Tube and tube plate sealing weld joint of steam generator and welding method

Abstract

The invention belongs to the technical field of welding, and provides a pipe and pipe plate sealing weld joint of a steam generator and a welding method, and the weld joint is subjected to wire filling welding by adopting a welding head with yawing and reducing rotation functions; the welding seam comprises a base layer, a filling layer and a covering layer, the bottoming layer covers the groove of the tube plate and the end part of the tube and has a penetration depth; the width of the base layer ranges from 5.3 mm to 5.7 mm, and the thickness of the base layer ranges from 1.3 mm to 1.7 mm. The fusion depth ranges from 0.3 mm to 0.7 mm; the filling layer covers the base layer; the width of the filling layer is 4.8 to 5.2 mm, and the thickness of the filling layer is 1 to 1.4 mm; the surface covering layer covers the filling layer; the width of the covering layer ranges from 6.8 mm to 7.2 mm, and the thickness of the covering layer ranges from 1.3 mm to 1.7 mm. According to the method, the problems of root cracks, welding throat size and necking of nickel-based tube-tube plate seal welding can be effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a sealing weld of a tube sheet of a steam generator and a welding method. Background Art

[0002] The main steam tube sheet of the high temperature gas-cooled reactor steam generator is made of Incoloy 800H forgings, the heat exchange tube is Incoloy800H tube, the heat exchange tube specification is φ19×3, the tube sheet needs to be sealed and welded (sealing welding), and after welding, it is necessary to ensure that the inner diameter of the tube hole is not less than φ12.3, the weld throat size is ≥1e (tube wall thickness), and the weld thickness size control range is only 0.35mm. If the weld is too convex, the expansion rod of the subsequent hydraulic expansion process cannot enter, and if the weld has no convexity, the designed weld throat size will be insufficient.

[0003] However, since Incoloy 800H nickel-based alloy is a unidirectional austenite structure, it has the characteristics of poor liquid metal fluidity and shallow weld metal melting depth, and has a tendency to thermal cracks. Crystallization cracks are easily generated during welding. The thermal cracks of nickel-based materials are mainly caused by the large linear expansion coefficient and low thermal conductivity, which leads to the segregation and aggregation of impurity elements and low-melting-point substances in the weld at the grain boundary, forming a low-melting-point eutectic. In order to prevent thermal cracks, reasonable welding joint design is usually adopted in the design to reduce structural constraints and welding stress. In terms of technology, the temperature of the molten pool must be reduced as much as possible to shorten the high-temperature residence time while ensuring good weld fusion. The parameters related to the molten pool temperature are mainly heat input and filler metal amount, that is, a small heat input and a large filler metal amount must be used to avoid overheating of the molten pool, thereby reducing the sensitivity of thermal cracks.

[0004] In addition, for the tube-tube sheet sealing welding structure, the root of the weld is in a type I (opening) crack state due to the existence of an initial assembly gap. This gap can be regarded as the initial crack source, where obvious stress concentration will occur, which will cause a sharp drop in structural strength. Even smaller stresses and strains will cause crack initiation and expansion. Therefore, the root area of ​​the weld is the weakest point in the entire structure both during the welding process and in the subsequent product operation process.

[0005] In the field of nuclear power, the existing technology usually uses the Polysoldi tube and tube sheet machine head for welding the sealing welds of the tube and tube sheet of the steam generator of the main equipment of the nuclear island. This is the most mature process at present, with good process stability. The welding equipment mainly includes TS25 (self-melting), TS34 (self-melting), and TS2000 (filling wire). However, for the sealing welding structure of the tube and tube sheet of the steam generator of the new generation of nuclear power high-temperature gas-cooled reactor, higher requirements are placed on strength and sealing, and the weld throat size is required to be ≥1e (3mm), so self-melting welding cannot be used (the penetration depth cannot meet the requirements). The TS2000 equipment in the existing technology itself has certain limitations. The machine head has a simple structure, the position of the tungsten electrode relative to the workpiece is fixed, and it cannot be automatically adjusted. It is impossible to achieve swing welding and variable diameter welding, etc. Therefore, the weld size has a low degree of freedom for adjustment, and the weld forming size is strongly related to the welding parameters (current, voltage, speed), especially under the condition of specified welding heat input, the weld forming shape has a strong regularity (under the same heat input conditions, the width increases, the thickness decreases, and the penetration depth decreases).

[0006] When TS2000 welding is used under the above conditions, if multi-layer single-pass welding is used, considering that the weld needs to have sufficient internal convexity to ensure the 1e weld throat requirement, the weld shape will be as follows: Figure 1 As shown in the figure, the base weld is wide and thin, with shallow penetration and insufficient thickness, which reduces the crack resistance of the root, making it difficult to meet the minimum weld throat requirement and increasing the risk of cracking. If multi-layer and multi-pass welding is used, the theoretical formation of the weld will be as follows Figure 2 As shown in the figure, this state can meet the welding throat and crack problems at the same time; however, in practice, since the minimum arc diameter of the TS2000 equipment is 4-5mm, it is impossible to achieve such Figure 2 The weld bead arrangement shown in the figure, even if it is forced without considering the welding quality, will cause the weld to be too convex, thus failing to meet the requirements for the inner diameter of the pipe hole after welding; at the same time, the multi-layer and multi-pass weld bead arrangement increases the transverse tensile stress perpendicular to the gap, making it more likely to cause crack propagation.

[0007] Based on the above defects, it is necessary to propose a new sealing weld and welding method for the tube sheet of the steam generator to improve the sealing weld crack problem of the tube sheet. Summary of the invention

[0008] In order to overcome the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a tube sheet sealing weld for a steam generator, which can effectively solve the root crack problem of the tube sheet.

[0009] The technical solution adopted by the present invention to solve its technical problem is: A tube sheet sealing weld of a steam generator, which is welded by a welding head with a swing and diameter-changing rotation function; the weld includes a base layer, a filling layer and a cover layer; The base layer covers the tube sheet groove and the tube end and has a penetration depth; the width of the base layer is 5.3-5.7 mm, the thickness is 1.3-1.7 mm; the penetration depth is 0.3-0.7 mm; The filling layer covers the base layer; the width of the filling layer is 4.8-5.2 mm, and the thickness is 1-1.4 mm; The cover layer covers the filling layer; the cover layer has a width of 6.8-7.2 mm and a thickness of 1.3-1.7 mm.

[0010] Preferably, the surface of the primer layer is inclined from one side of the tube sheet to one side of the tube, and the primer layer does not cover the outer end of the groove of the tube sheet.

[0011] Preferably, the filling layer only covers the surface of the base layer, and the surface of the base layer is partially exposed, and the exposed portion is located at an end away from the inner hole of the tube; From the outside to the inside in the radial direction, the surface of the filling layer is curved, and its thickness gradually increases and then gradually decreases, and the maximum thickness is located at the end of the tube.

[0012] Preferably, the cover layer covers the tube sheet groove, the primer layer and the filling layer, and the direct welding point between the tube sheet groove and the cover layer has a penetration depth; The cap layer protrudes from the surface of the tube sheet.

[0013] Another object of the present invention is to provide a welding method for obtaining the above-mentioned weld structure.

[0014] A method for welding the sealing of a tube sheet of a steam generator, using a welding head with a swaying and diameter-changing rotation function to perform wire-filling welding, and pre-processing a groove on the inner side of the tube sheet sealing; comprising the following steps: S1. Welding a base layer at the groove of the tube sheet and the end of the tube; the width of the base layer is controlled at 5.3-5.7 mm, and the thickness is controlled at 1.3-1.7 mm; the base layer has a certain penetration depth, and the penetration depth is controlled at 0.3-0.7 mm; S2, welding a filling layer on the base layer; the width of the filling layer is controlled to be 4.8-5.2 mm, and the thickness is controlled to be 1-1.4 mm; S3, welding a capping layer on the base layer; the width of the capping layer is controlled to be 6.8-7.2 mm, and the thickness is controlled to be 1.3-1.7 mm.

[0015] According to a preferred embodiment of the present invention, before welding, the inner hole of the tube is subjected to positioning expansion treatment to eliminate the gap between the tube and the tube sheet; after the expansion treatment is completed, the expansion area and the welding area are cleaned.

[0016] A preferred solution of the present invention is to edit the welding program, input the welding parameters, and locate the pipe hole before the formal welding. Subsequently, the angle, position and rotation radius of the welding head are adjusted according to the position of the inner hole of the pipe; the wire feeding elbow position of the welding equipment is adjusted and fixed to ensure the relative position and distance between the fed welding wire and the tungsten electrode.

[0017] Preferably, during the welding process, the deviation between the actual value of the welding parameter and the input set value is monitored in real time, and the fluctuation range shall not exceed 2%.

[0018] A preferred embodiment of the present invention is that during the welding of the base layer, when the welding head reaches the 3 o'clock and 9 o'clock positions of the seal, the residence time on the tube side and the tube sheet side is equal; when the welding head reaches the 6 o'clock position of the seal, the residence time on the tube side is shorter than the residence time on the tube sheet side; when the welding head reaches the 12 o'clock position of the seal, the residence time on the tube side is longer than the residence time on the tube sheet side.

[0019] In a preferred embodiment of the present invention, the surface of the primer layer is inclined along the direction from the tube sheet groove to the tube end; When welding the filling layer, the residence time of the welding head on the tube sheet side is shorter than that on the tube side.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a reasonable weld shape and size of the base layer, the filling layer and the cover layer, so that the sealing welding effect of the tube and tube sheet of the steam generator is significantly improved, especially the matching method of the weld bead forming size, which can effectively solve the root cracks, weld throat size and shrinkage problems of the nickel-based tube and tube sheet sealing welding. In addition, the present invention applies a welding head with a swing function and a variable diameter rotation function to the tube and tube sheet sealing welding, so that the width of each weld is not limited by the filler metal specification and heat input, and the weld bead forming size is accurately controlled, and the weld bead width and thickness are freely controlled. Under the same heat input level, a good weld formation (weld flatness, small convexity, large thickness and suitable penetration depth) is obtained; in addition, the swing function makes the molten pool more symmetrical, so that the weld surface is smoother and better in quality, and the influence on the welding of the subsequent layer is reduced, and no surface treatment is required; in the swing welding process, the arc also has a stirring effect on the molten pool, which helps to discharge the gas, thereby reducing the generation of pores. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0022] Figure 1 Schematic diagram of the weld seam using TS2000 for multi-layer single-pass welding (the red filled area in the figure represents the weld pass, and the dotted circle range is the theoretical weld throat).

[0023] Figure 2 This is a schematic diagram of a weld using TS2000 for multi-layer and multi-pass welding (the red filled area in the figure represents the weld, and the dotted circle range is the theoretical weld throat).

[0024] Figure 3 The figure is a schematic diagram of the sealing weld of the tube and tube sheet of the steam generator of the present invention.

[0025] Figure 4 The figure is a diagram showing the actual forming effect of the sealing weld of the tube and tube sheet of the steam generator of the present invention.

[0026] in: 1-tube sheet, 2-tube, 3-base layer, 4-filling layer, 5-covering layer. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth in order to fully understand the present invention, and the embodiments described are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0029] See also Figure 3-Figure 4The present embodiment discloses a tube-tube sheet sealing weld of a steam generator, which is welded by a welding head with a swaying and variable diameter rotation function; the weld includes a primer layer 3, a filling layer 4 and a cover layer 5; the primer layer 3 covers the groove of the tube sheet 1 and the end of the tube 2, and has a penetration depth; the width W1 of the primer layer 3 is 5.3-5.7mm, and the thickness h1 is 1.3-1.7mm; the penetration depth is 0.3-0.7mm; the filling layer 4 covers the primer layer 3; the width W2 of the filling layer 4 is 4.8-5.2mm, and the thickness h2 is 1-1.4mm; the cover layer 5 covers the filling layer 4; the width W3 of the cover layer 5 is 6.8-7.2mm, and the thickness h3 is 1.3-1.7mm.

[0030] Furthermore, the surface of the primer layer 3 is inclined from the tube sheet 1 side to the tube 2 side, and the primer layer 3 does not cover the outer end of the groove of the tube sheet 1. Such a primer layer 3 is convenient for the subsequent filling layer 4 to be arranged, and is inclined and relatively flat, making the welding of the filling layer 4 more flexible and easy. Moreover, the primer layer 3 is particularly important for solving the crack problem of the tube sheet. When welding the primer layer 3, this embodiment has a certain penetration depth with the groove position of the tube sheet 1 and the end of the tube 2, so that the weld of the primer layer 3 has a more reliable stress effect on the tube sheet 1 and the tube 2, which can effectively improve the stress state of the joint and avoid the continuous effect of the welding residual stress generated by the subsequent layer and the root gap to induce cracks and expansion.

[0031] Furthermore, the filling layer 4 only covers the surface of the base layer 3, and the surface of the base layer 3 is partially exposed, and the exposed portion is located at an end away from the inner hole of the tube 2. From the outside to the inside along the radial direction, the surface of the filling layer 4 is curved, and its thickness gradually increases and then gradually decreases, and the maximum thickness position is located at the end of the tube 2.

[0032] More importantly, when welding the filling layer 4, the present embodiment takes advantage of the relatively flat surface structure of the base layer 3, making the welding of the filling layer 4 more convenient, and makes the surface of the filling layer 4 close to being flush with the tube sheet 1 during welding, thereby providing favorable conditions for the subsequent welding of the cover layer 5.

[0033] Furthermore, the cap layer 5 covers the groove of the tube sheet 1, the base layer 3 and the filling layer 4, and the direct welding between the groove of the tube sheet 1 and the cap layer 5 has a deep penetration; the cap layer 5 protrudes from the surface of the tube sheet 1. The cap layer 5 is in contact with the tube sheet 1, the base layer 3 and the filling layer 4, forming a mutual aggregation to strengthen the anti-cracking ability, which is conducive to making the strength of the entire weld greater and further avoiding the occurrence of cracks.

[0034] This embodiment also discloses a welding method for obtaining the above-mentioned weld structure, which uses a welding head with sway and variable diameter rotation functions for wire welding. The sway function of the welding head can be realized by adding a motor drive, and the corresponding software system is used for control during welding. The groove is pre-processed on the inner side of the sealing of the tube sheet 1, the angle between the groove and the end face is 40°, and the groove depth is 3-3.5mm; the following steps are included: S1. Welding a base layer 3 at the groove of the tube sheet 1 and the end of the tube 2; the width W1 of the base layer 3 is controlled at 5.3-5.7 mm, and the thickness h1 is controlled at 1.3-1.7 mm; the base layer 3 has a certain penetration depth, which is controlled at 0.3-0.7 mm; S2, welding a filling layer 4 on the base layer 3; the width W2 of the filling layer 4 is controlled to be 4.8-5.2 mm, and the thickness h2 is controlled to be 1-1.4 mm; S3, welding a capping layer 5 on the base layer 3; the width W3 of the capping layer 5 is controlled within a range of 6.8-7.2 mm, and the thickness h3 is controlled within a range of 1.3-1.7 mm.

[0035] Furthermore, before welding, the inner hole of the tube 2 is subjected to positioning expansion treatment to eliminate the gap between the tube 2 and the tube sheet 1; after the expansion treatment is completed, the expansion area and the welding area are cleaned. The inner hole of the tube 2 is expanded near the tube sheet 1, and the expansion distance is 15-30mm.

[0036] Furthermore, before the formal welding, edit the welding program, enter the welding parameters, and locate the hole of pipe 2. The positioning can be done by visual photography. Then, adjust the angle, position and rotation radius of the welding head according to the position of the inner hole of pipe 2; adjust and fix the wire feeding elbow position of the welding equipment to ensure the relative position and distance between the fed welding wire and the tungsten electrode. After the welding is completed, the weld surface should be visually inspected, the weld size, weld penetration, weld ray and destructive test of the witness piece should be carried out.

[0037] Furthermore, during the welding of the base layer 3, when the welding head reaches the 3 o'clock and 9 o'clock positions of the seal, the dwelling time on the tube 2 side and the tube sheet 1 side is equal; when the welding head reaches the 6 o'clock position of the seal, the dwelling time on the tube 2 side is shorter than the dwelling time on the tube sheet 1 side; when the welding head reaches the 12 o'clock position of the seal, the dwelling time on the tube 2 side is longer than the dwelling time on the tube sheet 1 side. For example, when the welding head is at the 9 o'clock and 3 o'clock positions, the dwelling time on the tube 2 side and the tube sheet 1 side is 0.2s; when the welding head reaches the 12 o'clock position, the dwelling time on the tube 2 side is 0.4s, and the dwelling time on the tube sheet 1 side is 0.2s. When the welding head reaches the 6 o'clock position, the dwelling time on the tube 2 side is 0.2s, and the dwelling time on the tube sheet 1 side is 0.4s. The base layer 3 is welded in this way to resist the influence of gravity on the formation of the molten pool, ensure that the amount of filling metal in the entire circumferential area is equivalent, the weld roundness is better, and the size is consistent. At the same time, it also avoids the influence of uneven residual stress after welding on the root gap and reduces the risk of cracking.

[0038] Furthermore, the surface of the base layer 3 is inclined along the direction from the groove of the tube sheet 1 to the end of the tube 2; when welding the filling layer 4, the residence time of the welding head on the tube sheet 1 side is shorter than the residence time on the tube 2 side. By setting the residence time parameter of the welding head, the surface of the weld of the filling layer 4 after welding is smoother, so that the convexity of the weld can be better controlled (if the weld surface is an inclined surface, the molten iron in the molten pool flows along the slope direction of the groove under the influence of gravity, and it is not easy to control the convexity of the weld), making the subsequent channeling simpler and easier to control the balance between the weld throat and the weld convexity, so as to meet the requirements of the weld throat and the weld convexity at the same time.

[0039] In addition, during the welding process, pay real-time attention to the deviation between the actual value of the welding parameter and the entered set value, and the fluctuation range shall not exceed 2%.

[0040] The welding parameters of this embodiment can be seen in the following table:

[0041] "T" in the table indicates the initial centering position of the welding head; "left stop" indicates that the welding head stays on the tube 2 side; "right stop" indicates that the welding head stays on the tube sheet 1 side.

[0042] This embodiment provides a reasonable weld shape and size of the base layer 3, the filling layer 4 and the cover layer 5, so that the welding effect of the tube sheet sealing of the steam generator is significantly improved, and the problem of weld cracks is effectively solved. In addition, the welding head with swing function and variable diameter rotation function is applied to the tube sheet sealing welding, so that the width of each weld is not limited by the filler metal specifications and heat input, and the weld width and thickness can be freely controlled. Under the same heat input level, a good weld formation (weld flatness, small convexity, large thickness and suitable penetration depth) is obtained; in addition, the swing function makes the molten pool more uniform, so that the weld surface is smoother and the quality is better, reducing the impact on the welding of the subsequent layers, and no surface treatment is required; during the swing welding process, the arc also has a stirring effect on the molten pool, which helps to discharge the gas, thereby reducing the generation of pores. At the same time, combined with the above welding parameters, controlling the temperature of the welding molten pool is conducive to reducing the high temperature residence time of the liquid metal in the molten pool and avoiding the generation of thermal cracks.

[0043] Through the weld joint and welding method of this embodiment, the inner convexity of the weld formed meets the requirements, thereby meeting the requirements of the inner diameter of the inner hole of the pipe 2 after welding; at the same time, the multi-layer and multi-pass weld arrangement increases the transverse tensile stress perpendicular to the gap, thereby solving the problem of crack extension.

[0044] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A tube sheet sealing weld of a steam generator, characterized in that: A welding head with a swing and diameter-changing rotation function is used for wire-filling welding; the weld includes a base layer, a filling layer and a cover layer; The base layer covers the tube sheet groove and the tube end and has a penetration depth; the width of the base layer is 5.3-5.7 mm, the thickness is 1.3-1.7 mm; the penetration depth is 0.3-0.7 mm; The filling layer covers the base layer; the width of the filling layer is 4.8-5.2 mm, and the thickness is 1-1.4 mm; The cover layer covers the filling layer; the cover layer has a width of 6.8-7.2 mm and a thickness of 1.3-1.7 mm.

2. The tube sheet sealing weld of a steam generator according to claim 1, characterized in that: The surface of the primer layer is inclined from one side of the tube sheet to one side of the tube, and the primer layer does not cover the outer end of the groove of the tube sheet.

3. The tube sheet sealing weld of the steam generator according to claim 2, characterized in that: The filling layer only covers the surface of the base layer, and the surface of the base layer is partially exposed, and the exposed portion is located at an end away from the inner hole of the pipe; From the outside to the inside in the radial direction, the surface of the filling layer is curved, and its thickness gradually increases and then gradually decreases, and the maximum thickness is located at the end of the tube.

4. The tube sheet sealing weld of the steam generator according to claim 3, characterized in that: The cover layer covers the tube sheet groove, the base layer and the filling layer, and the direct welding point between the tube sheet groove and the cover layer has a fusion depth; The cap layer protrudes from the surface of the tube sheet.

5. A welding method for obtaining the sealing weld of the tube sheet of a steam generator according to any one of claims 1 to 4, characterized in that: The welding head with the function of swaying and reducing diameter rotation is used for wire welding, and the groove is pre-processed on the inner side of the tube sheet seal; the following steps are included: S1. Welding a base layer at the groove of the tube sheet and the end of the tube; the width of the base layer is controlled at 5.3-5.7 mm, and the thickness is controlled at 1.3-1.7 mm; the base layer has a certain penetration depth, and the penetration depth is controlled at 0.3-0.7 mm; S2, welding a filling layer on the base layer; the width of the filling layer is controlled to be 4.8-5.2 mm, and the thickness is controlled to be 1-1.4 mm; S3, welding a capping layer on the base layer; the width of the capping layer is controlled to be 6.8-7.2 mm, and the thickness is controlled to be 1.3-1.7 mm.

6. The welding method according to claim 5, characterized in that: Before welding, the inner hole of the tube is positioned and expanded to eliminate the gap between the tube and the tube sheet; after the expansion treatment is completed, the expansion area and the welding area are cleaned.

7. The welding method according to claim 6, characterized in that: Before formal welding, edit the welding procedure, enter the welding parameters, and locate the pipe hole; Subsequently, the angle, position and rotation radius of the welding head are adjusted according to the position of the inner hole of the pipe; the wire feeding elbow position of the welding equipment is adjusted and fixed to ensure the relative position and distance between the fed welding wire and the tungsten electrode.

8. The welding method according to claim 6, characterized in that: During the welding process, pay real-time attention to the deviation between the actual value of the welding parameter and the entered set value, and the fluctuation range shall not exceed 2%.

9. The welding method according to claim 6, characterized in that: During the welding of the base layer, when the welding head reaches the 3 o'clock and 9 o'clock positions of the seal, the residence time on the tube side and the tube sheet side is equal; when the welding head reaches the 6 o'clock position of the seal, the residence time on the tube side is shorter than the residence time on the tube sheet side; when the welding head reaches the 12 o'clock position of the seal, the residence time on the tube side is longer than the residence time on the tube sheet side.

10. The welding method according to claim 9, characterized in that: The surface of the base layer is inclined along the direction from the tube sheet groove to the tube end; When welding the filling layer, the residence time of the welding head on the tube sheet side is shorter than that on the tube side.

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