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CN-121988838-A - Welding method of nuclear fuel element added with filling ring

CN121988838ACN 121988838 ACN121988838 ACN 121988838ACN-121988838-A

Abstract

The application belongs to the technical field of nuclear fuel element manufacturing, in particular to a welding method of a nuclear fuel element added with a filling ring, which performs integrated welding by designing an integral assembly welding structure with a cladding tube, an end plug and the filling ring, and the matching relation between the filling ring and the cladding tube structure and the welding centering method are optimized, and the pre-welding and post-welding heat treatment processes are determined, so that the technical problems that the hardness after welding is obviously improved, larger air holes, air inflation tendency and the like are easy to occur in the TIG welding of the existing nuclear fuel cladding tube and the end plug are solved.

Inventors

  • GUAN HUAI
  • Guo tianyang
  • ZHANG PENGJU
  • ZHANG MENGMENG
  • DONG NA
  • LIU CHANGCHENG
  • YUN WENTING

Assignees

  • 中核北方核燃料元件有限公司

Dates

Publication Date
20260508
Application Date
20251127

Claims (9)

  1. 1. A method for welding a nuclear fuel element with a filler ring added thereto, characterized in that, Firstly, processing a filling ring, wherein the filling ring is formed by turning and wire cutting, polishing with abrasive paper and scouring pad and electrochemical oxalic acid cleaning to remove surface oxidation color and processing trace, and the outer diameter and the wall thickness of the filling are consistent with those of the cladding tube, and the length of the filling is 1/3-1/2 of the wall thickness of the cladding tube; Step two, assembling the parts, namely integrally loading the assembled filling ring and the end plug into the cladding tube, wherein the end plug and the filling ring are in clearance fit, the assembling clearance is not more than 0.02mm, the end plug and the cladding tube are in interference fit, and the assembled whole is heated for a preset time period at a first preset temperature by adopting an oven, and the preset time period is not less than 20 minutes; Step three, adjusting a tungsten electrode, trimming the end part of the tungsten electrode to a cone angle of 30 degrees, adjusting the diameter of a tip platform to be 0.3mm, and adjusting 1/4 of the length of a tungsten electrode centering filling ring in real time through a servo motor to compensate thermal expansion deformation; setting welding parameters including welding current, pulse TIG and welding speed; and fifthly, performing postweld heat treatment, wherein the heat treatment of the weld joint is performed at a second preset temperature for 2 hours, the temperature rising speed is not more than 220 ℃ per hour, the heat treatment is performed in a vacuum state, argon shielding gas is adopted during cooling, and the lowest threshold value of the second preset temperature is larger than the highest threshold value of the first preset temperature.
  2. 2. A method of welding a nuclear fuel element incorporating a filler ring according to claim 1, wherein the interference of the end plug with the cladding tube interference fit is no more than 0.02mm.
  3. 3. A method of welding a nuclear fuel element with a filler ring added according to claim 1, characterized in that the material of the cladding tube is iron-horse steel, oxide dispersion strengthened steel or molybdenum-rhenium alloy.
  4. 4. The method of claim 1, wherein the first predetermined temperature is in the range of 150 ℃ to 400 ℃.
  5. 5. The welding method for a nuclear fuel element with a filler ring according to claim 4, wherein the iron-based steel has a first preset temperature of 150 ℃, the oxide dispersion strengthened steel has a first preset temperature of 200 ℃, and the molybdenum-rhenium alloy has a first preset temperature of 250 ℃.
  6. 6. The welding method for a nuclear fuel element with a filler ring according to claim 1, wherein the thickness of the cladding tube is 0.4 mm-0.65 mm, and the welding current is 25 a-35 a.
  7. 7. A method of welding a nuclear fuel element incorporating a filler ring according to claim 1, wherein the base current of the pulsed TIG is in the range 40% -60% and the duty cycle is in the range 40% -60%.
  8. 8. A method of welding a nuclear fuel element with a filler ring according to claim 1, characterized in that the welding speed is 15 °/s.
  9. 9. The welding method for a nuclear fuel element with a filler ring according to any one of claims 1 to 8, wherein the second preset temperature is 740 ℃ to 770 ℃.

Description

Welding method of nuclear fuel element added with filling ring Technical Field The application belongs to the technical field of nuclear fuel element manufacturing, and particularly relates to a welding method of a nuclear fuel element with a filling ring. Background In the 4 th generation nuclear energy system, the nuclear fuel is required to have high burnup, high power density, better economy and safety. Materials such as iron-horse steel, oxide dispersion strengthened steel (also called ODS steel), molybdenum-rhenium alloy and the like are widely applied to fast neutron stacks, nuclear fusion devices and aerospace nuclear energy devices. The welding performance of the materials is extremely high, and the high strength, the low defect rate and the high temperature and high pressure resistance are simultaneously required to be met. TIG welding (also known as tungsten inert gas welding) of a nuclear fuel cladding tube and an end plug is a core process for manufacturing a fuel element, and the welding of the cladding tube of each type of existing reactor is self-fluxing welding, and the self-fluxing welding of the cladding tube is easy to have the following defects: 1. The hardness after welding can be obviously improved, the comprehensive mechanical property of the welding seam is not facilitated, the base metal components are generally required to be adjusted, and the irradiation performance of the cladding tube is reversely restricted. 2. Deformation control, namely, uneven heat input is easy to generate ovalization or partial dent when the thin-wall pipe (the wall thickness is less than or equal to 1 mm) is welded, and the assembly precision is affected. 3. The process design is difficult to combine the appearance and the internal quality, and large air holes and air inflation tendency are easy to occur. 4. The filling mode influences the weld joint forming, the difficulty of filling wire welding on fuel cladding is high, batch manufacturing is not facilitated, the difference of thermal expansion coefficients of a filling ring and a cladding tube is large, and microcracks caused by insufficient interface diffusion are not solved by the traditional process. Disclosure of Invention In view of the above, the application provides a welding method for a nuclear fuel element added with a filling ring, which is characterized by designing a welding structure for integrally welding with an integral assembly of a cladding tube, an end plug and the filling ring, optimizing the matching relation between the filling ring and the cladding tube structure and a welding centering method, and determining the pre-welding and post-welding heat treatment processes so as to solve the technical problems that the hardness of the existing nuclear fuel cladding tube and the end plug is obviously improved after welding, and larger air holes, air swelling tendency and the like are easy to occur. The application provides a welding method of a nuclear fuel element added with a filling ring, which comprises the following steps: Firstly, processing a filling ring, wherein the filling ring is formed by turning and wire cutting, polishing with abrasive paper and scouring pad and electrochemical oxalic acid cleaning to remove surface oxidation color and processing trace, and the outer diameter and the wall thickness of the filling are consistent with those of the cladding tube, and the length of the filling is 1/3-1/2 of the wall thickness of the cladding tube; and step two, assembling the parts. And (3) integrally loading the filling ring and the end plug into the cladding tube after assembling, wherein the end plug and the filling ring are in clearance fit, the assembling clearance is not more than 0.02mm, and the end plug and the cladding tube are in interference fit. Heating the whole assembly by adopting an oven at a first preset temperature for a preset time period which is not less than 20min; And thirdly, adjusting the tungsten electrode. The end part of the tungsten electrode is trimmed to be 30-degree cone angle, the diameter of the tip platform is 0.3mm, and 1/4 of the length of the tungsten electrode centering filling ring is adjusted in real time through a servo motor to compensate thermal expansion deformation; and fourthly, setting welding parameters. Welding parameters include welding current, pulse TIG, and welding speed; fifth, post-welding heat treatment. And carrying out heat treatment on the welding seam at a second preset temperature for 2 hours, wherein the temperature rising speed is not more than 220 ℃ per hour, and carrying out heat treatment in a vacuum state, wherein argon shielding gas is adopted when cooling. The lowest threshold value of the second preset temperature is greater than the highest threshold value of the first preset temperature. In a specific embodiment of the application, the interference of the end plug with the cladding tube is not more than 0.02mm. In a specific embodiment of the applicati