Preheating-free thick plate narrow gap laser welding defect control method

Abstract

The invention discloses a preheating-free thick plate narrow-gap laser welding defect control method which comprises the following steps: S1, designing single-side or double-side narrow-gap grooves for thick plate workpieces with different thicknesses, machining the grooves in a machining manner, polishing and cleaning a to-be-welded area, and performing butt joint assembly and spot welding fixation on the grooves and the to-be-welded area; s2, a wire heating device is additionally arranged on the wire feeding mechanism, the positive electrode of the wire heating device is connected with a welding wire, and the negative electrode is connected with base metal; a wire feeding mechanism, a laser heat source and a shielding gas system are sequentially arranged in the welding direction. S3, a welding wire is preheated, the welding wire extends into the bottom of the groove and is centered, the total power of point ring laser, the point ring ratio, the swing mode, the swing amplitude and the swing frequency are adjusted, and backing welding and filling welding are carried out; s4, heat preservation after welding; s5, carrying out nondestructive testing; according to the thick plate narrow-gap welding process, by means of swing point ring laser matching, middle point laser wire fusing and outer ring laser swing defect control are achieved, and the common defects that the side wall of a narrow gap is not fused, cracks exist, and air holes exist are overcome.

Description

Technical Field

[0001] The invention relates to the technical field of thick plate narrow gap welding, and in particular to a method for controlling defects in thick plate narrow gap laser welding without preheating. Background Art

[0002] At present, the main welding methods used for thick plate welding are submerged arc welding, semi-automatic gas shielded welding and manual welding. Submerged arc welding has high welding efficiency, but the heat input is extremely large, which is not conducive to joint performance. Semi-automatic gas shielded welding and manual welding use manual welding, and the welding quality is greatly affected by human factors, making it difficult to ensure the consistency of welding quality. In addition, all three methods require large-sized grooves, multi-layer and multi-pass double-sided welding, which results in large deformation and low welding efficiency.

[0003] Narrow gap laser wire welding combines the advantages of laser welding and narrow gap, with less deformation after welding, which can improve welding quality and efficiency. It is a very potential alternative process to existing welding processes; however, due to the need for preheating of thick plates, it is inefficient and wastes resources.

[0004] In addition, conventional single-beam laser sources have high requirements on the processing accuracy of welding test plates and assembly accuracy of weldments, poor on-site adaptability, and a narrow process parameter window. They are unable to solve common defects in narrow gaps, such as lack of side wall fusion, lack of interlayer fusion, cracks, pores, and deformation, which restricts the application of laser narrow gap wire filling welding technology in shipbuilding.

[0005] In the prior art, authorization announcement number CN117532161A, a spot ring laser wire filling welding method, discloses the basic principle of spot ring laser and the benefits of heating the side wall, but because it has no hot wire capacity, cannot swing and does not adopt a deformation control strategy, it cannot solve the defects of interlayer unfusion, pores, cracks and deformation.

[0006] Authorization announcement number CN118342071A, a method for efficient non-post-heating welding of thick plates of 1100MPa ultra-high strength steel, discloses a process for thick plate narrow gap welding without post-heating, but the arc welding process is different from the laser welding control strategy and further research is needed.

[0007] Authorization announcement number CN117548829A, a laser-MIG composite welding method for titanium alloy thick plates, discloses laser composite welding of titanium alloy thick plates with controlled oxidation, achieving better forming and reliable connection of welds, but the composite welding equipment is complex, has strict process requirements and is only suitable for titanium alloys, and has a narrow range of applications. Summary of the invention

[0008] The purpose of the present invention is to provide a method for controlling defects in narrow gap laser welding of thick plates without preheating, so as to solve the problem in the prior art that narrow gap welding of thick plates requires preheating, wastes energy and the heating device affects the implementation of subsequent welding processes.

[0009] In order to achieve the above object, the technical solution of the present invention is: A method for controlling defects in narrow gap laser welding of thick plates without preheating, characterized in that it comprises the following steps: Step S1) Design a single-sided or double-sided narrow gap groove for thick plate workpieces of different thicknesses. The workpiece is a 10CrNi3MoV steel plate or a TC4 titanium plate. The groove is a U-shaped groove. When the plate thickness of the workpiece is t≤30mm, a single-sided groove is adopted; when the plate thickness of the workpiece is 30mm<t≤80mm, a double-sided groove is adopted, the groove inclination angle is 1°~1.5°, the groove root size is 3.5~4.5mm, and the blunt edge size is 3~8mm; The groove is machined, the area to be welded is polished and cleaned, and the two are butt-jointed and fixed by spot welding; Step S2) installing a hot wire device on the wire feeding mechanism, wherein the positive electrode of the hot wire device is connected to the welding wire, and the negative electrode is connected to the base material, and the wire feeding mechanism, the laser source and the shielding gas system are sequentially arranged along the welding direction; Step S3) The hot wire device preheats the welding wire, the welding wire is inserted into the bottom of the groove and centered, the total laser power of the laser source, the spot ring ratio, the swing mode, the swing amplitude and the swing frequency are adjusted, and the base welding and the filling welding are performed. The laser source adopts a point ring laser mode, the laser beam emitted by the laser source and the light wire spacing of the welding wire are 0-2 mm, the angle between the laser beam and the workpiece is 82°-87°, the welding wire is WM960S and TC4 welding wire with a diameter of 1.2 mm, the shielding gas system adopts 99.99% pure Ar shielding gas, the flow rate of the shielding gas is 25-40 L / min, ventilation is performed 5 minutes in advance before welding and continuous ventilation is performed 5 minutes after welding, the working voltage of the hot wire device is 2V, and the current is 65-80A; The laser source has a point laser power of 2.8-8.5 kW, a ring laser power of 1.0-2.0 kW, a defocus of +10-+20 mm, a circular swing mode, a swing amplitude of 1.8-2.2 mm, a swing frequency of 50-65 Hz, a welding speed of 0.4-1.2 m / s, and a wire feeding speed of 4-5 m / min; For single-side groove, welding is performed after a certain reverse deformation is preset, and the welding process is self-fluxing welding for base and single-pass multi-layer welding for filling; For double-sided grooves, dual laser sources are used for double-sided self-fusion welding to prime and fill both sides at the same time, or a single laser source is used for double-sided self-fusion welding to prime and fill. The filling order is 1 / 3 on the front side, 2 / 3 on the back side, 2 / 3 on the front side, and the remaining 1 / 3 on the back side to achieve the best deformation control. The interlayer temperature is controlled at 80~120℃. Step S4) After welding, the area within 200 mm to 300 mm on both sides of the weld is covered with asbestos blankets, and the insulation asbestos is removed after natural cooling for 72 hours; Step S5) After the heat preservation is completed, non-destructive testing is performed on the weld area.

[0010] Furthermore, in step S3, the single-layer welding height of the single-pass multi-layer welding is 1.4 mm to 1.7 mm, and the number of welding passes is 20 to 50 when the plate thickness is between 30 mm and 80 mm.

[0011] Furthermore, in step S1, the groove is processed by a milling machine, and the surface within 10 mm on both sides of the groove of the workpiece is polished using sandpaper, and the polished surface is cleaned by an acetone-water washing-acid washing-water washing-drying process to remove surface oil and rust.

[0012] Furthermore, in step S1, the spot welding is fixed by a fixture, the assembly gap is 0-0.2 mm, the spot welding length is 20 mm, and the spot welding interval is 80-100 mm.

[0013] The present invention adopts spot ring laser welding, which is composed of two laser beams, a middle spot laser and an outer circular ring laser. The middle spot laser is responsible for the fuse, and the outer circular ring laser swings to increase the range of the light beam, heat the side wall and the front of the weld, and stir the molten pool. Combined with a reasonable welding process and sequence, the effects of solving the problems of unfused side walls, unfused layers, cracks, pores, and deformation can be achieved. Effective control of the defects of narrow gap multi-layer single-pass wire filling welding of thick plates including steel and titanium can be achieved without preheating, thereby ensuring the molding quality and improving the adaptability and reliability of the latter half of the narrow gap welding process.

[0014] The present invention obtains the ideal thick plate narrow gap groove multi-layer single-pass welding formation by adjusting multiple groups of related process parameters such as spot laser power, ring laser power, swing scheme, etc. The preheating-free swing spot ring laser expands the adaptability of on-site welding, is suitable for the production and processing of various complex thick plate workpieces, has high implementation flexibility, and reduces production costs; The ring laser in front of the molten pool and the hot wire mechanism of the present invention play a role in preheating the thick plate and raising the temperature of the molten pool, and the ring laser in the rear of the molten pool has a certain degree of annealing effect on the weld, which helps to reduce the residual stress and deformation in the weld and solve the problems of interlayer unfusion and hot and cold cracks; the swinging ring laser can heat the left and right sides of the groove and stir the molten pool, which helps to solve the defects such as side wall unfusion and pores; for the single-sided groove, the reverse deformation is preset, and for the double-sided groove, the double-sided heat source is used for simultaneous welding or the front and back welding sequence is reasonably arranged, which can ensure the best deformation control effect, and can realize the high-reliability multi-layer single-pass welding of narrow gap laser welding of thick plates of different materials without preheating; Compared with conventional large groove arc welding, the narrow gap laser welding of the present invention simplifies the welding process, reduces the number of welding passes and welding deformation, and improves the efficiency and welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of laser welding of the present invention; Figure 2 This is a schematic diagram of the point ring laser and light filament distribution of the present invention; Figure 3 Schematic diagram of the narrow gap groove of the weld of the present invention; Figure 4 A schematic diagram of the anti-deformation arrangement of single-sided groove welding of the present invention; Figure 5 This is a real picture of the spot ring swing laser single-sided narrow gap groove weld of a 30mm thick plate in Example 1; Figure 6 This is a diagram showing the nondestructive testing results of a spot ring swing laser single-sided narrow gap weld on a 30 mm thick plate in Example 1; Figure 7 This is a real picture of Example 2, a spot ring swing laser double-sided narrow gap groove weld of an 80mm thick plate; Figure 8 This is a diagram showing the nondestructive testing results of the spot ring swing laser double-sided narrow gap weld of an 80 mm thick plate in Example 2; Fig. 9 This is a comparative example, a real picture of a 30mm thick plate ordinary laser single-sided narrow gap groove weld.

[0016] Reference numerals: 1 workpiece, 2 laser beam, 3 welding wire, 4 hot wire device, 5 groove, 6-point laser, 7-ring laser. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0018] (1) Welding materials 700MPa grade 10CrNi3MoV high strength steel plate with a thickness of 30mm, Welding wire 3 is WM960S welding wire 3, with a diameter of 1.2 mm, The shielding gas for welding is Ar gas with a volume fraction and a purity of 99.99%.

[0019] (2) The welding process includes the following steps: Step S1) groove 5 processing and assembly (pre-processing); Design as Figure 3 The single-sided narrow gap groove 5 shown is machined by machining the groove 5, and the surface within 10 mm on both sides of the groove 5 of the workpiece 1 is polished with sandpaper, and the polished surface is cleaned by acetone-water washing-acid washing-water washing-drying process to remove surface oil and rust, and the area to be welded is polished and cleaned, and the two are butt-assembled, with an assembly gap of 0-0.2 mm, and spot welded to the bottom of the thick plate, with a total of 9 spot welds, 100 mm intervals, and each weld point is 20 mm long; Step S2) welding equipment preparation; Welding settings such as Figure 1 As shown, a hot wire device 4 is installed on the wire feeding mechanism, the positive electrode of the hot wire device 4 is connected to the welding wire 3, and the negative electrode is connected to the base material. The wire feeding mechanism, the laser source, and the protective gas system are arranged in sequence along the welding direction. Among them, the laser beam 2 emitted by the laser source and the light wire of the welding wire 3 are spaced 0.5 mm apart, the angle between the laser beam 2 and the workpiece 1 is 82°, and the laser source adopts a point ring laser mode, as shown in FIG. Figure 2 As shown; Step S3) welding process; The hot wire device 4 uses 2V voltage and 80A current to preheat the welding wire 3. The welding wire 3 is inserted into the bottom of the groove 5 and centered. The power of the base welding spot laser 6 is 5.2 kW, the power of the ring laser 7 is 1.8 kW, the welding speed is 1m / min, the defocus amount is +15mm, the swing mode is circular, the swing amplitude is 2.2mm, and the swing frequency is 65Hz; The power of the laser 6 for filling the weld spot is 8.5 kW, the power of the ring laser 7 is 2.0 kW, the welding speed is 0.48 m / min, the wire feeding speed is 4.8 m / min, the defocus is +20 mm, the swing mode is circular, the swing amplitude is 2.2 mm, and the swing frequency is 65 Hz; for the single-sided groove 5, the preset is as follows Figure 4 The welding is performed after the reverse deformation shown to control the deformation; the interlayer temperature is controlled to be 120°C; The entire welding process uses 99.99% pure Ar shielding gas with a flow rate of 25L / min, and the ventilation is advanced and delayed by 5min respectively to ensure sufficient shielding gas; Step S4) heat preservation after welding; After the entire welding process is completed, the entire weld area is covered with asbestos blanket within 300mm on both sides, and the insulation asbestos is removed after natural cooling for 72 hours; Step S5) non-destructive testing; After the insulation is completed, the weld area is subjected to radiographic nondestructive testing to ensure that there are no defects, including lack of fusion of the side walls, lack of fusion between layers, cracks, and pores.

[0020] (3) Test results The weld formation of Example 1 is as follows Figure 5 As shown, Figure 6 The figure shows the nondestructive testing results obtained in Example 1. It can be seen that the laser power is reasonably selected, the weld is formed evenly, there is no obvious undercut on the weld surface, no large spatter, and no pores and cracks inside the weld. Example

[0021] (1) Welding materials 80mm thick 825MPa grade TC4 (Ti-6Al-4V) titanium plate, The welding wire 3 is TC4 welding wire 3, with a diameter of 1.2 mm. The shielding gas for welding is Ar gas with a volume fraction and a purity of 99.99%.

[0022] (2) The welding process includes the following steps: Step S1) groove processing and assembly (pre-processing); Design as Figure 3 The double-sided narrow gap groove 5 shown is machined by machining the groove 5, and the surfaces within 10 mm on both sides of the groove 5 of the workpiece 1 are polished with sandpaper, and the polished surface is cleaned by acetone-water washing-acid washing-water washing-drying process to remove surface oil stains and rust, and the area to be welded is polished and cleaned, and the two are butt-assembled, with an assembly gap of 0-0.2 mm, and spot welded to the bottom of the thick plate, with a total of 3 spot welds, 80 mm apart, and each weld point is 20 mm long; Step S2) welding equipment preparation; Welding settings such as Figure 1 As shown, a hot wire device 4 is installed on the wire feeding mechanism, the positive electrode of the hot wire device 4 is connected to the welding wire 3, and the negative electrode is connected to the base material; along the welding direction, the wire feeding mechanism, the laser source, and the protective gas system are arranged in sequence, wherein the laser beam 2 emitted by the laser source and the light wire of the welding wire 3 are spaced 0.25 mm apart, the angle between the laser beam 2 and the workpiece 1 is 87°, and the laser source adopts a point ring laser mode, as shown in FIG. Figure 2 As shown; Step S3) welding process; The welding wire 3 is preheated using a 2V voltage and a 65A current. The welding wire 3 is inserted into the bottom of the groove 5 and centered. The power of the base welding spot laser 6 is 2.8 kW, the power of the ring laser 7 is 1.0 kW, the welding speed is 1.2m / min, the defocus amount is +20mm, the swing mode is circular, the swing amplitude is 1.8 mm, and the swing frequency is 50Hz; The power of the laser 6 for filling the weld spot is 3.8 kW, the power of the ring laser 7 is 1.0 kW, the welding speed is 0.8 m / min, the wire feeding speed is 4.0 m / min, the defocus is +20 mm, the swing mode is circular, the swing amplitude is 1.8 mm, and the swing frequency is 50 Hz; Use a single laser source to fill both sides in turn. The filling order is 1 / 3 on the front side, 2 / 3 on the back side, 2 / 3 on the front side, and the remaining 1 / 3 on the back side to control deformation. The interlayer temperature is controlled at 80℃. The entire welding process uses 99.99% pure Ar shielding gas with a flow rate of 40L / min, and the ventilation is advanced and delayed by 5min respectively to ensure sufficient shielding gas; Step S4) heat preservation after welding; After the entire welding process is completed, the entire weld area is covered with asbestos blanket within 300mm on both sides, cooled naturally for 72 hours, and the insulation asbestos is removed; Step S5) non-destructive testing; After the insulation is completed, the weld area is subjected to radiographic nondestructive testing to ensure that there are no defects, including lack of fusion of the side walls, lack of fusion between layers, cracks, and pores.

[0023] (3) Test results The weld formation of Example 1 is as follows Figure 7 As shown, Figure 8 The figure shows the nondestructive testing results obtained in Example 2. It can be seen that the laser power is reasonably selected, the weld is formed evenly, there is no obvious undercut on the weld surface, no large spatter, and no pores and cracks inside the weld.

[0024] Comparative Example (1) Welding materials 700MPa grade 10CrNi3MoV high strength steel plate with a thickness of 30mm, Welding wire 3 is WM960S welding wire 3, with a diameter of 1.2 mm, The shielding gas for welding is Ar gas with a volume fraction and a purity of 99.99%.

[0025] (2) The welding process includes the following steps: Step S1) groove 5 processing and assembly (pre-processing); Design as Figure 3 The single-sided narrow gap groove 5 shown is machined by machining the groove 5, and the surface within 10 mm on both sides of the groove 5 of the workpiece 1 is polished with sandpaper, and the polished surface is cleaned by acetone-water washing-acid washing-water washing-drying process to remove surface oil and rust, and the area to be welded is polished and cleaned, and the two are butt-assembled, with an assembly gap of 0-0.2 mm, and spot welded to the bottom of the thick plate, with a total of 3 spot welds, 100 mm apart, and each weld point is 20 mm long; Step S2) welding equipment preparation; Welding settings such as Figure 1 As shown, a hot wire device 4 is installed on the wire feeding mechanism, the positive electrode of the hot wire device 4 is connected to the welding wire 3, and the negative electrode is connected to the base material; Along the welding direction, the wire feeding mechanism, laser source, and protective gas system are set in sequence, where the wire spacing is 0.5 mm, the angle between the laser source and the workpiece 1 is 82°, and the laser source mode adopts the point ring laser mode, such as Figure 2 As shown; Step S3) welding process; The welding wire 3 is preheated using a voltage of 2V and a current of 80A. The welding wire 3 is inserted into the bottom of the groove 5 and centered. The base welding laser power is 7.0 kW, the welding speed is 1m / min, and the defocus amount is +15mm. The laser power of the filling welding is 10.5 kW, the welding speed is 0.48 m / min, the wire feeding speed is 4.8 m / min, and the defocusing amount is +20 mm; for the single-side groove 5, the preset Figure 4 The welding is performed after the reverse deformation shown to control the deformation; the interlayer temperature is controlled to be 120°C; The entire welding process uses 99.99% pure Ar shielding gas with a flow rate of 25L / min, and the ventilation is advanced and delayed by 5min respectively to ensure sufficient shielding gas.

[0026] Step S4) heat preservation after welding; After the entire welding process is completed, the entire weld area is covered with asbestos blanket within 300mm on both sides, naturally cooled for 72 hours, and the insulation asbestos is removed.

[0027] (3) Test results Comparative weld formation pictures Fig. 9 As shown, it can be seen that the comparative welding formation is poor, with obvious spatter, pores, side wall incomplete fusion and interlayer incomplete fusion.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling defects in narrow gap laser welding of thick plates without preheating, characterized in that: The following steps are involved: Step S1) Designing a single-sided or double-sided narrow gap groove (5) for thick plate workpieces (1) of different thicknesses, wherein the workpiece (1) is a 10CrNi3MoV steel plate or a TC4 titanium plate, and the groove (5) is a U-shaped groove. When the plate thickness of the workpiece (1) is t≤30 mm, a single-sided groove is used; when the plate thickness of the workpiece (1) is 30 mm<t≤80 mm, a double-sided groove (5) is used; the groove (5) has an inclination angle of 1° to 1.5°, a root size of the groove (5) of 3.5 to 4.5 mm, and a blunt edge size of 3 to 8 mm; The groove (5) is machined, the area to be welded is polished and cleaned, and the two are butt-jointed and fixed by spot welding; Step S2) A hot wire device (4) is installed on the wire feeding mechanism, wherein the positive electrode of the hot wire device (4) is connected to the welding wire (3), and the negative electrode is connected to the base material. The wire feeding mechanism, the laser source and the shielding gas system are sequentially arranged along the welding direction. Step S3) The hot wire device (4) preheats the welding wire (3), the welding wire (3) is inserted into the bottom of the groove (5) and centered, and the total laser power of the laser source, the spot ring ratio, the swing mode, the swing amplitude and the swing frequency are adjusted to perform the base welding and the filling welding. The laser source adopts a point ring laser mode, the distance between the laser beam (2) emitted by the laser source and the light wire (3) is 0-2 mm, the angle between the laser beam (2) and the workpiece (1) is 82°-87°, the welding wire (3) is a WM960S or TC4 welding wire with a diameter of 1.2 mm, the shielding gas system adopts 99.99% pure Ar shielding gas, the flow rate of the shielding gas is 25-40 L / min, ventilation is performed 5 minutes in advance before welding and continuous ventilation is performed 5 minutes after welding, the working voltage of the hot wire device (4) is 2 V, and the current is 65-80 A; The point laser (6) power of the laser source is 2.8-8.5 kW, the ring laser (7) power is 1.0-2.0 kW, the defocusing amount is +10-+20 mm, the swing mode is circular, the swing amplitude is 1.8-2.2 mm, the swing frequency is 50-65 Hz, the welding speed is 0.4-1.2 m / s, and the wire feeding speed is 4-5 m / min; For the single-side groove (5), welding is performed after a certain reverse deformation is preset, and the welding process is self-fluxing welding for base welding and single-pass multi-layer welding for filling; For the double-sided groove (5), dual laser sources are used for double-sided self-fusion welding to prime and fill the two sides at the same time, or a single laser source is used for double-sided self-fusion welding to prime and fill the two sides in sequence, and the filling order is to fill 1 / 3 on the front side, then 2 / 3 on the back side, then 2 / 3 on the front side, and finally the remaining 1 / 3 on the back side, so as to achieve the best deformation control; Control the interlayer temperature to 80~120℃; Step S4) After welding, the area within 200 mm to 300 mm on both sides of the weld is covered with asbestos blankets, and the insulation asbestos is removed after natural cooling for 72 hours; Step S5) After the heat preservation is completed, non-destructive testing is performed on the weld area.

2. The method for controlling defects in narrow gap laser welding of thick plates without preheating according to claim 1 is characterized in that: In the step S3, the single-layer welding height of the single-pass multi-layer welding is 1.4 mm to 1.7 mm, and the number of welding passes is 20 to 50 when the plate thickness is between 30 mm and 80 mm.

3. The method for controlling defects in narrow gap laser welding of thick plates without preheating according to claim 1 is characterized in that: In step S1, the groove (5) is processed by a milling machine, and the surface within a range of 10 mm on both sides of the groove (5) of the workpiece (1) is polished using sandpaper, and the polished surface is cleaned by an acetone-water washing-acid washing-water washing-drying process to remove surface oil stains and rust.

4. The method for controlling defects in narrow gap laser welding of thick plates without preheating according to claim 1, characterized in that: In the step S1, the spot welding is fixed by a fixture, the assembly gap is 0-0.2 mm, the spot welding length is 20 mm, and the spot welding interval is 80-100 mm.

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