A laser adaptive welding method

Abstract

The present invention discloses a laser adaptive welding method. By experimentally matching the parameter function P and the defect function S, a parameter-defect database is established. Before welding, basic parameter variables are obtained and an initial scheme is output. During the welding process, the stability of the molten pool and the macro and micro defects of the weld seam are monitored in real time to obtain defect variables. Then, the parameters are adjusted in real time through the database, ultimately achieving the purpose of online monitoring and control of defects during the welding process. According to the real-time feedback parameter variables and defect variables, the data processing system judges the real-time parameter function P T and the defect function S T If the requirements are not met, the data processing system will retrieve the compatible parameter function in the database to adjust the parameters, thereby realizing the real-time control of defects. The present invention realizes the online monitoring and control of defects during the laser welding process, solves the problem that it is difficult to control defects in real time, and achieves the purpose of intelligent, high-quality and efficient laser welding process.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent laser welding, and particularly relates to a laser adaptive welding method. Background Art

[0002] In the field of aerospace manufacturing, with the urgent demand for material lightweight and structural lightweight, titanium alloy is widely used in the manufacturing of important components such as aircraft fuselage and tail nozzle due to its excellent corrosion resistance, specific strength, and specific modulus. For thin-sheet titanium alloy, the traditional riveting process cannot well meet the lightweight requirement and will reduce the mechanical properties of components. Laser welding has the advantages of high energy density, good penetration, narrow weld seam, high production efficiency, easy automation and flexibility, etc., so it is widely used in the fields of aerospace, engineering manufacturing, etc.

[0003] For the laser beam welding unit technology of complex thin-walled components in aerospace, there is generally a major difficulty at present: due to the use of sheet metal forming and mechanical cutting in the pre-welding manufacturing method, the straightness of the edge area to be welded is extremely poor, resulting in the unevenness of the gap between the welded parts after assembly not meeting the requirements. In order to make up for the defects of uneven or too large gaps, it is usually necessary to manually measure the gaps and mark them in sections, and use different welding techniques and specifications according to different gaps, but this leads to a reduction in production efficiency, a sharp increase in the number of weld joints, the destruction of weld integrity, and an increase in the defect rate. Welding defects are the most influential factors in the laser welding process. Macroscopically, they include incomplete penetration, welding leakage, etc. Reducing or suppressing the generation of welding defects is the most effective and fundamental method to improve weld quality and component quality. However, in the actual welding process, the welding defects can only be detected and repaired after welding is completed, and it is impossible to achieve real-time monitoring and control of welding defects during the welding process, resulting in an increase in production costs and a reduction in production efficiency. Summary of the Invention

[0004] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention aims to propose a laser adaptive welding method, which obtains defect variables by real-time monitoring of the macroscopic defects of the weld seam during the welding process, and then adjusts the process parameters in real time through a parameter-defect database, and finally achieves the purpose of online monitoring and control of defects during the welding process while ensuring the integrity of the weld seam.

[0005] In order to achieve the above purpose, the specific technical solution of the present invention is as follows:

[0006] A laser adaptive welding method for realizing real-time monitoring and control of defects during the laser welding process of workpieces with uneven gaps, comprising the following steps:

[0007] 1 Parameter-defect matching: Establish the laser power L P, the functional relationships of four parameter variables, namely laser power L, welding speed V, defocus amount F, and weld gap G, are established, and a parameter function P is calculated; the functional relationships of two defect variables, namely penetration depth N and welding leakage state L, are established, and a defect function S is calculated. The parameter function P and the defect function S are matched to form a highly adaptable parameter-defect database;

[0008] 2 Initial plan output: Before the formal welding starts, a laser scanner is used to identify the welding path, the initial weld gap G0 is collected, and it is fed back to the data processing system. The data processing system calculates the initial parameter function P0 based on the functional relationships of the four parameter variables, namely laser power L P , welding speed V, defocus amount F, and weld gap G, to preliminarily formulate the process plan;

[0009] 3 On-line defect monitoring: During the welding process, the surface morphology of the weld is scanned and monitored in real time, and the weld defects are monitored in real time through an X-ray flaw detector. The defect variables, namely penetration depth N and welding leakage state L, are associated with the data processing system in real time. The data processing system calculates the defect variables based on the functional relationships of the two defect variables, namely penetration depth N and welding leakage state L, and calculates the real-time defect function S T ;

[0010] 4 Real-time parameter adjustment: The data processing system compares and determines the real-time defect function S T and the real-time parameter function P T . If 0.9P T ≤ S T ≤ 1.1P T , the welding state meets the process requirements and no parameter adjustment is required; if S T > 1.1P T or S T < 0.9P T , the welding state cannot meet the process requirements. The data processing system retrieves the compensation parameter function P1 adapted to the current defect function S T from the parameter-defect database to adjust the parameters. The adjusted parameter function P T = P0 + P1, so as to achieve real-time control of defects during the laser welding process.

[0011] The weld gap G changes randomly and unevenly within the range of 0 - 0.4 mm.

[0012] The parameter-defect database conducts laser welding tests on test plates with unevenly changing weld gaps G, establishes a matching model of laser power L P , welding speed V, defocus amount F and weld gap G, and calculates a parameter function P; then monitors the defects generated during the welding process, and includes the penetration depth N PIntegrate the defect variables in the welding leakage state L into a defect function S, and associate and match it with the parameter function P to establish a parameter-defect database.

[0013] The parameter function P and the laser power L P , the welding speed V, the defocus amount F, and the weld gap G satisfy:

[0014]

[0015] where, dx represents any welding segment in the welding process, and the laser power L P , the welding speed V, the defocus amount F, and the weld gap G can all be directly or indirectly expressed as functions of the position x.

[0016] The relationship between the defect function S and the penetration depth N and the welding leakage state L satisfies:

[0017] S-(2N+L)

[0018] where, the value of L is 1 when there is no welding leakage, and the value of L is 0.5 when there is welding leakage.

[0019] The beneficial technical effects brought by the present invention are as follows: Aiming at a series of welding problems caused by uneven gaps in the actual laser welding process of thin-walled titanium alloys, including the destruction of weld integrity and the increase in defect rate, and only being able to detect and repair welding defects after welding is completed, and being unable to achieve real-time monitoring and control of welding defects during the welding process, a laser adaptive welding method is proposed. This method monitors the weld defects in real time during the welding process, obtains defect variables, and then adjusts the process parameters in real time through the parameter-defect database to achieve the purpose of online monitoring and control of defects during the welding process while ensuring weld integrity. According to the real-time feedback parameter variables and defect variables, the data processing system judges the real-time parameter function P T and the defect function S T . If the requirements are not met, the data processing system will retrieve the appropriate parameter function in the database to adjust the parameters, so as to achieve real-time control of defects. The present invention realizes online monitoring and control of defects during the laser welding process, ensures weld integrity, solves the problem that defects are difficult to control in real time, and achieves the purpose of intelligent, high-quality, and efficient laser welding process.

[0020] The following further illustrates the present system in conjunction with the drawings and embodiments. Description of the Drawings

[0021] Figure 1 is the flowchart of the laser adaptive welding method described in the present invention.

[0022] Figure 2This is the flowchart of the method for establishing the parameter-defect database of the present invention.

[0023] Figure 3 This is the schematic diagram of the laser adaptive welding of the present invention.

[0024] Explanation of the numbers in the figure: 1 Laser scanner, 2 High-speed camera, 3 X-ray flaw detector, 4 Laser head, 5 Laser beam, 6 Shielding gas nozzle, 7 Weldment, 8 Weld seam. Detailed implementation manners

[0025] The present invention will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention rather than all structures are shown in the drawings.

[0026] Referring to Figure 1 as shown, the present invention is a laser adaptive welding method, which mainly includes four major steps: parameter-defect matching, initial scheme output, online defect monitoring, and real-time parameter adjustment;

[0027] Referring to Figure 1 、 Figure 3 as shown, before the formal welding starts, the laser scanner 1 is used to identify the welding path, collect the weld gap G, and feed it back to the data processing system. The data processing system calculates and obtains the initial parameter function P0 to achieve the preliminary formulation of the process plan; the laser welding equipment is turned on to make the laser head 4 emit the laser beam 5. The shielding gas nozzle 6 is fixed to the laser head 4 by mechanical fastening. The shielding gas nozzle 6 is connected to an inert gas, and the inert gas is introduced into the laser beam 5 during welding to achieve the anti-oxidation protection of the laser weld seam 8 during welding; then laser welding is carried out. During the welding process, the high-speed camera 2 is used to monitor the morphology of the weld seam 8 in real time, and the X-ray flaw detector 3 is used to monitor the weld defects in real time. And these defect variables will be fed back to the data processing system in real time. The data processing system calculates the defect variables to obtain the real-time defect function S T ; the data processing system compares and determines the real-time defect function S T and the real-time parameter function P T . If 0.9P T ≤S T ≤1.1P T , the welding state is good, and no parameter adjustment is required, and the process continues to be welded; if S T >1.1P T or S T <0.9P T , the welding state is poor, and the data processing system will retrieve the parameter-defect database for the current defect function S TThe adapted compensation parameter function P1 is used to adjust the parameters. The adjusted parameter function P T = P0 + P1. Then, the subsequent welding is carried out with the adjusted parameter function P T In this way, the real-time control of defects during the laser welding process is achieved through such cycling. When the entire welding process meets the requirements, the welding ends.

[0028] Refer to Figure 2 As shown, the parameter-defect database is established by conducting laser welding tests on test plates with unevenly changing weld gaps G, collecting and organizing the test results, establishing a matching model for laser power L P , welding speed V, defocus amount F and weld gap G, and integrating them into a parameter function P. Then, the defects generated during the welding process are monitored, and the penetration depth N and welding leakage state L are integrated into a defect function S. Continuing to explore the relationship between parameter variables such as laser power L P , welding speed V, defocus amount F and defect variables such as penetration depth N and welding leakage state L to obtain the control law. Finally, the parameter function P and the defect function S are associated and matched to establish a highly adapted parameter-defect database.

[0029] Taking a laser adaptive method as an example, the complete process used in the present invention is described below.

[0030] First, 400 groups of laser welding tests are carried out on 1.0 mm thick TC4 titanium alloy thin plates. Among them, 80 groups of laser welding tests are carried out for each of the five weld gaps of 0 mm, 0.1 mm, 0.2 mm, 0.3 mm, and 0.4 mm. According to the test results, the functional relationships of parameter variables such as laser power L P , welding speed V, defocus amount F and weld gap G are established and integrated into a parameter function P,

[0031]

[0032] The functional relationships of defect variables such as penetration depth N and welding leakage state L are established and integrated into a defect function S,

[0033] S = (2N + L)

[0034] And the parameter function P and the defect function S are matched to form a highly adapted parameter-defect database.

[0035] Before the formal welding starts, a laser scanner is used to identify the welding path of the workpiece to be welded 7, and the initial weld gap G0 is collected as 0.08 mm and fed back to the data processing system. The data processing system calculates and obtains the initial parameter function P0 = 2.92 to achieve the preliminary formulation of the process plan.

[0036] Then, during the welding process, the surface morphology of the weld seam is monitored in real time by a high-speed camera, and the defects of the weld seam 8 are monitored in real time by an X-ray flaw detector 3. The data processing system calculates the defect variables to obtain the real-time defect function S T . After 0.001 s of starting welding, 0.9P0 < S T0.001 = 3 < 1.1P0, the welding state is good, and no parameter adjustment is required. Keep this process and continue welding; when 12 s after starting welding, the weld gap G 12 is 0.23 mm. At this time, S T12 = 2.5 < 0.9P0, the welding state is poor. The data processing system retrieves the compensation parameter P1 = -0.16, and the compensated real-time parameter function P T12 = 2.76. At this time, 0.9P T12 < S T12 = 2.5 < 1.1P T12 , the welding state is good, and continue welding; thereafter, S T is all 3, satisfying 0.9P T < ST < 1.1P T , and keep this parameter until the welding is completed.

[0037] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manners and application scopes. The content of this specification should not be construed as a limitation of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A laser adaptive welding method for realizing real-time monitoring and control of defects during the laser welding process of workpieces with uneven gaps, characterized in that It includes the following steps: 1-1 Parameter - Defect Matching: Establish the functional relationship of four parameter variables, namely laser power L P , welding speed V, defocus amount F, and weld gap G, and calculate a parameter function P; establish the functional relationship of two defect variables, namely penetration depth N and welding leakage state L, and calculate a defect function S. Match the parameter function P and the defect function S to form a highly adaptable parameter - defect database; 1-2 Initial plan output: Before the formal welding starts, use a laser scanner to identify the welding path, collect the initial weld gap G0, and feedback it to the data processing system. The data processing system calculates the initial parameter function P0 based on the functional relationship of the four parameter variables of laser power L P , welding speed V, defocus amount F, and weld gap G, and realizes the preliminary formulation of the process plan; 1-3 Online defect monitoring: During the welding process, the surface morphology of the weld seam is scanned and monitored in real time. The weld seam defects are monitored in real time through an X-ray flaw detector, and the defect variables, the penetration depth N and the welding leakage state L, are real-time associated with the data processing system. The data processing system calculates the defect variables according to the functional relationship between the two defect variables, the penetration depth N and the welding leakage state L, and calculates the real-time defect function S T ; 1-4 Real-time parameter adjustment: The data processing system compares and determines the real-time defect function S T and the real-time parameter function P T If 0.9P T ≤S T ≤1.1P T , the welding state meets the process requirements and no parameter adjustment is required; if S T >1.1P T or S T <0.9P T , the welding state does not meet the process requirements. The data processing system retrieves the compensation parameter function P1 adapted to the current defect function S T from the parameter-defect database and adjusts the parameters. The adjusted parameter function P T = P0 + P1, thereby achieving real-time control of defects during the laser welding process.

2. The laser adaptive welding method according to claim 1, characterized in that The weld gap G changes randomly and unevenly within the range of 0 - 0.4 mm.

3. The laser adaptive welding method according to claim 1, characterized in that The parameter-defect database conducts laser welding tests on test plates with unevenly varying weld gaps G, establishes a matching model for laser power L P , welding speed V, defocus amount F, and weld gap G, and calculates a parameter function P; then monitors the defects generated during the welding process, and integrates defect variables including penetration depth N P , weld leakage state L into a defect function S, and correlates and matches it with the parameter function P to establish a parameter-defect database.

4. The laser adaptive welding method according to claim 1, characterized in that The parameter function P and the laser power L P , the welding speed V, the defocus amount F, and the weld gap G satisfy: wherein, dx represents any welding segment during the welding process, and the laser power L P , welding speed V, defocus amount F, and weld gap G can all be directly or indirectly expressed as functions of the position x.

5. The laser adaptive welding method according to claim 1, characterized in that The relationship between the defect function S, the penetration depth N, and the welding leakage state L satisfies: s = (2N + L) Wherein, when there is no welding leakage, the value of L is 1, and when there is welding leakage, the value of L is 0.5.

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