Local area inert gas protection auxiliary vacuum environment laser welding device and method

Abstract

The invention discloses a local area inert gas protection auxiliary vacuum environment laser welding device and method, belongs to the technical field of laser welding, and aims to solve the problem that the laser welding quality of an existing easily-oxidized material is insufficient. A local area inert gas protection auxiliary vacuum environment laser welding device comprises a monitoring and feedback control system, a gas precise control system and a vacuum cavity, a gas nozzle, a workbench and a laser welding head are all arranged in the vacuum cavity, the laser welding head is located above the workbench, the gas nozzle is arranged on one side of the laser welding head, and the gas nozzle is arranged on the other side of the laser welding head. The vacuum pumping system is connected with the vacuum cavity, the laser welding head is connected with the laser welding machine, the gas precise control system controls the flow and the mixing proportion of inert gas jetted by the gas nozzle, and the monitoring and feedback control system monitors the temperature, the vacuum degree, the oxygen content and the plasma state of a welding area. And data are fed back to carry out closed-loop regulation control on various welding parameters. And the welding quality is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser welding, and particularly relates to a local area inert gas protection assisted vacuum environment laser welding device and method, which are particularly suitable for high-quality laser welding of easily oxidized materials such as titanium alloy, zirconium alloy, hafnium alloy, tantalum alloy, magnesium alloy, aluminum alloy, nickel-based superalloy, cobalt-based superalloy, and iron-nickel-based superalloy. Background Technique

[0002] As an advanced material connection process, laser welding technology has outstanding advantages such as high energy density, fast welding speed, small heat input, small weld deformation, and high automation degree. It is widely used in many industrial fields such as aerospace, shipbuilding, automotive industry, construction machinery, electronic industry, and medical devices, and plays an important role especially in the field of high-end equipment manufacturing.

[0003] However, during the laser welding of easily oxidized metal materials such as titanium alloy, aluminum alloy, magnesium alloy, stainless steel, copper alloy, nickel-based superalloy, etc., the high-temperature molten pool in the welding area is extremely easy to react strongly with oxygen and other active gases in the environment, generating defects such as oxide inclusions, pores, and even cracks, seriously reducing the mechanical properties and service stability of the weld, and restricting the further popularization and application of laser welding technology.

[0004] In the prior art, to solve the welding protection problem of easily oxidized metals, the following three typical technical means are usually adopted:

[0005] (1) Atmospheric pressure inert gas protection welding technology

[0006] The conventional atmospheric pressure protection method is to spray a large amount of inert gas (such as Ar, He, N2 or their mixed gas) in the welding area for protection, in order to reduce the oxygen content in the welding area. However, this method has the following deficiencies:

[0007] ① Under atmospheric pressure environment, oxygen in the air around the welding area is easy to enter the molten pool through turbulence and diffusion, and the inert gas protection effect is limited;

[0008] ② A large amount of high-purity inert gas needs to be used, and the welding production cost is relatively high;

[0009] ③ When the gas protection area is unstable or uneven, it is difficult to guarantee the weld quality, and oxidation discoloration, pores or inclusion defects are easy to occur.

[0010] (2) Overall vacuum laser welding technology

[0011] The overall vacuum laser welding places the welding workpiece in a vacuum chamber, and reduces the oxygen content by pumping vacuum to inhibit the oxidation reaction. This method can effectively avoid the oxidation of the welding molten pool, and the weld quality is significantly improved. However, this technology still has the following limitations:

[0012] ① The overall vacuum environment has high requirements for equipment, and the size of the vacuum chamber is limited, making it difficult to meet the welding needs of larger or complex structural parts.

[0013] ② The vacuum pumping process takes a long time and the production efficiency is relatively low.

[0014] ③ Under medium and low vacuum conditions (such as 10-1 Pa to 103 Pa), the plasma shielding effect will still occur during laser welding, interfering with the effective input of laser energy, resulting in a decrease in the weld depth-width ratio and a reduction in welding stability.

[0015] (III) Local vacuum welding technology

[0016] In response to the above problems, some studies have also tried to use a local vacuum cover to protect the welding area. This method can greatly reduce the volume of the protected area and has certain advantages. However, the current local protection technology still has the following problems:

[0017] ① It is difficult to seal the local vacuum cover, and it is difficult to reach the required vacuum degree, and the oxygen content control during the welding process is unstable.

[0018] ② There is a lack of effective real-time monitoring and feedback control means, and it is difficult to achieve precise control of the oxygen content in the welding area.

[0019] Therefore, the existing technology cannot simultaneously meet multiple requirements such as a low-oxygen environment, suppression of the plasma shielding effect, economy, and real-time precise control of the oxygen content in the welding area, which has become an important bottleneck problem restricting the development of high-quality laser welding technology for easily oxidized metal materials.

[0020] To sum up, at the present stage, there is an urgent need to develop a new type of laser welding protection technology solution that can not only effectively reduce the oxygen content in the welding area, but also significantly suppress the plasma shielding effect during laser welding, and can precisely control the welding environment parameters in real time, taking into account production efficiency and economy while ensuring welding quality, so as to further promote the wide application of laser welding technology in the field of easily oxidized metal materials. Summary of the Invention

[0021] The present invention aims to provide a local area inert gas protection-assisted vacuum environment laser welding device and method, which realizes precise control of the oxygen content in the welding area and suppresses the plasma shielding effect by combining micro-area dynamic inert gas curtain protection in a high-vacuum background environment, thereby significantly improving the laser welding quality of easily oxidized materials. The technical solutions adopted by the present invention are as follows:

[0022] Local area inert gas protection assisted vacuum environment laser welding device, including a monitoring and feedback control system, a gas precision control system and a vacuum chamber. A gas nozzle, a workbench and a laser welding head are all arranged in the vacuum chamber. The laser welding head is located above the workbench, and the gas nozzle is arranged on one side of the laser welding head. A vacuum pumping system is connected to the vacuum chamber, and the laser welding head is connected to a laser welder;

[0023] The gas precision control system includes a gas flow controller, a gas mixing ratio control device and a gas flow feedback sensor. The inlet of the gas mixing ratio control device is respectively connected to an argon gas source and a helium gas source. The outlet of the gas mixing ratio control device is connected to the gas nozzle through the gas flow controller. The gas flow feedback sensor is arranged on the pipeline between the gas flow controller and the gas nozzle. The gas flow feedback sensor monitors the flow rate of the flowing gas and feeds back data to PID regulate the gas flow controller;

[0024] The monitoring and feedback control system includes a closed-loop feedback control unit, a laser power monitoring unit, a plasma monitoring unit, an oxygen content monitoring unit and a temperature and pressure monitoring unit. The vacuum pumping system, the laser welder, the gas flow controller, the gas mixing ratio control device, the gas flow feedback sensor, the laser power monitoring unit, the plasma monitoring unit, the oxygen content monitoring unit and the temperature and pressure monitoring unit are respectively electrically connected to the closed-loop feedback control unit. The oxygen content monitoring unit, the temperature and pressure monitoring unit and the plasma monitoring unit are all arranged in the welding area.

[0025] Further, the gas nozzle is a sleeve-shaped member. The outlet end of the gas nozzle is provided with a single circular jet orifice, and the diameter of the circular jet orifice is equal to the through diameter of the gas nozzle. Or, the outlet end of the gas nozzle is provided with a head, and a plurality of jet holes are arranged on the head.

[0026] Further, the vacuum pumping system includes at least one stage of molecular pump or a composite vacuum pump set.

[0027] Further, the workpiece is a component made of titanium alloy, aluminum alloy, magnesium alloy, stainless steel, copper alloy, nickel-based alloy or other easily oxidized metal materials.

[0028] Further, the workpiece is a sheet, a pipe, a thin-walled structural member or a special-shaped member.

[0029] The present invention also provides a local area inert gas protection assisted vacuum environment laser welding method realized by using the above local area inert gas protection assisted vacuum environment laser welding device, including the following steps:

[0030] Step 1: Place the workpiece on the workbench, with the laser welding head facing the weld seam to be welded on the workpiece. The distance between the laser welding head and the weld seam to be welded is 1 - 5 mm, and the gas outlet end of the gas nozzle faces the weld seam to be welded. The distance between the gas outlet end of the gas nozzle and the weld seam to be welded is 5 - 20 mm. Use the vacuum pumping system to pump the vacuum degree in the vacuum cavity to less than or equal to 10 -1 Pa;

[0031] Step 2: Start the gas precision control system to make the inert mixed gas ejected from the gas nozzle form a dynamic inert protective gas curtain in the welding area, and control the oxygen content in the welding area to be less than or equal to 50 ppm;

[0032] Step 3: Start the laser welder and apply a laser beam to the workpiece through the laser welding head for laser welding;

[0033] Step 4: Use the monitoring and feedback control system to monitor the oxygen content, temperature, pressure, and plasma state in the welding area in real time, and perform closed-loop feedback adjustment according to the monitoring results.

[0034] Furthermore, the welding process is continuous welding, spot welding, seam welding, or dissimilar material welding.

[0035] Furthermore, the inert protective gas curtain in Step 2 is formed by an inert mixed gas. The inert mixed gas is composed of argon and helium, and the mixing ratio range of argon and helium is 5:1 - 1:5. The injection flow rate range of the inert mixed gas is 0.5 m / s - 5 m / s.

[0036] Furthermore, the closed-loop feedback control in Step 4 is specifically as follows:

[0037] When the oxygen content in the welding area is greater than 50 ppm, the oxygen content monitoring unit sends a signal, and the closed-loop feedback control unit increases the flow rate of the gas flow controller or the gas mixing ratio;

[0038] When it is monitored that the shielding effect of the plasma in the welding area is enhanced to the critical electron density of 1×10 20 m -3 , the plasma monitoring unit sends a signal, and the closed-loop feedback control unit increases the power of the laser welder or the flow rate of the flow controller to weaken the plasma shielding effect;

[0039] When the vacuum degree in the welding area is greater than 10 -1 , the temperature and pressure monitoring unit sends a signal, and the closed-loop feedback control unit increases the power of the vacuum pumping system;

[0040] When the temperature in the welding area is higher than the boiling point temperature of the workpiece, reduce the power or increase the flow rate of the protective gas to restore the welding process to the optimized state.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] 1. The vacuum pumping system is used to pump the vacuum chamber to form a low-oxygen environment with a vacuum degree less than or equal to 10 - 1 Pa, which can effectively eliminate the plasma shielding effect and significantly improve the effective utilization rate of laser energy.

[0043] 2. By spraying an inert mixed gas on the welding area to form a dynamic inert protective gas curtain, precise control of the oxygen content in the welding area less than or equal to 50 ppm is achieved, greatly improving the welding quality and solving the problem of welding protection for easily oxidized metals.

[0044] 3. Compared with the protection methods of overall vacuum or overall inert gas, the present invention can significantly reduce the consumption of inert gas and the energy consumption of vacuum pumping, and reduce the welding cost.

[0045] 4. Precise control and intelligent optimization of the welding process are achieved through the monitoring and feedback control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0047] Figure 2 It is a schematic diagram of the structure of the gas nozzle;

[0048] Figure 3 It is a monitoring and feedback control flow block diagram of the welding process of the present invention;

[0049] Figure 4 It is a weld appearance diagram of laser welding of 20mm TC4 titanium alloy using inert gas protection in the atmospheric environment;

[0050] Figure 5 It is a cross-sectional weld appearance diagram of laser welding of 20mm TC4 titanium alloy by the device of the present invention;

[0051] Figure 6 It is a surface diagram of the weld of tantalum tungsten alloy for laser welding in a low vacuum environment (8×10 -2 Pa);

[0052] Figure 7 It is a surface diagram of the weld of tantalum tungsten alloy for laser welding by the device of the present invention.

[0053] In the figure, 100, vacuum chamber; 200, laser welding head; 300, gas nozzle; 400, workpiece; 500, workbench; 600, vacuum pumping system. DETAILED DESCRIPTION OF THE INVENTION

[0054] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be described below through specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0055] The connections mentioned in the present invention are divided into fixed connections and detachable connections. The fixed connection is an inseparable connection, including but not limited to conventional fixed connection methods such as hemming connection, rivet connection, bonding connection, and welding connection. The detachable connection includes but not limited to conventional disassembly methods such as bolt connection, snap connection, pin connection, and hinge connection. When the specific connection method is not clearly defined, it is defaulted that at least one connection method can be found among the existing connection methods to achieve this function, and those skilled in the art can select it according to their needs. For example: welding connection is selected for the fixed connection, and bolt connection is selected for the detachable connection.

[0056] The present invention will be further described in detail below with reference to the accompanying drawings. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments.

[0057] Embodiment 1: As Figure 1 、 Figure 2 shown, a local area inert gas protection assisted vacuum environment laser welding device includes a monitoring and feedback control system, a gas precision control system, and a vacuum chamber 100. A gas nozzle 300, a workbench 500, and a laser welding head 200 are all arranged in the vacuum chamber 100. The laser welding head 200 is located above the workbench 500, and the gas nozzle 300 is arranged on one side of the laser welding head 200. A vacuum pumping system 600 is connected to the vacuum chamber 100, and the laser welding head 200 is connected to a laser welder;

[0058] The gas precision control system includes a gas flow controller, a gas mixing ratio control device, and a gas flow feedback sensor. The inlet of the gas mixing ratio control device is respectively connected to an argon gas source and a helium gas source. The outlet of the gas mixing ratio control device is connected to the gas nozzle 300 through the gas flow controller. The gas flow feedback sensor is arranged on the pipeline between the gas flow controller and the gas nozzle 300. The gas flow feedback sensor monitors the flow rate of the flowing gas and feeds back data to PID regulate the gas flow controller;

[0059] The monitoring and feedback control system includes a closed-loop feedback control unit, a laser power monitoring unit, a plasma monitoring unit, an oxygen content monitoring unit, and a temperature and pressure monitoring unit. The vacuum pumping system 600, the laser welder, the gas flow controller, the gas mixing ratio control device, the gas flow feedback sensor, the laser power monitoring unit, the plasma monitoring unit, the oxygen content monitoring unit, and the temperature and pressure monitoring unit are respectively electrically connected to the closed-loop feedback control unit. A region formed between a 15-mm-wide range on each side of the weld joint to be welded on the workpiece 400 and a circular range with a circumferential radius of 30 mm of the laser welding head 200 is defined as the welding region. The oxygen content monitoring unit, the temperature and pressure monitoring unit, and the plasma monitoring unit are all arranged in the welding region.

[0060] The gas nozzle 300 is a sleeve-shaped member. A single circular jet orifice is provided at the gas outlet end of the gas nozzle 300, and the diameter of the circular jet orifice is equal to the through diameter of the gas nozzle 300. Alternatively, a sealing head is provided at the outlet end of the gas nozzle 300, and a plurality of jet holes are provided on the sealing head.

[0061] The vacuum pumping system 600 includes at least one stage of molecular pump or composite vacuum pump unit.

[0062] The workpiece 400 is a component made of titanium alloy, zirconium alloy, hafnium alloy, tantalum alloy, magnesium alloy, aluminum alloy, nickel-based superalloy, cobalt-based superalloy, or iron-nickel-based superalloy.

[0063] The workpiece 400 is a plate, a pipe, a thin-walled structural member, or a special-shaped member.

[0064] Example 2: As Figures 1 - 7 shown, a local area inert gas protection assisted vacuum environment laser welding method realized by using the local area inert gas protection assisted vacuum environment laser welding device described in Example 1 includes the following steps:

[0065] Step 1: Place the workpiece 400 on the workbench 500, with the laser welding head 200 facing the weld joint to be welded on the workpiece 400. The laser welding head 200 is 1 - 5 mm away from the weld joint to be welded, and the gas outlet end of the gas nozzle 300 faces the weld joint to be welded. The gas outlet end of the gas nozzle 300 is 5 - 20 mm away from the weld joint to be welded. Use the vacuum pumping system 600 to pump the vacuum degree in the vacuum chamber 100 to be less than or equal to 10 -1 Pa;

[0066] Step 2: Start the gas precision control system to make the inert mixed gas ejected from the gas nozzle 300 form a dynamic inert protection gas curtain in the welding region, and control the oxygen content in the welding region to be less than or equal to 50 ppm.

[0067] Step 3: Start the laser welding machine, and apply a laser beam to the workpiece 400 through the laser welding head 200 for laser welding;

[0068] Step 4: Real-time monitor the oxygen content, temperature, pressure, and plasma state in the welding area through the monitoring and feedback control system, and perform closed-loop feedback adjustment according to the monitoring results to ensure the stable progress of the welding process and the optimization of the welding quality.

[0069] The welding process is continuous welding, spot welding, seam welding, or dissimilar material welding.

[0070] The inert protective gas curtain in Step 2 is formed by an inert mixed gas, which is composed of argon and helium. The mixing ratio range of argon and helium is 5:1 to 1:5, and the injection flow rate range of the inert mixed gas is 0.5 m / s to 5 m / s.

[0071] The specific closed-loop feedback control in Step 4 is as follows:

[0072] When the oxygen content in the welding area is greater than 50 ppm, the oxygen content monitoring unit sends a signal, and the closed-loop feedback control unit increases the flow rate of the gas flow controller or the gas mixing ratio;

[0073] When it is monitored that the shielding effect of the plasma in the welding area is enhanced to the critical electron density of 1×10 20 m -3 , the plasma monitoring unit sends a signal, and the closed-loop feedback control unit increases the power of the laser welding machine or the flow rate of the flow controller to weaken the plasma shielding effect;

[0074] When the vacuum degree in the welding area is greater than 10 -1 Pa, the temperature and pressure monitoring unit sends a signal, and the closed-loop feedback control unit increases the power of the vacuum pumping system 600;

[0075] When the temperature in the welding area is higher than the boiling point temperature of the workpiece 400, the welding process is restored to the optimized state by reducing the power or increasing the flow rate of the protective gas.

[0076] The advantages of the present invention are as follows:

[0077] 1. The vacuum pumping system 600 is used to evacuate the vacuum chamber 100 to form a low-oxygen environment with a vacuum degree less than or equal to 10 -1 Pa in the vacuum chamber 100, which can effectively eliminate the plasma shielding effect and significantly improve the effective utilization rate of laser energy.

[0078] 2. By spraying an inert mixed gas on the welding area to form a dynamic inert protective gas curtain, precise control of the oxygen content in the welding area less than or equal to 50 ppm is achieved, greatly improving the welding quality and solving the problem of welding protection for easily oxidizable metals.

[0079] 3. Compared with the protection methods of overall vacuum or overall inert gas, the present invention can significantly reduce the consumption of inert gas and the energy consumption of vacuum pumping, and reduce the welding cost.

[0080] 4. Achieve precise control and intelligent optimization of the welding process through the monitoring and feedback control system.

[0081] Figure 3 The monitoring and feedback control flow chart of the welding process of the present invention is given. The oxygen content in the welding area is monitored in real time through the oxygen content monitoring unit, the temperature and pressure in the welding area are monitored in real time through the temperature and pressure monitoring unit, the power and energy density of the laser output by the laser welding head are monitored in real time through the laser power monitoring unit, and the plasma state generated during the welding process is monitored in real time through the plasma monitoring unit. The data collected by the oxygen content monitoring unit, the temperature and pressure monitoring unit, the laser power monitoring unit, and the plasma monitoring unit are sent to the closed-loop feedback control unit. The closed-loop feedback control unit judges whether the parameters in the welding process are within the preset range and the amount to be adjusted through intelligent algorithms, and adjusts the flow rate, mixing ratio of the inert mixed gas, the power of the laser welder, the welding temperature, the welding vacuum degree, and the plasma through the execution control module of the closed-loop feedback control unit to precisely control the oxygen content in the welding area and achieve the optimization and stability of the welding process state.

[0082] The differences between the present invention and traditional laser welding are further illustrated through the following two application examples:

[0083] 1. Laser welding of titanium alloy plates:

[0084] The specific steps are as follows:

[0085] (1) Take the titanium alloy plate as the workpiece 400, perform surface cleaning and degreasing treatment to ensure the cleanliness of the workpiece surface, and place it on the workbench 500;

[0086] (2) Close the sealing door of the vacuum chamber 100, and pump the vacuum degree in the vacuum chamber 100 to 5×10 -1 Pa through the vacuum pumping system 600 and keep it stable for more than 5 minutes to ensure that the oxygen content in the vacuum environment in the vacuum chamber 100 is extremely low;

[0087] (3) Start the gas precision control system, spray the inert mixed gas towards the welding area at the joint of the workpiece 400 through the gas nozzle 300. The inert mixed gas is composed of high-purity argon and helium with a volume ratio of 2:1, and the flow rate of the inert mixed gas is controlled at about 2 m / s. The oxygen content in the welding area is monitored in real time to stably control the oxygen content in the welding area at ≤50 ppm;

[0088] (4) Start the laser welding machine, set the power of the laser welding machine to 5KW, the welding speed to 1m / min, focus the laser beam on the surface of the workpiece 400, and perform continuous welding;

[0089] (5) During the welding process, the monitoring and feedback control system continuously monitors the oxygen content, temperature, air pressure, and plasma state in the welding area, and through the intelligent feedback control algorithm, automatically fine-tunes the flow rate, mixing ratio of the inert gas mixture, and laser power according to the real-time monitoring data to ensure the stability of the oxygen content in the welding area and suppress the plasma shielding effect;

[0090] (6) After the welding is completed, keep the pressure for 30 seconds and then turn off the laser welding machine. After the normal pressure is restored in the vacuum chamber 100, take out the workpiece 400;

[0091] After inspection, for the titanium alloy plate welded by the present invention, the weld surface is smooth and flat, without obvious pores, cracks, and oxide defects. As Figure 5 shown, the weld strength reaches more than 95% of the base metal strength, and the welding quality is significantly better than that of the traditional welding process using inert gas protection in the atmospheric environment as Figure 4 shown.

[0092] 2. Laser welding of tantalum tungsten alloy:

[0093] (1) Conduct a comparative test on tantalum tungsten alloy plates with a thickness of 2mm using the conventional low-vacuum laser welding method and the local area inert gas protection welding method in the vacuum environment of the present invention respectively;

[0094] (2) Set the vacuum degree in the vacuum chamber 100 to 2×10 -1 Pa, set the mixing ratio of argon and helium to 3:2, control the oxygen content at ≤50ppm, set the power of the laser welding machine to 5KW, and the welding speed to 2.5m / min;

[0095] (3) The traditional device only controls the vacuum degree to be set at 8×10 -2 Pa;

[0096] (4) After the welding is completed, analyze the oxidation inhibition effect on the weld surface of the device proposed by the present invention through visual inspection and comparison of the weld surface;

[0097] The experimental results show that there is no surface oxidation on the tantalum tungsten alloy welds welded by the method of the present invention, as Figure 7 shown; while there is an obvious oxide film on the surface of the welds obtained by laser welding only in a low-vacuum environment, as Figure 6 shown.

[0098] The preferred ranges of the parameters involved in the present invention are as follows:

[0099] Parameter Name Preferred Range Vacuum Degree <![CDATA[≤1×10 -1 Pa <!-- 6 -->]]> Oxygen Content in Welding Area ≤50 ppm Argon / Helium Mixing Ratio 5:1～1:5 Flow Rate of Inert Mixed Gas 0.5 - 5 m / s Power of Laser Welder 0.5 - 6 kW Welding Speed 1 - 6 m / min

[0100] The above embodiments are only illustrative descriptions of the present invention and do not limit its protection scope. Those skilled in the art can also make partial changes to it, as long as they do not exceed the spiritual essence of the present invention, they are within the protection scope of the present invention.

Claims

1. A local area inert gas protection assisted vacuum environment laser welding device, characterized in that, It includes a monitoring and feedback control system, a gas precision control system and a vacuum chamber (100). A gas nozzle (300), a workbench (500) and a laser welding head (200) are all arranged inside the vacuum chamber (100). The laser welding head (200) is located above the workbench (500), and the gas nozzle (300) is arranged on one side of the laser welding head (200). A vacuum pumping system (600) is connected to the vacuum chamber (100), and the laser welding head (200) is connected to a laser welding machine; The gas precision control system includes a gas flow controller, a gas mixing ratio control device and a gas flow feedback sensor. The inlet of the gas mixing ratio control device is respectively connected to an argon gas source and a helium gas source. The outlet of the gas mixing ratio control device is connected to the gas nozzle (300) through the gas flow controller. The gas flow feedback sensor is arranged on the pipeline between the gas flow controller and the gas nozzle (300). The gas flow feedback sensor monitors the flow rate of the flowing gas and feeds back data to PID regulate the gas flow controller; The monitoring and feedback control system includes a closed-loop feedback control unit, a laser power monitoring unit, a plasma monitoring unit, an oxygen content monitoring unit and a temperature and pressure monitoring unit. The vacuum pumping system (600), the laser welding machine, the gas flow controller, the gas mixing ratio control device, the gas flow feedback sensor, the laser power monitoring unit, the plasma monitoring unit, the oxygen content monitoring unit and the temperature and pressure monitoring unit are respectively electrically connected to the closed-loop feedback control unit. The area formed between the 15-mm-width range on each side of the weld joint to be welded of the workpiece (400) and the circular range with a circumferential radius of 30 mm of the laser welding head (200) is defined as the welding area. The oxygen content monitoring unit, the temperature and pressure monitoring unit and the plasma monitoring unit are all arranged in the welding area.

2. The local area inert gas protection assisted vacuum environment laser welding device according to claim 1, wherein The gas nozzle (300) is a sleeve-shaped component. The outlet end of the gas nozzle (300) is provided with a single circular jet orifice, and the diameter of the circular jet orifice is equal to the through diameter of the gas nozzle (300). Or, the outlet end of the gas nozzle (300) is provided with a head, and a plurality of jet holes are arranged on the head.

3. The local area inert gas protection assisted vacuum environment laser welding device according to claim 1, characterized in that, The vacuum pumping system (600) includes at least one stage of molecular pump or a composite vacuum pump set.

4. The local area inert gas protection assisted vacuum environment laser welding device according to claim 1, characterized in that, The workpiece (400) is a component made of titanium alloy, zirconium alloy, hafnium alloy, tantalum alloy, magnesium alloy, aluminum alloy, nickel-based superalloy, cobalt-based superalloy or iron-nickel-based superalloy material.

5. The local area inert gas protection assisted vacuum environment laser welding device according to claim 1, characterized in that, The workpiece (400) is a plate, a pipe, a thin-walled structural member or a special-shaped member.

6. A local area inert gas protection assisted vacuum environment laser welding method realized by using the local area inert gas protection assisted vacuum environment laser welding device according to any one of claims 1-5, characterized in that, It includes the following steps: Step 1: Place the workpiece (400) on the workbench (500). The laser welding head (200) faces the weld joint to be welded on the workpiece (400). The laser welding head (200) is 1 - 5 mm away from the weld joint to be welded. The gas outlet end of the gas nozzle (300) faces the weld joint to be welded, and the gas outlet end of the gas nozzle (300) is 5 - 20 mm away from the weld joint to be welded. Use the vacuum pumping system (600) to pump the vacuum degree in the vacuum chamber (100) to be less than or equal to 10 -1 Pa; Step 2: Start the gas precision control system to make the inert mixed gas ejected from the gas nozzle (300) form a dynamic inert protective gas curtain in the welding area, and control the oxygen content in the welding area to be less than or equal to 50 ppm; Step 3: Start the laser welding machine and apply a laser beam to the workpiece (400) through the laser welding head (200) for laser welding; Step 4: Monitor the oxygen content, temperature, pressure, and plasma state in the welding area in real time through a monitoring and feedback control system, and perform closed-loop feedback regulation according to the monitoring results.

7. The method for laser welding in a local area inert gas protection assisted vacuum environment according to claim 6, characterized in that The welding process is continuous welding, spot welding, seam welding, or dissimilar material welding.

8. The local area inert gas protection assisted vacuum environment laser welding method according to claim 6, wherein, The inert protective gas curtain in Step 2 is formed by an inert mixed gas, which is composed of argon and helium. The mixing ratio range of argon and helium is 5:1 to 1:5, and the injection flow rate range of the inert mixed gas is 0.5 m / s to 5 m / s.

9. The local area inert gas protection assisted vacuum environment laser welding method according to claim 6, characterized in that, The closed-loop feedback control in Step 4 is specifically as follows: When the oxygen content in the welding area is greater than 50 ppm, the oxygen content monitoring unit sends a signal, and the closed-loop feedback control unit increases the flow rate or gas mixing ratio of the gas flow controller. When it is monitored that the shielding effect of the plasma in the welding area is enhanced to the critical electron density of 1×10 20 m -3 , the plasma monitoring unit sends out a signal, and the closed-loop feedback control unit increases the power of the laser welder or the flow rate of the flow controller to weaken the plasma shielding effect; When the vacuum degree within the welding area is greater than 10 -1 Pa, the temperature and pressure monitoring unit sends out a signal, and the closed-loop feedback control unit increases the power of the vacuum pumping system (600); When the temperature in the welding area is higher than the boiling point temperature of the workpiece (400), the welding process is restored to the optimized state by reducing the power or increasing the protective gas flow rate.

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