CN114985878B - Welding method for large-caliber girth weld - Google Patents

Abstract

The invention discloses a welding method of a large-caliber girth weld, which adopts argon arc welding for bottoming and submerged arc welding for filling a cover surface. The welding method has the advantages that high weld linearity and full MIG welding effect are achieved by adopting common argon arc welding equipment and submerged arc welding equipment, dependency on the technical level of operators is reduced, the cost is low, the welding quality is stable, the working efficiency is high, and the operability is good. The method comprises the steps of groove processing and assembly, argon arc welding root bottoming, hot welding layer welding, submerged arc welding filling, submerged arc welding cover surface, ultrasonic flaw detection and welding joint performance inspection, and is characterized in that argon arc welding double synchronous welding bottoming is performed, cover surfaces are filled by other welding methods, and the straightness of welding seams is guaranteed in the welding process.

Description

Welding method for large-caliber girth weld

Technical Field

The invention belongs to the technical field of welding, and relates to a method for welding a large-caliber girth weld.

Background

The welding joint has high strength and compactness requirements during welding of the pressure container, strict welding quality requirements and high radiographic inspection requirements. In the prior art, the welding method with high requirement on the pipeline adopts argon arc welding to carry out single-sided welding double-sided forming of a root backing weld bead, and manual welding is adopted to carry out welding of a filling cover surface. The single-sided welding double-sided forming bottoming process with strict welding quality requirements is the first process of thick plate welding and is also the most difficult process. The difficulty is to prevent both incomplete penetration and burn-through. The argon tungsten-arc welding has the advantages that the electric arc can be stably burnt under the condition of small current, when the pulse TIG is adopted, the pulse current with larger amplitude can be used for ensuring penetration of welding, and the pilot arc current with smaller amplitude can be used for preventing penetration of welding, so that the welding is more convenient to control by virtue of heat input, the welding is more beneficial to single-sided welding double-sided forming, and the high-quality forming of the root welding bead of the node can be realized. Under the condition of manual welding, a welder can make various adjustments in time according to the size and the flowing condition of a molten pool so as to prevent burn-through. When MAG welding is used for steel structural members with high requirements on low-temperature toughness, the welding workers with single-sided welding and double-sided forming technologies can be mastered in a flexible manner, and the main problem is that burn-through is easy to occur. Experiments show that when MAG is directly adopted for backing welding, welding current and root gap are key factors influencing backing forming, corresponding assembly requirements are extremely harsh, particularly allowable fluctuation of the gap is small, and even trace gap fluctuation caused by factors such as material deformation is likely to cause burn-through or incomplete welding.

When welding large-diameter pipelines, if one person can not finish the operation by adopting the inner filling wire, the operation can be finished by two persons, and the requirements on the cooperation mercy degree and the operation proficiency degree of the two persons are high, so that the welding is generally performed by adopting the outer filling wire. When the external filler wire is adopted, the groove gap must be larger than the diameter of the welding wire, so that the welding wire is guaranteed to be sent to the back of the near-seam, the residual height of the back of the welding seam is guaranteed to be flush with or slightly higher than the base metal, but the concave parts with different depths always appear, and the welding quality cannot be guaranteed. While there are some efficiently automated welding robot devices, construction cost investment and return on profit are not directly proportional to the general industry, and the use of such devices is limited in places where construction sites are complex.

Chinese patent CN106825874B provides a submerged arc welding single-sided welding double-sided molding process, in which an inner liner and an air bag support member are laid on the back surface of a pipe, and the requirement on the bonding tightness of the back surface is high, so that the collapse or arc leakage of a molten pool is easy to occur.

Chinese patent CN108856989B provides a priming method for MIG welding of consumable electrodes in pipe welding, which requires a high level of operation for the welder and cannot guarantee the quality of the priming layer when there is a misalignment of the pipe.

Disclosure of Invention

The patent aims at providing a welding method of a large-caliber girth weld, wherein argon arc welding is adopted for bottoming, and submerged arc welding is adopted for filling a cover surface. The welding method has the advantages that high weld linearity and full MIG welding effect are achieved by adopting common argon arc welding equipment and submerged arc welding equipment, dependency on the technical level of operators is reduced, the cost is low, the welding quality is stable, the working efficiency is high, and the operability is good.

The technical scheme of the invention is as follows:

the welding method of the large-caliber girth weld comprises the following steps of argon arc welding root bottoming, hot welding layer welding, submerged arc welding filling, submerged arc welding cover surface, ultrasonic flaw detection and welding joint performance inspection, wherein the key process steps comprise:

(1) And (3) blanking: carrying out workpiece blanking according to drawing requirements;

(2) Machining: the groove is processed into a V-shaped groove with the angle of 32-40 degrees;

(3) And (3) assembling: polishing and assembling the workpiece subjected to blanking according to the drawing requirement to form a workpiece to be welded, wherein the groove gap is 2-3 mm, polishing and cleaning the groove area of the welding seam before welding, removing rust and grease on the surface of the groove and nearby, polishing the groove area to be 20-30 mm away from the edge of the welding seam groove, and scrubbing by adopting acetone or alcohol after polishing and brightening; spot welding is carried out before welding, the spot welding length is 40-70 mm, and the interval is 400-550 mm;

(4) Priming by argon arc welding: sectional welding, namely firstly welding 3 points to 12 points, then welding 9 points to 6 points, then welding 12 points to 9 points, and finally welding 6 points to 3 points; the welding parameters are as follows: 2-3 mm in tungsten electrode diameter, 2-3 mm in welding wire diameter, 10-12mm in nozzle caliber inner wall, 10-12mm in nozzle caliber outer wall, 9-12L/min in argon flow, 60-70A in welding current inner wall, 70-80A in welding current outer wall and 18-19V in welding voltage; welding the outer welding path by a welding gun at one side of the outer wall, forming an angle of 80-85 degrees with the outer wall, welding the inner welding path by a welding gun at one side of the inner wall, forming a right angle with the inner wall, and simultaneously running the two electric arcs aiming at the same position of the root and adding welding wires;

(5) Welding a hot welding bead: the submerged arc welding machine uses an alternating current welding mode, and the current is regulated to be 360-380A;

(6) Filling: the submerged arc welding machine adopts an alternating current or direct current reverse connection mode, and the current is regulated to 450-650A; the angle of the inclined conductive nozzle is 5-20 degrees when the straight edge is welded, and the distance between the end part of the welding wire and the straight edge is 2-6 mm;

(7) Submerged arc welding cover surface: the submerged arc welding machine adopts an alternating current or direct current reverse connection mode, and the current is regulated to 450-620A;

(8) Ultrasonic flaw detection: scanning a welding joint, determining the grade of a flaw detection test piece, and marking the position of a welding defect;

(9) And (3) performance test: and detecting physical properties of the welded joint.

The invention has the beneficial effects that: 1) The priming welding method has excellent adaptability, the common argon arc welder can meet the requirement of welding performance, and the requirement on welder level is not high; 2) The priming welding method has the advantages that the welding line is attractive in appearance, good in compactness, full, smooth and attractive in welding joint position transition, and low in requirements on the level of welding workers, and the defects of pits, collapse and the like do not occur at the root position; 3) The straight edge straightness after the welding is finished is kept good, the position of the welding line is completely positioned at the joint of the coarse grain region of the heat affected zone of the welding joint and the weld metal, the performance of different regions of the heat affected zone of the welding joint, particularly the performance of the welding line, is favorable to be mastered, and the welding line is also the position where the welding is most prone to occurrence of problems. Because the straight edge only maintains linearity after welding, the performance change condition of the test piece after the welding thermal cycle can be reflected in the subsequent sampling test process, and the material performance can be mastered conveniently.

Drawings

FIG. 1 is a photograph of the nozzle position of argon arc welding.

Fig. 2 is a schematic view of a butt joint.

Fig. 3 is a photograph of a cross-sectional macro-topography.

FIG. 4 is a photograph of metallographic structure of the sample.

FIG. 5 is a Charpy V-notch test piece position for a butt weld.

FIG. 6 is a schematic diagram of a butt weld hardness measurement.

Detailed Description

The present invention will be further described with reference to examples.

Examples: welding method for large-caliber girth weld

The steel comprises the following chemical components in percentage by mass: c=0.09, si=0.32, mn=1.25, p=0.009, s=0.0014, ti=0.013, cr=0.478, mo=0.439, ni=0.44, the balance Fe and unavoidable impurities, comprising the following process steps:

(1) And (3) blanking: performing test piece blanking on the phi 720 x delta 80mm pipe according to the drawing size requirement;

(2) Machining: the groove is processed into a 35-degree V-shaped groove, so that proper dry extension can be ensured to penetrate into the root without touching the inner wall of the groove, and a smaller groove angle can be obtained to reduce the filling quantity of welding materials;

(3) And (3) assembling: polishing and assembling the workpiece subjected to blanking according to the drawing requirement to form a workpiece to be welded, wherein the gap of a groove is 2-3 mm, removing dirt such as water, oil, rust and the like at the position of the groove, and polishing out a region to be welded by using an angle grinder within 50mm until metallic luster is exposed; carrying out spot welding fixation before welding, and keeping the spot welding position to be subjected to pre-welding preheating treatment in advance, wherein the spot welding length is 60-70 mm and the interval is 500-550 mm, and the preheating temperature is kept consistent with the preheating temperature during welding;

(4) Preheating: because the diameter of the pipe is larger, the thickness of the pipe wall is thicker, and the carbon equivalent and the Pcm value are higher, in order to prevent cracks and deformation of the test piece in the welding process, a ceramic heating plate is required to preheat the test piece to 130 degrees;

(5) Priming by argon arc welding: sectional welding, namely firstly welding 3 points to 12 points, then welding 9 points to 6 points, then welding 12 points to 9 points, and finally welding 6 points to 3 points; the welding gun on one side of the outer wall is used for outer welding channel welding and forms an angle of 80-85 degrees with the outer wall, the welding gun on one side of the inner wall is used for inner welding channel welding and forms a right angle with the inner wall, and the two electric arcs are aligned to the same position of the root part and simultaneously run and welding wires are added. Welding parameters: welding parameters: the diameter of the tungsten electrode is 2.5mm, the diameter of the welding wire is 2.5, the caliber inner wall of the nozzle is 11mm, the caliber outer wall of the nozzle is 11mm, the argon flow is 11L/min, the welding current inner wall 60A, the welding current outer wall 70A and the welding voltage is 18-19V;

(6) Welding a hot welding bead: the submerged arc welding machine uses an alternating current welding mode, the current is adjusted to 360-380A, the voltage is 25-26V, and the welding speed is 50-52 cm/min;

(7) Filling: after the welding of the hot welding layers is finished, the submerged arc welding machine adopts an alternating current or direct current reverse connection mode, the current is adjusted to 480-650A according to the welding process requirements, the specific welding process parameters are shown in table 1, the angle between the conducting nozzle and the straight edge is 5-15 degrees when the welding bead on the straight edge side is welded in the welding process, and the distance between the end part of the welding wire and the straight edge is 3-5 mm;

(8) Submerged arc welding cover surface: after filling, selecting an alternating current or direct current reverse connection mode for the submerged arc welding machine, and adjusting the current to 450-620A;

(9) Ultrasonic flaw detection: scanning a welding joint area, marking the position of a welding defect, and meeting the requirements of GB/T11345 on I-level qualification of a flaw detection test piece;

physical property detection results are carried out on the welded joint:

(1) butt joint tensile test: samples were sampled laterally, 2 full thickness tensile samples, and tensile test results are shown in Table 2, respectively;

(2) butt joint bending test: the side bending test adopted in the test has a bending diameter D=40mm and a bending angle of 180 DEG, the test is carried out at room temperature, and the test result is shown in Table 3;

(3) the results of the impact test of the butt joint are shown in tables 4 and 5, respectively;

(4) welded joint hardness (HV 10) test: the positions of the hardness test points of the butt joint are shown in fig. 5 and 6, and the test results are shown in tables 6 and 7.

TABLE 1 submerged arc welding process parameters

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TABLE 2 Butt joint tensile test results

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TABLE 3 results of Butt joint lateral bending test

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Table 4 results of joint impact test

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Table 5 results of joint impact test

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Table 6X 65Q-11 Butt joint hardness test (HV 10) results (heat input 15KJ/cm, as-welded)

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Table 7X 65Q-12 results of Butt joint hardness test (HV 10) (heat input 35KJ/cm, as welded)

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Analysis of results: the standard API 5L standard is implemented, the yield strength is required to be 450-600, the tensile strength is 535-760, the full-size impact is only more than or equal to 27 at the temperature of 0 ℃, the performance of the welding joint is excellent and consistent with that of a test tube, and the hardness value of the welding joint is within 325 (HV 10).

Claims (1)

1. The welding method of the large-caliber girth weld comprises the following technical processes of groove processing and assembly, argon arc welding root bottoming, hot welding layer welding, submerged arc welding filling, submerged arc welding cover surface, ultrasonic flaw detection and welding joint performance inspection, and is characterized by comprising the following key technical steps:

(1) And (3) blanking: carrying out workpiece blanking according to drawing requirements;

(2) Machining: the groove is processed into a V-shaped groove with the angle of 32-40 degrees;

(3) And (3) assembling: polishing and assembling the workpiece subjected to blanking according to the drawing requirement to form a workpiece to be welded, wherein the groove gap is 2-3 mm, polishing and cleaning the groove area of the welding seam before welding, removing rust and grease on the surface of the groove and nearby, polishing the groove area to be 20-30 mm away from the edge of the welding seam groove, and scrubbing by adopting acetone or alcohol after polishing and brightening; spot welding is carried out before welding, the spot welding length is 40-70 mm, and the interval is 400-550 mm;

(4) Priming by argon arc welding: sectional welding, namely firstly welding 3 points to 12 points, then welding 9 points to 6 points, then welding 12 points to 9 points, and finally welding 6 points to 3 points; welding the outer welding path by a welding gun at one side of the outer wall, forming an angle of 80-85 degrees with the outer wall, welding the inner welding path by a welding gun at one side of the inner wall, forming a right angle with the inner wall, and simultaneously running the two electric arcs aiming at the same position of the root and adding welding wires; 2-3 mm in tungsten electrode diameter, 2-3 mm in welding wire diameter, 10-12mm in nozzle caliber inner wall, 10-12mm in nozzle caliber outer wall, 9-12L/min in argon flow, 60-70A in welding current inner wall, 70-80A in welding current outer wall and 18-19V in welding voltage;

(5) Welding a hot welding bead: the submerged arc welding machine uses an alternating current welding mode, and the current is regulated to be 360-380A;

(6) Filling: the submerged arc welding machine adopts an alternating current or direct current reverse connection mode, and the current is regulated to 450-650A; the angle of the inclined conductive nozzle is 5-20 degrees when the straight edge is welded, and the distance between the end part of the welding wire and the straight edge is 2-6 mm;

(7) Submerged arc welding cover surface: the submerged arc welding machine adopts an alternating current or direct current reverse connection mode, and the current is regulated to 450-620A;

(8) Ultrasonic flaw detection: scanning a welding joint, determining the grade of a flaw detection test piece, and marking the position of a welding defect;

(9) And (3) performance test: and detecting physical properties of the welded joint.