feeding speed;

[0040] fuse the first control signal and the second control signal to generate a final control instruction and output it to the laser and the wire feeder to perform compound control on the cladding process.

[0041] The above technical scheme of the present application has the following advantages compared with the prior art:

[0042] The ultralong pipeline inner wall global laser cladding process disclosed by the present application no longer only corrects geometric deviation, but cooperatively intervenes from the physical source of deviation, i.e., axial thermal dynamic unevenness, not only ensures uniformity of the cladding layer thickness in the full-length range from a macroscopic scale, but also actively intervenes and optimizes the solidification process under different thermal environments from a microscopic scale, realizes compound control on the axial thickness and microscopic uniformity of the cladding layer, and thus significantly improves the consistency of the ultralong pipeline inner wall cladding layer in the uniformity of the microstructure, mechanical properties and corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in combination with the drawings, in which:

[0044] Figure 1 is a step flow chart of the ultralong pipeline inner wall global laser cladding process of the present application;

[0045] Figure 2 is a step flow chart of the axial region division and temperature threshold value determination of the present application;

[0046] Figure 3 is a step flow chart of the fusion of the first control signal and the second control signal to execute the laser cladding process control of the present application;

[0047] Figure 4 is a structural schematic diagram of the ultralong pipeline inner wall global laser cladding device of the present application;

[0048] Figure 5 is a structural schematic diagram of the laser cladding head of the present application.

[0049] Description of the Drawings: 1, laser; 2, laser cladding head; 3, wire feeder; 4, numerical control roller frame; 5, linear guide mechanism; 6, online monitoring mechanism. DETAILED DESCRIPTION

[0050] The application will be further described in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the application and implement it, but the embodiments are not limiting to the application.

[0051] As mentioned before, the prior art adopts a dynamic adjustment strategy, visually detects the thickness of the cladding layer and adjusts the welding parameters according to the geometric parameter difference, but there is still a defect of uneven quality of the cladding layer on the inner wall. Through observation, it is found that the cladding layer morphology of the starting section and the end section of the pipeline always differs from that of the middle section. In order to solve this problem, the present application has carried out in-depth research and made a key discovery: behind the above-mentioned uneven thickness in the axial direction, there is a deeper and long-neglected root cause, that is, the axial heat distribution of the pipeline is dynamic and extremely uneven during the continuous cladding process of more than ten meters. When the cladding starts, the whole pipeline is in a cold state and the heat dissipation is very fast. With the continuous cladding, the huge heat energy is continuously input and accumulated in the pipeline body, resulting in a significant increase in the temperature of the middle and rear pipeline body. This axial thermal gradient not only causes subtle thermal deformation of the supporting mechanism and interferes with the working distance, but also fundamentally changes the solidification cooling dynamics of the molten pool, thereby affecting the geometric size and micro metallurgical quality of the cladding layer. It is this coupling effect of heat and force that makes the single working distance compensation lose both sides and eventually leads to the failure of regulation and control.

[0052] Based on this breakthrough cognition, referring to the drawings shown in Figure 1 The present application provides a kind of long pipeline inner wall global laser cladding process, abandon single regulation and control logic, introduce double mode collaborative control mechanism, first, process is before starting to carry out zoning to pipeline inner wall, and is divided into starting area, stable area and termination area, and establishes reference working distance independently for each area.The significance of this measure is that it sets up the scale of local conditions for subsequent accurate control, and realizes that different regions need different reference due to different thermal states.

[0053] The pipeline rotation and laser cladding head axial feeding are started to perform the inner wall laser cladding; in the cladding process, the real-time working distance from the cladding layer surface to the laser cladding head is monitored in real time, and the feature cooling temperature of the solidified area behind the molten pool is monitored in real time through the infrared thermal imager; based on the real-time data collected above, two sets of monitoring and control logic are executed in parallel: the real-time working distance is compared with the reference working distance at the current axial position to generate a first regulation signal for first-level coordinated adjustment of the laser power and the wire feeding rate; at the same time, based on the comparison of the feature cooling temperature and a preset temperature threshold dependent on the axial zone, a second regulation signal is generated; wherein: the first set of logic adjusts the laser power and the wire feeding rate by monitoring the working distance in real time, which effectively ensures the axial uniformity of the cladding layer thickness and overcomes the thickness fluctuation caused by mechanical deformation or initial centering error; the second set of logic sensitively captures the feature cooling temperature of the solidified area behind the molten pool through the infrared thermal imager, which is a key window for revealing the metallurgical quality of the cladding layer because it is directly related to the cooling rate of the metal, and the cooling rate is a decisive factor for determining the grain size, phase composition and residual stress.

[0054] Based on this, the present application implements an asymmetric intelligent regulation strategy: in the cladding starting area, the whole pipeline is in room temperature state, and the heat dissipation capacity is extremely strong, if the monitored feature cooling temperature is lower than the preset threshold value of the area, it indicates that the cladding layer is cooling at too fast a rate; too fast cooling has significant metallurgical risks: first, it may cause the molten pool metal to harden, forming hard and brittle structure and causing micro-cracks; second, the molten pool exists for too short a time, which is not conducive to the escape of gas and inclusions, and is easy to produce pores, un-melted and other defects; therefore, the second regulation signal of the present application instructs to reduce the laser power or increase the wire feeding power, so that the formed molten pool volume is smaller, the existence time is shorter, and the overall heat is lower, so that under the condition of strong heat dissipation, the molten pool will not be overheated, its cooling curve becomes flat, and the cooling rate is reduced, the essence of this operation is to actively reduce the heat input to this area, and the purpose is to slow down the cooling rate of the cladding layer, so that it is out of the dangerous fast cooling interval, so as to obtain a dense, crack-free and well-metallurgical bonded cladding layer.

[0055] In contrast, in the termination zone, due to the continuous heat input and accumulation in front, the pipe body temperature has been significantly increased, and the heat dissipation capacity is seriously insufficient. If the monitored characteristic cooling temperature is higher than the preset threshold value of this zone, it indicates that the cladding layer cools too slowly. The main risk of slow cooling is that the molten pool metal stays in the high temperature zone for too long, and the grains have sufficient conditions to coarsen and grow, and the alloying elements are prone to adverse segregation, which will lead to significant deterioration of the mechanical properties and corrosion resistance of the cladding layer. At this time, the second control signal of the present application will take completely opposite instructions: increase the laser power or reduce the wire feeding power. This operation is not to further heat, but to form a molten pool with higher energy, more stable, and longer existence time in a harsh thermal environment. Although this may slow down the cooling, its primary goal is to ensure the formation of a high-quality, defect-free molten pool. A molten pool with sufficient energy and stable state has better fluidity, which can better ensure the quality of metallurgical bonding with the base material and make its solidification process still relatively controllable under macroscopic thermal disturbance, and finally form a high-quality cladding layer with relatively small grains and uniform composition. The essence of this operation is to actively increase the heat input to this area to resist the thermal influence of the surrounding high-temperature environment with the heat of the molten pool itself, so that the solidification process is more stable, which helps to obtain more uniform and dense structure.

[0056] Finally, the first control signal from the geometric dimension and the second control signal from the thermal-metallurgical dimension are intelligently fused to drive the actuator to complete the global laser cladding, thereby achieving composite control of the axial thickness and microstructure uniformity of the cladding layer.

[0057] Referring to Figure 2 The embodiment further proposes how to divide into a starting zone, a stable zone and a termination zone along the axial direction, and how to determine the preset temperature threshold value of each zone after the division:

[0058] Before starting the cladding, the laser cladding head is controlled to scan the inner wall of the pipe at a preset scanning power at a constant speed in a no-wire feeding state; during the scanning process, the axial temperature distribution curve of the inner wall of the pipe is monitored and recorded synchronously by an infrared thermal imager; two characteristic inflection points on the axial temperature distribution curve are identified: the first inflection point is the turning point where the temperature changes from rapid rise to slow rise, and the second inflection point is the turning point where the temperature changes from slow rise to accelerated rise again; the axial region between the pipe opening and the first inflection point is defined as the starting zone; the axial region between the first inflection point and the second inflection point is defined as the stable zone; and the axial region between the second inflection point and the end of the pipe is defined as the termination zone.

[0059] Specifically, the no-wire feeding state refers to a state of not feeding materials during the scanning process, and only the self-thermal characteristics of the pipe are excited by the laser to obtain pure axial thermal response data; wherein the infrared thermal imager can be a high-sensitivity non-contact temperature measuring device, which can capture the dynamic change trend of temperature along the axial direction in real time, and ensure the continuity and integrity of the temperature data. In practical applications, the feature inflection point can be identified by mathematical algorithms, such as a mutation point detection method based on temperature change rate, which aims to define the region boundary according to the change of physical properties, so that the region division is dynamically coupled with the actual thermal behavior.

[0060] In detail, in the whole scheme, the thermal response reference of the inner wall of the pipe is constructed by pre-performing no-wire feeding scanning, and the objective quantification of region division is realized based on the feature inflection point of the temperature distribution curve. This inflection point identification method based on physical properties makes the starting zone correspond to the region where insufficient heat accumulation easily leads to insufficient cladding, the stable zone correspond to the region where heat balance is suitable for standard cladding, and the termination zone correspond to the region where excessive heat dissipation easily leads to over-heating of cladding. In this way, accurate geographical coordinates are provided for subsequent sub-region control, ensuring that the adjustment strategy of laser power and wire feeding rate is strictly matched with the thermal characteristics of the region. In addition, the scheme is combined with the aforementioned technology of dividing the axial direction into a starting zone, a stable zone and a termination zone, which fundamentally solves the problem of inaccurate control caused by subjective setting of region boundaries, thereby significantly improving the reliability of the axial uniformity control of the cladding layer.

[0061] Further, the axial scanning process under the no-wire feeding state can also be used to determine the preset temperature threshold of the axial zone in a synchronous manner, which specifically includes: during the no-wire feeding scanning process, after identifying the axial boundaries of the starting zone, the stable zone and the termination zone, the average values of the corresponding data of the axial temperature distribution curves recorded in the starting zone, the stable zone and the termination zone are calculated respectively; the calculated starting zone temperature average value, stable zone temperature average value and termination zone temperature average value are directly set as the feature cooling temperature thresholds of the starting zone, the stable zone and the termination zone respectively.

[0062] In detail, in the no-wire feeding scanning stage, the actual temperature distribution data of the inner wall of the pipeline is obtained, and a temperature threshold value matched with the thermal behavior of the pipeline is dynamically generated, thereby avoiding the deviation problem caused by the preset threshold value. On this basis, based on the determined regional boundary information, the region is divided directly by using the characteristic inflection point of the temperature distribution curve, so that the region division is closely related to the actual thermodynamic characteristics, and a reliable spatial reference is provided for subsequent threshold setting. Further, by statistically processing the original temperature data recorded by each region scanning, such as calculating the regional average temperature, the subjectivity of the preset is eliminated, and it is ensured that the threshold value can accurately represent the typical cooling state of each region. Finally, the calculated average value is directly set as the characteristic cooling temperature threshold value, which simplifies the setting logic and ensures that the threshold value is highly consistent with the regional thermal characteristics, thereby ensuring that the second control signal accurately reflects the cooling state of the molten pool during the cladding process, and realizing the dynamic optimization control of the cladding layer quality.

[0063] By the above technical solution, the control deviation problem caused by the inaccurate preset temperature threshold value is solved, and since the scheme fully utilizes the actual data of the no-wire feeding scanning stage, the additional measurement link is avoided, thereby improving the efficiency and reliability of the overall process.

[0064] In the application scenario of an ultra-long pipeline, multiple reference points can be selected in each region of the starting zone, the stable zone and the termination zone. After performing a standard cladding process at each reference point in the region, the initial reference working distance of the point is measured and recorded, the arithmetic mean of the multiple initial reference working distances in the same region is calculated, and the final reference working distance of the region is determined.

[0065] Specifically, the multiple reference points refer to a plurality of sampling positions uniformly distributed in each axial partition of the inner wall of the pipeline, and the purpose is to reduce the influence of local abnormalities on the overall reference through multi-point coverage in space. In actual application, the number of these reference points can be flexibly adjusted according to the length of the pipeline and the process precision requirement, for example, it can be set to 3 to 10 or more; the initial reference working distance refers to the distance between the laser cladding head and the inner wall surface of the pipeline under the condition of the standard cladding process, which can be collected in real time by an optical distance measuring module; the arithmetic mean refers to the result obtained by adding all the initial reference working distances in the same region and dividing by the number of reference points, and the purpose is to eliminate random errors through mathematical processing, thereby obtaining more representative reference data.

[0066] In detail, the scheme selects multiple reference points in the starting area, the stable area and the termination area respectively, ensures that the spatial distribution of the reference points can comprehensively cover different positions of each area, avoids accidental deviation caused by single point selection, obtains the initial reference working distance through the optical distance measuring module after performing the standard cladding process at each reference point, and this process ensures high correlation between the measurement result and the actual process condition; then, the multiple initial reference working distances in the same area are subjected to arithmetic average processing, which effectively offsets the random error or local anomaly that may exist in a single measurement point, such as the influence of the small concave-convex on the inner wall surface of the pipeline, the instantaneous interference of the sensor or the slight fluctuation of the process parameters; and the finally determined regional reference working distance serves as the unified reference for subsequent cladding regulation, so that the real-time working distance comparison and the regulation signal generation are based on the overall state of the region rather than the local point, thereby significantly improving the accuracy of the laser power and the wire feeding rate adjustment, and realizing the optimization control of the axial thickness uniformity of the cladding layer.

[0067] The embodiment further proposes a method for first-level coordinated adjustment of the laser power and the wire feeding rate by using the first regulation signal, which comprises the following steps: calculating the laser power compensation value required to maintain the energy density per unit area constant according to the deviation value of the real-time working distance and the reference working distance; based on the adjustment direction and amplitude of the laser power compensation value, the adjustment value of the wire feeding rate is calculated synchronously according to the preset wire feeding rate-laser power matching ratio; wherein when the laser power is adjusted upwards, the wire feeding rate is adjusted upwards in proportion, and when the laser power is adjusted downwards, the wire feeding rate is adjusted downwards in proportion; the laser power compensation value and the wire feeding rate adjustment value are encapsulated together to generate the first regulation signal.

[0068] Specifically, the real-time working distance refers to the actual distance between the cladding layer surface and the laser cladding head obtained by continuously monitoring through the optical distance measuring module during the cladding process, which can be realized by a non-contact laser displacement sensor or an ultrasonic ranging device; the reference working distance is the ideal working distance of each region determined by the standard cladding process in advance, and its purpose is to provide a reference for deviation calculation; the laser power compensation value refers to the power adjustment amount calculated to offset the influence of working distance change on the energy density per unit area, which can be determined according to the principle of energy conservation combined with specific process parameters; the wire feeding rate-laser power matching ratio is a kind of preset correlation, which can be realized in various ways such as linear function, piecewise function or lookup table method, and its purpose is to ensure the coordination between material supply and energy input.

[0069] Specifically, the scheme solves the energy density fluctuation problem by constructing a complete dynamic adjustment mechanism. First, real-time working distance data is continuously collected and compared with the pre-stored reference working distance. After calculating the difference, the required laser power compensation value is derived according to the energy density formula. Then, based on the preset matching ratio rule, the corresponding wire feeding rate adjustment value is automatically calculated according to the direction and amplitude of the laser power compensation value. This synchronous adjustment mechanism ensures that when the laser power changes, the wire feeding rate can be adjusted in time, thereby maintaining the stability of the energy density during the cladding process. Finally, by encapsulating and integrating the laser power compensation value and the wire feeding rate adjustment value, a unified first control signal is output to the actuator, ensuring the strict synchronization in time and the accurate matching in proportion of the two parameter adjustments.

[0070] Through the above technical scheme, not only the energy density imbalance problem caused by working distance fluctuation is solved, but also the precise control in the cladding process is realized by establishing the linkage mechanism of laser power and wire feeding rate. This method is particularly suitable for super-long pipeline inner wall cladding scenarios and can maintain good control effect in the starting zone, stable zone and termination zone, significantly improving the quality consistency of the cladding layer.

[0071] On the basis of the above embodiment, the present application further proposes that the wire feeding rate-laser power matching ratio is different in the starting zone, stable zone and termination zone, wherein: the wire feeding rate-laser power matching ratio adopted in the termination zone is greater than the matching ratio adopted in the stable zone; the wire feeding rate-laser power matching ratio adopted in the stable zone is greater than the matching ratio adopted in the starting zone.

[0072] In detail, in the super-long pipeline inner wall full-area laser cladding process, due to the significant difference in heat accumulation state in different axial regions of the pipeline, a unified matching ratio cannot meet the actual needs of each region. Therefore, by differentiating the matching ratio of wire feeding rate and laser power, the heat condition characteristics of different axial regions of the pipeline inner wall can be optimized. In the starting zone, due to fast heat dissipation at the pipe opening and low heat accumulation, a lower matching ratio can avoid the problem of material not being fully melted or accumulated due to excessively high wire feeding rate. In the stable zone, the heat condition is relatively balanced, and a medium matching ratio is adopted to maintain the stable balance of energy and material. In the termination zone, due to high heat accumulation and rising molten pool temperature, a higher matching ratio is adopted to ensure that the wire feeding rate can be significantly increased when the laser power changes, effectively compensating for the problem of excessive heat input. This way of setting the matching ratio in different regions not only solves the problem of uneven cladding layer thickness in the axial direction, but also significantly improves the uniformity of the microstructure, thereby achieving continuous and uniform control of the quality of the cladding layer in the axial full area.

[0073] Reference Figure 3As shown, the application further discloses fusing the first control signal and the second control signal to jointly act on the current cladding process, including: taking the first control signal as the basic execution instruction to perform basic adjustment of laser power and wire feeding rate; while adjusting based on the first control signal, judging the trigger state of the second control signal in real time; when the characteristic cooling temperature continuously exceeds the temperature threshold of the axial partition to which it belongs and reaches a stable length of time, it is determined that the second control signal is activated; superimposing the instructions about laser power and wire feeding speed in the second control signal and the first control signal to form a comprehensive laser power instruction as the final cooperative control instruction output to the execution mechanism.

[0074] Specifically, this scheme solves the problem that thickness control and heat management are difficult to cooperate in the cladding process of the inner wall of the ultra-long pipeline through a layered fusion control architecture. First, the first control signal is taken as the basic execution instruction to adjust the laser power and the wire feeding rate, ensuring that the unit area energy density is constant, thereby maintaining the uniformity of the cladding layer thickness from being disturbed by the geometric change of the pipeline. On this basis, the trigger state of the second control signal is monitored in real time at the same time. This parallel processing mechanism avoids mutual interference between basic adjustment and heat compensation. When the characteristic cooling temperature continuously exceeds the preset threshold and reaches a stable length of time, it is determined that the heat compensation mechanism needs to be started. This design effectively filters transient measurement noise, ensuring that parameter adjustment is only performed when the real heat effect exists. Finally, by superimposing the laser power and wire feeding speed instructions in the two control signals, a comprehensive control instruction is formed which can respond to distance changes and adapt to the differences in axial partition heat characteristics, realizing stable control of the cladding process in a dynamic heat environment.

[0075] The application further proposes that when the second control signal is activated, a dynamic laser power adjustment amount and a dynamic wire feeding rate adjustment amount are generated according to the degree of deviation of the current characteristic cooling temperature from the temperature threshold; the laser power instruction in the first control signal is superimposed with the laser power adjustment amount to form a comprehensive laser power instruction; at the same time, the wire feeding rate instruction in the first control signal is superimposed with the wire feeding rate adjustment amount to form a comprehensive wire feeding rate instruction; and the comprehensive laser power instruction and the comprehensive wire feeding rate instruction are combined as the final cooperative control instruction output.

[0076] Specifically, the dynamic laser power adjustment amount refers to a compensation value calculated based on the specific value of the characteristic cooling temperature deviating from the temperature threshold, which can be realized through a proportional-integral-derivative control algorithm or a fuzzy logic control algorithm, aiming to accurately match the abnormality degree of the actual cladding state. The dynamic wire feeding rate adjustment amount can be understood as a parameter linked with the laser power adjustment amount, and its adjustment is also based on the deviation degree of the characteristic cooling temperature. Specifically, it can be calculated through a preset wire feeding rate-laser power matching ratio, aiming to ensure the real-time matching of the wire feeding rate and the laser power, and prevent the dilution rate fluctuation or un-melted defects caused by single parameter adjustment.

[0077] In the embodiment, the dynamic quantification mechanism of temperature deviation degree is introduced, which significantly improves the adaptive control accuracy of the cladding process. In the cladding process, when the second control signal is activated, the dynamic adjustment amount is generated according to the specific value of the characteristic cooling temperature deviating from the temperature threshold, instead of relying only on the simple threshold overrun judgment. This mechanism enables the adjustment amount of the laser power and the wire feeding rate to accurately reflect the abnormality degree of the actual cladding state, thereby avoiding the problems of over-response or insufficient compensation caused by fixed adjustment amount. On this basis, the laser power instruction in the first control signal is superimposed with the dynamically generated laser power adjustment amount to form a comprehensive laser power instruction. This operation not only retains the energy density maintenance function based on the working distance feedback, but also integrates the dynamic compensation of temperature deviation, thereby more comprehensively maintaining the stability of the molten pool. Similarly, the wire feeding rate instruction in the first control signal is superimposed with the dynamically generated wire feeding rate adjustment amount to form a comprehensive wire feeding rate instruction. Through the linked adjustment of the wire feeding rate and the laser power, the real-time matching of the cladding material supply and the heat input is ensured. Finally, the comprehensive laser power instruction and the comprehensive wire feeding rate instruction are combined and output, realizing the closed-loop control of the two-parameter cooperation.

[0078] Specifically, when the inner wall laser cladding is performed by starting the pipe rotation and the axial feeding of the laser cladding head, the rotation speed of the pipe is set to 0.1-5 RPM, the wire feeding rate of the laser cladding head is set to 3000-4000 mm / min, and the laser power of the laser cladding head is set to 8-12 kw.

[0079] It should be noted that the rotation speed of the pipe refers to the angular velocity of the pipe rotating around its own axis during the laser cladding process, which can be realized by the driving mode of numerical control roller frame. In actual application, the rotation speed is set in the range of 0.1-5 RPM, aiming to avoid the problem of excessive heat accumulation caused by too low speed leading to too long residence time of the molten pool, or the problem of discontinuous cladding layer caused by too high speed, so as to ensure that the molten pool maintains uniform spreading in the axial movement. The wire feeding rate of the laser cladding head refers to the length of the metal wire fed into the molten pool per unit time, which can be realized by accurate control of the wire feeder. Among them, the wire feeding rate is controlled in the interval of 3000-4000 mm / min, aiming to maintain real-time matching of wire feeding and melting according to the dynamic adjustment requirement of laser power, prevent insufficient wire feeding leading to insufficient cladding layer height or excessive wire feeding causing unmelted defects, and thus ensure the interlayer bonding quality. The laser power of the laser cladding head refers to the energy density output by the laser, which can be realized by adjusting the output parameters of the laser. In actual application, the laser power is limited to the threshold of 8-12 kw, aiming to provide sufficient energy to realize reliable metallurgical bonding of the base material and the cladding material based on the correlation between the heat conduction characteristics of the pipe inner wall and the melting point of the material, while inhibiting excessive melting of the base material caused by excessive power or loose cladding layer caused by insufficient power.

[0080] Specifically, in the above scheme, by accurately defining the operation window of the core process parameters, stable basic operating conditions are provided for the cladding process, thereby supporting the effective implementation of the aforementioned regulation mechanism. The coordinated setting of the rotation speed of the pipe, the wire feeding rate and the laser power not only provides an operable benchmark platform for the work distance monitoring and temperature regulation signal, but also reduces the interference of initial parameter drift on the axial uniformity of the cladding layer from the source, so that the double-signal regulation mechanism can respond more accurately to regional characteristic changes. On this basis, the selection of these parameter ranges in combination with the division of the aforementioned starting zone, stable zone and termination zone further optimizes the uniformity control effect of the cladding layer thickness and microstructure. For example, in the starting zone and the termination zone, due to the particularity of temperature distribution, the setting of the above parameter range can effectively alleviate the problem of abnormal dilution rate or decreased bonding strength, thereby significantly improving the overall quality of the inner wall cladding of the super-long pipe.

[0081] Specifically, in order to realize accurate temperature measurement, the present embodiment is used to solve the problem of insufficient temperature monitoring accuracy caused by the axial thermal dynamic difference of the inner wall of the super-long pipe. The present embodiment implants a exposed K-type thermocouple at the key positions of the starting zone, stable zone and termination zone of the pipe inner wall, forms a "point-surface-geometry" three-modal sensing system with the infrared thermal imager and the optical distance measuring module, compensates for the surface average defect of the infrared thermal imager through the point measurement accuracy of the thermocouple, superimposes the point-surface cooperative regulation instruction to make the temperature threshold of each zone completely match the actual thermal characteristics of the pipe, and realizes the accurate measurement of the cooling temperature of the cladding layer.

[0082] In another embodiment, referring to Figure 4 Fig. 1 shows a schematic diagram of an embodiment of the application, which discloses a kind of ultra-long pipeline inner wall global laser cladding equipment, including:

[0083] Laser cladding mechanism, including laser 1, laser cladding head 2 and wire feeder 3;

[0084] Motion execution mechanism, including numerical control roller frame 4 for driving pipeline rotates around its axis, and linear guide mechanism 5 for driving laser cladding head 2 along the axial feed of pipeline;

[0085] Integrated in laser cladding head 2 on-line monitoring mechanism 6, including optical distance measuring module for real-time measurement of the distance between cladding layer surface and laser cladding head 2, and infrared thermal imager for monitoring the temperature of solidified area behind molten pool;

[0086] Central control system, with motion execution mechanism, on-line monitoring mechanism, laser 1 and wire feeder 3 communication connection;Central control system is configured to: receive the real-time working distance data sent by optical distance measuring module, and compare it with the pre-stored reference working distance of current axial position, generate the first control signal for adjusting the power of laser 1 and the speed of wire feeder 3;Receive the characteristic cooling temperature data sent by infrared thermal imager, and compare it with the pre-stored temperature threshold value dependent on axial zone, generate the second control signal;Wherein, when the characteristic cooling temperature in the starting zone is lower than the threshold value, the laser power is instructed to be reduced or the wire speed is instructed to be increased, and when the characteristic cooling temperature in the termination zone is higher than the threshold value, the laser power is instructed to be increased or the wire speed is instructed to be reduced;Fusion first control signal and second control signal, generate the final control instruction and output to laser 1 and wire feeder 3, to carry out compound control on cladding process.

[0087] The core innovation of the application is that by combining zoned control with double feedback mechanism, the problems of uneven axial thickness and inconsistent quality of cladding layer in the process of laser cladding of ultra-long pipeline inner wall are solved. Specifically, this scheme introduces a zoned processing method based on axial thermal distribution characteristics, sets different reference working distances and temperature thresholds for starting zone, stable zone and termination zone respectively, and realizes region-specific adaptive regulation;At the same time, by real-time monitoring the distance between cladding layer surface and laser cladding head 2 and the characteristic cooling temperature of solidified area behind molten pool, a double regulation channel of working distance feedback and temperature feedback is established, which respectively deals with geometric state change and heat accumulation problem. This combination not only overcomes the limitations of existing technology relying only on working distance feedback, but also significantly improves the consistency of cladding layer thickness and microstructure, achieving high-quality cladding effect.

[0088] In practical applications, the above-mentioned device solves the problems of uneven axial thickness and poor overall consistency caused by single feedback in the laser cladding process of the inner wall of the ultra-long pipeline by partition control and double feedback mechanism, combined with real-time monitoring and signal fusion.

[0089] Specifically, in order to further verify the beneficial effects of the global laser cladding process of the inner wall of the ultra-long pipeline of the present application compared with the prior art, comparative tests are also carried out in the present application:

[0090] Comparative Example 1: Conventional electric arc welding technology: GTAW (Gas Tungsten Arc Welding) process is used to carry out surfacing on the inner wall of an ultra-long pipeline with a length of 12 m and an inner diameter of 300 mm.

[0091] Comparative Example 2: Laser cladding process based only on real-time working distance feedback to regulate laser power, the equipment and core parameters are the same as those of the present application, but the characteristic cooling temperature is not monitored and there is no second regulation signal.

[0092] Example: The global laser cladding process and equipment described in the present application are used.

[0093] The three groups of tests all complete the inner wall circumferential welding or cladding of the whole 12-meter-long pipeline, and after the welding or cladding is completed, samples are taken at the starting zone, stable zone and termination zone of each pipeline for the following tests:

[0094] Cladding layer thickness uniformity: use an ultrasonic thickness gauge to measure one point every 10 cm along the axial direction, and calculate the average value and standard deviation of the thickness of each zone.

[0095] Surface morphology quality: use a surface roughness meter to measure the surface roughness (Ra) of the cladding layer;

[0096] Microstructure: prepare metallographic samples, observe and measure the grain size in the middle region of the cladding layer under an optical microscope;

[0097] Residual stress distribution: use X-ray diffraction method to measure the residual stress value on the surface of the cladding layer.

[0098] Specifically, the typical test data of the above-mentioned three groups of tests are compared with the results shown in Table 1.

[0099] Table 1

[0100]

[0101] As can be seen from Comparative Example 1, the conventional electric arc welding technology has obvious uneven thickness (large thickness standard deviation), and the difference in organization and performance between the starting zone and the termination zone is huge. The termination zone has coarse grains due to the accumulation of heat input, and the residual stress level is the highest. Especially in the starting zone, high tensile stress can significantly reduce the fatigue resistance and stress corrosion resistance of the structure.

[0102] As can be seen from Comparative Example 2, single geometric parameter regulation is superior to electric arc welding in thickness control and surface finish, proving that laser cladding itself has advantages, but the fundamental problem is that it cannot solve the metallurgical quality problem caused by axial heat unevenness, and the grain size of the termination zone is still much larger than that of the starting zone, and most importantly, the residual stress distribution shows an unfavorable trend: the starting zone causes high tensile stress due to rapid cooling, and the termination zone causes higher tensile stress than the starting zone due to heat accumulation and slow cooling, which shows that this method cannot effectively control the internal stress of the entire manufacturing process.

[0103] As can be seen from the examples of the present application, all data are significantly better than the two comparative examples, the thickness standard deviation is the smallest, proving that it has the best geometric uniformity; the grain size is the smallest and most uniform, and the values of the starting zone and the termination zone are close, proving that the asymmetric regulation strategy of the present application effectively manages the cooling process in different regions and inhibits grain coarsening; the residual stress level is the lowest and the distribution is the most uniform, the present application actively manages heat input and cooling rate, significantly reduces thermal stress in the cladding process, avoids high tensile stress in the starting zone due to supercooling and in the termination zone due to overheating, and greatly improves the mechanical state of the component.

[0104] Obviously, the above examples are only examples for the sake of clarity, and are not a limitation on the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A full-area laser cladding process for the inner wall of an ultra-long pipe, characterized in that, Includes the following steps: The entire inner wall of the pipeline to be clad is divided into a starting zone, a stable zone, and a termination zone along the axial direction. At least one reference point is selected in each of the starting zone, stable zone, and termination zone, and a standard cladding process is performed to determine the reference working distance of the reference point in each zone. Start the pipe rotation and axial feed of the laser cladding head to perform inner wall laser cladding; During the cladding process, the real-time working distance from the surface of the cladding layer to the laser cladding head is monitored, and the characteristic cooling temperature of the solidified area behind the molten pool is monitored simultaneously using an infrared thermal imager. The real-time working distance is compared with the reference working distance at the current axial position to generate a first control signal, which is used to perform a first-level coordinated adjustment of the laser power and wire feed rate; at the same time, a second control signal is generated based on the comparison of the characteristic cooling temperature with a preset temperature threshold dependent on the axial region. In the initial region, if the characteristic cooling temperature is lower than the temperature threshold, the second control signal instructs to reduce the laser power or increase the wire feeding power; in the termination region, if the characteristic cooling temperature is higher than the temperature threshold, the second control signal instructs to increase the laser power or decrease the wire feeding power. The first and second control signals are integrated and act together on the current cladding process to achieve composite control of the axial thickness and microstructure uniformity of the cladding layer.

2. The laser cladding process for the entire inner wall of ultra-long pipelines according to claim 1, characterized in that: The region is divided along the axial direction into a starting region, a stable region, and a ending region, including: Before officially starting the cladding process, the laser cladding head is controlled to scan the inner wall of the pipe at a uniform speed once with a preset scanning power in a state without wire feeding. During the scanning process, the axial temperature distribution curve of the inner wall of the pipe is monitored and recorded simultaneously using an infrared thermal imager; Identify two characteristic inflection points on the axial temperature distribution curve: the first inflection point is the turning point where the temperature changes from an initial rapid rise to a slow rise, and the second inflection point is the turning point where the temperature changes from a slow rise to an accelerated rise again. The axial region between the pipe inlet and the first inflection point is defined as the starting region; the axial region between the first inflection point and the second inflection point is defined as the stable region; and the axial region between the second inflection point and the end of the pipe is defined as the ending region.

3. The laser cladding process for the entire inner wall of ultra-long pipelines according to claim 2, characterized in that: The preset axial region-dependent temperature threshold is determined synchronously during the axial scanning process in a wire-free state, specifically including: During the wire-free scanning process, after identifying the axial boundaries of the starting zone, stable zone, and ending zone, the average values ​​of the corresponding data of the axial temperature distribution curves recorded in the starting zone, stable zone, and ending zone are calculated respectively. The calculated average temperatures of the starting zone, the stable zone, and the ending zone are directly set as the characteristic cooling temperature thresholds for the starting zone, the stable zone, and the ending zone, respectively.

4. The full-area laser cladding process for the inner wall of ultra-long pipelines according to claim 1, characterized in that: When selecting multiple reference points in each of the starting, stable, and ending zones, after performing the standard cladding process at each reference point within the zone, the initial reference working distance of that point is measured and recorded. The arithmetic mean of multiple initial reference working distances within the same zone is calculated and determined as the final reference working distance for that zone.

5. The full-area laser cladding process for the inner wall of ultra-long pipes according to claim 1, characterized in that: The first level of coordinated adjustment of laser power and wire feed rate is performed using the first control signal, including: Based on the deviation between the real-time working distance and the reference working distance, the laser power compensation value required to maintain a constant energy density per unit area is calculated. Based on the adjustment direction and magnitude of the laser power compensation value, the adjustment value of the wire feeding rate is calculated synchronously according to the preset wire feeding rate-laser power matching ratio; wherein, when the laser power is increased, the wire feeding rate is increased synchronously in proportion, and when the laser power is decreased, the wire feeding rate is decreased synchronously in proportion. The laser power compensation value and the wire feed rate adjustment value are packaged together to generate the first control signal.

6. The full-area laser cladding process for the inner wall of ultra-long pipes according to claim 5, characterized in that: The wire feed rate-laser power matching ratio is different in the starting region, the stable region, and the ending region. Specifically, the wire feed rate-laser power matching ratio used in the ending region is greater than that used in the stable region; and the wire feed rate-laser power matching ratio used in the stable region is greater than that used in the starting region.

7. The full-area laser cladding process for the inner wall of ultra-long pipelines according to claim 1, characterized in that: The first and second control signals are integrated and act together on the current cladding process, including: The first control signal is used as the basic execution command to make basic adjustments to the laser power and wire feeding rate; While adjusting based on the first control signal, the triggering state of the second control signal is judged in real time; when the characteristic cooling temperature continuously exceeds the temperature threshold of its axial partition and reaches a stable duration, it is determined that the second control signal is activated. The second control signal is superimposed with the instructions regarding laser power and wire feeding speed in the first control signal to form a comprehensive laser power instruction, which is then output to the actuator as the final coordinated control instruction.

8. The full-area laser cladding process for the inner wall of ultra-long pipes according to claim 7, characterized in that: Once the second control signal is activated, a dynamic laser power adjustment and a dynamic wire feed rate adjustment are generated simultaneously based on the degree to which the current characteristic cooling temperature deviates from the temperature threshold. The laser power command and laser power adjustment amount in the first control signal are superimposed to form a comprehensive laser power command; at the same time, the wire feed rate command and wire feed rate adjustment amount in the first control signal are superimposed to form a comprehensive wire feed rate command. The combined laser power command and the combined wire feed rate command are combined to form the final coordinated control command output.

9. The full-area laser cladding process for the inner wall of ultra-long pipelines according to claim 1, characterized in that: When starting the pipe rotation and the laser cladding head axially feeds to perform inner wall laser cladding, the pipe rotation speed is 0.1-5 RPM, the wire feeding rate of the laser cladding head is 3000-4000 mm / min, and the laser power of the laser cladding head is 8-12 kW.

10. A laser cladding device for the entire inner wall of an ultra-long pipe, used to perform the process described in any one of claims 1 to 9, characterized in that: include: The laser cladding mechanism includes a laser, a laser cladding head, and a wire feeder; The motion actuator includes a CNC roller frame for driving the pipe to rotate about its axis, and a linear guide mechanism for driving the laser cladding head to feed axially along the pipe. The online monitoring mechanism integrated into the laser cladding head includes an optical ranging module for measuring the distance from the surface of the cladding layer to the laser cladding head in real time, and an infrared thermal imager for monitoring the temperature of the solidified area behind the molten pool. The central control system is communicatively connected to the motion actuator, the online monitoring mechanism, the laser, and the wire feeder; the central control system is configured as follows: The system receives real-time working distance data sent by the optical ranging module and compares it with the pre-stored reference working distance of the current axial position to generate a first control signal for coordinating the adjustment of the laser power and the wire feeder speed. The system receives characteristic cooling temperature data sent by the infrared thermal imager and compares it with a pre-stored, axial region-dependent temperature threshold to generate a second control signal. Specifically, when the characteristic cooling temperature in the starting region is lower than the threshold, the system instructs to reduce the laser power or increase the wire feeding rate, and when the characteristic cooling temperature in the ending region is higher than the threshold, the system instructs to increase the laser power or reduce the wire feeding rate. The first and second control signals are integrated to generate the final control command and output to the laser and wire feeder for composite control of the cladding process.

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