A laser-guided and arc-constrained narrow gap welding method and device

Abstract

The present invention relates to a narrow gap welding method and device that guides and constrains an arc with laser. During welding, a laser machine is first turned on to emit a laser beam, and the laser beam is converted by a laser head so that a laser spot with a solid center and an annular periphery is formed at the bottom of the welding gap just below the tip of the welding wire of the welding gun. The central laser part of the laser spot vaporizes and ionizes the base material to form a photo-induced plasma, and the photo-induced plasma forms a preferential conductive channel for the arc, thereby guiding the arc and promoting the depth of penetration. The tip of the welding wire starts the arc with the base material at the bottom of the welding gap through the conductive channel. The annular laser part can constrain the arc divergence, so that the arc at the bottom of the welding gap gathers, and the energy density of the arc at the bottom of the welding gap is increased; it ensures that the arc always burns stably at the bottom of the welding gap under the action of the laser. Prevent the arc from climbing due to the welding wire being too close to the side wall of the welding gap during narrow gap welding.

Description

Technical Field

[0001] The invention relates to the technical field of narrow gap welding, and in particular to a narrow gap welding method and device guided by laser and constraining an arc. Background Art

[0002] With the increasing application of medium and thick plate and thick plate structural parts in the fields of industry, shipbuilding and engineering machinery, narrow gap welding methods have received widespread attention. Narrow gap welding has many technical and economic advantages, including: (1) The groove and cross-sectional area of ​​the weld are greatly reduced, and the consumption of welding materials and welding energy is greatly reduced, which can significantly improve welding efficiency and control costs; (2) During the narrow gap welding process, the amount of hot compression plastic deformation is greatly reduced, and it is more uniform along the plate thickness direction, thereby reducing the residual stress and residual deformation of the joint; (3) The deep and narrow side wall is conducive to the metallurgical protection of the weld zone, and the metallurgical purity of the weld zone metal is higher; (4) The smaller welding line energy reduces the toughness and plastic damage of the heat affected zone.

[0003] However, under the constraint of narrow gap, when the distance from the end of the welding wire to the side wall of the gap is less than the distance to the bottom of the gap, due to the minimum voltage principle, the arc will first choose a shortest conductive path for burning. At this time, the dry extension length will also decrease. Due to the self-regulating effect of the arc, the length of the arc will also increase accordingly. However, the distance from the end of the welding wire to the side wall of the gap is certain. At this time, the arc length is certain, and the arc length can only be increased by melting the welding wire. Therefore, the dry extension length of the welding wire continues to decrease, resulting in the phenomenon that the arc continues to climb upward along the side wall.

[0004] The phenomenon of arc climbing in narrow gap welding will seriously affect the welding quality. As the arc burning position along the side wall continues to increase, it cannot melt the base material at the bottom of the gap well. In addition, as the arc burning position relative to the side wall also changes continuously, the fusion effect of the side wall is also very unsatisfactory. Therefore, ensuring that the arc can burn stably at the bottom of the gap is the most important factor in ensuring the quality of narrow gap welding. Summary of the invention

[0005] The purpose of the present invention is to provide a narrow gap welding method with laser guidance and arc confinement to solve the problem of poor welding quality caused by arc climbing in narrow gap welding in the prior art; the purpose of the present invention is also to provide a narrow gap welding device for implementing the above method.

[0006] To achieve the above-mentioned purpose, a laser-guided and arc-constrained narrow gap welding method of the present invention adopts the following technical scheme: A laser-guided and arc-constrained narrow gap welding method comprises the following steps:

[0007] 1) Irradiate the welding gap with a laser beam so that the laser beam forms a laser spot at the bottom of the welding gap just below the tip of the welding wire of the welding gun. The laser spot includes a coaxial solid central laser part and a ring-shaped laser part located on the periphery of the central laser part and surrounding the central laser part, and there is a blank lightless area between the central laser part and the ring-shaped laser part;

[0008] 2) Start the welding gun;

[0009] In step 1), the central laser part of the laser spot vaporizes and ionizes the base material to form a photo-induced plasma, and the photo-induced plasma forms a conductive channel, through which the tip of the welding wire strikes an arc with the base material at the bottom of the welding gap; the annular laser part can constrain the divergence of the arc, gather the arc at the bottom of the welding gap, and increase the energy density of the arc at the bottom of the welding gap, ensuring that the arc always burns stably at the bottom of the welding gap under the action of the laser.

[0010] The spot area and energy density of the laser spot can be adjusted.

[0011] A narrow gap welding device for implementing the above method of the present invention adopts the following technical scheme: a narrow gap welding device for implementing the narrow gap welding method, comprising a welding gun and a welding machine, and also comprising a laser head and a laser, wherein the laser is connected to the laser head through an optical fiber to transmit the laser; the laser head comprises a shell and an optical system located inside the shell, wherein the shell has a laser inlet and a laser outlet, and the optical system is used to convert the laser beam transmitted from the laser inlet and output from the laser outlet, wherein the converted laser beam is irradiated on the bottom of the welding gap directly below the welding wire tip of the welding gun to form a laser spot, wherein the laser spot comprises a coaxial solid central laser portion and an annular laser portion located on the periphery of the central laser portion and surrounded by the central laser portion, and there is a blank lightless area between the central laser portion and the annular laser portion.

[0012] The optical system comprises a beam expander, a collimator, a combination mirror, a first condenser and a second condenser arranged in sequence along the laser transmission direction. The combination mirror comprises an internal beam splitter reflector and an external reflector which are spaced apart from each other. The beam expander is used to expand the cross section of the laser beam transmitted from the optical fiber. The collimator converts the laser beam expanded by the beam expander into a parallel laser beam with a constant cross section. The beam splitter reflector has a central hole for part of the parallel laser beam to pass through. The beam splitter reflector has an outer conical reflective surface with a small end facing the collimator and used to reflect part of the parallel laser beam to the reflector. The reflector has a small end. The inner conical reflection surface facing the collimator is used to receive the laser beam reflected by the beam splitter and convert the laser beam into a parallel laser beam with a constant cross-section and then transmit it to the first condenser; the first condenser is an annular structure, and the first condenser has a central channel for the laser beam passing through the central hole of the beam splitter, the annular mirror body of the first condenser is used to irradiate the laser beam reflected by the reflector and form the annular laser part after passing through, and the second condenser is directly opposite to the central channel of the first condenser and is used to irradiate the laser beam passing through the central hole of the beam splitter to form the central laser part after passing through.

[0013] The first condenser can be moved closer to or farther away from the second condenser in parallel, and the laser spot size can be adjusted by the movement of the first condenser.

[0014] The laser head and welding gun are coupled together by a clamp, the angle between the laser beam output by the laser head and the normal direction of the substrate on which the parent material is placed is 10-15 degrees, the angle between the wire feeding direction of the welding gun and the normal direction of the substrate is 20-25 degrees, and the laser spot of the laser beam is located directly below the tip of the welding wire.

[0015] The beneficial effects of the present invention are as follows: during welding, the laser machine is first turned on to emit a laser beam, and the laser beam is converted through the laser head so that a laser spot with a solid center and an annular periphery is formed at the bottom of the welding gap just below the tip of the welding wire of the welding gun. The central laser part of the laser spot vaporizes and ionizes the base material to form a photo-induced plasma, and the photo-induced plasma forms a preferential conductive channel for the arc, thereby guiding the arc and promoting the penetration. The tip of the welding wire starts the arc with the base material at the bottom of the welding gap through the conductive channel. The annular laser part can restrain the arc divergence, so that the arc at the bottom of the welding gap is gathered, and the energy density of the arc at the bottom of the welding gap is increased; it is ensured that the arc always burns stably at the bottom of the welding gap under the action of the laser. Under the joint action of the central laser part and the annular laser part, the stability of the arc during narrow gap welding is promoted, and the phenomenon of arc climbing caused by the preferential establishment of a conductive channel between the end of the welding wire and the side wall due to the welding wire being too close to the side wall of the welding gap (groove) during narrow gap welding is prevented. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a schematic structural diagram of an embodiment of a laser-guided and arc-confined narrow gap welding device of the present invention;

[0017] Figure 2 yes Figure 1 Schematic diagram of the installation structure of the laser head and welding gun;

[0018] Figure 3 yes Figure 1 Schematic diagram of the optical system in the laser head

[0019] Figure 4 yes Figure 3 Schematic diagram of the structure of the beam splitter reflector. DETAILED DESCRIPTION

[0020] An embodiment of a laser-guided and arc-confined narrow gap welding method of the present invention comprises the following steps:

[0021] 1) Irradiate the welding gap with a laser beam so that the laser beam forms a laser spot at the bottom of the welding gap just below the tip of the welding wire of the welding gun. The laser spot includes a solid central laser part and a ring laser part located outside the central laser part and surrounding the central laser part. The central laser part and the ring laser part are coaxial, and there is a blank lightless area between the central laser part and the ring laser part. In this step, the spot area and energy density of the laser spot can be adjusted.

[0022] 2) Start the welding gun;

[0023] In step 1), the central laser part of the laser spot vaporizes and ionizes the base material to form a photo-induced plasma, and the photo-induced plasma forms a conductive channel, through which the tip of the welding wire strikes an arc with the base material at the bottom of the welding gap; the annular laser part can constrain the divergence of the arc, gather the arc at the bottom of the welding gap, and increase the energy density of the arc at the bottom of the welding gap, ensuring that the arc always burns stably at the bottom of the welding gap under the action of the laser.

[0024] When in use, the laser is turned on first, so that the laser beam is irradiated on the bottom of the welding gap just below the tip of the welding wire of the welding gun and forms a laser spot with a solid center and an annular periphery. The central laser part of the laser spot vaporizes and ionizes the base material to form a photo-induced plasma, which forms a preferential conductive channel for the arc, thereby guiding the arc and promoting the depth of penetration. The tip of the welding wire starts the arc with the base material at the bottom of the welding gap through the conductive channel. The annular laser part can restrain the arc divergence, gather the arc at the bottom of the welding gap, and increase the energy density of the arc at the bottom of the welding gap; ensure that the arc always burns stably at the bottom of the welding gap under the action of the laser.

[0025] An embodiment of a laser-guided and arc-confined narrow gap welding device of the present invention is as follows: Figure 1-4 As shown, it includes a welding gun, a welding machine, a laser head and a laser, the laser is also connected to a water cooling device, the welding machine is connected to a shielding gas source for supplying shielding gas to the welding gun, and the laser head is connected to the laser head through an optical fiber to transmit the laser. The laser head and the welding gun are mounted together by a clamp coupling, the angle between the laser beam output by the laser head and the normal direction of the substrate on which the parent material is placed is 10-15 degrees, the angle between the wire feeding direction of the welding gun and the normal direction of the substrate is 20-25 degrees, and the laser spot of the laser beam is located directly below the tip of the welding wire. In other embodiments, the installation angle of the laser head and the installation angle of the welding gun can be adjusted according to actual needs.

[0026] The laser head includes a shell and an optical system located inside the shell. The shell has a laser inlet and a laser outlet. The laser inlet can be an optical fiber inlet or a connection between the optical fiber and the shell as required. The optical system includes a beam expander, a collimator, a combination mirror, a first condenser and a second condenser arranged in sequence along the laser transmission direction. The combination mirror includes an internal beam splitter reflector and an external reflector that are spaced apart inside and outside. Specifically, the beam expander is used to expand the cross section of the laser beam transmitted from the optical fiber to form a beam expansion effect. The collimator converts the laser beam expanded by the beam expander into a parallel laser beam with a constant cross section. The beam splitter reflector has a central hole for part of the above parallel laser beam to pass through. The beam splitter reflector has an outer cone reflection surface with a small end facing the collimator for reflecting part of the parallel laser beam to the reflector. The reflector has an inner cone reflection surface with a small end facing the collimator for receiving the laser beam reflected by the beam splitter reflector and converting the laser beam into a parallel laser beam with a constant cross section and then transmitting it to the first condenser. The first condenser is an annular structure, and has a central channel for the laser beam passing through the central hole of the reflector. The annular mirror body of the first condenser is used for the laser beam reflected by the reflector to irradiate and pass through to form the above-mentioned annular laser portion. The second condenser is directly opposite to the central channel of the first condenser and the central hole of the beam splitter reflector, and is used for the laser beam passing through the central hole of the beam splitter reflector to irradiate and pass through to form the above-mentioned central laser portion. The difference between the radius of the solid laser beam and the inner diameter of the annular laser beam is the area of ​​the blank lightless area between the two beams after the beam splitting, and the area of ​​this area is related to the radial size of the beam splitter reflector and the reflector. The energy ratio adjustment of the central solid laser and the peripheral annular laser can only be achieved by the area of ​​the hollow area of ​​the beam splitter reflector. For a specific laser head, when the cross-sectional area of ​​the hollow area of ​​the beam splitter reflector is determined, the energy ratio of the central solid laser and the peripheral annular laser can no longer be adjusted, but the laser spot area and energy density can be adjusted according to the defocus amount.

[0027] The first condenser can be parallel to or away from the second condenser, and the laser spot size can be adjusted by the movement of the first condenser. In this embodiment, the substrate can also move closer to or farther from the laser head. On the substrate irradiated by the laser, a solid spot with a high energy density in the center is formed, and the periphery is a ring-shaped laser spot with a lower energy density, wherein the area and energy density of the ring-shaped laser spot can be adjusted by the height of the first condenser. The solid light beam and the ring-shaped light beam pass through the second condenser and the first condenser located below respectively. The position of the second condenser is fixed, and the focal length is L1. By adjusting the height of the substrate, the appropriate defocus amount of the central laser is selected. The height of the first condenser can be adjusted relative to the second condenser. The focal length of the second condenser is L2. In this embodiment, L1-L2=10mm. The specific values ​​of L1 and L2 in other embodiments can be adjusted according to actual needs. L1-L2=10mm, that is, when the first condenser and the second condenser are located on the same horizontal plane, the focus of the central laser beam is located on the substrate, and the focus of the annular laser beam is located 10mm above the substrate. At this time, the annular laser forms a circular ring with a certain area on the substrate. By adjusting the height of the first condenser, the spot area and energy density of the annular laser can be adjusted within a certain range.

[0028] When in use, before welding, turn on the laser, adjust the distance between the laser head and the bottom of the welding gap, determine the appropriate defocus of the solid laser in the middle, and at the same time change the height of the annular laser focus from the substrate by adjusting the height of the first condenser, so as to obtain the area covered by the annular laser spot on the substrate. The outer ring laser beam adopts positive defocus, that is, the focus is above the substrate. The larger the defocus, the larger the area of ​​the outer ring laser beam irradiated on the substrate, and the energy density is correspondingly reduced. During welding, the laser is placed in front and forms a certain angle with the vertical direction. The welding gun adjusts the angle and height through the fixture, selects the appropriate wire dry extension, and adjusts the angle so that the laser spot is located directly below the tip of the welding wire. The laser is turned on first, and the laser spot irradiates the bottom of the welding gap. The solid high-energy-density laser in the center acts on the weld metal, causing the metal to be vaporized and ionized to form a photo-induced plasma, providing a conductive channel for the arc. The resistance in this channel is the smallest. According to the minimum voltage principle, the tip of the welding wire will arc with the bottom of the gap through this channel, rather than with the gap side wall which is closer. In traditional narrow gap welding, the arc divergence angle is too large and the contact area with the gap side wall is too much. In this case, the energy-dispersed arc not only cannot promote the full fusion of the side wall, but also causes the two sides of the gap bottom weld to be unfused. The addition of the peripheral annular laser beam in the present invention can also guide the arc in a similar manner to the above, and the arc periphery is attracted near this area, that is, by adjusting the outer diameter of the annular laser, the arc divergence is constrained. Under the guidance of the central high energy density and the constraint of the peripheral annular laser, the arc can burn stably at the bottom of the gap, and the arc divergence angle and energy density can also be adjusted to a certain extent by changing the size of the annular laser. When performing narrow gap welding with different gap sizes, the concentrated area of ​​arc burning can be controlled by adjusting the outer diameter of different environmental lasers to ensure the full fusion of each layer of weld. A narrow gap welding method and device for laser-guided and arc-constrained narrow gap welding of the present invention is mainly used for welding joints with a plate thickness of 15-200mm, a gap of 5-20mm, and an I-type or U-shaped groove.

[0029] The above is only a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A laser-guided and arc-confined narrow gap welding device, comprising a welding gun and a welding machine, characterized in that: It also includes a laser head and a laser, the laser is connected to the laser head through an optical fiber to transmit laser light; the laser head includes a shell and an optical system located inside the shell, the shell has a laser inlet and a laser outlet, the optical system is used to convert the laser beam transmitted from the laser inlet and output from the laser outlet, the converted laser beam is irradiated on the bottom of the welding gap just below the welding wire tip of the welding gun to form a laser spot, the laser spot includes a coaxial solid central laser part and a ring laser part located on the periphery of the central laser part and surrounded by the central laser part, and there is a blank lightless area between the central laser part and the ring laser part; The optical system comprises a beam expander, a collimator, a combination mirror, a first condenser and a second condenser arranged in sequence along the laser transmission direction, the combination mirror comprises an internal beam splitter reflector and an external reflector which are spaced apart from each other; the beam expander is used to expand the cross section of the laser beam transmitted from the optical fiber, and the collimator converts the laser beam expanded by the beam expander into a parallel laser beam with a constant cross section; The beam splitter reflector has a central hole for part of the above-mentioned parallel laser beam to pass through, the beam splitter reflector has an outer cone reflection surface with a small end facing the collimator, which is used to reflect part of the parallel laser beam to the reflector, and the reflector has an inner cone reflection surface with a small end facing the collimator, which is used to receive the laser beam reflected by the beam splitter reflector and convert the laser beam into a parallel laser beam with a constant cross-section and then transmit it to the first condenser; the first condenser is an annular structure, the first condenser has a central channel for the laser beam passing through the central hole of the beam splitter reflector, and the annular mirror body of the first condenser is used for the laser beam reflected by the reflector to irradiate and pass through the rear-shaped The second condenser is directly opposite to the central channel of the first condenser for irradiating the laser beam passing through the central hole of the beam splitter and forming the central laser portion after passing through; the central laser portion of the laser spot vaporizes and ionizes the base material to form a photo-induced plasma, and the photo-induced plasma forms a conductive channel, and the tip of the welding wire strikes an arc with the base material at the bottom of the welding gap through the conductive channel; the annular laser portion can constrain the divergence of the arc, so that the arc at the bottom of the welding gap is gathered, and the energy density of the arc at the bottom of the welding gap is increased; it is ensured that the arc always burns stably at the bottom of the welding gap under the action of the laser; The first condenser can be moved closer to or farther away from the second condenser in parallel, and the size and energy density of the annular laser part of the laser spot can be adjusted through the movement of the first condenser.

2. The laser-guided and arc-confined narrow gap welding device according to claim 1, characterized in that: The laser head and welding gun are coupled together by a clamp, the angle between the laser beam output by the laser head and the normal direction of the substrate on which the parent material is placed is 10-15 degrees, the angle between the wire feeding direction of the welding gun and the normal direction of the substrate is 20-25 degrees, and the laser spot of the laser beam is located directly below the tip of the welding wire.

3. A method for using the laser guided and arc constrained narrow gap welding device as claimed in claim 1, characterized in that: The following steps are involved: 1) Irradiate the welding gap with a laser beam so that the laser beam forms a laser spot at the bottom of the welding gap just below the tip of the welding wire of the welding gun. The laser spot includes a coaxial solid central laser part and a ring-shaped laser part located on the periphery of the central laser part and surrounding the central laser part, and there is a blank lightless area between the central laser part and the ring-shaped laser part; 2) Start the welding gun; In step 1), the central laser part of the laser spot vaporizes and ionizes the base material to form a photo-induced plasma, and the photo-induced plasma forms a conductive channel, through which the tip of the welding wire strikes an arc with the base material at the bottom of the welding gap; the annular laser part can constrain the divergence of the arc, gather the arc at the bottom of the welding gap, and increase the energy density of the arc at the bottom of the welding gap, ensuring that the arc always burns stably at the bottom of the welding gap under the action of the laser.

4. The method for using the laser-guided and arc-confined narrow gap welding device according to claim 3, characterized in that: The spot area and energy density of the annular laser part of the laser spot can be adjusted.

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