阅读说明：本技术 一种用于电站锅炉上厚壁的联箱及管道的环缝焊接工艺 (Girth welding process for header and pipeline with thick wall on power station boiler ) 是由 刘波 崔玉伟 苏美荣 彭莹莹 张佳宦 邢磊 赵洪玉 刘延龙 王春龙 李红 赵红 于 2021-08-09 设计创作，主要内容包括：一种用于电站锅炉上厚壁的联箱及管道的环缝焊接工艺,涉及一种环缝焊接工艺。本发明是为了解决现有的埋弧焊对于直径Φ219mm、壁厚20～55mm的电站锅炉联箱及管道进行焊接容易产生击穿的问题,无法通过埋弧自动焊的方法精准、快速的完成环缝焊接的问题。本发明通过焊接坡口加工、焊接坡口表面清理、工件坡口对接、焊前预热、氩弧焊封底、手工电弧焊填充增厚、埋弧焊和焊后后热或消氢处理这八个工序解决了传统电站锅炉联箱及管道Φ219×20～55mm这一规格环缝焊接过程中存在的一系列问题,提高了焊接质量及焊接效率。本发明主要用于焊接电站锅炉上厚壁的联箱及管道。(A girth welding process for a header and a pipeline with thick walls on a power station boiler relates to a girth welding process. The submerged arc welding method aims to solve the problems that the existing submerged arc welding is easy to generate breakdown when a power station boiler header and a pipeline with the diameter phi of 219mm and the wall thickness of 20-55 mm are welded, and the circular seam welding cannot be accurately and quickly completed by a submerged arc automatic welding method. According to the invention, a series of problems existing in the conventional girth welding process of the boiler header and the pipe phi 219 x 20-55 mm of the power station are solved through eight procedures of welding groove processing, welding groove surface cleaning, workpiece groove butt joint, preheating before welding, argon arc welding bottom sealing, manual arc welding filling thickening, submerged arc welding and post-welding heat or hydrogen elimination treatment, and the welding quality and the welding efficiency are improved. The invention is mainly used for welding the thick-wall header and the pipeline on the power station boiler.)

1. The utility model provides a circumferential weld welding process that is used for header and pipeline of power plant boiler upper thick wall which characterized in that: the process flow is as follows:

s1, welding groove treatment: carrying out UV groove machining on the opposite end faces of the two workpieces to be welded;

the welding groove comprises a V-shaped groove (1), a U-shaped groove (2) and a truncated edge (3), wherein the V-shaped groove (1) is positioned right above the U-shaped groove (2), the U-shaped groove (2) is positioned right above the truncated edge (3), the bottom of the V-shaped groove (1) is connected with the groove of the U-shaped groove (2), the bottom of the U-shaped groove (2) is connected with the upper end opening of the truncated edge (3), and the V-shaped groove (1) and the U-shaped groove (2) form a UV groove;

s2, cleaning the surface of the welding groove: removing residual dirt on the surface of the welding groove and in areas extending 20mm to two sides of the welding groove by using a grinder and a steel wire brush, and drying oil stain and water on the surface of the welding groove by using a flame heating mode to ensure the cleanliness of the surface of the welding groove;

s3, butt joint of workpiece grooves: aligning the two workpieces, ensuring that vertical surfaces at the truncated edges between the two workpieces are parallel, and controlling the gap between the vertical surfaces of the two workpieces to be 2-3 mm;

s4, preheating before welding: preheating and preserving heat in areas extending 100-150 mm from two sides of a welding groove of a welding workpiece by using a flame or a crawler heater until the workpiece is welded, and controlling the temperature between layers within 300 ℃ during welding;

s5, GTAW back cover: carrying out back cover welding on the truncated edge of the workpiece;

s6, SMAW lane filling: filling the UV groove bottom after bottom sealing by channels for 2 channels, wherein the specification of the welding rod adopts a welding rod with phi 3.2 or phi 4.0;

s7, SAW welding: by using SAW welding equipment and tire rotating equipment, the specification of a welding wire is phi 3.2; the workpiece welding is finished through an arc starting process, an intermediate welding operation process and a cover process, and the interlayer temperature is controlled within 300 ℃ during welding;

s8, post-welding heat or hydrogen elimination: for the material with delayed crack tendency after welding, after the welding process is interrupted and the welding is finished, the workpiece is immediately subjected to post-heating or dehydrogenation treatment and heat preservation according to requirements, and then is naturally cooled after heat preservation.

2. The girth welding process for thick-walled headers and pipes on utility boilers as claimed in claim 1, wherein: in S1, the slope of the processed V-shaped slope is 10 degrees, the radius of the arc-shaped slope at the U-shaped slope is 5mm, and the height of the vertical surface of the truncated edge is 2-2.5 mm.

3. The girth welding process for thick-walled headers and pipes on utility boilers as claimed in claim 2, wherein: and in the step S4, the preheating temperature is 100-250 ℃, and the heat is preserved until the temperature of the workpiece is 100-250 ℃ before the welding of the workpiece is finished.

4. The girth welding process for thick-walled headers and pipes on utility boilers as claimed in claim 3, wherein: in S5, the thickness of the back cover is not less than 3mm and the welding quality of the back is guaranteed, the current of the phi 2.4 argon arc welding wire is controlled to be 120-150A, the voltage is controlled to be 24-25V, and the welding speed is 8-11 mm/S.

5. The girth welding process for thick-walled headers and pipes on utility boilers as claimed in claim 4, wherein: in the step S6, the filling thickness is not less than 4 mm.

6. The girth welding process for thick-walled headers and pipes on utility boilers as claimed in claim 5, wherein: in S6, when the specification of the welding rod is phi 3.2, the current is 110-120A, the voltage is 20-24V, and the welding speed is 13-18 mm/S; when the specification of the welding rod selects a welding rod with phi 4.0, the current is 155-165A, the voltage is 22-26V, and the welding speed is 15-20 mm/s.

7. The girth welding process for thick-walled headers and pipes on utility boilers as claimed in claim 6, wherein: in S7, the SAW welding process is as follows:

s7.1, an arc striking process: carrying out two SAW channel filling on the bottom of the filled UV groove, controlling the current at 280-290A, controlling the voltage at 28-32V, and controlling the welding speed at 11-15 mm/s;

s7.2, intermediate welding operation: filling the middle part of the UV groove layer by layer in a way until the filling reaches 2 times before the facing process; wherein for the welding of the 1 st to 2 nd tracks, the current is controlled to be 280-300A, the voltage is controlled to be 28-32V, the welding speed is 11-13 mm/s, for the welding of the 3 rd to 4 th tracks, the current is controlled to be 300-350A, the voltage is controlled to be 32-34V, the welding speed is 10-13 mm/s, for the welding of the 5 th to 8 th tracks, the current is controlled to be 350-380A, the voltage is controlled to be 32-35V, the welding speed is 11-15 mm/s, for the welding of the 9 th to 18 th tracks, the current is controlled to be 380-450A, the voltage is controlled to be 32-35V, and the welding speed is 12-15 mm/s; for subsequent welding, the current is controlled to be 400-450A, the voltage is controlled to be 32-36V, and the welding speed is 12-15 mm/s;

s7.3, a facing process: and filling the last 2 channels of the UV groove, controlling the current to be 450-480A, controlling the voltage to be 34-36V, and controlling the welding speed to be 12-15 mm/s.

8. The girth welding process for thick-walled headers and pipes on utility boilers of claim 7, wherein: in S8, the postweld heat temperature range of the workpiece is 200-250 ℃, and the postweld heat preservation time of the workpiece is 1-2 hours.

9. The girth welding process for thick-walled headers and pipes on utility boilers of claim 7, wherein: in S8, the hydrogen elimination temperature range of the workpiece is 300-400 ℃, and the hydrogen elimination time is 2-3 h.

Technical Field

The invention relates to a girth welding process, in particular to a girth welding process for a thick-wall header and a pipeline on a power station boiler.

Background

The header and the pipeline (hereinafter, collectively referred to as a workpiece) on the utility boiler are important components of the utility boiler, and the girth welding quality of the header and the pipeline on the utility boiler directly influences the quality of the boiler and the safe and stable operation of the boiler. Examples of the girth welding method include Shielded Metal Arc Welding (SMAW), Submerged Arc Welding (SAW), Gas Tungsten Arc Welding (GTAW), and the like, and submerged arc welding is a welding method commonly used for girth welding.

Submerged Arc Welding (SAW) is a method for welding by burning electric arcs under a flux layer, has the excellent characteristics of good welding consistency, high accuracy, high production efficiency, stable welding quality, no arc light radiation and the like, and is widely applied to the girth welding process of pipelines. However, in the actual operation process of the submerged arc welding, it is difficult to weld all headers and pipes of various specifications, and in the face of the possibility that base metal of a smaller specification is easy to break down during welding, especially for the power station boiler header and pipe with a common welding wire diameter of 3.2mm, a base metal specification of 219mm and a wall thickness of 20-55 mm, it is impossible to accurately and quickly complete the girth welding of the power station boiler header and pipe by the submerged arc automatic welding method, which becomes a difficult problem that technicians in the welding field need to overcome urgently, and restricts the continuous development of the welding technology, so that it is very critical and important to develop a girth welding process of the power station boiler header and pipe in order to break through the existing technical barriers.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: the existing submerged arc welding is easy to generate breakdown when a header and a pipeline of a power station boiler with the diameter of 219mm and the wall thickness of 20-55 mm are welded, and the circular seam welding cannot be accurately and quickly completed by a submerged arc automatic welding method; further provides a girth welding process for the thick-wall header and the pipeline on the utility boiler.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the girth welding process for the header and the pipeline with the thick wall on the power station boiler comprises the following specific process flows:

s1, welding groove treatment: carrying out UV groove machining on the opposite end faces of the two workpieces to be welded;

the welding groove comprises a V-shaped groove 1, a U-shaped groove 2 and a truncated edge 3, wherein the V-shaped groove 1 is positioned right above the U-shaped groove 2, the U-shaped groove 2 is positioned right above the truncated edge 3, the slope bottom of the V-shaped groove 1 is connected with the groove of the U-shaped groove 2, the slope bottom of the U-shaped groove 2 is connected with the upper port of the truncated edge 3, and the V-shaped groove 1 and the U-shaped groove 2 form a UV groove;

s2, cleaning the surface of the welding groove: removing residual dirt on the surface of the welding groove and in areas extending 20mm to two sides of the welding groove by using a grinder and a steel wire brush, and drying oil stain and water on the surface of the welding groove by using a flame heating mode to ensure the cleanliness of the surface of the welding groove;

s3, butt joint of workpiece grooves: aligning the two workpieces, ensuring that vertical surfaces at the truncated edges between the two workpieces are parallel, and controlling the gap between the vertical surfaces of the two workpieces to be 2-3 mm;

s4, preheating before welding: preheating and preserving heat in areas extending 100-150 mm from two sides of a welding groove of a welding workpiece by using a flame or a crawler heater until the workpiece is welded, and controlling the temperature between layers within 300 ℃ during welding;

s5, GTAW back cover: carrying out back cover welding on the truncated edge of the workpiece;

s6, SMAW lane filling: filling the UV groove bottom after bottom sealing by channels for 2 channels, wherein the specification of the welding rod adopts a welding rod with phi 3.2 or phi 4.0;

s7, SAW welding: by using SAW welding equipment and tire rotating equipment, the specification of a welding wire is phi 3.2; the workpiece welding is finished through an arc starting process, an intermediate welding operation process and a cover process, and the interlayer temperature is controlled within 300 ℃ during welding;

s8, post-welding heat or hydrogen elimination: for the material with delayed crack tendency after welding, after the welding process is interrupted and the welding is finished, the workpiece is immediately subjected to post-heating or dehydrogenation treatment and heat preservation according to requirements, and then is naturally cooled after heat preservation.

Further, in S1, the slope of the processed V-shaped slope is 10 degrees, the radius of the arc-shaped slope at the U-shaped slope is 5mm, and the height of the vertical surface of the blunt edge is 2-2.5 mm.

Further, in S4, the preheating temperature is 100-250 ℃ and the temperature is kept until the temperature of the workpiece is not lower than 100-250 ℃ before the welding of the workpiece is finished.

Further, in S5, the thickness of the back cover is not less than 3mm and the welding quality of the back surface is guaranteed, the current of the phi 2.4 argon arc welding wire is controlled to be 120-150A, the voltage is controlled to be 24-25V, and the welding speed is 8-11 mm/S.

Further, in the step S6, the filling thickness is not less than 4 mm.

Further, in S6, when a welding rod with a diameter of phi 3.2 is selected as the welding rod specification, the current is 110-120A, the voltage is 20-24V, and the welding speed is 13-18 mm/S; when the specification of the welding rod selects a welding rod with phi 4.0, the current is 155-165A, the voltage is 22-26V, and the welding speed is 15-20 mm/s.

Further, in S7, the SAW welding process is as follows:

s7.1, an arc striking process: carrying out two SAW channel filling on the bottom of the filled UV groove, controlling the current at 280-290A, controlling the voltage at 28-32V, and controlling the welding speed at 11-15 mm/s;

s7.2, intermediate welding operation: filling the middle part of the UV groove layer by layer in a way until the filling reaches 2 times before the facing process; wherein for the welding of the 1 st to 2 nd tracks, the current is controlled to be 280-300A, the voltage is controlled to be 28-32V, the welding speed is 11-13 mm/s, for the welding of the 3 rd to 4 th tracks, the current is controlled to be 300-350A, the voltage is controlled to be 32-34V, the welding speed is 10-13 mm/s, for the welding of the 5 th to 8 th tracks, the current is controlled to be 350-380A, the voltage is controlled to be 32-35V, the welding speed is 11-15 mm/s, for the welding of the 9 th to 18 th tracks, the current is controlled to be 380-450A, the voltage is controlled to be 32-35V, and the welding speed is 12-15 mm/s; for subsequent welding, the current is controlled to be 400-450A, the voltage is controlled to be 32-36V, and the welding speed is 12-15 mm/s;

s7.3, a facing process: and filling the last 2 channels of the UV groove, controlling the current to be 450-480A, controlling the voltage to be 34-36V, and controlling the welding speed to be 12-15 mm/s.

Further, in the step S8, when the workpiece needs to be subjected to post-heat treatment, the post-welding heat temperature range of the workpiece is 200-250 ℃, and the post-heat preservation time of the workpiece is 1-2 hours.

Further, in the step S8, when the workpiece needs to be subjected to dehydrogenation treatment, the dehydrogenation temperature of the workpiece ranges from 300 ℃ to 400 ℃, and the dehydrogenation time is 2-3 hours.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, through argon arc welding back cover, manual electric arc welding filling thickening and final filling cover surface of submerged arc welding, a series of problems in the circular seam welding process of the specification phi 219 x 20-55 mm of the traditional header and power station boiler pipeline are solved, and the welding quality and the welding efficiency are improved.

2. According to the invention, after argon arc welding back cover, manual electric arc welding filling is used to increase the thickness of the groove bottom, so that the problem of breakdown in the subsequent submerged arc welding process caused by over-thin argon arc welding back cover is avoided.

3. The invention adopts submerged arc welding to carry out layer-by-layer welding, has higher automation degree, lightens the labor intensity of welding operators, avoids the internal defect caused by excessive welding joints of manual electric arc welding, effectively improves the welding quality, improves the production efficiency, has no arc light radiation, greatly reduces the harm to the bodies of the operators and ensures the safety of operation.

4. The reasonable interlayer temperature control is carried out in the submerged arc welding operation process, so that the internal stress of the welding material can be effectively reduced, the generation of defects such as cracks in the welding process is avoided, and the service performance of the material can be effectively ensured.

5. According to the invention, the post-heat or dehydrogenation treatment is carried out on the material with the tendency of delaying cracks after welding, so that the hydrogen existing in the welding seam is eliminated, and the risk of cracks generated in the welding seam is effectively solved.

Drawings

FIG. 1 is a flow chart of header and pipe girth welding process for a utility boiler;

fig. 2 is a schematic view of a UV groove:

FIG. 3 is a schematic view of a bottom seal of argon arc welding;

FIG. 4 is a schematic view of a manual arc welding fill;

FIG. 5 is a schematic view of a submerged arc welding.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The girth welding process for the header and the pipeline with the thick wall on the power station boiler comprises the following specific process flows:

s1, welding groove treatment: the method is characterized in that UV beveling is carried out on the opposite end faces of two workpieces to be welded, the slope of the processed V-shaped slope is 10 degrees, the radius of the arc-shaped slope at the U-shaped slope is 5mm, and the height of the vertical surface of the truncated edge is 2-2.5 mm, so that a welding gun and a machine head can normally operate conveniently, and the welding seam of a weldment can be uniformly and completely welded and fused in the subsequent process;

as shown in fig. 2, the welding groove comprises a V-shaped groove 1, a U-shaped groove 2 and a truncated edge 3, the V-shaped groove 1 is positioned right above the U-shaped groove 2, the U-shaped groove 2 is positioned right above the truncated edge 3, the bottom of the V-shaped groove 1 is connected with the groove of the U-shaped groove 2, the bottom of the U-shaped groove 2 is connected with the upper port of the truncated edge 3, and the V-shaped groove 1 and the U-shaped groove 2 form a UV groove;

s2, cleaning the surface of the welding groove: removing residual dirt such as rust and the like on the surface of the welding groove and in an area extending 20mm to two sides of the welding groove by using a grinding wheel machine and a steel wire brush, and drying oil stain and water on the surface of the welding groove by using a flame heating mode to ensure the cleanness of the surface of the welding groove;

s3, butt joint of workpiece grooves: aligning the two workpieces, ensuring that vertical surfaces at the truncated edges between the two workpieces are parallel, and controlling the gap between the vertical surfaces of the two workpieces to be 2-3 mm;

s4, preheating before welding: preheating areas extending by 100-150 mm at two sides of a welding groove of a welding workpiece by using a flame or a crawler heater, wherein the preheating temperature is 100-250 ℃, and preserving heat until the temperature of the workpiece is kept between 100-250 ℃ before the welding of the workpiece is finished, and the interlayer temperature is controlled within 300 ℃;

s5, GTAW back cover: as shown in fig. 3, back cover welding is carried out on the truncated edge of the workpiece, the thickness of the back cover is not less than 3mm, the welding quality of the back face is guaranteed, the current of a phi 2.4 argon arc welding wire is controlled to be 120-150A, the voltage is controlled to be 24-25V, and the welding speed is 8-11 mm/s;

s6, SMAW lane filling: filling (welding) the UV groove bottom after bottom sealing in a way of dividing to increase the slope bottom thickness of the welding groove, filling 2 ways (as shown in figure 4), wherein the filling thickness is not less than 4mm, and the problem of breakdown in the subsequent SAW welding process is avoided, and the specification of the welding rod adopts a welding rod of phi 3.2 or phi 4.0; when the specification of the welding rod selects a welding rod with the diameter of phi 3.2, the current is 110-120A, the voltage is 20-24V, and the welding speed is 13-18 mm/s; when the specification of the welding rod selects a welding rod with the diameter of 4.0, the current is 155-165A, the voltage is 22-26V, and the welding speed is 15-20 mm/s;

s7, SAW welding: by utilizing SAW welding equipment and tire rotating equipment, welding wires with the specification of phi 3.0 or phi 3.2 are selected, workpiece welding is completed through an arc starting process, an intermediate welding operation process and a cover process, and the interlayer temperature is controlled within 300 ℃ during welding, so that the internal stress of a welding material can be effectively reduced, the generation of defects such as cracks in the welding process is avoided, and the use performance of the material can be effectively ensured;

s7.1, an arc striking process: carrying out two SAW channel filling on the bottom of the filled UV groove, controlling the current at 280-290A, controlling the voltage at 28-32V, and controlling the welding speed at 11-15 mm/s;

s7.2, intermediate welding operation: filling the middle part of the UV groove layer by layer in a way until the filling reaches 2 times before the facing process; wherein for the welding of the 1 st to 2 nd tracks, the current is controlled to be 280-300A, the voltage is controlled to be 28-32V, the welding speed is 11-13 mm/s, for the welding of the 3 rd to 4 th tracks, the current is controlled to be 300-350A, the voltage is controlled to be 32-34V, the welding speed is 10-13 mm/s, for the welding of the 5 th to 8 th tracks, the current is controlled to be 350-380A, the voltage is controlled to be 32-35V, the welding speed is 11-15 mm/s, for the welding of the 9 th to 18 th tracks, the current is controlled to be 380-450A, the voltage is controlled to be 32-35V, and the welding speed is 12-15 mm/s; for subsequent welding, the current is controlled to be 400-450A, the voltage is controlled to be 32-36V, and the welding speed is 12-15 mm/s;

s7.3, a facing process: filling the last 2 channels of the UV groove, controlling the current to be 450-480A, controlling the voltage to be 34-36V, and controlling the welding speed to be 12-15 mm/s;

s8, post-welding heat or hydrogen elimination: for the material with delayed crack tendency after welding, performing post-heating or dehydrogenation treatment on the workpiece according to requirements, wherein when the workpiece needs post-heating treatment, the post-heating temperature range of the workpiece is 200-250 ℃, and the post-heating heat preservation time of the workpiece is 1-2 hours;

when the workpiece needs to be subjected to dehydrogenation treatment, the dehydrogenation temperature range is 300-400 ℃, and the dehydrogenation time is 2-3 h; and then naturally cooling, eliminating hydrogen of the welding line, avoiding the generation of defects such as cracks and the like, finally completing the welding of the header and the pipeline circumferential weld, and improving the welding quality and the welding efficiency.

According to the invention, after argon arc welding bottom sealing, manual electric arc welding filling is used to increase the thickness of the groove bottom, so that the problem of breakdown in the subsequent submerged arc welding process caused by over-thin argon arc welding bottom sealing in the traditional header and power station boiler pipeline phi 219 x 20-55 mm girth welding process is avoided; the submerged arc welding is adopted for welding layer by layer, the automation degree is higher, the labor intensity of welding operators is reduced, the internal defect caused by excessive welding joints of manual electric arc welding is avoided, the welding quality is effectively improved, the production efficiency is improved, in addition, the arc light radiation is avoided, the harm to the bodies of the operators is greatly reduced, and the operation safety is ensured.

Example 1: the girth welding process of the invention is explained in detail below by taking a pipe with a base material of 12Cr1MoVG, a specification of 219mm diameter and a pipe wall thickness of 45mm as an example, and the process flow is specifically as follows:

s1, welding groove treatment: carrying out UV groove processing on the opposite end surfaces of two pipelines to be welded, wherein the slope of the processed V-shaped slope is 10 degrees, the radius of the arc-shaped slope at the U-shaped slope is 5mm, and the height of the vertical surface of the truncated edge is 2.5 mm;

s2, cleaning the surface of the welding groove: removing residual dirt such as rust and the like on the surface of the welding groove and in an area extending 20mm to two sides of the welding groove by using a grinding wheel machine and a steel wire brush, and drying oil stain and water on the surface of the welding groove by using a flame heating mode;

s3, butt joint of workpiece grooves: aligning the two workpieces, ensuring that the vertical surfaces at the truncated edges between the two workpieces are parallel, and controlling the gap between the vertical surfaces of the two workpieces to be 3 mm;

s4, preheating before welding: preheating areas extending by 100-150 mm from two sides of a welding groove of a welding workpiece by using a flame or a crawler heater, wherein the preheating temperature is 200-250 ℃, and preserving heat until the temperature of the workpiece is not lower than 200 ℃ before the welding of the workpiece is finished, and the interlayer temperature is controlled within 300 ℃;

s5, GTAW back cover: as shown in FIG. 3, the root of the workpiece is subjected to back cover welding, the thickness of the back cover is not less than 3mm, the welding quality of the back face is ensured, the current of a phi 2.4 argon arc welding wire ER55-B2-MnV is controlled to be 120-150A, the voltage is controlled to be 24-25V, and the welding speed is 8-11 mm/s;

s6, SMAW lane filling: filling the UV groove bottom after bottom sealing in a way of dividing to increase the slope bottom thickness of the welding groove, filling 2 ways (as shown in figure 4), wherein the filling thickness is 5mm, the specification of the welding rod adopts a phi 3.2R 317 welding rod, the current is 110-120A, the voltage is 20-24V, and the welding speed is 13-18 mm/s;

s7, SAW welding: by using SAW welding equipment and tire rotating equipment, welding wires H08CrMoV with the specification of phi 3.2 are matched with a welding flux HJ350, workpiece welding is completed through an arc starting procedure, an intermediate welding operation procedure and a cover procedure, the interlayer temperature is controlled to be 250-300 ℃ during welding, and the service performance of a weldment is effectively ensured;

s7.1, an arc striking process: carrying out two SAW channel filling on the bottom of the filled UV groove, controlling the current at 280-290A, controlling the voltage at 28-32V, and controlling the welding speed at 11-15 mm/s;

s7.2, intermediate welding operation: filling the middle part of the UV groove layer by layer in a way until the filling reaches 2 times before the facing process; wherein for the welding of the 1 st to 2 nd tracks, the current is controlled to be 280-300A, the voltage is controlled to be 28-32V, the welding speed is 11-13 mm/s, for the welding of the 3 rd to 4 th tracks, the current is controlled to be 300-350A, the voltage is controlled to be 32-34V, the welding speed is 10-13 mm/s, for the welding of the 5 th to 8 th tracks, the current is controlled to be 350-380A, the voltage is controlled to be 32-35V, the welding speed is 11-15 mm/s, for the welding of the 9 th to 18 th tracks, the current is controlled to be 380-450A, the voltage is controlled to be 32-35V, and the welding speed is 12-15 mm/s; for subsequent welding, the current is controlled to be 400-450A, the voltage is controlled to be 32-36V, and the welding speed is 12-15 mm/s;

s7.3, a facing process: filling the last 2 channels of the UV groove, controlling the current to be 450-480A, controlling the voltage to be 34-36V, and controlling the welding speed to be 12-15 mm/s;

s8, post-welding heat treatment: after welding, controlling the post-heating temperature of the workpiece at 200-250 ℃, preserving heat for 1-2 h, then naturally cooling, eliminating hydrogen of a welding seam, avoiding generation of defects such as cracks and the like, and finally completing welding of a header and a pipeline circular seam.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and is not intended to limit the practice of the invention to these embodiments. Variations and modifications of the present invention may become apparent to those of ordinary skill in the art to which the invention pertains, and such variations and modifications are to be considered within the scope of the invention as defined by the appended claims.