CN111269020A - Vacuum diffusion welding method for protective layer of miniature high-temperature oxygen concentration sensor - Google Patents
Vacuum diffusion welding method for protective layer of miniature high-temperature oxygen concentration sensor Download PDFInfo
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Abstract
The invention belongs to the field of sensor manufacturing, and relates to a vacuum diffusion welding method for a protective layer of a 59 mm-volume 3 miniature high-temperature oxygen concentration sensor, in particular to a vacuum diffusion welding method for an alumina/zirconia ceramic structure with a diameter of 5.5 mm. Two brazing filler metal foils of B-Ag85Zr15 and B-Ti72Ni28 are selected and added into an alumina ceramic prefabricated ring groove, sensors assembled in sequence are placed on a workbench of a vacuum heating furnace, and a pressing block is arranged outside the alumina ceramic plate for welding. The welding process parameters are as follows: the heating maximum temperature is 1040-1120 ℃, the heat preservation time is 30-60 min, the pressure is 0.08-0.10 MPa, and the vacuum degree is 6.5 multiplied by 10 < -4 > Pa. The invention has the advantages of low heating temperature, capability of obtaining a low-stress and high-strength structure, realization of mass production and the like, obtains a connection structure which has no crack, uniform spreading of brazing filler metal, no overflow and beautiful appearance, and can meet the requirements of high-temperature use stability and high oxygen measurement precision of the sensor.
Description
Technical Field
The invention belongs to the field of sensor manufacturing, and relates to a vacuum diffusion welding method for a protective layer of a 59 mm-volume 3 miniature high-temperature oxygen concentration sensor, in particular to a vacuum diffusion welding method for an alumina/zirconia ceramic structure with a diameter of 5.5 mm.
Background
The zirconia type oxygen concentration sensor has high oxygen measurement precision and high temperature stability, and is widely applied to the detection fields of internal combustion engine tail gas emission, nuclear power reactor gas content, oxygen content of an oxygen mask of an aviation aircraft and the like. In order to ensure the insulation between the heater and the sensing component, the alumina ceramic layer and the zirconia ceramic layer outside the zirconia oxygen concentration sensor are usually connected by high temperature sintering or bonding. The bonding mode is obviously not suitable for the high-temperature (above 650 ℃) use requirement of the sensor, and the high-temperature sintering mode (above 1500 ℃) is adopted, so that the physical properties of the aluminum oxide and the zirconium oxide are greatly different, and a large residual stress can be generated in the cooling process after sintering, so that the connecting structure is cracked and fails. It has also been studied to obtain a high-strength and high-performance interconnect by sintering a green material, which is the same as the ceramic to be connected and has plasticity after modification, at 1500 ℃ or higher for 120 minutes, but for a micro zirconia-type oxygen concentration sensor, the connecting surface is small and a platinum electrode is usually placed or coated in the middle, which makes the structure more complicated, and it is difficult to obtain a high-quality interconnect by sintering a thick gradient interlayer. Therefore, it is important to find a proper and reliable connection method for the alumina/zirconia structure of the protective layer of the miniature high-temperature oxygen concentration sensor.
The vacuum diffusion welding method is a low-temperature solid phase connection mode, the heating temperature is 0.8Tm (Tm is a melting point) of the melting point of a connected workpiece during welding, an intermediate layer can be added or not added on a connection interface, the two interfaces are in close contact by applying lower pressure, the diffusion connection of the interfaces or the intermediate layer is realized, and the residual stress of the connection interface can be greatly reduced. Aiming at the complex structure characteristics of the alumina ceramic/platinum electrode/zirconia ceramic connection structure of the micro sensor, a proper intermediate layer material is selected and the connection interface is optimally designed, so that a high-quality connection structure is expected to be obtained, and simultaneously, in view of the severe requirements of the zirconia type oxygen concentration sensor on the working environment of an oxygen pump and a concentration cell, the types of the intermediate layer material elements are reduced as much as possible during connection.
Disclosure of Invention
The invention aims to solve the problems that the prior art fails due to larger residual stress, cracks and the like in the connecting process of a protective layer of a miniature high-temperature oxygen concentration sensor, the miniaturization of the structure of the miniature high-temperature oxygen concentration sensor cannot be realized due to the overlarge middle layer, and the like.
The invention provides a vacuum diffusion welding method for a protective layer of a miniature high-temperature oxygen concentration sensor, which is realized by the following steps:
(1) two brazing filler metal foils B-Ti72Ni28 and B-Ag85Zr15 are selected to prepare an annular structure with the inner diameter of 2.2mm and the outer diameter of 5.2 mm;
(2) cleaning the connected areas of the brazing filler metal foil, the aluminum oxide ceramic wafer and the zirconium oxide ceramic substrate before welding;
(3) sequentially adding two solder foils B-Ag85Zr15 and B-Ti72Ni28 into prefabricated annular grooves of the alumina ceramic plates on two sides, and then sequentially placing the alumina ceramic plates with the solder foils added, the porous platinum-coated cobalt dioxide electrodes and the zirconia ceramic substrates with the platinum electrodes coated on the inner sides on a workbench of a vacuum heating furnace according to the assembly sequence of sensors, wherein pressing blocks are preset on the outer sides of the alumina ceramic plates;
(4) before welding, the vacuum heating furnace is vacuumized for 30min, and then heated up at the heating rate of 5 ℃/min. When the temperature is raised to 450 ℃, the temperature is preserved for 5 min; when the temperature is increased to 900 ℃, carrying out heat preservation for 10min, then increasing the temperature to the highest temperature and carrying out heat preservation; and after the heat preservation is finished, the welded workpiece is cooled along with the furnace, and the welding is finished. The technological parameters of vacuum diffusion welding are as follows: the heating maximum temperature is 1040-1120 ℃, the heat preservation time is 30-60 min, the loading pressure is 0.08-0.10 MPa, and the vacuum degree is 6.5 multiplied by 10-4Pa。
In the step (1), the thickness of the B-Ag85Zr15 brazing filler metal foil is 0.05mm, and the chemical components are Ag 85.0% and Zr 15.0%; the thickness of the B-Ti72Ni28 solder foil is 0.06mm, and the chemical components are Ti 72.0% and Ni 28.0%. The brazing temperature of the B-Ag85Zr15 foil is 1020-1050 ℃, the brazing temperature of the B-Ti72Ni28 foil is 1080-1140 ℃, and brazing flux is not needed in the process.
In the step (2), the pre-welding cleaning means that oil stains and impurities on the connected areas of the alumina ceramic and the zirconia ceramic are removed, oil stains and oxides on the surfaces of a cobalt dioxide electrode coated with porous platinum, a B-Ag85Zr15 brazing foil sheet, a B-Ti72Ni28 brazing foil sheet and the like are simultaneously removed, and the prefabricated annular grooves of the two alumina ceramic sheets are mainly cleaned (see figure 2). The cleaning method comprises the following steps: putting the alumina ceramic plate, the zirconia ceramic plate, the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrode into a glass container with acetone, carrying out ultrasonic cleaning for 30min at the temperature of 50 ℃, then carrying out secondary cleaning with alcohol and drying, and keeping the alumina ceramic plate and the zirconia ceramic plate for later use. And performing secondary surface treatment on the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrode by using an argon plasma cleaning technology.
In the step (3), the inner diameter of the ring groove prefabricated by the aluminum oxide ceramic plate is 2.2mm, the outer diameter of the ring groove is 5.2mm, and the depth of the ring groove is 0.095 mm; the edges of the annular groove close to the aluminum oxide ceramic plate and the platinum electrode are reserved with 0.3mm and 0.2mm intervals respectively so as to avoid the overflow of pollutants entering the platinum electrode or the brazing filler metal caused by the excessive spreading of the brazing filler metal. When two brazing filler metal foils of B-Ti72Ni28 and B-Ag85Zr15 are filled in the annular groove, the precise fit between the two brazing filler metal platinum sheets and the annular groove is ensured, and the phenomena of dislocation, fluctuation and the like are avoided. The pressurizing block is made of alumina ceramic, and the size of the pressurizing block is prepared according to the pressure required by the sensor structure.
By adopting the vacuum diffusion welding method for the protective layer of the miniature high-temperature oxygen concentration sensor, the effective connection of the protective layer of the sensor can be realized, and the connection structure which has no crack in high-temperature use, uniform spreading of the brazing filler metal, no overflow, beautiful appearance and accordance with the actual use strength requirement is obtained. The vacuum diffusion connection method adopting different brazing filler metals has the advantages of low heating temperature, capability of obtaining a low-stress and high-strength structure, realization of single-processing mass production and the like, and can meet the requirements of the miniature high-temperature oxygen concentration sensor on use stability and high oxygen measurement accuracy.
Drawings
FIG. 1 is a schematic view of an oxygen concentration sensor according to the present invention;
FIG. 2 is a schematic view of the structure of an alumina ceramic protective layer according to the present invention;
description of the symbols in the drawings
1. A zirconia ceramic substrate; 2. a platinum electrode; 3. an alumina ceramic wafer; 4. a diffusion bonding region; 5. sealing the high-temperature glass glaze; 6. a platinum electrode; 7. a zirconia ceramic substrate; 8. a connecting interface region; 9. an alumina ceramic wafer; 10. a platinum electrode; closing the cavity; 12. sealing the high-temperature glass glaze; 13. a platinum electrode structure embedded in aluminum oxide; 14. an annular groove.
Detailed Description
The invention will now be further illustrated by the following non-limiting examples
Example 1
In the embodiment, an alumina ceramic plate with the thickness of 0.4mm and the diameter of 5.5mm and a zirconia ceramic plate with the thickness of 0.6mm and the diameter of 5.5mm are used as workpieces to be welded, and a platinum electrode clamping groove and an annular groove with the inner diameter of 2.2mm, the outer diameter of 5.2mm and the depth of 0.095mm are machined on the connecting surface of the alumina ceramic plate, and the specific structures are shown in a sensor structure schematic diagram (figure 1) and an alumina ceramic protective layer structure schematic diagram (figure 2). Two brazing filler metal foils of B-Ti72Ni28 and B-Ag85Zr15 are selected and connected by vacuum diffusion welding.
The vacuum diffusion welding process for the alumina/zirconia ceramic structure of the protective layer of the micro oxygen concentration sensor comprises the following steps:
(1) B-Ti72Ni28 with the thickness of 0.05mm and B-Ag85Zr15 with the thickness of 0.06mm are selected to prepare an annular structure with the inner diameter of 2.2mm and the outer diameter of 5.2 mm;
(2) before welding, oil stains and impurities on the connected areas of the alumina ceramics 3 and 9 and the zirconia ceramics 1 and 7 are removed, meanwhile, oil stains and oxides on the surfaces of the cobalt dioxide electrodes 2 and 10 coated with porous platinum and B-Ag85Zr15 and B-Ti72Ni28 brazing filler metal foils are removed, and the prefabricated annular grooves 4, 8 and 13 of the two alumina ceramic plates are mainly removed. The cleaning method comprises the following steps: putting the alumina ceramic plates 3 and 9, the zirconia ceramic plates 1 and 7, the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrodes 2 and 10 into a glass container with acetone, carrying out ultrasonic cleaning for 30min at the temperature of 50 ℃, then carrying out secondary cleaning by alcohol and blow-drying, and keeping the alumina ceramic plates and the zirconia ceramic plates for later use. And performing secondary surface treatment on the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrode by using an argon plasma cleaning technology.
(3) Sequentially adding two solder foils B-Ag85Zr15 and B-Ti72Ni28 into prefabricated annular grooves 13 of the alumina ceramic plates on two sides, then sequentially placing the alumina ceramic plates 3 and 9 added with the solder foils, the cobalt dioxide electrodes 2 and 10 coated with porous platinum and the zirconia ceramic plates 1 and 7 coated with the platinum electrodes 6 on the inner sides on a workbench of a vacuum heating furnace according to the assembly sequence of the sensor, and presetting a pressurizing block outside the alumina ceramic plates 3 and 9;
(4) before welding, the vacuum heating furnace is vacuumized for 30min, and then heated up at the heating rate of 5 ℃/min. When the temperature is raised to 450 ℃, the temperature is preserved for 5 min; when the temperature is increased to 900 ℃, carrying out heat preservation for 10min, then increasing the temperature to the highest temperature and carrying out heat preservation; and after the heat preservation is finished, the welded workpiece is cooled along with the furnace, and the welding is finished. The technological parameters of vacuum diffusion welding are as follows: heating to maximum temperature of 1040 deg.C, holding for 60min, loading pressure of 0.095MPa, vacuum degree of 6.5 × 10-4Pa。
The sensor alumina/zirconia ceramic structure obtained by the vacuum diffusion welding process has excellent forming performance. After a thermocouple heating experiment at 650 ℃ for 30min, the defects of overflow, cracks, non-fusion and the like of the middle layer are not found through appearance inspection and metallographic microscope observation; and the compression strength of the single-side alumina/zirconia ceramic structure of the sensor can reach 420MPa (the compression strength of the zirconia ceramic plate is 480 MPa), and the high-temperature use requirement of the connected structure of the oxygen concentration sensor is met.
Example 2
In the embodiment, an alumina ceramic plate with the thickness of 0.4mm and the diameter of 5.5mm and a zirconia ceramic plate with the thickness of 0.6mm and the diameter of 5.5mm are used as workpieces to be welded, and a platinum electrode clamping groove and an annular groove with the inner diameter of 2.2mm, the outer diameter of 5.2mm and the depth of 0.095mm are machined on the connecting surface of the alumina ceramic plate, and the specific structures are shown in a sensor structure schematic diagram (figure 1) and an alumina ceramic protective layer structure schematic diagram (figure 2). Two brazing filler metal foils of B-Ti72Ni28 and B-Ag85Zr15 are selected and connected by vacuum diffusion welding.
The vacuum diffusion welding process for the alumina/zirconia ceramic structure of the protective layer of the micro oxygen concentration sensor comprises the following steps:
(1) B-Ti72Ni28 with the thickness of 0.05mm and B-Ag85Zr15 with the thickness of 0.06mm are selected to prepare an annular structure with the inner diameter of 2.2mm and the outer diameter of 5.2 mm;
(2) before welding, oil stains and impurities on the connected areas of the alumina ceramics 3 and 9 and the zirconia ceramics 1 and 7 are removed, meanwhile, oil stains and oxides on the surfaces of the cobalt dioxide electrodes 2 and 10 coated with porous platinum and B-Ag85Zr15 and B-Ti72Ni28 brazing filler metal foils are removed, and the prefabricated annular grooves 4, 8 and 13 of the two alumina ceramic plates are mainly removed. The cleaning method comprises the following steps: putting the alumina ceramic plates 3 and 9, the zirconia ceramic plates 1 and 7, the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrodes 2 and 10 into a glass container with acetone, carrying out ultrasonic cleaning for 30min at the temperature of 50 ℃, then carrying out secondary cleaning by alcohol and blow-drying, and keeping the alumina ceramic plates and the zirconia ceramic plates for later use. And performing secondary surface treatment on the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrode by using an argon plasma cleaning technology.
(3) Sequentially adding two solder foils B-Ag85Zr15 and B-Ti72Ni28 into prefabricated annular grooves 13 of the alumina ceramic plates on two sides, then sequentially placing the alumina ceramic plates 3 and 9 added with the solder foils, the cobalt dioxide electrodes 2 and 10 coated with porous platinum and the zirconia ceramic plates 1 and 7 coated with the platinum electrodes 6 on the inner sides on a workbench of a vacuum heating furnace according to the assembly sequence of the sensor, and presetting a pressurizing block outside the alumina ceramic plates 3 and 9;
(4) before welding, the vacuum heating furnace is vacuumized for 30min, and then heated up at the heating rate of 5 ℃/min. When the temperature is raised to 450 ℃, the temperature is preserved for 5 min; when the temperature is increased to 900 ℃, carrying out heat preservation for 10min, then increasing the temperature to the highest temperature and carrying out heat preservation; and after the heat preservation is finished, the welded workpiece is cooled along with the furnace, and the welding is finished. The technological parameters of vacuum diffusion welding are as follows: heating to 1060 deg.C, holding for 50min, loading pressure of 0.09MPa, vacuum degree of 6.5 × 10-4Pa。
The sensor alumina/zirconia ceramic structure obtained by the vacuum diffusion welding process is excellent in forming, and after a thermocouple heating experiment at 650 ℃ for 30min, the defects of overflow, cracks, non-fusion and the like of the middle layer are not found through appearance inspection and metallographic microscope observation; and the compression strength of the single-side alumina/zirconia ceramic structure of the sensor can reach 440MPa (the compression strength of the zirconia ceramic plate is 480 MPa), and the high-temperature use requirement of the connected structure of the oxygen concentration sensor is met.
Example 3
In the embodiment, an alumina ceramic plate with the thickness of 0.4mm and the diameter of 5.5mm and a zirconia ceramic plate with the thickness of 0.6mm and the diameter of 5.5mm are used as workpieces to be welded, and a platinum electrode clamping groove and an annular groove with the inner diameter of 2.2mm, the outer diameter of 5.2mm and the depth of 0.095mm are machined on the connecting surface of the alumina ceramic plate, and the specific structures are shown in a sensor structure schematic diagram (figure 1) and an alumina ceramic protective layer structure schematic diagram (figure 2). Two brazing filler metal foils of B-Ti72Ni28 and B-Ag85Zr15 are selected and connected by vacuum diffusion welding.
The vacuum diffusion welding process for the alumina/zirconia ceramic structure of the protective layer of the micro oxygen concentration sensor comprises the following steps:
(1) B-Ti72Ni28 with the thickness of 0.05mm and B-Ag85Zr15 with the thickness of 0.06mm are selected to prepare an annular structure with the inner diameter of 2.2mm and the outer diameter of 5.2 mm;
(2) before welding, oil stains and impurities on the connected areas of the alumina ceramics 3 and 9 and the zirconia ceramics 1 and 7 are removed, meanwhile, oil stains and oxides on the surfaces of the cobalt dioxide electrodes 2 and 10 coated with porous platinum and B-Ag85Zr15 and B-Ti72Ni28 brazing filler metal foils are removed, and the prefabricated annular grooves 4, 8 and 13 of the two alumina ceramic plates are mainly removed. The cleaning method comprises the following steps: putting the alumina ceramic plates 3 and 9, the zirconia ceramic plates 1 and 7, the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrodes 2 and 10 into a glass container with acetone, carrying out ultrasonic cleaning for 30min at the temperature of 50 ℃, then carrying out secondary cleaning by alcohol and blow-drying, and keeping the alumina ceramic plates and the zirconia ceramic plates for later use. And performing secondary surface treatment on the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrode by using an argon plasma cleaning technology.
(3) Sequentially adding two solder foils B-Ag85Zr15 and B-Ti72Ni28 into prefabricated annular grooves 13 of the alumina ceramic plates on two sides, then sequentially placing the alumina ceramic plates 3 and 9 added with the solder foils, the cobalt dioxide electrodes 2 and 10 coated with porous platinum and the zirconia ceramic plates 1 and 7 coated with the platinum electrodes 6 on the inner sides on a workbench of a vacuum heating furnace according to the assembly sequence of the sensor, and presetting a pressurizing block outside the alumina ceramic plates 3 and 9;
(4) before welding, the vacuum heating furnace is vacuumized for 30min, and then heated up at the heating rate of 5 ℃/min. When the temperature is raised to 450 ℃, the temperature is preserved for 5 min; when the temperature is increased to 900 ℃, carrying out heat preservation for 10min, then increasing the temperature to the highest temperature and carrying out heat preservation; and after the heat preservation is finished, the welded workpiece is cooled along with the furnace, and the welding is finished. The technological parameters of vacuum diffusion welding are as follows: heating to a maximum temperature of 1080 deg.C, holding for 40min, loading pressure of 0.085MPa, vacuum degree of 6.5 × 10-4Pa。
The sensor alumina/zirconia ceramic structure obtained by the vacuum diffusion welding process is excellent in forming, and after a thermocouple heating experiment at 650 ℃ for 30min, the defects of overflow, cracks, non-fusion and the like of the middle layer are not found through appearance inspection and metallographic microscope observation; and the compressive strength of the single-side alumina/zirconia ceramic structure of the sensor can reach 445MPa (the compressive strength of the zirconia ceramic plate is 480 MPa), and the high-temperature use requirement of the connected structure of the oxygen concentration sensor is met.
Example 4
In the embodiment, an alumina ceramic plate with the thickness of 0.4mm and the diameter of 5.5mm and a zirconia ceramic plate with the thickness of 0.6mm and the diameter of 5.5mm are used as workpieces to be welded, and a platinum electrode clamping groove and an annular groove with the inner diameter of 2.2mm, the outer diameter of 5.2mm and the depth of 0.095mm are machined on the connecting surface of the alumina ceramic plate, and the specific structures are shown in a sensor structure schematic diagram (figure 1) and an alumina ceramic protective layer structure schematic diagram (figure 2). Two brazing filler metal foils of B-Ti72Ni28 and B-Ag85Zr15 are selected and connected by vacuum diffusion welding.
The vacuum diffusion welding process for the alumina/zirconia ceramic structure of the protective layer of the micro oxygen concentration sensor comprises the following steps:
(1) B-Ti72Ni28 with the thickness of 0.05mm and B-Ag85Zr15 with the thickness of 0.06mm are selected to prepare an annular structure with the inner diameter of 2.2mm and the outer diameter of 5.2 mm;
(2) before welding, oil stains and impurities on the connected areas of the alumina ceramics 3 and 9 and the zirconia ceramics 1 and 7 are removed, meanwhile, oil stains and oxides on the surfaces of the cobalt dioxide electrodes 2 and 10 coated with porous platinum and B-Ag85Zr15 and B-Ti72Ni28 brazing filler metal foils are removed, and the prefabricated annular grooves 4, 8 and 13 of the two alumina ceramic plates are mainly removed. The cleaning method comprises the following steps: putting the alumina ceramic plates 3 and 9, the zirconia ceramic plates 1 and 7, the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrodes 2 and 10 into a glass container with acetone, carrying out ultrasonic cleaning for 30min at the temperature of 50 ℃, then carrying out secondary cleaning by alcohol and blow-drying, and keeping the alumina ceramic plates and the zirconia ceramic plates for later use. And performing secondary surface treatment on the brazing filler metal foil and the porous platinum-coated cobalt dioxide electrode by using an argon plasma cleaning technology.
(3) Sequentially adding two solder foils B-Ag85Zr15 and B-Ti72Ni28 into prefabricated annular grooves 13 of the alumina ceramic plates on two sides, then sequentially placing the alumina ceramic plates 3 and 9 added with the solder foils, the cobalt dioxide electrodes 2 and 10 coated with porous platinum and the zirconia ceramic plates 1 and 7 coated with the platinum electrodes 6 on the inner sides on a workbench of a vacuum heating furnace according to the assembly sequence of the sensor, and presetting a pressurizing block outside the alumina ceramic plates 3 and 9;
(4) before welding, the vacuum heating furnace is vacuumized for 30min, and then heated up at the heating rate of 5 ℃/min. When the temperature is raised to 450 ℃, the temperature is preserved for 5 min; when the temperature is increased to 900 ℃, carrying out heat preservation for 10min, then increasing the temperature to the highest temperature and carrying out heat preservation; and after the heat preservation is finished, the welded workpiece is cooled along with the furnace, and the welding is finished. The technological parameters of vacuum diffusion welding are as follows: heating to a maximum temperature of 1110 deg.C, holding for 30min, loading pressure of 0.086MPa, and vacuum degree of 6.5 × 10-4Pa。
The sensor alumina/zirconia ceramic structure obtained by the vacuum diffusion welding process is excellent in forming, and after a thermocouple heating experiment at 650 ℃ for 30min, the defects of overflow, cracks, non-fusion and the like of the middle layer are not found through appearance inspection and metallographic microscope observation; and the compressive strength of the single-side alumina/zirconia ceramic structure of the sensor can reach 436MPa (the compressive strength of the zirconia ceramic plate is 480 MPa), so that the high-temperature use requirement of the connected structure of the oxygen concentration sensor is met.
The above-described embodiments are merely illustrative of the present invention and are not intended to be limiting thereof.
Claims (3)
1. A vacuum diffusion welding method for a protective layer of a miniature high-temperature oxygen concentration sensor is characterized in that the vacuum diffusion welding method for an alumina/zirconia ceramic structure with the diameter of 5.5mm comprises the following steps:
(1) two brazing filler metal foils B-Ti72Ni28 and B-Ag85Zr15 are selected to prepare an annular structure with the inner diameter of 2.2mm and the outer diameter of 5.2 mm;
(2) cleaning the connected areas of the brazing filler metal foil, the aluminum oxide ceramic wafer and the zirconium oxide ceramic substrate before welding;
(3) sequentially adding two solder foils B-Ag85Zr15 and B-Ti72Ni28 into prefabricated annular grooves of the alumina ceramic plates on two sides, and then sequentially placing the alumina ceramic plates with the solder foils added, the porous platinum-coated cobalt dioxide electrodes and the zirconia ceramic substrates with the platinum electrodes coated on the inner sides on a workbench of a vacuum heating furnace according to the assembly sequence of sensors, wherein pressing blocks are preset on the outer sides of the alumina ceramic plates;
(4) before welding, vacuumizing a vacuum heating furnace for 30min, and then heating at a temperature rise speed of 5 ℃/min;
when the temperature is raised to 450 ℃, the temperature is preserved for 5 min; when the temperature is increased to 900 ℃, carrying out heat preservation for 10min, then increasing the temperature to the highest temperature and carrying out heat preservation; after the heat preservation is finished, the welded workpiece is cooled along with the furnace to finish welding;
the technological parameters of vacuum diffusion welding are as follows: the heating maximum temperature is 1040-1120 ℃, the heat preservation time is 30-60 min, the loading pressure is 0.08-0.10 MPa, and the vacuum degree is 6.5 multiplied by 10-4Pa。
2. The vacuum diffusion welding method for the micro high-temperature oxygen concentration sensor protective layer according to claim 1, wherein in the step (1), the thickness of the B-Ag85Zr15 solder foil is 0.05mm, and the chemical components are Ag 85.0% and Zr 15.0%; the thickness of the B-Ti72Ni28 brazing filler metal foil is 0.06mm, and the chemical components are Ti 72.0% and Ni 28.0%; the brazing temperature of the B-Ag85Zr15 foil is 1020-1050 ℃, the brazing temperature of the B-Ti72Ni28 foil is 1080-1140 ℃, and brazing flux is not needed in the process.
3. The vacuum diffusion welding method for the protective layer of the micro high temperature oxygen concentration sensor as claimed in claim 1, wherein: in the step (3), the inner diameter of the ring groove prefabricated by the aluminum oxide ceramic plate is 2.2mm, the outer diameter of the ring groove is 5.2mm, and the depth of the ring groove is 0.095 mm; the edges of the annular groove close to the alumina ceramic plate and the platinum electrode are respectively reserved with 0.3mm and 0.2mm intervals so as to avoid the overflow of pollutants entering the platinum electrode or the brazing filler metal caused by the excessive spreading of the brazing filler metal; when two brazing filler metal foils B-Ti72Ni28 and B-Ag85Zr15 are filled in the annular groove, the precise fit of the two brazing filler metal platinum sheets and the annular groove is ensured, and the phenomena of dislocation, fluctuation and the like are avoided; the pressurizing block is made of alumina ceramic, and the size of the pressurizing block is prepared according to the pressure required by the sensor structure.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116471780A (en) * | 2023-04-24 | 2023-07-21 | 安徽省安瑞机电科技有限公司 | Oxygen sensor heat dissipation shell for pilot mask and preparation method thereof |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116471780A (en) * | 2023-04-24 | 2023-07-21 | 安徽省安瑞机电科技有限公司 | Oxygen sensor heat dissipation shell for pilot mask and preparation method thereof |
| CN116471780B (en) * | 2023-04-24 | 2024-02-23 | 安徽省安瑞机电科技有限公司 | Oxygen sensor heat dissipation shell for pilot mask |
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