A molten pool temperature regulation method with programmable control of pulsed laser energy and distribution

Abstract

The application provides a molten pool temperature regulation method with programmable control of pulse laser energy and distribution, comprising: obtaining thicknesses of different positions of a material to be worked, dividing a laser working area on the material to be worked into different temperature regions according to a pulse laser scanning path based on characteristics of welding heat input of the material to be worked varying with different thicknesses; and adjusting pulse laser waveform size and landing point distribution of the pulse laser in the different temperature regions based on the different temperature regions to control a distribution region of pulse laser energy. The application solves the problems of low welding quality and use performance of a welded part and small applicable working condition range caused by the fact that the prior art cannot achieve precise regulation of molten pool temperature for complex metal welding.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a method for regulating the temperature of a molten pool by programmable control of pulsed laser energy and distribution. Background Technology

[0002] The demands for performance, precision, and turnaround time of dense metal parts in key technology fields such as aerospace and defense are becoming increasingly stringent, leading to the rapid emergence of precision welding, additive manufacturing, and repair / remanufacturing technologies using laser beams as heat sources. Modern high-end manufacturing is accelerating its shift from mass-production, low-cost, extensive manufacturing to small-batch, customized, high-standard, shape- and property-controlled precision flexible manufacturing. The impact and heating of the molten pool surface by conventional lasers directly affects the final weld morphology and quality, inevitably leading to unintended consequences such as porosity, deformation, grain coarsening, and welding spatter.

[0003] Traditional laser linear welding is prone to plasma shielding and low-temperature alloy element burn-off, leading to problems such as keyhole instability and reduced joint strength, severely affecting welding quality and the performance of the weldment. Ultimately, this stems from the thermal distribution of the overall molten pool temperature field. Oscillating (oscillating scanning) beam laser welding and dual-beam welding methods can alter the scanning trajectory to cause the beam to oscillate, reducing the assembly precision of the workpiece, increasing the molten pool width, decreasing the temperature gradient, and extending the molten pool stabilization time.

[0004] While it demonstrates good results for conventional, simple laser welding / additive manufacturing / repair / remanufacturing, its optimization effect on complex, variable-thickness metal / non-metal welding, dissimilar material joining, additive manufacturing shape control, interlayer heat accumulation control, crack repair with unequal gaps, and repair / remanufacturing of complex, irregularly shaped parts is not significant. In summary, existing technologies suffer from the problems of inability to precisely control the molten pool temperature for complex metal welding, leading to poor weld quality and workpiece performance, and a limited range of applicable operating conditions. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a method for controlling the molten pool temperature through programmable control of pulsed laser energy and distribution. This invention solves the problems in existing technologies, such as the inability to achieve precise control of the molten pool temperature for complex metal welding, leading to poor welding quality and workpiece performance, and a limited range of applicable working conditions.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A method for controlling the temperature of a molten pool by programmable control of pulsed laser energy and distribution includes:

[0008] The thickness of the material to be worked at different locations is obtained. Based on the characteristics of the welding heat input of the material to be worked changing with different thicknesses, the laser working area on the material to be worked is divided into different temperature regions according to the pulsed laser scanning path.

[0009] Based on the different temperature regions, the pulsed laser waveform size and the distribution of the pulsed laser's landing point in the different temperature regions are adjusted to control the distribution area of ​​the pulsed laser energy.

[0010] Preferably, the pulsed laser frequency range is 10-10000Hz, and the pulsed laser power range is 1-20000W.

[0011] Preferably, the material to be worked comprises:

[0012] Variable thickness structural metal / non-metal welding, dissimilar material connection; additive manufacturing shape control, interlayer heat accumulation control; crack repair with unequal gaps, repair / remanufacturing process for complex and irregular morphological parts.

[0013] Preferably, the pulsed laser scanning path method includes:

[0014] Horizontal, zigzag, circular, elliptical, triangular, and rectangular scan paths.

[0015] Preferably, obtaining the thickness of the material at different locations includes:

[0016] The outline of the material to be worked is obtained using a laser scanner;

[0017] The contour line or three-dimensional model of the welding position is calculated based on the contour of the material to be worked.

[0018] The thickness of the material to be worked at different locations is obtained by using the contour line or three-dimensional model of the welding position.

[0019] Preferably, adjusting the size of a single pulse laser waveform includes:

[0020] The size of the pulsed laser waveform is adjusted based on SPR.

[0021] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] This invention provides a method for regulating the temperature of a molten pool by programmable control of pulsed laser energy and distribution. By adjusting the pulsed laser, this invention performs real-time programming control of the pulsed laser based on the thermal input thickness characteristics of the work material under test, effectively improving welding quality and weldment performance, and is applicable to various working conditions. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart of a method for regulating molten pool temperature by programmable control of pulsed laser energy and distribution is provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of a precision welding system with programmable control of pulsed laser energy and distribution provided in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of precise temperature control of the molten pool provided in an embodiment of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The purpose of this invention is to provide a method for regulating the temperature of the molten pool by programmable control of pulsed laser energy and distribution. This invention solves the problems in the prior art where the molten pool temperature cannot be precisely controlled for welding complex metals, resulting in poor welding quality and workpiece performance, as well as the problem of limited applicable working conditions.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 As shown, the present invention provides a method for regulating the temperature of a molten pool by programmable control of pulsed laser energy and distribution, comprising:

[0031] Step 100: Obtain the thickness of the material to be worked at different locations. Based on the characteristics of the welding heat input of the material to be worked changing with different thicknesses, divide the laser working area on the material to be worked into different temperature regions according to the pulsed laser scanning path.

[0032] Step 200: Based on the different temperature regions, adjust the pulsed laser waveform size and the distribution of the pulsed laser's landing point in the different temperature regions to control the distribution area of ​​the pulsed laser energy.

[0033] Specifically, before dividing the laser working area on the work material into different temperature zones according to the pulsed laser scanning path, the spatial position of the laser and the work material to be tested is adjusted so that the laser spot is focused or defocused according to the process requirements to irradiate the required welding starting point (without turning on the laser).

[0034] Specifically, the pulsed laser frequency range is 10-10000Hz, and the pulsed laser power range is 1-20000W. Adjusting the pulsed laser waveform includes adjusting the pulsed laser power and duty cycle.

[0035] By inputting the control ideas / programs for pulsed laser energy and distribution into the internal controller or external laser controller of the laser, precise "programmable control" of pulsed laser energy and distribution can be achieved. This enables precise control of the heat and force input to the molten pool, allowing for precise control of the temperature and force fields of the molten pool during the forming process, as well as precise control of the solidification morphology, so that the energy input can adapt to real-time changes in thickness.

[0036] The pulsed laser can also be a continuous laser. By controlling the average laser power of different scanning segments, precise programmable control of the molten pool temperature field can be achieved.

[0037] Furthermore, the materials to be worked include:

[0038] Variable thickness structural metal / non-metal welding, dissimilar material connection; additive manufacturing shape control, interlayer heat accumulation control; crack repair with unequal gaps, repair / remanufacturing process for complex and irregular morphological parts.

[0039] Specifically, the pulsed laser scanning path method includes:

[0040] Horizontal, zigzag, circular, elliptical, triangular, and rectangular scan paths.

[0041] Specifically, obtaining the thickness of the material at different locations includes:

[0042] The outline of the material to be worked is obtained using a laser scanner;

[0043] The contour line or three-dimensional model of the welding position is calculated based on the contour of the material to be worked.

[0044] The thickness of the material to be worked at different locations is obtained by using the contour line or three-dimensional model of the welding position.

[0045] Specifically, adjusting the size of a single laser pulse includes:

[0046] The size of the pulsed laser waveform is adjusted based on SPR.

[0047] This embodiment also discloses a schematic diagram of a precision welding system with programmable control of pulsed laser energy and distribution, such as... Figure 2 As shown, 1, 2, and 3 represent the working paths of the computer system, the 3D laser scanner, and the laser welding system. After fixing the spatial positions of all equipment, the computer control system sends a switch signal to the 3D laser scanner. The 3D laser scanner scans the contour of the variable thickness welding plate and calculates the contour line / 3D model of the welding position, which is then fed back to the computer system.

[0048] The computer system calculates the thickness of the plate at different locations in the variable thickness welded plate based on the contour line / 3D model, and controls different single-pulse laser energy and multi-pulse laser distribution according to different thicknesses.

[0049] Specific controls, such as Figure 3 As shown, single-pulse laser energy control is as follows: Figure 3 As shown, (a1) is a schematic diagram of traditional continuous laser welding, (a2) is a schematic diagram of pulsed laser welding, and (a3) ​​is a schematic diagram of single laser energy control. On the one hand, SPR (edge ​​slope) is added to the traditional square wave to make the energy controllability of a single pulse stronger. On the other hand, by increasing or decreasing the average power of a single laser and using symbols such as P, P-, P+, and P0 to represent it, the energy of a single pulse can be controlled more precisely.

[0050] (b1) is a schematic diagram of the traditional continuous laser scanning welding process; (b2) is a schematic diagram of the pulsed laser scanning welding process; (b3) is a schematic diagram of the control method when the pulse frequency is below 50Hz. Specifically, depending on the thickness of the plate, the energy distribution can be controlled by changing the landing points of P, P-, P+, and P0, that is, by changing the energy distribution of each laser pulse on the scanning path. When the pulsed laser frequency is greater than 50Hz, the laser adjustment time is shorter, and the average power of different segments can be controlled by the method shown in (b4). By combining the above two control methods, precise control of the molten pool temperature field during the welding process can be achieved, and control can be performed as needed. The control method and ideas are then used to generate corresponding programs. Among them, EXTPWR ANALOG(EA): switch to analog interface;

[0051] This indicates power below the average laser power. The average power of the laser; Higher than the average laser power; ○ indicates no laser pulse irradiation; the difference between the average laser power and higher than the average laser power charts lies in their size.

[0052] The computer control system generates a control program and sends it to the laser welding system. The laser welding system then transmits the scanning trajectory name to the Y and X axis galvanometers and transmits the pulsed laser energy control command to the laser welding head via optical fiber. This forms a scanning laser beam with precisely controllable pulsed laser energy and distribution, enabling precise on-demand adjustment of the molten pool temperature field and allowing the energy input to adapt to real-time changes in thickness.

[0053] To address the application needs of precision and efficient welding and additive manufacturing, this invention discloses a method for precise control of molten pool temperature through programmable control of pulsed laser energy and distribution. The principle is as follows: First, an edge slope (SPR) is added to the control of individual laser pulse energy (LE), with the magnitudes of "A" and "B" representing the degree of higher or lower power than the average power, allowing for more precise adjustment of the individual laser pulse energy. Second, "C" represents no laser pulse, and the distribution of laser pulse energy (PD) can be precisely controlled by changing the distribution of "ABC". The individual laser energy and multiple pulse distributions are programmed according to actual conditions according to "SPR+SPT+WLS+ABC", termed "programmable digital control". This precise "programmable control" of pulsed laser energy and distribution can accurately regulate the thermal and force input to the molten pool, adapting the energy input to real-time changes in thickness, and achieving precise control of the molten pool's thermal and force selective zones, mass transfer process, and solidification morphology during the forming process.

[0054] The beneficial effects of this invention are as follows:

[0055] (1) Precise control of the molten pool temperature can reduce the heat input to the substrate during the process, and make the energy input adapt to the real-time changes of the plate thickness / crack size / additive shape, etc., which can effectively control the serious heat accumulation and molten pool overheating; reduce the assembly accuracy during welding, effectively control deformation, and improve energy utilization.

[0056] (2) This control method can be widely applied to various working conditions, including but not limited to: welding of metal / non-metal structures with varying thickness, joining of dissimilar materials; shape control in additive manufacturing, control of interlayer heat accumulation; repair of cracks with unequal gaps, and repair / remanufacturing of parts with complex and irregular shapes.

[0057] (3) Although a lot of process parameters need to be adjusted in the early stage, the overall control principle is simple and the method is easy to implement.

[0058] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0059] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for regulating the temperature of a molten pool by programmable control of pulsed laser energy and distribution, characterized in that, include: The thickness of the material to be worked at different locations is obtained. Based on the characteristics of the welding heat input of the material to be worked changing with different thicknesses, the laser working area on the material to be worked is divided into different temperature regions according to the pulsed laser scanning path. Based on the different temperature regions, the pulsed laser waveform size and the distribution of the pulsed laser's landing point in the different temperature regions are adjusted to control the distribution area of ​​the pulsed laser energy. The process of obtaining the thickness of the material at different locations includes: The outline of the material to be worked is obtained using a laser scanner; The contour line or three-dimensional model of the welding position is calculated based on the contour of the material to be worked. The thickness of the material to be worked at different locations is obtained by using the contour line or three-dimensional model of the welding position; Adjusting the waveform size of a single laser pulse includes: The size of the pulsed laser waveform is adjusted based on the edge slope; By adding an edge slope to the control of single-pulse laser energy and using the magnitudes of "A" and "B" to represent the degree of power above or below the average power, the energy of a single pulse laser can be adjusted more precisely. Secondly, "C" represents no laser pulse, and the distribution of laser pulse energy can be precisely controlled by changing the distribution of "ABC".

2. The method for controlling the temperature of a molten pool by programmable control of pulsed laser energy and distribution according to claim 1, characterized in that, The pulsed laser frequency range is 10-10000Hz, and the pulsed laser power range is 1-20000W.

3. The method for controlling the temperature of a molten pool by programmable control of pulsed laser energy and distribution according to claim 1, characterized in that, The materials to be worked include: Variable thickness structural metal / non-metal welding, dissimilar material connection; additive manufacturing shape control, interlayer heat accumulation control; crack repair with unequal gaps, repair / remanufacturing process for complex and irregular morphological parts.

4. The method for controlling the temperature of a molten pool by programmable control of pulsed laser energy and distribution according to claim 1, characterized in that, The pulsed laser scanning path method includes: Horizontal, zigzag, circular, elliptical, triangular, and rectangular scan paths.

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