Sealing method for large-size sapphire water cooling window

Abstract

The invention discloses a large-size sapphire water-cooling window sealing method which comprises the following steps: carrying out metallization treatment on a sapphire window sheet, and putting the metallized sapphire window sheet and a kovar transition piece into a hydrogen furnace for high-temperature brazing; the stainless steel flange and the kovar transition piece welded to the sapphire window piece are put into a hydrogen furnace to be subjected to high-temperature brazing; and the stainless steel water joint and the stainless steel flange are sealed by adopting an argon arc welding method. The sealing method has the advantages of being higher in sealing strength, better in air tightness and higher in size precision, and the manufactured water cooling window can work stably and reliably.

Description

Technical Field

[0001] The invention belongs to the technical field of electric vacuum device packaging, and in particular relates to a large-size sapphire water-cooling window sealing method. Background Art

[0002] The large-sized sapphire water-cooled window is about Φ140mm~Φ150mm in size, of which the sapphire window is about Φ100mm in size. It is mainly composed of sapphire window, Kovar transition piece, stainless steel flange and stainless steel water joint. Its sealing strength is the basic requirement of the vacuum use environment, and it is also an important guarantee for the reliability of the water cooling circulation system, and it is an important parameter indicator. There are many types of vacuum sealing, including resistance welding, brazing, electron beam welding, argon arc welding, laser welding, tin welding, etc. Each welding method has its advantages and disadvantages. In view of this, it is very important to choose the appropriate sealing type to ensure the sealing strength of the product.

[0003] With the current brazing technology, the expansion coefficient of stainless steel is much greater than that of kovar metal. This difference often causes large deformation of the stainless steel flange during brazing with the kovar transition piece, and the weld is pulled apart by stress, causing air leakage, and the sealing strength and air tightness deteriorate. The stainless steel water joint and flange are soldered with a low welding temperature (about 200°C), insufficient welding strength, and weak resistance to thermal shock, which often causes cracks at the welding position during the water cooling cycle, leading to water and air leakage. Summary of the invention

[0004] The purpose of the present invention is to provide a large-size sapphire water-cooled window sealing method in view of the above-mentioned deficiencies in the prior art, so as to solve the problems that the existing stainless steel flange has a large deformation during the brazing process with the Kovar transition piece, the weld is pulled apart by stress, resulting in air leakage, and the sealing strength and air tightness are deteriorated, and the stainless steel water joint and the flange are welded by tin soldering, the welding temperature is low (about 200°C), the welding strength is insufficient, and the thermal shock resistance is not strong, which often causes the welding position to crack during the water cooling cycle, resulting in water leakage and air leakage.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A large-size sapphire water-cooled window sealing method comprises the following steps:

[0007] S1. Metallizing the sapphire window, and placing the metallized sapphire window and the Kovar transition piece in a hydrogen furnace for high-temperature brazing;

[0008] S2, placing the stainless steel flange and the Kovar transition piece welded on the sapphire window into a hydrogen furnace for high-temperature brazing;

[0009] S3. Use argon arc welding to seal the stainless steel water joint and the stainless steel flange.

[0010] Furthermore, the S1 comprises the following sub-steps:

[0011] S11, using a sintered metal powder method to perform a molybdenum-manganese metallization treatment on the surface of the sapphire window to form a molybdenum-manganese layer, and performing a secondary metallization treatment on the molybdenum-manganese layer to form a nickel layer;

[0012] S12, performing electroplating nickel layer treatment on the surface of the Kovar transition piece, wherein the thickness of the electroplating nickel layer is 5-10 microns;

[0013] S13, placing the sapphire window after secondary metallization in S11, the kovar transition piece after the nickel plating treatment in S12, and the solder wire into a hydrogen furnace for high-temperature brazing.

[0014] Furthermore, the S11 specifically includes:

[0015] The sapphire window is coated with Mo-Mn metallization powder on the outer circle of the surface by sintering metal powder method, wherein the Mo-Mn metallization powder comprises 50%-70% Mo, 10%-20% Mn, 10%-20% Al 2 O 3 1%-3% SiO 2 , 1%-3% CaO, placing the sapphire window coated with Mo-Mn metallization powder into a hydrogen furnace for a metallization treatment to form a molybdenum-manganese layer, wherein the metallization temperature is 1400°C to 1500°C, the holding time is 1-2h, and the thickness of the metallized molybdenum-manganese layer is 20-40 microns;

[0016] The metallized sapphire window is taken out, ultrafine spherical nickel powder is coated on the molybdenum manganese layer, and placed in a hydrogen furnace for secondary metallization treatment to form a nickel layer on the surface of the molybdenum manganese layer. The secondary metallization temperature is 900°C to 1000°C, the insulation time is 10-20 minutes, and the nickel layer thickness is 8-15 microns.

[0017] Furthermore, in S13, the high temperature brazing process in the hydrogen furnace includes:

[0018] Heating stage 1: heating from room temperature to 200°C, heating time is 8 min;

[0019] Heating stage 2: heating from 200°C to 960°C, heating time is 60 min;

[0020] Insulation stage 1, the insulation temperature is 960℃ and the insulation time is 20min;

[0021] Heating stage three, heating from 960°C to 1008°C, heating time is 7 min;

[0022] In the second insulation stage, the insulation temperature is 1008℃ and the insulation time is 2min;

[0023] Cooling stage 1: cooling from 1008°C to 900°C, the cooling time is 14 minutes;

[0024] The second cooling stage is from 900°C to 500°C, and the cooling time is 70 minutes.

[0025] Furthermore, the S2 specifically includes:

[0026] Performing nickel electroplating on the stainless steel flange to form a nickel layer;

[0027] After the stainless steel flange treated with nickel electroplating and the sapphire window with the Kovar transition piece welded to it are assembled, they are placed in a hydrogen furnace together with the solder wire for high-temperature brazing.

[0028] Furthermore, in S2, the high temperature brazing process in the hydrogen furnace includes:

[0029] Heating stage 1: heating from room temperature to 200°C, heating time is 8 min;

[0030] Heating stage 2: heating from 200°C to 760°C, heating time is 40 min;

[0031] In the first insulation stage, the insulation temperature is 760°C and the insulation time is 20 minutes;

[0032] Heating stage three: heating from 760°C to 820°C, heating time is 10 min;

[0033] In the second insulation stage, the insulation temperature is 820℃ and the insulation time is 2min;

[0034] Cooling stage 1: cooling from 820°C to 750°C, the cooling time is 12 minutes;

[0035] Insulation stage three, the insulation temperature is 750℃ and the insulation time is 25min;

[0036] Cooling stage 2, cooling from 750°C to 600°C, cooling time is 40min;

[0037] In the fourth insulation stage, the insulation temperature is 600°C and the insulation time is 30 minutes;

[0038] Cooling stage three, cooling from 600℃ to 450℃, the cooling time is 50min.

[0039] Furthermore, the S3 specifically includes:

[0040] Assemble and fix the stainless steel water joint and the stainless steel flange;

[0041] TIG welding is used to strike an arc between the welding gun electrode and the metal to be welded. The heat generated melts the metal at the welding point, thereby completing the sealing of the stainless steel water joint and the stainless steel flange.

[0042] Among them, the argon arc welding process includes:

[0043] Continuous welding is adopted, the welding current is 65A, the arc starting time is 0.5s, the arc falling time is 0.5s, the speed is 2.5m / min, and the arc starting and falling time is 0.5s.

[0044] The large-size sapphire water-cooling window sealing method provided by the present invention has the following beneficial effects:

[0045] The sealing technology used in the present invention ensures the sealing strength to achieve the purpose of stable and reliable operation of the water-cooled window. It is carried out by combining brazing and argon arc welding. The brazing is carried out in a reducing medium (hydrogen) or in a vacuum. The entire furnace is heated to melt the solder into liquid, so that the solder wets the base metal and flows on its surface, and fills the weld with the help of the capillary action of the joint fitting gap. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The present invention is a flow chart of the large-size sapphire water-cooled window sealing method.

[0047] Figure 2 This is a welding package diagram between the sapphire window and the Kovar transition piece of the present invention.

[0048] Figure 3 This is a welding package diagram between the stainless steel flange and the sapphire window of the present invention.

[0049] Figure 4 This is the water-cooled window assembly structure of the present invention.

[0050] Among them, 1. Sapphire window; 2. Kovar transition piece; 3. Solder wire; 4. Stainless steel flange; 5. Silver-copper solder wire; 6. Water-cooled window body; 7. Stainless steel water joint; 8. TIG welding. DETAILED DESCRIPTION

[0051] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0052] Example 1

[0053] The large-size sapphire water-cooled window sealing method of this embodiment has the advantages of greater sealing strength, better airtightness, and higher dimensional accuracy, and the manufactured water-cooled window can work stably and reliably. Figure 1 , which specifically includes the following:

[0054] Step S1, metallizing the sapphire window 1, and placing the metallized sapphire window 1 and the kovar transition piece 2 in a hydrogen furnace for high-temperature brazing;

[0055] refer to Figure 2 The sapphire window sealing assembly of this embodiment includes a sapphire window sheet 1, a Kovar transition piece 2 and a pure Ag solder wire 3, which specifically includes the following steps:

[0056] Step S11, metallization of the sapphire window 1;

[0057] In this embodiment, the sintering metal powder method is preferred, and the surface of the sapphire window 1 is subjected to molybdenum-manganese metallization treatment to form a molybdenum-manganese layer, and a secondary metallization treatment is performed on the molybdenum-manganese layer to form a nickel layer;

[0058] Specifically, the primary metallization process is as follows:

[0059] The sintered metal powder method is used to coat the outer circle of the surface of the sapphire window 1 with Mo-Mn metallization powder, wherein the Mo-Mn metallization powder includes 50%-70% Mo, 10%-20% Mn, and 10%-20% Al by mass. 2 O 3 1%-3% SiO 2 , 1%-3% CaO;

[0060] The sapphire window 1 coated with Mo-Mn metallization powder is placed in a hydrogen furnace for a metallization treatment to form a molybdenum-manganese layer, wherein the metallization temperature is 1400°C to 1500°C, the insulation time is 1-2h, and the thickness of the metallized molybdenum-manganese layer is 20-40 microns.

[0061] The second metallization process is as follows:

[0062] The metallized sapphire window 1 is taken out, ultrafine spherical nickel powder is coated on the molybdenum-manganese layer, and the window is placed in a hydrogen furnace for secondary metallization treatment to form a nickel layer on the surface of the molybdenum-manganese layer, wherein the secondary metallization temperature is 900° C. to 1000° C., the holding time is 10-20 min, and the nickel layer thickness is 8-15 μm;

[0063] In this embodiment, nickel is evenly sintered on the surface of the molybdenum-manganese layer, and the solder has a good wetting and spreading effect on the sealing surface, so that the solder fills the welding gap evenly after melting, which can effectively ensure the bonding strength and airtightness between sapphire and metal.

[0064] Step S12, electroplating a nickel layer on the surface of the Kovar transition piece 2, the thickness of the electroplated nickel layer is 5-10 microns, the purpose is to make the solder melted into liquid form good wetting and spreading on the metal surface, to ensure that the weld can be evenly filled with liquid solder;

[0065] Step S13, assembling the sapphire window 1 after secondary metallization in S11, the kovar transition piece 2 after electroplating the nickel layer in S12 and the solder wire 3 by a fixture, and placing them in a hydrogen furnace for high-temperature brazing, heating at high temperature, and melting and dispersing the solder to complete the sealing;

[0066] The high temperature brazing process in the hydrogen furnace of this embodiment is shown in the following table:

[0067]

[0068] As can be seen from the above table, the high temperature brazing process of this embodiment includes the following stages:

[0069] Heating stage 1: heating from room temperature to 200°C, heating time is 8 min;

[0070] Heating stage 2: heating from 200°C to 960°C, heating time is 60 min;

[0071] In the first insulation stage, the insulation temperature is 960℃ and the insulation time is 20min. In this stage, an insulation platform is set up to ensure that the temperature zones at various positions in the furnace are uniform and there is no excessive temperature difference.

[0072] Heating stage three, heating from 960℃ to 1008℃, heating time is 7min, during this stage the solder slowly begins to melt;

[0073] In the second insulation stage, the insulation temperature is 1008℃ and the insulation time is 2min. In this stage, the solder is completely melted and flows into the joint weld.

[0074] Cooling stage 1, from 1008℃ to 900℃, the cooling time is 14min, in this stage, the temperature drops quickly, the solder solidifies quickly, and the transition interface reacts all the time to prevent overflow;

[0075] Cooling stage 2: Cooling from 900°C to 500°C for 70 minutes. In this stage, the temperature is slowly cooled to prevent excessive deformation of parts, excessive stress, pulling the weld, and affecting the airtight reliability.

[0076] This embodiment adopts the combination of cooling stage one and cooling stage two to perform multi-stage cooling to release stress.

[0077] Step S2, placing the stainless steel flange 4 and the kovar transition piece 2 welded on the sapphire window 1 into a hydrogen furnace for high-temperature brazing;

[0078] This embodiment is used for high temperature brazing of a stainless steel flange 4 and a Kovar transition piece 2, referring to Figure 3 , which specifically includes the following:

[0079] Performing nickel electroplating on the stainless steel flange 4 to form a nickel layer;

[0080] After the stainless steel flange 4 treated with electroplating nickel and the sapphire window 1 welded with the Kovar transition piece 2 are assembled, they are placed in a hydrogen furnace together with the silver-copper solder wire 5 for high-temperature brazing. The solder melts and disperses during high-temperature heating to complete the sealing. After the high-temperature brazing in this step, the airtightness can be guaranteed, and the weld is flat and smooth after welding, without gaps, and the welding strength is high.

[0081] In this step, the high temperature brazing process in the hydrogen furnace is shown in the following table:

[0082]

[0083] As can be seen from the above table, the high temperature brazing process of this embodiment includes the following stages:

[0084] Heating stage 1: heating from room temperature to 200°C, heating time is 8 min;

[0085] Heating stage 2: heating from 200°C to 760°C, heating time is 40 min;

[0086] In the first insulation stage, the insulation temperature is 760℃ and the insulation time is 20min. In this stage, an insulation platform is set up to ensure that the temperature zones at various positions in the furnace are uniform and there is no excessive temperature difference.

[0087] Heating stage three: heating from 760°C to 820°C for 10 minutes. During this stage, the solder slowly begins to melt.

[0088] In the second insulation stage, the insulation temperature is 820℃ and the insulation time is 2min. In this stage, the solder is completely melted and flows into the joint weld.

[0089] Cooling stage 1, from 820℃ to 750℃, the cooling time is 12min, in this stage, the temperature drops quickly, the solder solidifies quickly, and the transition interface reacts all the time to prevent overflow;

[0090] In the third insulation stage, the insulation temperature is 750℃ and the insulation time is 25min. In this stage, a cooling platform is set to homogenize the temperature of each point of the product to prevent the temperature difference from causing large local stress;

[0091] Cooling stage 2: Cooling from 750°C to 600°C for 40 minutes; further slow cooling to reduce excessive stress concentration and release the stress gradually;

[0092] In the fourth insulation stage, the insulation temperature is 600℃ and the insulation time is 30min. In this stage, a cooling platform is set to homogenize the temperature of each point of the product to prevent the temperature difference from causing large local stress;

[0093] Cooling stage three: cooling from 600°C to 450°C for 50 minutes, further slow cooling to reduce excessive stress concentration and release stress stably;

[0094] This embodiment arranges multi-stage cooling including cooling stage one, cooling stage two and cooling stage three, which can effectively release stress in multiple stages.

[0095] In this embodiment, the thermal expansion coefficients of the stainless steel flange 4 and the Kovar transition piece 2 are quite different, and the thermal expansion coefficient of the stainless steel is 18×10 -6 / ℃, Kovar thermal expansion coefficient 6.5×10 -6 / ℃, the high temperature welding process generates stress and pulls the weld. Based on this, this embodiment adopts the method of high temperature brazing in a hydrogen furnace, and the solder is silver-copper 28 alloy solder, and the welding temperature is about 820℃. The stainless steel flange 4 is electroplated with nickel, firstly to increase the wettability of the solder on the welding surface, and secondly to prevent hydrogen from reacting with stainless steel to produce a black layer, which affects the solder flow and wetting. At the same time, formulate a suitable welding process curve, optimize the cooling rate, set a multi-stage cooling platform, slowly release stress, and reduce the influence of residual stress on the strength of the weld.

[0096] Step S3, using argon arc welding to seal the stainless steel water joint 7 and the stainless steel flange 4;

[0097] This step is used for welding the stainless steel water joint 7 and the stainless steel flange 4. The sealing airtightness requirement must be ensured. Due to the large size of the product, this embodiment uses argon arc welding with unlimited sealing space. Arc discharge is generated between the welding gun electrode and the welded workpiece. The heat generated melts the metal at the welding point to connect the workpieces. The advantages are fast welding speed and high welding strength. Figure 4 , which specifically includes the following:

[0098] Fix the stainless steel water connector 7 to the stainless steel flange 4 fixed on the water-cooled window body 6;

[0099] Argon arc welding 8 is used to strike an arc between the welding gun electrode and the metal to be welded, and the heat generated melts the metal at the welding point, thereby completing the sealing of the stainless steel water joint 7 and the stainless steel flange 4;

[0100] Among them, the argon arc welding process includes:

[0101] Continuous welding is adopted, the welding current is 65A, the arc starting time is 0.5s, the arc falling time is 0.5s, the speed is 2.5m / min, and the arc starting and falling time is 0.5s.

[0102] The 0.5s starting and lowering arc of this embodiment ensures that the parts have a slow temperature rise, which can prevent the weld from cracking due to sudden rapid temperature rise and fall. The speed of 2.5m / min ensures that the next molten pool overlaps with the previous molten pool by more than 60%, preventing the weld from cracking due to the rapid cooling of the previous molten pool, thereby ensuring an airtight connection.

[0103] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for sealing a large-size sapphire water-cooled window, characterized in that: The following steps are involved: S1. Metallizing the sapphire window, and placing the metallized sapphire window and the Kovar transition piece in a hydrogen furnace for high-temperature brazing; S2, placing the stainless steel flange and the Kovar transition piece welded on the sapphire window into a hydrogen furnace for high-temperature brazing; S3. Use argon arc welding to seal the stainless steel water joint and the stainless steel flange.

2. The large-size sapphire water-cooled window sealing method according to claim 1, characterized in that: The S1 comprises the following sub-steps: S11, using a sintered metal powder method to perform a molybdenum-manganese metallization treatment on the surface of the sapphire window to form a molybdenum-manganese layer, and performing a secondary metallization treatment on the molybdenum-manganese layer to form a nickel layer; S12, performing electroplating nickel layer treatment on the surface of the Kovar transition piece, wherein the thickness of the electroplating nickel layer is 5-10 microns; S13, placing the sapphire window after secondary metallization in S11, the kovar transition piece after the nickel plating treatment in S12, and the solder wire into a hydrogen furnace for high-temperature brazing.

3. The large-size sapphire water-cooled window sealing method according to claim 2, characterized in that: The S11 specifically includes: The sapphire window is coated with Mo-Mn metallization powder on the outer circle of the surface of the sapphire window by a sintered metal powder method, wherein the Mo-Mn metallization powder includes 50%-70% Mo, 10%-20% Mn, 10%-20% Al2O3, 1%-3% SiO2, and 1%-3% CaO by mass, and the sapphire window coated with the Mo-Mn metallization powder is placed in a hydrogen furnace for a metallization treatment to form a molybdenum-manganese layer, wherein the metallization temperature is 1400° C. to 1500° C., the heat preservation time is 1-2 hours, and the thickness of the metallized molybdenum-manganese layer is 20-40 microns; The metallized sapphire window is taken out, ultrafine spherical nickel powder is coated on the molybdenum manganese layer, and placed in a hydrogen furnace for secondary metallization treatment to form a nickel layer on the surface of the molybdenum manganese layer. The secondary metallization temperature is 900°C to 1000°C, the insulation time is 10-20 minutes, and the nickel layer thickness is 8-15 microns.

4. The large-size sapphire water-cooled window sealing method according to claim 2, characterized in that: In S13, the high temperature brazing process in the hydrogen furnace includes: Heating stage 1: heating from room temperature to 200°C, heating time is 8 min; Heating stage 2: heating from 200°C to 960°C, heating time is 60 min; Insulation stage 1, the insulation temperature is 960℃ and the insulation time is 20min; Heating stage three, heating from 960°C to 1008°C, heating time is 7 min; In the second insulation stage, the insulation temperature is 1008℃ and the insulation time is 2min; Cooling stage 1: cooling from 1008°C to 900°C, the cooling time is 14 minutes; The second cooling stage is from 900°C to 500°C, and the cooling time is 70 minutes.

5. The large-size sapphire water-cooled window sealing method according to claim 1, characterized in that: The S2 specifically includes: Performing nickel electroplating on the stainless steel flange to form a nickel layer; After the stainless steel flange treated with nickel electroplating and the sapphire window with the Kovar transition piece welded to it are assembled, they are placed in a hydrogen furnace together with the solder wire for high-temperature brazing.

6. The large-size sapphire water-cooled window sealing method according to claim 5, characterized in that: In S2, the high temperature brazing process in the hydrogen furnace includes: Heating stage 1: heating from room temperature to 200°C, heating time is 8 min; Heating stage 2: heating from 200°C to 760°C, heating time is 40 min; In the first insulation stage, the insulation temperature is 760°C and the insulation time is 20 minutes; Heating stage three: heating from 760°C to 820°C, heating time is 10 min; In the second insulation stage, the insulation temperature is 820℃ and the insulation time is 2min; Cooling stage 1: cooling from 820°C to 750°C, the cooling time is 12 minutes; Insulation stage three, the insulation temperature is 750℃ and the insulation time is 25min; Cooling stage 2, cooling from 750°C to 600°C, cooling time is 40min; In the fourth insulation stage, the insulation temperature is 600°C and the insulation time is 30 minutes; Cooling stage three, cooling from 600℃ to 450℃, the cooling time is 50min.

7. The large-size sapphire water-cooled window sealing method according to claim 1, characterized in that: The S3 specifically includes: Assemble and fix the stainless steel water joint and the stainless steel flange; TIG welding is used to strike an arc between the welding gun electrode and the metal to be welded. The heat generated melts the metal at the welding point, thereby completing the sealing of the stainless steel water joint and the stainless steel flange. Among them, the argon arc welding process includes: Continuous welding is adopted, the welding current is 65A, the arc starting time is 0.5s, the arc falling time is 0.5s, the speed is 2.5m / min, and the arc starting and falling time is 0.5s.

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