A method for laser welding of large-size duplex stainless steel annular workpieces

Abstract

The present invention relates to a method for laser welding of a large-size duplex stainless steel annular workpiece, and belongs to the field of laser welding technology. The main steps include: coaxially butting and assembling a first workpiece, a second workpiece, and a third workpiece; making a laser welding inner wall support tooling; fitting the first workpiece, the second workpiece, and the third workpiece that have been positioned onto the outer wall of the laser welding inner wall support tooling; making a laser welding outer wall gas shielding tooling; adjusting an external laser welder to be perpendicular to the butt joint, adjusting the distance e between the laser welding outer wall gas shielding tooling and the weld, and the angle d between the laser welding outer wall gas shielding tooling and the external laser welder; laser welding the butt joint of the first workpiece and the second workpiece, and the butt joint of the second workpiece and the third workpiece, respectively. The present invention achieves an increase in the X-ray inspection pass rate of the laser weld of the duplex stainless steel annular workpiece from 30% to 90%, avoiding the problem of delays in the progress and increased costs caused by unqualified X-ray inspections.

Description

Technical Field

[0001] The invention belongs to the technical field of laser welding and relates to a method for laser welding a large-size duplex stainless steel annular workpiece. Background Art

[0002] In the past, this type of 1Cr21Ni5Ti duplex stainless steel annular workpiece was welded by automatic argon arc welding. The disadvantages are: the large heat input of automatic argon arc welding leads to large deformation of the weld, and the difficulty and workload of post-welding correction are large; and after the butt weld of the 1Cr21Ni5Ti duplex stainless steel annular workpiece is changed to laser welding, the X-ray inspection pass rate of the weld is extremely low, about 30%, because the laser weld is prone to pore defects. Unqualified products need to be polished to eliminate defects and then repaired by manual argon arc welding, which seriously affects the production progress of the product. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to propose a method for laser welding of a large-sized duplex stainless steel annular workpiece, to increase the X-ray inspection pass rate of the laser weld of the duplex stainless steel annular workpiece from 30% to 90%, and to avoid the problem of delays in repair progress and increased costs caused by unqualified X-ray inspection.

[0004] The solution of the present invention is:

[0005] A method for laser welding of a large-size duplex stainless steel annular workpiece comprises the following steps:

[0006] Step 1: clean the joint parts of the first workpiece, the second workpiece and the third workpiece, assemble the first workpiece, the second workpiece and the third workpiece coaxially and position them by manual argon arc welding;

[0007] Step 2: Make a laser welding inner wall support tooling, including a main shaft, a small support plate, a large support plate, a small support plate total air intake joint, a large support plate total air intake joint, n small support plate partition air intake joints, n large support plate partition air intake joints and a lifting ring;

[0008] Step 3: Clamp the laser welding inner wall support tooling onto the external laser welding machine turntable through the lifting ring; and set the positioned first workpiece, second workpiece, and third workpiece onto the outer wall of the laser welding inner wall support tooling to ensure that the inner wall of the large diameter end of the first workpiece is tightly fitted with the outer wall of the small support plate, and the inner wall of the small diameter end of the third workpiece is tightly fitted with the outer wall of the large support plate;

[0009] Step 4: Make laser welding outer wall gas protection tooling; including steel pipe, copper pipe, ceramic nozzle and filter;

[0010] Step 5. Adjust the external laser welder to be perpendicular to the butt joint, adjust the distance e between the laser welding outer wall gas shielding tooling and the weld, and the angle d between the laser welding outer wall gas shielding tooling and the external laser welder; perform laser welding on the butt joints between the first workpiece and the second workpiece, and the butt joints between the second workpiece and the third workpiece, respectively.

[0011] In the above-mentioned method for laser welding of large-size duplex stainless steel annular workpieces, in step 1, the first workpiece, the second workpiece and the third workpiece are all hollow cone section structures; the materials of the first workpiece, the second workpiece and the third workpiece are all 1Cr21Ni5Ti stainless steel with a thickness of 2mm-3mm; the third workpiece is axially vertically arranged at the lowest end, and the small diameter end is placed upward; the second workpiece is coaxially docked at the top of the third workpiece, and the large diameter end of the second workpiece is docked with the small diameter end of the third workpiece; the first workpiece is coaxially docked at the top of the second workpiece, and the large diameter end of the first workpiece is docked with the small diameter end of the second workpiece.

[0012] In the above-mentioned method for laser welding of a large-size duplex stainless steel annular workpiece, in step 1, the process parameters of manual argon arc welding are:

[0013] The length of the positioning point is 10-20mm; the distance between two adjacent positioning points is 20-30mm; after correction and docking, the misalignment is required to be no more than 0.15mm and the gap is required to be no more than 0.15mm.

[0014] In the above-mentioned method for laser welding of large-size duplex stainless steel annular workpieces, in step 2, the specific structure of the laser welding inner wall support tooling is:

[0015] The main shaft is placed vertically; the lifting ring is fixedly installed on the top of the main shaft; the small support plate is horizontally mounted on the outer wall of the main shaft, and the small support plate corresponds to the joint between the first workpiece and the second workpiece; n small support plate partition air intake joints are evenly installed on the bottom of the small support plate along the circumferential direction; the small support plate total air intake joint is fixedly installed on the side wall of the main shaft and is located below the small support plate; the small support plate total air intake joint is connected with the n small support plate partition air intake joints; the large support plate is horizontally mounted on the outer wall of the main shaft, and the large support plate corresponds to the joint between the second workpiece and the third workpiece; n large support plate partition air intake joints are evenly installed on the bottom of the large support plate along the circumferential direction; the large support plate total air intake joint is fixedly installed on the side wall of the main shaft and is located below the large support plate; the large support plate total air intake joint is connected with the n large support plate partition air intake joints.

[0016] In the above-mentioned method for laser welding of large-size duplex stainless steel annular workpieces, the small support plate is a conical section structure; the outer surface of the side wall of the small support plate is adapted to the inner surfaces of the first workpiece and the second workpiece; the large support plate is a conical section structure; the outer surface of the side wall of the large support plate is adapted to the inner surfaces of the second workpiece and the third workpiece.

[0017] In the above-mentioned method for laser welding of a large-size duplex stainless steel annular workpiece, a first annular groove is circumferentially arranged on the outer wall of the small support disk, and the position of the first annular groove corresponds to the butt joint between the first workpiece and the second workpiece; the first annular groove has n first through holes evenly distributed along the circumference; the n first through holes correspond one-to-one to and are connected with the n partitioned air inlet joints of the small support disk; the width b of the first annular groove is 15-20 mm, and the depth c is 5-12 mm; the diameter a of the first through hole is 4-6 mm.

[0018] In the above-mentioned method for laser welding of a large-size duplex stainless steel annular workpiece, a second annular groove is circumferentially arranged on the outer wall of the large support disk, and the position of the second annular groove corresponds to the butt joint between the second workpiece and the third workpiece; the second annular groove has n second through holes evenly distributed along the circumference; the n second through holes correspond one-to-one to and are connected with the n partitioned air inlet joints of the large support disk; the width b of the second annular groove is 15-20 mm, and the depth c is 5-12 mm; the diameter a of the second through hole is 4-6 mm; n is a positive integer and 6≤n≤8.

[0019] In the above-mentioned method for laser welding of large-size duplex stainless steel annular workpieces, the specific structure of the laser welding outer wall gas protection tooling is:

[0020] The copper tube is coaxially sleeved on the axial bottom end of the steel tube and welded; the ceramic nozzle is sleeved on the axial bottom end of the copper tube, and the ceramic nozzle is threadedly connected to the copper tube; a channel connected to the copper tube is arranged inside the ceramic nozzle; 2-4 layers of filter screens with a mesh size of 70-100 are arranged in the ceramic nozzle channel.

[0021] In the above-mentioned method for laser welding of large-size duplex stainless steel annular workpieces, the distance e between the laser welding outer wall gas shielding tooling and the weld is 1-2 mm; the angle d between the laser welding outer wall gas shielding tooling and the external laser welder is 45°-60°.

[0022] In the above-mentioned method for laser welding of large-size duplex stainless steel annular workpieces, during laser welding, the external shielding gas enters the partitioned air inlet joints of each small support plate through the total air inlet joint of the small support plate, and then enters the first annular groove; the external shielding gas enters the partitioned air inlet joints of each large support plate through the total air inlet joint of the large support plate, and then enters the second annular groove; the external shielding gas is sprayed on the welding area through the steel pipe, copper pipe, and ceramic nozzle in turn; the welding process parameters are: laser power is 3000-4500W, and welding speed is 1200-2100mm / min.

[0023] The beneficial effects of the present invention compared with the prior art are:

[0024] (1) The present invention adopts optimized special laser welding tooling, front gas shielding tooling, and appropriate laser welding parameters, which ultimately increases the first-time pass rate of X-ray inspection from 30% to more than 90%, avoiding the rework caused by unqualified X-ray inspection and reducing production costs;

[0025] (2) The present invention adopts a front gas protection tooling that combines ceramics and metals, which prolongs the continuous use time of the front gas protection tooling, so that the continuous use time of the front gas protection tooling is extended from 20 seconds to 40 seconds, thereby avoiding deformation and damage of the front gas protection tooling under the action of laser thermal radiation, thereby affecting the gas protection effect;

[0026] (3) The laser welding tooling and front gas shielding tooling designed and manufactured by the present invention greatly improve the gas shielding effect during laser welding, while extending the service life of the front gas shielding tooling and increasing the length of a single continuous welding, thereby improving welding efficiency; in addition, the present invention effectively reduces the probability of pores appearing inside the weld, avoids the need for rework due to excessive pore quantity and size inside the weld, and reduces production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the cooperation between the laser welding inner wall support tooling and three workpieces of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of the gas shielding tooling for laser welding outer wall of the present invention.

[0029] Reference numerals:

[0030] 1-first workpiece; 2-second workpiece; 3-third workpiece; 4-spindle; 7-small support plate; 8-large support plate; 9-small support plate total air inlet connector; 10-large support plate total air inlet connector; 11-small support plate partition air inlet connectors; 12-large support plate partition air inlet connectors; 13-lifting ring; 15-steel pipe; 16-copper pipe; 17-ceramic nozzle; 18-filter. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the embodiments.

[0032] The present invention provides a method for laser welding of a large-sized duplex stainless steel annular workpiece, which greatly improves the gas protection effect during laser welding, prolongs the service life of the front gas protection tooling, increases the length of a single continuous welding, and thus improves welding efficiency. In addition, the present invention effectively reduces the probability of pores appearing inside the weld, avoids the need for repair work inside the weld due to the number and size of pores exceeding tolerance, and reduces production costs.

[0033] The method for laser welding of a large-size duplex stainless steel annular workpiece specifically comprises the following steps:

[0034] Step 1: Clean the joints of the first workpiece 1, the second workpiece 2 and the third workpiece 3, and assemble the first workpiece 1, the second workpiece 2 and the third workpiece 3 coaxially and position them by manual argon arc welding; the first workpiece 1, the second workpiece 2 and the third workpiece 3 are all hollow cone structures; the materials of the first workpiece 1, the second workpiece 2 and the third workpiece 3 are all 1Cr21Ni5Ti stainless steel with a thickness of 2mm-3mm. The diameter is Φ500mm-Φ900mm and the height is 500mm-700mm. The third workpiece 3 is axially and vertically set at the lowest end, and the small diameter end is placed upward; the second workpiece 2 is coaxially docked at the top of the third workpiece 3, and the large diameter end of the second workpiece 2 is docked with the small diameter end of the third workpiece 3; the first workpiece 1 is coaxially docked at the top of the second workpiece 2, and the large diameter end of the first workpiece 1 is docked with the small diameter end of the second workpiece 2.

[0035] The process parameters of manual argon arc welding are:

[0036] The length of the positioning point is 10-20mm; the distance between two adjacent positioning points is 20-30mm; after correction and docking, the misalignment is required to be no more than 0.15mm and the gap is required to be no more than 0.15mm.

[0037] After correction and docking, the misalignment is required to be no more than 0.15mm and the gap is required to be no more than 0.15mm.

[0038] Step 2: Make a laser welding inner wall support tooling, including a main shaft 4, a small support plate 7, a large support plate 8, a small support plate total air intake connector 9, a large support plate total air intake connector 10, n small support plate partition air intake connectors 11, n large support plate partition air intake connectors 12 and a lifting ring 13. The specific structure is as follows: Figure 1 As shown. n is a positive integer and 6≤n≤8.

[0039] The specific structure of the laser welding inner wall support tooling is:

[0040] The spindle 4 is placed axially vertically; the lifting ring 13 is fixedly installed on the top of the spindle 4; the small support plate 7 is horizontally mounted on the outer wall of the spindle 4, and the small support plate 7 corresponds to the joint between the first workpiece 1 and the second workpiece 2; n small support plate partition air intake joints 11 are evenly installed at the bottom of the small support plate 7 along the circumferential direction; the small support plate total air intake joint 9 is fixedly installed on the side wall of the spindle 4 and is located below the small support plate 7; the small support plate total air intake joint 9 is connected with the n small support plate partition air intake joints 11; the large support plate 8 is horizontally mounted on the outer wall of the spindle 4, and the large support plate 8 corresponds to the joint between the second workpiece 2 and the third workpiece 3; n large support plate partition air intake joints 12 are evenly installed at the bottom of the large support plate 8 along the circumferential direction; the large support plate total air intake joint 10 is fixedly installed on the side wall of the spindle 4 and is located below the large support plate 8; the large support plate total air intake joint 10 is connected with the n large support plate partition air intake joints 12.

[0041] The small support plate 7 is a conical section structure; the outer surface of the side wall of the small support plate 7 is adapted to the inner surfaces of the first workpiece 1 and the second workpiece 2; the large support plate 8 is a conical section structure; the outer surface of the side wall of the large support plate 8 is adapted to the inner surfaces of the second workpiece 2 and the third workpiece 3.

[0042] A first annular groove is circumferentially arranged on the outer wall of the small support plate 7, and the position of the first annular groove corresponds to the joint between the first workpiece 1 and the second workpiece 2; the first annular groove has n first through holes evenly distributed along the circumference; the n first through holes correspond one-to-one to and are connected with the n small support plate partition air inlet connectors 11; the width b of the first annular groove is 15-20mm, and the depth c is 5-12mm; the diameter a of the first through hole is 4-6mm.

[0043] A second annular groove is circumferentially arranged on the outer wall of the large support plate 8, and the position of the second annular groove corresponds to the joint between the second workpiece 2 and the third workpiece 3; the second annular groove has n second through holes evenly distributed along the circumference; the n second through holes correspond one-to-one to and are connected with the n large support plate partition air inlet joints 12; the width b of the second annular groove is 15-20mm, and the depth c is 5-12mm; the diameter a of the second through hole is 4-6mm.

[0044] Step three, clamp the laser welding inner wall support tooling to the external laser welding machine turntable through the lifting ring 13; and mount the positioned first workpiece 1, second workpiece 2 and third workpiece 3 on the outer wall of the laser welding inner wall support tooling to ensure that the inner wall at the large diameter end of the first workpiece 1 is tightly fitted with the outer wall of the small support plate 7, and the inner wall at the small diameter end of the third workpiece 3 is tightly fitted with the outer wall of the large support plate 8.

[0045] Step 4: Make the laser welding outer wall gas protection tooling, such as Figure 2As shown, it specifically includes a steel tube 15, a copper tube 16, a ceramic nozzle 17 and a filter 18; the copper tube 16 is coaxially sleeved on the axial bottom end of the steel tube 15 and welded; the ceramic nozzle 17 is sleeved on the axial bottom end of the copper tube 16, and the ceramic nozzle 17 is threadedly connected to the copper tube 16; a channel connected to the copper tube 16 is arranged inside the ceramic nozzle 17; 2-4 layers of filter 18 with a mesh size of 70-100 are arranged in the channel of the ceramic nozzle 17.

[0046] Step 5. Adjust the external laser welder to be perpendicular to the butt joint, adjust the distance e between the laser welding outer wall gas shielding tooling and the weld, and the angle d between the laser welding outer wall gas shielding tooling and the external laser welder; perform laser welding on the butt joints of the first workpiece 1 and the second workpiece 2, and the butt joints of the second workpiece 2 and the third workpiece 3 respectively.

[0047] The distance e between the laser welding outer wall gas shielding tooling and the weld is 1-2mm; the angle d between the laser welding outer wall gas shielding tooling and the external laser welder is 45°-60°. The notch below the ceramic nozzle is ground to pass the laser beam. The notch width f is 10mm-15mm, and the notch length g is 6mm-10mm. Figure 2 shown.

[0048] During laser welding, the external shielding gas enters the partitioned air inlet joints 11 of each small support plate through the total air inlet joint 9 of the small support plate, and then enters the first ring groove; the external shielding gas enters the partitioned air inlet joints 12 of each large support plate through the total air inlet joint 10 of the large support plate, and then enters the second ring groove; the external shielding gas is sprayed on the welding area through the steel pipe 15, the copper pipe 16, and the ceramic nozzle 17 in turn; the welding process parameters are: the laser power is 3000-4500W, and the welding speed is 1200-2100mm / min. The shielding gas is argon, the front shielding gas flow rate is 12L / min-20L / min, the back shielding gas flow rate is 12L / min-20L / min, and the defocus amount is +2mm-+8mm; the segmented laser welding method is adopted, and the length of each segment is 600mm-700mm.

[0049] After welding is completed, disassemble the workpiece and tooling, grind the back of the weld to remove any leaks, correct the weld, and perform an X-ray inspection on the weld. The gap between the sample and the inner surface of the weld is required to be no greater than 0.3mm.

[0050] Example 1

[0051] (1) The materials of the first workpiece 1, the second workpiece 2, and the third workpiece 3 are all 1Cr21Ni5Ti stainless steel, with a thickness of 2 mm, a diameter of Φ500 mm, and a height of 500 mm; the large and small end diameters of the second workpiece 2 are respectively machined according to the small end diameters of the third workpiece 3 and the large end diameters of the first workpiece 1; the butt joints of the first workpiece 1, the second workpiece 2, and the third workpiece 3 are cleaned, and the first workpiece 1, the second workpiece 2, and the third workpiece 3 are butt-assembled, and are positioned by manual argon arc welding, with a positioning point length of 10 mm and a distance between two adjacent positioning points of 20 mm; the butt joints are corrected, with a misalignment of 0-0.1 mm and a gap of 0-0.1 mm. Through the hoisting ring 13, the combination of the special laser welding tool spindle 4, the small support plate 7, and the large support plate 8 is clamped to the laser welding machine turntable, ensuring that the large support plate 8 is at the bottom, and the spindle 4 is clamped with the turntable three-claw; the first workpiece 1, the second workpiece 2, and the third workpiece 3 that have been positioned are hoisted to the tooling, ensuring that the first workpiece 1 and the small support plate 7 are tightly fitted; the third workpiece 3 and the large support plate 8 are tightly fitted; the outer surface profile of the small support plate 7 and the large support plate 8 is consistent with the inner profile of the workpiece, and a ring for back gas protection of the weld is processed respectively. Groove, the width b of the ring groove is 15mm, the depth c of the ring groove is 5mm, and a hole with a diameter a of Φ4mm is processed all around the ring groove, which is connected to the ring groove; the small support plate 7 is evenly arranged with 6 small support plate partition air intake joints 11 connected to the ring groove, and the large support plate 8 is evenly arranged with 6 large support plate partition air intake joints 12 connected to the ring groove, and the partition air intake joints must be arranged parallel to the axis of the main shaft 4; after the first workpiece 1, the second workpiece 2, and the third workpiece 3 are clamped to the laser welding fixture, it is necessary to ensure that the butt welds are located in the ring grooves of the small support plate 7 and the large support plate 8 respectively. Use a five-way joint and an air pipe to connect the partition air intake joints 11 of each small support plate together, and finally connect them to the total air intake joint 9 of the small support plate, and use a five-way joint and an air pipe to connect the partition air intake joints 12 of each large support plate together, and finally connect them to the total air intake joint 10 of the large support plate; tilt the laser welder at a certain angle so that the weld is in the vertical direction.

[0052] (2) The front gas shielding tooling uses manual argon arc welding to weld the steel pipe 15 and the copper pipe 16 together. The copper pipe 16 and the ceramic nozzle 17 are connected by threads. At the same time, two layers of filter screens 18 with a mesh size of 70 are placed inside the ceramic nozzle near the end. When the front gas shielding tooling is used, the shielding gas inlet pipe is connected to the steel pipe 15, and the ceramic nozzle 17 is at the bottom. The front gas shielding tooling is fixed on the laser welding head, and the angle d between the front gas shielding tooling and the vertical direction is 45°; the distance between the front gas shielding tooling and the weld surface is adjusted, and the distance e between the ceramic nozzle 17 and the weld surface is 1mm; the notch below the ceramic nozzle is ground to pass the laser beam, and the notch width f is 10mm and the notch length g is 6mm. Find the weld position and teach to obtain the coordinate point. Laser welding is performed on the butt welds of the first workpiece 1 and the second workpiece 2, and the butt welds of the second workpiece 2 and the third workpiece 3, respectively. The laser power is 3000W, the welding speed is 1200mm / min, the shielding gas is argon, the front shielding gas flow rate is 12L / min, the back shielding gas flow rate is 12L / min, and the defocus amount is +2mm; the segmented laser welding method is adopted, and the length of each segment is 600mm.

[0053] (3) After welding is completed, disassemble the workpiece and tooling, grind the back of the weld to remove any leaks and correct the weld. Use a standard profile template to check the inner profile. The gap between the template and the inner profile of the weld should not exceed 0.3mm. Perform an X-ray inspection of the weld.

[0054] Example 2

[0055] (1) The materials of the first workpiece 1, the second workpiece 2, and the third workpiece 3 are all 1Cr21Ni5Ti stainless steel, with a thickness of 3 mm, a diameter of Φ900 mm, and a height of 700 mm; the large and small end diameters of the second workpiece 2 are respectively machined according to the small end diameters of the third workpiece 3 and the large end diameters of the first workpiece 1; the butt joints of the first workpiece 1, the second workpiece 2, and the third workpiece 3 are cleaned, and the first workpiece 1, the second workpiece 2, and the third workpiece 3 are butt-assembled, and are positioned by manual argon arc welding, with a positioning point length of 20 mm and a distance between two adjacent positioning points of 30 mm; the butt joints are corrected, with a misalignment of 0.05 mm-0.1 mm and a gap of 0.05 mm-0.1 mm. Through the hoisting ring 13, the combination of the special laser welding tool spindle 4, the small support plate 7, and the large support plate 8 is clamped to the laser welding machine turntable, ensuring that the large support plate 8 is at the bottom, and the spindle 4 is clamped with the turntable three-claw; the first workpiece 1, the second workpiece 2, and the third workpiece 3 that have been positioned are hoisted to the tooling, ensuring that the first workpiece 1 fits tightly with the small support plate 7; and the third workpiece 3 fits tightly with the large support plate 8; the outer surface profile of the small support plate 7 and the large support plate 8 is consistent with the inner surface of the workpiece, and an annular groove for back gas protection of the weld is processed respectively , the width b of the annular groove is 20mm, the depth c of the annular groove is 12mm, and a hole with a diameter a of Φ6mm is processed all around the annular groove, which is connected to the annular groove; the small support plate 7 is evenly arranged with 8 small support plate partition air intake joints 11 connected to the annular groove, and the large support plate 8 is evenly arranged with 8 large support plate partition air intake joints 12 connected to the annular groove, and the partition air intake joints must be arranged parallel to the axis of the main shaft 4; after the first workpiece 1, the second workpiece 2, and the third workpiece 3 are clamped to the laser welding fixture, it is necessary to ensure that the butt welds are located in the annular grooves of the small support plate 7 and the large support plate 8 respectively. Use a five-way joint and an air pipe to connect the partition air intake joints 11 of each small support plate together, and finally connect them to the total air intake joint 9 of the small support plate, and use a five-way joint and an air pipe to connect the partition air intake joints 12 of each large support plate together, and finally connect them to the total air intake joint 10 of the large support plate; tilt the laser welder at a certain angle so that the weld is in the vertical direction.

[0056] (2) The front gas shielding tooling uses manual argon arc welding to weld the steel pipe 15 and the copper pipe 16 together. The copper pipe 16 and the ceramic nozzle 17 are connected by threads. At the same time, a 4-layer filter 18 with a mesh size of 100 is placed inside the ceramic nozzle near the end. When the front gas shielding tooling is used, the shielding gas inlet pipe is connected to the steel pipe 15, and the ceramic nozzle 17 is at the bottom. The front gas shielding tooling is fixed on the laser welding head, and the angle d between the front gas shielding tooling and the vertical direction is 60°; the distance between the front gas shielding tooling and the weld surface is adjusted, and the distance e between the ceramic nozzle 17 and the weld surface is 2mm; the notch below the ceramic nozzle is ground to pass the laser beam, and the notch width f is 15mm and the notch length g is 10mm. Find the weld position and teach to obtain the coordinate point. Laser welding is performed on the butt welds of the first workpiece 1 and the second workpiece 2, and the butt welds of the second workpiece 2 and the third workpiece 3, respectively. The laser power is 4500W, the welding speed is 2100mm / min, the shielding gas is argon, the front shielding gas flow is 20L / min, the back shielding gas flow is 20L / min, and the defocus amount is +8mm; the segmented laser welding method is adopted, and the length of each segment is 700mm.

[0057] (3) After welding is completed, disassemble the workpiece and tooling, grind the back of the weld to remove any leaks and correct the weld. Use a standard profile template to check the inner profile. The gap between the template and the inner profile of the weld should not exceed 0.3mm. Perform an X-ray inspection of the weld.

[0058] Example 3

[0059] (1) The materials of the first workpiece 1, the second workpiece 2, and the third workpiece 3 are all 1Cr21Ni5Ti stainless steel, with a thickness of 2.5 mm, a diameter of Φ700 mm, and a height of 600 mm; the large and small end diameters of the second workpiece 2 are respectively machined according to the small end diameters of the third workpiece 3 and the large end diameters of the first workpiece 1; the butt joints of the first workpiece 1, the second workpiece 2, and the third workpiece 3 are cleaned, and the first workpiece 1, the second workpiece 2, and the third workpiece 3 are butt-assembled, and are positioned by manual argon arc welding, with a positioning point length of 15 mm and a distance between two adjacent positioning points of 25 mm; the butt joints are corrected, with a misalignment of 0.05 mm-0.15 mm and a gap of 0.05 mm-0.15 mm. Through the hoisting ring 13, the combination of the special laser welding tool spindle 4, the small support plate 7, and the large support plate 8 is clamped to the laser welding machine turntable, ensuring that the large support plate 8 is at the bottom, and the spindle 4 is clamped with the turntable three-claw; the first workpiece 1, the second workpiece 2, and the third workpiece 3 that have been positioned are hoisted to the tooling, ensuring that the first workpiece 1 and the small support plate 7 are tightly fitted; the third workpiece 3 and the large support plate 8 are tightly fitted; the outer surface profile of the small support plate 7 and the large support plate 8 is consistent with the inner profile of the workpiece, and a ring for back gas protection of the weld is processed respectively. Groove, the width b of the ring groove is 17mm, the depth c of the ring groove is 9mm, and a hole with a diameter a of Φ5mm is processed all around the ring groove, which is connected to the ring groove; the small support plate 7 is evenly arranged with 6 small support plate partition air intake joints 11 connected to the ring groove, and the large support plate 8 is evenly arranged with 6 large support plate partition air intake joints 12 connected to the ring groove, and the partition air intake joints must be arranged parallel to the axis of the main shaft 4; after the first workpiece 1, the second workpiece 2, and the third workpiece 3 are clamped to the laser welding fixture, it is necessary to ensure that the butt welds are located in the ring grooves of the small support plate 7 and the large support plate 8 respectively. Use a five-way joint and an air pipe to connect the partition air intake joints 11 of each small support plate together, and finally connect them to the total air intake joint 9 of the small support plate, and use a five-way joint and an air pipe to connect the partition air intake joints 12 of each large support plate together, and finally connect them to the total air intake joint 10 of the large support plate; tilt the laser welder at a certain angle so that the weld is in the vertical direction.

[0060] (2) The front gas shielding tooling uses manual argon arc welding to weld the steel pipe 15 and the copper pipe 16 together. The copper pipe 16 and the ceramic nozzle 17 are connected by threads. At the same time, a three-layer filter 18 with a mesh size of 80 is placed inside the ceramic nozzle near the end. When the front gas shielding tooling is used, the shielding gas inlet pipe is connected to the steel pipe 15, and the ceramic nozzle 17 is at the bottom. The front gas shielding tooling is fixed on the laser welding head, and the angle d between the front gas shielding tooling and the vertical direction is 50°; the distance between the front gas shielding tooling and the weld surface is adjusted, and the distance e between the ceramic nozzle 17 and the weld surface is 1.5mm; the notch below the ceramic nozzle is ground to pass the laser beam, and the notch width f is 13mm and the notch length g is 8mm. Find the weld position and teach to obtain the coordinate point. Laser welding is performed on the butt weld between the first workpiece 1 and the second workpiece 2, and the butt weld between the second workpiece 2 and the third workpiece 3. The laser power is 4000W, the welding speed is 1800mm / min, the shielding gas is argon, the front shielding gas flow is 16L / min, the back shielding gas flow is 16L / min, and the defocus amount is +6mm; the segmented laser welding method is adopted, and the length of each segment is 650mm.

[0061] (3) After welding is completed, disassemble the workpiece and tooling, grind the back of the weld to remove any leaks and correct the weld. Use a standard profile template to check the inner profile. The gap between the template and the inner profile of the weld should not exceed 0.3mm. Perform an X-ray inspection of the weld.

[0062] The present invention provides a method for laser welding a duplex stainless steel annular workpiece. The method adopts a dedicated optimized back gas shielding tool and a front gas shielding tool and uses optimized laser welding parameters, so that the X-ray inspection pass rate of the laser weld of the duplex stainless steel annular workpiece is increased from 30% to 90%, thereby avoiding the problem of delaying the repair progress and increasing the cost due to unqualified X-ray inspection.

[0063] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for laser welding of large-size duplex stainless steel annular workpieces, characterized in that: The steps include: Step 1: cleaning the butt joints of the first workpiece (1), the second workpiece (2) and the third workpiece (3), coaxially butt-jointing the first workpiece (1), the second workpiece (2) and the third workpiece (3) and positioning them by manual argon arc welding; Step 2: manufacturing a laser welding inner wall support tooling, including a main shaft (4), a small support plate (7), a large support plate (8), a small support plate total air intake connector (9), a large support plate total air intake connector (10), n small support plate partition air intake connectors (11), n ​​large support plate partition air intake connectors (12) and a lifting ring (13); Step 3: Clamp the laser welding inner wall support tooling onto the external laser welding machine turntable by means of a lifting ring (13); and mount the positioned first workpiece (1), the second workpiece (2) and the third workpiece (3) onto the outer wall of the laser welding inner wall support tooling, ensuring that the inner wall at the large diameter end of the first workpiece (1) is tightly fitted with the outer wall of the small support plate (7), and the inner wall at the small diameter end of the third workpiece (3) is tightly fitted with the outer wall of the large support plate (8); Step 4: Making a laser welding outer wall gas protection tooling; including a steel pipe (15), a copper pipe (16), a ceramic nozzle (17) and a filter (18); Step 5: adjust the external laser welder to be perpendicular to the butt joint, adjust the distance e between the laser welding outer wall gas shielding tooling and the weld, and the angle d between the laser welding outer wall gas shielding tooling and the external laser welder; and perform laser welding on the butt joint between the first workpiece (1) and the second workpiece (2), and the butt joint between the second workpiece (2) and the third workpiece (3), respectively.

2. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 1, characterized in that: In the step 1, the first workpiece (1), the second workpiece (2) and the third workpiece (3) are all hollow cone-section structures; the materials of the first workpiece (1), the second workpiece (2) and the third workpiece (3) are all 1Cr21Ni5Ti stainless steel with a thickness of 2 mm-3 mm; the third workpiece (3) is axially arranged vertically at the lowest end, and the small diameter end is placed upward; the second workpiece (2) is coaxially butted against the top of the third workpiece (3), and the large diameter end of the second workpiece (2) is butted against the small diameter end of the third workpiece (3); the first workpiece (1) is coaxially butted against the top of the second workpiece (2), and the large diameter end of the first workpiece (1) is butted against the small diameter end of the second workpiece (2).

3. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 1, characterized in that: In the step 1, the process parameters of manual argon arc welding are: The length of the positioning point is 10-20mm; the distance between two adjacent positioning points is 20-30mm; after correction and docking, the misalignment is required to be no more than 0.15mm and the gap is required to be no more than 0.15mm.

4. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 1, characterized in that: In step 2, the specific structure of the laser welding inner wall support tooling is: The main shaft (4) is placed vertically in the axial direction; the lifting ring (13) is fixedly installed on the top of the main shaft (4); the small support plate (7) is horizontally mounted on the outer wall of the main shaft (4), and the small support plate (7) corresponds to the joint between the first workpiece (1) and the second workpiece (2); n small support plate partition air intake joints (11) are evenly installed on the bottom of the small support plate (7) along the circumferential direction; the small support plate total air intake joint (9) is fixedly installed on the side wall of the main shaft (4) and is located below the small support plate (7); the small support plate total air intake joint (9) and the n small support plates are connected to each other. The support plate partition air inlet connectors (11) are connected; the large support plate (8) is horizontally mounted on the outer wall of the main shaft (4), and the large support plate (8) corresponds to the joint between the second workpiece (2) and the third workpiece (3); n large support plate partition air inlet connectors (12) are evenly installed on the bottom of the large support plate (8) along the circumferential direction; the large support plate total air inlet connector (10) is fixedly installed on the side wall of the main shaft (4) and is located below the large support plate (8); the large support plate total air inlet connector (10) is connected to the n large support plate partition air inlet connectors (12).

5. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 4, characterized in that: The small support plate (7) is a conical section structure; the outer profile of the side wall of the small support plate (7) is adapted to the inner profile of the first workpiece (1) and the second workpiece (2); the large support plate (8) is a conical section structure; the outer profile of the side wall of the large support plate (8) is adapted to the inner profile of the second workpiece (2) and the third workpiece (3).

6. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 5, characterized in that: The outer wall of the small support plate (7) is provided with a first annular groove in the circumferential direction, and the position of the first annular groove corresponds to the joint between the first workpiece (1) and the second workpiece (2); the first annular groove is uniformly distributed with n first through holes along the circumferential direction; the n first through holes correspond to and are connected with the n small support plate partition air inlet joints (11) in a one-to-one manner; the width b of the first annular groove is 15-20 mm, and the depth c is 5-12 mm; the diameter a of the first through hole is 4-6 mm.

7. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 6, characterized in that: The outer wall of the large support plate (8) is provided with a second annular groove in the circumferential direction, and the position of the second annular groove corresponds to the joint between the second workpiece (2) and the third workpiece (3); the second annular groove is evenly distributed with n second through holes along the circumferential direction; the n second through holes correspond to and are connected with the n large support plate partition air inlet joints (12) in a one-to-one manner; the width b of the second annular groove is 15-20 mm, and the depth c is 5-12 mm; the diameter a of the second through hole is 4-6 mm; n is a positive integer and 6≤n≤8.

8. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 7, characterized in that: The specific structure of the laser welding outer wall gas protection tooling is: The copper tube (16) is coaxially sleeved on the axial bottom end of the steel tube (15) and welded; the ceramic nozzle (17) is sleeved on the axial bottom end of the copper tube (16), and the ceramic nozzle (17) and the copper tube (16) are threadedly connected; a channel communicating with the copper tube (16) is arranged inside the ceramic nozzle (17); and 2-4 layers of filter screens (18) with mesh sizes of 70-100 are arranged in the channel of the ceramic nozzle (17).

9. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 8, characterized in that: The distance e between the laser welding outer wall gas shielding tooling and the weld is 1-2 mm; the angle d between the laser welding outer wall gas shielding tooling and the external laser welder is 45°-60°.

10. The method for laser welding of large-size duplex stainless steel annular workpiece according to claim 9, characterized in that: During laser welding, the external shielding gas enters the partitioned air inlet joints (11) of each small support plate through the total air inlet joint (9) of the small support plate, and then enters the first annular groove; the external shielding gas enters the partitioned air inlet joints (12) of each large support plate through the total air inlet joint (10) of the large support plate, and then enters the second annular groove; the external shielding gas is sprayed on the welding area through the steel pipe (15), the copper pipe (16), and the ceramic nozzle (17) in sequence; the welding process parameters are: the laser power is 3000-4500W, and the welding speed is 1200-2100mm / min.

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