A method for suppressing laser welding hump defects

Abstract

The application discloses a laser welding hump defect suppression method and relates to the field of welding, which comprises the following steps: S1, micro-groove structures are processed on a first welding surface of a first to-be-welded piece and / or a second welding surface of a second to-be-welded piece; alloy powder is filled into each micro-groove structure; and S2, the first welding surface and the second welding surface are welded together in a penetrating welding mode. By processing the micro-groove structures on the first welding surface and / or the second welding surface and adding the alloy powder into the micro-groove structures, the surface tension of liquid metal in the welding process is increased, the alloy powder can not only supplement the shortage of the surface tension, reduce or avoid the generation of the hump, but also compensate for the burning loss of beneficial alloy elements in the high-power laser welding process, control the microstructure of the weld and optimize the mechanical properties of the weld. The application can realize the suppression of the hump defect without additional auxiliary equipment, obtain a weld with good appearance and performance and has a wide application range.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a method for suppressing hump defects in laser welding. Background Technology

[0002] Thick plate welding is a key process in the manufacturing of large equipment such as aerospace, shipbuilding, rail transportation, and engineering machinery, and its quality directly determines the service performance and lifespan of the equipment. With the continuous development of social demands and industrial technology, the structure and service environment of large equipment are becoming increasingly complex, which places more stringent requirements on the welding and manufacturing of thick plates. In recent years, laser welding has been widely used in various fields such as aerospace, micro-parts processing, and thin-walled material processing. Compared with traditional multi-layer, multi-pass electric arc welding, laser welding has advantages such as high welding speed, high efficiency, and low deformation and residual stress; compared with electron beam welding, laser welding has advantages such as not requiring a vacuum environment, easy implementation of welding large and complex structures, and strong process adaptability; compared with friction stir welding, laser welding has advantages such as high speed, high flexibility, strong adaptability, and no need for subsequent processing. Therefore, laser welding technology has unique advantages in terms of high efficiency, high quality, and high adaptability, and has become one of the important research directions in the field of thick plate welding in recent years.

[0003] Commonly used laser welding methods for thick plates include multi-pass laser filler welding (with or without arc initiation of the welding wire) and single-pass laser penetration welding. Multi-pass laser filler welding primarily fills the groove by melting the welding wire. However, its filler thickness is limited by factors such as the amount of welding wire melt, droplet transfer stability, and molten pool flow. Therefore, multi-pass laser filler welding is generally required for thick plate welding. In contrast, laser penetration welding refers to a laser welding method where the molten pool or keyhole completely penetrates the test plate during the welding process. Laser penetration welding relies on the high energy density and strong penetrating power of the laser, eliminating the need for a groove and filler material to completely penetrate and melt the material, thus achieving single-pass welding of thick plates. Compared to laser filler welding, laser penetration welding significantly improves efficiency and reduces heat input. Its application is of great significance for further shortening the manufacturing and maintenance cycle of large equipment and improving its service performance and lifespan.

[0004] However, during laser penetration welding, hump defects are highly likely to occur. A hump refers to a uniformly distributed weld bead appearing on the back side of the weld. Because metal accumulates on the back side to form the weld bead, the front side of the weld is often concave, leading to derivative defects such as indentations and undercut. This causes stress concentration and severely weakens the joint performance. Currently, hump defects generated during laser penetration welding of thick plates have become a significant obstacle limiting the application of this technology in related fields and urgently need to be overcome. Existing research shows that during ultra-high power laser welding of thick plates, the interaction between the laser and the material is intense, causing a surge in the volume of the molten pool and the number of plumes. The surface tension of the molten pool is difficult to balance the downward gravity and the reaction force of the plume ejection. This force difference drives the molten pool to flow and accumulate on the back side of the weld, forming a hump defect. Therefore, an excessively large backflow driving force of the molten pool is a necessary condition for the formation of hump defects in the weld. Reducing the force difference on the molten pool is an effective way to suppress hump defects. The backflow driving force of the molten pool refers to the force difference between the downward plume ejection reaction force and gravity and the upward surface tension.

[0005] Currently, the main methods for suppressing hump defects in thick plate laser welding include vacuum method, magnetic field-assisted method, gas chamber-assisted method, and bottom padding method. Among them, the vacuum method involves placing the test plate in a vacuum chamber for low-pressure or vacuum welding, which yields relatively ideal welding results. However, the vacuum chamber is complex to build, costly, and the welding area is limited, so it is basically limited to the laboratory stage. The magnetic field-assisted method requires the construction of electromagnetic field equipment to compensate for insufficient surface tension and suppress hump defects by applying an external magnetic field. This method is complex to build, and the magnetic field effect is uneven, making it difficult to achieve ideal results. The gas chamber-assisted method involves setting up a gas chamber on the back of the test plate to compensate for insufficient surface tension and suppress hump defects by applying gas pressure. This method has high requirements for airtightness and is not suitable for long or curved welds. The bottom padding method requires placing a thin metal sheet on the back of the test plate to physically support the collapsed molten pool. The effect is not ideal, and post-weld grinding is required.

[0006] Chinese patent CN111872551B provides a method for suppressing hump defects on the back side of laser welds. It uses a special airflow nozzle to apply a high-speed cross-flow above the molten pool, creating a pressure difference between the top and bottom of the molten pool due to the Bernoulli effect. The resulting differential pressure acts on the molten pool, suppressing the flow of the molten pool to the back side of the weld, thereby suppressing the generation of hump defects on the back side of the weld. This patent has the following drawbacks: 1. This patent generates a pressure difference through a horizontal airflow to create a Bernoulli effect to compensate for insufficient surface tension of the bottom molten pool. The effective pressure range it can generate is within a small section of airflow starting from the nozzle end, and the airflow path is horizontal. It is only applicable to straight welds and difficult to apply to curved welds. For oblique welds (welds that are inclined relative to the horizontal plane), the gravity state of the molten pool changes due to the inclination, and whether the pressure difference generated by the airflow can effectively suppress the hump remains to be verified. It is difficult to apply to oblique welds, and its application range is limited. 2. In order to generate a sufficient pressure difference in the molten pool, the airflow velocity applied to the front weld is relatively high. The high-speed airflow may directly act on the molten pool of the front weld, causing it to be impacted and resulting in welding instability. 3. As the plate thickness increases, the gravity of the molten pool and the back pressure it experiences are greater, and the force difference generated by the airflow may not meet the actual needs. 4. The stress and flow state of the molten pool on the back of the weld are different. The force difference generated by this method is theoretically almost uniform, making it difficult to achieve uniform suppression of defects.

[0007] Chinese patent CN108406145A discloses a gas buoyancy-assisted welding device and a welding method using the device. The basic principle is that an auxiliary device forms a closed gas chamber with the workpiece below the weld. The gas chamber is filled with gas at a certain pressure. By controlling the flow rate of the solenoid valve at the outlet and the solenoid valve at the inlet 206, the gas pressure in the gas chamber is kept stable, creating a high-pressure atmosphere at the bottom of the weld. The pressure difference between the upper and lower surfaces of the weld is used to balance the gravity and dynamic pressure that cannot be balanced by the surface tension of the lower surface of the molten pool, thereby achieving the purpose of molten pool stability, eliminating welding defects such as collapse and humps, and thus improving welding quality. The patent has the following drawbacks: First, it requires setting up a gas chamber and controlling the gas flow rate, making the equipment relatively complex. Second, the gas chamber needs to be tightly fitted to the test plate to ensure airtightness, which is complex to operate in actual production and has low adaptability. Third, during the welding process, the gas chamber needs to be placed on the back of the weld and remain stationary. After completing the partial welding, it needs to be disassembled, repositioned, and reinstalled before the subsequent welding of a single long weld can be completed, which is complex and inefficient. If a large-length gas chamber is customized, it will increase costs and working space, making it almost impossible to meet the actual production needs. Fourth, it is difficult to customize a gas chamber suitable for curved or oblique welds, and it is difficult to ensure the airtightness of the gas chamber, making it unsuitable for curved or oblique welds. Summary of the Invention

[0008] The purpose of this invention is to provide a method for suppressing hump defects in laser welding, so as to solve the problems existing in the prior art. It can reduce or avoid the generation of hump, and obtain a weld with beautiful shape and good performance; it can optimize the mechanical properties of the weld; and it has a wide range of applications.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] This invention provides a method for suppressing hump defects in laser welding, comprising the following steps:

[0011] S1. Microgroove structures are machined on the first welding surface of the first part to be welded and / or the second welding surface of the second part to be welded; alloy powder is filled into each of the microgroove structures.

[0012] S2. The first welding surface and the second welding surface are welded together by penetration welding.

[0013] Preferably, S1 includes: after filling each of the microgroove structures with the alloy powder, compacting the alloy powder in the microgroove structures.

[0014] Preferably, S1 includes: the microgroove structure includes a plurality of first microgrooves arranged in a lattice, and the first welding surface and the second welding surface are rectangular surfaces.

[0015] Preferably, the opening of each of the first microgrooves is circular.

[0016] Preferably, S1 includes: before filling the alloy powder into each of the microgroove structures, obtaining the required mass of the alloy powder using Formula 1, as follows:

[0017] M = (ρVat) / (mn) Formula 1

[0018] Where M is the mass of the alloy powder required for each of the microgroove structures; ρ is the density of the alloy powder; and V is the volume of each of the first microgrooves. a and t These are the length and width of the rectangular surface, respectively; m The distance between the centers of two adjacent first microgrooves along the length of the rectangular surface of each of the microgrooves structures; n The distance between the centers of two adjacent first microgrooves along the width direction of the rectangular surface is defined as the microgroove structure.

[0019] Preferably, S1 includes: each of the microgroove structures includes a plurality of strip-shaped second microgrooves, and the plurality of second microgrooves of each of the microgroove structures are arranged in an interlaced mesh.

[0020] Preferably, each of the second micro-grooves is a rectangular groove.

[0021] Preferably, S1 includes: before filling the alloy powder into each of the microgroove structures, obtaining the required mass of the alloy powder using Formula 2, where Formula 1 is as follows:

[0022] M =[ atH- ( l-s ) * ( ks ) * ( t / l ) * ( a / k )] ρ Formula 2

[0023] in, a and t Here, H represents the length and width of the rectangular surface, respectively; H is the depth of each of the second micro-grooves; the centerline of each of the second micro-grooves along the length direction of the rectangular surface is the first centerline, and the centerline of each of the second micro-grooves along the width direction of the rectangular surface is the second centerline. l The distance between two adjacent first center lines of each of the aforementioned microgroove structures is given. k The distance between two adjacent second center lines of each of the microgroove structures; s The width of each of the second micro-grooves.

[0024] Preferably, S1 includes: the method for obtaining the first welding surface includes: milling the first workpiece to be welded to obtain a flat first welding surface; the method for obtaining the second welding surface includes: milling the second workpiece to be welded to obtain a flat second welding surface.

[0025] Preferably, S1 includes: using a pulsed laser to process a microgroove structure on the first welding surface and / or the second welding surface.

[0026] The present invention achieves the following technical effects compared to the prior art:

[0027] This invention provides a method for suppressing hump defects in laser welding. Microgroove structures are fabricated on a first welding surface of a first workpiece to be welded and / or a second welding surface of a second workpiece to be welded. Alloy powder is filled into each microgroove structure. The first and second welding surfaces are then welded together using a through-welding method. This invention, by fabricating microgroove structures on the first and / or second welding surfaces and adding alloy powder to these structures, increases the surface tension of the liquid metal during subsequent welding. The alloy powder not only compensates for insufficient surface tension, reducing or avoiding the formation of humps, but also mitigates the loss of beneficial alloying elements during high-power laser welding, regulates the weld microstructure, and optimizes the mechanical properties of the weld. This invention can suppress hump defects without the need for external auxiliary equipment, resulting in aesthetically pleasing and high-performance welds; it has a wide range of applications. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the laser welding hump defect suppression method provided by the present invention;

[0030] Figure 2 A schematic diagram of a rectangular surface with a first microgroove provided for the present invention;

[0031] Figure 3 for Figure 2 Enlarged view of A in the middle;

[0032] Figure 4 for Figure 3 A cross-sectional view of QQ;

[0033] Figure 5 A schematic diagram of a rectangular surface with a second microgroove provided by the present invention;

[0034] Figure 6 for Figure 5 Enlarged view of B in the middle;

[0035] Figure 7 for Figure 6 A sectional view of XX;

[0036] In the figure: 1. First part to be welded; 2. Second part to be welded; 3. Rectangular surface; 4. Laser beam; 5. Protective gas nozzle. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The purpose of this invention is to provide a method for suppressing hump defects in laser welding, so as to solve the problems existing in the prior art. It can reduce or avoid the generation of hump, and obtain a weld with beautiful shape and good performance; it can optimize the mechanical properties of the weld; and it has a wide range of applications.

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] like Figures 1-7 As shown, the present invention provides a method for suppressing hump defects in laser welding, comprising the following steps:

[0041] S1. Microgroove structures are machined on the first welding surface of the first part to be welded 1 and / or the second welding surface of the second part to be welded 2; alloy powder is filled into each microgroove structure.

[0042] S2. The first welding surface and the second welding surface are welded together by penetration welding.

[0043] This invention involves fabricating microgrooves on the first and / or second welding surfaces and adding alloy powder to these grooves. This increases the surface tension of the liquid metal during subsequent welding. The alloy powder not only compensates for insufficient surface tension, reducing or preventing the formation of humps, but also mitigates the loss of beneficial alloying elements during high-power laser welding, thereby regulating the weld microstructure and optimizing its mechanical properties. This invention can suppress hump defects without the need for external auxiliary equipment, resulting in aesthetically pleasing and high-performance welds. Since this method involves adding alloy powder to the workpiece, it is not limited by weld type and is applicable to various weld types, including straight, curved, and oblique welds, thus having a wide range of applications.

[0044] In this invention, S1 includes: filling each microgroove structure with alloy powder and then compacting the alloy powder in the microgroove structure.

[0045] As a possible implementation method, such as Figure 2 As shown, S1 includes: a microgroove structure comprising multiple first microgrooves arranged in a lattice, and a first welding surface and a second welding surface being rectangular surfaces 3. The regular distribution of the microgroove structure can reduce or avoid powder agglomeration in the molten pool.

[0046] In this invention, the opening of each first microgroove is circular.

[0047] In this invention, S1 includes: before filling the microgroove structures with alloy powder, obtaining the required mass of alloy powder using Formula 1, as follows:

[0048] M=(ρVat) / (mn) Formula 1

[0049] Where M is the mass of alloy powder required for each microgroove structure; ρ is the density of the alloy powder; V is the volume of each first microgroove, which is determined by the diameter d and depth h of each first microgroove. a t and t represent the length and width of rectangular face 3, respectively; m The distance between the centers of two adjacent first microgrooves along the length of the rectangular surface 3 is the distance between the centers of each microgroove structure. n The distance between the centers of two adjacent first microgrooves along the width direction of the rectangular surface 3 is defined as the microgroove structure. By changing the arrangement spacing m and n of the first microgrooves in the z and x directions, and the volume V of a single first microgroove, quantitative control of the filling powder can be achieved.

[0050] As another feasible implementation method, such as Figure 3 As shown, S1 includes: each microgroove structure includes multiple strip-shaped second microgrooves, and the multiple second microgrooves of each microgroove structure are staggered in a mesh pattern. The regular distribution of the microgroove structure can reduce or avoid the agglomeration of powder in the molten pool.

[0051] In this invention, each of the second microgrooves is a rectangular groove.

[0052] In this invention, S1 includes: before filling the microgroove structures with alloy powder, obtaining the required mass of alloy powder using Formula 2, where Formula 1 is as follows:

[0053] M =[ atH- ( l-s ) * ( ks ) * ( t / l ) * ( a / k )] ρ Formula 2

[0054] in, a t and t represent the length and width of rectangular surface 3, respectively; H represents the depth of each second microgroove; the centerline of each second microgroove along the length direction of rectangular surface 3 is the first centerline, and the centerline of each second microgroove along the width direction of rectangular surface 3 is the second centerline. l The distance between two adjacent first center lines of each microgroove structure.k The distance between two adjacent second center lines of each microgroove structure; s The width of each second microgroove is given. By changing the spacing m and n of the grid-like second microgrooves in the z and x directions, as well as the depth H of the second microgrooves, quantitative control of the filling powder can be achieved.

[0055] In this invention, S1 includes: the method for obtaining the first welding surface includes: milling the first workpiece 1 to be welded to obtain a flat first welding surface; the method for obtaining the second welding surface includes: milling the second workpiece 2 to be welded to obtain a flat second welding surface.

[0056] It should be noted that the microgroove structure of the present invention is not limited to the two feasible embodiments described above, and can also be other microstructure forms capable of filling metal powder.

[0057] In this invention, S1 includes: using a pulsed laser to process a microgroove structure on the first welding surface and / or the second welding surface.

[0058] This invention is applicable to the welding of thick plates. In the figure, the x-direction is the welding direction, and the z-direction is the thickness direction of the parts to be welded. The length of the first part to be welded 1 or the second part to be welded 2 is a, the width is t, and the thickness is b. Microgrooves are machined on the first welding surface of the first part to be welded 1 and the second welding surface of the second part to be welded 2, and then they are welded together along the welding direction. It should be noted that this invention is also applicable to the welding of other weld seams, such as curved and oblique weld seams.

[0059] During welding, a laser beam 4 can be used, and a protective gas can be sprayed at the welding point through a protective gas nozzle 5. The angle between the laser beam 4 and the vertical plane is 5°.

[0060] In this invention, the selection principles for alloy powder include: 1. increasing the surface tension of the molten pool; 2. minimizing negative impacts on the microstructure and properties of the weld. Taking 316L as an example, adding small amounts of elements such as silicon or molybdenum can increase the surface tension of the molten pool. Silicon can also enhance the metal's oxidation resistance, and molybdenum can enhance the metal's stability at high temperatures. However, the addition of these elements must be controlled within an appropriate range to avoid loss of other properties. It should be noted that the amount of alloy powder added can be obtained through experiments, etc., which will not be elaborated here.

[0061] This invention is applicable to all penetration welding processes facing hump defects, such as laser penetration welding, laser-arc hybrid penetration welding, and the first pass lock-in weld in arc welding.

[0062] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for suppressing hump defects in laser welding, characterized in that: Includes the following steps: S1. Microgroove structures are machined on the first welding surface of the first workpiece to be welded and / or the second welding surface of the second workpiece to be welded; alloy powder is filled into each of the microgroove structures; the alloy powder can increase the surface tension of the liquid metal during the welding process and compensate for the loss of beneficial alloying elements during high-power laser welding; the microgroove structure includes a plurality of first microgrooves arranged in a lattice, and the first welding surface and the second welding surface are rectangular surfaces; S2. The first welding surface and the second welding surface are welded together by penetration welding.

2. The laser welding hump defect suppression method according to claim 1, characterized in that: S1 includes: After filling each of the microgroove structures with the alloy powder, the alloy powder in the microgroove structures is compacted.

3. The laser welding hump defect suppression method according to claim 1, characterized in that: The opening of each of the first microgrooves is circular.

4. The laser welding hump defect suppression method according to claim 1, characterized in that: S1 includes: Before filling the alloy powder into each of the microgrooves, the required mass of the alloy powder is obtained using Formula 1, as follows: M = (ρVat) / (mn) Formula 1 Where M is the mass of the alloy powder required for each of the microgroove structures; ρ is the density of the alloy powder; and V is the volume of each of the first microgrooves. a and t These are the length and width of the rectangular surface, respectively; m The distance between the centers of two adjacent first microgrooves along the length of the rectangular surface of each of the microgrooves structures; n The distance between the centers of two adjacent first microgrooves along the width direction of the rectangular surface is defined as the microgroove structure.

5. A method for suppressing hump defects in laser welding, characterized in that: Includes the following steps: S1. Microgroove structures are machined on the first welding surface of the first workpiece to be welded and / or the second welding surface of the second workpiece to be welded; alloy powder is filled into each of the microgroove structures; the alloy powder can increase the surface tension of the liquid metal during the welding process and compensate for the loss of beneficial alloying elements during high-power laser welding; each of the microgroove structures includes multiple strip-shaped second microgrooves, and the multiple second microgrooves of each microgroove structure are staggered in a mesh pattern; S2. The first welding surface and the second welding surface are welded together by penetration welding.

6. The laser welding hump defect suppression method according to claim 5, characterized in that: S1 includes: After filling each of the microgroove structures with the alloy powder, the alloy powder in the microgroove structures is compacted.

7. The laser welding hump defect suppression method according to claim 5, characterized in that: Each of the second micro-grooves is a rectangular groove.

8. The laser welding hump defect suppression method according to claim 5, characterized in that: S1 includes: Before filling the alloy powder into each of the microgrooves, the required mass of the alloy powder is obtained using Formula 2, which is as follows: M =[ atH- ( l-s ) * ( ks ) * ( t / l ) * ( a / k )] ρ Formula 2 Where a and t are the length and width of the rectangular surface, respectively; H is the depth of each of the second micro-grooves; the centerline of each of the second micro-grooves along the length direction of the rectangular surface is the first centerline, and the centerline of each of the second micro-grooves along the width direction of the rectangular surface is the second centerline. l The distance between two adjacent first center lines of each of the aforementioned microgroove structures is given. k The distance between two adjacent second center lines of each of the microgroove structures; s The width of each of the second micro-grooves.

9. The laser welding hump defect suppression method according to claim 5, characterized in that: S1 includes: The method for obtaining the first welding surface includes: milling the first workpiece to be welded to obtain a flat first welding surface; the method for obtaining the second welding surface includes: milling the second workpiece to be welded to obtain a flat second welding surface.

10. The laser welding hump defect suppression method according to claim 5, characterized in that: S1 includes: A microgroove structure is fabricated on the first welding surface and / or the second welding surface using a pulsed laser.

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