Laser welding method and device for stainless steel super-thick plate

Abstract

The invention provides a stainless steel ultra-thick plate laser welding method and device, and the method comprises the steps that a to-be-welded end face of ultra-thick stainless steel is subjected to groove machining, the groove form is a combined form of a large truncated edge and a U-shaped groove, with the groove as a boundary, one end is a first base material, and the other end is a second base material; placing the workpiece according to a corresponding welding method, tightly butting the first base metal and the second base metal, fixing by using a clamp, and then cleaning a to-be-welded surface; the relative positions of the laser beam and the protective gas hood and the base metal are adjusted according to parameters required by the process, and a welding path is programmed or demonstrated; setting welding process parameters; and opening a protective gas valve, starting welding after the welding area is filled with protective gas, and performing front welding, back welding or front and back cover welding. The method can be used for penetration welding of stainless steel super-thick plates or backing welding of deep-groove and thick-truncated-edge super-thick plates, the welding efficiency can be remarkably improved, welding deformation is reduced, and the post-welding machining allowance of high-precision products is reduced.

Description

Technical Field

[0001] The present invention relates to the field of welding manufacturing technology, and in particular to a laser welding method and device for ultra-thick stainless steel plates, and in particular to an ultra-high power laser welding method for ultra-thick stainless steel plates for nuclear power equipment. Background Art

[0002] In recent years, the development of human society has faced severe resource shortages. The development of efficient, clean, safe, environmentally compatible strategic and sustainable new energy is urgent, and the development and utilization of nuclear fusion energy has attracted global attention. In the field of nuclear power equipment manufacturing, due to the large size and weight of the equipment, it cannot be formed as a whole and must be spliced ​​in multiple sections, which involves a large number of thick plate welding application scenarios, and has strict requirements on the welding quality and welding efficiency of the joints. Austenitic stainless steel is widely used in the field of nuclear power due to its excellent room temperature and low temperature mechanical properties and corrosion resistance.

[0003] For the welding of thick stainless steel plates, narrow gap hot wire TIG welding is currently widely used for multi-layer and multi-pass filling. The welding number of layers and passes is large, the welding efficiency is low, the heat input is large, the welding thermal deformation is large, the post-welding processing allowance is large, and the dimensional accuracy is difficult to control. In order to improve the welding efficiency and quality, some other improved welding methods have also been proposed.

[0004] Patent document CN102632330A discloses a submerged arc welding method for ultra-low carbon stainless steel thick plates. By adopting large line energy and high interlayer temperature, it can maintain sufficient melting in the molten pool and effectively avoid the appearance of micro crack defects, thereby obtaining a weld with high performance indicators, fundamentally breaking the process principle of not allowing preheating and requiring the use of baseline energy when welding stainless steel, and the obtained weld chemical composition, mechanical properties, weld internal defects, intergranular corrosion resistance and other indicators all meet the technical requirements. However, on the one hand, the invention uses large line energy, which brings the problem of excessive heat input to the product and softening of the heat affected zone of the weld joint, which is easy to cause adverse effects on the performance and service life of the joint; on the other hand, according to the data published by the invention, the limit thickness of the plate welding does not exceed 20mm, which is difficult to adapt to the current manufacturing industry's requirements for the increasing thickness of plate welding.

[0005] Patent document CN114226928A discloses a titanium alloy thick plate welding process and device, including a vacuum welding box, which provides a vacuum environment for welding work; a vacuum pump, which is connected to the internal space of the vacuum welding box through a pipeline, and is used to extract the air in the welding box to form a vacuum environment; a water-cooled back-argon welding tool, which is arranged in the vacuum welding box, and is used to carry and fix the workpiece for welding; an argon inlet, which is connected to the water-cooled back-argon welding tool through a pipeline, and argon is supplied to it; a refrigeration circulation water tank, which is connected to the water-cooled back-argon welding tool through a pipeline, and circulating water is passed into it for cooling. However, this method still requires a deeper groove to be opened for the welding parent material, and the metal filling amount is large, and multiple wire filling welding is required to fill the groove, and the vacuum degree of the welding environment, the heat dissipation of the workpiece and the equipment must be additionally set during the welding process, resulting in great welding difficulty and low welding efficiency; in addition, the vacuum welding box mentioned in the invention has restrictions on the size of the welding parent material, and it is difficult to adapt to the welding of large-sized workpieces in actual production.

[0006] Patent document CN113732468A discloses a method for welding thick plates of different specifications of 60 mm and above, including pre-welding treatment, cleaning the welding surface by laser cleaning, cleaning the area within 40 mm of the welding seam, cutting a welding groove of 45° to 60°, and preheating the area within 100 mm of the welding seam to 200-300°C; welding operation, using a plasma welder, welding the root weld without filling wire; after the root welding is completed, gas shielded welding is used, the welding parameters are 190-210A, the voltage is 22-24V, and the welding speed is 24-28cm / mi n, hammer the weld between each welding layer, and once the welding is not continuous, the preheating temperature needs to be maintained at 200-400℃; after the gas shielded welding is completed, submerged arc welding is performed; after the welding process is completed, the infrared heater is used to heat the entire weld to raise the temperature and control it at 200-220℃. The heating range is the area within 100mm on both sides of the weld. The temperature is measured at 50mm from the center line of the weld. After the heating process is completed, insulation cotton is used for insulation. The insulation time period is calculated as 1 hour per 30mm plate thickness. When the temperature drops to 150℃, the insulation cotton is uncovered to allow it to cool naturally; and post-weld inspection and other steps. This invention can realize the welding of plates thicker than 60mm, but the operation steps are cumbersome, the process is complicated, the workload of the welding workers is too large, and the welding groove angle is too large, which seriously affects the welding efficiency.

[0007] In general, the current welding efficiency of ultra-thick stainless steel plates is low, the one-time penetration depth is small, the thermal deformation is large, and the process is complicated, which makes it difficult to adapt to the rapid development of nuclear power technology. In addition, according to the retrieved literature, there is no method for directly using ultra-high power lasers to weld stainless steel thicker than 20mm with large penetration depth. Summary of the invention

[0008] In view of the defects in the prior art, the object of the present invention is to provide a laser welding method and device for ultra-thick stainless steel plates.

[0009] A laser welding method for ultra-thick stainless steel plates provided by the present invention comprises:

[0010] Step S1: performing groove processing on the end face of the ultra-thick stainless steel to be welded, wherein the groove is a combination of a large blunt edge and a U-shaped groove, with one end of the groove as a dividing line being the first parent material and the other end being the second parent material;

[0011] Step S2: placing the workpiece according to the corresponding welding method, closely butting the first parent material and the second parent material and fixing them with a clamp, and then cleaning the surface to be welded;

[0012] Step S3: adjusting the relative positions of the laser beam, the protective gas hood and the base material according to the parameters required by the process, and programming or teaching the welding path;

[0013] Step S4: setting welding process parameters;

[0014] Step S5: Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, and perform front side welding, back side welding, or front and back side cap welding.

[0015] Preferably, the U-shaped groove angle is 0-12 degrees, and the single-side groove angle is 0-6 degrees;

[0016] The width of the U-shaped groove is 4 to 14 mm, excluding 14;

[0017] The filling depth of the U-groove is determined by the remaining plate thickness.

[0018] Preferably, the ultra-thick stainless steel base material has a thickness of 30 to 300 mm;

[0019] The blunt edge thickness is more than 12mm for single-sided base welding and more than 20mm for double-sided base welding.

[0020] Preferably, when the thickness of the welded plate far exceeds the maximum penetration depth of the ultra-high power laser, ultra-high power ultra-deep penetration welding is used as the base welding of the ultra-thick component, and a shallow groove is opened above the base weld.

[0021] The shallow groove is used to fill the weld metal expanded by the base welding.

[0022] Preferably, the welding method includes flat welding, horizontal welding or vertical welding;

[0023] The parameters required by the process include defocusing amount and welding gun angle;

[0024] The laser beam is tilted backward or forward by 5 to 10 degrees for welding, and the laser defocus is -5 to -40 mm;

[0025] The protective gas cover is located at the rear side of the laser beam, the protective gas cover is 4 to 12 mm away from the laser beam, and the protective gas cover is 1 to 12 mm away from the surface of the base material.

[0026] Preferably, the welding process parameters include laser power, welding speed, shielding gas flow rate, whether the laser beam swings, swing mode and swing parameters;

[0027] The laser power is 20-60kw, the laser spot diameter is 0.40-0.8mm, and the welding speed is 0.3-1.6m / min;

[0028] The swing frequency is 50-200Hz, the swing amplitude is 1.0-6.0mm, and the molten pool is stirred by swinging;

[0029] The protective gas is nitrogen, and the gas flow rate is 40-100L / min.

[0030] Preferably, the shielding gas valve is opened, and welding is started after the shielding gas fills the welding area. The high-power laser is projected at the center of the groove, and the base material is rapidly melted, evaporated, and vaporized to form a keyhole, and deep penetration welding is performed. At the same time, the welding gun moves forward to achieve deep penetration welding on the front or back of the base material.

[0031] The front and back cover welding comprises the following steps: cleaning the base weld before welding, and then using CMT cold metal transfer or laser-CMT composite welding for cover welding. Similarly, after the back side base is completed, if the remaining filling thickness can be used to cover the surface, then cover welding can be performed directly, otherwise filling is required before covering the surface.

[0032] Preferably, the penetration depths of the forward and reverse passes of welding have an overlap inside the parent material.

[0033] Preferably, if the thickness of the welded plate is within the range of ultra-high power laser deep penetration welding, the capping welding can be performed directly after deep penetration welding;

[0034] The laser power is 0-10000w during cover welding; the welding speed is 0.3-1.6m / min;

[0035] The wire feeding speed of CMT for cap welding is 4-11 m / min; the shielding gas is a mixture of 98% argon and 2% carbon dioxide, and the gas flow rate is 15-40 L / min.

[0036] Preferably, it comprises a first parent material, a second parent material, and a protective gas cover;

[0037] After the end face of the ultra-thick stainless steel to be welded is grooved, one end of the groove is the first base material and the other end is the second base material, and the protective gas cover is located at the rear side of the laser beam;

[0038] By placing the workpieces according to the corresponding welding method, closely butting the first parent material and the second parent material and fixing them with a clamp, and then cleaning the surfaces to be welded;

[0039] Adjust the relative positions of the laser beam, protective gas hood and base material according to the parameters required by the process, and program or teach the welding path;

[0040] According to the set welding process parameters, open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, and perform front welding, back welding, or front and back cover welding.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The present invention uses ultra-high power laser for deep melting welding, with a single-sided melting depth of ≥20mm and a double-sided melting depth of ≥30mm or more, and can achieve direct penetration of 40 to 120mm (single or double sides), significantly reducing the filling amount of weld metal. The welding efficiency is more than 10 times that of the current mature narrow gap hot wire TIG welding, and the deformation is less than 1 / 5 of the narrow gap hot wire TIG multi-layer and multi-pass welding. The processing allowance is less than 1 / 5 of the traditional welding method, which significantly improves the welding efficiency and product quality.

[0043] 2. When the present invention uses ultra-high power laser for deep penetration welding, a negative defocus welding method is adopted, which can allow the focus position with the highest energy density to penetrate into the groove, increase the penetration depth, and help reduce spatter and improve weld formation.

[0044] 3. According to the thickness of the welding plate, the present invention can be directly welded and formed, and can also be used for base welding of ultra-thick plates. When the plate thickness is within the penetration depth range of ultra-high power laser (including front and back penetration), only ultra-high power base + cover is needed for direct forming; and when the welding depth far exceeds the penetration depth range of ultra-high power laser, this method can be used for base welding, and the rest can be filled by narrow gap hot wire TIG multi-layer and multi-pass, or (swinging) laser-cold / hot wire multi-layer filling. When used as base welding for ultra-thick plates, the extremely small heat input of the ultra-high power laser can control the entire thermal deformation to about 1mm, and the large rigidity constraint of the ultra-thick deep-penetration base makes the subsequent multi-layer filling basically not deformed, which significantly reduces the difficulty of subsequent weld planning and parameter adjustment, and significantly improves the efficiency of filling welding and the consistency of welding quality, as well as the dimensional accuracy of the product.

[0045] 4. When the present invention adopts ultra-high power for ultra-thick base welding, the molten pool can be stirred by the swing of the laser beam to achieve uniform mass and heat transfer, reduce welding residual stress, and reduce the risk of shrinkage holes or cracks at the bottom or center of the weld. Furthermore, by stabilizing the swing of the laser beam and increasing the keyhole opening, the welding process is guaranteed to be stable and the generation of process pores is suppressed, which is more important for the base welding of ultra-thick plates.

[0046] 5. The method of opening a shallow groove above the base weld of the ultra-thick plate in the present invention makes it convenient for the weld metal expanded by the base welding to directly fill the shallow groove, thereby reducing the workload of pre-weld grinding for filling welding of ultra-thick plates, reducing work intensity, and reducing preparation time before filling welding. In addition, by opening the shallow groove, the generation of plasma can be restrained and reduced to a certain extent, thereby ensuring the stability of welding penetration.

[0047] 6. Compared with the traditional multi-layer and multi-pass filling groove of more than 14 mm, the 4-14 mm U-shaped groove in the present invention has a narrower width, fewer filling passes, less welding wire consumption, higher welding efficiency, and significantly reduces economic and time costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0049] Figure 1 This is a schematic diagram of the groove opening of the first parent material and the second parent material for single-side penetration welding of ultra-thick stainless steel plates.

[0050] Figure 2 Schematic diagram of ultra-high power laser welding device for ultra-thick stainless steel plates.

[0051] Figure 3 This is a schematic diagram of the groove opening of the first parent material and the second parent material for double-sided penetration and double-sided welding of ultra-thick stainless steel plates.

[0052] Figure 4 This is a schematic diagram of the groove opening of the first parent material and the second parent material for single-side bottom welding of ultra-thick stainless steel plates.

[0053] Figure 5 This is a schematic diagram of the groove opening of the first parent material and the second parent material for double-sided bottom welding of ultra-thick stainless steel plates.

[0054] Figure 6 Schematic diagram of the bevel and shallow groove of the first and second base materials for double-sided bottom welding of ultra-thick stainless steel plates.

[0055] The symbols in the above figures represent: 1-first base material, 2-second base material, 3-laser beam, 4-protective gas cover. DETAILED DESCRIPTION

[0056] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0057] The present invention uses ultra-high power laser to perform deep penetration welding on one or both sides of the material to be welded, and can be used for penetration welding of ultra-thick stainless steel plates or bottom welding of ultra-thick plates with deep grooves and thick blunt edges, including groove processing, assembly and cleaning, welding path teaching, setting welding process parameters, front welding, and also includes back welding, front and back cover welding, etc. It can significantly improve welding efficiency, reduce welding deformation, and reduce post-welding processing allowances for high-precision products.

[0058] Example 1

[0059] A laser welding method for ultra-thick stainless steel plates provided by the present invention comprises the following steps:

[0060] Step S1: groove processing. The end face of the ultra-thick stainless steel to be welded is grooved, and the groove form is a combination of large blunt edge + U-shaped groove. The U-shaped groove angle is 0-12 degrees, the single-sided groove angle is 0-6 degrees, and the U-shaped groove width is 4 to 14 mm, excluding 14. The filling depth of the U-shaped groove is determined by the remaining plate thickness, and is usually required to be greater than 2-12 mm. For 304 or 316 stainless steel with a base material thickness of 30 to 300 mm or even more; for single-sided bottom welding, the blunt edge thickness is more than 12 mm, such as 15 mm, 20 mm; for double-sided bottom welding, the blunt edge thickness can be more than 20 mm, such as 22 mm, 25 mm.

[0061] When the thickness of the welded plate far exceeds the maximum penetration depth of the ultra-high power laser, ultra-high power ultra-deep penetration welding can be used as the base welding of ultra-thick components. At this time, a shallow groove is further opened above the base weld to fill the weld metal expanded by the base welding, reducing the pre-weld grinding workload of ultra-thick plate filling welding, reducing the work intensity of workers, and reducing the preparation time before filling welding. The method of opening a shallow groove above the base weld of ultra-thick plates facilitates the weld metal expanded by the base welding to directly fill the shallow groove. In addition, the method of opening a shallow groove can restrain and reduce the generation of plasma to a certain extent, ensuring the stability of the welding penetration.

[0062] Step S2: Assembly and cleaning. Place the workpiece according to the corresponding welding method, and closely connect the first parent material and the second parent material and fix them with a clamp, then clean the surface to be welded, and remove oil, dust, etc. on the surface and in the groove. The welding method includes flat welding, horizontal welding or vertical welding.

[0063] Step S3: Programming or teaching the welding path. Adjust the relative positions of the laser beam, the protective gas hood and the base material according to the defocus amount and welding gun angle required by the process, and program or teach the welding path. The laser beam is tilted backward or forward by 5 to 10 degrees for welding, and the laser defocus amount is -5 to -40 mm. The protective gas hood is located at the rear side of the laser beam, and the protective gas hood is 4 to 12 mm away from the laser beam, and the protective gas hood is 1 to 12 mm away from the surface of the base material.

[0064] Step S4: Set welding process parameters. The welding process parameters include laser power, welding speed, shielding gas flow, whether the laser beam swings, swing mode and swing parameters. The laser power is 20-60kw, the laser spot diameter is 0.40-0.8mm, and the welding speed is 0.3-1.6m / min. During base welding, the swing mode of the laser beam can be used: "|" lateral swing perpendicular to the welding direction, "○" circular swing and "8" 8-shaped swing perpendicular to the welding direction, "∞" ∞-shaped swing parallel to the welding direction and other modes. Swing frequency: 50-200Hz, swing amplitude: 1.0-6.0mm, by swinging and stirring the molten pool, the mass transfer and heat transfer are uniformed, the welding residual stress is reduced, and the keyhole opening is increased by swinging to ensure the stability of the welding process. The shielding gas is nitrogen, and the gas flow rate is 40-100L / min.

[0065] Step S5: Open the protective gas valve, wait for the protective gas to fill the welding area, start welding, and perform front welding, back welding, or front and back cover welding. According to the thickness of the selected base material and the laser power, you can choose to directly complete the welding by single-sided or double-sided welding combined with cover. For example, for ultra-thick stainless steel plates of 48mm or 88mm and above, use a 25-30kW laser beam for single-sided and double-sided welding respectively; it can also be used only for the base welding of workpieces whose plate thickness far exceeds the maximum penetration depth of ultra-high power. For example, for ultra-thick stainless steel plates with blunt edges of 48mm or 88mm and above, use a 25-30kW laser beam for single-sided and double-sided base welding respectively, which is used to improve welding efficiency and control welding deformation.

[0066] Front welding. Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser at the center of the groove, the base material quickly melts, evaporates, and vaporizes to form a keyhole, and deep penetration welding is performed. At the same time, the welding gun moves forward to achieve deep penetration welding on the front of the base material.

[0067] Reverse side welding. Decide whether to weld the reverse side as needed. If welding the reverse side, repeat steps 3 and 4: welding path programming and setting process parameters, and then welding. Similarly, first open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, and move the welding gun forward to achieve deep penetration welding on the reverse side of the parent material. To ensure sufficient strength, the penetration depth of the two passes of welding must overlap to a certain extent inside the parent material, so as to finally achieve complete penetration of the first parent material and the second parent material.

[0068] Front and back cover welding. Decide whether to cover welding according to needs. If the welding plate thickness is within the range of ultra-high power laser deep penetration welding, the cover welding can be completed directly after deep penetration welding. Before welding, clean the base weld with a grinder, alcohol, etc., and then use CMT (cold metal transition) or laser-CMT composite welding for cover welding. Similarly, after the back base is completed, the remaining filling thickness can be covered, then cover welding can be performed directly, otherwise it is necessary to fill before covering. The preferred laser power for cover welding is 0-10000w; the welding speed is 0.3-1.6m / min. The wire feeding speed of CMT for cover welding is 4-11m / min. The shielding gas is a mixture of 98% argon and 2% carbon dioxide, and the gas flow rate is 15-40L / min. According to different materials, structures, stress levels and other factors, the laser parameters used for front and back welding do not necessarily need to be completely consistent, that is, the penetration depth of welding on both sides does not have to be completely equal.

[0069] This method is applicable to various welding methods such as flat welding, horizontal welding and vertical welding. In order to ensure the welding of the front and back sides and reduce spatter, horizontal welding or vertical welding can usually achieve better welding results.

[0070] The invention aims to fundamentally solve the problems of low efficiency, large metal filling amount, large heat input, too wide heat affected zone, and too large post-welding processing allowance when welding thick plates using traditional welding processes.

[0071] Further, in conjunction with the instructions Figures 1 to 6 The laser welding method for ultra-thick stainless steel plates of the present invention is further described with reference to the following specific embodiments.

[0072] Example 2: An ultra-high power laser single-side penetration welding method for ultra-thick 316 stainless steel plates with a thickness of 48 mm or more is performed according to the following steps:

[0073] Step 1: Beveling. Bevel the end surface of the ultra-thick stainless steel to be welded. The bevel form is a large blunt edge + U-shaped bevel form, the blunt edge is 44mm, the single-side groove is 2-4mmx4mm (angle 0 degrees), and the bottom diameter is 1mm chamfered. Figure 1 As shown, a represents the groove width, b represents the groove depth, and H represents the blunt edge thickness.

[0074] Step 2: Assembly and cleaning. Use the flat welding method to place the workpiece flat, then closely connect the first parent material 1 and the second parent material 2 and fix them with a clamp, clean the surface to be welded, and remove oil, dust, etc. on the surface and in the groove.

[0075] Step 3: Welding path teaching. Adjust the relative position of the laser beam 3, the protective gas hood 4 and the base material, and teach the welding path, such as Figure 2 As shown; the laser beam 3 is located in front of the protective gas hood 4, the guiding spot of the laser beam 3 is located in the center of the shallow groove, 4 to 6 mm away from the front end of the protective gas hood 4; the bottom end of the protective gas hood 4 is 1 to 2 mm away from the surface of the base material;.

[0076] Step 4: Set welding process parameters. Set the power of laser beam 3 to 25-30 kW, the defocus to -10-20 mm, the laser beam back tilt to 8°, the welding speed to 0.6 m / min, the shielding gas to nitrogen, and the shielding gas flow rate to 80 L / min.

[0077] Step 5: Laser welding. Open the shielding gas valve, wait for the shielding gas to fill the welding area, turn on the laser, start welding, and project the high-power laser beam 3 at the center of the groove. At the same time, the welding gun moves forward to achieve deep penetration welding of the base material.

[0078] Step 6: Cover welding. Decide whether to cover the surface according to the needs (the consistency of the test plate is good, and cover welding is not required, but when welding the product, it is difficult to ensure the cover formation due to gap misalignment, so cover welding is usually required). Before welding, clean the base weld with a grinder, alcohol, etc., and then use CMT (cold metal transfer) or laser-CMT composite welding for cover welding. The laser power is 0-3000W, the welding speed is 0.6m / min, the wire feeding speed is 8-10m / min, and the shielding gas is a mixture of 98% argon and 2% carbon dioxide.

[0079] The above method can achieve high-quality and high-efficiency welding of single-sided 48mm thick 316LN stainless steel plates.

[0080] Example 3: An ultra-high power laser double-side penetration welding method for ultra-thick 316 stainless steel plates with a thickness of 88 mm or more is performed according to the following steps:

[0081] Step 1: Beveling. Beveling the end face of the ultra-thick stainless steel to be welded, the beveling form is a large blunt edge + U-shaped bevel, the blunt edge thickness is 80mm, the single-side slot size is 4mmx4-6mm, the bevel angle is 0 degrees, and the bottom diameter is 1mm chamfered. Figure 3 shown.

[0082] Step 2: Assembly and cleaning. Use the horizontal welding method to place the workpiece horizontally. Then closely connect the first parent material 1 and the second parent material 2 and fix them with a clamp, clean the surface to be welded, and remove oil, dust, etc. on the surface and in the groove.

[0083] Step 3: Welding path teaching. Adjust the relative positions of the laser beam 3, the protective gas hood 4 and the base material, and program or teach the welding path; the laser beam 3 is located in front of the protective gas hood 4, and the guide spot of the laser beam 3 is located in the center of the shallow groove, 4 to 6 mm away from the front end of the protective gas hood 4; the bottom end of the protective gas hood 4 is 1 to 2 mm away from the surface of the base material.

[0084] Step 4: Set welding process parameters. Set the power of laser beam 3 to 25-30 kW, the defocus to -10-30 mm, the laser beam back tilt to 8°, the welding speed to 0.6 m / min, the shielding gas to nitrogen, and the shielding gas flow rate to 80 L / min.

[0085] Step 5: Front welding. Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser beam 3 at the center of the groove, and move the welding gun forward to achieve deep penetration welding on the front of the base material.

[0086] Step 6: Back welding. Repeat steps 3 and 4, open the shielding gas valve, wait for the shielding gas to fill the welding area, turn on the laser, start welding, project the high-power laser beam 3 at the center of the groove, and move the welding gun forward to achieve deep penetration welding on the back of the parent material. To ensure sufficient strength, the penetration depth of the two welding passes must overlap inside the parent material to achieve complete penetration of the first parent material 1 and the second parent material 2.

[0087] Step 7: Cover welding on both sides. Decide whether to cover welding according to needs (the consistency of the test plate is good, and cover welding is not required, but when welding products, it is difficult to ensure the cover formation due to gap misalignment, so cover welding is usually required). Before welding, clean the base weld with a grinder, alcohol, etc., and then use CMT (cold metal transfer) or laser-CMT composite welding for cover welding. The laser power is 0-3000W, the welding speed is 0.6m / min, the wire feeding speed is 8-10m / min, and the shielding gas is a mixture of 98% argon and 2% carbon dioxide.

[0088] The above method can achieve high-quality and high-efficiency welding of 88mm thick 316LN stainless steel plates on both sides.

[0089] Example 4: A method for single-side ultra-high power laser rooting welding of a 134 mm 316 stainless steel ultra-thick plate is performed according to the following steps:

[0090] Step 1: Beveling. Beveling the end face of the ultra-thick stainless steel to be welded, the beveling form is a large blunt edge + U-shaped bevel, the blunt edge thickness is 40mm, the U-shaped bevel angle is 4-8 degrees (single side 2-4 degrees), the bevel bottom width is 14mm, R = 5mm chamfer, and the filling depth is 94mm. Figure 4 As shown, H represents the total thickness of the stainless steel super-thick plate to be welded, h represents the blunt edge thickness, A represents the width of the bottom of the U-shaped groove, B represents the depth of the U-shaped groove, R represents the radius of the chamfer at the bottom of the U-shaped groove, and γ represents the single-side angle of the U-shaped groove.

[0091] Step 2: Assembly and cleaning. Use the horizontal welding method to place the workpiece horizontally. Butt the first base material 1 and the second base material 2 tightly and fix them with a clamp, clean the surface to be welded, and remove oil, dust, etc. on the surface and in the groove.

[0092] Step 3: Programming or teaching the welding path. Adjust the relative positions of the laser beam 3, the protective gas hood 4 and the base material, and teach the welding path; the laser beam 3 is located in front of the protective gas hood 4, and the guide spot of the laser beam 3 is located in the center of the groove, 4 to 6 mm away from the front end of the protective gas hood 4; the bottom end of the protective gas hood 4 is 5 to 10 mm away from the bottom of the groove.

[0093] Step 4: Set welding process parameters. Set the power of laser beam 3 to 25-30 kW, the defocus to -10-30 mm, the laser beam back tilt to 8°, the welding speed to 0.6 m / min, the shielding gas to nitrogen, and the shielding gas flow rate to 80 L / min.

[0094] Step 5: Laser welding. Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser beam 3 at the center of the groove, and move the welding gun forward to achieve full penetration welding of the base material.

[0095] The above method achieves high-quality and high-efficiency root welding of 316LN stainless steel ultra-thick plates with a thickness of 134 mm on one side and a thickness of 40 mm on the blunt edge. The large blunt edge ensures sufficient rigidity, and the deformation after root welding is only about 1 mm, which can greatly reduce the thermal deformation of the workpiece, improve welding efficiency, and lay the foundation for subsequent layer-by-layer filling.

[0096] Example 5: A method for ultra-high power laser double-side bottom welding of a 268 mm 316 stainless steel ultra-thick plate is performed according to the following steps:

[0097] Step 1: Beveling. Beveling the end face of the ultra-thick stainless steel to be welded is processed. The beveling form is a large blunt edge + U-shaped bevel. The blunt edge thickness is 80mm, the U-shaped bevel angle is 4-8 degrees (single side 2-4 degrees), the width is 14mm, the bevel bottom chamfer R = 5mm, and the single-side filling depth is 94mm. Figure 5 shown.

[0098] Step 2: Assembly and cleaning. Use the horizontal welding method to place the workpiece horizontally. Tightly connect the first base material 1 and the second base material 2 and fix them with a clamp, then clean the surface to be welded and remove oil, dust, etc. on the surface and groove.

[0099] Step 3: Programming or teaching the welding path. Adjust the relative positions of the laser beam 3, the protective gas hood 4 and the base material, and teach the welding path; the laser beam 3 is located in front of the protective gas hood 4, and the guide spot of the laser beam 3 is located at the center of the groove, 4 to 6 mm away from the front end of the protective gas hood 4; the bottom end of the protective gas hood 4 is 5 to 10 mm away from the bottom of the groove.

[0100] Step 4: Set welding process parameters. Set the power of laser beam 3 to 25-40kW, the defocus to -10-30mm, the laser beam back tilt to 8°, the welding speed to 0.6m / min, the shielding gas to nitrogen, and the shielding gas flow rate to 80L / min;

[0101] Step 5: Front welding. Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser beam 3 at the center of the groove, and move the welding gun forward to achieve deep penetration welding on the front of the base material;

[0102] Step 6: Back welding. Repeat steps 3 and 4, open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser beam 3 at the center of the groove, and move the welding gun forward to achieve deep penetration welding on the back of the parent material. To ensure sufficient strength, the penetration depth of the two passes of welding must overlap inside the parent material to achieve complete penetration of the first parent material 1 and the second parent material 2.

[0103] The above method achieves high-quality and high-efficiency root welding of 316LN stainless steel ultra-thick plates with a total thickness of 268 mm on both sides and a blunt edge thickness of 80 mm. The large blunt edge ensures sufficient rigidity, and the deformation after root welding is only about 1 mm, which can greatly reduce the thermal deformation of the workpiece, improve welding efficiency, and lay the foundation for subsequent layer-by-layer filling.

[0104] Example 6: A method for ultra-high power laser double-side bottom welding of 316 stainless steel ultra-thick plate, performed according to the following steps:

[0105] Step 1: Beveling. Bevel the end face of the ultra-thick stainless steel to be welded. The bevel form is a large blunt edge + U-shaped bevel + shallow groove in the bottom center. The blunt edge is 40-80mm, the U-shaped bevel angle is 4-8 degrees (2-4 degrees on one side), the width is 14mm, the bottom chamfer of the bevel R = 5mm, the single-side filling depth is 94mm, and a shallow groove is processed in the center of the bottom of the bevel, with a width of 4-6mm and a depth of 2-4mm. Figure 6 shown.

[0106] Step 2: Assembly and cleaning. Use the horizontal welding method to place the workpiece horizontally. Tightly connect the first base material 1 and the second base material 2 and fix them with a clamp, then clean the surface to be welded and remove oil, dust, etc. on the surface and groove.

[0107] Step 3: Programming or teaching the welding path. Adjust the relative positions of the laser beam 3, the protective gas hood 4 and the base material, and teach the welding path; the laser beam 3 is located in front of the protective gas hood 4, and the guiding spot of the laser beam 3 is located in the center of the shallow groove at the bottom of the groove, 4 to 6 mm away from the front end of the protective gas hood 4; the bottom end of the protective gas hood 4 is 5 to 10 mm away from the bottom of the groove.

[0108] Step 4: Set welding process parameters. Set the power of laser beam 3 to 20-40 kW, the defocus to -10-30 mm, the laser beam back tilt to 8°, the welding speed to 0.6 m / min, the shielding gas to nitrogen, and the shielding gas flow rate to 80 L / min.

[0109] Step 5: Front welding. Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser beam 3 at the center of the groove, and move the welding gun forward to achieve deep penetration welding on the front of the base material.

[0110] Step 6: Back welding. Repeat steps 3 and 4, open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser beam 3 at the center of the groove, and move the welding gun forward to achieve deep penetration welding on the back of the parent material. To ensure sufficient strength, the penetration depth of the two passes of welding must overlap inside the parent material to achieve complete penetration of the first parent material 1 and the second parent material 2.

[0111] Through the above method, the expanded weld metal of the base welding can directly fill the shallow groove, which can reduce the pre-weld grinding workload of ultra-thick plate filling welding, reduce work intensity, and reduce the preparation time before filling welding. In addition, by opening the shallow groove method, the generation of plasma can be restrained and reduced to a certain extent, ensuring the stability of welding penetration.

[0112] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0113] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A laser welding method for ultra-thick stainless steel plates, characterized in that: include: Step S1: performing groove processing on the end face of the ultra-thick stainless steel to be welded, wherein the groove is a combination of a large blunt edge and a U-shaped groove, with one end of the groove as a dividing line being the first parent material and the other end being the second parent material; Step S2: placing the workpiece according to the corresponding welding method, closely butting the first parent material and the second parent material and fixing them with a clamp, and then cleaning the surface to be welded; Step S3: adjusting the relative positions of the laser beam, the protective gas hood and the base material according to the parameters required by the process, and programming or teaching the welding path; Step S4: setting welding process parameters; Step S5: Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, and perform front side welding, back side welding, or front and back side cap welding.

2. The laser welding method for ultra-thick stainless steel plates according to claim 1, characterized in that: The U-shaped groove angle is 0-12 degrees, and the single-side groove angle is 0-6 degrees; The width of the U-shaped groove is 4 to 14 mm, excluding 14; The filling depth of the U-groove is determined by the remaining plate thickness.

3. The laser welding method for ultra-thick stainless steel plates according to claim 1, characterized in that: The ultra-thick stainless steel base material has a thickness of 30 to 300 mm; The blunt edge thickness is more than 12mm for single-sided base welding and more than 20mm for double-sided base welding.

4. The laser welding method for ultra-thick stainless steel plates according to claim 1, characterized in that: When the thickness of the welded plate far exceeds the maximum penetration depth of the ultra-high power laser, ultra-high power ultra-deep penetration welding is used as the base welding of the ultra-thick component, and a shallow groove is opened above the base weld. The shallow groove is used to fill the weld metal expanded by the base welding.

5. The laser welding method for ultra-thick stainless steel plates according to claim 1, characterized in that: The welding method includes flat welding, horizontal welding or vertical welding; The parameters required by the process include defocusing amount and welding gun angle; The laser beam is tilted backward or forward by 5 to 10 degrees for welding, and the laser defocus is -5 to -40 mm; The protective gas cover is located at the rear side of the laser beam, the protective gas cover is 4 to 12 mm away from the laser beam, and the protective gas cover is 1 to 12 mm away from the surface of the base material.

6. The laser welding method for ultra-thick stainless steel plates according to claim 1, characterized in that: The welding process parameters include laser power, welding speed, shielding gas flow rate, whether the laser beam swings, swing mode and swing parameters; The laser power is 20-60kw, the laser spot diameter is 0.40-0.8mm, and the welding speed is 0.3-1.6m / min; The swing frequency is 50-200Hz, the swing amplitude is 1.0-6.0mm, and the molten pool is stirred by swinging; The protective gas is nitrogen, and the gas flow rate is 40-100L / min.

7. The laser welding method for ultra-thick stainless steel plates according to claim 1, characterized in that: Open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, project the high-power laser at the center of the groove, the base material quickly melts, evaporates, and vaporizes to form a keyhole, and deep penetration welding is performed. At the same time, the welding gun moves forward to achieve deep penetration welding on the front or back of the base material. The front and back cover welding comprises the following steps: cleaning the base weld before welding, and then using CMT cold metal transfer laser-CMT composite welding for cover welding. Similarly, after the back side base is completed, if the remaining filling thickness can be used to cover the surface, then cover welding can be performed directly, otherwise filling is required before covering the surface.

8. The laser welding method for ultra-thick stainless steel plates according to claim 7, characterized in that: The penetration depths of the forward and reverse passes of welding overlap within the parent material.

9. The laser welding method for ultra-thick stainless steel plates according to claim 7, characterized in that: If the thickness of the welded plate is within the range of ultra-high power laser deep penetration welding, the cover welding can be performed directly after deep penetration welding; The laser power is 0-10000w during cover welding; the welding speed is 0.3-1.6m / min; The wire feeding speed of CMT for cap welding is 4-11 m / min; the shielding gas is a mixture of 98% argon and 2% carbon dioxide, and the gas flow rate is 15-40 L / min.

10. A laser welding device for ultra-thick stainless steel plates, characterized in that: It includes a first base material, a second base material, and a protective gas cover; After the end face of the ultra-thick stainless steel to be welded is grooved, one end of the groove is the first base material and the other end is the second base material, and the protective gas cover is located at the rear side of the laser beam; By placing the workpieces according to the corresponding welding method, closely butting the first parent material and the second parent material and fixing them with a clamp, and then cleaning the surfaces to be welded; Adjust the relative positions of the laser beam, protective gas hood and base material according to the parameters required by the process, and program or teach the welding path; According to the set welding process parameters, open the shielding gas valve, wait for the shielding gas to fill the welding area, start welding, and perform front welding, back welding, or front and back cover welding.

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