Welding method and apparatus capable of suppressing the peak defect

Abstract

This invention discloses a welding method capable of suppressing hump defects, relating to the field of welding, comprising: S1, processing microstructures 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; S2, aligning the first welding surface of the first workpiece to be welded with the second welding surface of the second workpiece to be welded; and welding the first welding surface and the second welding surface together by laser penetration welding. This invention also discloses a welding apparatus, comprising a microstructure processing device and a welding device, wherein the microstructure processing device is used to process microstructures on the first welding surface and / or the second welding surface, and the welding device is used to weld the first welding surface and the second welding surface. This invention also discloses a corresponding welding apparatus. This invention can complete welding with lower laser power, suppress hump defects, and obtain welds with good performance; it requires no external auxiliary equipment, ensuring the flexibility of the weld joint, and has low welding costs; it has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and in particular to a welding method and apparatus capable of suppressing hump defects. 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, with the advent of fiber lasers and the continuous advancement of laser technology, the beam quality, photoelectric conversion efficiency, and output power of lasers have been continuously improved, laying a solid foundation for their rapid development in the field of thick plate welding. 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 welding methods for thick plates to suppress hump defects include laser multi-pass filler welding (with or without arc initiation of the welding wire) and laser single-pass penetration welding. Laser multi-pass filler welding mainly fills the groove through the melting and transition of the welding wire. Due to limitations such as the amount of welding wire melting, droplet transfer stability, and molten pool flow, the filling thickness of single-pass filler welding is limited. Therefore, this method generally requires multiple weld passes to achieve thick plate welding. In contrast, laser penetration welding refers to a welding method that suppresses hump defects by completely penetrating the test plate through the molten pool or keyhole during the welding process. Laser penetration welding relies on the high energy density and strong penetrability of the laser, and can completely penetrate and melt the material without the need for a groove or filler material, thus achieving single-pass welding of thick plates. Compared with laser filler welding, laser penetration welding significantly improves efficiency and significantly reduces heat input. Its application is of great significance for further shortening the manufacturing and maintenance cycle of large equipment and improving the service performance and lifespan of large equipment.

[0004] However, during single-pass 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 accompanied by a depression, forming derivative defects such as dents. Irregular depressions on the front side of the weld often lead to stress concentration, severely deteriorating the weld's strength and fatigue performance, and consequently significantly weakening the joint performance. Currently, hump defects generated during laser penetration welding of thick plates have become a major obstacle limiting the application of this technology in related fields and urgently need to be overcome. 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 requires placing the test plate in a vacuum chamber for low-pressure or vacuum welding, and the welding effect is relatively ideal. However, the vacuum chamber is complex to build, costly, and the welding area is limited, so it is basically still in 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. However, the construction of electromagnetic field equipment is complex, the magnetic field effect is uneven, and it is difficult to obtain ideal results. The gas chamber-assisted method requires setting up a gas chamber on the back of the test plate to compensate for insufficient surface tension and suppress hump defects by using air pressure. This method has high requirements for airtightness and is not suitable for long welds 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.

[0005] Chinese patent CN111872551B discloses a method for suppressing back-side hump defects in laser-welded welds. It utilizes a specially designed airflow nozzle to apply a high-speed, horizontally blowing airflow above the molten pool, creating a pressure difference between the top and bottom of the molten pool due to the Bernoulli effect. This differential pressure acts on the molten pool, inhibiting its flow towards the back of the weld and thus suppressing the formation of back-side hump defects. However, this patent has the following drawbacks: 1. The patent uses a horizontally blowing airflow to generate a pressure difference and create a Bernoulli effect to compensate for insufficient surface tension at the bottom of the molten pool. The effective pressure range is limited to a small section of airflow starting from the nozzle end, and the airflow path is horizontal. This method is only suitable for straight welds and difficult to apply to curved welds. For oblique welds (welds inclined relative to the horizontal plane), the tilt of the molten pool alters its gravitational state, and whether the pressure difference generated by the airflow can effectively suppress the hump remains to be verified. Therefore, it is difficult to apply this method to oblique welds, limiting its application scope. 2. To generate sufficient pressure in the molten pool… The following are some of the problems with the airflow rate: 1. High airflow velocity applied to the front weld can directly impact the molten pool, causing instability in the welding process; 2. As plate thickness increases, the gravity and recoil pressure on the molten pool increase, making it difficult for the airflow force difference to meet practical requirements; 3. The stress and flow state of the molten pool on the back of the weld are inconsistent, and the force difference generated by this method is theoretically almost uniform, making it difficult to achieve uniform defect suppression; 4. Specialized airflow nozzles and high-velocity surface airflow are required, increasing auxiliary equipment and reducing the flexibility of the weld joint; moreover, the use of airflow increases welding costs.

[0006] 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

[0007] The purpose of this invention is to provide a welding method and apparatus capable of suppressing hump defects, thereby solving the problems existing in the prior art. It can complete welding with lower laser power parameters, suppress hump defects, and obtain welds with good performance. It does not require external auxiliary equipment to suppress hump defects, does not affect the welding process, does not affect the flexibility of the weld joint, and has a low welding cost. It also has a wide range of applications.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] This invention provides a welding method capable of suppressing hump defects, comprising the following steps:

[0010] S1. Microstructures 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.

[0011] S2. Align the first welding surface of the first workpiece to be welded with the second welding surface of the second workpiece to be welded; weld the first welding surface and the second welding surface together by laser penetration welding.

[0012] Preferably, S1 includes: removing oxide film and impurities on the first welding surface while performing microstructure processing on the first welding surface; and removing oxide film and impurities on the second welding surface while performing microstructure processing on the second welding surface.

[0013] Preferably, S1 includes: processing the microstructure on the first welding surface and / or the second welding surface using a pulsed laser.

[0014] Preferably, S2 includes: performing laser welding on the first workpiece to be welded and the second workpiece to be welded using a welding head, wherein during welding, the angle between the welding head and a straight line perpendicular to the first workpiece to be welded is greater than 0°.

[0015] Preferably, S2 includes: during welding, the angle between the welding head and the straight line perpendicular to the first workpiece to be welded is 5°.

[0016] Preferably, S2 includes: the method for joining the first and second welded parts includes: making a portion of the first welding surface contact a portion of the second welding surface; when the first and second welded parts are in a joined state, the distance between the first and second welding surfaces on any cross section perpendicular to the welding direction is the initial gap, and the ratio of the average value of all initial gaps of the first and second welding surfaces to the beam diameter of the laser used for welding is 1 / 12 to 1 / 3.

[0017] Preferably, S1 further includes: before performing the microstructure processing, milling the first weldment and / or the first weldment to be welded to obtain a flat first welding surface and / or a flat second welding surface.

[0018] Preferably, S2 includes: spraying a protective gas onto the weld seam between the first workpiece to be welded and the second workpiece to be welded during welding.

[0019] The present invention provides a welding apparatus for the welding method capable of suppressing hump defects, comprising a microstructure processing apparatus and a welding apparatus. The microstructure processing apparatus is used to process the microstructure on the first welding surface and / or the second welding surface, and the welding apparatus is used to weld the first welding surface and the second welding surface.

[0020] Preferably, the welding device further includes a protective gas injection device, and the welding device includes a welding head; the protective gas injection device is used to inject protective gas into the weld seam between the first workpiece to be welded and the second workpiece to be welded; the angle between the welding head and a straight line perpendicular to the first workpiece to be welded is greater than 0°.

[0021] The present invention achieves the following technical effects compared to the prior art:

[0022] This invention provides a welding method and apparatus capable of suppressing hump defects, comprising the following steps: S1, processing microstructures 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; S2, welding the first welding surface and the second welding surface together by laser penetration welding. By processing the microstructures, the gap and surface roughness of the butt weld can be increased, thereby increasing the absorption of laser energy on the first welding surface and / or the second welding surface. Welding can be completed with lower laser power parameters, suppressing hump defects and obtaining a weld with good performance. Hump defect suppression does not require external auxiliary equipment, does not affect the welding process, does not affect the flexibility of the weld joint, and has low welding costs. Since the microstructures are processed on the workpieces to be welded to increase the absorption of laser energy during welding, this method is not limited by weld type and can be applied to various weld types such as straight welds, curved welds, and oblique welds, with a wide range of applications. Attached Figure Description

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

[0024] Figure 1 A schematic diagram of the welding method for suppressing hump defects provided by the present invention;

[0025] Figure 2 This is a schematic diagram of the laser beam at the butt joint during welding;

[0026] In the figure: 100, welding device; 1, first part to be welded; 101, first welding surface; 2, second part to be welded; 201, second welding surface; 3, welding head; 4, protective gas injection device; d, initial gap; S, welding gap area; t, welding length. Detailed Implementation

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

[0028] The purpose of this invention is to provide a welding method and apparatus capable of suppressing hump defects, thereby solving the problems existing in the prior art. It can complete welding with lower laser power parameters, suppress hump defects, and obtain welds with good performance. It does not require external auxiliary equipment to suppress hump defects, does not affect the welding process, does not affect the flexibility of the weld joint, and has a low welding cost. It also has a wide range of applications.

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

[0030] Example 1

[0031] like Figures 1-2 As shown, the present invention provides a welding method capable of suppressing hump defects, comprising the following steps:

[0032] S1. Microstructures are machined on the first welding surface 101 of the first part to be welded 1 and / or the second welding surface 201 of the second part to be welded 2.

[0033] S2. The first welding surface 101 of the first part to be welded 1 and the second welding surface 201 of the second part to be welded 2 are joined together by laser penetration welding.

[0034] By processing microstructures, the gap and surface roughness of the butt weld can be increased. The rough surface microstructures allow more laser light to enter the weld and increase the number of laser reflections, thereby increasing the absorption of laser energy by the first welding surface 101 and / or the second welding surface 201. Welding can be completed with lower laser power parameters, suppressing hump defects and obtaining a weld with good performance. Hump defect suppression does not require external auxiliary equipment, does not affect the welding process, does not affect the flexibility of the welding head 3, and has low welding cost. Since the microstructures are processed on the workpiece to be welded to increase the absorption of laser energy during the welding process, this method is not limited by the type of weld and can be applied to various weld types such as straight welds, curved welds, and oblique welds, with a wide range of applications.

[0035] In this embodiment, S1 includes: removing the oxide film and impurities on the first welding surface 101 while performing microstructure processing on the first welding surface 101; and removing the oxide film and impurities on the second welding surface 201 while performing microstructure processing on the second welding surface 201. Generally, removing the oxide film and impurities is required before welding. However, the process of preparing the microstructure in this embodiment itself also removes the oxide film and impurities, so that the entire welding process does not require additional steps, resulting in high efficiency and low cost.

[0036] In this embodiment, S1 includes: processing microstructures on the first welding surface 101 and / or the second welding surface 201 using a pulsed laser. The pulsed laser can achieve both laser cleaning and microstructure processing.

[0037] In this embodiment, S2 includes: performing laser welding on the first workpiece 1 and the second workpiece 2 to be welded through the welding head 3. During welding, the angle between the welding head 3 and the straight line perpendicular to the first workpiece 1 to be welded is greater than 0°.

[0038] In this embodiment, S2 includes: during welding, the angle between the welding head 3 and the straight line perpendicular to the first workpiece 1 to be welded is 5° to protect the welding head 3 from damage caused by laser reflection. During processing, the workpiece is generally horizontal, and the angle between the welding head 3 and the vertical direction is 5°.

[0039] In this embodiment, S1 further includes: before performing microstructure processing, milling the first weldable part 1 and / or the first weldable part 1 to obtain a flat first welding surface 101 and / or a flat second welding surface 201.

[0040] In this embodiment, S2 includes: the method for joining the first weldable component 1 and the second weldable component 2 includes: making a portion of the welding surface of the first welding surface 101 contact a portion of the welding surface of the second welding surface 201; when the first weldable component 1 and the second weldable component 2 are in a joined state, the first welding surface 101 and the second welding surface 201 are in any one of the directions perpendicular to the welding direction ( Figure 1 The distance on the cross-section (in the direction indicated by the middle arrow) is the initial gap d. The ratio of the average value of all initial gaps d on the first welding surface 101 and the second welding surface 201 to the beam diameter of the laser used for welding is 1 / 12 to 1 / 3. The milled first welding surface 101 and / or the second welding surface 201 are very flat, while the microstructure morphology of the first welding surface 101 and / or the second welding surface 201 can be changed according to requirements after microstructure processing. For example... Figure 2 As shown, when the first welding surface 101 and the second welding surface 201 are brought into contact, they cannot fully contact each other; only a portion of the welding surfaces can make contact. The average value of the initial gap d between the first workpiece 1 and the second workpiece 2 during welding is D. A rougher surface microstructure means a larger D. As D increases, more laser light can directly enter the gap and undergo multiple reflections. Simultaneously, the rough surface microstructure increases the number of laser reflections, resulting in more laser energy being absorbed. It is important to note that when D exceeds a certain threshold (1 / 12 to 1 / 3 of the laser beam diameter used for welding), the laser will pass directly through the gap, making normal welding impossible; therefore, D cannot be too large. When D is less than this threshold, due to the smaller gap, less laser energy is absorbed, and the surface microstructure has almost no impact on the welding process; therefore, D cannot be too small. By increasing the absorption of laser energy by the workpieces during welding through microstructure, the hump defect can be suppressed at lower laser power. This embodiment can greatly reduce the dependence on laser power, requires no additional auxiliary equipment, has strong applicability, low production cost, uniform effect, and does not require post-weld grinding.

[0041] In a preferred embodiment, the same process parameters are used to perform microstructure processing on the first welding surface 101 and the second welding surface 201 to prevent significant differences in the surface structure of the first welding surface 101 and the second welding surface 201, thereby ensuring the consistency of weld formation.

[0042] In this embodiment, the method for obtaining the average value of all initial gaps d between the first welding surface 101 and the second welding surface 201 is as follows: obtain the welding gap area S between the first welding surface 101 and the second welding surface 201 in the butt joint state; obtain the welding length, when the lengths of the first welding surface 101 and the second welding surface 201 along the perpendicular welding direction are the same, the lengths of the first welding surface 101 and the second welding surface 201 along the perpendicular welding direction are the welding length t; when the lengths of the first welding surface 101 and the second welding surface 201 along the perpendicular welding direction are not the same, the smaller of the lengths of the first welding surface 101 and the second welding surface 201 along the perpendicular welding direction is the welding length t; the average value of all initial gaps d between the first welding surface 101 and the second welding surface 201 is the ratio of the welding gap area S to the welding length t.

[0043] In this embodiment, S2 includes: during welding, spraying protective gas into the weld seam between the first workpiece 1 and the second workpiece 2, the protective gas acting on the weld pool.

[0044] The welding method for suppressing hump defects provided in this embodiment is applicable to the welding of components of various thicknesses that can be welded through by laser in a single pass and have a certain cross-sectional area for fabricating microstructures, such as the welding of plates with a thickness of 5mm to 25mm.

[0045] Table 1 compares the weld formation of 20mm stainless steel test plates under different cross-sectional (welding surface) conditions with varying laser welding parameters. Group 1 in Table 1, using low-speed welding, exhibited a hump defect. Group 3 in Table 1, using high-speed welding, achieved a well-formed weld joint without any external equipment or measures, representing the most convenient and effective method for suppressing hump defects. However, for laser penetration welding, increasing the welding speed requires greater laser power, placing higher demands on the maximum power of the laser. Using a higher-power laser means higher equipment and production costs. The occurrence of hump defects is often related to insufficient welding heat input. Further reducing the heat input often leads to incomplete penetration; further increasing the heat input may result in a well-formed weld. However, if the welding speed is reduced to increase the heat input based on the parameters of Group 1, the molten pool is more prone to collapse, forming severe concave defects, as shown in Group 2 of Table 1. Therefore, reducing the welding speed to increase the heat input should be avoided. This embodiment increases the absorption of laser energy by the workpiece during welding through microstructure, thereby enabling welding to be completed with lower laser power parameters than in Group 1, thus suppressing hump defects, as shown in the results of Group 4 in Table 1. This embodiment greatly reduces dependence on laser power, requires no additional auxiliary equipment, has strong applicability, and low production costs.

[0046] Table 1. Formation of 20mm stainless steel test plates under different cross-sectional conditions with varying laser welding parameters.

[0047]

[0048] Example 2

[0049] This embodiment provides a welding apparatus 100 for the welding method in Embodiment 1 that can suppress hump defects. It includes a microstructure processing device and a welding device. The microstructure processing device processes microstructures on the first welding surface 101 and / or the second welding surface 201, and the welding device welds the first welding surface 101 and the second welding surface 201. The first welding surface 101 and / or the second welding surface 201, after being processed by the microstructure processing device, are welded by the welding device. This allows welding to be completed with relatively low laser power parameters, suppressing hump defects and obtaining a high-performance weld. No additional auxiliary equipment is required, making it highly applicable and cost-effective.

[0050] In this embodiment, a protective gas injection device 4 is also included, and the welding device includes a welding head 3. The protective gas injection device 4 is used to inject protective gas into the weld seam between the first workpiece to be welded 1 and the second workpiece to be welded 2. The angle between the welding head 3 and a straight line perpendicular to the first workpiece to be welded 1 is greater than 0°.

[0051] 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 welding method capable of suppressing hump defects, characterized in that: Includes the following steps: S1. Microstructures are processed 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; the rough surface microstructures enable more laser light to enter the weld and increase the number of laser reflections. S2. Connect the first welding surface of the first workpiece to be welded to the second welding surface of the second workpiece to be welded; The first welding surface and the second welding surface are welded together by laser penetration welding. S2 includes: the method for joining the first and second welded parts includes: making a portion of the first welding surface contact a portion of the second welding surface; when the first and second welded parts are in a joined state, the distance between the first and second welding surfaces on any cross section perpendicular to the welding direction is the initial gap, and the ratio of the average value of all initial gaps of the first and second welding surfaces to the beam diameter of the laser used for welding is 1 / 12 to 1 / 3.

2. The welding method for suppressing hump defects according to claim 1, characterized in that: S1 includes: While performing microstructural processing on the first welding surface, the oxide film and impurities on the first welding surface are removed; while performing microstructural processing on the second welding surface, the oxide film and impurities on the second welding surface are removed.

3. The welding method for suppressing hump defects according to claim 1, characterized in that: S1 includes: The microstructure is fabricated on the first welding surface and / or the second welding surface using a pulsed laser.

4. The welding method for suppressing hump defects according to claim 1, characterized in that: S2 includes: Laser welding is performed on the first and second parts to be welded using a welding head. During welding, the angle between the welding head and a straight line perpendicular to the first part to be welded is greater than 0°.

5. The welding method for suppressing hump defects according to claim 4, characterized in that: S2 includes: During welding, the angle between the welding head and the straight line perpendicular to the first workpiece to be welded is 5°.

6. The welding method for suppressing hump defects according to claim 1, characterized in that: S1 further includes: before performing the microstructure processing, milling the first weldment and / or the first weldment to be welded to obtain a flat first welding surface and / or a flat second welding surface.

7. The welding method for suppressing hump defects according to claim 1, characterized in that: S2 includes: During welding, a protective gas is sprayed onto the weld seam between the first and second parts to be welded.

8. A welding apparatus used in the welding method for suppressing hump defects according to any one of claims 1 to 7, characterized in that: It includes a microstructure processing device and a welding device. The microstructure processing device is used to process the microstructure on the first welding surface and / or the second welding surface, and the welding device is used to weld the first welding surface and the second welding surface.

9. The welding apparatus according to claim 8, characterized in that: It also includes a protective gas injection device, and the welding device includes a welding head; the protective gas injection device is used to inject protective gas into the weld seam between the first workpiece to be welded and the second workpiece to be welded; the angle between the welding head and a straight line perpendicular to the first workpiece to be welded is greater than 0°.

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