CN117548767B - Brazing method for cooperatively improving creep strength and toughness - Google Patents
Brazing method for cooperatively improving creep strength and toughness Download PDFInfo
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- CN117548767B CN117548767B CN202410043814.7A CN202410043814A CN117548767B CN 117548767 B CN117548767 B CN 117548767B CN 202410043814 A CN202410043814 A CN 202410043814A CN 117548767 B CN117548767 B CN 117548767B
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- 238000005219 brazing Methods 0.000 title claims abstract description 133
- 238000000034 method Methods 0.000 title claims abstract description 68
- 238000010438 heat treatment Methods 0.000 claims abstract description 39
- 239000002184 metal Substances 0.000 claims abstract description 38
- 229910052751 metal Inorganic materials 0.000 claims abstract description 38
- 238000009792 diffusion process Methods 0.000 claims abstract description 36
- 239000000945 filler Substances 0.000 claims abstract description 31
- 239000000463 material Substances 0.000 claims abstract description 27
- 238000001816 cooling Methods 0.000 claims abstract description 20
- 229910000679 solder Inorganic materials 0.000 claims description 15
- 239000010953 base metal Substances 0.000 claims description 11
- 239000011261 inert gas Substances 0.000 claims description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 229910001220 stainless steel Inorganic materials 0.000 claims description 7
- 239000010935 stainless steel Substances 0.000 claims description 7
- 229910001067 superalloy steel Inorganic materials 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 230000002195 synergetic effect Effects 0.000 claims description 3
- 238000003466 welding Methods 0.000 abstract description 34
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 238000009826 distribution Methods 0.000 abstract description 5
- 230000000593 degrading effect Effects 0.000 abstract description 4
- 238000007711 solidification Methods 0.000 abstract description 4
- 230000008023 solidification Effects 0.000 abstract description 4
- 239000013078 crystal Substances 0.000 abstract description 3
- 230000000630 rising effect Effects 0.000 abstract description 3
- 238000012545 processing Methods 0.000 abstract description 2
- 239000002585 base Substances 0.000 description 28
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 21
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 18
- 238000004140 cleaning Methods 0.000 description 10
- 238000004321 preservation Methods 0.000 description 7
- 239000011888 foil Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000009835 boiling Methods 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 238000007789 sealing Methods 0.000 description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 239000003513 alkali Substances 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 238000005554 pickling Methods 0.000 description 4
- 238000005498 polishing Methods 0.000 description 4
- 239000000853 adhesive Substances 0.000 description 3
- 230000001070 adhesive effect Effects 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 238000004452 microanalysis Methods 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 238000007781 pre-processing Methods 0.000 description 2
- 238000005476 soldering Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/008—Soldering within a furnace
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K3/00—Tools, devices, or special appurtenances for soldering, e.g. brazing, or unsoldering, not specially adapted for particular methods
- B23K3/08—Auxiliary devices therefor
- B23K3/087—Soldering or brazing jigs, fixtures or clamping means
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Pressure Welding/Diffusion-Bonding (AREA)
Abstract
The invention provides a brazing method for cooperatively improving creep strength and toughness, and belongs to the technical field of metal processing. After the brazing is finished, the heat treatment step of diffusion treatment is followed, so that the element distribution in the whole braze joint can be more uniform in the diffusion treatment process, and a large amount of boride in the braze joint brazing filler metal area and the diffusion area can be dissolved and broken at the same time, thereby increasing the high-temperature creep strength and toughness of the braze joint. The invention omits the solidification process of cooling the welding sample to room temperature in the conventional post-welding heat treatment and the temperature rising step in the post-welding heat treatment process, thereby greatly reducing the time of the welding process and the cost. Meanwhile, the whole welding and heat treatment process is under the clamping action of the clamp, so that the deformation generated in the heat treatment process can be effectively reduced, and the manufacturing precision is improved. The invention carries out diffusion treatment in a vacuum environment, and the reasonable diffusion treatment temperature can not cause coarsening of crystal grains, thereby not degrading the performance of the base material and the joint.
Description
Technical Field
The invention relates to the technical field of metal processing, in particular to a brazing method for cooperatively improving creep strength and toughness.
Background
Under the background of a new era, the energy system is integrated and intelligent, the theme of high energy utilization efficiency and low emission is more and more clear, and the higher requirements are provided for the future energy development of China. The heat exchange system is used as a key for improving the energy utilization rate in the high-energy consumption fields of modern petrochemical industry, aerospace, nuclear power and the like. The heat exchanger has been used in engineering machinery, refrigeration and other relatively low temperature environments, and is also a key device for realizing high temperature waste heat recovery and utilization and further improving energy utilization rate. In recent years, compared with the traditional heat exchangers such as shell-and-tube heat exchangers, the heat exchanger manufactured by the brazing technology, such as a miniature gas turbine heat exchanger, an aero-engine heat regenerator and a plate-fin heat exchanger for a high-temperature gas cooled reactor, has greatly improved heat exchange efficiency and structural compactness, meets the requirements of green development better, and has wide market application prospects.
Along with the expansion of the application field of the heat exchanger, higher requirements are put on the reliability and service life of the heat exchanger, the design temperature and pressure of the special heat exchanger are improved to 900 ℃ and 15 MPa, and the design life of the special heat exchanger in the nuclear power field is as long as 60 years. Creep is one of the main failure modes of heat exchangers under high temperature and severe environments, and it is counted that more than about 30% of heat exchangers are caused by creep rupture. The heat exchanger manufactured by the brazing technology has a large number of brazing joints in the internal structure, which is the weakest part of the structure, and failure cracks are usually initiated and spread at the brazing joints. The creep strength and toughness of the braze joint are of great significance for long life reliability operation of the high temperature heat exchanger. However, current research shows that the creep strength and toughness of braze joints are far lower than the properties of the parent material. According to the brazing principle, melting point of the brazing filler metal is reduced and fluidity after melting is increased by adding melting-reducing elements such as boron and the like into the brazing filler metal, but due to incomplete diffusion of the boron elements caused by a brazing process, a large number of brittle phases can be generated in the center of a joint braze joint and a diffusion area, and the risk of brittle fracture of a brazing joint is increased; meanwhile, various brazing defects such as air holes, inclusions and the like can be generated in the brazing process, so that the brazed joint is in a complex stress state, microcracks are more easily initiated and continuously expanded at the defects in service, and finally structural failure is caused. At present, the structure and distribution in the soldered joint are improved by prolonging the heat preservation time and performing postweld heat treatment in the soldering process, so that the quality of the joint is improved. For the method for prolonging the heat preservation time, although the brittle phase in the soldered joint can be reduced by long-time heat preservation, the property of the joint and the parent metal is easily degraded by long heat preservation time, which is not beneficial to the improvement of the integral property of the soldered structure. For the method of post-welding heat treatment, although the creep strength and toughness of the welded structure can be greatly improved, in the actual operation process, the conventional welding process is adopted for brazing, the brazing sample is cooled to room temperature for solidification and then is heated to the heat treatment temperature for heat treatment, and the repeated temperature rise and drop greatly improve the welding manufacturing cost and time, and meanwhile, the welded structure is greatly deformed, so that the manufacturing precision is influenced.
Disclosure of Invention
The invention aims to provide a brazing method for cooperatively improving creep strength and toughness, which can not cause performance degradation of a joint and a base metal while cooperatively improving the creep strength and the toughness, greatly reduce the time of a welding process, reduce the cost and not influence the manufacturing precision.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a brazing method for cooperatively improving creep strength and toughness, which comprises the following steps: assembling the brazing filler metal and the two base materials, and clamping and fixing the brazing filler metal and the two base materials by using a clamp to obtain an assembled brazing sample; each base metal is independently nickel-base superalloy or stainless steel;
under the vacuum condition, heating the assembled brazing sample to 800-900 ℃ for 30-40 min;
secondly, heating to a brazing temperature, and preserving heat for 30-40 min, wherein the brazing temperature is 1050-1100 ℃; after brazing is completed, cooling to 800-900 ℃ for the first time, so that the brazing filler metal in the brazing joint is completely solidified;
thirdly heating the brazing sample solidified by the joint to 1100-1170 ℃ and preserving heat for 3-6 hours to perform diffusion treatment;
and cooling the brazing sample subjected to diffusion treatment to 600-700 ℃, and filling inert gas to cool the brazing sample to room temperature.
Preferably, the vacuum condition has a pressure of 0.001Pa or less.
Preferably, before the assembling, the method further comprises the step of respectively preprocessing the base metal and the brazing filler metal.
Preferably, the clamping force of the clamp is 3-5 MPa.
Preferably, the first heating rate is 10-15 ℃/min.
Preferably, the second heating rate is 10-15 ℃/min.
Preferably, the third heating rate is 10-15 ℃/min.
Preferably, the inert gas comprises nitrogen.
Preferably, the contact surfaces of the upper and lower clamping plates of the clamp and the brazing sample are coated with solder resist.
Preferably, the solder is BNi-2.
The invention provides a brazing method for cooperatively improving creep strength and toughness, which comprises the following steps: assembling the brazing filler metal and the two base materials, and clamping firmly by using a clamp to obtain an assembled brazing sample; each base metal is independently nickel-base superalloy or stainless steel; under the vacuum condition, heating the assembled brazing sample to 800-900 ℃ for 30-40 min; secondly, heating to a brazing temperature, and preserving heat for 30-40 min, wherein the brazing temperature is 1050-1100 ℃; after brazing is completed, cooling to 800-900 ℃ for the first time, so that the brazing filler metal in the brazing joint is completely solidified; thirdly heating the brazing sample solidified by the joint to 1100-1170 ℃ and preserving heat for 3-6 hours to perform diffusion treatment; and cooling the brazing sample subjected to diffusion treatment to 600-700 ℃, filling inert gas into the brazing sample to cool the brazing sample to room temperature, and removing the clamp.
In the welding process, the components of the brazing solder and the base metal have certain difference, so that the element distribution difference of the brazing joint solder area, the diffusion area and the base metal is larger; meanwhile, more boride is generated in a solder area and a diffusion area of the soldered joint in the welding process, so that the creep strength and toughness of the soldered joint are poor. After the brazing is finished, the heat treatment step of one-step diffusion treatment is followed, so that the element distribution in the whole braze joint can be more uniform in the diffusion treatment process, and a large amount of boride in a braze joint brazing material area and a diffusion area can be dissolved and broken at the same time, thereby increasing the high-temperature creep strength and toughness of the braze joint. The invention omits the solidification process of cooling the welding sample to room temperature in the conventional post-welding heat treatment and the temperature rising step in the post-welding heat treatment process, greatly reduces the time of the whole welding process (as shown in figure 1, the preparation time is removed, and the time can be saved by about 30% only in the welding and diffusion processes), and reduces the cost. Meanwhile, the whole welding and heat treatment process is under the clamping action of the clamp, so that the deformation generated in the heat treatment process can be effectively reduced, and the manufacturing precision is improved. The invention is carried out in a vacuum environment, the diffusion treatment temperature is less than the melting point temperature of the base material, and the reasonable diffusion treatment temperature can not cause coarsening of crystal grains, thereby not degrading the performance of the base material and the joint.
Drawings
FIG. 1 is a graph of temperature versus time for a braze process with synergistic improvement in creep strength and toughness provided by the present invention;
FIG. 2 is a graph comparing creep strength and toughness of a conventional welding process with a braze joint obtained according to the present invention;
fig. 3 is a graph of a microstructure analysis of a braze joint obtained in accordance with the present invention and a conventional welding process.
Detailed Description
As shown in FIG. 1, the invention provides a brazing method with cooperative improvement of creep strength and toughness, which comprises the following steps: assembling the brazing filler metal and the two base materials, and clamping and fixing the brazing filler metal and the two base materials by using a clamp to obtain an assembled brazing sample; each base metal is independently nickel-base superalloy or stainless steel;
under the vacuum condition, heating the assembled brazing sample to 800-900 ℃ for 30-40 min;
secondly, heating to a brazing temperature, and preserving heat for 30-40 min, wherein the brazing temperature is 1050-1100 ℃; after brazing is completed, cooling to 800-900 ℃ for the first time, so that the brazing filler metal in the brazing joint is completely solidified;
thirdly heating the brazing sample solidified by the joint to 1100-1170 ℃ and preserving heat for 3-6 hours to perform diffusion treatment;
and cooling the brazing sample subjected to diffusion treatment to 600-700 ℃, and filling inert gas to cool the brazing sample to room temperature.
In the present invention, the raw materials used are commercially available products well known in the art, unless specifically described otherwise.
According to the invention, the brazing filler metal and the two base materials are assembled, and clamped and fixed by the clamp, so that an assembled brazing sample is obtained.
In the present invention, each base material is independently nickel-base superalloy or stainless steel, and the present invention does not require any special requirements for the specific kind of the nickel-base superalloy and stainless steel, and both nickel-base superalloy and stainless steel known in the art may be used. In the embodiment of the invention, the two base materials are specifically 625 nickel-based alloys. In the present invention, the brazing filler metal is preferably BNi-2.
Before the assembly, the invention preferably further comprises the steps of respectively preprocessing the base metal and the brazing filler metal; the pretreatment of the base material preferably includes: pickling a parent metal, boiling with a sodium hydroxide solution, cleaning with hot water, and finally cleaning with acetone and drying; polishing the cleaned brazing surface of the parent metal, boiling the parent metal with sodium hydroxide solution after polishing, cleaning with hot water and acetone respectively, and drying and sealing for later use. In the invention, the pickling solution used for pickling is preferably sulfuric acid solution with the mass fraction of 10%; the mass fraction of the sodium hydroxide solution is preferably 10%.
In the present invention, the pretreatment of the brazing filler metal preferably includes: and (5) cutting the solder according to the size, and cleaning with acetone.
The present invention has no special requirements for the assembly process, and the assembly process well known in the art can be adopted. In the embodiment of the invention, the brazing filler metal foil is preset between two base materials, the adhesive is smeared on the contact surface, and the brazing filler metal foil is clamped firmly by a clamp to prevent the assembly from dislocation in the process of carrying and brazing.
In the invention, the clamping force of the clamp is preferably 3-5 MPa, more preferably 3.5-4.5 MPa.
In the present invention, the contact surfaces of the upper and lower clamping plates of the jig and the brazing sample are preferably coated with a solder resist. The invention coats the solder resist on the clamp, which can prevent the clamp and the brazing sample from fusing into a whole at high temperature.
After the assembled brazing sample is obtained, the assembled brazing sample is placed in a vacuum brazing furnace for the following steps.
In the invention, under the vacuum condition, the temperature of the assembled brazing sample is raised to 800-900 ℃, preferably 820-880 ℃, and more preferably 840-860 ℃; the temperature is kept for 30-40 min, preferably 32-38 min, and more preferably 34-36 min.
In the present invention, the pressure of the vacuum condition is preferably 0.001Pa or less; the first heating rate is preferably 10-15 ℃/min, more preferably 11-14 ℃/min, and even more preferably 12-13 ℃/min. According to the invention, the assembled sample is heated to 800-900 ℃ for 30-40 min, so that the sample can be uniformly distributed.
After the heat preservation is finished, the temperature is increased to the brazing temperature for 30-40 min. In the invention, the brazing temperature is 1050-1100 ℃, preferably 1060-1090 ℃, and more preferably 1070-1080 ℃; the heat preservation time of the brazing is preferably 32-38 min, more preferably 34-36 min. In the present invention, the second temperature rising rate is preferably 10 to 15 ℃/min, more preferably 11 to 14 ℃/min, and even more preferably 12 to 13 ℃/min.
After brazing is completed, the temperature is reduced to 800-900 ℃, preferably 820-880 ℃, and more preferably 840-860 ℃ for the first time, so that the brazing filler metal in the brazing joint is completely solidified. The invention has no special requirement on the first cooling rate, and ensures that the brazing filler metal in the brazing joint is completely solidified.
And then the third temperature of the soldering sample solidified by the joint is raised to 1100-1170 ℃ and kept for 3-6 hours for diffusion treatment. In the invention, the temperature of the diffusion treatment is preferably 1110-1160 ℃, more preferably 1120-1150 ℃; the heat preservation time of the diffusion treatment is preferably 3.5-4.5 h, more preferably 4h. After the brazing is finished, the diffusion treatment is carried out immediately, so that the element distribution in the whole braze joint can be more uniform in the diffusion treatment process, and a large amount of boride in the braze joint brazing filler metal area and the diffusion area can be dissolved and broken at the same time, thereby increasing the high-temperature creep strength and toughness of the braze joint.
After the diffusion treatment is finished, the second temperature of the brazed sample after the diffusion treatment is reduced to 600-700 ℃, and inert gas is filled to cool the brazed sample to room temperature.
The invention has no special requirement on the second cooling rate. In the present invention, the inert gas preferably includes nitrogen. The invention can prevent oxidation of soldered joint and can also realize rapid cooling by filling inert gas. The invention preferably starts the fan of the vacuum brazing furnace for cooling.
And after cooling to room temperature, discharging.
According to the invention, the solidification process of cooling the welding sample to room temperature in the conventional post-welding heat treatment and the heating step in the post-welding heat treatment process are omitted, the temperature is directly reduced to 800-900 ℃ after the brazing is finished so as to solidify the joint, and then the temperature is increased to 1100-1170 ℃ so as to perform diffusion treatment, thereby greatly reducing the time of the welding process and reducing the cost. Meanwhile, the whole welding and heat treatment process is under the clamping action of the clamp, so that the deformation generated in the heat treatment process can be effectively reduced, and the manufacturing precision is improved. The invention is carried out in a vacuum environment, the diffusion treatment temperature is less than the melting point temperature of the base material, and the reasonable diffusion treatment temperature can not cause coarsening of crystal grains, thereby not degrading the performance of the base material and the joint.
The following is a detailed description of the method of brazing with synergistic improvements in creep strength and toughness provided by the present invention, but they should not be construed as limiting the scope of the invention.
Example 1
(1) Pre-welding pretreatment process: by using 10% by mass of H 2 SO 4 The base metal (625 nickel base alloy for both base metals) is pickled by the solution, boiled by NaOH alkali liquor (the mass fraction is 10%), washed by hot water, finally washed by acetone and dried, and oxides on the surface are thoroughly removed. Polishing the brazing surface of the base material, boiling the base material with NaOH alkali liquor (the mass fraction is 10%), cleaning with hot water and acetone respectively, and drying and sealing for later use. Cutting BNi-2 solder according to the size, cleaning with acetone, sealing and preserving.
(2) Welding part assembly: the brazing filler metal foil is preset between two base materials, adhesive is coated on the contact surface, and the brazing filler metal foil is clamped firmly by a special clamp, so that the assembly is prevented from being misplaced in the carrying and brazing processes. The contact surfaces of the upper clamping plate and the lower clamping plate of the clamp and the alloy plate are coated with solder resist to prevent the solder resist from fusing into a whole at high temperature.
(3) After assembly, placing the assembly into a vacuum brazing furnace, and vacuumizing the furnace to below 0.001 Pa;
(4) Welding and heating: heating to 850 ℃ at a speed of 15 ℃/min for a first time, and preserving heat for 30min;
(5) And (3) welding: then raising the temperature to 1065 ℃ at a speed of 15 ℃ for the second time, and preserving heat for 40min to finish brazing;
(6) And (3) cooling and solidifying: slowly cooling the sample from vacuum to 800 ℃ to ensure that the brazing filler metal in the braze joint is completely solidified;
(7) Diffusion treatment process: starting to raise the temperature to 1150 ℃ at a speed of 15 ℃/min on the basis of the step (6), and preserving the temperature for 3 hours to dissolve, break and redistribute boride in the soldered joint, wherein elements in the soldered joint are redistributed;
(8) And (3) a cooling process: slowly reducing the sample from the diffusion treatment temperature to 700 ℃ to reduce residual stress in the braze joint; then charging N into the furnace 2 And simultaneously starting a fan of the vacuum brazing furnace to enable the structure to be cooled to 25 ℃ rapidly and then discharging.
Comparative example 1
The conventional welding process is adopted, and the specific steps are as follows:
(1) Pre-welding pretreatment process: by using 10% by mass of H 2 SO 4 The solution is used for pickling the parent metal, then NaOH alkali liquor (the mass fraction is 10%) is used for boiling, hot water is used for cleaning, finally acetone is used for cleaning and drying, and oxides on the surface are thoroughly removed. Polishing the brazing surface of the base material, boiling the base material with NaOH alkali liquor (the mass fraction is 10%), cleaning with hot water and acetone respectively, and drying and sealing for later use. Cutting BNi-2 solder according to the size, cleaning with acetone, sealing and preserving.
(2) Welding part assembly: the brazing filler metal foil is preset between two base materials, adhesive is coated on the contact surface, and the brazing filler metal foil is clamped firmly by a special clamp, so that the assembly is prevented from being misplaced in the carrying and brazing processes. The contact surfaces of the upper clamping plate and the lower clamping plate of the clamp and the alloy plate are coated with solder resist to prevent the solder resist from fusing into a whole at high temperature.
(3) After assembly, placing the assembly into a vacuum brazing furnace, and vacuumizing the furnace to below 0.001 Pa;
(4) Welding and heating: first heating to 850 deg.C at 15 deg.C/min o C, preserving heat for 30min;
(5) And (3) welding: followed by a second temperature increase to a braze temperature 1065 at a rate of 15 DEG C o C, preserving heat for 40min, and completing brazing;
(6) And (3) cooling and solidifying: the sample was slowly cooled from vacuum to 700 ℃, then nitrogen was purged into the vacuum brazing furnace to rapidly cool to room temperature and then discharged.
The creep tensile test was used to test the creep strength and toughness of the braze joints of comparative example 1 and example 1, the test results are shown in FIG. 2, and the specific data corresponding to FIG. 2 are shown in Table 1.
TABLE 1 creep strength and toughness data for conventional welding processes and braze joints obtained according to the present invention
In the present invention, the definition of creep strength improvement is: the longer the creep time of the test specimen at the same stress level, the higher the creep strength of the test specimen, or the higher the corresponding fracture stress of the test specimen at the same creep rupture time, the greater the fracture strength of the test specimen. The toughness refers to a creep strain corresponding to creep rupture, and the larger the creep strain value is, the higher the toughness is.
As can be seen from fig. 2, the creep rupture time and creep rupture strain of the braze joint obtained according to the present invention are significantly higher than those obtained by conventional processes at the same stress level.
As can be seen from Table 1, compared with the braze joint obtained by the conventional process (comparative example 1), the creep rupture life of the braze joint obtained by the invention is improved by 145.1-210.6% and the creep rupture strain is improved by 13.3-17.1% at the same stress level, so that the cooperative improvement of the creep strength and toughness of the braze joint is realized.
The results of the microanalysis of the braze joints of comparative example 1 and example 1 are shown in fig. 3, and in fig. 3, (a) is a microanalysis diagram of the braze joint obtained in the conventional process for comparative example 1, and (b) is a microanalysis diagram of the braze joint obtained in example 1. As can be seen from the figures, the grain size of the braze joint obtained by the process of the invention is substantially the same as that of the conventional process, thus illustrating that the process of the invention is practiced without degrading the properties of the base material and joint. Compared with the prior art, the number of boride is greatly reduced, and the boride is more uniformly distributed, so that the creep strength and toughness of the soldered joint are improved.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A method of brazing with synergistic improvement in creep strength and toughness, comprising the steps of: assembling the brazing filler metal and the two base materials, and clamping and fixing the brazing filler metal and the two base materials by using a clamp to obtain an assembled brazing sample; each base metal is independently nickel-base superalloy or stainless steel;
under the vacuum condition, heating the assembled brazing sample to 800-900 ℃ for 30-40 min;
secondly, heating to a brazing temperature, and preserving heat for 30-40 min, wherein the brazing temperature is 1050-1100 ℃; after brazing is completed, cooling to 800-900 ℃ for the first time, so that the brazing filler metal in the brazing joint is completely solidified;
thirdly heating the brazing sample solidified by the joint to 1100-1170 ℃ and preserving heat for 3-6 hours to perform diffusion treatment;
and cooling the brazing sample subjected to diffusion treatment to 600-700 ℃, and filling inert gas to cool the brazing sample to room temperature.
2. The brazing method according to claim 1, wherein the vacuum condition has a pressure of 0.001Pa or less.
3. The brazing method according to claim 1, further comprising pre-treating the base material and the brazing filler metal, respectively, prior to the assembling.
4. The brazing method according to claim 1, wherein the clamping force of the clamp is 3-5 mpa.
5. The brazing method according to claim 1, wherein the first temperature rise rate is 10-15 ℃/min.
6. The brazing method according to claim 1, wherein the second temperature rise rate is 10-15 ℃/min.
7. The brazing method according to claim 1, wherein the third temperature rise rate is 10-15 ℃/min.
8. The brazing method according to claim 1, wherein the inert gas comprises nitrogen.
9. The brazing method according to claim 1 or 4, wherein the contact surfaces of the upper and lower jaws of the jig and the brazing specimen are coated with a solder resist.
10. A brazing method according to claim 1 or 3, wherein the brazing filler metal is BNi-2.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3292255A (en) * | 1964-06-25 | 1966-12-20 | James C Marshall | Brazing alloys for tungsten and molybdenum |
| CN106914673A (en) * | 2017-04-13 | 2017-07-04 | 中国石油大学(华东) | A kind of nickel-base material soldered fitting composition and mechanical property homogenization method |
| CN111889835A (en) * | 2020-07-27 | 2020-11-06 | 中国石油大学(华东) | Method for reducing residual stress in brazed joint |
| CN114799395A (en) * | 2022-03-29 | 2022-07-29 | 北京科技大学 | Vacuum brazing method for dissimilar nickel-based high-temperature alloy for improving strength stability of joint |
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- 2024-01-12 CN CN202410043814.7A patent/CN117548767B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3292255A (en) * | 1964-06-25 | 1966-12-20 | James C Marshall | Brazing alloys for tungsten and molybdenum |
| CN106914673A (en) * | 2017-04-13 | 2017-07-04 | 中国石油大学(华东) | A kind of nickel-base material soldered fitting composition and mechanical property homogenization method |
| CN111889835A (en) * | 2020-07-27 | 2020-11-06 | 中国石油大学(华东) | Method for reducing residual stress in brazed joint |
| CN114799395A (en) * | 2022-03-29 | 2022-07-29 | 北京科技大学 | Vacuum brazing method for dissimilar nickel-based high-temperature alloy for improving strength stability of joint |
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