A method for vacuum brazing a polygonal ceramic block container to a metal Cu rod

Abstract

The present application belongs to the technical field of vacuum brazing, and particularly relates to a vacuum brazing method for a polygonal ceramic block container and a metal Cu rod, which comprises the following steps: punching the polygonal ceramic block container, the hole depth of the formed hole being up to a metal coil embedded in the polygonal ceramic block container; setting the gap between the metal Cu and the hole side wall to be 0.01-0.05 mm; placing the punched ceramic block container and the metal Cu rod into anhydrous ethanol for cleaning, cutting a silver-based brazing filler metal foil according to the size of the hole, and setting the gap between the brazing filler metal foil cutting piece and the hole side wall to be 0.01-0.02 mm; assembling the brazing assembly; and brazing the workpiece with the assembled brazing filler metal under vacuum conditions. The method of the present application has high connection strength of the ceramic block container and the metal Cu rod, and can also protect the polygonal ceramic block container from being damaged.

Description

Technical Field

[0001] This invention belongs to the field of vacuum brazing technology, specifically relating to a vacuum brazing method for a polygonal ceramic block container and a metal Cu rod. Background Technology

[0002] The polygonal ceramic block container is a key component of the alloy forming equipment, used to hold the alloy to be processed. Three coils of metal are embedded inside the container. Holes need to be drilled at designated locations, reaching the connectors of the metal coils, before a copper rod is reliably connected to the connectors within the holes.

[0003] When the alloy to be processed requires induction heating and melting, alternating current is passed through a copper rod to excite a high-frequency alternating magnetic field generated by a metal coil inside the ceramic block. The coil generates Joule heating under the influence of eddy currents and resistance losses, achieving induction heating and melting of the alloy within the ceramic container. The electromagnetic force generated by the alternating magnetic field drives the melt flow, creating electromagnetic stirring, which inhibits the directional growth of columnar crystals and promotes the nucleation and growth of equiaxed crystals, thereby refining the alloy's solidification structure. The combined effect of electromagnetic convection and electromagnetic force causes residual solute atoms and non-metallic inclusions in the melt to agglomerate towards the edge regions, reducing the impurity concentration in the central region. Some inclusions are removed through collision and aggregation, thus purifying the melt and ultimately improving the compositional uniformity and mechanical properties of the alloy after forming.

[0004] Because metal coils are prone to oxidation reaction with oxygen in the air at high temperatures, a reliable sealed connection must be achieved between the metal copper rod and the ceramic hole to avoid the risk of short circuits.

[0005] Currently, common methods for connecting ceramic holes to copper rods include mechanical connection, adhesive bonding, diffusion welding, and vacuum brazing. Among these, mechanical and adhesive bonding suffer from insufficient connection strength; diffusion welding requires applying pressure, which can easily cause the copper rod to crack the polygonal ceramic block container, thus affecting the alloy forming quality. Therefore, vacuum brazing is the optimal choice for connecting the polygonal ceramic block container to the copper rod.

[0006] Vacuum brazing offers high weld strength, minimizes the impact on polygonal ceramic block containers, and heats the entire component, resulting in uniform heating and minimal deformation. Currently, the primary vacuum brazing method for ceramics to metals is active metal brazing, specifically using Ag-Cu-Ti (silver-copper-titanium) active brazing filler metal. Under high vacuum, the titanium (Ti) active element in the filler metal reacts chemically with the ceramic matrix to form a reactive wetting layer, achieving a metallurgical bond between the ceramic and copper. However, this brazing method suffers from drawbacks such as a mismatch in the thermal expansion coefficients of the ceramic and metal, leading to high residual stress, poor joint sealing, and a high risk of ceramic cracking. Therefore, technical improvements to this existing vacuum brazing method are necessary.

[0007] Invention CN115464226B, entitled "A Vacuum Brazing Connection Method for Ceramics and Nb," employs a Ti-Co-Nb-Zr-Ni brazing filler metal system to weld ceramics and Nb. The addition of Zr improves the wettability of the filler metal to the ceramic and allows it to form a eutectic structure with Ni, enhancing the joint strength. Co is primarily used to ensure the high-temperature performance of the joint. Nb can be infinitely dissolved in Ti, improving the joint's performance and also enhancing the wettability of the filler metal to the Nb base material. During processing, a Mo interlayer is added as a low-expansion transition layer to mitigate excessive stress during welding caused by the significant difference in expansion coefficients between Nb and the ceramic. However, Cu has a melting point of 1083℃, while Ti-Co-Nb-Zr-Ni has a melting point of around 1100℃. At these temperatures, Cu melts or undergoes high-temperature creep, grain coarsening, and strength loss. Therefore, this high-melting-point filler metal is not suitable for vacuum brazing Cu connections.

[0008] Invention CN111747769B: A type of AlMgB 14 The paper "A Vacuum Brazing Method for TiB2 Composite Ceramics and TiAl-based Alloys" discloses an AlMgB2... 14 -A vacuum brazing method for TiB2 composite ceramics and TiAl-based alloys includes the following steps: (1) mechanically ball-milling boron powder particles and AgCu eutectic powder for 1-4 hours to obtain composite brazing filler metal; (2) mixing AlMgB2 composite ceramics with TiAl-based alloys. 14 - TiB2 composite ceramic matrix and TiAl-based alloy are pretreated respectively, and then assembled with composite brazing filler metal to obtain brazed joint; (3) The brazed joint is placed in a vacuum furnace, heated to 820~920℃ in a vacuum environment, held for 10~60min, and cooled to complete the process. No active elements need to be added. The joint structure can reduce the aggregation of brittle and hard phases, effectively alleviate the residual stress of the joint, and realize AlMgB 14 The efficient, rapid, and reliable connection between TiB2 composite ceramics and TiAl-based alloys yields brazed joints with a shear strength as high as 82.5 MPa, demonstrating significant application value. However, using Ag-Cu-B solder to connect with copper base material creates an alloy region dominated by copper and silver with high resistance, potentially affecting current transmission efficiency. Therefore, it is unsuitable for vacuum brazing of polygonal ceramic block containers with metal Cu rods.

[0009] Invention CN106007773B, entitled "A Vacuum Brazing Method for Porous Silicon Nitride Ceramics and TiAl-based Alloys," discloses a vacuum brazing method for porous silicon nitride ceramics and TiAl-based alloys. The method involves: Step 1, mechanically ball-milling 1.5-3 wt.% nano-silicon nitride particles, 2-4 wt.% Ti powder, and AgCu powder for 4-6 hours to obtain a composite brazing filler metal; Step 2, assembling the ball-milled composite brazing filler metal with a pretreated TiAl-based alloy and a porous silicon nitride substrate, maintaining the brazing filler metal powder thickness between 50-200 μm; Step 3, placing the assembled brazed joint into a vacuum furnace and heating it to 840℃-900℃ under vacuum, holding for 5-30 minutes. This achieves a high-strength and effective connection between the porous ceramic and the alloy matrix. This technical solution effectively solves the connection problem between porous ceramics and TiAl-based alloys, resulting in brazed joints with excellent mechanical properties. The core of this invention lies in using Ag-Cu-based brazing filler metal and adding Ti powder and nano-silicon nitride particles to achieve connection with porous silicon nitride ceramics and TiAl alloys. However, the mechanical properties of the welded joint are not disclosed. Since the welded joint between the metal coil connector and the metal Cu rod inside the polygonal ceramic block container requires high mechanical properties, it is not suitable for vacuum brazing of polygonal ceramic block containers and metal Cu rods. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a vacuum brazing method for a polygonal ceramic block container and a metal Cu rod, which can solve the problem of low welding strength during welding and protect the polygonal ceramic block container.

[0011] To address the aforementioned technical problems, this invention provides a vacuum brazing method for bonding a polygonal ceramic block container to a metal Cu rod, comprising the following steps: 1) Drill holes (round holes) into the polygonal ceramic block container, with the depth of the holes extending to the metal coil embedded inside the polygonal ceramic block container. When the metal Cu rod is inserted into the hole, the gap between the metal Cu and the sidewall of the hole is 0.01~0.05mm; 2) Place the perforated ceramic block container and metal Cu rod obtained in step 1) into anhydrous ethanol for cleaning (to remove surface contaminants and grease). 3) The silver-based solder foil is an alloy foil containing Ag, Cu, and Ti, with a mass ratio of Ag:Cu:Ti of 64~70.5:26.5~34.5:1.5~4.5 and a thickness of 0.1~0.5mm; The silver-based brazing foil is cut according to the size of the hole in step 1). The cut silver-based brazing foil is named brazing foil cut piece. When the brazing foil cut piece is placed in the hole, the gap between the brazing foil cut piece and the side wall of the hole is 0.01~0.02mm. 4) Assembly of brazed components: First, place 1-3 pieces of solder foil cut pieces (stacked one on top of the other) in the holes of the cleaned polygonal ceramic block container. When the amount of solder foil cut pieces is ≥2 pieces, place a piece of foam Cu between the two layers of solder foil cut pieces, and then insert a cleaned metal Cu rod, so that the bottom end of the metal Cu rod fully contacts the top layer of solder foil cut piece, and apply pressure to the top end of the Cu rod; thus forming a workpiece with solder foil assembled. 5) Braze the workpiece with the brazing filler metal assembled under vacuum conditions. The brazing temperature is 810~900℃ and the holding time is 10~30min.

[0012] As an improvement to the vacuum brazing method of the polygonal ceramic block container and the metal Cu rod of the present invention: the length of the metal Cu rod is greater than the hole depth. Note: The hole depth is generally 8~12mm, and the length of the metal Cu rod is generally 20~25mm.

[0013] As a further improvement to the vacuum brazing method of the polygonal ceramic block container and the metal Cu rod of the present invention: the diameter of the hole is 5~15mm.

[0014] As a further improvement to the vacuum brazing method of the polygonal ceramic block container and the metal Cu rod of the present invention: the thickness of the foamed Cu is 1~5mm.

[0015] Note: The porosity of foamed Cu is 70%~95%, and the pore size is mostly 0.1~5 mm.

[0016] As a further improvement to the vacuum brazing method of the polygonal ceramic block container and the metal Cu rod of the present invention: a graphite block of 6 to 15 g is placed at the top of the Cu rod to form pressure.

[0017] As a further improvement to the vacuum brazing method of the polygonal ceramic block container and the metal Cu rod of the present invention: the cleaning in step 2) is ultrasonic cleaning, and the cleaning time is 5~15min (frequency is 20KHZ-30KHZ).

[0018] As a further improvement to the vacuum brazing method for the polygonal ceramic block container and the metal Cu rod of the present invention, the brazing in step 5) is as follows: the workpiece with the brazing filler metal assembled is placed in the heating area of ​​the vacuum brazing furnace, and the vacuum degree in the furnace is set to 3×10⁻⁶. -2 pa~2×10 -5 Pa, with a heating rate of 5~20℃ / min.

[0019] Once the furnace has cooled to room temperature, the workpiece is removed, and the brazing process is complete.

[0020] Explanation: The above brazing process is a precise process in which the filler metal is melted by heating, the gaps are filled by capillary action, and a metallurgical bond is formed through dissolution and diffusion at the liquid-solid interface. Finally, it is cooled and solidified into a single integral joint. The vacuum environment ensures the purity of the process and avoids oxidation, thereby obtaining a dense, strong, and highly conductive permanent connection.

[0021] As a preferred embodiment of the present invention: The brazing temperature is 850~880℃, the holding time is 15±1min, and the thickness of the foamed Cu is 1~3mm; The mass ratio of Ag:Cu:Ti is 70.1~70.3: 26.9~28.2: 1.5~3.

[0022] This invention has the following technical advantages: 1. This invention uses vacuum brazing, which has high welding strength, has little impact on the polygonal ceramic block container, and heats the components (ceramic block container and metal Cu rod) as a whole, resulting in uniform heating of the components and less deformation.

[0023] 2. The gap between the polygonal ceramic block container's hole and the metal Cu rod is small, and the welding surface is hidden and narrow, making it difficult to weld using other methods. However, vacuum brazing, which involves placing or coating brazing filler metal on the welding surface, can weld even hidden and narrow weld surfaces. In other words, vacuum brazing can solve the problem of the extremely narrow and thin welding surface between the ceramic block container and the metal Cu rod, resulting in difficult welding. It also provides high connection strength and protects the polygonal ceramic block container from damage.

[0024] 3. Diffusion welding and other welding processes can only be performed on one product at a time, but this vacuum brazing furnace has a large chamber and can braze multiple parts simultaneously, which can meet the batch welding process requirements of parts and reduce production costs.

[0025] 4. Compared with the prior art, the method of the present invention has lower welding difficulty, better welded joint performance, and can effectively reduce processing costs. Attached Figure Description

[0026] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] Figure 1 This is an assembly diagram of the welding points of the components; Figure 2 This is a scanning electron microscope image of the brazing interface.

[0028] In the diagram: 1 represents a metal Cu rod; 2 represents a "sandwich" structure: silver-based solder / foamed Cu / silver-based solder; 3 represents a polygonal ceramic block container. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto: Example 1: A vacuum brazing method for a polygonal ceramic block container and a metal Cu rod, comprising the following steps: 1) First, drill holes (round holes) in the polygonal ceramic block container (hereinafter referred to as ceramic block container). The diameter of the holes should be 5~15mm, and the hole depth should be sufficient to reach the metal coil connector (the hole depth is generally 8~12mm depending on the embedding depth of the metal coil connector in the polygonal ceramic block container).

[0030] The relationship between the diameter of the Cu rod and the hole diameter is as follows: when the Cu rod is inserted into the hole, the gap between it and the hole sidewall is controlled at 0.01~0.05mm. The relationship between the length of the Cu rod and the hole depth is as follows: the Cu rod length is much greater than the hole depth. The length of the selected Cu rod is generally 20~25mm.

[0031] 2) Place the perforated ceramic block container and metal Cu rod obtained in step 1) into anhydrous ethanol and perform conventional room temperature ultrasonic cleaning in an ultrasonic cleaning device for 5~15 minutes (frequency 20KHZ~30KHZ) to remove surface contaminants and grease.

[0032] 3) The silver-based brazing foil is an alloy foil containing Ag, Cu and Ti elements, with a mass ratio of Ag:Cu:Ti = 64~70.5:26.5~34.5:1.5~4.5, and a thickness of 0.1~0.5mm.

[0033] As a matter of common sense: polish the surface of the silver-based solder foil to remove the oxide layer, wipe it with a lint-free cloth dampened with anhydrous ethanol, and then cut it.

[0034] The silver-based solder foil is cut into round pieces, and the cut silver-based solder foil is named solder foil cut piece. The solder foil cut piece is placed exactly into the hole of the ceramic block container, that is, the gap between the solder foil cut piece and the side wall of the hole is controlled at 0.01~0.02mm. 4) Assembly of brazed components: First, place 1-3 pieces of brazing foil cut pieces (stacked vertically) into the holes of the cleaned ceramic block container. When the number of brazing foil cut pieces is ≥2, place a piece of foam Cu with a thickness of 1-5mm between the two layers of brazing foil cut pieces. Then, insert the cleaned metal Cu rod and rotate it 3 times to ensure that the bottom end of the metal Cu rod fully contacts the top layer of brazing foil cut piece. Press the top of the Cu rod down with a graphite block weighing 6-15g. The assembly diagram of the brazing assembly is shown below. Figure 1 As shown. This forms a workpiece with the solder filler metal assembled.

[0035] Note: The porosity of foamed Cu is 70%–95%, and the pore size is mostly 0.1~5 mm.

[0036] 5) Place the workpiece with the brazing filler metal assembled into the heating area of ​​the vacuum brazing furnace, and evacuate the furnace to a vacuum level of 3×10⁻⁶. -2 pa~2×10 -5 Between pa, the brazing process is started, with a heating rate of 5~20℃ / min, a brazing temperature of 810~900℃, and a holding time of 10~30min. After the furnace cools to room temperature, the workpiece is removed, and the brazing process ends.

[0037] Explanation: The above brazing process is a precise process in which the filler metal is melted by heating, the gaps are filled by capillary action, and a metallurgical bond is formed through dissolution and diffusion at the liquid-solid interface. Finally, it is cooled and solidified into a single integral joint. The vacuum environment ensures the purity of the process and avoids oxidation, thereby obtaining a dense, strong, and highly conductive permanent connection.

[0038] Experiment 1: Several experimental groups were set up according to Example 1. The specific parameters in steps 1) to 5) of Example 1 are shown in Table 1 below. Then, the pull-out force was tested according to GB / T 45594-2025. The pull-out force data under different brazing processes are shown in Table 1 below.

[0039] Table 1

[0040] Notes: The heating rate is 10±1℃ / min; the hole diameter is 10mm; the hole depth is 10mm. The length of the Cu rod is approximately 22mm; two pieces of solder foil are used. The porosity of the Cu foam is approximately 75~85%, and the pore size is approximately 0.2~1mm. The mass of the graphite block is approximately 13~15g.

[0041] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for vacuum brazing of a polygonal ceramic block container to a metal Cu rod, characterized by Includes the following steps: 1) Drill holes in the polygonal ceramic block container, with the depth of the holes extending to the metal coil embedded inside the polygonal ceramic block container. When the metal Cu rod is inserted into the hole, the gap between the metal Cu and the sidewall of the hole is 0.01~0.05mm; 2) Clean the perforated ceramic block container and the metal Cu rod obtained in step 1) in anhydrous ethanol. 3) The silver-based solder foil is an alloy foil containing Ag, Cu, and Ti, with a mass ratio of Ag:Cu:Ti of 64~70.5:26.5~34.5:1.5~4.5 and a thickness of 0.1~0.5mm; The silver-based brazing foil is cut according to the size of the hole in step 1). The cut silver-based brazing foil is named brazing foil cut piece. When the brazing foil cut piece is placed in the hole, the gap between the brazing foil cut piece and the side wall of the hole is 0.01~0.02mm. 4) Assembly of brazed components: First, place 1-3 pieces of brazing foil cut pieces in the holes of the cleaned ceramic block container. When the amount of brazing foil cut pieces is ≥2 pieces, place a piece of foam Cu between the two layers of brazing foil cut pieces, and then insert a cleaned metal Cu rod, so that the bottom end of the metal Cu rod fully contacts the top layer of brazing foil cut pieces, and apply pressure to the top end of the Cu rod; thus forming a workpiece with brazing foil assembled. 5) Braze the workpiece with the brazing filler metal assembled under vacuum conditions. The brazing temperature is 810~900℃ and the holding time is 10~30min.

2. A vacuum brazing method of a polygonal ceramic block container and a metal Cu rod according to claim 1, characterized by: The length of the metal Cu rod is greater than the hole depth.

3. A method of vacuum brazing a polygonal ceramic block vessel to a metal Cu rod according to claim 2, characterized in that: The diameter of the hole is 5~15mm.

4. A method of vacuum brazing a polygonal ceramic block vessel to a metal Cu rod according to claim 3, characterized in that: The thickness of the foamed Cu is 1~5mm.

5. A method of vacuum brazing a polygonal ceramic block vessel to a metal Cu rod according to claim 4, characterized in that: A 6-15g graphite block is placed at the top of the Cu rod to create pressure.

6. A method of vacuum brazing a polygonal ceramic block vessel to a metal Cu rod according to claim 5, characterized in that: Step 2) involves ultrasonic cleaning for 5-15 minutes.

7. A vacuum brazing method for a polygonal ceramic block container and a metal Cu rod according to any one of claims 1 to 6, characterized in that: Step 5) brazing is performed as follows: Place the workpiece with the brazing filler metal assembled into the heating area of ​​the vacuum brazing furnace, and set the vacuum level inside the furnace to 3 × 10⁻⁶. -2 pa~2×10 -5 Pa, with a heating rate of 5~20℃ / min.

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