Preparation method and use method of self-repairing flow resistance agent for high-temperature brazing
By using a self-healing flow retardant formulated with sodium silicate and aluminum bromide solution, the problem of solder flow under high-temperature brazing and complex curved surface conditions was solved, achieving stable flow retardant effect and joint strength at high temperatures, and avoiding the carbonization risk of organic flow retardants.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2025-08-14
- Publication Date
- 2026-07-31
AI Technical Summary
Existing flow-blocking agents cannot be used stably under high-temperature brazing and complex curved surface conditions, resulting in excessive flow of the brazing filler metal, which affects the weld ratio and strength of the joint. At the same time, organic flow-blocking agents carbonize at high temperatures, generating brittle compounds that affect the mechanical properties of the joint.
Sodium silicate is used to prepare an inorganic adhesive, which is combined with aluminum bromide solution and alumina, silicon oxide and yttrium oxide powder to form a self-healing flow barrier. At high temperature, aluminum bromide decomposes to generate alumina particles, which dynamically compensate for the solder resist layer and restrict the flow of solder.
It maintains good adhesion at high temperatures, prevents brazing filler metal flow, avoids carbonization contamination, and is suitable for various brazing environments. In particular, it forms a dense barrier on complex curved surfaces, improving joint quality.
Smart Images
Figure CN120862153B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of brazing. Background Technology
[0002] In vacuum brazing, the excellent wettability of the filler metal on the base material surface is beneficial for forming a reliable connection between the base materials, resulting in a high-quality brazed joint. However, excellent wettability can lead to excessive flow of the molten filler metal on the base material surface. If the filler metal flows into non-brazing areas of the base material, it can easily cause filler metal loss, affecting the joint weld ratio and strength. If the filler metal flows to the contact surface between the brazing fixture and the base material, it can cause abnormal adhesion between the two, creating problems for subsequent processes. Therefore, a flow-retardant is needed during brazing to prevent excessive filler metal flow.
[0003] Currently, commonly used commercial solder resist fluxes mainly consist of polymer binders and solder resist oxide powder. In use, the binder and powdered solder resist oxide powder are mixed evenly to form a flow-blocking slurry with a certain viscosity. This slurry is then evenly applied to the surface of the base material, forming a physical barrier layer. This oxide barrier layer does not react with the solder, effectively restricting the flow path of the liquid solder. However, this type of flow-blocking flux also has the following limitations: 1. When the brazing temperature exceeds 400℃, the organic binder undergoes pyrolysis and carbonization, leading to adhesion failure between the flow-blocking layer and the base material surface, thus losing its flow-blocking effect; 2. The carbonized organic binder and solder resist material are carried away by the flowing solder and easily migrate to the weld area, not only forming defects such as slag inclusions and porosity, but also potentially reacting with the metal base material to form brittle compounds, affecting the mechanical properties of the joint.
[0004] To overcome the temperature limitations of organic brazing resists, some solder resists currently employ inorganic binders, such as copper phosphate and aluminum phosphate. While these resists perform reasonably well on conventional flat brazing surfaces, they reveal new problems in applications with complex geometries. For example, on workpieces with curved or multi-directional planes, such as turbine blade tenons or three-dimensional flow channels in heat exchangers, inorganic brazing resists struggle to form a continuous and dense barrier. Under the influence of gravity and capillary forces, especially on vertical or chamfered surfaces, the molten solder accumulates at the edges of the solder resist layer. Under the influence of gravity, this liquid metal may flow across the surface of the brazing resist, forming "overflow channels" and resulting in poor flow resistance. Therefore, there is an urgent need to develop a brazing resist that can be stably used under high-temperature brazing and complex curved surface conditions. Summary of the Invention
[0005] This invention aims to solve the problem that existing flow-blocking agents cannot be used stably under high-temperature brazing and complex curved surface conditions, and thus provides a method for preparing and using a self-healing flow-blocking agent for high-temperature brazing.
[0006] A method for preparing a self-healing flow-blocking agent for high-temperature brazing, comprising the following steps:
[0007] I. Preparation of Inorganic Adhesive:
[0008] Sodium silicate powder was slowly added to deionized water and stirred until completely dissolved to obtain an inorganic adhesive.
[0009] II. Preparation of aluminum bromide solution:
[0010] Slowly add aluminum bromide powder to deionized water and stir until completely dissolved to obtain an aluminum bromide solution;
[0011] III. Preparation of flow-blocking agent liquid:
[0012] The inorganic adhesive and aluminum bromide solution were stirred evenly to obtain a flow-blocking agent liquid;
[0013] IV. Powder Preparation:
[0014] Weigh out 50 to 90 parts by weight of alumina powder, 5 to 40 parts by weight of silica powder and 5 to 40 parts by weight of yttrium oxide powder, and mix them evenly to obtain a mixed powder.
[0015] V. Preparation of flow-retardant agent:
[0016] The flow barrier liquid and the mixed powder are stirred and mixed to obtain a self-healing flow barrier for high-temperature brazing.
[0017] A method for using a self-healing flow-retardant for high-temperature brazing is as follows:
[0018] Apply the self-healing flow barrier agent for high-temperature brazing evenly to the non-welding area of the base material to be welded and the surface of the welding fixture. Let it stand at room temperature for 0.5 min to 5 min, then perform vacuum brazing at the brazing temperature. Finally, cool it to room temperature and remove it to remove the flow barrier agent. This completes the application method of the self-healing flow barrier agent for high-temperature brazing.
[0019] The beneficial effects of this invention are:
[0020] 1. This invention solves the problem of organic flow inhibitors being unable to withstand high temperatures. The inorganic adhesive formulated with sodium silicate can withstand temperatures up to 900°C and has strong adhesion, breaking through the 400°C temperature limit of organic flow inhibitors. It is suitable for various brazing environments and has broad application prospects.
[0021] 2. The flow barrier prepared by this invention does not contain organic components, effectively eliminating the risk of contaminating the weld after the organic flow barrier carbonizes at high temperatures.
[0022] 3. This invention solves the problem of poor flow-blocking effect of inorganic flow-blocking agents on complex weldments by introducing a dynamic self-healing flow-blocking mechanism. The flow-blocking agent prepared in this invention contains aluminum bromide in its liquid component. This component can decompose into alumina particles when the temperature rises above 500°C. During high-temperature brazing, in addition to the oxide solder resist layer originally applied to the weldment, the aluminum bromide in the liquid will continuously generate a new alumina solder resist layer. Even on vertical or chamfered surfaces, under the influence of gravity, the newly grown alumina particles will grow in situ on the original solder resist layer, forming a dynamic compensation for the solder resist layer. This creates a dense, continuous barrier on the weldment surface, providing a self-healing function and thus restricting the flow of molten solder, resulting in a good flow-blocking effect. Attached Figure Description
[0023] Figure 1 The image shows the physical state of the self-healing flow barrier agent for high-temperature brazing prepared in Example 1.
[0024] Figure 2 This is a comparison diagram of the state of the flow-blocking agent on the surface of the right-angled graphite fixture before and after vacuum brazing in Example 3;
[0025] Figure 3 This is a comparison diagram of the state of the flow-blocking agent on the surface of the disc graphite fixture before and after vacuum brazing in Example 3;
[0026] Figure 4 The images show a comparison of the surface conditions of the brazed sample after applying the self-healing flow barrier agent for high-temperature brazing in Example 2 and the brazed sample without the flow barrier agent in the comparative example. a is the brazed sample in Example 2 without the flow barrier agent removed, b is the brazed sample in Example 2 with the flow barrier agent removed, and c is the comparative example. Detailed Implementation
[0027] Specific Implementation Method 1: This implementation method describes a method for preparing a self-healing flow-blocking agent for high-temperature brazing, which is carried out according to the following steps:
[0028] I. Preparation of Inorganic Adhesive:
[0029] Sodium silicate powder was slowly added to deionized water and stirred until completely dissolved to obtain an inorganic adhesive.
[0030] II. Preparation of aluminum bromide solution:
[0031] Slowly add aluminum bromide powder to deionized water and stir until completely dissolved to obtain an aluminum bromide solution;
[0032] III. Preparation of flow-blocking agent liquid:
[0033] The inorganic adhesive and aluminum bromide solution were stirred evenly to obtain a flow-blocking agent liquid;
[0034] IV. Powder Preparation:
[0035] Weigh out 50 to 90 parts by weight of alumina powder, 5 to 40 parts by weight of silica powder and 5 to 40 parts by weight of yttrium oxide powder, and mix them evenly to obtain a mixed powder.
[0036] V. Preparation of flow-retardant agent:
[0037] The flow barrier liquid and the mixed powder are stirred and mixed to obtain a self-healing flow barrier for high-temperature brazing.
[0038] The beneficial effects of this embodiment are:
[0039] 1. This embodiment solves the problem of organic flow inhibitors being unable to withstand high temperatures. The inorganic adhesive formulated with sodium silicate in this embodiment can withstand high temperatures up to 900°C and has strong adhesion, breaking through the 400°C temperature limit of organic flow inhibitors. It is suitable for various brazing environments and has broad application prospects.
[0040] 2. The flow barrier prepared in this embodiment does not contain organic components, effectively eliminating the risk of contaminating the weld after the organic flow barrier carbonizes at high temperature.
[0041] 3. This embodiment solves the problem of poor flow-blocking effect of inorganic flow-blocking agents on complex weldments by introducing a dynamic self-healing flow-blocking mechanism. The flow-blocking agent prepared in this embodiment contains aluminum bromide in its liquid component. This component can decompose into alumina particles when the temperature rises above 500°C. During the high-temperature brazing process, in addition to the oxide solder resist layer originally applied to the weldment, the aluminum bromide in the liquid will continuously generate a new alumina solder resist layer. Even on vertical or chamfered surfaces, under the influence of gravity, the newly grown alumina particles will grow in situ on the original solder resist layer, forming a dynamic compensation for the solder resist layer. This creates a dense, continuous barrier on the surface of the weldment, providing a self-healing function and thus restricting the flow of molten solder, resulting in a good flow-blocking effect.
[0042] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass ratio of sodium silicate powder to deionized water in step one is 1:(1~3); and the sodium silicate powder is slowly added to the deionized water at an addition rate of 0.1g / s~5g / s in step one. Everything else is the same as in Specific Implementation Method One.
[0043] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the mass ratio of aluminum bromide powder to deionized water in step two is 1:(5~10); and the aluminum bromide powder is slowly added to the deionized water at an addition rate of 0.1g / s~3g / s in step two. Everything else is the same as in Specific Implementation Method One or Two.
[0044] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the mass ratio of the inorganic adhesive to the aluminum bromide solution in step three is 1:(1~3). Everything else is the same as in Specific Implementation Method Three.
[0045] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the particle size of the mixed powder in step four is 1μm to 500μm; the uniform mixing in step four specifically involves stirring at a rotation speed of 200rpm to 300rpm for 1 to 3 hours. Everything else is the same as in Specific Implementation Methods One to Four.
[0046] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the mass ratio of the flow-blocking agent liquid to the mixed powder in step five is 1:(1~4). Everything else is the same as in Specific Implementation Methods One to Five.
[0047] Specific Implementation Method Seven: This implementation method describes a method for using a self-healing flow-blocking agent for high-temperature brazing, which is carried out according to the following steps:
[0048] Apply the self-healing flow barrier agent for high-temperature brazing evenly to the non-welding area of the base material to be welded and the surface of the welding fixture. Let it stand at room temperature for 0.5 min to 5 min, then perform vacuum brazing at the brazing temperature. Finally, cool it to room temperature and remove it to remove the flow barrier agent. This completes the application method of the self-healing flow barrier agent for high-temperature brazing.
[0049] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the coating thickness of the self-healing flow-blocking agent for high-temperature brazing is 10μm~500μm. Everything else is the same as in Specific Implementation Method Seven.
[0050] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Seven or Eight in that the brazing temperature is 600℃~900℃. Everything else is the same as Specific Implementation Method Seven or Eight.
[0051] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods Seven to Nine in that the removal of the flow-blocking agent is specifically carried out under conditions of 10W~100W power, with ultrasonic water washing for 1min~20min. Everything else is the same as Specific Implementation Methods Seven to Nine.
[0052] The beneficial effects of the present invention are verified using the following embodiments:
[0053] Example 1:
[0054] A method for preparing a self-healing flow-blocking agent for high-temperature brazing, comprising the following steps:
[0055] I. Preparation of Inorganic Adhesive:
[0056] Sodium silicate powder was slowly added to deionized water at an addition rate of 2 g / s and stirred until completely dissolved to obtain an inorganic adhesive.
[0057] The mass ratio of sodium silicate powder to deionized water is 1:2.5;
[0058] II. Preparation of aluminum bromide solution:
[0059] Add aluminum bromide powder slowly to deionized water at a rate of 0.5 g / s and stir until completely dissolved to obtain an aluminum bromide solution.
[0060] The mass ratio of the aluminum bromide powder to deionized water is 1:5;
[0061] III. Preparation of flow-blocking agent liquid:
[0062] The inorganic adhesive and aluminum bromide solution were stirred evenly to obtain a flow-blocking agent liquid;
[0063] The mass ratio of the inorganic adhesive to the aluminum bromide solution is 1:1.
[0064] IV. Powder Preparation:
[0065] Weigh out 60 parts by weight of alumina powder, 30 parts by weight of silica powder and 10 parts by weight of yttrium oxide powder, and stir at 300 rpm for 1 hour to obtain a mixed powder.
[0066] The alumina powder has an average particle size of 75 μm; the silica powder has an average particle size of 50 μm; and the yttrium oxide powder has an average particle size of 100 μm.
[0067] V. Preparation of flow-retardant agent:
[0068] The flow barrier liquid and the mixed powder are stirred and mixed to obtain a self-healing flow barrier for high-temperature brazing.
[0069] The mass ratio of the flow-blocking agent liquid to the mixed powder is 1:1.5.
[0070] Example 2: A method for using a self-healing flow-retardant agent for high-temperature brazing, which is carried out according to the following steps:
[0071] With a coating thickness of 100μm~300μm, the self-healing flow barrier agent for high-temperature brazing prepared in Example 1 was uniformly coated on the non-welding area of the base material to be welded and the surface of the welding fixture. After standing at room temperature for 1 minute, vacuum brazing was performed at a brazing temperature of 820℃ for 0.5 hours. Finally, the temperature was lowered to room temperature and the sample was removed to obtain a brazed sample. This completes the method of using the self-healing flow barrier agent for high-temperature brazing.
[0072] The base material to be soldered is an alloy of TC4 and GH3536, and the solder is AgCuTi, with an atomic percentage of Ag:Cu:Ti of 68.8:26.7:4.5.
[0073] The removal of the flow barrier agent specifically involves ultrasonic water washing for 10 minutes at a power of 30W.
[0074] Comparative Example: This comparative example differs from Example 2 in that the coating of the self-healing flow-blocking agent for high-temperature brazing is omitted. Everything else is the same as Example 2.
[0075] Example 3: To verify the stable use of self-healing flow-blocking agents for high-temperature brazing under high-temperature and complex curved surface conditions:
[0076] With a coating thickness of 100μm~300μm, the high-temperature brazing self-healing anti-flow agent prepared in Example 1 was uniformly coated on the surface of the welding fixture, left to stand at room temperature for 1 minute, and then heated at 800℃ for 20 minutes. The surface anti-flow agent state was then compared. The welding fixture is a right-angle graphite clamp or a disc graphite clamp.
[0077] Figure 1 The image shows the physical state of the self-healing flow inhibitor for high-temperature brazing prepared in Example 1. As can be seen from the image, the prepared brazing agent is a white, viscous paste that can be applied to any complex curved surface.
[0078] Figure 2 The image shows a comparison of the state of the flow-blocking agent on the surface of the right-angled graphite fixture before and after vacuum brazing in Example 3. It can be seen that after the high-temperature brazing process at 800℃, the flow-blocking agent on multiple surfaces of the graphite fixture still maintains a good state, which indicates that the flow-blocking agent still has a flow-blocking effect on complex planes. Furthermore, the change in the morphology of the flow-blocking agent on the surface of the fixture proves that a new flow-blocking layer is generated during the brazing process.
[0079] Figure 3 This is a comparison image of the state of the flow-blocking agent on the surface of the circular graphite fixture before and after vacuum brazing in Example 3; and Figure 2 Similarly, after a high-temperature brazing process at 800°C, the flow-blocking agent on multiple surfaces of the disc graphite tooling remained in good condition, and the morphology of the flow-blocking agent on the tooling surface changed, proving that a new flow-blocking layer was formed during the brazing process. This demonstrates that the flow-blocking agent of the present invention can still exert a good flow-blocking effect on complex planes.
[0080] Figure 4The images show a comparison of the surface conditions of the brazed sample after applying the self-healing flow inhibitor for high-temperature brazing in Example 2 and the brazed sample without the flow inhibitor in the comparative example. Image a shows the sample after brazing in Example 2 without removing the flow inhibitor; image b shows the sample after brazing in Example 2 with the flow inhibitor removed; and image c shows the comparative example. It can be seen that after applying the flow inhibitor, the flow of the brazing material is controlled within a certain range, and the oxide barrier layer does not react with the solder, effectively limiting the flow path of the liquid solder and preventing it from spreading everywhere. In contrast, the sample without the flow inhibitor shows solder spreading everywhere, and the surface appears golden yellow.
Claims
1. A method for preparing a self-repairing flow restrictor for high temperature brazing, characterized in that It is done in the following steps: I. Preparation of Inorganic Adhesive: Sodium silicate powder was slowly added to deionized water at a rate of 0.1 g / s to 5 g / s and stirred until completely dissolved to obtain an inorganic adhesive. The mass ratio of sodium silicate powder to deionized water is 1:(1~3); II. Preparation of aluminum bromide solution: Add aluminum bromide powder slowly to deionized water at a rate of 0.1 g / s to 3 g / s, and stir until completely dissolved to obtain an aluminum bromide solution. The mass ratio of the aluminum bromide powder to deionized water is 1:(5~10); III. Preparation of flow-blocking agent liquid: The inorganic adhesive and aluminum bromide solution were stirred evenly to obtain a flow-blocking agent liquid; The mass ratio of the inorganic adhesive to the aluminum bromide solution is 1:(1~3); IV. Powder Preparation: Weigh out 50 to 90 parts by weight of alumina powder, 5 to 40 parts by weight of silica powder and 5 to 40 parts by weight of yttrium oxide powder, and mix them evenly to obtain a mixed powder. V. Preparation of flow-retardant agent: The flow barrier liquid and the mixed powder are stirred and mixed to obtain a self-healing flow barrier for high-temperature brazing. The mass ratio of the flow-blocking agent liquid to the mixed powder is 1:(1~4).
2. The method for preparing a self-healing flow-blocking agent for high-temperature brazing according to claim 1, characterized in that... The particle size of the mixed powder mentioned in step four is 1μm~500μm; the uniform mixing mentioned in step four specifically refers to stirring for 1h~3h at a rotation speed of 200rpm~300rpm.
3. The method of using the flow-blocking agent prepared by the preparation method according to claim 1, characterized in that... It is done in the following steps: Apply the self-healing flow barrier agent for high-temperature brazing evenly to the non-welding area of the base material to be welded and the surface of the welding fixture. Let it stand at room temperature for 0.5 min to 5 min, then perform vacuum brazing at the brazing temperature. Finally, cool it to room temperature and remove it to remove the flow barrier agent. This completes the use of the self-healing flow barrier agent for high-temperature brazing.
4. The method of use according to claim 3, characterized in that... The coating thickness of the self-healing flow-blocking agent for high-temperature brazing is 10μm~500μm.
5. The method of use according to claim 3, characterized in that... The brazing temperature is 600℃~900℃.
6. The method of use according to claim 3, characterized in that... The removal of the flow barrier is specifically carried out by ultrasonic water washing for 1 min to 20 min under a power of 10W to 100W.