CN114713928B - Connection method of special-shaped carbon/carbon and metal composite heat dissipation long tube with segmented fins - Google Patents

Abstract

The invention relates to a method for connecting a special-shaped carbon/carbon and metal composite heat dissipation long tube with segmented fins. The invention belongs to the field of connection of carbon/carbon composite materials and metal materials, and aims to solve the problems of material deformation and joint cracking caused by overlarge residual stress in connection of long tubular metal and special-shaped carbon/carbon composite tubes. The invention carries out sectional pretreatment on the fins of the special-shaped carbon/carbon composite tube, and then adopts a vacuum brazing method to realize the brazing connection of the special-shaped carbon/carbon radiating tube with the fins and the metal long tube, the obtained composite radiating long tube joint is fully connected, the radiating carbon/carbon special-shaped tube matrix and the radiating fins have no deformation and cracking, and the connection strength can reach more than 20MPa. The process method provided by the invention has the advantages of easiness in operation, low cost, safety and reliability, and is particularly suitable for connecting long tubular brazing special pipes.

Description

A connection method for segmented finned carbon/carbon and metal composite heat dissipation long tubes

technical field

The invention belongs to the connection technology of special-shaped composite material parts and metal long pipes, and relates to a connection method of finned segmented special-shaped carbon/carbon and metal composite heat dissipation long pipes.

Background technique

With the continuous combination and development of national defense and aerospace fields and nuclear energy fields, space nuclear reactor power supplies have outstanding performance in high-power earth orbit satellites, unmanned deep space probes, manned deep space exploration, and power supply for lunar planetary bases. Its component heat pipe radiator can discharge a large amount of waste heat due to the low thermoelectric conversion efficiency of nuclear power sources into space. The heat transfer unit of the heat pipe radiator is composed of heat pipes, fins and other related coatings. With the rapid development of material science, carbon fiber reinforced carbon (carbon/carbon) composite materials can effectively reduce the weight of components and improve heat transfer efficiency due to their low density, high thermal conductivity, high strength and ablation resistance. Excellent choice for fin material.

Therefore, in order to realize the structural and functional integration of carbon/carbon fins and metal heat pipes, carbon/carbon composite materials are usually connected with metals to form composite components. Brazing is currently the most convenient and feasible method. However, due to the high thermal expansion coefficient mismatch between carbon/carbon composites and metals (CTE _{carbon/carbon} = 0-2×10 ^-6 K ^-1 ), high residual stresses exist in the joints of the two, severely weakening the joint mechanics performance. On the other hand, the stable connection of long pipe fittings in the field of brazing has always been a research hotspot and difficulty, and its gap control, process setting, assembly and pressurization methods all play an important role in the safe and long-term use of the joint. However, in actual operation, it is difficult to solve problems such as structural deformation and damage of composite parts caused by excessive residual stress generated during the long pipe welding process. Therefore, it is necessary to develop a new method to connect the carbon/carbon heat dissipation special-shaped tube and the metal long tube to obtain a dense joint without deformation and cracking of the fins.

Contents of the invention

The invention aims to solve the problems of large deformation and easy cracking when special-shaped carbon/carbon composite materials are connected to metal long pipe fittings, and provides a connection method of finned segmented special-shaped carbon/carbon and metal composite heat dissipation long pipes.

The connection method that the present invention uses realizes according to the following steps:

Step 1. Carbon/carbon fin processing: In the case of ensuring that the base of the carbon/carbon heat dissipation special-shaped tube is not damaged, the fins are processed in 3-5 sections, each section is 150-200mm long, and the gap between the two sections is The opening width is 0.5-2.5mm, and the opening depth is 1-2mm from the edge of the fin to the root of the carbon/carbon heat pipe base;

Step 2. Surface treatment to be welded: Mechanically grind the inner wall of the carbon/carbon heat dissipation special-shaped tube with emery cloth, and mechanically grind the outer wall of the metal tube, then clean it with absolute ethanol, and then dry it in a vacuum drying oven;

Step 3. Joint assembly: Assemble the processed carbon/carbon heat dissipation special-shaped tube with the metal long tube, fill and fix the solder between the two, and send the assembled joint into the tube furnace in parallel, and ensure that in a horizontal position;

Step 4. Vacuum brazing: the vacuum degree of brazing is not lower than 5×10 ^-3 Pa, and a pressure of 2-5 MPa is applied to the inner wall of the metal tube; the multi-platform heating process: firstly, the heating rate is 3-5°C/min from Raise the temperature from room temperature to 200-340°C for 30-60min, then raise the temperature from room temperature to 580-620°C at a heating rate of 5-10°C/min and keep it for 10-15min, then raise the temperature at a rate of 5-10°C/min to 850- 1100°C heat preservation for 8-15min; multi-platform cooling process: cooling at a rate of 1-5°C/min to 920-950°C for 30-60min, cooling at a rate of 1-5°C/min to 820-850°C for 30- 60min, cool down to 720-750°C at a rate of 1-5°C/min and keep warm for 30-60min, cool down to 620-650°C at a rate of 1-5°C/min and keep warm for 30-60min, at a rate of 1-5°C/min The temperature is lowered to 520-550° C. and kept for 30-60 minutes, and finally cooled to room temperature with the furnace to obtain the special-shaped carbon/carbon and metal composite heat dissipation long tube.

The length of the carbon/carbon heat dissipation special-shaped tube in step 1 is 300-800mm.

The solder in step 3 is Ag-Cu-Ti, BNi-2, TiZrNiCu, and the solder state is foil or paste.

The connection method of a finned segmented special-shaped carbon/carbon and metal composite heat dissipation long pipe according to the present invention mainly includes the following beneficial effects:

1. The solder used in the present invention can significantly improve the strength of the brazed joint. It can realize the connection between the carbon/carbon heat-dissipating special-shaped tube and the metal long tube. The joint solder is fully filled, and the joint can work in a high temperature environment. The final joint The strength reaches above 20MPa.

2. The method of segmenting the fins in the present invention can significantly reduce the residual stress at the central part of the overall fin without affecting the heat dissipation capacity of the product, avoid the deformation of the heat dissipation fins during the brazing process of the long tube, and improve the product quality. Use performance.

3. The pressurization method used in the present invention is conducive to the full connection of the joints.

4. The present invention sets multi-stage heat preservation platforms in the cooling stage to release the internal stress generated in the high temperature stage, which is beneficial to relieve the residual stress caused by the excessive difference in linear expansion coefficient between the composite material and the metal in the cooling process, and achieve long pipe welding the goal of.

5. The method used in the present invention is safe and reliable in operation, convenient and convenient, efficient and fast in the connection process, low in cost, strong in repeatability, and the resulting product is overall beautiful, fully connected in joints, stable in strength, and suitable for industrial applications.

Description of drawings

Figure 1 is a schematic diagram of the connection between the carbon/carbon heat dissipation special-shaped tube and the long metal tube with fins.

1 is the metal material, 2 is the solder, 3 is the carbon/carbon special-shaped tube, and 4 is the segment of the fin.

specific implementation plan

The present invention will be further described below in conjunction with specific embodiments.

Example 1:

Step 1. Carbon/carbon fin processing: select the carbon/carbon heat dissipation special-shaped tube with a length of 600mm; in the case of ensuring that the carbon/carbon heat dissipation special-shaped The length is 150mm, the opening width between the two sections is 0.5mm, and the opening depth is 2mm from the edge of the fin to the root of the carbon/carbon heat pipe base;

Step 2. Surface treatment to be welded: Mechanically grind the inner wall of the carbon/carbon heat dissipation special-shaped tube with emery cloth, and mechanically grind the outer wall of the metal tube, then clean it with absolute ethanol, and then dry it in a vacuum drying oven;

Step 3. Joint assembly: Assemble the processed carbon/carbon heat dissipation special-shaped tube and metal long tube, fill and fix the amorphous BNi-2 foil solder between the two, and send the assembled joint into the In the tube furnace, and ensure that it is in a horizontal position;

Step 4. Vacuum brazing: the vacuum degree of brazing is not lower than 5×10 ^-3 Pa, and a pressure of 3 MPa is applied to the inner wall of the metal tube; the multi-platform heating process: firstly, the temperature is raised from room temperature to 280 at a heating rate of 5°C/min. ℃ for 40 minutes, then heat up from room temperature to 600°C at a heating rate of 5°C/min for 10 minutes, then heat up to 1050°C at a rate of 8°C/min and hold for 8 minutes; multi-platform cooling process: cool down at a rate of 2°C/min Heat at 950°C for 40 minutes, cool to 850°C at a rate of 2°C/min and hold for 40 minutes, cool at a rate of 2°C/min to 750°C and hold for 40 minutes, cool at a rate of 2°C/min to 650°C and hold for 60 minutes, The temperature is lowered at a rate of ℃/min to 550 ℃ for 60 minutes, and finally cooled to room temperature with the furnace to obtain the special-shaped carbon/carbon and metal composite heat dissipation long tube.

The joints of the obtained special-shaped connectors are fully filled with solder, the welds have no cracks, and the carbon/carbon heat dissipation fins have no deformation and no cracks. The average room temperature shear strength of the tested joints is 20 MPa.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. All simple modifications made to the above embodiments according to the technical essence of the present invention, equivalent changes and modifications, all belong to the technology of the present invention. within the scope of the program.

Claims (3)

1. The connection method of the special-shaped carbon/carbon and metal composite heat dissipation long tube with the fins is characterized by comprising the following steps of:

step 1, processing a carbon/carbon fin: under the condition of ensuring that the carbon/carbon heat dissipation special-shaped tube matrix is not damaged, carrying out 3-5 sections of opening segmentation treatment on the fins, wherein the length of each section is 150-200mm, the opening width between the two sections is 0.5-2.5mm, and the opening depth is 1-2mm from the edge of the fin to the root of the carbon/carbon heat dissipation tube matrix;

step 2, surface treatment to be welded: mechanically polishing the inner wall of the carbon/carbon heat dissipation special-shaped tube by using abrasive cloth, mechanically polishing the outer wall of the metal tube, cleaning by using absolute ethyl alcohol, and drying in a vacuum drying oven;

step 3, joint assembly: assembling the treated carbon/carbon heat dissipation special-shaped tube and the metal long tube, filling brazing filler metal between the two tubes and fixing the tubes, and feeding the assembled joint into a tube furnace in parallel and ensuring the joint to be in a horizontal position;

step 4, vacuum brazing: vacuum degree of brazing is not lower than 5×10 ^-3 Pa, and applying 2-5MPa pressure to the inner wall of the metal pipe; multi-platform heating process: firstly heating from room temperature to 200-340 ℃ at a heating rate of 3-5 ℃/min for 30-60min, and then heating from room temperature to 580-620 ℃ at a heating rate of 5-10 ℃/min for 10-15min, then heating to 850-1100 ℃ at a speed of 5-10 ℃/min, and preserving heat for 8-15min; multi-platform cooling process: cooling to 920-950 ℃ at the speed of 1-5 ℃/min, preserving heat for 30-60min, cooling to 820-850 ℃ at the speed of 1-5 ℃/min, preserving heat for 30-60min, cooling to 720-750 ℃ at the speed of 1-5 ℃/min, preserving heat for 30-60min, cooling to 620-650 ℃ at the speed of 1-5 ℃/min, preserving heat for 30-60min, cooling to 520-550 ℃ at the speed of 1-5 ℃/min, and finally cooling to room temperature along with a furnace to obtain the special-shaped carbon/carbon and metal composite heat dissipation long tube.

2. The method for connecting a fin-segmented special-shaped carbon/carbon and metal composite heat dissipation long tube according to claim 1, wherein the length of the carbon/carbon heat dissipation special-shaped tube in the step 1 is 300-800mm.

3. The method for connecting the fin segmented special-shaped carbon/carbon and metal composite heat dissipation long tube according to claim 1, wherein the brazing filler metal in the step 3 is Ag-Cu-Ti, BNi-2 or TiZrNiCu, and the brazing filler metal is foil or paste.

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