Method for welding zirconium alloy circular pipe and stainless steel circular pipe and zirconium alloy and stainless steel connecting piece

Abstract

The embodiment of the invention relates to the field of non-electric welding using impact or other pressure, in particular to a method for welding a zirconium alloy circular pipe and a stainless steel circular pipe and a zirconium alloy and stainless steel connecting piece. The method comprises the following steps: S10, treating a zirconium alloy circular tube and a stainless steel circular tube to be welded; s20, the to-be-welded zirconium alloy circular pipe and the to-be-welded stainless steel circular pipe treated in the step S10 are fixed to a graphite clamp; s30, the graphite clamp where the zirconium alloy circular pipe and the stainless steel circular pipe to be welded are fixed is placed in welding equipment and welded under the vacuum condition; in the welding process, staged heating and heat preservation are adopted, and staged cooling is adopted after welding is completed; and S40, after welding is completed, air tightness testing is conducted on the structure obtained through welding. According to the method provided by the embodiment of the invention, the zirconium alloy circular pipe and the stainless steel circular pipe can form the high-strength and high-compactness welding connector, and the welding quality and the reliability and durability of the welding connector can be improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of non-electric welding using impact or other pressures, and specifically to a method for welding a zirconium alloy round tube and a stainless steel round tube, and a zirconium alloy and stainless steel connecting piece. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] Zirconium alloys and stainless steel are widely used in the nuclear industry because zirconium alloys have excellent corrosion resistance, low neutron absorption cross-section and good mechanical properties, and stainless steel has excellent corrosion resistance, heat resistance, strength and good machinability. For example, zirconium alloys are used in the fuel cladding and structural components of nuclear reactors, and stainless steel is used in the piping systems, pressure vessels and heat exchange equipment of nuclear reactors.

[0004] However, in some special application scenarios, such as the cooling system of a nuclear power plant or the highly corrosive environment of chemical equipment, both the excellent corrosion resistance of zirconium alloy and the outstanding strength and mechanical properties of stainless steel are required, making it difficult to meet the use requirements by using only zirconium alloy or only stainless steel. Therefore, it is necessary to connect zirconium alloy and stainless steel to meet the use requirements of the application scenario. Summary of the invention

[0005] A brief overview of the present application is provided below in order to provide a basic understanding of certain aspects of the present application. It should be understood that this overview is not an exhaustive overview of the present application. It is not intended to identify the key or important parts of the present application, nor is it intended to limit the scope of the present application. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0006] The embodiments of the present application provide a method for welding a zirconium alloy round tube and a stainless steel round tube, and a zirconium alloy and stainless steel connecting piece.

[0007] In a first aspect, an embodiment of the present application provides a method for welding a zirconium alloy round tube and a stainless steel round tube, which comprises the following steps: S10, processing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded; S20, fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded processed in step S10 on a graphite clamp; S30, placing the graphite clamp fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded into a welding device and welding under vacuum conditions; wherein, during the welding process, a staged heating and heat preservation method is adopted, and after the welding is completed, a staged cooling method is adopted; S40, after the welding is completed, the air tightness test of the welded structure is performed.

[0008] The method provided in the embodiment of the present application adopts a staged heating and heat preservation method during the welding process, and a staged cooling method after the welding is completed, which is conducive to the mutual diffusion of atoms between the zirconium alloy round tube and the stainless steel round tube to achieve welding, so as to ensure that the zirconium alloy round tube and the stainless steel round tube can form a high-strength and high-density welding interface, thereby helping to improve the welding quality as well as the reliability and durability of the welding interface.

[0009] In a second aspect, an embodiment of the present application further provides a zirconium alloy and stainless steel connecting piece, which is obtained by welding using the method provided in the embodiment of the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other objects and advantages of the present application will become apparent from the following description of the embodiments of the present application with reference to the accompanying drawings, and will help to provide a comprehensive understanding of the present application.

[0011] Figure 1 It is a schematic flow chart of a method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application.

[0012] Figure 2 It is a structural schematic diagram of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded.

[0013] Figure 3 It is a flow chart of the heating stage, the heat preservation stage and the cooling stage in the method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application.

[0014] Description of reference numerals:

[0015] 21. zirconium alloy round tube; 210. conical structure; 22. stainless steel round tube; 220. inverted conical structure;

[0016] 31. The first heating and heat preservation stage; 32. The second heating and heat preservation stage; 33. The third heating and heat preservation stage;

[0017] 34. The first cooling stage; 35. The second cooling stage;

[0018] 301, first predetermined temperature; 302, second predetermined temperature; 303, third predetermined temperature; 304, fourth predetermined temperature; 305, fifth predetermined temperature.

[0019] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding. DETAILED DESCRIPTION

[0020] Exemplary embodiments of the present application will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual implementation are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual implementation in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary from implementation to implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is only a routine task for those skilled in the art who benefit from the content of this application.

[0021] It is also necessary to explain here that, in order to avoid obscuring the present application due to unnecessary details, only the device structure and / or processing steps closely related to the scheme according to the present application are shown in the accompanying drawings, while other details that are not very relevant to the present application are omitted.

[0022] In the related art, zirconium alloy and stainless steel are usually fixedly connected by welding the zirconium alloy and the intermediate layer material, and by welding the stainless steel and the intermediate layer material. However, due to the involvement of the intermediate layer material, the welding steps are more complicated, the welding efficiency is low, and in particular, the welding quality often fails to meet the requirements.

[0023] In view of the above problems, the embodiments of the present application provide a method for welding a zirconium alloy round tube and a stainless steel round tube, and a zirconium alloy and stainless steel connecting piece.

[0024] The embodiment of the present application provides a method for welding a zirconium alloy round tube and a stainless steel round tube, see Figure 1 , Figure 1 It is a flow chart of a method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application, which comprises the following steps: S10, processing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded; S20, fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded processed in step S10 on a graphite clamp; S30, placing the graphite clamp with the zirconium alloy round tube to be welded and the stainless steel round tube to be welded fixed in a welding device and welding under vacuum conditions; wherein, during the welding process, a staged heating and heat preservation method is adopted, and after the welding is completed, a staged cooling method is adopted; S40, after the welding is completed, performing an air tightness test on the structure obtained by welding.

[0025] The method provided in the embodiment of the present application adopts a staged heating and heat preservation method during the welding process, and a staged cooling method after the welding is completed, which is conducive to the mutual diffusion of atoms between the zirconium alloy round tube and the stainless steel round tube to achieve welding, so as to ensure that the zirconium alloy round tube and the stainless steel round tube can form a high-strength and high-density welding interface, thereby helping to improve the welding quality as well as the reliability and durability of the welding interface.

[0026] In some embodiments, the outer diameter of the zirconium alloy round tube and the stainless steel round tube may be 15-20 mm, and the inner diameter may be 2-4 mm.

[0027] In some embodiments, the welding equipment may be a vacuum diffusion welding equipment. In some embodiments, during the welding process, the vacuum degree does not exceed 10 -5 Pa to avoid oxidation affecting welding quality.

[0028] In some embodiments, in step S30, a graphite fixture fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded can be placed on the welding platform of the vacuum diffusion welding equipment, and the upper and lower welding machine pressure heads of the vacuum diffusion welding equipment can be aligned to apply pressure to the zirconium alloy round tube and the stainless steel round tube.

[0029] See also Figure 2 , Figure 2 It is a structural schematic diagram when the zirconium alloy round tube to be welded and the stainless steel round tube to be welded are matched. In some embodiments, in step S10, the following steps are also included: S11, forming a conical structure 210 on the outer wall of one end of the zirconium alloy round tube 21 to be welded; S12, forming an inverted conical structure 220 relative to the conical structure 210 on the inner wall of one end of the stainless steel round tube 22 to be welded, and the inverted conical structure 220 is matched with the conical structure 210. Due to the large difference in linear expansion coefficients between zirconium alloy and stainless steel, there is a problem of stress concentration at the welding interface during the welding process. In the embodiment of the present application, by forming a conical structure 210 on the outer wall of one end of the zirconium alloy circular tube 21 to be welded, and forming an inverted conical structure 220 that matches the conical interface on the inner wall of one end of the stainless steel circular tube 22 to be welded, the contact area between the zirconium alloy circular tube 21 and the stainless steel circular tube 22 can be increased to improve the stress concentration problem at the welding interface, thereby helping to improve the quality of welding; at the same time, it can also offset the difference in thermal expansion between zirconium alloy and stainless steel to ensure that the stress distribution of the welding interface during heating and cooling is uniform, thereby improving the strength and reliability of the welding interface. In particular, the mutual diffusion between metal atoms can be further improved so that the welding area can form a dense metallurgical bonding area.

[0030] In some embodiments, before step S11, it may also include determining to form a conical structure 210 on the zirconium alloy tube according to the difference in linear expansion coefficients between the zirconium alloy and the stainless steel, and determining to form an inverted conical structure 220 matching the conical structure 210 on the stainless steel tube.

[0031] In some embodiments, the opening angle of the conical structure 210 formed by the zirconium alloy round tube and the opening angle of the inverted conical structure 220 formed by the stainless steel round tube can both be 10°-15°.

[0032] In some embodiments, in step S10, the following steps are also included: S13, roughening the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded, and cleaning the treated zirconium alloy round tube to be welded and the stainless steel round tube to be welded; S14, drying the zirconium alloy round tube to be welded and the stainless steel round tube to be welded after the treatment in step S13 at a predetermined temperature for a predetermined time. In such an embodiment, by roughening the zirconium alloy round tube and the stainless steel round tube to be welded, the surface roughness of the zirconium alloy round tube and the stainless steel round tube is within a preset range, so as to ensure that the zirconium alloy round tube and the stainless steel round tube have a good diffusion bonding effect during the welding process and improve the welding quality.

[0033] In some embodiments, the surface roughness of the zirconium alloy round tube and the stainless steel round tube to be welded after roughening treatment is Ra 0.8-1.6 μm.

[0034] In some embodiments, in step S13, the treated zirconium alloy round tube to be welded and the stainless steel round tube to be welded can be cleaned with chemical reagents to remove oxide impurities and oil impurities on the surface of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded.

[0035] In some embodiments, in step S14, the predetermined drying temperature can be 120°C and the predetermined drying time can be 60 minutes to ensure that the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded are completely dry and clean to avoid residual contaminants affecting the welding quality.

[0036] In some embodiments, in step S30, during the welding process, a pressure within a preset pressure range is applied to the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded. In such an embodiment, by applying pressure to the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded, atoms of the zirconium alloy round tube and the stainless steel round tube can diffuse through the surface, thereby achieving diffusion welding of the zirconium alloy round tube and the stainless steel round tube; at the same time, applying a pressure within a preset pressure range is conducive to improving the welding quality, so as to ensure that the zirconium alloy round tube and the stainless steel round tube can form a high-strength, high-density welding interface, thereby helping to improve the welding quality and improve the reliability and durability of the welding interface.

[0037] In some embodiments, the preset pressure range of the pressure applied to the welding surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded is 12-14 MPa, for example, 13 MPa.

[0038] In some embodiments, in step S30, after welding is completed, the pressure is gradually released until the welding temperature drops to a predetermined value. In such an embodiment, the above arrangement is conducive to improving the welding quality and avoiding affecting the compactness of the welding interface between the zirconium alloy round tube and the stainless steel round tube.

[0039] In some embodiments, the predetermined value may be 500° C., that is, the pressure is gradually released after the welding temperature is lower than 500° C.

[0040] See also Figure 3 , Figure 3 It is a flow chart of the heating stage, the insulation stage and the cooling stage in the method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application. In some embodiments, in step S30, the staged heating and insulation method adopted may specifically include a first heating and insulation stage 31, a second heating and insulation stage 32 and a third heating and insulation stage 33. The first heating and insulation stage 31: heating to a first predetermined temperature 301 at a first heating rate and maintaining the first predetermined time; the second heating and insulation stage 32: heating to a second predetermined temperature 302 at a second heating rate and maintaining the second predetermined time; the third heating and insulation stage 33: heating to a third predetermined temperature 303 at a third heating rate and maintaining the third predetermined time. In such an embodiment, by raising the temperature in stages to the first predetermined temperature 301, the second predetermined temperature 302 and the third predetermined temperature 303, and maintaining the first predetermined time, the second predetermined time and the third predetermined time respectively, the zirconium alloy round tube and the stainless steel round tube can be diffusion welded under appropriate temperature conditions, which is conducive to forming a high-strength and high-density welding interface.

[0041] In some embodiments, the first heating rate is equal to the second heating rate, and the second heating rate is greater than the third heating rate; the first predetermined temperature 301 is less than the second predetermined temperature 302, and the second predetermined temperature 302 is less than the third predetermined temperature 303; the first predetermined time is less than the second predetermined time, and the second predetermined time is less than the third predetermined time. In such an embodiment, the above settings are conducive to more precise control of the welding temperature, which can effectively avoid stress concentration and deformation in the zirconium alloy round tube and the stainless steel round tube, and further improve the quality of welding and the reliability and durability of the obtained welding interface.

[0042] In some embodiments, the first heating rate is 10-15°C / min, the second heating rate is 10-15°C / min, and the third heating rate is 5-10°C / min; the first predetermined temperature 301 is 500°C, the second predetermined temperature 302 is 800°C, and the third predetermined temperature 303 is 1030°C; the first predetermined time is 20-30min, the second predetermined time is 20-30min, and the third predetermined time is 1-1.5h.

[0043] In some embodiments, in step S30, the staged cooling method specifically includes a first cooling stage 34, a second cooling stage 35, and a third cooling stage. The first cooling stage 34: cooling to a fourth predetermined temperature 304 at a first cooling rate; the second cooling stage 35: cooling to a fifth predetermined temperature 305 at a second cooling rate; the third cooling stage: cooling from the fifth predetermined temperature 305 to room temperature. In such an embodiment, the above arrangement also enables the zirconium alloy round tube and the stainless steel round tube to be diffusion welded under appropriate temperature conditions, which is conducive to forming a high-strength, high-density welding interface.

[0044] In some embodiments, the first cooling rate is less than the second cooling rate, and the fourth predetermined temperature 304 is greater than the fifth predetermined temperature 305. In such an embodiment, the above configuration is conducive to more accurate control of the temperature during the cooling process, and can effectively avoid stress concentration and deformation in the zirconium alloy round tube and the stainless steel round tube, further improving the quality of welding and the reliability and durability of the obtained welding interface.

[0045] In some embodiments, the first cooling rate is equal to the third heating rate, and the fourth predetermined temperature 304 is equal to the second predetermined temperature 302 ; the second cooling rate is equal to the first heating rate, and the fifth predetermined temperature 305 is less than the first predetermined temperature 301 .

[0046] In some embodiments, the first cooling rate is 5-10°C / min, the second cooling rate is 10-15°C / min; the fourth predetermined temperature 304 is 800°C, and the fifth predetermined temperature 305 is 400°C.

[0047] In some embodiments, in step S30, the temperature of the zirconium alloy round tube and the stainless steel round tube can be reduced from the fifth predetermined temperature 305 to room temperature by natural cooling, so as to avoid large thermal stress at the welding interface and ensure the integrity of the welding interface.

[0048] In some embodiments, in step S20, a solder resist is further provided on the surface of the graphite fixture in contact with the zirconium alloy round tube to be welded and the stainless steel round tube to be welded. In such an embodiment, the above-mentioned setting can prevent the zirconium alloy round tube and the stainless steel round tube from adhering to the graphite fixture during the welding process, so as to avoid affecting the welding of the zirconium alloy round tube and the stainless steel round tube.

[0049] In some embodiments, in step S40, the air tightness test of the structure obtained by welding includes: sealing one end of the structure obtained by welding; introducing gas of a predetermined pressure into the structure obtained by welding through the unsealed end of the structure obtained by welding, and maintaining the air pressure in the structure obtained by welding at the predetermined pressure; if no leakage occurs within a predetermined time, the air tightness of the structure obtained by welding is good and can meet the use requirements; if leakage occurs before the predetermined time, the air tightness of the structure obtained by welding is poor and cannot meet the use requirements.

[0050] In some embodiments, in step S40, when performing an air tightness test on the structure obtained by welding, the preset pressure of the gas introduced into the structure obtained by welding may be 13-15 MPa, and the preset time may be 60 seconds.

[0051] The following is a description of the process of welding a zirconium alloy round tube and a stainless steel round tube using the method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application; wherein the zirconium alloy round tube is a Zr-3 zirconium alloy round tube with an outer diameter of 17 mm and an inner diameter of 6 mm, and the stainless steel round tube is a 304 stainless steel round tube with an outer diameter of 17 mm and an inner diameter of 2.8 mm.

[0052] First, the ends of the Zr-3 zirconium alloy round tube and the 304 stainless steel round tube to be welded are processed respectively to form a conical structure 210 with an opening angle of 10° at the end of the Zr-3 zirconium alloy round tube to be welded, and an inverted conical structure 220 with an opening angle of 10° is formed at the end of the 304 stainless steel round tube to be welded.

[0053] Afterwards, the processed Zr-3 zirconium alloy round tube and 304 stainless steel round tube are roughened to ensure that the surface roughness of the Zr-3 zirconium alloy round tube and 304 stainless steel round tube after the roughening treatment reaches Ra 0.8μm; and the surfaces of the Zr-3 zirconium alloy round tube and 304 stainless steel round tube after the roughening treatment are cleaned with chemical reagents, and after the cleaning is completed, the cleaned Zr-3 zirconium alloy round tube and 304 stainless steel round tube are placed in a drying oven and dried at 120°C for 60 minutes.

[0054] Afterwards, the cleaned and dried Zr-3 zirconium alloy round tube and 304 stainless steel round tube are taken out of the drying oven, the conical structure 210 of the Zr-3 zirconium alloy round tube is inserted into the inverted conical structure 220 of the 304 stainless steel round tube, and the Zr-3 zirconium alloy round tube and the 304 stainless steel round tube are fixed in a graphite fixture; and solder resist is sprayed on the contact surface of the graphite fixture with the Zr-3 zirconium alloy round tube and the contact surface of the graphite fixture with the 304 stainless steel round tube.

[0055] After that, the graphite fixture and the Zr-3 zirconium alloy round tube and 304 stainless steel round tube fixed on it are placed on the welding platform of the vacuum diffusion welding equipment, the upper and lower welding machine pressure heads are aligned, and the equipment is started to evacuate until the vacuum degree reaches 10 -5 Pa, start the welding process; during the welding process, first heat up to 500℃ at a heating rate of 12℃ / min and keep it for 20min, then heat up to 800℃ at a heating rate of 12℃ / min and keep it for 25min, then heat up to 1030℃ at a heating rate of 8℃ / min and keep it for 1.5h; during the whole welding process, a pressure of 13MPa is always applied to the surface of the Zr-3 zirconium alloy round tube and the 304 stainless steel round tube to be welded, and the pressure is gradually released after the temperature drops to 500℃.

[0056] After welding is completed, the cooling process begins; during the cooling process, the temperature is first cooled to 800°C at a cooling rate of 8°C / min, then cooled to 400°C at a cooling rate of 12°C / min, and then naturally cooled to room temperature.

[0057] After the cooling is completed, the welded structure is taken out of the vacuum diffusion welding equipment, and the welding interface is tested for air tightness: one end of the welded structure is sealed, and 15MPa of gas is introduced into the welded structure from the unsealed end and the pressure is maintained for 60s to ensure that there is no gas leakage, so as to determine that the welding interface is airtight.

[0058] An embodiment of the present application further provides a zirconium alloy and stainless steel connecting piece, which is obtained by welding a zirconium alloy round tube and a stainless steel round tube according to any embodiment of the present application.

[0059] Regarding the embodiments of the present application, it should also be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other to obtain new embodiments.

[0060] The above are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. The protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for welding a zirconium alloy round tube and a stainless steel round tube, characterized in that: It includes the following steps: S10, processing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded; S20, fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded processed in step S10 on a graphite fixture; S30, placing a graphite fixture fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded into a welding device and welding them under vacuum conditions; wherein, during the welding process, a staged heating and heat preservation method is adopted, and after the welding is completed, a staged cooling method is adopted; S40. After welding is completed, an air tightness test is performed on the structure obtained by welding.

2. The method according to claim 1, characterized in that In step S10, the following steps are also included: S11, forming a tapered structure on the outer wall of one end of the zirconium alloy round tube to be welded; S12. An inverted cone structure relative to the cone structure is formed on the inner wall of one end of the stainless steel round tube to be welded, and the inverted cone structure matches the cone structure.

3. The method according to claim 2, characterized in that In step S10, the following steps are also included: S13, roughening the welding surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded, and cleaning the treated zirconium alloy round tube to be welded and the stainless steel round tube to be welded; S14, drying the zirconium alloy round tube to be welded and the stainless steel round tube to be welded after being processed in step S13 at a predetermined temperature for a predetermined time.

4. The method according to claim 1, characterized in that In step S30, during the welding process, a pressure within a preset pressure range is applied to the welding surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded.

5. The method according to claim 4, characterized in that In step S30, after welding is completed, the pressure is gradually released until the welding temperature drops to a predetermined value.

6. The method according to claim 1, characterized in that In step S30, the staged heating and heat preservation method specifically includes the following stages: Heating to a first predetermined temperature at a first heating rate and maintaining the temperature for a first predetermined time; The temperature is raised to a second predetermined temperature at a second heating rate and maintained for a second predetermined time, The temperature is increased to a third predetermined temperature at a third temperature increase rate and maintained for a third predetermined time.

7. The method according to claim 6, characterized in that The first heating rate is equal to the second heating rate, and the second heating rate is greater than the third heating rate; The first predetermined temperature is lower than the second predetermined temperature, and the second predetermined temperature is lower than the third predetermined temperature; The first predetermined time is shorter than the second predetermined time, and the second predetermined time is shorter than the third predetermined time.

8. The method according to claim 7, characterized in that In step S30, the staged cooling method adopted specifically includes the following stages: Cooling down to a fourth predetermined temperature at a first cooling rate; Cooling the temperature to a fifth predetermined temperature at a second cooling rate; And the temperature is lowered from the fifth predetermined temperature to room temperature.

9. The method according to claim 8, characterized in that The first temperature drop rate is smaller than the second temperature drop rate, and the fourth predetermined temperature is larger than the fifth predetermined temperature.

10. The method according to claim 8, characterized in that The first temperature reduction rate is equal to the third temperature increase rate, and the fourth predetermined temperature is equal to the second predetermined temperature; The second temperature reduction rate is equal to the first temperature increase rate, and the fifth predetermined temperature is lower than the first predetermined temperature.

11. The method according to claim 1, characterized in that: In step S20, it also includes providing a solder resist on the surface of the graphite fixture that contacts the zirconium alloy round tube to be welded and the stainless steel round tube to be welded.

12. A zirconium alloy and stainless steel connector, characterized in that: The connecting piece is obtained by welding using the method described in any one of claims 1 to 11.

Images