CN117102626A

CN117102626A - Welding method for single-sided welding and double-sided forming

Info

Publication number: CN117102626A
Application number: CN202311157010.1A
Authority: CN
Inventors: 陈强; 贾庆广; 赵海平
Original assignee: Zhuhai Senbo Low Temperature Energy Equipment Co ltd
Current assignee: Zhuhai Senbo Low Temperature Energy Equipment Co ltd
Priority date: 2023-09-07
Filing date: 2023-09-07
Publication date: 2023-11-24

Abstract

The invention relates to the technical field of welding, in particular to a welding method for single-sided welding and double-sided forming. The technical problems to be solved by the technical proposal are as follows: the method adopts a four-layer method for welding, wherein the four-layer method is as follows: the first layer, the priming layer, the second layer, the third layer, the filling layer, the fourth layer and the covering layer; the root of the welding piece is provided with a joint, the joint is provided with two side polishing grooves and groove edge lines, the polishing groove angle is 45-60 degrees, the edge line is lower than the welding piece by 1-1.5 mm, the angle between the welding piece and the welding rod is 60-80 degrees, the distance between the welding piece and the welding rod is the left-right arc swinging method and the left-right arc connecting swinging method, and the arc collecting position is on the edges of the left-right welding piece. The beneficial effects of this technical scheme are: the joint is firstly connected with weldments which need to be connected together, then a groove is polished on the joint, the angle of the groove is 45-60 degrees, the weld joint is enabled to form complete connection and not to break, an arc point is arranged at the edge of the weldment, and air bubbles can not be discharged in the middle of the weld joint, so that the technical condition that the weld joint of a welding product subjected to technical supervision achieves the second-level or third-level of radiographic inspection is achieved.

Description

Welding method for single-sided welding and double-sided forming

Technical Field

The invention relates to the technical field of welding, in particular to a welding method for single-sided welding and double-sided forming.

Background

The conventional welding process generally needs to be performed on two sides, especially when circular welding parts such as pipelines and the like are faced, the conventional process for welding two sides is difficult to operate, unstable welding quality is easy to cause, flaw detection of a welding line is not up to standard, and the like.

Disclosure of Invention

The technical problems to be solved by the technical proposal are as follows:

in order to achieve the above purpose, the invention adopts the technical scheme that: a welding method for single-sided welding and double-sided forming comprises a first layer, a bottom layer, a second layer, a third layer, a filling layer, a fourth layer and a cover layer; the welding part root on be equipped with a plurality of joints, connect even distribution between two welding parts, the joint on be equipped with both sides groove and groove edge line of polishing, groove gradient be 45-60 degrees, edge line be less than welding part 1mm-1.5mm, the intermediate position between joint and the joint is equipped with the arc point, the groove of joint is from the bottom both ends of joint beginning wide back narrow polishing to the joint top centre, there is V style of calligraphy to the mouth in the middle of the welding part, the angle is 60-70, one side that the welding part bottom did not open the mouth is equipped with the blunt limit, the thickness of blunt limit is 0.5-2.0mm, gap between the welding part root is greater than welding rod diameter 0.5-1.0mm.

The beneficial effects of this technical scheme are: the joint is firstly connected with weldments which need to be connected together, then the bevel is polished on the joint, the angle of the polished bevel is 45-60 degrees like a mountain peak, the weld joint is formed into a complete connection without breaking, an arc point can prevent a line bubble from being generated in the middle of the weld joint at the edge of the weldment, and if the arc point is in the middle, a small hole can be formed in the middle of the weld joint due to sudden cooling of the temperature during welding.

Further, the primer layer welding comprises the following steps:

striking an arc at the middle position of two joints at the upper end part of the positioning welding line, wherein the downward inclination angle of the welding rod and a welding piece is 75-80 degrees, the included angle between the welding rod and the left and right sides of the welding line is 90 degrees, when the welding rod is welded to the tail part of the positioning welding line, the arc is slightly stopped for 1-2 seconds to elongate the arc for preheating, the welding rod is pressed down to the top part of a joint groove, and a melting hole is opened in front of a molten pool; when the broken down melting hole is welded up along with the continuous melting of the welding rod, arc extinction is started before the molten pool is blown up to round belly, the temperature of the molten pool is rapidly reduced after arc extinction, a white and shiny connecting line is arranged between the liquid metal and the solid metal, and arc striking is performed again after the contour of the connecting line is rapidly reduced to a point and disappears; when the length of the connecting line is reduced to 1-1.5 times of the diameter of the welding rod, the re-striking position is 1-2mm below the front edge of the connecting line, one half of the electric arc completely melts the front groove, the other half of the electric arc remelts a part of the solidified molten pool to form a new molten pool, one part of the new molten pool moves on the original deposited metal to continuously form a welding seam with good root penetration degree, and when the temperature of the molten pool is found to be too high, arc extinction is carried out again to wait for cooling of the molten pool, and the whole welding seam can be obtained by repeated welding; when arc is received before the welding rod is replaced by the backing layer welding, firstly, a melting hole is formed above a molten pool, then arc extinguishing is carried out after about 10mm of reflow, and a slope shape is formed; and (3) cooling, when the molten pool is cooled, polishing the arc-receiving part of the welding bead by using an angular grinding wheel or an inner body to form a slope of about 10mm, striking an arc at the slope, preheating, pressing the welding rod along a pre-made melting hole to the root of a weldment when the welding rod is welded to the lowest part of the slope, polishing and cleaning after cooling, and recovering the normal angle of the welding rod to continue the filling layer welding.

The beneficial effects after this technical scheme improves are: preventing the root back of the weldment from forming weld flash easily; or the back of the upper joint or the weldment is not easy to be connected, the concave is easy to be formed, and the welded joint is naturally cooled or is quickly cooled, so that the tendency of intergranular corrosion caused by overheating is prevented.

Further, the filling layer is of a concave structure and is lower than the edge line of the groove by about 1mm, the filling layer starts to strike an arc about 10mm above two joints of the welding line of the priming layer, the angle between the welding rod and the welding piece is 70-80 degrees, the welding rod stays for 1-2 seconds when reaching the position of the groove, the concave structure of the filling layer can be overlapped with a third layer for secondary filling, the welding method is a left-right arc swinging method or a left-right arc connecting arc swinging method, and the welding strip is in a transverse zigzag shape or a crescent shape.

The beneficial effects after this technical scheme improves are: the welding adopts a continuous welding method, reduces the process defects, thoroughly cleans the bottom welding, repairs the uneven part, does not influence the quality of the next welding seam, is beneficial to fusion and slag discharge of the polished groove, and can ensure that the surface layer and the surface of a weldment at the back keep a uniform plane.

The technical problems to be solved by the improvement of the technical scheme are as follows:

further, the arc striking operation method of the cover layer melting groove edge line is 1-2mm, the arc striking operation method is the same as that of the filling layer, filling and repairing are carried out, the downward inclination angle of the welding rod and the plate is 70-80 degrees, a zigzag or crescent strip is adopted, when the welding rod is from one side to the other side, the middle arc is slightly lifted, the advancing speed is uniform, each new molten pool covers 2/3-3/4 of the previous molten pool, preferably, when the welding rod is replaced and then is welded, the arc striking position is about 15mm above the pit, the arc striking is carried out at the weld metal position of the filling layer, then the arc is quickly pulled back to the original molten pool, and the welding is continued after the arc pit is filled.

The beneficial effects after this technical scheme improves are: the welding meat is consistent in height and does not exceed the groove surface of the weldment, and the appearance is attractive by keeping the contour of the groove and one-time cover surface.

The invention utilizes butt joint and joint of weldment through arc welding, proper blunt edge and bevel, adopts a semi-breakdown welding method to melt the root of the weldment, leads a molten pool to form a molten hole, welds the molten hole, then breaks down and melts the blunt edge, and forms the molten hole, thereby achieving the purpose of single-sided welding and double-sided molding in a reciprocating manner.

Drawings

Fig. 1 is a diagram showing a molding structure of the present invention.

Fig. 2 is a structural view of a weldment joint of the present invention.

Fig. 3 is a view of the underlying weld of the present invention.

Fig. 4 is a weld pattern of the filler layer of the present invention.

Fig. 5 is a welded view of the facing layer of the present invention.

Fig. 6 is a diagram of embodiment 1 of the present invention.

Fig. 7 is a diagram of embodiment 2 of the present invention.

In the figure: 1. a weldment; 2. a joint; 3. groove; 31. edge lines; 4. a blunt edge; 5. welding seams; A. a bottom layer is formed; B. a filling layer; b1, a filling layer 1; b2, a filling layer 2; C. and (3) a cover layer.

Detailed Description

In order that those skilled in the art may better understand the technical solutions of the present invention, the following detailed description of the present invention with reference to the accompanying drawings is provided for exemplary and explanatory purposes only and should not be construed as limiting the scope of the present invention.

16MnDR is a low-temperature low-alloy high-strength structural steel, which has excellent low-temperature impact performance, good durability and toughness, excellent low-temperature impact performance, can bear a high-pressure environment at low temperature, and ensures the safety and stability of substances in a container, so that the steel is widely applied to the fields of pressure containers, liquid ammonia storage tanks, liquefied gas storage tanks and the like, and has high requirements on welding technology. In order to remarkably improve the welding quality in the manufacturing process, an advanced welding technology needs to be actively applied, so that the welding quality is ensured, the welding efficiency is improved, and the construction cost is reduced. Therefore, the invention provides a welding method for single-sided welding and double-sided forming, and as shown in fig. 1, the welding piece comprises a bottom layer, a filling layer and a cover layer before welding and forming. Each layer has a corresponding welding process so as to ensure the welding quality and the requirements of flaw detection standards which can be met by the welding seam.

As shown in figure 2, the welding parts are processed before welding, firstly, the butt joint between the welding parts is polished, so that the butt joint angle between the two welding parts is in a V-shaped or Y-shaped structure of 60-70 degrees, when the welding parts are in a plate structure, the Y-shaped structure can be selected, if the welding parts are in a circular structure, the butt joint is preferably in a V-shaped structure, meanwhile, proper root gaps are reserved at the root parts of the welding parts, welding rods can be guaranteed to be sent to the root parts, and the arc can be guaranteed to penetrate through a part of the back part and penetrate through the root parts. In order to easily achieve uniform permeability, the size deviation of the root gap of a general weldment should be about 1 millimeter. At the same time, the root gap size of the weldment should be equal to the diameter of the welding rod or larger than the diameter by about 0.5-1.0mm. While the root of the weldment is left with a blunt edge, which is the end face portion that is not open in the thickness direction of the weldment. A blunt edge with the size of 0.5-2.0mm is generally reserved according to the thickness of the workpiece, for example, when the wall thickness is 3mm, the blunt edge is 0.5mm, for example, when the wall thickness is more than 12 mm, the thickness is generally 1.5mm, preferably, the maximum thickness is not more than 2mm, the root of the blunt edge is easy to be not welded through, and the blunt edge is too thin and easy to be broken down, so that a larger molten hole is formed. The arc preheating device has a blunt edge, the time for preheating the workpiece by using the electric arc after arc striking can be longer, and the preheating range can be wider, thereby improving the welding process conditions, increasing the fluidity of liquid metal and easily ensuring penetration.

In particular, when welding round pressure pipes and pressure vessels, a joint is required to be arranged between a weldment and the root of the weldment, the joint can play a role in preliminary fixed connection, displacement of the weldment in the welding process is prevented, and in order not to influence flaw detection of later-stage welding seams, the joint is required to be polished, the joint is polished into a shape similar to a peak in width at the upper tip and the lower width, two sides of the joint are polished simultaneously, an edge line is formed at the top of the joint, the top edge line of the joint is lower than the surface of the weldment, the effect of the edge line can be used as a reference line when the weldment is filled, and the surface of the weld is lower than the surface of the weldment, so that the surface of the weld is smooth and attractive after the cover layer is welded, and flaw detection is not influenced.

In particular, when the joint is polished, two sides of the joint are polished from bottom to top and simultaneously form a welding bead with a wide bottom and a narrow top towards the position of the edge line, the welding bead can be melted together with the blunt edge to form a molten pool, and meanwhile, when a round weldment is welded, the welding gun moves forward along the welding bead direction, and the welding gun meets at the edge line to form a perfect weld joint.

The specific operation method of the bottom layer welding shown in fig. 3 is that after arc striking, when the semi-melting state is reached (namely, when sweat beads appear on the preheated butt edge under the electric welding goggles for about 3-4 seconds), the arc is pressed down, the blunt edge is melted and broken down, when the welding is carried out to the tail part of a positioning welding line, the arc is stretched for preheating after a small pause of 1-2 seconds, the welding rod is pressed down to the top of a joint groove, and a melting hole is opened in front of a melting pool, so that a part of deposited metal is ensured to be transited to the root part and the back surface of the welding line and form the melting pool together with a melted joint base metal.

Then, continuing to melt along with the welding rod, after a broken down melting hole is welded, indicating that the temperature is too high when the molten pool is inflated to a round belly, starting arc extinction, after arc extinction, rapidly reducing the temperature of the molten pool, and when the contour of the interface line is rapidly reduced to a point and disappears, striking an arc again, wherein a white and shiny interface line exists between the liquid metal and the solid metal; when the length of the connecting line is reduced to 1-1.5 times of the diameter of the welding rod, the re-striking position is 1-2mm below the front edge of the connecting line, one half of the electric arc completely melts the front groove, the other half of the electric arc remelts a part of the solidified molten pool to form a new molten pool, one part of the new molten pool moves on the original deposited metal to continuously form a welding seam with good root penetration degree, and when the temperature of the molten pool is found to be too high, arc extinction is carried out again to wait for cooling of the molten pool, and the whole welding seam can be obtained by repeated welding; when arc is received before the welding rod is replaced by the backing layer welding, firstly, a melting hole is formed above a molten pool, then arc extinguishing is carried out after about 10mm of reflow, and a slope shape is formed; and (3) cooling, when the molten pool is cooled, polishing the arc-receiving part of the welding bead by using an angular grinding wheel or an inner body to form a slope of about 10mm, striking an arc at the slope, preheating, pressing the welding rod along a pre-made melting hole to the root of a weldment when the welding rod is welded to the lowest part of the slope, namely a half breakdown welding method of a priming layer, polishing and cleaning after cooling, and recovering the normal angle of the welding rod to continue the welding of the filling layer.

As shown in the welding of the filling layer in FIG. 4, the filling layer is welded with a concave structure and is about 1mm lower than the edge line of the groove, the filling layer starts to strike an arc about 10mm at the welding joint of the priming layer, the angle between the welding rod and the weldment is 70-80 degrees, the concave structure of the filling layer can be overlapped with a third layer for secondary filling, the third layer welding method is a left-right arc swinging method or a left-right arc connecting swinging method, the welding rod stays for 1-2 seconds when reaching the position of the joint groove, and the welding method is the same as the welding of the priming layer, so that a part of deposited metal is ensured to be transited to the priming layer and forms a molten pool together with the melted joint parent metal.

As shown in figure 5, the arc striking operation method of the cover surface layer melting groove edge line is 1-2mm, the arc striking operation method is the same as that of the filling layer, filling and repairing are carried out, the downward inclination angle of the welding rod and the plate is 70-80 degrees, a zigzag or crescent strip is adopted, when the welding rod is from one side to the other side, the middle arc is slightly lifted, the advancing speed is uniform, each new molten pool covers 2/3-3/4 of the previous molten pool, when the welding rod is replaced and then welding is carried out, the arc striking position is about 15mm above the pit, the arc striking is carried out at the metal part of the filling layer welding seam, then the arc is quickly pulled back to the original molten pool, and the welding is continued after the arc pit is filled.

Example 1 tubular weldment horizontal fixed upward welding

Welding pipe fitting materials and specification materials 16Mn; the specification is 133mm multiplied by 10mm, welding material welding rods E5015 and 3.2mm are dried according to the specified requirements, the butt form and the size v shape are butt, and the butt surface angle is 32 degrees plus 2 degrees; and the blunt edge is 1-1.5 mm, the joint insert made of the same material as the weldment is assembled to fix the welded pipe fitting, the axis of the welded pipe fitting is checked to be aligned before the welding pipe fitting is positioned and welded, the offset edge is reduced as much as possible, and the gap is ensured to meet the process requirement.

TABLE 1 welding process parameters

The welding pipe fitting horizontal fixed position welding is carried out in two semicircles, and the right semicircle is formed by welding the position (overhead welding) corresponding to the 6 point of the clock of the section of the pipeline to the position (vertical welding) corresponding to the 12 point of the clock of the section of the pipeline. The left semicircle is arc-turned from the position corresponding to the "clock 6 point" (overhead welding) to the position corresponding to the "clock 12 point" (vertical welding) via the position corresponding to the "clock 9 point" (vertical welding). When the welding rod is ignited at the overhead welding position and the vertical welding position, the arc is pressed down to move to the tip of the joint edge line, the arc is slightly stopped, the joint groove edge is melted to form a molten pool, the welding rod is directly inclined to the joint of the lower edge of the groove and the blunt edge from the tip of the joint edge line, and the lower edge is melted to form the molten pool, so that normal welding is performed. The welding sequence is to weld the right half circle first and then the left half circle. In the welding, the angle of the electrode changes with the change of the welding position, and the change of the angle is shown in fig. 6.

Referring to fig. 2, 3 and 6, the welding method of the welding rod arc welding primer layer is that after the welding rod ignites the arc on the opposite side (corresponding to the position of the clock 6 point), the arc is immediately pressed down, and the welding rod is moved to a starting welding point (the starting welding point is 10-15 mm after the position of the clock 6 point). The front end of the welding rod is aligned with the center of the butt joint, the welding rod is upwards jacked and performs left-right arc stabilizing action, the butt joint blunt edge is broken down by means of the arc blowing force, and after the arc penetrating sound emitted by the inside of the pipe is heard by the formed molten pool, the first melting hole and the molten pool are formed. After the puddle is formed, the welding rod returns to the middle position of the puddle of the joint to rapidly extinguish arc. When the first molten pool metal turns dark red, the welding rod immediately ignites the electric arc at the middle position of the molten pool, then small transverse swinging is carried out to move the welding rod to the molten hole, the butt blunt edges at the two sides are broken down, a new molten hole molten pool is formed, and then the welding rod returns to the middle position of the molten pool of the joint to extinguish the electric arc. When welding in the overhead welding section, the welding rod is required to prop against the outer edge of the butt-joint blunt edge, and the lower the arc voltage is, the better the arc voltage is, so that the plumpness of metal in the pipe is ensured, and the generation of concave is prevented. When welding in vertical welding position and horizontal welding position, the pressure of the welding rod to the opposite opening is shallow, so as to prevent weld flash. In addition, before each welding strip is completely welded and extinguished, 2-3 drops of molten iron are filled into a molten pool to quench arcs, so that arc pit shrinkage is prevented. When the molten pool has enough temperature, the welding rod is quickly replaced, an electric arc is ignited at the position of 5-10 mm above the welding bead behind the molten pool, the welding rod is welded to the welding rod Kong Yadi electric arc, and an arc stabilizing action is performed to break down the blunt edge of the groove. When the arc penetration sound in the pipe is heard, normal arc breaking welding can be carried out, and when the arc is welded to the position corresponding to the 'clock 12 point', the arc is recovered after the arc passes through the center by 10-15 mm.

After the right half cycle is welded, a slope of 10-15 degrees can be processed at the welding point and the tail end by using a saw blade or a flat shovel to ensure the quality of the joint. When the left half cycle is welded, the lap joint is adopted, namely, the arc starting point still exceeds the center by 10-15 mm, the arc is pressed down after the arc is ignited, the strip is transported to the slope of the welding starting point, the welding rod is jacked up and performs arc stabilizing action, and the molten drops are sent to the back surface to form a melting hole and a molten pool, so that normal welding can be performed. When the welding strip is welded to the tail end of the right half cycle to be connected, the elevation angle of the welding rod is adjusted to be 85-90 degrees gradually, the front end of the welding rod is aligned to an arc starting point, the arc is stabilized by pressing the arc under a slight force, when the arc breakdown sound is heard from the back, enough molten iron is supplied, and the arc can be extinguished when the welding rod is welded to the position of 5-10 mm from the central line. After the bottom layer is welded, slag, splashes, joint bulges and the like on the welding line of the bottom layer are cleaned up and leveled by a flat shovel, so that slag inclusion and unfused welding during welding of other layers are prevented.

In connection with the welding of the filling layers of fig. 2, 4 and 6, the filling layers are welded by adopting a connecting arc welding method, the welding rod angle is the same as that of the bottom layer welding method, and the welding joints of the overhead welding and the flat welding are staggered. During welding, the welding rod ignites an electric arc near the position corresponding to the 6 point of the clock, moves to the middle of a bottoming welding seam with the 10-15 mm of the over center, presses down the electric arc, and swings to grooves on two sides after a molten pool is formed. The strip conveying method adopts crescent or zigzag uniform strip conveying. The welding rod stays for a long time at the two sides of the butt joint, and the speed is high at the middle position, so that the included angle and slag inclusion at the two sides of the butt joint can be prevented. When the welding rod is retracted, 2-3 drops of molten iron are filled in a molten pool in a small amount by adopting an arc extinguishing method at the center of the welding seam, and then arc extinguishing is carried out. When striking arc again, the welding rod is quickly replaced, the arc is ignited 10-15 mm above the arc pit, the welding rod is drawn to the middle of the welding bead at the arc receiving position, 2/3 of the molten pool at the arc receiving position is pressed to slightly stop, the molten pool is formed and then swings transversely, and when the arc receiving position is seen to be completely melted, normal welding can be performed. When the filling layers are welded, the cleaning between the layers is careful, the angle of the welding rod is correct along with the change of the spatial position of a weldment during welding, the butt edge of the pipe fitting is not damaged by the welding seam of the last layer, and the butt edge is about 1mm lower than an edge line, so that groove type filling is formed.

Referring to fig. 2, 5-6, the cover layer surface welding method is substantially the same as the filler layer, but the electrode swings laterally wider than the filler layer. It should be noted that the swing amplitude of the welding rod is uniform, the lower the arc voltage at the two sides of the butt joint is, the better the arc voltage is, the melting of the edges of the butt joint of the pipe fitting is 0.5-1 mm, the welding seam of the cover layer covers the edge line on the joint, the welding rod ensures that the welding of the outer edges of the butt joint of the pipe fitting is good when the welding rod stays at the two sides of the groove, and the undercut is avoided, so that the welding seam is formed attractive.

Example 2 tube weldment horizontal rotation climbing welding

The lower pipe fitting is welded in the horizontal position by adopting the method as shown in fig. 7, and the welding mode is flat welding or climbing welding, which is very beneficial to the operation of welders and the formation of welding seams. Gap between the opposite ends: 2-3 mm; amount of misalignment: less than or equal to 1mm; and (3) blunt edges: 0.5-1 mm; the tack welds are located at the "10 o 'clock" and "2 o' clock" positions on the pipe cross-section.

The bottom layer weld joint is formed by single-sided welding and double-sided forming, so that the penetration of the root of the groove is ensured, and burning through or weld flash formation is prevented. The welding method is the same as the specific embodiment, the diameter of the welding rod is 2.5mm, and the welding current is 60-80A. The operation sequence of the backing welding is as follows: and (3) starting welding from the position corresponding to 10-half-clock on the section of the pipeline, performing climbing welding, rotating the pipe fitting once every welding is finished, and rotating the joint to the position corresponding to 10-half-clock on the section of the pipeline. The angle of the welding rod is 60-80 degrees, and the welding rod stretches into the butt joint to enable 1/3-1/4 arc column to burn in the pipe so as to melt the blunt edges on two sides. The procedure of example 1 was repeated except that the weld holes were formed 0.5mm deep into the base materials of the weld members on both sides and the welding rod was replaced to make the intermediate joint of the weld joint. When the welding process passes through the positioning weld joint, the arc is only needed to be pressed into the butt joint, and the arc can pass through the starting point of the positioning weld joint at a higher speed and is transited to the joint groove for welding.

And (3) filling layer welding, namely welding by adopting continuous arc welding, and cleaning slag and splash of a bottoming layer before welding. The diameter of the welding rod is 3.2mm, the welding current is 90-120A, and the angle of the welding rod is the same as that of the priming layer. The strip conveying method adopts crescent or zigzag uniform strip conveying. The welding rod stays for a long time at the two sides of the butt joint, and the speed is high at the middle position, so that the included angle and slag inclusion at the two sides of the butt joint can be prevented. When the welding rod is retracted, 2-3 drops of molten iron are filled in a molten pool in a small amount by adopting an arc extinguishing method at the center of the welding seam, and then arc extinguishing is carried out. When striking arc again, the welding rod is quickly replaced, the arc is ignited 10-15 mm above the arc pit, the welding rod is drawn to the middle of the welding bead at the arc receiving position, 2/3 of the molten pool at the arc receiving position is pressed to slightly stop, the molten pool is formed and then swings transversely, and when the arc receiving position is seen to be completely melted, normal welding can be performed. When the filling layers are welded, the cleaning between the layers is careful, the angle of the welding rod is correct along with the change of the spatial position of a weldment during welding, the butt edge of the pipe fitting is not damaged by the welding seam of the last layer, and the filling layer 1 is lower than an edge line by about 1mm to form groove type filling.

And the cover surface layer is welded, the cover surface welding seam meets the geometric size requirement of the welding seam, the appearance is attractive, the welding seam is smoothly transited with the base metal, and the welding seam is free of defects. Slag and splash of the filling layer should be cleaned before welding. The diameter of the welding rod is 3.2mm, and the welding current is 90-110A. The welding rod angle and the strip conveying method are the same as those of the filling welding, but the horizontal and transverse swinging amplitude of the welding rod should be wider than that of the filling welding, the electric arc should be faster from one side to the other side, the electric arc should be further shortened when swinging to the opposite sides, and the electric arc should be stopped slightly to avoid undercut, the opposite edges of the pipe fitting are melted by 0.5-1 mm, and the joint edges of the joint are covered between the joint of the welding seams of the cover layers.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. The foregoing is merely illustrative of the preferred embodiments of the invention, and it is noted that there is virtually no limit to the specific structure which may be imposed by those skilled in the art without departing from the spirit of the invention, and that modifications, adaptations, or variations of the foregoing features may be combined in a suitable manner; such modifications, variations and combinations, or the direct application of the inventive concepts and aspects to other applications without modification, are contemplated as falling within the scope of the present invention.

Claims

1. A welding method for single-sided welding and double-sided forming adopts a four-layer method for welding, wherein the four-layer method is as follows: the first layer, the priming layer, the second layer, the third layer, the filling layer, the fourth layer and the covering layer; the welding part root on be equipped with a plurality of joints, connect even distribution between two welding parts, the joint on be equipped with both sides groove and groove edge line of polishing, groove gradient be 45-60 degrees, edge line be less than welding part 1mm-1.5mm, the intermediate position between joint and the joint is equipped with the arc point, the groove of joint is from the bottom both ends of joint beginning wide back narrow polishing to the middle of joint top, there is V style of calligraphy to the mouth angle in the middle of the welding part to be 60-70, one side of welding part bottom unopened is equipped with the blunt limit, the thickness of blunt limit is 0.5-2.0mm, gap between the welding part root is greater than welding rod diameter 0.5-1.0mm.

2. The welding method for single-sided welding and double-sided molding according to claim 1, wherein: the priming welding comprises the following steps: and (3) striking an arc at the middle position of two joints at the upper end part of the positioning welding line, wherein the downward inclination angle of the welding rod and a welding piece is set to be 75-80 degrees, the included angle between the welding rod and the left and right sides of the welding line is 90 degrees, when the welding rod is welded to the tail part of the positioning welding line, the arc is slightly stopped for 1-2 seconds to elongate the arc for preheating, the welding rod is pressed down to the top part of a joint groove, and a melting hole is opened in front of a molten pool.

3. The welding method for single-sided welding and double-sided molding according to claim 1, wherein: the priming welding comprises the following steps: arc extinction, after the broken melting hole is welded up along with the continuous melting of the welding rod, starting arc extinction before the molten pool is blown up to round belly, after arc extinction, quickly reducing the temperature of the molten pool, and when the contour of the interface line is quickly reduced to a point and disappears, striking arc again, wherein a white and shiny interface line exists between the liquid metal and the solid metal.

4. The welding method for single-sided welding and double-sided molding according to claim 1, wherein: the priming welding comprises the following steps: when arc is drawn before the welding rod is replaced, a melting hole is firstly formed above a molten pool, then arc extinguishing is carried out after about 10mm of reflow, and a slope shape is formed.

5. The welding method for single-sided welding and double-sided molding according to claim 1, wherein: the priming welding comprises the following steps: and (3) cooling, when the molten pool is cooled, polishing the arc-receiving part of the welding bead by using an angular grinding wheel or an inner body to form a slope of about 10mm, striking an arc at the slope, preheating, pressing the welding rod along a pre-made melting hole to the root of a weldment when the welding rod is welded to the lowest part of the slope, polishing and cleaning after cooling, and recovering the normal angle of the welding rod to continue the filling layer welding.

6. The welding method for single-sided welding and double-sided molding according to claim 1, wherein: the filling layer is of a concave structure and is lower than the edge line of the groove by about 1mm, the filling layer starts to strike an arc about 10mm above two joints of a welding line of the bottom layer, the angle between the welding rod and a weldment is 70-80 degrees, the welding rod stays for 1-2 seconds when reaching the position of the groove, and the welding strip is in a transverse zigzag shape or a crescent shape.

7. The welding method for single-sided welding and double-sided molding according to claim 1, wherein: the arc striking operation method of the cover surface layer melting groove edge line is 1-2mm, the cover surface welding arc striking operation method is the same as that of a filling layer, the downward inclination angle of the welding rod and a welding piece is 70-80 degrees, a zigzag or crescent-shaped conveying strip is adopted, when the welding rod moves from one side to the other side, the middle arc is slightly lifted, the advancing speed is uniform, each new molten pool covers 2/3-3/4 of the previous molten pool, when the welding rod is replaced and then is welded, the arc striking position is about 15mm above the middle of two joints at the position of the filling layer weld metal, then the arc is quickly pulled back to the original molten pool, and welding is continued after the arc pit is filled.

8. The welding method for single-sided welding and double-sided molding according to claim 6, wherein: the concave structure of the filling layer can be overlapped with a third layer of filling, and the welding method is a left-right arc swinging method or a left-right arc connecting arc swinging method.

9. The welding method for single-sided welding and double-sided molding according to claim 2, wherein: after preheating, the arc is pressed down when the arc reaches a semi-melting state, and the blunt edge of the melting breakdown weldment is melted to obtain a melting hole, so that part of deposited metal is transited to the root part and the back surface of the welding seam and forms a molten pool together with the root part of the melting weldment.

10. A welding method for single-sided welding and double-sided molding according to claim 3, wherein: when the length of the connecting line is reduced to 1-1.5 times of the diameter of the welding rod, the re-striking time is selected, the re-striking position is 1-2mm below the front edge of the connecting line, one half of the electric arc completely melts the front groove, the other half of the electric arc re-melts a part of the solidified molten pool to form a new molten pool, one part of the new molten pool moves on the original deposited metal to continuously form a welding seam with good root penetration degree, and when the temperature of the molten pool is found to be too high, the arc extinguishing is carried out again, the molten pool is waited for cooling, and the whole welding seam can be obtained by repeated welding.