In-situ high-entropy brazing connection method for TZM and Kovar alloy dissimilar materials

Abstract

The invention provides an in-situ high-entropy brazing connection method for TZM and Kovar alloy dissimilar materials. Vacuum brazing is conducted on the TZM and Kovar alloy dissimilar materials through brazing materials under the heating condition. Compared with the prior art, the method has the advantages that the adopted brazing material is the multi-element medium-entropy alloy brazing material, elements contained in the multi-element medium-entropy alloy brazing material have high metallurgical compatibility with the TZM base material and the kovar alloy, the generation trend of brittle compounds can be reduced, the residual stress of a joint can be relieved, and the solid solution strengthening effect can be achieved; and meanwhile, the brazing material is heated to the brazing temperature in a stepped heating mode and is matched with a slow cooling mode, two high-entropy solid solution structures which are the same in orientation and have a coherent relationship can be generated in situ after brazing, in-situ high-entropy strengthening and toughening of a connector are achieved, then the mechanical property of the connector is improved, and the brazing material does not contain toxic and harmful elements and is environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of brazing, and particularly relates to a brazing connection method for in-situ high-entropy transformation of dissimilar materials of TZM and Kovar alloys. Background Technique

[0002] Kovar alloy is a Fe-Ni-Co series low-expansion alloy with a melting temperature of about 1450 °C. It is a low-expansion alloy with a thermal expansion coefficient lower than that of traditional steels and superalloys. It has good cold and hot working characteristics and is mainly used for manufacturing the shells of vacuum devices. TZM alloy has a relatively high recrystallization temperature, and the starting recrystallization temperature reaches 1350 °C, and it has a small thermal expansion coefficient. It is widely used in the manufacture of high-temperature components in the fields of aerospace and the like. Since the thermal expansion coefficients of these two types of alloys are relatively close, the connection of the two alloys will be involved in actual use. However, the compositional differences between Kovar alloy and TZM alloy are large, and their performance characteristics are different. Therefore, it is difficult to achieve the welding of the two.

[0003] When using traditional AgCu and AgCuTi brazing fillers for brazing, although the connection of the two can be achieved, the melting temperature of the brazing filler is relatively low, and the service temperature of the joint generally does not exceed 500 °C, which is difficult to meet the high-temperature use requirements of TZM. Using BNi-2 brazing filler and Cu-Mn-Co / Ni series brazing fillers can also achieve better connection of Kovar alloy and TZM alloy, but the high-temperature thermal shock resistance of the joint is insufficient, which is difficult to meet the actual application requirements. Therefore, there is an urgent need to develop a brazing filler and its welding process that can meet the long-life service requirements of high temperature resistance and heat cycle resistance of the joint between TZM alloy and Kovar alloy. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a brazing connection method for in-situ high-entropy transformation of dissimilar materials of TZM and Kovar alloys. This connection method uses in-situ high-entropy strengthening brazing connection, and the brazed joint has excellent mechanical properties at room temperature and high temperature, meeting the long-life service requirements.

[0005] The present invention provides a brazing connection method for in-situ high-entropy transformation of dissimilar materials of TZM and Kovar alloys. Vacuum brazing is carried out on the dissimilar materials of TZM and Kovar alloys with a brazing filler under heating conditions; the heating is carried out in a stepped heating manner; in terms of mass percentage, the brazing filler includes: Cu 24.0% - 28.0%, Pd 13.0% - 18.0%, Ni 2.0% - 5.0%, Co 0.0% - 5.0%, Cr 0.0% - 4.0%, Fe 0.0% - 3.0%, and the balance is Au.

[0006] Preferably, the stepwise temperature increase is specifically as follows: first, increase the temperature at a rate not exceeding 10 °C / min to 850 °C - 950 °C, hold for 10 - 30 min, and then increase the temperature at a rate not exceeding 10 °C / min to the vacuum brazing temperature.

[0007] Preferably, after the vacuum brazing is completed, cool down slowly; the slow cooling is specifically as follows: cool down at a rate not exceeding 6 °C / min to below 900 °C, and then cool in the furnace to room temperature.

[0008] Preferably, the vacuum pressure of the vacuum brazing is not higher than 1×10 -2 Pa; the brazing temperature is 1060 °C - 1120 °C; the holding time for brazing is 15 - 30 min.

[0009] Preferably, by mass percentage, the brazing filler metal includes: Cu 24.0% - 28.0%, Pd 13.0% - 18.0%, Ni 2.0% - 4.0%, Co 1.0% - 4.0%, Cr 1.0 - 3.0%, Fe 1.0% - 2.0%, and the balance is Au.

[0010] Preferably, by mass percentage, the brazing filler metal includes: Cu 26.0% - 28.0%, Pd 13.0% - 15.0%, Ni 2.0% - 3.0%, Co 2.0% - 4.0%, Cr 2.0%, Fe 1.0% - 2.0%, and the balance is Au.

[0011] Preferably, by mass percentage, the brazing filler metal includes: Cu 28.0%, Pd 13.0%, Ni 3.0%, Co 4.0%, Cr 2.0%, Fe 2.0%, and the balance is Au;

[0012] Or, it includes: Cu 28.0%, Pd 15.0%, Ni 3.0%, Co 2.0%, Cr 2.0%, Fe 1.0%, and the balance is Au;

[0013] Or, it includes: Cu 28.0%, Pd 15.0%, Ni 2.0%, Co 2.0%, Cr 2.0%, Fe 2.0%, and the balance is Au.

[0014] Preferably, the form of the brazing filler metal is block, strip, wire or alloy powder.

[0015] Preferably, the brazing filler metal is prepared according to the following method:

[0016] Prepare Cu, Pd, Ni, Co, Fe and Au according to the weight ratio, and melt them to obtain the brazing filler metal for brazing dissimilar materials.

[0017] Preferably, the melting is vacuum induction melting; the vacuum pressure of the vacuum induction melting is less than 10 Pa; the temperature of the vacuum induction melting does not exceed 1400 °C; the time is 5 to 20 min.

[0018] The present invention provides a brazing connection method for in-situ high-entropyization of dissimilar materials of TZM and kovar alloy. Vacuum brazing is carried out on the dissimilar materials of TZM and kovar alloy by using a brazing filler metal under heating conditions; the heating is carried out in a stepped heating manner; by mass percentage, the brazing filler metal includes: Cu 24.0% - 28.0%, Pd 13.0% - 18.0%, Ni 2.0% - 5.0%, Co 0.0% - 5.0%, Cr 0.0 - 4.0%, Fe 0.0% - 3.0%, and the balance is Au. Compared with the prior art, the brazing filler metal used in the present invention is a multi-component medium-entropy alloy brazing filler metal, and the elements contained therein have high metallurgical compatibility with the TZM base material and the kovar alloy, which can reduce the generation tendency of brittle compounds, relieve the residual stress of the joint, and can achieve the effect of solid solution strengthening. At the same time, by heating to the brazing temperature in a stepped heating manner and cooperating with a slow cooling method, two high-entropy solid solution structures with the same orientation and coherent relationship can be in-situ generated after brazing, realizing in-situ high-entropy strengthening and toughening of the joint, thereby improving the mechanical properties of the joint, and the brazing filler metal does not contain toxic and harmful elements, which is green and environmentally friendly.

[0019] The experimental results show that the room-temperature tensile strength of the joint obtained by using the brazing connection method provided by the present invention for brazing dissimilar materials of TZM and kovar alloy reaches 493 MPa, and the high-temperature tensile strength at 680 °C reaches 177 MPa. Detailed implementation manners

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] The present invention provides a brazing connection method for in-situ high-entropyization of dissimilar materials of TZM and kovar alloy. Vacuum brazing is carried out on the dissimilar materials of TZM and kovar alloy by using a brazing filler metal under heating conditions; the heating is carried out in a stepped heating manner; by mass percentage, the brazing filler metal includes: Cu 24.0% - 28.0%, Pd 13.0% - 18.0%, Ni 2.0% - 5.0%, Co 0.0% - 5.0%, Cr 0.0 - 4.0%, Fe 0.0% - 3.0%, and the balance is Au.

[0022] Among them, the present invention does not have special restrictions on the sources of all raw materials, and commercially available ones can be used.

[0023] In a specific embodiment provided by the present invention, in terms of mass percentage, the brazing filler metal preferably comprises: Cu 24.0% - 28.0%, Pd 13.0% - 18.0%, Ni 2.0% - 5.0%, Co 1.0% - 4.0%, Cr 1.0 - 3.0%, Fe 1.0% - 2.0%, and the balance is Au; more preferably, it comprises: Cu 24.0% - 28.0%, Pd 13.0% - 18.0%, Ni 2.0% - 3.0%, Co 2.0% - 4.0%, Cr 2.0%, Fe 1.0% - 2.0%, and the balance is Au; still more preferably, it comprises: Cu 26.0% - 28.0%, Pd 13.0% - 15.0%, Ni 2.0% - 3.0%, Co 2.0% - 4.0%, Cr 2.0%, Fe 1.0% - 2.0%, and the balance is Au; most preferably, it comprises: Cu 28.0%, Pd 13.0% - 15.0%, Ni 2.0% - 3.0%, Co 2.0% - 4.0%, Cr 2.0%, Fe 1.0% - 2.0%, and the balance is Au.

[0024] In a specific embodiment provided by the present invention, in terms of mass percentage, the brazing filler metal preferably comprises: Cu 24.0% - 26.0%, Pd 13.0% - 18.0%, Ni 3.0% - 5.0%, Co 3.0% - 4.0%, Fe 1.0% - 2.0%, and the balance is Au.

[0025] In a specific embodiment provided by the present invention, in terms of mass percentage, the brazing filler metal preferably comprises: Cu 26.0% - 28.0%, Pd 13.0% - 15.0%, Ni 2.0% - 4.0%, Co 0.0% - 4.0%, Cr 1.0 - 3.0%, Fe 0.0% - 2.0%, and the balance is Au.

[0026] In a specific embodiment provided by the present invention, in terms of mass percentage, the brazing filler metal preferably comprises: Cu 24.0% - 28.0%, Pd 13.0% - 14.0%, Ni 4.0% - 5.0%, Co 1.0% - 3.0%, Cr 1.0 - 3.0%, Fe 0.0% - 2.0%, and the balance is Au.

[0027] In a specific embodiment provided by the present invention, in terms of mass percentage, the brazing filler metal preferably comprises: Cu 26.0% - 28.0%, Pd 13.0% - 18.0%, Ni 2.0% - 5.0%, Co 2.5% - 3.5%, Cr 1.0 - 3.0%, Fe 0.0% - 1.0%, and the balance is Au.

[0028] In a specific embodiment provided by the present invention, in terms of mass percentage, the brazing filler metal preferably comprises: Cu 24.5% - 26.5%, Pd 14.5% - 16.5%, Ni 2.0% - 4.0%, Co 1.0% - 3.0%, Cr 2.0%, Fe 1.0% - 2.0%, and the balance is Au.

[0029] In some embodiments provided by the present invention, in terms of mass percentage, the brazing filler metal comprises: Cu 28.0%, Pd 13.0%, Ni 3.0%, Co 4.0%, Cr 2.0%, Fe 2.0%, and the balance is Au; or, it comprises: Cu 28.0%, Pd 15.0%, Ni 3.0%, Co 2.0%, Cr 2.0%, Fe 1.0%, and the balance is Au; or, it comprises: Cu 28.0%, Pd 15.0%, Ni 2.0%, Co 2.0%, Cr 2.0%, Fe 2.0%, and the balance is Au.

[0030] According to the present invention, the form of the brazing filler metal can be the form well-known to those skilled in the art, without special limitations. In the present invention, it is preferably in the form of blocks, strips, wires or alloy powders.

[0031] The brazing filler metal provided by the present invention is a multi-component medium-entropy alloy brazing filler metal. The elements it contains have high metallurgical compatibility with the TZM base material, can reduce the generation tendency of brittle compounds, relieve the residual stress of the joint, and can achieve the effect of solid solution strengthening, improve the mechanical properties of the joint, and this brazing filler metal does not contain toxic and harmful elements, and is green and environmentally friendly.

[0032] In a specific embodiment provided by the present invention, the brazing filler metal is prepared by the following method: Cu, Pd, Ni, Co, Fe and Au are prepared according to the weight ratio, and melted to obtain an alloy brazing filler metal.

[0033] In a specific embodiment provided by the present invention, the melting is preferably vacuum induction melting; the vacuum pressure of the vacuum induction melting is less than 10 Pa, more preferably less than 5 Pa; the temperature of the vacuum induction melting is preferably not more than 1400 °C, more preferably 1200 °C - 1400 °C; optionally, the temperature of the vacuum induction melting is 1200 °C, 1300 °C, 1400 °C or the range between any two of the above values; the time of the vacuum induction melting is preferably 5 - 20 min; optionally, the time of the vacuum induction melting is 5 min, 10 min, 15 min, 20 min or the range between any two of the above values.

[0034] In a specific embodiment provided by the present invention, the form of the brazing filler metal is alloy powder, and after melting, it is preferably made into powder by high-pressure atomization method, and more preferably by high-purity argon gas atomization method.

[0035] In a specific embodiment provided by the present invention, the form of the brazing filler metal is strip, and after melting, it is preferably made into strip-shaped brazing filler metal by rolling method.

[0036] The TZM and Kovar alloy dissimilar materials are vacuum brazed with the brazing filler metal under heating conditions. Kovar alloy is a low-expansion alloy of Fe-Ni-Co system, with a melting temperature of about 1450 °C. It is a low-expansion alloy, with a thermal expansion coefficient lower than that of traditional steels and superalloys, and has good cold and hot working characteristics. It is mainly used for manufacturing the outer shells of vacuum devices. TZM alloy has a relatively high recrystallization temperature, and the starting recrystallization temperature reaches 1350 °C, and it has a small thermal expansion coefficient, and is widely used in the manufacture of high-temperature components in the fields of aerospace and so on. Since the thermal expansion coefficients of these two types of alloys are relatively close, the connection of the two alloys will be involved in actual use. However, the composition differences between Kovar alloy and TZM alloy are large, and their performance characteristics are different, so it is difficult to realize the welding of the two. The content of element Ni in Kovar alloy is as high as 29 wt.%, and Ni and Mo elements have a strong affinity, so brittle phases are easily formed in the joint of Kovar alloy and TZM alloy, seriously affecting the interfacial mechanical properties. At the same time, there are differences in the physical properties of the two base materials to be welded, and there are large internal stresses at the heterogeneous interface. After service, cracks or even macroscopic fractures are likely to occur in the structure, which cannot meet the requirements of long-term thermal shock cycle use. The alloy brazing filler metal provided by the present invention is a multi-component medium-entropy alloy brazing filler metal. Through the interfacial reaction and element diffusion during the brazing process, two high-entropy solid solutions with coherent relationship are in-situ formed at the joint, greatly improving the performance of the heterogeneous joint and meeting the requirements of long-life service.

[0037] In a specific embodiment provided by the present invention, the main components of the TZM alloy are (0.4 - 0.6)% Ti, (0.06 - 0.12) Zr, Mo (the balance) (wt%)

[0038] The heating is carried out in a stepped heating manner; in a specific embodiment provided by the present invention, the stepped heating is specifically as follows: first, the temperature is raised to 850 °C - 950 °C at a heating rate not exceeding 10 °C / min, and held for 10 - 30 min, and then the temperature is raised to the vacuum brazing temperature at a heating rate not exceeding 10 °C / min.

[0039] In a specific embodiment provided by the present invention, the vacuum pressure of the vacuum brazing is preferably not higher than 1.0×10 -2Pa; the temperature of the brazing is preferably 1060°C to 1120°C, more preferably 1060°C to 1100°C; the holding time of the brazing is preferably 15 to 30 minutes.

[0040] In a specific embodiment provided by the present invention, after brazing, it is preferably cooled slowly; the slow cooling specifically is: cooling at a cooling rate not exceeding 6°C / min to below 900°C, and then cooling with the furnace to room temperature.

[0041] In the present invention, the solder used for brazing dissimilar materials of TZM alloy and Kovar alloy has the following advantages: 1) In terms of solder composition design and metallurgical compatibility, the alloy elements used in the multi-component medium-entropy alloy solder interlayer are Au, Cu, Pd, Ni, Fe, Co, and Cr, which have good metallurgical compatibility with the base metals of the brazed TZM and Kovar alloys respectively. Combining with the binary phase diagram, the mutual solubility between these elements is very excellent. For example, elements such as Au / Pd, Au / Cu, Au / Ni, and Ni / Co can be completely mutually soluble, which can reduce the generation tendency of brittle compounds, relieve the residual stress at the joint, and achieve the effect of solid solution strengthening; 2) In terms of the microstructure at the brazed joint interface, a small amount of (Mo-Ni, Fe, Cr, Co, Pd) compound phase with a mixing entropy of 1.11R (R is the gas constant) is formed at the interface, which greatly relieves the brittleness of the Mo-Ni phase. In addition, two FCC high-entropy solid solution structures of (Au, Cu, Pd, Ni, Fe, Co, Mo) and (Fe, Ni, Co, Pd, Cu, Au, Mo) are in-situ formed after brazing, with a mixing entropy as high as 1.51R - 1.69R, and the two solid solution phases show the same orientation and have a coherent relationship, achieving in-situ high-entropy strengthening and toughening of the joint; 3) The melting temperature range of the solder provided by the present invention is 1020°C - 1080°C, and it can be welded at a brazing temperature of 1060°C - 1120°C. Compared with the previous AuCuPd-based solder, the brazing temperature is further reduced, reducing the influence on the microstructure and properties of the brazed base metal, while ensuring high joint strength. At the same time, the brazing holding time is short, only 15 - 30 min, which can reduce production costs and be popularized and applied to industrial production; 4) The brazed joint obtained by the brazing method has excellent room-temperature and high-temperature mechanical properties. The room-temperature tensile strength of the joint reaches 493 MPa, exceeding the yield strength of the Kovar alloy base metal (~400 MPa) and reaching 93.7% of the tensile strength of the Kovar alloy base metal (~526 MPa); the high-temperature tensile strength of the joint at 680°C reaches 177 MPa, also exceeding the yield strength of the Kovar alloy base metal at 680°C (~148 MPa) and reaching 87.2% of the tensile strength of the Kovar alloy base metal at 680°C (~203 MPa). After 1000 thermal shock cycles of 680°C - room temperature in the atmospheric environment, the joint remains intact and crack-free, having excellent oxidation resistance and long-life tissue stability. The joint performance exceeds that of other existing conventional solders and can meet the requirements of long-term and harsh service.

[0042] In order to further illustrate the present invention, the following is a detailed description of a brazing connection method for in-situ high-entropy of dissimilar materials of TZM and Kovar alloys provided by the present invention in combination with embodiments.

[0043] The reagents used in the following examples are all commercially available; the main components of the TZM alloy used in the examples are (0.4 - 0.6)% Ti, (0.06 - 0.12) Zr, and Mo (the balance) (wt%).

[0044] Example 1

[0045] (1) First, a filler alloy was prepared by vacuum induction melting (vacuum pressure less than 10 Pa, the process was maintained for 10 min, the molten pool temperature measured by the temperature measuring device did not exceed 1400 °C, casting was carried out after melting, and the shell was removed by air cooling), and then powder was made by high-vacuum argon atomization method to obtain filler alloy powder. The composition was (wt%): 28% Cu, 13% Pd, 3% Ni, 4% Co, 2.0% Cr, 2% Fe, and the balance was Au.

[0046] (2) Using this filler alloy, brazing was carried out under the specification of stepwise heating at 1060 °C / 15 min (vacuum pressure not higher than 1.0×10 -2 Pa) for dissimilar materials of TZM alloy and Kovar alloy, and then the temperature was slowly decreased. The stepwise heating was specifically as follows: heating was carried out at a rate of 10 °C / min to 900 °C, after holding for 20 min, then heating was carried out at a rate of 10 °C / min to the brazing temperature. After the holding ended, the temperature was slowly decreased at a rate of 5 °C / min to below 900 °C, and then cooled to room temperature in the furnace.

[0047] (3) After the joint underwent 1000 thermal shock cycles from 680 °C to room temperature in the atmospheric environment, it remained intact and crack-free.

[0048] The results of the high-temperature tensile properties of the obtained joints of TZM and Kovar dissimilar materials are shown in Table 1.

[0049] Table 1 Tensile property test results of joints of TZM and Kovar dissimilar materials obtained in Example 1

[0050]

[0051] Example 2

[0052] (1) First, a filler alloy was prepared by vacuum induction melting (vacuum pressure less than 10 Pa, the process was maintained for 10 min, the molten pool temperature measured by the temperature measuring device did not exceed 1400 °C, casting was carried out after melting, and the shell was removed by air cooling), and then a filler alloy strip was obtained by rolling method. The composition was (wt%): 28% Cu, 15% Pd, 2% Ni, 2% Co, 2.0% Cr, 2% Fe, and the balance was Au.

[0053] (2) Using this filler alloy, brazing was carried out under the specification of stepwise heating at 1100 °C / 15 min (vacuum pressure not higher than 1.0×10 -2Pa) The dissimilar materials of TZM alloy and Kovar alloy are then slowly cooled. The stepwise heating is specifically as follows: heating at a rate of 10 °C / min to 900 °C, after holding for 20 min, then heating at a rate of 10 °C / min to the brazing temperature. After the holding is completed, it is slowly cooled at a rate of 5 °C / min to below 900 °C, and then cooled to room temperature in the furnace.

[0054] (3) After the joint has undergone 1000 thermal shock cycles from 680 °C to room temperature in the atmospheric environment, it still remains intact and crack-free.

[0055] The room-temperature tensile property results of the obtained TZM and Kovar dissimilar material joints are shown in Table 2.

[0056] Table 2 Tensile property test results of the TZM and Kovar dissimilar material joints obtained in Example 2

[0057] Specimen number Test temperature Tensile strength / MPa Remarks 1 Room temperature 477 Brazed joint 2 Room temperature 475 After 1000 thermal shock cycles of the brazed joint Kovar alloy base material Room temperature 537 Measured value of the base material

[0058] Example 3

[0059] (1) First, a filler metal alloy is prepared by the vacuum induction melting method (the vacuum pressure is less than 10 Pa, the process lasts for 10 min, the molten pool temperature measured by the temperature measuring device does not exceed 1400 °C, after melting is completed, it is cast, and air-cooled to remove the shell), and then a filler metal alloy strip is obtained by the rolling method. The composition is (wt%): 28% Cu, 15% Pd, 3% Ni, 2% Co, 2.0% Cr, 1% Fe, and the balance is Au.

[0060] (2) Using this filler metal alloy, brazing is carried out under the 1080 °C / 30 min specification with stepwise heating (the vacuum pressure is not higher than 1.0×10 -2 Pa) The dissimilar materials of TZM alloy and Kovar alloy are then slowly cooled. The stepwise heating is specifically as follows: heating at a rate of 10 °C / min to 900 °C, after holding for 20 min, then heating at a rate of 10 °C / min to the brazing temperature. After the holding is completed, it is slowly cooled at a rate of 5 °C / min to below 900 °C, and then cooled to room temperature in the furnace.

[0061] (3) After the joint has undergone 1000 thermal shock cycles from 680 °C to room temperature in the atmospheric environment, it still remains intact and crack-free.

[0062] The room-temperature tensile property results of the obtained TZM and Kovar dissimilar material joints are shown in Table 3.

[0063] Table 3 Tensile property test results of the TZM and Kovar dissimilar material joints obtained in Example 3

[0064]

[0065]

[0066] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for in-situ high entropy brazing connection of TZM and Kovar alloy dissimilar materials, characterized in that: The brazing material is used to vacuum braze TZM and Kovar alloy dissimilar materials under heating conditions; the heating adopts a step-by-step temperature increase method; the brazing material includes, in mass percentage, Cu 24.0% to 28.0%, Pd 13.0% to 18.0%, Ni 2.0% to 5.0%, Co 0.0% to 5.0%, Cr 0.0% to 4.0%, Fe 0.0% to 3.0%, and the balance is Au.

2. The brazing connection method according to claim 1, characterized in that: The step-wise heating is specifically as follows: firstly heating to 850°C-950°C at a heating rate not exceeding 10°C / min, keeping the temperature for 10-30 minutes, and then heating to the vacuum brazing temperature at a heating rate not exceeding 10°C / min.

3. The brazing connection method according to claim 1, characterized in that: After the vacuum brazing is completed, the temperature is slowly lowered; the slow cooling is specifically: the temperature is lowered to below 900°C at a cooling rate not exceeding 6°C / min, and then cooled to room temperature along with the furnace.

4. The brazing connection method according to claim 1, characterized in that: The vacuum pressure of the vacuum brazing is not higher than 1×10 -2 Pa; the brazing temperature is 1060°C to 1120°C; the brazing insulation time is 15 to 30 minutes.

5. The brazing connection method according to claim 1, characterized in that: Calculated in mass percentage, the solder comprises: Cu 24.0%-28.0%, Pd 13.0%-18.0%, Ni 2.0%-4.0%, Co 1.0%-4.0%, Cr 1.0%-3.0%, Fe 1.0%-2.0%, and the balance is Au.

6. The brazing connection method according to claim 1, characterized in that: Calculated in mass percentage, the brazing material comprises: Cu 26.0%-28.0%, Pd 13.0%-15.0%, Ni 2.0%-3.0%, Co 2.0%-4.0%, Cr2.0%, Fe 1.0%-2.0%, and the balance is Au.

7. The brazing connection method according to claim 1, characterized in that: In terms of mass percentage, the brazing material comprises: Cu 28.0%, Pd 13.0%, Ni 3.0%, Co 4.0%, Cr 2.0%, Fe 2.0%, and the balance is Au; Or, comprising: Cu 28.0%, Pd 15.0%, Ni 3.0%, Co 2.0%, Cr 2.0%, Fe 1.0%, and the balance is Au; Alternatively, it includes: Cu 28.0%, Pd 15.0%, Ni 2.0%, Co 2.0%, Cr 2.0%, Fe 2.0%, and the balance is Au.

8. The brazing connection method according to claim 1, characterized in that: The brazing material is in the form of blocks, strips, wires or alloy powders.

9. The brazing connection method according to claim 1, characterized in that: The solder is prepared according to the following method: Cu, Pd, Ni, Co, Fe and Au are prepared according to a weight ratio, and smelted to obtain a brazing material.

10. The brazing connection method according to claim 9, characterized in that: The smelting is vacuum induction smelting; the vacuum pressure of the vacuum induction smelting is less than 10Pa; the temperature of the vacuum induction smelting does not exceed 1400°C; and the time is 5 to 20 minutes.

Images