Pipe weld overlay and method of welding

Abstract

The application discloses a pipe welding layer and a welding method thereof. The pipe welding layer comprises: a plurality of horizontal welding segments arranged on the side wall of the pipe and spaced along the circumference of the pipe; and a plurality of transverse welding segments arranged on the side wall of the pipe. Each transverse welding segment is located between two adjacent horizontal welding segments, and the transverse welding segments and the horizontal welding segments are connected to form a ring-shaped welding layer. The application can reduce the restraint degree of each welding seam by the staggered distribution of the horizontal welding segments and the transverse welding segments, thereby avoiding welding seam cracking and improving the reliability of the welding layer.

Description

Technical Field

[0001] This invention relates to the field of nuclear power equipment technology, and in particular to a weld overlay layer for pipe fittings and a weld overlay method thereof. Background Technology

[0002] Nuclear power is gaining increasing attention as a new type of energy source, and with the deepening research into nuclear power technology, nuclear power equipment is constantly being updated and improved. Unlike traditional pressurized water reactors, some heat exchangers in fourth-generation pressurized water reactors operate at temperatures exceeding 500℃, using liquid sodium as the heat exchange medium. The heat exchanger structure incorporates multiple layers of tubing for primary and secondary heat exchange, with the innermost tubing having an outer diameter of approximately 300mm and the outermost tubing approximately 600-900mm. To ensure a service life of 40 years or more for the heat exchanger under high-temperature liquid sodium conditions, a weld overlay is typically installed on the outer wall of the inner tubing. This provides high hardness (380-450 HBW) at the contact points between the inner and outer tubing, ensuring wear resistance, heat resistance, and corrosion resistance.

[0003] However, existing welding processes are generally used for welding on flat plates, with two or fewer layers. If used for welding on pipe fittings, the weld restraint of the pipe fitting weld overlay is greater than that of the weld overlay on the plate, making the pipe fitting weld overlay more prone to cracking, resulting in transverse cracks and reduced reliability. Therefore, improvements are needed to the structure of the pipe fitting weld overlay and its welding method. Summary of the Invention

[0004] The purpose of this invention is to provide a weld overlay layer for pipe fittings and a weld overlay method thereof. By staggering the distribution of horizontal and transverse weld overlay sections, the weld overlay layer has multiple weld seams, which can reduce the constraint of each weld seam without changing the pipe diameter, thereby avoiding weld cracking.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A weld overlay on a pipe fitting, comprising:

[0007] Several horizontal weld overlay sections are disposed on the sidewall of the pipe fitting and are spaced apart circumferentially along the pipe fitting; and

[0008] Several horizontal weld overlay sections are disposed on the side wall of the pipe fitting; each of the horizontal weld overlay sections is located between two adjacent horizontal weld overlay sections, and the horizontal weld overlay sections and the horizontal weld overlay sections are connected to form an annular weld overlay layer.

[0009] Optionally, each of the horizontal weld overlay sections includes a plurality of horizontal weld beads, each of the horizontal weld beads extending circumferentially along the pipe fitting, all the horizontal weld beads being arranged parallel to each other along the axial direction of the pipe fitting, and there being no gap between adjacent horizontal weld beads.

[0010] Optionally, each of the transverse weld sections includes a plurality of transverse weld beads, each of the transverse weld beads extending axially along the pipe fitting, all of the transverse weld beads being arranged in parallel along the circumference of the pipe fitting, and there being no gap between adjacent transverse weld beads.

[0011] On the other hand, the present invention also provides a method for welding the weld overlay layer of a pipe fitting as described above, comprising:

[0012] The area to be welded on the side wall of the pipe fitting is divided into a horizontal weld overlay area and a transverse weld overlay area.

[0013] Welding is performed along the circumference of the pipe fitting in the horizontal weld overlay area to form a horizontal weld overlay section;

[0014] Welding is performed along the axial direction of the pipe fitting in the transverse weld overlay area to form a transverse weld overlay section; and

[0015] The horizontal weld overlay section and the transverse weld overlay section undergo post-heat treatment.

[0016] Optionally, all the horizontal weld overlay zones are distributed at circumferential intervals along the pipe fitting, with each horizontal weld overlay zone located between two adjacent horizontal weld overlay zones.

[0017] Optionally, the step of welding along the circumference of the pipe fitting in the horizontal weld overlay area to form the horizontal weld overlay section includes:

[0018] The pipe fitting is fixed to a rotating mechanism to allow the pipe fitting to rotate.

[0019] Preheat the horizontal weld overlay area to a first preset temperature and maintain it; and

[0020] Welding is performed along the circumference of the pipe fitting within the horizontal weld overlay zone to form a layer of horizontal weld beads that extend circumferentially and are arranged axially along the pipe fitting; and all horizontal weld beads in the same layer constitute a horizontal weld overlay segment.

[0021] Optionally, the step of welding along the axial direction of the pipe fitting in the transverse weld overlay area to form the transverse weld overlay section includes:

[0022] This prevents the pipe fitting from rotating;

[0023] Preheat the transverse overlay welding zone to a second preset temperature and maintain it; and

[0024] Welding is performed along the axial direction of the pipe fitting within the horizontal weld overlay zone to form a layer of horizontal weld beads that extend along the axial direction of the pipe fitting and are arranged circumferentially along the pipe fitting; and all horizontal weld beads in the same layer constitute a layer of horizontal weld overlay segment.

[0025] Optionally, when the number of weld overlay layers on the pipe fitting is greater than one, it further includes:

[0026] Welding is performed circumferentially on the preceding horizontal weld overlay section to form a subsequent horizontal weld bead extending circumferentially and arranged axially along the pipe fitting; and all horizontal weld beads of the subsequent layer constitute the subsequent horizontal weld overlay section; and

[0027] Welding is performed along the axial direction of the pipe fitting on the previous layer of horizontal weld overlay to form a subsequent layer of horizontal weld overlay extending along the axial direction of the pipe fitting and arranged circumferentially along the pipe fitting; and all the horizontal weld overlays of the subsequent layer constitute the subsequent layer of horizontal weld overlay.

[0028] Optionally, the horizontal weld overlay section and the horizontal weld overlay section in the same layer form a weld layer, and the current used when welding the latter weld layer is greater than the current used when welding the former weld layer.

[0029] Optionally, both the first preset temperature and the second preset temperature are greater than or equal to 200°C;

[0030] The temperature between adjacent horizontal weld beads and the temperature between adjacent transverse weld beads are both less than or equal to 500℃.

[0031] Compared with the prior art, the present invention has at least one of the following advantages:

[0032] The present invention provides a weld overlay layer for pipe fittings and a weld overlay method thereof. Horizontal weld overlay sections are arranged at intervals along the circumference of the pipe fitting, and a transverse weld overlay section is arranged between two adjacent horizontal weld overlay sections. The transverse weld overlay section and the horizontal weld overlay section are connected to form an annular weld overlay layer. At the same time, the staggered distribution of the horizontal weld overlay section and the transverse weld overlay section results in the weld overlay layer having multiple welds. This reduces the constraint of each weld without changing the pipe diameter, thereby avoiding weld cracking and improving the reliability of the weld overlay layer.

[0033] In this invention, the horizontal weld bead in the horizontal weld overlay section extends along the circumference of the pipe fitting, and the horizontal weld bead in the transverse weld overlay section extends along the axial direction of the pipe fitting. The extension directions of the horizontal weld bead and the transverse weld bead are perpendicular, which can also reduce the constraint of the weld at the connection between the horizontal weld bead and the transverse weld bead, and at the same time facilitate the welding of the transverse weld bead.

[0034] In this invention, when welding along the circumference of the pipe fitting in the horizontal weld overlay zone to form a horizontal weld overlay section and welding along the axial direction of the pipe fitting in the transverse weld overlay zone to form a transverse weld overlay section, the horizontal weld overlay zone and the transverse weld overlay zone are preheated to 300°C or higher throughout the welding process, which can reduce the hardening tendency.

[0035] In this invention, after welding is completed, post-heat treatment is performed on the horizontal and transverse weld overlay sections, i.e., the weld overlay layers. This can accelerate the escape of hydrogen from the weld metal, greatly reduce the hydrogen content in the weld and heat-affected zone, thereby achieving the purpose of eliminating hydrogen from the weld overlay layer and thus preventing weld cracking.

[0036] This invention is applicable to welding on pipe fittings with a large diameter (greater than 200 mm). By eliminating hydrogen in the weld overlay, reducing weld restraint, and reducing hardening tendency, the thickness and number of weld overlays on the sidewall of the pipe fitting can be increased to meet different welding requirements. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a weld overlay layer for a pipe fitting according to an embodiment of the present invention;

[0038] Figure 2 This is a cross-sectional schematic diagram of a weld overlay layer on a pipe fitting provided in an embodiment of the present invention;

[0039] Figure 3 This is a flowchart of a welding method for a weld overlay layer on a pipe fitting according to an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram illustrating the division of the horizontal and transverse welding zones in a welding method for a pipe fitting weld overlay provided in an embodiment of the present invention. Detailed Implementation

[0041] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the weld overlay layer for pipe fittings and its welding method proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, intended only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes and to enable those skilled in the art to understand and read them, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0042] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0043] Combined with appendix Figures 1-2 As shown, this embodiment provides a pipe fitting weld overlay layer, including: a plurality of horizontal weld overlay sections 110 disposed on the side wall of the pipe fitting 100 and distributed at intervals along the circumference of the pipe fitting 100; and a plurality of transverse weld overlay sections 120 disposed on the side wall of the pipe fitting 100; each transverse weld overlay section 120 is located between two adjacent horizontal weld overlay sections 110, and the transverse weld overlay section 120 and the horizontal weld overlay section 110 are connected to form a closed annular weld overlay layer.

[0044] Specifically, a weld is formed at the connection between each horizontal weld overlay segment 110 and the corresponding horizontal weld overlay segment 120. The horizontal weld overlay segments 110 and 120 are staggered, allowing the weld overlay layer to have multiple welds. This reduces the constraint of each weld while maintaining the same pipe diameter, thus preventing weld cracking and improving the reliability of the weld overlay layer. More specifically, the number of horizontal weld overlay segments 110 and horizontal weld overlay segments 120 can be determined according to specific requirements and the outer or inner diameter of the pipe fitting 100. In the circumferential direction of the pipe fitting, the sum of the arc lengths of all horizontal weld overlay segments 110 can account for 80% to 95% of the circumference of the pipe fitting 100, and the sum of the arc lengths of all horizontal weld overlay segments 120 can account for 5% to 20% of the circumference of the pipe fitting 100. Preferably, the cross-sectional shape of the weld overlay is symmetrical, that is, all the horizontal weld overlay segments 110 and all the transverse weld overlay segments 120 are symmetrically distributed, with the same degree of restraint for each weld, but the present invention is not limited thereto.

[0045] In this embodiment, the horizontal weld overlay section 110 and the transverse weld overlay section 120 are disposed on the outer side wall of the pipe fitting 100; the outer diameter of the pipe fitting 100 is 300 mm, and there are two of each of the horizontal weld overlay section 110 and the transverse weld overlay section 120, with the arc length of each transverse weld overlay section 120 being 30 mm to 50 mm. Preferably, the material of the pipe fitting 110 is 316H stainless steel.

[0046] Please also refer to Figure 1 and Figure 2 Each of the horizontal weld overlay sections 110 includes a plurality of horizontal weld beads 1101, each of the horizontal weld beads 1101 extending circumferentially along the pipe fitting 100, all the horizontal weld beads 1101 being arranged parallel to each other along the axial direction of the pipe fitting 100, and there being no gap between adjacent horizontal weld beads 1101.

[0047] It is understood that each of the transverse weld sections 120 includes a plurality of transverse weld beads 1201, each of the transverse weld beads 1201 extending along the axial direction of the pipe fitting 100, all the transverse weld beads 1201 being arranged in parallel along the circumference of the pipe fitting 100, and there being no gap between adjacent transverse weld beads 1201.

[0048] Specifically, in this embodiment, the horizontal weld bead 1101 and the transverse weld bead 1201 extend in perpendicular directions, which can reduce the constraint of the weld at the connection between the horizontal weld bead 1101 and the transverse weld bead 1201, and also facilitate the welding of the transverse weld bead 1201. Preferably, both the horizontal weld bead 1101 and the transverse weld bead 1201 can be made of D547Mo material with a diameter of 4 mm, so that the weld overlay has good wear resistance, heat resistance, corrosion resistance and other properties, but the present invention is not limited thereto.

[0049] On the other hand, combined with the appendix Figures 3-4 As shown, this embodiment provides a welding method for the weld overlay layer of a pipe fitting as described above, including: step S1, dividing the area to be welded on the side wall of the pipe fitting 100 into a horizontal weld overlay area 101 and a transverse weld overlay area 102; step S2, welding is performed in the horizontal weld overlay area 101 along the circumference of the pipe fitting 100 to form a horizontal weld overlay section 110; step S3, welding is performed in the transverse weld overlay area 102 along the axial direction of the pipe fitting 100 to form a transverse weld overlay section 120; and step S4, performing post-heat treatment on the horizontal weld overlay section 110 and the transverse weld overlay section 120.

[0050] Specifically, in step S1, all the horizontal weld overlay areas 101 are distributed at intervals along the circumference of the pipe fitting 100, and each horizontal weld overlay area 102 is located between two adjacent horizontal weld overlay areas 101, that is, the gap between two adjacent horizontal weld overlay areas 101 is the horizontal weld overlay area 102, so that the horizontal weld overlay area 102 and the horizontal weld overlay area 101 are connected to form a closed circular area to be welded, thereby making the horizontal weld overlay section 120 and the horizontal weld overlay section 110 connected to form a closed annular weld overlay layer. More specifically, in the circumferential direction of the pipe fitting 100, the sum of the arc lengths of all the horizontal weld overlay areas 101 can account for 80% to 95% of the circumference of the pipe fitting 100, and the sum of the arc lengths of all the transverse weld overlay areas 102 can account for 5% to 20% of the circumference of the pipe fitting 100; and all the horizontal weld overlay areas 101 and all the transverse weld overlay areas 102 are symmetrically distributed, so that all the horizontal weld overlay segments 110 and all the transverse weld overlay segments 120 are also symmetrically distributed, thereby ensuring that the restraint degree of each weld between the horizontal weld overlay segment 110 and the transverse weld overlay segment 120 is the same, but the present invention is not limited thereto.

[0051] In this embodiment, the outer diameter of the pipe fitting 100 is 300 mm; the number of the horizontal weld overlay area 101 and the transverse weld overlay area 102 on the outer side wall of the pipe fitting 100 is two, and the arc length of each transverse weld overlay area 102 in the circumferential direction of the pipe fitting 100 is 30 mm to 50 mm.

[0052] Please continue to refer to this. Figure 4 Step S2 includes: step S201, fixing the pipe fitting 100 to a rotating mechanism to rotate the pipe fitting 100; step S202, preheating the horizontal weld overlay area 101 to a first preset temperature and maintaining it; and step S203, welding along the circumference of the pipe fitting 100 in the horizontal weld overlay area 101 to form a layer of horizontal weld beads 1101 extending along the circumference of the pipe fitting 100 and arranged along the axial direction of the pipe fitting 100; and all the horizontal weld beads 1101 in the same layer constitute a layer of horizontal weld overlay segment 110.

[0053] It is understood that when the number of weld overlay layers of the pipe fitting is greater than 1 layer, step S2 further includes: step S204, welding along the circumference of the pipe fitting 100 on the previous horizontal weld overlay section to form a subsequent horizontal weld overlay extending along the circumference of the pipe fitting 100 and arranged along the axial direction of the pipe fitting 100; and all the horizontal weld overlays of the subsequent layer constitute the subsequent horizontal weld overlay section.

[0054] It is understood that the horizontal weld overlay section and the transverse weld overlay section on the same layer form a stack of weld layers, and the current used when welding the latter stack of weld layers is greater than the current used when welding the former stack of weld layers.

[0055] Specifically, in this embodiment, before performing step S2, the area to be welded and its surrounding 50mm area need to be cleaned with alcohol or acetone to ensure that the surface to be welded and its edges are free of water stains, oxides, oil stains, slag, and any other foreign substances that may affect the welding quality. In step S201, when the pipe fitting 100 is assembled onto the rotating mechanism, the axis of the pipe fitting 100 can be adjusted to a horizontal position, and the axis of the pipe fitting 100 remains unchanged, i.e., always in a horizontal position, during the rotation of the pipe fitting 100 driven by the rotating mechanism. This allows the operator to weld the horizontal weld overlay area 101 on the rotating pipe fitting 100 from a flat welding position. Preferably, the rotating mechanism is a positioner, but the present invention is not limited thereto.

[0056] Specifically, in this embodiment, there are two horizontal weld overlay areas 101, which can be referred to as the first horizontal weld overlay area and the second horizontal weld overlay area, respectively. When welding the first horizontal weld overlay area, it is necessary to preheat the first horizontal weld overlay area to the first preset temperature throughout the welding process to reduce the hardening tendency. Under the conditions of the first preset temperature and the rotation of the pipe fitting 100, a manual argon arc welding process is used to weld along the circumference of the pipe fitting 100 to form a layer of horizontal weld beads 1101 extending along the circumference of the pipe fitting 100 and arranged along the axial direction of the pipe fitting 100 in the first horizontal weld overlay area. During welding, it is also necessary to control the temperature between adjacent horizontal weld beads to be less than or equal to 500°C, preferably less than or equal to 450°C. More specifically, the number of weld overlay layers can be four, referred to as the first weld overlay layer, the second weld overlay layer, the third weld overlay layer, and the fourth weld overlay layer, respectively. Then, the number of layers of the horizontal weld overlay section 110 is also four, referred to as the first horizontal weld overlay section, the second horizontal weld overlay section, the third horizontal weld overlay section, and the fourth horizontal weld overlay section, respectively. In the first horizontal weld overlay area, the first horizontal weld overlay section can be a horizontal weld overlay section directly welded onto the pipe fitting 100. At this time, it is also necessary to weld a second horizontal weld overlay section along the circumference of the pipe fitting 100 on the already welded first horizontal weld overlay section, weld a third horizontal weld overlay section along the circumference of the pipe fitting 100 on the second horizontal weld overlay section, and weld a fourth horizontal weld overlay section along the circumference of the pipe fitting 100 on the third horizontal weld overlay section. Optionally, the first preset temperature is greater than or equal to 200°C, preferably, the first preset temperature is greater than or equal to 300°C; the current used when welding the subsequent horizontal weld overlay section is greater than the current used when welding the previous horizontal weld overlay section, wherein detailed welding parameters are shown in Table 1, but the present invention is not limited thereto.

[0057] Table 1 Welding parameters

[0058]

[0059] Similarly, four horizontal weld overlay sections are completed in the second horizontal weld overlay area, and the welding process for the second horizontal weld overlay area is the same as the welding process for the first horizontal weld overlay area, but the present invention is not limited thereto.

[0060] Please continue to refer to this. Figure 1 Step S3 includes: step S301, preventing the pipe fitting from rotating; step S302, preheating the horizontal weld overlay area to a second preset temperature and maintaining it; and step S303, performing welding along the axial direction of the pipe fitting in the horizontal weld overlay area to form a layer of horizontal weld overlays extending along the axial direction of the pipe fitting and arranged circumferentially along the pipe fitting; and all horizontal weld overlays in the same layer constitute a layer of horizontal weld overlays.

[0061] It is understood that when the number of weld overlay layers of the pipe fitting is greater than 1 layer, step S3 further includes: step S304, welding along the axial direction of the pipe fitting on the previous layer of horizontal weld overlay section to form a subsequent layer of horizontal weld overlay that extends along the axial direction of the pipe fitting and is arranged circumferentially along the pipe fitting; and all the horizontal weld overlays of the subsequent layer constitute the subsequent layer of horizontal weld overlay section.

[0062] Specifically, in this embodiment, after all layers of horizontal weld overlay sections on the pipe fitting 100 are welded, step S3 can be executed. Before executing step S3, the arc initiation and arc termination points of the horizontal weld overlay section 110 need to be ground to make it smoothly transition with the pipe fitting 100. The area to be welded and the surrounding 50mm area are cleaned with alcohol or acetone to ensure that the surface to be welded and the edges are free of water stains, oxides, oil stains, slag, and any other foreign substances that may affect the welding quality. However, the present invention is not limited thereto.

[0063] Specifically, in this embodiment, the two transverse weld overlay zones 102 can be referred to as the first transverse weld overlay zone and the second transverse weld overlay zone, respectively. When welding the first transverse weld overlay zone, it is necessary to preheat the first transverse weld overlay zone to the second preset temperature throughout the welding process to reduce the hardening tendency. Under the conditions of the second preset temperature and the pipe fitting 100 being stationary, a manual argon arc welding process is used to weld along the axial direction of the pipe fitting 100 to form a layer of transverse weld beads 1201 extending along the axial direction of the pipe fitting 100 and arranged circumferentially in the first transverse weld overlay zone. During welding, it is also necessary to control the temperature between adjacent transverse weld beads 1201 to be less than or equal to 500°C, preferably less than or equal to 450°C. More specifically, since the number of layers of the weld overlay is 4, the number of layers of the horizontal weld overlay section 120 is also 4, respectively referred to as the first horizontal weld overlay section, the second horizontal weld overlay section, the third horizontal weld overlay section and the fourth horizontal weld overlay section; in the first horizontal weld overlay area, the first horizontal weld overlay section can be a horizontal weld overlay section directly welded on the pipe fitting 100. At this time, it is also necessary to weld the second horizontal weld overlay section along the axial direction of the pipe fitting 100 on the already welded first horizontal weld overlay section, weld the third horizontal weld overlay section along the axial direction of the pipe fitting 100 on the second horizontal weld overlay section, and weld the fourth horizontal weld overlay section along the axial direction of the pipe fitting 100 on the third horizontal weld overlay section. Optionally, the second preset temperature is greater than or equal to 200°C; preferably, the second preset temperature is greater than or equal to 300°C; the current used when welding the subsequent horizontal overlay section is greater than the current used when welding the previous horizontal overlay section, wherein detailed welding parameters are shown in Table 1, but the present invention is not limited thereto.

[0064] Similarly, four layers of horizontal weld overlay are completed in the second horizontal weld overlay area, and the welding process for the second horizontal weld overlay area is the same as the welding process for the first horizontal weld overlay area. Preferably, the welding of each layer of horizontal weld overlay in the first horizontal weld overlay area and the welding of the same layer of horizontal weld overlay in the second horizontal weld overlay area are performed simultaneously. If they cannot be performed simultaneously, the same layer of horizontal weld overlay in the first and second horizontal weld overlay areas should be alternately welded as quickly as possible, but the present invention is not limited thereto.

[0065] Specifically, in this embodiment, in step S4, after all welding work is completed, the weld overlay can be post-heat treated by electric infrared or flame heating to accelerate the escape of hydrogen from the weld metal, greatly reduce the hydrogen content in the weld and heat-affected zone, thereby achieving hydrogen removal from the weld overlay and preventing weld cracking. Preferably, the post-heat treatment temperature is 350℃~400℃ and the treatment time is greater than or equal to 6 hours, but the present invention is not limited thereto.

[0066] In addition, in this embodiment, the following should be noted during the welding of the horizontal weld overlay area and the transverse weld overlay area: (1) Avoid oscillating welding as much as possible. If oscillation is necessary, the oscillation amplitude should be as small as possible, and the oscillation width of the weld overlay should not exceed 3 times the diameter of the weld core; (2) The overlapping area between weld overlays in the same layer must be ground. The obvious arc pits generated by arc initiation or arc termination must be ground. The undercut edges and poorly formed areas of the weld overlay must be ground immediately to ensure that the weld overlay surface is smooth and continuously transitioned to the adjacent area; (3) Each weld overlay layer must be ground. It should be ground flat, and the depth of the unground parts should not exceed 1 mm.

[0067] In summary, this embodiment provides a weld overlay layer for a pipe fitting and its welding method. Horizontal weld overlay sections are spaced circumferentially along the pipe fitting, and a transverse weld overlay section is provided between two adjacent horizontal weld overlay sections. The transverse weld overlay sections and the horizontal weld overlay sections are connected to form an annular weld overlay layer. The staggered distribution of the horizontal and transverse weld overlay sections results in multiple weld seams in the weld overlay layer, thereby reducing the constraint of each weld seam while maintaining the pipe diameter, thus preventing weld cracking and improving the reliability of the weld overlay layer. In this embodiment, the horizontal weld beads in the horizontal weld overlay sections extend circumferentially along the pipe fitting, and the transverse weld beads in the transverse weld overlay sections extend axially along the pipe fitting. The extension directions of the horizontal and transverse weld beads are perpendicular, which also reduces the constraint of the weld seam at the connection between the horizontal and transverse weld beads and facilitates the welding of the transverse weld beads. Furthermore, in this embodiment, when welding along the circumference of the pipe fitting in the horizontal weld overlay zone to form a horizontal weld overlay section and welding along the axial direction of the pipe fitting in the transverse weld overlay zone to form a transverse weld overlay section, the horizontal weld overlay zone and the transverse weld overlay zone are preheated to 300°C or higher throughout the welding process, which can reduce the hardening tendency. After the welding is completed, the horizontal weld overlay section and the transverse weld overlay section, i.e. the weld overlay layer, are subjected to post-heat treatment, which can accelerate the escape of hydrogen in the weld metal, greatly reduce the hydrogen content in the weld and heat-affected zone, thereby achieving the purpose of removing hydrogen from the weld overlay layer and thus avoiding weld cracking.

[0068] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A weld overlay layer for a pipe fitting, characterized in that, include: Several horizontal weld overlay sections (110) are disposed on the sidewall of the pipe fitting (100) and are distributed at intervals along the circumference of the pipe fitting (100); and Several horizontal weld overlay sections (120) are disposed on the side wall of the pipe fitting (100); each of the horizontal weld overlay sections (120) is located between two adjacent horizontal weld overlay sections (110), and the horizontal weld overlay sections (120) and the horizontal weld overlay sections (110) are connected to form an annular weld overlay layer. Each of the horizontal weld overlay sections (110) includes a plurality of horizontal weld beads (1101), each of the horizontal weld beads (1101) extends circumferentially along the pipe fitting (100), all the horizontal weld beads (1101) are arranged parallel to each other along the axial direction of the pipe fitting (100), and there is no gap between adjacent horizontal weld beads (1101). Each of the horizontal weld overlay sections (120) includes a plurality of horizontal weld beads (1201), each of the horizontal weld beads (1201) extending along the axial direction of the pipe fitting (100), all of the horizontal weld beads (1201) being arranged in parallel along the circumference of the pipe fitting (100), and there being no gap between adjacent horizontal weld beads (1201).

2. A method for welding the weld overlay layer of a pipe fitting as described in claim 1, characterized in that, include: The area to be welded on the side wall of the pipe fitting is divided into a horizontal weld overlay area and a transverse weld overlay area. Welding is performed along the circumference of the pipe fitting in the horizontal weld overlay area to form a horizontal weld overlay section; Welding is performed along the axial direction of the pipe fitting in the transverse weld overlay area to form a transverse weld overlay section; and The horizontal weld overlay section and the transverse weld overlay section undergo post-heat treatment.

3. The welding method for the weld overlay layer of pipe fittings as described in claim 2, characterized in that, All of the horizontal weld overlay zones are distributed circumferentially along the pipe fitting, with each horizontal weld overlay zone located between two adjacent horizontal weld overlay zones.

4. The welding method for the weld overlay layer of pipe fittings as described in claim 3, characterized in that, The step of welding along the circumference of the pipe fitting in the horizontal weld overlay area to form the horizontal weld overlay section includes: The pipe fitting is fixed to a rotating mechanism to allow the pipe fitting to rotate. Preheat the horizontal weld overlay area to a first preset temperature and maintain it; and Welding is performed along the circumference of the pipe fitting within the horizontal weld overlay zone to form a layer of horizontal weld beads that extend circumferentially and are arranged axially along the pipe fitting; and all horizontal weld beads in the same layer constitute a horizontal weld overlay segment.

5. The welding method for the weld overlay layer of pipe fittings as described in claim 4, characterized in that, The step of welding along the axial direction of the pipe fitting in the transverse weld overlay zone to form the transverse weld overlay section includes: This prevents the pipe fitting from rotating; Preheat the transverse overlay welding zone to a second preset temperature and maintain it; and Welding is performed along the axial direction of the pipe fitting within the horizontal weld overlay zone to form a layer of horizontal weld beads that extend along the axial direction of the pipe fitting and are arranged circumferentially along the pipe fitting; and all horizontal weld beads in the same layer constitute a layer of horizontal weld overlay segment.

6. The welding method for the weld overlay layer of pipe fittings as described in claim 5, characterized in that, When the number of weld overlay layers on the pipe fitting is greater than one, it also includes: Welding is performed circumferentially on the preceding horizontal weld overlay section to form a subsequent horizontal weld bead extending circumferentially and arranged axially along the pipe fitting; and all horizontal weld beads of the subsequent layer constitute the subsequent horizontal weld overlay section; and Welding is performed along the axial direction of the pipe fitting on the previous layer of horizontal weld overlay to form a subsequent layer of horizontal weld overlay extending along the axial direction of the pipe fitting and arranged circumferentially along the pipe fitting; and all the horizontal weld overlays of the subsequent layer constitute the subsequent layer of horizontal weld overlay.

7. The welding method for the weld overlay layer of pipe fittings as described in claim 6, characterized in that, The horizontal and horizontal weld overlay sections in the same layer form a weld layer, and the current used when welding the latter weld layer is greater than the current used when welding the former weld layer.

8. The welding method for the weld overlay layer of pipe fittings as described in claim 6, characterized in that, Both the first preset temperature and the second preset temperature are greater than or equal to 200°C; The temperature between adjacent horizontal weld beads and the temperature between adjacent transverse weld beads are both less than or equal to 500℃.

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