Stainless steel pipe and copper pipe-based welding method for silver-free brazing of air conditioner connecting pipe

Abstract

The invention relates to the field of welding, in particular to an air conditioner connecting pipe silver-free brazing welding method based on a stainless steel pipe and a copper pipe, which comprises the following steps: firstly, removing an oxide layer of the copper pipe, determining the surface roughness, and determining a wetting parameter according to the surface roughness; arranging a camera to obtain a welding ripple image and calculating a fluctuation characterization value, and judging whether the unit welding process reaches the standard or not and determining the abnormal fluctuation frequency according to the fluctuation characterization value; according to the abnormal fluctuation frequency, whether the whole welding process reaches the standard or not and the reason for substandard are judged, and wetting parameters are adjusted; and then the welding process is checked, and if the welding process does not reach the standard, deoxidation layer treatment compensation is carried out. According to the method, through the technologies of quantifying correlation between the surface roughness and wetting parameters, judging abnormal fluctuation in a grading mode, monitoring ripples in real time, dynamically adjusting the parameters and the like, precious metal silver is abandoned, toxic gas is avoided, the environment-friendly requirement is met, and an efficient and stable scheme is provided for air conditioner connecting pipe manufacturing.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a silver-free brazing method for connecting pipes of air conditioners based on stainless steel pipes and copper pipes. Background Art

[0002] In air conditioning manufacturing, the connection between stainless steel and copper pipes is a critical link in refrigeration systems. Traditionally, silver brazing is used, but silver, as a precious metal, is expensive and scarce, resulting in high welding costs. Furthermore, the silver brazing process requires stringent operating conditions and can generate hazardous gases, posing potential risks to worker health and the environment. As the air conditioning industry evolves towards higher efficiency, environmental friendliness, and lower costs, silver-free brazing technology has become a hot topic of research.

[0003] Silver-free brazing aims to achieve weld strength and sealing comparable to silver brazing while reducing costs by optimizing the brazing filler metal formula and improving the welding process. However, the physical properties of stainless steel and copper pipes differ significantly, requiring more stringent surface treatment and flux formulation during the silver-free brazing process. Failure to do so can easily lead to defects such as poor wetting, porosity, and cracks, seriously impacting weld quality. Therefore, achieving a reliable connection between the two materials through process control is a core challenge in silver-free brazing technology. Summary of the Invention

[0004] To this end, the present invention provides a silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes, so as to overcome the problems of poor wetting, pores and cracks that are easily generated during the welding process in the prior art.

[0005] To achieve the above object, the present invention provides, including: Step S1, removing the surface oxide layer at the welding position of the copper tube and obtaining the surface roughness of the welding position; Step S2, determining the wetting parameters for brazing the stainless steel tube and the copper tube according to the surface roughness of the welding position, the wetting parameters including preheating temperature and shielding gas flow rate; Step S3, placing a camera just above the welding point to obtain an image of the welding ripples at the welding point within a unit welding process; Step S4, obtaining a fluctuation characterization value based on the welding corrugation image of the welding point; Step S5, when it is determined based on the fluctuation characterization value that the welding process of the stainless steel pipe and the copper pipe in the unit welding process does not meet the standard, the entire welding process is completed and the frequency of abnormal fluctuation is determined; Step S6, determining the reason why the overall welding process of the stainless steel pipe and the copper pipe does not meet the standard based on the frequency of abnormal fluctuations, and adjusting the wetting parameters of the overall welding process that does not meet the standard; Step S7, checking whether the welding process of the stainless steel pipe and the copper pipe meets the standard according to the corrected abnormal fluctuation frequency threshold value after the wetting parameter is adjusted, and compensating for the deoxidation layer treatment of the copper pipe whose welding process does not meet the standard.

[0006] Furthermore, the fluctuation characterization value is a variance value of the height of each peak in the welding ripple.

[0007] Furthermore, whether the welding process of the stainless steel pipe and the copper pipe within a unit welding process meets the standard is determined based on the fluctuation characterization value, wherein: If the fluctuation characterization value is less than the preset fluctuation characterization value threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe in the unit welding process meets the standard; If the fluctuation characterization value is greater than or equal to the preset fluctuation characterization threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe in the unit welding process does not meet the standard.

[0008] Furthermore, the result of determining that the welding process of the stainless steel pipe and the copper pipe within a unit welding process does not meet the standard is recorded as an abnormal fluctuation, and the number of abnormal fluctuations in the welding process of the stainless steel pipe and the copper pipe within the entire welding process is recorded as the abnormal fluctuation frequency.

[0009] Furthermore, whether the overall welding process of the stainless steel pipe and the copper pipe meets the standard is determined based on the frequency of the abnormal fluctuation, wherein: If the abnormal fluctuation frequency is less than a first preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe and the copper pipe meets the standard; If the abnormal fluctuation frequency is greater than or equal to the first preset abnormal fluctuation frequency threshold and is less than the second preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe and the copper pipe does not meet the standard, and the reason for the overall welding process not meeting the standard is that the shielding gas flow rate in the wetting parameter is too large; If the abnormal fluctuation frequency is greater than or equal to a second preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe and the copper pipe does not meet the standard, and the reason for the overall welding process not meeting the standard is that the preheating temperature in the wetting parameters is low.

[0010] Furthermore, in response to the fact that the overall welding process does not meet the standard due to the large shielding gas flow in the wetting parameters, the shielding gas flow for the next batch of connecting pipe welding is reduced, and the reduction amplitude of the shielding gas flow is positively correlated with the difference between the abnormal fluctuation frequency and the first preset abnormal fluctuation frequency threshold.

[0011] Furthermore, in response to the overall welding process failing to meet the standard due to a low preheating temperature in the wetting parameters, the preheating temperature for the next batch of connecting pipes is increased, and the preheating temperature adjustment amplitude is positively correlated with the difference between the abnormal fluctuation frequency and a second preset abnormal fluctuation frequency threshold. Furthermore, the welding process of the stainless steel pipe and the copper pipe is checked to see whether it meets the standard based on the corrected abnormal fluctuation frequency threshold after the wetting parameters are adjusted, wherein: If the corrected abnormal fluctuation frequency is less than a preset corrected abnormal fluctuation frequency threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe meets the standards; If the corrected abnormal fluctuation frequency is greater than or equal to a preset corrected abnormal fluctuation frequency threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe does not meet the standards.

[0012] Furthermore, in response to the fact that the welding process of the stainless steel tube and the copper tube after the wetting parameters are adjusted does not meet the standards, the surface roughness of the welding position of the next batch of copper tubes is increased.

[0013] Furthermore, the increase in the surface roughness of the welding positions of the next batch of copper tubes is positively correlated with the difference between the corrected abnormal fluctuation frequency and the preset corrected abnormal fluctuation frequency threshold.

[0014] Compared with existing technologies, this invention offers significant advantages: by quantifying the correlation between copper tube surface roughness and wetting parameters, it addresses the poor wetting problem between stainless steel and copper tubes caused by differences in physical properties. For example, dynamically adjusting the preheating temperature based on surface roughness ensures uniform solder spread at the dissimilar metal interface, eliminating lack of fusion defects and improving weld strength.

[0015] Furthermore, based on the abnormal fluctuation frequency grading judgment mechanism, the root cause of welding defects can be quickly identified, avoiding the inefficiency caused by "blindly adjusting parameters" in traditional methods.

[0016] Furthermore, a camera captures real-time images of weld ripples and calculates the variance of each wave peak's height, transforming subjective judgments into objective data metrics. For example, the system automatically triggers parameter adjustments, shortening response time and significantly improving the lag inherent in traditional post-weld inspections. Based on the difference between the frequency of abnormal fluctuations and preset values, the shielding gas flow rate or preheat temperature is dynamically adjusted to ensure the welding process remains within the optimal process window.

[0017] Furthermore, when abnormal fluctuations still exist after the wetting parameters are adjusted, the system further improves the surface roughness of the copper tube by increasing the mesh size of the sandpaper to eliminate the influence of the residual microscopic oxide layer on the wettability.

[0018] Furthermore, by completely abandoning the precious metal silver, the cost of solder is reduced by more than 60%, while avoiding the toxic gases produced during the silver brazing process, complying with environmental regulations such as RoHS.

[0019] The present invention solves the problems of poor wetting and defect location in silver-free brazing of dissimilar metals through innovative technologies such as quantitative correlation between surface roughness and wetting parameters, abnormal fluctuation classification and judgment, real-time ripple monitoring and dynamic parameter adjustment, and realizes efficient, low-cost, environmentally friendly and compliant stable welding, providing an efficient, stable and low-cost solution for the manufacture of air-conditioning connecting pipes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of a silver-free brazing method for connecting air conditioner pipes based on stainless steel pipes and copper pipes according to an embodiment of the present invention; Figure 2 This is a flow chart of an embodiment of the present invention for determining whether a welding process of a stainless steel pipe and a copper pipe within a unit welding process meets the standards based on a fluctuation characterization value; Figure 3 This is a flow chart of an embodiment of the present invention for determining whether the overall welding process of a stainless steel pipe and a copper pipe meets the standards based on the frequency of abnormal fluctuations; Figure 4 This is a flow chart of an embodiment of the present invention for verifying whether the welding process of a stainless steel pipe and a copper pipe meets the standards according to the corrected abnormal fluctuation frequency threshold value after adjusting the wetting parameters; Figure 5 This is a schematic diagram of the welding structure of the silver-free brazing of the air-conditioning connecting pipe of the stainless steel pipe and the copper pipe according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the welding ripples of the welding point according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the overall structure of the silver-free brazing of air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to an embodiment of the present invention; In the figure: 1. Stainless steel pipe; 2. Copper pipe; 3. Image of welding corrugation; 4. Unit welding process. DETAILED DESCRIPTION

[0021] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0022] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] See also Figure 1-6 As shown, they are respectively a flow chart of a welding method for silver-free brazing of air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to an embodiment of the present invention; a flow chart of determining whether the welding process of stainless steel pipes and copper pipes within a unit welding process meets the standards based on a fluctuation characterization value according to an embodiment of the present invention; a flow chart of determining whether the overall welding process of stainless steel pipes and copper pipes meets the standards according to the abnormal fluctuation frequency according to an embodiment of the present invention; a flow chart of checking whether the welding process of stainless steel pipes and copper pipes meets the standards according to the corrected abnormal fluctuation frequency threshold after adjusting the wetting parameters according to an embodiment of the present invention; a schematic diagram of the welding structure of silver-free brazing of air-conditioning connecting pipes of stainless steel pipes and copper pipes according to an embodiment of the present invention; an image schematic diagram of welding corrugations at welding points according to an embodiment of the present invention.

[0024] An embodiment of the present invention provides a silver-free brazing method for connecting pipes of an air conditioner based on stainless steel pipes and copper pipes, comprising: Step S1, removing the surface oxide layer at the welding position of the copper tube 2 and obtaining the surface roughness of the welding position; Step S2, determining the wetting parameters for brazing the stainless steel tube 1 and the copper tube 2 according to the surface roughness of the welding position, the wetting parameters including preheating temperature and shielding gas flow rate; Step S3, arranging a camera just above the welding point to obtain an image 3 of the welding ripples of the welding point within a unit welding process 4; Step S4, obtaining a fluctuation characterization value based on the welding corrugation image of the welding point; Step S5, when it is determined based on the fluctuation characterization value that the welding process of the stainless steel tube 1 and the copper tube 2 in the unit welding process 4 does not meet the standard, the entire welding process is completed and the abnormal fluctuation frequency is determined; Step S6, determining the reason why the overall welding process of the stainless steel tube 1 and the copper tube 2 does not meet the standard based on the frequency of abnormal fluctuations, and adjusting the wetting parameters of the overall welding process that does not meet the standard; Step S7, checking whether the welding process of the stainless steel tube 1 and the copper tube 2 meets the standard according to the corrected abnormal fluctuation frequency threshold after the wetting parameter is adjusted, and compensating for the deoxidation layer treatment of the copper tube 2 whose welding process does not meet the standard; wherein, the overall welding process is the welding circumference of the contact between the copper tube 2 and the stainless steel tube 1, and the overall welding process is divided into 16 sections, and the unit welding process 4 is any one of them.

[0025] Specifically, the specific implementation method for removing the oxide layer is to select sandpaper with a grit size of 400 to ensure that the oxide layer can be effectively removed without causing excessive damage to the surface of the copper tube 2. Then, polish evenly along the axial direction of the copper tube 2 until the oxide layer is completely removed. During the polishing process, the surface condition of the copper tube 2 needs to be monitored in real time: avoid local thinning exceeding 20% ​​of the original wall thickness; ensure that the surface roughness of the copper tube is less than or equal to 3.2μm; polish until the surface contact angle is less than or equal to 20°. After completing the deoxidation treatment, first blow the surface with compressed air, then clean the remaining debris with anhydrous ethanol, and finally wipe it dry with a clean cotton cloth to ensure that the surface cleanliness of the copper tube 2 reaches ISO 8593-1 Grade B (or the cleanliness standard required by the specific welding process), providing a good foundation for subsequent welding.

[0026] Specifically, the surface of the copper tube 2 needs to be carefully inspected to obtain a specific roughness value. Professional measurement tools, such as a surface roughness tester, can accurately assess the surface condition of the copper tube 2. Wetting parameters are then set based on the roughness data and the welding process requirements.

[0027] Specifically, the wetting parameters include preheat temperature and shielding gas flow rate. The appropriate preheat temperature is selected based on the pipe material. For example, when welding copper pipe 2, heat it to a dark red color (approximately 600-700°C), the shielding gas flow rate can be set to 10.0 L / min. The fluctuation characteristic value is the variance of the height of each peak in the weld ripple.

[0028] Specifically, the welding machine is set in a fixed position, the stainless steel tube 1 and the copper tube 2 are vertically connected, and the outer diameter of the contact surface of the stainless steel tube 1 and the copper tube 2 is rotated and welded around the brazing material of the welding machine; the brazing material can be BNi-2 or BNi-5, and there is no specific limitation, as long as the welding result of the air-conditioning connecting pipe of the stainless steel tube 1 and the copper tube 2 is silver-free brazing.

[0029] Specifically, a camera such as an infrared camera is arranged directly above the welding point. There is no specific limitation, as long as it can output a corresponding image result based on the input welding point image.

[0030] Specifically, whether the welding process of the stainless steel tube 1 and the copper tube 2 in the unit welding process 4 meets the standard is determined based on the fluctuation characterization value, wherein: If the fluctuation characterization value is less than the preset fluctuation characterization value threshold, it is determined that the welding process of the stainless steel pipe 1 and the copper pipe 2 in the unit welding process 4 meets the standard; If the fluctuation characterization value is greater than or equal to the preset fluctuation characterization threshold, it is determined that the welding process of the stainless steel tube 1 and the copper tube 2 in the unit welding process 4 does not meet the standard; wherein, the preset fluctuation characterization value threshold is set to 2.1. It should be pointed out that the data in this embodiment are all results obtained by preliminary experimental verification of the system described in the present invention before the system is operated. Each preset value can be adjusted according to the specific usage, as long as the system method described in the present invention can clearly define different specific situations in the single judgment process through the obtained numerical values.

[0031] Specifically, the result of the welding process of the stainless steel pipe 1 and the copper pipe 2 in the unit welding process 4 being judged as not meeting the standard is recorded as one abnormal fluctuation, and the number of abnormal fluctuations in the welding process of the stainless steel pipe 1 and the copper pipe 2 in the entire welding process is recorded as the abnormal fluctuation frequency.

[0032] Specifically, whether the overall welding process of the stainless steel tube 1 and the copper tube 2 meets the standard is determined based on the abnormal fluctuation frequency, wherein: If the abnormal fluctuation frequency is less than the first preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe 1 and the copper pipe 2 meets the standard; If the abnormal fluctuation frequency is greater than or equal to the first preset abnormal fluctuation frequency threshold and less than the second preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe 1 and the copper pipe 2 does not meet the standard, and the reason for the overall welding process not meeting the standard is that the shielding gas flow rate in the wetting parameter is too large; If the abnormal fluctuation frequency is greater than or equal to the second preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel tube 1 and the copper tube 2 does not meet the standard, and the reason for the overall welding process not meeting the standard is the low preheating temperature in the wetting parameters; the first preset abnormal fluctuation frequency threshold is 5 times, and the second preset abnormal fluctuation frequency threshold is 10 times.

[0033] Specifically, in response to the fact that the overall welding process does not meet the standard due to the large shielding gas flow rate in the wetting parameter, the shielding gas flow rate of the next batch of connecting pipe welding is reduced, and the reduction in shielding gas flow rate is positively correlated with the difference between the abnormal fluctuation frequency and the first preset abnormal fluctuation frequency threshold. It is understandable that the positive correlation, such as linear positive correlation or nonlinear positive correlation, is not specifically limited, and the slope of the linear positive correlation is also not specifically limited. It can be set according to the actual preparation conditions, and it is only necessary to meet the requirement that the greater the difference between the abnormal fluctuation frequency and the first preset abnormal fluctuation frequency threshold, the greater the reduction in shielding gas flow rate. For example, the reduction in shielding gas flow rate is set to △Q, and the difference between the abnormal fluctuation frequency and the first preset abnormal fluctuation frequency threshold is set to △Φ, then △Q=α×(△Φ+Φ0), α is the flow adjustment coefficient, α is set to 1.03, and Φ0 is a constant.

[0034] Specifically, in response to the overall welding process failing to meet the standard due to a low preheating temperature in the wetting parameter, the preheating temperature for the next batch of connecting pipes is increased, and the preheating temperature adjustment amplitude is positively correlated with the difference between the abnormal fluctuation frequency and the second preset abnormal fluctuation frequency threshold. It is understood that the positive correlation, such as a linear positive correlation or a nonlinear positive correlation, is not specifically limited, and the slope of the linear positive correlation is also not specifically limited. It can be set according to the actual preparation conditions, and it is only necessary to meet the requirement that the greater the difference between the abnormal fluctuation frequency and the second preset abnormal fluctuation frequency threshold, the greater the increase in preheating temperature. For example, the increase in preheating temperature is set to ΔT, and the difference between the abnormal fluctuation frequency and the second preset abnormal fluctuation frequency threshold is set to Δλ, then ΔT=β×(Δλ+λ0), where β is the temperature adjustment coefficient, β is set to 0.86, and λ0 is a constant.

[0035] Specifically, the welding process of the stainless steel tube 1 and the copper tube 2 is checked to see whether it meets the standard according to the modified abnormal fluctuation frequency threshold after the wetting parameter adjustment, wherein: If the corrected abnormal fluctuation frequency is less than the preset corrected abnormal fluctuation frequency threshold, it is determined that the welding process of the stainless steel tube 1 and the copper tube 2 meets the standards; If the corrected abnormal fluctuation frequency is greater than or equal to the preset corrected abnormal fluctuation frequency threshold, the welding process of the stainless steel tube 1 and the copper tube 2 is determined to be substandard. The preset corrected abnormal fluctuation frequency threshold is set to 3 times. It should be noted that this threshold is an optimized value derived from statistical analysis of previous experimental data and can effectively reflect the stability of the welding process. If the corrected abnormal fluctuation frequency is lower than this threshold, it indicates that the current welding process parameters have reached the ideal state and subsequent welding operations can continue. In actual application, the operator can fine-tune the threshold according to the specific working conditions to achieve the optimal welding effect.

[0036] Specifically, in response to the fact that the welding process between the stainless steel tube 1 and the copper tube 2 does not meet the standards after the wetting parameters are adjusted, the surface roughness of the welding position of the copper tube 2 in the next batch is increased. The surface roughness of the copper tube 2 welding position of the copper tube 2 determined to have failed to meet the standards is increased by reducing the grit of the sandpaper used for the oxide layer removal treatment. It is worth noting that while low-grit sandpaper can quickly remove the oxide layer, it is prone to leaving tiny pits or uneven areas, which in turn affect the wetting performance. Therefore, in actual operation, it is recommended to verify the treatment effects at different grits through experiments and establish standardized reference data to achieve the optimal balance between efficiency and cost while ensuring welding quality.

[0037] Specifically, the increase in surface roughness at the welding position of the next batch of copper tubes 2 is positively correlated with the difference between the corrected abnormal fluctuation frequency and the preset corrected abnormal fluctuation frequency threshold. It is understood that the positive correlation, such as a linear positive correlation or a nonlinear positive correlation, is not specifically limited, and the slope of the linear positive correlation is also not specifically limited. It can be set according to the actual preparation conditions, as long as the difference between the corrected abnormal fluctuation frequency and the preset corrected abnormal fluctuation frequency threshold is greater, the greater the reduction in the grit of the replaced sandpaper. For example, the reduction in the grit of the replaced sandpaper is set to △M, and the difference between the abnormal fluctuation frequency and the second preset abnormal fluctuation frequency threshold is set to △μ, then △M=γ×(△μ+μ0), where γ is the grit adjustment coefficient, γ is set to 1.06, and μ0 is a constant.

[0038] Specifically, if Figure 7This is a schematic diagram of the overall structure of the silver-free brazing of the stainless steel tube and the copper tube for the air-conditioning connecting pipe according to an embodiment of the present invention. This schematic diagram clearly shows the connection between the stainless steel tube 1 and the copper tube 2 formed by the silver-free brazing, wherein the end of the stainless steel tube 1 is tightly fitted with the outer wall of the copper tube 2, the solder layer at the welding point is evenly filled in the gap between the two, and the welding corrugations are regularly distributed in annular shapes without obvious bubbles, cracks or unfused defects. The connection structure formed by the above-mentioned welding method can achieve a high-strength, high-sealing connection between the stainless steel tube and the copper tube without the use of silver-based solder, effectively reducing production costs while meeting the corrosion resistance and mechanical performance requirements of the air-conditioning connecting pipe during long-term use.

[0039] The present invention solves the problems of poor wetting and defect location in silver-free brazing of dissimilar metals through innovative technologies such as quantitative correlation between surface roughness and wetting parameters, abnormal fluctuation classification and judgment, real-time ripple monitoring and dynamic parameter adjustment, and realizes efficient, low-cost, environmentally friendly and compliant stable welding, providing an efficient, stable and low-cost solution for the manufacture of air-conditioning connecting pipes.

[0040] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0041] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes, characterized in that: include: Step S1, removing the surface oxide layer at the welding position of the copper tube and obtaining the surface roughness of the welding position; Step S2, determining the wetting parameters for brazing the stainless steel tube and the copper tube according to the surface roughness of the welding position, the wetting parameters including preheating temperature and shielding gas flow rate; Step S3, placing a camera just above the welding point to obtain an image of the welding ripples at the welding point within a unit welding process; Step S4, obtaining a fluctuation characterization value based on the welding corrugation image of the welding point; Step S5, when it is determined based on the fluctuation characterization value that the welding process of the stainless steel pipe and the copper pipe in the unit welding process does not meet the standard, the entire welding process is completed and the frequency of abnormal fluctuation is determined; Step S6, determining the reason why the overall welding process of the stainless steel pipe and the copper pipe does not meet the standards based on the frequency of abnormal fluctuations, and adjusting the wetting parameters of the overall welding process; Step S7, checking whether the welding process of the stainless steel pipe and the copper pipe meets the standard according to the corrected abnormal fluctuation frequency threshold value after the wetting parameter is adjusted, and compensating for the deoxidation layer treatment of the copper pipe whose welding process does not meet the standard.

2. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 1 is characterized in that: The fluctuation characterization value is the variance value of the height of each peak in the welding corrugation.

3. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 2 is characterized in that: Based on the fluctuation characterization value, it is determined whether the welding process of the stainless steel pipe and the copper pipe in the unit welding process meets the standard, wherein: If the fluctuation characterization value is less than the preset fluctuation characterization value threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe in the unit welding process meets the standard; If the fluctuation characterization value is greater than or equal to the preset fluctuation characterization threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe in the unit welding process does not meet the standard.

4. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 3 is characterized in that: The result of judging that the welding process of the stainless steel pipe and the copper pipe in a unit welding process does not meet the standard is recorded as an abnormal fluctuation, and the number of abnormal fluctuations in the welding process of the stainless steel pipe and the copper pipe in the entire welding process is recorded as the abnormal fluctuation frequency.

5. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 4 is characterized in that: Determine whether the overall welding process of the stainless steel pipe and the copper pipe meets the standard based on the abnormal fluctuation frequency, wherein: If the abnormal fluctuation frequency is less than a first preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe and the copper pipe meets the standard; If the abnormal fluctuation frequency is greater than or equal to the first preset abnormal fluctuation frequency threshold and is less than the second preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe and the copper pipe does not meet the standard, and the reason for the overall welding process not meeting the standard is that the shielding gas flow rate in the wetting parameter is too large; If the abnormal fluctuation frequency is greater than or equal to a second preset abnormal fluctuation frequency threshold, it is determined that the overall welding process of the stainless steel pipe and the copper pipe does not meet the standard, and the reason for the overall welding process not meeting the standard is that the preheating temperature in the wetting parameters is low.

6. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 5 is characterized in that: In response to the fact that the overall welding process does not meet the standard due to the large shielding gas flow in the wetting parameters, the shielding gas flow for the next batch of connecting pipe welding is reduced, and the reduction amplitude of the shielding gas flow is positively correlated with the difference between the abnormal fluctuation frequency and the first preset abnormal fluctuation frequency threshold.

7. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 6, characterized in that: In response to the overall welding process failing to meet the standard due to the low preheating temperature in the wetting parameters, the preheating temperature for the welding of the next batch of connecting pipes is increased, and the preheating temperature adjustment amplitude is positively correlated with the difference between the abnormal fluctuation frequency and the second preset abnormal fluctuation frequency threshold.

8. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 6 or 7, characterized in that: The welding process of the stainless steel pipe and the copper pipe is checked to see whether it meets the standard according to the modified abnormal fluctuation frequency threshold after the wetting parameter adjustment, wherein: If the corrected abnormal fluctuation frequency is less than a preset corrected abnormal fluctuation frequency threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe meets the standards; If the corrected abnormal fluctuation frequency is greater than or equal to a preset corrected abnormal fluctuation frequency threshold, it is determined that the welding process of the stainless steel pipe and the copper pipe does not meet the standards.

9. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 8, characterized in that: In response to the fact that the welding process of the stainless steel tube and the copper tube after the wetting parameters are adjusted does not meet the standards, the surface roughness of the welding position of the next batch of copper tubes is increased.

10. The silver-free brazing method for air-conditioning connecting pipes based on stainless steel pipes and copper pipes according to claim 9, characterized in that: The increase in the surface roughness of the welding position of the next batch of copper tubes is positively correlated with the difference between the corrected abnormal fluctuation frequency and the preset corrected abnormal fluctuation frequency threshold.

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