A j-groove welding method

Abstract

The application discloses a J-type groove welding method for a pressure container. A through hole is arranged on a top cover of the pressure container to pass through a penetrating piece. An inner surface of the top cover is provided with a stainless steel overlay. A J-type groove is formed on the inner side of the top cover and close to the through hole. The J-type groove welding method comprises the following steps: welding around the edge of the J-type groove on the stainless steel overlay to form a boss; welding on the surface of the J-type groove to form an isolation layer; removing the boss; assembling the penetrating piece into the through hole; and welding the J-type groove on the isolation layer to form a main welding part. A groove is reserved at the junction of the main welding part close to the top of the isolation layer. The groove is welded to fill the groove. The application can reduce the dilution rate of the surface of dissimilar metals, effectively improve the quality of the nickel-based dissimilar metal weld, and reduce the generation of PT display defects.

Description

Technical Field

[0001] This invention relates to the field of pressure vessel technology, and in particular to a J-groove welding method. Background Technology

[0002] Among the components of a reactor pressure vessel (RPV), the control rod drive mechanism (CRDM) is a through-hole component on the top cover of the reactor pressure vessel (hereinafter referred to as the CRDM through-hole component). Its welding to the top cover is a pressure boundary pressure-bearing weld, which needs to withstand harsh service conditions such as high temperature, high pressure and strong neutron radiation. Therefore, the integrity, mechanical properties and corrosion resistance of this weld joint are subject to high requirements.

[0003] In existing technology, a stainless steel weld overlay is formed on the inner surface of the top cover, and the CRDM through-piece is welded to the top cover using a J-groove. Since the CRDM through-piece is made of a nickel-based alloy, this J-groove welding involves welding the stainless steel weld overlay to the nickel-based alloy, and the welding position is irregular. Currently, at the junction of the stainless steel weld overlay and the nickel-based alloy, excessive weld dilution often leads to defects shown in penetration testing (PT).

[0004] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art. Summary of the Invention

[0005] The purpose of this invention is to provide a J-groove welding method that can reduce the dilution rate of dissimilar metal surfaces, effectively improve the quality of nickel-based dissimilar metal welds, and thus reduce the occurrence of PT (potentially induced spectral defects).

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: A J-groove welding method for a pressure vessel; the pressure vessel's top cover has a through hole for a penetrating member to pass through; the inner surface of the top cover has a stainless steel weld overlay, and the J-groove is formed on the inner side of the top cover and near the through hole; the J-groove welding method includes: Weld around the edge of the J-groove on the stainless steel weld overlay to form a ring of bosses; Welding is performed on the surface of the J-groove to form an isolation layer; Remove the boss; The through-hole is assembled into the through-hole; The J-shaped groove is welded on the isolation layer to form the main weld; wherein, a groove is reserved at the junction of the main weld near the top of the isolation layer. Weld the trench to fill it.

[0007] Optionally, the main weld portion includes a filler layer and a reinforcement layer; the step of welding the J-groove on the isolation layer includes: The J-groove is filled with filler weld on the isolation layer to form the filler layer; Welding is performed layer by layer upwards from the filler layer to form the reinforcement layer; and the reinforcement layer extends beyond the surface of the stainless steel weld overlay.

[0008] Optionally, the step of performing a filler weld on the J-groove on the isolation layer includes: The root pass is applied by using a first welding rod of a first diameter close to the outer wall of the through-hole; When welding layer by layer from the root pass upwards, the welds close to the outer wall of the through-piece and the last two welds close to the isolation layer are welded using the first welding rod, while the welds in the remaining areas are welded using a second welding rod with a second diameter greater than the first diameter; and each layer of welding starts from the side close to the outer wall of the through-piece and proceeds towards the side close to the isolation layer.

[0009] Optionally, when welding the augmentation layer, the weld bead close to the outer wall of the through member is welded using the first welding rod, and the weld bead in the remaining area is welded using the second welding rod; and each layer of welding starts from the side close to the outer wall of the through member and proceeds outwards in a row of welds.

[0010] Optionally, the welding step of the trench includes: welding layer by layer from the bottom of the trench upwards to fill the trench; and each layer of welding starts from the side close to the filling layer and proceeds to the side close to the isolation layer for channel welding.

[0011] Optionally, the welding material for the boss is stainless steel.

[0012] Optionally, the height of the boss is greater than 5mm, and the width of the boss is greater than 15mm.

[0013] Optionally, the welding material of the isolation layer, as well as the first welding electrode and the second welding electrode, are all nickel-based welding electrodes.

[0014] Optionally, the first diameter is less than or equal to 2.4 mm.

[0015] Optionally, the width and depth of the trench are both greater than or equal to 8 mm and less than or equal to 15 mm.

[0016] Compared with the prior art, the present invention has at least one of the following advantages: The J-groove welding method provided by this invention forms a ring of bosses around the edge of the J-groove on the stainless steel weld overlay, which avoids the problem of excessive dilution caused by the small geometric angle of the original stainless steel-nickel-based interface. At the same time, the bosses can also provide better residence space for molten slag and gas, thereby improving the slag and gas protection effect of the welding electrode and further reducing the dilution rate.

[0017] In this invention, when welding the filler layer, a small-diameter (e.g., first-diameter) welding rod is used for the root pass and the area near the through-hole. This effectively reduces local heat input, prevents overheating of the through-hole, and ensures good fusion of the outer wall of the through-hole, thereby reducing the dilution rate. Using a small-diameter (e.g., first-diameter) welding rod for the last two layers and the area near the isolation layer (i.e., the easily diluted area) also reduces the dilution rate by lowering local heat input. Furthermore, using a large-diameter (e.g., second-diameter) welding rod in the remaining areas ensures welding efficiency.

[0018] This invention addresses the problem of multi-layer, multi-pass welding and heat accumulation in the dissimilar metal interface area (i.e., the stainless steel-nickel-based interface) by reserving and filling the trench at the end. This makes the dissimilar metal interface area, which is most prone to dilution, a final and independent process. This overcomes the problem of multi-layer, multi-pass welding and heat accumulation in the dissimilar metal interface area when no trench is reserved in the prior art. This ensures the purity of the nickel-based metal in the surface weld and reduces the dilution rate.

[0019] This invention controls the dilution rate of dissimilar metal surfaces by adding bosses, adjusting weld parameters and layout, and reserving grooves, effectively improving the quality of nickel-based dissimilar metal welds, thereby reducing the occurrence of PT (potentially precipitated) defects and reducing rework time. Attached Figure Description

[0020] Figure 1 This is a flowchart of a J-groove welding method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure in one embodiment of the present invention, showing the welding forming an isolation layer; Figure 3 This is a schematic diagram of the structure of the main body formed by welding in one embodiment of the present invention; Figure 4 This is a schematic diagram of an asymmetrical J-shaped bevel provided in one embodiment of the present invention. Detailed Implementation

[0021] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the J-groove 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 aid those skilled in the art, 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.

[0022] Combination Figures 1 to 3 As shown, this embodiment provides a J-groove welding method for pressure vessels. The pressure vessel has a sealed chamber inside, and the top cover 110 of the pressure vessel (see...) Figure 2 The inner surface of the top cover 110 has a stainless steel weld overlay 120 to prevent corrosion of the inner surface of the top cover 110 by substances (e.g., coolant) within the sealed cavity. Further, the top cover 110 is provided with a through-hole 130 (see... Figure 3 Through-hole 111 (see) Figure 2 The J-shaped bevel 100 is formed on the inner side of the top cover 110 and near the through hole 111; it is understood that the J-shaped bevel 100 exposes part of the top cover and part of the stainless steel weld overlay. Optionally, the material of the through member 130 is a nickel-based alloy; the pressure vessel is a reactor pressure vessel, and the through member 130 is a CRDM through member.

[0023] Please continue to refer to this. Figures 1 to 3 The J-groove welding method provided in this embodiment includes: Step S1, welding around the edge of the J-groove 100 on the stainless steel weld overlay 120 to form a boss 210. Step S2, welding on the surface of the J-groove 100 to form an isolation layer 220. Step S3, removing the boss 210. Step S4, assembling the through member 130 into the through hole 111. Step S5, welding the J-groove 100 on the isolation layer 220 to form a main weld portion 230; wherein a groove 240 is reserved at the junction of the main weld portion 230 and the top of the isolation layer 220. Step S6, welding the groove 240 to fill the groove 240.

[0024] Specifically, in step S1, the boss 210 is disposed in close contact with the edge of the J-shaped bevel 100, and the boss 210 is a process auxiliary structure for subsequent steps. More specifically, the welding material of the boss 210 is the same as the welding material of the stainless steel weld overlay 120, that is, the welding material of the boss 210 is stainless steel, so as to avoid the setting of the boss 210 affecting the stainless steel weld overlay 120.

[0025] Optionally, the height of the boss 210 is greater than 5 mm, and the width of the boss 210 is greater than 15 mm; and at the edge of the J-shaped bevel with a large slope, the width of the boss 210 can be appropriately increased. In one embodiment, the height of the boss 210 is 8 mm, and the width of the boss 210 is 20 mm, but the present invention is not limited thereto.

[0026] Specifically, in step S2, the isolation layer 220 can be formed by welding on the surface of the J-groove 100 using a manual welding method. Optionally, the welding material for the isolation layer 220 is a nickel-based welding electrode.

[0027] It should be noted that when the isolation layer 220 is welded, the boss 210 can avoid the problem of excessive dilution caused by the small geometric angle of the original stainless steel-nickel-based interface; at the same time, the boss 210 can also provide better residence space for molten slag and gas, thereby improving the slag and gas protection effect of the welding electrode and further reducing the dilution rate.

[0028] Specifically, in step S3, after the isolation layer 220 is welded and passes inspection, the boss 210 can be removed by mechanical grinding or machining to expose the surface 1201 of the stainless steel weld overlay layer 120 (see...). Figure 3 The original outline is restored to prevent the boss 210 from affecting subsequent assembly and welding operations. It is understood that in step S4, after the through member 130 is inserted into the through hole 111, the J-shaped bevel 100 is located outside the through member 130, and a welding area is formed between the outer wall of the through member 130 and the J-shaped bevel 100.

[0029] Specifically, in step S5, by welding the J-shaped bevel 100 onto the isolation layer 220 to form the main weld portion 230, the through-piece 130 and the top cover 110 can be fixedly connected. More specifically, the main weld portion 230 includes a filler layer and a reinforcing layer, and step S5 includes: step S51, performing filler welding on the J-shaped bevel 100 onto the isolation layer 220 to form the filler layer; step S52, welding layer by layer upwards from the filler layer to form the reinforcing layer. It can be understood that the filler layer is flush with the surface 1201 of the stainless steel weld overlay layer 120, and the reinforcing layer extends beyond the surface 1201 of the stainless steel weld overlay layer 120 to further fix the through-piece 130.

[0030] Specifically, the step of welding the filler layer, i.e., step S51, includes: Step S511, applying a first welding rod with a first diameter close to the outer wall of the through-piece 130 as the root pass. Step S512, when welding layer by layer from the root pass upwards, the welds close to the outer wall of the through-piece 130 and the last two welds close to the isolation layer 220 are applied using the first welding rod, while the welds in the remaining areas are applied using a second welding rod with a second diameter, which is larger than the first diameter; and each layer of welding starts from the side close to the outer wall of the through-piece 130 and proceeds towards the side close to the isolation layer 220.

[0031] It should be noted that when welding the filler layer, using a small-diameter (e.g., first-diameter) welding rod for the root pass and the area near the through-hole 130 can effectively reduce local heat input, prevent the through-hole 130 from overheating, and ensure good fusion of the outer wall of the through-hole 130, thereby reducing the dilution rate. Using a small-diameter (e.g., first-diameter) welding rod for the last two layers and the area near the isolation layer 220 (i.e., the easily diluted area) can also reduce the dilution rate by reducing local heat input. Furthermore, using a large-diameter (e.g., second-diameter) welding rod in the remaining areas can ensure welding efficiency.

[0032] Optionally, both the first and second welding electrodes are nickel-based welding electrodes; the first diameter is less than or equal to 2.4 mm. In one embodiment, the first diameter is 2.4 mm, and the second diameter is 3.2 mm or 4.0 mm, but the present invention is not limited thereto.

[0033] In one embodiment, when welding the reinforcement layer, the weld beads close to the outer wall of the through-member 130 are welded using the first welding rod to reduce local heat input, thereby preventing the through-member 130 from overheating and ensuring good fusion of the outer wall of the through-member 130, thus reducing the dilution rate; the weld beads in the remaining areas are welded using the second welding rod to ensure welding efficiency. Further, each layer of welding starts from the side close to the outer wall of the through-member 130 and proceeds outwards in a row. Optionally, the cross-section of the reinforcement layer is triangular or trapezoidal, but the invention is not limited thereto.

[0034] Specifically, step S6 includes: welding layer by layer from the bottom of the trench 240 upwards to fill the trench 240; and each layer of welding starts from the side close to the filler layer and proceeds towards the side close to the isolation layer 220. Optionally, the weld beads filling the trench 240 are applied using the first welding rod to reduce the dilution rate by reducing local heat input. Optionally, the trench 240 is filled using a manual welding method.

[0035] It should be noted that, in this embodiment, by reserving and finally filling the trench 240, the dissimilar metal interface area (i.e., the stainless steel-nickel-based interface) which is most prone to dilution problems is completed as a final and independent process. This overcomes the problems of multi-layer and multi-pass welding and multi-layer and multi-pass thermal cycling accumulation in the dissimilar metal interface area when no trench is reserved in the prior art, thereby ensuring the purity of the nickel-based metal in the surface weld and reducing the dilution rate.

[0036] Optionally, the width and depth of the trench are both greater than 8 mm and less than or equal to 15 mm; it is understood that the depth of the trench refers to the depth of the indentation from the surface 1201 of the stainless steel weld overlay 120 downwards. In one embodiment, the width and depth of the trench are both 10 mm, but the present invention is not limited thereto.

[0037] In this embodiment, each weld bead is ground during the welding process to ensure that there are no remaining fish-scale patterns, oxide films, or fly-foot-like defects at the overlapping positions, and that the transition is smooth, thereby guaranteeing welding quality. Furthermore, after filling the groove 240, the weld surface is also ground.

[0038] It is understood that the welding method provided in this embodiment is also applicable to, for example, Figure 4 The asymmetrical J-shaped bevel is shown.

[0039] Furthermore, through actual product welding work inspection, the welding method provided in this embodiment meets the relevant product technical requirements and fully meets the quality requirements of the weld. Based on the original equipment, the process is improved, the occurrence of PT indication is reduced, the adverse impact of handling non-conformities in nickel-based alloy weld defects on the product manufacturing cycle is reduced, and the level of nickel-based alloy welding technology and quality management is greatly improved.

[0040] 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.

[0041] In the description of this invention, it should be understood that the terms "center," "height," "thickness," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0042] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0044] 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 J-groove welding method for a pressure vessel; the top cover of the pressure vessel is provided with a through hole for a through-hole to pass through; characterized in that, The inner surface of the top cover has a stainless steel weld overlay, and the J-shaped bevel is formed on the inner side of the top cover and near the through hole; the J-shaped bevel welding method includes: Weld around the edge of the J-groove on the stainless steel weld overlay to form a ring of bosses; Welding is performed on the surface of the J-groove to form an isolation layer; Remove the protrusion; The through-hole is assembled into the through-hole; The J-shaped groove is welded on the isolation layer to form the main weld; wherein, a groove is reserved at the junction of the main weld near the top of the isolation layer. Weld the trench to fill it.

2. The J-groove welding method as described in claim 1, characterized in that, The main weld section includes a filler layer and a reinforcement layer; the step of welding the J-groove on the isolation layer includes: The J-groove is filled with filler weld on the isolation layer to form the filler layer; Welding is performed layer by layer upwards from the filler layer to form the reinforcement layer; and the reinforcement layer extends beyond the surface of the stainless steel weld overlay.

3. The J-groove welding method as described in claim 2, characterized in that, The step of performing filler welding on the J-groove on the isolation layer includes: The root pass is applied by using a first welding rod of a first diameter close to the outer wall of the through-hole; When welding layer by layer from the root pass upwards, the welds close to the outer wall of the through-piece and the last two welds close to the isolation layer are welded using the first welding rod, and the welds in the remaining areas are welded using a second welding rod with a second diameter greater than the first diameter; and each layer of welding starts from the side close to the outer wall of the through-piece and proceeds towards the side close to the isolation layer.

4. The J-groove welding method as described in claim 3, characterized in that, When welding the augmentation layer, the weld bead close to the outer wall of the through member is welded using the first welding rod, and the weld bead in the remaining area is welded using the second welding rod; and each layer of welding starts from the side close to the outer wall of the through member and proceeds outwards in a row of welds.

5. The J-groove welding method as described in claim 2, characterized in that, The steps of welding the trench include: welding layer by layer from the bottom of the trench upwards to fill the trench; and each layer of welding starts from the side close to the filling layer and proceeds to the side close to the isolation layer.

6. The J-groove welding method as described in claim 1, characterized in that, The welding material for the boss is stainless steel.

7. The J-groove welding method as described in claim 1, characterized in that, The height of the boss is greater than 5mm, and the width of the boss is greater than 15mm.

8. The J-groove welding method as described in claim 3, characterized in that, The welding material for the isolation layer, as well as the first and second welding electrodes, are all nickel-based welding electrodes.

9. The J-groove welding method as described in claim 3, characterized in that, The first diameter is less than or equal to 2.4 mm.

10. The J-groove welding method as described in claim 1, characterized in that, The width and depth of the groove are both greater than or equal to 8 mm and less than or equal to 15 mm.

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