Dissimilar metal laser welding device with external magnetic field and preset gradient coating

Abstract

The utility model discloses a dissimilar metal laser welding device with an external magnetic field and a preset gradient coating, which comprises a left lifting system, a right lifting rotating system, a laser welding system, a welding fixture, an electromagnetic field powder mixing electroplating system, an electroplating power supply, a magnetic field power supply, a blowing nozzle, a left upright post, a right upright post and a workbench, according to the electromagnetic field powder mixing electroplating system, a gradient magnetic field is additionally arranged in an electroplating machining area, a middle metal coating distributed in a gradient mode is deposited on the surface of a lower plate test piece, a left lifting system and a right lifting rotating system are matched, and a dissimilar metal upper plate test piece and the lower plate test piece are attached; and the laser welding system is used for carrying out laser lap welding on dissimilar metal materials by utilizing a high-power laser beam. The mechanical property of the dissimilar metal welding seam can be effectively improved, the device is simple in structure and convenient to operate, and the machining quality and the machining efficiency can be improved.

Description

Technical Field

[0001] The utility model relates to a laser welding device after a gradient coating is preset by applying an external magnetic field, and belongs to the field of welding processing of dissimilar metal materials. Background Art

[0002] As the number of cars owned by people increases year by year, energy shortages caused by oil consumption and environmental pollution caused by exhaust gas begin to affect the development of the modern automobile industry. Energy conservation and emission reduction have become the focus of the development of the automobile industry, and automobile lightweighting is an important way to achieve energy conservation and emission reduction. Therefore, it is urgent to develop a welding method that can effectively reduce weld defects and optimize the organizational composition of the weld area to obtain high-quality aluminum-steel joints.

[0003] The biggest problem with dissimilar metal welding is that due to the difference in the thermophysical properties of the two metals, the weld structure is prone to form brittle metal compounds, resulting in poor weld performance and low welding quality. Adding an intermediate layer of metal between dissimilar metals is beneficial to improving weld quality. The general method is to add metal foil or metal powder to assist in dissimilar metal welding, but there is a problem of poor controllability of welding quality.

[0004] Electroplating is the process of electroplating a thin layer of other metals or alloys on a metal surface using the principle of electrochemical cathode deposition. This technology is an effective method for preparing an intermediate layer for dissimilar metal welding. However, the energy of the laser beam used for welding is generally Gaussian, and a corresponding gradient coating is required as the intermediate metal. Therefore, there is an urgent need for an effective device for preparing a gradient coating as an intermediate metal and seamlessly connecting it with dissimilar metals. Utility Model Content

[0005] In view of the technical demand for gradient coating for welding of dissimilar materials, the utility model provides a dissimilar metal laser welding device with a preset gradient coating by applying an external magnetic field. The technical solution adopted by the utility model to solve the technical problem is:

[0006] A dissimilar metal laser welding device with a preset gradient coating in an external magnetic field, characterized in that it includes a left lifting system, a right lifting and rotating system, a laser welding system, a welding fixture, an electromagnetic field mixed powder electroplating system, an electroplating power supply, a magnetic field power supply, an air blowing nozzle, a left column, a right column and a workbench, the left column is fixed on the left side of the workbench, the laser welding system is fixed on the left column, the left lifting system includes a hydraulic cylinder, a telescopic rod, a pressing plate, an upper plate fixture, an upper plate test piece, and the hydraulic cylinder is fixed on the workbench; the welding fixture is fixed on the workbench, and is composed of two square materials with a processing gap in the middle; the right lifting and rotating system is fixed to the workbench by bolts and is placed on the right side of the welding fixture, the right column is fixed to the right end of the workbench and is divided into three layers: upper, middle and lower, the upper layer is fixed with an air blowing nozzle, the middle layer is placed with a magnetic field power supply, the lower layer is placed with an electroplating power supply, and the electromagnetic field mixed powder electroplating system is fixed on the workbench on the right side of the right lifting and rotating system;

[0007] As a further preferred embodiment of the utility model, the electromagnetic field mixed powder electroplating system includes an electroplating tank, a magnetic field insulating seat, a terminal, a conductive coil, an insulating electroplating fixture, a copper plate electrode, magnetic particles and a lower plate specimen. Four partitions are welded inside the electroplating tank. Two cavities formed by two partitions on the left and right are used to place the magnetic field insulating seat. There are two magnetic field insulating seats with cavities inside. The terminal is fixed inside the cavity. The terminal is in the shape of an "I". The conductive coil is wound around the terminal. The number of turns of the conductive coil is the largest in the middle of the terminal, and decreases successively towards the two ends, presenting a gradient distribution. A mixed powder electroplating area is formed between the two middle partitions in the electroplating tank to store the electroplating solution. The outer cavities on the left and right sides are water bath heating areas for storing pure water; two horizontal bars are fixed above the magnetic field insulation seat, and the insulating electroplating fixture and the copper plate electrode are suspended in the mixed powder electroplating area through the two horizontal bars; the copper plate electrode is connected to the positive pole of the electroplating power supply, the lower end of the lower plate specimen is inserted into the insulating electroplating fixture, the non-electroplating area of ​​the lower plate specimen is protected by the insulating electroplating fixture, and only the area to be electroplated is exposed, and the upper end of the lower plate specimen is connected to the negative pole of the electroplating power supply; magnetic particles are mixed in the electroplating solution in the mixed powder electroplating area, and the conductive coil is connected to the magnetic field power supply and energized to form an external gradient magnetic field outside the mixed powder electroplating area. Under the action of the external gradient magnetic field, the magnetic particles form a gradient distribution in the mixed powder electroplating area;

[0008] As a further preferred embodiment of the utility model, the right lifting and rotating system includes a guide rail, a rotating shaft, a fixed rotating shaft, a steering gear, a support plate, a support rod pin, a support rod, a nut shaft, a displacement fixture, a lifting motor, a lifting motor coupling, a screw rod, a rotating base, a chassis, a rotating motor coupling, a rotating motor and a bearing seat. The rotating base is fixed to the workbench by bolt connection, the rotating motor is fixed to the center of the rotating base, and the chassis is connected to the rotating motor through the rotating motor coupling; the lifting motor is fixed to the left side of the chassis, the screw rod is connected to the lifting motor output shaft through the lifting motor coupling, and bearing seats are provided at both ends of the screw rod; four support rods are installed on the chassis, and every two cross-shaped X-shaped One group, the support rod pins connect the two groups of X-shaped support rods, the lower right corners of the two groups of X-shaped support rods are fixed to the base frame through fixed rotating shafts, the lower left corners of the two groups of X-shaped support rods are connected to the nut shaft, the nut shaft is threadedly connected to the screw rod, the upper right corners of the two groups of X-shaped support rods are fixed to the bottom of the support plate through fixed rotating shafts, and the upper left corners of the two groups of X-shaped support rods are installed in the guide rail through the rotating shaft, and the guide rail is fixed to the bottom of the support plate; a servo is fixed to the bottom of the right end of the support plate, a displacement fixture is fixed to the servo and realizes a vertical to horizontal flip by connecting the servo, and the upper end of the lower plate specimen is fixed in the displacement fixture, and when the displacement fixture is in a suspended state, it ensures that the lower plate specimen is aligned with the insulating electroplating fixture in the electromagnetic field powder mixing system;

[0009] As a further preferred embodiment of the present invention, the laser welding system comprises a laser, an incident tube, a total reflector, a focusing lens, a plane mirror, a nozzle and a focusing tube. The laser beam emitted by the laser enters the incident tube, is reflected by the total reflector fixed in the tube, vertically enters the focusing tube, passes through the focusing lens and the plane mirror, and is emitted from the nozzle to the processing gap of the welding fixture.

[0010] As a further preferred embodiment of the present invention, the magnetic field power supply is a DC power supply with a voltage range of 50-80V;

[0011] As a further preferred embodiment of the present invention, the cross-sectional area of ​​the terminal is 5-15 mm 2 ;

[0012] As a further preferred embodiment of the present invention, the diameter of the magnetic particles is 500-800 nm;

[0013] As a further preferred embodiment of the present invention, the electroplating solution is a copper sulfate solution, the copper sulfate concentration is 150-250 g / L, and 50-60 g / L of sulfuric acid is added;

[0014] As a further preferred embodiment of the present invention, the laser is a Nd:YAG laser with a power of 500-1500W.

[0015] Through the above technical solution, compared with the prior art, the utility model has the following beneficial effects:

[0016] 1. The method of the utility model is mainly based on electrochemical deposition. On the basis of electrochemical deposition, a gradient magnetic field is applied to form a preset gradient coating. After the electroplating is completed, the workpiece is welded using a high-energy laser beam to finally obtain a weld with good forming and excellent mechanical properties.

[0017] 2. The device of the utility model has a simple structure and is easy to install and detect.

[0018] 3. The device of the utility model can reuse the electroplating solution and magnetic particles, which can effectively reduce costs and protect the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0020] Figure 1 It is a schematic diagram of the overall structure of the utility model regarding the dissimilar metal laser welding device with external magnetic field and preset gradient coating;

[0021] Figure 2 This is a schematic diagram of the structure of the right lifting and rotating system of the utility model;

[0022] Figure 3 This is a schematic diagram of the structure of the electromagnetic field mixed powder electroplating system of the utility model;

[0023] Figure 4 It is a schematic diagram of the gradient distribution of magnetic particles under the action of an external magnetic field in the utility model;

[0024] In the figure: 1 is the left lifting system, 2 is the laser welding system, 3 is the right lifting and rotating system, 4 is the blowing nozzle, 5 is the electromagnetic field mixing powder electroplating system, 6 is the magnetic field power supply, 7 is the electroplating power supply, 8 is the workbench, 9 is the welding fixture, 10 is the processing gap, 11 is the lower plate specimen, 12 is the right column, 13 is the left column, 101 is the hydraulic cylinder, 102 is the telescopic rod, 103 is the pressure plate, 104 is the upper plate fixture, 105 is the upper plate specimen, 201 is the laser, 202 is the incident tube, 203 is the full reflector, 204 is the focusing lens, 205 is the plane mirror, 206 is the nozzle, 207 is the focusing tube, 3 01 is a guide rail, 302 is a rotating shaft, 303 is a fixed rotating shaft, 304 is a servo, 305 is a support plate, 306 is a support pin, 307 is a support rod, 308 is a nut shaft, 309 is a displacement fixture, 310 is a lifting motor, 311 is a lifting motor coupling, 312 is a screw rod, 313 is a rotating base, 314 is a base frame, 315 is a rotating motor coupling, 316 is a rotating motor, 317 is a bearing seat, 501 is a magnetic field insulating seat, 503 is an insulating electroplating fixture, 504 is a copper plate electrode, 505 is a terminal, 506 is an electroplating tank, 508 is a conductive coil, and 509 is a magnetic particle. DETAILED DESCRIPTION

[0025] The utility model is now further described in detail with reference to the accompanying drawings. In the description of this application, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or position relationship based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the utility model and simplifying the description. The specific dimensions used in this embodiment are only for illustrating the technical solution and do not limit the protection scope of the utility model.

[0026] Specifically, the present application provides a preferred embodiment, such as Figure 1 As shown, in general, the dissimilar metal laser welding device of the present application includes a left lifting system 1, a right lifting and rotating system 3, a laser welding system 2, a welding fixture 9, an electromagnetic field mixed powder electroplating system 5, an electroplating power supply 7, a magnetic field power supply 6, an air blowing nozzle 4, a left column 13, a right column 12 and a workbench 8.

[0027] The left column 13 is fixed on the left side of the workbench 8, the laser welding system 2 is fixed on the left column 13, the hydraulic cylinder 101 is fixed on the workbench 8, the welding fixture 9 is fixed on the workbench 8, and is composed of two square materials with a processing gap 10 in the middle. The right lifting and rotating system 3 is fixed on the workbench 8 by bolts and is placed on the right side of the welding fixture 9. The right column 12 is fixed on the right end of the workbench 8 and is divided into three layers: upper, middle and lower. The upper layer fixes the blowing nozzle 4, the middle layer places the magnetic field power supply 6, and the lower layer places the electroplating power supply 7. The electromagnetic field mixed powder electroplating system 5 is fixed on the workbench 8 on the right side of the right lifting and rotating system 3.

[0028] The right lifting and rotating system in the utility model is as follows Figure 2 As shown, the rotating base 313 is fixed on the workbench 8 by bolt connection, the rotating motor 316 is fixed at the center of the rotating base 313, and the base frame 314 is connected to the rotating motor 316 through the rotating motor coupling 315; the lifting motor 310 is fixed on the left side of the base frame 314, the screw rod 312 is connected to the output shaft of the lifting motor 310 through the lifting motor coupling 311, and bearing seats 317 are provided at both ends of the screw rod 312; four support rods 307 are installed on the base frame 314, and every two cross-shaped X-shaped support rods form a group, and the support rod pins 306 connect the two groups of X-shaped support rods, and the lower right corners of the two groups of X-shaped support rods are fixed to the base frame 314 through the fixed rotating shaft 303, and the lower left corners of the two groups of X-shaped support rods The nut shaft 308 is connected to the screw rod 312 by a threaded connection. The upper right corners of the two groups of X-shaped support rods are fixed to the bottom of the support plate 305 through the fixed rotating shaft 303. The upper left corners of the two groups of X-shaped support rods are installed in the guide rail 301 through the rotating shaft 302. The guide rail 301 is fixed to the bottom of the support plate 305. A steering gear 304 is fixed to the bottom of the right end of the support plate 305. The displacement fixture 309 is fixed to the steering gear 304 and realizes the vertical to horizontal flipping by connecting the steering gear 304. The upper end of the lower plate specimen 11 is fixed in the displacement fixture 309. When the displacement fixture 309 is in a suspended state, it ensures that the lower plate specimen 11 is aligned with the insulating electroplating fixture 503 in the electromagnetic field powder mixing system 5.

[0029] Figure 3Schematic diagram of electroplating powder mixing system. Four partitions are welded inside the electroplating tank 506. Two cavities formed by two partitions on the left and right are used to place the magnetic field insulation seat 501. The magnetic field insulation seat 501 has two cavities 502. The terminal 505 is fixed inside the cavity 502. The terminal 505 is in the shape of an "I". The conductive coil 508 is wound around the terminal 505. The number of turns of the conductive coil 508 is the largest in the middle of the terminal 505, and decreases toward both ends in a gradient distribution. A mixed powder electroplating area 507 is formed between the two middle partitions in the electroplating tank 506 to store the electroplating solution. The outer cavities 511 on the left and right sides of the electroplating tank 506 are water bath heating areas to store pure water. The magnetic field insulation seat 50 1, two horizontal bars are fixed on the top, and the insulating electroplating fixture 503 and the copper plate electrode 504 are suspended in the mixed powder electroplating area 507 through the two horizontal bars; the copper plate electrode 504 is connected to the positive pole of the electroplating power supply 7, the lower end of the lower plate specimen 11 is inserted into the insulating electroplating fixture 503, the non-electroplating area of ​​the lower plate specimen 11 is protected by the insulating electroplating fixture 503, only the area to be electroplated is exposed, and the upper end of the lower plate specimen 11 is connected to the negative pole of the electroplating power supply 7; the electroplating solution in the mixed powder electroplating area 507 is mixed with magnetic particles 509, the conductive coil 508 is connected to the magnetic field power supply 6 and energized, and an external gradient magnetic field is formed outside the mixed powder electroplating area 507, and the magnetic particles 509 form a gradient distribution in the mixed powder electroplating area 507 under the action of the external gradient magnetic field;

[0030] The different number of turns of the conductive coil forms a gradient magnetic field under the action of the magnetic field power supply, such as Figure 4 As shown, the magnetic particles are distributed in a gradient due to the gradient magnetic field, which affects the current density distribution on the surface of the lower plate specimen serving as the cathode, thereby depositing a gradient-distributed intermediate metal coating on the surface of the lower plate specimen.

[0031] In the utility model, the magnetic field power supply is a DC power supply with a voltage range of 50-80V; the cross-sectional area of ​​the terminal is 5-15mm 2 ; The diameter of the magnetic particles is 500-800nm; the electroplating solution is a copper sulfate solution with a copper sulfate concentration of 150-250g / L, and 50-60g / L of sulfuric acid is added; the laser is a Nd:YAG laser with a power of 500-1500W.

[0032] The following is a detailed description of the method of the utility model in conjunction with specific embodiments:

[0033] The upper plate specimen 105 is domestically made cold-rolled DP590 dual-phase steel, and the lower plate specimen 11 is made of 6061 aluminum alloy. The dimensions of the workpiece are: 100 mm in length, 100 mm in width, and 0.5 mm in thickness.

[0034] The processing method comprises the following steps:

[0035] The lower plate specimen DP590 dual-phase steel is connected to the negative pole of the electroplating power supply, fixed on the displacement fixture by a pressing plate, the lifting motor in the right lifting system is turned on, the lower plate specimen is lowered and inserted into the insulating electroplating fixture in the electromagnetic field mixed powder electroplating system, and the copper plate electrode is connected to the positive pole of the electroplating power supply; the magnetic field power supply is turned on, and the magnetic particles in the electroplating solution in the mixed powder electroplating area are distributed in a gradient with the change of the number of turns of the conductive coil; the electroplating power supply is turned on, and with the assistance of the magnetic particles, the electrochemical deposition begins in the electroplating area of ​​the lower plate specimen, and a gradient coating is gradually formed; after the electroplating reaches a predetermined time, the electroplating power supply and the magnetic field power supply are turned off in turn to complete the gradient coating deposition;

[0036] Turn on the lifting motor, the screw rod rotates, the nut shaft moves on the screw rod, the two sets of support rods deform and drive the support plate to rise, and the DP590 dual-phase steel that has completed the gradient coating deposition is completely taken out from the insulating electroplating fixture, and the lifting motor is turned off; turn on the servo, the displacement fixture and the lower plate sample that has completed the electroplating are flipped from the vertical state to the horizontal state, and the lower plate sample is tightly attached to the bottom of the support plate, and the blowing nozzle is turned on to dry the surface of the lower plate sample with the gradient coating; turn on the rotating motor, the chassis rotates to the top of the welding fixture, and the processing gap position between the lower plate specimen and the welding fixture corresponds; turn on the lifting motor, press down the support plate, and press the support plate, DP590 dual-phase steel and welding fixture tightly; turn on the hydraulic cylinder, so that the telescopic rod drives the pressing plate to descend, so that the upper plate specimen fits the lower plate specimen, and the two are pressed together on the surface of the welding fixture;

[0037] Finally, turn on the laser, align the focused laser beam with the processing gap, and perform laser lap welding on the two plates.

[0038] The above description is only an exemplary embodiment of the present invention, and does not limit the scope of patent protection of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of the present invention.

Claims

1. A laser welding device for dissimilar metals with a preset gradient coating using an external magnetic field, characterized in that: The invention comprises a left lifting system (1), a right lifting and rotating system (3), a laser welding system (2), a welding fixture (9), an electromagnetic field powder mixing electroplating system (5), an electroplating power supply (7), a magnetic field power supply (6), an air blowing nozzle (4), a left column (13), a right column (12) and a workbench (8), wherein the left column (13) is fixed on the left side of the workbench (8), the laser welding system (2) is fixed on the left column (13), and the left lifting system (1) comprises a hydraulic cylinder (101), a telescopic rod (102), a pressing plate (103), an upper plate fixture (104), and an upper plate specimen (105). , a hydraulic cylinder (101) is fixed on a workbench (8); a welding fixture (9) is fixed on the workbench (8) and is composed of two square materials with a processing gap (10) in the middle; a right lifting and rotating system (3) is fixed on the workbench (8) by bolts and is placed on the right side of the welding fixture (9); a right column (12) is fixed on the right end of the workbench (8) and is divided into three layers: upper, middle and lower; an air blowing nozzle (4) is fixed on the upper layer, a magnetic field power supply (6) is placed on the middle layer, and an electroplating power supply (7) is placed on the lower layer; an electromagnetic field mixed powder electroplating system (5) is fixed on the workbench (8) on the right side of the right lifting and rotating system (3).

2. According to claim 1, a laser welding device for dissimilar metals with a pre-gradient coating by applying an external magnetic field is characterized in that: The electromagnetic field mixed powder electroplating system (5) comprises an electroplating tank (506), a magnetic field insulating seat (501), a terminal (505), a conductive coil (508), an insulating electroplating fixture (503), a copper plate electrode (504), magnetic particles (509) and a lower plate specimen (11). Four partitions are welded inside the electroplating tank (506). Two cavities formed by two partitions on the left and two on the right are used to place the magnetic field insulating seat (501). There are two magnetic field insulating seats (501), each of which has a cavity (502) therein. The terminal (505) is fixed to the cavity (502). Inside, the terminal (505) is in the shape of an "I" character, and the conductive coil (508) is wound around the terminal (505). The number of turns of the conductive coil (508) is the largest in the middle of the terminal (505), and decreases towards both ends, presenting a gradient distribution. A mixed powder electroplating area (507) is formed between two middle partitions in the electroplating tank (506) for storing electroplating liquid. The outer cavities (511) on the left and right sides of the electroplating tank (506) are water bath heating areas for storing pure water. Two horizontal bars are fixed above the magnetic field insulating seat (501), and the insulating electroplating fixture (503) The copper plate electrode (504) is suspended in the mixed powder electroplating area (507) through the two horizontal bars; the copper plate electrode (504) is connected to the positive electrode of the electroplating power supply (7); the lower end of the lower plate specimen (11) is inserted into the insulating electroplating fixture (503); the non-electroplating area of ​​the lower plate specimen (11) is protected by the insulating electroplating fixture (503), and only the area to be electroplated is exposed; the upper end of the lower plate specimen (11) is connected to the negative electrode of the electroplating power supply (7); magnetic particles (509) are mixed in the electroplating solution of the mixed powder electroplating area (507); the conductive coil (508) is connected to the magnetic field power supply (6) and energized, and an external gradient magnetic field is formed outside the mixed powder electroplating area (507); the magnetic particles (509) form a gradient distribution in the mixed powder electroplating area (507) under the action of the external gradient magnetic field.

3. The laser welding device for dissimilar metals with a pre-gradient coating by applying an external magnetic field according to claim 1, characterized in that: The right lifting and rotating system (3) comprises a guide rail (301), a rotating shaft (302), a fixed rotating shaft (303), a steering gear (304), a support plate (305), a support rod pin (306), a support rod (307), a screw shaft (308), a displacement fixture (309), a lifting motor (310), a lifting motor coupling (311), a screw rod (312), a rotating base (313), a base frame (314), a rotating motor coupling (315), a rotating motor (316) and a bearing seat (317), wherein the rotating base (313 ) is fixed on the workbench (8) by bolt connection, the rotating motor (316) is fixed at the center of the rotating base (313), and the base frame (314) is connected to the rotating motor (316) through the rotating motor coupling (315); the lifting motor (310) is fixed on the left side of the base frame (314), the screw rod (312) is connected to the output shaft of the lifting motor (310) through the lifting motor coupling (311), and bearing seats (317) are provided at both ends of the screw rod (312); four support rods (307) are installed on the base frame (314), and every two of them are crossed to form an X The two groups of X-shaped support rods are connected as a group, and the support rod pin (306) connects the two groups of X-shaped support rods. The lower right corners of the two groups of X-shaped support rods are fixed to the base frame (314) through the fixed shaft (303). The lower left corners of the two groups of X-shaped support rods are connected to the nut shaft (308), and the nut shaft (308) is threadedly connected to the screw rod (312). The upper right corners of the two groups of X-shaped support rods are fixed to the bottom of the support plate (305) through the fixed shaft (303). The upper left corner of the shaped support rod is installed in the guide rail (301) through a rotating shaft (302), and the guide rail (301) is fixed to the bottom of the support plate (305); a steering gear (304) is fixed to the bottom of the right end of the support plate (305), and a displacement fixture (309) is fixed to the steering gear (304) and realizes a vertical to horizontal flip by connecting to the steering gear (304); the upper end of the lower plate specimen (11) is fixed in the displacement fixture (309), and when the displacement fixture (309) is in a suspended state, it ensures that the lower plate specimen (11) is aligned with the insulating electroplating fixture (503) in the electromagnetic field mixed powder electroplating system (5).

4. The laser welding device for dissimilar metals with a pre-gradient coating by applying an external magnetic field according to claim 1, characterized in that: The laser welding system (2) comprises a laser (201), an incident tube (202), a full reflector (203), a focusing lens (204), a plane mirror (205), a nozzle (206), and a focusing tube (207). The laser beam emitted by the laser (201) enters the incident tube (202), is reflected by the full reflector (203) fixed in the tube, vertically enters the focusing tube (207), passes through the focusing lens (204) and the plane mirror (205), is emitted from the nozzle (206), and enters the processing gap (10) of the welding fixture (9).

5. The laser welding device for dissimilar metals with a pre-gradient coating by applying an external magnetic field according to claim 2, characterized in that: The magnetic field power supply is a DC power supply with a voltage range of 50-80V.

6. The laser welding device for dissimilar metals with a pre-gradient coating by applying an external magnetic field according to claim 2, characterized in that: The cross-sectional area of ​​the terminal is 5-15mm2.

7. The laser welding device for dissimilar metals with a pre-gradient coating by applying an external magnetic field according to claim 2, characterized in that: The diameter of magnetic particles is 500-800nm.

8. The dissimilar metal laser welding device with a pre-gradient coating by applying an external magnetic field according to claim 3, characterized in that: The laser (201) is a Nd:YAG laser with a power of 500-1500W.

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