A TiAl-based Ti-Mn-Fe-Ni-Nb-Zr medium-entropy solder and its application method

Abstract

This invention provides a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal for TiAl and its application method. The filler metal comprises, by mass percentage: Mn 17.0–22.0%; Fe 13.0–17.0%; Ni 2.0–8.0%; Nb 2.0–9.0%; Zr 0–5.0%; balance Ti; and the Ni to Nb content ratio is (45–50):(55–50). The invention achieves the following results: the average room temperature tensile strength of the brazed joint obtained under conditions of (1140–1170)℃ / (20–75)min reaches 421–457 MPa, and the high-temperature tensile strengths at 700℃, 750℃, and 850℃ are 427–468 MPa, 435–465 MPa, and 386–415 MPa, respectively.

Description

Technical Field

[0001] This invention belongs to the field of aerospace brazing technology, and particularly relates to a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal for TiAl and its application method. Background Technology

[0002] The main advantages of TiAl-based alloys include low density (3.9–4.2 g / cm³), high specific strength and specific stiffness, and good creep resistance, oxidation resistance, and flame retardancy below 800°C. Compared to traditional titanium alloys, parts manufactured using TiAl-based alloys in the aerospace field can withstand long-term operating temperatures of 700–850°C, significantly increasing the long-term service temperature of components. Furthermore, compared to traditional nickel-based superalloys, TiAl-based alloys have lower density and higher specific strength. Therefore, TiAl-based alloys have broad prospects for high-temperature applications in the aerospace field.

[0003] However, TiAl-based alloys are inherently brittle, with room temperature plasticity of only 1-3%, making them highly susceptible to cracking during welding. From a feasibility and cost-effectiveness perspective, brazing is a highly suitable joining technology for TiAl-based alloys. Currently, research on TiAl-based alloy brazing technology focuses on improvements in brazing methods, brazing filler metals, brazing processes, brazing process control, and room temperature / high temperature strength of brazed joints. However, the brazing temperature of the filler metal and the strength of the brazed joint remain inconsistent. Ag-based or Al-based filler metals have lower brazing temperatures, but their high-temperature strength is significantly insufficient. While Ti-based filler metals have improved room temperature strength, their high-temperature strength remains insufficient, and some Ti-based filler metals require very high brazing temperatures, such as exceeding 1200℃, which can easily damage the base material. Therefore, the key to TiAl-based alloy brazing filler metals lies in achieving brazing at relatively low temperatures (below 1200℃) while simultaneously ensuring high room temperature / high temperature (750-850℃) strength of the brazed joint. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal for TiAl and its application method. This medium-entropy alloy brazing filler metal can effectively solve the problems of excessively high brazing temperature and insufficient room temperature / high temperature (750~850℃) strength of brazed joints in the prior art.

[0005] This invention provides a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder for TiAl, comprising the following components by mass percentage:

[0006] Mn 17.0–22.0%; Fe 13.0–17.0%; Ni 2.0–8.0%; Nb 2.0–9.0%; Zr 0–5.0%; balance Ti;

[0007] The content ratio of Ni to Nb is (45-50):(55-50).

[0008] Preferably, the content of Mn is 17.0-22.0%; Fe is 13.0-17.0%; Ni is 2.5-8.0%; Nb is 2.5-9.0%; Zr is 0-5.0%; the balance is Ti; and the content ratio of Ni to Nb is (45-50):(55-50).

[0009] Preferably, the brazing filler metal is used in one or more of the following forms: block, granular, sheet, powder, rapidly cooled foil strip, or powder sintered body.

[0010] This invention provides a method for preparing the Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder for TiAl as described in the above technical solution, comprising the following steps:

[0011] The materials were proportioned according to the mass percentage of the solder and melted using an electric arc melting method to obtain a Ti-Mn-Fe-Ni-Nb-Zr hexa-entropy alloy solder.

[0012] The above technical solution describes the application of Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal in the connection of TiAl alloys, Ti-Al-Nb alloys, Ti-based composite materials, TiAl-based composite materials, other multi-element medium-entropy or high-entropy alloy matrix materials containing Ti as one element, or other brazing multi-element medium-entropy or high-entropy alloy matrix materials containing both Ti and Al elements.

[0013] This invention provides a brazing method for TiAl alloys, comprising the following steps:

[0014] S1. Preparation of base material to be welded: Pre-treatment of the surface of the base material and the welding position;

[0015] S2. Assembly: Add solder to the position of the base material to be soldered to obtain the assembled component; the solder is the solder described in the above technical solution or the solder prepared by the preparation method described in the above technical solution;

[0016] S3. Brazing: Brazing the assembled components.

[0017] Preferably, the brazing is vacuum brazing;

[0018] The vacuum brazing process includes:

[0019] The vacuum level inside the furnace is better than 8×10-3 Pa, heat at a rate of 10-40℃ / min to 600℃, then heat at a rate of 10-30℃ / min to 900℃, then heat at a rate of 10-25℃ / min to 1140-1170℃ and hold at that temperature for 20-75 minutes; after holding, cool down at a rate of 10-40℃ / min and cool with the furnace.

[0020] Preferably, the gap between the base material and the welding position is 0.03 to 0.07 mm.

[0021] This invention provides a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal for TiAl, comprising the following components by mass percentage: Mn 17.0–22.0%; Fe 13.0–17.0%; Ni 2.0–8.0%; Nb 2.0–9.0%; Zr 0–5.0%; balance Ti; with a Ni to Nb content ratio of (45–50):(55–50). When applied to brazing TiAl alloys, the brazing filler metal provides solid solution strengthening and grain refinement, resulting in brazed joints with high room temperature / high temperature strength. Experimental results show that the average room temperature tensile strength of the joint obtained under brazing conditions of (1140~1170)℃ / (20~75)min is 421~457MPa, the tensile strength at 700℃ is 427~468MPa, the tensile strength at 750℃ is 435~465MPa, and the tensile strength at 850℃ is 386~415MPa. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the assembly structure in step S2;

[0023] Figure 2 The front morphology of a brazing sample prepared according to a certain embodiment of the present invention;

[0024] Figure 3 Microstructure of a brazed joint cross section prepared according to a certain embodiment of the present invention;

[0025] Figure 4 The Ti-Mn-Fe ternary phase diagram;

[0026] Figure 5 The Ti-Ni-Nb ternary phase diagram;

[0027] Figure 6 The Ni-Nb binary phase diagram;

[0028] Figure 7 This is a Ni-Zr binary phase diagram. Detailed Implementation

[0029] This invention provides a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder for TiAl, comprising the following components by mass percentage:

[0030] Mn 17.0–22.0%; Fe 13.0–17.0%; Ni 2.0–8.0%; Nb 2.0–9.0%; Zr 0–5.0%; balance Ti;

[0031] The content ratio of Ni to Nb is (45-50):(55-50).

[0032] The medium-entropy alloy brazing filler metal provided by the present invention comprises Mn 7.0-22.0%, preferably 17.0-21.0%.

[0033] The medium-entropy alloy brazing filler metal provided by the present invention comprises Fe 13.0-17.0%, preferably 13.0-16.0%.

[0034] The medium-entropy alloy brazing filler metal provided by the present invention comprises 2.0-8.0% Ni, preferably 2.5-8.0%, and more preferably 3.0-7.8%.

[0035] The medium-entropy alloy brazing filler metal provided by the present invention comprises Nb 2.0-9.0%, preferably 2.5-9.0%, and more preferably 3.5-9.0%.

[0036] The medium-entropy alloy brazing filler metal provided by this invention comprises 0-5.0% Zr. The medium-entropy alloy brazing filler metal provided by this invention also includes the balance Ti.

[0037] In a specific embodiment of the present invention, the TiAl is a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder, which comprises the following components by mass percentage:

[0038] Ti 57.63%, Fe 15.52%, Mn 20.35%, Ni 3.00%, Nb 3.50%;

[0039] Or Ti 55.17%, Fe 14.85%, Mn 19.48%, Ni 5.00%, Nb 5.50%;

[0040] Or Ti 51.16%, Fe 13.77%, Mn 18.07%, Ni 7.00%, Nb 7.50%;

[0041] Or Ti 53.63%, Fe 14.43%, Mn 18.94%, Ni 5.00%, Nb 5.50%, Zr 2.50%;

[0042] Or Ti 48.18%, Fe 13.00%, Mn 17.02%, Ni 7.80%, Nb 9.00%, Zr 5.00%.

[0043] The solder of this invention significantly reduces the interfacial reaction between the solder and the TiAl base material being soldered. Taking into account the metallurgical effects of the aforementioned elements, a composition range for the Ti-Mn-Fe-Ni-Nb-Zr alloy solder for TiAl is proposed. Thermodynamic calculations show that the mixing entropy of the Ti-Mn-Fe-Ni-Nb-Zr alloy solder is between 8.84 and 11.16 J·mol⁻¹. -1 ·K -1 The solder's properties, falling within the key parameters of a multi-principal alloy (1.0R to 1.5R), indicate that it is a medium-entropy alloy solder. This type of multi-element alloy solder does not undergo a violent chemical reaction with the TiAl base material being soldered, which is beneficial for achieving a good metallurgical connection.

[0044] The brazing filler metal described in this application has a solidus temperature of 1000.3–1083.5 °C and a liquidus temperature of 1062.0–1106.7 °C, enabling lower temperature brazing (T... b =1140~1170℃). Conversely, if the liquidus temperature of the solder is T L Too high, natural brazing temperature T b This will also be higher, making the brazing production process not only excessively energy-intensive and environmentally unfriendly, but also resulting in excessively high T emissions. b It affects the structure of the near-joint zone and can also greatly damage the properties of the base material.

[0045] The brazing filler metal provided by this invention can be prepared in a wide range of forms. TiAl using Ti-Mn-Fe-Ni-Nb-Zr alloy can be prepared into various application forms, allowing for multiple applications during brazing. After the Ti-Mn-Fe-Ni-Nb-Zr alloy is smelted, different preparation methods can be used to produce corresponding application forms. The application form of the brazing filler metal is one or more of the following shapes: block, granular, sheet, powder, rapidly cooled foil strip, or powder sintered body.

[0046] The brazing filler metal provided by this invention does not contain precious metals: Ti, Fe, Ni, and Mn are all conventional metallic elements, and the content of refractory metal elements Nb and Zr is low. Since it does not contain precious metals, it has a great price advantage in terms of economy.

[0047] This invention provides a method for preparing the Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder for TiAl as described in the above technical solution, comprising the following steps:

[0048] The materials were proportioned according to the mass percentage of the solder and melted using the electric arc melting method to obtain the TiAl Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder.

[0049] This application provides the application of the Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal described in the above technical solution in the connection of TiAl alloy, Ti-Al-Nb alloy, Ti-based composite material, TiAl-based composite material, other multi-element medium-entropy or high-entropy alloy matrix materials containing Ti as one element, or other brazing multi-element medium-entropy or high-entropy alloy matrix materials containing both Ti and Al elements.

[0050] This application also provides an application of the Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal described in the above technical solution in TiAl alloy brazing connections.

[0051] This invention provides a brazing method for TiAl alloys, comprising the following steps:

[0052] S1. Preparation of base material to be welded: Pre-treatment of the surface of the base material and the welding position;

[0053] S2. Assembly: Add solder to the position of the base material to be soldered to obtain the assembled component; the solder is the solder described in the above technical solution or the solder prepared by the preparation method described in the above technical solution;

[0054] S3. Brazing: Brazing the assembled components.

[0055] This application utilizes the design concept of multi-element medium-high entropy alloys, adding more than five alloying elements to the brazing filler metal. By comprehensively utilizing the solid solution strengthening of different elements, the strengthening effect is refined, thus improving the strength of the brazed joint. In the medium-entropy alloy material provided by this application, Fe and Mn elements can refine the grains and provide solid solution strengthening, thereby improving the room temperature and high temperature mechanical properties of the TiAl joint. When the Ni element content in the joint is 0.25–2.0 at.%, it can promote dynamic recrystallization, stabilize the work hardening rate, reduce the softening rate and degree, and improve the hot working plasticity of the TiAl joint. Nb element is beneficial for improving the room temperature toughness and room temperature / high temperature strength of the TiAl joint. When the Zr element content in the joint is 0.5–3.0 at.%, it can significantly improve the yield strength of the TiAl joint, and improve toughness and fracture behavior.

[0056] This invention pre-treats the surface of the base material and the welding position, specifically by removing oil and impurities from the surface of the base material and removing oxides from the welding position.

[0057] This invention involves adding brazing filler metal to the locations on the base materials to be welded, resulting in an assembled component. The invention controls the brazing gap between the base materials to be welded to be 0.03–0.07 mm using machining or tooling fixtures. See also... Figure 1 .

[0058] The brazing temperature described in this invention is 1140–1170°C.

[0059] The brazing process of this invention preferably employs vacuum brazing; the vacuum brazing process includes:

[0060] The vacuum level inside the furnace is better than 8×10 -3 Pa, heat at a rate of 10-40℃ / min to 600℃, then heat at a rate of 10-30℃ / min to 900℃, then heat at a rate of 10-25℃ / min to 1140-1170℃ and hold at that temperature for 20-75 minutes; after holding, cool down at a rate of 10-40℃ / min and cool with the furnace.

[0061] The present invention performs brazing under verified brazing conditions, preferably at (1140~1170)℃ / (20~75)min; in specific embodiments, the brazing conditions are (1160~1170)℃ / 45min, (1150~1160)℃ / 60min, (1140~1150)℃ / 60min or (1140~1150)℃ / 75min.

[0062] Figure 2 This is a front view of a brazing sample prepared according to a certain embodiment of the present invention. Figure 3 The cross-sectional microstructure of a brazed joint prepared according to a certain embodiment of the present invention.

[0063] In some embodiments of the present invention, brazing is performed using the brazing filler metal of the present invention at (1140~1170)℃ / (20~75)min. The microstructure of the brazed joint is mainly γ-TiAl and α2-Ti3Al. During the brazing process, the alloying elements in the brazing filler metal diffuse into the TiAl alloy matrix to be welded, thereby making the alloying element content in the brazed joint reach the following levels: 0.5%≤Fe≤4.0%, 0.5%≤Mn≤4.0%, 0.25%≤Ni≤2.0%, 1.0%≤Nb≤6.0%, and 0.5%≤Zr≤3.0% (at.%). These alloying elements play a small or trace strengthening role in the γ-TiAl phase of the brazed joint.

[0064] The TiAl / TiAl brazed joints obtained by the brazing filler metal in this invention exhibit significantly better high-temperature strength in the wide temperature range of 700–850°C than the brazed joints corresponding to simple ternary and quaternary brazing filler metal alloys such as Ti-Fe-Mn, Ti-Zr-Ni-Cu, Ti-Ni-Nb, or Ti-Zr-Ni-Nb.

[0065] This invention is based on the Ti-Mn-Fe ternary phase diagram. Ti exhibits good compatibility with Mn and Fe elements, and a ternary eutectic composition of Ti-(19-24)Mn-(14-19)Fe (wt.%) exists, with a eutectic temperature of approximately 1126℃. Simultaneously, based on the Ni-Nb binary phase diagram, a binary eutectic composition of Ni-(50-55)Nb (wt.%) exists, with a eutectic temperature of 1175℃. Furthermore, based on the Ti-Ni-Nb ternary phase diagram, a ternary eutectic composition of Ti-(32-37)Ni-(14-19)Nb (wt.%) exists, with a eutectic temperature of 900.3℃. Additionally, based on the Ni-Zr binary phase diagram, a binary eutectic composition of Ni-(45-50)Zr (wt.%) exists, with a eutectic temperature of 1061-1070℃. The Ni-Zr eutectic composition can further lower the alloy's melting point. See [link to relevant documentation]. Figures 4-7 Ti, Zr, and Nb are infinitely soluble in each other, exhibiting excellent compatibility.

[0066] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder for TiAl and its application method, should not be construed as limiting the scope of protection of the present invention.

[0067] Examples 1-3

[0068] The brazing filler metal raw materials are proportioned according to the mass percentages described in Table 1, and the alloy ingots are obtained by electric arc melting.

[0069] Table 1

[0070] Example Ti Fe Mn Ni Nb Zr 1 57.63 15.52 20.35 3.00 3.50 0 2 55.17 14.85 19.48 5.00 5.50 0 3 51.16 13.77 18.07 7.00 7.50 0

[0071] The alloy ingots are prepared into brazing filler metals of different shapes using different manufacturing processes, including blocks, powders, powder sintered bodies, and rapidly cooled foil strips.

[0072] The TiAl-based alloy matrix material is used, with a nominal composition of Ti-46Al-(3~4)Nb-(2~3)(Cr,Ta,B) (at.%). Pure Ti foil strips with a thickness of 0.03~0.07mm are cut into narrow strips with a width of 0.5~1mm and spot-welded to one side of the base material to be welded using a spot welding machine. The base materials on both sides are then clamped with tooling to control the brazing gap to 0.03~0.07mm. Then, brazing filler powder is pre-formed on the base material at the position to be welded to assemble the assembly.

[0073] The assembled components are placed in a vacuum furnace for brazing, with a vacuum level of 5.0 × 10⁻⁶. -3 Pa, brazing temperature is 1140~1170℃, to obtain brazed joint.

[0074] The brazed joints of this invention underwent performance testing, and the results are shown in Table 2:

[0075] Table 2

[0076]

[0077] The brazing temperature of the brazing filler metal of this invention is 1140-1170℃; under suitable brazing specifications, the brazed joint has high room temperature / high temperature tensile strength.

[0078] Examples 4-5

[0079] The brazing filler metal raw materials are proportioned according to the mass percentages described in Table 3, and the alloy ingots are obtained by electric arc melting.

[0080] Table 3

[0081] Example Ti Fe Mn Ni Nb Zr 4 53.63 14.43 18.94 5.00 5.50 2.50 5 48.18 13.00 17.02 7.80 9.00 5.00

[0082] The alloy ingots are prepared into brazing filler metals of different shapes using different manufacturing processes, including blocks, powders, and rapidly cooled foil strips.

[0083] The base material is a TiAl-based alloy with a nominal composition of Ti-46Al-(3~4)Nb-(2~3)(Cr,Ta,B) (at.%). Pure Ti foil strips with a thickness of 0.03~0.07mm are cut into narrow strips with a width of 0.5~1mm and spot-welded to one side of the base material to be welded using a spot welding machine. The base materials on both sides are then clamped with tooling to control the brazing gap to 0.03~0.07mm. Then, brazing filler powder is pre-formed on the base material at the position to be welded to assemble the assembly.

[0084] The assembled components are placed in a vacuum furnace for brazing, with a vacuum level of 5.0 × 10⁻⁶. -3 Pa, select a brazing temperature of 1140~1170℃ to obtain a brazed joint.

[0085] The brazed joints of this invention underwent performance testing, and the results are shown in Table 4:

[0086] Table 4

[0087]

[0088] The brazing temperature of the brazing filler metal of this invention is 1140-1170℃; under suitable brazing specifications, the brazed joint has high room temperature / high temperature tensile strength.

[0089] This invention provides a Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy brazing filler metal for TiAl, comprising the following components by mass percentage: Mn 17.0–22.0%; Fe 13.0–17.0%; Ni 2.0–8.0%; Nb 2.0–9.0%; Zr 0–5.0%; balance Ti; with a Ni to Nb content ratio of (45–50):(55–50). By introducing Ni, Nb, and Zr into the Ti-Mn-Fe matrix alloy and controlling the content of each component, this brazing filler metal, when applied to the brazing of TiAl alloys, results in brazed joints with lower brazing temperatures and higher room temperature / high temperature tensile strength.

[0090] As can be seen from the above embodiments, the average room temperature tensile strength of the joint obtained using the brazing filler metal of the present invention under brazing conditions of (1140~1150)℃ / (50~75)min reaches 421~428MPa, and the average tensile strengths at high temperatures of 700℃, 750℃, and 850℃ are 438MPa, 447MPa, and 399MPa, respectively. The room temperature tensile strength of the joint obtained under brazing conditions of (1150~1160)℃ / (40-60)min reaches 426~440MPa, and the average tensile strengths at high temperatures of 700℃, 750℃, and 850℃ are 445MPa, 453MPa, and 404MPa, respectively. The room temperature tensile strength of the joint obtained under the conditions of (1160~1170)℃ / (20~50)min reached 434~457MPa, and the average tensile strength at high temperatures of 700℃, 750℃ and 850℃ were 456MPa, 459MPa and 411MPa, respectively.

[0091] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder for TiAl, characterized in that, It comprises the following components by weight percentage: Mn 17.0~22.0%; Fe 13.0~17.0%; Ni 5~8.0%; Nb 5.5~9.0%; Zr 2.5~5.0%; Balance Ti; The content ratio of Ni to Nb is (45~50): (55~50); The brazing filler metal is used for brazing at 1140~1170℃ for 20~75min. The filler metal results in a brazed joint microstructure mainly composed of γ-TiAl and α2-Ti3Al. During the brazing process, alloying elements in the filler metal diffuse into the TiAl alloy matrix being brazed, thereby achieving the following alloying element content in the brazed joint, in atomic percentage: 0.5%≤Fe≤4.0%, 0.5%≤Mn≤4.0%, 0.25%≤Ni≤2.0%, 1.0%≤Nb≤6.0%, and 0.5%≤Zr≤3.0%.

2. The Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder for TiAl according to claim 1, characterized in that, The brazing filler metal is used in one or more of the following forms: block, granular, sheet, powder, or rapidly cooled foil / strip.

3. A method for preparing the TiAl Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder according to any one of claims 1 to 2, comprising the following steps: The materials were proportioned according to the mass percentage of the solder and melted using the electric arc melting method to obtain the TiAl Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder.

4. The application of the Ti-Mn-Fe-Ni-Nb-Zr medium-entropy alloy solder according to any one of claims 1 to 2 in the joining of TiAl alloys, Ti-Al-Nb alloys, Ti-based composite materials, TiAl-based composite materials, other multi-element medium-entropy or high-entropy alloy matrix materials containing Ti as one element, or other multi-element medium-entropy or high-entropy alloy matrix materials containing both Ti and Al elements.

5. A brazing method for TiAl alloy, characterized in that, Includes the following steps: S1. Preparation of base material to be welded: Pre-treatment of the surface of the base material and the welding position; S2. Assembly: Adding brazing filler metal to the location of the base material to be welded to obtain the assembled component; the brazing filler metal is the brazing filler metal according to any one of claims 1 to 2 or the brazing filler metal prepared by the preparation method according to claim 3; S3. Brazing: Brazing the assembled components.

6. The brazing method according to claim 5, characterized in that, The brazing is vacuum brazing; The vacuum brazing process includes: The vacuum level inside the furnace is better than 8×10 -3 Pa, heat up to 600℃ at a rate of 10~40℃ / min, then heat up to 900℃ at a rate of 10~30℃ / min, then heat up to 1140~1170℃ at a rate of 10~25℃ / min and hold for 20~75min; after holding, cool down at a rate of 10~40℃ / min and cool with the furnace.

7. The brazing method according to claim 5, characterized in that, The gap between the base material and the welding position is 0.03~0.07mm.

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