Pressure resistance welding electrode

Abstract

A pressure resistance welding electrode comprises an electrode front plate, an electrode back plate and a metal sheet group, the metal sheet group is located between the electrode front plate and the electrode back plate, the electrode back plate introduces current, the metal sheet group comprises a plurality of metal sheets for guiding the current to flow, the metal sheet comprises a body layer and a sprayed layer, the sprayed layer is attached to at least one side of the body layer, and the sprayed layer causes the current to be shunted along the plurality of metal sheets. The application can prolong the length of the cladding tube end heating zone and solve the problems of short service life, poor reliability, uneven current distribution and narrow welding range of the prior art pressure resistance welding electrode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, in particular to a pressure resistance welding electrode. BACKGROUND

[0002] In the field of nuclear power, the fuel rod with the core block inside is a key component, and once it is damaged, it will cause great harm to the safety of the unit. The weld between the cladding tube and the end plug is a weak link. Because fusion welding is prone to various defects, and the weld is sensitive to contaminants, the probability of breakage during operation is relatively high. In recent years, with the gradual maturity of the fuel rod pressure resistance welding process and its own technical advantages, pressure resistance welding will become the main process for fuel rod manufacturing.

[0003] The principle of the existing fuel rod pressure resistance welding process is to apply current between the cladding tube and the end plug, and the resistance heat makes the metal at the junction of the cladding tube and the end plug in a softened state. Then, a top forging force is applied between the cladding tube and the end plug, so that the softened metal surface between the end plug and the inner wall of the cladding tube is rubbed and displaced. Under the action of high temperature and pressure, the bonding surface produces metal key bonding to form a welded joint. The key to the formation of the fuel rod pressure resistance welding is that the longitudinal resistance value of the tube electrode should match the cladding tube. When the current is applied between the cladding tube and the end plug, the tube electrode changes the current flow direction, prolongs the length of the heating zone at the end of the cladding tube, and can ensure the top forging amount, i.e. the bonding length of the end plug and the cladding tube. Otherwise, the current flows along the path with the smallest resistance, and only a small area at the end of the tube can heat the cladding tube, making it difficult to form a long and reliable weld. At the same time, the tube electrode in contact with the surface of the cladding tube carries away the heat from the surface of the cladding tube, preventing the surface of the cladding tube from melting and burning.

[0004] Invention CN107900504A discloses a fuel rod pressure resistance welding chuck, which includes a chuck body, the chuck body includes a chuck front end and a chuck rear end, and a metal sheet layer is arranged between the chuck front end and the chuck rear end. The surfaces of the adjacent two metal sheets in contact with each other are provided with an insulating coating, and the surface of the metal sheet in contact with the chuck body is also provided with an insulating coating. All the metal sheets are stacked and distributed along the axial direction of the fuel rod. All the metal sheets, the chuck front end and the chuck rear end are connected through at least one conductive body, and the resistance values of the conductive body, the cladding tube and the end plug are matched with each other. The fuel rod pressure resistance welding electrode adopts a transverse conductive body type, and the current flow direction is changed through the intermediate conductive body. Due to this structure, the existing fuel rod pressure resistance welding electrode has the following problems:

[0005] 1. The current distribution on the radial cross section of the cladding tube is uneven. As shown in the figure, the conductive body is located in the middle of the electrode block, and the shunted current flows to the cladding tube along the shortest path, making the current density distribution on the circumference of the cladding tube uneven. The fewer the number of electrode blocks, the more uneven the distribution, and the heat in the area between the electrode blocks is insufficient, affecting the welding formation. Figure 1 ​

[0006] 2. Unreliable contact between the conductor and the metal sheet. To ensure sufficient current flow through the metal sheet, a tight fit is required. However, manufacturing deviations can easily lead to incomplete connections between the conductor and the metal sheet. Furthermore, the thin insulating layer on the surface of the metal sheet is prone to damage during machining, or plastic deformation during machining can cause direct contact between adjacent metal substrates, resulting in current shunting failure and affecting the electrode's shunting performance and lifespan.

[0007] 3. Small welding range, prone to metal sheet instability. The conductor not only meets the conductivity requirement, but also provides radial support for the metal sheet. It is generally made of stainless steel or nickel-based alloy. In order to match the resistance of the cladding tube, the diameter of the conductor is required to be small enough, resulting in poor current carrying capacity of the conductor. Moreover, the metal sheet of the entire electrode is prone to instability after the upsetting force is applied.

[0008] In view of the above technical problems, this invention is hereby introduced. Summary of the Invention

[0009] The main objective of this invention is to provide a pressure resistance welding electrode that solves problems such as uneven radial current distribution on the cross-section of the cladding tube of existing pressure resistance welding electrodes, unreliable contact between the conductor and the metal sheet, small welding range, and easy instability of the sheet.

[0010] To achieve the above objectives, the present invention provides a pressure resistance welding electrode, comprising a front electrode plate, a rear electrode plate, and a metal sheet assembly, wherein the metal sheet assembly is located between the front electrode plate and the rear electrode plate, the rear electrode plate introduces current, and the metal sheet assembly comprises multiple metal sheets for guiding the current direction. Each metal sheet comprises a body layer and a coating layer, the coating layer being attached to at least one side of the body layer, and the coating layer causing the current to be shunt along the multiple metal sheets.

[0011] Furthermore, the body layer has a first resistivity, and the sprayed layer has a second resistivity, the second resistivity being greater than the first resistivity.

[0012] Furthermore, the coating layer is a mixture of conductive and insulating materials.

[0013] Furthermore, the resistance value of the electrode can be adjusted by changing the ratio of conductive material to insulating material to regulate the second resistivity.

[0014] Furthermore, the coating layer is a mixture of copper alloy and ceramic materials.

[0015] Furthermore, the mixture is melted by plasma or electric arc and then sprayed to form a coating layer.

[0016] Furthermore, the thickness of the sprayed coating is uniform and less than that of the base layer.

[0017] Further, the metal sheet set includes 3-8 metal sheets.

[0018] Further, the metal sheet set includes 5 metal sheets

[0019] Further, the electrode front plate, the electrode rear plate and the body layer are all copper alloys.

[0020] Further, the electrode further includes positioning pins for positioning, the positioning pins passing through the electrode front plate, the electrode rear plate and the metal sheet set.

[0021] Further, the positioning pins are insulating materials.

[0022] Further, the electrode further includes fasteners for fastening the electrode front plate, the electrode rear plate and the metal sheet set together.

[0023] Further, the fasteners are surface-insulated.

[0024] Further, the electrode is composed of a plurality of electrode blocks uniformly distributed in the circumferential direction, each electrode block including an electrode front plate, an electrode rear plate and a metal sheet set.

[0025] Further, the electrode block further includes positioning pins and fasteners.

[0026] The technical scheme of the present application at least achieves the following beneficial effects:

[0027] 1. The pressure resistance welding electrode can ensure the consistency of the radial resistance value by using metal sheets with different conductive layers to conduct current, and the uniform distribution of the radial shunt current on the cross section of the cladding tube makes the current density in the circumferential direction of the cladding tube uniform, thereby improving the welding quality of the pressure resistance welding.

[0028] 2. The spray coating of the metal sheet of the pressure resistance welding electrode has strong adhesion and the thickness can be accurately controlled, which not only ensures a long enough electrode life, but also avoids the direct contact of the adjacent metal sheet body layers due to plastic deformation caused by machining, causing the failure of current shunt.

[0029] 3. The pressure resistance welding electrode has a wide welding range, and by adjusting the component ratio of the spray mixture, the longitudinal resistance value of the tube electrode and the resistance value of the cladding tube can be accurately matched, and the pressure resistance welding of cladding tubes of different materials or sizes can be adapted.

[0030] 4. The pressure resistance welding electrode uses multiple positioning pins and fasteners, which can maintain the stable contact between the metal sheets and between the front and rear plates and the metal sheet set without affecting the conduction effect of the current, and can enhance the structural stability of the metal sheet set. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The embodiments of the application, and their

[0032] Figure 1 A prior art fuel rod pressure resistance welding chuck radial current schematic is shown;

[0033] Figure 2 A front view schematic of an electrode in an embodiment of the application is shown;

[0034] Figure 3 A rear view schematic of an electrode in an embodiment of the application is shown;

[0035] Figure 4 A current flow schematic in an embodiment of the application is shown.

[0036] Wherein, the above-mentioned drawings include the following reference signs:

[0037] 1, electrode front plate; 2, electrode rear plate; 3, metal sheet group; 30, metal sheet; 31, body layer; 32, spray layer; 4, positioning pin; 5, fastener; 6, cladding tube; 7, end plug; 8, electric conductor; 9, metal sheet layer; 10, electrode block. DETAILED DESCRIPTION

[0038] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0039] The present application will be further described in detail below in conjunction with specific embodiments, which cannot be understood as limiting the scope of the present application. The term "comprising" is used to indicate the presence of a feature, but does not exclude the presence or addition of one or more other features; the terms "lateral", "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only used for convenience of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application; in addition, the terms "first", "second" are only used for description purposes, and cannot be understood as indicating or implying relative importance.

[0040] In the description, it needs to be explained that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In addition, in the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0041] Embodiments:

[0042] The present application provides a pressure resistance welding electrode, which is mainly used for pressure resistance welding of fuel rod cladding tube and end plug. By setting multiple metal sheets and making the metal sheets have body layer and spraying layer with different conductivities, the current is shunted and the longitudinal resistance value of the tube electrode and the resistance value of the cladding tube are matched. When the current is applied between the cladding tube and the end plug, the length of the end heating zone of the cladding tube is extended, and the problems of short service life, poor reliability, uneven current distribution and narrow welding range of the prior art pressure resistance welding electrode are solved.

[0043] As shown in Figure 2 The pressure resistance welding electrode provided by the present application includes an electrode front plate 1, an electrode rear plate 2 and a metal sheet group 3, and the metal sheet group 3 is located between the electrode front plate 1 and the electrode rear plate 2. The metal sheet group 3 includes multiple metal sheets 30 for guiding the current flow. Preferably, the electrode front plate 1 and the electrode rear plate 2 are both made of low-resistance copper alloy to meet the requirements of conductivity and structural stiffness. The electrode front plate 1 and the electrode rear plate 2 are used for current conduction and heat dissipation.

[0044] As shown in Figure 4 When the electrode is used for pressure resistance welding of the fuel rod cladding tube 6 and the end plug 7, one pole of the welding power source is connected to the electrode rear plate 2, and the other pole is connected to the rear end of the end plug 7. The welding current passes through the electrode rear plate 2, one way directly to the cladding tube 6, and the other way gradually shunted to the cladding tube 6 along each metal sheet 30 when passing through the metal sheet group 3, and finally converges to the end plug 7 at the front end of the cladding tube 6. Thus, the length of the end heating zone of the cladding tube is extended, and the bonding length of the end plug and the cladding tube is ensured.

[0045] The metal sheet is the core of the pressure resistance welding electrode provided by the present application, and each metal sheet 30 includes a body layer 31 and a spraying layer 32 with different conductivities, the spraying layer 32 is attached to at least one side of the body layer 31, the body layer 31 has a first resistivity, and the spraying layer 32 has a second resistivity. The second resistivity of the spraying layer 32 can be adjusted, and the second resistivity is greater than the first resistivity. The welding current can be shunted along the direction of each metal sheet through the spraying layer.

[0046] Specifically, the body layer 31 is made of a metal conductive material, and the spraying layer 32 can be made of a mixture of conductive material and insulating material, so that the resistivity of the spraying layer 32 is greater than that of the body layer 31. Preferably, the body layer 31 is made of the same copper alloy as the electrode front plate 1 and the electrode back plate 2, and in the embodiment, the spraying layer 32 is a mixture of copper alloy and ceramic material. The difference in resistivity between the spraying layer and the body layer enables the current flowing through the metal sheet layer to be shunted in the direction of each metal sheet.

[0047] In the manufacturing of the metal sheet 30, the ceramic and metal-based powder are mixed in a certain proportion, and then the powdered mixture is melted by plasma or arc and sprayed onto the surface of the body layer 31 at high speed to form a spraying layer 32 with uniform thickness, certain thickness and certain resistance. The thickness of the body layer 31 should be greater than that of the spraying layer 32.

[0048] The application does not limit the thickness ratio of the body layer 31 and the spraying layer 32, but if the thickness of the spraying layer 32 is too large, it will affect the processing performance of the metal sheet. Preferably, the body layer 31 is made of high-quality copper alloy with a thickness of 0.5 mm as the base material, and the thickness of the spraying layer is not more than 0.1 mm.

[0049] The spraying layer in the application also has the following functions: the second resistivity of the spraying layer can be adjusted by adjusting the composition or ratio of the spraying mixture, so as to adjust the longitudinal resistance of the electrode to a certain range. The longitudinal resistance of the tube electrode and the resistance value of the cladding tube can be precisely matched, which can adapt to the pressure resistance welding of cladding tubes of different materials or sizes, so that the welding range of the pressure resistance welding electrode is wider. The second resistivity can be adjusted by adding insulating materials to the conductive material or changing the ratio of the conductive material and the insulating material, which in the embodiment is embodied as changing the ratio of copper alloy and ceramic insulating material to adjust the resistance of the spraying layer.

[0050] In addition, the spraying layer has strong adhesion on the body layer, and the thickness of the spraying layer can be precisely controlled, which not only ensures a long enough electrode life, but also avoids the direct contact of the body layers of adjacent metal sheets due to plastic deformation caused by machining, resulting in the failure of current shunting.

[0051] The metal sheet group in the application contains 3-8 metal sheets, preferably 5 layers of metal sheets are used in the manufacturing of the pressure resistance welding electrode, and the metal sheets are pressed and tightly assembled by using a pressing tool.

[0052] As Figures 2-3As shown, the pressure resistance welding electrode further comprises positioning pins 4 and fasteners 5 for positioning, the positioning pins 4 and fasteners 5 passing through the electrode front plate 1, the electrode rear plate 2 and the metal sheet group 3. The positioning pins 4 are made of insulating material, and the fasteners 5 are made of surface-insulated metal material. Preferably, the fasteners 5 are clamping bolts subjected to surface insulation treatment. The insulation of the positioning pins 4 and the fasteners 5 does not affect the current conduction in the electrode.

[0053] The fasteners 5 are used to press and fix the electrode front plate 1, the electrode rear plate 2 and the metal sheet group 3 together, so that the current can be stably conducted in the electrode. The positioning pins 4 play a positioning role during assembly and a supporting role for the metal sheet group 3 during welding. The metal sheet group has low strength and is prone to deformation during welding, which causes the resistance characteristics of the entire electrode clamp to change. The positioning pins can effectively prevent the metal sheet group 3 from being deformed under stress during welding. The pressure resistance welding electrode proposed in the present application can keep the contact between the metal sheets and between the front and rear plates and the metal sheet group stable and can enhance the structural stability of the metal sheet group without affecting the conduction effect of the current by using multiple positioning pins and fasteners.

[0054] The pressure resistance welding electrode is composed of multiple electrode blocks 10 uniformly distributed in the circumferential direction, each electrode block 10 comprising an electrode front plate 1, an electrode rear plate 2 and a metal sheet group 3, and further comprising positioning pins 4 and fasteners 5. As shown, Figures 2-3 Preferably, the pressure resistance welding electrode in the present embodiment is composed of three electrode blocks uniformly distributed in the circumferential direction, each electrode block having one positioning pin and two fasteners, the positioning pin being located in the middle of the fasteners and having good fastening and supporting effects. Under the conditions that the thickness of the sprayed layer is 0.01 mm, the thickness of the substrate layer is 0.5 mm, and the proportion of ceramic material in the sprayed mixture is 25%, the resistance value of each electrode block is controlled to be between 0.6 and 0.7 milliohms.

[0055] The pressure resistance welding electrode of the embodiment is implemented by the following steps: 1. The sprayed layer is formed by melting the mixture of copper alloy and ceramic material in powder form by using a plasma or arc heat source, and spraying the mixture at high speed onto the surface of the copper alloy sheet to form an alloy layer with a certain thickness and resistance value. 2. The electrode front plate, a certain number of metal sheets and the electrode rear plate are assembled by using positioning pins, and then the electrode front plate, the metal sheet group and the electrode rear plate are compressed and fixed by using surface-insulated clamping bolts. The bolt head side is sealed and fixed by using epoxy resin glue. 3. The whole is finished to the required size, and then the electrode is cut into three pieces by using wire cutting to form three electrode blocks. 4. The three electrode blocks are fixed on the electrode seat by metal bolts, and the radial clamping of the electrode to the cladding tube is realized under the action of pneumatic or electric power, and then the end plug is in contact with the cladding tube under the action of the end plug on the top end. 5. One pole of the welding power source is connected to the electrode rear plate, and the other pole is connected to the rear end of the end plug; the current passes through the electrode rear plate, one way directly to the cladding tube, and the other way gradually shunts to the cladding tube along the metal sheet, and finally flows to the end plug at the front end of the tube. 6. The effective combination of the end plug and the cladding tube is realized under the action of the top forging force on the end plug side.

[0056] From the above, the pressure resistance welding electrode adopts metal sheets with different conductive layers to conduct current, which can ensure that the resistance value along the radial direction of the electrode is uniform, and the radial shunt current distribution on the cross section of the cladding tube is uniform, so that the current density distribution in the circumferential direction of the cladding tube is uniform, thereby improving the welding quality of the pressure resistance welding. In addition, in order to ensure that the current along the axial direction of the electrode is as uniform as possible, the current conducted along each metal sheet should be as uniform as possible, and the spraying time and thickness of the sprayed layer need to be accurately controlled to ensure that the sprayed layer is uniform enough, and the pressure received by each metal sheet is consistent, and the assembly conditions are consistent.

[0057] In summary, from the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects: 1. The pressure resistance welding electrode can ensure the consistency of the radial resistance value by adopting the metal sheet with different conductive layers to conduct current, and the uniform distribution of the radial shunt current on the cross section of the cladding tube makes the current density distribution uniform in the circumferential direction of the cladding tube, thereby improving the welding quality of the pressure resistance welding. 2. The spraying layer of the metal sheet of the pressure resistance welding electrode has strong adhesion and the thickness can be accurately controlled, which not only ensures that the service life of the electrode is long enough, but also avoids the direct contact of the adjacent metal sheet body layers due to plastic deformation caused by machining, thereby causing the failure of current shunt. 3. The pressure resistance welding electrode has a wide welding range, and by adjusting the composition or ratio of the spraying mixture, the longitudinal resistance value of the tube electrode and the resistance value of the cladding tube can be accurately matched, and the pressure resistance welding of cladding tubes with different materials or sizes can be adapted. 4. The pressure resistance welding electrode adopts multiple positioning pins and fasteners, which can keep the contact between the metal sheets, the front and rear plates and the metal sheet groups stable without affecting the conduction effect of the current, and can enhance the structural stability of the metal sheet group.

[0058] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A resistance pressure welding electrode comprising an electrode front plate (1), an electrode back plate (2) and a metal sheet pack (3) located between the electrode front plate (1) and the electrode back plate (2), the electrode back plate (2) introducing a current, the metal sheet pack (3) comprising a plurality of metal sheets (30) for guiding the current, characterized in that: The metal sheet (30) comprises a body layer (31) and a spraying layer (32) attached to at least one side of the body layer (31), the spraying layer (32) makes the current shunt along a plurality of the metal sheets (30); the spraying layer (32) is a mixture of conductive material and insulating material; the electrode is composed of a plurality of electrode blocks (10) uniformly distributed in the circumferential direction, each of the electrode blocks (10) comprises the electrode front plate (1), the electrode back plate (2) and the metal sheet group (3); the current passes through the electrode back plate (2) and is directly flowed to the cladding tube in one way and is gradually shunted to the cladding tube along the metal sheet (30) in another way, and is converged to the end plug at the front end of the cladding tube.

2. The electrode of claim 1, wherein: The body layer (31) has a first resistivity, and the spraying layer (32) has a second resistivity, the second resistivity is greater than the first resistivity.

3. The electrode of claim 2, wherein: The second resistivity is adjusted by changing the proportion of the conductive material and the insulating material to adjust the resistance value of the electrode.

4. The electrode of claim 2, wherein: The spraying layer (32) is a mixture of copper alloy and ceramic material.

5. The electrode of claim 2, wherein: The spraying layer (32) is formed by spraying after melting the mixture in a plasma or arc manner.

6. The electrode of claim 1, wherein: The thickness of the spraying layer (32) is uniform and smaller than the thickness of the body layer (31).

7. The electrode of claim 1, wherein: The metal sheet group (3) comprises 3-8 metal sheets (30).

8. The electrode of claim 7, wherein: The metal sheet group (3) comprises 5 metal sheets (30).

9. The electrode of claim 1, wherein: The electrode front plate (1), the electrode back plate (2) and the body layer (31) are all copper alloys.

10. The electrode of claim 1, wherein: The electrode further comprises a positioning pin (4) for positioning, the positioning pin (4) passes through the electrode front plate (1), the electrode back plate (2) and the metal sheet group (3).

11. The electrode of claim 10, wherein: The positioning pin (4) is an insulating material.

12. The electrode of claim 10, wherein: The electrode further comprises a fastener (5) for fastening the electrode front plate (1), the electrode back plate (2) and the metal sheet group (3) together.

13. The electrode of claim 12, wherein: The surface of the fastener (5) is insulated.

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