Strip-shaped silver-copper-tin-titanium active brazing filler metal and preparation method thereof

Abstract

The invention relates to the technical field of brazing filler metal, and particularly discloses strip-shaped silver-copper-tin-titanium active brazing filler metal which comprises the following raw materials in percentage by weight: the balance of silver-copper alloy powder, 1-10 wt% of tin powder and 1-7 wt% of titanium-based powder, and the sum of the weight percentages of all the raw materials is 100 wt%. The particle size ratio of the silver-copper alloy powder to the titanium-based powder is larger than or equal to 3, and the particle size of the titanium-based powder is larger than or equal to tin powder; carrying out cold pressing, sintering and cold rolling on the raw material powder to prepare strip-shaped brazing filler metal; through powder particle size design, silver-copper alloy powder is used as a raw material, high-plasticity, low-melting-point and small-particle-size tin powder is introduced, the powder compact strength is improved, the sintering temperature is cooperatively reduced, generation of a brittle Cu-Ti intermetallic compound is effectively inhibited, titanium is dispersed and distributed in the form of a simple substance, and the high-plasticity, low-melting-point and small-particle-size titanium powder is obtained. The technical problem that the high-titanium-content active silver brazing filler metal is prone to cracking when rolled into a strip is effectively solved, the machining and manufacturing difficulty is lowered, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of solder technology, and in particular to a strip-shaped silver-copper-tin-titanium active solder and its preparation method. Background Technology

[0002] Ceramic materials are widely used in aerospace, energy, machinery, automobile, electronics and optics fields due to their excellent properties such as high strength, high hardness, high temperature resistance, corrosion resistance and wear resistance. However, ceramic materials generally have problems such as poor plasticity and toughness, difficult processing and difficulty in making large and complex structures. In practical applications, they are often connected with metal materials to form composite components.

[0003] There are various methods for joining ceramics and metals. Among them, brazing is the most commonly used method due to its advantages such as aesthetically pleasing joints, high reliability, and the ability to weld multiple parts at once. Because the physical and chemical properties of metals and ceramics differ significantly, making simultaneous wetting difficult, brazing methods include indirect brazing (pre-metallizing the ceramic) and direct brazing (using active brazing filler metal). Direct brazing eliminates the need for metallization of the ceramic, resulting in a shorter production process and lower costs, making it a key focus of research and application in ceramic-metal joining.

[0004] Among the many types of brazing filler metals, silver-copper-titanium brazing filler metals are the most commonly used in direct ceramic brazing. The activity of the filler metal depends on the titanium element in it. The higher the titanium content, the greater the activity of the filler metal. However, titanium in the filler metal reacts with copper to form Cu-Ti brittle intermetallic compounds, which is not conducive to the brazing process.

[0005] Currently, using powder metallurgy technology, silver-copper alloy powder and titanium powder are mixed, pressed and sintered to form alloy ingots, and then rolled to produce silver-copper-titanium brazing foil strips with a titanium content of >3wt%. However, the copper-titanium compound size of the ingot is still relatively large, requiring multiple rolling passes and resulting in a low yield. The brazing filler metal often cracks during processing. Summary of the Invention

[0006] To address the technical problems existing in the background art, this invention proposes a strip-shaped silver-copper-tin-titanium active solder, wherein the raw materials of the active solder comprise, by weight percentage: silver-copper alloy powder: balance, tin powder: 1-10 wt%, titanium-based powder: 1-7 wt%, and the total weight percentage of all raw materials is 100 wt%. Preferably, the titanium-based powder is 3-7 wt%.

[0007] In this invention, silver-copper alloy powder is used as raw material. Compared with elemental powder, alloy powder has better processing performance and lower sintering temperature. Furthermore, the introduction of tin powder with high plasticity and low melting point further improves the quality of powder compact. During sintering, the tin powder melts first and fills the pores, allowing the compact to be sintered at a lower temperature and inhibiting the formation of Cu-Ti brittle intermetallic compounds.

[0008] Preferably, the particle size ratio of the silver-copper alloy powder to the titanium-based powder is ≥3, and the particle size of the titanium-based powder is ≥ the particle size of the tin powder.

[0009] In this invention, when the particle size ratio of the silver-copper alloy powder to the titanium-based powder is ≥3, the small-diameter titanium powder is distributed in the gaps of the densely packed structure formed by the large-diameter silver-copper alloy powder during powder pressing, which is beneficial to improving the density of the powder compact. Moreover, the fine titanium elements dispersed after sintering have little impact on the overall alloy plasticity, and alloy billets with excellent plasticity can be prepared, which is beneficial to subsequent processing. Furthermore, the particle size of the titanium-based powder is ≥ the particle size of the tin powder, which is beneficial to the mechanical interlocking of the tin powder with the surrounding powder, and it is not easy to form large-sized Ti-Sn intermetallic compounds after sintering.

[0010] Preferably, the silver-copper alloy powder is spherical powder with a sphericity ≥0.8 and a particle size of 50-350μm; More preferably, the silver content in the silver-copper alloy powder can be 50wt%, 60wt%, 72wt%, or 85wt%. More preferably, the silver content in the silver-copper alloy powder is 72wt%, and the oxygen content is ≤200ppm.

[0011] In this invention, the ratio of silver to copper in the silver-copper alloy powder is not specified. The appropriate content can be selected according to actual production. The silver content is not limited to the aforementioned cases.

[0012] The tin powder is an irregularly shaped powder or a spherical powder with a sphericity ≥ 0.8; Preferably, the tin powder is an irregularly shaped powder.

[0013] In this invention, the tin powder with good plasticity can form mechanical engagement with the surrounding powder during powder pressing, thereby improving the quality of the pressed blank. When the tin powder is an irregularly shaped powder, the tin powder will generate more mechanical engagement with the surrounding powder.

[0014] Preferably, the titanium-based powder is spherical powder with a sphericity ≥ 0.8.

[0015] More preferably, the titanium-based powder is pure titanium powder or TiH2 powder; More preferably, the titanium-based powder is TiH2 powder; More preferably, the oxygen content of the titanium-based powder is ≤600ppm.

[0016] In this invention, when TiH2 powder is selected as the titanium-based powder, the oxidation of titanium elements during the sintering process can be reduced, thus ensuring the activity of the solder.

[0017] This invention also proposes a method for preparing the above-mentioned strip-shaped silver-copper-tin-titanium active solder, comprising the following steps: S1. Cold press the brazing filler metal mixture containing silver-copper alloy powder, tin powder and titanium-based powder into a powder compact; S2. Heat-treat the powder compact in an oxygen-free environment to obtain a sintered compact; S3. After cold rolling the sintered billet, a strip of silver-copper-tin-titanium active brazing filler metal is obtained.

[0018] In this invention, the powder pressing methods used include, but are not limited to: compression molding, isostatic pressing, powder injection molding, powder rolling, and powder extrusion.

[0019] Preferably, in step S1, the cold pressing pressure is 350-600 MPa.

[0020] Preferably, in step S2, the heat treatment temperature is 450-650℃, the heat treatment time is 0.5-4h, and the heat treatment pressure is 1-6MPa. More preferably, the oxygen-free environment during the heat treatment is a vacuum environment or a protective atmosphere; More preferably, the vacuum level of the vacuum environment is ≤1×10⁻⁶. -2 Pa.

[0021] Preferably, in step S3, the rolling deformation during cold rolling can reach 60%; More preferably, during the cold rolling process, annealing is performed when the rolling deformation reaches 40%-60%; More preferably, the annealing is vacuum annealing at 450~650℃ for 3 hours.

[0022] In this invention, although the rolling reduction and the number of rolling passes can indicate that the material has good processing performance, they are related to the original thickness of the brazing filler metal. Therefore, in this invention, the amount of deformation is used to measure the ease of rolling the brazing filler metal. The deformation amount is the reduction amount / original size, and the deformation amount will not exceed 100%. In the prior art, the deformation amount during Ag-Cu-Ti brazing filler metal rolling is generally low, while the present invention improves the process so that the rolling deformation amount of this type of brazing filler metal can reach up to 60%.

[0023] Beneficial effects of this invention: (1) The present invention uses powder metallurgy to mix small-particle-size titanium powder and tin powder with large-particle-size silver-copper alloy powder. Tin has good plasticity and forms mechanical interlocking with the surrounding powder during the powder pressing process, which improves the strength of the powder compact and sintered compact. Combined with appropriate pressing and sintering conditions, it effectively avoids the reaction between Ti and Cu elements to form brittle intermetallic compounds, so that the active brazing filler metal has good plastic deformation ability and reduces the number of rolling processing passes. (2) Tin has a low melting point (about 232°C) and melts first during the sintering process. It fills the gaps between powders through the liquid phase sintering mechanism, which promotes the densification of the billet. The molten tin wraps around and wets the titanium powder particles, blocking the direct contact between Ti and Cu. In addition, tin and silver-copper alloy powder work together to reduce the overall sintering temperature. Low-temperature sintering inhibits the violent reaction between Cu and Ti. The sintered billet prepared in the end has good plasticity, which reduces the number of rolling passes in the subsequent cold rolling. (3) The titanium element can reach up to 7wt%, and the titanium element is dispersed in the solder strip in the form of elemental titanium, resulting in extremely high activity of the final brazing filler metal; (4) The addition of tin not only reduces the sintering temperature during the preparation process, but also reduces the melting temperature of the brazing filler metal, which can achieve low-temperature active brazing and improve the fluidity of the brazing filler metal during the brazing process. Attached Figure Description

[0024] Figure 1 The image shows the metallographic structure of the brazing filler metal blank in Example 1. Figure 2 This is a picture of the strip-shaped silver-copper-titanium active solder product in Comparative Example 1; Figure 3 This is a cracking diagram of the strip silver-copper-tin-titanium active brazing filler metal product in Comparative Example 2 during two-roll rolling. Detailed Implementation

[0025] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0027] The technical solution of the present invention will now be described more clearly and completely with reference to specific embodiments and comparative examples.

[0028] Example 1

[0029] This embodiment proposes a strip-shaped silver-copper-tin-titanium active solder, the preparation method of which is shown below: (1) Prepare the raw material powder for the solder according to the ratio of 94 parts silver-copper alloy powder, 4 parts pure titanium powder, and 2 parts tin powder. Place the powder in a V-type mixer and mix for 4 hours to obtain the solder mixed powder, wherein: Silver-copper alloy powder: silver content is 72wt%, the balance is copper, particle size is 75-350μm, sphericity ≥0.8, oxygen content ≤200ppm; Pure titanium powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤600ppm; Tin powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤200ppm; (2) The brazing filler metal powder is loaded into a mold and pressed into a blank under a pressure of 400 MPa. (3) Place the billet into a vacuum sintering furnace for vacuum hot pressing sintering, and evacuate the vacuum to 5×10. -3 After Pa, the temperature is increased to 500℃ at 10℃ / min, held for 2 hours, and sintered at a pressure of 4MPa. Then, it is cooled in the furnace to obtain the sintered billet. (4) The sintered billet is thinned by multiple passes of cold rolling using two-roll and four-roll mills. When the rolling deformation reaches 60% during cold rolling, vacuum annealing is performed. The rolling reduction is 0.2-0.3 mm, the annealing temperature is 500℃, and the annealing time is 3h to obtain a strip with a thickness of 0.1 mm. Finally, it is cut to obtain a strip silver-copper-tin-titanium active brazing filler metal with a thickness of 0.1 mm and a width of 80 mm. Its composition is: Ag: 67.7 wt%, Cu: 26.3 wt%, Sn: 2 wt%, Ti: 4 wt%.

[0030] The sintered blank in Example 1 was tested, and its metallographic structure showed that titanium particles (dark color) were distributed in an isolated and diffuse form in the silver-copper-tin matrix (light color).

[0031] Example 2

[0032] This embodiment proposes a strip-shaped silver-copper-tin-titanium active solder, the preparation method of which is shown below: (1) Prepare the raw material powder for the solder according to the ratio of 91 parts silver-copper alloy powder, 5 parts pure titanium powder, and 4 parts tin powder. Place the powder in a V-type mixer and mix for 4 hours to obtain the solder mixed powder, wherein: Silver-copper alloy powder: silver content is 72wt%, the balance is copper, particle size is 75-350μm, sphericity ≥0.8, oxygen content ≤200ppm; Pure titanium powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤600ppm; Tin powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤200ppm; (2) The brazing filler metal powder is loaded into a mold and pressed into a block under a pressure of 350 MPa to obtain a blank; (3) Place the billet into a vacuum sintering furnace for vacuum hot pressing sintering, and evacuate the vacuum to 5×10. -3After Pa, the temperature is increased to 475℃ at 10℃ / min, held for 2 hours, and sintered at a pressure of 5MPa. Then, it is cooled in the furnace to obtain the sintered billet. (4) The sintered billet is thinned by multiple passes of cold rolling using two-roll and four-roll mills. When the rolling deformation reaches 50% during cold rolling, vacuum annealing is performed. The rolling reduction is 0.2-0.3 mm, the annealing temperature is 475℃, and the annealing time is 3 hours to obtain a strip with a thickness of 0.1 mm. Finally, it is cut to obtain a strip silver-copper-tin-titanium active brazing filler metal with a thickness of 0.1 mm and a width of 80 mm. Its composition is: Ag: 65.5 wt%, Cu: 25.5 wt%, Sn: 4 wt%, Ti: 5 wt%.

[0033] Example 3

[0034] This embodiment proposes a strip-shaped silver-copper-tin-titanium active solder, the preparation method of which is shown below: (1) Prepare the raw material powder for the solder according to the ratio of 88 parts silver-copper alloy powder, 7 parts TiH2 powder, and 5 parts tin powder. Place the powder in a V-type mixer and mix for 4 hours to obtain the solder mixed powder, wherein: Silver-copper alloy powder: silver content is 50wt%, the balance is copper, particle size is 75-350μm, sphericity ≥0.8, oxygen content ≤200ppm; TiH2 powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤600ppm; Tin powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤200ppm; (2) The brazing filler metal powder is loaded into a mold and pressed into a blank under a pressure of 500 MPa. (3) Place the billet into a vacuum sintering furnace for vacuum hot pressing sintering, and evacuate the vacuum to 5×10. -3 After Pa, the temperature is increased to 650℃ at 10℃ / min and held for 2 hours. The sintering pressure is 3MPa, and then the furnace is cooled to obtain the sintered billet. (4) The sintered billet is thinned by multiple passes of cold rolling using two-roll and four-roll mills. When the rolling deformation reaches 40% during cold rolling, vacuum annealing is performed. The rolling reduction is 0.2-0.25 mm, the annealing temperature is 650℃, and the annealing time is 3 hours to obtain a strip with a thickness of 0.1 mm. Finally, it is cut to obtain a strip of silver-copper-tin-titanium active brazing filler metal with a thickness of 0.1 mm and a width of 80 mm. Its composition is: Ag: 44 wt%, Cu: 44 wt%, Sn: 5 wt%, Ti: 7 wt%.

[0035] Comparative Example 1 This comparative example presents a strip-shaped silver-copper-tin-titanium active solder, the preparation method of which is shown below: (1) Prepare the raw material powder for the brazing filler metal according to the ratio of 96 parts silver-copper alloy powder and 4 parts pure titanium powder. Place the powder in a V-type mixer and mix for 4 hours to obtain the brazing filler metal mixed powder, wherein: Silver-copper alloy powder: silver content is 72wt%, the balance is copper, particle size is 75-350μm, sphericity ≥0.8, oxygen content ≤200ppm; Pure titanium powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤600ppm; (2) The brazing filler metal powder is loaded into a mold and pressed into a blank under a pressure of 400 MPa. (3) Place the billet into a vacuum sintering furnace for vacuum hot pressing sintering, and evacuate the vacuum to 5×10. -3 After Pa, the temperature is increased to 500℃ at 10℃ / min, held for 2 hours, and sintered at a pressure of 4MPa. Then, it is cooled in the furnace to obtain the sintered billet. (4) The sintered billet is thinned by multiple cold rolling passes using two-roll and four-roll mills. When the rolling deformation reaches 60% during cold rolling, vacuum annealing is performed. The rolling reduction is 0.2-0.3 mm, the annealing temperature is 500℃, and the annealing time is 3 hours to obtain a strip with a thickness of 0.1 mm. Finally, it is cut to obtain a strip of silver-copper-tin-titanium active solder with a thickness of 0.1 mm and a width of 80 mm. Its composition is: Ag: 69.1 wt%, Cu: 26.9 wt%, Ti: 4 wt%. During four-roll precision rolling, the edge of the solder strip is prone to cracking. See details. Figure 2 .

[0036] Comparative Example 2 This comparative example presents a strip-shaped silver-copper-tin-titanium active solder, the preparation method of which is the same as that of Example 1, except that in step (1), the raw material powder required for the solder is prepared according to the ratio of 94 parts silver-copper alloy powder, 4 parts pure titanium powder, and 2 parts tin powder. The powder is placed in a V-type mixer and mixed for 4 hours to obtain the solder mixed powder, wherein: Silver-copper alloy powder: silver content is 72wt%, the balance is copper, particle size is 75-350μm, sphericity ≥0.8, oxygen content ≤200ppm; Pure titanium powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤600ppm; Tin powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤200ppm; Change to: "(1) Prepare the raw material powder for the solder according to the ratio of 67.7 parts silver powder, 26.3 parts copper powder, 4 parts pure titanium powder, and 2 parts tin powder. Place the powder in a V-type mixer and mix for 4 hours to obtain the solder mixed powder, wherein: Silver powder: particle size 75-350μm, sphericity ≥0.8, oxygen content ≤200ppm; Copper powder: particle size 75-350μm, sphericity ≥0.8, oxygen content ≤200ppm Pure titanium powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤600ppm; Tin powder: particle size ≤25μm, sphericity ≥0.8, oxygen content ≤200ppm;

[0037] The appearance of the products from Examples 1-3 and Comparative Examples 1 and 2 is compared, as detailed in Table 1: Table 1 Performance data for each embodiment and comparative example

[0038] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A ribbon-shaped silver-copper-tin-titanium active brazing material, characterized by comprising: 0.1 to 0.5% by mass of titanium; and 0.1 to 0.5% by mass of copper. The raw materials of the active brazing filler material include, by weight percentage: silver-copper alloy powder: balance, tin powder: 1-10 wt%, titanium-based powder: 1-7 wt%, the total weight percentage of each raw material being 100 wt%.

2. The ribbon-shaped silver-copper-tin-titanium active brazing material according to claim 1, wherein The particle size ratio of the silver-copper alloy powder and the titanium-based powder is ≥3, and the particle size of the titanium-based powder is ≥ the particle size of the tin powder.

3. The ribbon-shaped silver-copper-tin-titanium active brazing material according to claim 1 or 2, characterized by The silver-copper alloy powder is spherical powder, the sphericity being ≥0.8, and the particle size being 50-350 μm.

4. The ribbon-shaped silver-copper-tin-titanium active brazing material according to any one of claims 1 to 3, characterized by, The tin powder is irregularly shaped powder or spherical powder with a sphericity ≥0.

8. Preferably, the tin powder is irregularly shaped powder.

5. The ribbon-shaped silver-copper-tin-titanium active brazing material according to any one of claims 1 to 4, characterized by, The titanium-based powder is spherical powder, the sphericity being ≥0.

8.

6. The ribbon-shaped silver-copper-tin-titanium active brazing material according to any one of claims 1 to 5, characterized by, The titanium-based powder is pure titanium powder or TiH2 powder. Preferably, the titanium-based powder is TiH2 powder.

7. A method of producing the silver-copper-tin-titanium active brazing material in strip form according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1. Cold-pressing the brazing filler material mixed powder containing silver-copper alloy powder, tin powder and titanium-based powder into a powder compact; S2. Heat-treating the powder compact in an oxygen-free environment to obtain a sintered compact; S3. Cold-rolling the sintered compact to obtain a silver-copper-tin-titanium active brazing filler material in strip form.

8. The method of claim 7, wherein the silver-copper-tin-titanium active ribbon filler material is prepared by the steps of: melting a silver-copper-tin-titanium alloy; and casting the silver-copper-tin-titanium alloy into a ribbon. In step S1, the cold-pressing pressure is 350-600 MPa.

9. The method of producing the silver-copper-tin-titanium active brazing material in strip form according to claim 7 or 8, characterized in that, In step S2, the heat-treatment temperature is 450-650 °C, the heat-treatment time is 0.5-4 h, and the heat-treatment pressure is 1-6 MPa.

10. The method of producing the silver-copper-tin-titanium active brazing material in strip form according to any one of claims 7 to 9, characterized in that, In step S3, the rolling deformation amount during cold-rolling can reach 60%.

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