Method for welding niobium / molybdenum fillet weld of heat pipe by using laser reflection principle

Abstract

The invention discloses a method for realizing niobium / molybdenum fillet weld welding of a heat pipe by utilizing the laser reflection principle, comprising the following steps: 1) pre-treating the end face of a molybdenum end plug and the outer surface of a niobium tube; 2) passing the niobium tube through a reserved hole on the molybdenum end plug; 3) sleeve-fitting a niobium ring on the niobium tube so that the niobium ring contacts the end face of the molybdenum end plug; 4) adjusting the angle between the incident direction of a laser beam and the axial direction of the niobium tube and the incident position of the laser beam, and then performing multiple passes of welding by laser welding to complete the niobium / molybdenum fillet weld welding of the heat pipe by utilizing the laser reflection principle, and the method realizes the fillet weld welding of niobium and molybdenum.

Description

Technical Field

[0001] The invention belongs to the technical field of welding and relates to a method for realizing niobium / molybdenum fillet welding of a heat pipe by utilizing the laser reflection principle. Background Art

[0002] Molybdenum has a high melting point (2600°C), high thermal conductivity (138W / (m·K)), and high high-temperature strength, making it very suitable for manufacturing ultra-high temperature heat pipes for small nuclear reactors. A molybdenum heat pipe includes: a molybdenum tube, a molybdenum end plug, and a liquid-filled tube. Since niobium has a melting point of up to 3000°C, good plasticity at high and room temperatures, and can be cold processed, it is usually used as a liquid-filled tube for heat pipes. The liquid-filled tube is used to fill the heat pipe with alkali metals. After filling, part of the niobium tube must be flattened to achieve a mechanical sealing effect. In the manufacturing process of the molybdenum heat pipe, it is necessary to weld and assemble the molybdenum tube / end plug and the end plug / niobium tube, that is, it is necessary to realize the welding of niobium and molybdenum corner welds. However, no similar disclosure is given in the prior art. Summary of the invention

[0003] The purpose of the present invention is to overcome the disadvantages of the prior art and provide a method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle. The method realizes the welding of niobium and molybdenum fillet welds.

[0004] To achieve the above object, the method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle of the present invention comprises the following steps:

[0005] 1) Pre-treating the end surface of the molybdenum end plug and the outer surface of the niobium tube;

[0006] 2) Pass the niobium tube through the reserved hole on the molybdenum end plug;

[0007] 3) Sleeve the niobium ring onto the niobium tube so that the niobium ring contacts the end surface of the molybdenum end plug;

[0008] 4) adjusting the angle between the incident direction of the laser beam and the axial direction of the niobium tube and the incident position of the laser beam, and then performing multiple passes of welding by laser welding to complete the niobium / molybdenum fillet weld of the heat pipe using the principle of laser reflection.

[0009] The specific operation process of step 1) is: polishing the end surface of the molybdenum end plug and the outer surface of the niobium tube, then immersing them in acetone for ultrasonic cleaning, and then blowing the surfaces of the molybdenum end plug and the niobium tube dry.

[0010] The ultrasonic cleaning time is greater than or equal to 10 minutes.

[0011] The length of the niobium tube passing through the reserved hole on the molybdenum end plug is 10 mm.

[0012] The niobium tube and the reserved hole are interference fit.

[0013] The inner diameter of the niobium ring is the same as the outer diameter of the niobium tube.

[0014] Both ends of the niobium tube are sleeved with niobium rings.

[0015] The specific operations of step 4) are:

[0016] The niobium tube and the molybdenum end plug are placed at an angle of 35° counterclockwise to the horizontal plane, the incident direction of the laser beam is at an angle of 45° counterclockwise to the axial direction of the niobium tube, and the incident position of the laser beam is located on the upper surface of the niobium ring, so that the incident spot position of the laser beam is all located on the upper surface of the niobium ring, realizing the distribution of laser energy on the niobium ring, the end face of the molybdenum end plug and the outer surface of the niobium tube.

[0017] The present invention has the following beneficial effects:

[0018] In the method for realizing niobium / molybdenum fillet weld of heat pipe by utilizing laser reflection principle, the angle between the incident direction of laser beam and the axial direction of niobium tube and the incident position of laser beam are adjusted during specific operation, so as to realize energy distribution of laser at the position of niobium tube / molybdenum end plug fillet weld, ensure full melting of filling material, reduce welding penetration rate of niobium tube, ensure good fusion between filling material and niobium tube, reduce heat input on the side of molybdenum end plug, suppress possible overheating and embrittlement problems, and realize high-strength connection of niobium / molybdenum fillet weld. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1a is a schematic diagram of a cross section of an ultra-high temperature molybdenum heat pipe;

[0020] Figure 1b Schematic diagram of the cross section of the niobium tube 5 end plug welding joint

[0021] Figure 2a is a specific dimension diagram of the niobium tube 5;

[0022] Figure 2b The specific dimension diagram of the molybdenum end plug 2;

[0023] Figure 3 It is a schematic diagram of the assembly position of each component of the niobium tube 5 / molybdenum end plug 2 fillet weld;

[0024] Figure 4 It is a schematic diagram of the fillet weld of the niobium tube 5 / molybdenum end plug 2;

[0025] Figure 5 is the incident optical path diagram of the laser beam 4;

[0026] Figure 6 It is an enlarged view of the laser incident light path diagram;

[0027] Figure 7 This is a physical picture of the fillet weld of the niobium tube 5 / molybdenum end plug 2.

[0028] Among them, 1 is a niobium ring, 2 is a molybdenum end plug, 3 is argon gas, 4 is a laser beam, and 5 is a niobium tube. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and is not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0030] The accompanying drawings show schematic diagrams of structures according to embodiments disclosed in the present invention. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0031] The method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle of the present invention comprises the following steps:

[0032] 1) grinding the end surface of the molybdenum end plug 2 and the outer surface of the niobium tube 5, then immersing them in acetone for ultrasonic cleaning, and then drying the surfaces of the molybdenum end plug 2 and the niobium tube 5, and the ultrasonic cleaning time is greater than or equal to 10 minutes;

[0033] 2) passing the niobium tube 5 through the reserved hole on the molybdenum end plug 2;

[0034] 3) Sleeve the niobium ring 1 onto the niobium tube 5 so that the niobium ring 1 contacts the end surface of the molybdenum end plug 2;

[0035] 4) The niobium tube 5 and the molybdenum end plug 2 are placed at an angle of 35° counterclockwise to the horizontal plane, the incident direction of the laser beam 4 is at an angle of 45° counterclockwise to the axial direction of the niobium tube 5, and the incident position of the laser beam 4 is located on the upper surface of the niobium ring 1, so that the incident spot positions of the laser beam 4 are all located on the upper surface of the niobium ring 1, and the laser energy is distributed on the niobium ring 1, the end surface of the molybdenum end plug 2 and the outer surface of the niobium tube 5.

[0036] The length of the niobium tube 5 passing through the reserved hole on the molybdenum end plug 2 is 10 mm. The niobium tube 5 and the reserved hole are interference fit, and the inner diameter of the niobium ring 1 is the same as the outer diameter of the niobium tube 5 .

[0037] Both ends of the niobium tube 5 are sleeved with niobium rings 1 .

[0038] Embodiment 1

[0039] Select a niobium tube 5 with an outer diameter of 6 mm and a wall thickness of 0.8 mm, such as Figure 2a As shown, a molybdenum end plug 2 with an outer diameter of 16 mm and a through hole diameter of 5.9 mm is selected. Figure 2b As shown, the specific process is:

[0040] 1) polishing the end surface of the molybdenum end plug 2 and the outer surface of the niobium tube 5, and then immersing them in acetone for ultrasonic cleaning, wherein the cleaning time is greater than or equal to 10 minutes, and then drying them for standby use;

[0041] 2) Pass the end of the niobium tube 5 through the reserved hole of the molybdenum end plug 2, wherein the protruding length is 10 mm;

[0042] 3) Niobium rings 1 are sleeved on both ends of the niobium tube 5, wherein the outer diameter of the niobium ring 1 is 8 mm, the inner diameter is 6 mm, and the thickness is 2 mm. The upper and lower surfaces of the niobium ring 1 are flat, wherein one surface contacts the end surface of the molybdenum end plug 2. The structure after assembly is as follows: Figure 3 As shown;

[0043] 4) Place the assembled niobium tube 5 / molybdenum end plug at a 35° counterclockwise angle to the horizontal plane, and adjust the incident direction of the laser beam 4 to a 45° counterclockwise angle with the axial direction of the niobium tube 5, such as Figure 4 As shown; the incident position of the laser beam 4 is located on the upper surface of the niobium ring 1, ensuring that the incident laser is all on the niobium ring 1, as shown Figure 5 and Figure 6 As shown, after the laser beam 4 acts on the niobium ring 1, part of the energy is used to melt the end faces of the niobium ring 1 and the molybdenum end plug 2, and the other part of the energy is reflected. According to the law of reflection of light, the reflected laser will act on the outer surface of the niobium tube 5, and part of the laser energy will be used to heat the niobium tube 5, such as Figure 5 and Figure 6 As shown, in this example, the incident angle of the laser beam 4 is selected so that most of the energy is used to melt the niobium tube 5, and a small part of the energy is used to melt the molybdenum end plug 2, thereby avoiding the occurrence of cracks at the toe position of the fillet weld and obtaining a well-formed weld, such as Figure 7 shown.

Claims

1. A method for welding niobium / molybdenum fillet welds of heat pipes using the principle of laser reflection. It is characterized in that The following steps are involved: 1) pre-treating the end surface of the molybdenum end plug (2) and the outer surface of the niobium tube (5); 2) passing the niobium tube (5) through the reserved hole on the molybdenum end plug (2); 3) Sleeving the niobium ring (1) onto the niobium tube (5) so that the niobium ring (1) is in contact with the end surface of the molybdenum end plug (2); 4) adjusting the angle between the incident direction of the laser beam (4) and the axial direction of the niobium tube (5) and the incident position of the laser beam (4), and then performing multiple passes of welding by laser welding to complete the niobium / molybdenum fillet weld of the heat pipe by using the laser reflection principle; The niobium tube (5) and the molybdenum end plug (2) are placed at an angle of 35° counterclockwise to a horizontal plane, the incident direction of the laser beam (4) is at an angle of 45° counterclockwise to the axial direction of the niobium tube (5), and the incident position of the laser beam (4) is located on the upper surface of the niobium ring (1), so that the incident spot position of the laser beam (4) is all located on the upper surface of the niobium ring (1), thereby achieving the distribution of laser energy on the niobium ring (1), the end surface of the molybdenum end plug (2) and the outer surface of the niobium tube (5).

2. The method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle according to claim 1, It is characterized in that The specific operation process of step 1) is: polishing the end surface of the molybdenum end plug (2) and the outer surface of the niobium tube (5), then immersing them in acetone for ultrasonic cleaning, and then blowing the surfaces of the molybdenum end plug (2) and the niobium tube (5) dry.

3. The method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle according to claim 2, It is characterized in that The ultrasonic cleaning time is greater than or equal to 10 minutes.

4. The method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle according to claim 1, It is characterized in that The length of the niobium tube (5) passing through the reserved hole on the molybdenum end plug (2) is 10 mm.

5. The method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle according to claim 1, It is characterized in that The niobium tube (5) and the reserved hole are interference fit.

6. The method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle according to claim 1, It is characterized in that The inner diameter of the niobium ring (1) is the same as the outer diameter of the niobium tube (5).

7. The method for welding niobium / molybdenum fillet welds of heat pipes using the laser reflection principle according to claim 1, It is characterized in that Both ends of the niobium tube (5) are sleeved with niobium rings (1).

Images