CN116393823A - Laser welding method - Google Patents
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/20—Bonding
- B23K26/21—Bonding by welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
- B23K26/70—Auxiliary operations or equipment
- B23K26/702—Auxiliary equipment
Abstract
A laser welding method comprises the steps of respectively milling and processing a unilateral groove on two workpieces to be welded; assembling and aligning two workpieces to be welded after cleaning; non-penetrating welding is carried out in a thermal conduction welding mode by using a laser swing wire filling welding method, and only a wire metal is used for filling up the groove at the upper part of the test plate, so that a first wire filling welding seam with obvious surplus height is obtained; and (3) performing full penetration welding in a small hole welding mode by using a laser self-fluxing welding method, and enabling the laser beam to penetrate through the first filler wire welding seam and the whole thickness of the workpiece at the same time to obtain a second full penetration welding seam. In the second full penetration welding process, the upper first filling metal part is melted and moves downwards under the convection action of a molten pool, the residual height of the upper surface of the final welding seam is only slightly reduced under the action of surface tension, and the lower surface forms obvious residual height.
Description
Technical Field
The invention relates to the technical field of laser ablation, in particular to a laser welding method.
Background
The surface forming control, surface deformation and overall heat input requirements of the welding seam are more and more strict, wherein the problems of insufficient back surface height of the welding seam and more defects of the air holes of the welding seam always exist in the welding process. Insufficient weld seam excess and weld seam porosity. Defects become a big problem in the welding process, and also easily generate defects such as air holes, stress concentration and the like, so the surplus height is a requirement of the welding process. The traditional arc welding method often cannot meet the requirements of a new structure on precision and strength due to the reasons of large welding residual deformation, high processing efficiency and the like, and the playing space of the innovative design of the structure is limited. Laser welding has the advantages of high energy density, less heat input, small heating area, small residual deformation, large depth-to-width ratio of welding seams, easiness in realizing automation and the like, and has been developed rapidly in recent years. However, laser welding is currently used less frequently in the welding manufacture of aerospace vehicle structures. The large-size blunt edge 'two-pass' laser welding of the medium-thickness plate is an efficient welding method. The medium-thickness metal structure is widely applied in the fields of aerospace, chemical industry, ships, traffic vehicles, petroleum pipelines and the like, so that the welding quality and the welding efficiency of the medium-thickness metal plate are general problems which are paid attention to by manufacturing industry.
For a long time, the most common method for welding the metal sheet with medium thickness is to adopt a multi-layer multi-pass filler wire welding method after chamfering, wherein the adopted welding heat source is usually an arc heat source with smaller penetrating power, and the blunt edge height of the root of the chamfer is usually 1-2 mm so as to ensure that the arc heat source can completely penetrate through the root area. The smaller blunt edge height results in a larger groove space that needs to be filled. At present, the number of layers and the number of passes of each layer are large in arc welding of the medium-thickness plate, and the filling quantity of weld metal is large, so that the problems of low welding efficiency, large welding deformation, serious performance degradation after repeated heating of a welding zone, large interlayer defects and the like are caused. The high-power laser welding has the remarkable advantages of high energy density, strong penetrating power and large deep hole ratio of the welding line. Taking a 10kW multimode fiber laser as an example, it can easily penetrate a low alloy steel sheet of about 10mm thickness at a time to form a deep and narrow weld comparable to electron beam welding. By utilizing the advantage of laser welding, researchers at home and abroad propose a method for welding a medium-thickness plate with a large-size blunt edge height by using laser, the method is used for welding from bottom to top, a full penetration welding mode is adopted to realize self-fusion welding of a butt joint area with the large-size blunt edge at the lower part, then a groove area near the upper surface is filled by filler wire welding, and a weld seam surplus height is formed on the upper surface, so that a complete welded joint is obtained. Compared with single-pass laser full-penetration self-fusion welding, the method obtains good weld formation with weld seam surplus height due to filler wire welding near the upper surface. Compared with arc welding, the groove space required to be filled after the height of the blunt edge is increased is greatly reduced, the number of welding layers is greatly reduced, the welding deformation is obviously reduced, and the welding efficiency is greatly improved. However, this "bottom-up" medium thickness plate laser welding method has been found to have a number of problems in practical use:
firstly, when welding is carried out from bottom to top, the welding quality of the first lower laser penetration welding is very sensitive to an assembly gap, the requirement on the processing size of a workpiece before welding is high, the requirement on the assembly quality is high, and for a complex-shape structure, the number of out-of-tolerance workpieces is increased, the efficiency is reduced, and the cost is increased. Zero assembly gap is almost impossible when the work pieces are assembled, while assembly gap is generally not constant but varies randomly under the welding path. The spot diameter of the high-power multimode laser is mostly in the range of 0.2-0.4 mm, the existence of gaps and random variation thereof can lead to fluctuation variation of the reduction of the laser energy absorptivity, and finally, the instability of the weld joint forming quality is caused.
Secondly, when welding is carried out from bottom to top, the total height of molten pool metal is smaller than the thickness of a test plate in the first pass through welding process, so that the molten pool liquid metal generally tends to move upwards under the action of surface tension, and finally the lower surface of a welding line is recessed. The concave shape of the lower surface of the welding seam weakens the bearing capacity of the welding joint, and particularly, the concave shape of the lower surface of the welding seam is not allowed for the welding structure serving in severe working conditions in the fields of aerospace, chemical industry and the like.
And secondly, when welding is carried out from bottom to top, the interaction between light and wire and molten pool and plasma in the second non-penetrating laser filler wire welding is complex, the molten drop transition and molten pool flowing behavior is complex, and the stability of the molten pool is poor, so that the porosity is higher.
Finally, the welding wire composition of the second non-penetrating laser filler wire welding is generally different from the base material composition, or the types and the contents of beneficial elements for improving the plasticity and toughness in the welding wire are different, or the contents of harmful elements such as C, S, P in the welding wire are more strictly controlled. When welding is carried out from bottom to top, the molten metal of the welding wire can only fill the upper groove and improve the plastic toughness of the metal of the upper welding seam, and the metal of the lower part of the welding seam is formed by resolidifying after the base metal is melted, so that the plastic toughness of the metal of the lower part of the welding seam cannot be improved by filling the welding wire.
The information disclosed in the background section is only for enhancement of understanding of the background of the invention and therefore may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
In response to the deficiencies or drawbacks of the prior art, a laser welding method is provided. The traditional welding scheme that filling metal is welded from the root of a welding line, and finally the welding filling of the welding line on the upper surface is finished is abandoned, the welding is carried out by adopting a reverse construction scheme from top to bottom which firstly forms the welding line on the upper surface, and welding wires are filled in the first welding process, so that the thickness of a welding area is larger than that of a base metal after the first welding process with a larger assembly gap after workpiece assembly is allowed, and then the welding area penetrates through the lower surface of the welding area, and the upper surface and the lower surface of the welding line can form residual height under the action of surface tension, thereby eliminating the phenomenon of the concave lower surface of the welding line; the tendency of generating air holes is small during full penetration welding, and the air holes in the first welding line are promoted to escape from the welding line of the first non-penetration welding line, so that the defect of the air holes of the final welding joint is effectively restrained; the beneficial alloy element components of the welding wire metal can be spread over the whole thickness range of the welding seam under the convection action of a molten pool after the first non-penetrating welding seam is melted, and the improvement of the plastic toughness of the metal at the lower part of the welding seam is facilitated.
The aim of the invention is achieved by the following technical scheme.
A method of laser welding includes the steps of,
the upper surfaces and the lower surfaces of the welding seam parts on the two workpieces to be welded are communicated with protective gas, and grooves are formed in the upper surfaces of the welding seam parts;
welding the groove position of the upper surface of the welding seam part, and filling the groove of the upper surface of the full welding seam part to obtain a first filler wire welding seam, wherein the first filler wire welding seam is higher than the upper surface of the welding seam part;
and the laser beam penetrates through the welding completely, and simultaneously penetrates through the first filler wire welding seam and the full thickness of the workpiece to be welded at the welding seam part to obtain a second full-penetration welding seam, wherein the upper surface and the lower surface of the second full-penetration welding seam are all formed to be the residual height, and the full thickness is the thickness from the upper surface to the lower surface of the welding seam part to be welded.
In the method, a laser swing filler wire welding method is adopted to weld the groove position of the upper surface of the welding seam part in a thermal conduction welding mode so as to obtain a first filler wire welding seam.
In the method, a laser self-fluxing welding method is adopted to carry out full penetration welding in a small hole welding mode so as to obtain a second full penetration welding seam.
In the method, the workpiece to be welded is a metal plate with the thickness of 5-25 mm, the blunt edge height of the groove is 5-10 mm, and the wire filling amount of the first laser wire filling swing welding can respectively form the surplus height of 0.5-1.5 mm on the upper surface and the lower surface of the workpiece to be welded on the basis of filling the groove space and the lower butt joint gap space.
In the method, when a laser full-penetration self-fluxing welding method penetrates through a first filler wire welding line on the upper surface and a blunt edge area on the lower part at one time, a keyhole penetrating through the full thickness is formed in a molten pool, a channel laser beam is provided for detachment and escape of bubbles in the molten pool after the keyhole to do transverse swing at the amplitude of 5% -15% of the plate thickness so as to stir the molten pool, molten pool metal flows around the keyhole, and convection exchange of materials occurs between the upper part and the lower part of the molten pool.
In the method, unilateral grooves are respectively milled on two workpieces to be welded, and the unilateral grooves on the two workpieces to be welded are assembled to form grooves of welding seam parts of the workpieces to be welded.
In the method, unilateral grooves are respectively milled on two workpieces to be welded, and the two workpieces to be welded are polished, cleaned, assembled, aligned, clamped and fixed to form the grooves of the welding seam parts of the workpieces to be welded.
In the method, the shielding gas is argon.
In the method, before welding the groove position of the upper surface of the welding seam part, a welding head is sent to the welding part of a workpiece to be welded by a robot, and the gesture planning and the welding path planning of the robot and the welding head are carried out; under the condition of not emitting laser, the welding head moves along a welding path, and the light spot shape of the surface of the workpiece to be welded is observed; and confirming that the laser beam is perpendicularly incident to the surface of the workpiece to be welded and the defocusing amount is constant in the welding path planning.
In the method, a laser swing wire filling welding method is adopted to fill the groove, and the blunt edge area at the lower part of the workpiece to be welded is not melted at the moment; and then a laser full penetration self-fusion welding method is adopted to simultaneously penetrate the first filler wire welding line on the upper surface and the blunt edge area on the lower part.
Advantageous effects
When the invention adopts a top-down scheme of forming an upper welding seam firstly for welding, in the first non-penetrating laser filler wire welding, welding wire molten metal enters a groove to bridge the gap at the root of the groove after the interaction of light and wires, the laser energy absorption behavior is not influenced by the gap any more, the laser energy absorption rate and the flow behavior of a molten pool are greatly improved, and the welding quality is stable.
Secondly, when the welding is carried out by adopting a top-down scheme of firstly forming an upper welding line, the thickness of a welding area is larger than that of a base metal after the first welding, and then the upper welding line and the base metal are completely penetrated through in a second full penetration welding process, so that the upper surface and the lower surface of the welding line can be formed to be higher under the action of surface tension, and the phenomenon of the concave lower surface of the welding line is eliminated;
and secondly, when the invention adopts a top-down scheme of firstly forming an upper welding line for welding, the upper welding line and the full thickness range of a base metal are completely penetrated in the second full penetration welding process, a 'keyhole' penetrating through the full thickness is formed in a molten pool, and a smooth 'shortcut' is provided for the detachment and escape of bubbles in the molten pool after the 'keyhole' appears, so that the air hole defect can be obviously reduced. In particular, for the air hole defect formed in the upper welding seam during the first wire filling welding process, an additional floating overflow opportunity can be obtained because the metal around the air hole is remelted during the second full penetration welding process, so that the air hole defect formed in the first wire filling welding seam is eliminated.
Finally, when the invention adopts a top-down scheme of firstly forming an upper welding line for welding, the upper welding line and the full thickness range of a parent metal are fully penetrated in the second full penetration welding process, a keyhole and a molten pool which penetrate through the full thickness are formed in a molten pool, molten pool metal flows around the keyhole, and convection exchange of materials occurs between the upper part and the lower part of the molten pool, so that beneficial elements in a welding wire for improving the plasticity and toughness are convected to the middle part and the lower part of the molten pool, and the effect of improving the plasticity and toughness of the metals in the middle part and the lower part of the welding line is achieved.
The description is merely an overview of the technical solutions of the present invention, in order to make the technical means of the present invention more clearly apparent to those skilled in the art, and in order to make the description of the present invention and other objects, features and advantages of the present invention more obvious, the following description of the specific embodiments of the present invention will be exemplified.
Drawings
Various other advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. It is evident that the figures described below are only some embodiments of the invention, from which other figures can be obtained without inventive effort for a person skilled in the art. Also, like reference numerals are used to designate like parts throughout the figures.
In the drawings:
FIG. 1 is a schematic diagram of a laser swing welding flow of the D406A ultra-high strength steel;
FIG. 2 is a schematic diagram of the size of a narrow gap groove of the D406A ultra-high strength steel according to the invention;
FIG. 3 is a weld cross section of a D406A ultra-high strength steel butt joint test plate according to the invention under the "top-down" laser welding process method of the invention;
FIG. 4 is a photograph of x-ray flaw detection of a weld joint of a D406A ultra-high strength steel butt joint test plate according to the invention under the "top-down" laser welding process method of the invention;
FIG. 5 is a graph of the scanning result of the alloy element distribution surface of the welding seam cross section of the D406A ultra-high strength steel butt joint test plate under the 'top-down' laser welding process method;
FIG. 6 is a cross section of a D406A ultra-high strength steel butt joint test plate according to the invention under a conventional "bottom-up" laser welding process;
FIG. 7 is an x-ray flaw detection picture of a weld joint of a D406A ultra-high strength steel butt joint test plate according to the invention under a traditional 'bottom-up' laser welding process method;
FIG. 8 is a graph of a scanning result of a distribution surface of alloy elements of a welding seam cross section of a D406A ultra-high strength steel butt joint test plate under a traditional 'bottom-up' laser welding process method;
fig. 9 is a schematic diagram comparing the laser welding process of the present invention and a conventional laser welding process.
The invention is further explained below with reference to the drawings and examples.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to fig. 1 to 9. While specific embodiments of the invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It should be noted that certain terms are used throughout the description and claims to refer to particular components. Those of skill in the art will understand that a person may refer to the same component by different names. The description and claims do not identify differences in terms of components, but rather differences in terms of the functionality of the components. As used throughout the specification and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The description hereinafter sets forth a preferred embodiment for practicing the invention, but is not intended to limit the scope of the invention, as the description proceeds with reference to the general principles of the description. The scope of the invention is defined by the appended claims.
For the purpose of facilitating an understanding of the embodiments of the invention, reference will now be made to the drawings of several embodiments illustrated in the drawings, and the accompanying drawings are not to be taken as limiting the embodiments of the invention.
As shown in fig. 1 to 8, the laser welding method includes,
a) Milling and processing unilateral grooves on the two workpieces 1 and 2 to be welded respectively;
b) The two workpieces 1 and 2 to be welded are assembled, aligned, clamped and fixed after being polished and cleaned;
c) Argon shielding gas is introduced to the front and the back of the welding seam part of the workpiece;
d) The robot motion sends the welding head to a welding part on the surface of the workpiece;
e) Planning the postures of the robot and the welding head and planning a welding path;
f) Under the condition that laser is not emitted, the welding head moves along a welding path, and the shape of a light spot on the surface of a workpiece is observed;
g) Confirming that the laser beam is perpendicularly incident on the surface of the workpiece on the whole path and the defocus amount is constant;
h) Welding in a thermal conduction welding mode by using a laser swing filler wire welding method, filling a groove near the upper surface to obtain a first filler wire welding seam 3;
i) And (3) carrying out full penetration welding in a small hole welding mode by using a laser self-fluxing welding method, and simultaneously penetrating the welding seam obtained by the first filler wire welding and the full thickness of the workpiece by using a laser beam to obtain a second full penetration welding seam 4.
In a preferred embodiment, the method is suitable for welding medium-thickness sheet metal having a thickness in the range of about 5 to 25 mm; the depth of a welding groove near the upper surface of the medium-thickness plate is far smaller than that of a traditional arc welding groove; the blunt edge height of the bevel near the lower surface of the middle-thickness plate is 5-10 mm far greater than the blunt edge height (1-2 mm) of the bevel of the traditional arc welding.
In a preferred embodiment, a reverse welding sequence is adopted, namely, a laser swing filler wire welding method is adopted for welding and filling a welding groove near the upper surface of the middle-thickness plate in the first pass, and the lower blunt edge area is not melted at the moment; and then the second pass adopts a laser full penetration self-fluxing welding method to simultaneously penetrate the weld metal near the upper surface and the lower blunt edge area at one time to form a complete welding joint, and the welding flow is schematically shown in figure 1.
In a preferred embodiment, the first pass uses a laser swing filler wire welding method to weld the welding groove near the upper surface of the full medium thickness plate, during the welding process, the 'light-wire' interaction causes the welding wire to melt and enter the groove, and the liquid metal fills the gap at the root of the groove, so that the laser energy absorption behavior is not affected by the gap any more, the stability of the molten pool is improved, and the stability of the welding quality is improved.
In a preferred embodiment, after the first laser filler wire is subjected to swing welding, not only the groove is filled, but also a more obvious surplus height is formed on the upper surface of the workpiece, so that the thickness of a welding area is larger than that of a base material; when the second laser full penetration welding is carried out, the upper welding seam and the full thickness range of the base metal are fully penetrated, and the upper surface and the lower surface of the welding seam can be formed to be the surplus height under the action of surface tension, so that the phenomenon of depression of the lower surface of the welding seam is eliminated.
In a preferred embodiment, the second full penetration weld penetrates the upper weld and the base metal through the full thickness, forming a "keyhole" in the molten pool through the full thickness, which provides a clear "shortcut" for the release and escape of bubbles in the molten pool after the occurrence of the keyhole, thereby significantly reducing blow hole defects. In particular, for the vent defects formed in the upper weld during the first filler wire weld, an additional opportunity for floating up is obtained during the second full penetration weld because the metal surrounding the vent is remelted, thereby eliminating the vent defects already formed in the first filler wire weld 3.
In a preferred embodiment, the upper weld joint and the full thickness range of the base metal are fully penetrated in the second full penetration welding process, a key hole and a molten pool which penetrate through the full thickness are formed in the molten pool, the laser beam transversely swings at the thickness of 5% -15% to stir the molten pool, molten pool metal flows around the key hole, and convection exchange of materials occurs between the upper part and the lower part of the molten pool, so that beneficial elements in the welding wire for improving the plasticity and toughness of the metal in the middle part and the lower part of the weld joint are convected to the middle part and the lower part of the molten pool, and the effect of improving the plasticity and toughness of the metal in the middle part and the lower part of the weld joint is achieved.
In a preferred embodiment, the filler wire quantity of the first laser filler wire swing welding is ensured to be obviously rich on the basis of filling the groove space and the lower butt joint gap space, and the weld seam surplus height of 0.5-1.5 mm can be respectively formed on the upper surface and the lower surface of the workpiece.
In a preferred embodiment, the upper first filler metal portion melts and moves downwardly under the convection of the molten pool during the second full penetration weld, and the final weld bead has a slightly reduced upper surface height and a significantly lower surface height under surface tension.
In one example, the test material was 6.6mm thick annealed D406A ultra-high strength steel, the chemical element composition is shown in Table 1, the annealing temperature is 650 ℃, the structure is granular pearlite, and H10 welding wire (H10 SiMnCrNiMoV) is selected.
TABLE 1 chemical composition/wt% of annealed D406A ultra-high strength steel
TABLE 2 chemical composition/wt% of H10 welding wire (H10 SiMnCrNiMoVA)
Main equipment of the D406A ultra-high-strength steel laser swing filler wire welding system comprises a Pritz YW52 laser swing welding head, a MOTOMAN 6-axis mechanical arm, a YASKAWA MOTOMAN-HP20D robot, a precise three-dimensional platform, an IPG YLS-8000 optical fiber laser, an MXN-10 wire feeder and the like. For protecting a laser lens protecting device and the like, the laser head deflects to the right by an inclination angle of 5 degrees, a paraxial front wire feeding mode is adopted, the included angle between the wire feeding gun head and the horizontal direction is 45 degrees, and the parameters are constant values if no explanation exists.
At present, the groove form shown in fig. 2 is mainly adopted to carry out D406A ultra-high strength steel narrow gap laser swing filler wire welding, namely, the plate thickness is 6.6mm, the width of the bottom of the groove is set to be 2mm, the height of the blunt edge is 5mm, and the outward inclination angles of two sides of the groove are 5 degrees.
The following scheme is adopted for welding:
milling and processing unilateral grooves on the two workpieces 1 and 2 to be welded respectively;
the two workpieces 1 and 2 to be welded are assembled, aligned, clamped and fixed after being polished and cleaned;
argon shielding gas is introduced into the front and the back of the welding seam part of the workpiece;
the robot motion sends the welding head to a welding part on the surface of the workpiece;
planning the postures of the robot and the welding head and planning a welding path;
under the condition that laser is not emitted, the welding head moves along a welding path, the shape of a light spot on the surface of a workpiece is observed, and the fact that the laser beam vertically enters the surface of the workpiece on the whole path and the defocusing amount is constant is confirmed;
welding in a thermal conduction welding mode by using a laser swing filler wire welding method, filling the groove, and obtaining a first filler wire welding seam 3, wherein the specific welding parameters are shown in Table 3;
and carrying out full penetration welding in a small hole welding mode by using a laser self-fluxing welding method, wherein the laser beam penetrates through the first filler wire welding seam 3 and the whole thickness of the workpiece at the same time to obtain a second full penetration welding seam 4, and specific welding parameters are shown in Table 3.
The welding parameters used in particular are shown in the following table:
TABLE 3 welding parameters for the "top-down" laser welding examples of the present invention
The cross section of the welding seam of the 'top-down' laser welding process method is shown in figure 3, the corresponding x-ray flaw detection image is shown in figure 4, the number of welding seam air holes is obviously reduced, the air holes, unfused and crack defects meet the industry requirements, and the welding process method is proved to effectively inhibit the welding seam air hole defects and has the advantages of high efficiency, large welding seam depth-to-width ratio and low defect rate, and is a laser welding method with low defects.
The welding wire composition can be adjusted, the H10 welding wire is changed into a stainless steel welding wire, the alloy element distribution surface scanning is respectively carried out on the cross section and the longitudinal section of the welding seam under the traditional 'bottom-up' laser welding process method and the 'top-down' laser welding process method, the surface scanning results are respectively shown in fig. 5 and 8, and the graph shows that the welding wire element composition can be adjusted for the welding seam composition and the performance. The molten pool metal flows around the keyhole, and convection exchange of materials occurs between the upper part and the lower part of the molten pool, so that beneficial elements for improving the plasticity and toughness in the welding wire are convected to the middle part and the lower part of the molten pool, and the effect of improving the plasticity and toughness of the metal in the middle part and the lower part of the welding seam is achieved, so that the 'top-down' laser welding process method is a low-defect laser welding method.
Comparative example
In order to illustrate the technical advantages of the "top-down" reverse multi-layer welding scheme employed by the present technology by comparison, the implementation results of the conventional "bottom-up" multi-layer welding scheme are presented herein, as follows:
the test material is 6.6mm thick annealed D406A ultra-high strength steel, the chemical element composition is shown in table 1, the annealing temperature is 650 ℃, the structure is granular pearlite, and an H10 welding wire (H10 SiMnCrNiMoV) is selected.
TABLE 1 chemical composition/wt% of annealed D406A ultra-high strength steel
TABLE 2 chemical composition/wt% of H10 welding wire (H10 SiMnCrNiMoVA)
The main equipment for welding the D406A ultra-high strength steel laser swing filler wire comprises a Pritz YW52 laser swing welding head, a MOTOMAN 6-axis mechanical arm, a YASKAWA MOTOMAN-HP20D robot, a precise three-dimensional platform, an IPG YLS-8000 optical fiber laser, an MXN-10 wire feeder and the like. For protecting a laser lens protecting device and the like, the laser head deflects to the right by an inclination angle of 5 degrees, a paraxial front wire feeding mode is adopted, the included angle between the wire feeding gun head and the horizontal direction is 45 degrees, and the parameters are constant values if no explanation exists.
At present, the groove form shown in fig. 2 is mainly adopted to carry out D406A ultra-high strength steel narrow gap laser swing filler wire welding, namely, the plate thickness is 6.6mm, the width of the bottom of the groove is set to be 2mm, the height of the blunt edge is 5mm, and the outward inclination angles of two sides of the groove are 5 degrees.
The following scheme is adopted for welding:
milling and processing unilateral grooves on the two workpieces 1 and 2 to be welded respectively;
2) The two workpieces 1 and 2 to be welded are assembled, aligned, clamped and fixed after being polished and cleaned;
argon shielding gas is introduced into the front and the back of the welding seam part of the workpiece;
the robot motion sends the welding head to a welding part on the surface of the workpiece;
planning the postures of the robot and the welding head and planning a welding path;
under the condition that laser is not emitted, the welding head moves along a welding path, the shape of a light spot on the surface of a workpiece is observed, and the fact that the laser beam vertically enters the surface of the workpiece on the whole path and the defocusing amount is constant is confirmed;
carrying out full penetration welding in a small hole welding mode by using a laser self-fluxing welding method, realizing the connection of the lower blunt edge area, and forming a lower welding line, wherein the specific welding parameters are shown in Table 4;
and (3) welding in a thermal conduction welding mode by using a laser swing filler wire welding method, filling the upper groove, and completing the first filler wire welding seam at the upper part to obtain a complete welding joint, wherein the specific welding parameters are shown in the table 4 below.
The welding parameters used in particular are shown in the following table:
TABLE 4 welding parameters for a conventional "bottom-up" laser welding embodiment
The cross section of such a conventional "bottom-up" laser welded weld is shown in fig. 6, and the x-ray inspection image of the weld is shown in fig. 7. Referring to fig. 9, by comparing the conventional "bottom-up" laser welding process with the "top-down" laser welding process of the present invention, it can be found that the upper and lower surfaces of the weld joint can be formed to be higher by the "top-down" laser welding process of the present invention, thereby eliminating the phenomenon of the depression of the lower surface of the weld joint; the number of weld seam air holes is obviously reduced, the unfused defects are eliminated, and the air holes, unfused and crack defects meet the industry requirements. The invention shows that the top-down laser welding process method effectively inhibits the pore defect of the welding line, eliminates the phenomenon of the concave lower surface of the welding line, has high efficiency and is a laser welding method with low defect.
Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the specific embodiments and fields of application described, which are illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may effect numerous forms of the invention without departing from the scope of the invention as claimed.
Claims (10)
1. A laser welding method is characterized in that the method comprises the following steps,
the upper surfaces and the lower surfaces of the welding seam parts on the two workpieces to be welded are communicated with protective gas, and grooves are formed in the upper surfaces of the welding seam parts;
welding the groove position of the upper surface of the welding seam part, and filling the groove of the upper surface of the full welding seam part to obtain a first filler wire welding seam, wherein the first filler wire welding seam is higher than the upper surface of the welding seam part;
and the laser beam penetrates through the welding completely, and simultaneously penetrates through the first filler wire welding seam and the full thickness of the workpiece to be welded at the welding seam part to obtain a second full-penetration welding seam, wherein the upper surface and the lower surface of the second full-penetration welding seam are all formed to be the residual height, and the full thickness is the thickness from the upper surface to the lower surface of the welding seam part to be welded.
2. The method of claim 1, wherein the groove location of the upper surface of the weld is welded in a thermal conduction mode using a laser swing filler wire welding method to obtain a first filler wire weld.
3. The method of claim 1 or 2, wherein the full penetration welding is performed in a keyhole welding mode using a laser self-fluxing welding method to obtain a second full penetration weld.
4. The method according to claim 2, wherein the workpiece to be welded is a metal plate with a thickness of 5-25 mm, the blunt edge of the groove is 5-10 mm in height, and the filler wire quantity of the first laser filler wire swing welding enables the surplus height of 0.5-1.5 mm to be formed on the upper surface and the lower surface of the workpiece to be welded on the basis of filling the groove space and the lower butt joint gap space.
5. A method according to claim 3, wherein a keyhole is formed in the molten pool through the full thickness when the laser full penetration self-fluxing welding method simultaneously penetrates the first filler wire weld and the lower blunt edge region of the upper surface at a time, the keyhole is followed by providing a passage for the escape and escape of bubbles in the molten pool with a laser beam oscillating laterally in an amount of 5% to 15% of the thickness of the sheet to agitate the molten pool, the molten pool metal flows around the keyhole, and convective exchange of material occurs between the upper and lower parts of the molten pool.
6. The method according to claim 1, wherein the two workpieces to be welded are respectively milled with a single-side groove, and the single-side grooves on the two workpieces to be welded are assembled to form the groove of the welding seam part of the workpieces to be welded.
7. The method of claim 6, wherein the two workpieces to be welded are respectively milled with a single-side groove, and the two workpieces to be welded are assembled in alignment after being polished and cleaned and then clamped and fixed to form the groove of the welding seam part of the workpieces to be welded.
8. The method of claim 1, wherein the shielding gas is argon.
9. The method according to claim 1, wherein before welding the groove position of the upper surface of the weld joint part, the robot sends the welding head to the welding part of the workpiece to be welded for carrying out, and the robot and the welding head pose planning and the welding path planning; under the condition of not emitting laser, the welding head moves along a welding path, and the light spot shape of the surface of the workpiece to be welded is observed; and confirming that the laser beam is perpendicularly incident to the surface of the workpiece to be welded and the defocusing amount is constant in the welding path planning.
10. The method of claim 1, wherein the groove is filled by welding by a laser swing filler wire welding method, and wherein the blunt edge area of the lower part of the workpiece to be welded is not melted; and then a laser full penetration self-fusion welding method is adopted to simultaneously penetrate the first filler wire welding line on the upper surface and the blunt edge area on the lower part.
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