CN111203614B - Device for assisting LSAW pipe welding process through pulse current and using method - Google Patents
Device for assisting LSAW pipe welding process through pulse current and using method Download PDFInfo
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- CN111203614B CN111203614B CN202010057943.3A CN202010057943A CN111203614B CN 111203614 B CN111203614 B CN 111203614B CN 202010057943 A CN202010057943 A CN 202010057943A CN 111203614 B CN111203614 B CN 111203614B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/18—Submerged-arc welding
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/02—Seam welding; Backing means; Inserts
- B23K9/025—Seam welding; Backing means; Inserts for rectilinear seams
- B23K9/0253—Seam welding; Backing means; Inserts for rectilinear seams for the longitudinal seam of tubes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/235—Preliminary treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K2101/00—Articles made by soldering, welding or cutting
- B23K2101/04—Tubular or hollow articles
- B23K2101/06—Tubes
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Abstract
The invention relates to a device for assisting a LSAW pipe welding process by pulse current and a using method thereof. The invention can effectively refine crystal grains in a heat affected zone, increase dislocation density and reduce residual stress after welding, and improve the uniformity of the structure of the heat affected zone, thereby improving the reliability of the LSAW tube in the actual service process.
Description
Technical Field
The invention relates to a device for assisting a LSAW pipe welding process by pulse current and a using method thereof, belonging to the technical field of longitudinal double-sided submerged arc welded pipes.
Background
In the last decade, the yield and consumption of natural gas in China keep a continuous increasing trend, and the production place of the natural gas is far away from the demand place and needs pipeline transportation. At present, a natural gas conveying network in one region of China adopts a spiral submerged arc welded pipe, and longitudinal submerged arc welded pipes or high-frequency longitudinal welded pipes are adopted in the second, third and fourth regions of China; and the foreign natural gas transportation trunk line takes a longitudinal submerged arc welded pipe as a main body, and the spiral submerged arc welded pipes are fewer. For a long time, the advantages of longitudinal submerged arc welding pipes are more and more prominent due to the characteristics of high conveying pressure, large pipe diameter, thick wall and the like.
The longitudinal seam double-sided submerged arc welded pipe mainly adopts a UOE/JCOE forming technology, and is provided with a longitudinal welding seam, and the inner welding seam and the outer welding seam are formed by adopting one-time submerged arc welding. The traditional single wire submerged arc welding speed is too slow, so that the heat input is too large, the grains of a welding seam and a heat affected zone are coarse, and the plasticity and the toughness are greatly reduced. The multi-wire submerged-arc welding not only improves the deposition rate, but also accelerates the welding speed, reduces the welding heat input, improves the plasticity and the toughness of a joint, and leads the chemical composition of a welding seam to be very close to that of a parent metal, so the multi-wire submerged-arc welding is adopted in the internal and external welding of the longitudinal double-sided submerged-arc welding pipe in the market. However, even the longitudinal double-sided submerged arc welded pipe with good test performance sometimes leaks in actual service, which is mainly because the measured test performance is actually a comprehensive reflection of the performance of the base material, the welding seam and the heat affected zone, and does not reflect the toughness of the weakest part of the welded joint, and the heat cycles of the heat affected zone are different due to different distances from each part of the heat affected zone to the welding seam, so that the texture distribution of the heat affected zone is extremely uneven, and the heat affected zone is the weakest area of the longitudinal double-sided submerged arc welded pipe.
Therefore, the method has important engineering practical significance on solving the problem of extremely uneven texture distribution of the heat affected zone of the longitudinal double-sided submerged arc welded pipe.
Disclosure of Invention
The invention aims to provide a device for assisting a LSAW tube welding process by pulse current and a using method thereof, which can effectively refine grains in a heat affected zone, increase dislocation density and reduce residual stress after welding, and improve the uniformity of a heat affected zone structure, thereby improving the reliability of the LSAW tube in the actual service process.
In order to achieve the purpose, the invention adopts the technical scheme that:
the utility model provides a device and application method of supplementary LSAW pipe welding process of pulse current, includes nut, graphite electrode, base, roof beam, first support, second support, servo motor, gear, collar and installation arm, nut and graphite electrode coaxial arrangement are on the base, the installation spring between graphite electrode and the base, nut, graphite electrode and base setting are two sets of to be installed respectively on the roof beam through fastening bolt, first support and second support are installed respectively through the bolt to the another side of roof beam, first support and second support adopt insulating material to make, the tip that the roof beam was kept away from to first support and second support passes through the bolt and installs the collar, and the collar is vertical to be put, the coaxial direction installation collar of keeping away from the roof beam of collar.
The technical scheme of the invention is further improved as follows: the distance from the graphite electrode to the nut is 15-20mm, and the nut is screwed to drive the graphite electrode to compress the spring.
The technical scheme of the invention is further improved as follows: the end of the graphite electrode far away from the screw cap is arranged into a 30-45-degree inclination angle shape.
The technical scheme of the invention is further improved as follows: the base is made into a sliding block, the distance can be adjusted in the beam, and the sliding block is fixed through a fastening bolt.
The technical scheme of the invention is further improved as follows: the beam is connected with the first support and the second support through the connecting column, and the angle of the connecting column at the position where the connecting column is connected with the first support and the second support is the same as the top of the graphite electrode.
The technical scheme of the invention is further improved as follows: the tail parts of the first support and the second support, which are far away from the beam, are provided with gears which are meshed with each other, the gears are connected with a servo motor, and the servo motor is fixed on the mounting arm.
The technical scheme of the invention is further improved as follows: the two beams are connected to a retainer in a sliding mode, the retainer is made of insulating materials, and the retainer is perpendicular to the length direction of the welded pipe and moves back and forth along the length direction of the welded pipe.
The technical scheme of the invention is further improved as follows: the method comprises the following steps:
firstly, edge milling, groove preparation and welded pipe forming;
preheating before welding, namely respectively installing a pulse current applying device on an upper slope opening and a lower slope opening of the welded pipe, and heating the groove of the welded pipe by using the heat effect of pulse current to preheat before welding;
thirdly, prewelding, namely prewelding when the welded pipe joints to form a thinner prewelded joint in order to prevent the welded pipe from generating the problems of misalignment, over-tolerance and the like;
turning the welded pipe by 180 degrees, enabling an inner groove to face upwards, adopting four-wire submerged arc welding for inner welding, mounting graphite electrodes on two sides of a welding gun, refining coarse crystal grains in a heat affected zone of a welding joint by applying pulse current, enabling the crystal grain tissues to be uniformly distributed, finishing inner welding, and removing slag and burrs;
step five, external welding, namely turning the welded pipe 180 degrees again, enabling an external slope to be upward, adopting four-wire submerged arc welding for external welding, installing graphite electrodes on two sides of a welding gun, refining coarse crystal grains in a heat affected zone of a welding joint by applying pulse current, enabling the crystal grain structure to be uniformly distributed, finishing external welding, and removing slag and burrs;
step six, finishing, chamfering flat ends, and testing performance indexes through a hydrostatic test and the like;
and seventhly, marking and warehousing.
The technical scheme of the invention is further improved as follows: the welding gun I and the welding gun II of the four-wire submerged arc welding are set to be forward inclined, the welding gun III and the welding gun IV are sequentially transited to backward inclined, and the forward inclination angle alpha of the welding gun I1Is 10 degrees to 20 degrees, and the front rake angle alpha of a welding gun II20 to 5 degrees, and a back rake angle alpha of a welding gun III3Is 5 degrees to 10 degrees, and the back inclination angle alpha of a welding gun IV410-20 degrees, and the distance between adjacent welding gun nozzles is 60-80 mm.
Due to the adoption of the technical scheme, the invention has the following technical effects:
1. the wall thickness of the LSAW tube is 8-40mm, flame preheating is usually adopted before welding, and the high-frequency pulse current is adopted to rapidly heat the quenching layer delta at the edge of the groove of the welded tube to about 200 ℃ so as to achieve the preheating effect, effectively improve the structure of a heat affected zone after welding, effectively prevent welding cold cracks and simultaneously avoid the defects of high cost and low efficiency of flame preheating.
2. Compared with the traditional external field treatment mode, after pulse current treatment, a larger temperature difference exists between the high-temperature heat affected zone of the welding seam and the low-temperature parent metal, so that the heat affected zone has the characteristics of higher cooling speed, larger supercooling degree and the like, the solid solution capacity of the heat affected zone of the welding seam is enhanced, and the strength of the heat affected zone of the welding seam is favorably improved.
3. The LSAW pipe internal and external welding adopts four-wire submerged arc welding, pulse current with certain parameters is introduced in the welding process, due to skin effect, the pulse current is mainly concentrated in a groove quenching layer delta', namely a coarse crystal area of a heat affected zone, the width is 1-2mm, the pulse current flows out from a pulse power supply along a beam → a graphite electrode → a heat affected zone → a welding seam → the heat affected zone → the graphite electrode → the beam flows back to the pulse power supply, coarse crystal grains in the heat affected zone of the LSAW pipe welding joint can be refined through pulse current treatment, the distribution uniformity of a microstructure is effectively improved, meanwhile, the pulse current treatment can also further improve the weld structure performance, and the reliability in the service process of the welding pipe is obviously improved.
Drawings
FIG. 1 is a flow chart of the operation of the apparatus of the present invention;
FIG. 2 is a schematic diagram of the apparatus of the present invention;
FIG. 3 is a schematic view of the electrode mounting of the apparatus of the present invention;
FIG. 4 is a schematic structural view of the apparatus of the present invention during external welding;
FIG. 5 is a schematic diagram of the electrode structure of the device of the present invention;
FIG. 6 is a partial schematic view of a portion of the components of the electrode configuration schematic of the apparatus of the present invention;
FIG. 7 is a schematic cross-sectional view of a portion of the components of the electrode configuration of the device of the present invention;
fig. 8 is a schematic diagram of the structure of the adjustable pulse power supply of the device of the present invention.
Wherein, 1, welding a pipe; 101. a base material; 102. pre-welding a welding seam; 103. welding seams are welded inside; 103a, a first inner welding seam; 103b, second inner welding seams; 103c, a third inner welding seam; 103d, a fourth inner welding seam; 104. welding seams are welded outside; 104a, a first external welding seam; 104b, second external welding seam; 104c, a third external welding seam; 104d, a fourth external welding seam; 105. a heat affected zone; 2. a graphite electrode; 21. an electrode I; 22. an electrode II; 23. an electrode III; 24. an electrode IV; 3. a nut; 4. a base; 5. fastening a bolt; 6. a beam; 7. a first bracket; 8. a mounting ring; 9. a second bracket; 10. mounting an arm; 11. a holder; 12. a gear; 13. a servo motor; 141. a welding gun I; 142. a welding gun II; 143. a welding gun III; 144. a welding gun IV; 15. a spring.
Detailed Description
The invention is described in further detail below with reference to the following figures and specific embodiments:
the invention aims to provide a device for assisting a LSAW tube welding process by pulse current and a using method thereof, so as to refine the structure of a heat affected zone of the LSAW tube and improve the distribution uniformity of the structure, thereby improving the overall welding quality of a welding joint and further improving the reliability of the LSAW tube in the service process.
As shown in fig. 4-7, the device for pulse current assisted LSAW tube welding process of the present invention includes a graphite electrode 2, a base 4, a beam 6, a first support 7, a second support 9, a mounting ring 8 and a mounting arm 10, wherein the nut 3 and the graphite electrode 2 are coaxially mounted on the base 4, the distance from the graphite electrode 2 to the nut 3 is 15-20mm, a spring 15 is mounted between the graphite electrode 2 and the base 4, the base 4 is mounted on the beam 6, the first support 7 and the second support 9 are respectively mounted with the beam 6 by bolts, the first support 7 and the second support 9 are made of insulating materials and mounted on the mounting ring 8 by bolts, the mounting ring 8 is coaxially mounted at the end of the mounting arm 10, the two beams 6 are symmetrically mounted at two sides of the groove of the welding tube 1, and the top of the graphite electrode 2 is in close contact with the welding tube 1.
The top of the graphite electrode 2 and the top of the beam 6 are cut into 30-45 degrees, the beam 6 is connected with the first bracket 7 and the second bracket 9 by arranging a connecting column, and the angle of the connecting position of the connecting column and the first bracket 7 and the second bracket 9 is the same as that of the top of the graphite electrode 2; the sharp angle at the top of the graphite electrode 2 is 1-2mm away from the edge of the groove of the welding tube 1, the graphite electrode 2 is coaxially arranged on a base 4, the base 4 is made into a sliding block, the distance between every two bases 4 can be adjusted, the distance is adjusted and then fixed on a beam 6 through a fastening screw, the two beams 6 are respectively arranged on a first support 7 and a second support 9, the tail parts of the first support 7 and the second support 9 are milled with gear teeth and are mutually meshed, the tail part of the first support 7 is externally meshed with a gear 12, the gear 12 is connected with a servo motor 13, the servo motor 13 is fixed on an installation arm 10, the gear 12 is controlled by the servo motor 13 to rotate forwards and backwards to realize the simultaneous unfolding or folding of the first support 7 and the second support 9, the first support 7 and the second support 9 are always symmetrically distributed at two sides of the welding tube 1, the two beams 6 are slidably connected on a, the holder 11 is vertical to the length direction of the welding tube 1 and moves back and forth along the length direction of the welding tube 1, the holder 11 can keep the beam 6 always parallel to the length direction of the welding tube 1, and the graphite electrode 2, the pulse power supply and the to-be-welded area of the welding tube 1 form a loop.
The longitudinal double-sided submerged arc welded pipe 1 is mainly composed of three parts, namely a weld (an inner weld 103 and an outer weld 104), a Heat Affected Zone (HAZ)105 and a base material 101. For the reliability and safety of the gas transmission project, the performance index of the straight-seam double-sided submerged arc welded pipe 1 is strictly required, the submerged arc welding joint mainly comprises a base material 101, welding seams (an inner welding seam 103 and an outer welding seam 104) and a heat affected zone 105, but in practice it is measured that the properties of the parent metal 101, the weld (inner weld 103 and outer weld 104) and the heat affected zone 105 are reflected in combination, while the grain size of the heat affected zone 105 may be significantly coarsened near the weld line, coarser during subsequent thermal cycles, and, in addition, for a multi-wire submerged arc welded steel pipe, the heat affected zone 105 of the second weld overlaps the heat affected zone 105 of the first weld, the coarse grain zone of the heat affected zone 105 is the weakest area in the heat affected zone of the weld, the device for improving the welding quality of the LSAW pipe on line can improve the mechanical property of the heat affected zone 105 of the welding joint of the double-sided submerged arc welded pipe 1 in a targeted manner so as to improve the reliability of the LSAW pipe in the service process.
In addition, generally, the higher the temperature of the metal, the greater its resistance, and the greater the degree of change in resistance with temperature than with its conductive distance. In this embodiment, for the inner and outer welding processes of the multi-wire submerged arc welding steel pipe, the temperature of the second welding seam is higher than that of the first welding seam at the beginning, so the resistance of the second welding seam is relatively high, so the pulse current preferentially goes through the first welding seam, and when the temperature of the second welding seam is cooled to be close to that of the first welding seam, the pulse current preferentially goes through the path with the shortest distance (smaller resistance), namely the second welding seam, so the pulse current sequentially flows through each welding seam.
In the present embodiment, preheating is performed before welding, the pulse power is adjusted to mode one, and the plugs A and A' of the graphite electrode 2 are respectively connected with the output terminals of the pulse powerI and VIII, plugs B and B' are respectively connected with output terminals II and III, pulse current flows back to the inner graphite electrode 2 from the outer graphite electrode 2 through the parent metal of the welded pipe 1, and in the pulse current treatment process, the current is blocked to select the nearest channel to flow through the parent metal 101, namely I2However, due to skin effect, the local current density is obviously improved, and the pulse current is mainly concentrated in the groove quenching layer delta of the welded pipe 1, namely I1In which I1＞＞I2The joule heat in the pulse current discharge process causes the area to be welded to be rapidly heated to about 200 ℃, and the area to be welded is preheated before welding, so that the welding stress and deformation are reduced, and the welding crack is prevented;
in addition, after preheating before welding is finished, pre-welding is required for preventing welded pipe 1 from degrading or being scrapped due to misalignment and the like, the pre-welding is an important component of the welding process of longitudinal submerged arc welded pipe 1, and a relatively thin pre-welding seam 102 is formed after the pre-welding;
further, in the present embodiment, the inner and outer welding of the X80 Φ 1060 × 31mm longitudinal submerged arc welded pipe 1 are all four-wire submerged arc welding process, and are respectively welded according to the welding process sequence of inner welding and outer welding, the inner and outer welding are all continuously welded and completed at one time by four welding seams, the first welding seam is a bottom layer, the second and third welding seams are filling layers, and the fourth welding seam is a cover layer. In order to obtain better implementation effect, the device is provided with a pair of graphite electrodes 2 for each welding gun, the graphite electrodes 2 and the base 4 are designed into independent modules due to different inclination angles and distances of each welding gun, each pair of graphite electrodes 2 is accurately installed on two sides of a molten pool corresponding to each welding gun by adjusting the distance, wherein the height h of each welding gun from a pipe blank is 20mm, and the forward inclination angle alpha of each welding gun I141 is 20mm115 °, rake angle α of welding gun ii 1422Back rake angle α of welding gun iii 143 being 5 °3Back rake angle α of welding gun iv 144 of 10 °415 °, distance s between welding gun ii 142 and welding gun i 1412Distance s between welding gun III 143 and welding gun I141 of 68mm3140mm, distance s between welding gun IV 144 and welding gun I1414210mm, the distance l between the electrode II 22 and the electrode I212＝s2+h(tanα2-tanα1) Approximately equal to 72mm, and the distance l between the electrode III 23 and the electrode I213＝s3-h(tanα1+tanα3) Approximately equal to 141mm, and the distance l between the electrode IV 24 and the electrode I214＝s2-h(tanα1+tanα4)≈199mm。
The pulse current treatment of the invention improves the recrystallization nucleation rate of the welding heat affected zone 105 and reduces the recrystallization growth rate to reduce the size of the fully recrystallized grains, the driving force of dislocation slip and climb is increased under the action of instant hot-pressing stress and electronic wind power during the pulse current treatment, and a large number of dislocation loops are formed after dislocations slip through solute or nano-scale carbide particle particles, which is beneficial to improving the dislocation density of the heat affected zone 105. The pulse current treatment can significantly improve the uniformity of the structure of the heat affected zone 105, thereby improving the service reliability of the welded pipe.
Specifically, after prewelding is finished, the welding pipe is rotated by 180 degrees, an inner groove faces upwards, then a pulse current application device is installed, in order to prevent the graphite electrode 2 from being damaged due to the fact that the graphite electrode 2 contacts a molten pool in the welding process, the graphite electrode 2 is 2mm away from the edge of the groove of the welding pipe 1 during installation, a pulse power supply is adjusted to be in a mode II, and a plug A 'of the graphite electrode 2'Ⅰ(A′Ⅱ、A′Ⅲ、A′Ⅳ) And B'Ⅰ(B′Ⅱ、B′Ⅲ、B′Ⅳ) The output terminals I and VIII of the pulse power supply are connected respectively, the frequency of the pulse current during the internal and external welding is lower than that during the preheating, and the hardening depth is inversely proportional to the frequency, so'>δ. Performing a first inner welding, wherein a pulse current flows out from a pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the prewelded seam 102 → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply, and the welding gun I141 forms a first inner welded seam 103 a; performing a second inner welding, wherein the pulse current flows out from the pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the first inner welding seam 103a → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply, and the welding gun II 142 forms a second inner welding seam 103 b; performing a third inner welding, wherein a pulse current flows out from the pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the second inner welding seam 103b → the heat affected zone 105 → the graphite electrodeThe pole 2 → the beam 6 flows back to the pulse power supply, and the welding gun III 143 forms a third inner welding seam 103 c; performing a fourth inner welding, wherein a pulse current flows out from the pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the third inner welding seam 103c → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply, and a fourth inner welding seam 103d is formed by the welding gun IV 144; when the temperature of the fourth inner weld seam 103d is close to that of the third inner weld seam 103c, the pulse current flows from the pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the fourth inner weld seam 103d → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply. In the pulse current treatment process, the weld heat affected zone 105 reaches a high-temperature austenitizing temperature instantly, and the extremely high superheat degree increases the nucleation rate of austenite. Because the action time of the pulse current is short, the nucleated fine austenite is not long enough to grow, and after the discharge is finished, because the heat exchange exists between the high-temperature heat-affected zone 105 and the low-temperature base material 101, the austenite structure is rapidly transformed at low temperature, so that the structure of the heat-affected zone 105 is fine and uniform. In addition, in the pulse current application process, the expansion of the high temperature heat affected zone 105 is restricted by the low temperature base material 101, and the hot pressing stress is formed in the heat affected zone 105. Under the conditions of high temperature and high pressure, coarse-grained carbides are decomposed and partially dissolved into the base material 101, the solid solubility of the base material 101 is increased, and supersaturated carbon is re-precipitated in the cooling process to form dispersed fine carbides.
More specifically, after the internal welding is finished, the welding pipe is rotated by 180 degrees, an outer slope is enabled to face upwards, then a pulse current application device is installed, in order to prevent the graphite electrode 2 from being damaged by contacting with a molten pool in the welding process, the graphite electrode 2 is 2mm away from the edge of a groove 1 of the welding pipe during installation, and a plug A of the graphite electrode 2Ⅰ(AⅡ、AⅢ、AⅣ) And BⅠ(BⅡ、BⅢ、BⅣ) And the output terminals are respectively connected with the output terminals II and III of the pulse power supply. Performing first external welding, wherein pulse current flows out from a pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the prewelded seam 102 → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply, and the welding gun I141 forms a first external welded seam 104 a; performing a second external welding with a pulse current flowing from a pulse power supplyLeading along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the first outer weld 104a → the heat affected zone 105 → the graphite electrode 2 → the beam 6 to flow back to the pulse power supply, and the welding torch II 142 forms the second outer weld 104 b; performing a third inner welding, wherein a pulse current flows out from the pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the second outer welding seam 104b → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply, and a welding gun III 143 forms a third outer welding seam 104 c; performing a fourth inner welding, wherein a pulse current flows out from the pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the third outer welding seam 104c → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply, and a fourth outer welding seam 104d is formed by a welding gun IV 144; when the temperature of the fourth inner weld seam 104d is close to that of the third inner weld seam 104c, the pulse current flows from the pulse power supply along the beam 6 → the graphite electrode 2 → the heat affected zone 105 → the third inner weld seam 103d → the heat affected zone 105 → the graphite electrode 2 → the beam 6 and flows back to the pulse power supply. The pulse current treatment refines the structure of the welding seam heat affected zone 105, the dislocation density of the heat affected zone 105 is increased, coarse crystallization of the heat affected zone 105 into finer nanometer carbide precipitation is facilitated, dislocation movement is effectively pinned when plastic slip deformation is carried out inside crystal grains, plastic deformation resistance of the welding seam heat affected zone 105 is increased, tensile strength is obviously increased, and elongation is reduced.
The invention also provides a process for assisting the LSAW tube welding process by using the pulse current, which comprises the following steps:
the method comprises the following steps of firstly, edge milling and groove preparation, wherein the groove is an asymmetric X-shaped groove, the outer groove is narrow and deep, the angle alpha of the groove is 30 degrees, the depth is 16mm, the edge width a is 17.19mm, the inner groove is wide and shallow, the angle beta of the groove is 45 degrees, the depth is 6mm, the edge width b is 13.29mm, and then the strip steel is formed into a cylindrical shape of a welded pipe 1 through roll forming;
preheating before welding, namely respectively installing a pulse current applying device on the upper slope opening and the lower slope opening of the welded pipe 1, adjusting a pulse power supply to a high-frequency gear, switching on a graphite electrode 2 and the pulse power supply, rapidly heating the slope opening of the welded pipe 1 to about 200 ℃ by using the heat effect of the high-frequency pulse current, preheating before welding, and reducing welding stress;
thirdly, prewelding, namely prewelding when the welded pipe 1 is jointed to prevent the welded pipe 1 from degrading or being scrapped due to the reason of misalignment, out-of-tolerance and the like, and prewelding to form a relatively thin prewelded joint 102;
step four, inner welding, namely turning the welded pipe 1 for 180 degrees, enabling the downward slope to be upward, adopting four-wire submerged arc welding for inner welding, installing graphite electrodes 2 on two sides of a welding gun, refining coarse-grained grains in a heat affected zone of a welding joint by applying pulse current, enabling microstructures to be uniformly distributed, finishing inner welding, forming an inner welding seam 103, and removing slag and burrs;
step five, external welding, namely turning the welded pipe 1 for 180 degrees again, enabling an upper groove to be upward, adopting four-wire submerged arc welding for external welding, installing graphite electrodes 2 on two sides of a welding gun, refining coarse-grained grains in a heat affected zone of a welding joint by applying pulse current, enabling microstructures to be uniformly distributed, finishing external welding, forming an external welding seam 104, and removing slag and burrs;
step six, finishing, chamfering flat ends, and testing performance indexes through a hydrostatic test and the like;
and seventhly, marking and warehousing.
The parameters of the pulse current are shown in the following table:
the principle and the implementation mode of the invention are explained by applying a specific example, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Alternative materials for the various components are listed in the description of the invention, but it will be understood by those skilled in the art that: the above list of component materials is not intended to be limiting and non exhaustive, and the various components may be replaced by other equivalent materials not mentioned in the present description, while still achieving the objects of the present invention. The specific embodiments mentioned in the description are to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In addition, the range of the amount of each component of the present invention includes any combination of any lower limit and any upper limit mentioned in the specification, and also includes any range where the specific content of the component in each specific example is made up as a combination of the upper limit or the lower limit: all such ranges are intended to be included within the scope of the present invention for brevity and clarity only and are not intended to be exhaustive or to limit the scope of the invention to the precise forms disclosed. Each feature of the invention described in this specification may be combined with any other feature of the invention which combination is not specifically disclosed in the specification for the sake of brevity.
Claims (4)
1. The utility model provides a supplementary LSAW pipe welding process's of pulse current device, includes nut, graphite electrode, base, roof beam, first support, second support, servo motor, gear, collar and installation arm, its characterized in that: the nut and the graphite electrode are coaxially arranged on the base, a spring is arranged between the graphite electrode and the base, and the end part of the graphite electrode, which is far away from the nut, is arranged into a 30-45-degree inclination angle shape; the nut, the graphite electrode and the base are provided with two groups which are respectively arranged on the beam through fastening bolts, the base is made into a sliding block, the distance can be adjusted in the beam, and the sliding block is fixed through the fastening bolts; the two beams are symmetrically arranged on two sides of the groove of the welded pipe, and the top of the graphite electrode is in close contact with the welded pipe; the two beams are connected to a retainer in a sliding manner, the retainer is made of insulating materials, and the retainer is perpendicular to the length direction of the welded pipe and moves back and forth along the length direction of the welded pipe; the beam is connected with the first bracket and the second bracket through a connecting column, and the angle of the connecting position of the connecting column and the first bracket and the second bracket is the same as the angle of the top of the graphite electrode; the first support and the second support are made of insulating materials and are symmetrically distributed on two sides of a welding seam of the welded pipe all the time; the end parts, far away from the beam, of the first support and the second support are provided with mounting rings through bolts, the mounting rings are vertically placed, and mounting arms are mounted on the mounting rings in the direction of coaxially far away from the beam; the tail parts of the first support and the second support, which are far away from the beam, are provided with gears which are meshed with each other, the gears are connected with a servo motor, and the servo motor is fixed on the mounting arm.
2. The apparatus of claim 1 for a pulse current assisted LSAW tube welding process, wherein: the distance from the graphite electrode to the nut is 15-20mm, and the nut is screwed to drive the graphite electrode to compress the spring.
3. The method of using the apparatus for pulse current assisted LSAW tube welding process of any of claims 1-2, wherein: the method comprises the following steps:
firstly, edge milling, groove preparation and welded pipe forming;
preheating before welding, namely respectively installing a pulse current applying device on an upper slope opening and a lower slope opening of the welded pipe, and heating the groove of the welded pipe by using the heat effect of pulse current to preheat before welding;
thirdly, prewelding, namely prewelding when the welded pipe joints to form a thinner prewelded joint in order to prevent the welded pipe from generating the misalignment and out-of-tolerance problems;
turning the welded pipe by 180 degrees, enabling an inner groove to face upwards, adopting four-wire submerged arc welding for inner welding, enabling graphite electrodes arranged on two sides of a welding gun to work, refining coarse-grained grains in a heat affected zone of a welding joint by applying pulse current, enabling the grain structure to be uniformly distributed, finishing inner welding, and removing slag and burrs;
step five, outer welding, namely turning the welded pipe 180 degrees again, enabling an outer slope to face upwards, adopting four-wire submerged arc welding for outer welding, enabling graphite electrodes arranged on two sides of a welding gun to work, refining coarse crystal grains in a heat affected zone of a welding joint by applying pulse current, enabling the crystal grain structure to be uniformly distributed, finishing outer welding, and removing slag and burrs;
step six, finishing, namely chamfering flat ends, and testing performance indexes through a hydrostatic test;
and seventhly, marking and warehousing.
4. The method of using the apparatus for a pulse current assisted LSAW tube welding process of claim 3, wherein: the welding gun I and the welding gun II of the four-wire submerged arc welding are set to be forward inclined, the welding gun III and the welding gun IV are sequentially transited to backward inclined, and the forward inclination angle of the welding gun I
Is 10 degrees to 20 degrees, and the front rake angle of a welding gun II
0 to 5 degrees, and a back inclination angle of a welding gun III
Is 5-10 degrees, and the back inclination angle of a welding gun IV
10-20 degrees, and the distance between adjacent welding gun nozzles is 60-80 mm.
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| CN109234501A (en) * | 2018-11-20 | 2019-01-18 | 燕山大学 | A kind of device and technique of the pulse current auxiliary online induction heating of rail |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102744505A (en) * | 2012-07-17 | 2012-10-24 | 上海中油天宝巴圣钢管有限公司 | Automatic five-wire submerged arc welding method for thick-wall welded pipes |
| CN104028883A (en) * | 2014-06-25 | 2014-09-10 | 燕山大学 | Device for pulse current assisted electric arc welding process |
| CN105880952A (en) * | 2016-06-03 | 2016-08-24 | 合肥紫金钢管股份有限公司 | Production process of longitudinal submerged arc welded pipe for oil and gas transmission |
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